UV Light Transmission Research Articles

Ultraviolet-blocking Greenhouse Plastic Films for Management of Insect Pests

Most greenhouse polyethylene plastic films contain ultraviolet (UV) light-blocking components added to prolong the life of the material and maintain high levels of transmission of photosynthetically active radiation (PAR). Standard greenhouse films generally block the majority of UV light transmission at wavelengths below 360 nm; however, some materials block a greater portion of the UV light spectrum by blocking transmission below 380 nm (Antignus et al., 1996; Costa and Robb, 1999). Previous studies conducted in completely enclosed greenhouses reported reductions in whitefly, aphid, and thrips infestations in vegetable crops grown under <380-nm blocking plastic compared to those grown under <360-nm blocking plastics (Antignus et al., 1996, 2001). The presumed method of insect population reduction is the alteration of normal UV wavelength patterns used by insects during orientation and flight (Antignus, 2000; Antignus et al., 1996, 2001). When silverleaf whitefly (Bemisia argentifolii Bellows and Perring), greenhouse whitefly (Trialeurodes vaporariorum Westwood), or western flower thrips [Frankliniella occidentalis (Pergande)] were released in small, completely enclosed tunnels, sticky trap catches were lower under <380-nm plastics than <360-nm plastics, indicating a preference to enter tunnels that transmitted more UV light (Costa and Robb 1999; Costa et al., 2002). Greenhouse structures in Southern California and other moderate climates often have sides or roof vents that open to allow natural ventilation and cooling. A previous study on flowering crops conducted in small (4 × 8 × 3 m) open-sided hoop-houses found significantly with six to eight yellow sticky traps per treatment (each 10 ×18 cm; Seabright, Emeryville, Calif.) adjusted to plant canopy height. Traps were replaced and the number of insects recorded weekly. In addition, three leaves from five plants per bay (30–40 plants per treatment) were randomly sampled weekly and the total number of insects present was recorded. Greenhouse whitefly and western flower thrips were the dominant insect species observed in these trials. Over the course of the three replicates, the mean number of whiteflies and thrips trapped on sticky cards under the <380-nm plastic-covered houses was not significantly different from the number trapped under the standard <360-nm plastic (whiteflies: F = 0.64, df = 1374, P = 0.426; thrips: F = 2.14, df = 1374, P < 0.145). Similarly, there was no significant difference in the mean numbers of whiteflies (F = 0.08 = df = 1374, P = 0.777) or thrips (F < 0.01, df = 1374, P < 0.963) counted on plants under the two types of plastics. However, the mean number of leafminers (Liriomyza sp.) trapped on sticky cards and counted on plants under the <380nm plastic-covered houses was significantly lower than the number trapped under <360-nm plastic (cards: F = 26.81, df = 1374, P < 0.001; plants: F = 14.35, df = 1374, P < 0.001). Aphid populations were too low to make meaningful statistical comparisons. In a previous study using smaller opensided greenhouses, we found that populations of thrips were lower under <380-nm plastics compared to <360-nm (Costa et al., 2002). However, no effects on thrips populations were observed in this study. Thus, it appears that increasing the overall covered area did not increase the effectiveness of the <380-nm plastic in reducing insect pests. In the open-sided greenhouses the presence of some unfiltered light and the passive movement of insects into the greenhouses by wind may have reduced effects of the UV-blocking materials. The benefits to integrating the use of high-UV-blocking plastics into an existing pest management program will vary with the type of greenhouse structures used and types of insect and disease pressures commonly encountered. The effect of the high UV-blocking material on insects has been greatest when used in completely closed structures with little or no unfiltered light entering the system.

Influence of sandwinds on the durability of polyethylene greenhouse aged under sub-saharan climatic conditions

Sandwinds have been simulated with an apparatus developed in our laboratory. Infra red and UV visible spectroscopies, contact angle and interferential microscopy investigations have been performed on untreated polyethylene film sample and on samples submitted at 40 ©C to a simulated sandwind for times up to 4 hours. The surface roughness is modified, leading to drastic decrease of the ultra-violet visible light transmission. This phenomenon is due to the presence of small sand particles inlaid in the sample surface and due to surface erosion. In the time range of our experiments, no chemical action due to the sandwind is observed.

Field Trials Measuring the Effects of Ultraviolet-Absorbing Greenhouse Plastic Films on Insect Populations

Field studies were conducted to compare insect population levels in greenhouse crops covered with plastics that block the transmission of UV light in two wavelength ranges. Crops grown in greenhouses under a plastic that blocked UV light at wavelengths of 380 nm and below had lower numbers of aphids and thrips compared with a plastic that blocked UV light at wavelengths of 360 nm and below. This is consistent with the results found for thrips in previous studies using small, completely enclosed tunnels with no plant material. The effects were not as dramatic in the commercial greenhouses, perhaps due to unfiltered light entering through the open sides of those greenhouses. There was no reduction in greenhouse whitefly, Trialeurodes vaporariorum Westwood, populations under the <380 UV-absorbing plastic compared to <360 nm UV-absorbing plastic in these field trials. This is inconsistent with results found in small, completely enclosed tunnels, where sticky traps caught a significantly higher proportion (95 +/- 2%) of released greenhouse whiteflies inside tunnels covered with <360 nm absorbing plastic compared with the <380 nm absorbing plastic. The results of these studies suggest that the type of greenhouse plastic used in a structure can affect population levels of some insect species, and may be useful tools in developing integrated pest management programs for insect management. The design of the greenhouse and amount of unfiltered light that enters the system appear to be important factors in determining the level of effect.

Increased Persistence of Beauveria bassiana Spore Viability Under High Ultraviolet-blocking Greenhouse Plastic

A field study was conducted to assess the effect of various commercially available polyethylene plastic greenhouse coverings on the persistence of viable spores of the microbial insecticide Beauveria bassiana. Selected coverings blocked the transmission of UV light with wavelengths of 360 nm and below or 380 nm and below. Two coverings also contained an infrared blocking component. A commercial formulation of B. bassiana was applied for 3 consecutive weeks to plants growing in the plastic covered hoop houses. The percentage of viable spores was calculated up to 13 days after the final application. The persistence of viable B. bassiana spores was significantly longer under the plastic that blocked a greater portion of the UV spectrum (&lt;380 nm) than the plastics that only blocked UV wavelengths below 360 nm. One week after application, percentage of spore germination was at least twice as high under the &lt;380 nm blocking plastic compared to &lt;360 nm blocking plastics.

Transmittance properties of flurandrenolide tape for psoriasis: helpful adjunct to phototherapy.

Flurandrenolide tape is a valuable agent in the treatment of lichen simplex chronicus and in psoriasis. The corticosteroid is helpful for reducing the symptoms and induration of the lichen simplex chronicus lesion, and occlusion of the lesion with the tape reduces the patient's opportunity to rub and scratch the affected area. The purpose of this study was to determine to what extent flurandrenolide tape may block ultraviolet (UV) light and interfere with phototherapy of psoriasis. Flurandrenolide tape was applied to quartz spectroscopy cuvettes, and the absorption spectrum was determined using a Beckman DU-600 spectrophotometer. The effect of the tape on UV light transmission was also determined using our UVA-UVB office phototherapy unit. Flurandrenolide tape has considerable UV absorption in the UVC range with less absorption in the UVB and UVA range. The transmittance is greater (less absorption) with longer wavelengths. There was greater UV absorption in the UVB range than in the UVA range. Although flurandrenolide tape may be left in place during PUVA therapy, adjustment of UV dose or removal of the tape is probably needed during UVB phototherapy.

Factors Influencing Ultraviolet Disinfection Performance Part I: Light Penetration to Wastewater Particles

A technique is described for measuring UV absorbance and internal scattering characteristics of wastewater solids. Wastewater solids developed as part of trickling filter and activated‐sludge processes were observed to be strictly absorbing, with light attenuation following the Beer–Lambert law. Absorbance of solids ranged from 3300 to 569 000 cm−1 Although absorbance was found to vary with treatment process type, even the lowest measured value is sufficient to block transmission of UV light to solid material. It is unlikely that wastewater treatment processes can be tailored to allow light transmission to solid material. Extremely high absorbance observed indicates that UV light can only penetrate particles because of high particle porosity, not by transmission through solid material. Also, regions exist within some particles that completely block applied UV light. Longer wavelength UV light was not observed to penetrate particles better than lower wavelength UV light.

Natural UV-Screening Mechanisms of Norway Spruce (Picea abies [L.] Karst.) Needles.

Ultraviolet-light screening potential of Norway spruce (Picea abies [L.] Karst.) needles was investigated by UV-spectroscopic, microscopic, fluorescence spectroscopic techniques as well as by HPLC, mass spectrometry and NMR spectroscopy. Results showed four potential barriers of UV screening by Norway spruce needles: (1) UV-light screening via reflectance of UV/violet light by epidermis, (2) UV-light screening via reduction of transmission of UV light by special anatomical arrangement of the epidermal cells containing the UV-screening allomelanins as well as by the light-reflecting hyaline hypodermal cells, (3) conversion of UV light by epidermis into photosynthetically active radiation (PAR; blue and red spectral bands) via fluorescence and (4) UV-light screening by absorption of UV light by UV-screening substances contained in the epidermis, whereby the latter was found to be the most important UV-screening mechanism. Staining of needle cross sections with Naturstoffreagenz A showed the localization of bound flavonoids and its derivatives in the cell walls of the outer epidermal cell layer as revealed by confocal laser scanning microscopy. By fluorescence spectroscopy and confocal laser scanning microscopy, the conversion of UVA light into PAR in the epidermis was related to various UV-screening substances contained in the epidermis. The methanol-soluble UV-absorbing substances were found to create novel UV-screening barrier zones: UVC, >200-253 nm; UVC/UVB, >253-300/303 nm; and UVB/UVA, >300-362/368 nm in epidermis as well as in mesophyll (±vascular bundles) tissues, suggesting the protective functions of epidermis for the underlying mesophyll as well as of mesophyll for the underlying vascular bundles. The following sequence of efficiency of UV-screening barrier zones of the methanol-soluble extracts of the needle epidermis and mesophyll (± vascular bundles) for various UV-spectral bands was detected: UVC screening at less than 265 nm > UVC screening at 265-280 nm > UVB screening at 280–320 nm > UVA screening at 320–400 nm, whereby the UV screening at 280-320 nm was suggested as the most relevant barrier against enhanced UVB radiation. A blend of various UV-screening substances occurred in the methanol-soluble fractions of needle epidermis, whereby p-hydroxybenzoic acid 4-O-β-D-glucopyranoside, picein, (+)-catechin, p-hydroxyacetophenone, benzoic acid and astragalin were identified as UVC/UVB-screening substances; picein, (+)-catechin, astringin, p-hydroxyacetophenone and astragalin(s) as UVB-screening substances and astragalin(s) as UVA/B-screening substances. Alkaline hydrolysis of methanol-insoluble epidermal cell wall fractions released p-coumaric acid, ferulic acid and as-tragalin(s) as major UVB-screening substances. Loss of vitality of Norway spruce trees (forest decline disease) led to a significant reduction of UVB (315 nm)-screening ability of methanol-soluble fractions from epidermis, mesophyll (±vascular bundles) and whole needles. The HPLC analysis showed that the loss of vitality is due to a reduction in accumulation of UVB-absorbing substances, mainly picein, (+)-catechin, isorhapontin and astragalin(s) in the epidermis of needles from the second needle year in accordance with the detected loss of UVB-screening ability. It is concluded that the natural UV-screening mechanisms of Norway spruce needles are highly complex but mainly actively mediated by the ability of methanol-soluble UV-absorbing substances to form variable UVB-AJVA-screening barrier zones and passively by the ability of epidermal cell wall-bound UV-screening substances to screen UV light, whereby in the epidermis a conversion of excess UV light into PAR takes place.

Optical Filter for Fabricating Self-Aligned Amorphous Si TFTS

AbstractSelf-aligned structures for bottom-gate amorphous Si TFTs provide a number of advantages, including reduced parasitic capacitance, smaller device dimensions, and improved uniformity in device performance for large-area electronics. A difficult challenge in making self-aligned TFT structures is the necessity of making source/drain contacts that exhibit low contact resistances and that are precisely aligned relative to the gate electrode. In this article, we describe a novel process for fabricating self-aligned amorphous Si TFTs. This process utilizes a pulsed excimer laser (308 nm) to dope or to activate dopants in a-Si to form the source/drain contacts. An important feature of the device design is an optical filter to protect the a-Si channel region from radiation damage during the 308 nm laser process. However, the optical filter allows the transmission of the uv light for lithography exposure from the backside of the substrate to align the channel region with the gate electrode. This new process enables the fabrication of high performance self-aligned a-Si TFTs with poly-Si source and drain contacts.

The “Aachen” Keratoprosthesis: A New Approach towards Successful Keratoprosthesis-Surgery

None of the keratoprostheses available today is absolutely successful in the long term, neither the problems of extrusion, retroprosthetic membrane formation and intraocular pressure rise are yet solved. A new type of keratoprosthesis is required which can show improved ingrowth characteristics and allow intraocular pressure measurements. In order to possibly meet the above mentioned requirements we developed a flexible silicone keratoprosthesis with scleral fixation and chemical surface modification. The one-piece keratoprosthesis is made of silicone rubber. Its optical zone has a diameter of 11 mm and is 0.3 mm thick. The surface-modified haptic consists of a scleral rim and eight branches for scleral fixation. A ridge at the back of the keratoprosthesis fitting into the trephination hole shall avoid leakage and retroprosthetic membrane formation. Optical and mechanical qualities are characterised by tensile tests, spectrophotometry and topography. A method for keratoprosthesis-production was established. The optical quality of the device was improved by submicron lathing of the mould. Spectrophotometry showed high visible and ultraviolet light transmission of the silicone. Mechanical tests with silicone samples revealed high tensile strength and elongation at break. The mechanical properties were not impaired by surface modification. The production of a flexible silicone keratoprosthesis with high optical and mechanical properties was established. Its use both for the treatment of permanently opacified corneas and as temporary keratoprosthesis seems to be possible.

The soft X-ray and extremely ultraviolet filters with negligible pinholes transmittance

It is proposed to fabricate two-layer thin film filters without pinholes transmittance of visible and UV light. We describe the design and performance of these filters. Filter consists of two layers of thin metal films fixed to each side of porous membrane with thorough pores or transmission diffraction grating as support. As examples it was made Al or Rh two-layer thin film filters on metallized porous track membrane supports with the 10 −9–10 −10 level of visible and UV light rejection at transmittance T∼0.1 ÷ 0.01 in the Extreme ultraviolet region. Proposed filter is appropriate in the optical experiments with strong continuous X-ray and Extreme ultraviolet radiation sources such as laser plasma, SR sources and the Sun.

The “Aachen” keratoprosthesis: A New Approach towards Successful Keratoprosthesis-Surgery

Background None of the keratoprostheses available today is absolutely successful in the long term, neither the problems of extrusion, retroprosthetic membrane formation and intraocular pressure rise are yet solved. A new type of keratoprosthesis is required which can show improved ingrowth characteristics and allow intraocular pressure measurements. In order to possibly meet the above mentioned requirements we developed a flexible silicone keratoprosthesis with scleral fixation and chemical surface modification. Methods The one-piece keratoprosthesis is made of silicone rubber. Its optical zone has a diameter of 11 mm and is 0.3 mm thick. The surface-modified haptic consists of a scleral rim and eight branches for scleral fixation. A ridge at the back of the keratoprosthesis fitting into the trephination hole shall avoid leakage and retroprosthetic membrane formation. Optical and mechanical qualities are characterised by tensile tests, spectrophotometry and topography. Results A method for keratoprosthesis-production was established. The optical quality of the device was improved by submicron lathing of the mould. Spectrophotometry showed high visible and ultraviolet light transmission of the silicone. Mechanical tests with silicone samples revealed high tensile strength and elongation at break. The mechanical properties were not impaired by surface modification. Conclusions The production of a flexible silicone keratoprosthesis with high optical and mechanical properties was established. Its use both for the treatment of permanently opacified corneas and as temporary keratoprosthesis seems to be possible.

UV and optical light transmission properties in deep ice at the South Pole

Both absorption and scattering of light at wavelengths 410 to 610 nanometers were measured in the South Pole ice at depths 0.8 to 1 kilometer with the laser calibration system of the Antarctic Muon And Neutrino Detector Array (AMANDA). At the shortest wavelengths the absorption lengths exceeded 200 meters—an order of magnitude longer than has been reported for laboratory ice. The absorption shows a strong wavelength dependence while the scattering length is found to be independent of the wavelength, consistent with the hypothesis of a residual density of air bubbles in the ice. The observed linear decrease of the inverse scattering length with depth is compatible with an earlier measurement by the AMANDA collaboration (at ∼515 nanometers).

Emollients and photo(chemo)therapy: a call for caution.

Emollients used for skin care, treatment of a disease or lubrication, before irradiation during the course of phototherapy or photochemotherapy, may significantly interfere with the transmission of UV light and may influence the outcome of the therapy. These experiments should characterize and quantify the possible interactions of usual emollients with UV light transmission. The method was an in vitro technique similar to the one already used for the determination of sun protection factors of topical sunscreen preparations. Among the products tested, two showed a significant photoprotection capable of interfering with the course of therapy. Oils enhanced UV light transmission significantly. Emollients may show significant interference with UV light transmission during phototherapy or photochemotherapy. The outcome and course of the therapy could thus be significantly modified.

Measurement of transmission of ultraviolet and visible light in the living rabbit cornea.

Corneal transmittance in pigmented rabbits was measured at ultraviolet and visible wavelengths from the ratio of fluorescence of dyes in the anterior chamber to fluorescence of the same dyes in a quartz cuvette. Aqueous humor was drained through a limbal incision and the anterior chamber was reformed with a mixture of a viscoelastic material and a fluorophore (fluorescein, O-methyl pyranine, or sulforhodamine B). Excitation spectra, emission spectra, or both were measured in the anterior chamber with a new scanning ocular fluorophotometer, at wavelengths between 250 nm and 700 nm. Fluorescence spectra were also measured from the same fluorophore in a quartz cuvette. External transmittance of the cornea was calculated at each wavelength from the ratio of fluorescence in the anterior chamber to fluorescence in the cuvette. Transmittance was 93% +/- 1.4% (mean +/- SD, n = 8 rabbits) at 500 nm and was 89% to 93% between 370 nm and 500 nm. Transmittance decreased to 82% +/- 5.7% at 350 nm, to 50% +/- 5.9% at 310 nm, and to less than 2% at 290 nm. Between 370 nm and 500 nm, the wavelength range most frequently used in fluorophotometry, average transmittance varied by less than 5%. These results suggest that fluorescence measured at two or more wavelengths within this spectrum needs little if any correction for differential attenuation by the cornea. At wavelengths shorter than 370nm, measurements should be corrected. This technique provides a simple and minimally invasive means of studying visible and ultraviolet transparency of the cornea in the living eye.

Observations of ultraviolet light reflection and transmission by first‐year sea ice

As part of a comprehensive program investigating the electromagnetic properties of sea ice, measurements were made of the optical properties of young ice and first‐year sea ice at ultraviolet wavelengths. Young sea ice observations were made in a specially designed sea ice pond at the Cold Regions Research and Engineering Laboratory (Hanover, NH), while first‐year sea ice was examined in the Chukchi Sea and Beaufort Sea near Barrow, Alaska. The results indicated that, in general, albedo increased with increasing wavelength from 305 to 380 nm, with values for first‐year ice in the 0.4 to 0.6 range. Transmittance through bare first‐year ice was roughly 0.5 to 2 percent. Extinction coefficients for bare sea ice were between 2 and 4 m−1 and decreased with increasing wavelength. The presence of a snow cover had a profound impact on ultraviolet light levels under sea ice, with even a thin (0.1‐m‐thick) snow cover reducing transmitted ultraviolet light by more than an order of magnitude. Observed transmittances indicated that the attenuation of ultraviolet light by sea ice and snow was greater than that of the photosynthetically active radiation.

Do Human Tears Absorb Ultraviolet Light?

We analyzed human tears by ultraviolet (UV) spectrophotometry for transmittance of UV light. Ultraviolet light was readily transmitted through human tears in the UV-A (320-400 nm) and UV-B (290-320 nm) ranges. Tears partially absorbed UV light in the UV-C (100-290 nm) range. The clinical implications of these findings include prevention of phototoxic ocular damage and effects upon excimer laser corneal photoablative techniques.

Silicon nitride films grown by hydrogen radical enhanced chemical vapor deposition utilizing trisdimethylaminosilane

The growth of silicon nitride films using trisdimethylaminosilane (TDMAS) as a source material is described. TDMAS was decomposed by hydrogen radicals generated with a microwave plasma. Methyl groups included in the TDMAS were extracted from the film growing surface by hydrogen radicals. Composition, optical and electrical properties of SiN films have been examined with the aid of infrared absorption spectroscopy, electron-probe microanalysis, ultraviolet and visible light transmission spectra and voltage-current measurements. Transparent and insulating SiN films were obtained at low temperature.

Optical Properties of the Pod Wall of the Pea ( Pisum sativum L.). III. The Effects of Senescence and Pod Desiccation

Summary The transmission, reflection and absorption spectra of pods of Pisum sativum L. variety JI 141 were measured at various stages of senescence. These optical properties were correlated with the percentage water content and levels of chlorophyll a, b and total chlorophyll of the pod wall at each stage. Photomorphogenic effects of pod senescence on the seed environment were deduced from changes in the ratio of 660/730 nm light transmitted through the pod wall. Structural aspects of the final stages of pod desiccation were also investigated using scanning electron microscopy. The significance of these results are discussed in relation to the use of optical properties to monitor pod moisture content and the photoenvironment of the senescing pod as it affects 1) phytochrome levels before final seed desiccation and 2) near UV light transmission to the drying seed.

Sensitivity of stratospheric composition to oxygen absorption of solar radiation (175?210 nm)

We have used a two dimensional radiative-chemical-transport model of the stratosphere to investigate the sensitivity of trace gas distributions to absorption of oxygen in the wavelength region 175–210 nm. Two different formulations for the Herzberg continuum absorption cross sections are used. The calculated transmission of ultra-violet light in the stratosphere is lower and higher than observed, depending on the choice of absorption cross section. For the higher transmission O3, ClO, and HO2 are found to be significantly increased in the lower stratosphere. Calculated O3 in the upper stratosphere, chlorofluorocarbons, N2O and odd-nitrogen are lower. The photolysis of oxygen is considerably faster at high latitudes implying that the photochemical recovery of depleted polar ozone is faster than currently assumed.

A theoretical model of ultraviolet light transmission through Antarctic Sea ice

Much of the region of the Earth most affected by stratospheric ozone depletion is covered by a seasonal or perennial sea ice cover, which is the habitat of a productive and extensive sea ice microbial community. To assess the impact of enhanced incident ultraviolet irradiance on this community, a knowledge of the amount of light transmitted through a sea ice cover is necessary. A two‐stream radiative transfer model is used to estimate the penetration of ultraviolet radiation through Antarctic sea ice. Sea ice optical properties were used as proxies to infer scattering and absorption coefficients at ultraviolet wavelengths. Case studies are reported for sea ice in McMurdo Sound and in the Weddell Sea. Values of spectral transmittance are computed as well as integrated transmitted UV‐B, UV‐A, biologically effective irradiance (BEI), and photosynthetically active radiation (PAR). UV‐B light levels under meter‐thick ice are a few percent of incident values. The presence of a snow cover results in a large decrease in transmitted ultraviolet. Snow and ice ameliorate the biological impact of enhanced levels of incident ultraviolet radiation by reducing the BEI relative to the PAR.