564 research outputs found
Magnetic Properties of the low dimensional spin system (VO)PO: ESR and susceptibility
Experimental results on magnetic resonance (ESR) and magnetic susceptibility
are given for single crystalline (VO)PO. The crystal growth
procedure is briefly discussed. The susceptibility is interpreted numerically
using a model with alternating spin chains. We determine =51 K and
=0.2. Furthermore we find a spin gap of meV from our ESR
measurements. Using elastic constants no indication of a phase transition
forcing the dimerization is seen below 300 K.Comment: 7 pages, REVTEX, 7 figure
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Profoundly reduced neovascularization capacity of bone marrow mononuclear cells derived from patients with chronic ischemic heart disease
Backgroundâ Cell therapy with bone marrowâderived stem/progenitor cells is a novel option for improving neovascularization and cardiac function in ischemic heart disease. Circulating endothelial progenitor cells in patients with coronary heart disease are impaired with respect to number and functional activity. However, whether this impairment also extends to bone marrowâderived mononuclear cells (BM-MNCs) in patients with chronic ischemic cardiomyopathy (ICMP) is unclea
Anisotropic Exchange in LiCuVO probed by ESR
We investigated the paramagnetic resonance in single crystals of LiCuVO
with special attention to the angular variation of the absorption spectrum. To
explain the large resonance linewidth of the order of 1 kOe, we analyzed the
anisotropic exchange interaction in the chains of edge-sharing CuO
octahedra, taking into account the ring-exchange geometry of the
nearest-neighbor coupling via two symmetric rectangular Cu-O bonds. The
exchange parameters, which can be estimated from theoretical considerations,
nicely agree with the parameters obtained from the angular dependence of the
linewidth. The anisotropy of this magnetic ring exchange is found to be much
larger than it is usually expected from conventional estimations which neglect
the bonding geometry. Hence, the data yield the evidence that in copper oxides
with edge-sharing structures the role of the orbital degrees of freedom is
strongly enhanced. These findings establish LiCuVO as one-dimensional
compound at high temperatures.
PACS: 76.30.-v, 76.30.Fc, 75.30.EtComment: 18 pages, 6 figure
A generalized framework towards structural mechanics of three-layered composite structures
Three-layered composite structures find a broad application. Increasingly, composites are being used whose layer thicknesses and material properties diverge strongly. In the perspective of structural mechanics, classical approaches to analysis fail at such extraordinary composites. Therefore, emphasis of the present approach is on arbitrary transverse shear rigidities and structural thicknesses of the individual layers. Therewith we employ a layer-wise approach for multiple (quasi-) homogeneous layers. Every layer is considered separately whereby this disquisition is based on the direct approach for deformable directed surfaces. We limit our considerations to geometrical and physical linearity. In this simple and familiar setting we furnish a layer-wise theory by introducing constraints at interfaces to couple the layers. Hereby we restrict our concern to surfaces where all material points per surface are coplanar and all surfaces are plane parallel. Closed-form solutions of the governing equations enforce a narrow frame since they are strongly restrictive in the context of available boundary conditions. Thus a computational solution approach is introduced using the finite element method. In order to determine the required spatially approximated equation of motion, the principle of virtual work is exploited. The discretization is realized via quadrilateral elements with quadratic shape functions. Hereby we introduce an approach where nine degrees of freedom per node are used. In combination with the numerical solution approach, this layer-wise theory has emerged as a powerful tool to analyze composite structures. In present treatise, we would like to clarify the broad scope of this approach
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Transplantation of progenitor cells and regeneration enhancement in acute myocardial infarction - (TOPCARE-AMI)
Background - Experimental studies suggest that transplantation of blood-derived or bone marrowâderived progenitor cells beneficially affects postinfarction remodeling. The safety and feasibility of autologous progenitor cell transplantation in patients with ischemic heart disease is unknown
Spin correlations and Dzyaloshinskii-Moriya interaction in CsCuCl
We report on electron spin resonance (ESR) studies of the spin relaxation in
CsCuCl. The main source of the ESR linewidth at temperatures K is attributed to the uniform Dzyaloshinskii-Moriya interaction. The
vector components of the Dzyaloshinskii-Moriya interaction are determined from
the angular dependence of the ESR spectra using a high-temperature
approximation. Both the angular and temperature dependence of the ESR linewidth
have been analyzed using a self-consistent quantum-mechanical approach. In
addition analytical expressions based on a quasi-classical picture for spin
fluctuations are derived, which show good agreement with the quantum-approach
for temperatures K. A small modulation of the
ESR linewidth observed in the -plane is attributed to the anisotropic
Zeeman interaction, which reflects the two magnetically nonequivalent Cu
positions
On the Kernel of -Linear Hadamard Codes
The -additive codes are subgroups of ,
and can be seen as a generalization of linear codes over and
. A -linear Hadamard code is a binary Hadamard
code which is the Gray map image of a -additive code. It is
known that the dimension of the kernel can be used to give a complete
classification of the -linear Hadamard codes. In this paper, the
kernel of -linear Hadamard codes and its dimension are
established for . Moreover, we prove that this invariant only provides a
complete classification for some values of and . The exact amount of
nonequivalent such codes are given up to for any , by using
also the rank and, in some cases, further computations
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