2,380 research outputs found
Continuous area spectrum in regular black hole
We investigate highly damped quasinormal modes of regular black hole coupled
to nonlinear electrodynamics. Using the WKB approximation combined with
complex-integration technique, we show that the real part of the frequency
disappears in the highly damped limit. If we use the Bohr's correspondence
principle, the area spectrum of this black hole is continuous. We discuss its
implication in the loop quantum gravity.Comment: 5 pages, 1 figure
Black String Perturbations in RS1 Model
We present a general formalism for black string perturbations in
Randall-Sundrum 1 model (RS1). First, we derive the master equation for the
electric part of the Weyl tensor . Solving the master equation
using the gradient expansion method, we give the effective Teukolsky equation
on the brane at low energy. It is useful to estimate gravitational waves
emitted by perturbed rotating black strings. We also argue the effect of the
Gregory-Laflamme instability on the brane using our formalism.Comment: 14 pages, Based on a talk presented at ACRGR4, the 4th Australasian
Conference on General Relativity and Gravitation, Monash University,
Melbourne, January 2004. To appear in the proceedings, in General Relativity
and Gravitatio
Phase-Remapping Attack in Practical Quantum Key Distribution Systems
Quantum key distribution (QKD) can be used to generate secret keys between
two distant parties. Even though QKD has been proven unconditionally secure
against eavesdroppers with unlimited computation power, practical
implementations of QKD may contain loopholes that may lead to the generated
secret keys being compromised. In this paper, we propose a phase-remapping
attack targeting two practical bidirectional QKD systems (the "plug & play"
system and the Sagnac system). We showed that if the users of the systems are
unaware of our attack, the final key shared between them can be compromised in
some situations. Specifically, we showed that, in the case of the
Bennett-Brassard 1984 (BB84) protocol with ideal single-photon sources, when
the quantum bit error rate (QBER) is between 14.6% and 20%, our attack renders
the final key insecure, whereas the same range of QBER values has been proved
secure if the two users are unaware of our attack; also, we demonstrated three
situations with realistic devices where positive key rates are obtained without
the consideration of Trojan horse attacks but in fact no key can be distilled.
We remark that our attack is feasible with only current technology. Therefore,
it is very important to be aware of our attack in order to ensure absolute
security. In finding our attack, we minimize the QBER over individual
measurements described by a general POVM, which has some similarity with the
standard quantum state discrimination problem.Comment: 13 pages, 8 figure
Renormalization and black hole entropy in Loop Quantum Gravity
Microscopic state counting for a black hole in Loop Quantum Gravity yields a
result proportional to horizon area, and inversely proportional to Newton's
constant and the Immirzi parameter. It is argued here that before this result
can be compared to the Bekenstein-Hawking entropy of a macroscopic black hole,
the scale dependence of both Newton's constant and the area must be accounted
for. The two entropies could then agree for any value of the Immirzi parameter,
if a certain renormalization property holds.Comment: 8 pages; v2: references added, typos corrected, version to appear in
CQ
Particle velocity in noncommutative space-time
We investigate a particle velocity in the -Minkowski space-time,
which is one of the realization of a noncommutative space-time. We emphasize
that arrival time analyses by high-energy -rays or neutrinos, which
have been considered as powerful tools to restrict the violation of Lorentz
invariance, are not effective to detect space-time noncommutativity. In
contrast with these examples, we point out a possibility that {\it low-energy
massive particles} play an important role to detect it.Comment: 16 pages, corrected some mistake
Improved Hepatic Function in the 24-Hour Preserved Rat Liver With UW-Lactobionate Solution and SRI 63-441
The present study compares rat liver preservation for 9, 12, and 24 h in the standard Eurocollins solution with preservation for the same time periods in the new UW-Iactobionate solution. Pharmacologic manipulation with a potent plateletactivating factor antagonist, SRI 63-441, was also evaluated. After cold storage in each of the test solutions, the livers underwent 90 min of warm, oxygenated, sanguinous perfusion. A significant increase in liver weight was noted in Eurocollinsstored versus UW-Iactobionate-stored livers. After 90 min of perfusion, livers preserved in UW-lactobionate produced significantly more bile and liberated significantly less glucose and transaminases when compared with Eurocollins-stored livers. Significant augmentation of bile production was observed when donor animals were pretreated with SRI 63-441 and the livers were then stored in UW-lactobionate for 24 h. Eurocollins-stored livers demonstrated increased hepatocyte vacuolization and endothelial disruption when compared with UW-lactobionate-stored livers after 12 and 24 h of preservation. This study demonstrates the superiority of UW-lactobionate solution in liver preservation and suggests that SRI 63-441 may be beneficial in the further reduction of cold ischemic injury. © 1988, American Gastroenterological Association. All rights reserved
Decoy state quantum key distribution with two-way classical post-processing
Decoy states have recently been proposed as a useful method for substantially
improving the performance of quantum key distribution protocols when a coherent
state source is used. Previously, data post-processing schemes based on one-way
classical communications were considered for use with decoy states. In this
paper, we develop two data post-processing schemes for the decoy-state method
using two-way classical communications. Our numerical simulation (using
parameters from a specific QKD experiment as an example) results show that our
scheme is able to extend the maximal secure distance from 142km (using only
one-way classical communications with decoy states) to 181km. The second scheme
is able to achieve a 10% greater key generation rate in the whole regime of
distances
Dyonic BIon black hole in string inspired model
We construct static and spherically symmetric particle-like and black hole
solutions with magnetic and/or electric charge in the
Einstein-Born-Infeld-dilaton-axion system, which is a generalization of the
Einstein-Maxwell-dilaton-axion (EMDA) system and of the Einstein-Born-Infeld
(EBI) system. They have remarkable properties which are not seen for the
corresponding solutions in the EMDA and the EBI system.Comment: 13 pages, 15 figures, Final version in PR
Validation of oral fluid samples to monitor serological changes to Plasmodium falciparum: An observational study in southern Zambia
<p>Abstract</p> <p>Background</p> <p>In formerly endemic areas where malaria transmission has declined, levels of population immunity to <it>Plasmodium falciparum </it>provide information on continued malaria transmission and potentially susceptible populations. Traditional techniques for measuring serological responses to <it>P. falciparum </it>antigens use plasma or dried blood spots (DBS). These invasive procedures pose a biohazard and may be unacceptable to communities if performed frequently. The use of oral fluid (OF) samples to detect antibodies to <it>P. falciparum </it>antigens may be a more acceptable strategy to monitor changes in population immunity.</p> <p>Methods</p> <p>An enzyme immunoassay was optimized to detect antibodies to whole, asexual stage <it>P. falciparum </it>antigens. Optical density (OD) values from paired DBS and OF samples collected as part of a community-based survey of malaria parasitaemia were compared.</p> <p>Results</p> <p>Oral fluid and dried blood spot samples were collected from 53 participants in Southern Province, Zambia. Their ages ranged from 1 to 80 years and 45% were female. A statistically significant correlation (r = 0.79; P < 0.01) was observed between OD values from OF and DBS samples. The OF assay identified all DBS-confirmed positive and negative samples, resulting in 100% sensitivity and specificity.</p> <p>Conclusions</p> <p>Oral fluid is a valid alternative specimen for monitoring changes in antibodies to <it>P. falciparum </it>antigens. As OF collection is often more acceptable to communities, poses less of a biohazard than blood samples and can be performed by community volunteers, serological surveys using OF samples provide a strategy for monitoring population immunity in regions of declining malaria transmission.</p
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