• Electrical & Electronic Materials
• /
• v.10 no.5
• /
• pp.461-466
• /
• 1997

In this paper, we developed the new non-rubbing liquid crystal (LC) alignment techniques in the cell with slanted non-polarized ultraviolet (UV) light irradiation on polyimide (PI) film. It is shown that the uniform alignment for nematic (N) LC is obtained by using slanted non-polarized UV light irradiation on PI surface. We successfully obtained that the pretilt angle of NLC is generated about 3.3 degree in the cell with slanted non-polarized UV light irradiation with 70 degree on PI surface, for the first time. It is considered that the pretilt angle generation in NLC is attributed to interaction between the LC molecular and the PI, which is broken the polymer by slanted non-polarized UV irradiation. Therefore, we concluded that the uniform LC alignment is attributed to anisotropic dispersion force due to photo depolymerization with slanted non-polarized UV light irradiation on PI surface.

• Journal of Microbiology and Biotechnology
• /
• v.33 no.4
• /
• pp.419-429
• /
• 2023

Ultraviolet C (UV-C, 200-280 nm) light has germicidal properties that inactivate a wide range of pathogenic and spoilage microorganisms. UV-C has been extensively studied as an alternative to thermal decontamination of fruit juices. Recent studies suggest that the efficacy of UV-C irradiation in reducing microorganisms in fruit juices is greatly dependent on the characteristics of the target microorganisms, juice matrices, and parameters of the UV-C treatment procedure, such as equipment and processing. Based on evidence from recent studies, this review describes how the characteristics of target microorganisms (e.g., type of microorganism/strain, acid adaptation, physiological states, single/composite inoculum, spore, etc.) and fruit juice matrices (e.g., UV absorbance, UV transmittance, turbidity, soluble solid content, pH, color, etc.) affect the efficacy of UV-C. We also discuss the influences on UV-C treatment efficacy of parameters, including UV-C light source, reactor conditions (e.g., continuous/batch, size, thickness, volume, diameter, outer case, configuration/arrangement), pumping/flow system conditions (e.g., sample flow rate and pattern, sample residence time, number of cycles), homogenization conditions (e.g., continuous flow/recirculation, stirring, mixing), and cleaning capability of the reactor. The collective facts indicate the immense potential of UV-C irradiation in the fruit juice industry. Existing drawbacks need to be addressed in future studies before the technique is applicable at the industrial scale.

• International Journal of Industrial Entomology and Biomaterials
• /
• v.17 no.1
• /
• pp.121-124
• /
• 2008

The caspase family proteins play an important role in programmed cell death (apoptosis). To date, the expression profiles of the caspase family genes in Bombyx mori (Bm) are poorly known. In this study, we examined the expression profiles of two novel Bm caspase family genes (ice-2 and ice-5), the potential change of the mitochondrial membrane and the morphology in Bm cells after stimulation of ultraviolet (UV) irradiation. The results showed the potential change of the mitochondrial membrane occurred at 5 hours after UV irradiation treatment. Analysis of fluorescent quantitative RT-PCR demonstrated that both the ice-2 and ice-5 might be involved in UV induced apoptosis in Bm cells. Notably, after UV irradiating, expression pattern of ice-2 and ice-5 were remarkably different. The ice-2 gene was highly expressed at two time points, 0.5 and 5 hours after UV stimulating, while the expression level of ice-5 only peaked at 5 hours after UV stimulating. It indicated that apoptosis induced by UV irradiation was involved in the mitochondrial pathway and the two isoforms of Bm ice may act but play different role during the apoptosis of Bm cells.

• Journal of the Korea Furniture Society
• /
• v.26 no.4
• /
• pp.428-434
• /
• 2015

In this study, we received each wood plastic composites (WPC) from three manufacturers. These WPCs were evaluated regarding their physical and mechanical properties of both before and after accelerated weathering by ultraviolet (UV) irradiation. The total time of exposure of the WPCs to UV irradiation was 1800 h. The water absorption, volumetric swelling and shrinkage of WPCs did not affected by UV irradiation. Among the mechanical properties, there was no significant differences in bending strength and screw withdrawal resistance of UV treated WPCs compared with those of reference WPCs. However, surface hardness of WPCs showed decrease under UV irradiation. Stereoscopic microscopy observation revealed deterioration of the surface layer polymer in all weathered WPCs by UV. Exposure of the WPCs to UV irradiation caused decomposition and disappearance of the polymer layer. From this result, we can estimate that damage of polymer by UV led to a decrease in the surface hardness of the WPCs. The wood flours retained original shape after accelerated weathering by UV irradiation.

• Journal of Korean Society of Water and Wastewater
• /
• v.20 no.5
• /
• pp.755-761
• /
• 2006

Recently, there is growing interest in ultraviolet (UV) irradiation as a disinfection technic in drinking water production due to its effectiveness to inactivate microorganisms such as Crytosporidium parvum without forming disinfection byproducts. However, UV disinfection is known for its drawback such as photoreactivation. Despite many works concerning the photoreactivation, most of works were focused on indicator or non pathogenic microorganisms. The objective of this study is to examine the photoreactivation of Pseudomonas aeruginosa which is an opportunistic pathogen as UV radiation by LP and MP UV lamp was applied. The result showed that P. aeruginosa had high photo repair efficiency regardless of the type of UV irradiation. Both of the effective log repair values of LP and MP UV irradiation were found approximately 2.6 log. In addition, photo repaired P. aeruginosa was not significantly different in forming biofilm in comparison with non treated P. aeruginosa.

• Food Science of Animal Resources
• /
• v.34 no.6
• /
• pp.815-821
• /
• 2014

The effects of ultraviolet (UV) radiation were investigated with regards to the microbial growth inhibitory effect on the shelf life of Korean native cattle (Hanwoo) beef prior to refrigerated storage. The Hanwoo samples were exposed to UV radiation ($4.5mW/cm^2$) for 0, 5, 10, 15, and 20 min. The UV-irradiated beef that was exposed for 20 min showed significantly reduced mesophilic and psychrotrophic bacterial populations to the extent of approximately 3 log cycles, as compared to that of non-irradiated beef. About 2.5 Log CFU/g of mesophilic bacteria were different compared with UV-irradiated and non-irradiated meat. UV irradiation showed the most significant growth inhibition effects on mesophilic and psychrotrophic bacteria. Coliform and Gram-negative bacteria were also reduced by 1 log cycle. The population of L. monocytogenes, S. Typhimurium, and E. coli O157:H7 decreased significantly to 53.33, 39.68, and 45.76% after 10 min of UV irradiation. They decreased significantly to 84.64, 80.76, and 84.12%, respectively, after 20 min of UV irradiation. The results show that UV irradiation time and the inhibitory effect were proportional. These results verified that UV radiation prior to refrigeration can effectively reduce the number of pathogenic bacteria on the surface of meat and improve the meat's microbial safety.

• Journal of Conservation Science
• /
• v.27 no.2
• /
• pp.191-199
• /
• 2011

A study was done to compare the properties of artificially deteriorated silk with ultraviolets for reinforcing of loss area of paintings on silk. Deteriorated surface of raw silk irradiated by long-wavelength ultraviolet(UV-A) than short-wavelength ultraviolet(UV-C) was similar to naturally aged raw silk. UV-A irradiation raw silk was slowly decreased in tensile tenacity and elongation and lowered in yellowness index than that of UV-C. Water content of UV-A irradiation raw silk than that of UV-C was higher. UV-A irradiation raw silk had no problem in dyeing and inpainting for conservation because of low yellowness index. UV-C irradiation raw silk was brittle, but UV-A irradiation raw silk was seemed to tough and similar to naturally aged raw silk. Korean painting conservator estimated that UV-A irradiation raw silk was more proper for reinforcing of loss area of paintings on silk than that of UV-C.

• Journal of Korean Society of Water and Wastewater
• /
• v.33 no.6
• /
• pp.469-480
• /
• 2019

This study was conducted to evaluate the degradation and mineralization of PPCPs (Pharmaceuticals and Personal Care Products) using a CBD(Collimated Beam Device) of UV/H₂O₂ advanced oxidation process. The decomposition rate of each substance was regarded as the first reaction rate to the ultraviolet irradiation dose. The decomposition rate constants for PPCPs were determined by the concentration of hydrogen peroxide and ultraviolet irradiation intensity. If the decomposition rate constant is large, the PPCPs concentration decreases rapidly. According to the decomposition rate constant, chlortetracycline and sulfamethoxazole are expected to be sufficiently removed by UV irradiation only without the addition of hydrogen peroxide. In the case of carbamazepine, however, very high UV dose was required in the absence of hydrogen peroxide. Other PPCPs required an appropriate concentration of hydrogen peroxide and ultraviolet irradiation intensity. The UV dose required to remove 90% of each PPCPs using the degradation rate constant can be calculated according to the concentration of hydrogen peroxide in each sample. Using this reaction rate, the optimum UV dose and hydrogen peroxide concentration for achieving the target removal rate can be obtained by the target PPCPs and water properties. It can be a necessary data to establish design and operating conditions such as UV lamp type, quantity and hydrogen peroxide concentration depending on the residence time for the most economical operation.

• Applied Biological Chemistry
• /
• v.51 no.4
• /
• pp.276-280
• /
• 2008

To elucidate the effects of ultraviolet (UV) irradiation on molecular properties of ovalbumin, the molecular weight profile, secondary structure and tertiary structure of proteins were examined after irradiation by UV with 254 nm wavelength for 4, 8, 16 and 32 hrs, respectively. UV irradiation of protein solution caused the disruption on the native state of protein molecules. SDS-PAGE and gel permeation chromatography indicated that radiation caused initial fragmentation of polypeptide chains and as a result subsequent aggregation due to cross-linking of protein molecules. Circular dichroism (CD) study showed that UV irradiation caused the change on the secondary structure resulting in decrease of helical structure or compact denature on structure of protein depending on irradiation period. Fluorescence spectroscopy indicated that irradiation quenched the emission intensity excited at 280 nm. These results suggest that UV irradiation affect the molecular properties of ovalbumin and may have potential as a means to change the antigenicity of protein allergen.

• Journal of the Korea Society of Computer and Information
• /
• v.26 no.2
• /
• pp.119-124
• /
• 2021

In this study, we propose an antibacterial efficiency according to the direction of UV irradiation. In the experiment, we measured the effective irradiation angle of UVC using S.aureus, a Gram-positive bacterium, and the variation of the antibacterial region according to the distance according to the direction of ultraviolet irradiation. Also, as a method to increase the antibacterial efficiency during horizontal irradiation of ultraviolet rays, we tested reflecting leaking UVC. As a result, the angle of ultraviolet irradiation was measured smaller than the product description, and in the case of the antibacterial area according to the direction of ultraviolet irradiation, the distance from the sample was increased during vertical irradiation, and the antibacterial area was increased as the distance from the sample was closer during horizontal irradiation. In addition, it was confirmed that antibacterial efficiency can be increased by reflecting leaking UVC during horizontal irradiation of UVC.