536 research outputs found

    International Space Station Environmental Control and Life Support System Status: 2011-2012

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    The International Space Station (ISS) Environmental Control and Life Support (ECLS) system includes regenerative and non-regenerative technologies that provide the basic life support functions to support the crew, while maintaining a safe and habitable shirtsleeve environment. This paper provides a summary of the U.S. ECLS system activities over the past year and the impacts of the international partners activities on them, covering the period of time between March 2011 and February 2012. The ISS continued permanent crew operations including the continuation of six crew members being on ISS. Work continues on the commercial cargo resupply vehicles, and work to try and extend ISS service life from 2015 to no later than 2028.

    International Space Station Environmental Control and Life Support System Status for the Prior Year: 2010-2011

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    The International Space Station (ISS) Environmental Control and Life Support (ECLS) system includes regenerative and non-regenerative technologies that provide the basic life support functions to support the crew, while maintaining a safe and habitable shirtsleeve environment. This paper provides a summary of the U.S. ECLS system activities over the prior year, covering the period of time between March 2010 and February 2011. The ISS continued permanent crew operations including the continuation of six crew members being on ISS. Work continues on the last of the Phase 3 pressurized elements, the commercial cargo resupply vehicles, and work to try and extend ISS service life from 2015 to no later than 2028

    Fluid Flows of Mixed Regimes in Porous Media

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    In porous media, there are three known regimes of fluid flows, namely, pre-Darcy, Darcy and post-Darcy. Because of their different natures, these are usually treated separately in literature. To study complex flows when all three regimes may be present in different portions of a same domain, we use a single equation of motion to unify them. Several scenarios and models are then considered for slightly compressible fluids. A nonlinear parabolic equation for the pressure is derived, which is degenerate when the pressure gradient is either small or large. We estimate the pressure and its gradient for all time in terms of initial and boundary data. We also obtain their particular bounds for large time which depend on the asymptotic behavior of the boundary data but not on the initial one. Moreover, the continuous dependence of the solutions on initial and boundary data, and the structural stability for the equation are established.Comment: 33 page

    Chronic cerebrospinal venous insufficiency in multiple sclerosis: a historical perspective

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    Chronic cerebrospinal venous insufficiency (CCSVI) is a term used to describe impaired venous drainage from the central nervous system (CNS) caused by abnormalities in anatomy and flow affecting the extracranial veins. Recently, it has been proposed that CCSVI may contribute to the pathogenesis of multiple sclerosis (MS). It is hypothesized that venous obstruction results in abnormal flow that promotes inflammation at the blood-brain barrier and that this triggers a process marked by a disturbance of homeostasis within the CNS that leads to demyelination and neurodegeneration. The venous abnormalities of CCSVI are often diagnosed by ultrasound or magnetic resonance venography, however the prevalence of CCSVI detailed in groups of MS patients and patients without MS varies widely in published reports. Increased standardization of diagnostic studies to evaluate both anatomical and physiological findings associated with CCSVI is needed. The purpose of this article is to provide a background to understand the development of the theory of CCSVI and to frame the relevant issues regarding its diagnosis and relationship to the pathogenesis of MS

    Mitochondrial Targeted Coenzyme Q, Superoxide, and Fuel Selectivity in Endothelial Cells

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    Background Previously, we reported that the “antioxidant” compound “mitoQ” (mitochondrial-targeted ubiquinol/ubiquinone) actually increased superoxide production by bovine aortic endothelial (BAE) cell mitochondria incubated with complex I but not complex II substrates. Methods and Results To further define the site of action of the targeted coenzyme Q compound, we extended these studies to include different substrate and inhibitor conditions. In addition, we assessed the effects of mitoquinone on mitochondrial respiration, measured respiration and mitochondrial membrane potential in intact cells, and tested the intriguing hypothesis that mitoquinone might impart fuel selectivity in intact BAE cells. In mitochondria respiring on differing concentrations of complex I substrates, mitoquinone and rotenone had interactive effects on ROS consistent with redox cycling at multiple sites within complex I. Mitoquinone increased respiration in isolated mitochondria respiring on complex I but not complex II substrates. Mitoquinone also increased oxygen consumption by intact BAE cells. Moreover, when added to intact cells at 50 to 1000 nM, mitoquinone increased glucose oxidation and reduced fat oxidation, at doses that did not alter membrane potential or induce cell toxicity. Although high dose mitoquinone reduced mitochondrial membrane potential, the positively charged mitochondrial-targeted cation, decyltriphenylphosphonium (mitoquinone without the coenzyme Q moiety), decreased membrane potential more than mitoquinone, but did not alter fuel selectivity. Therefore, non-specific effects of the positive charge were not responsible and the quinone moiety is required for altered nutrient selectivity. Conclusions In summary, the interactive effects of mitoquinone and rotenone are consistent with redox cycling at more than one site within complex I. In addition, mitoquinone has substrate dependent effects on mitochondrial respiration, increases repiration by intact cells, and alters fuel selectivity favoring glucose over fatty acid oxidation at the intact cell level.This work was supported by Veterans Affairs Medical Research Funds and grant DK25295 from the National Institutes of Health

    Case report and literature review: transient Inab phenotype and an agglutinating anti-IFC in a patient with a gastrointestinal problem

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    The Inab phenotype is a rare deficiency of all Cromer antigens. These antigens are carried on the decay-accelerating factor (DAF, CD55) molecule that is attached to the red blood cell (RBC) membrane by a glycosylphosphatidylinositol (GPI) anchor. Although typically inherited, an acquired and transient form of the Inab phenotype also exists. A patient with the triad of transient Inab phenotype, a direct-agglutinating anti-IFC, and gastrointestinal (GI) abnormalities is reported. CASE REPORT: An 18-month-old boy with gastroesophageal reflux disease requiring a feeding tube, milk and soy intolerance, and severe growth retardation, as well as vision and hearing deficits from cytomegalovirus infection, was identified when pretransfusion testing revealed a potent panagglutinin (titer > 2000 at 4°C). This antibody did not react with Dr(a–) and IFC RBCs, and the autocontrol was negative. The patient’s RBCs lacked CD55 by flow cytometric techniques but had normal levels of CD59 and antigens such as Yt a and Emm, carried on GPI-linked proteins, thus excluding paroxysmal nocturnal hemoglobinuria. Several months after initial detection, the anti-IFC was virtually undetectable and his cells reacted weakly with anti-IFC, anti-Dr a , and anti-CD55. RBCs from the propositus’ parents and brother demonstrated normal CD55 and CD59 expression. CONCLUSION: This is the first example of a direct-agglutinating anti-IFC. The cause of the transient depression in CD55 protein (and thus Cromer system antigens) and appearance of anti-IFC remains unknown, as does the relationship between the patient’s GI system abnormalities and these serologic findings.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71992/1/j.1537-2995.2006.00933.x.pd

    The first example of a paraben-dependent antibody to an Rh protein

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    Parabens are added to a commercial LISS (C-LISS) to retard microbial growth. Paraben-dependent anti-Jk a has been detected by the use of C-LISS. CASE REPORT: Serum from a D+ woman reacted in antiglobulin tests with RBCs stored (2-4 hours, 22-25 C) in C-LISS (L w and Messeter formulation, Immucor). Freshly prepared C-LISS-suspended RBCs did not react; nor did RBCs stored in LISS-additive reagents, PEG, saline, or homemade LISS. RESULTS: Studies using C-LISS-stored RBCs revealed an antibody that reacted with D+ and rrV+ RBCs, but not with r r, r r, or rrV-VS- RBCs. All partial D RBC phenotypes tested reacted, as did D+LW-, r G r, r G r, r y r, r s rV+VS+, and r s rV-VS+ RBCs. The active ingredient in C-LISS was propylparaben. Other LISS ingredients were not required; saline solutions of propylparaben, ethylparaben, methyl salicylate, 2-phenoxyethanol, and butylparaben were active. Methylparaben and methyl- m -hydroxybenzoate were inactive. Reactivity to C-LISS-stored RBCs could not be inhibited by propylparaben. Reactivity with D+V- and D-V+VS+ RBCs was not separable by adsorption-elution. CONCLUSIONS: This antibody likely detects a neoantigen formed between active compounds and RBC membranes. Review of the structure of active compounds suggests that proximity between methyl and hydroxyl groups is important for binding with RBC membranes. The role of RhD is unclear; no single portion of RhD protein appears to be implicated.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73085/1/j.1537-2995.2001.41030371.x.pd

    Fluid flow through porous media using distinct element based numerical method

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    Many analytical and numerical methods have been developed to describe and analyse fluid flow through the reservoir’s porous media. The medium considered by most of these models is continuum based homogeneous media. But if the formation is not homogenous or if there is some discontinuity in the formation, most of these models become very complex and their solutions lose their accuracy, especially when the shape or reservoir geometry and boundary conditions are complex. In this paper, distinct element method (DEM) is used to simulate fluid flow in porous media. The DEM method is independent of the initial and boundary conditions, as well as reservoir geometry and discontinuity. The DEM based model proposed in this study is appeared to be unique in nature with capability to be used for any reservoir with higher degrees of complexity associated with the shape and geometry of its porous media, conditions of fluid flow, as well as initial and boundary conditions. This model has first been developed by Itasca Consulting Company and is further improved in this paper. Since the release of the model by Itasca, it has not been validated for fluid flow application in porous media, especially in case of petroleum reservoir. In this paper, two scenarios of linear and radial fluid flow in a finite reservoir are considered. Analytical models for these two cases are developed to set a benchmark for the comparison of simulation data. It is demonstrated that the simulation results are in good agreement with analytical results. Another major improvement in the model is using the servo controlled walls instead of particles to introduce tectonic stresses on the formation to simulate more realistic situations. The proposed model is then used to analyse fluid flow and pressure behaviour for hydraulically induced fractured and naturally fractured reservoir to justify the potential application of the model

    The need to address fragmentation and silos in mortality information systems: the case of Ghana and Peru

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    Objectives: We aimed to understand the information architecture and degree of integration of mortality surveillance systems in Ghana and Peru. Methods: We conducted a cross-sectional study using a combination of document review and unstructured interviews to describe and analyse the sub-systems collecting mortality data. Results: We identified 18 and 16 information subsystems with independent databases capturing death events in Peru and Ghana respectively. The mortality information architecture was highly fragmented with a multiplicity of unconnected data silos and with formal and informal data collection systems. Conclusion: Reliable and timely information about who dies where and from what underlying cause is essential to reporting progress on Sustainable Development Goals, ensuring policies are responding to population health dynamics, and understanding the impact of threats and events like the COVID-19 pandemic. Integrating systems hosted in different parts of government remains a challenge for countries and limits the ability of statistics systems to produce accurate and timely information. Our study exposes multiple opportunities to improve the design of mortality surveillance systems by integrating existing subsystems currently operating in silos
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