Tribological behavior of functionalized 1-2 layered graphene/uhmwpe composites

In this work we present the evaluation of pristine and functionalized graphene as reinforcements for UHMWPE-based composites. These composites were manufactured by physically blending graphene particles and medical grade UHMWPE powder followed by a thermo-compression process. Mechanical behaviour by means of uniaxial tension and biaxial load by small punch were carried out. Friction coefficient and wear rate were measured. In some cases composites enhanced stiffness and yield stress, although with loss of toughness. This mechanical behaviour was recuperated after a thermal treatment. Small positive changes were obtained with some graphene concentrations respect to the friction coefficient. However, 20 % of reduction in wear rate was obtained when the graphene was functionalized. In general these composites present a good trend to be a potential alternative to the current highly crosslinked polyethylenes.We thank the Ministry of Science and Education of Spain by means of the projects MAT2010-16175) and CONSOLIDER CSD2008-00023 (FUNCOAT) for financial suppor

Introducing the 'First European Symposium on the Evolution of Crocodylomorpha'

The First European Symposium on the Evolution of Crocodylomorpha took place during the XVI Annual Meeting of the European Association of Vertebrate Palaeontologists (EAVP) organized by NOVA University of Lisbon (UNL) in Caparica, Portugal. Fourteen lectures and five posters were presented at the symposium in June 26th-July 1st, 2018. This special issue showcases twelve papers based on symposium contributions.publishersversionpublishe

Exceptional crocodylomorph biodiversity of “La Cantalera” site (Lower barremian; lower cretaceous) in Teruel, Spain

The palaeontological site of La Cantalera in Teruel, Spain (Blesa Formation, Lower Cretaceous) can be characterized as the site with the greatest biodiversity of vertebrates (32 taxa) from the lower Barremian of the Iberian Peninsula. Remains of amphibians, lizards, turtles, crocodiles, pterosaurs, dinosaurs and mammals have been recovered. The most common taxa are crocodylomorphs, and their most abundant remains are small isolated teeth. Six morphotypes have been identified, which may correspond to at least four different sympatric crocodylomorph taxa. This site presents a similar assemblage to other European Lower Cretaceous sites, with morphotypes that may correspond to the families Goniopholididae, Bernissartiidae, Atoposauridae and multiple ziphodont crocodylomorphs. The crocodylomorph assemblage of La Cantalera is characterized by the absence of large individuals and presents a wide variety of dental morphologies adapted to diets ranging from generalist to highly specialized. This rich biodiversity could be due to concentration of vertebrates into restricted flooded areas during dry seasons within a marsh ecosystem. Furthermore, La Cantalera could also be close to a nesting area, which would explain the abundance of small-sized individuals and the presence of fossil crocodiloid eggshells

New material from a huge specimen of "Anteophthalmosuchus" cf. "escuchae" (Goniopholididae) from the Albian of Andorra (Teruel, Spain): Phylogenetic implications

In 2011 the partial skeleton of a goniopholidid crocodylomorph was recovered in the ENDESA coal mine Mina Corta Barrabasa (Escucha Formation, lower Albian), located in the municipality of Andorra (Teruel, Spain). This new goniopholidid material is represented by abundant postcranial and fragmentary cranial bones. The study of these remains coincides with a recent description in 2013 of at least two new species of goniopholidids in the palaeontological site of Mina Santa María in Ariño (Teruel), also in the Escucha Formation. These species are Anteophthalmosuchus escuchae, Hulkepholis plotos and an undetermined goniopholidid, AR-1-3422. In the present paper, we describe the postcranial and cranial bones of the goniopholidid from Mina Corta Barrabasa and compare it with the species from Mina Santa María. For the first time, we include the taxa from the Escucha Formation in a phylogenetic analysis to establish their relationships within Goniopholididae, adding to what is known of the goniopholidid fossil assemblages from this time interval. The results indicate that the specimen from Mina Corta Barrabasa is closely related to Anteophthalmosuchus escuchae and may be the same species. Together with Hulkepholis plotos and other taxa from England and Belgium, these taxa form an endemic European clade. The Escucha Fm. goniopholidids are the youngest Eurasian members of the group and may be the youngest globally, depending on how North American taxa are eventually resolved.En 2011 se recuperó parte de un esqueleto de crocodilomorfo goniofolídido en la mina de carbón Mina Corta Barrabasa (Formación Escucha, Albiense inferior). Esta mina pertenece a la compañía ENDESA, y está localizada en Andorra (Teruel, España). Este nuevo ejemplar de crocodilomorfo está representado por abundante material postcraneal y restos craneales fragmentarios. Nuestro estudio coincide con la reciente descripción en 2013 de las nuevas especies de goniofolídidos Anteophthalmosuchus escuchae y Hulkepholis plotos en la Formación Escucha (Mina Santa María en Ariño, Teruel). En este trabajo se describen los restos postcraneales y craneales del goniofolídido de Mina Corta Barrabasa y se comparan con las nuevas especies de Mina Santa María, además se propone por primera vez una codificación cladística para los taxones de la Formación Escucha. Esta información se ha incorporado a un análisis filogenético para establecer las relaciones filogenéticas de estos taxones dentro de Goniopholididae ayudando a comprender las asociaciones fósiles de los goniofolídidos dentro de este intervalo temporal. Los resultados indican que el espécimen de Mina Corta Barrabasa está estrechamente relacionado con Anteophthalmosuchus escuchae y podría pertenecer a la misma especie. Ambos taxones, junto a Hulkepholis plotos y otros taxones de Inglaterra y Bélgica, forman un clado endémico europeo. Los goniofolídidos de la Fm. Escucha son los miembros más jóvenes de Goniopholididae en Eurasia, y podrían ser los más modernos del mundo dependiendo de cómo se resuelvan finalmente la posición de los taxones norteamericanos

Influence of processing conditions on microstructural, mechanical and tribological properties of graphene nanoplatelet reinforced UHMWPE

Ultra-high molecular weight polyethylene (UHMWPE) is a relevant thermoplastic in industry and a well-proven standard biomaterial in joint replacements. To enhance its tribological properties while preserving its bulk ones, composite coatings on a UHMWPE substrate were prepared using non-functionalised graphene nanoplatelet (GNP) at reinforcement concentration of 0.1–5 wt% and two mechanical mixing techniques (ball mill or blade mixer) with different consolidation temperatures of 175–240 °C. Changes in morphology and size of the UHMWPE particles before hot-pressing were observed in function of the mechanical mixing techniques applied. Wear rate was affected by graphene content, reaching a minimum at 0.5 wt% GNP, with a reduction of 20 and 15%, for ball milling and blade mixer, respectively. However, blade mixer increased the wear rate by around twice respect the ball milling results, for all the studied materials. The coefficient of friction decreased notably, by ~25%, below 3 wt% GNP content, and hardness increased by 24%, regardless of the mechanical mixing process used. Finally, consolidation temperature had a positive influence on wear rate at temperatures of around 195 °C, which could be related to the free radical scavenger effect of the GNP

Neuroanatomy of the crocodylomorph Portugalosuchus azenhae from the late cretaceous of Portugal

We present the first detailed braincase anatomical description and neuroanatomical study of Portugalosuchus azenhae, from the Cenomanian (Late Cretaceous) of Portugal. This eusuchian crocodylomorph was originally described as a putative Crocodylia and one of the oldest representatives of this clade; however, its phylogenetic position remains controversial. Based on new data obtained from high resolution Computed Tomography images (by micro-CT scan), this study aims to improve the original description of this taxon and also update the scarce neuroanatomical knowledge of Eusuchia and Crocodylia from this time interval, a key period to understand the origin and evolution of these clades. The resulting three-dimensional models from the CT data allowed a detailed description of its well-preserved neurocranium and internal cavities. Therefore, it was possible to reconstruct the cavities of the olfactory region, nasopharyngeal ducts, brain, nerves, carotid arteries, blood vessels, paratympanic sinus system and inner ear, which allowed to estimate some neurosensorial capabilities. By comparison with other crocodylomorphs, these analyses showed that Portugalosuchus, back in the Cenomanian, already displayed an olfactive acuity, sight, hearing and cognitive skills within the range of that observed in other basal eusuchians and crocodylians, including extant species. In addition, and in order to test its disputed phylogenetic position, these new anatomical data, which helped to correct and complete some of the original observations, were included in one of the most recent morphology-based phylogenies. The position of Portugalosuchus differs slightly from the original publication since it is now located as a "thoracosaurid" within Gavialoidea, but still as a crocodylian. Despite all this, to better contrast these results, additional phylogenetic analyses including this new morphological character coding together with DNA data should be performed

A new plesiosaur from the Lower Jurassic of Portugal and the early radiation of Plesiosauroidea

A new plesiosaur partial skeleton, comprising most of the trunk and including axial, limb, and girdle bones, was collected in the lower Sinemurian (Coimbra Formation) of Praia da Concha, near São Pedro de Moel in central west Portugal. The specimen represents a new genus and species, Plesiopharos moelensis gen. et sp. nov. Phylogenetic analysis places this taxon at the base of Plesiosauroidea. Its position is based on this exclusive combination of characters: Presence of a straight preaxial margin of the radius; transverse processes of mid-dorsal vertebrae horizontally oriented; ilium with sub-circular cross section of the shaft and subequal anteroposterior expansion of the dorsal blade; straight proximal end of the humerus; and ventral surface of the humerus with an anteroposteriorly long shallow groove between the epipodial facets. In addition, the new taxon has the following autapomorphies: Iliac blade with less expanded, rounded and convex anterior flank; highly developed ischial facet of the ilium; apex of the neural spine of the first pectoral vertebra inclined posterodorsally with a small rounded tip. This taxon represents the most complete and the oldest plesiosaur species in the Iberian Peninsula. It is also the most complete, best preserved, and oldest marine vertebrate in the region and testifies to the incursion of marine reptiles in the newly formed proto-Atlantic sea, prior to the Atlantic Ocean floor spreading in the Early Cretaceous.publishersversionpublishe

A new crocodylomorph related ootaxon from the late Maastrichtian of the Southern Pyrenees (Huesca, Spain)

Crocodylomorph eggs and eggshells are known as old as the Late Jurassic and are frequent components of most multiootaxic eggshell assemblages. Classified within the oofamily Krokolithidae, thei histo- and ultrastructures are conservative throughout geological time, characterised by inverted-trapezoid-shaped shell units that grow from highly spaced basal knobs and present a diagnostic tabular ultrastructure. Here, we report 327 eggshell fragments from a new fossil site from the Maastrichtian of the Southern Pyrenees, Veracruz 1, and erect a new oogenus and oospecies, Pachykrokolithus excavatum oogen. et oosp. nov. characterised by crocodyloid morphotype and a prominent rugosocavate ornamentation. Eggshells from the slightly older locality of Blasi 2b, previously reported as aff. Krokolithidae, are also assigned to this new ootaxon. Different crocodylomorph taxa coexisted during the Late Cretaceous of the Tremp Basin, hindering the attribution of Pachykrokolithus excavatum oogen. et oosp. nov. to a single clade. Nevertheless, allodaposuchid eusuchians were dominant in this ecosystem, and are the most probable producers of Pachykrokolithus excavatum oogen. et oosp. nov. eggs

A new vertebrate assemblage from the matute formation of the Cameros Basin (Ágreda, Spain): implications for the diversity during the jurassic/cretaceous boundary

Altres ajuts: Open Access funding provided thanks to the CRUE-CSIC agreement with Springer Nature.The Ribota site (Ágreda, Soria, Spain) is a new locality in the Matute Formation (Tithonian-Berriasian) composed of several carbonate layers, outstandingly rich in macrovertebrate remains. Fossils show an unusual replacement of the original bioapatite by quartz, and are found as positive reliefs protruding from lacustrine limestone beds. This type of conservation has allowed the identification of around one hundred vertebrate bone accumulations in an outcrop of more than 10 hectares. Osteichthyans (articulated partial skeletons, cranial material, and isolated postcranial bones and scales), crocodylomorphs (disarticulated cranial material, isolated teeth, vertebrae and osteoderms), turtles (partial carapaces and plastra, but also isolated plates) and pterosaurs (cranial and appendicular elements) have been identified. Around 80 specimens have been collected and a preliminary study of part of the collection (35 specimens) has allowed the identification of at least 5 different taxa: Halecomorphi indet., Neoginglymodi indet., Goniopholididae indet., Testudinata indet., and Pterodactyloidea indet. This new site represents one of the few sites from this time interval preserved in a fully lacustrine environment, so these vertebrate assemblages are unique and composed of different animals that presumably lived around and within the lake. They are dominated by aquatic and amphibian vertebrates and was formed by attrition in this lacustrine environment, possibly far from the lake shoreline. These macrovertebrate assemblages provide new data about the diversity in the faunal ecosystems from the Jurassic/Cretaceous transition of the Iberian Basin Rift System

Palynostratigraphical review of the K–Pg boundary from the Ibero-Armorican Island: New data from the Maastrichtian dinosaur outcrop Veracruz 1 (Pyrenees, NE Iberian Peninsula)

The palynostratigraphy of the K-Pg boundary interval in SW Europe has been a subject of ongoing debate, despite numerous palynological studies in the region. To address this, we review previous publications and conduct analysis of new deposits to establish a palynostratigraphical chart. A total of 40 palynological studies within the Normapolles palynological province were reexamined to elucidate key taxa restricted to the Cretaceous (K-taxa), to the Maastrichtian-Danian interval (KPg-taxa) and those restricted to the Paleogene (Pg-taxa). Eventually, we propose 18 key taxa to differentiate a Maastrichtian from a Danian palynological assemblage within the Normapolles Province. Afterward, a palynostratigraphical analysis was carried out in Veracruz 1 (Aragonese Pyrenees), one of the more modern dinosaurbearing sites of Europe. The palynological assemblage corresponded to an upper Maastrichtian age and was composed by pteridophyte spores, gymnosperms, angiosperms, dinoflagellate cysts, algae, and fungal spores. It was predominated by angiosperm pollen (Liliaceae, post-Normapolles, and triporate pollen). The plant communities in Veracruz 1 seem to be characterized by plants from an open coastal forest prevailed by Liliaceae flowering herbs and Juglandaceae/Myricaceae dicotyledonous trees and shrubs thriving in temperate-warm paleoclimate. The Gondwanan botanical influence was also supported by the presence of Bacumorphomonocolpites sp., as this taxon was previously recorded in other upper Maastrichtian deposits from Europe.Agencia Estatal de Investigación | Ref. PID2021-122612OB-I00Xunta de Galicia | Ref. ED431C-2019/28Xunta de Galicia | Ref. ED481A-2020/175Universidad Nacional Autónoma de México | Ref. UNAM-DGAPA 2023–2024Swedish Research Council | Ref. VR 2022-03920Universidade de Vigo/CISU