Three dimensional model of a high temperature PEMFC using PBI doped phosphoric acid membranes. Study of the flow field effect on performance

A three-dimensional isothermal model of a high temperature polymer membrane fuel cell equipped with polybenzimidazole (PBI) membrane is described. All major transport phenomena were taken into account except the species cross-over thought the membrane. The cathode catalyst layer was treated as spherical catalyst agglomerates with porous inter-agglomerate spaces. The inter-agglomerate spaces were filled with a mixture of electrolyte (hot phosphoric acid) and polytetrafluoroethylene (PTFE). This approach proved to be an essential requirement for accurate simulation. In this particular paper the influence of different flow field designs and dimensions on performance was intensely study. Traditional configurations were tested (straight, serpentine, pin-in and interdigitated), and a new designs were proposed. With these new designs we tried to maximize performance by providing homogeneous reactants distribution over the active area keeping low pressure drop and relatively high velocity. The dimension and position of the inlet and outlet manifolds were also analysed. From the obtained results was observed a massive influence of the manifolds position and dimension on performance. This fact leaded to an optimization of the manifolds which can give important guidelines for future bipolar plates production

X-ray spectral modelling of the AGN obscuring region in the CDFS: Bayesian model selection and catalogue

AGN are known to have complex X-ray spectra that depend on both the properties of the accreting SMBH (e.g. mass, accretion rate) and the distribution of obscuring material in its vicinity ("torus"). Often however, simple and even unphysical models are adopted to represent the X-ray spectra of AGN. In the case of blank field surveys in particular, this should have an impact on e.g. the determination of the AGN luminosity function, the inferred accretion history of the Universe and also on our understanding of the relation between AGN and their host galaxies. We develop a Bayesian framework for model comparison and parameter estimation of X-ray spectra. We take into account uncertainties associated with X-ray data and photometric redshifts. We also demonstrate how Bayesian model comparison can be used to select among ten different physically motivated X-ray spectral models the one that provides a better representation of the observations. Despite the use of low-count spectra, our methodology is able to draw strong inferences on the geometry of the torus. For a sample of 350 AGN in the 4 Ms Chandra Deep Field South field, our analysis identifies four components needed to represent the diversity of the observed X-ray spectra: (abridged). Simpler models are ruled out with decisive evidence in favour of a geometrically extended structure with significant Compton scattering. Regarding the geometry of the obscurer, there is strong evidence against both a completely closed or entirely open toroidal geometry, in favour of an intermediate case. The additional Compton reflection required by data over that predicted by toroidal geometry models, may be a sign of a density gradient in the torus or reflection off the accretion disk. Finally, we release a catalogue with estimated parameters such as the accretion luminosity in the 2-10 keV band and the column density, $N_{H}$, of the obscurer.Comment: 28 pages, 18 figures, catalogue available from https://www.mpe.mpg.de/~jbuchner/agn_torus/analysis/cdfs4Ms_cat/, software available from https://github.com/JohannesBuchner/BX

Enhancing photocatalytic properties of rutile TiO2 by codoping with N and metals e Ab initio study

Substitutional N to O and M to Ti (M = Pt, V, Sb) codoped rutile TiO2 was investigated using density functional theory (DFT) based calculations with both standard and hybrid exchange-correlation functionals. The band gaps calculated using generalized gradient approximation (GGA) exhibited narrowing compared to the pure rutile TiO2 in all the investigated cases. In contrast, the results obtained with hybrid exchange-correlation functional showed that there was no band gap narrowing, but doping induced localized states within the band gap just above the valence band, as well as below the conduction band for Pt doped TiO2. The presence of broad intermediate states (IS) in the band gap could enhance visible light absorption through a two step optical transition from the valence to the conduction band via the IS and at the same time lower recombination of the photogenerated charges

Photon pair-state preparation with tailored spectral properties by spontaneous four-wave mixing in photonic-crystal fiber

We study theoretically the generation of photon pairs by spontaneous four-wave mixing (SFWM) in photonic crystal optical fiber. We show that it is possible to engineer two-photon states with specific spectral correlation (``entanglement'') properties suitable for quantum information processing applications. We focus on the case exhibiting no spectral correlations in the two-photon component of the state, which we call factorability, and which allows heralding of single-photon pure-state wave packets without the need for spectral post filtering. We show that spontaneous four wave mixing exhibits a remarkable flexibility, permitting a wider class of two-photon states, including ultra-broadband, highly-anticorrelated states.Comment: 17 pages, 7 figures, submitte

Regeneração de espécies silvestres brasileiras de arroz através do cultivo de embrião.

O objetivo deste trabalho foi regenerar os acessos das espécies silvestres de arroz brasileiras através do cultivo de embriões

Production management model through MPS and line balancing to reduce the non-fulfillment of orders in lingerie clothing MSEs in Peru

The focus of this research is to establish control and planning management in the sewing production process of lingerie clothing to better prepare companies for demand growth. The lack of improvement tools in this sector, the lack of staff training and a lack of quality culture has led to companies, especially MYPES, not being able to meet the established delivery times and non-fulfillment of orders with the customers, which represents 80% of dissatisfied orders due to the limited production capacity and non-productive time in the plant. This problem is due to limited production capacity, deficient production planning, and lack of materials. In order to solve this problem, industrial engineering tools were used. The application of these tools improved production from 79% to 95%

Trace fossils from the Upper Cretaceous Capacete Formation, Sanfranciscana Basin, Central Brazil

The Upper Cretaceous Capacete Formation, from the intracratonic Sanfranciscana Basin, central Brazil, consists of epiclastic sediments with a significant aeolian contribution. This unit has been traditionally interpreted as deposited by alluvial fans distally grading to braided rivers in an arid- to semiarid climate within the central part of southwestern Gondwana. Locally, some expositions with wide lateral extension show architectural ele-ments indicative of deposition in meandering rivers, such as floodplain fines (FF) interbedded with crevasse splay (CR), lateral-accretion macroforms (LA), and channels (CH). Bioturbation within the meandering fluvial deposits is commonly associated with the floodplain element, mainly occurring in fine-grained sandstone and mudstone. The lateral-accretion elements and channel deposits are barren of trace fossils. Sandstone with climbing ripples (Sr) from the element CR show low bioturbation of meniscate trace fossils assigned to Taenidium, Beaconites, and Scoyenia ichnogenera. Simple vertical and horizontal burrows identified as Skolithos and Palaeophycus occur associated with Taenidium and Camborygma in sandstone facies (Sr, St and Sh), as well as rhizoliths, representing the Scoyenia ichnofacies. The predominance of trace fossils related to the FF and CR architectural elements attests to the colonization mostly by insects in episodic and vegetated flood plains of the meandering river system from the Capacete Formation. Thus, despite the primarily arid to semiarid conditions interpreted for the inner parts of the newly formed South American continent during the Upper Cretaceous, our new data support deposition under humid conditions in some intervals of the Capacete Formation from the Sanfranciscana Basin

Genetic variability analysis of elite upland rice genotypes with SSR markers.

Rice is one of the staple foods consumed worldwide, and rice breeding programmes have become important to warrant high yield levels and grain quality in upland rice. Laboratory experiments were conducted to study the genetic variation of 30 elite genotypes from a VCU trial, of the upland rice breeding programme of Embrapa, Brazil, using 25 SSR markers. A total of 131 alleles were obtained, with an average of 5.2 alleles per locus and a mean PIC equal to 0.61. Results indicated that genetically different elite parents from the breeding programme and selection in segregating families have given rise to broad-based rice genotypes. Based on the analysis of different combinations of 10 SSR markers, it was observed that the use of more informative markers is essential to explain the genetic divergence consistently with the pedigree of each rice genotype.

Demographic shifts, inter-group contact, and environmental conditions drive language extinction and diversification

Humans currently collectively use thousands of languages1,2. The number of languages in a given region (i.e. language “richness”) varies widely3–7. Understanding the processes of diversification and homogenization that produce these patterns has been a fundamental aim of linguistics and anthropology. Empirical research to date has identified various social, environmental, geographic, and demographic factors associated with language richness3. However, our understanding of causal mechanisms and variation in their effects over space has been limited by prior analyses focusing on correlation and assuming stationarity3,8. Here we use process-based, spatially-explicit stochastic models to simulate the emergence, expansion, contraction, fragmentation, and extinction of language ranges. We varied combinations of parameter settings in these computer-simulated experiments to evaluate the extent to which different processes reproduce observed patterns of pre-colonial language richness in North America. We find that the majority of spatial variation in language richness can be explained by models in which environmental and social constraints determine population density, random shocks alter population sizes more frequently at higher population densities, and population shocks are more frequently negative than positive. Language diversification occurs when populations split after reaching size limits, and when ranges fragment due to population contractions following negative shocks or due to contact with other groups that are expanding following positive shocks. These findings support diverse theoretical perspectives arguing that language richness is shaped by environmental and social conditions, constraints on group sizes, outcomes of contact among groups, and shifting demographics driven by positive innovations, such as new subsistence strategies, or negative events, such as war or disease

Utricular hypofunction in patients with type 2 diabetes mellitus

Lobiettivo di questo studio è stato quello di valutare la funzione utricolare e la funzione dei canali semicircolari laterali in pazienti con diabete mellito di tipo 2, con o senza cadute, afferenti allassistenza sanitaria di base. Sono stati arruolati 101 pazienti con diabete mellito di tipo 2 (26 con storia di cadute, 75 senza), di età compresa tra 34 e 84 anni, e 51 volontari sani di età compresa tra 40 e 83 anni, i quali hanno negato vertigini, capogiri, instabilità, ipoacusia o disordini neurologici. Nessuno di loro era in cerca di cure per deficit sensoriali o dellequilibrio. Dopo aver effettuato una valutazione clinica e dopo aver indagato i sintomi relativi alla sfera dellequilibrio con lausilio di un questionario standardizzato, la funzione dei canali semicircolari laterali è stata studiata con il test sinusoidale alle velocità di 0,16 Hz e 1,28 Hz (il picco della velocità è stato fissato a 60°/s); la funzione otolitica, invece, è stata studiata con la verticale visiva soggettiva, determinata sia tramite test statico sia tramite test dinamico, durante centrifugazione unilaterale (300°/s a 3.5 cm); è stata eseguita inoltre la posturografia statica, su pedana soffice e dura, ad occhi aperti e chiusi. Confrontando i risultati ottenuti nei pazienti diabetici e in quelli sani, i pazienti diabetici hanno mostrato risposte inferiori alla centrifugazione unilaterale, ma risposte simili alla stimolazione dei canali semicircolari laterali, indipendentemente da età, neuropatie periferiche o storia di cadute (ANCoVA p < 0.05). I pazienti con storia di cadute, rispetto a quelli senza storia di cadute, erano per lo più donne e hanno raggiunto più facilmente un punteggio maggiore o pari a 4 al questionario sui sintomi relativi al senso dellequilibrio; tuttavia i due gruppi hanno mostrato simili età, indice di massa corporea e neuropatia periferica. Nei pazienti con diabete di tipo 2, afferenti allassistenza sanitaria di base e non in cerca di cure per deficit sensoriali o dellequilibrio, la funzione utricolare potrebbe essere alterata, anche in assenza di disfunzione dei canali semicircolari laterali o di storia di cadute