Charge order with unusual star-of-David lattice in monolayer NbTe2

Interplay between fermiology and electron correlation is crucial for realizing exotic quantum phases. Transition-metal dichalcogenide (TMD) 1T-TaS2 has sparked a tremendous attention owing to its unique Mott-insulating phase coexisting with the charge-density wave (CDW). However, how the fermiology and electron correlation are associated with such properties has yet to be claried. Here we demonstrate that monolayer 1T-NbTe2 is a new class of two-dimensional TMD which has the star-of-David lattice similarly to bulk TaS2 and isostructural monolayer NbSe2, but exhibits a metallic ground state with an unusual lattice periodicity root19xroot19 characterized by the sparsely occupied star-of-David lattice. By using angle-resolved photoemission and scanning-tunneling spectroscopies in combination with first-principles band-structure calculations, we found that the hidden Fermi-surface nesting and associated CDW formation are a primary cause to realize this unique correlated metallic state with no signature of Mott gap. The present result points to a vital role of underlying fermiology to characterize the Mott phase of TMDs.Comment: To be published in Physical Review

Surface-termination-dependent electronic states in kagome superconductors AV3Sb5 (A = K, Rb, Cs) studied by micro-ARPES

Recently discovered kagome superconductors AV3Sb5 (A = K, Rb, Cs) exhibit exotic bulk and surface physical properties such as charge-density wave (CDW) and chirality, whereas their origins remain unresolved. By using micro-focused angle-resolved photoemission spectroscopy, we discovered that AV3Sb5 commonly exhibits two distinct polar surfaces depending on the termination; electron- and hole-doped ones for the A- and Sb-termination, respectively. We observed that the kagome-derived band shows a clear splitting in the A-terminated surface while it is absent in the Sb-terminated counterpart, indicative of the polarity-dependent CDW at the surface. Close comparison of the band-dependent splitting reveals that the three-dimensional CDW structure of the K-terminated surface is different from that of the Rb- or Cs-terminated surface, suggesting the diversity of the CDW ground state. These results provide important insight into the origin of CDW in kagome superconductors AV3Sb5.Comment: 10 pages, 8 figure

Characteristics and environmental conditions of quasi-stationary convective clusters during the warm season in Japan

The characteristics and environmental properties of warm-season quasi-stationary convective clusters (QSCCs) in Japan were statistically investigated using operational weather radar and upper-air sounding data from May to October during 2005-2012. The characteristics of the environmental conditions for the development of QSCCs were described through a comparison with those for no-rain cases. We identified 4133 QSCCs over the Japanese major islands. By compiling numerous QSCC samples, the horizontal scales of QSCCs with a circular shape are about 20 km on average with a maximum of 72 km, indicating that warm-season QSCCs in Japan are meso-β-scale phenomena. The analyses of the environmental conditions for the QSCC and no-rain cases showed that the amount of moisture in the lower layer controls the stability condition for the development of the QSCCs, and that the magnitudes of the wind shear and the helicity in the lower troposphere distinguish the kinematic environments for the development of the QSCCs. An increase in the middle-level moisture leads to a larger amount of precipitable water vapour in the QSCC environments, suggesting that atmospheric moistening before the development stage of convection plays an important role in the development of the QSCCs. Additionally, the precipitation intensity has a higher correlation with the convective instability, whereas the precipitation area correlates with the shear intensity. A comparison between slower- and faster-moving CCs indicated that the precipitation intensity of the slower-moving CCs is stronger. This feature is related to a higher convective instability for the slower-moving ones

A 1998-2013 climatology of Kyushu, Japan: seasonal variations of stability and rainfall

The seasonal variation of the atmospheric structure, vertical shear, stability, and rainfall distribution over the island of Kyushu, southern Japan, is studied using 16 years of observational data, from 1998 to 2013. Over 20 000 twice-daily rawinsonde observations from the cities of Kagoshima (southern Kyushu) and Fukuoka (northern Kyushu) are utilized along with daily precipitation data from 120 Japan Meteorological Agency stations located across the island. Understanding the local atmospheric circulation and climatological behaviour of the island is important both locally due to the island's large population and regionally, due to its position in relation to the tracks of typhoons generated annually over the Pacific ocean and make landfall here, the rainy season associated with the Asian monsoon, and the large number of active volcanoes located on or near the island, emitting volcanic gases and ash on a daily basis. Using a categorisation based on convective available potential energy and precipitable water, three sounding categories are distinguished, described using the origins of the air masses involved, as seen from trajectory modelling: continental (dry), oceanic (moist/unstable), and mixed (moist/stable). Mean soundings for each category are examined, along with information on their annual and seasonal variability. Each sounding category is linked with a rainfall response: low amounts of rainfall, heavy convective rainfall, and heavy, non-convective rainfall, respectively. Despite the large difference in the potential for heavy rainfall rates, average daily rainfall rate is similar for the two moist categories, but peak rainfall rates for convective rainfall are twice as large as those for non-convective. Despite the simplicity of the criteria, the three sounding categories are statistically robust and exhibit a relatively small amount of variability. The monthly combination of the sounding categories is shown to be a deciding factor in the seasonal variation of the atmospheric circulation, weather, and precipitation over the island

[18F]-BMS-747158-02PET imaging for evaluating hepatic mitochondrial complex 1dysfunction in a mouse model of non-alcoholic fatty liver disease

Abstract Background Mitochondrial dysfunction is one of the main causes of non-alcohol fatty liver disease (NAFLD). [18F]-BMS-747158-02 (18F-BMS) which was originally developed as a myocardial perfusion imaging agent was reported to bind mitochondrial complex-1 (MC-1). The aim of this study was to investigate the potential use of 18F-BMS for evaluating hepatic MC-1 activity in mice fed a methionine- and choline-deficient (MCD) diet. Male C57BL/6J mice were fed a MCD diet for up to 2 weeks. PET scans with 18F-BMS were performed after 1 and 2 weeks of the MCD diet. 18F-BMS was intravenously injected into mice, and the uptake (standardized uptake value (SUV)) in the liver was determined. The binding specificity for MC-1 was assessed by pre-administration of rotenone, a specific MC-1 inhibitor. Hepatic MC-1 activity was measured using liver homogenates generated after each positron emission tomography (PET) scan. Blood biochemistry and histopathology were also assessed. Results In control mice, hepatic 18F-BMS uptake was significantly inhibited by the pre-injection of rotenone. The uptake of 18F-BMS was significantly decreased after 2 weeks of the MCD diet. The SUV at 30–60 min was well correlated with hepatic MC-1 activity (r = 0.73, p < 0.05). Increases in plasma ALT and AST levels were also noted at 1 and 2 weeks. Mild hepatic steatosis with or without minimal inflammation was histopathologically observed at 1 and 2 weeks in mice liver on the MCD diet. However, inflammation was observed only at 2 weeks in mice on the MCD diet. Conclusions The present study demonstrated that 18F-BMS is a potential PET probe for quantitative imaging of hepatic MC-1 activity and its mitochondrial dysfunction induced by steatosis and inflammation, such as in NAFLD

Carrier Injection and Manipulation of Charge-Density Wave in Kagome Superconductor CsV3Sb5

Kagome metals AV3Sb5 (A = K, Rb, and Cs) exhibit a unique superconducting ground state coexisting with charge-density wave (CDW), whereas how these characteristics are affected by carrier doping remains unexplored because of the lack of an efficient carrier-doping method. Here we report successful electron doping to CsV3Sb5 by Cs dosing, as visualized by angle-resolved photoemission spectroscopy. We found that the electron doping with Cs dosing proceeds in an orbital-selective way, as characterized by a marked increase in electron filling of the Sb 5pz and V 3dxz/yz bands as opposed to relatively insensitive nature of the V 3dxy/x2-y2 bands. By monitoring the temperature evolution of the CDW gap around the M point, we found that the CDW can be completely killed by Cs dosing while keeping the saddle point with the V 3dxy/x2-y2 character almost pinned at the Fermi level. The present result suggests a crucial role of multi-orbital effect to the occurrence of CDW, and provides an important step toward manipulating the CDW and superconductivity in AV3Sb5.Comment: 7 pages, 3 figure

Preliminary results of the TH99 geological and geophysical survey in the Cooperation Sea and Prydz Bay area

Geophysical and geological surveys were carried out in the 1999-2000 austral summer season for the TH99 cruise aboard the R/V Hakurei-maru. The survey includes the abyssal basin and the continental rise area of the Cooperation Sea (CS) and Prydz Bay (PB), offshore of Mac Robertson Land and Princess Elizabeth Land, Antarctica. In the northern abyssal plain of the CS, a mantle-like sequence (G) appears at a depth of 10 s two-way travel time (TWT), or approximately 13 km. The sequence disappears south of 64°S, in the southern part of the CS. These observations suggest that the southern part of the CS and PB is underlain by intermediate type crust that is characteristic of oceanic and continental material. The deep structure of most of the PB continental shelf is not clear due to strong seafloor multiples. More than 7 km of thick sedimentary sequences in the northwest area of PB are confirmed by the MCS survey. Very thick sedimentary sequences, interpreted as prerift, rift and drift sediment can be observed under thick pelagic sediment. Geological samples, which were recovered in the CS and PB, offer important evidence on the recent history of drift sediments caused by iceberg floes. Two cores reached 0.78 Ma (Bruhnes-Matsuyama (B-M) boundary) in magneto-stratigraphic measurements, and they gave distinct age determinations for recent sediments