Search

• We present numerical simulations of dynamic elastoplastic plates by using the non-incremental (BEN) principle. • Unlike the standard incremental procedure, the BEN principle characterizes the entire trajectory. • Two kinds of plates: the Love-Kirchhoff and the Reissner-Mindlin circular plates undergoing uniform pressure are studied. • The analytical results are compared against numerical one derived by the FEM. This paper is devoted to the numerical simulations of elastoplastic plates at small strains by using the non-incremental Brezis-Ekeland-Nayroles (BEN) principle. This space-time variational principle is based on the energy dissipation and transforms the boundary value problem into a null minimization one under constraints. Unlike the standard incremental procedure, the BEN principle characterizes the entire trajectory and delivers the mechanical fields at all time steps simultaneously. Two kinds of plates: the thin plate Love-Kirchhoff and the thick Reissner-Mindlin circular plates undergoing uniform pressure are studied respectively. The description of the dicretization of the principle using the mixed finite element method and the implementation are detailed. The obtained results are compared against analytical solutions provided in the literature and numerical predictions derived by the classical incremental procedure. [ABSTRACT FROM AUTHOR]

Ferroelectric memories show great potential in applications of portable electronics due to low power consumption, high reliability and fast response speed. Therefore, non-destructive readout of ferroelectric memories using the ferroelectric photovoltaic effect attracted tremendous research attention. In this investigation, flexoelectric-enhanced photovoltaic effect (FPV effect) were systematically investigated in curved 3D-printed BaTiO 3 /PVDF composite films. In the bending process, a strain gradient field was formed between the BaTiO 3 (BTO) particles, which led to a relatively large flexoelectric effect. Compared with that of pristine PVDF, the flexoelectric coefficient of BTO/PVDF-15 (15% BTO) was increased 3.7-fold to 2.65 × 10−9 C/m. Furthermore, we found that the photovoltaic current I pv of the BTO/PVDF-15 (15% BTO) composite film increased by 3.4 times compared with the pristine PVDF film at the same curvature. This is mainly attributed to the FPV effect. In addition, "polarization channels" were found for the first time inside nanocomposite materials using the flexoelectricity effect through 2D phase-field simulations, and the channels can be artificially controlled by simply bending the film. Most importantly, the BTO/PVDF-based composite film was designed as flexible ferroelectric memories. We demonstrated for the first time that the intensity difference of the signal for 0 and 1 of the BTO/PVDF-based memories were more than 10 times, which can be read directly using a laser. This investigation shows great promise that flexoelectricity in piezoelectric polymer nanocomposite can greatly benefit the nondestructive readout of ferroelectric memory devices. [Display omitted] • FPV effect were systematically investigated in curved 3D-printed BTO/PVDF composite films. • Strain gradient field was formed between the BaTiO 3 particles which led to a large flexoelectric and FPV effect. • Artificially controlled polarization channels were firstly found in the curved composite films. • Flexible ferroelectric memories was designed and "NANO" pattern was generated using different polarized positions. [ABSTRACT FROM AUTHOR]

Abstract: Di-ionizable calix[4]arene-1,3-crown-4 compounds locked in 1,3-alternate, cone, and partial-cone conformations are synthesized for evaluation in metal ion separations. The ionizable functions include carboxylic acid and N-(X)sulfonyl carboxamide groups in which the acidity is tuned by variation of the electron-withdrawing ability of X. Similar synthetic routes were employed for preparation of the cone and 1,3-alternate ligand series. A different preparative route utilizing protection and deprotection was required to obtain the partial-cone analogues. Ligand conformations were confirmed by their proton and/or carbon NMR spectra. X-ray diffraction verified an unusual 1,2-alternate conformation in the solid-state for one synthetic intermediate. Effects of ligand conformation and ionizable group variations on competitive solvent extractions of alkali and alkaline earth metal cations from aqueous solutions into chloroform were assessed. Single species solvent extractions of Hg2+ and Pb2+ were also performed. [Copyright &y& Elsevier]

Abstract: A series of calix[4]arene-dithiacrown-5 and -dithiacrown-6 compounds in cone and 1,3-alternate conformations has been synthesized. Responses of these ionophores to Hg2+ and competing metal ions were determined in solvent polymeric membrane electrodes. High potentiometric selectivity for Hg2+ over Na+ and a variety of transition and heavy metal ions was obtained. [Copyright &y& Elsevier]

Lead-free ceramics have attracted considerable research attention owing to their environmentally friendly properties as well as their relatively good piezoelectric properties. Herein, we doped BiCoO 3 (BCO) onto (Bi 0.5 Na 0.5)TiO 3 –6BaTiO 3 (BNT-6BT) solid solution at various concentrations and investigated their dielectric and piezoelectric properties. After comparing the Rietveld refinement data with X-ray diffraction (XRD) results, it was found that all the BNT-6BT- x BCO ceramics (x = 0, 0.5%, 1%, and 1.5%) showed the morphotropic phase boundary conformation with coexisting tetragonal (P4bm) and cubic (Pm 3 (＿) m) phases. XRD refinement data also demonstrated that with increasing BCO concentration to 1.5%, the mole ratio between the tetragonal and cubic phases was close to 1:1, which enhanced the piezoelectric performance of the ceramic composites. At a BCO concentration of 1.5%, the strain and piezoelectric coefficient (d 33) of the sample reached 0.31% and 196 pC/N, respectively. The highest effective d 33 * of 489 pm/V was obtained at 110 °C with BNT-6BT-1.5BCO ceramics. The BNT-6BT-xBCO ceramics show great promise for use in high-temperature actuator applications. [ABSTRACT FROM AUTHOR]

Schistosomiasis remains a serious public health concern in China. BALB/c mice are susceptible to Schistosoma japonicum infection, whereas the Wistar rats are less susceptible. Apoptosis phenomenon was observed in 42 d adult worms of S. japonicum from both rats and mice at the morphologic, DNA, cellular, and gene levels by transmission electron microscopy (TEM), fluorometric terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) analysis, fluorescein isothiocyanate-annexin-V/propidium iodide staining flow cytometry (FCM) analysis, and real-time PCR. The results showed that the apoptotic state in worms from two different susceptible hosts was diverse. Several classical hallmarks of apoptosis, including cell shrinkage, chromatin condensation and lunate marginalization, splitting of the nucleoli, nuclear shrinkage and apoptotic body formation were observed by TEM. TUNEL analysis showed that there were much more apoptosis spots in adult worms from rats than those from mice. Statistical analysis revealed that the degree of apoptosis and percentage of necrotic cells in adult worms from Wistar rats were significantly greater ( P < 0.01) than those from BALB/c mice by flow cytometry. A total of 15 apoptosis-associated genes including the major components of an intrinsic cell-death pathway were identified from S. japonicum in this study, suggested that a similar apoptosis pathway might occur in S. japonicum . Real-time PCR analyses revealed that the expression levels of most of the tested apoptosis-associated genes, except CASP7 , were significantly higher or at the similar level in adult worms from Wistar rats, as compared to those from BALB/c mice. The results obtained in this study collectively demonstrated that differential development of adult S. japonicum in less-susceptible rats and susceptible mice was significantly associated with apoptosis in the worm, and provided valuable information to guide further investigations of the mechanisms governing apoptosis and host interactions in schistosome infection. [ABSTRACT FROM AUTHOR]