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1.
We reconsider the evolution of strongly degenerate neutrinos in the early universe. Our chief concern is the validity of the entropy conservation after the neutrino annihilation process has frozen out (so that the establishment of chemical equilibrium is not trivial). We argue that the entropy indeed conserves because elastic scattering keeps the neutrino and antineutrino distribution functions in the equilibrium form and the sum of their chemical potential keeps zero even after the neutrino annihilation freeze-out. We also simulate the evolution of the degenerate neutrino spectrum to support the argument. We conclude that the change in the neutrino degeneracy parameter when the relativistic degrees of freedom in the universe decreases is calculated using the entropy conservation and the lepton number conservation without worrying about at what temperature the neutrino annihilation process freezes out. 相似文献
2.
T. Ishii M. Asai A. Makishima I. Hossain P. Kleinheinz M. Ogawa M. Matsuda S. Ichikawa 《The European Physical Journal A - Hadrons and Nuclei》2002,13(1-2):15-19
Nuclei in the neutron-rich Ni region have been studied by γ-ray spectroscopy. Gamma-rays emitted from isomers, with T
1/2 > 1 ns, produced in heavy-ion deep-inelastic collisions were measured with an isomer-scope. The nuclear structure of the
doubly magic 68Ni and its neighbor 69,71Cu is discussed on the basis of the shell model. Future experiments for more neutron-rich Ni nuclei are also viewed.
Received: 1 May 2001 / Accepted: 4 December 2001 相似文献
3.
10Gbit/s time-spread/wavelength-hop optical code generation and decoding are performed by dispersion-compensating fiber Bragg grating (FBG) en/decoder pair. Error-free 10km single mode fiber (SMF) transmission of 10Gbit/s optical code division multiplexing (OCDM) has been experimentally demonstrated. 相似文献
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The acute influences of arsenic compounds on the metabolism of porphyrins and heme in various organs of rats after oral or intratracheal administration of disodium arsenate (Na2HAsO4) and gallium arsenide (GaAs) were examined and compared. For the oral administration experiments, 21 or 84 mg of Na2HAsO4, or 2 or 4 g of GaAs, per cm3 saline per kg body weight of each animal was administered to Jcl: Wistar male rats and the organs were removed after exsanguination from the vein of the right axilla under anesthesia with ether, 16 h after administration. In the case of intratracheal administration, rats given 8.2 or 16.4 mg of Na2HAsO4, or 0.2 or 0.4 g GaAs per cm3 saline per kg body weight were examined under the same experimental conditions as for the administration route. Increase in the body weight of rats was suppressed after intratracheal administration of the two arsenic compounds. In these rats the hematocrit value increased significantly. These changes were not shown by the orally administered rats. Elevation in δ-aminolevulinate synthase (ALA-S, EC 2.3.1.37) activity in erythroblasts by Na2HAsO4 was much higher after intratracheal administration than after oral administration. Suppression in the activities of δ-aminolevulinate dehydratase (ALA-D, EC 4.2.1.24) and porphobilinogen deaminase (PBG-D, EC 4.3.1.8) in peripheral erythrocytes by Na2HAsO4 and GaAs were stronger by intratracheal administration than by the oral route. Influences of GaAs on the activity of PBG-D in rat liver were shown to be more effective by oral administration than by the intratracheal route. Oral administration of Na2HAsO4 and GaAs had a stronger suppression effect on the activities of ALA-D and PBG-D in rat kidney. It seems from these results that the different extents of the influence of arsenic compounds might depend on the routes of intake. 相似文献
6.
Hideyuki Yoshida Yuki Ohno Kenichiro Yoshikuni Kenichiro Todoroki Hitoshi Nohta Masatoshi Yamaguchi 《Analytical sciences》2003,19(2):317-319
A simple and sensitive fluorometric high-performance liquid chromatographic method was developed for the determination of midodrine in human plasma. After liquid-liquid extraction from plasma, the drug and 2-phenylglycinol (internal standard) were convened into the corresponding fluorescent derivatives by reaction with 3,4-dihydro-6,7-dimethoxy-4-methyl-3-oxoquinoxaline-2-carbonyl chloride, a fluorescence derivatization reagent for amines. The derivatives were separated within 30 min on a reversed-phase column using isocratic elution with acetonitrile-methanol-water (10:30:60, v/v) and were detected spectrofluorometrically at 485 nm with excitation at 400 nm. The detection limit for midodrine was 0.3 pmol (76 pg) per mL plasma at a signal-to-noise ratio of 3. 相似文献
7.
Y. Nagame M. Asai H. Haba K. Tsukada I. Nishinaka S. Goto A. Toyoshima K. Akiyama M. Sakama Y. L. Zhao S. Ichikawa H. Nakahara 《Physics of Atomic Nuclei》2003,66(6):1131-1136
The present status of heavy element nuclear chemistry research at JAERI (Japan Atomic Energy Research Institute) is reviewed. Production of the transactinide nuclei 261Rf and 262Db via the reactions of 248Cm(18O,5n) and 248Cm(19F, 5n), respectively, at the JAERI tandem accelerator is reported. Study of the aqueous chemistry of Rf is being carried out with a newly developed rapid ion-exchange separation apparatus. Anion-exchange behavior of Rf in acidic solution is briefly discussed. Recent experimental results on decay studies of neutron-deficient actinide nuclei using the gas-jet coupled JAERI-ISOL are given. We also discuss characteristics of nuclear deformation properties at scission in symmetric and asymmetric fission of actinides. Prospects for studies in the near future are briefly considered. 相似文献
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9.
Akikazu Matsumoto Daisuke Furukawa Hideyuki Nakazawa 《Journal of polymer science. Part A, Polymer chemistry》2006,44(17):4952-4965
We report the stereocontrol of diene polymers by the topochemical polymerization of alkoxy-substituted benzyl muconates in the solid state. A monomer stacking structure is controlled by the weak intermolecular interactions in the monomer crystals, depending on the structure and position of the alkoxy-substituent. The translational and alternating types of molecular stacking structures in a column provide diisotactic and disyndiotactic polymers, respectively, by the solid-state polymerization under UV and γ-ray irradiation. On the other hand, the meso and racemo structures of the resulting polymers are determined by the molecular symmetry of the used muconate monomers. The various substituted benzyl ester polymers are transformed into the same ethyl ester polymers with the four types of tacticities. The structure and crystallization behavior of the substituted benzyl ester polymers as well as the ethyl ester polymers have been revealed in detail. We clarify the effects of the tacticity on the crystallization property of the stereoregular polymuconates. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4952–4965, 2006 相似文献
10.