4,199 research outputs found
Quantization of Yang-Mills Theories without the Gribov Ambiguity
A gauge condition is presented here to quantize non-Abelian gauge theory on
the manifold , which is free from the
Gribov ambiguity. Perturbative calculations in the new gauge behave like the
axial gauge in ultraviolet region, while infrared behaviours of the
perturbative series are quite nontrivial. The new gauge condition, which reads
, may not satisfy the requirement that
in conventional perturbative calculations. However, such
contradiction is not harmful for gauge theories constructed on the manifold
.Comment: 11page
Primordial Non-Gaussianity from LAMOST Surveys
The primordial non-Gaussianity (PNG) in matter density perturbation is a very
powerful probe of the physics of the very early Universe. The local PNG can
induce a distinct scale-dependent bias on the large scale structure
distribution of galaxies and quasars, which could be used for constraining it.
We study the detection limits on PNG from the surveys of the LAMOST telescope.
The cases of the main galaxy survey, the luminous red galaxy (LRG) survey, and
the quasar survey of different magnitude limits are considered. We find that
the MAIN1 sample (i.e. the main galaxy survey with one magnitude deeper than
the SDSS main galaxy survey, or r<18.8) could only provide very weak constraint
on PNG. For the MAIN2 sample (r<19.8) and the LRG survey, the 2\sigma (95.5%)
limit on the PNG parameter f_{NL} are |f_{NL}|<145 and |f_{NL}|<114
respectively, comparable to the current limit from cosmic microwave background
(CMB) data. The quasar survey could provide much more stringent constraint, and
we find that the 2\sigma limit for |f_{NL}| is between 50 and 103, depending on
the magnitude limit of the survey. With Planck-like priors on cosmological
parameters, the quasar survey with g<21.65 would improve the constraints to
|f_{NL}|<43 (2\sigma). We also discuss the possibility of further tightening
the constraint by using the relative bias method proposed by Seljak(2008).Comment: 8 pages, 2 figures, RAA accepte
Quantum imaginary time evolution and quantum annealing meet topological sector optimization
Optimization problems are the core challenge in many fields of science and
engineering, yet general and effective methods are scarce for searching optimal
solutions. Quantum computing has been envisioned to help solve such problems,
for example, the quantum annealing (QA) method based on adiabatic evolution has
been extensively explored and successfully implemented on quantum simulators
such as D-wave's annealers and some Rydberg arrays. In this work, we
investigate topological sector optimization (TSO) problem, which attracts
particular interests in the quantum many-body physics community. We reveal that
the topology induced by frustration in the spin model is an intrinsic
obstruction for QA and other traditional methods to approach the ground state.
We demonstrate that the optimization difficulties of TSO problem are not
restricted to the gaplessness, but are also due to the topological nature which
are often ignored for the analysis of optimization problems before. To solve
TSO problems, we utilize quantum imaginary time evolution (QITE) with a
possible realization on quantum computers, which exploits the property of
quantum superposition to explore the full Hilbert space and can thus address
optimization problems of topological nature. We report the performance of
different quantum optimization algorithms on TSO problems and demonstrate that
their capability to address optimization problems are distinct even when
considering the quantum computational resources required for practical QITE
implementations
Measuring the boundary gapless state and criticality via disorder operator
The disorder operator is often designed to reveal the conformal field theory
(CFT) information in the quantum many-body system. By using large-scale quantum
Monte Carlo simulation, we study the scaling behavior of disorder operator on
the boundary in the two-dimensional Heisenberg model on the square-octagon
lattice with gapless topological edge state. In the Affleck-Kennedy-Lieb-Tasaki
(AKLT) phase, the disorder operator is shown to hold the perimeter scaling with
a logarithmic term associated with the Luttinger Liquid parameter K. This
effective Luttinger Liquid parameter K reflects the low energy physics and CFT
for (1+1)d boundary. At bulk critical point, the effective K is suppressed but
keep finite value, indicating the coupling between the gapless edge state and
bulk fluctuation. The logarithmic term numerically capture this coupling
picture, which reveals the (1+1)d SU(2)_1 CFT and (2+1)d O(3) CFT at boundary
criticality. Our work paves a new way to study the exotic boundary state and
boundary criticality.Comment: 8 Pages,7 figure
Matrine enhances the inhibitory effect of 5-FU on SW480 cells in vitro and in vivo
We investigated the antitumor effects of the combination of matrine-a purified alkaloid extracted from Sophora flavescence-and 5-fluorouracil (5-FU) on SW480 cells. This combination inhibited the growth of SW480 cells in a synergistic or additive manner by disrupting their progression through the cell cycle. Exposure of SW480 cells to matrine and 5-FU was followed by an increased rate of expression for caspase-3, caspase-9 and poly-ADP ribose polymerase (PARP) and inhibited the subcutaneous transplantation of SW480 tumors into Balb/c nude mice. Histopathological analysis showed that this effect was most pronounced in the spleens of treated animals. Typical cytotoxic effects observed in 5-FU-treated mice included fibrosis and lymphopenia, whereas in mice treated with 5-FU combined with matrine, the spleen ultrastructure remained intact. These findings indicate that matrine may enhance the therapeutic effectiveness of 5-FU in SW480 tumors by enhancing apoptosis and overcome the threat to immunocompetence associated with 5-FU
The value of left atrial strain and strain rate in predicting left atrial appendage stasis in patients with nonvalvular atrial fibrillation
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Background: This study aimed to investigate the value of left atrial (LA) strain and strain rate (S/SR) by transthoracic echocardiography (TTE) in predicting left atrial appendage (LAA) stasis, in order to find a way for LAA stasis screening which is easily performed in patients with nonvalvular atrial fibrillation (NVAF).
Methods: One hundred and thirty NVAF patients prepared for AF ablation were enrolled. TTE and transesophageal echocardiography (TEE) were performed in all patients. LA S/SR in each phase was analyzed off-line. LAA blood flow state and LAA function were assessed by using TEE.
Results: LA S/SRs during atrial reservoir phase (LA Sres/SRres) were significantly negatively corÂrelated with LAA spontaneous echo contrast (SEC) grade (r = −0.567 and −0.520, respectively; all p < 0.01), and positively correlated with LAA emptying fraction (r = 0.602 and 0.619, respectively; all p < 0.01) and with LAA peak emptying flow velocity (r = 0.623 and 0.642, respectively; all p < 0.01). The multivariate logistic regression analysis showed LA Sres to be the strongest independent predictor of LAA stasis, followed by LA volume index. LA Sres < 13% was recommended to predict LAA stasis with sensitivity of 90% and specificity of 74%.
Conclusions: LA Sres by TTE can noninvasively predict LAA stasis and may be used as a screening tool to assist in the detection of LAA stasis in patients with NVAF. (Cardiol J 2018; 25, 1: 87–96
Use of low-dose computed tomography to assess pulmonary tuberculosis among healthcare workers in a tuberculosis hospital
BACKGROUND: According to the World Health Organization, China is one of 22 countries with serious tuberculosis (TB) infections and one of the 27 countries with serious multidrug-resistant TB strains. Despite the decline of tuberculosis in the overall population, healthcare workers (HCWs) are still at a high risk of infection. Compared with high-income countries, the TB prevalence among HCWs is higher in low- and middle-income countries. Low-dose computed tomography (LDCT) is becoming more popular due to its superior sensitivity and lower radiation dose. However, there have been no reports about active pulmonary tuberculosis (PTB) among HCWs as assessed with LDCT. The purposes of this study were to examine PTB statuses in HCWs in hospitals specializing in TB treatment and explore the significance of the application of LDCT to these workers. METHODS: This study retrospectively analysed the physical examination data of healthcare workers in the Beijing Chest Hospital from September 2012 to December 2015. Low-dose lung CT examinations were performed in all cases. The comparisons between active and inactive PTB according to the CT findings were made using the Pearson chi-square test or the Fisher’s exact test. Comparisons between the incidences of active PTB in high-risk areas and non-high-risk areas were performed using the Pearson chi-square test. Analyses of active PTB were performed according to different ages, numbers of years on the job, and the risks of the working areas. Active PTB as diagnosed by the LDCT examinations alone was compared with the final comprehensive diagnoses, and the sensitivity and positive predictive value were calculated. RESULTS: A total of 1 012 participants were included in this study. During the 4-year period of medical examinations, active PTB was found in 19 cases, and inactive PTB was found in 109 cases. The prevalence of active PTB in the participants was 1.24%, 0.67%, 0.81%, and 0.53% for years 2012 to 2015. The corresponding incidences of active PTB among the tuberculosis hospital participants were 0.86%, 0.41%, 0.54%, and 0.26%. Most HCWs with active TB (78.9%, 15/19) worked in the high-risk areas of the hospital. There was a significant difference in the incidences of active PTB between the HCWs who worked in the high-risk and non-high-risk areas (odds ratio [OR], 14.415; 95% confidence interval (CI): 4.733 – 43.896). Comparisons of the CT signs between the active and inactive groups via chi-square tests revealed that the tree-in-bud, cavity, fibrous shadow, and calcification signs exhibited significant differences (P = 0.000, 0.021, 0.001, and 0.024, respectively). Tree-in-bud and cavity opacities suggest active pulmonary tuberculosis, whereas fibrous shadow and calcification opacities are the main features of inactive pulmonary tuberculosis. Comparison with the final comprehensive diagnoses revealed that the sensitivity and positive predictive value of the diagnoses of active PTB based on LDCT alone were 100% and 86.4%, respectively. CONCLUSIONS: Healthcare workers in tuberculosis hospitals are a high-risk group for active PTB. Yearly LDCT examinations of such high-risk groups are feasible and necessary. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40249-017-0274-6) contains supplementary material, which is available to authorized users
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