Thermally induced atomic reconstruction into fully commensurate structures of transition metal dichalcogenide layers.

Twist angle between two-dimensional layers is a critical parameter that determines their interfacial properties, such as moiré excitons and interfacial ferro-electricity. To achieve better control over these properties for fundamental studies and various applications, considerable efforts have been made to manipulate twist angle. However, due to mechanical limitations and the inevitable formation of incommensurate regions, there remains a challenge in attaining perfect alignment of crystalline orientation. Here we report a thermally induced atomic reconstruction of randomly stacked transition metal dichalcogenide multilayers into fully commensurate heterostructures with zero twist angle by encapsulation annealing, regardless of twist angles of as-stacked samples and lattice mismatches. We also demonstrate the selective formation of R- and H-type fully commensurate phases with a seamless lateral junction using chemical vapour-deposited transition metal dichalcogenides. The resulting fully commensurate phases exhibit strong photoluminescence enhancement of the interlayer excitons, even at room temperature, due to their commensurate structure with aligned momentum coordinates. Our work not only demonstrates a way to fabricate zero-twisted, two-dimensional bilayers with R- and H-type configurations, but also provides a platform for studying their unexplored properties.

Chitosan-Based Multifunctional Platforms for Local Delivery of Therapeutics.

Chitosan has been widely used as a key biomaterial for the development of drug delivery systems intended to be administered via oral and parenteral routes. In particular, chitosan-based microparticles are the most frequently employed delivery system, along with specialized systems such as hydrogels, nanoparticles and thin films. Based on the progress made in chitosan-based drug delivery systems, the usefulness of chitosan has further expanded to anti-cancer chemoembolization, tissue engineering, and stem cell research. For instance, chitosan has been used to develop embolic materials designed to efficiently occlude the blood vessels by which the oxygen and nutrients are supplied. Indeed, it has been reported to be a promising embolic material. For better anti-cancer effect, embolic materials that can locally release anti-cancer drugs were proposed. In addition, a complex of radioactive materials and chitosan to be locally injected into the liver has been investigated as an efficient therapeutic tool for hepatocellular carcinoma. In line with this, a number of attempts have been explored to use chitosan-based carriers for the delivery of various agents, especially to the site of interest. Thus, in this work, studies where chitosan-based drug delivery systems have successfully been used for local delivery will be presented along with future perspectives.

Coherent scattering microscopy as an effective inspection tool for analyzing performance of phase shift mask.

The imaging performance of a half-tone phase shift mask (PSM) has been analyzed using coherent scattering microscopy (CSM), which allows analysis of the actinic characteristics of an extreme ultraviolet (EUV) mask such as its reflectivity, diffraction efficiency, and phase information. This paper presents the 1st experimental result showing the effect of 180° phase difference between the absorber and reflector in EUV mask. This reveals that a PSM offers a 46% improvement in 1st/0th diffraction efficiency and 14% improvement in image contrast when compared to a binary intensity mask (BIM). The horizontal-vertical critical dimension (H-V CD) bias is also reduced by 1.37 nm at 22 nm line and space (L/S) patterns. Since the performance of PSM can be evaluated without a wafer patterning process, CSM is expected to be a useful inspection tool for the development of novel EUV masks.

Association between serum mercury concentration and leukocyte differential count in children.

There have been a number of animal studies on the immunological effects of mercury. However, there is a lack of studies investigating the effects of mercury in children. We investigated the association between serum mercury and leukocyte differential count in Korean children. The relationship between mercury and leukocyte differential count (segment, lymphocyte, monocyte, basophil, and eosinophil counts) was analyzed by multivariate linear analysis adjusted for sex, BMI, parental smoking, lead, cadmium, and allergic sensitization in 311 children. Mercury showed a positive correlation with lymphocyte count (coefficient 113.8, 95% confidence interval 26.7-200.9). However, mercury was not associated with total leukocyte, segment, monocyte, basophil, or eosinophil count. Mercury was associated with the increased of lymphocyte count in Korean children. Further studies will be required to ascertain the clinical significance of this association.

Partial purification and properties of a cysteine protease from citrus red mite Panonychus citri.

Several studies have reported that the citrus red mites Panonychus citri were an important allergen of citrus-cultivating farmers in Jeju Island. The aim of the present study was to purify and assess properties of a cysteine protease from the mites acting as a potentially pathogenic factor to citrus-cultivating farmers. A cysteine protease was purified using column chromatography of Mono Q anion exchanger and Superdex 200 HR gel filtration. It was estimated to be 46 kDa by gel filtration column chromatography and consisted of 2 polypeptides, at least. Cysteine protease inhibitors, such as trans poxy-succinyl-L-leucyl-amido (4-guanidino) butane (E-64) and iodoacetic acid (IAA) totally inhibited the enzyme activities, whereas serine or metalloprotease inhibitors did not affect the activities. In addition, the purified enzyme degraded human IgG, collagen, and fibronectin, but not egg albumin. From these results, the cysteine protease of the mites might be involved in the pathogenesis such as tissue destruction and penetration instead of nutrient digestion.

Atom-by-atom imaging of moiré transformations in 2D transition metal dichalcogenides.

Understanding the atomic-scale mechanisms that govern the structure of interfaces is critical across materials systems but particularly so for two-dimensional (2D) moiré materials. Here, we image, atom-by-atom, the thermally induced structural evolution of twisted bilayer transition metal dichalcogenides using in situ transmission electron microscopy. We observe low-temperature, local conversion of moiré superlattice into nanoscale aligned domains. Unexpectedly, this process occurs by nucleating a new grain within one monolayer, whose crystal orientation is templated by the other. The aligned domains grow through collective rotation of moiré supercells and hopping of 5|7 defect pairs at moiré boundaries. This provides mechanistic insight into the atomic-scale interactions controlling moiré structures and illustrates the potential to pattern interfacial structure and properties of 2D materials at the nanoscale.

Optical grade transformation of monolayer transition metal dichalcogenides via encapsulation annealing.

Monolayer transition metal dichalcogenides (TMDs) have emerged as highly promising candidates for optoelectronic applications due to their direct band gap and strong light-matter interactions. However, exfoliated TMDs have demonstrated optical characteristics that fall short of expectations, primarily because of significant defects and associated doping in the synthesized TMD crystals. Here, we report the improvement of optical properties in monolayer TMDs of MoS2, MoSe2, WS2, and WSe2, by hBN-encapsulation annealing. Monolayer WSe2 showed 2000% enhanced photoluminescence quantum yield (PLQY) and 1000% increased lifetime after encapsulation annealing at 1000 °C, which are attributed to dominant radiative recombination of excitons through dedoping of monolayer TMDs. Furthermore, after encapsulation annealing, the transport characteristics of monolayer WS2 changed from n-type to ambipolar, along with an enhanced hole transport, which also support dedoping of annealed TMDs. This work provides an innovative approach to elevate the optical grade of monolayer TMDs, enabling the fabrication of high-performance optoelectronic devices.

Nucleation and Growth of Monolayer MoS2 at Multisteps of MoO2 Crystals by Sulfurization.

Two-dimensional (2D) materials and their heterostructures are promising for next-generation optoelectronics, spintronics, valleytronics, and electronics. Despite recent progress in various growth studies of 2D materials, mechanical exfoliation of flakes is still the most common method to obtain high-quality 2D materials because precisely controlling material growth and synthesizing a single domain during the growth process of 2D materials, for the desired shape and quality, is challenging. Here, we report the nucleation and growth behaviors of monolayer MoS2 by sulfurizing a faceted monoclinic MoO2 crystal. The MoS2 layers nucleated at the thickness steps of the MoO2 crystal and grew epitaxially with crystalline correlation to the MoO2 surface. The epitaxially grown MoS2 layer expands outwardly on the SiO2 substrate, resulting in a monolayer single-crystal film, despite multiple nucleations of MoS2 layers on the MoO2 surface owing to several thickness steps. Although the photoluminescence of MoS2 is quenched owing to efficient charge transfer between MoS2 and metallic MoO2, the MoS2 stretched out to the SiO2 substrate shows a high carrier mobility of (15 cm2 V-1 s-1), indicating that a high-quality monolayer MoS2 film can be grown using the MoO2 crystal as a seed and precursor. Our work shows a method to grow high-quality MoS2 using a faceted MoO2 crystal and provides a deeper understanding of the nucleation and growth of 2D materials on a step-like surface.

PLGA Microspheres with Alginate-Coated Large Pores for the Formulation of an Injectable Depot of Donepezil Hydrochloride.

As the main symptom of Alzheimer's disease-related dementia is memory loss, patient compliance for donepezil hydrochloride (donepezil), administered as once-daily oral formulations, is poor. Thus, we aimed to design poly(lactic-co-glycolic acid) (PLGA) microspheres (MS) with alginate-coated large pores as an injectable depot of donepezil exhibiting sustained release over 2-3 weeks. The PLGA MS with large pores could provide large space for loading drugs with high loading capacity, and thereby sufficient amounts of drugs were considered to be delivered with minimal use of PLGA MS being injected. However, initial burst release of donepezil from the porous PLGA MS was observed. To reduce this initial burst release, the surface pores were closed with calcium alginate coating using a spray-ionotropic gelation method. The final pore-closed PLGA MS showed in vitro sustained release for approximately 3 weeks, and the initial burst release was remarkably decreased by the calcium alginate coating. In the prediction of plasma drug concentration profiles using convolution method, the mean residence time of the pore-closed PLGA MS was 2.7-fold longer than that of the porous PLGA MS. Therefore, our results reveal that our pore-closed PLGA MS formulation is a promising candidate for the treatment of dementia with high patient compliance.

Caregiver burden among caregivers of Koreans with dementia.

BACKGROUND: Most studies on caregiver burden have been conducted in Western countries, while few studies on the correlates of caregiver burden have been performed in Korea. OBJECTIVE: To suggest better policies for the care of dementia patients by using a nationwide database to identify factors that affect caregiver burden in Korea. METHODS: The database of the Korean National Health Insurance (KNHI) and National Medical Aid (NMA) programs, which covers all Koreans, was used. A sample of 609 dementia patients and their caregivers was selected from a total of 85,281 dementia patients in 2004 and interviewed to evaluate the total cost of care and caregiver burden. Stepwise multiple linear regression analysis was then performed to identify significant independent predictors of caregiver burden. RESULTS: Among caregiver-related factors, caregiver burden was higher in those who were female, had a history of home care during the previous year, and had less education. Among patient-related factors, poor ADL/IADL function was significant. The most interesting result was that subjective sense of socioeconomic status (good/fair/poor) was a stronger predictor of caregiver outcome than actual economic costs. CONCLUSION: The results of this study suggest that interventions to assist patients with dementia should focus on female caregivers, especially those considered likely to be suffering from an economic burden. Interventions should also aim to improve the ADL and IADL capacities of patients.

Effects of obesity and obesity-induced stress on depressive symptoms in Korean elementary school children.

BACKGROUND: Obesity is becoming prevalent in Korean children. Because body image is becoming increasingly important, it is likely that obesity-induced stress has a significant effect on childhood depression. AIMS: To examine the correlation between obesity-induced stress and depressive symptoms in Korean elementary school students. METHODS: The study participants were 2,305 elementary school children and their parents in the districts of Jeju-si, Seogwipo-si, Namjeju-gun and Bukjeju-gun on Jeju Island, Korea, who completed questionnaires involving demographic information, an obesity-induced stress scale and the Korean form of Kovacs' Children's Depression Inventory (CDI) from September to December 2006. RESULTS: After controlling for significant independent variables that are wellknown correlates of depressive symptoms in children (e.g. age, gender, residence, family monthly income, obesity status of both parents, family history of chronic illness, and time spent with mother), obesity-induced stress had an odds ratio of 1.128 (95% CI 1.111-1.146). CONCLUSIONS: Reducing the prevalence of depressive symptoms in elementary school children in Jeju Island will require special attention, particularly the development of coping strategies to resolve obesity-induced stress in various areas including school, family and society.

Chronological changes in rhinitis symptoms present in school-aged children with allergic sensitization.

INTRODUCTION: It is difficult to accurately predict the natural course of allergic rhinitis (AR), because it is affected by a wide variety of environmental influences, as well as genetic predisposition. Considering the high prevalence of allergic rhinitis in children and adolescents, caregivers should be given appropriate information regarding the disease course. This study aimed to understand the prognosis of allergic rhinitis by examining the relationship between allergic sensitization and rhinitis symptoms during this developmental period. METHODS: This cross-sectional study included 1069 children aged 9-16 years from the Korean International Study of Asthma and Allergies in Childhood Survey database who had completed health questionnaires, and for whom skin prick test results were available. Data were collected during May 2016. The distribution of sensitization and allergic symptoms was compared by age groups (elementary, middle, and high school). Data were analyzed using linear-by-linear analysis. RESULTS: Sensitization to at least one tested allergen differed by age (59.2%, 58.3%, 68.2%, in elementary, middle, and high school students, respectively; p = 0.025), and seasonal allergen sensitization (35.0%, 37.1%, 53.9%, respectively) increased with age (p < 0.001). Conversely, the proportion of rhinitis symptoms among sensitized children decreased as age increased (58.80%, 52.90%, 49.70%, respectively; p = 0.047). However, the rate of non-allergic rhinitis was age-independent. CONCLUSION: With increasing age during childhood and adolescence, symptomatic allergic rhinitis decreases; thus, subclinical allergic rhinitis increases. This suggests that the symptoms of later-sensitized children are less clearly manifested, or that the symptoms reduce as previously sensitized children mature. This should be clarified further in a longitudinal study.

Seeking better topical delivery technologies of moisturizing agents for enhanced skin moisturization.

INTRODUCTION: An adequate hydration level is essential to maintain epidermal barrier functions and normal physiological activities of skin tissues. Diverse moisturizing agents and pharmaceutical formulations for dermal deliveries have thus extensively been investigated. This review comprehensively discusses scientific outcomes of moisturizing agents and pharmaceutical vehicles for skin moisturization, thereby providing insight into designing innovative pharmaceutical formulations for effective skin moisturization. AREAS COVERED: We discussed the functions of various moisturizing agents ranging from conventional creams to novel moisturizers which has recently been explored. In addition, novel pharmaceutical formulations for efficient dermal delivery of the moisturizers, in particular, nanocarriers, were discussed along with their uses in commercial products. EXPERT OPINION: Although various moisturizing agents have demonstrated their promising effects, exploitation of pharmaceutical formulations for their dermal delivery have been limited to few commonly used moisturizing agents. Thus, combinatorial investigation of novel moisturizers and pharmaceutical vehicles should be further conducted. As a new concept for improving skin moisturization, skin regeneration technologies using therapeutic cells have recently shown great promise for skin moisturization, but major challenges remain, such as efficient delivery and prolonged survival of such cells. Thus, novel approaches for improving skin moisturization require continuous efforts of pharmaceutical scientists to address the remaining problems.

Prevalence of depression and correlates of depressive symptoms for residents in the urban part of Jeju Island, Korea.

AIMS: This study examined the prevalence of depression and depressive symptoms, and the correlates of depressive symptoms, and proposes some methods for reducing risk of depression in residents of the urban part of Jeju Island in Korea. METHODS: In all, 1050 residents were selected using multiphasic cluster sampling to represent each district. Of the 981 respondents, 413 were men and 568 were women. The Center for Epidemiologic Studies Depression Scale (CES-D) was used to evaluate depression (CES-D score over 25) and depressive symptoms (CES-D score over 21). Multiple logistic regression analysis was performed for comparisons. RESULTS: The prevalence of depression in males and females was comparable, at 9.47 and 11.36%, respectively. The prevalence of depressive symptoms in men was 15.01%, while in women the level rose to 18.37%. Those with high self-assessed level of stress scores were significantly more likely to have depressive symptoms than those with low self-assessed level of stress scores (odds ratio (OR) = 5.73 (95% confidence interval (95% CI), 1.29-25.36)). Residents at high risk of problem drinking (CAGE score over 3) were significantly more likely to have depressive symptoms than those with a CAGE score under 1 (OR = 3.43 95% CI, 1.77-6.66). Respondents who slept poorly had more depressive symptoms than respondents who slept well (OR = 2.11 95% CI, 1.37-3.23). Females were significantly more likely to have more depressive symptoms than males (OR = 1.70 95% CI, 1.08-2.68). CONCLUSIONS: The prevalence of depression and depressive symptoms in urban Jeju Island is similar to that in a nation-wide sample. By providing intensive mental health services to those who have high stress levels, problem drinking, and poor health behavior, early detection of depressive symptoms in the community will be important for improving general health status.

[A study on regional differentials in death caused by suicide in South Korea].

PURPOSE: The purpose of this study was to compare suicide mortality by region in South Korea. METHOD: Suicide mortality differentials were calculated for several mortality indicators by geographical regions from raw data of the cause of death from KNSO. RESULTS: The results are as follows; the Crude suicide death rate was 22.63 per 100,000. The highest was in Kangwon showing 37.84% whereas, Chungnam, and Jeonbuk followed after. Suicide was 4.4% of all causes of death, but Inchon and Ulsan showed a higher proportion. The male suicide death rate was 31.12 per 100,000 and females 14.09. The ratio of gender suicide mortality was 2.21, per 100,000 and was the highest in Jeju. For age-specific suicide death rates, the rate increased as age advanced, showing 2.33 per 100,000 in 0-19 years, 18.68 in 20-39, 30.48 in 40-59,63.33 in 60 years and over. In Ulsan, Kangwon, and Inchon, age-specific suicide death rates of the 60 and over age group were higher than other regions, Daegu, Busan, and Kangwon showed a higher age-specific suicide mortality of the 40-59 age group, and Kangwon, Jeonnam, and Chungnam had a higher age-specific suicide mortality of the 20-39 age group. CONCLUSIONS: Suicide mortality differed by region. These results can be used for a regional health care plan and planning for suicide prevention by regions.

The association between the parenting stress of the mother and the incidence of allergic rhinitis in their children.

OBJECTIVES: The prevalence of allergic rhinitis and the social burden related to the management of allergic rhinitis have persistently increased. There are many studies investigating the association between the allergic diseases of children and the stress of their parent. However, the relationship between parenting stress and the incidence of allergic rhinitis among children requires further investigation. We aimed to investigate the significance of parenting stress for mothers with children treated for allergic rhinitis. METHODS: The mothers of 250 children in the second and third grade of elementary school were involved in this study. The Parenting Stress Index-Short Form (PSI-SF) was used to measure parenting stress. Additionally, the monthly household income, treatment history for allergic diseases (atopic dermatitis, asthma, and allergic rhinitis) during the past 12 months, and maternal education status were investigated using the questionnaire. RESULTS: Parenting stress index score was significantly higher among the mothers of children treated for allergic rhinitis (76.41 ± 9.35) compared with the parents of children without treatment history for allergic rhinitis (70.06 ± 13.74). Nonetheless, there were no significant differences between the cases of children with atopic dermatitis and those with asthma. We analyzed the association between allergic rhinitis and parenting stress adjusted for the monthly household income, and maternal education status, and showed that a treatment history of allergic rhinitis was significantly associated with parenting stress (coefficient 7.477, 95% interval 1.703-13.252; p = 0.011). CONCLUSION: Treatment of the children for allergic rhinitis significantly affects the parenting stress of their mother. We recommend that mothers with children with allergic rhinitis should receive appropriate counseling about parenting stress.

Serum periostin level is not associated with allergic rhinitis or allergic sensitization in Korean children.

OBJECTIVES: Periostin is a matricellular protein, synthesized in the airway epithelium and induced by interleukin (IL)-4 and IL-13. The significance of periostin as a biomarker of T helper type 2 cell (Th2)-induced airway inflammation, and as a measure of the response to Th2-targeted therapy, has recently been highlighted. We explored the relationship between serum periostin and allergic rhinitis in Korean children. METHODS: Data for fifth and sixth grade children from six randomly selected elementary schools located in Jeju and Seogwipo City, Korea, were investigated. Serum periostin levels were determined by enzyme-linked immunosorbent assay. Sex, school grade, body mass index, and presence of allergic nasal symptoms were obtained via a self-reported survey and skin prick testing was performed. RESULTS: There were no significant differences between groups, when stratification was applied according to sex, grade, presence of atopy, and presence of allergic nasal symptoms. Sex and body mass index were significantly associated with serum periostin levels in multivariate linear regression analysis. However, allergic rhinitis was not associated with serum periostin levels. CONCLUSION: Allergic rhinitis or allergic sensitization in Korean children did not influence serum periostin levels. Further studies are required to investigate the significance of serum periostin levels in pediatric allergic rhinitis.

Marine polysaccharides: therapeutic efficacy and biomedical applications.

The ocean contains numerous marine organisms, including algae, animals, and plants, from which diverse marine polysaccharides with useful physicochemical and biological properties can be extracted. In particular, fucoidan, carrageenan, alginate, and chitosan have been extensively investigated in pharmaceutical and biomedical fields owing to their desirable characteristics, such as biocompatibility, biodegradability, and bioactivity. Various therapeutic efficacies of marine polysaccharides have been elucidated, including the inhibition of cancer, inflammation, and viral infection. The therapeutic activities of these polysaccharides have been demonstrated in various settings, from in vitro laboratory-scale experiments to clinical trials. In addition, marine polysaccharides have been exploited for tissue engineering, the immobilization of biomolecules, and stent coating. Their ability to detect and respond to external stimuli, such as pH, temperature, and electric fields, has enabled their use in the design of novel drug delivery systems. Thus, along with the promising characteristics of marine polysaccharides, this review will comprehensively detail their various therapeutic, biomedical, and miscellaneous applications.

Absorption Study of Genistein Using Solid Lipid Microparticles and Nanoparticles: Control of Oral Bioavailability by Particle Sizes.

In this study, the effect of particle size of genistein-loaded solid lipid particulate systems on drug dissolution behavior and oral bioavailability was investigated. Genistein-loaded solid lipid microparticles and nanoparticles were prepared with glyceryl palmitostearate. Except for the particle size, other properties of genistein-loaded solid lipid microparticles and nanoparticles such as particle composition and drug loading efficiency and amount were similarly controlled to mainly evaluate the effect of different particle sizes of the solid lipid particulate systems on drug dissolution behavior and oral bioavailability. The results showed that genistein-loaded solid lipid microparticles and nanoparticles exhibited a considerably increased drug dissolution rate compared to that of genistein bulk powder and suspension. The microparticles gradually released genistein as a function of time while the nanoparticles exhibited a biphasic drug release pattern, showing an initial burst drug release, followed by a sustained release. The oral bioavailability of genistein loaded in solid lipid microparticles and nanoparticles in rats was also significantly enhanced compared to that in bulk powders and the suspension. However, the bioavailability from the microparticles increased more than that from the nanoparticles mainly because the rapid drug dissolution rate and rapid absorption of genistein because of the large surface area of the genistein-solid lipid nanoparticles cleared the drug to a greater extent than the genistein-solid lipid microparticles did. Therefore, the findings of this study suggest that controlling the particle size of solid-lipid particulate systems at a micro-scale would be a promising strategy to increase the oral bioavailability of genistein.

Moisturizing effect of serine-loaded solid lipid nanoparticles and polysaccharide-rich extract of root Phragmites communis incorporated in hydrogel bases.

This study evaluated the moisturizing effect of serine-loaded solid lipid nanoparticles (serine-SLN) and polysaccharide-rich reed (Phragmites communis) root extract (RRE) incorporated in hydrogel bases. The hydrogels with serine-SLN and/or RRE were carefully applied on the volar forearm of human volunteers. Their moisturizing efficacy was evaluated by monitoring conductance values using a skin surface hygrometer. The values of the area under the normalized conductance-time curve (AUCC) were developed and compared as a parameter for the water holding capacity of the skin. Hydrogels with serine-SLN did not significantly moisturize the skin, while hydrogel containing 0.25% RRE produced a significant increase in the moisture content of the skin. However, adding more than 0.25% of RRE into the hydrogel base decreased the moisturizing effect due to the marked reduction of viscosity. Significantly enhanced moisturizing effect was observed with the hydrogel containing 0.25% RRE and 3% serine-SLN, with AUCC increased 2.21 times compared to than blank hydrogel. The results imply that effective delivery of serine into the skin is possible using lipid-based nanocarriers and RRE, which could be a promising strategy to moisturize the skin effectively.