Thermomechanical performance of continuous carbon fibre composite materials produced by a modified 3D printer.

First of all, this article aimed to evidence the role of a modified printer developed for continuous carbon fibre reinforced PolyAmide (cCF/PA6-I) together with the use of a fully open slicing step on the printing quality and the longitudinal/transverse tensile and in-plane shear properties. A comprehensive assessment of the microstructure and properties with a similar material (cCF/PA6-I), but produced with a commercial printer (i.e., Markforged® MarkTwo) has been achieved. Our customised printer and the open slicer used have made possible to better control the print conditions (i.e., layer height and distance between filaments), to reduce the porosity from more than 10% to about 2% and improve the mechanical properties. Moreover, the understanding of the behaviour of these 3D printed composites with wide-ranging external temperatures is mandatory for future use in a severe environment and/or development of new thermally active 4D printed composites. The 3D printed cCF/PA6-I composites have been then thermomechanically characterised along different printing directions (0, 90 and ± 45°) from -55 to +100 °C. Unlike the longitudinal properties that hardly change with temperature, the transverse and in-plane shear stiffness and strength of these 3D printed composites were particularly sensitive to temperature variations, with decreases of 25-30% and 30-55%, respectively. This was due to the high sensitivity of the polymer matrix, the fibre/matrix and interfilament interfaces when the composites were loaded along those directions, because damages induced by internal thermal stresses. Fractography has also been carried out to reveal damage mechanisms.

On the intensity decay of tropical cyclones before landfall.

It remains unclear how tropical cyclones (TCs) decay from their ocean lifetime maximum intensity (LMI) to landfall intensity (LI), yet this stage is of fundamental importance governing the socio-economic impact of TCs. Here we show that TCs decay on average by 25% from LMI to LI. A logistic decay model of energy production by ocean enthalpy input and surface dissipation by frictional drag, can physically connect the LMI to LI. The logistic model fits the observed intensity decay as well as an empirically exponential decay does, but with a clear physical foundation. The distance between locations of LMI and TC landfall is found to dominate the variability of the decay from the LMI to LI, whereas environmental conditions are generally less important. A major TC at landfall typically has a very large LMI close to land. The LMI depends on the heating by ocean warming, but the LMI location is also important to future landfall TC intensity changes which are of socio-economic importance.

More tropical cyclones are striking coasts with major intensities at landfall.

In this study, we show that the number of annual global tropical cyclone (TC) landfalls with major landfall intensity (LI ≥ 50 m s-1) has nearly doubled from 1982 to 2020. The lifetime maximum intensity (LMI) of global major landfalling TCs has been increasing by 0.8 m s-1 per decade (p < 0.05), but this significance of intensity change disappears at landfall (0.3 m s-1 per decade, p = 0.69). The lack of a significant LI trend is caused by the much larger variance of LI than that of LMI in all basins and explains why a significant count change of TCs with major intensity at landfall has only now emerged. Basin-wide TC trends of intensity and spatial distribution have been reported, but this long-term major TC landfall count change may be the most socio-economic significant.

Probiotic bacteria lactobacillus and bifidobacterium attenuate inflammation in dextran sulfate sodium-induced experimental colitis in mice.

It is widely accepted that inflammatory Bowel disease (IBD) arises from a dysregulated mucosal immune response to the enteric microbiota in the gut of a genetically susceptible individual. No definitive therapies are available for this inflammatory disorder. Therefore it became imperative to develop new strategies for treating this disease. Probiotics have emerged as a potential new therapeutic strategy for IBD, however their exact mechanisms of action is still poorly defined. In this study, we address the potential effect of a probiotic cocktail (Ultrabiotique®) composed of four live bacterial strains (L. acidophilus, L. plantarum, B. lactis and B.breve) to promote recovery from acute colitis. Probiotic was given to mice by oral gavage after the onset of colitis and the establishment of dextran sulfate sodium (DSS)-induced intestinal injury. Clinical parameters were monitored daily, histological scores of colitis and the production of nitric oxide (NO) and interferon-γ (IFN-γ) were determined. In addition, TLR4, NF-κB and iNOS colonic expression were examined. Probiotic treatment ameliorated clinical symptoms and histological scores. NO and IFN-γ production in plasma were decreased by probiotic. These results were associated with reduced TLR4, iNOS and NF-кB expression in colonic tissue. In conclusion, probiotic exerted anti-inflammatory effects and contributed to a rapid recovery of DSS-induced acute colitis.

Open Air Laboratories (OPAL): a community-driven research programme.

OPAL is an English national programme that takes scientists into the community to investigate environmental issues. Biological monitoring plays a pivotal role covering topics of: i) soil and earthworms; ii) air, lichens and tar spot on sycamore; iii) water and aquatic invertebrates; iv) biodiversity and hedgerows; v) climate, clouds and thermal comfort. Each survey has been developed by an inter-disciplinary team and tested by voluntary, statutory and community sectors. Data are submitted via the web and instantly mapped. Preliminary results are presented, together with a discussion on data quality and uncertainty. Communities also investigate local pollution issues, ranging from nitrogen deposition on heathlands to traffic emissions on roadside vegetation. Over 200,000 people have participated so far, including over 1000 schools and 1000 voluntary groups. Benefits include a substantial, growing database on biodiversity and habitat condition, much from previously unsampled sites particularly in urban areas, and a more engaged public.

Long-memory analysis of time series with missing values.

The estimation of long memory is often restricted by missing data. We examine the effects on the estimation of long memory of three simple gap-filling techniques: interpolation, random, and mean filling. Numerical simulations show that the gap-filling techniques introduce significant deviations from the expected scaling behavior for both persistent and antipersistent time series. For persistent time series the interpolation method provides a reliable estimation of long memory for scales longer than the largest likely gap.

The "Ozone Deficit" Problem: O2(X, v ge 26) + O(3P) from 226-nm Ozone Photodissociation.

Highly vibrationally excited O(2)(X(3)sigmag(-), v >/= 26) has been observed from the photodissociation of ozone (O(3)), and the quantum yield for this reaction has been determined for excitation at 226 nanometers. This observation may help to address the "ozone deficit" problem, or why the previously predicted stratospheric O(3) concentration is less than that observed. Recent kinetic studies have suggested that O(2)(X(3)sigmag(-), v >/= 26) can react rapidly with O(2) to form O(3) + O and have led to speculation that, if produced in the photodissociation of O(3), this species might be involved in resolving the discrepancy. The sequence O(3) + hv --> O(2)(X(3)sigmag(-), v >/= 26) + O; O(2)(X(3)sigmag(-), v >/= 26) + O(2) --> O(3) + O (where hv is a photon) would be an autocatalytic mechanism for production of odd oxygen. A two-dimensional atmospheric model has been used to evaluate the importance of this new mechanism. The new mechanism can completely account for the tropical O(3) deficit at an altitude of 43 kilometers, but it does not completely account for the deficit at higher altitudes. The mechanism also provides for isotopic fractionation and may contribute to an explanation for the anomalously high concentration of heavy O(3) in the stratosphere.

Role of sulphur photochemistry in tropical ozone changes after the eruption of Mount Pinatubo.

RECENT observations suggest that the eruption of Mount Pinatubo in June 1991 has had a considerable effect on ozone concentrations in the tropical stratosphere (refs 1, 2, and J. W. Waters, personal communication). Although stratospheric ozone losses following volcanic eruptions are generally attributed to the presence of sulphate aerosol3-7, we present model calculations which demonstrate that gas-phase sulphur chemistry may have played a part in the tropical ozone perturbations that followed the Pinatubo eruption. We find that in the first month or so after the eruption, the large amount of SO2 injected into the tropical atmosphere catalyses mid-stratospheric ozone production. On the other hand, the SO2 cloud absorbs solar radiation, thereby reducing the rate of O2 photolysis (and hence of ozone production) below it. These two effects cancel each other out at an altitude of about 25 kilometres. After one or two months, most of the SO2 has been oxidized to sulphate; the efficiency of these two mechanisms then becomes negligible (although ozone remains perturbed in the lower stratosphere because of its long photochemical lifetime in this region). The model features show good agreement with initial ozone measurements following the eruption, including both the mid-altitude switch from ozone loss to ozone gain1, and the increase and subsequent decrease in the total ozone column2,7.