737 research outputs found

    System control of an autonomous planetary mobile spacecraft

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    The goal is to suggest the scheduling and control functions necessary for accomplishing mission objectives of a fairly autonomous interplanetary mobile spacecraft, while maximizing reliability. Goals are to provide an extensible, reliable system conservative in its use of on-board resources, while getting full value from subsystem autonomy, and avoiding the lure of ground micromanagement. A functional layout consisting of four basic elements is proposed: GROUND and SYSTEM EXECUTIVE system functions and RESOURCE CONTROL and ACTIVITY MANAGER subsystem functions. The system executive includes six subfunctions: SYSTEM MANAGER, SYSTEM FAULT PROTECTION, PLANNER, SCHEDULE ADAPTER, EVENT MONITOR and RESOURCE MONITOR. The full configuration is needed for autonomous operation on Moon or Mars, whereas a reduced version without the planning, schedule adaption and event monitoring functions could be appropriate for lower-autonomy use on the Moon. An implementation concept is suggested which is conservative in use of system resources and consists of modules combined with a network communications fabric. A language concept termed a scheduling calculus for rapidly performing essential on-board schedule adaption functions is introduced

    XASH genes promote neurogenesis in Xenopus embryos

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    Neural development in Drosophila is promoted by a family of basic helix-loop-helix (bHLH) transcription factors encoded within the Achaete Scute-Complex (AS-C). XASH- 3, a Xenopus homolog of the Drosophila AS-C genes, is expressed during neural induction within a portion of the dorsal ectoderm that gives rise to the neural plate and tube. Here, we show that XASH-3, when expressed with the promiscuous binding partner XE12, specifically activates the expression of neural genes in naive ectoderm, suggesting that XASH-3 promotes neural development. Moreover, XASH-3/XE12 RNA injections into embryos lead to hypertrophy of the neural tube. Interestingly, XASH-3 misexpression does not lead to the formation of ectopic neural tissue in ventral regions, suggesting that the domain of XASH proneural function is restricted in the embryo. In contrast to the neural inducer noggin, which permanently activates the NCAM gene, the activation of neural genes by XASH-3/XE12 is not stable in naive ectoderm, yet XASH-3/XE12 powerfully and stably activates NCAM, Neurofilament and type III ÎČ-tubulin gene expression in noggintreated ectoderm. These results show that the XASH-3 promotes neural development, and suggest that its activity depends on additional factors which are induced in ectoderm by factors such as noggin

    Development and Validation of Preenlistment Screening Composites for Army Enlisted Personnel

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    Prepared for: US Army Recruiting Command Program Analysis and Evaluation Directorate Research and Studies Divisionhttp://archive.org/details/developmentvalid56zimmNAN

    A Tool for Combating Trichinosis

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    Trichinosis control or eradication has been limited by the lack of an effective diagnostic test. This article tells about a new method of testing developed at Iowa State University and how it may help eradicate the disease

    Changes in hospital mortality for United States intensive care unit admissions from 1988 to 2012

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    Introduction A decrease in disease-specific mortality over the last twenty years has been reported for patients admitted to United States (US) hospitals, but data for intensive care patients are lacking. The aim of this study was to describe changes in hospital mortality and case-mix using clinical data for patients admitted to multiple US ICUs over the last 24 years. Methods We carried out a retrospective time series analysis of hospital mortality using clinical data collected from 1988 to 2012. We also examined the impact of ICU admission diagnosis and other clinical characteristics on mortality over time. The potential impact of hospital discharge destination on mortality was also assessed using data from 2001 to 2012. Results For 482,601 ICU admissions there was a 35% relative decrease in mortality from 1988 to 2012 despite an increase in age and severity of illness. This decrease varied greatly by diagnosis. Mortality fell by \u3e60% for patients with chronic obstructive pulmonary disease, seizures and surgery for aortic dissection and subarachnoid hemorrhage. Mortality fell by 51% to 59% for six diagnoses, 41% to 50% for seven diagnoses, and 10% to 40% for seven diagnoses. The decrease in mortality from 2001 to 2012 was accompanied by an increase in discharge to post-acute care facilities and a decrease in discharge to home. Conclusions Hospital mortality for patients admitted to US ICUs has decreased significantly over the past two decades despite an increase in the severity of illness. Decreases in mortality were diagnosis specific and appear attributable to improvements in the quality of care, but changes in discharge destination and other confounders may also be responsible

    On the design and simulation of an airlift loop bioreactor with microbubble generation by fluidic oscillation

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    Microbubble generation by a novel fluidic oscillator driven approach is analyzed, with a view to identifying the key design elements and their differences from standard approaches to airlift loop bioreactor design. The microbubble generation mechanism has been shown to achieve high mass transfer rates by the decrease of the bubble diameter, by hydrodynamic stabilization that avoids coalescence increasing the bubble diameter, and by longer residence times offsetting slower convection. The fluidic oscillator approach also decreases the friction losses in pipe networks and in nozzles/diffusers due to boundary layer disruption, so there is actually an energetic consumption savings in using this approach over steady flow. These dual advantages make the microbubble generation approach a promising component of a novel airlift loop bioreactor whose design is presented here. The equipment, control system for flow and temperature, and the optimization of the nozzle bank for the gas distribution system are presented. (C) 2009 The Institution of Chemical Engineers. Published by Elsevier B.V All rights reserved

    Community and Clinical Epidemiology of Borderline Personality Disorder

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    Several studies of the prevalence of Borderline Personality Disorder (BPD) in community and clinical settings have been carried out to date. Although results vary according to sampling method and assessment method, median point prevalence of BPD is roughly 1%, with higher or lower rates in certain community subpopulations. In clinical settings, BPD prevalence is around 10-12% in outpatient psychiatric clinics and 20-22% among inpatient clinics. Further research is needed to identify the prevalence and correlates of BPD in other clinical settings (e.g., primary care) and to investigate the impact of demographic variables on BPD prevalence

    Survival rates of band‐tailed pigeons estimated using passive integrated transponder tags

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    Obtaining survival estimates on the Interior population of band-tailed pigeons (Patagioenas fasciata) is challenging because they are trap shy, but the joint use of passive integrated transponder (PIT) tags and bands is a potential solution. We investigated the use of PIT tags to passively recapture band‐tailed pigeon at 3 locations in New Mexico, USA, to estimate survival. From 2013–2015, we captured, banded, and marked \u3e600 individual band‐tailed pigeons with PIT tags. To estimate annual survival rates, we used a Barker multi‐state joint live and dead encounters and resighting model. Survival models excluding transience had survival estimates across site, sex, and year of 0.86 (95% CI = 0.84–0.88) for after hatch year birds and 0.63 (95% CI = 0.48–0.76) for hatch year birds. These results are consistent with other survival estimates reported for the Interior population of band‐tailed pigeons using band return data and potentially provide an effective alternative method of monitoring survival of this population

    The Anabaena-Azolla symbiosis: Diversity and relatedness of neotropical host taxa

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    The Anabaena-Azolla association has proved to be an effective biofertilizer in tropical regions of wetland rice production. Three neotropical host species, A. microphylla, A. caroliniana , and A. mexicana , are similar in vegetative morphology (growth habits, frond dimensions, trichome cell number) and ecophysiology (relative heat tolerance). They were observed during our investigation to also be genetically alike and distinct from other taxa.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43461/1/11104_2004_Article_BF02187450.pd

    Effects of transport and phase equilibrium on fast, nearly irreversible reactive extraction

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    Abstract Integration of reaction and separation can be exploited to drive reversible reactions in the direction of the desired product using multiphase flow contacting. In the case of nearly irreversible, fast reactions, however, the dynamics of the product have little influence on the reactor efficiency in say liquid-liquid reactive extraction. A similar intensification in reaction efficiency to reactive separation can be achieved by exploiting phase equilibrium or asymmetry in mass transfer rates of the reactants. Here, a model for two-layer biphasic flow and homogeneous reaction is proposed for co-current reactive extraction, demonstrating that localization and intensification of reaction occurs in the region between the entrance and crossover. Crossover occurs if the reactant in stoichiometric deficit preferentially populates the reacting phase due to sufficient imbalance in either mass transfer coefficients or phase equilibrium. We develop an infinite Peclet number (convection dominates over bulk diffusion) model that indicates that crossover occurs when for fast, irreversible reactions. u 0 and v 0 are initial charges to the tubular reactor, the 's are mass transfer coefficients for each side of the fluid interface and the h's are Henry's Law coefficients for reactants U and V . The interpretation of this formula is that if v 0 > u 0 , then crossover will occur if the overall mass transfer rate of U is faster than the overall mass transfer rate for V . Downstream of the crossover point, the reactant in stoichiometric excess also dominates the reacting phase due to relative exhaustion of the more-mobile component. A finite Peclet number theory for fast, irreversible reaction shows that the above formula is a conservative limit for crossover-if it holds, crossover will occur regardless of the Peclet number. A formula for the larger parametric region for crossover with finite Peclet number is derived. Verification that crossover is achieved is found by finite-element numerical analysis of the full governing equations. Both theory and numerical analysis predict localization and intensification of the reaction due to crossover. Crossover sets the length scale as approximately two and a half crossover lengths for completed reaction for sufficiently high Peclet number with strong kinetic asymmetry. The theory predicts that taking the ratio of inlet concentrations S = u 0 /v 0 to be the critical value at fixed physical parameters for mass transfer and phase equilibrium maximizes localization and reactor efficiency. Similarly, the kinetic asymmetry should be as large as possible to exploit the benefits of crossover.
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