10,846 research outputs found
Inferring meta-covariates in classification
This paper develops an alternative method for gene selection that combines model based clustering and binary classification. By averaging the covariates within the clusters obtained from model based clustering, we define “meta-covariates” and use them to build a probit regression model, thereby selecting clusters of similarly behaving genes, aiding interpretation. This simultaneous learning task is accomplished by an EM algorithm that optimises a single likelihood function which rewards good performance at both classification and clustering. We explore the performance of our methodology on a well known leukaemia dataset and use the Gene Ontology to interpret our results
Adhesion Induced DNA Naturation
DNA adsorption and naturation is modeled via two interacting flexible
homopolymers coupled to a solid surface. DNA denatures if the entropy gain for
unbinding the two strands overcomes the loss of binding energy. When adsorbed
to a surface, the entropy gain is smaller than in the bulk, leading to a
stronger binding and, upon neglecting self-avoidance, absence of a denatured
phase. Now consider conditions where the binding potentials are too weak for
naturation, and the surface potential too weak to adsorb single strands. In a
variational approach it is shown that their combined action may lead to a
naturated adsorbed phase. Conditions for the absence of naturation and
adsorption are derived too. The phase diagram is constructed qualitatively.Comment: 4 pages, 1 figur
Transient Local Bone Remodeling Effects of rhBMP-2 in an Ovine Interbody Spine Fusion Model
Background: Recombinant human bone morphogenetic protein-2 (rhBMP-2) is a powerful osteoinductive morphogen capable of stimulating the migration of mesenchymal stem cells (MSCs) to the site of implantation and inducing the proliferation and differentiation of these MSCs into osteoblasts. Vertebral end-plate and vertebral body resorption has been reported after interbody fusion with high doses of rhBMP-2. In this study, we investigated the effects of 2 rhBMP-2 doses on peri-implant bone resorption and bone remodeling at 7 time points in an end-plate-sparing ovine interbody fusion model. Methods: Twenty-one female sheep underwent an end-plate-sparing discectomy followed by interbody fusion at L2-L3 and L4-L5 using a custom polyetheretherketone (PEEK) interbody fusion device. The PEEK interbody device was filled with 1 of 2 different doses of rhBMP-2 on an absorbable collagen sponge (ACS): 0.13 mg (1·) or 0.90 mg (7·). Bone remodeling and interbody fusion were assessed via high-resolution radiography and histological analyses at 1, 2, 3, 4, 8, 12, and 20 weeks postoperatively. Results: Peri-implant bone resorption peaked between 3 and 8 weeks in both the 1· and the 7· rhBMP-2/ACS-dose group. Osteoclastic activity and corresponding peri-implant bone resorption was dose-dependent, with moderate-tomarked resorption at the 7·-dose level and less resorption at the 1·-dose level. Both dose (p \u3c 0.0007) and time (p \u3c 0.0025) affected bone resorption significantly. Transient bone-resorption areas were fully healed by 12 weeks. Osseous bridging was seen at all but 1 spinal level at 12 and at 20 weeks. Conclusions: In the ovine end-plate-sparing interbody fusion model, rhBMP-2 dose-dependent osteoclastic resorption is a transient phenomenon that peaks at 4 weeks postoperatively. Clinical Relevance: Using the U.S. Food and Drug Administration (FDA)-approved rhBMP-2 concentration and matching the volume of rhBMP-2/ACS with the volume of desired bone formation within the interbody construct may limit the occurrence of transient bone resorption
Radion Dynamics and Phenomenology in the Linear Dilaton Model
We investigate the properties of the radion in the 5D linear dilaton model
arising from Little String Theory. A Goldberger-Wise type mechanism is used to
stabilise a large interbrane distance, with the dilaton now playing the role of
the stabilising field. We consider the coupled fluctuations of the metric and
dilaton fields and identify the physical scalar modes of the system. The
wavefunctions and masses of the radion and Kaluza-Klein modes are calculated,
giving a radion mass of order the curvature scale. As a result of the direct
coupling between the dilaton and Standard Model fields, the radion couples to
the SM Lagrangian, in addition to the trace of the energy-momentum tensor. The
effect of these additional interaction terms on the radion decay modes is
investigated, with a notable increase in the branching fraction to photons. We
also consider the effects of a non-minimal Higgs coupling to gravity, which
introduces a mixing between the Higgs and radion modes. Finally, we calculate
the production cross section of the radion at the LHC and use the current Higgs
searches to place constraints on the parameter space.Comment: 28 pages, 7 figures; v2: error in radion-gauge boson Feynman rules
corrected, version published in JHE
Construction of the Hill48 and Yld89 for Auto-body Steel Sheets considering the Strain Rate
This paper deals with the anisotropic material properties and the initial yield locus considering the strain rate. Uni-axial tensile tests are performed with variation of the strain rate in order to obtain flow stress curves and the tensile properties. The R-values have been measured with a high speed camera by analyzing the deformation history during the tensile test. Anisotropy of auto-body steel sheets have been described by using Hill48 and Yld89 (Barlat89) yield functions according to the strain rate ranged from 0.001/sec to 100/sec. Hill48 and Yld89 yield loci of auto-body steel sheets at various strain rates have been constructed in order to visualize the initial yield state. The performance of two yield criteria is evaluated by comparing yield loci constructed in the principal stress plane. The initial yield locus becomes different from the static one when the strain rate is considered to describe the anisotropy of the steel sheets
Unitarity constraints on the stabilized Randall-Sundrum scenario
Recently proposed stabilization mechanism of the Randall-Sundrum metric gives
rise to a scalar radion, which couples universally to matter with a weak
interaction ( TeV) scale. Demanding that gauge boson scattering as
described by the effective low enerrgy theory be unitary upto a given scale
leads to significant constraints on the mass of such a radion.Comment: 10 page Latex 2e file including 4 postscript figures. Accepted in
Journal of Physics
Weak localization and electron-electron interactions in Indium-doped ZnO nanowires
Single crystal ZnO nanowires doped with indium are synthesized via the
laser-assisted chemical vapor deposition method. The conductivity of the
nanowires is measured at low temperatures in magnetic fields both perpendicular
and parallel to the wire axes. A quantitative fit of our data is obtained,
consistent with the theory of a quasi-one-dimensional metallic system with
quantum corrections due to weak localization and electron-electron
interactions. The anisotropy of the magneto-conductivity agrees with theory.
The two quantum corrections are of approximately equal magnitude with
respective temperature dependences of T^-1/3 and T^-1/2. The alternative model
of quasi-two-dimensional surface conductivity is excluded by the absence of
oscillations in the magneto-conductivity in parallel magnetic fields.Comment: 13 pages, Corrected forma
A combinatorial approach to knot recognition
This is a report on our ongoing research on a combinatorial approach to knot
recognition, using coloring of knots by certain algebraic objects called
quandles. The aim of the paper is to summarize the mathematical theory of knot
coloring in a compact, accessible manner, and to show how to use it for
computational purposes. In particular, we address how to determine colorability
of a knot, and propose to use SAT solving to search for colorings. The
computational complexity of the problem, both in theory and in our
implementation, is discussed. In the last part, we explain how coloring can be
utilized in knot recognition
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