Current-Induced Motion of Narrow Domain Walls and Dissipation in Ferromagnetic Metals

Spin transport equations in a non-homogeneous ferromagnet are derived in the limit where the sd exchange coupling between the electrons in the conduction band and those in the d band is dominant. It is shown that spin diffusion in ferromagnets assumes a tensor form. The diagonal terms are renormalized with respect to that in normal metals and enhances the dissipation in the magnetic system while the off-diagonal terms renormalize the precessional frequency of the conduction electrons and enhances the non-adiabatic spin torque. To demonstrate the new physics in our theory, we show that self-consistent solutions of the spin diffusion equations and the Landau-Lifshitz equations in the presence of a current lead to a an increase in the terminal velocity of a domain wall which becomes strongly dependent on its width. We also provide a simplified equation that predicts damping due to the conduction electrons

Search for supersymmetry in trilepton final states with the D0 detector.

Subm. to AIP Conf. Proc.International audienceThe data taken by the D0 experiment at the proton-antiproton collider Tevatron has been used to search for signatures with two or more leptons and missing transverse energy as they are expected for the decay of pair produced Charginos and Neutralinos. No excess above the Standard Model prediction has been observed and the results have been used to set mass limits for these particles

The role of surfactant in asthma

Pulmonary surfactant is a unique mixture of lipids and surfactant-specific proteins that covers the entire alveolar surface of the lungs. Surfactant is not restricted to the alveolar compartment; it also reaches terminal conducting airways and is present in upper airway secretions. While the role of surfactant in the alveolar compartment has been intensively elucidated both in health and disease states, the possible role of surfactant in the airways requires further research. This review summarizes the current knowledge on surfactant functions regarding the airway compartment and highlights the impact of various surfactant components on allergic inflammation in asthma

Unfolding the Sulcus

Sulci are localized furrows on the surface of soft materials that form by a compression-induced instability. We unfold this instability by breaking its natural scale and translation invariance, and compute a limiting bifurcation diagram for sulcfication showing that it is a scale-free, sub-critical {\em nonlinear} instability. In contrast with classical nucleation, sulcification is {\em continuous}, occurs in purely elastic continua and is structurally stable in the limit of vanishing surface energy. During loading, a sulcus nucleates at a point with an upper critical strain and an essential singularity in the linearized spectrum. On unloading, it quasi-statically shrinks to a point with a lower critical strain, explained by breaking of scale symmetry. At intermediate strains the system is linearly stable but nonlinearly unstable with {\em no} energy barrier. Simple experiments confirm the existence of these two critical strains.Comment: Main text with supporting appendix. Revised to agree with published version. New result in the Supplementary Informatio

Independent Information of Nonspecific Biomarkers in Exhaled Breath Condensate

Background: Exhaled breath condensate (EBC) has been used for diagnosing and monitoring respiratory disorders. For clinical purposes the assessment of easy-to-obtain nonspecific markers seems particularly interesting. Objectives: As these measures are related to each other, our objective was to extract the independent information in global EBC markers across a range of respiratory disorders. Methods: EBC was collected from patients with asthma (n = 18), chronic obstructive pulmonary disease (n = 17), and cystic fibrosis (n = 46), as well as from lung transplant (LTX) recipients (n = 14) and healthy controls (n = 26). Samples were assessed for electrical conductivity, ammonia, pH, and nitrite/nitrate. pH was measured after both deaeration with argon and CO(2) standardization. Additionally, the fraction of exhaled nitric oxide (FE(NO)) was assessed. Factor analysis was applied to identify major factors concerning these measures. Results: Three independent factors were detected; the first comprised conductivity, ammonia, and pH, especially when standardized using CO(2), the second nitrite/nitrate, and the third FE(NO). Conductivity and ammonia were highly correlated (r = 0.968; p < 0.001). FE(NO) provided independent information mainly in asthma. The nonspecific EBC markers showed considerable overlap between patient groups and healthy subjects. However, conductivity, ammonia, pH standardized for CO(2) and nitrite/nitrate were increased in LTX recipients compared to healthy controls (p < 0.05 each). Conclusions: A panel of nonspecific easy-to-obtain exhaled breath markers could be reduced to 3 independent factors. The information content of conductivity, ammonia, and pH after CO(2) equilibration appeared to be similar, while FE(NO) was independent. The increased levels of these biomarkers in LTX might indicate a potential for their use in these patients. Copyright (C) 2010 S. Karger AG, Base

Ultrafast Spin Dynamics in Nickel

The spin dynamics in Ni is studied by an exact diagonalization method on the ultrafast time scale. It is shown that the femtosecond relaxation of the magneto-optical response results from exchange interaction and spin-orbit coupling. Each of the two mechanisms affects the relaxation process differently. We find that the intrinsic spin dynamics occurs during about 10 fs while extrinsic effects such as laser-pulse duration and spectral width can slow down the observed dynamics considerably. Thus, our theory indicates that there is still room to accelerate the spin dynamics in experiments.Comment: 4 pages, Latex, 4 postscript figure

Ultrafast electron dynamics at metal surfaces: Competition between electron-phonon coupling and hot-electron transport

An experimental scheme (double pump/reflectivity probe using femtosecond laser pulses) enables the investigation of nonequilibrium electron dynamics at metal surfaces by measuring the equilibrated surface temperature. The competition between electron-phonon coupling and hot-electron transport gives rise to a reduced equilibrated temperature when the two pump pulses overlap in time, and provides a way of accurately determining the electron-phonon coupling constant. These observations have important consequences for femtosecond photochemical investigations

Review: ‘Gimme five’: future challenges in multiple sclerosis. ECTRIMS Lecture 2009

This article is based on the ECTRIMS lecture given at the 25th ECTRIMS meeting which was held in Düsseldorf, Germany, from 9 to 12 September 2009. Five challenges have been identified: (1) safeguarding the principles of medical ethics; (2) optimizing the risk/benefit ratio; (3) bridging the gap between multiple sclerosis and experimental autoimmune encephalitis; (4) promoting neuroprotection and repair; and (5) tailoring multiple sclerosis therapy to the individual patient. Each of these challenges will be discussed and placed in the context of current research into the pathogenesis and treatment of multiple sclerosis

First US Performance Measurements of Next Generation 3D USCT 2.5 Transducers

The KIT’s 3D Ultrasound Computer Tomography (USCT) II system has a multistatic setup of 2041 ultrasound transducers with approx. 1.5 MHz 6dB bandwidth and 36◦ 3 dB opening angle for 2.5 MHz. To increase the region of interest for a next USCT generation, the opening angle should be increased to approx. 60◦ and the bandwidth doubled. To increase the opening angle the size of the transducer elements was decreased to approximately half the size. A circular aperture was chosen for homogenicity of the radiation pattern in 3D. The transducer design utilizes piezo-fibres by the established Fraunhofer IMT piezo-fibre composite technology. The fibres were fabricated from PZT powder using the polysulfone spinning process. 17 fibres were positioned with a mechanical mask and filled with a matrix of epoxy. From this rod piezo composite discs were sawed and polarized. Electrodes were generated by silver-filled epoxy adhesive on the top and bottom side. Materials for acoustic backing is a Tungsten-Polyurethane composite and for acoustic matching ia aluminium oxide composite material (TMM4). Ultrasound characteristics were evaluated quantitatively with a Onda HNC-400 hydrophone in a 3-axis water tank for a randomly selected sample transducer (see Fig. a.)). Characteristics evaluated were the pressure field as function over frequency and angle in the far-field (see Fig. b.)), following the use-case. For excitation a linear encoded chirp was used, for SNR improvements averaging of measurements (64 to 256 times) was conducted. The analysis compensated for the hydrophon’s frequency and angular damping characteristics. The presented results show that the desired characteristics were mostly achieved: the 6 dB bandwidth could be vastly improved by roughly 200% (see Fig. d.)). The 6 dB pressure opening angle was approx. 50◦ (see Fig. c.)), not completly fullfilling the simulated expectations, an improvement by 31% was achieved. The results are promising for the next 3D USCT III generation