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91.
Andreas Leemann Barbara Lothenbach Cédric Thalmann 《Construction and Building Materials》2011,25(1):344-350
The use of superplasticizers (SP) is widespread in today’s concrete production. Usually, SP are used when specific demands in regard to workability, strength or durability have to be met. As they contain sodium sulphate, they have the potential to increase the alkalinity in the pore solution and the risk of damages due to alkali-silica reaction. In this study, the effect of two SP on the potential reactivity of concrete is examined by analyzing pore solutions of pastes and mortars and by measuring concrete expansion. The use of a naphthalene–sulphonate-based SP (Na content referred to liquid: 2.8%) leads to an increase in hydroxide concentration in the pore solution during the first two weeks going together with an accelerated concrete expansion during this period. The effects of a polycarboxylate-based SP (Na content referred to liquid: 0.5%) are less pronounced and do not result in an increased concrete expansion. 相似文献
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Intellectual structure of stem cell research: a comprehensive author co-citation analysis of a highly collaborative and multidisciplinary field 总被引:1,自引:0,他引:1
This study is an attempt to approach the intellectual structure of the stem cell research field 2004–2009 through a comprehensive author co-citation analysis (ACA), and to contribute to a better understanding of a field that has been brought to the forefront of research, therapy and political and public debates, which, hopefully, will in turn better inform research and policy. Based on a nearly complete and clean dataset of stem cell literature compiled from PubMed and Scopus, and using automatic author disambiguation to further improve results, we perform an exclusive all-author ACA of the 200 top-ranked researchers of the field by fractional citation count. We find that, despite the theoretically highly interdisciplinary nature of the field, stem cell research has been dominated by a few central medical research areas—cancer and regenerative medicine of the brain, the blood, the skin, and the heart—and a core of cell biologists trying to understand the nature and the molecular biology of stem cells along with biotechnology researchers investigating the practical identification, isolation, creation, and culturing of stem cells. It is also remarkably self-contained, drawing only on a few related areas of cell biology. This study also serves as a baseline against which the effectiveness of a range of author-based bibliometric methods and indicators can be tested, especially when based on less comprehensive datasets using less optimal analysis methods. 相似文献
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Dadhichi Paretkar Marleen Kamperman Andreas S. Schneider David Martina Costantino Creton Eduard Arzt 《Materials science & engineering. C, Materials for biological applications》2011,31(6):1152-1159
We developed a dry synthetic adhesive system inspired by gecko feet adhesion that can switch reversibly from adhesion to non-adhesion with applied pressure as external stimulus. Micropatterned polydimethylsiloxane (PDMS) surfaces with pillars of 30 μm length and 10 μm diameter were fabricated using photolithography and moulding. Adhesion properties were determined with a flat probe as a function of preload. For low and moderate applied compressive preloads, measured adhesion was 7.5 times greater than on flat controls whereas for high applied preloads adhesion dropped to very low values. In situ imaging shows that the increased preload caused the pillars to deform by bending and/or buckling and to lose their adhesive contact. The elasticity of PDMS aids the pillar recovery to the upright position upon removal of preload enabling repeatability of the switch. 相似文献
99.
A. V. Shlyakhtina S. N. Savvin A. V. Levchenko A. V. Knotko Petra Fedtke Andreas Busch Torsten Barfels Marion Wienecke L. G. Shcherbakova 《Journal of Electroceramics》2010,24(4):300-307
The electrical conductivity of new solid electrolytes Eu2.096Hf1.904O6.952 and Gd2Hf2O7 have been compared with those for different pyrochlores including titanates and zirconates Ln2+xМ2−xO7−δ (Ln = Sm-Lu; M = Ti, Zr; x = 0−0.81). Impedance spectroscopy data demonstrate that Eu2.096Hf1.904O6.952 and Gd2Hf2O7 synthesized from mechanically activated oxides have high ionic conductivity, comparable to that of their zirconate analogues.
The bulk and grain-boundary components of conductivity in Sm2.096Hf1.904O6.952 (Тsynth = 1600oС), Eu2.096Hf1.904O6.952 and Gd2Hf2O7 (Тsynth = 1670oС) have been determined. The highest bulk conductivity is offered by the disordered pyrochlores prepared at 1600oC
and 1670oC: ~1.5 × 10−4 S/cm for Sm2.096Hf1.904O6.952, 5 × 10−3 S/cm for Eu2.096Hf1.904O6.952 and 3 × 10−3 S/cm for Gd2Hf2O7 at 780oС, respectively. The conductivity of the fluorite-like phases at the phase boundaries of the Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x ~ 0.286) solid solutions, as well as that of the high-temperature fluorite-like phases Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.286), is lower than the conductivity of the disordered pyrochlores Ln2+xМ2−xO7−δ (Ln = Eu, Gd; M = Zr, Hf; x = 0−0.096). 相似文献
100.
In this paper, the electrochemical characteristics of semi conductive silicon thin films (n-type and p-type silicon) anodes
integrated with the solid polymer electrolyte for lithium polymer batteries were investigated. The charge/discharge cycling
tests revealed that the phosphorus-doped n-type silicon electrode shows the most stable cyclic performance after the 40th cycle and still maintains a reversible specific capacity of about 2,500 mAh/g. The enhanced electrochemical performance of
the doped silicon anode was attributed to the enhancement of its electrical conductivity, which was further confirmed by impedance
spectroscopy and surface analysis by XPS. 相似文献