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21.
The primary goal with this work is to create electrically conductive cellulose fibres, this has been done to explore possible new applications for fibre based material. This research uses various methods to create polyelectrolyte multilayers (PEMs) on bleached softwood fibres and on SiO2 model surfaces, by sequentially treating these materials with poly(3,4-ethylenedioxythiophene):poly(styrene sulphonate) (PEDOT:PSS) and poly(allyl amine) (PAH). Paper sheets were then produced from the PEM-modified pulp and evaluated in terms of tensile strength, adsorbed amount of polymer, and electrical conductivity. To evaluate the influence of fibre charge on the measured paper properties, pulps of two different initial fibre charge densities were prepared via carboxymethylation. Because of the bluish colour of PEDOT:PSS, the build-up of PEM could be easily followed, since the fibres grew increasingly darker blue throughout the modification sequence. The conductivity of the fibre network increased by 2−3 orders of magnitude when the pulp of a higher fibre charge density was used. This suggests that it is more important to create a fibrous network with a high fibre-fibre joint strength and a large total joined area in the sheet rather than to maximize the adsorbed amount of PEDOT:PSS. A difference in conductivity could also be noted depending on the polyelectrolyte adsorbed in the outer layer, PAH lowered the conductivity compared to PEDOT:PSS. Evaluating the mechanical properties revealed that the use of PEDOT:PSS reduces the tensile strength of the paper. When five double layers had been adsorbed onto the carboxymethylated sample in which PEDOT:PSS formed the outer layer, calculations indicated a 25% decrease in tensile strength compared to that of reference material without PEMs. ESEM studies indicate that PEM treatment produces a significantly changed and somewhat smoother fibre surface. 相似文献
22.
Elucidating the assembly mechanism of the collagen at interfaces is important. In this work, the structures of type I collagen molecules adsorbed on bare mica and on LB films of propanediyl-bis(dimethyloctadecylammonium bromide) transferred onto mica at zero surface pressure was characterized by AFM. On mica, the granular morphologies randomly distributed as elongated structures were observed, which were resulted from the interlacement of the adsorbed collagen molecules. On the LB films, the topographical evolution of the adsorbed collagen layers upon the increasing adsorption time was investigated. After 30 s, the collagen assembled into network-like structure composed of the interwoven fibrils, called as the first adlayer, which was attributed to its adsorption on the LB film by means of a limited number of contact points followed by the lateral association. One minute later, the second adlayer was observed on the top of the first adlayer. Up to 5 min, collagen layers, formed by inter-twisted fibrils, were observed. Under the same conditions after 1 min adsorption on LB film, the AFM image of the layer obtained in the diluted hydrochloric acid solution is analogous to the result of the sample dried in air, indicating that it is the LB film that leads to the formation of the network structure of collagen and the formation of the network structures of collagen layers is tentatively ascribed to the self-assembly of type I collagen molecules on LB film, not to the dewetting of the collagen solution during drying. 相似文献
23.
Sylvain S. Bosquain Antoine Dorcier Paul J. Dyson Mikael Erlandsson Luca Gonsalvi Gábor Laurenczy Maurizio Peruzzini 《应用有机金属化学》2007,21(11):947-951
The water‐soluble ruthenium(II) complexes [Cp′RuX(PTA)2]Y and [CpRuCl(PPh3)(mPTA)]OTf (Cp′ = Cp, Cp*, X = Cl and Y = nil; or X = MeCN and Y = PF6; PTA = 1,3,5‐triaza‐7‐phosphaadamantane; mPTA = 1‐methyl‐1,3,5‐triaza‐7‐phosphaadamantane) were used as catalyst precursors for the hydrogenation of CO2 and bicarbonate in aqueous solutions, in the absence of amines or other additives, under relatively mild conditions (100 bar H2, 30–80 °C), with moderate activities. Kinetic studies showed that the hydrogenation of HCO3? proceeds without an induction period, and that the rate strongly depends on the pH of the reaction medium. High‐pressure multinuclear NMR spectroscopy revealed that the ruthenium(II) chloride precursors are quantitatively converted into the corresponding hydrides under H2 pressure. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
24.
Rikard Wärme Lars Juhlin 《Phosphorus, sulfur, and silicon and the related elements》2013,188(12):2402-2408
Cyanuric fluoride, in solution or loaded onto a Wang resin, is successfully used as a fluorinating agent for phosphorus oxy acids. The reaction is very efficient with high yields and easy workup procedures, thereby in general generating products in quantitative yields. The cyanuric fluoride is proven suitable for micromolar scale synthesis of analytical standards, particularly in its resin-bound form. 相似文献
25.
B. Erlandsson K. Nilson A. Marcinkowski J. Piotrowski 《Zeitschrift für Physik A Hadrons and Nuclei》1979,293(1):43-51
The64Ni(p, γ)65Cu reaction has been studied in the proton energy rangeE p =2.05–2.55 MeV. The gamma-ray spectra were recorded with a three-crystal pair spectrometer at proton energy differences of 19 keV covering the proton energy range. An average gamma-ray spectrum was formed by adding all the individual spectra after proper adjustment as a result of the alterations in proton energy. The intensities of the gamma rays to final states with knownJ π-values were tested against theoretical calculations based on the Hauser-Feshbach theory. The gamma-ray strength function for energies lower than 9 MeV has been extracted from the experiment. 相似文献
26.
The50Cr(d, n)51Mn and54Fe(d, n)55Co reactions have been studied at an incident deuteron energy of 5.5 MeV. Angular distributions of neutron groups to a number of low-lying levels in the residual nuclei have been recorded. Time-of-flight techniques have been used to record neutron spectra. A liquid scintillator with pulse-shape discrimination property has been used as neutron detector. DWBA calculations have been performed and relative spectroscopic strengths determined for transitions with variousl p values. The ratios between spectroscopic strengths forl p =3 andl p =1 transitions were found to be considerably larger than corresponding ratios obtained from the (3He,d) reactions. Two-step stripping processes competing with the direct stripping process are suggested as explanation of the discrepancy between the (d, n) and the (3He,d) results. 相似文献
27.
Rikard Olofsson 《Communications in Mathematical Physics》2009,286(3):1051-1072
This paper concerns the behavior of eigenfunctions of quantized cat maps and in particular their supremum norm. We observe
that for composite integer values of N, the inverse of Planck’s constant, some of the desymmetrized eigenfunctions have very small support and hence very large
supremum norm. We also prove an entropy estimate and show that our functions satisfy equality in this estimate. In the case
when N is a prime power with even exponent we calculate the supremum norm for a large proportion of all desymmetrized eigenfunctions
and we find that for a given N there is essentially at most four different values these assume. 相似文献
28.
When solving elliptic boundary value problems using integral equation methods one may need to evaluate potentials represented by a convolution of discretized layer density sources against a kernel. Standard quadrature accelerated with a fast hierarchical method for potential field evaluation gives accurate results far away from the sources. Close to the sources this is not so. Cancellation and nearly singular kernels may cause serious degradation. This paper presents a new scheme based on a mix of composite polynomial quadrature, layer density interpolation, kernel approximation, rational quadrature, high polynomial order corrected interpolation and differentiation, temporary panel mergers and splits, and a particular implementation of the GMRES solver. Criteria for which mix is fastest and most accurate in various situations are also supplied. The paper focuses on the solution of the Dirichlet problem for Laplace’s equation in the plane. In a series of examples we demonstrate the efficiency of the new scheme for interior domains and domains exterior to up to 2000 close-to-touching contours. Densities are computed and potentials are evaluated, rapidly and accurate to almost machine precision, at points that lie arbitrarily close to the boundaries. 相似文献
29.
30.
A facile one-pot synthesis providing vicinal diols and 1,3-diols in >95% stereoisomeric purity from commercially available enantiopure hydroxy esters has been developed. The esters were reduced with DIBALH and alkylated in situ with 4-pentenylmagnesium bromide, which after workup generated the title diols as diastereomeric pairs. These pairs were easily separated by preparative chromatography, affording products with retained stereoisomeric purity from the starting materials. This method represents an expedient preparation of many common natural products, such as cerambycid beetle pheromones and intermediates towards bicyclic acetal bark beetle pheromones. 相似文献