Visibilidad de los ingresos públicos por niveles territoriales de gobierno: análisis internacional

Se puede definir el concepto de ilusión fiscal como la percepción sistemáticamente sesgada de los parámetros fiscales, debido a un error o ignorancia del lado de la demanda o por una conducta abusiva del lado de la oferta. Es decir, el sesgo sistemático en la percepción por parte de los individuos del tamaño de la carga de los impuestos y otros ingresos soportados por ellos y los beneficios recibidos del gasto público, y su influencia sobre las decisiones del gasto público sobre diferentes instituciones de decisión colectiva. L a ilusión fiscal, tanto de los ingresos como de los gastos públicos, puede por tanto modificar las decisiones presupuestarias. Esta comunicación propone un índice para medir la visibilidad fiscal de los ingresos públicos y lo aplica a los países pertenecientes a la Unión Europea

Bioelectrical model of head-tail patterning based on cell ion channels and intercellular gap junctions

Robust control of anterior-posterior axial patterning during regeneration is mediated by bioelectric signaling. However, a number of systems-level properties of bioelectrochemical circuits, including stochastic outcomes such as seen in permanently de-stabilized "cryptic" flatworms, are not completely understood. We present a bioelectrical model for head-tail patterning that combines single-cell characteristics such as membrane ion channels with multicellular community effects via voltage-gated gap junctions. It complements the biochemically-focused models by describing the effects of intercellular electrochemical coupling, cutting plane, and gap junction blocking of the multicellular ensemble. We provide qualitative insights into recent experiments concerning planarian anterior/posterior polarity by showing that: (i) bioelectrical signals can help separated cell domains to know their relative position after injury and contribute to the transitions between the abnormal double-head state and the normal head-tail state; (ii) the bioelectrical phase-space of the system shows a bi-stability region that can be interpreted as the cryptic system state; and (iii) context-dependent responses are obtained depending on the cutting plane position, the initial bioelectrical state of the multicellular system, and the intercellular connectivity. The model reveals how simple bioelectric circuits can exhibit complex tissue-level patterning and suggests strategies for regenerative control in vivo and in synthetic biology contexts

Simple molecular model for the binding of antibiotic molecules to bacterial ion channels

A molecular model aimed at explaining recent experimental data by Nestorovich et al. [Proc. Natl. Acad. Sci. USA 99, 9789 (2002)] on the interaction of ampicillin molecules with the constriction zone in a channel of the general bacterial porin, OmpF (outer membrane protein F), is presented. The model extends T. L. Hill’s theory for intermolecular interactions in a pair of binding sites [J. Am. Chem. Soc. 78, 3330 (1956)] by incorporating two binding ions and two pairs of interacting sites. The results provide new physical insights on the role of the complementary pattern of the charge distributions in the ampicillin molecule and the narrowest part of the channel pore. Charge matching of interacting sites facilitates drug binding. The dependence of the number of ampicillin binding events per second with the solution pH and salt concentration is explained qualitatively using a reduced number of fundamental concepts.Salvador.Mafé@uv.e

Kinetic modeling of ion conduction in KcsA potassium channel

KcsA constitutes a potassium channel of known structure that shows both high conduction rates and selectivity among monovalent cations. A kinetic model for ion conduction through this channel that assumes rapid ion transport within the filter has recently been presented by Nelson. In a recent, brief communication, we used the model to provide preliminary explanations to the experimental current-voltage J‐V and conductance-concentration g‐S curves obtained for a series of monovalent ions (K+,Tl+, and Rb+). We did not assume rapid ion transport in the calculations, since ion transport within the selectivity filter could be rate limiting for ions other than native K+. This previous work is now significantly extended to the following experimental problems. First, the outward rectification of the J‐V curves in K+ symmetrical solutions is analyzed using a generalized kinetic model. Second, the J‐V and g‐S curves for NH4+ are obtained and compared with those of other ions (the NH4+ J‐V curve is qualitatively different from those of Rb+ and Tl+). Third, the effects of Na+ block on K+ and Rb+ currents through single KcsA channels are studied and the different blocking behavior is related to the values of the translocation rate constants characteristic of ion transport within the filter. Finally, the significantly decreased K+ conductance caused by mutation of the wild-type channel is also explained in terms of this rate constant. In order to keep the number of model parameters to a minimum, we do not allow the electrical distance (an empirical parameter of kinetic models that controls the exponential voltage dependence of the dissociation rate) to vary with the ionic species. Without introducing the relatively high number of adjustable parameters of more comprehensive site-based models, we show that ion association to the filter is rate controlling at low concentrations, but ion dissociation from the filter and ion transport within the filter could limit conduction at high concentration. Although some experimental data from other authors were included to allow qualitative comparison with model calculations, the absolute values of the effective rate constants obtained are only tentative. However, the relative changes in these constants needed to explain qualitatively the experiments should be of [email protected]

Donnan phenomena in membranes with charge due to ion adsorption. Effects of the interaction between adsorbed charged groups

A physical model for the modified Donnan phenomenon associated with ion adsorption on localized membrane sites is presented. This model accounts for the dependence of the concentration of adsorbed ions on electrolyte concentration and pH as it is influenced by the electrostatic interaction between adsorbed ions. The equilibrium thermodynamic concepts employed are based on the Donnan formalism for the ion equilibria between membrane and solution, and the Bragg–Williams approximation for an adsorption isotherm that incorported interaction between adsorbed ions. Our results include the concentration of charged groups in the membrane, the pH of the membrane phase solution, and the Donnan potential as functions of the pH and the electrolyte concentration of the external solution for different degrees of the electrostatic interaction. These magnitudes are of considerable interest in biopolymers, membranes, and conducting [email protected] ; [email protected]

Asymmetric nanopore rectification for ion pumping, electrical power generation, and information processing applications

Single-track, asymmetric nanopores can currently be functionalised with a spatially inhomogeneous distribution of fixed charges and a variety of pore tip shapes. Optimising the asymmetric nanopore characteristics is crucial for practical applications in nanofluidics. We have addressed here this question for three cases based on different input/output chemical and electrical signals: (i) ion pumping up a concentration gradient by means of a periodic, time-dependent bias potential, (ii) information processing with a single nanopore acting as the nanofluidic diode of a logic gate, and (iii) electrical energy harvesting using a nanopore that separates two solutions of different salt concentrations. The results show the nanopore characteristics (size, shape, and charge distribution) that should be optimised for each application. In particular, the control of the pore tip size and charge appears to be crucial in all cases because it is in this narrow region where the interaction of the ions and the pore surface occurs, and this will eventually determine the nanodevice performance. © 2011 Elsevier Ltd. All rights reserved.We acknowledge the financial support from the Ministry of Science and Innovation of Spain and FEDER, Programme of Materials (project No. MAT2009-07747).Cervera, J.; Ramirez Hoyos, P.; Mafé, S.; Stroeve, P. (2011). Asymmetric nanopore rectification for ion pumping, electrical power generation, and information processing applications. Electrochimica Acta. 56(12):4504-4511. https://doi.org/10.1016/j.electacta.2011.02.056S45044511561