Volume 8, Issue 5
May 1977, pages 395-488
pp 395-401 May 1977 Solids
The present paper reports that triboluminescence (TBL) does not appear at the instant of impact of the load but a certain time lag is required for its appearance which depends on the value of the stress applied to the crystal. Since TBL appears in sugar crystals during the creation of new surfaces, the fracture-initiation time of the crystal has been taken to be the delay time in observing TBL pulse after the application of stress. The dependence of fracture-initiation time,tfσ, of crystals on the stress, σ, may be expressed astfσ=to exp (− ασ), whereto and α are constants. The values of the lattice energy, and the change in lattice energy per unit stress, of sugar crystals have been calculated from TBL measurements and they have been found to be 21·2 kcal mole−1 and 0·41 × 10−8 kcal mole−1 dyne−1 cm2 respectively.
pp 402-407 May 1977 Solids
The third-order elastic constants of single crystal GaSb are determined using ultrasonic pulse interferometer at 10 MHz. The constants at 300°K, in units of 1011 N.m.−2, are Cl11 = ™ 4 ·75 ± 0·06 C144 = + 0·50 ± 0·25 C113 = ™ 3 ·08 ± 0·02 C166 = ™ 2·16 ± 0·13 C123 = ™ 0 ·44 ± 0·29 C456 = ™ 0·25 ± 0·15 These constants are used to evaluate the three anharmonic first and second neighbour force constants based on modified Keating’s model. The constants are (in units of 1011 N.m−2)γ=− 2·406;δ=0·407;ε=−0·222.
pp 408-416 May 1977 Solids
The lattice dynamics of CaF2 has been studied on the basis of a noncentral model using CGW type angular forces. The experimental data agree with the data obtained for the dispersion curves. The model has also been used to calculate lattice specific heat and Debye-Waller factors.
pp 417-419 May 1977 Solids
It is suggested that anomalous neutron scattering could prove a powerful experimental tool in studying ferroelectric phase transition, the sublattice displacements of the soft modes as well as their symmetry characteristics.
pp 420-426 May 1977 Optics
A method employing pulsed illumination for the holographic analysis of vibration with space-variant phase is described. Superimposition of two stroboscopically recorded interference patterns to get the amplitude and the phase of vibration at the intersections of fringes is suggested. Contour maps of these two quantities over the entire object surface can then be prepared by interpolation. Detailed solutions are presented for single and double frequency vibrations.
pp 427-432 May 1977 Plasma Physics
The differences between the soliton solutions of the K-dV equation for a homogeneous, collisionless plasma, consisting of cold ions and isothermal electrons arising due to the two different sets of stretched co-ordinates have been discussed. In particular, the differences between the amplitudes and the widths of the solitons and their variations with the soliton velocity have been indicated. Further, the experimental implications of these differences and also of the two sets of stretched co-ordinates have been discussed.
pp 433-437 May 1977 Atomic Physics
L-shell photoelectric cross section measurements have been made at 36·818 and 74·409 keV for four elements in the range 81 ≤Z ≤ 92. The measurements at 74·409 keV are found to agree with theory, within experimental uncertainties, but the experimental values at 36·818 keV are found to be higher than the theoretical predictions. The possible reasons for the observed discrepancy are discussed.
pp 438-446 May 1977 Astronomy and Astrophysics
In this paper we have made a spectral analysis study of matter distribution in the asteroidal belt. We have Fourier analysed this distribution and obtained the autocorrelation and power spectrum, and have identified the ratios from the resonance theory. We have shown that the Kirkwood gaps cannot be satisfactorily interpreted as due to mere resonance between the asteroid and Jupiter orbital motions. We propose that they may be regarded as a consequence of density waves generated in the gas dise in the ecliptic plane in the neighbourhood of the Sun. We have also shown that the process is non-Marcovian and hence cannot be subjected to a hydrodynamical analysis.
pp 447-456 May 1977 Astronomy and Astrophysics
We have developed a kinematical theory for the asteroidal belt and Kirkwood gaps from the point of view of stellar dynamics. We have generated the potential that would produce these gaps and have made a spectral analysis study. We have shown that these gaps could be due to spiral tubes of matter in the ecliptic plane as a consequence of differential rotation and spatial interference of density waves. We have also shown that this mechanism could account for depletion of matter from this region.
pp 457-461 May 1977 Nuclear And Particle Physics
On the basis of crossing symmetry a new set of exact relations involving theππ partial wave amplitudes have been derived, using Roskies’ amplitudes.
pp 462-470 May 1977 Nuclear And Particle Physics
Relations among the magnetic moments of charmed and uncharmed baryons are derived in the framework of SU(4) and SU(8) symmetries. The SU(3) resultμ (Σo)=−μ(Λ) is not present in SU(4), but is obtained in SU(8). Higher order effects are further considered to improve the situation.
pp 471-477 May 1977 Nuclear And Particle Physics
Bethe-Faddeev wave functions are generalized toN-body clusters. A comparison made between the Bethe approximation and the Day approximation in the three body cluster indicates that the two approximations should be competitive for the higher body clusters.
pp 478-488 May 1977 Nuclear And Particle Physics
High resolution gamma-ray spectra have been measured from the27Al (p,γ)28Si reaction for the resonances atEp=2·482, 2·511 and 2·735 MeV at ϑpγ=0°, 30°, 55° and 90° using a Ge (Li) gamma spectrometer. From the spectra and the angular distributions the properties of the resonance states have been obtained. These states are the isobaric analogues of the levels at 4·69, 4·75 and 4·93MeV levels respectively in the parent nucleus A28l.
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