ABSTRACT
The necessity for portable cooling devices to prevent thermal-related diseases in workers wearing protective clothing in hot outdoor weather conditions, such as COVID-19 quarantine sites, is increasing. Coolers for such purposes require a compact design and low-power consumption characteristics to maximize wearability and operating time. Therefore, a thermoelectric device based on the Peltier effect has been widely used rather than a relatively bulky system based on a refrigeration cycle accompanying the phase change of a refrigerant. Despite a number of previous experimental and numerical studies on the Peltier cooling device, there remains much research to be conducted on the effect and removal of motor-related internal heat sources deteriorating the cooling performance. Specifically, this paper presents thermo-electro-fluidic simulations on the impact of heat from an air blower on the coefficient of performance of a Peltier cooler. In addition, a numerical study on the outcome of heat source removal is also evaluated and discussed to draw an improved design of the cooler in terms of cooling capacity and coefficient of performance. The simulation results predicted that the coefficient of performance could be raised by 10.6% due to the suppression of heat generation from a blower motor. Accordingly, the cooling capacity of the specific Peltier cooler investigated in this study was expected to be considerably improved by 80.6% from 4.68 W to 8.45 W through the design change.
ABSTRACT
INTRODUCTION: Rhabdomyolysis describes a condition where muscle tissue destruction occurs. Mortality and morbidity can be significant especially when multi-organ injury ensues. In very few instances, myocarditis has been described in association with this condition. DESCRIPTION: An 11-year-old previously healthy female presents with vomiting, diarrhea, tactile fever, worsening severe bilateral leg pain and gross hematuria for four days. At the Emergency Department, her ECG showed ST depression in lateral leads and abnormal Q waves. Laboratory studies were notable for significantly elevated CK >330,000 U/L. Elevated Troponin T and Troponin I at 3.60 ng/ml and 0.54 ng/mL, respectively. Elevation of CRP 23.5 mg/dl, ALT 1,966 U/L, AST 5,956 U/L, and Ferritin 712.1 ng/ml. Patient had dark brown urine, which was positive for blood, and urine myoglobin peaked at 2690 ng/mL. Her renal function was normal with blood urea nitrogen 8 mg/dl and creatinine 0.4 mg/dl. C3 and C4 levels were decreased, 45 mg/dl and 5 mg/dl, respectively. Anti-dsDNA negative, ANCA negative, and ANA negative. Nasopharyngeal PCR was negative for Mycoplasma pneumoniae, influenza A and B. Blood enterovirus PCR negative. COVID PCR and antibodies negative. Neuromuscular genetic testing was non-diagnostic. Her echocardiography showed thin rim of pericardial effusion and normal ejection fraction. Cardiac MRI demonstrated myocardial edema and regional sub-epicardial delayed enhancement consistent with acute myocarditis. Patient was started on hyperhydration therapy, Solumedrol and intravenous immunoglobulin. The rhabdomyolysis resulted in severe extremity weakness requiring prolonged rehabilitation. Her condition and biomarkers normalized and was subsequently discharged home. Follow up cardiac MRI 6 months later showed increased extracellular volume (ECV) of 38% suggestive of focal and diffuse areas of fibrosis. Patient remains under physical activity restrictions and is being followed by cardiology service. DISCUSSION: Our case highlights severe rhabdomyolysis in association with acute myocarditis and subsequent cardiac structural abnormalities. Although it remains unclear whether myocarditis evolved as a complication of rhabdomyolysis or was triggered by same inciting agent, an infectious etiology overall remains the most likely culprit.
ABSTRACT
The observed monthly mean PM2.5 concentration in South Korea during December 2020 has decreased by 2.3 mu g/m(3), compared to that during the same month in the previous year, but the drivers of the change have been veiled yet.This study quantitatively examines the roles of the potential drivers of the PM2.5 decrease during December 2020. Air quality simulations for December 2019 and December 2020 show that the change in meteorology conditions have increased the PM2.5 concentrations by 1.4 mu g/m(3) in South Korea, but the changes in the Northeast Asian emissions have decreased the PM(2.5 )concentrations by 3.7 mu g/m(3) in the country. In addition, foreign emission impact on the nationwide PM2.5 concentrations estimated from a set of the sensitivity simulations with the Community Multi-scale Air Quality model and adjusted with the surface observations in China has increased by 1.9 mu g/m(3) in December 2020, compared to that for December 2019. It means that the upwind foreign emission condition was not helpful in the downwind PM2.5 decrease. On the contrary, the domestic impact has decreased by 4.2 mu g/m(3) over the country, which compensated the increase in the foreign impact for the month. The observed monthly mean NO2 concentrations have decreased by 5% and 8% for South Korea and the Seoul Metropolitan Area, respectively, compared to the same month in 2019. When a simple observation-based emission adjustment was applied, a 5% decrease in the national total NO, emissions for the month was estimated. The causality of NO2 decrease still needs further investigations, but the seasonal PM2.5 management and social distancing after the COVID-19 re-outbreak at the end of November might have led to the reduction in the anthropogenic emissions (i.e., NOx) and thus the PM2.5 concentrations during the month.
ABSTRACT
The observed monthly mean PM2.5concentration in South Korea during December 2020 has decreased by 2.3 μg/m3, compared to that during the same month in the previous year, but the drivers of the change have been veiled yet. This study quantitatively examines the roles of the potential drivers of the PM2.5decrease during December 2020. Air quality simulations for December 2019 and December 2020 show that the change in meteorology conditions have increased the PM2.5concentrations by 1.4 μg/m3in South Korea, but the changes in the Northeast Asian emissions have decreased the PM2.5concentrations by 3.7 μg/m3in the country. In addition, foreign emission impact on the nationwide PM2.5concentrations estimated from a set of the sensitivity simulations with the Community Multi-scale Air Quality model and adjusted with the surface observations in China has increased by 1.9 μg/m3in December 2020, compared to that for December 2019. It means that the upwind foreign emission condition was not helpful in the downwind PM2.5decrease. On the contrary, the domestic impact has decreased by 4.2 μg/m3over the country, which compensated the increase in the foreign impact for the month. The observed monthly mean NO2concentrations have decreased by 5% and 8% for South Korea and the Seoul Metropolitan Area, respectively, compared to the same month in 2019. When a simple observation-based emission adjustment was applied, a 5% decrease in the national total NOxemissions for the month was estimated. The causality of NO2decrease still needs further investigations, but the seasonal PM2.5management and social distancing after the COVID-19 re-outbreak at the end of November might have led to the reduction in the anthropogenic emissions (i.e., NOx) and thus the PM2.5concentrations during the month. © 2021. All Rights Reserved.