Stir Casting Routes for Processing Metal Matrix Syntactic Foams: A Scoping Review

Metal matrix syntactic foams (MMSFs) are advanced lightweight materials constituted by a metallic matrix and a dispersion of hollow/porous fillers. Physical and mechanical properties can be fitted regarding matrix and filler properties and processing parameters. Their properties make them potential materials for sectors where density is a limiting parameter, such as transport, marine, defense, aerospace, and engineering applications. MMSFs are mainly manufactured by powder metallurgy, infiltration, and stir casting techniques. This study focuses on the current stir casting approaches and on the advances and deficiencies, providing processing parameters and comparative analyses on porosity and mechanical properties. PRISMA approaches were followed to favor traceability and reproducibility of the study. Stir casting techniques are low-cost, industrially scalable approaches, but they exhibit critical limitations: buoyancy of fillers, corrosion of processing equipment, premature solidification of molten metal during mixing, cracking of fillers, heterogeneous distribution, and limited incorporation of fillers. Six different approaches were identified; four focus on limiting buoyancy, cracking, heterogeneous distribution of fillers, and excessive oxidation of sensitive matrix alloys to oxygen. These improvements favor reaching the maximum porosity of 54%, increasing the fillers size from a few microns to 45 mm, reducing residual porosity by ±4%, synthesizing bimodal MMSFs, and reaching maximum incorporation of 74 vol%.</jats:p

Leaf litter traits of invasive alien species slow down decomposition compared to Spanish natives: a broad phylogenetic comparison.

Leaf traits related to the performance of invasive alien species can influence nutrient cycling through litter decomposition. However, there is no consensus yet about whether there are consistent differences in functional leaf traits between invasive and native species that also manifest themselves through their "after life" effects on litter decomposition. When addressing this question it is important to avoid confounding effects of other plant traits related to early phylogenetic divergences and to understand the mechanism underlying the observed results to predict which invasive species will exert larger effects on nutrient cycling. We compared initial leaf litter traits, and their effect on decomposability as tested in standardized incubations, in 19 invasive-native pairs of co-familial species from Spain. They included 12 woody and seven herbaceous alien species representative of the Spanish invasive flora. The predictive power of leaf litter decomposition rates followed the order: growth form > family > status (invasive vs. native) > leaf type. Within species pairs litter decomposition tended to be slower and more dependent on N and P in invaders than in natives. This difference was likely driven by the higher lignin content of invader leaves. Although our study has the limitation of not representing the natural conditions from each invaded community, it suggests a potential slowing down of the nutrient cycle at ecosystem scale upon invasion. © Springer-Verlag 2009

Coastal Dunes and Marshes in Doñana National Park

Doñana Natural Park is a good global example of the sedimentary filling of a broad tidal estuary during the Mid-Late Holocene, after the last postglacial sea-level rise. The timing of this rise is not well defined yet in the Gulf of Cádiz, since the oldest evidence of coastal sedimentation, located at the right bank of the mouth of the old Guadalquivir Estuary, dates ack to ca. 5,000 ears ago. The first evolutionary stages of the embayment indicate an obvious marine influence, dominated by waves and storms from the SW. Since ca. 4,000 years ago, protection provided by the growing coastal spit barrier of Doñana favored the development of a sheltered marsh dominated by tides and fluvial currents. About 2,200 years ago, since the time Romans controlled the area, the estuary was dominated by marshlands with a wide lagoon at its mouth (Lacus Ligustinus), and the current landscape of Doñana started to form. The evolution of the last 2,000 years includes the quick and continuous growth of coastal barriers by longshore drift, the origin of the present-day marshland landscape and the development of dune fields migrating inland towards the wetlands

Demonstration of event position reconstruction based on diffusion in the NEXT-white detector

Noble element time projection chambers are a leading technology for rare event detection in physics, such as for dark matter and neutrinoless double beta decay searches. Time projection chambers typically assign event position in the drift direction using the relative timing of prompt scintillation and delayed charge collection signals, allowing for reconstruction of an absolute position in the drift direction. In this paper, alternate methods for assigning event drift distance via quantification of electron diffusion in a pure high pressure xenon gas time projection chamber are explored. Data from the NEXT-White detector demonstrate the ability to achieve good position assignment accuracy for both high- and low-energy events. Using point-like energy deposits from 83mKr calibration electron captures (E∼45&nbsp;keV), the position of origin of low-energy events is determined to 2&nbsp;cm precision with bias &lt;1mm. A convolutional neural network approach is then used to quantify diffusion for longer tracks (E≥1.5&nbsp;MeV), from radiogenic electrons, yielding a precision of 3&nbsp;cm on the event barycenter. The precision achieved with these methods indicates the feasibility energy calibrations of better than 1%&nbsp;FWHM at Qββ in pure xenon, as well as the potential for event fiducialization in large future detectors using an alternate method that does not rely on primary scintillation