• Applied Chemistry for Engineering
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• v.10 no.7
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• pp.963-968
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• 1999

The global environmental problems have been caused by the release of CFCs. Therefore, methods for safe destruction of recoverd CFCs will be eventually needed. The objective of this study was to develop and test a catalyst operating at a mild condition for the decomposition of CFC-113. In this work, catalytic oxidative decomposition of CFC-113 was carried out over aerosol $TiO_2/SiO_2(ATS)$ catalysts prepared by the sol-gel method. All ATS catalysts(Ti/Si mol ratio=1, 2, 2.33, 4) showed high initial activity. However, the deactivation of ATS catalysts was found that more remarkable due to an attack of fluorine and the destruction of ATS structure(Si-F reaction) from analyses of SEM-EDX, XRD than $TiO_2/SiO_2(ATS)$ catalyst prepared by the precipitation method. ATS catalysts prepared by more acidic prehydrolysis condition were found to have still more activity and longer life-time by increasing of acidity. The activity of ATS catalyst also depend on the content of $TiO_2$. There was reason that the acidity of the ATS catalyst was increased with the increased content of $TiO_2$ from 50 to 80 mol %. Solid superacid catalyst ($ATX/SO_4{^{2-}}$) modified with $H_2SO_4$ solution was prepared for high activity and lower deactivation. The reaction of $ATS/SO_4{^{2-}}$ catalyst also exhibited even higher activity and lower deactivation than the original ATS catalyst. It is suggested that the addition of the sulphate species clearly inhibit the deactivation.

• Radiation Oncology Journal
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• v.9 no.1
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• pp.7-15
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• 1991

Pentoxifylline (PENTO) has been known to improve RBC fluidity, and thus improve the flux of RBC through narrow capillaries. Additionally, PENTO also decreases the $O_2$ affinity of hemoglobin by increasing 2,3-DPG levels, thereby increasing the $O_2$ release from RBC. Nicotinamide (NA) has been reported to decrease the number of acutely hypoxic cells in tumors by temporarily increasing tumor blood flow. Therefore, the purpose of this study was to examine whether the combination of PENTO and NA (PENTO+NA) would reduce the radioresistance of the Fsall murine fibrosarcoma by oxygenating the hypoxic cells. We obsewed a significantly enhanced radiation-induced growth delay of the FSaII tumors by PENTO+NA. Thus the enhancement ratio was between 2.5 and 2.8 in growth delay assay. The $TCD_{50}$ of control tumors was about 57 Gy, but that of PENTO+NA treated tumors was about 32Gy. Thus $TCD_{50}$ was modified by a factor of 1.8. We also observed that PENTO+NA exerted no effect on the radiation-induced skin damage after the legs without bearing tumors were exposed to X-irradiation. In order to clarify radiosensitizing effects of PENTO+ NA, changes in tumor blood flow and intratumor pOf were measured using laser Doppler flowmetry and $O_2$ microelectrode methods. The tumor blood flow significantly increased at 10 min. after injection of PENTO+ NA. Furthermore, we also found that PENTO+ NA significantly increased intratumor $pO_2$ from 8 to 19 mmHg. We concluded that PENTO+MA was far more effective than NA alone or PENTO alone. The increase in the response of tumors in vivo to X-irradiation appeared to be due mainly to an increase in the tumor oxygenation. Further studies using various concentrations of PENTO alone and in combination with NA to obtain better sequencing and maximal radiosensitization are warranted.

• Korean Journal of Environmental Biology
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• v.20 no.3
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• pp.224-231
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• 2002

Photoperiod (length of light per day) is a major factor in regulating reproductive function in golden hamsters. The information of photoperiod is transmitted to the reproductive endocrine system by melatonin. Thus the effects of melatonin aye investigated in male golden hamsters exposed to photoperiods. Paired testicular weights were markedly reduced in the animals housed in short photoperiod $(SP,\le{12\;hours\;day^{-1})$ and injected with melatonin in the evening, but not in long photoperiod $(LP,\le{12.5}\;hours\;day^{-1})$ and injected with melatonin in the morning. The histological examination of regressed testes showed reduction of tubular lumen diameter including the numbers of cells and Leydig cell number. The mean values of both follicle stimulating hormone (FSH) and luteinizing hormone (LH) were also lowered in the sexually inactive animals than in the sexually active animals. Melatonin receptor was identified by reverse-transcription polymerase chain reaction (RT-PCR) and its expression was examined in various tissues to scrutinize the action site of melatonin. It turned out 309 nucleotides and was definitely expressed in hypothalamus and pituitary including spleen, retina, and epididymis. And gonadotropin releasing hormone (GnRH) gene, which is a key element in regulating reproduction, was identified by RT-PCR but the expression of GnRH was not modified by the treatment of melatonin. Taken together, photoperiod via melatonin indirectly affects reproductive endocrine system, possibly through the release of GnRH, not the synthesis of GnRH.

• Journal of the Korean earth science society
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• v.22 no.6
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• pp.512-527
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• 2001

Separated flows passed complex geometries are modeled by discrete vortex techniques. The flows are assumed to be rotational and inviscid, and a new techlnique is described to determine the stream functions for linear shear profiles. The geometries considered are the snow cornice and the backward-facing step, whose edges allow for the separation of the flow and reattachment downstream of the recirculation regions. A point vortex has been added to the flows in order to constrain the separation points to be located at the edges, while the conformal mappings have been modified in order to smooth the sharp edges and to let the separation points free to oscillate around the points of maximum curvature. Unsteadiness is imposed to the flow by perturbing the vortex location, either by displacing the vortex from the equilibrium, or by imposing a random perturbation with zero mean to the vortex in equilibrium. The trajectories of passive scalars continuously released upwind of the separation point and trapped by the recirculating bubble are numerically integrated, and concentration time series are calculated at fixed locations downwind of the reattachment points. This model proves to be capable of reproducing the trapping and intermittent release of scalars, in agreement with the simulation of the flow passed a snow cornice performed by a discrete multi-vortex model, as well as with direct numerical simulations of the flow passed a backward-facing step. The results of simulation indicate that for flows undergoing separation and reattachment the unsteadiness of the recirculating bubble is the main mechanism responsible for the intense large-scale concentration fluctuations downstream.

• Korean journal of applied entomology
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• v.31 no.3
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• pp.205-240
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• 1992

In reality, it is a green revolution of the entire agricultural matrix in Korea that integrated pest control plays an important role in the possible breakthrough in rice self-sufficiency. In paddy agroecosystem as man-modified environment, rice is newly established every year by transplantation under diverse water regimes which affect a microclimate. Standing water benefits rice by regulating the microclimate, but it favors the multiplication of certain pets through the amelioration of the microclimate. Further, the introduction of high yielding varieties with the changing of cultural practices results in changing occurrence pattern of certain pests. In general, japonica type varieties lack genes resistant to most of the important pests and insect-borne virus diseases, whereas indica type possesses more genes conferring varietal resistance. Thus, this differences among indica type, form the background of different approaches to pest management. The changes in rice cultivation such as double cropping, growing high-yielding varieties requiring heavy fertilization, earlier transplanting, intensvie-spacing transplanting, and intensive pesticide use as a consequence of the adoption of improves rice production technology, have intensified the pest problems rather than reduced them. The cultivation of resistant varieties are highly effective to the pest, their long term stability is threathened because of the development of new biotypes which can detroy these varieties. So far, three biotypes of N. lugens are reported in Korea. Since each resistant variety is expected to maintain several years the sequential release of another new variety with a different gene at intervals is practised as a gene rotation program. Another approach, breeding multilines that have more than two genes for resistance in a variety are successfully demonstrated. The average annual rice losses during the last 15 years of 1977-’91 are 9.3% due to insect pests without chemical control undertaken, wehreas there is a average 2.4% despite farmers’insecticide application at the same period. In other words, the average annual losses are prvented by 6.9% when chemical control is properly employed. However, the continuous use of a same group of insecticides is followed by the development of pest resistance. Resistant development of C. suppressalis, L. striatellus and N. cincticeps is observed to organophosphorous insecticides by the mid-1960s, and to carbamates by the early 1970s in various parts of the country. Thus, it is apparent that a scheduled chemical control for rice production systems becomes uneconomical and that a reduction in energy input without impairing the rice yield, is necessarily improved through the implementation of integrated pest management systems. Nationwide pest forecasting system conducted by the government organization is a unique network of investigation for purpose of making pest control timely in terms of economic thresholds. A wise plant protection is expected to establish pest management systems in appropriate integration of resistant varieties, biological agents, cultural practices and other measures in harmony with minimizing use of chemical applications as a last weapon relying on economic thresholds.

• Biomedical Science Letters
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• v.12 no.3
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• pp.289-301
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• 2006

Cardiopulmonary bypass (CPB) for cardiac surgery triggers the production and release of numerous chemotactic substances and cytokines, ensuing systemic inflammatory response that leads to postoperative major organ dysfunction. Traditionally, corticosteroids (steroid) have been administered to patients undergoing cardiac surgery to ward off these detrimental physiologic alterations. However, the majority of the studies have been performed on adult patients with high-dose steroid. We carried out a randomized, prospective, double-blind study to compare the efficacy of low-dose steroid with that of high-dose steroid and to determine the adequate dose of pretreated-steroid for prophylactic effects in pediatric cardiac surgery. Thirty pediatric patients scheduled for elective cardiac surgery were randomly assigned to two groups; fifteen patients received low-dose methylprednisolone (10mg/kg intravenously, n=15, low-dose group) and the others received high-dose methylprednisolone (30mg/kg intravenously, n=15, high-dose group) 1 hour prior to CPB. Arterial blood samples were taken before CPB (Pre-CPB), 10 minutes after start of CPB (CPB-10), and immediately after CPB-end (CPB-OFF) for measuring total leukocyte counts (T-WBC) and diff-counts, platelet counts, interleukin-6 (IL-6), myeloperoxidase (MPO), total antioxidant (TAO), neuron-specific enolase (NSE), troponin I (TNI), aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatinine, and blood urea nitrogen (BUN) levels. Other parameters such as volumes of urine output, pulmonary index $(PI,\;PaO_2/FiO_2)$, mechanical ventilating period, intensive care unit (ICU)-staying period, postoperative complications (fever, wound problem), postoperative 24 hrs and total volumes in blood loss, and hospitalized days were also assessed. All parameters were compared between two groups. There were no significant differences in T-WBC counts, monocyte fraction, platelet counts, TA levels, NSE levels, creatinine levels, BUN levels, the volumes of total urine output, PI, the incidences of fever and wound problem, postoperative 24hrs- and total-blood loss volumes and ICU-staying period between two groups (P>0.05). At CPB-OFF, neutrophil fraction, MPO level, TNI level, and AST level were higher in the high-dose group than in the low-dose group (P<0.05). IL-6 level at CPB-10 was higher in the high dose-group than in the low-dose group (P<0.05). Furthermore, mechanical ventilating periods and hospitalized days of the high-dose group were significantly longer than those of low-dose group (P<0.05). The high-dose group had significantly low lymphocyte fi-action at CPB-OFF compared with the low-dose group (P<0.001). These findings suggest that pretreatment of high-dose steroid is not superior to that of low-dose steroid regrading its potential benefits in pediatric cardiac surgery. Therefore, the conventional strategy of steroid treatment, high-dose pretreatment, should be modified in the cardiac surgery with CPB. However, further studies must be performed on the larger number of patients in as much as small number of patients in this study.

• Fire Science and Engineering
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• v.26 no.3
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• pp.21-28
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• 2012

The objective of this study is to evaluate the prediction accuracy of FDS(Fire Dynamic Simulator) for the thermal and chemical characteristics of under-ventilated fire with unsteady fire growth in a semi-closed compartment. To this end, a standard doorway width of the full-scale ISO 9705 room was modified to 0.1 m and the flow rate of heptane fuel was increased linearly with time (until maximum 2.0 MW based on ideal heat release rate) using a spray nozzle located at the center of enclosure. To verify the capability of FDS, the predicted results were compared with a previous experimental data under the identical fire conditions. It was observed that with an appropriate grid system, the numerically predicted temperature and heat flux inside the compartment showed reasonable agreement with the experimental data. On the other hand, there were considerable limitations to predict accurately the unsteady behaviors of CO and $CO_2$ concentration under the condition of continuous fire growth. These results leaded to a discrepancy between the present evaluation of FDS and the previous evaluation conducted for steady-state under-ventilated fires. It was important to note that the prediction of transient CO production characteristics using FDS was approached carefully for the under-ventilated fire in a semi-closed compartment.

• Journal of Chest Surgery
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• v.16 no.2
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• pp.231-242
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• 1983

A clinical study was performed on 75 cases of the esophageal cancer and benign esophageal diseases experienced at Department of thoracic & cardiovascular surgery, School of Medicine, Keimyung University during 3 year period from 1978 to 1982. Of 75 cases of the surgical esophageal diseases, there were 35 patients of the esophageal cancer. 17 patients of benign esophageal stenosis, 10 patients of esophageal perforation, 4 patients of diverticulum. 3 patients of achalasia, 2 patients of congenital T-E fistula, one of upper esophageal web, one of esophageal foreign body, one of leiomyoma and patient of hemangioma. First, esophageal carcinoma was more frequent in men than in women by a ratio of five to one, and the peak incidence occurred in the 5th to 6th decade. Dysphagia was the most common symptom in 88.6 percent of our cases. The tumor was located mostly in the middle & the lower one third [91.4%]. The histological diagnosis was made in 35 cases. The squamous cell carcinoma was the most common [82.9%] and the rest was the adenocarcinoma in the lower one third [17.1%]. Thirty-five cases were operated and resection was feasible in the twenty-five patients [71.4%] with 2 cases of hospital mortality [5.7%]. All but two of the esophageal stenosis were caused by corrosive esophagitis and ages ranged from 7 to 70 years with average age of 32 years. Corrective operations were performed on 17 patients of esophageal stenosis of whom 12 patients had esophagocologastrostomy, 3 patients esophagogastrostomy and in non-corrosive esophageal stenosis one case and esophagoplasty and another case had release of external compression. There was one complication of stenosis of the esophageal perforation were traumatic in five cases, empyema in three cases, caustics in one case and postemetic in one case. 10 patients of the esophageal perforation underwent operation: primary closure in 5 cases, two staged colon interposition in 2, esophagogastrostomy in 1 and closed thoracotomy in 2 cases There were 2 complications of leakage of anastomosis sites in postoperative period. 4 patients of traction type of diverticulum underwent diverticulectomy & 3 patients of achalasia underwent modified Heller`s operation. 2 patients of congenital esophageal atresia had distal tracheoesophageal fistula & underwent one staged operation with the results of one death caused by pneumonia. Upper esophageal web had divulsion through the esophagoscope and foreign body in upper esophagus was removed through cervical esophagotomy. One case of leiomyoma in esophagus had esophagectomy and reconstruction with right colon. And one case of hemangioma in esophagus had esophagectomy & esophagogastrostomy.

• Clinical and Experimental Reproductive Medicine
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• v.31 no.3
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• pp.155-168
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• 2004

Objective: Melatonin, which is secreted by pineal gland play an important role in the regulation of ovarian function via seasonal rhythm and sleep in most mammals. It also has a role in the protection of cells by removing toxic oxygen free radicals brought about by metabolism. In the present study, effects of melatonin on the mouse oocyte maturation were examined using two different culture conditions provided with 5% or 21% oxygen concentration. Material and Method: Immature mouse oocytes were obtained from the ovarian follicles of $3{\sim}4$ weeks old ICR strain mice intraperitoneally injected with 5 I.U. PMSG 44 hour before. Under stereomicroscope, morphologically healthy oocytes with distinct germinal vesicle (GV) were liberated from the graafian follicles and collected using mouth-controlled micropipette. They were then cultured for 17 hour at $37^{circ}C$, 5% $CO_2$ and 21% $O_2$ (95% air) or 5% $CO_2$, 5% $O_2$ and 90% $N_2$. New modified Hank's balanced salt solution (New MHBS) was used as a culture medium throughout the experiments. Effects of melatonin were examined at a concentration of $0.0001{\mu}M$, $0.01{\mu}M$ or $1.0{\mu}M$. For the prevention of spontaneous maturation of immature oocytes during culture, dibutyryl cyclic AMP (dbcAMP) and/or hypoxanthine were included in the medium. Results: Under 21% oxygen condition, oocytes cultured in the presence of $0.01{\mu}M$ melatonin showed a significantly higher maturation rates, in terms of germinal vesicle breakdown (95.0% vs 89.0%) and polar body formation (88.1% vs 75.4%), compared to those cultured with $0.0001{\mu}M$ or $1.0{\mu}M$ melatonin. However, no difference was observed in oocytes cultured under 5% oxygen whether they were treated with melatonin or not. In the presence of $0.01{\mu}M$ melatonin, oocytes either cultured under 21% or 5% oxygen exhibited no difference in the polar body formation (85.6% vs 86.7%). However, in the absence of melatonin, oocytes cultured under 21% oxygen exhibited lower polar body formation (74.7%). When oocytes were cultured in the presence of dbcAMP alone or with varying concentrations of melatonin, those treated with both compounds always showed better maturation, i.e., germinal vesicle breakdown and polar body formation, compared to those cultured with dbcAMP alone. At the same concentration of melatonin, however, oocytes exposed to 21% oxygen showed poor maturation than those to 5% oxygen. Similar results were obtained from the experiments using hypoxanthine instead of dbcAMP. Conclusion: Based upon these results, it is suggested that melatonin could enhance the meiotic maturation of mouse oocytes under 21% oxygen concentration, and release oocytes from the meiotic arrest by dbcAMP or hypoxanthine regardless of the concentration of oxygen, probably via the removal of oxygen free radicals.

• Journal of Life Science
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• v.31 no.9
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• pp.849-855
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• 2021

Recently, as nanotechnology has been introduced and used in various fields, the development of new drugs has been accelerating. Nanoparticles have maintained blood drug concentration for extended periods of time with a single administration of the drug. The drug can then be selectively released only at the pathological site, thereby reducing side effects to other non-pathological sites. In addition, nanoparticles can be modified for selective target sites delivery for other specific diseases, with polymers being widely used in the manufacture of these nanoparticles. Poly (D,L-lactic-co-glycolic acid ) (PLGA) is one of the most extensively developed biodegradable polymers. PLGA is widely used in drug delivery for a variety of applications. It has also been approved by the FDA as a drug delivery system and is widely applied in controlled release formulations, such as in gene therapy treatments. PLGA nanoparticles have been developed as delivery systems with high efficiency to specific cell types by using passive and active targeting methods. After the development of a drug delivery system using PLGA nanoparticles, the drug is selectively delivered to the target site, and the effective blood concentration for extended periods of time is optimized according to the disease. In this review paper, we focus on ways to improve cell-specific treatment outcomes by examining the development of astrocyte selective nanoparticles based on PLGA nanomaterials for gene therapy.