Degradational effects on bisphenol A polycarbonate extruded at high shear stresses

Bisphenol A polycarbonate was repeatedly extruded in a capillary rheometer at high, constant shear stresses (0.15–0.95 MPa) and at temperatures between 275 and 320°C. Changes in molecular weight and molecular weight distribution were determined. Polymer degradation occurred to a much larger extent during extrustion than under static conditions; a difference explained by viscous heating effects. The chain scission reaction had an activation energy of 113 kJ mol^?1 for static as well as dynamic conditions, which indicates similar degradation mechanisms in both cases. The molecular scission followed non-random kinetics.     

The effect of PEG(400)DA crosslinking agent on swelling behaviour of acrylamide-maleic acid hydrogels

Summary Acrylamide (AAm)-maleic acid (MA) hydrogels with different monomer ratios were prepared in an aqueous solution by radical polymerization using a new crosslinking agent, polyethyleneglycol (400) diacrylate (PEG (400) DA) and also using N, N’-methylenebisacrylamide (NMBA) for comparison purpose. The hydrogels were characterized by acid group content and FTIR spectroscopy. Their swelling and deswelling behavior were studied as a function of maleic acid content, pH and crosslinking agent. Incorporation of MA in hydrogels significantly increased their swelling ability and their equilibrium degree of swelling (EDS) values changed between 100–269 g water/g polymer in water while AAm polymers swollen less (22–23 g water/g polymer). The AAm hydrogels showed Fickian type diffusion but the all AAm-MA hydrogels showed non-Fickian type behavior. Their swelling degree increased with the increase of pH of the external medium and an instantaneous increase was observed near a pH value of 7.0. The use of PEG (400) DA instead of NMBA as a crosslinking agent also increased the swelling rate and capacity of the gel. The swelling constant (K) and the diffusion coefficient (D) of hydrogels were also increased. The swelling-deswelling cycles in acidic-basic solutions showed that they could be used as pH responsive gels without any decrease in swelling capacity.     

Stability of SrFeO3-Based Materials in H2O/CO2-Containing Atmospheres at High Temperatures and Pressures

The chemical stability of SrFeO₃-based perovskites in H₂O- and CO₂-containing atmospheres at high temperatures and pressures has been examined. The extent of reaction as a function of p CO₂, p H₂O, temperature, and time has been determined. Either strontium carbonate or Sr(OH)₂·H₂O was observed on sample surfaces after exposure. Observation of two different reaction-rate behaviors could be explained by the formation of different products. The stability of the perovskite has been found to increase when the activity of Sr is decreased. Chemical stability in H₂O/CO₂ is important to understand in order to use these membrane materials for syngas production.     

7075/SiCp复合材料时效组织与力学性能

研究了T6热处理对多层喷射共沉积制备的7075／SiCp复合材料组织和力学性能的影响。结果表明，材料经470℃固溶1h水淬后，120℃时效24h达到峰时效，材料的最高抗拉强度可达735MPa。     

金属材料表面强流脉冲离子束辐照强化

介绍了TEMP型强流脉冲离子束(HIPIB)装置及其工作原理。总结了HIPIB辐照不同金属材料表面后的硬度、耐磨性和耐蚀性的试验结果。HIPIB的瞬间高能量密度沉积导致金属表面快速加热冷却，产生显著的热-力学效应。辐照表面发生的细晶强化、加工硬化和相变强化，使金属材料在较大的深度范围(约100μm)内硬度提高，耐磨性改善；同时，辐照表面金属成分纯净化和组织结构均匀化，有利于提高金属材料耐蚀性。     

Connection Method for Dynamic Modelling and Simulation of Parallel Kinematic Mechanism (PKM) Machines

The design of a PKM (parallel kinematic mechanism) machine usually concentrates on a kinematic analysis but its dynamic control behaviour is not paid equal attention, so there is a need to model a PKM machine dynamically. This paper presents a connection method for dynamic modeling of a PKM machine by introducing active and passive matrices. Using computer algebra, this method makes the dynamic modeling processes available, even though the kinematic constraint Eq. cannot be solved as analytical solutions. The modeling is used succesfully for a planar PKM machine, called PAMELA (parallel mechanism with linear actuators). Using dynamic modeling and simulation, we can anticipate the dynamic behaviour of the PAMELA machine and develop a suitable algorithm for the motion control. This enables a better dynamic configuration of the PAMELA machine to be obtained. As a consequence, it speeds up the design process and reduces the development cost before a physical machine is built. RID=" ID=" <E5>Correspondence and offprint requests to</E5>: Dr Q. Huang, Department of Manufacturing Systems, The Royal Institute of Technology, 100 44 Stockholm, Sweden. E-mail: qhu&commat;cadcam.kth.se     

考虑杆长误差平面机构运动分析及软件研制

给出了连杆机构运动分析和考虑杆长误差的运动误差计算公式,运用VB6.0高级语言开发出相应的计算软件,利用该软件可实现计入杆长误差的连杆机构运动分析。     

Peptide mapping of proteins in human body fluids using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Human body fluids have been rediscovered in the post-genomic era as great sources of biological markers and perhaps particularly as sources of potential protein biomarkers of disease. Analytical tools that allow rapid screening, low sample consumption, and accurate protein identification are of great importance in studies of complex biological samples and clinical diagnosis. Mass spectrometry is today one of the most important analytical tools with applications in a wide variety of fields. One of the fastest growing applications is in proteomics, or the study of protein expression in an organism. Mass spectrometry has been used to find post-translational modifications and to identify key functions of proteins in the human body. In this study, we review the use of human body fluids as sources for clinical markers and present new data that show the ability of Fourier transform ion cyclotron resonance (FTICR) mass spectrometry (MS) to identify and characterize proteins in four human body fluids: plasma, cerebrospinal fluid (CSF), saliva, and urine. The body fluids were tryptically digested without any prior separation, purification, or selection, and the digest was introduced into a 9.4 T FTICR mass spectrometer by direct-infusion electrospray ionization (ESI). Even though these samples represent complex biological mixtures, the described method provides information that is comparable with traditional 2D-PAGE data. The sample consumption is extremely low, a few microliters, and the analysis time is only a few minutes. It is, however, evident that the separation of proteins and/or peptides must be included in the methodology, in order to detect low-abundance proteins and other proteins of biological relevance.     

Application of the electroluminescence phenomenon to the examination of the area of real contact

An experiment that uses the electroluminescence phenomenon to determine the area of real contact (ARC) between metal and phosphor is described. An electroluminescent cell was constructed in which one of the electrodes is a metal sample of a given roughness. The influence of the roughness of the sample on the intensity of luminosity of the electroluminescent cell was examined. It is found that the changes in the intensity of luminosity are related to the changes in the ARC.