Communications in Physics

This paper presents a Monte-Carlo code to simulate the time sequences of the \(\beta\)-decay following implantation of a continuous radioactive ion beam in to a segmented silicon detector. We extended our simulation to the \(\beta\)-delayed neutron process. Ananalis is procedure, which has been developed to obtain simultaneously the \(\beta\)-decay half-life and the \(\beta\)-delayed multi-neutron emission probability, was verified by the simulation data.

The gold nanoparticle solutions are well known as an extremely sensitive biomedical analytical tool due to the strong dependence of their absorption in the visible range on the environment. In this work, the colloidal nano golds were synthesized from metal precursor chloroauric acid (HAuCl4) using trisodium citrate dehydrate (C6H5O7Na3) as reducing and stabilizing agents. The optical characterization - absorption of colloidal gold solution have been investigated under the different synthetic conditions such as: reducing agent concentration, concentration of auric ion, pH, duration of reaction and aging time. The results show that the absorption and the stability of the colloidal gold nanoparticles depend robustly on the synthetic conditions and pH of environment.

With the advantages of selectivity, spectral resolution and reduction of interference on account of light scattering, synchronous luminescence spectroscopy (SLS) is successfully applied to analyze complex mixtures with overlapped emission and/or excitation spectra. In fact, it is difficult to clearly distinguish the contributions of various luminescence centers to low-energy band of semiconductor nanocrystals (NCs). Herein, we report the application of SLS method to detect luminescence centers in colloidal Cd_0.3Zn_0.7S NCs. Their conventional luminescence and synchronous luminescence spectra were comparatively investigated. Differently from conventional luminescence spectrum, the emission peaks at 460 and 515 nm were found using SLS method. They are attributed to the emission transitions related to sulfur and zinc/cadmium vacancies. The obtained results are useful to clarify the nature of luminescence centers as well as relaxation mechanism in Cd_xZn_1-xS NCs.

In this article a two-ports nonlinear fiber Mach-Zehnder interferometer is proposed. The expression for output-input intensity relation and the transmittance function are derived based on principle operation of optical coupler. The expression of coupling coefficient of coupler is presented. The bell shape of the transmittance function is simulated. The results lead to investigate bistability of two-ports-nonlinear fiber Mach-Zehnder interferometer and to confirm bistable character of it in the future.

The study of variation of the size, armchair and zigzag types effects on the melting process of graphene nanoribbon. A numerical  thermodynamical model has been devoted for the study. The phase transition has first order behaviour. The formation of different defects, ring size and coordination number is dependent on the size and the edge type of GNR. The nuclei of heating appear at temperature around 2300K and that can be considered as pre-melting point. The melting process shows the case that the results of Berezinsky-Kosterlitz-Thouless-Nelson-Halperin-Young (BKTNHY) theory cannot be applied. 

Starting from the generalized electromagnetic field equations of dyons, the magnetohydrodynamics (MHD) of plasma for particles carrying simultaneously the electric and magnetic charges (namely dyons), has been reformulated in terms of the electromagnetic duality. Consequently, the frequency of dyonic plasma is obtained for real value of wave number \(k\). In this case, only those generalized electromagnetic waves are allowed to pass, for which the usual frequency is greater than the plasma frequency (i.e. \(\omega>\omega_{p})\). Accordingly, the Ohm's law has been re-described to derive the plasma oscillation equation, Magnetohydrodynamic wave equation and to calculate the energy of dyons in unique and consistent manner.

In the current work, we report a facile synthesis of n-SnO2/p-NiO nanowire heterojunctions by a drop-coating approach. The pure SnO2 and NiO nanowires (NWs) were grown by chemical vapor deposition (CVD) and hydrothermal methods, respectively. Morphology, composition and crystal structures of the NWs and heterojunctions were investigated by means of field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD), respectively. The data showed that SnO2 NWs were grown with their average diameter of 200 nm and length of about 10 mm. The NiO NWs were also synthesized with a shorter average length and smaller average diameter compared to those of the SnO2 NWs. The EDS results indicated no impurity present in both SnO2 and NiO NWs. The XRD patterns pointed out the tetragonal rutile and cubic structures of SnO2 and NiO, respectively. Interestingly, electrical properties of the NWs and heterojunctions were studied through the Keithley 2602A sourcemeter-based I-V characterizations. The results confirm the nature of the metal semiconducting oxides. The formation of the n-SnO2/p-NiO heterojunctions was certified through the rectifying behavior of the I-V curves with the rectification ratio of about 5 at ± 3V and 350 oC. The potential energy barrier between the NWs was also estimated to be about 1.16 eV. The band energy structure was also proposed to get insight into characteristics of the n-SnO2/p-NiO heterojunction.

The thermodynamic properties of the metal thin film with face-centered cubic structure at zero pressure are investigated using the statistical moment method \((SMM)\), including the anharmonicity effects of thermal lattice vibrations. The Helmholtz free energy, linear thermal expansion coefficients, specific heats at the constant volume and those at the constant pressure, \(C_V\) and \(C_p\) are derived in closed analytic forms in terms of the power moments of the atomic displacements. Numerical calculations for thermodynamic quantities of Al, Au and Ag thin films are found to be in good agreement with those of the other theoretical results and experimental data.

The condition to match the pumped-volume's width with the laser mode-volume's waist in a diode four side pumped solid-state laser is analyzed by numeric solutions of the approximation equation. As a result, the dependences of pumped volume's width on pumping diode parameter and laser mode volume's waist on cavity parameter were found. Such a matching condition was simultaneously determined by cavity, pumping beam and laser rod parameters.%Key words: Laser diode side-pumped, Coherent pump, Excitred active center distribution.

Optical tweezers have seen as an essential tool for the manipulation dielectric microparticles and nanoparticles due to its non-contact action and high resolution of optical force. Up to now, there has been a lot of optical tweezers applications in the fields of biophysics, chemistry, medical science and nanoscience. Recently, optical tweezers have been theoretically and experimentally developing for the nanomechanical characterization of various kinds of biological cells. The configuration of optical tweezers has been day after day improving to enhance the trapping efficiency, spatial and temporal resolution and easy to control trapped objects. In common trend of optical tweezers improvements, we will discuss in detail of the several configurations of nonlinear optical tweezers using nonlinear materials as the added lens. We will also address the advantages of nonlinear optical tweezers, such as enhance optical efficiency, reduce trapping region, simplify controlling all-optical method. Finally, we present discussions about the specific properties of nonlinear optical tweezers used for stretch DNA molecule as example and an ideal to improve nonlinear  optical tweezers using thin layer of organic dye  proposed for going time.