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It has been recently predicted that nonsymmorphic crystalline insulators can host two exotic topological surface states (TSSs). One is the "hourglass fermion", and the other is the "wallpaper Dirac fermion". For the former, a few real materials were predicted and already confirmed experimentally. For the latter, however, no bulk-insulating and experimentally accessible candidate has been identified yet. Here we show that the localized 5f-electrons in PuB4, the single crystal of which was recently synthesized and was found to exhibit Kondo-insulating nature, form a closed manifold over the Brillouin zone via the Kondo coherence effect at low temperature, and host hitherto unobserved wallpaper Dirac fermions at the nonsymmorphic symmetry-preserving (001) surface. The topological nature of TSSs in PuB4 can be described by topological invariants of two Z4 indices [(χx, χy) = (1, 1)] of double-glide symmetries of p4g wallpaper group; thus, PuB4 is a 3D nonsymmorphic topological insulator that exhibits the TSSs of peculiar 4-fold surface Dirac fermions as well as 2-fold double-glide spin-Hall and nodal-line-type fermions. On top of its interesting 5f-electron Kondo-insulating nature, the unique 4-fold wallpaper Dirac fermions in PuB4, which are quite distinct from previously reported nonsymmorphic Dirac insulator or hourglass TCI fermions, broaden our recognition of the embedded fermions in strongly correlated Kondo systems with nonsymmorphic symmetries.

North Korea conducted the sixth underground nuclear test on September 3, 2017 at the Punggye-ri Nuclear Test Site (NTS). In contrast to the previous five nuclear tests, several induced earthquakes occurred around the NTS after the sixth nuclear test and this may have caused radioxenon leakages at the site. Considering these reported earthquakes, we performed atmospheric dispersion simulations on some radioxenon emission scenarios for this event using our Lagrangian Atmospheric Dose Assessment System (LADAS) model by employing the Unified Model (UM) based numerical weather prediction data produced by the Korea Meteorological Administration (KMA). To find out possible detection locations and times, we combined not only daily and weekly based delayed releases but also leakages after the reported earthquakes around the NTS to create emission scenarios. Our simulation results were generally in good agreement with the measured data of the Nuclear Safety and Security Commission and International Monitoring System (IMS) stations operated by the Comprehensive nuclear Test-Ban-Treaty Organization (CTBTO).

Ji, Y.-Y.; Joung, S.; Min, B.I., and Suh, K.-S., 2021. Development and performance of underwater gamma-ray spectrometry for riverbed monitoring. In: Lee, J.L.; Suh, K.-S.; Lee, B.; Shin, S., and Lee, J. (eds.), Crisis and Integrated Management for Coastal and Marine Safety. Journal of Coastal Research, Special Issue No. 114, pp. 330–334. Coconut Creek (Florida), ISSN 0749-0208. The atmospheric release and fallouts of radionuclides have produced the radioactive contamination over wide area in the accident at the Fukushima Daiichi nuclear power plant (FDNPP). They still affect the environment around the Fukushima Prefecture, such as resident area, fields, mountainous area, river and stream, and reservoir. In JAEA (Japan Atomic Energy Agency), diverse monitoring platforms have been developing and successfully applying to the assessment of environmental radiation and deposited nuclides. Especially, there are about 3,700 irrigation reservoirs around the Fukushima Prefecture, which can be effected from direct fallouts in reservoirs as well as dispersions of the contamination in the other sites, depending on weather conditions. Underwater survey system is an important tool to assess the radioactive contamination in the river, stream and reservoir, including the bottom sediments. In this study, underwater gamma-ray spectrometry, named as MARK-U1, was developed to rapidly estimate the underwater radioactivity for the emergency preparedness, according to the lesson learned from the nuclear accident of FDNPP. A 3”φx3” NaI(Tl) detector is equipped in this underwater system and the lateral shielding around a detector was also designed using lead with a thickness of 1 cm to confine the field of view. Finally, its performance test was conducted by evaluating the natural radioactivity of 214Bi, 208Tl, and 40K in the riverbed of reservoir.

Crystal structure prediction and in silico physical property observations guide experimental synthesis in high-pressure research. Here, we used magnesium carbides as a representative example of computational high-pressure studies. We predicted various compositions of Mg–C compounds up to 150 GPa and successfully reproduced previous experimental results. Interestingly, our proposed MgC2 at high pressure >7 GPa consists of extended carbon bonds, one-dimensional graphene layers, and Mg atomic layers, which provides a good platform to study superconductivity of metal intercalated graphene nano-ribbons. We found that this new phase of MgC2 could be recovered to ambient pressure and exhibited a strong electron-phonon coupling (EPC) strength of 0.6 whose corresponding superconductivity transition temperature reached 15 K. The EPC originated from the cooperation of the out-of-plane and the in-plane phonon modes. The geometry confinement and the hybridization between the Mg s and C pz orbitals significantly affect the coupling of phonon modes and electrons. These results show the importance of the high-pressure route to the synthesis of novel functional materials, which can promote the search for new phases of carbon-based superconductors.

Radioactive materials are released into the air and deposited on the surface soil after a nuclear accident. Radionuclides deposited in soil are transported by precipitation to nearby environments and contaminate the surface water system. Basic data on surface watershed and soil erosion models have been collected and analyzed to evaluate the behavior of radionuclides deposited on surface soil after a nuclear accident. Data acquisition and analysis in aquatic environment were performed to investigate the physical characteristics and variation of biota in rivers and lakes of the Nakdong river area near the Wolsong nuclear power plant. For these purposes, a digital map, and hydrological, water quality and biota data were gathered and a systematic database (DB) was constructed in connection with them. Constructed aquatic DB will be supplied and used in surface watershed and soil erosion models for investigation of long-term movement of radionuclides in adsorptive form in surface soil. Finally, basic data and established models will be utilized for general radiological impact assessment in aquatic environment.

A source detective system has been developed to estimate unknown source regions and release rates of radionuclides released into the air from covert nuclear activities and accidents. This system is composed of trajectory, atmospheric dispersion, and source term estimation models. Simulated results were compared with the measurements of a field tracer experiment performed at the Yeonggwang nuclear power plant in Korea in May 1996. Two trajectories among five computed backward trajectories moved toward the original release point, and the comparative results contained some error due to single operation of the backward trajectory model. An atmospheric dispersion model was used to minimize the error of the trajectory model and to improve the accuracy of the source detective system. The results generated by the trajectory and atmospheric dispersion models together agreed better with the measurements than those obtained using the trajectory model alone.

The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) resulted in the deposition of large quantities of radionuclides over parts of eastern Japan. Radioactive contaminants have been observed over a large area including forests, cities, rivers and lakes. Due to the strong adsorption of radioactive cesium by soil particles, radioactive cesium migrates with the eroded soil, follows the surface flow paths, and is delivered downstream of population-rich regions and eventually to coastal areas. In this study, we developed a model to simulate the transport of contaminated sediment in a watershed hydrological system and this model was compared with observation data from eroded soil observation instruments located at the Korea Atomic Energy Research Institute. Two methods were applied to analyze the soil particle size distribution of the collected soil samples, including standardized sieve analysis and image analysis methods. Numerical models were developed to simulate the movement of soil along with actual rainfall considering initial saturation, rainfall infiltration, multilayer and rain splash. In the 2019 study, a numerical model will be used to add rainfall shield effect by trees, evaporation effect and shield effects of surface water. An eroded soil observation instrument has been installed near the Wolsong nuclear power plant since 2018 and observation data are being continuously collected. Based on these observations data, we will develop the numerical model to analyze long-term behavior of radionuclides on land as they move from land to rivers, lakes and coastal areas.

A number of marine radionuclide dispersion models (both Eulerian and Lagrangian) were applied to simulate 137Cs releases from Fukushima Daiichi nuclear power plant accident in 2011 over the Pacific at oceanic scale. Simulations extended over two years and both direct releases into the ocean and deposition of atmospheric releases on the ocean surface were considered. Dispersion models included an embedded biological uptake model (BUM). Three types of BUMs were used: equilibrium, dynamic and allometric. Model results were compared with 137Cs measurements in water (surface, intermediate and deep layers), sediment and biota (zooplankton, non-piscivorous and piscivorous fish). A reasonable agreement in model/model and model/data comparisons was obtained.

A Lagrangian model which describes radionuclide transport in the northern Indian Ocean is described. Water circulation is obtained from HYCOM ocean model for year 2017. The model includes advection by currents, turbulent mixing and radionuclide interactions between water and sediments, described in a dynamic way using kinetic transfer coefficients. Hypothetical releases from five coastal nuclear power plants operating in the northern Indian Ocean were simulated. Releases were supposed to start both during the winter and summer monsoons, to study reversing circulation effects. Age distributions of releases were calculated, which adds information about circulation and radionuclide pathways. It was found that, for some of the NPPs, radionuclide distributions resulting from releases starting in both seasons were not as different as could be expected from the opposed circulation schemes during each monsoon. Effective 137Cs half-lives in the ocean surface were calculated and results were two orders of magnitude below previous estimations.

It has been recently predicted that nonsymmorphic crystalline insulators can host two exotic topological surface states (TSSs). One is the "hourglass fermion", and the other is the "wallpaper Dirac fermion". For the former, a few real materials were predicted and already confirmed experimentally. For the latter, however, no bulk-insulating and experimentally accessible candidate has been identified yet. Here we show that the localized 5f-electrons in PuB

This paper finds that f-electrons play a crucial role in the nontrivial Z2 topology. They demonstrate the coherent quasi-particle band formation of f-electrons in CeN even at room temperature, which brings about the topological Kondo nature originating from the f-d band inversion. The distinct topological properties in CeN and CeBi, Dirac cones and helical spin textures at their respective surfaces, provide evidence of the dual-nature of f-electrons.

Accidentally released radionuclides are dispersed into the environment and cause human exposure through various pathways. Concerns about radiological impacts of a possible Nuclear power plant (NPP) accident in neighboring countries, especially in China, are increasing in Korea. Dose assessments for the hypothetical nuclear accidents in Korea (Hanbit and Wolsong NPPs) and China (Tianwan NPP) were conducted using the developed Korean code system. The results show that there is a possibility that a Tianwan NPP accident could have a slightly greater or similar impact on certain parts of Korea compared to accidents occurring at domestic NPPs, and could affect Korea within a few days of the accident. This research is expected to be used as basic material for preparing against nuclear accidents in neighboring countries.

A numerical model, previously validated with other radionuclides, was applied to simulate the dispersion of 236U released from European nuclear fuel reprocessing plants in the North Atlantic and Shelf Seas using a published reconstruction of Sellafield and La Hague releases. Model results are in better agreement with observations if the lowest estimation of such releases are used. This implies that approximately 40 kg of 236U has been discharged from Sellafield. It was found that adsorption of 236U on bed sediments of the shallow European Shelf Seas plays an essential role in its dispersion patterns. This contrasts strongly with the more conservative behaviour of 129I in the same area. This has two important implications in the use of 236U as oceanographic tracer; i) special care must be taken in coastal areas, as sediments might act as sinks and sources of 236U; ii) the annual input function of 236U into the Arctic is not directly controlled by the annual discharges from Sellafield and La Hague, since sediments from the Irish, Celtic and North Sea modulate and smooth the signal. Only 52% of the total releases enter into the Arctic Ocean.

We have investigated electronic structures and magnetic properties of double perovskite Iridate Ba2YIrO6 with 5 d 4 configuration, employing the exact diagonalization method for multi-site clusters. We have considered a many-body Hamiltonian for all d states ( e g and t 2 g ) including all relevant physical parameters such as the Coulomb correlation, spin-orbit coupling, crystal-field effect, and Hund coupling. We have found that the ground state of Ba2YIrO6 is nonmagnetic and that the Hund coupling plays an important role in the magnetic properties of the 5 d 4 systems, unlike the well-studied 5 d 5 systems.

By employing soft X-ray magnetic circular dichroism (XMCD) and soft X-ray absorption spectroscopy (XAS), we have investigated the temperature (T)-dependent valence and spin states of Cr ions in half-metallic ferromagnet CrO2 nanorod powder. The lineshape-analysis of both the Cr 2 p XAS and XMCD spectra of CrO2 reveals that the Cr ions in bulk CrO2 have both Cr 4 + t 2 g 2 ↑ and Cr 3 + t 2 g 3 ↑ valence configurations. This work provides the direct experimental evidence for the Cr 3 + - Cr 4 + mixed-valent states in bulk CrO2 ( Cr 3.8 + ) , demonstrating that the half-metallic ferromagnetism in CrO2 originates from the double-exchange interaction. The T-dependent intensity variation of the Cr 2 p XMCD spectrum agrees well with the bulk magnetization M(T) and the Curie temperature, indicating that the measured Cr 2 p XMCD data represent the intrinsic bulk ferromagnetism in CrO2, and support the above finding of the XMCD lineshape analysis.

Ingestion of radionuclide contaminated food is one of the major concerns in long-term exposure following a nuclear accident. A terrestrial food chain model was developed to evaluate radioactivity in terrestrial food and ingestion doses under the Korean agricultural environment. The influence of the radionuclides released from the Fukushima Daiichi Nuclear Power Plant accident on contamination of agricultural food and livestock produced in Japan and the ingestion doses for people living in Fukushima Prefecture was calculated using the developed model.

We present the electronic characterization of single-layer 1H-TaSe2 grown by molecular beam epitaxy using a combined angle-resolved photoemission spectroscopy, scanning tunneling microscopy/spectroscopy, and density functional theory calculations. We demonstrate that 3 × 3 charge-density-wave (CDW) order persists despite distinct changes in the low energy electronic structure highlighted by the reduction in the number of bands crossing the Fermi energy and the corresponding modification of Fermi surface topology. Enhanced spin-orbit coupling and lattice distortion in the single-layer play a crucial role in the formation of CDW order. Our findings provide a deeper understanding of the nature of CDW order in the two-dimensional limit.

Min, B.-I.; Suh, K.-S., and Park, K., 2017. Analysis of continuing cesium release to the sea from the Fukushima Dai-ichi nuclear power plant until 2013. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 80–84. Coconut Creek (Florida), ISSN 0749-0208. A two year time-series of 137Cs concentration is presented from the ocean surface observed at sites 20 km radius from Fukushima Daiichi Nuclear Power Plant (FDNPP). The data used in this study were publicly released by the Tokyo Electric Power Company (TEPCO) and are available on websites of TEPCO. Publicly released data on 137Cs radioactivity in seawater near the power plant strongly suggest a continuing release of radionuclides to the sea. The 137Cs radioactivity in the harbour water was substantially higher than that of seawater outside and remained relatively stable after June 2011. The consistent gradient of radioactivity b...

Suh, K.-S.; Kim, S., and Min, B.-I., 2017. Atmospheric dispersion and sea surface deposition of radionuclides by the Fukushima nuclear accident. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 85–88. Coconut Creek (Florida), ISSN 0749-0208. A large amount of radioactive material was released to the atmosphere and to the sea by the Fukushima nuclear accident in 2011. Most of the radioactive materials released into the air were moved to the Pacific Ocean due to the westerly jet stream, and some of them dispersed on land in Japan and were deposited in the area northwest of the Fukushima Daiichi power plant. A lot of radionuclides transported to the Pacific Ocean were deposited on the sea surface by a dry/wet deposition process, seawater and seabed sediments along the coastline of Fukushima Prefecture were contaminated. All of this deposition occurred in the early phase of the...

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A theoretically designed van der Waals ferromagnet Fe4GeTe2 is synthesized and shows the nearly room temperature ferromagnetism., In spintronics, two-dimensional van der Waals crystals constitute a most promising material class for long-distance spin transport or effective spin manipulation at room temperature. To realize all-vdW-material–based spintronic devices, however, vdW materials with itinerant ferromagnetism at room temperature are needed for spin current generation and thereby serve as an effective spin source. We report theoretical design and experimental realization of a iron-based vdW material, Fe4GeTe2, showing a nearly room temperature ferromagnetic order, together with a large magnetization and high conductivity. These properties are well retained even in cleaved crystals down to seven layers, with notable improvement in perpendicular magnetic anisotropy. Our findings highlight Fe4GeTe2 and its nanometer-thick crystals as a promising candidate for spin source operation at nearly room temperature and hold promise to further increase Tc in vdW ferromagnets by theory-guided material discovery.

A typical $f$-electron Kondo lattice system Ce exhibits a well-known isostructural transition, the so-called $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\alpha}$ transition, accompanied by an enormous volume collapse. Most interestingly, we have discovered that a topological phase transition also takes place in elemental Ce, concurrently with the $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\alpha}$ transition. Based on the dynamical mean-field theory approach combined with density functional theory, we have unraveled that the nontrivial topology in $\ensuremath{\alpha}$-Ce is driven by the $f\ensuremath{-}d$ band inversion, which arises from the formation of a coherent $4f$ band around the Fermi level. We captured the formation of the $4f$ quasiparticle band that is responsible for the Lifshitz transition and the nontrivial ${\mathrm{Z}}_{2}$ topology establishment across the phase boundary. This discovery provides a concept of a ``topology switch'' for topological Kondo systems. The ``on'' and ``off'' switching knob in Ce is versatile in a sense that it is controlled by the available pressure ($\ensuremath{\lesssim}1$ GPa) at room temperature.

We demonstrate theoretically that the golden phase of SmS ($g$-SmS), a correlated mixed-valent system, exhibits nontrivial surface states with diverse topology. It turns out that this material is an ideal playground to investigate different band topologies in different surface terminations. We have explored surface states on three different (001), (111), and (110) surface terminations. Topological signature in the (001) surface is not apparent due to a hidden Dirac cone inside the bulk-projected bands. In contrast, the (111) surface shows a clear gapless Dirac cone in the gap region, demonstrating the unambiguous topological Kondo nature of $g$-SmS. Most interestingly, the (110) surface exhibits both topological-insulator-type and topological-crystalline-insulator (TCI)-type surface states simultaneously. Two different types of double Dirac cones, Rashba-type and TCI-type, realized on the (001) and (110) surfaces, respectively, are analyzed with the mirror eigenvalues and mirror Chern numbers obtained from the model-independent \emph{ab initio} band calculations., 4 figures, 1 table

The semimetallic behavior of the so-called ``failed Kondo insulator'' CeNiSn has been ascribed to a nodal line in the Kondo hybridization derived from a particular symmetry of the Ce $4f$ orbitals ground state. Here we investigate the geometry of the CeNiSn conduction band by combined angle-resolved photoemission spectroscopy (ARPES) in the high-temperature regime and Open core generalized gradient approximation plus spin-orbit coupling calculations, in order to determine how the nodal hybridization takes place. We identify the Fermi sheet involved in the semimetallic regime from its locus and its shape, respectively, in agreement with the expected nodal line and with quantum oscillations. We further extrapolate and discuss the low-temperature Fermi surface in terms of the expected nodal hybridization with a localized $f$-level. The obtained hypothetical low-temperature Fermi surface is compatible with the description from quantum oscillations, and with both the highly anisotropic magnetoresistance and the isotropic Nernst effect. This work offers an overview of the conduction band of CeNiSn before hybridization, and it paves the way to a definitive understanding of its low-temperature state. In addition, this work serves as a basis for more challenging low-temperature ARPES measurements.

We have investigated the electronic structures of Ce Kondo systems, CeNiSn, CeRhAs, and CeRhSb, which have attracted recent attention as promising candidates of ``M\"obius Kondo insulators.'' In the conventional density functional theory calculations, all three systems are obtained to be semimetallic, while only CeRhAs opens a full gap in the band calculation incorporating the more elaborate (modified Becke-Jones) exchange-correlation potential. Intriguingly, for all three systems, we have obtained the hourglass-type bulk band crossings around $\mathbf{k}=S$, which produce Dirac nodal-loop structures enclosing S in the [100] Brillouin zone boundary. Such topologically protected hourglass-type band structures arise from the spin-orbit coupling on top of the nonsymmorphic crystal symmetry $(Pnma)$ of these systems. Our finding suggests that Ce Kondo insulators would display temperature $(T)$ -dependent topological phase transitions from a potential M\"obius Kondo insulator at low $T$ to a Dirac nodal-loop semimetal at high $T$.

Excitonic insulator (EI) was proposed in the 1960s as a distinct insulating state originating from pure electronic interaction, but its material realization has been elusive with extremely few material candidates and with only limited evidence such as anomalies in transport properties, band dispersions, or optical transitions. We investigate the real-space electronic states of the low-temperature phase in ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$ with atomic resolution to clearly identify the quasiparticle energy gap together with the strong electron-hole band renormalization using scanning tunneling microscopy and spectroscopy (STS). These results are in good agreement with the EI transition scenario in ${\mathrm{Ta}}_{2}{\mathrm{NiSe}}_{5}$. Our spatially resolved STS data and theoretical calculations reveal further the orbital inversion at band edges, which indicates the exciton condensation close to the Bardeen-Cooper-Schrieffer regime.

A radiological emergency preparedness system in Korea has been developed to predict the behavior of radioactive material released into the environment and estimate the dose assessment for humans in case of a nuclear accident in neighboring countries, including Korea. The system is composed of atmospheric dispersion, marine dispersion, and dose assessment models, along with a graphic user interface module. It can evaluate the dispersion patterns of radionuclides in the air and ocean, and the short-term and long-term radiological effects of a nuclear accident on humans. It has been constructed on the web to allow users to access it easily and simply through an intrinsic IP address, username, and password. The atmospheric dispersion, marine dispersion, and dose assessment models have already been validated by model-to-model comparisons and measurements from the Chernobyl and Fukushima accidents. The described system is now in operation for government and nuclear-related organizations in Korea in case of a nuclear accident.

인접 국가인 일본의 후쿠시마 원전에서 극한 자연재해로 인한 중대사고가 발생하면서, 국내에서 중대사고 및 확률론적 안전성 평가 (PSA, Probabilistic Safety Assessment)에 대한 중요성이 재인식되었다. 국내에서는 원전의 소외결말을 평가하는 3단계 PSA에 대한 연구개발이 최근까지 거의 이루어지지 않았다. 본 논문에서는 국외 3단계 PSA 전산코드 중, 미국의MACCS2 (MELCORE Accident Consequence Code System 2), 유럽의 COSYMA (COde SYstem from Maria) 그리고 일본의OSCAAR (Off-Site Consequence Analysis code for Atmospheric Releases in reactor accidents)에 대한 간략한 분석과 미국의 MACCS2에 대한 단점 및 한계점 분석을 수행하였다. 국내·외 전문가들에 의해 공통적으로 지적되어 온 MACCS2의 한계점은 다수호기사고와 사용후핵연료 저장조로부터의 방출 모사의 불가능, 그리고 대기확산모델을 단순 가우시안 플륨모델을 기본으로 한다는 것이며, 이중 일부는 MACCS2업데이트 버전을 통해 개선되어 왔다. Food chain 모델의 모사의 제한, 해양 및 수계 확산모델의 부재, 제한된 범위의 경제영향평가 등 또한 개선되어야 할 사항이다. 기술보고의 결과는 국내 3단계 PSA 관련 기술 개발을 위한 기초자료로 활용될 수 있을 것으로 기대된다.

A Lagrangian model which simulates the dispersion of 137Cs in the North Atlantic has been developed. The model includes water/sediment interactions. It has been tested comparing calculated and measured 137Cs concentrations in water and sediments of the European Shelf resulting after the releases from the nuclear fuel reprocessing plants of Sellafield and La Hague. Some additional numerical experiments have been carried out. First, the redissolution of 137Cs from contaminated sediments after the reduction in releases from the reprocessing plants has been studied. This allowed to calculate effective half-lives of 137Cs in several sub-basins. Later, potential leakage of 137Cs from dumped nuclear wastes in several locations of the Atlantic has been investigated. Even in worst-case scenarios, these leakages should not lead to any radiological implications.

Quasi-two-dimensional (2D) metallicity in a ternary layered transition metal chalcogenide of single crystalline Ti2PTe2 is studied by transport prop-erties measurements and electronic structure analyses. The logarithmic dependence of resistivity in the low temperature region appears as a charac-teristic feature of the quasi-2D transport in a weakly disordered metallic system. A large Sommerfeld coefficient value of 6.94 mJ/mol·K2 and negative temperature dependence of the Hall coefficient indicate that electron-electron interaction is dominant in a phase-breaking mechanism originating from bipolar behavior. Angle-resolved photoemission spectroscopy combined with theoretical calculations successfully proves that quasi-2D elec-tron pockets encompassing a small three-dimensional hole pocket mainly determine the quasi-2D metallic transport properties. We also adopt an orbital character calculation to verify that Ti character is dominant in valence bands, revealing that 2D Ti-networks form quasi-2D conducting ...

A three-dimensional trajectory model has been developed to estimate the emission area of radioisotopes measured at the international monitoring stations of the Comprehensive Nuclear-Ban Treaty Organization (CTBTO). Calculated backward trajectories were compared with measurements of the European Tracer Experiment (ETEX). These trajectories generally moved toward the original release point and detected within the release duration of the tracer experiment. However, the comparative results had uncertainties with regard to starting time and the height of the tracer in the backward trajectory model. An atmospheric dispersion model based on the Fields of Regards (FOR) technique was used to reduce the uncertainties of trajectory model and to improve the accuracy of detective technology. The simulated results generated by the trajectory and atmospheric dispersion models together were agreed better with the measurements compared to those obtained from the trajectory model alone.

In this study, the dispersion process of pollutant substances in a port under wave and current environments was evaluated by a hydraulic experiment. Once the contaminants washed ashore into the port of Wolseong nuclear power plant, transport processes of pollutants were investigated by tracking the tracer according to the variations of experimental condition through a hydraulic experiment. Several hydraulic experiments were performed to analyze the pollutant discharge rate of the surface coming from the different coastal environments. From the hydraulic experiment results, the tracer concentration decreased exponentially. These results suggested that, after the tracer was transported to the open sea, a different gradient was shown under different conditions. For the case of a diluted condition, the half-life of flow rate was 2.70, 10.40, and 26.39 days for 30, 20 and 10 rpm in the left-side, respectively. The decrease of the tracer concentration under conditions of 30 rpm was much faster than that under conditions of 10 rpm. For the wave condition, the half-life of flow rate was 4.59 and 15.35 days for the right and left side of the port in a hydraulic scale prototype, respectively.

Background: It is necessary to consider the overall countermeasure for analysis of nuclear activities according to the increase of the nuclear facilities like nuclear power and reprocessing plants in the neighboring countries including China, Taiwan, North Korea, Japan and South Korea. South Korea and comprehensive nuclear-test-ban treaty organization (CTBTO) are now operating the monitoring instruments to detect radionuclides released into the air. It is important to estimate the origin of radionuclides measured using the detection technology as well as the monitoring analysis in aspects of investigation and security of the nuclear activities in neighboring countries. Materials and methods: A three-dimensional forward/backward trajectory model has been developed to estimate the origin of radionuclides for a covert nuclear activity. The developed trajectory model was composed of forward and backward modules to track the particle positions using finite difference method. Results and discussion: A three-dimensional trajectory model was validated using the measured data at Chernobyl accident. The calculated results showed a good agreement by using the high concentration measurements and the locations where was near a release point. The three-dimensional trajectory model had some uncertainty according to the release time, release height and time interval of the trajectory at each release points. An atmospheric dispersion model called long-range accident dose assessment system (LADAS), based on the fields of regards (FOR) technique, was applied to reduce the uncertainties of the trajectory model and to improve the detective technology for estimating the radioisotopes emission area. Conclusion: The detective technology developed in this study can evaluate in release area and origin for covert nuclear activities based on measured radioisotopes at monitoring stations, and it might play critical tool to improve the ability of the nuclear safety field.

The interplay between spin states and metallization in compressed CoCl2 is investigated by combining diffraction, resistivity and spectroscopy techniques under high-pressure conditions and ab-initio calculations. A pressure-induced metallization along with a Co2+ high-spin (S = 3/2) to low-spin (S = 1/2) crossover transition is observed at high pressure near 70 GPa. This metallization process, which is associated with the p-d charge-transfer band gap closure, maintains the localization of 3d electrons around Co2+, demonstrating that metallization and localized Co2+ -3d low-spin magnetism can coexist prior to the full 3d-electron delocalization (Mott-Hubbard d-d breakdown) at pressures greater than 180 GPa.

Author(s): Ryu, Hyejin; Chen, Yi; Kim, Heejung; Tsai, Hsin-Zon; Tang, Shujie; Jiang, Juan; Liou, Franklin; Kahn, Salman; Jia, Caihong; Omrani, Arash A; Shim, Ji Hoon; Hussain, Zahid; Shen, Zhi-Xun; Kim, Kyoo; Min, Byung Il; Hwang, Choongyu; Crommie, Michael F; Mo, Sung-Kwan | Abstract: Corrections to the original paper are the following: Page 692, line 6, left column. "centered at Λ (-0.5 eV l E l 0)" should be "centered at Λ (E l -1 eV)". Page 692, line 2, right column. "E ∼ -0.5 eV" should be "V ∼ +0.6 V".

An interesting van der Waals material, Ta2NiSe5 has been known one of strong excitonic insulator candidates since it has very small or zero bandgap and can have a strong exciton binding energy because of its quasi-one-dimensional crystal structure. Here we investigate a single crystal Ta2NiSe5 using optical spectroscopy. Ta2NiSe5 has quasi-one-dimensional chains along the a-axis. We have obtained anisotropic optical properties of a single crystal Ta2NiSe5 along the a- and c-axes. The measured a- and c-axis optical conductivities exhibit large anisotropic electronic and phononic properties. With regard to the a-axis optical conductivity, a sharp peak near 3050 cm−1 at 9 K, with a well-defined optical gap ($${{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}\,{\boldsymbol{\simeq }}$$ΔopEI≃ 1800 cm−1) and a strong temperature-dependence, is observed. With an increase in temperature, this peak broadens and the optical energy gap closes around ∼325 K ($${{\boldsymbol{T}}}_{{\boldsymbol{c}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}$$TcEI). The spectral weight redistribution with respect to the frequency and temperature indicates that the normalized optical energy gap $$({{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}({\boldsymbol{T}})/\,{{\boldsymbol{\Delta }}}_{{\boldsymbol{o}}{\boldsymbol{p}}}^{{\boldsymbol{E}}{\boldsymbol{I}}}{\bf{(0)}})$$(ΔopEI(T)/ΔopEI(0)) is $${\bf{1}}{\boldsymbol{-}}{({\boldsymbol{T}}/{{\boldsymbol{T}}}_{{\boldsymbol{c}}}^{{\boldsymbol{E}}{\boldsymbol{I}}})}^{{\bf{2}}}$$1−(T/TcEI)2. The temperature-dependent superfluid plasma frequency of the excitonic condensation in Ta2NiSe5 has been determined from measured optical data. Our study may pave new avenues in the future research on excitonic insulators.

The interaction between a magnetic impurity, such as cerium (Ce) atom, and surrounding electrons has been one of the core problems in understanding many-body interaction in solid and its relation to magnetism. Kondo effect, the formation of a new resonant ground state with quenched magnetic moment, provides a general framework to describe many-body interaction in the presence of magnetic impurity. In this Letter, a combined study of angle-resolved photoemission (ARPES) and dynamic mean-field theory (DMFT) on Ce-intercalated graphene shows that Ce-induced localized states near Fermi energy, $E_{\rm F}$, hybridized with the graphene $\pi$ band, exhibit gradual increase in spectral weight upon decreasing temperature. The observed temperature dependence follows the expectations from the Kondo picture in the weak coupling limit. Our results provide a novel insight how Kondo physics emerges in the sea of two-dimensional Dirac electrons., Comment: 17 pages, 4 figures

Introduction Non-small-cell lung cancer (NSCLC) is one of the most common cancers and the leading cause of cancer-related deaths. In East Asia, traditional herbal medicine (THM) is commonly used in clinical settings for the treatment of cancer. Therefore, the aim of the present review was to systematically assess the efficacy of THM with varied components for the treatment of NSCLC. Methods This study identified randomized controlled trials (RCTs) that evaluated the effectiveness of combined THM and chemotherapy (CTx) in searches of English, Chinese, Japanese, and Korean language databases. Results This meta-analysis systematically reviewed 27 RCTs involving 2382 patients and found that THM improved the quality of life (QoL) significantly for patients with NSCLC. Improvement in QoL was seen in 19 studies using the Karnofsky Performance Status score, three studies using the Eastern Cooperative Oncology Group scale, three studies using the Functional Assessment of Cancer Therapy-Lung scale, and six studies using the European Organization for Research and Treatment of Cancer. Conclusions The pooled results of this systematic review and meta-analysis suggest that THM significantly improved the QoL for patients with NSCLC.

Summary Objectives To assess the effectiveness of traditional herbal medicine (THM) as adjunctive therapy for breast cancer as evidenced by randomized controlled trials (RCTs). Methods Five electronic English and Chinese databases were systematically searched up to February, 2014. All RCTs involving THM in combination with conventional cancer therapy for breast cancer were included. Results Eight RCTs involving 798 breast cancer patients were systematically reviewed. Three studies reported a significant difference in the improvement of quality of life (QOL) compared to the control group. Two studies reported an increase in the white blood cell count after treatment. Data on hot flashes and sleep quality were evaluated. However, no significant differences in immediate tumor response were observed. Conclusion THM combined with conventional therapy in the treatment of breast cancer is efficacious in improving QOL and in decreasing the number of hot flashes per day. More research and well-designed, rigorous, large clinical trials are necessary to further address these issues.

We present the electronic characterization of single-layer 1H-TaSe

A quantitative evaluation of the fate of (129)I, released from the European reprocessing plants of Sellafield (UK) and La Hague (France), has been made by means of a Lagrangian dispersion model. Transport of radionuclides to the Arctic Ocean has been determined. Thus, 5.1 and 16.6 TBq of (129)I have been introduced in the Arctic from Sellafield and La Hague respectively from 1966 to 2012. These figures represent, respectively, 48% and 55% of the cumulative discharge to that time. Inventories in the North Atlantic, including shelf seas, are 4.4 and 13.8 TBq coming from Sellafield and La Hague respectively. These figures are significantly different from previous estimations based on field data. The distribution of these inventories among several shelf seas and regions has been evaluated as well. Mean ages of tracers have been finally obtained, making use of the age-averaging hypothesis. It has been found that mean ages for Sellafield releases are about 3.5 year larger than for La Hague releases.