A new tunable optical filter has been developed which rejects a narrow wavelength interval ( 90%). This filter will be useful in optics, in spectroscopy, and for laser applications. The active element of the filter is a crystalline colloidal array of polystyrene spheres. The rejected wavelengths are Bragg diffracted from this ordered array. For a particular sphere concentration and scattering from a particular set of lattice planes, tunability can be achieved by the altering of the angle between the filter and incident light beam. Bragg diffraction and light rejection of these filters are monitored by transmission measurements. The utility of this filter for spectroscopic measurements is demonstrated for Raman spectroscopy. Raman measurements are shown for polypropylene, a highly scattering material with numerous low-frequency modes. The filter selectively attenuates the elastically scattered light and allows the low frequency peaks to be observed. Use of this wavelength rejection filter to reject the Rayleigh scattered light simplifies the instrumentation, decreases the cost, and increases the sensitivity of Raman spectral measurements. This filter also has the potential to replace dispersive elements such as gratings and prisms in a variety of spectroscopic and optical applications.
Abstract Exposure of ICR 2A frog cells to photoreactivating light (PRL) following irradiation with a fluorescent sun lamp (FSL) resulted in an enhancement in survival compared with FSL‐irradiated cells incubated in the dark. Hence, pyrimidine dimers played a role in the killing of cells exposed to the UV produced by this source. However, when the light was passed through a series of filters to remove increasing segments of the wavelength region shorter than 320 nm, the effect of the PRL progressively decreased, demonstrating that non‐dimer photoproducts play an increasingly important role in the killing of cells exposed to wavelengths approaching 320 nm. Cells were also exposed to 313 nm UV produced by a monochromator and it was found, once again, that the effectiveness of the PRL treatment depended on the filter the beam was passed through. These results indicate that for both FSL‐produced UV and 313 nm UV emitted by a monochromator, that the critical photoproducts induced within the cell depend on the filter used in conjunction with the UV source.
The viscoelastic behavior of epoxy acrylate prepolymer during ultraviolet (UV) curing was studied by the use of an oscillating plate rheometer. The dynamic viscosity increases rapidly after a certain period of irradiation; the UV curing process has the minimum exposure energy required to start polymerization. Beyond the minimum exposure energy, the double logarithmic plots of dynamic viscosity against the exposure energy lie close to a straight line with a constant slope irrespective of sample thickness. The minimum exposure energy remarkably increases with sample thickness; this shows that the degree of curing under irradiation varies in the direction perpendicular to the plate. Curing efficiency depends on the light intensity at a given depth of the film. When UV light is applied through a UV filter, the curing behavior is analyzed by a single exponential decay of light with depth. The theoretical curve of dynamic viscosity shows a good agreement with the experimental results. On the other hand, when UV light from the UV lamp whose output spectrum is continuous, is applied, the initiation of polymerization can be explained by a combination of energy absorption at different wavelengths.
The design and operating characteristics of the prototype imaging microchannel plate (MCP) detector for the Extreme Ultraviolet Explorer (EUVE) Satellite  are discussed. We show that this detector has achieved high position resolution performance (> 512×512 pixels) and has low (< 1%) image distortion. In addition, the channel plate scheme used has tight pulse height distributions (< 40% FWHM) for UV radiation and displays low (<.2 cnt cm-2 sec-1) dark background counting rates. We also describe work that has been done on EUV filters in relation to the envisaged filter and photocathode complement.
A TPC-type RICH-counter with a 200 × 200 mm 2 quartz window and a 1.27 mm wire pitch MWPC has been tested in a 10 GeV/c π - beam. The MWPC is equipped with optical screens (called "cloisons") between the anode wires, with the purpose of absorbing the secondary UV-photons emitted from the charge avalanches around the wires. The test results show that the cloisons effectively suppress the noise caused by the photon reemission, without affecting the detection efficiency for single photoelectrons in the MWPC.
The new process was developed to offer a superior method of forming a resist pattern on a copper-clad laminate acting as plating and etch resist. The advantages over existing methods include superior resolution, increased automation, improved reliability, and lower applied cost. The process is unique, combining the precise coating of the blank board with UV coating resist, exposing the resist through a phototool held precisely off-contact and the development of the formed latent image with an aqueous solution. The processing is carried out using fully automated equipment without any manual handling of either laminates or phototool.
Nondividing (arrested) populations of primary human fibroblasts from normal individuals exposed to an initial dose (1.5 or 3 J· m ) of far-UV (254 nm) radiation and then incubated in medium containing low (0.5%) serum develop enhanced resistance to inactivation of cloning efficiency by a second (challenge) dose of UV. The resistance develops within 2-4 days, after which there is a decline. Resistance develops to a higher degree and more rapidly (1-2 days) in cells derived from patients with the variant form of xeroderma pigmentosum. Excision-deficient cells from xeroderma pigmentosum complementation group A individuals also develop UV resistance after a lower (0.2 J· m ) exposure to UV. Enhanced UV resistance does not develop in UV-irradiated cell populations incubated with the protein synthesis inhibitor cycloheximide (5 μ M). These observations are consistent with the interpretation that exposure of human fibroblasts to low doses of UV induces synthesis of a protein involved in a metabolic pathway that transiently enhances the capacity of cells to repair potentially lethal damage resulting from a subsequent dose of UV.
The mRNAs encoding two enzymes of phenylpropanoid metabolism, phenylalanine ammonia-lyase (PAL; EC 126.96.36.199) and 4-coumarate:CoA ligase (4CL; EC 188.8.131.52), were induced in cultured parsley cells (Petroselinum hortense) either by irradiation with UV light or by treatment with elicitor, a cell-wall fraction of the fungus Phytophthora megasperma f. sp. glycinea. Two-dimensional gel electrophoresis of the encoded PAL and 4CL proteins revealed that the mRNAs induced by either treatment were very similar if not identical. RNA blot hybridization with cDNAs complementary to these mRNAs was used to measure changes in the mRNA amounts at various times after either treatment. Total cellular PAL and 4CL mRNA amounts increased coordinately after UV irradiation to a maximum at 7 hr and then decreased to uninduced levels by 30 hr with the same kinetics as observed previously for the changes in the translational activities. Treatment with the fungal elicitor also caused coordinated, but more rapid, changes in PAL and 4CL mRNA translational activities, with a sharp peak occurring 3 hr after the addition of elicitor. Corresponding changes in mRNA amounts were observed only for 4CL, whereas the amount of PAL mRNA continued to increase at least up to 20 hr after elicitor addition. Our results suggest that parsley cells respond to UV irradiation or addition of fungal elicitor by increased rates of transcription of genes involved in the synthesis of compounds related to UV or disease resistance, respectively.