Anquilosis de la articulación coxofemoral y alteraciones biomecánicas en un individuo medieval de la necrópolis de la catedral de Sigüenza (Guadalajara)

X Congreso Nacional de Paleopatología. Univesidad Autónoma de Madrid, septiembre de 200

On the properties of zeros of Bessel series in the real line

For a given sequence of real numbers (Formula presented.), we define the function (Formula presented.) where (Formula presented.), (Formula presented.) denotes the Bessel function of order µ, and (Formula presented.) are the positive zeros of  (Formula presented.). In this paper, we study the function (Formula presented.) and some outstanding instances of it on the whole real line and propose a number of conjectures about its positive zeros

Effects of environmental conditions on the micro-mechanical properties of formulated waterborne coatings

Waterborne colloidal polymer coatings are widely used in architectural and agricultural applications where they are subject to challenging environments, such as extremes of temperatures and relative humidities (RH). This research investigates the effects of adding two common co-formulants, poly(acrylic acid) (PAA) and xanthan gum (XG), to waterborne polymer composite coatings in these environments. The mechanical properties of the resulting coatings are of particular interest. Hardness, creep and tack properties of thick (similar to 400 mu m) formulated model coatings were characterized using a micro-indentation technique operating in a single cycle within a bespoke environmental chamber. Measurements were made at three temperatures (16, 20 and 30 degrees C), which span the glass transition temperature (T-g) of the acrylic copolymer binder, and over three RH values of 10%, 43%, and 90%. The creep data were analysed using the Burgers model to extract characteristic viscoelastic properties. The tack was found by recording the force when withdrawing the probe from the sample and using it to obtain nominal stress (knowing the indentation depth and probe geometry) during the indenter's withdrawal and hence the work of adhesion (W-Adh) to detach from the coating. Tack adhesion is completely lost below the binder's T-g but increases when the ambient temperature increases. In formulated coatings, both the tack and creep deformation increase as the relative humidity increases, and this trend is observed at each temperature. There is no evidence from thermal analysis for plasticization of the acrylic polymer by moisture sorption, but the two co-formulants are hydrophilic. The observed softening of the coatings at high RH can be attributed to water sorption in the components. The presence of glassy PAA has the effect of raising the hardness of glassy coatings, but only at low RH when there is no plasticization by water. The addition of hydrophilic XG surprisingly reduces tack adhesion while also raising the viscosity of the coating. These findings will inform the formulation of waterborne colloidal coatings to function in a range of environments.work was funded by EPSRC (Grant EP/L016788/1) through the Doctoral Training Centre in Micro- and NanoMaterials and Technology (MiNMaT). We benefited from useful discussions with Dr. Marco Ram- aioli (INRAE, AgroParisTech - Center de Massy) and Dr. Nicholas Ballard (University of the Basque Country). We thank Violeta Doukova and Dave Jones (University of Surrey) for laboratory assistance and Dr. Agata Gajewicz-Jaromin for performing DSC and TGA analyses. We also thank Dr. James Adams (Cubica Technology) for his assistance in writing data analysis scripts. We thank Richard Turner (Acal BFI UK Ltd.) for the relative humidity and temperature probes, and for his assistance with their setup

Cultivo de tejidos y transformación genética en Glycine max (L.) Merrill

This work is a brief overview on the background of in vitro tissue culture and genetic transformation of soybean, as well as a brief introduction to the origin, distribution and importance of the crop. It is also aimed to present a series of worldwide results as a preamble to the development of future researches on genetic improvement of this crop using biotechnological methods.Key words: biotechnology, culture, in vitro, genetic improvement, soybeanEn este trabajo se realiza una breve revisión sobre los antecedentes del cultivo de tejidos y la transformación genética en el cultivo de la soya, así como una introducción al origen, distribución e importancia del cultivo. Se pretende poner a disposición del lector un compendio de resultados como preámbulo para el desarrollo de futuras investigaciones en la mejora genética de este cultivo por métodos biotecnológicos.Palabras clave: biotecnológicos, cultivo, in vitro, mejora genética, soy

Incipient sediment transport for non-cohesive landforms by the discrete element method (DEM)

The determination of the shear stress at which a sediment grain of a given size and density starts to move has been treated with theoretical, experimental and numerical procedures by many authors. The seminal contribution of Shields [7] addresses a relationship for the non-dimensional critical shear stress in terms of the friction Reynolds number for a single particle in a flat bed. This work focusses on the incipient transport of particles for bedforms. The proposed numerical approach to the problem integrates the Discrete Element Method (DEM) [9] with a continuous finite element approximation. The DEM simulates the motion of the landform, defined as an aggregate of rigid discs that interact by contact and friction. The continuous finite element approach predicts the boundary shear stress field coming from the fluid flow over the bed (for basic formulation, see [4] and reference therein). Both methods are coupled through the flow-particle force transmission using drag coefficients. While for single particles (or very simple sets of particles) incipient motion (and consequently, the threshold stress) is clearly defined, for complex forms the use of the concept of incipient transport becomes necessary, and critical shear stress is established in terms of a threshold sediment flux over the bed surface. We present a series of numerical experiments for single particles, showing good agreement with Shields curve for the whole range of Reynolds number. In this communication we show some of these results, in compare with the basic Shields curves for flat bed and single grains

The error function in the study of singularly perturbed convection-diffusion problems with discontinuous boundary data

We show the importance of the error function in the approximation of the solution of singularly perturbed convection-diffusion problems with discontinuous boundary conditions. It is observed that the error function (or a combination of them) provides an excellent approximation and reproduces accurately the effect of the discontinuities on the behaviour of the solution at the boundary and interior layers

First order approximation of an elliptic 3D singular perturbation problem

A three-dimensional elliptic singular perturbation problem with discontinuous boundary values is considered. The solution of the problem is written in terms of a double integral. A saddle point analysis is used to obtain a first approximation, which is expressed in terms of a function that can be viewed as a generalization of the complementary error functio

Multi-point Taylor approximations in one-dimensional linear boundary value problems

We consider second-order linear differential equations in a real interval $I$ with mixed Dirichlet and Neumann boundary data. We consider a representation of its solution by a multi-point Taylor expansion. The number and location of the base points of that expansion are conveniently chosen to guarantee that the expansion is uniformly convergent $\forall x\in I$. We propose several algorithms to approximate the multi-point Taylor polynomials of the solution based on the power series method for initial value problems

A three-point Taylor algorithm for three-point boundary value problems

We consider second-order linear differential equations $\varphi(x)y''+f(x)y'+g(x)y=h(x)$ in the interval $(-1,1)$ with Dirichlet, Neumann or mixed Dirichlet-Neumann boundary conditions given at three points of the interval: the two extreme points $x=\pm 1$ and an interior point $x=s\in(-1,1)$. We consider $\varphi(x)$, $f(x)$, $g(x)$ and $h(x)$ analytic in a Cassini disk with foci at $x=\pm 1$ and $x=s$ containing the interval $[-1,1]$. The three-point Taylor expansion of the solution $y(x)$ at the extreme points $\pm 1$ and at $x=s$ is used to give a criterion for the existence and uniqueness of the solution of the boundary value problem. This method is constructive and provides the three-point Taylor approximation of the solution when it exists. We give several examples to illustrate the application of this technique