In recent years a large effort has been made to protect electro-optic systems from various laser threats. One approach has been to use multilayer dielectric rejection filters as part of the system. This paper will discuss the effects of temperature humidity and UV irradiation on the optical performance of these filters. 2.
Ultrapure water systems in semiconductor plants consist of many components. The purpose is to explore the interactions of these units when they are placed in series and the effect of sequencing of these units and to establish conditions where these techniques can be used in combination. Two examples of these interactions are studied: UV interactions with membrane filters and UV interactions with the ion exchange units. An ultraviolet sterilization unit (Aquafine SL-1-TOC) generated radiation at both 185 nm and 254 nm wavelengths. The results indicate that the sequencing of UV and filter affects the TOC removal efficiency and that it is preferable to have a filter before UV. UV followed by ion exchange is an effective configuration for some impurities but can be undesirable for some contaminants and particles.
The paraflagellar bodies (PFBs) of isolated flagella of Euglena gracilis were investigated microspectrophotometrically using a visible- and infrared-light microscope with image analyzer and microspectrophotometer. Flagella with attached PFBs were separated from the cell bodies by a short exposure to near-UV light. Fluorescence-emission spectra (excitation at 365 nm) of single PFBs had maxima near 470 and 520 nm, indicating the presence of pterins and flavins. No fluorescence was associated with the flagella themselves. Pterin- and flavin-like fluorescence emission was also found in blue-fluorescing vesicles distributed throughout the entire cell body of Euglena. Their characterization by microfluorimetry was greatly aided by the use of chlorophyll-free mutants in which the signal-to-noise ratio was distinctly enhanced because of the lack of chlorophyll fluorescence. Our finding of flavin-like fluorescence associated with PFB strengthens similar earlier reports in the literature. The occurrence of pterin-like fluorescence in the PFB lends further support to our earlier proposal that pterins as well as flavins may function as photoreceptor pigments for near-UV and blue light.
Trends in optical thin film interference filters have created an increasing demand for the production of high tolerance designs for a wide number of applications. Much has been achieved by conventional filter designs but more novel structures such as distributed Bragg filters (DBR) and rugates are of increasing interest. Such filters require a highly controlled deposition technology as many of the constituent layers are only a few tens of angstroms thick. At this previous conference (Hamburg 1988) the potential of molecular beam epitaxy (MBE) was discussed with reference to the manufacture of such demanding structures. Although MBE equipment is usually associated with the epitaxial growth of IIIV semiconductor material, the application has lead to the the availability of a wide range of ultra high vacuum (UHV) equipment suitable for the deposition of optical thin films. To date, considerable development has taken place with the commissioning of e Vacuum Generators V9OH production GaAs machine, adapted for optical thin film fabrication. This unit has a single 4" substrate capacity or multiples of smaller dimensions. Film thickness uniformity of better than +1- 0.5% have been routinely achieved over the maximum substrate area using a single rotation. Materials under current study include ZnSe, ZnS, BaF2 and PbF2. These offer candidate low and high index pairs from the UV to the IR region of the spectra and have been shown to be compatible for incorporation in a single chamber environment with minimal cross contamination. In this paper, current results will be presented from this unique deposition facility with particular emphasis on the gains made in depositing highly complex multilayer structures. An assessment will be given as to the potential of molecular beam deposition (MBD) as a production technique.
The light emitted by halogen lamps induced mutations in Salmonella typhimurium and DNA damage in Escherichia coli, as shown by the hypersensitivity of DNA repair-deficient strains. The mutagenicity of halogen lamps was considerably higher than that of fluorescent light and of sunlight, even at much lower illuminance levels. Excision mechanisms and SOS functions were involved in repairing light-induced base-pair substitutions and frameshift errors in bacterial DNA. At variance with solar irradiation, which produces mutagenic effects over a wide UV spectrum, genotoxicity of halogen lamps was almost exclusively due to far-UV wavelengths transmissible through UV-R-250 and UV-R-280 interference filters. The main mutagenic component of fluorescent light was transmitted through the UV-R-280 filter. Far-UV wavelengths (254 nm) were almost 10(4)-fold more mutagenic than near-UV wavelengths (365 nm). All light sources exhibited some residual mutagenicity even following filtration through various cloths. On the other hand, appropriate glass or plastic covers consistently prevented mutagenic effects. This emphasizes the urgent need for a compulsory shielding of halogen and fluorescent lamps in order to prevent unnecessary exposures to genotoxic and potentially carcinogenic UV radiations.
Cells from patients with Cockayne syndrome (CS) are hypersensitive to UV-irradiation but have an apparently normal ability to remove pyrimidine dimers from the genome overall. We have measured the repair of pyrimidine dimers in defined DNA sequences in three normal and two CS cell strains. When compared to a nontranscribed locus, transcriptionally active genes were preferentially repaired in all three normal cell strains. There was no significant variation in levels of repair between various normal individuals or between two constitutively expressed genes, indicating that preferential repair may be a consistent feature of constitutively expressed genes in human cells. Neither CS strain, from independent complementation groups, was able to repair transcriptionally active DNA with a similar rate and to the same extent as normal cells, indicating that the genetic defect in CS lies in the pathway for repair of transcriptionally active DNA. These results have implications for understanding the pleiotropic clinical effects associated with disorders having defects in the repair of DNA damage. In particular, neurodegeneration appears to be associated with the loss of preferential repair of active genes and is not simply correlated with reduced levels of overall repair.
Four-channel multiplexers and four-wavelength bandpass filters based on elliptical Bragg reflectors (EBRs) are discussed. The channel spacing is 50 AA near 1.56 mu m. The EBRs are narrowband elliptical mirrors that can refocus light from an input waveguide to any one of a number of output waveguides. Spectrally, they perform similarly to Bragg reflectors. The devices were fabricated on silicon using silica-based waveguide technology. The elliptical gratings with 0.53- mu m periods were patterned using deep UV spatial frequency doubling photolithography. Multiplexers with single filtering and double filtering were demonstrated. With single filtering, the fiber-to-fiber insertion loss was 3.0+or-0.5 dB, and the crosstalk was -20 dB; with double filtering, the insertion loss was 4.0+or-0.5 dB, and the crosstalk was -30 dB. About 2 dB of this loss was due to coupling between the fibers and the waveguide. The additive loss associated with the EBR, including propagation, Bragg reflection, and coupling between input and output waveguides, was about 1 dB.