We report results from the spectral analysis of pointed ROSAT PSPC observations of six PG quasars and the weak-bump quasar PHL 1657. Disregarding other frequency bands, the PSPC data are represented best by simple power-law source spectra (dN=dE / EΓ) with a slope Γ = 2:5 0:4 and do not show evidence for a more complex structure. However, within the limits given by statistics and systematical e...

An extensive grid of synthetic midand far-ultraviolet spectra for accretion disks in cataclysmic variables has been presented by Wade and Hubeny (1998). In those models, the disk was assumed to be in steady-state, that is Teff(r) is specified completely by the mass MWD and radius RWD of the accreting white dwarf star and the mass transfer rate Ṁ which is constant throughout the disk. In these m...

copper (ii) phthalocyanine and 2,9,16,23 tetrakis nitro copper (ii) phthalocyaninehas been synthesized respectively from phthalonitrile and 4-nitro phthalonitrile under solvent-free condition using two different catalystsovernanodimensionalzeolites. 4-nitro phthalonitrile synthesized from phthalimide in three steps. the newly prepared compounds have been characterized by ir, uv-vis, 1hnmr and m...

Raman spectra of germanosilicate core fibers before and after UV irradiation were investigated. Significant changes of the Raman spectra after irradiation indicate transformation of the glass structure. A possible interpretation of the observed changes is proposed.

UV–Vis absorption spectra of one-electron reduction products and MLCT excited states of [ReCl(CO)3(N,N)] (N,N = 2,20-bipyridine, bpy; 1,10-phenanthroline, phen) have been measured by low-temperature spectroelectrochemistry and UV–Vis transient absorption spectroscopy, respectively, and assigned by open-shell TD-DFT calculations. The characters of the electronic transitions are visualized and an...

We have obtained low-dispersion spectra of NGC 3227 with the Space Telescope Imaging Spectrograph (STIS) to study the intrinsic UV absorption and the reddening of the nucleus in this Seyfert 1 galaxy. The UV spectra show a wealth of absorption lines at the systemic redshift that span a wide range in ionization state (Mg I to N V). The equivalent widths of the lines are consistent with our earli...

In this paper we discuss the design, implementation and performance of two neural network algorithms, one for ozone concentration profile, and the second for tropospheric ozone column retrieval from ESA-Envisat SCIAMACHY Level 1b data. The performances of the two algorithms were checked through tests against ozone sondes measurements. Both algorithms make use of visible radiation whose role has...

The circular dichroism (CD) spectrum of polyproline I1 (PPII) has heretofore been moderately well calculated from exciton theory only at the expense of assuming unreasonable chain conformations and accepting a conservative spectrum in the 180250-nm region (which is not observed). We have incorporated far uv transitions in the polarisability approximation and, together with the r2r* transition, ...

zno nanowires with a diameter of 70 nm and nanorods with a diameter in the range of 100-150 nm and two micrometer in length were grown on glass substrates by resistive evaporation method and applying a two step oxidation process at low temperatures, without using any catalyst, template or buffer layer. xrd pattern of these nanostructures indicated a good crystallinity property with wurtzite hex...

The effects of ultraviolet (UV) radiation on ionizing radiation biodosimetry were studied in human tooth enamel samples using the technique of electron paramagnetic resonance (EPR) in X-band. For samples in the form of grains, UV-specific EPR spectra were spectrally distinct from those produced by exposure to gamma radiation. From larger enamel samples, the UV penetration depth was determined t...