What do students do in a F2F CSCL classroom? The optimization of multiple communications modes

This exploratory study analyzes how students use different communication modes to share information, negotiate meaning and construct knowledge in the process of doing a group learning activity in a Primary Grade 5 blended learning environment in Singapore. Small groups of students interacted face-to-face over a computer-mediated communication (CMC) technology called Group Scribbles (GS) to jointly complete a learning task. The lesson designers attempted to optimize the use of CMC technology and face-to-face (F2F) discussion in students’ collaborative learning, with the aim of harnessing the specific features of each medium. Building on notions from communication studies and from interaction analysis, we observed the construction and evolution of the interactions through analyzing the artifacts that were produced by a group of students – in verbal talk, gestures, and sketches drawn and text inscribed in GS. F2F and GS interactions intertwined to support collaborative learning. The findings from this study could inform design aspects concerning integrating and reinforcing the strengths of both communication modes when introducing computer-assisted collaborative learning (CSCL) in a F2F classroom.     

Interpenetrating polymer network structured thermosets prepared from epoxidized soybean oil/diglycidyl ether of bisphenol A

Epoxidized soybean oil (ESO)/diglycidyl ether of bisphenol A (DGEBA) in various blend ratios (i.e. 100/0, 90/10, 80/20, 70/30, 60/40, 50/50) was thermally cured using methylhexahydrophthalic anhydride in the presence of 2‐ethyl‐4‐methylimidazole catalyst. The tensile properties and fracture toughness of the ESO/DGEBA thermoset blends were determined. Thermal properties of the blends were characterized using dynamic mechanical analysis, differential scanning calorimetry and thermogravimetric analysis. Blending of ESO and DGEBA gave synergistic effects on the modulus, strength, glass transition temperature and thermal stability. However, the fracture toughness and elongation at break of ESO/DGEBA blends are lower than those of ESO, as expected. The enhancement in certain mechanical and thermal properties of ESO/DGEBA can be associated with the crosslink density, gel content and possible interpenetrating network of the resulting thermoset blends. © 2013 Society of Chemical Industry     

Sintering and mechanical properties of MgO-doped nanocrystalline hydroxyapatite

Hydroxyapatite (HA) has been extensively studied for its exceptional ability in promoting osseointegration as in bone graft substitute and biomimetic coating of prosthetic implants. However poor mechanical properties of HA, in particular its low fracture toughness, has made its widespread adaption in a number of biomedical applications challenging. Here we employ an optimized wet precipitation method to synthesize nanocrystalline HA with significantly improved mechanical properties. In addition doping by MgO is found to effectively suppress grain growth and enhance fracture toughness by nearly 50% while good densification and phase stability in all samples regardless of concentration of dopant are fully maintained. Microstructural analysis further suggests that the exceptionally superior mechanical properties can be explained by migration of MgO to grain boundaries where they transform the more common transgranular fracture into an intergranular mode. Our biodegradation tests also confirm that MgO-doped HA is indeed a suitable candidate for load bearing implants.     

Preparation and formation mechanism of nano-iron oxide black pigment from blast furnace flue dust

A mixed solution of ferrous and ferric sulfate leached from blast furnace (BF) flue dust was used to prepare nanometer-sized iron oxide black pigment (Fe₃O₄, magnetite) by the co-precipitation method. The pH value played a very important role in affecting the color and particle size of Fe₃O₄ and the evolution of green rust in to Fe₃O₄ or FeOOH. The experimental conditions including the solution pH, the way of adding precipitant, volume of air and reaction time for the formation of nano-iron oxide black pigment were investigated carefully in order to determine the optimal ones. The color, morphology and particle size of as-prepared Fe₃O₄ pigment were characterized by means of a color measurement instrument, X-ray diffraction (XRD) and transmission electron microscopy (TEM) respectively. The results showed that the obtained pigment had low average spectral reflectance (<4%), good oil absorption (～23%), high black intensity and narrow size distribution of 60–70 nm. Furthermore, the formation mechanism of Fe₃O₄ from the mixed solution of ferrous and ferric sulfate was discussed.     

铁法盆地煤层气采收率分析

根据煤层气抽采的相关概念及解吸吸附原理,分析了国内外煤层气采收率的现状,依据铁法盆地的煤层气地质条件,通过对现有资料及实际测定数据的分析计算,得出铁法盆地煤层气采收率约为39.88%～64.73%的结论,认为具有较高的开采价值.     

当代城市文化背景下的城市功能再生——另一种生态建筑

本文从现代城市文化的角度着手深入探讨了影响城市功能再生的诸多深层社会因素，指出城市功能的再生便是城市文化的再生，城市文化的再生便是城市人文精神的重塑，建筑学意义上的现代城市人文的重塑便是现代城市人对自身生存空间的心理归属，指出存在于现代建筑空间中的另一种生态体系——心理生态，进而提出基于非物质基础上的另一种生态建筑概念.     

结合旧城更新的旅游资源挖掘——以南京南捕厅街区为例

旧城更新是城市发展的必要过程,其中也潜藏了新的旅游资源。该文选取南京南捕厅历史风貌保护区进行实践应用研究。首先对南捕厅的现有资源状况进行整理,对其历史文化的沿革和积淀进行梳理,着重总结南捕厅的文化及空间资源特征。然后针对南捕厅旅游开发的可行性从瓶颈和潜力两方面展开分析,并提出了该地区旅游发展对策。     

Preliminary studies on the use of modified ALCELL lignin as a coupling agent in the biofiber composites

ALCELL lignin has been employed as a coupling agent in empty fruit bunch fiber (EFBF)–polypropylene (PP) composites. The lignin has been chemically modified with toluene diisocyanate (TDI) to various weight loadings. The evidence of the reaction between TDI and lignin has been observed by using Fourier transform infrared (FTIR) analysis. The effect of lignin as a coupling agent on mechanical properties has been studied. The results show that the TDI‐modified lignin is able to impart greater compatibility between EFBF and PP. This is reflected in the greater mechanical properties shown by the composites with TDI‐modified lignin than in those with the unmodified lignin. Scanning electron microscopy (SEM) studies showed that TDI modification of lignin resulted in a better blending and compatibility between lignin and PP matrix. The glass‐transition temperature of the lignin increases as the WPG is increased. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1333–1340, 2001     

Effect of Co γ-irradiation on postharvest quality and selected enzyme activities of Pleurotus nebrodensis

Freshly harvested Pleurotus nebrodensis fruit bodies were exposed to four different doses (0.8-2.0 kGy) of ⁶⁰Co γ-irradiation and various physiological changes associated with postharvest deterioration, as well as the activities of selected enzymes (proteinase, polyphenoloxidase, superoxide dismutase, catalase) thought to play a role in the process of deterioration, were monitored during 22 days of subsequent storage at 4 °C and 65-70% relative humidity. An irradiation dose of 1.2 kGy significantly delayed (by 6-9 days) the onset of fruit body softening, splitting and browning compared with non-irradiated controls and test samples subjected to lower or higher irradiation doses. Irradiation with 1.2 and 1.6 kGy also had a positive effect on other indicators of mushroom tissue senescence, resulting in smaller decreases in soluble protein levels and more protracted increases in proteinase activity. Peak levels of polyphenoloxidase activity, widely recognized as causing postharvest browning of mushroom tissue, were also significantly lower (P < 0.05) in fruit bodies exposed to 1.2 kGy compared with non-irradiated controls. Our data increase our understanding of the effects of γ-irradiation on the biochemical changes associated with postharvest deterioration in P. nebrodensis, and improve the prospects of more targeted strategies for extending the shelf life of both this and other mushrooms.     

Transparent Mirror

正Western Han Dynasty(206 BC–8 AD)Diameter:12.1 cm;weight:280 g High-tin bronze This marvelous artifact is a cast metal circular disc with interesting relief patterns on the back.When sunlight falls on the surface of the mirror,made 2,000 years ago,the reflected image on a wall shows the pattern on the back of the mirror.