920 research outputs found

    The tropospheric gas composition of Jupiter's north equatorial belt (NH3, PH3, CH3D, GeH4, H2O) and the Jovian D/H isotropic ratio

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    The gas composition of the troposphere of Jupiter in the clearest regions of the North Equatorial Belt (NEB) was derived from the Voyager 1 IRIS data. The infrared spectrum for this homogeneous cloud free region was modeled to infer altitude profiles for NH3, PH3, GeH4 and H2O. The Profiles for NH3 and PH3 were found to be depleted in the upper troposphere but otherwise in agreement with their solar values at the 1 bar level. The mole fraction for CH3D was determined to be 3.5(+1.0 or -1.3) x 10 to the minus 7th power. The GeH4 mole fraction of 7+ or -2 x 10 to the minus 10th power at the 2 to 3 bar level is a factor of 10 lower than the solar value. The H2O mole fraction is approximately 1 x 0.00001 at the 2.5 bar level and is increasing to approximately 3 x 0.00001 at 4 bars where it is a factor of 30 lower than solar. Using IRIS infrared values for the mole fractions of CH3D and CH4 a value of D/H = 3.6(+1.0 or -1.4)x 0.00001 is derived. Assuming this Jovian D/H ratio is representative of the protosolar nebula, and correcting for chemical galactic evolution, yields a value of 5.5 - 9.0 x 0.00001 for the primordial D/H ratio and an upper limit of 1.8 to 2.4 x 10 to the minus 31st power cu cm for the present day baryon density

    Nucleon Resonances and Quark Structure

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    A pedagogical review of the past 50 years of study of resonances, leading to our understanding of the quark content of baryons and mesons. The level of this review is intended for undergraduates or first-year graduate students. Topics covered include: the quark structure of the proton as revealed through deep inelastic scattering; structure functions and what they reveal about proton structure; and prospects for further studies with new and upgraded facilities, particularly a proposed electron-ion collider.Comment: 21 pages, 15 figure

    Correlated Infrared and X-ray Flux Changes Following the 2002 June Outburst of the Anomalous X-ray Pulsar 1E 2259+586

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    We present the results of a near-infrared monitoring program of the Anomalous X-ray Pulsar 1E 2259+586, performed at the Gemini Observatory. This program began three days after the pulsar's 2002 June outburst, and spans ~1.5 years. We find that after an initial increase associated with the outburst, the near-infrared flux decreased continually and reached the pre-burst quiescent level after about one year. We compare both the near-infrared flux enhancement and its decay to those of the X-ray afterglow, and find them to be remarkably consistent. Fitting simple power laws to the RXTE pulsed flux and near-infrared data for t>1 day post-burst, we find the following decay indices: alpha=-0.21+/-0.01 (X-ray), alpha=-0.21+/-0.02 (near-infrared), where flux is a function of time such that F is proportional to t^alpha. This suggests that the enhanced infrared and X-ray fluxes have a physical link post-outburst, most likely from the neutron-star magnetosphere.Comment: 11 pages, 1 figure, accepted for publication in ApJL; minor wording changes, added observation program IDs, improved figure resolutio

    Positive selection of novel peroxisome biogenesis-defective mutants of the yeast Pichia pastoris

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    We have developed two novel schemes for the direct selection of peroxisome-biogenesis-defective (pex) mutants of the methylotrophic yeast Pichia pastoris. Both schemes take advantage of our observation that methanol-induced pex mutants contain little or no alcohol oxidase (AOX) activity. AOX is a peroxisomal matrix enzyme that catalyzes the first step in the methanol-utilization pathway. One scheme utilizes allyl alcohol, a compound that is not toxic to cells but is oxidized by AOX to acrolein, a compound that is toxic. Exposure of mutagenized populations of AOX-induced cells to allyl alcohol selectively kills AOX-containing cells. However, pex mutants without AOX are able to grow. The second scheme utilizes a P. pastoris strain that is defective in formaldehyde dehydrogenase (FLD), a methanol pathway enzyme required to metabolize formaldehyde, the product of AOX. AOX-induced cells of fld1 strains are sensitive to methanol because of the accumulation of formaldehyde. However, fld1 pex mutants, with little active AOX, do not efficiently oxidize methanol to formaldehyde and therefore are not sensitive to methanol. Using these selections, new pex mutant alleles in previously identified PEX genes have been isolated along with mutants in three previously unidentified PEX group

    Web-based self-management for patients with lymphoma:Assessment of the reach of intervention of a randomized controlled trial

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    Background: Randomized controlled trials (RCTs) often provide accurate estimates of the internal validity of an intervention but lack information on external validity (generalizability). We conducted an RCT on the effectiveness of a self-management intervention among patients with lymphoma in a population-based setting. Objective: The objectives of the current study were to describe the proportion of RCT participants compared to all patients invited to participate, and compare sociodemographic and clinical characteristics of RCT participants with all respondents, all patients invited to participate, and all patients selected from the Netherlands Cancer Registry (NCR) to determine the reach of the intervention. An additional objective was to assess differences on RCT outcome variables between RCT and paper respondents. Methods: Patients with lymphoma or chronic lymphocytic leukemia ≥18 years old at diagnosis from 13 hospitals in the Netherlands were selected from the population-based NCR, which routinely collects data on sociodemographic and clinical characteristics. Eligible patients were invited to participate in an RCT and complete a questionnaire. Web-based completion determined RCT enrollment, whereas paper respondents were followed observationally. Results: A total of 1193 patients were selected from the NCR, 892 (74.77%) of whom were invited to participate in the trial by their hematologist after verifying eligibility. Among those invited, 25.4% (227/892) completed the web-based questionnaire and were enrolled in the RCT. The RCT participants were younger and there was a higher proportion of men than nonparticipants (P<.001). In addition, 25.7% (229/892) of those invited opted to participate in the paper-based observational follow-up study. Compared with paper respondents, RCT participants were younger (P<.001), with a higher proportion of men (P=.002), and had higher education levels (P=.02). RCT participants more often wanted to receive all available information on their disease (P<.001), whereas paper respondents reported higher levels of emotional distress (P=.009). Conclusions: From a population-based sample of eligible patients, the participation rate in the RCT was approximately 25%. RCT participants may not be representative of the target population because of different sociodemographic and clinical characteristics. Since RCT participants represent a minority of the target population, RCT results should be interpreted with caution as patients in the RCT may be those least in need of a self-management intervention. Trial Registration: Netherlands Trial Register NTR5953; https://www.trialregister.nl/trial/579

    Real-time simulation and hardware-in-the-loop approaches for integrating renewable energy sources into smart grids  : challenges & actions

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    The integration of distributed renewable energy sources and the multi-domain behaviours inside the cyber-physical energy system (smart grids) draws up major challenges. Their validation and roll out requires careful assessment, in term of modelling, simulation and testing. The traditional approach focusing on a particular object, actual hardware or a detailed model, while drastically simplifying the remainder of the system under test, is no longer sufficient. Real-time simulation and Hardware-in-the-Loop (HIL) techniques emerge as indispensable tools for validating the behaviour of renewable sources as well as their impact/interaction to with the cyber-physical energy system. This paper aims to provide an overview of the present status-quo of real-time and HIL approaches used for smart grids and their readiness for cyber-physical experiments. We investigate the current limitations of HIL techniques and point out necessary future developments. Subsequently, the paper highlights challenges that need specific attention as well as ongoing actions and further research directions

    Upstream transcription factor 1 (USF1) in risk of type 2 diabetes:Association study in 2000 Dutch Caucasians

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    Type 2 diabetes shares substantial genetic and phenotypic overlap with familial combined hyperlipidemia. Upstream stimulatory factor 1 (USF7), a well-established susceptibility gene for familial combined hyperlipidemia, is postulated to be such a shared genetic determinant. We evaluated two established variants in familial combined hyperlipidemia (rs2073658 and rs3737787) for association with type 2 diabetes in two Dutch case-control samples (N=2011). The first case-control sample comprised 501 subjects with type 2 diabetes from the Breda cohort and 920 healthy blood bank donors of Dutch Caucasian origin. The second case-control sample included 211 subjects with type 2 diabetes, and 379 normoglycemic controls. SNP rs2073658 and SNP rs3737787 were in perfect linkage disequilibrium. In the first case-control sample, prevalence of the major allele was higher in patients than in controls (75% versus 71%, OR=1.25, p=0.018). A similar effect-size and -direction was observed in the second case-control sample (76% versus 72%, OR=1.22, p=0.16). A combined analysis strengthened the evidence for association (OR=1.23, p=0.006). Notably, the increased risk for type 2 diabetes could be ascribed to the major allele, and its high frequency translated to a substantial population attributable risk of 14.5%. In conclusion, the major allele of rs2073658 in the USF1 gene is associated with a modestly increased risk to develop type 2 diabetes in Dutch Caucasians, with considerable impact at the population level. (c) 2008 Elsevier Inc. All rights reserved
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