THE PRE-CUSP PHASE OF TORMAC IV AND V

An heuristic analysis of the pre-cusp phase of the present Tormac experiments has been carried out. The immediate goal has been to identify the requirements for producing a stabilized pinch in Tormac V qualitatively similar to that in Tormac IV. Concurrently, V has been modified to increase the pinch current and experimental investigation is underway. The experimental procedure is to introduce a toroidal magnetic field into the gas filled chamber. A toroidal electric field is then induced which ionizes the gas; the associated toroidal current simultaneously pinches the discharge. Uncertainty about the details of this process, in particular, about the amount of toroidal flux trapped within the pinch, has led to a one parameter theory. Speculation about the plasma heating mechanism and the subsequent interaction of pinch and cusp is left aside at this time. The chambers are basically rectangular in cross section; but, for simplicity, an equivalent radius is used. Although the experimental discharge probably evolves into a diffuse pinch, a cylindrical sheet pinch model is studied as a first step in understanding the qualitative features of the experiment. A simple Alfven scaling for instability time scales, appropriate for the previous weak pinch and considered in the design of the ringing frequency of the induction circuit is now supplemented by the sheet pinch model. If merited, a more quantitative numerical diffuse pinch model can be developed later. It should be pointed out that cusp confinement, the central problem of the Tormac program, is not addressed here. The goal is simply to identify the requirements for reproducing this particular phase of the Tormac IV experiment

Preclinical Assessment of HIV Vaccines and Microbicides by Repeated Low-Dose Virus Challenges

BACKGROUND: Trials in macaque models play an essential role in the evaluation of biomedical interventions that aim to prevent HIV infection, such as vaccines, microbicides, and systemic chemoprophylaxis. These trials are usually conducted with very high virus challenge doses that result in infection with certainty. However, these high challenge doses do not realistically reflect the low probability of HIV transmission in humans, and thus may rule out preventive interventions that could protect against “real life” exposures. The belief that experiments involving realistically low challenge doses require large numbers of animals has so far prevented the development of alternatives to using high challenge doses. METHODS AND FINDINGS: Using statistical power analysis, we investigate how many animals would be needed to conduct preclinical trials using low virus challenge doses. We show that experimental designs in which animals are repeatedly challenged with low doses do not require unfeasibly large numbers of animals to assess vaccine or microbicide success. CONCLUSION: Preclinical trials using repeated low-dose challenges represent a promising alternative approach to identify potential preventive interventions

Long Range Forces from Pseudoscalar Exchange

Using dispersion theoretic techniques, we consider coherent long range forces arising from double pseudoscalar exchange among fermions. We find that Yukawa type coupling leads to $1/r^3$ spin independent attractive potentials whereas derivative coupling renders $1/r^5$ spin independent repulsive potentials.Comment: 27 pages, REVTeX, 3 figures included using epsfi

Does the complex deformation of the Riemann equation exhibit shocks?

The Riemann equation $u_t+uu_x=0$, which describes a one-dimensional accelerationless perfect fluid, possesses solutions that typically develop shocks in a finite time. This equation is \cP\cT symmetric. A one-parameter \cP\cT-invariant complex deformation of this equation, $u_t-iu(iu_x)^\epsilon= 0$ ($\epsilon$ real), is solved exactly using the method of characteristic strips, and it is shown that for real initial conditions, shocks cannot develop unless $\epsilon$ is an odd integer.Comment: latex, 8 page

Effects of Bose-Einstein Condensation on forces among bodies sitting in a boson heat bath

We explore the consequences of Bose-Einstein condensation on two-scalar-exchange mediated forces among bodies that sit in a boson gas. We find that below the condensation temperature the range of the forces becomes infinite while it is finite at temperatures above condensation.Comment: 10 pages, 2 figure

Addendum to Finite-size effects on multibody neutrino exchange

The interaction energy of the neutrons due to massless neutrino exchange in a neutron star has recently been proved, using an effective theory, to be extremely small and infrared-safe. Our comment here is of conceptual order: two approaches to compute the total interaction energy density have recently been proposed. Here, we study the connection between these two approaches. From CP invariance, we argue that the resulting interaction energy has to be even in the parameter $b=-G_F n_n /\sqrt{2}$, which expresses the static neutrino potential created by a neutron medium of density $n_n$.Comment: Latex file (Revtex), 9 pages, 1 figure, one reference change

Transparent Nuclei and Deuteron-Gold Collisions at RHIC

The current normalization of the cross section of inclusive high-pT particle production in deuteron-gold collisions measured RHIC relies on Glauber calculations for the inelastic d-Au cross section. These calculations should be corrected for diffraction. Moreover, they miss the Gribov's inelastic shadowing which makes nuclei more transparent (color transparency). The magnitude of this effect rises with energy and it may dramatically affect the normalization of the RHIC data. We evaluate these corrections employing the light-cone dipole formalism and found a rather modest corrections for the current normalization of the d-Au data. The results of experiments insensitive to diffraction (PHENIX, PHOBOS) should be renormalized by about 20% down, while those which include diffraction (STAR), by only 10%. Such a correction completely eliminates the Cronin enhancement in the PHENIX data for pions. The largest theoretical uncertainty comes from the part of the inelastic shadowing which is related to diffractive gluon radiation, or gluon shadowing. Our estimate is adjusted to data for the triple-Pomeron coupling, however, other models do not have such a restrictions and predict much stronger gluon shadowing. Therefore, the current data for high-pT hadron production in d-Au collisions at RHIC cannot exclude in a model independent way the possibility if initial state suppression proposed by Kharzeev-Levin-McLerran. Probably the only way to settle this uncertainty is a direct measurement of the inelastic d-Au cross sections at RHIC. Also d-Au collisions with a tagged spectator nucleon may serve as a sensitive probe for nuclear transparency and inelastic shadowing. We found an illuminating quantum-mechanical effect: the nucleus acts like a lens focusing spectators into a very narrow cone.Comment: Latex 50 pages. Based on lectures given by the author at Workshop on High-pT Correlations at RHIC, Columbia University, May-June, 2003. The version to appear in PR

Does State Antitrust Enforcement Drive Establishment Exit?

Previous work has shown that state-level antitrust enforcement activity may have impacts on entry and relocation behavior by U.S. firms. Significant state-level antitrust activity may be an indicator of a perceived adverse business environment and it is found to deter establishment entry, particularly for larger firms in the retail and wholesale sectors. An obvious question is whether establishment exit is affected in a symmetric way, or whether sunk costs of market entry may lead to a smaller impact in terms of the exit decisions. We first combine US Census establishment exit panel data with data for 1998-2006 on US state-level antitrust activity and other measures of state-level business activities that may affect establishment exit. We also consider establishment exit across different broad industry types - manufacturing, retail and wholesale - and several firm size categories. Local business cycle factors seem to be the primary driver of exit, though there is some evidence of political and antitrust determinants as well. In another approach, we examine firmlevel exit decisions and the extent to which these respond to state antitrust enforcement, with some indication of antitrust enforcement effects here as well, especially in the wholesale and retail sectors

Atomic excitations during the nuclear {\ss}- decay in light atoms

Probabilities of various final states are determined numerically for a number of {\ss}- decaying light atoms. In our evaluations of the final state probabilities we have used the highly accurate atomic wave functions constructed for each few-electron atom/ion. We also discuss an experimental possibility to observe negatively charged ions which form during the nuclear {\ss}+ decays. High order corrections to the results obtained for {\ss}+/- decays in few-electron atoms with the use of sudden approximation are considered.Comment: 26 pages, 40 references, 6 tables and 0 figure

Light from Cascading Partons in Relativistic Heavy-Ion Collisions

We calculate the production of high energy photons from Compton and annihilation processes as well as fragmentation off quarks in the parton cascade model. The multiple scattering of partons is seen to lead to a substantial production of high energy photons, which rises further when parton multiplication due to final state radiation is included. The photon yield is found to be proportional to the number of collisions among the cascading partons.Comment: revised version: 4 pages, 4 figures, uses REVTEX