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2.
E. Rodriguez E. Jimenez G.J. Jacob A.A.R. Neves C.L. Cesar L.C. Barbosa 《Physica E: Low-dimensional Systems and Nanostructures》2005,26(1-4):361
Multilayer PbTe quantum dots (QDs) and SiO2 were grown by pulsed laser deposition (PLD) and Plasma enhanced chemical vapor deposition (PECVD) techniques. The crystalline structure, QD size and size dispersion were observed by high-resolution transmission electron microscopy (HRTEM) measurements. This technique allows one to grow PbTe QDs as small as 1.8 nm diameter and 0.6 nm size dispersion. The whole structure can be used in a Fabry–Perot cavity for an optical device operating at the mid-infrared region. 相似文献
3.
Edgar G. Goodaire Cesar Polcino Milies 《Rendiconti del Circolo Matematico di Palermo》1988,37(1):126-135
This paper first settles the “isomorphism problem” for alternative loop rings; namely, it is shown that a Moufang loop whose integral loop ring is alternative is determined up to isomorphism by that loop ring. Secondly, it is shown that every normalized automorphism of an alternative loop ringZ L is the product of an inner automorphism ofQ L and an authomorphism ofL. 相似文献
4.
[reaction: see text] The fluorescence quenching of 2,3-diazabicyclo[2.2.2]oct-2-ene (DBO) by nucleotides has been studied. The quenching mechanism was analyzed on the basis of deuterium isotope effects, tendencies for exciplex formation, and the quenching efficiency in the presence of a molecular container (cucurbit[7]uril). Exciplex-induced quenching appears to prevail for adenosine, cytidine, and uridine, while hydrogen abstraction becomes competitive for thymidine and guanosine. Compared to other fluorescent probes, DBO responds very selectively to the type of nucleotide. 相似文献
5.
6.
Grumelli DE Forzani ES Morales GM Miras MC Barbero CA Calvo EJ 《Langmuir : the ACS journal of surfaces and colloids》2004,20(6):2349-2355
The sulfonation of polyaniline (PANI) films by nucleophilic addition of sulfite ion has been controlled through the polymer oxidation state under electrochemical control. The process was monitored by in situ electrochemical quartz crystal microbalance (EQCM), and the polymer oxidation was accomplished by electrode potential steps in sulfite aqueous solutions. The nucleophilic addition of sulfite to PANI only takes place on the oxidized polymer. From the ratio of added mass to the injected charge, the degree of sulfonation has been obtained with a yield as high as 50%. It has been observed that the ion-exchange mechanism during the oxidation-reduction process in the resulting sulfonated polymer is analogous to the polymer produced by electrophilic sulfonation of polyaniline or by copolymerization of aniline with aminosulfonic acids, unlike the ionic exchange observed for unmodified PANI. 相似文献
7.
Amidines can be prepared on a solid support by reducing polymer-bound amidoximes with SnCl2·2H2O. The method has proved to be straightforward and highly efficient. Amidoximes attached to the solid support are readily available by treating resin-bound nitriles with hydroxylamine. 相似文献
8.
Robin J. Marles James B. Hudson Elizabeth A. Graham Chantal Soucy-Breau Peter Morand R. Lilia Compadre Cesar M. Compadre G. H. Neil Towers J. Thor Arnason 《Photochemistry and photobiology》1992,56(4):479-487
The photoactivated antiviral and cytotoxic activities of the naturally occurring thiophene, alpha-terthienyl (1), and 15 synthetic analogues were evaluated against murine cytomegalovirus and Sindbis virus, and murine mastocytoma cells. After irradiation with near UV light, alpha-terthienyl and most of its analogues had significant toxicity, with minimum inhibitory concentrations in the range of 0.02-40 microM. In the absence of near UV irradiation, only one analogue had antiviral activity and five were cytotoxic. The most active analogues were those containing carboxylic acid, hydroxyl, or cyano substituents. Quantitative structure-activity relationship analysis of thiophene phototoxicity suggested that the rate of singlet oxygen production is the primary determinant of antiviral and cytotoxic activities. For phototoxicity against murine cytomegalovirus, a significant role for hydrophobicity was also demonstrated. Tricyclic thiophenes show significant potential for photochemotherapy of viral infections and cancer, and further evaluation in animal models is recommended. 相似文献
9.
The binding and availability of metals (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Zn) in therapeutically applied peat (Grosses Gifhorner Moor, Sassenburg/North Germany) was characterized by means of a versatile extraction approach. Aqueous extracts of peat were obtained by a standardized batch equilibrium procedure using high-purity water (pH 4.5 and 5.0), 0.01 mol l(-1) calcium chloride solution, 0.01 mol l(-1) ethylenediaminetetraacetic acid (EDTA) and 0.01 mol l(-1) diethylenetriamine pentaacetic acid (DTPA) solution as metal extractants. In addition, the availability of peat-bound metal species was kinetically studied by collecting aliquots of extracts after different periods of extraction time (5, 10, 15, 30, 60 and 120 min). Metal determinations were performed by atomic spectrometry methods (AAS, ICP-OES) and dissolved organic matter (DOM) was characterized by UV/Vis measurements at 254 and 436 nm, respectively. Of the extractants studied Ca, Mg and Mn were the most available metals, in contrast to peat-bound Fe and Al. The relative standard deviation s(r) of the developed extraction procedures was mostly in the range of 4 to 20%, depending on the metal and its concentration in peat. A pH increase favored the extraction of metals and DOM from peat revealing complex extraction kinetics. Moreover, a competitive exchange between peat-bound metal species and added Cu(II) ions showed that >100 mg of Cu(II) per 50 g wet peat was necessary to exchange the maximum of bound metals (e.g. 21.8% of Al, 3.9% of Fe, 79.0% of Mn, 81.9% of Sr, related to their total content). 相似文献
10.
Valmore S. Rodriguez Mohamed S. El-Aasser Jose M. Asua Cesar A. Silebi 《Journal of polymer science. Part A, Polymer chemistry》1989,27(11):3659-3671
Miniemulsion copolymerization of 50 : 50 weight fraction of styrene–methyl methacrylate monomer, using hexadecane as the cosurfactant, was carried out in both unseeded and seeded polymerizations. Effects of the hexadecane concentration and the ultrasonification time on the conversion–time curves and particle size of the final latex were investigated for unseeded polymerization. The kinetic and particle size distribution results showed that an increase in hexadecane concentration and ultrasonification time cause faster polymerization rate and smaller particle size. The mechanism of mass transport from miniemulsion droplets to polymer particles was also investigated for seeded polymerization. For this purpose a monomer miniemulsion was mixed with a fraction of a previously prepared miniemulsion latex particles prior to initiation of polymerization, using residual oil-soluble initiator in the seed latex. The concentration of hexadecane and a water-insoluble inhibitor (2,5 di-tert-butyl hydroquinone) in the miniemulsions were the main variables. Seeded polymerizations were also carried out in the presence of miniemulsion droplets containing a water-insoluble inhibitor and water-soluble initiator. The inhibitor concentration and the agitation speed during the course of polymerization were the experimental variables. The kinetic and particle size results from these seeded experiments suggested that collision between miniemulsion droplets and polymer particles may play a major role in the transport of highly water-insoluble compounds. 相似文献