Geopolitics vs. Public Health? Determinants of U.S. Overseas COVID-19 Vaccine Donations

This thesis investigates the factors driving the U.S. decision to prioritize particular countries over others in its COVID-19 vaccine donations. The United States has claimed that it provides vaccines to countries in need. However, descriptive evidence suggests that factors other than need influence U.S. donations, as apparent in its contributions to high-income nations. The literature presents three theories to explain why the United States gives aid: response to countries' perceived needs, commitment to allies, and quid pro quo for other goals. To examine the extent to which each of these accounts for U.S. vaccine diplomacy, this thesis regresses the cumulative U.S. deliveries of vaccine doses abroad on measures of recipients' needs and their geopolitical importance to the United States. The regression results suggest that: a) the United States donated more vaccines per capita to nations with lower GDP per capita; b) countries in the Middle East and NATO members received fewer doses per capita; c) nations with significant U.S. military presence, major non-NATO allies, and those physically closer to the United States received more doses per capita. These results are robust to other confounders and alternative formulations of the dependent variable. In addition to the usual robustness checks, this thesis conducts sensitivity analyses to test its findings. The results imply that U.S. COVID-19 vaccine diplomacy manifests a dual mandate of charity and self-interest by concurrently donating to countries in need and to those that contemporaneous U.S. foreign policy values more

Experimental Study on Effects of Lubricant Oil in a Domestic Refrigerator-Freezer

Lubricant oil is essential for lubricating moving parts and cooling the components in a refrigerant compressor. However, the oil deteriorates heat transfer performance in the heat exchangers, and increases pressure drop in a refrigeration circuit. In this study, investigation of the effects of lubricant oil circulating in heat exchangers on the performance of the domestic refrigerator-freezer was carried out by performing some experiments. The experiments were conducted for conventional and oil-less systems with using a linear compressor in an environmental chamber to compare the cooling capacity, power consumption, and operating characteristics such as temperatures and pressures at inlets and outlets of each component, mass flow rate, and cooling time. The cooling capacity and power consumption of two systems were measured during the on-off cyclic tests. Comparing the experimental data for the conventional and the oil-less systems, the discharge temperature of the oil-less system is higher than that of the conventional system more than 20℃. However, due to the oil removal, the heat transfer performance was improved and the condenser outlet temperature was measured lower than the conventional about 1℃. The power consumption of the oil-less system was reduced by about 4.0% compared to the system with the lubricant oil

Numerical Investigation on Effects of Sub-cooling Methods on Performance of Multi-split Variable Refrigerant Flow Systems with Bypass and Vapor Injection Techniques

The pipeline connected between outdoor units and indoor units is lengthened in the VRF systems because the VRF systems are generally used in light commercial buildings. Therefore, a sub-cooler is installed in the VRF systems to avoid flash gas caused by pressure drop and heat transfer in the liquid pipeline. Usually, the liquid refrigerant in the pipeline can be cooled by bypass and refrigerant injection techniques with an internal heat exchanger (IHX) and electric expansion valve (EEV). In this study, the performance of the VRF systems using bypass and refrigerant injection cycles are compared by numerical method. The simulation for multi-split VRF is developed with considering application of vapor injection and bypass cycle and validated with experimental data. The bypass and refrigerant injection have improvement potential for cooling capacity by 3.11% and 15.5%, respectively due to increasing enthalpy difference in evaporators. The vapor injection technique has more improvement potential of performance than bypass technique. Subcooling degree at inlet of EEV is above 10°C degree in two systems, which can avoid flash gas generation

Prediction of Refrigerant Leakage for Discharge Valve System in A Rolling Piston Rotary Compressor

The flow coefficient of a discharge valve system with lift height was functionalized by experiments and Computational Fluid Dynamics(CFD) simulation to predict the mass flow rate through a discharge valve system in a rolling piston compressor with different compressor frequency and operating conditions. The flow coefficients of the discharge valve system were determined by both experiments and CFD simulation for specifically configured condition with varying discharge port diameter, valve lift height and valve shape to consider operating and geometric conditions. The experiment and CFD simulation were conducted under the incompressible flow and steady state. Ambient air was used as a working fluid. In order to verify the reliability of CFD simulation, the computational results were compared with those of experiment. The flow coefficient maps for each discharge valve system could be obtained from the computational results. The functional flow coefficient model was derived from the maps. It was applied to compressor performance simulation to calculate mass flow rate at the discharge valve system as a function of diameter of discharge port and lift height of the valve. Energy Efficiency Ratio(EER) obtained from the functional flow coefficient model with varying compressor frequency showed good agreement with experimental data. The Functionalization of flow coefficient may improve the precision of compressor performance simulation

Pentoxifylline Attenuates Methionine- and Choline-Deficient-Diet-Induced Steatohepatitis by Suppressing TNF- α

Background. Pentoxifylline (PTX) anti-TNF properties are known to exert hepatoprotective effects in various liver injury models. The aim of this study was to investigate whether PTX has beneficial roles in the development of methionine- and choline-deficient-(MCD-) diet-induced NAFLD SD rats in vivo and TNF-α-induced Hep3B cells in vitro. Methods. SD Rats were classified according to diet (chow or MCD diet) and treatment (normal saline or PTX injection) over a period of 4 weeks: group I (chow + saline, n=4), group II (chow + PTX), group III (MCD + saline), and group IV (MCD + PTX). Hep3B cells were treated with 100 ng/ml TNF-α (24 h) in the absence or presence of PTX (1 mM). Results. PTX attenuated MCD-diet-induced serum ALT levels and hepatic steatosis. In real-time PCR and western blotting analysis, PTX decreased MCD-diet-induced TNF-alpha mRNA expression and proapoptotic unfolded protein response by ER stress (GRP78, p-eIF2, ATF4, IRE1α, CHOP, and p-JNK activation) in vivo. PTX (1 mM) reduced TNF-α-induced activation of GRP78, p-eIF2, ATF4, IRE1α, and CHOP in vitro. Conclusion. PTX has beneficial roles in the development of MCD-diet-induced steatohepatitis through partial suppression of TNF-α and ER stress

Impact of successful restoration of sinus rhythm in patients with atrial fibrillation and acute heart failure: Results from the Korean Acute Heart Failure registry

Background: Restoring and maintaining sinus rhythm (SR) in patients with atrial fibrillation (AF) failed to show superior outcomes over rate control strategies in prior randomized trials. However, there is sparse data on their outcomes in patients with acute heart failure (AHF).Methods: From December 2010 to February 2014, 5,625 patients with AHF from 10 tertiary hospitals were enrolled in the Korean Acute Heart Failure registry, including 1,961 patients whose initial electrocardiogram showed AF. Clinical outcomes of patients who restored SR by pharmacological or electrical cardioversion (SR conversion group, n = 212) were compared to those of patients who showed a persistent AF rhythm (AF persistent group, n = 1,662).Results: All-cause mortality both in-hospital and during the follow-up (median 2.5 years) were significantly lower in the SR conversion group than in the AF persistent group after adjustment for risk factors (adjusted hazard ratio [HR]; 95% confidence interval [CI] = 0.26 [0.08–0.88], p = 0.031 and 0.59 [0.43–0.82], p = 0.002, for mortality in-hospital and during follow-up, respectively). After 1:3 propensity score matching (SR conversion group = 167, AF persistent group = 501), successful restoration of SR was associated with lower all-cause mortality (HR [95% CI] = 0.68 [0.49–0.93], p = 0.015), heart failure rehospitalization (HR [95% CI] = 0.66 [0.45–0.97], p = 0.032), and composite of death and heart failure rehospitalization (HR [95% CI] = 0.66 [0.51–0.86], p = 0.002).Conclusions: Patients with AHF and AF had significantly lower mortality in-hospital and during follow-up if rhythm treatment for AF was successful, underscoring the importance of restoring SR in patients with AHF

Decreased Expression of Angiogenin in the Eutopic Endometrium from Women with Advanced Stage Endometriosis

Angiogenin, a potent inducer of angiogenesis, is expressed in human endometrium. This study was performed to compare the expression of angiogenin mRNA level in the eutopic endometrium from women with and without endometriosis. Thirty-two women with advanced stage endometriosis and 29 control women were recruited. Following isolation of total RNA from endometrial tissue and reverse transcription, cDNA samples were amplified by real time polymerase chain reaction to quantify the expression of angiogenin genes. In selected patients, immunohistochemical staining was utilized to localize the area of angiogenin expression. Angiogenin mRNA level was significantly lower in the endometriosis group than in the control group during the secretory phase, especially the mid-secretory phase, and the decline was observed mainly in the women who presented with infertility. Within the endometriosis group, angiogenin mRNA levels did not differ between the proliferative and secretory phases, but, in the control group, the level in the secretory phase was higher than that during the proliferative phase. Immunohistochemistry showed that the glandular epithelial cell layer was decorated positively in both groups. These findings suggest that the relative deficiency of angiogenin expression in the secretory endometrium could impair implantation in women with advanced stage endometriosis

Characteristics, Outcomes and Predictors of Long-Term Mortality for Patients Hospitalized for Acute Heart Failure: A Report From the Korean Heart Failure Registry

BACKGROUND AND OBJECTIVES: Acute heart failure (AHF) is associated with a poor prognosis and it requires repeated hospitalizations. However, there are few studies on the characteristics, treatment and prognostic factors of AHF. The aims of this study were to describe the clinical characteristics, management and outcomes of the patients hospitalized for AHF in Korea. SUBJECTS AND METHODS: We analyzed the clinical data of 3,200 hospitalization episodes that were recorded between June 2004 and April 2009 from the Korean Heart Failure (KorHF) Registry database. The mean age was 67.6±14.3 years and 50% of the patients were female. RESULTS: Twenty-nine point six percent (29.6%) of the patients had a history of previous HF and 52.3% of the patients had ischemic heart disease. Left ventricular ejection fraction (LVEF) was reported for 89% of the patients. The mean LVEF was 38.5±15.7% and 26.1% of the patients had preserved systolic function (LVEF ≥50%), which was more prevalent in the females (34.0% vs. 18.4%, respectively, p<0.001). At discharge, 58.6% of the patients received beta-blockers (BB), 53.7% received either angiotensin converting enzyme-inhibitors or angiotensin receptor blockers (ACEi/ARB), and 58.4% received both BB and ACEi/ARB. The 1-, 2-, 3- and 4-year mortality rates were 15%, 21%, 26% and 30%, respectively. Multivariate analysis revealed that advanced age {hazard ratio: 1.023 (95% confidence interval: 1.004-1.042); p=0.020}, a previous history of heart failure {1.735 (1.150-2.618); p=0.009}, anemia {1.973 (1.271-3.063); p=0.002}, hyponatremia {1.861 (1.184-2.926); p=0.007}, a high level of serum N-terminal pro-B-type natriuretic peptide (NT-proBNP) {3.152 (1.450-6.849); p=0.004} and the use of BB at discharge {0.599 (0.360-0.997); p=0.490} were significantly associated with total death. CONCLUSION: We present here the characteristics and prognosis of an unselected population of AHF patients in Korea. The long-term mortality rate was comparable to that reported in other countries. The independent clinical risk factors included age, a previous history of heart failure, anemia, hyponatremia, a high NT-proBNP level and taking BB at discharge.ope