Distribution of Gamma-Ray Bursts in Halo Neutron Star-Comet Models

The motions of comets and neutron stars have been integrated over five billion years in the Galactic potential to determine a gamma-ray burst distribution, presuming that bursts are the result of interactions between these two families of objects. The comets originate in two distinct populations - one from ejection by stars in the Galactic disk, and the other from ejection by stars in globular clusters. No choice of the free parameters resulted in agreement with both the isotropy data and the $\log(N>F) - \log(F)$ data.Comment: 4 pages LaTex and two style files, tarred, compressed, and uuencoded. One postscript figure. To appear in Astrophysics and Space Science as part of the proceedings of the 29th ESLAB Symposium 'Toward the Source of Gamma-Ray Bursts' held in Noordwijk, 1995. A postscript version can be found at http://astro.queensu.ca/~mark/preprints.htm

The Deutsch Field Gamma-Ray Pulsar - Paper I: The Model Basics

A new model for the high-energy emission from pulsars is developed by considering charged particle motion in the fields of a spinning, highly magnetised and conducting sphere in vacuum. A generally applicable approximation to the particle motion in strong fields is developed and applied to the numerical modelling, and the radiation emitted by curvature emission is summed to generate light curves. The model predicts many of the observed features of pulsar light curves. This paper outlines the basic properties of the model; a subsequent paper will discuss the statistical properties of a population of model pulsars and apply the model to the known gamma-ray pulsars.Comment: 11 pages LaTex, 10 postscript figures included with psfig. The paper can also be found at ftp://astro.queensu.ca/pub/mark/preprints/paper1.ps.Z as a compressed postscript file. Submitted to MNRA

Explaining Inequality the World Round: Cohort Size, Kuznets Curves, andOpenness

Klaus Deininger and Lyn Squire have recently produced an inequality data base for a panel of countries from the 1960s to the 1990s. We use these data to decompose the sources of inequality into three central parts: the demographic or cohort size effect; the so-called Kuznets Curve or demand effects; and the commitment to globalization or policy effects. We also control for education supply, the so-called natural resource curse and other variables suggested by the literature. While the Kuznets Curve comes out of hiding when the inequality relationship is conditioned by the other two, cohort size seems to be the most important force at work. We resolve the apparent conflict between this macro finding on cohort size and the contrary implications of recent research based on micro data.

Nonlinear r-modes in a spherical shell: issues of principle

We use a simple physical model to study the nonlinear behaviour of the r-mode instability. We assume that r-modes (Rossby waves) are excited in a thin spherical shell of rotating incompressible fluid. For this case, exact Rossby wave solutions of arbitrary amplitude are known. We find that: (a) These nonlinear Rossby waves carry ZERO physical angular momentum and positive physical energy, which is contrary to the folklore belief that the r-mode angular momentum and energy are negative. (b) Within our model, we confirm the differential drift reported by Rezzolla, Lamb and Shapiro (1999). Radiation reaction is introduced into the model by assuming that the fluid is electrically charged; r-modes are coupled to electromagnetic radiation through current (magnetic) multipole moments. We find that: (c) To linear order in the mode amplitude, r-modes are subject to the CFS instability, as expected. (d) Radiation reaction decreases the angular velocity of the shell and causes differential rotation (which is distinct from but similar in magnitude to the differential drift reported by Rezzolla et al.) prior to saturation of the r-mode growth. This is contrary to the phenomenological treatments to date, which assume that the loss of stellar angular momentum is accounted for by the r-mode growth. We demonstrate, for the first time, that r-mode radiation reaction leads to differential rotation. (e) We show that for l=2 r-mode electromagnetic radiation reaction is equivalent to gravitational radiation reaction in the lowest post-Newtonian order.Comment: 8 pages, no figures, uses MNRAS style, abstract abridged to fit into 24 line

Genetic Transformation, Regeneration and Analysis of Transgenic Peanut

Crop Production/Industries,

Oil prices: backward to the future?

A useful first guess about the future spot price of a commodity is usually found in its current futures price. But it doesn’t work that way when the commodity in question is oil. This Commentary explains why the characteristics of oil, particularly the value it can offer its owner by remaining in the ground, cloud the information that oil futures prices give about future oil prices.Petroleum industry and trade ; Futures

Entanglement-enhanced measurement of a completely unknown phase

The high-precision interferometric measurement of an unknown phase is the basis for metrology in many areas of science and technology. Quantum entanglement provides an increase in sensitivity, but present techniques have only surpassed the limits of classical interferometry for the measurement of small variations about a known phase. Here we introduce a technique that combines entangled states with an adaptive algorithm to precisely estimate a completely unspecified phase, obtaining more information per photon that is possible classically. We use the technique to make the first ab initio entanglement-enhanced optical phase measurement. This approach will enable rapid, precise determination of unknown phase shifts using interferometry.Comment: 6 pages, 4 figure

Wave packet dynamics of potassium dimers attached to helium nanodroplets

The dynamics of vibrational wave packets excited in K$_2$ dimers attached to superfluid helium nanodroplets is investigated by means of femtosecond pump-probe spectroscopy. The employed resonant three-photon-ionization scheme is studied in a wide wavelength range and different pathways leading to K$^+_2$-formation are identified. While the wave packet dynamics of the electronic ground state is not influenced by the helium environment, perturbations of the electronically excited states are observed. The latter reveal a strong time dependence on the timescale 3-8 ps which directly reflects the dynamics of desorption of K$_2$ off the helium droplets

Quality interoperability within digital libraries: the DL.org perspective

Quality is the most dynamic aspect of DLs, and becomes even more complex with respect to interoperability. This paper formalizes the research motivations and hypotheses on quality interoperability conducted by the Quality Working Group within the EU-funded project DL.org (<a href="http://www.dlorg.eu">http://www.dlorg.eu/</a>). After providing a multi-level interoperability framework – adopted by DL.org - the authors illustrate key-research points and approaches on the way to the interoperability of DLs quality, grounding them in the DELOS Reference Model. By applying the DELOS Reference Model Quality Concept Map to their interoperability motivating scenario, the authors subsequently present the two main research outcomes of their investigation - the Quality Core Model and the Quality Interoperability Survey