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UV Range (uv + range)
Selected AbstractsTetragonal Ba2MgGe2O7 , a novel multifunctional optical crystal with numerous manifestations of nonlinear-laser effects: almost sesqui-octave Stokes and anti-Stokes combs and cascaded ,(3),,(2) lasing with involved second and third harmonic generationLASER PHYSICS LETTERS, Issue 12 2008A.A. Kaminskii Abstract Melilite-type Ba2MgGe2O7 was found to be an attractive, simultaneously ,(2) - and ,(3) -active nonlinear optical crystal. Under one-micron picosecond pumping we observed several manifestations of nonlinear interactions, namely almost sesqui-octave Stokes and anti-Stokes lasing combs, collinear and "Cherenkov"-type SHG, THG, SFG, and cascaded selfconversion ,(3),,(2) generation in the visible and UV range. All recorded lasing components were identified and attributed to a single SRS-promoting vibration mode ,SRS = 771.5 cm,1. A short review of melilite-type compounds is given. (© 2008 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Structure and Properties of CdS/Regenerated Cellulose NanocompositesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 10 2005Dong Ruan Abstract Summary: Novel inorganic-organic hybrid materials composed of cadmium sulfide (CdS) semiconducting nanocrystals and regenerated cellulose (RC) were prepared by using in situ synthesizing method. Cellulose was dissolved in a 6 wt.-% NaOH/4 wt.-% urea/thiourea aqueous solution at low temperature followed by addition of cadmium chloride (CdCl2), resulting that the CdS nanocrystals were successfully grown in situ in the cellulose solution. Nanocomposite films containing homogeneous CdS nanoparticles were obtained by casting the resulting solution. Their structure and optical properties were characterized by X-ray photoelectron spectroscopy, wide-angle X-ray diffraction, thermogravimetry analysis, dynamic mechanical analysis, atomic force microscopy, transmittance electronic microscope, UV-vis spectroscopy, and photoluminescence spectroscopy. The experimental results confirmed that the CdS nanocrystalline existed in the composite films, and cellulose matrix provided a confined medium for CdS particle growth in uniform size. The CdS/RC composites showed narrow emission in photoluminescence spectra, and their optical absorbance in the UV range was higher than that of the cellulose film without CdS. This work provided a simple method to prepare cellulose functional materials in NaOH/urea aqueous solution. Photoluminescence of CdS/RC nanocomposites and TEM image of CdS nanocrystals dispersed in RC matrix. [source] Xanthopterin in the Oriental Hornet (Vespa orientalis): Light Absorbance Is Increased with Maturation of Yellow Pigment GranulesPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2009Marian Plotkin The Oriental hornet bears both brown and yellow colors on its cuticle. The brown component is contributed by the pigment melanin, which is dispersed in the brown cuticle and provides protection against insolation, while the yellow-colored part contains within pockets in the cuticle granules possessing a yellow pigment. These yellow granules (YG) are formed about 2 days prior to eclosion of the imago, and their production continues for about 3 days posteclosion. Xanthopterin is the main component of the granule and lends it its yellow color. Xanthopterin produces a characteristic excitation/emission maximum at 386/456 nm. Characterization by use of mass spectrometry showed the compound to have a molecular ion of 179, as expected from xanthopterin. Spectroscopic examination of the absorption of an entire stripe of yellow cuticle in the course of its metamorphosis revealed that the absorption steadily increases throughout the process to a maximal level of absorption about 3 days posteclosion. In the absence of the YG, the cuticle is permeable to the passage of all wavelengths within the visible range and to the UV range (290,750 nm) in all age groups of hornets. The newly ecloded hornets depart the nest to engage in activities requiring exposure to insolation only as the process of granule formation terminates, namely, when the layer of YG in the cuticle suffices to absorb all the harmful UV radiation. [source] Structural Effects on the Electronic Absorption Properties of 5,6-Dihydroxyindole Oligomers: The Potential of an Integrated Experimental and DFT Approach to Model Eumelanin Optical Properties,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2008Marco D'Ischia Elucidation of the relationships between structural features and UV,visible absorption properties of 5,6-dihydroxyindole oligomers is an essential step towards an understanding of the unique optical properties of eumelanins. Herein, we report the first combined experimental and density functional theory (DFT) investigation of the 5,6-dihydroxyindole oligomers so far isolated. 2,2,-Biindolyl 2 and the 2,4,-biindolyl 3 absorb at longer wavelengths relative to 2,7,-biindolyl 4 and their spectra were well predicted by DFT analysis. The absorption bands of 2,4,:2,,4,,- and 2,4,:2,,7,,-triindolyls 5 and 6 also fall at different wavelengths and can be interpreted by DFT simulations as being due to a combination of two main separate transitions. Tetramer 7, in which two 2,4,-biindolyl units are linked through a 2,3,-connection, exhibits a broad chromophore extending over the entire UV range without well defined absorption maxima. Within the dimer,tetramer range examined, three key points emerge: (1) an increase in oligomer chain length does not result in any regular and predictable bathochromic shift; (2) a marked broadening of the absorption bands occurs when going from the monomer to the tetramer structure; and (3) the mode of coupling of the indole units is a crucial, hitherto unrecognized, structural parameter affecting the electronic absorption properties of 5,6-dihydroxyindole oligomers. It is concluded that use of experimentally characterized oligomeric scaffolds as a basis for DFT calculations is a most promising approach to building reliable structural models for studies of eumelanins optical properties. [source] Antisite defect-related luminescence in (LaLu)3Lu2Ga3O12 garnet single crystalsPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 9 2007Yu. Zorenko Abstract Intrinsic luminescence of the undoped (LaLu)3Lu2Ga3O12 garnet (LLGG) single crystals with high concentration of LuLa antisite defects (AD) has been studied for the first time under excitation by 1.5 ns pulse X-ray radiation. It has been found that the host luminescence of LLGG crystal consists of two emission bands in the UV range. The band peaked at 3.80 eV at 77 K has been related to the luminescence of localized excitons (LE) perturbed by the presence of AD whereas the band peaked at 3.37 eV has been related to the radiative annihilation of bound-state excitons localized directly at LuLa AD. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Commercial applications of porous Si: optical filters and componentsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007V. Kochergin Abstract It is shown that porous Silicon in various geometries and morphologies can be used for novel optical elements by combining theoretical insights with suitable porous structures and some pre- and post-processing of the Silicon. The paper restricts itself to light propagation in the pore direction. Theoretical and experimental results will be presented for the following novel optical elements: environmentally stable optical components from mesoporous Silicon, long wave pass filters, macroporous Silicon UV Filters, and polarization components for the UV range. Either new components are presented, mostly with first experimental results, or the state-of-the art for previously discussed elements is considerably improved upon. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Melanin biosynthesis by Frankia strain CeI5PHYSIOLOGIA PLANTARUM, Issue 2 2007Wenlin Yuan Many Frankia strains are pigmented and presumed to produce melanin. However, melanin biosynthesis has yet to be rigorously characterized in Frankia. This study was initiated to determine whether or not Frankia strain CeI5 produced melanin and to identify the biochemical pathway of pigment production. Frankia strain CeI5 first produced a dark pigment in mycelial and other tissue and then in the liquid culture medium when grown in a defined medium containing l -tyrosine. The pigment resisted solvents, lightened when subjected to the action of oxidants, as well as reductants, and produced a flocculent brown precipitate with FeCl3. Spectroscopic characteristics of the extracted pigment were those of melanin. When subjected to gradual dilution, the absorbance decreased unevenly, occurring in the near red range first, then in the visible range, and lastly in the UV range. This observation might resolve the question of why quite different descriptions of melanin UV,visible light absorption spectra exist in the literature. The tyrosinase cofactor copper greatly enhanced melanin biosynthesis at 5.3 × 10,6 M, while 1 × 10,8 M 3,4-dihydroxy- l -phenylalanine hastened pigmentation. The copper-chelating agent KCN and the tyrosinase inhibitor tropolone decreased melanin production at the same concentration of 1 × 10,5 M. This evidence suggests that Frankia strain CeI5 produces melanin via the Raper and Mason pathway. [source] Microspectrophotometric Analysis of Intact Chromatophores of the Japanese Medaka, Oryzias latipesPIGMENT CELL & MELANOMA RESEARCH, Issue 2 2000TINA N. ARMSTRONG To investigate the possible photoprotective role of chromatophores in fish, the absorbances of four types of intact chromatophores in adult and larval Japanese medaka were analyzed using microspectrophotometric techniques. The absorbance spectrum of each chromatophore class was obtained from 300 to 550 nm. The absorbance spectra of intact leucophores, melanophores and xanthophores were very similar to the published absorbance spectra of the isolated pure pigments contained in each chromatophore type, pteridines, melanin and carotenoids or pteridines, respectively. Based on these absorbance spectra, leucophores and melanophores should provide the most ultraviolet (UV) photoprotection to fish since the compounds they contain, pteridines and melanin, correspondingly, have strong absorbances in the UV region of the spectrum. Xanthophores containing carotenoids are not likely to provide much protection to fish from UV-induced damage since carotenoids have low absorbances in the UV range. Xanthophores containing colored pteridines, however, may provide somewhat greater UV protection to fish, since pteridines absorb more light than carotenoids in the UV portion of the spectrum. The relative frequency, coverage and thickness of these two types of xanthophores should determine how much protection xanthophores as a chromatophore type would provide against UV-induced damage. [source] Effect of Substrate Temperature and RF Biasing on the Optical Properties of Titania-Like Thin Films Obtained by Plasma Enhanced Chemical Vapor DepositionPLASMA PROCESSES AND POLYMERS, Issue S1 2009Axel Sonnenfeld Abstract A low pressure radio frequency (RF) discharge (200,W) was operated in argon/oxygen with small admixtures of titanium(IV)isopropoxide (TTIP). By regulating the cooling temperature of the RF driven electrode, the influence of the substrate temperature and of the ion bombardment caused by the negative DC self-bias of the RF electrode was investigated comparatively. Thin titania-like films were obtained and characterized with respect to their cut-off wavelength and their spectral absorption coefficient in the UV range. Accordingly, the cut-off wavelength was found to be higher for films obtained on the DC-self-biased electrode. Here, its value appears independent of the substrate temperature and attained successively its maximum at 340,nm with deposition time. Furthermore, the absorption coefficients of films deposited on the DC self-biased electrode are well superior to those obtained on the grounded substrate holder. [source] Ultraviolet reflectance and cryptic sexual dichromatism in the ocellated lizard, Lacerta (Timon) lepida (Squamata: Lacertidae)BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2009ENRIQUE FONT Ultraviolet (UV) colorations have garnered extensive theoretical and empirical treatment in recent years, although the majority of studies have concerned themselves with avian taxa. However, many lizards have acute visual systems with retinal photoreceptors that are sensitive to UV wavelengths, and also display UV-reflecting colour patches. In the present study, we used UV photography and full-spectrum reflectance spectrophotometry to describe intra- and intersexual colour variation in adult ocellated lizards Lacerta (Timon) lepida and to obtain evidence of UV-based ornamentation. We also investigated whether any colour traits correlate with morphological traits potentially related to individual quality. The results obtained show that the prominent eyespots and blue outer ventral scales (OVS) that ocellated lizards have on their flanks reflect strongly in the UV range and are best described as UV/blue in coloration. The eyespots of males are larger and cover a larger surface area than those of females. However, these differences can be entirely accounted for by sex differences in body size, with males being generally larger than females. We also found differences in the shape of reflectance curves from males and females, with the eyespots and blue OVS of males being more UV-shifted than those of females. Other body regions have extremely low UV reflectance and are not sexually dichromatic. Eyespot size and the total surface area covered by eyespots increases with body size in males but not in females, suggesting that they may be signalling an intrinsic individual characteristic such as body size or male fighting ability. We also discuss the alternative and non-exclusive hypothesis that eyespots may function in lizards of both sexes as protective markings against predators. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 97, 766,780. [source] UV/Vis to NIR Photoconduction in Cyclopalladated ComplexesCHEMISTRY - AN ASIAN JOURNAL, Issue 7 2009Nicolas Godbert Abstract Funky discotics: Photoconductivity is measured in newly synthesized cyclopalladated metallomesogens exhibiting hexagonal columnar mesophases at room temperature. The tuning of the HOMO/LUMO energy levels by modification of the chain/core linkage (ester 1 vs ether 2) makes compound 2 photoconductive across the whole UV/Vis/NIR range. The incorporation of a rigid core, formed by a cyclopalladated azobenzene fragment bonded to an ancillary Schiff base ligand, into molecules with 12 or 11 peripheral alkyl chains has been successfully achieved. These new complexes, 1 and 2, respectively, are columnar liquid crystals between room temperature and about 50,°C. Both cyclometallated and ancillary ligands have been polyalkylated through either aryl ester (electron-withdrawing group) or aryl ether (electron-releasing group) linkages, in order to tune the HOMO/LUMO energy levels. The photoconductive properties of 1 and 2 have been studied as a function of their absorption properties before and after annealing, from the UV/Vis to NIR region. Compared with the reference compounds, tris-alkynyl benzene discotics, these new materials gave similar performances (,/I,8×10,13,S,cm,W,1 with E=10,V,,m,1 at ,=370,nm). Moreover, complex 2 shows a normalized photoconductivity ,/I=8.5×10,13,S,cm,W,1 at ,=760,nm. Organic photoconductors in such a high wavelength spectral range are not common and are usually assembled by mixing dyes with organic semiconductors. [source] | ||||||||||||||||