Spontaneous and stimulated-radiation of impurity molecular crystals with optical and electron pumping

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 6, pp. 966–972, June, 1989.     

Chemistry of di- and tetrahydropyrans 8. Epoxidation of 3-aryloxy-4-methyl-3,6-dihydro-2H-pyrans

Conclusions Reaction of 3-aryloxy-4-methyl-3,6-dihydro-2H-pyrans with peracids takes place stereo-selectively to give trans-3-aryloxy-4-methyl-4,5-epoxytetrahydropyrans.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 623–627, March, 1988.     

Variational study of the ground state energy of theE−b 1,b 2 Jahn-Teller system

In this paper a variational method for the ground state energy approximation of theE−b ₁,b ₂ Jahn-Teller system is presented. This method is based on the choice of a suitable variational ground state wave function. This trial wave function — a correlated squeezed state — is used to account for the correlation and anharmonicity of the interaction between the two vibrational modes; the anharmonicity of both modes is taken into account by the squeeze effects of these modes. The ground state of mode 1 in this trial wave function is considered as a linear combination of the two displaced harmonic oscillators. The ground state energies for the linearE - e Jahn-Teller system calculated by this method are not only in good agreement with the exact diagonalization results, but they are also better than those from the previous analytical studies. Another conclusion which results from the presented model is the following one: the squeezing effect of mode 1 for the linearE - e Jahn-Teller system is substantially smaller, in contrast with the results which are presented in the previous analytical studies.     

Directionality and mode structure of radiation of semiconductor lasers with electron-beam pumping

We present results of investigations of the directionality diagram and mode structure of radiation of semiconductor lasers with electron pumping that have microrelief reflectors instead of a blind mirror and output mirrors, whose coefficient of reflection depends on the wavelength and the angle of light propagation. Application of such mirrors allows one to narrow the spectrum of output radiation of the lasers, simultaneously reducing the threshold and increasing the output power. The discovered multilobe structure of the directionality diagrams is explained on the basis of geometrical optics. The possibility of controlling the directionality of radiation depending on the spectral and angular characteristics of the output mirror is shown. Reported at the Second International Scientific and Technical Conference on Quantum Electronics, Minsk, November 23–25, 1998. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 5, pp. 092–697, Septemter–October, 1999.     

Structure and Physicochemical Mechanisms of Interaction of Bone Tissue with Titanium Implants in Cases of Tuberculous Osteitis

Technical Physics - The structural and physicochemical mechanisms of interaction of bone tissue with titanium implants under conditions of tuberculous osteitis are studied using scanning electron...     

Continuous structural evolution of calcium carbonate particles: a unifying model of copolymer-mediated crystallization

Two double-hydrophilic block copolymers, each comprising a nonionic block and an anionic block comprising pendent aromatic sulfonate groups, were used as additives to modify the crystallization of CaCO3. Marked morphological changes in the CaCO3 particles were observed depending on the reaction conditions used. A poly(ethylene oxide)-b-poly(sodium 4-styrenesulfonate) diblock copolymer was particularly versatile in effecting a morphological change in calcite particles, and a continuous structural transition in the product particles from polycrystalline to mesocrystal to single crystal was observed with variation in the calcium concentration. The existence of this structural sequence provides unique insight into the mechanism of polymer-mediated crystallization. We propose that it reflects continuity in the crystallization mechanism itself, spanning the limits from nonoriented aggregation of nanoparticles to classical ion-by-ion growth. The various pathways to polycrystalline, mesocrystal, and single-crystal particles, which had previously been considered to be distinct, therefore all form part of a unifying crystallization framework based on the aggregation of precursor subunits.