Toward Green Synthesis of Graphene Oxide Using Recycled Sulfuric Acid via Couette-Taylor Flow

Developing eco-friendly and cost-effective processes for the synthesis of graphene oxide (GO) is essential for its widespread industrial applications. In this work, we propose a green synthesis technique for GO production using recycled sulfuric acid and filter-processed oxidized natural graphite obtained from a Couette-Taylor flow reactor. The viscosity of reactant mixtures processed from Couette-Taylor flow was considerably lower (???200 cP at 25 ??C) than that of those from Hummers' method, which enabled the simple filtration process. The filtered sulfuric acid can be recycled and reused for the repetitive GO synthesis with negligible differences in the as-synthesized GO qualities. This removal of sulfuric acid has great potential in lowering the overall GO production cost as the amount of water required during the fabrication process, which takes a great portion of the total production cost, can be dramatically reduced after such acid filtration. The proposed eco-friendly GO fabrication process is expected to promote the commercial application of graphene materials into industry shortly

Seawater Battery-Based Wireless Marine Buoy System with Battery Degradation Prediction and Multiple Power Optimization Capabilities

This paper presents a wireless marine buoy system based on the seawater battery (SWB), providing self-powered operation, power-efficient management, and degradation prediction and fault detection. Since conventional open circuit voltage (OCV) methods cannot be applied due to inherent cell characteristics of SWB, the coulomb counting (CC) method is adopted for the state of charge (SOC) monitoring. For the state of health (SOH), a variance-based detection scheme is proposed to provide degradation prediction and fault detection of the SWB. The self-powered operation is augmented by two proposed power optimization schemes such as multiple power management and three-step LED light control. A wireless buoy system prototype is manufactured, and its functional feasibility is experimentally verified, where its location and SOC are periodically monitored in a smartphone-based wireless platform

Molecular Mechanism of Selective Al2O3 Atomic Layer Deposition on Self-Assembled Monolayers

Area-selective atomic layer deposition (AS-ALD) of insulatingmetallicoxide layers could be a useful nanopatterning technique for makingincreasingly complex semiconductor circuits. Although the alkanethiolself-assembled monolayer (SAM) has been considered promising as anALD inhibitor, the low inhibition efficiency of the SAM during ALDprocesses makes its wide application difficult. We investigated thedeposition mechanism of Al2O3 on alkanethiol-SAMsusing temperature-dependent vibrational sum-frequency-generation spectroscopy.We found that the thermally induced formation of gauche defects inthe SAMs is the main causative factor deteriorating the inhibitionefficiency. Here, we demonstrate that a discontinuously temperature-controlledALD technique involving self-healing and dissipation of thermallyinduced stress on the structure of SAM substantially enhances theSAM's inhibition efficiency and enables us to achieve 60 ALDcycles (6.6 nm). We anticipate that the present experimental resultson the ALD mechanism on the SAM surface and the proposed ALD methodwill provide clues to improve the efficiency of AS-ALD, a promisingnanoscale patterning and manufacturing technique.11Nsciescopu

Metabolic Syndrome as a Risk Factor of Endometrial Cancer: A Nationwide Population-Based Cohort Study of 2.8 Million Women in South Korea

BackgroundA positive relationship was reported between metabolic syndrome and the risk of endometrial cancer. Studies on the relationship between metabolic syndrome and endometrial cancer have been mainly conducted in post-menopausal women. We aimed to investigate the risk of endometrial cancer according to metabolic syndrome and menopausal status using the Korean nationwide population-based cohort. MethodsWe enrolled 2,824,107 adults (endometrial cancer group; N = 5,604 and control group; N= 2,818,503) from the Korean National Health Insurance Service checkup database from January 1 to December 31, 2009. The median follow-up duration was 8.37 years. Metabolic syndrome was diagnosed as having at least three of the following five components: abdominal obesity, hypertriglyceridemia, low levels of high-density lipoprotein cholesterol, raised blood pressure, and hyperglycemia. Multivariate Cox proportional hazard models were used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) to estimate endometrial cancer risk. ResultsThe endometrial cancer risk was higher in the metabolic syndrome group than that in the non-metabolic syndrome group (HR, 1.362; 95% CI, 1.281-1.449). The association between metabolic syndrome and endometrial cancer risk was significant in the premenopausal subgroup (HR, 1.543; 95% CI, 1.39-1.713) and postmenopausal subgroup (HR, 1.306; 95% CI, 1.213-1.407). The incidence of endometrial cancer was more closely related to metabolic syndrome components in the pre-menopausal subgroup than those in the post-menopausal subgroup (for waist circumference, blood pressure, triglycerides and high-density lipoprotein cholesterol, all p for interaction <0.0001 respectively, and for fasting blood glucose, p for interaction 0.0188). The incidence of endometrial cancer positively correlated with the number of metabolic syndrome components (log-rank p <0.0001). ConclusionOur large population-based cohort study in Korean women suggests that metabolic syndrome and its accumulated components may be risk factors for endometrial cancer, particularly in the pre-menopausal women.N

Does Coronary Vasospasm Show a Better Prognosis in Out of Hospital Cardiac Arrest: Data from the Korean Cardiac Arrest Research Consortium (KoCARC) Registry

BACKGROUND: Previous cohort studies focused on relative risk stratification among patients diagnosed with vasospastic angina, and it is unknown how much vasospasm accounts for the cause of out-of-hospital cardiac arrest, and whether prognosis differs. METHODS: From a registry data collected from 65 hospitals in Korea, 863 subjects who survived hospital cardiac arrest were evaluated. The patients with insignificant coro- nary lesion, vasospasm, and obstructive lesion were each grouped as group I, group II, and group III, respectively. The primary and secondary outcomes were survival to hospital discharge and good neurological function at discharge defined as cerebral performance index 1. RESULTS: At hospital discharge, 529 subjects (61.3%) survived. There was no significant dif- ference in survival according to coronary angiographic findings (P = .133 and P = .357, group II and group III compared to group I), but the neurological outcome was significantly bet- ter in groups II and III (P = .046 and P = .022, groups II and III compared to group I). Two mul- tivariate models were evaluated to adjust traditional risk factors and cardiac biomarkers. The presence of coronary artery vasospasm did not affect survival to hospital discharge (P = 0.060 and P = .162 for both models), but neurological function was significantly better (OR: 1.965, 95% CI: 1.048-3.684, P = .035, and OR: 1.706, 95% CI: 1.012-2.878, P = .045 for vasospasm, models I and II, respectively). CONCLUSIONS: Coronary vasospasm does not show better survival to hospital discharge, but shows better neurological outcomes. Aggressive coronary angiography and intensive medical treatment for adequate control of vasospasm should be emphasized to prevent and manage fatal events.N