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71.
Gerhard Jany Timo Repo Marina Gustafsson Martti Klinga Adnan S. Abu‐Surrah Markku Leskel 《无机化学与普通化学杂志》2000,626(9):1897-1900
The synthesis and characterization of the unsymmetric hafnium dialkyl [1‐(η5‐9‐fluorenyl)‐2‐(η5‐1‐indenyl)ethane]HfCl2 ( 2 ) and corresponding dimethyl complex [1‐(η5‐9‐fluorenyl)‐2‐(η5‐1‐indenyl)ethane]Hf(CH3)2 ( 3 ) is described. The dialkyl hafnocene ( 3 ) crystallizes in monoclinic space group P21/c (No. 14) with a = 9.458(8), b = 8.541(8), c = 23.733(11) Å, β = 93.16(5) deg., V = 1914(3) Å3, Z = 4. Further on, complex 3 was activated with methylaluminiumoxane (MAO) and utilized as a catalyst in ethene polymerization. 相似文献
72.
Husu H Mäkitalo J Siikanen R Genty G Pietarinen H Lehtolahti J Laukkanen J Kuittinen M Kauranen M 《Optics letters》2011,36(12):2375-2377
We introduce a concept to control the spectral and dichroic properties of metamaterials. The approach is based on anisotropic metal nanoparticles and on varying their mutual orientation in a periodic lattice. Even seemingly inconsequential changes in particle ordering strongly modify the dichroic properties of the arrays and result in either very narrow resonances or ultrabroad extinction ranges. The results arise from long-range diffractive coupling between the particles, as determined by the dependence of the array unit cell size on particle ordering. 相似文献
73.
Milena Stepien Jarkko J. SaarinenHannu Teisala Mikko TuominenMikko Aromaa Jurkka KuusipaloJyrki M. Mäkelä Martti Toivakka 《Applied Surface Science》2011,257(6):1911-1917
Liquid flame spray process (LFS) was used for depositing TiOx and SiOx nanoparticles on paperboard to control wetting properties of the surface. By the LFS process it is possible to create either superhydrophobic or superhydrophilic surfaces. Changes in the wettability are related to structural properties of the surface, which were characterized using scanning electron microscope (SEM) and atomic force microscope (AFM). The surface properties can be ascribed as a correlation between wetting properties of the paperboard and the surface texture created by nanoparticles. Surfaces can be produced inline in a one step roll-to-roll process without need for additional modifications. Furthermore, functional surfaces with adjustable hydrophilicity or hydrophobicity can be fabricated simply by choosing appropriate liquid precursors. 相似文献
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76.
Vinay Kumar Roger Bollström Arthas Yang Qingxia Chen Gang Chen Pekka Salminen Douglas Bousfield Martti Toivakka 《Cellulose (London, England)》2014,21(5):3443-3456
Nanocellulose is an interesting building block for functional materials and has gained considerable interest due to its mechanical robustness, large surface area and biodegradability. It can be formed into various structures such as solids, films and gels such as hydrogels and aerogels and combined with polymers or other materials to form composites. Mechanical, optical and barrier properties of nanofibrillated cellulose (NFC) and microfibrillated cellulose (MFC) films were studied in order to understand their potential for packaging and functional printing applications. Impact of raw material choice and nanocellulose production process on these properties was evaluated. MFC and NFC were produced following two different routes. NFC was produced using a chemical pretreatment followed by a high pressure homogenization, whereas MFC was produced using a mechanical treatment only. TEMPO-mediated oxidation followed by one step of high pressure (2,000 bar) homogenization seems to produce a similar type of NFC from both hardwood and softwood. NFC films showed superior mechanical and optical properties compared with MFC films; however, MFC films demonstrated better barrier properties against oxygen and water vapor. Both the MFC and NFC films were excellent barriers against mineral oil used in ordinary printing inks and dichlorobenzene, a common solvent used in functional printing inks. Barrier properties against vegetable oil were also found to be exceptionally good for both the NFC and MFC films. 相似文献
77.
Valtonen M.J. Byrd G.G. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1990,18(1):38-42
Computer simulations of interacting galaxies are used to determine the contribution of halos in disk galaxies. It appears that generally the halo is less massive than the disk. Redshift asymmetries are used to separate binary pairs from optical pairs in catalogs of galaxy pairs. It is found that true binary pairs give a rather low mass for the components. Redshift asymmetries also indicate that groups of galaxies are ill-suited for mass determination, either because they are in an unknown state of expansion or because they are not gravitationally bound at all. It is argued that so-called cluster missing mass cannot exist for dynamical reasons, and the high-velocity dispersion of member galaxies is more likely to indicate incomplete virialization than a high mass. The commonly quoted density parameter value Ω≅0.2 appears to be definitely too high, at least in scales less than 10 Mpc 相似文献
78.
A nonreciprocal and nonsymmetric transmission line is one which has different line parameters for waves propagating in opposite directions. Such a concept emerges in problems of electromagnetic wave propagation in layered structures of biisotropic (nonreciprocal chiral) media. It is shown that the well-known transmission-line formulas can be generalized for the present transmission line 相似文献
79.
Louhivuori M Otten R Lindorff-Larsen K Annila A 《Journal of the American Chemical Society》2006,128(13):4371-4376
The discovery of dilute liquid crystalline media to align biological macromolecules has opened many new possibilities to study protein and nucleic acid structures by NMR spectroscopy. We inspect the basic alignment phenomenon for an ensemble of protein conformations to deduce relative contributions of each member to the residual dipolar coupling signals. We find that molecular fluctuations can affect the alignment and discover a resulting emphasis of certain conformations. However, the internal fluctuations are largely uncorrelated with those of the alignment, implying that proteins have liquidlike molecular surfaces. Furthermore, we consider the implications of a dynamic bias to structure determination using data from the weak alignment method. 相似文献
80.
Kolehmainen V Vanne A Siltanen S Järvenpää S Kaipio JP Lassas M Kalke M 《IEEE transactions on medical imaging》2006,25(2):218-228
Diagnostic and operational tasks based on dental radiology often require three-dimensional (3-D) information that is not available in a single X-ray projection image. Comprehensive 3-D information about tissues can be obtained by computerized tomography (CT) imaging. However, in dental imaging a conventional CT scan may not be available or practical because of high radiation dose, low-resolution or the cost of the CT scanner equipment. In this paper, we consider a novel type of 3-D imaging modality for dental radiology. We consider situations in which projection images of the teeth are taken from a few sparsely distributed projection directions using the dentist's regular (digital) X-ray equipment and the 3-D X-ray attenuation function is reconstructed. A complication in these experiments is that the reconstruction of the 3-D structure based on a few projection images becomes an ill-posed inverse problem. Bayesian inversion is a well suited framework for reconstruction from such incomplete data. In Bayesian inversion, the ill-posed reconstruction problem is formulated in a well-posed probabilistic form in which a priori information is used to compensate for the incomplete information of the projection data. In this paper we propose a Bayesian method for 3-D reconstruction in dental radiology. The method is partially based on Kolehmainen et al. 2003. The prior model for dental structures consist of a weighted /spl lscr//sup 1/ and total variation (TV)-prior together with the positivity prior. The inverse problem is stated as finding the maximum a posteriori (MAP) estimate. To make the 3-D reconstruction computationally feasible, a parallelized version of an optimization algorithm is implemented for a Beowulf cluster computer. The method is tested with projection data from dental specimens and patient data. Tomosynthetic reconstructions are given as reference for the proposed method. 相似文献