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排序方式: 共有163条查询结果,搜索用时 31 毫秒
31.
High and low molecular weight (Mw) carboxymethyl celluloses (CMC) were adsorbed on a well-characterized fiber substrate (long fibers of a commercial bleached birch kraft pulp with the carboxylic acid groups in Na-form) to increase the charge of the fibers in a controlled fashion. The Mw played a role in the utilization of CMCs as a strength additive in paper sheets nearly doubling the tensile strength with the high Mw CMC. Swelling properties of the CMC treated fibers were measured with water retention value (WRV). The WRV increased more with the high Mw CMC. The swelling was further tuned by two highly cationic polyelectrolytes; high Mw poly(diallyldimethyl ammonium chloride) (PDADMAC) and low Mw polybrene (hexadimethrine bromide, [3,6]-ionene). They were chosen because of their known ability to neutralize the anionic charge either exclusively on the surface or in the whole fiber, respectively. Adsorption of PDADMAC could reduce WRV of the CMC pre-treated fibers to the level of the untreated reference, while polybrene adsorbed pulps with 3–10 times more cationic polyelectrolyte deswelled the fibers only slightly more than the surface neutralized fibers. These results indicated surface conformation differences with low and high Mw CMCs. While the conformation did play a role after physical alteration (drying and rewetting) of the fibers, the paper sheets produced from these fibers showed remarkable differences. In extreme cases, the strength of the paper could be retained after drying (low Mw CMC + PDADMAC) or paper, resistant to disintegration, could be achieved (CMC + polybrene). 相似文献
32.
Niko Guskos Spiros Glenis Janusz Typek Grzegorz Zolnierkiewicz Pawel Berczynski Kamil Wardal Aleksander Guskos Daniel Sibera Dariusz Moszyński Witold Lojkowski Urszula Narkiewicz 《Central European Journal of Physics》2012,10(2):470-477
Fine particles of ZnFe2O4 were synthesized by a wet chemical method in the (80 wt.% Fe2O3 + 20 wt.% ZnO) system. The morphological and structural properties of the mixed system were investigated by scanning electron microscopy, X-ray diffraction, inductively coupled plasma atomic emission, and X-ray photoelectron spectroscopy. The major phase was determined to be the ZnFe2O4 spinel with particle size of 11 nm. The magnetic properties of the material were investigated by ferromagnetic resonance (FMR) in the temperature range from liquid helium to room temperature. A very intense, asymmetric FMR signal from ZnFe2O4 nanoparticles was recorded, which has been analyzed in terms of two Callen-lineshape lines. Temperature dependence of the FMR parameters was obtained from fitting the experimental lines with two component lines. Analysis of the FMR spectra in terms of two separate components indicates the presence of strongly anisotropic magnetic interactions. 相似文献
33.
Artem Plyusnin Jingwei He Cindy Elschner Miho Nakamura Julia Kulkova Axel Spickenheuer Christina Scheffler Lippo V. J. Lassila Niko Moritz 《Molecules (Basel, Switzerland)》2021,26(5)
The use of bioresorbable fracture fixation plates made of aliphatic polyesters have good potential due to good biocompatibility, reduced risk of stress-shielding, and eliminated need for plate removal. However, polyesters are ductile, and their handling properties are limited. We suggested an alternative, PLAMA (PolyLActide functionalized with diMethAcrylate), for the use as the matrix phase for the novel concept of the in situ curable bioresorbable load-bearing composite plate to reduce the limitations of conventional polyesters. The purpose was to obtain a preliminary understanding of the chemical and physical properties and the biological safety of PLAMA from the prospective of the novel concept. Modifications with different molecular masses (PLAMA-500 and PLAMA-1000) were synthesized. The efficiency of curing was assessed by the degree of convergence (DC). The mechanical properties were obtained by tensile test and thermomechanical analysis. The bioresorbability was investigated by immersion in simulated body fluid. The biocompatibility was studied in cell morphology and viability tests. PLAMA-500 showed better DC and mechanical properties, and slower bioresorbability than PLAMA-1000. Both did not prevent proliferation and normal morphological development of cells. We concluded that PLAMA-500 has potential for the use as the matrix material for bioresorbable load-bearing composite fracture fixation plates. 相似文献
34.
Niko Naumann 《Comptes Rendus Mathematique》2003,336(4):289-292
R. Pellikaan (Arithmetic, Geometry and Coding Theory, Vol. 4, Walter de Gruyter, Berlin, 1996, pp. 175–184) introduced a two variable zeta-function Z(t,u) for a curve over a finite field which, for u=q, specializes to the usual zeta-function and he proved rationality: Z(t,u)=(1?t)?1(1?ut)?1P(t,u) with . We prove that P(t,u) is absolutely irreducible. This is motivated by a question of J. Lagarias and E. Rains about an analogous two variable zeta-function for number fields. To cite this article: N. Naumann, C. R. Acad. Sci. Paris, Ser. I 336 (2003). 相似文献
35.
Niko Ernsting 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》1994,106(5):608-609
36.
Phillips ST Piersanti G Rüth M Gubernator N van Lengerich B Bartlett PA 《Organic letters》2004,6(24):4483-4485
The synthesis of @-tide beta-strand peptidomimetics has been improved such that oligomers now can be obtained from solution- and solid-phase synthesis protocols approaching the efficiency and flexibility of peptide chemistry. These methods enable the synthesis of @-tide oligomers with a variety of amino acids and with lengths up to 13 units. [reaction: see text] 相似文献
37.
Dual Effect of Manganese Oxide Micromotors: Catalytic Degradation and Adsorptive Bubble Separation of Organic Pollutants 下载免费PDF全文
Owies M. Wani Muhammad Safdar Dr. Niko Kinnunen Prof. Janne Jänis 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(4):1244-1247
Manganese oxide (MnO2) based micromotors exhibiting a dual effect, that is, catalytic degradation and adsorptive bubble separation, were employed for water remediation. The dual effect of MnO2 microparticles led to a greater than 90 % of decolorization of non‐biodegradable organic dyes in just 1 h, without the need for external agitation or bubble generation. These findings suggest high potential of MnO2 micromotors for decontamination of organic pollutants from wastewaters or natural water reserves. 相似文献
38.
Based on the order parameter expansion, we present an approximate method which allows us to reduce large systems of coupled differential equations with diverse parameters to three equations: one for the global, mean field, variable and two which describe the fluctuations around this mean value. The method is based on a systematic perturbation expansion and can be applied around the vicinity of the homogeneous state. With this tool we analyze phase transitions induced by microscopic disorder in three prototypical models of phase transitions which have been studied previously in the presence of thermal noise. We study how macroscopic order is induced or destroyed by time-independent local disorder and analyze the limits of the approximation by comparing the results with the numerical solutions of the self-consistency equation which arises from the property of self-averaging. Finally, we carry on a finite-size analysis of the numerical results and calculate the corresponding critical exponents. 相似文献
39.
Ultrasonic studies of the group of halogens of benzene and particularly dependence of acoustic parameters on the structure of organic liquids, demonstrate some interesting regularities in the group of these compounds in gas and liquid states. In this paper results for five cyclic liquids: bromo-, chloro-, fluoro- and jodobenzene are discussed and compared to benzene. Vibrational relaxation was observed in all the compounds. The studies reported here as well as other experimental for great number of compounds support the conclusion that almost all vibrational relaxation processes in liquids can be described using a single relaxation time. It also seems that all vibrational degrees of freedom of the molecule take part in this vibrational process. It seems that differences in transition probabilities between molecules studied could be caused by additional attraction between of molecules having a significant dipole moments. 相似文献
40.