72 research outputs found

    Strategies and limits in multi-stage single-point incremental forming

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    Abstract: Multi-stage single-point incremental forming (SPIF) is a state-of-the-art manufac-turing process that allows small-quantity production of complex sheet metal parts with vertical walls. This paper is focused on the application of multi-stage SPIF with the objective of producing cylindrical cups with vertical walls. The strategy consists of forming a conical cup with a taper angle in the first stage, followed by three subsequent stages that progressively move the conical shape towards the desired cylindrical geometry. The investigation includes material characterization, determination of forming-limit curves and fracture forming-limit curves (FFLCs), numerical simulation, and experimentation, namely the evaluation of strain paths and fracture strains in actual multi-stage parts. Assessment of numerical simulation with experimentation shows good agreement between computed and measured strain and strain paths. The results also reveal that the sequence of multi-stage forming has a large effect on the location of strain points in the principal strain space. Strain paths are linear in the first stage and highly non-linear in the subsequent forming stages. The overall results show that the experimentally determined FFLCs can successfully be employed to establish the forming limits of multi-stage SPIF

    The yeast ABC transporter Pdr18 (ORF YNR070w) controls plasma membrane sterol composition, playing a role in multidrug resistance

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    The action of multidrug efflux pumps in MDR (multidrug resistance) acquisition has been proposed to partially depend on the transport of physiological substrates which may indirectly affect drug partition and transport across cell membranes. In the present study, the PDR18 gene [ORF (open reading frame) YNR070w], encoding a putative PDR (pleiotropic drug resistance) transporter of the ATP-binding cassette superfamily, was found to mediate plasma membrane sterol incorporation in yeast. The physiological role of Pdr18 is demonstrated to affect plasma membrane potential and is proposed to underlie its action as a MDR determinant, conferring resistance to the herbicide 2,4-D (2,4-dichlorophenoxyacetic acid). The action of Pdr18 in yeast tolerance to 2,4-D, which was found to contribute to reduce [14C]2,4-D intracellular accumulation, may be indirect, given the observation that 2,4-D exposure deeply affects the sterol plasma membrane composition, this effect being much stronger in a Ī”pdr18 background. PDR18 activation under 2,4-D stress is regulated by the transcription factors Nrg1, controlling carbon source availability and the stress response, and, less significantly, Yap1, involved in oxidative stress and MDR, and Pdr3, a key regulator of the yeast PDR network, consistent with a broad role in stress defence. Taken together, the results of the present study suggest that Pdr18 plays a role in plasma membrane sterol incorporation, this physiological trait contributing to an MDR phenotype

    Double-balloon catheter for induction of labour in women with a previous cesarean section, could it be the best choice?

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    INTRODUCTION: We analysed the efficacy and safety of double-balloon catheter for cervical ripening in women with a previous cesarean section and which were the most important variables associated with an increased risk of repeated cesarean delivery. MATERIALS AND METHODS: We designed an observational retrospective study of 418 women with unfavourable cervices (Bishop Scoreā€‰<5), a prior cesarean delivery, and induction of labour with a double-balloon catheter. Baseline maternal data and perinatal outcomes were recorded for a descriptive, bivariate, and multivariate analysis. A p valueā€‰<0.05 was considered statistically significant. RESULTS: Most women improved their initial Bishop Score (89.5%) although only a 20.8% of them went into spontaneous active labour. Finally, 51.4% of the women achieved a vaginal delivery. Five cases of intrapartum uterine rupture (1.2%) occurred. After multivariate analysis, main risk factors for repeated cesarean section were dystocia in the previous pregnancy (OR 1.744; CI 95% 1.066ā€“2.846), the absence of previous vaginal delivery (OR 2.590; CI 95% 1.066ā€“6.290), suspected fetal macrosomia (OR 2.410; CI 95% 0.959ā€“6.054), and duration of oxytocin induction period (OR 1.005; CI 95% 1.004ā€“1.006). The area under the curve was 0.789 (pā€‰<ā€‰0.001). CONCLUSIONS: Double-balloon catheter seems to be safe and effective for cervical ripening in women with a previous cesarean delivery and unfavourable cervix. In our study, most women could have a vaginal delivery in spite of their risk factors for cesarean delivery. A multivariate model based on some clinical variables has moderate predictive value for intrapartum cesarean section

    Influencer les jugements de l'adversaire au cours des interactions sportives compƩtitives: Un exemple en tennis de table

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    International audienceThis study analysed the masking activity of table tennis players, and any activity attempting to influence opponent's perceptions. We studied the activity of five French table tennis players during national matches in reference to the course of action theory (Theureau, 1992). Matches were videotaped, and the players' verbalizations as they viewed the tapes were collected a posteriori. The data were analysed by 1) transcribing the players' actions and verbalizations, 2) decomposing their activity into elementary units of meaning, and 3) analysing the meaningful structures of the course of action. The results showed that a large part of the table tennis players activity attempts to influence opponent's judgments. This activity aims to 1) modify the opponent's emotional experience, and 2) influence the opponent's perception of adversarial relationship. It is expressed through strokes and behaviors not related to the game. Our results lead to a new perspective of table tennis matches analysis in term of collective activity and "shared context" (Salembier and Zouinar, 2004
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