2,852 research outputs found
Feedback-induced nonlinearity and superconducting on-chip quantum optics
Quantum coherent feedback has been proven to be an efficient way to tune the
dynamics of quantum optical systems and, recently, those of solid-state quantum
circuits. Here, inspired by the recent progress of quantum feedback
experiments, especially those in mesoscopic circuits, we prove that
superconducting circuit QED systems, shunted with a coherent feedback loop, can
change the dynamics of a superconducting transmission line resonator, i.e., a
linear quantum cavity, and lead to strong on-chip nonlinear optical phenomena.
We find that bistability can occur under the semiclassical approximation, and
photon anti-bunching can be shown in the quantum regime. Our study presents new
perspectives for engineering nonlinear quantum dynamics on a chip.Comment: 10 pages, 9 figure
Absorbable versus silk sutures for surgical treatment of trachomatous trichiasis in Ethiopia: a randomised controlled trial.
BACKGROUND: Trachoma causes blindness through an anatomical abnormality called trichiasis (lashes touching the eye). Trichiasis can recur after corrective surgery. We tested the hypothesis that using absorbable sutures instead of silk sutures might reduce the risk of recurrent disease among patients with major trichiasis in a randomised trial. METHODS AND FINDINGS: 1,300 individuals with major trichiasis from rural villages in the Amhara Region of Ethiopia were recruited and assigned (1:1) by computer-generated randomisation sequence to receive trichiasis surgery using either an absorbable suture (polyglactin-910) or silk sutures (removed at 7-10 days) in an otherwise identical surgical technique. Participants were examined every 6 months for 2 years by clinicians masked to allocation. The primary outcome measure was recurrent trichiasis (≥one lash touching the eye) at 1 year. There was no difference in prevalence of recurrent trichiasis at 1 year (114 [18.2%] in the absorbable suture group versus 120 [19.7%] in the silk suture group; odds ratio = 0.90, 95% CI 0.68-1.20). The two groups also did not differ in terms of corneal opacification, visual acuity, conjunctival inflammation, and surgical complications. CONCLUSIONS: There was no evidence that use of absorbable polyglactin-910 sutures was associated with a lower prevalence of trichiasis recurrence at 1 year postsurgery than silk sutures. However, from a programmatic perspective, polyglactin-910 offers the major advantage that patients do not have to be seen soon after surgery for suture removal. The postoperative review after surgery using absorbable polyglactin-910 sutures can be delayed for 3-6 months, which might allow us to better determine whether a patient needs additional surgery. TRIAL REGISTRATION: ClinicalTrials.gov NCT00522860
Classical and Quantum Equations of Motion for a BTZ Black String in AdS Space
We investigate gravitational collapse of a -dimensional BTZ black
string in AdS space in the context of both classical and quantum mechanics.
This is done by first deriving the conserved mass per unit length of the
cylindrically symmetric domain wall, which is taken as the classical
Hamiltonian of the black string. In the quantum mechanical context, we take
primary interest in the behavior of the collapse near the horizon and near the
origin (classical singularity) from the point of view of an infalling observer.
In the absence of radiation, quantum effects near the horizon do not change the
classical conclusions for an infalling observer, meaning that the horizon is
not an obstacle for him/her. The most interesting quantum mechanical effect
comes in when investigating near the origin. First, quantum effects are able to
remove the classical singularity at the origin, since the wave function is
non-singular at the origin. Second, the Schr\"odinger equation describing the
behavior near the origin displays non-local effects, which depend on the energy
density of the domain wall. This is manifest in that derivatives of the
wavefunction at one point are related to the value of the wavefunction at some
other distant point.Comment: 9 pages, 1 figure. Minor Clarification and corrections. Accepted for
Publication in JHE
Spawning rings of exceptional points out of Dirac cones
The Dirac cone underlies many unique electronic properties of graphene and
topological insulators, and its band structure--two conical bands touching at a
single point--has also been realized for photons in waveguide arrays, atoms in
optical lattices, and through accidental degeneracy. Deformations of the Dirac
cone often reveal intriguing properties; an example is the quantum Hall effect,
where a constant magnetic field breaks the Dirac cone into isolated Landau
levels. A seemingly unrelated phenomenon is the exceptional point, also known
as the parity-time symmetry breaking point, where two resonances coincide in
both their positions and widths. Exceptional points lead to counter-intuitive
phenomena such as loss-induced transparency, unidirectional transmission or
reflection, and lasers with reversed pump dependence or single-mode operation.
These two fields of research are in fact connected: here we discover the
ability of a Dirac cone to evolve into a ring of exceptional points, which we
call an "exceptional ring." We experimentally demonstrate this concept in a
photonic crystal slab. Angle-resolved reflection measurements of the photonic
crystal slab reveal that the peaks of reflectivity follow the conical band
structure of a Dirac cone from accidental degeneracy, whereas the complex
eigenvalues of the system are deformed into a two-dimensional flat band
enclosed by an exceptional ring. This deformation arises from the dissimilar
radiation rates of dipole and quadrupole resonances, which play a role
analogous to the loss and gain in parity-time symmetric systems. Our results
indicate that the radiation that exists in any open system can fundamentally
alter its physical properties in ways previously expected only in the presence
of material loss and gain
Quality of life after curative gastrectomy for gastric cancer in a randomised controlled trial
Quality of life (QOL) was studied in gastric cancer patients treated on a randomised, controlled trial comparing D1 (level 1) with D3 (levels 1, 2 and 3) lymphadenectomy. A total of 221 patients were randomly assigned to D1 (n=110) and D3 (n=111) surgery. Quality-of-life assessments included functional outcomes (a 14-item survey about treatment-specific symptoms) and health perception (Spitzer QOL Index) was performed before and after surgery at disease-free status. Patients suffered from irrelative events such as loss of partners was excluded thereafter. Main analyses were done by intention-to-treat. Thus, 214 D1 (106/110=96.4%) and D3 (108/111=97.3%) R0 patients were assessed. Longitudinal analysis showed that functional outcomes decreased at 6 months after surgery and increased over time thereafter, while health perceptions increased over time in general. On the basis of linear mixed model analyses, patients having total gastrectomy, advanced cancer and hemipancreaticosplenectomy, but not complications had poorer QOL than those without. D1 and D3 patients showed no significant difference in QOL. The results suggest that changes of QOL were largely due to scope of gastric resection, disease status and distal pancreaticosplenectomy, rather than the extent of lymph node dissection. This indicates that nodal dissection can be performed for a potentially curable gastric cancer
Avalanches in self-organized critical neural networks: A minimal model for the neural SOC universality class
The brain keeps its overall dynamics in a corridor of intermediate activity
and it has been a long standing question what possible mechanism could achieve
this task. Mechanisms from the field of statistical physics have long been
suggesting that this homeostasis of brain activity could occur even without a
central regulator, via self-organization on the level of neurons and their
interactions, alone. Such physical mechanisms from the class of self-organized
criticality exhibit characteristic dynamical signatures, similar to seismic
activity related to earthquakes. Measurements of cortex rest activity showed
first signs of dynamical signatures potentially pointing to self-organized
critical dynamics in the brain. Indeed, recent more accurate measurements
allowed for a detailed comparison with scaling theory of non-equilibrium
critical phenomena, proving the existence of criticality in cortex dynamics. We
here compare this new evaluation of cortex activity data to the predictions of
the earliest physics spin model of self-organized critical neural networks. We
find that the model matches with the recent experimental data and its
interpretation in terms of dynamical signatures for criticality in the brain.
The combination of signatures for criticality, power law distributions of
avalanche sizes and durations, as well as a specific scaling relationship
between anomalous exponents, defines a universality class characteristic of the
particular critical phenomenon observed in the neural experiments. The spin
model is a candidate for a minimal model of a self-organized critical adaptive
network for the universality class of neural criticality. As a prototype model,
it provides the background for models that include more biological details, yet
share the same universality class characteristic of the homeostasis of activity
in the brain.Comment: 17 pages, 5 figure
Association between the c.*229C>T polymorphism of the topoisomerase IIb binding protein 1 (TopBP1) gene and breast cancer
Topoisomerase IIb binding protein 1 (TopBP1)
is involved in cell survival, DNA replication, DNA damage
repair and cell cycle checkpoint control. The biological
function of TopBP1 and its close relation with BRCA1
prompted us to investigate whether alterations in the
TopBP1 gene can influence the risk of breast cancer.
The aim of this study was to examine the association
between five polymorphisms (rs185903567, rs116645643,
rs115160714, rs116195487, and rs112843513) located in
the 30UTR region of the TopBP1 gene and breast cancer
risk as well as allele-specific gene expression. Five hundred
thirty-four breast cancer patients and 556 population controls
were genotyped for these SNPs. Allele-specific Top-
BP1 mRNA and protein expressions were determined by
using real time PCR and western blotting methods,
respectively. Only one SNP (rs115160714) showed an
association with breast cancer. Compared to homozygous
common allele carriers, heterozygous and homozygous for
the T variant had significantly increased risk of breast
cancer (adjusted odds ratio = 3.81, 95 % confidence
interval: 1.63–8.34, p = 0.001). Mean TopBP1 mRNA and
protein expression were higher in the individuals with the
CT or TT genotype. There was a significant association
between the rs115160714 and tumor grade and stage. Most
carriers of minor allele had a high grade (G3) tumors
classified as T2-T4N1M0. Our study raises a possibility
that a genetic variation of TopBP1 may be implicated in
the etiology of breast cancer
Epilation for minor trachomatous trichiasis: four-year results of a randomised controlled trial.
BACKGROUND: Trachomatous trichiasis (TT) needs to be managed to reduce the risk of vision loss. The long-term impact of epilation (a common traditional practice of repeated plucking of lashes touching the eye) in preventing visual impairment and corneal opacity from TT is unknown. We conducted a randomized controlled trial of epilation versus surgery for the management of minor TT (fewer than six lashes touching the eye) in Ethiopia. Here we report the four-year outcome and the effect on vision and corneal opacity. METHODOLOGY/ PRINCIPAL FINDINGS: 1300 individuals with minor TT were recruited and randomly assigned to quality trichiasis surgery or repeated epilation using high quality epilation forceps by a trained person with good near vision. Participants were examined six-monthly for two-years, and then at four-years after randomisation. At two-years all epilation arm participants were offered free surgery. At four-years 1151 (88.5%) were re-examined: 572 (88%) and 579 (89%) from epilation and surgery arms, respectively. At that time, 21.1% of the surgery arm participants had recurrent TT; 189/572 (33%) of the epilation arm had received surgery, while 383 (67%) declined surgery and had continued epilating ("epilation-only"). Among the epilation-only group, 207 (54.1%) fully controlled their TT, 166 (43.3%) had minor TT and 10 (2.6%) had major TT (>5 lashes). There were no differences between participants in the epilation-only, epilation-to-surgery and surgery arm participants in changes in visual acuity and corneal opacity between baseline and four-years. CONCLUSIONS/ SIGNIFICANCE: Most minor TT participants randomised to the epilation arm continued epilating and controlled their TT. Change in vision and corneal opacity was comparable between surgery and epilation-only participants. This suggests that good quality epilation with regular follow-up is a reasonable second-line alternative to surgery for minor TT for individuals who either decline surgery or do not have immediate access to surgical treatment
The Effect of a DNA Damaging Agent on Embryonic Cell Cycles of the Cnidarian Hydractinia echinata
The onset of gastrulation at the Mid-Blastula Transition can accompany profound changes in embryonic cell cycles including the introduction of gap phases and the transition from maternal to zygotic control. Studies in Xenopus and Drosophila embryos have also found that cell cycles respond to DNA damage differently before and after MBT (or its equivalent, MZT, in Drosophila). DNA checkpoints are absent in Xenopus cleavage cycles but are acquired during MBT. Drosophila cleavage nuclei enter an abortive mitosis in the presence of DNA damage whereas post-MZT cells delay the entry into mitosis. Despite attributes that render them workhorses of embryonic cell cycle studies, Xenopus and Drosophila are hardly representative of diverse animal forms that exist. To investigate developmental changes in DNA damage responses in a distant phylum, I studied the effect of an alkylating agent, Methyl Methanesulfonate (MMS), on embryos of Hydractinia echinata. Hydractinia embryos are found to differ from Xenopus embryos in the ability to respond to a DNA damaging agent in early cleavage but are similar to Xenopus and Drosophila embryos in acquiring stronger DNA damage responses and greater resistance to killing by MMS after the onset of gastrulation. This represents the first study of DNA damage responses in the phylum Cnidaria
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