Measurements of Sheath Currents and Equilibrium Potential on the Explorer VIII Satellite (1960 xi)

Experimental data were obtained from the Explorer VIII satellite on five parameters pertinent to the problem of the interaction of space vehicles with an ionized atmosphere. The five parameters are: photoemission current due to electrons emitted from the satellite surfaces as a result of solar radiation; electron and positive ion currents due to the diffusion of charged particles from the medium to the spacecraft; the vehicle potential relative to the medium, and the ambient electron temperature. Included in the experimental data is the aspect dependence of the photoemission and diffusion currents. On the basis of the observations, certain characteristics of the satellite's plasma sheath are postulated

Path integrals on a flux cone

This paper considers the Schroedinger propagator on a cone with the conical singularity carrying magnetic flux (``flux cone''). Starting from the operator formalism and then combining techniques of path integration in polar coordinates and in spaces with constraints, the propagator and its path integral representation are derived. "Quantum correction" in the Lagrangian appears naturally and no a priori assumption is made about connectivity of the configuration space.Comment: LaTeX file, 9 page

Aspects of classical and quantum motion on a flux cone

Motion of a non-relativistic particle on a cone with a magnetic flux running through the cone axis (a ``flux cone'') is studied. It is expressed as the motion of a particle moving on the Euclidean plane under the action of a velocity-dependent force. Probability fluid (``quantum flow'') associated with a particular stationary state is studied close to the singularity, demonstrating non trivial Aharonov-Bohm effects. For example, it is shown that near the singularity quantum flow departs from classical flow. In the context of the hydrodynamical approach to quantum mechanics, quantum potential due to the conical singularity is determined and the way it affects quantum flow is analysed. It is shown that the winding number of classical orbits plays a role in the description of the quantum flow. Connectivity of the configuration space is also discussed.Comment: LaTeX file, 21 pages, 8 figure

Approach to Perturbative Results in the N-Delta Transition

We show that constraints from perturbative QCD calculations play a role in the nucleon to Delta(1232) electromagnetic transition even at moderate momentum transfer scales. The pQCD constraints, tied to real photoproduction data and unseparated resonance response functions, lead to explicit forms for the helicity amplitudes wherein the E2/M1 ratio remains small at moderately large momentum transfer.Comment: 4 pages, 2 figures, ReVTe

Phase Space Reduction and Vortex Statistics: An Anyon Quantization Ambiguity

We examine the quantization of the motion of two charged vortices in a Ginzburg--Landau theory for the fractional quantum Hall effect recently proposed by the first two authors. The system has two second-class constraints which can be implemented either in the reduced phase space or Dirac-Gupta-Bleuler formalism. Using the intrinsic formulation of statistics, we show that these two ways of implementing the constraints are inequivalent unless the vortices are quantized with conventional statistics; either fermionic or bosonic.Comment: 14 pages, PHYZZ

Nucleon to Delta Weak Excitation Amplitudes in the Non-relativistic Quark Model

We investigate the nucleon to Delta(1232) vector and axial vector amplitudes in the non-relativistic quark model of the Isgur-Karl variety. A particular interest is to investigate the SU(6) symmetry breaking, due to color hyperfine interaction. We compare the theoretical estimates to recent experimental investigation of the Adler amplitudes by neutrino scattering.Comment: \documentstyle[aps]{revtex}, 21pages; 11 postscript figures. Accepted for publication by Phys. Rev.

Curved branes from string dualities

We describe a simple method for generating new string solutions for which the brane worldvolume is a curved space. As a starting point we use solutions with NS-NS charges combined with 2-d CFT's representing different parts of space-time. We illustrate our method with many examples, some of which are associated with conformally invariant sigma models. Using U-duality, we also obtain supergravity solutions with RR charges which can be interpreted as D-branes with non-trivial worldvolume geometry. In particular, we discuss the case of a D5-brane wrapped on AdS_3 x S^3, a solution interpolating between AdS_3 x S^3 x R^5 and AdS_3 x S^3 x S^3 x R, and a D3-brane wrapped over S^3 x R or AdS_2 x S^2. Another class of solutions we discuss involves NS5-branes intersecting over a 3-space and NS5-branes intersecting over a line. These solutions are similar to D7-brane or cosmic string backgrounds.Comment: 21 pages, harvmac; misprint correcte

Efficacy of a combination of imidacloprid 10%/moxidectin 2.5% spot-on (Advocate® for dogs) in the prevention of canine spirocercosis (Spirocerca lupi)

The nematode Spirocerca lupi is a major canine parasite in warm regions of the world, classically causing parasitic nodules in the esophagus, aortic aneurysms, and spondylitis. This study evaluated the preventive efficacy of monthly treatment with imidacloprid 10%/moxidectin 2.5% spot-on (Advocate® for dogs) administered over a period of 9 months in young dogs naturally exposed to S. lupi on Réunion island. One hundred and twelve puppies, aged from 2.0 to 4.0 months and with a negative spirocerca fecal examination at inclusion, completed the study. They were randomly allocated to two groups. Group A puppies (n = 58) received nine spot-on treatments with Advocate® at the minimum dose of 2.5 mg moxidectin/kg bw at monthly intervals. Control group B puppies (n = 54) received no treatment for S. lupi. During the study, regular clinical and fecal examinations were performed, as was final upper gastrointestinal endoscopy. Endoscopy showed that 19 dogs from group B had spirocerca nodules, corresponding to a prevalence of 35.2% in dogs aged 12 to 14 months. In contrast, only one dog from group A had a nodule, corresponding to a preventive efficacy of 94.7% (p < 0.0001). None of the 378 fecal examinations were positive for spirocerca. This study confirms a high prevalence of canine spirocercosis on Réunion and shows that infestation occurs in very young puppies. Furthermore, it demonstrates that monthly spot-on administration of a combination of imidacloprid 10%/moxidectin 2.5% (Advocate® for dogs) in puppies starting at the age of 2 to 4 months achieves effective and safe prevention of canine spirocercosis

Neutral weak currents in pion electroproduction on the nucleon

Parity violating asymmetry in inclusive scattering of longitudinally polarized electrons by unpolarized protons with $\pi^0$ or $\pi^+$ meson production, is calculated as a function of the momentum transfer squared $Q^2$ and the total energy $W$ of the $\pi N$-system. This asymmetry, which is induced by the interference of the one-photon exchange amplitude with the parity-odd part of the $Z^0$-exchange amplitude, is calculated for the $\gamma^*(Z^*)+p\to N+\pi$ processes ($\gamma^*$ is a virtual photon and $Z^*$ a virtual Z-boson) considering the $\Delta$-contribution in the $s-$channel, the standard Born contributions and vector meson ($\rho$ and $\omega$) exchanges in the $t-$channel. Taking into account the known isotopic properties of the hadron electromagnetic and neutral currents, we show that the P-odd term is the sum of two contributions. The main term is model independent and it can be calculated exactly in terms of fundamental constants. It is found to be linear in $Q^2$. The second term is a relatively small correction which is determined by the isoscalar component of the electromagnetic current. Near threshold and in the $\Delta$-region, this isoscalar part is much smaller (in absolute value) than the isovector one: its contribution to the asymmetry depend on the polarization state (longitudinal or transverse) of the virtual photon.Comment: 30 pages 9 figure

Effective Lagrangian Approach to the Theory of Eta Photoproduction in the N∗(1535)N^{*}(1535) Region

We investigate eta photoproduction in the $N^{*}(1535)$ resonance region within the effective Lagrangian approach (ELA), wherein leading contributions to the amplitude at the tree level are taken into account. These include the nucleon Born terms and the leading $t$-channel vector meson exchanges as the non-resonant pieces. In addition, we consider five resonance contributions in the $s$- and $u$- channel; besides the dominant $N^{*}(1535)$, these are: $N^{*}(1440),N^{*}(1520),N^{*}(1650)$ and $N^{*}(1710)$. The amplitudes for the $\pi^\circ$ and the $\eta$ photoproduction near threshold have significant differences, even as they share common contributions, such as those of the nucleon Born terms. Among these differences, the contribution to the $\eta$ photoproduction of the $s$-channel excitation of the $N^{*}(1535)$ is the most significant. We find the off-shell properties of the spin-3/2 resonances to be important in determining the background contributions. Fitting our effective amplitude to the available data base allows us to extract the quantity $\sqrt{\chi \Gamma_\eta} A_{1/2}/\Gamma_T$, characteristic of the photoexcitation of the $N^{*}(1535)$ resonance and its decay into the $\eta$-nucleon channel, of interest to precise tests of hadron models. At the photon point, we determine it to be $(2.2\pm 0.2)\times 10^{-1} GeV^{-1}$ from the old data base, and $(2.2\pm 0.1) \times 10^{-1} GeV^{-1}$ from a combination of old data base and new Bates data. We obtain the helicity amplitude for $N^{*}(1535)\rightarrow \gamma p$ to be $A_{1/2}=(97\pm 7)\times 10^{-3} GeV^{-1/2}$ from the old data base, and $A_{1/2}=(97\pm 6)\times 10^{-3} GeV^{-1/2}$ from the combination of the old data base and new Bates data, compared with the results of the analysis of pion photoproduction yielding $74\pm 11$, in the same units.Comment: 43 pages, RevTeX, 9 figures available upon request, to appear in Phys. Rev.