Luo F.,CAS Institute of Physics |
Zheng J.,CAS Institute of Physics |
Chu G.,CAS Institute of Physics |
Liu B.,CAS Institute of Physics |
And 3 more authors.
Acta Chimica Sinica | Year: 2015
Alloy anode materials, such as Si, Sn, have attracted much attention due to their much higher theoretical capacities than that of the commercially used graphite electrodes. However, their commercial applications are limited because of the short cycle life due to the large volume changes and non-healable fracture during electrochemical cycling. In this work, we prepared metal Ga thin film electrodes on stainless steel substrate (diameter 1.4 cm, mass load 1.5~2 mg/cm2) to study the self-healing behavior of Ga anodes. After 25 cycles, the cells were disassembled in Ar-filled glove box and the metal Ga thin film electrodes were washed by dimethyl carbonate (DMC) to remove residual LiPF6 and then dried in the vacuum chamber for more than 2 hours before SEM analysis. Based on SEM observation and crack size statistical distribution, we found that the characteristic size of the self-healing area reduced to 34 μm after 25 cycles and gradually reduced with the increasing cycles using low-melting point metal Ga film electrodes at a temperature above the melting point of Ga. Energy dispersive spectrometer (EDS) analysis showed that there was a large amount of F, O and C at the surface of metal Ga thin film electrodes, which are considered as main components of the solid electrolyte interface (SEI) layer. The formation of the SEI layer degrades the self-healing capability of Ga metal thin films because the layer may attach on the crack surfaces after full delithiation, hindering self-healing of the Ga films. Metal Ga powder electrodes (mass load 4.3 mg/cm2) were prepared by simple liquid dispersion method. The size of the Ga metal powder was 3.43 μm, which is smaller than that of effective self-healing area. Electrochemical performance showed improved durability of the metal Ga powder electrodes compared to the metal Ga thin film electrodes. After 25 cycles, the average crack size of the metal Ga powder electrodes was 1 μm based on SEM images. This shows that the self-healing ability of metal Ga in liquid electrolyte is limited. Metal Ga is expected to be used as crack healing agent in non-liquid electrolyte systems, such as the solid-state batteries. © 2015 Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences. Source
Fu Y.,Shanghai JiaoTong University |
Wu J.,Shanghai JiaoTong University |
Sun R.,Shanghai JiaoTong University |
Ding Z.-R.,Shanghai JiaoTong University |
And 2 more authors.
Yiyong Shengwu Lixue/Journal of Medical Biomechanics | Year: 2015
Objective: To study the effect of ghost red blood cells (GRBCs) on white blood cell (WBC)-mediated adhesion of tumor cells (TCs) on endothelial cells (ECs) in shear flow. Methods: GRBCs with hematocrit (Hct) of 20% were added in the parallel plate flow chamber to observe changes in the number of tethered WBCs on ECs, the collision between TCs and adhesive WBCs, and the number of firmly adhered TCs at different shear rates of 62.5, 100, 200 s-1, respectively. Results: GRBCs could increase the number of adhered WBCs on ECs and the collision between TCs and adhesive WBCs, and finally enhance the adhesion of TCs on ECs, especially at high shear rate (200 s-1). However, the adhesion efficiency of TCs was not significantly influenced by GRBCs. Conclusions: GRBCs in shear flow can promote TC adhesion on ECs, and the research finding will provide a theoretical basis for cancer therapy. Copyright © 2015 by the Editorial Board of Journal of Medical Biomechanics. Source
Deng C.,China University of Geosciences |
Deng C.,Coal Reservoir Laboratory of National Engineering Research |
Tang D.,China University of Geosciences |
Tang D.,Coal Reservoir Laboratory of National Engineering Research |
And 5 more authors.
Journal of Natural Gas Science and Engineering | Year: 2015
Mineral matter is widely accepts as one of the important factors influencing the gas sorption capacity of coal. By analyzing ash content and Langmuir volume of coals, studies have reported positive, negative, and poor impacts of mineral matter on sorption capacity without convincing reasons explaining the contradictory results. This paper proposes a new analysis method to correlate minerals and gas sorption capacity by connecting the mineral matter compositions to sorption capacity through the variations in the microstructure. In addition to mineral content, mineral occurrence modes and compositions were also studied to investigate their relations with gas sorption capacity.A total of 22 coal samples are used to interpret the characterization of minerals, including mineral content by proximate analysis, mineral occurrence mode by scanning electron microscope (SEM) and energy-dispersive X-ray spectrometer (EDX) analyses, and mineral compositions by X-ray powder diffraction (XRD) analysis. Low-temperature nitrogen adsorption and high pressure methane adsorption analyses of selected samples are applied to characterize microstructure and gas adsorption capacity.We found that mineral content, occurrence mode, and composition are three controlling factors that together determined the influence of mineral matter on gas sorption capacity. In fact, some factors have potential for both positive and negative influence. This is why both negative and positive influences have been previously observed. The direction and magnitude of influence depends on the relative weights of the driving factors. For samples in this study, clay mineral content showed the strongest positive relation to SBET, total VBJH, and VL, compared to total mineral and brittle mineral content. The relation of other minerals to SBET, total VBJH, and VL is weak. The final result indicated that mineral matter had a positive influence on gas sorption capacity. © 2015 Elsevier B.V. Source
Rigg K.K.,University of South Florida |
Monnat S.M.,The Pennsylvania State University
Addictive Behaviors | Year: 2015
Introduction: Prescription painkiller misuse (PPM) is a major U.S. public health concern. However, as prescribing practices have tightened and prescription painkillers have become less accessible, many users have turned to heroin as a substitute. This trend suggests the face of heroin users has likely changed over the past several years. Understanding the demographic, socioeconomic, psychosocial, and substance use characteristics of different groups of opiate users is important for properly tailoring interventions. Methods: This study used data from the 2010-2013 National Survey on Drug Use and Health to examine differences in characteristics of U.S. adults in three mutually exclusive categories of past-year opiate use: heroin-only (H-O, N. =. 179), prescription painkiller-only (PP-O, N. =. 9,516), and heroin and prescription painkiller (H-PP, N. =. 506). Results: Socioeconomic disadvantage, older age, disconnection from social institutions, criminal justice involvement, and easy access to heroin were associated with greater odds of being in the H-O group. HH-P users were more likely to be young white males with poor physical and mental health who also misuse other prescription medications and began such misuse as adolescents. PP-O users were the most economically stable, most connected to social institutions, least likely to have criminal justice involvement, and had the least access to heroin. Conclusions: Results suggest the socio-demographic characteristics of heroin users versus PP misusers vary widely, and the conditions leading to heroin use versus PPM versus both may be different. Ultimately, a one-size-fits-all approach to opiate prevention and treatment is likely to fail. Interventions must account for the unique needs of different user groups. © 2015. Source
Song C.,Chongqing Jiaotong University |
Lu Y.,Chongqing University |
Tang H.,Chongqing Jiaotong University |
Jia Y.,Chongqing University |
Jia Y.,The Pennsylvania State University
Journal of Natural Gas Science and Engineering | Year: 2016
Hydraulic fracturing technology, a technique for increasing productivity applicable in low-permeability oil-gas reservoir, has been used in the extraction of coal seam methane in underground coal mines. However, because of the more complex structure of coal seam compared with that of oil-gas reservoir, the hydrofracture propagation can easily extend to roof-floor rocks, limiting the range of permeability and making damages of roof-floor rocks in subsequent coal mining and support difficulty. How to control the hydrofracture propagation well-aligned in a large area of coal seam has become the key to long-time highly effective extraction of coal seam methane. Firstly, it starts with the perspective of stress field of crack tip, by means of thermal elasticity fracture mechanics theory, to get the stress intensity factor of hydrofracture tip while taking pore pressure into consideration. Next, a laboratory fracturing experiment using sandstone specimens was conducted to study the impact of non-uniform pore pressure on the direction of hydrofracture propagation. Lastly, a numerical simulation software RFPA2D-Flow is adopted to further verify the theoretical and experimental results. The study shows that pore pressure can effectively increase the stress intensity factor of the crack tip, the more pressure of pore, the smaller the needed fluid pressure for hydrofracture propagation. In a large area, affected by the direction and distribution of pore pressure gradient, the hydrofracture will propagate along higher pore pressure area. A method is put forward for controlling hydrofracture propagation in underground coal mines accordingly. Meanwhile, the matching relationship between the space between boreholes and the water injection maintaining pressure and maintaining time are studied together, with methods and steps for calculating key fracture parameters established. © 2016 Elsevier B.V. Source
Hessburg P.F.,U.S. Department of Agriculture |
Spies T.A.,U.S. Department of Agriculture |
Perry D.A.,Oregon State University |
Skinner C.N.,U.S. Department of Agriculture |
And 14 more authors.
Forest Ecology and Management | Year: 2016
Increasingly, objectives for forests with moderate- or mixed-severity fire regimes are to restore successionally diverse landscapes that are resistant and resilient to current and future stressors. Maintaining native species and characteristic processes requires this successional diversity, but methods to achieve it are poorly explained in the literature. In the Inland Pacific US, large, old, early seral trees were a key historical feature of many young and old forest successional patches, especially where fires frequently occurred. Large, old trees are naturally fire-tolerant, but today are often threatened by dense understory cohorts that create fuel ladders that alter likely post-fire successional pathways. Reducing these understories can contribute to resistance by creating conditions where canopy trees will survive disturbances and climatic stressors; these survivors are important seed sources, soil protectors, and critical habitat elements. Historical timber harvesting has skewed tree size and age class distributions, created hard edges, and altered native patch sizes. Manipulating these altered forests to promote development of larger patches of older, larger, and more widely-spaced trees with diverse understories will increase landscape resistance to severe fires, and enhance wildlife habitat for underrepresented conditions.Closed-canopy, multi-layered patches that develop in hot, dry summer environments are vulnerable to droughts, and they increase landscape vulnerability to insect outbreaks and severe wildfires. These same patches provide habitat for species such as the northern spotted owl, which has benefited from increased habitat area. Regional and local planning will be critical for gauging risks, evaluating trade-offs, and restoring dynamics that can support these and other species. The goal will be to manage for heterogeneous landscapes that include variably-sized patches of (1) young, middle-aged, and old, closed-canopy forests growing in upper montane, northerly aspect, and valley bottom settings, (2) a similar diversity of open-canopy, fire-tolerant patches growing on ridgetops, southerly aspects, and lower montane settings, and (3) significant montane chaparral and grassland areas. Tools to achieve this goal include managed wildfire, prescribed burning, and variable density thinning at small to large scales. Specifics on "how much and where?" will vary according to physiographic, topographic and historical templates, and regulatory requirements, and be determined by means of a socio-ecological process. © 2016 Elsevier B.V. Source
Veit H.,University of Bern |
May J.-H.,Albert Ludwigs University of Freiburg |
Madella A.,University of Bern |
Delunel R.,University of Bern |
And 4 more authors.
Journal of Quaternary Science | Year: 2016
In the Lluta Valley, northern Chile, climate is hyperarid and vegetation is restricted to the valley floors and lowermost footslopes. Fossil tree trunks and leaves of predominantly Escallonia angustifolia, however, are abundant up to ∼15m above the present valley floor, where they are intercalated with slope deposits, reflecting higher water levels in the past. A total of 17 samples have been radiocarbon dated, yielding ages between 38 and 15k cal a BP. The youngest ages of 15.4k cal a BP are interpreted as reflecting the beginning of river incision and lowering of the valley floor, impeding the further growth of trees at higher parts of the slopes. The most plausible scenario for this observation is intensified river incision after 15.4k cal a BP due to increased stream power and runoff from the Río Lluta headwaters in the Western Cordillera and Altiplano corresponding to the highstand of the Tauca and Central Andean Pluvial Event (CAPE) wet phase. © 2016 John Wiley & Sons, Ltd. Source
Sircar S.,Pennsylvania State University |
Sircar S.,Intel Corporation |
Pramanik S.,Rutgers University |
Li J.,Rutgers University |
And 3 more authors.
Journal of Colloid and Interface Science | Year: 2015
The "universal adsorption theory" (UAT) extends the principle of corresponding states for gas compressibility to describe the excess density of an adsorbed phase at comparable reduced conditions. The UAT helps to describe experimental trends and provide predictive capacity for extrapolation from one adsorption isotherm to that of a different adsorbate. Here, we extend the UAT to a flexible metal-organic framework (MOF) as a function of adsorbate, temperature, and pressure. When considered via the UAT, the adsorption capacity and GO pressure of multiple gases to Cu(dhbc)2(4,4'-bpy) [H2dhbc=2,5-dihydroxybenzoic acid, bpy=bipyridine] show quantifiable trends over a considerable temperature and pressure range, despite the chemical and structural heterogeneity of the adsorbent. Exceptions include quantum gases (such as H2) and prediction of maximum capacity for large and/or polar adsorbates. A method to derive the heat of gate opening and heat of expansion from experimental trends is also presented, and the parameters can be treated as separable and independent over the temperature and pressure range studied. We demonstrate the relationship between the UAT and the common Dubinin analysis, which was not previously noted. © 2015 Elsevier Inc. Source
Lunkenheimer E.,Colorado State University-Pueblo |
Tiberio S.S.,Oregon Social Learning Center |
Buss K.A.,The Pennsylvania State University |
Lucas-Thompson R.G.,Colorado State University-Pueblo |
And 2 more authors.
Developmental Psychobiology | Year: 2015
The coordination of physiological processes between parents and infants is thought to support behaviors critical for infant adaptation, but we know little about parent-child physiological coregulation during the preschool years. The present study examined whether time-varying changes in parent and child respiratory sinus arrhythmia (RSA) exhibited coregulation (across-person dynamics) accounting for individual differences in parent and child RSA, and whether there were differences in these parasympathetic processes by children's externalizing problems. Mother-child dyads (N=47; Child age M=31/2 years) engaged in three laboratory tasks (free play, clean up, puzzle task) for 18min, during which RSA data were collected. Multilevel coupled autoregressive models revealed that mothers and preschoolers showed positive coregulation of RSA such that changes in mother RSA predicted changes in the same direction in child RSA and vice versa, controlling for the stability of within-person RSA over time and individual differences in overall mean RSA. However, when children's externalizing behaviors were higher, coregulation was negative such that changes in real-time mother and child RSA showed divergence rather than positive concordance. Results suggest that mothers and preschoolers do coregulate RSA during real-time interactions, but that children's higher externalizing behavior problems are related to disruptions in these processes. © 2015 Wiley Periodicals, Inc. Source
Lee H.,Pukyong National University |
Choi Y.,Pukyong National University |
Suh J.,The Pennsylvania State University |
Lee S.-H.,Mine Reclamation Corporation
International Journal of Environmental Research and Public Health | Year: 2016
Understanding spatial variation of potentially toxic trace elements (PTEs) in soil is necessary to identify the proper measures for preventing soil contamination at both operating and abandoned mining areas. Many studies have been conducted worldwide to explore the spatial variation of PTEs and to create soil contamination maps using geostatistical methods. However, they generally depend only on inductively coupled plasma atomic emission spectrometry (ICP-AES) analysis data, therefore such studies are limited by insufficient input data owing to the disadvantages of ICP-AES analysis such as its costly operation and lengthy period required for analysis. To overcome this limitation, this study used both ICP-AES and portable X-ray fluorescence (PXRF) analysis data, with relatively low accuracy, for mapping copper and lead concentrations at a section of the Busan abandoned mine in Korea and compared the prediction performances of four different approaches: the application of ordinary kriging to ICP-AES analysis data, PXRF analysis data, both ICP-AES and transformed PXRF analysis data by considering the correlation between the ICP-AES and PXRF analysis data, and co-kriging to both the ICP-AES (primary variable) and PXRF analysis data (secondary variable). Their results were compared using an independent validation data set. The results obtained in this case study showed that the application of ordinary kriging to both ICP-AES and transformed PXRF analysis data is the most accurate approach when considers the spatial distribution of copper and lead contaminants in the soil and the estimation errors at 11 sampling points for validation. Therefore, when generating soil contamination maps for an abandoned mine, it is beneficial to use the proposed approach that incorporates the advantageous aspects of both ICP-AES and PXRF analysis data. © 2016 by the authors; licensee MDPI, Basel, Switzerland. Source
Laube P.,University of Zurich |
Gottfried B.,University of Bremen |
Klippel A.,The Pennsylvania State University |
Billen R.,University of Liege |
van de Weghe N.,Ghent University
Journal of Spatial Information Science | Year: 2011
This paper reports on the first Workshop on Movement Pattern Analysis, held as a pre-GIScience 2010 workshop in September 2010 in Zurich, Switzerland. The report outlines the scientific motivation for the event, summarizes its main contributions and outcomes, discusses the implications of the gathering, and indicates directions for the road ahead. © by the author(s). Source
Li Z.,Capital Medical University |
Wang A.,Capital Medical University |
Cai J.,Peking Union Medical College |
Gao X.,The Pennsylvania State University |
And 4 more authors.
European Journal of Neurology | Year: 2015
Background and purpose: Persons with chronic kidney disease, defined by a reduced estimated glomerular filtration rate and proteinuria, have an increased risk of cardiovascular disease including stroke. However, data from developing countries are limited. Our aim was to assess the relationship between chronic kidney disease and risk of stroke and its subtypes in a community-based population in China. Methods: The study was based on 92 013 participants (18-98 years old; 73 248 men and 18 765 women) of the Kailuan study who at baseline were free from stroke and myocardial infarction and had undergone tests for serum creatinine or proteinuria. Glomerular filtration rate was estimated using the Chronic Kidney Disease Epidemiology Collaboration formula and proteinuria by the urine dipstick result in laboratory databases. The primary outcome was the first occurrence of stroke. Data were analyzed using Cox proportional hazards models adjusted for relevant confounders and results are presented as hazard ratios (HRs) with 95% confidence intervals (CIs). Results: During a follow-up of 4 years, 1575 stroke events (1128 ischaemic, 406 intracerebral hemorrhagic and 41 subarachnoid hemorrhagic strokes) occurred. After adjustment for variable confounders, patients with proteinuria were found to have increased HRs for the total and subtypes of stroke events (HR 1.61; 95% CI 1.35-1.92 for total stroke; HR 1.53; 95% CI 1.24-1.89 for ischaemic stroke; and HR 1.90; 95% CI 1.35-2.67 for hemorrhagic stroke). However, estimated glomerular filtration rate was not associated with incident stroke after adjustment for established cardiovascular risk factors. Conclusions: Proteinuria increased the risk of stroke in a general Chinese population. © 2014 EAN. Source
Moratz R.,University of Maine |
Wallgrun J.O.,The Pennsylvania State University
Journal of Spatial Information Science | Year: 2012
We present an approach for supplying existing qualitative direction calculi with a distance component to support fully fledged positional reasoning. The general underlying idea of augmenting points with local reference properties has already been applied in the OPRAm calculus. In this existing calculus, point objects are attached with a local reference direction to obtain oriented points and able to express relative direction using binary relations. We show how this approach can be extended to attach a granular distance concept to direction calculi such as the cardinal direction calculus or adjustable granularity calculi such as OPRAm or the Star calculus. We focus on the cardinal direction calculus and extend it to a multi-granular positional calculus called EPRAm. We provide a formal specification of EPRAm including a composition table for EPRA2 automatically determined using real algebraic geometry. We also report on an experimental performance analysis of EPRA2 in the context of a topological map-learning task proposed for benchmarking qualitative calculi. Our results confirm that our approach of adding a relative distance component to existing calculi improves the performance in realistic tasks when using algebraic closure for consistency checking. © by the author(s). Source
Hanks E.M.,The Pennsylvania State University |
Schliep E.M.,Duke University |
Hooten M.B.,U.S. Geological Survey |
Hooten M.B.,Colorado State University-Pueblo |
Hoeting J.A.,Colorado State University-Pueblo
Environmetrics | Year: 2015
In spatial generalized linear mixed models (SGLMMs), covariates that are spatially smooth are often collinear with spatially smooth random effects. This phenomenon is known as spatial confounding and has been studied primarily in the case where the spatial support of the process being studied is discrete (e.g., areal spatial data). In this case, the most common approach suggested is restricted spatial regression (RSR) in which the spatial random effects are constrained to be orthogonal to the fixed effects. We consider spatial confounding and RSR in the geostatistical (continuous spatial support) setting. We show that RSR provides computational benefits relative to the confounded SGLMM, but that Bayesian credible intervals under RSR can be inappropriately narrow under model misspecification. We propose a posterior predictive approach to alleviating this potential problem and discuss the appropriateness of RSR in a variety of situations. We illustrate RSR and SGLMM approaches through simulation studies and an analysis of malaria frequencies in The Gambia, Africa. © 2015 John Wiley & Sons, Ltd. Source
A group of researchers from Nankai University in China, the University of Pittsburgh, and The Pennsylvania State University have demonstrated, for the first time, a synthetic mechanism for N-unsubstituted benzazetidines that is high yielding and practical. Their synthetic strategy can be used to make a variety of benzazetidine-based compounds for possible drug design exploration. Their work appears in Nature Chemistry. Researchers have made headway in nitrogen-based heterocycle chemistry using a palladium-catalyzed intramolecular dehydrogenative C-H amination (IDCA) reaction. In this reaction, the oxidized palladium catalyst coordinates to the target carbon and the amine. Ideally, this would result in a reductive elimination reaction in which the palladium is reduced back to its original oxidation state and the dehydrogenated carbon and amine would form a ring-closing bond. However, in practice, this reaction is difficult to accomplish in high yields. Four-membered rings are hindered due to ring strain. This leads to side products that are more thermodynamically favored than forming the four-membered ring. Gang He, Gang Lu, Zhengwei Guo, Peng Liu, and Gong Chen have devised a synthetic scheme that results in the desired benzazetidine using N-benzyl-picolinamide (PAs) as the reactant and Pd(OAc) as the catalyst. Key to the success of their synthetic scheme is rigid ligand structures both from the N-benzyl-picolinamide and the oxidant. They developed the phenyl-iodonium dimethylmalonate (PhI(DMM)) as their oxidant after seeing that PhI(OAc) , which is known to promote C-H acetoxylation using similar starting materials, formed a small amount of their target benzazetidine. However, the C-N ring closing reaction is thermodynamically unfavored compared to forming a C-OAc bond. After looking at computational studies to see how they could prevent the carbon-oxygen bond from forming, they decided to tether the oxygen on the carbonyl of the acetate to prevent it from reacting with the target carbon atom for the reductive elimination. After trying several tethers, they landed upon PhI(DMM), which proved to enhance the yield of the desired benzazetidine (48%). The next step was to see if this reaction was generalizable by changing the R group on the N-benzyl picolinamide reactant. Even in cases where the benzazetidine product could be formed using PhI(OAc) , He, et al. saw better yields with PhI(DMM). Furthermore, their reaction worked with a variety of functional groups, although, interestingly, did not work for unsubstituted benzylamine. An additional advantage of their scheme is that the PA protecting group was easily removed with sodium hydroxide in methanol, THF, and water at room temperature. He, et al. conducted mechanistic studies in hopes of understanding the reaction better so that it may be optimized for later research,. They found that the transition state involves a bimetallic Pd(III)/Pd(III) complex instead of a monomeric Pd(IV) compound. It is this bimetallic complex with the PhI(DMM) tether that promotes the desired reductive elimination pathway and blocks the C-OAc bond from forming. This research opens the door to the possibility of finding pharmaceuticals that involve a benzazetidine. This synthetic mechanism is versatile for various functional groups and, using the PhI(DMM) oxidizing agent, produces product yields that make this reaction pathway significantly more practical than the limited reaction mechanisms that were previously used to make benzazetidines. More information: Gang He et al. Benzazetidine synthesis via palladium-catalysed intramolecular C−H amination, Nature Chemistry (2016). DOI: 10.1038/nchem.2585 Abstract Small-sized N-heterocycles are important structures in organic synthesis and medicinal chemistry. Palladium-catalysed intramolecular aminations of the C−H bonds of unfunctionalized amine precursors have recently emerged as an attractive new method for N-heterocycle synthesis. However, the way to control the reactivity of high-valent Pd intermediates to form the desired C−N cyclized products selectively remains poorly addressed. Herein we report a strategy to control the reductive elimination (RE) pathways in high-valent Pd catalysis and apply this strategy to achieve the synthesis of highly strained four-membered benzazetidines via the Pd-catalysed intramolecular C−H amination of N-benzyl picolinamides. These reactions represent the first practical synthetic method for benzazetidines and enable access to a range of complex benzazetidines from easily obtainable starting materials. The use of a newly designed phenyliodonium dimethylmalonate reagent is critical, as oxidation of Pd(II) palladacycles with this reagent favours a kinetically controlled C−N RE pathway to give strained ring-closed products.
Home > Press > Scientists take key step toward custom-made nanoscale chemical factories: Berkeley Lab researchers part of team that creates new function in tiny protein shell structures Abstract: Scientists have for the first time reengineered a building block of a geometric nanocompartment that occurs naturally in bacteria. They introduced a metal binding site to its shell that will allow electrons to be transferred to and from the compartment. This provides an entirely new functionality, greatly expanding the potential of nanocompartments to serve as custom-made chemical factories. Scientists hope to tailor this new use to produce high-value chemical products, such as medicines, on demand. The sturdy nanocompartments, which are polyhedral shells composed of triangle-shaped sides and resemble 20-sided dice, are formed by hundreds of copies of just three different types of proteins. Their natural counterparts, known as bacterial microcompartments or BMCs, encase a wide variety of enzymes that carry out highly specialized chemistry in bacteria. Researchers at the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) devised synthetic shell structures derived from those found in a rod-shaped, ocean-dwelling bacterium, Haliangium ochraceum, and reengineered one of the shell proteins to serve as a scaffold for an iron-sulfur cluster found in many forms of life. The cluster is known as a "cofactor" because it can serve as a helper molecule in biochemical reactions. BMC-based shells are tiny, durable and naturally self-assemble and self-repair, which makes them better-suited for a range of applications than completely synthetic nanostructures. "This is the first time anyone has introduced functionality into a shell. We thought the most important functionality to introduce was the ability to transfer electrons into or out of the shell," said Cheryl Kerfeld, a structural biologist at Berkeley Lab and corresponding author in this study. Kerfeld's research group focuses on BMCs. Kerfeld holds joint appointments with Berkeley Lab's Molecular Biophysics and Integrated Bioimaging (MBIB) Division, UC Berkeley and the MSU-DOE Plant Research Laboratory at Michigan State University (MSU). "That greatly enhances the versatility of the types of chemistries you can encapsulate in the shell and the spectrum of products to be produced," she said. "Typically, the shells are thought of as simply passive barriers." Researchers used X-rays at Berkeley Lab's Advanced Light Source (ALS) to show, in 3-D and at the atomic scale, how the introduced iron-sulfur cluster binds to the engineered protein. The study is now online in the Journal of the American Chemical Society. Enzymes inside natural BMCs can convert carbon dioxide into organic compounds that can be used by the bacteria, isolate toxic or volatile compounds from the surrounding cell, and carry out other chemical reactions that provide energy for the cell. In this study, researchers introduced the iron-sulfur cluster into the tiny pores in the shell building block. This engineered protein serves as an electron relay across the shell, which is key to controlling the chemical reactivity of substances inside the shell. Clement Aussignargues, the lead author of the study and postdoctoral researcher in the MSU-DOE Plant Research Laboratory in Michigan, said, "The beauty of our system is that we now have all the tools, notably the crystallographic structure of the engineered protein, to modify the redox potential of the system--its ability to take in electrons (reduction) or give off electrons (oxidation). "If we can control this, we can expand the range of chemical reactions we can encapsulate in the shell. The limit of these applications will be what we put inside the shells, not the shells themselves." He added, "Creating a new microcompartment from scratch would be very, very complicated. That's why we're taking what nature put before us and trying to add to what nature can do." To design the metal binding site, Kerfeld's group first had to solve the structures of the building blocks of the nanocompartment to use as the template for design. These building blocks self-assemble into synthetic shells, which measure just 40 nanometers, or billionths of a meter, in diameter. The natural form of the shells can be up to 12 times larger. The iron-sulfur cofactor of the engineered protein, which was produced in E. coli bacteria, was very stable even when put through several redox cycles--a characteristic essential for future applications, Aussignargues said. "The engineered protein was also more stable than its natural counterpart, which was a big surprise," he said. "You can treat it with things that normally make proteins fall apart and unwind." A major challenge in the study was to prepare the engineered protein in an oxygen-free environment to form tiny crystals that best preserve their structure and their cofactor for X-ray imaging, Kerfeld said. The crystals were prepared in an air-sealed glovebox at MSU, frozen, and then shipped out for X-ray studies at Berkeley Lab's ALS and SLAC National Accelerator Laboratory's Stanford Synchrotron Radiation Lightsource (SSRL). In follow-up work, the research team is exploring how to incorporate different metal centers into BMC shells to access a different range of chemical reactivity, she said. "I'm working on incorporating a completely different metal center, which has a very positive reduction potential compared to the iron-sulfur cluster," said Jeff Plegaria, a postdoctoral researcher at the MSU-DOE Plant Research Laboratory who contributed to the latest study. "But it is the same sort of idea: To drive electrons in or out of the compartment." He added, "The next step is to encapsulate proteins that can accept electrons into the shells, and to use that as a probe to watch the electron transfer from the outside of the compartment to the inside." That will bring researchers closer to creating specific types of pharmaceuticals or other chemicals. ### Other scientists involved in the study were from MSU, The Pennsylvania State University and Brooklyn College. The work was supported by the U.S. DOE Office of Science, MSU AgBio Research and the European Union's PEPDIODE project. The ALS and SLAC's SSRL are both DOE Office of Science User Facilities. About Berkeley Lab Lawrence Berkeley National Laboratory addresses the world's most urgent scientific challenges by advancing sustainable energy, protecting human health, creating new materials, and revealing the origin and fate of the universe. Founded in 1931, Berkeley Lab's scientific expertise has been recognized with 13 Nobel prizes. The University of California manages Berkeley Lab for the U.S. Department of Energy's Office of Science. For more, visit www.lbl.gov. The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov. For more information, please click If you have a comment, please us. Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.
Understanding and tailoring materials’ properties usually requires trial and error, and a bit of luck. But, as a special issue of Computational Materials Science [112, Part B, 405-546, Computational Materials Science in China.] shows, the latest generation of computation techniques and new algorithms can now model novel materials and explore existing ones better than ever before. China is embracing these new possibilities, making fast progress over the last decade as access to computation resources has become more widespread, according to Xingao Gong of Fudan University. The university is home to a Key Laboratory for Computational Physical Sciences, which has over the last five years successfully used computational tools to clarify long-held misunderstandings about the structure and properties of quaternary semiconductors tagged for future solar cells. “The profile of computational materials science as a discipline has been rising quickly in China over the last few years,” adds Editor-in-Chief, Professor Susan Sinnott of The Pennsylvania State University. “So this is an ideal time to highlight some of the best work in the field that is being carried out there.” Exploring the electronic and magnetic properties of materials theoretically begins with a simple model. By considering a few tens or hundreds of atoms at a time, computational methods can calculate properties that are scalable to larger dimensions. These basic models can be finely tuned to improve accuracy. At the University of Science and Technology of China, for example, Lixin He and colleagues are using atomic orbitals as the basic unit for ab initio electronic structure calculations of silicon, group IV and III-V semiconductors including technologically important GaAs and GaN, as well as alkali and 3d transition metals. Focusing on orbital physics can be a helpful tactic in unpicking the novel electronic and magnetic behavior of transition metal oxides, which are a platform for many functional devices, according to Hua Wu at Fudan University. The combination of charge, spin, and orbital degrees of freedom in these materials leads to unusual – and useful – effects such as colossal magnetoresistance and multiferroicity. First principles calculations based on density functional theory (DFT), where quantum mechanical equations determine the density of electrons, are proving effective and versatile in understanding the new generation of planar materials, such as graphene, silicene, and boron nitride. Despite being well known for decades, DFT has been refined in recent years so it can now be used to tailor the physical properties of 2D materials for applications. DFT can also help unravel the science behind exotic materials like topological insulators, which have an insulating core but surface conducting electrons. Researchers at Beijing Institute of Technology are using this approach to explore such fantastic phenomena as these in solid materials that would be difficult to comprehend by other means. Likewise, modeling is effective when it comes to identifying and assessing materials for extreme environments. A group at Beihang University is using DFT to identify materials able to withstand the extreme temperatures and irradiation levels inside thermonuclear reactors. Taking a different approach to models, meanwhile, can yield new insights. A group at Jilin University, for example, has devised a computational method based on a ‘swarm intelligence’ algorithm inspired by natural systems such as ant colonies, bee swarms, and flocks of birds. The self-improving approach works particularly well with atomic and molecular clusters, nanoparticles, and 3D bulk materials. “I am very excited to see that young scientists in China now have a strong interest in developing new algorithms and first principles approaches based on local atomic orbitals,” says Gong. The rise of computational methods to understand materials behaviors and properties, and drive new materials’ discovery, has been particularly impressive in China, agrees Baptiste Gault, senior publisher at Elsevier. “It is very timely to provide an overview of the state-of-the-art here and Computational Materials Science is the preeminent forum.” This special issue is published in Computational Materials Science- 112, Part B, 405-546 "Computational Materials Science in China". To find out more about each article included within this special issue, please follow the below links: The novel electronic and magnetic properties in 5d transition metal oxides system First-principles investigations on the Berry phase effect in spin–orbit coupling materials Recent progresses in real-time local-basis implementation of time dependent density functional theory for electron–nucleus dynamics Modeling and simulation of helium behavior in tungsten: A first-principles investigation Recent advances in computational studies of organometallic sheets: Magnetism, adsorption and catalysis Tailoring physical properties of graphene: Effects of hydrogenation, oxidation, and grain boundaries by atomistic simulations
Kang D.,The Pennsylvania State University |
Lilik G.,The Pennsylvania State University |
Dillstrom V.,University of Michigan |
Agudelo J.,University of Antioquia |
And 3 more authors.
Combustion and Flame | Year: 2015
The ignition process of ethylcyclohexane (ECH) and its two isomers, 1,3-dimethylcyclohexane (13DMCH) and 1,2-dimethylcyclohexane (12DMCH) was investigated in a modified CFR engine. The experiment was conducted with intake air temperature of 155. °C, equivalence ratio of 0.5 and engine speed of 600. rpm. The engine compression ratio (CR) was gradually increased in a stepwise manner until autoignition occurred. It was found that ECH exhibited a significantly higher oxidation reactivity compared to its two isomers. The autoignition criterion was based on CO emissions and the apparent heat release rates. Ethylcyclohexane (ECH) indicated noticeable two stage ignition behavior, while less significant heat release occurred for the two isomers at comparable conditions. The mole fractions of unreacted fuel and stable intermediate species over a wide range of compression ratios were analyzed by GC-MS and GC-FID. Most of the species indicated constant rates of formation and the trends of relative yield to unreacted fuel are well in agreement with the oxidation reactivity in the low temperature regime. The major intermediate species are revealed as a group of conjugate olefins, which possess the same molecular structure as the original fuel compound except for the presence of a double carbon bond. Conjugate olefins were mostly formed through (1,4) H-shift isomerization during the low temperature oxidation of alkylcyclohexanes. Conformation analysis explains the reactivity differences in the three isomers as well as the fractions of intermediate species. The hydrogen availability located in alkyl substituents plays an important role in determining oxidation reactivity, requiring less activation energy for abstraction through the (1,5) H-shift isomerization. This reactivity difference contributes to building up the major intermediate species observed during oxidation of each test fuel. 12DMCH, whose ignition reactivity is the lowest, less favors β-scission of C-C backbone of cyclic ring, thereby resulting in lower concentrations of small olefins and higher concentrations of conjugate olefins and large oxygenated species in the low temperature regime, prior to autoignition. © 2014 The Combustion Institute. Source
In the early fifties, before Richard Feynman famously seeded the concept of nanoscience in his 1959 talk “there’s plenty of room at the bottom” , and well before the concept of nanotechnology became popular in the late 80’s, a significant research effort was already underway into the fundamental nanoscience associated with high-field effects at surfaces and the resulting emission of ions and electrons . Born from this work, in 1955, field ion microscopy (FIM) became the first true atomic scale microscopy technique, allowing us to ‘see atoms’ for the very first time . The technique, invented by Erwin Müller in 1951 employed a specimen shaped into a sharp point, enabling it to act as a point projection field ion emitter. The specimen was cooled to 78K in the presence of He gas. This gas was adsorbed and subsequently field ionized and detected, with the distribution of detected atoms showing the arrangement of the specimen atoms at the surface of the tip. Sixty years on, this seminal work by Erwin Müller has spurred important and wide-ranging research, including many significant discoveries and inventions . Progressive field evaporated of surface atoms can be detected  and their positions reconstructed to create high-resolution 3D atom maps in a technique known as atom probe tomography , which has become an established microscopy technique. It’s use in materials characterisation has led to ground-breaking research including the first 3D images of segregation to dislocations , understanding the growth of nanowires , determining the kinetics of elemental steps of catalytic surface reactions , revealing precipitation pathways in important engineering alloys  and confirmation of the dating of the oldest minerals on earth , to name just a few examples. Other contributions from field-emission science include the development of the liquid metal ion source that now forms the basis of focused ion beam instruments , field electron emission from new forms of emitter  along with the sustained development of theory around high-field effects at surfaces . It is timely that we recognize these exceptional contributions. The International Field Emission Society (IFES) originally grew from pioneering research on high-field nanoscience, and supports the development and application of techniques and instruments based on these effects. It has hosted symposia since 1952 occurring every one to two years. In 2016, this conference, “Atom Probe Tomography & Microscopy (55th IFES)” will be held in Gyeongju, South Korea (June 12-17). At the event, the Steering Committee of the IFES (see note at end of this article for a list of members) is proud to award an inaugural round of “Fellows of the International Field Emission Society”, elected in recognition of eminence in the field of field emission, field ionization, and related phenomena. These individuals have been nominated and elected by their peers for outstanding research that has pushed the frontiers of knowledge in the field. Many have also undertaken distinguished service to the IFES. Those to be honored as IFES fellows in 2016 are listed below: Hans-Olof Andren, Chalmers University of Technology: For development of atom probe techniques, and for his use of atom probe instruments as materials science tools to study the detailed microstructure of primarily metallic materials. Didier Blavette, Université de Rouen: For unique contributions to atom probe field ion microscopy spanning the fundamental physics of the technique, instrumentation, and cutting-edge materials characterization. Alfred Cerezo, University of Oxford: For development of the position sensitive atom probe, which opened new dimensions and perspectives in both material science and instrumentation. Paul Cutler, The Pennsylvania State University: For working on theory of field electron and ion emission over more than 50 years, developing quantum mechanical models to explain and predict the behavior of field electron emitters. Richard Forbes, University of Surrey: For his many contributions to the growth of the theory and understanding of field electron and ion emission as well as his contributions to the society. Georgiy Fursey, St Petersburg University of Telecommunications: For wide-ranging, outstanding contributions to field electron emission science and technology, particularly explosive emission and emission from semiconductors. Robert Gomer, University of Chicago: For outstanding contributions to science, especially areas of field electron and ion emission and their application to problems in surface chemistry, and for public service. Kazuhiro Hono, National Institute for Materials Science: For key contributions to the growth of atom probe, developments in instrumentation, and broad utilization of the technique to impact the study of magnetic materials and precipitation hardening. Gary Kellogg, Retired: For fundamental technical contributions to laser-pulsed atom probe instrumentation and numerous aspects of surface and materials science, and for extraordinary service to the nanoscience community. Thomas Kelly, Cameca Inc.: For revolutionizing atom probe technology with the invention of the LEAP, and for service to the IFES community as President of the society. Hans-Juergen Kreuzer, Dalhousie University: Published more than 325 papers, 8 books, and 6 patents in the area of physics and chemistry of high electric fields. Norbert Kruse, Washington State University: For sustained contributions towards understanding chemical physics at materials surfaces and outstanding service to the high field nanoscience and atom probe communities. Allan Melmed, Retired: One of the most distinguished scientists of the IFES community, with a lifetime experience in field emission since his PhD thesis with the late EW Müller. Michael Miller, Retired: For seminal contributions in the development and application of atom probe tomography as demonstrated by his 600+ publications, service to the community, and impactful collaborations with numerous international scientists and engineers in their development and use of atom probe tomography. Marwan Mousa, Mu'tah University: For outstanding contributions to field emission science and for service to the society including organization of the 45th IFES. Osamu Nishikawa, Kanazawa Institute of Technology: For outstanding contributions to atom probe becoming a mainstream scientific instrument in hundreds of laboratories around the world. John Panitz, University New Mexico: As one of the inventors of the atom probe technique, John Panitz’ contributions and vision for the technique enabled its large acceptance in the international realm of materials characterization. Simon Ringer, The University of Sydney: For outstanding research in atom probe science, sustained IFES community service, including as Vice President and conference organiser and his role in training a new generation of field emission scientists. Guido Schmitz, University of Stuttgart: For his contribution to understanding diffusion and other atomic scale metallurgical processes studied using atom probe tomography. David Seidman, Northwestern University: Having advised more than 120 individuals and with 450+ publications, David Seidman's materials research based on APT and technique developments has laid a solid groundwork for atom probe groups worldwide. George Smith, University of Oxford: For more than 45 years of contributions and commitment to the field of atom probe field ion microscopy. Krystyna Stiller, Chalmers University of Technology: For fruitful use and development of atom probe techniques contributing to understanding of radiation damage, phase transformations, interfacial segregation and high temperature oxidation, and for promoting atom probe techniques. Lynwood Swanson, FEI: For outstanding scientific contributions to characterisation and development of field electron/ion emitters, and technical and managerial leadership of FEI Company in commercially developing these emitters and related instruments. Tien Tsong, Academia Sinica: For observation of the interaction between adsorbates on metal surfaces and for seminal research involving the use of a laser to promote thermal field evaporation. The Steering Committee of the IFES currently consists of:  Feynman RP. There's Plenty of Room at the Bottom. Engineering and Science 1960:22-36.  Cerezo A, Godfrey TJ, Smith GDW. Application of a position-sensitive detector to atom probe microanalysis. Review of Scientific Instruments 1988;59:862-6.  Perea DE, Hemesath ER, Schwalbach EJ, Lensch-Falk JL, Voorhees PW, Lauhon LJ. Direct measurement of dopant distribution in an individual vapour-liquid-solid nanowire. Nature Nanotechnology 2009;4:315-9.  Kruse N, Abend G, Block JH. The kinetics of adsorption and thermal desorption of NO on stepped Pt single crystal surfaces. The Journal of Chemical Physics 1988;88:1307-12.  Ringer SP, Hono K. Microstructural evolution and age hardening in aluminium alloys: atom probe field-ion microscopy and transmission electron microscopy studies. Materials Characterization 2000;44:101-31.  Valley JW, Cavosie AJ, Ushikubo T, Reinhard DA, Lawrence DF, Larson DJ, et al. Hadean age for a post-magma-ocean zircon confirmed by atom-probe tomography. Nature Geoscience 2014;7:219-23.  Li Z, Xu N, Kreuzer HJ. Coherent field emission image of graphene predicted with a microscopic theory. Physical Review B - Condensed Matter and Materials Physics 2012;85.  Forbes RG, Edgcombe CJ, Valdrè U. Some comments on models for field enhancement. Ultramicroscopy 2003;95:57-65.
« Volvo Car to make Gen 2 Pilot Assist standard on new S90 sedan | Main | Volvo Cars cracks 500,000 unit marker in annual global sales for first time » Researchers at The Pennsylvania State University have synthesized highly crumpled nitrogen-doped graphene (NG) sheets with ultrahigh pore volume (5.4 cm3) and large surface area (1158 m2/g), which enable strong polysulfide adsorption and high sulfur content for use as a cathode material in Li-sulfur batteries. The wrinkled graphene sheets are interwoven rather than stacked, resulting in rich nitrogen-containing active sites. Lithium–sulfur battery cells using these wrinkled graphene sheets as both sulfur host and interlayer achieved a high capacity of 1227 mAh/g and long cycle life (75% capacity retention after 300 cycles) even at high sulfur content (≥80 wt %) and sulfur loading (5 mg sulfur/cm2). A high capacity of 1082 mAh/g was still achieved with an ultrahigh sulfur content of 90 wt %, and a capacity of 832 mAh/g was retained after 200 cycles. Areal capacity was 5 mAh/cm2. A paper on their work is published in the ACS journal Nano Letters. … practical applications of Li−S batteries are highly hindered by the low electrical conductivity of sulfur and the diffusion of soluble lithium polysulfides intermediates generated during cycling, which lead to lower utilization of sulfur, loss of active material from the cathode, and polysulfide shuttle phenomenon. As a result, Li−S cells experience a fast capacity fading, low Coulombic efficiency, and poor rate capability. To address these issues, various types of cathode materials, including porous carbon−sulfur, low-dimensional conducting material (such as carbon nanotube and graphene−sulfur), and conducting polymer−sulfur composites, have been exploited to improve the overall electrochemical performance of the Li−S cells. Nitrogen-doping of carbon has been shown to be effective for improving the overall electrochemical performance of sulfur cathodes in Li–S batteries. Nitrogen-doped carbon is also highly conductive and thus allows for direct redox and utilization of adsorbed material rather than requiring desorption and diffusion of polysulfides to an electrochemically active surface. However, current nanoporous nitrogen-doped carbons suffer from limited pore volume, resulting in relatively low sulfur content (≤70 wt %) and sulfur loading (2 mg sulfur/cm2)—less than ideal for practical application. Nitrogen-doped could combine the advantages of graphene and nitrogen-doped carbon. However, graphene sheets tend to form irreversible agglomerates or even restack to form graphite, resulting in the loss of specific surface area. This lowers the polysulfides adsorption capacity due to a decrease of accessible active sites. Although the advances have been made in the pursuit of nitrogen-doped graphene as sulfur host for Li–S batteries recently, the electrochemical performance such as the cycling stability and sulfur utilization is still unsatisfied. This indicates that preventing graphene aggregation to maintain the accessible active surface and constructing adequate pore volume to host sulfur are of particular importance when graphene sheets are used as electrode materials for Li–S batteries. The Penn State team synthesized their highly crumpled nitrogen doped-graphene sheets through a facile thermally induced expansion approach with cyanamide serving as both nitrogen source and porogen. This obviated the need for other templates. The performance of the material presents a promising path for further development in Li−S batteries and can be potentially exploited for other applications such as supercapacitors and oxygen reduction reaction catalysts, the researchers said.
McHugh M.,Northwestern University |
Shi Y.,The Pennsylvania State University |
McClellan S.R.,Abt Associates |
Shortell S.M.,University of California at Berkeley |
And 4 more authors.
Healthcare | Year: 2016
Background: Multi-stakeholder alliances - groups of payers, purchasers, providers, and consumers that work together to address local health goals - are frequently used to improve health care quality within communities. Under the Aligning Forces for Quality (AF4Q) initiative, multi-stakeholder alliances were given funding and technical assistance to encourage the use of health information technology (HIT) to improve quality. We investigated whether HIT adoption was greater in AF4Q communities than in other communities. Methods: Drawing upon survey data from 782 small and medium-sized physician practices collected as part of the National Study of Physician Organizations during July 2007 - March 2009 and January 2012-November 2013, we used weighted fixed effects models to detect relative changes in four measures representing three domains: use of electronic health records (EHRs), receipt of electronic information from hospitals, and patients' online access to their medical records. Results: Improvement on a composite EHR adoption measure was 7.6 percentage points greater in AF4Q communities than in non-AF4Q communities, and the increase in the probability of adopting all five EHR capabilities was 23.9 percentage points greater in AF4Q communities. There was no significant difference in improvement in receipt of electronic information from hospitals or patients' online access to medical records between AF4Q and non-AF4Q communities. Conclusion: By linking HIT to quality improvement efforts, AF4Q alliances may have facilitated greater adoption of EHRs in small and medium-sized physician practices, but not receipt of electronic information from hospitals or patients' online access to medical records. Implications: Multi-stakeholder alliances charged with promoting HIT to advance quality improvement may accelerate adoption of EHRs. © 2016 Elsevier Inc. Source