Journal of Contemporary Physics (Armenian Academy of Sciences)最新文献

Peculiarities of X-ray beam diffraction from potassium and rubidium bi-phthalate piezo crystals under the condition of excitation of transverse ultrasonic vibrations are investigated. Previously, under a similar influence in quartz crystals, the effect of X-ray acoustic redistribution was observed, in which the intensity of diffracted radiation in the exact Bragg position increases significantly with a simultaneous decrease in the intensity of the transmitted beam, down to zero for certain parameters for reflecting atomic planes, called the full pumping effect. This effect can be used for controlled tuning of the diffracted beam intensity. In this work, to search for new materials for the creation of elements that allow such a rearrangement, we studied the dependences of the degree of amplification of diffracted radiation on the amplitude of the control signal for potassium and rubidium bi-phthalates crystals. The actual possibility of X-ray intensity modulation using transverse vibrations in these crystals is demonstrated.

A new type of atomic interferometer in which the registration is carried out by absorption spectroscopy of probing radiation is theoretically presented. To split the input atomic beam, the interaction with counterpropagating resonant waves is used. In addition, the atom also acquires equal populations at internal energy levels. The interaction with the subsequent traveling wave results in the interference between neighboring momentum states of the atom, and the distribution periodically varies with a strong asymmetry relative to the input momentum value. At the measurement stage, the result of the interference of matter waves is reproduced by the spectral distribution of the probing electromagnetic wave.

The article describes a new detector, a volume filled with hexane at low pressure (3 Torr), containing multi-wire proportional chambers and a silicon semiconductor detector. Using this setup, alpha particles emitted during the decay of the radioactive isotope ²²⁶Ra were detected. The device has an energy resolution of ≤ 5% and allows measuring the ionization energy losses of alpha particles as well. Thus, the LPMWPC and SSD-based experimental setup is a good tool for studying both binary and ternary fission of heavy nuclei, in which the third fragment is a high-energy alpha particle.

The structural and optical properties of tandem silicon/perovskite structures with a hierarchical antireflective surface at the interface have been studied. The surface consisted of micro-sized pyramids and nano-sized short needles formed respectively by chemical and reactive ion etching of silicon substrates. It is shown that a perovskite film without pores and voids covers a hierarchical surface with high conformity. The manufactured samples are characterized by low reflectance over a wide range of radiation wavelengths.

For the first time in Armenia, gamma activation analysis of geological samples of obsidian was carried out using beams of bremsstrahlung photons at the linear electron accelerator of the A. Alikhanyan National Scientific Laboratory (AANL). It is shown that the results of the chemical composition of the obsidian sample are comparable with the results of instrumental neutron activation analysis (INAA) of the same sample, carried out at the Curt-Engelhom-Center for Archaeometry (Mannheim, Germany), after irradiation with neutrons in a specialized nuclear reactor TRIGA at the Institute of Nuclear Chemistry of the Mainz University. It is also shown that gamma activation analysis makes it possible to determine the content of a number of elements for which the use of INAA is impossible or difficult.

A sensor sensitive to hydrogen peroxide vapor based on Fe₂O₃:ZnO (80 : 20 wt %) nanostructured film was studied. Investigation of the Fe₂O₃:ZnO sensor has been carried out by impedance spectroscopy. Based on the analysis of the frequency dependences of the real and imaginary parts of the complex impedance, the equivalent electrical circuit for the studied sensor structure was proposed, the parameters of its constituent elements were estimated, and approximating curves were computed. Scanning electron microscopy (SEM) images of the Fe₂O₃:ZnO film showed a nanoparticle structure. This type of sensor can be used in alternating signal-based detectors for sensing the hydrogen peroxide vapors, at the same time the sensor must be tuned to achieve maximum sensitivity by selecting an appropriate operating frequency range.

The interaction of nutritional preservative and dye erythrosine B with bovine serum albumin (BSA) under the influence of millimeter range electromagnetic waves (MM EMW) with frequencies 41.8 and 51.8 GHz has been studied by the UV-denaturation and spectroscopic methods (absorption, fluorescence, and circular dichroism (CD)). We show that the irradiation by MM EMW with the frequency 51.8 GHz stabilizes the complex BSA-erythrosine B. At the same time, denaturation parameters of the complex at the irradiation of BSA solution with the frequency 41.8 GHz do not differ from those obtained for non-irradiated samples within the limits of experimental error. We also show that under the influence of the irradiation by 51.8 GHz frequency there is no conformational change of BSA. However, a change in the protein conformation takes place in the case of the complex BSA-erythrosine B. In addition, the complex-formation process is thermodynamically beneficial and implemented because of the additional hydrogen bonds and van-der-Waals interaction between BSA and erythrosine B under the influence of MM EMW.

Within the frameworks of the defect isotopic model, new expressions for the rapid estimation of the absorption coefficients of longitudinal and transverse hypersonic waves in the alloyed lithium niobate single crystals in the Akhiezer regime have been obtained. It is shown that the introduction of impurities in the crystal results in a change in both the magnitude of the sound attenuation coefficient and its temperature dependence.

Vector non-stationary diffraction electromagnetic fields and fields of charges in an arbitrarily chosen volume in both homogeneous and inhomogeneous media are considered. These formulas are presented in two forms, each of which has its advantages in applications. The generalization of the Kirchhoff–Kottler vector formulas for discontinuous fields in the non-stationary case is also directly obtained.

The electrically small phased antenna array is investigated. High permittivity dielectric and magnetodielectric materials (MDM) are used for antenna array substrates to miniaturize antenna size. To analyze material parameter influence on antenna performance, the same refractive index is considered for dielectric and MDM. The basic parameters of high permittivity-based, and MDM-based microstrip patch antenna arrays are compared. The simulation results show that the usage of MDM results in the improvement in bandwidth and isolation between elements, perfect impedance matching (voltage standing wave ratio (VSWR) < (~1.1) for center frequency) between material and free space over a much wider bandwidth.