2,825 research outputs found
Estimates on the isospin-violating decays and the mixing
We analyse the two purely isospin-violating decays and , proceed merely via
the exchange topologies, in the framework of perturbative QCD approach.
Assuming baryon belongs to the idealized isospin triplet with quark
components of , the branching ratios of the two decay modes are predicted
to be tiny, of the order , leading to a difficulty in
observing them. We then extend our study to include the
mixing.It is found that the mixing has significant effect on the
decays, especially it can greatly increase the
rate of the process, by as much as two orders of magnitude, yield
, which should be searchable in the future. We also estimate a set of
asymmetry observables with and without the mixing effect, which will be tested
in coming experiments.Comment: 23 pages, 1 figure, 10 tables; to appear in PR
Mixing effects of in decays
We perform a thorough analysis of the mixing effects on the
decays based on the perturbative QCD
(PQCD) factorization approach. Branching ratios, up-down and direct
asymmetries are computed by considering four popular mixing schemes, such as
, , , and
mixing formalism, where represents the physical pseudoscalar gluball. The
PQCD predictions with the four mixing schemes does not change much for the
channel but changes significantly for the one. In particular,
the value of in the
mixing scheme exceeds the present experimental bound by a
factor of 2, indicates the related mixing angles may be overestimated. Because
of the distinctive patterns of interference between -wave and -wave
amplitudes, the predicted up-down asymmetries for the two modes differ
significantly. The obvious discrepancies among different theoretical analyses
should be clarified in the future. The direct violations are predicted to
be at the level of a few percent mainly due to the tree contributions of the
strange and nonstrange amplitudes suffer from the color suppression and CKM
suppression. Finally, as a byproduct, we investigate the process, which has a large branching ratio of order ,
promising to be measured by the LHCb experiment. Our findings are useful for
constraining the mixing parameters, comprehending the
configurations, and instructing experimental measurements.Comment: 19 pages,1 figure,7 tables, updated to match published versio
Estimates of exchange topological contributions and -violating observables in decay
The penguin-dominated two-body weak decay of is studied based on the perturbative QCD approach. In addition to the
penguin emission diagrams, the penguin exchange and exchange ones are also
accounted for. It is found that the penguin exchange contribution is in fact
important and comparable to the penguin emission one, while the exchange
contribution is highly Cabibbo-Kobayashi-Maskawa (CKM) suppressed. The
predicted branching ratio, , is larger than the previous
theoretical estimates but in comparison with the data from Particle Data Group
at the level of 1 standard deviation. We also explore some pertinent decay
asymmetry parameters that characterize the angular decay distributions. The
inclusion of the exchange contribution provides the nonzero weak phase
difference, consequently, allowing us to estimate the direct violation and
true triple product asymmetries in the concerned process. The numerical results
demonstrate that the direct violation is at the level of a few percent,
and the true triple product asymmetries are also predicted to be tiny, of order
. The observed small -violating observables have shown no
significant deviations from zero. Our predictions will be subject to stringent
tests with precise data from LHCb in the future.Comment: 22 pages, 4 figures, 12 table
Successful radiofrequency ablation of a right posteroseptal accessory pathway through an anomalous inferior vena cava and azygos continuation in a patient with incomplete situs inversus
We present a 43-year-old patient with paroxysmal supraventricular tachycardia. In the process
of catheter ablation, we found interruption of the inferior vena cava with azygos continuation
with incomplete situs inversus. In this patient, we adopted the lower approach via the anomalous
inferior vena cava and azygos continuation to achieve stability of radiofrequency catheter
for right posteroseptal accessory pathway, and successfully abolished the preexcitation
Significance of the lipid profile and endothelium-dependent vasodilatation in the pathogenesis of microvascular angina
Background: To investigate the significance of lipid disorders and endothelial dysfunction in
the pathogenesis of microvascular angina.
Methods: Levels of plasma lipids, lipoproteins and apolipoproteins were assessed in 21 patients
with microvascular angina and 24 healthy subjects as controls. Also, the endothelium-dependent
vasodilatation function was determined with high-resolution ultrasound in both groups.
Results: Levels of serum total cholesterol (TC), low density lipoprotein-cholesterol (LDL-C),
apolipoprotein B100 (ApoB100) and lipoprotein(a) [Lp(a)] in microvascular angina group
were significantly higher than those in healthy subjects (each p < 0.05). The flow-mediated
dilatation (FMD) in brachial arteries in patients with microvascular angina declined significantly
as compared with that in control subjects (4.7 ± 1.9% vs. 12.8 ± 3.7%, p < 0.001).
However, no significant difference was observed in response to nitroglycerin between groups
(19.7 ± 8.1% vs. 21.2 ± 6.6%; p > 0.05). Linear correlation analysis revealed a significant
negative correlation between the FMD of brachial arteries and the serum levels of LDL-C and
Lp(a) in the microvascular angina group (r = -0.5125 and -0.4271, respectively, both p < 0.001). Subsequently, all subjects were pooled and divided into two groups (groups A and B)
according to the degree of FMD in brachial arteries (A £ 4% and B > 4%). The serum LDL-C
level was found to be significantly higher in group A than in group B (4.09 ± 0.65 mmol/L vs.
2.59 ± 0.49 mmol/L; p < 0.05).
Conclusions: Plasma lipid disorders and vascular endothelial dysfunction may play important
roles in the development of microvascular angina. The dysfunction of endothelium-dependent vasodilation was mainly associated with anomalies in LDL-C and Lp(a), and
myocardial endothelial dysfunction was aggravated by lipid abnormalities in patients with
microvascular angina
Dynamic Anchor Learning for Arbitrary-Oriented Object Detection
Arbitrary-oriented objects widely appear in natural scenes, aerial
photographs, remote sensing images, etc., thus arbitrary-oriented object
detection has received considerable attention. Many current rotation detectors
use plenty of anchors with different orientations to achieve spatial alignment
with ground truth boxes, then Intersection-over-Union (IoU) is applied to
sample the positive and negative candidates for training. However, we observe
that the selected positive anchors cannot always ensure accurate detections
after regression, while some negative samples can achieve accurate
localization. It indicates that the quality assessment of anchors through IoU
is not appropriate, and this further lead to inconsistency between
classification confidence and localization accuracy. In this paper, we propose
a dynamic anchor learning (DAL) method, which utilizes the newly defined
matching degree to comprehensively evaluate the localization potential of the
anchors and carry out a more efficient label assignment process. In this way,
the detector can dynamically select high-quality anchors to achieve accurate
object detection, and the divergence between classification and regression will
be alleviated. With the newly introduced DAL, we achieve superior detection
performance for arbitrary-oriented objects with only a few horizontal preset
anchors. Experimental results on three remote sensing datasets HRSC2016, DOTA,
UCAS-AOD as well as a scene text dataset ICDAR 2015 show that our method
achieves substantial improvement compared with the baseline model. Besides, our
approach is also universal for object detection using horizontal bound box. The
code and models are available at https://github.com/ming71/DAL.Comment: Accepted to AAAI 2021. The code and models are available at
https://github.com/ming71/DA
B-vitamin consumption and the prevalence of diabetes and obesity among the US adults: population based ecological study
<p>Abstract</p> <p>Background</p> <p>The global increased prevalence of obesity and diabetes occurred after the worldwide spread of B-vitamins fortification, in which whether long-term exposure to high level of B vitamins plays a role is unknown. Our aim was to examine the relationships between B-vitamins consumption and the obesity and diabetes prevalence.</p> <p>Methods</p> <p>This population based ecological study was conducted to examine possible associations between the consumption of the B vitamins and macronutrients and the obesity and diabetes prevalence in the US population using the per capita consumption data from the US Economic Research Service and the prevalence data from the US Centers for Disease Control and Prevention.</p> <p>Results</p> <p>The prevalences of diabetes and adult obesity were highly correlated with per capita consumption of niacin, thiamin and riboflavin with a 26-and 10-year lag, respectively (<it>R</it><sup>2 </sup>= 0.952, 0.917 and 0.83 for diabetes, respectively, and <it>R</it><sup>2 </sup>= 0.964, 0.975 and 0.935 for obesity, respectively). The diabetes prevalence increased with the obesity prevalence with a 16-year lag (<it>R</it><sup>2 </sup>= 0.975). The relationships between the diabetes or obesity prevalence and per capita niacin consumption were similar both in different age groups and in male and female populations. The prevalence of adult obesity and diabetes was highly correlated with the grain contribution to niacin (<it>R</it><sup>2 </sup>= 0.925 and 0.901, respectively), with a 10-and 26-year lag, respectively. The prevalence of obesity in US adults during 1971-2004 increased in parallel with the increase in carbohydrate consumption with a 10-year lag. The per capita energy and protein consumptions positively correlated with the obesity prevalence with a one-year lag. Moreover, there was an 11-year lag relationship between per capita energy and protein consumption and the consumption of niacin, thiamin and riboflavin (<it>R</it><sup>2 </sup>= 0.932, 0.923 and 0.849 for energy, respectively, and <it>R</it><sup>2 </sup>= 0.922, 0.878 and 0.787 for protein, respectively).</p> <p>Conclusions</p> <p>Long-term exposure to high level of the B vitamins may be involved in the increased prevalence of obesity and diabetes in the US in the past 50 years. The possible roles of B-vitamins fortification and excess niacin consumption in the increased prevalence of obesity and diabetes were discussed.</p
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