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951.
Artur J.M. Valente Ana C.F. RibeiroMarigese B.B.J. Rita Rui A. CarvalhoMiguel A. Esteso Victor M.M. Lobo 《Journal of Molecular Liquids》2011,161(3):125-131
Mutual diffusion coefficients and electrical conductivity of a well-known food additive and supplement, or excipient in pharmaceutical formulations, calcium lactate, have been measured in the absence and presence of β-cyclodextrin in aqueous solutions, at 298.15 K. The dependence of conductivity on concentration has been analysed using the Fuoss-Edelson method. The values of the Nernst diffusion coefficients, for binary solutions, derived from conductance and from diffusion experiments are in good agreement. The presence of β-cyclodextrin leads to a non-expected effect on the transport properties of the aqueous solutions of calcium lactate. These data have been justified with help of 1H NMR spectroscopy. The effect on the water structure, reducing the hydration shell of lactate, is argued. This leads to an increase of the effective concentration of calcium lactate in solution contributing to an increase in the diffusion coefficients and a decrease in the dependence of the electrical conductance on the concentration. 相似文献
952.
The mean first passage time (MFPT) as dwell time in high spin metastable state of spin-crossover solids is investigated both analytically and numerically. Calculations showed that the MFPT decreases with the increases of a distance from metastable state. The probability density function has also been examined. 相似文献
953.
Andréa F. da Silva Artur S. Gouveia-Neto Elias A. Silva Jr. Ernande B. Costa 《Optics Communications》2011,284(19):4501-4503
In this report the optical properties and energy-transfer frequency upconversion luminescence of Er3+/Yb3+-codoped laponite-derived powders under 975 nm infrared excitation is investigated. The 75%(laponite):25%(PbF2) samples doped with erbium and ytterbium ions, generated high intensity red emission around 660 nm and lower intensity green emission around 525, and 545 nm. The observed emission signals were examined as a function of the excitation power and annealing temperature. The results indicate that energy-transfer, and excited-state absorption are the major upconversion excitation mechanism for the erbium excited-state red emitting level. The precursor glass samples were also heat treated at annealing temperatures of 300 °C, 400 °C, 500 °C, and 600 °C, for a 2 h period. The dependence of the visible upconversion luminescence emission upon the annealing temperature indicated the existence of an optimum temperature which leads to the generation of the most intense and spectrally pure red emission signal. 相似文献
954.
Artur Alho 《Physics letters. [Part B]》2011,703(5):537-542
We consider the evolution of covariant and gauge invariant linear density perturbations of scalar field cosmologies using a dynamical systems? approach. We find conditions for which the perturbations decay in time, so that the spacetime approaches a homogeneous solution which inflates, for quadratic and exponential potentials. This pre-inflationary homogenization is found to be stable in the potentials? parameter spaces. Furthermore, in each case, we determine the minimum size of the resultant homogeneous patch and show that, for quadratic potentials, the resulting inflationary solutions include those with the necessary number of e-folds. 相似文献
955.
We investigate the leading terms of the spectral action for odd-dimensional Riemannian spin manifolds with the Dirac operator
perturbed by a scalar function. We calculate first two Gilkey–de Witt coefficients and make explicit calculations for the
case of n-spheres with a completely symmetric Dirac. In the special case of dimension 3, when such perturbation corresponds to the
completely antisymmetric torsion, we carry out the noncommutative calculation following Chamseddine and Connes (J Geom Phys
57:121, 2006) and study the case of SU
q
(2). 相似文献
956.
We prove that the set of all complex series which are nonabsolutely convergent is c-algebrable. We establish a similar result for the set of all divergent complex series with bounded partial sums. 相似文献
957.
We prove exponential contraction of renormalization along hybrid classes of infinitely renormalizable unimodal maps (with
arbitrary combinatorics), in any even degree d. We then conclude that orbits of renormalization are asymptotic to the full renormalization horseshoe, which we construct.
Our argument for exponential contraction is based on a precompactness property of the renormalization operator (“beau bounds”),
which is leveraged in the abstract analysis of holomorphic iteration. Besides greater generality, it yields a unified approach
to all combinatorics and degrees: there is no need to account for the varied geometric details of the dynamics, which were
the typical source of contraction in previous restricted proofs. 相似文献
958.
Cywinski PJ Moro AJ Ritschel T Hildebrandt N Löhmannsröben HG 《Analytical and bioanalytical chemistry》2011,399(3):1215-1222
Novel fluorescent nanosensors, based on a naphthyridine receptor, have been developed for the detection of guanosine nucleotides,
and both their sensitivity and selectivity to various nucleotides were evaluated. The nanosensors were constructed from polystyrene
nanoparticles functionalized by (N-(7-((3-aminophenyl)ethynyl)-1,8-naphthyridin-2-yl)acetamide) via carbodiimide ester activation. We show that this naphthyridine
nanosensor binds guanosine nucleotides preferentially over adenine, cytosine, and thymidine nucleotides. Upon interaction
with nucleotides, the fluorescence of the nanosensor is gradually quenched yielding Stern–Volmer constants in the range of
2.1 to 35.9 mM−1. For all the studied quenchers, limits of detection (LOD) and tolerance levels for the nanosensors were also determined.
The lowest (3σ) LOD was found for guanosine 3’,5’-cyclic monophosphate (cGMP) and it was as low as 150 ng/ml. In addition,
we demonstrated that the spatial arrangement of bound analytes on the nanosensors’ surfaces is what is responsible for their
selectivity to different guanosine nucleotides. We found a correlation between the changes of the fluorescence signal and
the number of phosphate groups of a nucleotide. Results of molecular modeling and ζ-potential measurements confirm that the
arrangement of analytes on the surface provides for the selectivity of the nanosensors. These fluorescent nanosensors have
the potential to be applied in multi-analyte, array-based detection platforms, as well as in multiplexed microfluidic systems. 相似文献
959.
960.
Airoldi C Cardona F Sironi E Colombo L Salmona M Silva A Nicotra F La Ferla B 《Chemical communications (Cambridge, England)》2011,47(37):10266-10268
A small library of glyco-fused benzopyran compounds has been synthesised. Their interaction features with Aβ peptides have been characterised by using STD-NMR and trNOESY experiments. The conformational analysis of the compounds has also been carried out through molecular mechanics (MM) and molecular dynamics (MD) simulations. 相似文献