Current in coherent quantum systems connected to mesoscopic Fermi reservoirs

We study particle current in a recently proposed model for coherent quantum transport. In this model, a system connected to mesoscopic Fermi reservoirs (meso-reservoir) is driven out of equilibrium by the action of super-reservoirs thermalized to prescribed temperatures and chemical potentials by a simple dissipative mechanism described by the Lindblad equation. We compare exact (numerical) results with theoretical expectations based on the Landauer formula.

Foundations and applications of non-equilibrium statistical mechanics

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Cubic and hexagonal InGaAsN dilute arsenides by unintentional homogeneous incorporation of As into InGaN

Arsenic alloying is observed for epitaxial layers nominally intended to be In0.75Ga0.25N. Voids form beneath their interfaces with GaAs substrates, acting as sources of Ga + As out-diffusion into the growing epilayers. As a result, heteroepitaxial single-phase quaternary InxGa1-xAsyN1-y, films are formed with x similar to 0.55 and 0.05 menor que y menor que 0,10. While an undoped epilayer retains the wurtzite structure, a Mn-doped sample showed randomly spaced dopant segregations, which, together with a slightly higher As concentration, led to a transformation from the hexagonal to the twinned cubic phase.

Nanocrack-induced leakage current in AlInN/AlN/GaN

Here we report on the study of nano-crack formation in Al1−xInxN/AlN/GaN heterostructures, on its association with composition fluctuation and on its local electrical properties. It is shown here that indium segregation at nano-cracks and threading dislocations originating from the non-pseudomorphic AlN interlayer could be the cause of the high reverse-bias gate leakage current of Ni/Au Schottky contacts on Al1−xInxN/AlN/GaN heterostructures and significantly affects the contact rectifying behavior. Segregation of indium around crack tips in Al1−xInxN acting as conductive paths was assessed with conductive atomic force microscopy.

On the production of N-2(+) ions at the N 1s edge of the nitrogen molecule

The N+2 ion yield of the N2 molecule has been measured at the N 1s → Rydberg excitations. It displays Fano-type line shapes due to interference between direct outer-valence photoionization and participator decay of the core-excited Rydberg states. The N+2 ion yield is compared with the total intensity of the outer-valence photoelectron lines obtained recently with electron spectroscopy (Kivimäki et al 2012 Phys. Rev. A 86 012516). The increasing difference between the two curves at the higher core-to-Rydberg excitations is most likely due to soft x-ray emission processes that are followed by autoionization. The results also suggest that resonant Auger decay from the core–valence doubly excited states contributes to the N+2 ion yield at the photon energies that are located on both sides of the N 1s ionization limit.

Grain size gradient length scale in ballistic properties optimization of functionally graded nanocrystalline steel plates

The last few years have highlighted the existence of two relevant length scales in the quest to ultrahigh-strength polycrystalline metals. Whereas the microstructural length scale – e.g. grain or twin size – has mainly be linked to the well-established Hall–Petch relationship, the sample length scale – e.g. nanopillar size – has also proven to be at least as relevant, especially in microscale structures. In this letter, a series of ballistic tests on functionally graded nanocrystalline plates are used as a basis for the justification of a “grain size gradient length scale” as an additional ballistic properties optimization parameter.

¿Planificar los comunes? Autogestión, regulación comunal del suelo y su eclipse en la Inglaterra precapitalista.

El progresivo adelgazamiento del Estado del Bienestar y la privatización de bienes y servicios públicos han propiciado la aparición de discursos que reclaman la recuperación de los comunes y su autogestión colectiva. En ese contexto las tierras y derechos comunales de la Inglaterra pre-capitalista han dejado de ser un asunto académico, reapareciendo intensamente en los imaginarios socioespaciales del activismo global. Aunque esa reapropiación del pasado parece legítima, dichas narrativas ignoran a menudo la complejidad implícita en la gestión, planificación y evolución de los comunes históricos. Para subsanar estas lagunas estudiamos las instituciones y modos de gobierno que sustentaban el régimen comunal de la tierra en este período, enfatizando su condición de planificación autogestionada de los usos del suelo y las prácticas asociadas al mismo. Este régimen fue sustituido por las leyes de cercamiento, dando paso a una lógica de planificación centralizada e insolidaria: una lógica en la que estaba implícita no sólo la extinción del control comunal y la privatización de la tierra, sino también la desposesión de los trabajadores rurales y su progresiva proletarización. Palabras clave: comunes, derecho comunal, planificación socioespacial, leyes de cercamiento, autogestión. ....................................................... The ongoing eclipse of the Welfare State and the privatisation of public goods and services have triggered the appearance of discourses that claim the recovery of the commons and their collective self-management. In this context historical common lands and rights in pre-capitalist England are no longer a mere academic issue, as they reappear intensely in the sociospatial imaginaries of global activism. This reappropriation of the past seems legitimate, but such narratives often ignore the complexity of the management, planning and evolution of the historical commons. To fill these lacunae I study the institutions and modes of government that underpinned the communal regime in this period, emphasizing its condition of self-managed land use planning. Enclosure acts destroyed this regime, introducing a new logic of centralized, iniquitous planning: a logic which included not only the extinction of communal institutions and privatisation of land, but also the dispossession of rural labourers and their progressive proletarianisation.

Manufacturing of self-passivating tungsten based alloys by different powder metallurgical routes

Self-passivating tungsten based alloys will provide a major safety advantage compared to pure tungsten when used as first wall armor of future fusion reactors, due to the formation of a protective oxide layer which prevents the formation of volatile and radioactive WO3 in case of a loss of coolant accident with simultaneous air ingress. Bulk WCr10Ti2 alloys were manufactured by two different powder metallurgical routes: (1) mechanical alloying (MA) followed by hot isostatic pressing (HIP) of metallic capsules, and (2) MA, compaction, pressureless sintering in H2 and subsequent HIPing without encapsulation. Both routes resulted in fully dense materials with homogeneous microstructure and grain sizes of 300 nm and 1 μm, respectively. The content of impurities remained unchanged after HIP, but it increased after sintering due to binder residue. It was not possible to produce large samples by route (2) due to difficulties in the uniaxial compaction stage. Flexural strength and fracture toughness measured on samples produced by route (1) revealed a ductile-to-brittle-transition temperature (DBTT) of about 950 °C. The strength increased from room temperature to 800 °C, decreasing significantly in the plastic region. An increase of fracture toughness is observed around the DBTT.