Bias-Flip Technique for Frequency Tuning of Piezo-Electric Energy Harvesting Devices

Devices that harvest electrical energy from mechanical vibrations have the problem that the frequency of the source vibration is often not matched to the resonant frequency of the energy harvesting device. Manufacturing tolerances make it difficult to match the Energy Harvesting Device (EHD) resonant frequency to the source vibration frequency, and the source vibration frequency may vary with time. Previous work has recognized that it is possible to tune the resonant frequency of an EHD using a tunable, reactive impedance at the output of the device. The present paper develops the theory of electrical tuning, and proposes the Bias-Flip (BF) technique, to implement this tunable, reactive impedance

Loss-of-function mutations in Lysyl-tRNA synthetase cause various leukoencephalopathy phenotypes

Objective: To expand the clinical spectrum of lysyl-tRNA synthetase (KARS) gene–related diseases, which so far includes Charcot-Marie-Tooth disease, congenital visual impairment and microcephaly, and nonsyndromic hearing impairment. Methods: Whole-exome sequencing was performed on index patients from 4 unrelated families with leukoencephalopathy. Candidate pathogenic variants and their cosegregation were confirmed by Sanger sequencing. Effects of mutations on KARS protein function were examined by aminoacylation assays and yeast complementation assays. Results: Common clinical features of the patients in this study included impaired cognitive ability, seizure, hypotonia, ataxia, and abnormal brain imaging, suggesting that the CNS involvement is the main clinical presentation. Six previously unreported and 1 known KARS mutations were identified and cosegregated in these families. Two patients are compound heterozygous for missense mutations, 1 patient is homozygous for a missense mutation, and 1 patient harbored an insertion mutation and a missense mutation. Functional and structural analyses revealed that these mutations impair aminoacylation activity of lysyl-tRNA synthetase, indicating that de- fective KARS function is responsible for the phenotypes in these individuals. Conclusions: Our results demonstrate that patients with loss-of-function KARS mutations can manifest CNS disorders, thus broadening the phenotypic spectrum associated with KARS-related disease

catena-Poly[[dibromidomercury(II)]-μ-3-(1-methyl­pyrrolidin-2-yl)pyridine-κ2 N:N′]

In the title polymeric complex, [HgBr2(C10H14N2)]n, each nicotine mol­ecule is bonded to two adjacent Hg atoms, one through the pyrrolidine N atom and the other through the pyridine N atom, forming zigzag chains along [010]. The coordination around mercury is completed by two bromido ligands resulting in a distorted tetra­hedral arrangement

Dislocation based plasticity in the case of nanoindentation

Understanding plasticity initiation and evolution in nanoindentation tests is a fundamental issue. In this study, a continuum model is developed to analytically predict the force-depth curve by coupling the classical Hertzian solution for elastic field and the evolution of dislocation density. By considering multiple slip systems, the present model predicts the “pop-in” event well. Large-scale molecular dynamics simulations are performed to evaluate the mechanical behavior of bcc Fe under nanoindentation of a spherical indenter and to verify the continuum model. The comparison between molecular dynamics simulations and model predictions shows that the initiation and evolution of dislocation networks is strongly dependent on the loading orientation, which is associated with different deformation patterns. Applying the transition state theory, we investigate the slip-twinning transition as a function of loading rate, which supports the basic hypothesis in the continuum model that the activation of shear loop requires lower energy compared with twin nucleation, although twins can nucleate temporally and annihilate into shear loops finally. The present model provides a general framework to evaluate and rationalize the “pop-in” behavior of any materials with elastoplastic response.submittedVersionThis is a submitted manuscript of an article published by Elsevier Ltd in International Journal of Mechanical Sciences, 31 August 201

A Cross Cultural Study on the Theme of Women Salvation in Two Literary Works

Women salvation is a common depicted theme in literatures about women worldwide. Chinese novel Ju Yan and American autobiographical novel Eat Pray Love are all centered on the theme of their female characters’ salvation under different cultural backgrounds. As a feminist interpretation of these two novels, this paper makes a cross cultural study on the theme of women salvation. Under the influence of gender culture and the different national cultures, the two women characters in the novels have quite distinctive experiences, a deep understanding of which may bring insight into cross cultural perception, thereby promote successful intercultural communication.Key words: Cross cultural study; Women salvation; Ju Yan; Eat Pray Lov

An extended Rice model for intergranular fracture

The plastic events occurring during the process of intergranular fracture in metals is still not well understood due to the complexity of grain boundary (GB) structures and their interactions with crack-tip dislocation plasticity. By considering the local GB structural transformation after dislocation emission from a GB in the Peierls-type Rice-Beltz model, herein we established a semi-analytical transition-state-theory-based framework to predict the most probable Mode-I stress intensity factor (SIF) for dislocation emission from a cracked GB. Using large-scale molecular dynamics (MD) simulations, we studied the fracture behaviors of bi-crystalline Fe samples with 12 different symmetric tilt GBs inside. The MD results demonstrate that the presence of GB could significantly change the SIF required for the activation of plastic events, confirming the theoretical predictions that attributes this to the energy change caused by the transformation of GB structure. Both the atomistic simulation and the theoretical model consistently indicate that, the critical dynamic SIF ( ) at which the dynamic SIF KI(t) deviates from the linearity with respect to the strain ε, increases with the increasing loading rate. However, the classical Rice model underestimates the due to its failure to consider the effects of localized fields. The present theoretical model provides a mechanism-based framework for the application of grain boundary engineering in the design and fabrication of nano-grained metals.An extended Rice model for intergranular fractureacceptedVersio

Nanoconfined Water Dynamics in Multilayer Graphene Nanopores

Water dynamics in frictionless carbon nanotubes and across ultrathin graphene nanopores have been extensively studied. In contrast, the fundamental properties of nanoconfined water in multilayer graphene nanopores (MGPNs), namely nanopores with rough inner wall, are yet not explored. In this study, nanoconfined water in MGPNs with diameter D ranging from 0.82 to 3.4 nm were investigated by molecular dynamic simulations, providing key dynamics parameters including diffusion coefficient, friction coefficient and shear viscosity. The confinement effect of MGPNs was fully revealed, which indicated a critical pore diameter (Dc) of 1.36 nm determining internal water structure and dynamics. Confined water in MGPNs with diameter smaller than or equal to Dc exhibited layer structure and abnormal diffusion. For better understanding water dynamics in MGPNs, water flux and flow enhancement factor were characterized. All the calculated structural and dynamics properties of nanoconfined water in MGPNs were also compared with published results obtained from carbon nanotubes with similar sizes, which for the first time unveiled the impact of inner wall topology of nanopore on nanoconfined water. The results of this study thus laid the solid basis of potential applications of MGPNs and other nanopores with rough inner wall in adsorption and separation of complex fluids, DNA sequencing, seawater desalination, and many others.acceptedVersionLocked until 22.7.2021 due to copyright restrictions. This document is the Accepted Manuscript version of a Published Work that appeared in final form in [JournalTitle], copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see http://dx.doi.org/10.1021/acs.jpcc.0c0489

A Multi-State Comparative Coarse-Grained Modeling of Semi-Crystalline Poly(vinyl alcohol)

Poly(vinyl alcohol) (PVA) is a promising material with exceptional mechanical properties, adhesion, and abrasion resistance. To accurately predict its mesoscopic properties, such as crystal size and morphology, while improving computational efficiency, novel coarse-grained (CG) potentials are developed using iterative Boltzmann inversion (IBI) coupled with density correction. These CG potentials are derived from various thermodynamic states based on two different mapping schemes to overcome the limitations of traditional CG potentials in predicting the glass transition, crystallization, and melting temperatures. By comparing the simulation results obtained from these CG potentials with atomistic molecular dynamics (MD) simulations and experimental data, we identify the most suitable CG model of semicrystalline PVA that effectively reproduces both atomistic structures and thermodynamic properties. In particular, X-ray diffraction (XRD) experiments are used to further validate the accuracy of the CG potentials. This multistate comparative CG strategy provides efficient and accurate CG models for deeper investigations of PVA and other semicrystalline polymers. Our study paves the way for establishing a systematic and comprehensive database of CG potentials, serving as a valuable resource for future research on semicrystalline polymers.A Multi-State Comparative Coarse-Grained Modeling of Semi-Crystalline Poly(vinyl alcohol)acceptedVersionpublishedVersio