排序方式: 共有44条查询结果,搜索用时 15 毫秒
1.
Eero Immonen 《Journal of Mathematical Analysis and Applications》2004,300(1):79-101
In this article, we study the effect of the chosen representation of a point value (and point evaluation) on the class of periodic signals realizable using a certain type of infinite-dimensional linear system. By suitably representing the point evaluation at the origin in a Hilbert space, we are able to give a complete characterization of its extensions. These extensions involve a new concept called δ-sequence, the use of which as an observation operator of an infinite-dimensional linear system is studied in this article. In particular, we consider their use in the realization of periodic signals. We also investigate how the use of δ-sequences affects the convergence properties of such realizations; we consider the rate and character of convergence and the removal of the Gibbs phenomenon. As still a further demonstration of the significance of the chosen concept of a point value, we discuss the use of distributional point values in the realization of periodic distributions. The possible applications of this work lie in regulator problems of infinite-dimensional control theory, as is indicated by the well-known internal model principle. 相似文献
2.
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
3.
Tiia‐Riikka Tero Dr. Kirsi Salorinne Dr. Heli Lehtivuori Prof. Janne A. Ihalainen Prof. Maija Nissinen 《化学:亚洲杂志》2014,9(7):1860-1867
An unexpected and previously unknown resorcinarene mono‐crown with a fused benzofuran moiety in its macrocyclic core was obtained as a byproduct from a bridging reaction of tetramethoxy resorcinarene with tetraethylene glycol ditosylate. The formation of the fused benzofuran moiety in the resorcinarene macrocycle resulted in a unique rigid and puckered boat conformation, as shown by XRD studies in the solid state. Modification of the macrocycle was also observed to affect the photophysical properties in solution by enhancing the fluorescence brightness compared with a conventional resorcinarene macrocycle. The fluorescent properties enabled unique detection of structural features, that is, the rigid boat conformation with the conjugated benzofuran system and the more flexible crown bridge part, in solution. 相似文献
4.
Applying human and pig hepatic in vitro experiments for sulfur mustard study: Screening and identification of metabolites by liquid chromatography/tandem mass spectrometry 下载免费PDF全文
5.
Heiskanen JP Omar WA Ylikunnari MK Haavisto KM Juan MJ Hormi OE 《The Journal of organic chemistry》2007,72(3):920-922
Quinolines with a hydroxyl group at the 8-position and an alkoxy group at the 4-position are rare compounds. In this paper the synthesis of five 4-alkoxy-8-hydroxyquinolines is reported. The key reaction in the synthetic route is a selective protection of the hydroxyl group at C-atom 8 in 4,8-dihydroxyquinoline with a tosyl group and the hydrolytic removal of the protective group after the alkylation. The tosyl group is stable during the alkylations with various alkylating agents in the presence of sodium hydride. 相似文献
6.
7.
Harju K Vahermo M Mutikainen I Yli-Kauhaluoma J 《Journal of combinatorial chemistry》2003,5(6):826-833
The solid-phase synthesis of 1,2,3-triazoles via 1,3-dipolar cycloaddition of polymer-bound azides to various alkynes is reported. Polymer-bound azides were synthesized from polymer-bound halides and sodium azide and reacted with alkynes to produce polymer-bound 1,2,3-triazoles. Cleavage of the triazoles was performed with trifluoroacetic acid. A traceless synthesis of 1,2,3-triazoles was developed using 2-methoxy-substituted resin (polymer-bound 4-hydroxy-2-methoxybenzyl alcohol). In addition, a synthesis of 4-hydroxybenzyl-substituted 1,2,3-triazoles from the bromo-Wang resin (4-(bromomethyl)phenoxymethyl polystyrene) was achieved. 相似文献
8.
Harju K Kylänlahti I Paananen T Polamo M Nielsen J Yli-Kauhaluoma J 《Journal of combinatorial chemistry》2006,8(3):344-349
Study was made of the 1,3-dipolar cycloaddition of polymer-bound alkynes to azomethine imines generated in situ from N-aminopyridine iodides. Aromatization of the cycloadducts gives polymer-bound pyrazolopyridines that can be released from the resin as carboxylic acids with trifluoroacetic acid or as methyl esters with sodium methoxide. 相似文献
9.
Carp (Cyprinus carpio) were repeatedly exposed to 0, 60, 120 and 240 mJ/cm2 ultraviolet B (UVB) radiation three times in 1 week (short-term exposure) or 12 times in 4 weeks (long-term exposure). The effect of UVB on the functioning of the carp immune system was studied on day 2 after the final irradiation. After short-term UVB exposure, the whole-blood respiratory burst and cytotoxic activity were markedly enhanced, with parallel responses in both the number of circulating granulocytes and in the plasma cortisol concentration of the fish. These changes were not detectable after long-term exposure. The respiratory burst by head kidney granulocytes was suppressed dose dependently after both exposures, but cytotoxic activity was not affected. Exposure to UVB also modulated lymphocyte functions: nonstimulated and PHA-stimulated proliferation of head kidney lymphocytes in vitro was enhanced by both short-term and long-term exposure. LPS-stimulated proliferation was not affected by exposure nor was the number of immunoglobulin-secreting cells in the head kidney. In long-term exposure, the highest dose reduced the level of plasma IgM. This study indicates that UVB irradiation induces immunomodulation in the blood and head kidney of the carp and that the effects of short- and long-term exposure differ from each other. The results emphasize the potentially harmful impact of increased solar UVB radiation on fish immune functions. 相似文献
10.
Sebastian Kröner Kirsi Eloranta Michiel F. Bergstra Michael Bartke 《Macromolecular Symposia》2007,259(1):284-294
Summary: The kinetic behaviour of a supported metallocene catalyst in slurry polymerisation of ethylene with 1-hexene under industrially relevant reaction conditions has been studied. Polymerisation experiments were carried out in a 5-litre stirred tank reactor in a temperature range from 60 to 80 °C and ethylene partial pressures from 5 to 15 bar. Comonomer and hydrogen amounts were varied as well. The catalyst showed pronounced activation and slow deactivation during runtimes of about 1 hour. Strong influences of 1-hexene (“hexene effect”) and hydrogen (“hydrogen effect”) on the activity profiles were observed. Based on the experimental results, a kinetic model has been derived in order to describe and predict important polymerisation data such as activity profile, comonomer content and molecular weight distributions with respect to the reaction conditions. The presented kinetic model is able to describe the observed effects of 1-hexene and hydrogen on the activity profiles, as well as the comonomer incorporation across a broad range of polymerisation conditions. The molecular weight distributions can be simulated with good qualitative agreement to the experimental data. 相似文献