Influence of amplitude and load rate on quantity of dissipated energy during cyclic torsion loading of aluminium alloy

W pracy zaprezentowano wyniki badań stopu aluminium PA6 poddanego cyklicznemu skręcaniu w zakresie małej liczby cykli przy wymuszeniu naprężeniowym. Przedstawiono zależność energii dyssypowanej w funkcji amplitudy naprężenia dla różnych prędkości obciążenia. Określono charakter pękania elementów poddanych cyklicznemu skręcaniu.The paper presents experimental results of PA6 aluminium alloy subjected to cyclic torsion loading at a range of low numbers of cycles with stress control. Dependence of dissipated energy value on a stress amplitude and load rate is presented. Kinds of cracks in elements under cyclic torsion loading were determined

Impact of cardiovascular risk factors on carotid intima–media thickness: sex differences

Maria Łoboz-Rudnicka,1 Joanna Jaroch,1 Zbigniew Bociąga,1 Barbara Rzyczkowska,1 Izabella Uchmanowicz,2 Jacek Polański,3 Krzysztof Dudek,4 Andrzej Szuba,5 Krystyna Łoboz-Grudzień2   1Department of Cardiology, T. Marciniak Hospital, 2Public Health Department, Wroclaw Medical University, 3Private Practice, Na Biskupinie, Wroclaw, 4Faculty of Mechanical Engineering, Wroclaw University of Technology, 5Division of Angiology, Wroclaw Medical University, Wroclaw, Poland Background and purpose: There has been growing interest in the sex-related differences in the impact of cardiovascular (CV) risk factors on carotid intima–media thickness (CIMT). Therefore, we aimed at examining the influence of CV risk factors on CIMT in men and women and identifying differences between males and females in the risk profiles affecting CIMT. Patients and methods: The study group consisted of 256 patients (mean age 54.7 years), including 134 females (52%), with the following CV risk factors: arterial hypertension, type 2 diabetes mellitus, dyslipidemia, nicotine addiction, overweight, and obesity. Subjects with the history of any overt CV disease were excluded. CIMT was measured through B-mode ultrasound examination of the right common carotid artery. In the analysis of CIMT values at different ages, the patients were divided into three age groups: 1) <45 years, 2) 45–60 years, and 3) >60 years. Regression analysis was used to examine the influence of CV risk factors on CIMT in men and women. Results: CIMT increased with age in both men and women. Women had lower values of CIMT than men (0.54 mm vs 0.60 mm, P=0.011). The analysis in three age subgroups revealed that CIMT values were comparable in men and women in group 1 (0.48 mm vs 0.48 mm, P=0.861), but over the age of 45 years, CIMT values became significantly lower in women compared to men (group 2: 0.51 mm vs 0.63 mm, P=0.005; group 3: 0.63 mm vs 0.72 mm, P=0.020). Significant differences were observed between the sexes in terms of risk factor impact on CIMT. In men, only three factors significantly affected CIMT: age (b=+0.009, P<0.0001), hypertension (b=+0.067, P<0.05), and type 2 diabetes (b=+0.073, P<0.05). In women, apart from age (b=+0.008, P<0.0001) and type 2 diabetes (b=+0.111, P<0.01), significant factors were pulse pressure (PP; b=+0.005, P<0.0001), body mass index (b=+0.007, P<0.05), increased waist circumference (b=+0.092, P<0.01), and metabolic syndrome (b=+0.071, P<0.05). In the multiple regression analysis, independent CIMT determinants for the entire group were age (β=0.497, P<0.001) and body mass index (β=0.195, P=0.006). For males, age was the only independent determinant of CIMT (β=0.669, P<0.001). For females, these were PP (β=0.317, P=0.014), age (β=0.242, P=0.03), and increased waist circumference (β=0.207, P=0.048). Conclusion: CIMT values are lower in women than in men, which is most pronounced over the age of 45 years. There are sex-related differences in the profile of CV risk factors affecting CIMT: in males, CIMT is mostly determined by age, while in females, by age, PP, and increased waist circumference. Keywords: carotid intima media thickness, risk factors, sex difference

CDC6 controls dynamics of the first embryonic M-phase entry and progression via CDK1 inhibition

International audienceCDC6 is essential for S-phase to initiate DNA replication. It also regulates M-phase exit by inhibiting the activity of the major M-phase protein kinase CDK1. Here we show that addition of recombinant CDC6 to Xenopus embryo cycling extract delays the M-phase entry and inhibits CDK1 during the whole M-phase. Down regulation of endogenous CDC6 accelerates the M-phase entry, abolishes the initial slow and progressive phase of histone H1 kinase activation and increases the level of CDK1 activity during the M-phase. All these effects are fully rescued by the addition of recombinant CDC6 to the extracts. Diminution of CDC6 level in mouse zygotes by two different methods results in accelerated entry into the first cell division showing physiological relevance of CDC6 in intact cells. Thus, CDC6 behaves as CDK1 inhibitor regulating not only the M-phase exit, but also the M-phase entry and progression via limiting the level of CDK1 activity. We propose a novel mechanism of M-phase entry controlled by CDC6 and counterbalancing cyclin B-mediated CDK1 activation. Thus, CDK1 activation proceeds with concomitant inhibition by CDC6, which tunes the timing of the M-phase entry during the embryonic cell cycle