• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.50-50
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• 2008

ZnO has been extensively studied for optoelectronic applications such as blue and ultraviolet (UV) light emitters and detectors, because it has a wide band gap (3.37 eV) anda large exciton binding energy of ~60 meV over GaN (~26 meV). However, the fabrication of the light emitting devices using ZnO homojunctions is suffered from the lack of reproducibility of the p-type ZnO with high hall concentration and mobility. Thus, the ZnO-based p-n heterojunction light emitting diode (LED) using p-Si and p-GaN would be expected to exhibit stable device performance compared to the homojunction LED. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducibleavailability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices with low defect density. However, the electroluminescence (EL) of the device using n-ZnO/p-GaN heterojunctions shows the blue and greenish emissions, which are attributed to the emission from the p-GaN and deep-level defects. In this work, the n-ZnO:Ga/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated at different growth temperatures and carrier concentrations in the n-type region. The effects of the growth temperature and carrier concentration on the electrical and emission properties were investigated. The I-V and the EL results showed that the device performance of the heterostructure LEDs, such as turn-on voltage and true ultraviolet emission, developed through the insertion of a thin intrinsic layer between n-ZnO:Ga and p-GaN:Mg. This observation was attributed to a lowering of the energy barriers for the supply of electrons and holes into intrinsic ZnO, and recombination in the intrinsic ZnO with the absence of deep level emission.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.7
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• pp.8-16
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• 2010

In this paper, we investigated the effects of $O_2$ fraction on the properties of Al-doped ZnO (AZO) thin films prepared by radio frequency (RF) magnetron sputtering. Hall, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS) measurements revealed that the p-type conductivity was exhibited for AZO films with an $O_2$ fraction of 0.9 while the n-type conductivity was observed for films with $O_2$ fractions in range of 0 - 0.6. PL and XPS also showed that the acceptor-like defects, such as zinc vacancies and oxygen interstitials, increased in films prepared by an $O_2$ fraction of 0.9, resulting in the p-type conductivity in the films. Hall results indicated that AZO films prepared by $O_2$ fractions in range of 0 - 0.6 can be used for electrode layers in the applications of transparent thin film transistor. We concluded from the X-ray diffraction analysis that worse crystallinity with a smaller grain size as well as higher tensile stress was observed in the films prepared by a higher $O_2$ fraction, which is related to incorporation of more oxygen atoms into the films during deposition. The study of atomic force microscope suggested that the smoother surface morphology was observed in films prepared by using $O_2$ fraction, which causes the higher resistivity in those films, as evidenced by Hall measurements.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.15 no.2
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• pp.87-92
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• 2015

Mucopolysaccharidosis (MPS) is an inherited disease entity associated with lysosomal enzyme deficiencies. MPS type 2, also known as Hunter syndrome, has a characteristic morphology primarily involving x-l inked recessive defects and iduronate-2-sulfatase gene mutation. The purpose of this case report is to provide important clues to help pediatricians identify Hunter syndrome patients earlier (i.e., before the disease progresses). A 30-month-old boy showed developmental delay and decreased speech ability. Physical examinations revealed a flat nose and extensive Mongolian spots. Brain magnetic resonance images (MRIs) showed bilateral multiple patchy T2 hyperintense lesions in the periventricular and deep white matter, several cyst-like lesions in the body of the corpus callosum, and diffuse brain atrophy, which were in keeping with the diagnosis. Based on these findings, the patient was suspected of having MPS. In the laboratory findings, although the genetic analysis of IDS (Iduronate-2-sulfatase) did not show any pathogenic variant, the enzymatic activity of IDS was not detected. We could confirm the diagnosis of MPS, because other sulfatases, such as ${\alpha}$-L-iduronidase, were detected in the normal range. Early enzymatic replacement therapy is essential and has a relatively good prognosis. Therefore, early diagnosis should be made before organ damage becomes irreversible, and brain MRIs can provide additional diagnostic clues to help distinguish the disorder.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.6 no.1
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• pp.15-23
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• 2006

Purpose: Glycogen storage disease type III (GSD-III), is a rare autosomal recessive disorder of glycogen metabolism. The affected enzyme is amylo-1,6-glucosidase, 4-alpha-glucanotransferase (AGL, glycogen debranching enzyme), which is responsible for the debranching of the glycogen molecule during catabolism. The disease has been demonstrated to show clinical and biochemical heterogeneity, reflecting the genotype-phenotype heterogeneity among different patients. In this study, we analyzed mutations of the AGL gene in three unrelated Korean GSD-III patients and discussed their clinical and laboratory implications. Methods: We studied three GSD-III patients and the clinical features were characterized. Sequence analysis of 35exons and part exon-intron boundaries of the AGLgene in patients were carried out by direct DNA sequencing method using genomic DNA isolated from patients' peripheral leukocytes. Results: The clinical features included hepatomegaly (in all patients), seizures (in patient 2), growth failure (in patients 1), hyperlipidemia (in patients 1 and 3), raised transaminases and creatinine kinase concentrations (in all patients) and mild EKG abnormalities (in patients 2). Liver transplantation was performed in patient 2due to progressive hepatic fibrosis. Administration of raw-corn-starch could maintain normoglycemia and improve the condition. DNA sequence analysis revealed mutations in 5 out of 6 alleles. Patient 1 was a compound heterozygote of c.1282 G>A (p.R428K) and c.1306delA (p.S603PfsX6), patient 2 with c.1510_1511insT (p.Y504LfsX10), and patient 3 with c.3416 T>C (p.L1139P) and c.l735+1 G>T (Y538_R578delfsX4) mutations. Except R428K mutation, 4 other mutations identified in3 patients were novel. Conclusion: GSD-III patients have variable phenotypic characteristics resembling GSD-Ia. The molecular defects in the AGL gene of Korean GSD-III patients were genetically heterogeneous.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.18 no.1
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• pp.30-34
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• 2018

Niemann Pick type C disease (NPC) is an inherited progressive neurodegenerative disorder, due to defects of intracellular lipid trafficking and storage. Hepatosplenomegaly may prevail, while progressive neurodegenerative symptoms such as cerebellar involvement, dystonia, vertical supranuclear ophthalmoplegia, cataplexy, and eventually seizures starting at juvenile or late infantile period may accompany after normal early development. Here we describe a 3-year-old Korean boy with NPC who presented with splenomegaly at age 3. Liver biopsy showed characteristic foamy cell stained by periodic acid-schiff, and molecular analysis for NPC1 identified the compound heterozygous mutations, novel mutation of c.1631G>A (p.Trp544Ter) and c.2662C>T (p. Pro888Ser) as a known mutation. Filipin was strongly stained with unesterified cellular cholesterol in the patient's skin fibroblasts. The patient has received migulstat since age 3 years and his long-term outcome is needed to be observed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.8
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• pp.4736-4741
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• 2014

This study examined PCB component cleaning on a PCB component surface, which has defects of precipitation type washing (existing rinse method), sealant and foreign material formed in the adhesive process that could not be removed easily. The spin jig was developed for PCB component cleaning, in which the PCB component settled down, to solve the conventional problem of the removal of foreign material with the centrifugal force by high speed rotation. The results are as follows. With decreasing fraction defect in PCB component washing, the development and substrate damage decreased by more than 80% according to the abstergent in the rotary type using the centrifugal force in the existing precipitation type. When the base plate showed a large difference with the time to include the process after washing the design using the existing method, easy attachment and separation of the PCB component could be possible. The washing time was enhanced 90% compared to the existing time. The reliability of the security and washing collaboration of the design and stability of the cleaning process could be secured so that there was no phenomenon of secession, the PCB component fixed for a cleansing rotation jig could maintain a fixed force by the centrifugal force. The stability and reliability of the washing process and the defective rate could be improved to less than 1%.

• Clinical and Experimental Pediatrics
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• v.45 no.6
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• pp.754-763
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• 2002

Purpose : The incidence of type 2 diabetes in children and adolescents has been reported to increase recently. The aim of this study is to investigate the clinical features of type 2 diabetes developing during childhood and adolescent period. Methods : The medical records of 33 patients with type 2 diabetes were reviewed. We analysed clinical manifestations, demographic data, and modes and responses of treatment. Results : Age at diagnosis was $13.4{\pm}1.8$ years. Seventy percent of patients revealed pubertal signs at diagnosis. Half of the patients had BMI more than $25kg/m^2$. Seventy-three percent of patients had family history of type 2 diabetes. Acanthosis nigricans were found in 18% of patients. Nineteen(57.6%) patients were diagnosed incidentally by random urine or blood glucose test without any typical diabetic symptom or sign. The modes of therapy to control hyperglycemia were insulin alone(75.8%), oral hypoglycemic agents alone(9.1%), insulin and oral hypoglycemia agents(9.1%), and only diet with exercise(6%). At the time of investigation, 45.5% of patients were not using insulin. The typical diabetic symptoms at diagnosis were more prevalent in patients who required insulin for more than two years than patients who did not(P<0.05). Conclusion : The development of type 2 diabetes in children and adolescents is possibly related to puberty, obesity, family history, and defects in insulin secretion rather than insulin resistance. Many children and adolescents with type 2 diabetes required insulin initially and some of them could discontinue. More than half of the patients were diagnosed as diabetes without any typical symptom or sign, which might be one of the predictive factors of the prolonged insulin requirement.

• Journal of Chest Surgery
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• v.30 no.9
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• pp.869-875
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• 1997

Perimembranous ventri ular septal defects(PMVSDS) are the most common type of ventricular septal defects(VSDs) and consist morphologically of deficiency of the membranous septum and variable portions of the adjacent muscular septum. Repair of VSD has begun via a right ventriculotomy. Even with this exposure, however, it mght lead to ventricular dysfunction. Transatrial exposure of VSDs is luiown to a versatile approach to PMVSDS and even malaligunent defects can be repaired by this method. Although transatrial exposure can be improved by taking down'the atrioventricular valve at the annulus, surgeons have been hesitant to do so because of concern for valvular competence. Therefore, this study was undertaken to clarity the effects of transamlular approach of tricuspid valve (TATV) at operation of PMVSD. During last 5 years, twenty eight cases from 96 patients of PMVSD were closed by TATV and follow up study was done from 3 months to 33 months and results were obtained as follows. 1. Age at operation was fr m 4 months to 38 years and most patients(17, 62%) were above 5 years. 2. Preoperative pulmonary-systemic flow ratio(QPIQS) was ranged from 1 to 2.8 and 22 patients(79%) were less than 2. 3. Peak systolic pulmonary artery pressure was below 30mmHg in 8, 30-50mmHg in 17, above 50mmHg in 3 patients and 25 patients(89%) were less than 50mmHg. 4. Preoperative tricuspid regurgitation(TR) is none in 12, trivial in 6, mild in 3, moderate in 5, severe in 2 patients but postoperative TR was none in 18, trivial in 6, mild in 4 patients, so TR in most patients had decreased or not. 5. Indications for operation were based on the presence of a significant shunt. However, in patients with small shunts, indications for operation were included additional factors, tricuspid valve pouch, RVOT obstruction(right ventricular outflow tract obstruction), subacute bacterial endocarditis and associated anomalies. 6. There were no hospital deaths and residual shunts in postoperative echocardiography. Therefore TATV is especially a good method in PMVSn where patients have trcuspid valve pouch. And it is a safe and effective technique that improves exposure for PMVSD repair and does not adversely affect tricuspid valvular competence.

• Journal of Chest Surgery
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• v.31 no.5
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• pp.466-471
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• 1998

Purpose: The safety and efficacy of minimally invasive techniques in congenital heart surgery were tested in this study. Materal and method: Between July 1997 and November 1997, a total of 46 children were underwent minimally invasive cardiac operations at Seoul National University Children's Hospital. Age and body weight of the patients averaged 34.6${\pm}$41.8 (Range: 1∼148) months and 14.5${\pm}$9.9(Range: 3.0∼40.0) kg, respectively. Twenty eight patients were male. Preoperative surgical indications included 15 atrial septal defects, 25 ventricular septal defects, 1 foreign body in aorta, 3 partial atrioventricular septal defects, 1 total anomalous pulmonary venous connection(cardiac type), and 1 tetralogy of Fallot. After creating a small lower midline skin incision starting as down as possible from the sternal notch, a vertical midline sternotomy extended from xyphoid process to the level of the second intercostal space, where one of the T-, J-, I- or inverted C-shaped lower lying mini-sternotomy was completed with a creation of unilateral right or bilateral trap door sternal opening. A conventional direct aortic and bicaval cannulation was routine. Result: A mean length of skin incision was 6.1${\pm}$1.0(range: 4.0∼9.0) cm. A mean distance between the suprasternal notch and the upper most point of the skin incision was 4.0${\pm}$1.1 (range: 2.0∼7.0) cm. Mean cardiopulmonary bypass time, aortic cross-clamp time, and the operation time were 62.9${\pm}$20.0(range: 28∼147), 29.8${\pm}$12.8(range: 11∼79), and 161.1${\pm}$34.5 (range: 100-250) minutes. A mean total amount of postoperative blood transfusion was 71.0${\pm}$68.1 (range: 0∼267) cc. All patients were extubated mean 11.3${\pm}$13.8(range: 1∼73) hours after operation. A mean total amount of analgesics used was 0.8${\pm}$1.8(range: 0∼9) mg of morphine. The mean duration of stay in intensive care unit and hospital stay were 35.0${\pm}$32.2 (range: 10∼194) hours and 6.2${\pm}$2.0(range: 3∼11) days. There were no wound complications and hospital deaths. Conclusion: This short-term experience disclosed that the minimally invasive technique can be feasibly applied in a selected group of congenital heart disease as well as is cosmetically more attractive approach.

• Journal of Chest Surgery
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• v.38 no.3 s.248
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• pp.181-190
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• 2005

The results of biventricular repair for double outlet right ventricle have been improved in recent series. We studied the surgical and long term results for total correction of double outlet right ventricle by the type of ventricular septal defect. Material and Method: Between November 1979 and December 2003, 126 patients had biventricular repair for double outlet right ventricle. The mean age was 1.8 years (range 1$\~$44) and 86 patients ($68.3\%$) were male. We classified and studied this disease by the type of VSD. Result: The locations of VSD were subaortic in 79 ($62.7\%$), subpulmonary in 17 ($13.5\%$), doubly committed in 16 ($12.7\%$) and noncommitted in 14 ($11.1\%$). 28 patients had palliative operation before total correction and the mean interval to total correction was 41.0$\pm$45.1 months. The methods of total correction were intraventricular baffling in 37 ($29.4\%$), intraventricular baffling with patch enlargement of right ventricular outflow tract in 49 ($38.9\%$), intraventricular baffling with Rastelli procedure in 15 ($11.9\%$), arterial switch operation in 8 ($6.3\%$) and REV procedure in 4 ($3.2\%$), etc. Hospital mortality rate was $10.3\%$ (13 patients) and 25 reoperations were performed in 24 patients ($19.0\%$). The risk factors for hospital mortality and reoperation were cardiopulmonary bypass time (p=0.020) and previous palliative operation (p=0.013), respectively. Follow up was possible in 98 patients and mean follow up period was 118.9$\pm$70.7 months. The percent survival and survival for freedom from reoperation at 15 years were $82.5\%$ and $66.7\%$, respectively. The survival rate was significantly lower (p=0.003) in transposition of great artery type and remote type than in simple ventricular septal defect type and tetralogy of Fallot type, but there was no statistical differences in survival rate for freedom from reoperation. Conclusion: It is thought to be that acceptible surgical and long term results can be obtained with application of appropriate methods of repair for double outlet right ventricle.