Maximum UVA Research Articles

STUDY OF ULTRAVIOLET SOLAR RADIATION IN DUHOK CITY UNDER CLEAR SKY CONDITIONS

This work focused on the UV solar radiation measurements under clear sky conditions for typical days in months (April to July) when the UV radiation is expected to have the highest values in Duhok city. Two types of UV, (UVA and UVB) were measured from April to July under clear sky conditions. The maximum UVA (wavelength 315-400 nm) irradiance (38 and 37) W/m2 was measured at noon in June and July, respectively. The minimum UVA of 30 W/m2 was recorded at April noon. In July, the hourly UVA ranged between 2.6 W/m2 at 6:00 pm to 37 W/m2 at 12:00 pm; maximum UVB (wavelength 280-315 nm) irradiance of 1.9 W/m2 was measured in July noon’s, and a minimum of 1.4 W/m2 at April noon. The effect of the atmosphere (solar zenith angle) on the UVB clearness index was investigated and a functional relationship between them was developed. Finally, the time required for UVB minimum erythemal dose was estimated.

Spectral Blocking of Solar Radiation in High Tunnels by Poly Covers: Its Impact on Nutritional Quality Regarding Essential Nutrients and Health-Promoting Phytochemicals in Lettuce and Tomato

Spectral characteristics of solar radiation have a major role in plant growth and development and the overall metabolism, including secondary metabolism, which is important for the accumulation of health-promoting phytochemicals in plants. The primary focus of this study was to determine the effect of spectral characteristics of solar radiation on the nutritional quality of lettuce (Lactuca sativa L., cv. red leaf ‘New Red Fire’ and green leaf ‘Two Star’ and tomato (Solanum lycopersicum L., cv. BHN-589) grown in high tunnels in relation to the accumulation of essential nutrients and phytochemicals. Solar spectrum received by crops was modified using photo-selective poly covers. Treatments included commonly used standard poly, luminescence poly (diffuse poly), clear poly, UV blocking poly, exposure of crops grown under the standard poly to full sun 2 weeks prior to harvest (akin to movable tunnel), and 55% shade cloth on the standard poly. All the poly covers and shade cloth reduced the PAR levels in the high tunnels, and the largest reduction was by the shade cloth, which reduced the solar PAR by approximately 48%. Clear poly allowed the maximum UV-A and UV-B radiation, while standard poly allowed only a small fraction of the solar UV-A and UV-B (between 15.8% and 16.2%). Clear poly, which allowed a higher percentage of solar UV-A (60.5%) and UV-B (65%) than other poly covers, increased the total phenolic concentration and the antioxidant capacity in red leaf lettuce. It also increased the accumulation of flavonoids, including quercetin-3-glucoside, luteolin-7-glucoside, and apigenin-3-glucoside in red leaf lettuce, compared to the standard poly. Brief exposure of crops grown in high tunnels to full sun prior to harvest produced the largest increase in the accumulation of quercetin-3-glucoside, and it also resulted in an increase in luteolin-7-glucoside and apigenin-3-glucoside in red leaf lettuce. Thus, clear poly and brief exposure of red leaf lettuce to the full sun, which can increase UV exposure to the plants, produced a positive impact on its nutritional quality. In contrast, shade cloth which allowed the lowest levels of solar PAR, UV-A and UV-B relative to the other poly covers had a negative impact on the accumulation of the phenolic compounds in red leaf lettuce. However, in green leaf lettuce, luminesce poly, clear poly, UV-block poly, and shade treatments increased the accumulation of many essential nutrients, including protein, magnesium, and sulfur in green leaf lettuce compared to the standard poly. Poly cover treatments including shade treatment did not affect the accumulation of either carotenoids (lutein, β-carotene, and lycopene) or essential nutrients in mature tomato fruits. The results show that clear poly cover can enhance the accumulation of many phenolic compounds in red leaf lettuce, as does the brief exposure of the crop to the full sun prior to harvest. Thus, UV radiation plays an important role in the accumulation of phenolic compounds in red leaf lettuce while the overall spectral quality of solar radiation has a significant influence on the accumulation of essential nutrients in green leaf lettuce.

Factors affecting ultraviolet-A photon emission from β-irradiated human keratinocyte cells

The luminescence intensity of nm photons emitted from HaCaT (human keratinocyte) cells was investigated using a single-photon-counting system during cellular exposure to 90Y β-particles. Multiple factors were assessed to determine their influence upon the quantity and pattern of photon emission from β-irradiated cells. Exposure of cells/5 mL to 703 μCi resulted in maximum UVA photoemission at counts per second (cps) from live HaCaT cells (background: 1–5 cps); a 16-fold increase above cell-free controls. Significant biophoton emission was achieved only upon stimulation and was also dependent upon presence of cells. UVA luminescence was measured for 90Y activities 14 to 703 μCi where a positive relationship between photoemission and 90Y activity was observed. Irradiation of live HaCaT cells plated at various densities produced a distinct pattern of emission whereby luminescence increased up to a maximum at cells/5 mL and thereafter decreased. However, this result was not observed in the dead cell population. Both live and dead HaCaT cells were irradiated and were found to demonstrate different rates of photon emission at low β activities (⩽400 μCi). Dead cells exhibited greater photon emission rates than live cells which may be attributable to metabolic processes taking place to modulate the photoemissive effect. The results indicate that photon emission from HaCaT cells is perturbed by external stimulation, is dependent upon the activity of radiation delivered, the density of irradiated cells, and cell viability. It is postulated that biophoton emission may be modulated by a biological or metabolic process.

The angular distributions of ultraviolet spectral irradiance at different solar elevation angles under clear sky conditions.

To investigate the angular distributions of UVA, UVB, and effective UV for erythema and vitamin D (vitD) synthesis, the UV spectral irradiances were measured at ten inclined angles (from 0° to 90°) and seven azimuths (from 0° to 180°) at solar elevation angle (SEA) that ranged from 18.8° to 80° in Shanghai (31.22° N, 121.55° E) under clear sky and the albedo of ground was 0.1. The results demonstrated that in the mean azimuths and with the back to the sun, the UVA, UVB, and erythemally and vitD-weighted irradiances increased with the inclined angles and an increase in SEA. When facing toward the sun at 0°-60° inclined angles, the UVA first increased and then decreased with an increase in SEA; at other inclined angles, the UVA increased with SEA. At 0°-40° inclined angles, the UVB and erythemally and vitD-weighted irradiances first increased and then decreased with an increase in SEA, and their maximums were achieved at SEA 68.7°; at other inclined angles, the above three irradiances increased with an increase in SEA. The maximum UVA, UVB, and erythemally and vitD-weighted irradiances were achieved at an 80° inclined angle at SEA 80° (the highest in our measurements); the cumulative exposure of the half day achieved the maximum at a 60° inclined angle, but not on the horizontal. This study provides support for the assessment of human skin sun exposure.

Are the Surgeons Safe During UV-A Radiation Exposure in Collagen Cross-Linking Procedure?

To quantify the effect of scattered UV-A radiation used in the collagen cross-linking (CXL) procedure and the amount of radiation reaching the surgeon and the surrounding area and to estimate the dampening effect by various protective devices. In this case series, 3 patients [aged 25-30 (±2.5) years] with keratoconus underwent a CXL procedure with UV-A light and riboflavin. Irradiance was measured using a spectrometer (Model USB2000; Ocean Optics, Inc) for various distances from the source, at various angles, and for different durations of radiation. The spectrometer was also used to measure the dampening effect produced by gown, latex gloves, and UV-protective glasses. Maximum UV-A radiation (1.4 × 10(-9) mW/cm(2)) was measured at 2 cm from the limbus, when the probe was held at a 45-degree angle to the floor. UV-A radiation reaching the surgeon's eye and the abdomen was 3.403 × 10(-11) and 2.36 × 10(-11) mW/cm(2), respectively. Gown, latex gloves, and UV-protective glasses showed dampening effects of 99.58%, 95.01%, and 99.73%, respectively. CXL appears to be a safe procedure with respect to UV-A radiation exposure to the surgeon. Further safety can be ensured by UV-protective devices.

Optimizing Solar UV-Radiation Exposures for Vitamin D3: Comparing Global and Diffuse Spectral UV Radiation

Currently, there is a major gap in the knowledge that is needed to optimize the beneficial effects related to ultraviolet (UV) radiation at wavelengths that induce vitamin D(3) synthesis (UV(D3)) compared to reducing the biologically damaging overexposure to UV radiation. The aim of this study was to investigate the use of diffuse (radiation that is scattered from all directions) UV radiation to optimize exposures to UV(D3) radiation and maximize the reduction of exposure to UVA radiation. Data on global and diffuse solar UV-radiation spectra were collected at 10-min intervals in the Southern Hemisphere in the late spring and summer from 1 November 2006 to 28 February 2007. For a solar zenith angle (SZA) of approximately 5 degrees , the observed maximum UV(D3) irradiances were 0.80 W/m(2) and 0.46 W/m(2) for global and diffuse UV radiation, respectively. The observed maximum UVA irradiances were 79.0 W/m(2) and 36.2 W/m(2) for global and diffuse UV radiation, respectively. For diffuse UV radiation, the maximum ratio of vitamin D(3) to UVA radiation was 1.75% at a SZA of approximately 10 degrees , whereas the maximum ratio for global UV was 1.27% at 10 degrees . For SZAs of 25 degrees and less, more UV radiation is in the wavelength region contributing to vitamin D(3) synthesis (UV(D3)) than in the UVA region for diffuse UV radiation than for global UV radiation.

Porphyra-334, a potential natural source for UVA protective sunscreens

The mycosporine-like amino acid (MAA), porphyra-334 (lambda(max) = 334 nm; epsilon = 42,300 M(-1) cm(-1)), was isolated from the aquatic cyanobacterium Aphanizomenon flos-aquae (AFA) and its structure was verified by spectroscopic methods. The UVA absorption properties of the crude methanolic extract were determined against two commercial sun care products in terms of mean critical wavelength, mean UVA/UVB ratios and UVA protection category (Boots the Chemists, Ltd.). The crude methanolic extract from AFA exhibited maximum UVA protection comparable to that determined for Boots SPF 4.

Penetration of Solar Radiation into the Waters of Messina Strait (Italy)

The optical properties of the waters of five different stations, three located in the Messina Strait and two near the Strait (open sea), were analysed. Direct spectral measurements of the downward solar irradiance (290 - 800 nm) at different depths (0.5 m, 7 m, 10 m, 13 m, 20 m) were made using a cosine sensor connected to a spectroradiometer. Water samples were collected in the surface layer and their absorption spectra were analysed. The natural fluorescence profiles, along the water column, were determined using a fluorometer (SBE 911plus - Sea Teach). The spectral attenuation coefficient (K(lambda)), the variation of K(lambda) in different wavelength ranges (deltaK(deltalambda)), the wavelength corresponding to minimum value of K(lambda), the spectral depths of penetration of both 1% and 10% of the sub-surface irradiance values (P(lambda)), the depths of 1% of penetration of UVB, UVA and PAR, the depth ranges of the maxim concentration of Chl a and superficial CDOM were measured at each station. The maximum solar UVB penetration was about 65% of the photic zone and the maximum UVA penetration was nearly 100% (data of the Ionic sea station). Thus, a large part of the photic zone was exposed to UV radiation sufficient to cause a possible reduction in the photosynthetic activity of phytoplankton. The spectral penetration of solar radiation, especially UVB radiation, was significantly different in the three stations of the Strait with respect to the two stations studied in the open sea. This shows that variations in the spectral attenuation along the water column can be used as an indicator of properties of the water body.

Peripheral light focusing as a potential mechanism for phakic dysphotopsia and lens phototoxicity.

Our aim was to examine secondary image formation in the anterior segment caused by peripheral light focusing (PLF) in the human cornea, and in particular the crystalline lens. Non-sequential ray-tracing (OptiCAD) was applied to an anatomically based human eye model, which incorporates a gradient index crystalline lens. For analysis of the limbal effect, we varied the incident angle from 100 to 122 degrees, while for the crystalline lens effect, the incident angle was varied from 60 to 90 degrees. The corneal shapes studied included central radii from 7.4 to 8.2 mm with a range of shape factors. In each case, we computed the peak and average intensities, and the area of exposure at the limbus or lens periphery. The computation was repeated with a previous model eye for comparison. For the limbal effect, a peak intensity gain of x22.5 was found at an incident angle of 104 degrees which compares well with previous results. The average intensity gain at this angle was x7.5 over an area of 0.23 mm2. Steeper corneal curvature produced a greater PLF effect. For the crystalline lens effect, maximum UVA (365 nm) intensity gain peaked at x8.6 at 84 degrees with average intensity gain of x2.3. The area of UVA exposure peaked at 4.7 mm2 at 70 degrees. A relatively wide range (30 degrees ) of incident angles produced peak PLF gains of x3 or more in the lens. Significant focusing of light is directed to the nasal limbus, and to a lesser extent to the crystalline lens over a broad range of incident angles. PLF in the nasal cornea is reduced by an order of magnitude when a UV-blocking soft contact lens is used. The concentration levels and intraocular sites of PLF action on UV and visible light suggest a new mechanism of phakic dysphotopsia and lens phototoxicity.

Enhanced spectral UV irradiance: a 1 year preliminary study

The ultraviolet (UV) spectra on cloudy days were compared to those on cloud free days to determine which part of the UV spectrum has the greatest enhancement due to the cloud compared to both corresponding measured clear sky spectra as well as other enhanced spectra. In this preliminary study, cloud enhanced UV spectra selected for maximum UVA enhancement compared to a clear sky UV spectrum at similar solar zenith angle (SZA) and ozone values, showed that the ratio of the two sets of spectral irradiances was approximately wavelength independent (approximately 1.1) above the cut-off wavelength of approximately 306 nm. Similarly, above 306 nm the average ratio of the spectral irradiances of a maximum UVB enhanced UV spectrum compared to a clear sky spectrum was 1.2 with maximum values generally above this average between 316 and 344 nm and generally below 1.2 above the wavelength of 344 nm. The UVA and UVB enhanced spectra were separated into five SZA ranges and the irradiance at each wavelength averaged for each range and compared to clear sky spectra in each of the ranges. Above approximately 306 nm, the ratios are wavelength independent for all SZA. However, with the exception of the SZA range centred on 20°, there is an increasing dependency with shorter wavelengths below the 306 nm. Also there appears to be two distinct groupings of the average irradiance ratios, corresponding to the SZA range centred on 20°, 37° and 49° (ratio of 1.2) and 32° and 42° (ratio 1.0), the latter cases suggesting that on average there is no enhancement for these SZA, except for wavelengths less than 306 nm.

Effects of Titanium Oxide on the Optical Properties of Cerium Oxide

Abstract Cerium oxide and CeO2-TiO2 mixed oxide particles were prepared using sol-gel method. Addition of TiO2 changed the apparent bandgap energy to shift the UV-absorption edge to higher wavelengths, and the maximum UV-A absorption was attained in the 50CeO2-50TiO2 (in mol%) sample. The results on XRD and TEM showed that crystallinity of the particles became lower with increasing in the TiO2 content, and both thermal- and photo-catalyses were deactivated by the formation of CeO2-TiO2 mixed oxides.

UVA and UVB Transmission of Fabrics: Critical Wavelength Based on Absorbance and Effective Dose

Background: The degree to which a fabric protects the skin from ultraviolet (UV) rays is given as its UV protection factor (UPF) that is predominantly influenced by UVB transmission through the fabric. However, the UVA-blocking properties of a fabric are of significance as UVA plays also a role in photocarcinogenesis, photo-aging and provocation of photosensitive disorders. Objectives: The objective of this study was to present some overall performance of the protection against UVA radiation compared to the protection against UVB radiation of apparel fabrics. For this purpose, we aimed to study the ratio of the average UVA and UVB transmission and to calculate the critical wavelength (CW) of a large collection of fabric materials. Methods: We studied 196 different fabric materials. The fabrics were spectrophotometrically assessed in accordance with the European standard (part 1). We determined the mean UVB (290–320 nm) and UVA (320–400 nm) transmission, mean UVB/UVA ratios, maximum UVA transmission and CW based on absorbance and effective dose (ED). Results: We observed that about 90% of the fabrics had UVB/UVA ratios smaller than 1. This indicates that the average UVA transmission was higher than the average UVB transmission. For 20% of the fabrics, the average UVA transmission was at least twice as high as the average UVB transmission. When calculating the CW based on the absorbance for the sample set, we found that the CW of fabric materials is generally higher than 370 nm and is usually close to 380 nm. When the ED was used, a much smaller CW was found compared to the calculations based on absorbance. Conclusions: UVA transmission through fabrics is usually higher than UVB transmission. Despite a high UPF, increased UVA transmission through clothing may be of significance in triggering photosensitive disorders. The UVB/UVA ratio of fabric materials strongly correlates with the CW based on ED. Because frequently a UG-11 fluorescence filter has to be used in UPF assessment, the CW based on the ED is more relevant and less prone to measurement error.

Estimate of Annual Ultraviolet-A Exposures in Cars in Australia

[Abstract]: The annual solar UVA exposures in four cars were estimated by measuring the UVA irradiances in the vehicles in each of the four seasons and in the morning, noon and afternoon. For the cars with untinted windows the maximum UVA irradiances in cars do not necessarily occur at noon when the outside irradiances are at their highest. Additionally, they do not occur in summer. The range of annual UVA exposures between 9:00 and 15:00 EST is 1918 to 6177 J cm-2 for the cars without the after market window tint. These correspond to 5% to 17% of the ambient UVA on a horizontal plane over the same period outside the cars. The range is for the different sites in the car. For the car with the aftermarket window tint, the range of the annual UVA exposures were 489 to 2969 J cm-2 or 1% to 8% of the ambient UVA.

Analysis of cumulus solar irradiance reflectance (CSIR) events

Clouds are extremely important with regard to the transfer of solar radiation at Earth's surface. This study investigates Cumulus Solar Irradiance Reflection (CSIR) using ground-based pyranometers. CSIR events are short-term increases in solar radiation observed at the surface as a result of reflection off the sides of convective clouds. When Sun-cloud observer geometry is favorable, these occurrences produce characteristic spikes in the pyranometer traces and solar irradiance values may exceed expected clear-sky values. Ultraviolet CSIR events were investigated during the summer of 1995 using UVA and UVB pyranometers. Observed data were compared to clear-sky curves which were generated using a third degree polynomial best-fit line technique. Periods during which the observed data exceeded this clear-sky curve were identified as CSIR events. The magnitude of a CSIR event was determined by two different quantitative calculations. The MAC (magnitude above clear-sky) is an absolute measure of the difference between the observed and clear-sky irradiances. Maximum MAC values of 3.4 Win −2 and 0.0169 Wm −2 were observed at the UV-A and UV-B wavelengths, respectively. The second calculation determined the percentage above clear-sky (PAC) which indicated the relative magnitude of a CSIR event. Maximum UV-A and UV-B PAC magnitudes of 10.1% and 7.8%, respectively, were observed during the study. Also of interest was the duration of the CSIR events which is a function of Sun-cloud-sensor geometry and the speed of cloud propagation over the measuring site. In both the UV-A and UV-B wavelengths, significant CSIR durations of up to 30 minutes were observed. C 1997 Elsevier Science B.V.

The efficacy of localized PUVA therapy for chronic hand and foot dermatoses

The response to treatment of all patients enrolled over an 18-month period for localized oral or topical psoralen photochemotherapy (PUVA) of chronic hand and foot dermatoses was retrospectively reviewed. There were broadly similar success rates for the two groups for complete clearance: 61.5% (eight of 13 patients who completed therapy)--oral PUVA, 47.8% (11 of 23 patients who completed therapy)--topical PUVA, and for significant improvement: 23.1% (three of 13 patients)--oral PUVA, 30.4% (seven of 23 patients)--topical PUVA; there were no significant differences in response when diagnostic subgroupings of the hand dermatoses were taken into account. The mean number of treatments (22 for oral PUVA and 24 for topical), treatment durations (122 and 129 days), maximum UVA doses (11.2 and 12.3 J/cm2) and to a lesser extent cumulative UVA doses (189.3 and 237.0 J/cm2) for the therapies were similar in the two groups; adverse effects were minimal for both treatment protocols. However, at least five of the eight patients in the oral PUVA group and five of the 11 in the topical group who cleared completely relapsed after a mean 86 (range 19-245) and 174 (range 23-596) days, respectively. These findings are in broad agreement with those of previous studies. Therefore to avoid generalized photosensitivity and a higher likelihood of adverse effects with systemic therapy, as well as a possible slower relapse rate, topical therapy seems preferable.

Palmoplantar psoriasis: Experience with 8-methoxypsoralen soaks plus ultraviolet A with the use of a high-output metal halide device

The use of 8-methoxypsoralen water soaks plus ultraviolet A was evaluated retrospectively in 11 patients with moderate to severe palmoplantar psoriasis that had been resistant to previous topical therapies. Patients received twice- or thrice-weekly 30-minute hand and/or foot soaks in 8-methoxypsoralen, 2.5 mg/L, followed by UVA irradiation. The condition of one patient cleared completely, and seven showed good improvement. The range of treatments required for maximal improvement was 14 to 43 with a mean of 28. The range of maximum UVA dosage per treatment was 3.5 to 17.5 joules/cm2, and the range of cumulative UVA required for maximal improvement was 45 to 388 joules/cm2 with a mean of 165 joules/cm2. The mean serum level of 8-methoxypsoralen 60 minutes after completion of hand and foot soaks was 2.5 +/- 0.5 ng/ml compared with 95.75 +/- 10.43 ng/ml after oral 8-methoxypsoralen, 0.5 mg/kg. In our experience this treatment has been a safe and relatively effective form of therapy for resistant palmoplantar psoriasis.