Aluminium metallisation for interdigitated back contact silicon heterojunction solar cells

Back contact silicon heterojunction solar cells with an efficiency of 22 were manufactured, featuring a simple aluminium metallisation directly on the doped amorphous silicon films. Both the open circuit voltage and the fill factor heavily depend on the parameters of the annealing step after aluminium layer deposition. Using numerical device simulations and in accordance with the literature, we demonstrate that the changes in solar cell parameters with annealing can be explained by the formation of an aluminium silicide layer at temperatures as low as 150 C, improving the contact resistance and thus enhancing the fill factor. Further annealing at higher temperatures initialises the crystallisation of the amorphous silicon layers, yielding even lower contact resistances, but also introduces more defects, diminishing the open circuit voltag

The Cyborg Astrobiologist: Testing a Novelty-Detection Algorithm on Two Mobile Exploration Systems at Rivas Vaciamadrid in Spain and at the Mars Desert Research Station in Utah

(ABRIDGED) In previous work, two platforms have been developed for testing computer-vision algorithms for robotic planetary exploration (McGuire et al. 2004b,2005; Bartolo et al. 2007). The wearable-computer platform has been tested at geological and astrobiological field sites in Spain (Rivas Vaciamadrid and Riba de Santiuste), and the phone-camera has been tested at a geological field site in Malta. In this work, we (i) apply a Hopfield neural-network algorithm for novelty detection based upon color, (ii) integrate a field-capable digital microscope on the wearable computer platform, (iii) test this novelty detection with the digital microscope at Rivas Vaciamadrid, (iv) develop a Bluetooth communication mode for the phone-camera platform, in order to allow access to a mobile processing computer at the field sites, and (v) test the novelty detection on the Bluetooth-enabled phone-camera connected to a netbook computer at the Mars Desert Research Station in Utah. This systems engineering and field testing have together allowed us to develop a real-time computer-vision system that is capable, for example, of identifying lichens as novel within a series of images acquired in semi-arid desert environments. We acquired sequences of images of geologic outcrops in Utah and Spain consisting of various rock types and colors to test this algorithm. The algorithm robustly recognized previously-observed units by their color, while requiring only a single image or a few images to learn colors as familiar, demonstrating its fast learning capability.Comment: 28 pages, 12 figures, accepted for publication in the International Journal of Astrobiolog

Quantum Calogero-Moser Models: Integrability for all Root Systems

The issues related to the integrability of quantum Calogero-Moser models based on any root systems are addressed. For the models with degenerate potentials, i.e. the rational with/without the harmonic confining force, the hyperbolic and the trigonometric, we demonstrate the following for all the root systems: (i) Construction of a complete set of quantum conserved quantities in terms of a total sum of the Lax matrix (L), i.e. (\sum_{\mu,\nu\in{\cal R}}(L^n)_{\mu\nu}), in which ({\cal R}) is a representation space of the Coxeter group. (ii) Proof of Liouville integrability. (iii) Triangularity of the quantum Hamiltonian and the entire discrete spectrum. Generalised Jack polynomials are defined for all root systems as unique eigenfunctions of the Hamiltonian. (iv) Equivalence of the Lax operator and the Dunkl operator. (v) Algebraic construction of all excited states in terms of creation operators. These are mainly generalisations of the results known for the models based on the (A) series, i.e. (su(N)) type, root systems.Comment: 45 pages, LaTeX2e, no figure

Targeted colonic release formulations of mesalazine - A clinical pharmaco-scintigraphic proof-of-concept study in healthy subjects and patients with mildly active ulcerative colitis.

Colonic targeting of orally applied therapeutic drugs remains a challenge. Tablet coatings relying on gastrointestinal pH and colonic bacterial enzymes as triggers in association with an inner alkaline layer are expected to improve targeting efficiency. Mesalazine release from three differently coated tablets labelled with 1 MBq 153Sm was characterised in a single centre, open-label, parallel group study in nineteen healthy subjects and seven patients with mildly active ulcerative colitis. Two semi-organic and one aqueous-based outer coating with different ratios of enteric polymer and resistant starch were tested. All coatings showed comparable release lagtimes in biorelevant dissolution media and were not affected by neutron-activation of the samarium tracer. Mesalazine pharmacokinetics and gamma scintigraphy were used to characterise drug release, anatomical site of tablet disintegration and gastrointestinal transit. Initial tablet disintegration occurred at the ileo-caecal junction or beyond in 92% of the subjects Time to initial tablet disintegration was inversely correlated with maximal plasma concentrations and systemic mesalazine exposure. Although high inter-subject variability precluded detection of differences between solvent types and different enteric polymer to polysaccharide ratios, the dual pH and enzymatic triggered release system in combination with an inner alkaline layer promoted mesalazine release at the target site with high accuracy

Preliminary results for RR Lyrae stars and Classical Cepheids from the Vista Magellanic Cloud (VMC) Survey

The Vista Magellanic Cloud (VMC, PI M.R. Cioni) survey is collecting $K_S$-band time series photometry of the system formed by the two Magellanic Clouds (MC) and the "bridge" that connects them. These data are used to build $K_S$-band light curves of the MC RR Lyrae stars and Classical Cepheids and determine absolute distances and the 3D geometry of the whole system using the $K$-band period luminosity ($PLK_S$), the period - luminosity - color ($PLC$) and the Wesenhiet relations applicable to these types of variables. As an example of the survey potential we present results from the VMC observations of two fields centered respectively on the South Ecliptic Pole and the 30 Doradus star forming region of the Large Magellanic Cloud. The VMC $K_S$-band light curves of the RR Lyrae stars in these two regions have very good photometric quality with typical errors for the individual data points in the range of $\sim$ 0.02 to 0.05 mag. The Cepheids have excellent light curves (typical errors of $\sim$ 0.01 mag). The average $K_S$ magnitudes derived for both types of variables were used to derive $PLK_S$ relations that are in general good agreement within the errors with the literature data, and show a smaller scatter than previous studies.Comment: 7 pages, 6 figure. Accepted for publication in Astrophysics and Space Science. Following a presentation at the conference "The Fundamental Cosmic Distance Scale: State of the Art and the Gaia Perspective", Naples, May 201

The Physical Conditions in Starbursts Derived from Bayesian Fitting of Mid-IR SEDS: 30 Doradus as a Template

To understand and interpret the observed Spectral Energy Distributions (SEDs) of starbursts, theoretical or semi-empirical SED models are necessary. Yet, while they are well-founded in theory, independent verification and calibration of these models, including the exploration of possible degeneracies between their parameters, are rarely made. As a consequence, a robust fitting method that leads to unique and reproducible results has been lacking. Here we introduce a novel approach based on Bayesian analysis to fit the Spitzer-IRS spectra of starbursts using the SED models proposed by Groves et al. (2008). We demonstrate its capabilities and verify the agreement between the derived best fit parameters and actual physical conditions by modelling the nearby, well-studied, giant HII region 30 Dor in the LMC. The derived physical parameters, such as cluster mass, cluster age, ISM pressure and covering fraction of photodissociation regions, are representative of the 30 Dor region. The inclusion of the emission lines in the modelling is crucial to break degeneracies. We investigate the limitations and uncertainties by modelling sub-regions, which are dominated by single components, within 30 Dor. A remarkable result for 30 Doradus in particular is a considerable contribution to its mid-infrared spectrum from hot ({\simeq} 300K) dust. The demonstrated success of our approach will allow us to derive the physical conditions in more distant, spatially unresolved starbursts.Comment: 17 pages, 10 figures. Accepted por publication in the Astrophysical Journa

Continental response to active ridge subduction

[1] Apatite fission track ages from a ∼2000 m elevation transect from the Patagonian fold and thrust belt (47.5°S) allow us to quantify the denudational and orographic response of the upper plate to active ridge subduction. Accelerated cooling started at 17 Ma, predating the onset of ridge collision (14–10 Ma), and was followed by reheating between 10 and 6 Ma. Thermal modeling favors reheating on the order of 60°C at ∼28°C/Ma due to east-migration of a slab window after the ridge-trench collision. Final rapid cooling since 4 Ma of ∼18°C/Ma (geothermal gradient of 14°C/km) correlates with the presence of an orographic barrier and >1 km rock uplift in this region between 17.1 and 6.3 Ma. Increased precipitation and erosion since 4 Ma caused asymmetric exhumation, with 3–4 km on the leeside. Repeated crustal unroofing in response to active ridge subduction can explain the positive gravity anomaly south of the Chile Triple Junction

STEP: the VST survey of the SMC and the Magellanic Bridge - I : Overview and first results

STEP (the SMC in Time: Evolution of a Prototype interacting late-type dwarf galaxy) is a Guaranteed Time Observation survey being performed at the VST (the ESO VLT Survey Telescope). STEP will image an area of 74 sq. deg. covering the main body of the Small Magellanic Cloud (32 sq. deg.), the Bridge that connects it to the Large Magellanic Cloud (30 sq. deg.) and a small part of the Magellanic Stream (2 sq. deg.). Our g, r, i, Hα photometry is able to resolve individual stars down to magnitudes well below the main-sequence turn-off of the oldest populations. In this first paper, we describe the observing strategy, the photometric techniques and the upcoming data products of the survey. We also present preliminary results for the first two fields for which data acquisition is completed, including some detailed analysis of the two stellar clusters IC 1624 and NGC 419.Peer reviewedFinal Accepted Versio