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1.
Pirita Rämänen Paavo A. Penttilä Kirsi Svedström Sirkka Liisa Maunu Ritva Serimaa 《Cellulose (London, England)》2012,19(3):901-912
Cellulose whiskers were prepared from wood- and cotton-based microcrystalline cellulose and dried by two methods: freeze-drying
or air-drying. The effect of drying method on the properties and structure of the whiskers were studied. Furthermore, the
influence of the source of cellulose on the nanoscale structure was investigated. Drying method was observed to slightly influence
the thermal stability of cellulose whiskers, whereas the char residue varied significantly depending on the drying process
performed. Small- and wide-angle X-ray scattering and solid state nuclear magnetic resonance spectroscopy were used to examine
the crystallinity and nanoscale structure of the dried whiskers. It was observed that the crystal structure and crystallinity
of cellulose whiskers remained during all treatments, whereas their nanoscale structure was significantly influenced by drying
method, neutralization, and source of cellulose. Relationships between thermal behavior and nanoscale structure were reported
and discussed. 相似文献
2.
The aim of this article is to consider the hyperbolic version of the standard Clifford analysis. The need for such a modification
arises when one wants to make sure that the power function x
m is included. The leading idea is that the power function is the conjugate gradient of a harmonic function, defined with respect
to the hyperbolic metric of the upper half space. In this paper we give a new approach to this hyperbolic function theory
and survey some of its results. 相似文献
3.
Minimal positive operators on a Hilbert spaceH are characterized in terms of so-called parallel addition of operators. It is also shown how these operators can be used to reproduce the inverse, respectively generalized inverse, of any positive operator onH. 相似文献
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5.
Sirkka-Liisa Eriksson Marko Kotilainen Visa Latvala 《Advances in Applied Clifford Algebras》2007,17(3):425-436
Harmonic functions with respect to the Poincare metric on the unit ball are called hyperbolic harmonic functions. We establish
the weak formulation of hyperbolic harmonic functions and use it in the study of hyperbolic harmonic function spaces. In particular,
we give the Carleson measure characterization for the whole spectrum of spaces, whose analytic counterparts include among
else Bloch spaces, Bergman-spaces, Besov-spaces, and Qp-spaces.
The second author was supported by the Finnish Cultural Foundation. 相似文献
6.
A new Cauchy-type formula for hypermonogenic functions is derived. Hypermonogenic functions, introduced in [6], are a generalization
of holomorphic functions to several dimensions. The power function xm is hypermonogenic.
This paper is dedicated to the memory of our friend and colleague Jarolim Bureš 相似文献
7.
Tiina Liitiä Sirkka Liisa Maunu Bo Hortling Tarja Tamminen Osmo Pekkala Antero Varhimo 《Cellulose (London, England)》2003,10(4):307-316
Solid-state 13C NMR spectroscopy was used to determine the degree of cellulose crystallinity (CrI) in kraft, flow-through kraft and polysulphide–anthraquinone (PS–AQ) pulps of pine and birch containing various amounts of hemicelluloses. The applicability of acid hydrolysis and the purely spectroscopic proton spin-relaxation based spectral edition (PSRE) method to remove the interfering hemicellulose signals prior to the determination of CrI were also compared. For softwood pulps, the spectroscopic removal of hemicelluloses by PSRE was found to be more efficient than the removal of hemicelluloses by acid hydrolysis. In addition to that, the PSRE method also provides information on the associations between cellulose and hemicelluloses. On the basis of the incomplete removal of xylan from the cellulose subspectra by PSRE, the deposition of xylan on cellulose fibrils and therefore an ordered ultrastructure of xylan in birch pulps was suggested. The ordered structure of xylan in birch pulps was also supported by the observed change of xylan conformation after regeneration. Similarly, glucomannan in pine pulps may have an ordered structure. According to the 13C CPMAS measurements conducted after acid hydrolysis, the degree of cellulose crystallinity was found to be slightly lower in birch pulps than in the pine pulps. Any significant differences in cellulose crystallinity were not found between the pulps obtained by the various pulping methods. Only in pine PS–AQ pulp, the degree of cellulose crystallinity may be slightly lower than in the kraft pulps containing less hemicelluloses. 相似文献
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9.
Miia Hiltunen Joonas Siirilä Sirkka Liisa Maunu 《Journal of polymer science. Part A, Polymer chemistry》2012,50(15):3067-3076
Various copper‐based catalyst systems and reaction conditions were studied in the graft copolymerization of N,N‐dimethylacrylamide (DMAam) with a cellulose‐based macroinitiator by controlled radical polymerization. The cellulose macroinitiator with degree of substitution DS = 0.44 was synthesized from dissolving softwood pulp in a LiCl/DMAc solution. The graft copolymerizations of DMAam, using the cellulose macroinitiator and various copper‐based catalyst systems, were then carried out in DMSO solutions. The copolymerization kinetics was followed by 1H NMR. Water‐soluble cellulose‐g‐PDMAam copolymers were comprehensively characterized by ATR‐FTIR and 1H NMR spectroscopies and SEC analyses. DLS and steady‐shear viscosity measurements revealed that when the DPgraft of the cellulose‐g‐PDMAam copolymer is high enough, the copolymer forms a more compact structure in water. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 相似文献
10.
In this paper we study the solutions of the equation $$\Delta w- \frac{\alpha}{y}\partial_{y}w = 0,$$ where w is a complex valued function. This equation is related to the generalized axially symmetric potential theory which has been studied notably by Weinstein, see [12]. We have researched this equation earlier in higher dimensions in connection with the hyperbolic function theory. In this paper will see how this equation is related to the generalized analytic functions in the hyperbolic upper half-plane. We also study harmonic differential forms in the hyperbolic plane and using these we obtain special type of solutions for the preceding equation. 相似文献