• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.581-584
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• 2014

In this paper, a micro-scale photovoltaic(PV) energy harvesting system is proposed where an MPPT(Maximum Power Point Tracking) control is implemented using an energy distribution technique. Miniature PV cells output very low energy and low voltages, and thus, they cannot be used to directly power the MPPT controller. In the proposed system, a start-up circuit boosts an internal Vcp, and the boosted Vcp is used to operate the internal MPPT control block. When the Vcp reaches a predefined value, a detector circuit makes the start-up block turn off and provide a power converter with the energy from the PV cell. When the Vcp decreases such that the MPPT controller can not be operated, the energy transferred to the power converter is blocked and the start-up circuit is reactivated. In this way, the MPPT function is achieved by alternately operating the start-up circuit and the power converter using the energy distribution technique, and the harvested energy is transferred to a load through a PMU(Power Management Unit). The proposed circuit is designed in a 0.35um CMOS process and its functionality has been verified through extensive simulations. The designed chip area including pads is $1430um{\times}1110um$.

• Clinical and Experimental Pediatrics
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• v.45 no.4
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• pp.439-448
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• 2002

Purpose : The aim of this study is to determine and compare the effects of adjunctive therapy with different doses of recombinant human granulocyte-colony stimulating factor(rhG-CSF) on reversing sepsis-associated neonatal neutropenia, and their survival rate in a group I/II-type trial. Methods : RhG-CSF was injected subcutaneously to 10 septic-neutropenic neonates with doses of $10{\mu}g/kg$ from Oct. 1995 to Sep. 1996, and was administered to another 12 septic-neutropenic neonates with doses of $5{\mu}g/kg$ from Oct. 1996 to Sep. 1997. Neutrophilic responses and the outcomes of both groups were compared. Results : In the rhG-CSF $10{\mu}g/kg$ treated group and in the $5{\mu}g/kg$ treated group, the absolute neutrophil count(ANC) was $1,065{\pm}89$($mean{\pm}SEM$) and $1,053{\pm}131$, respectively. The only difference between the two groups was the peak ANC at 48 hours. Eight patients from the remaining nine of rhG-CSF $10{\mu}g/kg$ treated group(88.9％) and ten in $5{\mu}g/kg$ treated group(83.3％) survived the sepsis and were discharged without any problems. Conclusions : RhG-CSF can increase the neutrophil count in critically ill septic neutropenic neonats. The survival rate of both groups were up to 90％. This finding suggests that both doses of rhG-CSF may be effective in a therapeutically useful time frame to treat septic neonates with neonatal neutropenia attributable to bone marrow supression or neutrophil consumption.

• Clinical and Experimental Pediatrics
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• v.52 no.10
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• pp.1153-1160
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• 2009

Purpose:To evaluate the risk factors for mortality and prognostic factors in pediatric hemato-oncology patients admitted to the pediatric intensive care unit (PICU). Methods:We retrospectively reviewed the medical records of pediatric hemato-oncology patients admitted at the PICU of the Asan Medical Center between September 2005 and July 2008. Patients admitted at the PICU for perioperative or terminal care were excluded. Results:Total 88 patients were analyzed. Overall ICU mortality rate was 34.1%. Mean age at PICU admission was $7.0{\pm}5.7$ years and mean duration of PICU stay was $18.1{\pm}22.2$ days. Hematologic diseases contributed to 77.3% of all the primary diagnoses, and the primary cause of admission was respiratory failure (39.8%). The factors related to increased mortality were C-reactive protein level (P<0.01), ventilation or dialysis requirement (P<0.01), and hematopoietic stem cell transplantation (P<0.05). In all, 3 scoring systems were investigated [Number of Organ System Failures (OSF number), the Pediatric Risk of Mortality III (PRISM III) score, and the Sequential Organ Failure Assessment (SOFA) score]; higher score correlated with worse outcome (P<0.01). The Oncological Pediatric Risk of Mortality (O-PRISM) scores of the 21 patients who had received hematopoietic stem cell transplantation were higher among the non-survivors, but not statistically significant (P=0.203). Conclusion:The PRISM III and SOFA scores obtained within 24 hours of PICU admission were found to be useful as early mortality predictors. The highest OSF number during the PICU stay was closely related to poor outcome.

• Pediatric Infection and Vaccine
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• v.27 no.2
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• pp.102-110
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• 2020

Purpose: This study aimed to investigate the clinical characteristics of human parechovirus (HPeV) infection in sepsis-like syndrome in infants aged under 3 months. Methods: Medical records of infants aged under 3 months with sepsis-like symptoms who were admitted between July 1, 2018 and August 31, 2018 were reviewed. A multiplex reverse transcription-polymerase chain reaction panel test was performed on the cerebrospinal fluid (CSF). Thirty-nine enrolled infants were categorized into three groups: 11 in group 1 (HPeV detected in the CSF), 13 in group 2 (enterovirus detected in the CSF), and 15 in group 3 (no virus detected in the CSF). Results: Compared with groups 2 and 3, a higher proportion of group 1 had tachycardia, tachypnea, apnea, and hypotension (P<0.05). A significantly lower white blood cell (WBC) count was noted in group 1 than in groups 2 and 3 (5,622±2,355/μL, 9,397±2,282/μL, and 12,312±7,452/μL, respectively; P=0.005). The CSF WBC count was lower in group 1 than in groups 2 and 3 (0.9±1.7/μL, 85.1±163.6/μL, and 3.7±6.9/μL, respectively; P=0.068). The proportion of patients requiring inotrope support (36.6% vs. 0% and 6.6%), mechanical ventilation (18.1% vs. 0% and 0%), and high flow nasal cannula (45.4% vs. 15.3% and 6.6%) was higher in group 1 than in groups 2 and 3. All patients recovered completely without complications. Conclusions: HPeV infection shows a severe clinical course and can cause a severe sepsis-like syndrome in infants aged under 3 months. Early diagnosis and proper treatment of HPeV infection are required.

• Tuberculosis and Respiratory Diseases
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• v.66 no.1
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• pp.6-12
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• 2009

Background: The efficacy of several thrombolytic agents for treating massive pulmonary thromboembolism (PTE) has been reported to be similar. However, the difference of the bleeding complications caused by two commonly used thrombolytic agents in PTE patients is not well known. The aim of this study was to compare the therapeutic efficacy and the bleeding complications between urokinase and recombinant tissue-type plasminogen activatior (rt-PA, alteplase) in a Korean medical center. Methods: We retrospectively reviewed the clinical data of the patients who were treated with thrombolytic agents (urokinase and alteplase) because of massive PTE. Results: A total of 40 patients were included: 16 (40%) treated with urokinase and 24 (60%) with alteplase. The patients treated with alteplase showed a shorter duration of using vasopressor agents than did the patients who were given urokinase, but the duration of mechanical ventilation, the length of the ICU stay and the hospital stay were not different between the thrombolytic agents. Five patients treated with urokinase and eight patients treated with alteplase died (p=0.565): One patient in the urokinase group and four patients in the alteplase group died due to pulmonary thromboembolism. Bleeding complications after thrombolysis were observed in 3 patients (7.5%) treated with urokinase and in 11 (27.5%) patients treated with alteplase (p=0.079). Major bleeding complication occurred in 2 patients who were treated with alteplase. Conclusion: Urokinase seems to have fewer bleeding complications with an equivalent efficacy, as compared to alteplase, in Korean patients who suffer with massive pulmonary thromboembolism.

• Childhood Kidney Diseases
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• v.11 no.2
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• pp.247-254
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• 2007

Purpose : Continuous renal replacement therapy(CRRT) has been the first choice for the treatment of acute renal failure in critically ill children not only in western countries but also in Korea. However, there are very few studies that have analyzed the outcome and prognosis of this modality in Korean children. We performed this study to evaluate the factors associated with the outcome and prognosis of patients treated with CRRT. Methods : We retrospectively reviewed the medical records of 32 children who had received CRRT at Severance hospital from 2003 to 2006. The mean age was 7.5 years(range 4 days-16 years) and the mean body weight was 25.8 kg (range 3.2-63 kg). Results : Eleven(34.4%) of the 32 patients survived. Bone marrow transplantation and malignancy were the most common causes of death and underlying disease leading to the need for CRRT Mean patient weight, age, duration of CRRT, number of organ failures, urine output, estimated glomerular filtration rate(eGFR), C-reactive protein, and blood urea level did not differ significantly between survivors and nonsurvivors. (1) Pediatric risk of mortality(PRISM) III score at CRRT initiation($9.8{\pm}5.3$ vs. $26.7{\pm}7.6$, P<0.0001), (2) maximum pressor number ($2.1{\pm}1.2$ vs. $3.0{\pm}1.0$, P=0.038), and (3) the degree of fluid overload($5.2{\pm}6.0$ vs. $15.0{\pm}8.9$, P=0.002) were significantly lower in survivers than in nonsurvivors. Multivariate analysis revealed that fluid overload was the only independent factor reducing survival rate. Conclusion : CRRT was successfully applied to the treatment of acute renal failure in a wide range of critically ill children. To improve survival, we suggest the early initiation of CRRT to prevent the systemic worsening and progression of fluid overload in critically ill children with acute renal failure. (J Korean Soc Pediatr Nephrol 2007;11:247-254)