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101.
Short synthetic routes to the title compounds 1,–3, from readily available Diels-Alder adduct 5 of 6,6-dimethylfulvene and acrylonitrile are described. 相似文献
102.
Various Bishop type decompositions for vector function spaces are introduced and discussed. Conditions are given under which some of them coincide. Several examples and counter examples are also given. 相似文献
103.
In this communication, we reanalyze the causes of the singularities of canonical perturbation theory and show that some of
these singularities can be removed by using time-dependent canonical perturbation theory. A study of the local and global
properties (in terms of the perturbation parameter) is also undertaken. 相似文献
104.
M. L. Mehta 《Communications in Mathematical Physics》1971,20(3):245-250
Dyson's method is adopted here for the so called Gaussian ensembles. Incidently this confirms the long cherished belief that the statistical properties of a small number of eigenvalues is the same for the two kinds of ensembles, the circular and the Gaussian ones. 相似文献
105.
S.C.L. Sharma G.K. Mehta R.K. Choudhury D.M. Nadkarni S.S. Kapoor 《Nuclear Physics A》1981,355(1):13-24
The emission probabilities per fission of α-particles, tritons and protons have been measured in fast neutron induced fission of 235U. The measurements were carried out at neutron energies of 120, 180, 230 and 550 keV. AΔE-E semiconductor detector telescope was used to identify different light charged particles and the fission fragments were detected with an ionization chamber. The three-parameter data corresponding to the pulse heights from the ΔE-E detectors and the ion-chamber were recorded event by event on magnetic tape and were analyzed off-line by computer. No significant variation in the most probable energy () and the standard deviation (σE) of the energy spectra of different light charged particles with incident neutron energy was observed, although was seen to have a slightly higher value beyond En = 230 keV. The yield of α-particles in fission induced by neutrons of En ~ 200 keV was found to be higher by about 20 % than that in thermal neutron induced fission. The yields of tritons and protons were found to increase significantly with neutron energy. 相似文献
106.
The instability in a horizontal layer of a partially ionized self gravitating plasma has been studied to include simultaneously the effects of Hall currents, viscosity and finiteness of Larmor radius (FLR). The ambient magnetic field is assumed to be uniform and vertical. Proper solutions have been obtained through the variational methods for a semi-infinite plasma in which the density has an exponential gradient along the vertical. The dispersion relation obtained has been solved numerically and it is found that the growth rate of unstable perturbations decreases with the effects of viscosity, neutral gas friction and FLR. The influence of effects of viscosity, neutral gas friction and FLR are consequently stabilizing. It is found that the Hall currents have a destabilizing influence as the growth rate is found to increase with this effect. 相似文献
107.
A new synthesis of homoisoflavanones (3-benzyl-4-chromanones) 总被引:2,自引:0,他引:2
Two 7-hydroxyhomoisoflavanones (
/
) have been synthesized from corresponding 2'-hydroxydihydrochalcones (
/
) in about 33% overall yields. The stages are : (1) selective protection of C4'-hydroxyl in (
/
) with EtO.CH2Cl (1 molar equiv.) In the presence of dry K2C03 and acetone at r.t.; (ii) reaction with one more molar equiv. of EtO.CH2Cl at 60–70° without Isolating products (
/
) (iii) cyclizatlon of resulting α-hydroxymethyl derivatives (
/
) with 4% aq. aIc. Na2C03 and (iv) deprotection of resulting 7-ethoxymethoxy homoisoflavanones (
/
) with 10% CH30H-HC1. The explanations for the formation of (
/
) and (
/
) are given. 相似文献
108.
109.
The yield and energy distribution of long-range alpha-particles (lra) emitted from neutron-induced fission of235U have been measured at neutron energies; thermal, 125±12, 155±11, 185±10, 210±9, 240±9, 365±50 and 480±45 keV. The long-range
alpha-particles were detected in cellulose nitrate track detector foils. Results showed an increase of about 50% in the yield
at neutron energies in the region 150 keV≤E
n≤220 keV as compared to that of thermal neutrons. A calculation has been carried out to extract thelra to binary fission ratio forp-wave neutron induced fission. 相似文献
110.
The total (p, n) reaction cross section for48Ca has been measured as a function of proton energy in the energy range 1.885 to 5.100 MeV with an overall resolution of ∼
2 keV and in ∼ 5 keV energy steps. The fluctutions in fine resolution data have been analysed to determine the average coherence
width 〈Γ〉. The excitation function averaged over large energy intervals has been analyzed in terms of the optical model. The
isobaric analogue resonances atE
p
∼ 1.95 and 4 MeV have been shape-analyzed to extract the proton partial width and the spectroscopic factorS
n
. A comparison of the gross structures observed in ∼ 55 keV averaged excitation function with the predictions of Izumo’s partial
equilibrium model has also been made. 相似文献