Residual stresses influence on the fatigue strength of structural components

Several production processes, both conventional and innovative, may result in residual stresses arising in critical areas of a component. The main issues include high distortion, reduced fatigue life, fracturing or delamination. In this context, standard fatigue design codes traditionally consider residual stresses through conservative assumptions, leading to either sub-optimal design or unexpected failures. Recently, innovative computational techniques have been developed to address residual stresses in a more comprehensive way. As a result, a more effective material utilisation and a more accurate fatigue life assessment can be achieved. The present work examines the influence of residual stresses on the fatigue endurance of S355JR structural steel components. Both welded and notched components were analysed, carrying out numerical and experimental analyses. In the case of welded components, residual stresses resulting from the welding process were numerically evaluated by means of an uncoupled thermal-structural simulation, while for notched specimens a preload causing limited yielding was used to induce a local residual stress field comparable to that obtained for welded specimens nearby the critical locations. Even if he work is still in progress, tests carried out with different specimens under different loading conditions allowed to understand the effect of residual stresses on the fatigue life

Comparative Methylation of ERVWE1/Syncytin-1 and Other Human Endogenous Retrovirus LTRs in Placenta Tissues

Human endogenous retroviruses (HERVs) are globally silent in somatic cells. However, some HERVs display high transcription in physiological conditions. In particular, ERVWE1, ERVFRDE1 and ERV3, three proviruses of distinct families, are highly transcribed in placenta and produce envelope proteins associated with placenta development. As silencing of repeated elements is thought to occur mainly by DNA methylation, we compared the methylation of ERVWE1 and related HERVs to appreciate whether HERV methylation relies upon the family, the integration site, the tissue, the long terminal repeat (LTR) function or the associated gene function. CpG methylation of HERV-W LTRs in placenta-associated tissues was heterogeneous but a joint epigenetic control was found for ERVWE1 5′LTR and its juxtaposed enhancer, a mammalian apparent LTR retrotransposon. Additionally, ERVWE1, ERVFRDE1 and ERV3 5′LTRs were all essentially hypomethylated in cytotrophoblasts during pregnancy, but showed distinct and stage-dependent methylation profiles. In non-cytotrophoblastic cells, they also exhibited different methylation profiles, compatible with their respective transcriptional activities. Comparative analyses of transcriptional activity and LTR methylation in cell lines further sustained a role for methylation in the control of functional LTRs. These results suggest that HERV methylation might not be family related but copy-specific, and related to the LTR function and the tissue. In particular, ERVWE1 and ERV3 could be developmentally epigenetically regulated HERVs

Assessment, control, and prevention of microbiological and chemical hazards in seasonal swimming pools of the Versilia district (Tuscany, central Italy).

Abstract Although in Europe the quality of swimming pools (SPs) is dictated by regulations, microbiological and chemical hazards are described in the literature. Environmental bacteria or toxic disinfection by-product (DBP) compounds may indeed be recovered in waters even after disinfection. We evaluated the water quality from 26 outdoor seasonal SPs of the Versilia district, according to requirements of Regional Decree 54R/2015. In spring 2017, supply and reinstatement waters were collected after shock hyperchlorination (10 mg/L) while in summertime, a second sampling of waters before entering the pools, as well as in the pools, was performed after SPs were open to the public. In all samples, microbiological and chemical parameters were determined as defined by Directive 98/83/EC and the Italian Health Ministry. Microbiological data were within suggested limits. The first chemical analyses showed that in 35% of the feeding-pool seawater samples, the halogenated organic compounds were higher than the maximum permissible concentrations (30 μg/L). Pool waters were then dechlorinated and re-treated with hydrogen peroxide (10 mg/L) to ensure the abatement of DBPs (from 164 ± 107 to 0.9 ± 0.8 μg/L; p = 0.002). Results highlighted the need of self-controlled procedures for the SPs waters to prevent waterborne diseases and suggested hydrogen peroxide as the most appropriate disinfection method

RhoE Is Regulated by Cyclic AMP and Promotes Fusion of Human BeWo Choriocarcinoma Cells

Fusion of placental villous cytotrophoblasts with the overlying syncytiotrophoblast is essential for the maintenance of successful pregnancy, and disturbances in this process have been implicated in pathological conditions such as pre-eclampsia and intra-uterine growth retardation. In this study we examined the role of the Rho GTPase family member RhoE in trophoblast differentiation and fusion using the BeWo choriocarcinoma cell line, a model of villous cytotrophoblast fusion. Treatment of BeWo cells with the cell permeable cyclic AMP analogue dibutyryl cyclic AMP (dbcAMP) resulted in a strong upregulation of RhoE at 24h, coinciding with the onset of fusion. Using the protein kinase A (PKA)-specific cAMP analogue N6-phenyl-cAMP, and a specific inhibitor of PKA (14–22 amide, PKI), we found that upregulation of RhoE by cAMP was mediated through activation of PKA signalling. Silencing of RhoE expression by RNA interference resulted in a significant decrease in dbcAMP-induced fusion. However, expression of differentiation markers human chorionic gonadotrophin and placental alkaline phosphatase was unaffected by RhoE silencing. Finally, we found that RhoE upregulation by dbcAMP was significantly reduced under hypoxic conditions in which cell fusion is impaired. These results show that induction of RhoE by cAMP is mediated through PKA and promotes BeWo cell fusion but has no effect on functional differentiation, supporting evidence that these two processes may be controlled by separate or diverging pathways

(Homo)glutathione Deficiency Impairs Root-knot Nematode Development in Medicago truncatula

Root-knot nematodes (RKN) are obligatory plant parasitic worms that establish and maintain an intimate relationship with their host plants. During a compatible interaction, RKN induce the redifferentiation of root cells into multinucleate and hypertrophied giant cells essential for nematode growth and reproduction. These metabolically active feeding cells constitute the exclusive source of nutrients for the nematode. Detailed analysis of glutathione (GSH) and homoglutathione (hGSH) metabolism demonstrated the importance of these compounds for the success of nematode infection in Medicago truncatula. We reported quantification of GSH and hGSH and gene expression analysis showing that (h)GSH metabolism in neoformed gall organs differs from that in uninfected roots. Depletion of (h)GSH content impaired nematode egg mass formation and modified the sex ratio. In addition, gene expression and metabolomic analyses showed a substantial modification of starch and γ-aminobutyrate metabolism and of malate and glucose content in (h)GSH-depleted galls. Interestingly, these modifications did not occur in (h)GSH-depleted roots. These various results suggest that (h)GSH have a key role in the regulation of giant cell metabolism. The discovery of these specific plant regulatory elements could lead to the development of new pest management strategies against nematodes

Widely variable endogenous retroviral methylation levels in human placenta

It is generally assumed that transposable elements, including endogenous retroviruses (ERVs), are silenced by DNA methylation/chromatin structure in mammalian cells. However, there have been very few experimental studies to examine the methylation status of human ERVs. In this study, we determined and compared the methylation status of the 5′ long terminal repeats (LTRs) of different copies of the human endogenous retrovirus (HERV) family HERV-E, which are inserted in various genomic contexts. We found that three HERV-E LTRs which function as alternative gene promoters in placenta are unmethylated in that tissue but heavily methylated in blood cells, where these LTRs are not active promoters. This difference is not solely due to global hypomethylation in placenta, since two general measures of methylation levels of HERV-E and HERV-K LTRs suggest only 10–15% lower overall HERV methylation in placenta compared to blood. Comparisons between methylation levels of the LTR-derived gene promoters and six random HERV-E LTRs in placenta showed that the former display significantly lower methylation levels than random LTRs. Moreover, the differences in methylation between LTRs cannot always be explained by their genomic environment, since methylation of flanking sequences can be very different from methylation of the LTR itself

Krüppel-Like Factor 6 Expression Changes during Trophoblast Syncytialization and Transactivates ßhCG and PSG Placental Genes

BACKGROUND: Krüppel-like factor-6 (KLF6) is a widely expressed member of the Sp1/KLF family of transcriptional regulators involved in differentiation, cell cycle control and proliferation in several cell systems. Even though the highest expression level of KLF6 has been detected in human and mice placenta, its function in trophoblast physiology is still unknown. METHODOLOGY/PRINCIPAL FINDINGS: Herein, we explored KLF6 expression and sub-cellular distribution in human trophoblast cells differentiating into the syncytial pathway, and its role in the regulation of genes associated with placental development and pregnancy maintenance. Confocal immunofluorescence microscopy demonstrated that KLF6 is expressed throughout human cytotrophoblast differentiation showing no evident modifications in its nuclear and cytoplasmic localization pattern. KLF6 transcript and protein peaked early during the syncytialization process as determined by qRT-PCR and western blot assays. Overexpression of KLF6 in trophoblast-derived JEG-3 cells showed a preferential nuclear signal correlating with enhanced expression of human β-chorionic gonadotropin (βhCG) and pregnancy-specific glycoprotein (PSG) genes. Moreover, KLF6 transactivated βhCG5, PSG5 and PSG3 gene promoters. Deletion of KLF6 Zn-finger DNA binding domain or mutation of the consensus KLF6 binding site abolished transactivation of the PSG5 promoter. CONCLUSIONS/SIGNIFICANCE: Results are consistent with KLF6 playing a role as transcriptional regulator of relevant genes for placental differentiation and physiology such as βhCG and PSG, in agreement with an early and transient increase of KLF6 expression during trophoblast syncytialization

Cell fusions in mammals

Cell fusions are important to fertilization, placentation, development of skeletal muscle and bone, calcium homeostasis and the immune defense system. Additionally, cell fusions participate in tissue repair and may be important to cancer development and progression. A large number of factors appear to regulate cell fusions, including receptors and ligands, membrane domain organizing proteins, proteases, signaling molecules and fusogenic proteins forming alpha-helical bundles that bring membranes close together. The syncytin family of proteins represent true fusogens and the founding member, syncytin-1, has been documented to be involved in fusions between placental trophoblasts, between cancer cells and between cancer cells and host cells. We review the literature with emphasis on the syncytin family and propose that syncytins may represent universal fusogens in primates and rodents, which work together with a number of other proteins to regulate the cell fusion machinery

RESISTENZA A FATICA DI GIUNZIONI SALDATE SOLLECITATE CON CARICO COMBINATO DI FLESSIONE E TORSIONE

Nel presente lavoro vengono discussi i risultati di una estesa campagna sperimentale di caratterizzazione della resistenza a fatica di giunzioni saldate. La giunzione esaminata, collegamento con cordone d’angolo tra un tubo ed una piastra entrambi in acciaio SR355, è impiegata nella realizzazione di carrelli ferroviari. Sono state eseguite prove in flessione pura, torsione pura e con carico combinato in fase e fuori fase, con due diversi rapporti flessione/torsione, con R = 0 e R = -1. L’arresto della prova era determinato dal segnale di un sensore che rilevava la pressione interna al tubo (un brusco calo di pressione è indice di una fessura passante). I risultati, interpretati con il metodo delle tensioni nominali, mostrano come generalmente i criteri di progettazione forniti dalle normative di riferimento siano cautelativi e come, allo stesso tempo, la resistenza a fatica di giunzioni saldate in presenza di condizioni di carico multiassiale debba considerarsi un campo di ricerca ancora aperto

Analytical model for the power losses in rubber V-belt continuously variable transmission (CVT)

In the present work closed form relationships for the power losses in rubber V-belt CVT are obtained, together with expressions for the axial thrust on both the driving and driven pulleys, starting fromsimple physical hypotheses. Losses have been grouped into threemain contributions: frictional sliding losses, longitudinal and lateral material hysteresis and frictional losses due to the engagement/disengagement of the belt at the entrance and exit from the pulleys. In order to keep the model simple and to obtain a closed form solution, circumferential slip is assumed to take place mainly in the driven pulley and the sliding angle is assumed constant along the sliding portion of the contact arc. Themodel was validated through comparisonwith experimental results obtained on a dedicated test bench capable of measuring the transmitted torques and the axial thrusts on both pulleys, the pulleys rotating speeds and the total belt tension. The sliding angle γ and the damping coefficient Ψ,which were introduced in the analytical relationships,were determined by a best fit procedure on the basis of the obtained experimental results. After having obtained those parameters, the model appeared to be capable of reproducing with a fairly satisfactory agreement the power losses, as well as the axial loads on the pulleys, which were obtained in different operating conditions; thus it is proposed as a useful tool for the design of this kind of transmission