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141.
Markus Junker 《Israel Journal of Mathematics》1999,109(1):273-298
Zariski groups are ℵ0-stable groups with an axiomatically given Zariski topology and thus abstract generalizations of algebraic groups. A large
part of algebraic geometry can be developed for Zariski groups. As a main result, any simple smooth Zariski group interprets
an algebraically closed field, hence is almost an algebraic group over an algebraically closed field. 相似文献
142.
A. M. de Bettencourt M. F. Duarte S. Facchetti M. H. Florêncio M. L. Gomes H. A. van't Klooster L. Montanarella R. Ritsema L. F. Vilas-Boas 《应用有机金属化学》1997,11(5):439-450
Five species of halophytes were sampled in the salt marshes of the Tagus estuary, dried, ground and digested. They were further extracted with ethanol and the extracts passed through weak and strong cationic ion-exchange resins, purified through TLC and submitted to pyrolysis mass spectrometry and HPLC–ICP/MS. Arsenic content and hydride-forming arsenic species were verified, in each step, by GF–AA and HG–QFAA. A high content of arsenic was found in the samples of halophytes studied, both di- and tri-methylated arsenic compounds being present. A considerable fraction of this arsenic content seems to be refractory to hydride generation. Moreover, the arsenic fraction found seems to have the same ion-exchange behaviour as the refractory fractions formerly studied in estuarine water. A partial characterization of these structures by pyrolysis–GC–MS suggests the presence of arsenobetaine and arsenocholine compounds. Furthermore, HPLC–ICP/MS data seem to confirm the presence of these compounds. In addition, the latter hyphenated technique strongly suggests the presence of a number of other organoarsenicals including tetramethylarsonium (TMAs), trimethylarsine oxide (TMAO), cacodylate (DMA) and possibly an arsenosugar-type compound. © 1997 by John Wiley & Sons, Ltd. 相似文献
143.
This paper aims to systematically investigate the cataracting-centrifuging transition in a rotary drum involving spherical and nonspherical particles by using t... 相似文献
144.
Yong P. Chen J. Hitchcock D. Dries M. Junker C. Welford S.E. Pollack T.A. Corcovilos R.G. Hulet 《Physica D: Nonlinear Phenomena》2009,238(15):1321-1325
We review recent studies of the effects of disorder on an atomic Bose-Einstein condensate (BEC). We focus particularly on our own experiments with 7Li BECs in laser speckle. Both the interaction, which gives rise to the nonlinearity in a BEC, and the disorder can be tuned experimentally. This opens many opportunities to study the interplay of interaction and disorder in both condensed matter physics and nonlinear science. 相似文献
145.
S.M. Duarte Queirós 《Physics letters. A》2009,373(17):1514-1518
In this Letter we analyse the behaviour of the probability density function of the sum of N deterministic variables generated from the triangle map of Casati-Prosen. For the case in which the map is both ergodic and mixing the resulting probability density function quickly concurs with the Normal distribution. However, when the map is weakly chaotic, and fuzzily not mixing, the resulting probability density functions are described by power-laws. Moreover, contrarily to what it would be expected, as the number of added variables N increases the distance to Gaussian distribution increases. This behaviour goes against standard central limit theorem. By extrapolation of our finite size results we preview that in the limit of N going to infinity the distribution has the same asymptotic decay as a Lorentzian (or a q=2-Gaussian). 相似文献
146.
M. Teresa Duarte M. Ftima M. Piedade M. Paula Robalo Antnio P. S. Teixeira M. Helena Garcia 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(8):m386-m389
The title compound, (η5‐cyclopentadienyl)(4‐nitrobenzonitrile‐κN)(trimethylphosphine‐κP)(triphenylphosphite‐κP)iron(II) hexafluorophosphate, [Fe(C5H5)(C7H4N2O2)(C18H15O3P)(C3H9P)]PF6, has been characterized by spectroscopic and X‐ray diffraction in order to evaluate the tuning of the electron density at the metal centre and the extension of the π delocalization on the molecule due to the presence of phosphite and phosphine co‐ligands. The compound crystallizes in the centrosymmetric space group P21/c, which destroys the possibility of exhibiting any quadratic non‐linear optical properties. The packing shows a supramolecular zigzag chain of antiparallel cations connected via the PF6− anions through C—H⋯Fδ− interactions, with H⋯F distances ranging from 2.39 to 2.67 Å. Each zigzag chain is composed of isomeric organometallic fragments containing either R or S molecules. These chains are connected through weak intermolecular C—H⋯C interactions, forming a two‐dimensional plane parallel to (101). 相似文献
147.
Valderes Moraes de Almeida Alexandre José da Silva Góes Carlos Roque Duarte Correia 《Tetrahedron letters》2009,50(6):684-687
Novel aza-bicyclic 2-isoxazolines, 4,5-dihydroisoxazole[5,4-b]pyrrolidines, and 4,5-dihydroisoxazole[5,4-b]piperidines were synthesized in a highly regioselective manner through a 1,3-dipolar cycloaddition reaction of 5- and 6-membered endocyclic enecarbamates and enamides with several nitrile oxides in good to excellent yields. Hydrogenolysis of 5- and 6-membered Cbz-cycloadducts led to secondary amines, which presented distinctive stabilities. 2-Isoxazoline bisamides were obtained in good yields through a N-benzoylation, followed by ammonolysis of the secondary amine, or directly from ammonolysis of the cycloadducts. 相似文献
148.
An optical fiber biosensor has been developed for the determination of catecholamines (dopamine, norepinephrine and epinephrine) based on the recognition capacity of the enzyme laccase. In this study, a glass tube constituted by a fused silica fiber coated with a film of polystyrene/divinylbenzene resin (PS/DVB) was used for catecholamines separation. Firstly, the analyzer was tested for calibration and its analytical performance for catecholamines detection was compared with a classical analytical method, namely high performance liquid chromatography-electrochemical detector (HPLC-ED). The developed analytical device shows a high potential for catecholamines quantification with a detection limit of 2.1, 2.6 and 3.4 pg mL−1 for dopamine, norepinephrine and epinephrine, respectively. The analytical sensitivity, inferred from the slope of the calibration curves established for a range of concentrations between 5 and 125 pg mL−1, was found to be 0.344, 0.252 and 0.140 dB/pg mL−1 for dopamine, norepinephrine and epinephrine, respectively. Furthermore, catecholamines speciation with the PS/DVB fiber was completely achieved in 3 min. The analytical performance of the reported sensor was also evaluated and found adequate for catecholamines determination in human urine and plasma samples. 相似文献
149.
Fátima Duarte Freire C. Flávio Soares Aragão T. Flávio Accioly de Lima e Moura Fernanda Nervo Raffin 《Journal of Thermal Analysis and Calorimetry》2009,97(1):355-357
Chlorpropamide ((4-chloro-N-(propylamino)-carbonyl)-benzenesulfonamide) belongs to compounds having sulfonylurea group and is widely used as an oral
antidiabetic agent. In this work differential scanning calorimetry (DSC) was used during pre-formulation of chlorpropamide
tablets to determine the drug-excipients compatibility. The DSC curves of chlorpropamide and binary mixtures with excipients
(sodium croscarmellose, sodium lauryl sulfate, microcrystalline cellulose, magnesium stearate and calcium carbonate) showed
that chlorpropamide exhibited interaction with magnesium stearate and sodium lauryl sulfate. The binary mixtures of chlorpropamide–magnesium
stearate presented a single endothermic process at 96–108 °C and chlorpropamide–sodium lauryl sulfate showed a wide endotherm
at 99–120 °C. 相似文献
150.
Sara Abalde‐Cela Szushen Ho Benito Rodríguez‐González Dr. Miguel A. Correa‐Duarte Dr. Ramón A. Álvarez‐Puebla Dr. Luis M. Liz‐Marzán Prof. Nicholas A. Kotov Prof. 《Angewandte Chemie (International ed. in English)》2009,48(29):5326-5329
Feature film : Thin films made by exponential layer‐by‐layer growth display high diffusivity and can be readily infiltrated with inorganic nanoparticles. They can sequestrate molecular systems from solution as a function of the composition of their layers, while providing intense surface‐enhanced Raman scattering (SERS) signals (see picture).