Samarium enolate on crosslinked polystyrene beads. III. Anionic initiator for well‐defined synthesis of poly(hydroxyethyl methacrylate) on solid support

A solid‐supported samarium enolate successfully initiated the polymerization of 2‐(trimethylsilyloxy)ethyl methacrylate (TMS‐HEMA) through the living anionic process. In addition, the silyl group was readily removed by treatment of the beads with a weak acid to afford the corresponding well‐defined poly(methacrylate) having a hydroxyethyl group in the side chain (PHEMA). The hydroxyl group of the immobilized PHEMA on the beads was successfully acetylated to give poly(2‐acetoxyethyl methacrylate), which could be quantitatively isolated from the beads by trifluoroacetic acid treatment. Moreover, the hydroxyl group of the immobilized PHEMA could be utilized as an initiator for acid promoted ring opening polymerization of lactone to yield the corresponding graft copolymer. In this method, the residual and excess reagents could be removed by filtration, which demonstrated the applicability of the present technique to a novel method for construction of functional polymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4417–4423, 2004     

Preconcentration and determination of cadmium by GFAAS after solid-phase extraction with synthetic zeolite.

The solid-phase extraction (SPE) method for the preconcentration of trace amounts of cadmium using synthetic zeolite A-4 and its determination by graphite furnace atomic absorption spectrometry (GFAAS) was investigated. The preconcentration conditions, such as the optimum pH range of the sample solution for the adsorption of cadmium and the kind of acid solution for dissolving the cadmium-adsorbed synthetic zeolite A-4, as well as the measurement conditions for the determination of cadmium by GFAAS, e.g., the ashing and atomizing temperature, were investigated. Quantitative recovery of cadmium onto zeolite A-4 from the sample solution over the pH range 2.0 - 9.0 was achieved by the batch method. After the solid-phase (cadmium-adsorbed zeolite A-4) was separated from the sample solution by a membrane filter, it was dissolved in 2.0 cm(3) of 2.0 mol dm(-3) nitric acid. An aliquot of the resulting solution was injected into the graphite furnace. In GFAAS measurements an alternate gas (Ar, 90%; O(2), 10%) was used as a sheath gas, and the ashing temperature and atomizing temperature were 400 degrees C and 1600 degrees C, respectively. The detection limit (3 sigma) for cadmium was 0.002 microg dm(-3). The relative standard deviation at 0.010 microg dm(-3) was 3.5 - 4.5% (n = 5). The proposed method has been successfully applied to the analysis of trace cadmium in environmental water samples.     

Real-time monitoring of monochlorinated benzene and polychlorinated biphenyls in the gas phase with on-line detection: High chemical selectivity of resonance-enhanced two-photon ionization.

The development of molecular spectroscopy has enabled us to select chlorinated aromatic hydrocarbons very rapidly. In particular, the laser ionization TOFMS (time-of-flight mass spectrometry) method is expected to be useful as an on-line, selective, and sensitive method. In the present work, real-time laser ionization TOFMS measurements were carried out on gaseous chlorinated aromatic hydrocarbons. The laser ionization method used resonance-enhanced two-photon ionization with the direct introduction of gas into the vacuum chamber. This method for analyzing aromatic hydrocarbons was developed using a pulsed supersonic molecular beam method. In the context of developing a highly selective and sensitive method, excitation of monochlorinated benzene at lambda = 263.07 nm was found to be effective in the wavelength region from 263 nm to 265 nm. Also the excitation of polychlorinated biphenyls at lambda = 266 nm was found to be substantially more effective than at lambda = 280, 300 or 320 nm. The achievable sensitivity for real-time (1 min) measurements using the laser ionization TOFMS technique was found to be in the ppbV range.     

Ground state for point particles interacting through a massless scalar Bose field

We consider a massless scalar Bose field interacting with two particles, one of them infinitely heavy. Neither an infrared nor an ultraviolet cutoff is imposed. In case the charge of the particles is of the same sign and sufficiently small, we prove the existence of a ground state.     

Gel formation with multiple interunit junctions. II—mixture of different functional molecules

Number‐ and weight‐average molecular weight of condensation polymers formed in the mixture of primary molecules carrying different species of functional groups A and B are derived by the cascade theory. These functional groups are allowed to form multiple junctions of arbitrary multiplicity k. From the weight average, the gel point condition is found to be given by 1 ? (f_w ? 1)(μ_A,A ? 1) ? (g_w ? 1)(μ _B,B ? 1) + (f_w ? 1)(g_w ? 1)D_μ = 0, where f_w and g_w are average functionality of the primary molecules, μ _αβ the average multiplicity of β groups in the junctions where a path of an α‐group enters, and D_μ ≡ (μ_A,A ? 1)(μ _B,B ? 1) ? μ _A,Bμ _B,A the multiplicity determinant. Possible applications to thermoreversible gelation are suggested. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 2413–2421, 2003     

Direct inhibition of pepsinogen secretion from rat gastric chief cells by somatostatin

Effects of somatostatin on pepsinogen secretion was investigated in the rat in vivo and in vitro. In the perfused rat stomach, somatostatin inhibited secretagogue-induced acid secretion in dose-dependent manner. However, effects of somatostatin on secretagogue-induced pepsinogen secretion were obscure. To clarify the effects of somatostatin on the chief cells, gastric mucosal cells were isolated by a proteolytic enzyme. Somatostatin inhibited carbachol- and cholecystokinin octapeptide-induced pepsinogen secretion from dispersed gastric mucosal cells in a dose-dependent manner. Histamine-induced pepsinogen secretion, which was recovered by culturing, was also inhibited by somatostatin. These results suggest that somatostatin inhibits secretagogue-induced pepsinogen secretion directly.     

Ion-size effects on the structure and superconductivity of La-214 compounds at 1/8 doping

A structural transition to a low-temperature tetragonal (TLT) phase occurs below T_d2≈60 K in La_2−xBa_xCuO₄ only around x=0.125, accompanied by sharp suppression of superconductivity. In this study we investigated the effects of partial substitution of smaller divalent cations for Ba²⁺ ions (Ba²⁺ > Sr²⁺ > Ca²⁺) on these anomalous low-temperature properties. The suppression of superconductivity is strongly affected by the appearance of the TLT phase for this carrier concentration. We also show that the variations of T_d2 and T_c are quantitatively scaled by the averaged size of cations at the La site. This dependence can be interpreted as chemical effects acting effectively as applied pressure. We discuss how our observation is related to recent reports which claim that the TLT structure itself does not necessarily destroy the superconductivity.     

Intergranular fracture surface analysis of molybdenum

Bend properties of plasma beam and/or electron beam melted molybdenum and several dilute alloys containing C, B, T, V and Re were investigated. Fracture surfaces and microstructure were examined in detail by SEM and AES. Considerable intergranular fracture occurred in almost all of the samples as the test temperature decreased. But proper alloy addition, such as B and Ti, and hot-rolling induced a change in the fracture mode to a transgranular mode. Segregation of nitrogen and/or oxygen to grain boundaries was often recognized in plasma beam or electron beam melted ingots and decreased the strength of grain boundaries. Small precipitates due to comparatively low alloy addition such as C, B, Ti and Re, were effective to enhance the grain boundary cohesion.