Integrated Analysis of Pressure Transient Tests in the Gulf of Mexico

Imperial Users onl

Deconstructing the Antlia cluster core

The present literature does not give a satisfactory answer to the question about the nature of the "Antlia galaxy cluster". The radial velocities of galaxies found in the region around the giant ellipticals NGC 3258/3268 range from about 1000 km/s to 4000 km/s. We characterise this region and its possible kinematical and population substructure. We have obtained VLT--VIMOS multi-object spectra of the galaxy population in the inner part of the Antlia cluster and measure radial velocities for 45 potential members. We supplement our galaxy sample with literature data, ending up with 105 galaxy velocities. We find a large radial velocity dispersion for the entire sample as reported in previous papers. However, we find three groups at about 1900 km/s, 2800 km/s, and 3700 km/s, which we interpret as differences in the recession velocities rather than peculiar velocities. The high radial velocity dispersion of galaxies in the Antlia region reflects a considerable extension along the line of sight.Comment: 11 pages, 7 figures, accepted in A&

FIML estimation of an endogenous switching model for count data

We develop FIML code for estimating a Poisson Count data model with lognormal unobserved heterogeneity and an endogenous dummy variable as proposed by Terza (1998). Gauss-Hermite quadrature is used for calculating the log-likelihood and a -ml d0- method is employed. We present an example and discuss the problems found during the development of the code.

Small entries of neutrino mass matrices

We consider phenomenologically allowed structures of the neutrino mass matrix in the case of three light neutrino species. Constraints from the solar, atmospheric and reactor neutrino experiments as well as those from the neutrinoless double beta decay are taken into account. Both hierarchical and quasi-degenerate neutrino mass cases are studied. Assuming maximal $\nu_\mu-\nu_\tau$ mixing we derive simple approximate expressions giving the values of the neutrino masses and remaining lepton mixing angles in terms of the entries of the neutrino mass matrix. Special attention is paid to the small entries which are usually not specified in discussions of the neutrino mass matrix textures. We specifically discuss the stability of neutrino masses and lepton mixing angles with respect to the choice and variations of these small entries.Comment: LaTeX, 12 pages, no figures. A few minor typos correcte

Reducing the Number of Annotations in a Verification-oriented Imperative Language

Automated software verification is a very active field of research which has made enormous progress both in theoretical and practical aspects. Recently, an important amount of research effort has been put into applying these techniques on top of mainstream programming languages. These languages typically provide powerful features such as reflection, aliasing and polymorphism which are handy for practitioners but, in contrast, make verification a real challenge. In this work we present Pest, a simple experimental, while-style, multiprocedural, imperative programming language which was conceived with verifiability as one of its main goals. This language forces developers to concurrently think about both the statements needed to implement an algorithm and the assertions required to prove its correctness. In order to aid programmers, we propose several techniques to reduce the number and complexity of annotations required to successfully verify their programs. In particular, we show that high-level iteration constructs may alleviate the need for providing complex loop annotations.Comment: 15 pages, 8 figure

A model for the ESR-STM phenomenon

We propose a model to account for the observed ESR-like signal at the Larmor frequency in the current noise STM experiments identifying spin centers on various substrates. The theoretical understanding of this phenomenon, which allows for single spin detection on surfaces at room temperature, is not settled for the experimentally relevant case that the tip and substrate are not spin polarized. Our model is based on a direct tip-substrate tunneling in parallel with a current flowing via the spin states. We find a sharp signal at the Larmor frequency even at high temperatures, in good agreement with experimental data. We also evaluate the noise in presence of an ac field near resonance and predict splitting of the signal by the Rabi frequency.Comment: 5 pages, 3 figure

Relation Between Local Temperature Gradients and the Direction of Heat Flow in Quantum Driven Systems

We introduce thermometers to define the local temperature of an electronic system driven out-of-equilibrium by local ac fields. We discuss the behavior of the local temperature along the sample, showing that it exhibits spatial fluctuations following an oscillatory pattern. We show explicitly that the local temperature is the correct indicator for heat flow.Comment: 3 pages, 2 figure

On the Top Mass Reconstruction Using Leptons

I discuss the feasibility of measuring the top quark mass by the using of final states with leptons and J/\psi at hadron colliders. I also investigate the impact of matrix-element corrections to the HERWIG simulation of top decays.Comment: 4 pages, 3 figures. Talk given at the UK Phenomenology Workshop on Collider Physics, Durham, U. K., 19-24 September 1999. Revised version with updated result

Multi-rate demodulator architecture

A unique digital multi-rate demodulator (MRD) architecture is presented for onboard satellite communications processing. The multi-rate feature enables the same demodulator hardware to process either one wideband channel (WBC), or process up to thirty-two independent narrowband channels (NBC) that are time division multiplexed (TDM). The MRD can process many quadrature modulation format such as offset quadrature phase shift keying (OQPSK). Possible applications include voice and data transmission for commercial or military users