212 research outputs found
Magnetic field control of the spin Seebeck effect
The origin of the suppression of the longitudinal spin Seebeck effect by
applied magnetic fields is studied. We perform numerical simulations of the
stochastic Landau-Lifshitz-Gilbert equation of motion for an atomistic spin
model and calculate the magnon accumulation in linear temperature gradients for
different strengths of applied magnetic fields and different length scales of
the temperature gradient. We observe a decrease of the magnon accumulation with
increasing magnetic field and we reveal that the origin of this effect is a
field dependent change of the frequency distribution of the propagating
magnons. With increasing field the magnonic spin currents are reduced due to a
suppression of parts of the frequency spectrum. By comparison with measurements
of the magnetic field dependent longitudinal spin Seebeck effect in YIG thin
films with various thicknesses, we find that our model describes the
experimental data very well, demonstrating the importance of this effect for
experimental systems
Inherited thrombophilia in pediatric venous thromboembolic disease: Why and who to test
Venous thromboembolic disease in childhood is a multifactorial disease. Risk factors include acquired clinical risk factors such as a central venous catheter and underlying disease and inherited thrombophilia. Inherited thrombophilia is defined as a genetically determined tendency to develop venous thromboembolism. In contrast to adults, acquired clinical risk factors play a larger role than inherited thrombophilia in the development of thrombotic disease in children. The contributing role of inherited thrombophilia is not clear in many pediatric thrombotic events, especially catheter-related thrombosis. Furthermore, identification of inherited thrombophilia will not often influence acute management of the thrombotic event as well as the duration of anticoagulation. In some patients, however, detection of inherited thrombophilia may lead to identification of other family members who can be counseled for their thrombotic risk. This article discusses the potential arguments for testing of inherited thrombophilia, including factor V Leiden mutation, prothrombin mutation, and deficiencies of antithrombin, protein C, or protein S and suggests some patient groups in childhood, which may be tested
Impact of Particle Size Distribution on Performance of LithiumâIon Batteries
This work reveals the impact of particle size distribution of spherical graphite active material on negative electrodes in lithiumâion batteries. Basically all important performance parameters, i.âe. charge/discharge characteristics, capacity, coulombic and energy efficiencies, cycling stability and Cârate capability are shown to be affected by distribution shapes. A narrow distribution with smaller particles results in better cell performance than broader and coarser distributions. However, particle size reduction has a limitation as extremely small particles show negative effect in performance. More critically, independent of the particle size distribution, the existence of coarse particles are found to promote lithium plating, which lowers cell performance and threatens the safety of battery operation. Furthermore, impedance analysis and cycling stability show huge differences for different electrodes. Our study shows that a better understanding of the influence of particle size distribution is an important base to engineer electrodes with higher Cârate capability, higher performance, and lower safety risk due to lithium plating
Optimizing a Rodent Model of Parkinson's Disease for Exploring the Effects and Mechanisms of Deep Brain Stimulation
Deep brain stimulation (DBS) has become a treatment for a growing number of neurological
and psychiatric disorders, especially for therapy-refractory Parkinson's disease (PD). However, not all of the symptoms of PD are sufficiently improved in all patients, and side effects may occur. Further progress depends on a deeper insight into the mechanisms of
action of DBS in the context of disturbed brain circuits. For this, optimized animal models have to be developed. We review not only charge transfer mechanisms at the electrode/tissue interface and strategies to increase the stimulation's energy-efficiency but also the electrochemical, electrophysiological, biochemical and functional effects of DBS. We introduce a hemi-Parkinsonian rat model for long-term experiments with chronically
instrumented rats carrying a backpack stimulator and implanted platinum/iridium electrodes. This model is suitable for (1) elucidating the electrochemical processes at the electrode/tissue interface, (2) analyzing the molecular, cellular and behavioral stimulation effects, (3) testing new target regions for DBS, (4) screening for potential neuroprotective DBS effects, and (5) improving the efficacy and safety of the method. An outlook is given on further developments of experimental DBS, including the use of transgenic animals and the testing of closed-loop systems for the direct on-demand application of electric stimulation
Revealing the Impact of Particle Size Distribution on Ageing of LithiumâIon Batteries with Frequency Response Analysis
In-depth analyses, including discharge behaviour, electrochemical impedance analysis, and for the first time, nonlinear frequency response analysis, are conducted on the ageing of negative electrodes with varying particle size distribution. The electrode-resolved analysis is used to distinguish the kinetic and transport losses at the respective electrodes. For fine to medium-sized particles at the negative electrode, ageing impacts are found more on the positive electrode: the impedance and nonlinear responses increase, suggesting that the charge transfer process at the positive electrode is worsened. Meanwhile, for coarse and broad negative particles, the impedance and nonlinear responses at negative electrodes decrease due to improved kinetics from micro-cracking. The second harmonic reveals a change in the nature of the charge transfer during ageing: the charge transfer process at the positive electrode becomes asymmetric for fine and medium-sized negative particles. Vice versa, the charge transfer process at the negative electrode becomes symmetric for coarse and broad negative particles
Spin transport across antiferromagnets induced by the spin Seebeck effect
For prospective spintronics devices based on the propagation of pure spin
currents, antiferromagnets are an interesting class of materials that
potentially entail a number of advantages as compared to ferromagnets. Here, we
present a detailed theoretical study of magnonic spin current transport in
ferromagnetic-antiferromagnetic multilayers by using atomistic spin dynamics
simulations. The relevant length scales of magnonic spin transport in
antiferromagnets are determined. We demonstrate the transfer of angular
momentum from a ferromagnet into an antiferromagnet due to the excitation of
only one magnon branch in the antiferromagnet. As an experimental system, we
ascertain the transport across an antiferromagnet in
YIGIrMnPt heterostructures. We determine the spin transport
signals for spin currents generated in the YIG by the spin Seebeck effect and
compare to measurements of the spin Hall magnetoresistance in the
heterostructure stack. By means of temperature-dependent and
thickness-dependent measurements, we deduce conclusions on the spin transport
mechanism across IrMn and furthermore correlate it to its
paramagnetic-antiferromagnetic phase transition.Comment: 10 pages, 6 figure
Cross-Sectional Comparison to Siblings and Peers
Objectives. To investigate self-reported health-related quality of life
(HrQoL) in children and adolescents with chronic medical conditions compared
with siblings/peers. Methods. Group 1 (6 treatment centers) consisted of 74
children/adolescents aged 8â16 years with hereditary bleeding disorders (HBD),
12 siblings, and 34 peers. Group 2 (one treatment center) consisted of 70
children/adolescents with stroke/transient ischemic attack, 14 siblings, and
72 peers. HrQoL was assessed with the ârevised KINDer
LebensqualitĂ€tsfragebogenâ (KINDL-R) questionnaire. Multivariate analyses
within groups were done by one-way ANOVA and post hoc pairwise single
comparisons by Studentâs -tests. Adjusted pairwise comparisons were done by
hierarchical linear regressions with individuals nested within treatment
centers (group 1) and by linear regressions (group 2), respectively. Results.
No differences were found in multivariate analyses of self-reported HrQoL in
group 1, while in group 2 differences occurred in overall wellbeing and all
subdimensions. These differences were due to differences between patients and
peers. After adjusting for age, gender, number of siblings, and treatment
center these differences persisted regarding self-worth () and friend-related
wellbeing (). Conclusions. In children with HBD, HrQoL was comparable to
siblings and peers. In children with stroke/TIA HrQoL was comparable to
siblings while peers, independently of relevant confounder, showed better
self-worth and friend-related wellbeing
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