3,099 research outputs found
Bifurcation and chaos of a flag in an inviscid flow
A two-dimensional model is developed to study the flutter instability of a flag immersed in an inviscid flow. Two dimensionless parameters governing the system are the structure-to-fluid mass ratio M⁎ and the dimensionless incoming flow velocity U⁎. A transition from a static steady state to a chaotic state is investigated at a fixed M⁎=1 with increasing U⁎. Five single-frequency periodic flapping states are identified along the route, including four symmetrical oscillation states and one asymmetrical oscillation state. For the symmetrical states, the oscillation frequency increases with the increase of U⁎, and the drag force on the flag changes linearly with the Strouhal number. Chaotic states are observed when U⁎ is relatively large. Three chaotic windows are observed along the route. In addition, the system transitions from one periodic state to another through either period-doubling bifurcations or quasi-periodic bifurcations, and it transitions from a periodic state to a chaotic state through quasi-periodic bifurcations
Targeting PML-RARα and Oncogenic Signaling Pathways by Chinese Herbal Mixture Tien-Hsien Liquid in Acute Promyelocytic Leukemia NB4 Cells
Tien-Hsien Liquid (THL) is a Chinese herbal mixture that has been used worldwide as complementary treatment for cancer patients in the past decade. Recently, THL has been shown to induce apoptosis in various types of solid tumor cells in vitro. However, the underlying molecular mechanisms have not yet been well elucidated. In this study, we explored the effects of THL on acute promyelocytic leukemia (APL) NB4 cells, which could be effectively treated by some traditional Chinese remedies containing arsenic trioxide. The results showed THL could induce G2/M arrest and apoptosis in NB4 cells. Accordingly, the decrease of cyclin A and B1 were observed in THL-treated cells. The THL-induced apoptosis was accompanied with caspase-3 activation and decrease of PML-RARα fusion protein. Moreover, DNA methyltransferase 1 and oncogenic signaling pathways such as Akt/mTOR, Stat3 and ERK were also down-regulated by THL. By using ethyl acetate extraction and silica gel chromatography, an active fraction of THL named as EAS5 was isolated. At about 0.5–1% of the dose of THL, EAS5 appeared to have most of THL-induced multiple molecular targeting effects in NB4 cells. Based on the findings of these multi-targeting effects, THL might be regarding as a complementary and alternative therapeutic agent for refractory APL
A line search filter approach for the system of nonlinear equations
AbstractSome constrained optimization approaches have been recently proposed for the system of nonlinear equations (SNE). Filter approach with line search technique is employed to attack the system of nonlinear equations in this paper. The system of nonlinear equations is transformed into a constrained nonlinear programming problem at each step, which is then solved by line search strategy. Furthermore, at each step, some equations are treated as constraints while the others act as objective functions, and filter strategy is then utilized. In essence, constrained optimization methods combined with filter technique are utilized to cope with the system of nonlinear equations
Physical Information Neural Networks for Solving High-index Differential-algebraic Equation Systems Based on Radau Methods
As is well known, differential algebraic equations (DAEs), which are able to
describe dynamic changes and underlying constraints, have been widely applied
in engineering fields such as fluid dynamics, multi-body dynamics, mechanical
systems and control theory. In practical physical modeling within these
domains, the systems often generate high-index DAEs. Classical implicit
numerical methods typically result in varying order reduction of numerical
accuracy when solving high-index systems.~Recently, the physics-informed neural
network (PINN) has gained attention for solving DAE systems. However, it faces
challenges like the inability to directly solve high-index systems, lower
predictive accuracy, and weaker generalization capabilities. In this paper, we
propose a PINN computational framework, combined Radau IIA numerical method
with a neural network structure via the attention mechanisms, to directly solve
high-index DAEs. Furthermore, we employ a domain decomposition strategy to
enhance solution accuracy. We conduct numerical experiments with two classical
high-index systems as illustrative examples, investigating how different orders
of the Radau IIA method affect the accuracy of neural network solutions. The
experimental results demonstrate that the PINN based on a 5th-order Radau IIA
method achieves the highest level of system accuracy. Specifically, the
absolute errors for all differential variables remains as low as , and
the absolute errors for algebraic variables is maintained at ,
surpassing the results found in existing literature. Therefore, our method
exhibits excellent computational accuracy and strong generalization
capabilities, providing a feasible approach for the high-precision solution of
larger-scale DAEs with higher indices or challenging high-dimensional partial
differential algebraic equation systems
Unified underpinning of human mobility in the real world and cyberspace
Acknowledgments This work is supported by National Science Foundation of China (Grant No. 61573064, 61074116 and 11547188), the Youth Scholars Program of Beijing Normal University (grant No. 2014NT38), and the Fundamental Research Funds for the Central Universities Beijing Nova Programme, China. XYY acknowledges the support from the National Natural Science Foundation of China (Grant No. 61304177) and the Fundamental Research Funds of BJTU (Grant No. 2015RC042).Peer reviewedPublisher PD
Apoptotic Cell Death and Inhibition of Wnt/β-Catenin Signaling Pathway in Human Colon Cancer Cells by an Active Fraction (HS7) from Taiwanofungus camphoratus
Aberrant activation of Wnt/β-catenin signaling plays an important role in the development of colon cancer. HS7 is an active fraction extracted from Taiwanofungus camphoratus, which had been widely used as complementary medicine for Taiwan cancer patients in the past decades. In this study, we demonstrated the effects of HS7 on the growth inhibition, apoptosis induction, and Wnt/β-catenin signaling suppression in human colon cancer cells. HS7 significantly inhibited proliferation of HT29, HCT116, and SW480 colon cancer cells in a dose- and time-dependent manner. The apoptosis induction was evidenced by DNA fragmentation and subG1 accumulation, which was associated with increased Bax/Bcl-2 ratio, activation of caspase-3 and cleavage of PARP. By using Tcf-dependent luciferase activity assay, HS7 was found to inhibit the β-catenin/Tcf transcriptional activities. In addition, HS7 strongly suppressed the binding of Tcf complexes to its DNA-binding site shown in electrophoretic mobility shift assay. This inhibition was further confirmed by the decreased protein levels of Tcf-4 and β-catenin. The β-catenin/Tcf downstream target genes, such as survivin, c-myc, cyclin D1, MMP7, and MT1-MMP involved in apoptosis, invasion, and angiogenesis were also diminished as well. These results indicate that Taiwanofungus camphoratus may provide a benefit as integrative medicine for the treatment of colon cancer
Lasing on nonlinear localized waves in curved geometry
The use of geometrical constraints opens many new perspectives in photonics
and in fundamental studies of nonlinear waves. By implementing surface
structures in vertical cavity surface emitting lasers as manifolds for curved
space, we experimentally study the impacts of geometrical constraints on
nonlinear wave localization. We observe localized waves pinned to the maximal
curvature in an elliptical-ring, and confirm the reduction in the localization
length of waves by measuring near and far field patterns, as well as the
corresponding dispersion relation. Theoretically, analyses based on a
dissipative model with a parabola curve give good agreement remarkably to
experimental measurement on the transition from delocalized to localized waves.
The introduction of curved geometry allows to control and design lasing modes
in the nonlinear regime.Comment: 6 pages, 6 figure
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