Characterization of lead zirconate titanate (53/47) films fabricated by a simplified sol–gel acetic-acid route

Lead zirconate titanate [PZT (53/47)] films (around 200 nm thick) were prepared by the sol–gel acetic-acid route, spin-coating onto Si/SiO₂/Pt substrates. A simple thermal annealing program rendered complete crystallization to the perovskite phase and full removal of the organic material. The 53/47 film composition was attained in the bulk, however, X-ray photoelectron spectroscopy detected a different titanium/zirconium ratio at the film surface. Hysteresis loops were measured using a film-tester constructed at our laboratory. The single-annealed films showed a high resistive leakage. A second annealing cycle led to a better film densification and a marked reduction in surface roughness, significantly enhancing the ferroelectric response. Ferroelectric domains were mapped by piezoresponse force measurements. The relatively-simple experimental procedure applied allowed the fabrication of good quality ferroelectric films.     

Identifying Strategies to Support Junior Secondary Students to Engage in Scientific Investigation Tasks

Abstract

This article describes the outcome of a collaborative project between the Hong Kong Institute of Education and four secondary schools that aims to promote the development of scientific investigation skills. The project team designed scientific investigation tasks collaboratively with the teachers and provided school-based support when the tasks were implemented. A total of six teachers and 575 students were involved. Data were collected through questionnaires completed by the students and individual interviews with science teachers about their classroom practice after the completion of the project. The findings suggest that the students did not meet many difficulties and that there were positive influences on students’ interest in learning science. The teachers perceived that there were challenges related to raising students’ self-regulated learning abilities, structuring tasks that were at appropriate levels of difficulty, and promoting group cooperation among the students. Finally, the article argues that the strategies implemented in this study were effective, though it takes much time and effort to help students develop self-regulated learning abilities. The conclusion suggests that teachers consider these challenges collectively and proposes a two-staged model for planning scientific investigation tasks.     

我是怎么服务80家奥迪4S店的——一个4S店服务商心中的5个“关键词”

正张宏明先生作为奥通汽车用品有限公司负责人,自07年就开始从事奥迪专项的项目工作。在上海追得"智慧·创新·分享"发布会行业交流论坛上,张宏明先生凭借自身4S服务商的经验,向与会的众多商协会领导、行业思想领袖、企业代表、渠道代表分享了自己从一线的管理中实践出来的行业认知——一个4S店服务商心中的5个"关键词"。     

Induction of Oxidative Stress and Antioxidative Mechanisms in Arabidopsis thaliana after Uranium Exposure at pH 7.5

To evaluate the environmental impact of uranium (U) contamination, it is important to investigate the effects of U at ecologically relevant conditions. Since U speciation, and hence its toxicity, strongly depends on environmental pH, the present study aimed to investigate dose-dependent effects of U at pH 7.5. Arabidopsis thaliana plants (Mouse-ear Cress) were exposed for three days to different U concentrations at pH 7.5. In the roots, the increased capacities of ascorbate peroxidase and glutathione reductase indicate an important role for the ascorbate-glutathione cycle during U-induced stress. However, a significant decrease in the ascorbate redox state was observed after exposure to 75 and 100 µM U, indicating that those roots are severely stressed. In accordance with the roots, the ascorbate-glutathione cycle plays an important role in the antioxidative defence systems in A. thaliana leaves exposed to U at pH 7.5 as the ascorbate and glutathione biosynthesis were upregulated. In addition, small inductions of enzymes of the antioxidative defence system were observed at lower U concentrations to counteract the U-induced stress. However, at higher U concentrations it seems that the antioxidative defence system of the leaves collapses as reductions in enzyme activities and gene expression levels were observed.     

Seaweed Allelopathy Against Coral: Surface Distribution of a Seaweed Secondary Metabolite by Imaging Mass Spectrometry

Coral reefs are in global decline, with seaweeds increasing as corals decrease. Although seaweeds inhibit coral growth, recruitment, and survivorship, the mechanism of these interactions is poorly understood. Here, we used field experiments to show that contact with four common seaweeds induces bleaching on natural colonies of Porites rus. Controls in contact with inert, plastic mimics of seaweeds did not bleach, suggesting seaweed effects resulted from allelopathy rather than shading, abrasion, or physical contact. Bioassay-guided fractionation of the hydrophobic extract from the red alga Phacelocarpus neurymenioides revealed a previously characterized antibacterial metabolite, neurymenolide A, as the main allelopathic agent. For allelopathy of lipid-soluble metabolites to be effective, the compounds would need to be deployed on algal surfaces where they could transfer to corals on contact. We used desorption electrospray ionization mass spectrometry (DESI-MS) to visualize and quantify neurymenolide A on the surface of P. neurymenioides, and we found the molecule on all surfaces analyzed, with highest concentrations on basal portions of blades.     

Microbial growth,communities and sensory characteristics of vacuum and modified atmosphere packaged lamb shoulders

Packaging fresh lamb in a vacuum (VAC) versus a 100% CO₂ modified atmosphere (MAP) may influence product shelf-life and the bacterial communities. While VAC is a common packing method and 100% CO₂ MAP is used in some countries, there is little information about how these different techniques affect the growth of spoilage bacteria and sensory attributes of lamb. The aim of this study was to assess changes in microbiological and organoleptic properties, and determine differences in microbial communities by terminal restriction fragment length polymorphism (TRFLP) and 454 pyrosequencing, in bone-in (BI) and bone-out (BO) MAP- and VAC-packed lamb shoulders stored at −0.3 °C over 12 wk. VAC and MAP lamb shoulders were acceptable in sensory test scores over 12 wk of storage at −0.3 °C, despite total viable count (TVC) and lactic acid bacteria (LAB) levels increasing to 8 log₁₀ CFU/cm² for VAC lamb and 4–6 log₁₀ CFU/cm² for MAP lamb. Similar to the sensory results, there were no significant differences in microbial communities between BI and BO product. However, types of bacteria were different between VAC and MAP packaging. Specifically, while VAC shoulder became dominated by Carnobacterium spp. in the middle of the storage period, the MAP shoulder microbial population remained similar from the start until later storage times.     

Modeling of a membrane reactor system for crude palm oil transesterification. Part II: Transport phenomena

The mechanistic modeling of biodiesel production process in membrane reactor with the consideration of chemical reaction, phase equilibrium, and ultrafiltration is important for the membrane reactor design. In part II of this work, the chemical and phase equilibrium (CPE) model for crude palm oil transesterification reaction in the membrane reactor developed in part I is extended to an integration of CPE with modified Maxwell–Stefan model, which considers multicomponent mass transport phenomena of concentration polarization and intramembrane. A good fit of simulated permeate fluxes and apparent solute rejection to the experimental data shows that the model has a good prediction capability. Reversible fouling was found to be the major fouling and no pore plugging was observed. Simulation results verified that micelles were retained by the membrane at CPO:MEOH molar ratio of 1:24 and catalyst concentration of 0.5 wt %. However, phase inversion happened when catalyst concentration of 0.05 and 0.1 wt % were used. © 2015 American Institute of Chemical Engineers AIChE J, 61: 1981–1996, 2015     

Passive 350 GHz Video Imaging Systems for Security Applications

Journal of Infrared, Millimeter, and Terahertz Waves - Passive submillimeter-wave imaging is a concept that has been in the focus of interest as a promising technology for personal security...