Simulation of microalgal growth in a continuous photobioreactor with sedimentation and partial biomass recycling

Microalgae are considered as promising feedstocks for the third generation of biofuels. They are autotrophic organisms with high growth rate and can stock an enormous quantity of lipids (about 20 \u2013 40% of their dried cellular weight). This work was aimed at studying the cultivation of Scenedesmus obliquus in a two-stage system composed of a photobioreactor and a settler to concentrate and partially recycle the biomass as a way to enhance the microalgae cellular productivity. It was attempted to specify by simulation and experimental data a relationship between the recycling rate, kinetic parameters of microalgal growth and photobioreactor operating conditions. Scenedesmus obliquus cells were cultivated in a lab-scale flat-plate reactor, homogenized by aeration, and running in continuous flow with a residence time of 1.66 day. Experimental data for the microalgal growth were used in a semi-empirical simulation model. The best results were obtained for Fw = 0.2FI , when R = 1 and kd = 0 and 0.05 day-1, with the biomass production in the reactor varying between 8 g L -1 and 14 g L-1, respectively. The mathematical model fitted to the microalgal growth experimental data was appropriate for predicting the efficiency of the reactor in producing Scenedesmus obliquus cells, establishing a relation between cellular productivity and the minimum recycling rate that must be used in the system

Multi-phase semicrystalline microstructures drive exciton dissociation in neat plastic semiconductors

The optoelectronic properties of macromolecular semiconductors depend fundamentally on their solid-state microstructure. For example, the molecular-weight distribution influences polymeric- semiconductor properties via diverse microstructures; polymers of low weight-average molecular weight (Mw) form unconnected, extended-chain crystals, usually of a paraffinic structure. Because of the non-entangled nature of the relatively short-chain macromolecules, this leads to a polycrystalline, one-phase morphology. In contrast, with high-Mw materials, where average chain lengths are longer than the length between entanglements, two-phase morphologies, comprised of crystalline moieties embedded in largely unordered (amorphous) regions, are obtained. We investigate charge photogeneration processes in neat regioregular poly(3-hexylthiophene) (P3HT) of varying Mw by means of time-resolved photoluminescence (PL) spectroscopy. At 10 K, PL originating from recombination of long-lived charge pairs decays over microsecond timescales. Both the amplitude and decay rate distribution depend strongly on Mw. In films with dominant one-phase chain-extended microstructures, the delayed PL is suppressed as a result of a diminished yield of photoinduced charges, and its decay is significantly faster than in two-phase microstructures. However, independent of Mw, charge recombination regenerates singlet excitons in torsionally disordered chains forming more strongly coupled photophysical aggregates than those in the steady-state ensemble, with delayed PL lineshape reminiscent of that in paraffinic morphologies at steady state. We conclude that highly delocalized excitons in disordered regions between crystalline and amorphous phases dissociate extrinsically with yield and spatial distribution that depend intimately upon microstructure.Comment: 19 pages, 4 figure

Dimensional hyper-reduction of nonlinear finite element models via empirical cubature

We present a general framework for the dimensional reduction, in terms of number of degrees of freedom as well as number of integration points (“hyper-reduction”), of nonlinear parameterized finite element (FE) models. The reduction process is divided into two sequential stages. The first stage consists in a common Galerkin projection onto a reduced-order space, as well as in the condensation of boundary conditions and external forces. For the second stage (reduction in number of integration points), we present a novel cubature scheme that efficiently determines optimal points and associated positive weights so that the error in integrating reduced internal forces is minimized. The distinguishing features of the proposed method are: (1) The minimization problem is posed in terms of orthogonal basis vector (obtained via a partitioned Singular Value Decomposition) rather that in terms of snapshots of the integrand. (2) The volume of the domain is exactly integrated. (3) The selection algorithm need not solve in all iterations a nonnegative least-squares problem to force the positiveness of the weights. Furthermore, we show that the proposed method converges to the absolute minimum (zero integration error) when the number of selected points is equal to the number of internal force modes included in the objective function. We illustrate this model reduction methodology by two nonlinear, structural examples (quasi-static bending and resonant vibration of elastoplastic composite plates). In both examples, the number of integration points is reduced three order of magnitudes (with respect to FE analyses) without significantly sacrificing accuracy.Peer ReviewedPostprint (published version

Brincadeira: marcos temporais e memória

A brincadeira, expressão maior das culturas lúdicas da infância e do saber popular infantil que colora o folclore das crianças e que entre elas constitui prática singular, tem marcos temporais indeléveis que lhe (de)marcaram um tempo e que a memória guardou para sempre. A linearidade que, durante quase todo o tempo antes da chegada da TV, a brincadeira transportou, a revolução das suas práticas que a partir daí se operou e acentuou com a chegada das novas tecnologias da comunicação e informação à vida das crianças e a consequente transformação radical do seu habitus lúdico (da rua para casa e daqui para o quarto) balizam eras distintas de tempos sociais paralelas às que ditaram, consequentemente, a transformação que as artes de e para brincar foram, historicamente, sofrendo. Ao resgatar a brincadeira pela voz das crianças, muitas das vezes expressa pela voz dos adultos que hoje são, faz-se o registo, que neste artigo se guarda, de um pedaço da herança cultural lúdica que foi passando entre as quatro gerações que estudamos qualitativamente a partir de entrevistas grupais feitas em contexto familiar, que serviram de base para o que a seguir fica relatado. A brincadeira e a parafernália que a acompanha fazem parte da história de vida de todos nós e, por isso, a cada um cabe velar para que nunca pereça.Abstract Playful, highest expression of playful cultures of childhood and popular knowledge of children which color the folklore of children and which among them consist in singular practice, has indelible timeless marks and marked them a time which was kept in memory forever. The linearity which during most of the time before the arrival of TV was carried by playful, the revolution of its practices operated from there and accentuated with the arrival of new information and communication technologies to the life of children and consequent radical transformation of their playful habitus (from street to home and consequently to the room), delineate distinct eras of social times parallel to those which dictated, consequently, the transformation which the arts to and for play were, historically, suffering. Redeem by the voice of children, often expressed by the voice of adults who are today, is made the record, which in this article is kept, from a piece of the cultural playful heritage which was passing between four generations studied qualitatively from group interviews made in the family background. From where we confirm what is reported below. Playful and related paraphernalia are part of the life story of all of us and therefore it is up to each of us to ensure that never perish.Résumé Le jeu, la plus grande expression des cultures ludiques de l‟enfance et du savoir populaire enfantin qui colore le folklore des enfants et constitue, parmi eux, une pratique singulière, laisse des marques temporelles indélébiles qui restent gravées pour toujours, dans la mémoire. La linéarité que le jeu a transporté, pendant la plupart du temps avant l'arrivée de la TÉLÉ, et la révolution de ses pratiques qui, à partir de ce moment s‟est opérée et accentuée avec l'arrivée des nouvelles technologies de l'information et de la communication dans la vie des enfants et, la conséquente transformation radicale de leur habitus ludique (de la rue à la maison, de la maison à la chambre) délimitent des époques distinctes de temps sociaux qui sont parallèles à celles qui, conséquemment, ont dicté la transformation que les arts de et pour jouer ont historiquement subi. Recueilli par la voix des enfants, souvent exprimée par les adultes qu‟ils sont devenus, nous avons noté et gardé dans cet article, un morceau de l‟héritage culturel ludique qui atraversé les quatre génération que nous avons étudiées qualitativement à partir d'entretiens de groupes faits en contexte familial. C‟est à partir de cette étude que nous affirmons ce qui est rapporté ci-dessous. Le jeu et l'attirail qui l‟accompagne font partie de l'histoire de vie de nous tous donc, chacun de nous doit veiller à ce que rien ne soit jamais oublié ni perdu

Ciência, Cultura, Teorias, Práticas, Objetos, Sentidos, Valores

Este artigo reflete, e corporiza ele mesmo, uma intersecção: entre ciência e cultura; entre experiência, experimentação, sentidos, sentido e significado; entre a pluralidade de argumentos sustentadores da expressão motriz e matriz ‘culturas experimentais’. Sustentando a necessidade de se transcender uma abordagem essencialista de ‘cultura’ ede transgredir delimitações dos conceitos ‘experiência’ e ‘experimentação’, os autores recorrem à ideia de ‘paisagem’ para designar a quebra dos dualismos teoria-prática e ação-pensamento. Isto dita o repensar das fronteiras entre linguagens disciplinares, em direção a uma ‘ecologia conceptual’que contribua para perspetivas mais amplas e integradoras dos campos educativo, profissional e científico-artístico-cultural.This article reflects, and embodies itself, an intersection: between science and culture; between experience, experimentation, senses, sense and meaning; between the pluralityof arguments that may support the motive andmatricialexpr ession‘experimental cultures’. Sustaining the need to transcend an essencialistic approach to ‘culture’ and to transgressdelimitationsof the concepts ‘experience’ and ‘experimentation’, theauthors resort to the ideaof ‘landscape’ to name the fracture of the dualisms theory-practice and action-though. This leads to rethinking the borders between disciplinary languages, towards a ‘conceptual ecology’that contributes to wider and integrated perspectives of the educational, professional and scientific-artistic-cultural fields

Beyond the Unrealistic Solution for Development Provided by the Appendix of the Berne Convention on Copyright

The standards of copyright protection promoted by the Berne Convention are highly problematic for developing countries because these countries need to ensure a wide dissemination of works for teaching, scholarship, and research purposes. In order to accommodate these needs and to promote accession to this Convention, the 1971 Paris Act of the Berne Convention, included an Appendix that allowed developing countries to issue compulsory licenses for translating and/or reproducing foreign works into languages of general use in their territories. Unfortunately, the Appendix has not met the needs of developing countries, which, instead, have relied on idiosyncratic solutions. Additionally, the instrument does not provide solutions for other needs, such as those of linguistic and cultural minorities, and it is arguable whether the Appendix applies online. Section one of this paper provides background information on the needs of developing countries and shows how the Appendix of the Berne Convention tried to meet them. Section two analyzes the main limitations of the mechanism of compulsory licensing adopted by the Appendix. Although, the mere fact that the Appendix does not comply with its very purpose should be enough to warrant a new instrument, section three discusses two additional reasons in favor of adopting a new instrument to meet the needs of developing countries. In particular, this section focuses on general welfare and the economic benefits for authors and right holders. Finally, section four outlines the issues that should be included in a new instrument that effectively meets development needs