The electron-furfural scattering dynamics for 63 energetically open electronic states

We report on integral-, momentum transfer-and differential cross sections for elastic and electronically inelastic electron collisions with furfural (C5H4O2). The calculations were performed with two different theoretical methodologies, the Schwinger multichannel method with pseudopotentials (SMCPP) and the independent atom method with screening corrected additivity rule (IAM-SCAR) that now incorporates a further interference (I) term. The SMCPP with N energetically open electronic states (N-open) at either the static-exchange (N-open ch-SE) or the static-exchange-plus-polarisation (N-open ch-SEP) approximation was employed to calculate the scattering amplitudes at impact energies lying between 5 eV and 50 eV, using a channel coupling scheme that ranges from the 1ch-SEP up to the 63ch-SE level of approximation depending on the energy considered. For elastic scattering, we found very good overall agreement at higher energies among our SMCPP cross sections, our IAM-SCAR+I cross sections and the experimental data for furan (a molecule that differs from furfural only by the substitution of a hydrogen atom in furan with an aldehyde functional group). This is a good indication that our elastic cross sections are converged with respect to the multichannel coupling effect for most of the investigated intermediate energies. However, although the present application represents the most sophisticated calculation performed with the SMCPP method thus far, the inelastic cross sections, even for the low lying energy states, are still not completely converged for intermediate and higher energies. We discuss possible reasons leading to this discrepancy and point out what further steps need to be undertaken in order to improve the agreement between the calculated and measured cross sections. (C) 2016 AIP Publishing LLC.

Oxide Semiconductors For Organic Opto-electronic Devices

Development of transparent oxide semiconductors (TOS) from Earth-abundant materials is of great interest for cost-effective thin film device applications, such as solar cells, light emitting diodes (LEDs), touch-sensitive displays, electronic paper, and transparent thin film transistors. The need of inexpensive or high performance electrode might be even greater for organic photovoltaic (OPV), with the goal to harvest renewable energy with inexpensive, lightweight, and cost competitive materials. The natural abundance of zinc and the wide bandgap ($sim$3.3 eV) of its oxide make it an ideal candidate. In this dissertation, I have introduced various concepts on the modulations of various surface, interface and bulk opto-electronic properties of ZnO based semiconductor for charge transport, charge selectivity and optimal device performance. I have categorized transparent semiconductors into two sub groups depending upon their role in a device. Electrodes, usually 200 to 500 nm thick, optimized for good transparency and transporting the charges to the external circuit. Here, the electrical conductivity in parallel direction to thin film, i.e bulk conductivity is important. And contacts, usually 5 to 50 nm thick, are optimized in case of solar cells for providing charge selectivity and asymmetry to manipulate the built in field inside the device for charge separation and collection. Whereas in Organic LEDs (OLEDs), contacts provide optimum energy level alignment at organic oxide interface for improved charge injections. For an optimal solar cell performance, transparent electrodes are designed with maximum transparency in the region of interest to maximize the light to pass through to the absorber layer for photo-generation, plus they are designed for minimum sheet resistance for efficient charge collection and transport. As such there is need for material with high conductivity and transparency. Doping ZnO with some common elements such as B, Al, Ga, In, Ge, Si, and F result in n-type doping with increase in carriers resulting in high conductivity electrode, with better or comparable opto-electronic properties compared to current industry-standard indium tin oxide (ITO). Furthermore, improvement in mobility due to improvement on crystallographic structure also provide alternative path for high conductivity ZnO TCOs. Implementing these two aspects, various studies were done on gallium doped zinc oxide (GZO) transparent electrode, a very promising indium free electrode. The dynamics of the superimposed RF and DC power sputtering was utilized to improve the microstructure during the thin films growth, resulting in GZO electrode with conductivity greater than 4000 S/cm and transparency greater than 90 %. Similarly, various studies on research and development of Indium Zinc Tin Oxide and Indium Zinc Oxide thin films which can be applied to flexible substrates for next generation solar cells application is presented. In these new TCO systems, understanding the role of crystallographic structure ranging from poly-crystalline to amorphous phase and the influence on the charge transport and optical transparency as well as important surface passivation and surface charge transport properties. Implementation of these electrode based on ZnO on opto-electronics devices such as OLED and OPV is complicated due to chemical interaction over time with the organic layer or with ambient. The problem of inefficient charge collection/injection due to poor understanding of interface and/or bulk property of oxide electrode exists at several oxide-organic interfaces. The surface conductivity, the work function, the formation of dipoles and the band-bending at the interfacial sites can positively or negatively impact the device performance. Detailed characterization of the surface composition both before and after various chemicals treatment of various oxide electrode can therefore provide insight into optimization of device performance. Some of the work related to controlling the interfacial chemistry associated with charge transport of transparent electrodes are discussed. Thus, the role of various pre-treatment on poly-crystalline GZO electrode and amorphous indium zinc oxide (IZO) electrode is compared and contrasted. From the study, we have found that removal of defects and self passivating defects caused by accumulation of hydroxides in the surface of both poly-crystalline GZO and amorphous IZO, are critical for improving the surface conductivity and charge transport. Further insight on how these insulating and self-passivating defects cause charge accumulation and recombination in an device is discussed. With recent rapid development of bulk-heterojunction organic photovoltaics active materials, devices employing ZnO and ZnO based electrode provide air stable and cost-competitive alternatives to traditional inorganic photovoltaics. The organic light emitting diodes (OLEDs) have already been commercialized, thus to follow in the footsteps of this technology, OPV devices need further improvement in power conversion efficiency and stable materials resulting in long device lifetimes. Use of low work function metals such as Ca/Al in standard geometry do provide good electrode for electron collection, but serious problems using low work-function metal electrodes originates from the formation of non-conductive metal oxide due to oxidation resulting in rapid device failure. Hence, using low work-function, air stable, conductive metal oxides such as ZnO as electrons collecting electrode and high work-function, air stable metals such as silver for harvesting holes, has been on the rise. Devices with degenerately doped ZnO functioning as transparent conductive electrode, or as charge selective layer in a polymer/fullerene based heterojunction, present useful device structures for investigating the functional mechanisms within OPV devices and a possible pathway towards improved air-stable high efficiency devices. Furthermore, analysis of the physical properties of the ZnO layers with varying thickness, crystallographic structure, surface chemistry and grain size deposited via various techniques such as atomic layer deposition, sputtering and solution-processed ZnO with their respective OPV device performance is discussed. We find similarity and differences in electrode property for good charge injection in OLEDs and good charge collection in OPV devices very insightful in understanding physics behind device failures and successes. In general, self-passivating surface of amorphous TCOs IZO, ZTO and IZTO forms insulating layer that hinders the charge collection. Similarly, we find modulation of the carrier concentration and the mobility in electron transport layer, namely zinc oxide thin films, very important for optimizing device performance.

First-order transition in a three-dimensional disordered system

We present the first detailed numerical study in three dimensions of a first-order phase transition that remains first order in the presence of quenched disorder (specifically, the ferromagnetic-paramagnetic transition of the site-diluted four states Potts model). A tricritical point, which lies surprisingly near the pure-system limit and is studied by means of finite-size scaling, separates the first-order and second-order parts of the critical line. This investigation has been made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that plague the standard approach. Entropy, rather than free energy, is the basic object in this approach that exploits a recently introduced microcanonical Monte Carlo method.

First Order Phase Transition in a 3D disordered system

We present a detailed numerical study on the effects of adding quenched impurities to a three dimensional system which in the pure case undergoes a strong first order phase transition (specifically, the ferromagnetic/paramagnetic transition of the site-diluted four states Potts model). We can state that the transition remains first-order in the presence of quenched disorder (a small amount of it) but it turns out to be second order as more impurities are added. A tricritical point, which is studied by means of Finite-Size Scaling, separates the first-order and second-order parts of the critical line. The results were made possible by a new definition of the disorder average that avoids the diverging-variance probability distributions that arise using the standard methodology. We also made use of a recently proposed microcanonical Monte Carlo method in which entropy, instead of free energy, is the basic quantity.

Onset of energy dissipation in ballistic atomic wires

Electronic transport at finite voltages in free-standing gold atomic chains of up to seven atoms in length is studied at low temperatures using a scanning tunneling microscope. The conductance vs voltage curves show that transport in these single-mode ballistic atomic wires is nondissipative up to a finite voltage threshold of the order of several mV. The onset of dissipation and resistance within the wire corresponds to the excitation of the atomic vibrations by the electrons traversing the wire and is very sensitive to strain.

VO: a strongly correlated metal close to a Mott-Hubbard transition

Here, we present experimental and computational evidences to support that rocksalt cubic VO is a strongly correlated metal with non-Fermi-liquid thermodynamics and an unusually strong spin-lattice coupling. An unexpected change of sign of metallic thermopower with composition is tentatively ascribed to the presence of a pseudogap in the density of states. These properties are discussed as signatures of the proximity to a magnetic quantum phase transition. The results are summarized in an electronic phase diagram for the 3d monoxides, which resembles that of other strongly correlated systems. The structural and electronic simplicity of 3d monoxides makes them ideal candidates to progress in the understanding of highly correlated electron systems.

Paleoenvironmental changes during the late Miocene (Messinian)–Pliocene transition (Bajo Segura Basin, southeastern Spain): sedimentological and ichnological evidence

A detailed sedimentological and paleontological analysis of the uppermost Miocene (Messinian)–Pliocene boundary at the northern border of the Bajo Segura Basin, southeastern Spain, was carried out in order to describe the evolution of the regional paleocoastline during the Pliocene reflooding of the Mediterranean immediately after the sea-level fall related to the Messinian Salinity Crisis. Multiple trace fossils typical of firm- and hardgrounds were recognized, allowing identification of Glossifungites (two different types), Entobia, and Gnathichnus ichnofacies. Trace-fossil analysis showed that lithology and media consistency exerted considerable control on the development of the different ichnocoenoses and that there was a clear decrease in hydrodynamic energy from a coastal to a shallow-water shelf environment related to progressive sea-level rise. Ichnological and sedimentological data provide evidence that the definitive flooding of the Mediterranean was rapid and synchronous throughout the northern margin of the Bajo Segura Basin. The following model for the Pliocene transgression in the study area is therefore proposed: (1) the marine ingression penetrated along the incised paleovalleys carved as a consequence of the fall in sea level, where the first two Pliocene systems were deposited (P0–P1); (2) during the maximum flooding surface of the transgression, the sea overflowed the margins of the paleovalleys and extended throughout the entire northern margin of the basin; and (3) the third Pliocene system was deposited, forming the lower part of a highstand systems tract (P2).

Electronic properties of the MoS2-WS2 heterojunction

We study the electronic structure of a heterojunction made of two monolayers of MoS2 and WS2. Our first-principles density functional calculations show that, unlike in the homogeneous bilayers, the heterojunction has an optically active band gap, smaller than the ones of MoS2 and WS2 single layers. We find that the optically active states of the maximum valence and minimum conduction bands are localized on opposite monolayers, and thus the lowest energy electron-holes pairs are spatially separated. Our findings portray the MoS2-WS2 bilayer as a prototypical example for band-gap engineering of atomically thin two-dimensional semiconducting heterostructures.

Derivation of the spin Hamiltonians for Fe in MgO

A method to calculate the effective spin Hamiltonian for a transition metal impurity in a non-magnetic insulating host is presented and applied to the paradigmatic case of Fe in MgO. In the first step we calculate the electronic structure employing standard density functional theory (DFT), based on generalized gradient approximation (GGA), using plane waves as a basis set. The corresponding basis of atomic-like maximally localized Wannier functions is derived and used to represent the DFT Hamiltonian, resulting in a tight-binding model for the atomic orbitals of the magnetic impurity. The third step is to solve, by exact numerical diagonalization, the N electron problem in the open shell of the magnetic atom, including both effects of spin–orbit and Coulomb repulsion. Finally, the low energy sector of this multi-electron Hamiltonian is mapped into effective spin models that, in addition to the spin matrices S, can also include the orbital angular momentum L when appropriate. We successfully apply the method to Fe in MgO, considering both the undistorted and Jahn–Teller (JT) distorted cases. Implications for the influence of Fe impurities on the performance of magnetic tunnel junctions based on MgO are discussed.

Retombées du cirque social (Cirque du Soleil) en contexte de réadaptation sur la participation sociale de jeunes adultes avec déficiences physiques en transition vers la vie active : étude qualitative

Introduction : Les adolescents avec déficiences physiques en transition vers la vie adulte éprouvent des difficultés à établir une participation sociale optimale. Cette étude explore les retombées d'un programme de cirque social sur la participation sociale de ces jeunes selon leur point de vue et celui de leurs parents. Méthode : Étude qualitative exploratoire d’orientation phénoménologique. Neuf personnes avec déficiences physiques, âgées de 18 et 25 ans, ont participé au programme pendant neuf mois. Données recueillies : perceptions de leur qualité de participation sociale à partir d’entrevues semi-structurées en pré, mi-temps et post-intervention avec les participants et un de leurs parents. Le guide d’entrevue validé est ancré sur le Modèle du développement humain- Processus de production du handicap - 2 (HDM-PPH2). L’enregistrement audio des entretiens a été transcrit en verbatim. Le contenu a été analysé avec le logiciel Nvivo 9 à travers une grille de codage préalablement validée (co-codage, codage-inverse). Résultats : Corpus de 54 entrevues. L’âge moyen des jeunes était de 20,0 ± 1,4 années et de 51 ± 3,6 années pour les parents. Selon tous, la participation sociale des jeunes adultes a été optimisée, surtout sur le plan de la communication, des déplacements, des relations interpersonnelles, des responsabilités et de la vie communautaire. La perception de soi et les habiletés sociales, également améliorées, ont favorisé une plus grande auto-efficacité. Conclusion : Cette étude soutient donc le potentiel du cirque social comme approche novatrice et probante en réadaptation physique pour cette population, et appuie la pertinence d’autres études rigoureuses mesurant les diverses retombées possibles et identifiées.

Réaction d’amination intramoléculaire de liens C-H à partir de N-mésyloxycarbamates catalysée par des complexes de rhodium et d’autres métaux de transition : s ynthèse verte d’oxazolidinones

La réaction d’amination de liens C-H, impliquant la transformation directe d’un lien C-H en lien C-N constitue une approche synthétique d’avenir pour la préparation de composés azotés. L’application de cette stratégie de manière intramoléculaire apparaît comme une approche puissante pour la synthèse de composés hétérocycliques. En particulier, les oxazolidinones, carbamates cycliques à cinq chaînons, constituant une nouvelle classe d’antibiotiques très prometteuse, pourraient être synthétisées par cette méthode. Il y a moins d’une dizaine d’années, notre groupe de recherche a travaillé sur le développement de méthodologies utilisant des espèces nitrènes métalliques pour l’amination intra et intermoléculaire. Les N-tosyloxycarbamates, en présence d’une base et d’un catalyseur dimère de rhodium (II) tétracarboxylate sont les précurseurs de ces espèces nitrènes métalliques, capables de faire l’insertion de liens C(sp3)-H. Dans ces travaux de thèse, nous avons travaillé sur le développement d’une méthode plus « verte » d’amination intramoléculaire. Les N-mésyloxycarbamates, plus légers que leurs homologues N-tosyloxycarbamates, ont été identifiés comme d’excellents précurseurs de nitrènes. La méthodologie développée ne nécessite que 3 mol % de dimère de rhodium Rh2(tpa)4 et de 1,5 équivalents de solution aqueuse saturée de K2CO3, le tout dans l’acétate d’éthyle et donne de bons rendements de cyclisation. Une étude de l’étendue réactionnelle a été effectuée, montrant la tolérance et les limitations de notre système catalytique : les hétéroatomes ne posent pas de problèmes hormis l’atome d’azote, qui doit être protégé afin de garantir la transformation. En outre, nous avons constaté que les liens C-H aliphatiques secondaires sont moins réactifs que les liens tertiaires. Après avoir tenté de développer des conditions réactionnelles spécifiques aux liens C-H non activés, nous avons montré la possibilité d’aminer des liens C-H propargyliques de manière chimiosélective ; la triple liaison C-C peut ensuite être dérivatisée efficacement, donnant accès à la formule saturée correspondante ainsi qu’à d’autres motifs. Dans un désir de substituer les complexes de rhodium par d’autres complexes de métaux plus abondants et moins dispendieux, nous nous sommes tournés, dans un premier temps, vers les complexes de fer et par la suite, vers les pinceurs de nickel. Les phtalocyanines de fer ont été identifiées comme étant de bons catalyseurs de l’amination intramoléculaire de N-mésyloxycarbamates. Le chlorure de phtalocyanine de fer (III), en présence d’un sel de AgBF4 et de K2CO3, dans le 1,1,2,2-tétrachloroéthane anhydre, permet l’obtention de la 4-phenyloxazolidin-2-one avec 63% de rendement. En outre, il est possible d’atteindre un rendement de 49% à partir du même substrat N-mésyloxycarbamate, par catalyse avec un pinceur de nickel de type POCN, en présence d’un sel de mésylate. Des indices sur le mécanisme des ces deux transformations ont pu être recueillis lors de la courte étude de ces systèmes.

Impact of the Decarbonisation of the Energy System on Employment in Europe. CEPS Special Report No. 82, February 2014

This paper presents a methodology for calculating the potential impact of the new socio-ecological transition away from fossil fuels on employment in EU energy supply. The methodology is based on “employment factors” (i.e. labour intensities) of different energy technologies. These employment factors are applied to changing energy mixes as projected by the decarbonisation scenarios of the European Commission’s Energy Roadmap 2050. In particular, we analyse quantitative (number of jobs) and qualitative (qualification levels) impacts on employment in extraction and processing of primary (fossil) fuels and in the power sector for the years 2020, 2030 and 2050. The results show that the energy sector will provide not only more jobs as the new socio-ecological transition unfolds, but also jobs requiring higher-level qualifications when compared with the current energy sector.

The Potential Evolution of the European Energy System to 2020 and 2050. CEPS Working Document No. 392, 26 March 2014

This paper assesses the impact of decarbonisation of the energy sector on employment in Europe. Setting the stage for such an assessment, the paper provides an analysis of possible pathways to decarbonise Europe’s energy system, taking into account EU greenhouse gas emissions reduction targets for 2020 and 2050. It pays particular attention to various low-carbon technologies that could be deployed in different regions of the EU. It concludes that efficiency and renewables play a major role in any decarbonisation scenario and that the power sector is the main enabler for the transition to a low-carbon economy in Europe, despite rising electricity demand. The extent of the decline in the share of fossil fuels will largely depend on the existence of carbon capture and storage (CCS), which remains a major source of uncertainty.

Low key but not low impact: the results of the EU's 'transition' summit. EPC Post-Summit Analysis, 27 October 2014

The European Council Summit of 23-24 October 2014 may have been relatively low key, but many important decisions were made which could encourage historical changes. In this post-summit analysis, Janis A. Emmanouilidis examines the agreement reached on a new climate and energy policy framework for 2020-2030 which despite falling short of the European Commission’s original proposals, it nevertheless delivers a positive message to international community ahead of the global climate negotiations next year. He also highlights the significance of the request from euro-zone leaders for a new report on ‘better economic governance’ by December. More broadly, he uses this moment of transition in the EU’s leadership to analyse the current state and future direction of the Union, and underlines the need to provide a coherent and holistic response to the damage caused by the crisis and the challenges facing the Union, on the basis of an ambitious but pragmatic ‘package deal’ – a new pact between EU governments, and between the Union and its citizens – to heal the divisions of recent years and restore public faith in the benefits of EU membership.

Germany's energy transformation: difficult beginnings. OSW Report, March 2013

Initiated in May 2011, several months after the Fukushima nuclear disaster, Germany’s energy transformation (Energiewende) has been presented as an irrevocable plan, and – due to the speed of change required – it represents a new quality in Germany’s energy strategy. Its main objectives include: nuclear energy being phased out by 2022, the development of renewable energy sources (OZE), the expansion of transmission networks, the construction of new conventional power plants and an improvement in energy efficiency.The cornerstone of the strategy is the development of renewable energy. Under Germany's amended renewable energy law, the proportion of renewable energy in electricity generation is supposed to increase steadily from the current level of around 20% to approximately 38% in 2020. In 2030, renewable energy is expected to account for 50% of electricity generation. This is expected to increase to 65% in 2040 and to as much as 80% in 2050. The impact of the Energiewende is not limited to the sphere of energy supplies. In the medium and long term, it will change not only to the way the German economy operates, but also the functioning of German society and the state. Facing difficulties with the expansion of transmission networks, the excessive cost of building wind farms, and problems with the stability of electricity supplies, especially during particularly cold winters, the federal government has so far tended to centralise power and limit the independence of the German federal states with regard to their respective energy policies, justifying this with the need for greater co-ordination. The Energiewende may also become the beginning of a "third industrial revolution", i.e. a transition to a green economy and a society based on sustainable development. This will require a new "social contract" that will redefine the relations between the state, society and the economy. Negotiating such a contract will be one of the greatest challenges for German policy in the coming years.