215 research outputs found
Limb Darkening and Planetary Transits: Testing Center-to-limb Intensity Variations and Limb-Darkening Directly from Model Stellar Atmospheres
The transit method, employed by MOST, \emph{Kepler}, and various ground-based
surveys has enabled the characterization of extrasolar planets to unprecedented
precision. These results are precise enough to begin to measure planet
atmosphere composition, planetary oblateness, star spots, and other phenomena
at the level of a few hundred parts-per-million. However, these results depend
on our understanding of stellar limb darkening, that is, the intensity
distribution across the stellar disk that is sequentially blocked as the planet
transits. Typically, stellar limb darkening is assumed to be a simple
parameterization with two coefficients that are derived from stellar atmosphere
models or fit directly. In this work, we revisit this assumption and compute
synthetic planetary transit light curves directly from model stellar atmosphere
center-to-limb intensity variations (CLIV) using the plane-parallel
\textsc{Atlas} and spherically symmetric \textsc{SAtlas} codes. We compare
these light curves to those constructed using best-fit limb-darkening
parameterizations. We find that adopting parametric stellar limb-darkening laws
lead to systematic differences from the more geometrically realistic model
stellar atmosphere CLIV of about 50 -- 100 ppm at the transit center and up to
300 ppm at ingress/egress. While these errors are small they are systematic,
and appear to limit the precision necessary to measure secondary effects. Our
results may also have a significant impact on transit spectra.Comment: 12 pages, 14 figures, accepted for publication in ApJ after revision
Implications of Pseudospin Symmetry on Relativistic Magnetic Properties and Gamow - Teller Transitions in Nuclei
Recently it has been shown that pseudospin symmetry has its origins in a
relativistic symmetry of the Dirac Hamiltonian. Using this symmetry we relate
single - nucleon relativistic magnetic moments of states in a pseudospin
doublet to the relativistic magnetic dipole transitions between the states in
the doublet, and we relate single - nucleon relativistic Gamow - Teller
transitions within states in the doublet. We apply these relationships to the
Gamow - Teller transitions from to its mirror nucleus .Comment: 17 pages, 2 figures, to be published in PRC. Slightly revised text
with one reference adde
Revalidation and electronic cataract surgery audit: a Scottish survey on current practice and opinion
PURPOSE: To determine current knowledge and opinion on revalidation, and methods of cataract surgery audit in Scotland and to outline the current and future possibilities for electronic cataract surgery audit. METHODS: In 2010 we conducted a prospective, cross-sectional, Scottish-wide survey on revalidation knowledge and opinion, and cataract audit practice among all senior NHS ophthalmologists. Results were anonymised and recorded manually for analysis. RESULTS: In all, 61% of the ophthalmologists surveyed took part. Only 33% felt ready to take part in revalidation, whereas 76% felt they did not have adequate information about the process. Also, 71% did not feel revalidation would improve patient care, but 85% agreed that cataract surgery audit is essential for ophthalmic practice. In addition, 91% audit their cataract outcomes; 52% do so continuously. Further, 63% audit their subspecialist surgical results. Only 25% audit their cataract surgery practice electronically, and only 12% collect clinical data using a hospital PAS system. Funding and system incompatibility were the main reasons cited for the lack of electronic audit setup. Currently, eight separate hospital IT patient administration systems are used across 14 health boards in Scotland. CONCLUSION: Revalidation is set to commence in 2012. The Royal College of Ophthalmologists will use cataract outcome audit as a tool to ensure surgical competency for the process. Retrospective manual auditing of cataract outcome is time consuming, and can be avoided with an electronic system. Scottish ophthalmologists view revalidation with scepticism and appear to have inadequate knowledge of the process. However, they strongly agree with the concept of cataract surgery audit. The existing and future electronic applications that may support surgical audit are commercial electronic records, web-based applications, centrally funded software applications, and robust NHS connections between community and hospital
Development of Sow Lameness Classification Trees Using an Embedded Microcomputer-based Force Plate in a Commercial Setting
Background and Objectives: The objectives of this study were: 1) to examine the relationship between forces applied by each leg as measured by the force plate and the degree of visually assessed lameness under conditions applicable to a commercial herd, and 2) to develop an automated lameness detection algorithm based on the force plate output.
Methods and Findings: The microcomputer-based embedded force plate system provides an objective approach to lameness detection by measuring the force generated by each individual limb. The force plate device was installed within an Electronic Sow Feeder (ESF) and used to monitor a subset of the 120 multiparous gestating sows housed in a dynamic group over a 21 day period. Each day sows entered the ESF station one at a time to eat. At times when the sow stood squarely and applied pressure to all quadrants of the device, the force applied by each foot was recorded once per second. Sows were visually scored for the presence of lameness using a four-point scale (0=normal to 3=severely lame) on a weekly basis and classified based on this visual assessment as non-lame (score ≤ 1) or lame (score ≥ 2). An ensemble learning method called Random Forest was used to identify the optimal decision tree for classifying the force plate data into similar categories of non-lame and lame. A Kappa Statistics test was used to measure the level of agreement between the visual scoring and force plate results. Changes in lameness status, as well as the first day of lameness identification for each detection method, were also analyzed. Seven variables were included in the classification tree with the most weight given to the difference between the forces applied to the 2 hind legs. The two lameness detection methods assigned the same lameness classification in 95% of cases and had substantial agreement (Kappa Statistic=0.79; P\u3c0.05). However, the classification tree algorithm detected lameness almost 5 days earlier than the visual scoring system (P\u3c0.001). Additionally, comparing lameness of sows from the time of entry into the group, showed an increase in lameness after the first week regardless of the lameness scoring method.
Conclusions: Lameness detection typically is based on subjective visual evaluation, which requires time, training, and can be biased between and within individuals. Results demonstrate that under conditions applicable to a commercial herd, the force plate can accurately detect lameness sooner than a weekly visual lameness assessment
Targeting Several CAG Expansion Diseases by a Single Antisense Oligonucleotide
To date there are 9 known diseases caused by an expanded polyglutamine repeat, with the most prevalent being Huntington's disease. Huntington's disease is a progressive autosomal dominant neurodegenerative disorder for which currently no therapy is available. It is caused by a CAG repeat expansion in the HTT gene, which results in an expansion of a glutamine stretch at the N-terminal end of the huntingtin protein. This polyglutamine expansion plays a central role in the disease and results in the accumulation of cytoplasmic and nuclear aggregates. Here, we make use of modified 2′-O-methyl phosphorothioate (CUG)n triplet-repeat antisense oligonucleotides to effectively reduce mutant huntingtin transcript and protein levels in patient-derived Huntington's disease fibroblasts and lymphoblasts. The most effective antisense oligonucleotide, (CUG)7, also reduced mutant ataxin-1 and ataxin-3 mRNA levels in spinocerebellar ataxia 1 and 3, respectively, and atrophin-1 in dentatorubral-pallidoluysian atrophy patient derived fibroblasts. This antisense oligonucleotide is not only a promising therapeutic tool to reduce mutant huntingtin levels in Huntington's disease but our results in spinocerebellar ataxia and dentatorubral-pallidoluysian atrophy cells suggest that this could also be applicable to other polyglutamine expansion disorders as well
Transcriptome Analysis of Neisseria meningitidis in Human Whole Blood and Mutagenesis Studies Identify Virulence Factors Involved in Blood Survival
During infection Neisseria meningitidis (Nm) encounters multiple
environments within the host, which makes rapid adaptation a crucial factor for
meningococcal survival. Despite the importance of invasion into the bloodstream
in the meningococcal disease process, little is known about how Nm adapts to
permit survival and growth in blood. To address this, we performed a time-course
transcriptome analysis using an ex vivo model of human whole
blood infection. We observed that Nm alters the expression of ≈30% of
ORFs of the genome and major dynamic changes were observed in the expression of
transcriptional regulators, transport and binding proteins, energy metabolism,
and surface-exposed virulence factors. In particular, we found that the gene
encoding the regulator Fur, as well as all genes encoding iron uptake systems,
were significantly up-regulated. Analysis of regulated genes encoding for
surface-exposed proteins involved in Nm pathogenesis allowed us to better
understand mechanisms used to circumvent host defenses. During blood infection,
Nm activates genes encoding for the factor H binding proteins, fHbp and NspA,
genes encoding for detoxifying enzymes such as SodC, Kat and AniA, as well as
several less characterized surface-exposed proteins that might have a role in
blood survival. Through mutagenesis studies of a subset of up-regulated genes we
were able to identify new proteins important for survival in human blood and
also to identify additional roles of previously known virulence factors in
aiding survival in blood. Nm mutant strains lacking the genes encoding the
hypothetical protein NMB1483 and the surface-exposed proteins NalP, Mip and
NspA, the Fur regulator, the transferrin binding protein TbpB, and the L-lactate
permease LctP were sensitive to killing by human blood. This increased knowledge
of how Nm responds to adaptation in blood could also be helpful to develop
diagnostic and therapeutic strategies to control the devastating disease cause
by this microorganism
Public health campaigns and obesity - a critique
<p>Abstract</p> <p>Background</p> <p>Controlling obesity has become one of the highest priorities for public health practitioners in developed countries. In the absence of safe, effective and widely accessible high-risk approaches (e.g. drugs and surgery) attention has focussed on community-based approaches and social marketing campaigns as the most appropriate form of intervention. However there is limited evidence in support of substantial effectiveness of such interventions.</p> <p>Discussion</p> <p>To date there is little evidence that community-based interventions and social marketing campaigns specifically targeting obesity provide substantial or lasting benefit. Concerns have been raised about potential negative effects created by a focus of these interventions on body shape and size, and of the associated media targeting of obesity.</p> <p>Summary</p> <p>A more appropriate strategy would be to enact high-level policy and legislative changes to alter the obesogenic environments in which we live by providing incentives for healthy eating and increased levels of physical activity. Research is also needed to improve treatments available for individuals already obese.</p
Aircraft Regional-Scale Flux Measurements over Complex Landscapes of Mangroves, Desert, and Marine Ecosystems of Magdalena Bay, Mexico
Natural ecosystems are rarely structurally simple or functionally homogeneous. This is true for the complex coastal region of Magdalena Bay, Baja California Sur, Mexico, where the spatial variability in ecosystem fluxes from the Pacific coastal ocean, eutrophic lagoon, mangroves, and desert were studied. The Sky Arrow 650TCN environmental research aircraft proved to be an effective tool in characterizing land–atmosphere fluxes of energy, CO2, and water vapor across a heterogeneous landscape at the scale of 1 km. The aircraft was capable of discriminating fluxes from all ecosystem types, as well as between nearshore and coastal areas a few kilometers distant. Aircraft-derived average midday CO2 fluxes from the desert showed a slight uptake of −1.32 μmol CO2 m−2 s−1, the coastal ocean also showed an uptake of −3.48 μmol CO2 m−2 s−1, and the lagoon mangroves showed the highest uptake of −8.11 μmol CO2 m−2 s−1. Additional simultaneous measurements of the normalized difference vegetation index (NDVI) allowed simple linear modeling of CO2 flux as a function of NDVI for the mangroves of the Magdalena Bay region. Aircraft approaches can, therefore, be instrumental in determining regional CO2 fluxes and can be pivotal in calculating and verifying ecosystem carbon sequestration regionally when coupled with satellite-derived products and ecosystem models
DETORQUEO, QUIRKY, and ZERZAUST Represent Novel Components Involved in Organ Development Mediated by the Receptor-Like Kinase STRUBBELIG in Arabidopsis thaliana
Intercellular signaling plays an important role in controlling cellular behavior in apical meristems and developing organs in plants. One prominent example in Arabidopsis is the regulation of floral organ shape, ovule integument morphogenesis, the cell division plane, and root hair patterning by the leucine-rich repeat receptor-like kinase STRUBBELIG (SUB). Interestingly, kinase activity of SUB is not essential for its in vivo function, indicating that SUB may be an atypical or inactive receptor-like kinase. Since little is known about signaling by atypical receptor-like kinases, we used forward genetics to identify genes that potentially function in SUB-dependent processes and found recessive mutations in three genes that result in a sub-like phenotype. Plants with a defect in DETORQEO (DOQ), QUIRKY (QKY), and ZERZAUST (ZET) show corresponding defects in outer integument development, floral organ shape, and stem twisting. The mutants also show sub-like cellular defects in the floral meristem and in root hair patterning. Thus, SUB, DOQ, QKY, and ZET define the STRUBBELIG-LIKE MUTANT (SLM) class of genes. Molecular cloning of QKY identified a putative transmembrane protein carrying four C2 domains, suggesting that QKY may function in membrane trafficking in a Ca2+-dependent fashion. Morphological analysis of single and all pair-wise double-mutant combinations indicated that SLM genes have overlapping, but also distinct, functions in plant organogenesis. This notion was supported by a systematic comparison of whole-genome transcript profiles during floral development, which molecularly defined common and distinct sets of affected processes in slm mutants. Further analysis indicated that many SLM-responsive genes have functions in cell wall biology, hormone signaling, and various stress responses. Taken together, our data suggest that DOQ, QKY, and ZET contribute to SUB-dependent organogenesis and shed light on the mechanisms, which are dependent on signaling through the atypical receptor-like kinase SUB
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