Peculiar Features of the Interaction Potential between Hydrogen and Antihydrogen at Intermediate Separations

We evaluate the interaction potential between a hydrogen and an antihydrogen using the second-order perturbation theory within the framework of the four-body system in a separable two-body basis. We find that the H-Hbar interaction potential possesses the peculiar features of a shallow local minimum located around interatomic separations of r ~ 6 a.u. and a barrier rising at r~5 a.u. Additional theoretical and experimental investigations on the nature of these peculiar features will be of great interest.Comment: 13 pages, 6 figure

Insulin-like growth factor I is an independent coregulatory modulator of natural killer (NK) cell activity.

We aimed to investigate the natural killer (NK) cell activity in hGH-deficient adults and to analyze the effect of insulin-like growth factor (IGF)-I in uivo and in vitro on NK cell activity. NK cell activity was measured in a 4-h nonisotopic assay with europium-labeled and cryopreserved K-562 cells. NK-cell numbers were measured after incubation with murine monoclonal CD3 and CD16 antibodies by flow cytometry analysis. In a cross-sectional study, the basal and interferon- p (IFN-P) stimulated (1000 IU/ml) NK cell activity of 15 hGHdeficient patients and 15 age- and sex-matched controls was measured. The percentages and absolute numbers of CD3./16+ NK-cells were not significantly different in the patient vs. control group. The basal and IFN-P stimulated NK cell activity however was significantly decreased in the patient vs. control group at all effecter/target (E/T) cell ratios from 12.5-100 (e.g. 17 ? 3 vs. 28 ? 3% lysis without IFN-P, P < 0.05, and 42 t 4 vs. 57 2 4% lysis with IFN-0, P < 0.05; both at E/T 50). IGF-I levels of patients and controls showed a significant positive correlation with NK cell activity (r = 0.37; P < 0.05). In an IGF-I in vitro study (IGF-I in vitro 250-1250 kg/L), the basal and IFN-P stimulated NK cell activity of 13 hGH-deficient patients and of 18 normal subjects was significantly enhanced by IGF-I in vitro (e.g. GH-deficient patients: 9 ? 2 us. 10 2 2% lysis without IFN-P, P < 0.05 and 25 + 4 vs. 30 + 4% lysis with IFN-/3, P < 0.005; and normal subjects: 15 + 3 vs. 23 ? 3% lysis without IFN-/3, P < 0.001 and 35 2 4 us. 44 + 5% lysis with IFN-P, P < 0.001; both at IGF-I 500 pg/L). In summary, in our cross-sectional study, adult GH-deficient patients showed a significantly lower basal and IFN-P stimulated NK cell activity than matched controls, despite equal NK cell numbers. IGF-I levels of patients and controls showed a weak positive correlation with NK cell activity. In an in vitro study, IGF-I significantly enhanced basal and IFN-P stimulated NK cell activity of hGH-deficient patients and also of normal subjects. The decreased NK cell activity in GHdeficient patients may be caused at least in part by low serum IGF-I levels. IGF-I appears to be an independent coregulatory modulator of NK cell activity. (Endocrinology 137: 5332-5336, 1996

Hydrogen molecule-antihydrogen atom potential energy surface and scattering calculations

We have calculated ground state interaction energies for an antihydrogen atom and a hydrogen molecule within the Born–Oppenheimer approximation. Leptonic energies were calculated using a large basis set of explicitly correlated Gaussian functions. Energies were calculated at over 2800 geometries including different proton–proton distances. The energies have been fit to functional forms using a neural network for the short-range interaction which is combined with asymptotic formulas at long range. A two-dimensional rigid rotor and a three-dimensional atom–molecule potential energy surface (PES) have been determined. Rigid-rotor scattering calculations on these surfaces have been carried out using the S-matrix Kohn variational method with a two-dimensional Gaussian basis set. We have calculated cross sections for elastic, rotationally inelastic and annihilation collisions on the two-dimensional PES. This includes the first calculation of leptonic annihilation for this system

Growth Hormone (GH)-Releasing Peptide Stimulation of GH Release from Human Somatotroph Adenoma Cells: Interaction with GH-Releasing Hormone, Thyrotropin- Releasing Hormone, and Octreotide.

The synthetic hexapeptide GH-releasing peptide (GHRP; His-D-Trp-Ala-Trp-D-Phe-Lys-NH2) specifically stimulates GH secretion in humans in vivo and in animals in vitro and in vivo via a still unknown receptor and mechanism. To determine the effect of GHRP on human somatotroph cells in vitro, we stimulated cell cultures derived from 12 different human somatotroph adenomas with GHRP alone and in combination with GH-releasing hormone (GHRH), TRH, and the somatostatin analog octreotide. GH secretion of all 12 adenoma cultures could be stimulated with GHRP, whereas GHRH was active only in 6 adenoma cultures. In GHRH-responsive cell cultures, simultaneous application of GHRH and GHRP had an additive effect on GH secretion. TRH stimulated GH release in 4 of 7 adenoma cultures; in TRH-responsive cell cultures there was also an additive effect of GHRP and TRH on GH secretion. In 5 of 9 adenoma cultures investigated, octreotide inhibited basal GH secretion. In these cell cultures, GHRP-induced GH release was suppressed by octreotide. In 5 of 5 cases, the protein kinase-C inhibitor phloretin partly inhibited GHRP-stimulated GH release, but not basal GH secretion. In summary, GH secretion was stimulated by GHRP in all somatotroph adenomas investigated, indicating that its unknown receptor and signaling pathway are expressed more consistently in somatotroph adenoma cells than those for GHRH, TRH, and somatostatin. Our data give further evidence that GHRP-stimulated GH secretion is mediated by a receptor different from that for GHRH or TRH, respectively, and that protein kinase-C is involved in the signal transduction pathway. Because human somatotroph adenoma cell cultures respond differently to various neuropeptides (GHRH, TRH, somatostatin, and others), they provide a model for further investigation of the mechanism of action of GHRP-induced GH secretion

Helping veterans achieve work: A Veterans Health Administration nationwide survey examining effective job development practices in the community.

Objective: Veterans Health Administration vocational services assist veterans with mental illness to acquire jobs; one major component of these services is job development. The purpose of this study was to characterize the nature of effective job development practices and to examine perceptions and intensity of job development services. Method: A national mixed-methods online survey of 233 Veterans Health Administration vocational providers collected data regarding frequency of employer contacts, perceptions of job development ease/difficulty, and effective job development practices when dealing with employers. Qualitative responses elucidating effective practices were analyzed using content analysis. Results: Vocational providers had a modest number of job development employer contacts across 2 weeks (M = 11.0, SD = 10.6) and fewer were face-to-face (M = 7.6, SD = 8.4). Over 70% of participants perceived job development to be difficult. Six major themes emerged regarding effective job development practices with employers: using an employer-focused approach; utilizing a targeted marketing strategy; engaging in preparation and follow-up; going about the employer interaction with genuineness, resilience, and a strong interpersonal orientation; serving as an advocate for veterans and educator of employers; utilizing specific employer-tailored strategies, such as arranging a one-on-one meeting with a decision maker and touring the business, individualizing a prescripted sales pitch, connecting on a personal level, and engaging in ongoing communication to solidify the working relationship. Conclusions and implications for practice: Respondents highlight several potentially effective job development strategies; tools and resources may be developed around these strategies to bolster job development implementation and allow opportunities for fruitful employer interactions

Variational calculations for the hydrogen-antihydrogen system with a mass-scaled Born-Oppenheimer potential

The problem of proton-antiproton motion in the ${\rm H}$--${\rm \bar{H}}$ system is investigated by means of the variational method. We introduce a modified nuclear interaction through mass-scaling of the Born-Oppenheimer potential. This improved treatment of the interaction includes the nondivergent part of the otherwise divergent adiabatic correction and shows the correct threshold behavior. Using this potential we calculate the vibrational energy levels with angular momentum 0 and 1 and the corresponding nuclear wave functions, as well as the S-wave scattering length. We obtain a full set of all bound states together with a large number of discretized continuum states that might be utilized in variational four-body calculations. The results of our calculations gives an indication of resonance states in the hydrogen-antihydrogen system

Surfaces immersed in su(N+1) Lie algebras obtained from the CP^N sigma models

We study some geometrical aspects of two dimensional orientable surfaces arrising from the study of CP^N sigma models. To this aim we employ an identification of R^(N(N+2)) with the Lie algebra su(N+1) by means of which we construct a generalized Weierstrass formula for immersion of such surfaces. The structural elements of the surface like its moving frame, the Gauss-Weingarten and the Gauss-Codazzi-Ricci equations are expressed in terms of the solution of the CP^N model defining it. Further, the first and second fundamental forms, the Gaussian curvature, the mean curvature vector, the Willmore functional and the topological charge of surfaces are expressed in terms of this solution. We present detailed implementation of these results for surfaces immersed in su(2) and su(3) Lie algebras.Comment: 32 pages, 1 figure; changes: major revision of presentation, clarifications adde

Large dimension Configuration Interaction calculations of positron binding to the group II atoms

The Configuration Interaction (CI) method is applied to the calculation of the structures of a number of positron binding systems, including e+Be, e+Mg, e+Ca and e+Sr. These calculations were carried out in orbital spaces containing about 200 electron and 200 positron orbitals up to l = 12. Despite the very large dimensions, the binding energy and annihilation rate converge slowly with l, and the final values do contain an appreciable correction obtained by extrapolating the calculation to the l to infinity limit. The binding energies were 0.00317 hartree for e+Be, 0.0170 hartree for e+Mg, 0.0189 hartree for e+Ca, and 0.0131 hartree for e+Sr.Comment: 13 pages, no figs, revtex format, Submitted to PhysRev

Hydrogen molecule-antihydrogen atom potential energy surface and scattering calculations

We are grateful for helpful discussions with Edward Armour, Martin Plummer and Gleb Gribakin. This work was supported by the UK Engineering and Physical Sciences Research Council (EPSRC) via a Doctoral Training Account studentship for BPM, grant number EP/K502960/1. The contribution of KS was financed by the statutory activity subsidy from the Polish Ministry of Science and Higher Education for the Faculty of Chemistry of Wrocław University of Science and Technology (contract number 0401/0121/18). We thank the EPSRC-funded CCPQ consortium and the Royal Society of Chemistry for further financial support. We also thank the referees for their comments on the manuscript.Peer reviewedPublisher PD