Assessing several fungal contaminants and their associated mycotoxins in maize cultivated on cornfields of Republic of Moldova.

Maize is an important crop for the Republic of Moldova and one of the crops most contaminated with mycotoxins. Maize grain obtained from plants cultivated on Moldavian cornfields in 2021 and 2022 were tested for mycotoxigenic risk using qPCR with primers to several fungal genome sequences engaged in mycotoxin synthesis and ELISA test to screen total aflatoxins, fumonisin B1, zearalenone, deoxynivalenol and T-2 toxin. Except for T-2 toxin, the mycotoxin concentrations were under the limits of detection and did not exceed maximum admissible levels for unprocessed grain.

Bias-Tunable Quantum Well Infrared Photodetector.

With the rapid advancement of Artificial Intelligence-driven object recognition, the development of cognitive tunable imaging sensors has become a critically important field. In this paper, we demonstrate an infrared (IR) sensor with spectral tunability controlled by the applied bias between the long-wave and mid-wave IR spectral regions. The sensor is a Quantum Well Infrared Photodetector (QWIP) containing asymmetrically doped double QWs where the external electric field alters the electron population in the wells and hence spectral responsivity.

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.

Graphene-based plasmonic metamaterial for terahertz laser transistors.

This paper reviews recent advances in the research and development of graphene-based plasmonic metamaterials for terahertz (THz) laser transistors. The authors' theoretical discovery on THz laser transistors in 2007 was realized as a distributed-feedback dual-gate graphene-channel field-effect transistor (DFB-DG-GFET) in 2018, demonstrating ∼0.1 µW single-mode emission at 5.

Far-infrared and terahertz emitting diodes based on graphene/black-P and graphene/MoS heterostructures.

We propose the far-infrared and terahertz emitting diodes (FIR-EDs and THz-EDs) based on the graphene-layer/black phosphorus (GL/b-P) and graphene-layer/MoS (GL/MoS) heterostructures with the lateral hole and vertical electron injection and develop their device models. In these EDs, the GL serves as an active region emitting the FIR and THz photons. Depending on the material of the electron injector, the carriers in the GL can be either cooled or heated dictated by the interplay of the vertical electron injection and optical phonon recombination.

Far-infrared photodetectors based on graphene/black-AsP heterostructures.

We develop the device models for the far-infrared interband photodetectors (IPs) with the graphene-layer (GL) sensitive elements and the black Phosphorus (b-P) or black-Arsenic (b-As) barrier layers (BLs). These far-infrared GL/BL-based IPs (GBIPs) can operate at the photon energies smaller than the energy gap, Δ, of the b-P or b-As or their compounds, namely, at ≲2 /3 corresponding to the wavelength range ≳(6-12) m. The GBIP operation spectrum can be shifted to the terahertz range by increasing the bias voltage.

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.

Nonlinear response of infrared photodetectors based on van der Waals heterostructures with graphene layers.

We report on the device model for the infrared photodetectors based on the van der Waals (vdW) heterostructures with the radiation absorbing graphene layers (GLs). These devices rely on the electron interband photoexcitation from the valence band of the GLs to the continuum states in the conduction band of the inter-GL barrier layers. We calculate the photocurrent and the GL infrared photodetector (GLIP) responsivity at weak and strong intensities of the incident radiation and conclude that the GLIPs can surpass or compete with the existing infrared and terahertz photodetectors.

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.

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.

Quantum Dot Infrared Photodetectors: Photoresponse Enhancement Due to Potential Barriers.

Potential barriers around quantum dots (QDs) play a key role in kinetics of photoelectrons. These barriers are always created, when electrons from dopants outside QDs fill the dots. Potential barriers suppress the capture processes of photoelectrons and increase the photoresponse.

Effective harvesting, detection, and conversion of IR radiation due to quantum dots with built-in charge.

We analyze the effect of doping on photoelectron kinetics in quantum dot [QD] structures and find two strong effects of the built-in-dot charge. First, the built-in-dot charge enhances the infrared [IR] transitions in QD structures. This effect significantly increases electron coupling to IR radiation and improves harvesting of the IR power in QD solar cells.

Luminescence of colloidal CdSe/ZnS nanoparticles: high sensitivity to solvent phase transitions.

We investigate nanosecond photoluminescence processes in colloidal core/shell CdSe/ZnS nanoparticles dissolved in water and found strong sensitivity of luminescence to the solvent state. Several pronounced changes have been observed in the narrow temperature interval near the water melting point. First of all, the luminescence intensity substantially (approximately 50%) increases near the transition.

Strong enhancement of solar cell efficiency due to quantum dots with built-in charge.

We report a 50% increase in the power conversion efficiency of InAs/GaAs quantum dot solar cells due to n-doping of the interdot space. The n-doped device was compared with GaAs reference cell, undoped, and p-doped devices. We found that the quantum dots with built-in charge (Q-BIC) enhance electron intersubband quantum dot transitions, suppress fast electron capture processes, and preclude deterioration of the open circuit voltage in the n-doped structures.

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.

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 View Article and Find Full Text PDF

[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).

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.

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.

[Retention of tumorigenicity in radioresistant progeny of cells surviving exposure to high doses of gamma irradiation].

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.

[A postoperative osteosarcoma recurrence after bone distraction by Ilizarov method in a dog].

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.

[Secondary osteosarcoma (in a dog) after bone fracture healed on the secondary type].

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.