CELL: a Python package for cluster expansion with a focus on complex alloys

We present the Python package CELL, which provides a modular approach to the cluster expansion (CE) method. CELL can treat a wide variety of substitutional systems, including one-, two-, and three-dimensional alloys, in a general multi-component and multi-sublattice framework. It is capable of dealing with complex materials comprising several atoms in their parent lattice. CELL uses state-of-the-art techniques for the construction of training data sets, model selection, and finite-temperature simulations. The user interface consists of well-documented Python classes and modules (http://sol.physik.hu-berlin.de/cell/). CELL also provides visualization utilities and can be interfaced with virtually any ab initio package, total-energy codes based on interatomic potentials, and more. The usage and capabilities of CELL are illustrated by a number of examples, comprising a Cu-Pt surface alloy with oxygen adsorption, featuring two coupled binary sublattices, and the thermodynamic analysis of its order-disorder transition; the demixing transition and lattice-constant bowing of the Si-Ge alloy; and an iterative CE approach for a complex clathrate compound with a parent lattice consisting of 54 atoms

Isothermal tuning of exchange bias using pulsed fields

This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.Exchange bias,HE, and coercivity,HC, of antiferromagnetic (AFM)/ferromagnetic bilayers can be adjusted, after deposition, at temperatures below the Néel temperature of the AFM by subjecting the samples to large pulsed fields (in excess of HPulse=550 kOe). The efficiency of the process depends on the AFM system and the direction of the applied field with respect of the unidirectional anisotropy direction. Textured (111) Fe19Ni81/Fe50Mn50 bilayers show an HE reduction and a HC increase when the pulse field is applied antiparallel to the unidirectional anisotropy, while they only exhibit a reduction in HC when the pulse is applied parallel to their unidirectional anisotropy. On the other hand, textured (111) NiO/Co bilayers exhibit a change of the angular dependence of HE when the pulse is applied away from the unidirectional anisotropy. The effects could be caused by field induced changes in the domain structure of the AFM or transitions in the AFM (spin-flop or AFM-paramagnetic)

Parlante superdireccional de matriz paramétrica

In this work, a directional loudspeaker, also known as a parametric array loudspeaker (PAL), is designed and constructed. The operation is based on the phenomenon called self-demodulation that happens when high-frequency beams interact in a viscous medium, due to its non-linear properties. The sound obtained after the self-demodulation is formed in the beam of the ultrasonic carrier signal propagating beyond the absorption distance in which the carrier has been sufficiently attenuated. This generates a focused audible signal and therefore a directional polar pattern of narrow angle. In this paper two modulation methods are evaluated: double-sideband amplitude (AM-DBL) and pulse-width modulation (PWM). Its effect on directionality, sound pressure level and harmonic distortion is experimentally analyzed.Este trabajo trata sobre el diseño y construcción de un altoparlante direccional, también conocido como parlante de matriz paramétrica (PAL). El funcionamiento del mismo se basa en los principios de un fenómeno denominado autodemodulación que sucede cuando haces de alta frecuencia interactúan en un medio viscoso, debido a las propiedades no lineales del mismo. El sonido obtenido luego de la autodemodulación se forma en el haz de la señal portadora ultrasónica propagándose más allá de la distancia en la que la portadora ha sido suficientemente atenuada. Esto genera una señal audible focalizada y por ende un patrón polar direccional de ángulo angosto. En el presente trabajo se evalúan dos métodos de modulación: en amplitud con doble banda lateral (AM-DBL) y por variación de ancho de pulso (PWM). Se analiza experimentalmente su efecto en la direccionalidad, nivel de presión sonora y distorsión armónica

ALMA observations of Elias 2–24: a protoplanetary disk with multiple gaps in the Ophiuchus molecular cloud

We present ALMA 1.3 mm continuum observations at 0. 2 (25 au) resolution of Elias 2–24, one of the largest and brightest protoplanetary disks in the Ophiuchus Molecular Cloud, and we report the presence of three partially resolved concentric gaps located at ∼20, 52, and 87 au from the star. We perform radiative transfer modeling of the disk to constrain its surface density and temperature radial profile and place the disk structure in the context of mechanisms capable of forming narrow gaps such as condensation fronts and dynamical clearing by actively forming planets. In particular, we estimate the disk temperature at the locations of the gaps to be 23, 15, and 12 K (at 20, 52, and 87 au, respectively), very close to the expected snowlines of CO (23–28 K) and N2 (12–15 K). Similarly, by assuming that the widths of the gaps correspond to 4–8× the Hill radii of forming planets (as suggested by numerical simulations), we estimate planet masses in the range of 0.2 1.5 – MJup, 1.0 8.0 – MJup, and 0.02 0.15 – MJup for the inner, middle, and outer gap, respectively. Given the surface density profile of the disk, the amount of “missing mass” at the location of each one of these gaps (between 4 and 20 MJup) is more than sufficient to account for the formation of such planets.Fil: Cieza, Lucas A.. Universidad Diego Portales; ChileFil: Casassus, Simon. Universidad de Chile; ChileFil: Pérez, Sebastian. Universidad de Chile; ChileFil: Hales, Antonio. Alma Observatory; ChileFil: Cárcamo, Miguel. Universidad de Chile; ChileFil: Ansdell, Megan. University of California at Berkeley; Estados UnidosFil: Avenhaus, Henning. Universitat Zurich; SuizaFil: Bayo, Amelia. Universidad de Valparaiso; ChileFil: Bertrang, Gesa H.-M.. Universidad Diego Portales; ChileFil: Cánovas, Hector. Agencia Espacial Europea; EspañaFil: Christiaens, Valentin. Universidad de Chile; ChileFil: Dent, William. Alma Observatory; ChileFil: Ferrero, Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Olofsson, Johan. Universidad de Valparaiso; ChileFil: Orcajo, Santiago. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Astrofísica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas. Instituto de Astrofísica La Plata; ArgentinaFil: Osses, Axel. Universidad de Chile; ChileFil: Peña Ramirez, Karla. Universidad de Antofagasta; ChileFil: Principe, David. Massachusetts Institute of Technology; Estados UnidosFil: Ruíz Rodríguez, Dary. Rochester Institute Of Technology; Estados UnidosFil: Schreiber, Matthias R.. Universidad de Valparaiso; ChileFil: Plas, Gerrit van der. Univ. Grenoble Alpes; SuizaFil: Williams, Jonathan P.. Institute For Astronomy, University Of Hawaii; Estados UnidosFil: Zurlo, Alice. Universidad Diego Portales; Chil

Superdirectional Parametric Array Loudspeaker

In this work, a directional loudspeaker, also known as a parametric array loudspeaker (PAL), is designed and constructed. The operation is based on the phenomenon called self-demodulation that happens when high-frequency beams interact in a viscous medium, due to its non-linear properties. The sound obtained after the self-demodulation is formed in the beam of the ultrasonic carrier signal propagating beyond the absorption distance in which the carrier has been sufficiently attenuated. This generates a focused audible signal and therefore a directional polar pattern of narrow angle. In this paper two modulation methods are evaluated: double-sideband amplitude (AM-DBL) and pulse-width modulation (PWM). Its effect on directionality, sound pressure level and harmonic distortion is experimentally analyzed.Este trabajo trata sobre el diseño y construcción de un altoparlante direccional, también conocido como parlante de matriz paramétrica (PAL). El funcionamiento del mismo se basa en los principios de un fenómeno denominado autodemodulación que sucede cuando haces de alta frecuencia interactúan en un medio viscoso, debido a las propiedades no lineales del mismo. El sonido obtenido luego de la autodemodulación se forma en el haz de la señal portadora ultrasónica propagándose más allá de la distancia en la que la portadora ha sido suficientemente atenuada. Esto genera una señal audible focalizada y por ende un patrón polar direccional de ángulo angosto. En el presente trabajo se evalúan dos métodos de modulación: en amplitud con doble banda lateral (AM-DBL) y por variación de ancho de pulso (PWM). Se analiza experimentalmente su efecto en la direccionalidad, nivel de presión sonora y distorsión armónica.Instituto de Investigaciones en Electrónica, Control y Procesamiento de Señale

Metastasizing Pleomorphic Adenoma: A Fascinating Enigma

Among salivary gland neoplasms, metastasizing pleomorphic adenoma (MPA) constitutes an extremely rare group of tumors. The present paper reports a case of pleomorphic adenoma (PA) in submandibular gland that, after more than 30 years of initial treatment, recurred and metastasized to ipsilateral neck lymph nodes and parotid gland. In an attempt to elucidate the malignant behavior of metastasizing pleomorphic adenoma, we performed Ki-67, p53, p16, and bcl-2 immunohistochemistry staining of our case sample. Many immunohistochemistry staining studies have been done on malignant salivary gland tumors. However, to the best of our knowledge no immunohistochemistry staining of the aforementioned markers has been previously performed on metastasizing pleomorphic adenoma

Deep weathering in the semi-arid Coastal Cordillera, Chile

The weathering front is the boundary beneath Earth’s surface where pristine rock is converted into weathered rock. It is the base of the “critical zone”, in which the lithosphere, biosphere, and atmosphere interact. Typically, this front is located no more than 20 m deep in granitoid rock in humid climate zones. Its depth and the degree of rock weathering are commonly linked to oxygen transport and fluid flow. By drilling into fractured igneous rock in the semi-arid climate zone of the Coastal Cordillera in Chile we found multiple weathering fronts of which the deepest is 76 m beneath the surface. Rock is weathered to varying degrees, contains core stones, and strongly altered zones featuring intensive iron oxidation and high porosity. Geophysical borehole measurements and chemical weathering indicators reveal more intense weathering where fracturing is extensive, and porosity is higher than in bedrock. Only the top 10 m feature a continuous weathering gradient towards the surface. We suggest that tectonic preconditioning by fracturing provided transport pathways for oxygen to greater depths, inducing porosity by oxidation. Porosity was preserved throughout the weathering process, as secondary minerals were barely formed due to the low fluid flow