4,577 research outputs found
The Antiferromagnetic Heisenberg Model on Fullerene-Type Symmetry Clusters
The nearest neighbor antiferromagnetic Heisenberg model is
considered for spins sitting on the vertices of clusters with the connectivity
of fullerene molecules and a number of sites ranging from 24 to 32. Using
the permutational and spin inversion symmetries of the Hamiltonian the low
energy spectrum is calculated for all the irreducible representations of the
symmetry group of each cluster. Frustration and connectivity result in
non-trivial low energy properties, with the lowest excited states being
singlets except for . Same hexagon and same pentagon correlations are the
most effective in the minimization of the energy, with the
symmetry cluster having an unusually strong singlet intra-pentagon correlation.
The magnetization in a field shows no discontinuities unlike the icosahedral
fullerene clusters, but only plateaux with the most pronounced for
. The spatial symmetry as well as the connectivity of the clusters appear
to be important for the determination of their magnetic properties.Comment: Extended to include low energy spectra, correlation functions and
magnetization data of clusters up to 32 site
Large area CMOS active pixel sensor x‐ray imager for digital breast tomosynthesis: Analysis, modeling, and characterization
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134791/1/mp2368.pd
Pseudomembranous Trigonitis: A Common but Underrecognized Urological Entity
Pseudomembranous trigonitis is the term used to describe squamous metaplastic changes of the bladder trigone, which affect nearly 40% of adult females. We present the characteristics of this underrecognized clinical entity and encourage further relevant research
NDM-526: INVESTIGATION OF STABLE AND UNSTABLE FIBER-REINFORCED ELASTOMERIC ISOLATORS
Fiber-reinforced elastomeric isolators (FREIs) are a potentially low-cost alternative to conventional steel-reinforced elastomeric isolators. FREIs can exhibit a non-linear horizontal force-displacement relationship characterized by a softening and stiffening phase, similar to other adaptive isolation devices such as the triple friction pendulum. This non-linear relationship is a consequence of unique deformations that occur during horizontal displacement denoted as rollover, which causes softening, and full rollover, which causes stiffening. The magnitude of the softening due to rollover is primarily governed by the width-to-total height aspect ratio of the FREI. If the aspect ratio is low, below about 2.5, the isolator may be susceptible to horizontal instability where the tangential stiffness becomes negative before increasing due to full rollover. Design codes prevent the use of an isolation system susceptible to horizontal instability within the design displacement. In this paper, experimental testing is used to calibrate a numerical model of a base isolated structure using horizontally unstable and stable FREIs. The performance of the structure is evaluated based on peak displacement of the isolation layer and peak acceleration of the base isolated structure. For the isolators considered, it is shown that the horizontal instability does not have a negative impact on the performance of the structure. It is postulated that some level of horizontal instability may be allowed in the design of unbonded FREIs
Spin Polaron Effective Magnetic Model for La_{0.5}Ca_{0.5}MnO_3
The conventional paradigm of charge order for La_{1-x}Ca_xMnO_3 for x=0.5 has
been challenged recently by a Zener polaron picture emerging from experiments
and theoretical calculations. The effective low energy Hamiltonian for the
magnetic degrees of freedom has been found to be a cubic Heisenberg model, with
ferromagnetic nearest neighbor and frustrating antiferromagnetic next nearest
neighbor interactions in the planes, and antiferromagnetic interaction between
planes. With linear spin wave theory and diagonalization of small clusters up
to 27 sites we find that the behavior of the model interpolates between the A
and CE-type magnetic structures when a frustrating intraplanar interaction is
tuned. The values of the interactions calculated by ab initio methods indicate
a possible non-bipartite picture of polaron ordering differing from the
conventional one.Comment: 21 pages and 8 figures (included), Late
Stem cell-like populations and immunoregulatory molecules in periodontal granulation tissue
Background and Objectives:
Determine the presence of mesenchymal stem cells (MSCs) in healthy periodontal tissue and periodontal granulation tissue (GT) and explore associations between immuno‐regulatory molecules and selected subgingival microorganisms.
Material and Methods:
Mesenchymal stem cells were isolated, propagated and characterised by flow cytometry from a region of healthy gingival tissue and inflamed GT of 10 systemically healthy non‐smokers with chronic periodontitis. Tissue levels of immunoregulatory molecules were determined by qPCR and Gingival Crevicular Fluid (GCF) levels by ELISA. Subgingival plaque levels of periodontal pathogens were determined by qPCR
Results:
Cells with MSC‐properties were isolated from both inflamed GT and healthy gingival (G) tissue. A pro‐inflammatory process predominated in GT which was partly reflected in GCF and putative periodontal pathogens were higher at diseased sites. However, there was no significant difference in surface levels of mesenchymal (CD90, CD73, CD146, CD271, STRO‐1), endothelial (CD105, CD106), hematopoietic (CD34, CD45) and embryonic (SSEA‐4) stem cell markers between MSCs isolated from GT and G tissue.
Conclusion:
Periodontal lesions, albeit inflamed, retain healing potential as inferred by the presence of MSC‐like cells with similar immunophenotypic characteristics to those found in healthy periodontal tissue. Therefore, there might be merits for healing in preserving sufficient GT in‐situ during periodontal surgery
"Where is My Parcel?" Fast and Efficient Classifiers to Detect User Intent in Natural Language
We study the performance of customer intent classifiers designed to predict the most popular intent received through ASOS.com Customer Care Department, namely “Where is my order?”. These queries are characterised by the use of colloquialism, label noise and short message length. We conduct extensive experiments with twowell established classification models: logistic regression via n-grams to account for sequences in the dataand recurrent neural networks that perform the extraction of these sequential patterns automatically. Maintaining the embedding layer fixed to GloVe coordinates, a Mann-Whitney U test indicated that the F1 score on aheld out set of messages was lower for recurrent neural network classifiers than for linear n-grams classifiers (M1=0.828, M2=0.815; U=1,196, P=1.46e-20), unless all layers were jointly trained with all other network parameters (M1=0.831, M2=0.828, U=4,280, P=8.24e-4). This plain neural network produced top performance on a denoised set of labels (0.887 F1) matching with Human annotators (0.889 F1) and superior to linear classifiers (0.865 F1). Calibrating these models to achieveprecision levels above Human performance (0.93 Precision), our results indicate a small difference in Recall of 0.05 for the plain neural networks (training under 1hr), and 0.07 for the linear n-grams (training under 10min), revealing the latter as a judicious choice of model architecture in modern AI production systems
- …