Showing papers by "United States Department of Energy published in 2010"
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TL;DR: An updated evaluation of potential target structures using similar selection methodology, and an overview of the technology developments that led to the inclusion of a given compound are presented.
3,536 citations
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ETH Zurich1, INAF2, University of Padua3, University of Hawaii4, California Institute of Technology5, University of Toulouse6, European Southern Observatory7, Max Planck Society8, University of Bologna9, Space Telescope Science Institute10, United States Department of Energy11, Centre national de la recherche scientifique12
TL;DR: In this paper, the authors explore the simple interrelationships between mass, star formation rate, and environment in the SDSS, zCOSMOS, and other deep surveys.
Abstract: We explore the simple inter-relationships between mass, star formation rate, and environment in the SDSS, zCOSMOS, and other deep surveys. We take a purely empirical approach in identifying those features of galaxy evolution that are demanded by the data and then explore the analytic consequences of these. We show that the differential effects of mass and environment are completely separable to z ~ 1, leading to the idea of two distinct processes of "mass quenching" and "environment quenching." The effect of environment quenching, at fixed over-density, evidently does not change with epoch to z ~ 1 in zCOSMOS, suggesting that the environment quenching occurs as large-scale structure develops in the universe, probably through the cessation of star formation in 30%-70% of satellite galaxies. In contrast, mass quenching appears to be a more dynamic process, governed by a quenching rate. We show that the observed constancy of the Schechter M* and α_s for star-forming galaxies demands that the quenching of galaxies around and above M* must follow a rate that is statistically proportional to their star formation rates (or closely mimic such a dependence). We then postulate that this simple mass-quenching law in fact holds over a much broader range of stellar mass (2 dex) and cosmic time. We show that the combination of these two quenching processes, plus some additional quenching due to merging naturally produces (1) a quasi-static single Schechter mass function for star-forming galaxies with an exponential cutoff at a value M* that is set uniquely by the constant of proportionality between the star formation and mass quenching rates and (2) a double Schechter function for passive galaxies with two components. The dominant component (at high masses) is produced by mass quenching and has exactly the same M* as the star-forming galaxies but a faint end slope that differs by Δα_s ~ 1. The other component is produced by environment effects and has the same M* and α_s as the star-forming galaxies but an amplitude that is strongly dependent on environment. Subsequent merging of quenched galaxies will modify these predictions somewhat in the denser environments, mildly increasing M* and making α_s slightly more negative. All of these detailed quantitative inter-relationships between the Schechter parameters of the star-forming and passive galaxies, across a broad range of environments, are indeed seen to high accuracy in the SDSS, lending strong support to our simple empirically based model. We find that the amount of post-quenching "dry merging" that could have occurred is quite constrained. Our model gives a prediction for the mass function of the population of transitory objects that are in the process of being quenched. Our simple empirical laws for the cessation of star formation in galaxies also naturally produce the "anti-hierarchical" run of mean age with mass for passive galaxies, as well as the qualitative variation of formation timescale indicated by the relative α-element abundances.
1,860 citations
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Agricultural Research Service1, Oregon State University2, University of California, Berkeley3, John Innes Centre4, United States Department of Energy5, United States Department of Agriculture6, University of California, Davis7, University of Silesia in Katowice8, China Agricultural University9, Iowa State University10, Washington State University11, University of Florida12, University of Massachusetts Amherst13, University of Wisconsin-Madison14, Technische Universität München15, Cornell University16, University of Zurich17, University of Helsinki18, Universidade Federal de Pelotas19, Purdue University20, University of Texas at Arlington21, National Center for Genome Resources22, University of Delaware23, Joint BioEnergy Institute24, University of Copenhagen25, Kyung Hee University26, Ghent University27, Centre national de la recherche scientifique28, Oak Ridge National Laboratory29, Ohio State University30, Institut national de la recherche agronomique31, University of Picardie Jules Verne32, Illinois State University33, Sabancı University34, Donald Danforth Plant Science Center35
TL;DR: The high-quality genome sequence will help Brachypodium reach its potential as an important model system for developing new energy and food crops and establishes a template for analysis of the large genomes of economically important pooid grasses such as wheat.
Abstract: Three subfamilies of grasses, the Ehrhartoideae, Panicoideae and Pooideae, provide the bulk of human nutrition and are poised to become major sources of renewable energy. Here we describe the genome sequence of the wild grass Brachypodium distachyon (Brachypodium), which is, to our knowledge, the first member of the Pooideae subfamily to be sequenced. Comparison of the Brachypodium, rice and sorghum genomes shows a precise history of genome evolution across a broad diversity of the grasses, and establishes a template for analysis of the large genomes of economically important pooid grasses such as wheat. The high-quality genome sequence, coupled with ease of cultivation and transformation, small size and rapid life cycle, will help Brachypodium reach its potential as an important model system for developing new energy and food crops.
1,603 citations
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TL;DR: In this paper, a flow chart with standard procedures for PEC characterization techniques for planar photoelectrode materials (i.e., not suspensions of particles) with a focus on single band gap absorbers is presented.
Abstract: Photoelectrochemical (PEC) water splitting for hydrogen production is a promising technology that uses sunlight and water to produce renewable hydrogen with oxygen as a by-product. In the expanding field of PEC hydrogen production, the use of standardized screening methods and reporting has emerged as a necessity. This article is intended to provide guidance on key practices in characterization of PEC materials and proper reporting of efficiencies. Presented here are the definitions of various efficiency values that pertain to PEC, with an emphasis on the importance of solar-to-hydrogen efficiency, as well as a flow chart with standard procedures for PEC characterization techniques for planar photoelectrode materials (i.e., not suspensions of particles) with a focus on single band gap absorbers. These guidelines serve as a foundation and prelude to a much more complete and in-depth discussion of PEC techniques and procedures presented elsewhere.
1,008 citations
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TL;DR: The latest research on the pathways of entry into live mammalian and plant cells together with intracellular trafficking are described, and the current research progress on the biocompatibility of this material in vitro and in vivo is discussed.
Abstract: The application of nanotechnology in the field of drug delivery has attracted much attention in the latest decades. Recent breakthroughs on the morphology control and surface functionalization of inorganic-based delivery vehicles, such as mesoporous silica nanoparticles (MSNs), have brought new possibilities to this burgeoning area of research. The ability to functionalize the surface of mesoporous-silica-based nanocarriers with stimuli-responsive groups, nanoparticles, polymers, and proteins that work as caps and gatekeepers for controlled release of various cargos is just one of the exciting results reported in the literature that highlights MSNs as a promising platform for various biotechnological and biomedical applications. This review focuses on the most recent progresses in the application of MSNs for intracellular drug delivery. The latest research on the pathways of entry into live mammalian and plant cells together with intracellular trafficking are described. One of the main areas of interest in this field is the development of site-specific drug delivery vehicles; the contribution of MSNs toward this topic is also summarized. In addition, the current research progress on the biocompatibility of this material in vitro and in vivo is discussed. Finally, the latest breakthroughs for intracellular controlled drug release using stimuli-responsive mesoporous-silica-based systems are described.
915 citations
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United States Department of Energy1, J. Craig Venter Institute2, University of California, Berkeley3, Heidelberg University4, University of California, Irvine5, Technische Universität München6, National Institutes of Health7, Pomona College8, Salk Institute for Biological Studies9, University of Kiel10, National Institute of Genetics11, University of Vienna12, University of Kansas13, University of Innsbruck14, Dartmouth College15, North Carolina State University16, Ludwig Maximilian University of Munich17
TL;DR: Comparisons of the Hydra genome to the genomes of other animals shed light on the evolution of epithelia, contractile tissues, developmentally regulated transcription factors, the Spemann–Mangold organizer, pluripotency genes and the neuromuscular junction.
Abstract: The freshwater cnidarian Hydra was first described in 17021 and has been the object of study for 300 years. Experimental studies of Hydra between 1736 and 1744 culminated in the discovery of asexual reproduction of an animal by budding, the first description of regeneration in an animal, and successful transplantation of tissue between animals2. Today, Hydra is an important model for studies of axial patterning3, stem cell biology4 and regeneration5. Here we report the genome of Hydra magnipapillata and compare it to the genomes of the anthozoan Nematostella vectensis6 and other animals. The Hydra genome has been shaped by bursts of transposable element expansion, horizontal gene transfer, trans-splicing, and simplification of gene structure and gene content that parallel simplification of the Hydra life cycle. We also report the sequence of the genome of a novel bacterium stably associated with H. magnipapillata. Comparisons of the Hydra genome to the genomes of other animals shed light on the evolution of epithelia, contractile tissues, developmentally regulated transcription factors, the Spemann–Mangold organizer, pluripotency genes and the neuromuscular junction.
754 citations
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TL;DR: The results show that both amplicon length and primer pair markedly influence estimates of richness and evenness, however, estimates of species evenness are consistent among different primer pairs targeting the same region, highlighting the importance of experimental methodology when comparing diversity estimates across communities.
Abstract: Pyrosequencing of 16S rRNA gene amplicons for microbial community profiling can, for equivalent costs, yield more than two orders of magnitude more sensitivity than traditional PCR cloning and Sanger sequencing. With this increased sensitivity and the ability to analyze multiple samples in parallel, it has become possible to evaluate several technical aspects of PCR-based community structure profiling methods. We tested the effect of amplicon length and primer pair on estimates of species richness (number of species) and evenness (relative abundance of species) by assessing the potentially tractable microbial community residing in the termite hindgut. Two regions of the 16S rRNA gene were sequenced from one of two common priming sites, spanning the V1–V2 or V8 regions, using amplicons ranging in length from 352 to 1443 bp. Our results show that both amplicon length and primer pair markedly influence estimates of richness and evenness. However, estimates of species evenness are consistent among different primer pairs targeting the same region. These results highlight the importance of experimental methodology when comparing diversity estimates across communities.
568 citations
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United States Department of Energy1, Salk Institute for Biological Studies2, University of New Brunswick3, University of Maryland, Baltimore County4, Nara Women's University5, University of California, Berkeley6, University of Freiburg7, Genetic Information Research Institute8, University of Regensburg9, Washington University in St. Louis10
TL;DR: In this paper, the authors sequenced the 138-mega-base pair genome of V. carteri and compared its approximately 14,500 predicted proteins to those of its unicellular relative Chlamydomonas reinhardtii.
Abstract: The multicellular green alga Volvox carteri and its morphologically diverse close relatives (the volvocine algae) are well suited for the investigation of the evolution of multicellularity and development. We sequenced the 138-mega-base pair genome of V. carteri and compared its approximately 14,500 predicted proteins to those of its unicellular relative Chlamydomonas reinhardtii. Despite fundamental differences in organismal complexity and life history, the two species have similar protein-coding potentials and few species-specific protein-coding gene predictions. Volvox is enriched in volvocine-algal-specific proteins, including those associated with an expanded and highly compartmentalized extracellular matrix. Our analysis shows that increases in organismal complexity can be associated with modifications of lineage-specific proteins rather than large-scale invention of protein-coding capacity.
509 citations
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TL;DR: Although bacteria are continually acquired over the lifetime of an individual, the phylogenetic relationships of great ape species is mirrored in the compositions of their gut microbial communities.
Abstract: Multiple factors over the lifetime of an individual, including diet, geography, and physiologic state, will influence the microbial communities within the primate gut. To determine the source of variation in the composition of the microbiota within and among species, we investigated the distal gut microbial communities harbored by great apes, as present in fecal samples recovered within their native ranges. We found that the branching order of host-species phylogenies based on the composition of these microbial communities is completely congruent with the known relationships of the hosts. Although the gut is initially and continuously seeded by bacteria that are acquired from external sources, we establish that over evolutionary timescales, the composition of the gut microbiota among great ape species is phylogenetically conserved and has diverged in a manner consistent with vertical inheritance.
469 citations
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TL;DR: In this article, the synthesis and thermoelectric characterization of composite nanocrystals composed of a tellurium core functionalized with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) was reported.
Abstract: We report the synthesis and thermoelectric characterization of composite nanocrystals composed of a tellurium core functionalized with the conducting polymer poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Solution processed nanocrystal films electronically out perform both PEDOT:PSS and unfunctionalized Te nanorods while retaining a polymeric thermal conductivity, resulting in a room temperature ZT ∼ 0.1. This combination of electronic and thermal transport indicates the potential for tailored transport in nanoscale organic/inorganic heterostructures.
459 citations
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TL;DR: Transgenic mouse assays of 130 candidate regions revealed that most function reproducibly as enhancers active in the heart, irrespective of their degree of evolutionary constraint, suggesting that the evolutionary conservation of embryonic enhancers can vary depending on tissue type.
Abstract: Accurate control of tissue-specific gene expression plays a pivotal role in heart development, but few cardiac transcriptional enhancers have thus far been identified. Extreme noncoding-sequence conservation has successfully predicted enhancers that are active in many tissues but has failed to identify substantial numbers of heart-specific enhancers. Here, we used ChIP-Seq with the enhancer-associated protein p300 from mouse embryonic day 11.5 heart tissue to identify over 3,000 candidate heart enhancers genome wide. Compared to enhancers active in other tissues we studied at this time point, most candidate heart enhancers were less deeply conserved in vertebrate evolution. Nevertheless, transgenic mouse assays of 130 candidate regions revealed that most function reproducibly as enhancers active in the heart, irrespective of their degree of evolutionary constraint. These results provide evidence for a large population of poorly conserved heart enhancers and suggest that the evolutionary conservation of embryonic enhancers can vary depending on tissue type.
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TL;DR: Results provide direct evidence that the CAD risk interval has a pivotal role in regulation of cardiac Cdkn2a/b expression, and suggest that this region affects CAD progression by altering the dynamics of vascular cell proliferation.
Abstract: Sequence polymorphisms in a 58-kilobase (kb) interval on chromosome 9p21 confer a markedly increased risk of coronary artery disease (CAD), the leading cause of death worldwide. The variants have a substantial effect on the epidemiology of CAD and other life-threatening vascular conditions because nearly one-quarter of Caucasians are homozygous for risk alleles. However, the risk interval is devoid of protein-coding genes and the mechanism linking the region to CAD risk has remained enigmatic. Here we show that deletion of the orthologous 70-kb non-coding interval on mouse chromosome 4 affects cardiac expression of neighbouring genes, as well as proliferation properties of vascular cells. Chr4(Delta70kb/Delta70kb) mice are viable, but show increased mortality both during development and as adults. Cardiac expression of two genes near the non-coding interval, Cdkn2a and Cdkn2b, is severely reduced in chr4(Delta70kb/Delta70kb) mice, indicating that distant-acting gene regulatory functions are located in the non-coding CAD risk interval. Allele-specific expression of Cdkn2b transcripts in heterozygous mice showed that the deletion affects expression through a cis-acting mechanism. Primary cultures of chr4(Delta70kb/Delta70kb) aortic smooth muscle cells exhibited excessive proliferation and diminished senescence, a cellular phenotype consistent with accelerated CAD pathogenesis. Taken together, our results provide direct evidence that the CAD risk interval has a pivotal role in regulation of cardiac Cdkn2a/b expression, and suggest that this region affects CAD progression by altering the dynamics of vascular cell proliferation.
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TL;DR: The Naegleria genome facilitates substantially broader phylogenomic comparisons of free-living eukaryotes than previously possible, allowing us to identify thousands of genes likely present in the pan-eukaryotic ancestor, with 40% likely eukARYotic inventions.
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TL;DR: In this article, the authors used spectroscopic imaging-scanning tunneling microscopy to study the electronic structure of a representative compound CaFe1.94Co0.06As2 in the "parent" state from which this superconductivity emerges.
Abstract: The mechanism of high-temperature superconductivity in the newly discovered iron-based superconductors is unresolved. We use spectroscopic imaging-scanning tunneling microscopy to study the electronic structure of a representative compound CaFe1.94Co0.06As2 in the "parent" state from which this superconductivity emerges. Static, unidirectional electronic nanostructures of dimension eight times the inter-iron-atom distance a(Fe-Fe) and aligned along the crystal a axis are observed. In contrast, the delocalized electronic states detectable by quasiparticle interference imaging are dispersive along the b axis only and are consistent with a nematic alpha2 band with an apparent band folding having wave vector q vector congruent with +/-2pi/8a(Fe-Fe) along the a axis. All these effects rotate through 90 degrees at orthorhombic twin boundaries, indicating that they are bulk properties. As none of these phenomena are expected merely due to crystal symmetry, underdoped ferropnictides may exhibit a more complex electronic nematic state than originally expected.
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TL;DR: The present perspective paper briefly reviews the mechanisms underlying nanoparticle sintering, and gives an overview of emerging approaches towards stabilizing metal nanoparticles for heterogeneous catalysis, highlighting the current needs for further developments in the field.
Abstract: Metal nanoparticles hold great promise for heterogeneous catalysis due to their high dispersion, large concentration of highly undercoordinated surface sites, and the presence of quantum confinement effects, which can drastically alter their reactivity. However, the poor thermal stability of nano-sized particles limits their use to low temperature conditions and constitutes one of the key hurdles towards industrial application. The present perspective paper briefly reviews the mechanisms underlying nanoparticle sintering, and then gives an overview of emerging approaches towards stabilizing metal nanoparticles for heterogeneous catalysis. We conclude by highlighting the current needs for further developments in the field.
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TL;DR: In this paper, the power generation from these nanochannels placed between two potassium chloride solutions with various combinations of concentrations was investigated, and the highest power density measured was 7.7 W/m2.
Abstract: In an aqueous solution, the surface of inorganic nanochannels acquires charges from ionization, ion adsorption, and ion dissolution. These surface charges draw counter-ions toward the surface and repel co-ions. In the presence of a concentration gradient, counter-ions are transported through nanochannels much more easily than co-ions, which results in a net charge migration of one type of ions. The Gibbs free energy of mixing, which forces ion diffusion, thus can be converted into electrical energy by using inorganic ion-selective nanochannels. Silica nanochannels with heights of 4, 26, and 80 nm were used in this study. We experimentally investigated the power generation from these nanochannels placed between two potassium chloride solutions with various combinations of concentrations. The power generation per unit channel volume increases when the concentration gradient increases, and also increases as channel height decreases. The highest power density measured was 7.7 W/m2. Our data also indicate that the energy conversion efficiency and the ion selectivity increase with a decrease of concentrations and channel height. The best efficiency obtained was 31%. Power generation from concentration gradients in inorganic ion-selective nanochannels could be used in a variety of applications, including micro batteries and micro power generators.
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TL;DR: A series of CdSe quantum dot-sensitized TiO2 heterostructures have been synthesized, characterized, and tested for the photocatalytic reduction of CO2 in the presence of H2O.
Abstract: A series of CdSe quantum dot (QD)-sensitized TiO2 heterostructures have been synthesized, characterized, and tested for the photocatalytic reduction of CO2 in the presence of H2O. Our results show that these heterostructured materials are capable of catalyzing the photoreduction of CO2 using visible light illumination (λ > 420 nm) only. The effect of removing surfactant caps from the CdSe QDs by annealing and using a hydrazine chemical treatment have also been investigated. The photocatalytic reduction process is followed using infrared spectroscopy to probe the gas-phase reactants and gas chromatography to detect the products. Gas chromatographic analysis shows that the primary reaction product is CH4, with CH3OH, H2, and CO observed as secondary products. Typical yields of the gas-phase products after visible light illumination (λ > 420 nm) were 48 ppm g−1 h−1 of CH4, 3.3 ppm g−1 h−1 of CH3OH (vapor), and trace amounts of CO and H2.
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TL;DR: In this article, the authors reviewed the interconnect materials and coatings for metallic interconnects for solid oxide fuel cells (SOFCs) and compared them with other SOFC ceramic components, and found that the requirements of interconnect are the most demanding, i.e., to maintain high electrical conductivity, good stability in both reducing and oxidizing atmospheres, and close coefficient of thermal expansion (CTE) match and good compatibility with other SoFC ceramic component.
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TL;DR: A similarity-based approach for prognostics of the Remaining Useful Life (RUL) of a system, i.e. the lifetime remaining between the present and the instance when the system can no longer perform its function.
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TL;DR: In this paper, a comparison of statistical models based on time series applied to predict half daily values of global solar irradiance with a temporal horizon of 3 days is presented. And the validation process shows that all models essayed improve persistence.
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TL;DR: Metagenomic analysis of a stressed groundwater microbial community reveals that prolonged exposure to high concentrations of heavy metals, nitric acid and organic solvents has resulted in a massive decrease in species and allelic diversity as well as a significant loss of metabolic diversity.
Abstract: Understanding adaptation of biological communities to environmental change is a central issue in ecology and evolution. Metagenomic analysis of a stressed groundwater microbial community reveals that prolonged exposure to high concentrations of heavy metals, nitric acid and organic solvents ( approximately 50 years) has resulted in a massive decrease in species and allelic diversity as well as a significant loss of metabolic diversity. Although the surviving microbial community possesses all metabolic pathways necessary for survival and growth in such an extreme environment, its structure is very simple, primarily composed of clonal denitrifying gamma- and beta-proteobacterial populations. The resulting community is overabundant in key genes conferring resistance to specific stresses including nitrate, heavy metals and acetone. Evolutionary analysis indicates that lateral gene transfer could have a key function in rapid response and adaptation to environmental contamination. The results presented in this study have important implications in understanding, assessing and predicting the impacts of human-induced activities on microbial communities ranging from human health to agriculture to environmental management, and their responses to environmental changes.
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University of Düsseldorf1, Istituto Superiore di Sanità2, Charité3, Harvard University4, Boston Children's Hospital5, Casa Sollievo della Sofferenza6, Goethe University Frankfurt7, University of Freiburg8, Partners HealthCare9, St George's Hospital10, University of Turin11, Catholic University of the Sacred Heart12, Charles University in Prague13, United States Department of Energy14, Lawrence Berkeley National Laboratory15, Icahn School of Medicine at Mount Sinai16, Max Planck Society17
TL;DR: Evidence is provided for an obligate dependency on proper NRAS function in human development and growth and for germline NRAS mutations conferring enhanced stimulus-dependent MAPK activation in some cases of Noonan syndrome.
Abstract: Noonan syndrome, a developmental disorder characterized by congenital heart defects, reduced growth, facial dysmorphism and variable cognitive deficits, is caused by constitutional dysregulation of the RAS-MAPK signaling pathway. Here we report that germline NRAS mutations conferring enhanced stimulus-dependent MAPK activation account for some cases of this disorder. These findings provide evidence for an obligate dependency on proper NRAS function in human development and growth.
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TL;DR: The view that gravity is a manifestation of space-time curvature, an underlying principle of general relativity that has come under scrutiny in connection with the search for a theory of quantum gravity, is supported.
Abstract: A central prediction of general relativity states that a gravitational field slows the running of a clock. Previous measurements of this effect, known as gravitational redshift, have involved clocks at different heights, and until now this has been the least accurately determined of the parameters supporting curved space-time theories. Now this prediction has been confirmed to unprecedented accuracy using the results of lab experiments performed more than 10 years ago in a study of the acceleration of free fall. Analysis of the data — on quantum interference of single caesium atoms bobbing up and down in an atomic fountain — provides a measurement based on matter-wave interference that improves accuracy by a factor of 10,000. One of the central predictions of general relativity is that a clock in a gravitational potential well runs more slowly than a similar clock outside the well. This effect, known as gravitational redshift, has been measured using clocks on a tower, an aircraft and a rocket, but here, laboratory experiments based on quantum interference of atoms are shown to produce a much more precise measurement. One of the central predictions of metric theories of gravity, such as general relativity, is that a clock in a gravitational potential U will run more slowly by a factor of 1 + U/c2, where c is the velocity of light, as compared to a similar clock outside the potential1. This effect, known as gravitational redshift, is important to the operation of the global positioning system2, timekeeping3,4 and future experiments with ultra-precise, space-based clocks5 (such as searches for variations in fundamental constants). The gravitational redshift has been measured using clocks on a tower6, an aircraft7 and a rocket8, currently reaching an accuracy of 7 × 10-5. Here we show that laboratory experiments based on quantum interference of atoms9,10 enable a much more precise measurement, yielding an accuracy of 7 × 10-9. Our result supports the view that gravity is a manifestation of space-time curvature, an underlying principle of general relativity that has come under scrutiny in connection with the search for a theory of quantum gravity11. Improving the redshift measurement is particularly important because this test has been the least accurate among the experiments that are required to support curved space-time theories1.
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TL;DR: In this paper, a review summarizes the recent progress in the understanding of the geometrical and electronic structure of the anchor bond and the involvement of gold adatoms at all stages of alkanethiol self-assembly, including the dissociation of the disulfide (S−S) and hydrogen-sulfide(S−H) bonds and subsequent formation of the self-assembled structure.
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TL;DR: In this paper, a rapid and facile synthesis route to the monodisperse spherical MCM-48 mesoporous silica nanoparticles (MSN) with cubic Ia3d mesostructure is developed based on the modified Stober method.
Abstract: A rapid and facile synthesis route to the monodisperse spherical MCM-48 mesoporous silica nanoparticles (MSN) with cubic Ia3d mesostructure is developed based on the modified Stober method. The phase domain of MCM-48-type MSNs can be extended by controlling the stirring rate and molar ratios of silica source and surfactant. The formation of monodispersed spherical MCM-48-type MSNs is obtained using triblock copolymer Pluronic F127 as a particle size designer. The average size of monodisperse spherical MSN can be controlled within the range of 70−500 nm depending on the amount of F127. Moreover, the pore diameter of MSNs can be precisely controllable in pore diameters from 2.3 to 3.3 nm using different alkyl chain surfactants and simple posthydrothermal treatment. An investigation of MCM-48-type MSN materials using powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and nitrogen physisorption clearly reveals that MSNs show high specific surface area, high pore volumes...
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TL;DR: To assess the progression of the infant microbiota toward an adult-like state and to evaluate the contribution of maternal GIT bacteria to the infant gut, this work compares the infant’s microbiota with that of the mother at 1 and 11 months after delivery.
Abstract: Colonization of the gastrointestinal tract (GIT) of human infants with a suitable microbial community is essential for numerous aspects of health, but the progression of events by which this microbiota becomes established is poorly understood Here, we investigate two previously unexplored areas of microbiota development in infants: the deployment of functional capabilities at the community level and the population genetics of its most abundant genera To assess the progression of the infant microbiota toward an adult-like state and to evaluate the contribution of maternal GIT bacteria to the infant gut, we compare the infant’s microbiota with that of the mother at 1 and 11 months after delivery These comparisons reveal that the infant’s microbiota rapidly acquires and maintains the range of gene functions present in the mother, without replicating the phylogenetic composition of her microbiota Microdiversity analyses for Bacteroides and Bifidobacterium, two of the main microbiota constituents, reveal that by 11 months, the phylotypes detected in the infant are distinct from those in the mother, although the maternal Bacteroides phylotypes were transiently present at 1 month of age The configuration of genetic variants within these genera reveals populations far from equilibrium and likely to be undergoing rapid growth, consistent with recent population turnovers Such compositional turnovers and the associated loss of maternal phylotypes should limit the potential for long-term coadaptation between specific bacterial and host genotypes
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TL;DR: It is demonstrated, using single-molecule experiments, that an RNA enzyme folds into multiple distinct native states that interconvert on a timescale much longer than that of catalysis.
Abstract: Just as the funnel hypothesis is used to describe protein folding, it has been suggested that the process of RNA folding involves a rugged energy terrain in which the molecule samples different valleys until it finds the single lowest-energy state — the global minimum. In this study, Solomatin et al. report the surprising finding that a group I intron RNA can stably exist in one of several catalytically active native states (representing local minima). These RNA conformations are able to interconvert, which promises interesting new avenues of study to determine how this occurs, and how the different native states vary at the molecular level. The 'thermodynamic hypothesis' proposes that the sequence of a biological macromolecule defines its folded, active structure as a global energy minimum in the folding landscape; however, it is not clear whether there is only one global minimum or several local minima corresponding to active conformations. Here, using single-molecule experiments, an RNA enzyme is shown to fold into multiple distinct native states that interconvert. According to the ‘thermodynamic hypothesis’, the sequence of a biological macromolecule defines its folded, active (or ‘native’) structure as a global energy minimum in the folding landscape1,2. However, the enormous complexity of folding landscapes of large macromolecules raises the question of whether there is in fact a unique global minimum corresponding to a unique native conformation or whether there are deep local minima corresponding to alternative active conformations3. The folding of many proteins is well described by two-state models, leading to highly simplified representations of protein folding landscapes with a single native conformation4,5. Nevertheless, accumulating experimental evidence suggests a more complex topology of folding landscapes with multiple active conformations that can take seconds or longer to interconvert6,7,8. Here we demonstrate, using single-molecule experiments, that an RNA enzyme folds into multiple distinct native states that interconvert on a timescale much longer than that of catalysis. These data demonstrate that severe ruggedness of RNA folding landscapes extends into conformational space occupied by native conformations.
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TL;DR: The authors reviewed the historical development of gasification and compared the process to combustion, and provided a short discussion on integrated gasification, combined cycle processes, and the most likely gas composition from each of the technologies when using a variety of fuels under different conditions from air blown to oxygen blown and atmospheric pressure to several atmospheres.
Abstract: This paper has been put together to provide a single source document that not only reviews the historical development of gasification but also compares the process to combustion. It also provides a short discussion on integrated gasification and combined cycle processes. The major focus of the paper is to describe the twelve major gasifiers being marketed today. Some of these are already fully developed while others are in various stages of development. The hydrodynamics and kinetics of each are reviewed along with the most likely gas composition from each of the technologies when using a variety of fuels under different conditions from air blown to oxygen blown and atmospheric pressure to several atmospheres.
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TL;DR: In this article, the stability and hydrogen desorption of NaBH4 were investigated using the van't Hoff equation and the density functional theory approach, and a decomposition temperature of Tdec = 534 ± 10 °C at 1 bar of H2 was obtained.
Abstract: We investigate the stability and hydrogen desorption of NaBH4. Dynamic pcT (pressure, concentration, and temperature) measurements under constant hydrogen flows are used to determine thermodynamic parameters of reaction. From the van’t Hoff equation the enthalpy and entropy of reaction, −108 ± 3 kJ mol−1 of H2 and 133 ± 3 J K−1 mol−1 of H2 released, are obtained, respectively. This corresponds to a decomposition temperature of Tdec = 534 ± 10 °C at 1 bar of H2. The decomposition thereby occurs in one step; i.e., only one plateau is visible in the pressure composition isotherms. Elemental Na is identified as the major solid component in the residue by X-ray diffraction. The experimental results are discussed on the basis of theoretical calculations using the density functional theory approach. Starting from the optimized structure of the cubic α-phase of NaBH4, we discuss possible decomposition routes involving elemental Na and B as well as Na−H and Na−B binary compounds as residual products.
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TL;DR: In this article, the authors present a method that, based on only one power flow solution and one matrix operation, can directly determine the maximum power that can be injected by distributed generators into each system bus without leading to steady-state voltage violations.
Abstract: One of the main factors that may limit the penetration level of distributed generation (DG) in typical distribution systems is the steady-state voltage rise. The maximum amount of active power supplied by distributed generators into each system bus without causing voltage violations can be determined by using repetitive power flow studies. However, this task is laborious and usually time-consuming, since different loading level and generation operation modes have to be evaluated. Therefore this article presents a method that, based on only one power flow solution and one matrix operation, can directly determine the maximum power that can be injected by distributed generators into each system bus without leading to steady-state voltage violations. This method is based on the determination of voltage sensitivities from a linearised power system model. In addition, this article proposes a numerical index to quantify the responsibility of each generator for the voltage level rise in a multi-DG system. Based on this index, utility managers can decide which generators, and in which degree, should be penalised by the voltage rise or rewarded by not depreciating the voltage profile. The method is applied to a 70-bus distribution network. The results are compared with those obtained by repetitive power flow solutions in order to validate the proposed method.