Youth Perspectives on Permanency

"What do foster youth think about permanency?" CPYP, in partnership with the California Youth Connection (CYC), held interviews and focus groups with several foster youth to talk about this question. This document explores some of their answers

Nanovoid nucleation by vacancy aggregation and vacancy-cluster coarsening in high-purity metallic single crystals

A numerical model to estimate critical times required for nanovoid nucleation in high-purity aluminum single crystals subjected to shock loading is presented. We regard a nanovoid to be nucleated when it attains a size sufficient for subsequent growth by dislocation-mediated plasticity. Nucleation is assumed to proceed by means of diffusion-mediated vacancy aggregation and subsequent vacancy cluster coarsening. Nucleation times are computed by a combination of lattice kinetic Monte Carlo simulations and simple estimates of nanovoid cavitation pressures and vacancy concentrations. The domain of validity of the model is established by considering rate-limiting physical processes and theoretical strength limits. The computed nucleation times are compared to experiments suggesting that vacancy aggregation and cluster coarsening are feasible mechanisms of nanovoid nucleation in a specific subdomain of the pressure-strain rate-temperature space

Non-equilibrium entanglement in a driven Dicke model

We study the entanglement dynamics in the externally-driven single-mode Dicke model in the thermodynamic limit, when the field is in resonance with the atoms. We compute the correlations in the atoms-field ground state by means of the density operator that represents the pure state of the universe and the reduced density operator for the atoms, which results from taking the partial trace over the field coordinates. As a measure of bipartite entanglement, we calculate the linear entropy, from which we analyze the entanglement dynamics. In particular, we found a strong relation between the stability of the dynamical parameters and the reported entanglement.Comment: Contribution to the SLAFES XIX. This version to appear in J. Phys.: Conference Serie

Scheme Independence of the Effective Hamiltonian for b→s γb \rightarrow s \, \gamma and b→s gb \rightarrow s \, g Decays

We present a calculation of the effective weak Hamiltonian which governs $b \rightarrow s\, \gamma$ and $b \rightarrow s \, g$ transitions in two different renormalization schemes (NDR and HV). In the leading logarithmic approximation, we show that the coefficients of the effective Hamiltonian are scheme independent only when one takes correctly into account the scheme dependence of one- and two- loop diagrams. We demonstrate that in NDR there are contributions which were missed in previous calculations. These contributions are necessary to obtain scheme independent coefficients in the final results.Comment: 16 pp + 5 figures not included (available by anonymous ftp at amisan.iss.infn.it (141.108.15.215), directory /ftp/bsgamma), LaTeX, LPTENS 93/28, ROME 93/958, ULB-TH 93/0

Note on islands in path-length sequences of binary trees

An earlier characterization of topologically ordered (lexicographic) path-length sequences of binary trees is reformulated in terms of an integrality condition on a scaled Kraft sum of certain subsequences (full segments, or islands). The scaled Kraft sum is seen to count the set of ancestors at a certain level of a set of topologically consecutive leaves is a binary tree.Comment: 4 page