Precision limits of the twin-beam multiband URSULA

URSULA is a multiband astronomical photoelectric photometer which minimizes errors introduced by the presence of the atmosphere. It operates with two identical channels, one for the star to be measured and the other for a reference star. After a technical description of the present version of the apparatus, some measurements of stellar sources of different brightness, and in different atmospheric conditions are presented. These measurements, based on observations made with the 91 cm Cassegrain telescope of the Catania Astrophysical Observatory, are used to check the photometer accuracy and compare its performance with that of standard photometers

Double-Slit Interferometry with a Bose-Einstein Condensate

A Bose-Einstein "double-slit" interferometer has been recently realized experimentally by (Y. Shin et. al., Phys. Rev. Lett. 92 50405 (2004)). We analyze the interferometric steps by solving numerically the time-dependent Gross-Pitaevski equation in three-dimensional space. We focus on the adiabaticity time scales of the problem and on the creation of spurious collective excitations as a possible source of the strong dephasing observed experimentally. The role of quantum fluctuations is discussed.Comment: 4 pages, 3 figure

SELECTED METABOLIC AND HEMODYNAMIC RESPONSES TO REPEATED STEADY-STATE BOUTS OF INDOOR CYCLING, UTILISING MARGINAL INCREASES IN MECHANICAL POWER OUTPUT: CONSIDERATIONS FOR THE EVALUATION OF INDIVIDUAL COMPETITIVE ROAD CYCLISTS USING A PORTABLE ON-BICYCLE C

Introduction It has been demonstrated by Sanderson, Cavanaugh et a1. (1985), and the authors, (1987 , that impul e and average net power distributions (W) generated about the pedal spindle and crank arms, vary with individual cyclists, either creating a mechanically desirable circular cycling pattern where the impulse is 'smoothed', or a 'butterfly' distribution indicating unequal force distribution(s throughout each pedaling cycle. Based on research performed indoors by Cavanaugh (1985), and Anderson (1986), and this group outdoors at the United States Cycling Federation Camp in Colorado in 1987 and 1988, it appears that techniques employed to reduce the counter-propulsive tangential crank arm forces could possible improve average net power magnitudes produced by individual elite cyclists outdoors during competition, and thus improve their overall time(s) recorded for selected events

Tuning the tribological performance of plasma-treated hybrid layers of PEEK-GO-DLC

Graphene and graphene oxide (GO)-based coatings are of great interest due to their mechanical, electrical and/or thermal performance that add functionalities to materials employed in many industrial and biomedical applications. Hybrid diamond-like carbon (DLC)/GO coatings on poly ether etherketone (PEEK) devices, e.g. orthopaedic implants, can add multiple functionalities, such as an enhanced bioactivity. In this work, we describe the mechanical stability and tribological behaviour of such coating, comparing it to a DLC-coated bare PEEK. The GO functionalisation of PEEK is realised from a water solution, whereas the DLC coatings are obtained through plasma-enhanced chemical vapour deposition, using various combinations of different precursor gases. We employ atomic force microscopy to investigate the morphology and interfacial adhesion characteristics of the materials. Then, the scratch coefficient of friction of the samples is measured under both constant-load and progressive-load conditions, also in combination with acoustic emission signals. We identify the most effective and promising plasma treatments to ensure stable coating, and discuss the effect of the presence of an intermediate GO layer