UV-B Lamps Research Articles

Validation of a semiautomated method of minimal erythema dose testing for narrowband ultraviolet B phototherapy

The most widely used method for establishing the minimal erythema dose (MED) before narrowband ultraviolet (UV) B phototherapy is time-consuming, inconvenient and may yield inconsistent results. To assess the equivalence of MED assessment using a filtered xenon arc lamp UV source, a semiautomated MED tester, and a UV-opaque template method of MED determination with a panel of TL-01 311-nm UVB fluorescent tubes. Secondly, to gauge the current usage of MED testing, and the method used, in a large sample of U.K. phototherapy units. Thirdly, to assess variation in UV output of the semiautomated skin tester immediately after switching on to identify optimum warm-up time. Finally, to assess reproducibility of MED testing by assessing within-patient variability and interobserver variability of MED test results. Sixty-five patients about to undergo UVB phototherapy had their MED determined using three different methods. Within each patient we compared the values of MED determined by a semiautomated Durham MED tester, a panel of narrowband UVB lamps with a UV-opaque template constructed by a phototherapist, and a 310-nm filtered xenon arc lamp with a liquid light guide. MED test results were assessed by clinical evaluation using a 6500 K colour temperature examination lamp. The output of the semiautomated MED tester was measured by spectroradiometer over a period of 20 min in order to identify the time to steady output. Reproducibility of MED testing with the semiautomated MED tester was carried out in 25 normal volunteers. All MEDs were assessed by at least two independent observers. A postal questionnaire was sent to 78 U.K. phototherapy units to assess routine practice concerning MED testing prior to narrowband UVB phototherapy. The semiautomated MED tester showed consistency with the panel method (r = 0.92, panel MED = -0.57 + 1.14 x Durham MED). The semiautomated MED tester produced a slightly lower MED result than the panel MED. Reproducibility tests showed high interobserver agreement (kappa value = 0.79), and high consistency for successive day testing (kappa value = 0.79). Questionnaires were returned from 67 of 78 phototherapy units (85%) and revealed that 19 units (28%) were routinely using MED testing prior to UVB therapy. This study has shown the Durham MED tester to be a convenient, valid and reproducible method for determining patient MED values prior to narrowband UVB phototherapy when used under carefully controlled lighting, by experienced observers.

Comparison of Changes in Metal Toxicity Following Exposure of Water with High Dissolved Organic Carbon Content to Solar, UV‐B and UV‐A Radiation

This study examines the effects of natural solar radiation on the metal-binding capacity of dissolved organic matter (DOM). Newington Bog water (35.5 mg L(-1) dissolved organic carbon [DOC]) was irradiated for 20 days under UV-B lamps in the laboratory and under natural solar radiation. In the presence of irradiated DOM, IC(50) (contaminant concentration required to reduce algal growth by 50%) was significantly decreased with UV-B treatment for four metals: Pb, 64%; Cu, 63%; Ni, 35% and Cd, 40%. Solar radiation also significantly decreased IC(50) of Pb (58%) and Cu (49%), DOC concentration (11%), DOM fluorescence (DOMFL, 33%) and DOC-specific UV absorbance. Further experiments on Raisin River water (20.7 mg DOC L(-1)) exposed to 20 days of artificial UV-A and UV-B radiation produced significant decreases in IC(50) for Cu (48%) with UV-A and for Pb (43%) with UV-B. DOC concentration was decreased 20% by UV-B and 24% by UV-A. DOMFL decreased 51.5% in the first 5 days of UV-A exposure, an effect that was not observed with the UV-B treatment. The UV-A treatment decreased UV absorbance more at longer wavelengths and over a broader wavelength band than did the UV-B treatment. Change in toxicity with UV irradiation was inconsistent among the metals tested in this study, indicating that some organic metal-binding ligands were more quickly removed or altered than others. The DOM remaining after irradiation appears to be qualitatively different from the unirradiated DOM. The much greater irradiance of UV-A makes its contribution to the removal and/or alteration of DOM at least as important as the influence of higher energy UV-B.

Chemical stability and SPF determination of Pothomorphe umbellata extract gel and photostability of 4-nerolidylcathecol

Due to its antioxidant and photoprotective properties, Pothomorphe umbellata is a promising candidate for use in cosmetic and pharmaceutical formulations. These properties arise from the presence of 4-nerolidylcathecol (4-NC), a polyphenolic compound isolated from P. umbellata roots. This study investigates its photostability properties, as well as the chemical and the in vitro sun protection factor (SPF) of P. umbellata root extract in a gel formulation. A high performance liquid chromatography method was used to evaluate the chemical stability using 4-NC as marker at 5, 25 and 45 °C for 103 days. The photostability and the sun protection factor were analyzed by ultraviolet (UV) spectophotometry using samples irradiated with UVB lamp. No significant difference of the 4-NC concentration was found in formulations stored at 5 and 25 °C. All samples stored at 45 °C, however, showed degradation of gel structure. After 2 h of UVB exposure, there was no change in the absorption profile of 4-NC. The sun protection factor of P. umbellata root extract gel to final concentration of 0.1% 4-NC was not expressive (SPF = 3.35 ± 0.02), suggesting the predominance of its antioxidant activity.

Effect of UV‐B and different PAR intensities on the primary production of the mixotrophic planktonic ciliate Stentor araucanus

Stentor araucanus is a mixotrophic ciliate that, in Andean lakes, inhabits the upper epilimnetic levels, which are commonly avoided by other planktonic organisms. This freshwater heterotrich has dark pigmented cortical granules and lives autotrophically with endosymbiotic algae. The effect of photosynthetically active radiation (PAR) and ultraviolet (UV)‐B radiation on primary production was analyzed during summer 2003–2004 in Lake Moreno Oeste, a highly transparent ultraoligotrophic lake (mean summer Kd = 0.16 m−1). Primary production (PP) was measured in the field in the euphotic zone during both static and variable‐depth incubations. Static exposure of the organisms was examined at different depths (0.30, 10, and 20 m), and the variable depth exposure involved experimental containers moved continuously up and down the epilimnion (0–15 m). In the static exposure closest to the surface and in the mobile incubation, quartz tubes were incubated with and without a UV‐B screen (Mylar™). Additionally, PP was measured in the laboratory with and without previous exposure to a UV‐B lamp (290–315 nm). S. araucanus was present throughout the summer with highest abundances at or above 15 m in depth. A high proportion of the ciliate population (80%) was, therefore, exposed to UV radiation, and between 30% and 60% of the population occupied depths at which UV‐B (305 nm) exceeded 1% of surface incidence. PP values were higher in the epilimnion than below it and were not reduced by exposure to high irradiances of PAR+UV‐A and PAR+UV‐A+UV‐B. The laboratory experiments showed no difference between UV‐B and PAR preexposure treatments. The variable‐depth epilimnetic incubations gave similar PP values and did not differ from the static incubations. The average PAR irradiance of the epilimnion was high, around 600 µmol photons m−2 s−1, which was the value at which S. araucanus reached a saturation level in the laboratory. In contrast, the incubations at 20 m differed significantly from those in the epilimnion, exhibiting lower values, except when PAR irradiance was higher than 100 µmol photons m−2 s−1. These results indicate that pigmented mixotrophs like S. araucanus achieve high population densities in the epilimnion because they receive sufficient irradiance (PAR between 100 and 1,600 µmol photons m−2 s−1) to allow endosymbiotic algae to produce.

UV incites diverse levels of DNA breaks in different cellular compartments of a branching coral species

This study evaluates in vitro the effects of UVB irradiation on three cellular compartments of a shallow water coral species. Coral tissues were dissociated by Ca(2+)-Mg(2+)-free artificial seawater. Cell suspensions were divided into the major cellular compartments (animal cells, algal cells, holobiont entities) by sucrose gradient and then by detergent treatments. Cell fractions were irradiated by UVB lamp (4.05, 8.1 and 12.2 kJ m(-2)) and subjected to the comet assay. UVB radiation, at levels that induced a moderate DNA breakage to the non-symbiotic coral and algal cell compartments, caused dramatic increase in DNA breakage to the holobiont entities. After a 1 h repair period, DNA breakage levels in the algal and animal cell fractions were augmented as compared with a reduction in DNA breakage in the holobiont fraction. This discordancy in DNA breakage between the three cellular compartments reveals that the holobiont cell fraction is more vulnerable to increased natural UV irradiation and associated anthropogenic genotoxic impacts, providing another possible explanation for recent increase in worldwide coral bleaching events.

EFFECTS OF UV-B RADIATION ON PROTEIN AND NUCLEIC ACID SYNTHESIS IN THREE SPECIES OF MARINE RED-TIDE MICROALGAE

Because destruction of the ozone layer is becoming increasingly more serious, the amount of ultraviolet radiation reaching the earth's surface, esp. UV-B radiation that is harmful to the DNA of organisms, has increased. The increase in UV-B radiation has altered ecological systems on the earth and has emerged as one of the most noticeable forces of global change. Interest on the potential dangers and injuries from enhanced UV radiation on marine organisms (esp. marine plankton) has increased. A lot of work has been done on UV-B radiation effects on marine microalgae at the molecular, cellular, physiological and biochemical levels; however, there are few reports on red-tide microalgae. In this study, the effects of UV-B radiation on the protein and nucleic acid synthesis of three red-tide microalgae species, Heterosigma akashiwo, Alexandrium tamarense and Skeletonema costatum, were investigated to better understand the influence of UV-B radiation on marine ecological systems and the mechanism and occurrence of red tides. The microalgae were cultured in Erlenmeyer flasks with f/2 medium. Salinity of the seawater was (30.0±1.0)‰ and the initial pH of the culture was ( 8.0 ±0.1). Cultures were grown at (19±1) ℃ under a 12 h∶12 h dark-light cycle at an illumination intensity of 3 000 Lx. Ultraviolet B radiation was provided by two UV-B tubes (Philips TL 40 w/12 uv) covered by a film of cellulose acetate (0.12 mm) to remove all radiation below 280 nm. In order to minimize the change of the filter properties of the film, the cellulose acetate was pre-burned for 48 h at a distance of 1 m from two UV-B lamps. Algae were exposed to UV-B radiation treatments of 0, 0.3, 0.6, 0.9, 1.2, 1.5 , 1.8 , 2.1 , 2.4 , 2.7, and 3.0 J·m -2 , respectively, for 4 days. All experiments were carried out in triplicate. The responses of protein and nucleic acid synthesis in H. akashiwo, A. tamarense and S. costatum to UV-B radiation were studied using isotope-tracing methods. The results showed that the order of sensitivity from high to low in three red-tide microalgae to UV-B radiation was H. akashiwo, A. tamarense and S. costatum. The growth and DNA synthesis of H. akashiwo were inhibited. Whereas lower doses of UV-B radiation stimulated the growth and DNA synthesis of A. tamarense and S. costatum, higher doses had an inhibitory effect. The RNA and protein synthesis in all three species decreased with increased levels of UV-B radiation, but decreases in H. akashiwo were greater than in A. tamarense and S. costatum. Therefore, the sensitivity of RNA and protein synthesis to UV-B radiation enhancement in H. akashiwo was higher than that in A. tamarense and S. costatum.

Provocation testing in polymorphic light eruption using fluorescent ultraviolet (UV) A and UVB lamps

Provocation testing is frequently performed during investigation of patients with suspected polymorphic light eruption (PLE). Techniques are not standardized between centres. We sought to evaluate the efficacy of different fluorescent ultraviolet (UV) radiation lamps for provocation testing in PLE. We analysed results in 68 patients referred consecutively for phototesting in whom a diagnosis of PLE seemed likely based on clinical history. Patients' case notes were reviewed and responses recorded to provocation testing on forearm skin over three consecutive days using broadband UVA, narrowband and broadband UVB lamps. A positive papular response to broadband UVA exposure was seen in 38 patients [56%, estimated 95% population confidence interval (CI) 43-67.9]. Thirty-four patients (50%) had a positive papular response to narrowband UVB exposure (95% CI 37.6-62.4). The probability of a positive provocation test following irradiation with both lamps was 80.9% (95% CI 69.5-89.4). From April 1999, 34 patients also had provocation testing with broadband UVB. Although six patients (18%) had a positive papular response, they all showed a positive response to one or both of the other lamp types. Provocation testing with fluorescent UVA and UVB lamps is a cheap and readily available method that can be used as a diagnostic aid to investigate patients with suspected PLE. Using both broadband UVA and narrowband UVB lamps for testing increases the likelihood of confirming the diagnosis than if either lamp is used alone.

A field methodology to study effects of UV radiation on fish larvae

There is a considerable lack of in situ specific information about the effects of UV-B radiation on limnic animals studied in the field. We exposed larval pike ( Esox lucius L.) in two types of cuvettes (glass and quartz) placed at different depths (5 or 15 cm) to natural solar UV or to artificially enhanced UV-B (lamps on 3 h per day), simulating the scenarios for coming decades. Dose realism and comparability with earlier laboratory experiments was the main purpose, and therefore UV-B irradiances to the surface as well as underwater irradiances were directly measured. Result showed that UV-B dose rates in natural waters are low even though DOC concentration was low (4.8 mg/l) in our study lake. A slight increase in ambient UV-B dose rates was enough to cause neurobehavioral symptoms in pike larvae. However, the dose rates applied were inadequate to affect superoxide dismutase (SOD) or HSP70. While assessing the suggested risks due to increased UV, conclusions emphasize the importance of conducting field UV studies as supplements to laboratory experiments. We also recommend direct measurements of UV-radiation at sites where the target organisms are actually exposed.

Micronucleus evaluation in mitogen-stimulated lymphocytes of narrow-band (311 nm TL01) UVB-treated patients.

Narrow-band UVB (311 nm) lamps (TL01) are being increasingly used for phototherapy of psoriasis and other dermatoses, for their excellent effect compared with broad-band UVB sources and photochemotherapy. It is acknowledged that the TL01 lamp is probably two to three times more carcinogenic per minimum erythema dose than broad-band UVB, but the cumulative dose is considerably less than broadband UVB sources. Micronucleus (MN) test is used to detect both clastogenic (breaking) and aneugenic (abnormal segregation) effect of physical/chemical agents on chromosomes. The aim of this study is to evaluate MN frequencies in mitogen-stimulated lymphocytes of narrow-band UVB-treated patients. Frequency of micronuclei in 72 h cultivated/mitogen-stimulated lymphocytes of 36 patients (age 7-73 years, mean+/-SD: 25.33+/-18.54) have been evaluated at pretreatment and after 20, 40, 60 sessions of narrowband UVB treatment. While the beginning MN frequency +/-SD (%) was 1.07+/-0.63, it increased to 1.47+/-0.92, 1.47+/- 0.77, 1.41+/-0.31 corresponding, respectively, to 20, 40, 60 sessions. These sessions reciprocally correspond to 0.85+/-0.23, 2.97+/-0.72, 5.68+/-1.46 J/cm(2) doses of narrow-band UVB. Difference of MN frequency was statistically significant (P=0.002). Significant differences have been observed between the initial MN frequency and after that of 20, 40, 60 sessions (P=0.001, 0.004, 0.002, respectively). The results of this study show that narrow-band UVB treatment causes a detectable chromosome damaging effect.

Effect of the spectral range of a UV lamp on the production of cyclobutane pyrimidine dimers in human skin in situ.

Ultraviolet (UV) irradiation has a broad spectrum of biological effects and a capacity to initiate skin carcinogenesis through DNA damage. The effect of different wave bands of UV light on the production of DNA damage in human skin in situ was studied with a broadband UV-B lamp TL-12 and a narrowband UV-B lamp TL-01. Eight psoriasis patients participated in the study. Their minimal erythema dose was assessed separately for the two UV-B wave band ranges. Test areas of buttock skin were irradiated with the two spectrally differing lamps using erythemally equivalent UV doses of 40 and 80 mJ/cm2 CIE (Commission International de I'Eclairage). Punch biopsies were taken from the irradiated areas, and UV-induced DNA lesions (cyclobutane pyrimidine dimers, CPDs) in the skin were analyzed with a 32P high-performance liquid chromatography postlabelling method. No UV source-dependent differences in the induced levels of CPDs were detected in this study. CPD production with broadband TL-12 and narrowband TL-01 UV-B lamps in situ did not differ when erythemally equivalent UV doses were used. The preliminary result needs to be confirmed in a larger study.

Narrowband UVB therapy in the treatment of lichen planus.

Recently, UVB lamps with a peak emission around 311 nm have been used successfully for the treatment of many dermatologic diseases known to be treated with psoralen plus UVA (PUVA). Narrowband UVB (NBUVB) radiation causes less erythema and carcinogenicity with lower cumulative doses than PUVA, while the treatment response remains high. Lichen planus (LP) is a cell-mediated immune response of unknown origin. We present our results of NBUVB therapy administered to 10 LP patients. The sessions were administered three to four times weekly with an average cumulative dose of 17.7+/-1.6 J/cm2. Five patients responded completely, and four were partially responsive at the end of the 30th session. Three of the partially responsive cases responded completely at the 31st, 36th and 51st sessions, respectively. Clinical improvements observed in our study as well as the potential advantages of NBUVB imply that it is an inevitable treatment alternative for resistant cases of LP.

Effects of UVB preconditioning on heat tolerance of cucumber ( Cucumis sativus L.)

To study the preconditioning effects of exposure to UVB on heat tolerance (44–48 °C), 10-day-old cucumber ( Cucumis sativus L.) seedlings were irradiated for 6 days with a daily dose of either 3.4, 5.5 or 10.6 kJ m −2 of biologically effective UVB (UVB BE). Cellulose diacetate-filtered UVB lamps were used to supply UVB. These approximated low, ambient (medium) and twice-ambient (high) UVB doses, respectively, at 42°N latitude on a clear day during the summer solstice. A parallel group of control plants, held under polyester (PE)-filtered UVB lamps, received no UVB. UVB treatment increased the level of methanol-extractable UV-absorbing phenols in cotyledons and primary leaves. In a further HPLC analysis of acid-hydrolyzed leaf extract, eight peaks were separated. The two major peaks were co-chromatographed with authentic flavonoids, quercetin and kaempferol. The quercetin-like compound was preferentially enhanced in UVB-exposed plants. When the low and medium UVB-irradiated plants were later heat-stressed (46 °C, 1 h), survival improved by 112 and 82% and height growth increased by 35 and 40%, respectively, compared with controls that received no UVB. In contrast to low and ambient levels of UVB, which reduced membrane leakage, twice-ambient levels increased lipid peroxidation and electrolyte leakage. Although exposure to above-ambient levels of UVB was injurious, low and ambient doses of UVB promoted survival and growth of cucumber seedlings. Such a synergism between UVB and heat tolerance could be used to precondition seedlings grown in UVB-deficient greenhouses and may benefit plants under the predicted global warming scenario.

Photosynthesis and Growth in Seedlings of Five Forest Tree Species with Contrasting Leaf Anatomy Subjected to Supplemental UV-B Radiation

Abstract Seeds or cuttings of five forest tree species with contrasting leaf anatomies and shoot growth characteristics were cultivated under three different UV-B radiation regimes: ambient (7.5 kJ m-2 d-1 = 1×), two times ambient (2×), or three times ambient (3×) biologically effective UV-B radiation (UV-BBE) USA at the summer solstice, as calculated for Pullman, Washington. Experiments were conducted in glasshouses using a nonmodulated UV-B lamp system. Gas exchange was measured in recently mature leaves after six months of exposure. Photosynthetic rates were reduced by 2× and 3× treatments in Populus trichocarpa, and by the 3× regime for Pseudotsuga menziesii. Photosynthetic rates increased under the 2× treatment for Pseudotsuga menziesii and under the 3× treatment for Picea engelmannii. For Pinus ponderosa and Quercus rubra, photosynthetic rates were unchanged. Dark respiration increased under both 2× and 3× treatments for Picea engelmannii and by the 3× level in Quercus rubra, but was unaffected in the other species. Transpiration and stomatal conductance generally mirrored changes in photosynthesis. Water use efficiency increased for Pinus ponderosa (2× treatment) and Quercus rubra (2× and 3×), was reduced for Populus trichocarpa (2× & 3×), and remained unchanged in the other species. Enhanced UV-B radiation changed the shape of light response curves for all species. Quantum yields were unchanged for Pinus ponderosa, increased for Pseudotsuga menziesii (2×) and Picea engelmannii (2× and 3×) and were reduced in Populus trichocarpa (2×) and Quercus rubra (3×). Light compensation points were higher in the conifers (3×) and reduced in the angiosperms (2×). Chlorophylls were generally reduced by higher UV-B radiation in the conifers and for Populus trichocarpa (3×), but increased for Quercus rubra. Ultraviolet-absorbing compounds increased in the conifers and were unchanged in the angiosperms by enhanced UV-B radiation. Height growth increased (Pinus ponderosa, 3×; Quercus rubra, 2×), decreased (Picea engelmannii, 3×) or was unchanged (Pseudotsuga menziesii, Populus trichocarpa) by higher levels of UV-B radiation. Stem diameter and plant biomass were generally reduced, and shoot: root ratios increased for all species except Populus trichocarpa. Our results do not appear to support the hypothesis that inherent leaf anatomy or shoot growth pattern in these species directly determine the response of photosynthesis and growth to enhanced UV-B radiation. FOR SCI. 49(2):176–187.

UV-B induced production of MMP-2 and MMP-9 in human corneal cells

The purpose of this study was to determine the production of metalloproteinases (MMP) 2 and 9 following UV-B irradiation in human corneal epithelial cells and fibroblasts. Epithelial cells and fibroblasts were separated from human donor corneas and exposed to UV-B lamp irradiation for 20, 40, 80 and 120 s. Media samples were collected at 8, 24, 48 and 72 h and gelatinase A and B production was assayed by the ELISA test. Statistical significance of production was assessed by the paired t-test. Increased production of MMP-2 was found in human corneal fibroblasts in response to UV-B irradiation. A statistically significant production of MMP-2 was not observed in human corneal epithelial cells following UV-B exposure. We did not detect any increase in MMP-9 after irradiation in either epithelial cells or fibroblasts. MMP-2 is produced by the corneal fibroblasts in the acute phase after UV-B irradiation. MMP-9 is not released in vitro following UV-B irradiation damage and therefore does not directly participate in the pathophysiology of acute photokeratitis.

Demonstrating the influence of UV rays on living things

Ultraviolet (UV) rays are used in our daily lives for a variety of purposes, including detection of counterfeit banknotes and passports, sterilisation in hospitals and water treatment plants, and in medical treatments for diseases such as athlete's foot. However, a majority of students are unaware of UV rays and their effects. This practical introduces students to the different types of UV rays and their effects on living things, using appropriate teaching materials and equipment. The effects of exposure to UV-B (fluorescent) and UV-C (germicidal)lamps are demonstrated using bananas, duckweed and the fruit fly. Students can observe photo reactivation when living samples are exposed to the UV-C followed by irradiation with the UV-B lamp.

Influence of UVB radiation on hatching success of marine copepod Paracalanus parvus s. l.

Influence of UVB radiation (UVBR) on hatching success of the marine copepod Paracalanus parvus s. l. was determined in the laboratory using UVB lamps and the same effect was confirmed in the field under natural solar radiation condition. Hatching success antisigmoidally decreased with UVB dose. The dose-specific mortality of eggs was higher when the UVBR exposure included shorter wavelength than 290 nm. The UVB dose which decreased the hatching success by 50% (LD 50) showed that P. parvus egg was more sensitive to UVB than other previously reported marine copepods. UVB-induced influence was not a simple function of UVB dose but also of UVB exposure time. Relatively long exposure of low UVBR was more detrimental than a short exposure of high UVBR for equal cumulative doses. Sensitivity to UVB decreased with time after spawning. After exposure to solar UVBR, the hatching success decreased in a similar manner to the experiment using UVB lamps. The depths where 10% and 20% egg mortalities are expected were estimated as 1.4 and 3.0 m, respectively, assuming the median attenuation coefficient of UVBR at 305 nm in the water off Hokkaido (0.44 m −1) and the same solar UVBR during the experiment. Solar UVBR at mid-latitude area is estimated as a factor affecting the recruitment of P. parvus even under the present level of ozone concentration.

Quantitative assessment of narrow-band UVB induced tanning during phototherapy in Korea.

Narrow-band (TL-01) UVB lamps are being increasingly used for phototherapy of psoriasis and other dermatoses, for their excellent effect compared with broad-band UVB sources. Many patients receiving phototherapy have complained about the tanning effect of ultraviolet radiation especially in dark-skinned ones. So we wished to know the degree of pigmentation induced by phototherapy during narrow-band UVB treatment. A total of 20 psoriasis patients receiving narrow-band UVB phototherapy were included in this study. A Minolta spectrophotometer CM-2002 was used to measure pigmentation. All patients were evaluated for skin color every seventh day for 7 weeks. The L* value (luminance) gives information about the relative lightness ranging from total black to pure white. The a* value represents the balance between red and green, and the b* value between yellow and blue. The L* values which indicate luminance decreased continuously until the 5th week, when maximum tanning was obtained. Afterwards minimal change was observed until the 7th week. The change of a* and b* values also showed the pattern that was compatible with the above results. The mean individual typology angle of our subjects was 41.9 degrees, which indicated they fell into "light" group of constitutional skin color category. From this study, we found that pigmentation induced by narrow-band UVB phototherapy increased continuously until the 5th week and then did not progress. Our results provide standard data of skin pigmentation during narrow-band UVB phototherapy in Korean brown skin.

Effect of Carbon Black on UV stability of LLDPE films under artificial weathering conditions

Carbon Black is recognised for its ability to stabilise polyolefins against UV degradation. Linear low density polyethylene (LLDPE) 75 μm extruded films containing a variety of carbon black with different particle size, structure and concentrations were exposed to two accelerated artificial weathering devices, a xenon arc source, e.g. Xenotest 150S, and fluorescent tube sources with UVA and UVB lamps, under controlled temperature and humidity. The changes in physicochemical properties during exposures were studied using tensile testing, Fourier transform infrared (FTIR) spectroscopic and differential scanning calorimetric (DSC) methods. Presence of each carbon black shows significant improvement in UV stabilisation compared to clear films, especially for those with small particle sizes as expected. There is no consistent effect of carbon black structure on UV stabilisation for various particle-sized carbon blacks. An increase in carbon black concentration from 1.5 to 3.5% w/w also improved UV stabilisation. For UVA and UVB sources, presence of carbon black, while increasing carbonyl group generation with respect to unit loss in tensile property with respect to unfilled LLDPE, also appears to suppress Norrish Type II scissions at photochemically generated carbonyl centers in polymer chains. This is especially the case for the smallest (20 nm) particle sizes. Thus the photostabilising efficiency of carbon black is based on both physical surface-area-dependent UV absorption and photochemical activity. Under xenon arc exposure, however, this latter is minimal.

Inhibitory effect of different UV lamps on the infectivity of taeniid eggs.

The expanding distribution of alveolar echinococcosis in Hokkaido, Japan necessitates a search for control measures, particularly for killing Echinococcus eggs; and UV radiation is a potential tool. To determine the effective UV lamp and its optimum duration of exposure to inhibit the infectivity of taeniid eggs, three UV lamps (UVA, UVB and UVC) with peak emissions at different wavelengths were used to irradiate eggs of Taenia taeniaeformis. Irradiation was done in durations of 30, 90, 270, 810, 2,430 and 7,290 s. Infectivity of the irradiated eggs was tested by oral inoculation into rats. The inhibitory effect of the UV lamps at different exposure durations was determined by the reduction in the larval cyst establishment and by the delay of larval development. The UVC lamp (narrow peak at 254 nm) was found to be the most effective lamp at an exposure duration of more than 2,430 s (2,430 mJ/cm2), attaining 100% reduction. Also, shorter exposure durations produced a significant effect on the development of irradiated eggs in a greater percentage of small cysts (> 1 mm) among the metacestodes. Irradiation delayed the development of some cysts, as observed in histopathological sections. UVA and UVB lamps were not able to attain 100% reduction. It is concluded that the UVC lamp can be used as a tool in sterilizing taeniid eggs and is thus a promising method to control echinococcosis, although it may require a higher intensity of exposure.

Degradation of polymer coating systems studied by positron annihilation spectroscopy. IV. Oxygen effect of UV irradiation

AbstractThe effect of oxygen on the photodegradation of a polyurethane coating induced by accelerated UV irradiation was studied with two different light sources: 313‐nm UVB and Xe lamps. Doppler‐broadened energy spectra (DBES) and positron annihilation lifetimes were measured as a function of incident positron energy (0–30 keV) and irradiation time (0–100 h). The photodegradation of the coating was characterized in terms of subnanometer defect changes. Significant variations of the S parameter (a defect parameter from DBES) and the ortho‐positronium lifetime and intensity were observed as a function of oxygen concentration during exposure to UV irradiation. These results showed a significant enhancement in photodegradation due to the presence of oxygen, as indicated by a decrease in free volume and holes at the atomic level. Enhanced degradation in the presence of oxygen, as indicated by increased free‐radical production (observed with electron spin resonance spectroscopy), was also observed. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2035–2047, 2001