Theoretical study of production of unique glasses in space

The potential of producing the glassy form of selected materials in the weightless, containerless nature of space processing is examined through the development of kinetic relationships describing nucleation and crystallization phenomena. Transformation kinetics are applied to a well-characterized system (SiO2), an excellent glass former (B2O3), and a poor glass former (Al2O3) by conventional earth processing methods. Viscosity and entropy of fusion are shown to be the primary materials parameters controlling the glass forming tendency. For multicomponent systems diffusion-controlled kinetics and heterogeneous nucleation effects are considered. An analytical empirical approach is used to analyze the mullite system. Results are consistent with experimentally observed data and indicate the promise of mullite as a future space processing candidate

Joint Compression Therapy in the Prevention of Osteopenia of Prematurity:Current Research and Future Considerations

Osteopenia of prematurity is a metabolic bone disease affecting neonates born during the second trimester of pregnancy and classified as very low birth weight, or less than 1500 grams at birth. Improvements in neonatal nutrition have reduced osteopenia of prematurity by increasing available calcium, phosphorus, magnesium and vitamin D for bone mineralization. Ossification also requires the presence of adequate bone matrix for mineralization to be completed. Passive mechanical stimulation such as joint compression replicates the resistance and weight bearing movements of the fetus in utero. Fetal osteoprogenitor cells are signaled to develop into osteoblasts, thus creating bone matrix which can then be mineralized. Research into the effects of passive physical exercise with joint compression on the prevention of osteopenia of prematurity are compared and discussed to ascertain recommendations for future implementation and considerations

Active Structural Control of Single and Multi-Span Beam Structures Subjected to Transient Loads

This study directly addresses the problem of active control of beam structures under the action of moving masses. In this regard, experimental implementations of the particular active control solutions are still rarely seen in the literature. The main objective is to experimentally implement and validate active control solutions for two small-scale test stands with the aim to reduce the structural deflection. The first supporting structure is modelled as an Euler–Bernoulli simply supported beam, acted upon by moving masses of different weights and velocities. The experimental implementation of the proposed optimal controller poses a particular set of challenges as compared with numerical solutions. Specifically, it can include errors due to discretization and the states cannot be directly measured. The resulting limitations of classical optimal observer techniques are stated and consequently the states are estimated by a method utilizing the mode shapes. It is shown both numerically and experimentally that using electromagnetic actuation, a reduced order controller designed using a time-varying algorithm, provides a reduction of the maximum deflection of up to 38% as compared with the uncontrolled structure. Herein an augmented system model is utilised, which includes the moving mass in the system equation. The controller performance and robustness were tested against a representative set of possible moving load parameters. In consequence of the variations in moving mass weight and speed, the controller gain requires a supplementary adaptation. A simple algorithm that schedules the gain as a function of the weight and speed of the moving mass can achieve both a good performance and an adjustment of the control effort to the specific design requirements. In the second part of this study cubic and linear displacement feedback control approaches are studied experimentally for a simply supported beam as well as for the two-span continuous beam. The two-span beam structure is modelled by approximating the support by spring damper elements of high stiffness and damping coefficient. Piezoelectric macro fibre composites serve as actuators. The control methods are, compared to the previous approach, more straightforward to implement and can handle a stream of moving masses. However, optimality and stability cannot be guaranteed and have to be validated experimentally. The linear displacement feedback shows better performance for low weights of the moving masses whereas the cubic displacement feedback achieves higher deflection reduction for higher weights. In the last part, constrained model predictive control is studied numerically for both of the structures. This is currently the only control approach which can take into account saturation limits explicitly by quadratic programming. In this way, better performance is achieved for both test structures as compared to the displacement feedback control approaches

Michelle Nunn’s midterm result shows that Georgia’s demographics may be shifting to favor the Democrats

In Georgia’s Senate race Republican David Purdue defeated Democrat Michelle Nunn by nearly eight points, despite polling that had shown a much closer contest. Jamie L. Carson, Joel Sievert, and Ryan D. Williamson reflect on Georgia’s midterm election results, writing that in gaining more than 40 percent of the vote, Nunn outperformed many previous Democratic candidates in the state. They argue that if the Democratic Party continues to field good candidates in Georgia, shifting demographics may mean that they will be able to take statewide races within a few election cycles

Religious minority identity associates with stress and psychological health among Muslim and Hindu women in Bangladesh and London

This study examined the association of minority religious identification (Hindu or Muslim) with self-reported stress and psychological symptoms among sedentee and immigrant Bangladeshi women. Women, aged 35-59 (n = 531) were drawn from Sylhet, Bangladesh and London, England. Muslim immigrants in London and Hindu sedentees in Sylhet represented minority religious identities. Muslim sedentees in Sylhet and Londoners of European descent represented majority religious identities. In bivariate analyses, minority religious identity was examined in relation to self-reported measures of stress, nervous tension, and depressed mood. Logistic regression was applied to examine the relationship between these variables while adjusting for marital status, parity, daily walking, and perceived financial comfort. In bivariate analyses, religious minorities reported more stress than religious majorities in all group comparisons (p < .05), and minority Muslims reported more nervous tension and depressed mood than majority Muslims (p < .05). In logistic regression models, minority Muslims had greater odds of high stress than majority Muslims (OR 2.00, 95% CI 1.18-3.39). Minority Muslims had greater odds of stress (OR 3.05, 95% CI 1.51-6.17) and nervous tension (OR 3.37, 95% CI 1.66-6.87) than majority Londoners. Financial comfort reduced odds of stress and symptoms in all models. Socioeconomic situation, immigration history, and minority ethnicity appear to influence the relationship between religious identity and psychosomatic symptoms in Bangladeshi women. Attention to personal and socioeconomic context is important for research examining the association between religion and mental health

Active Vibration Control of a Small-Scale Flexible Structure Subject to Moving-Loads and Experimental Validation

This study directly addresses the problem of optimal control of a structure under the action of moving masses. The main objective is to experimentally implement and validate an active control solution for a small-scale test stand. The supporting structure is modeled as an Euler–Bernoulli simply supported beam, acted upon by moving masses of different weights and velocities. The experimental implementation of the active controller poses a particular set of challenges as compared with the numerical solutions. It is shown both numerically and experimentally that using electromagnetic actuation, a reduced order controller designed using a time-varying algorithm provides a reduction of the maximum deflection of up to 18% as compared with the uncontrolled structure. The controller performance and robustness were tested against a representative set of possible moving load parameters. In consequence of the variations in moving mass weight and speed, the controller gain requires a supplementary adaptation. A simple algorithm that schedules the gain as a function of the weight and speed of the moving mass can achieve both a good performance and an adjustment of the control effort to the specific design requirements

Characterization of an autotrophic sulfide-oxidizing marine Arcobacter sp. that produces filamentous sulfur

Author Posting. © American Society for Microbiology, 2002. This article is posted here by permission of American Society for Microbiology for personal use, not for redistribution. The definitive version was published in Applied and Environmental Microbiology 68 (2002): 316-325, doi:10.1128/AEM.68.1.316-325.2002.A coastal marine sulfide-oxidizing autotrophic bacterium produces hydrophilic filamentous sulfur as a novel metabolic end product. Phylogenetic analysis placed the organism in the genus Arcobacter in the epsilon subdivision of the Proteobacteria. This motile vibrioid organism can be considered difficult to grow, preferring to grow under microaerophilic conditions in flowing systems in which a sulfide-oxygen gradient has been established. Purified cell cultures were maintained by using this approach. Essentially all 4',6-diamidino-2-phenylindole dihydrochloride-stained cells in a flowing reactor system hybridized with Arcobacter-specific probes as well as with a probe specific for the sequence obtained from reactor-grown cells. The proposed provisional name for the coastal isolate is "Candidatus Arcobacter sulfidicus." For cells cultured in a flowing reactor system, the sulfide optimum was higher than and the CO2 fixation activity was as high as or higher than those reported for other sulfur oxidizers, such as Thiomicrospira spp. Cells associated with filamentous sulfur material demonstrated nitrogen fixation capability. No ribulose 1,5-bisphosphate carboxylase/oxygenase could be detected on the basis of radioisotopic activity or by Western blotting techniques, suggesting an alternative pathway of CO2 fixation. The process of microbial filamentous sulfur formation has been documented in a number of marine environments where both sulfide and oxygen are available. Filamentous sulfur formation by "Candidatus Arcobacter sulfidicus" or similar strains may be an ecologically important process, contributing significantly to primary production in such environments.This work was supported by National Science Foundation grant IBN-9630054

Comparative proteomics of related symbiotic mussel species reveals high variability of host-symbiont interactions.

Deep-sea Bathymodiolus mussels and their chemoautotrophic symbionts are well-studied representatives of mutualistic host-microbe associations. However, how host-symbiont interactions vary on the molecular level between related host and symbiont species remains unclear. Therefore, we compared the host and symbiont metaproteomes of Pacific B. thermophilus, hosting a thiotrophic symbiont, and Atlantic B. azoricus, containing two symbionts, a thiotroph and a methanotroph. We identified common strategies of metabolic support between hosts and symbionts, such as the oxidation of sulfide by the host, which provides a thiosulfate reservoir for the thiotrophic symbionts, and a cycling mechanism that could supply the host with symbiont-derived amino acids. However, expression levels of these processes differed substantially between both symbioses. Backed up by genomic comparisons, our results furthermore revealed an exceptionally large repertoire of attachment-related proteins in the B. thermophilus symbiont. These findings imply that host-microbe interactions can be quite variable, even between closely related systems