The parameter tuning of a multi-stable energy harvester is crucial to enhancing harvesting efficiency. In this paper, the bifurcation theory is applied to quantitatively reveal the effects of ...structural parameters on the statics and dynamics of a quad-stable energy harvester (QEH). Firstly, a novel QEH system utilizing the geometric nonlinearity of springs is proposed. Static bifurcation analysis is carried out to design quad-stable working conditions. To investigate the cross-well and high-energy vibration, the complex dynamic frequency (CDF) method, suitable for both weakly and strongly nonlinear dynamic problems, is then applied to deduce the primary response solution. By using the unfolding analysis in singularity theory, four steady-state properties and dozens of primary resonance modes are demonstrated. Based on the transition set, the effective bandwidth for energy harvesting can be customized to adapt well to various vibration environments by parametric adjustment. Finally, the experimental tests verify that the output power can reach up to 1 mW. The proposed QEH and its mechanics optimization can guide energy supply for next-generation wireless systems and low-power sensors under magnetic forbidding environments.
Imbalances in bone formation and resorption cause osteoporosis. Mounting evidence supports that brain-derived neurotrophic factor (BDNF) implicates in this process. 7,8-Dihydroxyflavone (7,8-DHF), a ...plant-derived small molecular TrkB agonist, mimics the functions of BDNF. We show that both BDNF and 7,8-DHF promoted the proliferation, osteogenic differentiation, and mineralization of MC3T3-E1 cells. These effects might be attributed to the activation of the Wnt/β-catenin signaling pathway as the expression of cyclin D1, phosphorylated-glycogen synthase kinase-3β (p-GSK3β), β-catenin, Runx2, Osterix, and osteoprotegerin (OPG) was all significantly up-regulated. Knockdown of β-catenin restrained the up-regulation of Runx2 and Osterix stimulated by 7,8-DHF. In particular, blocking TrkB by its specific inhibitor K252a suppressed 7,8-DHF-induced osteoblastic proliferation, differentiation, and expression of osteoblastogenic genes. Moreover, BDNF and 7,8-DHF repressed osteoclastic differentiation of RAW264.7 cells. The transcription factor c-fos and osteoclastic genes such as tartrate-resistant acid phosphatase (TRAP), matrix metalloprotein-9 (MMP-9), Adamts5 were inhibited by 7,8-DHF. More importantly, 7,8-DHF attenuated bone loss, improved trabecular microarchitecture, tibial biomechanical properties, and bone biochemical indexes in an ovariectomy (OVX) rat model. The current work highlights the dual regulatory effects that 7,8-DHF exerts on bone remodeling.
•Prophylactic effect of p-coumaric acid (CA) against hypoxic cerebral edema in mice.•CA upregulated occludin expression and improved blood-brain-barrier integrity.•·CA enhanced Na+-K+-ATPase activity ...and restored mitochondrial membrane potential.•CA reduced the hypoxia induced oxidative stress and inflammation in brain tissues.
Our previous study found that the anti-hypoxia effect of Tibetan turnip (Brassica rapa ssp. rapa) is directly related to its p-Coumaric acid (CA) and glucoside (pCoumaric acid-beta-d-glucopyranoside, CAG) contents. The present study aimed to investigate the role and mechanism of CA against hypoxic cerebral edema. Male mice were randomly divided into one normoxia group and three hypoxia groups, which were gavaged with sterilized water, CA, or dexamethasone, respectively, once daily for 4 days. The mice were then exposed to normoxia or hypoxia (9.5% O2) for 24 h. The results showed that the brain water content (BWC) and blood-brain-barrier permeability were significantly lower in the CA treatment group than in the hypoxia vehicle group. Mice in the CA treatment group showed good blood-brain-barrier integrity; increased Na+-K+-ATPase activity and mitochondrial membrane potential; decreased oxidative stress and inflammation; and increased occludin protein levels. Prophylactic administration of CA and dexamethasone exerted similar effects against hypoxic cerebral edema. The mechanism involved improving the integrity of the blood-brain-barrier, and inhibiting oxidative stress and inflammation.
A class of bipolar electrostatically actuated micro-resonators is presented in this paper. Two parametric equations are proposed for changing the microbeam shape of the upper and lower sections. The ...mechanical properties of a micro-resonator can be enhanced by optimizing the two section parameters. The electrostatic force nonlinearity, neutral surface tension, and neutral surface bending are considered in the model. First, the theoretical results are verified with finite element results from COMSOL Multiphysics simulations. The influence of section variation on the electrostatic force, pull-in behaviors and safe working area of the micro-resonator are studied. Moreover, the impact of residual stress on pull-in voltage is discussed. The multi-scale method (MMS) is used to further study the vibration of the microbeam near equilibrium, and the relationship between the two section parameters of the microbeam under linear vibration was determined. The vibration amplitude and resonance frequency are investigated when the two section parameters satisfy the linear vibration. In order to research dynamic analysis under the case of large amplitude. The Simulink dynamics simulation was used to study the influence of section variation on the response frequency. It is found that electrostatic softening increases as the vibration amplitude increases. If the nonlinearity initially shows hardening behavior, the frequency response will shift from hardening to softening as the amplitude increases. The position of softening-hardening transition point decreases with the increase of residual stress. The relationship between DC voltage, section parameters, and softening-hardening transition points is presented. The accuracy of the results is verified using theoretical, numerical, and finite element methods.
A new triterpenoid saponin, named terpengustifol A (
), and two new lignan glucosides, phengustifols A and B (
and
), were isolated from the flowers of
. Their structures were determined by the ...extensive analysis of the spectroscopic data (including NMR and HRMS) and ECD calculations. Compound
possesses an unusual monoterpene (
)-6-hydroxy-2,6-dimethylocta-2,7-dienoyl unit at C-21. Compounds
and
are a pair of diastereoisomers, while their aglycones are a pair of enantiomers. Compounds
and
exhibited moderate cytotoxic activities against A375 cell lines with IC
values at 12.1 and 15.6 μM, respectively. This is firstly reported the triterpenoid saponin and lignans isolated from the
flowers.
Phytochemical investigation of the methanolic extract of the fruiting bodies of Fomes officinalis led to the isolation of eight 24-methyl-lanostane triterpenes named officimalonic acids A−H, along ...with one known lanostane triterpene. Their structures were elucidated based on the analysis of spectroscopic data, single-crystal X-ray diffraction, and electronic circular dichroism. Officimalonic acid A represents a previously unknown triterpene type with a 24-methyl-7(8 → 9)abeo-lanostane skeleton, and all of the compounds possessed a malonate half-ester moiety at C-3. Anti-inflammatory assay revealed that officimalonic acids D, E, G, H, and fomitopsin A showed potent inhibitory effects (IC50 = 5.1–8.9 μM) on nitric oxide production in lipopolysaccharide-induced RAW264.7 cells. Officimalonic acids E, G, H showed moderate cytotoxicity against H460, HepG2 and BGC-823 human cell lines.
Eight 24-methyl-lanostane triterpenes, officimalonic acids A−H, were isolated and identified from the fruiting bodies of Fomes officinalis. Some of them showed potent inhibitory effects on NO production in LPS-induced RAW264.7 cells. Display omitted
•Eight 24-methyl-lanostane triterpenes were isolated and identified from fruiting bodies of Fomes officinalis.•One of them has a 24-methyl-7(8 → 9)abeo-lanostane skeleton.•All of the compounds possessed a malonate half-ester moiety.•Some of the compounds showed potent inhibitory effects on NO production in LPS-induced RAW264.7 cells.
In the current study, further chemical investigation of the fruiting bodies of
led to isolate seven new 24-methyl-lanostane triterpenoids, named officimalonic acids I-O (
-
). Their structures were ...elucidated based on the analysis of spectroscopic data (HR-MS, 1D and 2D NMR, UV, IR). Compounds
-
possessed an unusual C-23 spirostructure moiety, while compounds
-
had 23,26-lactone unit. Anti-inflammatory assay revealed that compounds
and
exhibited significant inhibitory activities against NO production in LPS-induced RAW 264.7 cells and cyclooxygenase (COX-2).
Hypha essential genes (HEGs) of Candida Albicans have been emerging into scholar's attention, little known about their functions in oral lichen planus (OLP) with an uncovered etiology. This research ...aimed to observe necessary genes in biphasic C. albicans from OLP and study their relevance in pathogenesis, so as to evaluate possible roles of morphologic switching in etiology of OLP.
Samples were collected from OLP lesions of patients, mycelia were cultured and total RNA was extracted then subjected to reverse transcription-PCR and real-time PCR.
HWP1 and HGC1 were significantly expressed in hyphae phase and weakly detected in yeast phase, while there was no significant difference of EFG1, ALS3, and ECE1 between in yeast and mycelia.
HGC1 and HWP1 were confirmed to be hypha essential genes, with HGC1 for hypha morphogenesis and HWP1 for adhesion invasion in pathogenesis of C. albicans in OLP. ALS3, ECE1 and EFG1 played minor roles in hyphae maintenance and adhesion for hyphae. These might be deemed as hints for the etiology of OLP and indicate HGC1 and HWP1 to be a priority of potential drug target.
The nonlinear modal coupling in a T-shaped piezoelectric resonator, when the former two natural frequencies are away from 1:2, is studied. Experimentally sweeping up the exciting frequency shows that ...the horizontal beam exhibits a nonlinear hardening behavior. The first primary resonance of the vertical beam, owing to modal coupling, exhibits an abrupt amplitude increase, namely the Hopf bifurcation. The frequency comb phenomenon induced by modal coupling is measured experimentally. A Duffing-Mathieu coupled model is theoretically introduced to derive the conditions of the modal coupling and frequency comb phenomenon. The results demonstrate that the modal coupling results from nonlinear stiffness hardening and is strictly dependent on the loading range and sweeping form of the driving voltage and the frequency of the piezoelectric patches.
This paper is concerned with the existence of positive solutions for asymptotically periodic quasilinear Schrödinger equations. By using a Nehari-type constraint and Moser iteration, we get the ...existence results which is a complement to the ones in Chu and Liu Nonlinear Anal. Real World Appl. 44(2018), 118–127. Moreover, we consider a new reformative asymptotic processes of the potential function and the nonlinearity term is only locally defined.
PDF
