136 research outputs found
A quartic system and a quintic system with fine focus of order 18
AbstractBy using an effective complex algorithm to calculate the Lyapunov constants of polynomial systems En: zË=iz+Rn(z,zÂŻ), where Rn is a homogeneous polynomial of degree n, in this note we construct two concrete examples, E4 and E5, such that in both cases, the corresponding orders of fine focus can be as high as 18. The systems are given, respectively, by the following ordinary differential equations:E4:zË=iz+2iz4+izzÂŻ3+5227820723eiΞzÂŻ4, where Ξâ{kϱÏ6,kÏ+Ï2,kâZ}, andE5:zË=iz+3z5+20(c+3)9c2â15z4zÂŻ+zzÂŻ4+20(c+3)c29c2â15zÂŻ5, where c is the root between (â3,â5/3) of the equation4155c6â10716c5â63285c4â18070c3+168075c2+205450c+60375=0
A Facile Synthesis and Optical Properties of Bundle-Shaped TbPO 4
Bundle-shaped TbPO4·H2O nanorods have been prepared by a facile hydrothermal technique and characterized by XRD, SEM, TEM, UV-Vis diffuse reflectance spectrum (DRS), photoluminescence (PL) spectrum, and lifetime. The results indicate that the obtained sample has hexagonal structure of TbPO4·H2O and is composed of nanorods bundles which is assembled from many single crystalline nanorods with the diameter of around 45ânm and the length of 2.3âÎŒm. The growth of the single crystalline nanorod is along the (001) plane direction. Under the UV light irradiation, TbPO4·H2O nanorods bundles exhibit bright green emission corresponding to the D54âF7J (J=6,5,4,3) transitions of the Tb3+ ions, and the lifetime is determined to be about 0.24âms
Unique normal forms for Hopf-zero vector fields
We consider normal forms of Hopf-zero vector fields in R-3. Unique normal forms under conjugacy and orbital equivalence for the generic case are given.MathematicsSCI(E)4ARTICLE4345-34833
Discovery and Identification of Pyrazolopyramidine Analogs as Novel Potent Androgen Receptor Antagonists
Androgen receptor (AR), an important target in the current androgen derivation therapy, plays a critical role in the development and progress of prostate cancer (PCa). Nonsteroidal antiandrogens, such as enzalutamide and bicalutamide, are commonly used in clinic to treat PCa. Though they are very effective at the beginning, drug resistance problem appears after about 18 months. One of the reasons is that these antiandrogens share similar structure skeleton. Therefore, it is urgent to discover novel antiandrogens with different skeletons for resistance problem. Herein, we combined structure- and ligand-based methodologies for virtual screening chemical databases to identify potent AR antagonists. Then the cytotoxic activities of the screened hit samples were evaluated by using LNCaP prostate cancer cells. Virtual screening and biological evaluation assay results suggest that several chemicals with novel pyrazolopyrimidine skeleton can inhibit the proliferation of prostate cancer cells with similar, or even higher, bioactivities to bicalutamide. AR reporter gene assay experiments proved that Compound III showed potential antagonistic effects. In addition, molecular dynamics simulations results proved that Compound III can properly bind to AR and prevent helix 12 (H12) from closing to distort the formation of activation function 2 (AF2) site, resulting in the invalid transcription. Hence, pyrazolopyrimidine was discovered as a novel, potent and promising antiandrogen skeleton deserved to be further studied
A Survey on Label-efficient Deep Image Segmentation: Bridging the Gap between Weak Supervision and Dense Prediction
The rapid development of deep learning has made a great progress in image
segmentation, one of the fundamental tasks of computer vision. However, the
current segmentation algorithms mostly rely on the availability of pixel-level
annotations, which are often expensive, tedious, and laborious. To alleviate
this burden, the past years have witnessed an increasing attention in building
label-efficient, deep-learning-based image segmentation algorithms. This paper
offers a comprehensive review on label-efficient image segmentation methods. To
this end, we first develop a taxonomy to organize these methods according to
the supervision provided by different types of weak labels (including no
supervision, inexact supervision, incomplete supervision and inaccurate
supervision) and supplemented by the types of segmentation problems (including
semantic segmentation, instance segmentation and panoptic segmentation). Next,
we summarize the existing label-efficient image segmentation methods from a
unified perspective that discusses an important question: how to bridge the gap
between weak supervision and dense prediction -- the current methods are mostly
based on heuristic priors, such as cross-pixel similarity, cross-label
constraint, cross-view consistency, and cross-image relation. Finally, we share
our opinions about the future research directions for label-efficient deep
image segmentation.Comment: Accepted to IEEE TPAM
Calibrating the absorption imaging of cold atoms under high magnetic fields
We develop a theoretical model for calibrating the absorption imaging of cold
atoms under high magnetic fields. Comparing to zero or low magnetic fields, the
efficiency of the absorption imaging becomes lower while it requires an
additional correction factor to obtain the absolute atom number under the
Beer-Lambert law. Our model is based on the rate equations and can account many
experimental imperfections such as Zeeman level crossing, failures of hyperfine
structures, off-resonant couplings, and low repumping efficiency, etc. Based on
this method, we can precisely calculate the correction factor for atom number
measurement without any empirical or fitting parameters. Meanwhile, we use a
cold-atom apparatus of rubidium-85 to experimentally verify our model. Besides
these, we find our work can also serve as a benchmark to measure the
polarization impurity of a circular-polarized laser beam with high
sensitivities. We believe this work will bring convenience for most of
cold-atom experiments using absorption imaging.Comment: 9 pages, 5 figure
Timed Up and Go Test can predict recurrent falls: a longitudinal study of the community-dwelling elderly in China
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