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Primary ovarian insufficiency (POI) can lead to menstrual disturbance, resulting in ovarian dysfunction before age 40. Prevalence of POI is usually less than 1%; however, ethnicity or population characteristics may affect prevalence. POI is a heterogeneous disease that results from abnormalities in immunological and hormonal factors. Genetic factors can also contribute to POI. Here, we examine FSHR, ESR1, and BMP15 polymorphisms in patients with POI, and controls. We examined a hormonal gene that is important for pregnancy, follicle-stimulating hormone receptor (FSHR), as well as estrogen receptor 1 (ESR1), and associated it with FSHR expression, ovulation rate, and bone morphogenetic protein 15 (BMP15). We examined 139 Korean patients under age 40 with POI, and 350 Korean control participants without POI. Genotyping was performed by a polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP) and TaqMan assays. Each identified genotype was subjected to statistical analysis to determine the odds ratios (ORs) and 95% confidence intervals (CIs). In combination genotype analyses, FSHR rs6165 A > G combined with ESR1 rs9340799 A > G, AG/GG (OR: 5.693; 95% CI: 1.088–29.792), as well as FSHR rs6166 A > G combined with ESR1 rs9340799 C > T, AG/GG (OR: 5.940; 95% CI: 1.134–31.131), were significantly associated with POI prevalence. Furthermore, an FSHR rs6165 A > G and BMP rs17003221 C > T, AG/CC combination was associated with POI prevalence (OR: 1.874; 95% CI: (1.059–3.316; p-value: 0.031)). In meta-analysis, FSHR rs6165 AA vs. AG + GG is associated with POI (p = 0.0013), and ESR1 rs2234693 AA vs. AG + GG is also associated with POI (p = 0.0101). Here, we compared the genotypes of FSHR, ESR1, and BMP15 in patients with POI, and controls. We found significant differences in genotype combinations between polymorphisms in FSHR and other genes. Through meta-analysis, we found that ESR1 rs9340799 and rs2234693 are associated with POI prevalence, and that BMP15 rs17003221 increases POI risk. These findings help to improve POI diagnosis in Korean women.

Purpose The lifestyle changes during the coronavirus disease 2019 pandemic possibly affected mental health among the pediatric population. We aimed to analyze changes in psychiatric emergency-related visits to the emergency department (ED). Methods We reviewed cases of pediatric patients (≤ 18 years) who visited the ED of a tertiary hospital with psychiatric emergency as a chief complaint from March 2019 through February 2021. The study period was dichotomized by March 2020, starting point of social distancing, into the pandemic and control periods. Clinical data were collected and compared between the 2 periods. Results A total of 246 cases with a mean age of 15.2 years were included. The overall visits to the ED decreased to 43.8% whereas the proportion of psychiatric emergency-related visits increased during the pandemic period, compared to the control period (0.5% vs. 1.0%; P < 0.001). The cases with suicidality, including ideation and attempt, increased in both number and proportion during the pandemic period (51 [38.9%] vs. 63 [54.8%]; P = 0.013). Conclusion Pediatric psychiatric emergency-related visits, particularly suicidality, proportionally increased during the pandemic. This finding may be useful to prepare psychiatric resources in EDs.

As a disease with high mortality and prevalence rates worldwide, colorectal cancer (CRC) has been thoroughly investigated. Mucins are involved in the induction of CRC and the regulation of intestinal homeostasis but a member of the mucin gene family MUC4 has a controversial role in CRC. MUC4 has been associated with either decreased susceptibility to or a worse prognosis of CRC. In our study, the multifunctional aspects of MUC4 were elucidated by genetic polymorphism analysis in a case-control study of 420 controls and 464 CRC patients. MUC4 rs1104760 A>G polymorphism had a protective effect on CRC risk (AG, AOR = 0.537; GG, AOR = 0.297; dominant model, AOR = 0.493; recessive model, AOR = 0.382) and MUC4 rs2688513 A>G was associated with an increased mortality rate of CRC (5 years, GG, adjusted HR = 6.496; recessive model, adjusted HR = 5.848). In addition, MUC4 rs1104760 A>G showed a high probability of being a potential biomarker for CRC patients with low-density lipoprotein cholesterol (LDL-C) in the risk range while showing a significant synergistic effect with the LDL-C level. This is the first study to indicate a significant association between MUC4 genetic polymorphisms and CRC prevalence, suggesting a functional genetic variant with the LDL-C level, for CRC prevention.

We report a case of inguinal hernia that contained the entire uterus and both adnexa, presenting with an irreducible soft mass in the left groin and asymmetric labia majora, in a 2-month-old, full-term girl who visited the emergency department. Ultrasonography was performed immediately, and urgent surgical repair was performed without complications. Although inguinal hernia is a common surgical disease, it is rare that the hernia contains the uterus with its adnexa, and presents as a mass of the labia majora. Unlike the bowel herniation, the entity can be complicated by strangulation of the ovary, leading to infertility. To preserve fertility, rapid and accurate diagnosis using ultrasonography should be considered in an infant with an irreducible inguinal mass and asymmetric labia majora.

Button battery ingestion requires emergency endoscopic removal since severe complications, such as esophageal perforation, can develop within 4 hours of the ingestion. Given that guardians do not witness the children’s foreign body ingestion 40% of the time, physicians can only guess what was swallowed based on plain radiography. We report a case of a 45-month-old-boy who visited the emergency department after swallowing an unknown foreign body and whose radiographs showed “circle-within-a-circle appearance” on the anteroposterior view and “step-off appearance” on the lateral view, suggesting button battery ingestion. We conducted emergency endoscopic removal, and found stacked coins mimicking a button battery on the radiographs. The coins were pushed into the stomach and came out through defecation 3 weeks later without further complications. Distinguishing between stacked coins and a button battery through radiography may help avoid unnecessary emergency endoscopy.

As populations around the world age, interest in healthy aging is growing. One of the first physical changes that occurs with aging is the loss of muscle mass and strength, termed sarcopenia. Sarcopenia limits the activity of older people, reduces their quality of life, and increases the likelihood of their developing disease. In the present study, we aimed to evaluate the effects of the ingestion of acid-hydrolyzed silk peptide (SP) on the muscle mass and strength of mice of >22 months of age with naturally occurring sarcopenia, and to identify the mechanisms involved. The daily administration of SP for 8 weeks increased the activation of the Akt/mTOR/FoxO3a signaling pathways and increased the muscle mass and strength of the old mice. In addition, SP inhibited oxidative stress and inflammation in muscle, which are direct causes of sarcopenia. Therefore, SP represents a promising potential treatment for sarcopenia that may improve the healthy lifespan and quality of life of older people.

Abstract Background Fever in infants under 90 days of age is highly likely to be caused by a severe bacterial infection (SBI) and it accounts for a large number of patients visiting the pediatric emergency room. In order to predict the bacterial infection and reduce unnecessary treatment, the classic classification system is based on white blood cell (WBC) count, urinalysis, and x-ray, and it is modified and applied at each center by incorporating recently studied biomarkers such as c-reactive protein (CRP) or procalcitonin (PCT). This study analyzed the usefulness of PCT in predicting SBI when applied along with the existing classification system, including CRP, among infants less than 90 days old who visited with a fever at a single institution pediatric emergency center. Methods We retrospectively reviewed the medical records of patients younger than 3 months of age who presented with fever at the Seoul Asan Medical Center pediatric emergency room between July 2017 and October 2018. Results A total of 317 patients were analyzed, and 61 were diagnosed with SBI, among which urinary tract infection (UTI) accounted for the largest proportion (55/61, 90.2%). There were differences in WBC, neutrophil proportion, CRP, and PCT between the SBI group and the non-SBI group, and the AUC values of WBC, CRP, and PCT were 0.651, 0.804, and 0.746, respectively. When using the cut-off values of CRP and PCTs as 2.0 mg/dL and 0.3 ng/mL, respectively, the sensitivity and specificity for SBI were 49.2/89.5, and 54.1/87.5, respectively. WBC, CRP, and PCT were statistically significant for predicting SBI in multivariate analysis (odds ratios 1.066, 1.377, and 1.291, respectively). When the subjects were classified using the existing classification criteria, WBC and CRP, the positive predictive value (PPV) and negative predictive value (NPV) were 29.3 and 88.7%, respectively, and when PCT was added, the PPV and NPV were 30.7 and 92%, respectively, both increased. Conclusion PCT is useful for predicting SBI in children aged 3 months or less who visit the emergency room with a fever. It is useful as a single biomarker, and when used in conjunction with classic biomarkers, its diagnostic accuracy is further increased.

Abstract Background This study aimed to verify the usefulness of point-of-care ultrasound (POCUS) performed by pediatric emergency physicians for detecting intussusception at an early stage. Methods This retrospective study included 1-month- to 6-year-old children with clinically suspected intussusception, who underwent POCUS in the pediatric emergency department between December 2016 and February 2018. The criteria for performing POCUS were set to broader standards: presenting any one of intermittent abdominal pain/irritability or bloody stool, or ≥ 2 symptoms among nonspecific abdominal pain/irritability, abdominal mass/distension, vomiting, or lethargy. POCUS results were interpreted and categorized as “negative” or “suspicious,” and a radiologist performed confirmatory ultrasound in “suspicious” cases. Results We analyzed 575 POCUS scans from 549 patients (mean age, 25.5 months). Among the 92 “suspicious” cases (16.0%), 70 (12.2%) were confirmed to have intussusception. POCUS showed 100% sensitivity, 95.6% specificity, and 97.8% accuracy. Patients with confirmed intussusception were mainly diagnosed in the early stages, with a mean symptom duration of 11.7 h, and most patients (97.1%) were treated successfully via air enema reduction. Compared to the non-intussusception group, the intussusception group had more intermittent abdominal pain (P

Abstract Background Intussusception decreases blood flow to the bowel, and tissue hypoperfusion results in increased lactic acid levels. We aimed to determine whether lactic acid levels are associated with pediatric intussusception outcomes. Methods The electronic medical records of our emergency department pediatric patients diagnosed with intussusception, between January 2015 and October 2018, were reviewed. An outcome was considered poor when intussusception recurred within 48 h of reduction or when surgical reduction was required due to air enema failure. Results A total of 249 patients were included in the study, including 39 who experienced intussusception recurrence and 11 who required surgical reductions; hence, 50 patients were included in the poor outcome group. The poor and good outcome groups showed significant differences in their respective blood gas analyses for pH (7.39 vs. 7.41, P = .001), lactic acid (1.70 vs. 1.30 mmol/L, P

Abstract Background Recurrent implantation failure (RIF) is the failure of embryos to implant more than two times in a given individual. There is debate about a precise definition for RIF, but we consider more than two implantation failures for individuals who undergo in vitro fertilization-embryo transfer (IVF-ET) to constitute RIF. There are many potential reasons for RIF, including embryonic factors, immunological factors, uterine factors, coagulate factors, and genetic factors. Genetic variation has been suggested as one of the contributing factors leading to RIF, and a number of single-nucleotide polymorphisms (SNPs) have been reported to be associated with RIF. The recent elucidation of miRNA functions has provided new insight into the regulation of gene expression. Methods We investigated associations between polymorphisms in four miRNAs and RIF in 346 Korean women: 118 patients with RIF and 228 controls. We determined the genotypes of the miRNAs in the study participants by polymerase chain reaction-restriction fragment-length polymorphism (PCR-RFLP) analysis. We analyzed the effects of genotypes, allele combinations, and environmental and clinical factors on the risk of RIF. Results The miR-25 T/miR-125aT/miR-222G (odds ratio (OR), 0.528; 95% confidence interval (CI), 0.282–0.990; P = 0.044) and miR-25 T/miR-125aT allele combinations were associated with a reduced risk of RIF. The miR-25 T/miR-32C/miR-125aC/miR-222 T allele combination was associated with an increased risk of RIF. The miR-222GT+TT genotypes interacted with high prothrombin time (≥ 12 s) to increase the risk of RIF. Conclusions MicroRNA polymorphisms are significantly different between patients that experience RIF and healthy controls. Combinations of microRNA polymorphisms were associated with the risk of RIF. Interactions between environmental factors and genotypes increased the risk of RIF in Korean women.

In this study, we evaluated the immunostimulatory effect of silk peptide in subjects with peripheral blood leukocyte levels of 4–8 × 103/μl by a randomized, double-blind, placebo-controlled clinical trial. The subjects were randomly assigned to one of two groups, the placebo control or silk peptide intervention group, for 8 weeks. As a result, evaluation of efficacy in 97 subjects showed no significant difference between the groups in immunostimulatory parameters. However, after separate analysis of 61 non-season influenza vaccine subjects, the natural killer cell activity (%) with an effector cell: target cell (E: T) ratio of 10:1 was increased significantly from 30.7 ± 2.28% at week 0 to 41.8 ± 2.71% at week 8 (p

Context: Silk peptide from cocoons of silkworm (Bombyx mori L., Bombycidae) has been employed as a biomedical material and exhibits various bioactivities, including immune-modulating activity. Objective: We analyzed whether silk peptide exerts direct modulating effects on NK cells using an NK cell line in vitro and ex vivo splenocytes. We also attempted to delineate the mechanism underlying the modulation. Material and methods: In vitro activity of silk peptide on NK cells was determined by measurement of cytolytic activity against K562 cells at an effector-to-target ratio of 5:1 after incubation of NK-92MI cells with silk peptide (0–2000 μg/mL) for 48 and 72 h. Ex vivo activity of silk peptide on mouse splenic NK cells was determined similarly by using YAC-1 cells. Results: Treatment of NK-92MI NK cells with silk peptide (500–2000 μg/mL) significantly increased cytolytic activity on target cells by 2- to 4-fold. The same concentrations (500–2000 μg/mL) of silk peptide treatment also significantly enhanced the cytolytic activity of splenic NK cells against YAC-1 cells. Silk peptide treatment of IL-2-stimulated splenocytes induced enhanced expression of Th1, 2 and 17 cytokines including TNF-α, IFN-γ, IL-6, IL-4 and IL-17. Finally, ex vivo treatment with silk peptide on mouse splenocytes significantly enhanced the degree of NK cell maturation in a dose-dependent manner from 3.49 to 23.79%. Discussion and conclusions: These findings suggest that silk peptide stimulates NK cells, thereby influencing systemic immune functions and improving natural immunity. Thus, silk peptide could be useful as a complementary therapy in cancer patients.

Recurrent pregnancy loss (RPL) is typically defined as two or more consecutive pregnancy losses prior to 20 weeks of gestation. Although the causes of idiopathic RPL are not completely understood, vascular development and glucose concentration were reported to correlate with the pregnancy loss. The TGF-β signaling pathway which plays a significant role in pregnancy is activated by the interaction between high glucose and SMAD signaling and affects the vascular cells. SMAD5 and RUNX-1 are involved in the TGF-β signaling pathway and contribute to advanced glycation end products (AGEs) production and vascular development. FN3KRP, a newly described gene, is also associated with vascular diseases and suggested to relate to AGEs. Therefore, in the present study, we investigated associations between RPL risk and genetic polymorphisms of SMAD5, FN3KRP, and RUNX-1 in 388 women with RPL and 280 healthy control women of Korean ethnicity. Participants were genotyped using real-time polymerase chain reaction and restriction fragment length polymorphism assay to determine the frequency of SMAD5 rs10515478 C>G, FN3KRP rs1046875 G>A, and RUNX-1 rs15285 G>A polymorphisms. We found that women with RPL had lower likelihoods of the FN3KRP rs1046875 AA genotype (adjusted odds ratio (AOR), 0.553; p = 0.010) and recessive model (AOR, 0.631; p = 0.017). Furthermore, combination analysis showed that SMAD5 rs10515478 C>G and FN3KRP rs1046875 G>A mutant alleles were together associated with reduced RPL risk. These findings suggest that the FN3KRP rs1046875 G>A polymorphism has a significant role on the prevalence of RPL in Korean women. Considering that it is the first study indicating a significant association between FN3KRP and pregnancy disease, RPL, our results suggest the need for further investigation of the role of FN3KRP in pregnancy loss.

(1) Background: First-pass success (FPS) of endotracheal intubation is more challenging in children than in adults. We aimed to identify factors associated with FPS of intubation in acute care settings. (2) Methods: We analyzed data of children aged p = 0.018), were less frequently in their infancy (36.1% vs. 50.5%; p = 0.017), and were less likely to have respiratory compromise (41.4% vs. 55.0%; p = 0.030). The children with FPS tended to be more often intubated by experienced intubators than those without FPS (87.0% vs. 78.4%; p = 0.057). Desaturation was rarer in those with FPS. Factors associated with FPS were experienced intubators (aOR, 1.93; 95% CI, 1.01–3.67) and children’s age ≥12 months (1.84; 1.13–3.02). (4) Conclusion: FPS of intubation can be facilitated by deploying or developing clinically competent intubators, particularly for infants, in acute care settings.

Anti-aging research suggests that immunosenescent cells can play deleterious roles in the immune system. Here, young (2 months old) and old (14 months old) C57BL/6 mice received a daily oral dose (100 or 750 mg/kg/day) of acid-hydrolyzed silk peptide (SP) for a period of 5 weeks. Mouse spleen, lymph node, and serum were analyzed to determine the immune homeostasis of SP by flow cytometry, Western blotting, ELISA, and qRT-PCR. The results suggest that SP ameliorates age-related dysfunction of T and B cells. Amelioration of B cell dysfunction improved the immunoglobulin response in aged mice. Taken together, the results suggest that SP restores immune homeostasis with respect to immunosenescent cells.

In colorectal carcinogenesis, the unique molecular and genetic changes that occur within cells result in specific CRC phenotypes. The involvement of the long non-coding RNA, HOTAIR, in cancer development, progression, and metastasis is well-established. Various studies have reported on the contribution of HOTAIR to cancer pathogenesis. Therefore, we selected four HOTAIR polymorphisms (rs7958904G>C, rs1899663G>T, rs4759314A>G, and rs920778T>C) to evaluate the association of each variant with CRC prevalence and prognosis. We conducted a case–control study of 850 individuals to identify the genotype frequencies of each polymorphism. The study population included 450 CRC patients and 400 control individuals that were randomly selected following a health screening. Notably, rs7958904 and rs1899663, their hetero genotype, and the dominant model were significantly different when compared to the healthy control group (rs7958904; AOR = 1.392, 95% CI = 1.052–1.843, P = 0.021). To evaluate the effect of HOTAIR polymorphisms on the survival rate, we analyzed patient mortality and relapse occurrence within 3 and 5 years with Cox-regression analysis. The rs7958904 CC polymorphism mortality rate was significantly higher than the GG polymorphism mortality rate (adjusted HR = 2.995, 95% CI = 1.189–7.542, P = 0.021). In addition, the rs920778 CC genotype was significantly different than the TT genotype (adjusted HR = 3.639, 95% CI = 1.435–9.230, P = 0.007). In addition, this study confirmed that genetic variants of HOTAIR alter the mRNA expression level (P < 0.01). We suggest that HOTAIR rs7958904G>C which is associated with CRC prevalence and mortality is a potential biomarker for CRC. The association between HOTAIR gene polymorphisms and CRC prevalence were reported for the first time.

Copper sulfide allows for high-performance sodium ion storage, yet its sodiation mechanism is poorly understood. Here, the authors examine the atomic structures of sodiated phases via in situ transmission electron microscopy, showing a non-equilibrium reaction pathway.

Coronavirus disease 2019 (COVID-19) changed the epidemiology of various diseases. The present study retrospectively investigates the epidemiologic and clinical changes in pediatric intussusception for ages ≤ 7 years before (February 2019–January 2020) and after (February 2020–January 2021) the COVID-19 outbreak in a single pediatric emergency department of a university-affiliated tertiary hospital. The incidence of communicable diseases—defined as infectious diseases with the potential for human-to-human transmission via all methods, non-communicable diseases, and intussusception were decreased following the COVID-19 outbreak (15,932 to 3880 (24.4%), 12,994 to 8050 (62.0%), and 87 to 27 (31.0%), respectively). The incidence of intussusception correlated significantly with the change in incidence of communicable diseases (Poisson log-linear regression, odds ratio = 2.15, 95% CI = 1.08–4.26, and p = 0.029). Compared with the pre-pandemic period, patients of the pandemic period showed higher proportions of pathologic leading point (PLP) and hospitalization (14.8% vs. 2.3% and 18.5% vs. 4.6%, respectively), lower base excesses (−4.8 mmol/L vs. −3.6 mmol/L), and higher lactate concentrations (1.7 mmol/L vs. 1.5 mmol/L). The incidence of pediatric intussusception decreased after the COVID-19 pandemic. This reduced incidence may be related to the reduced incidence of communicable diseases. However, the proportions of more severe diseases and PLPs were higher after the COVID-19 pandemic.

Acid-hydrolyzed silk peptide (SP) is a valuable material that has been used traditionally to treat various diseases, however, the mechanism by which it affects inflammatory responses is unknown. To examine the effects of SP on inflammatory responses, we used macrophages as a vehicle for examining signaling via toll-like receptor 4 (TLR4), which plays an important role in innate immune responses to pathogenic infections and pathogen-derived molecules such as lipopolysaccharide (LPS). We then confirmed the anti-inflammatory effects of SP by examining lymph node, spleen, and serum samples from C57BL/6 mice injected with LPS. We also used LPS-induced bone marrow-derived macrophages and RAW264.7 cells (a murine macrophage cell line) to identify the mechanism by which SP modulates immune responses via the TLR4 signaling pathway. In addition, we showed that SP prevents LPS-induced production of nitric oxide and reactive oxygen species. In summary, SP inhibits LPS-induced inflammatory responses by modulating the TLR4 signaling pathway.

Obesity is associated with excess body fat accumulation that can cause hyperglycemia and reduce skeletal muscle function and strength, which characterize the development of sarcopenic obesity. In this study, we aimed to determine the mechanism whereby acid-hydrolyzed silk peptide (SP) prevents high-fat diet (HFD)-induced obesity and whether it regulates glucose uptake and muscle differentiation using in vivo and in vitro approaches. Our findings demonstrate that SP inhibits body mass gain and the expression of adipogenic transcription factors in visceral adipose tissue (VAT). SP also had an anti-diabetic effect in VAT and skeletal muscle because it upregulated glucose transporter type 4 (GLUT4) and uncoupling protein 3 (UCP3) expression. Furthermore, SP reduced ubiquitin proteasome and promoted myoblast determination protein 1 (MyoD)/myogenic factor 4 (myogenin) expression, implying that it may have potential for the treatment of obesity-induced hyperglycemia and obesity-associated sarcopenia.

Despite its rarity, a tracheoinnominate artery fistula can result in catastrophic hemorrhage. Here, we describe a case of a 13-year-old boy with such a condition following tracheostomy. After identification of pulsatile bleeding from the tracheostoma, temporary control of hemorrhage was obtained using hyperinflation of the tracheostomy tube cuff. Subsequently, a lesion indicative of a tracheoinnominate artery fistula was found on a computed tomography scan, and the diagnosis was confirmed at surgery. After surgery, he was discharged with no recurrent bleeding. This case highlights the importance of high suspicion and prompt management of tracheoinnominate artery fistula.

Objective The clavicle is almost always seen in skull X-rays of infants. The objectives of this study were to determine how often the clavicle and clavicle fractures are visible but missed on the skull anterior-posterior view (skull AP) of infants and which factors are associated with missing the diagnosis. Methods We retrospectively studied patients aged 1 year or younger who had a skull AP taken for any injury survey at a single urban, academic hospital between April 1999 and July 2012. Outcomes of interest were the numbers and percentages of visible clavicles; clavicle fractures, including missed ones on skull AP; and the factors associated with missing the diagnosis of a clavicle fracture. Results Both clavicles were visible in 734 patients (89.6%). Of these, 10 patients (1.4%) had confirmed clavicle fractures, and 6 patients (0.8%) had fractures that were missed at presentation. Although we tried to determine the factors that might be associated with missed diagnoses, including age

Purpose The more younger the child, the more complications of endotracheal intubation are likely, such as deep intubation, extubation, atelectasis, or barotraumas, because of the small diameter and short length of the trachea. Therefore, the exact placement of tube tip in the middle third of trachea is very important; however, normal reference ranges of the length from incisors to middle third of the trachea for Korean children is not prepared yet. Methods A retrospective study was conducted on 48 children, who underwent endotracheal intubation in the emergency department of Asan Medical Center, between February 1997 and October 2007. After correcting the depth in actual tip positions by the difference between the actual intubation depths and calculated or measured depths by various methods, such as PALS guidelines, APLS formula, formula method, Broselow tape, and new formula, a comparison between these various methods was done. Results Most commonly, the tube position was too deep including position in the right main bronchus (71%). Among the children who underwent right main bronchus intubation, more than half were children less than 2 years of age (58%). The highest rate of appropriate tube position was observed when corrected using the PALS guideline (69%), and the lowest rate was observed in formula method (26%). Conclusion Meticulous intubation technique requires not to intubate too deep especially in young children less than 2 years of age. Physicians responsible for acute care of children should be knowledgeable of the PALS guideline for the appropriate depth of tracheal tube. However, it is also important to note the possibility of deep intubation while adhering to this guideline (approximately 40%). The development of methods or devices based on the distance from incisors to mid-portion of the trachea for Korean children is necessary.

The constituents, distribution, and characteristics of the phases formed on the coating layer of boron steel hot-dipped in Al-7wt%Ni-6wt%Si were evaluated in detail. In particular, the microstructure and phase constitution of the reaction layer were characterized. Moreover, the microstructural evolution mechanism of the phase was presented with reference to the (Al-7wt%Ni-6wt%Si)-xFe from the pseudo-binary phase diagram. The solidification layer consisted mainly of Al, Al3Ni, and Si phases. Reaction layers were formed in the order of Al9FeNi(Τ), Fe4Al13(θ), and Fe2Al5(η) from the solidification layer side. In addition, the κ (Fe3AlC) layer was formed at the Fe2Al5(η)/steel interface. From pseudo-binary phase diagram analysis, it was found that Fe4Al13(θ) can form when the Fe concentration is over 2.63 wt% in the 690 °C Al-7wt%Ni-6wt%Si molten metal. When the concentration of Fe increased to 10.0⁻29.0 wt%, isothermal solidification occurred in the Fe4Al13(θ) and Al9FeNi(Τ) phases simultaneously. Moreover, given that the T phase does not dissolve Si, it was discharged, and the Si phase was formed around the Al9FeNi(T) phase. The Fe2Al5(η) phase was formed by a diffusion reaction between Fe4Al13(θ) and steel, not a dissolution reaction. Moreover, Al2Fe3Si3(τ1) was formed at the Fe4Al13(θ)-Fe2Al5(η) interface by discharging Si from Fe4Al13(θ) without Si solubility. Furthermore, the Fe3AlC(κ) layer was formed by carbon accumulation that discharged in the Fe2Al5(η) region transformed from steel to Fe2Al5(η). The twin regions in the Fe4Al13(θ) and Fe2Al5(η) grain were due to the strains caused by the lattice transformation in the constrained state, wherein the phases are present between the Al9FeNi(Τ) layer and steel.

This study investigated the nucleation and growth mechanism of reaction layers and phases of hot-dipped boron steel in pure Al at 690 °C for 0–120 s. In the case of a dipping time of 30 s, reaction nuclei of width 10–15 μm and height 10 μm were formed on the steel surface in the flow direction of the liquid Al. This reaction layer was formed as a mixture of θ (Fe4Al13) phase of several nm to 2 μm, θ and η (Fe2Al5) of several nm, a columnar η region, and a β (FeAl) region of 500 nm thickness at the steel interface. At the grain boundaries of ferrite, in contact with the η phase, κ (Fe3AlC) was formed. Using the calculated Fe-Al phase diagram, it was determined that when Fe was dissolved in liquid Al from the steel above 2.5 at% (0.6 wt%), the θ phase was formed. Although most of the θ phases continuously grew toward the liquid phase, the θ phase in contact with the steel was transformed into the η phase with minimal differences in composition due to the inter-diffusion of Al and Fe. It was therefore concluded that the η phase formed at the interface became a growth nucleus and grew in a columnar form toward the steel.

Specimen charging that is associated with the electron bombardment on the sample is a practical hindrance to high-resolution transmission electron microscopy (HRTEM) analysis because it causes a severe loss of resolution in either diffraction or image data. Conductive thin film deposition on an insulating specimen has been proposed as an effective approach to the mitigation of the specimen charging; however, this method is generally not useful in HRTEM imaging of materials because the deposited film induces another artifact in the HRTEM image contrast. In this study, we propose practical methods to mitigate the specimen charging that takes place during the HRTEM of materials. For bulk-type specimens prepared by either an ion-thinning or focused-ion beam (FIB) process, a plasma cleaning treatment is significantly effective in eliminating the charging phenomenon. In the case of low-dimensional nanomaterials such as nanowires and nanoparticles, the plasma cleaning is not feasible; however, the charging effect can be effectively eliminated by adjusting the electron illumination condition. The proposed methods facilitate a decrease in the buildup of specimen charging, thereby enhancing the quality of high-resolution images significantly.

The post-weld heat treatment (PWHT) cracking susceptibility of a coarse grain heat-affected zone (CGHAZ) in SA213-T23 (2.25Cr-1.6W steel) that was used for boiler tubes employed in thermal power plants was investigated using a Gleeble thermal cycle simulator. The PWHT cracking susceptibility test was performed at 650 °C, 700 °C, and 750 °C, and it can be judged that the lower the reduction of the area, the more susceptible it is to PWHT cracking. The results of the test also showed higher cracking susceptibility at 650 °C and 700 °C, which mostly involved intergranular fracture, while at 750 °C, transgranular fracture was exhibited. Therefore, the PWHT cracking susceptibility is considered to be closely related to grain boundary. The microstructure of the simulated CGHAZ and PWHT at 650 °C, 700 °C, and 750 °C was observed after etching with nital and alkaline sodium picrate etchants. Alkaline sodium picrate-etched microstructures showed a white band at the grain boundary at 650 °C, 700 °C, and 750 °C, which did not appear in nital etching. An analysis of the white band using an electron probe micro-analyzer (EPMA), TEM, and nanoindentation revealed that it was intergranular ferrite depleted with C, W, and Cr as compared with that in the matrix. Based on these results, we investigated the mechanism of intergranular ferrite formation during PWHT and its effect on PWHT cracking susceptibility at 650 °C, 700 °C, and 750 °C.