Boosting Learning for LDPC Codes to Improve the Error-Floor Performance

Low-density parity-check (LDPC) codes have been successfully commercialized in communication systems due to their strong error correction capabilities and simple decoding process. However, the error-floor phenomenon of LDPC codes, in which the error rate stops decreasing rapidly at a certain level, presents challenges for achieving extremely low error rates and deploying LDPC codes in scenarios demanding ultra-high reliability. In this work, we propose training methods for neural min-sum (NMS) decoders to eliminate the error-floor effect. First, by leveraging the boosting learning technique of ensemble networks, we divide the decoding network into two neural decoders and train the post decoder to be specialized for uncorrected words that the first decoder fails to correct. Secondly, to address the vanishing gradient issue in training, we introduce a block-wise training schedule that locally trains a block of weights while retraining the preceding block. Lastly, we show that assigning different weights to unsatisfied check nodes effectively lowers the error-floor with a minimal number of weights. By applying these training methods to standard LDPC codes, we achieve the best error-floor performance compared to other decoding methods. The proposed NMS decoder, optimized solely through novel training methods without additional modules, can be integrated into existing LDPC decoders without incurring extra hardware costs. The source code is available at https://github.com/ghy1228/LDPC_Error_Floor .Comment: 17 pages, 10 figure

The ancient phosphatidylinositol 3-kinase signaling system is a master regulator of energy and carbon metabolism in algae

Algae undergo a complete metabolic transformation under stress by arresting cell growth, inducing autophagy and hyperaccumulating biofuel precursors such as triacylglycerols and starch. However, the regulatory mechanisms behind this stress-induced transformation are still unclear. Here, we use biochemical, mutational, and “omics” approaches to demonstrate that PI3K signaling mediates the homeostasis of energy molecules and influences carbon metabolism in algae. In Chlamydomonas reinhardtii, the inhibition and knockdown (KD) of algal class III PI3K led to significantly decreased cell growth, altered cell morphology, and higher lipid and starch contents. Lipid profiling of wild-type and PI3K KD lines showed significantly reduced membrane lipid breakdown under nitrogen starvation (-N) in the KD. RNA-seq and network analyses showed that under -N conditions, the KD line carried out lipogenesis rather than lipid hydrolysis by initiating de novo fatty acid biosynthesis, which was supported by tricarboxylic acid cycle down-regulation and via acetyl-CoA synthesis from glycolysis. Remarkably, autophagic responses did not have primacy over inositide signaling in algae, unlike in mammals and vascular plants. The mutant displayed a fundamental shift in intracellular energy flux, analogous to that in tumor cells. The high free fatty acid levels and reduced mitochondrial ATP generation led to decreased cell viability. These results indicate that the PI3K signal transduction pathway is the metabolic gatekeeper restraining biofuel yields, thus maintaining fitness and viability under stress in algae. This study demonstrates the existence of homeostasis between starch and lipid synthesis controlled by lipid signaling in algae and expands our understanding of such processes, with biotechnological and evolutionary implications.Ministry of Science, ICT and Future Planning 2015M3A6A2065697Ministry of Oceans and Fisheries 2015018

Ultra-Processed Food Consumption and Obesity in Korean Adults

Background This study aimed to investigate the association between consumption of ultra-processed foods (UPF) and obesity in Korean adults. Methods We included the Cardiovascular and Metabolic Diseases Etiology Research Center cohort study baseline data of adults aged 30 to 64 years who completed a validated food frequency questionnaire. UPF was defined using the NOVA food classification. Multivariable linear and logistic regression analyses were performed to assess the association of dietary energy contribution of UPF with obesity indicators (body mass index [BMI], obesity, waist circumference [WC], and abdominal obesity). Results Consumption of UPF accounted for 17.9% of total energy intake and obesity and abdominal obesity prevalence was 35.4% and 30.2%, respectively. Compared with those in the lowest quartile of UPF consumption, adults in the highest quartile had greater BMI (β=0.36; 95% confidence interval [CI], 0.15 to 0.56), WC (β=1.03; 95% CI, 0.46 to 1.60), higher odds of having obesity (odds ratio [OR], 1.24; 95% CI, 1.07 to 1.45), and abdominal obesity (OR, 1.34; 95% CI, 1.14 to 1.57), after adjusting for sociodemographic characteristics, health-related behaviors, and family history of diseases. Dose-response associations between UPF consumption and obesity indicators were consistently found (all P trend <0.01). However, the strength of association was halved for all obesity indicators after further adjustments for total energy intake and overall diet quality score, and the trend toward association for obesity and WC disappeared. Conclusion Our finding supports the evidence that consumption of UPF is positively associated with obesity among Korean adults

Design of grating Al2O3 passivation structure optimized for high-efficiency Cu(In,Ga)Se2 solar cells

In this paper, we propose an optimized structure of thin Cu(In,Ga)Se2 (CIGS) solar cells with a grating aluminum oxide (Al2 O3) passivation layer (GAPL) providing nano-sized contact openings in order to improve power conversion efficiency using optoelectrical simulations. Al2 O3 is used as a rear surface passivation material to reduce carrier recombination and improve reflectivity at a rear surface for high efficiency in thin CIGS solar cells. To realize high efficiency for thin CIGS solar cells, the optimized structure was designed by manipulating two structural factors: the contact opening width (COW) and the pitch of the GAPL. Compared with an unpassivated thin CIGS solar cell, the efficiency was improved up to 20.38% when the pitch of the GAPL was 7.5–12.5 µm. Furthermore, the efficiency was improved as the COW of the GAPL was decreased. The maximum efficiency value occurred when the COW was 100 nm because of the effective carrier recombination inhibition and high reflectivity of the Al2 O3 insulator passivation with local contacts. These results indicate that the designed structure has optimized structural points for high-efficiency thin CIGS solar cells. Therefore, the photovoltaic (PV) generator and sensor designers can achieve the higher performance of photosensitive thin CIGS solar cells by considering these results. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.1

Management of right main bronchial rupture with a double lumen endotracheal tube in a patient with blunt chest trauma

Tracheobronchial disruption is one of the most severe injuries caused by blunt chest trauma. It may cause airway obstruction and resulting life-threatening respiratory deficiency. However, the clinical presentations are variable and frequently difficult to diagnose. We report a case of a previously healthy 16-year-old man with complete right main bronchial transection sustained after a vehicular accident, who had progressive dyspnea, subcutaneous emphysema in the neck and anterior chest wall, and bilateral tension pneumothorax. Prompt chest tube drainage for suspected bilateral tension pneumothorax and a tracheal intubation were performed. Shortly after the positive pressure ventilation, severe subcutaneous emphysema developed and he was at risk for developing shock. Additional chest tubes were inserted. An emergency bronchoscopy showed rupture of the right main bronchus. After changing to a double lumen endotracheal tube, the patient’s condition improved. A surgical closure was performed and postoperative bronchoscopy showed good repair. The patient was discharged without complications

Factors associated with delayed emergency room visits in adult immigrant patients with mild abdominal pain in Korea

Objective To determine the factors associated with unmet needs in immigrant patients complaining of abdominal pain, by analyzing those associated with the time from symptom onset to emergency room visit. Methods We retrospectively reviewed the medical records of immigrants with abdominal pain who visited a tertiary hospital emergency department from January to December 2016. The dependent variable was the time from symptom onset to emergency room visit. The independent variables were age, sex, vital signs, disposition, health insurance status, date of visit, time of visit, level of education, employment status, economic satisfaction, marital status, living with family, duration of residence, having a native spouse, and subjective proficiency in Korean. We analyzed the association of the dependent variable with each independent variable. Results In total, 102 immigrant patients with abdominal pain were enrolled in this study. The patients who had earlier visits had good subjective proficiency in Korean, high economic satisfaction, longer durations of residence, a tendency to have a native spouse, and a high employment rate. After linear regression analysis, the time from symptom onset to emergency room visit was negatively associated with employment (adjusted odds ratio, -13.67; 95% confidence interval, -23.25 to -4.09; P=0.006) and having a native spouse (adjusted odds ratio, -11.7; 95% confidence interval, -20.61 to -2.8; P=0.011). Conclusion The factors influencing the time from symptom onset to emergency room visit in immigrant patients with abdominal pain are associated with social capital, which improves access to emergency care. Policies that improve immigrant access to emergency care should be considered