Hydrogen-induced Sulfur Vacancies on the MoS2 Basal Plane Studied by Ambient Pressure XPS and DFT Calculations.

Sulfur vacancy on an MoS2 basal plane plays a crucial role in device performance and catalytic activity; thus, an understanding of the electronic states of sulfur vacancies is still an important issue. We investigate the electronic states on an MoS2 basal plane by ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and density functional theory calculations while heating the system in hydrogen. The AP-XPS results show a decrease in the intensity ratio of S 2p to Mo 3d, indicating that sulfur vacancies are formed. Furthermore, low-energy components are observed in Mo 3d and S 2p spectra. To understand the changes in the electronic states induced by sulfur vacancy formation at the atomic scale, we calculate the core-level binding energies for the model vacancy surfaces. The calculated shifts for Mo 3d and S 2p with the formation of sulfur vacancy are consistent with the experimentally observed binding energy shifts. Mulliken charge analysis indicates that this is caused by an increase in the electronic density associated with the Mo and S atoms around the sulfur vacancy as compared to the pristine surface. The present investigation provides a guideline for sulfur vacancy engineering.

Elucidation of the atomic-scale processes of dissociative adsorption and spillover of hydrogen on the single atom alloy catalyst Pd/Cu(111).

Hydrogen spillover is a crucial process in the selective hydrogenation reactions on Pd/Cu single atom alloy catalysts. In this study, we report the atomic-scale perspective of these processes on the single atom alloy catalyst Pd/Cu(111) based on the experimental and theoretical results, including infrared reflection absorption spectroscopy (IRAS), temperature programmed desorption (TPD), high-resolution X-ray photoelectron spectroscopy (HR-XPS), and density functional theory (DFT) calculations for core-level excitation. The hydrogen spillover onto Cu(111) was successfully observed in real time using time-resolved IRAS measurements at 80 K. The chemical shifts of Pd 3d5/2 indicate that H2 is dissociated and adsorbed at the Pd site. In addition, a "two-step" chemical shift of the Pd 3d5/2 binding energy was observed, indicating two types of hydrogen adsorption states at the Pd site. The proposed mechanism of the hydrogen dissociation and spillover processes is as follows: (i) a hydrogen molecule is dissociated at a Pd site, and the hydrogen atoms are adsorbed on the Pd site; (ii) the number of hydrogen atoms on the Pd site increases up to three; and (iii) the hydrogen atoms will spill over onto the Cu surface.

Evaporation-Crystallization Method to Promote Coalescence-Induced Jumping on Superhydrophobic Surfaces.

Biphilic surfaces exhibit outstanding condensation efficiency compared to surfaces having homogeneous wettability. Especially, hydrophilic patterns on a superhydrophobic substrate significantly promote the coalescence-induced jumping of condensed droplets by increasing the nucleation rate of condensation, thus enhancing the condensation efficiency drastically. However, the application of biphilic surfaces in practical industries remains challenging because controlling the size and spacing of the hydrophilic spots on large and complex surfaces is difficult. In this study, we have achieved heterogeneous wettability using the evaporation-crystallization method, which can be applied to various surfaces as required by industries. The crystals generated using the evaporation-crystallization process drastically increased the number density of condensed droplets on a superhydrophobic surface (SHS), so the developed biphilic surface increased the cumulative volume of jumping droplets by up to 63% compared to that on a conventional superhydrophobic surface. Furthermore, the condensation dynamics on the biphilic surface were analyzed with the classical nucleation theory and the Ohnesorge number. The analysis results indicated that the generated hydrophilic crystals can reduce the nucleation energy barrier and decrease the available excessive surface energy of coalesced droplets on the biphilic surface; this implies that the size distribution of the crystals determines the condensation dynamics. In sum, this study not only introduced an effective surface tailoring approach for enhancing condensation but also provided insights into the design of optimum biphilic surfaces for various conditions, creating new opportunities to widen the applicability of biphilic surfaces in practical industries that exploit condensation.

A Retrospective Mid- and Long-term Follow-up Study on the Changes in Hematologic Parameters in the Highly Exposed Residents of the Hebei Spirit Oil Spill in Taean, South Korea.

OBJECTIVES: This study aimed to analyze changes in hematologic parameters in the residents of the areas highly contaminated by the Hebei Spirit Oil Spill in 2007 and those who participated in the clean-up activities. METHODS: According to demographic characteristics, health status and behavior, and level of exposure to oil, we compared the hematologic results in 2009 and 2012 among 701 residents. The hematologic parameters were composed of white blood cell (WBC) count, and levels of hemoglobin, hematocrit (Hct), aspartate aminotransferase (AST), alanine aminotransferase (ALT), glucose, glycosylated hemoglobin (HbA1c), blood urea nitrogen (BUN), creatinine (Cr), total cholesterol (T-chol), high-density lipoprotein (HDL), and triglyceride (TG). RESULTS: Paired t-test revealed that the WBC count and levels of Hct, AST, ALT, glucose, and HbA1c significantly increased, whereas the BUN, Cr, HDL, and TG levels significantly decreased. Multiple linear regression modelling showed a relationship between the level of exposure to oil and temporal changes in Hct, glucose, HbA1c, and BUN levels. CONCLUSION: Our results suggest a relationship between level of exposure to oil and changes in hematologic parameters over 3 years. Further studies should be conducted to determine the impact of oil spill on health such as the occurrence of diseases.

A new method for estimating the prevalence of clonorchiasis in Korea: A proposal to replace arbitrary riverside sampling.

South Korea presently uses an arbitrary sampling method to monitor the prevalence of Clonorchis sinensis infection in the endemic areas of the country. However, the present method is not standardized and focuses primarily on individuals who reside nearest to the mainstream river. We propose a new sampling method that combines cluster sampling with proportionate quota sampling to ensure that the entire endemic area is accurately represented. We tested the new method in Okcheon-gun, South Korea, and determined that the C sinensis infection prevalence (8.9%) in 2013 was higher than that (6.9%) estimated in 2012 when the arbitrary method was used. Additionally, no difference was observed in the prevalence based on the distance from the riverside areas, including branches and creeks, between the areas <1 and >1 km away from the riversides. Therefore, health authorities should place equal emphasis on all regions within the endemic areas. Based on the findings, we recommend the following: the clonorchiasis prevalence rate must be measured using probability sampling, (clear guidelines on survey coverage should be provided to include the riverside areas and all areas nearby branch streams, and regional cohorts should be created for continuous monitoring of prevalence rates across the region.

Psychological Vulnerability of Residents of Communities Affected by the Hebei Spirit Oil Spill.

OBJECTIVE: Psychological health is an important issue after disasters. This study aimed to investigate the prevalence of psychological symptoms among 993 residents of Taean District in South Korea after the Hebei Spirit oil spill and to examine determinants of vulnerability in residents' psychological symptoms. METHODS: Symptoms of post-traumatic stress (PTS), depression, suicidal ideation, and anxiety were assessed by questionnaires, and the responses were analyzed by using the survey analysis considering the sampling frame. RESULTS: Among the study subjects, the symptom prevalences of PTS, depression, suicidal ideation, and anxiety were 19.5%, 22.0%, 2.3%, and 4.2%, respectively, and symptoms were higher in people who were female, were older, were less educated, and had lower family income. People with fishery or related occupations compared to those with unrelated livelihoods and people residing in the vicinity of the oil band in the contaminated coastline showed additively increased symptom risks of PTS. Risk of suicidal ideation was predominantly increased in people with fishery or related occupations compared with those with unrelated livelihoods. CONCLUSIONS: Social supports, including compensation for income loss and community mental health programs, and longer follow-up studies are needed for residents in the communities affected by the Hebei Spirit oil spill.

Oxidative stress biomarkers in long-term participants in clean-up work after the Hebei Spirit oil spill.

BACKGROUND: The oil tanker Hebei Spirit spilled 12,547kL of oil near the western coastline of Korea on December 7, 2007. We aimed to investigate the relationship between oil spill exposure and oxidative stress in residents living near the affected area. METHODS: Study subjects were 671 residents who participated in a health examination between February and September 2009. As surrogates for oil spill exposure, we used the total duration of clean-up work and levels of urinary metabolites of polycyclic aromatic hydrocarbons (PAHs), 1-hydroxypyrene (1-OHP) and 2-naphthol (2-NAPH). Oxidative stress was measured using urinary levels of malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG), indicators of lipid peroxidation and oxidative DNA damage, respectively. RESULTS: Levels of oxidative stress biomarkers were significantly increased with longer involvement in clean-up work over one year after the Hebei Spirit oil spill (MDA, p-trend<0.0001; 8-OHdG, p-trend<0.0001). As more time elapsed since the last involvement in clean-up, the total duration of clean-up work participation and levels of PAH metabolites (1-OHP and 2-NAPH), as well as levels of the oxidative stress biomarkers (MDA and 8-OHdG) decreased further. The level of 1-OHP had a significant positive correlation with the total duration of clean-up work involvement, with a higher level found in those who participated in clean-up for >100 days. Increasing levels of 1-OHP were significantly associated with increased MDA and 8-OHdG after adjusting for covariates, while the strength of association weakened as time passed since the last participation in clean-up work. The significance of the association was maintained for up to 12 months after the last clean-up work. CONCLUSIONS: The results suggested that oil exposure from prolonged clean-up activity likely induced oxidative stress in clean-up participants up to at least one year after the last exposure.

Respiratory effects of the hebei spirit oil spill on children in taean, Korea.

PURPOSE: The oil spill from the Heibei Spirit in December 2007 contaminated the Yellow Coast of South Korea. We evaluated the respiratory effects of that spill on children who lived along the Yellow Coast. METHODS: Of 662 children living in the area exposed to the oil spill, 436 (65.9%) were enrolled as subjects. All subjects completed a modified International Study of Asthma and Allergies in Childhood questionnaire. A health examination, including a skin prick test, pulmonary function test, and methacholine bronchial provocation test (MBPT), was administered. The children were assigned to two groups: those who lived close to the oil spill area and those who lived far from the oil spill area. RESULTS: The children who lived close to the oil spill area showed a significantly lower forced expiratory volume in one second (FEV1), an increased prevalence of 'asthma ever' (based on a questionnaire), and 'airway hyperresponsiveness' (based on the MBPT) than those who lived far from the oil spill area (FEV1; P=0.011, prevalence of 'asthma ever' based on a questionnaire; P=0.005, prevalence of 'airway hyperresponsiveness' based on the MBPT; P=0.001). The onset of wheezing after the oil spill was significantly higher in children who lived close to the oil spill area than in those who lived far from the oil spill area among the 'wheeze ever' group (P=0.002). In a multiple logistic regression analysis, male sex, family history of asthma, and residence near the oil spill area were significant risk factors for asthma (sex [male/female]: odds ratio [OR], 2.54; 95% confidence interval [CI], 1.31-4.91; family history of asthma [No/Yes]: OR, 3.77; 95% CI, 1.83-7.75; exposure group [low/high]; OR, 2.43; 95% CI, 1.27-4.65). CONCLUSIONS: This study suggests that exposure to an oil spill is a risk factor for asthma in children.

Burden of disease attributable to the Hebei Spirit oil spill in Taean, Korea.

OBJECTIVES: We aimed to assess the burden of disease (BOD) of the residents living in contaminated coastal area with oil spill and also analysed the BOD attributable to the oil spill by disease, age, sex and subregion. DESIGN: Health impact assessment by measuring years lived with disability (YLD) due to an oil spill. SETTING: A whole population of a community affected by an anthropogenic environmental disaster and secondary health outcome data. PARTICIPANTS: Based on the health outcome survey including 10 171 individuals (male 4354; female 5817), BOD of 66 473 populations (male 33 441; female 33 032) was measured. INTERVENTIONS: None. Observational study on the effect of a specific environmental health hazard. PRIMARY AND SECONDARY OUTCOME MEASURES: Using disability adjusted life year (DALY) method, BOD including physical and mental diseases was measured. For the BOD measurement, excess incidences of illnesses related to oil spill were estimated from the comparison of prevalence of the health outcomes between contaminated areas and reference area without contamination. RESULTS: YLD attributable to the oil spill were estimated to be 14 724 DALYs (male 7425 DALYs; female 7299 DALYs) for the year 2008. The YLD of mental diseases including post-traumatic stress disorder (PTSD) and depression for men were higher than that for women. The YLD for women was higher in asthma and allergies (rhinitis, dermatitis, conjunctivitis) than that for men. The effects of asthma and allergies were the greatest for people in their 40s, with the burden of mental illness being the greatest for those in their 20s. Proximity to the spill site was associated with increased BOD. CONCLUSIONS: An oil spill near a coastline can cause substantial adverse health effects. As the health effects of hazardous pollutants from oil spills are long-lasting, close follow-up studies are required to identify chronic health effects.

Activation of p38 mitogen-activated protein kinase is required for death receptor-independent caspase-8 activation and cell death in response to sphingosine.

Sphingosine induces activation of multiple signaling pathways that play critical roles in controlling cell death. However, the precise molecular mechanism of cell death induced by sphingosine remains to be clarified. In this study, we show that sphingosine induces death receptor-independent caspase-8 activation and apoptotic cell death via p38 mitogen-activated protein kinase (MAPK) activation and that suppression of the MAPK/extracellular signal-regulated kinase (ERK) kinase/ERK pathway by protein phosphatase 2A (PP2A) is required for p38 MAPK activation. Treatment of cells with sphingosine induced suppression of ERK and activation of p38 MAPK. Inhibition of p38 MAPK led to the marked suppression of death receptor-independent caspase-8 activation and subsequent cell death induced by sphingosine. Interestingly, pretreatment with phorbol 12-myristate 13-acetate or transfection of MAPK/ERK kinase/ERK resulting in ERK activation completely attenuated sphingosine-induced p38 MAPK activation. PP2A activity was additionally elevated on sphingosine treatment. Small interfering RNA targeting of PP2A effectively attenuated sphingosine-induced p38 MAPK activation through restoration of ERK activity, suggesting PP2A-mediated opposing regulation of ERK and p38 MAPK. Our findings clearly imply that activation of p38 MAPK promotes death receptor-independent activation of caspase-8 and apoptotic cell death pathways, thus providing a novel cellular mechanism for the anticancer activity of sphingolipid metabolites.

Opposing roles of c-Jun NH2-terminal kinase and p38 mitogen-activated protein kinase in the cellular response to ionizing radiation in human cervical cancer cells.

Exposure of cells to ionizing radiation induces activation of multiple signaling pathways that play critical roles in determining cell fate. However, the molecular basis for cell death or survival signaling in response to radiation is unclear at present. Here, we show opposing roles of the c-jun NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) pathways in the mitochondrial cell death in response to ionizing radiation in human cervical cancer cells. Ionizing radiation triggered Bax and Bak activation, Bcl-2 down-regulation, and subsequent mitochondrial cell death. Inhibition of JNK completely suppressed radiation-induced Bax and Bak activation and Bcl-2 down-regulation. Dominant-negative forms of stress-activated protein kinase/extracellular signal-regulated kinase kinase 1 (SEK-1)/mitogen-activated protein kinase kinase-4 (MKK-4) inhibited JNK activation. Radiation also induced phosphoinositide 3-kinase (PI3K) activation. Interestingly, inhibition of PI3K effectively attenuated radiation-induced mitochondrial cell death and increased clonogenic survival. Inhibition of PI3K also suppressed SEK-1/MKK-4 and JNK activation, Bax and Bak activation, and Bcl-2 down-regulation. In contrast, inhibition of p38 MAPK led to enhanced Bax and Bak activation and mitochondrial cell death. RacN17, a dominant-negative form of Rac1, inhibited p38 MAPK activation and increased Bax and Bak activation. Exposure of cells to radiation also induced selective activation of c-Src among Src family kinases. Inhibition of c-Src by pretreatment with Src family kinase inhibitor PP2 or small interfering RNA targeting of c-Src attenuated radiation-induced p38 MAPK and Rac1 activation and enhanced Bax and Bak activation and cell death. Our results support the notion that the PI3K-SEK-1/MKK-4-JNK pathway is required for the mitochondrial cell death in response to radiation, whereas the c-Src-Rac1-p38 MAPK pathway plays a cytoprotective role against mitochondrial cell death.