1,827 research outputs found
Healing of a Topological Scar: Coordination Defects in a Honeycomb Lattice
A crystal structure with a point defect typically returns to its ideal local
structure upon moving a few bond lengths away from the defect; topological
defects such as dislocations or disclinations also heal rapidly in this regard.
Here we describe a simple point defect -- a two-fold atom incorporated at the
growth edge of a 2D hexagonal honeycomb material -- whose healing may require a
defect complex with 50 or more atoms. the two-fold
atom disappears into a single 'long bond' between its neighbors, thereby
inducing a pentagonal disclination. However, this
disclination occupies as much physical space as a six-fold ring. This
incompatibility of chemistry and topology can cause a ''ringing'' of the
Gaussian curvature that creates an expansive healing region and may even spawn
a semi-infinite grain boundary propagating outwards from the topological scar.Comment: 4 pages, 3 figures; SI is 7 pages, 4 figures, 1 table. Ancillary
files include a 7-zip file with particle positions, excel/csv files with
structure energies, and movies (explained in the SI) of the simulation
proces
RG Flow from Theory to the 2D Ising Model
We study 1+1 dimensional theory using the recently proposed method
of conformal truncation. Starting in the UV CFT of free field theory, we
construct a complete basis of states with definite conformal Casimir,
. We use these states to express the Hamiltonian of the full
interacting theory in lightcone quantization. After truncating to states with
, we numerically diagonalize the
Hamiltonian at strong coupling and study the resulting IR dynamics. We compute
non-perturbative spectral densities of several local operators, which are
equivalent to real-time, infinite-volume correlation functions. These spectral
densities, which include the Zamolodchikov -function along the full RG flow,
are calculable at any value of the coupling. Near criticality, our numerical
results reproduce correlation functions in the 2D Ising model.Comment: 31+12 page
Understanding police officer resistance to body-worn cameras
Purpose
Body-worn cameras (BWCs) have been adopted in police agencies across the USA in efforts to increase police transparency and accountability. This widespread implementation has occurred despite some notable resistance to BWCs from police officers in some jurisdictions. This resistance poses a threat to the appropriate implementation of this technology and adherence to BWC policies. The purpose of this paper is to examine factors that could explain variation in officer receptivity to BWCs. Design/methodology/approach
The authors assess differences between officers who volunteered to wear a BWC and officers who resisted wearing a BWC as part of a larger randomized controlled trial of BWCs in the Phoenix Police Department. The authors specifically examine whether officer educational attainment, prior use of a BWC, attitudes toward BWCs, perceptions of organizational justice, support for procedural justice, noble cause beliefs, and official measures of officer activity predict receptivity to BWCs among 125 officers using binary logistic regression. Findings
The findings indicate limited differences between BWC volunteers and resistors. Volunteers did have higher levels of educational attainment and were more likely to agree that BWCs improve citizen behaviors, relative to their resistant counterparts. Interestingly, there were no differences in perceptions of organizational justice, self-initiated activities, use of force, or citizen complaints between these groups. Originality/value
Though a growing body of research has examined the impact of BWCs on officer use of force and citizen complaints, less research has examined officer attitudes toward the adoption of this technology. Extant research in this area largely focusses on general perceptions of BWCs, as opposed to officer characteristics that could predict receptivity to BWCs. This paper addresses this limitation in the research
Relativistic non-instantaneous action-at-a-distance interactions
Relativistic action-at-a-distance theories with interactions that propagate
at the speed of light in vacuum are investigated. We consider the most general
action depending on the velocities and relative positions of the particles. The
Poincare invariant parameters that label successive events along the world
lines can be identified with the proper times of the particles provided that
certain conditions are impossed on the interaction terms in the action. Further
conditions on the interaction terms arise from the requirement that mass be a
scalar. A generic class of theories with interactions that satisfy these
conditions is found. The relativistic equations of motion for these theories
are presented. We obtain exact circular orbits solutions of the relativistic
one-body problem. The exact relativistic one-body Hamiltonian is also derived.
The theory has three components: a linearly rising potential, a Coulomb-like
interaction and a dynamical component to the Poincar\'e invariant mass. At the
quantum level we obtain the generalized Klein-Gordon-Fock equation and the
Dirac equation
Attitudinal Changes Toward Body-Worn Cameras: Perceptions of Cameras, Organizational Justice, and Procedural Justice Among Volunteer and Mandated Officers
Little is known about officer perceptions of body-worn cameras (BWCs), and whether perceptions change following implementation within their agencies. BWC deployment varies, with some agencies mandating officers to wear BWCs and others using volunteers. Researchers have yet to assess attitudinal differences between volunteers and mandated officers. This study addresses these gaps using data from an evaluation of BWCs in the Phoenix Police Department to examine officer perceptions of the utility of BWCs, perceptions of organizational justice, and support for using procedural justice. We use inverse propensity weighted difference-in-difference models to examine changes in officer perceptions over time between randomly selected officers who were mandated to wear a BWC, BWC volunteers, officers who resisted BWCs, and control officers. We identified limited significant differences in perceptions of BWCs over time, though effect sizes suggest that BWC volunteers and mandated officers were more subdued in their expectations about BWCs at the posttest
Effect of Transarterial Axillary Block yersus General Anesthesia on Paresthesiae 1 Year after Hand Surgery
Krüppel-like factor 5 is an important mediator for lipopolysaccharide-induced proinflammatory response in intestinal epithelial cells
Lipopolysaccharide (LPS) is a bacterially-derived endotoxin that elicits a strong proinflammatory response in intestinal epithelial cells. It is well established that LPS activates this response through NF-κB. In addition, LPS signals through the mitogen-activated protein kinase (MAPK) pathway. We previously demonstrated that the Krüppel-like factor 5 [KLF5; also known as intestine-enriched Krüppel-like factor (IKLF)] is activated by the MAPK. In the current study, we examined whether KLF5 mediates the signaling cascade elicited by LPS. Treatment of the intestinal epithelial cell line, IEC6, with LPS resulted in a dose- and time-dependent increase in KLF5 messenger RNA (mRNA) and protein levels. Concurrently, mRNA levels of the p50 and p65 subunits of NF-κB were increased by LPS treatment. Pretreatment with the MAPK inhibitor, U0126, or the LPS antagonist, polymyxin B, resulted in an attenuation of KLF5, p50 and p65 NF-κB subunit mRNA levels from LPS treatment. Importantly, suppression of KLF5 by small interfering RNA (siRNA) resulted in a reduction in p50 and p65 subunit mRNA levels and NF-κB DNA binding activity in response to LPS. LPS treatment also led to an increase in secretion of TNF-α and IL-6 from IEC6, both of which were reduced by siRNA inhibition of KLF5. In addition, intercellular adhesion molecule-1 (ICAM-1) levels were increased in LPS-treated IEC6 cells and this increase was associated with increased adhesion of Jurkat lymphocytes to IEC6. The induction of ICAM-1 expression and T cell adhesion to IEC6 by LPS were both abrogated by siRNA inhibition of KLF5. These results indicate that KLF5 is an important mediator for the proinflammatory response elicited by LPS in intestinal epithelial cells
The set of realizations of a max-plus linear sequence is semi-polyhedral
We show that the set of realizations of a given dimension of a max-plus
linear sequence is a finite union of polyhedral sets, which can be computed
from any realization of the sequence. This yields an (expensive) algorithm to
solve the max-plus minimal realization problem. These results are derived from
general facts on rational expressions over idempotent commutative semirings: we
show more generally that the set of values of the coefficients of a commutative
rational expression in one letter that yield a given max-plus linear sequence
is a semi-algebraic set in the max-plus sense. In particular, it is a finite
union of polyhedral sets
Topological Strings and (Almost) Modular Forms
The B-model topological string theory on a Calabi-Yau threefold X has a
symmetry group Gamma, generated by monodromies of the periods of X. This acts
on the topological string wave function in a natural way, governed by the
quantum mechanics of the phase space H^3(X). We show that, depending on the
choice of polarization, the genus g topological string amplitude is either a
holomorphic quasi-modular form or an almost holomorphic modular form of weight
0 under Gamma. Moreover, at each genus, certain combinations of genus g
amplitudes are both modular and holomorphic. We illustrate this for the local
Calabi-Yau manifolds giving rise to Seiberg-Witten gauge theories in four
dimensions and local P_2 and P_1 x P_1. As a byproduct, we also obtain a simple
way of relating the topological string amplitudes near different points in the
moduli space, which we use to give predictions for Gromov-Witten invariants of
the orbifold C^3/Z_3.Comment: 62 pages, 1 figure; v2: minor correction
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