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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 60 (1989), S. 1351-1352 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We have modified the standard heat-pulse method using digital techniques to measure the heat capacity of small samples (100–200 mg) with a resolution of better than 0.2% in the temperature range of 77–300 K. In this note, we describe fully the technique and the instrumentation. Some of the results obtained with high Tc superconducting samples are also reported.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have measured longitudinal ultrasonic attenuation along the [110] direction in normal and superconducting states in two single crystals of lead, one made from high-purity lead and the other made with high-purity lead doped with 0.1 at % gold. In both specimens an amplitude-dependent effect in the superconducting state has been observed. The data have been taken in the frequency range from 12 to 108 MHz. In high-purity lead the amplitude-independent ratio αs/αn shows the frequency dependence observed by Randorff and Marshall, whereas in the doped specimen this ratio shows a very small spread with frequency. In both specimens deformation does not change the αs/αn ratio appreciably.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Longitudinal and shear wave ultrasonic attenuations have been measured in high-purity Pb on two single crystals obtained from the same ingot. The measurements were done at low temperatures, at different frequencies, and in transverse magnetic fields, up to a field of 7.3 kG. The propagation directions in the two crystals were along [100] and [110]. For some propagation and polarization directions the α s /α n ratio is found to be frequency-independent, while for others, large divergences in the α s /α n ratios at different frequencies are observed. A sharp decrease of α s /α n nearT c is observed for a particular longitudinal wave propagation, but not in any shear wave propagation. In some cases α s /α n is found to be abnormally high and this feature is associated with a peak in attenuation α n and a relatively high α n at 7.2 K. None of the α s /α n curves fits closely to any BCS energy gap. For longitudinal waves the high magnetic field (H) dependence of the normal state attenuation was found to agree qualitatively with the free electron theory for propagation along [100], but not for propagation along [110]. For shear waves the high-field attenuations do not extrapolate to zero asH tends to infinity. For all propagation and polarization directions the high-field attenuations show 1/H 2 field dependence.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1436-5065
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography , Physics
    Notes: Summary An intercomparison of the characteristic features of the Indian summer monsoon has been carried out for the monsoon months (June to September) of 1995 using the mean monthly analyses/forecasts from the operational centres of ECMWF, JMA, UKMO and NCMRWF. This exercise was undertaken to determine how well the large scale monsoon features over India were reproduced in the operational output in 1995 and also to assess the performance of the NCMRWF assimilation/forecast system. For this purpose, precipitation, mean sea level pressure, circulation features in the lower (850 hPa) and upper (200 hPa) troposphere, mid-tropospheric (500 hPa) temperature, and latent heat flux were examined. It is found that all the dominant features of the Indian summer monsoon are fairly well represented in the analysis and medium range forecasts of the ECMWF, JMA and UKMO. The NCMRWF output agrees well with those from other centres except for a sharp gradient in precipitation across the west coast which was not captured well in the forecasts due to the relatively coarse horizontal resolution of the model compared to that used at other operational centres. Other important features of the southwest monsoon, like the heat low over the northwestern part of the country, the lower level westerly jet and upper level easterly jet etc. are found to be reasonably well represented in the output of all operational centres. The JMA analyses and forecasts possessed greater levels of moisture compared to the NCMRWF output possibly due to the synthetic moisture information used at JMA. The evolution characteristics of the summer monsoon onset over the southern tip of India are found to be comparable in the output of JMA and NCMRWF.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Czechoslovak journal of physics 23 (1973), S. 1149-1158 
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The problem of determining the representation matrices of SU(4) is investigated. A convenient set of parameters is first introduced by writing the general element of the group as a product of exponential functions of the generators, and the generators are expressed as differential operators involving these parameters. Special matrix elements of finite transformations with a SU(3) singlet as the initial state are then obtained by solving the eigenvalue equation of the quadratic Casimir operator of SU(4). The solution has the form of a product of elementary functions and threed m′m j functions of SU(2) and is free from summation over intermediate states. By expanding one of thed m′m j functions in an appropriate series a sum rule for the special matrix elements of the permutation operator 1234→3412 is obtained. The discussions are strictly confined to SU(4), but, some of the results given here can be extended to unitary groups of higher dimensions.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Czechoslovak journal of physics 28 (1978), S. 374-384 
    ISSN: 1572-9486
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A set of recurrence relations connecting the matrix elements of finite transformation belonging to the same irreducible representation of SU(4) is used to obtain a wide class of matrix elements. An expression for the Clebsch-Gordan coefficient is obtained by integrating the product of three matrix elements belonging to three different irreducible representations of the group. The symmetry properties of the matrix elements and the Clebsch-Gordan coefficients are discussed.
    Type of Medium: Electronic Resource
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