Singapore, Singapore
Singapore, Singapore

The National University of Singapore is a comprehensive research university located in Singapore, being the flagship tertiary institution of the country which has a global approach to education and research. Founded in 1905, it is the oldest higher learning institute in Singapore, as well as the largest university in the country in terms of student enrolment and curriculum offered. It was ranked as the best university in Asia by QS University Rankings in 2014.The university's main campus is located in southwest Singapore at Kent Ridge, with an area of approximately 1.83 km2 . The Bukit Timah campus houses the Faculty of Law, Lee Kuan Yew School of Public Policy and research institutes, while the Duke-NUS Graduate Medical School Singapore is located at the Outram campus. Wikipedia.


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Patent
National University of Singapore | Date: 2015-02-13

System, device and methods for brainwave-based technologies. The system for measuring and processing brainwave data of a user comprises one or more electrodes for measuring the brainwave data of the user, and a processing unit coupled to the electrodes and configured to process the brainwave data for determining a current mental state of the user and to generate, based on the current mental state of the user, a control signal for instructing activation of a means for manipulating the current mental state of the user.


Patent
Singapore Health Services Pte, National University Hospital Singapore and National University of Singapore | Date: 2015-01-30

Defining proximal as toward the heart and distal as away from the heart, a sheath includes a proximal opening and multiple fenestrations maintainable in position slightly beyond a site or point of sheath entry into a vessel by way of an anchoring assembly having a set of radially displaceable anchoring elements configured for abutting a superficial vessel wall. The fenestrations and/or anchoring element(s) are arranged obliquely or non-obliquely around peripheral portions of the sheath. The sheath can receive blood from a pumping source at a proximal opening, and channel the blood toward, to, and through the fenestrations. The fenestrations, in combination with the proximal opening, enable the perfusion of blood into the cannulated vessel in a set of distal directions for perfusing a distal tissue or organ. Flow of blood out of fenestrations directs blood distally towards the limb, head, or other distal region, mitigating the risk of or preventing ischemia.


Patent
National University of Singapore and Dso National Laboratories | Date: 2016-06-01

Compositions and methods for the treatment or prevention of Dengue virus infection in a vertebrate subject are provided. In particular, human neutralizing monoclonal antibodies to Dengue virus isolated from EBV immortalized B cells derived from patients who have recovered from Dengue infection are disclosed. Methods are provided for administering such antibodies to a vertebrate subject in an amount effective to reduce, eliminate, or prevent relapse from infection.


Patent
National University of Singapore | Date: 2016-07-08

Cell-culture devices and methods for determining the integrity of cell-cell adhesion are described. A cell culture device includes a channel-defining body that defines a plurality of channels in a cell-culture dish and a removable mask located above the channel-defining body. Channels of the cell-culture dish can be seeded and maintained under conditions in which a cell sheet can be formed in each of the channels. The mask defines test regions of cell sheets when cell sheets are present within the channels. A cell-substrate cleaving solution can be applied to the test regions to lift the cell sheet in the test region, causing the inherent tension due to cell spreading to be borne solely by the cell-cell junctions, such that the integrity of the cell sheets can be observed. The tension in the lifted cell sheet can be controlled by controlling the vertical design width of the channel on either side of the constriction included in the test region.


Patent
Agency For Science and National University of Singapore | Date: 2015-03-23

The present invention relates to a method for determining or making of a prognosis if a patient has cancer or is at an increased risk of having cancer, the method comprising testing for the presence of one or more cancer-associated fusion genes, or proteins derived thereof, in a sample obtained from a patient. More specifically, the present invention relates to fusion genes CLEC16A-EMP2, SNX2-PRDM6, MLL3-PRKAG2, DUS2L-PSKH1 and CLDN18-ARHGAP26 in gastric cancer. Use of the method and a kit when used in the method are also provided.


Disclosed herein are methods of forming chiral 1,2-aminoalcohols and -aminoacids from alkene starting materials by way of an enzymatic cascade reaction sequence that may be accomplished in a single reaction vessel without the need to isolate any intermediates. Also disclosed herein are recombinant nucleic acids, vectors and host cells for use in the methods of the invention.


Patent
National University of Singapore and INC Research | Date: 2015-05-14

The present invention provides, in certain aspects, a natural killer (NK) cell that expresses all or a functional portion of interleukin-15 (IL-15), and methods for producing such cells. The invention further provides methods of using a natural killer (NK) cell that expresses all or a functional portion of interleukin-15 (IL-15) to treat cancer in a subject or to enhance expansion and/or survival of NK cells.


Analog-to-digital converter (ADC) circuitry includes a first binary-weighted capacitor array having a total capacitance of 2^(n-2)C. The value of n represents number of bits of a digital signal that represents an analog signal. The ADC circuitry also includes a second binary-weighted capacitor array having a total capacitance of 2^(n-2)C. In addition to that, the ADC circuitry further includes a comparator circuit having first and second terminals. The first terminal is coupled to the first binary-weighted capacitor array, and the second terminal is coupled to the second binary weighted capacitor array. The switching circuit within the second binary-weighted capacitor array may be configurable to couple a largest capacitance capacitor within the second binary-weighted capacitor array from remaining capacitors within the second binary weighted capacitor array.


Patent
National University of Singapore | Date: 2015-05-07

A device for analysing a specimen is disclosed. The device comprises a first polarizer for polarizing a first beam of electromagnetic radiation; an optical device for directing the polarized beam of electromagnetic radiation at the specimen to enable interaction between the polarized beam of electromagnetic radiation and the specimen to cause generation of a second beam of electromagnetic radiation; a plurality of second polarizers for dividing the wavefront of the second beam of electromagnetic radiation into a plurality of beams of electromagnetic radiation polarized with different polarization states; and at least one spectrometer for analysing respective electromagnetic spectrums of the plurality of polarized beams of electromagnetic radiation to enable the specimen to be characterised. A related method is also disclosed.


Patent
National University of Singapore | Date: 2015-04-24

The present invention provides a method of predicting response of a cancer patient to a therapy. The method comprises the step of determining a presence or absence of at least one mutation of ITCH (SEQ ID NO: 1) in a first sample isolated from a cancer patient, wherein the presence of a mutation is predictive of response of the cancer patient to a therapy selected from the group consisting of: Wnt pathway-, EGFR-, Her2-, hormonal- and WBP2-based therapy.


Patent
National University of Singapore | Date: 2016-09-30

A method for determining a presence or absence of one or more target analytes in a sample includes contacting the sample with an array of particles comprising at least first and second particle subsets disposed therein with a known particle number ratio with respect to each other. The first particle subset has at least one binding site configured to bind with a first target analyte and the second particle subset has at least one binding site configured to bind with a second, different target analyte. Changes are detected in a detectable signal emitted by the particles after contacting the sample with the array. A number of the particles that emit the change in the detectable signal are counted and this number is compared to the known particle number ratio of the subsets so as to determine the presence or absence of the one or more of the target analytes.


Patent
National University of Singapore | Date: 2014-09-26

The invention relates to compositions and methods for utilizing lysophosphatidylcholine scaffolds. The compositions and methods can be used for LPC-mediated delivery of fatty acids and other molecules; to screen and identify fatty acid formulations for parenteral nutrition; and for live animal organ imaging, among other uses. The invention also provides compositions and methods for utilizing mutations and polymorphisms in human Mfsd2a as markers for neurological deficits.


Patent
National University of Singapore | Date: 2016-07-29

A method of protecting a magnetic layer of a magnetic recording medium is provided to reduce the thickness of the magnetic spacing while improving corrosion resistance and tribological performance of the magnetic recording medium.


Chae J.,National University of Singapore
Journal of Psychosocial Oncology | Year: 2017

Cancer information acquisition is beneficial for cancer prevention. However, for some people, information exposure brings about greater uncertainty and anxiety, which prompt them to engage in subsequent exposure. This study tested whether intolerance of uncertainty (IU), a strong predictor of information exposure, can be used to identify such people in the cancer context. A longitudinal survey in South Korea (N = 1,130 at Wave 1 and 813 at Wave 2) revealed that the effect of past information exposure about cancer on future exposure is stronger for people with high IU. The results suggest that those with high IU feel greater cancer-related anxiety, resulting from the past exposure, and more eagerly engage in future exposure. Although highly correlated with IU, trait anxiety did not moderate the relationship between past and future exposure, suggesting that the role of IU in the cancer context is distinct from other neurotic traits. © 2017 Taylor & Francis Group, LLC


Ong L.T.,National University of Singapore
IEEE Region 10 Annual International Conference, Proceedings/TENCON | Year: 2017

This paper presents experimental results of spatial smoothing techniques using a software receiver based linear array processing platform. The array system consists of an multi-element uniform linear array prototype and 7V-USRPs as receiving units. Forward spatial smoothing (FSS) and forward-backward spatial smoothing (FBSS) coupled with multiple signal classification (MUSIC) algorithms for direction of arrival (DOA) estimation of coherent signals are considered. Measurement results are provided to valid ate the performance of FBSS and FSS over a wide range of signal to noise ratio scenarios. © 2016 IEEE.


Tung N.,National University of Singapore
IEEE Region 10 Annual International Conference, Proceedings/TENCON | Year: 2017

In this paper, a triple-band rectifier design is proposed for the ambient RF energy harvesting. Given the increasing popularity of Wireless Sensor Nodes (WSN) for the Internet of Things (IoT) application, a multi-band rectifier design offers an excellent option as power supply. The multiband approach has the advantages of achieving higher RF-to-DC conversion efficiency than the conventional single band approach, while keeping the overall size of the circuit compact. The circuit operates at three frequency bands-GSM 1800, UMTS 2100 and LTE 2600, and is able to achieve high RF-to-DC conversion efficiency, reaching 35% at input power of-20 dBm. The harvest energy is sufficient to power a number of sensors commonly used in WSN. © 2016 IEEE.


Zhang X.,National University of Singapore | Soh S.,National University of Singapore
Advanced Materials | Year: 2017

Chemical logic gates can be fabricated by synthesizing molecules that have the ability to detect external stimuli (e.g., temperature or pH) and provide logical outputs. It is, however, challenging to fabricate a system that consists of many logic gates using this method: complex molecules can be difficult to synthesize and these logic gates typically cannot be integrated together. Here, we fabricated different types of logic gates by assembling a combination of different types of stimuli-responsive hydrogels that change their size under the influence of one type of stimulus. Importantly, the preparation of these stimuli-responsive hydrogels is widely reported and technically simple. Through designing the geometry of the systems, we fabricated the YES, NOT, OR, AND, NOR, and NAND gates. Although the hydrogels respond to different types of stimuli, their outputs are the same: a change in size of the hydrogel. Hence, we show that the logic gates can be integrated easily (e.g., by connecting an AND gate to an OR gate). In addition, we fabricated a standalone system with the size of a normal drug tablet (i.e., a "smart tablet") that can analyze (or diagnose) different stimuli and control the release of a chemical (or drug) via the logic gates. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ramanathan K.,National University of Singapore
Critical Care Medicine | Year: 2017

OBJECTIVES:: Extracorporeal membrane oxygenation is a rescue therapy used to support severe cardiorespiratory failure. Data on outcomes from severe community-acquired pneumonia in adults receiving rescue extracorporeal membrane oxygenation are mainly confined to single-center experiences or specific pathogens. We examined data from the Extracorporeal Life Support Organisation registry to identify risk factors for poor outcomes in adult patients with community-acquired pneumonia. DESIGN:: Retrospective data analysis. SETTING:: Extracorporeal Life Support Organization Registry database. PATIENTS:: We collected deidentified data on adult patients (> 18 yr) receiving extracorporeal membrane oxygenation for community-acquired pneumonia between 2002 and 2012. Patients with incomplete data or brain death were excluded. The primary outcome measure was in-hospital mortality. Other measurements included demographic information, pre-extracorporeal membrane oxygenation mechanical ventilation and biochemical variables, inotrope requirements, extracorporeal membrane oxygenation mode, duration, and complications. Initial univariate analysis assessed potential associations between survival and various pre-extracorporeal membrane oxygenation and extracorporeal membrane oxygenation factors. Variables with p values of less than 0.1 were considered for logistic regression analysis to identify predictors of mortality. INTERVENTIONS:: None. MEASUREMENTS AND MAIN FINDINGS:: One thousand fifty-five patients, who satisfied inclusion criteria, were included in the final analysis. There was an increase in the number of patients cannulated per annum over the 10-year period studied. Univariate analysis identified pre-extracorporeal membrane oxygenation and extracorporeal membrane oxygenation variables associated with high mortality. Further multiple regression analysis identified certain pre-extracorporeal membrane oxygenation factors as predictors of mortality, including duration of mechanical ventilation prior to extracorporeal membrane oxygenation, lower arterial pressure, fungal pneumonia, and advancing age. Type and duration of extracorporeal membrane oxygenation, neurologic complications, and presence of more than three complications on extracorporeal membrane oxygenation were also associated with higher mortality. CONCLUSIONS:: The majority (66%) of adults with community-acquired pneumonia supported on extracorporeal membrane oxygenation survived. Certain potentially modifiable risk factors were associated with increased mortality. Copyright © by 2017 by the Society of Critical Care Medicine and Wolters Kluwer Health, Inc. All Rights Reserved.


STUDY DESIGN.: Prospective comparative study OBJECTIVE.: To predict physiological alignment of the cervical spine and study its morphology in different postures. SUMMARY OF BACKGROUND DATA.: There is increasing evidence that normal cervical spinal alignment may vary from lordosis to neutral to kyphosis, or form S-shaped or reverse S-shaped curves. METHODS.: Standing, erect sitting and natural sitting whole spine radiographs were obtained from 26 consecutive patients without cervical spine pathology. Sagittal vertebral axis (SVA), global cervical lordosis (CL), lower cervical alignment (LCA) C4-T1, C0-C2 angle, T1-slope, C0-C7 SVA and C2-7SVA, SVA, thoracic kyphosis (TK), thoracolumbar junctional angle (TL), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI) were measured. Statistical analysis was performed to elucidate differences in cervical alignment for all postures. Predictive values of T1-slope and SVA for cervical kyphosis were evaluated. RESULTS.: Most patients (73.0%) do not have lordotic cervical alignment (C2-C7) upon standing (mean -0.6, SD 11.1°). Lordosis increases significantly when transitioning from standing to erect sitting, as well as from erect to natural sitting (mean -17.2, SD 12.1°). Transition from standing to natural sitting also produces concomitant increases in SVA (-8.8 to 65.2mm) and T1-slope (17.4 to 30.2°). T1-slope and SVA measured during standing significantly predicts angular cervical spine alignment in the same position. SVA < -10mm significantly predicts C4-C7 kyphosis (p<0.001), and to a lesser extent, C2-C7 kyphosis (p=0.02). T1-slope <20° is both predictive of C2-C7 and C4-7 kyphosis (p=0.001 and p=0.023 respectively). For global cervical Cobb angle, T1-slope seems to be a more significant predictor of kyphosis than SVA (OR 17.33, p=0.001 vs. OR 11.67, p=0.02 respectively). CONCLUSIONS.: The cervical spine has variable normal morphology. Key determinants of its alignment include SVA and T1-slope. Lordotic correction of the cervical spine is not always physiological and thus correction targets should be individualized.Level of Evidence: 4 Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.


Chu S.,National University of Singapore
Transportation | Year: 2017

Singapore’s Vehicle Quota System, implemented in 1990, uses uniform-price auctions to allocate Certificates of Entitlement (COE) or registration rights in five categories presently. Four of these are restricted to small and big cars, commercial vehicles and motorcycles. The fifth one is unrestricted as it allows successful bidders to register a vehicle in any restricted category of their choice. Owners are incentivised via another policy to deregister their vehicle by the tenth year expiry of the COE instead of revalidating it. Each deregistration results in a new COE. Currently, 10% of the COEs from each restricted category is channelled to the unrestricted category. However, hardly any of the expensive COEs in the unrestricted category has been used to register motorcycles. The sharp decline in the number of motorcycle COEs since 2014 has led to a surge in auction premiums at about twice the price of an entry-level motorcycle. The auction process before 2014 is shown to be exemplary with the COE premium driven by its inertia and a host of exogenous factors. After 2014 however, it appears to be unresponsive to the historically low quota levels. This undesirable auction trait needs to be remedied by a reformulation of the COE quota in order to help those most in need of a motorcycle to earn a living. Measures announced in the February 2017 Singapore Budget trudge in that direction. © 2017 Springer Science+Business Media New York


STUDY DESIGN.: . A prospective cross-sectional study. OBJECTIVE.: To compare lumbar spine alignment in 6 common postures, and estimate loss in range of motion (ROM) relative to standing. SUMMARY OF BACKGROUND DATA.: Ideal position for fusion of lumbar spine remains unknown. While surgical fusion is necessary for deformity correction and symptom relief, the final position in which the vertebrae are immobilized should provide maximum residual function. METHODS.: Data was collected prospectively from 70 patients with low back pain recruited over a year. All subjects had X-rays performed in slump sitting, forward bending, supine, half squatting, standing and backward bending postures. ROM quantified in terms of sagittal global and segmental Cobb angles was measured from L1 to S1. Loss of ROM relative to standing was calculated for each posture. ANOVA and unpaired t-tests were used to identify differences in alignment between postures. RESULTS.: Slump sitting gives the greatest lumbar flexion followed by forward bending, and supine postures (p?


Mahendran R.,National University of Singapore
Translational Cancer Research | Year: 2017

Bladder cancer is not life threatening but it is characterized by frequent recurrences which may progress to muscle invasive disease. The standard therapy for intermediate and high grade non muscle invasive bladder cancer is tumor removal followed by Mycobacterium bovis, Bacillus Calmette-Guérin (BCG) immunotherapy. This consists of weekly intravesical instillations of BCG that are divided into induction and maintenance phases. BCG immunotherapy stimulates the immune system and this leads to tumor removal. While BCG immunotherapy is regarded as the most successful immunotherapy, it is associated with side-effects that can in some cases be so severe that patients cannot complete this therapy. Those who fail to complete therapy are more likely to have a recurrence. Some 30-50% of patients will have a recurrence despite therapy. Thus most clinical and laboratory analyses are aimed at improving the response to BCG immunotherapy and trying to identify those will respond to therapy from non-responders. These are not trivial problems as clinical studies on BCG immunotherapy are not all similar. These studies are conducted in different countries and use different BCG strains, doses and schedules of therapy such as frequency of induction and maintenance instillations. Patient genetic polymorphisms and tumor characteristics are also known to impact response to therapy. These differences do make improving BCG therapy challenging. A recent study has proposed a novel strategy of dose increase to improve BCG induced cytotoxicity. The study is discussed in the context of our current knowledge of the response to BCG immunotherapy. © Translational Cancer Research. All rights reserved.


Yu G.D.,National University of Singapore
International Journal of Simulation Modelling | Year: 2016

This paper addresses an emergency scheduling for manufacturing resources (ESMR) problem and a method based on event-driven rolling optimization according to the production task priority is developed for solving it. A mathematical model aiming to maximum resource scheduling satisfaction, minimize tardiness penalties and minimize crash cost is proposed firstly. Then, the priority of the tasks in rolling window is analysed based on production system vulnerability. An adaptive multi-objective dynamic resource scheduling algorithm is proposed as a solution of the model above. Analytic results show that it is not only able to effectively reduce the complexity of ESMR, but also to reveal influence of task importance on ESMR. With the analysis, it can provide way of measuring the overall emergency impacts on the systems, and allow the decision-makers to respond to unexpected events that what the best way of resources scheduling is. © 2016, Vienna University of Technology. All rights reserved.


Setyawati M.I.,National University of Singapore | Leong D.T.,National University of Singapore
ACS Applied Materials and Interfaces | Year: 2017

Tumors depend heavily on angiogenesis for nutrient derivation and their subsequent metastasis. Targeting tumor induced angiogenesis per se can address both tumor growth and progression simultaneously. Here, we show that we could elegantly restrict the endothelial cells angiogenic behavior through digital size control of mesoporous silica nanoparticle (MSN). This antiangiogenesis effect was derived from the particle size dependent uptake and production of intracellular reactive oxygen species (ROS) that directly interfered with p53 tumor suppressor pathway. The resulting signaling cascade wrestled back the tumoral control of endothelial cells' migration, invasion, and proliferation. Overall, a mere control over the size of a highly oxidative reactive surfaced nanoparticle could provide an alternative strategy to curb the tumor induced angiogenesis process in a conventional drug-free manner. © 2017 American Chemical Society.


Han H.,National University of Singapore
Journal of Environment and Development | Year: 2017

The rapid economic development of Singapore has been attributed to its plan-rational technocratic elite, according to the developmental state model. However, few studies have addressed the impacts of the country’s deeply entrenched developmental state tradition on its environment and environmental governance. This article establishes the nexus between these two by examining Singapore’s transition into a garden city. It demonstrates how the Singaporean government has maintained a top-down, nonparticipatory approach to policy making in line with the postulations of authoritarian environmentalism and how this mode of governance is related to the developmental state legacy. While Singapore’s environmental policy resulted in its international reputation as a model green city with a remarkable expansion of green spaces and infrastructure, these outputs signify the results of the developmental state’s deliberate planning and management based on a utilitarian view toward nature rather than on the outcomes of an organic and comprehensive transition to a green society. © 2016, © The Author(s) 2016.


Dutta M.J.,National University of Singapore
International Journal of Environmental Research and Public Health | Year: 2017

Construction workers globally face disproportionate threats to health and wellbeing, constituted by the nature of the work they perform. The workplace fatalities and lost-time injuries experienced by construction workers are significantly greater than in other forms of work. This paper draws on the culture-centered approach (CCA) to dialogically articulate meanings of workplace risks and injuries, voiced by Bangladeshi migrant construction workers in Singapore. The narratives voiced by the participants suggest an ecological approach to workplace injuries in the construction industries, attending to food insecurity, lack of sleep, transportation, etc. as contextual features of work that shape the risks experienced at work. Moreover, participant voices point to the barriers in communication, lack of understanding, and experiences of incivility as features of work that constitute the ways in which they experience injury risks. The overarching discourses of productivity and efficiency constitute a broader climate of threats to worker safety and health. © 2017 by the authors; licensee MDPI, Basel, Switzerland.


Connolly C.,National University of Singapore
Journal of Political Ecology | Year: 2017

This article details the social construction of the 'swiftlet farming' industry in George Town, Malaysia. It argues that narratives of health and disease continually police which landscape practices are acceptable for the increasingly globalizing and image conscious city. 'Swiftlet farming' refers to the use of inner city shophouses and other commercial buildings for harvesting the edible nests of swiftlets (constructed from their saliva). Due to the high global demand and prices for birds' nests, the number of swiftlet farms have exploded in cities and towns across the country over the past decade, as entrepreneurs have been trying to cash in on the lucrative industry. The competing discourses and reactions to swiftlet farming in George Town, particularly in relation to its alleged potential for causing outbreaks of disease such as avian flu or dengue fever offer an apt entry point for studying this contested normative landscape. In doing so, I draw on recent writing on land-scape and political ecology to analyze how swiftlet farm(er)s have been politicized by various stakeholders as (in)appropriate for the urban landscape. The article concludes by considering the significance of such an approach can help to make sense of the contradictions and uncertainties that abound in urban health controversies.


Sun Z.,National University of Singapore
Nature Cell Biology | Year: 2017

Throughout development, tissues undergo complex morphological changes, resulting from cellular mechanics that evolve over time and in three-dimensional space. During Drosophila germ-band extension (GBE), cell intercalation is the key mechanism for tissue extension, and the associated apical junction remodelling is driven by polarized myosin-II-dependent contraction. However, the contribution of the basolateral cellular mechanics to GBE remains poorly understood. Here, we characterize how cells coordinate their shape from the apical to the basal side during rosette formation, a hallmark of cell intercalation. Basolateral rosette formation is driven by cells mostly located at the dorsal/ventral part of the rosette (D/V cells). These cells exhibit actin-rich wedge-shaped basolateral protrusions and migrate towards each other. Surprisingly, the formation of basolateral rosettes precedes that of the apical rosettes. Basolateral rosette formation is independent of apical contractility, but requires Rac1-dependent protrusive motility. Furthermore, we identified Src42A as a regulator of basolateral rosette formation. Our data show that in addition to apical contraction, active cell migration driven by basolateral protrusions plays a pivotal role in rosette formation and contributes to GBE. © 2017 Nature Publishing Group


Taneja R.,National University of Singapore
Cell Research | Year: 2017

Transcriptional activator-like effectors (TALEs) have emerged as powerful tools for genome editing. A recent study published by Cell Research reports that fusion of thioredoxin to TALEs unlocks their full potential in live-cell imaging to accurately analyze genome instability, telomere attrition and epigenetic alterations that are hallmarks of aging. © 2017 Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences


Nian V.,National University of Singapore
Progress in Nuclear Energy | Year: 2017

The size of a nuclear reactor has increased from below 300 MWe to more than 1000 MWe to achieve better economies of scale since the 1950s. Across the 1970s and 1980s, severe nuclear accidents, completion time overrun, escalating construction cost, and strong negative public perception are among the main factors leading to a slowdown in nuclear energy developments. Post-Fukushima, nuclear energy remains an important option for addressing energy security and decarbonization for developing economies, especially those in the Association of South East Asian Nations (ASEAN). However, a Fukushima-scale accident occurring in ASEAN could lead to severe trans-boundary impacts to several ASEAN members due to close geographical proximity. With the emergence of small modular reactors (SMRs), the conceivable advantages of SMRs over large reactors in the ASEAN context is yet to be assessed. In response, this study provides an analysis on the economic, safety, and other aspects of SMRs, and a review on the developments in nuclear energy in ASEAN. Findings from this study suggest SMRs as a strategic option in ASEAN's long-term energy planning. While SMRs are still under design and development (some under demonstration), ASEAN needs to build up competence in nuclear energy through training and education, and international and regional cooperation. © 2017 Elsevier Ltd.


Ong K.C.G.,National University of Singapore
Procedia Engineering | Year: 2017

Many cities around the world can afford the old model of urban sprawl, where the city boundary grows outwards. However, in small city states like Singapore, evolving the city of the future will be very different. Singapore requires development of holistic sustainable technologies and solutions for sustainable infrastructure to meet future social and economic needs. This includes adopting building designs, construction methods and materials that are environmentally-friendly, as well as using materials and resources that have sustainable supplies. A brief update of some research findings to address Singapore's infrastructural sustainability needs is presented. © 2017 The Authors.


Tsang M.,National University of Singapore
New Journal of Physics | Year: 2017

I propose a spatial-mode demultiplexing (SPADE) measurement scheme for the far-field imaging of spatially incoherent optical sources. For any object too small to be resolved by direct imaging under the diffraction limit, I show that SPADE can estimate its second or higher moments much more precisely than direct imaging can fundamentally do in the presence of photon shot noise. I also prove that SPADE can approach the optimal precision allowed by quantum mechanics in estimating the location and scale parameters of a subdiffraction object. Realizable with far-field linear optics and photon counting, SPADE is expected to find applications in both fluorescence microscopy and astronomy. © 2017 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.


Feng Q.,National University of Singapore | Straughan P.T.,National University of Singapore
Journals of Gerontology - Series B Psychological Sciences and Social Sciences | Year: 2017

Objectives: We explore the culturally specific meaning of successful aging in Singapore, an ethnically diverse city-state in Asia. We aim to investigate lay perceptions of successful aging among the elderly individuals in Singapore and further examine variations of these perceptions. Methods: We applied a mixed-method research design. Firstly, we conducted qualitative interviews with 49 elderly respondents, generating 12 main subjective components of successful aging. Next, we did a national survey with a sample of 1,540 local residents aged 50 to 69 years, in which respondents were asked to evaluate the importance of each subjective component of successful aging. We used the regression models and latent class analysis to analyze the correlatives of successful aging and to classify the elderly individuals by perception types. Results: Among 12 components of successful aging, those related to self-sufficiency received the highest acknowledgment among the elderly individuals in Singapore. At least half of them simultaneously highlighted independence from family and dependence on family. Malays and Indians in Singapore valued more of the roles of spouse and children in successful aging, as compared with Chinese. The latent class analysis classified four groups of the elderly individuals according to their lay views on successful aging. Discussion: As compared with the western model of successful aging, the elderly individuals in Singapore perceived successful aging with a strong focus on familism. These lay perceptions also significantly varied among these elderly individuals. © The Author 2016. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved.


Dolejsova M.,National University of Singapore
Conference on Human Factors in Computing Systems - Proceedings | Year: 2016

A life without food - a leitmotiv of science fiction dystopias is becoming a voluntary choice for thousands of people consuming the powdered food replacement soylent. The DIY soylent powders are designed by a group of nutrition hobbyists who distrust existing healthy eating standards and crowdsource experimental soylent recipes in their online user forums. This DIY food-tech rebellion offers an opportunity to look at the issues around present food standards and policies from the HCI perspective. This paper reports findings from in-depth interviews with 21 soylent dieters, with the aim of identifying the risks and opportunities of the expert-amateur DIY food practices. © 2016 Authors.


Mohammad F.,National University of Singapore
Nature Methods | Year: 2017

Optogenetics uses light exposure to manipulate physiology in genetically modified organisms. Abundant tools for optogenetic excitation are available, but the limitations of current optogenetic inhibitors present an obstacle to demonstrating the necessity of neuronal circuits. Here we show that anion channelrhodopsins can be used to specifically and rapidly inhibit neural systems involved in Drosophila locomotion, wing expansion, memory retrieval and gustation, thus demonstrating their broad utility in the circuit analysis of behavior. © 2017 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.


Despite extensive effort, there has been limited progress in the development of direct RAS inhibitors. Targeting isoprenylcysteine carboxylmethyltransferase (ICMT), a unique enzyme of RAS post-translational modification, represents a promising strategy to inhibit RAS function. However, there lacks direct genetic evidence on the role of ICMT in RAS-driven human cancer initiation and maintenance. Using CRISPR/Cas9 genome editing, we have created Icmt loss-of-function isogenic cell lines for both RAS-transformed human mammary epithelial cells (HME1) and human cancer cell lines MiaPaca-2 and MDA-MB-231 containing naturally occurring mutant KRAS. In both in vitro and in vivo tumorigenesis studies, Icmt loss-of-function abolishes the tumor initiation ability of all major isoforms of mutant RAS in HME1 cells, and the tumor maintenance capacity of MiaPaca-2 and MDA-MB-231 cells, establishing the critical role of ICMT in RAS-driven cancers.Oncogene advance online publication, 13 February 2017; doi:10.1038/onc.2016.508. © 2017 The Author(s)


Chen J.,National University of Singapore
Geographical Journal | Year: 2017

This paper focuses on the question of how interpersonal relationships in international development volunteering (IDV) affect its development impact. While the IDV literature examines care, power and cross-cultural relationships between volunteers and hosts, it has not clearly elucidated the link between these relationships and development impact. Moreover, although scholars and practitioners posit IDV as a less-hierarchical and relationship-focused way to do development, others particularly critique short-term volunteers' abilities in providing development impact. This paper thus seeks to understand development impact through a relational approach, by unpacking how and why interpersonal relationships matter in the process of doing development. It also explores the notion of temporality in development impact in terms of impact sustainability and volunteering duration. I analyse the Singapore International Foundation's capacity building Specialist Projects in Cambodia through qualitative fieldwork in 2014 and 2015 with various Cambodian and Singaporean IDV actors. I show how reciprocal relationships over time are crucial in creating intangible and sustainable development impact. More significantly, these findings shed light on the indispensable role of hosts in successful development impact, and make a case for the re-centring of IDV on host perspectives and contributions. © 2017 Royal Geographical Society (with the Institute of British Geographers).


The transcription factor TAL1/SCL is one of the most prevalent oncogenes in T-cell acute lymphoblastic leukemia (T-ALL), a malignant disorder resulting from leukemic transformation of thymus T-cell precursors. TAL1 is normally expressed in hematopoietic stem cells (HSCs) but is silenced in immature thymocytes. We hypothesize that TAL1 contributes to leukemogenesis by activating genes that are normally repressed in immature thymocytes. Herein, we identified a novel TAL1-regulated super-enhancer controlling the GIMAP locus, which resides within an insulated chromosomal locus in T-ALL cells. The GIMAP genes are expressed in HSCs and mature T cells but are downregulated during the immature stage of thymocyte differentiation. The GIMAP enhancer is activated by TAL1, RUNX1 and GATA3 in human T-ALL cells but is repressed by E-proteins. Overexpression of human GIMAP genes in immature thymocytes alone does not induce tumorigenesis but accelerates leukemia development in zebrafish. Our results demonstrate that aberrant activation of the GIMAP enhancer contributes to T-cell leukemogenesis.Leukemia advance online publication, 27 January 2017; doi:10.1038/leu.2016.392. © 2017 Macmillan Publishers Limited, part of Springer Nature.


Zhou J.,National University of Singapore
Anti-Cancer Drugs | Year: 2017

Hepatocellular carcinoma (HCC) is the second leading cause of cancer-related death worldwide, with a dismal 5-year survival rate less than 15%. The present study aimed to investigate whether AKT inhibition and glucose deprivation could synergistically kill HCC cells and the molecular mechanisms involved. HCC cells were starved in glucose deprivation, and then the resultant cell death was determined by flow cytometry and mitochondrial oxygen consumption rates using a Seahorse XF-24 Extracellular Flux Analyzer. Glucose deprivation reduced mitochondrial oxygen consumption rates for ATP production, enhanced mitochondrial proton leaks, reduced Mcl-1 expression, and subsequently caused significant cell death in the sensitive HepG2 and HCC-M cells. In the resistant Hep3B and Huh7 cells that survived, glucose starvation induced time-dependent AKT activation. However, blockage of AKT activation using chemical inhibitors (ZSTK474 and LY290042) or specific AKT1-targeting siRNAs could not markedly sensitize glucose deprivation-induced cell death. In contrast, AKT inhibitors or AKT1-targeting siRNAs significantly protected the sensitive HepG2 cells from glucose deprivation-induced cell death. More importantly, AKT inhibition mechanically suppressed mTOR activity and induced the prosurvival autophagy pathway in the sensitive HCC cells. Taken together, these data demonstrated that AKT activity was not essential for HCC cell survival during glucose deprivation. The reduction of mTOR activity and induction of the autophagy pathway may hinder the potential application of AKT inhibitors in the cancer therapy of solid tumors such as HCC. Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.


Herbert I.,National University of Singapore
Computability | Year: 2016

A real is called integer-valued random if no integer-valued martingale can win arbitrarily much capital betting against it. A real, A, is low for integer-valued randomness if no integer-valued martingale recursive in A can succeed on an integer-valued random real. We show that lowness for integer-valued randomness coincides with recursiveness, as is the case for computable randomness. © 2016 - IOS Press and the authors. All rights reserved.


Ng Q.X.,National University of Singapore
Journal of Child and Adolescent Psychopharmacology | Year: 2017

Introduction: Attention-deficit/hyperactivity disorder (ADHD) is one of the most prevalent neuropsychiatric disorders of childhood and adolescence. Stimulants are usually the first choice of drug; however, as many as 20% of patients do not respond to them. Stimulants may also worsen comorbid sleep, mood, and anxiety disorders, and they are associated with problems of misuse and diversion. Bupropion, a dopamine and norepinephrine reuptake inhibitor, is a promising nonstimulant alternative with reports of positive outcomes for ADHD management in both adolescent and adult populations. This study systematically reviews clinical trials on the subject. Methods: Using the keywords bupropion or Wellbutrin or Zyban or Elontril and attention deficit hyperactivity disorder or ADHD or ADDH, a preliminary search on the PubMed and Ovid databases yielded 25,455 articles published in English between January 1, 1988 and May 1, 2016. Of these, there were only six articles on clinical trials involving children. Full articles were also reviewed for references of interest. Results: All available open, controlled, and randomized trials demonstrated bupropion's efficacy in improving ADHD symptoms. The three head-to-head trials found that bupropion had efficacy comparable to methylphenidate (p > 0.05). However, a large double-blind, placebo-controlled multicenter study of bupropion found smaller effect sizes for bupropion, as quantified using teacher and parent ratings of ADHD symptoms, than methylphenidate. In terms of tolerability, a head-to-head trial found that headache was observed more frequently in the methylphenidate-treated group than in the bupropion-treated group, whereas the frequency of other side effects did not differ significantly. Conclusion: Current findings should be interpreted with caution because of the very limited database. Bupropion should be considered for pharmacological management of childhood and adolescent ADHD, but more randomized controlled trials with larger sample sizes are warranted. There is also some evidence of its benefits in children with comorbid ADHD and conduct, substance use, or depressive disorders. © Copyright 2017, Mary Ann Liebert, Inc. 2017.


News Article | April 17, 2017
Site: www.scientificamerican.com

For the past five years the Quantum Shorts initiative from the Center for Quantum Technologies at the National University of Singapore has inspired artists and writers from around the world to try their hand at a unique kind of scientific storytelling. The contest alternates each year between calls for films or short stories that explore the ramifications of quantum mechanics. The key requirement? Each entry must take no more than five minutes to watch or read. For 2016 the contest focused on film and drew more than 200 entries, with 10 finalists selected. Now, in partnership with Scientific American and Nature (as well as with several scientific institutions), Quantum Shorts 2016 has revealed this year’s first- and second-place winners as selected by a six-member panel of expert judges as well as a “people’s choice” winner selected via public online polling. The overall winner is Novae, filmmaker Thomas Vanz’s breathtakingly beautiful visualization of a giant star’s explosive death by supernova and subsequent transformation into a black hole. Like a latter-day William Blake—the English poet and painter who famously mused about seeing “a world in a grain of sand” and “a heaven in a wild flower”—Vanz envisioned a supernova in drops of colored ink. Working for months in his garage in Paris, he filmed inks billowing through a water-filled fish tank, later using computer software to stitch and process the raw footage into his dramatic vision of stellar death. His behind-the-scenes shorts detailing the making of Novae are at least as entertaining as the final film itself. A supernova can form a black hole by compressing a star’s core to an infinitesimally minuscule size, creating a gravitational field so intense that it devours light itself. The compressed core of a black hole—a “singularity,” in the parlance of physics—is thus hidden behind a black, lightless “event horizon,” the boundary beyond which anything falling in cannot come back out. Black holes represent a mysterious union between gravity, which dictates the overall structure of the universe, and quantum mechanics, which describes the cosmos at subatomic scales. Probing the properties of these strange macroscale quantum objects is likely to be our best path forward to a deeper understanding of the nature of reality. The runner-up, The Guardian, is also the people’s choice winner. The film uses a love triangle between three people to explore the counterintuitive nature of the quantum world, in which an entity can exist either as a particle or as a wave—or, really, as both at the same time, in a hazy cloud of probability. It is the brainchild of Chetan  Kotabage, an assistant professor of physics at KLS Gogte Institute of Technology in Karnataka, India. “I love that it is looking at quantum physics through a cultural lens,” says Eliene Augenbraun, Scientific American’s video producer and multimedia managing editor for Nature Research Group, who also served as a contest judge and chose The Guardian as her favorite. Other entries that earned honorable mentions from the judges include Approaching Reality, Together—Parallel Universe and Bolero. Charlotte Stoddart, Nature’s chief multimedia editor and contest judge, says she was “really impressed by the quality of the filmmaking and the ideas.” You can watch all the finalists here. The next call for Quantum Shorts entries will occur later this year. Continuing its annual alternation between cinema and prose, 2017’s contest will be for short stories. Announcements will be available via the Quantum Shorts Twitter account and Facebook page.


News Article | April 17, 2017
Site: www.newscientist.com

A system of sensors and electrodes can digitally transmit the basic colour and sourness of a glass of lemonade to a tumbler of water, making it look and taste like a different drink. The idea is to let people share sensory experiences over the internet. “People are always posting pictures of drinks on social media – what if you could upload the taste as well? That’s the ultimate goal,” says Nimesha Ranasinghe at the National University of Singapore. Ranasinghe and his team used an RGB colour sensor and a pH sensor to capture the colour and acidity of a freshly poured glass of lemonade. This data was sent to a special tumbler in another location that was filled with water. An electrode around the rim of the tumbler mimicked the sourness of the lemonade by stimulating the drinker’s taste buds with a pulse of electricity. LED lights replicated the colour. To test the effectiveness of the digital tumbler, the team got 13 people to taste a variety of real and virtual lemonades, without knowing which was which. The lemonades came in three colours: yellow, green and cloudy white. The volunteers were trained to rest their tongue on the rim of the tumbler while drinking, so they would benefit from the electrical stimulation. They were asked to rate each drink on how sour it looked, and then how sour it tasted. On average, people reported that the real lemonade tasted sourer than the virtual version. However, they perceived the virtual cloudy lemonade as sourer based on its colour alone, perhaps because of the brightness of the LEDs. The researchers presented the work at the Conference on Tangible, Embedded and Embodied Interaction in Yokohama, Japan, in March. The current system is not yet able to transmit the full flavour profile of a drink. “Unless you simulate olfaction, true flavour cannot be reproduced,” says Amol Bhondekar at the Central Scientific Instruments Organisation in India. But the team plans to add other functions. “We’re working on a full virtual cocktail with smell, taste and colour all covered. We want to be able to create any drink,” says Ranasinghe. Beyond social media sharing, virtual flavourings could help people enjoy digital versions of sugary drinks without consuming calories or damaging their teeth, he says.


News Article | April 23, 2017
Site: news.yahoo.com

The Middle East has an outsize impact on energy here on Earth. One analyst thinks some regional powerhouses may leverage that role into the development of natural resources in space. Countries like the United Arab Emirates and Saudi Arabia are developing space programs and investing in nascent private space commodity initiatives, said Tom James, a partner at energy consultant Navitas Resources. Doing so could give them a foothold in building extraterrestrial reserves of water -- a substance likely to fuel travel within space -- and other resources that could be used for in-space manufacturing. “Water is the new oil of space,” James said in Singapore. “Middle East investment in space is growing as it works to shift from an oil-based to a knowledge-based economy.” Prospecting satellites can be built for tens of millions of U.S. dollars each and an asteroid-harvesting spacecraft could cost $2.6 billion, in line with mining operations on Earth, Goldman Sachs Group Inc. analysts including Noah Poponak said in an April 4 research note. Most resources would be processed and used in space although it may be economic to ship some commodities, such as platinum, back to Earth, according to James and Goldman. “Space mining is still a long way from commercial viability, but it has the potential to further ease access to space,” Poponak wrote. “Water and platinum group metals that are abundant on asteroids are highly disruptive from a technological and economic standpoint.” Navitas expects companies to launch satellites searching for rare gases and metals in asteroids within five years, with actual mining happening within eight. A single asteroid might contain 175 times more platinum than the Earth mines in a year, Goldman said, citing a project associated with the Massachusetts Institute of Technology. That much platinum could be worth $25 billion to $50 billion, although it would likely crater the market for the metal. “You could go massively short on platinum and then show up at settlement with an asteroid, but you probably could only do that once,” James said in an interview after a presentation at the National University of Singapore’s Middle East Institute. “I don’t think the counter-party would take that trade a second time.” Platinum futures for July delivery fell 0.6 percent to $972.10 an ounce on the New York Mercantile Exchange on Monday. In the long term, most of the commodities mined in space will stay in space to power a low-orbit space economy built around satellites and space stations, James said. In that scenario, water accumulated in space would become valuable as it could be used for rocket fuel for interstellar voyages. The substance is too heavy and costly to transport from Earth. Water can be used as a propellant in space or split into hydrogen and oxygen, and then recombined and combusted. Deep Space Industries Inc., an asteroid mining company, has developed a thruster that heats water into a steam propellant, according to Goldman. The U.A.E. and Saudi Arabia already have space programs, with the Saudis signing a pact with Russia in 2015 for cooperation on space exploration, according to a report from Arab News.  Abu Dhabi is an investor in Richard Branson’s space tourism venture, Virgin Galactic. In addition to money, the Middle East also has geography on its side. See also: At $27 billion, mining in space could lost less than a gas plant The closer a country is to the equator, the more surface velocity there is from spinning around the Earth’s axis, meaning space ships need to burn less fuel to exit the atmosphere. That benefits some Middle Eastern countries as launch sites, James said. “The Middle East builds the tallest buildings, the biggest shopping complexes,” said James. “Certainly they’re having a big impact on the space and satellite industries as well.”


News Article | March 21, 2017
Site: www.techtimes.com

Drinking tea reduces the risk of cognitive decline in elder people by 50 percent. Additionally, people who have genetic predispositions to develop Alzheimer's disease have an 86 percent lower risk of developing the disease, should they consume tea on a daily basis. The study responsible for this statement was carried out by specialists at the Department of Psychological Medicine at the National University of Singapore's Yong Loo Lin School of Medicine. The study was published in The Journal of Nutrition, Health & Aging. The longitudinal study involved 957 Chinese people over the age of 55, suggesting that regular tea consumption is associated with a much lower risk of cognitive decline. APOE e-4 gene carriers, who are people prone to developing Alzheimer's disease, are also very advantaged by this habit. The researchers who conducted the study also noticed that the neuroprotective role of tea consumption when it comes to cognitive function is not associated with a specific type of tea, as any kind of tea leave, from green tea to oolong tea or black tea, has the same protective role. A limitation of the research is that it was conducted only on Chinese elderly. However, researchers have reasons to be optimistic that these findings can easily apply to any other race when it comes to dementia prevention. The scientific attention has been focused on developing different drug trials that can prevent cognitive decline or constitute an efficient therapy for dementia. However, the current means of treating neurocognitive disorders are far from satisfactory. Since tea is one of the most widely consumed beverages in the world, embracing the habit of drinking tea could benefit people worldwide. Tea is also a low-cost beverage, which means that many categories of people, including the ones in poorer countries or individuals from low-income families could easily include tea in their daily routines. "The data from our study suggests that a simple and inexpensive lifestyle measure such as daily tea drinking can reduce a person's risk of developing neurocognitive disorders in late life," noted assistant professor Feng Lei, lead author of the research. According to one of the researchers who carried out this study, tea leaves are so beneficial due to a series of compounds, among which theaflavins, catechins, L-theanine and thearubigins. These compounds have antioxidant and anti-inflammatory functions, which can be effective against neural degradation, preventing brain damage. More research will have to be carried out in order for scientists to better understand the biological mechanisms that are activated when people consume tea, which could help developing new and more effective strategies to combat and treat brain damage and cognitive decline. "Regular tea consumption was associated with lower risk of neurocognitive disorders among Chinese elderly. Gender and genetic factors could possibly modulate this association," concluded the study. Another study, published The Journals of Gerontology: Series A, in October 2016, showed that consuming more than 261 mg of caffeine can prevent dementia as well. Women who consumed this amount of caffeine on a daily basis had a significant, 36 percent drop in the overall risks of suffering from dementia in the following 10 years. This amount of caffeine can be translated into up to six 8-ounce cups of black tea, three 8-ounce cups of coffee or eight 12-ounce cans of cola. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


News Article | April 11, 2017
Site: www.cemag.us

A team of scientists led by Associate Professor Yang Hyunsoo from the Department of Electrical and Computer Engineering at the National University of Singapore’s (NUS) Faculty of Engineering has invented a novel ultra-thin multilayer film which could harness the properties of tiny magnetic whirls, known as skyrmions, as information carriers for storing and processing data on magnetic media. The nano-sized thin film, which was developed in collaboration with researchers from Brookhaven National Laboratory, Stony Brook University, and Louisiana State University, is a critical step towards the design of data storage devices that use less power and work faster than existing memory technologies. The invention was reported in prestigious scientific journal Nature Communications on March 10. The digital transformation has resulted in ever-increasing demands for better processing and storing of large amounts of data, as well as improvements in hard drive technology. Since their discovery in magnetic materials in 2009, skyrmions, which are tiny swirling magnetic textures only a few nanometers in size, have been extensively studied as possible information carriers in next-generation data storage and logic devices. Skyrmions have been shown to exist in layered systems, with a heavy metal placed beneath a ferromagnetic material. Due to the interaction between the different materials, an interfacial symmetry breaking interaction, known as the Dzyaloshinskii-Moriya interaction (DMI), is formed, and this helps to stabilise a skyrmion. However, without an out-of-plane magnetic field present, the stability of the skyrmion is compromised. In addition, due to its tiny size, it is difficult to image the nano-sized materials. To address these limitations, the researchers worked towards creating stable magnetic skyrmions at room temperature without the need for a biasing magnetic field. The NUS team, which also comprises Dr. Shawn Pollard and Yu Jiawei from the NUS Department of Electrical and Computer Engineering, found that a large DMI could be maintained in multilayer films composed of cobalt and palladium, and this is large enough to stabilize skyrmion spin textures. In order to image the magnetic structure of these films, the NUS researchers, in collaboration with Brookhaven National Laboratory, employed Lorentz transmission electron microscopy (L-TEM). L-TEM has the ability to image magnetic structures below 10 nanometers, but it has not been used to observe skyrmions in multilayer geometries previously as it was predicted to exhibit zero signal. However, when conducting the experiments, the researchers found that by tilting the films with respect to the electron beam, they found that they could obtain clear contrast consistent with that expected for skyrmions, with sizes below 100 nanometers. Pollard explains, “It has long been assumed that there is no DMI in a symmetric structure like the one present in our work, hence, there will be no skyrmion. It is really unexpected for us to find both large DMI and skyrmions in the multilayer film we engineered. What’s more, these nanoscale skyrmions persisted even after the removal of an external biasing magnetic field, which are the first of their kind.” Yang adds, “This experiment not only demonstrates the usefulness of L-TEM in studying these systems, but also opens up a completely new material in which skyrmions can be created. Without the need for a biasing field, the design and implementation of skyrmion based devices are significantly simplified. The small size of the skyrmions, combined with the incredible stability generated here, could be potentially useful for the design of next-generation spintronic devices that are energy efficient and can outperform current memory technologies.” Yang and his team are currently looking at how nanoscale skyrmions interact with each other and with electrical currents, to further the development of skyrmion based electronics.


News Article | May 4, 2017
Site: www.cemag.us

Scientists from the National University of Singapore (NUS) have developed a novel nanodiamond-based contrast agent — a chemical "dye" used to enhance the visibility of internal body structures in magnetic resonance imaging (MRI) — that improves visualization of liver cancer tumors. Better and more sensitive imaging contributes towards detecting liver cancer and is crucial for planning for treatment. MRI is a medical imaging technique commonly used for cancer diagnosis and to track the progress of patients after treatment. Currently, there are two modes of MRI imaging, T1-weighted and T2-weighted imaging, and patients are often given contrast agents to improve imaging quality. However, each imaging mode requires a specific class of contrast agent which cannot be used together. This poses a greater challenge in the diagnosis of liver cancer, where T2-weighted imaging is still not considered reliable, and both T1- and T2-weighted imaging can be confounded by tumor vascularity. A research team led by Assistant Professor Edward Chow, Principal Investigator from the Cancer Science Institute of Singapore at NUS and Department of Pharmacology at NUS Yong Loo Lin of Medicine, has developed a dual-mode contrast agent which enables clearer and more accurate images of tumors to be obtained in both T1- and T2-weighted MRI scans, and with lower dosages of contrast agent. The novel dual-mode contrast agent, which was developed using nanodiamonds in combination with a manganese base, provides greater imaging contrast than existing clinical agents which are used to improve quality of MRIs. The team also found that liver tumors that are unable to be visualized without contrast agents become readily visible even at low dosages of the novel compound. Contrast agents work by altering the magnetic properties of nearby water molecules, which enhances the quality of MR images. Nanodiamonds, which are carbon-based particles of two to eight nanometers in diameter, have unique chemical properties that allow them to attract water molecules. This enables them to promote proton exchange between water molecules and paramagnetic ions (i.e. contrast agents) that accumulate in tissues. As a result, T1 and T2 relaxation is enhanced, giving better quality images. This is unlike existing nanotechnology-based approaches, where nanomaterials are used to improve delivery of paramagnetic ions to specific tumor sites. “Our experiments suggest that our dual-mode contrast agent holds great promise in improving imaging for liver cancer. We are hopeful that this advancement in nanomedicine will lead to safer and more accurate diagnosis of liver cancer. Moving forward, we plan to conduct further pre-clinical safety studies for our contrast agents, with the end goal being clinical implementation. We are also looking into using our contrast agents to improve imaging for glioma and ovarian cancer,” says Chow. The study was conducted in collaboration with the NUS Comparative Medicine Imaging Facility and the Agency for Science, Technology and Research’s Singapore Bioimaging Consortium. The findings of the study were published in the scientific journal Nanomedicine: Nanotechnology, Biology and Medicine in April 2017.


Carbon steel, an alloy made from iron and carbon, is the single largest class of alloys in use today. It's used to make a range of products from fences and springs to steel wires and pipelines, and for structural support in buildings, bridges, as well as nuclear power and fossil fuel power plants. The corrosion of carbon steel, however, is a huge cost to industry and is of enormous practical importance. One common corrosion inhibitor used in the construction industry, calcium nitrite, is quite toxic to humans, impairing the ability of red blood cells to transport oxygen. Seeking safer corrosion inhibitors, Yong Teck Tan and colleagues from the National University of Singapore and Singapore Institute of Manufacturing Technology investigated molybdate as a potential alternative and developed a technique to determine its suitability. Molybdate is non-toxic, and protects the carbon steel from corrosion by competitive adsorption against chloride on the passive film surface, and, in the presence of calcium cations, can also deposit a layer of calcium molybdate. "Our aim was to first determine the suitability of molybdate as a corrosion inhibitor for carbon steel in alkaline environments, and then to investigate its effect on the passivation of carbon steel," says Tan. "Previous studies using electrochemical techniques have focused on corrosion inhibition efficiency at a particular time, which provides a snapshot of the level of corrosion at that instant," explains Tan. "Depending on whether it was assessed over short or long timescales, different conclusions were drawn." So the research team took a longer look. They used an electrochemical method for estimating the extent of corrosion over the entire duration of the investigation, and could assess the overall effectiveness of molybdate. "Even though molybdate resulted in a slightly higher passive current in the later stages, faster passivation in the early stages resulted in a lower overall level of corrosion," says Tan. The researchers found that incomplete coverage of the carbon steel by the calcium molybdate led to slightly higher corrosion rates compared with untreated surfaces. By controlling the composition of the molybdate solution, however, the calcium molybdate film covered the entire surface, resulting in improved corrosion resistance. "Overall, molybdate proved to be an effective corrosion inhibitor," says Tan. "We will now explore its effectiveness in solutions containing other ions." Explore further: Improved corrosion protection with flake-type particles of zinc-phosphate More information: Yong Teck Tan et al. Effect of Molybdate on the Passivation of Carbon Steel in Alkaline Solutions under Open-Circuit Conditions, Journal of The Electrochemical Society (2016). DOI: 10.1149/2.0651610jes


News Article | May 4, 2017
Site: www.ictsd.org

28 April, Geneva, Switzerland. G20 AND THE EVOLUTION OF THE GLOBAL TRADE AND INVESTMENT REGIME: FROM CRISIS MANAGEMENT TO VISION AND LEADERSHIP? This dialogue is jointly organised by the International Centre for Trade and Sustainable Development (ICSTD) and the Friedrich-Ebert-Stiftung (FES) Geneva office. The focus of the dialogue will be on the trade and investment agenda for the G20, first reviewing and reflecting on this year’s agenda and then moving to the prospects for 2017 and 2018. The sessions will be followed by a roundtable discussion on the interlinkages between trade and climate policy, specifically within the context of the G20’s work. Please note that attendance for this event is by invitation only. For more information, please visit the ICTSD website. 2 May, London, UK. CHATHAM HOUSE PRIMER: THE VOTE FOR BREXIT. This Chatham House event will feature as its guest speaker Matthew Goodwin, co-author of “Brexit: Why Britain Voted to leave the European Union,” to examine what factors motivated a majority of British voters to vote for leaving the EU. The talk will address topics ranging from the driving forces behind Euroscepticism and possible Brexit deals that would win the approval of those who voted to leave. To learn more and to register, please visit the Chatham House website. 1-3 May, Yokohama, Japan. GLOBAL THINK TANK SUMMIT 2017. This two-day summit is jointly organised by the Asian Development Bank Institute (ADBI) and the Think Tanks and Civil Societies Program (TTCSP) of the University of Pennsylvania. This conference aims to bring together policymakers and think tank representatives from dozens of organisations across the world to discuss key policy issues of today. Please note that attendance is by invitation only. For more information on this summit, please visit the ADBI website. An updated list of forthcoming WTO meetings is posted here. Please bear in mind that dates and times of WTO meetings are often changed, and that the WTO does not always announce the important informal meetings of the different bodies. Unless otherwise indicated, all WTO meetings are held at the WTO, Centre William Rappard, rue de Lausanne 154, 1211 Geneva, Switzerland, and are open to WTO Members and accredited observers only. 3 May: Council for Trade in Services – Special Session 10 May, Geneva, Switzerland. 10TH ANNUAL UPDATE ON WTO DISPUTE SETTLEMENT. This event will be held at the Graduate Institute and will consist of an overview session followed by a roundtable discussion. The event will cover the WTO’s dispute-related activities and developments over the past year. Its speakers will include WTO Deputy Director-General Karl Brauner, South African WTO Ambassador and Dispute Settlement Body Chairperson Xavier Carim, and Appellate Body Chairperson Thomas Graham, among others. To learn more and to register, please visit the Graduate Institute website. 11 May, London, UK, and online. REFUGEES: ARE JOBS THE ANSWER? This event is organised by the Overseas Development Institute (ODI) and will feature an expert panel to discuss the creation of economic opportunities for refugees. Specifically, the panel will discuss the possibility of creating Special Economic Zones (SEZ) where business and trade laws could be revised to allow refugees to work within the zone. This event is open to the public and will be streamed online. To learn more and register, or watch online, visit the ODI website. 19-20 May, Singapore. THIRD CONFERENCE ON GLOBAL VALUE CHAINS, TRADE AND DEVELOPMENT. This conference is being organised by the Centre for Economic Policy Research (CEPR) and the World Bank Group and will feature as its guest speakers Shang-Jin Wei from the Columbia Business School and CEPR and David Chor from the National University of Singapore. The aim of this conference will be to foster new ideas and research on the subject of global value chains. To learn more and to register, please visit the World Bank website. 23 May, Stockholm, Sweden. TRADE AND CLIMATE ACTION POST-PARIS: LEVERAGING SYNERGIES. This event is being organised jointly by the International Centre for Trade and Sustainable Development (ICTSD) and Sida, Sweden’s development policy agency. The event will examine the relationship between trade, sustainable development, and climate action in the context of the UN’s Paris Agreement on climate change. The objective is to have a discussion over ways trade policy can support climate action, along with ensuring that efforts to support the latter objective do not have overly trade-distorting effects. For more information, including an event programme, please visit the ICTSD website. 26-28 September, Geneva, Switzerland. WTO PUBLIC FORUM 2017. This year’s edition of the WTO’s outreach event will have as its theme “Trade: Behind the Headlines.” The meeting will aim to look at the real-life implications of trade, as opposed to rhetoric, and will also look at how trade can support the 2030 Agenda for Sustainable Development and related issues. A call for proposals is currently open for those who wish to organise sessions at this year’s forum, with a due date of 4 June 2017. To learn more, please visit the WTO website.


News Article | May 8, 2017
Site: www.marketwired.com

HONG KONG, CHINA--(Marketwired - May 8, 2017) - ChoZan, a resources platform for social media marketing in China, announces its expansion to Singapore. The Founder of ChoZan, Ashley Galina Dudarenok, and her team will be in Singapore from May 15th - 18th, introducing themselves to the Singapore market in response to great interest in the region from businesses wanting to engage with Chinese customers on social media, such as WeChat and Weibo. China is Singapore's 3rd largest trading partner so there are strong business links between these two markets. There are also strong family and cultural ties. Second and third generation Chinese entrepreneurs have established many businesses in Singapore and play a strong role in the community. However, recent shifts to online marketing and the huge influence of social media have left some businesses behind. They lack the necessary tools and skills to reach modern Chinese consumers... and modern Chinese consumers are becoming ever more sophisticated at a rapid pace. ChoZan, which is specifically designed to help marketing teams and agencies use Chinese social media, can help businesses fill these gaps and tap into China's swiftly changing and expanding markets. It sees Singapore as a vital step in its expansion before proceeding to wider international markets such as Australia, the US and the UK. The demand has been clear to ChoZan's Managing Director for some time. "Since our launch in January this year, we've received an overwhelming number of enquiries from businesses in Singapore," says Dudarenok. "WeChat is a hot topic and local and international businesses headquartered in Singapore are eagerly exploring opportunities. The Singapore Tourism Board, Singapore Airlines and Banyan Tree are all doing a great job in this area and small businesses need services like these." The need for information about China's social media landscape has also been noticed by Melissa Lim, founding member of Ladyboss Asia. "There will definitely be interest to learn as China is a nearby market with a huge population. I believe that Chinese consumers would appreciate Singapore products too." At the moment, Chinese social media isn't widely used in Singapore for marketing but she believes this is about to change, as she puts it, "once people discover the vast functionalities that exists just within WeChat." General Assembly Singapore, the female entrepreneurs' club Ladyboss Asia, and BNCS invited Ashley to conduct a series of large-scale workshops to demonstrate how to effectively use Chinese social media platforms for marketing. During this trip, the ChoZan team will also conduct a session with the Business Alumni Group of the National University of Singapore (NUS) to share experiences in WeChat marketing. Below is the schedule of the workshops: 2. "How to Advertise on China's Most Popular Social Media" Date & time: 16 May, 2017 (Tue) 2 - 4 pm Organizer: Ladyboss Asia Admission: Early Bird: $35 / Standard: $50 Venue: 6 Raffles Quay, Level 16 Registration: wechatadvertising.peatix.com 3. "WeChat - A 360 Understanding of China's Most Powerful Social Media" Date & time: 16 May, 2017 (Tue) 7:30 - 9:30 pm Organizer: BNCS Admission: Free-of-charge Venue: 60 Paya Lebar Square #10-23, Paya Lebar Rd, Singapore 409051 Registration: Please contact Warren (WeChat: Warren_Maruyama) To introduce the platform to more in-house marketers in the region, the ChoZan team is seeking partnerships with local social media agencies and business associations which work closely with local brands and constantly receive enquiries about marketing in China. ChoZan welcomes various modes of partnership such as client referrals and content sharing. If you want to know more about marketing in China, please join one of our events listed above. If you work in marketing and are looking for opportunities, join ChoZan as a partner, contact Ashley Dudarenok at (+852) 37092258 or info@chozan.co. About ChoZan ChoZan is a marketing training and resource platform specializing in Chinese social media. It was created by a team of Chinese social media marketers, strategists, designers and bloggers based in Hong Kong. Officially launched in Hong Kong in January 2017, ChoZan is expanding to Singapore in May followed by other key international markets. ChoZan works with clients to improve their understanding of Chinese consumers, by providing information, updates and advice regarding Chinese social media channels, tools, and marketing best practices. ChoZan Academy, an online and certification course, will launch in summer 2017. In this self-study course, participants will learn detailed information about marketing on WeChat and Weibo. ChoZan currently has over 200 subscribers and estimates that it will have over 2000 subscribers by the end of the year. About Ashley Galina Dudarenok Ashley worked in China for 5 years before moving to Hong Kong in 2010. For over 10 years she worked with Chinese social media, opinion leader marketing and creative campaigns. In 2011 Ashley established Alarice International (www.alarice.com.hk), a marketing agency with a focus on Chinese social media. In 2013 she co-founded the Russian Business Club in Hong Kong (www.rusbc.com.hk) and in 2017, she launched ChoZan (www.chozan.co), a membership platform for China-focused marketers. Ashley often shares her knowledge and experience in a variety of magazines, including the SCMP, China Daily, Hong Kong Economic Times, WenWeiPo, Jumpstart Magazine, Do Marketing, Macau Business Daily and others. Moreover, Ashley is a frequent speaker at General Assembly, WeChat Conference, Women Foundation, The Rotary Club, The Executive Group, TEDx and others. About General Assembly General Assembly is a pioneer in education and career transformation, specializing in today's most in-demand skills. The leading source for training, staffing, and career transitions, we foster a flourishing community of professionals pursuing careers they love. About Ladyboss Asia LadyBoss Asia is a community that aims to empower and inspire women in leadership roles. They connect women entrepreneurs at their networking events and provide a peer support group to help each other grow. Their panel discussion sand workshops seek to equip women with practical knowledge. About BNCS Established in 1999, BNCS is engaged in marketing and after sales service for Telco companies in Singapore. BNCS started to develop WeChat marketing since 2013, assisting companies to leverage on WeChat to connect with audience in and outside China.


News Article | April 19, 2017
Site: www.eurekalert.org

A team of scientists from Singapore has discovered new ways in which cancers can escape the body's immune system. Focusing on gastric cancer (GC), the third leading cause of cancer death worldwide, the team's findings may also prove applicable to other major cancers with potential implications for how cancers might be better treated with immunotherapy, one of the most promising classes of anti-cancer drugs today. Promoters are regions in the genome that regulate the expression of genes, similar to the switch of a light bulb. Using an ultra-sensitive technique called NanoChIP-seq, the team surveyed the promoter landscape for GC to better understand the epigenetic mechanisms contributing to GC development. The team found that in GCs, gene promoters are dysregulated in a way that alters a tumour's antigenic profile to evade the body's immune system. The study, published in the leading journal Cancer Discovery, involved scientists and clinicians from Duke-NUS Medical School, Genome Institute of Singapore, Cancer Science Institute of Singapore (CSI Singapore) at the National University of Singapore (NUS), and National Cancer Centre Singapore (NCCS). "Using the NanoChIP-seq platform invented in Singapore, we created comprehensive epigenetic profiles for both GC and normal tissues," explained team leader Professor Patrick Tan. "Epigenetics is a process by which a cell's DNA is chemically modified by the environment, to change gene expression. By comparing the epigenetic profiles of gastric tumours to normal tissues from the same patient, we were able to identify those promoters specifically altered in GC tissues." Professor Tan is a Faculty Member of Duke-NUS Medical School, Deputy Executive Director of the Biomedical Research Council at the Agency for Science, Technology and Research (A*STAR), and also Senior Principal Investigator at CSI Singapore and Principal Investigator at NCCS. Just like how a light can be controlled by multiple switches to influence its intensity and colour, the team identified hundreds of genes controlled by multiple promoters, causing alternate versions of that gene to be produced. The team demonstrated that some of these gene variants are capable of stimulating cancer growth. Strikingly, the team also found that many of these alternate gene variants produced in gastric tumours were also less likely to stimulate the immune system compared with their normal counterparts. "Our data, combining computational, experimental assays, and analyses of human gastric cancers, indicates that the use of these less immunogenic variants may enhance the ability of a tumour to bypass the host's immune system. This process is referred to as tumour immunoediting," added Ms Aditi Qamra, graduate student at the Genome Institute of Singapore and first author of this study. She is also a graduate student with the Department of Physiology at the NUS Yong Loo Lin School of Medicine. The findings provide important insights into mechanisms used in cancer development and may have implications for cancer immunotherapy. While striking clinical responses have been seen in some patients treated with immunotherapy, these drugs are expensive, associated with side effects, and not all patients respond to the treatment. The team's results suggest that studying the promoter profiles of tumours may possibly identify those patients who would be responsive to immunotherapy. Moreover, the team also identified cellular pathways required by the tumour cell to maintain expression of the less immunogenic gene variants. The team is now exploring if targeting these pathways, combined with immunotherapy, can increase the proportion of patients that might respond to such drugs.


News Article | April 20, 2017
Site: www.forbes.com

It's easy to say Philippine President Rodrigo Duterte needs help from China for his country’s development in exchange for laying aside a maritime sovereignty dispute. In October Beijing pledged $24 billion in aid and investment for the country where a quarter of the 102 million people lives in poverty. And after years of friction, Beijing now firmly controls Scarborough Shoal, a major South China Sea fishery coveted by boats based out of the Philippine island Luzon just 220 kilometers away. But here's a new reality: China needs the Philippines just as much, maybe more, as the other way around. You can tell by how mildly the Chinese foreign ministry reacted April 7 – just voicing “concern” – after Duterte said he would militarize the Spratly Islands in the same contested sea. Duterte backpedaled over the following week, ending on a milder commitment to improve infrastructure on nine islets held already by the Philippines. China quickly buried its concern, probably not something it would do over concern about, say, Japan or the United States. Beijing needs its 7-month-old friend Manila to hold off pressure from more powerful countries. If China can choreograph its own relations with all four Southeast Asian nations that dispute its aggressive, decade-old expansion in the same 3.5 million-square-kilometer sea, it can easily ignore threats from the United States, the world court or power blocs such as the G7. The G7 (group of seven big countries) foreign ministers issued a joint communique this month indirectly calling on China to live by a world arbitration court ruling in The Hague last year. The statement expresses “strong opposition” to any unilateral actions such as threats of force, “large-scale” land reclamation or military use of the sea’s islets. The arbitration court said China lacked a legal basis to claim 95% of the sea and occupy the 370-kilometer exclusive economic zones of the other countries. If unsatisfied with China, the Philippines can re-embrace U.S. military help through a series of mutual aid agreements dating back to 1951. China fears most an American role in the maritime dispute because of its large, sophisticated military compared to those in Southeast Asia. Duterte is also friendly with Japan, an old China foe that tracks the United States in trying to contain Chinese influence at sea. "I don't think Duterte has to do anything else to impress China," says Eduardo Araral, associate professor at the National University of Singapore’s public policy school. "What he has already done, badmouthing (U.S. ex-president) Obama and putting The Hague ruling aside, has already won him in good stead with the Chinese." A falling-out with Beijing might cost Manila aid and investment, but the Philippines has other survival means given its speedy economic growth. Duterte has enchanted China by angrily rejecting more U.S. influence in the Philippines since he took office in June. But for China, a new split with the Philippines will put a troublesome naysayer at its doorstep again. Beijing has entered friendly talks with Brunei, Malaysia and Vietnam -- other states with competing South China Sea claims. It was Duterte’s predecessor Benigno Aquino III who filed for world court arbitration in the Scarborough Shoal dispute going back to 2012. A lot of Filipinos remain leery of Chinese influence in their country. Any re-inflammation of problems would re-energize U.S. and Japanese support for the Philippines. It could pile criticism on Beijing at international forums that it cares about. It’s unclear, for example, to what degree Western European G7 countries will attend China’s “New Silk Road” summit next month to discuss Pan-Eurasian investment led by Beijing, some scholars say. To keep things smooth, China will probably avoid revisiting the Pacific Ocean side of the Philippine exclusive economic zone after public anger over Chinese ships that lingered there last year at a resource-rich undersea plateau called Benham Rise. Beijing’s coast guard may keep control of Scarborough Shoal, but people in one Luzon Island fishing town say it avoids pressing further into the Philippine exclusive economic zone in the South China Sea. Vessels from Taiwan and Vietnam aren't always so kind, they add. It helps that Duterte is playing along, too. “Given that Duterte has been careful to clarify that there will be no militarization of the (Spratly Island) features and that the intent is to improve the living conditions on the currently occupied features, I do not think China will be overly critical,” says Carl Baker, director of programs with the think tank Pacific Forum CSIS in Honolulu.


News Article | April 25, 2017
Site: www.eurekalert.org

These changes, known as epigenetic modifications, control the activity of our genes without changing the actual DNA sequence. One of the main epigenetic modifications is DNA methylation, which plays a key role in embryonic development and the formation of different cell types, regulating when and where genes are switched on. Although DNA methylation was originally thought to be a very stable modification, which once established in early life was then maintained throughout the life span of an individual, there is now growing evidence that the level of DNA methylation can be affected by a range of environmental factors such as parental health, diet and lifestyle. Researchers from the University of Southampton, as part of the EpiGen Global Consortium, analysed the levels of DNA methylation, in umbilical cord tissue of babies born in the Southampton Women's Survey. They compared DNA methylation levels present at birth with the amount of fat tissue in the child at four and six years of age. They found that lower DNA methylation at the CDKN2A gene, which regulates the production of fat cells, was associated with a greater risk of the child developing obesity in later life. Analysis showed that a 10 percent decrease in methylation at the CDKN2A gene was associated with an increase in fat mass of around 220g, at age 4 years. The results, published in EBio Medicine, were replicated in other groups of children and adults, notably the Singapore GUSTO study, the Australian RAINE study and the UK BIOCLAIMS cohort. Lead author Karen Lillycrop said: "This is exciting new evidence that epigenetic changes detectable at birth are linked to a child's health as they grow up. It was very promising to see our initial findings confirmed in so many other cohorts. Not only does it strengthen the body of evidence that shows a mothers health during pregnancy can affect the future health of her child, but it could also allow us to more accurately predict the future risk of obesity. If we can do this, then preventative strategies can be developed in early life to prevent the development of obesity." Professor Keith Godfrey, from the Medical Research Council Lifecourse Epidemiology Unit and the National Institute for Health Research Southampton Biomedical Research Centre and a member of the study team said: "The new findings provide the first direct evidence linking faltering of a baby's growth in the womb with epigenetic modifications that themselves may increase the risk of childhood obesity. The findings are now helping us to trial new nutritional interventions before and during pregnancy to reduce the baby's risk on obesity in childhood and later life, and strengthen the view that effective prevention of childhood obesity has to begin before the baby is born. The new findings may also lead to innovative approaches to the treatment of established obesity in later life." The EpiGen Global Consortium brings together expertise from the Human Development and Health Academic Unit, MRC Lifecourse Epidemiology Unit and Centre for Biological Sciences, University of Southampton; Singapore Institute for Clinical Sciences; National University of Singapore; Auckland UniServices Limited and the Liggins Institute, University of Auckland. The Consortium's aim is to improve human health through the life course by further understanding developmental and environmental processes. The research includes a focus on epigenetics, the biology of understanding how gene function is regulated by environmental factors, such as maternal nutrition, during the very early stages of development. This research was carried out as part of a collaboration with the Nestlé Research Centre, in Lausanne, Switzerland.


News Article | April 9, 2017
Site: www.techtimes.com

The Earth has been around for millions of years so it is not surprising that humans still have a lot to discover about the Earth's ecosystem, especially since creatures continue to adapt to the changing environment. In December 2016, scientists discovered six new marine species in the Indian Ocean floor with the help of a robot. Now a professor of Aquatic Biology from the University of Kerala confirms that an elusive spider-like creature spotted in trees in Kerala is actually a new species. Sightings of a spider-like crab that climbs and lives in trees in the Western Ghats of South India were first reported by the Kani tribe in 2014. Incidentally, Professor Biju Kumar was in the area at that time to survey freshwater crabs but, even with the help of his student and members of the Kani tribesmen, it took Professor Kumar months before he was finally able to track down and capture a couple of the elusive long-legged crabs. In honor of the tribe that led to the discovery, the new crab species has been named Kani maranjandu which is, basically, the name of the Kani tribe and the local term for "tree crab." The crabs can supposedly fit in the palm of a human hand and has a deep bluish-black body that is broad, swollen, and convex. They also have long legs with slim, curved, and sharp ends that allow the crustaceans to get a good grip on the trees they climb. However, what makes the newly discovered creatures so striking is not its appearance but its behavior and way of life. According to Professor Kumar's study published in the Journal of Crustacean Biology, the Kani maranjandu lives up high in water-filled holes of tall deciduous and evergreen trees. The crustaceans are able to move rapidly as they climb up and down tree trunks but are very shy and tend to quickly hide in their holes when approached. Younger crabs, however, climb up and take shelter even higher in tree canopies that are about 30 feet above the ground. Scientists note that other tree-dwelling crab species climb only up to a few feet up a tree so the Kani maranjandu's behavior is pretty unusual for crabs. Professor Kumar also observed that the crab heavily relies on rainwater collected in tree hollows for survival, noting that the creatures abandon a hollow when it dries up. The crab's body shape enables it to hold water as it searches for a new tree hollow with water to occupy. Biologist Peter K.L. Ng from the National University of Singapore helped classify the new species and he believes that the Kani maranjandu is a good illustration of crab evolution. "The exciting thing for me is that these crabs, regardless of where they have been found, and how they are related (or unrelated) to each other, they have nevertheless evolved to use specialized habitats to enhance their survival," he says. © 2017 Tech Times, All rights reserved. Do not reproduce without permission.


Inaugural events offer effective strategic platform for industry leaders, experts, and next generation of talent to advance regional growth potential The inaugural Rotorcraft Asia, the region's first-ever dedicated event for civil helicopter industry is focused on offering an effective strategic platform for industry leaders, potential partners and experts to forge partnerships, engage in dialogues and showcase new innovative technologies, to unlock the region's growing industry. Top executives, regulators, industry experts, academics and leading industry players from more than 45 countries across 4 continents will converge at Rotorcraft Asia 2017 to drive discussions on industry challenges, emerging needs and new innovative solutions. Adding dimensions to the discourse, the co-located Unmanned Systems Asia 2017 will explore the "Future of Drones" that will feature diverse insights into unmanned systems and showcase the advances of the 21st century. Held from 18 to 20 April 2017 at the Changi Exhibition Centre in Singapore, over 80 companies from close to 20 countries will gather to showcase a vast spectrum of cutting edge and innovative solutions in rotorcraft and unmanned systems. In addition to featuring new technologies and innovations, the events will also engage young talent with the focus on cultivating and grooming the next generation of industry leaders. "The growing necessity to integrate smart technologies to drive efficiency and competitiveness has increased the need for the rotorcraft industry to continuously evolve and invest in new innovative technologies," said Mr Leck Chet Lam, Managing Director, Experia Events. "The events are co-located to ensure industry players have one single effective platform to advance regional growth potential." "The inaugural events not only provide a networking platform and access to a wide spectrum of growth opportunities in Asia-Pacific's thriving civil helicopter and unmanned systems markets, they also enhance Singapore's position as the leading aerospace hub in the region," said Mr Tan Kong Hwee, Director, Transport Engineering, Singapore Economic Development Board. -Shaping The Innovation Agenda Through Insightful Dialogues Rotorcraft Asia and Unmanned Systems Asia will feature a series of strategic conferences and forums over the three days. The Unmanned Systems Asia 2017 Forum, held on 18 April, will explore the theme of "Future of Drones" to present varied views from commercial users of aerial drones in different industries, with the aim of providing thought provoking discussions on the future potential of having aerial drones performing more varied tasks. The Rotorcraft Asia Conference, themed "Innovation in Rotorcraft", will be held on 19 and 20 April, with the focus on new technologies and solutions for rotary wing aircraft. The two-day conference will feature keynote and panel speakers who will seek to explore the future landscape of how rotorcraft will fly and operate, through the application of next generation innovative technologies, mindset and engineering processes. -Strategic Springboard to Enable Collaboration Across Markets The VIP Buyers Programme demonstrates the role of Rotorcraft Asia and Unmanned Systems Asia as a strategic springboard to enable exhibitors and potential buyers to network and collaborate on business opportunities in this region. Through pre-arranged meetings, exhibitors can use this dedicated face time to forge strategic new partnerships. The VIP Buyers attending include senior public sector representatives from the Ministry of Public Security of the Socialist Republic of Vietnam, Philippine National Police, Royal Malaysia Police, Ministry of Natural Resources and Environmental Conservation, Myanmar, and Royal Brunei Technical Services; as well as commercial buyers including BP, Shell Aviation, PT Derazona Air Service, Macquarie Rotorcraft Leasing, PhilJets, Thai Helicopter Services, Waypoint Leasing among others. -Next-Generation Industry Talents At The Forefront With Drone Innovations The University R&D Showcase will display innovative unmanned systems solutions of tomorrow that have been developed by Singapore's top universities and tertiary institutions, contributing to Singapore's vision to be a Smart Nation. Participating IHLs include Singapore Polytechnic, National University of Singapore (NUS), Nanyang Technological University (NTU), Singapore University of Technology and Design (SUTD), and University of Glasgow Singapore in partnership with Singapore Institute of Technology. Rotorcraft Asia 2017 and Unmanned Systems Asia 2017 are organised by Experia Events with the support of the Civil Aviation Authority of Singapore, the Defence Science and Technology Agency, International Enterprise Singapore, the Ministry of Transport, Singapore, the Singapore Economic Development Board and the Singapore Exhibition and Convention Bureau. For more information, visit www.rotorcraft-asia.com and www.unmannedsystems-asia.com. About Rotorcraft Asia Rotorcraft Asia is a dedicated commercial and para-public helicopter event for the thriving Asia Pacific Market. It is the premier business and networking platform for manufacturers, owners and operators, MROs, distributors of products and services for the rotorcraft and related industry. Comprising an exhibition, conference and static aircraft display, the inaugural Rotorcraft Asia will be an integrated marketplace to springboard and tap into opportunities in this dynamic region. For more information, visit www.rotorcraft-asia.com. About Unmanned Systems Asia The premier unmanned systems event in Asia presents the future of drones across a vast spectrum of commercial and defence applications, showcasing cutting edge technologies and solutions in aerial, ground, surface and underwater systems. Unmanned Systems Asia offers a highly effective platform for stakeholders to advance their search and rescue, communications, monitoring and surveillance capabilities. The show brings together manufacturers, suppliers, service providers, buyers, academia, governments, research and regulatory bodies to explore the limitless opportunities of unmanned systems. For more information, visit www.unmannedsystems-asia.com. About Experia Events Pte Ltd Experia Events specialises in organising and managing exhibitions and conferences of strategic interest, fostering industry development and thought leadership. It has built a strong portfolio in aerospace and defence with the highly successful Singapore Airshow, Asia's largest aerospace and defence event, as well as the inaugural Singapore International Robo Expo and key events such as IMDEX Asia, Asia Pacific's flagship maritime defence show; Rotorcraft Asia, the premier dedicated event for the global civil helicopter industry; Unmanned Systems Asia, which presents the future of unmanned systems across a vast spectrum of commercial and defence applications; and Cybertech Asia, a strategic platform for the international cyber community. Experia Events' expertise also extends to the government and lifestyle sectors, through key events such as the World Cities Summit, Singapore International Water Week and CleanEnviro Summit Singapore. With a proven track record underscoring its aspirations to stage events that influence, Experia Events aims to diversify its range of strategic events globally. For more information, visit www.experiaevents.com. For further enquiries, please contact: Marilyn Ho Experia Events Pte Ltd Director, Communications Tel: +65 6595 6130 Email: Ranjeet Kaur Hill+Knowlton Strategies Tel: +65 9025 7674 Email:


The success of the first Rotorcraft Asia and Unmanned Systems Asia saw the participation of key industry leaders and quality discussions The inaugural editions of Rotorcraft Asia and Unmanned Systems Asia, held from 18 to 20 April 2017, received very strong reception and participation from the breadth of leading industry companies and experts, regulators, top executives and academics, establishing them as key touchstone events for the industry. The inaugural editions hosted over 3,000 trade attendees from 52 countries, of which 24 percent attendees were from overseas. The attendees engaged in high-quality discussions on industry challenges, showcased innovative solutions, and forged strategic partnerships to unlock and drive the industry's growth potential in the region. "Home to Singapore Airshow, Asia's largest aerospace and defence event, and now to Rotorcraft Asia and Unmanned Systems Asia, Singapore has established its leading position in providing key strategic platforms for the global fixed wing, rotary wing and unmanned systems industry participants to converge, forge partnerships and tap into the region's growth potential," said Mr Leck Chet Lam, Managing Director, Experia Events. "We are very encouraged by the positive response to the inaugural events and the fact that industry players are looking at Rotorcraft Asia and Unmanned Systems Asia as must-attend events with its offering of business collaborations, industry knowledge and networking opportunities. We will continue to have a pulse on the industry and bring more exciting dimensions to the future editions." "We are very thrilled to see that the attendance at the Rotorcraft Asia and Unmanned Systems Asia 2017 is concentrated around the innovations in the industry, especially as both industries start to converge. Participating at the events as founding sponsors reaffirms our commitment to the industries in Singapore and the Asia-Pacific region," said Christophe Nurit, Regional Executive Asia Pacific, Sikorsky, a Lockheed Martin Company. - Contributing to the vibrancy of Singapore's Aviation Landscape The robust networking and business opportunities that the inaugural Rotorcraft Asia and Unmanned Systems Asia have provided for the Asia-Pacific region and beyond make it a critical part of the ecosystem of Singapore's aviation and aerospace industry, contributing to the long-term sustainability of the industry and opening doors to key markets for local and global companies alike. "Rotorcraft Asia and Unmanned Systems Asia are very targeted events that have allowed us the opportunity to interact with a myriad of audience who represent the industry's entire ecosystem," said Lu Weiyao, Co-Founder and Technical Director, Flare Dynamics Pte Ltd. "The level of exposure that we have attained by participating in the events have gone through the roof and we are certain that from the leads generated at the events, we will be able to expand our network further." Additionally, networking programmes such as the VIP Buyers Programme facilitated strategic meetings with public sector representatives from Vietnam, the Philippines, Malaysia, Myanmar, Brunei as well as leading industry players such as BP, Shell Aviation, PT Derazona Air Service, Macquarie Rotorcraft Leasing, PhilJets Group, Thai Helicopter Services, Waypoint Leasing among others. "Rotorcraft Asia and Unmanned Systems Asia have established a unique platform for us to meet with high-level executives and manufacturers as well as learn more about the industry trends and forecasts for the region," said Thierry Tea, CEO, PhilJets Group. "As we continue to grow and expand, the events give us an edge into this dynamic industry." - Catalyst for Strategic Partnerships Across the Region Rotorcraft Asia and Unmanned Systems Asia also saw the announcement of several significant collaborations, affirming its position as an effective strategic platform of choice for leading industry companies, solutions providers and innovators from across the industry. Announcements made at the inaugural events include the Airbus Helicopters and SingPost partnership for drone delivery trials. The project, named "Skyways", aims to develop an aerial drone delivery system for urban environments like Singapore. An initial trial involving transporting small packages using a drone around the National University of Singapore (NUS) campus is expected to take place in early 2018. "It is a well-organised event. We are happy to meet various customers, partners and suppliers at this event, to share ideas and discuss opportunities to grow the market in this region. We hope to see even more participants from the various mission systems for a more sustainable showcase," said Philippe Monteux, Head of Region, Southeast Asia & Pacific, Airbus Helicopters. Bell Helicopter also had leveraged the events to solidify several partnerships and deliveries across key markets such as Indonesia, India and Vietnam. Tata Steel Group has purchased a second Bell 429 helicopter to support their steel production operations. Air Pacific Utama (PT APU) also signed a purchase agreement of the first Bell 407GXP and Customer Advantage Plan (CAP), the first Asia-based customer to sign for the new service solution, at Rotorcraft Asia and Unmanned Systems Asia. "We are pleased with the response to the first edition of the biennial Rotorcraft Asia and Unmanned Systems Asia exhibition," said Sameer A. Rehman, Managing Director, Bell Helicopter Asia Pacific. "We were able to celebrate multiple successes during the exhibition as well as showcase our emerging product technologies and share our vision for the future of rotorcraft." Rotorcraft Asia 2017 and Unmanned Systems Asia 2017 are organised by Experia Events with the support of the Civil Aviation Authority of Singapore, the Defence Science and Technology Agency, International Enterprise Singapore, the Ministry of Transport, Singapore, the Singapore Economic Development Board and the Singapore Exhibition and Convention Bureau. The second edition of Rotorcraft Asia and Unmanned Systems Asia, held from 16 to 18 April 2019 at Changi Exhibition Centre, will continue to demonstrate industry relevance to exhibitors and visitors by anticipating market trends, introducing new features as well as offering exhibitors the opportunity to present their latest and most innovative technologies to potential buyers. For more information, visit www.rotorcraft-asia.com and www.unmannedsystems-asia.com. About Rotorcraft Asia Rotorcraft Asia is a dedicated commercial and para-public helicopter event for the thriving Asia Pacific Market. It is the premier business and networking platform for manufacturers, owners and operators, MROs, distributors of products and services for the rotorcraft and related industry. Comprising an exhibition, conference and static aircraft display, Rotorcraft Asia will be an integrated marketplace to springboard and tap into opportunities in this dynamic region. For more information, visit www.rotorcraft-asia.com. About Unmanned Systems Asia The premier unmanned systems event in Asia presents the future of drones across a vast spectrum of commercial and defence applications, showcasing cutting edge technologies and solutions in aerial, ground, surface and underwater systems. Unmanned Systems Asia offers a highly effective platform for stakeholders to advance their search and rescue, communications, monitoring and surveillance capabilities. The show brings together manufacturers, suppliers, service providers, buyers, academia, governments, research and regulatory bodies to explore the limitless opportunities of unmanned systems. For more information, visit www.unmannedsystems-asia.com. About Experia Events Pte Ltd Experia Events specialises in organising and managing exhibitions and conferences of strategic interest, fostering industry development and thought leadership. It has built a strong portfolio in aerospace and defence with the highly successful Singapore Airshow, Asia's largest aerospace and defence event, as well as the inaugural Singapore International Robo Expo and key events such as IMDEX Asia, Asia Pacific's flagship maritime defence show; Rotorcraft Asia, the premier dedicated event for the global civil helicopter industry; Unmanned Systems Asia, which presents the future of unmanned systems across a vast spectrum of commercial and defence applications; and Cybertech Asia, a strategic platform for the international cyber community. Experia Events' expertise also extends to the government and lifestyle sectors, through key events such as the World Cities Summit, Singapore International Water Week and CleanEnviro Summit Singapore. With a proven track record underscoring its aspirations to stage events that influence, Experia Events aims to diversify its range of strategic events globally. For more information, visit www.experiaevents.com. For further enquiries, please contact: Marilyn Ho Experia Events Pte Ltd Director, Communications Tel: +65 6595 6130 Email: Ranjeet Kaur Hill+Knowlton Strategies Tel: +65 9025 7674 Email: Home | About us | Services | Partners | Events | Login | Contact us | Privacy Policy | Terms of Use | RSS


Zhang R.,Institute for Infocomm Research | Zhang R.,National University of Singapore
IEEE Journal on Selected Areas in Communications | Year: 2010

Block diagonalization (BD) is a practical linear precoding technique that eliminates the inter-user interference in downlink multiuser multiple-input multiple-output (MIMO) systems. In this paper, we apply BD to the downlink transmission in a cooperative multi-cell MIMO system, where the signals from different base stations (BSs) to all the mobile stations (MSs) are jointly designed with the perfect knowledge of the downlink channels and transmit messages. Specifically, we study the optimal BD precoder design to maximize the weighted sum-rate of all the MSs subject to a set of per-BS power constraints. This design problem is formulated in an auxiliary MIMO broadcast channel (BC) with a set of transmit power constraints corresponding to those for individual BSs in the multi-cell system. By applying convex optimization techniques, this paper develops an efficient algorithm to solve this problem, and derives the closed-form expression for the optimal BD precoding matrix. It is revealed that the optimal BD precoding vectors for each MS in the per-BS power constraint case are in general non-orthogonal, which differs from the conventional orthogonal BD precoder design for the MIMO-BC under one single sum-power constraint. Moreover, for the special case of single-antenna BSs and MSs, the proposed solution reduces to the optimal zero-forcing beamforming (ZF-BF) precoder design for the weighted sum-rate maximization in the multiple-input single-output (MISO) BC with per-antenna power constraints. Suboptimal and low-complexity BD/ZF-BF precoding schemes are also presented, and their achievable rates are compared against those with the optimal schemes. © 2006 IEEE.


Herranz H.,Institute of Molecular and Cell Biology | Cohen S.M.,Institute of Molecular and Cell Biology | Cohen S.M.,National University of Singapore
Genes and Development | Year: 2010

Biological systems are continuously challenged by an environment that is variable. Yet, a key feature of developmental and physiological processes is their remarkable stability. This review considers how microRNAs contribute to gene regulatory networks that confer robustness. © 2010 by Cold Spring Harbor Laboratory Press.


Lei Z.,National University of Singapore | Zhang J.,National University of Singapore | Zhao X.S.,National University of Singapore
Journal of Materials Chemistry | Year: 2012

Growing MnO2 nanofibers on graphitic hollow carbon spheres (GHCS) is conducted by refluxing GHCS in a KMnO4 aqueous solution aimed to enhance the electrochemically active surface area of MnO2. The stoichiometric redox reaction between GHCS and MnO4 - yields GHCS-MnO2 composites with controllable MnO2 content. It is found that these ultrathin MnO2 nanofibers are vertically grown on the external surface of the GHCS, yielding a composite electrode showing good electron transport, rapid ion penetration, fast and reversible Faradic reaction, and excellent rate performance when used as supercapacitor electrode materials. An asymmetric supercapacitor cell with GHCS-MnO2 as the positive electrode and GHCS as the negative electrode can be reversibly charged/discharged at a cell voltage of 2.0 V in a 1.0 mol L-1 Na2SO4 aqueous electrolyte, delivering an energy density of 22.1 Wh kg-1 and a power density of 7.0 kW kg-1. The asymmetric supercapacitor exhibits an excellent electrochemical cycling stability with 99% initial capacitance and 90% coulombic efficiency remained after 1000 continuous cycles measured using the galvanostatic charge-discharge technique.


Knee G.C.,University of Oxford | Gauger E.M.,University of Oxford | Gauger E.M.,National University of Singapore
Physical Review X | Year: 2014

The application of postselection to a weak quantum measurement leads to the phenomenon of weak values. Expressed in units of the measurement strength, the displacement of a quantum coherent measuring device is ordinarily bounded by the eigenspectrum of the measured observable. Postselection can enable an interference effect that moves the average displacement far outside this range, bringing practical benefits in certain situations. Employing the Fisher-information metric, we argue that the amplified displacement offers no fundamental metrological advantage, due to the necessarily reduced probability of success. Our understanding of metrological advantage is the possibility of a lower uncertainty in the estimate of an unknown parameter with a large number of trials. We analyze a situation in which the detector is pixelated with a finite resolution and in which the detector is afflicted by random displacements: imperfections that degrade the fundamental limits of parameter estimation. Surprisingly, weak-value amplification is no more robust to them than a technique making no use of the amplification effect brought about by a final, postselected measurement.


Hagen T.,National University of Singapore
Biochemistry Research International | Year: 2012

Hypoxia inducible factor (HIF) is known as the master regulator of the cellular response to hypoxia and is of pivotal importance during development as well as in human disease, particularly in cancer. It is composed of a constitutively expressed β subunit (HIF-1β) and an oxygen-regulated α subunit (HIF-1α and HIF-2α), whose stability is tightly controlled by a family of oxygen- and iron-dependent prolyl hydroxylase enzymes. Whether or not mitochondria-derived reactive oxygen species (ROS) are involved in the regulation of Hypoxia Inducible Factor-1α has been a matter of contention for the last 10 years, with equally compelling evidence in favor and against their contribution. A number of recent papers appear to tip the balance against a role for ROS. Thus, it has been demonstrated that HIF prolyl hydroxylases are unlikely to be physiological targets of ROS and that the increase in ROS that is associated with downregulation of Thioredoxin Reductase in hypoxia does not affect HIF-1α stabilization. Finally, the protein CHCHD4, which modulates cellular HIF-1α concentrations by promoting mitochondrial electron transport chain activity, has been proposed to exert its regulatory effect by affecting cellular oxygen availability. These reports are consistent with the hypothesis that mitochondria play a critical role in the regulation of HIF-1α by controlling intracellular oxygen concentrations. © 2012 Thilo Hagen.


Bilger M.,National University of Singapore | Carrieri V.,University of Salerno
Journal of Health Economics | Year: 2013

Using a rich Italian cross-sectional dataset, we estimate the effect of a neighborhood problems aggregate (including pollution, crime, and noise) on self-assessed health, presence of chronic conditions and limitations in daily activities. We address the self-selection of the residents in their neighborhoods, as well as the possible endogeneity of income with respect to health, through instrumental variable methods and several endogeneity tests. The main novelty is the sound estimation of the neighborhood effect on health using observational data, which has the advantage of providing general results that are not dependent on any experimental design. This allows us to fully compare the neighborhood effect with the traditional socioeconomic determinants of health. Our main findings are that low quality neighborhoods are strongly health damaging. This effect is comparable to the primary/upper secondary education health differential and is even higher than the impact that poor economic circumstances have on health. © 2012 Elsevier B.V.


Ibanez C.F.,Karolinska Institutet | Ibanez C.F.,National University of Singapore
Cold Spring Harbor Perspectives in Biology | Year: 2013

The identification of the ret oncogene by Masahide Takahashi and Geoffrey Cooper in 1985 was both serendipitous and paradigmatic (Takahashi et al. 1985). By transfecting total DNA from a human lymphoma into mouse NIH3T3 cells, they obtained one clone, which in secondary transformants yielded more than 100-fold improvement in transformation efficiency. Subsequent investigations revealed that the RET oncogene was not present as such in the primary lymphoma, but was derived by DNA rearrangement during transfection from normal human sequences of the ret locus. At the time, activation by DNA rearrangement had not been previously described for a transforming gene with the NIH3T3 transfection assay. The discovery of RET opened a field of study that has had a profound impact in cancer research, developmental biology, and neuroscience, and that continues to yield surprises and important insights to this day. © 2013 Cold Spring Harbor Laboratory Press; all rights reserved.


Lim S.Y.,National University of Singapore | Shen W.,National University of Singapore | Gao Z.,National University of Singapore
Chemical Society Reviews | Year: 2015

Fluorescent carbon nanoparticles or carbon quantum dots (CQDs) are a new class of carbon nanomaterials that have emerged recently and have garnered much interest as potential competitors to conventional semiconductor quantum dots. In addition to their comparable optical properties, CQDs have the desired advantages of low toxicity, environmental friendliness low cost and simple synthetic routes. Moreover, surface passivation and functionalization of CQDs allow for the control of their physicochemical properties. Since their discovery, CQDs have found many applications in the fields of chemical sensing, biosensing, bioimaging, nanomedicine, photocatalysis and electrocatalysis. This article reviews the progress in the research and development of CQDs with an emphasis on their synthesis, functionalization and technical applications along with some discussion on challenges and perspectives in this exciting and promising field. © The Royal Society of Chemistry 2015.


Idris N.M.,National University of Singapore | Gnanasammandhan M.K.,National University of Singapore | Zhang J.,National University of Singapore | Ho P.C.,National University of Singapore | And 2 more authors.
Nature Medicine | Year: 2012

Conventional photodynamic therapy (PDT) is limited by the penetration depth of visible light needed for its activation. Here we used mesoporous-silica- coated upconversion fluorescent nanoparticles (UCNs) as a nanotransducer to convert deeply penetrating near-infrared light to visible wavelengths and a carrier of photosensitizers. We also used the multicolor-emission capability of the UCNs at a single excitation wavelength for simultaneous activation of two photosensitizers for enhanced PDT. We showed a greater PDT efficacy with the dual-photosensitizer approach compared to approaches using a single photosensitizer, as determined by enhanced generation of singlet oxygen and reduced cell viability. In vivo studies also showed tumor growth inhibition in PDT-treated mice by direct injection of UCNs into melanoma tumors or intravenous injection of UCNs conjugated with a tumor-targeting agent into tumor-bearing mice. As the first demonstration, to the best of our knowledge, of the photosensitizer-loaded UCN as an in vivo-targeted PDT agent, this finding may serve as a platform for future noninvasive deep-cancer therapy. © 2012 Nature America, Inc. All rights reserved.


Chan M.F.,National University of Singapore
Journal of Clinical Nursing | Year: 2010

Aim: To examine nurses' attitudes to practising spiritual care and determine factors associated with nurses' attitudes to practising spiritual care. Background: Today, health is no longer viewed as a passive state of being, but as a dynamic process of achieving higher levels of wellness. In practices, nurse has increasingly focused on treating the whole person, including the four domains: physical, mental, social and spiritual. Of these four domains, the spiritual domain is the most neglected in daily nursing practice. Design: This is retrospective study. Methods: A convenience sampling was used and 110 nurses completed a structured questionnaire at a public hospital in September 2006. Outcome measures: Nurses' demographic data and perceptions and practices scores on spiritual care. Results: The results showed that nurses who more likely had religious beliefs (p = 0·028), were more likely to be married (p = 0·01), had past hospitalisation experiences (p = 0·009), worked in the obstetrics and gynaecology department (p < 0·001) and had higher perception levels towards spiritual care (p < 0·001) were significantly more likely to be practising spiritual care. Conclusion: As nurses are with patients all day, they are in a position to safeguard the wholeness and integrity of the patient. As mentioned in the results, there is a positive correlation between spiritual care perceptions and spiritual care practice among nurses, which means that the greater the nurse's spiritual care perceptions, the more frequently spiritual care is included in that nurse's practice. This correlation is vital and meaningful; it can drive hospitals to promote nurses' awareness of spiritual care to improve the quality of their spiritual care practice. Relevant to clinical practices: To facilitate collaboration between nurses and clergy, it might be beneficial for nurses to communicate more with the clergy, include clergy in patient profile discussions and treat clergy as members of the health care team. Given the influence of the spiritual dimension on the physical realm, it would be more economically viable in the long term to ensure that adequate staffing levels are maintained so that staff has enough time to spend with patients to attend to their spiritual needs. © 2009 Blackwell Publishing Ltd.


Monteiro A.,National University of Singapore
Annual Review of Entomology | Year: 2015

This article reviews the latest developments in our understanding of the origin, development, and evolution of nymphalid butterfly eyespots. Recent contributions to this field include insights into the evolutionary and developmental origin of eyespots and their ancestral deployment on the wing, the evolution of eyespot number and eyespot sexual dimorphism, and the identification of genes affecting eyespot development and black pigmentation. I also compare features of old and more recently proposed models of eyespot development and propose a schematic for the genetic regulatory architecture of eyespots. Using this schematic I propose two hypotheses for why we observe limits to morphological diversity across these serially homologous traits. © 2015 by Annual Reviews. All rights reserved.


He J.,National University of Singapore | Chen J.P.,National University of Singapore
Bioresource Technology | Year: 2014

Heavy metals contamination has become a global issue of concern due to their higher toxicities, nature of non-biodegradability, high capabilities in bioaccumulation in human body and food chain, and carcinogenicities to humans. A series of researches demonstrate that biosorption is a promising technology for removal of heavy metals from aqueous solutions. Algae serve as good biosorbents due to their abundance in seawater and fresh water, cost-effectiveness, reusability and high metal sorption capacities. This article provides a comprehensive review of recent findings on performances, applications and chemistry of algae (e.g., brown, green and red algae, modified algae and the derivatives) for sequestration of heavy metals. Biosorption kinetics and equilibrium models are reviewed. The mechanisms for biosorption are presented. Biosorption is a complicated process involving ion-exchange, complexation and coordination. Finally the theoretical simulation tools for biosorption equilibrium and kinetics are presented so that the readers can use them for further studies. © 2014 Elsevier Ltd.


Singh L.,National University of Singapore
Child Development | Year: 2014

The interconnectedness of bilingual memory remains a topic of great debate. Semantic priming provides a powerful methodological tool with which to investigate this issue in early bilingual toddlers. Semantic priming effects were investigated in 21 bilingual toddlers (2.5 years) within and across each of their languages. Results revealed the first evidence of cross-language and within-language semantic priming in bilingual toddlers. However, priming effects were only observed when the prime was presented in the dominant language and were comparable in magnitude within and across languages. Findings point to high interconnectivity across languages; however, there appear to be strong influences of language dominance on semantic facilitation. Findings serve to inform and refine developmental models of bilingual memory. Child Development © 2014 The Society for Research in Child Development, Inc.


Campana D.,National University of Singapore
Current Hematologic Malignancy Reports | Year: 2012

In acute lymphoblastic leukemia (ALL), the advent of methods to measure disease not detectable by morphology, ie, minimal residual disease (MRD), has set a new standard to define remission. The clinical importance of MRD has been demonstrated by numerous studies using either flow cytometry or polymerase chain reaction and involving thousands of patients. Results are in remarkable agreement on the association between MRD persistence and risk of subsequent relapse, regardless of the MRD detection method used. More recent data indicate that MRD can also be informative in specific subgroups of ALL patients, such as infants or those with T-lineage ALL. Hence, MRD is now being used in clinical trials to inform treatment decisions and guide patients' clinical management. This article reviews MRD methodologies and clinical applications with emphasis on recently reported technical advances and prognostic associations, and the practical issues related to the implementation of MRD monitoring in the clinic. © 2012 Springer Science+Business Media, LLC.


We developed in this research a nanoparticle system for targeted drug delivery across the blood-brain barrier (BBB), which consists of the transferrin (Tf) conjugated nanoparticles of poly(lactide)-d-α-Tocopheryl polyethylene glycol succinate (PLA-TPGS) diblock copolymer. The NPs were prepared by the nanoprecipitation method and characterized for their various physicochemical and pharmaceutical properties. Cellular uptake and cytotoxicity of the Tf-conjugated PLA-TPGS NPs formulation of coumarin 6 as a model imaging agent or Docetaxel as a model drug were investigated in close comparison with those for the PLGA NPs formulation, the bare PLA-TPGS NPs formulation as well as with the clinical Taxotere®. The Tf-conjugated PLA-TPGS NPs formulation demonstrated great advantages over the other two NPs formulations and the original imaging/therapeutic agents. IC50 data showed that the Tf-conjugated PLA-TPGS NPs formulation of Docetaxel could be 23.4%, 16.9% and 229% more efficient than the PLGA NPs, the PLA-TPGS NPs formulations and Taxotere® after 24 h treatment, respectively. Moreover, our preliminary ex vivo biodistribution investigation demonstrated that although not as satisfactory, the Tf-conjugated PLA-TPGS NPs formulation could be able to deliver imaging/therapeutic agents across the BBB. © 2010 Elsevier Ltd.


Ning Y.,National University of Singapore
International Journal of Project Management | Year: 2014

Past studies have found that network strategies can contribute to better company and project performance. The adoption of network strategies is motivated by a set of factors (i.e., drivers), but also faces numerous challenges (i.e., barriers). The appreciation of the factors motivating and deterring networking strategies is beneficial to the successful implementation of network strategies. In the context of public construction projects, this study aims to examine the quantitative effect of drivers and barriers on three network strategies (i.e., trust, information sharing and joint problem solving). The results of a questionnaire-survey of 104 public projects show that the adoption of network strategies in public construction is mainly cost-driven. The results indicate that four barriers impede network strategies in public projects: (i) a lack of continuity and (ii) ethos of public services are harmful to trust; (iii) institutional constraints hinder information sharing; and (iv) a lack of capability is a hurdle to information sharing and trust. It is also found that one barrier (i.e., ethos of public services) has a positive influence on trust between clients and consultants. Recommendations on enhancing network strategies through the appreciation of drivers and barriers are provided. © 2013 Elsevier Ltd and IPMA.


Fu H.,Dong - A University | Liu Y.,National University of Singapore | Zeng H.,National University of Singapore
Chemical Communications | Year: 2013

The use of multiple-center intramolecular H-bonds for the efficient construction of macrocycles of varying structures and functions is among the newest and the most noteworthy additions to the toolbox for macrocycle synthesis. This strategy has allowed the creation of sizable interior cavities as small as 2.8 Å and as large as 15 Å in radius in these H-bonded macrocycles with a number of them expressing tailor-made functions. While concentrating on our recent contributions to this fast-growing field, we will further summarize the latest advances on the design, synthesis, structure and function of these shape-persistent H-bonded macrocyclic foldamers that have helped to create a whole new dimension of scientific research, markedly expanding both the structural and functional repertoires of shape-persistent macrocycles. © 2013 The Royal Society of Chemistry.


Huynh H.V.,National University of Singapore | Teng Q.,National University of Singapore
Chemical Communications | Year: 2013

The synthesis of a bromopropyl-substituted NHC-Pd(ii) complex, which can undergo exemplary and versatile 2nd and 3rd generation post-modifications easily affording 7 new functionalised NHC complexes, is demonstrated. © 2013 The Royal Society of Chemistry.


Lane D.P.,National University of Singapore
Discovery medicine | Year: 2011

A common step in human cancer is the inactivation of the p53 tumor suppressor pathway. This occurs either by mutations in the coding region of the p53 gene itself, or equally commonly, by inactivation of pathways that are required for p53 to exert its cellular function. Dramatic new results from animal models and the widespread availability of p53 activating small molecules are yielding important new insights into the therapeutic and toxic effects of p53 and how these can be exploited for improving therapy of cancer and other diseases.


Chen F.,National University of Singapore | Tan C.K.,National University of Singapore | Yeung Y.-Y.,National University of Singapore
Journal of the American Chemical Society | Year: 2013

A catalytic asymmetric bromocyclization of trisubstituted olefinic amides that uses a C2-symmetric mannitol-derived cyclic selenium catalyst and a stoichiometric amount of N-bromophthalimide is reported. The resulting enantioenriched pyrrolidine products, which contain two stereogenic centers, can undergo rearrangement to yield 2,3-disubstituted piperidines with excellent diastereoselectivity and enantiospecificity. © 2013 American Chemical Society.


Singh A.P.,National University of Singapore | Wohland T.,National University of Singapore
Current Opinion in Chemical Biology | Year: 2014

Imaging fluorescence correlation spectroscopy (imaging FCS), or the acquisition of fluorescence correlation functions at contiguous points in an imaging format, is a recent addition to quantitative bioimaging. Imaging FCS has been implemented in various modalities. These techniques provide excellent time resolution, have single molecules sensitivity and can be combined with super-resolution techniques, thus combining high spatial and temporal resolution. Although still at its beginning it has been applied in different forms to biological problems. This review looks at applications of imaging FCS in the last two years with the aim to give the reader an overview of the capabilities of these new techniques. © 2014 Elsevier Ltd.


Li K.,Institute of Materials Research and Engineering of Singapore | Liu B.,Institute of Materials Research and Engineering of Singapore | Liu B.,National University of Singapore
Chemical Society Reviews | Year: 2014

Polymer encapsulated organic nanoparticles have recently attracted increasing attention in the biomedical field because of their unique optical properties, easy fabrication and outstanding performance as imaging and therapeutic agents. Of particular importance is the polymer encapsulated nanoparticles containing conjugated polymers (CP) or fluorogens with aggregation induced emission (AIE) characteristics as the core, which have shown significant advantages in terms of tunable brightness, superb photo- and physical stability, good biocompatibility, potential biodegradability and facile surface functionalization. In this review, we summarize the latest advances in the development of polymer encapsulated CP and AIE fluorogen nanoparticles, including preparation methods, material design and matrix selection, nanoparticle fabrication and surface functionalization for fluorescence and photoacoustic imaging. We also discuss their specific applications in cell labeling, targeted in vitro and in vivo imaging, blood vessel imaging, cell tracing, inflammation monitoring and molecular imaging. We specially focus on strategies to fine-tune the nanoparticle property (e.g. size and fluorescence quantum yield) through precise engineering of the organic cores and careful selection of polymer matrices. The review also highlights the merits and limitations of these nanoparticles as well as strategies used to overcome the limitations. The challenges and perspectives for the future development of polymer encapsulated organic nanoparticles are also discussed. © 2014 the Partner Organisations.


Electron transfer at the contact between an Al electrode and Au nanoparticles of polymer:nanoparticle devices is studied by ac impedance spectroscopy. The devices have a polystyrene layer embedded with Au nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Al and MoO3/Al electrodes, and they exhibit electrode-sensitive resistive switches. The devices in the pristine or high resistance state have high capacitance. The capacitance decreases after the devices switch to a low resistance state by a voltage scan. The change in the capacitance is attributed to the voltage-induced change on the electronic structure of the contact between the Al electrode and Au nanoparticles. © 2013 AIP Publishing LLC.


Thamburaja P.,National University of Singapore
Journal of the Mechanics and Physics of Solids | Year: 2011

Some recent experiments on sub-micron and nano-sized metallic glass (amorphous alloy) specimens have shown that the shear localization process becomes more stable and less catastrophic when compared to the response exhibited by large sample sizes. This leads to the discovery that the shear localization process and fracture can be delayed by decreasing sample volume. In this work we develop a non-local and finite-deformation-based constitutive model using thermodynamic principles and the theory of micro-force balance to study the causes for the aforementioned observations. The constitutive model has also been implemented into a commercially available finite-element program by writing a user-material subroutine. With the aid of finite-element simulations, our constitutive model predicts that metallic glass samples have the intrinsic ability to exhibit: (a) the delaying of (catastrophic) shear localization with decreasing sample size, and (b) homogeneous deformation behavior for sample volumes smaller than the shear band nucleus. The cause for the observations listed above is the increasing influence of a non-local interaction stress with decreasing sample volume. This interaction stress has energetic origins and it affects plastic deformation due to the strong coupling between plastic shearing and free-volume generation. Akin to strain-gradient plasticity theory, the role of the interaction stress is to strengthen the material at locations where the defect density/free volume is higher compared to the rest of metallic glass sample. © 2011 Elsevier Ltd. All rights reserved.


Li Y.,National University of Singapore | Oruganti R.,National University of Singapore
IEEE Transactions on Power Electronics | Year: 2012

The unfolding-type flyback inverter operating in discontinuous conduction mode (DCM) is popular as a low-cost solution for a photovoltaic (PV) ac module application. This paper aims to improve the efficiency by using a scheme based on continuous conduction mode (CCM) for this application. Design issues, both for the power scheme and the control scheme, are identified and trade-offs investigated. An open-loop control of the secondary current, based on feedback control of the primary current, is proposed in order to bypass the difficulties posed by the moving right half plane zero in the duty cycle to secondary current transfer function. The results presented show an improvement of 8 in California efficiency compared to the benchmark DCM scheme for a 200-W PV module application. The output power quality at rated power level is capable of meeting IEC61727requirements. The stability of the flyback inverter in CCM has been verified at selected working conditions. © 2011 IEEE.


Izad M.M.,National University of Singapore | Heng C.-H.,National University of Singapore
IEEE Journal of Solid-State Circuits | Year: 2012

Frequency synthesizers based on sub-harmonic injection- locked oscillators can reduce power and area effectively. However, they suffer from unwanted side-bands caused by undesirable harmonics in the injection pulse. This paper presents a pulse shaping technique that reduces these undesirable harmonics in the injection pulse and produces low-spur synthesized output. The robustness of the proposed technique and the impact of circuit non-idealities are also discussed in depth. A test chip tailored to the first band group of WiMedia UWB is fabricated in 0.13- m CMOS technology to verify the effectiveness of this technique. Experimental results show that the proposed pulse shaping attenuates the spurs by 22 dB and suppresses them below 47 dBc. The prototype achieves a switching time of less than 4.7 ns and phase noise of 122 dBc/Hz@1 MHz offset at 4.488 GHz. The chip occupies an active area of 0.15 mm and draws only 18 mA from a 1.2-V supply. © 2012 IEEE.


Bi S.,National University of Singapore | Zhang Y.J.,Chinese University of Hong Kong
IEEE Transactions on Smart Grid | Year: 2014

The normal operation of power system relies on accurate state estimation that faithfully reflects the physical aspects of the electrical power grids. However, recent research shows that carefully synthesized false-data injection attacks can bypass the security system and introduce arbitrary errors to state estimates. In this paper, we use graphical methods to study defending mechanisms against false-data injection attacks on power system state estimation. By securing carefully selected meter measurements, no false data injection attack can be launched to compromise any set of state variables. We characterize the optimal protection problem, which protects the state variables with minimum number of measurements, as a variant Steiner tree problem in a graph. Based on the graphical characterization, we propose both exact and reduced-complexity approximation algorithms. In particular, we show that the proposed tree-pruning based approximation algorithm significantly reduces computational complexity, while yielding negligible performance degradation compared with the optimal algorithms. The advantageous performance of the proposed defending mechanisms is verified in IEEE standard power system testcases. © 2010-2012 IEEE.


Chen W.,National University of Singapore | Chen X.,National University of Singapore
Applied Physics Letters | Year: 2013

Ghost imaging has become increasingly popular in quantum and optical application fields. Here, we report three-dimensional (3D) optical security using ghost imaging. The series of random phase-only masks are sparsified, which are further converted into particle-like distributions placed in 3D space. We show that either an optical or digital approach can be employed for the encoding. The results illustrate that a larger key space can be generated due to the application of 3D space compared with previous works. © 2013 AIP Publishing LLC.


Dai M.-Q.,National University of Singapore | Yung L.-Y.L.,National University of Singapore
Chemistry of Materials | Year: 2013

We demonstrated a facile and general method to transfer oleophilic quantum dots (QDs) to the aqueous phase with a high transfer efficiency (∼100%) and essentially retaining the photoluminescence quantum yield (>80%). The transfer is based on a ligand-exchange process mediated by ethylenediamine (EDA). The addition of EDA prior to strong bifunctional ligands (i.e., mercaptocarboxylic acids) to oleophilic QDs was proved to be the critical step. The roles of EDA in this process are the following: (1) reacts with and strips off original ligands; (2) reversibly adsorbs on the surface of stripped QDs in the organic phase and transfers QDs to the aqueous phase; and (3) spontaneously desorbs from the QD surface in the aqueous phase and leaves reactive surface sites to strong ligands. These three roles of EDA work convergently to facilitate efficient transfer of QDs while essentially preserving surface properties of the solid component of QDs. In addition, the EDA-capped QDs were found to be substantially reactive toward incoming strong ligands, due to the complete opening of surface reactive sites to the environment. This method is promising to obtain high-quality QDs in the aqueous phase for subsequent surface functionalization (DNA, protein, peptides, etc.) for various biomedical applications. © 2013 American Chemical Society.


Li Z.,National University of Singapore | Zeng H.C.,National University of Singapore | Zeng H.C.,Institute of Materials Research and Engineering of Singapore
Journal of the American Chemical Society | Year: 2014

Metal-organic frameworks (MOFs) are a class of fascinating supramolecular soft matters but with relatively weak mechanical strength. To enforce MOF materials for practical applications, one possible way seems to be transforming them into harder composites with a stronger secondary phase. Apparently, such a reinforcing phase must possess larger porosity for ionic or molecular species to travel into or out of MOFs without altering their pristine physicochemical properties. Herein we report a general synthetic approach to coat microporous MOFs and their derivatives with an enforcing shell of mesoporous silica (mSiO2). Four well-known MOFs (ZIF-8, ZIF-7, UiO-66, and HKUST-1), representing two important families of MOFs, have served as a core phase in nanocomposite products. We show that significant enhancement in mechanical properties (hardness and toughness) can indeed be achieved with this "armoring approach". Excellent accessibility of the mSiO 2-wrapped MOFs and their metal-containing nanocomposites has also been demonstrated with catalytic reduction of 4-nitrophenol. © 2014 American Chemical Society.


Sangeeth C.S.S.,National University of Singapore | Wan A.,National University of Singapore | Nijhuis C.A.,National University of Singapore
Journal of the American Chemical Society | Year: 2014

The electrical characteristics of molecular tunnel junctions are normally determined by DC methods. Using these methods it is difficult to discriminate the contribution of each component of the junctions, e.g., the molecule-electrode contacts, protective layer (if present), or the SAM, to the electrical characteristics of the junctions. Here we show that frequency-dependent AC measurements, impedance spectroscopy, make it possible to separate the contribution of each component from each other. We studied junctions that consist of self-assembled monolayers (SAMs) of n-alkanethiolates (S(CH2)n-1CH3 SCn with n = 8, 10, 12, or 14) of the form AgTS-SCn//GaOx/EGaIn (a protective thin (∼0.7 nm) layer of GaOx forms spontaneously on the surface of EGaIn). The impedance data were fitted to an equivalent circuit consisting of a series resistor (RS, which includes the SAM-electrode contact resistance), the capacitance of the SAM (CSAM), and the resistance of the SAM (RSAM). A plot of RSAM vs n C yielded a tunneling decay constant β of 1.03 ± 0.04 nC -1, which is similar to values determined by DC methods. The value of CSAM is similar to previously reported values, and RS (2.9-3.6 × 10-2 Ω·cm2) is dominated by the SAM-top contact resistance (and not by the conductive layer of GaOx) and independent of nC. Using the values of R SAM, we estimated the resistance per molecule r as a function of nC, which are similar to values obtained by single molecule experiments. Thus, impedance measurements give detailed information regarding the electrical characteristics of the individual components of SAM-based junctions. © 2014 American Chemical Society.


Shen W.,National University of Singapore | Deng H.,National University of Singapore | Gao Z.,National University of Singapore
Journal of the American Chemical Society | Year: 2012

A simple and ultrasensitive colorimetric DNA assay based on the detection of the product of a ligation chain reaction (LCR) and the use of gold nanoparticles (AuNPs) as signal generators has been developed. During LCR, the AuNPs were ligated together, resulting in a distinct color change in real time after a sufficient number of thermal cycles. The cumulative nature of the protocol produced a detection limit of 20 aM with a selectivity factor of 103. © 2012 American Chemical Society.


Ang B.W.,National University of Singapore
Energy Policy | Year: 2015

Since it was first used by researchers to analyze industrial electricity consumption in the early 1980s, index decomposition analysis (IDA) has been widely adopted in energy and emission studies. Lately its use as the analytical component of accounting frameworks for tracking economy-wide energy efficiency trends has attracted considerable attention and interest among policy makers. The last comprehensive literature review of IDA was reported in 2000 which is some years back. After giving an update and presenting the key trends in the last 15 years, this study focuses on the implementation issues of the logarithmic mean Divisia index (LMDI) decomposition methods in view of their dominance in IDA in recent years. Eight LMDI models are presented and their origin, decomposition formulae, and strengths and weaknesses are summarized. Guidelines on the choice among these models are provided to assist users in implementation. © 2015 Elsevier Ltd.


Li Z.,National University of Singapore | Zeng H.C.,National University of Singapore
Chemistry of Materials | Year: 2013

Integration of other functional materials onto the surfaces or into the matrixes of metal-organic frameworks (MOFs) is a new strategy to acquire multifunctionality for MOFs. Herein, we report a novel means that can integrate ultrafine metal (Au or Ag) nanoparticles onto designated crystallographic planes of zeolitic imidazolate framework (i.e., ZIF-8). The key challenge herein is to determine appropriate surfactants that can help to generate the interaction between the incorporated metal nanoparticles and ZIF-8 phase. In our current work, single-layered metal nanoparticles have been added onto exterior surfaces and/or into interior bulk matrixes of ZIF-8 by forming coordination bonds. Such bonding is actually attained through the coordinative interaction between the surfactants of metal nanoparticles and partially coordinated Zn2+ions on the exterior surface of ZIF-8 crystals. Additional epitaxial growth of ZIF-8 can also be carried out, which turns the surface metal nanoparticles into ZIF-8 bulk phase. Adequate synthetic flexibility has been attained for complex architectures of metal-MOFs hybrid nanocomposites for the first time. Our Au-containing ZIF-8 also shows high catalytic activity for 4-nitrophenol reduction. © 2013 American Chemical Society.


Sun Z.,National University of Singapore | Huang K.-W.,King Abdullah University of Science and Technology | Wu J.,National University of Singapore
Journal of the American Chemical Society | Year: 2011

A soluble and stable heptazethrene derivative was synthesized and characterized for the first time. This molecule exhibits a singlet biradical character in the ground state, which is the first case among zethrene homologue series. Exceptional stability of this heptazethrenebis(dicarboximide) raises the likelihood of its practical applications in materials science. © 2011 American Chemical Society.


Chen X.,National University of Singapore
IEEE Transactions on Geoscience and Remote Sensing | Year: 2010

This paper investigates a modified version of the subspace-based optimization method for solving inversescattering problems. The method is found to share several properties with the contrast-source-inversion method. The essence of the subspace-based optimization method is that part of the contrast source is determined from the spectrum analysis without using any optimization, whereas the rest is determined by optimization method. This feature significantly speeds up the convergence of the algorithm. There is a great flexibility in partitioning the space of induced current into two orthogonal complementary subspaces: the signal subspace and the noise subspace. This flexibility enables the algorithm to perform robustly against noise. Numerical simulations validate the efficacy of the proposed method: fast convergent and robust against noise. © 2009 IEEE.


Ito Y.,National University of Singapore | Bae S.-C.,Chungbuk National University | Chuang L.S.H.,National University of Singapore
Nature Reviews Cancer | Year: 2015

RUNX proteins belong to a family of metazoan transcription factors that serve as master regulators of development. They are frequently deregulated in human cancers, indicating a prominent and, at times, paradoxical role in cancer pathogenesis. The contextual cues that direct RUNX function represent a fast-growing field in cancer research and could provide insights that are applicable to early cancer detection and treatment. This Review describes how RUNX proteins communicate with key signalling pathways during the multistep progression to malignancy; in particular, we highlight the emerging partnership of RUNX with p53 in cancer suppression. © 2015 Macmillan Publishers Limited. All rights reserved.


Ashok J.,National University of Singapore | Kawi S.,National University of Singapore
ACS Catalysis | Year: 2014

Iron-alumina-supported nickel-iron alloy catalysts were tested in a fixed-bed reactor for steam reforming of toluene as a biomass tar model compound. The influence of the calcination temperature of the iron-alumina support was also explored for the steam reforming reaction. Ni supported on an Fe2O3-Al2O3 support calcined at 500 C [NFA(500)] gave superior catalytic performance in terms of activity and stability over other catalysts. NFA(500) gave a toluene conversion of more than 90% for a period of 26 h with a H2/CO value of 4.5. According to XRD analysis, the Ni-Fe alloys were formed and stable throughout the reforming reaction. It was observed from XPS results that the surface of the reduced NFA(500) catalyst was enriched with Fe species, where the other catalysts were enriched with Ni species. These surface Fe species play the role of cocatalysts by increasing the coverage of oxygen species during the reforming reaction to enhance the reaction of toluene and suppresses coke formation. The presence of oxygen species in the reduced catalysts was confirmed by temperature-programmed surface reaction (TPSR) with toluene and water over NFA catalysts. A temperature-programmed oxidation (TPO) study on spent catalysts revealed that the NFA(500) and NFA(700) catalysts have an additional low-temperature oxidation peak at around 525 and 535 C, respectively, suggesting the presence of a higher amount of amorphous carbon compared with the NFA(900) catalyst. The presence of a low-temperature oxidation peak at 525 C for the NFA(500) catalyst is one of the reasons for its stable catalytic performance compared with other catalysts. © 2013 American Chemical Society.


Zhang L.,National University of Singapore
IEEE/ACM Transactions on Computational Biology and Bioinformatics | Year: 2011

When gene copies are sampled from various species, the resulting gene tree might disagree with the containing species tree. The primary causes of gene tree and species tree discord include incomplete lineage sorting, horizontal gene transfer, and gene duplication and loss. Each of these events yields a different parsimony criterion for inferring the (containing) species tree from gene trees. With incomplete lineage sorting, species tree inference is to find the tree minimizing extra gene lineages that had to coexist along species lineages; with gene duplication, it becomes to find the tree minimizing gene duplications and/or losses. In this paper, we present the following results: 1) The deep coalescence cost is equal to the number of gene losses minus two times the gene duplication cost in the reconciliation of a uniquely leaf labeled gene tree and a species tree. The deep coalescence cost can be computed in linear time for any arbitrary gene tree and species tree. 2) The deep coalescence cost is always not less than the gene duplication cost in the reconciliation of an arbitrary gene tree and a species tree. 3) Species tree inference by minimizing deep coalescence events is NP-hard. © 2011 IEEE.


The secretory pathway delivers proteins synthesized at the rough endoplasmic reticulum (RER) to various subcellular locations via the Golgi apparatus. Currently, efforts are focused on understanding the molecular machineries driving individual processes at the RER and Golgi that package, modify and transport proteins. However, studies are routinely performed using non-dividing cells. This obscures the critical issue of how the secretory pathway is affected by cell division. Indeed, several studies have indicated that protein trafficking is down-regulated during mitosis. Moreover, the RER and Golgi apparatus exhibit gross reorganization in mitosis. Here I provide a relatively neglected perspective of how the mitotic cyclin-dependent kinase (CDK1) could regulate various stages of the secretory pathway. I highlight several aspects of the mitotic control of protein trafficking that remain unresolved and suggest that further studies on how the mitotic CDK1 influences the secretory pathway are necessary to obtain a deeper understanding of protein transport. © 2013 WILEY Periodicals, Inc.


Yokomizo T.,Erasmus Medical Center | Yokomizo T.,National University of Singapore | Dzierzak E.,Erasmus Medical Center
Development | Year: 2010

Hematopoietic cell clusters in the aorta of vertebrate embryos play a pivotal role in the formation of the adult blood system. Despite their importance, hematopoietic clusters have not been systematically quantitated or mapped because of technical limitations posed by the opaqueness of whole mouse embryos. Here, we combine an approach to make whole mouse embryos transparent, with multicolor marking, to allow observation of hematopoietic clusters using high-resolution 3-dimensional confocal microscopy. Our method provides the first complete map and temporal quantitation of all hematopoietic clusters in the mouse embryonic vasculature. We show that clusters peak in number at embryonic day 10.5, localize to specific vascular subregions and are heterogeneous, indicating a basal endothelial to non-basal (outer cluster) hematopoietic cell transition. Clusters enriched with the c-Kit+CD31 +SSEA1- cell population contain functional hematopoietic progenitors and stem cells. Thus, three-dimensional cartography of transparent mouse embryos provides novel insight into the vascular subregions instrumental in hematopoietic progenitor/stem cell development, and represents an important technological advancement for comprehensive in situ hematopoietic cluster analysis. © 2010. Published by The Company of Biologists Ltd.


Wakerley B.R.,Gloucestershire Royal Hospital | Uncini A.,University of Chieti Pescara | Yuki N.,National University of Singapore
Nature Reviews Neurology | Year: 2014

Guillain-Barré syndrome (GBS) and its variant, Miller Fisher syndrome (MFS), exist as several clinical subtypes with different neurological features and presentations. Although the typical clinical features of GBS and MFS are well recognized, current classification systems do not comprehensively describe the full spectrum of either syndrome. In this Perspectives article, GBS and MFS are classified on the basis of current understanding of the common pathophysiological profiles of each disease phenotype. GBS is subclassified into classic and localized forms (for example, pharyngeal-cervical-brachial weakness and bifacial weakness with paraesthesias), and MFS is divided into incomplete (for example, acute ophthalmoparesis, acute ataxic neuropathy) and CNS subtypes (Bickerstaff brainstem encephalitis). Diagnostic criteria based on clinical characteristics are suggested for each condition. We believe this approach to be more inclusive than existing systems, and argue that it could facilitate early clinical diagnosis and initiation of appropriate immunotherapy. © 2014 Macmillan Publishers Limited. All rights reserved.


In a recent paper we proposed and compared various approaches to compute the ground state and dynamics of the Schrödinger-Poisson-Slater (SPS) system for general external potential and initial condition, concluding that the methods based on sine pseudospectral discretization in space are the best candidates. This note is concerned with the case that the external potential and initial condition are spherically symmetric. For the SPS system with spherical symmetry, via applying a proper change of variables into the reduced quasi-1D model we simplify the methods proposed for the general 3D case such that both the memory and computational load are significantly reduced. © 2011 Elsevier Inc.


Shen H.-M.,National University of Singapore | Codogno P.,University Paris - Sud
Experimental Cell Research | Year: 2012

Macroautophagy or autophagy is a self-digesting mechanism that the cellular contents are engulfed by autophagosomes and delivered to lysosomes for degradation. Although it has been well established that autophagy is an important protective mechanism for cells under stress such as starvation via provision of nutrients and removal of protein aggregates and damaged mitochondria, there is a very complex relation between autophagy and cell death. At present, the molecular cross-talk between autophagy and apoptosis has been well discussed, while the relationship between autophagy and programmed necrotic cell death is less understood. In this review we focus on the role of autophagy in necrotic cell death by detailed discussion on two important forms of necrotic cell death: (i) necroptosis and (ii) poly-(ADP-ribose) polymerase (PARP)-mediated cell death. It is believed that one important aspect of the pro-survival function of autophagy is achieved via its ability to block various forms of necrotic cell death. © 2012 Elsevier Inc.


Wu Z.,National University of Singapore
Journal of Geophysical Research: Solid Earth | Year: 2010

[1] The hidden Markov model (HMM) and related algorithms provide a powerful framework for statistical inference on partially observed stochastic processes. HMMs have been successfully implemented in many disciplines, though not as widely applied as they should be in earthquake modeling. In this article, a simple HMM earthquake occurrence model is proposed. Its performance in declustering is compared with the epidemic-type aftershock sequence model, using a data set of the central and western regions of Japan. The earthquake clusters and the single earthquakes separated using our model show some interesting geophysical differences. In particular, the log-linear Gutenberg-Richter frequency-magnitude law (G-R law) for the earthquake clusters is significantly different from that for the single earthquakes. © Copyright 2010 by the American Geophysical Union.


Su B.,National University of Singapore | Ang B.W.,National University of Singapore
Applied Energy | Year: 2014

Energy-related CO2 emissions embodied in international trade have been widely studied at the national level in recent years. The embodiment estimates help to explain the "weak carbon leakage" between industrial and developing countries and to reveal the so-called "consumption-based" emissions (or carbon footprint). These findings have implications on national climate policy and international negotiations. For a large country like China, spatial aggregation issues are important in embodied emission studies. Dividing the country into several regions, previous studies propose the hybrid emissions embodied in trade (HEET) approach for regional emission studies and use step-wise distribution of emissions embodied in trade (SWD-EET) analysis to explain indirect absorption patterns. In this paper, we combine the HEET approach and SWD-EET analysis to conduct a comprehensive study of China's regional emission embodiments. We explain how inter-regional trade and international trade affect China's regional domestic emissions, and present the resulting regional carbon footprint. Policy implications from the empirical results obtained are discussed. © 2013 Elsevier Ltd.


Danner A.J.,National University of Singapore | Tyc T.,Masaryk University | Leonhardt U.,University of St. Andrews
Nature Photonics | Year: 2011

Birefringence, from the very essence of the word itself, refers to the splitting of light rays into two parts. In natural birefringent materials, this splitting is a beautiful phenomenon, resulting in the perception of a double image. In optical metamaterials, birefringence is often an unwanted side effect of forcing a device designed through transformation optics to operate in dielectrics. One polarization is usually implemented in dielectrics, and the other is sacrificed. Here we show, with techniques beyond transformation optics, that this need not be the case, that both polarizations can be controlled to perform useful tasks in dielectrics, and that rays, at all incident angles, can even follow different trajectories through a device and emerge together as if the birefringence did not exist at all. A number of examples are shown, including a combination Maxwell fisheye/Luneburg lens that performs a useful task and is achievable with current fabrication materials. © 2011 Macmillan Publishers Limited. All rights reserved.


Evans T.A.,National University of Singapore | Forschler B.T.,University of Georgia | Kenneth Grace J.,University of Hawaii at Manoa
Annual Review of Entomology | Year: 2013

The number of recognized invasive termite species has increased from 17 in 1969 to 28 today. Fourteen species have been added to the list in the past 44 years; 10 have larger distributions and 4 have no reported change in distribution, and 3 species are no longer considered invasive. Although most research has focused on invasive termites in urban areas, molecular identification methods have answered questions about certain species and found that at least six species have invaded natural forest habitats. All invasive species share three characteristics that together increase the probability of creating viable propagules: they eat wood, nest in food, and easily generate secondary reproductives. These characteristics are most common in two families, the Kalotermitidae and Rhinotermitidae (which make up 21 species on the invasive termite list), particularly in three genera, Cryptotermes, Heterotermes, and Coptotermes (which together make up 16 species). Although it is the largest termite family, the Termitidae (comprising 70% of all termite species) have only two invasive species, because relatively few species have these characteristics. Islands have double the number of invasive species that continents do, with islands in the South Pacific the most invaded geographical region. Most invasive species originate from Southeast Asia. The standard control methods normally used against native pest termites are also employed against invasive termites; only two eradication attempts, in South Africa and New Zealand, appear to have been successful, both against Coptotermes species. © 2013 by Annual Reviews. All rights reserved.


Xuewei P.,National University of Singapore | Rathore A.K.,National University of Singapore
IEEE Transactions on Industrial Electronics | Year: 2014

A novel naturally clamped zero-current commutated soft-switching bidirectional current-fed full-bridge isolated dc/dc converter is proposed. This proposed secondary-modulation technique naturally clamps the voltage across the primary-side devices with zero-current commutation, eliminating the necessity for active-clamp circuit or passive snubbers. Switching losses are reduced significantly owing to zero-current switching of primary-side devices and zero-voltage switching of secondary-side devices. Soft switching and voltage clamping are inherent and load independent. The voltage across primary-side devices is independent of duty cycle with varying input voltage and output power and clamped at rather low reflected output voltage, enabling the use of semiconductor devices of low voltage rating. These merits make the converter promising for fuel cell vehicles application, front-end dc/dc power conversion for fuel cell inverters, and energy storage. Steady-state operation, analysis, design, simulation results using PSIM 9.0.4, and experimental results are presented. © 2013 IEEE.


Cai J.F.,University of California at Los Angeles | Candes E.J.,Applied and Computational Mathematics Caltech | Shen Z.,National University of Singapore
SIAM Journal on Optimization | Year: 2010

This paper introduces a novel algorithm to approximate the matrix with minimum nuclear norm among all matrices obeying a set of convex constraints. This problem may be understood as the convex relaxation of a rank minimization problem and arises in many important applications as in the task of recovering a large matrix from a small subset of its entries (the famous Netflix problem). Off-the-shelf algorithms such as interior point methods are not directly amenable to large problems of this kind with over a million unknown entries. This paper develops a simple first-order and easy-to-implement algorithm that is extremely efficient at addressing problems in which the optimal solution has low rank. The algorithm is iterative, produces a sequence of matrices {X k,Y k}, and at each step mainly performs a soft-thresholding operation on the singular values of the matrix Y k. There are two remarkable features making this attractive for low-rank matrix completion problems. The first is that the soft-thresholding operation is applied to a sparse matrix; the second is that the rank of the iterates {X k} is empirically nondecreasing. Both these facts allow the algorithm to make use of very minimal storage space and keep the computational cost of each iteration low. On the theoretical side, we provide a convergence analysis showing that the sequence of iterates converges. On the practical side, we provide numerical examples in which 1, 000 × 1, 000 matrices are recovered in less than a minute on a modest desktop computer. We also demonstrate that our approach is amenable to very large scale problems by recovering matrices of rank about 10 with nearly a billion unknowns from just about 0.4% of their sampled entries. Our methods are connected with the recent literature on linearized Bregman iterations for-1 minimization, and we develop a framework in which one can understand these algorithms in terms of well-known Lagrange multiplier algorithms. Copyright © 2010, Society for Industrial and Applied Mathematics.


See C.-T.,National University of Singapore | Sim M.,National University of Singapore
Operations Research | Year: 2010

The valuation of the real option to store natural gas is a practically important problem that entails dynamic optimization of inventory trading decisions with capacity constraints in the face of uncertain natural gas price dynamics. Stochastic dynamic programming is a natural approach to this valuation problem, but it does not seem to be widely used in practice because it is at odds with the high-dimensional natural gas price evolution models that are widespread among traders. According to the practice-based literature, practitioners typically value natural gas storage heuristically. The effectiveness of the heuristics discussed in this literature is currently unknown because good upper bounds on the value of storage are not available. We develop a novel and tractable approximate dynamic programming method that, coupled with Monte Carlo simulation, computes lower and upper bounds on the value of storage, which we use to benchmark these heuristics on a set of realistic instances. We find that these heuristics are extremely fast to execute but significantly suboptimal compared to our upper bound, which appears to be fairly tight and much tighter than a simpler perfect information upper bound; computing our lower bound takes more time than using these heuristics, but our lower bound substantially outperforms them in terms of valuation. Moreover, with periodic reoptimizations embedded in Monte Carlo simulation, the practicebased heuristics become nearly optimal, with one exception, at the expense of higher computational effort. Our lower bound with reoptimization is also nearly optimal, but exhibits a higher computational requirement than these heuristics. Besides natural gas storage, our results are potentially relevant for the valuation of the real option to store other commodities, such as metals, oil, and petroleum products. © 2010 INFORMS.


Balakrishnan J.,National University of Singapore | Kok Wai Koon G.,National University of Singapore | Jaiswal M.,National University of Singapore | Jaiswal M.,Indian Institute of Technology Madras | And 2 more authors.
Nature Physics | Year: 2013

Graphene's extremely small intrinsic spin-orbit (SO) interaction makes the realization of many interesting phenomena such as topological/quantum spin Hall states and the spin Hall effect (SHE) practically impossible. Recently, it was predicted that the introduction of adatoms in graphene would enhance the SO interaction by the conversion of sp 2 to sp 3 bonds. However, introducing adatoms and yet keeping graphene metallic, that is, without creating electronic (Anderson) localization, is experimentally challenging. Here, we show that the controlled addition of small amounts of covalently bonded hydrogen atoms is sufficient to induce a colossal enhancement of the SO interaction by three orders of magnitude. This results in a SHE at zero external magnetic fields at room temperature, with non-local spin signals up to 100 Ω; orders of magnitude larger than in metals. The non-local SHE is, further, directly confirmed by Larmor spin-precession measurements. From this and the length dependence of the non-local signal we extract a spin relaxation length of ∼1 μm, a spin relaxation time of ∼ 90 ps and a SO strength of 2.5 meV. © 2013 Macmillan Publishers Limited. All rights reserved.


Neo C.Y.,National University of Singapore | Ouyang J.,National University of Singapore
Carbon | Year: 2013

We report the formation of organogels of 3-methoxypropionitrile (MPN) using graphene oxide (GO) as the gelator and the use of these gels as the quasi-solid state electrolyte of dye-sensitized solar cells (DSCs). GO-MPN gels are prepared by mechanically grinding or ultrasonicating GO in MPN. The GO sheets form 3-dimensional solid networks in the gels, which hold the MPN solvent. The GO loading can be as low as 2.5 wt.% for the gel formation. Gel electrolytes were prepared by dispersing I2, 1-methyl-3-propylimidazolium iodide, guanidine thiocynate and 4-tert butyl pyridine into GO-MPN gels, and these were used for DSCs. The GO sheets can be fragmented into small pieces by ultrasonication, and smaller GO sheets can lead to a higher diffusion constant of the triiodide and a higher photovoltaic efficiency for the DSCs. DSCs with a GO-MPN gel electrolyte exhibit a photovoltaic efficiency of 6.70% under AM 1.5 G illumination (100 mW cm-2), quite close to that (7.18%) of the control liquid DSCs. © 2012 Elsevier Ltd. All rights reserved.


Shu Z.,National University of Singapore | Jirutitijaroen P.,National University of Singapore
IEEE Transactions on Power Systems | Year: 2011

This paper proposes Latin hypercube sampling (LHS) methods for reliability analysis of power systems including renewable energy sources, with an emphasis on the fluctuation of bus loads and intermittent behavior of renewable generations such as wind and solar power. The LHS methods that are applicable for systems with correlated random variables - system load and renewable generation - are proposed. Reliability indices such as loss of load expectation and loss of load probability are estimated. Results from Monte Carlo (MC) sequential sampling, MC nonsequential sampling, and that from the proposed LHS methods are compared. It is shown that the proposed methods are as accurate as the other sampling methods while requiring much less CPU time. Two case studies modified from the Electric Reliability Council of Texas (ERCOT) and IEEE Reliability Test System (IEEE RTS) are presented to demonstrate the performances of the proposed sampling methods. © 2006 IEEE.


Chian K.S.,Nanyang Technological University | Leong M.F.,Institute Of Bioengineering And Nanotechnology, Singapore | Kono K.,National University of Singapore | Kono K.,Fukushima Medical University
The Lancet Oncology | Year: 2015

Removal of malignant tissue in patients with oesophageal cancer and replacement with autologous grafts from the stomach and colon can lead to problems. The need to reduce stenosis and anastomotic leakage after oesophagectomy is a high priority. Developments in tissue-engineering methods and cell-sheet technology have improved scaffold materials for oesophageal repair. Despite the many successful animal studies, few tissue-engineering approaches have progressed to clinical trials. In this Review, we discuss the status of oesophagus reconstruction after surgery. In particular, we highlight two clinical trials that used decellularised constructs and epithelial cell sheets to replace excised tissues after endoscopic submucosal dissection or mucosal resection procedures. Results from the trials showed that both decellularised grafts and epithelial-cell sheets prevented stenosis. By contrast, animal studies have shown that the use of tissue-engineered constructs after oesophagectomy remains a challenge. © 2015 Elsevier Ltd.


Petersson F.,National University of Singapore
Seminars in Diagnostic Pathology | Year: 2015

Nasopharyngeal carcinoma is an umbrella term for a group of malignant epithelial tumors with different etiopathogenesis and a broad range of histopathological appearances. Some types have a dramatically skewed geographical and ethnic distribution and shows virtually 100% association with Epstein Barr virus. The field of other/contributing etiological factors are only partially known and recently a subset of this carcinoma has been linked to transcriptionally active Human Papilloma virus. As with all malignant tumors, the clinical stage of disease is of paramount importance. Despite loco-regionally advanced disease, a large proportion of these patients respond well to radiotherapy, either alone or in combination with chemotherapy and long term sequelae including, but not limited to, development of secondary, radiation-induced malignant tumors is a real clinical problem. This review attempts to provide the practicing pathologist with an overview of nasopharyngeal carcinoma and recent advances in the multifaceted understanding of this group of neoplasms. In addition, some information on prognosis, staging, treatment and treatment related complications in this group of patients is provided. © 2015 Elsevier Inc.


Xu L.,University of California at Davis | Li S.,National University of Singapore | Stohr B.A.,University of California at San Francisco
Annual Review of Pathology: Mechanisms of Disease | Year: 2013

Telomere biology plays a critical and complex role in the initiation and progression of cancer. Although telomere dysfunction resulting from replicative attrition constrains tumor growth by engaging DNA-damage signaling pathways, it can also promote tumorigenesis by causing oncogenic chromosomal rearrangements. Expression of the telomerase enzyme enables telomere-length homeostasis and allows tumor cells to escape the antiproliferative barrier posed by short telomeres. Telomeres and telomerase also function independently of one another. Recent work has suggested that telomerase promotes cell growth through pathways unrelated to telomere maintenance, and a subset of tumors elongate telomeres through telomerase-independent mechanisms. In an effort to exploit the integral link between telomere biology and cancer growth, investigators have developed several telomerase-based therapeutic strategies, which are currently in clinical trials. Here, we broadly review the state of the field with a particular focus on recent developments of interest. © 2013 by Annual Reviews. All rights reserved.


Luo J.,National University of Singapore | Tong Y.W.,National University of Singapore
ACS Nano | Year: 2011

Molecular assembly of protein and peptide is highly specific and frequently occurs in biological systems. Collagen, which is the most abundant component in extracellular matrix, can assemble into fiber and play an essential role in cell adhesion and growth. Since native collagen is difficult to modify and can engender pathogenic and immunological side effects, its application on tissue regeneration is limited. The preparation of collagen-mimetic materials, hence, is gaining interest in the field of tissue regeneration. Collagen peptides have been synthesized to mimic some properties of collagen, such as its triple helix. However, few studies have been done to prepare artificial collagen fiber to mimic its high-level structure and biofunctions. In this work, a novel collagen-mimetic peptide amphiphile (CPA) was prepared by conjugating a single hydrophobic tail with a collagen-mimetic peptide, supplemented with bioactive glycine-phenylalanine-hydroxyproline-glycine-glutamate-arginine (GFOGER). The physical studies indicated that the CPA had a collagen-mimetic triple-helical conformation and was able to self-assemble into nanofiber. In addition, the CPA conjugated with the integrin-specific GFOGER sequence was shown to promote collagen-mimetic cell adhesion and development. The self-assembled peptide nanofiber was shown to have the ability to structurally and biologically mimic native collagen fiber. We anticipate that this artificial collagen fiber holds great potential as collagen-mimetic materials for tissue regeneration applications. © 2011 American Chemical Society.


Goh J.,National University of Singapore | Sim M.,National University of Singapore
Operations Research | Year: 2010

In this paper we focus on a linear optimization problem with uncertainties, having expectations in the objective and in the set of constraints. We present a modular framework to obtain an approximate solution to the problem that is distributionally robust and more flexible than the standard technique of using linear rules. Our framework begins by first affinely extending the set of primitive uncertainties to generate new linear decision rules of larger dimensions and is therefore more flexible. Next, we develop new piecewise-linear decision rules that allow a more flexible reformulation of the original problem. The reformulated problem will generally contain terms with expectations on the positive parts of the recourse variables. Finally, we convert the uncertain linear program into a deterministic convex program by constructing distributionally robust bounds on these expectations. These bounds are constructed by first using different pieces of information on the distribution of the underlying uncertainties to develop separate bounds and next integrating them into a combined bound that is better than each of the individual bounds. © 2010 INFORMS.


Xu J.,National University of Singapore | Zhang R.,National University of Singapore | Zhang R.,Institute for Infocomm Research
IEEE Journal on Selected Areas in Communications | Year: 2014

Characterizing the fundamental tradeoffs for maximizing energy efficiency (EE) versus spectrum efficiency (SE) is a key problem in wireless communication. In this paper, we address this problem for a point-to-point additive white Gaussian noise (AWGN) channel with the transmitter powered solely via energy harvesting from the environment. In addition, we assume a practical on-off transmitter model with non-ideal circuit power, i.e., when the transmitter is on, its consumed power is the sum of the transmit power and a constant circuit power. Under this setup, we study the optimal transmit power allocation to maximize the average throughput over a finite horizon, subject to the time-varying energy constraint and the non-ideal circuit power consumption. First, we consider the off-line optimization under the assumption that the energy arrival time and amount are a priori known at the transmitter. Although this problem is non-convex due to the non-ideal circuit power, we show an efficient optimal solution that in general corresponds to a two-phase transmission: the first phase with an EE-maximizing on-off power allocation, and the second phase with a SE-maximizing power allocation that is non-decreasing over time, thus revealing an interesting result that both the EE and SE optimizations are unified in an energy harvesting communication system. We then extend the optimal off-line algorithm to the case with multiple parallel AWGN channels, based on the principle of nested optimization. Finally, inspired by the off-line optimal solution, we propose a new online algorithm under the practical setup with only the past and present energy state information (ESI) known at the transmitter. © 2014 IEEE.


Motegi F.,National University of Singapore | Seydoux G.,Johns Hopkins University
Philosophical Transactions of the Royal Society B: Biological Sciences | Year: 2013

To become polarized, cells must first 'break symmetry'. Symmetry breaking is the process by which an unpolarized, symmetric cell develops a singularity, often at the cell periphery, that is used to develop a polarity axis. The Caenorhabditis elegans zygote breaks symmetry under the influence of the sperm-donated centrosome, which causes the PAR polarity regulators to sort into distinct anterior and posterior cortical domains. Modelling analyses have shown that cortical flows induced by the centrosome combined with antagonism between anterior and posterior PARs (mutual exclusion) are sufficient, in principle, to break symmetry, provided that anterior and posterior PAR activities are precisely balanced. Experimental evidence indicates, however, that the system is surprisingly robust to changes in cortical flows, mutual exclusion and PAR balance. We suggest that this robustness derives from redundant symmetry-breaking inputs that engage two positive feedback loops mediated by the anterior and posterior PAR proteins. In particular, the PAR-2 feedback loop stabilizes the polarized state by creating a domain where posterior PARs are immune to exclusion by anterior PARs. The two feedback loops in the PAR network share characteristics with the two feedback loops in the Cdc42 polarization network of Saccharomyces cerevisiae. © 2013 The Authors.


Ng S.-Y.,Genome Institute of Singapore | Ng S.-Y.,National University of Singapore | Johnson R.,Bioinformatics and Genomics Group | Stanton L.W.,Genome Institute of Singapore | Stanton L.W.,National University of Singapore
EMBO Journal | Year: 2012

Long non-coding RNAs (lncRNAs) are a numerous class of newly discovered genes in the human genome, which have been proposed to be key regulators of biological processes, including stem cell pluripotency and neurogenesis. However, at present very little functional characterization of lncRNAs in human differentiation has been carried out. In the present study, we address this using human embryonic stem cells (hESCs) as a paradigm for pluripotency and neuronal differentiation. With a newly developed method, hESCs were robustly and efficiently differentiated into neurons, and we profiled the expression of thousands of lncRNAs using a custom-designed microarray. Some hESC-specific lncRNAs involved in pluripotency maintenance were identified, and shown to physically interact with SOX2, and PRC2 complex component, SUZ12. Using a similar approach, we identified lncRNAs required for neurogenesis. Knockdown studies indicated that loss of any of these lncRNAs blocked neurogenesis, and immunoprecipitation studies revealed physical association with REST and SUZ12. This study indicates that lncRNAs are important regulators of pluripotency and neurogenesis, and represents important evidence for an indispensable role of lncRNAs in human brain development. © 2012 European Molecular Biology Organization | All Rights Reserved.


Abraham S.N.,Duke University | Abraham S.N.,National University of Singapore | Miao Y.,Duke University
Nature Reviews Immunology | Year: 2015

The urinary tract is constantly exposed to microorganisms that inhabit the gastrointestinal tract, but generally the urinary tract resists infection by gut microorganisms. This resistance to infection is mainly ascribed to the versatility of the innate immune defences in the urinary tract, as the adaptive immune responses are limited particularly when only the lower urinary tract is infected. In recent years, as the strengths and weaknesses of the immune system of the urinary tract have emerged and as the virulence attributes of uropathogens are recognized, several potentially effective and unconventional strategies to contain or prevent urinary tract infections have emerged. © 2015 Macmillan Publishers Limited.


Korzh V.,National University of Singapore
Development Growth and Differentiation | Year: 2014

Neurulation is defined as a process of neural tube closure. Recent reports suggested that upon completion of this process the major factors of neurulation remain in force at least until the central canal of the neural tube is formed. Hence, an idea has been put forward to define the two periods of neurulation: early neurulation corresponds to the period of neural tube closure and late neurulation corresponds to the period of formation of the central canal. These ideas are discussed in a context of neural tube defects that may affect late neurulation and result in distention of the central canal. © 2014 Japanese Society of Developmental Biologists.


Fu X.,National University of Singapore | Tan C.-H.,National University of Singapore
Chemical Communications | Year: 2011

This feature article discusses the various mechanistic aspects of guanidine-catalyzed reactions. Guanidines are well known as strong organic bases; however, in the first section, three most common commercially available guanidines, TMG, TBD and MTBD, will be used to illustrate the use of guanidines as nucleophilic catalysts. In the second section, different modes of hydrogen bonding interactions of the conjugate acid of guanidine, the guanidinium, are discussed. Particularly interesting are the possibilities of mono-functional or bifunctional activation of a nucleophile and an electrophile by guanidinium. © 2011 The Royal Society of Chemistry.


Voorhoeve P.M.,National University of Singapore
Biochimica et Biophysica Acta - Reviews on Cancer | Year: 2010

The realization that microRNAs are intimately linked to cancer pathogenesis has spawned an explosion of research activity in recent years. Their presence is not merely predictive of tumor origin and behavior, they are causally linked to the emergence and development of cancer by acting as oncogenes or tumor suppressors. The understanding of the functional consequences of altered microRNA expression in cancer is progressing rapidly, even though the prediction of microRNA targets is still a hit and miss process. MicroRNAs may not act primarily by strongly reducing the expression of a few prominent cancer-regulatory genes, but by influencing the properties of the network of which these regulators are a central part. By coordinately regulating many genes, microRNAs are exquisitely suited to act as stabilizers of networks and to prevent extreme variations in phenotype due to intrinsic and extrinsic disturbances. Many advanced tumors show defects in microRNA expression and processing, which could increase phenotypic variability within tumors. This allows small subsets of cells with altered characteristics to emerge, which can have grave consequences as typically a small fraction of tumor cells is responsible for metastasis and treatment resistance, and ultimately treatment failure. Investigating microRNAs from the perspective of master regulators of network stability in cancer calls for new experimental approaches and may help to understand causes of cancer heterogeneity and disease progression. © 2009 Elsevier B.V. All rights reserved.


Ingouff M.,National University of Singapore | Berger F.,National University of Singapore
Chromosoma | Year: 2010

Regulation of chromatin activity by covalent histone modifications has been long recognized. Histones that constitute the nucleosome are encoded by large families of genes and display a strong degree of conservation. However, histone variants exist and it is becoming clear that they play important roles in genome regulation. While most studies of the role of histone3 (H3) variants in transcriptional control comes from animal models, emerging data in plants suggest functional conservation, although plant-specific roles are likely. We review these data and speculate on the biological significance of H3 variants in plants. © 2009 Springer-Verlag.


Corlett R.T.,National University of Singapore
Biodiversity and Conservation | Year: 2010

Tropical East Asia (TEA) has numerous islands, both continental and oceanic. This study uses information on invasive aliens in terrestrial habitats on these islands to test the generality of the continental-oceanic contrast in invasibility, assess the conservation impacts of invasive species, and suggest ways to mitigate these. The continental islands of Hong Kong and Singapore are worst-case scenarios for continental invasibility and alien species often dominate in chronically disturbed sites, but very few have successfully invaded closed forests, with the exception of birds in Hong Kong. On other, less densely populated, continental islands, closed-canopy forests appear to resist invasions by all taxa, with few known exceptions. Forests on oceanic islands isolated by <100 km during the last glacial maximum appear no more susceptible to plant and invertebrate invasions than those on continental islands, but invasions by mammals are widespread. Snake invasions may be under-recognized. The remote oceanic Ogasawara (Bonin) Islands, >1000 km from the nearest continent, have a native biota of largely tropical East Asian origin and are suffering from alien forest invasions across the taxonomic spectrum. These patterns of invasibility are consistent with the idea that alien invasion is facilitated by the absence of native species in the same functional group. Alien invasives are not yet a major conservation problem in TEA, except on remote islands, but their dominance on disturbed sites may slow or prevent recovery of native biodiversity. Strict quarantine is impractical in TEA, although some major introduction routes could be blocked. Management efforts should focus on early recognition and immediate control of potential problem species. © Springer Science+Business Media B.V. 2009.


Priyam A.,National University of Singapore | Idris N.M.,National University of Singapore | Zhang Y.,National University of Singapore
Journal of Materials Chemistry | Year: 2012

Lanthanide-doped upconversion nanocrystals (UCN) converting low energy photons to high energy photons have emerged as an efficient and versatile bioimaging and therapeutic tool. However, the upconversion efficiency of the UCNs is low, which limits their applications. Plasmonic modulation makes it possible to enhance the luminescence of these nanocrystals. We hypothesize that the enhancement of the upconversion luminescence for all the emission peaks simultaneously could be achieved if the UCNs are coated with a gold nanoshell and the surface plasmon resonance (SPR) peak is tuned to the near-infrared (NIR) region and made resonant with the absorption of the UCNs, thereby substantially increasing the excitation flux via local field enhancement (LFE) effect. Furthermore, the nanoparticles could be used for darkfield imaging due to the light scattering caused by the gold nanoshell. Herein, we report a poly-(amino acid)-templated gold-shell encapsulation of the silica coated NaYF 4:Yb,Er UCNs and show how a deft tuning of the SPR peak from visible to NIR region dramatically transforms the luminescence quenching into an enhancement effect and how the nanoparticles are used for combined upconversion fluorescence and darkfield light scattering imaging. © The Royal Society of Chemistry 2011.


Adams S.,National University of Singapore | Rao R.P.,National University of Singapore
Journal of Materials Chemistry | Year: 2012

Due to their favourable combination of high ionic conductivity and stability versus elemental lithium, garnet-related lithium ion conductors Li 7La 3Zr 2O 12 have raised strong interest for both all-solid-state batteries and as protective layers for anode materials. Here we study the correlation between structure and ion mobility in Li 7-xLa 3(Zr 2-xM x)O 12 (x = 0, 0.25; M = Ta 5+, Nb 5+) combining Molecular Dynamics (MD) simulations, bond valence (BV) studies and experimental characterisation. In situ XRD demonstrates a tetragonal-to-cubic phase transition above 450 K for Li xLa 3Zr 2O 12. MD simulations using our new BV-based Morse-type force field reproduce static (lattice constants, thermal expansion, phase transition) and dynamic characteristics of this material. Simulations and structure refinements for the tetragonal phase accordingly yield an ordered Li distribution. The majority of Li fully occupies the 16f and 32g octahedral sites. Out of the two tetrahedral sites only the 8a site is fully occupied leaving the 16e tetrahedral sites with slightly higher site energy due to the tetragonal distortion vacant. For the cubic phase recent structural studies either suggest a major Li + redistribution to nearly fully occupied tetrahedral sites and distorted octahedral sites with a low occupancy (which leads to unphysically short Li-Li distances) or suggest the existence of additional Li sites. MD simulations however show that the lithium distribution just above the phase transition closely resembles that in the tetragonal phase with only slightly more than 1/3 of the now equivalent tetrahedral 24d sites and almost half of the distorted octahedral 96h sites occupied, so that overly short Li-Li distances are avoided. Pentavalent doping enhances ionic conductivity by increasing the vacancy concentration and by reducing local Li ordering. At higher temperatures Li is gradually redistributed to the tetrahedral sites that can be occupied up to a site occupancy factor of 0.56. BV pathway analysis and closely harmonizing Li trajectories demonstrate that the two partially occupied Li sites of similar site energy form a 3D network suitable for fast ion conduction. The simulated diffusion coefficient and its activation energy closely match the experimental conductivities. The degree of correlation of the vacancy-type Li + ion migration is analyzed in terms of the van Hove correlation function. © The Royal Society of Chemistry 2012.


Halliwell B.,National University of Singapore | Lee C.Y.J.,National University of Singapore
Antioxidants and Redox Signaling | Year: 2010

The measurement of F2-isoprostanes by methods utilizing mass spectrometry is widely regarded as the best currently available biomarker of lipid peroxidation. F2-isoprostanes and their metabolites can be measured accurately in plasma, urine, and other body fluids using mass spectrometric techniques, and detailed protocols have been published in several papers. However, many clinical studies and intervention studies with diets or supplements, have employed single "spot" measurements of F 2-isoprostanes on either plasma/serum or urine to estimate "oxidative stress." This review examines the validity of the common assumption that plasma and urinary F2-isoprostane measurements are equivalent. It identifies scenarios where they may not be and where "spot" measurements can be misleading, with examples from the literature. We also discuss the controversial issue of whether and how F 2-isoprostane levels in plasma should be standardized against lipids, and, if so, which lipids to use. © Copyright 2010, Mary Ann Liebert, Inc. 2010.


Zhang T.H.,Soochow University of China | Liu X.Y.,Xiamen University | Liu X.Y.,National University of Singapore
Chemical Society Reviews | Year: 2014

In the last few decades, the controlled colloidal assembly was adopted as a new modelling technology for the study of the crystallization mechanism. In colloidal systems, the movement of particles is slow enough to follow and the particle dynamics can be monitored at the single-particle level using normal optical microscopes. So far, the studies of colloidal crystallization have produced a number of insights, which have significantly improved our understanding of crystallization. In this review, we summarize the recent advances in understanding the mechanism of crystallization, which were achieved using colloidal model systems, i.e., the kinetics of nucleation, growth and defect formation. Such model systems allow us to not only visualize some "atomic" details of nucleation and surface processes of crystallization, but also quantify previous models to such an extent that has never been achieved before by other approaches. In the case of nucleation, the quantitative observation of the kinetic process was made at the single-particle level; the results include the ideal case and the deviations from classical theories. The deviations include multi-step crystallization, supersaturation-driven structural mismatch nucleation, defect creation and migration kinetics, surface roughening, etc. It can be foreseen that this approach will become a powerful tool to study the fundamental process of crystallization and other phase transitions. This journal is © the Partner Organisations 2014.


McInnes B.,National University of Singapore
Nuclear Physics B | Year: 2010

The quark matter phase diagram is believed to contain two distinguished points, lying on the boundary of the Quark-Gluon Plasma phase: a critical point and a triple point. In the holographic ["AdS/QCD"] approach, the region of relatively low chemical potentials around the phase transition near the critical point may be described using generalizations of the Hawking-Page transition. We propose that the other QGP phase line, beginning at the triple point and rising towards the region of extremely high temperatures and chemical potentials, is described instead by a non-perturbative string effect discovered by Seiberg and Witten. Using an assumed position for the critical point, we are able to use this proposal to obtain a holographic lower bound on the temperature of the triple point. Combined with Shuryak's upper bound on this temperature, this leads to a rough estimate of the location of the triple point, at a temperature of around 70 MeV, and a chemical potential of about 1100 MeV. © 2010 Elsevier B.V. All rights reserved.


A novel and fast procedure, sonication-assisted emulsification microextraction combined with vortex-assisted porous membrane protected micro-solid-phase extraction (SAEME-VA-μ-SPE), was developed for the gas chromatography-mass spectrometric determination of acidic drugs from environmental water samples. One advantage of the new procedure is that any solvent immiscible with water can be used as extractant solvent of SAEME and any solid sorbent can be used for μ-SPE in the SAEME-VA-μ-SPE process. In the present work, zeolite imidazolate framework 8 (ZIF-8) was employed as extraction sorbent for μ-SPE and 1-octanol as extractant solvent for SAEME. ZIF-8 has very good thermal, chemical and water stability, which make it a suitable material for the extraction of trace analytes from aqueous samples. Under the optimized extraction conditions, the developed method exhibited low limits of detection (0.01-0.04ng/ml), good linearity (with r2 between 0.9965 and 0.9993) from 0.5 to 50ng/ml and satisfactory repeatability (between 4.1% and 7.6%). In essence SAEME-VA-μ-SPE is a combination of two different and efficient miniaturized techniques. It was demonstrated to be a fast, accurate, and convenient pretreatment procedure for trace analysis of environmental water samples. © 2012 Elsevier B.V.


Mixed zeolitic imidazolate framework 8 (ZIF-8) (nanometer and micron-sized) material were synthesized and applied as sorbent to sonication-assisted emulsification microextraction coupled to vortex-assisted porous membrane-protected micro-solid-phase extraction (SAE-VA-μ-SPE) of polycyclic aromatic hydrocarbons (PAHs) from water samples. Better extraction results was obtained by using the mixed sorbent for the extraction of PAHs from aqueous samples, than either nanometer or micron-sized ZIF-8 separately. The developed method proved to be a time-saving, highly efficient (total extraction procedure was less than 10. min), accurate and robust method for water sample pretreatment. Parameters influencing the extraction efficiency such as desorption solvent, extraction solvent volume, emulsification time, desorption time and salt concentration were investigated and optimized. The limits of detection from gas chromatography-mass spectrometric analysis of six PAHs after SAE-VA-μ-SPE ranged between 0.004 and 0.011. ng/ml. The linear ranges were from 0.05 to 50. ng/ml, and the correlation coefficient was higher than 0.9943. The proposed method provides an interesting and innovative approach of combining different microscale sample preparation methods to solve analytical problems that are not easily addressed by the individual procedure alone. © 2012 Elsevier B.V.


Ouyang J.,National University of Singapore
Organic Electronics: physics, materials, applications | Year: 2013

Electronic devices with an polystyrene (PS) layer blended with Au nanoparticles capped with conjugated 2-naphthalenethiol (Au-2NT NPs) sandwiched between Au and Al electrodes exhibit bipolar resistive switches sensitive to the electrodes. This paper reports the effects of materials, including electrode materials, capping ligands of Au nanoparticles and matrix polymers, on the electrical behavior of the polymer:nanoparticle memory devices. Although the devices using Cu to replace Au as the top electrode exhibit resistive switches similar to those with Au, the threshold voltage for the resistive switch is higher, and the current density for the devices in the low conductivity state is lower. However, the threshold voltage and the current density are almost the same as those with Au as the top electrode, when a semiconductor, MoO 3, is used to replace Au as the top electrode of the devices. The effects of these electrodes are attributed to the charge transfer at the contacts between Au-2NT NPs and the electrodes. The resistive switches are also sensitive to the capping organic ligand of the Au nanoparticles. The threshold voltage decreases and the current density increases, when conjugated benzenethiol is used to replace 2-naphthalenethiol. However, the current density dramatically decreases and the threshold voltage increases, when 2-benzeneethanethiol, a partially conjugated molecule, is adopted as the capping ligand of the Au nanoparticles. The effect of the capping ligands is ascribed to their effect on the charge tunneling across the Au-2NT NPs in the active layer and the contacts between Au-2NT NPs and electrodes. The devices with poly(methyl methacrylate) (PMMA) replacing PS as the polymer matrix exhibit resistive switches almost the same as those with PS, which indicates that the Au-2NT NPs rather than the polymer is the active material responsible for the resistive switches. © 2013 Elsevier B.V. All rights reserved.


Halliwell B.,National University of Singapore
Nutrition Reviews | Year: 2012

This article looks back to the antioxidant/free radical field in 1994 and discusses how it has progressed in the past 18 years. In some areas, there has been little change: the role of oxygen radicals and other reactive oxygen species (ROS) in the origin or progression of most human diseases remains uncertain, with cancer and neurodegenerative disease being likely exceptions. Even in diseases in which ROS are involved there has been little progress in developing effective antioxidant treatments. Mega-doses of dietary antioxidants have also generally failed to prevent human disease, in part because they do not decrease oxidative damage in vivo (as revealed by robust biomarkers). However, some strategies that are known to delay disease onset may act, at least in part, by decreasing oxidative damage levels. Nevertheless, far more is known today about endogenous antioxidant defenses and how they are regulated, which has led to a deeper understanding of how some ROS can act as signaling molecules. Increasing endogenous antioxidant levels (e.g., by supplying "pro-oxidants") may be a better approach to therapeutics and disease prevention than consuming large doses of "dietary antioxidants". © 2012 International Life Sciences Institute.


A fast and efficient method for the determination of trace level of carbamate pesticides using a lower-density-than-water solvent for ultrasound-assisted emulsification microextraction coupled to on-column derivatization and analysis by GC-MS has been developed and studied. In this approach, a soft plastic Pasteur pipette was employed as a convenient extraction device. Fifty microliters of extraction solvent, of lower density than water, was injected into the sample solution held in the pipette. The latter was immediately immersed in an ultrasound water bath to form an emulsion. After 2. min extraction, the emulsion was fractionated into two layers by centrifugation. The upper layer (organic extract) could be collected conveniently by squeezing the bulb of the pipette, now held upside down, to move it into the narrow stem of the device, facilitating its retrieval for analysis. The extract was then combined with trimethylphenylammonium hydroxide and directly injected into a gas chromatography-mass spectrometry (GC-MS) system for on-column derivatization and analysis. The on-column derivatization provided an added convenience (since a separate step was not necessary). Parameters affecting the derivatization and extraction were investigated. Under the most favorable conditions, the method demonstrated high extraction efficiency with low limits of detection of between 0.01 and 0.1 μg/L, good linearity in the range of 0.05-50 μg/L, to 0.5-100 μg/L, and good repeatability (RSD below 9.2%, n= 5). The proposed method was evaluated by determining carbamate pesticides in river water samples. © 2012 Elsevier B.V.


Zhang Y.,National University of Singapore | Lee H.K.,National University of Singapore
Journal of Chromatography A | Year: 2012

For the first time, a simple solvent microextraction method termed vortex-assisted liquid-liquid microextraction (VADLLME) coupled with gas chromatography-mass spectrometry (GC-MS) has been developed and used for the analysis of six benzophenone ultraviolet (UV) filters (i.e. benzhydrol, 2,4-dihydroxybenzophenone, benzophenone, 2-hydroxy-4-methoxybenzophenone, ethylhexyl salicylate and homosalate) in water samples. The most favorable extraction variables in the VADLLME process were determined. In the extraction procedure, 40 μL of tetrachloroethene as extraction solvent were directly injected into a 15-mL centrifuge tube containing 10. mL of aqueous sample, adjusted to pH 4 for VADLLME. After VADLLME, the extract was evaporated under a gentle nitrogen gas stream and then reconstituted with N,. O-bis-(trimethylsilyl)trifluoroacetamide (BSTFA), thus allowing the target analytes to be converted into their trimethylsilyl derivatives to optimize the GC-MS analysis. No centrifugation and disperser solvent were required in this microextraction procedure. Significantly, short extraction time and high extraction efficiency were achieved. This method opens up a potentially new horizon for on-site dispersive liquid-liquid microextraction. Under the optimum conditions, the proposed method provided good enrichment factors up to 310, with relative standard deviations ranging from 6.1 to 12.9%. The limits of quantification were in the range of 20-100. ng/L, depending on the analytes. The linearities were between 0.05 and 10 μg/L and 0.1 and 10 μg/L for different UV filters. Finally, the proposed method was successfully applied to the determination of UV filters from spiked genuine water samples and acceptable recoveries over the range of 71.0-120.0% were obtained. © 2012 Elsevier B.V.


Ferreira A.,National University of Singapore | Peres N.M.R.,University of Minho
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We show that surface-plasmon polaritons excited in negative permittivity metamaterials having shallow periodic surface corrugation profiles can be explored to push the absorption of single and continuous sheets of graphene up to 100%. In the relaxation regime, the position of the plasmonic resonances of the hybrid system is determined by the plasma frequency of the metamaterial, allowing the frequency range for enhanced absorption to be set without the need of engineering graphene. © 2012 American Physical Society.


Ge D.,National University of Singapore | Lee H.K.,National University of Singapore
Journal of Chromatography A | Year: 2012

Hollow fiber protected liquid phase microextraction using an ionic liquid as supported phase and acceptor phase (IL-HF-LPME) is proposed for the determination of four ultraviolet (UV) filters (benzophenone, 3-(4-methylbenzylidene)-camphor, 2-hydroxy-4-methoxybenzophenone and 2,4-dihydroxybenzophenone) in water samples for the first time. In the present study, four different ILs 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate) [HMIM][FAP], 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate [BMPL][FAP], 1-butyl-3-methylimidazolium phosphate ([BMIM][PO 4]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF 6]) were evaluated as extraction solvent. Only [HMIM][FAP] showed high chemical affinity to the analytes which permits a selective isolation of the UV filters from the sample matrix, allowing also their preconcentration. IL-HF-LPME and high performance liquid chromatography provides repeatability from 1.1% to 8.2% and limits of detection between 0.3 and 0.5ng/ml. Real water samples spiked with the analytes extracted were analyzed, and yielded relative recoveries ranging from 82.6% to 105.9%. © 2012 Elsevier B.V.


Blyth E.,University of Huddersfield | Blyth E.,National University of Singapore
Human Reproduction | Year: 2012

Background It is widely accepted that infertility and involuntary childlessness, and the decision to engage with assisted reproduction technology (ART) services as a patient, donor or surrogate can entail wide-ranging psychosocial issues. Psychosocial counselling has, therefore, become valued as an integral element of ART services. The objective of this study was to begin to map out what exists globally by the way of guidelines for infertility counselling. Methods Data were analysed from formal guidelines produced by seven national infertility counselling bodies, onetransnational infertility counselling organization, reports of the American Society for Reproductive Medicine Ethics Committee and Practice Committee and the ESHRE Task Force on Ethics and Law. Additional sources of data were the International Infertility Counseling Organization and counselling colleagues internationally. Results Four broad areas concerning contemporary practice in infertility counselling are identified: (i) the legal mandate for counselling; (ii) eligibility credentials for individuals carrying out professional counselling activities; (iii) different forms of counselling and (iv) counselling practice in relation to specific elements of assisted reproduction treatment. Conclusions Internationally, the development of infertility guidelines is best described as a 'work in progress', although key trends are evident. © The Author 2012. Published by Oxford University Press on behalf of the European Society of Human Reproduction and Embryology. All rights reserved.


Kono K.,National University of Singapore
Journal of Stem Cells and Regenerative Medicine | Year: 2014

To prove clinical benefits of cancer vaccine is currently difficult, except for one phase III trial has documented improved overall survival with the vaccine, Sipuleucel-T, although induction of anti-tumor immune responses through cancer vaccine is theoretically promising and would be straightforward. In contrast, immune checkpoint blockade with anti-CTLA4 mAb and anti-PD-1 mAb has demonstrated clear evidence of objective responses including improved overall survival and tumor shrinkage, driving renewed enthusiasm for cancer immunotherapy in multiple cancer types. In addition, there is a promising novel cancer immunotherapy, CAR therapy-a personalized treatment that involves genetically modifying a patient's T- cells to make them target tumor cells. We are now facing new era of cancer immunotherapy. © Journal of Stem Cells and Regenerative Medicine. All rights reserved.


Thakor N.V.,National University of Singapore | Thakor N.V.,Johns Hopkins University
Science Translational Medicine | Year: 2013

Brain-machine and brain-computer interface technologies hold great promise for use in the recovery of sensory and motor functions lost as a result of nervous-system injuries or limb amputations. This Perspective describes the current state of noninvasive and invasive technologies with a view to potential applications. The scientific and technological challenges and barriers to translation are critically analyzed for a variety of approaches.


Coustan-Smith E.,National University of Singapore | Campana D.,National University of Singapore
Current Opinion in Hematology | Year: 2013

Purpose of Review: In patients with acute myeloid leukemia (AML), measuring response to treatment is essential to guide clinical decisions. Methods for detecting disease beyond the resolution limit of morphology (i.e., minimal residual disease, MRD) are now widely available. We here discuss their merits and the results of side-to-side comparisons. Recent Findings: The ever-increasing comprehension of the molecular genetics of AML has led to the identification of targets for molecular monitoring of MRD in the majority of AML cases. Likewise, virtually all cases express aberrant immunophenotypes suitable for MRD monitoring by flow cytometry, a progress bolstered by powerful new-generation instruments. The clinical significance of MRD monitoring by either approach has been corroborated by recent results. However, with few exceptions, most of the studies continue to rely on retrospectively determined cut-off levels and time points. Moreover, when applied in parallel, the two approaches have yielded contradictory results. SUMMARY: MRD monitoring can help predicting the risk of relapse better than morphology and also provide endpoints for clinical testing of experimental agents. MRD can be applied to guide therapy but one must carefully consider the characteristics of the methods used and the degree of expertise of the laboratory performing the test. © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins.


Zhang J.,National University of Singapore | Joshi S.P.,National University of Singapore
Journal of the Mechanics and Physics of Solids | Year: 2012

We present a single crystal plasticity model for pure Mg incorporating slip and deformation twinning. The model uses the basic framework of Kalidindi (1998), but proposes constitutive descriptions for the slip and twin evolution and their interactions that are motivated by experimental observations. Based on compelling experimental evidences, we distinguish between the constitutive descriptions of the tension and compression twinning to better represent their roles in the overall hardening of Mg single crystals. With these improved phenomenological descriptions, we first calibrate material parameters for the different slip and twin modes by performing three-dimensional simulations mimicking the plane-strain compression experiments by Kelley and Hosford (1967, 1968) on single crystal pure Mg. In doing so, these computational responses are critically compared with their corresponding orientation-dependent microscopic (slip and twin activities) and macroscopic (stressstrain responses) experimental observations. Then, the calibrated parameters are used to predict several other experimental results on pure single- and poly-crystal Mg under different loading conditions. We also investigate the role of pre-existing heterogeneities such as initial twin population and stiff, elastic inclusions on the single crystal macroscopic and microscopic responses. Microstructural characteristics show that such heterogeneities strongly influence the local and global evolution of the slip and twin activities, and in some cases modulate the strength anisotropy that is commonly observed in monolithic single crystals. These results may provide useful indicators toward designing novel composite Mg microstructures. © 2012 Elsevier Ltd. All rights reserved.


Anand A.,National University of Singapore | Kai T.,National University of Singapore
EMBO Journal | Year: 2012

In Drosophila ovaries, distinct Piwi-interacting RNA (piRNA) pathways defend against transposons in somatic and germline cells. Germline piRNAs predominantly arise from bidirectional clusters and are amplified by the ping-pong cycle. In this study, we characterize a novel Drosophila gene, kumo and show that it encodes a conserved germline piRNA pathway component. Kumo contains five tudor domains and localizes to nuage, a unique structure present in animal germline cells, which is considered to be the processing site for germline piRNAs. Transposons targeted by the germline piRNA pathway are derepressed in kumo mutant females. Moreover, germline piRNA production is significantly reduced in mutant ovaries, thereby indicating that kumo is required to generate germline piRNAs. Kumo localizes to the nuage as well as to nucleus early female germ cells, where it is required to maintain cluster transcript levels. Our data suggest that kumo facilitates germline piRNA production by promoting piRNA cluster transcription in the nucleus and piRNA processing at the nuage. © 2012 European Molecular Biology Organization | All Rights Reserved.


Du W.,National University of Singapore
Nature Photonics | Year: 2016

Molecular electronic control over plasmons offers a promising route for on-chip integrated molecular plasmonic devices for information processing and computing. To move beyond the currently available technologies and to miniaturize plasmonic devices, molecular electronic plasmon sources are required. Here, we report on-chip molecular electronic plasmon sources consisting of tunnel junctions based on self-assembled monolayers sandwiched between two metallic electrodes that excite localized plasmons, and surface plasmon polaritons, with tunnelling electrons. The plasmons originate from single, diffraction-limited spots within the junctions, follow power-law distributed photon statistics, and have well-defined polarization orientations. The structure of the self-assembled monolayer and the applied bias influence the observed polarization. We also show molecular electronic control of the plasmon intensity by changing the chemical structure of the molecules and by bias-selective excitation of plasmons using molecular diodes. © 2016 Nature Publishing Group


Sovacool B.K.,National University of Singapore
Energy Policy | Year: 2011

This article begins by defining energy services and identifying how they differ according to sector, urban and rural areas, and direct and indirect uses. It then investigates household energy services divided into three classes: lower income, middle income, and upper income. It finds that the primary energy technologies involved with low-income households involve a greater number of fuels and carriers, ranging from dung and fuelwood to liquefied petroleum gas and charcoal, but a fewer number of services. Middle-income households throughout the world tend to rely on electricity and natural gas, followed by coal, liquefied petroleum gas, and kerosene. These homes utilize energy to produce a much broader range services. The upper class or rich have access to the same energy fuels, carriers, and technologies as middle-income homes and families, but consume more energy (and more high luxury items). The study highlights how focusing on energy services reorients the direction of energy policy interventions, that energy services are neither uniform nor innate, and by noting exciting areas of potential research. © 2010 Elsevier Ltd.


Chowdhury S.,National University of Singapore | Balasubramanian R.,National University of Singapore
Advances in Colloid and Interface Science | Year: 2014

Adsorption technology is widely considered as the most promising and robust method of purifying water at low cost and with high-efficiency. Carbon-based materials have been extensively explored for adsorption applications because of their good chemical stability, structural diversity, low density, and suitability for large scale production. Graphene - a single atomic layer of graphite - is the newest member in the family of carbon allotropes and has emerged as the "celeb" material of the 21st century. Since its discovery in 2004 by Novoselov, Geim and co-workers, graphene has attracted increased attention in a wide range of applications due to its unprecedented electrical, mechanical, thermal, optical and transport properties. Graphene's infinitely high surface-to-volume ratio has resulted in a large number of investigations to study its application as a potential adsorbent for water purification. More recently, other graphene related materials such as graphene oxide, reduced graphene oxide, and few-layered graphene oxide sheets, as well as nanocomposites of graphene materials have also emerged as a promising group of adsorbent for the removal of various environmental pollutants from waste effluents. In this review article, we present a synthesis of the current knowledge available on this broad and versatile family of graphene nanomaterials for removal of dyes, potentially toxic elements, phenolic compounds and other organic chemicals from aquatic systems. The challenges involved in the development of these novel nanoadsorbents for decontamination of wastewaters have also been examined to help identify future directions for this emerging field to continue to grow. © 2013 Elsevier B.V.


Sovacool B.K.,National University of Singapore
Energy Policy | Year: 2011

Drawing from work on governance, this article explores four programs and policies that respond in some way to the challenges induced by climate change and modern energy use. Relying primarily on original data collected from research interviews and field research in seven countries along with four case studies, the article notes that polycentric approaches - those that mix scales (such as local/national or national/global), mechanisms (such as subsidies, tax credits, and mandates), and actors (such as government regulators, business stakeholders, and members of civil society) - can foster equity, inclusivity, information, accountability, organizational multiplicity, and adaptability that result in the resolution of climate and energy related problems. After explaining its case selection and research methods, defining climate and energy governance, and conceptualizing polycentrism, the study explores cases related to electricity supply in Denmark, ethanol production in Brazil, small-scale renewable energy in Bangladesh, and off-grid energy use in China. It concludes by highlighting how polycentrism may enhance effective climate and energy governance, but that further research is needed to fully substantiate that claim. © 2011 Elsevier Ltd.


Sovacool B.K.,National University of Singapore
Energy Policy | Year: 2011

This article offers a critical review of eight tradable permit markets: water permits at Fox River, Wisconsin; the U.S. leaded gasoline phase-out; sulfur dioxide credits under the U.S. Clean Air Act Amendments of 1990; the Regional Clean Air Incentives Market (RECLAIM) for controlling ozone and acid rain in Southern California; renewable energy credit trading at the regional level in the United States; individual transferrable quotas for fisheries at the national level in New Zealand; carbon credits traded under the European Union-Emissions Trading Scheme; and carbon offsets permitted under the Clean Development Mechanism of the Kyoto Protocol. By "critical" the article does not fully weigh the costs and benefits of each tradable credit scheme and instead identifies key challenges and problems. By "review" the author relied exclusively on secondary data from an interdisciplinary review of the academic literature. Rather than performing as economic theory suggests, the article shows that in many cases credit markets are prone to compromises in program design, transaction costs, price volatility, leakage, and environmental degradation. The article concludes by discussing the implications of these problems for those seeking to design more equitable and effective public policies addressing environmental degradation and climate change. © 2010 Elsevier Ltd.


Xiao Y.,National University of Singapore | Chung T.-S.,National University of Singapore
Energy and Environmental Science | Year: 2011

A novel strategy to design molecularly the cavity size and free volume of flexible polyimide materials via thermal treatment of rigid and cross-linkable polyimides grafted with thermal liable side beta-cyclodextrin (CD) molecules is demonstrated in this study. The spaces occupied by the labile groups may become microvoids after low-temperature thermal degradation while the rigid polyimide backbone prevails. The thermal induced cross-linking reaction among polyimide chains may create ultra-fine micro-pores that integrally connect with microvoids. As a result, the thermally cured membranes fabricated from dense polyimide precursors show gas separation performance surpassing the trade-off lines, with tough and flexible mechanical properties. Thermal annealing at 425 °C produces polyimide membranes with the best CO2 permeability of 4016 Barrer with reasonable gas pair selectivity. © 2011 The Royal Society of Chemistry.


Molecular genetic analyses of parentage provide insights into mating systems. Although there are 22,000 members in Malacostraca, not much has been known about mating systems in Malacostraca. The freshwater shrimp Caridina ensifera blue, is a new species belonging to Malacostraca which was discovered recently in Sulawesi, Indonesia. Due to its small body size and low fecundity, this species is an ideal species to study the occurrence and frequency of multiple paternity and to understand of how the low fecundity species persist and evolve. In this study, we developed four polymorphic microsatellites from C. ensifera and applied them to investigate the occurrence and frequency of multiple paternity in 20 C. ensifera broods caught from Lake Matano, Sulawesi. By genotyping the mother and all offspring from each brood we discovered multiple paternity in all 20 broods. In most of the 20 broods, fathers contributed skewed numbers of offspring and there was an apparent inverse correlation between reproductive success of sires and their relatedness to mothers. Our results in combination with recent reports on multiple paternity in crayfish, crab and lobster species suggests that multiple paternity is common in Malacostraca. Skewed contribution of fathers to the numbers of offspring and inverse correlation between reproductive success of sires and their relatedness to mothers suggest that sperm competition occurred and/or pre- and postcopulatory female choice happen, which may be important for avoiding the occurrence of inbreeding and optimize genetic variation in offspring and for persistence and evolution of low fecundity species.


Srinivasan T.N.,National University of Singapore | Gopi Rethinaraj T.S.,National University of Singapore
Energy Policy | Year: 2013

The Fukushima nuclear accident on March 11, 2011 in Japan has severely dented the prospects of growth of civilian nuclear power in many countries. Although Japan's worst nuclear accident was triggered by an unprecedented earthquake and tsunami, inadequate safety countermeasures and collusive ties between the plant operators, regulators, and government officials left the Fukushima Daiichi nuclear plant beyond redemption. A critical examination of the accident reveals that the accumulation of various technical and institutional lapses only compounded the nuclear disaster. Besides technical fixes such as enhanced engineering safety features and better siting choices, the critical ingredient for safe operation of nuclear reactors lie in the quality of human training and transparency of the nuclear regulatory process that keeps public interest-not utility interest-at the forefront. The need for a credible and transparent analysis of the social benefits and risks of nuclear power is emphasized in the context of energy portfolio choice. © 2012 Elsevier Ltd.


Colas J.T.,California Institute of Technology | Hsieh P.-J.,National University of Singapore
Human Brain Mapping | Year: 2014

Intuition and an assumption of basic rationality would suggest that people evaluate a stimulus on the basis of its properties and their underlying utility. However, various findings suggest that evaluations often depend not only on what is being evaluated, but also on contextual factors. Here we demonstrate a further departure from normative decision making: Aesthetic evaluations of abstract fractal art by human subjects were predicted from pre-stimulus patterns of BOLD fMRI signals across a distributed network of frontal regions before the stimuli were presented. This predictive power was dissociated from motor biases in favor of pressing a particular button to indicate one's choice. Our findings suggest that endogenous neural signals present before stimulation can bias decisions at multiple levels of representation when evaluating stimuli. © 2013 Wiley Periodicals, Inc.


Valentine S.V.,National University of Singapore
Energy Policy | Year: 2011

This paper analyzes Japan's national power generation strategy with a view to explaining Japan's phlegmatic approach to wind energy development. The analysis concludes that Japan's current power generation strategy is not optimized to achieve the government's three strategic energy objectives of simultaneously enhancing economic security, national energy security and environmental security (3Es). To achieve long-run energy sustainability, Japan needs to strive to phase out nuclear power, which is the centerpiece of its current power generation strategy. The analysis concludes by offering four suggestions for a sustainable 3E power generation strategy: (1) internalize all external costs associated with power generation technologies in order to level the economic playing field, (2) increase feed-in mandates for renewable energy to 20%, (3) fully liberalize the power generation industry and (4) intensify R&D in energy storage technologies to support intermittent renewable technologies. © 2009 Elsevier Ltd.


Lei Z.,National University of Singapore | Christov N.,National University of Singapore | Zhao X.S.,National University of Singapore
Energy and Environmental Science | Year: 2011

A method for preparing three-dimensional (3D) carbon-based architectures consisting of mesoporous carbon spheres intercalated between graphene sheets is demonstrated in this paper. Colloidally dispersed negatively charged graphene oxide (GO) sheets strongly interacted with positively charged mesoporous silica spheres (MSS) to form a MSS-GO composite. The MSS were then used as template for replicating mesoporous carbon spheres (MCS) via a chemical vapor deposition process, during which the GO sheets were reduced to reduced graphene oxide (RGO). Removal of the silica spheres left behind a 3D hierarchical porous carbon architecture with slightly crumpled graphene sheets intercalated with MCS. The 3D carbon structure contained a low amount of oxygen (3.2% of atomic ratio of O/C) than a RGO sample (10.1%), which was prepared by using the chemical reduction method with hydrazine as the reducing agent. Thermal annealing of the 3D carbon structure in ammonia atmosphere further reduced the O/C atomic ratio to 1.6%. The capacitive performance of the samples as supercapacitor electrodes was investigated using the cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy techniques. The 3D carbon structure showed a substantially lower equivalent series resistance and a higher power capability than the RGO electrode. In addition, the 3D carbon electrode exhibited an excellent electrochemical cyclability with 94% capacitance retention after 1000 cycles of galvanostatic charge-discharge. The method demonstrated in this work opens up a new route to the preparation of 3D graphene-based architectures for supercapacitor applications. © The Royal Society of Chemistry 2011.


Alkema L.,National University of Singapore | You D.,United Nations Childrens Fund
PLoS Medicine | Year: 2012

Background: Millennium Development Goal 4 calls for a reduction in the under-five mortality rate (U5MR) by two-thirds between 1990 and 2015. In 2011, estimates were published by the United Nations Inter-agency Group for Child Mortality Estimation (UN IGME) and the Institute for Health Metrics and Evaluation (IHME). The difference in the U5MR estimates produced by the two research groups was more than 10% and corresponded to more than ten deaths per 1,000 live births for 10% of all countries in 1990 and 20% of all countries in 2010, which can lead to conflicting conclusions with respect to countries' progress. To understand what caused the differences in estimates, we summarised differences in underlying data and modelling approaches used by the two groups, and analysed their effects. Methods and Findings: UN IGME and IHME estimation approaches differ with respect to the construction of databases and the pre-processing of data, trend fitting procedures, inclusion and exclusion of data series, and additional adjustment procedures. Large differences in U5MR estimates between the UN IGME and the IHME exist in countries with conflicts or civil unrest, countries with high HIV prevalence, and countries where the underlying data used to derive the estimates were different, especially if the exclusion of data series differed between the two research groups. A decomposition of the differences showed that differences in estimates due to using different data (inclusion of data series and pre-processing of data) are on average larger than the differences due to using different trend fitting methods. Conclusions: Substantial country-specific differences between UN IGME and IHME estimates for U5MR and the number of under-five deaths exist because of various differences in data and modelling assumptions used. Often differences are illustrative of the lack of reliable data and likely to decrease as more data become available. Improved transparency on methods and data used will help to improve understanding about the drivers of the differences. Please see later in the article for the Editors' Summary. © 2012 Alkema, You.


Raju A.,National University of Singapore | Chang D.W.,University of Chicago
Annals of Surgery | Year: 2015

Objective: A comprehensive literature review of VLNT with updates and comparisons on current application, techniques, results, studies and possible future implications. Background: Lymphedema is a debilitating condition that often results secondary to treatment of cancer. Unfortunately there is no cure. However, microsurgical procedures such as VLNT has gained popularity as there have been increasing reports that VLNT may help alleviate the severity of lymphedema. Methods: A review of literature was conducted over major medical indices (PubMed-MEDLINE, Factiva, Scopus, Sciencedirect, EMBASE). Search terms were focused on vascularized, lymph node transfer (also autologous, lymph node transplant) to cover both human and animal studies. Each study was verified for the nature of the procedure; a free microsurgical flap containing lymph nodes for the purpose of relieving lymphedema. Results: There are human and animal studies that individually report clear benefits, but because of methodological shortcomings comparative studies with uniform patient selection and monitoring are lacking. Conclusions: Although the results with the use of VLNT for treatment of lymphedema have been largely positive, further exploration into standardized protocols for diagnosis, treatment optimization, and patient outcomes assessment is needed. © 2014 Wolters Kluwer Health, Inc. All rights reserved.


Huang D.,University of California at San Diego | Huang D.,National University of Singapore
PLoS ONE | Year: 2012

A substantial proportion of the world's living species, including one-third of the reef-building corals, are threatened with extinction and in pressing need of conservation action. In order to reduce biodiversity loss, it is important to consider species' contribution to evolutionary diversity along with their risk of extinction for the purpose of setting conservation priorities. Here I reconstruct the most comprehensive tree of life for the order Scleractinia (1,293 species) that includes all 837 living reef species, and employ a composite measure of phylogenetic distinctiveness and extinction risk to identify the most endangered lineages that would not be given top priority on the basis of risk alone. The preservation of these lineages, not just the threatened species, is vital for safeguarding evolutionary diversity. Tests for phylogeny-associated patterns show that corals facing elevated extinction risk are not clustered on the tree, but species that are susceptible, resistant or resilient to impacts such as bleaching and disease tend to be close relatives. Intensification of these threats or extirpation of the endangered lineages could therefore result in disproportionate pruning of the coral tree of life. © 2012 Danwei Huang.


Adams S.,National University of Singapore
Structure and Bonding | Year: 2014

Based on an investigation of empirical links of the bond valence method to observable quantities, especially the electron density at the bond critical point as well as absolute electronic potential and hardness values in the frame of the hard and soft acids and bases concept, it is ascertained that bond valence can be understood as a functional of valence electron density. Therefrom a systematic approach for deriving bond valence parameters and related quantities such as coordination numbers and bond breaking energies is discussed that together allow for a conversion of the bond valence method to a simple effective atomistic forcefield. © Springer-Verlag Berlin Heidelberg 2013.


Bharadwaj A.,National University of Singapore | Ting Y.-P.,National University of Singapore
Bioresource Technology | Year: 2013

Bioleaching of spent hydrotreating catalyst by thermophillic archae Acidianus brierleyi was investigated. The spent catalyst (containing Al, Fe, Ni and Mo as major elements) was characterized, and the effect of pretreatment (decoking) on two-step and spent medium leaching was examined at 1% w/v pulp density. Decoking resulted in removal of carbonaceous deposits and volatile impurities, and affected the solubility of metal compounds through oxidization of the metal sulfides. Nearly 100% extraction was achieved using spent medium leaching for Fe, Ni and Mo, and 67% for Al. Bioleaching reduced nickel concentration in the leachate below the regulated levels for safe waste disposal. Chemical (i.e. abiotic) leaching using equimolar concentration of sulfuric acid produced by the bacteria during two-step process achieved a lower leaching efficiency (by up to 30%). Results indicated that A. brierleyi successfully leached heavy metals from spent catalyst. © 2012 Elsevier Ltd.


Li X.,National University of Singapore | Lee A.Y.W.,National University of Singapore
Journal of Biological Chemistry | Year: 2010

Semaphorins and plexins are implicated in the progression of various types of cancer, although the molecular basis has not been fully elucidated. Here, we report the expression of plexin-B3 in glioma cells, which upon stimulation by its ligand Sema5A results in significant inhibition of cell migration and invasion. A search for the underlying mechanism revealed direct interaction of plexin-B3 with RhoGDP dissociation inhibitor α (RhoGDIα), a negative regulator of RhoGTPases that blocks guanine nucleotide exchange and sequesters them away from the plasma membrane. Glioma cells challenged with Sema5A indeed showed a marked reduction in Rac1-GTP levels by 60%, with a concomitant disruption of lamellipodia. The inactivation of Rac1 was corroborated to contribute to the impediment of glioma cell invasion by Sema5A, as supported by the abolishment of effect upon forced expression of a constitutively active Rac1 mutant. Furthermore, silencing the endogenous expression of RhoGDIα in glioma cells was found to be sufficient in abrogating the down-regulation of Rac1-GTP and the ensuing suppression of glioma cell motility induced by Sema5A. Mechanistically, we provide evidence that Sema5A promotes Rac1 recruitment to RhoGDIα and reduces its membrane localization in a plexin-B3-dependent manner, thereby preventing Rac1 activation. This represents a novel signaling of semaphorin and plexin in the control of cell motility by indirect inactivation of Rac1 through RhoGDIα © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.


Tsang M.,National University of Singapore
Physical Review Letters | Year: 2012

I propose a general quantum hypothesis testing theory that enables one to test hypotheses about any aspect of a physical system, including its dynamics, based on a series of observations. For example, the hypotheses can be about the presence of a weak classical signal continuously coupled to a quantum sensor, or about competing quantum or classical models of the dynamics of a system. This generalization makes the theory useful for quantum detection and experimental tests of quantum mechanics in general. In the case of continuous measurements, the theory is significantly simplified to produce compact formulas for the likelihood ratio, the central quantity in statistical hypothesis testing. The likelihood ratio can then be computed efficiently in many cases of interest. Two potential applications of the theory, namely, quantum detection of a classical stochastic waveform and test of harmonic-oscillator energy quantization, are discussed. © 2012 American Physical Society.


Tsang M.,National University of Singapore
Physical Review Letters | Year: 2012

I propose quantum versions of the Ziv-Zakai bounds as alternatives to the widely used quantum Cramér-Rao bounds for quantum parameter estimation. From a simple form of the proposed bounds, I derive both a Heisenberg error limit that scales with the average energy and a limit similar to the quantum Cramér-Rao bound that scales with the energy variance. These results are further illustrated by applying the bound to a few examples of optical phase estimation, which show that a quantum Ziv-Zakai bound can be much higher and thus tighter than a quantum Cramér-Rao bound for states with highly non-Gaussian photon-number statistics in certain regimes and also stay close to the latter where the latter is expected to be tight. © 2012 American Physical Society.


Novitsky A.,Technical University of Denmark | Qiu C.-W.,National University of Singapore | Lavrinenko A.,Technical University of Denmark
Physical Review Letters | Year: 2012

A Bessel beam without an axial gradient can exert a pulling force on an object [A. Novitsky, C.W. Qiu, and H. Wang, Phys. Rev. Lett. 107, 203601 (2011)PRLTAO0031-900710.1103/PhysRevLett.107.203601]. However, it cannot be called a "tractor beam" per se, as long as the light pulling effect is ultrasensitive to the object's material and size, a perturbation of which will make the optical traction go away. In this Letter, we investigate and report on the universality for a Bessel beam to be either a material-independent or size-independent optical tractor beam within the dipolar regime. Moreover, a general condition for a nonparaxial laser to be simultaneously a material- and size-independent tractor beam is proposed. These universal pulling effects and conditions are discussed in association with insight on modified far-field scattering, scattering resonances, and induced polarizabilities. Interestingly, we find that the acoustic pulling force exhibits only size independence, owing to the acoustic scattering theory in contrast to the light scattering counterpart. The findings pave the way for the realistic engineering and application of universal tractor beams pulling a wide variety of objects. © 2012 American Physical Society.


Ho D.Y.H.,National University of Singapore | Gong J.,National University of Singapore
Physical Review Letters | Year: 2012

Though topological aspects of energy bands are known to play a key role in quantum transport in solid-state systems, the implications of Floquet band topology for transport in momentum space (i.e., acceleration) have not been explored so far. Using a ratchet accelerator model inspired by existing cold-atom experiments, here we characterize a class of extended Floquet bands of one-dimensional driven quantum systems by Chern numbers, reveal topological phase transitions therein, and theoretically predict the quantization of adiabatic transport in momentum space. Numerical results confirm our theory and indicate the feasibility of experimental studies. © 2012 American Physical Society.


Wang Z.,National University of Singapore | Ho P.C.,National University of Singapore
Biomaterials | Year: 2010

We reported a precise engineered nanocapsule encapsulating a neovasculature disruption agent, combretastatin A4 (CA4) in a matrix that was made up of paclitaxel (PTX) conjugated amphiphilic polyester. The nanocapsule was able to release CA4 and PTX sequentially for temporal antiangiogenesis and anticancer activities. The nanocapsule has a small particle size at 68 nm with narrow size distribution (∼0.15). Cellular uptake of the nanocapsule was efficient, and detectable at as early as 20 min, and drugs sequestered in the nanocapsule could exert effective therapeutic effects on tumor neovasculature and cancer cells, respectively. Biodistribution experiments demonstrated the long circulation of nanocapsule in body fluid and the preferential accumulation of nanocapsule in tumor. Both in vivo artificial pro-angiogenesis and tumor xenograft assays demonstrated the promising therapeutic effect of the nanocapsule on tumor vasculature disruption, tumor cell proliferation inhibition and tumor cell apoptosis induction. The intrasplenic liver metastasis experiment also confirmed the liver metastatic prevention capacity of this nanocapsule. In summary, the findings indicated that this dual drug loaded nanocapsule with sequential drug delivery capacity is a promising candidate in combinatorial therapy in fighting against cancer, and may open an avenue for cancer therapy and diagnosis. © 2010 Elsevier Ltd.


Arnold K.J.,National University of Singapore | Baden M.P.,National University of Singapore | Barrett M.D.,National University of Singapore
Physical Review Letters | Year: 2012

We make a detailed experimental study of the threshold for the self-organization of thermal Rb87 atoms coupled to a high-finesse cavity over a range of atom numbers and cavity detunings. We investigate the difference between probing with a traveling wave and a retroreflected lattice. These two scenarios lead to qualitatively different behavior in terms of the response of the system as a function of cavity detuning with respect to the probe. In both cases, we confirm a N -1 scaling of the threshold with atom number. © 2012 American Physical Society.


Chatterjee D.K.,National University of Singapore | Gnanasammandhan M.K.,National University of Singapore | Zhang Y.,National University of Singapore
Small | Year: 2010

Fluorescent labels have been widely used for biological applications, primarily in imaging and assays. Traditional fluorophores such as fluorescent dyes are mainly based on downconversion fluorescence, which have several drawbacks such as photobleaching, high background noise from autofluorescence, and considerable photodamage to biological materials. Upconverting fluorescent nanoparticles emit detectable photons of higher energy in the near-infrared (NIR) or visible range upon irradiation with an NIR light in a process termed 'upconversion.' They overcome some of the disadvantages faced by conventional downconversion labels, thus making them an ideal fluorescent label for biological applications. This review looks at the development of these particles, critically examines the reported applications, and discusses their future in biomedicine. Upconverting fluorescent nanoparticles emit detectable photons of higher energy in the near-infrared (NIR) or visible range upon irradiation with an NIR light in a process termed 'upconversion.' They overcome some of the disadvantages faced by conventional downconversion labels, thus making them an ideal fluorescent label for biological applications. The lead-in photograph depicts rare-earth upconversion nanoparticles and their use in cell imaging. Copyright © 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Veluswamy H.P.,National University of Singapore | Kumar R.,CSIR - National Chemical Laboratory | Linga P.,National University of Singapore
Applied Energy | Year: 2014

Hydrogen is looked upon as the next generation clean energy carrier, search for an efficient material and method for storing hydrogen has been pursued relentlessly. Improving hydrogen storage capacity to meet DOE targets has been challenging and research efforts are continuously put forth to achieve the set targets and to make hydrogen storage a commercially realizable process. This review comprehensively summarizes the state of the art experimental work conducted on the storage of hydrogen as hydrogen clathrates both at the molecular level and macroscopic level. It identifies future directions and challenges for this exciting area of research. Hydrogen storage capacities of different clathrate structures - sI, sII, sH, sVI and semi clathrates have been compiled and presented. In addition, promising new approaches for increasing hydrogen storage capacity have been described. Future directions for achieving increased hydrogen storage and process scale up have been outlined. Despite few limitations in storing hydrogen in the form of clathrates, this domain receives prominent attention due to more environmental-friendly method of synthesis, easy recovery of molecular hydrogen with minimum energy requirement, and improved safety of the process. © 2014 Elsevier Ltd.


Bernhammer J.C.,National University of Singapore | Huynh H.V.,National University of Singapore
Organometallics | Year: 2014

A series of six benzimidazolium salts with an alkyl-alkyl thioether moiety in the side chain has been synthesized. While it was impossible to obtain the platinum(II) complexes by direct reaction between ligand precursors and basic platinum salts, the mild silver carbene transfer reaction gave the desired complexes in all cases. X-ray crystallography confirmed the expected κ2C,S coordination mode of the benzimidazolin-2-ylidene ligands, with a cis arrangement of the carbene and the hemilabile thioether moieties in all complexes. Preliminary studies of the catalytic activity of these complexes showed them to be active catalysts for the intermolecular hydroamination of alkynes with sterically hindered anilines in conjunction with silver triflate. Additionally, the complexes catalyzed the hydrosilylation of alkenes with excellent yields and good regioselectivity. © 2013 American Chemical Society.


Wang F.,Institute of Materials Research and Engineering of Singapore | Wang F.,National University of Singapore | Liu X.,Institute of Materials Research and Engineering of Singapore | Liu X.,National University of Singapore
Accounts of Chemical Research | Year: 2014

ConspectusLanthanide-doped nanoparticles exhibit unique luminescent properties, including large Stokes shift, sharp emission bandwidth, high resistance to optical blinking, and photobleaching, as well as the unique ability to convert long-wavelength stimulation into short-wavelength emission. These attributes are particularly needed for developing luminescent labels as alternatives to organic fluorophores and quantum dots. In recent years, the well-recognized advantages of upconversion nanocrystals as biomarkers have been manifested in many important applications, such as highly sensitive molecular detection and autofluorescence-free cell imaging. However, their potential in multiplexed detection and multicolor imaging is rarely exploited, largely owing to the research lagging on multicolor tuning of these particles.Lanthanide doping typically involves an insulating host matrix and a trace amount of lanthanide dopants embedded in the host lattice. The luminescence observed from these doped crystalline materials primarily originates from electronic transitions within the [Xe]4fn configuration of the lanthanide dopants. Thus a straightforward approach to tuning the emission is to dope different lanthanide activators in the host lattice. Meanwhile, the host lattice can exert a crystal field around the lanthanide dopants and sometimes may even exchange energy with the dopants. Therefore, the emission can also be modulated by varying the host materials. Recently, the advance in synthetic methods toward high quality core-shell nanocrystals has led to the emergence of new strategies for emission modulation. These strategies rely on precise control over either energy exchange interactions between the dopants or energy transfer involving other optical entities.To provide a set of criteria for future work in this field, we attempt to review general and emerging strategies for tuning emission spectra through lanthanide doping. With significant progress made over the past several years, we now are able to design and fabricate nanoparticles displaying tailorable optical properties. In particular, we show that, by rational control of different combinations of dopants and dopant concentration, a wealth of color output can be generated under single-wavelength excitation. Strikingly, unprecedented single-band emissions can be obtained by careful selection of host matrices. By incorporating a set of lanthanide ions at defined concentrations into different layers of a core-shell structure, the emission spectra of the particles are largely expanded to cover almost the entire visible region, which is hardly accessible by conventional bulk phosphors. Importantly, we demonstrate that an inert-shell coating provides the particles with stable emission against perturbation in surrounding environments, paving the way for their applications in the context of biological networks. © 2014 American Chemical Society.


Sun Z.,National University of Singapore | Zeng Z.,National University of Singapore | Wu J.,National University of Singapore | Wu J.,Institute of Materials Research and Engineering of Singapore
Accounts of Chemical Research | Year: 2014

ConspectusResearchers have studied polycyclic aromatic hydrocarbons (PAHs) for more than 100 years, and most PAHs in the neutral state reported so far have a closed-shell electronic configuration in the ground state. However, recent studies have revealed that specific types of polycyclic hydrocarbons (PHs) could have a singlet biradical ground state and exhibit unique electronic, optical, and magnetic activities. With the appropriate stabilization, these new compounds could prove useful as molecular materials for organic electronics, nonlinear optics, organic spintronics, organic photovoltaics, and energy storage devices. However, before researchers can use these materials to design new devices, they need better methods to synthesize these molecules and a better understanding of the fundamental relationship between the structure and biradical character of these compounds and their physical properties. Their biradical character makes these compounds difficult to synthesize. These compounds are also challenging to physically characterize and require the use of various experimental techniques and theoretic methods to comprehensively describe their unique properties.In this Account, we will discuss the chemistry and physics of three types of PHs with a significant singlet biradical character, primarily developed in our group. These structures are zethrenes, Z-shaped quinoidal hydrocarbons; hydrocarbons that include a proaromatic extended p-quinodimethane unit; and periacenes, acenes fused in a peri-Arrangement. We used a variety of synthetic methods to prepare these compounds and stabilized them using both thermodynamic and kinetic approaches. We probed their ground-state structures by electronic absorption, NMR, ESR, SQUID, Raman spectroscopy, and X-ray crystallography and also performed density functional theory calculations. We investigated the physical properties of these PHs using various experimental methods such as one-photon absorption, two-photon absorption, transient absorption spectroscopy, electrochemistry, and spectroelectrochemistry.These systematic studies revealed that aromaticity played a very important role in determining their singlet biradical character, which is critically related to both their physical properties and their chemical reactivity. In particular, we found that Clars aromatic sextet rule, which is useful for the closed-shell PAHs, can also predict the relative biradical character of benzenoid PH-based singlet biradicaloids. Other factors, such as structural flexibility of the biradical and quinoid resonance forms and the participation of the substitution in the π-conjugation, also influence the biradical character. These molecular materials demonstrate a number of unique properties such as near-infrared absorption, redox amphotericity, large two-photon absorption cross section, short excited state lifetime, stimuli-responsive magnetic activity, and singlet fission, which suggests promise for future applications. © 2014 American Chemical Society.


Wang F.,National University of Singapore | Wang J.,National University of Singapore | Liu X.,National University of Singapore
Angewandte Chemie - International Edition | Year: 2010

A series of Yb/Tm co-doped NaGdF4nanoparticles without or with a thin surface protection layer provide direct evidence of a surface quenching effect on size-dependent upconversion luminescence (see picture). The coating preserves the optical integrity of the nanoparticles (right-hand spectrum) and minimizes emission loss induced by surface quenching. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.


Lucky S.S.,National University of Singapore | Soo K.C.,National Cancer Center Singapore | Zhang Y.,National University of Singapore | Zhang Y.,Zhejiang Normal University
Chemical Reviews | Year: 2015

The application of nanoparticles in photodynamic therapy (PDT) has been a major stride forward in resolving some of the challenges associated with classic photosensitizer (PS). These nanoparticles are very versatile due to the existence of a variety of polymers and manufacturing methods, and thus the chemical composition and architecture of the nanoparticles can be customized to accommodate PSs with varying degrees of hydrophobicity, molecular weight, or charge. Furthermore, the surface properties, morphologies, and compositions of polymeric matrices can be easily optimized to achieve controlled degradation of the polymer and drug release kinetics. PDT using upconversion nanoparticles (UCNs) doped with PS is becoming the new sensation in the field with clear advantages over most other nanoparticles. UCNs act both as carriers of PS as well as enables indirect excitation of the accompanying PS with upconverted light upon excitation with low energy NIR light. The future of PDT lies in the development of a single versatile and efficient nanoparticle that encompasses its applicability in both bioimaging as well as PDT.


Zhu Q.,National University of Singapore | Lu Y.,National University of Singapore
Chemical Communications | Year: 2010

Novel l-threonine-derived bifunctional organic catalysts containing primary amine and sulfonamide groups were utilized to promote asymmetric conjugate addition of α,α-disubstitued aldehydes to 1,1-bis(benzenesulfonyl) ethylene. The adducts with quaternary stereogenic centers adjacent to an aldehyde group were obtained in high yield and with good enantioselectivity. © 2010 The Royal Society of Chemistry.


Bansal A.,National University of Singapore | Zhang Y.,National University of Singapore
Accounts of Chemical Research | Year: 2014

Conspectus"Smart" stimuli-responsive nanomaterials are becoming popular as targeted delivery systems because they allow the use of internal or external stimuli to achieve spatial or temporal control over the delivery process. Among the stimuli that have been used, light is of special interest because it is not only noninvasive but also controllable both spatially and temporally, thus allowing unprecedented control over the delivery of bioactive molecules such as nucleic acids, proteins, drugs, etc. This is particularly advantageous for biomedical applications where specificity and selectivity are highly desired.Several strategies have evolved under the umbrella of light based delivery systems and can be classified into three main groups. The first strategy involves "caging" of the bioactive molecule using photolabile groups, loading these caged molecules onto a carrier and then "uncaging" or activating them at the targeted site upon irradiation with light of a particular wavelength. The second strategy makes use of nanocarriers that themselves are made photoresponsive either through modification with photosensitive groups or through the attachment of photolinkers on the carrier surface. These nanoparticles upon irradiation dissociate, releasing the cargo encapsulated within, or the photolinkers attaching the cargo to the surface get cleaved, resulting in release. The third approach makes use of the surface plasmon resonance of noble metal based nanoparticles. Upon irradiation with light at the plasmon resonant frequency, the resulting thermal or nonthermal field enhancement effects facilitate the release of bioactive molecules loaded onto the nanoparticles. In addition, other materials, certain metal sulfides, graphene oxide, etc., also exhibit photothermal transduction that can be exploited for targeted delivery. These approaches, though effective, are constrained by their predominant use of UV or visible light to which most photolabile groups are sensitive. Near infrared (NIR) excitation is preferred because NIR light is safer and can penetrate deeper in biological tissues. However, most photolabile groups cannot be excited by NIR light directly. So light conversion from NIR to UV/visible is required. Nanomaterials that display upconversion or two-photon-excitation properties have been developed that can serve as nanotransducers, converting NIR to UV/visible light to which the aforementioned photoresponsive moieties are sensitive. This Account will review the existing light-based nanoparticle delivery systems, their applications, the limitations they face, and the technologies that have emerged in an effort to overcome these limitations. © 2014 American Chemical Society.


Brunham L.R.,University of British Columbia | Hayden M.R.,University of British Columbia | Hayden M.R.,National University of Singapore
Science | Year: 2012

Whole-genome sequencing may dramatically alter medicine, but there are obstacles to broad implementation.


Qiu G.,National University of Singapore | Ting Y.-P.,National University of Singapore
Bioresource Technology | Year: 2013

An osmotic membrane bioreactor was developed for wastewater treatment. The effects of salt accumulation on system performance and microbial community dynamics were investigated. Evident deterioration of biological activity, especially nitrification, was observed, which resulted in significant accumulation of organic matter and NH4 +-N within the bioreactor. Arising from the elevation of salinity, almost all the dominant species was taken over by high salt-tolerant species. Significant succession among different species of Nitromonas was observed for ammonia-oxidizing bacteria. For nitrite-oxidizing bacteria, Nitrospira was not evidently affected, whereas Nitrobacter was eliminated from the system. Salt accumulation also caused significant shifts in denitrifying bacterial community from α- to γ-Proteobacteria members. Overall, the microbial community adapted to the elevated salinity conditions and brought about a rapid recovery of the biological activity. Membrane fouling occurred but was insignificant. Biofouling and inorganic scaling coexisted, with magnesium/calcium phosphate/carbonate compounds identified as the inorganic foulants. © 2013 Elsevier Ltd.


Qin Y.,National University of Singapore
Asian Economic Policy Review | Year: 2016

China has been heavily investing in transportation infrastructure since the 1990s. Consequently, connectivity has been significantly improved, both within China and between China and other countries. Such large-scale investments have been made possible by various financing mechanisms from the central government, local governments, and the private sector. Research findings generally indicate that these infrastructure investments bring economic prosperity to the country, affect the distribution of economic activities, reduce poverty to a certain extent, and promote economic integration. The future trends of connectivity changes in China and relevant policy recommendations are also discussed in this paper. © 2016 Japan Center for Economic Research


Zhang X.,National University of Singapore | Bian J.-S.,National University of Singapore
ACS Chemical Neuroscience | Year: 2014

Hydrogen sulfide (H2S) used to be known as a toxic gas. However, in the last two decades, accumulating evidence has revealed its role as a bioactive molecule in the biological systems. H2S has relatively high expression in the brain, exerting multiple functions in both health and diseases. It modulates neurotransmission by influencing behaviors of NMDA receptors and second messenger systems including intracellular Ca2+ concentration and intracellular cAMP levels and so forth. H2S shows potential therapeutic value in several CNS diseases including Alzheimer's disease, Parkinson's disease, ischemic stroke, and traumatic brain injury. As a neuroprotectant, H2S produces antioxidant, anti-inflammatory, and antiapoptotic effects in pathological situations. Sulfhydration of target proteins is an important mechanism underlying these effects. This Review summarizes the current understanding of H2S in the central nervous system, with emphasis on its role as a neuromodulator and a neuroprotectant. © 2014 American Chemical Society.


Carod-Artal F.J.,Raigmore Hospital | Carod-Artal F.J.,International University of Catalonia | Wichmann O.,Robert Koch Institute | Farrar J.,National University of Singapore | Gascon J.,University of Barcelona
The Lancet Neurology | Year: 2013

Dengue is the second most common mosquito-borne disease affecting human beings. In 2009, WHO endorsed new guidelines that, for the first time, consider neurological manifestations in the clinical case classification for severe dengue. Dengue can manifest with a wide range of neurological features, which have been noted-depending on the clinical setting-in 0·5-21% of patients with dengue admitted to hospital. Furthermore, dengue was identified in 4-47% of admissions with encephalitis-like illness in endemic areas. Neurological complications can be categorised into dengue encephalopathy (eg, caused by hepatic failure or metabolic disorders), encephalitis (caused by direct virus invasion), neuromuscular complications (eg, Guillain-Barré syndrome or transient muscle dysfunctions), and neuro-ophthalmic involvement. However, overlap of these categories is possible. In endemic countries and after travel to these regions, dengue should be considered in patients presenting with fever and acute neurological manifestations. © 2013 Elsevier Ltd.


Berger F.,National University of Singapore | Twell D.,University of Leicester
Annual Review of Plant Biology | Year: 2011

The flowering plant germline is produced during the haploid gametophytic stage. Defining the germline is complicated by the extreme reduction of the male and female gametophytes, also referred to as pollen and embryo sac, respectively. Both male and female gamete progenitors are segregated by an asymmetric cell division, as is the case for the germline in animals. Genetic studies and access to the transcriptome of isolated gametes have provided a regulatory framework for the mechanisms that define the male germline. What specifies female germline identity remains unknown. Recent evidence indicates that an auxin gradient provides positional information and plays a role in defining the identity of the female gamete lineage. The animal germline is also marked by production of small RNAs, and recent evidence indicates that this trait might be shared with the plant gamete lineage. Copyright © 2011 by Annual Reviews. All rights reserved.


Leong D.T.,National University of Singapore | Ng K.W.,Nanyang Technological University
Advanced Drug Delivery Reviews | Year: 2014

For decades, 2D cell culture format on plastic has been the main workhorse in cancer research. Though many important understandings of cancer cell biology were derived using this platform, it is not a fair representation of the in vivo scenario. In this review, both established and new 3D cell culture systems are discussed with specific references to anti-cancer drug and nanomedicine applications. 3D culture systems exploit more realistic spatial, biochemical and cellular heterogeneity parameters to bridge the experimental gap between in vivo and in vitro settings when studying the performance and efficacy of novel nanomedicine strategies to manage cancer. However, the complexities associated with 3D culture systems also necessitate greater technical expertise in handling and characterizing in order to arrive at meaningful experimental conclusions. Finally, we have also provided future perspectives where cutting edge 3D culture technologies may be combined with under-explored technologies to build better in vitro cancer platforms. © 2014 Elsevier B.V.


Tang Z.,National University of Singapore | Tang C.-H.,National University of Singapore | Gong H.,National University of Singapore
Advanced Functional Materials | Year: 2012

The demand for advanced energy storage devices such as supercapacitors and lithium-ion batteries has been increasing to meet the application requirements of hybrid vehicles and renewable energy systems. A major limitation of state-of-art supercapacitors lies in their relatively low energy density compared with lithium batteries although they have superior power density and cycle life. Here, we report an additive-free, nano-architectured nickel hydroxide/carbon nanotube (Ni(OH) 2/CNT) electrode for high energy density supercapacitors prepared by a facile two-step fabrication method. This Ni(OH) 2/CNT electrode consists of a thick layer of conformable Ni(OH) 2 nano-flakes on CNT bundles directly grown on Ni foams (NFs) with a very high areal mass loading of 4.85 mg cm -2 for Ni(OH) 2. Our Ni(OH) 2/CNT/NF electrode demonstrates the highest specific capacitance of 3300 F g -1 and highest areal capacitance of 16 F cm -2, to the best of our knowledge. An asymmetric supercapacitor using the Ni(OH) 2/CNT/NF electrode as the anode assembled with an activated carbon (AC) cathode can achieve a high cell voltage of 1.8 V and an energy density up to 50.6 Wh/kg, over 10 times higher than that of traditional electrochemical double-layer capacitors (EDLCs). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Xiong S.,National University of Singapore | Chen J.S.,Nanyang Technological University | Lou X.W.,Nanyang Technological University | Zeng H.C.,National University of Singapore
Advanced Functional Materials | Year: 2012

In this work, a novel hydrothermal route is developed to synthesize cobalt carbonate hydroxide, Co(CO 3) 0.5(OH)·0. 11H 2O. In this method, sodium chloride salt is utilized to organize single-crystalline nanowires into a chrysanthemum-like hierarchical assembly. The morphological evolution process of this organized product is investigated by examining different reaction intermediates during the synthesis. The growth and thus the final assembly of the Co(CO 3) 0.5(OH) ·0.11H 2O can be finely tuned by selecting preparative parameters, such as the molar ratio of the starting chemicals, the additives, the reaction time and the temperature. Using the flower-like Co(CO 3) 0.5(OH)·0.11H 2O as a solid precursor, quasi-single-crystalline mesoporous Co 3O 4 nanowire arrays are prepared via thermal decomposition in air. Furthermore, carbon can be added onto the spinel oxide by a chemical-vapor-deposition method using acetylene, which leads to the generation of carbon-sheathed CoO nanowire arrays (CoO@C). Through comparing and analyzing the crystal structures, the resultant products and their high crystallinity can be explained by a sequential topotactic transformation of the respective precursors. The electrochemical performances of the typical cobalt oxide products are also evaluated. It is demonstrated that tuning of the surface texture and the pore size of the Co 3O 4 products is very important in lithium-ion-battery applications. The carbon-decorated CoO nanowire arrays exhibit an excellent cyclic performance with nearly 100% capacity retention in a testing range of 70 cycles. Therefore, this CoO@C nanocomposite can be considered to be an attractive candidate as an anode material for further investigation. The controlled, NaCl-mediated synthesis of chrysanthemum-like Co(CO 3) 0.5(OH)·0.11H 2O is demonstrated. The effects of the synthetic conditions are investigated in detail. The Co(CO 3) 0.5(OH)·0.11H 2O is converted to Co 3O 4 nanowire arrays by direct thermal decomposition and then to carbon-coated CoO (CoO@C) under the reducing ambience of C 2H 2. These CoO@C nanowire arrays are promising candidates for lithium-ion-battery applications. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Diao Y.Y.,National University of Singapore | Liu X.Y.,National University of Singapore
Advanced Functional Materials | Year: 2012

This paper aims to give an overview on the recent progress of controlled colloidal assembly as a unique experimental modeling system to study the general crystallization mechanism, i.e., the kinetics of nucleation, growth, and defects formation, and as a template for photonic crystals engineering. Such a system allows us not only to visualize some "atomic" details of the nucleation and surface process of crystallization, but also to treat quantitatively the previous models to an extent that has never been achieved before by other approaches. As such, the kinetic process of nucleation was quantitatively examined at the single particle level for the first time, allowing the identification of the deviations from the classical theories. The application of the electrically controlled colloidal crystallization to the modeling of the kinetics of some important processes of crystallization, i.e., multistep crystallization, supersaturation-driven structural mismatch nucleation, defect creation and migration kinetics, surface roughening, etc., has brought our knowledge to a new phase. Apart from the fundamental aspects, the controlled colloidal crystallization has attracted significant attention in many applications. In this regard, the application of colloidal crystallization to the fabrication of photonic crystals and the biomimicking of natural structure colors will be examined. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Bambawale M.J.,National University of Singapore | Sovacool B.K.,National University of Singapore
Applied Energy | Year: 2011

The article explores the energy security concerns faced by China from the point of view of energy users working in government, university, civil society and business sectors. The authors first derive a set of seven hypotheses related to Chinese energy security drawn from a review of the recent academic literature. We then explain each of these seven hypotheses, relating to (1) security of energy supply, (2) geopolitics, (3) climate change, (4) decentralization, (5) energy efficiency, (6) research and innovation of new energy technologies, and (7) self sufficiency and trade. Lastly, the article tests these hypotheses through a survey distributed in English and Mandarin completed by 312 Chinese participants. The conclusion presents insights for policymakers and energy scholars. © 2010 Elsevier Ltd.


Ladoux B.,University Paris Diderot | Ladoux B.,National University of Singapore | Nicolas A.,Joseph Fourier University
Reports on Progress in Physics | Year: 2012

The minimal structural unit that defines living organisms is a single cell. By proliferating and mechanically interacting with each other, cells can build complex organization such as tissues that ultimately organize into even more complex multicellular living organisms, such as mammals, composed of billions of single cells interacting with each other. As opposed to passive materials, living cells actively respond to the mechanical perturbations occurring in their environment. Tissue cell adhesion to its surrounding extracellular matrix or to neighbors is an example of a biological process that adapts to physical cues. The adhesion of tissue cells to their surrounding medium induces the generation of intracellular contraction forces whose amplitude adapts to the mechanical properties of the environment. In turn, solicitation of adhering cells with physical forces, such as blood flow shearing the layer of endothelial cells in the lumen of arteries, reinforces cell adhesion and impacts cell contractility. In biological terms, the sensing of physical signals is transduced into biochemical signaling events that guide cellular responses such as cell differentiation, cell growth and cell death. Regarding the biological and developmental consequences of cell adaptation to mechanical perturbations, understanding mechanotransduction in tissue cell adhesion appears as an important step in numerous fields of biology, such as cancer, regenerative medicine or tissue bioengineering for instance. Physicists were first tempted to view cell adhesion as the wetting transition of a soft bag having a complex, adhesive interaction with the surface. But surprising responses of tissue cell adhesion to mechanical cues challenged this view. This, however, did not exclude that cell adhesion could be understood in physical terms. It meant that new models and descriptions had to be created specifically for these biological issues, and could not straightforwardly be adapted from dead matter. In this review, we present physical concepts of tissue cell adhesion and the unexpected cellular responses to mechanical cues such as external forces and stiffness sensing. We show how biophysical approaches, both experimentally and theoretically, have contributed to our understanding of the regulation of cellular functions through physical force sensing mechanisms. Finally, we discuss the different physical models that could explain how tissue cell adhesion and force sensing can be coupled to internal mechanosensitive processes within the cell body. © 2012 IOP Publishing Ltd.


Chang T.C.,National University of Singapore
Urban Studies | Year: 2016

The phrases ‘new uses need old buildings’ and ‘old buildings require new uses’ emphasise the mutually reinforcing relationships between historic buildings and new activities in cities. What the phrases do not say are the challenges and incompatibilities that are part of the urban redevelopment process. Singapore’s inner city has been transformed since the 1990s with the introduction of new economies. This paper focuses on one precinct that has undergone land use change – Little India. The concept of ‘gentrification aesthetics’ provides a suggestive frame to explore the form and outcome of urban change, as well as its contestations when new arts and cultural activities occupy historic buildings. Gentrification aesthetics as conceptualised in the West takes on different perspectives in Singapore, prompting questions on whether a ‘Singapore style gentrification’ is evolving – one that melds urban redevelopment with state ideology in arts enhancement and aesthetic regulation. © 2014, © Urban Studies Journal Limited 2014.


Howard S.D.,National University of Singapore | Bickford D.P.,National University of Singapore
Diversity and Distributions | Year: 2014

Aim: To apply mathematical models to the task of predicting extinction risk for species currently listed as 'Data Deficient' (DD) by the International Union for the Conservation of Nature (IUCN). We demonstrate this approach by applying it globally to amphibians, the vertebrate group recognized as being most extinction threatened and having the largest proportion of DD species. We combine model predictions with current extinction risk knowledge to highlight regions of greatest disparity between known and predicted risk, where potential species extinctions may be overlooked. Location: Global. Methods: Using global amphibian distribution data obtained from the IUCN and species trait data, we apply machine learning randomForest models to predict extinction risk of DD species from life history traits, environmental variables and habitat loss. These models are trained using data for species that have been assigned to an extinction risk category (other than DD) by the IUCN. We then combine predictions for DD species with IUCN assessment data in a GIS framework to highlight anomalies between current knowledge of amphibian extinction risk and our model predictions. Results: We show that DD amphibian species are likely to be more threatened with extinction than their fully assessed counterparts. Regions in South America, central Africa and North Asia are particularly at risk due to lack of species knowledge and higher extinction risk than currently recognized. Main conclusions: Application of predictive models ranking regions and species most in need of primary research allows prioritization of limited resources in an informed context, minimizing risk of unnoticed species' extinction. © 2014 John Wiley & Sons Ltd.


Barker N.,Singapore Institute of Medical Biology | Barker N.,University of Edinburgh | Barker N.,National University of Singapore
Nature Reviews Molecular Cell Biology | Year: 2014

Small populations of adult stem cells are responsible for the remarkable ability of the epithelial lining of the intestine to be efficiently renewed and repaired throughout life. The recent discovery of specific markers for these stem cells, together with the development of new technologies to track endogenous stem cell activity in vivo and to exploit their ability to generate new epithelia ex vivo, has greatly improved our understanding of stem cell-driven homeostasis, regeneration and cancer in the intestine. These exciting new insights into the biology of intestinal stem cells have the potential to accelerate the development of stem cell-based therapies and ameliorate cancer treatments. © 2014 Macmillan Publishers Limited. All rights reserved.


Cable H.,National University of Singapore | Durkin G.A.,NASA
Physical Review Letters | Year: 2010

We explore the advantages offered by twin light beams produced in parametric down-conversion for precision measurement. The symmetry of these bipartite quantum states, even under losses, suggests that monitoring correlations between the divergent beams permits a high-precision inference of any symmetry-breaking effect, e.g., fiber birefringence. We show that the quantity of entanglement is not the key feature for such an instrument. In a lossless setting, scaling of precision at the ultimate "Heisenberg" limit is possible with photon counting alone. Even as photon losses approach 100% the precision is shot-noise limited, and we identify the crossover point between quantum and classical precision as a function of detected flux. The predicted hypersensitivity is demonstrated with a Bayesian simulation. © 2010 The American Physical Society.


Danner A.J.,National University of Singapore
New Journal of Physics | Year: 2010

The refractive index profiles for some optical instruments such as Eaton lenses or invisible spheres include point singularities where the refractive index approaches infinity. A photorealistic visualization of imperfectly approximating such a singularity with realistic materials is presented and a method involving replacing regions near optical singularities with nonsingular birefringent materials is expanded upon in order to allow transmutations without introducing surface reflections when combining rescaling and transmutation operations. A new method, not derivable through transformation optics, for removing point singularities in optical instruments without introducing birefringence is also introduced. Both methods may prove useful in the design of gradient index optical devices. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.


Beny C.,National University of Singapore | Oreshkov O.,Autonomous University of Barcelona
Physical Review Letters | Year: 2010

We derive necessary and sufficient conditions for the approximate correctability of a quantum code, generalizing the Knill-Laflamme conditions for exact error correction. Our measure of success of the recovery operation is the worst-case entanglement fidelity. We show that the optimal recovery fidelity can be predicted exactly from a dual optimization problem on the environment causing the noise. We use this result to obtain an estimate of the optimal recovery fidelity as well as a way of constructing a class of near-optimal recovery channels that work within twice the minimal error. In addition to standard subspace codes, our results hold for subsystem codes and hybrid quantum-classical codes. © 2010 The American Physical Society.


Vu K.M.,National University of Singapore
Telecommunications Policy | Year: 2011

This paper examines the hypothesis that ICT penetration has positive effects on economic growth. On theoretical grounds, this paper discusses three channels through which ICT penetration can affect growth: (i) fostering technology diffusion and innovation; (ii) enhancing the quality of decision-making by firms and households; and (iii) increasing demand and reducing production costs, which together raises the output level. This paper conducts three empirical exercises to provide a comprehensive documentation of the role of ICT as a source of growth in the 19962005 period. The first exercise shows that growth in 19962005 improved relative to the previous two decades and experienced a very significant structural change. The second exercise uses the traditional cross-country regression method to identify a strong association between ICT penetration and growth during 19962005, controlling for other potential growth drivers and country-fixed effects. The third exercise uses the system Generalized Method of Moment (GMM) for dynamic panel data analysis to tease out the causal link between ICT penetration and growth. This analysis also shows that, for the average country, the marginal effect of the penetration of internet users was larger than that of mobile phones, which in turn is larger than that of personal computers. The marginal effect of ICT penetration, however, lessens as the penetration increases. This paper points out several policy implications drawn from its analyses and findings. © 2011 Elsevier Ltd. All rights reserved.


Tan Y.K.,National University of Singapore | Panda S.K.,National University of Singapore
IEEE Transactions on Industrial Electronics | Year: 2011

In this paper, a hybrid of indoor ambient light and thermal energy harvesting scheme that uses only one power management circuit to condition the combined output power harvested from both energy sources is proposed to extend the lifetime of the wireless sensor node. By avoiding the use of individual power management circuits for multiple energy sources, the number of components used in the hybrid energy harvesting (HEH) system is reduced and the system form factor, cost and power losses are thus reduced. An efficient microcontroller-based ultra low power management circuit with fixed voltage reference based maximum power point tracking is implemented with closed-loop voltage feedback control to ensure near maximum power transfer from the two energy sources to its connected electronic load over a wide range of operating conditions. From the experimental test results obtained, an average electrical power of 621 μW is harvested by the optimized HEH system at an average indoor solar irradiance of 1010 lux and a thermal gradient of 10 K, which is almost triple of that can be obtained with conventional single-source thermal energy harvesting method. © 2010 IEEE.


Gee H.Y.,Yonsei University | Noh S.H.,Yonsei University | Tang B.L.,National University of Singapore | Kim K.H.,Yonsei University | Lee M.G.,Yonsei University
Cell | Year: 2011

The most prevalent disease-causing mutation of CFTR is the deletion of Phe508 (ΔF508), which leads to defects in conventional Golgi-mediated exocytosis and cell surface expression. We report that ΔF508-CFTR surface expression can be rescued in vitro and in vivo by directing it to an unconventional GRASP-dependent secretion pathway. An integrated molecular and physiological analysis indicates that mechanisms associated with ER stress induce cell surface trafficking of the ER core-glycosylated wild-type and ΔF508-CFTR via the GRASP-dependent pathway. Phosphorylation of a specific site of GRASP and the PDZ-based interaction between GRASP and CFTR are critical for this unconventional surface trafficking. Remarkably, transgenic expression of GRASP in ΔF508-CFTR mice restores CFTR function and rescues mouse survival without apparent toxicity. These findings provide insight into how unconventional protein secretion is activated, and offer a potential therapeutic strategy for the treatment of cystic fibrosis and perhaps diseases stemming from other misfolded proteins. © 2011 Elsevier Inc.


Lateef A.,National University of Singapore
Arthritis research & therapy | Year: 2012

Systemic lupus erythematosus (SLE) is an autoimmune disease of diverse manifestations, with onset usually in young women in the third to fourth decade of life. The chronic nature of this relapsing remitting disease leads to organ damage accrual over time. Mortality and morbidity are increased in patients with SLE compared with the general population. Therapeutic advances over the last few decades have led to significant improvements in patient outcomes. Five-year survival has improved to over 90% from a low of 50% in the 1950s. However, multiple aspects of the management of SLE patients are still far from optimal. Early diagnosis remains a challenge; diagnostic delays leading to delay in definitive treatment are common. Monitoring treatment remains problematic due to the paucity of sensitive biomarkers. Current treatment regimens rely heavily on corticosteroids, even though corticosteroids are well known to cause organ damage. Treatment of refractory disease manifestations such as nephritis, recalcitrant cutaneous lesions and neurological involvement require new approaches with greater efficacy. Cognitive dysfunction is common in SLE patients, but early recognition and adequate treatment are yet to be established. Premature accelerated atherosclerosis remains a leading cause of morbidity and mortality. Fatigue is one of the most disabling symptoms, and contributes to the poor quality of life in patients with SLE. Ongoing research in SLE faces many challenges, including enrollment of homogeneous patient populations, use of reliable outcome measures and a standard control arm. The current review will highlight some of the outstanding unmet challenges in the management of this complex disease.


Agasthian T.,National University of Singapore
European Journal of Cardio-thoracic Surgery | Year: 2013

OBJECTIVES: Bronchial-origin involvement by endobronchial tumours or direct invasion by tumour or metastatic lymph nodes is a relative contraindication for video-assisted thoracoscopic (VATS) lobectomy. However, selected cases can be resected by VATS bronchoplasty. METHODS: Between 2006 and 2009, 21 of 231 (9.1%) VATS lobectomy cases underwent VATS bronchoplasty. Cases with endobronchial involvement and limited non-bulky invasion of bronchus by tumour or metastatic nodes without major vascular invasion were selected for bronchoplasty by preoperative bronchosocpy and CT scan thorax. Patients underwent a simple/wedge bronchoplasty (bronchus divided at origin and closed flush or transversely), sleeve bronchoplasty or others (bronchoplasty combined with other extended resections). All bronchoplasties were done totally endoscopically by directly watching a TV monitor. Bronchial margins were all subjected to intraoperative pathological analysis. Anastomosis was done with interrupted sutures. Integrity of anastomosis was checked by intraoperative bronchoscopy. The follow-up was done by 6-monthly CT scans and bronchoscopy. RESULTS: Eleven patients were females. Mean age was 64.9 years (range, 47-83 years). Indications were endobronchial tumours in 3, direct invasion in 6 and metastatic nodes in 12. In 4 cases, invasion was detected at the time of surgery. Mean hospital stay was 5.2 days (range, 3-8 days). Mean duration of surgery was 287 min (range, 135-540 min). Nine had simple/wedge bronchoplasty, 8, sleeve bronchoplasty and 4, extended bronchoplasties. Histology was non-small-cell carcinoma (NSCLC) in 19, carcinoid in 1 and colonic metastasis in 1. In the NSCLC, 5 patients were in stage IB, 5 in stage IIA, 2 in stage IIB and 7 were in IIIA. All bronchial margins were negative for malignancy. The mean follow-up was 26.2 months (range, 6-32 months). There was no operative mortality, but 1 patient developed bronchopleural fistula. To date, there have been no local tumour recurrences. CONCLUSIONS: Selected endobronchial and non bulky tumours with limited invasion at bronchial origin can be resected by VATS bronchoplasty. © The Author 2013. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved.


Shanmugam M.K.,National University of Singapore
Sub-cellular biochemistry | Year: 2013

There is considerable evidence suggesting that epigenetic mechanisms may mediate development of chronic inflammation by modulating the expression of pro-inflammatory cytokine TNF-α, interleukins, tumor suppressor genes, oncogenes and autocrine and paracrine activation of the transcription factor NF-κB. These molecules are constitutively produced by a variety of cells under chronic inflammatory conditions, which in turn leads to the development of major diseases such as autoimmune disorders, chronic obstructive pulmonary diseases, neurodegenerative diseases and cancer. Distinct or global changes in the epigenetic landscape are hallmarks of chronic inflammation driven diseases. Epigenetics include changes to distinct markers on the genome and associated cellular transcriptional machinery that are copied during cell division (mitosis and meiosis). These changes appear for a short span of time and they necessarily do not make permanent changes to the primary DNA sequence itself. However, the most frequently observed epigenetic changes include aberrant DNA methylation, and histone acetylation and deacetylation. In this chapter, we focus on pro-inflammatory molecules that are regulated by enzymes involved in epigenetic modifications such as arginine and lysine methyl transferases, DNA methyltransferase, histone acetyltransferases and histone deacetylases and their role in inflammation driven diseases. Agents that modulate or inhibit these epigenetic modifications, such as HAT or HDAC inhibitors have shown great potential in inhibiting the progression of these diseases. Given the plasticity of these epigenetic changes and their readiness to respond to intervention by small molecule inhibitors, there is a tremendous potential for the development of novel therapeutics that will serve as direct or adjuvant therapeutic compounds in the treatment of these diseases.


Yang G.,National University of Singapore
IEEE Transactions on Wireless Communications | Year: 2011

In a recent paper (IEEE Trans. Wireless Commun., vol. 9, no. 11, 2010), Chang and Tsai presented a self-verified mobile authentication scheme for large-scale wireless networks. In this letter, we show that there is a serious security flaw in the key delegation phase of the scheme: two colluding mobile users can retrieve the long-term secret key of their home server without performing any active attacks. We then present a suggestion to fix the problem without losing any features (such as high efficiency and scalability) of the original scheme. © 2011 IEEE.


Gopal P.,National University of Singapore | Dick T.,National University of Singapore
Current Opinion in Microbiology | Year: 2014

Reactive multi-target fragments, old synthetic antimycobacterials that are activated inside Mycobacterium tuberculosis bacilli and are smaller than the usual drug-like, single-target molecules, represent critical components of current tuberculosis chemotherapies. Recent studies showed that para-aminosalicylic acid is recognized as a substrate by dihydropteroate synthase and poisons the downstream folate pathway. Pyrazinamide, a key relapse-reducing drug, is metabolized by an amidase and the reaction product interferes with trans-translation, membrane potential and other targets. However, the mechanism of action of pyrazinamide remains ill-defined and needs to be understood to rationally approach treatment shortening. The success of small dirty drugs and prodrugs suggests that fragment-based whole cell screens should be re-introduced in our current antimycobacterial drug discovery efforts. © 2014 The Authors.


Huang C.,Texas A&M University | Zhang R.,National University of Singapore | Cui S.,Texas A&M University
IEEE Journal on Selected Areas in Communications | Year: 2013

This paper considers the use of energy harvesters, instead of conventional time-invariant energy sources, in wireless cooperative communication. For the purpose of exposition, we study the classic three-node Gaussian relay channel with decode-and-forward (DF) relaying, in which the source and relay nodes transmit with power drawn from energy-harvesting (EH) sources. Assuming a deterministic EH model under which the energy arrival time and the harvested amount are known prior to transmission, the throughput maximization problem over a finite horizon of N transmission blocks is investigated. In particular, two types of data traffic with different delay constraints are considered: delay-constrained (DC) traffic (for which only one-block decoding delay is allowed at the destination) and no-delay-constrained (NDC) traffic (for which arbitrary decoding delay up to N blocks is allowed). For the DC case, we show that the joint source and relay power allocation over time is necessary to achieve the maximum throughput, and propose an efficient algorithm to compute the optimal power profiles. For the NDC case, although the throughput maximization problem is non-convex, we prove the optimality of a separation principle for the source and relay power allocation problems, based upon which a two-stage power allocation algorithm is developed to obtain the optimal source and relay power profiles separately. Furthermore, we compare the DC and NDC cases, and obtain the sufficient and necessary conditions under which the NDC case performs strictly better than the DC case. It is shown that NDC transmission is able to exploit a new form of diversity arising from the independent source and relay energy availability over time in cooperative communication, termed «energy diversity», even with time-invariant channels. © 2013 IEEE.


There are 3108 valid and named native fish species in the inland waters of Southeast Asia between the Irrawaddy and Red River drainages, the small coastal drainages between the Red River and Hainan, the whole Indochinese Peninsula, Andaman and Nicobar Islands, Indonesia (excluding Papua Province, Waigeo, Aru [but Kai is included]), and the Philippines. They belong to 137 families. Their taxonomy and nomenclature are reviewed. The original descriptions of all 7047 recorded species-group names and 1980 genus-group names have been checked in the original works for correct spelling, types, type locality and bibliographic references. The bibliography includes about 4700 titles. Synonymies are given, based on published information as well as unpublished observations. The names of 49 introduced species and 347 extralimital taxa cited in the discussions have also been checked. The original descriptions of all species not present in the covered area but cited as type species of genera have been checked for availability, authorship, date and correct spelling. The availability of some family-group names has been checked when there was suspicion of possible nomenclatural problems. Bibliographic notes include new informations on the dates of publication of works by, among others, Bleeker, Bloch, Heckel and Steindachner and discussion of authorship of names in various works. © National University of Singapore and the author.


Schmid K.,University of Oxford | Ramiah A.A.,National University of Singapore | Hewstone M.,University of Oxford
Psychological Science | Year: 2014

This research reported here speaks to a contentious debate concerning the potential negative consequences of diversity for trust. We tested the relationship between neighborhood diversity and out-group, in-group, and neighborhood trust, taking into consideration previously untested indirect effects via intergroup contact and perceived intergroup threat. A large-scale national survey in England sampled White British majority (N = 868) and ethnic minority (N = 798) respondents from neighborhoods of varying degrees of diversity. Multilevel path analyses showed some negative direct effects of diversity for the majority group but also confirmed predictions that diversity was associated indirectly with increased trust via positive contact and lower threat. These indirect effects had positive implications for total effects of diversity, cancelling out most negative direct effects. Our findings have relevance for a growing body of research seeking to disentangle effects of diversity on trust that has so far largely ignored the key role of intergroup contact. © The Author(s) 2014.


Lok S.-M.,National University of Singapore
Trends in Microbiology | Year: 2016

Dengue virus (DENV) infects ~400 million people annually, and there is no available vaccine or therapeutics. It is not clear why candidate vaccines provide only modest protection. In addition to the presence of four different dengue serotypes, there is also structural heterogeneity in DENV infectious particles, even within a strain. This severely complicates the development of vaccines and therapeutics. The currently known different morphologies of DENV are: immature, partially mature, compact mature, and expanded mature forms of the virus. In this review I describe these forms of the virus, their infectivity, and how antibodies could recognize these morphologies. I also discuss possible vaccine and antibody therapeutic formulations to protect against all morphologies. Although dengue virus (DENV) infects approximately 400 million people annually, there are currently no effective therapeutics or a vaccine.Due to the potential of causing enhancement of disease, a DENV vaccine has to stimulate equal protective responses towards all four dengue serotypes. Additionally, the presence of different dengue virus morphologies within a strain may further complicate vaccine and therapeutic design.Antibodies may have different potencies against different DENV morphologies.A vaccine may need to represent all DENV morphologies.Antibody therapeutics should contain antibodies against all morphologies. © 2015 Elsevier Ltd.


Xu J.-X.,National University of Singapore
Journal of the Franklin Institute | Year: 2012

In this paper, the sliding mode control (SMC) method is integrated with a nonlinear suboptimal control method based on control Lyapunov function (CLF). According to the system nominal part, a CLF is first constructed in general to facilitate the nonlinear optimal system design and Sontag's formula is used in particular to generate a suboptimal controller. To take system uncertainties into account, the SMC mechanism is designed based on the CLF. By integration, the suboptimal control and SMC are made to function in a complementary manner. When the system state is far away from the equilibrium and the system nominal part is predominant, the nonlinear optimal control part will govern the system response as well as drive the system state approach the equilibrium in an optimal fashion. On the contrary, when approaching the equilibrium such that system perturbations become the main factor, the SMC will take over the control task to warrant the desired robustness property and achieve precise control. © 2011 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.


Finkelstein E.A.,National University of Singapore | Strombotne K.L.,Rti International
American Journal of Clinical Nutrition | Year: 2010

The rise in obesity rates, both nationally and internationally, is a result of changes in the environment that have simultaneously lowered the cost of food production, lowered the time and monetary cost of food consumption, increased the real cost of being physically active at work and at home, and decreased the health consequences that result from obesity by bringing a host of new drugs and devices to the market to better manage the adverse health effects that obesity promotes. This changing environment is in response to consumers' demand for labor-saving technology and convenient, affordable food. To be successful, efforts to combat obesity therefore need to recognize and address these realities. © 2010 American Society for Nutrition.


Thibault G.,National University of Singapore | Ng D.T.W.,National University of Singapore
Cold Spring Harbor Perspectives in Biology | Year: 2012

Protein misfolding is a common cellular event that can produce intrinsically harmful products. To reduce the risk, quality control mechanisms are deployed to detect and eliminate misfolded, aggregated, and unassembled proteins. In the secretory pathway, it is mainly the endoplasmic reticulum-associated degradation (ERAD) pathways that perform this role. Here, specialized factors are organized to monitor and process the folded states of nascent polypeptides. Despite the complex structures, topologies, and posttranslational modifications of client molecules, the ER mechanisms are the best understood among all protein quality-control systems. This is the result of convergent and sometimes serendipitous discoveries by researchers from diverse fields. Although major advances in ER quality control and ERAD came from all model organisms, this review will focus on the discoveries culminating from the simple budding yeast. © 2012 Cold Spring Harbor Laboratory Press; all rights reserved.


Wong P.P.,National University of Singapore
Wiley Interdisciplinary Reviews: Climate Change | Year: 2011

In the international climate change negotiations, the Small Island Developing States (SIDS) have emerged as a credible group through the AOSIS (Alliance of Small Island States) and have called for a global temperature rise of 1.5°C above preindustrial levels. Whatever the outcomes of the negotiations, they are exacerbated by climate change and a rising sea level. Many share common characteristics of small size, high population density, limited land resources, vulnerability to natural hazards, threatened biodiversity, high dependence on tourism, and limited funds and human resources. The suggestions put forward for a research agenda for the SIDS include a comprehensive assessment of the SIDS as a group, a focused attention on oceans, increased development on renewable energy, inclusion of climate adaptation under natural disaster reduction, a strategy of 'save some islands rather than not to have any' for some SIDS, and large-scale modular mangrove planting for coastal protection and adaptation to sea-level rise. These suggestions could provide an expanded scope of adaptation for the SIDS. © 2010 John Wiley & Sons, Ltd.


Cheong J.K.,National University of Singapore | Virshup D.M.,National University of Singapore
International Journal of Biochemistry and Cell Biology | Year: 2011

The CK1 family of serine/threonine kinases regulates diverse cellular processes, through binding to and phosphorylation a myriad of protein substrates. CK1 prefers substrates primed by prior phosphorylation, and works closely with other kinases in the Wnt pathway. CK1 is itself regulated by posttranslational modification, including autophosphorylation. We provide a brief overview of the fundamentals of CK1 biology with an emphasis on scaffold binding and kinase regulation in Wnt signaling and circadian rhythms. © 2010 Elsevier Ltd. All rights reserved.


Sabapathy K.,Humphrey Oei Institute of Cancer Research | Sabapathy K.,National University of Singapore
Progress in Molecular Biology and Translational Science | Year: 2012

The c-Jun-NH 2-terminal kinase (JNK) signaling pathway plays a critical role in regulating cell fate, being implicated in a multitude of diseases ranging from cancer to neurological and immunological/inflammatory conditions. Not surprisingly, therefore, it has been sought after for therapeutic intervention, and its inhibition has been shown to ameliorate many pathological conditions in experimental systems, paving the way for initial clinical trials. However, the fundamental problem in fully harnessing the potential provided by the JNK pathway has been the lack of specificity, due to the multiple JNK forms that are involved in multiple cellular processes in various cell types. Moreover, lack of sufficient knowledge of all JNK-interacting proteins and substrates has also hindered progress. This review will therefore focus on the role of the JNKs in human diseases and appraise the efforts to inhibit JNK signaling to ameliorate disease conditions, assessing potential challenges and providing insights into possible future directions to efficiently target this pathway for therapeutic use. © 2012 Elsevier Inc.


Zaidel-Bar R.,National University of Singapore
Journal of Cell Science | Year: 2013

This article is part of a Minifocus on Adhesion. For further reading, please see related articles: 'Cycling around cell-cell adhesion with Rho GTPase regulators' by Jessica McCormack et al. (J. Cell Sci. 126, 379-391). 'E-cadherin-integrin crosstalk in cancer invasion and metastasis' by Marta Canel et al. (J. Cell Sci. 126, 393-401). 'Mechanosensitive systems at the cadherin-F-actin interface' by Stephan Huveneers and Johan de Rooij. © 2013. Published by The Company of Biologists Ltd.


Dengue virus (DENV) is a rapidly re-emerging flavivirus that causes dengue fever (DF), dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), diseases for which there are no available therapies or vaccines.  The DENV-2 positive-strand RNA genome contains 5' and 3' untranslated regions (UTRs) that have been shown to form secondary structures required for virus replication and interaction with host cell proteins.  In order to comprehensively identify host cell factors that bind the DENV-2 UTRs, we performed RNA chromatography, using the DENV-2 5' and 3' UTRs as "bait", combined with quantitative mass spectrometry.  We identified several proteins, including DDX6, G3BP1, G3BP2, Caprin1, and USP10, implicated in P body (PB) and stress granule (SG) function, and not previously known to bind DENV RNAs.  Indirect immunofluorescence microscopy showed these proteins to colocalize with the DENV replication complex.  Moreover, DDX6 knockdown resulted in reduced amounts of infectious particles and viral RNA in tissue culture supernatants following DENV infection. DDX6 interacted with DENV RNA in vivo during infection and in vitro this interaction was mediated by the DB1 and DB2 structures in the 3' UTR, possibly by formation of a pseudoknot structure.  Additional experiments demonstrate that, in contrast to DDX6, the SG proteins G3BP1, G3BP2, Caprin1 and USP10 bind to the variable region (VR) in the 3' UTR.  These results suggest that the DENV-2 3' UTR is a site for assembly of PB and SG proteins and, for DDX6, assembly on the 3' UTR is required for DENV replication.


Collins M.A.,Australian National University | Cvitkovic M.W.,National University of Singapore | Bettens R.P.A.,National University of Singapore
Accounts of Chemical Research | Year: 2014

ConspectusChemistry, particularly organic chemistry, is mostly concerned with functional groups: amines, amides, alcohols, ketones, and so forth. This is because the reactivity of molecules can be categorized in terms of the reactions of these functional groups, and by the influence of other adjacent groups in the molecule. These simple truths ought to be reflected in the electronic structure and electronic energy of molecules, as reactivity is determined by electronic structure. However, sophisticated ab initio quantum calculations of the molecular electronic energy usually do not make these truths apparent. In recent years, several computational chemistry groups have discovered methods for estimating the electronic energy as a sum of the energies of small molecular fragments, or small sets of groups. By decomposing molecules into such fragments of adjacent functional groups, researchers can estimate the electronic energy to chemical accuracy; not just qualitative trends, but accurate enough to understand reactivity. In addition, this has the benefit of cutting down on both computational time and cost, as the necessary calculation time increases rapidly with an increasing number of electrons. Even with steady advances in computer technology, progress in the study of large molecules is slow.In this Account, we describe two related "fragmentation" methods for treating molecules, the combined fragmentation method (CFM) and systematic molecular fragmentation (SMF). In addition, we show how we can use the SMF approach to estimate the energy and properties of nonconducting crystals, by fragmenting the periodic crystal structure into relatively small pieces. A large part of this Account is devoted to simple overviews of how the methods work.We also discuss the application of these approaches to calculating reactivity and other useful properties, such as the NMR and vibrational spectra of molecules and crystals. These applications rely on the ability of these fragmentation methods to accurately estimate derivatives of the molecular and crystal energies. Finally, to provide some common applications of CFM and SMF, we present some specific examples of energy calculations for moderately large molecules. For computational chemists, this fragmentation approach represents an important practical advance. It reduces the computer time required to estimate the energies of molecules so dramatically, that accurate calculations of the energies and reactivity of very large organic and biological molecules become feasible. © 2014 American Chemical Society.


Shi X.,National University of Singapore
Renewable and Sustainable Energy Reviews | Year: 2016

This paper assesses competing outlooks for energy mix in the Association of Southeast Asian Nations (ASEAN), highlighting the paradox of its fossil fuel-dominated outlooks when contrasted with its aspirations to move toward a green energy mix, and reviews green energy strategies using the strengths, weaknesses, opportunities, and threats (SWOT) analysis method. The paper argues that despite the looming brown outlooks due to the expected surge of coal, the ASEAN region has many advantages in providing cleaner energy for its green vision. However, reduction of CO2 emissions has not been explicitly set in the region's policy agenda and thus green energy potential is underdeveloped. To achieve a greener energy mix, ASEAN needs to make further efforts such as cleaner use and removal of subsidies of fossil fuels, promotion of renewables and energy efficiency, regional market integration and connectivity, and execution of existing plans by nations. Ultimately, each of these strategies will require sustained leadership, political determination, and concrete actions from stakeholders, in particular, national governments across the region. © 2015 Elsevier Ltd. All rights reserved.


Young R.D.,National University of Singapore
Chemistry - A European Journal | Year: 2014

Alkane σ-complexes have evolved from a curious phenomenon to an intermediate of intense interest, fuelling research into the area. Over the last fifteen years, metal alkane complex characterisation has evolved to incorporate reports employing UV/Vis, IR and NMR spectroscopy, and X-ray and neutron diffractometry. Previously, due to the sparse geometric characterisation of alkane σ-complexes, assumptions regarding bonding geometries and selectivities were made by comparison to related σ-complexes, or by analysis of C-H activation products. This minireview assembles relevant literature that illuminates the metrics of alkane-metal bonding, and critically analyses the binding mode, selectivity and stability of alkane complexes. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Ouyang J.,National University of Singapore
Organic Electronics: physics, materials, applications | Year: 2013

Electrode-sensitive bipolar resistive switches are observed on devices with a polystyrene film blended with gold nanoparticles capped with conjugated 2-naphthalenethiol (Au-2NT NPs) sandwiched between Al and Au electrodes. The bipolar resistive switches render the devices important application as nonvolatile memory devices. This manuscript reports the operation mechanism of these polymer:nanoparticle memory devices through the analyses of conduction mechanisms, investigation of the effects of the active film thickness and the Au-2NT NP loading on the resistive switches, and Raman spectroscopy of Au-2NT NPs for the devices in two resistance states. The electrical contact between the Al electrode and Au-2NT NPs plays a key role in the resistive switches. The total resistance for the charge transport through the polymer:nanoparticle memory devices includes the resistance (Rf) for the charge transport across the active polymer:nanoparticle film and the resistance (Rc) through the electrical contact between the active film and the Al electrode. Both resistances change during the resistive switches, but the change in R c is the dominant factor. The threshold voltage (Vth) for the resistive switch is predominantly affected by the contact between the active film and the Al electrode, and it also slightly depends on the thickness of the active film and the loading of Au-2NT NPs in the active film. The changes in Rc and Rf are ascribed to the effect of the external electric field on the charge transfer between the Al electrode and Au-2NT NPs and the electrical field-induced charge trapping on Au-2NT NPs, respectively. © 2012 Elsevier B.V. All rights reserved.


Jiang S.,National University of Singapore | Zhang Y.,National University of Singapore
Langmuir | Year: 2010

Investigation of the intracellular fate of small interference RNA (siRNA), after their delivery into cells by nanoparticles, is of great interest to the development of more efficient methods for transfection of siRNA. The fluorescence resonance energy transfer (FRET) based method using upconversion fluorescent nanoparticles (UCN) as energy donor is established to study intracellular release and biostability of siRNA in live cells. The UCN/siRNA-BOBO3 complex is prepared where BOBO-3-stained siRNAs are attached to the surface of amino-group-modified silica/NaYF4:Yb,Er UCN. The energy is transferred from the UCN donor to the BOBO-3 acceptor under excitation of a near-infrared (NIR) laser. The FRET efficiency is established as a reliable parameter to follow the release and biostability of siRNA in phosphate buffered saline (PBS) and live cells. Intracellular FRET analysis shows that siRNA is gradually released into cells for a duration of 24 h, which is confirmed by confocal microscopy colocalization measurements. The application of this straightforward and sensitive upconversion FRET technique can gain real-time information on intracellular fate of siRNA and provide a bright outlook for in vitro and even in vivo detection of biological molecules. © 2010 American Chemical Society.


Schirmer A.,National University of Singapore
PLoS ONE | Year: 2010

The present study explored the effect of speaker prosody on the representation of words in memory. To this end, participants were presented with a series of words and asked to remember the words for a subsequent recognition test. During study, words were presented auditorily with an emotional or neutral prosody, whereas during test, words were presented visually. Recognition performance was comparable for words studied with emotional and neutral prosody. However, subsequent valence ratings indicated that study prosody changed the affective representation of words in memory. Compared to words with neutral prosody, words with sad prosody were later rated as more negative and words with happy prosody were later rated as more positive. Interestingly, the participants' ability to remember study prosody failed to predict this effect, suggesting that changes in word valence were implicit and associated with initial word processing rather than word retrieval. Taken together these results identify a mechanism by which speakers can have sustained effects on listener attitudes towards word referents. © 2010 Annett Schirmer.


Reddy M.V.,National University of Singapore | Subba Rao G.V.,National University of Singapore | Chowdari B.V.R.,National University of Singapore
Chemical Reviews | Year: 2013

Researchers explore the use of metal oxides and oxysalts as anode materials for lithium (Li) ion batteries (LIB). LIB packs can satisfy the requirements of high-power and high-energy-density applications. They have been explored and implemented for vehicular transport over a period of time. LIBs are also actively being considered for power tools, back-up power supply units and off-peak energy storage from the electric grid in addition to vehicular transport. LIBs need to satisfy four important criteria for all these uses, including cost reduction and safety-in-operation. Improvements in the low- and high-temperature operation of these batteries can drive their use in a wide range of applications. Research efforts are being made to satisfy the needs of some of these uses by finding alternative electrode materials based on cheap and environmentally friendly compounds, which will work on principles that are different from the Li intercalation-deintercalation reactions.


Alam H.,Qtech Nanosystems Pte. Ltd | Ramakrishna S.,National University of Singapore
Nano Energy | Year: 2013

Thermal management and energy crisis have been two major problems in this 21st century. The thermoelectric concept is seen as a perfect solution for the both issues provided its figure of merit is large enough to compete with the traditional techniques. Since the use of semiconductor materials for thermoelectric applications, there has been a huge quest for improving its figure of merits (ZT) to cross 3 in order to make it commercially viable. This review starts with thermoelectric concepts and explains briefly the challenges in enhancing the figure of merits. It also reports the various approaches adopted in bulk materials, complex structures and the recent nanostructures to circumvent the interdependency of parameters in achieving higher ZT. It ends with discussion of the future trends of nanocomposite materials and its underlying challenges of fabrication. © 2012 Elsevier Ltd.


Bernhammer J.C.,National University of Singapore | Huynh H.V.,National University of Singapore
Organometallics | Year: 2012

Ten palladium(II) complexes bearing a pyrazolin-5-ylidene ligand have been synthesized by oxidative addition and silver carbene transfer pathways. The weakly bound acetonitrile ligand in the initially obtained trans-[PdBr 2(MeCN)(Pyry)] complex (6, Pyry = 1-phenyl-2,3-dimethylpyrazolin-5- ylidene) could be replaced by other donor ligands, and additional NHC ligands were introduced either by silver carbene transfer reactions or via reaction with in situ generated free carbenes. Using our previously reported 13C NMR-based electronic parameter, the pyrazolin-5-ylidene ligand is estimated to be among the most strongly donating ligands on our scale so far. The complexes obtained were employed as catalysts for the direct arylation of pentafluorobenzene with moderate to good yields under optimized conditions. © 2012 American Chemical Society.


Cambria E.,National University of Singapore
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

The ways people express their opinions and sentiments have radically changed in the past few years thanks to the advent of social networks, web communities, blogs, wikis, and other online collaborative media. The distillation of knowledge from the huge amount of unstructured information on the Web can be a key factor for marketers who want to create an image or identity in the minds of their customers for their product or brand. These online social data, however, remain hardly accessible to computers, as they are specifically meant for human consumption. The automatic analysis of online opinions, in fact, involves a deep understanding of natural language text by machines, from which we are still very far. To this end, concept-level sentiment analysis aims to go beyond a mere word-level analysis of text and provide novel approaches to opinion mining and sentiment analysis that enable a more efficient passage from (unstructured) textual information to (structured) machine-processable data, in potentially any domain. © Springer-Verlag 2013.


Pang C.H.J.,National University of Singapore
Mathematical Programming | Year: 2014

We study how the supporting hyperplanes produced by the projection process can complement the method of alternating projections and its variants for the convex set intersection problem. For the problem of finding the closest point in the intersection of closed convex sets, we propose an algorithm that, like Dykstra’s algorithm, converges strongly in a Hilbert space. Moreover, this algorithm converges in finitely many iterations when the closed convex sets are cones in Rn satisfying an alignment condition. Next, we propose modifications of the alternating projection algorithm, and prove its convergence. The algorithm converges superlinearly in Rn under some nice conditions. Under a conical condition, the convergence can be finite. Lastly, we discuss the case where the intersection of the sets is empty. © 2014, Springer-Verlag Berlin Heidelberg and Mathematical Optimization Society.


Corlett R.T.,National University of Singapore
Biological Conservation | Year: 2012

As a broad scientific consensus in support of anthropogenic global warming emerged in the 1980s, a few biologists were quick to make predictions of the likely impacts in the tropics. Most conservation biologists, however, saw climate change as a much less immediate threat to tropical terrestrial ecosystems than deforestation, logging, and hunting. There has been a rapid shift in opinion in the last few years, with the widespread recognition that the climate is already changing at a rate that is relevant to current conservation actions in the tropics. Unfortunately, more than a decade of relative neglect of climate change research has left tropical biologists with little hard information on which to plan a response. The most widely used climate projections for the tropics do not represent the full range of model possibilities and do not reflect the current rates of greenhouse gas emission. The 2-3. °C rise that is commonly assumed could be 4-6, or even 7. °C, while projections for rainfall and other climate variables have still greater uncertainty. These climatic uncertainties are compounded by our ignorance about the potential biological consequences of these changes. It is very likely, however, that the majority of the tropics will soon be subject to climatic conditions that have not existed anywhere on Earth for millions of years. It's a new world and all bets are off. © 2011 Elsevier Ltd.


Baaquie B.E.,National University of Singapore
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2016

A review is made of the statistical generalization of microeconomics by Baaquie (Baaquie 2013 Phys. A 392, 4400-4416. (doi:10.1016/ j.physa.2013.05.008)), where the market price of every traded commodity, at each instant of time, is considered to be an independent random variable. The dynamics of commodity market prices is given by the unequal time correlation function and is modelled by the Feynman path integral based on an action functional. The correlation functions of the model are defined using the path integral. The existence of the action functional for commodity prices that was postulated to exist in Baaquie (Baaquie 2013 Phys. A 392, 4400-4416. (doi:10.1016/j.physa. 2013.05.008)) has been empirically ascertained in Baaquie et al. (Baaquie et al. 2015 Phys. A 428, 19-37. (doi:10.1016/j.physa.2015.02.030)). The model's action functionals for different commodities has been empirically determined and calibrated using the unequal time correlation functions of the market commodity prices using a perturbation expansion (Baaquie et al. 2015 Phys. A 428, 19-37. (doi:10.1016/j.physa.2015.02.030)). Nine commodities drawn from the energy, metal and grain sectors are empirically studied and their auto-correlation for up to 300 days is described by the model to an accuracy of R2 >0.90-using only six parameters. © 2015 The Author(s) Published by the Royal Society. All rights reserved.


Chen W.,National University of Singapore | Javidi B.,University of Connecticut | Chen X.,National University of Singapore
Advances in Optics and Photonics | Year: 2014

Information security with optical means, such as double random phase encoding, has been investigated by various researchers. It has been demonstrated that optical technology possesses several unique characteristics for securing information compared with its electronic counterpart, such as many degrees of freedom. In this paper, we present a review of optical technologies for information security. Optical security systems are reviewed, and theoretical principles and implementation examples are presented to illustrate each optical security system. In addition, advantages and potential weaknesses of each optical security system are analyzed and discussed. It is expected that this review not only will provide a clear picture about current developments in optical security systems but also may shed some light on future developments. © 2014 Optical Society of America.


Sun Z.,National University of Singapore | Ye Q.,National University of Singapore | Chi C.,National University of Singapore | Wu J.,National University of Singapore | Wu J.,Institute of Materials Research and Engineering of Singapore
Chemical Society Reviews | Year: 2012

Low band gap (E g < 1.5 eV) polycyclic hydrocarbons have become one of the most important types of materials for many applications, for example, as semiconductors in organic field effect transistors (OFETs), as light-harvesting dyes in organic solar cells and photodetectors, as near infrared (NIR) fluorescent probes in high resolution bio-imaging and bio-sensing, and as chromophores in non-linear optics. The benzenoid polycyclic hydrocarbons as nano-sized graphene fragments also serve as perfect model compounds to understand the fundamental structure-property relationship of graphene. The ground state of these molecules can be described as either a closed-shell or an open-shell structure on the basis of their molecular size and edge structure. In this review, a summary will be given on a series of low band gap polycyclic hydrocarbons about their synthesis, physical properties and material applications. This journal is © The Royal Society of Chemistry 2012.


Koh C.H.,National University of Singapore
BMC bioinformatics | Year: 2012

Statistical model checking techniques have been shown to be effective for approximate model checking on large stochastic systems, where explicit representation of the state space is impractical. Importantly, these techniques ensure the validity of results with statistical guarantees on errors. There is an increasing interest in these classes of algorithms in computational systems biology since analysis using traditional model checking techniques does not scale well. In this context, we present two improvements to existing statistical model checking algorithms. Firstly, we construct an algorithm which removes the need of the user to define the indifference region, a critical parameter in previous sequential hypothesis testing algorithms. Secondly, we extend the algorithm to account for the case when there may be a limit on the computational resources that can be spent on verifying a property; i.e, if the original algorithm is not able to make a decision even after consuming the available amount of resources, we resort to a p-value based approach to make a decision. We demonstrate the improvements achieved by our algorithms in comparison to current algorithms first with a straightforward yet representative example, followed by a real biological model on cell fate of gustatory neurons with microRNAs.


Srihari S.,National University of Singapore
BMC bioinformatics | Year: 2012

Complexes of physically interacting proteins are one of the fundamental functional units responsible for driving key biological mechanisms within the cell. With the advent of high-throughput techniques, significant amount of protein interaction (PPI) data has been catalogued for organisms such as yeast, which has in turn fueled computational methods for systematic identification and study of protein complexes. However, many complexes are dynamic entities - their subunits are known to assemble at a particular cellular space and time to perform a particular function and disassemble after that - and while current computational analyses have concentrated on studying the dynamics of individual or pairs of proteins in PPI networks, a crucial aspect overlooked is the dynamics of whole complex formations. In this work, using yeast as our model, we incorporate 'time' in the form of cell-cycle phases into the prediction of complexes from PPI networks and study the temporal phenomena of complex assembly and disassembly across phases. We hypothesize that 'staticness' (constitutive expression) of proteins might be related to their temporal "reusability" across complexes, and test this hypothesis using complexes predicted from large-scale PPI networks across the yeast cell cycle phases. Our results hint towards a biological design principle underlying cellular mechanisms - cells maintain generic proteins as 'static' to enable their "reusability" across multiple temporal complexes. We also demonstrate that these findings provide additional support and alternative explanations to findings from existing works on the dynamics in PPI networks.


Fu J.H.,National University of Singapore
European journal of oral implantology | Year: 2012

Occlusal overloading is the primary cause of biomechanical implant complications, which include fracture and/or loosening of the implant fixture and/or prosthetic components. It may also disrupt the intricate bond between the implant surface and bone, leading to peri-implant bone loss and eventual implant failure. This paper was aimed at identifying and evaluating clinical and radiographic parameters relevant for diagnosing occlusal overloading of oral implants. It also discusses its management in order to prevent peri-implant marginal bone loss. An electronic literature search for relevant studies, examining the relationship between occlusal overloading and peri-implant bone loss, was conducted in the PubMed database. Clinical human studies published in English with a minimum of 10 implants were included. Seven articles were identified. Occlusal overloading was found to be positively associated with peri-implant marginal bone loss. Preventing occlusal overloading involves conducting comprehensive examinations, treatment planning, precise surgical and prosthetic treatment executions, and regular maintenance. If occlusal overloading occurs, management of biomechanical implant complications and preventing/treating peri-implant bone loss involves surgical and prosthetic treatment modalities. They include occlusal treatment, repair and replacement of defective prosthetic components, and surgical treatment of the bony craters.


Kim H.,National University of Singapore
Optics Express | Year: 2010

We propose and demonstrate a pulsed-incoherent-light-inj ected Fabry-Perot laser diode (FP-LD) which generates incoherent return-to-zero (RZ) signals for wavelength-division-multiplexing passive optical networks. For the generation of the RZ signals, we first convert the continuous-wave (CW) amplified spontaneous emission (ASE) into an ASE pulse train with a pulse carver, spectrum-slice it into multiple channels with a waveguide grating router, and then inject them into FP-LDs for data modulation. Thanks to a wide slicing bandwidth of the injected incoherent light, the spectral linewidth of the generated RZ signals is determined by the slicing bandwidth, without being affected by the use of the RZ format. Thus, compared to incoherent non-return-to-zero (NRZ) signals generated with CW-ASE-injected FP-LDs, the RZ signals have a similar spectral linewidth but a wide timing margin between adjacent bits. Thus, the proposed transmitter can offer better dispersion tolerance than the NRZ signals. For example, our experimental demonstration performed at 1.25 Gb/s shows ∼50% higher dispersion tolerance than the NRZ signals generated with CW ASE-injected FP-LDs. Despite the large slicing bandwidth of 0.67 nm for the injected ASE, we were able to transmit 1.25-Gb/s signals over 45-km standard single-mode fiber without dispersion compensation. The receiver sensitivity is also improved by 1.5 dB by using the RZ format. © 2010 Optical Society of America.


Novitsky A.,Technical University of Denmark | Qiu C.-W.,National University of Singapore | Wang H.,Data Storage Institute Singapore
Physical Review Letters | Year: 2011

Usually a light beam pushes a particle when the photons act upon it. We investigate the optical forces by nonparaxial gradientless beams and find that the forces can drag suitable particles all the way towards the light source. The major criterion of realizing the backward dragging force is the strong nonparaxiality of the light beam, which contributes to the pulling force owing to momentum conservation. The nonparaxiality of the Bessel beam can be manipulated to possess a dragging force along both the radial longitudinal directions, i.e., a "tractor beam" with stable trajectories is achieved. © 2011 American Physical Society.


Danner A.J.,National University of Singapore
Optics Express | Year: 2010

Photorealistic ray tracing methods have been developed that allow us to see how devices such as imperfect invisible spheres and invisibility cloaks would appear if actually constructed and placed in outdoor environments. The methods developed allow photorealistic depiction of devices with gradient indices of refraction and birefringence or trirefringence in non-Cartesian coordinate systems (and hence accurately handle ray splitting/beam walkoff). The resulting images, which can be rendered in real time to produce animations as will be shown, allow subjective assessment of the performance of optical instruments such as invisibility devices in environments in which they are intended to ultimately be used. © 2010 Optical Society of America.


Liu X.,National University of Singapore | Liu X.,Institute of Materials Research and Engineering of Singapore
Angewandte Chemie - International Edition | Year: 2012

Morphologies Ala carte: A kinetic control strategy has been utilized to fabricate bimetallic nanoparticles. Using cubic Pd nanocrystals as seeds and a syringe pump that enables precise control over precursor injection rate, it is possible to synthesize Pd-Ag bimetallic nanoparticles with tailored shapes (see picture: dimers, eccentric hybrid bars, and core-shell structures) and tunable localized surface plasmon resonances. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Chua K.J.,National University of Singapore
International Journal of Thermal Sciences | Year: 2013

Structural blood networks and blood perfusion rate of a tumor impact the manner in which cryosurgery is carried. In locations where complex vascular systems exist, the freezing temperature of the cryoprobes must account for these additional heat sources while maximizing the eradication of cancer cells. In this study, a computational cryo-freezing model that incorporates a simplified mathematical description of the vascular morphology has been constructed. Complex vascular network with varied blood flows were simplified and modeled as tree-like branched fractal network. The present work evolved a simplified and time-saving methodology to accurately simulate complex blood vessel network in order to reduce simulation tediousness and computational cost. A thermal freezing algorithm has been employed to generate transient temperature profiles, to visualize isotherms in the anatomical region of interest and to provide essential information the ice-front propagation. Extensive experimental validation of the proposed model has been performed with good agreement of up to 4.3%. Effects of combining cryosurgery with advanced nanotechnology to better regulate ice-ball development within a biological tissue were quantitatively investigated. Depending on the thermal properties of different nanoparticles, they could either enhance heat conduction or retard freezing to minimize unintended cryoinjury to the neighboring tissue. Hence, key results have confirmed that while certain nanoparticles act as therapeutic freezing agents that promote cryoablation, others are capable of protecting surrounding healthy tissue. © 2013 Elsevier Masson SAS. All rights reserved.


Parida V.,National University of Singapore | Ng H.Y.,National University of Singapore
Desalination | Year: 2013

In this study, organic fouling behavior of forward osmosis (FO) membrane operated in FO mode (i.e., the dense layer facing the feed solution) and pressure retarded osmosis (PRO) mode (i.e., the porous layer facing the feed solution) was investigated. Organic foulants prepared from the reverse osmosis reject of a water reclamation plant were used at low concentration. The results on the effect of membrane orientation on fouling revealed that in the PRO mode, the FO membrane fouled more easily than when operated in the FO mode, and the fouling became more severe with increasing organic concentration in the feed solution. With TOC of 50ppm and lesser, even in the presence of 5mM Ca2+, minimal membrane fouling was observed in the FO mode, corroborating membrane resilience. In the PRO mode, severe membrane fouling was observed when Ca2+ was present together with 30 and 50ppm of TOC in the feed solution. The fouling layer resistance in the absence of Ca2+ was found to be an order of magnitude lower than the membrane inherent resistance. However, in the presence of 5mM Ca2+, the fouling layer resistance was higher, but in the same order of magnitude as the membrane inherent resistance. © 2012 Elsevier B.V.


Tan C.H.,National University of Singapore | Ng H.Y.,National University of Singapore
Desalination | Year: 2013

Previous modified external concentration polarization (ECP) model can only accurately account for the ECP effect of the forward osmosis (FO) process with NaCl or KCl as the draw solute, when Schmidt number (Sc) values are less than 800 and water fluxes are low. However, for other solutes (i.e., MgSO4, MgCl2, CaCl2 and glucose) that have considerable variation of solutes diffusivities with concentration and high Sc values, the previous modified ECP model under-predicted the effect of ECP on flux. To improve accuracy of flux prediction, the previous ECP model was revised to include dilution/suction and property (diffusivity) variation effects. The modified ICP model was also improved by considering a solute resistivity constant, Ks, that is specific to each membrane for each draw solute used, due to different degree of interactions of different solutes with the porous matrix membrane material. The revised ECP and ICP models, proposed in this study, improved the overall accuracy of flux prediction for the FO process when different draw solutions were considered. The overall FO model was verified by data obtained from laboratory-scale experiments and the appropriate FO models could be selected based on the feed and draw solutes under both pressure-retarded-osmosis and forward-osmosis mode of operation. © 2012 Elsevier B.V.


Huang S.,National University of Singapore | Tan K.K.,National University of Singapore
IEEE Transactions on Industrial Electronics | Year: 2012

In this paper, we consider the friction compensation problem for a class of mechanical systems. The friction behavior is described by a nonlinear dynamical model. Since it is difficult to know the nonlinear parts in the frictional model accurately, two neural networks (NNs) are employed in the proposed intelligent controller. Due to the learning capability of the NNs, the designed NN controller can compensate the effects of the nonlinear friction. Stability of the thus proposed learning control system is guaranteed by a rigid proof. Simulation and experimental results are provided to verify the effectiveness of the proposed intelligent scheme. © 2012 IEEE.


Feng S.-S.,National University of Singapore
Cellular and Molecular Bioengineering | Year: 2011

This article is made for the special issue of Cellular and Molecular Bioengineering-''Mechanobiology: A Tribute to Shu Chien's Scientific Achievement'' for his 80th Anniversary. Shu Chien is well known as a founder and pioneer of bioengineering. He is the only one in the world who simultaneously holds six academicians: US National Academy of Sciences, US National Academy of Engineering, US Institute of Medicine, and American Academy of Arts and Sciences, as well as Chinese Academy of Sciences and Academia Sinica Taiwan. As one of Shu Chien's PhD students at Columbia University, the author emphasizes in this article the significant contribution of Professor Shu Chien in creating and defining chemotherapeutic engineering as an emerging and prospective multidisciplinary area, which is defined as application and further development of engineering especially chemical engineering principles to solve the problems in chemotherapy of cancer and other fatal diseases such as cardiovascular disease and AIDS. Proof-of-concepts experimental results obtained so far are summarized. Safety issue is addressed. Prospect and outlook are described. In the author's point of view, chemotherapeutic engineering may change the way we make drugs and the way we take drugs, and will thus make significant contribution to the twentieth century medicine. © 2011 Biomedical Engineering Society.


Xu H.,National University of Singapore | Caramanis C.,University of Texas at Austin | Sanghavi S.,University of Texas at Austin
IEEE Transactions on Information Theory | Year: 2012

Singular-value decomposition (SVD) [and principal component analysis (PCA)] is one of the most widely used techniques for dimensionality reduction: successful and efficiently computable, it is nevertheless plagued by a well-known, well-documented sensitivity to outliers. Recent work has considered the setting where each point has a few arbitrarily corrupted components. Yet, in applications of SVD or PCA, such as robust collaborative filtering or bioinformatics, malicious agents, defective genes, or simply corrupted or contaminated experiments may effectively yield entire points that are completely corrupted. We present an efficient convex optimization-based algorithm that we call outlier pursuit, which under some mild assumptions on the uncorrupted points (satisfied, e.g., by the standard generative assumption in PCA problems) recovers the exact optimal low-dimensional subspace and identifies the corrupted points. Such identification of corrupted points that do not conform to the low-dimensional approximation is of paramount interest in bioinformatics, financial applications, and beyond. Our techniques involve matrix decomposition using nuclear norm minimization; however, our results, setup, and approach necessarily differ considerably from the existing line of work in matrix completion and matrix decomposition, since we develop an approach to recover the correct column space of the uncorrupted matrix, rather than the exact matrix itself. In any problem where one seeks to recover a structure rather than the exact initial matrices, techniques developed thus far relying on certificates of optimality will fail. We present an important extension of these methods, which allows the treatment of such problems. © 2011 IEEE.


Sovacool B.K.,National University of Singapore
Renewable Energy | Year: 2013

This article summarizes the threats that wind farms pose to birds before surveying the recent literature on avian mortality and summarizing common methodological problems with such studies. Based on operating performance in the United States and Europe, the paper then offers a preliminary calculation of the number of birds killed per kilowatt-hour kWh generated for wind electricity, fossil fuel, and nuclear power systems. The study estimates that wind farms and nuclear power stations are responsible each for between 0.3 and 0.4 fatalities per gigawatt-hour (GWh) of electricity while fossil fueled power stations are responsible for about 5.2 fatalities per GWh. Within the uncertainties of the data used, the estimate means that wind farms killed approximately 20,000 birds in the United States in 2009 but nuclear plants killed about 330,000 and fossil fueled power plants more than 14 million. The paper concludes that further study is needed, but also that fossil fueled power stations appear to pose a much greater threat to birds and avian wildlife than wind farms and nuclear power plants. © 2012.


Neoh K.G.,National University of Singapore | Kang E.T.,National University of Singapore
Soft Matter | Year: 2012

Stem cell implantation is increasingly viewed as a promising strategy for the treatment of many diseases. A key aspect of stem cell therapies is the ability to distinguish the implanted cells from the host tissue cells and to understand their fate. Ex vivo labeling of the stem cells combined with non-invasive real time imaging modalities such as magnetic resonance imaging (MRI) are highly advantageous for this purpose. Superparamagnetic iron oxide nanoparticles (SPIONs) are promising as a labeling agent but they have to be modified to increase uptake by stem cells in order to generate sufficient contrast from the unlabeled tissues. This review provides a summary of the methods for the synthesis of SPIONs, their properties, and strategies for their modification to increase the efficiency in labeling stem cells. The challenges faced in using SPIONs for stem cell tracking by MRI are also discussed. © 2011 The Royal Society of Chemistry.


Zhang J.,National University of Singapore | Zhao X.S.,National University of Singapore | Zhao X.S.,University of Queensland
ChemSusChem | Year: 2012

Supercapacitors, which are attracting rapidly growing interest from both academia and industry, are important energy-storage devices for acquiring sustainable energy. Recent years have seen a number of significant breakthroughs in the research and development of supercapacitors. The emergence of innovative electrode materials (e.g., graphene) has clearly provided great opportunities for advancing the science in the field of electrochemical energy storage. Conversely, smart configurations of electrode materials and new designs of supercapacitor devices have, in many cases, boosted the electrochemical performance of the materials. We attempt to summarize recent research progress towards the design and configuration of electrode materials to maximize supercapacitor performance in terms of energy density, power density, and cycle stability. With a brief description of the structure, energy-storage mechanism, and electrode configuration of supercapacitor devices, the design and configuration of symmetric supercapacitors are discussed, followed by that of asymmetric and hybrid supercapacitors. Emphasis is placed on the rational design and configuration of supercapacitor electrodes to maximize the electrochemical performance of the device. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Bao Q.,National University of Singapore | Loh K.P.,National University of Singapore
ACS Nano | Year: 2012

Graphene has been hailed as a wonderful material in electronics, and recently, it is the rising star in photonics, as well. The wonderful optical properties of graphene afford multiple functions of signal emitting, transmitting, modulating, and detection to be realized in one material. In this paper, the latest progress in graphene photonics, plasmonics, and broadband optoelectronic devices is reviewed. Particular emphasis is placed on the ability to integrate graphene photonics onto the silicon platform to afford broadband operation in light routing and amplification, which involves components like polarizer, modulator, and photodetector. Other functions like saturable absorber and optical limiter are also reviewed. © 2012 American Chemical Society.


Shi L.,National University of Singapore | Chew M.Y.L.,National University of Singapore
Renewable and Sustainable Energy Reviews | Year: 2012

This paper reviewed the state of the art in designing renewable energy systems specifically solar-based energy system, ground source-based system and day-lighting system, to gain optimum performances in sustainable buildings. Efficiency of each of these systems in reducing resource consumption was evaluated. Geometric conditions have a determining effect on the performances of solar-based energy system and day-lighting system. In solar-based energy system, designing factors, such as system selection, building's orientation, installation location, area of installation, tilt angle and surface temperature, are needed to be considered. Factors of day-lighting system, such as fenestration option, material, area or size, shape, orientation, position, ceiling and shading devices, are needed to be designed carefully to optimize the quality of the luminous environment for occupants. For ground source-based energy system, season condition, operating condition, mode of system, selection of compressor, ground heat exchanger, pump, are important to improve system's performance and reduce cost. © 2011 Elsevier Ltd. All rights reserved.


Adams S.,National University of Singapore | Prasada Rao R.,National University of Singapore
Journal of Materials Chemistry | Year: 2012

Dynamic lithium distribution, structural stability and ion transport mechanism in the new ultrafast ion conductor Li 10GeP 2S 12 are clarified with the help of atomistic molecular dynamics simulations, revealing only a weak anisotropy of Li + diffusion, and a coupling of Li + cation diffusion to PS 4 3- anion rotational mobility. The role of a previously overlooked Li site and the limited structural stability at elevated temperatures are discussed for the first time. © 2012 The Royal Society of Chemistry.


Micro-solid-phase extraction (μ-SPE) was developed for the determination of trace level of 16 United States Environmental Protection Agency priority polycyclic aromatic hydrocarbons (PAHs) in river water samples with gas chromatography-mass spectrometry (GC-MS). In the μ-SPE device, multiwalled carbon nanotubes was employed as sorbent and was packed inside an porous polypropylene membrane "envelope" whose edges were heat-sealed to secure the contents. The μ-SPE device was placed in a stirred sample solution to extract the analytes. The porous polypropylene membrane envelope in μ-SPE device acts as a filter to exclude potential interferences, such as eliminating or reducing the influence of particles that are bigger than the pore size. After extraction, analyte desorption was carried out with a suitable organic solvent under ultrasonication. Important extraction parameters were optimized in detail, including the selection and amount of sorbent materials, the extraction temperature and extraction time, desorption solvent and desorption time, amount of organic modifier, agitation speed and sample ionic strength. Under the developed extraction conditions, the proposed method provided good linearity in the range of 0.1-50 μg/L, low limits of detection (4.2-46.5. ng/L), and good repeatability of the extractions (relative standard deviations, <12%, n= 5). The developed μ-SPE method was successfully applied to the extraction of PAHs in river water samples. The μ-SPE method was demonstrated to be a fast and efficient method for the determination of PAHs from environmental water samples. © 2011 Elsevier B.V.


Schmidt H.,National University of Singapore | Giustiniano F.,National University of Singapore | Eda G.,National University of Singapore
Chemical Society Reviews | Year: 2015

Recent explosion of interest in two-dimensional (2D) materials research has led to extensive exploration of physical and chemical phenomena unique to this new class of materials and their technological potential. Atomically thin layers of group 6 transition metal dichalcogenides (TMDs) such as MoS2 and WSe2 are remarkably stable semiconductors that allow highly efficient electrostatic control due to their 2D nature. Field effect transistors (FETs) based on 2D TMDs are basic building blocks for novel electronic and chemical sensing applications. Here, we review the state-of-the-art of TMD-based FETs and summarize the current understanding of interface and surface effects that play a major role in these systems. We discuss how controlled doping is key to tailoring the electrical response of these materials and realizing high performance devices. The first part of this review focuses on some fundamental features of gate-modulated charge transport in 2D TMDs. We critically evaluate the role of surfaces and interfaces based on the data reported in the literature and explain the observed discrepancies between the experimental and theoretical values of carrier mobility. The second part introduces various non-covalent strategies for achieving desired doping in these systems. Gas sensors based on charge transfer doping and electrostatic stabilization are introduced to highlight progress in this direction. We conclude the review with an outlook on the realization of tailored TMD-based field-effect devices through surface and interface chemistry. © The Royal Society of Chemistry.


Yue G.H.,National University of Singapore
Fish and Fisheries | Year: 2014

Aquaculture is the fastest growing sector in agriculture. Substantial genetic gains have been achieved in a few cultured species using conventional selective breeding approaches. However, the majority of fish and shellfish species remain in their wild state. Due to the recognition of the enormous potential of marker-assisted selection (MAS) to speed up genetic gain through early selection, aquaculture scientists have constructed linkage maps in over 40 species and mapped quantitative trait loci (QTL) for important traits in over 20 species since the 1990s. Although MAS and genomic selection (GS) have not been widely used in aquaculture, their application in breeding programmes is expected to be a fertile area of research. In this paper, I summarized the recent advances of linkage and QTL mapping, as well as MAS in aquaculture species. I also discussed the potentials of genome-wide association studies (GWAS) and GS in aquaculture species. © 2013 John Wiley & Sons Ltd.


Bender M.A.,Tokutek, Inc. | Gilbert S.,National University of Singapore
Proceedings - Annual IEEE Symposium on Foundations of Computer Science, FOCS | Year: 2011

This paper presents a new algorithm for mutual exclusion in which each passage through the critical section costs amortized O(log 2 log n) RMRs with high probability. The algorithm operates in a standard asynchronous, local spinning, shared memory model with an oblivious adversary. It guarantees that every process enters the critical section with high probability. The algorithm achieves its efficient performance by exploiting a connection between mutual exclusion and approximate counting. © 2011 IEEE.


Neo C.Y.,National University of Singapore | Ouyang J.,National University of Singapore
Journal of Power Sources | Year: 2013

In this paper, we report a novel method to effectively fabricate the mesoporous TiO2 films of dye-sensitized solar cells (DSCs) by formulating new TiO2 pastes. Graphene oxide (GO) is added into TiO2 nanoparticles pastes as an auxiliary binder. Thick mesoporous TiO2 films free of crack can be prepared by only single printing. TiO2-GO pastes and films were characterized by dynamic mechanical analysis, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), X-ray diffraction (XRD), thermogravimetric analysis (TGA), and FTIR spectroscopy. TiO2 pastes added with GO exhibit gel behavior. GO helps bind TiO2 nanoparticles together through the interactions between functional groups on GO and the surface species of TiO2 nanoparticles. The presence of 0.8 wt.% GO in the TiO2 paste (GO weight percentage with respect to the weight of TiO2) is sufficient to fabricate thick and crack-free TiO2 films via single printing. These mesoporous TiO2 films fabricated from the TiO2-GO pastes are investigated as the anode of DSCs. They can give rise to a power conversion efficiency (PCE) of 7.70% for DSCs under AM1.5G illumination, which is almost the same as that of control devices with the TiO2 mesoporous electrode fabricated from the conventional TiO2 paste without GO via four-fold printings. © 2012 Elsevier B.V. All rights reserved.


Ge Q.,National University of Singapore | Chung T.-S.,National University of Singapore
Chemical Communications | Year: 2013

A new class of draw solutes from hydroacid complexes is presented. With hydroacid complexes as draw solutes in FO, superior performance is achieved in terms of high water fluxes and negligible reverse solute fluxes. The characteristics of expanded configurations, abundant hydrophilic groups and ionic species are essential for hydroacid complexes as competent draw solutes. © The Royal Society of Chemistry 2013.


Tan C.K.,National University of Singapore | Yeung Y.-Y.,National University of Singapore
Chemical Communications | Year: 2013

Bromination reactions have been made a lot more convenient since the invention of N-bromoamide reagents. These reagents are more easily handled when compared to molecular bromine. In comparison to other halogens, brominating reagents sit in between chlorine and iodine on the reactivity scale, giving them an advantage in some cases. Recently, several important advances in enantioselective bromofunctionalization of alkenes using such reagents have been reported. This article will highlight the challenges and methods to surmount these problems. In addition, this article will also show the use of N-bromoamide reagents in expanding the scope of diastereoselective bromofunctionalization of alkenes. Examples include bromine initiated cyclic ether cascades and novel multicomponent reactions (MCRs). © 2013 The Royal Society of Chemistry.


Morgan I.G.,Australian National University | Morgan I.G.,Sun Yat Sen University | Ohno-Matsui K.,Tokyo Medical and Dental University | Saw S.-M.,National University of Singapore | Saw S.-M.,Singapore Eye Research Institute
The Lancet | Year: 2012

Myopia has emerged as a major health issue in east Asia, because of its increasingly high prevalence in the past few decades (now 80-90% in school-leavers), and because of the sight-threatening pathologies associated with high myopia, which now affects 10-20% of those completing secondary schooling in this part of the world. Similar, but less marked, changes are occurring in other parts of the world. The higher prevalence of myopia in east Asian cities seems to be associated with increasing educational pressures, combined with life-style changes, which have reduced the time children spend outside. There are no reported major genes for school myopia, although there are several genes associated with high myopia. Any genetic contribution to ethnic differences may be small. However, to what extent many genes of small effect and gene-environment interactions contribute to variations in school myopia within populations remains to be established. There are promising optical and pharmacological interventions for preventing the development of myopia or slowing its progression, which require further validation, and promising vision-sparing treatments for pathological myopia.


I argue in this paper that transaction cost is central to the analytics of climate adaptation in the local commons. I illustrate this by bringing together insights from Coase on tradability of property rights, Ostrom on institutional design principles for long lived commons and Williamson on transaction cost and governance mechanisms. I call this the COW model on the analytics of climate adaptation, which I illustrate using grounded theory in the case of the 400-year old zangjera irrigation societies in Northern Philippines. The zangjeras are highly vulnerable to climatic risks but has successfully managed to adapt steadily overtime. I argue that their ability to adapt is a function of transaction cost which is associated with some ingenious principles of institutional design such as: (1) clear allocation and tradability of rights and obligations; (2) fairness in the allocation of risks, costs and benefits; (3) reliance on prices and incentives as adaptation mechanisms; (4) adaptive efficiency, i.e. maximization of welfare at least adaptation cost; (5) reliable enforcement mechanisms; and (6) a polycentric structure of governance. I conclude that the COW model can provide a useful foundation for the analytics of climate adaptation. © 2012 Elsevier Ltd.


Kay A.,National University of Singapore | Kay A.,Keble College
Physical Review Letters | Year: 2011

We analyze the effect of typical, unknown perturbations on the 2D toric code when acting as a quantum memory, incorporating the effects of error correction on readout. By transforming the system into a 1D transverse Ising model undergoing an instantaneous quench, and making extensive use of Lieb-Robinson bounds, we prove that for a large class of perturbations, the survival time of stored information grows at least logarithmically with the system size. A uniform magnetic field saturates this scaling behavior. We show that randomizing the stabilizer strengths gives a polynomial survival time with a degree that depends on the strength of the perturbation. © 2011 American Physical Society.


Ding J.,National University of Singapore | Kostylev M.,University of Western Australia | Adeyeye A.O.,National University of Singapore
Physical Review Letters | Year: 2011

We show that periodic magnetic nanostructures represent a perfect system for studying excitations on disordered periodical lattices because of the possibility of controlled variation of the degree of disorder by varying the applied magnetic field. Magnetic force microscopy images and ferromagnetic resonance (FMR) data collected inside minor hysteresis loops for a periodic array of Permalloy nanowires were used to demonstrate correlation between the type of FMR response and the degree of disorder of the magnetic ground state. © 2011 American Physical Society.


Han X.,National University of Singapore | Zhong F.,National University of Singapore | Wang Y.,Henan University | Lu Y.,National University of Singapore
Angewandte Chemie - International Edition | Year: 2012

A fast one: The title reaction proceeds in the presence of 5 mol % of the catalyst 1, and is complete within an hour. The 2-alkyl- and 2-aryl-substituted 3-pyrroline products are obtained in good yield and with high enantioselectivity. The application of the method to the concise formal synthesis of (+)-trachelanthamidine is also demonstrated. Boc=tert- butoxycarbonyl, M.S.=molecular sieves, TBDPS=tert-butyldiphenylsilyl. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Xiong S.,National University of Singapore | Zeng H.C.,National University of Singapore
Angewandte Chemie - International Edition | Year: 2012

Transformation in a shell: Ion exchange is used for the fabrication of multishelled inorganic hollow materials. The transformation of solid Cu 2O to Cu 2S hollow spheres is investigated as a model reaction (see picture; PVP=poly(vinylpyrrolidone)). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Adams S.,National University of Singapore
Journal of Solid State Electrochemistry | Year: 2010

Determining ion transport pathways as regions of low bond valence mismatch represents a simple, reliable way of characterizing ion transport pathways in local structure models, provided that the local structure model captures the essential structural features. The examples of LiFePO 4 and other olivine-type mixed conductors discussed here demonstrate the impact of structural disorder on the ion transport pathway and mechanism. The effect of Li' Fe antisite defects on the transition from one- to two-dimensional conduction pathway dimensionality as well the possibility of heterogeneous doping of LiFePO 4 by a lithium phosphate glass surface layer are discussed in detail. © Springer-Verlag 2010.


Muller C.A.,National University of Singapore
Applied Physics B: Lasers and Optics | Year: 2011

Two aspects of bright matter-wave solitons in weak external potentials are discussed. First, we briefly review recent results on the Anderson localization of an entire soliton in disordered potentials, as a paradigmatic showcase of genuine quantum dynamics beyond simple perturbation theory. Second, we calculate the linear response of the mean-field soliton shape to a weak, but otherwise arbitrary, external potential, with a detailed application to lattice potentials. © 2011 Springer-Verlag.


We show that, in a gravitational theory [in any number of dimensions greater than 3] which admits BPS branes and AdS-Reissner-Nordström black holes with flat event horizons, the specific [dimensionless] temperature of such a black hole is bounded below by ≈0.156875. This confirms the recent suggestion by Hartnoll and Tavanfar, to the effect that no such black hole can be arbitrarily cold, since from the AdS/CFT dual point of view the low-temperature degrees of freedom should not be concealed by the equivalent of an event horizon. © 2011 Elsevier B.V.


Pereira B.P.,National University of Singapore
Annals of Anatomy | Year: 2013

Background: Recent studies have designated the anconeus muscle as an option for use as a pedicled flap for covering soft tissue defects about the elbow, with reported minimal risk of morbidity. This has raised the question as to the importance of the anconeus muscle and as to whether this is truly an accessory muscle that can be sacrificed, or whether the anconeus muscle significantly contributes to elbow and forearm stability? This study revisits the anatomy and biomechanics of the anconeus muscle and aims to investigate the neuromuscular compartments of the anconeus muscle and to determine the changes in the muscle length, fibre length and moment arm over a range of elbow flexion angles for each compartment. Methods: An anatomical study on 8 human cadavers (51-77 years of age) was done and a 2-dimensional kinematic elbow model developed to determine changes in the muscle length and moment arm of the muscle related to changes in elbow flexion angles. Findings: The muscle was modelled with two possible lines of action, one along the posterior and another on the anterior edge of the muscle as they had different muscle fibre lengths (posterior: average of 32. mm, anterior: average of 20. mm). The anterior edge also had an aponeurosis which was 70% of its length. From 0 to 120° elbow flexion, the length of the posterior and anterior edges increased with a maximum change recorded at 90° elbow flexion (31.7. ±. 1.0. mm and 65.3. ±. 1.4. mm, respectively). The moment arm is 14-mm at 0° flexion, but between the posterior and anterior edges it decreases at different rates with increasing elbow flexion angle. Beyond 80°, the anterior edge behaves as an elbow flexor, while the posterior edge remains an elbow extensor. The study demonstrates that the anconeus muscle has two neuromuscular compartments each with distinct intramuscular innervations and muscle fibre lengths. Interpretation: The posterior and deep aspect of the muscle functions as an elbow extensor decreasing in influence with increasing elbow flexion angle. The anterior superficial aspect which is adjacent and parallel to the lateral collateral ligaments, would most likely work in unison to provide constraint to the posterolateral stability of the elbow. © 2012.


Tan C.-S.,National University of Singapore | Gilligan D.,University of Cambridge | Pacey S.,University of Cambridge
The Lancet Oncology | Year: 2015

Discovery of activating mutations in EGFR and their use as predictive biomarkers to tailor patient therapy with EGFR tyrosine kinase inhibitors (TKIs) has revolutionised treatment of patients with advanced EGFR-mutant non-small-cell lung cancer (NSCLC). At present, first-line treatment with EGFR TKIs (gefitinib, erlotinib, and afatinib) has been approved for patients harbouring exon 19 deletions or exon 21 (Leu858Arg) substitution EGFR mutations. These agents improve response rates, time to progression, and overall survival. Unfortunately, patients develop resistance, limiting patient benefit and posing a challenge to oncologists. Optimum treatment after progression is not clearly defined. A more detailed understanding of the biology of EGFR-mutant NSCLC and the mechanisms of resistance to targeted therapy mean that an era of treatment approaches based on rationally developed drugs or therapeutic strategies has begun. Combination approaches-eg, dual EGFR blockade-to overcome resistance have been trialled and seem to be promising but are potentially limited by toxicity. Third-generation EGFR-mutant-selective TKIs, such as AZD9291 or rociletininb, which target Thr790Met-mutant tumours, the most common mechanism of EGFR TKI resistance, have entered clinical trials, and exciting, albeit preliminary, efficacy data have been reported. In this Review, we summarise the scientific literature and evidence on therapy options after EGFR TKI treatment for patients with NSCLC, aiming to provide a guide to oncologists, and consider how to maximise therapeutic advances in outcomes in this rapidly advancing area. © 2015 Elsevier Ltd.


Zeolite imidazolate framework 8 (ZIF-8) has permanent porosity, high surface area, hydrophobic property, open metal sites and remarkable water stability. These novel properties characterize the material as being different from other moisture sensitive metal-organic frameworks and endow ZIF-8 with the potential to extract trace analytes from environmental water samples. In the present study, ZIF-8 was synthesized and used as a sorbent for micro-solid-phase extraction of 6 polycyclic aromatic hydrocarbons (PAHs) from environmental water samples for the first time. Parameters influencing the extraction efficiency such as desorption time, extraction time, desorption solvent and salt concentration were investigated. Environmental water samples collected from a local lake were processed using this novel μ-SPE procedure. ZIF-8 proved to be a very efficient extraction sorbent for the extraction of trace analytes from water samples. The limits of detection from gas chromatography-mass spectrometric analysis of PAHs were 0.002-0.012. ng/ml. The linear ranges were 0.1-50 or 0.5-50. ng/ml. The relative standard deviations for five replicates of the extractions were in the range of 2.1-8.5%. © 2011 Elsevier B.V.


Subbaiah V.K.,National University of Singapore
Oncogene | Year: 2015

Tat-interacting protein of 60 kDa (TIP60) is an essential lysine acetyltransferase implicated in transcription, DNA damage response and apoptosis. TIP60 protein expression is reduced in cancers. In cervical cancers, human papillomavirus (HPV) E6 oncogene targets cellular p53, Bak and some of the PDZ domain-containing proteins for proteasome-mediated degradation through E6AP ligase. Recently, E6 oncogene from high-risk and low-risk categories was also shown to target TIP60. However, the molecular mechanisms and whether destabilization of TIP60 contributes to HPV E6-mediated transformation remain unanswered. Our proteomic analyses revealed EDD1 (E3 identified by differential display), an E3 ligase generally overexpressed in cancers as a novel interacting partner of TIP60. By investigating protein turnover and ubiquitination assays, we show that EDD1 negatively regulates TIP60’s stability through the proteasome pathway. Strikingly, HPV E6 uses this function of EDD1 to destabilize TIP60. Colony-formation assays and soft agar assays show that gain of function of TIP60 or depletion of EDD1 in HPV-positive cervical cancer cells significantly inhibits cell growth in vitro. This phenotype is strongly supported by the in-vivo studies where re-activation of TIP60 in cervical cancer cells dramatically reduces tumor formation. In summary, we have discovered a novel ligase through which E6 destabilizes TIP60. Currently, in the absence of an effective therapeutic vaccine for malignant cervical cancers, cervical cancer still remains to be a major disease burden. Hence, our studies implying a distinct tumor suppressor role for TIP60 in cervical cancers show that reactivation of TIP60 could be of therapeutic value.Oncogene advance online publication, 3 August 2015; doi:10.1038/onc.2015.268. © 2015 Macmillan Publishers Limited


Karunaratne G.P.,National University of Singapore
Geotextiles and Geomembranes | Year: 2011

The use of prefabricated vertical drains to consolidate soft clay is a common ground improvement method. In large projects laboratory testing of PVDs for selection and quality assurance is considered important. This paper presents a review of PVD laboratory testing. The need to provide simulated site conditions in the test is emphasized. In addition instrumented PVDs show that installation stresses in deep soft clay deposits could cause filter rupture under tensile failure. It is also shown that the maximum required discharge capacity of a PVD is obtained by equating the flow rate of the PVD under the installation and consolidation states to the maximum rate of volume reduction of the influential clay cylinder of the PVD. Consolidation can be enhanced much faster in clay soils if vertical drains manufactured with conducting polymer are used. Some laboratory tests, field tests and field applications of such electric vertical drains (EVD) are presented. A minimum current density at appropriate applied voltage is required to benefit from the electric osmosis (EO) application. EVD in dewatering clay soils, extracting heavy metals in clay soils and few other geotechnical applications are also presented. © 2010.


Madan B.,National University of Singapore
Oncogene | Year: 2015

Enhanced sensitivity to Wnts is an emerging hallmark of a subset of cancers, defined in part by mutations regulating the abundance of their receptors. Whether these mutations identify a clinical opportunity is an important question. Inhibition of Wnt secretion by blocking an essential post-translational modification, palmitoleation, provides a useful therapeutic intervention. We developed a novel potent, orally available PORCN inhibitor, ETC-1922159 (henceforth called ETC-159) that blocks the secretion and activity of all Wnts. ETC-159 is remarkably effective in treating RSPO-translocation bearing colorectal cancer (CRC) patient-derived xenografts. This is the first example of effective targeted therapy for this subset of CRC. Consistent with a central role of Wnt signaling in regulation of gene expression, inhibition of PORCN in RSPO3-translocated cancers causes a marked remodeling of the transcriptome, with loss of cell cycle, stem cell and proliferation genes, and an increase in differentiation markers. Inhibition of Wnt signaling by PORCN inhibition holds promise as differentiation therapy in genetically defined human cancers.Oncogene advance online publication, 10 August 2015; doi:10.1038/onc.2015.280. © 2015 Macmillan Publishers Limited


Murray T.H.,Hastings Center | Murray T.H.,National University of Singapore
Science | Year: 2014

How much discretion should parents be granted in determining what sort of child they have?


Mei X.,National University of Singapore | Ouyang J.,National University of Singapore
Carbon | Year: 2011

A green method is reported to effectively and rapidly reduce graphene oxide to graphene with zinc powder at room temperature. The reduction is carried out by mixing graphene oxide and zinc powder in solution under ultrasonication. The reduction is complete within 1 min. The weight of the Zn powder should be at least as twice as that of graphene oxide to complete the reduction. The reduction of graphene oxide is confirmed by FTIR, UV-Vis absorption spectroscopy and Raman spectroscopy. The carbon/oxygen atomic ratio has increased from 2.58 to 33.5 after the reduction as determined by X-ray photoelectron spectroscopy. The reduced graphene oxide can have a conductivity of 15,000 S/m. It also has good thermal stability with the weight loss at 590 ° C in air. The reduced graphene oxide can be readily re-dispersed into solutions of various surfactants. © 2011 Elsevier Ltd. All rights reserved.


Pandey K.,National University of Singapore
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

The well-known Λ system using two ground-state hyperfine levels, Fg=1 and Fg=2 of 5S1/2, and one hyperfine level, Fe=2 of excited state of 5P3/2 of 87Rb, has been recently studied using two counterpropagating control lasers. The experiment shows conversion of electromagnetically induced transparency into electromagnetically induced absorption because the doubly driven Λ system forms various subsystems. We here present a detailed theoretical study of the different possible subsystems created by this configuration. We also explore the possibility of tuning the strength of individual subsystems by changing the polarization of the control lasers. © 2013 American Physical Society.


Olsher D.J.,National University of Singapore
Proceedings - 12th IEEE International Conference on Data Mining Workshops, ICDMW 2012 | Year: 2012

If NLP systems could better simulate how people would evaluate various states of the world in contexts of interest, this would make it easier to accurately extract embedded sentiments and avoid being led astray by solely linguistic cues. If this knowledge could then be combined with 'full-semantics' linguistic processing capable of modeling the interplay between lexical and syntactic semantics and then interweaving these with domain knowledge, this would allow the use of important semantic information (including argument and, especially, valence structure) implicit in phrases such as 'Critics say' and 'Despite this.' The present paper seeks to implement these insights, employing domain models grounded in the INTELNET/COGVIEW 'energy-based' knowledge representation formalism and the Radical Construction Grammar-based COGPARSE parser, bringing together concepts, knowledge, language processing, and opinion mining. © 2012 IEEE.


Leong W.L.,National University of Singapore | Vittal J.J.,Gyeongsang National University
Chemical Reviews | Year: 2011

Complexity and diversity in structures, properties, and applications are examined. Zigzag type conformation is also ubiquitous in 1D CPs. The construction of zigzag CPs stemmed from flexible exoditopic ligands and linear or cis-coordinated octahedral metal centers or tetrahedral metal ions. Infinite helical structural motif has special place in supramolecular chemistry because of its similarities in biological systems and enantioselective catalysis. Generally, utilization of flexible or chiral ligands is a facile approach to achieve helical CPs, while many successful examples of spontaneous chirality induction from achiral ligands also have been widespread in the literature. Conformationally flexible ligands are the key success of self-assembly of structural motifs, such as polycatenanes, helices, braids, Borromean rings and rotaxanes.


Baaquie B.E.,National University of Singapore
Physica A: Statistical Mechanics and its Applications | Year: 2013

A statistical generalization is made of microeconomics in the spirit of going from classical to statistical mechanics. The price and quantity of every commodity1 traded in the market, at each instant of time, is considered to be an independent random variable: all prices and quantities are considered to be stochastic processes, with the observed market prices being a random sample of the stochastic prices. The dynamics of market prices is determined by an action functional and, for concreteness, a specific model is proposed. The model can be calibrated from the unequal time correlation of the market commodity prices. A perturbation expansion for the correlation functions is defined in powers of the inverse of the total budget of the aggregate consumer and the propagator for the market prices is evaluated. © 2013 Elsevier B.V. All rights reserved.


Chhowalla M.,Rutgers University | Shin H.S.,Ulsan National Institute of Science and Technology | Eda G.,National University of Singapore | Li L.-J.,Academia Sinica, Taiwan | And 2 more authors.
Nature Chemistry | Year: 2013

Ultrathin two-dimensional nanosheets of layered transition metal dichalcogenides (TMDs) are fundamentally and technologically intriguing. In contrast to the graphene sheet, they are chemically versatile. Mono- or few-layered TMDs-obtained either through exfoliation of bulk materials or bottom-up syntheses-are direct-gap semiconductors whose bandgap energy, as well as carrier type (n- or p-type), varies between compounds depending on their composition, structure and dimensionality. In this Review, we describe how the tunable electronic structure of TMDs makes them attractive for a variety of applications. They have been investigated as chemically active electrocatalysts for hydrogen evolution and hydrosulfurization, as well as electrically active materials in opto-electronics. Their morphologies and properties are also useful for energy storage applications such as electrodes for Li-ion batteries and supercapacitors. © 2013 Macmillan Publishers Limited. All rights reserved.


Kole G.K.,National University of Singapore | Vittal J.J.,National University of Singapore | Vittal J.J.,Gyeongsang National University
Chemical Society Reviews | Year: 2013

This tutorial review discusses recent literature on coordination polymers and metal-organic frameworks (MOFs) that exhibit solid-state reactivity and structural transformation under various experimental conditions. Removal or exchange of solvents and guest molecules, exposure to reactive vapours, and external stimuli such as heat, light or mechanochemical force cause such structural transformations and these are often manifested by various physical properties such as colour, magnetism, luminescence, chirality, porosity, etc. due to change in coordination number and geometry, dimensionality, interpenetration, etc. More drastic transformations related to the exchange of metal ions, pillar ligands and insertion of additional ligands between the layers have also been demonstrated. The vast area of dynamic behaviour of coordination polymers and their stimuli-responsive properties have also been addressed briefly. © 2013 The Royal Society of Chemistry.


Guo L.,National University of Singapore | Lee H.K.,National University of Singapore
Journal of Chromatography A | Year: 2011

For the first time, an ionic liquid based three-phase liquid-liquid-liquid solvent bar microextraction (IL-LLL-SBME) was developed for the analysis of phenols in seawater samples. The ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), was used as the intermediary solvent for LLL-SBME, enhancing the extraction efficiency for polar analytes. In the procedure, the analytes were extracted from the aqueous sample into the ionic liquid intermediary and finally, back-extracted into an aqueous acceptor solution in the lumen of the hollow fiber. The porous polypropylene membrane acted as a filter to prevent potential interfering materials from being extracted, and no additional cleanup was required. After extraction, the acceptor solution could be directly injected into a high-performance liquid chromatographic system for analysis. Six phenols, 2-nitrophenol, 4-chlorophenol, 2,3-dichlorophenol, 2,4-dichlorophenol, 2,4,6-trichlorophenol and pentachlorophenol were selected here as model compounds for developing and evaluating the method. The most influential extraction parameters were evaluated, including the ionic liquid, the composition of donor solution and acceptor solution, the extraction time and the extraction temperature, the effect of ionic strength, and the agitation speed. Under the most favorable extraction parameters, the method showed good linearity (from 0.05-50 to 0.5-50μg/L, depending on the analytes) and repeatability of extractions (RSD below 8.3%, n=5). The proposed method was compared to conventional three-phase LLL-SBME and ionic liquid supported hollow fiber protected three-phase liquid-liquid-liquid microextraction, and showed higher extraction efficiency. The proposed method was demonstrated to be a simple, fast, and efficient method for the analysis of phenols from environmental water samples. © 2011 Elsevier B.V.


Nhan H.S.,University of California at San Diego | Chiang K.,University of California at San Diego | Koo E.H.,University of California at San Diego | Koo E.H.,National University of Singapore
Acta Neuropathologica | Year: 2015

The amyloid precursor protein (APP) has occupied a central position in Alzheimer’s disease (AD) pathophysiology, in large part due to the seminal role of amyloid-β peptide (Aβ), a proteolytic fragment derived from APP. Although the contribution of Aβ to AD pathogenesis is accepted by many in the research community, recent studies have unveiled a more complicated picture of APP’s involvement in neurodegeneration in that other APP-derived fragments have been shown to exert pathological influences on neuronal function. However, not all APP-derived peptides are neurotoxic, and some even harbor neuroprotective effects. In this review, we will explore this complex picture by first discussing the pleiotropic effects of the major APP-derived peptides cleaved by multiple proteases, including soluble APP peptides (sAPPα, sAPPβ), various C- and N-terminal fragments, p3, and APP intracellular domain fragments. In addition, we will highlight two interesting sequences within APP that likely contribute to this duality in APP function. First, it has been found that caspase-mediated cleavage of APP in the cytosolic region may release a cytotoxic peptide, C31, which plays a role in synapse loss and neuronal death. Second, recent studies have implicated the –YENPTY– motif in the cytoplasmic region as a domain that modulates several APP activities through phosphorylation and dephosphorylation of the first tyrosine residue. Thus, this review summarizes the current understanding of various APP proteolytic products and the interplay among them to gain deeper insights into the possible mechanisms underlying neurodegeneration and AD pathophysiology. © 2014, Springer-Verlag Berlin Heidelberg.


Jennings J.R.,National University of Singapore | Wang Q.,National University of Singapore
Journal of Physical Chemistry C | Year: 2010

Varying Li+ concentration in the electrolyte of dye-sensitized solar cells equipped with compact TiO2 blocking layers is found to alter the mean slopes of semilogarithmic open-circuit photovoltage-intensity and dark current-voltage plots. Almost identical values of ideality factor or transfer coefficient are required to fit data in the dark and under illumination for each Li+ concentration. It is found that cell characteristics become progressively more "ideal" as Li+ concentration is increased, with a transfer coefficient of ca.1 for 1 M Li+ in the electrolyte. We find that trends in photovoltage-intensity data are well fitted using a model which assumes that electron transfer to acceptor species in the electrolyte occurs from both the conduction band of the TiO2and an exponential distribution of band gap surface states. Changes in the mean ideality factor and linearity of semilogarithmic photovoltage-intensity plots can be rationalized by considering the variation in overlap between occupied donor states (conduction band and surface states) with electron acceptor states in the electrolyte, as the conduction band edge is shifted positive by increasing Li+ concentration. In accordance with previous studies, this positive shift in conduction band edge is also found to cause a dramatic increase in the photocurrent generation efficiency of the cells, especially in the long-wavelength region of the photocurrent action spectrum. It is argued that this improvement in photocurrent is predominantly due to an increase in wavelength-dependent electron injection efficiency, as opposed to an increase in electron collection efficiency. Copyright © 2010 American Chemical Society.


McInnes B.,National University of Singapore
Nuclear Physics B | Year: 2011

The AdS/CFT correspondence may give a new way of understanding field theories in extreme conditions, as in the quark-gluon plasma phase of quark matter. The correspondence normally involves asymptotically AdS black holes with dual field theories which are defined on locally flat boundary spacetimes; the implicit assumption is that the distortions of spacetime which occur under extreme conditions do not affect the field theory in any unexpected way. However, AdS black holes are [to varying degrees] fragile, in the sense that they become unstable to stringy effects when their event horizons are sufficiently distorted. This implies that field theories on curved backgrounds may likewise be unstable in a suitable sense. We investigate this phenomenon, focussing on the "fragility" of AdS5 black holes with flat event horizons. We find that, when they are distorted, these black holes are always unstable in string theory. This may have consequences for the detailed structure of the quark matter phase diagram at extreme values of the spacetime curvature. © 2010 Elsevier B.V.


China's huge investment on water infrastructure for sustainable water use, followed by recently frequent natural disasters, caused worldwide concerns, i. e., continuously published by Nature and Science. Most researchers emphasized challenges on this investment; yet, we argue that the 2011-plan, targeting reservoirs, wells, irrigation systems, inter-basin water transfer projects, is the most effective adaptation to climate change, drought and flooding, as well as food security. This provides a good case of water management and development, particularly for the current uneven water resources and food security by climate change. © 2011 Springer Science+Business Media B.V.


Chow E.K.-H.,National University of Singapore | Ho D.,University of California at Los Angeles
Science Translational Medicine | Year: 2013

Nanotechnology-based chemotherapeutics and imaging agents represent a new era of "cancer nanomedicine" working to deliver versatile payloads with favorable pharmacokinetics and capitalize on molecular and cellular targeting for enhanced specificity, efficacy, and safety. Despite the versatility of many nanomedicine-based platforms, translating new drug or imaging agents to the clinic is costly and often hampered by regulatory hurdles. Therefore, translating cancer nanomedicine may largely be application-defined, where materials are adapted only toward specific indications where their properties confer unique advantages. This strategy may also realize therapies that can optimize clinical impact through combinatorial nanomedicine. In this review, we discuss how particular materials lend themselves to specific applications, the progress to date in clinical translation of nanomedicine, and promising approaches that may catalyze clinical acceptance of nano.


Sovacool B.K.,National University of Singapore