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71.
The inclusional complexation between γ-cyclodextrin and acenaphthene in aqueous solution was investigated by spectroscopic techniques. A 1:1 complex was detected and its formation constant was determined. After adding bromoalcohols such as 2,3-dibromopropane-1-ol or 2-bromoethanol both a decrease of the fluorescence and an enhancement of the room-temperature phosphorescence (RTP) of acenaphthene were observed. The RTP signals from acenaphthene included in γ-cyclodextrin were optimized. The apparent formation constant of the ternary γ-cyclodextrin-acenaphthene-2,3-dibromopropane-1-ol complex was determined from RTP data. On the other hand, the inclusion complex formed between γ-cyclodextrin, acenaphthene and 2-bromoethanol was found to be very labile and its equilibrium constant could not be determined with accuracy. Large RTP signals were obtained in both ternary systems, even in the absence of sodium sulfite as deoxygenant agent. This fact would indicate that in these complexes the acenaphthene is protected from the action of quenchers such oxygen. 相似文献
72.
Cristina Vázquez Ana Albornoz Adam Hajduk Dolores Elkin Graciela Custo Alba Obrustky 《Spectrochimica Acta Part B: Atomic Spectroscopy》2008
Archaeometry is an interdisciplinary research area involved in the development and use of scientific methods in order to answer questions concerned with the human history. In this way the knowledge of archaeological objects through advanced chemical and physical analyses permits a better preservation and conservation of the cultural heritage and also reveals materials and technologies used in the past. In this sense, analytical techniques play an important role in order to provide chemical information about cultural objects. Considering the non destructive characteristic of this study, analytical techniques must be adequate in order to prevent any alteration or damage and in addition to allow the conservation of their integrity. Taking into account the irreplaceable character of the archaeological and artistic materials considered in this study, analytical techniques must be adequate in order to prevent any alteration or damage and in addition to allow the conservation of their integrity. 相似文献
73.
Sánchez-Flores NA Pacheco-Malagón G Pérez-Romo P Armendáriz H Valente JS Guzmán-Castillo Mde L Alcaraz J Baños L Blesa JM Fripiat JJ 《Journal of colloid and interface science》2008,323(2):359-364
Well crystallized silicalite-1 has been obtained from three sources of amorphous silica, namely, rice hull ashes, commercial Davisil, and a fume silica from Aldrich. The silicas were first dissolved in glycerol according to a recently described reaction. This reaction transforms rapidly and efficiently large surface area silicates into poly-alkoxide gels. It can be schematized as an etherification of an alcohol function of glycerol by the weakly acid surface silanol groups. The facile hydrolysis of the alkoxide permits the preparation of relatively pure and reactive silica, keeping the mesoporous character of the parent starting material. We insist on the mesoporous character of the solids obtained upon hydrolyzing the organo-silicic gel because we believe the gel plays a role of template in the secondary synthesis of mesoporous structures. The hydrolysis is carried out in presence of a structure directing agent, namely tetra-propylammonium hydroxide, TPAOH. After aging, the residue is dried and calcined. The first advantage of using the organo-silicic gel is probably related to the high degree of depolymerization of silica, witness by the C/Si ratio. The second one, more subtle to define, is to provide an intermediate silica with hydrophilic a hydrophobic regions, interfering differently with the surfactant. After calcination at 500 degrees C, well crystallized silicalite-1 is obtained. The texture of the starting silica influences the textural characteristics of the final silicalite-1. 相似文献
74.
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76.
Based on green analytical chemistry principles, an efficient approach was applied for the simultaneous determination of galantamine, a widely used cholinesterase inhibitor for the treatment of Alzheimer's disease, and its major metabolites in serum samples. After a simple serum deproteinization step, second-order data were rapidly obtained (less than 6 min) with a chromatographic system operating in the isocratic regime using ammonium acetate/acetonitrile (94:6) as mobile phase. Detection was made with a fast-scanning spectrofluorimeter, which allowed the efficient collection of data to obtain matrices of fluorescence intensity as a function of retention time and emission wavelength. Successful resolution was achieved in the presence of matrix interferences in serum samples using multivariate curve resolution-alternating least-squares (MCR-ALS). The developed approach allows the quantification of the analytes at levels found in treated patients, without the need of applying either preconcentration or extraction steps. Limits of detection in the range between 8 and 11 ng mL−1, relative prediction errors from 7 to 12% and coefficients of variation from 4 to 7% were achieved. 相似文献
77.
AS Peinetti LP Méndez De Leo GA González F Battaglini 《Journal of colloid and interface science》2012,366(1):44-50
A novel and environmentally friendly method based on mixing of colloidal polymer particles and graphene sheets has been developed. It is found that colloidal polymers can be employed to stabilize graphene oxide (GO) sheets during reduction to graphene. Adsorption of polymer particles at the surface of graphene layers seems to be underlying mechanism of stabilization of graphene sheets. Surface polarity of the polymer particles is crucial for the successful stabilization of graphene layers. Presence of colloidal particles at the surface of graphene prohibits restacking and agglomeration of nanolayers, resulting in fine dispersion of graphene throughout the polymeric matrix. Formation of strong bond between polar segments of the polymer chain and oxygen groups of graphene sheets generates a strong interface improving final properties of the composites. Inclusion of merely 2 wt% of graphene into an acrylic resin resulted in an increase of 522% and 242% in modulus and hardness, respectively. 相似文献
78.
Graciela Domenech Hector Freytes Christian de Ronde 《Mathematical Logic Quarterly》2009,55(3):307-319
In this paper we enrich the orthomodular structure by adding a modal operator, following a physical motivation. A logical system is developed, obtaining algebraic completeness and completeness with respect to a Kripkestyle semantic founded on Baer*‐semigroups as in [22] (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
79.
Our aim in this paper is to take quite seriously Heinz Post’s claim that the non-individuality and the indiscernibility of
quantum objects should be introduced right at the start, and not made a posteriori by introducing symmetry conditions. Using a different mathematical framework, namely, quasi-set
theory, we avoid working within a label-tensor-product-vector-space-formalism, to use Redhead and Teller’s words, and get
a more intuitive way of dealing with the formalism of quantum mechanics, although the underlying logic should be modified.
We build a vector space with inner product, the Q-space, using the non-classical part of quasi-set theory, to deal with indistinguishable
elements. Vectors in Q-space refer only to occupation numbers and permutation operators act as the identity operator on them,
reflecting in the formalism the fact of unobservability of permutations. Thus, this paper can be regarded as a tentative to
follow and enlarge Heinsenberg’s suggestion that new phenomena require the formation of a new “closed” (that is, axiomatic)
theory, coping also with the physical theory’s underlying logic and mathematics.
G. Domenech is a fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Argentina.
D. Krause is a fellow of the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Brazil. 相似文献
80.
Graciela Domenech Hector Freytes Christian de Ronde 《International Journal of Theoretical Physics》2008,47(1):168-174
Kochen–Specker theorem rules out the non-contextual assignment of values to physical magnitudes. Here we enrich the usual
orthomodular structure of quantum mechanical propositions with modal operators. This enlargement allows to refer consistently
to actual and possible properties of the system. By means of a topological argument, more precisely in terms of the existence
of sections of sheaves, we give an extended version of Kochen–Specker theorem over this new structure. This allows us to prove
that contextuality remains a central feature even in the enriched propositional system.
Graciela Domenech is a fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Hector Freytes
is a fellow of the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). 相似文献