26,662 research outputs found
Macroscopic Floquet topological crystalline steel pump
The transport of a steel sphere on top of two dimensional periodic magnetic
patterns is studied experimentally. Transport of the sphere is achieved by
moving an external permanent magnet on a closed loop around the two dimensional
crystal. The transport is topological i.e. the steel sphere is transported by a
primitive unit vector of the lattice when the external magnet loop winds around
specific directions. We experimentally determine the set of directions the
loops must enclose for nontrivial transport of the steel sphere into various
directions
Casimir interactions in Ising strips with boundary fields: exact results
An exact statistical mechanical derivation is given of the critical Casimir
forces for Ising strips with arbitrary surface fields applied to edges. Our
results show that the strength as well as the sign of the force can be
controled by varying the temperature or the fields. An interpretation of the
results is given in terms of a linked cluster expansion. This suggests a
systematic approach for deriving the critical Casimir force which can be used
in more general models.Comment: 10 pages, 4 figure
Lattice-corrected strain-induced vector potentials in graphene
The electronic implications of strain in graphene can be captured at low
energies by means of pseudovector potentials which can give rise to
pseudomagnetic fields. These strain-induced vector potentials arise from the
local perturbation to the electronic hopping amplitudes in a tight-binding
framework. Here we complete the standard description of the strain-induced
vector potential, which accounts only for the hopping perturbation, with the
explicit inclusion of the lattice deformations or, equivalently, the
deformation of the Brillouin zone. These corrections are linear in strain and
are different at each of the strained, inequivalent Dirac points, and hence are
equally necessary to identify the precise magnitude of the vector potential.
This effect can be relevant in scenarios of inhomogeneous strain profiles,
where electronic motion depends on the amount of overlap among the local Fermi
surfaces. In particular, it affects the pseudomagnetic field distribution
induced by inhomogeneous strain configurations, and can lead to new
opportunities in tailoring the optimal strain fields for certain desired
functionalities.Comment: Errata for version
Dissipative Visco-plastic Deformation in Dynamic Fracture: Tip Blunting and Velocity Selection
Dynamic fracture in a wide class of materials reveals "fracture energy"
much larger than the expected nominal surface energy due to the
formation of two fresh surfaces. Moreover, the fracture energy depends on the
crack velocity, . We show that a simple dynamical theory of
visco-plasticity coupled to asymptotic pure linear-elasticity provides a
possible explanation to the above phenomena. The theory predicts tip blunting
characterized by a dynamically determined crack tip radius of curvature. In
addition, we demonstrate velocity selection for cracks in fixed-grip strip
geometry accompanied by the identification of and its velocity
dependence.Comment: 4 pages, 1 figures; presentation improved, refs. changed, figure
omitte
Multipartite Continuous Variable Solution for the Byzantine Agreement Problem
We demonstrate that the Byzantine Agreement (detectable broadcast) is also
solvable in the continuous-variable scenario with multipartite entangled
Gaussian states and Gaussian operations (homodyne detection). Within this
scheme we find that Byzantine Agreement requires a minimum amount of
entanglement in the multipartite states used in order to achieve a solution. We
discuss realistic implementations of the protocol, which consider the
possibility of having inefficient homodyne detectors, not perfectly correlated
outcomes, and noise in the preparation of the resource states. The proposed
protocol is proven to be robust and efficiently applicable under such non-ideal
conditions.Comment: This paper supersedes and extends arXiv:quant-ph/0507249, title
changed to match the published version, 11 pages, 3 figures, published
versio
Spectral origin of the colossal magnetodielectric effect in multiferroic DyMn2O5
The origin of the colossal magnetodielectric effect in DyMn2O5 [1] has been
an outstanding question in multiferroics. Here, we report the activation of the
electric dipole mode at 4-5 cm-1 in an applied magnetic field which fully
accounts for the CMD effect. We examine two alternative explanations of this
mode: an electromagnon and transitions between f-electron levels of Dy3+ ions.
The experimental and theoretical evidence supports the electromagnon origin of
the CMD effect.Comment: 5 pages, 4 figures, submitted to PR
Advancing Entry-Level OTD Students from Novice to Competent with Foundational Skills Using Cognitive Apprenticeship Constructs
This manuscript describes how one entry-level occupational therapy doctoral (OTD) program used an innovative approach to scaffolding assignments through a cognitive apprenticeship (CA) framework. Cognitive apprenticeship strategies include learning in the context or culture of the profession. This is achieved through observation, coaching, engagement, and discovery of strategies by the instructor. This framework was implemented to facilitate the learning of occupational, activity, and task (OAT) analyses through a four-week module within a first-semester foundations course. Cognitive apprenticeship constructs were used as instructional teaching strategies including active learning, group facilitated assignments, hands on observation, and immediate feedback and modeling of professional reasoning by the instructor. The assessment of findings supporting the effectiveness of the use of CA to implement this module included a mixed methods approach. A quantitative analysis of pre- and post-test surveys measuring confidence levels related to entry-level occupational therapy practice skills demonstrated that each survey item was statistically significant for increased confidence. A qualitative analysis of open-ended questions identified themes related to teaching strategies and the development of a foundational occupational therapy identity. The aim of this project is to expand the use of similar evidence-based applications for CA to progress student professional reasoning and occupational therapy practice skills while also supporting development of an emerging professional identity. This manuscript makes a substantive contribution to the teaching and application of analyses within OT education and the use of professional terminology, particularly the foundational understanding of the Occupational Therapy Practice Framework-IV and how it is applied in practice. The module demonstrated successful scaffolding of concepts built across several weeks. Cognitive apprenticeship constructs facilitated students\u27 progression from novice to competent problem solvers within an OT context, which positively impacted the reported confidence of associated entry-level skills
Expression of citrulline and homocitrulline residues in the lungs of non-smokers and smokers : implications for autoimmunity in rheumatoid arthritis
Introduction: Smoking is a well-established risk factor for rheumatoid arthritis (RA), and it has been proposed that smoking-induced citrullination renders autoantigens immunogenic. To investigate this mechanism, we examined human lung tissue from 40 subjects with defined smoking status, with or without chronic obstructive pulmonary disease (COPD), and control tissues from other organs for citrullinated proteins and the deiminating enzymes peptidylarginine deiminase type-2 (PAD2) and -4 (PAD4).
Methods: Lung tissue samples, dissected from lobectomy specimens from 10 never smokers, 10 smokers without airflow limitation, 13 COPD smokers and eight COPD ex-smokers, and control tissue samples (spleen, skeletal muscle, liver, ovary, lymph node, kidney and heart), were analysed for citrullinated proteins, PAD2 and PAD4 by immunoblotting. Citrulline and homocitrulline residues in enolase and vimentin were analysed by partial purification by gel electrophoresis followed by mass spectrometry in 12 of the lung samples and one from each control tissues. Band intensities were scored semi-quantitatively and analysed by two-tailed Mann-Whitney T-test.
Results: Within the lung tissue samples, citrullinated proteins, PAD2 and PAD4 were found in all samples, with an increase in citrullination in COPD (P = 0.039), but minimal difference between smokers and non-smokers (P = 0.77). Citrullination was also detected at lower levels in the tissues from other organs, principally in lymph node, kidney and skeletal muscle. Mass spectrometry of the lung samples showed that vimentin was citrullinated at positions 71, 304, 346, 410 and 450 in non-smokers and smokers both with and without COPD. A homocitrulline at position 104 was found in four out of six COPD samples and one out of six non-COPD. Citrulline-450 was also found in three of the control tissues. There were no citrulline or homocitrulline residues demonstrated in a-enolase.
Conclusions: We have shown evidence of citrullination of vimentin, a major autoantigen in RA, in both non-smokers and smokers. The increase in citrullinated proteins in COPD suggests that citrullination in the lungs of smokers is mainly due to inflammation. The ubiquity of citrullination of vimentin in the lungs and other tissues suggests that the relationship between smoking and autoimmunity in RA may be more complex than previously thought
The Corrosion Protection of Copper and Copper Alloys using an Electrodeposited Conducting Polypyrrole Coating
Adherent polypyrrole films were electropolymerized from a near
neutral sodium oxalate solution at pure Cu, CuZn and CuNi electrodes.
The growth of these films was facilitated by the formation of a
pseudo-passive oxalate layer. This layer was sufficiently protective to minimize dissolution of the substrate, but sufficiently conductive to enable the electropolymerization of pyrrole at the interface, and the generation of an adherent polypyrrole film. The rate of
electropolymerization at the CuNi layer was reduced significantly by the formation of a nickel-rich oxide phase, however, the presence of Cu2+ increased the rate of polymer growth, enabling the formation of a thin polypyrrole layer during the early stages of polymerization.
Likewise, the presence of zinc in the oxalate layer generated at the
CuZn electrode reduced somewhat the rate of polymer formation.
These films exhibited good corrosion protection properties in an
acidified chloride solution
Topological quantum field theory and invariants of graphs for quantum groups
On basis of generalized 6j-symbols we give a formulation of topological
quantum field theories for 3-manifolds including observables in the form of
coloured graphs. It is shown that the 6j-symbols associated with deformations
of the classical groups at simple even roots of unity provide examples of this
construction. Calculational methods are developed which, in particular, yield
the dimensions of the state spaces as well as a proof of the relation,
previously announced for the case of by V.Turaev, between these
models and corresponding ones based on the ribbon graph construction of
Reshetikhin and Turaev.Comment: 38 page
- …