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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 6177-6181 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dc voltage output from a hysteretic Josephson junction which is locked to an ac frequency source differs from the ideal Josephson relation if the junction drives a current about a closed superconducting circuit. The difference in voltage ΔV from two hysteretic Josephson junctions driven in series opposition is proportional to the difference in their driving frequencies Δω if the junctions are each biased to the nth voltage step. It is shown here, however, that ΔV is systematically smaller than the voltage difference ΔV0 predicted by the ideal junction relation ΔV0=(n(h-dash-bar)/2e)Δω. If the loop inductance approaches zero, the smallest detectable voltage difference ΔV0 between two junctions is limited by the intrinsic Josephson inductance. For arrays of more than one junction, however, ΔV0 remains proportional to the loop inductance.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 5161-5163 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Spin injection into and spin transport through silicon spacer layers in iron/silicon/cobalt structures has been investigated. Ultrahigh vacuum evaporated silicon spacers of varying crystal quality from amorphous to epitaxial of thicknesses from 10 to 200 Å were shown to improve their electrical conduction with increasing crystallinity, but no spin dependent transport was observed through the structure. Silicon and iron interdiffusion was also observed at the interfacial region. Device quality silicon was studied using 460 and 540 μm doped silicon wafers of resistivity 0.1 and 1 Ω cm, respectively, polished on both sides, onto which were deposited iron and cobalt layers. Sharp metal-semiconductor interfaces were achieved in this way, but no spin dependent transport, putting an upper limit on the spin diffusion length in device quality silicon wafers. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Boston, MA, USA : Blackwell Science Inc
    Restoration ecology 11 (2003), S. 0 
    ISSN: 1526-100X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract One of the greatest challenges for ecologists this century will be restoring forests on degraded tropical lands. This restoration will require understanding complex processes that shape successional pathways, including interactions between trees and other plants. Shrub species often quickly invade disturbed tropical lands, yet little is known about whether they facilitate or inhibit subsequent tree recruitment and growth. We examined how shrubs and other vegetation (e.g., vines, grasses, herbs) affect tree recruitment, survival, and growth during the first 6 years of forest succession in Kibale National Park, Uganda. The study was undertaken in two recently logged exotic softwood plantations. We studied the successional trajectories in two recently logged areas that varied in their initial densities of trees and shrubs. Analyses suggested tree seedling presence and density were not strongly related to shrub density or height during succession. Tree sapling presence and density were positively significantly related to shrub density and height. We found little response in the tree community to experimental shrub removal, and although removal of all nontree vegetation temporarily enhanced tree growth, the effect disappeared after 2 years. Some early-successional trees benefited from reduced competition, whereas some mid-successional trees benefited from the presence of other vegetation. Some specific tree species responded strongly to vegetation removal. We interpret our findings in light of designing manipulations promoting forest restoration for biodiversity conservation and conclude with four tentative guidelines: (1) manage at the species level, not the community level; (2) increase facilitation for seedlings, reduce competition for saplings; (3) be cautious of assumptions about plant interactions; and (4) be adaptable and creative with new strategies when manipulations fail.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 61 (1993), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Hippocampal mossy fiber (MF) nerve endings may be isolated in a subcellular fraction (P3) that releases both prodynorphin-derived peptides and glutamate (Glu) in a calcium-dependent manner when depolarized. However, this isolation procedure does not yield a pure preparation of MF synaptosomes. The present study evaluates the proportion of dynorphin (Dyn) and Glu that is released from synaptosomes in the P3 fraction that are of MF origin. We have addressed this issue by determining the degree to which a selective lesion of the dentate granule cell/MF system in vivo concomitantly reduces the exocytosis of Dyn and Glu from the P3 subcellular fraction. Unilateral injections of colchicine into the dentate gyrus resulted in a substantial and selective degeneration of the granule cell/ MF pathway in the rat hippocampal formation. The overall integrated density of the Timm-stained band, which corresponds to the position of the MF terminal field, was estimated to be reduced by 75%. After this extensive loss of MF boutons, the K+-evoked release of Dyn and Glu from the P3 fraction was reduced by 95 and 51 %, respectively. The loss of Timm staining and evoked Dyn release indicate that colchicine effectively eliminated MF synaptosomes from the P3 fraction. Those subcellular entities that were not destroyed by colchicine comprised ∼50% of the protein and evoked Glu release measured by using the P3fraction. In addition, the present results demonstrate that the inhibitory potency of the K opioid agonist U-50.488H was not altered by the elimination of MF boutons from this synaptosomal preparation. This finding indicates that U-50,488H is capable of suppressing Glu exocytosis from both MF and non-MF synaptosomes. These results are consistent with the hypothesis that Dyn peptides and Glu are coreleased from hippocampal MF terminals.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Biochemistry 28 (1989), S. 742-747 
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1520-4995
    Source: ACS Legacy Archives
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 87 (2000), S. 4846-4848 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetorefractive effect (MRE) has been demonstrated in reflection for giant magnetoresistive Co30Ag70/Si(100) granular films, 400 and 1000 Å thick. Measurements of infrared radiation in the 2–14 μm range indicate a sensitivity to polarization of the incident light and an enhanced response at oblique angles of incidence. Direct correlation with dc magnetoresistance measurements has been demonstrated but computer simulations show that current theory is unable to satisfactorily model experimental observation. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A number of enzymes have been measured in the striatum of rats in which the dopamine-containing nerve terminals had been unilaterally destroyed by means of unipolar electrolytic lesions of the medial fore-brain bundle. Fourteen and 28 days after such lesions the tyrosine hydroxylase activity of the striatum was reduced to immeasurably low values, but neither aldehyde dehydrogenase, aldehyde reductase, nor acetylcholine esterase was affected when compared with the striatum from the intact side of the same rat or with those from control rats. These results indicate that in the rat the 3 enzymes are not localized with tyrosine hydroxylase, in the dopaminergic nerve terminals of the striatum. This conclusion is supported by a study of the subcellular localization of aldehyde dehydrogenase in rat brain. This enzyme is distributed between the cytosol and the particulate fraction of brain homogenates separated by centrifugal techniques. with no exceptionally high concentration of the enzyme in the synaptosomal fraction. Because neither of the enzymes of post-deaminative catabolism of dopamine is concentrated in the dopaminergic nerve terminals of the striatum of the rat, it is proposed that in this species the amine is not necessarily taken up by the nerve terminals prior to catabolism.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of neurochemistry 22 (1974), S. 0 
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The Michaelis constants of purified aldehyde dehydrogenase (aldehyde: NAD oxidoreductase, EC 1.2.1.3) and aldehyde reductases (alcohol: NADP oxidoreductase, EC 1.1.1.2) from pig brain have been obtained for a number of biologically important aldehydes. The aldehydes include 3,4-dihydroxyphenylacetaldehyde, D-3,4-dihydroxyphenylglycolaldehyde, and 5-hydroxyindoleacetaldehyde. The relative activities of the aldehyde-catabolizing enzymes in the soluble fractions of the cerebral cortex and caudate nucleus of pig brain have also been obtained. The values are used to show that the metabolic fates of the various aldehydes—and hence of the parent amines—may be explained in terms of the simple kinetics of these enzymes. It is also shown that the metabolic fates of the aldehydes may be influenced by their rates of synthesis. As the rate of aldehyde production increases the proportion of aldehyde reduced may be expected to increase at the expense of the proportion of aldehyde oxidized.It is further concluded from the kinetic constants that selective inhibition of aldehyde dehydrogenase may greatly affect the catabolism of dopamine and 5-hydroxytryptamine by altering the relevant aldehyde concentrations, while the catabolism of norepinephrine is little affected under these circumstances. Conversely, it is concluded that selective inhibition of the aldehyde reductases should scarcely affect the catabolism of dopamine and 5-hydroxytryptamine, but that the catabolism of norepinephrine should be markedly affected.The results also indicate that the concentrations of the various deaminated metabolites of the biogenic amines could be selectively controlled by modulation of the activity of the enzymes of aldehyde catabolism in brain.
    Type of Medium: Electronic Resource
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