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21.
Bruna Bovio 《Journal of organometallic chemistry》1983,252(1):71-82
Crystals of C24H36N6O6Cr2 are monoclinic, a 15.380(3), b 13.965(2), c 14.459(3) Å, β 92.18(1)°; Z = 4; space group P21 with two independent molecules in the asymmetric unit. The crystal structure was determined from X-ray diffractometer data by direct methods and refined by least-squares methods to R = 0.066 for 2430 independent observed reflections. It consists of discrete molecules, in which each Cr atom is surrounded by three cis carbonyl groups and three cis nitrogen atoms of three 3,3,4,4-tetramethyl-1,2-diazetine ligands, in a deformed octahedral coordination. There is no evidence of intramolecular Cr ? Cr interaction. 相似文献
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Bruna Cláudia Lourenção Roberta Antigo Medeiros Romeu C. Rocha‐Filho Orlando Fatibello‐Filho 《Electroanalysis》2010,22(15):1717-1723
A cathodically pretreated boron‐doped diamond electrode was used for the simultaneous anodic determination of ascorbic acid (AA) and caffeine (CAF) by differential pulse voltammetry. Linear calibration curves (r=0.999) were obtained from 1.9×10?5 to 2.1×10?4 mol L?1 for AA and from 9.7×10?6 to 1.1×10?4 mol L?1 for CAF, with detection limits of 19 μmol L?1 and 7.0 μmol L?1, respectively. This method was successfully applied for the determination of AA and CAF in pharmaceutical formulations, with results equal to those obtained using a HPLC reference method. 相似文献
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25.
In this work we show that it is possible to obtain a generalized statistical mechanics (thermostatistics) based on Renyi entropy, to be maximized with adequate constraints. The equilibrium probability distribution thus obtained has a very interesting property. Indeed, it reminds us the statistical distribution proposed by Tsallis, known to conveniently describe a variety of phenomena in nonextensive systems. Moreover, some examples are worked out in order to illustrate the main features of the herein introduced formalism. 相似文献
26.
Márcia M. Favaro Bruna T. Rego Márcia C. Branciforti Rosario E. S. Bretas 《Journal of Polymer Science.Polymer Physics》2010,48(2):113-127
An intercalated nanocomposite made of montmorillonite nanoclay, MMT, and poly(trimethylene terephthalate), PTT, was produced by twin screw extrusion and characterized by wide angle X‐ray diffraction, WAXD, and transmission electron microscopy, TEM. The quiescent isothermal and non‐isothermal and the flow‐induced crystallization of the nanocomposite were studied by differential scanning calorimetry, DSC, polarized light optical microscopy, PLOM, and rheometry. The quiescent results showed that the nanoclay acted as an efficient nucleating agent for the PTT, which result in an anticipation of the transition temperature between regimes II and III of crystallization. The fold interfacial free energy, σe, of the PTT in the nanocomposite during regime III was lower than in the pure state; that is, the pure PTT developed spherulites, whereas in the nanocomposite it produced a paracrystalline morphology. Under shear rate, the total times for crystallization in the nanocomposite were higher than in the pure PTT. In flow‐induced crystallization, a fibrillar nucleus must be formed as a result of chain orientation. In the nanocomposite, chain orientation only occurred after the percolated structure was broken. Therefore, the formation of a fibrillar nucleus in the nanocomposite took more time, which increased the total crystallization time. Inc. J Polym Sci Part B: Polym Phys 48: 113–127, 2010 相似文献
27.
Bruna P Baldi G Pineda E Serrano J Suck JB Crespo D Monaco G 《The Journal of chemical physics》2011,135(10):101101
Using high resolution inelastic x-ray scattering we studied the collective dynamics of the Pd(77)Si(16.5)Cu(6.5) metallic glass, focusing on the energy-momentum region where the boson peak appears. The dispersion relation and the width of the acoustic excitations are determined showing how the longitudinal acoustic modes maintain their dispersive character for frequencies well above the boson peak frequencies. Moreover, we prove that close to these frequencies there is a softening of the apparent sound speed indicating a failure of the Debye continuum approximation at the boson peak frequencies and challenging previous results on other metallic glasses. 相似文献
28.
We consider the problem of the existence of uniform interpolants in the modal logic K4. We first prove that all ${\square}$ -free formulas have uniform interpolants in this logic. In the general case, we shall prove that given a modal formula ${\phi}$ and a sublanguage L of the language of the formula, we can decide whether ${\phi}$ has a uniform interpolant with respect to L in K4. The ${\square}$ -free case is proved using a reduction to the G?del L?b Logic GL, while in the general case we prove that the question of whether a modal formula has uniform interpolants over transitive frames can be reduced to a decidable expressivity problem on the???-calculus. 相似文献
29.
Giacomo Lenzi 《Mathematical Logic Quarterly》2011,57(5):474-480
We introduce a quite natural Frege‐style set theory, which we call Strong‐Frege‐2 $(\mathsf {SF}_2)$, a sort of simplification of the theory considered in 13 (under the name Strong‐Frege‐3) and 1 (under the name F2). We give a model of a weaker variant of $\mathsf {SF}_2$, called $\mathsf {SF}_2\mathsf {AC}$, where atoms and coatoms are allowed. To construct the model we use an enumeration “almost without repetitions” of the Π11 sets of natural numbers; such an enumeration can be obtained via a classical priority argument much in the style of 5 and 15 . © 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim 相似文献
30.
The electrical response of an electrolytic cell in which the diffusion of mobile ions in the bulk is governed by a fractional diffusion equation of distributed order is analyzed. The boundary conditions at the electrodes limiting the sample are described by an integro-differential equation governing the kinetic at the interface. The analysis is carried out by supposing that the positive and negative ions have the same mobility and that the electric potential profile across the sample satisfies the Poisson's equation. The results cover a rich variety of scenarios, including the ones connected to anomalous diffusion. 相似文献