Artificial van der Waals heterostructures with two-dimensional (2D) atomic crystals are promising as an active channel or as a buffer contact layer for next-generation devices. However, genuine 2D heterostructure devices remain limited because of impurity-involved transfer process and metastable and inhomogeneous heterostructure formation. We used laser-induced phase patterning, a polymorph engineering, to fabricate an ohmic heterophase homojunction between semiconducting hexagonal (2H) and metallic monoclinic (1T') molybdenum ditelluride (MoTe2) that is stable up to 300°C and increases the carrier mobility of the MoTe2 transistor by a factor of about 50, while retaining a high on/off current ratio of 10(6). In situ scanning transmission electron microscopy results combined with theoretical calculations reveal that the Te vacancy triggers the local phase transition in MoTe2, achieving a true 2D device with an ohmic contact.

Background While considerable evidence has been produced showing a link between nursing characteristics and patient outcomes in the U.S. and Europe, little is known about whether similar associations are present in South Korea. Objective To examine the effects of nurse staffing, work environment, and education on patient mortality. Methods This study linked hospital facility data with staff nurse survey data (N=1,024) and surgical patient discharge data (N = 76,036) from 14 high-technology teaching hospitals with 700 or more beds in South Korea, collected between January 1, 2008 and December 31, 2008. Logistic regression models that corrected for the clustering of patients in hospitals were used to estimate the effects of the three nursing characteristics on risk-adjusted patient mortality within 30 days of admission. Results Risk-adjusted models reveal that nurse staffing, nurse work environments, and nurse education were significantly associated with patient mortality (OR 1.05, 95% CI 1.00–1.10; OR 0.52, 95% CI 0.31–0.88; and OR 0.91, CI 0.83–0.99; respectively). These odds ratios imply that each additional patient per nurse is associated with an 5% increase in the odds of patient death within 30 days of admission, that the odds of patient mortality are nearly 50% lower in the hospitals with better nurse work environments than in hospitals with mixed or poor nurse work environments, and that each 10% increase in BSN nurse is associated with a 9% decrease in patient deaths. Conclusions Nurse staffing, nurse work environments, and percentages of BSN nurses in South Korea are associated with patient mortality. Improving hospital nurse staffing and work environments and increasing the percentages of BSN nurses would help reduce the number of preventable in-hospital deaths.

Doping two-dimensional (2D) semiconductors beyond their degenerate levels provides the opportunity to investigate extreme carrier density-driven superconductivity and phase transition in 2D systems. Chemical functionalization and the ionic gating have achieved the high doping density, but their effective ranges have been limited to ∼1 nm, which restricts the use of highly doped 2D semiconductors. Here, we report on electron diffusion from the 2D electride [CaN]·e to MoTe over a distance of 100 nm from the contact interface, generating an electron doping density higher than 1.6 × 10 cm and a lattice symmetry change of MoTe as a consequence of the extreme doping. The long-range lattice symmetry change, suggesting a length scale surpassing the depletion width of conventional metal-semiconductor junctions, was a consequence of the low work function (2.6 eV) with highly mobile anionic electron layers of [CaN]·e. The combination of 2D electrides and layered materials yields a novel material design in terms of doping and lattice engineering.

Stroke is a leading public health problem in Korea in terms of the economic burden. The indirect costs were identified as the largest component of the overall cost.

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Piezoelectricity crystallographically exists only in the in-plane direction in two-dimensional transition metal dichalcogenides. Here, we demonstrated flexoelectricity-tunable out-of-plane piezoelectricity in semiconducting 2H-MoTe flakes by creating surface corrugation. In particular, the strong out-of-plane piezoelectricity and its spatial variation depending on local flexoelectricity was observed even though crystallographically there exists only in-plane piezoelectricity. Surface corrugation-mediated flexoelectricity tuning can be applied to other two-dimensional or thin-layered materials and, furthermore, the results could provide useful information on the interweaving nature between mechanical stimulus and electric dipole in low-dimensional materials.

This study aims to investigate the association of particulate matter with an aerodynamic diameter smaller than 10 μm (PM10) and greenness with cause-specific mortality and their interactions in seven Korean metropolitan cities. We obtained the annual standardized cause-specific mortality rates, annual mean concentration of PM10, and annual Normalized Difference Vegetation Index (NDVI) for 73 districts for the period 2008–2016. We used negative binomial regression with city-specific random effects to estimate the association of PM10 and greenness with mortality. The models were adjusted for potential confounders and spatial autocorrelation. We also conducted stratified analyses to investigate whether the association between PM10 and mortality differs by the level of greenness. Our findings suggest an increased risk of all causes examined, except respiratory disease mortality, with high levels of PM10 and decreased risk of cardiovascular-related mortality with a high level of greenness. In the stratified analyses, we found interactions between PM10 and greenness, but these interactions in the opposite direction depend on the cause of death. The effects of PM10 on cardiovascular-related mortality were attenuated in greener areas, whereas the effects of PM10 on non-accidental mortality were attenuated in less green areas. Further studies are needed to explore the underlying mechanisms.

Korea has a single National Health Insurance program and all citizens are covered under this program, accounting 97% of the population, approximately 50 million people. Claims submitted by Health care providers are reviewed by Health Insurance Review and Assessment (HIRA) for the reimbursement. HIRA database contains not only individual beneficiary's information, but also healthcare service information such as diagnosis, procedures, prescriptions and tests for them. HRA database has gained attention as importance source for research due to its rich healthcare information and the demand of HIRA database has increased. Due to its tremendous size, however, researchers have had problems in accessing the database to conduct research. To meet this demand, we conducted a study to develop the inpatient sample data from HIRA database for research. This study has two purposes: 1) to determine a needed sample size; 2) to test reliability and validity of the sample data. We determined an adequate sample size to ensure representativeness and generality with additional consideration for convenience of calculation. The minimum sample size was 729,904 for the generality, and 488,861 for representativeness. After considering the convenience of calculation, our final sample size was 13% of the population, which was about 7.7 million beneficiaries. Age (5 years interval) and gender were used as stratification variables for sampling. In order to examine whether this sample data appropriately reflect population, we tested the reliability and validity of the sample data. From the sample data, we computed average expenditure of total claims per inpatient for 2011, frequency of top 30 disease, estimation of the number of stroke patients from the sample data, and then compared them to those from the population. Results confirmed reliability and validity of the sample data .