Presentations of Trivial Extensions of Finite Dimensional Algebras and a Theorem of Sheila Brenner

AbstractLet Λ be a finite dimensional algebra over an algebraically closed field such that any oriented cycle in the ordinary quiver of Λ is zero in Λ. We describe the ordinary quiver and relations for T(Λ)=Λ⋉D(Λ), the trivial extension of Λ by its minimal injective cogenerator D(Λ), and also for the repetitive algebra [formula] of Λ. Associated with this description we give an application of a theorem of Sheila Brenner

Marine diatoms from Buenos Aires coastal waters (Argentina). II. Thalassionemataceae and Rhaphoneidaceae

This study describes the diversity of the species belonging to the diatom families Thalassionemataceae Round and Rhaphoneidaceae Forti frequently found in the temperate marine coastal waters of Buenos Aires Province, Argentina, from October 1994 to September 2000. It comprises morphological, taxonomic and distributional analysis of species found in planktonic samples collected at San Clemente del Tuyú, Santa Teresita, La Lucila del Mar, Mar de Ajó, Nueva Atlantis, Pinamar and Villa Gesell. Raw and cleaned samples were analysed with light and scanning electron microscopy. Four taxa of the genus Thalassionema Grunow ex Mereschkowsky amend. Hallegraeff, one of the genus Lioloma Hasle, two of the genus Delphineis Andrews and one of the genus Rhaphoneis Ehrenberg, were identified. Thalassionema pseudonitzschioides (Schuette & Schrader) Hasle, Thalassionema synedriforme (Greville) Hasle and Lioloma pacificum (Cupp) Hasle in Hasle & Syvertsen are new records for Argentina.Facultad de Ciencias Naturales y Muse

Ecology of Fucus vesiculosus (Phaeophyceae) at its southern limit of distribution: Growth and production of the early stages of development.

Growth and survival of two populations of Fucus vesiculosus were studied at its southern limit of distribution on the eastern Atlantic coast. Experimentally denuded areas at an estuarine and a semi-exposed site in an upwelling area (NW Spain) were followed for 17 months. Three different cohorts were detected during the sampling period. Differences among the three cohorts in terms of growth, reproduction and survival were detected. These differences may be due to the different time of appearance of the different cohorts or the presence of the previously established individuals when the second and third cohorts were recruited. Although the growth of the cohorts recruiting in autumn was higher than for the cohorts recruiting in spring and summer, the individual growth was represented in all cases by a logistic function, as the fastest rates of increase in length occurred during the first 6 months of life, and maximum length was attained after the thallus reached 1 year in age. In the same way, production was maximum for the first cohort, recruiting in autumn, even when it had the lowest survival rate, because of the rapid growth of survivors during spring and summer. For both populations, reproduction was continuous through the year but it was maximal during spring and summer. Protection from waves might have been thought to favour higher production and standing stock biomass values at the estuarine site compared with the semi-exposed site, while turnover rates of biomass were higher at the latter. Contrary to expectations, most of the nutrients available for the studied populations were not related to upwelling. Despite the fast initial growth of new recruits, both populations appeared to be very sensitive to denudation.Projects ANILE (CTM2009-08396, CTM2010-09904-E) Plan Nacional I+D+i and RADIALES (IEO)En prensa1,828

Thermophysical Characterization of Sorption TCM

AbstractThermochemical materials (TCM) are proposed for thermal energy storage as one of the future options to achieve lower energy consumption in buildings and other industrial applications, as well as to store energy from solar energy. In this study, the thermophysical properties of two TCM, CaCl2 and zeolite, are determined with TGA and DSC and samples are cycled 4 times with TGA. Results show that the material with the highest energy density is the salt, CaCl2. Moreover, both materials under study present noble cyclability

Industrial carnallite-waste for thermochemical energy storage application

The key to successful development and implementation of thermochemical storage systems is the identification of high energy density and low-cost storage materials. In this work, an industrial waste based on a double salt hydrate, coming from non-metallic mining was studied for thermochemical storage applications. Initially, chemical characterization was performed and determined that carnallite-waste material consists of 73.54 wt% of KCl·MgCl2·6H2O and impurities such as NaCl (23.04 wt%), KCl (1.76 wt%) and CaSO4 (1.66 wt%). Using thermal analyses methods, the operating conditions such as temperatures and partial pressures, were optimized for seasonal thermochemical storage applications to PHy = 1.3 kPa and ϑHy = 40 °C, and to PDe = 4.0 kPa and ϑDe = 110 °C. Under these conditions, the reaction reversibility over 10 cycles (10 years) was significantly high, with only 8.5% decrease in chemical reversibility. Furthermore, the duration of dehydration and hydration isotherms was optimized to 15 and 360 min, respectively. Finally, 1.129 GJ/m3 energy storage density was calculated after the tenth cycle of hydration/dehydration for this material. Hence 7.1 m3 of carnallite was estimated to meet the demand of 8 GJ of energy for an average household during the six months of cold seasons. These results are comparable and competitive with an energy storage density of materials such as K2CO3 and MgCl2, reported as promising for seasonal thermochemical storage applications. It should be noted that carnallite- waste material has no commercial value so far and its use contributes to developing sustainable low-cost thermochemical energy storage systems

Review of the use of phase change materials (PCMs) in buildings with reinforced concrete structures

Phase change materials are capable of storing and releasing energy in the form of heat in determined temperature ranges, so to increase a building"s thermal inertia, stabilize its indoor temperatures and reduce its energetic demand. Therefore, if we used these materials we could have more energetically efficient buildings. Nevertheless, are these materials most appropriate to be used in buildings? Could the incorporation of phase change materials in buildings with concrete structures be generalized? This article aims to carry out a review of these phase change materials from construction professionals" points of view, study their applications for buildings with reinforced concrete structures and the key points for these applications, draw conclusions and provide recommendations useful for all professionals within the sector who are considering the application of these materials.Revisión crítica del uso de materiales de cambio de fase en edificios con estructuras de hormigón armado. Los materiales de cambio de fase son capaces de almacenar y liberar energía en forma de calor en un determinando rango de temperaturas, y así aumentar la inercia térmica de un edificio, estabilizar las temperaturas en el interior y reducir la demanda energética. En consecuencia, si utilizáramos estos materiales podríamos tener un parque de edificios más eficientes energéticamente. No obstante, ¿estos materiales son apropiados para usarse en edificios? ¿Se podría generalizar la incorporación de materiales de cambio de fase en edificios con estructuras de hormigón? Este artículo tiene como objetivos hacer una revisión del estado del arte de estos materiales de cambio de fase desde el punto de vista de los profesionales de la construcción, estudiar las aplicaciones en edificios con estructuras de hormigón armado y los puntos clave para estas aplicaciones, extraer conclusiones y recomendaciones útiles para los profesionales del sector que se planteen la utilización de estos materiales.This research was partially funded by the Spanish government (ENE2011-28269-C03-02). The authors would like to acknowledge the support received from the Concrete Technology Research Group of Barcelona Tech (UPC). The authors would also like to thank the Catalan Government for the quality accreditation given to the research group GREA (2009 SGR 534) and the research group DIOPMA (2009 SGR 645)

Corrosion performance of alloy 800H and alloy 625 for potential use as molten salts solar receiver materials in concentrating solar power tower plants

Two high corrosion resistant super-alloys, alloy 800H and alloy 625, were evaluated for corrosion compatibility with molten nitrate salts at 565 °C under air atmosphere since these super-alloys are possible candidates for the manufacturing of molten salts solar receivers in the CSP tower technology. Both alloys are tested in two different molten nitrate salts grades to identify how the impurities of the final mixture affect to corrosion damage. Accordingly, a technical grade molten nitrate salt (Solar_Salt_T) and refined molten nitrate salt (Solar_Salt_R) are selected as test media. In addition to corrosion rates calculation, techniques such as XRD, EDS, optical and scanning electron microscopy are used to identify the corrosion morphology and oxides layers chemistry. Alloy 800H and alloy 625 show uniform corrosion after testing without detecting localized phenomena such as pitting, stress corrosion cracking, crevice, or intergranular corrosion. While alloy 800H develops a duplex oxide layer consisting of iron oxides in its external part, and chromium oxide in its innermost layer, alloy 625 generates a compact and highly adherent oxide layer consisting mainly of nickel oxide. Corrosion rates decrease with time, being higher for alloys exposed to Solar_Salt_T mixtures. Moreover, alloy 625 shows lower corrosion rates than alloy 800H in all conditions tested in this study.The research leading to these results has received funding from CENIT ConSOLida. This work was partially funded by the Ministerio de Ciencia, Innovación y Universidades de España (RTI2018-093849-B-C31 - MCIU/AEI/FEDER, UE and RTI2018-093849-B-C32 - MCIU/AEI/FEDER, UE) and by the Ministerio de Ciencia, Innovación y Universidades - Agencia Estatal de Investigación (AEI) (RED2018-102431-T). The authors from University of Lleida and University of Barcelona would like to thank the Catalan Government for the quality accreditation given to their research group GREiA (2017 SGR 1537) and research group DIOPMA (2017 SGR 138). GREiA and DIOPMA are certified agents TECNIO in the category of technology developers from the Government of Catalonia. This work is partially supported by ICREA under the ICREA Academia programme

Marine diatoms from Buenos Aires coastal waters (Argentina). II. Thalassionemataceae and Rhaphoneidaceae

This study describes the diversity of the species belonging to the diatom families Thalassionemataceae Round and Rhaphoneidaceae Forti frequently found in the temperate marine coastal waters of Buenos Aires Province, Argentina, from October 1994 to September 2000. It comprises morphological, taxonomic and distributional analysis of species found in planktonic samples collected at San Clemente del Tuyú, Santa Teresita, La Lucila del Mar, Mar de Ajó, Nueva Atlantis, Pinamar and Villa Gesell. Raw and cleaned samples were analysed with light and scanning electron microscopy. Four taxa of the genus Thalassionema Grunow ex Mereschkowsky amend. Hallegraeff, one of the genus Lioloma Hasle, two of the genus Delphineis Andrews and one of the genus Rhaphoneis Ehrenberg, were identified. Thalassionema pseudonitzschioides (Schuette & Schrader) Hasle, Thalassionema synedriforme (Greville) Hasle and Lioloma pacificum (Cupp) Hasle in Hasle & Syvertsen are new records for Argentina.Facultad de Ciencias Naturales y Muse

Thermochemical energy storage by consecutive reactions for higher efficient concentrated solar power plants (CSP): Proof of concept

Concentrated solar power plants (CSP) combined with thermal energy storage (TES) offers the benefit to provide continuous electricity production by renewable energy feed. There are several TES technologies to be implemented, being the thermochemical energy storage the less studied and the most attractive since its volumetric energy density is 5 and 10 times higher than latent and sensible TES, respectively. Thermochemical energy storage technology is based on reversible chemical reactions, also named thermochemical materials (TCM). One of the main challenges of TCM is to achieve a proper reversibility of the reactions, which in practical conditions leads to lower efficiencies than the theoretically expected. A new concept based on changing from reversible TCM reactions towards TCM consecutive reactions aims to eliminate reversibility problems and therefore improve the overall efficiency. Consecutive TCM reactions can either be based in one cycle, where reactants are needed to feed the reaction, or two coupled cycles which offer the possibility to work without any extra mass reactants input. The plausibility of the implementation of both concepts in CSP is detailed in this paper and case studies are described for each one

Influence of nanoparticle morphology and its dispersion ability regarding thermal properties of water used as phase change material

Nanoparticles with different morphologies were added to water to study if the morphology of the nanoparticles affects the main parameters of water used as phase change material (PCM). Considered morphologies were spherical, tubes and sheets in the form of spherical carbon black nanoparticles (CB), multiwalled carbon nanotubes (MWCNT), and graphene oxide nanosheets (GO). Results demonstrate that effectively the morphology of nanoparticles affect the thermophysical properties of the nano-enhanced PCM (NePCM). Depending on the morphology of the added nanoparticle, the final NePCM will have different subcooling and thermal conductivity, whereas its phase change enthalpy is not affected and, therefore, is the same for all produced NePCM