Cascaded quasi-zero stiffness nonlinear low-frequency vibration isolator inspired by human spine

Human motion induced vibration has very low frequency,ranging from 2 Hz to 5 Hz.Traditional vibration isolators are not effective in low-frequency regions due to the trade-off between the low natural frequency and the high load capacity.In this paper,inspired by the human spine,we propose a novel bionic human spine inspired quasi-zero stiffness(QZS)vibration isolator which consists of a cascaded multi-stage negative stiffness structure.The force and stiffness characteristics are investigated first,the dynamic model is established by Newton’s second law,and the isolation performance is analyzed by the harmonic balance method(HBM).Numerical results show that the bionic isolator can obtain better low-frequency isolation performance by increasing the number of negative structure stages,and reducing the damping values and external force values can obtain better low-frequency isolation performance.In comparison with the linear structure and existing traditional QZS isolator,the bionic spine isolator has better vibration isolation performance in low-frequency regions.It paves the way for the design of bionic ultra-low-frequency isolators and shows potential in many engineering applications.

DEM simulation of particle flow and separation in a vibrating flip-flow screen

Vibrating flip-flow screens(VFFS)with stretchable polyurethane sieve mats have been widely used in screening fine-grained materials in recent years.In this work,the discrete element method(DEM)is used to study the screening process in VFFS to explain particle flow and separation behavior at the particle scale.Unlike traditional vibrating screens,for VFFS,the amplitude response of each point on the elastic sieve mat is different everywhere.This study measures the kinematics of the elastic sieve mat under different conditions such as different stretched lengths and material loads.To establish the elastic sieve mat model in a DEM simulation,the continuous elastic sieve mat is discretized into multiple units,and the displacement signal of each unit tested is analyzed by Fourier series.The Fourier series analysis results of each unit are used as the setting parameters for motion.In this way,the movement of the elastic sieve mat is approximately simulated,and a DEM model of VFFS is produced.Through the simulation,the flow and separation of different-sized particles in VFFS are studied,and the reasonability of the simulation is verified by a pilot-scale screening experiment.The present study demonstrates the potential of the DEM method for the analysis of screening processes in VFFS.

SEL1L preserves CD8^(+) T-cell survival and homeostasis by fine-tuning PERK signaling and the IL-15 receptor-mediated mTORC1 axis

SEL1L-mediated endoplasmic reticulum-associated degradation(ERAD)plays critical roles in controlling protein homeostasis by degrading misfolded or terminal unfolded proteins.However,it remains unclear how SEL1L regulates peripheral T-cell survival and homeostasis.Herein,we found that SEL1L deficiency led to a greatly reduced frequency and number of mature T cells,which was further validated by adoptive transfer experiments or bone marrow chimera experiments,accompanied by the induction of multiple forms of cell death.Furthermore,SEL1L deficiency selectively disrupted naïve CD8+T-cell homeostasis,as indicated by the severe loss of the naïve T-cell subset but an increase in the memory T-cell subset.We also found that SEL1L deficiency fueled mTORC1/c-MYC activation and induced a metabolic shift,which was largely attributable to enhanced expression of the IL-15 receptorαandβchains.Mechanistically,single-cell transcriptomic profiling and biochemical analyses further revealed that Sel1l−/−CD8+T cells harbored excessive ER stress,particularly aberrant activation of the PERK-ATF4-CHOP-Bim pathway,which was alleviated by supplementing IL-7 or IL-15.Importantly,PERK inhibition greatly resolved the survival defects of Sel1l−/−CD8+T cells.In addition,IRE1αdeficiency decreased mTORC1 signaling in Sel1l−/−naïve CD8+T cells by downregulating the IL-15 receptorαchain.Altogether,these observations suggest that the ERAD adaptor molecule SEL1L acts as an important checkpoint for preserving the survival and homeostasis of peripheral T cells by regulating the PERK signaling cascade and IL-15 receptor-mediated mTORC1 axis.