8,007 research outputs found
The strong Atiyah conjecture for right-angled Artin and Coxeter groups
We prove the strong Atiyah conjecture for right-angled Artin groups and
right-angled Coxeter groups. More generally, we prove it for groups which are
certain finite extensions or elementary amenable extensions of such groups.Comment: Minor change
Pathways to formally assessed work placement : employers\u27 perspectives on collaborative education in the Australian construction industry
The QS and construction industry is uniquely impacted by project-based work environments. This creates special challenges for collaborative, work-integrated education of pre-professional students. This research is based on investigating the attitudes of employer’s towards the use of formally assessed internships. The study comprised two stages- firstly a series of pilot interviews were undertaken with employers to test a number known issues and secondly, the results from the interviews were used to refine a set of questions that were put to a large focus group of employers who were invited from across the property and construction sector in Australia. The results showed that many employer organisations expressed considerable goodwill towards collaborative education with universities. However, the challenges caused by project-based work environments restrict employers\u27 ability to provide comprehensive learning opportunities. This research discusses some of the distinctive issues associated with work-integrated learning in the construction industry and proposes some potential opportunities for overcoming these restrictions
Influence of classical resonances on chaotic tunnelling
Dynamical tunnelling between symmetry-related stable modes is studied in the
periodically driven pendulum. We present strong evidence that the tunnelling
process is governed by nonlinear resonances that manifest within the regular
phase-space islands on which the stable modes are localized. By means of a
quantitative numerical study of the corresponding Floquet problem, we identify
the trace of such resonances not only in the level splittings between
near-degenerate quantum states, where they lead to prominent plateau
structures, but also in overlap matrix elements of the Floquet eigenstates,
which reveal characteristic sequences of avoided crossings in the Floquet
spectrum. The semiclassical theory of resonance-assisted tunnelling yields good
overall agreement with the quantum-tunnelling rates, and indicates that partial
barriers within the chaos might play a prominent role
Excitation spectrum of bosons in a finite one-dimensional circular waveguide via the Bethe ansatz
The exactly solvable Lieb-Liniger model of interacting bosons in
one-dimension has attracted renewed interest as current experiments with
ultra-cold atoms begin to probe this regime. Here we numerically solve the
equations arising from the Bethe ansatz solution for the exact many-body wave
function in a finite-size system of up to twenty particles for attractive
interactions. We discuss the novel features of the solutions, and how they
deviate from the well-known string solutions [H. B. Thacker, Rev. Mod. Phys.\
\textbf{53}, 253 (1981)] at finite densities. We present excited state string
solutions in the limit of strong interactions and discuss their physical
interpretation, as well as the characteristics of the quantum phase transition
that occurs as a function of interaction strength in the mean-field limit.
Finally we compare our results to those of exact diagonalization of the
many-body Hamiltonian in a truncated basis. We also present excited state
solutions and the excitation spectrum for the repulsive 1D Bose gas on a ring.Comment: 13 pages, 12 figure
Polarization restricts hepatitis C virus entry into HepG2 hepatoma cells
The primary reservoir for hepatitis C virus (HCV) replication is believed to be hepatocytes, which are highly polarized with tight junctions (TJ) separating their basolateral and apical domains. HepG2 cells develop polarity over time, resulting in the formation and remodeling of bile canalicular (BC) structures. HepG2 cells expressing CD81 provide a model system to study the effects of hepatic polarity on HCV infection. We found an inverse association between HepG2-CD81 polarization and HCV pseudoparticle entry. As HepG2 cells polarize, discrete pools of claudin-1 (CLDN1) at the TJ and basal/lateral membranes develop, consistent with the pattern of receptor staining observed in liver tissue. The TJ and nonjunctional pools of CLDN1 show an altered association with CD81 and localization in response to the PKA antagonist Rp-8-Br-cyclic AMPs (cAMPs). Rp-8-Br-cAMPs reduced CLDN1 expression at the basal membrane and inhibited HCV infection, supporting a model where the nonjunctional pools of CLDN1 have a role in HCV entry. Treatment of HepG2 cells with proinflammatory cytokines, tumor necrosis factor alpha and gamma interferon, perturbed TJ integrity but had minimal effect(s) on cellular polarity and HCV infection, suggesting that TJ integrity does not limit HCV entry into polarized HepG2 cells. In contrast, activation of PKC with phorbol ester reduced TJ integrity, ablated HepG2 polarity, and stimulated HCV entry. Overall, these data show that complex hepatocyte-like polarity alters CLDN1 localization and limits HCV entry, suggesting that agents which disrupt hepatocyte polarity may promote HCV infection and transmission within the liver
One Loop Predictions of the Finely Tuned SSM
We study the finely tuned SSM, recently proposed by Arkani-Hamed and
Dimopoulos, at the one loop level. The runnings of the four gaugino Yukawa
couplings, the mu term, the gaugino masses, and the Higgs quartic coupling are
computed. The Higgs mass is found to be 130 - 170 GeV for M_s > 10^6 GeV. If
the Yukawa coupling constants are measured at the 1% level, this can determine
the SUSY breaking scale to within an order of magnitude. Measuring the
relationships between the couplings to this accuracy provides a striking signal
for this model.Comment: 5 pages, 4 figures; v2: Minor corrections to anomalous dimensions and
beta functions. Numerical results are not significantly affected. v3: Minor
changes to figures and references, as published in PR
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