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The small, simple, and effective characteristics of a Supercritical CO2 (S–CO2) power system make it an ideal candidate for distributed power generation. However, the distributed power generation will be required with constant changes in the operating conditions to meet the varying demand. Thus, it is necessary for the S–CO2 power system to demonstrate that it can operate safely and efficiently under all anticipated operating conditions. One of the key issues in the S–CO2 power system is controlling the compressor inlet conditions. This paper focused on the control of the compressor inlet temperature. In this paper, a system dynamic simulation code is used to model the precooler system for the compressor inlet control first. Based on the analysis results to obtain the transfer function and the state space, a linear quadratic controller was designed using optimal control theory. Since the controller was estimated to have steady-state error, a disturbance observer was also used. To validate the designed controller, experiments were conducted. The experimental results show that the proposed controller can be used to maintain the S–CO2 compressor inlet conditions under various transient scenarios without additional tuning.

Instabilities such as stall and surge have been widely studied in open loop gas turbine system for several decades. However, researches on instabilities in a closed loop are limited. Especially, no experimental investigation in a supercritical CO2 compressor has been performed thoroughly before. An integral test loop equipped with a turbo-alternator-compressor using active magnetic bearing was utilized to study the instabilities in a supercritical CO2 compressor. The compressor performance testing was conducted including near stall and surge operating conditions. The mass flow rate of compressor was greatly reduced even beyond surge limit and pressure was measured with high frequency transducer to observe the characteristics. It was observed that as the inertia of the system was changed by altering the compressor inlet conditions, the characteristics of the supercritical CO2 compressor in unstable operating conditions also vary. This can be qualitatively explained by using the theory Greitzer proposed previously.

A supercritical CO2 (S-CO2) Brayton cycle is a compact and simple power conversion system with competitive efficiency. However, the strong real gas effects of S-CO2 pose challenges to the design of a cycle and its components. In particular, designing turbomachinery for expansion and compression processes has to accurately reflect real gas effects. Windage loss is one of the major losses that affects the motor load and heat generation in turbomachinery. The windage loss has a substantial impact on the overall turbomachinery efficiency especially in an S-CO2 power cycle since the windage loss is reported to be the dominant loss mechanism due to high fluid density and high rotational speed. Therefore, an accurate windage loss model reflecting the real gas effect of S-CO2 is essential to obtaining an optimal design of turbomachinery as well as maximizing the performance of an S-CO2 power cycle. In this study, existing windage loss models are first compared to the recently obtained data from S-CO2 windage loss experiments conducted by the KAIST research team under S-CO2 conditions in order to understand the turbomachinery performance uncertainty caused by the windage loss models. This is followed by proposing a new windage model which explains data better.

Gas Brayton cycles have been considered the next promising power cycles for microreactors. Especially the open-air and closed supercritical CO2 (S-CO2) Brayton cycles have received attention due to their high thermal efficiency and compact component sizes when compared to the steam Rankine cycle. In this research, the performances of the open-air and closed S-CO2 Brayton cycle at microreactor power range are compared with polytropic turbomachinery efficiency. When optimizing the cycle, three different optimization parameters are considered in this paper: maximum efficiency, maximum cycle specific work, and maximum of the product of both indicators. For the air Brayton cycle, the maximum of the product of both indicators allows to consider both efficiency and specific work while optimizing the cycle. However, for the S-CO2 Brayton cycle, the best performing conditions follow either maximum efficiency or the maximum cycle specific work conditions. In general, the S-CO2 power cycle should be designed and optimized to maximize the cycle specific work for commercial-scale application. The results show that the air Brayton cycle can achieve near 45% efficiency when it can couple with a microreactor with a core outlet temperature higher than 700 °C. However, the S-CO2 power cycle can still achieve above 30% efficiency when it is coupled with a microreactor with a core outlet temperature higher than 500 °C, whereas the air Brayton cycle cannot even reach breakeven condition.

Background: Numerous studies have investigated methods of predicting postoperative pulmonary complications (PPCs) in lung cancer surgery, with chronic obstructive pulmonary disease (COPD) and low forced expiratory volume in 1 second (FEV1) being recognized as risk factors. However, predicting complications in COPD patients with preserved FEV1 poses challenges. This study considered various diffusing capacity of the lung for carbon monoxide (DLCO) parameters as predictors of pulmonary complication risks in mild COPD patients undergoing lung resection. Methods: From January 2011 to December 2019, 2,798 patients undergoing segmentectomy or lobectomy for non-small cell lung cancer (NSCLC) were evaluated. Focusing on 709 mild COPD patients, excluding no COPD and moderate/severe cases, 3 models incorporating DLCO, predicted postoperative DLCO (ppoDLCO), and DLCO divided by the alveolar volume (DLCO/VA) were created for logistic regression. The Akaike information criterion and Bayes information criterion were analyzed to assess model fit, with lower values considered more consistent with actual data. Results: Significantly higher proportions of men, current smokers, and patients who underwent an open approach were observed in the PPC group. In multivariable regression, male sex, an open approach, DLCO

This study investigates the effect of minor Li addition on the solute clustering and thermal stability of precipitates in artificially aged Al–Mg–Si–Cu (AA6061) alloys. Li addition hinders the initial changes in hardness and electrical conductivity by delaying solute clustering during early aging. The delay in cluster formation is attributed to the disturbance of Mg enrichment by the formation of Si–Li clusters, unlike the Sn element with vacancy-trapping effect. Additionally, Li addition is found to coarsen the precipitates during over aging, thereby reducing the thermal stability of the Al–Mg–Si–Cu alloy. Gibbsian interfacial excess calculations of the Li solute indicate that the low coarsening resistance of the Li-containing precipitate is mainly caused by the small amount of equilibrium Li segregation at the internal interface between the matrix and over-aged precipitate. A decrease in the number of nucleation sites, originating from the suppression of cluster formation in the early-aging stage, is also suggested as a reason for the coarse precipitate structure. Finally, despite the high solubility of Li into precipitates, Li addition does not disorder or change the crystal structure of the precipitates. It simply increases the volume of the precipitate by an amount equivalent to or greater than the added Li, without increasing the thermal stability.

Abstract Climate extremes, such as hot temperature and heavy precipitation events, have devastating effects on human societies. As the planet gets warmer, they have become more intense and more frequent. To avoid irreversible damages from climate extremes, many countries have committed to achieving net‐zero anthropogenic carbon emissions, or carbon neutrality, by the 2050s. Here, we quantify the impact of carbon neutrality on population exposure to climate extremes using multi‐model projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6) Shared Socioeconomic Pathway (SSP)1‐1.9 and SSP3‐7.0 scenarios. It is found that the increasing population exposure to hot‐temperature and heavy‐precipitation extremes under SSP3‐7.0 scenario can be substantially reduced by 87%–98% in the late 21st century by achieving the carbon neutrality based on SSP1‐1.9 scenario. The benefits of carbon neutrality are particularly pronounced in Africa and Asia. The potential benefits of carbon neutrality are also significant in North America, Europe, and Oceania, where a reduction in climate extremes is more than twice as important as population decline in reducing population exposure to climate extremes. These results provide important scientific support for ongoing efforts to achieve net‐zero carbon emissions by the 2050s to reduce potential climate risk and its inequity across continents.

In this study, it is suggested that the daily PM10 level in East Asia is remotely controlled by the convection over the equatorial Indian Ocean and western Pacific. This tropical modulation explains up to 15% of daily PM10 variability in the region.

Abstract To investigate the response of the general circulation and global transport of heat through both atmosphere and ocean to two-types of carbon dioxide removal scenario, we performed an earth system model experiment in which we imposed a pulse-type quadrupling of CO2 forcing for 50 years and a gradual peak-and-decline of four-time CO2 forcing. We found that the results from two experiments are qualitatively similar to each other. During the forcing-on period, a dominant warming in the upper troposphere over the tropics and on the surface at high latitudes led to a slowdown in the Hadley circulation, but the poleward atmospheric energy transport was enhanced due to an increase in specific humidity. This counteracted the reduction in poleward oceanic energy transport owing to the suppression of the meridional overturning circulation in both Hemispheres. After returning the original CO2 level, the hemispheric thermal contrast was reversed, causing a southward shift of the intertropical convergence zone. To reduce the hemispheric thermal contrast, the northward energy transports in the atmosphere and ocean surface were enhanced while further weakening of the global-scale Atlantic meridional overturning circulation led to southward energy transport in the deep ocean.

Abstract Children born very preterm are at significant risk of neurodevelopmental impairment. This study sought to identify differences in cognitive function in children born very preterm compared to term-born controls and investigate alteration in white matter microstructure and functional connectivity (FC) based on tract-based spatial statistics (TBSS) and resting-state functional MRI, respectively. At 6 years of age, 36 children born very preterm (

Abstract Antarctic ozone has been regarded as a major driver of the Southern Hemisphere (SH) circulation change in the recent past. Here, we show that Antarctic ozone can also affect the subseasonal-to-seasonal (S2S) prediction during the SH spring. Its impact is quantified by conducting two reforecast experiments with the Global Seasonal Forecasting System 5 (GloSea5). Both reforecasts are initialized on September 1st of each year from 2004 to 2020 but with different stratospheric ozone: one with climatological ozone and the other with year-to-year varying ozone. The reforecast with climatological ozone, which is common in the operational S2S prediction, shows the skill re-emergence in October after a couple of weeks of no prediction skill in the troposphere. This skill re-emergence, mostly due to the stratosphere–troposphere dynamical coupling, becomes stronger in the reforecast with year-to-year varying ozone. The surface prediction skill also increases over Australia. This result suggests that a more realistic stratospheric ozone could lead to improved S2S prediction in the SH spring.

Cranial ultrasound (CUS) is an initial screening imaging tool used to evaluate the neonatal brain. It is an accessible, inexpensive, and harmless technique that can be used at bedside as frequently as required. Timely focused CUS in the neonatal care unit can play a major role in the diagnosis, follow-up, and management of brain damage. Despite the increasing use of point-of-care ultrasonography by intensive care physicians, neonatologist-performed CUS remains unusual. This review aims to provide an overview of neonatal CUS to neonatologists, focusing on the optimal settings, standard planes of the brain, and main pathologies in preterm infants. Adding Doppler studies allows evaluation of the patency of intracranial arteries and veins, flow velocities, and indices. This may provide an opportunity for earlier targeted circulatory support to prevent brain injury and improve long-term neurodevelopmental outcomes.

Summary: Purpose: The purpose of this study is to develop and apply a neonatal supportive positioning (NSP) training video program for premature infants, using a position support mat for nurses in neonatal intensive care units (NICUs), and to verify its effect on nurses' performance. Methods: Thirty-five NICU nurses were included in the study. For the pre-test, preliminary check-ups were conducted, questionnaires about NSP knowledge on preterm infants were distributed, and NSP performance using neonatal dolls were video recorded for each participant. PowerPoint presentations and videos were used to educate participants on NSP. Furthermore, a 20-minute one-on-one training session was conducted using an NPS kit. Two weeks after the training, we repeated the process of distributing questionnaires about NSP knowledge and recording nurses’ performance videos using neonatal dolls. Questionnaires and videos collected before and after the training were compared. Results: After NSP training, the mean knowledge score of the participants improved significantly from 23.71 ± 3.62 to 29.51 ± 2.29 (Z = −5.09, p

Background/Aims While distal radial artery (DRA) access is increasingly being used for diagnostic coronary angiography, limited information is available regarding DRA size. We aimed to determine the DRA reference diameters of Korean patients and identify the predictors of DRA diameter < 2.3 mm. Methods The outer bilateral DRA diameters were assessed using a linear ultrasound probe in 1,162 consecutive patients who underwent transthoracic echocardiography. The DRA diameter was measured by the perpendicular angle in the dorsum of the hand, and the average values were compared by sex. DRA diameter < 2.3 mm was defined as unsuitable for routine diagnostic coronary angiography using a 5 Fr introducer sheath. Results The mean DRA diameters were 2.31 ± 0.43 mm (right) and 2.35 ± 0.45 mm (left). The DRA was smaller in women than men (right: 2.15 ± 0.38 mm vs. 2.43 ± 0.44 mm, p < 0.001; left: 2.18 ± 0.39 mm vs. 2.47 ± 0.45 mm, p < 0.001). The DRA diameter was approximately 20% smaller than the radial artery diameter. A total of 630 (54.2%) and 574 (49.4%) patients had DRA diameter < 2.3 mm in the right and left hands, respectively. Female sex, low body mass index (BMI), and low body surface area (BSA) were significant predictors of DRA diameter < 2.3 mm. Conclusions We provided reference DRA diameters for Korean patients. Approximately 50% of the studied patients had DRA diameter < 2.3 mm. Female sex, low BMI, and low BSA remained significant predictors of DRA diameter < 2.3 mm.

Background and Purpose Previous studies have revealed the diverse neuroprotective effects of GV1001. In this study, we investigated the effects of GV1001 on focal cerebral ischemia-reperfusion injury (IRI) in rats and oxygen-glucose deprivation/reoxygenation (OGD/R)-induced injury in neural stem cells (NSCs) and cortical neurons. Methods Focal cerebral IRI was induced by transient middle cerebral artery occlusion (MCAO). Brain diffusion-weighted imaging (DWI) was performed 2 hours after occlusion, and a total of 37 rats were treated by reperfusion with GV1001 or saline 2 hours after occlusion. Fluid-attenuated inversion recovery (FLAIR) magnetic resonance imaging, immunohistochemistry, and neurobehavioral function analyses were performed. Additionally, OGD/R-injured NSCs and cortical neurons were treated with different GV1001 concentrations. Cell viability, proliferation, migration, and oxidative stress were determined by diverse molecular analyses. Results In the stroke model, GV1001 protected neural cells against IRI. The most effective dose of GV1001 was 60 μM/kg. The infarct volume on FLAIR 48 hours after MCAO compared to lesion volume on DWI showed a significantly smaller ratio in the GV1001-treated group. GV1001-treated rats exhibited better behavioral functions than the saline-treated rats. Treatment with GV1001 increased the viability, proliferation, and migration of the OGD/R-injured NSCs. Free radicals were significantly restored by treatment with GV1001. These neuroprotective effects of GV1001 have also been demonstrated in OGD/R-injured cortical neurons. Conclusions The results suggest that GV1001 has neuroprotective effects against IRI in NSCs, cortical neurons, and the rat brain. These effects are mediated through the induction of cellular proliferation, mitochondrial stabilization, and anti-apoptotic, anti-aging, and antioxidant effects.

Abstract The subseasonal relationship between Arctic and Eurasian surface air temperature (SAT) is re-examined using reanalysis data. Consistent with previous studies, a significant negative correlation is observed in cold season from November to February, but with a local minimum in late December. This relationship is dominated not only by the warm Arctic-cold Eurasia (WACE) pattern, which becomes more frequent during the last two decades, but also by the cold Arctic-warm Eurasia (CAWE) pattern. The budget analyses reveal that both WACE and CAWE patterns are primarily driven by the temperature advection associated with sea level pressure anomaly over the Ural region, partly cancelled by the diabatic heating. It is further found that, although the anticyclonic anomaly of WACE pattern mostly represents the Ural blocking, about 20% of WACE cases are associated with non-blocking high pressure systems. This result indicates that the Ural blocking is not a necessary condition for the WACE pattern, highlighting the importance of transient weather systems in the subseasonal Arctic-Eurasian SAT co-variability.

Abstract The modern reanalysis datasets provide not only meteorological variables, but also atmospheric chemical compositions such as tropospheric ozone and aerosol concentration. However, the quality of chemical compositions has been rarely assessed especially over East Asia. To better understand the characteristics of reanalysis datasets on regional scale, the present study evaluates tropospheric ozone derived from seven reanalyses against five independent ozonesonde observations in East Asia. The reanalysis datasets are the ECMWF Reanalysis 5th (ERA5), Monitoring Atmospheric Composition and Climate reanalysis (MACCRA), Copernicus Atmosphere Monitoring Service reanalysis (CAMSRA), as well as the NCEP Climate Forecast System Reanalysis (CFSR), NASA Modern-Era Retrospective analysis for Research and Applications version 2 (MERRA2), Japanese 55-year Reanalysis (JRA-55), and updated Tropospheric Chemistry Reanalysis (TCR-2). It turns out that MACCRA, CAMSRA, and TCR-2, which incorporate chemical transport model, depict most reasonable spatio-temporal variability of tropospheric ozone in East Asia. The MACC exhibits a better quality with relatively small mean biases of 6.4 ± 1.3% in tropospheric column ozone than biases of 7.8 ± 2.7% and 7.8 ± 2.8% for CAMSRA and TCR-2. The CAMSRA further shows a significant monthly correlation with the observation of up to 0.7 at 850 hPa. Among the seven reanalyses, MACC, CAMSRA, and TCR-2 are suitable for local tropospheric ozone study on seasonal to inter-annual time scales. However, none of the seven reanalysis datasets reproduce the observed trend of tropospheric ozone. This result suggests that even the latest datasets are inadequate for the long-term ozone change study.

Floating-Harbor syndrome is a rare autosomal dominant disorder that presents with short stature, facial dysmorphism, significantly delayed bone age, skeletal abnormalities, speech and language problems, and intellectual disabilities. Although short stature is one of the main clinical manifestations, use of growth hormone therapy in Floating-Harbor syndrome patients has been limited. Only a few reports have investigated the response to growth hormone therapy with regard to final adult height. We report the case of a 7-year-old girl with FloatingHarbor syndrome and a heterozygous mutation, c.7330C > T (p.Arg2444*), in the SRCAP gene. The patient exhibited dysmorphic facial features, severe intellectual disabilities, obsessive-compulsive and aggressive behaviors, and short stature without growth hormone deficiency. Her height standard deviation score improved after 55 months of growth hormone therapy.

Background: As the population of patients with end-stage renal disease has grown older, the proportion of patients with poorly preserved vasculature has concomitantly in-creased. Thus, arteriovenous grafts (AVG) have been used more frequently to access blood vessels for hemodialysis. Despite this increasing demand, studies of AVG are limited. In this study, we examined the surgical outcomes of upper-limb AVG creation.Methods: Among the arteriovenous fistula formation procedures performed between January 2014 and March 2019 at Dankook University Hospital, 42 cases involved AVG cre-ation. We compared patients in whom the axillary vein was used (group A; brachioaxillary AVG [B-Ax AVG]; n=20) with those in whom upper limb veins were used (group B; bra-chiobasilic AVG or brachioantecubital AVG; n=22).Results: The 1-year primary patency rate was higher in group A than in group B (57.9% vs. 41.7%; p=0.262). The incidence of postoperative complications was not significantly different between groups.Conclusion: AVG using the axillary vein showed no major differences in safety or func-tionality compared to AVG using other veins. Therefore, accounting for age, underlying disease, and expected patient lifespan, B-Ax AVG can be considered an acceptable surgical method.