Probable Observation of Quantized Vortex Lines Through Solid He Under DC Rotation

We report how one can detect quantized vortices in superfluids contained in cylindrical vessels in well-designed torsional oscillator (TO) experiments under DC rotation. We show the case of an artificial 3D superfluid (Fukuda et al. in Phys. Rev. B 71:212502, 2005) which is made of Kosterlits-Thouless 2D He film condensed on a porous glass substrate with a 3D connected surface of well-controlled pore size. We understand the TO experimental results with an extra energy dissipation peak under DC rotation by considering the circular quantized superflow around each of the vortex lines and interaction with thermally excited 2D vortices as discussed in Fukuda et al. (Phys. Rev. B 71:212502, 2005) and in Nemirovskii and Sonin (Phys. Rev. B 76: 224507, 2007). We discuss here the case of hcp solid ⁴He (see for ex. Balibar and Caupin in J. Phys., Condens. Matter 20:173201-1-19, 2008) and show the evidence of observation of the vortex lines penetration below a supersolid transition temperature (Kubota et al. in J. Low Temp. Phys. 158:572, 2010), T _c , where macroscopic phase coherence is realized. It is found at exactly the same temperature T _c , below which the hysteresis occurrs (Shimizu et ail. in arXiv:0903.1326, 2009). For hcp solid ⁴He we have reported the vortex fluid (VF) state onset temperature (Penzev et al. in Phys. Rev. Lett. 101:065301, 2008) T _o =??500 mK, by detailed drive velocity, V _ac dependence study using TO technique. The TO response of the hcp ⁴He is characterized by the energy dissipation peaked at T _p near 100 mK similar to the behavior in a KT transition. The real supersolid (SS) state occurs at T _c below T _p and much lower than T _o . Our observation of the evidence of vortex lines penetration just below T _c together with the VF state properties gives support for the idea that hcp ⁴He shares some features with the ??new type of superconductors??, where the vortex state, involving the VF as well as various vortex solid states, has been commonly discussed (Fisher et al. in Phys. Rev. B 43(1):130, 1991; Leggett in Quantum Liquids, Oxford University Press, London, 2006).     

Current status of radiological protection at nuclear power stations in Japan

The radiation dose to workers at nuclear power stations (NPSs) in Japan was drastically reduced between the late-1970s and the early-1990s by continuous dose-reduction programmes. The total collective dose of radiation workers in FY 2008 was 84.04 person Sv, while the average collective dose was 1.5 person Sv per reactor. The average annual individual dose was 1.1 mSv and the maximum annual individual dose was 19.5 mSv. These values are sufficiently lower than the regulatory dose limits. Radioactive effluent released from NPSs is already so trivial that additional protective measures will not be necessary. Experience in radiation protection at NPSs has been accumulated over 40 y and will be very useful in establishing a rational radiation control system in the future.     

Ni(2+) and H(2)PO(4)(-) uptake properties of compounds in the CaTiO(3)-CaFeO(2.5) system

A batch method was used to investigate the uptake of heavy metal cations and anions by the compounds in the CaTiO(3)-CaFeO(2.5) system, in which a series of oxygen vacancies was systematically introduced into a perovskite structure as the x-value of Ca(Fe(x)Ti(1-x))O(3-x/2) was increased. Samples of CaTiO(3), CaFe(0.1)Ti(0.9)O(2.95), CaFe(0.5)Ti(0.5)O(2.75), CaFe(0.67)Ti(0.33)O(2.67) and CaFeO(2.5) were prepared by solid mixing (SM), co-precipitation (CP) and gel evaporation (GE) methods. The resulting samples were calcined at temperatures between 400 and 1000 °C. The target crystalline phases differed according to the preparation method, but in most cases were formed at 700-800 °C. The Ni(2+) sorption isotherms of all the samples were fitted better by the Langmuir model than by the Freundlich model, while in the case of H(2)PO(4)(-) sorption isotherms, these were better fitted by the latter model. The uptake ability increased with increasing x value of the samples. The maximum values for the saturated sorption of Ni(2+) (Q(0)(Ni(2+)) = 2.83 mmol/g) and H(2)PO(4)(-) (K(F)(H(2)PO(4)(-)) = 2.95 mmol/g) were achieved for x = 1 (i.e. CaFeO(2.5)) sample.     

Basic study of single crystal fibers of Pr:Lu3Al5O12 scintillator for gamma-ray imaging applications

Single-crystalline fibers were grown from 0.25, 0.70, and 1.50 mol% Pr-doped Lu₃Al₅O₁₂ (LuAG) melts by the micro-pulling down (μ-PD) method with a diameter of 0.3-0.5 mm and a length of about 200 mm. They were cut to 10 mm long specimens, and their scintillation properties, including light yield and decay time profile, were examined. These results were compared with corresponding properties of the specimens (0.8×0.8×10 mm³) cut from the bulk crystals produced by conventional Czochralski (CZ) growth. The μ-PD-grown fibers demonstrated relatively low light yield and had the same decay time constant when compared with those of the samples cut from the CZ-grown crystals. The fiber crystals were used to assemble scintillating arrays with dimensions of Ø 0.5×10 mm²×20 pixels and Ø 0.3×10 mm²×30 pixels coated by a BaSO₄ reflector. After optical coupling with a position sensitive photomultiplier tube, the fiber-based arrays demonstrated acceptable imaging capability with a spatial resolution of about 0.5 mm.     

Present status and future perspectives on the development of bioartificial kidneys for the treatment of acute and chronic renal failure patients

A bioartificial renal tubule device (BTD) consisting of a hollow-fiber module and human proximal tubular epithelial cells has been completed technically by Humes and colleagues and a few other groups. Humes and colleagues developed BTD, treated acute kidney injury patients with multiorgan failure by continuous hemofiltration (CHF) in conjunction with BTD, and reported a significantly higher survival rate than that by CHF with BTD without cells in the Food and Drug Administration phase IIa trial. However, BTD has never been approved by the US Government, as the CHF+BTD treatment did not show a significant difference from the control group in the phase IIb trial. Human proximal tubular epithelial cells were confirmed to be overgrown on artificial membrane, which resulted in the inhibition of active transports and the metabolism of essential substances. Function of the BTD could be maintained in a U0126-contained medium, even if the BTD had to have been waited by a new acute kidney injury patient for several weeks. For wearable kidneys, heparin-covalently bound membrane or methacryloyloxyethyl phosphorylcholine (MPC) polymer-coated membranes are candidates for antithrombogenic hemofilters, while endothelial progenitor cells from a cord blood, CD133(+) cells-attached hemofilter in which the permeability of the cells was enhanced by the enlarged diameter of fenestrae by treating with cytochalasin B are another candidate. The MPC blend membrane containing 1% of the MPC polymer in polysulfone was developed as a BTD module. MPC was 7 times larger at the sponge layer than at the skin layer of the membrane, resulting in hemocompatibility at the sponge layer and cytocompatibility at the skin layer.     

Organic tailored batteries materials using stable open-shell molecules with degenerate frontier orbitals

Secondary batteries using organic electrode-active materials promise to surpass present Li-ion batteries in terms of safety and resource price. The use of organic polymers for cathode-active materials has already achieved a high voltage and cycle performance comparable to those of Li-ion batteries. It is therefore timely to develop approaches for high-capacity organic materials-based battery applications. Here we demonstrate organic tailored batteries with high capacity by using organic molecules with degenerate molecular orbitals (MOs) as electrode-active materials. Trioxotriangulene (TOT), an organic open-shell molecule, with a singly occupied MO (SOMO) and two degenerate lowest-unoccupied MOs (LUMOs) was investigated. A tri-tert-butylated derivative ((t-Bu)(3)TOT)exhibited a high discharge capacity of more than 300 A h kg(-1), exceeding those delivered by Li-ion batteries. A tribrominated derivative (Br(3)TOT) was also shown to increase the output voltage and cycle performance up to 85% after 100 cycles of the charge-discharge processes.     

Charge-carrier injection into pentacene thin film formed on Si(111) probed by STM spectroscopy

The injection of charge carriers into a pentacene thin film formed on a Si substrate was investigated by scanning tunneling microscopy (STM). Tip height versus bias voltage (z-V) spectroscopy reveals the characteristic charge transport properties of the molecular film, i.e., the conductivity and the threshold energy of charge injection. The abrupt descent of the tip into the film owing to the transition of film conductance, which depends on the degree of charge carrier injection, was observed for crystallized pentacene thin films. The lower film conductance at around zero bias voltage is still higher than that of a vacuum. This indicates that the carrier injection barrier between the pentacene and the semiconducting substrate is extremely low. The convergence of the carrier injection endpoints into a narrow range of electric-field intensity implies that the main factor contributing to barrier formation and collapse is not the bias voltage but the electric field.     

Facile fabrication and photocatalytic application of Ag nanoparticles-TiO2 nanofiber composites

A novel chemical method has been developed for the fabrication of Ag nanoparticles-coated TiO2 nanofiber composites. The method involves dispersion of TiO2 nanofibers in silver salt solution under ultrasonication, followed by addition of sodium citrate as a reducing agent. The Ag-coated TiO2 composites were characterized by high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and X-ray photoelectron microscopy (XPS). Furthermore, the photocatalytic performance was evaluated by the photocatalytic degradation of methyl orange under UV-light irradiation. It was found that the heterogeneous Ag-TiO2 composite showed a higher activity than the pure TiO2 nanofiber; the enhanced activity can be attributed to the excellent distribution and interaction of Ag nanoparticles with the TiO2 nanofiber support. A plausible mechanism for the formation of the Ag-coated TiO2 composite and reasons for the enhancement of photocatalytic activity are also discussed.     

Boron-assisted transformation to rod-like graphitic carbons from multi-walled carbon nanotubes in boron-mixed multi-walled carbon nanotube solids

We produced boron-mixed multi-walled carbon nanotube solids (B-mixed MWCNT solids) by heating and pressing the powder of purified MWCNTs mixed with 1, 5, and 10 wt % boron in the temperature range 1400-1800 °C every 200 °C under a constant pressure of 20 MPa in vacuo, and investigated the influence of boron addition on nanotube structure and the mechanical and electrical properties of the resulting B-mixed MWCNT solids. The structure of the prepared material was characterized by scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy-electron energy loss spectroscopy, Raman scattering spectroscopy, and X-ray diffraction, and their mechanical properties and conductivity were measured using a mechanical and Vickers indentation tester and an electric resistor, respectively. It is notable that part of the nanotubes in the B-mixed MWCNT solids solidified at 1800 °C had dramatically changed into rod-like graphitic carbons (RLGCs). The occupancy distribution of RLGCs increased with increasing boron contents. However, boron was not detected in the energy-loss near-edge structure spectrum of RLGCs. Furthermore, RLGCs were not observed in the boron-unmixed sample treated with the same solidified condition, indicating that adding boron causes a remarkable ability to transform the phase of MWCNT. Transformation from MWCNTs to RLGCs resulted in increased specific bending strength and modulus, Vickers hardness, and electrical conductivity of B-mixed MWCNT solids with increasing boron content and solidified temperature.