4,302 research outputs found
Saccadic latency in amblyopia.
We measured saccadic latencies in a large sample (total n = 459) of individuals with amblyopia or risk factors for amblyopia, e.g., strabismus or anisometropia, and normal control subjects. We presented an easily visible target randomly to the left or right, 3.5° from fixation. The interocular difference in saccadic latency is highly correlated with the interocular difference in LogMAR (Snellen) acuity-as the acuity difference increases, so does the latency difference. Strabismic and strabismic-anisometropic amblyopes have, on average, a larger difference between their eyes in LogMAR acuity than anisometropic amblyopes and thus their interocular latency difference is, on average, significantly larger than anisometropic amblyopes. Despite its relation to LogMAR acuity, the longer latency in strabismic amblyopes cannot be attributed either to poor resolution or to reduced contrast sensitivity, because their interocular differences in grating acuity and in contrast sensitivity are roughly the same as for anisometropic amblyopes. The correlation between LogMAR acuity and saccadic latency arises because of the confluence of two separable effects in the strabismic amblyopic eye-poor letter recognition impairs LogMAR acuity while an intrinsic sluggishness delays reaction time. We speculate that the frequent microsaccades and the accompanying attentional shifts, made while strabismic amblyopes struggle to maintain fixation with their amblyopic eyes, result in all types of reactions being irreducibly delayed
Decoherence of multi-dimensional entangled coherent states
For entangled states of light both the amount of entanglement and the
sensitivity to noise generally increase with the number of photons in the
state. The entanglement-sensitivity tradeoff is investigated for a particular
set of states, multi-dimensional entangled coherent states. Those states
possess an arbitrarily large amount of entanglement provided the number of
photons is at least of order . We calculate how fast that entanglement
decays due to photon absorption losses and how much entanglement is left. We
find that for very small losses the amount of entanglement lost is equal to
ebits per absorbed photon, irrespective of the amount
of pure-state entanglement one started with. In contrast, for larger losses
it tends to be the remaining amount of entanglement that is independent of .
This may provide a useful strategy for creating states with a fixed amount of
entanglement.Comment: 6 pages, 5 figure
Spherically Symmetric Solutions to Fourth-Order Theories of Gravity
Gravitational theories generated from Lagrangians of the form f(R) are
considered. The spherically symmetric solutions to these equations are
discussed, paying particular attention to features that differ from the
standard Schwarzschild solution. The asymptotic form of solutions is described,
as is the lack of validity of Birkhoff's theorem. Exact solutions are presented
which illustrate these points and their stability and geodesics are
investigated.Comment: 10 pages, published versio
Lorentz-Invariant "Elements of Reality" and the Question of Joint Measurability of Commuting Observables
It is shown that the joint measurements of some physical variables
corresponding to commuting operators performed on pre- and post-selected
quantum systems invariably disturb each other. The significance of this result
for recent proofs of the impossibility of realistic Lorentz invariant
interpretation of quantum theory (without assumption of locality) is discussed.Comment: 15 page
The design and construction of a weld heat-affected zone simulator
Investigation of the structure and properties of the heat-affected zones
in welded joints is usually limited by their small size and their complexity.
One method of overcoming this problem is to simulate the structure at a
particular point in the heat-affected zone in a specimen of larger size by
imposing on it the thermal cycle sustained at that point.
The equipment described in this note uses a.c. resistance heating and
water cooling to impose thermal cycles on 2.5" x O.W' x O.W' specimens, the
thermal cycle being chosen by adjustment of a bank of variable resistors to
construct a voltage analogue. Control of specimen temperature is achieved
using a thyristor and two ignitrons to control the input at 44ov. to a
welding transformer. Feedback is applied from a thermocouple welded to the
specimen hot-zone. The equipment has been shown to produce the desired
thermal cycles in a reproducible manner
Moving from Cars to People
The twenty-page comic includes a dialogue, taking place in various urban settings, between characters Kelly and Kristi who are based on National Institute for Transportation and Communities (NITC) researchers Kelly Clifton of the University of British Columbia and Kristina Currans of the University of Arizona. The two have a long history of collaboration around the data, methods, and processes used to plan for multimodal transportation impacts of new development. This short graphic synopsis is an engaging, approachable way for anyone – no matter their level of expertise in this topic – to learn about their findings.
Illustrated by PSU Master of Fine Arts student Joaquin Golez, the comic was authored by Clifton and Currans and developed in conjunction with Susan Kirtley, director of the Comic Studies Program at Portland State University (PSU), and Portland, OR-based illustrator Ryan Alexander-Tanner, who has worked on academic comics before and drew on his experience to help guide the collaborative process
Dynamics of a lattice Universe
We find a solution to Einstein field equations for a regular toroidal lattice
of size L with equal masses M at the centre of each cell; this solution is
exact at order M/L. Such a solution is convenient to study the dynamics of an
assembly of galaxy-like objects. We find that the solution is expanding (or
contracting) in exactly the same way as the solution of a
Friedman-Lema\^itre-Robertson-Walker Universe with dust having the same average
density as our model. This points towards the absence of backreaction in a
Universe filled with an infinite number of objects, and this validates the
fluid approximation, as far as dynamics is concerned, and at the level of
approximation considered in this work.Comment: 14 pages. No figure. Accepted version for Classical and Quantum
Gravit
Investigating hookworm genomes by comparative analysis of two Ancylostoma species
Background
Hookworms, infecting over one billion people, are the mostly closely related major human parasites to the model nematode Caenorhabditis elegans. Applying genomics techniques to these species, we analyzed 3,840 and 3,149 genes from Ancylostoma caninum and A. ceylanicum.
Results
Transcripts originated from libraries representing infective L3 larva, stimulated L3, arrested L3, and adults. Most genes are represented in single stages including abundant transcripts like hsp-20 in infective L3 and vit-3 in adults. Over 80% of the genes have homologs in C. elegans, and nearly 30% of these were with observable RNA interference phenotypes. Homologies were identified to nematode-specific and clade V specific gene families. To study the evolution of hookworm genes, 574 A. caninum / A. ceylanicum orthologs were identified, all of which were found to be under purifying selection with distribution ratios of nonsynonymous to synonymous amino acid substitutions similar to that reported for C. elegans / C. briggsae orthologs. The phylogenetic distance between A. caninum and A. ceylanicum is almost identical to that for C. elegans / C. briggsae.
Conclusion
The genes discovered should substantially accelerate research toward better understanding of the parasites' basic biology as well as new therapies including vaccines and novel anthelmintics
Generic Bell correlation between arbitrary local algebras in quantum field theory
We prove that for any two commuting von Neumann algebras of infinite type,
the open set of Bell correlated states for the two algebras is norm dense. We
then apply this result to algebraic quantum field theory -- where all local
algebras are of infinite type -- in order to show that for any two spacelike
separated regions, there is an open dense set of field states that dictate Bell
correlations between the regions. We also show that any vector state cyclic for
one of a pair of commuting nonabelian von Neumann algebras is entangled (i.e.,
nonseparable) across the algebras -- from which it follows that every field
state with bounded energy is entangled across any two spacelike separated
regions.Comment: Third version; correction in the proof of Proposition
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