Showing papers by "Rutgers University published in 2009"
Kevork N. Abazajian1, Jennifer K. Adelman-McCarthy2, Marcel A. Agüeros3, S. Allam2 +220 more•Institutions (77)
TL;DR: A series of improvements to the spectroscopic reductions are described, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
Abstract: This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11,663 deg^2 of imaging data, with most of the ~2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry on a 120° long, 2°.5 wide stripe along the celestial equator in the Southern Galactic Cap, with some regions covered by as many as 90 individual imaging runs. We include a co-addition of the best of these data, going roughly 2 mag fainter than the main survey over 250 deg^2. The survey has completed spectroscopy over 9380 deg^2; the spectroscopy is now complete over a large contiguous area of the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog, reducing the rms statistical errors at the bright end to 45 milliarcseconds per coordinate. We further quantify a systematic error in bright galaxy photometry due to poor sky determination; this problem is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities.
5,665 citations
University of Georgia1, Rutgers University2, United States Department of Energy3, Stanford University4, University of California, Berkeley5, North China University of Science and Technology6, University of Zurich7, Clemson University8, University of Düsseldorf9, Cold Spring Harbor Laboratory10, Purdue University11, International Crops Research Institute for the Semi-Arid Tropics12, Texas A&M University13, Cornell University14, University of Illinois at Urbana–Champaign15, Mississippi State University16, National Institute for Biotechnology and Genetic Engineering17, United States Department of Agriculture18
TL;DR: An initial analysis of the ∼730-megabase Sorghum bicolor (L.) Moench genome is presented, placing ∼98% of genes in their chromosomal context using whole-genome shotgun sequence validated by genetic, physical and syntenic information.
Abstract: Sorghum, an African grass related to sugar cane and maize, is grown for food, feed, fibre and fuel. We present an initial analysis of the approximately 730-megabase Sorghum bicolor (L.) Moench genome, placing approximately 98% of genes in their chromosomal context using whole-genome shotgun sequence validated by genetic, physical and syntenic information. Genetic recombination is largely confined to about one-third of the sorghum genome with gene order and density similar to those of rice. Retrotransposon accumulation in recombinationally recalcitrant heterochromatin explains the approximately 75% larger genome size of sorghum compared with rice. Although gene and repetitive DNA distributions have been preserved since palaeopolyploidization approximately 70 million years ago, most duplicated gene sets lost one member before the sorghum-rice divergence. Concerted evolution makes one duplicated chromosomal segment appear to be only a few million years old. About 24% of genes are grass-specific and 7% are sorghum-specific. Recent gene and microRNA duplications may contribute to sorghum's drought tolerance.
2,809 citations
TL;DR: It is shown that NC-endophytes represent three distinct functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts, and key questions for future work in endophyte biology are highlighted.
Abstract: Summary 1 Summary All plants in natural ecosystems appear to be symbiotic with fungal endophytes. This highly diverse group of fungi can have profound impacts on plant communities through increasing fitness by conferring abiotic and biotic stress tolerance, increasing biomass and decreasing water consumption, or decreasing fitness by altering resource allocation. Despite more than 100 yr of research resulting in thousands of journal articles, the ecological significance of these fungi remains poorly characterized. Historically, two endophytic groups (clavicipitaceous (C) and nonclavicipitaceous (NC)) have been discriminated based on phylogeny and life history traits. Here, we show that NC-endophytes represent three distinct functional groups based on host colonization and transmission, in planta biodiversity and fitness benefits conferred to hosts. Using this framework, we contrast the life histories, interactions with hosts and potential roles in plant ecophysiology of C- and NC-endophytes, and highlight several key questions for future work in endophyte biology.
2,278 citations
30 Jul 2009
1,806 citations
TL;DR: A detailed description of the electronic properties, chemical state, and structure of uniform single and few-layered graphene oxide (GO) thin films at different stages of reduction is reported in this paper.
Abstract: A detailed description of the electronic properties, chemical state, and structure of uniform single and few-layered graphene oxide (GO) thin films at different stages of reduction is reported. The residual oxygen content and structure of GO are monitored and these chemical and structural characteristics are correlated to electronic properties of the thin films at various stages of reduction. It is found that the electrical characteristics of reduced GO do not approach those of intrinsic graphene obtained by mechanical cleaving because the material remains significantly oxidized. The residual oxygen forms sp3 bonds with carbon atoms in the basal plane such that the carbon sp2 bonding fraction in fully reduced GO is ∼0.80. The minority sp3 bonds disrupt the transport of carriers delocalized in the sp2 network, limiting the mobility, and conductivity of reduced GO thin films. Extrapolation of electrical conductivity data as a function of oxygen content reveals that complete removal of oxygen should lead to properties that are comparable to graphene.
1,646 citations
TL;DR: The recent state of the art CAD technology for digitized histopathology is reviewed and the development and application of novel image analysis technology for a few specific histopathological related problems being pursued in the United States and Europe are described.
Abstract: Over the past decade, dramatic increases in computational power and improvement in image analysis algorithms have allowed the development of powerful computer-assisted analytical approaches to radiological data. With the recent advent of whole slide digital scanners, tissue histopathology slides can now be digitized and stored in digital image form. Consequently, digitized tissue histopathology has now become amenable to the application of computerized image analysis and machine learning techniques. Analogous to the role of computer-assisted diagnosis (CAD) algorithms in medical imaging to complement the opinion of a radiologist, CAD algorithms have begun to be developed for disease detection, diagnosis, and prognosis prediction to complement the opinion of the pathologist. In this paper, we review the recent state of the art CAD technology for digitized histopathology. This paper also briefly describes the development and application of novel image analysis technology for a few specific histopathology related problems being pursued in the United States and Europe.
1,644 citations
TL;DR: It is found that bulk electric conduction in ferroelectric monodomain BiFeO3 crystals is highly nonlinear and unidirectional.
Abstract: Unidirectional electric current flow, such as that found in a diode, is essential for modern electronics. It usually occurs at asymmetric interfaces such as p-n junctions or metal/semiconductor interfaces with Schottky barriers. We report on a diode effect associated with the direction of bulk electric polarization in BiFeO3: a ferroelectric with a small optical gap edge of ∼2.2 electron volts. We found that bulk electric conduction in ferroelectric monodomain BiFeO3 crystals is highly nonlinear and unidirectional. This diode effect switches its direction when the electric polarization is flipped by an external voltage. A substantial visible-light photovoltaic effect is observed in BiFeO3 diode structures. These results should improve understanding of charge conduction mechanisms in leaky ferroelectrics and advance the design of switchable devices combining ferroelectric, electronic, and optical functionalities.
1,610 citations
TL;DR: In this article, a method for probing a target sequence of messenger ribonucleic acid molecules (mRNA's) in a fixed, permeabilized cell, including at least 30 non- overlapping probe binding regions of 15-100 nucleotides, was proposed.
Abstract: A method for probing a target sequence of messenger ribonucleic acid molecules (mRNA's) in a fixed, permeabilized cell, said target sequence including at least 30 non- overlapping probe binding regions of 15-100 nucleotides, comprising immersing said cell in an excess of at least 30 nucleic acid hybridization probes, each singly labeled with the same fluorescent label and each containing a nucleic acid sequence that is complementary to a different probe binding region of said target sequence; washing said fixed cell to remove unbound probes; and detecting fluorescence from said probes.
1,480 citations
TL;DR: Defective autophagy is a mechanism for p62 upregulation commonly observed in human tumors that contributes directly to tumorigenesis likely by perturbing the signal transduction adaptor function of p62-controlling pathways critical for oncogenesis.
1,466 citations
TL;DR: This work emphasizes the importance of regulated recycling in processes as diverse as cytokinesis, cell adhesion, morphogenesis, cell fusion, learning and memory.
Abstract: Endocytic recycling is coordinated with endocytic uptake to control the composition of the plasma membrane. Although much of our understanding of endocytic recycling has come from studies on the transferrin receptor, a protein internalized through clathrin-dependent endocytosis, increased interest in clathrin-independent endocytosis has led to the discovery of new endocytic recycling systems. Recent insights into the regulatory mechanisms that control endocytic recycling have focused on recycling through tubular carriers and the return to the cell surface of cargo that enters cells through clathrin-independent mechanisms. Recent work emphasizes the importance of regulated recycling in such diverse processes as cytokinesis, cell adhesion and morphogenesis, cell fusion, and learning and memory.
1,314 citations
TL;DR: It is found that selective elimination of SPW-Rs during post-training consolidation periods resulted in performance impairment in rats trained on a hippocampus-dependent spatial memory task, providing evidence for a prominent role of hippocampal SPW -Rs in memory consolidation.
Abstract: Sharp wave-ripple (SPW-R) complexes in the hippocampus-entorhinal cortex are believed to be important for transferring labile memories from the hippocampus to the neocortex for long-term storage. We found that selective elimination of SPW-Rs during post-training consolidation periods resulted in performance impairment in rats trained on a hippocampus-dependent spatial memory task. Our results provide evidence for a prominent role of hippocampal SPW-Rs in memory consolidation.
TL;DR: A highly luminescent microporous metal-organic framework is capable of very fast and reversible detection of the vapors of the nitroaromatic explosive 2,4-dinitrotoluene and the plastic explosive taggant 2,3-dimethyl-2,3 -dinitrobutane through redox fluorescence quenching with unprecedented sensitivity.
Abstract: Ein hoch empfindlicher Sensor: Mit dem intensiv lumineszierenden mikroporosen Metall-organischen Gerust [Zn2(bpdc)2(bpee)] (bpdc=4,4′-Biphenyldicarboxylat; bpee=1,2-Bipyridylethen) lassen sich Dampfe des Nitrosprengstoffs 2,4-Dinitrotoluol und von 2,3-Dimethyl-2,3-dinitrobutan, das Plastiksprengstoff als Markierung zugemischt wird, durch Redox-Fluoreszenzloschung sehr schnell, reversibel und mit unerreichter Empfindlichkeit nachweisen (siehe Spektren).
TL;DR: It is shown that the carboxy-terminal domain of EED specifically binds to histone tails carrying trimethyl-lysine residues associated with repressive chromatin marks, and that this leads to the allosteric activation of the methyltransferase activity of PRC2.
Abstract: Polycomb group proteins have an essential role in the epigenetic maintenance of repressive chromatin states. The gene-silencing activity of the Polycomb repressive complex 2 (PRC2) depends on its ability to trimethylate lysine 27 of histone H3 (H3K27) by the catalytic SET domain of the EZH2 subunit, and at least two other subunits of the complex: SUZ12 and EED. Here we show that the carboxy-terminal domain of EED specifically binds to histone tails carrying trimethyl-lysine residues associated with repressive chromatin marks, and that this leads to the allosteric activation of the methyltransferase activity of PRC2. Mutations in EED that prevent it from recognizing repressive trimethyl-lysine marks abolish the activation of PRC2 in vitro and, in Drosophila, reduce global methylation and disrupt development. These findings suggest a model for the propagation of the H3K27me3 mark that accounts for the maintenance of repressive chromatin domains and for the transmission of a histone modification from mother to daughter cells.
TL;DR: The two major nodes comprising the DMN are differentiated with respect to the specific brain systems with which they interact, suggesting greater heterogeneity within this network than is commonly appreciated.
Abstract: The default mode network (DMN), based in ventromedial prefrontal cortex (vmPFC) and posterior cingulate cortex (PCC), exhibits higher metabolic activity at rest than during performance of externally-oriented cognitive tasks. Recent studies have suggested that competitive relationships between the DMN and various task-positive networks involved in task performance are intrinsically represented in the brain in the form of strong negative correlations (anticorrelations) between spontaneous fluctuations in these networks. Most neuroimaging studies characterize the DMN as a homogenous network, thus few have examined the differential contributions of DMN components to such competitive relationships. Here we examined functional differentiation within the default mode network, with an emphasis on understanding competitive relationships between this and other networks. We used a seed correlation approach on resting-state data to assess differences in functional connectivity between these two regions and their anticorrelated networks. While the positively correlated networks for the vmPFC and PCC seeds largely overlapped, the anticorrelated networks for each showed striking differences. Activity in vmPFC negatively predicted activity in parietal visual spatial and temporal attention networks, whereas activity in PCC negatively predicted activity in prefrontal-based motor control circuits. Granger causality analyses suggest that vmPFC and PCC exert greater influence on their anticorrelated networks than the other way around, suggesting that these two default mode nodes may directly modulate activity in task-positive networks. Thus, the two major nodes comprising the default mode network are differentiated with respect to the specific brain systems with which they interact, suggesting greater heterogeneity within this network than is commonly appreciated.
TL;DR: In this paper, the authors examined the impact of innovation on organizational performance by analyzing innovative activity in a panel of 428 public service organizations in the UK over four years and found that consistency in adopting the same composition of innovation types over the years has no effect, and divergence from the industry norm in adopting innovation types could possibly be beneficial to organizational performance.
Abstract: Innovation research suggests that innovation types have different attributes, determinants, and effects. This study focuses on consequences of adoption of three types of innovation (service, technological process, and administrative process) in service organizations. Its main thesis is that the impact of innovation on organizational performance depends on compositions of innovation types over time. We examine this proposition by analysing innovative activity in a panel of 428 public service organizations in the UK over four years. Our findings suggest that focus on adopting a specific type of innovation every year is detrimental, consistency in adopting the same composition of innovation types over the years has no effect, and divergence from the industry norm in adopting innovation types could possibly be beneficial to organizational performance. We discuss the implications of these findings for theory and research on innovation types.
TL;DR: Evaluating how the functional status of autophagy influences tumorigenesis and treatment response is important will provide new approaches to cancer therapy and prevention.
Abstract: Macroautophagy (autophagy) is a lysosomal degradation pathway for the breakdown of intracellular proteins and organelles. Although constitutive autophagy is a homeostatic mechanism for intracellular recycling and metabolic regulation, autophagy is also stress responsive, in which it is important for the removal of damaged proteins and organelles. Autophagy thereby confers stress tolerance, limits damage, and sustains viability under adverse conditions. Autophagy is a tumor-suppression mechanism, yet it enables tumor cell survival in stress. Reconciling how loss of a prosurvival function can promote tumorigenesis, emerging evidence suggests that preservation of cellular fitness by autophagy may be key to tumor suppression. As autophagy is such a fundamental process, establishing how the functional status of autophagy influences tumorigenesis and treatment response is important. This is especially critical as many current cancer therapeutics activate autophagy. Therefore, efforts to understand and modulate the autophagy pathway will provide new approaches to cancer therapy and prevention.
TL;DR: There is considerable evidence that tea polyphenols, in particular (−)-epigallocatechin-3-gallate, inhibit enzyme activities and signal transduction pathways, resulting in the suppression of cell proliferation and enhancement of apoptosis, as well as the inhibition of cell invasion, angiogenesis and metastasis.
Abstract: Extracts of tea, especially green tea, and tea polyphenols have been shown to inhibit the formation and development of tumours at different organ sites in animal models. There is considerable evidence that tea polyphenols, in particular (-)-epigallocatechin-3-gallate, inhibit enzyme activities and signal transduction pathways, resulting in the suppression of cell proliferation and enhancement of apoptosis, as well as the inhibition of cell invasion,angiogenesis and metastasis. Here, we review these biological activities and existing data relating tea consumption to human cancer risk in an attempt to understand the potential use of tea for cancer prevention.
TL;DR: In this article, Kowalski et al. combined the CfA3 supernovae Type Ia (SNIa) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w.r.t.
Abstract: We combine the CfA3 supernovae Type Ia (SN Ia) sample with samples from the literature to calculate improved constraints on the dark energy equation of state parameter, w. The CfA3 sample is added to the Union set of Kowalski et al. to form the Constitution set and, combined with a BAO prior, produces 1 + w = 0.013+0.066 –0.068 (0.11 syst), consistent with the cosmological constant. The CfA3 addition makes the cosmologically useful sample of nearby SN Ia between 2.6 and 2.9 times larger than before, reducing the statistical uncertainty to the point where systematics play the largest role. We use four light-curve fitters to test for systematic differences: SALT, SALT2, MLCS2k2 (RV = 3.1), and MLCS2k2 (RV = 1.7). SALT produces high-redshift Hubble residuals with systematic trends versus color and larger scatter than MLCS2k2. MLCS2k2 overestimates the intrinsic luminosity of SN Ia with 0.7 < Δ < 1.2. MLCS2k2 with RV = 3.1 overestimates host-galaxy extinction while RV 1.7 does not. Our investigation is consistent with no Hubble bubble. We also find that, after light-curve correction, SN Ia in Scd/Sd/Irr hosts are intrinsically fainter than those in E/S0 hosts by 2σ, suggesting that they may come from different populations. We also find that SN Ia in Scd/Sd/Irr hosts have low scatter (0.1 mag) and reddening. Current systematic errors can be reduced by improving SN Ia photometric accuracy, by including the CfA3 sample to retrain light-curve fitters, by combining optical SN Ia photometry with near-infrared photometry to understand host-galaxy extinction, and by determining if different environments give rise to different intrinsic SN Ia luminosity after correction for light-curve shape and color.
Columbia University1, University of Miami2, University of North Carolina at Chapel Hill3, SUNY Downstate Medical Center4, University College London5, Cambridge University Hospitals NHS Foundation Trust6, University of California, San Francisco7, University of California, Los Angeles8, University of Alabama at Birmingham9, Rio de Janeiro State University10, University of Guadalajara11, University of Düsseldorf12, New York University13, University of Barcelona14, Shanghai Jiao Tong University15, University of Lisbon16, Stellenbosch University17, Guy's and St Thomas' NHS Foundation Trust18, Oregon Health & Science University19, University of Padua20, University of Leeds21, North Shore-LIJ Health System22, Northwestern University23, Medical University of South Carolina24, University of Birmingham25, Sun Yat-sen University26, Lille University of Science and Technology27, Charité28, Rutgers University29, Federal University of São Paulo30, University of Debrecen31, Imperial College London32, Emory University33, University of Liège34, University of Pittsburgh35, University of Paris36, University of the Witwatersrand37, California State University, Long Beach38, Royal Melbourne Hospital39, University of Texas Southwestern Medical Center40, Autonomous University of Barcelona41, Pennsylvania State University42, Johns Hopkins University43, University of Szeged44, Duke University45, University of Colorado Denver46, Harvard University47, University of Cape Town48, University of Malaya49, Peking Union Medical College50
TL;DR: Although most patients in both treatment groups experienced clinical improvement, the study did not meet its primary objective of showing that MMF was superior to IVC as induction treatment for lupus nephritis.
Abstract: Recent studies have suggested that mycophenolate mofetil (MMF) may offer advantages over intravenous cyclophosphamide (IVC) for the treatment of lupus nephritis, but these therapies have not been compared in an international randomized, controlled trial. Here, we report the comparison of MMF and IVC as induction treatment for active lupus nephritis in a multinational, two-phase (induction and maintenance) study. We randomly assigned 370 patients with classes III through V lupus nephritis to open-label MMF (target dosage 3 g/d) or IVC (0.5 to 1.0 g/m(2) in monthly pulses) in a 24-wk induction study. Both groups received prednisone, tapered from a maximum starting dosage of 60 mg/d. The primary end point was a prespecified decrease in urine protein/creatinine ratio and stabilization or improvement in serum creatinine. Secondary end points included complete renal remission, systemic disease activity and damage, and safety. Overall, we did not detect a significantly different response rate between the two groups: 104 (56.2%) of 185 patients responded to MMF compared with 98 (53.0%) of 185 to IVC. Secondary end points were also similar between treatment groups. There were nine deaths in the MMF group and five in the IVC group. We did not detect significant differences between the MMF and IVC groups with regard to rates of adverse events, serious adverse events, or infections. Although most patients in both treatment groups experienced clinical improvement, the study did not meet its primary objective of showing that MMF was superior to IVC as induction treatment for lupus nephritis.
TL;DR: The findings provide a solid foundation for continued examination of resting state fcMRI in typical and atypical populations, and short- and long-term measures of the consistency of global connectivity patterns were highly robust.
Abstract: Recent years have witnessed an upsurge in the usage of resting-state functional magnetic resonance imaging (fMRI) to examine functional connectivity (fcMRI), both in normal and pathological populations. Despite this increasing popularity, concerns about the psychologically unconstrained nature of the “resting-state” remain. Across studies, the patterns of functional connectivity detected are remarkably consistent. However, the test–retest reliability for measures of resting state fcMRI measures has not been determined. Here, we quantify the test–retest reliability, using resting scans from 26 participants at 3 different time points. Specifically, we assessed intersession (>5 months apart), intrasession ( nonsignificant), 2) correlation valence (positive > negative), and 3) network membership (default mode > task positive network). Short- and long-term measures of the consistency of global connectivity patterns were highly robust. Finally, hierarchical clustering solutions were highly reproducible, both across participants and sessions. Our findings provide a solid foundation for continued examination of resting state fcMRI in typical and atypical populations.
TL;DR: In this paper, the authors report results from a program to determine the Hubble constant to approximately 5% precision from a refurbished distance ladder based on extensive use of differential measurements using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) Camera 2 through the F160W filter on the Hubble Space Telescope (HST).
Abstract: This is the second of two papers reporting results from a program to determine the Hubble constant to ~5% precision from a refurbished distance ladder based on extensive use of differential measurements. Here we report observations of 240 Cepheid variables obtained with the Near-Infrared Camera and Multi-Object Spectrometer (NICMOS) Camera 2 through the F160W filter on the Hubble Space Telescope (HST). The Cepheids are distributed across six recent hosts of Type Ia supernovae (SNe Ia) and the maser galaxy NGC 4258, allowing us to directly calibrate the peak luminosities of the SNe Ia from the precise, geometric distance measurements provided by the masers. New features of our measurement include the use of the same instrument for all Cepheid measurements across the distance ladder and homogeneity of the Cepheid periods and metallicities, thus necessitating only a differential measurement of Cepheid fluxes and reducing the largest systematic uncertainties in the determination of the fiducial SN Ia luminosity. In addition, the NICMOS measurements reduce the effects of differential extinction in the host galaxies by a factor of ~5 over past optical data. Combined with a greatly expanded set of 240 SNe Ia at z < 0.1 which define their magnitude-redshift relation, we find H 0 = 74.2 ? 3.6 km s?1 Mpc?1, a 4.8% uncertainty including both statistical and systematic errors. To independently test the maser calibration, we use 10 individual parallax measurements of Galactic Cepheids obtained with the HST fine guidance sensor and find similar results. We show that the factor of 2.2 improvement in the precision of H 0 is a significant aid to the determination of the equation-of-state parameter of dark energy, w = P/(?c 2). Combined with the Wilkinson Microwave Anisotropy Probe five-year measurement of ? M h 2, we find w = ?1.12 ? 0.12 independent of any information from high-redshift SNe Ia or baryon acoustic oscillations (BAO). This result is also consistent with analyses based on the combination of high-redshift SNe Ia and BAO. The constraints on w(z) now including high-redshift SNe Ia and BAO are consistent with a cosmological constant and are improved by a factor of 3 due to the refinement in H 0 alone. We show that future improvements in the measurement of H 0 are likely and should further contribute to multi-technique studies of dark energy.
Mayo Clinic1, Wayne State University2, Virginia Commonwealth University3, Memorial Sloan Kettering Cancer Center4, University of Texas MD Anderson Cancer Center5, University of Florida6, University of Utah7, University of California, San Francisco8, Rutgers University9, Thomas Jefferson University10
TL;DR: AAPM Task Group 119 has produced quantitative confidence limits as baseline expectation values for IMRT commissioning and locally derived confidence limits that substantially exceed these baseline values may indicate the need for improved IM RT commissioning.
Abstract: AAPM Task Group 119 has produced quantitative confidence limits as baseline expectation values for IMRT commissioning. A set of test cases was developed to assess the overall accuracy of planning and delivery of IMRT treatments. Each test uses contours of targets and avoidance structures drawn within rectangular phantoms. These tests were planned, delivered, measured, and analyzed by nine facilities using a variety of IMRT planning and delivery systems. Each facility had passed the Radiological Physics Center credentialing tests for IMRT. The agreement between the planned and measured doses was determined using ion chamber dosimetry in high and low dose regions, film dosimetry on coronal planes in the phantom with all fields delivered, and planar dosimetry for each field measured perpendicular to the central axis. The planar dose distributions were assessed using gamma criteria of 3%/3 mm. The mean values and standard deviations were used to develop confidence limits for the test results using the concept confidence limit = /mean/ + 1.96sigma. Other facilities can use the test protocol and results as a basis for comparison to this group. Locally derived confidence limits that substantially exceed these baseline values may indicate the need for improved IMRT commissioning.
01 Mar 2009
TL;DR: Data collected in three phases from multiple sources revealed significant differences between management and employee perspectives of HPWSs and how the two perspectives relate to employee individual performance in the service context.
Abstract: Extant research on high-performance work systems (HPWSs) has primarily examined the effects of HPWSs on establishment or firm-level performance from a management perspective in manufacturing settings. The current study extends this literature by differentiating management and employee perspectives of HPWSs and examining how the two perspectives relate to employee individual performance in the service context. Data collected in three phases from multiple sources involving 292 managers, 830 employees, and 1,772 customers of 91 bank branches revealed significant differences between management and employee perspectives of HPWSs. There were also significant differences in employee perspectives of HPWSs among employees of different employment statuses and among employees of the same status. Further, employee perspective of HPWSs was positively related to individual general service performance through the mediation of employee human capital and perceived organizational support and was positively related to individual knowledge-intensive service performance through the mediation of employee human capital and psychological empowerment. At the same time, management perspective of HPWSs was related to employee human capital and both types of service performance. Finally, a branch's overall knowledge-intensive service performance was positively associated with customer overall satisfaction with the branch's service.
TL;DR: The quintessential collective quantum behaviour in two dimensions, the fractional quantum Hall effect (FQHE), has so far resisted observation in graphene despite intense efforts and theoretical predictions of its existence and it is believed that these results will open the door to the physics of FQHE and other collective behaviour in graphene.
Abstract: The fractional quantum Hall effect is a quintessential manifestation of the collective behaviour associated with strongly interacting charge carriers confined to two dimensions and subject to a strong magnetic field. It is predicted that the charge carriers present in graphene — an atomic layer of carbon that can be seen as the 'perfect' two-dimensional system — are subject to strong interactions. Nevertheless, the phenomenon had eluded experimental observation until now: in this issue two groups report fractional quantum Hall effect in suspended sheets of graphene, probed in a two-terminal measurement setup. The researchers also observe a magnetic-field-induced insulating state at low carrier density, which competes with the quantum Hall effect and limits its observation to the highest-quality samples only. These results pave the way for the study of the rich collective behaviour of Dirac fermions in graphene. The fractional quantum Hall effect (FQHE) is the quintessential collective quantum behaviour of charge carriers confined to two dimensions but it has not yet been observed in graphene, a material distinguished by the charge carriers' two-dimensional and relativistic character. Here, and in an accompanying paper, the FQHE is observed in graphene through the use of devices containing suspended graphene sheets; the results of these two papers open a door to the further elucidation of the complex physical properties of graphene. In graphene, which is an atomic layer of crystalline carbon, two of the distinguishing properties of the material are the charge carriers’ two-dimensional and relativistic character. The first experimental evidence of the two-dimensional nature of graphene came from the observation of a sequence of plateaus in measurements of its transport properties in the presence of an applied magnetic field1,2. These are signatures of the so-called integer quantum Hall effect. However, as a consequence of the relativistic character of the charge carriers, the integer quantum Hall effect observed in graphene is qualitatively different from its semiconductor analogue3. As a third distinguishing feature of graphene, it has been conjectured that interactions and correlations should be important in this material, but surprisingly, evidence of collective behaviour in graphene is lacking. In particular, the quintessential collective quantum behaviour in two dimensions, the fractional quantum Hall effect (FQHE), has so far resisted observation in graphene despite intense efforts and theoretical predictions of its existence4,5,6,7,8,9. Here we report the observation of the FQHE in graphene. Our observations are made possible by using suspended graphene devices probed by two-terminal charge transport measurements10. This allows us to isolate the sample from substrate-induced perturbations that usually obscure the effects of interactions in this system and to avoid effects of finite geometry. At low carrier density, we find a field-induced transition to an insulator that competes with the FQHE, allowing its observation only in the highest quality samples. We believe that these results will open the door to the physics of FQHE and other collective behaviour in graphene.
Proceedings Article•
07 Dec 2009TL;DR: It is shown that a high dimensional nonlinear function can be approximated by a global linear function with respect to this coding scheme, and the approximation quality is ensured by the locality of such coding.
Abstract: This paper introduces a new method for semi-supervised learning on high dimensional nonlinear manifolds, which includes a phase of unsupervised basis learning and a phase of supervised function learning. The learned bases provide a set of anchor points to form a local coordinate system, such that each data point x on the manifold can be locally approximated by a linear combination of its nearby anchor points, and the linear weights become its local coordinate coding. We show that a high dimensional nonlinear function can be approximated by a global linear function with respect to this coding scheme, and the approximation quality is ensured by the locality of such coding. The method turns a difficult nonlinear learning problem into a simple global linear learning problem, which overcomes some drawbacks of traditional local learning methods.
University of Chicago1, University of Washington2, Wayne State University3, Fermilab4, University of Copenhagen5, University of Queensland6, Rutgers University7, New Mexico State University8, University of Portsmouth9, University of Pennsylvania10, University of Cape Town11, Stanford University12, Ludwig Maximilian University of Munich13, Texas A&M University14, University of Tokyo15, Institute for the Physics and Mathematics of the Universe16, University of California, Berkeley17, Harvard University18, University of Notre Dame19, University of Göttingen20, Stockholm University21, Ohio State University22, Rochester Institute of Technology23, Johns Hopkins University24, Space Telescope Science Institute25, Pennsylvania State University26, University of Texas at Austin27
TL;DR: In this article, the authors present measurements of the Hubble diagram for 103 Type Ia supernovae with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey.
Abstract: We present measurements of the Hubble diagram for 103 Type Ia supernovae (SNe) with redshifts 0.04 < z < 0.42, discovered during the first season (Fall 2005) of the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. These data fill in the redshift "desert" between low- and high-redshift SN Ia surveys. Within the framework of the MLCS2K2 light-curve fitting method, we use the SDSS-II SN sample to infer the mean reddening parameter for host galaxies, RV = 2.18 ± 0.14stat ± 0.48syst, and find that the intrinsic distribution of host-galaxy extinction is well fitted by an exponential function, P(AV ) = exp(–AV /τV), with τV = 0.334 ± 0.088 mag. We combine the SDSS-II measurements with new distance estimates for published SN data from the ESSENCE survey, the Supernova Legacy Survey (SNLS), the Hubble Space Telescope (HST), and a compilation of Nearby SN Ia measurements. A new feature in our analysis is the use of detailed Monte Carlo simulations of all surveys to account for selection biases, including those from spectroscopic targeting. Combining the SN Hubble diagram with measurements of baryon acoustic oscillations from the SDSS Luminous Red Galaxy sample and with cosmic microwave background temperature anisotropy measurements from the Wilkinson Microwave Anisotropy Probe, we estimate the cosmological parameters w and ΩM, assuming a spatially flat cosmological model (FwCDM) with constant dark energy equation of state parameter, w. We also consider constraints upon ΩM and ΩΛ for a cosmological constant model (ΛCDM) with w = –1 and non-zero spatial curvature. For the FwCDM model and the combined sample of 288 SNe Ia, we find w = –0.76 ± 0.07(stat) ± 0.11(syst), ΩM = 0.307 ± 0.019(stat) ± 0.023(syst) using MLCS2K2 and w = –0.96 ± 0.06(stat) ± 0.12(syst), ΩM = 0.265 ± 0.016(stat) ± 0.025(syst) using the SALT-II fitter. We trace the discrepancy between these results to a difference in the rest-frame UV model combined with a different luminosity correction from color variations; these differences mostly affect the distance estimates for the SNLS and HST SNe. We present detailed discussions of systematic errors for both light-curve methods and find that they both show data-model discrepancies in rest-frame U band. For the SALT-II approach, we also see strong evidence for redshift-dependence of the color-luminosity parameter (β). Restricting the analysis to the 136 SNe Ia in the Nearby+SDSS-II samples, we find much better agreement between the two analysis methods but with larger uncertainties: w = –0.92 ± 0.13(stat)+0.10 –0.33(syst) for MLCS2K2 and w = –0.92 ± 0.11(stat)+0.07 –0.15 (syst) for SALT-II.
TL;DR: In this paper, the authors developed direct and moderating hypotheses for the relationship between innovation characteristics, manager characteristics, and innovation adoption in public organizations, and tested these hypotheses using survey data on the adoption of 25 innovations in 725 local governments in the United States and data from a panel of experts.
Abstract: Studies of the association between innovation characteristics and innovation adoption at the level of organization are scarce. This study develops direct and moderating hypotheses for the relationship between innovation characteristics, manager characteristics, and innovation adoption in public organizations. The hypotheses are tested using survey data on the adoption of 25 innovations in 725 local governments in the United States and data from a panel of experts. The findings suggest that both innovation characteristics and manager characteristics influence the adoption of innovation; however, they do not reveal significant moderating effects of manager characteristics on the relationship between innovation characteristics and innovation adoption. The implications of the findings are discussed for further research on innovation adoption in the public sector.
TL;DR: The authors conducted a meta-analysis of 729 elasticities taken from 34 different studies to make sense of the range of values for agglomeration economies found in the literature by identifying some key characteristics that affect the magnitude of the results obtained.
TL;DR: It is suggested that resting state fMRI can be used to investigate human amygdala networks at a greater level of detail than previously appreciated, allowing for the further advancement of translational models.
TL;DR: The orbital motion of electrons in a three-dimensional solid can generate a pseudoscalar magnetoelectric coupling theta, a fact that can be generalized to the many-particle wave function and defines the 3D topological insulator in terms of a topological ground-state response function.
Abstract: The orbital motion of electrons in a three-dimensional solid can generate a pseudoscalar magnetoelectric coupling $\ensuremath{\theta}$, a fact we derive for the single-particle case using a recent theory of polarization in weakly inhomogeneous materials. This polarizability $\ensuremath{\theta}$ is the same parameter that appears in the ``axion electrodynamics'' Lagrangian $\ensuremath{\Delta}{\mathcal{L}}_{EM}=(\ensuremath{\theta}{e}^{2}/2\ensuremath{\pi}h)\mathbf{E}\ifmmode\cdot\else\textperiodcentered\fi{}\mathbf{B}$, which is known to describe the unusual magnetoelectric properties of the three-dimensional topological insulator ($\ensuremath{\theta}=\ensuremath{\pi}$). We compute $\ensuremath{\theta}$ for a simple model that accesses the topological insulator and discuss its connection to the surface Hall conductivity. The orbital magnetoelectric polarizability can be generalized to the many-particle wave function and defines the 3D topological insulator, like the integer quantum Hall effect, in terms of a topological ground-state response function.