Ripples in a string coupled to Glauber spins

Each oscillator in a linear chain (a string) interacts with a local Ising spin in contact with a thermal bath. These spins evolve according to Glauber dynamics. Below a critical temperature, a rippled state in the string is accompanied by a nonzero spin polarization. The system is shown to form ripples in the string which, for slow spin relaxation, vibrates rapidly about quasi-stationary states described as snapshots of a coarse-grained stroboscopic map. For moderate observation times, ripples are observed irrespective of the final thermodynamically stable state (rippled or not).Comment: 5 pages, 2 figure

Emergence of skyrmion lattices and bimerons in chiral magnetic thin films with nonmagnetic impurities

Skyrmions are topologically protected field structures with particlelike characteristics that play important roles in several areas of science. Recently, skyrmions have been directly observed in chiral magnets. Here, we investigate the effects of pointlike nonmagnetic impurities on the distinct initial states (random or helical ones) and on the formation of the skyrmion crystal in a discrete lattice. Using Monte Carlo techniques, we have found that even a small percentage of spin vacancies present in the chiral magnetic thin film considerably affects the skyrmion order. The main effects of impurities are somewhat similar to thermal effects. The presence of these spin vacancies also induces the formation of bimerons in both the helical and skyrmion states. We also investigate how adjacent impurities forming a hole affect the skyrmion crystal

Tilting table for ergometer and for other biomedical devices

The apparatus is for testing the human body in a variety of positions, ranging from the vertical to the supine, while exercising on an ergometer; and can also be used for angular positioning of other biomedical devices. It includes a floor plate and a hinged plate upon which to fix the ergometer, a back rest and a head rest attached at right angles to said hinged plate and behind the seat of the ergometer, dual hydraulic cylinders for raising and lowering the hinged plate through 90 deg by means of a self contained hydraulic system, with valve means for control and positive stops on the apparatus to prevent over travel. Tests can be made with the subject positioned on the seat of the ergometer, through the various angles, with a substantially normal body attitude relative to the seat and ergometer

Simple method for forming thin-wall pressure vessels

Application of internal hydrostatic pressure to seam-welded circular cylindrical tanks having corner-welded, flat, circular ends forms large thin-walled high quality tanks. Form limits expansion of cylindrical portion of final tank while hemispherical ends develop freely; no external form or restraint is required to fabricate spherical tanks

Fluvio-deltaic avulsions during relative sea-level fall.

Understanding river response to changes in relative sea level (RSL) is essential for predicting fluvial stratigraphy and source-to-sink dynamics. Recent theoretical work has suggested that rivers can remain aggradational during RSL fall, but field data are needed to verify this response and investigate sediment deposition processes. We show with field work and modeling that fluvio-deltaic systems can remain aggradational or at grade during RSL fall, leading to superelevation and continuation of delta lobe avulsions. The field site is the Goose River, Newfoundland-Labrador, Canada, which has experienced steady RSL fall of around 3–4 mm yr⁻¹ in the past 5 k.y. from post-glacial isostatic rebound. Elevation analysis and optically stimulated luminescence dating suggest that the Goose River avulsed and deposited three delta lobes during RSL fall. Simulation results from Delft3D software show that if the characteristic fluvial response time is longer than the duration of RSL fall, then fluvial systems remain aggradational or at grade, and continue to avulse during RSL fall due to superelevation. Intriguingly, we find that avulsions become more frequent at faster rates of RSL fall, provided the system response time remains longer than the duration of RSL fall. This work suggests that RSL fall rate may influence the architecture of falling-stage or forced regression deposits by controlling the number of deposited delta lobes

Some model-independent phenomenological consequences of flexible brane worlds

In this work we will review the main properties of brane-world models with low tension. Starting from very general principles, it is possible to obtain an effective action for the relevant degrees of freedom at low energies (branons). Using the cross sections for high-energy processes involving branons, we set bounds on the different parameters appearing in these models. We also show that branons provide a WIMP candidate for dark matter in a natural way. We consider cosmological constraints on its thermal and non-thermal relic abundances. We derive direct detection limits and compare those limits with the preferred parameter region in the case in which the EGRET excess in the diffuse galactic gamma rays is due to dark matter annihilation. Finally we will discuss the constraints coming from the precision tests of the Standard Model and the muon anomalous magnetic moment.Comment: 10 pages, 6 figures. Contribution to the Proceedings of the Second International Conference on Quantum Theories and Renormalization Group in Gravity and Cosmology, IRGAC 2006, Barcelona, 11-15 July, 200

Tilt table for ergometers and other biomedical devices

Table adjusts to any position between horizontal and vertical. Apparatus includes - floor plate, plate hinged to floor plate, for carrying ergometer, hydraulic cylinder and piston on plate sides, linking them, hydraulic system, positive stops, padded backrest and headrest, one hand controls, and constraint system