A photon accelerator -- Large blueshifting of femtosecond pulses in semiconductors

The availability of relatively high intensity (I > 10{sup 9}Wcm{sup {minus}2}) [but moderate ({approximately} nJ) total energy], femtosecond laser pulses with wavelengths ranging from the ultraviolet to the mid-infrared has opened the doors for a serious investigation of the nonlinear optical properties of matter on ultrashort time scales in a new parameter regime. Even small intensity-dependent nonlinearities can begin to play a major role in the overall electrodynamics, and in determining the fate of the propagating pulse. It is shown that a femtosecond pulse propagating near a two-photon transition in a semiconductor waveguide can undergo a large blueshift

MERCURY ADSORPTION BY ARTHOBACTER GLOBIFORMIS AND SPIRULINA PLATENSIS

Abstract. The increasing contamination of soil, sediment, and water with heavy metals by natural and industrial processes is a worldwide problem. Many bacteria and microalgae have demonstrated ability to absorb toxic elements. To study mercury biosorption by bacteria Arthrobacter globiformis and microalga Spirulina platensis neutron activation analysis (NAA) was applied. The process of mercury biosorption by these media was described by Freundlich and Langmuir-Freundlich Model. Both microorganisms showed a great potential to be used as biosorbing agents for mercury removal from the environment

SYNTHESIS OF GOLD NANOPARTICLES BY BLUE-GREEN ALGAE Spirulina platensis

Kalabegishvili T. et al. E14-2012-31 Synthesis of Gold Nanoparticles by Blue-Green Algae Spirulina platensis The synthesis of gold nanoparticles by one of the many popular microorganisms Å blue-green algae Spirulina platensis was studied. The complex of optical and analytical methods was applied for investigation of experimental samples after exposure to chloroaurate (HAuCl4) solution at different doses and for different time intervals. To characterize formed gold nanoparticles UV-vis, TEM, SEM, EDAX, and XRD were used. It was shown that after 1.5Ä2 days of exposure the extracellular formation of nanoparticles of spherical form and the distribution peak within the interval of 20Ä30 nm took place. To determine gold concentrations in the Spirulina platensis biomass, neutron activation analysis (NAA) and atomic absorption spectrometry (AAS) were applied. The results obtained evidence that the concentration of gold accumulated by Spirulina biomass is rapidly growing in the beginning, followed by some increase for the next few days. The obtained substance of Spirulina biomass with gold nanoparticles may be used for medical, pharmaceutical, and technological purposes. The investigation has been performed a

Dynamics of space-time self-focusing of a femtosecond relativistic laser pulse in an underdense plasma.

The propagation of femtosecond, multiterawatt, relativistic laser pulses in a transparent plasma is studied. The spatio-temporal dynamics of ultrashort, high-power laser pulses in underdense plasmas differs dramatically from that of long laser beams. We present the results of numerical studies of these dynamics within a model which systematically incorporates finite pulse length effects (i.e., dispersion) along with diffraction and nonlinear refraction in a strongly nonlinear, relativistic regime. New space-time patterns of self-compression, self-focusing and self-phase-modulation, typical of ultrashort, high-intensity laser pulses, are analyzed. The parameters of our numerical simulations correspond to a new class of high-peak-power (> 100 TW), ultrashort-pulsed laser systems, producing pulses with a duration in the 10 – 20 femtosecond range. Spatio-temporal dynamics of these self-effects and underlying physical mechanisms are discussed

MERCURY ADSORPTION BY ARTHOBACTER GLOBIFORMIS AND SPIRULINA PLATENSIS

The increasing contamination of soil, sediment, and water with heavy metals by natural and industrial processes is a worldwide problem. Many bacteria and microalgae have demonstrated ability to absorb toxic elements. To study mercury biosorption by bacteria Arthrobacter globiformis and microalga Spirulina platensis neutron activation analysis (NAA) was applied. The process of mercury biosorption by these media was described by Freundlich and Langmuir-Freundlich Model. Both microorganisms showed a great potential to be used as biosorbing agents for mercury removal from the environment