905 research outputs found

    Alendronate and Resistive Exercise Countermeasures Against Bed Rest-Induced Bone Loss: Biochemical Markers of Bone and Calcium Metabolism

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    Weightlessness-induced bone loss must be counteracted to ensure crew health during extendedduration space missions. Studies were conducted to assess two bone loss countermeasures in a ground-based model: horizontal bed rest. Following a 3-wk ambulatory adaptation period, male and female subjects (aged 21-56 y) completed a 17-wk bed rest protocol. Subjects were assigned to one of three treatments: alendronate (ALEN; 10 mg/d, n=6), resistive exercise (RE; 1.5 h/d, 6 d/wk, n=8), or control (CN; no countermeasure, n=8). Dietary intake was adjusted to maintain body weight. Endocrine and biochemical indices were measured in blood and urine using standard laboratory methods. All data reported are expressed as percent change from individual pre-bedrest data. Serum calcium changed little during bed rest, and tended to decrease (4-8%) in ALEN subjects. In RE subjects, bone alkaline phosphatase and osteocalcin were increased >65 and >30%, respectively, during bed rest, while these were unchanged or decreased in ALEN and CN subjects. Urinary calcium was increased 50% in CN subjects, but was unchanged or decreased in both ALEN and RE groups. Urinary n-telopeptide excretion was increased 40-50% in CN and RE subjects, but decreased 20% in ALEN subjects. Pyridinium crosslink and deoxypyridinoline excretion were increased 20-50% during bed rest. These data suggest that RE countermeasures are effective at increasing markers of bone formation in an analog of weightlessness, while ALEN reduces markers of bone resorption. Counteracting the bone loss of space flight may require both pharmacologic and exercise countermeasures

    Unconfined Specimens

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    ABSTRACT: Effective diffusion coefficients, D*, of chloride and zinc diffusing in saturated, unconfined specimens of a compacted sandclay mixture are measured for three specimen lengths, L (2.91, 5.83, and 11.60 cm) and three test durations (7, 14, and 21 days). For a specimen length of 2.91 cm, both the chloride and zinc D* values tend to decrease with increasing test duration, possibly due to the measurement of concentration-dependent D* values. For a 14-day test duration, no consistent trend in D* with specimen length is observed, but the overall effect of specimen length on D* is minor relative to the range of measured D* values. A 21-day test duration provides the best correlation between the D* values based on reservoir concentrations, DiScs, and the D* values based on soil concentrations, D~oil, for chloride for a given test regardless of the specimen length. The effect of test duration on the correlation between D~cs and D~oit for zinc is minor based on the relatively narrow range of measured zinc D* values. The observed effects of specimen length on the correlation between D~¢s and D~oil for a given test are consistent with the more uniform final porosity distributions in the shorter specimens and the contrasting effects of the non-linear distributions in porosity and dry density that become less significant as the specimen length increases. KEYWORDS: adsorption, attapulgite clay, batch equilibrium, chloride diffusion, contaminant transport, diffusion testing, Freundlich isotherm, sand-clay mixture, swelling, zinc diffusion Over the past -30 years, diffusion testing has been performed in several different disciplines (e.g., soil science, geology, oceanography, geotechnical engineering) for several different purposes, including diffusion of nutrients to plant roots (Olsen and Kemper 1968), characterization of pore water in geologic deposits Several different types of diffusion testing procedures can be used, test durations have ranged from a few hours to several months, and the specimen volumes have ranged from as small as 10 cm 3 to more than 944 cm 3 (Shacketford 1991). Practical limitations to some, if not all, of the different test methods undoubtedly exist, and variability in test duration and specimen size may have an effect on determination of the measured diffusion coefficients. As a result, an evaluation of the factors potentially affecting the measurement of effective diffusion coefficients is needed. Such an evaluation is particularly of interest to geotechnical engineers associated with the design and evaluation of waste containment barriers because of the increasing importance placed on contaminant transport, in general, and diffusive transport, in particular, in such applications. The primary objective of this study is to evaluate the potential influence of test duration and specimen length on the diffusion of chloride and zinc in compacted, unconfined specimens of a sandclay mixture. The evaluation is based on the single reservoir, decreasing source concentration method that has been used extensively in the measurement of effective diffusion coefficients associated with waste disposal applications Materials and Methods Soil The soil used in this study is a mixture of 75% sand and 25% attapulgite clay (dry weight basis). Physical and chemical properties of the sand and attapulgite clay are provided i

    Skeletal Recovery Following Long-Duration Spaceflight Missions as Determined by Preflight and Postflight DXA Scans of 45 Crew Members

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    Introduction: The loss of bone mineral in astronauts during spaceflight has been investigated throughout the more than 40 years of bone research in space. Consequently, it is a medical requirement at NASA that changes in bone mass be monitored in crew members by measurements of bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA). This report is the first to evaluate medical data to address the recovery of bone mineral that is lost during spaceflight. Methods: DXA scans are performed before and after flight in astronauts who serve on long-duration missions (4-6 months) to ensure that medical standards for flight certification are met, to evaluate the effects of spaceflight and to monitor the restoration to preflight BMD status after return to Earth. Through cooperative agreements with the Russian Space Agency, the Bone and Mineral Lab at NASA Johnson Space Center (Houston, TX), also had access to BMD data from cosmonauts who had flown on long-duration missions yielding data from a total of 45 individual crew members. Changes in BMD (between 56 different sets of pre- and postflight measurements) were plotted as a function of time (days after landing); plotted data were fitted to an exponential mathematical model that determined i) BMD change at day 0 after landing and ii) the number of days after which 50% of the lost bone was recovered ("Recovery Half-Life"). These fits were performed for BMD of the lumbar spine, trochanter, pelvis, femoral neck and calcaneus. Results: In sum, averaged losses of bone mineral after spaceflight ranged between 2-9% for sites in the axial and appendicular skeleton. The fitted postflight BMD values predicted a 50% recovery of bone loss for all sites within 9 months

    Recovery of Spaceflight-induced Bone Loss: Bone Mineral Density after Long-Duration Missions as Fitted with an Exponential Function

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    The loss of bone mineral in NASA astronauts during spaceflight has been investigated throughout the more than 40 years of space travel. Consequently, it is a medical requirement at NASA Johnson Space Center (JSC) that changes in bone mass be monitored in crew members by measuring bone mineral density (BMD) with dual-energy x-ray absorptiometry (DXA) before and after flight on astronauts who serve on long-duration missions (4-6 months). We evaluated this repository of medical data to track whether there is recovery of bone mineral that was lost during spaceflight. Our analysis was supplemented by BMD data from cosmonauts ( by convention, a space traveler formally employed by the Russia Aviation and Space Agency or by the previous Soviet Union) who had also flown on long-duration missions. Data from a total of 45 individual crew members -- a small number of whom flew on more than one mission -- were used in this analysis. Changes in BMD (between 56 different sets of pre- and postflight measurements) were plotted as a function of time (days after landing). Plotted BMD changes were fitted to an exponential mathematical function that estimated: i) BMD change on landing day (day 0) and ii) the number of days after landing when 50% of the lost bone would be recovered ("50% recovery time") in the lumbar spine, trochanter, pelvis, femoral neck and calcaneus. In sum, averaged losses of bone mineral after long-duration spaceflight ranged between 2-9% across all sites with our recovery model predicting a 50% restoration of bone loss for all sites to be within 9 months

    Predicting aged pork quality using a portable Raman device

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    The utility of Raman spectroscopic signatures of fresh pork loin (1 d & 15 d postmortem) in predicting fresh pork tenderness and slice shear force (SSF) was determined. Partial least square models showed that sensory tenderness and SSF are weakly correlated (R2 = 0.2). Raman spectral data were collected in 6 s using a portable Raman spectrometer (RS). A PLS regression model was developed to predict quantitatively the tenderness scores and SSF values from Raman spectral data, with very limited success. It was discovered that the prediction accuracies for day 15 post mortem samples are significantly greater than that for day 1 postmortem samples. Classification models were developed to predict tenderness at two ends of sensory quality as “poor” vs. “good”. The accuracies of classification into different quality categories (1st to 4th percentile) are also greater for the day 15 postmortem samples for sensory tenderness (93.5% vs 76.3%) and SSF (92.8% vs 76.1%). RS has the potential to become a rapid on-line screening tool for the pork producers to quickly select meats with superior quality and/or cull poor quality to meet market demand/expectations
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