Bulletin of the Lebedev Physics Institute最新文献

A change was found in the characteristics of a ZnSe:Fe²⁺ sample subjected to external pressure and a magnetic field at room temperature. It is demonstrated that long (2 years) exposure to pressure and a magnetic field alters the transmission spectrum and luminescent characteristics in the range of 450 to 700 nm. The results of measuring the transmission spectra of the ZnSe:Fe²⁺ sample before and after the annealing process in liquid Zn are presented. It is shown that the changes in transmission spectra caused by pressure and a magnetic field and changes in transmission spectra after annealing the sample in liquid Zn are similar, although not identical.

The paper examines the possibility of using a xenon gamma-ray spectrometer (XGRS) to determine the dose load on a patient during boron neutron capture therapy (BNCT) at the IRT MEPhI research reactor. The possibilities of using semiconductor gamma-ray spectrometers in neutron capture therapy (NCT) are discussed. The results of testing of the remote-control measuring system of the XGRS are presented. Model experiments are performed to study the spectrometric characteristics of the XENON experimental measurement complex. The dependence of the absorbed dose on the solution concentration in the target under its irradiation (an aqueous solution of boric acid) with thermal neutrons at flux densities ranging from 3.3 × 10⁵ to 7.87 × 10⁸ neutrons/(cm² s) is obtained. The experimental results confirm the potential of using the XGRS for monitoring the dose load on patients during BNCT.

Metal molybdate nanocomposites have recently drawn scientific interest for supercapacitor devices, because of their benefits, including good redox reactions and low synthesis costs. This work successfully produced CoMoO₄/CuMoO₄ nanocomposites (CCMO NCs) grown on nickel foam using a single-pot hydrothermal approach. Furthermore, X-ray diffraction (XRD) confirms that CCMO NCs are well crystalline structure. The formation of the metal – oxygen functional groups of CCMO NCs was confirmed by FTIR spectroscopy. The chemical states of the aimed CCMO NCs were measured using X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) revealed that this material had a rodlike structure. Also, CCMO NCs used as an electrode and employed directly as supercapacitor applications. The CCMO electrode had achieved the specific capacitance (Cs) value of 2500 F g^–1 at a current density of 2 A g^–1. It also demonstrated cycling stability of 38.46% retention after 10 000 cycles.

We report an investigation of the influence of potential contamination of a background sample used for training and optimizing a selection by a small fraction of signal events on the multivariate classifier performance. The performance of the boosted decision tree (BDT) classifier trained and optimized on contaminated background sample containing mislabeled signal events is compared to the idealized case of pure training samples. It is demonstrated that the training of the selection is not significantly affected by the absolute number of mislabeled signal events for a given relative background sample contamination value (1000 : 1 background-to-signal ratio). In contrast, the resulting optimization of the selection requirement decreases as the mislabeled signal contribution increases.

Based on in-situ photoluminescence measurements, we study the regimes of pulsed laser irradiation of diamond at low temperatures (77 K), at which a hot phonon spot is formed due to multiphoton absorption in the diamond matrix. It is shown that a hot phonon spot with a temperature of 300 K leads to quenching of the luminescence of SiV^‒ centers, maintaining the width of the emission line unchanged. It is found that at a temperature of 1000 K, caused by excitation with an energy density of about 0.5 J/cm², a fragment is chipped off the diamond matrix, accompanied by broadening of the luminescence lines of SiV^‒ centers.

A scientific equipment was developed by the Lebedev Physical Institute for the Solntse-Terahertz space experiment to be installed onboard the Russian segment of the International Space Station. The experiment aims to collect data on the Sun’s terahertz radiation and to study solar active regions and solar flares. The Solntse-Terahertz scientific apparatus includes eight detection channels sensitive to radiation at frequencies ranging from 0.4 to 12.0 THz. A blackbody simulator (BBS) was used to experimentally calibrate the equipment. The calibration factors for each channel were determined by calculating, with numerical integration methods, the correlation between the intensity of BBS radiation passing through a filter system and the equipment’s response to BBS radiation found experimentally. The original BBS spectrum was successfully recovered to verify the quality of the calibration.

As part of the Large High Altitude Air Shower Observatory (LHAASO) project in China, ENDA-64—an extension of the original electron‒neutron detector array (ENDA) consisting of 16 detectors to 64 detectors—has been put into operation. The new array is intended for studying extensive air showers (EAS’s) at energies above 1 PeV and reconstructing the primary energy spectrum and chemical composition of cosmic rays. A prototype of the ENDA cluster has been fabricated on the territory of the Institute for Nuclear Research of the Russian Academy of Sciences in Moscow (ENDA-INR). The paper describes a program developed for fast simulation of the array response. The results obtained using the developed program, the Geant4 simulation software, and experimental data are compared.

The paper examines the effect of magnetically dependent heating on amplification of fast magnetoacoustic kink waves in a coronal plasma with thermal imbalance. Based on the theoretical model of a thin magnetic layer, we derive an analytical expression for the decrement (increment) of waves in the low-frequency limit. The influence of magnetically dependent heating, plasma temperature, and density contrast on amplification of kink waves in the layer is established. The results contribute to understanding the mechanisms of long-lived oscillations in the solar corona.

Vanadium-doped zinc oxide nanoparticles are synthesized by the hydrothermal method with different doping concentrations. The main objective of the research is to analyze the role of doping concentration against septicemia and human colon cancer. The prepared nanoparticles are extensively characterized by the X-ray diffraction technique. The crystallite size, stain, lattice constants, and bond lengths are examined. The vanadium doping enhances the antibacterial activity against bacterial strains. The in vitro anticancer activity of the prepared nanoparticles is tested by MTT assay, EtBr and DAPI staining. The concentration-dependent enhancement in the antitumor activity is observed in human colon cancer cells by inducing apoptosis. The change in cell morphology and the induction of apoptosis is also observed in our study. This interesting finding will undoubtedly make substantial contributions to developing successful therapeutic agents for septicemia and colon cancer.

A wavelength-dispersive technique of targeted absorption spectrometry of the K-jump region of X-ray photoabsorption during diffraction of a collimated polychromatic beam in a mosaic texture of highly oriented pyrographite is proposed. Comparative results of measuring the absorption spectra of Br in an aqueous solution of KBr by wavelength-dispersive and energy-dispersive methods with a silicon drift detector (SDD) are presented. This scheme makes it possible to reach an energy resolution of ΔE/E ~ 10^‒3 and can be used in laboratory practice and medical and biological diagnostics to determine the content of contrasting agents and study the dynamics of their transfer under stationary and repetitively pulsed irradiation regimes.