Manopt, a matlab toolbox for optimization on manifolds

Optimization on manifolds is a rapidly developing branch of nonlinear optimization. Its focus is on problems where the smooth geometry of the search space can be leveraged to design effcient numerical algorithms. In particular, optimization on manifolds is well-suited to deal with rank and orthogonality constraints. Such structured constraints appear pervasively in machine learning applications, including low-rank matrix completion, sensor network localization, camera network registration, independent component analysis, metric learning, dimensionality reduction and so on. The Manopt toolbox, available at www.manopt.org, is a user-friendly, documented piece of software dedicated to simplify experimenting with state of the art Riemannian optimization algorithms. By dealing internally with most of the differential geometry, the package aims particularly at lowering the entrance barrier. © 2014 Nicolas Boumal.

Seeding nets with neutral spores of the red alga Porphyra umbilicalis (L.) Kutzing for use in integrated multi-trophic aquaculture (IMTA)

Nets in traditional Porphyra mariculture are seeded with conchospores derived from the conchocelis phase, and spend a nursery period in culture tanks or calm coastal waters until they reach several centimeters in length. Some species of Porphyra can regenerate the foliose phase directly through asexual reproduction, which suggests that the time, infrastructure, and costs associated with conchocelis culture might be avoided by seeding nets with asexual spores. Here, we present work from a short-term mariculture study using nets seeded with asexual spores (neutral spores) of a native Maine species of Porphyra. Porphyra umbilicalis (L.) Kutzing was selected for this proof of concept research because of its reproductive biology, abundance across seasons in Maine, and evidence of its promise as a mariculture crop. We studied the maturation, release, and germination of the neutral spores to develop an appropriate seeding protocol for nets, followed by development of a nursery raceway to provide an easily manipulated environment for the seeded nets. Neutral spores were produced throughout the year on the central Maine coast,however, there was a temporal variability in the number and survival of released neutral spores, depending upon thallus position in the intertidal zone. Small thalli were strictly vegetative, but most thalli reproduced by neutral spores- sexual reproduction was absent. Neutral spores germinated quickly at 10 and 15 'C, but germination was delayed at 5 degrees C. Unlike some algal zygotes and spores, neutral spores of R umbilicalis required light to germinate; however, irradiances of 25 and 100 mu mol photons M-2 S-1 were equally sufficient for germination. Rafts of seeded nets were deployed in Cobscook Bay, Maine, at two distances from salmon aquaculture pens and at a control site on a nearby, fallow aquaculture site (no salmon). There was no difference in nitrogen content of harvested thalli; however, both the density and the surface area of harvested thalli were different among the sites. The possible causes of these differences are discussed in the context of potential use of P umbilicalis in IMTA. (C) 2007 Elsevier B.V. All rights reserved.

Desire Amongst the Dodgems: Alain Platel and the Scene of Seduction

Kear, Adrian, 'Desire Amongst the Dodgems: Alain Platel and the Scene of Seduction', In: Contemporary Theatres in Europe: A Critical Companion, Joe Kelleher and Nicholas Ridout (eds), (New York: Routledge), pp.106-119, 2006 RAE2008

Coronica general de la Orden de San Benito, Patriarca de Religiosos

Colofón en v.1, v.2, v.5, v.6, y v.7.

Formation and electrical interfacing of nanocrystal-molecule nanostructures

The objective of this thesis work is to develop methods for forming and interfacing nanocrystal-molecule nanostructures in order to explore their electrical transport properties in various controlled environments. This work demonstrates the potential of nanocrystal assemblies for laterally contacting molecules for electronic transport measurements. We first propose a phenomenological model based on rate equations for the formation of hybrid nanocrystal-molecule (respectively: 20 nm – 1.2 nm) nanostructures in solution. We then concentrate on nanocrystals (~ 60 nm) assembled between nano-gaps (~ 40 nm) as a contacting strategy for the measurement of electronic transport properties of thiophene-terminated conjugated molecules (1.5 nm long) in a two-terminal configuration, under vacuum conditions. Similar devices were also probed with a three-terminal configuration using thiophene-terminated oxidation-reduction active molecules (1.8 nm long) in liquid medium for the demonstration of the electrolytic gating technique. The experimental and modelling work presented in this thesis project brings into light physical and chemical processes taking place at the extremely narrow (~1 nm separation) and curved interface between two nanocrystals or one nanocrystal and a grain of a metallic electrode. The formation of molecular bridges at this kind of interface necessitates molecules to diffuse from a large liquid reservoir into the region in the first place. Molecular bonding must occur to the surface for both molecular ends: this is a low yield statistical process in itself as it depends on orientation of surfaces, on steric hindrance at the surface and on binding energies. On the other hand, the experimental work also touched the importance of the competition between potentially immiscible liquids in systems such that (organo-)metallic molecules solvated by organic solvent in water and organic solvent in contact with hydrated citrate stabilised nanocrystals dispersed in solutions or assembled between electrodes from both experimental and simulations point of view.

DC/DC converter 3D assembly for autonomous sensor nodes

This paper reports on the design and the manufacturing of an integrated DCDC converter, which respects the specificity of sensor node network: compactness, high efficiency in acquisition and transmission modes, and compatibility with miniature Lithium batteries. A novel integrated circuit (ASIC) has been designed and manufactured to provide regulated Voltage to the sensor node from miniaturized, thin film Lithium batteries. Then, a 3D integration technique has been used to integrate this ASIC in a 3 layers stack with high efficiency passives components, mixing the wafer level technologies from two different research institutions. Electrical results have demonstrated the feasibility of this integrated system and experiments have shown significant improvements in the case of oscillations in regulated voltage. However, stability of this output voltage toward the input voltage has still to be improved.

Development and assessment of new sensor systems in food packaging applications

The use of optical sensor technology for non-invasive determination of key quality pack parameters improved package/product quality. This technology can be used for optimization of packaging processes, improvement of product shelf-life and maintenance of quality. In recent years, there has been a major focus on O2 and CO2 sensor development as these are key gases used in modified atmosphere packaging (MAP) of food. The first and second experimental chapters (chapter 2 and 3) describe the development of O2, pH and CO2 solid state sensors and its (potential) use for food packaging applications. A dual-analyte sensor for dissolved O2 and pH with one bi-functional reporter dye (meso-substituted Pd- or Ptporphyrin) embedded in plasticized PVC membrane was developed in chapter 2. The developed CO2 sensor in chapter 3 was comprised of a phosphorescent reporter dye Pt(II)- tetrakis(pentafluorophenyl) porphyrin (PtTFPP) and a colourimetric pH indicator α-naphtholphthalein (NP) incorporated in a plastic matrix together with a phase transfer agent tetraoctyl- or cetyltrimethylammonium hydroxide (TOA-OH or CTA-OH). The third experimental chapter, chapter 4, described the development of liquid O2 sensors for rapid microbiological determination which are important for improvement and assurance of food safety systems. This automated screening assay produced characteristic profiles with a sharp increase in fluorescence above the baseline level at a certain threshold time (TT) which can be correlated with their initial microbial load and was applied to various raw fish and horticultural samples. Chapter 5, the fourth experimental chapter, reported upon the successful application of developed O2 and CO2 sensors for quality assessment of MAP mushrooms during storage for 7 days at 4°C.

Mechanically stacked solar cells for concentrator photovoltaics

The power output of dual-junction mechanically stacked solar cells comprising different sub-cell materials in a terrestrial concentrating photovoltaic module has been evaluated. The ideal bandgap combination of both cells in a stack was found using EtaOpt. A combination of 1.4 eV and 0.7 eV has been found to produce the highest photovoltaic conversion efficiency under the AM1.5 Direct Solar Spectrum with x500 concentration. As EtaOpt does not consider the absorption profile of solar cell materials; the practical power output per unit area of a dual junction mechanically stacked solar cell has been modelled considering the optical absorption co-efficients and thicknesses of the individual solar cells. The model considered a GaAs top cell and a Ge, GaSb, Ga0.47In0.53As or Si bottom cell. It was found that GaSb gives the highest power contribution as a bottom cell in a dual junction configuration followed by Ge and GaInAs. While the additional power provided by a Si bottom cell is less than these it remains a suitable candidate for a bottom cell owing to its lower cost

Self-organized vegetation patterning as a fingerprint of climate and human impact on semi-arid ecosystems

Spatially periodic vegetation patterns are well known in arid and semi-arid regions around the world. Mathematical models have been developed that attribute this phenomenon to a symmetry-breaking instability. Such models are based on the interplay between competitive and facilitative influences that the vegetation exerts on its own dynamics when it is constrained by arid conditions, but evidence for these predictions is still lacking. Moreover, not all models can account for the development of regularly spaced spots of bare ground in the absence of a soil prepattern. We applied Fourier analysis to high-resolution, remotely sensed data taken at either end of a 40-year interval in southern Niger. Statistical comparisons based on this textural characterization gave us broad-scale evidence that the decrease in rainfall over recent decades in the sub-Saharan Sahel has been accompanied by a detectable shift from homogeneous vegetation cover to spotted patterns marked by a spatial frequency of about 20 cycles km-1. Wood cutting and grazing by domestic animals have led to a much more marked transition in unprotected areas than in a protected reserve. Field measurements demonstrated that the dominant spatial frequency was endogenous rather than reflecting the spatial variation of any pre-existing heterogeneity in soil properties. All these results support the use of models that can account for periodic vegetation patterns without invoking substrate heterogeneity or anisotropy, and provide new elements for further developments, refinements and tests. This study underlines the potential of studying vegetation pattern properties for monitoring climatic and human impacts on the extensive fragile areas bordering hot deserts. Explicit consideration of vegetation self-patterning may also improve our understanding of vegetation and climate interactions in arid areas. © 2006 The Authors.

A note on spin-s duality

Duality is investigated for higher spin (s ≥ 2), free, massless, bosonic gauge fields. We show how the dual formulations can be derived from a common "parent", first-order action. This goes beyond most of the previous treatments where higher-spin duality was investigated at the level of the equations of motion only. In D = 4 spacetime dimensions, the dual theories turn out to be described by the same Pauli-Fierz (s = 2) or Fronsdal (s ≥ 3) action (as it is the case for spin 1). In the particular s = 2 D = 5 case, the Pauli-Fierz action and the Curtright action are shown to be related through duality. A crucial ingredient of the analysis is given by the first-order, gauge-like, reformulation of higher spin theories due to Vasiliev. © SISSA/ISAS 2003.

EMG Biofeedback Videogame System for the Gait Rehabilitation of Hemiparetic Individuals

Gemstone Team CHIP

Multi-touch and keyboard/mouse devices comparison in an information search task: influence on cognitive load and task engagement

Nowadays multi-touch devices (MTD) can be found in all kind of contexts. In the learning context, MTD availability leads many teachers to use them in their class room, to support the use of the devices by students, or to assume that it will enhance the learning processes. Despite the raising interest for MTD, few researches studying the impact in term of performance or the suitability of the technology for the learning context exist. However, even if the use of touch-sensitive screens rather than a mouse and keyboard seems to be the easiest and fastest way to realize common learning tasks (as for instance web surfing behaviour), we notice that the use of MTD may lead to a less favourable outcome. The complexity to generate an accurate fingers gesture and the split attention it requires (multi-tasking effect) make the use of gestures to interact with a touch-sensitive screen more difficult compared to the traditional laptop use. More precisely, it is hypothesized that efficacy and efficiency decreases, as well as the available cognitive resources making the users’ task engagement more difficult. Furthermore, the presented study takes into account the moderator effect of previous experiences with MTD. Two key factors of technology adoption theories were included in the study: familiarity and self-efficacy with the technology.Sixty university students, invited to a usability lab, are asked to perform information search tasks on an online encyclopaedia. The different tasks were created in order to execute the most commonly used mouse actions (e.g. right click, left click, scrolling, zooming, key words encoding…). Two different conditions were created: (1) MTD use and (2) laptop use (with keyboard and mouse). The cognitive load, self-efficacy, familiarity and task engagement scales were adapted to the MTD context. Furthermore, the eye-tracking measurement would offer additional information about user behaviours and their cognitive load.Our study aims to clarify some important aspects towards the usage of MTD and the added value compared to a laptop in a student learning context. More precisely, the outcomes will enhance the suitability of MTD with the processes at stakes, the role of previous knowledge in the adoption process, as well as some interesting insights into the user experience with such devices.

Consistent deformations of [p,p]-type gauge field theories

Using BRST-cohomological techniques, we analyze the consistent deformations of theories describing free tensor gauge fields whose symmetries are represented by Young tableaux made of two columns of equal length p, p > 1. Under the assumptions of locality and Poincaré invariance, we find that there is no consistent deformation of these theories that non-trivially modifies the gauge algebra and/or the gauge transformations. Adding the requirement that the deformation contains no more than two derivatives, the only possible deformation is a cosmological-constant-like term. © SISSA/ISAS 2004.