Revisiting theoretical description of the retrograde motion of cathode spots of vacuum arcs

A fresh attempt to develop a self-consistent descrip tion of the retrograde motion of cathode spots on volatile cathodes is undertaken. Three potential mechanisms of effect of transversal magnetic field on the distribution of parameters in the spot are studied: the effect of magnetic field on hydrodynamics processes in the spot, in particular, on the formation of liquid-metal jet and the droplet detachment, and the effect of transversal magnetic field over the motion of ions and emitted electrons in the near-cathode space-charge sheath. It is found that for typical conditions of cathode spots in vacuum arcs the effect of magnetic field over the formation of liquid-metal jet and the droplet detachment is negligible; the motion of the ions in the near-cathode space-charge sheath is not disturbed; and the motion of the emitted electrons is disturbed only marginally. Thus, the above-mentioned potential mechanisms are hardly relevant and the first-principle understanding is still missing. A phenomenological description of the retrograde motion is developed as an alternative. The description employs general considerations without relying on specific assumptions and the (only) unknown parameter can be determined from comparison with the experiment.info:eu-repo/semantics/publishedVersio

Detailed numerical simulation of cathode spots in vacuum arcs—I

A model of cathode spots in high-current vacuum arcs is developed, with account of the plasma cloud left over from a previously existing spot, all mechanisms of current transfer to the cathode surface, including the contribution of the plasma produced by ionization of the metal vapor emitted in the spot, and the Joule heat generation in the cathode body. The simulation results allow one to clearly identify the different phases of life of an individual spot: the ignition, the expansion over the cathode surface, and the thermal explosion. The expansion phase is associated with a nearly constant maximum temperature of the cathode, which occurs at the surface and is approximately 4700–4800 K. Thermal explosion is a result of thermal instabil ity (runaway), which develops below the cathode surface when the Joule heating comes into play. The development of the spot is interrupted if the plasma cloud has been extinguished: the spot is destroyed by heat removal into the bulk of the cathode due to thermal conduction. Therefore, different scenarios are possible depending on the time of action of the cloud: the spot may be quenched before having been formed or during the expansion phase, or even at the initial stage of thermal explosion.info:eu-repo/semantics/publishedVersio

Key Factors Influencing Economic Relationships and Communication in Finnish Food Chains

The aim of this report is to discuss the role of the relationship type and communication in two Finnish food chains, namely the pig meat-to-sausage (pig meat chain) and the cereal-to-rye bread (rye chain) chains. Furthermore, the objective is to examine those factors influencing the choice of a relationship type and the sustainability of a business relationship. Altogether 1808 questionnaires were sent to producers, processors and retailers operating in these two chains of which 224 usable questionnaires were returned (the response rate being 12.4%). The great majority of the respondents (98.7%) were small businesses employing less than 50 people. Almost 70 per cent of the respondents were farmers. In both chains, formal contracts were stated to be the most important relationship type used with business partners. Although for many businesses written contracts are a common business practice, the essential role of the contracts was the security they provide regarding the demand/supply and quality issues. Relative to the choice of the relationship types, the main difference between the two chains emerged especially with the prevalence of spot markets and financial participation arrangements. The usage of spot markets was significantly more common in the rye chain when compared to the pig meat chain, while, on the other hand, financial participation arrangements were much more common among the businesses in the pig meat chain than in the rye chain. Furthermore, the analysis showed that most of the businesses in the pig meat chain claimed not to be free to choose the relationship type they use. Especially membership in a co-operative and practices of a business partner were mentioned as the reasons limiting this freedom of choice. The main business relations in both chains were described as having a long-term orientation and being based on formal written contracts. Typical for the main business relationships was also that they are not based on the existence of the key persons only; the relationship would remain even if the key people left the business. The quality of these relationships was satisfactory in both chains and across all the stakeholder groups, though the downstream processors and the retailers had a slightly more positive view on their main business partners than the farmers and the upstream processors. The businesses operating in the pig meat chain seemed also to be more dependent on their main business relations when compared to the businesses in the rye chain. Although the communication means were rather similar in both chains (the phone being the most important), there was some variation between the chains concerning the communication frequency necessary to maintain the relationship with the main business partner. In short, the businesses in the pig meat chain seemed to appreciate more frequent communication with their main business partners when compared to the businesses in the rye chain. Personal meetings with the main business partners were quite rare in both chains. All the respondent groups were, however, fairly satisfied with the communication frequency and information quality between them and the main business partner. The business cultures could be argued to be rather hegemonic among the businesses both in the pig meat and rye chains. Avoidance of uncertainty, appreciation of long-term orientation and independence were considered important factors in the business cultures. Furthermore, trust, commitment and satisfaction in business partners were thought to be essential elements of business operations in all the respondent groups. In order to investigate which factors have an effect on the choice of a relationship type, several hypotheses were tested by using binary and multinomial logit analyses. According to these analyses it could be argued that avoidance of uncertainty and risk has a certain effect on the relationship type chosen, i.e. the willingness to avoid uncertainty increases the probability to choose stable relationships, like repeated market transactions and formal written contracts, but not necessary those, which require high financial commitment (like financial participation arrangements). The probability of engaging in financial participation arrangements seemed to increase with long-term orientation. The hypotheses concerning the sustainability of the economic relations were tested by using structural equation model (SEM). In the model, five variables were found to have a positive and statistically significant impact on the sustainable economic relationship construct. Ordered relative to their importance, those factors are: (i) communication quality, (ii) personal bonds, (iii) equal power distribution, (iv) local embeddedness and (v) competition

Gender and class in Britain and France

This article examines the treatment of women's oppression in feminist theory, focusing on the engagement of second wave feminists with the concept of class and its relation to gender. This examination is carried out with reference to British and French feminisms, identifying the main trends and shifts that have developed over the last 35 years and noting that while these are undoubtedly influenced by a particular national context they are also shaped by increasing European integration and social, political and cultural exchanges at a global level. The authors find evidence of a number of similarities in the questions that feminist theorists have asked in Britain and France but also demonstrate that there are significant differences. They conclude that areas of convergent theoretical interests will extend along with cross-border flows of peoples and information

A LATA MÁGICA: ESCLARECENDO O CONCEITO DE ENERGIA

As expressões vinculadas ao termo “energia” são transmitidas constantemente por todas as mídias (televisão, rádio, jornal, revista, internet, propaganda veiculada em ambientes externos), sem o devido cuidado em esclarecer o conceito, que normalmente é distorcido ou confundido com os conceitos de força e potência. A lata mágica é uma ferramenta didática extremamente útil, divertida e poderosa que pode ser utilizada pelo professor em sala de aula para trabalhar os conceitos de energia, considerados básicos e de significado imediato para o aluno, pois faz parte do seu cotidiano vivencial. O experimento físico “a lata mágica”, de construção ligeiramente simples, aborda o conceito de energia e seu funcionamento, além de explorar outros tópicos vinculados ao tema: tipos de energia, conservação de energia e transferência de energia. Considerando o sistema conservativo, as energias envolvidas no experimento são as energias cinética e potencial elástica. A lata quando em movimento de rolamento possui dois tipos de energia cinética: uma energia cinética de rotação associada à rotação em torno do centro de massa e uma energia cinética de translação associada à translação do centro de massa. Por sua vez, a energia potencial elástica é uma forma de energia armazenada em um sistema quando ele é deformado por uma força externa, sendo característica de sistemas elásticos, como molas, borrachas ou elásticos, que possuem a capacidade de sofrer deformações reversíveis quando submetidas à ação de uma força. O experimento envolve uma lata vazia, geralmente metálica, que possui uma tampa ajustada firmemente. E dentro dela há um peso enrolado em um elástico e em cada lado da lata tem um parafuso para prender o elástico. Quando empurramos a lata, a força que aplicamos sobre ela realiza trabalho, causando um movimento caracterizado como rolamento (translação e rotação). Inicialmente, a energia cinética associada ao rolamento da lata é transferida gradativamente para o elástico, que se encontra no interior da lata, causando uma torção máxima, que o impede de girar junto com a lata devido ao peso (parafuso) no interior da lata. Durante a torção do elástico, gradativamente a lata perde energia cinética e o elástico ganha energia potencial. Quando a lata interrompe totalmente o seu movimento de rolamento, a energia que foi armazenada na forma de energia potencial passa a ser transferida na forma de energia cinética de rolamento, fazendo com que a lata retorne à sua posição inicial, se não houver forças dissipativas. Neste trabalho, pretende-se investigar os tipos de energia envolvidos durante o movimento da lata, verificar se há conservação de energia mecânica e contextualizar a teoria com a prática. Os materiais a serem utilizados para a confecção da lata mágica são: lata com tampa, garrafa de plástico transparente, elásticos, parafusos, pregos e fita adesiva. Além disso, pretende-se substituir a lata por uma garrafa transparente, com o intuito de verificar o que ocorre com os materiais dentro da lata, durante o seu movimento

Elementos Externos Que Influem Em Doenças Autoimunes

A lúpus eritematoso sistêmico (LES) é uma doença autoimune de amplo espectro que afeta múltiplos órgãos. Sua fisiopatologia é desencadeada por vias de apoptose que chegam a afetar inúmeros anticorpos do organismo infectado, como por exemplo linfócitos apoptóticos. Entretanto, a LES não responde apenas à vias de apoptose; o nível de metilação, acetilação e desacetilação também induzem ao desenvolvimento desta doença autoimune. Alguns fatores epignéticos podem influenciar na progressão do quadro da lúpus. Sendo que, alterações no padrão epigenômico alteram a expressão gênica, e portanto, a gravidade manifestada pela doença de LES. Além disso, há fatores externos que alteram o quadro patogênico. Estudos evidenciaram o papel da dieta alimentar no desenvolvimento da LES; evidenciando que as dietas podem influenciar em inflamações cutâneas, microbiota do intestino, quadros de diabetes mellitus, problemas cardiovasculares e etc. Muitos estudos concentram suas pesquisas nos estudos de vitamina D, A e ácidos graxos poli-insaturados. Há também evidencias de que a poluição do ar influencia na progressão da lúpus assim como a dieta. Nesses casos, os poluentes do ar alteram as características fisiológicas do pulmão, levando o mesmo a iniciar processos autoimunes. Nesta dinâmica, os poluentes se ligam a receptores específicos que levam à produção de citocinas pró-inflamatórias. Por último, observa-se que há outros fatores que também influenciam no quadro da lúpus eritematosa sistêmica, como o sexo biológico, tabagismo, exposição à agrotóxicos, entre outros

Cytoplasmic poly-GA aggregates impair nuclear import of TDP-43 in C9orf72 ALS/FTLD

A repeat expansion in the non-coding region of C9orf72 gene is the most common mutation causing frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS). Sense and antisense transcripts are translated into aggregating dipeptide repeat (DPR) proteins in all reading frames (poly-GA,-GP,-GR,-PA and -PR) through an unconventional mechanism. How these changes contribute to cytoplasmic mislocalization and aggregation of TDP-43 and thereby ultimately leading to neuron loss remains unclear. The repeat RNA itself and poly-GR/PR have been linked to impaired nucleocytoplasmic transport. Here, we show that compact cytoplasmic poly-GA aggregates impair nuclear import of a reporter containing the TDP-43 nuclear localization (NLS) signal. However, a reporter containing a non-classical PY-NLS was not affected. Moreover, poly-GA expression prevents TNF alpha induced nuclear translocation of p65 suggesting that poly-GA predominantly impairs theimportin-alpha/beta-dependent pathway. In neurons, prolonged poly-GA expression induces partial mislocalization of TDP-43 into cytoplasmic granules. Rerouting poly-GA to the nucleus prevented TDP-43 mislocalization, suggesting a cytoplasmic mechanism. In rescue experiments, expression of importin-alpha (KPNA3, KPNA4) or nucleoporins (NUP54, NUP62) restores the nuclear localization of the TDP reporter. Taken together, inhibition of nuclear import of TDP-43 by cytoplasmic poly-GA inclusions causally links the two main aggregating proteins in C9orf72 ALS/FTLD pathogenesis

CyTOF workflow: differential discovery in high-throughput high-dimensional cytometry datasets [version 3; peer review: 2 approved]

High-dimensional mass and flow cytometry (HDCyto) experiments have become a method of choice for high-throughput interrogation and characterization of cell populations. Here, we present an updated R-based pipeline for differential analyses of HDCyto data, largely based on Bioconductor packages. We computationally define cell populations using FlowSOM clustering, and facilitate an optional but reproducible strategy for manual merging of algorithm-generated clusters. Our workflow offers different analysis paths, including association of cell type abundance with a phenotype or changes in signalling markers within specific subpopulations, or differential analyses of aggregated signals. Importantly, the differential analyses we show are based on regression frameworks where the HDCyto data is the response; thus, we are able to model arbitrary experimental designs, such as those with batch effects, paired designs and so on. In particular, we apply generalized linear mixed models or linear mixed models to analyses of cell population abundance or cell-population-specific analyses of signaling markers, allowing overdispersion in cell count or aggregated signals across samples to be appropriately modeled. To support the formal statistical analyses, we encourage exploratory data analysis at every step, including quality control (e.g., multi-dimensional scaling plots), reporting of clustering results (dimensionality reduction, heatmaps with dendrograms) and differential analyses (e.g., plots of aggregated signals)

Red seaweeds Grateloupia turuturu and Porphyra umbilicalis as nutraceuticals and functional food: nutritional/chemical composition and immunostimulatory activity

1st Natural Products Application: health, cosmetic and food - International online conference, 4-5 February 2021The number of nutraceuticals and functional foodsfrom marine origin is increasing in the worldwide market. Specifically, the red seaweeds Grareloupia turuturu and Porphyra umbilicalis have shown their potential considering relevant bioactive compounds and nutritional value [1,2]. Nevertheless, it is pertinent to explore knowledge gaps regarding their nutritional/chemical composition and bioactivities. Hence firstly G. turuturu and P. umbilicalis proximate composition and lipid classes were determined; secondly, after preparing hydroethanolic and aqueous infusion and decoction) seaweed extracts, mycosporine-like ami no acids (MAAs) and carbohydrates were quantified. and the immunomodulatory potential was assessed using RAW 264.7 cell line. Results show that dietary fibre was the most abundant nutritional parameter for both seaweed species, followed by relevant ash and protein contents. Free fatty acids were the main lipid class in both seaweed species, whereas tocopherols exhibited residual contentsby RP-HPLC-FLD. For hydroethanolic and aqueous extracts, several MAAs were quantified by RP-HPLC-DAD and LC-DAD ESI-MS. P. umbilicalis extracts demonstrated greater MAAs content than G. turuturu, and porphyra-334 was the main MAA. The aqueous extracts of both seaweeds showed higher carbohydrate contents than the hydroethanolic, with P. umbilicalis decoction exhibiting the highest level. Concerning the immunomodulatory activity, for 0.02 mg/mL, the exposure to P. umbilicalis aqueous extracts resulted in the most accentuated 'NO production by RAW 264.7 cells, showing immunostimulatory potential. MAAs and carbohydrates are believed to be responsible for the immunostimulatory activity [3,4]. G. turuturu and P. umbilicalis potential as functional food and nutraceuticals, relying on their relevance as sources of bioactive compounds to the food, pharmaceutical and cosmetic industries, is thus reinforcedThis work was financed by European Funds FEDER/COMPETE/POCI under project POCI-01-0145-FEDER-006958 (CITAB), and by FCT to CECAV (UIDB/CVT/00772/2020), CITAB (UlDB/04033/2020) and CESAM (UIDP/5001712020+UIDB/50017/2020). FCT is also acknowledged for a doctoral grant to Joao Ferreira (SFRH/BD/144882/2019)N