numerical and experimental validation of a non standard specimen for uniaxial tensile test

Abstract Material testing is a fundamental activity for the characterization of materials mechanical properties and for the certification of product quality. With concepts such as Smart Factories and Industry 4.0 coming to the fore, testing and measurement is moving away from laboratories and closer to the production floor: MaCh 3D is a miniaturized tensile testing machine developed for products and materials certification directly on the production site. The heart of the technology is the specimen with non-conventional geometry for tensile tests developed so as to be easily installed on the machine. The objective of this work is to illustrate the process of determining the geometry of specimen and fixtures by numerical analysis and their experimental validation, comparing the results with those obtained from specimens according to ASTM D638 standard, ASTM International, (1999)

Spatial and metallogenic relationships between different hydrothermal vein systems in the Southern Arburèse district (SW Sardinia)

The SW Sardinian basement hosts various ore deposits linked to geological processes active from Cambrian to post-Variscan times. In particular, the Southern Arburèse district hosts several granite-related W-Sn-Mo deposits and a 10 km-long system of Ni-Co-As-Bi-Ag±Au-bearing five-element veins. New investigations in the eastern and central parts of the district (Pira Inferida mine sector) were performed to understand the poorly documented spatial and metallogenic relationships between these systems. The granite-related deposits consist of massive wolframite quartz (W-Bi-Te-Au) and molybdenite-quartz veins, linked to the early Permian (289±1 Ma) Mt. Linas granite, that are cross-cut by the five-element veins. The wolframite-quartz veins, observed by optical and electron (SEM-EDS) microscopy, show abundant native Bi, Bi-Te phases and native Au suggesting a W-Bi-Te-Au hydrothermal system. The five-elements veins exhibit breccia and cockade textures enveloping clasts of the Ordovician host-rocks and locally small fragments of the earlier W-Mo-quartz veins. The five-element vein paragenesis includes three main stages, from older to younger: 1) native elements (Bi±Au); 2) Ni-Co arsenides-sulfarsenides in quartz gangue; and 3) Pb-Zn-Cu±Ag sulfides in siderite gangue. The mineralogical, geochemical and isotopic features of the five-element vein swarm are closely comparable to five-element deposits elsewhere in Europe (Germany, Switzerland, Italian Alps). While the source of Ni and Co is still unknown, the high Bi contents as well as Au enrichment in the five-element veins suggest selective remobilization of these elements, and perhaps others, from the granite-related W-Bi-Te-Au veins. The five-element vein system was likely formed during a post-289±1 Ma and post-Variscan metallogenic event

MINERALOGICAL STUDIES OF THE W-Sn VEIN SKARNS OF MONTE TAMARA (NUXIS, SULCIS DISTRICT): INSIGHTS FOR STRATEGIC MINERALS EXPLORATION IN SW SARDINIA (ITALY).

Skarn deposits are a relevant source of critical raw materials such as W, Sn, and In. Recent studies conducted in South Sardinia pointed out the relationships between various Sn-W-Mo deposits and the early Permian (289-286 Ma) F-bearing, ilmenite-series ferroan granites (e.g., Sulcis pluton). This new evidence triggered a broad re-examination of granite-related deposits including skarn deposits hosted by Cambrian limestones of the low-grade Variscan basement of the Sulcis district (SW Sardinia). With this purpose, field investigations and OM, SEM-EDS, EMPA, and LA-ICP-MS observations, and analyses have been conducted on the skarn ores of Monte Tamara (Nuxis, northern Sulcis) where scheelite has been reported in the old San Pietro and Sinibidraxiu mines. The San Pietro mine exploited a 1-5 m thick and 70 m deep, steeply dipping skarn orebody located at the tectonized contact between early Cambrian sandstones and limestones. The orebody includes layers of Grt-Cpx-Wo, magnetite, and Zn-Pb-Cu-Fe sulfide bands. Prograde and retrograde stages with oxides and sulfides can be recognized. Clinopyroxene is the foremost mineral of the prograde stage; garnets (andradite-grossular) are usually dark green with typical anomalous birefringence and distinctly zoned (Fe-rich cores and Al-rich rims). Hematite turned to mushketovite, and Mo-rich scheelite, followed by In-bearing cassiterite, occasionally occur in the prograde assemblages. Amphiboles and epidotes mark the retrograde stage, together with abundant Zn-Cu-Fe-Pb sulfides and accessory molybdenite, stannite, bismuthinite, and Bi-Ag-Pb sulfosalts. At San Pietro, dominant sphalerite displays highly variable Fe, Mn, and Cd contents. Relictlooking blebs of Fe-Mn-poor Sp are scattered in high-Fe-Mn Sp where Sn EMPA peaks may correlate with cassiterite-stannite micro-inclusions. Galena composition suggests localized intergrowths with micro-inclusions of bismuthinite, Bi-Se, and Bi-Te sulfosalts. The stannite-sphalerite geothermometer provided a temperature range of 325-200°C for the sulfide stage. The Sinibidraxiu old mine exploited a 1,5 m thick and 60 m deep columnar body, hosted in early Cambrian marbles. It consists of a sphalerite-wollastonite assemblage with late sulfides, quartz, and calcite, hosting cm-sized arsenopyrite and scheelite. Scheelite is Mo-poor; Sn-, other Mo-phases and Bi-phases are absent. High-Fe Sp, rimmed by low-Fe Sp and blebby galena, is finely intergrown with wollastonite cockades. The results from this study suggest that a wide range of skarn-related mineralizing phenomena occurred in the Monte Tamara area. Both orebodies resulted from a structurally controlled migration of metasomatic fluids inside the hosting carbonate formation. Mineral zonation and composition of the San Pietro skarn point towards skarn development under varying fO2 conditions, oxidizing then rapidly turning to moderately reducing within the prograde W-Sn skarn stage and into the sulfide stage. The features of the Sinibidraxiu orebody (e.g., Mo-poor, As-devoid scheelite) suggest a formation from reducing metasomatic fluids but S-poor compared to San Pietro, probably at more distal environments (e.g. low Sn-Bi contents). From this point of view, the Monte Tamara area still maintains an economic potential, linked to the possible presence of proximal skarn ores at depth; thereby representing a key area for further exploration for granite-related strategic and critical metals in SW Sardinia

Mineralogy of the scheelite-bearing ores of Monte Tamara, SW Sardinia: insights for the evolution of a Late Variscan W–Sn skarn system

Southwestern Sardinia, Italy, hosts several skarn, W–Sn–Mo greisen and hydrothermal deposits related to a 289±1 Ma Late Variscan granite suite. Among them, the most representative scheelite-bearing skarns belong to the San Pietro and Sinibidraxiu localities, in the Monte Tamara area, Sulcis region. The San Pietro deposit is a typical calc-silicate skarn whereas Sinibidraxiu is a sharply bounded orebody hosted in a marble unit. Optical petrographic observations and compositional data of major and trace elements were obtained for samples from both localities. San Pietro data suggests evolution from an oxidising prograde skarn stage (andradite–diopside, hematite and scheelite), to progressively more reducing conditions from the early retrograde (magnetite–cassiterite) to the late sulfide stage (arsenopyrite, stannite, molybdenite, Bi sulfosalts and Zn–Cu–Pb–Fe sulfides); Sinibidraxiu has diffuse carbonate–quartz intergrowths pseudomorphic over an early mineral assemblage with fibrous habit, followed by abundant ore mineral precipitation under reducing conditions (scheelite, arsenopyrite and Pb–Zn–Cu–Fe sulfides). Geothermometers indicate a comprehensive temperature range of 460–270°C for the sulfide stages of both deposits. The differences between the two deposits might be controlled by the distance from the source intrusion coupled with the different reactivity of the host rocks. The San Pietro mineralogy represents a more proximal skarn, contrasting with more distal mineralogical and chemical features characterising the Sinibidraxiu orebody (lack of Mo–Sn–Bi phases; LREE–MREE–HREE signature of scheelite). This investigation contributes for the first time to the identification of a W–Sn skarn system in SW Sardinia, thereby suggesting the Monte Tamara area and its surroundings as favourable for further exploration

Mixing-Length Estimates From Binary Systems. A Theoretical Investigation on the Estimation Errors

We performed a theoretical investigation on the biases and random uncertainties affecting the recovery of the mixing-length parameter αml from an ideal eclipsing double-lined binary system, with well constrained masses and radii. We focused on a test case composed by a primary of mass M = 0.95 M⊙ and a secondary of M = 0.85 M⊙. Synthetic stars were generated coevally and with a common chemical composition by sampling from a dense grid of stellar models. Observational errors were simulated by adding random perturbations to mock data. The αml parameter was then recovered by means of the SCEPtER-binary pipeline. Several Monte Carlo simulations were conducted considering three metallicities, coupled to three different evolutionary stages of the primary. For each configuration, artificial data were sampled assuming an increasing difference between the mixing-length of the two stars. The mixing length values were then reconstructed adopting three alternative set-ups. A first method, which assumes full independence between the two stars, showed a great difficulty to constrain the mixing-length values; the recovered values were nearly unconstrained with a standard deviation of about 0.40. The second technique imposes the constraint of common age and initial chemical composition for the two stars in the fit. We found that αml, 1 values closely match the ones recovered under the previous configuration, but αml, 2 values are much more peaked around unbiased estimates. This occurs because the primary star provides a much tighter age constraint in the joint fit than the secondary, thus leading to the rejection of several extreme solutions for the secondary. Within this second scenario we also explored, for systems sharing a common αml = 2.0, the difference in the mixing-length values of the two stars only due to random fluctuations owing to the observational errors. The posterior distribution of these differences was peaked around zero, with a somewhat large standard deviation of 0.3 (about 15% of the solar-scaled value). Therefore, about 32% of systems with true identical αml are expected to show differences higher than that only owing to random errors. The third technique also imposes the constraint of a common mixing-length value for the two stars. This assumption is generally not true for the sample stars and served as a test for identifying wrong fitting assumptions. In this case, the common mixing-length is mainly dictated by the value of αml, 2. However, an increasing share of systems cannot be fitted by the algorithm as the differences of αml between the two stars in the synthetic systems increases. For Δαml > 0.4, less than half of the systems can be recovered and only 20% at Δαml = 1.0

A Fe2+-dependent self-inhibited state influences the druggability of human collagen lysyl hydroxylase (LH/PLOD) enzymes

Multifunctional human collagen lysyl hydroxylase (LH/PLOD) enzymes catalyze post-translational hydroxylation and subsequent glycosylation of collagens, enabling their maturation and supramolecular organization in the extracellular matrix (ECM). Recently, the overexpression of LH/PLODs in the tumor microenvironment results in abnormal accumulation of these collagen post-translational modifications, which has been correlated with increased metastatic progression of a wide variety of solid tumors. These observations make LH/PLODs excellent candidates for prospective treatment of aggressive cancers. The recent years have witnessed significant research efforts to facilitate drug discovery on LH/PLODs, including molecular structure characterizations and development of reliable high-throughput enzymatic assays. Using a combination of biochemistry and in silico studies, we characterized the dual role of Fe2+ as simultaneous cofactor and inhibitor of lysyl hydroxylase activity and studied the effect of a promiscuous Fe2+ chelating agent, 2,2'-bipyridil, broadly considered a lysyl hydroxylase inhibitor. We found that at low concentrations, 2,2'-bipyridil unexpectedly enhances the LH enzymatic activity by reducing the inhibitory effect of excess Fe2+. Together, our results show a fine balance between Fe2+-dependent enzymatic activity and Fe2+-induced self-inhibited states, highlighting exquisite differences between LH/PLODs and related Fe2+, 2-oxoglutarate dioxygenases and suggesting that conventional structure-based approaches may not be suited for successful inhibitor development. These insights address outstanding questions regarding druggability of LH/PLOD lysyl hydroxylase catalytic site and provide a solid ground for upcoming drug discovery and screening campaigns

contrast enhanced echocardiography to rule out active intrapericardial bleeding following coronary artery perforation

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Back to the Past. The paleogeography as key to understand the Middle Palaeolithic peopling at Grotta dei Santi (Mt Argentario – Tuscany)

The mobility of hunter-gatherer groups is crucial in understanding Palaeolithic settlement dynamics. The concept of mobility cannot be separated from the space in which it occurs, including landscape components, localization of critical resources and of other sites, and routes between them. Nevertheless, the landscape is not constant in time due to the geomorphological changes that occurred in the long timescale of Prehistory. Here we present a paleogeographic reconstruction of the coastal area around Grotta dei Santi during the Neandertal occupation. A GIS-based approach, combining geological, bathymetric, and sea-level fluctuations data, allows us to reconstruct the landscape around the cave at about 45 ky BP. The cave today opens onto a cliff facing the sea. The Neandertal occupation occurred with a sea-level 74 m lower than present-day. Consequently, the cave faced a vast coastal plain, playing a strategic role due to its position, allowing both proximity and control of essential resources