Facile Synthesis and Tensile Behavior of TiO<Subscript>2</Subscript> One-Dimensional Nanostructures

High-yield synthesis of TiO₂ one-dimensional (1D) nanostructures was realized by a simple annealing of Ni-coated Ti grids in an argon atmosphere at 950 °C and 760 torr. The as-synthesized 1D nanostructures were single crystalline rutile TiO₂ with the preferred growth direction close to [210]. The growth of these nanostructures was enhanced by using catalytic materials, higher reaction temperature, and longer reaction time. Nanoscale tensile testing performed on individual 1D nanostructures showed that the nanostructures appeared to fracture in a brittle manner. The measured Young’s modulus and fracture strength are ~56.3 and 1.4 GPa, respectively.     

Tobacco etch virus protease: mechanism of autolysis and rational design of stable mutants with wild-type catalytic proficiency

Because of its stringent sequence specificity, the catalyticdomain of the nuclear inclusion protease from tobacco etch virus(TEV) is a useful reagent for cleaving genetically engineeredfusion proteins. However, a serious drawback of TEV proteaseis that it readily cleaves itself at a specific site to generatea truncated enzyme with greatly diminished activity. The rateof autoinactivation is proportional to the concentration ofTEV protease, implying a bimolecular reaction mechanism. Yet,a catalytically active protease was unable to convert a catalyticallyinactive protease into the truncated form. Adding increasingconcentrations of the catalytically inactive protease to a fixedamount of the wild-type enzyme accelerated its rate of autoinactivation.Taken together, these results suggest that autoinactivationof TEV protease may be an intramolecular reaction that is facilitatedby an allosteric interaction between protease molecules. Inan effort to create a more stable protease, we made amino acidsubstitutions in the P2 and P1' positions of the internal cleavagesite and assessed their impact on the enzyme's stability andcatalytic activity. One of the P1' mutants, S219V, was not onlyfar more stable than the wild-type protease (~100-fold), butalso a more efficient catalyst.     

如何使用可编程设计充电算法开发多化学性能电池充电器

许多手持设备设计人员会被为新产品选择合适化学性能的电池而苦恼。在某些应用中,设计工程师已经开始从使用低密度的基于镍的化学电池向使用密度更高的锂离子解决方案过渡。而在其他应用中,情况则正好相反：一些应用正在从使用锂离子材料向使用镍氢材料转变。     

Manipulation of thick-walled PEEK bushing crystallinity and modulus via instrumented compression molding

An instrumented hot compression molding apparatus was fabricated to allow real-time monitoring and precise temperature control during the compaction and consolidation of large polyether ether ketone (PEEK) products. The objective was to determine the impact of controlled variables on the properties of the molded article. Four different strategies were designed to control the mold thermal profiles. The average crystallinity in a commercial molding process is restricted due to large thermal masses with low thermal conductivity. In contrast, this research was able to reduce the crystallinity range from 33% to 6% by developing a special controlled apparatus and implementing new processing methodologies. In this study, PEEK showed a significant increase in the modulus compared to typical values measured on commercially produced analogs, and a higher degree of property uniformity. In a single commercially molded PEEK billet, compressive modulus variability was 13% at room temperature, and 21% at 225°C. Properties of billets produced using the laboratory apparatus showed a reduction in variability to 2%.     

Handle dynamics predictions for selected power hand tool applications

This study uses a previously developed single-degree-of-freedom mechanical model to predict the power hand tool operator handle kinematic response to impulsive reaction forces (Lin, 2001). The model considers the human operator as a lumped parameter passive mechanical system, consisting of stiffness, mass moment of inertia, and viscous damping elements. Six power nutrunners were operated by 9 volunteers (3 men, 6 women) in the laboratory, and corresponding handle kinematics were compared against model predictions. A full-factorial experiment considered torque buildup time and work location. Normalized forearm flexor EMG was measured to quantify muscle exertions and used to proportionally adjust the stiffness parameter. The measured handle displacement for actual tool operation strongly correlated to the model predictions (R = .98) for all handle configurations. The overall model prediction error was 3% for predicting tool handle responses to impulsive reaction forces for various tool and workstation parameters. This model should make it possible for designers to identify conditions that minimize the torque reaction experienced by power hand tool operators.     

Common needs and different agendas: How trainee teachers make progress in their ability to use ICT in subject teaching. Some lessons from the UK

The paper reports on the outcomes of a British Educational Communications and Technology Agency (BECTa) funded study which explored the views of teacher trainees and their mentors in two different school subjects on what strategies, interventions and resources had a positive impact on their ability to use ICT effectively in their subject teaching.The research aimed to explore both commonalities in trainees’ views of which strategies and interventions had a positive influence on their ability to use ICT effectively in subject teaching, and subject discipline dimensions of ICT use, i.e. the ways in which training needs might vary between trainees in different school subjects.The study focused on the views of two successive cohorts of science and history trainees (133 trainees in all), and 21 of their supervising mentors. The outcomes showed that some important determinants of progression in the ability to deploy ICT confidently and effectively in subject teaching were common to both subject groups, but that there were differing views on which ICT applications offered most potential for enhancing teaching and learning in their subject and differences in their preferred priorities for investment in ICT. The study also revealed that trainees felt that many of the experiences and resources which they had encountered in the course of their training had not been helpful.A follow up survey was undertaken of 114 trainees across six subject areas to further explore some of the findings from the initial survey. The concluding section of the paper suggests ways in which trainee teachers might be prepared more effectively for using ICT in their subject teaching.     

An empirical examination of a process-oriented IT business success model

The value of information technology (IT) to modern organizations is almost undeniable. However, the determination of that value has been elusive in research and practice. We used a process-oriented research model developed using two streams of IT research to examine the value of IT in business organizations. One stream is characterized by examining how IT and non-IT variables affect other so-called IT success variables. The second stream is commonly referred to as IT business value, defined as the contribution of IT to firm performance. The resulting research model is referred to in our paper as the IT business success model. Data was collected from 225 top IS executives in fairly large organizations to empirically examine several hypotheses derived from theory concerning the causal nature of the IT business success model. A set of measures for the IT business success model was developed through an intense investigation of the IT literature. The measures were tested for validity and reliability using confirmatory factor analysis. The hypotheses that resulted from past research and conceptually illustrated in the research model were assessed using structural equation analysis. The implications of these findings and the limitations of the study are discussed in an effort to contribute to building a process-oriented theory base for IT business success at the organizational level of analysis.