From droplets to particles: Transformation criteria

International audienceAtomization of liquid fuel has a direct impact on the production of pollutant emission in engineering propulsion devices. Due to the multiple challenges in experimental investigations, motivation for numerical study is increasing on liquid-gas interaction from injection till dispersed spray zone. Our purpose is to increase the accuracy of the treatment of droplets in atomized jet, which are typically 100 times smaller than the characteristic injection length size. As the characteristic length reduces downstream to the jet, it is increasingly challenging to track the interface of the droplets accurately. To solve this multiscale issue, a coupled tracking Eulerian-Lagrangian Method exists [1]. It consists in transforming the small droplets to Lagrangian droplets that are transported with drag models. In addition to the size transformation criteria, one can consider geometric parameters to determine if a droplet has to be transformed. Indeed, the geometric criteria are there for two reasons. The first one is the case where the droplets can break if there are not spherical. The second one is about the drag models that are based on the assumption that the droplet is spherical. In this paper we make a review of the geometric criteria used in the literature. New geometric criteria are also proposed. Those criteria are validated and then discussed in academic cases and a 3D airblast atomizer simulation. Following the analysis of the results the authors advise the use of the deformation combined with surface criteria as the geometric transformation criteria. Introduction Atomization is a phenomenon encountered in many applications such as sprays in cosmetic engineering or aerospace engineering for jet propulsion [2]. In the combustion chamber, the total surface of the interface separating the two phases is a key parameter. Primary and secondary breakup have been extensively investigated in the literature. However, in order to fully describe the complete process, one has to capture droplets in dispersed zone 100 times smaller than jet diameter. Atomization is then a multiphase and a multiscale flow phenomenon which is still far from being understood. Due to this wide range of scale, the Direct Numerical Simulation (DNS) of such process requires robust and efficient codes. DNS is an important tool to analyse the experimental results and go further into the atomization understanding. In the past few years, numerical schemes of Interface Capturing Method (ICM) have been improved but faced numerical limitation. For instance, the treatment of the small droplets is the most challenging part when the entire process is treated in DNS. When dealing with unresolved structures we face different problems such as the dilution or the creation of numerical instabilities. To avoir them, a strategy is to remove small structures during the simulation, see Shinjo et al. [3]. But, those methods do not collect information on smallest droplets in atomization application. Introduction of Adaptive Mesh Refinement (AMR) in DNS is a first answer to this issue, it consists in refining unresolved area under numerical concept and focus on the interface between two phases instead of refining the entire domain. In dense spray, AMR tends to refine the entire zone and becomes as expensive as a full domain refinement. A solution is to transform the smallest droplets into point particles and remove AMR in this area. This strategy is called Eulerian-Lagrangian coupling [1], it assumes that small droplets will no longer break during the simulation and that the Lagrangian models reproduce correctly the droplet transport. These physical assumptions are implemented to answer numerical issue and improve the computational cost. This Eulerian-Lagrangian coupling is based on transformation criteria that defines when an ICM structure has to be transformed into Lagrangian particle and when a Lagrangian particle has to be transformed back into ICM. The main purpose of the present communication is to provide a detailed analysis of the ICM to Lagrangian transformation criteria. The geometri

How the central domain of dystrophin acts to bridge F-actin to sarcolemmal lipids

Dystrophin is a large intracellular protein that prevents sarcolemmal ruptures by providing a mechanical link between the intracellular actin cytoskeleton and the transmembrane dystroglycan complex. Dystrophin deficiency leads to the severe muscle wasting disease Duchenne Muscular Dystrophy and the milder allelic variant, Becker Muscular Dystrophy (DMD and BMD). Previous work has shown that concomitant interaction of the actin binding domain 2 (ABD2) comprising spectrin like repeats 11 to 15 (R11-15) of the central domain of dystrophin, with both actin and membrane lipids, can greatly increase membrane stiffness. Based on a combination of SAXS and SANS measurements, mass spectrometry analysis of cross-linked complexes and interactive low-resolution simulations, we explored in vitro the molecular properties of dystrophin that allow the formation of ABD2-F-actin and ABD2-membrane model complexes. In dystrophin we identified two subdomains interacting with F-actin, one located in R11 and a neighbouring region in R12 and another one in R15, while a single lipid binding domain was identified at the C-terminal end of R12. Relative orientations of the dystrophin central domain with F-actin and a membrane model were obtained from docking simulation under experimental constraints. SAXS-based models were then built for an extended central subdomain from R4 to R19, including ABD2. Overall results are compatible with a potential F-actin/dystrophin/membrane lipids ternary complex. Our description of this selected part of the dystrophin associated complex bridging muscle cell membrane and cytoskeleton opens the way to a better understanding of how cell muscle scaffolding is maintained through this essential protein

Antifungal activity of amphotericin B conjugated to nanosized magnetite in the treatment of paracoccidioidomycosis

This study reports on in vitro and in vivo tests that sought to assess the antifungal activity of a newly developed magnetic carrier system comprising amphotericin B loaded onto the surface of pre-coated (with a double-layer of lauric acid) magnetite nanoparticles. The in vitro tests compared two drugs; i.e., this newly developed form and free amphotericin B. We found that this nanocomplex exhibited antifungal activity without cytotoxicity to human urinary cells and with low cytotoxicity to peritoneal macrophages. We also evaluated the efficacy of the nanocomplex in experimental paracoccidioidomycosis. BALB/c mice were intratracheally infected with Paracoccidioides brasiliensis and treated with the compound for 30 or 60 days beginning the day after infection. The newly developed amphotericin B coupled with magnetic nanoparticles was effective against experimental paracoccidioidomycosis, and it did not induce clinical, biochemical or histopathological alterations. The nanocomplex also did not induce genotoxic effects in bone marrow cells. Therefore, it is reasonable to believe that amphotericin B coupled to magnetic nanoparticles and stabilized with bilayer lauric acid is a promising nanotool for the treatment of the experimental paracoccidioidomycosis because it exhibited antifungal activity that was similar to that of free amphotericin B, did not induce adverse effects in therapeutic doses and allowed for a reduction in the number of applications

from genomic imprinting to development physiology: identifying stepping stones

info:eu-repo/semantics/publishe

From genomic imprinting to developmental physiology: Identifying stepping stones

SCOPUS: re.jinfo:eu-repo/semantics/publishe

AVALIAÇÃO DA PROATIVIDADE INDIVIDUAL NO PROCESSO DE SOCIALIZAÇÃO ORGANIZACIONAL: EVIDÊNCIA EXPLORATÓRIA ACERCA DAS PROPRIEDADES PSICOMÉTRICAS DA VERSÃO PORTUGUESA DA ESCALA DE COMPORTAMENTOS PROATIVOS (ECP-P) DE ASHFORD E BLACK

A proatividade individual desempenha um papel importante na integração dos novos colaboradores na organização, tendo um impacto positivo em múltiplas variáveis relacionadas com o seu respetivo processo de socialização organizacional, tais como a aprendizagem, o comprometimento organizacional e a satisfação e desempenho no trabalho. Este estudo centra-se na análise das características psicométricas da versão portuguesa (ECP-P) da escala de comportamentos proativos de Ashford e Black (1996). Trata-se de um instrumento que inclui a avaliação de três tipologias de comportamento proativo, que englobam seis comportamentos proativos específicos, designadamente o enquadramento positivo (positive framing), a atribuição de sentido (sense making, que integra os comportamentos de procura de informação e de solicitação de feedback), e o estabelecimento de relações (que inclui os comportamentos de socialização geral, de networking e de relacionamento com o supervisor). A validade de constructo e fiabilidade deste instrumento foram avaliadas tendo por base uma amostra de 102 estudantes do ensino superior, durante a realização do seu estágio de 9 meses na respetiva organização. Como esperado, os resultados da análise em componentes principais mostraram que os itens da escala se organizam numa estrutura composta por seis componentes, correspondentes aos comportamentos proativos previamente mencionados. As análises de fiabilidade relevaram valores adequados de consistência interna para a escala global e para as seis sub-dimensões. A consideração integrada destes resultados indica que a versão portuguesa da escala de Ashford e Black (1996) possui adequadas propriedades psicométricas, suportando a sua utilidade na avaliação da proatividade individual durante o processo de socialização organizacional

Epilepsy in Angelman syndrome.

Angelman syndrome is a neurogenetic disorder caused by lack of UBE3A gene expression from the maternally inherited chromosome 15 due to various 15q11-q13 abnormalities. In addition to severe developmental delay, virtual absence of speech, motor impairment, a behavioural phenotype that includes happy demeanor, and distinctive rhythmic electroencephalographic features, over 90% of patients have epilepsy. Many different seizure types may occur, atypical absences and myoclonic seizures being particularly prevalent. Non-convulsive status epilepticus is common, sometimes in the context of the epileptic syndrome referred to as myoclonic status in non-progressive encephalopathies. Epilepsy predominates in childhood, but may persist or reappear in adulthood. Management is difficult in a proportion of patients. It might be improved by better understanding of pathophysiology. Current hypotheses involve abnormal inhibitory transmission due to impaired regulation of GABAA receptors related to functional absence of UBE3A and abnormal hippocampal CaMKII activity.Journal ArticleReviewinfo:eu-repo/semantics/publishe