Intermixing at the InxSy/Cu2ZnSn(S,Se)4 Heterojunction and Its Impact on the Chemical and Electronic Interface Structure

We report on the chemical and electronic structure of the interface between a thermally co-evaporated InxSy buffer and a Cu2ZnSn(S,Se)4 (CZTSSe) absorber for thin-film solar cells. To date, such cells have achieved energy conversion efficiencies up to 8.6%. Using surface-sensitive X-ray and UV photoelectron spectroscopy, combined with inverse photoemission and bulk-sensitive soft X-ray emission spectroscopy, we find a complex character of the buffer layer. It includes oxygen, as well as selenium and copper that diffused from the absorber into the InxSy buffer, exhibits an electronic band gap of 2.50 ± 0.18 eV at the surface, and leads to a small cliff in the conduction band alignment at the InxSy/CZTSSe interface. After an efficiency-increasing annealing step at 180 °C in nitrogen atmosphere, additional selenium diffusion leads to a reduced band gap at the buffer layer surface (2.28 ± 0.18 eV)

Shifting Curatorial Strategies for Art from Latin America and Latino Art at the Museum of Fine Arts, Houston 1956 - 2004

This thesis explores changing curatorial strategies at the Museum of Fine Arts, Houston. This is preceded by an assessment of the Museum of Modern Art’s earlier role in systematizing and defining this field throughout the 1930s and 1940s. Three exhibitions of art from Latin America and Latino art will illustrate how the MFAH contributed to shifts in this field proposing parallel and expanded readings to those first introduced at MoMA. Firstly, the Gulf-Caribbean Art Exhibition (1956) was a collaboration with the Pan American Union. This exhibition was framed by Cold War modernist approaches and a re-imagined geographical conception of the Gulf region. Secondly, Hispanic Art in the United States- Thirty Contemporary Painters and Sculptors (1987) sought to include Latino art and reflect the community in Houston within this mainstream institution. This lead to traditional museum practices emphasising the quality of artworks, while the criteria for selection was based on the ethnicity of the artists. Finally, Inverted Utopias- Avant-Garde Art in Latin America (2004) revised curatorial structures that were based upon the geographical and national survey format. Six constellations emphasising nodal connections between movements from Latin America disrupted established narratives of this field. The extensive use of archival documents further aided this historical review. I will answer how political, diplomatic, social, and art historical contexts have influenced the curation of these exhibitions and the outcomes of each. I will argue that through the location of the MFAH in the south of the United States, this institution is able to experiment with curatorial approaches and contribute to reviewed readings of art and art history in the United States

Mapping Patent Classifications: Portfolio and Statistical Analysis, and the Comparison of Strengths and Weaknesses

The Cooperative Patent Classifications (CPC) jointly developed by the European and US Patent Offices provide a new basis for mapping and portfolio analysis. This update provides an occasion for rethinking the parameter choices. The new maps are significantly different from previous ones, although this may not always be obvious on visual inspection. Since these maps are statistical constructs based on index terms, their quality--as different from utility--can only be controlled discursively. We provide nested maps online and a routine for portfolio overlays and further statistical analysis. We add a new tool for "difference maps" which is illustrated by comparing the portfolios of patents granted to Novartis and MSD in 2016.Comment: Scientometrics 112(3) (2017) 1573-1591; http://link.springer.com/article/10.1007/s11192-017-2449-

The Science Space of Artificial Intelligence Knowledge Production

The present contribution seeks to map the development of Artificial Intelligence (AI) knowledge as indicated through scientific publications. A set of principal keywords is employed in order to identify those publications that are related to AI in the Web of Science and the metadata provided by the database is then utilized to map the evolution of the field across different scales, i.e. the national, country and regional level. This analysis allows for the identification of potential AI “hotspots”, while also establishing places that have been leading in the development of AI knowledge from the onset vis-à-vis those that have managed to catch up over time. In addition, a network that illustrates international collaborative efforts in AI knowledge creation via co-authorships across nations and via the evolution of keywords’ co-occurrence across three decades is illustrated. It is evident that these networks have become denser with time, and that they have changed across regions. The objective of the present analysis is to enhance our understanding about where and how scientific AI knowledge is created, which in turn should encourage and assist future research efforts looking to study AI knowledge and its consequences

Methane Decomposition and Carbon Growth on Y₂O₃, Yttria-Stabilized Zirconia, and ZrO₂

Carbon deposition following thermal methane decomposition under dry and steam reforming conditions has been studied on yttria-stabilized zirconia (YSZ), Y2O3 and ZrO2 by a range of different chemical, structural and spectroscopic characterization techniques, including aberration-corrected electron microscopy, Raman spectroscopy, electric impedance spectroscopy and volumetric adsorption techniques. Concordantly, all experimental techniques reveal the formation of a conducting layer of disordered nanocrystalline graphite covering the individual grains of the respective pure oxides after treatment in dry methane at temperatures T ≥ 1000 K. In addition, treatment under moist methane conditions causes additional formation of carbon-nanotube-like architectures by partial detachment of the graphite layers. All experiments show that during carbon growth, no substantial reduction of any of the oxides takes place. Our results therefore indicate that these pure oxides can act as efficient nonmetallic substrates for methane-induced growth of different carbon species with potentially important implications regarding their use in solid oxide fuel cells. By comparison of the three oxides we could moreover elucidate differences in the methane reactivities of the respective SOFC-relevant purely oxidic surfaces under typical SOFC operation conditions without the presence of metallic constituents

Active membranes:3D printing of elastic fibre patterns on pre-stretched textiles

There has been a steady growth, over several decades, in the deployment of fabrics in architectural applications; both in terms of quantity and variety of application. More recently 3D printing and additive manufacturing have added to the palette of technologies that designers in architecture and related disciplines can call upon. Here we report on research that brings those two technologies together - the development of active membrane elements and structures. We show how these active membranes have been achieved by laminating 3D printed elasto-plastic fibres onto pre-stretched textile membranes. We report on a set of experiments involving one-, two- and multi-directional geometric arrangements that take TPU 95 and Polypropylene filaments and apply them to lycra textile sheets, to form active composite panels. The process involves a parametrised design, actualized through a particular fabrication process. Our findings document the investigation into mapping between the initial two-dimensional geometries and their resulting three-dimensional doubly-curved forms, as well as accomplishments and products of the resulting, partly serendipitous, design process

Graph-Controlled Insertion-Deletion Systems

In this article, we consider the operations of insertion and deletion working in a graph-controlled manner. We show that like in the case of context-free productions, the computational power is strictly increased when using a control graph: computational completeness can be obtained by systems with insertion or deletion rules involving at most two symbols in a contextual or in a context-free manner and with the control graph having only four nodes.Comment: In Proceedings DCFS 2010, arXiv:1008.127

Physics at the e+ e- Linear Collider

A comprehensive review of physics at an e+e- Linear Collider in the energy range of sqrt{s}=92 GeV--3 TeV is presented in view of recent and expected LHC results, experiments from low energy as well as astroparticle physics.The report focuses in particular on Higgs boson, Top quark and electroweak precision physics, but also discusses several models of beyond the Standard Model physics such as Supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analyzed as well.Comment: 179 pages, plots and references updated, version to be published at EPJ