A first-principles study of tunneling magnetoresistance in Fe/MgAl2O4/Fe(001) magnetic tunnel junctions

We investigated the spin-dependent transport properties of Fe/MgAl2O4/Fe(001) magnetic tunneling junctions (MTJs) on the basis of first-principles calculations of the electronic structures and the ballistic conductance. The calculated tunneling magnetoresistance (TMR) ratio of a Fe/MgAl2O4/Fe(001) MTJ was about 160%, which was much smaller than that of a Fe/MgO/Fe(001) MTJ (1600%) for the same barrier thickness. However, there was an evanescent state with delta 1 symmetry in the energy gap around the Fermi level of normal spinel MgAl2O4, indicating the possibility of a large TMR in Fe/MgAl2O4/Fe(001) MTJs. The small TMR ratio of the Fe/MgAl2O4/Fe(001) MTJ was due to new conductive channels in the minority spin states resulting from a band-folding effect in the two-dimensional (2-D) Brillouin zone of the in-plane wave vector (k//) of the Fe electrode. Since the in-plane cell size of MgAl2O4 is twice that of the primitive in-plane cell size of bcc Fe, the bands in the boundary edges are folded, and minority-spin states coupled with the delta 1 evanescent state in the MgAl2O4 barrier appear at k//=0, which reduces the TMR ratio of the MTJs significantly.Comment: 5 pages, 6 figures, 1 tabl

Stationary shapes of deformable particles moving at low Reynolds numbers

Lecture Notes of the Summer School ``Microswimmers -- From Single Particle Motion to Collective Behaviour'', organised by the DFG Priority Programme SPP 1726 (Forschungszentrum J{\"{u}}lich, 2015).Comment: Pages C7.1-16 of G. Gompper et al. (ed.), Microswimmers - From Single Particle Motion to Collective Behaviour, Lecture Notes of the DFG SPP 1726 Summer School 2015, Forschungszentrum J\"ulich GmbH, Schriften des Forschungszentrums J\"ulich, Reihe Key Technologies, Vol 110, ISBN 978-3-95806-083-

The return trip effect: Why the return trip often seems to take less time

Three studies confirm the existence of the return trip effect: The return trip often seems shorter than the initial trip, even though the distance traveled and the actual time spent traveling are identical. A pretest shows that people indeed experience a return trip effect regularly, and the effect was found on a bus trip (Study 1), a bicycle trip (Study 2), and when participants watched a video of someone else traveling (Study 3). The return trip effect also existed when another, equidistant route was taken on the return trip, showing that it is not familiarity with the route that causes this effect. Rather, it seems that a violation of expectations causes this effect

Quantitative spectroscopy of single molecule interaction times

Funding Information: Deutsche Forschungsgemeinschaft (421152132 (subproject C03)), EXC 2046 (MATH+Incubator project IN-B2).Single molecule fluorescence tracking provides information at nanometer-scale and millisecond-temporal resolution about the dynamics and interaction of individual molecules in a biological environment. While the dynamic behavior of isolated molecules can be characterized well, the quantitative insight is more limited when interactions between two indistinguishable molecules occur. We address this aspect by developing a theoretical foundation for a spectroscopy of interaction times, i.e., the inference of interaction from imaging data. A non-trivial crossover between a power law to an exponential behavior of the distribution of the interaction times is highlighted, together with the dependence of the exponential term upon the microscopic reaction affinity. Our approach is validated with simulated and experimental datasets.Publisher PDFPeer reviewe

Alpha-buckets in High Energy Electron Storage Rings (Review of Existing Experiments and Feasibility Studies for Future Developments) Review

Electron storage rings operating at high energies have proven to be invaluable source of synchrotron radiation. Two and even three simultaneous beams of particles have been observed at different light source facilities worldwide. So called alpha-buckets were studied at Metrological Light Source (MLS) in Berlin (Germany), SOLEIL facility in France, DIAMOND light source in UK, NSLS ring in Brookhaven (USA). It is widely recognized that alpha buckets are general phenomena which is not restricted to a certain storage ring. However, earlier measurements showed essential limitations on parameters of alpha-buckets, strong dependence on high order (sextupole and octupoles) magnetic field imperfections and associated fast decay of electron current as well as reduced life time. Also a rising relevance of high order non-linear longitudinal beam dynamics is associated with new generation of diffraction limited light sources (DLSR) approaches, which all suffer nonlinear momentum compaction factor. A large variety of future generation electron synchrotrons require a comprehensive investigation of the physical processes involved into the operation of such rings. In this paper, we present review of high order non-linear longitudinal beam dynamics based on the longitudinal equations of motion and Hamiltonian expanded to a high order of the momentum compaction factor. Roots of the third order equation with a free term are derived in a form suitable for analytical estimations. The momentum independent term of orbit lengthening due to particle transverse excursions is estimated and taken into account. The results from simulations were benchmarked against existing experiments at the Karlsruhe Research Accelerator (KARA), SOLEIL and MLS rings. Parameters of three simultaneous beams and alpha buckets at MLS and SOLEIL have been reproduced with high accuracy. General conditions for stable operation of alpha buckets are presented. Based on analytical formulas and computer simulations, studies of longitudinal motion at KARA have been performed with an objective to estimate feasibility of filling and storing of beam in α-buckets. A Computer model was used to describe the behavior and dynamics of simultaneous beams in the KARA storage ring

Description of an advanced practice nursing consultative model to reduce restrictive siderail use in nursing homes

Researchers have demonstrated that the use of physical restraints in nursing homes can be reduced, particularly where advanced practice nurses (APNs) are utilized. We examined the link between APN practice, siderail reduction, and the costs of siderail alternatives in 273 residents in four Philadelphia nursing homes. The majority of participants were cognitively and physically impaired with multiple co-morbidities. APNs recommended a total of 1,275 siderail-alternative interventions aimed at reducing fall risk. The median cost of siderail alternatives to prevent falls per resident was $135. Residents with a fall history experienced a significantly higher cost of recommendation compared to non-fallers. Findings suggest that an APN consultation model can effectively be implemented through comprehensive, individualized assessment without incurring substantial costs to the nursing home. © 2007 Wiley Periodicals, Inc. Res Nurs Health 30: 131–140, 2007Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56001/1/20185_ftp.pd

Status of Negative Momentum Compaction Operation at KARA

For future synchrotron light sources different operation modes are of interest. Therefore various modes are currently being tested at the Karlsruhe Research Accelerator (KARA) including optics for a negative momentum compaction factor. These optics have been calculated and are under commissioning at KARA. Additionally, studies about expected collective effects in this regime are being performed, including the head-tail and microbunching instabilities. In this contribution we will present the status of operation in the negative momentum compaction regime and discuss expected collective effects that will be studied in this context