DCEMS Study of Thin Oxide Layers and Interface of Stainless Steel Films Deposited by Sputtering Austenitic AISI304

Hyperfine Interactions - Thin stainless steel films were deposited on surface oxidized Si plate using austenitic AISI304 stainless steel as target with a RF magnetron Ar sputtering method. The...     

Factors affecting product distributions in ethylene/styrene copolymerization by (aryloxo)(cyclopentadienyl)titanium complexes‐MAO catalyst systems

Ethylene/styrene copolymerizations using Cp′TiCl₂(O‐2,6‐ⁱPr₂C₆H₃) [Cp′ = Cp* (C₅Me₅, 1 ), 1,2,4‐Me₃C₅H₂ ( 2 ), tert‐BuC₅H₄ ( 3 )]‐MAO catalyst systems were explored under various conditions. Complexes 2 and 3 exhibited both high catalytic activities (activity: 504–6810 kg‐polymer/mol‐Ti h) and efficient styrene incorporations at 25, 40°C (ethylene 6 atm), affording relatively high molecular weight poly (ethylene‐co‐styrene)s with unimodal molecular weight distributions as well as with uniform styrene distributions (M_w = 6.12–13.6 × 10⁴, M_w/M_n = 1.50–1.71, styrene 31.7–51.9 mol %). By‐productions of syndiotactic polystyrene (SPS) were observed, when the copolymerizations by 1 – 3 ‐MAO catalyst systems were performed at 55, 70 °C (ethylene 6 atm, SPS 9.0–68.9 wt %); the ratios of the copolymer/SPS were affected by the polymerization temperature, the [styrene]/[ethylene] feed molar ratios in the reaction mixture, and by both the cyclopentadienyl fragment (Cp′) and anionic ancillary donor ligand (L) in Cp′TiCl₂(L) (L = Cl, O‐2,6‐ⁱPr₂C₆H₃ or N=C^tBu₂) employed. Co‐presence of the catalytically‐active species for both the copolymerization and the homopolymerization was thus suggested even in the presence of ethylene; the ratios were influenced by various factors (catalyst precursors, temperature, styrene/ethylene feed molar ratio, etc.). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4162–4174, 2008     

Quantification of ultrasonic intensity based on the decomposition reaction of porphyrin

A simple method is proposed for quantification of the effective ultrasonic intensity in the reaction vessel based on the decomposition reaction of 5,10,15,20-tetrakis(4-sulfotophenyl) porphyrin (H₂TPPS⁴⁻). The change of concentration of porphyrin in solution irradiated by the ultrasound wave depends on the irradiation time and the output power of ultrasound generator. The decomposition ratio of porphyrin is defined as the ratio of the concentration of porphyrin after ultrasonic irradiation to that before ultrasonic irradiation. A linear relationship between the decomposition ratio of porphyrin and the concentration Fe³⁺ in the Fricke solution under sonication was obtained. The decomposition ratio was related to the absorption dose in radiation chemistry.     

Triphenylstibine oxide–phosphorus(V) sulfide as a novel condensation catalyst system: application to the synthesis of dipeptides

Triphenylstibine oxide (Ph₃SbO) and phosphorus(V) sulfide (P₄S₁₀) synergistically catalyzed the aminolysis of N-protected amino-acids with amino-acid esters in benzene. Ph₃SbO accelerated both the initial conversion of carboxylic moieties into the corresponding thiocarboxylic moieties by P₄S₁₀ and the subsequent aminolysis of the resulting thiocarboxylic acids. Thus, dipeptides such as Z–A–A′–OEt (where Z = PhCH₂OC(O)– and A,A′ = Ala,Gly; Gly,Gly; Leu,Gly; Phe,Gly; Phe,Leu;Ser,Gly; Val,Gly, respectively) were conveniently prepared even at 35°C.     

The Proron threshold states in21MG relevant to the rp-process

More than ten new levels have been identified just above the proton threshold in²¹Mg. The lowest s-wave resonant state assumed previously for the calculation of the stellar reaction rate in the rp-process is found to be a bound state, suggesting a serious change for the early stage of the rp-process.     

Comparative study of dielectric,mechanical, and nuclear magnetic relaxations in linear polyethylene. II. Relaxation spectroscopy of the α, β, and γ loss bands with special emphasis on fine structure

Dielectric, mechanical, and NMR retardation (correlation) spectra for relaxations in linear polyethylene were calculated in normalized form and intercompared. For each of the two local-mode relaxations in the γ region, called γ₁ and γ₂, these spectra are found to be in excellent agreement. For the α region, the spectra for two mechanical processes, called α₁ and α₂, two NMR processes, called α′ and α, and one dielectric process α were calculated. Excellent agreement is found between the spectra for the dielectric α and NMR α′ processes and also spectra for the mechanical α₂ and NMR α processes, due to molecular motion in the interior of crystals. However, the spectrum for the mechanical α₁ process is different from that for the dielectric α and NMR α′ processes, though the activation energy for the first process is almost the same as for the other two. This behavior is interpreted on the assumption that the dielectric α and NMR α′ processes are caused by molecular motion in lamellar surface layers while the mechanical α₁ process is due to grain-boundary slip with viscous resistance of the surface layers in the boundaries. The shapes of the spectra, including the spectrum for the β process, are not affected by diluent.     

Synthesis of dl-vincadifformine,dl-eburcine and dl-3-epieburcine. Introduction of methoxycarbonyl function to c(3)-position of aspidosperma skeleton

Vincadifformine ($\text{7}$), eburcine ($\text{15}$) and 3-epieburcine ($\text{16}$) in racemic forms have been synthesized from 1,2-dehydroaspidospermidine ($\text{3}$) by introduction of methoxycarbonyl group to C(3)-position of aspidosperma skeleton.