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141.
The production of nanoparticles via femtosecond laser ablation of gold and copper is investigated experimentally involving measurements of the ablated mass, plasma diagnostics, and analysis of the nanoparticle size distribution. The targets were irradiated under vacuum with a spot of uniform energy distribution. Only a few laser pulses were applied to each irradiation site to make sure that the plume expansion dynamics were not altered by the depth of the laser-produced crater. Under these conditions, the size distribution of nanoparticles does not exhibit a maximum and the particle abundance monotonously decreases with size. Furthermore, the results indicate that two populations of nanoparticles exist within the plume: small clusters that are more abundant in the fast frontal plume component and larger particles that are located mostly at the back. It is shown that the ablation efficiency is strongly related to the presence of nanoparticles in the plume. 相似文献
142.
Tatiana B. Mikenas Vladimir A. Zakharov Lyudmila G. Echevskaya Michail A. Matsko 《Journal of polymer science. Part A, Polymer chemistry》2005,43(10):2128-2133
Data on ethylene polymerization over supported LFeCl2/MgCl2 catalysts {L = 2,6‐bis[1‐(2,6‐dimethylphenylimino)ethyl]pyridyl} containing AlR3 (R = Me, Et, i‐Bu, or n‐Oct) as an activator are presented. These catalysts are highly active (100–300 kg of polyethylene/g of Fe h bar of C2H4) and stable in ethylene polymerization at 70–80 °C. Data on the effects of the iron content, AlR3 type, Al(i‐Bu)3 concentration, and hydrogen presence on the catalyst activity are presented. The molecular structure of polyethylene produced with these catalysts (including the molecular masses, molecular mass distribution, branching, and number of C?C bonds) has been studied; data on the effects of AlR3 and hydrogen on the molecular structure are presented. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2128–2133, 2005 相似文献
143.
Cr. Simionescu Tatiana Lixandru Lucia Tǎtaru I. Mazilu I. Cocîrlǎ 《Journal of organometallic chemistry》1975,102(2):219-226
The synthesis and thermal polymerization of a new chloroformylated vinyl derivative containing a ferrocenyl residue are reported.The reactivity of α-chloro-β-formyl-p-ferrocenylstyrene in the polymerization reaction is discussed in the light of the experiment results and data obtained from molecular orbital calculations using the Hückel approximation. 相似文献
144.
145.
Samuel Braverman Tatiana Pechenick Hugo E. Gottlieb Milon Sprecher 《Tetrahedron letters》2004,45(44):8235-8238
The first successful preparation of propargylic and allylic chloroalkoxy disulfides in high yields is reported. Facile 1,4-electrophilic addition of these to 2,3-dimethyl-1,3-butadiene, followed by [2,3]-sigmatropic rearrangements affords mixed allyl allenic and bis-allylic thiosulfinates, respectively. Due to their similarity to allicin, the latter are of potential biological interest. 相似文献
146.
147.
New polyazines were synthesized by the polycondensation of hydrazine with acenaphthenequinone, 5-chloroacenaphthenequinone, 5-nitroacenaphthenequinone and 5,6-dinitroacenaphthenequinone. The influences of the catalyst and quinone/hydrazine mole ratio on the yield of soluble and insoluble compounds, as well as on the viscosity of a solution of the polymer in DMF, were studied. Some electrophysical properties as well as the polyazine behaviour under heating were also studied by thermogravimetrical analysis. 相似文献
148.
Zimnitsky DS Yurkshtovich TL Bychkovsky PM 《Journal of colloid and interface science》2005,285(2):502-508
The adsorption of amino acids (AA) (glycine, L-alanine, L-proline) on oxidized cellulose (OC) with various carboxyl contents and degrees of crystallinity from aqueous and water/ethanol solutions was studied. It was found that multilayer adsorption occurs in concentrated solutions of AA. It proceeds according to successive mechanisms via adsorption of AA zwitterions onto carboxyls of already adsorbed AA. This leads to formation of chain AA associates in the OC phase. A sharp increase in swelling accompanies multilayer adsorption. It was established that structural characteristics and degree of polymerization of OC are the main factors that affect multilayer adsorption. The distribution of carboxyls in the OC phase also plays an important role. Multilayer adsorption does not proceed in water/ethanol solutions and in the case of the cationic form of AA. 相似文献
149.
For κ ⩾ 0 and r0 > 0 let ℳ(n, κ, r0) be the set of all connected, compact n-dimensional Riemannian manifolds (Mn, g) with Ricci (M, g) ⩾ −(n−1) κ g and Inj (M) ⩾ r0. We study the relation between the kth eigenvalue λk(M) of the Laplacian associated to (Mn,g), Δ = −div(grad), and the kth eigenvalue λk(X) of a combinatorial Laplacian associated to a discretization X of M. We show that there exist constants c, C > 0 (depending only on n, κ and r0) such that for all M ∈ ℳ(n, κ, r0) and X a discretization of
for all k < |X|. Then, we obtain the same kind of result for two compact manifolds M and N ∈ ℳ(n, κ, r0) such that the Gromov–Hausdorff distance between M and N is smaller than some η > 0. We show that there exist constants c, C > 0 depending on η, n, κ and r0 such that
for all
.
Mathematics Subject Classification (2000): 58J50, 53C20
Supported by Swiss National Science Foundation, grant No. 20-101 469 相似文献
150.