Resonant plasmonic detection of terahertz radiation in field-effect transistors with the graphene channel and the black-As[Formula: see text]P[Formula: see text] gate layer.

We propose the terahertz (THz) detectors based on field-effect transistors (FETs) with the graphene channel (GC) and the black-Arsenic (b-As) black-Phosphorus (b-P), or black-Arsenic-Phosphorus (b-As[Formula: see text]P[Formula: see text]) gate barrier layer. The operation of the GC-FET detectors is associated with the carrier heating in the GC by the THz electric field resonantly excited by incoming radiation leading to an increase in the rectified current between the channel and the gate over the b-As[Formula: see text]P[Formula: see text] energy barrier layer (BLs). The specific feature of the GC-FETs under consideration is relatively low energy BLs and the possibility to optimize the device characteristics by choosing the barriers containing a necessary number of the b-As[Formula: see text]P[Formula: see text] atomic layers and a proper gate voltage. The excitation of the plasma oscillations in the GC-FETs leads to the resonant reinforcement of the carrier heating and the enhancement of the detector responsivity. The room temperature responsivity can exceed the values of [Formula: see text] A/W. The speed of the GC-FET detector's response to the modulated THz radiation is determined by the processes of carrier heating. As shown, the modulation frequency can be in the range of several GHz at room temperatures.

Nanocrystalline SiC film thermistors for cryogenic applications.

We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K-300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.

Complete voltage recovery in quantum dot solar cells due to suppression of electron capture.

Extensive investigations in recent years have shown that addition of quantum dots (QDs) to a single-junction solar cell decreases the open circuit voltage, VOC, with respect to the reference cell without QDs. Despite numerous efforts, the complete voltage recovery in QD cells has been demonstrated only at low temperatures. To minimize the VOC reduction, we propose and investigate a new approach that combines nanoscale engineering of the band structure and the potential profile. Our studies of GaAs solar cells with various InAs QD media demonstrate that the main cause of the VOC reduction is the fast capture of photoelectrons from the GaAs conduction band (CB) to the localized states in QDs. As the photoelectron capture into QDs is mainly realized via the wetting layers (WLs), we substantially reduced the WLs using two monolayer AlAs capping of QDs. In the structures with reduced WLs, the direct CB-to-QD capture is further suppressed due to charging of QDs via doping of the interdot space. The QD devices with suppressed photoelectron capture show the same VOC as the GaAs reference cell together with some improvements in the short circuit current.

Electronic states in heterostructures formed by ultranarrow layers.

Low-energy electronic states in heterostructures formed by ultranarrow layers (single or several monolayers in thickness) are studied theoretically. The host material is described within the effective mass approximation and the effect of ultranarrow layers is taken into account within the framework of the transfer matrix approach. Using the current conservation requirement and the inversion symmetry of an ultranarrow layer, the transfer matrix is evaluated through two phenomenological parameters. The binding energy of localized state, the reflection (transmission) coefficient for the single ultranarrow layer case, and the energy spectrum of the superlattice are determined by these parameters. The spectral dependency of absorption due to photoexcitation of electrons from localized states into minibands of the superlattice is determined by the ultranarrow layer characteristics. Such a dependency can be used for verification of the transfer matrix and should modify the characteristics of optoelectronic devices with ultranarrow layers. Comparison with experimental data shows that the effective mass approach is not valid for the description of ultranarrow layers.

Terahertz surface plasmons in optically pumped graphene structures.

We analyze the surface plasmons (SPs) propagating along optically pumped single-graphene layer (SGL) and multiple-graphene layer (MGL) structures. It is shown that at sufficiently strong optical pumping when the real part of the dynamic conductivity of SGL and MGL structures becomes negative in the terahertz (THz) range of frequencies due to the interband population inversion, the damping of the THz SPs can give way to their amplification. This effect can be used in graphene-based THz lasers and other devices. Due to the relatively small SP group velocity, the absolute value of their absorption coefficient (SP gain) can be large, substantially exceeding that of optically pumped structures with dielectric waveguides. A comparison of SGL and MGL structures shows that to maximize the SP gain the number of graphene layers should be properly chosen.

Crossover from Fermi liquid to multichannel Luttinger liquid in high-mobility quantum wires.

We investigate the electrical conductance of long, high-mobility quantum wires formed by the split-gate technique, which allows for adjustment of the wire width and the number of one-dimensional electron subbands, n. In wires with 3

[Genomic instability in sunflower interspecific hybrids].

The expression of genomic instability was studied at the phenotypical (morphological characters, electrophoretic spectra of seed storage proteins) and molecular (DNA amplification products) levels in interspecific hybrids (ISHs) from crosses of inbred lines of cultivated sunflower Helianthus annuus with perennial species of the genus Helianthus and in introgressive lines (ILs) produced on their basis. Unstable state of the locus determining the trait of lower branching was proved by the method of hybridological analysis. It was shown with the use of RAPD markers that the IL genome is characterized by instability even after long-term inbreeding (in generations F8-F12). In progenies of different combinations of interspecific crosses, identical polymorphous variants-were revealed for a seed storage protein, helianthinin, and for DNA fragments homologous to structural genes of functionally important proteins, suggesting the nonrandom character of ISH genome variation. This variation may be determined by genome reorganizations under the action of a genome shock induced by interspecific hybridization. The factors inducing reorganizations in the genome include the activity of mobile genetic elements (MGEs). Using primers specific to different MGE families, nucleotide sequences with a high level of homology to the sequences of fragments of the mobile elements MuDR, Far1, CACTA, Stowaway, and Tourist were identified in the sunflower genome. The possibility of using MGE fragments for sunflower genotyping was demonstrated.

Comparison of BNCT and GdNCT efficacy in treatment of canine cancer.

In this study efficacy of antineoplastic action of gadolinium NCT and boron NCT in cases of canine melanoma and osteosarcoma was compared. Canine spontaneous tumors, such as melanoma and osteosarcoma, have clinical common features with human malignancies, so these tumors in dogs can be considered as clinical model of human melanoma and osteosarcoma. The study has been carried out on 33 dogs with oral cavity melanoma and 9 dogs with osteosarcoma. Dogs with spontaneous melanoma of oral cavity and osteosarcoma of extremities were selected by the results of clinical examination. Irradiation was carried out at the NCT facility of the IRT MEPhI reactor. Neutron irradiation without boron or gadolinium was chosen as a control method to evaluate the efficacy of NCT.

Deformation electron-phonon coupling in disordered semiconductors and nanostructures.

We study the electron-phonon relaxation (dephasing) rate in disordered semiconductors and low-dimensional structures. The relaxation is determined by the interference of electron scattering via the deformation potential and elastic electron scattering from impurities and defects. We have found that in contrast with the destructive interference in metals, which results in the Pippard ineffectiveness condition for the electron-phonon interaction, the interference in semiconducting structures substantially enhances the effective electron-phonon coupling. The obtained results provide an explanation to energy relaxation in silicon structures.

[Retention of tumorigenicity in radioresistant progeny of cells surviving exposure to high doses of gamma irradiation]. / Sokhranenie tumorogennosti u radiorezistentnykh potomkov kletok, vyzhivshikh posle vozdeistviia gamma-izlucheniia v bol'shikh dozakh.

The cell tumorigenic ability and the cell clonogenicity in semi-solid medium of highly radioresistant variant cell line, PIC-20 (the progeny of djungarian hamster fibroblast cell line DX-TK- surviving acute exposure to 20 Gy of gamma-irradiation), were examined. In the absence of additional radiation, no differences between tested features of non-irradiated PIC-20 cells and parental DX-TK- cells were observed. On the contrary, after gamma-irradiation with high doses the essential differences in the properties of the examined cell lines were revealed. After exposure to 10 Gy the surviving fraction of PIC-20 cells was 20 times higher than that of the parental cells. Both irradiated and non-irradiated PIC-20 cells produced colonies of similar size. It is revealed that even after irradiation with doses of 5, 10 or 15 Gy, the PIC-20 cells kept their tumorigenicity as high as non-irradiated ones. In all these cases the 90-100% of animals had the tumour, with the average latent period of tumour appearance after inoculation being the same both for irradiated and non-irradiated PIC-20 cells. After irradiation of parental DX-TK- cells with the highest dose of 15 Gy, the amount animals with tumour decreased by 70% and the average latent period of tumour appearance increased fivefold as compared with that for non-irradiated DX-TK- cells. The data obtained indicate that PIC-20 is highly radioresistant cells, which are able to proliferate both in semi-solid medium and in an animal organism even after radiation exposure to high doses.

[Secondary osteosarcoma (in a dog) after bone fracture healed on the secondary type]. / Razvitie vtorichnoi osteogennoi sarkomy (u sobaki) na meste pereloma srosshegosia po vtorichnomu tipu.

A case is reported of osteosarcoma arising in a dog after the fracture of the femur. The tumor was diagnosed 6 years after the trauma. We suppose that the cause of malignant transformation in this case was a permanent mechanical trauma, restructuration and regeneration of the bone. This mechanism, possibly, also may take place in the genesis of primary osteosarcomas.

[A postoperative osteosarcoma recurrence after bone distraction by Ilizarov method in a dog]. / Posleoperatsionnye retsidivy osteogennoi sarkomy u sobak pri distraktsii kosti po metodu Ilizarova.

Distraction osteogenesis by Ilizarov's method is becoming popular for limb saving surgery today. In this article we report a case of osteosarcoma recurrence after using bone distraction in a dog with osteogenic sarcoma. This case suggests that stimulation of osteogenesis by bone distraction promotes tumor recurrence and metastases in osteosarcoma. We recommend to use this method only when allograft or endoprostheses can not save the limb after wide bone resection.