Tensor analyzing power T 20 of the dd → 3Hen and dd → 3Hp reactions at zero angle for energies 140, 200, and 270 MeV

RIKEN Accelerator Research Facility data on the tensor analyzing power T ₂₀ of the dd → ³Hen and dd → ³Hp reactions at zero angle for deuteron kinetic energies of 140, 200, and 270 MeV are reported. The observed positive sign of T ₂₀ clearly demonstrates the sensitivity to the D/S-wave ratio in the ³He and ³H wave functions in the energy range of the experiment. Data on T ₂₀ for the ³Hen channel are in agreement with those for the ³Hp channel within the experimental errors.     

Thermal decomposition of poly(sec-amyl methacrylate)

The thermal decomposition of poly(sec-amyl methacrylate) is studied by simultaneous thermogravimetry–gas chromatography–mass spectrometry and by pyrolysis–gas chromatography. The TG curve has four distinct breaks and a plateau. Results of the identification of the evolved gas at the individual breaks by GC–MS techniques lead to the conclusion that these breaks correspond to the individual processes in the decomposition mechanism like that of poly(tert-butyl methacrylate): the first break, the depolymerization initiated at the unsaturated chain ends; the second break, the depolymerization initiated at the saturated chain ends; the third break, the ester decomposition; the plateau, the inhibition of decomposition by the formation of poly(methacrylic anhydride); the fourth break, the decomposition of poly(methacrylic anhydride). The extent of ester decomposition is related to the substituent constants based on Hammett equation. The ester decomposition product is separated into three pentene isomers by pyrolysis–gas chromatography: trans-2-pentene, cis-2-pentene, and 1-pentene. As raising decomposition temperature, the composition ratio of trans-2-pentene decreases and becomes constant above 620 K, and the composition ratios of cis-2-pentene and 1-pentene increase and also become constant above 620 K. These results are accounted for by mobility of atoms included in the substituent at forming a ring transition state.     

Freeze-out conditions in ultrarelativistic heavy-ion collisions

We present recent results on single particle transverse momentum distributions of pions, kaons and protons, measured in CERN Experiment NA44, of 200 AGeV/c S+S and 158 AGeV/c Pb+Pb central collisions. By comparing these data with thermal and transport models, freeze-out parameters like the temperatureT _fo and the chemical potentials (μ _q ,μ _s ) are extracted and discussed.     

Triangle contraction in six-membered-ring silicon clusters

We propose the “triangle contraction” as an important reconstruction mechanism of six-membered-ring silicon clusters on the basis of the force and virial analysis for Si₆, Si₁₀, Si₁₄, Si₁₈, Si₂₂, and Si₂₆ clusters. Forces acting on atoms have been calculated using the local-density-functional scheme with linear-combination-of-atomic-orbitals-Xα method. Calculated forces show that most of the (111)-surface equilateral triangles have tendency to contract, indicating the generality of the triangle-contraction mechanism.     

DNA DAMAGE and ITS REPAIR IN Dictyostelium discoideum IRRADIATED BY HEALTH LAMP LIGHT (UV- B)

Irradiation by health lamp (HL) light (280–320 nm) more efficiently induced cell killing and mutation in a radiation sensitive mutant (TW8) of Dictyostelium discoideum as compared with the parental wild-type strain (NC4). This light as well as a germicidal lamp-light (254 nm) produced pyrimidine dimers. The dimers were removed from DNA molecules by excision repair in NC4, but more slowly in TW8. It is suggested that pyrimidine dimers are the main DNA damage caused by HL light in D. discoideum , and that this results in cell killing and induced mutation.     

Selective cleavage of polycyclic cyclopropanes by electrochemical oxidation

Anodic oxidation in acetic acid of polycyclic cyclopropanes, namely tricyclene, cyclofenchene, and longicyclene, followed by hydrolysis brought about stereo- and regioselective formation of the corresponding homoallylic alcohols as the main product in good yields.     

Scintigraphy in the small animals using a human gamma camera--evaluation of bone scintigraphy in the rat mandible and maxilla

In order to obtain clear scintigrams of small animals, some improvements were brought on a pinhole collimator. Then, using a human gamma camera with this collimator improved, bone scintigraphy was attempted in the rat mandible and maxilla, experimentally to examine the desirable conditions of scintigraphy. The most desirable bone scan images were obtained under the conditions that the pinhole was 1.5 mm in diameter, the distance between the collimator and the object was 0 cm, and the exposure was 400.     

Activation of transition metalalkyl bonds in methyl titanium,trichloride, dialkyl(bipyridine)nickel and other transition metal alkyls by interaction with organoaluminum compounds

Metalcarbon bonds of various alkyl-transition metal compounds including TiCH₃Cl₃, NiR₂Bipy, Cr(C₂H₅)Cl₂Py₃, FeR₂Bipy₂, CuCH₃(PPh₃)₃(C₆H₅CH₃) are activated and split on interaction with organoaluminum compounds [AlR′₃ and AlR′₂(OC₂H₅), where R′ = CH₃, C₂H₅, and n-C₃H₇]. Kinetics of the cleavage of the TiCH₃ bond in TiCH₃Cl₃ and NiR bonds in NiR₂Bipy in solutions containing the organoaluminum compounds were studied by volumetric and spectroscopic methods, respectively. In both cases the reactions were first order with respect to the concentrations of the alkyltransition metal compounds. The pseudo first order rate constants for the decomposition of NiR₂Bipy in THF solution on addition of AlR′₃ were proportional to [AlR′₃] for low concentrations of AlR′₃ and to 1/[AlR′₃] for high concentrations. Based on the kinetics, a mechanism is proposed which involves coordination of AlR′₃ with NiR₂Bipy, and splitting the NiR bonds of the binuclear adduct thus formed. The decrease of the rate constants at higher concentrations of AlR′₃ is attributed to displacement of the complexed organoaluminum component by interaction wit AlR′₃·THF.