Estimation of 47Sc and 177Lu production rates from their natural targets in Kyoto University Research Reactor

Journal of Radioanalytical and Nuclear Chemistry - To assess the capability of Kyoto University Research Reactor to supply the domestic needs of medical isotopes, its neutron flux has been fully...     

The Phosphorus Bond,or the Phosphorus-Centered Pnictogen Bond: The Covalently Bound Phosphorus Atom in Molecular Entities and Crystals as a Pnictogen Bond Donor

The phosphorus bond in chemical systems, which is an inter- or intramolecular noncovalent interaction, occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a covalently or coordinately bonded phosphorus atom in a molecular entity and a nucleophile in another, or the same, molecular entity. It is the second member of the family of pnictogen bonds, formed by the second member of the pnictogen family of the periodic table. In this overview, we provide the reader with a snapshot of the nature, and possible occurrences, of phosphorus-centered pnictogen bonding in illustrative chemical crystal systems drawn from the ICSD (Inorganic Crystal Structure Database) and CSD (Cambridge Structural Database) databases, some of which date back to the latter part of the last century. The illustrative systems discussed are expected to assist as a guide to researchers in rationalizing phosphorus-centered pnictogen bonding in the rational design of molecular complexes, crystals, and materials and their subsequent characterization.     

Preparation and properties of isotactic and syndiotactic poly(methyl methacrylate)s,uniform with respect to molecular weight

Highly isotactic (it-) and highly syndiotactic (st-) poly(methyl methacrylate)s (PMMAs) uniform with respect to molecular weight (stereoregular, uniform PMMAs) were isolated up to the 100mer from it- and st-PMMAs by supercritical fluid chromatography (SFC) and characterized by NMR and mass spectroscopies. Glass transition temperatures (Tg's) of the uniform it- and st-PMMAs were higher than those of the corresponding PMMAs with MWD and with similar molecular weight on average. The Tg values of the uniform it-and st-PMMAs series obeyed the relationship, Tg = Tg∞ - K/M, where M and Tg∞ denote molecular weight and Tg at infinite M, respectively. The reciprocal melting points (1/Tm) of uniform it-PMMA (degree of polymerization, DP = 28–44), obtained from methanol solutions by evaporating the solvent, increased linearly with increasing 1/DP. Extrapolation of the linear relation to 1/DP = 0 gave the Tm of it-PMMA with infinite DP; Tm∞ = 171.1°C. Thermal degradation behavior was studied by thermogravimetry and by SFC analysis of degradation products. In gel-permeation chromatography (GPC) measurements, the it-50mer eluted faster than the st-50mer. Calibration curves for it- and st-PMMAs could be obtained using series of the uniform PMMAs. The instrumental spreading factor determined using it-25mer, it-50mer, st-25mer and st-50mer for our GPC chromatograph was 0.070 ml when the volume of the sample solution was 0.003ml. GPC analysis of a mixture of the it- and st-50mers in tetrahydrofuran indicated formation of a stereocomplex in the solution, and was found quite useful to elucidate the minimum sequence length required for complex formation.     

Growth of corundum single crystals by the top-seeded solution growth technique (TSSG)

Single crystals of corundum were grown by the top-seeded solution growth technique from a cryolite, Na₃AlF₆, solvent. The relationship between the growth rate (mg/h) of a crystal and the temperature difference (= supersaturation) or the rotation rate of a seed crystal was investigated, and optimum growth conditions for obtaining single crystals with good quality are discussed.     

Module-based assembly of copper(II) chloranilate compounds: syntheses, crystal structures, and magnetic properties of [[Cu(2)(CA)(terpy)(2)][Cu(CA)(2)]](n)() and [[Cu(2)(CA)(terpy)(2)(dmso)(2)][Cu(CA)(2)(dmso)(2)](EtOH)](n)(H(2)CA = chloranilic acid, terpy = 2,2':6',2' '-terpyridine, dmso = dimethyl sulfoxide)

Two new copper(II) compounds of chloranilate and 2,2':6',2' '-terpyridine have been synthesized, and the structures have been solved by the single-crystal X-ray diffraction method. The crystal structure of [[Cu(2)(CA)(terpy)(2)][Cu(CA)(2)]](n)(1), where H(2)CA = chloranilic acid and terpy = 2,2':6',2' '-terpyridine, consists of two modules, the dimer unit [Cu(2)(CA)(terpy)(2)](2+) and the anionic mononuclear unit [Cu(CA)(2)](2)(-), forming an alternated chain. The chain is stabilized by semicoordinating and additional but efficient secondary bonding interactions. The crystal structure of [[Cu(2)(CA)(terpy)(2)(dmso)(2)][Cu(CA)(2)(dmso)(2)](EtOH)](n)(2), where dmso = dimethyl sulfoxide, consists of solvent molecules and two discrete modules, the dimer unit [Cu(2)(CA)(terpy)(2)(dmso)(2)](2+) and the anionic mononuclear unit [Cu(CA)(2)(dmso)(2)](2)(-). The dimer units form a layer by secondary bonding interactions, and the monomer units and ethanol molecules are introduced between the layers. The magnetic properties of 1 and 2 have been investigated in the temperature range 2.0-300 K. A weak ferromagnetic interaction was observed in 1, J(a) = 2.36 cm(-)(1) and zJ(b) = -0.68 cm(-)(1) while no exchange coupling was observed in 2.     

Direct Oxidation of Propylene with Molecular Oxygen Over Ti-Modified Sulfated Zirconia Catalyst, 2. In Situ Diffuse Reflectance FT-IR Study

During the reaction of propylene with O₂, in situ Diffuse Reflectance FT-IR measurements were performed over Ti-modified SZ and SZ catalysts. Without O₂, the main bands characteristic of (branched) hydrocarbons, formed by oligomerization leading to, finally, carbonaceous residue, appeared within the range of 3900-2750 cm^-1, which was affected by the bands of surface OH groups. Investigation of these IR bands showed the role of molecular oxygen not only to limit the formation of carbonaceous species on the catalyst surface, but also to form oxygenates and these findings were in good agreement with the results of catalytic reaction.     

Surface viscous flattening kinetics of soda-lime silicate glass by sinusoidal profile decay method

The kinetics of the flattening of surface corrugations of float glasses were investigated in dry nitrogen at 610 to 670°C. The amplitude of the sinusoidal surface profile decayed exponentially with time while its wavelength remained constant. The dependence of decay rate on wavelength indicated that the process is controlled by the viscous flow. From the obtained rate constant the viscosity was calculated using the surface energy value determined independently by the zero-creep method. The viscosity thus obtained reflects the mass transport property in the vicinity of the glass surface. It was several times larger than that determined by the fibre elongation or intrusion method which should reflect the bulk properties. No difference in the decay rate was observed on both the surfaces of float glass of which only one side had been exposed to molten tin during the glass manufacturing process.     

A New Imaging Method with a Spatial Filter for Incoherent Stream

A new imaging method using an incoherent-type pupil filter: SFINCS (Spatial Filter for INCoherent Stream) is presented. The new filter divides the imaging beam into several incoherent beams at the pupil plane thereby enlarging the depth-of-focus (DOF). The capabilities of SFINCS are studied by simulations and several ways to realize the method are also discussed. The experimental results show that SFINCS has excellent DOF expanding capabilities for a point-image such as a hole pattern in VLSI lithography, and that 1.7 μm DOF is obtained with a 0.30 μm hole pattern by an i-line projection lens with 0.57 NA (numerical aperture).Presented at the International Commission for Optics Topical Meeting, Kyoto, 1994.     

Coulometric titration of copper in CuxMo6S8−y(0⩽y⩽0.4) with solid Cu-electrolyte Rb4Cu16I7Cl13

In order to determine the copper content x of copper Chevrel compound Cu_xMo₆S_8?y(0?y?0.4) as a function of copper activity a_Cu and sulfur deficit y, a solid state electrochemical cell, Cu/Rb₄Cu₁₆I₇Cl₁₃/Cu_xMo₆S_8?y/Pt, was constructed and coulometric titration studies were made at 400 K. For the evaluation of the coulometric titration data, measurements were made on the electronic conductivity of copper-ion conductor Rb₄Cu₁₆I₇Cl₁₃. Also, a brief investigation was made on the condition of formation of single phase Chevrel Cu_xMo₆S_8?y with varying x and y at 1000°C. The structural change of Cu_xMo₆S_8?y with a change in x and y was studied by the X-ray diffraction method. It was found that x for constant a_Cu decreases with increasing y. The maximum value x_max of x in Cu_xMo₆S_8?y in equilibrium with metallic copper was found to be expressed by $\text{x}{}_{\mathrm{<mtext>max</mtext>}}\text{=-(}\text{10}\text{3}\text{)y+5}$. In the region of y<0.3, x_max exceeded 4, contrary to a presupposition that x_max is less than 4. X-ray analysis revealed that most of the copper Chevrel compounds denoted by Cu_xMo₆S₈ so far were sulfur deficient ones with y?0.4. The importance of sulfur deficit on the properties of the copper Chevrel compound was emphasized.