Improvement of a block co-polymer (PS-b-PMMA)-masked silicon etch profile using a neutral beam.

Bottom-up block copolymer (BCP) lithography mediated by self-assembly of polystyrene (PS)/poly-methyl methacrylate (PMMA) is widely used as an alternative patterning method for various deep nanoscale devices, such as optical devices and transistors, replacing conventional top-down photolithography. However, the nanoscale BCP mask features formed on the substrates after direct self-assembly of BCP tend to be easily damaged during exposure to the following plasma processing. In this study, silicon masked with a nanoscale BCP mask (PS) was etched by irradiating with a Cl2/Ar neutral beam in addition to a Cl2/Ar ion beam, and the effect of a Cl2/Ar neutral beam instead of a Cl2/Ar ion beam on damage to the PS mask and the silicon etch characteristics of nanodevices was investigated. The results show that the use of a neutral beam instead of an ion beam decreased degradation of the BCP mask during etching; therefore, a more anisotropic silicon etch profile in addition to improved etch selectivity of silicon compared to the BCP mask was observed. Moreover, by using the neutral beam, the sidewall roughness and sidewall angle also improved due to the decreased surface charge and reduced damage to the nanoscale PS mask resulting from use of a highly directional radical beam instead of a conventional ion-based beam.

Seropositivity among Korean Young Adults Approximately 2 Years after a Single-Dose Vaccination against Hepatitis A Virus.

We previously observed 80.7% seropositivity and a significant interaction between gender and hepatitis A virus (HAV) vaccine type (Havrix vs. Epaxal) on the seropositivity approximately 11 months after single-dose HAV vaccinations in Korean young adults. Our objective was to evaluate seropositivity approximately 2 years after a single-dose HAV vaccination and the influence of demographic characteristics on seropositivity, including the interaction between gender and vaccine type. Seronegative medical school students were randomly vaccinated with Havrix or Epaxal. Based on a total serum anti-HAV antibody titer cutoff of 20 IU/mL, 338 participants (76.0%) of the 445 vaccinees were seropositive 20-25 months after a single-dose HAV vaccination. The seropositive rates were similar after vaccination with Havrix (77.0%) and Epaxal (74.9%). Univariate analysis indicated that female (p = 0.052) and less obese (p < 0.001) participants had a higher seropositive rate, whereas other characteristics such as age, alcohol use, smoking history, vaccine type, and follow-up duration were not associated with seropositivity. Multivariate analysis indicated that women (p = 0.026) and participants with moderate alcohol use (p < 0.001) showed significantly higher seropositive rates than men and participants with no or low alcohol use, respectively. The seropositive rates after vaccination with Havrix and Epaxal were 70.9% and 67.5% in men and 87.7% and 91.3% in women, respectively (p for interaction = 0.304). Compared with the seropositive rate approximately 11 months after vaccination, the seropositive rate decreased substantially only in men in the Havrix group (11.0% points), and consequently, the interaction between gender and vaccine type disappeared while seropositivity remained high (87.7% and 91.3% in Havrix and Epaxal groups, respectively) among women approximately 2 years after vaccination. Further studies are needed to assess whether the seropositive rate would be maintained in all groups more than 2 years after a single-dose HAV vaccination.

The immunogenicity of a single dose of hepatitis A virus vaccines (Havrix® and Epaxal®) in Korean young adults.

PURPOSE: Assessing the immunogenicity of a single dose of hepatitis A virus (HAV) vaccines is important because some people receive only a single dose. However, previous studies have shown variable results and have not examined the effects of demographic characteristics other than gender. This study was performed to examine the immunogenicity of a single dose of HAV vaccine according to the vaccine type and demographic characteristics in young adults. MATERIALS AND METHODS: Seronegative medical school students were randomly allocated to receive either Havrix or Epaxal. RESULTS: After approximately 11 months, the seroconversion rate in 451 participants was 80.7%. In men, the Havrix group showed a significantly higher seroconversion rate (81.9%) than the Epaxal group (69.2%), whereas both vaccine groups showed similarly high immunogenicity in women (Havrix: 90.1%, Epaxal: 92.9%; P for interaction=0.062). According to the results of a multivariate analysis, Epaxal showed significantly lower immunogenicity than Havrix only in men. Age, obesity, drinking, smoking, and follow-up time did not significantly affect seroconversion in either gender. CONCLUSION: The seroconversion rate of single-dose HAV vaccines was low in men, particularly in those who received Epaxal. Our results suggest that gender effects should be considered when comparing the immunogenicity of different HAV vaccines.

Acute health effects of accidental chlorine gas exposure.

OBJECTIVES: This study was conducted to report the course of an accidental release of chlorine gas that occurred in a factory in Gumi-si, South Korea, on March 5, 2013. We describe the analysis results of 2 patients hospitalized because of chlorine-induced acute health problems, as well as the clinical features of 209 non-hospitalized patients. METHODS: We analyzed the medical records of the 2 hospitalized patients admitted to the hospital, as well as the medical records and self-report questionnaires of 209 non-hospitalized patients completed during outpatient treatment. RESULTS: Immediately after the exposure, the 2 hospitalized patients developed acute asthma-like symptoms such as cough and dyspnea, and showed restrictive and combined pattern ventilatory defects on the pulmonary function test. The case 1 showed asthma-like symptoms over six months and diurnal variability in peak expiratory flow rate was 56.7%. In case 2, his FEV1 after treatment (93%) increased by 25% compared to initial FEV1 (68%). Both cases were diagnosed as chlorine-induced reactive airways dysfunction syndrome (RADS) on the basis of these clinical features. The most frequent chief complaints of the 209 non-hospitalized patients were headache (22.7%), followed by eye irritation (18.2%), nausea (11.2%), and sore throat (10.8%), with asymptomatic patients accounting for 36.5%. The multiple-response analysis of individual symptom revealed headache (42.4%) to be the most frequent symptom, followed by eye irritation (30.5%), sore throat (30.0%), cough (29.6%), nausea (27.6%), and dizziness (27.3%). CONCLUSIONS: The 2 patients hospitalized after exposure to chlorine gas at the leakage site showed a clinical course corresponding to RADS. All of the 209 non-hospitalized patients only complained of symptoms of the upper airways and mucous membrane irritation.

Factors affecting the burden on caregivers of stroke survivors in South Korea.

OBJECTIVE: To elucidate the factors related to the caregiver burden in stroke survivors in Seoul, Korea. DESIGN: Cross-sectional study. SETTING: Outpatient clinic of a university hospital in Korea. PARTICIPANTS: We randomly selected 340 stroke patients and evaluated them for 3 years poststroke. Among them, 147 caregivers and patients were finally interviewed. INTERVENTIONS: Patients' demographic data, neurologic symptoms, depression, emotional incontinence, and Modified Rankin Scale (MRS) score were assessed. In addition, primary caregivers' demographic data, hours of care per day, relationship with the patients, health status, anxiety and depression, and the presence of alternative caregivers were assessed. MAIN OUTCOME MEASURES: Caregiver burden was evaluated with the Sense of Competence Questionnaire, which has 3 subdomains with a total of 27 items. RESULTS: Caregiver burden score was high as compared with reports from Western society. Patient factors related to the burden scores were being unemployed ( P <.05), the presence of diabetes mellitus ( P <.05), aphasia ( P <.01), dysarthria ( P <.05), dysphagia ( P <.01), cognitive dysfunction ( P <.01), severe MRS score ( P <.01), emotional incontinence ( P <.05), and depression ( P <.01). Caregiver factors related to high burden scores were being female ( P <.05), unemployment ( P <.01), being daughters-in-law ( P <.01), anxiety ( P <.01), depression ( P <.01), and long caregiving hours ( P <.05). On multivariate analysis, the most significant predictor for overall caregiver burden was caregiver anxiety followed by patient MRS score and caregivers being daughters-in-law. Caregiver depression, current employment status, and patient depression were also factors related to their burden. CONCLUSIONS: Caregiver anxiety, patient physical deficits, and caregivers being daughter-in-law are important factors related to the caregiver burden in our population. Strategies to reduce caregiver burden should be developed based on understanding of these factors.