• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.35-60
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• 1997

Physical properties of composite resins such as strength, resistance to wear, discoloration, etc, depend on the degree of conversion of the resin components. The clinical behavior of restorative resins varies brand to brand. Part of this variation is associated with the filler and differences in the polymer matrix. The polymer matrix of resins may differ because the involved monomers are dissimilar and because of variation in the catalyst system. The purpose of this study was to evaluate the degree of conversion of the composite resins according to the depth of cure and light curing time. 7mm diameter cylindrical aluminum molds were filled with each of five different hybrid light curing composite resins(Z-100, Charisma, Herculite XRV, Prisma TPH, Veridonfil) on the thin resin films. The molds were 1mm, 2mm, 3mm, 4mm, and 5mm in depth to produce resin films of various heights. Each sample was given 20sec, 40sec, and 60sec illumination with a light source. The degree of conversion of carbon double bonds to single bonds in the resin films was examined by means of Fourier Transform Infrared Spectrometer. The results were obtained as follows; 1. There was difference in the degree of conversion among five light curing composite resins according to the depth of cure for 20sec, 40sec, and 60sec illumination with light source with statistical significance(P<0.05). 2. Five light curing composite resins show lower degree of conversion at surface of the resin than depth of 1mm. 3. The degree of conversion of five light curing composite resins was siginificantly reduced from the maximum for the resin film when the light passed through as little as 1mm of each composite. 4. The degree of conversion of five light curing composite resins decrease significantly at the depth of 4mm, and polymerization was not occured at the depth of 5mm except for Prisma TPH. 5. The degree of conversion of five light curing composite resins was increased with increased light curing time, and there was no significant differences in the degree of conversion above 4mm in Z-100, 3mm in Charisma, and at depth of 5mm in Herculite XRV and Veridonfil(P>0.05).

• The Korea Journal of Herbology
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• v.31 no.5
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• pp.93-98
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• 2016

Objectives : Hwangheuk-san is a complex prescription composed of oriental traditional medicine and has been reported for antioxidant, antimicrobial and anticancer effects in the recent study. Methicillin-resistant Staphylococcus aureus (MRSA) is one of important causes of fatal infectious diseases such as septicemia, endocarditis, toxic shock syndrome, pneumonia, skin and soft tissue infections (SSTIs). S. aureus is reported as being for a variety of human diseases and its epidemiological relevance is mainly due to their ability of becoming highly resistant to common antimicrobials such as tetracycline, penicillin, cphalosporin and aminoglycoside. The objective of this study is to determine the antimicrobial effect of Hwangheuk-san ethanol extracts (HHS) and synergistic effects with antibiotics oxacillin against MRSA.Methods : The antimicrobial activity of HHS was measured by the disc diffusion method, broth microdilution method and the checkerboard dilution test, time-kill curve assay was performed to investigate synergistic effects with antibiotics oxacillin against MRSA.Results : HHS showed antimicrobial activity against MRSA with a MIC value of 125 ㎍/㎖. In the checkerboard test, the interaction of HHS with antibiotics oxacillin produced almost synergy or partial synergy against MRSA. This study showed that HHS reduced the MICs of oxacillin tested, and a remarkable antibacterial effect of HHS, with membrane permeability enhancers.Conclusions : These results suggest that HHS has the antimicrobial effect and synergistic effects with antibiotics oxacillin against MRSA. This study thus can be a valuable source for the development of a new drug with low MRSA resistance.

• Polymer(Korea)
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• v.35 no.5
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• pp.467-471
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• 2011

PET bottle is manufactured by blow molding the preform, which is molded by injection molding. The neck part of the preform of PET bottle for juice or grain-based beverage is crystallized before blowing to improve heat resistance at the entrance of the bottle. However, residual stress, developed during injection molding of preform, prevents the crystallization. In order to release the residual stress in the preform, the preform is annealed after the injection molding. If the residual stress is reduced by optimizing the injection molding conditions of preform the annealing time would be shortened. In this study, the optimum conditions for minimizing the residual stress and increasing dimensional accuracy of the injection molded preform are suggested through CAE analysis. In order to optimize the molding conditions, minimizing residual stress and shrinkage, computer simulations have been carried out with help of design of experiment scheduling. Injection temperature, initial packing pressure and filling time were selected for control parameters. Residual stress was affected by injection temperature and filling time. Shrinkage was affected by injection temperature. It was found that maximum residual stress, distribution of residual stress and shrinkage were decreased by 22%, 40% and 25%, respectively at an optimum molding condition compared with the results of previous molding condition.

• Elastomers and Composites
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• v.48 no.2
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• pp.172-179
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• 2013

Impact modifier reinforced polymers are frequently used. In this study, Izod impact test has been simulated to analyze the mechanism of impact reinforcement of Nylon6 which contains impact modifier. The modeling of rubber particles added to Nylon6 as an impact modifier has been attempted. Based on the modeling, simulation of Izod impact test has been performed to observe the distribution and direction of stress at the cross-section of impact specimen. Three computer simulation models for Nylon6 were investigated. Those were without impact modifier, containing impact modifier without surface treatment, and containing impact modifier with surface treatment in the Nylon6. Simulation results showed that the stress which originated at the notch surface propergated to the inside of specimen round a impact modifier. In addition to that, impact modifier reinforced Nylon6 specimen showed low stress ditribution in the cross-section specially at notch surface. Principal stress in perpendicular direction to crack was also lowered in impact modifier reinforced Nylon6. These enhanced impact resistance reduced and crack propergations. Through this study it was realized that the computer simulation can be utilized to investigate the property enhacement of composite materials.

• Journal of Life Science
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• v.25 no.3
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• pp.263-268
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• 2015

Coelomocytes are specialized cells that continually and nonspecifically scavenge fluid from the body cavity through endocytosis in Caenorhabditis elegans. Our previous study revealed that coelmocytes were specifically required for dietary-restriction-induced longevity in C. elegans. In the present study, we examined the effect of coelomocyte ablation on the response to environmental stressors and reproduction in C. elegans. Coelomocytes were ablated using diphtheria toxin specifically expressed in coelomocytes. After exposing worms to 20 J/cm²/min of ultraviolet irradiation in vivo, the survival of the worms was monitored daily. To examine their response to heat stress, their survival after 10 h of 35℃ heat shock was measured. Oxidative stress was induced using paraquat, and the susceptibility to oxidative stress was compared between wild-type control and coelomocyte-ablated worms. The total number of progeny produced was counted, and the time-course distribution of the progeny was determined. The worms with ablated coelomocytes showed reduced resistance to ultraviolet irradiation, but the ablation of coelomocytes had no effect on their response to heat or oxidative stress. The number of progeny produced during the gravid period was significantly decreased in the coelomocyte-ablated worms. These findings suggest that coelomocytes specifically modulate the response to ultraviolet irradiation and are required for normal reproduction in C. elegans. The findings could contribute to understanding of the mechanisms underlying dietary-restriction-induced longevity.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.580-586
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• 1996

Gelatinization behavior and morphology of epichlorohydrin-crosslinked potato starches (XPs) were investigated. Native potato starch showed a very steep single stage swlling pattern, but crosslinked starches showed various patterns with the degree of crosslinking. Swelling power, solubility and light transmittance were reduced drastically as the degree of crosslinking increased. Brabender initial pasting temperature and peak temperature of crosslinked starches increased because the crosslinking reinforces the intermolecular net work of the starches. Although the swelling of the potato starch granule was inhibited by crosslinking as compared to that of the native one, Brabender peak viscosities (6.5% w/v, db) were on the order of 2,500 units for the native potato starch, 3,700 for the XP with 2.300 anhydroglucose units per crosslinking (AGU/CL) and 3,400 for the XP with 2,100 AGU/CL, due to the decreased breakdown of the swollen granule resulting from the resistance to heat and shear. The XP with 1,900 AGU/CL, however, did not show the peak viscosity and the viscosity was on the order of 500 units because of the excessive unhibition of the swelling. Unlike the native potato starch, 6.5%(m/v, db) pastes of the crosslinked potato starches could form gels, which could be predicted from the Brabender setback and consistency index. When the degree of crosslinking is low, random contraction and radial swelling of the granule was possible. As the degree of crosslinking increased, morphological change became similar to the single dimensional tangential swelling observed from the lenticular wheat starch. These morphological change during heating in excess water explained the gelatinization behaviors of crosslinked starches tested.

• Food Science and Biotechnology
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• v.15 no.1
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• pp.63-69
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• 2006

The primary objective of this study is to determine whether a diet supplemented with brown rice koji (BRK) results in a reduced stress response in rats and mice. BRK, which has been suggested as a candidate for use as a stress- and fatigue-fighting supplement, was compared with red ginseng extract (RG) for its stress-reducing potential. The animals in this study were divided into no-stress, stress, RG, and BRK groups of 8 to 10 animals each. Stress was induced by means of immobilization (being restrained in plastic tubes for 30 min and electroshock (0.5 mA in mice or 2 mA in rats for 5 min). The no-stress group was not exposed to stress. Rats in the RG group received oral doses of 200 mg RG extract/kg body weight daily. The BRK group was fed a 30% BRK diet and exposed to stress. Animals were given supplements for 7 days before being exposed to stress, and then were given supplements for 5 days with exposure to stress. When the stress exposure ended, the animals were observed for stress-related changes in behavior and their plasma corticosterone levels were measured. BRK supplementation was associated with a partial blockade of the effects of stress on locomotion and elevated plus-maze test results in rats and mice. It was also associated with a partial reduction in stress-induced behaviors such as freezing, burrowing, smelling, face-washing, and rearing. BRK supplementation did not have a significant effect on plasma corticosterone levels, which were increased in the animals exposed to stress (p<0.01). The mice in the RG group received RG in water (2 mg RG/ mL $H_2O$), and the BRK group received a 30% BRK diet (weight) for 7 days. Both groups were evaluated for signs of fatigue. BRK supplementation increased endurance, as indicated by time on the rota-rod, in cold water, and on the horizontal wire. These results suggest that BRK supplementation partially protects the animal from the effects of stress and may also contribute to resistance to fatigue on physical exertion.

• Proceedings of the Microbiological Society of Korea Conference
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• 2000.05a
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• pp.23-36
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• 2000

Japanese encephalitis virus (JEV) is the causative agent of a mosquito-borne encephalitis and is transmitted to human via persistently infected mosquito vectors. Although the virus is known to cause only acute infection, there were reports that showed neurological sequelae, latent infection in peripheral mononuclear cells, and recurrence of the disease after acute encephalitis. Innate resistance of certain cell lines, abnormal SN1 expression of the virus, and anti-apoptotic effect of cullular bcl-2 have been suggested as probable causes of JEV persistence even in the absence of defective interfering (DI) particles. Although possible involvement of DI particles in JEV persistence was suggested, neither has a direct evidence for DI presence nor its molecular characterization been made. Two questions asked in this study are whether the DI virus plays any role in JEV persistent infection if it is associated with and what type of change(s) can be made in persistently infected cells to avoid apoptosis even with the continuous virus replication, DI-free standard stock of JEV was infected in BHK-21, Vero, and SW13 cells and serial high multiplicity passages were performed in order to generate DI particles. There different-sized DI RNA species which were defective in both structural and nonstructural protein coding genes. Rescued ORFs of the DI genome maintained in-frame and the presence of replicative intermediate or replicative form RNA of the DI particles confirmed their replication competence. On the other hand, several clones with JEV persistent infection were established from the cells survived acute infections during the passages. Timing of the DI virus generation during the passages seemed coincide to the appearance of persistently infected cells. The DI RNAs were identified in most of persistently infected cells and were observed throughout the cell maintenance. One of the cloned cell line maintained the viral persistence without DI RNA coreplication. The cells with viral persistence released the reduced but continuous infectious JEV particle for up to 9 months and were refractory to homologous virus superinfection but not to heterologous challenges. Unlike the cells with acute infection these cells were devoid of characteristic DNA fragmentation and JEV-induced apoptosis with or without homologous superinfection. Therefore, the DI RNA generated during JEV undiluted serial passage on mammalian cells was shown to be biologically active and it seemed to be responsible, at least in part, for the establishment and maintenance of the JEV persistence in mammalian cells. Viral persistence without DI RNA coreplication, as in one of the cell clones, supports that JEV persistent infection could be maintained with or without the presence of DI particles. In addition, the fact that the cells with JEV persistence were resistant against homologous virus superinfection, but not against heterologous one, suggests that different viruses have their own and independent pathway for cytopathogenesis even if viral cytopathic effect could be converged to an apoptosis after all.

• Journal of Korean Society of Environmental Engineers
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• v.27 no.5
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• pp.519-524
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• 2005

Due to the low C/N ratio of domestic wastewater characteristic, addition of external carbon source for the effective N and P removal is necessary. High organic content of food waste can be used for the external carbon source in biological nutrient removal processes, The applicability of condensate of food waste (CFW), which is produced during the high-rate fermentation process, was examined in membrane bioreactor for the nutrient removal. Under the various operating conditions, nutrient removal efficiencies and membrane fouling characteristics were evaluated using synthetic wastewater. From nitrate utilization rate (NUR) test, denitrification rate was 0.19 g $NO_3-N/g$ VSS/day. With the addition of CFW increased, average removal efficiencies of T-N and T-P could be increased up to 64% and 41%, respectively. Also the optimal retention time was 3 hr/5 hr for anoxic/aerobic reactor. When applied to real sewage, membrane fouling resistance was increased up to 60%, which could be reduced from $10.4{\times}10^{12}m^{-1}$ to $5.9{\times}10^{12}m^{-1}$ with the control of influent suspended solid concentration. In summary, it was suggested that CFW could be used as an economical and effective carbon source for membrane assisted biological N and P removal.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5D
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• pp.483-492
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• 2012

The early setting time of concrete is an important factor determining the slip up velocity of the slip-form system. Accordingly, need is for a technique evaluating the early setting time in order to secure the safety of the slip-form system and the construction quality of concrete. This paper intends to estimate the early setting time by evaluating the setting degree of concrete using surface wave velocity so as to determine the slip up time of the slip-form system. Penetration resistance test and compressive strength test are performed first to clarify the relationship between the early setting time of concrete and the compressive strength. Then, compressive strength test and ultrasonic wave test are conducted to examine the relation between the compressive strength and the surface wave velocity. Continuous wavelet transform is adopted to measure the surface wave velocity. Numerical analysis is carried out to demonstrate the appropriateness of the application of continuous wavelet transform. Based on these results, the propagation velocity of the surface wave required for the slip up of slip-form system is suggested. Finally, a reduced model test of the slip-form system is conducted to verify the feasibility of the proposed surface wave velocity for the determination of th slip up velocity.