Radiative charge transfer lifetime of the excited state of (NaCa)+^+

New experiments were proposed recently to investigate the regime of cold atomic and molecular ion-atom collision processes in a special hybrid neutral-atom--ion trap under high vacuum conditions. The collisional cooling of laser pre-cooled Ca$^+$ ions by ultracold Na atoms is being studied. Modeling this process requires knowledge of the radiative lifetime of the excited singlet A$^1\Sigma^+$ state of the (NaCa)$^+$ molecular system. We calculate the rate coefficient for radiative charge transfer using a semiclassical approach. The dipole radial matrix elements between the ground and the excited states, and the potential curves were calculated using Complete Active Space Self-Consistent field and M\"oller-Plesset second order perturbation theory (CASSCF/MP2) with an extended Gaussian basis, 6-311+G(3df). The semiclassical charge transfer rate coefficient was averaged over a thermal Maxwellian distribution. In addition we also present elastic collision cross sections and the spin-exchange cross section. The rate coefficient for charge transfer was found to be $2.3\times 10^{-16}$ cm$^3$/sec, while those for the elastic and spin-exchange cross sections were found to be several orders of magnitude higher ($1.1\times 10^{-8}$ cm$^3$/sec and $2.3\times 10^{-9}$ cm$^3$/sec, respectively). This confirms our assumption that the milli-Kelvin regime of collisional cooling of calcium ions by sodium atoms is favorable with the respect to low loss of calcium ions due to the charge transfer.Comment: 4 pages, 5 figures; v.2 - conceptual change

The effects of conjugated linoleic acid isomers cis-9,trans-11 and trans-10,cis-12 on in vitro bovine embryo production and cryopreservation

Conjugated linoleic acid (CLA) isomers can affect the lipid profile and signaling of cells and thereby alter their function. A total of 5,700 bovine oocytes were used in a structured series of experiments to test the effects of CLA cis-9,trans-11 and CLA trans-10,cis-12 in vitro. In experiment 1, high doses of each CLA isomer during in vitro maturation (IVM) were compared with high or low doses during the entire in vitro culture (IVC) of parthenogenetic embryos. High doses of the CLA isomers ranged from 50 to 200 μM and low doses were 15 and 25 μM. In experiment 2, the low doses of each CLA isomer were tested during IVM/IVC on embryos produced by in vitro fertilization (IVF). Experiment 3 compared the effects of 15 μM doses of each CLA isomer during IVM or IVC of IVF embryos. In experiment 4, post-rewarming survival rates and blastomere counts were assessed for embryos supplemented with each CLA isomer during IVM or for 36 h before vitrification. In experiment 1, when either CLA isomer was provided only during IVM, we observed no effects on overall rates of maturation, cleavage, or blastocysts (92.2 ± 1.6%, 78.3 ± 4.1%, and 28.9 ± 5.1%, respectively). However, high doses of each CLA isomer, but not low doses, during the entire embryo culture period decreased blastocyst rates (5-20%) in a dose-dependent manner. Cleavage rates improved with 15 or 50 μM CLA trans-10,cis-12. Progesterone concentrations in maturation media were significantly increased by high doses of each CLA isomer compared with control, but low doses of CLA isomers had no effect. In experiment 2 with IVF embryos, low doses of each CLA isomer did not alter cleavage rates (average 84.9 ± 1.9%) and only 25 μM CLA trans-10,cis-12 during IVC reduced blastocyst rates below those of controls (25.5 ± 2.1 vs. 38.2 ± 2.3%). The lipid content of embryos was increased and relative expression of the BIRC5 (baculoviral IAP repeat containing 5) gene was depressed by CLA trans-10,cis-12. In experiment 3, low doses (15μM) of each CLA isomer during IVC significantly reduced blastocyst rates (20.6 ± 2.4% and 27.7 ± 1.2% vs. 34.18 ± 1.2% for CLA trans-10,cis-12 and CLA cis-9,trans-11 compared with control, respectively) with less effect of each CLA during IVM. In experiment 4, adding 100 μM CLA cis-9,trans-11 during the final 36 h of culture resulted in a high survival rate after rewarming and culture, and the higher embryo blastomere count was comparable to that of control embryos not undergoing vitrification. In conclusion, supplementation with either CLA isomer did not improve embryo production, but inclusion of CLA cis-9,trans-11 before vitrification improved the quality of bovine IVF embryos after rewarming and culture

Ab-initio calculation of Kerr spectra for semi-infinite systems including multiple reflections and optical interferences

Based on Luttinger's formulation the complex optical conductivity tensor is calculated within the framework of the spin-polarized relativistic screened Korringa-Kohn-Rostoker method for layered systems by means of a contour integration technique. For polar geometry and normal incidence ab-initio Kerr spectra of multilayer systems are then obtained by including via a 2x2 matrix technique all multiple reflections between layers and optical interferences in the layers. Applications to Co|Pt5 and Pt3|Co|Pt5 on the top of a semi-infinite fcc-Pt(111) bulk substrate show good qualitative agreement with the experimental spectra, but differ from those obtained by applying the commonly used two-media approach.Comment: 32 pages (LaTeX), 5 figures (Encapsulated PostScript), submitted to Phys. Rev.

Dilepton Spectra from Decays of Light Unflavored Mesons

The invariant mass spectrum of the $e^{+}e^{-}$ and $\mu ^{+}\mu ^{-}$ pairs from decays of light unflavored mesons with masses below the $\phi (1020)$-meson mass to final states containing along with a dilepton pair one photon, one meson, and two mesons are calculated within the framework of the effective meson theory. The results can be used for simulations of the dilepton spectra in heavy-ion collisions and for experimental searches of dilepton meson decays.Comment: 73 pages, 19 figures, 3 tables, REVTeX, new references adde

‘Stumbling through’? Relationship-based social work practice in austere times

In recent times relationship-based practice has become a familiar term in social work practice and education. Despite its widespread adoption, how relationship-based practice is understood varies widely. Drawing on contemporary conceptualisations of the child and family and individuals as psychosocial subjects experiencing social suffering, this paper explores how current social work practice can be understood in the context of neoliberalism and austerity. Setting these ideas in an historical context helps to inform our understanding as to why social work seems to be the focus of sustained political discontent and scrutiny, making it difficult to retain a balanced relationship-based professional stance. Contemporary responses to the current challenges of everyday practice are outlined and the contribution of psychodynamic and systemic ideas to promoting relationship-based practice is explored. The paper concludes by considering how the concept of social systems as defences against anxiety can inform our understanding of the resistance amongst practitioners to relationship-based practice and emphasises the importance of reflective spaces and places for developing and maintaining integrated, mature relational approaches to practice which impact on practice at both the individual casework and social structural level

Topics in Chiral Perturbation Theory

I consider some selected topics in chiral perturbation theory (CHPT). For the meson sector, emphasis is put on processes involving pions in the isospin zero S-wave which require multi-loop calculations. The advantages and shortcomings of heavy baryon CHPT are discussed. Some recent results on the structure of the baryons are also presented.Comment: 30 pp, TeX, Review talk, Third Workshop on High Energy Particle Physics (WHEPP III), Madras, India, January 1994. 7 figures available upon request. CRN--94/0

Production and Decay of D_1(2420)^0 and D_2^*(2460)^0

We have investigated $D^{+}\pi^{-}$ and $D^{*+}\pi^{-}$ final states and observed the two established $L=1$ charmed mesons, the $D_1(2420)^0$ with mass $2421^{+1+2}_{-2-2}$ MeV/c$^{2}$ and width $20^{+6+3}_{-5-3}$ MeV/c$^{2}$ and the $D_2^*(2460)^0$ with mass $2465 \pm 3 \pm 3$ MeV/c$^{2}$ and width $28^{+8+6}_{-7-6}$ MeV/c$^{2}$. Properties of these final states, including their decay angular distributions and spin-parity assignments, have been studied. We identify these two mesons as the $j_{light}=3/2$ doublet predicted by HQET. We also obtain constraints on {\footnotesize $\Gamma_S/(\Gamma_S + \Gamma_D)$} as a function of the cosine of the relative phase of the two amplitudes in the $D_1(2420)^0$ decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by sending mail to: [email protected]