Evolution of the phase-space density and the Jeans scale for dark matter derived from the Vlasov-Einstein equation

We discuss solutions of Vlasov-Einstein equation for collisionless dark matter particles in the context of a flat Friedmann universe. We show that, after decoupling from the primordial plasma, the dark matter phase-space density indicator Q remains constant during the expansion of the universe, prior to structure formation. This well known result is valid for non-relativistic particles and is not "observer dependent" as in solutions derived from the Vlasov-Poisson system. In the linear regime, the inclusion of velocity dispersion effects permits to define a physical Jeans length for collisionless matter as function of the primordial phase-space density indicator: \lambda_J = (5\pi/G)^(1/2)Q^(-1/3)\rho_dm^(-1/6). The comoving Jeans wavenumber at matter-radiation equality is smaller by a factor of 2-3 than the comoving wavenumber due to free-streaming, contributing to the cut-off of the density fluctuation power spectrum at the lowest scales. We discuss the physical differences between these two scales. For dark matter particles of mass equal to 200 GeV, the derived Jeans mass is 4.3 x 10^(-6) solar masses.Comment: 18 pages, 2 figures. Accepted for publication in JCA

Recycling of Water Treatment Plant Waste for Production of Soil-Cement Bricks

AbstractThe water treatment plants generate large amounts of municipal sludge that must be discarded. A crucial issue is to find an ecological destination for its final disposal. This work studies the possibility of incorporating water treatment plant waste into soil-cement bricks for civil construction. A sample of this waste material was analyzed for chemical composition, X-ray diffraction, particle size, plasticity, and organic matter. Mixtures of soil-cement containing up to 5wt.% of waste as a partial substitute of soil were pressed and cured for 28 days. The effects of the incorporation of the water treatment plant waste were determined by evaluating different physical properties such as compressive strength, apparent density, and water absorption. The results indicated that the water treatment plant waste is a plastic material composed mainly of kaolinite particles. The results also showed that the water treatment plant waste could be used for production of soil-cement bricks, helping to reduce the environmental impacts of the water treatment plants

Avaliação multicritério e SIG vectorial: uma alternativa para planeamento de transportes

Este trabalho tem por objectivo apresentar um modelo concebido para permitir a integração de métodos de avaliação multicritério em ambiente SIG vectorial. A avaliação da acessibilidade, aqui modelada, para além de ser um problema típico, complexo e quase permanente no planeamento de transportes, adequa-se bem ao modelo concebido pelo fato de conter alguns dos principais elementos que caracterizam os problemas de transportes (caso da análise de fluxos em rede). O modelo proposto, além de basear-se na medição de afastamento incluindo o efeito da distância, permite também o desenvolvimento de cenários de avaliação baseados na atitude de risco e compensação entre critérios, obtendo-se desta forma um espectro estratégico de avaliação. Por fim, um exemplo de aplicação que consiste na avaliação interna de um campus universitário em Portugal, aponta o potencial do modelo proposto para a avaliação da acessibilidade, abrindo perspectivas para sua aplicação em outros problemas de transportes.The aim of this work is to present a model built to allow the integration of multicriteria evaluation methods into a vector GIS environment. The accessibility assessment, which was explored here, in addition to be a typical, complex and almost permanent problem of transport planning, fits well to the conceived model because it contains some of the main elements that characterize transport models (such as flow network analysis). The proposed modeling approach, which is more than merely a measure of separation incorporating the effect of distance, allows the development of evaluation scenarios based on different trade-off and risk attitudes, i.e., a decision strategy spectrum. Finally, an application example, which consists in the internal evaluation of a university campus in Portugal, reveals the potential of the proposed model for evaluating accessibility, therefore opening perspectives to its application to other transport problems

Biomimetic polysaccharide/bioactive glass nanoparticles multilayer membranes for guided tissue regeneration

Nowadays, guided tissue regeneration (GTR) research is centred in the development of composite bioabsorbable membranes with enhanced bioactivity and with processing controlled at the nanoscale. Inspired by this new focus of GTR research and also by nacre structure, layered freestanding membranes were produced using the Layer-by-Layer (LbL) deposition technique, combining chitosan (CHI), hyaluronic acid (HA) and bioactive glass nanoparticles (BGNPs). It is expected that the combination of these materials processed by this particular technique will result in nanostructured membranes with enhanced mechanical performance as well as improved bioactivity. Moreover, the effect of the modification of HA with catechol groups (HAD) on the adhesive properties of the membranes was also analysed. The results showed that it was possible to produce biomimetic membranes with different surface properties, improved adhesive strength and the ability to induce the formation of apatite, necessary for the formation of new bone. It was also possible to control the BGNPs content of the membranes by use of HAD instead of unmodified HA and changing the number of BGNPs' deposition steps. Moreover, it was shown that membranes with different concentrations of BGNPs possess different mechanical performance, swelling properties and degradation behaviour, which indicates the possibility to tune the membranes' properties by controlling the deposition of BGNPs onto the membranes

Bat-species richness in the Pantanal floodplain and its surrounding uplands

Estudamos a fauna de morcegos na planície do Pantanal e nos planaltos de entorno no Mato Grosso do Sul, Brasil, com base na coleção científica da Universidade Anhanguera – Uniderp e no banco de dados do Projeto Morcegos do Pantanal, UFMS, incluindo 9.037 capturas de 56 espécies, entre 1994 e 2007. Amostragens no Pantanal foram feitas nas sub-regiões da Nhecolândia, Aquidauana, Miranda e Paraguai; no planalto as amostragens foram realizadas nas formações de Maracaju, Bodoquena e Urucum. Espécies de morcegos foram registradas ao longo de 376 noites em 35 sítios, predominantemente com o uso de redes de neblina próximas a árvores frutíferas, abrigos e florestas. Na planície, foram registradas 46 espécies (n = 6.292 indivíduos) e no planalto 44 espécies (n = 2.745 indivíduos). Seis famílias foram encontradas: Phyllostomidae (30 espécies), Molossidae (12 espécies), Verpertilionidae (nove espécies), Noctilionidae (duas espécies), Emballorunidae (duas espécies) e Mormoopidae (uma espécie). A fauna de morcegos foi predominantemente composta de espécies insetívoras (32) e frugívoras (15). O frugívoro Artibeus planirostris (n = 3.101) foi a espécie mais comum na planície e no planalto. Outras espécies comuns foram Myotis nigricans (n = 762), Molossus molossus (n = 692), Noctilio albiventris (n = 681), Platyrrhinus lineatus (n = 633), Sturnira lilium (n = 461), Carollia perspicillata (n = 451), Glossophaga soricina (n = 436), Artibeus lituratus (n = 320) e Desmodus rotundus (n = 281). Na planície, ocorreram três espécies de morcegos insetívoros dentre as espécies mais comuns, contrastando com o planalto, onde houve dominância de frugívoros. A diversidade para os 35 sítios reunidos (H’ = 2,5) é comparável à encontrada em florestas tropicais. A fauna de morcegos apresentada aqui representa 34% das espécies brasileiras, e 62% das espécies já reportadas para a Bacia do Alto Paraguai. Adicionalmente, cinco espécies são reportadas pela primeira vez no Mato Grosso do Sul. ________________________________________________________________________________________ ABSTRACTWe studied the bat fauna of the Pantanal floodplain and its surrounding plateaus in Mato Grosso do Sul, Brazil, based on the scientific collection at Universidade Anhanguera – Uniderp and on the Projeto Morcegos do Pantanal data bank at UFMS, comprising 9,037 captures of 56 species recorded from 1994 to 2007. The Pantanal surveys were carried out in the Nhecolândia, Aquidauana, Miranda, and Paraguai sub-regions; the uplands surveys took place in the Maracaju, Bodoquena, and Urucum formations. Bat specimens were mist-netted over 376 nights in 35 sites, predominantly near fruiting trees, bat shelters, and forest patches. In the floodplain 46 species were recorded (n = 6,292 individuals), and 44 species were found in the uplands (n = 2,745 individuals). Six families were recorded: Phyllostomidae (30 species), Molossidae (12 species), Verpertilionidae (nine species) Noctilionidae (two species), Emballorunidae (two species) and Mormoopidae (one species). The bat fauna was predominantly composed of insectivore (32) and frugivore (15) species. The frugivorous Artibeus planirostris (n = 3,101 individuals) was the commonest species in floodplain and uplands. Other common species were Myotis nigricans (n = 762), Molossus molossus (n = 692), Noctilio albiventris (n = 681), Platyrrhinus lineatus (n = 633), Sturnira lilium (n = 461), Carollia perspicillata (n = 451), Glossophaga soricina (n = 436), Artibeus lituratus (n = 320), and Desmodus rotundus (n = 281). In the floodplain there were three insectivores among the most common species, contrasting with the uplands dominated by the frugivores. The diversity for the 35 sites assembled (H’ = 2.5) is comparable to that recorded for tropical forests. The bat fauna presented here represents 34% of the Brazilian bat species, and 62% of species reported for the Upper Paraguay River Basin. Additionally, five species are reported for the first time in Mato Grosso do Sul

Mobility helps problem-solving systems to avoid Groupthink

Groupthink occurs when everyone in a group starts thinking alike, as when people put unlimited faith in a leader. Avoiding this phenomenon is a ubiquitous challenge to problem-solving enterprises and typical countermeasures involve the mobility of group members. Here we use an agent-based model of imitative learning to study the influence of the mobility of the agents on the time they require to find the global maxima of NK-fitness landscapes. The agents cooperate by exchanging information on their fitness and use this information to copy the fittest agent in their influence neighborhoods, which are determined by face-to-face interaction networks. The influence neighborhoods are variable since the agents perform random walks in a two-dimensional space. We find that mobility is slightly harmful for solving easy problems, i.e. problems that do not exhibit suboptimal solutions or local maxima. For difficult problems, however, mobility can prevent the imitative search being trapped in suboptimal solutions and guarantees a better performance than the independent search for any system size

Porous functionally graded plates: na assessment of the influence of shear correction factor on static behavior

The known multifunctional characteristic of porous graded materials makes them very attractive in a number of diversified application fields, which simultaneously poses the need to deepen research efforts in this broad field. The study of functionally graded porous materials is a research topic of interest, particularly concerning the modeling of porosity distributions and th ecorresponding estimations of their material properties—in both real situations and from a material modeling perspective. This work aims to assess the influence of different porosity distribution approaches on the shear correction factor, used in the context of the first-order shear deformation theory, which in turn may introduce significant effects in a structure’s behavior. To this purpose, we evaluated porous functionally graded plates with varying composition through their thickness. The bending behavior of these plates was studied using the finite element method with two quadrilateral plate element models. Verification studies were performed to assess the representativeness of the developed and implemented models, namely, considering an alternative higher-order model also employed for this specific purpose. Comparative analyses were developed to assess how porosity distributions influence the shear correction factor, and ultimately the static behavior, of the plates.info:eu-repo/semantics/publishedVersio