Search results for "EXPANSION"
showing 10 items of 630 documents
El expansionismo comercial británico en el País Valenciano: el proyecto de creación de puerto franco en Alacant en 1706
1992
La ocupación de Madrid por los aliados en junio de 1706 hizo que los representantes de la reina Ana consideraran llegado el momento de proyectar sobre las colonias la nueva situación política y militar y plasmar en el papel las proyectadas nuevas relaciones comerciales entre Gran Bretaña y España. El enviado de la reina consideraba que la clara actitud antihabsburguesa de los castellanos, principales beneficiarios del comercio con América, uniría a británicos y a la Corona de Aragón, principales bastiones del austracismo, en el objetivo común de romper el monopolio de Castilla. Ante estas optimistas impresiones, la corte de Kensington decidió enviar a Stanhope en noviembre de 1706 un proyec…
Slow-roll corrections in multi-field inflation: a separate universes approach
2018
In view of cosmological parameters being measured to ever higher precision, theoretical predictions must also be computed to an equally high level of precision. In this work we investigate the impact on such predictions of relaxing some of the simplifying assumptions often used in these computations. In particular, we investigate the importance of slow-roll corrections in the computation of multi-field inflation observables, such as the amplitude of the scalar spectrum $P_\zeta$, its spectral tilt $n_s$, the tensor-to-scalar ratio $r$ and the non-Gaussianity parameter $f_{NL}$. To this end we use the separate universes approach and $\delta N$ formalism, which allows us to consider slow-roll…
Comparing normal means: new methods for an old problem
2007
Comparing the means of two normal populations is an old problem in mathematical statistics, but there is still no consensus about its most appropriate solution. In this paper we treat the problem of comparing two normal means as a Bayesian decision problem with only two alternatives: either to accept the hypothesis that the two means are equal, or to conclude that the observed data are, under the assumed model, incompatible with that hypothesis. The combined use of an information-theory based loss function, the intrinsic discrepancy (Bernardo and Rueda 2002}, and an objective prior function, the reference prior \citep{Bernardo 1979; Berger and Bernardo 1992), produces a new solution to this…
On the time function of the Dulac map for families of meromorphic vector fields
2003
Given an analytic family of vector fields in Bbb R2 having a saddle point, we study the asymptotic development of the time function along the union of the two separatrices. We obtain a result (depending uniformly on the parameters) which we apply to investigate the bifurcation of critical periods of quadratic centres.
A Unifying Framework for Perturbative Exponential Factorizations
2021
We propose a framework where Fer and Wilcox expansions for the solution of differential equations are derived from two particular choices for the initial transformation that seeds the product expansion. In this scheme, intermediate expansions can also be envisaged. Recurrence formulas are developed. A new lower bound for the convergence of theWilcox expansion is provided, as well as some applications of the results. In particular, two examples are worked out up to a high order of approximation to illustrate the behavior of the Wilcox expansion.
Melting of tantalum at high pressure determined by angle dispersive x-ray diffraction in a double-sided laser-heated diamond-anvil cell
2003
The high pressure and high temperature phase diagram of Ta has been studied in a laser-heated diamond-anvil cell (DAC) using x-ray diffraction measurements up to 52 GPa and 3800 K. The melting was observed at nine different pressures, being the melting temperature in good agreement with previous laser-heated DAC experiments, but in contradiction with several theoretical calculations and previous piston-cylinder apparatus experiments. A small slope for the melting curve of Ta is estimated (dTm/dP = 24 K/GPa at 1 bar) and a possible explanation for this behaviour is given. Finally, a P-V-T equation of states is obtained, being the temperature dependence of the thermal expansion coefficient an…
Behaviour of the non-linear optical material KTiOPO4in the temperature range 293-973 K studied by x-ray diffractometry at high resolution: alkaline d…
1999
The crystal structure of potassium titanyl phosphate, KTiOPO4 (space group Pna21), has been refined at room temperature, at 673 K, and at 973 K, by using accurate single-crystal x-ray diffraction techniques at high resolution (dmin = 0.35 A). The data show a large amount of anharmonic motion of the potassium ions, increasing with temperature. To describe this motion, two models are developed: a normal refinement including potassium anharmonic thermal displacement parameters, which describes the average motion of the alkaline sites, and another model in which the potassium sites are split within the harmonic approximation and the displacements of the potassium ions versus temperature are des…
High-Pressure High-Temperature Stability and Thermal Equation of State of Zircon-Type Erbium Vanadate.
2018
Inorganic chemistry 57(21), 14005 - 14012 (2018). doi:10.1021/acs.inorgchem.8b01808
Revisiting the charge density analysis of 2,5-dichloro-1,4-benzoquinone at 20 K
2017
A high-resolution X-ray diffraction measurement of 2,5-dichloro-1,4-benzoquinone (DCBQ) at 20 K was carried out. The experimental charge density was modeled using the Hansen–Coppens multipolar expansion and the topology of the electron density was analyzed in terms of the quantum theory of atoms in molecules (QTAIM). Two different multipole models, predominantly differentiated by the treatment of the chlorine atom, were obtained. The experimental results have been compared to theoretical results in the form of a multipolar refinement against theoretical structure factors and through direct topological analysis of the electron density obtained from the optimized periodic wavefunction. The si…
On the application of an experimental multipolar pseudo-atom library for accurate refinement of small-molecule and protein crystal structures
2007
International audience; With an increasing number of biomacromolecular crystal structures being measured to ultra-high resolution, it has become possible to extend to large systems experimental charge-density methods that are usually applied to small molecules. A library has been built of average multipole populations describing the electron density of chemical groups in all 20 amino acids found in proteins. The library uses the Hansen & Coppens multipolar pseudo-atom model to derive molecular electron density and electrostatic potential distributions. The library values are obtained from several small peptide or amino acid crystal structures refined against ultra-high-resolution X-ray diff…