X-Ray Diffraction Study of Correlated Electron System at Low Temperatures

By using an ultra-low temperature X-ray diffractometer, we studied low temperature phase transitions of several materials. These phase transitions are classified into a ferro quadrupole ordered phase, that is, Jahn–Teller distortion (TmVO, ZnCrO), an antiferro quadrupole ordered phase (CeB, PrPb), and a superconducrivity (MgB). We also investigated unknown phases, such as the low temperature phase in PrPtBi and the 4th phase in CeLaB. Our low temperature X-ray measurement gives rise to a fruitful information about the phase transition. Not only a whole profile of the reflection peaks, which can be analyzed by the Rietveld method, we also made the precise measurement of the temperature dependence of the integrated intensity of the reflection peak, the full width at half maximum, and the lattice spacing for some fixed reflections. The temperature dependence of the integrated intensity (I.I.) can be expressed by the Debye–Waller expression. At low temperatures, the change of the phonon frequency can be obtained from the I.I. through the Debye–Waller factor. In MgB we observed the hardening of the phonon and the softening of phonon above and below the superconducting transition temperature, respsctively. This result suggests the relevant mechanisim of superconductivity in MgB is the electron–phonon interaction. From the precise measurement of the lattice constant, we found the negative thermal expansion at low temperatures in many correlated electron system. This negative thermal expansion can be explained by the Fermi liquid theory by Misawa.     

In Situ Time-Resolved Energy-Dispersive XAFS Study on Reduction Behavior of Pt Supported on TiO2 and Al2O3

The dynamic reduction behavior of a highly dispersed Pt⁴⁺ to Pt⁰ particles on TiO₂ and Al₂O₃ surfaces under the reductive atmosphere with an in situ time-resolved energy-dispersive X-ray absorption fine structure (DXAFS) analysis. A highly dispersed Pt⁴⁺ on TiO₂ was reduced to Pt⁰ even at room temperature. In contrast, a highly dispersed Pt⁴⁺ on Al₂O₃ was gradually reduced to Pt⁰ even at 473 K. This result may suggest that the semiconductive behavior of TiO₂ promotes the low temperature adsorption of hydrogen and supply of hydrogen atom to Pt⁴⁺ to be reduced and the activation of hydrogen on Al₂O₃ requires high temperature.     

Organ dose conversions from ESR measurements using tooth enamel of atomic bomb survivors

Dose conversions were studied for dosimetry of atomic bomb survivors based upon electron spin resonance (ESR) measurements of tooth enamel. Previously analysed data had clarified that the tooth enamel dose could be much larger than other organ doses from a low-energy photon exposure. The radiation doses to other organs or whole-body doses, however, are assumed to be near the tooth enamel dose for photon energies which are dominant in the leakage spectrum of the Hiroshima atomic bomb assumed in DS02. In addition, the thyroid can be a candidate for a surrogate organ in cases where the tooth enamel dose is not available in organ dosimetry. This paper also suggests the application of new Japanese voxel phantoms to derive tooth enamel doses by numerical analyses.     

Intercomparison of irradiance measurements based on WRR and ETL irradiance scales

We report the corrected intercomparison of the World Radiometer Reference (WRR) irradiance scale and the Electrotechnical Laboratory (ETL) spectral irradiance scale. In addition, we confirm the intercomparison precision using the test facility where the irradiance of ETL 500 W standard lamp can be measured directly with the cavity radiometer. The results showed that the irradiance based on the WRR scale was 0.5–0.7% lower than the one based on the ETL scale.     

WAZA-ARI: computational dosimetry system for X-ray CT examinations II: development of web-based system

A web-based dose computation system, WAZA-ARI, is being developed for patients undergoing X-ray CT examinations. The system is implemented in Java on a Linux server running Apache Tomcat. Users choose scanning options and input parameters via a web browser over the Internet. Dose coefficients, which were calculated in a Japanese adult male phantom (JM phantom) are called upon user request and are summed over the scan range specified by the user to estimate a normalised dose. Tissue doses are finally computed based on the radiographic exposure (mA s) and the pitch factor. While dose coefficients are currently available only for limited CT scanner models, the system has achieved a high degree of flexibility and scalability without the use of commercial software.     

WAZA-ARI: computational dosimetry system for X-ray CT examinations. I. Radiation transport calculation for organ and tissue doses evaluation using JM phantom

A web system of WAZA-ARI is being developed to assess radiation dose to a patient in a computed tomography examination. WAZA-ARI uses one of organ dose data sets corresponding to the options selected by a user to describe examination conditions. The organ dose data have been derived by the Particle and Heavy Ion Transport code system, combined with Japanese male (JM) phantom. The configuration of JM phantom is adjusted to the averaged JM adult. In addition, a new phantom is introduced by removing arms from JM phantom to take into account for dose calculations in torso examinations. Some of the organ doses by JM phantom without arms are compared with results obtained by using a MIRD-type phantom, which was applied in some previous dosimetry systems.     

Designing scaffolds of peptides for phage display libraries

Phage display is a powerful method for the discovery of peptide ligands that are used for analytical tools, drug discovery, and target validations. Phage display technology can produce a huge number of peptides and generate novel peptide ligands. Recently, phage display technology has successfully managed to create peptide ligands that bind to pharmaceutically difficult targets such as the erythropoietin receptor. As a result of the structural analysis of their ligands, we found that the conformational design of peptides in library is important for selecting high-affinity ligands that bind to every target from a phage peptide library. Key issues concern constraints on the conformation of peptides on the phage and the development of chemically synthesized peptides derived from peptides on phage. This review discusses studies related to the conformation of peptides selected from phage display peptide libraries in addition to the conversion from peptides to non-peptides.     

Existence of a tungsten-binding protein in Acidithiobacillus ferrooxidans AP19-3

A tungsten-binding protein was purified from a plasma membrane preparation of the iron-oxidizing bacterium, Acidithiobacillus ferrooxidans AP19-3 in an electrophoretically homogenous state. The protein was composed of two subunits with apparent molecular masses of 12 and 20.7 kDa. The molecular mass of the native protein was estimated to be 26.4 kDa in the presence of 1.5% 1-o-octyl-D -glucopyranoside (OGL), indicating that the native tungsten-binding protein is a heterodimeric protein. The amounts of tungsten bound to 1 mg of plasma membranes of A. ferrooxidans AP19-3 and the purified tungsten-binding protein at pH 3.0 were 191 and 1506 mug, respectively. In contrast, the amounts of tungsten bound to 1 mg of albumin, aldolase, catalase, chymotrypsinogen A, ferritin, and ferredoxin at pH 3.0 were 13.1, 18.6, 12.8, 16.6, 11.4, and 6.1 mug, respectively. Incubation of the tungsten-binding protein for 1 h with 10 mM Na(2)WO(4) plus 10 mM metal ion, such as NaVO(3), Na(2)MoO(4), CuSO(4), NiSO(4), MnSO(4), CoSO(4), or CdCl(2), did not markedly affect the amount of tungsten bound to the tungsten-binding protein, suggesting that the protein specifically binds tungsten.     

Multi-fueled approach to DNA nano-robotics

An approach to multi-fueled DNA nano-robotics is described. We propose three types of driving force (i.e., fuel for DNA nano-robots): thermal fuel, pH fuel, and light fuel. The thermal fuel controls the hybridization of DNA molecules around the melting temperature. The pH fuel controls the hybridization of the so-called i-motif by changing the pH condition. The light fuel controls the hybridization of DNA oligomers that are intercalated with azobenzene by irradiation with UV or visible light. These three fuels are not mutually exclusive. However, experimental conditions for the fueling of DNA nano-robots show efficacy. Concrete ideas for using these three fuel types are proposed and discussed. In addition, the results of calibration experiments and preliminary results for refining pH fuel sequence are also shown.