Auxiliary potential in no-core shell-model calculations

The Lee-Suzuki iteration method is used to include the folded diagrams in the calculation of the two-body effective interaction $v^{(2)}_{\rm eff}$ between two nucleons in a no-core model space. This effective interaction still depends upon the choice of single-particle basis utilized in the shell-model calculation. Using a harmonic-oscillator single-particle basis and the Reid-soft-core {\it NN} potential, we find that $v^{(2)}_{\rm eff}$ overbinds ^4\mbox{He} in 0, 2, and $4\hbar\Omega$ model spaces. As the size of the model space increases, the amount of overbinding decreases significantly. This problem of overbinding in small model spaces is due to neglecting effective three- and four-body forces. Contributions of effective many-body forces are suppressed by using the Brueckner-Hartree-Fock single-particle Hamiltonian.Comment: 14 text pages and 4 figures (in postscript, available upon request). AZ-PH-TH/94-2

Синтез N-арилалкил-N'-ацилпроизводных мочевины и их фармакологическая активность

Source codec parameters determined by modern source encoders are usually very sensitive to noise on the transmission link. Natural residual redundancy of these parameters can be utilized by Soft Decision Source Decoding (SDSD) [1] to increase the error resistance. Serially concatenating Forward Error Correction (FEC) and SDSD leads to a Iterative Source-Channel Decoding (ISCD) scheme [2, 3] which offers further improvements in robustness. ISCD exploits natural residual source redundancy by SDSD and artificial channel coding redundancy due to FEC in an iterative Turbo-like process [4, 5]. The convergence behavior of ISCD schemes can be analyzed by EXtrinsic Information Transfer (EXIT) charts [6, 7]. However, if an advanced ISCD system design [8-11] is applied, offering incremental quality improvements for many iterations, the EXIT curves for SDSD do not specify a tight bound for the decoding trajectory anymore. In the initial iterations, the decoding trajectory "overshoo ts" the EXIT curves of SDSD, e.g. [12, 13]. In this paper, we give reasons for this overshooting effect. In addition, we propose a novel solution for determining the EXIT curve of SDSD which allows a more precise convergence analysis

Incidence, correlates, and origins of dioecy in the Island Flora of New Caledonia

Premise of research. Because it is an inherently risky sexual system, dioecy is globally rare. Attempts to explain unusually high incidences of dioecy on certain islands have generated a considerable literature on the relationships among dioecy, its ecological correlates, establishment after transoceanic dispersal, and postdispersal speciation. Nevertheless, few studies of dioecy on islands have included considerations of the origins and maintenance of dioecy on islands along with determinations of its incidence. Methodology. We used the literature, herbarium specimens, and fieldwork to determine the incidence of dioecy in the native angiosperm flora of New Caledonia. We inferred the number and characteristics of colonists needed to account for the extant dioecious flora. We made traditional species-based numerical assessments of associations between dioecy on New Caledonia and woodiness, plain flowers, fleshy fruit, habitat, and endemism, and we constructed a phylogenetic tree for New Caledonia's native angiosperms to investigate correlated evolution of dioecy and those associated traits. Pivotal results. This study is the first comprehensive survey of sexual systems for the flora of New Caledonia. One-fifth of New Caledonia's native angiosperms are dioecious. Dioecy is numerically overrepresented among species that are woody, have plain flowers, have fleshy fruit, occur in rainforest, or are endemic. However, we found strong evidence for correlated evolution only for dioecy and woodiness, plain flowers, and fleshy fruit. Dioecious groups with more of the widely accepted morphological correlates of dioecy tend to be more speciose. Approximately 90% of the colonists that gave rise to the extant dioecious flora were themselves dioecious. Approximately 60% of the colonists have two or more dioecious descendants, and those descendants comprise more than 90% of the extant dioecious species. Conclusions. Successful dispersal and establishment of already dioecious colonists and autochthonous speciation of dioecious lineages are primarily responsible for the high incidence of dioecy on New Caledonia. There were relatively few postdispersal transitions to dioecy. The associations of dioecy with woodiness, plain flowers, and fleshy fruit result from correlated evolution that occurred prior to dispersal to New Caledonia, while the associations of dioecy with rainforest habitat and endemism appear to result from autochthonous speciation of dioecious lineages. With similar to similar to 4% of the world's dioecious species occurring only there, New Caledonia should be a rich source of new information on the evolutionary ecology of dioecy. Realization of this potential will require both further study and concerted efforts to preserve the native flora

Soft computing methods in design of superalloys

Soft computing techniques of neural networks and genetic algorithms are used in the design of superalloys. The cyclic oxidation attack parameter K(sub a), generated from tests at NASA Lewis Research Center, is modeled as a function of the superalloy chemistry and test temperature using a neural network. This model is then used in conjunction with a genetic algorithm to obtain an optimized superalloy composition resulting in low K(sub a) values

A Legislative Proposal for Improving Materials Policymaking: Impacts and Issues

The materials data, forecasting, and analysis system is very important to the future materials policies of this country. Adequate, timely, and reliable data, forecasts, and analyses are not sufficient for effective policy to solve complicated national materials problems, but they are necessary for improving the public policymaking process. Under a contract from Congress’ Office of Technology Assessment, the present authors reviewed the existing repositories of materials information and the possibilities for improvement. We interviewed policymakers in government, private industry, and nonprofit organizations. In this Article we describe our principal recommendation resulting from that research, a proposal for a new Bureau of Materials Statistics and Forecasting, and analyze its probable effects on government, free enterprise, and the general public

Simple approximation for the starting-energy-independent two-body effective interaction with applications to 6Li

We apply the Lee-Suzuki iteration method to calculate the linked-folded diagram series for a new Nijmegen local NN potential. We obtain an exact starting-energy-independent effective two-body interaction for a multi-shell, no-core, harmonic-oscillator model space. It is found that the resulting effective-interaction matrix elements can be well approximated by the Brueckner G-matrix elements evaluated at starting energies selected in a simple way. These starting energies are closely related to the energies of the initial two-particle states in the ladder diagrams. The ``exact'' and approximate effective interactions are used to calculate the energy spectrum of 6Li in order to test the utility of the approximate form.Comment: 15 text pages and 2 PostScript figures (available upon request). University of Arizona preprint, Number unassigne

Phosphatidylserine colocalizes with epichromatin in interphase nuclei and mitotic chromosomes

Cycling eukaryotic cells rapidly re-establish the nuclear envelope and internal architecture following mitosis. Studies with a specific anti-nucleosome antibody recently demonstrated that the surface (“epichromatin”) of interphase and mitotic chromatin possesses a unique and conserved conformation, suggesting a role in postmitotic nuclear reformation. Here we present evidence showing that the anionic glycerophospholipid phosphatidylserine is specifically located in epichromatin throughout the cell cycle and is associated with nucleosome core histones. This suggests that chromatin bound phosphatidylserine may function as a nucleation site for the binding of ER and re-establishment of the nuclear envelope

Large-basis shell model studies of light nuclei with a multi-valued G-matrix effective interaction

Large-basis shell model studies of low-lying excitations in light nuclei from 4He to 7Li have been performed with a multi-valued G-matrix effective interaction, as recently suggested by Haxton et al.. Calculations were performed relative to the vacuum (``no core") using very large, separable model spaces containing all excitations with unperturbed energies up to 8\hbar\Omega. Using G matrices derived from a new Nijmegen potential, we achieve a very satisfactory description of these excitations