1,519 research outputs found

    Comment on `On the Quantum Theory of Molecules' [J. Chem.Phys. {\bf 137}, 22A544 (2012)]

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    In our previous paper [J. Chem.Phys. {\bf 137}, 22A544 (2012)] we argued that the Born-Oppenheimer approximation could not be based on an exact transformation of the molecular Schr\"{o}dinger equation. In this Comment we suggest that the fundamental reason for the approximate nature of the Born-Oppenheimer model is the lack of a complete set of functions for the electronic space, and the need to describe the continuous spectrum using spectral projection.Comment: 2 page

    Rent Control in California: Policy Review

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    The largest number of housing units subject to rent control can be found in California, but the policy environment is quite complex and is characterized by a series of interacting state and local laws. This complexity represents a significant barrier for researchers and policymakers seeking a clear and accurate picture of how rent control works in California, and how it incentivizes different behaviors among landlords and tenants alike. This technical report surveys rent control rules in California, with special attention paid to the recent statewide rent caps, historic developments, and the systems in Los Angeles and San Francisco. This report should be regarded as a selective snapshot of the current system, and researchers interested in pursuing their own analyses involving the California systems are encouraged to conduct supplemental legal research. This paper will be updated on a rolling basis as further information comes to light

    Statistical analysis to develop a three-dimensional surface model of a midsize-male foot

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    A representative midsize-male foot was generated via a statistical analysis of foot scans from 107 men with widely varying body size. Seventy-two surface landmarks were manually extracted from the original scan data. A template fitting method was used to represent each scan with a homologous mesh. A principal component analysis and least-squares linear regression were used to generate a foot surface model with landmarks using a reference stature of 1755 mm and a body mass of 83.19 kg. The statistical model can be used to generate a wide range of male foot sizes and shapes.US Army Tank Automotive Research, Development, and Engineering Center (TARDEC)http://deepblue.lib.umich.edu/bitstream/2027.42/116596/1/103232.pdfDescription of 103232.pdf : Final repor

    Know the Star, Know the Planet. III. Discovery of Late-Type Companions to Two Exoplanet Host Stars

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    We discuss two multiple star systems that host known exoplanets: HD 2638 and 30 Ari B. Adaptive optics imagery revealed an additional stellar companion to both stars. We collected multi-epoch images of the systems with Robo-AO and the PALM-3000 adaptive optics systems at Palomar Observatory and provide relative photometry and astrometry. The astrometry indicates that the companions share common proper motion with their respective primaries. Both of the new companions have projected separations less than 30 AU from the exoplanet host star. Using the projected separations to compute orbital periods of the new stellar companions, HD 2638 has a period of 130 yrs and 30 Ari B has a period of 80 years. Previous studies have shown that the true period is most likely within a factor of three of these estimated values. The additional component to the 30 Ari makes it the second confirmed quadruple system known to host an exoplanet. HD 2638 hosts a hot Jupiter and the discovery of a new companion strengthens the connection between hot Jupiters and binary stars. We place the systems on a color-magnitude diagram and derive masses for the companions which turn out to be roughly 0.5 solar mass stars.Comment: Accepted to Astronomical Journal, 16 pages, 5 Figure

    Population III star formation in a Lambda CDM universe, I: The effect of formation redshift and environment on protostellar accretion rate

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    (abridged) We perform 12 extremely high resolution adaptive mesh refinement cosmological hydrodynamic simulations of Population III star formation in a Lambda CDM universe, varying the box size and large-scale structure, to understand systematic effects in the formation of primordial protostellar cores. We find results that are qualitatively similar to those observed previously. We observe that the threshold halo mass for formation of a Population III protostar does not evolve significantly with time in the redshift range studied (33 > z > 19) but exhibits substantial scatter due to different halo assembly histories: Halos which assembled more slowly develop cooling cores at lower mass than those that assemble more rapidly, in agreement with Yoshida et al. (2003). We do, however, observe significant evolution in the accretion rates of Population III protostars with redshift, with objects that form later having higher maximum accretion rates, with a variation of two orders of magnitude (10^-4 - 10^-2 Msolar/year). This can be explained by considering the evolving virial properties of the halos with redshift and the physics of molecular hydrogen formation at low densities. Our result implies that the mass distribution of Population III stars inferred from their accretion rates may be broader than previously thought, and may evolve with redshift. Finally, we observe that our collapsing protostellar cloud cores do not fragment, consistent with previous results, which suggests that Population III stars which form in halos of mass 10^5 - 10^6 Msun always form in isolation.Comment: Accepted by The Astrophysical Journal. Some minor changes. 65 pages, 3 tables, 21 figures (3 color). To appear in January 1, 2007 issu

    Genome-Wide Occupancy of SREBP1 and Its Partners NFY and SP1 Reveals Novel Functional Roles and Combinatorial Regulation of Distinct Classes of Genes

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    The sterol regulatory element-binding protein (SREBP) family member SREBP1 is a critical transcriptional regulator of cholesterol and fatty acid metabolism and has been implicated in insulin resistance, diabetes, and other diet-related diseases. We globally identified the promoters occupied by SREBP1 and its binding partners NFY and SP1 in a human hepatocyte cell line using chromatin immunoprecipitation combined with genome tiling arrays (ChIP-chip). We find that SREBP1 occupies the promoters of 1,141 target genes involved in diverse biological pathways, including novel targets with roles in lipid metabolism and insulin signaling. We also identify a conserved SREBP1 DNA-binding motif in SREBP1 target promoters, and we demonstrate that many SREBP1 target genes are transcriptionally activated by treatment with insulin and glucose using gene expression microarrays. Finally, we show that SREBP1 cooperates extensively with NFY and SP1 throughout the genome and that unique combinations of these factors target distinct functional pathways. Our results provide insight into the regulatory circuitry in which SREBP1 and its network partners coordinate a complex transcriptional response in the liver with cues from the diet

    Can We Actually Improve Resident Wellness? Pilot Data from a Longitudinal Wellness Curriculum for Emergency Medicine Residents

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    Objectives/Background: The wellness of resident physicians, particularly in emergency medicine with its high rate of burnout, has become of paramount importance to residency programs. This study aims to evaluate the effects of the implementation of an evidence-based wellness curriculum on self-reported resident wellness across three emergency medicine residency programs. Methods: This is a prospective, interventional study of the impact of a well-defined, longitudinal wellness curriculum administered to all categorical residents in three emergency medicine residency programs. Anonymous surveys incorporating the Perceived Stress Scale (PSS) and the Connor-Davidson Resilience Scale (CD-RISC) were administered before and after implementation of the wellness curriculum. The curriculum consisted of three modules (Introduction to Wellness, Dealing with Medical Errors, and Shame and Debriefing Traumatic Events in the Emergency Department) over 3 months. Participation was anonymous and voluntary, and all data collection and analysis were provided by a third-party not affiliated with residency program leadership. Results: 64 out of 114 (56.1%) residents completed the pre-intervention survey and 58 (50.9%) residents completed the post-intervention survey. The mean of the PSS pre-intervention was 15.5 (SD±4.85) and post-intervention was 15.4 (SD±5.42) points while the mean of the CD-RISC was 75.1 (SD±8.9) pre-intervention and was 74.9 (SD±9.88) post-intervention. Both the PSS and CD-RISC scores showed an improvement post-intervention although only the CD-RISC was statistically significant (p=0.015). There was no statistically significant difference on either scoring system with respect to gender, post-graduate year of training, or residency training site. Conclusions: Implementation of a wellness curriculum in our cohort of residents was shown to improve resilience amongst residents. Gender, post-graduate year of training, and residency training site did not affect these outcomes. This represents the first longitudinal residency wellness curriculum in emergency medicine that has a proven beneficial effect on residents

    A Laboratory Model of a Hydrogen/Oxygen Engine for Combustion and Nozzle Studies

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    A small laboratory diagnostic thruster was developed to augment present low thrust chemical rocket optical and heat flux diagnostics at the NASA Lewis Research Center. The objective of this work was to evaluate approaches for the use of temperature and pressure sensors for the investigation of low thrust rocket flow fields. The nominal engine thrust was 110 N. Tests were performed at chamber pressures of about 255 kPa, 370 kPa, and 500 kPa with oxidizer to fuel mixture ratios between 4.0 and 8.0. Two gaseous hydrogen/gaseous oxygen injector designs were tested with 60 percent and 75 percent fuel film cooling. The thruster and instrumentation designs were proven to be effective via hot fire testing. The thruster diagnostics provided inner wall temperature and static pressure measurements which were compared to the thruster global performance data. For several operating conditions, the performance data exhibited unexpected trends which were correlated with changes in the axial wall temperature distribution. Azimuthal temperature distributions were found to be a function of operating conditions and hardware configuration. The static pressure profiles showed that no severe pressure gradients were present in the rocket. The results indicated that small differences in injector design can result in dramatically different thruster performance and wall temperature behavior, but that these injector effects may be overshadowed by operating at a high fuel film cooling rate

    Can Galvanic Vestibular Stimulation Reduce Simulator Adaptation Syndrome?

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    Electrical stimulation of the vestibular sensory system during virtual environment simulations has been proposed as a method to reduce the incidence of simulator adaptation syndrome (SAS). However, there is limited empirical evidence to support this hypothesis. It is especially important to provide vestibular stimulation in driving simulators because an absence of vestibular cues may alter driver behaviour and reduce vehicle control. This study examined the application of galvanic vestibular stimulation (GVS) as a technique to reduce symptoms of SAS and improve vehicular control in a fixed-based driving simulator. Nineteen participants drove two visually distinct virtual environments (high and low visual cues). In addition, each of these worlds was experienced with and without GVS. Post-drive scores on the Simulator Sickness Questionnaire (SSQ) were used to evaluate the effect of GVS on SAS. In addition, three driving variables were measured to examine driving performance: steering variability, lane departures, and average vehicular speed. GVS application while driving resulted in significant decreases in total SSQ and disorientation symptoms. Greater vehicular control was also observed (as shown by reduced steering variability) when GVS was used in combination with visual cues along the simulated edge of the road. These results support that GVS may be used in fixed-base driving simulators to create vestibular motion cues and reduce SAS

    Particle Backtracking Improves Breeding Subpopulation Discrimination and Natal-Source Identification in Mixed Populations

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    We provide a novel method to improve the use of natural tagging approaches for subpopulation discrimination and source-origin identification in aquatic and terrestrial animals with a passive dispersive phase. Our method integrates observed site-referenced biological information on individuals in mixed populations with a particle-tracking model to retrace likely dispersal histories prior to capture (i.e., particle backtracking). To illustrate and test our approach, we focus on western Lake Erie\u27s yellow perch (Perca flavescens) population during 2006-2007, using microsatellite DNA and otolith microchemistry from larvae and juveniles as natural tags. Particle backtracking showed that not all larvae collected near a presumed hatching location may have originated there, owing to passive drift during the larval stage that was influenced by strong river-and wind-driven water circulation. Re-assigning larvae to their most probable hatching site (based on probabilistic dispersal trajectories from the particle backtracking model) improved the use of genetics and otolith microchemistry to discriminate among local breeding subpopulations. This enhancement, in turn, altered (and likely improved) the estimated contributions of each breeding subpopulation to the mixed population of juvenile recruits. Our findings indicate that particle backtracking can complement existing tools used to identify the origin of individuals in mixed populations, especially in flow-dominated systems
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