Classical emulation of quantum-coherent thermal machines

The performance enhancements observed in various models of continuous quantum thermal machines have been linked to the buildup of coherences in a preferred basis. But, is this connection always an evidence of `quantum-thermodynamic supremacy'? By force of example, we show that this is not the case. In particular, we compare a power-driven three-level continuous quantum refrigerator with a four-level combined cycle, partly driven by power and partly by heat. We focus on the weak driving regime and find the four-level model to be superior since it can operate in parameter regimes in which the three-level model cannot, it may exhibit a larger cooling rate, and, simultaneously, a better coefficient of performance. Furthermore, we find that the improvement in the cooling rate matches the increase in the stationary quantum coherences exactly. Crucially, though, we also show that the thermodynamic variables for both models follow from a classical representation based on graph theory. This implies that we can build incoherent stochastic-thermodynamic models with the same steady-state operation or, equivalently, that both coherent refrigerators can be emulated classically. More generally, we prove this for any N-level weakly driven device with a `cyclic' pattern of transitions. Therefore, even if coherence is present in a specific quantum thermal machine, it is often not essential to replicate the underlying energy conversion process.Comment: 13 pages, 4 figures; references updated; appendix adde

Growth of Low-Density Vertical Quantum Dot Molecules with Control in Energy Emission

In this work, we present results on the formation of vertical molecule structures formed by two vertically aligned InAs quantum dots (QD) in which a deliberate control of energy emission is achieved. The emission energy of the first layer of QD forming the molecule can be tuned by the deposition of controlled amounts of InAs at a nanohole template formed by GaAs droplet epitaxy. The QD of the second layer are formed directly on top of the buried ones by a strain-driven process. In this way, either symmetric or asymmetric vertically coupled structures can be obtained. As a characteristic when using a droplet epitaxy patterning process, the density of quantum dot molecules finally obtained is low enough (2 × 108 cm−2) to permit their integration as active elements in advanced photonic devices where spectroscopic studies at the single nanostructure level are required

Surface Localization of Buried III–V Semiconductor Nanostructures

In this work, we study the top surface localization of InAs quantum dots once capped by a GaAs layer grown by molecular beam epitaxy. At the used growth conditions, the underneath nanostructures are revealed at the top surface as mounding features that match their density with independence of the cap layer thickness explored (from 25 to 100 nm). The correspondence between these mounds and the buried nanostructures is confirmed by posterior selective strain-driven formation of new nanostructures on top of them, when the distance between the buried and the superficial nanostructures is short enough (d = 25 nm)

Territorio en mutación: la industria textil-confección como factor de desarrollo local en Galicia

Textile and clothing industries have seen in Galicia a very important growth process during the last decades. This activity is located in a specific way in certain places and spaces, where local productive systems are configurated, while in the other ones their presence is weaker. Another characteristic of the sector is the contrast between two manegerial models: one linked to the multinational group Inditex, and the other one associated to a group of smaller companies, but showing great competitive ability in the quality segments linked to design. Both have decentralized a significative part of their productive process to a wide net of co-operatives and little workrooms, mainly located in rural areas. The current analysis presents as objectives: to present the managerial strategies of both existing productive models, to individualize those socioeconomic and territorial factors which have contributed to the development of the activity, to identify the main territorial implications that the sector has caused in those places where their presence is more significant.La industria textil y de la confección ha experimentado en Galicia un muy notable proceso de expansión en las últimas décadas. Esta actividad se localiza de modo específico en determinadas localidades y espacios, donde se configuran sistemas productivos locales, mientras en el resto su presencia es más débil. Otra de las características del sector es el contraste existente entre dos modelos empresariales: el vinculado al grupo multinacional Inditex y aquel asociado a un grupo de empresas de menor entidad, pero de gran capacidad competitiva en los segmentos de calidad asociados al diseño. El presente análisis presenta como objetivos: presentar las estrategias empresariales de los dos modelos productivos existentes, individualizar aquellos factores de carácter socioeconómico y territorial que han favorecido el desarrollo de la actividad e identificar las principales implicaciones territoriales que el sector ha generado en aquellas localidades donde su presencia es más significativ

Green supported liquid membranes: The permeability activity-based linear operation (PABLO) method

Supported liquid membranes (SLMs) containing novel green solvents are proposed as a sustainable alternative separation process in the recovery of biomolecules. In this work, succinic acid has been successfully extracted from model fermentation broths through a stripping phase-facilitated transport mechanism with four different green supported liquid membranes: two eutectic solvents (DL-menthol:OctA and N4444Cl:OctA), the bio-based solvent eucalyptol and the ionic liquid C4pyrr]Tf2N]. A permeability activity-based model that takes into account for the first time solute-phase affinities has been developed using the quantum chemical COSMO-RS method; the model corrects the mass transfer driving force and allows extraction predictions beyond the concentration equilibrium. The best recovery has been achieved experimentally for the eucalyptol-based SLM (concentration factor of 1.4) using an alkaline aqueous solution (0.5 M NaOH) as the stripping phase. A countercurrent cascade extraction process design is proposed, and a graphical method to determine the stage number, interstage concentrations as well as mass transfer area requirements is presented. This new tool, the Permeability Activity-Based Linear Operation (PABLO) method, will substantially enhance the process design of SLMs technology for the biorefinery industry

Charge control in laterally coupled double quantum dots

We investigate the electronic and optical properties of InAs double quantum dots grown on GaAs (001) and laterally aligned along the [110] crystal direction. The emission spectrum has been investigated as a function of a lateral electric field applied along the quantum dot pair mutual axis. The number of confined electrons can be controlled with the external bias leading to sharp energy shifts which we use to identify the emission from neutral and charged exciton complexes. Quantum tunnelling of these electrons is proposed to explain the reversed ordering of the trion emission lines as compared to that of excitons in our system.Comment: 4 pages, 4 figures submitted to PRB Rapid Com

El hijo del Hombre de Jn 3,13 a la luz de la literatura apocalíptica

Las palabras de Jesús en el diálogo con Nicodemo: «Nadie ha subido al cielo, sino el que bajó del cielo, el Hijo del Hombre» (Jn 3,13) parecen contradecir la tradición judía que asume los ascensos al cielo de patriarcas o profetas como Henoc, Elías, etc. Así lo sugiere el pronombre «nadie». El presente trabajo se propone ayudar a comprender mejor esta afirmación. En primer lugar se determina el contexto de 3,13 en la estructura del evangelio de Juan y se analiza el uso paralelo de los verbos y expresiones más relevantes de este versículo en el cuarto evangelio. A continuación, se presentan los relatos de ascensos al cielo en la literatura judía apocalíptica y la figura del Hijo del Hombre. Seguidamente, se proponen las características del Hijo del Hombre joánico y las posibles relaciones con el Hijo del Hombre y los viajeros celestiales apocalípticos. Finalmente, se analiza cómo este texto ha sido recibido por los Padres y autores eclesiásticos de los siglos II y III. El trabajo en su conjunto muestra la continuidad del evangelio con la tradición literaria anterior, al mismo tiempo que destaca la novedad de la figura de Jesús y la autoridad de su mensaje de salvación.The words of Jesus in dialogue with Nicodemus: «No one has ascended to heaven but he who descended from heaven, the Son of Man» (Jn 3:13) seem to contradict the Jewish tradition that assumes the ascent to heaven of patriarchs or prophets like Enoch, Elijah, etc. This is suggested by the phrase «no one». This paper aims to better understand this statement. First, the context of 3:13 in the structure of the Gospel of John is determined, and the parallel use of verbs and most relevant expressions of this verse in the fourth gospel are analyzed. Then the accounts of ascents to heaven in Jewish apocalyptic literature and the figure of the Son of Man are presented. Next, the features of the Johannine Son of Man and possible relations with the apocalyptic Son of Man and celestial travelers are proposed. Finally, it is discussed how this text has been received by the Fathers and ecclesiastical authors of the 2nd and 3rd centuries. The work as a whole shows the continuity of the Gospel with the previous literary tradition, while highlighting the novelty of the figure of Jesus and the authority of his message of salvation