Effects of Nb and Y substitution on negative thermal expansion of ZrV 2−XPXO7 (0≦X≦0.8)

Zirconium vanadates with a novel chemical composition including niobium and yttrium were synthesized by the sol-gel method. An aqueous solution of NH₄H₂PO₄ and NH₄V O₃ and an ethanol solution of ZrOCl₂,NbCl₅, and Y Cl₃ were prepared. These two solutions were stirred and mixed to prepare precursors of zirconium vanadates at 333 K, following the evaporation of the solvent at 363 K. The precursor gels obtained were heated at 373-973 K in air. A zirconium vanadate phase began to crystallize above 673 K and a single phase of zirconium vanadate was synthesized at 973 K. Although ZrV ₂O₇ generally had a positive thermal expansion in the temperature range above RT, the degree of positive thermal expansion decreased with the two types of substitution of P for V and a set of Nb and Y for Zr of ZrV ₂O₇. X-ray diffraction peaks due to a superlattice structure, causing a positive thermal expansion from RT, were not observed in the synthesized (Nb, Y)-substituted zirconium vanadates.     

Multiphoton ionization of metal cluster complexes Os3(CO)12 and Ir4(CO)12: Determination of the ionization energy and coordination energy of the complex ions

Multiphoton ionization and the subsequent dissociation process of metal cluster complexes Os₃(CO)₁₂ and Ir₄(CO)₁₂, prepared in a supersonic jet, were studied by means of multiphoton ionization with time-of-flight (TOF) mass detection. The ionization energies of Os₃(CO)₁₂ and Ir₄(CO)₁₂ were determined to be 7.95 and 8.3 eV, respectively, from the laser wavelength at the ionization threshold. The coordination energies of Os₃(CO)₁₂⁺ and Ir₄(CO)₁₂⁺ ions were also determined to be 1.6 and 1.2 eV, respectively, from the excitation energy needed to cause the appearance of fragment ions. The observed values agreed reasonably well with the ones calculated by using the density functional theory method.     

Photoactivatable HNO-releasing compounds using the retro-Diels-Alder reaction

We synthesized hetero-Diels-Alder cycloadducts from acyl nitroso derivatives and 9,10-dimethylanthracene, to be photo-inducible HNO-releasing agents and found that introduction of conjugated nitroaromatic groups effectively enhanced the responsiveness of HNO release to UV-A irradiation; we confirmed photoinduced HNO formation by EPR and GCMS analysis.     

Locating a silane coupling agent in silica-filled rubber composites by EFTEM

A silane coupling agent (SA) was added to silica/rubber composites at different mixing temperatures and the formation of a coupling layer at the silica/rubber interface was investigated by energy-filtering transmission electron microscopy. Bis(triethoxysilypropyl)tetrasulfane (TESPT), which was used as the SA, reacted with the silanol groups on the silica surface and with styrene-butadiene rubber to form an interfacial coupling layer. The silicon and sulfur elemental distributions were analyzed by electron energy loss spectroscopy (EELS) and elemental mapping. The amount of TESPT trapped in the rubber matrix could be qualitatively estimated by EELS, and the in situ formed coupling layer could be characterized by elemental mapping. The result indicated that the formation of the coupling layer was affected by the mixing temperature. The technique described here will contribute to the study of interface-property relationships and the evaluation of the role of SAs in polymeric composites.     

Comparison of a new dead‐time correction method and conventional models for SIMS analysis

Recently, secondary ion mass spectrometry (SIMS) has been used in the analysis of not only impurities but also matrix elements, thus requiring a wide dynamic range for SIMS analysis. However, SIMS detectors, which are mostly used in pulse counting systems, have difficulties with detector saturation. In this paper, we investigate whether a dead‐time model that was developed for X‐ray measurement is applicable for SIMS analysis. We then compare a new correction method with conventional correction methods for detector saturation in SIMS analysis. We report that the new method can better correct the intensity in regions of higher intensity than that achieved by conventional methods. Copyright © 2012 John Wiley & Sons, Ltd.     

Joint value distribution for zeta functions in disjoint strips

In this paper we investigate joint functional distribution for a set of zeta functions which belong to the Selberg class. Especially we establish a similar property to the joint universality theorem for the zeta functions.     

Analysis of the GCR method with mixed precision arithmetic using QuPAT

To verify computation results of double precision arithmetic, a high precision arithmetic environment is needed. However, it is difficult to use high precision arithmetic in ordinary computing environments without any special hardware or libraries. Hence, we designed the quadruple precision arithmetic environment QuPAT on Scilab to satisfy the following requirements: (i) to enable programs to be written simply using quadruple precision arithmetic; (ii) to enable the use of both double and quadruple precision arithmetic at the same time; (iii) to be independent of any hardware and operating systems.To confirm the effectiveness of QuPAT, we applied the GCR method for ill-conditioned matrices and focused on the scalar parameters α and β in GCR, partially using DD arithmetic. We found that the use of DD arithmetic only for β leads to almost the same results as when DD arithmetic is used for all computations. We conclude that QuPAT is an excellent interactive tool for using double precision and DD arithmetic at the same time.