[en] Full text. Synchrotron radiation has been used as light source in the UV and VUV region for the study of many biological systems. In the time domain, measurements are made that allow the observation of dynamics and kinetics of biomolecules like proteins and peptides, using the fluorescent properties of either intrinsic or extrinsic probes. Optical activity of groups inside biomolecules allows the use of circular dichroism techniques to generate structural information and to follow processes like protein folding. Confocal scanning of synchrotron light generates microscopy resolution below 100 nm, allowing the creation of high quality three dimensional images of biological samples, and the collection of fluorescence originated from microvolumes inside the samples. We propose a station at LNLS for these three techniques: time-resolved fluorescence, circular dischroism and confocal microscopy, using UV and VUV light. (author)

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No abstract available

[en] In order to study the properties and effects of high Galactic latitude dust, we present an analysis of 373,303 galaxies selected from the Galaxy Evolution Explorer All-Sky Survey and Wide-field Infrared Explorer All-Sky Data Release. By examining the variation in aggregate ultraviolet colors and number density of these galaxies, we measure the extinction curve at high latitude. We additionally consider a population of spectroscopically selected galaxies from the Sloan Digital Sky Survey to measure extinction in the optical. We find that dust at high latitude is neither quantitatively nor qualitatively consistent with standard reddening laws. Extinction in the FUV and NUV is ∼10% and ∼35% higher than expected, with significant variation across the sky. We find that no single R_V parameter fits both the optical and ultraviolet extinction at high latitude, and that while both show detectable variation across the sky, these variations are not related. We propose that the overall trends we detect likely stem from an increase in very small silicate grains in the interstellar medium.

[en] Photodestruction of nucleotides by vacuum UV (lambda < 200 nm) and near UV radiation in thin films has been studied: the products were analyzed by thin-layer chromatography. Vacuum UV photolysis leads to the rupture of the N-glycosidic bond with liberation of bases, the quantum yield of the process being about 2 x 10^-4 for guanosine-5'-monophosphate. No bases have been found among the products of near UV photolysis. Vacuum UV irradiation of aqueous solutions of adenosine-5'-monophosphate and guanosine-5'-monophosphate produces, along with bases, some other fluorescent substances. The identity of photoproducts of vacuum UV photolysis with those of γ-radiolysis is established. The mechanism of photochemical conversion is discussed. (author)

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[en] The evidence for the cellular and molecular effects of exposure to ultraviolet radiation (UVR) has been reviewed. Human exposure to UVR has been associated with the development of malignant skin tumours and this review concentrates on effects relevant to this process, with particular emphasis on wavelength dependence. There is evidence that UVR acts as a complete carcinogen influencing all three major stages of skin carcinogenesis, initiation, promotion and progression. The role of UVR as an initiating agent is probably the best established and results from photochemical modification of the genetic material DNA. Most damage is efficiently and accurately repaired, but if the damage burden is too great some may become fixed in the form of permanent mutations. Mutations which affect specific regulatory genes may be initiating events, and those which have been associated with UVR-induced skin cancer include the ras proto-oncogenes and the p53 tumour suppressor gene. The tumour promoting action of UVR probably results from its action as a specific cellular stressor which elicits a complex cellular response, presumably to ameliorate the effects of the stress. Exposure to UVR may influence tumour progression through a number of mechanisms, including further photochemical damage to DNA, induction of cellular responses which may increase genetic instability, and widespread changes in components of the immune system present in the skin. (author)

[en] The paper describes the development of an imaging photon counting detector using microchannel plates and a wedge-and-strip readout system. Several detectors of this type have already been fabricated ranging from open face detectors for the extreme ultraviolet to sealed tubes sensitive to far ultraviolet radiation. Recently, a similar sensor was developed to operate in the visible (400-800 nm) spectral region using a S20 photocathode. This device is compact and its construction is ruggedized and suitable for airborne and spaceborne applications. The results of evaluations of the visible sensor are described in terms of their position resolution, gain, pulse height, quantum efficiency, nonlinearity and dark count characteristics. Imaging applications of this sensor with a Fabry-Perot spectrometer are presented. 5 references

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[en] The possible radiative decay of massive neutrinos is discussed. Recent experimental observations on diffuse cosmic radiation in the Far Ultraviolet and Extreme Ultraviolet are summarized. (author). 10 refs., 1 fig