25,337 research outputs found
Effects of Hyperbaric Hypoxia on Some Enzyme Systems in the Mammalian Liver
The metabolic effects of hypobaric hypoxic stress on the mammalian liver were studied. The lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) activity of mouse liver homogenates were measured after exposure to an equivalent altitude of 36,000 feet and compared to controls kept at zero altitude. After six and twelve hour incubation periods, the altitude exposed samples demonstrated a significantly higher LDH activity than controls. SDH activity remained unchanged from controls after six hours but was significantly lower than controls after a 12 hour exposure to altitude. It is concluded that the changes in enzyme activity reflect a metabolic control mechanism attempting to maintain adequate energy production during periods of exposure to hypobaric hypoxic stress
Comparison of different methods for estimating snowcover in forested, mountainous basins using LANDSAT (ERTS) images
Snow-covered areas on LANDSAT (ERTS) images of the Santiam River basin, Oregon, and other basins in Washington were measured using several operators and methods. Seven methods were used: (1) Snowline tracing followed by measurement with planimeter, (2) mean snowline altitudes determined from many locations, (3) estimates in 2.5 x 2.5 km boxes of snow-covered area with reference to snow-free images, (4) single radiance-threshold level for entire basin, (5) radiance-threshold setting locally edited by reference to altitude contours and other images, (6) two-band color-sensitive extraction locally edited as in (5), and (7) digital (spectral) pattern recognition techniques. The seven methods are compared in regard to speed of measurement, precision, the ability to recognize snow in deep shadow or in trees, relative cost, and whether useful supplemental data are produced
Treatment approaches for dual diagnosis clients in England
Introduction - Dual diagnosis (DD, co-occurrence of substance use and mental health problems) prevalence data in England are limited to specific regions and reported rates vary widely. Reliable information on actual service provision for dual diagnosis clients has not been collated. Thus a national survey was carried out to estimate dual diagnosis prevalence in treatment populations and describe the service provision available for this client population in drug/alcohol (DAS) and mental health services (MHS). Design - A questionnaire was sent to managers of 706 DAS and 2374 MHS. Overall, 249 (39%) DAS and 493 (23%) MHS participated in the survey. Results - In both DAS and MHS, around 32% of clients were estimated to have dual diagnosis problems. However, fewer than 50% of services reported assessing clients for both problem areas. Regarding specific treatment approaches, most services (DAS: 88%, MHS: 87%) indicated working jointly with other agencies. Significantly fewer services used joint protocols (DAS: 55%, MHS: 48%) or shared care arrangements, including access to external drug/alcohol or mental health teams (DAS: 47%, MHS: 54%). Only 25% of DAS and 17% of MHS employed dual diagnosis specialists. Conclusions - Dual diagnosis clients constitute a substantial proportion of clients in both DAS and MHS in England. Despite recent policy initiatives, joint working approaches tend to remain unstructured
Response of single junction GaAs/GaAs and GaAs/Ge solar cells to multiple doses of 1 MeV electrons
A comparison of the radiation tolerance of MOCVD-grown GaAs cells and GaAs/Ge cells was undertaken using 1 MeV electrons. The GaAs/Ge cells are somewhat more tolerant of 1 MeV electron irradiation and more responsive to annealing than are the GaAs/GaAs cells examined in this study. However, both types of cells suffer a greater degradation in efficiency than has been observed in other recent studies. The reason for this is not certain, but it may be associated with an emitter thickness which appears to be greater than desired. The deep level transient spectroscopy (DLTS) spectra following irradiation are not significantly different for the GaAs/Ge and the GaAs/GaAs cells, with each having just two peaks. The annealing behavior of these peaks is also similar in the two samples examined. It appears that no penalty in radiation tolerance, and perhaps some benefit, is associated with fabricating MOCVD GaAs cells on Ge substrates rather than GaAs substrates
Overcoming the false-minima problem in direct methods: Structure determination of the packaging enzyme P4 from bacteriophage φ13
The problems encountered during the phasing and structure determination of the packaging enzyme P4 from bacteriophage φ13 using the anomalous signal from selenium in a single-wavelength anomalous dispersion experiment (SAD) are described. The oligomeric state of P4 in the virus is a hexamer (with sixfold rotational symmetry) and it crystallizes in space group C2, with four hexamers in the crystallographic asymmetric unit. Current state-of-the-art ab initio phasing software yielded solutions consisting of 96 atoms arranged as sixfold symmetric clusters of Se atoms. However, although these solutions showed high correlation coefficients indicative that the substructure had been solved, the resulting phases produced uninterpretable electron-density maps. Only after further analysis were correct solutions found (also of 96 atoms), leading to the eventual identification of the positions of 120 Se atoms. Here, it is demonstrated how the difficulties in finding a correct phase solution arise from an intricate false-minima problem. © 2005 International Union of Crystallography - all rights reserved
A Behavioral Confirmation and Reduction of the Natural versus Synthetic Drug Bias
Research reveals a biased preference for natural versus synthetic drugs; however, this research is based upon self-report and has not examined ways to reduce the bias. We examined these issues in five studies involving 1,125 participants. In a Pilot Study (N = 110), participants rated the term natural to be more positive than the term synthetic, which reveals a default natural-is-better belief. In Studies 1 (N = 109) and 2 (N = 100), after a supposed personality study, participants were offered a thank you “gift” of a natural or synthetic pain reliever. Approximately 86% (Study 1) and 93% (Study 2) of participants chose the natural versus synthetic pain reliever, which provide a behavioral choice confirmation of the natural drug bias. In Studies 3 (N = 350) and 4 (N = 356), participants were randomly assigned to a control or experimental condition and were asked to consider a scenario in which they had a medical issue requiring a natural versus synthetic drug. The experimental condition included a stronger (Study 3) or weaker (Study 4) rational appeal about the natural drug bias and a statement suggesting that natural and synthetic drugs can be good or bad depending upon the context. In both studies, the natural bias was reduced in the experimental condition, and perceived safety and effectiveness mediated this effect. Overall, these data indicate a bias for natural over synthetic drugs in preferences and behavioral choices, which might be reduced with a rational appeal
Research on the design of adaptive control systems, volume 1 Final report
Adaptive control systems - combined optimization and adaptive control, analysis-synthesis and passive adaptive systems, learning systems, and measurement adaptive system
Structure factor and thermodynamics of rigid dendrimers in solution
The ''polymer reference interaction site model'' (PRISM) integral equation
theory is used to determine the structure factor of rigid dendrimers in
solution. The theory is quite successful in reproducing experimental structure
factors for various dendrimer concentrations. In addition, the structure factor
at vanishing scattering vector is calculated via the compressibility equation
using scaled particle theory and fundamental measure theory. The results as
predicted by both theories are systematically smaller than the experimental and
PRISM data for platelike dendrimers.Comment: 7 pages, 5 figures, submitte
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