On Interaction between nano-Ag and P(AMPS-co-MMA) copolymer synthesized by ultrasonic

Nano-silver/poly(2-acrylamido-2-methylpropanesulfonic acid (AMPS)-methyl methacrylate (MMA)) [P(AMPS-co-MMA)]composite materials were prepared with the silver nitrate solution containing AMPS and MMA monomers without initiator or reducer, in which Ag⁺ ion was reduced to nanosilver particles and the monomers were copolymerized by ultrasonic simultaneously. The microstructure of the nanocomposite materials was characterized by means of the transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), UV-Vis and fluorescence spectrometer. The nanosilver particles were homogeneously dispersed in polymer matrix and the size of particles is in the range of 5~15 nm, the size and distribution of nano silver particles had something to do with ultrasonic time. Spectrum of FT-IR, UV-Vis and fluorescence were indicated that there is chemical action between namo-Ag and special group attached to the copolymer. X-ray photoelectron spectroscopy (XPS) was proved that the interaction between nano silver and the functional group attached to copolymer is of coordination. It is concluded that there is a kind of interaction phenomena of nanometal silver with effective polymer matrix in the nanocomposite materials.     

Electropolishing of 304 stainless steel: Interactive effects of glycerol content, bath temperature, and current density on surface roughness and morphology

In this study, surface roughness of 304 stainless steel (304SS) varying from ca. 7 to 45 nm can be controlled by changing electropolishing variables in glycerol-containing baths. On the basis of the adsorbate-acceptor mechanism and the model for preferential adsorption of shielding molecules, incorporating the molecular interaction concept is helpful to explain the interactive effects of glycerol content, bath temperature, and current density on the surface roughness (Ra) and morphologies of 304SS. In order to easily understand how to control the surface roughness of 304SS in the glycerol-containing electrolyte, a simplified scheme integrating the above two mechanisms was proposed. From the atomic force microscopy (AFM) analyses, a rough surface is easily obtained by electropolishing at high bath temperatures, which endows the 304SS substrate with pores.     

Developing alternative design concepts in VR environments using volumetric self-organizing feature maps

The conceptual design process has not benefited from conventional computer-aided design (CAD) technology to the same degree as embodiment design because the creative activities associated with developing and communicating alternative solutions, with minimal detail, is far less formulaic in its implementation. Any CAD system that seeks to support and enhance conceptual design must, therefore, enable natural and haptic modes of human–computer interaction. A computational framework for economically representing deformable solid objects for conceptual design is described in this paper. The physics-based deformation model consists of a set of point masses, connected by a series of springs and dampers, which undergo movement through the influence of external and internal forces. The location of each mass point corresponds to a node on a 3D mesh defined by a volumetric self-organizing feature map (VSOFM). A reference mesh is first created by fitting the exterior nodes of the VSOFM to sampled data from the surface of a primitive shape, such as a cube, and then redistributing the interior nodes to reflect evenly spaced hexahedral elements. Material properties are introduced to the mesh by assigning a mass value to individual nodes and spring coefficients to the nodal connections. Several illustrations involving the redesign of an ergonomic writing pen is used to demonstrate how the proposed virtual reality-based modeling system will permit the industrial designer to interactively change the shape and function of a design concept.     

Buckling analysis of multi-walled carbon nanotubes under combined loading considering the effect of small length scale

The torsional and axially compressed buckling of an individual embedded multi-walled carbon nanotube (MWNTs) subjected to an internal and/or external radial pressure was investigated in this study. The emphasis is placed on new physical phenomena which are due to both the small length scale and the surrounding elastic medium. Multiwall carbon nanotubes which are considered in this study are classified into three categories based on the radius to thickness ratio, namely, thin, thick, and almost solid. Explicit formulas are derived for the van der Waals (vdW) interaction between any two layers of an MWNT based on the continuum cylindrical shell model. In most of the previous studies, the vdW interaction between two adjacent layers was considered only and the vdW interaction among other layers was neglected. Moreover, in these works, the vdW interaction coefficient was treated as a constant that was independent of the radii of the tubes. However, in the present model the vdW interaction coefficients are considered to be dependent on the change of interlayer spacing and the radii of the tubes. The effect of the small length scale is also considered in the present formulation. The results show that there is a unique buckling mode (m,n) corresponding to the critical shear stress. This result is obviously different from what is expected for the pure axially compressed buckling of an individual multi-walled carbon nanotube.     

A comprehensive study of plastic deformation mechanism of the metallic materials by ‘X-ray’ computed tomography (‘X-ray’ CT)

The study of microstructure and texture deformation of the metallic materials necessitates detailed information of physical evidence about the plastic deformation mechanism, which involves a direct relationship between mechanical properties and their behaviours under the working conditions. Generally, the mechanical properties of materials are essentially the function of their structure and their compositions. So, the study of texture deformation of mechanical parts with an efficient way in manufacturing engineering is of considerable practical interest. The present paper entails the study of the deformation mechanism in microscopic scale—in situ observation of microstructure and texture deformation by using ‘X-ray’ computed tomography (CT) Medical Scanner installed in the CNAM-Paris, Industrial Materials Laboratory, for evaluating the plastic deformation mechanism. A tomographic inner-health analysis will be presented from 2D slices of the examined parts in the laboratory scale on the as-received and heat-treated aluminium specimens.     

Parent-child interactions during the initial weeks following brain injury in young children.

Objective: To understand how traumatic brain injury (TBI) affects parent-child interactions acutely following injury. Participants: Young children hospitalized for TBI (n = 80) and orthopedic injuries (OI; n = 113). Method: Raters coded videotaped interactions during free play and structured tasks for parental warmth/responsiveness and negativity and child warmth, behavior regulation, and cooperation. Raters also counted parental directives, critical/restricting statements, and scaffolds. Results: Parents of children with TBI exhibited less warm responsiveness and made more directive statements during a structured task than parents in the OI group. Children with TBI displayed less behavior regulation than children with OI. Parental warm responsiveness was more strongly related to child cooperativeness in the OI group than in the TBI group. Child behavior also mediated group differences in parental responsiveness and directiveness. TBI accounted for as much variance in parental behaviors as or more than did sociodemographic factors. Conclusion: TBI-related changes in child behavior may negatively influence parent-child interactions and disrupt the reciprocity between parent and child. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

水文土壤学理论及其应用研究进展

围绕水文土壤学的基本理论和核心科学问题,从地球关键区理论出发,介绍了水文土壤学的基本理论框架、水文土壤学所能填补的知识鸿沟,并回顾了水文土壤学在农业、流域管理、面源污染、湿地保护和环境政策制定以及土壤传递函数等方面的应用,最后对水文土壤学的发展和应用做了展望。     

Thermally Sprayed Coatings as Interlayers for DLC-Based Thin Films

This article examines the usefulness of a thick thermally sprayed interlayer (plasma-sprayed Ni-50%Cr, plasma-sprayed Al₂O₃-13%TiO₂, or high-velocity oxygen-fuel-sprayed WC-17%Co) for enhancing the wear resistance and the corrosion protectiveness of a diamond-like carbon (DLC)-based thin film deposited onto a carbon steel substrate. Scratch tests indicate that the Al₂O₃-13%TiO₂ and WC-17%Co interlayers definitely increase the critical spallation load of the thin film, but the Al₂O₃-13%TiO₂ interlayer itself undergoes brittle fracture under high-contact loads. Accordingly, during ball-on-disk tests at room temperature, no cracking and spallation occur in the DLC-based film deposited onto the WC-17%Co interlayer, whereas the one onto the Al₂O₃-13%TiO₂ interlayer is rapidly removed because the interlayer itself is fractured. At 300 °C, by contrast, the DLC-based film on the Al₂O₃-13%TiO₂ interlayer offers the best tribological performance, possibly thanks to the increased toughness of the ceramic interlayer at this temperature. Electrochemical polarization tests indicate that the thin film/WC-Co systems possess the lowest corrosion current density.     

Formation of Biocompatible Nanoparticles via the Self-Assembly of Chitosan and Modified Lecithin

ABSTRACT:  The formation of biocompatible nanoparticles via the self-assembly of chitosan (CHI) and modified lecithin (ML) was studied. Stable nanoparticles in the size range of 123 to 350 nm were formed at over a wide molar mixing ratios of CHI/ML solutions (amino group/phosphate group) (NH₃⁺/PO₃⁻) and total polyelectrolyte (PE) concentrations (0.1 to 1 wt%) except at intermediate molar ratios when the surface charge was close to neutrality. Zeta-potentials of the nanoparticles were found to be independent of the total PE concentrations. Nanoparticles exhibited excellent stability at over an extended pH (pHs 3 to 6) and ionic strength range (≤ 500 mM NaCl concentration). The particle size and zeta-potential of the nanoparticles increased with the molecular weight of CHI. Transmission electron microscopy suggested that nanoparticles were generally spherical in shape with CHI constituting the exterior of its surface at high molar mixing ratios. Dextran-fluorescein isothiocyanate, bovine serum albumin, and Coomassie brilliant blue as models of nonionic, positively and negatively charged compounds were encapsulated within the nanoparticles at between 8.7% and 62.7% efficiency. The ability of the nanoparticle suspensions to be converted to lyophilized powder or concentrated suspension was also demonstrated.     

RHEOLOGICAL AND SEM STUDIES ON THE INTERACTION BETWEEN SPENT BREWER'S YEAST β-GLUCANS AND κ-CARRAGEENAN

The microstructure of gel network produced by κ -carrageenan (KC), and spent brewer's yeast β -glucans (BYG) and the two polymers' mixture were analyzed through rheological and scanning electron microscopy (SEM) experiments. Small amplitude oscillatory tests in the linear domain of viscoelasticity were applied to study the rheological properties of the two polymers in different mixing ratios. The mechanical spectra measurements gave neat evidence that although KC played the dominant role in forming the gel network, BYG contributed to the gel system, especially in the mixtures with low concentration (0.05 and 0.1 wt%) KC. BYG strengthened the gel network attributing to its entanglement with KC molecules, instead of inhibiting the KC to form ordered structure. It indicated that the two polymers were compatible with possible interactions that might be due to the intermolecular force and hydrogen bond between the two polymers. The microstructure's shape of the two polymers in SEM images demonstrated support explanation for the rheological properties.

PRACTICAL APPLICATIONS

The fine particulate β -glucans filled the cavity of the κ -carrageenan network which enhances the mixed system gel strength. The results of this research might be useful for products development in food industry.