Altered pattern of theta and gamma oscillation to visual stimuli in patients with postconcussion syndrome.

Although many patients with mild traumatic brain injury (mTBI) suffer from postconcussional syndrome (PCS) including abnormal emotional responses, most conventional imaging studies fail to detect any causative brain lesion. We hypothesized that event-related electroencephalography (EEG) recordings with time-frequency analysis would show a distinguishable pattern in patients with mTBI with PCS compared with normal healthy controls. EEG signals were collected from a total of 18 subjects: eight patients with mTBI with PCS and 10 healthy control subjects. The signals were recorded while the subjects were presented with affective visual stimuli, including neutral, pleasant, and unpleasant emotional cues. Event-related spectral perturbation analysis was performed to calculate frontal midline theta activity and posterior midline gamma activity, followed by statistical analysis to identify whether patients with mTBI with PCS have distinct patterns of theta or gamma oscillations in response to affective stimuli. Compared with the healthy control group, patients with mTBI with PCS did not show a significant increase in the power of frontal theta activity in response to the pleasant stimuli, indicating less susceptibility toward pleasant cues. Moreover, the patient group showed attenuated gamma oscillatory activity, with no clear alteration in gamma oscillations in response to either pleasant or unpleasant cues. This study demonstrates that patients with mTBI with PCS exhibited altered patterns of oscillatory activities in the theta and gamma bands in response to affective visual stimuli compared with the normal control group. The current finding implicates that these distinguishable patterns of brain oscillation may represent the mechanism behind various psychiatric symptoms in patients with mTBI.NEW & NOTEWORTHY Patients with mild traumatic brain injury (mTBI) with postconcussional syndrome (PCS) exhibited altered patterns of changes in oscillatory activities in the theta and gamma bands in response to visual affective stimuli. Distinguishable patterns of brain oscillation may represent the mechanism behind various psychiatric symptoms in patients with mTBI.

Factors influencing discharge against medical advice (DAMA) in traumatic brain injury patients requiring decompressive surgery: a comprehensive analysis.

raumatic brain injury (TBI) is a significant global health concern, particularly affecting young individuals, and is a leading cause of mortality and morbidity worldwide. Despite improvements in treatment infrastructure, many TBI patients choose discharge against medical advice (DAMA), often declining necessary surgical interventions. We aimed to investigate the factors that can be associated with DAMA in TBI patients that were recommended to have surgical treatment. This study was conducted at single tertiary university center (2008-2018), by retrospectively reviewing 1510 TBI patients whom visited the emergency room. We analyzed 219 TBI surgical candidates, including 50 declining surgery (refused group) and the others whom agreed and underwent decompressive surgery. Retrospective analysis covered demographic characteristics, medical history, insurance types, laboratory results, CT scan findings, and GCS scores. Statistical analyses identified factors influencing DAMA. Among surgical candidates, 169 underwent surgery, while 50 declined. Age (60.8 ± 17.5 vs. 70.5 ± 13.8 years; p < 0.001), use of anticoagulating medication (p = 0.015), and initial GCS scores (9.0 ± 4.3 vs. 5.3 ± 3.2; p < 0.001) appeared to be associated with refusal of decompressive surgery. Based on our analysis, factors influencing DAMA for decompressive surgery included age, anticoagulant use, and initial GCS scores. Contrary to general expectations and some previous studies, our analysis revealed that the patients' medical conditions had a larger impact than socioeconomic status under the Korean insurance system, which fully covers treatment for TBI. This finding provides new insights into the factors affecting DAMA and could be valuable for future administrative plans involving national insurance.

Neural basis of opioid-induced respiratory depression and its rescue.

Opioid-induced respiratory depression (OIRD) causes death following an opioid overdose, yet the neurobiological mechanisms of this process are not well understood. Here, we show that neurons within the lateral parabrachial nucleus that express the µ-opioid receptor (PBL Oprm1 neurons) are involved in OIRD pathogenesis. PBL Oprm1 neuronal activity is tightly correlated with respiratory rate, and this correlation is abolished following morphine injection. Chemogenetic inactivation of PBL Oprm1 neurons mimics OIRD in mice, whereas their chemogenetic activation following morphine injection rescues respiratory rhythms to baseline levels. We identified several excitatory G protein-coupled receptors expressed by PBL Oprm1 neurons and show that agonists for these receptors restore breathing rates in mice experiencing OIRD. Thus, PBL Oprm1 neurons are critical for OIRD pathogenesis, providing a promising therapeutic target for treating OIRD in patients.

Amoebicidal effect of chlorine dioxide gas against pathogenic Naegleria fowleri and Acanthamoeba polyphaga.

The pathogenic free-living amoebae, Naegleria fowleri and Acanthamoeba polyphaga, are found in freshwater, soil, and unchlorinated or minimally chlorinated swimming pools. N. fowleri and A. polyphaga are becoming problematic as water leisure activities and drinking water are sources of infection. Chlorine dioxide (ClO2) gas is a potent disinfectant that is relatively harmless to humans at the concentration used for disinfection. In this study, we examined the amoebicidal effects of ClO2 gas on N. fowleri and A. polyphaga. These amoebae were exposed to ClO2 gas from a ready-to-use product (0.36 ppmv/h) for 12, 24, 36, and 48 h. Microscopic examination showed that the viability of N. fowleri and A. polyphaga was effectively inhibited by treatment with ClO2 gas in a time-dependent manner. The growth of N. fowleri and A. polyphaga exposed to ClO2 gas for 36 h was completely inhibited. In both cases, the mRNA levels of their respective actin genes were significantly reduced following treatment with ClO2 gas. ClO2 gas has an amoebicidal effect on N. fowleri and A. polyphaga. Therefore, ClO2 gas has been proposed as an effective agent for the prevention and control of pathogenic free-living amoeba contamination.

Antibiotics for Pediatric Patients With Laryngotracheobronchitis in Korea: A Nationwide Study Based on Administrative Data.

BACKGROUND: Antimicrobial resistance (AMR) is an important global public health concern in adults and children. Laryngotracheobronchitis (croup) is a common acute respiratory infection (ARI) among children, most often caused by a virus, and should not be treated with antibiotics. Reducing the usage of unnecessary antibiotics in ARI using an antimicrobial stewardship program (ASP) is an effective measure against AMR in children. This study investigates the antibiotic prescription pattern in pediatric patients with laryngotracheobronchitis in Korea. Our results will be useful to improve the ASP. METHODS: The data were obtained from the government agency Health Insurance Review and Assessment Service. We analyzed outpatient prescriptions issued to children ≤ 5 years of age with a first-listed diagnosis code for laryngotracheobronchitis, i.e., International Classification of Disease, 10th Revision, code J050 (croup), J040 (laryngitis), or J041 (tracheitis), during 2017-2020. For each prescription, demographic information and information about medical facilities visited (type of hospital, specialty of physician, location of hospital) were extracted. The overall antibiotic prescription rate was subsequently estimated, and multivariable analysis was conducted to determine the associated factors of antibiotic prescription. Prescribed antibiotics were described and classified into extended-spectrum penicillins, cephalosporin, and macrolides. RESULTS: Of 2,358,194 prescriptions reviewed, 829,172 (35.2%) contained antibiotics. In the multivariable analysis, management in a hospital was the strongest factor associated with antibiotic prescription (adjusted odds ratio [aOR], 22.33; 95% confidence interval [CI], 20.87-23.89; P < 0.001), followed by management in a clinic (aOR, 12.66; 95% CI, 11.83-13.54; P < 0.001) and management in a general hospital (aOR, 8.96; 95% CI, 8.37-9.59; P < 0.001). Antibiotic prescription was also significantly associated with patients who were ≤ 2 years of age, managed by a pediatric specialist, and treated at a hospital located in a non-metropolitan region. Overall, extended-spectrum penicillins were the most frequently prescribed (18.6%) antibiotics, followed by cephalosporins (9.4%) and macrolides (8.5%). CONCLUSION: The results of our study suggest that ASPs need to focus on physicians in hospitals, clinics, general hospitals, and pediatric specialties. Providing education programs to these groups to increase awareness of AMR and appropriate antibiotics use could be effective ASP policy and may help to reduce unnecessary prescriptions of antibiotics for laryngotracheobronchitis among pediatric patients and therefore potentially AMR in children in Korea.

Current Status of Latent Tuberculosis Infection Treatment Among Pediatric Patients in Korea: Prescription and Treatment Completion.

BACKGROUND: The treatment of pediatric patients with latent tuberculosis infection (LTBI) is a crucial TB control strategy. LTBI is not a reportable communicable disease, and data regarding LTBI treatment in pediatric patients in Korea are scarce. This study aimed to investigate the prescription patterns and treatment completion rates among pediatric patients with LTBI in Korea by analyzing National Health reimbursement claims data. METHODS: We retrospectively analyzed outpatient prescription records for pediatric patients aged 18 or younger with LTBI-related diagnostic codes from 2016 to 2020. We compared the frequency of prescriptions for the standard treatment regimen (9 months of isoniazid [9H]) and an alternative treatment regimen (3 months of isoniazid plus rifampicin [3HR]). We also assessed the treatment incompletion rates by age group, treatment regimen, treatment duration, the level of medical facility, physician's specialty, and hospital location. We performed multivariable analysis to identify factors influencing treatment incompletion. RESULTS: Among the 11,362 patients who received LTBI treatment, 6,463 (56.9%) were prescribed the 9H regimen, while 4,899 (43.1%) received the 3HR regimen. Patients in the 3HR group were generally older than those in the 9H group. The proportion of 3HR regimen prescriptions significantly greater in the later period (2018-2020), in primary hospitals, under the management of non-pediatric specialists, and in metropolitan regions. The overall treatment incompletion rate was 39.7% (9H group: 46.9%, 3HR group: 30.3%). In the multivariable analysis, 9H regimen prescription was the strongest factor associated with treatment incompletion (adjusted odds ratio, 2.42; 95% confidence interval, 2.20-2.66; P < 0.001). Additionally, management in a primary hospital, a hospital's location in a non-metropolitan region, and management by a non-pediatric specialist were also significant risk factors for treatment incompletion. CONCLUSION: Our study results suggest that promoting the use of 3HR regimen prescriptions could be an effective strategy to enhance treatment completion. Physicians in primary hospitals, hospitals located in non-metropolitan regions, and physicians without a pediatric specialty require increased attention when administering LTBI treatment to pediatric patients to ensure treatment completion.

Comedones and epidermal cysts on the abdominal skin of a dog occurring after a laparotomy.

An 8-year-old neutered male shih tzu dog underwent laparotomy for cystolithectomy. Ten days later, multiple various-sized cystic nodules were observed on the suture line and surrounding abdominal skin, although the surgical incision had healed well. Microscopically, various-sized cysts lined with thin walls of stratified squamous epithelium in the dermis were dilated and filled with keratin. Adnexal differentiation from the wall was not seen. Thus, the abdominal lesions were diagnosed as comedones and epidermal cysts. Herein, we describe the case of a dog with comedones and epidermal cysts on the abdominal skin after a laparotomy. Key clinical message: Multiple various-sized cystic lesions of the follicles are described. The implantation of epidermal fragments into the dermis by surgery may induce epidermal cysts and comedones in the skin of hyperadrenocorticism-affected dogs.

Comédons et kystes épidermiques sur la peau abdominale d'un chien survenant après une laparotomie. Un chien shih tzu mâle castré de 8 ans a subi une laparotomie pour cystolithectomie. Dix jours plus tard, de multiples nodules kystiques de différentes tailles ont été observés sur la ligne de suture et sur la peau abdominale environnante, bien que l'incision chirurgicale ait bien cicatrisé. Au microscope, des kystes de différentes tailles bordés de fines parois d'épithélium pavimenteux stratifié dans le derme étaient dilatés et remplis de kératine. Aucune différenciation annexielle par rapport à la paroi n'a été observée. Ainsi, les lésions abdominales ont été diagnostiquées comme des comédons et des kystes épidermiques. Nous décrivons ici le cas d'un chien présentant des comédons et des kystes épidermiques sur la peau abdominale après une laparotomie.Message clinique clé:De multiples lésions kystiques des follicules, de différentes tailles, sont décrites. L'implantation chirurgicale de fragments d'épiderme dans le derme peut provoquer des kystes épidermiques et des comédons dans la peau des chiens atteints d'hypercorticisme.(Traduit par Dr Serge Messier).

Surface figure correction with roughness reduction using carbon-doped platinum film for high-precision X-ray mirror fabrication.

To obtain the surface shape of an X-ray mirror with high precision, a differential deposition method was used instead of a direct removal method. To modify the mirror surface shape using the differential deposition method, it is necessary to coat it with a thick film, and the co-deposition method is used to suppress the increase in surface roughness. The addition of C to the Pt thin film, which is often used as an X-ray optical thin film, resulted in lower surface roughness compared with that with the Pt coating alone, and the stress change according to the thin film thickness was evaluated. Differential deposition controls the speed of the substrate during coating based on continuous motion. The stage was controlled by calculating the dwell time through deconvolution calculations based on the accurate measurement of the unit coating distribution and target shape. We successfully fabricated an X-ray mirror with high precision. This study indicated that an X-ray mirror surface could be manufactured by modifying the surface shape at a micrometer level through the coating. Changing the shape of existing mirrors can not only result in the manufacture of high-precision X-ray mirrors but also improve their performance.

KRAS activation in gastric cancer stem-like cells promotes tumor angiogenesis and metastasis.

Our previous work showed that KRAS activation in gastric cancer cells leads to activation of an epithelial-to-mesenchymal transition (EMT) program and generation of cancer stem-like cells (CSCs). Here we analyze how this KRAS activation in gastric CSCs promotes tumor angiogenesis and metastasis. Gastric cancer CSCs were found to secrete pro-angiogenic factors such as vascular endothelial growth factor A (VEGF-A), and inhibition of KRAS markedly reduced secretion of these factors. In a genetically engineered mouse model, gastric tumorigenesis was markedly attenuated when both KRAS and VEGF-A signaling were blocked. In orthotropic implant and experimental metastasis models, silencing of KRAS and VEGF-A using shRNA in gastric CSCs abrogated primary tumor formation, lymph node metastasis, and lung metastasis far greater than individual silencing of KRAS or VEGF-A. Analysis of gastric cancer patient samples using RNA sequencing revealed a clear association between high expression of the gastric CSC marker CD44 and expression of both KRAS and VEGF-A, and high CD44 and VEGF-A expression predicted worse overall survival. In conclusion, KRAS activation in gastric CSCs enhances secretion of pro-angiogenic factors and promotes tumor progression and metastasis.

Alignment properties of a ferroelectric nematic liquid crystal on the rubbed substrates.

The orientation characteristics of FNLC-919, a new material with a ferroelectric nematic phase at room temperature, were investigated. Its alignment characteristics varied greatly depending on the relative rubbing direction on both substrates of a liquid crystal cell. In a cell where the two substrates were rubbed in the same direction, they were arranged homogeneously along the rubbing direction without domains or defects in the ferroelectric nematic phase. In a cell where the two substrates were rubbed in the anti-parallel direction, the two domains were twisted in the opposite direction. We quantitatively obtained the twisted direction and angle by matching the experimental data and calculation results using Jones matrix calculations. From the electro-optical experiment, it was confirmed that the polarization direction was opposite to the rubbing direction. In addition, the wavelength and temperature dependence of birefringence was measured for FNLC-919. In a cell where the rubbing direction between two substrates was 90°, two domains of opposite directions were observed in the nematic phase. When it becomes a ferroelectric nematic phase on cooling, the twist is determined to be only in one direction. The twist direction and angle were quantitatively obtained in the nematic and ferroelectric nematic phases. It was twisted more in the ferroelectric nematic phase than in the nematic phase.

Electro-optical synaptic characteristics of ferroelectric liquid crystals for artificial intelligence.

We propose electro-optical synaptic devices using surface-stabilized ferroelectric liquid crystals. Typical synaptic characteristics were observed for varying pulse time intervals, numbers of pulses, and signal voltages. Plasticity only occurred when pulses were applied at intervals shorter than the response time of the ferroelectric liquid crystal. Moreover, the plasticity increased with a higher pulse voltage and number of pulses. This demonstrates the importance of repeated learning. The synaptic weights required to make connections through learning in an artificial neural network can be determined by tuning the pulse signal. We discuss the high-speed computational potential of optical neuromorphic devices using liquid crystals.

Comparison of the efficacy in improving trigeminal neuralgia in petroclival meningioma between microsurgery and radiosurgery: a meta-analysis.

The purpose of this study was to systematically review studies in the literature to assess the superiority between microsurgery and radiosurgery regarding the efficacy in improving petroclival meningioma (PCM)-related trigeminal neuralgia (TN). PubMed, Embase, Web of Science, and Cochrane clinical trial databases were systematically searched from the inception until December 08, 2022. The overall proportion of patients with improved TN after treatment in all six included studies was 56% (95% confidence interval [CI], 35-76.9%). Higgins I2 statistics showed significant heterogeneity (I2 = 90%). Subgroup analysis showed that the proportion of improved TN was higher in the microsurgery group than that in the radiosurgery group (89%; 95% CI, 81-96.5% vs. 37%, 95% CI, 22-52.7%, respectively, p < 0.01). Subgroup analysis (for studies that documented the number of posttreatment Barrow Neurological Institute scores 1 and 2) revealed that the proportion of pain-free without medication after treatment was higher in the microsurgery group than that in the radiosurgery group (90.7%; 95% CI, 81-99.7% vs. 34.5%, 95% CI, 21.3-47.7.7%, respectively, p < 0.01). Based on the results of this meta-analysis, we concluded that microsurgery is superior to radiosurgery in controlling PCM-related TN.

Twenty-Five Year Trend Change in the Etiology of Pediatric Invasive Bacterial Infections in Korea, 1996-2020.

BACKGROUND: The coronavirus disease-2019 (COVID-19) pandemic has contributed to the change in the epidemiology of many infectious diseases. This study aimed to establish the pre-pandemic epidemiology of pediatric invasive bacterial infection (IBI). METHODS: A retrospective multicenter-based surveillance for pediatric IBIs has been maintained from 1996 to 2020 in Korea. IBIs caused by eight bacteria (Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis, Staphylococcus aureus, Streptococcus agalactiae, Streptococcus pyogenes, Listeria monocytogenes, and Salmonella species) in immunocompetent children > 3 months of age were collected at 29 centers. The annual trend in the proportion of IBIs by each pathogen was analyzed. RESULTS: A total of 2,195 episodes were identified during the 25-year period between 1996 and 2020. S. pneumoniae (42.4%), S. aureus (22.1%), and Salmonella species (21.0%) were common in children 3 to 59 months of age. In children ≥ 5 years of age, S. aureus (58.1%), followed by Salmonella species (14.8%) and S. pneumoniae (12.2%) were common. Excluding the year 2020, there was a trend toward a decrease in the relative proportions of S. pneumoniae (rs = -0.430, P = 0.036), H. influenzae (rs = -0.922, P < 0.001), while trend toward an increase in the relative proportion of S. aureus (rs = 0.850, P < 0.001), S. agalactiae (rs = 0.615, P = 0.001), and S. pyogenes (rs = 0.554, P = 0.005). CONCLUSION: In the proportion of IBIs over a 24-year period between 1996 and 2019, we observed a decreasing trend for S. pneumoniae and H. influenzae and an increasing trend for S. aureus, S. agalactiae, and S. pyogenes in children > 3 months of age. These findings can be used as the baseline data to navigate the trend in the epidemiology of pediatric IBI in the post COVID-19 era.

Engineered Extracellular Vesicles with Compound-Induced Cargo Delivery to Solid Tumors.

Efficient delivery of functional factors into target cells remains challenging. Although extracellular vesicles (EVs) are considered to be potential therapeutic delivery vehicles, a variety of efficient therapeutic delivery tools are still needed for cancer cells. Herein, we demonstrated a promising method to deliver EVs to refractory cancer cells via a small molecule-induced trafficking system. We generated an inducible interaction system between the FKBP12-rapamycin-binding protein (FRB) domain and FK506 binding protein (FKBP) to deliver specific cargo to EVs. CD9, an abundant protein in EVs, was fused to the FRB domain, and the specific cargo to be delivered was linked to FKBP. Rapamycin recruited validated cargo to EVs through protein-protein interactions (PPIs), such as the FKBP-FRB interaction system. The released EVs were functionally delivered to refractory cancer cells, triple negative breast cancer cells, non-small cell lung cancer cells, and pancreatic cancer cells. Therefore, the functional delivery system driven by reversible PPIs may provide new possibilities for a therapeutic cure against refractory cancers.

Chromatographic Method for Monitoring of Pesticide Residues and Risk Assessment for Herbal Decoctions Used in Traditional Korean Medicine Clinics.

The presence of pesticide residues in herbs and the herbal products derived from them raises serious health concerns. This study was conducted to investigate the residual pesticide concentrations and assess potential human health risks from herbal medicines used in traditional Korean medicine clinics. A total of 40 samples of herbal decoctions were collected from 10 external herbal dispensaries. The pesticide residues were analyzed by the multiresidue method for 320 different pesticides using liquid chromatography tandem mass spectrometry (LC-MS/MS) and gas chromatography tandem mass spectrometry (GC-MS/MS). As a result of the monitoring, carbendazim was detected at 0.01 and 0.03 µg/g in eight samples and no pesticide was detected in the other herbal decoctions. Carbendazim was set for each individual item as less than 0.05 µg/g in Paeoniae radix, less than 0.05 µg/g in Cassiae semen, less than 2.0 µg/g in Lycii fructus, and less than 10 µg/g in Schisandrae fructus (dried). Therefore, the results of this study suggested that the detected pesticide residues in herbal decoctions could not be considered as posing a serious health risk.

Photonic Microbeads Templated by Oil-in-Oil Emulsion Droplets for High Saturation of Structural Colors.

Photonic microbeads containing crystalline colloidal arrays are promising as a key component of structural-color inks for various applications including printings, paintings, and cosmetics. However, structural colors from microbeads usually have low color saturation and the production of the beads requires delicate and time-consuming protocols. Herein, elastic photonic microbeads are designed with enhanced color saturation through facile photocuring of oil-in-oil emulsion droplets. Dispersions of highly-concentrated silica particles in elastomer precursors are microfluidically emulsified into immiscible oil to produce monodisperse droplets. The silica particles spontaneously form crystalline arrays in the entire volume of the droplets due to interparticle repulsion which is unperturbed by the diffusion of the surrounding oil whereas weakened for oil-in-water droplets. The crystalline arrays are permanently stabilized by photopolymerization of the precursor, forming elastic photonic microbeads. The microbeads are transferred into the refractive-index-matched biocompatible oil. The high crystallinity of colloidal arrays increases the reflectivity at stopband and the index matching reduces incoherent scattering at the surface of the microbeads, enhancing color saturation. The colors can be adjusted by mixing two distinctly colored microbeads. Also, low stiffness and high elasticity reduce foreign-body sensation and enhance fluidity, potentially serving as pragmatic structural colorants for photonic inks.

Clinical features and treatment strategies for vertex epidural hematoma: a systematic review and meta-analysis from individual participant data.

Vertex epidural hematoma (VEDH) is a rare extradural hematoma and often misdiagnosed because of its variety of clinical symptoms and characteristic location. Determining optimal timing and technique for VEDH surgery is difficult because of its midline location and atypical clinical course. This study aims to understand the clinical manifestations and current treatment strategies for VEDH. We searched the published literature regarding VEDH through PubMed and Google Scholar, and individual patient data (IPD) were obtained from the eligible articles. A systematic review and IPD meta-analysis were conducted. In total, 70 patients' individual participant data were gathered. Most patients were male (87%), and traffic-related accidents were the most common injury mechanism (49%). Approximately half the patients (47%) were neurologically intact with nonspecific symptoms such as headache, dizziness, and vomiting at admission. Motor weakness alone (17%) and symptoms related to cranial nerve dysfunction such as anosmia, blurred vision, or diplopia (10%) were also noted. A surgical approach was initially chosen for 20 patients (28%), but eventually chosen for 20 more (total 40, 57%) during the observation period (average delay to surgery, 5 days). Patients who received surgery showed significantly poorer neurological status and larger hematoma size. Totally, two patients (3%) died, but most patients (94%) had a favorable outcome scoring 5 on the Glasgow Outcome Scale. Although VEDH generally showed favorable outcomes, clinicians must be aware of a high rate of delayed neurological deterioration during the observation period, which can be fatal due to central downward herniation.

The Seroprevalence of SARS-CoV-2 in Children During Early COVID-19 Pandemic in Korea: A Nationwide, Population-Based Study.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is often asymptomatic and associated with mild clinical symptoms in children. Social distancing measures have led to a relatively small number of confirmed COVID-19 cases in Korea than in other countries in the earlier pandemic phase. Previous seroprevalence studies in Korean adults before the introduction of COVID-19 vaccination campaign have shown a low antibody positivity rate. However, data on COVID-19 seroprevalence in Korean children remained scarce. In this study, we assessed the seroprevalence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in children in Korea. METHODS: Between December 2020 and March 2021, stratified serum samples were collected from children aged 0-18 years in 17 different regions across the country. The SARS-CoV-2 antibody test was conducted using an electro-chemiluminescence immunoassay (ECLIA) to detect the antibodies against nucleocapsid antigens of SARS-CoV-2. Samples that tested positive using the ECLIA were reflexed to an additional plaque reduction neutralization test (PRNT) for SARS-CoV-2. RESULTS: A total of 1,887 samples were collected. Excluding 21 samples collected from regional medical centers, 1,866 samples were included in the final analysis. Two samples (0.11%) were positive for the antibodies against nucleocapsid antigens of SARS-CoV-2. Both samples were shown to have neutralizing antibodies for SARS-CoV-2 via PRNT. CONCLUSION: After 1 year since the start of COVID-19 pandemic, the seroprevalence of SARS-CoV-2 among Korean children was 0.11%, which was lower than the adults (0.52%) in another study conducted during a similar period. In the early stages of the COVID-19 pandemic, the seroprevalence of SARS-CoV-2 in Korea was lower than those of other countries, which was presumed to be the consequence of a very strong social distancing measures.

Effect of thermal aging on the transport and acoustic properties of partially reticulated polyurethane foams.

This study aims to investigate the acoustic effects of thermal aging on partially reticulated polyurethane (PU) foam. An accelerated test was performed under appropriate test conditions as determined by thermal analyses of the material. Measurements of the absorption coefficient showed that the performance of the partially reticulated PU foam can be significantly reduced by thermal aging. The transport parameters were evaluated to analyze the origin of this change in the absorption behavior. Sensitivity analyses revealed that a decrease in the static airflow resistivity had the greatest effect in terms of reducing the absorption coefficient owing to thermal aging. In addition, observation and characterization of the microstructure of the aged foam to determine the root cause of this acoustic degradation indicated that heat-induced damage to the membrane was the most important factor. To verify this assertion, a periodic unit cell model that mimicked the topology of the cellular structure was constructed, and the mechanism responsible for the change in the acoustic behavior was simulated. The results presented herein can be used as durability guidelines for maintaining the performances of partially reticulated PU foams that are employed in high-temperature environments.

Fiber-Optic Temperature Sensor Using Cholesteric Liquid Crystals on the Optical Fiber Ferrules.

Cholesteric liquid crystals (CLCs) can be applied to various physical and chemical sensors because their alignment structures are changed by external stimuli. Here, we propose a CLC device fabricated by vertically forming the helical axis of the CLC between the cross-sections of two optical fiber ferrules. An optical fiber temperature sensor was successfully implemented using the proposed optical fiber ferrule-based CLC device. A wideband wavelength-swept laser with a center wavelength of 1073 nm and scanning range of 220 nm was used as a light source to measure the variations in the reflection spectrum band according to the temperature change in the CLC cell. The wavelength variation of the reflection spectrum band according to the temperature applied to the CLC cell was reversible and changed linearly with a change in the temperature, and the long-wavelength edge variation rate according to the temperature change was -5.0 nm/°C. Additionally, as the temperature applied to the CLC cell increased, the reflection spectrum bandwidth gradually decreased; the reflection spectrum bandwidth varied at a rate of -1.89 nm/°C. The variations in the refractive indices with temperature were calculated from the band wavelengths of the reflection spectrum. The pitch at each temperature was calculated based on the refractive indices and it gradually decreased as the temperature increased.