Control/structures interaction study of two 300 KW dual-keel space station concepts

The results of an investigation of the influence of structural stiffness of the space station framework on the controllability of two 300 kw class, solar dynamic powered, dual-keel space station designs are presented. The two design concepts differed only in the truss bay dimensions of the structural framework of the stations. Two control studies were made: (1) A study of the interaction of the framework structural response with the reaction control system used for attitude control during an orbital reboost maneuver; and (2) A study of the stability of the space station attitude control system with sensors influenced by the elastic deformations of the station framework. Although both configurations had acceptable control characteristics, the configuration with the larger truss bay dimension and its increased structural stiffness had more attractive characteristics for pointing control of the solar dynamic system during reboost and for attitude control during normal in-orbit operations

Virtual Design of a Four-Bed Molecular Sieve for Exploration

Aboard the International Space Station, CO2 is removed from the cabin atmosphere by a four-bed molecular sieve (4BMS) process called the Carbon Dioxide Removal Assembly (CDRA).1 This 4BMS process operates by passing the CO2-laden air through a desiccant bed to remove any humidity and then passing the dried air through a sorbent bed to remove the CO2. While one pair of beds is in use, the other pair is thermally regenerated to allow for continuous CO2 removal

Uncertainty Analysis via Failure Domain Characterization: Polynomial Requirement Functions

This paper proposes an uncertainty analysis framework based on the characterization of the uncertain parameter space. This characterization enables the identification of worst-case uncertainty combinations and the approximation of the failure and safe domains with a high level of accuracy. Because these approximations are comprised of subsets of readily computable probability, they enable the calculation of arbitrarily tight upper and lower bounds to the failure probability. A Bernstein expansion approach is used to size hyper-rectangular subsets while a sum of squares programming approach is used to size quasi-ellipsoidal subsets. These methods are applicable to requirement functions whose functional dependency on the uncertainty is a known polynomial. Some of the most prominent features of the methodology are the substantial desensitization of the calculations from the uncertainty model assumed (i.e., the probability distribution describing the uncertainty) as well as the accommodation for changes in such a model with a practically insignificant amount of computational effort

Organochloride pesticides in California sea lions revisited

BACKGROUND: Dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants that have been banned in most countries, but considerable amounts continue to cycle the ecosphere. Top trophic level predators, like sea birds and marine mammals, bioaccumulate these lipophilic compounds, reflecting their presence in the environment. RESULTS: We measured concentrations of tDDT (p,p' - DDT + p,p' - DDD + p,p' - DDE) and PCBs in the blubber of dead California sea lions stranded along the California coast. tDDT and PCB concentrations were 150 ± 257 ug/g lipid weight (mean ± SD) and 44 ± 78 ug/g lipid weight, respectively. There were no differences in tDDT or PCB concentrations between animal categories varying in sex or age. There was a trend towards a decrease in tDDT and PCB concentrations from northern to southern California. The lipid content of the blubber was negatively correlated with levels of tDDT and PCBs. tDDT concentrations were approximately 3 times higher than PCB concentrations. CONCLUSIONS: tDDT levels in the blubber of California sea lions decreased by over one order of magnitude from 1970 to 2000. PCB level changes over time were unclear owing to a paucity of data and analytical differences over the years. Current levels of these pollutants in California sea lions are among the highest among marine mammals and exceed those reported to cause immunotoxicity or endocrine disruption

Organochloride pesticides in California sea lions revisited: Correction

<p/> <p>There has been an error in the publication of this paper <abbrgrp><abbr bid="B1">1</abbr></abbrgrp>; the title should read: 'Organochlorine pollutants in California sea lions revisited'.</p

Structural dynamics and attitude control study of early manned capability space station configurations

A study was performed to determine the vibration and attitude control characteristics of critical space station configurations featuring early manned capability during buildup from initial user support through the operations capability reference station. Five configurations were selected and were examined thus determining the changes that are likely to occur in the characteristics of the system as the station progresses from a single boom structure to a mature, dual keel, operations capability reference station. Both 9 foot and 5 meter truss bay sizes were investigated. All configurations analyzed were stable; however, the 5 meter truss bay size structure exhibited superior stability characteristics

Species-specific relative ahr1 binding affinities of 2,3,4,7,8-pentachlorodibenzofuran explain avian species differences in its relative potency

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Comparative Biochemistry and Physiology Part C: Toxicology & Pharmacology 161 (2014): 21-25, doi:10.1016/j.cbpc.2013.12.005.Results of recent studies showed that 2,3,4,7,8-pentachlorodibenzofuran (PeCDF) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are equipotent in domestic chicken (Gallus gallus domesticus) while PeCDF is more potent than TCDD in ring-necked pheasant (Phasianus colchicus) and Japanese quail (Coturnix japonica). To elucidate the mechanism(s) underlying these differences in relative potency of PeCDF among avian species, we tested the hypothesis that this is due to species-specific differential binding affinity of PeCDF to the aryl hydrocarbon receptor 1 (AHR1). Here, we modified a cell-based binding assay that allowed us to measure the binding affinity of dioxin-like compounds (DLCs) to avian AHR1 expressed in COS-7 (fibroblast-like cells). The results of the binding assay show that PeCDF and TCDD bind with equal affinity to chicken AHR1, but PeCDF binds with greater affinity than TCDD to pheasant (3-fold) and Japanese quail (5-fold) AHR1. The current report introduces a COS-7 whole-cell binding assay and provides a mechanistic explanation for differential relative potencies of PeCDF among species of birds.This research was supported by an unrestricted grant from the Dow Chemical Company to the University of Ottawa, Environment Canada’s Wildlife Toxicology and Disease and STAGE programs and, in part, by a Discovery Grant from the National Science and Engineering Research Council of Canada (Project # 326415-07). The authors wish to acknowledge the support of an instrumentation grant from the Canada Foundation for Infrastructure. Professor Giesy was supported by the Canada Research Chair program and an at large Chair Professorship at the Department of Biology and Chemistry and State Key Laboratory in Marine Pollution, City University of Hong Kong, and the Einstein Professor Program of the Chinese Academy of Sciences. M. Hahn was supported by NOAA Sea Grant (grant number NA06OAR4170021 (R/B-179))

2-chloro-s-triazine herbicides induce aromatase (CYP19) activity in H295R human adrenocortical carcinoma cells: a novel mechanism for estrogenicity?

There is increasing concern that certain chemicals in the environment can cause endocrine disruption in exposed humans and wildlife. Investigations of potential effects on endocrine function have been limited mainly to interactions with hormone receptors. A need exists for the development of alternate in vitro methods to evaluate chemicals for their potential to disturb various endocrine functions via other mechanisms. Our laboratory is using the human H295R adrenocortical carcinoma cell line to examine chemicals for their potential to interfere with the activity and/or expression of several key cytochrome P450 (CYP) enzymes involved in the biosynthesis of steroid hormones. In this report we demonstrated that the commonly used 2-chloro-s-triazine herbicides atrazine, simazine, and propazine dose-dependently (0 -30 M) induced aromatase (CYP19) activity to an apparent maximum of about 2.5-fold in H295R cells. Basal-and triazine-induced aromatase activity was completely inhibited by the irreversible aromatase inhibitor 4-hydroxyandrostenedione (100 M). The triazines increased levels of CYP19 messenger ribonucleic acid (mRNA) between 1.5-and 2-fold. The time-response profile of the induction of aromatase activity and CYP19 mRNA by the triazines was similar to that by 8-bromo-cyclic adenosine monophosphate, a known stimulant of the protein kinase-A pathway that mediates the induction of aromatase in these cells. The observed induction of aromatase, the rate-limiting enzyme in the conversion of androgens to estrogens, may be an underlying explanation for some of the reported hormonal disrupting and tumor promoting properties of these herbicides in vivo. Key Words: aromatase; atrazine; simazine; propazine; triazines; induction; adrenocortical carcinoma; CYP19; mRNA. In recent years, there has been growing concern that certain environmental contaminants and commercial products have the potential to disturb endocrine functions in exposed humans and wildlife. Disturbances by these &quot;endocrine disrupters&quot; may lead to impaired reproductive capacity and other toxicities related to sexual differentiation, growth, and development. Current research has focused on potential interactions with the sex hormone receptors, particularly the estrogen receptor The H295 and H295R (a subpopulation of H295 that forms a monolayer in culture) human adrenocortical carcinoma cell lines have been characterized in detail and shown to express most of the key enzymes necessary for steroidogenesis The triazine family of broad-leaved herbicides has been used increasingly since the 1960s to control weeds, particularly in maize crops, in North America and Europe. The estimated use 1 To whom correspondence should be addressed. Fax: 011-31-30 -253-5077. E-mail: [email protected]. TOXICOLOGICAL SCIENCES 54, 121-127 (2000) Copyright © 2000 by the Society of Toxicology 121 of atrazine in the United States was almost 35,000 tons in 1993 (U.S. MATERIALS AND METHODS Cell culture conditions. H295R cells were obtained from the American Type Culture Collection (ATCC # CRL-2128) and grown in 75-cm 2 flasks (Greiner, Germany) under culture conditions published previously Isolation and amplification of RNA. RNA was isolated using the RNA Insta-Pure System (Eurogentec, Belgium) according to the manufacturerЈs instructions and stored at -70°C. RT-PCRs were performed using the Access RT-PCR System (Promega, U.S.). Northern blotting was not considered as an option because of the low basal expression of aromatase, which could not be detected by other investigators using this technique Aromatase assay. The catalytic activity of aromatase was determined based on the method of RESULT