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931.
A study of hyperon semileptonic decays has been made in various quark models and compared with the standard Cabibbo analysis which is found to be in good agreement with experiments. Results obtained in a quasirelativistic constituent quark model are in reasonable agreement with the standard Cabibbo analysis and show no sizeableSU(3) symmetry breaking effects. Results in other quark models which take into account theSU(3) symmetry breaking effects in the dominant form factors are similar to the quasirelativistic constituent quark model. 相似文献
932.
Excitation functions for103Rh (α,xn);x = 1–4 and103Rh (α,αxn);x = 1–3 reactions were measured up to 50 MeV bombarding energy using stacked foil activation technique and high purity germanium
(HPGe) γ-ray spectroscopy method. The experimental results were compared with calculations considering equilibrium as well
as pre-equilibrium hybrid model of Blann (ALICE/90). It is found that the initial exciton configurationn
0 = 4(4p0h) gives fairly good agreements for (α,xn) reactions. There seems to be indication of direct inelastic scattering effects in (α,αxn)-type of reactions. 相似文献
933.
Parametric study of optical emission from two successive laser pulses produced chromium and magnesium plasma is presented.
The line emission from chromium and magnesium plasma showed an increase by more than six times for double laser pulse excitation
than for single-pulse excitation. An optimum increase in emission intensity was noted for inter-pulse delay of ∼2–3 μs for
all the elements. The experimental observations were qualitatively explained on the basis of absorption of second laser pulse
in the pre-formed (by first laser) coronal plasma by inverse Bremsstrahlung process, which were found responsible for the
excitation of more ions and atoms in the plasma. This process starts as the plasma scale length becomes greater than the laser
wavelength. This study further indicated the suitability of this technique in the field of elemental analysis 相似文献
934.
Jyotsna Galgale Nupinder Kaur Preeti Singh Manik Manake N. K. Gaur R. K. Singh 《Pramana》2004,63(2):413-417
An extended three-body force shell model (ETSM) has been applied to investigate the static and dynamic properties of KCN
x
Cl1−x
for the compositionx = 0.56 and 1.0 at 300 K. The phonon dispersion curves computed by us are compared with the single crystal neutron diffraction
data. The unusual features of these curves are the upward curvature seen in some of the acoustic branches. This is a result
ofK-dependent softening of the phonon due to translation-rotation coupling. The transverse acoustic branch is more soft near
the zone centre. 相似文献
935.
Fluorescence spectrum of Dy3+, Dy3+-Ho3+, Tb3+ and Tb3+-Er3+ doped in calibo glass have been studied using Ar+ and excimer lasers. Non-radiative energy transfer from trivalent dysprosium and terbium (donors) to holmium and erbium (acceptors)
respectively has been observed on the basis of decrease in the life time of the levels and reduction in fluorescence intensity
of Dy3+ and Tb3+ on increasing Ho and Er concentrations. The interaction mechanism of donor and acceptor ions is found to be dipole-dipole
in both cases. Various parameters such as donor-acceptor distances, non-radiative energy transfer efficiency (η) and energy transfer probability (P
da) have been computed. Stark splitting have also been marked in several intense transition of the two. 相似文献
936.
It is found from Maxwell's equations that the magnetic field lines are good analogues of relativistic strings. It is shown that the superconducting current in the neutron star's interior causes local rotation of magnetic flux tubes carrying quantized flux. 相似文献
937.
A system consisting of two interacting particles, one of which has the angular momentum 1/2 and the other of which has an arbitrary angular momentum (a muonium-like system) is considered. The possibility of reconstruction of all the elements of the spin density matrix with the help of the μSR method is shown. For entangled states (Einstein-Podolsky-Rosen and Schrödinger cat states), the time dependence of components of the polarization vector (μSR photographs) is demonstrated. It is shown that, to identify these states, two μSR photographs suffice. 相似文献
938.
New series of phenylantimony chloride and antimony chloride with Schiff base ligands, L1H and L2H having N∩S and N∩O donor systems were synthesized under microwave irradiation using a domestic microwave oven. The reaction time was brought down from hours to a few seconds with improved yield as compared with conventional heating. All the ligands and their antimony(III) derivatives were characterized on the basis of microanalysis, elemental analyses, molecular weight determinations and spectral studies including IR, NMR (1H and 13C) and electronic spectral studies. A distorted trigonal bipyramidal and pseudo‐octahedral geometry around the antimony atom was tentatively proposed for these derivatives. The compounds were screened in vitro against bacteria and fungi to test their antimicrobial property and in vivo in male albino rats to test their antifertility properties. The treatment with the ligands and their phenylantimony derivatives at dose levels of 20 mg per rat per day did not cause any significant change in body weight, but a significant reduction in the weights of reproductive organs was observed. Arrest of spermatogenesis was noted at various stages with production of primary spermatocytes (preleptotene and pachytene), secondary spermatocytes and step‐19 spermatids found to be decreased. Biochemical parameters of tissues, i.e. protein, sialic acid, cholesterol content of testes and seminal vesicular fructose also showed significant reduction. Further, the serum testosterone concentrations were also decreased after treatment with ligands and their antimony(III) derivatives. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
939.
K. Singh S.M. Pande S.W. Anwane S.S. Bhoga 《Applied Physics A: Materials Science & Processing》1998,66(2):205-215
2 SO4. The solid solubility limits up to x≤3 mole% for monovalent, x≤5.27 mole% for divalent and x≤3.63 mole% for trivalent cation
doped Ag2SO4 are set with XRD, SEM, IR and DSC techniques. A predominant dependence of conductivity on the ionic size of iso- and alio-valent
cations is observed. In particular, the conductivity enhances in both α and β phases, despite having a lower ionic-size dopant
cation (relative to that of Ag+) in the transition element cation doped Ag2SO4. Ca2+, Ba2+, Y3+ and Dy3+ doped samples show depature from the regular behaviour in the β-phase. The conductivity behaviour is discussed considering
ionic size, valence and electronic structure of the guest cations.
Received: 3 February 1997/Accepted: 27 May 1997 相似文献
940.
Manganese(III) acetate mediated oxidation of aporphines to oxoaporphines is described. The developed methodology was conveniently applied for the synthesis of naturally occurring oxoaporphine alkaloids, oxoglaucine, and atheroline, starting from commercially available boldine. 相似文献