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排序方式: 共有542条查询结果,搜索用时 15 毫秒
71.
Ziegler KJ Schmidt DJ Rauwald U Shah KN Flor EL Hauge RH Smalley RE 《Nano letters》2005,5(12):2355-2359
A two-phase liquid-liquid extraction process is presented which is capable of extracting water-soluble single-walled carbon nanotubes into an organic phase. The extraction utilizes electrostatic interactions between a common phase transfer agent and the sidewall functional groups on the nanotubes. Large length-dependent van der Waals forces for nanotubes allow the ability to control the length of nanotubes extracted into the organic phase as demonstrated by atomic force microscopy. 相似文献
72.
Conducted 3 experiments with 256 7–10 yr olds in which Ss were induced to donate some of their winnings from a game to poor children. They were then praised for their behavior (reinforcement), told they must have donated because they were helpful people (attribution), or told nothing (control). Subsequent donation, and behavior on a variety of tests of generalized altruism, was assessed. The donation of all Ss was increased both by reinforcement and attributions of prosocial behavior. Neither reinforcement nor attribution affected the generalized altruism of 5-yr-olds, only attribution affected the generalized altruism of 8-yr-olds, and both reinforcement and attribution affected the generalized altruism of 10-yr-olds. Findings are discussed in terms of the effects of reinforcement and attribution on the child's developing self-concept. (12 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
Supramolecular organized multilayers composed of glucose oxidase (GOx) and osmium-derivatized poly(allylamine) redox polymer have been self-assembled electrostatically from Os-polyelectrolyte solutions of variable pH (5.5-8.8) leading to a decrease of the linear charge density in the PAH-Os with increasing pH. The layer-by-layer enzyme multilayers were studied by ellipsometry, quartz crystal microbalance, AFM, cyclic voltammetry, and electrocatalytic oxidation of beta-D-glucose. At higher adsorption solution pH, an increase in the film thickness, enzyme loading, and redox charge was observed. While the electrocatalytic response increases with the increase of the adsorption solution pH (decrease of the polyelectrolyte linear charge), the FADH2 oxidation bimolecular rate constant has a maximum in the pH range 7.0-7.5 where a change in the film growth mechanism is observed. 相似文献
74.
Eduardo H. Diniz Erica S. Siqueira Eric van Heck 《Information Technology for Development》2019,25(1):69-91
ABSTRACTCommunity currencies are used to pay for products or services within specific groups defined by geographical boundaries or specific common interests. Financial crises, social emergence in developing countries, and increased access to digital devices have stimulated a growing number of communities worldwide to develop digital currency projects. These projects use technologies ranging from traditional plastic cards to mobile phones and blockchain technologies. Following the design science research approach, this paper analyzes digital community currencies (DCCs) by developing a taxonomy based on platform architecture, governance, transactionality and virtuality. By investigating 22 DCC platforms around the world, 4 groups were distinguished: local, proprietary, commons and cyber. The identification of these four different groups of digital community currencies allows us to better discuss the potentials and limitations of each one of them. The presented taxonomy can be useful to researchers and practitioners both to explain and to design DCC platforms. Discussing each of the emerging categories from the proposed taxonomy helps us to provide insights into DCCs, offering a new theoretical frame for investigating the particular case of digital payment platforms. 相似文献
75.
Justin D. Chaffin Sachidananda Mishra Douglas D. Kane Darren L. Bade Keara Stanislawczyk Kristen N. Slodysko Kevin W. Jones Eric M. Parker Erica L. Fox 《Journal of Great Lakes research》2019,45(2):277-289
Lake Erie western basin (WB) cyanobacterial blooms are a yearly summer occurrence; however, blooms have also been reported in the offshore waters of the central basin (CB), and very little is known about what drives these blooms or their potential for cyanobacterial toxins. Cyanobacteria Index was quantified using MODIS and MERIS data for the CB between 2003 and 2017, and water samples were collected between 2013 and 2017. The goals were to 1) quantify cyanobacteria, 2) determine environmental drivers of CB blooms, and 3) determine the potential for cyanobacterial toxins in the CB. Dolichospermum (Anabaena) occurred in the CB during July before the onset of the WB bloom, and then in August and September, the cyanobacteria community shifted towards Microcystis. The largest Dolichospermum blooms (2003, 2012, 2013, and 2015) were associated with reduced water clarity (Secchi disk depth?<?4?m), whereas large CB Microcystis blooms (2011 and 2015) were associated with large WB blooms. Dolichospermum blooms occurred in high nitrate concentrations (>20?μmol/L) and high nitrogen-to?phosphorus ratios (>100), which indicate nutrient concentrations or ratios did not select for Dolichospermum. Additionally, the sxtA gene, but not mcyE or microcystins, were detected in the CB during July 2016 and 2017. The mcyE gene and microcystins were detected in the CB during August 2016 and 2017. The results indicate the CB's potential for cyanotoxins shifts from saxitoxins to microcystins throughout the summer. Continued monitoring of cyanobacteria and multiple cyanobacterial toxins is recommended to ensure safe drinking water for CB coastal communities. 相似文献
76.
77.
We report on a hybrid chemical sensor that can perform either amperometric or conductometric detection alone or simultaneously. It consists of an array of electrode pairs in which the two electrodes in each pair are separated with micrometer to nanometer-scale gaps. The gaps are bridged with conducting polymer (polyaniline) so that one can measure the conductance of the polymer bridge like a conventional Chem-FET. The electrode geometries are designed to allow simultaneously detection of electrochemical current like a conventional microelectrode amperometric sensor. The hybrid device provides increased selectivity for detection of analytes in complex matrixes and may provide new insights into the electrochemical reaction mechanisms of analytes. As an example, we have demonstrated the detection of dilute neurotransmitter (dopamine) in the presence of its concentrated major physiological interferent, ascorbic acid, which is not possible using either the amperometric or the conductometric techniques alone. 相似文献
78.
Teixeira EC Piascik JR Stoner BR Thompson JY 《Journal of materials science. Materials in medicine》2007,18(6):1219-1224
Fracture strength and fatigue parameters of three ceramic materials submitted to dynamic fatigue were evaluated. A machinable
leucite-reinforced dental ceramic, aluminum oxide, and yttria-stabilized zirconia (YSZ) were tested. The inert strength of
the materials was determined in air (25 °C) at stressing rates of 70, 250, 400 MPa/s for Porcelain, Alumina and YSZ respectively.
The data was analyzed using a two-parameter Weibull distribution. The Weibull modulus (m) and the characteristic of fracture (σ
0) parameters were determined for each material. Specimens were also tested in 3-point bending at different stressing rates
in distilled/deionized water at 37 °C (dynamic fatigue) in order to calculate the fatigue parameters n and ln B. The strength for each material was characterized using Strength–Probability–Time (SPT) diagrams for 1 day, 1 year and 10 years.
YSZ showed a high-fracture strength σ
0 (1,459 MPa) at a failure probability of 63.2% and high resistance to subcritical crack growth. YSZ and alumina showed better
resistance to slow crack growth than porcelain, indicating less susceptibility to strength degradation by stress corrosion.
Lifetime predictions after 10 years indicate a reduction of 50%, 36% and 29% in strength for porcelain, alumina and YSZ respectively.
YSZ seems to be a very promising material for long-term dental and biomedical applications. 相似文献
79.
Pasquale Stano Tereza Pereira de Souza Paolo Carrara Emiliano Altamura Erica D’Aguanno Margherita Caputo 《先进材料力学与结构力学》2015,22(9):748-759
Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations. 相似文献
80.