174 research outputs found
On multi-transitivity with respect to a vector
A topological dynamical system is said to be multi-transitive if for
every the system is transitive. We introduce the concept of multi-transitivity with
respect to a vector and show that multi-transitivity can be characterized by
the hitting time sets of open sets, answering a question proposed by Kwietniak
and Oprocha [On weak mixing, minimality and weak disjointness of all iterates,
Erg. Th. Dynam. Syst., 32 (2012), 1661--1672]. We also show that
multi-transitive systems are Li-Yorke chaotic.Comment: 11 page
Thomson backscattering in combined two laser and magnetic field
The Thomson backscattering of an electron moving in combined fields is
studied by a dynamically assisted mechanism. The combined fields are composed
of two co-propagating laser fields and a magnetic field, where the first laser
field is strong and low-frequency while the second is weak and high-frequency,
relatively. The dependence of fundamental frequency of emission on the ratio of
incident laser high-to-low frequency is presented and the spectrum of
backscattering is obtained. It is found that, with a magnetic field, the peak
of the spectrum and the corresponding radiation frequency are significantly
larger in case of two-laser than that in case of only one laser. They are also
improved obviously as the frequency of the weak laser field. Another finding is
the nonlinear correlation between the emission intensity of the backscattering
and the intensity of the weak laser field. These results provide a new
possibility to adjust and control the spectrum by changing the ratios of
frequency and intensity of the two laser fields.Comment: 13 pages, 4 figure
Effects of steroid hormones on lipid metabolism in sexual dimorphism: A Mendelian randomization study
BackgroundAlthough the role of steroid hormones in lipid levels has been partly discussed in the context of separate sexes, the causal relationship between steroid hormones and lipid metabolism according to sex has not been elucidated because of the limitations of observational studies. We assessed the relationship between steroid hormones and lipid metabolism in separate sexes using a two-sample Mendelian randomization (MR) study.MethodsInstrumental variables for dehydroepiandrosterone sulfate (DHEAS), progesterone, estradiol, and androstenedione were selected. MR analysis was performed using inverse-variance weighted, MR-Egger, weighted median, and MR pleiotropy residual sum and outlier tests. Cochran’s Q test, the MR-Egger intercept test, and leave-one-out analysis were used for sensitivity analyses.ResultsThe results showed that the three steroid hormones affected lipid metabolism and exhibited sex differences. In males, DHEAS was negatively correlated with total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), and apolipoprotein B (P = 0.007; P = 0.006; P = 0.041, respectively), and progesterone was negatively correlated with TC and LDL-C (P = 0.019; P = 0.038, respectively). In females, DHEAS was negatively correlated with TC (P = 0.026) and androstenedione was negatively correlated with triglycerides and apolipoprotein A (P = 0.022; P = 0.009, respectively). No statistically significant association was observed between the estradiol levels and lipid metabolism in male or female participants.ConclusionsOur findings identified sex-specific causal networks between steroid hormones and lipid metabolism. Steroid hormones, including DHEAS, progesterone, and androstenedione, exhibited beneficial effects on lipid metabolism in both sexes; however, the specific lipid profiles affected by steroid hormones differed between the sexes
Galaxy Morphology Classification Using Multi-Scale Convolution Capsule Network
The classification of galaxy morphology is a hot issue in astronomical
research. Although significant progress has been made in the last decade in
classifying galaxy morphology using deep learning technology, there are still
some deficiencies in spatial feature representation and classification
accuracy. In this study, we present a multi-scale convolutional capsule network
(MSCCN) model for the classification of galaxy morphology. First, this model
improves the convolutional layers through using a multi-branch structure to
extract multi-scale hidden features of galaxy images. In order to further
explore the hidden information in the features, the multi-scale features are
encapsulated and fed into the capsule layer. Second, we use a sigmoid function
to replace the softmax function in dynamic routing, which can enhance the
robustness of MSCCN. Finally, the classification model achieving 97% accuracy,
96% precision, 98% recall, and 97% F1-score under macroscopic averaging. In
addition, a more comprehensive model evaluation were accomplished in this
study. We visualized the morphological features for the part of sample set,
which using the t-distributed stochastic neighbor embedding (t-SNE) algorithm.
The results shows that the model has the better generalization ability and
robustness, it can be effectively used in the galaxy morphological
classification
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