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  • 1
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Summary An apparatus consisting of (a) a small computer, (b) an oscilloscope light-dot controlled by it, and (c) a pencil-shaped peg containing three accelerometers, which are sampled at 150μsec intervals by the computer, has been used to measure simple reaction time for human hand-movement. The stimulus, a jump of the light dot, was presented without a warning signal in series of 100 jumps either after a fixed period or a random time. The average interstimulus interval (ISI) was between 1.3 and 15.8 sec. For every parameter set 1,000 reaction times (RTs) were accumulated during 10 different days. The main results are: (a) RT increases with increasing mean ISI; (b) RT is longer for random ISIs than for constant ones; (c) RT increases slightly with time accumulating during runs; (d) within a series of random ISIs, RT is neither depending on the value of the last ISI before reaction nor on that of the last but one; (e) the probability distribution of RTs has a standard deviation increasing with mean ISI and from periodic to random ISI, and a non-negligible, roughly constant skewness.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 11 (1972), S. 105-111 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract Simple reaction time has been measured using various distributions of interstimulus intervals (ISIs), which differed both in the shape of their envelope and in their degree of discretization. For each of 7 such conditions, and for three mean ISIs (2.0, 3.3, and 5.8 s) 600 responses of two subjects have been accumulated. Reaction times depend significantly on the shape of ISI-distributions but also on their degree of discretization. Within an experimental run they depend on single ISIs back to the third before reaction, and on sequences of ISIs. The latter effects are again influenced by the discretization of ISIs. Finally it was found that some learning of the distribution pattern (not the mere mean value) of ISIs takes place. Our results shed some light on existing hypotheses of RT. Some inconsistencies of earlier experimental results can probably be explained by insufficient consideration of the discretization and the learning effects.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 141 (1955), S. 6-15 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Zusammenfassung Die Hyperfeinstruktur des Thalliumfluorids wurde mit einer Molekülstrahlresonanzapparatur untersucht, die an Stelle der sonst üblichen Ablenkfelder elektrische Vierpollinsen benützt. Da beide Kerne den SpinI=1/2 haben, sind Quadrupolmomente nicht beobachtbar. Es wurden Übergänge zwischen den Starkeffekttermen der Hyperfeinstruktur innerhalb des RotationszustandesJ=1 und im Schwingungszustandv=0 undv=1 im sehr schwachen, schwachen und starken elektrischen Feld gemessen. Hieraus ließen sich die elektrischen Dipolmomente des TlF in beiden Schwingungszuständen, die beiden magnetischen Kernspin-Rotationswechselwirkungenc 1,c 2, die tensorielle Kerndipol-KerndipolWechselwirkungc 3 und eine skalare Wechselwirkungc 4 (I1I2) berechnen. Der Einfluß des irdischen Magnetfeldes wurde durch Überlagerung des elektrischen Feldes mit einem Magnetfeld geprüft und gleichzeitig ein angenäherter Wert des magnetischen Momentes des Moleküls ermittelt.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 168 (1962), S. 81-102 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As is well known, van der Waals forces between two atoms (not both in an S-state) have no spherical symmetry. We report on an experiment, which verifies this anisotropy by measuring it. The experiment consists in comparing the total scattering cross sections of Ga atoms in selected magnetic substatesm J=1/2 and 3/2 of the upper (2 P 3/2) level of the ground state doublet of Ga. Rare gases are used as the scatterer. The relative total cross section difference in units of 10−4 is 94.9±4.3 for Xe, 79.4±6.6 for Ar, and 195±5 for He as the scattering gas. In addition, measurements of the total scattering cross sections of Na and Ga on various gases have been made. The apparatus uses an atomic beam with magnetic selection, a common geometry, and a common detecting scheme for both states, which are compared in short intervalls by merely switching the selecting magnet's current. By converting the beam intensity to a pulse rate and summing the numbers of pulses in scalers, the sequence of alternate measurements could be automatized. In that way a comparison could be made every second, thus largely eliminating most drifts, which otherwise would have made impossible an intensity measurement of that accuracy. A theoretical estimate of the experimental results has been made on the following basis: 1. Only van der Waals forces are taken into account. 2. Matrix element sums in the expression for the van der Waals potential are approximately reduced to terms involving only the polarizability of the rare gases and matrix elements of Ga, which can be calculated from Hartree-Fock functions. 3. The Schiff approximation is used to calculate the scattering cross section. The calculations are in rough agreement with experiments, and errors are discussed.
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  • 6
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The development of 200 MeV electron-initiated showers has been simulated by the Monte-Carlo method on an electronic digital computer. Bremsstrahlung, ionization-loss, and multiple-scattering for electrons and pair-production, Compton scattering, and photo-effect for photons have been taken into account. The total cross-sections for the various processes have partly been corrected by empirical correction factors to provide the correct energy dependence. Electrons were followed down to 1·5MeV total energy and photons to 0·26 MeV. The results are compared with experimental data and the Monte-Carlo calculations ofMessel et al.
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  • 7
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The velocity dependence of the total scattering cross section has been measured for 10 different combinations of alkali atoms with rare gas atoms. By means of an automated fast comparison technique the precision of relative values ofQ(ν) can be increased to 10−3. In the eight cases where Ar, Kr or Xe is the scattering gas, undulations ofQ(ν) about its mean value have been observed. The precision of the method allows us in these cases to extract reliable information on the amplitude of the undulations. Use of this additional information makes it impossible to explain the experimental results with the simple, 2- or 3-parameter potentials that are generally used. Deferring a final evaluation to a later paper, we restrict ourselves here to giving, for the Lennard-Jones (8−6) potential, a table ofɛr m values.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 207 (1967), S. 294-307 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The differential sputtering ratio (energy spectrum) of polycrystalline potassium sputtered by Ar and Xe ions of 28 keV energy has been measured using surface ionization detection. The spectrum shows a maximum at 0.5 eV and drops to half the maximum value at 2.0 eV. The total sputtering ratio for incident Xe ions is found to be 2.7±1.3 atoms/ion. To check what influence the detector might have on the measured spectrum, different materials and temperatures were used. Below 3 eV the detection probability is energy independent, if the detector is properly heated. Above that energy the measured spectra become uncertain, probably because of the onset of reflexion. Therefore the “focussing energy” of sputtering theory cannot be deduced.
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  • 9
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Recent improvements in precision and the increase in number of molecular beam scattering experiments demand a reanalysis of the experimental data. The commonly used potential functions show a serious lack of flexibility, and fitting procedures are not unambigious. A new potential ansatz (which is a continuous modification of the (12-6)-potential) has been used to fit all available data on the alkali-rare gas systems Li-Kr, Na-Ar, Na-Kr, Na-Xe, K-Ar, and K-Kr. Aχ 2-minimum method is used as the procedure to fit the data and to estimate the errors of the parameters obtained (see Table 1). It turns out, that the shape of the potential is similar for all systems evaluated here but probably different from that derived for rare gas-rare gas systems.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The European physical journal 173 (1963), S. 352-358 
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The “rainbow” singularity in the differential scattering cross section for molecular collisions is a good means to get the potential depthε of the scattering potential in question. The connection between the “experimental” parameters (“rainbow”-angle, -width, and impact parameter) and the potential parameters of a given type of potential has to be given in tabular form. In this note such a table is given for the Kihara potential (2). Furthermore, it is shown that under conditions likely to occur in experiments, the usual approximation to the scattering cross section will have a nonnegligible error.
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