1,254 research outputs found
Non-Gaussian features from the inverse volume corrections in loop quantum cosmology
In this paper we study the non-Gaussian features of the primordial
fluctuations in loop quantum cosmology with the inverse volume corrections. The
detailed analysis is performed in the single field slow-roll inflationary
models. However, our results reflect the universal characteristics of
bispectrum in loop quantum cosmology. The main corrections to the scalar
bispectrum come from two aspects: one is the modifications to the standard
Bunch-Davies vacuum, the other is the corrections to the background dependent
variables, such as slow-roll parameters. Our calculations show that the loop
quantum corrections make of the inflationary models increase
0.1%. Moreover, we find that two new shapes arise, namely and
. The former gives a unique loop quantum feature which is less
correlated with the local, equilateral and single types, while the latter is
highly correlated with the local one.Comment: matched to the published version. 30 pages, 4 figure
Landau-Zener Tunnelling in a Nonlinear Three-level System
We present a comprehensive analysis of the Landau-Zener tunnelling of a
nonlinear three-level system in a linearly sweeping external field. We find the
presence of nonzero tunnelling probability in the adiabatic limit (i.e., very
slowly sweeping field) even for the situation that the nonlinear term is very
small and the energy levels keep the same topological structure as that of
linear case. In particular, the tunnelling is irregular with showing an
unresolved sensitivity on the sweeping rate. For the case of fast-sweeping
fields, we derive an analytic expression for the tunnelling probability with
stationary phase approximation and show that the nonlinearity can dramatically
influence the tunnelling probability when the nonlinear "internal field"
resonate with the external field. We also discuss the asymmetry of the
tunnelling probability induced by the nonlinearity. Physics behind the above
phenomena is revealed and possible application of our model to triple-well
trapped Bose-Einstein condensate is discussed.Comment: 8 pages, 8 figure
Explainable machine learning-based prediction model for diabetic nephropathy
The aim of this study is to analyze the effect of serum metabolites on
diabetic nephropathy (DN) and predict the prevalence of DN through a machine
learning approach. The dataset consists of 548 patients from April 2018 to
April 2019 in Second Affiliated Hospital of Dalian Medical University (SAHDMU).
We select the optimal 38 features through a Least absolute shrinkage and
selection operator (LASSO) regression model and a 10-fold cross-validation. We
compare four machine learning algorithms, including eXtreme Gradient Boosting
(XGB), random forest, decision tree and logistic regression, by AUC-ROC curves,
decision curves, calibration curves. We quantify feature importance and
interaction effects in the optimal predictive model by Shapley Additive
exPlanations (SHAP) method. The XGB model has the best performance to screen
for DN with the highest AUC value of 0.966. The XGB model also gains more
clinical net benefits than others and the fitting degree is better. In
addition, there are significant interactions between serum metabolites and
duration of diabetes. We develop a predictive model by XGB algorithm to screen
for DN. C2, C5DC, Tyr, Ser, Met, C24, C4DC, and Cys have great contribution in
the model, and can possibly be biomarkers for DN
Wigner solution of the quark gap equation
Solutions and their evolutions of the quark gap equation are studied within
the Nambu-Jona--Lasinio model, which is a basic issue for studying the QCD
phase structure and locating the possible critical end point. It is shown that
in the chiral limit case of the vacuum, chiral symmetry will hold if the
coupling strength is small, then the system only has the Wigner solution at
. If increasing , two symmetric minima will appear as the positive and
`negative' Nambu solutions, however, the solution now corresponds to a
maximum instead of a minimum of the thermodynamical potential, so is not a
physically stable state anymore (we call it `pseudo-Wigner solution'). Besides,
it is shown that as the current quark mass increases, the pseudo-Wigner
solution will become negative, and disappear together with the negative Nambu
solution if is large enough. Similar things happen if we increase the
temperature or quark chemical potential . Some interesting phenomenon is,
from some a second local minimum will show up. As increases
gradually, it will be stabler than the Nambu solution, survives even the Nambu
solution disappears, and approaches , which are just the features of the
Wigner solution we expect.Comment: version accepted for publication in the European Physical Journal
FXR1P but not FMRP regulates the levels of mammalian brain-specific microRNA-9 and microRNA-124
Mammalian brain-specific miR-9 and miR-124 have been implicated in several aspects of neuronal development and function. However, it is not known how their expression levels are regulated in vivo. We found that the levels of miR-9 and miR-124 are regulated by FXR1P but not by the loss of FXR2P or FMRP in vivo, a mouse model of fragile X syndrome. Surprisingly, the levels of miR-9 and miR-124 are elevated in fmr1/fxr2 double-knock-out mice, in part reflecting posttranscriptional upregulation of FXR1P. Indeed, FXR1P is required for efficient processing of pre-miR-9 and pre-miR-124 in vitro and forms a complex with Dicer and pre-miRNAs. These findings reveal differential roles of FMRP family proteins in controlling the expression levels of brain-specific miRNAs
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