4,807 research outputs found

    Mechanical behavior of carbon/flax hybrid composites for structural applications

    Get PDF
    In this work, the influence of an unidirectional carbon fabric layer on the mechanical performances of bidirectional flax fabric/epoxy composites used for structural applications was studied. Two different bidirectional flax fabrics were used to produce flax fabric reinforced plastic (FFRP) laminates by a vacuum bagging process: one is normally used to make curtains; the other, heavier and more expensive than the previous one, is usually used as reinforcement in composite structures. In order to realize hybrid structures starting from FFRP, an unidirectional UHM carbon fabric was used to replace a bidirectional flax fabric. Tensile and three-point bending tests were performed to evaluate the mechanical properties of the laminates investigated (both FFRP and hybrids). Furthermore, the mechanical behavior of the different bidirectional flax fabrics was analyzed by carrying out tensile tests. The experimental tests showed that the structures reinforced with flax fabrics, normally used to make curtains, present better flexural properties than that of others while, in tensile configuration, these last show higher modulus and strength. Moreover, both FFRP laminates show low mechanical properties, which do not allow their use in structural applications while the presence of one external layer of unidirectional carbon involves remarkable increase in their properties. According to this study, the hybrid composites realized could be used in several structural applications (i.e., nautical and automotive)

    The circle of GĂĄnovce. Natural history of an endocast

    Get PDF
    The natural endocranial cast of Gánovce was found in Slovakia in 1926, and then stored in the National Museum (Národní Muzeum) of Prague. The endocast was extensively studied by Emanuel Vlček (1925-2006), mostly during the 50s and 60s of the past century (e.g., Vlček, 1949, 1953, 1955, 1969), with a large set of analytical tools including radiographic and biochemical sur- veys, and outline shape analysis. He recognized the Neanderthal morphology of the cast, which was dated to 105 ka and which has an estimated volume of 1320cc. In particular, Vlček noticed a similarity with specimens such as Krapina 3, Gibraltar 1 and Saccopastore 1. In fact, these three specimens all display a similar overall cra- nial anatomy, being possibly representatives of an “early and small-brained” Neanderthal morpho- type (Bruner & Manzi, 2006, 2008)

    EGFR signalling is required for Paracentrotus lividus endomesoderm specification.

    Get PDF
    The EGFR pathway is critical for cell fate specification throughout the development of several organisms. Here we identified in sea urchin an EGFR-related antigen maternally expressed and showing a dynamic pattern of localization during development. To investigate the role played by the EGFR in Paracentrotus lividus development we blocked its activity by using the EGFR kinase inhibitor AG1478. This treatment produces decrease of EGFR phosphorylation, and embryos with various defects especially in the endomesoderm territory until to obtain an animalized phenotype. These effects are rescued by the addition of TGF-alpha, an EGFR ligand. The role played by EGFR-like along the animal/vegetal axis was also detected, after AG1478 treatment, by the extended distribution of HE and decreased nuclearization of beta-catenin in vegetal cells. Moreover, inhibition of EGFR-like reduced ERK phosphorylation, necessary for cell fate specification in the micromeres and their derivates. Taken together these results indicate that EGFR-like activity is required both for A/V axis formation and endomesoderm differentiation

    Time-space focused intrusion of genetically unrelated arc magmas in the early Paleozoic Ross-Delamerian Orogen (Morozumi Range, Antarctica)

    Get PDF
    The growth of continental crust in accretionary orogenic belts takes place through repeated cycles of subduction– accretion of rock units fromcontinental and oceanic magmatic arcs, supra-subduction zone backarcs and forearcs loaded with continent-derived materials. An ancient example relevant to magmatic arc accretion models is represented by the remnants of the Cambrian–Ordovician Ross Orogen in the Morozumi Range, Victoria Land (Antarctica). There, late Neoproterozoic phyllites host an intrusive complex which preserves a remarkably uncommon record of genetically unrelated magma pulses emplaced under a variable stress regime in a short time span: (1) a dominant K-feldspar–phyric granite, (2) fine-grained dioritic stocks and dykes, (3) a peraluminous granite; and (4) a tonalitic–granodioritic dyke swarm. Laserprobe U–Pb zircon dates cluster at late Cambrian times for all these units, yet they carry differential cargoes of relict cores. Unique geochemical– isotopic signatures for both the less evolved magmas (diorite and dyke tonalite) and the most acidic ones (granite and peraluminous granite) indicate that each one of them originated from distinct sources at depth. Additionally, field relationships and chemical evolutionary trends testify for a variety of shallow level open-system processes, such as magma mingling/mixing between diorite and main granite magmas, as well as progressive incorporation of the host schists by the dyke tonalite magma. In summary, crustal growth in the Morozumi intrusive complex was contributed by fresh mantle magma issuing from the metasomatised mantle wedge, while the production of othermelts did recycle different crustal portions/layers: the main granite derived fromGrenville-age granulitic lower crust; the peraluminous granite from late Proterozoic upper crust, and the tonalite magmas derived from subduction erosion-enriched subarc mantle and evolved by ingestion of local metasedimentary rocks. Overall, the Morozumi intrusive complex yields evidence for emplacement in the same site at the same time of magmas issuing fromdifferent sources that are usually found at a different depth in the arc lithospheric section. A likely scenario to activate this specific mechanism of melt production is a subduction zone affected by subduction erosion

    40Ar–39Ar dating of volcanogenic products from the AND-2A core (ANDRILL Southern McMurdo Sound Project, Antarctica): correlations with the Erebus Volcanic Province and implications for the age model of the core

    Get PDF
    The AND-2A drillcore (Antarctic Drilling Program—ANDRILL) was successfully completed in late 2007 on the Antarctic continental margin (Southern McMurdo Sound, Ross Sea) with the aim of tracking ice proximal to shallow marine environmental fluctuations and to document the 20-Ma evolution of the Erebus Volcanic Province. Lava clasts and tephra layers from the AND-2A drillcore were investigated from a petrographic and stratigraphic point of view and analyzed by the 40Ar–39Ar laser technique in order to constrain the age model of the core and to gain information on the style and nature of sediment deposition in the Victoria Land Basin since Early Miocene. Ten out of 17 samples yielded statistically robust 40Ar–39Ar ages, indicating that the AND-2A drillcore recovered ≀230 m of Middle Miocene (∌128–358 m below sea floor, ∌11.5–16.0 Ma) and >780 m of Early Miocene (∌358–1093 m below sea floor, ∌16.0–20.1 Ma). Results also highlight a nearly continuous stratigraphic record from at least 358 m below sea floor down hole, characterized by a mean sedimentation rate of ∌19 cm/ka, possible oscillations of no more than a few hundreds of ka and a break within ∌17.5–18.1 Ma. Comparison with available data from volcanic deposits on land, suggests that volcanic rocks within the AND-2A core were supplied from the south, possibly with source areas closer to the drill site for the upper core levels, and from 358 m below sea floor down hole, with the “proto-Mount Morning” as the main source

    Late Pleistocene-Holocene volcanic activity in northern Victoria Land recorded in Ross Sea (Antarctica) marine sediments

    Get PDF
    Eight pyroclastic fall deposits have been identified in cores of Late Pleistocene-Holocene marine sediments from the Ross Sea (Antarctica), and their components, granulometry and clast morphologies were analysed. Sedimentological, petrographic and geochemical analysis of clasts, with 40Ar-39Ar dating of alkali feldspar grains, indicate that during this period at least five explosive eruptions of mid to high intensity (plinian to subplinian) occurred, and that three of these eruptions took place from Mount Melbourne volcanic complex, between 137.1 \ub1 3.4 and 12 ka. Geochemical comparison of the studied tephra with micro and crypto-tephra recovered from deep Antarctic ice cores and from nearby englacial tephra at Frontier Mountain indicates that eruptive activity in the Melbourne Volcanic Province of northern Victoria Land was intense during the Late Pleistocene-Holocene, but only a general area of provenance for the majority of the identified tephra can be identified

    Histopathological aspects of transitional cell carcinoma of the bladder: Analysis of 20 years experience

    Get PDF
    Background: In this study we used histopathological examinations performed over a 20-year period to describe the characteristics of newly diagnosed transitional cell carcinoma (TCC) of the bladder in relation to patient age, and to verify changes in the TCC over different periods of observation or in relation to patient age. Methods: We reviewed all histopathological examinations performed from January 1979 to December 1998 in patients undergoing surgery who were newly diagnosed with TCC of the bladder. All examinations were performed by the same pathologist and reviewed by two pathologists. In each case analyzed, we evaluated T classification of the tumor, histological grade, size, localization, growth type, multiplicity and carcinoma in situ (CIS). Results: The study population included 3113 men and 620 women. The mean patient age was 66.31 +/- 10.84 years. A high percentage of Ta (52.2%) and T1 (27.7%) tumors were found. The number of cases observed and, in particular, the percentage of Ta tumors increased significantly and progressively from the first (1979-1983 = 376 cases; Ta = 37.8%) to the last (1994-1998 = 1732 cases; Ta = 56.3%) period of observation (P < 0.001). A significant difference in the distribution of histological grade and T classification in the different age decades was apparent (P < 0.001); in particular, for G1 and Ta tumors there was a trend to decrease, whereas for G3, T1 and T2 tumors there was a tendency to increase with age decades. Conclusion: In our analysis, age of patient and the period of examination significantly influenced different pathological characteristics of newly diagnosed TCC of the bladder

    Potential effects of E-cigarettes and vaping in pediatric asthma

    Get PDF
    Asthma is the most common chronic disease in childhood and exposure to tobacco smoke has been long recognized as a risk factor for its onset as well as for exacerbations and poor disease control. Since the early 2000s, electronic cigarettes have been marketed worldwide as a non-harmful electronic alternative to combustible cigarettes and as a device likely to help stop smoking, and their use is continuously rising, particularly among adolescents. However, several studies have shown that vape contains many different well-known toxicants, causing significant cytotoxic and pro-inflammatory effects on the airways in-vitro and in animal models. In humans, a variety of harmful lung effects related to vaping, ranging from bronchoconstriction to severe respiratory distress has been already reported
    • 

    corecore