Experimental Determination of Inflatable,Braided Tube Constitutive Properties

The primary objective of this study was to conduct constitutive tests of relatively large diameter inflatable, braided fabric tubes at different inflation pressures and braid angles in order to quantify the longitudinal modulus, in‐plane shear modulus and effective lamina stiffness properties. The stiffness properties quantified here are of high interest because the same braided fabric tubes have been used in the construction of test articles for a major, multi‐year, ground based test campaign led by the United States National Aeronautics and Space Administration. These properties are also input directly into high‐fidelity yet computationally intensive 3D shell‐based finite‐element simulations of the large, inflatable structures. Experimental methods employed during this study included tension–torsion testing, uniaxial tension testing of individual fibre tows, and uniaxial tension testing of gas bladder coupons. Digital image correlation was used to measure all of the geometric information that is necessary to perform netting theory calculations. The test results indicate that fabric in‐plane shear modulus is highly dependent on both braid angle and inflation pressure, but that longitudinal stiffness is quite small and relatively unaffected by braid angle and pressure. In addition to advancing the state‐of‐the art in experimental constitutive property determination of inflatable, braided fabric, this study includes the development of a method to back calculate lamina properties from the experimental results that are suitable for use as input to commonly used finite‐element programmes. The digital image correlation data revealed spatial variation of shear strain that was important to consider when computing the gross shear stiffness. Digital image correlation data also captured the braid surface flattening with increasing inflation pressure, which supports the fibre de‐crimping theory.     

A foetal energy balance equation based on maternal exercise and diet

Empirical data indicate that the maternal diet composition has a direct impact on foetal fat mass and resulting birth weights. Weight-bearing maternal exercise influences the placental volume, which has also been correlated to birth weight. A foetal energy balance equation, based on the first law of thermodynamics, that incorporates maternal diet and exercise is developed. Model parameters and validity are evaluated using published data.     

The structure of distress following trauma: Posttraumatic stress disorder, major depressive disorder, and generalized anxiety disorder.

The current report used confirmatory factor analysis to examine the latent structures of both key features and associated symptoms of three disorders that commonly develop following a traumatic event: posttraumatic stress disorder (PTSD), major depressive disorder (MDD), and generalized anxiety disorder (GAD). Participants were 228 motor-vehicle accident survivors who sought treatment for emotional difficulties. PTSD, MDD, and GAD were assessed with a combination of self-report and interview-based measures. The results of construct level analyses suggested that PTSD, MDD, and GAD are distinguishable but highly correlated disorders following a traumatic event. Symptom level analyses supported a model where the Reexperiencing, Avoidance, and Hypervigilance factors were subsumed under the PTSD construct. However, in this model the Dysphoria factor was a higher order construct correlated with the PTSD, MDD, and GAD factors, suggesting that the Dysphoria cluster may not be unique to PTSD. Diagnostic and theoretical implications of these results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of pulsed and continuous addition of H2 gas via membranes for stimulating PCE biodegradation in soil columns

Column experiments were performed to investigate a technology for remediating aquifers contaminated with chlorinated solvents. The technology involves installation of hollow-fiber membranes in the subsurface to supply hydrogen gas (H2) to groundwater to support biological reductive dechlorination in situ. Three laboratory-scale columns [control (N2 only), continuous H2, and pulsed H2] were packed with aquifer material from a trichloroethene (TCE)-contaminated wetland in Minnesota and supplied with perchloroethene (PCE)-contaminated synthetic groundwater. The main goals of the research were: (1) evaluate the long-term performance of the H2 supply system and (2) compare the effects of pulsed (4 h on, 20 h off) versus continuous H2 supply (lumen partial pressure approximately 1.2 atm) on PCE dechlorination and production of by-products (i.e. methane and acetate). The silicone-coated fiberglass membranes employed in these experiments were robust, delivering H2 steadily over the entire 349-day experiment. Methane production decreased when H2 was added in a pulsed manner. Nevertheless, the percentage of added H2 used to support methanogenesis was similar in both H2-fed columns (92-93%). For much of the experiment, PCE dechlorination (observed end product = dichloroethene) in the continuous and pulsed H2 columns was comparable, and enhanced in comparison to the natural attenuation observed in the control column. Dechlorination began to decline in the pulsed H2 column after 210 days, however, while dechlorination in the continuous H2 column was sustained. Acetate was detected only in the continuous H2 column, at concentrations of up to 36 microM. The results of this research suggest that in situ stimulation of PCE dechlorination by direct H2 addition requires the continuous application of H2 at high partial pressures, favoring the production of bioavailable organic matter such as acetate to provide a carbon source, electron donor, or both for dechlorinators. Unfortunately, this strategy has proven to be inefficient, with the bulk of the added H2 used to support methanogenesis.     

摄影画廊

旅行及风光摄影专家David Clapp首次为我们展示他最新拍摄的风光照片。     

A different kind of comorbidity: Understanding posttraumatic stress disorder and chronic pain.

Many traumatic events leave lingering physical injuries and chronic pain in their wake, in addition to trauma-related psychopathology. In this review, we provide an overview of developments in the recent literature on comorbid posttraumatic stress disorder (PTSD) and chronic pain. Starting with the conceptual models presented by Sharp and Harvey (2001) and Asmundson, Coons, Taylor, and Klatz (2002), this review summarizes newer studies that examine prevalence of these comorbid conditions. Additionally, we present an updated synthesis of research on factors that may maintain both chronic physical pain and PTSD in trauma survivors. Consideration of the impact of this comorbidity on psychosocial assessment and treatment also is discussed, with particular attention to issues that warrant additional research. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Architectures,protocols and design for highly dynamic optical networks

In order for dynamic optical networks to be commercially viable, it will be essential to have signaling protocols that can establish connections quickly and minimize the use of transponders for wavelength conversion and regeneration. Rough estimates indicate that in dynamic optical networks, transponders will comprise a significant component (e.g., 60%–70%) of the cost of the optical networking infrastructure. A key performance metric in dynamic networks is the connection blocking probability, and therefore a dynamic optical network infrastructure must be designed to meet stringent blocking requirements (e.g., <10^?3 blocking probability). A key element in achieving that blocking objective is the ability to design the network to support shared transponder pools at selected network nodes, and have the capability to efficiently size those transponder pools to meet the required blocking probabilities. This paper addresses how to size shared transponder pools once the nodes that support those pools have been determined. The methodology can efficiently design for very small transponder-related blocking probability (e.g., <10^?4) by using simple, straightforward simulation and analysis techniques. We also describe a 3-Way-Handshake (3WHS) signaling protocol that can quickly set up connections (e.g., in <100 ms) and identify available resources (available wavelengths, transponders) so the connection setup process minimizes the use of transponders.     

The one-year morphometric and neurodevelopmental outcome of the offspring of women who continued to exercise regularly throughout pregnancy

OBJECTIVE: Our purpose was to test the hypothesis that continuing regular exercise throughout pregnancy alters morphometric and neurodevelopmental outcome at 1 year. STUDY DESIGN: The offspring of 52 women who exercised were compared with those of 52 control subjects who were similar in terms of multiple prenatal and postnatal variables known to influence outcome. All women were enrolled before pregnancy and had clinically normal antenatal and postnatal courses. Neurodevelopment was assessed by blinded examiners at 1 year of age, and morphometrics were obtained at birth and at 1 year of age. RESULTS: At birth, the offspring of the exercising women weighed less (3.38 +/- 0.06 kg vs 3.58 +/- 0.07 kg) and had less body fat (9.5% +/- 0.8% vs 12.6% +/- 0.6%). However, at 1 year, all morphometric parameters were similar, and no clinically significant between-group differences were observed in performance on either the Bayley psychomotor (108 +/- 1 vs 101 +/- 2) or mental (120 +/- 1 vs 118 +/- 1) scales. CONCLUSIONS: These data indicate that the offspring of exercising mothers have normal growth and development during the first year of life.     

Model for In Situ Perchloroethene Dechlorination via Membrane-Delivered Hydrogen

A one-dimensional contaminant fate and transport model was developed to simulate reductive dechlorination of perchloroethene (PCE) in an anaerobic aquifer supplied with hydrogen via a gas-permeable membrane curtain. The model predicted that providing hydrogen at transfer rates equal to the reducing-equivalent demand associated with the groundwater PCE flux would mineralize 75% of the PCE-bound chlorine to chloride and, furthermore, that 0.55 moles of chloride would be released per mole of hydrogen transferred. Supplying higher hydrogen transfer rates was predicted to result in slightly lower dechlorination efficiencies and significantly lower dechlorination yields due to greater methanogenic growth and concomitant displacement of dehalorespirers away from the hydrogen-supply membranes. The model also predicted that high hydrogen-utilizing biomass concentrations would develop near the membranes, resulting in minimal hydrogen dispersal. Model predictions were qualitatively similar to results attained in experimental soil column studies; however, incorporation of homoacetogenesis and acetate utilization by dehalorespirers, as well as hydrogen production via fermentation of biomass decay products, would have improved agreement between model simulations and experimentally observed dechlorination performance.     

Nasal ventilation in pregnancy: treatment of nocturnal hypoventilation in a patient with kyphoscoliosis

The management of a young woman with congenital kyphoscoliosis, who developed symptomatic nocturnal hypoventilation during the third trimester of pregnancy, is described. Nasal intermittent positive pressure ventilation (NIPPV) was safely and effectively used to correct nocturnal hypoxaemia and hypercapnia from the 30th-36th week of gestation, when a healthy boy was delivered by Caesarean section. Following delivery, the mother no longer required NIPPV and returned to her prepregnancy level of activity.