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  • Springer  (13)
  • Blackwell Publishing Ltd  (1)
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  • 1
    ISSN: 1432-1106
    Keywords: Supplementary motor area (SMA) ; Cingulate cortex ; Premotor areas ; Medial wall of the hemisphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary We injected wheat germ agglutinin conjugated to horseradish peroxidase into different segments of the spinal cord in order to examine the topographic organization of corticospinal projections from the medial wall of the hemisphere. We observed that substantial projections to the spinal cord originate not only from the supplementary motor area (SMA) in area 6, but also from 2 regions within the cingulate sulcus. The distribution of labeled neurons following tracer injections into different spinal cord segments indicates that corticospinal projections from the SMA and from the 2 cingulate regions are somatotopically organized. These findings together with other recent anatomical observations suggest that the corticospinal projections from the medial wall of the hemisphere provide the basal ganglia and limbic system with a somatotopically organized access to spinal cord mechanisms.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The extraction and purification of gangliosides from brains of animals infected with the scrapie agent was evaluated by scaling-down a large-scale procedure currently used with bovine brains. Inactivation experiments employed hamster brains infected with the 263 K strain of scrapie. Residual infectivity was determined at different points of the procedure and in the final preparation by an in vivo animal bioassay. The efficacy of single steps, which included chemicals or physical techniques known to affect the viability of the scrapie agent, was verified by spiking experiments where known amounts of infectivity were added just before each single step. Infectivity was significantly diminished at early stages of the purification, and no infectivity was detected in the final preparation containing purified gangliosides. The significant reduction of infectivity at intermediate steps and the total absence of detectable infectivity in the final product confirmed that a combination of heat and exposure to sodium hydroxide, even in the presence of organic solvents, completely inactivated the scrapie agent.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0649
    Keywords: 82.50 ; 33
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 35 (2003), S. 143-152 
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. The dynamics of minority games with agents trading on different time scales is studied via dynamical mean-field theory. We analyze the case where the agents’ decision-making process is deterministic and its stochastic generalization with finite heterogeneous learning rates. In each case, we characterize the macroscopic properties of the steady states resulting from different frequency and learning rate distributions and calculate the corresponding phase diagrams. Finally, the different roles played by regular and occasional traders, as well as their impact on the system’s global efficiency, are discussed.
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  • 5
    ISSN: 1434-6036
    Keywords: PACS. 05.20.-y Classical statistical mechanics – 04.40.-b Self-gravitating systems – 64.60.Cn Order-disorder transformations; statistical mechanics of model systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We investigate the statistical equilibrium properties of a system of classical particles interacting via Newtonian gravity, enclosed in a three-dimensional spherical volume. Within a mean-field approximation, we derive an equation for the density profiles maximizing the microcanonical entropy and solve it numerically. At low angular momenta, i.e. for a slowly rotating system, the well-known gravitational collapse “transition” is recovered. At higher angular momenta, instead, rotational symmetry can spontaneously break down giving rise to more complex equilibrium configurations, such as double-clusters (“double stars”). We analyze the thermodynamics of the system and the stability of the different equilibrium configurations against rotational symmetry breaking, and provide the global phase diagram.
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  • 6
    ISSN: 1434-6079
    Keywords: PACS. 36.40.-c Atomic and molecular clusters - 34.30.+h Intramolecular energy transfer; intramolecular dynamics; dynamics of van der Waals molecules - 68.10.Jy Kinetics (evaporation, adsorption, condensation, catalysis, etc.)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We performed both experiments and molecular dynamics simulations for the scattering of mixed from a graphite surface under conditions where evaporation of thermalized small fragments is the main channel to evacuate the excess collision energy of the cluster impact. In spite of the expected thermal nature of the scattering process, we find average temperatures for the evaporating cluster particles that are considerably higher for krypton than for argon. We discuss the possible influence of the involved binding energies and the probable role of the incident cluster structure on these new results.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The binding of the potent adenosine uptake inhibitor [3H]nitrobenzylthioinosine ([3H]NBI) to brain membrane fractions was investigated. Reversible, saturable, specific, high-affinity binding was demonstrated in both rat and human brain. The Kd in both was 0.15 nM with Bmax values of 140–200 fmol/mg protein. Linear Scatchard plots were routinely obtained, indicating a homogeneous population of binding sites in brain. The highest density of binding sites was found in the caudate and hypothalamus in both species. The binding site was heat labile and trypsin sensitive. Binding was also decreased by incubation of the membranes in 0.05% Triton X-100 and by treatment with dithiothreitol and iodoacetamide. Of the numerous salt and metal ions tested, only copper and zinc had significant effects on [3H]NBI binding. The inhibitory potencies of copper and zinc were IC50= 160 μM and 6 mM, respectively. Subcellular distribution studies revealed a high percentage of the [3H]NBI binding sites on synaptosomes, indicating that these sites were present in the synaptic region. A study of the tissue distribution of the [3H]NBI sites revealed very high densities of binding in erythrocyte, lung, and testis, with much lower binding densities in brain, kidney, liver, muscle, and heart. The binding affinity in the former group was approximately 1.5 nM, whereas that in the latter group was 0.15 nM, suggesting two types of binding sites. The pharmacologic profile of [3H]NBI binding was consistent with its function as the adenosine transport site, distinct from the adenosine receptor, since thiopurines were very potent inhibitors of binding whereas adenosine receptor ligands, such as cyclohexyladenosine and 2-chloroadenosine, were three to four orders of magnitude less potent. [3H]NBI binding in brain should provide a useful probe for the study of adenosine transport in the brain.
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  • 8
    ISSN: 1432-1998
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The objective of the investigation was to determine what effect intracranial pathology has on alterations of superior sagittal sinus blood flow, and to determine the role of color flow Doppler imaging of the superior sagittal sinus in the diagnosis of intracranial pathology in the neonate and infant. One hundred examinations were performed prospectively in 96 patients. The velocity was determined with an angle correction at 30–60° and was obtained with and without gentle transducer compression. Superior sagittal sinus thrombosis was identified in two patients by the absence of flow. Multiplet-tests for independent measures showed no clinically significant differences between flow velocities with regard to intracranial hemorrhage, ventriculomegaly, extracorporeal membrane oxygenation therapy or prematurity. The authors conclude that color flow Doppler can accurately diagnose superior sagittal sinus thrombosis and may be used to screen high risk neonates such as those with thrombosis elsewhere or those treated with extracorporeal membrane oxygenation. No clinically significant associations were found between superior sagittal sinus flow velocity and any of the parameters evaluated in this study.
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  • 9
    ISSN: 1434-6079
    Keywords: PACS. 36.40.-c Atomic and molecular clusters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: We present two complementary techniques that provide detailed diagnostics of supersonic beams involving several species. First, surface scattering, together with quadrupole mass spectrometer detection, yields the monomer percentage for each species within the beam. Second, analyses of beam profiles for different masses after scattering by a buffer gas permit determination of mixed cluster presence and, if any, of cluster sizes and compositions. The two techniques are applied to supersonic expansions of an argon-nitrogen mixture. We discuss the results that provide new insight in binary nucleation processes.
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  • 10
    ISSN: 1434-6079
    Keywords: PACS. 36.40.-c Atomic and molecular clusters – 68.03.Fg Evaporation and condensation – 68.49.Fg Cluster scattering from surfaces
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: In this paper, we show how the use of a third non-condensable species gives both new insight and control on the binary nucleation process during supersonic expansion of gas mixtures. We present the case of an oxygen-nitrogen mixture diluted in various proportions of helium. Using beam diagnostics, we determine the mean cluster composition and size as well as the percentage of uncondensed matter present in the beam. The presence of helium permits us to understand the cooling and clustering role played by each species during the expansion process. We discuss, in particular, its influence on the dramatic composition change observed at the nucleation onset.
    Type of Medium: Electronic Resource
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