• Journal of Life Science
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• v.9 no.2
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• pp.136-145
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• 1999

The purpose of this study was to evaluate the effect of organic slovents and noise on hearing loss. We selected organic solvents exposed group of 32 cases, noise exposed group of 31 cases, both noise and solvent exposed group of 31 cases, and control group of 53 cases and studied the relation between exposure level of noise and organic solvents and degree of hearing loss. The results were as follows. The subjects under investigation were exposed to noise and organic solvents under threshold limit values and the amount of urinary hippuric acid excretion were also under biological exposure indices. In case of noise, both noise and organic solvents exposed group and noise exposed group were more exposed than organic solvents exposed group(p<0.05). When urinary hippuric acid excretion were concerned, both noise iud organic solvents exposed group and organic solvents exposed group showed higher values than noise exposed group(p<0.05). In comparison of mean auditory threshold values by frequency, on the air conduction test, both noise and organic solvents exposed group showed significantly higher hearing loss than noise exposed group in 500Hz of right ear, 500 and 2000Hz of left ear(p<0.05). Forty-three cases among 147 subjects were regarded as hearing loss group and average age(42.6years) of hearing loss group was higher than normal groups average age of 38.0 years. Urinary hippuric acid excretions of hearing loss group were significantly higher than normal group(p<0.05). Thirty-eight percent(12cases) of noise exposed group, 40.6 $\%$(13cases) of organic solvents exposed group, 51.6 $\%$(16cases) of both noise and organic solvents exposed group, and 3.8 $\%$(2cases) of unexposed group were regarded as hearing losers. Exposed groups showed higher incidence of hearing loss than unexposed group but there were no significant differences among the exposed groups. The variables showing significant correlation with hearing loss were age and the amount of hippuric acid in urinary excretion. When age were adjusted for the purpose of seeing the effects of hearing losses due to organic solvent, urinary excretion of hippuric acids was the only variable with significant correlation with hearing loss (p<0.05). When odds ratio to hearing loss between control and exposed groups was considered, noise exposed group showed 6.1 times (95 $\%$ CI: 3.3-8.7), organic solvents exposed group showed 7.4 times (95 $\%$ CI: 3.5-14.6) and both noise and organic solvents exposed group showed 17.2 times(95% CI: 5.6-31.8) higher values than unexposed group(p<0.01). Above results suggest that health screening test of hearing loss is also needed in organic solvents exposed workers.

• Journal of Chest Surgery
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• v.36 no.12
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• pp.911-920
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• 2003

In this study, we analyzed the long-term surgical outcome of partial atrioventricular septal defects during the past 17 years at Seoul National University Hospital. Material and Method: A retrospective analysis on mortality, survival, and reoperation and their risk factors was done in 93 patients who underwent surgical correction of partial atrioventricular septal defects between April 1986 and December 2002. 32 patients were male and 61 were female with a median age of 68 months (3∼818 months) and a mean follow-up period of 108 months (1∼200 months). Result: There were 4 operative deaths (4.3%) and one mortality during the follow-up period. 3, 5, 10, and 15 year actuarial survival rates were 95.7%, 94.3%, 94,3%, and 94.3%, respectively. After the surgical correction, left atrioventricular valve Incompetence was improved in 61patients (67.7%), remained same as the preoperative status in 14 patients (15.1%), and was aggravated in 12 patients (12.9%). Reoperation was performed in 8 patients (9.0%) after a mean interval of 38.6 months (3∼136 months). Freedom from reoperation rates at 3, 5, 10, and 15 years after surgical correction were 94.0%, 91.4%, 91.4%, and 88,2%, respectively Reasons for reoperation were 7 left atrioventricular valve incompetence, 2 left ventricular outflow tract obstruction, a residual atrial septal defect, a left atrioventricular valve stenosis, and a right ventricular failure. Left ventricular outflow tract obstruction was the only statistically significant factor. In ten patients, significant arrhythmia was developed and three of them were supraventricular arrhythmia. Complete atrioventricular block occurred in 7 patients and permanent pacemakers were implanted in six of them. Conclusion: Surgical corrections of partial atrioventricular septal defects were performed with low operative mortality. Since left atrioventricular valve incompetence was the most common cause of reoperation and left ventricular outflow tract obstruction was the only risk factor for reoperation, a precise estimation of the left atrioventricular valve morphology and the structure of left ventricular outflow tract are needed. Although left ventricular outflow tract obstruction rarely developed, reoperation was frequently required and resection of subaortic tissue could be peformed but the possibility of recurrence was high, so modified Konno operation could be performed with satisfactory results. Complete atrioventricular block developed frequently in early periods, but was overcome with a precise anatomical understanding of conduction system and experience.

• Journal of Bio-Environment Control
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• v.11 no.1
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• pp.5-11
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• 2002

In this study, new development of natural ventilation window was accomplished to control environment of greenhouse with no use of farced ventilation during hot season. The ventilation effect of developed ventilation window was investigated in experimental greenhouse which was designed using side wall panel and folding type panel fur natural ventilation. Folding panel type ventilation window was designed to open upper part of the side wall and top of the roof using two hinges which are located bottom of the side wall and the roof panel to grab one side of each panels and guide the other side along with the guidance rail. Developed ventilation window has top ventilation part with maximum moving distance X=ι (1-cos$\theta$)=848.5 mm and side ventilation part with maximum moving distance Y=ι/2 $\times$sin$\theta$=1,184.4 mm at 45$^{\circ}$ of theoretical opening angle. It took 4.5 minutes to open roof vent fully and temperature at 1.2 and 0.8 m height decreased after 1 minute from starting opening and became equilibrium state maintaining 3-4$^{\circ}C$ difference after 2 minutes from complete opening. Air exchange rate was 15.2~39.3 h$^{-1}$ which was more than 10~15 h$^{-1}$ of continuous type and Venlo type greenhouse. The descent effect of temperature by ventilation windows was two times higher than Venlo type greenhouse.

• Journal of Chest Surgery
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• v.38 no.3 s.248
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• pp.214-220
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• 2005

Extended transseptal approach can provide an excellent view of the mitral valve but the safety of this approach is controversial because this incision requires transaction of the sinus node artery, which in most cases and can result postoperative arrhythmia. The purpose of this study was to evaluate perioperative and longterm conduction disturbances and the cardiac rhythms of patients who underwent an extended transseptal approach for mitral valve surgery. Material and Method: Postoperative cardiac rhythms were analyzed in the 164 consecutive patients who received mitral valve replacements with a extended transseptal approach between March 1992 and July 2003. Result: Of the 84 patients in normal sinus rhythm, 34 ($39\%$) had developed transient junctional rhythm and atrial fibrillation after operation, lasting less than 72 hours in most of cases. No intractable arrhythmias occurred. Most of these arrhythmia were not detected at the time of discharge and only 8 patients ($9\%$) had atrial fibrillation at discharge. Postoperative PR intervals increased for 1 week, then decreased within 2 weeks postoperatively, and returned to normal range by 6 months postoperatively. During the postoperative period, 4 of the 78 patients with preoperative atrial fibrillation developed normal sinus thythm. Conclusion: The post-operative arrhythmias were temporary and showed no significant complications after extended transseptal approach for the mitral valve surgery.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.30 no.6
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• pp.465-473
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• 2004

Purpose : The essential triad for nerve regeneration is nerve conduit, supporting cell and neurotrophic factor. In order to improve the peripheral nerve regeneration, we used polyglycolic acid(PGA) tube and brain-derived neurotrophic factor(BDNF) gene transfected Schwann cells in sciatic nerve defects of SD rat. Materials and methods : Nerve conduits were made with PGA sheet and outer surface was coated with poly(lactic-co-glycolic acid) for mechanical strength and control the resorption rate. The diameter of conduit was 1.8mm and the length was 17mm Schwann cells were harvested from dorsal root ganglion(DRG) of SD rat aged 1 day. Schwann cells were cultured on the PGA sheet to test the biocompatibility adhesion of Schwann cell. Human BDNF gene was obtained from cDNA library and amplified using PCR. BDNF gene was inserted into E1 deleted region of adenovirus shuttle vector, pAACCMVpARS. BDNF-adenovirus was multiplied in 293 cells and purified. The BDNF-Adenovirus was then infected to the cultured Schwann cells. Left sciatic nerve of SD rat (250g weighing) was exposed and 14mm defects were made. After bridging the defect with PGA conduit, culture medium(MEM), Schwann cells or BDNF-Adenovirus infected Schwann cells were injected into the lumen of conduit, respectively. 12 weeks after operation, gait analysis for sciatic function index, electrophysiology and histomorphometry was performed. Results : Cultured Schwann cells were well adhered to PGA sheet. Sciatic index of BDNF transfected group was $-53.66{\pm}13.43$ which was the best among three groups. The threshold of compound action potential was between 800 to $1000{\mu}A$ in experimental groups which is about 10 times higher than normal sciatic nerve. Conduction velocity and peak voltage of action potential of BDNF group was the highest among experimental groups. The myelin thickness and axonal density of BDNF group was significantly greater than the other groups. Conclusion : BDNF gene transfected Schwann cells could regenerate the sciatic nerve gap(14mm) of rat successfully.

• Clinical and Experimental Pediatrics
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• v.46 no.7
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• pp.661-667
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• 2003

Purpose : This study was performed to find the chief clinical problems associated with the ages of adult patients of tetralogy of Fallot(TOF) who had undergone total correction. Methods : Of the 30 patients who were registered at the Grown-Up Congenital Heart Disease (GUCH) Clinic of Samsung Medical Center for TOF, a retrospective investigation was carried out on 28 patients who underwent total correction. Results : Mean age at retrospective study was 30.8(range : 16-53) years old. Age at total correction was 15.8(range : 2-49) years old. Problems after corrective surgery were assessed. They were arrhythmia, pulmonary valve regurgitation, left pulmonary artery stenosis, residual ventricular septal defect, mitral valve regurgitation, tricuspid valve regurgitation, right ventricle outflow tract obstruction, aortic valve regurgitation, infective endocarditis and protein losing enteropathy. After repair of TOF, such arrhythmias as atrial arrhythmia and AV conduction disturbances were observed in some patients. Cardiomegaly was found significantly in the subjects with arrhythmia(P<0.05), and arrhythmia was less observed in patients who underwent surgery at a young age. Eight patients required a reoperation; the main indications were residual ventricular septal defect, right ventricle outflow tract obstruction and peripheral pulmonary artery stenosis. Conclusion : The majority of the patients seemed to live normal lives after Tetralogy of Fallot repair. However, as residual anatomic and functional abnormalities exist postoperatively, continued careful follow-up is needed to detect and correct structural and functional abnormalities.

• Journal of the Korean Vacuum Society
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• v.20 no.1
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• pp.42-49
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• 2011

We deposited $SiN_x$ thin films by using PECVD technique at $200^{\circ}C$ with various flow ratios of the $SiH_4/N_2$ gases. The photoluminescence measurements revealed that the maximum emission wavelength shifted to long wavelength as the ratio increased, however, positions of the several peak wavelengths, such as 1.9, 2.2, 2.4, and 3.1 eV, were independent on the ratio. Changes of the photoluminescence spectra were measured in the $N_{2}-$, $H_{2}-$, and $O_2$-annealed films. The luminescence intensities increased after the annealing process. In particular, the maximum emission wavelength shifted to short wavelength after $H_{2}-$ or $O_2$-annealing. But there were still several peaks on the spectra of all annealed films, several peak positions remained to be unchanged after the annealing. As for the light emission mechanism, we have considered the defect states of the Si- and N- dangling bonds in the $SiN_x$ energy gap, so that the energy transitions from/to the conduction/valence bands and the defect states in the gap were attributed to the light emission in the $SiN_x$ films. The experimental results point to the possibility of a Si-based light emission materials for flexible Si-based electro-optic devices.

• Journal of Animal Science and Technology
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• v.49 no.2
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• pp.161-170
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• 2007

A submerged biofilm sequencing batch reactor (SBSBR) process, which liquor was internally circulated through sandfilter, was designed, and performances in swine wastewater treatment was evaluated under a condition of no external carbon source addition. Denitrification of NOx-N with loading rate in vertical and slope type of sandfilter was 19% and 3.8%, respectively, showing approximately 5 times difference, and so vertical type sandfilter was chosen for the combination with SBSBR. When the process was operated under 15 days HRT, 105L/hr.m3 of internal circulation rate and 54g/m3.d of NH4-N loading rate, treatment efficiencies of STOC, NH4-N and TN (as NH4-N plus NOx-N) was 75%, 97% and 85%, respectively. By conducting internal circulation through sandfilter, removal performances of TN were enhanced by 14%, and the elevation of nitrogen removal was mainly attributed to occurrence of denitrification in sandfilter. Also, approximately 57% of phosphorus was removed with the conduction of internal circulation through sandfilter, meanwhile phosphorus concentration in final effluent rather increased when the internal circulation was not performed. Therefore, It was quite sure that the continuous internal circulation of liquor through sandfilter could contribute to enhancement of biological nutrient removal. Under 60g/m3.d of NH4-N loading rate, the NH4-N level in final effluent was relatively low and constant(below 20mg/L) and over 80% of nitrogen removal was maintained in spite of loading rate increase up to 100g/m3.d. However, the treatment efficiency of nitrogen was deteriorated with further increase of loading rate. Based on this result, an optimum loading rate of nitrogen for the process would be 100g/m3.d.

• Clinical and Experimental Pediatrics
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• v.46 no.6
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• pp.585-590
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• 2003

Purpose : This study is designed to determine the prevalence of cardiovascular autonomic neuropathy and its relationship to risk factors in adolescents with diabetes mellitus(DM). Methods : Ninety-two diabetic patients(80 with type 1 DM and 12 with type 2 DM), ranging from eight to 26 years of age, were studied for cardiovascular autonomic function, and the relationship to age, duration of diabetes, glycated hemoglobin(HbA1c), urinary albumin excretion, and the presence of diabetic retinopathy and abnormal nerve conduction velocities(NCV) were analysed. Autonomic function was assessed by measuring heart rate variation during valsalva manoeuvre, deep breathing and standing from a lying position(30 : 15 ratio), and postural hypotension. Results : Among patients with type 1 DM, 22.5% had early, 8.7% had definite, and 1.3% had severe autonomic dysfunction, and among patients with type 2 DM, 16.7% had early, 8.3% had definite, and 8.3% had severe autonomic dysfunction. On logistic regression analysis including both type 1 and type 2 diabetic patients, the age of the patient(OR=1.133(1.003-1.279), P<0.05) and duration of diabetes(OR=1.148(1.009-1.307), P<0.05) significantly predicted cardiovascular autonomic dysfunction while HbA1c, blood pressure, urinary albumin excretion, and presence of diabetic retinopathy and abnormal NCV did not. The valsalva ratio was borderline or abnormal in 31.5% of patients, the heart rate variation on deep breathing in 41.3%, the 30 : 15 ratio in 14.1%, and postural hypotension in 9.8% of patients. The valsalva ratio and the heart rate variation on deep breathing significantly predicted cardiovascular autonomic dysfunction, but the 30 : 15 ratio and postural hypotension did not. Conclusion : Cardiovascular autonomic dysfunction was found in 32.6% of diabetic patients and 10.8 % of patients had definite or severe involvement. The risk of cardiovascular autonomic dysfunction increased with the patient's age and the duration of DM. This study suggests that the valsalva ratio and the heart rate variation on deep breathing are the most useful tests in evaluating the cardiovascular autonomic function in children and adolescents with DM.

• Journal of the Korean Magnetics Society
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• v.17 no.2
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• pp.81-85
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• 2007

MnTe layers of high crystalline quality were successfully grown on Si(100) : B and Si(111) substrates by molecular beam epitaxy (MBE). Under tellurium-rich condition and the substrate temperature around $400^{\circ}C$, a layer thickness of $700{\AA}$ could be easily obtained with the growth rate of $1.1 {\AA}/s$. We investigated the structural, magnetic and transport properties of MnTe layers by using x-ray diffraction (XRD), superconducting quantum interference device (SQUID) magnetometry, and physical properties measurement system (PPMS). Characterization of MnTe layers on Si(100) : B and Si(111) substrates by XRD revealed a hexagonal structure of polycrystals with lattice parameters, ${\alpha}=4.143{\pm}0.001{\AA}\;and\;c=6.707{\pm}0.001{\AA}$. Investigation of magnetic and transport properties of MnTe films showed anomalies unlike antiferromagnetic powder MnTe. The temperature dependence of the magnetization data taken in zero-field-tooling (ZFC) and field-cooling (FC) conditions indicates three magnetic transitions at around 21, 49, and 210 K as well as the great irreversibility between ZFC and FC magnetization in the films. These anomalies are attributable to a magnetic-elastic coupling in the films. Magnetization measurements indicate ferromagnetic behaviour with hysteresis loops at 5 and 300 K for MnTe polycrystalline film. The coercivity ($H_c$) values at 5 and 300 K are 55 and 44 Oe, respectively. In electro-transport measurements, the temperature dependence of resistivity revealed a noticeable semiconducting behaviours and showed conduction via Mott variable range hopping at low temperatures.