Abstract. In a previous work dedicated to non-relativistic quantum mechanics in the three-dimensional space with spherical symmetry, we have shown the possibility of reconstructing the ground state density from its moments in the case of bound states. The method is based on relationships connecting these moments to the lower energy of each state of angular momentum l. The ground state density yields the ground state wave function, which allows us to calculate the equivalent local potential by inverting the Schrödinger equation. This calculus uses the Fourier transform of the ground state density ρ(r). The aim of this work is to check how to improve the results by replacing the Fourier transform by the Laplace transform of the quantity r²ρ(r). The method is first presented. Then examples and results are compared to those obtained previously.

Abstract. We aim to construct a Liouville integrable Hamiltonian hierarchy from a specific matrix spectral problem with four potentials through the zero curvature formulation. The Liouville integrability of the resulting hierarchy is exhibited by a bi-Hamiltonian structure explored by using the trace identity. Illustrative examples of novel four-component coupled Liouville integrable nonlinear Schrödinger equations and modified Korteweg-de Vries equations are presented.

Abstract. In this work, we built a (3+1)-dimensional integrable equation. We started by reformulating the main equation of our model by combining the recursion operator of the Calogero-Bogoyavlenskii-Schiff equation with its inverse recursion operator. We confirm the complete integrability of our new developed equation by demonstrating that it satisfies the Painlevé property. We get a variety of lump solutions that are obtained under specific constraints. Furthermore, we used the simplified Hirota's direct approach to find multiple soliton solutions to the new evolution equation. In addition, other techniques are used to solve the new evolution equation, in order to get some physically relevant solutions.

Abstract. The evolution of merging black holes (BHs) and their associated processes will be the center-piece study for the upcoming gravitational waves (GWs) observatories, including the LISA Space Mission from ESA. We ran simulations specifically for studying the BH growth, in order to provide estimates regarding the detection rates for the future GW laboratories. Here, we describe the results of our investigations for a new implementation regarding the BH growth, star gulping (SG), in which stars are absorbed by BHs. The current scientific literature emphasizes two main mechanisms for the growth of BHs: accretion of surrounding material and merging with another BH. By taking into account both methods, one can begin to model the growth processes of the most massive BHs (MBHs) from the moment of their origin to current observations. Our previous work showed that even if you consider these processes at their maximum, it is very difficult to grow BHs to the masses and concentrations that we measure today. Therefore, we performed detailed simulations in order to study another growth mechanism, star gulping (SG), that has the potential to add more mass to BHs.

Abstract. The energy of near-infrared femtosecond laser pulses generated by optical parametric amplification (OPA) in β-barium borate (BBO) crystals pumped by femtosecond Ti:sapphire lasers is restricted to few-mJ due to the 20 mm limited diameter of available crystals. In a type I collinear OPA with an yttrium calcium oxoborate (YCOB) crystal, pumped with femtosecond Ti:sapphire lasers at 800 nm wavelength, the 1300 nm signal wavelength and 2080 nm idler wavelength are located in the normal and anomalous group velocity dispersion range, respectively. Due to the small group velocity mismatch (GVM) between signal and idler pulses, as broad as 27 THz gain bandwidth can be obtained in a 3-mm YCOB crystal at 100 GW/cm² pump intensity. A high parametric gain is the result of the increased parametric interaction length due to the different signs of GVM between pump-signal and pump-idler pulses. More than 10-mJ energy femtosecond laser pulses at 1300 nm wavelength can be generated by OPA in YCOB crystals with larger than 50 mm clear aperture.

Abstract. In this paper, we consider the dynamics of three-dimensional extremely short optical pulses in a medium with a spatially variable refractive index (photonic crystal) based on carbon nanotubes. The transitions between impurity levels in carbon nanotubes are taken into account. It has been established that pulses propagate stably with conservation of energy in a limited region of space. The effect of modulation parameters of the refractive index of a photonic crystal on the shape and group velocity of the pulse wave packet is obtained. The rate of one- and two-photon ionization in such medium is estimated.

Abstract. In this work, a transverse ⚬ spin-dependent shift (SDS) of the horizontal photonic spin Hall effect (PSHE) at a fixed frequency (5 THz) is simulated for detection of refractive index, chemical potential, and applied electrical voltage to a plasmonic sensor with four layers (germanium, organic layer, graphene, and gas medium). The variation of the refractive index of graphene with chemical potential and applied voltage is given from the simulated values. A refractive index resolution (1.73×10^-12 RIU) is obtained when the refractive index n₄ of the analyte layer is changed from 1 RIU to 1.1 RIU when the chemical potential µ_c is 0.003 eV and the amplified angle Δ is 0.1^⚬. A chemical potential resolution (6.32×10^-14 eV) and corresponding voltage resolution (6.83×10^-13 V) are obtained when the chemical potential is changed from 0.003 eV to 0.03 eV, the refractive index of gas medium n₄ is 1.1 RIU and the amplified angle is Δ = 0.1^⚬. These values are very good in comparison with the situation when the spin Hall effect is not applied (7.47×10^-6 RIU, 0.001166 eV, and 0.01259 V) for the same values of µ_c, n₄, and Δ.

Abstract. We report secure data transmission performed using chaotic lasers with different external cavity geometries and applying the chaotic masking method based on subcarrier and phase modulations of the chaotic optical carrier. Two semiconductor lasers with similar multimode emission spectra and self-optical feedback provided, respectively, by ring and linear external cavities, were optically coupled and chaotically synchronized into a master - slave scheme. The transmitted message frequency modulates the radio frequency signal which modulates in phase the master chaotic carrier. Based on the robustness of the used encryption method and the synchronization characteristics of the two lasers, the decryption is conducted by the simple radio frequency spectrum monitoring of the slave emission.

Abstract. We investigate the kinetic hysteresis of spin crossover molecular magnets, with the aim of unravelling the link between static and dynamical effects observed in the first order reversal curves (FORC) diagrams. Using a mean-field model, we establish how the FORCs distributions are influenced by both the kinetic effects and the physical parameters of the system.

Abstract. Magnetically active composites based on silicone rubber, silicone oil, carbonyl microparticles, graphene nanopallets and fabric, as a reinforcing element, are manufactured. For a constant amount of carbonyl iron microparticles and silicone oil, and for different ratios between the amounts of silicone rubber and graphene nanopalets, three composite samples are prepared. Using the plane capacitor method, the relative permittivity of the composites is determined. It is shown that by using graphene nanopallets, composites with giant values of relative dielectric permittivity can be obtained and that the relative dielectric permittivity values are sensitive to the magnetic force induced by the static magnetic field superimposed on the medium-frequency electric field. Using the model of the dipolar magnetic approximation and elements of the theory of dielectrics in medium frequency electric fields, the mechanisms participating in the obtained effects are described.

Abstract. This study reports an interesting idea to convert aqueous extracts of invasive terrestrial plants [Johnsongrass (Sorghum halepense L.) and Knotgrass (Polygonum aviculare L.)] into valuable silver nanoparticles (AgNPs), and used them against aquatic weeds (Cladophora). The phyto-generated AgNPs presented nano scaled dimension (estimated by DLS), and good antioxidant activities (evaluated by chemiluminescence technique). UV-Vis absorption spectroscopy confirmed the AgNPs phyto-development. The total polyphenols (TPC) and total flavonoid (TFC) contents of the aqueous herbal extracts and of AgNPs phyto-generated from them, revealed the major contribution of polyphenols and flavonoids to phyto-reduction of silver ions, and also, they are responsible for the antioxidant properties of the obtained samples. The bio impact of the prepared AgNPs against Cladophora depends on the AgNPs dose, and the time exposure. These findings could be useful in for various biomedical, agronomic and biotechnological applications.

Abstract. The manifestation of life, in all its aspects, is the result of an enormous number of specific biophysical and biochemical molecular interactions taking place ceaselessly into cells, in a highly ordered manner both spatially and temporally. Frequently, a product of any reaction, is not a final compound, but the initial reactant of another reaction taking place in a precise location and at right time into the intricate cellular reactions network. In this minireview, we will present, in an accessible manner, the nature and paramount importance of the specific interactions which constitute the essential basis for all life processes on the Earth.

Abstract. In this article, the Probable Maximum Precipitation (PMP) evaluation is done using a spatio-temporal approach - Diaconu's method - for a set of data series collected in the Dobrudja region for 41 years. The results are compared with those obtained by applying the classical method of Hershfield and the advantages of each method are emphasized.

Abstract. In the absence of earthquakes, seismic stations continuously record the Earth's vibrations, called ambient seismic noise (ASN). The main concern regarding the ASN records is improving the seismic data quality using different tools developed especially for this purpose. Power Spectral Densities (PSD) and their corresponding Probability Density Functions (PDF) are tools used to evaluate the station performance and reveal the noise level at the station's site. For high frequencies (> 1 Hz), the noise sources are from cultural activities and show diurnal variation, while for low frequencies (< 1 Hz), the noise is generated by natural sources and shows seasonal variation. In this study, we analyzed the vertical components of the Bucovina array seismic network (BURAR) to characterize the noise levels at the stations and investigate noise variations in space and time. We computed four-year spectrograms for some elements of the array that revealed an increase of ASN in the 2-5 Hz frequency range during the warmer seasons, contrary to the colder months. On the other hand, at lower frequencies (0.5-1 Hz), the power of seismic noise increases during the year's colder months. We examined the relationship between noise levels and weather parameters (e.g., wind speed) for the station where the seismic sensor is collocated, with a weather station. We observed that an increase in wind speed leads to an increase in the noise level at high frequencies (> 2 Hz).

Abstract. This paper presents our results investigation to evaluation effects of the electron beams radiation generated in multimode optical fibers at high irradiation doses in order to develop an ionizing radiation dosimeter. The radiation induced attenuation has been shown to exhibit a linear dependence as a function on the applied dose on a certain doses range and after the irradiation the optical fibers go through a “recovery process” during which the optical properties improve again. The surface morphological changes due to electron beam irradiation were investigated by Scanning Electron Microscopy and Atomic Force Microscopy.

Abstract. We report examples of obtaining the bistability effect in mechanics and the experimental demonstration of this effect. We propose to use the graphical method of solving physics problems. The method explains qualitatively the theoretical results. We investigate the influence of different parameters on bistability properties. Finally, the experiment shows a clear evidence of bistability in a mechanical system.

Abstract. Capillarity phenomena appear due to different molecular forces acting between fluid molecules located at the interface with either another fluid or a solid. The macroscopic description of the phenomenon can be done in terms of surface tension. In this paper, we determined the surface tension coefficient of aqueous solution of potassium permanganate by means of Jurin's law and also made diameter measurements and capillary ascents on images by using ImageJ software. Furthermore, we studied the capillary phenomena between two parallel and non-parallel plates. In the case of non-parallel plates, employing a special plugin of the ImageJ software, we determined the equation of the rectangular hyperbola drawn by the surface of liquid rising between plates. These experiments can be performed at elementary level and, additionally, used as a stimulus to discover more advanced topics.