Research on hunting stability and bifurcation characteristics of nonlinear stochastic wheelset system

A stochastic wheelset model with a nonlinear wheel-rail contact relationship is established to investigate the stochastic stability and stochastic bifurcation of the wheelset system with the consideration of the stochastic parametric excitations of equivalent conicity and suspension stiffness.The wheelset is systematized into a onedimensional(1D)diffusion process by using the stochastic average method,the behavior of the singular boundary is analyzed to determine the hunting stability condition of the wheelset system,and the critical speed of stochastic bifurcation is obtained.The stationary probability density and joint probability density are derived theoretically.Based on the topological structure change of the probability density function,the stochastic Hopf bifurcation form and bifurcation condition of the wheelset system are determined.The effects of stochastic factors on the hunting stability and bifurcation characteristics are analyzed,and the simulation results verify the correctness of the theoretical analysis.The results reveal that the boundary behavior of the diffusion process determines the hunting stability of the stochastic wheelset system,and the left boundary characteristic value cL=1 is the critical state of hunting stability.Besides,stochastic D-bifurcation and P-bifurcation will appear in the wheelset system,and the critical speeds of the two kinds of stochastic bifurcation decrease with the increase in the stochastic parametric excitation intensity.

An injectable self-adaptive polymer as a drug carrier for the treatment of nontraumatic early-stage osteonecrosis of the femoral head

Core decompression(CD)with the elimination of osteonecrotic bone is the most common strategy for treating early-stage nontraumatic osteonecrosis of the femoral head(ONFH).Adjuvant treatments are widely used in combination with CD as suitable methods of therapy.Existing augmentations have to be fabricated in advance.Here,we report a novel injectable glycerin-modified polycaprolactone(GPCL)that can adapt to the shape of the CD cavity.GPCL shows great flowability at 52.6℃.After solidification,its compressive modulus was 120 kPa at body temperature(37℃).This excellent characteristic enables the polymer to provide mechanical support in vivo.In addition,GPCL acts as a carrier of the therapeutic agent zoledronic acid(ZA),demonstrating sustained release into the CD region.ZA-loaded GPCL was injected into ONFH lesions to treat early-stage nontraumatic cases.Compared to that in the CD group,CD+ZA-loaded GPCL injection preserved bone density and increased the collagen level in the femoral head.At the interface between the GPCL and CD tunnel wall,osteogenesis was significantly promoted.In addition,morphological evaluations revealed that the femoral heads in the CD+ZA-GPCL group exhibited improved pressure resistance.These results suggest a strategy effective to preserve the bone density of the femoral head,thus decreasing the possibility of femoral head collapse.This novel injectable polymer has,therefore,considerable potential in clinical applications.

Low Shear Stress Induces Inflammatory Response via CX3CR1/NF-κB Signal Pathway in Human Umbilical Vein Endothelial Cells

Background Cardiovascular disease has become a major cause of death worldwide.Atherosclerosis is the pathological basis of many cardiovascular diseases.It is well established that hemodynamics also play an important role in endothelial cell mediated atherosclerotic development.In the process of inflammatory reaction,the damage of vascular endothelial cells is the initial link,and various factors can cause damage of endothelial cells.The change of shear stress is considered to be one of the important factors.In the body,vascular endothelial cells are constantly exposed to blood flow.Flow conditions critically regulate endothelial cell functions in the vasculature.Shear stress not only influences the endothelial cell morphology,migration,differentiation and proliferation,but also regulates the expression of proteins in the endothelial cells.Reduced shear stress resulting from disturbed blood flow can drive the development of vascular inflammatory lesions and promote the formation of atherosclerosis.In the present study,the objective of our study is the comprehensive identification of CX3CR1/NF-κB signaling pathway involved in low shear stress(LSS)-induced inflammation in HUVECs through protein profiling and cell function experiment.Methods Human umbilical vein endothelial cell was cultured onglass slides and placed in a parallel plate flow chamber.M199 culture medium was used for low laminar shear stress at 4.14 dyn/cm2,2 h for the testing group,CX3CR1 sh-RNA and NF-κB inhibitor PDTC are used to block the effects of CX3CR1 and P65.The expression levels of the protein were determined by western blot analysis.Mononuclear cell adhesion assays and scratch assays are used to detect cell adhesion and migration.Results Western blotting analyses revealed that compared with the controls,there is a significant increase in the expression of CX3CR1,nucleusP65,intercellular adhesion molecule-1(ICAM-1),vascular cell adhesion molecule-1(VCAM-1)and Interleukin-6(IL-6),while the expression of cytosolic P65 and IκB was significantly reduced in human umbilical vein endothelial cells(HUVECs)treated with LSS.CX3CR1 Sh-RNA was use to reveal its effect on LSS-induced inflammation.Further,specific NF-κB P65 inhibitors(PDTC)were used to reveal the downstream NF-κB P65 exclusively involved in LSS-induced inflammation in HUVECs,this effect can be abrogated by CX3CR1 sh-RNA and NF-κB inhibitors.Monocyte adhesion assay and scratch test revealed LSS promotes adhesion of monocytes and migration of cells,this effect can be abrogated by CX3CR1 sh-RNA and NF-κB inhibitors.LSS is involved in the expression of adhesion moleculesand chemokines,which are important for the initiation of endothelial inflammation-related atherosclerosis.Conclusions The activation of CX3CR1/NF-κB signaling pathway induced by low shear stress in endothelial cells may lead to the future therapeutic targets of atherosclerotic inflammation.

Synergistic effects of 1T MoS_(2)and interface engineering on hollow NiCoP nanorods for enhanced hydrogen evolution activity

Metallic 1T-phase molybdenum disulfide(1T-MoS_(2))shows more excellent electrocatalytic performance for hydrogen evolution reaction(HER)than semiconducting 2H-phase MoS_(2)(2H-MoS_(2)).Therefore,the facile controllable synthesis of hierarchical structure with rich 1T-MoS_(2)is desired for highly efficient electrocatalytic performance.In this work,a simple solvothermal method is proposed to fabricate hol-low NiCoP/MoS_(2)-V heterostructure with 63.2%1T-MoS_(2),in which the abundant catalytic active sites are exposed,the mass transfer properties are improved,and the electronic states are optimized.Moreover,the low energy difference between 2H and 1T phases and near zero free energy of hydrogen adsorption(△G H∗)result in fast kinetics and excellent catalytic performances.Specifically,the NiCoP/MoS_(2)-V com-posite exhibits enhanced HER activity with a low overpotential of 74.6 mV at 10 mA cm^(-2)and superior stability in alkaline electrolytes.This efficient design opens up new vistas for developing high-activity electrocatalysts.

The Morphology and Reciprocation Movement of Honeybee＇s Hairy Tongue for Nectar Uptake

A honeybee uses its brush-like tongue （glossa） to dip nectar and the setae densely distributed on it can increase the amount of trapped nectar observably. The glossa is often simplified as a cylinder covered by uniformly distributed and vertically erected setae during the drinking process, herein variations of the dimensions together with the erection angles of glossal setae are assumed to be negligible. In this paper, a dynamic model for the glossa retraction phase under the specific erection pattern of glossal setae is established, and the energy saving mechanism is extensively studied by comparing four types of erection pat- terns. Then the theoretically-optimal configuration, which satisfies the minimum energy consumption, is achieved from the dynamic model. Using the scanning electron microscope and a specially-designed high-speed camera system, we measure the dimensions of the glossal satae and capture dynamics of the hairy glossa in nectar feeding. It is proven that the erection angle of the glossal setae varies along the tongue axis, which shows a high concordance with our theoretically-optimal configuration. Compared with the hypothetical uniform distribution mode of glossal setae proposed by former researchers, we obtain a 16% increase in energy saving from actual erection pattern.

Laser-assisted synthesis of cobalt@N-doped carbon nanotubes decorated channels and pillars of wafer-sized silicon as highly efficient three-dimensional solar evaporator

The Co@NCNTs/Si pillars with channels is assemble to a suitable pure water gathering device,which is applied in seawater desalination and sewage purification to produce pure water by utilizing solar energy.High-efficiency utilization of solar energy to generate water vapor is popular,recyclable,and environmentally friendly for seawater desalination and sewage purification,helping to alleviate the global water shortage crisis.Here,we report an efficient and simple method to prepare a threedimensional(3 D) evaporator for steam generation by harnessing the power of the sun.This evaporation is composed of one-dimensional(1 D) cobalt embedded and nitrogen doped carbon nanotubes(Co@NCNTs) and 3 D silicon pillars array structure(Si pillars).The Co@NCNTs/Si pillars shows a wide light absorption range provided by carbon nanotubes and a long light absorption path because of the silicon pillars.The surface temperature of the sample rises rapidly in 1.5 min and exceed 80C under solar illumination of one sun.The water evaporation can be high as 1.21 kg m^(-2) h^(-1) under one sun irradiation(1 kW/m^(2)) with the energy efficiency up to 82.4%.This scalable Co@NCNTs/Si pillars can prepare pure water from seawater and sewage,where the removal rate of ions in seawater and pollutants in sewage is similar to 100%.Based on our research,this multistage three-dimensional structure is a simple and efficient novel photothermal material for extensive seawater desalination and sewage purification.