Super-roughening as a disorder-dominated flat phase

We study the phenomenon of super-roughening found on surfaces growing on disordered substrates. We consider a one-dimensional version of the problem for which the pure, ordered model exhibits a roughening phase transition. Extensive numerical simulations combined with analytical approximations indicate that super-roughening is a regime of asymptotically flat surfaces with non-trivial, rough short-scale features arising from the competition between surface tension and disorder. Based on this evidence and on previous simulations of the two-dimensional Random sine-Gordon model [Sanchez et al., Phys. Rev. E 62, 3219 (2000)], we argue that this scenario is general and explains equally well the hitherto poorly understood two-dimensional case.Comment: 7 pages, 4 figures. Accepted for publication in Europhysics Letter

Avoiding Interference in Planar Arrays through the Use of Artificial Neural Networks

[Abstract] This article implements an artificial neural network to find, through computer simulation, the excitations of a square planar array. The array is composed of 52 uniformly spaced subarrays, and has a quasi- in its radiation diagram. This simulation model includes the reduction of any signal interference in the shaped radiating zone after its position has been determined

Estudio de los materiales de partida de los suelos de la Terra Chá

[Resumen] Se realizó un estudio de campo y de fotointerpretación de los materiales terciarios y cuaternarios de la Terra Chá. Con ellos se completa la información que sobre los mismos figura en las hojas geológicas de Villalba, Lugo, Meira y Castroverde del IGME. Con todo el c6njunto de datos se realizó la cartografia de los principales materiales de partida sobre los que se desarrollan los suelos de la Terra Chá. Se identifican por di fracción de rayos X los distintos tipos de arcilla de los depósitos terciarios. Finalmente se caracterizan los sistemas de terrazas y material aluvial de los rios Anllo, Miño y Lea, tratando de establecer entre los mismos una relación genética

Equilibrium roughening transition in a 1D modified sine-Gordon model

We present a modified version of the one-dimensional sine-Gordon that exhibits a thermodynamic, roughening phase transition, in analogy with the 2D usual sine-Gordon model. The model is suited to study the crystalline growth over an impenetrable substrate and to describe the wetting transition of a liquid that forms layers. We use the transfer integral technique to write down the pseudo-Schr\"odinger equation for the model, which allows to obtain some analytical insight, and to compute numerically the free energy from the exact transfer operator. We compare the results with Monte Carlo simulations of the model, finding a perfect agreement between both procedures. We thus establish that the model shows a phase transition between a low temperature flat phase and a high temperature rough one. The fact that the model is one dimensional and that it has a true phase transition makes it an ideal framework for further studies of roughening phase transitions.Comment: 11 pages, 13 figures. Accepted for publication in Physical Review

Secondary dendritic arm spacing versus corrosion resistance on 316 stainless steels

Las aleaciones presentan una macroestructura característica que se forma a partir del proceso de solidificación de solidificación direccional, consistente en tres tipos principales de estructuras de granos: columnar, equiaxial, y una zona de transición de columnar a equiaxial (TCE). También se forma una microestructura dendrítica como forma de cristalización. Estas estructuras hacen que las aleaciones tipo acero 316 presenten modificaciones en las características mecánicas y en la resistencia a la corrosión. Con el objeto de estudiar la resistencia a la corrosión en los aceros en el presente trabajo se utilizaron probetas de diferente composición, a las cuales se les realizaron ensayos de polarización potenciodinámica cíclica para cada tipo de estructura (columnar, equiaxial y con TCE). A continuación se reveló la microestructura de cada probeta y se midieron los espaciamientos dendríticos secundarios. La mayor resistencia a la corrosión fue observada en las estructuras columnar y con TCE, mientras que la estructura equiaxial fue la más susceptible en la mayoría de los casos. Se encontraron mayores valores de espaciamientos dendríticos en la zona equiaxial de las probetas.The alloys exhibit a characteristic macrostructure formed during directional solidification process, which is consisting of three main types of grain structures: columnar, equiaxed, or with the columnar-to-equiaxed transition (CET). A dendritic structure it’s also formed as a type of crystallization. These structures make alloys like 316 stainless steels to present modifications on mechanical properties and corrosion resistance. In order to study the corrosion resistance on stainless steel, samples of different compositions were used, and polarization tests were conducted on each type of structure (columnar, equiaxed and CET). Microstructure of each sample was revealed and secondary dendritic arm spacing was measured. Columnar and CET structures were the most resistant to localized corrosion, whereas equiaxed structure was the most susceptible to corrosion. This structure presented the higher values of secondary dendritic arm spacing.Fil: Covinich, Mónica M.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; ArgentinaFil: Derna, Ana Mariela. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; ArgentinaFil: Giménez, J. R. A.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; ArgentinaFil: Mendez, C. M.. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; ArgentinaFil: Ares, Alicia Esther. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnológico Nordeste. Instituto de Materiales de Misiones; Argentin

Collective modes of coupled phase oscillators with delayed coupling

We study the effects of delayed coupling on timing and pattern formation in spatially extended systems of dynamic oscillators. Starting from a discrete lattice of coupled oscillators, we derive a generic continuum theory for collective modes of long wavelength. We use this approach to study spatial phase profiles of cellular oscillators in the segmentation clock, a dynamic patterning system of vertebrate embryos. Collective wave patterns result from the interplay of coupling delays and moving boundary conditions. We show that the phase profiles of collective modes depend on coupling delays.Comment: 5 pages, 2 figure

Thermoelectric power of bulk black-phosphorus

The potential of bulk black-phosphorus for thermoelectric applications has been experimentally studied. The Seebeck Coefficient (S) has been measured in the temperature range from 300 K to 385 K, finding a value of S = +335 +- 10 uV/K at room temperature (indicating a naturally occurring p-type conductivity). S increases with temperature, as expected for p-type semiconductors, which can be attributed to an increase of the charge carrier density. The electrical resistance drops up to a 40 % while heating in the studied temperature range. As a consequence, the power factor at 385 K is 2.7 times higher than that at room temperature. This work demonstrates the feasibility of black-phosphorus in thermoelectric applications, such as thermal energy scavenging, which typically require devices with high performance at temperatures above room temperature.Comment: 3 figure

Geochemistry and Geochronology of the Guajira Eclogites, northern Colombia : evidence of a metamorphosed primitive Cretaceous Caribbean Island-arc

The chemical composition of eclogites, found as boulders in a Tertiary conglomerate from the Guajira Peninsula, Colombia suggests that these rocks are mainly metamorphosed basaltic andesites. They are depleted in LILE elements compared to MORB, have a negative Nb-anomaly and flat to enriched REE patterns, suggesting that their protoliths evolved in a subduction related tectonic setting. They show island-arc affinities and are similar to primitive islandarc rocks described in the Caribbean. The geochemical characteristics are comparable to low-grade greenschists from the nearby Etpana Terrane, which are interpreted as part of a Cretaceous intra-oceanic arc. These data support evidence that the eclogites and the Etpana terrane rocks formed from the same volcano-sedimentary sequence. Part of this sequence was accreted onto the margin and another was incorporated into the subduction channel and metamorphosed at eclogite facies conditions. 40Ar-39Ar ages of 79.2±1.1Ma and 82.2±2.5Ma determined on white micas, separated from two eclogite samples, are interpreted to be related to the cooling of the main metamorphic event. The formation of a common volcano-sedimentary protolith and subsequent metamorphism of these units record the ongoing Late Cretaceous continental subduction of the South American margin within the Caribbean intra-oceanic arc subduction zone. This gave way to an arc-continent collision between the Caribbean and the South American plates, where this sequence was exhumed after the Campanian