Numerical Simulation of Aerodynamic Noise of Soundproof Enclosure of Air Compressor Unit

During the operation of the air compressor unit, the suction and exhaust process of the air compressor and the operation of other equipment will cause air flow pulsation, which is often accompanied by the generation of air compressor noise. Numerical simulation method, as an important means to study the flow field characteristics and noise characteristics of air compressors, has been widely used in recent years. This article takes the noise enclosure of a certain air compressor unit as the research object, and use numerical simulation method to study the air intake part of the enclosure. The influence of inlet louver and suction deflector on the aerodynamic performance of air compressor noise enclosure was analyzed, and the influence of different inlet louver structures and different suction deflector structures on noise was compared. This paper uses the broadband noise model to predict the distribution of air flow pulsation noise. In order to quantitatively study the noise, the FW-H model based on Lighthill\u27s acoustic analogy method was used for the aerodynamic noise simulation, and the frequency response of the aerodynamic noise of air compressor was obtained

Characterization of Curli A Production on Living Bacterial Surfaces by Scanning Probe Microscopy

AbstractCurli are adhesive surface fibers produced by many Enterobacteriaceae, such as Escherichia coli and Salmonella enterica. They are implicated in bacterial attachment and invasion to epithelial cells. In this study, atomic force microscopy was used to determine the effects of curli on topology and mechanical properties of live E. coli cells. Young's moduli of both curli-deficient and curli-overproducing mutants were significantly lower than that of their wild-type (WT) strain, while decay lengths of the former strains were higher than that of the latter strain. Surprisingly, topological images showed that, unlike the WT and curli-overproducing mutant, the curli-deficient mutant produced a large number of flagella-like fibers, which may explain why the strain had a lower Young's modulus than the WT. These results suggest that the mechanical properties of bacterial surfaces are greatly affected by the presence of filamentous structures such as curli and flagella

Effects of bilirubin on the development and electrical activity of neural circuits

In the past several decades, bilirubin has attracted great attention for central nervous system (CNS) toxicity in some pathological conditions with severely elevated bilirubin levels. CNS function relies on the structural and functional integrity of neural circuits, which are large and complex electrochemical networks. Neural circuits develop from the proliferation and differentiation of neural stem cells, followed by dendritic and axonal arborization, myelination, and synapse formation. The circuits are immature, but robustly developing, during the neonatal period. It is at the same time that physiological or pathological jaundice occurs. The present review comprehensively discusses the effects of bilirubin on the development and electrical activity of neural circuits to provide a systematic understanding of the underlying mechanisms of bilirubin-induced acute neurotoxicity and chronic neurodevelopmental disorders

The association between air pollutant exposure and cerebral small vessel disease imaging markers with modifying effects of PRS-defined genetic susceptibility

Studies have highlighted a possible link between air pollution and cerebral small vessel disease (CSVD) imaging markers. However, the exact association and effects of polygenic risk score (PRS) defined genetic susceptibility remains unclear. This cross-sectional study used data from the UK Biobank. Participants aged 40–69 years were recruited between the year 2006 and 2010. The annual average concentrations of NOX, NO2, PM2.5, PM2.5–10, PM2.5 absorbance, and PM10, were estimated, and joint exposure to multiple air pollutants was reflected in the air pollution index (APEX). Air pollutant exposure was classified into the low (T1), intermediate (T2), and high (T3) tertiles. Three CSVD markers were used: white matter hyper-intensity (WMH), mean diffusivity (MD), and fractional anisotropy (FA). The first principal components of the MD and FA measures in the 48 white matter tracts were analysed. The sample consisted of 44,470 participants from the UK Biobank. The median (T1–T3) concentrations of pollutants were as follows: NO2, 25.5 (22.4–28.7) μg/m3; NOx, 41.3 (36.2–46.7) μg/m3; PM10, 15.9 (15.4–16.4) μg/m3; PM2.5, 9.9 (9.5–10.3) μg/m3; PM2.5 absorbance, 1.1 (1.0–1.2) per metre; and PM2.5–10, 6.1 (5.9–6.3) μg/m3. Compared with the low group, the high group's APEX, NOX, and PM2.5 levels were associated with increased WMH volumes, and the estimates (95 %CI) were 0.024 (0.003, 0.044), 0.030 (0.010, 0.050), and 0.032 (0.011, 0.053), respectively, after adjusting for potential confounders. APEX, PM10, PM2.5 absorbance, and PM2.5–10 exposure in the high group were associated with increased FA values compared to that in the low group. Sex-specific analyses revealed associations only in females. Regarding the combined associations of air pollutant exposure and PRS-defined genetic susceptibility with CSVD markers, the associations of NO2, NOX, PM2.5, and PM2.5–10 with WMH were more profound in females with low PRS-defined genetic susceptibility, and the associations of PM10, PM2.5, and PM2.5 absorbance with FA were more profound in females with higher PRS-defined genetic susceptibility. Our study demonstrated that air pollutant exposure may be associated with CSVD imaging markers, with females being more susceptible, and that PRS-defined genetic susceptibility may modify the associations of air pollutants

Abordagem da história da ciência na construção de um terrário, numa perspetiva de educação para o desenvolvimento sustentável

Mestrado em Ensino de Biologia e Geologia no 3º Ciclo do Ensino Básico e no Ensino SecundárioEm Portugal, avanços têm-se feito notar no que toca à tecnologia, o que leva a que novas aptidões e competências sejam desenvolvidas pelos cidadãos de forma a adaptarem-se à Era da informação. Para tal, é necessário que os alunos saiam já bem preparados das escolas de modo a que as suas aprendizagens atendam a essas mudanças, pois o ensino também implica mudança, evolução e crescimento, não só por parte dos estudantes mas também dos professores, das escolas e de todos os órgãos associados. Desta forma, vários métodos poderão ser implementados nas salas de aulas e um deles é a abordagem à História da Ciência. O presente trabalho investigativo procurou conhecer quais as aprendizagens, comportamentos e atitudes que os alunos desenvolveram ao longo das aulas, dando a conhecer os contributos que a construção de um terrário, através da História da Ciência, pode levar à educação de cidadãos informados, numa perspetiva de Educação para o Desenvolvimento Sustentável. A abordagem foi aplicada a alunos do 8.º ano, na disciplina de Ciências Naturais, utilizando várias técnicas e instrumentos de recolha de dados, nomeadamente, a observação, a análise documental e questionário. O recurso à construção e utilização de um material didático-pedagógico e a abordagem à História da Ciência, permitiram cativar o interesse dos alunos e centraliza-los no processo de ensino e de aprendizagem, no qual o aluno tem o principal papel. Dessa forma, foi possível averiguar como se contextualizam as aprendizagens através da abordagem utilizada, recolher e descrever as perspetivas dos alunos e em desenvolver as aprendizagens, comportamentos e atitudes, numa perspetiva de Educação para o Desenvolvimento Sustentável.In Portugal, advances have been made when it comes to Technology, which leads to new skills and competences to be developed by citizens in order to adapt to the Information age. To this end, it is necessary that students need to be well prepared when they conclude their studies, so that their acquired knowledge could meet these changes, for the teaching also implies changes, evolution and growth, not only by students but also by teachers, schools and all the associated teaching groups. This way, various methods can be implemented in the classroom and one of them is the approach to the History of Science. This research work was aimed to know which learnings, behaviors and attitudes that students developed during the lessons, so that it could be possible to publish the contribution of the construction of a terrarium, based in the History of Science, leading to the education of informed citizens, in a perspective of an Education for Sustainable Development. The approach was applied to 8th grade students, in the discipline of Natural Sciences, using various techniques and data collection instruments, like observation, documental analysis and a questionnaire. Building and using didactic-pedagogic material and applying History of Science knowledge, allowed to captivate the students' interest and it helped centralizing them in the process of teaching and learning, in which the student has the main role. Thus, it was possible to find out how to contextualize the learning through the used approaches, to collect and describe the perspectives of the students and developing the learning subject, behaviors and attitudes on a perspective of Education for the Sustainable Development

Effect of Cu on the high-temperature wear behavior of FeAl-TiB2 coatings produced by extreme high-speed laser cladding

Abstracts: To enhance the tribological and wear properties of carbon steel at high temperatures, FeAl-TiB2-Cux coatings were produced using an extreme high-speed laser cladding process. The coatings had varying Cu content and were made from original powders including Fe, Al, Cu, and TiB2. The study focused on the phase composition, microstructure, and wear mechanism of the coating. Results showed that the composite coatings mainly consisted of FeAl, TiB2, and Cu9Al4 with uniformly distributed remelted TiB2 particles. When Cu content was less than 3wt%, plastic deformation and oxidation wear dominated the coating's wear mode; when it exceeded 3wt%, abrasive wear became more prominent alongside oxidation wear. It was found that the tribo-film was formed by metal oxides during the dry sliding process. Especially, the coating with 5wt% Cu content exhibited the lowest friction coefficient wear rate at 600℃ due to the self-lubricating properties of CuO