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638 result(s) for "Park, G.-H."
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Global ocean carbon uptake: magnitude, variability and trends
The globally integrated sea–air anthropogenic carbon dioxide (CO2) flux from 1990 to 2009 is determined from models and data-based approaches as part of the Regional Carbon Cycle Assessment and Processes (RECCAP) project. Numerical methods include ocean inverse models, atmospheric inverse models, and ocean general circulation models with parameterized biogeochemistry (OBGCMs). The median value of different approaches shows good agreement in average uptake. The best estimate of anthropogenic CO2 uptake for the time period based on a compilation of approaches is −2.0 Pg C yr−1. The interannual variability in the sea–air flux is largely driven by large-scale climate re-organizations and is estimated at 0.2 Pg C yr−1 for the two decades with some systematic differences between approaches. The largest differences between approaches are seen in the decadal trends. The trends range from −0.13 (Pg C yr−1) decade−1 to −0.50 (Pg C yr−1) decade−1 for the two decades under investigation. The OBGCMs and the data-based sea–air CO2 flux estimates show appreciably smaller decadal trends than estimates based on changes in carbon inventory suggesting that methods capable of resolving shorter timescales are showing a slowing of the rate of ocean CO2 uptake. RECCAP model outputs for five decades show similar differences in trends between approaches.
Data-based estimates of the ocean carbon sink variability – first results of the Surface Ocean pCO2 Mapping intercomparison (SOCOM)
Using measurements of the surface-ocean CO2 partial pressure (pCO2) and 14 different pCO2 mapping methods recently collated by the Surface Ocean pCO2 Mapping intercomparison (SOCOM) initiative, variations in regional and global sea–air CO2 fluxes are investigated. Though the available mapping methods use widely different approaches, we find relatively consistent estimates of regional pCO2 seasonality, in line with previous estimates. In terms of interannual variability (IAV), all mapping methods estimate the largest variations to occur in the eastern equatorial Pacific. Despite considerable spread in the detailed variations, mapping methods that fit the data more closely also tend to agree more closely with each other in regional averages. Encouragingly, this includes mapping methods belonging to complementary types – taking variability either directly from the pCO2 data or indirectly from driver data via regression. From a weighted ensemble average, we find an IAV amplitude of the global sea–air CO2 flux of 0.31 PgC yr-1 (standard deviation over 1992–2009), which is larger than simulated by biogeochemical process models. From a decadal perspective, the global ocean CO2 uptake is estimated to have gradually increased since about 2000, with little decadal change prior to that. The weighted mean net global ocean CO2 sink estimated by the SOCOM ensemble is -1.75 PgC yr-1 (1992–2009), consistent within uncertainties with estimates from ocean-interior carbon data or atmospheric oxygen trends.
Cyclic Loading Test for Precast Columns Using Slag-Based Concrete and Sleeve Splices
Slag-based zero-cement concrete (ZC) of high strength (60 MPa [8.70 ksi]) was developed as an eco-friendly construction material. In the present study, to investigate the structural behavior of precast columns using ZC, cyclic loading tests were performed for five column specimens with reinforcement details of ordinary moment frames. Longitudinal reinforcement was connected by sleeve splices at the precast column-footing joint. The test parameters included the concrete type (portland cement-based normal concrete [NC] versus ZC), construction method (monolithic versus precast), longitudinal reinforcement ratio, and sleeve size. The test results showed that the structural performance (failure mode, strength, stiffness, energy dissipation, and deformation capacity) of the precast ZC columns was comparable to that of the monolithic NC and precast NC columns, and the tested strengths agreed with the nominal strengths calculated by ACI 318-19. These results indicate that current design codes for cementitious materials and sleeve splice of longitudinal reinforcement are applicable to the design of precast ZC columns. Keywords: column; cyclic loading test; precast concrete; seismic performance; slag-based concrete; sleeve splice; zero-cement concrete.
Air-sea CO2 flux in the Pacific Ocean for the period 1990-2009
Air-sea CO2 fluxes over the Pacific Ocean are known to be characterized by coherent large-scale structures that reflect not only ocean subduction and upwelling patterns, but also the combined effects of wind-driven gas exchange and biology. On the largest scales, a large net CO2 influx into the extratropics is associated with a robust seasonal cycle, and a large net CO2 efflux from the tropics is associated with substantial interannual variability. In this work, we have synthesized estimates of the net air-sea CO2 flux from a variety of products, drawing upon a variety of approaches in three sub-basins of the Pacific Ocean, i.e., the North Pacific extratropics (18-66° N), the tropical Pacific (18° S-18° N), and the South Pacific extratropics (44.5-18° S). These approaches include those based on the measurements of CO2 partial pressure in surface seawater (pCO2 sw), inversions of ocean-interior CO2 data, forward ocean biogeochemistry models embedded in the ocean general circulation models (OBGCMs), a model with assimilation of pCO2 sw data, and inversions of atmospheric CO2 measurements. Long-term means, interannual variations and mean seasonal variations of the regionally integrated fluxes were compared in each of the sub-basins over the last two decades, spanning the period from 1990 through 2009. A simple average of the long-term mean fluxes obtained with surface water pCO2 diagnostics and those obtained with ocean-interior CO2 inversions are -0.47 ± 0.13 Pg C yr-1 in the North Pacific extratropics, +0.44 ± 0.14 Pg C yr-1 in the tropical Pacific, and -0.37 ± 0.08 Pg C yr-1 in the South Pacific extratropics, where positive fluxes are into the atmosphere. This suggests that approximately half of the CO2 taken up over the North and South Pacific extratropics is released back to the atmosphere from the tropical Pacific. These estimates of the regional fluxes are also supported by the estimates from OBGCMs after adding the riverine CO2 flux, i.e., -0.49 ± 0.02 Pg C yr-1 in the North Pacific extratropics, +0.41 ± 0.05 Pg C yr-1 in the tropical Pacific, and -0.39 ± 0.11 Pg C yr-1 in the South Pacific extratropics. The estimates from the atmospheric CO2 inversions show large variations amongst different inversion systems, but their median fluxes are consistent with the estimates from climatological pCO2 sw data and pCO2 sw diagnostics. In the South Pacific extratropics, where CO2 variations in the surface and ocean interior are severely undersampled, the difference in the air-sea CO2 flux estimates between the diagnostic models and ocean-interior CO2 inversions is larger (0.18 Pg C yr-1 ). The range of estimates from forward OBGCMs is also large (-0.19 to -0.72 Pg C yr-1 ). Regarding interannual variability of air-sea CO2 fluxes, positive and negative anomalies are evident in the tropical Pacific during the cold and warm events of the El Niño-Southern Oscillation in the estimates from pCO2 sw diagnostic models and from OBGCMs. They are consistent in phase with the Southern Oscillation Index, but the peak-to-peak amplitudes tend to be higher in OBGCMs (0.40 ± 0.09 Pg C yr-1 ) than in the diagnostic models (0.27 ± 0.07 Pg C yr-1 ).
Safe threshold of capillary blood glucose for predicting early future neonatal hypoglycaemia in babies born to mothers with gestational diabetes mellitus, an observational, retrospective cohort study
Background There is increasing pressure to get women and babies home rapidly after birth. Babies born to mothers with gestational diabetes mellitus (GDM) currently get 24-h inpatient monitoring. We investigated whether a low-risk group of babies born to mothers with GDM could be defined for shorter inpatient hypoglycaemia monitoring. Methods Observational, retrospective cohort study conducted in a tertiary maternity hospital in 2018. Singleton, term babies born to women with GDM and no other risk factors for hypoglycaemia, were included. Capillary blood glucose (BG) testing and clinical observations for signs of hypoglycaemia during the first 24-h after birth. BG was checked in all babies before the second feed. Subsequent testing occurred if the first result was < 2.0 mmol/L, or clinical suspicion developed for hypoglycaemia. Neonatal hypoglycaemia, defined as either capillary or venous glucose ≤ 2.0 mmol/L and/or clinical signs of neonatal hypoglycaemia requiring oral or intravenous dextrose (lethargy, abnormal feeding behaviour or seizures). Results Fifteen of 106 babies developed hypoglycaemia within the first 24-h. Maternal and neonatal characteristics were not predictive. All babies with hypoglycaemia had an initial capillary BG ≤ 2.6 mmol/L (Area under the ROC curve (AUC) 0.96, 95% Confidence Interval (CI) 0.91–1.0). This result was validated on a further 65 babies, of whom 10 developed hypoglycaemia, in the first 24-h of life. Conclusion Using the 2.6 mmol/L threshold, extended monitoring as an inpatient could have been avoided for 60% of babies in this study. Whilst prospective validation is needed, this approach could help tailor postnatal care plans for babies born to mothers with GDM.
Eating frequency is inversely associated with blood pressure and hypertension in Korean adults: analysis of the Third Korean National Health and Nutrition Examination Survey
Background/objectives: A lower eating frequency (EF) has been suggested to be important in the development of cardiovascular risk factors such as obesity and hyperlipidemia. However, the association between EF and blood pressure (BP) remains unclear. Subjects/methods: The aim of this study was to explore the association of EF with BP and hypertension after adjusting for confounding variables, including body mass index (BMI) and waist circumference (WC). This cross-sectional study used data from the Third Korean National Health and Nutrition Examination Survey. A total of 4625 subjects aged ⩾19 years were included. To explore the association of EF with BP and hypertension, we performed multiple linear regression analyses and multiple logistic regression analyses for survey design, respectively. Results: EF was inversely associated with systolic BP (SBP) and diastolic BP (DBP). As EF increased from ⩽2 to 3, 4 and ⩾5 times per day, estimated adjusted means of both SBP and DBP decreased, showing a significant linear trend independent of obesity (SBP: 120.66, 120.23, 119.18 and 117.92 mm Hg, respectively; P <0.001; DBP: 78.36, 77.78, 77.25 and 76.50 mm Hg, respectively; P =0.004). The inverse association between EF and hypertension was gradually attenuated and significant after adjustment for confounding variables including BMI and WC ( P =0.040). Conclusions: This study suggests that lower EF is significantly associated with higher BP, which may be partially mediated by the effect of central obesity. Further prospective studies are needed to verify this causal relationship.
A uniform, quality controlled Surface Ocean CO2 Atlas (SOCAT)
A well-documented, publicly available, global data set of surface ocean carbon dioxide (CO2 ) parameters has been called for by international groups for nearly two decades. The Surface Ocean CO2 Atlas (SOCAT) project was initiated by the international marine carbon science community in 2007 with the aim of providing a comprehensive, publicly available, regularly updated, global data set of marine surface CO2 , which had been subject to quality control (QC). Many additional CO2 data, not yet made public via the Carbon Dioxide Information Analysis Center (CDIAC), were retrieved from data originators, public websites and other data centres. All data were put in a uniform format following a strict protocol. Quality control was carried out according to clearly defined criteria. Regional specialists performed the quality control, using state-of-the-art web-based tools, specially developed for accomplishing this global team effort. SOCAT version 1.5 was made public in September 2011 and holds 6.3 million quality controlled surface CO2 data points from the global oceans and coastal seas, spanning four decades (1968-2007). Three types of data products are available: individual cruise files, a merged complete data set and gridded products. With the rapid expansion of marine CO2 data collection and the importance of quantifying net global oceanic CO2 uptake and its changes, sustained data synthesis and data access are priorities.
Surface Ocean CO2 Atlas (SOCAT) gridded data products
As a response to public demand for a well-documented, quality controlled, publically available, global surface ocean carbon dioxide (CO2 ) data set, the international marine carbon science community developed the Surface Ocean CO2 Atlas (SOCAT). The first SOCAT product is a collection of 6.3 million quality controlled surface CO2 data from the global oceans and coastal seas, spanning four decades (1968-2007). The SOCAT gridded data presented here is the second data product to come from the SOCAT project. Recognizing that some groups may have trouble working with millions of measurements, the SOCAT gridded product was generated to provide a robust, regularly spaced CO2 fugacity (fCO2 ) product with minimal spatial and temporal interpolation, which should be easier to work with for many applications. Gridded SOCAT is rich with information that has not been fully explored yet (e.g., regional differences in the seasonal cycles), but also contains biases and limitations that the user needs to recognize and address (e.g., local influences on values in some coastal regions).
Cellular responses to mild heat stress
Since its discovery in 1962 by Ritossa, the heat shock response has been extensively studied by a number of investigators to understand the molecular mechanism underlying the cellular response to heat stress. The most well characterized heat shock response is induction of the heat shock proteins that function as molecular chaperones and exert cell cycle regulatory and anti-apoptotic activities. While most investigators have focused their studies on the toxic effects of heat stress in organisms such as severe heat stress-induced cell cycle arrest and apoptosis, the cellular response to fever-ranged mild heat stress has been rather underestimated. However, the cellular response to mild heat stress is likely to be more important in a physiological sense than that to severe heat stress because the body temperature of homeothermic animals increases by only 1-2 degrees C during febrile diseases. Here we provide information that mild heat stress does have some beneficial role in organisms via positively regulating cell proliferation and differentiation, and immune response in mammalian cells.
Inhibitory effect of evodiamine alone and in combination with rosiglitazone on in vitro adipocyte differentiation and in vivo obesity related to diabetes
Objective: Evodiamine (evo) has been shown to exert anti-inflammatory, antinociceptive and anticancer effects. In this study, we investigated the effects of evo alone and in combination with rosiglitazone (rosi) on in vitro adipocyte differentiation and in vivo obesity related to diabetes. Methods: Adipocyte differentiation was investigated in vitro using 3T3-L1 and C3H10T1/2 cells. To determine the degree of differentiation, Oil Red O staining and reverse transcription-PCR were carried out. Four groups of db/db mice were treated intraperitoneally once per day with vehicle, evo, rosi and evo+rosi. The mice were killed after 14 days and the blood, liver and adipose tissue were analyzed. Results: The presence of evo or evo combined with rosi during adipogenic induction has been shown to inhibit adipocyte differentiation to a significant degree, particularly at the commitment and early induction stages. The evo and evo+rosi groups of db/db mice evidenced significant reductions in body weight gain. The ratio of epididymal white adipocyte tissue weight to body weight of the evo group was also significantly reduced. It is important to note that in the evo+rosi treatment, blood glucose levels were reduced to a degree similar to that of the rosi group, and plasma insulin levels were reduced significantly better than that of rosi group. Furthermore, hepatic lesions associated with fat and glycogen deposition were morphologically improved in the evo and evo+rosi groups. Conclusion: The results of this study showed that evo exerts an inhibitory effect on in vitro adipocyte differentiation and in vivo obesity, and also an improvement effect on insulin resistance. These desirable effects of evo were noted even in the presence of rosi. These results indicate that evo improves the undesirable effects of rosi, including adipogenesis, body weight gain and hepatotoxicity, while preserving its desirable blood-glucose-lowlowering effect.