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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 140 (1994), S. 153-161 
    ISSN: 1432-1424
    Keywords: Sinoatrial node cell ; Background current ; Chloride channel ; Angiotensin II ; AT1 receptor ; Protein kinase C
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Single sino-atrial cells from rabbit heart were voltage-clamped using the whole-cell configuration of the patch clamp technique under conditions in which most of the ionic and exchange currents known in pacemaker cardiac cells were minimized. Extracellular angiotensin II (AII) activated a time-independent background current. The current-voltage relation of this current showed an outward rectification. The reversal potential was −20 mV with 156 mm Cl− external solution and 54 mm Cl− internal solution. This reversal potential shifted with changes in the transmembrane Cl− gradient in the fashion expected for a chloride current. Anthracene-9-carboxylic acid and diphenylamine 2-carboxilic acid (chloride channels blockers) were found to be effective in blocking the AII-sensitive current. The linear segment of the current-voltage relation can be totally inhibited by the competitive AII-receptor (AT1) antagonist losartan and by the presence of intracellular protein kinase C inhibitor, whereas the outward rectification is only slightly changed. It is concluded that sino-atrial cells should contain protein-kinase-C-sensitive chloride channels which may be activated by angiotensin II via the stimulation of the AT1 receptors.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 800-800 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 478-480 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate midinfrared photodetection at λ=4.5 μm in a multi-quantum well detector using a strained InGaAs/AlGaAs alloy grown on a GaAs substrate. The detector shows very low dark current of a few pA, a peak unpolarized light responsivity R=12 mA/W for an external 45° angle of incidence, and a background-limited detectivity D*BL=4×1010 cm Hz1/2/W at temperatures up to 95 K in the same conditions. This opens the way to high performance 3–5 and 8–12 μm GaAs-based multispectral detectors
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 16 (1968), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Determining the shape of a pulse generated by an explosion solely from the data provided by the recorded seismic trace is a difficult and even ambitious task.Knowledge of parameters such as length and number of “arches” of the pulse under study is, in fact, indispensable in solving this problem.These parameters cannot be found directly in the seismic trace, which nevertheless contains a great amount of information. Autocorrelation, with its mathematical and statistical properties, is an efficient way of making the best of this information.We compute all the autocorrelations of reflections having a given number of arches which fulfil certain conditions determined in advance. Then, after statistical testing of some parameters pertaining to the autocorrelations (abcissae of zeros, of extrema …), we select only those with a maximum likelihood. It is sufficient to consider only the reflections whose autocorrelations have been selected and to arrange them in groups according to their shape and arch number in order to obtain average pulses.In so doing several solutions are arrived at, but when considering a given number of traces, a single record for instance, it is possible by comparing these results with each other to considerably reduce their number.In the last part of the paper the nature of the impulse obtained with our method is examined in order to find out whether it is “minimum phase” for carrying out deconvolutions.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical prospecting 13 (1965), S. 0 
    ISSN: 1365-2478
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Physics
    Notes: Attenuation caused by transmission is known to be the greater the closer the samples are taken together. As a result, the amplitudes of seismograms with multiple reflections can be expected to be negligible within a more or less brief time interval, as is the case for seismograms without multiple reflections with attenuation. This paper examines the process by which multiple reflections regenerate these greatly attenuated reflections. It is also ascertained that a sampling interval of one ms for continuous velocity logs is valid for any survey. For economic reasons, we recommend the selection of a larger interval without, however, overdoing things and thus losing too much information.
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 341-345 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have analyzed electronic transport through a single, 200-A(ring)-thick, Ga0.74Al0.36As barrier embedded in GaAs. At low temperatures and high electric field, the Fowler–Nordheim regime is observed, indicating that the barrier acts as insulating layers. At higher temperatures the thermionic regime provides an apparent barrier height, decreasing with the field, which is equal to the expected band offset when extrapolated to zero field. However, for some samples, the current is dominated by the presence of electron traps located in the barrier. A careful analysis of the temperature and field behavior of this current allows to deduce that the mechanism involved is field-enhanced emission from electron traps. The defects responsible are tentatively identified as DX centers, resulting from the contamination of the barrier by donor impurities.
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 1898-1900 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this study, we have realized a bicolor switchable detector, in which tunneling between two quantum well detectors of different widths is used to populate or deplete their ground level. The behavior of the bicolor detector is simulated using a self-consistent model, which shows that under electric field, only the downstream well detects. The performance of the sample as a modulator and as a bicolor detector are analyzed in a Fourier transform infrared spectrometer.
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  • 8
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 3312-3314 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoconductive gain measurements in quantum-well (QW) infrared detectors are used to determine the variation of the capture time of electrons in QWs as a function of barrier thickness. The capture time is shown to be proportional to the multi-quantum-well period, which is consistent with a quantum mechanical description of the capture process. The measured values are far higher than the ones measured by time-resolved photoluminescence, ranging from 8 to 150 ps, depending on the applied electric field and barrier thickness. The reasons for this discrepancy are discussed.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 215-217 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report on the observation of resonant intersubband second-harmonic generation in asymmetric GaAs/AlGaAs quantum wells using a cw or Q-switched tunable CO2 laser as the pumping source. The dependence of the second-harmonic intensity with the pump photon wavelength is presented for the first time. A Lorentzian-like second-harmonic line shape is found with a maximum at 10.9 μm and a linewidth of 0.4 μm (4.1 meV). These results are in good agreement with theoretical predictions. The expected quadratic dependence of the second-harmonic conversion efficiency with pump intensity is well verified for intensities up to 150 kW/cm2. The calibrated second-harmonic power reaches 0.13 μW for a cw pump power of 0.8 W. The value of 7.2×10−7 m/V deduced for the second-order nonlinear susceptibility is about 1900 times greater than that found in bulk GaAs.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 33-35 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using low-temperature photocurrent, steady-state and time-resolved photoluminescence, we have shown the importance of hole transport in the optical properties of n+in+ double-barrier diodes under operation. We have also seen evidence of resonant tunneling of minority holes in such an illuminated double-barrier diode.
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