827 research outputs found
Introduction: contains Cover, Table of Contents, Letter from the Editor, and Masthead
I hope you enjoy the third issue of the Richmond Journal of Law and Technology for the 2006-2007 academic year, our Annual Survey of Electronic Discovery. This is our first annual survey since the new amendments to the Federal Rules of Civil Procedure, which at the time of this publication have been in effect for several months, that affect electronic discovery in several significant ways. The entire staff of the Journal has worked diligently to bring these articles to our readers. Whether you are new to the Journal and electronic discovery, or whether you are a long-time reader, you will find the observations that follow enlightening
Probing topology by "heating": Quantized circular dichroism in ultracold atoms
We reveal an intriguing manifestation of topology, which appears in the
depletion rate of topological states of matter in response to an external
drive. This phenomenon is presented by analyzing the response of a generic 2D
Chern insulator subjected to a circular time-periodic perturbation: due to the
system's chiral nature, the depletion rate is shown to depend on the
orientation of the circular shake. Most importantly, taking the difference
between the rates obtained from two opposite orientations of the drive, and
integrating over a proper drive-frequency range, provides a direct measure of
the topological Chern number of the populated band (): this "differential
integrated rate" is directly related to the strength of the driving field
through the quantized coefficient . Contrary to the
integer quantum Hall effect, this quantized response is found to be non-linear
with respect to the strength of the driving field and it explicitly involves
inter-band transitions. We investigate the possibility of probing this
phenomenon in ultracold gases and highlight the crucial role played by edge
states in this effect. We extend our results to 3D lattices, establishing a
link between depletion rates and the non-linear photogalvanic effect predicted
for Weyl semimetals. The quantized circular dichroism revealed in this work
designates depletion-rate measurements as a universal probe for topological
order in quantum matter.Comment: 10 pages, 5 figures (including Sup. Mat.). Revised version, accepted
for publicatio
Oxygen isotope equilibrium in brachiopod shell fibres in the context of biological control
No abstract available
Rydberg-Atom Quantum Simulation and Chern Number Characterization of a Topological Mott Insulator
In this work we consider a system of spinless fermions with nearest and
next-to-nearest neighbor repulsive Hubbard interactions on a honeycomb lattice,
and propose and analyze a realistic scheme for analog quantum simulation of
this model with cold atoms in a two-dimensional hexagonal optical lattice. To
this end, we first derive the zero-temperature phase diagram of the interacting
model within a mean-field theory treatment. We show that besides a
semi-metallic and a charge-density-wave ordered phase, the system exhibits a
quantum anomalous Hall phase, which is generated dynamically, i.e. purely as a
result of the repulsive fermionic interactions and in the absence of any
external gauge fields. We establish the topological nature of this dynamically
created Mott insulating phase by the numerical calculation of a Chern number.
Based on the knowledge of the mean-field phase diagram, we then discuss in
detail how the interacting Hamiltonian can be engineered effectively by
state-of-the-art experimental techniques for laser-dressing of cold fermionic
ground-state atoms with electronically excited Rydberg states that exhibit
strong dipolar interactions.Comment: Revtex4 file, color figures. Final journal version. References
update
Structure and composition of the eggshell of a passerine bird, Setophaga ruticilla (Linnaeus, 1758)
Detection of Zak phases and topological invariants in a chiral quantum walk of twisted photons
Topological insulators are fascinating states of matter exhibiting protected
edge states and robust quantized features in their bulk. Here, we propose and
validate experimentally a method to detect topological properties in the bulk
of one-dimensional chiral systems. We first introduce the mean chiral
displacement, and we show that it rapidly approaches a multiple of the Zak
phase in the long time limit. Then we measure the Zak phase in a photonic
quantum walk, by direct observation of the mean chiral displacement in its
bulk. Next, we measure the Zak phase in an alternative, inequivalent timeframe,
and combine the two windings to characterize the full phase diagram of this
Floquet system. Finally, we prove the robustness of the measure by introducing
dynamical disorder in the system. This detection method is extremely general,
as it can be applied to all one-dimensional platforms simulating static or
Floquet chiral systems.Comment: 10 pages, 7 color figures (incl. appendices) Close to the published
versio
Quantum anomalous Hall phase in synthetic bilayers via twistronics without a twist
We recently proposed quantum simulators of "twistronic-like" physics based on
ultracold atoms and syntheticdimensions [Phys. Rev. Lett. 125, 030504 (2020)].
Conceptually, the scheme is based on the idea that aphysical monolayer optical
lattice of desired geometry is upgraded to a synthetic bilayer system by
identifyingthe internal states of the trapped atoms with synthetic spatial
dimensions. The couplings between the internalstates, i.e. between sites on the
two layers, can be exquisitely controlled by laser induced Raman transitions.By
spatially modulating the interlayer coupling, Moir\'e-like patterns can be
directly imprinted on the latticewithout the need of a physical twist of the
layers. This scheme leads practically to a uniform pattern across thelattice
with the added advantage of widely tunable interlayer coupling strengths. The
latter feature facilitates theengineering of flat bands at larger "magic"
angles, or more directly, for smaller unit cells than in conventionaltwisted
materials. In this paper we extend these ideas and demonstrate that our system
exhibits topologicalband structures under appropriate conditions. To achieve
non-trivial band topology we consider imanaginarynext-to-nearest neighbor
tunnelings that drive the system into a quantum anomalous Hall phase. In
particular,we focus on three groups of bands, whose their Chern numbers triplet
can be associated to a trivial insulator(0,0,0), a standard non-trivial
(-1,0,1) and a non-standard non-trivial (-1,1,0). We identify regimes of
parameterswhere these three situations occur. We show the presence of an
anomalous Hall phase and the appearance oftopological edge states. Our works
open the path for experiments on topological effects in twistronics without
atwistComment: 11 pages, 10 figure
Association of Plasmid Bearing Multi Drug Resistant Bacteria with High Mortalities in Nigerian Poultry
Bacteriological investigations were carried out on reported cases of low and high mortalities in commercial poultry in the year 2007-2009 in commercial flocks of breeders, layers, broilers, chicks and growers. Pure bacterial isolates obtained from dead birds, mainly Gram negative, were tested for their biochemical and antibiotic susceptibility profiles using Microscan® Dried Gram-negative Breakpoint Combo Pannels. The microscan panel analysis bacterial isolates for 24 biochemical tests and up to 25 antimicrobial agents following 16-20 hours of incubation at 35-37oC. Bacteria isolated were Escherichia coli, Salmonella Enteritidis, Salmonella Pullorum, Salmonella Gallinarum, Citrobacter youngae, Klebsiella ozaneae, Klebsiella variicola, Enterobacter cloaceae, Hafnia alvei, Pasteurella gallinarum and Pasteurella multocida. The bacterial isolates showed resistance to 6-23 of the 25 antibiotics tested. Tetracycline and ampicilllin were found as the least potent drugs, with 90 and 90.91% resistance respectively. Resistance was obtained against antibacterial agents that are not in use in Nigerian poultry industry, such as the cephalosporins, carbapenems, piperacillin, tircacillin, amikacin, tobramcycin and levofloxacin suggesting possible genetic contribution to resistance. Thirty-four (85%) of the 40 pathogenic bacteria isolates treated for plasmid profile were found to be carrying plasmids. Plasmid DNA size 11.50 kbp was commonly observed (about 65%) among all the plasmid borne mdr bacteria, plasmid DNA size 10kbp (incidence of about 22% in plasmid borne bacteria) as well as a 26.3 kbp plasmid DNA and a 6.6 kbp plasmid DNA. The susceptibility of the plasmid bearing bacteria to antibiotics was enhanced following plasmid curing with sodium deodecyl sulphate. Antibiotic susceptibility testing should guide treatment in all infections where organism can be cultured in veterinary medicine practice Keywords: Antibiotics, high mortalities, multi-drug resistant bacteria, plasmid, poultry
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