•A new numerical algorithm based on the LRBFCM is proposed.•The stability of the LRBFCM is greatly increased.•The boundary or interface condition of complex geometry can be easily treated.•The ...improved LRBFCM is applied to the PCs with a scatterer of complex geometry.
A numerical algorithm based on the local radial basis function collocation method (LRBFCM) is developed to efficiently compute the derivatives of primary field quantities. Instead of a direct calculation of the derivatives by partial differentiation of the shape functions as in traditional numerical approaches, the derivative calculation in the present work is performed using a simple finite difference scheme with an introduced fictitious node. The developed algorithm is geometrically very flexible and can be easily applied to the continuity and boundary conditions of arbitrary geometries, which require an accurate derivative computation of the primary field quantities. The developed LRBFCM are applied to phononic crystals with scatterers of arbitrary geometry, which has not yet been reported before to the authors’ knowledge. A few examples for anti-plane elastic wave propagation are modelled to validate the developed LRBFCM. A comparison with finite element modelling shows that the present method is efficient and flexible.
Both inflammatory processes and glutamatergic systems have been implicated in the pathophysiology of mood-related disorders. However, the role of caspase-1, a classic inflammatory caspase, in ...behavioral responses to chronic stress remains largely unknown. To address this issue, we examined the effects and underlying mechanisms of caspase-1 on preclinical murine models of depression. We found that loss of caspase-1 expression in Caspase-1
knockout mice alleviated chronic stress-induced depression-like behaviors, whereas overexpression of caspase-1 in the hippocampus of wild-type (WT) mice was sufficient to induce depression- and anxiety-like behaviors. Furthermore, chronic stress reduced glutamatergic neurotransmission and decreased surface expression of glutamate receptors in hippocampal pyramidal neurons of WT mice, but not Caspase-1
mice. Importantly, pharmacological inhibition of caspase-1-interleukin-1β (IL-1β) signaling pathway prevented the depression-like behaviors and the decrease in surface expression of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) in stressed WT mice. Finally, the effects of chronic stress on both depression- and anxiety-like behaviors can be mimicked by exogenous intracerebroventricular (i.c.v.) administration of IL-1β in both WT and Caspase-1
mice. Taken together, our findings demonstrate that an increase in the caspase-1/IL-1β axis facilitates AMPAR internalization in the hippocampus, which dysregulates glutamatergic synaptic transmission, eventually resulting in depression-like behaviors. These results may represent an endophenotype for chronic stress-induced depression.
This paper studies the dynamics and libration suppression of a tethered system with a moving climber in circular orbits. The tethered system is modeled by a two-piece dumbbell model that consists of ...one main satellite, one climber and one end-body connected by two straight, massless and inextensible tethers. A new tension control strategy to suppress the libration of the tethered system due to the moving climber is proposed by reeling in-out tether at the end-body without thrust. The control strategy is implemented with the sliding mode control to suppress the libration angle of the climber to zero by the end of climber’s transfer phase. The numerical results show that the proposed control strategy is very effective in suppressing the libration of the climber in the three-body tethered system with tension control only. Furthermore, cases with limited tension control are examined. It reveals that a longer tether between the climber and the end-body is required to supplement the limited tension in suppressing the libration of the climber.
Within the multimechanism framework, a micromechanics-based sand model is presented based upon the bounding surface and critical state theories. This model follows the assumption that the macroscopic ...responses of sands can be determined by summing the contributions from a macroscopic volumetric mechanism and an infinite number of virtual microscopic shear mechanisms in various orientations. Each virtual shear mechanism characterizes the microscopic shear deformations and the dilatancy-induced volumetric deformations in three mutually perpendicular directions. The deformations in each direction are described by using a microscopic shear stress–strain relationship founded upon the bounding surface theory and a microscopic stress–dilatancy relationship, respectively. The shear strength with the SMP yield criterion and the stress–dilatancy relationship introduce a state variable for compatibility with the critical state theory. The correlations between the microscopic and macroscopic model parameters are established, and most of them are defined by soil parameters with a clear physical meaning. With a spatial distribution of microscopic shear mechanisms, the model can intrinsically consider the stress-induced anisotropy, the non-coaxial behaviour of stress and strain increment in their principal directions, and the effect induced by principal stress rotations without requiring additional model parameters. The comparison of the simulated and experimental results indicates its excellent capability in predicting sand responses in stress–strain curve as well as stress path under different drainage and loading conditions.
•A micromechanics-based bounding surface model for sands is presented.•Relationships of microscopic stress-strain and stress-dilatancy are proposed.•Effects of anisotropy, non-coaxiality and stress axis rotation are considered.•Its excellent capabilities are shown by comparing simulation and test results.
The Wheeler equation, for electromagnetic disturbances in a gravitational field, was found by Fiziev to have exact solutions both above and below the event horizon, in the form of waves propagating ...both inwardly and outwardly. This observation can be interpreted and verified from the optical point of view, entirely on the basis of the Schwarzschild metric for length contraction and time dilation, in order to derive a differential version of Snell's law for the Schwarzschild black hole. It reveals interesting physics, including the correct amount of light deflection by the Sun, internal and external Oppenheimer-Snyder cones of the black hole, properties of its phonon sphere and the conclusion that light rays are kept below the horizon by length contraction and time dilation rather than deflection.
The Krüppel-like factor 5 (KLF5) is a zinc-finger transcription factor promoting cell proliferation, cell-cycle progression and survival. A high expression level of KLF5 mRNA has been shown to be ...associated with shorter breast cancer patient survival. However, the mechanism of KLF5 action in breast cancer is still not clear. In this study, we found that both KLF5 and its downstream gene fibroblast growth factor binding protein 1 (FGF-BP) are co-expressed in breast cell lines and primary tumors. Manipulation of the KLF5 expression can positively regulate the FGF-BP mRNA and protein levels in multiple breast cell lines. In addition, the secreted FGF-BP protein in the conditional medium is also regulated by KLF5. Furthermore, we demonstrated that KLF5 binds and activates the FGF-BP promoter through a GC box by luciferase reporter, oligo pull down and chromatin immunoprecipitation (ChIP) assays. When FGF-BP is depleted by siRNA, KLF5 fails to promote cell proliferation in MCF10A, SW527 and TSU-Pr1. We further demonstrated that overexpression or addition of FGF-BP rescues the KLF5-knockdown-induced growth arrest in MCF10A cells. Finally, KLF5 significantly promotes MCF7 breast cancer cell xenograft growth in athymic nude mice. These findings suggest that KLF5 may promote breast cancer cell proliferation at least partially through directly activating the FGF-BP mRNA transcription. Understanding the mechanism of KLF5 action in breast cancer may result in useful diagnostic and therapeutic targets.
Heisenberg interactions are ubiquitous in magnetic materials and play a central role in modelling and designing quantum magnets. Bond-directional interactions offer a novel alternative to Heisenberg ...exchange and provide the building blocks of the Kitaev model, which has a quantum spin liquid as its exact ground state. Honeycomb iridates, A2 IrO3 (A = Na, Li), offer potential realizations of the Kitaev magnetic exchange coupling, and their reported magnetic behaviour may be interpreted within the Kitaev framework. However, the extent of their relevance to the Kitaev model remains unclear, as evidence for bond-directional interactions has so far been indirect. Here we present direct evidence for dominant bond-directional interactions in antiferromagnetic Na2 IrO3 and show that they lead to strong magnetic frustration. Diffuse magnetic X-ray scattering reveals broken spin-rotational symmetry even above the Néel temperature, with the three spin components exhibiting short-range correlations along distinct crystallographic directions. This spin- and real-space entanglement directly uncovers the bond-directional nature of these interactions, thus providing a direct connection between honeycomb iridates and Kitaev physics.
Spacecraft formation maneuvering will inevitably induce flexible vibration from flexible appendages of spacecraft such as solar array appendages or antennae, which leads to complex disturbances with ...unknown fundamental frequencies. To achieve high performance of spacecraft formation flying, a novel adaptive iterative learning disturbance observer based on adaptive notch filter is designed to estimate and compensate unknown multi-frequency disturbances. Different from existing results on iterative learning disturbance observer, the newly proposed observer can estimate effectively both low-frequency disturbances and high-frequency periodic disturbances. Based on the proposed observer, an output feedback pose tracking law is derived by combining the proposed velocity observer and a feedback controller in dual quaternions description. The stability of the closed-loop system is approved based on the Lyapunov framework. Finally, the effectiveness and accuracy of the proposed observer and controller are demonstrated successfully by numerical simulations.
•Developed a novel adaptive iterative learning control for flexible spacecraft formation.•Developed adaptive iterative learning observer to estimate multi-frequency disturbances.•Formulated 6DOF spacecraft formation maneuvering by dual quaternions.
This paper develops a high-fidelity and high-accuracy dynamic model to investigate libration suppression of partial space elevator caused by a moving climber through tether deployment and/or ...retrieval at main and subsatellites. The model is based on the nodal position finite element method in the arbitrary Lagrangian–Eulerian description. In this approach, moving nodes are assigned to the climber and satellites and variable-length elements are used to represent the movement of climber and tether deployment and/or retrieval. In conjunction with the moving nodes, a merging and dividing element scheme is derived to describe the climber moving across the boundary of tether elements. The results show that the deployment of tether at the subsatellites produce a positive effect to suppress the libration motion of partial space elevator, while the retrieval of tether produce a negative effect.
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