593 research outputs found
Emission estimates of HCFCs and HFCs in California from the 2010 CalNex study
The CalNex 2010 (California Research at the Nexus of Air Quality and Climate Change) study was designed to evaluate the chemical composition of air masses over key source regions in California. During May to June 2010, air samples were collected on board a National Oceanic and Atmospheric Administration (NOAA) WP-3D aircraft over the South Coast Air Basin of California (SoCAB) and the Central Valley (CV). This paper analyzes six effective greenhouse gases - chlorodifluoromethane (HCFC-22), 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), 2-chloro-1,1,1,2-tetrafluoroethane (HCFC-124), 1,1,1,2- tetrafluoroethane (HFC-134a), and 1,1-difluoroethane (HFC-152a) - providing the most comprehensive characterization of chlorofluorocarbon (CFC) replacement compound emissions in California. Concentrations of measured HCFCs and HFCs are enhanced greatly throughout the SoCAB and CV, with highest levels observed in the SoCAB: 310 ± 92 pptv for HCFC-22, 30.7 ± 18.6 pptv for HCFC-141b, 22.9 ± 2.0 pptv for HCFC-142b, 4.86 ± 2.56 pptv for HCFC-124, 109 ± 46.4 pptv for HFC-134a, and 91.2 ± 63.9 pptv for HFC-152a. Annual emission rates are estimated for all six compounds in the SoCAB using the measured halocarbon to carbon monoxide (CO) mixing ratios and CO emissions inventories. Emission rates of 3.05 ± 0.70 Gg for HCFC-22, 0.27 ± 0.07 Gg for HCFC-141b, 0.06 ± 0.01 Gg for HCFC-142b, 0.11 ± 0.03 Gg for HCFC-124, 1.89 ± 0.43 Gg for HFC-134a, and 1.94 ± 0.45 Gg for HFC-152b for the year 2010 are calculated for the SoCAB. These emissions are extrapolated from the SoCAB region to the state of California using population data. Results from this study provide a baseline emission rate that will help future studies determine if HCFC and HFC mitigation strategies are successful. Key PointsHCFC and HFC emissions are calculated for the year 2010 for the SoCABEmissions are extrapolated to the state of CaliforniaEmissions are calculated using CalNex field measurements © 2013. American Geophysical Union. All Rights Reserved
Adsorption in non interconnected pores open at one or at both ends: A reconsideration of the origin of the hysteresis phenomenon
We report on an experimental study of adsorption isotherme of nitrogen onto
porous silicon with non interconnected pores open at one or at both ends in
order to check for the first time the old (1938) but always current idea based
on Cohan's description which suggests that the adsorption of gaz should occur
reversibly in the first case and irreversibly in the second one. Hysteresis
loops, the shape of which is usually associated to interconnections in porous
media, are observed whether the pores are open at one or at both ends in
contradiction with Cohan's model.Comment: 5 pages, 4 EPS figure
Bayesian modeling of recombination events in bacterial populations
Background: We consider the discovery of recombinant segments jointly with their origins within multilocus DNA sequences from bacteria representing heterogeneous populations of fairly closely related species. The currently available methods for recombination detection capable of probabilistic characterization of uncertainty have a limited applicability in practice as the number of
strains in a data set increases.
Results: We introduce a Bayesian spatial structural model representing the continuum of origins over sites within the observed sequences, including a probabilistic characterization of uncertainty related to the origin of any particular site. To enable a statistically accurate and practically feasible approach to the analysis of large-scale data sets representing a single genus, we have developed a novel software tool (BRAT, Bayesian Recombination Tracker) implementing the model and the
corresponding learning algorithm, which is capable of identifying the posterior optimal structure and to estimate the marginal posterior probabilities of putative origins over the sites.
Conclusion: A multitude of challenging simulation scenarios and an analysis of real data from seven
housekeeping genes of 120 strains of genus Burkholderia are used to illustrate the possibilities
offered by our approach. The software is freely available for download at URL http://web.abo.fi/fak/
mnf//mate/jc/software/brat.html
Optimizing the post-graduate institutional program evaluation process
Abstract
Background
Reviewing program educational efforts is an important component of postgraduate medical education program accreditation. The post-graduate review process has evolved over time to include centralized oversight based on accreditation standards. The institutional review process and the impact on participating faculty are topics not well described in the literature.
Methods
We conducted multiple Plan-Do-Study-Act (PDSA) cycles to identify and implement areas for change to improve productivity in our institutional program review committee. We also conducted one focus group and six in-person interviews with 18 committee members to explore their perspectives on the committee’s evolution. One author (MLL) reviewed the transcripts and performed the initial thematic coding with a PhD level research associate and identified and categorized themes. These themes were confirmed by all participating committee members upon review of a detailed summary. Emergent themes were triangulated with the University of Michigan Medical School’s Admissions Executive Committee (AEC).
Results
We present an overview of adopted new practices to the educational program evaluation process at the University of Michigan Health System that includes standardization of meetings, inclusion of resident members, development of area content experts, solicitation of committed committee members, transition from paper to electronic committee materials, and focus on continuous improvement. Faculty and resident committee members identified multiple improvement areas including the ability to provide high quality reviews of training programs, personal and professional development, and improved feedback from program trainees.
Conclusions
A standing committee that utilizes the expertise of a group of committed faculty members and which includes formal resident membership has significant advantages over ad hoc or other organizational structures for program evaluation committees.http://deepblue.lib.umich.edu/bitstream/2027.42/117363/1/12909_2016_Article_586.pd
Metabolic flexibility as a major predictor of spatial distribution in microbial communities
A better understand the ecology of microbes and their role in the global ecosystem could be achieved if traditional ecological theories can be applied to microbes. In ecology organisms are defined as specialists or generalists according to the breadth of their niche. Spatial distribution is often used as a proxy measure of niche breadth; generalists have broad niches and a wide spatial distribution and specialists a narrow niche and spatial distribution. Previous studies suggest that microbial distribution patterns are contrary to this idea; a microbial generalist genus (Desulfobulbus) has a limited spatial distribution while a specialist genus (Methanosaeta) has a cosmopolitan distribution. Therefore, we hypothesise that this counter-intuitive distribution within generalist and specialist microbial genera is a common microbial characteristic. Using molecular fingerprinting the distribution of four microbial genera, two generalists, Desulfobulbus and the methanogenic archaea Methanosarcina, and two specialists, Methanosaeta and the sulfate-reducing bacteria Desulfobacter were analysed in sediment samples from along a UK estuary. Detected genotypes of both generalist genera showed a distinct spatial distribution, significantly correlated with geographic distance between sites. Genotypes of both specialist genera showed no significant differential spatial distribution. These data support the hypothesis that the spatial distribution of specialist and generalist microbes does not match that seen with specialist and generalist large organisms. It may be that generalist microbes, while having a wider potential niche, are constrained, possibly by intrageneric competition, to exploit only a small part of that potential niche while specialists, with far fewer constraints to their niche, are more capable of filling their potential niche more effectively, perhaps by avoiding intrageneric competition. We suggest that these counter-intuitive distribution patterns may be a common feature of microbes in general and represent a distinct microbial principle in ecology, which is a real challenge if we are to develop a truly inclusive ecology
Surprises in the Orbital Magnetic Moment and g-Factor of the Dynamic Jahn-Teller Ion C_{60}^-
We calculate the magnetic susceptibility and g-factor of the isolated
C_{60}^- ion at zero temperature, with a proper treatment of the dynamical
Jahn-Teller effect, and of the associated orbital angular momentum, Ham-reduced
gyromagnetic ratio, and molecular spin-orbit coupling. A number of surprises
emerge. First, the predicted molecular spin-orbit splitting is two orders of
magnitude smaller than in the bare carbon atom, due to the large radius of
curvature of the molecule. Second, this reduced spin-orbit splitting is
comparable to Zeeman energies, for instance, in X-band EPR at 3.39KGauss, and a
field dependence of the g-factor is predicted. Third, the orbital gyromagnetic
factor is strongly reduced by vibron coupling, and so therefore are the
effective weak-field g-factors of all low-lying states. In particular, the
ground-state doublet of C_{60}^- is predicted to show a negative g-factor of
\sim -0.1.Comment: 19 pages RevTex, 2 postscript figures include
Patterns of Gene Flow Define Species of Thermophilic Archaea
A genomic view of speciation in Archaea shows higher rates of gene flow within coexisting microbial species than between them
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Genetic fixity in the human major histocompatibility complex and block size diversity in the class I region including HLA-E
BACKGROUND: The definition of human MHC class I haplotypes through association of HLA-A, HLA-Cw and HLA-B has been used to analyze ethnicity, population migrations and disease association. RESULTS: Here, we present HLA-E allele haplotype association and population linkage disequilibrium (LD) analysis within the ~1.3 Mb bounded by HLA-B/Cw and HLA-A to increase the resolution of identified class I haplotypes. Through local breakdown of LD, we inferred ancestral recombination points both upstream and downstream of HLA-E contributing to alternative block structures within previously identified haplotypes. Through single nucleotide polymorphism (SNP) analysis of the MHC region, we also confirmed the essential genetic fixity, previously inferred by MHC allele analysis, of three conserved extended haplotypes (CEHs), and we demonstrated that commercially-available SNP analysis can be used in the MHC to help define CEHs and CEH fragments. CONCLUSION: We conclude that to generate high-resolution maps for relating MHC haplotypes to disease susceptibility, both SNP and MHC allele analysis must be conducted as complementary techniques
Mark Carney and the gendered political economy of British central banking
In this article we explore Mark Carney’s place in the gendered political economy of British central banking. We document the gendered narratives surrounding Carney around the time of his appointment as Governor of the Bank of England, suggesting that they worked to naturalise certain gender constructions in finance. We show how Carney seemingly had the ability to successfully embody a combination of two ideal-types of masculinity: both ‘transnational business masculinity’ and ‘traditional bourgeois masculinity’. We argue this contributed to three depoliticising moves, each of which gain their strength in part from the naturalisation of masculinities in finance, while obfuscating important questions of gendered finance. To elucidate the latter, we highlight some of the gendered outcomes that are obscured by the furore surrounding Carney’s character, suggesting that the monetary and financial stability concerns of the Bank under his stewardship are likely to reproduce the uneven and exploitative relations of gendered finance
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