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  • 1
    Publication Date: 2013-09-19
    Description: Starting from the results regarding a nonvacuum technique to fabricate CIGS thin films for solar cells by means of single-step electrodeposition, we focus on the methodological problems of modeling at cell structure and photovoltaic module levels. As a matter of fact, electrodeposition is known as a practical alternative to costly vacuum-based technologies for semiconductor processing in the photovoltaic device sector, but it can lead to quite different structural and electrical properties. For this reason, a greater effort is required to ensure that the perspectives of the electrical engineer and the material scientist are given an opportunity for a closer comparison and a common language. Derived parameters from ongoing experiments have been used for simulation with the different approaches, in order to develop a set of tools which can be used to put together modeling both at single cell structure and complete module levels.
    Print ISSN: 1110-662X
    Electronic ISSN: 1687-529X
    Topics: Electrical Engineering, Measurement and Control Technology , Energy, Environment Protection, Nuclear Power Engineering
    Published by Hindawi
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  • 2
    Publication Date: 2013-07-16
    Description: The groundwater hydrochemical behaviour of the Langueyú creek basin (Argentina) has been evaluated through a systematic survey, followed by application of hydrological and chemometric multivariate techniques. Ten physicochemical parameters were determined in groundwater samples collected from 26 wells during 4 sampling campaigns (June, 2010; October, 2010; February, 2011 and June, 2011), originating a tridimensional experimental dataset X . Univariate statistical and graphical hydrochemical tools (contour maps and Piper diagrams) applied to individual campaigns, allowed to reach some preliminary conclusions. However, a best visualization of the aquifer behaviour was achieved by applying Principal Component Analysis (MA-PCA) and N-way PCA procedures, PARAFAC and Tucker3. Results were consistent with two-term models, being Tucker3 [2 2 1] the most adequate, explaining a large amount of the dataset variance (50.7 %) with a low complexity. The first Tucker3 [1 1 1] interaction (38.2% of variance) is related with (i) calcium/magnesium vs. sodium/potassium ion exchange processes; (ii) an increase of ionic concentration and (iii) a decrease of nitrate pollution, all processes along the direction of the groundwater flow. The second [2 2 1] interaction (12.5% of variance), accounts for the predominant role played by conductivity, bicarbonate and magnesium in the dataset. The seasonal variations are closely related to concentration/dilution phenomena originated by the variations of the phreatic levels, although this point will require additional sampling to establish a definitive hydrochemical model. This article is protected by copyright. All rights reserved.
    Print ISSN: 0885-6087
    Electronic ISSN: 1099-1085
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Published by Wiley
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  • 3
    Publication Date: 2013-04-12
    Description: Syntheses for 2-[1-(diarylphosphinoyl)-1-(pyridin-2-yl)methyl]pyridines, ( 8a, b ), and 2-[1-(diarylphosphinoyl)-1,1-bis(methylpyridin-2yl)methyl]pyridines, ( 11a, b ), (Ar = C 6 H 5 and 2-CF 3 C 6 H 4 ), based on substitution of 2-methylpyridine fragments onto the exo methylene carbon atom of 2-[(diaryl)phosphinoylmethyl]pyridine platforms, are described. N-oxidations of 8a, b and 11a, b produced the 2-[1-(diarylphosphinoyl)-1-(1-oxy-pyridin-2yl)methyl]pyridine N -oxides ( 5a, b ) and the 2-[1-(diarylphosphinoyl)-1,1-bis(1-oxy-methylpyridin-2-yl)methyl]pyridines ( 6a, b ), respectively. The “short-arm“ pyridine fragment of 11a, b resists N-oxidation, and the fully oxidized molecules, 2-[1-(diarylphosphinoyl)-1,1-bis(1-oxy-methylpyridin-2-yl)methyl]pyridine N -oxides ( 7a, b ) were not isolated. Molecular mechanics calculations for gas phase 1:1 ligand/lanthanide complexes indicated that 5a should accommodate a tridentate NO(meNO)PO coordination mode with minimal steric strain. In contrast, 7a cannot form tetradentate NO(meNO) 2 PO chelates; however, tridentate binding should be accessible with minimal ligand strain. Coordination complexes of 8a, b , 5a, b , 6a, b and 11a, b with Ln(NO 3 ) 3 salts were isolated and a X-ray crystal structure for [Er( 8a )(NO 3 ) 3 (MeOH) 2 ]·CH 2 Cl 2 , revealed a monodentate Er–O=P interaction. On the other hand, complexes formed by a more symmetrical trifunctional phenylphosphino-bis-2-methylpyridine N, N, P-trioxide ligand, (meNO) 2 PO* , {La[( meNO) 2 PO* )](OTf) 2 (MeOH) 3 (H 2 O) + }(OTf – ) and {Pr[ (meNO) 2 PO* )](OTf)(MeOH) 4 + }(OTf – ) 2 , realized a tridentate coordination mode. Solvent extraction behaviors for Eu III and Am III in nitric acid solutions using 5a, b , 6a, b , Ph 3 PO and the parent bifunctional ligand 2-[(diphenylphosphanyl)methyl]pyridine N, P-dioxide ( 3a ) in 1, 2-dichloroethane were assessed, and 5a, b and 6a, b were found to behave more like Ph 3 PO than 3a .
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 4
    Publication Date: 2013-03-13
    Description: Questions Are species from different biogeographic groups (mediterranean, alpine and endemic) filtered in different ways by altitude and topography in alpine plant communities? What is the relative performance of these environmental factors at predicting the species diversity of the communities as a whole and of the geographic species groups? Location Picos de Europa, Cantabrian Range (Spain). Methods We sampled the presence and cover of vascular plants in 5-m radius plots on alpine grasslands between 1900 and 2500 m a.s.l. Five GIS-based terrain variables at 15 m × 15 m were used to model species richness and cover per plot using generalized and linear models, and the variation in species composition with redundancy analysis. The same analyses were repeated for the whole data set and for subsets of species from alpine, mediterranean and endemic distributions. Results The influence of altitude and topography on species richness, cover and composition differed for the whole data set and for the geographic species groups. Altitude was the main variable affecting floristic diversity in the communities as a whole, but the separate species groups were more influenced by slope, topographic wetness index and solar radiation. Richness and cover of mediterranean species showed the strongest relationships with topography. Alpine and endemic species showed relationships with topography for species cover and composition, but not for species richness. Conclusions In alpine landscapes, biogeographic deconstruction of the species pool can provide a better understanding of the influence of altitude and topography on local communities than analysis of the entire community alone. Furthermore, the strong influence of local topography on species groups improves our understanding of how alpine species will respond to climate change. We studied the influence of high-resolution altitudinal and topographic variables on species groups with different biogeographic history. Diversity estimates of the geographic groups showed remarkable differences in the relationships with temperature-related factors that were neglected when using data for the whole community. This procedure provides a better understanding of the influence of topography in species assemblages of alpine communities.
    Print ISSN: 1100-9233
    Electronic ISSN: 1654-1103
    Topics: Biology
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  • 5
    Publication Date: 2013-05-21
    Description: The transformation process of clay minerals into pozzolanic products for use as active additives in cement matrixes has been closely studied by both the scientific community and the cement industry. Sourcing these additions from recycled waste products is widely prioritized in environmental policies, because of their associated environmental benefits. This article reports an exhaustive analysis of slate waste in Spain, for its eventual use as an alternative source of pozzolans, based on activated phyllosilicates. The analysis examines the effect of activation conditions on mineralogy and the formation and evolution of the hydrated phases that form during the pozzolanic reaction at 28 days. The results show good pozzolanic activity in the starting slate wastes activated between 800°C and 1100°C of temperature for 2 h of retention, on which basis 1000°C and 2 h were recommended as the more suitable activation conditions for these activated slate wastes (ASW), as total destruction of all phyllosilicates is ensured under those conditions. The hydrated phases formed during the pozzolanic reaction in the ASW/ Ca (\ OH ) 2 system were calcium silicate hydrate gels (CSH), randomly interstratified chlorite (Cl) /smectite with variables containing chlorite/smectite ratios 30% chlorite, 40% chlorite, 50% chlorite, 60% chlorite, respectively, and monosulfoaluminate ( C 3 A · SO 4 Ca ·12 H 2 O ) directly related to the activation process used in this article. All of these findings support the viability of slate waste for use as a pozzolanic addition.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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  • 6
    Publication Date: 2013-06-05
    Description: Phytoplankton phenology is primarily affected by physical forcing. However, its quantification is far from being completely understood. Among the physical forcing factors, the Mixed Layer Depth (MLD) is considered to have the strongest impact on phytoplankton dynamics, and consequently, on their phenology. The role of MLD variations in shaping the phytoplankton phenology was explored in the Mediterranean Sea, a basin displaying contrasting phenological regimes. A database of MLD estimations was merged with ocean color chlorophyll concentrations ([Chl] SAT ) to generate concomitant annual MLD and [Chl] SAT cycles. Several indices were calculated to quantitatively analyze these cycles. The relevance of indices summarizing the temporal difference between main characteristics of MLD and [Chl] SAT cycles was emphasized. As previously observed, two dominant phenological regimes co-exist in the Mediterranean Sea. The first is marked by a typical spring bloom, as in temperate regions. The second displays a low seasonality and an absence of an intense [Chl] SAT peak as in subtropical areas. The MLD is shown to play a key role in determining the dominant phenological regime in a given area. Results also show that regions having low seasonality display concomitant MLD and [Chl] SAT maxima, whereas [Chl] SAT peaks are generally observed 30 days after MLD peaks in regions with strongest seasonality. Over the whole basin, [Chl] SAT increase starts one month after the initiation of MLD deepening. Finally, after examining the impact of MLD on light and nutrient availability for phytoplankton, mechanisms were proposed to explain the time-lags between MLD and [Chl] SAT increase and MLD and [Chl] SAT maxima.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
    Publication Date: 2013-01-22
    Description: Biomass is one of the most promising renewable energy sources. Abundantly, the potential as an alternative source to meet the world energy demand has been widely acknowledged. Gasification is one of the most efficient processes concerning thermochemical conversion, having as objective the production of a gas with useful energy power, known as producer gas. In order to optimize thermochemical processes such as the combustion of gases and subsequent gas mixture, computer modeling is becoming an important tool. Aiming to improve the performance of a combustion chamber, previously coupled to a downdraft gasifier, a thermofluidynamic model was elaborated and validated, using the concepts of computational fluid dynamics (CFD). It was reported that temperature, pressure, and velocity distributions of the computational model showed good consistency with experimental data, which allows using this model to predict the performance of this type of combustion chambers.
    Print ISSN: 2090-7451
    Electronic ISSN: 2090-746X
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Hindawi
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  • 8
    Publication Date: 2013-08-30
    Description: Biomass is one of the most promising renewable energy sources. Abundantly, the potential as an alternative source to meet the world energy demand has been widely acknowledged. Gasification is one of the most efficient processes concerning thermochemical conversion, having as objective the production of a gas with useful energy power, known as producer gas. In order to optimize thermochemical processes such as the combustion of gases and subsequent gas mixture, computer modeling is becoming an important tool. Aiming to improve the performance of a combustion chamber, previously coupled to a downdraft gasifier, a thermofluidynamic model was elaborated and validated, using the concepts of computational fluid dynamics (CFD). It was reported that temperature, pressure, and velocity distributions of the computational model showed good consistency with experimental data, which allows using this model to predict the performance of this type of combustion chambers.
    Print ISSN: 2090-7451
    Electronic ISSN: 2090-746X
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Hindawi
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  • 9
    Publication Date: 2013-09-04
    Description: ABSTRACT The acute toxicity of cylindrospermopsin (CYN) has been established in rodents, based on diverse intraperitoneal an oral exposure studies and more recently in fish. But no data have been reported in fish after subchronic exposure to cyanobacterial cells containing this cyanotoxin, so far. In this work, tilapia ( Oreochromis niloticus ) were exposed by immersion to lyophilized Aphanizomenon ovalisporum cells added to the aquaria using two concentration levels of CYN (10 or 100 μg CYN L −1 ) and deoxy-cylindrospermopsin (deoxy-CYN) (0.46 or 4.6 μg deoxy-CYN L −1 ), during two different exposure times: 7 or 14 d. This is the first study showing damage in the liver, kidney, hearth, intestines, and gills of tilapia after subchronic exposure to cyanobacterial cells at environmental relevant concentrations. The major histological changes observed were degenerative processes and steatosis in the liver, membranous glomerulopathy in the kidney, myofibrolysis and edema in the heart, necrotic enteritis in the gastrointestinal tract, and hyperemic processes in gill lamellae and microhemorrhages. Moreover, these histopathological findings confirm that the extent of damage is related to the CYN concentration and length of exposure. Results from the morphometric study indicated that the average of nuclear diameter of hepatocytes and cross-sections of proximal and distal convoluted tubules are useful to evaluate the damage induced by CYN in the main targets of toxicity. © 2013 Wiley Periodicals, Inc. Environ Toxicol, 2013.
    Print ISSN: 1520-4081
    Electronic ISSN: 1522-7278
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Published by Wiley
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  • 10
    Publication Date: 2013-08-24
    Description: The percolation threshold in a composite depends on the processing conditions used to fabricate it along with the size and shape of the filler and the matrix. In this study, borosilicate glass microspheres were used as the matrix material, and nanosized antimony tin oxide (ATO) particles were used as the filler. The glass microsphere/ATO composites were fabricated by hot pressing at temperatures in the range between the glass transition temperature and the softening temperature of the glass to control the viscosity. The pressure and temperature applied allowed the ATO to be confined to the spaces between certain glass particles, forming percolating networks at low volume fractions of the ATO. The viscous flow of the glass allowed for the composite to have near full densities, while allowing for the nanoparticle segregation to occur. Even though apparently similar microstructures were made using different heating schedules, the percolation behavior and electrical conductivity showed noticeable differences. The percolation threshold ranged from 0.1 to 2.5 phr (parts per hundred glass) and the change in electrical conductivity was around seven to nine orders of magnitude. The differences were attributed to the interaction of the segregated ATO particles with one another. The electrical properties were examined using ac impedance spectroscopy along with current atomic force microscopy (C-AFM), which allowed for valuable insights in the structure–property–processing relationships in these materials.
    Print ISSN: 0002-7820
    Electronic ISSN: 1551-2916
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Wiley
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