24 research outputs found
A self-consistent spin-diffusion model for micromagnetics
We propose a three-dimensional micromagnetic model that dynamically solves
the Landau-Lifshitz-Gilbert equation coupled to the full spin-diffusion
equation. In contrast to previous methods, we solve for the magnetization
dynamics and the electric potential in a self-consistent fashion. This
treatment allows for an accurate description of magnetization dependent
resistance changes. Moreover, the presented algorithm describes both spin
accumulation due to smooth magnetization transitions and due to material
interfaces as in multilayer structures. The model and its finite-element
implementation are validated by current driven motion of a magnetic vortex
structure. In a second experiment, the resistivity of a magnetic multilayer
structure in dependence of the tilting angle of the magnetization in the
different layers is investigated. Both examples show good agreement with
reference simulations and experiments respectively
Molecular engineering of chiral colloidal liquid crystals using DNA origami
Establishing precise control over the shape and the interactions of the
microscopic building blocks is essential for design of macroscopic soft
materials with novel structural, optical and mechanical properties. Here, we
demonstrate robust assembly of DNA origami filaments into cholesteric liquid
crystals, 1D supramolecular twisted ribbons and 2D colloidal membranes. The
exquisite control afforded by the DNA origami technology establishes a
quantitative relationship between the microscopic filament structure and the
macroscopic cholesteric pitch. Furthermore, it also enables robust assembly of
1D twisted ribbons, which behave as effective supramolecular polymers whose
structure and elastic properties can be precisely tuned by controlling the
geometry of the elemental building blocks. Our results demonstrate the
potential synergy between DNA origami technology and colloidal science, in
which the former allows for rapid and robust synthesis of complex particles,
and the latter can be used to assemble such particles into bulk materials
A three-dimensional spin-diffusion model for micromagnetics
Published onlineJournal ArticleResearch Support, Non-U.S. Gov'tWe solve a time-dependent three-dimensional spin-diffusion model coupled to the Landau-Lifshitz-Gilbert equation numerically. The presented model is validated by comparison to two established spin-torque models: The model of Slonzewski that describes spin-torque in multi-layer structures in the presence of a fixed layer and the model of Zhang and Li that describes current driven domain-wall motion. It is shown that both models are incorporated by the spin-diffusion description, i.e., the nonlocal effects of the Slonzewski model are captured as well as the spin-accumulation due to magnetization gradients as described by the model of Zhang and Li. Moreover, the presented method is able to resolve the time dependency of the spin-accumulation.The financial support by the Austrian Federal Ministry of Science, Research and Economy and the National Foundation for Research, Technology and Development as well as the Austrian Science Fund (FWF) under grant W1245 and F4102 SFB ViCoM, the innovative projects initiative of Vienna University of Technology, the Vienna Science and Technology Fund (WWTF) under grant MA14-044, and the Royal Society under UF080837 is gratefully acknowledged
Resident Cardiac Immune Cells and Expression of the Ectonucleotidase Enzymes CD39 and CD73 after Ischemic Injury
BACKGROUND: The ectoenzymes CD39 and CD73 are expressed by a broad range of immune cells and promote the extracellular degradation of nucleotides to anti-inflammatory adenosine. This study explored the abundance of CD73 and CD39 on circulating and resident cardiac leukocytes and coronary endothelial cells under control conditions and in response to inflammation following myocardial ischemia and reperfusion (I/R). METHODS AND RESULTS: A method was elaborated to permit FACS analysis of non-myocardial cells (resident leukocytes, coronary endothelium and CD31(-) CD45(-) cells) of the unstressed heart. Under control conditions the murine heart contained 2.3 × 10(3) resident leukocytes/mg tissue, the most prominent fraction being antigen-presenting mononuclear cells (CD11b(+) CD11c(+) F4/80(+) MHCII(+)) followed by B-cells, monocytes and T-cells. CD73 was highly expressed on circulating and resident cardiac lymphoid cells with little expression on myeloid cells, while the opposite was true for CD39. Cardiomyocytes and erythrocytes do not measurably express CD39/CD73 and CD39 dominates on coronary endothelium. Three days after I/R, CD73 was significantly upregulated on invading granulocytes (2.8-fold) and T-cells (1.5-fold). Compared with coronary endothelial cells, CD73 associated with leukocytes comprised 2/3 of the total cardiac CD73. CONCLUSION: Our study suggests that extracellular ATP formed during I/R is preferentially degraded by CD39 present on myeloid cells, while the formation of immunosuppressive adenosine is mainly catalysed by CD73 present on granulocytes and lymphoid cells. Upregulated CD73 on granulocytes and T-cells infiltrating the injured heart is consistent with the existence of an autocrine adenosinergic loop which may promote the healing process