342 research outputs found

    Intermuscular Adipose Tissue Is Muscle Specific and Associated with Poor Functional Performance

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    Purpose. People with obesity, diabetes, and peripheral neuropathy have high levels of intermuscular adipose tissue (IMAT) volume which has been inversely related to physical function. We determined if IMAT is muscle specific, if calf IMAT is different between a healthy obese group (HO), a group with diabetes mellitus (D), and a group with diabetes mellitus and peripheral neuropathy (DN), and if IMAT volume or the ratio of IMAT/muscle volume is related to physical function in these groups. Methods. 10 healthy obese people, 11 with type 2 diabetes, 24 with diabetes and peripheral neuropathy, had assessments of muscle morphology, physical function and muscle performance. Results. The gastrocnemius muscle had a higher ratio of IMAT/muscle volume than any other muscle or compartment. There were no differences between groups in calf muscle or IMAT volumes. Calf IMAT was inversely related to physical performance on the 6-minute walk test (r = −0.47) and physical performance test (r = −0.36). IMAT/muscle volume was inversely related to physical performance (PPT, r = −0.44; 6 MW r = −0.48; stair power, r = −0.30). Conclusions. IMAT accumulation varies in calf muscles, is highest in the gastrocnemius muscle, and is associated with poor physical performance

    Carbon cycling in mesohaline Chesapeake Bay sediments 1: POC deposition rates and mineralization pathways

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    Organic carbon cycling in sediments at two locations in the mesohaline Chesapeake Bay was analyzed using available data on sediment sulfate reduction, sediment oxygen consumption, and particulate organic carbon (POC) deposition and burial. Estimates of POC deposition based on the sum of integrated sediment metabolism and POC burial compared well with direct estimates derived from chlorophyll-a collection rates in mid-water column sediment traps. The range of POC deposition estimates (15–31 mol C m−2 yr−1) accounted for a large fraction (36–74%) of average annual net primary production in the mesohaline Bay. The difference between rates of POC deposition and permanent burial indicated that 70–85% of deposited carbon is mineralized on the time scale of a year. Carbon mineralization through sulfate reduction accounted for 30–35% of average net primary production, and was likely responsible for 60–80% of total sediment carbon metabolism. Oxidation of reduced sulfur accounted for a large but quantitatively uncertain portion of SOC in mid-Bay sediments. Our results highlight the quantitative significance of organic carbon sedimentation and attendant anaerobic sediment metabolism in the carbon cycle of a shallow, highly productive estuary

    Papillary thyroid microcarcinoma: time to shift from surgery to active surveillance?

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    The incidence of differentiated thyroid cancer is increasing greatly in high-income countries. Roughly 50% of this increase is attributable to the identification of intrathyroidal papillary thyroid microcarcinomas. Since mortality associated with these tumours remains low and stable, the increasing diagnosis has led to concerns about overdiagnosis and overtreatment. Management of papillary thyroid microcarcinomas should take into account the reported absence of mortality when diagnosed in the absence of lymph node metastases and distant metastases, as shown even in recent studies promoting active surveillance; a low recurrence rate of 1-5%; and the risk of permanent complications from surgery that cannot be decreased to less than 1-3%, even in high-volume tertiary care centres with experienced surgeons. On the basis of these data, active surveillance with curative intent, in which active treatment is delayed until the cancer shows signs of significant progression to avoid side-effects of treatment, should be considered in properly selected patients

    NASA Space Rocket Logistics Challenges

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    The Space Launch System (SLS) is the new NASA heavy lift launch vehicle and is scheduled for its first mission in 2017. The goal of the first mission, which will be uncrewed, is to demonstrate the integrated system performance of the SLS rocket and spacecraft before a crewed flight in 2021. SLS has many of the same logistics challenges as any other large scale program. Common logistics concerns for SLS include integration of discreet programs geographically separated, multiple prime contractors with distinct and different goals, schedule pressures and funding constraints. However, SLS also faces unique challenges. The new program is a confluence of new hardware and heritage, with heritage hardware constituting seventy-five percent of the program. This unique approach to design makes logistics concerns such as commonality especially problematic. Additionally, a very low manifest rate of one flight every four years makes logistics comparatively expensive. That, along with the SLS architecture being developed using a block upgrade evolutionary approach, exacerbates long-range planning for supportability considerations. These common and unique logistics challenges must be clearly identified and tackled to allow SLS to have a successful program. This paper will address the common and unique challenges facing the SLS programs, along with the analysis and decisions the NASA Logistics engineers are making to mitigate the threats posed by each

    Fishery dynamics of the California market squid (Loligo opalescens), as measured by satellite remote sensing

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    Novel data on the spatial and temporal distribution of fishing effort and population abundance are presented for the market squid fishery (Loligo opalescens) in the Southern California Bight, 1992−2000. Fishing effort was measured by the detection of boat lights by the Defense Meteorological Satellite Program (DMSP) Operational Linescan System (OLS). Visual confirmation of fishing vessels by nocturnal aerial surveys indicated that lights detected by satellites are reliable indicators of fishing effort. Overall, fishing activity was concentrated off the following Channel Islands: Santa Rosa, Santa Cruz, Anacapa, and Santa Catalina. Fishing activity occurred at depths of 100 m or less. Landings, effort, and squid abundance (measured as landings per unit of effort, LPUE) markedly declined during the 1997−98 El Niño; landings and LPUE increased afterwards. Within a fishing season, the location of fishing activity shifted from the northern shores of Santa Rosa and Santa Cruz Islands in October, the typical starting date for squid fishing in the Bight, to the southern shores by March, the typical end of the squid season. Light detection by satellites offers a source of fine-scale spatial and temporal data on fishing effort for the market squid fishery off California, and these data can be integrated with environmental data and fishing logbook data in the development of a management plan

    SDSS-V Algorithms: Fast, Collision-Free Trajectory Planning for Heavily Overlapping Robotic Fiber Positioners

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    Robotic fiber positioner (RFP) arrays are becoming heavily adopted in wide field massively multiplexed spectroscopic survey instruments. RFP arrays decrease nightly operational overheads through rapid reconfiguration between fields and exposures. In comparison to similar instruments, SDSS-V has selected a very dense RFP packing scheme where any point in a field is typically accessible to three or more robots. This design provides flexibility in target assignment. However, the task of collision-less trajectory planning is especially challenging. We present two multi-agent distributed control strategies that are highly efficient and computationally inexpensive for determining collision-free paths for RFPs in heavily overlapping workspaces. We demonstrate that a reconfiguration path between two arbitrary robot configurations can be efficiently found if "folded" state, in which all robot arms are retracted and aligned in a lattice-like orientation, is inserted between the initial and final states. Although developed for SDSS-V, the approach we describe is generic and so applicable to a wide range of RFP designs and layouts. Robotic fiber positioner technology continues to advance rapidly, and in the near future ultra-densely packed RFP designs may be feasible. Our algorithms are especially capable in routing paths in very crowded environments, where we see efficient results even in regimes significantly more crowded than the SDSS-V RFP design.Comment: To be published in the Astronomical Journa

    NASA Space Rocket Logistics Challenges

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    The Space Launch System (SLS) is the new NASA heavy lift launch vehicle in development and is scheduled for its first mission in 2017. SLS has many of the same logistics challenges as any other large scale program. However, SLS also faces unique challenges. This presentation will address the SLS challenges, along with the analysis and decisions to mitigate the threats posed by each

    Spin relaxation in (110) and (001) InAs/GaSb superlattices

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    We report an enhancement of the electron spin relaxation time (T1) in a (110) InAs/GaSb superlattice by more than an order of magnitude (25 times) relative to the corresponding (001) structure. The spin dynamics were measured using polarization sensitive pump probe techniques and a mid-infrared, subpicosecond PPLN OPO. Longer T1 times in (110) superlattices are attributed to the suppression of the native interface asymmetry and bulk inversion asymmetry contributions to the precessional D'yakonov Perel spin relaxation process. Calculations using a nonperturbative 14-band nanostructure model give good agreement with experiment and indicate that possible structural inversion asymmetry contributions to T1 associated with compositional mixing at the superlattice interfaces may limit the observed spin lifetime in (110) superlattices. Our findings have implications for potential spintronics applications using InAs/GaSb heterostructures.Comment: 4 pages, 2 figure
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