Properties of (Ga1−x_{1-x}Inx_x)2_2O3_3 over the whole xx range

Using density-functional ab initio theoretical techniques, we study (Ga$_{1-x}$In$_x$)$_2$O$_3$ in both its equilibrium structures (monoclinic $\beta$ and bixbyite) and over the whole range of composition. We establish that the alloy exhibits a large and temperature-independent miscibility gap. On the low-$x$ side, the favored phase is isostructural with $\beta$-Ga$_2$O$_3$; on the high-$x$ side, it is isostructural with bixbyite In$_2$O$_3$. The miscibility gap opens between approximately 15\% and 55\% In content for the bixbyite alloy grown epitaxially on In$_2$O$_3$, and 15\% and 85\% In content for the free-standing bixbyite alloy. The gap, volume and band offsets to the parent compound also exhibit anomalies as function of $x$. Specifically, the offsets in epitaxial conditions are predominantly type-B staggered, but have opposite signs in the two end-of-range phases.Comment: 7 pages, 4 figure

Phase diagram and polarization of stable phases of (Ga1−x_{1-x}Inx_x)2_2O3_3

Using density-functional ab initio calculations, we provide a revised phase diagram of (Ga$_{1-x}$In$_{x})_2$O$_3$. Three phases --monoclinic, hexagonal, cubic bixbyite-- compete for the ground state. In particular, in the $x$$\sim$0.5 region we expect coexistence of hexagonal, $\beta$, and bixbyite (the latter separating into binary components). Over the whole $x$ range, mixing occurs in three disconnected regions, and non-mixing in two additional distinct regions. We then explore the permanent polarization of the various phases, finding that none of them is polar at any concentration, despite the possible symmetry reductions induced by alloying. On the other hand, we find that the $\varepsilon$ phase of Ga$_2$O$_3$ stabilized in recent growth experiments is pyroelectric --i.e. locked in a non-switchable polarized structure-- with ferroelectric-grade polarization and respectable piezoelectric coupling. We suggest that this phase could be used profitably to produce high-density electron gases in transistor structures.Comment: 5 pages, 3 figure

Structure and gap of low-xx (Ga1−x_{1-x}Inx_x)2_2O3_3 alloys

We study the electronic and local structural properties of pure and In-substituted $\beta$-Ga$_2$O$_3$ using density functional theory (DFT). Our main result is that the structural energetics of In in Ga$_2$O$_3$ causes most sites to be essentially inaccessible to In substitution, thus reducing the maximum In content in thi to somewhere between 12 and 25 \% in this phase. We also find that the gap variation with doping is essentially due to "chemical pressure", i.e. volume variations with doping.Comment: 4 pages, 3 figure

Low In solubility and band offsets in the small-xx β\beta-Ga2_2O3_3/(Ga1−x_{1-x}Inx_x)2_2O3_3 system

Based on first-principles calculations, we show that the maximum reachable concentration $x$ in the (Ga$_{1-x}$In$_x$)$_2$O$_3$ alloy in the low-$x$ regime (i.e. In solubility in $\beta$-Ga$_2$O$_3$) is around 10%. We then calculate the band alignment at the (100) interface between $\beta$-Ga$_2$O$_3$ and (Ga$_{1-x}$In$_x$)$_2$O$_3$ at 12%, the nearest computationally treatable concentration. The alignment is strongly strain-dependent: it is of type-B staggered when the alloy is epitaxial on Ga$_2$O$_3$, and type-A straddling in a free-standing superlattice. Our results suggest a limited range of applicability of low-In-content GaInO alloys.Comment: 3 pages, 3 figure

Very long distance connection of gigawatt size offshore wind farms: extra high-voltage ac versus high-voltage dc cost comparison

This study presents a cost comparison between commercially available high-voltage DC (HVDC) and extra high-voltage AC shore connection (±320 kV voltage source converter and 420 kV-50 Hz single-core and three-core cables), for a 1 GW offshore wind farm cluster, considering transmission distances up to 400 km. The HVDC system is a point-to-point connection whereas multiple AC intermediate compensating stations are envisaged for AC when needed. Capital costs are evaluated from recently awarded contracts, operating costs include energy losses and missed revenues due to transmission system unavailability, both estimated using North Sea wind production curves. Optimal AC intermediate compensation, if any, and reactive profiles are also taken into account. Resultsshow that HVDC has lower transmission losses at distances in excess of 130 km; however, due to the combined effect of lower AC capital cost and unavailability, using three-core aluminium cables can be more convenient up to 360 km distance

High thermoelectric figure of merit and thermopower in layered perovskite oxides

We predict high thermoelectric efficiency in the layered perovskite La$_2$Ti$_2$O$_7$, based on calculations (mostly ab-initio) of the electronic structure, transport coefficients, and thermal conductivity in a wide temperature range. The figure of merit $ZT$ computed with a temperature-dependent relaxation time increases monotonically from just above 1 at room temperature to over 2.5 at 1200 K, at an optimal carrier density of around 10$^{20}$ cm$^{-3}$. The Seebeck thermopower coefficient is between 200 and 300 $\mu$V/K at optimal doping, but can reach nearly 1 mV/K at low doping. Much of the potential of this material is due to its lattice thermal conductivity of order 1 W/(K m); using a model based on ab initio anharmonic calculations, we interpret this low value as due to effective phonon confinement within the layered-structure blocks.Comment: 18 preprint pages, 9 figures, accepted on PR Material

Portraits of the New Man: revolutionary subjectivity in Episodes of the Cuban Revolutionary War and “The parade begins”

Se examina la figura de sujeto esbozada en el cuento “Comienza el desfile”, de Reinaldo Arenas, tomando como referencia los Pasajes de la guerra revolucionaria de Ernesto “Che” Guevara, texto fundamental en la construcción del modelo de Hombre Nuevo postulado como ideal social y político por el Estado cubano después de 1959. A diferencia de lo que ocurre en las memorias guevarianas, se propone que para Arenas el acontecimiento revolucionario, lejos de ser experimentado como momento de des-alienación y emancipación de un sujeto originario hasta entonces reprimido, es vivido como oportunidad de de-sujeción, de suspensión de la creencia en las identidades socialmente prescritas (de hombre, de guerrero, de héroe) y de exploración de otras formas de subjetividad posibles.The New Man ideal depicted on Ernesto “Che” Guevara’s Episodes of the Cuban Revolutionary War, and invoked as a social model in the discourse of the new revolutionary Cuban state after 1959 is taken here as a reference for reading Reinaldo Arena’s short story “The parade begins”. Contrary to Guevara’s text, Arenas proposes that the revolutionary event does not mean the fi nal de-alienation and emancipation of the repressed original subject, but the chance of opening up a space that allows to escape from the socially prescribed identities (man, warrior, hero) and explore new possible forms of subjectivityFil: Maccioni, Laura. Universidad Nacional de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Córdoba. Centro de Investigaciones y Estudio sobre Cultura y Sociedad; Argentin

Un futuro hecho de pasado : texturas de la temporalidad en Antón Arrufat

Este artículo examina los modos de reorganizar el tiempo luego del triunfo de la revolución cubana en 1959, deteniéndose en particular en dos textos del escritor Antón Arrufat (1935) que abordan la cuestión de la herencia familiar: la novela Mi antagonista (1963) y la obra teatral Los siete contra Tebas (1968). Frente a la idea de la revolución como un nuevo origen, la lectura que realizo aquí propone que Arrufat entiende al tiempo como una textura compleja, en la que las transformaciones futuras están ligadas a la reapropiación de lo heredado. Así, Arrufat articula repetición y novedad de una manera singular en el horizonte cultural de los sesenta cubanos.This article examines the ways of reorganizing time after the triumph of the Cuban revolution in 1959, focusing in two texts of the Cuban writer Antón Arrufat (1935), where the question of family heritage is the main topic: the novel Mi antagonista (1963) and the theater play Los siete contra Tebas (1968). Confronting the official idea of the revolution as a new origin of history, this essay proposes that Arrufat conceives time as a complex texture, in which changes in the future are inevitably related to the reapropiation and rewriting of heritage. Thus, in the Cuban cultural field of the sixties, Arrufat questions in a very singular way the notion of novelty.Aquest article examina les maneres de reorganitzar el temps després del triomf de la revolució cubana en 1959, detenint-se en particular en dos textos de l'escriptor Antón Arrufat (1935) que aborden la qüestió de l'herència familiar: la novel·la Mi antagonista (1963) i l'obra teatral Los siete contra Tebas (1968). Es proposa que, davant la instauració de la revolució com un nou començ de la història per part de les autoritats revolucionaries, Arrufat concep al temps com una textura complexa, en la que les transformacions futures estan inevitablement lligades a la reapropiació i reescriptura de l' heretat. Així, en l'horitzó cultural dels anys setanta a l'illa, Arrufat problematitza d'una manera singular la noció de novetat

L'agricoltura sociale: profili giuridici

L'agricoltura sociale si \ue8 presentata, nel corso del tempo, sotto molteplici forme, si pensi solo alle esperienze cd. di farming for health (\u201cagricoltura per la salute\u201d), care farming, green care o green therapies (\u201cterapie verdi\u201d) riferibili alle cure, al reinserimento, alla riabilitazione o altro. Emergono due elementi sempre presenti: a) si tratta di attivit\ue0 che si svolgono in una azienda agricola; e b) sono prospettate per soggetti che - temporaneamente o in modo permanente - presentano specifiche necessit\ue0, incluse necessit\ue0 educative. Da parte sua, la legge italiana 18 agosto 2015, n. 141 (\u201cDisposizioni in materia di agricoltura sociale\u201d), \u201cpromuove l\u2019agricoltura sociale quale aspetto della multifunzionalit\ue0 delle imprese agricole\u201d (art.1, \u201cFinalit\ue0\u201d). L'intento, in questa sede, \ue8 quello di presentare le novit\ue0, al tempo stesso svolgendo alcune riflessioni, cercando di stimolarne altre in una disciplina interessante, ma ancora da perfezionare