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81.
82.
G Viesti M Lunardon D Fabris G Nebbia M Cinausero E Fioretto G Prete JB Natowitz K Hagel R Wada 《Pramana》1999,53(3):395-404
The transition of the level density parameter a
off from the low excitation energy value a
off=A/8 MeV−1 to the Fermi gas value a
FG ∼ A/15 MeV−1 was discovered a few years ago studying particle spectra evaporated from hot compound systems of A∼ 160. A number of experiments have been recently performed to confirm the earlier findings and extend the investigation to
other mass regions and to higher excitation energies. Furthermore, precision coincidence experiments have been done in the
lead region in which evaporation residues are tagged by low energy gammarays. Those experiments open the possibility of a
detailed study of the level densities in nuclei where the shell effects are important. 相似文献
83.
Sithole M. A. Sharpey Schafer J. F. Majola S. N. T. Bucher T. D. Dinoko T. R. S. Ntshangase S. S. Lawrie E. A. Khumalo N. A. Jongile S. Mdletshe L. Bark R. A. Erasmus N. Jones P. Kheswa B. V. Lawrie J. J. Makhathini L. Malatji K. L. Maqabuka B. Noncolela S. P. Ndayishimye J. Shirinda O. Zikhali B. R. Masiteng P. L. 《The European Physical Journal A - Hadrons and Nuclei》2019,55(10):1-52
The European Physical Journal A - Photon strength functions describing the average response of the nucleus to an electromagnetic probe are key input information in the theoretical modelling of... 相似文献
84.
85.
J. Carter A. A. Cowley H. Diesener R. W. Fearick S. V. Frtsch M. N. Harakeh J. J. Lawrie S. J. Mills P. von Neumann-Cosel R. T. Newman J. V. Pilcher A. Richter K. Schweda F. D. Smit G. F. Steyn S. Strauch D. M. Whittal 《Nuclear Physics A》1998,630(3-4)
The 40Ca(p,p′ α) reaction has been studied at an incident proton energy Ep = 99.5 MeV for proton laboratory scattering angles Θplab = 17°, 23° and 27°. Emission of α particles coincident with the scattered proton has been measured for an angular range Θα 0° − 180° relative to the recoil axis. A multipole decomposition for the α0-decay channel to the 36Ar ground state has been performed from the angular-correlation functions. The energy distribution of the dominating E2 strength deduced in the excitation energy range Ex = 11–21 MeV agrees reasonably well with the results from electron and α-induced α0-decay investigations. The exhaustion of the E2 energy-weighted sum rule in this channel up to an energy of 17 MeV is 16.1(4.0)%, in accord with the study of the (α, α′ α0) reaction. However, this value is twice what is found in the (e,e′ α0) experiment in the same energy region. Thus, the puzzling discrepancy in the E2 strengths derived from electromagnetic and hadronic probes remains unsolved. 相似文献
86.
87.
88.
In this paper we establish relaxation of an arbitrary 1-equivariant wave map from ${\mathbb{R}^{1+3}_{t,x}{\setminus} (\mathbb{R}\times B(0,1))\to S^3}$ of finite energy and with a Dirichlet condition at r = 1, to the unique stationary harmonic map in its degree class. This settles a recent conjecture of Bizoń, Chmaj, Maliborski who observed this asymptotic behavior numerically. 相似文献
89.
The isolation, structure determination and chemical characterization of eumelanins has been plagued by their very low solubility in organic solvents. To gain insights into the structure and reactivity of these unusual and important biologic macromolecules and to pave the way for their use in electronics, we have prepared soluble melanins via the synthesis of monomeric precursors containing lipophilic substituents. Two such monomers derived from 5,6-dihydroxyindole-2-carboxylic acid (DHICA) were prepared, namely the benzyl and octyl ester derivatives. Both benzyl and octyl ester monomers were oxidatively polymerized to yield dark, melanin-like pigments. These polymerization processes were followed by UV-visible, fluorescence and NMR spectroscopy. These studies showed that the polymerizations proceeded by cross-linking at the 4- and 7-positions of the indole nucleus and led to highly heterogeneous polymeric products. Incorporation of a lipophilic benzyl or octyl group resulted in enhanced solubility of the pigments in a wide range of organic solvents. The UV-visible spectra of the organically soluble synthetic melanins were essentially identical to that of natural eumelanin. 相似文献
90.
The preparation and characterisation of a novel, water-proof, irreversible, reusable, UV-activated, O(2) sensitive, smart plastic film is described. A pigment, consisting of a redox dye, methylene blue (MB), and a sacrificial electron donor, DL-threitol, coated onto an inorganic support with semiconductor functionality, TiO(2), has been extruded in low-density polyethylene (LDPE). The blue-coloured indicator is readily photobleached in <90 s using UVA light (4 mW cm(-2)), whereby MB is converted to its colourless, leuco form, leuco-methylene blue (LMB). This form persists in the absence of oxygen, but is re-oxidised to MB in ~2.5 days in air under ambient conditions (~21 °C, ~65% RH) within the O(2) smart plastic film. The rate of recovery is linearly dependent upon the ambient level of O(2). At the lower temperature of 5 °C, the kinetics of the photobleaching activation step is largely unchanged, whereas that of recovery is markedly reduced to t(1/2) = 36 h at 5 °C (cf. 9 h at 21 °C); the activation energy for the recovery step was calculated as 28 kJ mol(-1). The O(2)-sensitive recovery step was found to be moderately dependent upon humidity at 21 °C, but not significantly dependent upon humidity at 5 °C. The possible application of this type of indicator in food packaging is illustrated and discussed briefly. 相似文献