Magnetotransport effects of ultrathin Ni80Fe20 films probed in-situ

We have investigated the magnetoresistance of Permalloy (Ni80Fe20) films with thicknesses ranging from a single monolayer to 12 nm, grown on Al2O3, MgO and SiO2 substrates. Growth and transport measurements were carried out under cryogenic conditions in UHV. Applying in-plane magnetic vector fields up to 100 mT, the magnetotransport properties are ascertained during growth. With increasing thickness the films exhibit a gradual transition from tunneling magnetoresistance to anisotropic magnetoresistance. This corresponds to the evolution of the film structure from separated small islands to a network of interconnected grains as well as the transition from superparamagnetic to ferromagnetic behavior of the film. Using an analysis based on a theoretical model of the island growth, we find that the observed evolution of the magnetoresistance in the tunneling regime originates from the changes in the island size distribution during growth. Depending on the substrate material, significant differences in the magnetoresistance response in the transition regime between tunneling magnetoresistance and anisotropic magnetoresistance were found. We attribute this to an increasingly pronounced island growth and slower percolation process of Permalloy when comparing growth on SiO2, MgO and Al2O3 substrates. The different growth characteristics result in a markedly earlier onset of both tunneling magnetoresistance and anisotropic magnetoresistance for SiO2. For Al2O3 in particular the growth mode results in a structure of the film containing two different contributions to the ferromagnetism which lead to two distinct coercive fields in the high thickness regime.Comment: 8 pages, 7 figure

Estimating individual treatment effects from responses and a predictive biomarker in a parallel group RCT

When being interested in administering the best of two treatments to an individual patient i, it is necessary to know the individual treatment effects (ITEs) of the considered subjects and the correlation between the possible responses (PRs) for two treatments. When data are generated in a parallel–group design RCT, it is not possible to determine the ITE for a single subject since we only observe two samples from the marginal distributions of these PRs and not the corresponding joint distribution due to the ’Fundamental Problem of Causal Inference’ [Holland, 1986, p. 947]. In this article, we present a counterfactual approach for estimating the joint distribution of two normally distributed responses to two treatments. This joint distribution can be estimated by assuming a normal joint distribution for the PRs and by using a normally distributed baseline biomarker which is defined to be functionally related to the sum of the ITE components. Such a functional relationship is plausible since a biomarker and the sum encode for the same information in a RCT, namely the variation between subjects. As a result of the interpretation of the biomarker as a proxy for the sum of ITE components, the estimation of the joint distribution is subjected to some constraints. These constraints can be framed in the context of linear regressions with regard to the proportions of variances in the responses explained and with regard to the residual variation. As a consequence, a new light is thrown on the presence of treatment–biomarker interactions. We applied our approach to a classical medical data example on exercise and heart rate

Excellence at the University of Konstanz: past, present, and future

Proceeding of: Strategies for International Excellence of European Research Universities. Sharing best practices. April 16, 2010. Getafe, Madri

Magnetoresistance, Micromagnetism and Domain Wall Effects in Epitaxial Fe and Co Structures with Stripe Domains

We review our recent magnetotransport and micromagnetic studies of lithographically defined epitaxial thin film structures of bcc Fe and hcp Co with stripe domains. Micromagnetic structure and resistivity anisotropy are shown to be the predominant sources of low field magnetoresistance (MR) in these microstructures, with domain wall (DW) effects smaller but observable (DW-MR $\lesssim 1$). In Fe, at low temperature, in a regime in which fields have a significant effect on electron trajectories, a novel negative DW contribution to the resistivity is observed. In hcp Co microstructures, temperature dependent transport measurements for current perpendicular and parallel to walls show that any additional resistivity due to DW scattering is very small.Comment: 7 pages, 8 figures, to appear in Journal of Applied Physics 199

Towards Flexible Process Support on Mobile Devices

Ubiquitous computing is considered as enabler for linking everyday life with information and communication technology. However, developing pervasive and mobile applications that provide personalized user assistance still constitutes a challenge. Mobile application scenarios are diverse and encompass domains like healthcare, logistics, and sales. For their support two fundamental technologies with increasing maturity are emerging: development frameworks for mobile devices and light-weight process engines. Their integrated use, however, is in a rather premature state. Generally, the use of a process engine for supporting mobile collaboration raises many challenging issues. This paper picks up some of these challenges and shows how we have coped with them in the MARPLE project. MARPLE targets at a tight integration of process management technology with mobile computing frameworks in order to enable mobile process support in advanced application scenarios. We give insights into the MARPLE architecture and its components.In particular, we introduce the MARPLE process engine, which enables light-weight as well as flexible process support on mobile devices. This will be key for mobile user assistance in advanced application scenarios

Tibiofemoral and patellofemoral joint 3D-kinematics in patients with posterior cruciate ligament deficiency compared to healthy volunteers

Background: The posterior cruciate ligament (PCL) plays an important role in maintaining physiological kinematics and function of the knee joint. To date mainly in-vitro models or combined magnetic resonance and fluoroscopic systems have been used for quantifying the importance of the PCL. We hypothesized, that both tibiofemoral and patellofemoral kinematic patterns are changed in PCL-deficient knees, which is increased by isometric muscle flexion. Therefore the aim of this study was to simultaneously investigate tibiofemoral and patellofemoral 3D kinematics in patients suffering from PCL deficiency during different knee flexion angles and under neuromuscular activation. Methods: We enrolled 12 patients with isolated PCL-insufficiency as well as 20 healthy volunteers. Sagittal MR-images of the knee joint were acquired in different positions of the knee joint (0[degree sign], 30[degree sign], 90[degree sign] flexion, with and without flexing isometric muscle activity) on a 0.2 Tesla open MR-scanner. After segmentation of the patella, femur and tibia local coordinate systems were established to define the spatial position of these structures in relation to each other. Results: At full extension and 30[degree sign] flexion no significant difference was observed in PCL-deficient knee joints neither for tibiofemoral nor for patellofemoral kinematics. At 90[degree sign] flexion the femur of PCL-deficient patients was positioned significantly more anteriorly in relation to the tibia and both, the patellar tilt and the patellar shift to the lateral side, significantly increased compared to healthy knee joints. While no significant effect of isometric flexing muscle activity was observed in healthy individuals, in PCL-deficient knee joints an increased paradoxical anterior translation of the femur was observed at 90[degree sign] flexion compared to the status of muscle relaxation. Conclusions: Significant changes in tibiofemoral and patellofemoral joint kinematics occur in patients with isolated PCL-insufficiency above 30 degrees of flexion compared to healthy volunteers. Since this could be one reasonable mechanism in the development of OA our results might help to understand the long-term development of tibiofemoral and/or patellofemoral osteoarthritis in PCL-insufficient knee joints

Проблеми криптозахисту шифрувальної машинки «ЕНІГМА»

Шифрувальні пристрої дозволяють захистити інформацію, передану по радіоканалу, від перегляду сторонніми особами, і насамперед, спецслужбою супротивника. У загальному випадку букви і цифри повідомлення замінюються іншими символами, роблячи його абсолютно незрозумілим. Найпростіші шифри, що застосовувалися протягом століть, використовували схему прямого заміщення однієї букви інший, причому щоразу однієї і тієї ж