Effective Dissipation and Turbulence in Spectrally Truncated Euler Flows

A new transient regime in the relaxation towards absolute equilibrium of the conservative and time-reversible 3-D Euler equation with high-wavenumber spectral truncation is characterized. Large-scale dissipative effects, caused by the thermalized modes that spontaneously appear between a transition wavenumber and the maximum wavenumber, are calculated using fluctuation dissipation relations. The large-scale dynamics is found to be similar to that of high-Reynolds number Navier-Stokes equations and thus to obey (at least approximately) Kolmogorov scaling.Comment: 4 pages, 5 figures new version with only 4 figures; title changed; manuscript changed; accepted by PR

Research priorities in bronchiectasis:a consensus statement from the EMBARC Clinical Research Collaboration

Bronchiectasis is a disease of renewed interest in light of an increase in prevalence and increasing burden on international healthcare systems. There are no licensed therapies, and large gaps in knowledge in terms of epidemiology, pathophysiology and therapy. The European Multicentre Bronchiectasis Audit and Research Collaboration (EMBARC) is a European Respiratory Society (ERS) Clinical Research Collaboration, funded by ERS to promote high-quality research in bronchiectasis. The objective of this consensus statement was to define research priorities in bronchiectasis. From 2014 to 2015, EMBARC used a modified Delphi process among European bronchiectasis experts to reach a consensus on 55 key research priorities in this field. During the same period, the European Lung Foundation collected 711 questionnaires from adult patients with bronchiectasis and their carers from 22 European countries reporting important research priorities from their perspective. This consensus statement reports recommendations for bronchiectasis research after integrating both physicians and patients priorities, as well as those uniquely identified by the two groups. Priorities identified in this consensus statement provide the clearest possible roadmap towards improving our understanding of the disease and the quality of care for patients with bronchiectasis

Genetic polymorphisms of MMP1, MMP3 and MMP7 gene promoter and risk of colorectal adenoma

BACKGROUND: Matrix metalloproteinases (MMP) have been shown to play a role in colorectal cancer (CRC). More recently, MMP1, MMP3 and MMP7 functional gene promoter polymorphisms have been found to be associated with CRC occurrence and prognosis. To document the role of MMP polymorphisms in the early step of colorectal carcinogenesis, we investigated their association with colorectal adenoma risk in a case-control study comprising 295 patients with large adenomas (LA), 302 patients with small adenomas (SA) and 568 polyp-free (PF) controls. METHODS: Patients were genotyped using automated fragment analysis for MMP1 -1607 ins/del G and MMP3 -1612 ins/delA (MMP3.1) polymorphisms and allelic discrimination assay for MMP3 -709 A/G (MMP3.2) and MMP7 -181 A/G polymorphisms. Association between MMP genotypes and colorectal adenomas was first tested for each polymorphism separately and then for combined genotypes using the combination test. Adjustment on relevant variables and estimation of odds ratios were performed using unconditional logistic regression. RESULTS: No association was observed between the polymorphisms and LA when compared to PF or SA. When comparing SA to PF controls, analysis revealed a significant association between MMP3 -1612 ins/delA polymorphism and SA with an increased risk associated with the 6A/6A genotype (OR = 1.67, 95%CI: 1.20–2.34). Using the combination test, the best association was found for MMP3.1-MMP1 (p = 0.001) with an OR of 1.88 (95%CI: 1.08–3.28) for the combined genotype 2G/2G-6A/6A estimated by logistic regression. CONCLUSION: These data show a relation between MMP1 -1607 ins/del G and MMP3 -1612 ins/delA combined polymorphisms and risk of SA, suggesting their potential role in the early steps of colorectal carcinogenesis

Bending fatigue behaviour of 17-4 PH gears produced via selective laser melting

The possibility of producing parts via the addition of material, instead of its removing, given by Additive Manufacturing (AM) processes is changing the way in which parts are designed. However, the design of some mechanical components like gears, for instance, requires specific resistance data that, up to now, are not presented in literature. This paper presents a research project aimed at investigating the bending fatigue properties of 17-4 PH steel applied to gears produced via selective laser melting. Single Tooth bending Fatigue (STF) tests were conducted in order to investigate the S-N curve. Results are presented in terms of tooth root stress calculated according to the ISO standard in order to compare them with data of other materials. In addition, Scanning Electron Microscopy (SEM) of the fractured surfaces has been performed on the failed teeth to investigate failure origin and therefore to find causes of tooth breakage

Estimation of gear SN curve for tooth root bending fatigue by means of maximum likelihood method and statistic of extremes

Gear failure due to tooth root bending fatigue is one of the most dangerous gear failure modes. Therefore, the precise definition of gear bending fatigue strength is a key aspect in gear design. As a matter of fact, in order to assess a gear component, an accurate estimation of the component SN curve is required. This curve must properly take into account three main aspects: the slope of the fatigue strength region, the slope of the region ahead the fatigue knee and the position of the knee itself. In addition, with the aim of being able of considering different reliability levels, a proper estimation of the associated dispersion is required too. Single Tooth Bending Fatigue (STBF) tests are usually used to investigate the tooth load carrying capacity with respect to the bending failure mode. However, due to the test rig configuration, two main differences between test and real case are present. Firstly, the statistical behavior is different, since in the meshing gear the strength is determined by its weakest tooth, while in a STBF test the failing tooth is predetermined. Secondly, the load history is different.Therefore, additional effects have to be taken into account to obtain the gear SN curve starting from STBF tests. In this article, due to its capability of handling interrupted tests (e.g. runouts), Maximum Likelihood Estimation (MLE) has been used to estimate, in the most reliable way, the SN curve from experimental points. SoE (Statistic of Extremes) has been adopted to move from the STBF SN curve to the gear one, as, by means of a simple mathematical passage, SoE enables the estimation of the strength of the weakest tooth among the z gear teeth and, as a consequence, of the gear. The effect of the different load history is considered by adopting a literature-based approach (i.e. use of corrective coefficient). This paper describes in detail the proposed calculation method and shows its application to determine the SN curve in a practical case