Combined effect of Sn addition and pre-ageing on natural secondary and artificial ageing of Al–Mg–Si alloys

Both Sn addition and pre-ageing are known to be effective in maintaining the artificial ageing potential after natural ageing of Al–Mg–Si alloys. In this study, the combined effects of Sn addition and pre-ageing at 100 °C or 180 °C on natural secondary ageing and subsequent artificial ageing of an alloy AA6014 were investigated using hardness, electrical resistivity, differential scanning calorimetry and transmission electron microscopy characterizations. It is found that pre-ageing can suppress natural secondary ageing and improve the artificial ageing hardening kinetics and response after 1 week of natural secondary ageing in both alloys with and without Sn addition. The effect of pre-ageing at 100 °C is more pronounced in the Sn-free alloy while the combination of pre-ageing at 180 °C and adding Sn shows superiority in suppressing natural secondary ageing and thus avoiding the undesired hardening before artificial ageing. Moreover, when natural ageing steps up to 8 h are applied before pre-ageing at 100 °C, the effect of pre-ageing in Sn-added alloy can be further improved. The influence of Sn on vacancies at different ageing temperatures is discussed to explain the observed phenomena. Graphical abstract

Precipitation Effects in Cast, Heat-Treated and Cold-Rolled Aluminium AA7075 Alloy with Sc,Zr-Addition

The commercial Al–Zn–Mg–Cu-based alloys (7xxx series) are widely used in metalworking, automotive and aircraft industries as well as in aeronautical applications. The positive effect of the Sc,Zr-addition on mechanical properties of laboratory Al-based alloys is generally known. The microstructure, mechanical and thermal properties of the conventionally cast, heat-treated and cold-rolled Al–Zn–Mg–Cu (–Sc–Zr) alloys during isochronal annealing and natural ageing were studied. Microstructure observation by scanning electron microscopy and transmission electron microscopy proved the Zn,Mg,Cu-containing eutectic phase at grain boundaries. The distinct changes in microhardness curves as well as in a heat flow of the alloys studied are mainly caused by dissolution of the clusters/Guinier-Preston (GP) zones and precipitation of particles from the Al–Zn–Mg–Cu system. An easier diffusion of Zn, Mg and Cu atoms along dislocations in the cold-rolled alloys is responsible for the precipitation of the Zn,Mg,Cu-containing particles at lower temperatures compared to the cast alloys. Microhardness values of the heat-treated alloys increase immediately from the beginning of natural ageing due to the formation of the clusters/GP zones. Addition of Sc and Zr elements results in a higher hardness above ~ 270 °C due to a strengthening by coherent secondary Al3(Sc,Zr) particles with a good thermal stability. Sc,Zr-addition has probably no influence on the evolution of the solute clusters/GP zones.

Pulmonary Alveolar Stem Cell Senescence, Apoptosis, and Differentiation by p53-Dependent and -Independent Mechanisms in Telomerase-Deficient Mice

Pulmonary premature ageing and fibrogenesis as in idiopathic pulmonary fibrosis (IPF) occur with the DNA damage response in lungs deficient of telomerase. The molecular mechanism mediating pulmonary alveolar cell fates remains to be investigated. The present study shows that naturally occurring ageing is associated with the DNA damage response (DDR) and activation of the p53 signalling pathway. Telomerase deficiency induced by telomerase RNA component (TERC) knockout (KO) accelerates not only replicative senescence but also altered differentiation and apoptosis of the pulmonary alveolar stem cells (AEC2) in association with increased innate immune natural killer (NK) cells in TERC KO mice. TERC KO results in increased senescence-associated heterochromatin foci (SAHF) marker HP1γ, p21, p16, and apoptosis-associated cleaved caspase-3 in AEC2. However, additional deficiency of the tumour suppressor p53 in the Trp53−/− allele of the late generation of TERC KO mice attenuates the increased senescent and apoptotic markers significantly. Moreover, p53 deficiency has no significant effect on the increased gene expression of T1α (a marker of terminal differentiated AEC1) in AEC2 of the late generation of TERC KO mice. These findings demonstrate that, in natural ageing or premature ageing accelerated by telomere shortening, pulmonary senescence and IPF develop with alveolar stem cell p53-dependent premature replicative senescence, apoptosis, and p53-independent differentiation, resulting in pulmonary senescence-associated low-grade inflammation (SALI). Our studies indicate a natural ageing-associated molecular mechanism of telomerase deficiency-induced telomere DDR and SALI in pulmonary ageing and IPF.

Characterisation and Modelling of PLA Filaments and Evolution with Time

The properties of polylactic acid (PLA) filaments have not yet been analysed in detail, and they are strongly affected by the extrusion process used in some additive manufacturing systems. Here we present the mechanical, thermal, physical, and fractographical properties of an extruded filament (not the bulk material or scaffolds), the basic building block of any PLA structure printed via material extrusion. This research aims to create a reference point for the modelisation of additively manufactured structures via extrusion processes, as the main building block is characterised in detail for a deep understanding. Furthermore, we investigated the natural ageing (up to one year), the effect of the printing (extruding) temperature (180 and 190 °C), and the effect of the crosshead speed during the tensile tests (10−1 to 102 mm/min) to provide a deeper analysis of the material. The results showed that the material extruded at 190 °C performed better than the material extruded at 180 °C. However, after one hundred days of natural ageing, both materials behaved similarly. This was related to the flow-induced molecular orientation during the extrusion. The crosshead rate produced a logarithmic increase of the mechanical properties, consistent with the Eyring model. Additionally, the ageing produced significant changes in both the elastic modulus and the yield strength: from 2.4 GPa and 40 MPa, in one-day-aged samples, up to 4 GPa and 62 MPa once entirely aged. Finally, it was observed that the glass transition and the enthalpic relaxation increased with ageing, agreeing with the Kohlraushch–William–Watts model.

Comparative Morphological Investigation between Natural Photo-Aged of Two Different Low Density Polyethylene Green House Covers

This work studies and compares the degradation performance of two different types of blown extruded films of low density polyethylene films used as greenhouse covers. The first one is LDPE (B24/2) supplied by ENIP Skikda and the other one is LDPE (2100 T N00W) supplied by SABIC, Saudi Arabia. Both films are commonly used in Algeria as greenhouse covers. The films were exposed outdoors over a period of 8 months for natural ageing. XRD and DSC analysis were conducted to characterize the thermal properties of the materials and compare between their degradation behaviors. The results revealed that the degradation resistance of LDPE (B24/2) is better than LDPE (2100T N00W) in term of their degree of crystallinity. Keywords: Natural Ageing, LDPE (B24/2); LDPE (2100 T N00W); Degree of Crystallinity, XRD; DSC.

Sexuality in palliative care

Experiencing a life-limiting illness has the potential to radically transform every aspect of a person’s life, including how they feel about themselves, their body, and their sense of self within intimate and sexual relationships. For many people with a life-limiting illness, intimate and sexual moments are a vital aspect of their life, providing a sense of connectedness and assisting the person to explore and find meaning to living, dying, and death. Few health professionals view patients in their care as sexual beings and if they do, they struggle to know what and how to raise the topic of sexuality and intimacy within their clinical roles. This chapter defines patient sexuality and intimacy in the context of palliative care, explores the impact of natural ageing and treatment for cancer and chronic illnesses, and provides an introduction to opening communication and providing practical strategies to support the patient through intimate and sexual changes.

Accelerated Ageing Mediated Seed Longevity Prediction and Assessment of Seed Deterioration Pattern through 2D-Gel Electrophoresis in Chickpea (Cicer arietinum L.)

Background: Accelerated ageing is a method to assess seed storage performance by exposing the seeds to higher temperature and relative humidity to make seeds lose its vigour and viability quickly. The seed physiological parameters are then compared with the natural ageing to derive certain conclusions. But, the molecular pattern of seed deterioration under accelerated ageing varies compared to that of natural ageing.Methods: Chickpea, seed lots of variety JG-11 and Annigeri-1 were subjected to natural ageing in cloth bag with nine per cent initial seed moisture under ambient conditions. Simultaneously, representative sample of same seed lot were also aged at 41oC and 95±2% humidity up to 120 hours.Result: Both the ageing methods had significant negative effect on seed physiological and biochemical quality parameters. The germination potential of seeds tested after 48 hours of accelerated ageing (83.5%) was equal 10 months of natural ageing (85%) in JG-11, while also in Annigeri-1, 48 hours of accelerated ageing (78%) was nearly equal to 10 months of natural ageing (80%). The protein expression analyzed through 2D-PAGE at similar germination potential brought out by two independent ageing methods showed higher protein down regulation ratio (3.4) in accelerated ageing than in natural ageing (3.2) unveiling its rapidity in the seed deterioration process. Therefore, accelerated ageing can be used for predicting chickpea seed longevity.