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[en] The effects of temperature, dose rate, and monomer concentration on the heterogeneous polymerization of acrylamide in acetone--water mixtures have been studied. Heterogeneous polymerization takes place in mixtures containing less than 60 vol-percent water. The polymerization is steady in acetone and nonsteady in mixtures containing 10 to 50 vol-percent water. The average rate of polymerization is highest in mixtures with about 20 vol-percent water. Polymer molecular weight increases with the increasing water content in the range 0 to 10 vol-percent and does not change in the range of 30 to 70 vol-percent water. For the polymerization in acetone and an acetone-water 60/40 mixture, the activation energies are 2.3 and -1.8 kcal/mole, the dose rate exponents of rate are 0.78 and 0.52, and the monomer concentration exponents of rate are 0.5 and 1.6, respectively. The polymer molecular weight increases with decreasing dose rate, decreasing temperature, and increasing monomer concentration. These results are discussed in connection with the mechanism of heterogeneous polymerization and the solvent effect
[en] The radiation-induced polymerization of acrylamide was studied to prepare a high molecular weight and highly effective polyacrylamide flocculant. Among various solvents, mixtures of water--tert-butyl alcohol and water--acetone were found to be suitable for the synthesis of the high molecular weight polyacrylamide. For polymerization in acetone--water mixtures, the molecular weight of polymer increases with monomer concentration; but at the high concentration intermolecular imidation of amide groups tends to take place during the polymerization to form crosslinked and water-insoluble polymer. The water-soluble polymer with the largest molecular weight of 6.7 x 106 is produced in the polymerization with monomer concentration of 2.91 moles/l at 00C at a dose rate of 6.2 x 102 rad/hr in acetone--water mixture containing 60 vol. percent water. The crosslinking of polymer or the formation of water-insoluble polymer could be avoided by the addition of K2CO3 or NaOH to raise the pH of the reaction mixture above 6.5. The flocculation effects were evaluated from sedimentation speed of kaolin suspension and transparency of the separated water. The sedimentation speed is proportional to the intrinsic viscosity of the polymer in the range of 4 to 23 dl/g. The polymers prepared in this study show much higher sedimentation speed than commercial polyacrylamide flocculants. The transparency of the separated water is higher than 93 percent, similar to the results with commercial flocculants
[en] The quenching factor for proton recoils in a stilbene scintillator was measured with a 252Cf neutron source and was found to be 0.1-0.17 in the recoil energy range between 300 keV and 3 MeV. It was confirmed that the light yield depends on the direction of the recoil proton. The directional anisotropy of the quenching factor could be used to detect the wind of the WIMPs caused by the motion of the earth around the galactic center
[en] Development of low background CdZnTe detectors is in progress to study neutrino-less double beta decay. The μτ product (mobility times lifetime) for holes was measured in a set of CdZnTe detectors at various temperatures between +22 deg. C and -40 deg. C in order to investigate charge collection efficiencies for holes. The sensitivity of CdZnTe detectors to neutrino-less β+EC decays of 64Zn (64Zn+EC→64Ni+β+) is estimated from these data
[en] Heat of transport Q* of hydrogen isotopes in the α-phase of Zr have been measured in temperature regions from 623K to 673K for H and from 523K to 623K for T by analyzing the redistribution process under a thermal gradient. An isotope mass dependence of Q* has not been unequivocally established though a tendency that Q*(H)>Q*(T) has been observed. These data have been discussed on the basis of the biased-jump diffusion model, and a large negative bias effect has been pointed out as characteristics of Q* of hydrogen isotopes in group-IV metals in comparison with the case of group-V metals
[en] Vibrational distributions of CH(X2)PI) radicals produced from ion-molecule reactions between C+(2P) ions and ethylene, ethane, propylene, and propane have been studied in a flowing afterglow by a laser-induced fluorescence. The initial vibrational population ratios of CH(X:nu'' = 1/nu'' = 0) were similar (0.54-0.60) for all reactions. They were compared with statistical prior distributions for the three-body model in which polyatomic product ions were treated as atomic ions
[en] We have performed the underground dark matter search experiment with a sodium fluoride (NaF) bolometer array from 2002 through 2003 at Kamioka Observatory (2700 m.w.e.). The bolometer array consists of eight NaF absorbers with a total mass of 176 g, and sensitive NTD germanium thermistors glued to each of them. This experiment aims for the direct detection of weakly interacting massive particles (WIMPs) via spin-dependent interaction. With an exposure of 3.38 kg days, we derived the limits on the WIMP-nucleon coupling coefficients, ap and an. These limits confirmed and tightened those derived from our previous results with the lithium fluoride (LiF) bolometer. Our results excluded the parameter space complementary to the results obtained by Nal detectors of UKDMC experiment
[en] We studied a compact and simplified rotating plug seal structure and conducted experiments for key elements of the concept such us the mechanical seal structure and sodium deposit prevention system. Good characteristics were confirmed for the mechanical seal structure, which utilizes an elastomer seal and thin lathe bearing. Applicability of the density barrier concept was also confirmed as the sodium deposit prevention system. This concept can be applied to actual plants. (author)
[en] The NEWAGE project (NEw generation WIMP search with an Advanced Gaseous tracking device Experiment) is a direction-sensitive dark matter search experiment, searching for WIMPs (Weakly Interacting Massive Particle) via nuclear recoil. The NEWAGE detector, a micro time-projection-chamber with a 400μm pitch read out, detects three-dimensional nuclear tracks. A low-pressure gas study (76 torr) was performed in order to lower the energy threshold, one of the most effective improvements for the next underground measurement. We measured the gas gain, the angular resolution and the detection efficiency. We have consequently lowered the energy threshold from 100 keV to 50 keV by decreasing the gas pressure.
[en] The results of the third phase of the Super-Kamiokande solar neutrino measurement are presented and compared to the first and second phase results. With improved detector calibrations, a full detector simulation, and improved analysis methods, the systematic uncertainty on the total neutrino flux is estimated to be ±2.1%, which is about two thirds of the systematic uncertainty for the first phase of Super-Kamiokande. The observed 8B solar flux in the 5.0 to 20 MeV total electron energy region is 2.32±0.04(stat)±0.05(sys)x106 cm-2 sec-1 under the assumption of pure electron-flavor content, in agreement with previous measurements. A combined oscillation analysis is carried out using SK-I, II, and III data, and the results are also combined with the results of other solar neutrino experiments. The best-fit oscillation parameters are obtained to be sin2θ12=0.30-0.01+0.02(tan2θ12=0.42-0.02+0.04) and Δm212=6.2-1.9+1.1x10-5 eV2. Combined with KamLAND results, the best-fit oscillation parameters are found to be sin2θ12=0.31±0.01(tan2θ12=0.44±0.03) and Δm212=7.6±0.2x10-5 eV2. The 8B neutrino flux obtained from global solar neutrino experiments is 5.3±0.2(stat+sys)x106 cm-2 s-1, while the 8B flux becomes 5.1±0.1(stat+sys)x106 cm-2 s-1 by adding KamLAND results. In a three-flavor analysis combining all solar neutrino experiments, the upper limit of sin2θ13 is 0.060 at 95% C.L.. After combination with KamLAND results, the upper limit of sin2θ13 is found to be 0.059 at 95% C.L.