12,153 research outputs found
The relativistic interaction in the Wilson loop approach
We study the relativistic interaction starting from the
Feynman-Schwinger representation of the gauge-invariant quark-antiquark Green
function. We focus on the one-body limit and discuss the obtained
non-perturbative interaction kernel of the Dirac equation.Comment: 5 pages, Latex (espcrc2.sty) To be published in the proceedings of
High-Energy Physics International Euroconference on Quantum
Chromodynamics:QCD97; 25th Anniversary of QCD, Montpellier, France, 3-9 July
199
A Possible Universal Treatment of the Field Strength Correlator in the Abelian-Projected SU(2)-Theory
An integral relation between two functions parametrizing the bilocal field
strength correlator within the Stochastic Vacuum Model is obtained in the
effective Abelian-projected SU(2)-theory. This relation is independent of the
concrete properties of the ensemble of vortex loops, which are present in the
theory under study. By virtue of the lattice result stating that the infrared
asymptotic behaviours of these functions should have the same functional form,
the obtained relation enables one to find these behaviours, as well as the
infrared asymptotics of the bilocal correlator of densities of the vortex
loops. Those turn out to be exponentials, decreasing at the inverse mass of the
dual vector boson, times certain polynomials in the inverse integer powers of
the distance. This result agrees with the general predictions and the existing
lattice data better than the results of previous calculations, where these
powers were found to be half-integer ones.Comment: 9 pages, LaTeX2e, no figures, new discussions of the obtained results
are added, to appear in Phys. Lett.
Non-perturbative dynamics of the heavy-light quark system in the non-recoil limit
Starting from the relativistic gauge-invariant quark-antiquark Green function
we obtain the relevant interaction in the one-body limit, which can be
interpreted as the kernel of a non-perturbative Dirac equation. We study this
kernel in different kinematic regions, reproducing, in particular, for heavy
quark the potential case and sum rules results. We discuss the relevance of the
result for heavy-light mesons and the relation with the phenomenological Dirac
equations used up to now in the literature.Comment: 11 pages, LaTex, elsevier.sty, 2 figures included, minor changes, one
reference added, to appear in Phys. Lett.
Generating Cultural Capital? Impacts of Artists-in-Residence on Teacher Professional Learning
The introduction of the Australian Arts Curriculum and the rise of a twenty-first century creativity agenda in education signal an opportunity for teacher educators to re-examine the outcomes and potential of arts-based initiatives on teacher professional learning. This study re-visits the outcomes of the Australian Artist-in-Residence program in this context and analyses a subset of data collected for its evaluation. The study reveals that while teachers perceive an improvement in creative capital, it is important to consider questions about the capacity for such programs to generate long term changes in practice. The study illustrates how some States and Territories embedded opportunities for collective reflective activity to facilitate such change and suggests there is potential for AIR models to support pre-service and in-service professional learning in creative and critical thinking as well as the arts curriculum. With the Professional Engagement domain of the Australian Professional Standards for Teachers (Graduate teachers), in particular Standards 6 and 7, this is timely research
Confining Properties of Abelian-Projected Theories and Field Strength Correlators
We review the string representations of Abelian-projected SU(2)- and
SU(3)-gauge theories and their application to the evaluation of bilocal field
strength correlators. The large distance asymptotic behaviours of the latter
ones are shown to be in agreement with the Stochastic Vacuum Model of QCD and
existing lattice data.Comment: Invited talk given at the Euroconference ``QCD 99'', 7-13th July
1999, Montpellier (France), to appear in Nucl. Phys. B (Proc. Suppl.
Three-dimensional flow in Kupffer's Vesicle.
Whilst many vertebrates appear externally left-right symmetric, the arrangement of internal organs is asymmetric. In zebrafish, the breaking of left-right symmetry is organised by Kupffer's Vesicle (KV): an approximately spherical, fluid-filled structure that begins to form in the embryo 10 hours post fertilisation. A crucial component of zebrafish symmetry breaking is the establishment of a cilia-driven fluid flow within KV. However, it is still unclear (a) how dorsal, ventral and equatorial cilia contribute to the global vortical flow, and (b) if this flow breaks left-right symmetry through mechanical transduction or morphogen transport. Fully answering these questions requires knowledge of the three-dimensional flow patterns within KV, which have not been quantified in previous work. In this study, we calculate and analyse the three-dimensional flow in KV. We consider flow from both individual and groups of cilia, and (a) find anticlockwise flow can arise purely from excess of cilia on the dorsal roof over the ventral floor, showing how this vortical flow is stabilised by dorsal tilt of equatorial cilia, and (b) show that anterior clustering of dorsal cilia leads to around 40 % faster flow in the anterior over the posterior corner. We argue that these flow features are supportive of symmetry breaking through mechano-sensory cilia, and suggest a novel experiment to test this hypothesis. From our new understanding of the flow, we propose a further experiment to reverse the flow within KV to potentially induce situs inversus.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00285-016-0967-
Confinement, Monopoles and Wilsonian Effective Action
An effective low energy action for Yang-Mills theories is proposed, which
invokes an additional auxiliary field for the field strength
. For a particular relation between the parameters of this action
a gluon propagator with a behaviour for in the Landau gauge
is obtained. The abelian subsector of this action admits a duality
transformation, where the dual action contains a Goldstone boson as
the dual of , and corresponds to an abelian Higgs model in the
broken phase describing the condensation of magnetic charges. The Wilsonian
renormalization group equations for the parameters of the original action are
integrated in some approximation, and we find that the relation among the
parameters associated with confinement appears as an infrared attractive fixed
point.Comment: 25 pages, LaTex, 2 figure
Inhibition of in-stent stenosis by oral administration of bindarit in porcine coronary arteries
<p><b>Objective:</b> We have previously demonstrated that bindarit, a selective inhibitor of monocyte chemotactic proteins (MCPs), is effective in reducing neointimal formation in rodent models of vascular injury by reducing smooth muscle cell proliferation and migration and neointimal macrophage content, effects associated with the inhibition of MCP-1/CCL2 production. The aim of the current study was to evaluate the efficacy of bindarit on in-stent stenosis in the preclinical porcine coronary stent model.</p>
<p><b>Methods and Results:</b> One or 2 bare metal stents (Multi-Link Vision, 3.5 mm) were deployed (1:1.2 oversize ratio) in the coronary arteries of 42 pigs (20 bindarit versus 22 controls). Bindarit (50 mg/kg per day) was administered orally from 2 days before stenting until the time of euthanasia at 7 and 28 days. Bindarit caused a significant reduction in neointimal area (39.4%, P<0.001, n=9 group), neointimal thickness (51%, P<0.001), stenosis area (37%, P<0.001), and inflammatory score (40%, P<0.001) compared with control animals, whereas there was no significant difference in the injury score between the 2 groups. Moreover, treatment with bindarit significantly reduced the number of proliferating cells (by 45%, P<0.05; n=6 group) and monocyte/macrophage content (by 55%, P<0.01; n=5–6 group) in stented arteries at day 7 and 28, respectively. These effects were associated with a significant (P<0.05) reduction of MCP-1 plasma levels at day 28. In vitro data showed that bindarit (10–300 micromol/L) reduced tumor necrosis factor-alpha (50 ng/mL)–induced pig coronary artery smooth muscle cell proliferation and inhibited MCP-1 production.</p>
<p><b>Conclusion:</b> Our results show the efficacy of bindarit in the prevention of porcine in-stent stenosis and support further investigation for clinical application of this compound.</p>
The Queue-Number of Posets of Bounded Width or Height
Heath and Pemmaraju conjectured that the queue-number of a poset is bounded
by its width and if the poset is planar then also by its height. We show that
there are planar posets whose queue-number is larger than their height,
refuting the second conjecture. On the other hand, we show that any poset of
width has queue-number at most , thus confirming the first conjecture in
the first non-trivial case. Moreover, we improve the previously best known
bounds and show that planar posets of width have queue-number at most
while any planar poset with and has queue-number at most its
width.Comment: 14 pages, 10 figures, Appears in the Proceedings of the 26th
International Symposium on Graph Drawing and Network Visualization (GD 2018
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