A note on the Moody diagram

In this work we propose an alternate scaling for the head loss in the steady flow of Newtonian fluids through tubes. The characteristics of the proposed scaling render more clear the role of inertia in this flow and ensure that the trends of the relationship between dimensionless quantities are the same ones observed in the dimensional problem.Comment: 5 pages, 2 figure

Irreversible time-dependent rheological behavior of cement slurries : constitutive model and experiments

Over the last few decades, much focus has been given to investigating the reversible rheological behavior of thixotropic materials, but the description of the rheology of materials undergoing an irreversible process is still challenging. In this work, the time-dependent rheological behavior of a cement slurry is investigated. Different rheometric experiments are performed to evaluate the structure breakdown under shear, cement gelation, and curing process. A recently proposed thixotropic elasto-viscoplastic model [de Souza Mendes, Soft Matter 7, 2471-2483 (2011)] is modified to account for irreversible effects, which can be either of a chemical or physical nature, making the current model capable of describing reversible and irreversible processes with a single structure parameter. The parameters of the model are estimated from constant shear rate tests and from the flow curve of the fresh cement slurry. The model predictions are compared to step-down and step-up in stress experiments, and the results show that the model successfully describes experimental data obtained. Interesting phenomena are observed and discussed, including (i) thixotropic behavior during the dormant period, (ii) shear banding, (iii) irreversible changes in cement slurry rheology after the hydration reactions accelerate, and (iv) the existence of a characteristic time for the transition from a thixotropic-yield-stress material to a solid during curing. The predictive capability of the new model includes bifurcation, shear banding, stress overshoots, effects of chemical reactions, and irreversible shear degradation. It is argued that the ideas employed in the present work can be used to incorporate irreversible effects into other thixotropic models, giving rise to the possibility of describing the transient rheological behavior of complex materials in an unprecedented fashion. (c) 2019 The Society of Rheology

Using portable monitoring for heterogeneous clusters on Windows and Linux operating systems

This paper describes the advances obtained with the XPVM-W95 2.0, a novel monitoring tool for parallel applications that employ PVM-W95 (PVM for Windows) as well as PVM for Linux. The tool provides, at runtime, the appropriate information about parallel virtual machine configuration, parallel applications and workload from each node. The three more important aspects of the XPVM-W95 are: friendly graphical interface, portability and ability to deal with heterogeneity. These items were improved by version 2, mainly when considering the modularity rearrangement. Experiments demonstrate that XPVM-W95 has a stable behavior and reached the objectives proposed. XPVM-W95 allows a great portability of its source code and also allows the monitoring using different metrics. Empirical studies, realized by means of one single application, demonstrated an intrusion of 17,0% on Windows and 0,13% on Linux.Facultad de Informátic

A new and concise strategy to the enantioselective synthesis of (S)-2-amino-4-oxo-4-(pyridine-2-yl) butanoic acid from aspartic acid

The a-amino acid (S)-5 was synthesized using in the key step a chemoselective nucleophilic substitution between a diester derived from L-aspartic acid and 2-lithium pyridine. The overall yield (13%, 5 steps) was similar to those previously described by our group for the R isomer (the first exogen full agonist of the NMDA receptors) from D-mannitol (12%, 10 steps) and by Lovey and Copper for the racemic synthesis (17%, 5 steps)

Variação da composição e estrutura da assembleia de diatomáceas do Páramo de Frontino (Cordilheira Ocidental dos Andes, Colômbia) durante o Holoceno

This paper presents the analysis of temporal variation in composition and structure of Holocene diatom assemblages from the Llano Grande Basin, Frontino Páramo, located at 3,460 msnm in the northern portion of the Occidental Andes Cordillera Occidental, Colombia. The interval analyzed is constituted of 8.5 m of a core drilled in the central portion of the basin, corresponding to the Holocene. 57 levels were randomly sampled and permanent slides were prepared, from which the taxonomic composition of the assemblages and respective densities were performed. A high variability in the density, composition and structure of the diatoms assemblages was established. 292 species were recognized, including 149 with open taxonomic nomenclature, recognized at genus level. These last taxa should correspond to intraspecific variations of known species or new ones, demonstrating the biological richness of these environments, subject to particular stress conditions at high altitude. Along the core, 169 taxa disappeared, representing a loss of 40.9 % in taxonomic composition. These disappearances are attributed to environmental changes related to temperature, foreign input of volcanic ashes, demineralization and decrease in depth of the water column. In the interval correspondent to the early Holocene, strong environmental disturbances, as well as physical and chemical variations were recorded, with effect on the diatoms assemblage, causing drastic density reduction and change in the compositions towards the levels corresponding to the middle and late Holocene. Changes in the middle Holocene are interpreted as fluctuations in the volume and demineralization of the water body and the external addition of volcanic ashes. In the late Holocene, changes are related to the progressive decrease of the water level in the ecosystem and colonization by macrophytes.Neste trabalho é apresentada a variação temporal da composição e estrutura da assembleia de diatomáceas da Bacia Llano Grande, Páramo de Frontino, localizado a 3.460 m de altitude ao nordeste da Cordilheira Ocidental dos Andes, Colômbia. O material estudado é referente a um testemunho de 8,5 m perfurado na por- ção central da bacia, do qual 57 níveis holocênicos foram aleatoriamente amostrados para o estabelecimento da composição taxonômica da assembleia e sua densidade. Um total de 292 táxons foi reconhecido, incluindo 149 com nomenclatura taxonômica aberta, em nível de gênero. Estes últimos táxons podem correspondem a variações intraespecíficas de formas conhecidas ou novas espécies, demonstrando a riqueza biológica destes ambientes, sujeitos a condições particulares de estresse. Uma alta variabilidade na densidade, na composição e estrutura da assembleia de diatomáceas foi verificada ao longo do perfil sedimentar, com desaparecimento de 169 táxons, representando uma perda de 40,9 % da composição taxonômica. Os desaparecimentos são atribuídos a mudanças de temperatura, aportes externos de cinzas vulcânicas, desmineralização e diminuição da profundidade do corpo d’água. No trecho correspondente ao Holoceno inicial, as oscilações na composição, densidade e na estrutura da assembleia de diatomáceas são atribuídas a perturbações físicas e químicas da coluna d’água, que motivaram a diminuição da densidade e a substituição da maioria das espécies do intervalo por outras nos níveis correspondentes ao Holoceno médio e final. No Holoceno médio as variações são devidas às oscilações do volume e desmineralização do corpo d’água e ao aporte externo de cinzas dos vulcões. No final do Holoceno, as variações taxonômicas estão relacionadas à progressiva diminuição do nível d’água do ecossistema e colonização por macrófitas

Palinologia (esporos de fungos e pteridófitas, grãos de pólen de gimnopermas, cistos de algas e escolecodonte) das formações Solimões e Içá (Neogeno e Pleistoceno, Bacia do Solimões), Amazonas, Brasil

The palynological knowledge from Cenozoic units of the Solimões Basin has been substantially improved in last decades, based on subsurface and outcropping sampling. This work presents the taxonomic results from the study of 93 samples from 12 outcrops of Solimões and Içá formations, in the region of Coari (5 outcrops), and Alto Solimões (7 outcrops), state of Amazonas, Brazil, which revealed diversified, abundant and well preserved palynological assemblages. Here 53 species of palynomorphs recorded, comprising 11 fungi spores species, 31 fern spores, two pollen grains of gymnosperms, eight algae (seven chlorophyceae, one dinophyceae) and one scolecodont are listed and illustrated, as well as described when needed. The composition of both palynofloras is distinct: the Alto Solimões associations include Crassoretitriletes vanraadshooveni, Foveotriletes ornatus, Magnastriatites grandiosus and Multimarginites vanderhammenii, as well a dinoflagellate cyst. In the region of Coari it was recorded predominance of sporomorphs, with great diversity and abundance of fungi and ferns spores.O conhecimento palinológico dos depósitos das formações cenozoicas da Bacia do Solimões tem sido substancialmente aprimorado nas últimas décadas, a partir de materiais de subsuperfície, bem como de afloramentos. Este trabalho apresenta parte dos resultados taxonômicos do estudo de 93 amostras oriundas de 12 afloramentos das formações Solimões e Içá, na região de Coari (cinco afloramentos), e Alto Solimões (sete afloramentos), estado do Amazonas, Brasil, que revelaram conjuntos palinológicos abundantes, diversificados e bem preservados. Aqui são listadas e ilustradas 53 espécies de palinomorfos, compreendendo 11 espécies de esporos de fungos, 31 de esporos de pteridófitas e dois de grãos de pólen de gimnospermas, oito de algas (sete clorofíceas e uma dinofícea), e um de escolecodonte, com descrições quando necessário. A composição palinológica é distinta para as duas áreas analisadas, tendo na região do Alto Solimões documentação de formas como Crassoretitriletes vanraadshooveni, Foveotriletes ornatos, Magnastriatites grandiosus e a ocorrência de um cisto de dinoflagelado. Na região de Coari foi verificado predomínio de esporomorfos, com grande diversidade e abundância de esporos de fungo e pteridófitas

Rhythmic expression of the cycle gene in a hematophagous insect vector

BACKGROUND: A large number of organisms have internal circadian clocks that enable them to adapt to the cyclic changes of the external environment. In the model organism Drosophila melanogaster, feedback loops of transcription and translation are believed to be crucial for the maintenance of the central pacemaker. In this mechanism the cycle (or bmal1) gene, which is constitutively expressed, plays a critical role activating the expression of genes that will later inhibit their own activity, thereby closing the loop. Unlike Drosophila, the molecular clock of insect vectors is poorly understood, despite the importance of circadian behavior in the dynamic of disease transmission. RESULTS: Here we describe the sequence, genomic organization and circadian expression of cycle in the crepuscular/nocturnal hematophagous sandfly Lutzomyia longipalpis, the main vector of visceral leishmaniasis in the Americas. Deduced amino acid sequence revealed that sandfly cycle has a C-terminal transactivation domain highly conserved among eukaryotes but absent in D. melanogaster. Moreover, an alternative form of the transcript was also identified. Interestingly, while cycle expression in Drosophila and other Diptera is constitutive, in sandflies it is rhythmic in males and female heads but constitutive in the female body. Blood-feeding, which causes down-regulation of period and timeless in this species, does not affect cycle expression. CONCLUSION: Sequence and expression analysis of cycle in L. longipalpis show interesting differences compared to Drosophila suggesting that hematophagous vector species might present interesting new models to study the molecular control of insect circadian clocks

Monitoramento da população do besouro Rhynchophorus palmarum em dendezais no município de Igarapé-Açu, Pará.

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