• Neonatal Medicine
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• v.18 no.2
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• pp.320-327
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• 2011

Purpose: To determine the effect of changing practice guidelines designed to avoid hyperoxia or hypoxia in very low birth weight or very preterm infants. Methods: We analyzed a database of <1,500 g birth weight or <32 weeks of gestation infants who were born and admitted to the neonatal intensive care unit of Chungnam National University Hospital from January 2007 to July 2010. First, we defined the relationship between arterial partial pressure of oxygen ($PaO_2$) and pulse oxygen saturation ($SpO_2$). When we evaluated 96 pairs of $PaO_2$ and $SpO_2$ measurements, oxygen saturation was 90-94% at a $PaO_2$ of 43-79 mmHg on the oxyhemoglobin dissociation curve, according to pulse oximetry. Based on this observation, a change in practice was instituted in August 2008 with the objective of avoiding hypoxia and hyperoxia in preterm infants with targeting a $SpO_2$ 90-94% (period II). Before the change in practice, high alarms for $SpO_2$ were set at 100% and low alarms at 95% (period I). Results: Sixty-eight infants the met enrollment criteria and 38 (56%) were born during period II, after the change in $SpO_2$ targets. Demographic characteristics, except gender, were similar between the infants born in both periods. After correcting for the effect of confounding factors, the rates for mortality, severe retinopathy of prematurity, and IVH attended to be lower than those for infants in period II. No difference in the rate of patent ductus arteriosus needed to treat was observed. Conclusion: A change in the practice guidelines aimed at avoiding low oxygen saturation and hyperoxia did not increase neonatal complication rates and showed promising results, suggesting decreased mortality and improvements in short term morbidity. It is still unclear what range of oxygen saturation is appropriate for very preterm infants but the more careful saturation targeting guideline should be considered to prevent hypoxemic events and hyperoxia.

• Journal of the Korean Geotechnical Society
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• v.28 no.3
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• pp.55-66
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• 2012

To investigate the hysteresis of the suction stress in unsaturated weathered mudstone soils (CL), matric suction and volumetric water content were measured in both drying and wetting processes using Automated Soil-Water Characteristics Curve Apparatus. The drying and wetting processes in unsaturated soils were reproduced in the test; the drying process means to load matric suction to spill pore water from the soils, and the wetting process means to unload matric suction to inject pore water into the soils. Based on the measured result, Soil Water Characteristic Curve(SWCC)s were estimated by van Genuchten model (1980). SWCCs have nonlinear relationship between effective degree of saturation and matric suction. The hysteresis in SWCCs between drying and wetting processes occurred. As a result of estimating Suction Stress Characteristic Curve(SSCC) using Lu and Likos model (2006), the suction stress rapidly increased in the low level of matric suction and then increased slightly. Also, the hysteresis in SSCCs between drying and wetting processes occurred. In order to design geo-structures and check its stability considering unsaturated soil mechanics, therefore, it is more reasonable that the SSCC of drying process should be applied in the condition of rainfall infiltration and the SSCC of wetting process in the condition of evaporation or drainage.

• Toxicological Research
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• v.6 no.2
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• pp.205-213
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• 1990

The regulation of neurotoxicants has usually been based upon setting reference doses by dividing a no observed adverse effect level (NOAEL) by uncertainty factors that theoretically account for interspecies and intraspecies extraploation of experimental results in animals to humans. Recently, we have proposed a four-step alternative procedure which provides quantitative estimates of risk as a function of dose. The first step is to establish a mathematical relationship between a biological effect or biomarker and the dose of chemical administered. The second step is to determine the distribution (variability) of individual measurements of biological effects or their biomarkers about the dose response curve. The third step is to define an adverse or abnormal level of a biological effect or biomarker in an untreated population. The fourth and final step is to combine the information from the first three steps to estimate the risk (proportion of individuals exceeding on adverse or abnormal level of a biological effect or biomarker) as a function of dose. The primary purpose of this report is to enhance the certainty of the first step of this procedure by improving our understanding of the relationship between a biomarker and dose of administered chemical. Several factors which need to be considered include: 1) the pharmacokinetics of the parent chemical, 2) the target tissue concentrations of the parent chemical or its bioactivated proximate toxicant, 3) the uptake kinetics of the parent chemical or metabolite into the target cell(s) and/or membrane interactions, and 4) the interaction of the chemical or metabolite with presumed receptor site(s). Because these theoretical factors each contain a saturable step due to definitive amounts of required enzyme, reuptake or receptor site(s), a nonlinear, saturable dose-response curve would be predicted. In order to exemplify this process, effects of the neurotoxicant, methlenedioxymethamphetamine (MDMA), were reviewed and analyzed. Our results and those of others indicate that: 1) peak concentrations of MDMA and metabolites are ochieved in rat brain by 30 min and are negligible by 24 hr, 2) a metabolite of MDMA is probably responsible for its neurotoxic effects, and 3) pretreatment with monoamine uptake blockers prevents MDMA neurotoxicity. When data generated from rats administerde MDMA were plotted as bilolgical effect (decreases in hippocampal serotonin concentrations) versus dose, a saturation curve best described the observed relationship. These results support the hypothesis that at least one saturable step is involved in MDMA neurotoxicity. We conclude that the mathematical relationship between biological effect and dose of MDMA, the first step of our quantitative neurotoxicity risk assessment procedure, should reflect this biological model information generated from the whole of the dose-response curve.

• Journal of the Korean Geotechnical Society
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• v.30 no.3
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• pp.47-58
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• 2014

To investigate the unsaturated characteristics of the tailings obtained from the waste dump at Imgi mine, matric suction and volumetric water content were measured in both drying and wetting processes using Automated Soil-Water Characteristics Curve Apparatus. Based on the measured result, Soil Water Characteristic Curves (SWCC) were estimated by van Genuchten model. According to the unsaturated soil classification method, the tailings of the waste dump correspond to clayey sand. As a result of Suction Stress Characteristic Curve (SSCC) by Lu and Likos model, SSCC has a shape of S which is similar to SWCC. The hysteresis phenomenon occurred in SSCCs, which means the suction stress of drying path is larger than that of wetting path in the same effective degree of saturation. The effective stress of unsaturated soil is equal to that of saturated soil when matric suction is less than Air Entry Value (AEV). However, the effective stress of unsaturated soil is larger than that of saturated soil when matic suction is more than AEV. Meanwhile, unsaturated hydraulic conductivity by van Genuchten model decreased with increasing matric suction, and the hydraulic conductivity of drying path is larger than that of wetting path.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3006-3013
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• 2015

Flat tube heat exchangers can improve the thermal performance significantly compared with round tube heat exchangers. For proper design of flat tube heat exchangers, one should know the tubeside heat transfer coefficients. In this study, convective boiling heat transfer coefficients of R-410A were obtained in a flat extruded aluminum tube with $D_h=1.41mm$. The test range covered mass flux from 200 to $600kg/m^2s$, heat flux from 5 to $15kW/m^2$ and saturation temperature from $5^{\circ}C$ to $15^{\circ}C$. The heat transfer coefficient curve shows a decreasing trend after a certain quality(critical quality). The critical quality decreases as the heat flux increases, and as the mass flux decreases. The early dryout at a high heat flux results in a unique 'cross-over' of the heat transfer coefficient curves. The heat transfer coefficient increases as the mass flux increases. At a low quality region, however, the effect of mass flux is not prominent. The heat transfer coefficient increases as the saturation temperature increases. The effect of saturation temperature, however, diminishes as the heat flux decreases. Both the Shah and the Kaew-On et al. correlations reasonably predicted the present data.

• Tuberculosis and Respiratory Diseases
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• v.84 no.2
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• pp.125-133
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• 2021

Background: The coronavirus disease (COVID-19) can manifest in a range of symptoms, including both asymptomatic systems which appear nearly non-existent to the patient, all the way to the development of acute respiratory distress syndrome (ARDS). Specifically, COVID-19-associated pneumonia develops into ARDS due to the rapid progression of hypoxia, and although arterial blood gas analysis can assist in halting this deterioration, the current environment provided by the COVID-19 pandemic, which has led to an overall lack of medical resources or equipment, has made it difficult to administer such tests in a widespread manner. As a result, this study was conducted in order to determine whether the levels of oxygen saturation (SpO₂) and the fraction of inhaled oxygen (FiO₂) (SF ratio) can also serve as predictors of ARDS and the patient's risk of mortality. Methods: This was a retrospective cohort study conducted from February 2020 to Mary 2020, with the study's subjects consisting of COVID-19 pneumonia patients who had reached a state of deterioration that required the use of oxygen therapy. Of the 100 COVID-19 pneumonia cases, we compared 59 pneumonia patients who required oxygen therapy, divided into ARDS and non-ARDS pneumonia patients who required oxygen, and then investigated the different factors which affected their mortality. Results: At the time of admission, the ratios of SpO₂, FiO₂, and SF for the ARDS group differed significantly from those of the non-ARDS pneumonia support group who required oxygen (p<0.001). With respect to the predicting of the occurrence of ARDS, the SF ratio on admission and the SF ratio at exacerbation had an area under the curve which measured to be around 85.7% and 88.8% (p<0.001). Multivariate Cox regression analysis identified that the SF ratio at exacerbation (hazard ratio [HR], 0.916; 95% confidence interval [CI], 0.846-0.991; p=0.029) and National Early Warning Score (NEWS) (HR, 1.277; 95% CI, 1.010-1.615; p=0.041) were significant predictors of mortality. Conclusion: The SF ratio on admission and the SF ratio at exacerbation were strong predictors of the occurrence of ARDS, and the SF ratio at exacerbation and NEWS held a significant effect on mortality.

• Korean Journal of Radiology
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• v.22 no.5
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• pp.770-781
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• 2021

Objective: Chemical exchange-dependent saturation transfer (CEST) MRI is sensitive for detecting solid-like proteins and may detect changes in the levels of mobile proteins and peptides in tissues. The objective of this study was to evaluate the characteristics of chemical exchange proton pools using the CEST MRI technique in patients with dementia. Materials and Methods: Our institutional review board approved this cross-sectional prospective study and informed consent was obtained from all participants. This study included 41 subjects (19 with dementia and 22 without dementia). Complete CEST data of the brain were obtained using a three-dimensional gradient and spin-echo sequence to map CEST indices, such as amide, amine, hydroxyl, and magnetization transfer ratio asymmetry (MTR_asym) values, using six-pool Lorentzian fitting. Statistical analyses of CEST indices were performed to evaluate group comparisons, their correlations with gray matter volume (GMV) and Mini-Mental State Examination (MMSE) scores, and receiver operating characteristic (ROC) curves. Results: Amine signals (0.029 for non-dementia, 0.046 for dementia, p = 0.011 at hippocampus) and MTR_asym values at 3 ppm (0.748 for non-dementia, 1.138 for dementia, p = 0.022 at hippocampus), and 3.5 ppm (0.463 for non-dementia, 0.875 for dementia, p = 0.029 at hippocampus) were significantly higher in the dementia group than in the non-dementia group. Most CEST indices were not significantly correlated with GMV; however, except amide, most indices were significantly correlated with the MMSE scores. The classification power of most CEST indices was lower than that of GMV but adding one of the CEST indices in GMV improved the classification between the subject groups. The largest improvement was seen in the MTR_asym values at 2 ppm in the anterior cingulate (area under the ROC curve = 0.981), with a sensitivity of 100 and a specificity of 90.91. Conclusion: CEST MRI potentially allows noninvasive image alterations in the Alzheimer's disease brain without injecting isotopes for monitoring different disease states and may provide a new imaging biomarker in the future.

• Advances in aircraft and spacecraft science
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• v.5 no.4
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• pp.499-513
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• 2018

One of the major problems in glass fiber reinforced epoxy (GFRE) composite pipes is the durability under water absorption. This condition is generally recognized to cause degradations in strength and mechanical properties. Therefore, there is a need for an intelligent system for detecting the absorption rate and computing the mass of water absorption (M%) as a function of absorption time (t). The present work represents a new non-destructive evaluation (NDE) technique for detecting the water absorption rate by evaluating the dielectric properties of glass fiber and epoxy resin composite pipes subjected to internal hydrostatic pressure at room temperature. The variation in the dielectric signatures is employed to design an electrical capacitance sensor (ECS) with high sensitivity to detect such defects. ECS consists of twelve electrodes mounted on the outer surface of the pipe. Radius-electrode ratio is defined as the ratio of inner and outer radius of pipe. A finite element (FE) simulation model is developed to measure the capacitance values and node potential distribution of ECS electrodes on the basis of water absorption rate in the pipe material as a function of absorption time. The arrangements for positioning12-electrode sensor parameters such as capacitance, capacitance change and change rate of capacitance are analyzed by ANSYS and MATLAB to plot the mass of water absorption curve against absorption time (t). An analytical model based on a Fickian diffusion model is conducted to predict the saturation level of water absorption ($M_S$) from the obtained mass of water absorption curve. The FE results are in excellent agreement with the analytical results and experimental results available in the literature, thus, validating the accuracy and reliability of the proposed expert system.

• Korean Journal of Animal Reproduction
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• v.18 no.2
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• pp.95-99
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• 1994

The purpose of the present study was to determine the in vivo effect of oxytocin antagonist-I(Al) on uterine oxytocin receptor number (Rn) and/or binding affinity (Kd) in the estrous rat. Anesthetized rats were given a bolus infusion of control or 5${\mu}\textrm{g}$ of AI and sacri-ficed 0.5 and 4 hours later. The uterine tissue was removed, trimmed and frozen. Membrane oxytocin receptors were isolated after homogenization of uterine tissue and differential ultracentrifugation. The oxytocin receptor assay was performed by saturation with cold oxytocin competion with a high specific activity oxytocin antagonist. Rn and Kds were determined by nonlinear curve fitting methods. No differences(p>0.05) between the AI and control treated animals in either oxytocin receptor number or binding affinity was detected in this study. These data suggest that the major mode of action of AI is via competitive inhibition at the uterine oxytocin receptor and not by altering receptor number or binding affinity.

• Journal of the Korean Institute of Telematics and Electronics
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• v.26 no.5
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• pp.46-51
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• 1989

The degradation phenomena induced by hot-carrier injection was studied from the shift of threshold voltage and subthreshold current curve in LDD NMOSFET degraded under different DC stress-biases. Threshold voltage shift ${Delta}V_{tex}$ defined in saturation region was separated into contri butions due to trapped oxide charge $V_{ot}$ and interface traps ${Delta}V_{it}$ generated from midgap to threshold voltage. Under th positive stress electric field (TEX>$V_g>V_d$) condition, the shift of threshold voltage was attributed to the electrons traped ar gate oxide but subthreshold swing was not negative stress electric field ($V_g) condition, holes seems to be injected positive charges so threshold voltage and subthreshold swing were increased.