Superconductivity in Pristine 2H_{a}-MoS_{2} at Ultrahigh Pressure.

As a follow-up of our previous work on pressure-induced metallization of the 2H_{c}-MoS_{2} [Chi et al., Phys. Rev. Lett. 113, 036802 (2014)PRLTAO0031-900710.1103/PhysRevLett.113.036802], here we extend pressure beyond the megabar range to seek after superconductivity via electrical transport measurements. We found that superconductivity emerges in the 2H_{a}-MoS_{2} with an onset critical temperature T_{c} of ca. 3 K at ca. 90 GPa. Upon further increasing the pressure, T_{c} is rapidly enhanced beyond 10 K and stabilized at ca. 12 K over a wide pressure range up to 220 GPa. Synchrotron x-ray diffraction measurements evidenced no further structural phase transition, decomposition, and amorphization up to 155 GPa, implying an intrinsic superconductivity in the 2H_{a}-MoS_{2}. DFT calculations suggest that the emergence of pressure-induced superconductivity is intimately linked to the emergence of a new flat Fermi pocket in the electronic structure. Our finding represents an alternative strategy for achieving superconductivity in 2H-MoS_{2} in addition to chemical intercalation and electrostatic gating.

Magnetic Resonance Imaging of Internal Jugular Veins in Multiple Sclerosis: Interobserver Agreement and Comparison with Doppler Ultrasound Examination.

BACKGROUND: Doppler ultrasound (US) has been widely used to evaluate the cervical venous system of multiple sclerosis patients according to the hypothesis of chronic cerebrospinal venous insufficiency with contradictory results. Venous anatomy and pathology can be examined with less operator-dependent magnetic resonance imaging (MRI). Our aim is to assess the interobserver agreement in measuring internal jugular vein (IJV) cross-sectional area (CSA) in MR images and to explore the agreement between US and MRI in the detection of calibers of ≤0.3 cm2 in the IJV CSA in the prospective study. METHODS: Thirty-seven multiple sclerosis patients underwent MRI of the cervical venous system. Two independent neuroradiologists measured the CSA of IJV at the mid-thyroid level. Furthermore, the time from contrast enhancement of common carotid arteries to that of each IJV (transit time in seconds) was assessed, and recorded whether IJV or the vertebral plexus visualized first during the contrast passage. US examination had been performed earlier. RESULTS: Interobserver agreement for assessing IJV CSA in MR images was substantial: the measurements differed >0.5 cm2 between the examiners in only 5 IJVs (7%), Cohen's kappa 0.79. Transit times from common carotid artery to IJV varied between 5.1 and 14.1 sec. Fifteen patients had left-to-right asymmetry in the speed of IJV contrast filling. IJV CSA ≤ 0.3 cm2 was found in 51 IJVs on the basis of US. Ten of these IJVs (19.6%) showed IJV CSA ≤ 0.3 cm2 also in MRI. All IJVs defined as CSA ≤ 0.3 cm2 in MRI met this caliber criterion also in US. CONCLUSIONS: Interobserver agreement at the thyroid level of the IJV was good at MRI measurements. The US defines more IJVs as narrow (CSA ≤ 0.3 cm2) than MRI. The US measurements for IJV CSA are not comparable with these methods. The US seems too sensitive in terms of finding venous stenosis.

Superconductivity in room-temperature stable electride and high-pressure phases of alkali metals.

S-band metals such as alkali and alkaline earth metals do not undergo a superconducting transition (SCT) at ambient pressure, but their high-pressure phases do. By contrast, room-temperature stable electride [Ca(24)Al(28)O(64)](4+)⋅4e(-) (C12A7:e(-)) in which anionic electrons in the crystallographic sub-nanometer-size cages have high s-character exhibits SCT at 0.2-0.4 K at ambient pressure. In this paper, we report that crystal and electronic structures of C12A7:e(-) are close to those of the high-pressure superconducting phase of alkali and alkaline earth metals and the SCT of both materials is induced when electron nature at Fermi energy (EF) switches from s- to sd-hybridized state.

Pressure-induced metallization of molybdenum disulfide.

X-ray diffraction, Raman spectroscopy, and electrical conductivity measurements of molybdenum disulfide MoS(2) are performed at pressures up to 81 GPa in diamond anvil cells. Above 20 GPa, we find discontinuous changes in Raman spectra and x-ray diffraction patterns which provide evidence for isostructural phase transition from 2H(c) to 2H(a) modification through layer sliding previously predicted theoretically. This first-order transition, which is completed around 40 GPa, is characterized by a collapse in the c-lattice parameter and volume and also by changes in interlayer bonding. After the phase transition completion, MoS(2) becomes metallic. The reversibility of the phase transition is identified from all these techniques.

Popliteal vein entrapment syndrome associated with an accessory slip of the lateral head of the gastrocnemius muscle.

Popliteal vein entrapment syndrome (PVES) is a rare subtype of popliteal entrapment syndrome that leads to symptoms of chronic venous stasis. We report a case of isolated PVES in a young patient associated with an accessory slip of the lateral head of the gastrocnemius muscle. The patient underwent resection of the anomalous muscle, and the symptoms were relieved postoperatively. PVES should be considered in young patients with unexplained symptoms or signs of venous stasis. Surgical resection of the causative lesion compressing the popliteal vein is indicated for selected patients.

Buerger Disease: Pathological Changes in Elderly Patients.

Reports of vascular lesion changes in elderly Buerger disease patients are rare. Patients are expected to continue to have typical Buerger disease even after the age of 50. However, after 50, when patients suffer from atherosclerotic risk factors, such as hypertension, diabetes mellitus, or hyperlipidemia, what kind of changes will occur? We will report on 3 cases of hypertension, diabetes mellitus, or hyper lipidemia after or around 50 years of age. As a result, atherosclerosis was present in the iliac or aortic regions in the remaining thromboangiitis lesions below the groin area. (This is secondary publication from the J Jpn Coll Angiol 2021; 61: 107-113.).

Structural phase transitions and superconductivity in Fe(1+delta)Se0.57Te0.43 at ambient and elevated pressures.

The ternary iron chalcogenide, Fe(1.03)Se(0.57)Te(0.43) is a member of the recently discovered family of Fe-based superconductors with an ambient pressure T(c) of 13.9 K and a simple structure comprising layers of edge-sharing distorted Fe(Se/Te)(4) tetrahedra separated by a van der Waals gap. Here we study the relationship between its structural and electronic responses to the application of pressure. T(c) depends sensitively on applied pressure attaining a broad maximum of 23.3 K at approximately 3 GPa. Further compression to 12 GPa leads to a metallic but nonsuperconducting ground state. High-resolution synchrotron X-ray diffraction shows that the superconducting phase is metrically orthorhombic at ambient pressure but pressurization to approximately 3 GPa leads to a structural transformation to a more distorted structure with monoclinic symmetry. The exact coincidence of the crystal symmetry crossover pressure with that at which T(c) is maximum reveals an intimate link between crystal and electronic structures of the iron chalcogenide superconductors.

Preparation and characterization of a new graphite superconductor: Ca0.5Sr0.5C6.

We have produced a superconducting binary-elements intercalated graphite, CaxSr1-xCy, with the intercalation of Sr and Ca in highly-oriented pyrolytic graphite; the superconducting transition temperature, T c, was ~3 K. The superconducting CaxSr1-xCy sample was fabricated with the nominal x value of 0.8, i.e., Ca0.8Sr0.2Cy. Energy dispersive X-ray (EDX) spectroscopy provided the stoichiometry of Ca0.5(2)Sr0.5(2)Cy for this sample, and the X-ray powder diffraction (XRD) pattern showed that Ca0.5(2)Sr0.5(2)Cy took the SrC6-type hexagonal-structure rather than CaC6-type rhombohedral-structure. Consequently, the chemical formula of CaxSr1-xCy sample could be expressed as 'Ca0.5(2)Sr0.5(2)C6'. The XRD pattern of Ca0.5(2)Sr0.5(2)C6 was measured at 0-31 GPa, showing that the lattice shrank monotonically with increasing pressure up to 8.6 GPa, with the structural phase transition occurring above 8.6 GPa. The pressure dependence of T c was determined from the DC magnetic susceptibility and resistance up to 15 GPa, which exhibited a positive pressure dependence of T c up to 8.3 GPa, as in YbC6, SrC6, KC8, CaC6 and Ca0.6K0.4C8. The further application of pressure caused the rapid decrease of T c. In this study, the fabrication and superconducting properties of new binary-elements intercalated graphite, CaxSr1-xCy, are fully investigated, and suitable combinations of elements are suggested for binary-elements intercalated graphite.

Emergence of superconductivity in (NH3)yMxMoSe2 (M: Li, Na and K).

We report syntheses of new superconducting metal-doped MoSe2 materials (MxMoSe2). The superconducting MxMoSe2 samples were prepared using a liquid NH3 technique, and can be represented as '(NH3)yMxMoSe2'. The Tcs of these materials were approximately 5.0 K, independent of x and the specific metal atom. X-ray diffraction patterns of (NH3)yNaxMoSe2 were recorded using polycrystalline powders. An increase in lattice constant c showed that the Na atom was intercalated between MoSe2 layers. The x-independence of c was observed in (NH3)yNaxMoSe2, indicating the formation of a stoichiometric compound in the entire x range, which is consistent with the x-independence of Tc. A metallic edge of the Fermi level was observed in the photoemission spectrum at 30 K, demonstrating its metallic character in the normal state. Doping of MoSe2 with Li and K also yielded superconductivity. Thus, MoSe2 is a promising material for designing new superconductors, as are other transition metal dichalcogenides.

Origin of Pressure-induced Superconducting Phase in KxFe2-ySe2 studied by Synchrotron X-ray Diffraction and Spectroscopy.

Pressure dependence of the electronic and crystal structures of KxFe2-ySe2, which has pressure-induced two superconducting domes of SC I and SC II, was investigated by x-ray emission spectroscopy and diffraction. X-ray diffraction data show that compressibility along the c-axis changes around 12 GPa, where a new superconducting phase of SC II appears. This suggests a possible tetragonal to collapsed tetragonal phase transition. X-ray emission spectroscopy data also shows the change in the electronic structure around 12 GPa. These results can be explained by the scenario that the two SC domes under pressure originate from the change of Fermi surface topology. Our results here show the pronounced increase of the density of states near the Fermi surface under pressure with a structural phase transition, which can help address our fundamental understanding for the appearance of the SC II phase.

Emergence of double-dome superconductivity in ammoniated metal-doped FeSe.

The pressure dependence of the superconducting transition temperature (Tc) and unit cell metrics of tetragonal (NH3)yCs0.4FeSe were investigated in high pressures up to 41 GPa. The Tc decreases with increasing pressure up to 13 GPa, which can be clearly correlated with the pressure dependence of c (or FeSe layer spacing). The Tc vs. c plot is compared with those of various (NH3)yMxFeSe (M: metal atoms) materials exhibiting different Tc and c, showing that the Tc is universally related to c. This behaviour means that a decrease in two-dimensionality lowers the Tc. No superconductivity was observed down to 4.3 K in (NH3)yCs0.4FeSe at 11 and 13 GPa. Surprisingly, superconductivity re-appeared rapidly above 13 GPa, with the Tc reaching 49 K at 21 GPa. The appearance of a new superconducting phase is not accompanied by a structural transition, as evidenced by pressure-dependent XRD. Furthermore, Tc slowly decreased with increasing pressure above 21 GPa, and at 41 GPa superconductivity disappeared entirely at temperatures above 4.9 K. The observation of a double-dome superconducting phase may provide a hint for pursuing the superconducting coupling-mechanism of ammoniated/non-ammoniated metal-doped FeSe.

The effect of short saphenous vein stripping in patients with deep venous reflux.

OBJECT: We assessed whether or not deep venous reflux (DVR) improved after short saphenous vein (SSV) stripping was performed in patients with SSV reflux and DVR. MATERIALS AND METHODS: Sixty-eight patients with SSV reflux who underwent SSV striping every Monday between 2008 and 2011 at Ryougoku Ashino Clinic were enrolled in this study. Forty-six of the 68 patients were selected for the analysis because they underwent duplex ultrasound examinations before and after the operation. The DVR was classified into four categories: type 0, no reflux; type I, reflux in popliteal vein; type II, reflux from popliteal vein to the middle of the superficial femoral vein (SFV) and type III, reflux from the popliteal vein to the SFV. RESULTS: There were 23, 13, 2 and 8 patients with type 0, I, II, III before operation, respectively. There were 33, 8, 1, 4 patients with type 0, I, II, III after operation, respectively. There were no changes in 29 patients, improvement in 15 and new DVR in three (type 0 to I). CONCLUSION: SSV stripping is feasible in patients with DVR and the DVR might not be deteriorated even though that is performed.

Clinical Study of Phlebitis Migrans and Incompetence of the Leg's Superficial Vein in Buerger Disease.

Three of four (75%) vein biopsy samples from four patients (all male, mean onset: age 33.0, mean biopsy: age 59.7) of chronic phase phlebitis migrans showed positive periodontal bacteria DNA under the PCR (polymerase chain reaction) method. Of the 24 cases of Buerger disease (22 males, 2 females, mean onset: age 31.9, mean examination: age 62.6) that were investigated in our vascular laboratory, 65% of the patients suffered from moderate to severe varicose veins. Eight cases had a history of phlebitis migrans and three had an active ulcer or uncontrollable erosion in the foot. The rate of incidence was significantly higher than that of the well-matched control group. Other findings included one instance of deep vein thrombosis, and one instance of deep vein reflux. We could suggest that some intractable ulcer or erosion cases of Buerger disease may be complicated by superficial vein incompetence or other deep vein insufficiency. We also we need to check Buerger disease patients with duplex for vein reflux and other insufficiencies. Treatment of the varicose veins (including elastic stockings) was effective for all of the patients. (English Translation of Jpn J Phlebology 2011; 22: 25-31.).

Cryogenic implementation of charging diamond anvil cells with H2 and D2.

A cryogenic loading system for introducing H(2) and D(2) into the diamond anvil cell has been designed and constructed. The integration of pressure loading mechanism, ruby fluorescence spectrometer, and microscope camera allows for in situ tuning and calibrating the pressure. The performance of the system has been demonstrated by successful synthesis of hydride and deuteride of transition metal and rare earth metal. Our cryogenic methodology features facile start-over of loading and in situ electrical resistance measurement of as-synthesized sample.