ESTUDIO DE PROCESOS DE REVERSIÓN A LA MEDIA

Existen diversos procesos estocásticos adaptados para modelar comportamientos naturales, tales como biológicos, sociales, financieros, económicos… en delante se centrará la atención en presentar una descripción de un proceso particular, el de los procesos estocásticos con reversión a la media, los cuales han sido utilizados, por ejemplo, para representar el comportamiento de algunos mercados, como es el caso del mercado energético. El principal objetivo cuando se modela el comportamiento de alguna variable como un proceso con reversión a la media, consiste en determinar los parámetros presentes en el modelo, los cuales pueden o no tener algún significado “realista” o pueden representar simplemente algunos valores particulares. En el presente trabajo se mostrará una metodología en la estimación de parámetros en procesos con reversión a la media a partir de una revisión bibliográfica e implementación de algoritmos en MATLAB abarcando una amplia gama de situaciones con las cuales se hace evidente la importancia de la estimación de parámetros es la modelación de dichos procesos

Análisis, Descripción y Simulación de Modelos Estocásticos de Tasas de Interés

Los estudios acerca de los modelos de tasas de interés tienen una gran cantidad de aplicaciones en los campos económico, financiero, energético, productivo, entre otros. El descubrir la estructura que determina el comportamiento de las tasas de interés permite realizar análisis de una manera más eficiente, conociendo los potenciales y limitaciones los modelos desarrollados. Muchos modelos, tanto en el campo discreto como en el campo continuo, han sido propuestos para modelar el comportamiento de las tasas de interés, algunas veces partiendo de conocimientos a priori y algunas otras veces utilizando metodologías que permitan inferir particularidades del proceso. Los modelos de series de tiempo (en desarrollos discretos) y las ecuaciones diferenciales estocásticas (en los casos continuos) han sido dos de las metodologías más usadas tanto en la modelación como en el análisis de los procesos de tasas de interés. En este trabajo se presentan diferentes modelos teniendo como base las ecuaciones diferenciales estocásticas, aunque muchos de los análisis relacionados con ellos se desarrollen en el campo discreto, como se verá más adelante..

Heterogeneity in Kv2 Channel Expression Shapes Action Potential Characteristics and Firing Patterns in CA1 versus CA2 Hippocampal Pyramidal Neurons.

The CA1 region of the hippocampus plays a critical role in spatial and contextual memory, and has well-established circuitry, function and plasticity. In contrast, the properties of the flanking CA2 pyramidal neurons (PNs), important for social memory, and lacking CA1-like plasticity, remain relatively understudied. In particular, little is known regarding the expression of voltage-gated K+ (Kv) channels and the contribution of these channels to the distinct properties of intrinsic excitability, action potential (AP) waveform, firing patterns and neurotransmission between CA1 and CA2 PNs. In the present study, we used multiplex fluorescence immunolabeling of mouse brain sections, and whole-cell recordings in acute mouse brain slices, to define the role of heterogeneous expression of Kv2 family Kv channels in CA1 versus CA2 pyramidal cell excitability. Our results show that the somatodendritic delayed rectifier Kv channel subunits Kv2.1, Kv2.2, and their auxiliary subunit AMIGO-1 have region-specific differences in expression in PNs, with the highest expression levels in CA1, a sharp decrease at the CA1-CA2 boundary, and significantly reduced levels in CA2 neurons. PNs in CA1 exhibit a robust contribution of Guangxitoxin-1E-sensitive Kv2-based delayed rectifier current to AP shape and after-hyperpolarization potential (AHP) relative to that seen in CA2 PNs. Our results indicate that robust Kv2 channel expression confers a distinct pattern of intrinsic excitability to CA1 PNs, potentially contributing to their different roles in hippocampal network function

The health from the humanist perspective of Blas Álvarez de Miraval

A pesar de que existen diferentes estudios en las Ciencias de la Actividad Física y del Deporte sobre autores humanistas, el objetivo del presente trabajo es poner en valor la obra de una de las figuras más importantes del humanismo español, Blas Álvarez de Miraval, insigne médico y teólogo, a través del análisis pormenorizado de su obra cumbre, titulada De la conservación de la salud del cuerpo y el alma, cuyos resultados arrojan una visión única y diferente de lo que ha de ser la conservación de la salud desde una perspectiva integral por parte del individuoIn spite of the fact that there are different studies in the Sciences of the Sport on humanist authors, the aim of the present work is to put of relevancy the work of one of the most important figures of the Spanish humanism, Blas Álvarez de Miraval, celebrated doctor and theologian, with regard to the Sciences of the Physical Activity and of the Sport by means of the study detailed of his greatest work, "Of the conservation of the health of the body and the soul", which results throw an only and different vision from what has to be the conservation of the health from the integral care of the individua

Wireless internet architecture and testbed for wineglass

One of the most challenging issues in the area of mobile communication is the deployment of IPbased wireless multimedia networks in public and business environments. The public branch may involve public mobile networks, like UMTS as 3G system, while the business branch introduces local radio access networks by means of W-LANs. Conventional mobile networks realise mobile specific functionality, e.g. mobility management or authentication and accounting, by implementing appropriate mechanisms in specific switching nodes (e.g. SGSN in GPRS). In order to exploit the full potential of IP networking solutions a replacement of these mechanisms by IP-based solutions might be appropriate. In addition current and innovative future services in mobile environments require at least soft-guaranteed, differentiated QoS. Therefore the WINE GLASS project investigates and implements enhanced IP-based techniques supporting mobility and QoS in a wireless Internet architecture. As a means to verify the applicability of the implemented solutions, location-aware services deploying both IP-mobility and QoS mechanisms will be implemented and demonstratedPeer ReviewedPostprint (published version

Shifted loops and coercivity from field imprinted high energy barriers in ferritin and ferrihydrite nanoparticles

We show that the coercive field in ferritin and ferrihydrite depends on the maximum magnetic field in a hysteresis loop and that coercivity and loop shifts depend both on the maximum and cooling fields. In the case of ferritin we show that the time dependence of the magnetization also depends on the maximum and previous cooling fields. This behavior is associated to changes in the intra-particle energy barriers imprinted by these fields. Accordingly, the dependence of the coercive and loop shift fields with the maximum field in ferritin and ferrihydrite can be described within the frame of a uniform-rotation model considering a dependence of the energy barrier with the maximum and the cooling fields.Comment: 8 pages, 5 figures. Accepted for publication in Phys. Rev. B. Final version with improved writing and figure

A model for high-mass microquasar jets under the influence of a strong stellar wind

Context. High-mass microquasars (HMMQs) are systems from which relativistic jets are launched. At the scales of several times the binary system size, the jets are expected to follow a helical path caused by the interaction with a strong stellar wind and orbital motion.Such a trajectory has its influence on the non-thermal emission of the jets, which also depends strongly on the observing angle due to Doppler boosting effects. Aims. We explore how the expected non-thermal emission of HMMQ jets at small scales is affected by the impact of the stellar wind and the orbital motion on the jet propagation. Methods. We studied the broadband non-thermal emission, from radio to gamma rays, produced in HMMQ jets up to a distance of several orbital separations, taking into account a realistic jet trajectory, different model parameters, and orbital modulation. The jet trajectory is computed by considering momentum transfer with the stellar wind. Electrons are injected at the position where a recollimation shock in the jets is expected due to the wind impact. Their distribution along the jet path is obtained assuming local acceleration at the recollimation shock, and cooling via adiabatic, synchrotron, and inverse Compton processes. The synchrotron and inverse Compton emission is calculated taking into account synchrotron self-absorption within the jet, free-free absorption with the stellar wind, and absorption by stellar photons via pair production. Results. The spectrum is totally dominated by the jet over the counter-jet due to Doppler boosting. Broadband emission from microwaves to gamma rays is predicted, with radio emission being totally absorbed. This emission is rather concentrated in the regions close to the binary system and features strong orbital modulation at high energies. Asymmetric light curves are obtained owing to the helical trajectory of the jets. Conclusions. The presence of helical shaped jets could be inferred from asymmetries in the light curves, which become noticeable only for large jet Lorentz factors and low magnetic fields. Model parameters could be constrained if accurate phase-resolved lightcurves from GeV to TeV energies were available. The predictions for the synchrotron and the inverse Compton radiation are quite sensitive of the parameters determining the wind-jet interaction structure

Advanced surface characterization of silver nanocluster segregation in Ag-TiCN bioactive coatings by RBS, GDOES and ARXPS

Surface modification by means of wear protective and antibacterial coatings represents, nowadays, a crucial challenge in the biomaterials field in order to enhance the lifetime of bio-devices. It is possible to tailor the properties of the material by using an appropriate combination of high wear resistance (e.g., nitride or carbide coatings) and biocide agents (e.g., noble metals as silver) to fulfill its final application. This behavior is controlled at last by the outmost surface of the coating. Therefore, the analytical characterization of these new materials requires high-resolution analytical techniques able to provide information about surface and depth composition down to the nanometric level. Among these techniques are Rutherford backscattering spectrometry (RBS), glow discharge optical emission spectroscopy (GDOES), and angle resolved X-ray photoelectron spectroscopy (ARXPS). In this work, we present a comparative RBS–GDOES–ARXPS study of the surface characterization of Ag–TiCN coatings with Ag/Ti atomic ratios varying from 0 to 1.49, deposited at room temperature and 200 °C. RBS analysis allowed a precise quantification of the silver content along the coating with a non-uniform Ag depth distribution for the samples with higher Ag content. GDOES surface profiling revealed that the samples with higher Ag content as well as the samples deposited at 200 °C showed an ultrathin (1–10 nm) Ag-rich layer on the coating surface followed by a silver depletion zone (20–30 nm), being the thickness of both layers enhanced with Ag content and deposition temperature. ARXPS analysis confirmed these observations after applying general algorithm involving regularization in addition to singular value decomposition techniques to obtain the concentration depth profiles. Finally, ARXPS measurements were used to provide further information on the surface morphology of the samples obtaining an excellent agreement with SEM observations when a growth model of silver islands with a height d = 1.5 nm and coverage θ = 0.20 was applied to the sample with Ag/Ti = 1.49 and deposited at room temperature.This work was financially supported by the Spanish Ministry of Science and Innovation (projects FUNCOAT CSD2008-00023 and RyC2007-0026). This research is sponsored by FEDER funds through the program COMPETE "Programa Operacional Factores de Competitividade" and by national funds through FCT "Fundacao para a Ciencia e a Tecnologia", in the framework of the Strategic Projects PEST-C/FIS/UI607/2011, and PEST-C/EME/UI0285/2011 and under the project PTDC/CTM/102853/2008. The authors would like to acknowledge I. Caretti and R. Velasco for the fruitful discussions and the proofreading of the manuscript