Thermoelectric performance of novel single-layer ZrTeSe4.

In energy conversion techniques, two-dimensional (2D) thermoelectric materials with high performance are strongly required. This study scrutinizes the electronic and thermoelectric properties of 2D single-layer (1L) ZrTeSe4 based on first-principles calculations combined with Boltzmann transport theory. First-principles molecular dynamics simulations and phonon calculations confirm the thermodynamic stability of 1L-ZrTeSe4. Furthermore, the electron mobility of 1L-ZrTeSe4 is calculated to be ∼5706 cm2 V-1 s-1, which is much higher than that of the typical 2D semiconducting materials. Intriguingly, the calculated lattice thermal conductivity of 1L-ZrTeSe4 is found to be 3.16 W m-1 K-1 at room temperature, which is relatively smaller than that of 2D transition metal dichalcogenides. The maximum figure of merit ZT of 1L-ZrTeSe4 at 900 K is ∼0.8 for both p- and n-type doping at optimal carrier concentrations. As ZT could be improved through the manipulation of its electronic structure, this is an important clue indicating the enormous potential of 1L-ZrTeSe4 in thermoelectric application.

Diabetes mellitus increases mortality in acute pyelonephritis patients: a population study based on the National Health Insurance Claim Data of South Korea for 2010-2014.

OBJECTIVE: Diabetes mellitus has been suspected to increase mortality in acute pyelonephritis (APN) patients and the goal of this study is to verify this suspicion with a large data set based on almost the entire population of South Korea. METHODS: A nationwide cohort study was conducted using a South Korean Health Insurance Review and Assessment Service claim database. We collected demographic and clinical information including comorbidities of patients with APN as the primary discharge diagnosis during 2010-2014. Then we compared the in-hospital mortality and recurrence of APN across the diabetes and non-diabetes groups. RESULTS: Among 845,656 APN patients, 12.4% had diabetes mellitus. The median age was 65 in the diabetes group, which was much higher than 47 in the non-diabetes group; the female proportion was 91-92% in both groups. The in-hospital mortality rate was higher in the diabetes group (2.6/1000 events in the diabetes group vs. 0.3/1000 in the non-diabetes group, P < 0.001). When covariates (age, sex, and the modified Charlson comorbidity index) were controlled with panel logistic regression, diabetes was still associated with a higher in-hospital mortality in APN patients (OR 2.66, 95% CI 2.19-3.23). The increasing effect of diabetes on in-hospital mortality of APN patients varied greatly with age: the effect was large for age 15-49 (OR 15.06, 95% CI 5.27-43.05), slightly smaller for age 50-64 (OR 12.17, 95% CI 5.71-25.92), and much smaller for age ≥ 65 (OR 2.10, 95% CI 1.72-1.92). CONCLUSIONS: Our data indicate that the mortality of APN is higher in the patients with diabetes and this effect becomes stronger for young patients.

Trend of Antibiotic Usage for Hospitalized Community-acquired Pneumonia Cases in Korea Based on the 2010-2015 National Health Insurance Data.

BACKGROUND: This study is to describe the changes in prescribing practices of antibiotics to treat community-acquired pneumonia (CAP) in Korea during 2010-2015. METHODS: The claim database of the Health Insurance Review and Assessment Service in Korea was used to select adult patients (≥ 18 years of age) admitted between 2010 and 2015, with the International Classification of Diseases, Tenth Revision codes relevant to all-cause pneumonia for the first or second priority discharge diagnosis. The episodes with hospital-acquired or healthcare-associated pneumonia were excluded. Consumption of each antibiotic was converted to defined daily dose (DDD) per episode. The amount of antibiotic consumption was compared between patients with CAP aged < 65 years and those aged ≥ 65 years. RESULTS: The average amount of antibiotic consumption per episode was 15.5 DDD, which remained stable throughout the study period (P = 0.635). Patients aged ≥ 65 years received more antibiotics than those aged < 65 years (15.7 vs. 15.3 DDD). Third-generation cephalosporin (4.9 DDD/episode, 31.4%) was the most commonly prescribed, followed by macrolide (2.7 DDD/episode, 17.1%) and beta-lactam/beta-lactamase inhibitor (BL/BLI) (2.1 DDD/episode, 13.6%). The consumption amount of fourth-generation cephalosporin (4th CEP) (P = 0.001), BL/BLI (P = 0.003) and carbapenem (P = 0.002) increased each year during the study period. The consumption of 4th CEP and carbapenem was doubled during 2010-2015. CONCLUSION: The prescription of broad-spectrum antibiotics such as 4th CEP and carbapenem to treat CAP increased in Korea during 2010-2015.

Characteristics of Nonthermal Dupree Diffusion on Space-Charge Wave in a Kappa Distribution Plasma Column with Turbulent Diffusion.

The nonthermal diffusion effects on the dispersion equations of ion-acoustic space-charge wave (SCW) in a nonthermal plasma column composed of nonthermal turbulent electrons and cold ions are investigated based on the analysis of normal modes and the separation of variables. It is found that the real portion of the wave frequency of the SCW in a Maxwellian plasma is greater than that in a nonthermal plasma. It is also found that the magnitude of the damping rate of the SCW decreases with an increase of the spectral index of the nonthermal plasma. It is also shown that the magnitude of the scaled damping rate increases with an increase of the Dupree diffusion coefficient. Moreover, the influence of the nonthermal character of the nonthermal plasma on the damping rate is found to be more significant in turbulent plasmas with higher diffusion coefficient. The variations of the wave frequency and the growth rate due to the characteristics of nonthermal diffusion are also discussed.

Characteristics of Shannon's Information Entropy of Atomic States in Strongly Coupled Plasma.

The influence of shielding on the Shannon information entropy for atomic states in strong coupled plasma is investigated using the perturbation method and the Ritz variational method. The analytic expressions for the Shannon information entropies of the ground (1s) and the first excited states (2p) are derived as functions of the ion-sphere radius including the radial and angular parts. It is shown that the entropy change in the atomic state is found to be more significant in the excite state than in the ground state. It is also found that the influence of the localization on the entropy change is more significant for an ion with a higher charge number. The variation of the 1s and 2p Shannon information entropies are discussed.

Wigner Time-Delay and Distribution for Polarization Interaction in Strongly Coupled Semiclassical Plasmas.

The quantum effect on the Wigner time-delay and distribution for the polarization scattering in a semiclassical dense plasma is explored. The partial wave analysis is applied for a partially ionized dense plasma to derive the phase shift for the polarization interaction. The Wigner time-delay and the Wigner distribution are derived for the electron-atom polarization interaction including the effects of quantum-mechanical characteristic and plasma screening. In this work, we show that the Wigner time-delay and the Wigner distribution for the polarization interaction can be suppressed by the quantum effect. The Wigner time-delay and the Wigner distribution are also significantly suppressed by the increase of plasma shielding. The variation of the Wigner time-delay and the Wigner distribution function due to quantum screening is discussed.

Trend of antibiotics usage for acute pyelonephritis in Korea based on national health insurance data 2010-2014.

BACKGROUND: The objective of this study is to describe the changes in prescribing practices of antibiotics to treat acute pyelonephritis (APN) in Korea. METHODS: The claim data base of the Health Insurance Review and Assessment Service in Korea was used to select patients with ICD-10 codes N10 (acute tubulo-interstitial nephritis) or N12 (tubulo-interstitial nephritis, not specified as acute nor chronic) as the primary discharge diagnosis during 2010-2014. Consumption of each class of antibiotics was converted to Defined Daily Dose (DDD)/event. RESULTS: Throughout the five-year period, the average antibiotic consumption were 11.3 DDD per inpatient event and 6.0 DDD per outpatient event. The annual average antibiotic consumption increased for inpatients (P = 0.002), but remained stable for outpatients (P = 0.066). The use of parenteral antibiotics increased for inpatients (P < 0.001), but decreased for outpatients (P = 0.017). As for the the antibiotic classes, 3rd generation cephalosporins (3rd CEPs) was the most commonly prescribed (41.4%) for inpatients, followed by fluoroquinolones (FQs) (28.5%); for outpatient, FQs (54.8%) was the most commonly prescribed, followed by 3rd CEPs (13.1%). The use of 3rd CEPs (P < 0.001), beta-lactam/beta-lactamase inhibitors (P = 0.007), and carbapenems (P < 0.001) increased substantially for the treatment of hospitalized APN patients. In particular, carbapenems use increased 3.1-fold over the 5 years. CONCLUSIONS: Prescription of broad-spectrum antibiotics increased much for the treatment of APN in Korea during 2010-2014.

A few antibiotics can represent the total hospital antibiotic consumption.

BACKGROUND: Appropriate antibiotic use has become an important issue. However, collecting data on the use of all antibiotics in a hospital is difficult without an advanced computerized system and dedicated staff. This paper examines if 1-3 antibiotics can satisfactorily represent the total antibiotic consumption at the hospital level. METHODS: We collected antibiotic data from six large university hospitals in Korea for some years between 2004 and 2012. Since the total antibiotics consist of a few chosen representative antibiotics and the rest, we used those chosen antibiotics along with additional variables constructed only with t (time) such as t, t 2 , and t 3 to capture the time trend and whether t belongs to each month or not to capture the monthly variations. The ordinary least squares method was used to explain the total antibiotic amount with these variables, and then the estimated model was employed to predict the use for 2013. To determine which antibiotics were the most representative in tracking general trends in antibiotic use over time, we tried various combinations of antibiotics to find the combination that best minimized the 2013 prediction error. RESULTS: We found that fluoroquinolones and aminoglycosides were the most representative, followed by beta-lactam/beta-lactamase inhibitors and 4th-generation and 3rd-generation cephalosporins. The mean prediction error over 12 months in 2013 with these few antibiotics was only 1-3% of the monthly antibiotic consumption amount. CONCLUSIONS: The total antibiotic consumption amount at the hospital level can be represented sufficiently by a few antibiotics, such as fluoroquinolones and aminoglycosides, which means that hospitals can save resources by tracing only the usage of those few antibiotics instead of the entire inventory. Since the choice of fluoroquinolones and aminoglycosides is based solely on our Korean data, other hospitals may follow the same modelling methodology to find their own representative antibiotics.

Descriptive Epidemiology of Acute Pyelonephritis in Korea, 2010-2014: Population-based Study.

BACKGROUND: Acute pyelonephritis (APN) is one of the most common community-acquired bacterial infections. Recent increases of antimicrobial resistance in urinary pathogens might have changed the other epidemiologic characteristics of APN. The objective of this study was to describe the current epidemiology of APN in Korea, using the entire population. METHODS: From the claims database of the Health Insurance Review and Assessment Service in Korea, the patients with International Classification of Diseases, 10th Revision codes N10 (acute tubulo-interstitial nephritis) or N12 (tubulo-interstitial nephritis, neither acute nor chronic) as the primary discharge diagnosis during 2010-2014 were analyzed, with two or more claims during a 14-day period considered as a single episode. RESULTS: The annual incidence rate of APN per 10,000 persons was 39.1 and was on the increase year to year (35.6 in 2010; 36.7 in 2011; 38.9 in 2012; 40.1 in 2013; 43.8 in 2014, P = 0.004). The increasing trend was observed in both inpatients (P = 0.014) and outpatients (P = 0.004); in both men (P = 0.042) and women (P = 0.003); and those aged under 55 years (P = 0.014) and 55 years or higher (P = 0.003). Eleven times more women were diagnosed and treated with APN than men (men vs. women, 6.5 vs. 71.3), and one of every 4.1 patients was hospitalized (inpatients vs. outpatients, 9.6 vs. 29.4). The recurrence rate was 15.8%, and the median duration from a sporadic episode (i.e., no episode in the preceding 12 months) to the first recurrence was 44 days. The recurrence probability increased with the number of previous recurrences. The average medical cost per inpatient episode was USD 1,144, which was 12.9 times higher than that per outpatient episode (USD 89). CONCLUSION: The epidemiology of APN in Korea has been changing with an increasing incidence rate.

Ordinal response generalized difference in differences with varying categories: The health effect of a disability program in Korea.

We consider the use of difference in differences (DD) to evaluate the effect of an activity assistance program on the health of severely disabled Koreans. There are, however, 2 problems in the data: the number of response categories for self-assessed health changed over the waves of the repeated cross-section survey and the "parallel untreated response path" assumption for DD is suspect. We show how to overcome these problems by renormalizing parameters and applying "generalized difference in differences (GDD)." We find a significantly positive effect of the program with DD, but not with GDD. Our solutions should prove useful in applications in which one or other of these problems arise.

Deterministic Two-Dimensional Polymorphism Growth of Hexagonal n-Type SnS2 and Orthorhombic p-Type SnS Crystals.

van der Waals layered materials have large crystal anisotropy and crystallize spontaneously into two-dimensional (2D) morphologies. Two-dimensional materials with hexagonal lattices are emerging 2D confined electronic systems at the limit of one or three atom thickness. Often these 2D lattices also form orthorhombic symmetries, but these materials have not been extensively investigated, mainly due to thermodynamic instability during crystal growth. Here, we show controlled polymorphic growth of 2D tin-sulfide crystals of either hexagonal SnS2 or orthorhombic SnS. Addition of H2 during the growth reaction enables selective determination of either n-type SnS2 or p-type SnS 2D crystal of dissimilar energy band gap of 2.77 eV (SnS2) or 1.26 eV (SnS) as a final product. Based on this synthetic 2D polymorphism of p-n crystals, we also demonstrate p-n heterojunctions for rectifiers and photovoltaic cells, and complementary inverters.

Difference in differences for stayers with a time-varying qualification: health expenditure elasticity of the elderly.

In difference in differences, a treatment is applied only to a qualified group at some time point. The qualification may be time-constant as in gender, or time-varying as in residential location. When the qualification is time-varying, there appear four groups: the newly qualified (in-movers), the already qualified (in-stayers), the newly disqualified (out-movers), and the already disqualified (out-stayers). A change in qualification may affect the response variable of interest even when the treatment effect is zero, which is an 'untreated moving effect'. Also, when the treatment effect is not zero, it may be different across the four groups. The conventional difference in differences fails to remove untreated moving effects and ignores the possible treatment effect heterogeneity across the groups. This paper shows how to account for untreated moving effects and proposes 'the effect on in-stayers' as the main effect of interest. Our proposal can be implemented with least squares estimator for panel models or with nonparametric methods. An empirical analysis is provided using Korean data for the effects of the basic elder pension on health-care expenditure.

Interface engineering in ZnO/CdO hybrid nanocomposites to enhanced resistive switching memory for neuromorphic computing.

Resistive random-access memory (RRAMs) has attracted significant interest for their potential applications in embedded storage and neuromorphic computing. Materials based on metal chalcogenides have emerged as promising candidates for the fulfilment of these requirements. Due to its ability to manipulate electronic states and control trap states through controlled compositional dynamics, metal chalcogenide RRAM has excellent non-volatile resistive memory properties. In the present we have synthesized ZnO-CdO hybrid nanocomposite by using hydrothermal method as an active layer. The Ag/C15ZO/Pt hybrid nanocomposite structure memristors showed electrical properties similar to biological synapses. The device exhibited remarkably stable resistive switching properties that have a low SET/RESET (0.41/-0.2) voltage, a high RON/OFF ratio of approximately 105, a high retention stability, excellent endurance reliability up to 104 cycles and multilevel device storage performance by controlling the compliance current. Furthermore, they exhibited an impressive performance in terms of emulating biological synaptic functions, which include long-term potentiation (LTP), long-term depression (LTD), and paired-pulse facilitation (PPF), via the continuous modulation of conductance. The hybrid nanocomposite memristors notably achieved an impressive recognition accuracy of up to 92.6 % for handwritten digit recognition under artificial neural network (ANN). This study shows that hybrid-nanocomposite memristor performance could lead to efficient future neuromorphic architectures.

Regression Discontinuity for Binary Response and Local Maximum Likelihood Estimator to Extrapolate Treatment.

Regression discontinuity is popular in finding treatment/policy effects when the treatment is determined by a continuous variable crossing a cutoff. Typically, a local linear regression (LLR) estimator is used to find the effects. For binary response, however, LLR is not suitable in extrapolating the treatment, as in doubling/tripling the treatment dose/intensity. The reason is that doubling/tripling the LLR estimate can give a number out of the bound [-1, 1], despite that the effect should be a change in probability. We propose local maximum likelihood estimators which overcome these shortcomings, while giving almost the same estimates as the LLR estimator does for the original treatment. A simulation study and an empirical analysis for effects of an income subsidy program on religion demonstrate these points.

Interface roughness effects and relaxation dynamics of an amorphous semiconductor oxide-based analog resistance switching memory.

The analog resistive switching properties of amorphous InGaZnOx (a-IGZO)-based devices with Al as the top and bottom electrodes and an Al-Ox interface layer inserted on the bottom electrode are presented here. The influence of the electrode deposition rate on the surface roughness was established and proposed as the cause of the observed unusual anomalous switching effects. The DC electrical characterization of the optimized Al/a-IGZO/AlOx/Al devices revealed an analog resistive switching with a satisfactory value for retention levels, but the endurance was found to decrease after 200 cycles. The predominant conduction mechanism in these devices was found to be thermionic emission. An in-depth analysis was performed to explore the relaxation kinetics of the device and it was found that the current has a lower decay rate. The current level stability was tested and found reliable even after 5 h. The cost-effective and precious metal-free nature of the a-IGZO memristor investigated in this study makes it a highly desirable candidate for neuromorphic computing applications.

A fast, high-endurance and scalable non-volatile memory device made from asymmetric Ta2O(5-x)/TaO(2-x) bilayer structures.

Numerous candidates attempting to replace Si-based flash memory have failed for a variety of reasons over the years. Oxide-based resistance memory and the related memristor have succeeded in surpassing the specifications for a number of device requirements. However, a material or device structure that satisfies high-density, switching-speed, endurance, retention and most importantly power-consumption criteria has yet to be announced. In this work we demonstrate a TaO(x)-based asymmetric passive switching device with which we were able to localize resistance switching and satisfy all aforementioned requirements. In particular, the reduction of switching current drastically reduces power consumption and results in extreme cycling endurances of over 10(12). Along with the 10 ns switching times, this allows for possible applications to the working-memory space as well. Furthermore, by combining two such devices each with an intrinsic Schottky barrier we eliminate any need for a discrete transistor or diode in solving issues of stray leakage current paths in high-density crossbar arrays.

Modeling for multilevel switching in oxide-based bipolar resistive memory.

We report a physical model for multilevel switching in oxide-based bipolar resistive memory (ReRAM). To confirm the validity of the model, we conduct experiments with tantalum-oxide-based ReRAM of which multi-resistance levels are obtained by reset voltage modifications. It is also noticeable that, in addition to multilevel switching capability, the ReRAM exhibits extremely different switching timescales, i.e. of the order of 10(-7) s to 10(0) s, with regard to reset voltages of only a few volts difference which can be well explained by our model. It is demonstrated that with this simple model, multilevel switching behavior in oxide bipolar ReRAM can be described not only qualitatively but also quantitatively.

Zero-inflated endogenous count in censored model: effects of informal family care on formal health care.

If informal family health care is a substitute for formal health care, then there is a scope to reduce formal health care cost by promoting informal family health care. With the use of Korean data for the elderly, this paper estimates the effects of informal family health care on formal health care, where the former is measured by the number of caregivers and the latter is measured by the formal health care expenditure. This task, however, poses a number of difficulties. The first is that the number of the family caregivers is an endogenous count regressor. The second is that there are too many zeros in the count (85%). The third is that the response variable also has a nontrivial proportion of zeros (14%). This paper overcomes these problems by combining 'control function approach', 'zero-inflated' counts, and a semiparametric estimator for censored models. The resulting procedure avoids strong parametric assumptions and behaves well computationally. Our main empirical finding is that informal family health care has a large substitute effect for diabetics and that there are also weak evidences that informal family health care has substitute effects for high blood pressure and mental diseases.

Review and comparison of treatment effect estimators using propensity and prognostic scores.

In finding effects of a binary treatment, practitioners use mostly either propensity score matching (PSM) or inverse probability weighting (IPW). However, many new treatment effect estimators are available now using propensity score and "prognostic score", and some of these estimators are much better than PSM and IPW in several aspects. In this paper, we review those recent treatment effect estimators to show how they are related to one another, and why they are better than PSM and IPW. We compare 26 estimators in total through extensive simulation and empirical studies. Based on these, we recommend recent treatment effect estimators using "overlap weight", and "targeted MLE" using statistical/machine learning, as well as a simple regression imputation/adjustment estimator using linear prognostic score models.

Hydrogen diffusion and its electrical properties variation as a function of the IGZO stacking structure.

The oxygen vacancies and hydrogen in oxide semiconductors are regarded as the primary sources of charge carriers and various studies have investigated the effect of hydrogen on the properties of oxide semiconductors. However, the carrier generation mechanism between hydrogen and oxygen vacancies in an a-IGZO semiconductor has not yet been clearly examined. In this study we investigated the effect of hydrogen and the variation mechanisms of electrical properties of a thin film supplied with hydrogen from the passivation layer. SiOx and SiNx, which are used as passivation or gate insulator layers in the semiconductor process, respectively, were placed on the top or bottom of an a-IGZO semiconductor to determine the amount of hydrogen penetrating the a-IGZO active layer. The hydrogen diffusion depth was sufficiently deep to affect the entire thin semiconductor layer. A large amount of hydrogen in SiNx directly affects the electrical resistivity of a-IGZO semiconductor, whereas in SiOx, it induces a different behavior from that in SiNx, such as inducing an oxygen reaction and O-H bond behavior change at the interface of an a-IGZO semiconductor. Moreover, the change in electrical resistivity owing to the contribution of free electrons could be varied based on the bonding method of hydrogen and oxygen.