压电水声换能器的声学特性分析

压电水声换能器是一种既能作为驱动器又能作为传感器工作的水下探测装置。准确预测其在嘈杂水下环境中的声学特性对设计出坚固耐用的换能器是十分重要的。有限元方法对分析换能器在不同环境中的各种性能十分有效和实用。建立了一种Tonpilz型换能器的二维轴对称有限元模型,设计了基于有限元方法的程序,对其进行了动力学分析,包括模态分析和谐响应分析等,获得了一些声学特性。该程序分析的结果与ANSYS软件分析的结果显示出较好的吻合性。

Review of Cellulose Smart Material: Biomass Conversion Process and Progress on Cellulose-Based Electroactive Paper

Cellulose is a renewable biomass material and natural polymer which is abundantly available on Earth,and includes agricultural wastes,forestry residues,and woody materials.The excellent and smart characteristics of cellulose materials,such as lightweight,biocompatibility,biodegradability,high mechanical strength/stiffness and low thermal expansibility,have made cellulose a highpotential material for various industry applications.Cellulose has recently been discovered as a smart material in the electroactive polymers family which carries the name of cellulose-based electroactive paper(EAPap).The shear piezoelectricity in cellulose polymers is able to induce large displacement output,low actuation voltage,and low power consumption in the application of biomimetic sensors/actuators and electromechanical system.The present study provides an overview of biomass pretreatment from various lignocellulosic cellulose(LC)resources and nanocellulose production via TEMPO-mediated oxidation reaction,followed by the production of different types of EAPap versus its performance,and lastly the applications of EAPap in different areas and industries.Specifically,LC biomass consists mainly of cellulose having a small content of hemicelluloses and lignins which form a defensive inner structure against the degradation of plant cell wall.Thus,selective approaches are discussed to ensure proper extraction of cellulosic fibers from complex biomass for further minimization to nano-dimensions.In addition,a comprehensive review of the development of cellulose-based EAPap as well as fabrication,characterization,performance enhancement and applications of EAPap devices are discussed herein.

Fabrication of Piezoelectric Cellulose Paper and Audio Application

We report the fabrication process of piezoelectric cellulose paper and the enhancement method of its piezoelectric property. Stretching method with different wet-drawing ratios was introduced to increase the piezoelectric property of cellulose paper during regeneration process.It is observed that the Young's modulus and the piezoelectric charge constants are very dependent on the drawing ratio and the direction of nanofibrils of piezoelectric paper.Using the enhanced piezoelectric property,we prove that the flexible regenerated piezoelectric cellulose can be applied to the potential acoustic applications such as thin piezoelectric paper speaker.

Green Nanocomposites Made With Polyvinyl Alcohol and Cellulose Nanofibers Isolated From Recycled Paper

This paper reports green nanocomposites made by blending polyvinyl alcohol(PVA)with cellulose nanofiber(CNF)isolated from recycled deinked copy/printing paper(DIP).The reinforcement effect of DIPCNF in the nanocomposites is compared with other CNFs isolated from native cotton and hardwood by means of TEMPO-oxidation.The prepared PVA-CNF nanocomposites are characterized in terms of morphology,chemical interaction,structural,thermal and mechanical properties.X-ray diffraction and Fourier transform infrared spectroscopy confirm the reinforcing ability of cellulose nanofibers into PVA.By blending CNFs into PVA matrix,the thermal stability of the nanocomposites is improved and DIPCNF shows similar enhancement effect with COCNF and HWCNF.The prepared nanocomposites exhibit 50%Young’s modulus improvement by adding 6%of CNF and DIPCNF exhibits similar enhancement of the mechanical properties to COCNF and HWCNF in the nanocomposites.This indicates that the use of DIPCNF is beneficial for environment protection,resource retaining and save energy in comparison with COCNF and HWCNF.

The Phytophthora nucleolar effector Pi23226 targets host ribosome biogenesis to induce necrotrophic cell death

Pathogen effectors target diverse subcellular organelles to manipulate the plant immune system.Although the nucleolus has emerged as a stress marker and several effectors are localized in the nucleolus,the roles of nucleolar-targeted effectors remain elusive.In this study,we showed that Phytophthora infestans infection of Nicotiana benthamiana results in nucleolar inflation during the transition from the biotrophic to the necrotrophic phase.Multiple P.infestans effectors were localized in the nucleolus:Pi23226 induced cell death in N.benthamiana and nucleolar inflation similar to that observed in the necrotrophic stage of infection,whereas its homolog Pi23015 and a deletion mutant(Pi23226DC)did not induce cell death or affect nucleolar size.RNA immunoprecipitation and individual-nucleotide-resolution UV crosslinking and immunoprecipitation sequencing analysis indicated that Pi23226 bound to the 30 end of 25S rRNA precursors,resulting in accumulation of unprocessed 27S pre-rRNAs.The nucleolar stress marker NAC082 was strongly upregulated under Pi23226-expressing conditions.Pi23226 subsequently inhibited global protein translation in host cells by interacting with ribosomes.Pi23226 enhanced P.infestans pathogenicity,indicating that Pi23226-induced ribosome malfunction and cell death were beneficial for pathogenesis in the host.Our results provide evidence for the molecular mechanism underlying RNA-binding effector activity in host ribosome biogenesis and lead to new insights into the nucleolar action of effectors in pathogenesis.

Characterization of MAGEG2 with testis-specific expression in mice

Male germ cell development is a well-defined process occurring in numerous seminiferous tubules of the testis. Uncovering testicular novel genes related to intrinsic regulation of spermatogenesis is essential for the understanding of spermatogenesis. In the present study, we investigated mouse Mageg2, which belongs to a group of melanoma-associated antigens （MAGEs）. Mageg2 is transcribed in the testis specifically, and its expression level is increased at the pachytene spermatocyte stage, indicating that Mageg2 is expressed predominantly in germ cells. We generated an antibody against mouse MAGEG2 for further characterization at the protein level. Immunoblot analysis suggested that MAGEG2 has specific testicular expression and the expression primarily occurred in pachytene spermatocytes. Proteomic analyses demonstrated that mouse MAGEG2 binded to testicular germ cell-specific serine/threonine-protein kinase 31 （STK31） and heat shock protein 9 （HSPA9）. Direct binding with both interaction partners was confirmed by co-immunoprecipitation. We found that STK31 and HSPA9 bind MAGEG2 directly but not with each other. Interestingly, MAGEG2 reduced the kinase activity of STK31. Our study suggests that mouse MAGEG2 has at least two functions, including chaperone activity related to HSPA9 and regulation of pachytene spermatocyte-specific kinase, STK31. Altogether, our results provide the first information about MAGEG2 at the transcript and protein levels and suggest its potential molecular functions.

Transparent and semi-interpenetrating network P(vinyl alcohol)-P(Acrylic acid)hydrogels:pH responsive and electroactive application

In this paper,poly(vinyl alcohol)-poly(acrylic acid)based transparent semi-interpenetrating network(semi-IPN)hydrogels were synthesized by using a solvent mixture of dimethyl sulfoxide and deionized water via free radical polymerization and subsequent freeze-thaw technique.The formation of the semi-IPN hydrogels was conformed from FT-IR spectra.The acrylic acid concentration effect on the hydrogels was investigated in terms of transparency,crystalline structure and thermal stability by using UV-visible spectroscopy,X-ray diffraction and thermogravimetric analysis.Swelling behaviours of the semi-IPNPAP hydrogels were studied in deionized water and different pH solutions.The compression and electroactive behaviour was tested in fully hydrated stage by using compression test and by applying electrical voltage.The hydrogels showed displacements under the applying voltage and detailed experiment is illustrated.

Parameter identification of partially covered piezoelectric cantilever power scavenger based on the coupled distributed parameter solution

Among the various techniques of power scavenging,piezoelectric energy harvesting usually has more power density.Although piezoceramics are usually more efficient than other piezoelectric materials,since they are very brittle and fragile,researchers are looking for alternative materials.Recently Cellulose Electro-active paper(EAPap)has been recognized as a smart material with piezoelectric behavior that can be used in energy scavenging systems.The majority of researches in energy harvesting area,use unimorph piezoelectric cantilever beams.This paper presents an analytical solution based on distributed parameter model for partially covered pieoelectric cantilever energy harvester.The purpose of the paper is to describe the changes in generated power with damping and the load resistance using analytical calculations.The analytical data are verified using experiment on a vibrating cantilever substrate that is partially covered by EAPap films.The results are very close to each other.Also asymptotic trends of the voltage,current and power outputs are investigated and expressions are obtained for the extreme conditions of the load resistance.These new findings provide guidelines for identification and manipulation of effective parameters in order to achieve the efficient performance in different ambient source conditions.