Gimbal angle sensor

Detector flake located parallel to a slotted mask mechanical differentiator, senses the rotation of a gimballed reaction wheel mounting. As the gimbal moves light passes through the mask and strikes a section of the detector, the electrical output of which has been calibrated in terms of degrees of rotation

A Dynamical Self-Consistent Finite Temperature Kinetic Theory: The ZNG Scheme

We review a self-consistent scheme for modelling trapped weakly-interacting quantum gases at temperatures where the condensate coexists with a significant thermal cloud. This method has been applied to atomic gases by Zaremba, Nikuni, and Griffin, and is often referred to as ZNG. It describes both mean-field-dominated and hydrodynamic regimes, except at very low temperatures or in the regime of large fluctuations. Condensate dynamics are described by a dissipative Gross-Pitaevskii equation (or the corresponding quantum hydrodynamic equation with a source term), while the non-condensate evolution is represented by a quantum Boltzmann equation, which additionally includes collisional processes which transfer atoms between these two subsystems. In the mean-field-dominated regime collisions are treated perturbatively and the full distribution function is needed to describe the thermal cloud, while in the hydrodynamic regime the system is parametrised in terms of a set of local variables. Applications to finite temperature induced damping of collective modes and vortices in the mean-field-dominated regime are presented.Comment: Unedited version of chapter to appear in Quantum Gases: Finite Temperature and Non-Equilibrium Dynamics (Vol. 1 Cold Atoms Series). N.P. Proukakis, S.A. Gardiner, M.J. Davis and M.H. Szymanska, eds. Imperial College Press, London (in press). See http://www.icpress.co.uk/physics/p817.htm

Persistent currents in a bosonic mixture in the ring geometry

In this paper we analyze the possibility of persistent currents of a two-species bosonic mixture in the one-dimensional ring geometry. We extend the arguments used by Bloch to obtain a criterion for the stability of persistent currents for the two-species system. If the mass ratio of the two species is a rational number, persistent currents can be stable at multiples of a certain total angular momenta. We show that the Bloch criterion can also be viewed as a Landau criterion involving the elementary excitations of the system. Our analysis reveals that persistent currents at higher angular momenta are more stable for the two-species system than previously thought.Comment: 20 pages and 7 figure

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.

The level of chemokine CXCL5 in the cerebrospinal fluid is increased during the first 24 hours of ischaemic stroke and correlates with the size of early brain damage

Inflammation is an important feature of the pathophysiological response to ischaemic stroke. The ischaemic brain-invading leukocytes, neutrophils in particular, contribute to the exacerbation of tissue injury in stroke. Chemokines are a growing family of proteins performing chemotactic activity on selective leukocyte subpopulations. Chemokines are broadly divided into two major subfamilies on the basis of the arrangement of the two N-terminal cysteine residues, CXC and CC, depending on whether the first two cysteine residues have an amino acid between them (CXC) or are adjacent (CC). CXC chemokines possessing, close to the N terminus, the amino acid sequence glutamic acid-leucine-arginine (ELR motif) specifically act on neutrophils. CXCL5 is one of the ELR-expressing CXC chemokines and is a potent neutrophil attractant and activator. The objective of the study was to detect CXCL5 levels in the cerebrospinal fluid (CSF) and sera of stroke patients and to investigate the relation between these levels and the volume of brain computed tomography (CT) hypodense areas representing early ischaemic lesions. A total of 23 ischaemic stroke patients were studied. CSF and blood sampling and brain CT were performed within the first 24 hours of stroke. The control group consisted of 15 patients with tension headache. CXCL5 levels were determined by the ELISA method. CSF CXCL5 levels in stroke patients were significantly higher in comparison with the control group (38.2 &plusmn; 18.4 pg/ml vs. 18.7 &plusmn; 8.2 pg/ml; p < 0.001). No significant differences in serum CXCL5 levels were found between the stroke patients and the control group. CSF CXCL5 levels correlated positively with the volume of early brain CT hypodense areas (p < 0.0001). The results suggest that CXCL5 may play a role in the inflammatory reaction during the early phase of ischaemic stroke

Evaluation of a semi-active gravity gradient system. Volume I - Technical summary

Semi-active gravity gradient system for attitude control of earth oriented spacecraf

Transverse Magnetoresistance of GaAs/AlGaAs Heterojunctions in the Presence of Parallel Magnetic Fields

We have calculated the resistivity of a GaAs\slash AlGaAs heterojunction in the presence of both an in--plane magnetic field and a weak perpendicular component using a semiclassical Boltzmann transport theory. These calculations take into account fully the distortion of the Fermi contour which is induced by the parallel magnetic field. The scattering of electrons is assumed to be due to remote ionized impurities. A positive magnetoresistance is found as a function of the perpendicular component, in good qualitative agreement with experimental observations. The main source of this effect is the strong variation of the electronic scattering rate around the Fermi contour which is associated with the variation in the mean distance of the electronic states from the remote impurities. The magnitude of the positive magnetoresistance is strongly correlated with the residual acceptor impurity density in the GaAs layer. The carrier lifetime anisotropy also leads to an observable anisotropy in the resistivity with respect to the angle between the current and the direction of the in--plane magnetic field.Comment: uuencoded file containing a 26 page RevTex file and 14 postscript figures. Submitted to Phys. Rev.