Computation of the Spatial Distribution of Charge-Carrier Density in Disordered Media.

The space- and temperature-dependent electron distribution n(r,T) determines optoelectronic properties of disordered semiconductors. It is a challenging task to get access to n(r,T) in random potentials, while avoiding the time-consuming numerical solution of the Schrödinger equation. We present several numerical techniques targeted to fulfill this task.

Phenoxaphosphonium Mixed Ylides in Ring Expansion Reaction.

Treatment of mixed phosphonium-iodonium ylides featuring a six-membered phenoxaphosphonium fragment with aqueous tetrafluoroboronic acid induces a rearrangement, resulting in expansion of the phosphacycle and oxidation of the phosphorus atom. The target difficult-to-access dibenzo[,][1,4]oxaphosphepine oxides (3 examples) were isolated in excellent yields (up to 95%) as mixtures of stereoisomers. Hydrolysis of a five-membered mixed ylide, a dibenzophosphole derivative, predominantly preserves the phosphole system with cycle expansion occurring as a side process.

Energy Scales of Compositional Disorder in Alloy Semiconductors.

The study of semiconductor alloys is currently experiencing a renaissance. Alloying is often used to tune the material properties desired for device applications. It allows, for instance, to vary in broad ranges the band gaps responsible for the light absorption and light emission spectra of the materials.

Tunneling current modulation in atomically precise graphene nanoribbon heterojunctions.

Lateral heterojunctions of atomically precise graphene nanoribbons (GNRs) hold promise for applications in nanotechnology, yet their charge transport and most of the spectroscopic properties have not been investigated. Here, we synthesize a monolayer of multiple aligned heterojunctions consisting of quasi-metallic and wide-bandgap GNRs, and report characterization by scanning tunneling microscopy, angle-resolved photoemission, Raman spectroscopy, and charge transport. Comprehensive transport measurements as a function of bias and gate voltages, channel length, and temperature reveal that charge transport is dictated by tunneling through the potential barriers formed by wide-bandgap GNR segments.

One-Stage Formation of Two-Dimensional Photonic Crystal and Spatially Ordered Arrays of Self-Assembled Ge(Si) Nanoislandson Pit-Patterned Silicon-On-Insulator Substrate.

A new approach to improve the light-emitting efficiency of Ge(Si) quantum dots (QDs) by the formation of an ordered array of QDs on a pit-patterned silicon-on-insulator (SOI) substrate is presented. This approach makes it possible to use the same pre-patterned substrate both for the growth of spatially ordered QDs and for the formation of photonic crystal (PhC) in which QDs are embedded. The periodic array of deep pits on the SOI substrate simultaneously serves as a template for spatially ordering of QDs and the basis for two-dimensional PhCs.

Photoluminescence of compact GeSi quantum dot groups with increased probability of finding an electron in Ge.

The photoluminescence (PL) of the combined Ge/Si structures representing a combination of large (200-250 nm) GeSi disk-like quantum dots (nanodisks) and four-layered stacks of compact groups of smaller (30 nm) quantum dots grown in the strain field of nanodisks was studied. The multiple increase in the PL intensity was achieved by the variation of parameters of vertically aligned quantum dot groups. The experimental results were analyzed on the basis of calculations of energy spectra, electron and hole wave functions.

Theoretical tools for the description of charge transport in disordered organic semiconductors.

Hopping conduction is widely considered the dominant charge transport mechanism in disordered organic semiconductors. Although theories of hopping transport have been developed in detail for applications to inorganic amorphous materials, these theories are often out of scope for the community working with organic amorphous systems. Theoretical research on charge transport in organic systems is overwhelmed by phenomenological fittings of numerical results by equations, which often make little physical sense.

Energy position of the transport path in disordered organic semiconductors.

The concept of transport energy is the most transparent theoretical approach to describe hopping transport in disordered systems with steeply energy dependent density of states (DOS), in particular in organic semiconductors with Gaussian DOS. This concept allows one to treat hopping transport in the framework of a simple multiple-trapping model, replacing the mobility edge by a particular energy level called the transport energy. However, there is no consensus among researchers on the position of this transport level.

Carrier dynamics in InAs/AlAs quantum dots: lack in carrier transfer from wetting layer to quantum dots.

Structures with self-assembled InAs quantum dots (QDs) embedded in an AlAs matrix have been studied by steady-state and transient photoluminescence. It has been shown that in contrast to InAs/GaAs QD systems carriers are mainly captured by quantum dots directly from the AlAs matrix, while transfer of carriers captured by the wetting layer far away from QDs to the QDs is suppressed. At low temperatures the carriers captured by the wetting layer are localized by potential fluctuations at the wetting layer interface, while at high temperatures the carriers are delocalized but captured by nonradiative centers located in the wetting layer.

[Methods for detection and characterization of mechanical resistance of erythrocytes in healthy men (review of literature)].

Published reports on methods for evaluation of erythrocyte rheology and mechanical resistance are reviewed. The processes running in red blood cells under the effect of mechanical factors are described. An original method for studies of vibration resistance of erythrocytes is proposed.

[Emergency surgery of carotid and vertebral arteries in acute cerebral ischemia].

The efficacy of emergency surgical interventions on the carotid and vertebral arteries in patients with acute disorders of cerebral circulation is discussed. An organizational structure of rendering aid is suggested, which unites emergency ambulance service, neurology, and vascular surgery in one therapeutic institution. A clinical classification of the severity of acute cerebral ischemia and the optimal terms for operations were elaborated.

[Construction and analysis of the tularemia pathogen gene library in Escherichia coli].

The library of tularemia causative agent genes cloned on the pHC79 plasmid and the partial clonotek of these agents genes in Escherichia coli cells have been constructed. The immunochemical analysis has revealed seven clones of Escherichia coli harbouring the recombinant plasmids and expressing francisella antigens. The cloned sequences of francisella DNA as well as the recombinant plasmids containing them and coding for francisella antigens are capable of specific hybridization with the DNA from Francisella tularensis strains and Francisella novicida strain U112.

[Functional properties of the pOV13 plasmid as a vector for DNA cloning in a broad spectrum of gram negative bacteria].

The birepliconed plasmid pOV13 possesses all the properties of a vector for DNA cloning in a broad host range of bacterial cells. pOV13 is transfered by transformation and stably inherited by Escherichia coli, Brucella, Pseudomonas cells determining the resistance to streptomycin, tetrocycline and kanamycin in these bacteria. The plasmid pOV13 is a multicopy plasmid optimal in replication capacity (23kb).

[Isolation and characteristics of a recombinant pOV13 plasmid as a vector for DNA cloning in a broad range of bacterial hosts].

The hybrid plasmid pOV13 proposed as a potential vector for DNA cloning in a broad bacterial host range has been constructed on the basis of the broad host range plasmid RSF1010 and a shortened derivative of RP4, the plasmid pVZ115 serving a marker DNA fragment. The plasmid pOV13 contains the genes for streptomycin, kanamycin and tetracycline resistance and single cleavage sites for restriction endonucleases BamHI, BgIII, SalI, SmaI, PvuII, XhoI, as well as double cleavage sites for restriction endonucleases PstI and HindIII permitting one to clone DNA with insertional inactivation of genes. The physicogenetical map of the birepliconed plasmid pOV13 is presented.

[Maintenance of gaseous homeostasis in chronic coronary insufficiency].

Mechanical resistance of erythrocytes was studied in patients with chronic coronary insufficiency and normal subjects using an original method (the blood sample was subjected to vibration effects after which the percentage of destroyed cells was determined). Erythrocyte resistance was assessed at 40 dB vibration and the frequencies of 125, 250 and 500 Hz. A vibration of 40 dB at 250 Hz destroyed 33.

[Role of hyperbaric oxygenation and skin plasty in wound healing after minor amputations in patients with gangrene stage of obliterating endarteritis].

The article analyzes the treatment of 45 patients with a gangrene stage of obliterating endarteritis subjected to small amputations in combination with free skin autoplasty. The amputation and skin plasty were preceded by intensive therapy both before operation and in the postoperative period, HBO included. A method of HBO therapy by changing barometric pressure under conditions of hyperbaric oxygenation is described.