Numerical Computation of the Effective Potential and Renormalization

We present a novel way to compute the one-loop ring-improved effective potential numerically, which avoids the spurious appearence of complex expressions and at the same time is free from the renormalization ambiguities of the self-consistent approaches, based on the direct application of Schwinger-Dyson type equations to the masses.Comment: 8 pages, LATEX, 2 postscript figures available. e-mail : [email protected] , submitted to Mod. Phys. Letter

The delayed rectifier potassium conductance in the sarcolemma and the transverse tubular system membranes of mammalian skeletal muscle fibers.

A two-microelectrode voltage clamp and optical measurements of membrane potential changes at the transverse tubular system (TTS) were used to characterize delayed rectifier K currents (IK(V)) in murine muscle fibers stained with the potentiometric dye di-8-ANEPPS. In intact fibers, IK(V) displays the canonical hallmarks of K(V) channels: voltage-dependent delayed activation and decay in time. The voltage dependence of the peak conductance (gK(V)) was only accounted for by double Boltzmann fits, suggesting at least two channel contributions to IK(V). Osmotically treated fibers showed significant disconnection of the TTS and displayed smaller IK(V), but with similar voltage dependence and time decays to intact fibers. This suggests that inactivation may be responsible for most of the decay in IK(V) records. A two-channel model that faithfully simulates IK(V) records in osmotically treated fibers comprises a low threshold and steeply voltage-dependent channel (channel A), which contributes ∼31% of gK(V), and a more abundant high threshold channel (channel B), with shallower voltage dependence. Significant expression of the IK(V)1.4 and IK(V)3.4 channels was demonstrated by immunoblotting. Rectangular depolarizing pulses elicited step-like di-8-ANEPPS transients in intact fibers rendered electrically passive. In contrast, activation of IK(V) resulted in time- and voltage-dependent attenuations in optical transients that coincided in time with the peaks of IK(V) records. Normalized peak attenuations showed the same voltage dependence as peak IK(V) plots. A radial cable model including channels A and B and K diffusion in the TTS was used to simulate IK(V) and average TTS voltage changes. Model predictions and experimental data were compared to determine what fraction of gK(V) in the TTS accounted simultaneously for the electrical and optical data. Best predictions suggest that K(V) channels are approximately equally distributed in the sarcolemma and TTS membranes; under these conditions, >70% of IK(V) arises from the TTS

Effect of the nearby levels on the resonance fluorescence spectrum of the atom-field interaction

We study the resonance fluorescence in the Jaynes-Cummings model when nearby levels are taking into account. We show that the Stark shift produced by such levels generates a displacement of the peaks of the resonance fluorescence due to an induced effective detuning and also induces an asymmetry. Specific results are presented assuming a coherent and a thermal fields

Medios de comunicación y globalización : ¿destrucción o reconstrucción de identidades culturales?

La discusión sobre identidad y medios de comunicación ha estado dominada por la sensación de amenaza a los estilos de vida y a las percepciones, lenguajes y sensibilidades tradicionales como resultado de la globalización. Esta realidad, que ha alterado radicalmente los procesos de construcción de sentido y pertenencia, se ha traducido a menudo en una serie de prejuicios que hablan de catástrofes culturales y sociedades atomizadas por los media. A partir de esta constatación, el objetivo de este artículo es presentar las principales características que adquiere la relación «identidad, cultura y globalización» desde una perspectiva medial que permita una adecuada reflexión acerca de su impacto.The discussion about identity and the globalisation of communications often leads to prejudices and fears about cultural catastrophes and societies fragmented by the supposedly wicked influence of the media. Traditional ways of life seem threatened by new perceptions, languages, and sensibilities. This article therefore outlines the main characteristics of the relationship between identity, culture, and globalisation from the perspective of the mass media, in order to analyse its impact more adequately

Publicidad: ¿la "zanahoria metafísica" que mueve al burro o el color de nuestro tiempo?

In recent years, advertising has been characterized by gaining depth and penetration in the mass media, acquiring influence in the processes of world construction and the shaping of current culture. Parallel to this, advertising has been legitimized both in the field of educational and in the cultural sector as it is considered to be a reflection of society and indispensable for the survival of much of the media. As a consequence of the undeniable importance of advertising today, we attempt in this article to respond to the question of the current role it plays beyond the act of purchasing

Model for Dissipative Highly Nonlinear Waves in Dry Granular Systems

A model is presented for the characterization of dissipative effects on highly nonlinear waves in one-dimensional dry granular media. The model includes three terms: Hertzian, viscoelastic, and a term proportional to the square of the relative velocity of particles. The model outcomes are confronted with different experiments where the granular system is subject to several constraints for different materials. Excellent qualitative and quantitative agreement between theory and experiments is found.Comment: Link to the Journal: http://prl.aps.org/abstract/PRL/v104/i11/e11800