Temperature dependent local inhomogeneity and magnetic moments of (Li1-xFex)OHFeSe superconductors.

We have combined the extended X-ray absorption fine structure (EXAFS) and X-ray emission spectroscopy (XES) to investigate the local structure and the local iron magnetic moments of (Li1-xFex)OHFeSe (x∼0.2) superconductors. The local structure, studied by Fe K-edge EXAFS measurements, is found to be inhomogeneous that is characterized by different Fe-Se bond lengths. The inhomogeneous phase exhibits a peculiar temperature dependence with lattice anomalies in the local structural parameters at the critical temperature Tc (36 K) and at the spin density wave (SDW) transition temperature TN (130 K). Fe Kß XES shows iron to be in a low spin state with the local Fe magnetic moment evolving anomalously as a function of temperature. Apart from a quantitative measurement of the local structure of (Li1-xFex)OHFeSe, providing direct evidence of nanoscale inhomogeneity, the results provide further evidence of the vital role that the coupled electronic, lattice and magnetic degrees of freedom play in the iron-based superconductors.

The local structure of self-doped BiS2-based layered systems as a function of temperature.

We have studied the local structure of layered Eu(La,Ce)FBiS2 compounds by Bi L3-edge extended X-ray absorption fine structure (EXAFS) measurements as a function of temperature. We find that the BiS2 sub-lattice is largely distorted in EuFBiS2, characterized by two different in-plane Bi-S1 distances. The distortion is marginally affected by partial substitutions of Ce (Eu0.5Ce0.5FBiS2) and La (Eu0.5La0.5FBiS2). The temperature dependence of the local structure distortion reveals an indication of possible charge density wave like instability in the pristine self-doped EuFBiS2 and Ce substituted Eu0.5Ce0.5FBiS2 while it is suppressed in La substituted Eu0.5La0.5FBiS2. In compounds with higher superconducting transition temperature, the axial Bi-S2 bond distance is elongated and the related bond stiffness decreased, suggesting some important role of this in the charge transfer mechanism for self-doping in the active BiS2-layer. In-plane Bi-S1 distances are generally softer than the axial Bi-S2 distance and they suffer further softening by the substitutions. The results are discussed in relation to an important role of the Bi defect chemistry driven asymmetric local environment in the physical properties of these materials.

Asymmetric Phosphorus Incorporation in Homoepitaxial P-Doped (111) Diamond Revealed by Photoelectron Holography.

Diamond has two crystallographically inequivalent sites in the unit cell. In doped diamond, dopant occupation in the two sites is expected to be equal. Nevertheless, preferential dopant occupation during growth under nonequilibrium conditions is of fundamental importance, for example, to enhance the properties of nitrogen-vacancy (N-V) centers; therefore, this is a promising candidate for a qubit. However, the lack of suitable experimental techniques has made it difficult to study the crystal- and chemical-site-resolved local structures of dopants. Here, we confirm the identity of two chemical sites with asymmetric dopant incorporation in the diamond structure, via the photoelectron holography (PEH) of heavily phosphorus (P)-doped diamond prepared by chemical vapor deposition. One is substitutionally incorporated P with preferential site occupations and the other can be attributed to a PV split vacancy complex with preferential orientation. The present study shows that PEH is a valuable technique to study the local structures around dopants with a resolution of crystallographically inequivalent but energetically equivalent sites/orientations. Such information provides strategies to improve the properties of dopant related-complexes in which alignment is crucial for sensing of magnetic field or quantum spin register using N-V centers in diamond.

Temperature dependent local atomic displacements in NaSn2As2 system.

NaSn2As2 is mechanically exfoliable layered van der Waals (vdW) Zintl phase that is getting interesting due to its low thermal conductivity and recently observed superconductivity. Here, we have investigated the temperature dependent local structure of NaSn2As2 by a combined analysis of As K-edge and Sn K-edge extended x-ray absorption fine structure measurements. The system is intrinsically disordered with the interatomic distances largely consistent to those estimated by average structure measurements. The stretching force constants of different bond distances have been determined using temperature dependent mean square relative displacements. The Sn-As distance is the strongest bond in this system, having covalent nature, unlike the weaker interlayer distances which are characterized by vdW type bonding. Among them, As-Na distance is slightly weaker than Sn-Sn(i) below ∼200 K and tends to get stronger above this temperature. The anomalous behavior of As-Na bond suggests that the mechanical exfoliation in this system is likely to be temperature dependent. The anomaly in the interlayer atomic correlations may be due to a charge density wave-like instability around this temperature, indicated by earlier experiments. The local structure and disorder are discussed in relation to the physical properties of NaSn2As2.

Suppression of structural instability in LaOBiS2-x Se x by Se substitution.

Isovalent substitution of S by Se in LaOBiS2-x Se x has a substantial effect on its electronic structure and thermoelectric properties. To investigate the possible role of BiS2 structural instability, we have studied the local structure of LaOBiS2-x Se x ([Formula: see text]) using temperature dependent Bi L3-edge extended x-ray absorption fine structure measurements. The results reveal that the local structure of the two compounds is significantly different. The BiS2 sub-lattice is largely distorted in LaOBiS2 (x = 0.0), with two in-plane Bi-S1 distances separated by ∼0.4 Å instead LaOBiSSe (x = 1.0) showing much smaller local disorder with two in-plane Bi-Se distances in the plane being separated by ∼0.2 Å. Temperature dependent study shows that the two Bi-S1 distances are characterized by different bond strength in LaOBiS2 (x = 0.0) while it is similar for the Bi-Se distances in LaOBiSSe (x = 1.0). The out of plane Bi-S2 bond is harder in LaOBiSSe indicating that the structural instability of BiS2 layer has large effect on the out-of-plane atomic correlations. The results suggest that the local structure of LaOBiS2-x Se x is an important factor to describe differing electronic and thermal transport of the two compounds.

Metallic phase in stoichiometric CeOBiS2 revealed by space-resolved ARPES.

Recently CeOBiS2 system without any fluorine doping is found to show superconductivity posing question on its origin. Using space resolved ARPES we have found a metallic phase embedded in the morphological defects and at the sample edges of stoichiometric CeOBiS2. While bulk of the sample is semiconducting, the embedded metallic phase is characterized by the usual electron pocket at X point, similar to the Fermi surface of doped BiS2-based superconductors. Typical size of the observed metallic domain is larger than the superconducting correlation length of the system suggesting that the observed superconductivity in undoped CeOBiS2 might be due to this embedded metallic phase at the defects. The results also suggest a possible way to develop new systems by manipulation of the defects in these chalcogenides with structural instability.

Temperature dependent local atomic displacements in ammonia intercalated iron selenide superconductor.

Recently, ammonia-thermal reaction has been used for molecular intercalation in layered FeSe, resulting a new Lix(NH3)yFe2Se2 superconductor with Tc ~ 45 K. Here, we have used temperature dependent extended x-ray absorption fine structure (EXAFS) to investigate local atomic displacements in single crystals of this new superconductor. Using polarized EXAFS at Fe K-edge we have obtained direct information on the local Fe-Se and Fe-Fe bondlengths and corresponding mean square relative displacements (MSRD). We find that the Se-height in the intercalated system is lower than the one in the binary FeSe, suggesting compressed FeSe4 tetrahedron in the title system. Incidentally, there is hardly any effect of the intercalation on the bondlengths characteristics, revealed by the Einstein temperatures, that are similar to those found in the binary FeSe. Therefore, the molecular intercalation induces an effective compression and decouples the FeSe slabs. Furthermore, the results reveal an anomalous change in the atomic correlations across Tc, appearing as a clear decrease in the MSRD, indicating hardening of the local lattice mode. Similar response of the local lattice has been found in other families of superconductors, e.g., A15-type and cuprates superconductors. This observation suggests that local atomic correlations should have some direct correlation with the superconductivity.

Particle therapy for mucosal melanoma of the head and neck. A single-institution retrospective comparison of proton and carbon ion therapy.

PURPOSE: To retrospectively analyze treatment outcomes after particle therapy using protons or carbon ions for mucosal melanoma of the head and neck (HNMM) at the Hyogo Ion Beam Medical Center, as well as to compare proton therapy (PT) and carbon ion therapy (CIT). PATIENTS AND METHODS: Data from 62 HNMM patients without metastasis, treated with PT or CIT between October 2003 and April 2011 were analyzed. Median patient age was 70.5 years (range 33-89 years). Of the total patients, 33 (53 %) had received PT and 29 (47 %) had undergone CIT. Protocols for 65 or 70.2 GyE in 26 fractions were used for both ion types. RESULTS: Median follow-up was 18.0 months (range 5.2-82.7 months). The 1-/2-year overall survival (OS) and local control (LC) rates were 93 %/61 % and 93 %/78 % for all patients, 91 %/44 % and 92 %/71 % for the PT patients and 96 %/62 % and 95 %/59 % for the CIT patients, respectively. No significant differences were observed between PT and CIT. Local recurrence was observed in 8 patients (PT: 5, CIT: 3) and 29 (PT: 18, CIT: 11) experienced distant metastases. Acute reactions were acceptable and all patients completed the planned radiotherapy. Regarding late toxicity, grade 3 or greater events were observed in 5 patients (PT: 3, CIT: 2), but no significant difference was observed between PT and CIT. CONCLUSION: Our single-institution retrospective analysis demonstrated that particle therapy for HNMM achieved good LC, but OS was unsatisfactory. There were no significant differences between PT and CIT in terms of either efficacy or toxicity.

Particle therapy using carbon ions or protons as a definitive therapy for patients with primary sacral chordoma.

OBJECTIVE: This study retrospectively evaluated the efficacy and toxicity of particle therapy using carbon ions or protons for primary sacral chordomas. METHODS: We evaluated 23 patients with primary sacral chordoma treated with carbon ion therapy (CIT) or proton therapy (PT) between July 2005 and June 2011 at the Hyogo Ion Beam Medical Center, Hyogo, Japan. The median patient age was 72 years. 14 patients were treated with 70.4 Gy equivalents (GyE) in 16 fractions and 9 were treated with 70.4 GyE in 32 fractions. CIT was used for 16 patients, and PT was used for 7 patients. RESULTS: The median follow-up period was 38 months. At 3 years, local control (LC), overall survival (OS) and progression-free survival (PFS) for all patients were 94%, 83% and 68%, respectively. The log-rank test revealed that male sex was significantly related to better PFS (p=0.029). No other factors, including dose fractionation and ion type, were significant for LC, OS or PFS. In nine patients, ≥ Grade 3 acute dermatitis was observed, and ≥ Grade 3 late toxicities were observed in nine patients. The 32-fraction protocol reduced severe toxicities in both the acute and late phases compared with the 16-fraction protocol. CONCLUSION: Particle therapy for patients with sacral chordoma showed favourable LC and OS. Severe toxicities were successfully reduced by modifying the dose fractionation and treatment planning in the later treatment era. Thus, this therapeutic modality should be considered useful and safe. ADVANCES IN KNOWLEDGE: This is the first study including both CIT and PT for sacral chordomas.

Can a belly board reduce respiratory-induced prostate motion in the prone position?--assessed by cine-magnetic resonance imaging.

The purpose of this study is to evaluate the real-time respiratory motion of the prostate and surrounding tissues/organs in the supine and prone positions and to investigate, using cine-MRI, whether a belly board can reduce respiratory-induced motion in the prone position. Cine-MRI scans were made of 13 volunteers in the supine and prone positions on a flat board and in two different prone positions using a belly board. Images in cine mode were recorded for 20 seconds. For each session, the points of interest (POIs) were located at the apex, base, mid-anterior surface and mid-posterior surface of the prostate; the tip of the seminal vesicle; the pubic symphysis; and the sacrum. The maximum range and standard deviation (SD) of the displacement from the mean value were calculated. The SDs for each of the four different positions were compared using a paired t-test. Respiratory-induced prostate motion was significantly larger in the prone position than in the supine position. However, when a belly board was used in the prone position, motion in the prostate and surrounding tissues/organs was significantly reduced. There were no significant differences between the two different positions using a belly board in any of the POIs.

Improvement of lentiviral vector-mediated gene transduction by genetic engineering of the structural protein Pr55 Gag.

The lentiviral vector is a promising tool for human gene therapy because of its ability to transduce genes into many cell types. However, one of the technical problems associated with the lentiviral vector is that lentiviral titers in current production systems are relatively low compared with the other viral vectors. In this study, we provide genetic evidence that the attachment of heterologous myristoylation (myr) signals on the amino-terminus of human immunodeficiency virus type 1 Pr55(Gag) (Gag) can increase the viral yield up to 10-fold, leading to the enhancement of gene transduction in many cell lines. The myr signal Gag constructs behaved similarly to the wild-type Gag in targeting to detergent-resistant membrane compartments, Vps4-dependence for viral budding, and virion morphology. However, the myr signal Gag constructs showed improved oligomerization efficiency as measured by bioluminescence resonance energy transfer in living cells, contributing to increased viral production and efficient activation of the viral protease responsible for virion maturation. The genetically modified Gag represents the next generation lentiviral vector, and should contribute to the success of many lentiviral vector applications.

Evolution of a pairing-induced pseudogap from the superconducting gap of (Bi,Pb)2Sr2CuO6.

We have performed an ultrahigh-resolution angle-resolved photoemission spectroscopy study of slightly overdoped (Bi,Pb)2Sr2CuO6 to elucidate the origin of the pseudogap. By using a newly developed xenon-plasma light source, we determined the comprehensive momentum and temperature dependencies of the superconducting gap and the pseudogap. We found that the antinodal pseudogap persists far above the superconducting transition temperature and is smoothly connected to the nodal gap. The characteristic temperature of the pseudogap scales well with the superconducting gap size irrespective of the momentum location. The present experimental results point to the pairing origin of the pseudogap.

Fermi surface nesting induced strong pairing in iron-based superconductors.

The discovery of high-temperature superconductivity in iron pnictides raised the possibility of an unconventional superconducting mechanism in multiband materials. The observation of Fermi-surface (FS)-dependent nodeless superconducting gaps suggested that inter-FS interactions may play a crucial role in superconducting pairing. In the optimally hole-doped Ba(0.6)K(0.4)Fe(2)As(2), the pairing strength is enhanced simultaneously (2Delta/T(c) approximately 7) on the nearly nested FS pockets, i.e., the inner hole-like (alpha) FS and the 2 hybridized electron-like FSs, whereas the pairing remains weak (2Delta/T(c) approximately 3.6) in the poorly nested outer hole-like (beta) FS. Here, we report that in the electron-doped BaFe(1.85)Co(0.15)As(2), the FS nesting condition switches from the alpha to the beta FS due to the opposite size changes for hole- and electron-like FSs upon electron doping. The strong pairing strength (2Delta/T(c) approximately 6) is also found to switch to the nested beta FS, indicating an intimate connection between FS nesting and superconducting pairing, and strongly supporting the inter-FS pairing mechanism in the iron-based superconductors.

Anomalous momentum dependence of the superconducting coherence peak and its relation to the pseudogap of La1.85Sr0.15CuO4.

We performed high-resolution angle-resolved photoemission spectroscopy on La1.85Sr0.15CuO4 to study the nature of the single-particle excitation gap. We found that there is a well-defined superconducting coherence peak in the off-nodal region while it is strongly suppressed around the antinode. The momentum dependence of the single-particle excitation gap shows a striking deviation from the dx-y2--wave symmetry with anomalous enhancement around the antinode in both the superconducting and the pseudogap state. The observed close correlation between the superconducting coherence peak and the pseudogap suggests a substantial contribution of the pseudogap to the anomalous behavior of the gap in the superconducting state.

Role of Ca2+ transporters and channels in the cardiac cell volume regulation.

Na+/K+ pump is one of key mechanisms to maintain cell volume. When it is inhibited, cells are at risk of swelling. However, in guinea pig ventricular myocytes, the cell area as an index of cell volume was almost constant during 90 min Na+/K+ pump blockade with 40 microM ouabain despite the marked membrane depolarization. In this study, involvements of Ca2+ transporters and channels in the cardiac cell volume regulation were proposed by conducting the computer simulation in parallel with the experimental validation.

Modelling Cl- homeostasis and volume regulation of the cardiac cell.

We aim at introducing a Cl- homeostasis to the cardiac ventricular cell model (Kyoto model), which includes the sarcomere shortening and the mitochondria oxidative phosphorylation. First, we examined mechanisms underlying the cell volume regulation in a simple model consisting of Na+/K+ pump, Na+-K+-2Cl- cotransporter 1 (NKCC1), cystic fibrosis transmembrane conductance regulator, volume-regulated Cl- channel and background Na+, K+ and Cl- currents. The high intracellular Cl- concentration of approximately 30 mM was achieved by the balance between the secondary active transport via NKCC1 and passive currents. Simulating responses to Na+/K+ pump inhibition revealed the essential role of Na+/K+ pump in maintaining the cellular osmolarity through creating the negative membrane potential, which extrudes Cl- from a cell, confirming the previous model study in the skeletal muscle. In addition, this model well reproduced the experimental data such as the responses to hypotonic shock in the presence or absence of beta-adrenergic stimulation. Finally, the volume regulation via Cl- homeostasis was successfully incorporated to the Kyoto model. The steady state was well established in the comprehensive cell model in respect to both the intracellular ion concentrations and the shape of the action potential, which are all in the physiological range. The source code of the model, which can reproduce every result, is available from http://www.sim-bio.org/.

Nondispersive fermi arcs and the absence of charge ordering in the pseudogap phase of Bi2Sr2CaCu2O8+delta.

The autocorrelation of angle resolved photoemission data from the high temperature superconductor Bi(2)Sr(2)CaCu(2)O(8+delta) shows distinct peaks in momentum space which disperse with binding energy in the superconducting state, but not in the pseudogap phase. Although it is tempting to attribute a nondispersive behavior in momentum space to charge ordering, a deconstruction of the autocorrelation reveals that the nondispersive peaks arise from the tips of the Fermi arcs, which themselves do not change with binding energy.

Direct observation of a nonmonotonic dx2-y2- wave superconducting gap in the electron-doped high-Tc superconductor Pr0.89LaCe0.11CuO4.

We performed high-resolution angle-resolved photoemission spectroscopy on electron-doped high-Tc superconductor Pr0.89LaCe0.11CuO4 to study the anisotropy of the superconducting gap. The observed momentum dependence is basically consistent with the dx2-y2- wave symmetry, but obviously deviates from the monotonic dx2-y2- gap function. The maximum gap is observed not at the zone boundary, but at the hot spot where the antiferromagnetic spin fluctuation strongly couples to the electrons on the Fermi surface. The present experimental results suggest the spin-mediated pairing mechanism in electron-doped high-Tc superconductors.

Angle-resolved photoemission spectroscopy of the antiferromagnetic superconductor Nd1.87Ce0.13CuO4: anisotropic spin-correlation gap, pseudogap, and the induced quasiparticle mass enhancement.

We performed high-resolution angle-resolved photoemission spectroscopy on Nd1.87Ce0.13CuO4, which is located at the boundary of the antiferromagnetic (AF) and the superconducting phase. We observed that the quasiparticle (QP) effective mass around (pi,0) is strongly enhanced due to the opening of the AF gap. The QP mass and the AF gap are found to be anisotropic, with the largest value near the intersecting point of the Fermi surface and the AF zone boundary. In addition, we observed that the QP peak disappears around the Néel temperature (TN) while the AF pseudogap is gradually filled up at much higher temperatures, possibly due to the short-range AF correlation.