New T=1 effective interactions for the f5/2 p3/2 p1/2 g9/2 model space; Implications for valence-mirror symmetry and seniority isomers

New shell model Hamiltonians are derived for the T=1 part of the residual interaction in the f5/2 p3/2 p1/2 g9/2 model space based on the analysis and fit of the available experimental data for 57Ni-78Ni isotopes and 77Cu-100Sn isotones. The fit procedure, properties of the determined effective interaction as well as new results for valence-mirror symmetry and seniority isomers for nuclei near 78Ni and 100Sn are discussed.Comment: 4 pages, 5 figure

Molecular weight effects on chain pull-out fracture of reinforced polymeric interfaces

Using Brownian dynamics, we simulate the fracture of polymer interfaces reinforced by diblock connector chains. We find that for short chains the interface fracture toughness depends linearly on the degree of polymerization $N$ of the connector chains, while for longer chains the dependence becomes $N^{3/2}$. Based on the geometry of initial chain configuration, we propose a scaling argument that accounts for both short and long chain limits and crossover between them.Comment: 5 pages, 3 figure

The Rossi-Cholodny Technic as an Aid in the Study of the Decomposition of Lignin

The study of the soil microflora by direct microscopic examination offers the possibility of observing the activities of the microorganisms in their natural surroundings and the attention of soil microbiologists has been directed along this line from time to time. Rossi (4) and Cholodny (1) working independently proposed similar methods which yield results of a qualitative nature and their methods have come to be known as the Rossi-Cholodny technic. Recently, Conn (2 and 3), Winogradsky (6), and Ziemiecka (7) have contributed to the further development of the method, adapting it to laboratory conditions

Two-Pion Exchange in Proton-Proton Scattering

The contribution of the box and crossed two-pion-exchange diagrams to proton-proton scattering at 90$^{\circ}_{c.m.}$ is calculated in the laboratory momentum range up to 12 GeV/c. Relativistic form factors related to the nucleon and pion size and representing the pion source distribution based on the quark structure of the hadronic core are included at each vertex of the pion-nucleon interaction. These form factors depend on the four-momenta of the exchanged pions and scattering nucleons. Feynman-diagram amplitudes calculated without form factors are checked against those derived from dispersion relations. In this comparison, one notices that a very short-range part of the crossed diagram, neglected in dispersion-relation calculations of the two-pion-exchange nucleon-nucleon potential, gives a sizable contribution. In the Feynman-diagram calculation with form factors the agreement with measured spin-separated cross sections, as well as amplitudes in the lower part of the energy range considered, is much better for pion-nucleon pseudo-vector vis \`a vis pseudo-scalar coupling. While strengths of the box and crossed diagrams are comparable for laboratory momenta below 2 GeV/c, the crossed diagram dominates for larger momenta, largely due to the kinematics of the crossed diagram allowing a smaller momentum transfer in the nucleon center of mass. An important contribution arises from the principal-value part of the integrals which is non-zero when form factors are included. It seems that the importance of the exchange of color singlets may extend higher in energy than expected

Development of Replacement Heifers using Combinations of Three Forage Types and Feed Supplements (with or without Broiler Litter)

The proper management of replacement heifers is an essential component of successful cow/calf operations. The level of management and nutrition applied to replacement heifers as calves and yearlings can impact their subsequent reproductive performance and productivity

Shell-model calculations of two-neutrino double-beta decay rates of 48^{48}Ca with GXPF1A interaction

The two-neutrino double beta decay matrix elements and half-lives of $^{48}$Ca, are calculated within a shell-model approach for transitions to the ground state and to the $2^+$ first excited state of $^{48}$Ti. We use the full $pf$ model space and the GXPF1A interaction, which was recently proposed to describe the spectroscopic properties of the nuclei in the nuclear mass region A=47-66. Our results are $T_{1/2}(0^{+}\to 0^{+})$ = $3.3\times 10^{19}$ $yr$ and $T_{1/2}(0^{+}\to 2^{+})$ = $8.5\times 10^{23}$ $yr$. The result for the decay to the $^{48}$Ti 0$^+$ ground state is in good agreement with experiment. The half-life for the decay to the 2$^+$ state is two orders of magnitude larger than obtained previously.Comment: 6 pages, 4 figure

The Primordial Binary Population in OB Associations

For understanding the process of star formation it is essential to know how many stars are formed as singles or in multiple systems, as a function of environment and binary parameters. This requires a characterization of the primordial binary population, which we define as the population of binaries that is present just after star formation has ceased, but before dynamical and stellar evolution have significantly altered its characteristics. In this article we present the first results of our adaptive optics survey of 200 (mainly) A-type stars in the nearby OB association Sco OB2. We report the discovery of 47 new candidate companions of Sco OB2 members. The next step will be to combine these observations with detailed simulations of young star clusters, in order to find the primordial binary population.Comment: 2 pages, 1 figure, poster paper to appear in proceedings of IAU Coll. 191 "The environments and evolution of binary and multiple stars