Deconstructing temperature gradients across fluid interfaces: the structural origin of the thermal resistance of liquid-vapor interfaces

The interfacial thermal resistance determines condensation-evaporation processes and thermal transport across material-fluid interfaces. Despite its importance in transport processes, the interfacial structure responsible for the thermal resistance is still unknown. By combining non-equilibrium molecular dynamics simulations and interfacial analyses that remove the interfacial thermal fluctuations we show that the thermal resistance of liquid-vapor interfaces is connected to a low density fluid layer that is adsorbed at the liquid surface. This thermal resistance layer (TRL) defines the boundary where the thermal transport mechanism changes from that of gases (ballistic) to that characteristic of dense liquids, dominated by frequent particle collisions involving very short mean free paths. We show that the thermal conductance is proportional to the number of atoms adsorbed in the TRL, and hence we explain the structural origin of the thermal resistance in liquid-vapor interfaces.Comment: 4 pages, 4 figures, and supplementary informatio

Trade and credit : revisiting the evidence

Este trabajo investiga los efectos de shocks de crédito sobre las exportaciones de las empresas españolas. Para ello, combinamos la información procedente de los microdatos de transacciones con el exterior de la Balanza de Pagos con datos de crédito procedentes de la Central de Información de Riesgos a lo largo del período 2002-2013. A continuación, identificamos shocks de oferta de crédito específcos para cada banco y año siguiendo la metodología de Amiti y Weinstein (2018) y estimamos su efecto sobre las ventas exteriores de las empresas españolas. Los resultados indican que los shocks de crédito tienen efectos significativos tanto sobre el margen intensivo (cantidad exportada) como sobre el margen extensivo del comercio (probabilidad de empezar a exportar o dejar de hacerlo)This paper explores the effects of bank lending shocks on export behavior of Spanish firms. For that purpose, we combine Balance of Payments data on exports at the firm-product-destination level with a matched bank-firm dataset incorporating information on the universe of corporate loans from 2002 to 2013. Armed with this dataset, we identify bankyear specific credit supply shocks following Amiti and Weinstein (2018) and estimate their impact on firms’ exports at the product-destination level. According to our estimates, credit supply shocks have sizable effects on both the intensive margin (amount exported) and the extensive margin of trade (decision to export

Para una lectura crítico-genética de "El gato" como cuento, novela y concepto en la obra de Juan García Ponce

Crítica genética y literatura latinoamericana: aportes teóricos y lecturas crítica

Density correlation in liquid surfaces: Bedeaux-Weeks high order terms and non capillary wave background

We present Molecular Dynamics (MD) simulations of liquid-vapor surfaces, and their Intrinsic Sampling Method analysis, to get a quantitative test for the theoretical prediction of the capillary wave (CW) effects on density correlation done by Bedeaux and Weeks (BW) in 1985. The results are contrasted with Wertheim’s proposal which is the first term in BW series and are complemented with a (formally defined and computational accessible) proposal for the background of non-CW fluctuations. Our conclusion is that BW theory is both accurate and needed since it may differ significantly from Wertheim’s proposal. We discuss the implications for the analysis of experimental X-ray surface diffraction data and MD simulations.We acknowledge the support of the Spanish Secretariat for Research, Development, and Innovation (Grant Nos. FIS2017-86007-C3 and FPU2015/0248) and from the Maria de Maeztu Programme for Units of Excellence inR&D(No. MDM-2014-0377

Thickness and fluctuations of free and adsorbed liquid films

Effective mesoscopic Hamiltonians with the thickness of the adsorbed liquid films as a collective variable have been widely used in the study of adsorbed systems. In the present work, we show that the intrinsic surface of a liquid-vapor interface provides a very accurate way to evaluate the instantaneous film thickness in computer simulations. This film thickness follows with quantitative accuracy the predictions of simple model Hamiltonians, even for films as thin as one monolayer, and the effective interfacial potential has the simplest exponential form with a surprising accuracy, from a single monolayer to very thick films. For both the free liquid slabs and the adsorbed films and despite of the low vapor density, we have found that the fluctuations associated with the evaporation of particles to the vapor and their condensation in the liquid layer give an important contribution to the probability distributions of the liquid film thickness in our canonical (NVT) simulationsWe acknowledge the support of the Spanish Minister of Science and Innovation (Grant No. FIS2010-22047-C05) and the Comunidad Autonoma de Madrid under program MODELICO (Grant No. S2009/ESP-1691

Capillary wave spectrum at adsorbed liquid films

Capillary wave fluctuations at the edges of liquid wetting layers are analyzed in Monte Carlo simulations of a Lennard-Jones fluid adsorbed on a planar wall substrate. The analysis is based on the Fourier modes of the liquid surface, constructed via the intrinsic sampling method. For films thinner than four molecular layers we can quantify the damping of the capillary waves due to the wall potential. Our results are presented in the theoretical framework of the effective surface Hamiltonians, to establish a quantitative link between the molecular structure and the mesoscopic descriptions used for renormalization-group analysis. We observe the predicted exponential decay of the wall damping, with the correlation length of the liquid bulk. However, associated with the molecular layering of the density profiles, we observe a strong oscillatory dependence with respect to the mean film thickness, not included in any theoretical prediction. We discuss the possibility of finite-size effects in this respect. Three different definitions of the intrinsic surface at molecular level are tested, to show that the square gradient terms of the Hamiltonian are robust, while the surface bending (or nonlocal) terms are tied to each specific definitionWe acknowledge the support of the Spanish Minister of Science and Innovation (Grant No. FIS2010-22047-C05) and the Comunidad Autónoma de Madrid under program MODELICO (Grant No. S2009/ESP-1691

JUAN GARCÍA PONCE "EL MÍSTICO SIN FE":HACIA UNA REINTERPRETACIÓN DE SU ITINERARIO INTELECTUAL

In this dissertation I analyze Juan García Ponce's novel Crónica de la intervención (1980). There are four aspects of this novel that I am focusing on. The first aspect is the intellectual and cultural context reflected in the novel. This cultural context is at the same time a portrait and a critique of the intellectual dynamics in Mexico during the 1960's. In this aspect I show how the intellectual formation of García Ponce is reflected in the novel and how he defines his position in relation to the literary field. The second aspect is religion and how religious ideas emerge in this novel. Crónica de la intervención has numerous references to Catholic rituals and practices. On the one hand, the ritualistic and religious practices were important on García Ponce's life and work, and I propose that some of his ritual practices owed a lot to healing rituals; on the other, I propose that these religious references achieve a powerful critique of religion and shows how the social beliefs are in profound crisis since the beginning of the modernity, and how in Mexican society religion is a facade and lacks meaningful content. The third aspect is eroticism. In this part I respond to other critics of García Ponce about this element of his narration. I am analyzing this aspect on its socio-historical context. Taking off from two of García Ponce’s essays, I argue that he uses eroticism as a device of social subversion and as a powerful element to generate social changes through sexuality. I show that what he clearly states in these essays about subverting the humanist values of the sexuality and the conceptions of the body is reflected in Crónica. In the last part of this dissertation I analyze the relation of García Ponce to critical theory, principally with the ideas of Herbert Marcuse. García Ponce translated three books and other short writings by Marcuse. Marcuse's ideas were very influential on García Ponce's writings; I show in this part how this novel was conceived, taking in account many of the philosophical ideas assimilated through the work of translatio

Diffusion at the liquid-vapor interface

Recently, the intrinsic sampling method has been developed in order to obtain, from molecular simulations, the intrinsic structure of the liquid-vapor interface that is presupposed in the classical capillary wave theory. Our purpose here is to study dynamical processes at the liquid-vapor interface, since this method allows tracking down and analyzing the movement of surface molecules, thus providing, with great accuracy, dynamical information on molecules that are "at" the interface. We present results for the coefficients for diffusion parallel and perpendicular to the liquid-vapor interface of the Lennard-Jones fluid, as well as other time and length parameters that characterize the diffusion process in this system. We also obtain statistics of permanence and residence time. The generality of our results is tested by varying the system size and the temperature; for the later case, an existing model for alkali metals is also considered. Our main conclusion is that, even if diffusion coefficients can still be computed, the turnover processes, by which molecules enter and leave the intrinsic surface, are as important as diffusion. For example, the typical time required for a molecule to traverse a molecular diameter is very similar to its residence time at the surface.Comment: 25 pages, 7 figures. Submitted to J. Chem. Phy