Photoacoustic spectra and modes of vibration of TNT and RDX at CO2 laser wavelengths.

IR spectra in the 'Finger Print' spectral range has great importance in qualitative and quantitative analysis of explosives like trinitrotoluene (TNT) and cyclotrimethyltrinitramine (RDX). Highly resolved IR bands of these compounds have been recorded in the 9.6 and 10.6 microm regions of CO2 laser. TNT and RDX are large molecules each having 21 atoms and it is very difficult to assign the modes of vibrations by comparison with those in other molecules making the vibrational assignments of observed bands a difficult task. The ab initio quantum chemical calculation is used for determining the molecular geometries and modes of vibration of these molecules with a view to assign their normal modes in the high resolution vibrational photoacoustic spectra. These assignments are very reliable in view of the good agreement between the observed and calculated frequencies of deuterated TNT.

Biological process of arsenic removal using selected microalgae.

In the present investigation, growth of the organisms was reduced due to presence of arsenic (III) and (V) in the culture medium. In comparison to arsenic (V), arsenic (III) had more toxic effect on microalgae. Among the different algal strains, blue green algal species Oscillatoria-Lyngbya mixed culture showed maximum efficiency in removing arsenic (64%) after 21 days of incubation and the same algal species could remove arsenic (III), but 60% after 21 days when incubated in 0.1 mg/l arsenic (III) containing medium. Maximum removal was observed at their exponential growth phase and also so sometime extended to the stationary phase.

Postoperative intraocular pressure spikes: the need to treat.

Raised intraocular pressure (IOP) still holds pride of place as the principal risk factor for developing glaucoma. The detrimental effects of chronically elevated IOP on the optic disc are well known. However, the clinical significance of acutely raised IOP is less certain. Transient acute elevations of intraocular pressure (IOP spikes) occur following many surgical and laser procedures. Cataract extraction, glaucoma surgery, pars plana vitrectomy with fluid air exchange, Nd-YAG capsulotomy, or peripheral iridotomy, and laser trabeculoplasty all have been reported to be associated with variable IOP spikes in the early postoperative period. There is considerable diversity of opinion concerning how these IOP spikes should best be managed. We have reviewed the nature and quality of the available experimental and clinical data relating to IOP spikes and we offer some broad, general guidelines for their clinical management.

Temperature effects in AgGaS2 nonlinear devices.

Refractive indices of AgGaS2 crystal are measured at different temperatures using the classical minimum deviation technique and are fitted in appropriate dispersion relations. The variation of pump laser wavelength for noncritical upconversion of signal at 10.6 microm with the change in crystal temperature has been verified using the above data. Temperature tunable infrared generation by noncritically phase-matched difference- frequency mixing has been predicted from 3 to 18 microm.

Efficient Generation of 200-230-nm Radiation in Beta Barium Borate by Noncollinear Sum-Frequency Mixing.

Tunable ultraviolet radiation in the 200-230-nm region has been generated with beta barium borate crystals by type I sum-frequency mixing of the second harmonic with the fundamental beam from a dye laser pumped by the second harmonic of the same Nd:YAG laser. A noncollinear phase-matching configuration has made it possible to realize conversion efficiency of 21% at 208.3 nm with input power densities as low as 28 MW/cm(2) for the fundamental and 2.4 MW/cm(2) for its second-harmonic radiation. The absorption characteristic of a standard DNA sample has been studied with the generated tunable ultraviolet source, revealing additional features compared with those obtained with a spectrophotometer.

Generation of tunable 187.9-196-nm radiation in beta-Ba(2)BO(4).

Tunable 187.9-196-nm vacuum-ultraviolet radiation was generated at room temperature in a beta barium borate crystal by sum-frequency mixing of Nd:YAG laser radiation and the second harmonic of a dye laser pumped by the second harmonic of the same Nd:YAG laser. By use of the advantageous noncollinear phase-matching configuration, a peak power of 1.3 kW was obtained at 194 nm with input power densities as low as 79MW/cm(2) for 1064-nm and 0.65MW/cm(2) for 237.3-nm radiation.

Efficient generation of mid-infrared radiation in an AgGa(x)In(1-x)Se(2) crystal.

Efficient generation of mid-infrared radiation by noncritically phase-matched second-harmonic generation is demonstrated in a mixed chalcopyrite crystal, AgGa(x)In(1-x)Se(2), and compared with that in an AgGaSe(2) crystal. Nonlinear coeff icients d(36) of AgGa(x)In(1-x)Se(2) and AgGaSe(2) crystals have also been derived.

Generation of tunable 187.9-196-nm radiation in beta-BaB(2)O(4): errata.

In Ref. 1, the first full sentence in the right-hand column of p. 1608 should read as: 'Although BBO is phase matchable down to 187 nm and shorter in this configuration without a very large (2-4 degrees ) change in theta (and hence in d(eff)), and B2 is also suitable to accommodate the phase matching, tunability below 187.9 nm becomes limited by the exponential increase in crystal absorption.'