Linking rock fabric to fibrous mineralisation: a basic tool for the asbestos hazard

In recent years, many studies have addressed the effect on human health caused by asbestos exposures. As asbestos is a group of fibrous minerals that mainly occurs in mafic and ultramafic rocks (ophiolitic sequences), a close relationship between asbestos occurrence and the geological history of host rocks should be expected. By reviewing the existing literature and presenting characteristic examples, it is proposed a direct correspondence exists between the presence of fibrous minerals in ophiolites and the rock fabric systematics due to the combined activity of deformation, metamorphism/metasomatism, and rock/fluid interaction. Understanding the geological factors that may be at the origin of the nucleation/growth of fibrous minerals constitutes a necessary requirement for developing a methodological and analytical procedure to evaluate asbestos hazard (<I>A</I><sub>H</sub>) in the natural prototype (ophiolitic rocks). A parameterisation of the <I>A</I><sub>H</sub> in function of the main geological processes that produce the rock fabric systematics in different tectonic/geodynamic settings is discussed. A geological multidisciplinary approach (based on geological-structural field evidence combined with textural, mineralogical, petrological, and geochemical investigations) is proposed as the prerequisite for the evaluation of <I>A</I><sub>H</sub> in natural environments. This approach, in particular, can provide a robust basis to formulate a procedural protocol finalised to the mitigation of asbestos effects in environments where these effects are still a real threat

fe analysis of single bolt composite bolted joint by means of a simplified modeling technique

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a novel composite bolted joint element application to a single bolted joint

Abstract Based on an analytical solution of the theoretical reference model of the composite bolted joint undergoing in-plane loads, a modeling technique for this kind of demountable connections is presented. The novel composite bolted joint element substitutes a region of the original model, comprising the bolt and the peripheral area, with a set of radially arranged beams: the cross-section properties are opportunely tailored in order to establish a stiffness equivalence between the theoretical reference model and the presented finite element through the resolution of a system of algebraic equations. The in-plane load condition is considered in this work because of its prevalence in comparison with other ones in many practical applications as the double lap shear joint. Numerical case studies are provided to validate the novel composite bolted joint element comparing FE models of circular plates, featuring a quasi-isotropic lay-up, with an internal rigid core or with the presented FE tool

External Carotid Artery Shunting During Carotid Endarterectomy: An Alternative for Cerebral Protection?

AbstractObjectives: to assess the application of external carotid artery (ECA) shunting in cerebral protection during carotid endarterectomy (CEA). Design: prospective study. Materials and Methods: the study comprised 137 consecutive patients who underwent CEA under locoregional anaesthesia. Transcranial Doppler was used to monitor the mean velocity of the middle cerebral artery (mv-MCA): (1) before carotid clamping; (2) after clamping both the common and external carotid arteries; (3) after clamping the internal carotid artery alone (“ECA test”). The decision to shunt was based on the occurrence of neurological deficit during carotid clamping. If the ECA test revealed mv-MCA approaching the pre-clamping values ECA shunting was used, whereas the remaining patients in need of a shunt had a standard internal carotid artery (ICA) shunt. Results: shunting was necessary in 12/137 cases (9%). The ECA test indicated that in four cases – 3% of the whole series or 33% of the shunted cases. In these four patients ECA shunting reversed the neurological deficit, and CEA was successfully performed without any complications. Conclusions: ECA shunting could be considered as an alternative to standard ICA shunting. Suitable cases can be identified on the basis of the ECA test

TeO2-ZnO-La2O3 glass composition for mid infrared wavelengths generation and transmission in optical fibers

Numerous applications in the Mid InfraRed (Mid IR) wavelength region still require basic optical components such as sources and optical fibers as transmission medium. Thanks to its mid IR transparency and nonlinearity, tellurite glass allows for developing both these types of components. However, practical applications require materials able to handle high optical intensity through enhanced material damage threshold. We report on the synthesis of a tellurite glass in the TeO2-ZnO-La2O3 (TZL) system which presents enhanced thermo mechanical properties with respect to typical tellurite glass compositions. We measured for the TZL composition a glass transition of 626 K, hence 70 K higher than the glass transition temperature of “standard” TZN compositions. The coefficient of thermal expansion was measured to be 138.10-6/K as compared to typical value of 180.10-6/K for TZN glass. We manufactured two types of fibers to assess the prospect for achieving high average power SC sources and Mid IR transmission in TZL glass fibers. First, a high Numerical Aperture (NA) aperture fiber was developed through standard rod in tube technique, where the cladding glass tube was manufactured by extrusion. The 50 μm core fiber presents an optical attenuation value of 0.26 dB/m at 1.55 μm. As an intermediate step towards the fabrication of an antiresonant hollow core fiber for high power transmission, we manufactured a preform and drew it into a cane. A TZL glass tube, 120 mm long and 9 mm/12 mm of inner/outer diameters (ID/OD) was manufactured via rotational casting technique. This latter tube was drawn into a tube of 2 mm in diameter which was cut into sections 130 mm long. Seven of those were stacked in another tellurite glass tube 6.5 mm/12 mm of ID/OD diameters, respectively. This preform was then drawn into a microstructured cane 1.6 mm in diameter which features tubular structures periodically arranged and of uniform thickness

An original FE modelling of a longitudinal multi-passes seam welding

Abstract Both finite element and analytical methods for simulation of welding are essential to predict residual stress and distortions of welded components. Best FE modelling is obtained by using solid elements for thermo-structural simulation with high computational cost. In this contest, an equivalent modelling of plates based on shell elements is proposed in order to streamline the simulations. The equivalent model is composed of n levels of shell elements, centered on the weld seam, in order to evaluate rotations and translations typical of a multi-pass weld. There are as many levels as the number of the weld passes that compose the seam. The interconnection between the n shell levels is realized by rigid beam elements. The latter ones are connected to shell elements by constraint equations. Solid brick models of the plates are used as a benchmark for the equivalent models in thermal and mechanical simulations. The equivalent modelling is in good agreement with solid results, showing a strong decrease of computational burden, enabling the simulation of large welded models in operative conditions

Interactions between carnivore species: limited spatiotemporal partitioning between apex predator and smaller carnivores in a Mediterranean protected area

Background: There is need of information on ecological interactions that keystone species such as apex predators establish in ecosystems recently recolonised. Interactions among carnivore species have the potential to influence community-level processes, with consequences for ecosystem dynamics. Although avoidance of apex predators by smaller carnivores has been reported, there is increasing evidence that the potential for competitive-to-facilitative interactions is context-dependent. In a protected area recently recolonised by the wolf Canis lupus and hosting abundant wild prey (3 ungulate species, 20–30 individuals/km2, together), we used 5-year food habit analyses and 3-year camera trapping to (i) investigate the role of mesocarnivores (4 species) in the wolf diet; (ii) test for temporal, spatial, and fine-scale spatiotemporal association between mesocarnivores and the wolf. Results: Wolf diet was dominated by large herbivores (86% occurrences, N = 2201 scats), with mesocarnivores occurring in 2% scats. We collected 12,808 carnivore detections over > 19,000 camera trapping days. We found substantial (i.e., generally ≥ 0.75, 0–1 scale) temporal overlap between mesocarnivores—in particular red fox—and the wolf, with no support for negative temporal or spatial associations between mesocarnivore and wolf detection rates. All the species were nocturnal/crepuscular and results suggested a minor role of human activity in modifying interspecific spatiotemporal partitioning. Conclusions: Results suggest that the local great availability of large prey to wolves limited negative interactions towards smaller carnivores, thus reducing the potential for spatiotemporal avoidance. Our study emphasises that avoidance patterns leading to substantial spatiotemporal partitioning are not ubiquitous in carnivore guilds

Nuevos datos del uso de la costa en el extremo sur del continente por cazadores-recolectores durante el Holoceno tardío. El sitio Cabo Vírgenes 24 (Santa Cruz, Argentina)

El sitio Cabo Vírgenes 24 (CV24) se ubica en el extremo sureste de la Patagonia continental y presenta ocupaciones entre 753-888 (1270 ± 60 14C A.P - LP3229) y 545-626 años Cal A.P (619 ± 26 14C A.P - AA106800). Los artefactos líticos se confeccionaron con materias primas disponibles localmente (dacita y RGFO). El componente expeditivo de la tecnología concuerda con la de cazadores de guanacos del interior del continente. Se observa una baja densidad y riqueza moderada de especies marinas y terrestres con un énfasis en la explotación de pinnípedos (Arctocephalus australis y Otaria flavescens), seguida de guanacos (Lama guanicoe) y un menor uso de aves marinas (Phalacrocorax sp., Spheniscus magellanicus y Aptenodytes patagonicus). La información provista por CV24 reafirma las tendencias observadas respecto de la utilización esporádica y marginal de la localidad de Cabo Vírgenes por parte de cazadoresrecolectores desde el Holoceno tardío hasta el contacto con los europeos

The natural compound climacostol as a prodrug strategy based on pH activation for efficient delivery of cytotoxic small agents

We synthesized and characterized MOMO as a new small molecule analog of the cytotoxic natural product climacostol efficiently activated in mild extracellular acidosis. The synthesis of MOMO had a key step in the Wittig olefination for the construction of the carbon-carbon double bond in the alkenyl moiety of climacostol. The possibility of obtaining the target (Z)-alkenyl MOMO derivative in very good yield and without presence of the less active (E)-diastereomer was favored from the methoxymethyl ether (MOM)-protecting group of hydroxyl functions in aromatic ring of climacostol aldehyde intermediate. Of interest, the easy removal of MOM-protecting group in a weakly acidic environment allowed us to obtain a great quantity of climacostol in biologically active (Z)-configuration. Results obtained in free-living ciliates that share the same micro-environment of the climacostol natural producer Climacostomum virens demonstrated that MOMO is well-tolerated in a physiological environment, while its cytotoxicity is rapidly and efficiently triggered at pH 6.3. In addition, the cytostatic vs. cytotoxic effects of acidified-MOMO can be modulated in a dose-dependent manner. In mouse melanoma cells, MOMO displayed a marked pH-sensitivity since its cytotoxic and apoptotic effects become evident only in mild extracellular acidosis. Data also suggested MOMO being preferentially activated in the unique extra-acidic microenvironment that characterizes tumoural cells. Finally, the use of the model organism Drosophila melanogaster fed with an acidic diet supported the efficient activity and oral delivery of MOMO molecule in vivo. MOMO affected oviposition of mating adults and larvae eclosion. Reduced survival of flies was due to lethality during the larval stages while emerging larvae retained their ability to develop into adults. Interestingly, the gut of eclosed larvae exhibited an extended damage (cell death by apoptosis) and the brain tissue was also affected (reduced mitosis), demonstrating that orally activated MOMO efficiently targets different tissues of the developing fly. These results provided a proof-of-concept study on the pH-dependence of MOMO effects. In this respect, MOM-protection emerges as a potential prodrug strategy which deserves to be further investigated for the generation of efficient pH-sensitive small organic molecules as pharmacologically active cytotoxic compounds