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991.
Guan Y Zakrevskyy Y Stumpe J Antonietti M Faul CF 《Chemical communications (Cambridge, England)》2003,(7):894-895
In this communication we present the facile preparation and characterisation of thermotropic liquid-crystalline materials from the ionic self-assembly of a charged perylenediimide derivative and oppositely charged surfactants. 相似文献
992.
Enantioselective molecularly imprinted polymers (MIPs) have been synthesised via ROMP for the first time. 相似文献
993.
994.
A method for ytterbium determination in animal faeces by tungsten coil electrothermal atomic absorption spectrometry (TCAAS) was developed. Faeces were dry-ashed in a muffle furnace, the ashes were treated with hydrochloric acid, and 10 mul of sample solution were delivered into 150-W tungsten coil atomizer. A matrix-matching procedure employing a 66-s heating program proved to be efficient for obtaining accurate results. Characteristic mass and detection limit were 7.1 pg and 0.35 mug g(-1) Yb, respectively. The tungsten coil atomizer lifetime exceeded 300 firings with digested solutions and R.S.D. of measurements was 1.9% after ten consecutive injections of 10.0 mug l(-1) Yb. Accuracy of the proposed method was assessed by employing a graphite furnace atomic absorption spectrometric procedure. Application of the paired t-test did not reveal any significant difference for ytterbium contents determined by both methods at 95% confidence level. It was demonstrated that the proposed procedure can successfully be used for evaluation of kinetic passage rate of feed through digestive tract of animals. 相似文献
995.
Stable tungsten oxide coating sols suitable for electrochromic applications were prepared by a modified peroxotungstic acid route. Layers up to 250 nm thickness could be deposited on ITO-coated and/or FTO-coated glass substrates in a single dip-coating process. Optoelectrochemical measurements were employed to determine the variation of the electrochromic properties (change in optical density (OD) and switching times) of WO3-layers, investigated as a function of coating parameters, such as chamber humidity and the temperature of heat treatment. High resolution transmission electron microscopy (HR-TEM) has shown that the optimized layers possess a partially crystalline morphology with nanocrystalline regions 2–3 nm in size. 相似文献
996.
997.
998.
The impurity distribution inside crystalline layers in static layer crystallizations was explored theoretically and experimentally for a binary eutectic mixture of caprolactam and water. The impurity distribution in the layer is modeled by a mass balance equation coupled with an energy balance equation. The mass balance equation is established with a combination of the growth of the layer and the diffusional movement of impurity. The mathematical model was solved by a numerical method. The predictions are discussed with respect to the interfacial distribution coefficient, concentration, and temperature at the solid-liquid interface, crystalline layer thickness, and concentration of the layer. The impurity distribution obtained by the model was appropriately verified with the results obtained by the experiments. 相似文献
999.
L. Harju Jan-Olof Lill Kjell-Erik Saarela Sven-Johan Heselius Fredrik Joachim Hernberg Alf Lindroos 《Analytical and bioanalytical chemistry》1997,358(4):523-528
Thick-target Particle Induced X-ray Emission (TTPIXE) was used for the quantitative determination of trace-element concentrations
in trunk wood. The wood samples were preconcentrated by dry ashing to improve the reliability of the sampling and the sensitivity
of the analytical method. Samples of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) were collected from a polluted area (Harjavalta) as well as from a relatively nonpolluted area (Merimasku) in southwestern
Finland. The elements studied were P, S, K, Ca, Mn, Fe, Ni, Cu, Pb, Rb, Sr, Ba, Cd and Ag. TTPIXE combined with dry ashing
is a sensitive and reliable analytical technique for most elements studied. The method was validified by using several certified
reference materials and also by ICP-MS analysis. Due to the low ash content (0.2–0.4%) in wood a high preconcentration factor
can be obtained. Differences in trace-element uptake were observed between the two tree species studied. Trunk wood from the
polluted area contained higher concentrations of heavy metal ions.
Received: 30 August 1996 / Revised: 11 October 1996 / Accepted: 3 November 1996 相似文献
1000.
Joachim Schummer 《Foundations of Chemistry》2006,8(1):53-72
According to ‘standard histories’ of nanotechnology, the colorful pictures of atoms produced by scanning probe microscopists since the 1980s essentially inspired visions of molecular nanotechnology. In this paper, I provide an entirely different account that, nonetheless, refers to aesthetic inspiration, First, I argue that the basic idea of molecular nanotechnology, i.e., producing molecular devices, has been the goal of supramolecular chemistry that emerged earlier, without being called nanotechnology. Secondly, I argue that in supramolecular chemistry the production of molecular devices was inspired by an aesthetic phenomenon of gestalt switch, by certain images that referred to both molecules and ordinary objects, and thus symbolically bridged the two worlds. This opened up a new way of perceiving and drawing molecular images and new approaches to chemical synthesis. Employing Umberto Eco’s semiotic theory of aesthetics, I analyze the gestalt switch and the inspiration to build molecular devices and to develop a new sign language for supramolecular chemistry. More generally, I argue that aesthetic phenomena can play an important role in directing scientific research and that aesthetic theories can help understand such dynamics, such that they need to be considered in philosophy of science. 相似文献