678 research outputs found

    Research in the design of high-performance reconfigurable systems

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    An initial design for the Bit Processor (BP) referred to in prior reports as the Processing Element or PE has been completed. Eight BP's, together with their supporting random-access memory, a 64 k x 9 ROM to perform addition, routing logic, and some additional logic, constitute the components of a single stage. An initial stage design is given. Stages may be combined to perform high-speed fixed or floating point arithmetic. Stages can be configured into a range of arithmetic modules that includes bit-serial one or two-dimensional arrays; one or two dimensional arrays fixed or floating point processors; and specialized uniprocessors, such as long-word arithmetic units. One to eight BP's represent a likely initial chip level. The Stage would then correspond to a first-level pluggable module. As both this project and VLSI CAD/CAM progress, however, it is expected that the chip level would migrate upward to the stage and, perhaps, ultimately the box level. The BP RAM, consisting of two banks, holds only operands and indices. Programs are at the box (high-level function) and system level. At the system level initial effort has been concentrated on specifying the tools needed to evaluate design alternatives

    Parental experiences of end of life care decision-making for children with life-limiting conditions in the paediatric intensive care unit: a qualitative interview study

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    Objectives To provide an in-depth insight into the experience and perceptions of bereaved parents who have experienced end of life care decision-making for children with life-limiting or life-threatening conditions in the paediatric intensive care unit (PICU). Design An in-depth qualitative interview study with a sample of parents of children with life-limiting or life-threatening conditions who had died in PICU within the previous 12 months. A thematic analysis was conducted on the interview transcripts. Setting A PICU in a large National Health Service (NHS) tertiary childrenā€™s hospital in the West Midlands, UK. Participants 17 parents of 11 children who had died in the PICU. Results Five interconnected themes were identified related to end of life care decision-making:(1) parents have significant knowledge and experiences that influence the decision-making process.(2) Trusted relationships with healthcare professionals are key to supporting parents making end of life decisions.(3) Verbal and non-verbal communication with healthcare professionals impacts on the family experience.(4) Engaging with end of life care decision-making can be emotionally overwhelming, but becomes possible if parents reach a ā€˜place of acceptanceā€™.(5) Families perceive benefits to receiving end of life care for their child in a PICU. Conclusions and implications The death of a child is an intensely emotional experience for all involved. This study adds to the limited evidence base related to parental experiences of end of life care decision-making and provides findings that have international relevance, particularly related to place of care and introduction of end of life care discussions. The expertise and previous experience of parents is highly relevant and should be acknowledged. End of life care decision-making is a complex and nuanced process; the information needs and preferences of each family are individual and need to be understood by the professionals involved in their care

    Planetary Protection Concerns During Pre-Launch Radioisotope Power System Final Integration Activities

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    The Advanced Stirling Radioisotope Generator (ASRG) is a next-generation radioisotope-based power system that is currently being developed as an alternative to the Multi-Mission Radioisotope Thermoelectric Generator (MMRTG). Power sources such as these may be needed for proposed missions to solar system planets and bodies that have challenging Planetary Protection (PP) requirements (e.g. Mars, Europa, Enceladus) that may support NASA s search for life, remnants of past life, and the precursors of life. One concern is that the heat from the ASRG could potentially create a region in which liquid water may occur. As advised by the NASA Planetary Protection Officer, when deploying an ASRG to Mars, the current COSPAR/NASA PP policy should be followed for Category IVc mission. Thus, sterilization processing of the ASRG to achieve bioburden reduction would be essential to meet the Planetary Protection requirements. Due to thermal constraints and associated low temperature limits of elements of the ASRG, vapor hydrogen peroxide (VHP) was suggested as a candidate alternative sterilization process to complement dry heat microbial reduction (DHMR) for the assembled ASRG. The following proposed sterilization plan for the ASRG anticipates a mission Category IVc level of cleanliness. This plan provides a scenario in which VHP is used as the final sterilization process. Keywords: Advanced Stirling Radioisotope Generator (ASRG), Planetary Protection (PP), Vapor hydrogen peroxide (VHP) sterilization

    Growth and Characterization of 3C-SiC and 2H-AIN/GaN Films and Devices Produced on Step-Free 4H-SiC Mesa Substrates

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    While previously published experimental results have shown that the step-free (0 0 0 1) 4H-SiC mesa growth surface uniquely enables radical improvement of 3C-SiC and 2H-AlN/GaN heteroepitaxial film quality (greater than 100-fold reduction in extended defect densities), important aspects of the step-free mesa heterofilm growth processes and resulting electronic device benefits remain to be more fully elucidated. This paper reviews and updates recent ongoing studies of 3C-SiC and 2H-AlN/GaN heteroepilayers grown on top of 4H-SiC mesas. For both 3C-SiC and AlN/GaN films nucleated on 4H-SiC mesas rendered completely free of atomic-scale surface steps, TEM studies reveal that relaxation of heterofilm strain arising from in-plane film/substrate lattice constant mismatch occurs in a remarkably benign manner that avoids formation of threading dislocations in the heteroepilayer. In particular, relaxation appears to occur via nucleation and inward lateral glide of near-interfacial dislocation half-loops from the mesa sidewalls. Preliminary studies of homojunction diodes implemented in 3C-SiC and AlN/GaN heterolayers demonstrate improved electrical performance compared with much more defective heterofilms grown on neighbouring stepped 4H-SiC mesas. Recombination-enhanced dislocation motion known to degrade forward-biased 4H-SiC bipolar diodes has been completely absent from our initial studies of 3C-SiC diodes, including diodes implemented on defective 3C-SiC heterolayers grown on stepped 4H-SiC mesas

    Lateral Growth Expansion of 4H/6H-SiC m-plane Pseudo Fiber Crystals by Hot Wall CVD Epitaxy

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    Lateral expansion of small mixed polytype 4H/6H-SiC slivers were realized by hot wall chemical vapor deposition (HWCVD). Small slivers cut from m-oriented ..11..00.. SiC boule slices containing regions of 4H and 6H SiC were exposed to HWCVD conditions using standard silane/propane chemistry for a period of up to eight hours. The slivers exhibited approximately 1500 microns (1.5 mm) of total lateral expansion. Initial analysis by synchrotron white beam x-ray topography (SWBXT) confirms, that the lateral growth was homoepitaxial, matching the polytype of the respective underlying region of the seed sliver

    The origin of overpotential in lithium-mediated nitrogen reduction

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    The verification of the lithium-mediated nitrogen reduction system in 2019 has led to an explosion in the literature focussing on improving the metrics of faradaic efficiency, stability, and activity. However, while the literature acknowledges the vast intrinsic overpotential for nitrogen reduction due to the reliance on in situ lithium plating, it has thus far been difficult to accurately quantify this overpotential and effectively analyse further voltage losses. In this work, we present a simple method for determining the Reversible Hydrogen Electrode (RHE) potential in the lithium-mediated nitrogen reduction system. This method allows for an investigation of the Nernst equation and reveals sources of potential losses. These are namely the solvation of the lithium ion in the electrolyte and resistive losses due to the formation of the solid electrolyte interphase. The minimum observed overpotential was achieved in a 0.6 M LiClO4, 0.5 vol% ethanol in tetrahydrofuran electrolyte. This was āˆ’3.59 Ā± 0.07 V vs. RHE, with a measured faradaic efficiency of 6.5 Ā± 0.2%. Our method allows for easy comparison between the lithium-mediated system and other nitrogen reduction paradigms, including biological and homogeneous mechanisms

    Whole body vibration exposure on markers of bone turnover, body composition, and physical functioning in breast cancer patients receiving aromatase inhibitor therapy: A randomized controlled trial

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    Introduction: Women with breast cancer are often prescribed aromatase inhibitors, which can cause rapid loss of bone mass leading to significant potential for morbidity. Vibration training has been shown to be helpful in reducing bone turnover in postmenopausal women without cancer. Aim: To examine the effect of vibration stimulus on markers of bone turnover in breast cancer patients receiving aromatase inhibitors. Methods: Thirty-one breast cancer survivors undergoing treatment with aromatase inhibitors were randomized to vibration stimulus (n = 14) or usual care control (n = 17). Low-frequency and low-magnitude vibration stimulus (27-32 Hz, 0.3g) was delivered in supervised sessions via standing on a vibration platform for 20 minutes, 3 times per week for 12 weeks. The primary outcome was blood markers of bone resorption (serum N-telopeptide X/creatine) and formation (serum type 1 procollagen N-terminal propeptide; P1NP). Other study outcomes body composition as well as measures of physical functioning. Outcomes were compared between groups using analysis of covariance adjusted for baseline values as well as time on aromatase inhibitors. Outcomes: On average, participants were 61.5 years old and overweight (ie, body mass index = 28.5 kg/m2). Following vibration training, there was no significant difference between groups for bone resorption (adjusted group difference 0.5, P = .929) or formation (adjusted group difference 5.3, P = .286). There were also no changes in any measure of physical functioning body composition. Conclusions: Short-term low-magnitude vibration stimulus does not appear to be useful for reducing markers of bone turnover secondary to aromatase inhibitors in breast cancer patients; nor is it useful in improving physical function or symptoms. However, further investigations with larger samples and higher doses of vibration are warranted. Trial Registration: Australian and New Zealand Clinical Trials Registry (ACTRN12611001094965)
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