Two-wire waveguide and interferometer for cold atoms

A versatile miniature de Broglie waveguide is formed by two parallel current-carrying wires in the presence of a uniform bias field. We derive a variety of analytical expressions to describe the guide and present a quantum theory to show that it offers a remarkable range of possibilities for atom manipulation on the submicron scale. These include controlled and coherent splitting of the wave function as well as cooling, trapping, and guiding. In particular, we discuss a novel microscopic atom interferometer with the potential to be exceedingly sensitive.

Derivation of the probability distribution function for the local density of states of a disordered quantum wire via the replica trick and supersymmetry

We consider the statistical properties of the local density of states of a one-dimensional Dirac equation in the presence of various types of disorder with Gaussian white-noise distribution. It is shown how either the replica trick or supersymmetry can be used to calculate exactly all the moments of the local density of states.' Careful attention is paid to how the results change if the local density of states is averaged over atomic length scales. For both the replica trick and supersymmetry the problem is reduced to finding the ground state of a zero-dimensional Hamiltonian which is written solely in terms of a pair of coupled spins which are elements of u(1, 1). This ground state is explicitly found for the particular case of the Dirac equation corresponding to an infinite metallic quantum wire with a single conduction channel. The calculated moments of the local density of states agree with those found previously by Al'tshuler and Prigodin [Sov. Phys. JETP 68 (1989) 198] using a technique based on recursion relations for Feynman diagrams. (C) 2001 Elsevier Science B.V. All rights reserved.

Effect of cold wire inclination on temperature fluctuation measurements in a heated jet

Hot-wire anemometers at low operating currents are used as fast response resistance thermometers for the study of heated turbulent flows. Simultaneous measurement of temperature and velocity is generally performed with multi-wire arrays. In order to give good spatial resolution a new layout has been tested which uses an inclined temperature wire positioned parallel to the nearest inclined velocity wire. This leads to an asymmetric wire arrangement relative to the mean flow direction. As expected, a reduction in thermal interference from the velocity wires results when compared with an array containing a temperature wire placed normal to the flow. However, measurement of higher order moments of fluctuating quantities in an axisymmetric jet shows considerable distortion of radial distributions which is traced to alteration of the temperature field sensed by the temperature wire. When inclined velocity sensitive wires contain a temperature component, the latter may be affected by the same phenomenon.

Double-heater-wire circuits and heat-and-moisture exchangers and the risk of ventilator-associated pneumonia

Objective: To compare the incidence of ventilator-associated pneumonia (VAP) in patients ventilated in intensive care by means of circuits humidified with a hygroscopic heat-and-moisture exchanger with a bacterial viral filter (HME) or hot-water humidification with a heater wire in both inspiratory and expiratory circuit limbs (DHW) or the inspiratory limb only (SHW). Design: A prospective, randomized trial. Setting: A metropolitan teaching hospital's general intensive care unit. Patients: Three hundred eighty-one patients requiring a minimum period of mechanical ventilation of 48 hrs. Interventions: Patients were randomized to humidification with use of an HME (n = 190), SHW (n = 94), or DHW (n = 97). Measurements and Main Results. Study end points were VAP diagnosed on the basis of Clinical Pulmonary Infection Score (CPIS) (1), HME resistance after 24 hrs of use, endotracheal tube resistance, and HME use per patient. VAP occurred with similar frequency in all groups (13%, HME; 14%, DHW; 10%, SHW; p = 0.61) and was predicted only by current smoking (adjusted odds ratio [AOR], 2.1; 95% confidence interval [CI], 1.1-3.9; p =.03) and ventilation days (AOR, 1.05; 95% Cl, 1.0-1.2; p =.001); VAP was less likely for patients with an admission diagnosis of pneumonia (AOR, 0.40; 95% Cl, 0.4-0.2; p =.04). HME resistance after 24 hrs of use measured at a gas flow of 50 L/min was 0.9 cm H2O (0.4-2.9). Endotracheal tube resistance was similar for all three groups (16-19 cm H2O min/L; p =.2), as were suction frequency, secretion thickness, and blood on suctioning (p =.32, p =.06, and p =.34, respectively). The HME use per patient per day was 1.13. Conclusions: Humidification technique does not influence either VAP incidence or secretion characteristics, but HMEs may have air-flow resistance higher than manufacturer specifications after 24 hrs of use.

Balustrade detail, Brannigan House, St Lucia, Brisbane

Rigging screw tensioners to balustrade wire, central deck (North-East elevation).

Balustrading to deck, Brannigan House, St Lucia, Brisbane

Curved steel and stainless steel wire balustrade to central deck area (North-East elevation).

Characterization of turbulent jets from high-aspect-ratio rectangular nozzles

Turbulent free jets issuing from rectangular slots with various high aspect ratios (15-120) are characterized. The centerline mean and rms velocities are measured using hot-wire anemometry over a downstream distance of up to 160 slot heights at a slot-height-based Reynolds number of 10000. Experimental results suggest that a rectangular jet with sufficiently high aspect ratio (> 15) may be distinguished between three flow zones: an initial quasi-plane-jet zone, a transition zone, and a final quasi-axisymmetric-jet zone. In the quasi-plane-jet zone, the turbulent velocity field is statistically similar, but not identical, to those of a plane jet. (c) 2005 American Institute of Physics.

An "openable," high-strength gradient set for orthopedic MRI

A novel three-axis gradient set and RF resonator for orthopedic MRT has been designed and constructed. The set is openable and may be wrapped around injured joints. The design methodology used was the minimization of magnetic field spherical harmonics by simulated annealing. Splitting of the longitudinal coil presents the major design challenge to a fully openable gradient set and in order to efficiently design such coils, we have developed a new fast algorithm for determining the magnetic field spherical harmonics generated by an are of multiturn wire. The algorithm allows a realistic impression of the effect of split longitudinal designs. A prototype set was constructed based on the new designs and tested in a 2-T clinical research system. The set generated 12 mT/m/A with a linear region of 12 cm and a switching time of 100 mu s, conforming closely with theoretical predictions. Preliminary images from the set are presented. (C) 1999 Academic Press.

Is there a role for transversus abdominis in lumbo-pelvic stability?

There has been considerable interest in the literature regarding the function of transversus abdominis, the deepest of the abdominal muscles, and the clinical approach to training this muscle. With the development of techniques for the investigation of this muscle involving the insertion of fine-wire electromyographic electrodes under the guidance of ultrasound imaging it has been possible to test the hypotheses related to its normal function and function in people with low back pain. The purpose of this review is to provide an appraisal of the current evidence for the role of transversus abdominis in spinal stability, to develop a model of how the contribution of this muscle differs from the other abdominal muscles and to interpret these findings in terms of the consequences of changes in this function.

Determining complicated winding patterns for shim coils using stream functions and the target-field method

In a magnetic resonance imaging equipment, gradient and shim coils are needed to produce a spatially varying magnetic field throughout the sample being imaged. Such coils consist of turns of wire wound on the surface of a cylindrical tube. Shim coils in particular, must sometimes be designed to produce complicated magnetic fields to correct for impurities. Streamline patterns for shim coils are much more complicated than those for gradient coils, In this work we present a detailed analysis of streamline methods and their application to shim coil design, A method is presented for determining the winding patterns to generate these complicated fields. (C) 2002 John Wiley & Sons, Inc.

Fast-convergent iterative scheme for filtering velocity signals and finding Kolmogorov scales

The present fundamental knowledge of fluid turbulence has been established primarily from hot- and cold-wire measurements. Unfortunately, however, these measurements necessarily suffer from contamination by noise since no certain method has previously been available to optimally filter noise from the measured signals. This limitation has impeded our progress of understanding turbulence profoundly. We address this limitation by presenting a simple, fast-convergent iterative scheme to digitally filter signals optimally and find Kolmogorov scales definitely. The great efficacy of the scheme is demonstrated by its application to the instantaneous velocity measured in a turbulent jet.

The design of planar gradient coils. Part I: A winding path correction method

In this work a new approach for designing planar gradient coils is outlined for the use in an existing MRI apparatus. A technique that allows for gradient field corrections inside the diameter-sensitive volume is deliberated. These corrections are brought about by making changes to the wire paths that constitute the coil windings, and hence, is called the path correction method. The existing well-known target held method is used to gauge the performance of a typical gradient coil. The gradient coil design methodology is demonstrated for planar openable gradient coils that can be inserted into an existing MRI apparatus. The path corrected gradient coil is compared to the coil obtained using the target field method. It is shown that using a wire path correction with optimized variables, winding patterns that can deliver high magnetic gradient field strengths and large imaging regions can be obtained.

Timing of rotator cuff activation during shoulder external rotation in throwers with and without symptoms of pain

Study Design: Fine-wire EMG rotator cuff onset time analysis in 2 matched groups of throwers with and without pain. Objective: To identify if there is a difference in the activation patterns of the rotator cuff muscles during a rapid shoulder external rotation task between throwers with and without pain. Background: The coordinated action of the rotator cuff is recognized as essential for glenohumeral joint control in the throwing athlete. Identification of abnormalities occurring in muscle activation patterns for injured athletes is relevant when prescribing rehabilitative exercises. Methods and Measures: Twelve throwers with shoulder pain were compared to a matched group of 11 asymptomatic throwers. Participants were matched for age, height, body mass, and habitual activity. Fine-wire EMG electrodes were inserted into the subscapularis, supraspinatus, and infraspinatus. EMG activity was measured during a reaction time task of rapid shoulder external rotation in a seated position. The timing of onset of EMG activity was analyzed in relation to visualization of a light (reaction time) and to the onset of infraspinatus activity (relative latency). Results: In the group with shoulder pain, the onset of subscapularis activity was found to be significantly delayed (reaction time, P = .0018; relative latency, P = .0005) from the onset of infraspinatus activity when compared to the control group. Conclusions: The presence of shoulder pain in these athletes was associated with a difference in the onset of subscapularis EMG activity during a rapid shoulder external rotation movement. This was an initial step in the understanding of the joint protection mechanisms of the glenohumeral joint and the problems that occur in throwers. This information may assist in providing future guidelines for more effective rehabilitation and prevention strategies for this condition.