Active experiments using rocket-borne shaped charge barium releases

A reliable payload system and scaled down shaped charges were developed for carrying out experiments in solar-terrestrial magnetospheric physics. Four Nike-Tomahawk flights with apogees near 450 km were conducted to investigate magnetospheric electric fields, and two Taurus-Tomahawk rockets were flown in experiments on the auroral acceleration process in discrete auroras. In addition, a radial shaped charge was designed for plasma perturbation experiments

Ciproxifan, an H~3~ Receptor Antagonist, Improves Learning and Memory in the APP Mouse Model of Alzheimer's Disease

Mice that express the mutant form of the human amyloid precursor gene associated with early-onset familial Alzheimer's disease demonstrate memory deficits and amyloid plaques. We show here that ciproxifan, a prototypical antagonist of H~3~-type histamine receptors, alleviates two types of learning and memory impairments in such mice. These data support the idea that modulation of H~3~ receptors represents a viable therapeutic strategy in the treatment of Alzheimer's disease

The Highest Price Ever: The Great NYSE Seat Sale of 1928-1929 and Capacity Constraints

A surge in orders during the stock market boom of the late 1920s collided against the constraint created by the fixed number of brokers on the New York Stock Exchange. Estimates of the determinants of individual stock bid-ask spreads from panel data reveal that spreads jumped when volume spiked, confirming contemporary observers complaints that there were insufficient counterparties. When the position of the NYSE as the dominant exchange became threatened, the management of the exchange proposed a 25 percent increase in the number of seats in February 1929 by issuing a quarter-seat dividend to all members. While such a "stock split" would be expected to leave the aggregate value of the NYSE unchanged, an event study reveals that its value rose in anticipation of increased efficiency. These expectations were justified as bid-ask spreads became less sensitive to peak volume days after the increase in seats.

Uniaxial-stress induced phase transitions in [001]c-poled 0.955Pb(Zn1/3Nb2/3)O3-0.045PbTiO3

First-order, rhombohedral to orthorhombic, stress-induced phase transitions have been evidenced by bulk charge-stress measurements and X-ray diffraction derived lattice strain measurements in [001]c-poled PZN-4.5PT. The transitions are induced by uniaxial, compressive loads applied either along or perpendicular to the poling direction. In each case, they occur via rotation of the polar vector in the Cm monoclinic plane and the induced lattice strain is hysteretic yet reversible. Although no depoling is observed in the transverse mode, net depolarization is observed under longitudinal stress which is important for the use of [001]c-poled PZN-PT and PMN-PT single crystals in Tonpilz-type underwater projectors.Comment: To be published in Applied Physics Letters, 16 pages, 3 figure

ALESEP: A computer program for the analysis of airfoil leading edge separation bubbles

The ALESEP program for the analysis of the inviscid/viscous interaction which occurs due to the presence of a closed laminar transitional separation bubble on an airflow is presented. The ALESEP code provides a iterative solution of the boundary layer equations expressed in an inverse formulation coupled to a Cauchy integral representation of the inviscid flow. This interaction analysis is treated as a local perturbation to a known solution obtained from a global airfoil analysis. Part of the required input to the ALESEP code are the reference displacement thickness and tangential velocity distributions. Special windward differencing may be used in the reversed flow regions of the separation bubble to accurately account for the flow direction in the discretization of the streamwise convection of momentum. The ALESEP code contains a forced transition model based on a streamwise intermittency function and a natural transition model based on a solution of the integral form of the turbulent kinetic energy equation. Instructions for the input/output, and program usage are presented

Accounting for the Decline in AFDC Caseloads: Welfare Reform or Economic Growth?

Nationwide, AFDC caseloads have decreased by about 18 percent since March 1994, while some states, such as Wisconsin, Indiana, and Oregon, have seen declines of 40 percent or more. Two factors are frequently suggested as possible causes: state-level experiments with welfare reform and strong economic growth. In this paper, we use state-level monthly panel data from 1987 to 1996 to assess the importance of each of these factors by estimating a model of AFDC caseloads as a dynamic function of time-dependent state welfare reform variables (welfare waivers) and economic variables such as per capita employment. Our results from the dynamic model suggest that the decline in per capita AFDC caseloads is attributable largely to the economic growth of states and not to waivers from federal welfare policies. In the 26 states experiencing at least a 20 percent decline in per capita AFDC caseloads between 1993 and 1996, we attribute 78 percent of the decline to business-cycle factors and 6 percent to welfare waivers.

Chiral Vortons and Cosmological Constraints on Particle Physics

We investigate the cosmological consequences of particle physics theories that admit stable loops of current-carrying string - vortons. In particular, we consider chiral theories where a single fermion zero mode is excited in the string core, such as those arising in supersymmetric theories with a D-term. The resulting vortons formed in such theories are expected to be more stable than their non-chiral cousins. General symmetry breaking schemes are considered in which strings formed at one symmetry breaking scale become current-carrying at a subsequent phase transition. The vorton abundance is estimated and constraints placed on the underlying particle physics theories from cosmological observations. Our constraints on the chiral theory are considerably more stringent than the previous estimates for more general theories.Comment: minor corrections made. This version will appear in PR

Effects of temperature upon the collapse of a Bose-Einstein condensate in a gas with attractive interactions

We present a study of the effects of temperature upon the excitation frequencies of a Bose-Einstein condensate formed within a dilute gas with a weak attractive effective interaction between the atoms. We use the self-consistent Hartree-Fock Bogoliubov treatment within the Popov approximation and compare our results to previous zero temperature and Hartree-Fock calculations The metastability of the condensate is monitored by means of the $l=0$ excitation frequency. As the number of atoms in the condensate is increased, with $T$ held constant, this frequency goes to zero, signalling a phase transition to a dense collapsed state. The critical number for collapse is found to decrease as a function of temperature, the rate of decrease being greater than that obtained in previous Hartree-Fock calculations.Comment: 4 pages LaTeX, 3 eps figures. To appear as a letter in J. Phys.

AMPS definition study on Optical Band Imager and Photometer System (OBIPS)

A study was conducted to define the characteristics of a modular optical diagnostic system (OBIPS) for AMPS, to provide input to Phase B studies, and to give information useful for experiment planning and design of other instrumentation. The system described consists of visual and UV-band imagers and visual and UV-band photometers; of these the imagers are most important because of their ability to measure intensity as a function of two spatial dimensions and time with high resolution. The various subsystems of OBIPS are in themselves modular with modules having a high degree of interchangeability for versatility, economy, and redundancy

Dynamical correlation functions for an impenetrable Bose gas with Neumann or Dirichlet boundary conditions

We study the time and temperature dependent correlation functions for an impenetrable Bose gas with Neumann or Dirichlet boundary conditions $\langle \psi(x_1,0)\psi^\dagger(x_2,t)\rangle _{\pm,T}$. We derive the Fredholm determinant formulae for the correlation functions, by means of the Bethe Ansatz. For the special case $x_1=0$, we express correlation functions with Neumann boundary conditions $\langle\psi(0,0)\psi^\dagger(x_2,t)\rangle _{+,T}$, in terms of solutions of nonlinear partial differential equations which were introduced in \cite{kojima:Sl} as a generalization of the nonlinear Schr\"odinger equations. We generalize the Fredholm minor determinant formulae of ground state correlation functions $\langle\psi(x_1)\psi^\dagger(x_2)\rangle _{\pm,0}$ in \cite{kojima:K}, to the Fredholm determinant formulae for the time and temperature dependent correlation functions $\langle\psi(x_1,0)\psi^\dagger(x_2,t)\rangle _{\pm,T}$, $t \in {\bf R}$, $T \geq 0$