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  • 1
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Solid state phenomena Vol. 131-133 (Oct. 2007), p. 553-558 
    ISSN: 1662-9779
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Physics
    Notes: The effect of phonon confinement and impurity doping in silicon nanowires (SiNWs)synthesized by laser ablation were investigated. The diameter of SiNWs was controlled by thesynthesis parameters during laser ablation and the subsequent thermal oxidation. Thermal oxidationincreases the thickness of the SiNWs’ surface oxide layer, resulting in a decrease in their crystallineSi core diameter. This effect causes a downshift and asymmetric broadening of the Si optical phononpeak due to phonon confinement. Boron doping was also performed during the growth of SiNWs.Local vibrational modes of boron (B) in silicon nanowires (SiNWs) synthesized by laser ablationwere observed at about 618 and 640 cm–1 by Raman scattering measurements. Fano broadening dueto coupling between discrete optical phonons and the continuum of interband hole excitations wasalso observed in the Si optical phonon peak. These results prove that B atoms were doped in theSiNWs
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 24 (1975), S. 1-14 
    ISSN: 1432-1106
    Keywords: Cerebro-ponto-cerebellar pathway ; Pontine nuclei cells ; Fast and slow relays ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Cerebrally-induced responses of pontine nuclei cells (PN cells) were studied in cats anesthetized with pentobarbitone sodium and with the midbrain transected bilaterally sparing only the cerebral peduncles. After stimulating the subcortical white matter, the internal capsule or the cerebral peduncle, mass potentials were recorded from the cut end of fibres in the brachium pontis (BP) and in the pyramid at the level of the trapezoid body. These potentials were regarded as indicating, respectively, the size of an output volley of PN cells and the size of its causative input volley through the pyramidal tract. BP responses consisted of short- and long-latency potentials which were caused by fast and slow conducting pyramidal tract volleys, respectively. The input-output relations for fast component responses took a characteristic S-shaped form resembling those obtained for the monosynaptic spinal reflex. The input-output relations for slow component responses were almost linear. Both fast and slow BP responses were remarkably potentiated after single or relatively brief repetitive peduncular stimulation, but were depressed after long-lasting high-frequency activation. During repetitive stimulation with varied frequencies, fast and slow BP responses showed different patterns of frequency-dependence of their amplitudes. These results suggest the existence of two separate transmission lines with different properties in the cerebro-ponto-cerebellar pathway.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1106
    Keywords: Cerebro-ponto-cerebellar pathway ; Pontine nuclei cells ; Fast and slow relays ; Pyramidal collaterals ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Extracellular and intracellular recordings were made from single cells in the pontine nuclei (PN) of the cat. PN cells were identified by antidromic invasion from the cerebellum by stimulating either the brachium pontis (BP) or the white matter near the cerebellar nuclei. The cerebrally-induced impulses excited PN cells postsynaptically with a monosynaptic latency. Both fast and slow conducting cortical fibres contributed to the corticopontine excitation, so that the latency varied over a wide range. Measurements of the latencies for antidromic and corticopontine excitation and of the distances between stimulated sites permitted the calculation of conduction velocities of PN cell axons and of their cortical input fibres. PN cells with fast conducting axons received convergence from both fast and slow cortical fibres, whereas PN cells with slow axons were innervated only by slow cortical fibres. The majority of PN cells were also excited by stimulating the medullary pyramid through collaterals of the pyramidal tract. Evidence of abundant pyramidal collaterals was provided by the collision technique. The functional role of the PN is discussed in connection with the cerebro-cerebellar loop circuits.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-1106
    Keywords: Accommodation ; PT cell ; Membrane potential ; Fast-slow cell groups
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Threshold-latency curves were determined by intracellular application of linearly rising currents to cat pyramidal tract (PT) cells under various conditions of impalement. The nature of the curves was found to vary considerably, depending mainly upon the resting potential level. Three different types of curves were distinguished: (1) the ceiling type at relatively high resting potentials, (2) the simple type at moderate levels and (3) the minimal gradient type under depolarized conditions. In the first type, the ceiling increased with increasing membrane potential level. The second type attained an extremely low ceiling. 2. After eliminating the effects of the resting potential, a significant difference was still found between the ceilings of fast and slow PT cells, the ceilings being higher in the former than in the latter. 3. Parameters determining the threshold-latency curve were analyzed by applying current steps intracellularly, as described in previous paper. The variations of the ceiling due to the resting potential level were found to be dominated by the first exponential component of the membrane, while those between fast and slow cells were ascribable to the second exponential component.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Pontine nuclei cells ; Unitary EPSPs ; Synaptic organization ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Intracellular potentials of pontine nuclei (PN) cells were recorded in cats anesthetized with pentobarbitone sodium. 2. Stimulation of the cerebellar nuclear regions or the brachium pontis induced an antidromic action potential composed of IS-SD spikes, after-depolarization and after-hyperpolarization. 3. Cerebellar stimulation produced EPSPs only in a few PN cells. 4. Activation of the corticopontine or pyramidal tract produced in all PN cells an EPSP built up from the unitary components with variable amplitudes and time courses. Paired or repetitive activation revealed a property of the frequency potentiation of the EPSP. 5. Unitary EPSPs also occurred spontaneously. A great majority of these spontaneous EPSPs were cerebral in origin, and had amplitudes and time courses comparable with those evoked by stimulation of the corticopontine or pyramidal tract. 6. The half-width versus time to peak relationship of these unitary EPSPs suggested a dendritic location of the synapses with variable distances from the soma. It is assumed that large, proximal synapses serve for efficient relay of signals while small, distal synapses for their integration.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 11 (1970), S. 263-281 
    ISSN: 1432-1106
    Keywords: Repetitive discharge ; PT cell ; Fast-slow cell groups ; Kinetictonic patterns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Responses to current steps were recorded from pyramidal tract (PT) cells of the cat by means of intracellular microelectrodes. PT cells with resting potentials from -60 to -80 mV set up a well sustained repetitive discharge during stimulation. When comparing fast and slow PT cells, quantitative differences were found between them in the pattern of repetitive firing. Thus, (1) the rheobase is lower in slow PT cells (mean and S.D.; 0.53±0.63 nA) than in fast cells (1.57±1.11 nA). (2) Following stimulation with a current step twice rheobase the latency and the successive interspike intervals are shorter in fast PT cells than in slow cells. (3) The interspike interval distribution shows a greater irregularity in fast PT cells than in slow cells. At firing rates around 30 impulses/sec the coefficient of variation has a mean value of 0.243 for fast PT cells and 0.085 for slow cells. (4) Fast PT cells show a greater decrease of firing rate during the initial 300 msec of current stimulation (adaptation) than do slow cells. The mean value of this initial decrease is 1.85 times the later steady firing rate in fast PT cells and 0.56 times in slow cells. (5) The slope constant of the firing rate-current relationship is larger in fast PT cells, being five times or more than in slow cells. These characteristics of firing pattern are termed “kinetic” and “tonic” for fast and slow PT cells respectively, and their functional meanings are discussed in comparison with other neural organs.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-1106
    Keywords: Sodium ions ; Electrogenic Na pump ; Post-tetanic hyperpolarization ; PT cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Sodium ions were injected into cat pyramidal tract (PT) cells electrophoretically through an intracellular NaCl or Na glutamate-filled microelectrode. Following an injection there were decreases in the maximum rates of rise and fall of the spike potential and there was displacement of the inhibitory postsynaptic potential in a depolarizing direction. These changes recovered with an exponential time course, indicating concomitant changes in the internal sodium, potassium and chloride concentrations under the operation of the sodium pump in extruding excess sodium. From the exponential recovery curve, the rate constant of active sodium extrusion was estimated as about 60 hr−1 in fast PT cells and about 90 hr−1 in slow PT cells. It was suggested that the sodium pump was at least partly electrogenic, since the resting membrane was hyperpolarized by the sodium injection to the degree which depended on the amount of sodium-injecting current. Further support for this possibility was obtained by the experiment of high-frequency activation of PT cells, in which the sodium entry through the active membrane developed a slow post-tetanic hyperpolarization.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Experimental brain research 5 (1968), S. 173-188 
    ISSN: 1432-1106
    Keywords: Accommodation ; PT cell ; Membrane impedance ; Linearly rising currents ; Current steps
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary 1. Single glass microelectrodes were inserted into pyramidal tract (PT) cells of cat's cerebral cortex. Accommodative properties of their membranes were investigated by intracellular injection of depolarizing currents. 2. The threshold-latency curve was derived by applying linearly rising currents. When the rising slope of the current was decreased gradually, the threshold intensity first decreased, and then later increased, reaching a certain constant value in the manner of a ceiling. 3. Factors determining this characteristic threshold-latency curve were analyzed by using current steps. A special form of the membrane impedance was thus revealed; the time course of the potential changes induced by current steps can be approximated by the sum of three exponential curves, just as in motoneurones. Threshold-latency curves calculated for a triple exponential model of the membrane fit closely to the actual ones. It implies that the PT cells have no genuine accommodation under normal conditions. 4. Local responses and alterations in the critical depolarization were considered to contribute only minutely to the threshold-latency curve of the PT cell membrane.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    s.l. ; Stafa-Zurich, Switzerland
    Materials science forum Vol. 196-201 (Nov. 1995), p. 867-872 
    ISSN: 1662-9752
    Source: Scientific.Net: Materials Science & Technology / Trans Tech Publications Archiv 1984-2008
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: A loop-deleted mutant form of 3-isopropylmalate dehydrogenase from Thermus thermophilus was constructed to investigate the relationship between the flexibility of the structure and the thermostability of the enzyme. The structure of the mutant enzyme was determined by X-ray crystallography and was found to be almost the same as that of the native enzyme with a reduced temperature factor. Although the mutant protein had lost the flexible loop, its function and thermostability had remained unchanged. This phenomenon can be explained by an internal reprieve tolerance mechanism.
    Type of Medium: Electronic Resource
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