Ultrafiltración extractiva con ácido Di-nonilnaftalenosulfónico aplicado a la recuperación de betaína

En el presente trabajo se ha estudiado el proceso de ultrafiltración extractiva de betaína de disoluciones acuosas con ácido di-nonilnaftalenosufónico (DNNSA) disuelto en nheptano a 30 y 40ºC utilizando contactores de fibras huecas de polipropileno (Celgard X-50). Se ha analizado el proceso de re-extracción de betaína desde la fase orgánica cargada usando una disolución de hidróxido de sodio. Asimismo, se ha optimizado el proceso integrado de extracción- reextracción de betaína utilizando dos contactores de membrana dispuestos en serie, esta configuración asegura que no tenga lugar la saturación del agente extractante, ya que se regenera continuamente en el módulo de reextracción. La evaluación del proceso requiere la construcción de un modelo matemático que implica la resolución conjunta de los balances de materia en estado no estacionario a los tanques de mezcla y las ecuaciones cinéticas de transferencia de materia a través de los módulos de membranas. Esta modelización de los resultados permite cuantificar el coeficiente global de transferencia de materia, parámetro cinético necesario para el cambio de escala. En este estudio se examina la influencia de los siguientes factores sobre el coeficiente global de transferencia de materia: la concentración de DNNSA en la fase orgánica, la concentración de betaína en la fase acuosa, del pH, de la temperatura y la influencia de la velocidad de los flujos en el módul

Deterministic characterization of stochastic genetic circuits

For cellular biochemical reaction systems where the numbers of molecules is small, significant noise is associated with chemical reaction events. This molecular noise can give rise to behavior that is very different from the predictions of deterministic rate equation models. Unfortunately, there are few analytic methods for examining the qualitative behavior of stochastic systems. Here we describe such a method that extends deterministic analysis to include leading-order corrections due to the molecular noise. The method allows the steady-state behavior of the stochastic model to be easily computed, facilitates the mapping of stability phase diagrams that include stochastic effects and reveals how model parameters affect noise susceptibility, in a manner not accessible to numerical simulation. By way of illustration we consider two genetic circuits: a bistable positive-feedback loop and a negative-feedback oscillator. We find in the positive feedback circuit that translational activation leads to a far more stable system than transcriptional control. Conversely, in a negative-feedback loop triggered by a positive-feedback switch, the stochasticity of transcriptional control is harnessed to generate reproducible oscillations.Comment: 6 pages (Supplementary Information is appended

Información y pragmática: el problema de la exclusión

Se plantea la necesidad de una teoría filosófica de la información desde principios fenomenológicos. Se considera la condición ideológica de toda teoría y cómo, en la pragmática de Habermas, se muestra que ha dado lugar en la concepción tecnológica de lo social al dominio del hombre por el hombre, a la exclusión como forma de opresión y poder, lo que la misma pragmática no puede superar.This work carries out an analysis of the need of a Philosophical Theory of the Information established on phenomenologic principles. This analysis includes the ideological condition of any Theory, and as it makes possible to show in the writings Habermas's pragmatics, that this condition has given place in the technological conception of the social thing to the control of the man for the man, to the exclusion as way of oppression and power, what the same pragmatics cannot overcome

Dynamical Principles of Two-Component Genetic Oscillators

Genetic oscillators based on the interaction of a small set of molecular components have been shown to be involved in the regulation of the cell cycle, the circadian rhythms, or the response of several signaling pathways. Uncovering the functional properties of such oscillators then becomes important for the understanding of these cellular processes and for the characterization of fundamental properties of more complex clocks. Here, we show how the dynamics of a minimal two-component oscillator is drastically affected by its genetic implementation. We consider a repressor and activator element combined in a simple logical motif. While activation is always exerted at the transcriptional level, repression is alternatively operating at the transcriptional (Design I) or post-translational (Design II) level. These designs display differences on basic oscillatory features and on their behavior with respect to molecular noise or entrainment by periodic signals. In particular, Design I induces oscillations with large activator amplitudes and arbitrarily small frequencies, and acts as an “integrator” of external stimuli, while Design II shows emergence of oscillations with finite, and less variable, frequencies and smaller amplitudes, and detects better frequency-encoded signals (“resonator”). Similar types of stimulus response are observed in neurons, and thus this work enables us to connect very different biological contexts. These dynamical principles are relevant for the characterization of the physiological roles of simple oscillator motifs, the understanding of core machineries of complex clocks, and the bio-engineering of synthetic oscillatory circuits

Quantum manifestations of chaos in elastic atom-surface scattering

Quantum manifestations of chaos in the diffraction of atoms from corrugated surfaces, for a range of initial conditions easily attainable in scattering experiments, are presented and discussed. The appearance of strong oscillations in diffraction patterns is shown to be directly related to the presence of classical chaos and threshold effects. We also show that the autocorrelation function for some of the collision S-matrix elements over incident angles is sensitive to the character, hyperbolic or nonhyperbolic, of the underlying chaotic dynamics, in agreement with general semiclassical arguments for unbound chaotic systems. © 2001 The American Physical SocietyThis work was supported by DGES (Spain) under Contract Nos. PB95-71 and PB98-115 and the European Contract No. HPRN-CT-1999-00005. R.G. acknowledges financial support from CAM (Spain).Peer Reviewe

Hamiltonian theory for vibrational line shapes of atoms adsorbed on surfaces

An analytical theory which was based on a Hamiltonian equivalent of the generalized Langevin equation, for the line shape, temperature-dependent shift and broadening of the translational or T-mode peak is presented. The theory can be used to infer physical parameters of the adatom-surface interaction. For the line shape a first-order perturbative solution of the normal-mode coordinates was used. For the shift and broadening, a perturbative expansion in the instantaneous system frequency was employed.This work has been supported in part by DGICYT (Spain) under Contract No. BFM2001-2179. R.G. and J.L.V. thank the Ministry of Science and Technology (Spain) for a Ramón y Cajal Contract and a predoctoral F.P.I. grant, respectively. This work has also been supported by grants from the Israel Science Foundation, the Minerva Foundation (Munich) and the Volkswagen Foundation.Peer Reviewe

An application of interpolating scaling functions to wave packet propagation

Wave packet propagation in the basis of interpolating scaling functions (ISF) is studied. The ISF are well known in the multiresolution analysis based on spline biorthogonal wavelets. The ISF form a cardinal basis set corresponding to an equidistantly spaced grid. They have compact support of the size determined by the underlying interpolating polynomial that is used to generate ISF. In this basis the potential energy matrix is diagonal and the kinetic energy matrix is sparse and, in the 1D case, has a band-diagonal structure. An important feature of the basis is that matrix elements of a Hamiltonian are exactly computed by means of simple algebraic transformations efficiently implemented numerically. Therefore the number of grid points and the order of the underlying interpolating polynomial can easily be varied allowing one to approach the accuracy of pseudospectral methods in a regular manner, similar to high order finite difference methods. The results of numerical simulations of an H+H_2 collinear collision show that the ISF provide one with an accurate and efficient representation for use in the wave packet propagation method.Comment: plain Latex, 11 pages, 4 figures attached in the JPEG forma

A mathematical model for the rational design of chimeric ligands in selective drug therapies

Chimeric drugs with selective potential toward specific cell types constitute one of the most promising forefronts of modern Pharmacology. We present a mathematical model to test and optimize these synthetic constructs, as an alternative to conventional empirical design. We take as a case study a chimeric construct composed of epidermal growth factor (EGF) linked to different mutants of interferon (IFN). Our model quantitatively reproduces all the experimental results, illustrating how chimeras using mutants of IFN with reduced affinity exhibit enhanced selectivity against cell overexpressing EGF receptor. We also investigate how chimeric selectivity can be improved based on the balance between affinity rates, receptor abundance, activity of ligand subunits, and linker length between subunits. The simplicity and generality of the model facilitate a straightforward application to other chimeric constructs, providing a quantitative systematic design and optimization of these selective drugs against certain cell-based diseases, such as Alzheimer's and cancerThis work has been supported by the Ministry of Science and Technology of Spain via a Ramon y Cajal Fellowship (Ref. RYC-2010-07450) and a Project from Plan National framework (Ref. BFU2011-30303), and a Marie Curie International Reintegration Grant from the EU (Ref. 248346-NMSSBLS). V.D.M. acknowledges financial support to the Universidad Autónoma de Madrid for a FPI-UAM fellowshi

MOLAS FONT, Maria Dolors y SANTIAGO BAUTISTA, Aroa (eds.): La infancia en femenino: las niñas. Imágenes y figuras de la filiación

Noticias. Arenal 25(1), enero-junio de 201

The amendment of measures issued in a foreign judgment: a pending question (AP Cantabria, February 11, 2020)

La modificación de sentencias dictadas en países extranjeros sigue siendo una cuestión que no está definitivamente resuelta por nuestros tribunales. Hay dos cuestiones problemáticas. La primera de ellas es la duda acerca de la necesidad de solicitud de exequatur previo a la modificación de las medidas recogidas en una sentencia extranjera. La segunda es la falta de aplicación de las normas de competencia judicial internacional y su sustitución por normas de competencia judicial interna. Este auto muestra otra confusión que es otorgar la competencia para modificar las medidas de una sentencia extranjera al juez que dictó el exequatur.The amendment of judgments handed down in foreign countries is an issue that has not yet been definitively resolved by our Courts. There are two troubling questions that are repeated over time. The first one is the requirement or not of exequatur prior to the amendment of the foreign judgment. The second problem is the lack of application of the rules of international jurisdiction and their replacement by rules of domestic jurisdiction. This Order shows another confusing variable, pointing out that international jurisdiction to modify a judgment belongs to the judge who recognized the full effectiveness of the foreign divorce resolution, that is, the judge who pronounced the exequatur