Slow and fast magneto-optical response of magnetite nanoparticles suspension

DC magnetic field applied to Fe3O4 nanoparticle suspension affects its light scattering. Time dependent variations in the light intensity transmitted through a suspension are observed after the magnetic field is switched-on. Two types of variations can be distinguished. Fast response takes less than millisecond while slow variations occur at the time interval from seconds to hundreds of minutes. Possible mechanisms of these variations are discussed

Spatial variations in the field of velocities and real solar granulation

In this paper, the physical conditions within the inhomogeneous solar atmosphere have been reconstructed by means of solving the inverse problem of Non Local Thermodynamic Equilibrium (NLTE) radiative transfer. The profiles of $\lambda=523.42$ nm FeI spectral line of high spatial and time resolution were used as observational data. The velocity field has been studied for the real solar granulation in superadiabatic layer and overshooting convection region. Also, we investigate the vertical structure of inhomogeneous solar photosphere and consider penetration of granules from convective region into upper layers of stable atmosphere. The microturbulent velocity appears to be minimal at the bottom of overshooting convection region and increases sharply through superadiabatic layer and upper photosphere. High-turbulent layers emerge either in the central part of a flow or at the boundary of an incipient flow with following drift toward the centre of the flow. Wide descending flows tend to disintegrate into structures having turbulence augmented, these structures correspond to the flows of matter. High microturbulence of the intensive flows provokes steep temperature depression in upper photosphere leading to the second inversion of temperature for the intergranules. The inversion of vertical velocities is observed to be frequent in the solar granulation. Some of the convective flows reach the minimum temperature region. Vertical convective velocities of the matter flows were found to be smaller in the middle and upper photosphere. Also, the effect of finite resolution on the spacial variations of the velocities in solar photosphere has been estimated.Comment: 8 pages, 7 figure

Fabrication of Worm-Like Nanorods and Ultrafine Nanospheres of Silver Via Solid-State Photochemical Decomposition

Worm-like nanorods and nanospheres of silver have been synthesized by photochemical decomposition of silver oxalate in water by UV irradiation in the presence of CTAB and PVP, respectively. No external seeds have been employed for the synthesis of Ag nanorods. The synthesized Ag colloids have been characterized by UV-visible spectra, powder XRD, HRTEM, and selected area electron diffraction (SAED). Ag nanospheres of average size around 2 nm have been obtained in the presence of PVP. XRD and TEM analyses revealed that top and basal planes of nanorods are bound with {111} facets. Williamson–Hall plot has revealed the presence of defects in the Ag nanospheres and nanorods. Formation of defective Ag nanocrystals is attributed to the heating effect of UV-visible irradiation

Nonlinear-optical refraction of silver nanoparticle composites

In this paper, the experimental data on nonlinear refraction of silver nanoparticle composites using a standard Z-scan technique are presented. It was found that the colloids of silver nanoparticles of various size possess a defocusing ability. Based on general considerations, one can conclude thermal lens nature of the nonlinear refraction of the colloids. Significantly different magnitudes of the nonlinear refractive index of silver nanoparticles suspended in water and in glycerol can be explained by differences in the specific heat capacity of mentioned fluids. The effective thickness for nonlinear-optical interaction of light with a two-dimensional silver nanoparticle array was estimated

Spectroscopy of the Irradiated YBa2\text{}_{2}Cu3\text{}_{3}Ox\text{}_{x} Superconductors

Complex investigations of the photoinduced changes in YBa$\text{}_{2}$Cu$\text{}_{3}$O$\text{}_{x}$ single crystals were performed. As laser sources the low-power He-Ne, He-Cd, He-Se, N$\text{}_{2}$ lasers and YAG:Nd, XeCl pulsed lasers were used. For the investigations the crystalline samples both in super- and semiconducting phases were chosen. A considerably strong dependence of a defectiveness parameter x on the laser power, wavelength and external conditions was observed. The oxygen parameter x shows a tendency to increase for the initially semiconducting phase and to decrease for superconductors. The most interesting result were obtained using XeCl excimer laser, where corresponding changes were observed only under applied hydrostatic pressure (up to 200 MPa) in oxygen atmosphere. In all the cases the penetration depth of the new induced superconducting phase was within 5.5-6.5 μm