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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

Zhang Y.Y.,University of Western Sydney | Pei Q.X.,Institute of High Performance Computing of Singapore | Wang C.M.,National University of Singapore
Applied Physics Letters | Year: 2012

Graphyne is the allotrope of graphene. In this letter, four different graphynes (α, β, γ, and 6,6,12-graphenes) are investigated by molecular dynamics simulations to explore their mechanical properties and failure mechanisms. It is found that the presence of the acetylenic linkages in graphynes leads to a significant reduction in fracture stress and Young's modulus with the degree of reduction being proportional to the percentage of the linkages. This deterioration in mechanical properties stems from the low atom density in graphynes and weak single bonds in the acetylenic linkages where the facture is initiated. © 2012 American Institute of Physics.

Miao Y.,Duke University | Li G.,Duke University | Zhang X.,University of Michigan | Xu H.,University of Michigan | And 2 more authors.
Cell | Year: 2015

Vertebrate cells have evolved elaborate cell-autonomous defense programs to monitor subcellular compartments for infection and to evoke counterresponses. These programs are activated by pathogen- associated pattern molecules and by various strategies intracellular pathogens employ to alter cellular microenvironments. Here, we show that, when uropathogenic E. coli (UPEC) infect bladder epithelial cells (BECs), they are targeted by autophagy but avoid degradation because of their capacity to neutralize lysosomal pH. This change is detected by mucolipin TRP channel 3 (TRPML3), a transient receptor potential cation channel localized to lysosomes. TRPML3 activation then spontaneously initiates lysosome exocytosis, resulting in expulsion of exosome-encased bacteria. These studies reveal a cellular default system for lysosome homeostasis that has been co-opted by the autonomous defense program to clear recalcitrant pathogens. © 2015 Elsevier Inc.

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.

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.

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.

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.

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

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.

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.

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.

Duraiswamy S.,4 Engineering Drive 4 | Khan S.A.,4 Engineering Drive 4 | Khan S.A.,National University of Singapore
Nano Letters | Year: 2010

The availability of robust, scalable, and automated nanoparticle manufacturing processes is crucial for the viability of emerging nanotechnologies. Metallic nanoparticles of diverse shape and composition are commonly manufactured by solution-phase colloidal chemistry methods, where rapid reaction kinetics and physical processes such as mixing are inextricably coupled, and scale-up often poses insurmountable problems. Here we present the first continuous flow process to synthesize thin gold "nanoshells" and "nanoislands" on colloidal silica surfaces, which are nanoparticle motifs of considerable interest in plasmonics-based applications. We assemble an ordered, flowing composite foam lattice in a simple microfluidic device, where the lattice cells are alternately aqueous drops containing reagents for nanoparticle synthesis or gas bubbles. Microfluidic foam generation enables precisely controlled reagent dispensing and mixing, and the ordered foam structure facilitates compartmentalized nanoparticle growth. This is a general method for aqueous colloidal synthesis, enabling continuous, inherently digital, scalable, and automated production processes for plasmonic nanomaterials. © 2010 American Chemical Society.

Wasson R.J.,National University of Singapore
Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences | Year: 2012

River and catchment management usually proceeds from the identification of an undesirable state (e.g. pollution, sedimentation, excessive water extraction, dams, invasion by exotic species) to a strategy for reaching a desirable state described as a target. Desirable states are usually determined from community values, economic assessments and ecosystem functions, or a combination of these. Where a catchment is highly disturbed, the target is usually not a natural state, as that cannot be achieved while maintaining human uses, and a history is needed to document the disturbance, understand its cause and define the 'existence space', that is, the range of natural states that have occurred in the past. Where a catchment is less disturbed, a former natural state could provide a target for management. But which of the many natural (equilibrium) states that have occurred in the past should be the target? The paper reviews what is known of the quantitative difference between pre- and post-disturbance states, searches for the presence or otherwise of equilibrium and comments on the utility of this information for catchment management. The focus is on erosion and sediment transport. This journal is © 2012 The Royal Society.

Mazumder S.K.,University of Illinois at Chicago | Rathore A.K.,National University of Singapore
IEEE Transactions on Industrial Electronics | Year: 2011

Emerging trends of high-power-density power-electronics interfaces for renewable- and alternative-energy sources have led to the need for high-frequency-inverter designs without compromising energy-conversion efficiency. In that context, a zero-voltage-switching (ZVS)-based scheme is described in this letter, for a cycloconverter-type high-frequency-link inverter, which is applicable for renewable- and alternative-energy sources as well as other commercial applications. The proposed scheme achieves the primary-side-converter-assisted switching of the ac/ac converter switches under ZVS condition. The modes of operation of the ac/ac converter are explained to outline the behavioral response. The results on the efficacy of the ZVS-based inverter and its performance show satisfactory performances. © 2010 IEEE.

Lai A.Y.,National University of Singapore
Asia-Pacific Journal of Public Health | Year: 2012

Collaborative capacity serves for organizations as the capacity to collaborate with other network players. Organizational capacity matters as collaboration outcomes usually go beyond single-shot implementation efforts or a single-minded focus on either the vertical dimension of program or the horizontal component. This review article explores organizational collaborative capacities from the perspective of public management, in particular, network theory. By applying the 5 attributes of network theory-interdependence, membership, resources, information, and learning-to the explanation of collaborative capacity in fighting pandemic crises, I argue in some ways organizational collaborative capacity is very much like an organization in its own right. Studying collaborative capacity in the battle against pandemics facilitate our understanding of multisectoral collaboration in technical, political, and institutional dimensions, and greatly advances the richness of capacity vocabulary in pandemic response and preparedness. © 2012 Asia-Pacific Academic Consortium for Public Health.

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.

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.

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.

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.

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.

Leushacke M.,Singapore Institute of Medical Biology | Barker N.,Singapore Institute of Medical Biology | Barker N.,University of Edinburgh | Barker N.,National University of Singapore
Gut | Year: 2014

Limited pools of resident adult stem cells are critical effectors of epithelial renewal in the intestine throughout life. Recently, significant progress has been made regarding the isolation and in vitro propagation of fetal and adult intestinal stem cells in mammals. It is now possible to generate ever-expanding, three-dimensional epithelial structures in culture that closely parallel the in vivo epithelium of the intestine. Growing such organotypic epithelium ex vivo facilitates a detailed description of endogenous niche factors or stem-cell characteristics, as they can be monitored in real time. Accordingly, this technology has already greatly contributed to our understanding of intestinal adult stem-cell renewal and differentiation. Transplanted organoids have also been proven to readily integrate into, and effect the long- Term repair of, mouse colonic epithelia in vivo, establishing the organoid culture as a promising tool for adult stem cell/gene therapy. In another exciting development, novel genome-editing techniques have been successfully employed to functionally repair disease loci in cultured intestinal stem cells from human patients with a hereditary defect. It is anticipated that this technology will be instrumental in exploiting the regenerative medicine potential of human intestinal stem cells for treating human disorders in the intestinal tract and for creating near-physiological ex vivo models of human gastrointestinal disease.

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.

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.

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.

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.

Yi G.,Institute Of Bioengineering And Nanotechnology, Singapore | Peng Y.,Institute Of Bioengineering And Nanotechnology, Singapore | Gao Z.,National University of Singapore
Chemistry of Materials | Year: 2011

Near infrared (NIR)-to-red upconversion fluorescent nanoparticles of yttrium oxyfluoride, ytterbium, erbium/yttrium oxyfluoride (YOF:Yb,Er/YOF) with a core/shell structure have been prepared for the first time. Under 980 nm NIR excitation, they emitted strong red upconversion fluorescence with a sharp emission band topping at ∼669 nm. Compared with the most efficient green emitting hexagonal phase NaYF4:Yb,Er upconversion fluorescent nanoparticles, our red-emitting fluorescent nanoparticles exhibited even stronger fluorescence. The YOF shell played a dual-role in the upconversion: it greatly enhanced the red emission at ∼669 nm (∼18 times) and suppressed the green emission of erbium at ∼530 nm. These nanoparticles were rendered hydrophilic by using several strategies and were further conjugated to antibodies for cancer cell labeling and imaging. As both excitation and emission were in the long wavelength range (>650 nm), which are transparent to tissues, along with their strong and narrow emission, these red emission upconversion fluorescent nanoparticles offer excellent opportunities for biosensing and in vivo bioimaging applications. © 2011 American Chemical Society.

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.

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.

Lai R.C.,Agency for Science, Technology and Research Singapore | Yeo R.W.Y.,Agency for Science, Technology and Research Singapore | Lim S.K.,Agency for Science, Technology and Research Singapore | Lim S.K.,National University of Singapore
Seminars in Cell and Developmental Biology | Year: 2015

MSCs are an extensively used cell type in clinical trials today. The initial rationale for their clinical testing was based on their differentiation potential. However, the lack of correlation between functional improvement and cell engraftment or differentiation at the site of injury has led to the proposal that MSCs exert their effects not through their differentiation potential but through their secreted product, more specifically, exosomes, a type of extracellular vesicle. We propose here that MSC exosomes function as an extension of MSC's biological role as tissue stromal support cells. Like their cell source, MSC exosomes help maintain tissue homeostasis for optimal tissue function. They target housekeeping biological processes that operate ubiquitously in all tissues and are critical in maintaining tissue homeostasis, enabling cells to recover critical cellular functions and begin repair and regeneration. This hypothesis provides a rationale for the therapeutic efficacy of MSCs and their secreted exosomes in a wide spectrum of diseases. Here, we give a brief introduction of the biogenesis of MSC exosomes, review their physiological functions and highlight some of their biochemical potential to illustrate how MSC exosomes could restore tissue homeostasis leading to tissue recovery and repair. © 2015 Elsevier Ltd.

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.

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.

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.

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.

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.

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.

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.

Vashist S.K.,National University of Singapore
Analytica Chimica Acta | Year: 2012

The frequent monitoring of glucose is an essential part of diabetes management. Despite the fact that almost all the commercially successful blood glucose monitoring devices are invasive, there is an immense need to develop non-invasive glucose monitoring (NGM) devices that will alleviate the pain and suffering of diabetics associated with the frequent pricking of skin for taking the blood sample for glucose testing. There have been numerous developments in the field of NGM during the last decade, which stress the need for a critical review. This manuscript aims to review the various NGM techniques and devices. The challenges and future trends in NGM are also discussed. © 2012 Elsevier B.V.

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.

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.

Xu H.,National University of Singapore | Caramanis C.,University of Texas at Austin | Mannor S.,Technion - Israel Institute of Technology
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2012

We consider two desired properties of learning algorithms: sparsity and algorithmic stability. Both properties are believed to lead to good generalization ability. We show that these two properties are fundamentally at odds with each other: A sparse algorithm cannot be stable and vice versa. Thus, one has to trade off sparsity and stability in designing a learning algorithm. In particular, our general result implies that l1-regularized regression (Lasso) cannot be stable, while l2-regularized regression is known to have strong stability properties and is therefore not sparse. © 2012 IEEE.

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.

Chow E.K.-H.,National University of Singapore
Journal of Laboratory Automation | Year: 2013

Conventional therapy against cancer by chemotherapy and radiation therapy has proven successful at decreasing bulk tumor size when cancer is diagnosed early enough. These therapeutic approaches, however, often result in recurrence years later. A number of studies have begun to identify a subpopulation of tumor-initiating cells that may be critical to early tumorigenesis and subsequent recurrence. These cells have been termed cancer stem cells (CSCs) and have been demonstrated to have properties of self-renewal, differentiation into other tumor cell types, and enhanced drug resistance. Given the growing body of evidence that CSCs play a key role in tumor biology in many cancer types, it is important to take into account the properties of these cells when developing novel cancer drugs and designing enhanced methods of drug delivery. This review covers some of the mechanisms by which CSCs escape conventional therapy as well as the potential approaches to targeting CSCs that may be used during cancer drug development. © 2013 Society for Laboratory Automation and Screening.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Gaul C.,Complutense University of Madrid | Muller C.A.,National University of Singapore
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

We describe repulsively interacting Bose-Einstein condensates in spatially correlated disorder potentials of arbitrary dimension. The first effect of disorder is to deform the mean-field condensate. The second is that the quantum excitation spectrum and condensate population are affected. By a saddle-point expansion of the many-body Hamiltonian around the deformed mean-field ground state, we derive the fundamental quadratic Hamiltonian of quantum fluctuations. Importantly, a basis is used such that excitations are orthogonal to the deformed condensate. Via Bogoliubov-Nambu perturbation theory, we compute the effective excitation dispersion, including mean free paths and localization lengths. Corrections to the speed of sound and average density of states are calculated, due to correlated disorder in arbitrary dimensions, extending to the case of weak lattice potentials. © 2011 American Physical Society.

Barz S.,University of Vienna | Fitzsimons J.F.,Singapore University of Technology and Design | Fitzsimons J.F.,National University of Singapore | Kashefi E.,University of Edinburgh | Walther P.,University of Vienna
Nature Physics | Year: 2013

Quantum computers are expected to offer substantial speed-ups over their classical counterparts and to solve problems intractable for classical computers. Beyond such practical significance, the concept of quantum computation opens up fundamental questions, among them the issue of whether quantum computations can be certified by entities that are inherently unable to compute the results themselves. Here we present the first experimental verification of quantum computation. We show, in theory and experiment, how a verifier with minimal quantum resources can test a significantly more powerful quantum computer. The new verification protocol introduced here uses the framework of blind quantum computing and is independent of the experimental quantum-computation platform used. In our scheme, the verifier is required only to generate single qubits and transmit them to the quantum computer. We experimentally demonstrate this protocol using four photonic qubits and show how the verifier can test the computer's ability to perform quantum computation. © 2013 Macmillan Publishers Limited.

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.

Yang T.H.,National University of Singapore | Navascues M.,University of Bristol
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

Self-testing is a device-independent approach to estimate the state and measurement operators without the need to assume the dimension of our quantum system. In this paper, we show that one can self-test black boxes into any pure entangled two-qubit state by performing simple Bell-type experiments. The approach makes use of only one family of Bell inequalities with two inputs and two outputs. Furthermore, we outline the sufficient conditions for one to self-test any dimensional bipartite entangled state. All these methods are robust to small but inevitable experimental errors. © 2013 American Physical Society.

Varghese J.,Institute of Molecular and Cell Biology | Lim S.F.,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

Energy homeostasis depends on insulin signaling in metazoans. Insulin levels reflect the nutritional status of the animal to control levels of circulating sugar and regulate storage of resources in the form of glycogen and fat. Over the past several years, evidence has begun to accumulate that insulin production and secretion, as well as cellular responsiveness to insulin, are subject to regulation by microRNAs. Here we present evidence that miR-14 acts in the insulin-producing neurosecretory cells in the adult Drosophila brain to control metabolism. miR-14 acts in these cells through its direct target, sugarbabe. sugarbabe encodes a predicted zinc finger protein that regulates insulin gene expression in the neurosecretory cells. Regulation of sugarbabe levels by nutrients and by miR-14 combines to allow the fly to manage resource mobilization in a nutritionally variable environment. © 2010 by Cold Spring Harbor Laboratory Press.

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.

Alibrandi U.,National University of Singapore
Reliability Engineering and System Safety | Year: 2014

A Response Surface (RS) strategy is presented for the evaluation of the response statistics of dynamic systems subjected to stochastic excitation. The proposed approach adopts a strategy based on the High Dimensional Model Representation (HDMR), which gives a Gaussian Model (GM) of the response. The GM requires only a reduced number of analyses which can be adopted for all the degrees of freedom of a MDOF dynamic system and it can be successfully adopted for weakly nonlinear dynamic systems. For more strongly nonlinear systems a Non-Gaussian approximation may be necessary for the highest response thresholds. In this paper this issue is accomplished through the FORM solution, and the design point is obtained by using a response surface method recently proposed by the author and Der Kiureghian to this aim. The latter response surface is based on a variant of the Model Correction Factor Method (MCFM), which is here applied by using as a starting model the GM itself. In many applications of engineering interest, both the input and the response processes are stationary, so that the stochastic excitation through the Fourier series can be modeled in terms of the underlying Power Spectral Density (PSD). In these cases, it is seen that the dynamic computations required by the proposed approach can decrease significantly. The application to SDOF and MDOF hysteretic systems shows the effectiveness of the presented method. © 2014 Elsevier Ltd.

Lim E.W.C.,National University of Singapore
AIChE Journal | Year: 2010

Segregation of granular materials by virtue of density or size is a commonly encountered phenomenon in nature. Despite its widespread interest among many researchers in recent years, a complete and unified understanding of granular segregation remains elusive to date. Using molecular dynamics simulations, we report a novel technique of inducing density segregation in a binary mixture of granular materials subjected to vibrations by the use of a bumpy vibrating base. Density segregation in the vertical directions may be induced by oscillating the bumpy base composed of discrete solid particles vertically or horizontally. In both cases, lighter particles tended to rise to the top of the granular bed and form a layer above the heavier particles. We suggest that differences in granular temperature profiles arising from the two different modes of vibrations may play an important role in determining the extent of density segregation occurring in binary granular mixtures. © 2010 American Institute of Chemical Engineers (AIChE).

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.

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.

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.

Sovacool B.K.,National University of Singapore
Journal of Cleaner Production | Year: 2011

Changing the patterns of energy use requires investigating how energy consumers - not experts - conceive of energy challenges. This article explores the varying beliefs, attitudes, and views on energy security in the United States among experts and residents. Based primarily on an academic literature review to distill expert views, and a survey distributed to hundreds of residents in the U.S. to capture consumer views, the study begins by explaining its methodology before identifying seven suppositions related to energy security. These suppositions involve security of fuel supply, energy democracy, energy research and development, affordability of energy services, environmental pollution, and climate change adaptation and mitigation. The second section of the study tests these suppositions with a survey distributed to 427 respondents in the United States. Three suppositions are supported, two are unsupported, and two are neither supported nor unsupported. The final section of the study offers implications for U.S. energy policy and scholarship. © 2011 Elsevier Ltd. All rights reserved.

Yu S.-H.,National University of Singapore
Archive for Rational Mechanics and Analysis | Year: 2014

We study an initial value problem of the Boltzmann equation with a Euler shock wave as initial data. Our analysis exhibits the presence of three singular layers, the initial layer, formation layer, and the shock layer. An approximate solution is constructed based on a solution of the Burgers-type equation for the formation layer time scale. The macroscopic conservation laws are preserved for the approximate solution. The Green's function of the linearized Boltzmann equation around the approximate solution is constructed by a modification of the T-ℂ scheme introduced by Yu (Nonlinear wave propagation over a Boltzmann shock profile, 2013). With the Green's function approach and a wave tracing method, one shows that the error of the approximate solution converges to zero with the convergent rate O(1) {pipe}logε{pipe}ε(1+t)-(1-σ0) in pointwise norm {double pipe}·{double pipe}L∞ ξ,3 around the shock profile for σ0 ∈ (0,1/2) and with the rate O(1)ε(1+t)-1/2 outside the shock zone, where ε is the strength of the weak hyperbolic shock wave. © 2013 Springer-Verlag Berlin Heidelberg.

McInnes B.,National University of Singapore
Nuclear Physics B | Year: 2014

The quark chemical potential is one of the fundamental parameters describing the quark-gluon plasma produced by sufficiently energetic heavy-ion collisions. It is not large at the extremely high temperatures probed by the LHC, but it plays a key role in discussions of the beam energy scan programmes at the RHIC and other facilities. On the other hand, collisions at such energies typically (that is, in peripheral collisions) give rise to very high values of the angular momentum density. Here we explain that holographic estimates of the quark chemical potential of a rotating sample of plasma can be very considerably improved by taking the angular momentum into account. © 2014 The Authors.

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.

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.

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.

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.

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.

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.

Coles P.J.,National University of Singapore
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2013

The complementarity of two observables is often captured in uncertainty relations, which quantify an inevitable trade-off in knowledge. Here we study complementarity in the context of an information-processing task: we link the complementarity of two observables to their usefulness for superdense coding (SDC). In SDC, Alice sends two classical dits of information to Bob by sending a single qudit. However, we show that encoding with commuting unitaries prevents Alice from sending more than one dit per qudit, implying that complementarity is necessary for SDC to be advantageous over a classical strategy for information transmission. When Alice encodes with products of Pauli operators for the X and Z bases, we quantify the complementarity of these encodings in terms of the overlap of the X and Z basis elements. Our main result explicitly solves for the SDC capacity as a function of the complementarity, showing that the entropy of the overlap matrix gives the capacity, when the preshared state is maximally entangled. We generalize this equation to resources with symmetric noise such as a preshared Werner state. In the most general case of arbitrary noisy resources, we obtain an analogous lower bound on the SDC capacity. Our results shed light on the role of complementarity in determining the quantum advantage in SDC and also seem fundamentally interesting since they bear a striking resemblance to uncertainty relations. © 2013 American Physical Society.

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.

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.

Protein tyrosine phosphatases (PTPs) constitute a large family of enzymes that play key roles in cell signaling. Malfunctions of PTP activity have been linked to major human diseases including cancer. One key aspect in PTP biology is the elucidation of roles of PTPs, as well as substrates they act on, in different cellular events. Herein, a library of 144 putative peptide substrates against different PTPs was synthesized and immobilized onto a glass slide to generate the corresponding phosphopeptide microarray. Subsequent screening of the microarray against various PTPs provided a distinctive and comparative substrate fingerprint against each PTP. Several new substrates were identified, which might aid in the future design of potent and selective PTPs inhibitors. The signal-decrease microarray assay used in our studies provided a facile and efficient way for high-throughput determination of kinetic constants for peptide/PTP interactions en masse. Finally, our microarray results were independently verified by traditional microplate-based enzymatic assays. 2010 Wiley Periodicals, Inc.

Zhang W.,Hefei University of Technology | Leng C.,National University of Singapore
Biometrika | Year: 2012

We propose new regression models for parameterizing covariance structures in longitudinal data analysis. Using a novel Cholesky factor, the entries in this decomposition have a moving average and log-innovation interpretation and are modelled as linear functions of covariates. We propose efficient maximum likelihood estimates for joint mean-covariance analysis based on this decomposition and derive the asymptotic distributions of the coefficient estimates. Furthermore, we study a local search algorithm, computationally more efficient than traditional all subset selection, based on bic for model selection, and show its model selection consistency. Thus, a conjecture of Pan & MacKenzie (2003) is verified. We demonstrate the finite-sample performance of the method via analysis of data on CD4 trajectories and through simulations. © 2011 Biometrika Trust.

Cohen S.M.,Institute of Molecular and Cell Biology | Cohen S.M.,National University of Singapore
EMBO Journal | Year: 2014

Long non-coding RNAs have become the focus of considerable interest over the past few years. Intriguing novel functions have been reported for lincRNAs. Three recent papers identify lincRNAs that work in a more conventional way - encoding protein - in each case a small polypeptide with an interesting biological activity (Magny et al,; Pauli et al,), (Bazzini et al,). Recent advances in ribosome profiling, combined with computational tools and initial functional validations reveal the existence of numerous small peptides that await future functional characterization. © 2014 The Author.

Celik T.,National University of Singapore
ETRI Journal | Year: 2010

Conventional fire detection systems use physical sensors to detect fire. Chemical properties of particles in the air are acquired by sensors and are used by conventional fire detection systems to raise an alarm. However, this can also cause false alarms; for example, a person smoking in a room may trigger a typical fire alarm system. In order to manage false alarms of conventional fire detection systems, a computer vision-based fire detection algorithm is proposed in this paper. The proposed fire detection algorithm consists of two main parts: fire color modeling and motion detection. The algorithm can be used in parallel with conventional fire detection systems to reduce false alarms. It can also be deployed as a stand-alone system to detect fire by using video frames acquired through a video acquisition device. A novel fire color model is developed in CIE L*a*b* color space to identify fire pixels. The proposed fire color model is tested with ten diverse video sequences including different types of fire. The experimental results are quite encouraging in terms of correctly classifying fire pixels according to color information only. The overall fire detection system's performance is tested over a benchmark fire video database, and its performance is compared with the stateof- the-art fire detection method. © 2010 ETRI.

Chu S.,National University of Singapore
Transportation | Year: 2011

The Vehicle Quota System manages vehicle ownership in Singapore by making the procurement of a Certificate of Entitlement (COE) a prerequisite for the registration of a new vehicle. The procurement is done during uniform price auctions of quotas of COEs currently held on a twice-a-month schedule. The auction format which started out as sealed bids in May 1990 changed to open bids in July 2001. This paper uses a regression model framework to investigate if this shift in auction format has resulted in lower COE premium volatility and a better reflection of demand and supply forces. The empirical results are pertinent to transport policy analysis. A suggestion in the form of incentives for early bids is also made to improve the efficiency of the open bids auction. © 2010 Springer Science+Business Media, LLC.

Lin J.,National University of Singapore
Computers in Human Behavior | Year: 2014

This paper investigates gratifications of reading citizen journalism news by applying the research model drawn from the uses and gratifications approach, and the cognitive-affective-conative framework. Based on the uses and gratifications literature and the cognitive-affective-conative framework, the effects of gratifications on attitude (i.e., affective) and intention (i.e., conative) are examined. The indirect effects of gratifications on intention to read news (i.e., conation) through the interpretation of affection that users experienced are also examined. Using a survey conducted across nearly 300 users, the results show that all gratifications, except for escape, have direct effects on attitude. However, none of the gratifications has a direct effect on intention. The proposed model shows that attitude mediates the path between the effects of all gratifications and intention. The model explains a high percentage of variance with gratifications explaining about 46% of the variance in attitude. However, their effects on intention are limited when attitude is controlled. © 2014 Elsevier Ltd. All rights reserved.

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.

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.

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.

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.

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.

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

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?

Zhang L.L.,National University of Singapore | Xiong Z.,University of Queensland | Zhao X.S.,University of Queensland
Journal of Power Sources | Year: 2013

A novel 3D nanostructure consisting of Ni(OH)2 nanoparticles, carbon nanotubes (CNTs), and reduced graphene oxide with an extremely high electrocapacitance is described. The nanostructure consists of CNTs with embedded Ni(OH) 2 nanoparticles as pillars for reduced graphene oxide sheets. Electrochemical results show that the composite displays specific capacitances as high as 1235 and 780 F g-1 at current densities of 1 and of 20 A g-1, respectively. In addition, the composite retains 80% of its original capacity after 500 cycles at a discharge current density of 10 A g-1. This 3D pseudocapacitor electrode has a number of important features, such as fast ion and electron transfer, easy access of pseudoactive species and efficient utilization, and excellent reversibility of Ni(OH) 2 nanoparticles. © 2012 Elsevier B.V. All rights reserved.

Wilder-Smith E.P.,National University of Singapore
Medical Hypotheses | Year: 2013

Aquagenic wrinkling of the palms is an unusual and rare dermatosis characterized by rapidly appearing edema, whitish papules, and strong wrinkling of the palms after brief immersion in water. Aquagenic wrinkling of the palms is postulated to be a result of abnormal electrolyte fluxes that result in sodium retention within epidermal keratinocytes and osmotically induced cell volume increases. A clear understanding is lacking. It is closely linked to Cystic Fibrosis and has been proposed as a test of Cystic Fibrosis but can also be induced by Cyclooxygenase (COX-2) inhibitors and Aminoglycosides. Since both aquagenic wrinkling of the palms and water immersion wrinkling occur with water immersion, are restricted to the glabrous skin, and show features of sympathetic stimulation, I hypothesize that aquagenic wrinkling of the palms is part of the spectrum of water immersion wrinkling which has recently been shown to be due to sympathetic nervous system induced vasoconstriction of the palms and digits. Furthermore I hypothesize that both conditions are restricted to the glabrous palmar skin because of unique anatomical characteristics. Palmar skin is highly porous to water and contains abundant specialized vasculature densely innervated by sympathetic nerves and has unique epidermal anchoring for gripping purposes. I postulate that in conditions with sweat electrolyte disturbances such as Cystic Fibrosis or drug induced; the normal water immersion wrinkling response is exaggerated, leading to the typical clinical features of aquagenic wrinkling of the palms. © 2013 Elsevier Ltd.

Shivashankar G.V.,National University of Singapore
Annual Review of Biophysics | Year: 2011

Cells integrate physicochemical signals on the nanoscale from the local microenvironment, resulting in altered functional nuclear landscape and gene expression. These alterations regulate diverse biological processes including stem cell differentiation, establishing robust developmental genetic programs and cellular homeostatic control systems. The mechanisms by which these signals are integrated into the 3D spatiotemporal organization of the cell nucleus to elicit differential gene expression programs are poorly understood. In this review I analyze our current understanding of mechanosignal transduction mechanisms to the cell nucleus to induce differential gene regulation. A description of both physical and chemical coupling, resulting in a prestressed nuclear organization, is emphasized. I also highlight the importance of spatial dimension in chromosome assembly, as well as the temporal filtering and stochastic processes at gene promoters that may be important in understanding the biophysical design principles underlying mechanoregulation of gene transcription. © 2011 by Annual Reviews. All rights reserved.

Chu S.,National University of Singapore
Transportation | Year: 2014

Traffic congestion in city-state Singapore is managed by vehicle ownership restraint complemented with usage charges in bottleneck zones. A certificate of entitlement (COE) obtained from auctions held twice a month is required to register any new vehicle. As Singapore sticks to a target vehicle population, the quota of COEs availed in the auctions hinges critically on the number of vehicles deregistered before the 10 years expiry of the COE. The paper demonstrates that vehicle deregistrations are negatively influenced by the prevailing COE prices. This engenders boom and bust cycles in the COE quotas and thereby spurs price volatility. It is also shown that below an empirically-derived breakpoint quota, COE prices surge and they may also correlate negatively with bidding competition. To avoid such undesirable situations, a proposal is made to allocate the breakpoint quota as a minimum by borrowing from future quotas. This will help smooth quota and price volatilities while adhering to medium-term vehicle population targets. The practicality of the proposal is discussed against various alternatives. © 2014, Springer Science+Business Media New York.

Nian V.,National University of Singapore
Applied Energy | Year: 2015

The life cycle carbon emission factor (measured by t-CO2/GWh) of nuclear power is much lower than those of fossil fueled power generation technologies. However, the fact of nuclear energy being a low carbon power source comes with many assumptions. These assumptions range from system and process definitions, to input-output definitions, to system boundary and cut-offcriteria selections, and life cycle inventory dataset. However, there is a somewhat neglected but critical aspect - the design aspect. This refers to the impacts on the life cycle carbon emissions from the change in design parameters related to nuclear power. The design parameters identified in this paper include: (1) the uranium ore grade, (2) the critical process technologies, represented by the average initial enrichment concentration of 235U in the reactor fuel, and (3) the size of the nuclear power reactor (measured by the generating capacity). If not properly tested, assumptions in the design aspect can lead to an erroneous estimation on the life cycle carbon emission factor of nuclear power. In this paper, a methodology is developed using the Process Chain Analysis (PCA) approach to quantify the impacts of the changes in the selected design parameters on the life cycle carbon emission factor of nuclear power. The concept of doing so broadens the scope of PCAs on energy systems from "one-off" calculation to analysis towards favorable/preferred designs. The findings from the analyses can serve as addition to the life cycle inventory database for nuclear power as well as provide indications for the sustainability of nuclear energy systems. © 2015 Elsevier Ltd. All rights reserved.

Ho G.W.,National University of Singapore
Science of Advanced Materials | Year: 2011

Metal oxides are often the choice for conductometric gas sensing due to their thermal and environmental stability as well as good response reversibility. Due to the fact that sensing with these materials relies on interactions with the surface, one strategy to enhance the sensitivity is to increase the surface area or active sites by decreasing their physical dimensions. Nanoscale metal oxides such as nanoparticles, nanospheres, nanotubes, nanobelts and nanowires are routinely synthesized for development of solid-state gas sensors with improved sensing properties. In this review, gas sensing applications of a variety of metal oxide nanostructures in various device configurations; bulk, two-terminal and field effect transistor (FET) sensors are presented. The application of nanostructures as building blocks for sensor can be achieved by implementing effective assembly and integration techniques to transfer the nanostructures from growth substrates onto their respective device substrates. Two common methods have been reviewed which include transfer printing and dielectrophoretic alignment of nanowires. In essence, these approaches employ external forces to align the nanostructures via dry and wet media respectively. Finally, the non conventional substrates sensors such as textile and free standing nanowire sheet are reviewed. The non conventional substrates have the advantages of being flexible, shock proof, wearable and portable etc. © 2011 American Scientific Publishers.

Ong C.W.M.,Imperial College London | Ong C.W.M.,National University of Singapore | Elkington P.T.,University of Southampton | Friedland J.S.,Imperial College London
American Journal of Respiratory and Critical Care Medicine | Year: 2014

Tuberculosis (TB), a chronic infectious disease of global importance, is facing the emergence of drug-resistant strains with few new drugs to treat the infection. Pulmonary cavitation, the hallmark of established disease, is associated with very high bacillary burden. Cavitation may lead to delayed sputum culture conversion, emergence of drug resistance, and transmission of the infection. The host immunological reaction to Mycobacterium tuberculosis is implicated in driving the development of TB cavities. TB is characterized by a matrix-degrading phenotype in which the activity of proteolytic matrix metalloproteinases (MMPs) is relatively unopposed by the specific tissue inhibitors of metalloproteinases. Proteases, in particular MMPs, secreted from monocyte-derived cells, neutrophils, and stromal cells, are involved in both cell recruitment and tissue damage and may cause cavitation. MMP activity is augmented by proinflammatory chemokines and cytokines, is tightly regulated by complex signaling paths, and causes matrix destruction. MMP concentrations are elevated in human TB and are closely associated with clinical and radiological markers of lung tissue destruction. Immunomodulatory therapies targeting MMPs in preclinical and clinical trials are potential adjuncts to TB treatment. Strategies targeting patients with cavitary TB have the potential to improve cure rates and reduce disease transmission. Copyright © 2014 by the American Thoracic Society.

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.

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.

Chan T.E.,National University of Singapore
Medical Law Review | Year: 2013

Developments in medical technology, healthcare delivery, and commercial interests in medicine have increased both the potential for conflicts of interest on the part of physicians, and doubts over the sufficiency of patient autonomy as a justification for administering innovative therapy. The legal and regulatory treatment of innovative therapy is therefore an important question, on which there is a current lack of consensus on a number of issues. This paper discusses recent developments in Singapore and uses them as a springboard to flesh out basic regulatory issues that arise from the deployment of innovative treatment: the distinction between innovative treatment and clinical research, the adequacy of the current post hoc scrutiny of innovative therapy under existing legal principles and the need for further specialised regulatory oversight. © The Author [2012]. Published by Oxford University Press; all rights reserved.

Dall'Arno M.,National University of Singapore
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

The accessible information and the informational power quantify the amount of information extractable from a quantum ensemble and by a quantum measurement, respectively. So-called spherical quantum 2-designs constitute a class of ensembles and measurements relevant in testing entropic uncertainty relations, quantum cryptography, and quantum tomography. We provide lower bounds on the entropy of 2-design ensembles and measurements, from which upper bounds on their accessible information and informational power follow, as a function of the dimension only. We show that the statistics generated by 2-designs, although optimal for the above-mentioned protocols, never contains more than 1 bit of information. Finally, we specialize our results to the relevant cases of symmetric informationally complete sets and maximal sets of mutually unbiased bases, and we generalize them to the arbitrary-rank case. © 2014 American Physical 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.

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.

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.

Rodriguez-Lara B.M.,National University of Singapore
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

The dynamics of Glauber-Fock lattice of size N is given through exact diagonalization of the corresponding Hamiltonian; the spectra {λk} is given as the roots of the Nth Hermite polynomial, HN(λk/√2)=0, and the eigenstates are given in terms of Hermite polynomials evaluated at these roots. The exact dynamics is used to study coherent phenomena in discrete lattices. Due to the symmetry and spacing of the eigenvalues {λk}, oscillatory behavior is predicted with highly localized spectra, that is, near complete revivals of the photon number and partial recovery of the initial state at given waveguides. © 2011 American Physical Society.

Girolami D.,University of Oxford | Girolami D.,National University of Singapore
Physical Review Letters | Year: 2014

Quantum coherence is the key resource for quantum technology, with applications in quantum optics, information processing, metrology, and cryptography. Yet, there is no universally efficient method for quantifying coherence either in theoretical or in experimental practice. I introduce a framework for measuring quantum coherence in finite dimensional systems. I define a theoretical measure which satisfies the reliability criteria established in the context of quantum resource theories. Then, I present an experimental scheme implementable with current technology which evaluates the quantum coherence of an unknown state of a d-dimensional system by performing two programmable measurements on an ancillary qubit, in place of the O(d2) direct measurements required by full state reconstruction. The result yields a benchmark for monitoring quantum effects in complex systems, e.g., certifying nonclassicality in quantum protocols and probing the quantum behavior of biological complexes. © 2014 American Physical Society.

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.

Lim Y.-K.,National University of Singapore
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Geodesic equations of timelike and null charged particles in the Ernst metric are studied. We consider two distinct forms of the Ernst solution where the Maxwell potential represents either a uniform electric or magnetic field. Circular orbits in various configurations are considered, as well as their perturbations and stability. We find that the electric field strength must be below a certain charge-dependent critical value for these orbits to be stable. The case of the magnetic Ernst metric contains a limit which reduces to the Melvin magnetic universe. In this case the equations of motion are solved to reveal cycloidlike or trochoidlike motion, similar to those found by Frolov and Shoom around black holes immersed in test magnetic fields. © 2015 American Physical Society.

Ding M.,Harvard University | Bhupathiraju S.N.,Harvard University | Satija A.,Harvard University | Van Dam R.M.,Harvard University | And 2 more authors.
Circulation | Year: 2014

Background: Considerable controversy exists on the association between coffee consumption and cardiovascular disease (CVD) risk. A meta-analysis was performed to assess the dose-response relationship of long-term coffee consumption with CVD risk. Methods and Results: Results-PubMed and EMBASE were searched for prospective cohort studies of the relationship between coffee consumption and CVD risk, which included coronary heart disease, stroke, heart failure, and CVD mortality. Thirty-six studies were included with 1 279 804 participants and 36 352 CVD cases. A nonlinear relationship of coffee consumption with CVD risk was identified (P for heterogeneity=0.09, P for trend <0.001, P for nonlinearity <0.001). Compared with the lowest category of coffee consumption (median, 0 cups per day), the relative risk of CVD was 0.95 (95% confidence interval, 0.87-1.03) for the highest category (median, 5 cups per day) category, 0.85 (95% confidence interval, 0.80-0.90) for the second highest category (median, 3.5 cups per day), and 0.89 (95% confidence interval, 0.84-0.94) for the third highest category (median, 1.5 cups per day). Looking at separate outcomes, coffee consumption was nonlinearly associated with both coronary heart disease (P for heterogeneity=0.001, P for trend <0.001, P for nonlinearity <0.001) and stroke (P for heterogeneity=0.07, P for trend <0.001, P for nonlinearity <0.001; P for trend differences >0.05) risks. Conclusions: A nonlinear association between coffee consumption and CVD risk was observed in this meta-analysis. Moderate coffee consumption was inversely significantly associated with CVD risk, with the lowest CVD risk at 3 to 5 cups per day, and heavy coffee consumption was not associated with elevated CVD risk. © 2013 American Heart Association, Inc.

Chokkanathan S.,National University of Singapore
International Journal of Geriatric Psychiatry | Year: 2014

Background There is limited evidence for the multifactorial aetiology of elder mistreatment. The goal of this study is to investigate the factors associated with the mistreatment of older adults living in rural Tamil Nadu, India. Method A cross-sectional household survey was conducted in a sub-district of rural Tamil Nadu by using a standard questionnaire. Face to face interviews were conducted with 902 older adults aged 61 years and older. The relation between the characteristics of older adults, family members and family environments with reported mistreatment was examined by univariate and multivariate logistic regression analyses. Results The multivariate results reveal that elder mistreatment is related to several factors associated with the perpetrator and the family environment. Perpetrator factors include middle age, a tertiary education (protective), alcohol consumption and the mistreatment of other family members. Family environment factors include family stress and low cohesion. Among the factors related to older adults, only physical abuse of family members was associated with exposure to mistreatment. Conclusion The characteristics of older adults, family members and family environment are potent predictors of elder mistreatment. Multi-dynamic interventions should target dysfunctional families displaying alcohol use, relationship conflicts, low cohesion and the presence of some form of family violence. Copyright © 2014 John Wiley & Sons, Ltd.

Benosman M.,National University of Singapore
Mathematical Problems in Engineering | Year: 2010

Fault tolerant control (FTC) is the branch of control theory, dealing with the control of systems that become faulty during their operating life. Following the systems classification, as linear and nonlinear models, FTC can be classified in two different groups, linear FTC (LFTC) dealing with linear models, and the one of interest to us in this paper, nonlinear FTC (NFTC), which deals with nonlinear models. We present in this paper a survey of some of the results obtained in these last years on NFTC. © 2010 Mouhacine Benosman.

Kim J.,National University of Singapore | Waite L.J.,University of Chicago
Journals of Gerontology - Series B Psychological Sciences and Social Sciences | Year: 2014

Objectives. This paper introduces scales on shared activity and relationship quality for married and partnered older adults using multiple indicators from the second wave of National Social Life, Health, and Aging Project. Method. We assessed the reliability of the scales using Cronbach's alpha and the item-total correlation. We conducted exploratory factor analysis to explore the structure of the items and compared the distribution of each scale means by age group and gender. Results. We found that the relational quality scale has a 2-factor structure, including a positive and negative dimension. The shared activity scale has a 1-factor structure. We found that partnered men show both higher positive and higher negative relationship quality than do partnered women, suggesting that more older men than women experience ambivalent feelings toward their spouse or partner and more women than men have relationships of indifferent quality, with relatively low costs and relatively low benefits. Discussion. The separate conceptualization of shared activity and relationship quality provides one way to examine the dynamic nature of marital quality in later life such as the extent to which shared activities among couples promote or detract from relationships' quality. Analyses for individuals and for dyads are discussed. © 2014 © The Author 2014. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved.

Lateef A.,National University of Singapore | Petri M.,Johns Hopkins University
Journal of Autoimmunity | Year: 2012

Sex hormones, including estrogens, influence the immune system in a complex manner, playing an important role in the pathophysiology of autoimmune diseases. Estrogen receptors can be found in almost all cells, including those of the adaptive and innate immune systems. Depending on the relative preponderance and stimulation of different receptors in various tissues, estrogens may demonstrate pro-inflammatory or anti-inflammatory properties. Traditionally, exogenous estrogens were considered to have the potential of worsening the autoimmune processes and hence were avoided in patients with rheumatic diseases. Recent studies have demonstrated the efficacy of exogenous hormone therapies, either in the form of oral contraceptives or post-menopausal hormonal replacement therapy, in the majority of patients with rheumatic diseases. However, caution needs to be exercised as a higher incidence of mild to moderate flares of systemic lupus erythematosus was noted with hormonal replacement therapy in the large randomized controlled trial, HRT-SELENA. Exogenous estrogens can also increase the risk of thrombosis in patients with positive antiphospholipid antibodies and should be avoided in this subgroup. This review will discuss the current evidence on the efficacy, safety and impact of exogenous sex hormone therapies in patients with autoimmune rheumatic diseases. © 2011 Elsevier Ltd.

Lim E.W.C.,National University of Singapore
Industrial and Engineering Chemistry Research | Year: 2013

The discrete element method combined with computational fluid dynamics was coupled to an electrostatic force model for computational studies of mixing behaviors in gas fluidized bed systems with electrostatic effects. Due to the presence of strong electrostatic forces between particles and walls, there was a high tendency for particles to be adhered to the walls or other particles near the walls within the fluidized bed, resulting in less vigorous fluidization. This in turn resulted in lower mixing efficiencies in comparison with fluidization in the presence of weaker electrostatic effects. Particle-wall electrostatic forces were on average stronger than both fluid drag forces and particle-particle collision forces when strong electrostatic effects were present, and this accounted for the difficulty with which particles adhered to walls could be removed and transferred to other locations within the bed. Such transfers of particles were necessary for mixing to occur during fluidization but required strong electrostatic forces to be overcome. © 2013 American Chemical Society.

Tay Y.C.,National University of Singapore
Proceedings of the VLDB Endowment | Year: 2011

The Transaction Processing Council (TPC) has played a pivotal role in the database industry's growth over the last twenty-five years. However, its handful of domain-specific benchmarks are increasingly irrelevant to the multitude of data-centric applications, and its top-down process is slow. This mismatch calls for a paradigm shift to a bottomup community effort to develop tools for application-specific benchmarking. Such a development program would center around techniques for synthetically scaling (up or down) an empirical dataset. This engineering effort in turn requires the development of a database theory on attribute value correlation. © 2011 VLDB Endowment.

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is the most successful conducting polymer in terms of the practical application. It can be dispersed in water and some polar organic solvents, and high-quality PEDOT:PSS films can be readily prepared through solution processing. In addition, PEDOT:PSS is highly transparent in the visible range and has excellent thermal stability. Nevertheless, PEDOT:PSS has a problem of low conductivity. The as-prepared PEDOT:PSS films from its aqueous solution have a conductivity of lower than 1 S cm-1, which severely impedes the application of PEDOT:PSS in various aspects. It has been discovered that the conductivity of as-prepared PEDOT:PSS from its aqueous solution can be significantly enhanced by adding organic compounds like high-boiling point polar organic solvents, ionic liquids and surfactants or through a post-treatment of PEDOT:PSS films with organic compounds, including high-boiling point polar solvents, salts, zwitterions, cosolvents, organic and inorganic acids. Conductivity of more than 3000 S cm-1 was recently observed on PEDOT:PSS films after treated with sulfuric acid. This conductivity is comparable to that of indium tin oxide (ITO), the conventional transparent electrode material of optoelectronic devices. In addition, PEDOT:PSS has high mechanical flexibility while ITO is a brittle material. Thus, PEDOT:PSS is very promising to be the next-generation transparent electrode material. This article reviews the methods to enhance the conductivity of PEDOT:PSS, the mechanisms for the conductivity enhancements and the application of the highly conductive PEDOT:PSS films in polymer light-emitting diodes and polymer solar cells. © 2012 Elsevier B.V. All rights reserved.

Lao Y.-H.,Columbia University | Phua K.K.L.,National University of Singapore | Leong K.W.,Columbia University
ACS Nano | Year: 2015

Aptamer nanomedicine, including therapeutic aptamers and aptamer nanocomplexes, is beginning to fulfill its potential in both clinical trials and preclinical studies. Especially in oncology, aptamer nanomedicine may perform better than conventional or antibody-based chemotherapeutics due to specificity compared to the former and stability compared to the latter. Many proof-of-concept studies on applying aptamers to drug delivery, gene therapy, and cancer imaging have shown promising efficacy and impressive safety in vivo toward translation. Yet, there remains ample room for improvement and critical barriers to be addressed. In this review, we will first introduce the recent progress in clinical trials of aptamer nanomedicine, followed by a discussion of the barriers at the design and in vivo application stages. We will then highlight recent advances and engineering strategies proposed to tackle these barriers. Aptamer cancer nanomedicine has the potential to address one of the most important healthcare issues of the society. © 2015 American Chemical Society.

Tay S.B.,National University of Singapore
International journal of molecular sciences | Year: 2013

Quorum sensing is a cell density-dependent signaling phenomenon used by bacteria for coordination of population-wide phenotypes, such as expression of virulence genes, antibiotic resistance and biofilm formation. Lately, disruption of bacterial communication has emerged as an anti-virulence strategy with enormous therapeutic potential given the increasing incidences of drug resistance in pathogenic bacteria. The quorum quenching therapeutic approach promises a lower risk of resistance development, since interference with virulence generally does not affect the growth and fitness of the bacteria and, hence, does not exert an associated selection pressure for drug-resistant strains. With better understanding of bacterial communication networks and mechanisms, many quorum quenching methods have been developed against various clinically significant bacterial pathogens. In particular, Gram-negative bacteria are an important group of pathogens, because, collectively, they are responsible for the majority of hospital-acquired infections. Here, we discuss the current understanding of existing quorum sensing mechanisms and present important inhibitory strategies that have been developed against this group of pathogenic bacteria.

The rate of decline of antibody titers to influenza following infection can affect results of serological surveys, and may explain re-infection and recurrent epidemics by the same strain. We followed up a cohort who seroconverted on hemagglutination inhibition (HI) antibody titers (≥ 4-fold increase) to pandemic influenza A(H1N1)pdm09 during a seroincidence study in 2009. Along with the pre-epidemic sample, and the sample from 2009 with the highest HI titer between August and October 2009 (A), two additional blood samples obtained in April 2010 and September 2010 (B and C) were assayed for antibodies to A(H1N1)pdm09 by both HI and virus microneutralization (MN) assays. We analyzed pair-wise mean-fold change in titers and the proportion with HI titers ≥ 40 and MN ≥ 160 (which correlated with a HI titer of 40 in our assays) at the 3 time-points following seroconversion. A total of 67 participants contributed 3 samples each. From the highest HI titer in 2009 to the last sample in 2010, 2 participants showed increase in titers (by HI and MN), while 63 (94%) and 49 (73%) had reduction in HI and MN titers, respectively. Titers by both assays decreased significantly; while 70.8% and 72.3% of subjects had titers of ≥ 40 and 160 by HI and MN in 2009, these percentages decreased to 13.9% and 36.9% by September 2010. In 6 participants aged 55 years and older, the decrease was significantly greater than in those aged below 55, so that none of the elderly had HI titers ≥ 40 nor MN titers ≥ 160 by the final sample. Due to this decline in titers, only 23 (35%) of the 65 participants who seroconverted on HI in sample A were found to seroconvert between the pre-epidemic sample and sample C, compared to 53 (90%) of the 59 who seroconverted on MN on Sample A. We observed marked reduction in titers 1 year after seroconversion by HI, and to a lesser extent by MN. Our findings have implications for re-infections, recurrent epidemics, vaccination strategies, and for cohort studies measuring infection rates by seroconversion.

Shenzhen Special Economic Zone (SEZ) has been the flagship labouratory of Deng Xiaoping's reform and open-door policy and the forerunner of China's capitalist transformation. The initiation of the Shenzhen SEZ was driven by the imperative of political and economic survival along the state hierarchy and was informed by the international practices of export processing zones (EPZs). Shenzhen's capitalist fundamentals, such as the commodification of land and labour, were largely established through imitating its 'big master' Hong Kong across the border. However, Shenzhen's policy learning style has gradually shifted from laissez-faire Hong Kong to authoritarian Singapore, propelled by the aspiration, shared among policy-making party élites across China's administrative hierarchy, of perpetuating the single-party rule. Theoretically, this paper demonstrates how policy mobility is shaped path-dependently by the pre-structured institutional/ideological regime, in what ways the idiosyncratic geographical/historical conjuncture matters, and why political representation and participation are crucial to policy selection and mutation. © 2012 Urban Studies Journal Limited.

Zhang R.,National University of Singapore | Zhang R.,Institute for Infocomm Research | Ho C.K.,Institute for Infocomm Research
IEEE Transactions on Wireless Communications | Year: 2013

Wireless power transfer (WPT) is a promising new solution to provide convenient and perpetual energy supplies to wireless networks. In practice, WPT is implementable by various technologies such as inductive coupling, magnetic resonate coupling, and electromagnetic (EM) radiation, for short-/mid-/long- range applications, respectively. In this paper, we consider the EM or radio signal enabled WPT in particular. Since radio signals can carry energy as well as information at the same time, a unified study on simultaneous wireless information and power transfer (SWIPT) is pursued. Specifically, this paper studies a multiple-input multiple-output (MIMO) wireless broadcast system consisting of three nodes, where one receiver harvests energy and another receiver decodes information separately from the signals sent by a common transmitter, and all the transmitter and receivers may be equipped with multiple antennas. Two scenarios are examined, in which the information receiver and energy receiver are separated and see different MIMO channels from the transmitter, or co-located and see the identical MIMO channel from the transmitter. For the case of separated receivers, we derive the optimal transmission strategy to achieve different tradeoffs for maximal information rate versus energy transfer, which are characterized by the boundary of a so-called rate-energy (R-E) region. For the case of co-located receivers, we show an outer bound for the achievable R-E region due to the potential limitation that practical energy harvesting receivers are not yet able to decode information directly. Under this constraint, we investigate two practical designs for the co-located receiver case, namely time switching and power splitting, and characterize their achievable R-E regions in comparison to the outer bound. © 2002-2012 IEEE.

Sun Q.-Y.,National University of Singapore
Leukemia | Year: 2016

Partial tandem duplication of MLL (MLL-PTD) characterizes acute myeloid leukemia (AML) patients often with a poor prognosis. To understand the order of occurrence of MLL-PTD in relation to other major AML mutations and to identify novel mutations that may be present in this unique AML molecular subtype, exome and targeted sequencing was performed on 85 MLL-PTD AML samples using HiSeq-2000. Genes involved in the cohesin complex (STAG2), a splicing factor (U2AF1) and a poorly studied gene, MGA were recurrently mutated, whereas NPM1, one of the most frequently mutated AML gene, was not mutated in MLL-PTD patients. Interestingly, clonality analysis suggests that IDH2/1, DNMT3A, U2AF1 and TET2 mutations are clonal and occur early, and MLL-PTD likely arises after these initial mutations. Conversely, proliferative mutations (FLT3, RAS), typically appear later, are largely subclonal and tend to be unstable. This study provides important insights for understanding the relative importance of different mutations for defining a targeted therapeutic strategy for MLL-PTD AML patients.Leukemia advance online publication, 8 July 2016; doi:10.1038/leu.2016.160. © 2016 Macmillan Publishers Limited

Kong L.,National University of Singapore
Urban Studies | Year: 2012

In many land-scarce Asian cities, planning agencies have sought to reduce space for the dead to release land for the living, encouraging conversion from burial to cremation over several decades. This has caused secular principles privileging efficient land use to conflict with symbolic values invested in burial spaces. Over time, not only has cremation become more accepted, even columbaria have become overcrowded, and new forms of burials (sea and woodland burials) have emerged. As burial methods change, so too do commemorative rituals, including new on-line and mobile phone rituals. This paper traces the ways in which physical spaces for the dead in several east Asian cities have diminished and changed over time, the growth of virtual space for them, the accompanying discourses that influence these dynamics and the new rituals that emerge concomitantly with the contraction of land space. © 2011 Urban Studies Journal Limited.

Marsh T.,National University of Singapore
Entertainment Computing | Year: 2011

While many categorizations and definitions have attempted to elucidate the elusive term serious games, we are still some way off formulating an agreed understanding of what serious games are and can be. This article argues that the term serious games challenges our understanding of generally accepted characteristics such as, challenge, play and fun, which are largely associated with and borrowed from video games. It is argued that key to understanding what serious games encapsulate is to look beyond these characteristics. This article proposes a definition and way to frame serious games technologies, applications and environments along a continuum of gaming characteristics or gameness. From those with traditional gaming activities and characteristics (challenge, play, fun, etc.) at one end to those with minimal traditional gaming characteristics at the other end, whose main purpose is to provide experience and emotion to convey meaning. The main advantages of the definition and continuum are to establish a shared understanding and arena for current and emerging serious games, frame and connect currently fragmented groups into a cohesive serious games movement and community and open opportunities for future collaborative research and development. In addition, it helps in identifying characteristics for the design and assessment of serious games. © 2011 Elsevier B.V.

Yu F.,National University of Singapore | Schuldiner O.,Weizmann Institute of Science
Current Opinion in Neurobiology | Year: 2014

Pruning, a process by which neurons selectively remove exuberant or unnecessary processes without causing cell death, is crucial for the establishment of mature neural circuits during animal development. Yet relatively little is known about molecular and cellular mechanisms that govern neuronal pruning. Holometabolous insects, such as Drosophila, undergo complete metamorphosis and their larval nervous systems are replaced with adult-specific ones, thus providing attractive models for studying neuronal pruning. Drosophila mushroom body and dendritic arborization neurons have been utilized as two appealing systems to elucidate the underlying mechanisms of axon and dendrite pruning, respectively. In this review we highlight recent developments and discuss some similarities and differences in the mechanisms that regulate these two distinct modes of neuronal pruning in Drosophila. © 2014 Elsevier Ltd.

Smith G.J.D.,National University of Singapore | Donis R.O.,Centers for Disease Control and Prevention
Influenza and other Respiratory Viruses | Year: 2014

The divergence of the hemagglutinin gene of A/goose/Guangdong/1/1996-lineage H5N1 viruses during 2011 and 2012 (807 new sequences collected through December 31, 2012) was analyzed by phylogenetic and p-distance methods to define new clades using the pre-established nomenclature system. Eight new clade designations were recommended based on division of clade 1·1 (Mekong River Delta), 2·1·3·2 (Indonesia), 2·2·2 (India/Bangladesh), 2·2·1·1 (Egypt/Israel), and 2·3·2·1 (Asia). A simplification to the previously defined criteria, which adds a letter rather than number to the right-most digit of fifth-order clades, was proposed to facilitate this and future updates. © 2014 The Authors. Influenza and Other Respiratory Viruses Published by John Wiley & Sons Ltd.

Su L.L.,National University of Singapore
Cochrane database of systematic reviews (Online) | Year: 2012

Postpartum haemorrhage (PPH) is one of the major contributors to maternal mortality and morbidity worldwide. Active management of the third stage of labour has been proven to be effective in the prevention of PPH. Syntometrine is more effective than oxytocin but is associated with more side effects. Carbetocin, a long-acting oxytocin agonist, appears to be a promising agent for the prevention of PPH. To determine if the use of oxytocin agonist is as effective as conventional uterotonic agents for the prevention of PPH, and assess the best routes of administration and optimal doses of oxytocin agonist. We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (1 March 2011), the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2011, Issue 1 of 4), MEDLINE (1966 to 1 March 2011) and EMBASE (1974 to 1 March 2011). We checked references of articles and communicated with authors and pharmaceutical industry contacts. Randomised controlled trials which compared oxytocin agonist (carbetocin) with other uterotonic agents or with placebo or no treatment for the prevention of PPH. Two review authors independently assessed trials for inclusion, assessed risk of bias and extracted data. We included 11 studies (2635 women) in the review. Six trials compared carbetocin with oxytocin; four of these were conducted for women undergoing caesarean deliveries, one was for women following vaginal deliveries and one did not state the mode of delivery clearly. The carbetocin was administered as 100 μg intravenous dosage across the trials, while oxytocin was administered intravenously but at varied dosages. Four trials compared intramuscular carbetocin and intramuscular syntometrine for women undergoing vaginal deliveries. Three of the trials were on women with no risk factor for PPH, while one trial was on women with risk factors for PPH. One trial compared the use of intravenous carbetocin with placebo. Use of carbetocin resulted in a statistically significant reduction in the need for therapeutic uterotonics (risk ratio (RR) 0.62; 95% confidence interval (CI) 0.44 to 0.88; four trials, 1173 women) compared to oxytocin for those who underwent caesarean section, but not for vaginal delivery. Compared to oxytocin, carbetocin was associated with a reduced need for uterine massage following both caesarean delivery (RR 0.54; 95% CI 0.37 to 0.79; two trials, 739 women) and vaginal delivery (RR 0.70; 95% CI 0.51 to 0.94; one trial, 160 women). Pooled data also showed that carbetocin resulted in a lower risk of PPH compared to oxytocin in women who underwent caesarean delivery (RR 0.55; 95% CI 0.31 to 0.95; three trials, 820 women). This is, however, limited by the number of studies and risk of bias in the studies. Comparison between carbetocin and syntometrine showed a lower mean blood loss in women who received carbetocin compared to syntometrine (mean difference (MD) -48.84 ml; 95% CI -94.82 to -2.85; four trials, 1030 women). There was no statistically significant difference in terms of the need for therapeutic uterotonic agents, but the risk of adverse effects such as nausea and vomiting were significantly lower in the carbetocin group: nausea (RR 0.24; 95% CI 0.15 to 0.40; four trials, 1030 women); vomiting (RR 0.21; 95% CI 0.11 to 0.39; four trials, 1030 women). The incidence of postpartum hypertension was also significantly lower in women who received carbetocin compared to those who received syntometrine. Cost-effectiveness of carbetocin was investigated by one study published as an abstract, with limited data. There is evidence to suggest that 100 μg of intravenous carbetocin is more effective than oxytocin for preventing PPH in women undergoing caesarean deliveries, but more studies are needed to validate this finding. Carbetocin is associated with less blood loss compared to syntometrine in the prevention of PPH for women who have vaginal deliveries and is associated with significantly fewer adverse effects. Further research is needed to analyse the cost-effectiveness of carbetocin as a uterotonic agent.

Larsson A.,National University of Singapore
IEEE Transactions on Plasma Science | Year: 2012

Gas-discharge closing switches are still the main option for pulsed-power systems where high hold-off voltage and high-power handling capabilities are required. One property of the switch that often is of great importance is the precision in time when the switch is to be closed. This review is a survey of existing gas-discharge closing switches, and in particular of their switching time jitter. © 2012 IEEE.

Liaw H.C.,National University of Singapore | Shirinzadeh B.,Monash University
IEEE Transactions on Industrial Electronics | Year: 2011

This paper presents a robust adaptive constrained motion tracking control methodology for piezo-actuated flexure-based micro/nano manipulation mechanisms. This unique control approach is established for the tracking of desired motion trajectories in a constrained environment exhibiting some degree of uncertain stiffness. The control methodology is also formulated to accommodate not only the parametric uncertainties and unknown force conversion function, but also nonlinearities including the hysteresis effect and external disturbances in the motion systems. In this paper, the equations for the dynamic modeling of a flexure-hinged four-bar micro/nano manipulation mechanism operating in a constrained environment are established. A lumped parameter dynamic model that combines the piezoelectric actuator and the micro/nano manipulation mechanism is developed for the formulation of the control methodology. Stability analysis of the proposed closed-loop system is conducted and the convergence of the motion tracking errors is proven theoretically. Furthermore, precise motion tracking ability in following a desired motion trajectory is demonstrated in the experimental study. An important advantage of this control approach is that it does not require the exact values for the system parameters and the force conversion function in the physical realization. This proposed constrained motion tracking control methodology is very useful for applications demanding high-precision motion tracking with force sensing and feedback. © 2011 IEEE.

Valentine S.,National University of Singapore
Energy Policy | Year: 2010

This paper provides a critical evaluation of Australia's new Renewable Energy Target (RET) program with respect to its capacity to support wind power development. Four structural flaws associated with the RET which undermine its effectiveness as a catalyst for technological change in the electricity sector are discussed: (i) the inclusion of waste coal mine gas (WCMG) as an eligible fuel source which acts as an indirect coal industry subsidy, (ii) program duration which is too short and ill-structured, (iii) a multiplier that is well-intended to support small-scale renewable technologies but which creates "phantom capacity", and (iv) the capped target of 45,000. GWh which will stymie long-term wind power market investment. The paper concludes with recommendations which stress the importance of passing effective Carbon Pollution Renewable Scheme (CPRS) legislation to offset the weaknesses associated with the RET. If an effective CPRS cannot be implemented, the paper recommends that amendments be made to the RET to (i) remove WCMG from the list of approved alternative energy sources, and (ii) extend the RET targets to reach 120,000. GWh by 2030. © 2010 Elsevier Ltd.

Sovacool B.K.,National University of Singapore
Energy | Year: 2010

This study evaluates the applicability of eight renewable electricity policy mechanisms for Southeast Asian electricity markets. It begins by describing the methodology behind 90 research interviews of stakeholders in the electricity industry. It then outlines four justifications given by respondents for government intervention to support renewables in Southeast Asia: unpriced negative externalities, counteracting subsidies for conventional energy sources, the public goods aspect of renewable energy, and the presence of non-technical barriers. The article develops an analytical framework to evaluate renewable portfolio standards, green power programs, public research and development expenditures, systems benefits charges, investment tax credits, production tax credits, tendering, and feed-in tariffs in Southeast Asia. It assesses each of these mechanisms according to the criteria of efficacy, cost effectiveness, dynamic efficiency, equity, and fiscal responsibility. The study concludes that one mechanism, feed-in tariffs, is both the most preferred by respondents and the only one that meets all criteria. © 2010 Elsevier Ltd. All rights reserved.

Valentine S.V.,National University of Singapore
Energy Policy | Year: 2010

This paper investigates the impact that a federal government structure has on strategic selection of renewable energy policy instruments. The context for this study centers on wind power development in Canada. Canada is a nation that is blessed by all the attributes necessary to catalyze global leadership in installed wind power capacity. Unfortunately, the constitutional separation of powers that underpins Canada's federal system impedes the creation of a national wind power development strategy because Canada's provinces have constitutional authority over electricity governance. The insights gleaned from the case study are used to develop a conceptual framework for understanding the impact that federal structure has on policy instrument selection and efficacy under areas of federal, regional and concurrent policy jurisdiction. Finally, this framework is re-applied to identify specific approaches the Canadian federal government could take to resolve what currently amounts to be a fragmented, ineffective approach to wind power development planning. © 2009 Elsevier Ltd. All rights reserved.

Kuwabara S.,Chiba University | Yuki N.,National University of Singapore
The Lancet Neurology | Year: 2013

Acute motor axonal neuropathy (AMAN) is a pure motor axonal subtype of Guillain-Barré syndrome (GBS) that was identified in the late 1990s. In Asia and Central and South America, it is the major subtype of GBS, seen in 30-65% of patients. AMAN progresses more rapidly and has an earlier peak than demyelinating GBS; tendon reflexes are relatively preserved or even exaggerated, and autonomic dysfunction is rare. One of the main causes is molecular mimicry of human gangliosides by Campylobacter jejuni lipo-oligosaccharides. In addition to axonal degeneration, electrophysiology shows rapidly reversible nerve conduction blockade or slowing, presumably due to pathological changes at the nodes or paranodes. Autoantibodies that bind to GM1 or GD1a gangliosides at the nodes of Ranvier activate complement and disrupt sodium-channel clusters and axoglial junctions, which leads to nerve conduction failure and muscle weakness. Improved understanding of the disease mechanism and pathophysiology might lead to new treatment options and improve the outlook for patients with AMAN. © 2013 Elsevier Ltd.

Coles P.J.,National University of Singapore | Piani M.,University of Waterloo
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2014

The uncertainty principle can be expressed in entropic terms, also taking into account the role of entanglement in reducing uncertainty. The information exclusion principle bounds instead the correlations that can exist between the outcomes of incompatible measurements on one physical system, and a second reference system. We provide a more stringent formulation of both the uncertainty principle and the information exclusion principle, with direct applications for, e.g., the security analysis of quantum key distribution, entanglement estimation, and quantum communication. We also highlight a fundamental distinction between the complementarity of observables in terms of uncertainty and in terms of information. © 2014 American Physical Society.

Sreekumar T.T.,National University of Singapore
Information Society | Year: 2011

Studies that go beyond the ICT4D (Information and Communication Technologies for Development) framework emphasize the social and cultural dimensions of mobile phones. Nevertheless, the cultural dimension, in literature pertaining to both urban and rural use patterns, typically takes an individualistic orientation. The possibility of actualizing the collectivistic logic in a community's appropriation of new technologies is mostly overlooked. The present article explores how the fishers community in Kerala, India, use mobile phones in culturally enhancing and ecologically oriented ways that improve their working and living conditions. In the case of Kerala fishers, the impulse toward cooperation has long been ingrained in their culture, as often happens among marginalized groups. The availability of mobile technologies has allowed for the amplification of this impulse and enabled new modes of cooperation, especially in sharing of information on promising fishing spots and safety and rescue at sea. © Taylor & Francis Group, LLC.

Rorth P.,Institute of Molecular and Cell Biology | Rorth P.,National University of Singapore
Developmental Cell | Year: 2011

As individual cells or groups of cells move through the complex environment of the body, their migration is affected by multiple external cues. Some cues are diffusible signaling molecules, and some are solid biophysical features. How do cells respond appropriately? This perspective discusses the relationship between guidance input and the cellular output, considering effects from classical chemotaxis to contact-dependent guidance. The influences of membrane trafficking and of imposed constraints on directional movement are also considered. New insights regarding guidance and dynamic cell polarity have emerged from examining new cell migration models and from re-examining well known ones with new approaches and new tools. © 2011 Elsevier Inc.

Malik V.S.,Harvard University | Pan A.,National University of Singapore | Willett W.C.,Harvard University | Hu F.B.,Harvard University
American Journal of Clinical Nutrition | Year: 2013

Background: The relation between sugar-sweetened beverages (SSBs) and body weight remains controversial Objective: We conducted a systematic review and meta-analysis to summarize the evidence in children and adults Design: We searched PubMed, EMBASE, and Cochrane databases through March 2013 for prospective cohort studies and randomized controlled trials (RCTs) that evaluated the SSB-weight relation Separate meta-analyses were conducted in children and adults and for cohorts and RCTs by using random- and fixed-effects models Results: Thirty-two original articles were included in our meta-analyses: 20 in children (15 cohort studies, n = 25,745; 5 trials, n = 2772) and 12 in adults (7 cohort studies, n = 174,252; 5 trials, n = 292). In cohort studies, one daily serving increment of SSBs was associated with a 0.06 (95% CI: 0.02, 0.10) and 0.05 (95% CI: 0.03, 0.07)-unit increase in BMI in children and 0.22 kg (95% CI: 0.09, 0.34 kg) and 0.12 kg (95% CI: 0.10, 0.14 kg) weight gain in adults over 1 y in random- and fixedeffects models, respectively. RCTs in children showed reductions in BMI gain when SSBs were reduced [random and fixed effects: 20.17 (95% CI: 20.39, 0.05) and 20.12 (95% CI: 20.22, 20.2)], whereas RCTs in adults showed increases in body weight when SSBs were added (random and fixed effects: 0.85 kg; 95% CI: 0.50, 1.20 kg) Sensitivity analyses of RCTs in children showed more pronounced benefits in preventing weight gain in SSB substitution trials (compared with school-based educational programs) and among overweight children (compared with normal-weight children) Conclusion: Our systematic review and meta-analysis of prospective cohort studies and RCTs provides evidence that SSB consumption promotes weight gain in children and adults. © 2013 American Society for Nutrition.

Liu M.B.,CAS Institute of Mechanics | Liu G.R.,National University of Singapore
Archives of Computational Methods in Engineering | Year: 2010

Smoothed particle hydrodynamics (SPH) is a meshfree particle method based on Lagrangian formulation, and has been widely applied to different areas in engineering and science. This paper presents an overview on the SPH method and its recent developments, including (1) the need for meshfree particle methods, and advantages of SPH, (2) approximation schemes of the conventional SPH method and numerical techniques for deriving SPH formulations for partial differential equations such as the Navier-Stokes (N-S) equations, (3) the role of the smoothing kernel functions and a general approach to construct smoothing kernel functions, (4) kernel and particle consistency for the SPH method, and approaches for restoring particle consistency, (5) several important numerical aspects, and (6) some recent applications of SPH. The paper ends with some concluding remarks. © CIMNE, Barcelona, Spain 2010.

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.

Li F.,National University of Singapore
Cell Death and Differentiation | Year: 2016

The influenza virus infects millions of people each year and can result in severe complications. Understanding virus recognition and host responses to influenza infection will enable future development of more effective anti-viral therapies. Previous research has revealed diverse yet important roles for the annexin family of proteins in modulating the course of influenza A virus (IAV) infection. However, the role of Annexin-A1 (ANXA1) in IAV infection has not been addressed. Here, we show that ANXA1 deficient mice exhibit a survival advantage, and lower viral titers after infection. This was accompanied with enhanced inflammatory cell infiltration during IAV infection. ANXA1 expression is increased during influenza infection clinically, in vivo and in vitro. The presence of ANXA1 enhances viral replication, influences virus binding, and enhances endosomal trafficking of the virus to the nucleus. ANXA1 colocalizes with early and late endosomes near the nucleus, and enhances nuclear accumulation of viral nucleoprotein. In addition, ANXA1 enhances IAV-mediated apoptosis. Overall, our study demonstrates that ANXA1 plays an important role in influenza virus replication and propagation through various mechanisms and that we predict that the regulation of ANXA1 expression during IAV infection may be a viral strategy to enhance its infectivity.Cell Death and Differentiation advance online publication, 4 March 2016; doi:10.1038/cdd.2016.19. © 2016 Macmillan Publishers Limited

Coffman T.M.,Duke University | Coffman T.M.,National University of Singapore
Nature Medicine | Year: 2011

High blood pressure, or hypertension, is a very common disorder with a substantial impact on public health because of its associated complications. Despite the high prevalence of essential hypertension and years of research, the basic causes remain obscure. Here I review recent advances in understanding the pathophysiology of hypertension. I present a general overview of the field and, by necessity, use broad strokes to portray recent progress and place it in context. For this purpose, I use illustrative examples from the large number of important developments in hypertension research over the last five years. The intent of this review is to provide a sense of where the field is progressing, with an emphasis on work that sheds light on pathogenic mechanisms and that is therefore likely to inform new translational advances. © 2011 Nature America, Inc. All rights reserved.

Ingham P.W.,Institute of Molecular and Cell Biology | Ingham P.W.,National University of Singapore | Nakano Y.,Institute of Molecular and Cell Biology | Nakano Y.,Hyogo College of Medicine | Seger C.,Institute of Molecular and Cell Biology
Nature Reviews Genetics | Year: 2011

Hedgehog proteins constitute one of a small number of families of secreted signals that have a central role in the development of metazoans. Genetic analyses in flies, fish and mice have uncovered the major components of the pathway that transduces Hedgehog signals, and recent genome sequence projects have provided clues about its evolutionary origins. In this Review we provide an updated overview of the mechanisms and functions of this signalling pathway, highlighting the conserved and divergent features of the pathway, as well as some of the common themes in its deployment that have emerged from recent studies. © 2011 Macmillan Publishers Limited. All rights reserved.

Shen H.-M.,National University of Singapore | Codogno P.,University Paris - Sud
Autophagy | Year: 2011

The concept of autophagic cell death was first established based on observations of increased autophagic markers in dying cells. The major limitation of such a morphology-based definition of autophagic cell death is that it fails to establish the functional role of autophagy in the cell death process, and thus contributes to the confusion in the literature regarding the role of autophagy in cell death and cell survival. Here we propose to define autophagic cell death as a modality of non-apoptotic or necrotic programmed cell death in which autophagy serves as a cell death mechanism, upon meeting the following set of criteria: (i) cell death occurs without the involvement of apoptosis; (ii) there is an increase of autophagic flux, and not just an increase of the autophagic markers, in the dying cells; and (iii) suppression of autophagy via both pharmacological inhibitors and genetic approaches is able to rescue or prevent cell death. In light of this new definition, we will discuss some of the common problems and difficulties in the study of autophagic cell death and also revisit some wellreported cases of autophagic cell death, aiming to achieve a better understanding of whether autophagy is a real killer, an accomplice or just an innocent bystander in the course of cell death. At present, the physiological relevance of autophagic cell death is mainly observed in lower eukaryotes and invertebrates such as Dictyostelium discoideum and Drosophila melanogaster. We believe that such a clear definition of autophagic cell death will help us study and understand the physiological or pathological relevance of autophagic cell death in mammals. © 2011 Landes Bioscience.

Zhang W.,National University of Singapore
Magazine of Concrete Research | Year: 2016

Diagonal tension cracks in reinforced concrete members adversely affect the performance of flexural members strengthened by externally bonded fibre-reinforced polymer (FRP) materials. The interface between FRP materials and concrete is influenced by both shear and peeling for such conditions. The objective of this study is to understand bond behaviour in carbon FRP plates and concrete systems under a combination of fracture modes (peeling and shear) by double-lap shear bond tests. The specimens were designed for different initial angles at the middle of the specimen to ensure that the interface acts for both shear and peeling conditions. From the test results, the bond behaviour under the combination of fracture modes can be observed by their strain distribution and load-displacement relation. The results also confirm that the tensile load decreases as the peeling angle increases. Moreover, a new calculation method to predict the bond strength between carbon FRP plates and concrete under shear-peeling fracture is proposed and agrees well with the test results. © 2016, ICE Publishing. All rights reserved.

Englert B.-G.,National University of Singapore
European Physical Journal D | Year: 2013

Quantum theory is a well-defined local theory with a clear interpretation. No "measurement problem" or any other foundational matters are waiting to be settled. © EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2013.

Pan S.L.,National University of Singapore | Tan B.,University of Sydney
Information and Organization | Year: 2011

Despite an abundance of prescriptions and examples for the conduct of case research in the literature, the fact that most prescriptions tend to (1) articulate general principles/guidelines that are difficult to translate into specific, actionable steps, (2) hold only under idealized conditions and may be unworkable in the field, and (3) emphasize the need to be flexible without explaining how flexibility can be achieved, is creating a steep learning curve. To address these gaps, a structured-pragmatic-situational (SPS) approach to conducting case research is proposed with detailed instructions provided for each of its eight steps. The eight steps include (1) access negotiation, (2)conceptualizing the phenomenon,(3) collecting and organizing the initial data, (4) constructing and extending the theoretical lens, (5) confirming and validating data, (6) selective coding, (7) ensuring theory-data-model alignment, and (8) writing the case report. With its prescriptions, the SPS approach introduces a number of conceptual innovations, integrates the different recommendations of some of the most frequently cited works on the case research method into a coherent whole, and suggests resolutions for a number of common issues that confront case researchers. © 2011 Elsevier Ltd.

Lim G.G.,National University of Singapore
PloS one | Year: 2013

Disruption of the ubiquitin-proteasome system, which normally identifies and degrades unwanted intracellular proteins, is thought to underlie neurodegeneration. Supporting this, mutations of Parkin, a ubiquitin ligase, are associated with autosomal recessive parkinsonism. Remarkably, Parkin can protect neurons against a wide spectrum of stress, including those that promote proteasome dysfunction. Although the mechanism underlying the preservation of proteasome function by Parkin is hitherto unclear, we have previously proposed that Parkin-mediated K63-linked ubiquitination (which is usually uncoupled from the proteasome) may serve to mitigate proteasomal stress by diverting the substrate load away from the machinery. By means of linkage-specific antibodies, we demonstrated here that proteasome inhibition indeed promotes K63-linked ubiquitination of proteins especially in Parkin-expressing cells. Importantly, we further demonstrated that the recruitment of Ubc13 (an E2 that mediates K63-linked polyubiquitin chain formation exclusively) by Parkin is selectively enhanced under conditions of proteasomal stress, thus identifying a mechanism by which Parkin could promote K63-linked ubiquitin modification in cells undergoing proteolytic stress. This mode of ubiquitination appears to facilitate the subsequent clearance of Parkin substrates via autophagy. Consistent with the proposed protective role of K63-linked ubiquitination in times of proteolytic stress, we found that Ubc13-deficient cells are significantly more susceptible to cell death induced by proteasome inhibitors compared to their wild type counterparts. Taken together, our study suggests a role for Parkin-mediated K63 ubiquitination in maintaining cellular protein homeostasis, especially during periods when the proteasome is burdened or impaired.

TCDD is one of the most persistent environmental toxicants in biological systems and its effect through aryl hydrocarbon receptor (AhR) has been well characterized. However, the information on TCDD-induced toxicity in other molecular pathways is rather limited. To fully understand molecular toxicity of TCDD in an in vivo animal model, adult zebrafish were exposed to TCDD at 10 nM for 96 h and the livers were sampled for RNA-sequencing based transcriptomic profiling. A total of 1,058 differently expressed genes were identified based on fold-change>2 and TPM (transcripts per million) >10. Among the top 20 up-regulated genes, 10 novel responsive genes were identified and verified by RT-qPCR analysis on independent samples. Transcriptomic analysis indicated several deregulated pathways associated with cell cycle, endocrine disruptors, signal transduction and immune systems. Comparative analyses of TCDD-induced transcriptomic changes between fish and mammalian models revealed that proteomic pathway is consistently up-regulated while calcium signaling pathway and several immune-related pathways are generally down-regulated. Finally, our study also suggested that zebrafish model showed greater similarity to in vivo mammalian models than in vitro models. Our study indicated that the zebrafish is a valuable in vivo model in toxicogenomic analyses for understanding molecular toxicity of environmental toxicants relevant to human health. The expression profiles associated with TCDD could be useful for monitoring environmental dioxin and dioxin-like contamination.

Singh P.J.,University of Melbourne | Power D.,University of Melbourne | Chuong S.C.,National University of Singapore
Journal of Operations Management | Year: 2011

More than 900,000 organizations worldwide have registered to the ISO 9000 quality management standard. Despite its growing popularity, few studies have offered a coherent theoretical basis for the standard's appeal. A theory-based explanation enhances understanding and appreciation for the standard, and provides clarity on how the standard benefits organizations. In this paper, we invoke the resource dependence theory (RDT) to purport that the standard is used by organizations as a tool to manage their organizational environment. It does this by specifying procedures that organizations need to manage their organization-environment boundary spanning processes. Using the RDT perspective, a model with three key constructs embodying ISO 9000 was developed: internal processes, relationships with customers and relationships with suppliers. The latter two were treated as being part of the task environment. We predicted that the external aspects of the standard affect operating performance (a measure of effectiveness), both directly and through internal processes. Empirical data from 416 ISO 9000 registered Australian manufacturing plants validated the RDT perspective, and suggest that the three constructs, individually and in isolation, are not as effective as when they are considered together. By invoking RDT, a new theoretical viewpoint to ISO 9000 has been developed that adds to other theoretical perspectives, and goes some way to explaining the growing popularity of this standard with organizations. © 2010 Elsevier B.V.

McInnes B.,National University of Singapore
Nuclear Physics B | Year: 2015

For several crucial microseconds of its early history, the Universe consisted of a Quark-Gluon Plasma. As it cooled during this era, it traced out a trajectory in the quark matter phase diagram. The form taken by this trajectory is not known with certainty, but is of great importance: it determines, for example, whether the cosmic plasma passed through a first-order phase change during the transition to the hadron era, as has recently been suggested by advocates of the "Little Inflation" model. Just before this transition, the plasma was strongly coupled and therefore can be studied by holographic techniques. We show that holography imposes a strong constraint (taking the form of a bound on the baryonic chemical potential relative to the temperature) on the domain through which the cosmic plasma could pass as it cooled, with important consequences for Little Inflation. In fact, we find that holography applied to Little Inflation implies that the cosmic plasma must have passed quite close to the quark matter critical point, and might therefore have been affected by the associated fluctuation phenomena. © 2015 The Author.

McInnes B.,National University of Singapore
Nuclear Physics B | Year: 2015

Magnetic fields large enough to be observable are ubiquitous in astrophysics, even at extremely large length scales. This has led to the suggestion that such fields are seeded at very early (inflationary) times, and subsequently amplified by various processes involving, for example, dynamo effects. Many such mechanisms give rise to extremely large magnetic fields at the end of inflationary reheating, and therefore also during the quark-gluon plasma epoch of the early universe. Such plasmas have a well-known holographic description in terms of a thermal asymptotically AdS black hole. We show that holography imposes an upper bound on the intensity of magnetic fields (≈3.6×1018gauss at the hadronization temperature) in these circumstances; this is above, but not far above, the values expected in some models of cosmic magnetogenesis. © 2015 The Author.

Zhang Z.-X.,Institute of Materials Research and Engineering of Singapore | Liu K.L.,Institute of Materials Research and Engineering of Singapore | Li J.,Institute of Materials Research and Engineering of Singapore | Li J.,National University of Singapore
Angewandte Chemie - International Edition | Year: 2013

Smart stars: A novel star-star supramolecular architecture was self-assembled from a star-shaped adamantyl-terminated 8-arm poly(ethylene glycol) and a star-shaped poly(N-isopropylacrylamide) with a β-cyclodextrin core through inclusion complexation. The star-star supramolecules further self-aggregated into a 3D network in response to temperature change, forming a thermoresponsive reversible "smart" hydrogel. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Prasad D.K.,National University of Singapore
Optics Express | Year: 2013

This paper applies a recently proposed dominant point detection method - precision and reliability optimization (PRO) - for representing shapes in the microscopy images of fabricated structures. This method uses both the local and the global nature of fit for dominant point detection. A smaller value of its control parameter better represents the local curvature properties of the shape while a larger value better indicates the global curvature properties. The applicability of this method to a wide range of microscopy images is demonstrated using four microscopy examples of brightness enhancement films, electromagnetic and photonic band gap materials, and aspherical mirror alignments. It is shown that PRO can clearly highlight several image effects and imperfections which may not be easily identifiable by human eye or may be difficult to analyze and assess. Further, for large scale arrays, it can be used to generate useful fabrication accuracy statistics and detect features with low fidelity or more imperfections. © 2013 Optical Society of America.

Geiger T.,Tel Aviv University | Zaidel-Bar R.,National University of Singapore
Current Opinion in Cell Biology | Year: 2012

Cell biologists studying cell adhesion have already figured out that cell-extracellular matrix connections, mediated by integrin receptors, are diverse and extremely complex structures. Dozens of adaptors-linking integrins with the cytoskeleton, and numerous enzymes and signaling proteins-regulating adhesion site dynamics, collectively referred to as the integrin adhesome, cooperate in mediating adhesion and activating specific signaling networks. Recent proteomic studies indicate that the known adhesome complexity is just the tip of the iceberg. In each existing category of molecular function the number of candidate components more than double the known components and several new categories are suggested. Proteomic analysis of different integrin heterodimers points to integrin-specific variations in composition and analysis of adhesion complexes under varying tension regimes highlights the force-dependent recruitment of different components, most notably LIM domain proteins. © 2012 Elsevier Ltd.

Lateef A.,National University of Singapore | Petri M.,Johns Hopkins University
Nature Reviews Rheumatology | Year: 2012

Systemic lupus erythematosus (SLE) is an autoantibody-mediated systemic autoimmune disease, predominantly affecting young females. Pregnancy is increasingly common in the setting of SLE, as survival and quality of life of patients improve. Although live births can be achieved in the most cases, pregnancy in patients with SLE remains a high-risk condition. Maternal and fetal mortality and morbidity are considerably increased, compared with the general population. Aberrations in pregnancy-related maternal immune adaptations are likely contributors. Active maternal disease, renal involvement, specific autoantibody subsets and advanced organ damage are predictors of poor outcome. Therapeutic options are limited during pregnancy as maternal benefit has to be weighed against fetal risk. Prevention of preterm birth and refractory pregnancy loss, as well as management of established neonatal heart block remain unmet needs. Further research should address these important issues that affect young patients with SLE and their babies. © 2012 Macmillan Publishers Limited.

Gascoigne N.R.J.,National University of Singapore | Acuto O.,University of Oxford
Current Opinion in Immunology | Year: 2015

Genetic approaches identified THEMIS as a critical element driving positive selection of CD4+CD8+ thymocytes towards maturation. THEMIS is expressed only in the T-cell lineage, and is recruited to the proximity of signaling T-cell antigen receptors (TCR) by association with the membrane scaffold LAT. However, its molecular role remained an enigma until recently. Conventionally positively-selected T-cells are lacking in THEMIS-deficient mice, leading to the initial hypothesis that THEMIS positively regulates TCR signaling. Recent data show that THEMIS deficiency increases rather than decreases TCR signaling, leading to augmented apoptosis. The finding that THEMIS is constitutively bound to the tyrosine phosphatases SHP1 or SHP2, provides a mechanism for THEMIS action. When recruited onto LAT, THEMIS-SHP promotes immediate dephosphorylation of TCR-proximal signaling components. This negative feedback is central in setting sharp signaling thresholds and helps explain the exquisite ligand discrimination by the TCR, particularly during thymocyte selection. © 2015 Elsevier Ltd.

Scheffers B.R.,National University of Singapore | Scheffers B.R.,James Cook University | Joppa L.N.,Microsoft | Pimm S.L.,Duke University | Laurance W.F.,James Cook University
Trends in Ecology and Evolution | Year: 2012

Estimates of non-microbial diversity on Earth range from 2 million to over 50 million species, with great uncertainties in numbers of insects, fungi, nematodes, and deep-sea organisms. We summarize estimates for major taxa, the methods used to obtain them, and prospects for further discoveries. Major challenges include frequent synonymy, the difficulty of discriminating certain species by morphology alone, and the fact that many undiscovered species are small, difficult to find, or have small geographic ranges. Cryptic species could be numerous in some taxa. Novel techniques, such as DNA barcoding, new databases, and crowd-sourcing, could greatly accelerate the rate of species discovery. Such advances are timely. Most missing species probably live in biodiversity hotspots, where habitat destruction is rife, and so current estimates of extinction rates from known species are too low. © 2012 Elsevier Ltd.

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.

Chan C.,Duke University | St. John A.,Duke University | Abraham S.,Duke University | Abraham S.,National University of Singapore
Immunity | Year: 2013

The lower urinary tract's virtually inevitable exposure to external microbial pathogens warrants efficient tissue-specialized defenses to maintain sterility. The observation that the bladder can become chronically infected in combination with clinical observations that antibody responses after bladder infections are not detectable suggest defects in the formation of adaptive immunity and immunological memory. We have identified a broadly immunosuppressive transcriptional program specific to the bladder, but not the kidney, during infection of the urinary tract that is dependent on tissue-resident mast cells (MCs). This involves localized production of interleukin-10 and results in suppressed humoral and cell-mediated responses and bacterial persistence. Therefore, in addition to the previously described role of MCs orchestrating the early innate immunity during bladder infection, they subsequently play a tissue-specific immunosuppressive role. These findings may explain the prevalent recurrence of bladder infections and suggest the bladder as a site exhibiting an intrinsic degree of MC-maintained immune privilege. © 2013 Elsevier Inc.

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.

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.

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.

Ramdas K.,National University of Singapore
Environment and Planning A | Year: 2012

The author engages with narratives of graduate single Indian Singaporean women based in global cities for work, namely Singapore, Melbourne, and London. She interrogates how and why these single women are often portrayed as incomplete, occupying a cusp where they are perceived as waiting for marriage. The author makes use of secondary data and twenty-nine in-depth interviews with women based overseas and in Singapore to examine critically discourses of family, marriage, and 'singlehood'. She contests how single Indian women are constructed as 'women in waiting', and the hegemonic constructions of marriage and family that underlie such a discourse of waiting. By examining the experiences of the women in multiple cities, the author reveals how the women's experiences of singlehood disrupt discourses of waiting emerging from the context of the Singaporean state, Singapore-Indian community and their parents. Specifically, it is argued that singlehood cannot be understood without reference to the family, and a case is made for engaging in a politics of waiting which shows how gender, sexuality, and heteronormativity enable and constrain single Indian women's lives in Singapore and abroad, through the use of 'punctuations'. The author thus shows how singlehood is constituted as a struggle between state, community, family, and the individual across space and time. © 2012 Pion Ltd and its Licensors.

Salvo A.,National University of Singapore | Geiger F.M.,Northwestern University
Nature Geoscience | Year: 2014

Ethanol-based vehicles are thought to generate less pollution than gasoline-based vehicles, because ethanol emissions contain lower concentrations of mono-nitrogen oxides than those from gasoline emissions. However, the predicted effect of various gasoline/ethanol blends on the concentration of atmospheric pollutants such as ozone varies between model and laboratory studies, including those that seek to simulate the same environmental conditions. Here, we report the consequences of a real-world shift in fuel use in the subtropical megacity of São Paulo, Brazil, brought on by large-scale fluctuations in the price of ethanol relative to gasoline between 2009 and 2011. We use highly spatially and temporally resolved observations of road traffic levels, meteorology and pollutant concentrations, together with a consumer demand model, to show that ambient ozone concentrations fell by about 20% as the share of bi-fuel vehicles burning gasoline rose from 14 to 76%. In contrast, nitric oxide and carbon monoxide concentrations increased. We caution that although gasoline use seems to lower ozone levels in the São Paulo metropolitan area relative to ethanol use, strategies to reduce ozone pollution require knowledge of the local chemistry and consideration of other pollutants, particularly fine particles. © 2014 Macmillan Publishers Limited.

Lim S.,National University of Singapore | Lee A.,Center for Organization Development
Journal of Occupational Health Psychology | Year: 2011

This study extended incivility research beyond the confines of the workplace by exploring the relationships between incivility, work-to-family conflict and family support. Data collected from 180 employees from various organizations in Singapore showed that incivility is not a rare phenomenon in Asian cultures. Employees experienced more incivility from superiors than coworkers or subordinates, and these experiences were related to different outcomes. Coworker-initiated incivility was associated with decreased coworker satisfaction, increased perceptions of unfair treatment, and increased depression. On the other hand, superior-initiated incivility was associated with decreased supervisor satisfaction and increased work-to-family conflict. Results also revealed that employees with high family support showed stronger relationships between workplace incivility and negative outcomes, compared with employees with low family support. © 2011 American Psychological Association.

Alexandre S.S.,Federal University of Minas Gerais | Lucio A.D.,Federal University of Lavras | Neto A.H.C.,National University of Singapore | Nunes R.W.,Federal University of Minas Gerais
Nano Letters | Year: 2012

Ab initio calculations indicate that while the electronic states introduced by tilt grain boundaries in graphene are only partially confined to the defect core, a translational grain boundary introduces states near the Fermi level that are very strongly confined to the core of the defect, and display a ferromagnetic instability. The translational boundary lies along a graphene zigzag direction and its magnetic state is akin to that which has been theoretically predicted to occur on zigzag edges of graphene ribbons. Unlike ribbon edges, the translational grain boundary is fully immersed within the bulk of graphene, hence its magnetic state is protected from the contamination and reconstruction effects that have hampered experimental detection of the magnetic ribbon states. Moreover, our calculations suggest that charge transfer between grain boundaries and the bulk in graphene is short ranged, with charge redistribution confined to ∼5 Å from the geometric center of the 1D defects. © 2012 American Chemical Society.

Aulbach M.,National University of Singapore
International Journal of Quantum Information | Year: 2012

Quantum states that are symmetric with respect to permutations of their subsystems appear in a wide range of physical settings, and they have a variety of promising applications in quantum information science. In this thesis, the entanglement of symmetric multipartite states is categorized, with a particular focus on the pure multi-qubit case and the geometric measure of entanglement. An essential tool for this analysis is the Majorana representation, a generalization of the single-qubit Bloch sphere representation, which allows for a unique representation of symmetric n-qubit states by n points on the surface of a sphere. Here this representation is employed to search for the maximally entangled symmetric states of up to 12 qubits in terms of the geometric measure, and an intuitive visual understanding of the upper bound on the maximal symmetric entanglement is given. Furthermore, it will be seen that the Majorana representation facilitates the characterization of entanglement equivalence classes such as stochastic local operations and classical communication (SLOCC) and the degeneracy configuration (DC). It is found that SLOCC operations between symmetric states can be described by the Möbius transformations of complex analysis, which allows for a clear visualization of the SLOCC freedoms and facilitates the understanding of SLOCC invariants and equivalence classes. In particular, explicit forms of representative states for all symmetric SLOCC classes of up to five qubits are derived. Well-known entanglement classification schemes such as the four qubit entanglement families or polynomial invariants are reviewed in the light of the results gathered here, which leads to sometimes surprising connections. Some interesting links and applications of the Majorana representation to related fields of mathematics and physics are also discussed. © 2012 World Scientific Publishing Company.

Qian X.,National University of Singapore
International Journal of Pressure Vessels and Piping | Year: 2013

This paper reports the failure assessment curves for semi-elliptical surface cracks located at hot-spot positions in the circular hollow section X- and K-joints. The failure assessment curves derive from the square root of the ratio between the linear-elastic and the elastic-plastic energy release rates, computed from the domain-integral approach. This study examines both the material and geometric dependence of the failure assessment curves. The area reduction factor, used in defining the strength of the cracked joints, imposes a significant effect on the computed failure assessment curve. The failure assessment curves indicate negligible variations with respect to the crack-front locations and the material yield strength. The crack depth ratio exerts a stronger effect on the computed failure assessment curve than does the crack aspect ratio. This study proposes a parametric expression for the failure assessment curves based on the geometric parameters for surface cracks in circular hollow section X- and K-joints. © 2013 Elsevier Ltd.

Lim S.,Agency for Science, Technology and Research Singapore | Kaldis P.,Agency for Science, Technology and Research Singapore | Kaldis P.,National University of Singapore
Stem Cells | Year: 2012

During neurogenesis, cell cycle regulators play a pivotal role in ensuring proper proliferation, cell cycle exit, and differentiation of neural precursors. However, the precise role of cyclin-dependent kinases (Cdks) in these processes is not well understood. We generated Cdk2 and Cdk4 double knockout (DKO) mice and found a striking ablation of the intermediate zone and cortical plate in mouse embryonic brain. When neural stem cells (NSCs) were isolated and analyzed, DKO NSCs proliferated comparable to wild type as Cdk1 now binds to cyclin D1 and E1 and assumes the role vacated by the loss of Cdk2 and Cdk4 in phosphorylating Rb. Although compensation was sufficient for the maintenance of selfrenewal and multilineage potential, DKO NSCs displayed an altered cell cycle profile and were more prone to neuronal differentiation. This was manifested in vivo as a marked reduction in S-phase length and an increased tendency for neurogenic divisions that prevented proper expansion of the basal progenitor pool. Our data thus demonstrate the induction of neurogenic divisions in the absence of critical mediators of G1/S transition - Cdk2 and Cdk4, and highlight their evolutionary importance in the determination of cortical thickness. © AlphaMed Press.

McInnes B.,National University of Singapore
Nuclear Physics B | Year: 2012

The AdS/CFT dual description of a peripheral heavy ion collision involves an asymptotically AdS rotating black hole. The explicitly known black holes of this kind, with planar event horizon topology [the "KMV 0" spacetimes], have been shown to be unstable when string-theoretic effects are taken into account. It has been argued that this implies a "holographic" angular momentum cutoff for peripheral collisions at very high energies. However, the KMV 0 black hole corresponds to a specific velocity distribution in the aftermath of a peripheral collision, and this distribution is not realistic at all points of the interaction zone. It could therefore be argued that the angular momentum cutoff is an artefact of this particular choice of bulk geometry. We demonstrate that, on the contrary, a quark-gluon plasma with any physically reasonable internal velocity distribution corresponds to a black hole which is still unstable, in the same way as the KMV 0 spacetime. The angular momentum cutoff is therefore a universal prediction of the holographic description of these collisions. © 2012 Elsevier B.V.

Zhang T.,Advanced Digital science Center | Ghanem B.,King Abdullah University of Science and Technology | Liu S.,National University of Singapore | Ahuja N.,University of Illinois at Urbana - Champaign
International Journal of Computer Vision | Year: 2013

In this paper, we formulate object tracking in a particle filter framework as a structured multi-task sparse learning problem, which we denote as Structured Multi-Task Tracking (S-MTT). Since we model particles as linear combinations of dictionary templates that are updated dynamically, learning the representation of each particle is considered a single task in Multi-Task Tracking (MTT). By employing popular sparsity-inducing lp,q mixed norms (specifically p∈2,∞ and q=1), we regularize the representation problem to enforce joint sparsity and learn the particle representations together. As compared to previous methods that handle particles independently, our results demonstrate that mining the interdependencies between particles improves tracking performance and overall computational complexity. Interestingly, we show that the popular L1 tracker (Mei and Ling, IEEE Trans Pattern Anal Mach Intel 33(11):2259-2272, 2011) is a special case of our MTT formulation (denoted as the L11 tracker) when p=q=1. Under the MTT framework, some of the tasks (particle representations) are often more closely related and more likely to share common relevant covariates than other tasks. Therefore, we extend the MTT framework to take into account pairwise structural correlations between particles (e.g. spatial smoothness of representation) and denote the novel framework as S-MTT. The problem of learning the regularized sparse representation in MTT and S-MTT can be solved efficiently using an Accelerated Proximal Gradient (APG) method that yields a sequence of closed form updates. As such, S-MTT and MTT are computationally attractive. We test our proposed approach on challenging sequences involving heavy occlusion, drastic illumination changes, and large pose variations. Experimental results show that S-MTT is much better than MTT, and both methods consistently outperform state-of-the-art trackers. © 2012 Springer Science+Business Media New York.

Berrick A.J.,National University of Singapore
Tobacco Control | Year: 2013

The tobacco-free generation proposal advocates legislation precluding the sale and supply of tobacco to individuals born after a certain year. The measure is aimed at overcoming defects with current youth access laws that suffer from rite-of-passage and mixed signalling effects. Since its introduction in 2010, the proposal has attracted international attention, highlighting a number of matters that the present short article discusses. Efficacy issues, including retailer compliance, supply by surrogates and illicit sales, are addressed in the broader setting of community adherence to legislation. Encouragement for the likelihood of successful implementation is provided by historical precedents. In principle objections, relating to choice and generational fairness, are considered against the criteria of consistency and proportionality. It is concluded that the measure's emphasis on the welfare of future generations and its regard for the interests of existing stakeholders provide a feasible opportunity for the ultimate eradication of tobacco supply in appropriate jurisdictions.

Xu J.-X.,National University of Singapore
International Journal of Control | Year: 2011

In this article we review the recent advances in iterative learning control (ILC) for nonlinear dynamic systems. In the research field of ILC, two categories of system nonlinearities are considered, namely, the global Lipschitz continuous (GLC) functions and local Lipschitz continuous (LLC) functions. ILC for GLC systems is widely studied and analysed using contraction mapping approach, and the focus of recent exploration moves to application problems, though a number of theoretical issues remain open. ILC for LLC systems is currently a hot area and the recent research focuses on ILC design and analysis by means of Lyapunov approach. The objectives of this article are to introduce recent development and advances in nonlinear ILC schemes, highlight their effectiveness and limitations, as well as discuss the directions for further exploration of nonlinear ILC. © 2011 Taylor & Francis.

Lim W.Y.,National University of Singapore
American journal of epidemiology | Year: 2012

The authors examined relations between reproductive factors and 5 estrogen pathway gene polymorphisms (CYP17 rs743572, CYP19A1 rs10046, ERβ rs1256049, ERβ rs4986938, and COMT rs4680) among 702 Singapore Chinese female lung cancer cases and 1,578 hospital controls, of whom 433 cases (61.7%) and 1,375 controls (87.1%) were never smokers. Parity (per child, odds ratio (OR) = 0.92, 95% confidence interval (CI): 0.87, 0.97) and menstrual cycle length (for ≥30 days vs. <30 days, OR = 0.50, 95% CI: 0.32, 0.80) were inversely associated with lung cancer in never smokers, while age at first birth (for ages 21-25, 26-30, and ≥31 years vs. ≤20 years, ORs were 1.54, 2.17, and 1.30, respectively), age at menopause (for ages 49-51 and ≥52 years vs. ≤48 years, ORs were 1.37 and 1.59; P(trend) = 0.003), and reproductive period (for 31-33, 34-36, 37-39, and ≥40 years vs. ≤30 years, ORs were 1.06, 1.25, 1.45, and 1.47; P(trend) = 0.026) were positively associated. Among smokers, parity was inversely associated with lung cancer, but there was no association with other reproductive factors. The COMT rs4680 A allele was positively associated with lung cancer in never smokers (for G/A or A/A vs. G/G, OR = 1.46, 95% CI: 1.12, 1.90) but not in ever smokers. No associations were seen with other polymorphisms. These results support a risk-enhancing role of estrogens in lung carcinogenesis among never smokers.

Shahrizaila N.,University of Malaya | Yuki N.,National University of Singapore
Journal of Neurology, Neurosurgery and Psychiatry | Year: 2013

In the 1950s, Bickerstaff and Fisher independently described cases with a unique presentation of ophthalmoplegia and ataxia. The neurological features were typically preceded by an antecedent infection and the majority of patients made a spontaneous recovery. In the cases with Bickerstaff brainstem encephalitis, there was associated altered consciousness and in some, hyperreflexia, in support of a central pathology whereas in Fisher syndrome, patients were areflexic in keeping with a peripheral aetiology. However, both authors recognised certain similarities to Guillain-Barré syndrome such as the presence of peripheral neuropathy and cerebrospinal fluid albuminocytological dissociation. The discovery of immunoglobulin G anti-GQ1b antibodies in patients with Fisher syndrome and later in Bickerstaff brainstem encephalitis was crucial in providing the necessary evidence to conclude that both conditions were in fact part of the same spectrum of disease by virtue of their common clinical and immunological profiles. Following this, other neurological presentations that share anti-GQ1b antibodies emerged in the literature. These include acute ophthalmoparesis and acute ataxic neuropathy, which represent the less extensive spectrum of the disease whereas pharyngeal-cervical-brachial weakness and Fisher syndrome overlap with Guillain-Barré syndrome represent the more extensive end of the spectrum. The conditions can be referred to as the 'anti-GQ1b antibody syndrome'. In this review, we look back at the historical descriptions and describe how our understanding of Fisher syndrome and Bickerstaff brainstem encephalitis has evolved from their initial descriptions more than half a century ago.

Sidaway J.D.,National University of Singapore
Annals of the Association of American Geographers | Year: 2013

There has been considerable debate about the challenges and opportunities posed for geographical scholarship by globalization. In similar contexts, however, the discipline's relationship to area studies merits careful review and reworking. Three prospective pathways through this are presented here: the status of geographical knowledge in the aftermath of the critique of orientalism and associated postcolonial departures, debates about language and translation, and attention to the situatedness and operation of perspective in geographical imaginations. Charting these tracks, the article notes obstacles and highlights opportunities. © 2013 Taylor and Francis Group, LLC.

Ho E.L.-E.,National University of Singapore
Transactions of the Institute of British Geographers | Year: 2013

The interrelationship between forced migration, return migration and ethnicity remains relatively unexplored in current scholarship. By using the case of China's resettlement policy towards diasporic Chinese descendants expelled from Southeast Asia during 1949-1979 and examining their contemporary situation, this paper highlights the way scholarship on forced migration and ethnically privileged (return) migration can mutually enrich one another. The paper, first, examines the geopolitical context of Chinese forced migration and the premises of China's preferential policy towards co-ethnics, which labelled the 'refugees' as 'returnees' intentionally. It argues that metaphors of extraterritorial ethnic kinship and 'return' are used to justify ethnic privilege but the co-ethnics experienced socio-spatial exclusion in China because of their cultural distinctiveness. Second, the paper explores the impact of the post-1980s reforms on the rural overseas Chinese farms in which the co-ethnics were resettled. This discussion suggests that the rescaling of governance brought about policies that capitalise upon their distinctive Southeast Asian identities to reinvent the farms as economic zones and tourism sites. The sustainability of this economic strategy is, however, questioned in the third part of the paper, which considers intergenerational change now happening on the farms. It argues that international migration histories are transitioning to new internal migration flows. Such migration succession trends may transform the ethnically privileged status of the farms and their inhabitants. The qualitative findings in this paper direct broader inquiry into the complex ethnic geopolitics underpinning mobilisations of diasporic belonging and also the implications of intergenerational change. © 2012 The Author. Transactions of the Institute of British Geographers © 2012 Royal Geographical Society (with the Institute of British Geographers).

Corlett R.T.,National University of Singapore
Integrative Zoology | Year: 2011

In the present article, published and unpublished information regarding seed dispersal in the degraded landscape of Hong Kong, China, is reviewed. Information was available for 1681 native plant species, of which 1165 were assigned to probable seed dispersal modes. Endozoochory accounted for one-third (34.4%) of all species evaluated, half (54.4%) of those from forests, and more than two-thirds (69.2%) of all trees and tall shrubs. Wind dispersal (25.9%) and dispersal by an unknown agent (30.7%) accounted for most of the rest, with the unknown species mostly small-seeded herbs. Although the frugivore fauna of the Hong Kong region has been truncated since the late Pleistocene, there are few clear examples of failed mutualisms. The most striking is the absence of scatter-hoarding rodents from Hong Kong, despite the presence of forest trees that appear to require them for effective dispersal. There are also some large Lauraceae fruits that appear to be targeted at larger-gaped birds than currently present. Most endozoochorous species are dispersed by 3 small passerine birds (Pycnonotus jocosus, P. sinensis, and Zosterops japonicus), with larger birds, fruit bats (Cynopterus sphinx, Rousettus leschenaulti), rhesus macaques (Macaca mulatta), civets (Paguma larvata, Viverricula indica), and muntjacs (Muntiacus muntjac) accounting for the remainder. The low plant diversity in frugivore droppings, seed traps, and secondary vegetation suggests plant succession may be dispersal limited, although this has not been investigated experimentally. Planting underdispersed species is the simplest solution but, in the longer term, the (re)introduction of a scatter-hoarding rodent should be considered as well as that of other locally and regionally extinct frugivores. © 2011 ISZS, Blackwell Publishing and IOZ/CAS.

Madan V.,National University of Singapore
Leukemia | Year: 2016

Acute promyelocytic leukemia (APL) is a subtype of myeloid leukemia characterized by differentiation block at the promyelocyte stage. Besides the presence of chromosomal rearrangement t(15;17), leading to the formation of PML-RARA (promyelocytic leukemia-retinoic acid receptor alpha) fusion, other genetic alterations have also been implicated in APL. Here, we performed comprehensive mutational analysis of primary and relapse APL to identify somatic alterations, which cooperate with PML-RARA in the pathogenesis of APL. We explored the mutational landscape using whole-exome (n=12) and subsequent targeted sequencing of 398 genes in 153 primary and 69 relapse APL. Both primary and relapse APL harbored an average of eight non-silent somatic mutations per exome. We observed recurrent alterations of FLT3, WT1, NRAS and KRAS in the newly diagnosed APL, whereas mutations in other genes commonly mutated in myeloid leukemia were rarely detected. The molecular signature of APL relapse was characterized by emergence of frequent mutations in PML and RARA genes. Our sequencing data also demonstrates incidence of loss-of-function mutations in previously unidentified genes, ARID1B and ARID1A, both of which encode for key components of the SWI/SNF complex. We show that knockdown of ARID1B in APL cell line, NB4, results in large-scale activation of gene expression and reduced in vitro differentiation potential.Leukemia advance online publication, 6 May 2016; doi:10.1038/leu.2016.69. © 2016 Macmillan Publishers Limited

Dorner U.,National University of Singapore | Dorner U.,University of Oxford
New Journal of Physics | Year: 2012

We discuss strategies for quantum-enhanced estimation of atomic transition frequencies with ions stored in Paul traps or neutral atoms trapped in optical lattices. We show that only marginal quantum improvements can be achieved using standard Ramsey interferometry in the presence of collective dephasing, which is the major source of noise in relevant experimental setups. We therefore analyze methods based on decoherence free subspaces and prove that quantum enhancement can readily be achieved even in the case of significantly imperfect state preparation and faulty detections. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.

Gillen J.,National University of Singapore
Annals of the Association of American Geographers | Year: 2014

Using evidence from what is probably Vietnam's most visited tourism site, the War Remnants Museum in Ho Chi Minh City, this article explores the presentation of the “American War” in the construction of nationhood. The article has three objectives. First, I illustrate how nation-building in a postcolonial and postimperial context is generated through tourism, specifying how the Communist Party communicates Vietnam to lay international tourist audiences. Tourism's political instrumentality for the party is highlighted here. Second, I show how the United States is imaginatively constructed to shape Vietnam's identity. Finally, I use the conclusion to reflect on the implications for the “Asian Century” when considering Vietnam's multifaceted connections to the United States and the West. © 2014 by Association of American Geographers.

Lim L.S.,Singapore Eye Research Institute | Mitchell P.,University of Sydney | Seddon J.M.,Tufts University | Holz F.G.,University of Bonn | And 2 more authors.
The Lancet | Year: 2012

Age-related macular degeneration is a major cause of blindness worldwide. With ageing populations in many countries, more than 20% might have the disorder. Advanced age-related macular degeneration, including neovascular agerelated macular degeneration (wet) and geographic atrophy (late dry), is associated with substantial, progressive visual impairment. Major risk factors include cigarette smoking, nutritional factors, cardiovascular diseases, and genetic markers, including genes regulating complement, lipid, angiogenic, and extracellular matrix pathways. Some studies have suggested a declining prevalence of age-related macular degeneration, perhaps due to reduced exposure to modifiable risk factors. Accurate diagnosis combines clinical examination and investigations, including retinal photography, angiography, and optical coherence tomography. Dietary anti-oxidant supplementation slows progression of the disease. Treatment for neovascular age-related macular degeneration incorporates intra ocular injections of anti-VEGF agents, occasionally combined with other modalities. Evidence suggests that two commonly used anti-VEGF therapies, ranibizumab and bevacizumab, have similar efficacy, but possible differences in systemic safety are difficult to assess. Future treatments include inhibition of other angiogenic factors, and regenerative and topical therapies.

Doxzen K.,National University of Singapore
Integrative biology : quantitative biosciences from nano to macro | Year: 2013

Collective behavior refers to the emergence of complex migration patterns over scales larger than those of the individual elements constituting a system. It plays a pivotal role in biological systems in regulating various processes such as gastrulation, morphogenesis and tissue organization. Here, by combining experimental approaches and numerical modeling, we explore the role of cell density ('crowding'), strength of intercellular adhesion ('cohesion') and boundary conditions imposed by extracellular matrix (ECM) proteins ('constraints') in regulating the emergence of collective behavior within epithelial cell sheets. Our results show that the geometrical confinement of cells into well-defined circles induces a persistent, coordinated and synchronized rotation of cells that depends on cell density. The speed of such rotating large-scale movements slows down as the density increases. Furthermore, such collective rotation behavior depends on the size of the micropatterned circles: we observe a rotating motion of the overall cell population in the same direction for sizes of up to 200 μm. The rotating cells move as a solid body, with a uniform angular velocity. Interestingly, this upper limit leads to length scales that are similar to the natural correlation length observed for unconfined epithelial cell sheets. This behavior is strongly altered in cells that present a downregulation of adherens junctions and in cancerous cell types. We anticipate that our system provides a simple and easy approach to investigate collective cell behavior in a well-controlled and systematic manner.

Chokkanathan S.,National University of Singapore
Aging and Mental Health | Year: 2013

Objectives: Using the theory of religious effects (Journal for the Scientific Study of Religion, 42, 17-30 (2003)), the current study examined the relationship among religiosity, psychosocial resources (social support and mastery) and psychological distress. Method: Through face-to-face interviewing, data were collected from 321 randomly selected older adults in Chennai, India. Structural equation modelling (SEM) was conducted to test the direct-effect and the mediation models. The direct-effect model posited a direct inverse relation between religiosity and psychological distress. The mediation model posited that psychosocial resources mediate the influence of religiosity on psychological distress. Results: The fit indices supported a partial mediation model. Psychosocial resources partially mediated the influence of religiosity on psychological distress. Conclusion: These findings suggest the crucial role of religiosity in influencing the well-being of older adults. The need to integrate religiosity in interventions for older Indian adults is discussed. © 2013 Copyright Taylor and Francis Group, LLC.

Reslen J.,National University of Singapore
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2011

We study the spectral properties of a many-body system under a regime of electromagnetically induced transparency. A semi-classical model is proposed to incorporate the effect of inter-band interactions on an otherwise single-body scheme. We use a Hamiltonian with non-Hermitian terms to account for the effect of particle decay from excited levels. We explore the system response as a result of varying the interaction parameter. Then we focus on the highly interacting case, also known as the blockade regime. In this latter case, we present a perturbative development that allows us to get the transmission profile for a wide range of values of the system parameters. We observe a reduction of transmission when interaction increases and show how this property is linked to the generation of a strongly correlated many-body state. We study the characteristics of such a state and explore the mechanisms giving rise to various interesting features. © 2011 IOP Publishing Ltd.

Lim S.G.,National University of Singapore
World Journal of Gastroenterology | Year: 2015

AIM: To use existing hepatitis C virus (HCV) antiviral therapies as access to new treatments is limited. METHODS: A PubMed search for randomised control trials or meta-analysis related to response-guided therapy of HCV genotype 1 patients was undertaken using pegylated interferon and ribavirin (PR), boceprevir (B) and telaprevir (T) and lead-in where response-guided therapy at TW4(TW4), 8(TW8), 10(TW10), or 12(TW12) based on HCVRNA(+) or HCVRNA(-). Studies presented at major conferences were also used. Where necessary, a post-hoc analysis was performed. A response-guided management roadmap was created based on sustained virological response (SVR). RESULTS: Starting with PR, those with HCVRNA(-) at TW4 have > 86% SVR, while those are HCVRNA(+) have 34%-41.7% SVR. HCVRNA(-) TW4 patients can have 24 wk PR if HCVRNA < 400000 IU/mL. Alternatively, 28 wk BPR has similar SVR. If HCVRNA(+) at TW4, 72 wk PR leads to 53% SVR, hence BPR is a better option, and if HCVRNA(-) by TW8, 28 wk therapy is sufficient. If HCVRNA(+) at TW8, then HCVRNA should be checked at TW10 and TW12. By TW12, HCVRNA ≥ 100 IU/mL activates the stopping rule. This roadmap is applicable for treatment-naïve, treatment failures and cirrhotic patients. Validation from an Asia Pacific early access boceprevir program confirmed the findings that HCVRNA(-) at TW4, or TW8 conferred > 80% SVR, leading to the "80-80" rule. CONCLUSION: Using a roadmap based on HCVRNA(-) at TW4 or TW8 (the "80-80" rule), high SVR can be achieved, and guide the best choices for treatment, and also reduces drug exposure in poor responders. © The Author(s) 2015.

Low K.C.,Agency for Science, Technology and Research Singapore | Tergaonkar V.,Agency for Science, Technology and Research Singapore | Tergaonkar V.,National University of Singapore
Trends in Biochemical Sciences | Year: 2013

The hallmarks of cancer described by Hanahan and Weinberg are properties that cancer cells must possess for successful transformation. It is believed that each of these hallmarks is independently driven. Although elongation of telomeres is thought to be the prime function of reactivated telomerase reverse transcriptase, this activity does not account for all its effects, such as increasing cell proliferation, resistance to apoptosis, and invasion. Recent studies suggest that the telomerase subunit telomerase reverse transcriptase (TERT) has novel molecular functions including transcriptional regulation and metabolic reprogramming. We summarize these functions and discuss how they could directly regulate the various hallmarks of cancer. Finally, we suggest that therapeutics targeting noncanonical telomerase functions may work better than those that target its role in telomere extension. © 2013 Elsevier Ltd.

Ouyang J.,National University of Singapore
Organic Electronics: physics, materials, applications | Year: 2014

The interface between two bulk electronic materials can significantly affect the electrical behavior of electronic devices. But the interface between a bulk metal and metal nanoparticles has been rarely explored. This paper reports significant temperature effect on the asymmetrical resistive switches of polymer:nanoparticle memory devices. The devices have architecture of a polystyrene layer admixed with gold nanoparticles capped with conjugated 2-naphthalenethiol sandwiched between Au and Al electrodes. The devices exhibit significant resistive switches at room temperature. However, the resistive switches become less significant at temperature below 200 K, and they are not noticeable at 103 K. The temperature effect suggests that the resistive switches are assisted by the thermal energy. The charge transport through the devices has different mechanisms at high and low temperatures. At temperature above 220 K, the Poole-Frenkel emission is an important mechanism for the charge transport. At temperature below 220 K, the temperature-independent Fowler-Nordheim tunneling becomes an important process. © 2014 Elsevier B.V. All rights reserved.

Kim H.,National University of Singapore
IEEE Photonics Technology Letters | Year: 2011

We propose and demonstrate a dual-detector optical receiver for directly modulated reflective semiconductor optical amplifier (RSOA)-based transmitters employing a delay interferometer as an optical equalizer at the receiver. We show through experiment that the dual-detector receiver not only improves the receiver sensitivity but also lowers the error floor by widening the eye opening at the receiver. We also demonstrate upstream transmission of a 10-Gb/s RSOA signal over a 40-km single-fiber loopback configured network. © 2011 IEEE.

Tang S.S.,Singapore General Hospital | Apisarnthanarak A.,Thammasat University | Hsu L.Y.,National University of Singapore
Advanced Drug Delivery Reviews | Year: 2014

Alexander Fleming's discovery of penicillin heralded an age of antibiotic development and healthcare advances that are premised on the ability to prevent and treat bacterial infections both safely and effectively. The resultant evolution of antimicrobial resistant mechanisms and spread of bacteria bearing these genetic determinants of resistance are acknowledged to be one of the major public health challenges globally, and threatens to unravel the gains of the past decades. We describe the major mechanisms of resistance to β-lactam antibiotics - the most widely used and effective antibiotics currently - in both Gram-positive and Gram-negative bacteria, and also briefly detail the existing and emergent pharmacological strategies to overcome such resistance. The global epidemiology of the four major types of bacteria that are responsible for the bulk of antimicrobial-resistant infections in the healthcare setting - methicillin-resistant Staphylococcus aureus, vancomycin-resistant enterococci, Enterobactericeae, and Acinetobacter baumannii - are also briefly described. © 2014 Elsevier B.V.

Hui H.T.,National University of Singapore
Solid State Communications | Year: 2013

A new multi-valley effective-mass-theory (EMT) equation is derived for the phosphorus doped in silicon. This equation admits solutions which agree with the measured ground state energy and the square modulus of the ground-state wavefunction ΨA1(0)2 at the donor site accurately. This avoids the use of the so-called central-cell correction approximation method to calculate the hyperfine constant at the donor site. Furthermore, the energy levels for the upper lying states of T2 and E can also be predicted relatively accurately. The newly derived EMT equation has applications in the characterization of semiconductor or spintronics devices. © 2012 Elsevier Ltd.

Kim H.,National University of Singapore
IEEE Photonics Technology Letters | Year: 2011

We demonstrate the transmission of 10-Gb/s upstream signals over 20-km fiber using a 1.3-GHz-bandwidth reflective semiconductor optical amplifier and a 40-ps delay interferometer (DI) in a loopback configured wavelength-division- multiplexed (WDM) passive optical network. We show that a single DI can be used in a set-and-forget mode to equalize 34 WDM channels anchored at the 100-GHz spaced ITU grid, without any help of postdetection electronic processing. © 2011 IEEE.

Gilbert E.G.,University of Michigan | Ong C.-J.,National University of Singapore
Automatica | Year: 2011

This paper considers a nonlinear feedback control policy that is an extension of those provided by command governors and reference governors. As in these control approaches it applies to discrete-time linear systems with hard constraints and set bounded disturbances. The control policy retains the main properties of traditional governors, such as straightforward direct implementation and finite-settling-time response to arbitrarily specified set points. Its principal advantage over traditional governors is a significantly larger domain of attraction, that may compete in size with those obtained by dynamic programming. Connections to model predictive control are made. Numerical examples illustrate advantageous features of the proposed approach. © 2010 Elsevier Ltd. All rights reserved.

Yu H.,National University of Singapore
Distributed Computing | Year: 2011

Wireless sensor networks are often queried for aggregates such as predicate count, sum, and average. In untrusted environments, sensors may potentially be compromised. Existing approaches for securely answering aggregation queries in untrusted sensor networks can detect whether the aggregation result is corrupted by an attacker. However, the attacker (controlling the compromised sensors) can keep corrupting the result, rendering the system unavailable. This paper aims to enable aggregation queries to tolerate instead of just detecting the adversary. To this end, we propose a novel tree sampling algorithm that directly uses sampling to answer aggregation queries. It leverages a set sampling protocol to overcome a well-known obstacle in sampling-traditional sampling technique is only effective when the predicate count or sum is large. Set sampling can efficiently sample a set of sensors together, and determine whether any sensor in the set satisfies the predicate (but not how many). With set sampling as a building block, tree sampling can provably generate a correct answer despite adversarial interference, while without the drawbacks of traditional sampling techniques. © 2011 Springer-Verlag.

Wittek P.,University of Boras | Tan C.L.,National University of Singapore
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2011

Wavelet kernels have been introduced for both support vector regression and classification. Most of these wavelet kernels do not use the inner product of the embedding space, but use wavelets in a similar fashion to radial basis function kernels. Wavelet analysis is typically carried out on data with a temporal or spatial relation between consecutive data points. We argue that it is possible to order the features of a general data set so that consecutive features are statistically related to each other, thus enabling us to interpret the vector representation of an object as a series of equally or randomly spaced observations of a hypothetical continuous signal. By approximating the signal with compactly supported basis functions and employing the inner product of the embedding L-2 space, we gain a new family of wavelet kernels. Empirical results show a clear advantage in favor of these kernels. © 2011 IEEE.

Bertoletti A.,Agency for Science, Technology and Research Singapore | Bertoletti A.,National University of Singapore | Ferrari C.,Laboratory of Viral Immunopathology
Gut | Year: 2012

Knowledge of the immunological events necessary to control hepatitis B virus (HBV) infection has accelerated in recent years, but their translation towards therapeutic strategies able to achieve a durable HBV suppression has been challenging. The scenario of how HBV deals with the host immunity is presented and used to discuss how the immune response can be harnessed to potentially achieve infection control.

Tan Q.H.,National University of Singapore
Health and Place | Year: 2013

A persistent emphasis on the negative biomedical effects of cigarette smoking effectively glosses over the affectual-sensual and social wellbeing that smoking can enable. In addition, while tobacco research has recently been more attuned to the stigmatizing affects brought about by smoking de-normalization efforts, a lot less attention has been placed on how smokers negotiate these feelings of stigmatization so as to restore their personal spaces of wellbeing. In this paper, I situate my investigation of smoking geographies in the burgeoning literature on enabling spaces which focuses on how places co-constitute our ability to act/affect in empowering ways. By deploying qualitative research methods such as in-depth interviews, I argue that an acknowledgment of how smoking spaces in Singapore can be enabling along affectual, sensorial and social registers is long overdue. While it is not my purpose to systematically downplay the damaging health effects that smoking can engender, a focus on enabling smoking spaces emphasizes the role of smokers as creative agents capable of (re)fashioning their own holistic and subjective versions of wellbeing. In so doing, I hope to contribute to the existing research on smoking spaces and a recent profusion of work on relational geographies of affect. © 2013 Elsevier Ltd.

Shen H.-M.,National University of Singapore | Mizushima N.,University of Tokyo
Trends in Biochemical Sciences | Year: 2014

In the past decade, autophagy studies have largely focused on the early stage of autophagy: the molecular mechanisms leading to autophagosome formation. Recently, however, we have observed significant progress in understanding the role of lysosomes, the specific cellular organelle that degrades cellular components delivered via autophagy. The discoveries include connections between autophagy and lysosomal biogenesis, activation, reformation, and turnover, as well as the identification of an autophagosomal SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) protein in control of autophagosome-lysosome fusion. We illustrate these findings in the context of the underlying molecular mechanisms and the relevance to human health and disease. © 2013 Elsevier Ltd.

Hong W.,Institute of Molecular and Cell Biology | Hong W.,National University of Singapore | Hong W.,Xiamen University
Science Signaling | Year: 2013

The Hippo pathway regulates cell proliferation and apoptosis during development, tissue regeneration, and carcinogenesis. Nuclear translocation of the transcription factors Yes-associated protein (YAP) and transcriptional coactivator with PDZ-binding motif (TAZ) and their subsequent interaction with TEA domain (TEAD) transcriptional factors program pro-proliferative and antiapoptotic transcription. Scaffold proteins angiomotin (Amot) and angiomotin-related AmotL1 and AmotL2 were recently identifi ed as negative regulators of YAP and TAZ by preventing their nuclear translocation. In this issue of Science Signaling, Yi et al. show that Amot may also promote nuclear translocation of YAP and act as a transcriptional cofactor of the YAP-TEAD complex to facilitate proliferation of biliary epithelial cells and cancer development of the liver either in response to tissue injury or in the absence of the tumor suppressor Merlin. These seemingly controversial results highlight that our understanding of Amot proteins in the Hippo pathway is so far limited. Copyright © 2008 by the American Association for the Advancement of Science.

Hung I.W.,National University of Singapore | Labroo A.A.,University of Chicago
Journal of Consumer Research | Year: 2011

Across five studies, we show that firming one's muscles can help firm willpower and that firmed willpower mediates one's ability to withstand immediate pain, overcome food temptation, consume unpleasant medicines, and attend to immediately disturbing but essential information, provided that doing so is seen as providing long-term benefits. We draw on theories of embodied cognition to explain our results, and we add to that literature by showing for the first time that one's body can help firm willpower and facilitate the self-regulation essential for the attainment of long-term goals. © 2010 by JOURNAL OF CONSUMER RESEARCH, Inc.

Halliwell B.,National University of Singapore
Biomedical Journal | Year: 2014

Cell culture is widely used by biochemists and cell/molecular biologists, but the fluctuating (and often elevated) levels of O 2 to which cells in culture are exposed can affect many of their properties. So can the low level of antioxidants found in some cell culture media. Reagents, especially antioxidants, added to cell culture media can react with the constituents of the media to produce H 2 O 2 and degradation products that can influence cell behavior. Several published papers describing the cellular effects of ascorbate, polyphenols, and carotenoids have, in fact, reported artifacts due to the actions of the degradation products of these antioxidants. A greater awareness of the potential artifacts in cell culture studies is needed among the free radical/antioxidant community.

Musso D.,Institute Louis Malarde | Gubler D.J.,National University of Singapore
Clinical Microbiology Reviews | Year: 2016

Zika virus (ZIKV) is an arthropod-borne virus (arbovirus) in the genus Flavivirus and the family Flaviviridae. ZIKV was first isolated from a nonhuman primate in 1947 and from mosquitoes in 1948 in Africa, and ZIKV infections in humans were sporadic for half a century before emerging in the Pacific and the Americas. ZIKV is usually transmitted by the bite of infected mosquitoes. The clinical presentation of Zika fever is nonspecific and can be misdiagnosed as other infectious diseases, especially those due to arboviruses such as dengue and chikungunya. ZIKV infection was associated with only mild illness prior to the large French Polynesian outbreak in 2013 and 2014, when severe neurological complications were reported, and the emergence in Brazil of a dramatic increase in severe congenital malformations (microcephaly) suspected to be associated with ZIKV. Laboratory diagnosis of Zika fever relies on virus isolation or detection of ZIKVspecific RNA. Serological diagnosis is complicated by crossreactivity among members of the Flavivirus genus. The adaptation of ZIKV to an urban cycle involving humans and domestic mosquito vectors in tropical areas where dengue is endemic suggests that the incidence of ZIKV infections may be underestimated. There is a high potential for ZIKV emergence in urban centers in the tropics that are infested with competent mosquito vectors such as Aedes aegypti and Aedes albopictus. © 2016, American Society for Microbiology. All Rights Reserved.

Cabibihan J.-J.,National University of Singapore
PLoS ONE | Year: 2011

The concealment of amputation through prosthesis usage can shield an amputee from social stigma and help improve the emotional healing process especially at the early stages of hand or finger loss. However, the traditional techniques in prosthesis fabrication defy this as the patients need numerous visits to the clinics for measurements, fitting and follow-ups. This paper presents a method for constructing a prosthetic finger through online collaboration with the designer. The main input from the amputee comes from the Computer Tomography (CT) data in the region of the affected and the non-affected fingers. These data are sent over the internet and the prosthesis is constructed using visualization, computer-aided design and manufacturing tools. The finished product is then shipped to the patient. A case study with a single patient having an amputated ring finger at the proximal interphalangeal joint shows that the proposed method has a potential to address the patient's psychosocial concerns and minimize the exposure of the finger loss to the public. © 2011 John-John Cabibihan.

Kay A.,National University of Singapore | Kay A.,Singapore and Keble College
Physical Review Letters | Year: 2012

One of the many bizarre features of entanglement is that Alice, by sending a qubit to Bob in a separable state, can generate some entanglement between herself and Bob. This protocol is stripped down to the bare essentials to better elucidate the key properties of the initial resource state that enable this entanglement distribution. The necessary and sufficient conditions under which the correlations of a Bell-diagonal state serve as a useful resource are proven, giving upper and lower bounds on the entanglement that can be distributed when those conditions are met. © 2012 American Physical Society.

Karthikeyan O.P.,National University of Singapore | Visvanathan C.,Asian Institute of Technology
Reviews in Environmental Science and Biotechnology | Year: 2013

Dry anaerobic bio-conversion (D-AnBioC) of high-solid organic substrates (OS) is considered as a sustainable option for waste management practices in different parts of the world. The basic technology is well implemented, but the improvements are still under way in terms of optimization and pre- and post-treatments of the feed and end-products, respectively. The purpose of this review is mainly to: (1) provide existing knowledge and research advances in D-AnBioC systems to treat high-solid OS; (2) identify major issues involved in bioreactor designing; (3) present factors influencing the bio-conversion efficiency; (4) discuss the microbiology of system operation; (5) provide examples of existing commercial-scale plants; (6) discuss energy and economics requirements. From the detailed literature review, it is clear that the characteristics of OS are the major factors governing the overall process and economics. It shows that not all OS are profitably recycled using D-AnBioC systems. Compared to single-stage continuous systems, batch systems under a multi-stage configuration appears to be economically feasible, however, it must be noted that the available data sets are still inconclusive. Also, limited information is available on green house gas mitigation and restoration of nutrients from the digested residue during post-treatment schemes. A summary at the end presents important research gaps of D-AnBioC system to direct future research. © 2012 Springer Science+Business Media Dordrecht.

Summers S.A.,National University of Singapore | Summers S.A.,Duke University
Current Opinion in Lipidology | Year: 2010

Purpose of review: Inhibition of sphingolipid synthesis increases insulin sensitivity, resolves hepatic steatosis, and prevents the onset of diabetes in obese rodents. I herein review these interventional studies, aiming to summarize the five Ws - the 'Who, What, Where, When, and Why' questions that need to be addressed to understand roles of sphingolipids in the pathogenesis of diabetes. Recent findings: Who: ceramides and glucosylceramides are likely to be independent antagonists of insulin action. Where: recent data suggest that ceramides may inhibit insulin action in skeletal muscle, whereas glucosylceramides may be more efficacious in adipose tissue. In contrast, sphingolipid accumulation in the liver appears to be insufficient to induce insulin resistance. What: ceramides and glucosylceramides inhibit different insulin signaling events, but it is unclear whether these actions account for the broad spectrum of therapeutic benefits resulting from sphingolipid depletion. When: recent data suggest that obesity-induced inflammation is important for the induction of sphingolipid synthesis. Why: sphingolipids have an evolutionarily conserved role to starve cells of nutrients, and the inhibition of insulin action is possibly a component of this broader action. Summary: Despite considerable attention to the question of how sphingolipids induce metabolic disease, there exist enormous gaps in knowledge. Further elucidation of these molecular details will be essential for the development of new therapeutic strategies for inhibiting sphingolipid action and ameliorating metabolic diseases. © 2010 Wolters Kluwer Health-Lippincott Williams & Wilkins.

Luk'Yanchuk B.,Data Storage Institute Singapore | Zheludev N.I.,University of Southampton | Maier S.A.,Imperial College London | Halas N.J.,Rice University | And 4 more authors.
Nature Materials | Year: 2010

Since its discovery, the asymmetric Fano resonance has been a characteristic feature of interacting quantum systems. The shape of this resonance is distinctively different from that of conventional symmetric resonance curves. Recently, the Fano resonance has been found in plasmonic nanoparticles, photonic crystals, and electromagnetic metamaterials. The steep dispersion of the Fano resonance profile promises applications in sensors, lasing, switching, and nonlinear and slow-light devices. © 2010 Macmillan Publishers Limited. All rights reserved.

Ouyang J.,National University of Singapore
Organic Electronics: physics, materials, applications | Year: 2015

The electronic contact between a bulk metal and metal nanoparticles can be significantly different from that between two bulk metals due to the unique electronic structure in the nanometer size. In this work, the electronic contact between Au nanoparticles and Al is studied by X-ray photoelectron spectroscopy. Al is deposited on a layer of Au nanoparticles capped with conjugated 2-naphthalenethiol (Au-2NT NPs) in high vacuum by e-beam deposition at room temperature. The Au 4f X-ray photoelectron spectrum (XPS) significantly changes after the Al deposition. New XPS bands with higher binding energy appear. The angle dependence of the Au 4f XPS bands indicates that the electron transfer takes place at the contact between Al and Au-2NT NPs. In contrast, the Al deposition hardly changes the Au 4f XPS spectrum for Au nanoparticles capped with saturated 1-dodecanethiol. The effect of the Al deposition on the Au 4f XPS spectrum of Au nanoparticles capped with 2-naphthalenethiol is attributed to the electron transfer from Al through the conjugated 2-naphthalenehiol into the core of Au nanoparticles, as the Fermi energy of Al is higher than Au. This understanding on the contact between metal and metal nanoparticles provides guidance for the development of novel electronic devices. © 2015 Elsevier B.V. All rights reserved.

Yuki N.,National University of Singapore | Hartung H.-P.,Heinrich Heine University Dusseldorf
New England Journal of Medicine | Year: 2012

The Guillain-Barré syndrome, an acute immune-mediated neuropathy, still carries a grave prognosis. The syndrome is manifested as a spectrum of peripheral-nerve disorders with several clinical variants that are characterized by the distribution of weakness of the limbs or cranialnerve- innervated muscles, underlying pathological abnormalities, and associated autoantibodies. 5-7,34,35,37,85 The most frequent antecedent infection is C. jejuni infection, which is associated with 30% of cases of the Guillain-Barré syndrome and 20% of cases of the Miller Fisher syndrome.9,40 Molecular mimicry between the bacterial and peripheral-nerve components appears to elicit autoantibodies and induce the development of the axonal subtype of the Guillain-Barré syndrome or the Miller Fisher syndrome after enteritis with C. jejuni. 40,50,53,54 Eculizumab, erythropoietin, and fasudil, which have been used in the treatment of other, unrelated medical conditions, have shown promise in animal models of the Guillain- Barré syndrome, 57,58,60 but clinical studies are lacking. Copyright © 2012 Massachusetts Medical Society.

Trigueros-Motos L.,National University of Singapore
Clinical Genetics | Year: 2014

POT1 loss-of-function variants predispose to familial melanoma Robles-Espinoza et al. (2014) Nat Genet 46(5):478-481 Rare missense variants in POT1 predispose to familial cutaneous malignant melanoma Shi et al. (2014) Nat Genet 46(5):482-486. © 2014 John Wiley & Sons A/S.

Mohanty J.,National University of Singapore
Journal of Adolescence | Year: 2013

Positive identity development during adolescence in general is a complex process and may pose additional challenges for adolescents adopted from a different culture. Using a web-based survey design with a sample of 100 internationally adopted Asian adolescent and young adults, the present study examined the mediating role of multiple identities (i.e., ethnic, adoptive and interpersonal ego identities) in explaining the relationship between ethnic and racial socializations, ethnic neighborhood, and self-esteem. The results showed that (a) adoptive identity mediated the influence of racial socialization on psychological well-being, and (b) ethnic affirmation mediated the influence of ethnic socialization on adoptees' well-being. This study illustrates the importance of providing supportive counseling services for adoptees who are exploring their adoptive identity. © 2012 The Foundation for Professionals in Services for Adolescents.

Huang S.-L.,Fudan University | Lin Y.-J.,Fudan University | Hor T.S.A.,Institute of Materials Research and Engineering of Singapore | Hor T.S.A.,National University of Singapore | Jin G.-X.,Fudan University
Journal of the American Chemical Society | Year: 2013

A series of CpRh-based functional metallarectangles have been synthesized from metallaligands. Enlargement of one linker leads to the isolation of two novel Borromean link architectures. All these complexes are intact in solution, as evident from ESI-MS spectroscopic analysis. Arising from the combination of open Cu centers and favorable cavity space, {(CpRh)4(bpe) 2[Cu(opba)·2MeOH]2}4(OTf)·6MeOH shows extraordinary catalytic abilities with high efficiency and wide substrate selectivity in the acyl-transfer reaction. © 2013 American Chemical Society.

Teo P.,California Institute of Technology | Hor T.S.A.,National University of Singapore | Hor T.S.A.,Institute of Materials Research and Engineering of Singapore
Coordination Chemistry Reviews | Year: 2011

N,O-donating spacers are members of a class of ambidentate donors used in supramolecular self-assemblies. The skeletal adaptability and coordination flexibility of these ligands enable them to support a myriad of discrete molecular systems and extended network materials. This review focuses on pyridinecarboxylates as a representative of N,O-hetero-donating spacers and describes their recent developments in the coordination assemblies and highlights their functions and potential applications. © 2010 Elsevier B.V.

Hollon S.D.,Vanderbilt University | Ponniah K.,National University of Singapore
Depression and Anxiety | Year: 2010

Background: The mood disorders are prevalent and problematic. We review randomized controlled psychotherapy trials to find those that are empirically supported with respect to acute symptom reduction and the prevention of subsequent relapse and recurrence. Methods: We searched the PsycINFO and PubMed databases and the reference sections of chapters and journal articles to identify appropriate articles. Results: One hundred twenty-five studies were found evaluating treatment efficacy for the various mood disorders. With respect to the treatment of major depressive disorder (MDD), interpersonal psychotherapy (IPT), cognitive behavior therapy (CBT), and behavior therapy (BT) are efficacious and specific and brief dynamic therapy (BDT) and emotion-focused therapy (EFT) are possibly efficacious. CBT is efficacious and specific,mindfulnessbased cognitive therapy (MBCT) efficacious, and BDTand EFT possibly efficacious in the prevention of relapse/recurrence following treatment termination and IPT and CBT are each possibly efficacious in the prevention of relapse/recurrence if continued or maintained. IPT is possibly efficacious in the treatment of dysthymic disorder. With respect to bipolar disorder (BD), CBT and family-focused therapy (FFT) are efficacious and interpersonal social rhythm therapy (IPSRT) possibly efficacious as adjuncts to medication in the treatment of depression. Psychoeducation (PE) is efficacious in the prevention of mania/hypomania (and possibly depression) and FFT is efficacious and IPSRT and CBT possibly efficacious in preventing bipolar episodes. Conclusions: The newer psychological interventions are as efficacious as and more enduring than medications in the treatment of MDD and may enhance the efficacy of medications in the treatment of BD. © 2010 Wiley-Liss, Inc.

Lin Q.,National University of Singapore
Nature Chemical Biology | Year: 2016

Rhythmicity is prevalent in the cortical dynamics of diverse single and multicellular systems. Current models of cortical oscillations focus primarily on cytoskeleton-based feedbacks, but information on signals upstream of the actin cytoskeleton is limited. In addition, inhibitory mechanisms—especially local inhibitory mechanisms, which ensure proper spatial and kinetic controls of activation—are not well understood. Here, we identified two phosphoinositide phosphatases, synaptojanin 2 and SHIP1, that function in periodic traveling waves of rat basophilic leukemia (RBL) mast cells. The local, phase-shifted activation of lipid phosphatases generates sequential waves of phosphoinositides. By acutely perturbing phosphoinositide composition using optogenetic methods, we showed that pulses of PtdIns(4,5)P2 regulate the amplitude of cyclic membrane waves while PtdIns(3,4)P2 sets the frequency. Collectively, these data suggest that the spatiotemporal dynamics of lipid metabolism have a key role in governing cortical oscillations and reveal how phosphatidylinositol 3-kinases (PI3K) activity could be frequency-encoded by a phosphatase-dependent inhibitory reaction. © 2016 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.

Zhou P.,Nanjing University of Aeronautics and Astronautics | Ang B.W.,National University of Singapore | Zhou D.Q.,Nanjing University of Aeronautics and Astronautics
Applied Energy | Year: 2012

This paper proposes a parametric frontier approach to estimating economy-wide energy efficiency performance from a production efficiency point of view. It uses the Shephard energy distance function to define an energy efficiency index and adopts the stochastic frontier analysis technique to estimate the index. A case study of measuring the economy-wide energy efficiency performance of a sample of OECD countries using the proposed approach is presented. It is found that the proposed parametric frontier approach has higher discriminating power in energy efficiency performance measurement compared to its nonparametric frontier counterparts. © 2011 Elsevier Ltd.

Campana D.,National University of Singapore
Current Opinion in Hematology | Year: 2012

Purpose of review: This review summarizes recent advances in the application of minimal residual disease (MRD) testing in childhood acute lymphoblastic leukemia (ALL). Recent findings: Polymerase chain reaction amplification of antigen receptor genes, one of the two main methods to study MRD in ALL, could be made more rapid, sensitive and informative by the application of next-generation sequencing technologies. Advances in flow cytometric detection of MRD, the other main method, include the identification of new immunophenotypic markers to recognize ALL cells, the development of computerized approaches to automate data analysis, and the generation of instruments that can rapidly screen large number of cells for immunophenotypic abnormalities while visualizing their morphology. Recent data further corroborate the prognostic value of MRD at early time points during therapy, demonstrate the prognostic significance of MRD among ALL subtypes, and indicate that presenting features can complement the prognostic utility of MRD. Summary: MRD is replacing morphology to measure treatment response in ALL and is being used, with promising results, for risk-stratification in clinical protocols. Recent studies provide further evidence of its prognostic significance and point to possible strategies to increase the reliability, applicability and sensitivity of MRD testing. © 2012 Wolters Kluwer Health | Lippincott Williams & Wilkins.

Gandi V.R.,National University of Singapore
Tetrahedron | Year: 2013

An enantiospecific formal total synthesis of the macrolide (+)-aspicilin is accomplished from chiral pool tartaric acid. Key features of the synthesis include desymmetrization of the bis-dimethyl amide of tartaric acid and further elaboration to the title compound using olefin cross-metathesis and Yamaguchi macrolactonization as the pivotal steps. © 2013 Elsevier Ltd. All rights reserved.

Kong H.X.,National University of Singapore
Current Opinion in Solid State and Materials Science | Year: 2013

This paper reviews recent progress in hybrids based on carbon nanotubes (CNTs) and graphene (G) or graphene oxide (GO). The combination of CNTs, including single-walled (SW), double-walled (DW) and multi-walled (MW), and G or GO resulted in various hybrids. CNTs-G/GO hybrid thin films are usually prepared by using solution/suspension casting and layer-by-layer (LbL) deposition, free-standing sheets are fabricated by using vacuum filtration and 3D hierarchical structures are produced by using chemical vapor deposition (CVD). CNTs-G/GO hybrids have also been used as fillers to fabricate polymer composites with synergistic effects. The composites have significantly improved electrical, mechanical and thermal properties, which make them very useful for various potential applications, such as transparent electrodes replacing ITO, electrodes for supercapacitors, lithium-ion batteries and dye-sensitized solar cells. © 2012 Elsevier Ltd. All rights reserved.

Manzhos S.,National University of Singapore
MRS Communications | Year: 2013

Two new organic dyes, WS-2.1 and WS-2.2-derivatives of the known dye WS-2-are computationally designed using a recently developed approach with a broad absorption peak at around 775Â nm in acetonitrile for WS-2.2 versus 610Â nm for WS-2. The red shift includes a significant contribution due to vibrations and is not reproduced by standard computational methods. The oxidation and reduction potentials of the dye render it well suited for use in dye-sensitized solar cells. © 2013 Materials Research Society.

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.

Reddy Chichili V.P.,National University of Singapore
Scientific reports | Year: 2013