• Food Science and Preservation
• /
• v.24 no.3
• /
• pp.381-386
• /
• 2017

Ergocalciferol is known as having vitamin D activity. In this study, the effects of UV irradiation on the increase of egocalciferol content were investigated in 7 kinds of mushrooms, i.e, lily mushroom (Flammulina velutipes), oyster mushroom (Pleurotus ostreatus), young oyster mushroom (Pleurotus ostreatus), king oyster mushroom (Pleurotus eryngii), button mushroom (Agaricus bisporus), shiitake (Lentinula edodes), and wood ear mushroom (Auricularia auricula-judae). Mushrooms which were not exposed to UV light contained negligible amount of ergocalciferol in all kinds of tested mushrooms, but UV irradiation increased their content of ergocalciferol. Of UV A, B and C, UV B light was the most effective to increase ergocalciferol contents. In mushrooms, the increase in ergocalciferol content occurred only in the peel within 1 mm depth from the surface, which was directly exposed to the UV light. Therefore, when fresh whole mushrooms were irradiated with UV light, lily mushroom, the mushroom with a larger surface area compared to volume, such as lily mushroom, was more favorable in producing ergocalciferol. On the other hand when the mushrooms were freeze-dried and cut, the mushrooms with a higher ergosterol, such as king oyster mushroom, shiitake or button mushroom, were more favorable in generating ergocalciferol.

• The Korean Journal of Pesticide Science
• /
• v.3 no.3
• /
• pp.20-26
• /
• 1999

This study was to investigate the potential degradation of a herbicide paraquat by Fenton reagents(ferric ion and hydrogen peroxide) under UV light irradiation(365 nm) in an aqueous solution. When $10{\sim}500$ mg/L of paraquat was reacted with either ferric ion or hydrogen peroxide in the dark or under UV light, no degradation was occurred. However, the simultaneous application of both ferric ion(0.8 mM) and hydrogen peroxide(0.140 M) in paraquat solution(500 mg/L) caused dramatic degradation of paraquat both in the dark (approximately 78%) and under UV light(approximately 90%). The reaction approached an equilibrium state in 10 hours. In the dark, when $0.2{\sim}0.8$ mM ferric ion was added, $20{\sim}70%$ paraquat of $10{\sim}500$ mg/L was degraded, regardless of hydrogen peroxide concentrations($0.035{\sim}0.140$ M), while under UV light, 95% of 10 and 100 mg/L paraquat was degraded regardless of ferric ion and hydrogen peroxide concentrations. At paraquat concentration of 200 and 500 mg/L, paraquat degradation increased with increasing ferric ion concentrations as in the dark. However the increase in hydrogen peroxide concentration did not affect the extent of paraquat degradation. The initial reaction rate constants(k) for paraquat degradation ranged from 0.0004 to 0.0314, and 0.0023 to 0.0367 in the dark and under UV light, respectively. The initial reaction rate constant increased in proportion to the increase in ferric ion concentration in both conditions. The half-lives of paraquat degradation(t1/2) were 20 - 1,980 and 19 - 303 minutes in the dark and under UV light, respectively. This study indicates that Fenton reagents under UV light irradiation are more potent than in the dark in terms of herbicide paraquat degradation in an aqueous solution.

• Clean Technology
• /
• v.4 no.1
• /
• pp.35-44
• /
• 1998

Photodecomposition behaviors of volatile organic compounds (VOCs ; benzene, toluene, ethylbenzene and xylenes) over UV irradiation and UV irradiation with $TiO_2$ powder catalyst were studied and the extent of degradation were also investigated under various reaction conditions. The reactions were conducted in a quartz annular reactor equipped with a medium pressure mercury lamp. As a result, the extents of degradation were 92% for toluene and ethylbenzene, 83% for benzene, and 82% for xylenes under UV irradiation. And they were 92% for toluene, 82% for xylene and ethylbenzene, and 53% for benzene under UV irradiation with $TiO_2$ powder. Analyses of reacted samples by FID-gas chromatograph with Purge & Trap concentrator and GC-MS indicated that the aromatics formed many intermediates.

• Horticultural Science & Technology
• /
• v.30 no.5
• /
• pp.493-500
• /
• 2012

In order to confirm the possibility of UV utilization as a means for disease protection in grapevine the stilbene contents and the disease incidence in UV irradiated leaves were investigated. UV irradiation significantly increased the contents of resveratrol, piceatannol and piceid, in them, resveratrol and piceid showed in vitro inhibition of spore germination and mycelium growth of Botrytis cinerea. The accumulation of both the stilbenes in UV irradiated leaves seems to be enough to inhibit the B. cinerea growth, since the formation of necrotic spot on the leaves was considerably inhibited when they were inoculated with the conidial spores of B. cinerea. However the stilbenes were accumulated only in the leaves exposed directly to UV showing a limited translocation ability of the compounds. Thus it would be necessary to develop a method to evenly irradiate the entire crown of plant with UV in order to expect to protect them from disease by UV irradiation.

• Polymer(Korea)
• /
• v.26 no.2
• /
• pp.209-217
• /
• 2002

We studied the mechanism of orientation of polyimide molecules which were irradiated by polarized UU (PUV) using polarized Fourier transform infrared (FT-IR) spectroscopy and ultraviolet (UV) spectroscopy, According to the measured UV spectra, we found PI films mainly absorb UV light less than 350 nm wavelength, therefore, UV light less than 360 nm induces photochemical reaction of PI. PUV irradiation of PI films caused decrease of all peak intensities in the FT-IR spectra. except the newly formed broad peak at $3244 cm^{-1}$, due to degradation of the PI molecules. The remaining PI molecules after photo-degradation showed predominantly perpendicular molecular orientation to the irradiated PUV polarization direction, due to the preferential degradation of PI molecules parallel to irradiated PUV polarization direction. However the rubbing of PI films induced reorientation of the PI molecules parallel to the rubbing direction. We also investigated the alignment of the liquid crystal by rubbing or PUV irradiation. Liquid crystals align perpendicular to the PUV polarization direction and parallel to the rubbing direction.

• Elastomers and Composites
• /
• v.41 no.3
• /
• pp.182-193
• /
• 2006

The retardation effects of a new polymeric UV stabilizer, DGEBA-HALS, on the UV degradation of SBR and NR were investigated in this study. The UV degradation behaviors of three different rubber compounds, without any photostabilizer and with commercial Cyabsorb UV-3529 and DGEBA-HALS, were compared. Also, the physical characteristics such as Young's modulus, tensile strength, blow-off deformation and crosslink density were examined. The Young's modulus was increased by UV irradiation for all samples, and the tensile strength, after UV irradiation, of the compound with UV stabilizer was better than that of the compound without stabilizer. Especially, the tensile strength of UV irradiated NR was improved by adding DGEBA-HALS. The results of blow-off deformation were in accord with those of Young's modulus. The degree of transmission of SBR compounds obtained from UV-vis transmission spectra was improved about 4% by adding the UV stabilizer. Commercial Cyabsorb UJV-3529 and DGEBA-HALS showed similar trends of transmission. The SEM photographs of SBR surface showed that the size of cracks created by UV irradiation became smaller by adding UV stabilizer. In particular, it is observed that the stabilization effect of DGEBA-HALS was better than that of commercial Cyabsorb UV-3529.

• Journal of Korean Society of Environmental Engineers
• /
• v.22 no.7
• /
• pp.1307-1318
• /
• 2000

The purpose of this study is to investigate the degradation characteristics of oxalic acid and citric acid by $UV/H_2O_2$ oxidation. For this purpose, the effects of pH, $H_2O_2$ dosage and the concentration of each compounds on the degradation of oxalic acid and citric acid by $UV/H_2O_2$ were investigated. Oxalic acid was effectively degraded at the wavelength of 254 nm, while the degradation efficiency of citric acid was very low at the same wavelength. It was also found that both organic substances were not degraded by the injection of $H_2O_2$ only. The optimum pH of degradation of oxalic acid and citric acid was 4 and 4 to 6, respectively. In the case of $UV/H_2O_2$ oxidation, the degradation efficiency was increased by increasing $H_2O_2$ dosage. The degradation efficiency decreased when the dose of $H_2O_2$ exceeds 200 mg/L. From these results, it can be concluded that the optimum reaction conditions for the degradation of oxalic acid and citric acid by $UV/H_2O_2$ oxidation were pH 4 and 200mg/L of $H_2O_2$.

• Journal of Nutrition and Health
• /
• v.49 no.2
• /
• pp.63-71
• /
• 2016

Purpose: Skin pH, an indicator of skin health, is maintained by various organic factors, which include lactate, free amino acid (FAA), and free fatty acid (FFA). As skin ages or with illness, skin pH becomes less acidic, and functional food has been developed to maintain the acidic pH of skin. In this study, we determined the dietary effect of green tea extract (GTE) on skin pH of photo-aged mice, as measured by epidermal levels of lactate, FAA, and FFA. The protein expression and activity of lactate dehydrogenase (LDH), an enzyme of pyruvate reduction for lactate generation, was further determined. Methods: Albino hairless mice were fed a control diet (group UV+) or a diet with 1% GTE (group GTE) in parallel with UV irradiation for 10 weeks. A normal control group was fed a control diet without UV irradiation for 10 weeks (group UV-). Results: Skin pH was higher (less acidic) in group UV+ than in group UV-. In parallel, epidermal levels of lactate and FFA, as well as of LDH protein expression and activity, were reduced in group UV+. Dietary supplementation of GTE (group GTE) reduced skin pH to similar to the level of group UV-, and inversely increased epidermal levels of lactate, LDH protein expression and activity, but not of FFA. Although epidermal levels of FAA were similar in groups UV- and UV+, it was increased in group GTE to a level higher than in group UV-. In further analysis of major FFA, epidermal levels of palmitic acid [16:0], oleic acid [18:1(n-9)], and linoleic acid [18:2(n-6), but not of stearic acid [18:0] in group GTE were similar to or lower than those in group UV+. Conclusion: Dietary GTE normalized skin pH with increased levels of lactate and FAA, as well as with increased protein expression and activity of LDH in the epidermis of UVB irradiated hairless mice.

• Journal of Adhesion and Interface
• /
• v.5 no.4
• /
• pp.1-8
• /
• 2004

UV-curable pressure sensitive adhesives were prepared by blending acrylic copolymer, copolymerized with butyl acrylate, acrylic acid and methyl methacrylate by solution polymerization, and trimethylolpropane triacrylate. The PSAs were evaluated by adhesion strength with varying UV dose, and also glass transition temperature ($T_g$) of PSAs were measured. When exposed on UV irradiation, the PSAs showed the decreased adhesion strength and increased $T_g$. And following UV irradiation, the PSAs did not leave any residue on wafer after peel off PSA.

• Polymer(Korea)
• /
• v.32 no.4
• /
• pp.377-384
• /
• 2008

In this study, the microsphere silicone polymer beads were synthesized by UV irradiation and alkoxy hydrolysis. The coefficient of variation (CV) of microsphere silicone polymer beads were decreased with increasing UV intensity, reaction time. The mean particle diameter, refractive index, and pH value were $4.1{\mu}m$, 1.43 and 7.5, respectively. Also, the true and bulk specific gravity, moisture content were 1.30, and 0.40, below 2%. The mean particle diameter and CV were the lowest at 0.1 wt% hexamethyldisilazane (HMDS) and their roundnesses were $0.95{\sim}0.98{\mu}m$ values. The particle dispersion index of microsphere silicone polymer beads was 4.92 at 450 W, 90 min and the yield was increased to 11.3% at 20 wt% methyltrimethoxysilane (MTMS). The mean particle diameter was decreased with increasing the stirring rate and reaction temperature.