Free-electron optical absorption of Se-doped GaAs at room temperature is calculated and compared with existing experimental data. In addition to the standard features the theory takes into account a non-parabolic character of the conduction band, a short-range component of the Se donor potential and a plasmon generation in the presence of donors. Deformation potential constants for the conduction and the valence bands are calculated using the empirical pseudopotential method. A value of C = -15.7 eV is obtained for the conduction band and shown to agree with existing hydrostatic and uniaxial stress experiments. Assuming no impurity compensation and using no adjustable parameters we successfully describe the experimental free-electron absorption in GaAs as a function of photon wavelength for samples with various donor densities. 相似文献
A number of O-(benzyloxycarbonylglycyl) derivatives of alkyl-, phenyl-, and pyridyl-substituted oximes were synthesized, and their chemical properties and reactivities under aminolysis conditions were studied. The principal factor that determines the reactivities of the investigated compounds during the formation of a peptide bond is the presence of a weakly acidic catalyst; the different reactivities of the compounds under the same conditions are due to the influence of the electron-acceptor effects of the substituents attached to the carbon atom of the oxime group.The authors thank the Polish Academy of Sciences for financial support (state subsidy MR 1.12.1.6.1.5).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1336–1339, October, 1977. 相似文献
For 2 ≦ p ≦n and n ≧ 3, D(n, p) denotes the digraph with n vertices obtained from a directed cycle of length n by changing the orientation of p- 1 consecutives edges. In this paper, we prove that every tournament of order n ≧ 7 contains D(n, p) for p = 2, 3, …, n. Furthermore, we determine the tournaments of order n, 3 ≦ n ≦ 6, which do not contain D(n, p) for some p. 相似文献
It is shown that a metric continuum is a dendrite if and only if for every compact space and for every light open mapping such that there is a copy of in for which the restriction is a homeomorphism. Another characterization of dendrites in terms of continuous selections of multivalued functions is also obtained.
We predict theoretically the optical signatures of spin polarization of carriers in self-assembled quantum dots. The emission spectra are mapped out as a function of increasing electron spin polarization for a fixed number of electrons and holes. The spin-polarized spectra are determined using exact diagonalization techniques for up to 12 particles, corresponding to two lowest filled shells. We predict that the spin polarization leads to photon polarization, to redshifts of emission lines due to excess exchange interactions among the spin-polarized electrons, and to a complete breakup of emission lines for spin-polarized electronic shells. 相似文献
This paper presents the performance of a single‐photon‐counting hybrid pixel X‐ray detector with synchrotron radiation. The camera was evaluated with respect to time‐resolved experiments, namely pump–probe–probe experiments held at SOLEIL. The UFXC camera shows very good energy resolution of around 1.5 keV and allows the minimum threshold setting to be as low as 3 keV keeping the high‐count‐rate capabilities. Measurements of a synchrotron characteristic filling mode prove the proper separation of an isolated bunch of photons and the usability of the detector in time‐resolved experiments. 相似文献
The X-ray structure of 6-methyl-3,20-dioxo-4,6-pregnadien-17-yl acetate is reported. The crystals are monoclinic, space groupP21,Z=4,a=28.955(7),b=6.597(2),c=11.064(3) Å,/gb=90.80(2) °. The two crystallographically independent molecules have very similar overall geometries. The A rings have intermediate sofa-half-chair conformations and are bent relative to the steroid skeleton. The conformation of the 17-progesterone side chain is stabilized by the 17-ester substituent; the C(16)-C(17)-C(20)-O(20) torsion angle is –19.4(6) and –20.6(7)°. 相似文献
Skin injury leading to chronic wounds is of high interest due to the increasing number of patients suffering from this symptom. Proliferation, migration, and angiogenesis are key factors in the wound healing processes. For that reason, controlled promotion of these processes is required. In this work, we present the portable helium-dielectric barrier discharge (He-DBD)-based reaction-discharge system of controlled gas temperature for biological activities. To make this He-DBD-based reaction-discharge system safe for biological purposes, a multivariate optimization of the operating parameters was performed. To evaluate the effect of the He-DBD operating parameters on the rotational gas temperature Trot(OH), a design of experiment followed by a Response Surface Methodology was applied. Based on the suggested statistical model, the optimal operating conditions under which the Trot(OH) is less than 37 °C (310 K) were estimated. Then, the resulted model was validated in order to confirm its accuracy. After estimation the optical operating conditions of He-DBD operation, the spectroscopic characteristic of the He-DBD-based reaction-discharge system in relevance to the several optical temperatures in addition to electron number density has been carried out. Additionally, the qualitative and quantitative analyses of the reactive oxygen species and reactive nitrogen species were performed in order to investigate of reactions and processes running in the He-DBD-gaseous phase and in the He-DBD-treated liquid. Next, the developed portable He-DBD-based reaction-discharge system, working under the optimal operating conditions, was used to stimulate the wound healing process. It was found that a 30 s He-DBD treatment significantly increased the proliferation, migration, and angiogenesis of keratinocytes (HaCaT) and fibroblasts (MSU-1.1) cell lines, as well as human skin microvascular endothelial cells (HSkMEC.2). Hence, the application of the cold atmospheric pressure plasma generated in this He-DBD-based reaction-discharge system might be an alternative therapy for patient suffering from chronic wounds.