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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 14 (1977), S. 141-147 
    ISSN: 1432-0630
    Keywords: 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract We have determined by direct molecular beam velocity measurements that translational energy accommodation of O2 molecules scattered from a hot polycrystalline tungsten target is inefficient at high surface temperatures. Translational energy accommodation is inefficient whether the surface is clean or covered with oxygen to a varying extent, even though in the latter case the scattering is diffuse. On a clean tungsten surface the scattering of the O2 was approximately specular and the reaction probability of O2 was constant and greater than 90% over the temperature range 1000K to 2800 K. It was shown by simultaneous helium scattering that atomic surface roughness of an oxygen chemilayer, rather than trapping, is a major cause of the observed diffuse scattering of oxygen. At the lowest surface temperature of 1000 K, with an oxygen chemilayer present, the velocity of the most probable number density of the scattered O2 was lower than in the incoming beam or than that expected for complete equilibration with the surface.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Applied physics 14 (1977), S. 411-413 
    ISSN: 1432-0630
    Keywords: 82.65
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract A direct first step in the mechanism for the initial oxidation of a polycrystalline tungsten surface, the catalyzed dissociation of O2 on it, or the formation of WO X by O2 at intermediate temperatures is shown to occur in ∼10−13 s. Molecular beam experiments demonstrated that the reactivity was greater than 90%, the unreacted O2 was substantially unaccommodated in translational energy to the surface temperature, and the reaction probability was nearly independent of surface temperature from 2800 to 415 K although there was a small increase at 415 K. The general conditions when no molecular surface precursor state contributes to the surface reactivity are discussed.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1912
    Keywords: Key words Microdialysis ; 5-HT release ; Chronic antidepressant ; Citalopram ; 5-HT reuptake inhibitor ; Tolerance ; Autoreceptors ; Frontal cortex ; Dorsal hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Rats were administered the selective serotonin (5-HT) uptake blocker citalopram or saline for 14 days to determine if prolonged treatment would lead to changes in extracellular 5-HT or autoreceptor sensitivity. One day after drug withdrawal, dialysis probes were implanted in the frontal cortex and dorsal hippocampus. Dialysis experiments were carried out using chloral hydrate anesthetized rats. The experimental protocol comprised the administration of three consecutive drug challenges: (1) After stable baseline levels were obtained, citalopram was infused through the dialysis probes to locally block uptake in the forebrain. (2) Subsequently, a 5-HT1B receptor agonist (RU24969 or CP93,129) was infused through the probe to test for changes in terminal autoreceptor sensitivity. (3) Last, citalopram was administered systemically to test the effect of indirect activation of somatodendritic autoreceptors. Under these conditions, with uptake already blocked locally in the forebrain, systemic citalopram produces a decrease in extracellular 5-HT, an effect that can be inhibited by pretreatment with antagonists of 5-HT1A receptors. The results indicate that during local infusion of citalopram extracellular 5-HT was significantly higher in the dorsal hippocampus of the chronic citalopram as compared to saline treatment group. This difference persisted throughout the full time course of the experiment. However, the decreases in 5-HT levels produced by local infusion of a 5-HT1B receptor agonist or after systemic citalopram administration were not significantly different between the chronic citalopram and saline treated groups. There were no significant differences between chronic citalopram and saline treated animals in frontal cortex. These results suggest that prolonged inhibition of 5-HT uptake may produce a selective change in the regulation of release from median raphe 5-HT neurons, but this change could not be clearly linked to a change in nerve terminal or somatodendritic autoreceptor sensitivity.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1912
    Keywords: Microdialysis ; 5-HT release ; Chronic antidepressant ; Citalopram ; 5-HT reuptake inhibitor ; Tolerance ; Autoreceptors ; Frontal cortex Dorsal hippocampus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were administered the selective serotonin (5-HT) uptake blocker citalopram or saline for 14 days to determine if prolonged treatment would lead to changes in extracellular 5-HT or autoreceptor sensitivity. One day after drug withdrawal, dialysis probes were implanted in the frontal cortex and dorsal hippocampus. Dialysis experiments were carried out using chloral hydrate anesthetized rats. The experimental protocol comprised the administration of three consecutive drug challenges: (1) After stable baseline levels were obtained, citalopram was infused through the dialysis probes to locally block uptake in the forebrain. (2) Subsequently, a 5-HT1B receptor agonist (RU24969 or CP93,129) was infused through the probe to test for changes in terminal autoreceptor sensitivity. (3) Last, citalopram was administered systemically to test the effect of indirect activation of somatodendritic autoreceptors. Under these conditions, with uptake already blocked locally in the forebrain, systemic citalopram produces a decrease in extracellular 5-HT, an effect that can be inhibited by pretreatment with antagonists of 5-HT1A receptors. The results indicate that during local infusion of citalopram extracellular 5-HT was significantly higher in the dorsal hippocampus of the chronic citalopram as compared to saline treatment group. This difference persisted throughout the full time course of the experiment. However, the decreases in 5-HT levels produced by local infusion of a 5-HT1B receptor agonist or after systemic citalopram administration were not significantly different between the chronic citalopram and saline treated groups. There were no significant differences between chronic citalopram and saline treated animals in frontal cortex. These results suggest that prolonged inhibition of 5-HT uptake may produce a selective change in the regulation of release from median raphe 5-HT neurons, but this change could not be clearly linked to a change in nerve terminal or somatodendritic autoreceptor sensitivity.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1573-2967
    Keywords: carbon dioxide ; sequestration ; plume ; pH ; toxicity ; zooplankton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Feasibility studies suggest that the concept of capturing CO2 from fossil fuel power plants and discharging it to the deep ocean could help reduce atmospheric CO2 concentrations. However, the local reduction in seawater pH near the point of injection is a potential environmental impact. Data from the literature reporting on toxicity of reduced pH to marine organisms potentially affected by such a plume were combined into a model expressing mortality as a function of pH and exposure time. Since organisms exposed to real plumes would experience a time‐varying pH, methods to account for a variable exposure were reviewed and a new method developed based on the concept of isomortality. In part II of this paper, the method is combined with a random‐walk model describing the transport of passive organisms through a low pH plume leading to a Monte‐Carlo‐like risk assessment which is applied to several candidate CO2 injection scenarios.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2967
    Keywords: carbon dioxide ; plume ; pH ; random walk ; diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A method to evaluate aquatic mortality given a pollutant distribution is presented and applied to several sample low pH plumes representing various ocean CO2 disposal schemes. The method is an improvement over current analysis because it integrates the mortality due to time‐varying exposure to low pH with the probabilistic experiences of passive organisms subject to turbulent lateral diffusion as they pass through the plume. For the examples presented, the plume was discretized laterally into lanes and longitudinally by time steps, and a random walk model accounting for the scale‐dependent nature of relative diffusion was used to simulate the organism pathways over one time step. From these simulations, the probability that an organism will be in a given lane, $$\dot \jmath $$ , one time step after it starts from an initial lane, $$i$$ , was determined for all combinations of $$i$$ and $$\dot \jmath $$ . These probabilities were used to find the number of organisms following each of the possible pathways, and the mortality to the organisms due to their time varying exposure to low pH was determined by using the toxicity model described in part I of this paper. The integrated method allows the impact of the plume to be described in terms of total organism mortality as well as spatial deficit of organisms.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 29 (1997), S. 417-425 
    ISSN: 0887-3585
    Keywords: nonlinear dynamics ; chaotic motion in complex systems ; protein folding pathways ; molecular dynamics ; Lyapunov exponent ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: MD simulations, currently the most detailed description of the dynamic evolution of proteins, are based on the repeated solution of a set of differential equations implementing Newton's second law. Many such systems are known to exhibit chaotic behavior, i.e., very small changes in initial conditions are amplified exponentially and lead to vastly different, inherently unpredictable behavior. We have investigated the response of a protein fragment in an explicit solvent environment to very small perturbations of the atomic positions (10-3-10-9 Å). Independent of the starting conformation (native-like, compact, extended), perturbed dynamics trajectories deviated rapidly, leading to conformations that differ by approximately 1 Å RMSD within 1-2 ps. Furthermore, introducing the perturbation more than 1-2 ps before a significant conformational transition leads to a loss of the transition in the perturbed trajectories. We present evidence that the observed chaotic behavior reflects physical properties of the system rather than numerical instabilities of the calculation and discuss the implications for models of protein folding and the use of MD as a tool to analyze protein folding pathways. Proteins 29:417-425, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 37 (1903), S. 353-377 
    ISSN: 0863-1778
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 126 (1923), S. 54-54 
    ISSN: 0863-1786
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: No abstract.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Polymers for Advanced Technologies 3 (1992), S. 323-329 
    ISSN: 1042-7147
    Keywords: Polyanhydrides ; Pulmonary neoplasms ; Mice ; Chemotherapy ; Cisplatin ; BCNU ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Investigations were undertaken to determine whether anti-cancer drugs introduced locally into the lung using bioerodible polyanhydride microspheres as carriers would demonstrate both efficacy and reduced toxicity.BCNU (carmustine) and CDDP (cisplatin), loaded in polyanhydride microspheres, were administered to mice bearing either of two tumors selected for their affinity for the lung: the B16F10 melanoma and the recently established GL26F4 glioma. Following intravenous inoculation of these tumor cells, the number of metastatic foci formed in the lung follows a predictable time course and can readily be determined. Comparisons were made between the efficacy of microspheres introduced into the lung by intratracheal intubation (IT) and of those administered by intraperitoneal injection (IP). Administration of microspheres loaded either with BCNU or cisplatin reduced the detectable metastatic foci by 25-90% depending on the tumor load, both when administered IP and IT.Toxicity was assessed by flow cytometric analysis of bone marrow cellularity as well as by determination of mortality rates. Intratracheal administration of either cisplatin or BCNU reduced the deleterious systemic effects observed when the drug was administered by IP injection. This was seen at high drug levels, where significant mortality occurred only in animals given drug injections IP; and at lower levels where IP injection led to a reduction of bone marrow blast cells, while IT administration caused no detectable effect on marrow cellularity.Since local delivery of BCNU or cisplatin through bioerodible polyanhydride microspheres induces significantly less systemic damage while demonstrating efficacy equal to or exceeding that of IP injection, this mode of drug delivery warrants further and more detailed exploration. Moreover, the method may be applicable to the treatment of other chronic pulmonary pathologies.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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