Investigations in the imidazole series

The reactions of 2-mercaptonaphth[1,2-d]imidazole with 1,2-dichloro- and 1,2-dibromoethanes and the cyclization of 3-(-hydroxyethyl)- and 2-(-hydroxyethyl)mercaptonaphth[1,2-d]imidazoles were studied. 2,3-Dihydro derivatives of naphth[1,2-d]imidazo[1,2-b]thiazole and naphth[1,2-d]imidazo[3,2-b]thiazole were obtained.See [1] for communication LXX.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 257–259, February, 1972.     

Dirichlet norms,capacities and generalized isoperimetric inequalities for Markov operators

We define the notion of p-capacity for a reversible Markov operator on a general measure space and prove that uniform estimates for the ratio of capacity and measure are equivalent to certain imbedding theorems for the Orlicz and Dirichlet norms. As a corollary we get results on connections between embedding theorems and isoperimetric properties for general Markov operators and, particularly, a generalization of the Kesten theorem on the spectral radius of random walks on amenable groups for the case of arbitrary graphs with non-finitely supported transition probabilities.     

Mass spectra of pyrrolo [1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives

The closeness of the electronic structures of the ions formed in the first act of disintegration of the ions is responsible for the monotypic character of the subsequent fragmentation of pyrrolo[1,2-a]benzimidazole and imidazo[1,2-a]benzimidazole derivatives. The mass-spectrometric disintegration of the investigated systems has something in common with the fragmentation of thiazolo[3,2-a]benzimidazole derivatives.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, 1124–1127, August, 1975.     

Investigations in the imidazole series

Purinyl(theophyllinyl)-8-mercapto aldehydes and their acetals were synthesized by the reaction of 8-thio derivatives of purine and theophylline with -halo aldehydes and their acetals. The IR spectra demonstrated that the indicated aldehydes exist in the solid state as tautomeric forms — 3-hydroxy derivatives of thiazolino[2,3-f]purines(xanthines). Dehydration of the latter gave thiazolo[2,3-f]purine, 6,8-dimethylthiazolo[2,3-f]xanthine, and their 2-alkyl-substituted derivatives. The structures of the three-ring compounds were established by reductive desulfuration to 7-alkyl-substituted purines and theophyllines.See [1] for communication LXXVI.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 996–999, July, 1972.     

Recovery of 177Lu from Irradiated HfO2 Targets for Nuclear Medicine Purposes

A new method of production of one of the most widely used isotopes in nuclear medicine, ¹⁷⁷Lu, with high chemical purity was developed; this method includes irradiation of the HfO₂ target with bremsstrahlung photons. The irradiated target was dissolved in HF and then diluted and placed onto a column filled with LN resin. Quantitative sorption of ¹⁷⁷Lu could be observed during this process. The column later was rinsed with the mixture of 0.1 M HF and 1 M HNO₃ and then 2 M HNO₃ to remove impurities. Quantitative desorption of ¹⁷⁷Lu was achieved by using 6 M HNO₃. The developed method of ¹⁷⁷Lu production ensures high purification of this isotope from macroquantities of hafnium and zirconium and radioactive impurities of carrier-free yttrium. The content of ^177mLu in ¹⁷⁷Lu in photonuclear production was determined. Due to high chemical and radionuclide purity, ¹⁷⁷Lu obtained by the developed method can be used in nuclear medicine.     

Near-IR photoluminescence from Si/Ge nanowire-grown silicon wafers: effect of HF treatment

We present the room-temperature near-infrared (NIR) photoluminescence (PL) properties of Si/Ge nanowire (NW)-grown silicon wafers which were treated by vapor of HF:HNO₃ chemical mixture. This treatment activates or enhances the PL intensity in the NIR region ranging from 1000 nm to 1800 nm. The PL consists of a silicon band-edge emission and a broad composite band which is centered at around 1400–1600 nm. The treatment modifies the wafer surface particularly at defect sites especially pits around NWs and NW surfaces by etching and oxidation of Si and Ge. This process can induce spatial confinement of carriers where band-to-band (BB) emission is the dominant property in Si-capped strained Si/Ge NW-grown wafers. Strong signals were observed at sub-band-gap energies in Ge-capped Si/Ge NW-grown wafers. It was found that NIR PL is a competitive property between the Si BB transition and deep-level emission, which is mainly attributable to Si-related defects, Ge dots and strained Ge layers. The enhancement in BB and deep-level PL is discussed in terms of strain, oxygen-related defects, dot formation and carrier-confinement effects. The results demonstrate the effectiveness of this method in enhancing and tuning NIR PL properties for possible applications.     

A beam summation algorithm for wave radiation and guidance in stratified media

A Gaussian beams summation (GBS) algorithm for tracking source excited wave fields in plane stratified media is presented. In the present application the medium is described by layers with constant gradient of the wave speed, and the GB propagators are calculated recursively in a closed form. The algorithm is calibrated for numerical efficacy and accuracy by defining simple physical criteria for choosing the expansion parameters (the beam collimation and the spectral discretization and truncation) that allow for sparse representation of the source-excited angular spectrum of beams. It is validated for a source-excited example in layered media, where it provides a smooth and physically meaningful solution under multipath and caustic conditions and remains accurate for long propagation ranges where phase error tends to accumulate.     

Continuous-wave diode-pumped laser action of Nd³⁺-doped photo-thermo-refractive glass

Laser action of the photo-thermo-refractive (PTR) glass, which is the photosensitive material for holographic recording of volume Bragg gratings (VBGs), was demonstrated for the first time by introducing Nd3?. Nd:PTR glass has a bandwidth of 27.8 nm and 16.0 nm for luminescence and absorption, respectively. An uncoated 2 mm thick Nd:PTR element generated cw laser output of 124 mW, with a slope efficiency of 25%, by laser diode pumping. This Nd:PTR glass also performed wide bandwidth laser action at 1053.9-1063.3 nm, where the decrease of the pump-absorption efficiency was held off below 30%, even under a 3.5 nm shift of pump wavelength from its absorption center.