This study explore the dynamics of cosmic expansion through a detailed exploration of a novel form of the deceleration parameter, denoted as $q = \frac{\alpha(t^2-1)}{t^2+1}$, within the framework of $f(R,T)$ gravity theory. This study employs both observational and theoretical approaches to unveil the intricate interplay of cosmic forces and phenomena that have a profound influence on the ever-evolving universe. The primary objective of this investigation is to gain a deeper understanding of the expanding dynamics, particularly the transition from deceleration to acceleration. The findings of this paper shed light on the presence of a phase transition and an initial singularity, while remaining consistent with the ΛCDM model. Moreover, this study serves as a foundation for further exploration within the $f(R,T)$ gravity framework, providing fresh insights into the cosmos and offering a profound comprehension of the universe's dynamic evolution.

The fundamental modes of nonlinear optical weakly guiding fiber with circular cross section are studied analytically. The dielectric constant of the fiber core is assumed to be differing from the dielectric constant of the fiber cladding. The change between them occurs abruptly when the light intensity reaches a certain level. The core radius formed at a certain intensity level in dependence of the optical characteristics of the waveguide mode and fiber is specified. It is shown that the core radius can be reduced by increasing the frequency of the wave or the magnitude of the jump in the dielectric constant, and also by decreasing the propagation constant. The self-confinement core radius decreases with increasing frequency, but this increases the diameter of the light beam localization in the fiber cross section. Increasing the propagation constant has the opposite effect.

An energy momentum-dependent potential is considered to study nucleon-nucleon, nucleon-nucleus and nucleus-nucleus elastic scattering by exploiting the variable phase method to potential scattering. The velocity dependent potential, equivalent to Graz separable potential, has the ability to reproduce the correct nature and numerical values of the NN phase parameters up to 400 MeV. Also it works equally well for alpha-nucleon and alpha-alpha systems up to few higher partial waves. Our results are in close conformity with the previous theoretical and experimental data. For alpha-alpha scattering we have treated only s-wave case.

We present here the design, expected parameters and performance tests of a compact detector, based on INTPIX4 sensing device, developed in the framework of the Extreme Light Infrastructure – Nuclear Physics (ELI-NP) project, capable of measuring both polarization and energy of gamma rays, in the high energy range above 1 GeV. The detector, based on electron-positron pair creation in the BetheHeitler process, has been tested with cosmogenic muons and will allow unique experiments at the ELI-NP facility.

In this work we analyze a few of the phenomenological implications of a theory of gravity and matter (Y theory of fields) introduced and described in previous works. We show that the laws of elastic collisions and of electromagnetism can be derived directly as gravitational effects and in first orders they are conformal to the status-quo. However there are small experimental deviations from the actual knowledge in the presence of an external gravitational field. These are within reach of our experimental capability.

This paper is a study of a multilayer system with mixed spins $S = 1/2$ and spin $S = 3/2$ by the Blume Capel model using Monte Carlo simulation. The phase diagrams (at $T = 0$ and $T \ne 0$) as well as the total magnetization have been determined. The critical temperatures have been deduced from the different values of the system parameters, namely the exchange interactions $J_B$, the crystal field ∆ and the numbers of layers of the system $N_A$ and $N_B$. It became apparent that the system presents both the first and second-order transitions. In addition, we see the appearance of one of the serval phenomena which is compensation behavior. Moreover, the hysteresis behavior present single and multiples hysteresis loops for well-determined values. Finally, our results are compared with the other theoretical and experimental works.

The spin-1 antiferromagnetic Heisenberg model was investigated by the introduction of spin operators on a square lattice in terms of a mean-field approximation (MFA). The bilinear exchange interaction parameters $J_x$ and $J_z$, the crystal field interactions $D_x$ and $D_z$, and the external magnetic field components $H_x$ and $H_z$ along the $x-$ and $z-$axes were all incorporated in the model Hamiltonian. The effects of the Dzyaloshinskii-Moriya interaction (DMI), $\Delta_m$, were also included along the $y-$axis, i.e. containing the spin components only along the $x-$ and $z-$axis. Various phases of the model, including ferromagnetic (FM), antiferromagnetic (AFM), and random (R) were identified by studying the thermal variations of the order-parameters, susceptibilities, specific heats, and free energy of the sublattices. The second-order phase transition temperatures between these phases were identified, in addition to the existence of first-order phase transitions. Numerous critical points, including the three-phase coexistence, were observed on the phase diagrams. The reentrant behavior was also seen for appropriate values of the system parameters.

The improvement of heat transfer in MEMS remains today a major challenge because its importance in many engineering applications and industry. The objective of this paper is to analyze heat transfer and irreversibility in micro flows. The case of heated horizontal microchannel filled with nanoliquid in the slip flow regime is investigated by means of the LBM method. The slip velocity and the temperature jump conditions are applied to lower and upper walls. The flow is induced by wall injection. The effects of quadratic combination of several design factors such as Reynolds number (Re), Knudsen number (Kn), volume fraction (V_f) and nanoparticles diameter (D_p) on heat transfer enhancement and volumetric entropy generation were reported and a polynomial regression for the interaction between these parameters is determinate based on response surface methodology.

In this paper, we studied the effect of an electromagnetic field of an ultrahigh frequency on the I–V characteristics of tunnel diodes. The influence of thermionic current on the change in the ratio of the values of tunnel currents at depth and the peak formed in the tunnel diode as a result of a strong electromagnetic field and on the change in the ratio of the values of tunnel currents at the highest and lowest points without exposure to a strong electromagnetic field. The I–V characteristics of a tunnel diode under the action of a microwave field is determined based on the theory of Knott and Demassa and the Tsu-Esaki model. The characteristics of the Tsu-Esaki and Karlovsky models used to determine the effect of the tunnel current in the extremely high frequency field (EHF) are shown. Chynoweth's model and Knott and Demassa's theory have shown that in germanium-based tunnel diodes, under an extremely high frequency (EHF) field, the amount of excess current generated in the tunnel diode increases. According to the Tsu-Esaki theory and Knott and Demassa theory is found to decrease the value of the differential resistance of a tunnel diode with a p-n junction under the action of a microwave field, regardless of the type of heterostructure or doping level. According to the Tsu-Esaki theory and Knott and Demassa found decrease in the diffusion capacitance of a tunnel diode with a p-n junction under the action of a microwave field, regardless of the type of heterostructure or doping level. A decrease in the transparency coefficient due to an increase in the internal field at the p-n junction boundary of a Ge-based tunnel diode under the action of a microwave field has been established. A formula is determined for determining the total current of a tunnel diode under the action of both microwave and magnetic fields, taking into account the transparency coefficient of the tunnel diode.

In this paper high-resolution continuum source atomic absorption spectrometry (HRCS AAS) was used for the determination of metal concentrations in Danube water collected in the river lower sector in SE Romania (Braila-Galati-Tulcea). The evaluation of the water natural radioactivity was only performed in Galati sector based on selected radiological parameters: gross alpha/beta activity and radionuclides (²¹⁰Po, ²¹⁰Pb, ^natU, ^natTh and ²²⁶Ra) activity concentrations. The results indicate a temporal and spatial variability of contaminant levels due to anthropogenic inputs and seasonal conditions. For several heavy metals, the registered concentrations exceed the legislated values, imposing a regular monitoring of water quality especially in the case of using the water resource for human consumption, irrigation or aquaculture.

This study underlines the idea of valorizing vegetable waste in a “green” approach for water bioremediation. In this research, the possibility of using unpurified peroxidase obtained from cabbage leaf waste in the process of removing phenol from aqueous solutions was examined. This biocatalyst exhibits catalytic activity in a wide range of temperatures, pH values, and pollutant concentrations. The efficiency of phenol removal was monitored spectrophotometrically, by measuring the change in the residual amount of phenol in the reaction mixture. The influence of peroxidase, phenol, hydrogen peroxide, and polyethylene glycol (PEG) concentrations, as well as incubation time, temperature, pH value, and shaking rate on the efficiency of the phenol removal process, was comprehensively evaluated. The results showed that the use of raw, unpurified peroxidase from cabbage leaf waste can successfully replace commercial peroxidase and thereby significantly reduce the procedure cost. In addition, the presence of PEG as a peroxidase stabilizer showed little effect on the phenol removal efficiency, indicating that the extracted crude peroxidase is stable even without a commercial stabilizer, which could further cheapen the phenol removal process.

Lightning flashes result in an instantaneous emission of electromagnetic (EM) waves that encompass a broad spectrum of frequencies in the domain of radio waves. The signature of these impulses in the region of the very low frequency (VLF) of radio waves and bellow are called spherics. These impulsive signals traverse great distances in the waveguide between the Earth’s ionosphere and its surface. Due to the abundance of lightnings the lower end of the EM spectrum is dominated by the waveforms of these emission. It is called atmospheric radio noise because of its origin. This article outlines a straightforward approach for capturing spherics activity within the VLF radio wave range. Employing data processing techniques, we pinpoint the timestamps of spherics within time series data. The distribution of inter-spheric times is analyzed across various detection threshold levels. Utilizing recordings spanning two distinct years and seasons, we replicate the established form of the inter-spheric time distribution described in the literature. Notably, we demonstrate that by rescaling the time intervals between spherics with the mean time for a specific recording and given detection threshold, the distributions collapse to a master curve. This universal pattern is accurately characterized by a single-parameter mean-scaled Gamma distribution. Additionally, we note the similarities in the distribution of inter-spheric times with patterns found in earthquake recurrence times.

The decommissioning or refurbishing processes of nuclear facilities result in significant amounts of radioactive wastes. Radiological characterization is essential to ensure safe handling, transportation, and disposal of these wastes and includes the assessment of the radioactivity levels and types of radioactive materials present in the wastes. The present paper presents the tritium activity determination in used titanium tritide targets from different decommissioned nuclear facilities from Măgurele Area – Romania. The determination of tritium content in tritiated targets involves the use of the Total Combustion technique coupled with Liquid Scintillation Counting analysis of the resulting tritiated water. The tritiated testosterone controlled contaminated titanium powder was used to determine the overall yield of the Total Combustion facility. The determined yields were then used to correct the experimental values obtained during the process.