197 research outputs found

    High-performance yellow ceramic pigments Zr(Ti1-x-ySnx-yVyMy)O4 (M = Al, In, Y): crystal structure, colouring mechanism and technological properties

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    Zirconium titanate-stannate doped with V with co-dopants Al, In or Y was synthesised by solid state reaction and its structural (XRD, SEM), optical (DRS) and technological properties were determined to assess its potential use as ceramic pigment. These compounds have a srilankite-type, disordered orthorhombic structure, implying a random distribution of Zr, Ti, Sn and dopants in a single, strongly distorted octahedral site. Doping caused an increase of unit-cell dimensions, metal-oxygen distances and octahedron distortion. Optical spectra show crystal field electronic transitions of V4+ as well as intense bands in the blue-UV range due to V4+-V5+ intervalence charge transfer and/or to V-O charge transfer. The formation of oxygen vacancies is supposed to compensate the occurrence of V4+ ensuring the lattice charge neutrality. These srilankite-type oxides develop a deep and brilliant yellow shade with colourimetric parameters close to those of industrial ceramic pigments. Technological tests in several ceramic applications proved that zirconium titanate-stannate is very stable at high temperature, exhibiting an excellent performance in the 1200-1250?C range, even better than praseodymium-doped zircon

    I Modelli compartimentali nello studio della dinamica delle popolazioni naturali

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    Compartmental models are in common use in the study of many biological, agricultural and economic systems. The present paper is an attempt for a review of the great potentialities of the compartmental model originally proposed by Argentesi, De Bernardi and Di Cola (1974 a,b) for the study of the dynamics of single species populations with continuous recruitment. By means of this mathematical model it is possible to derive a simple methodology for an indirect estimation of some dynamic parameters which are not directly evaluable with experiments but which are essential for the biological interpretation of the biotic and abiotic interactions of the populations. The examples which are reported of application of the compartmental model to several experimental situations show that the methodology may be used to evidence the regulatory and perturbatory processes acting on fecundity and mortality rates of populations. In the compartmental framework the population dynamics can also be expressed as biomass in order to evaluate the population production. The parameters of the ordinary differential equations can be estimated via linear programming, which easily permits the introduction of constraints on the parameter value,and the derivative estimation via base function,that avoids the error amplifications of the numerical derivative

    Continual Cross-Dataset Adaptation in Road Surface Classification

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    Accurate road surface classification is crucial for autonomous vehicles (AVs) to optimize driving conditions, enhance safety, and enable advanced road mapping. However, deep learning models for road surface classification suffer from poor generalization when tested on unseen datasets. To update these models with new information, also the original training dataset must be taken into account, in order to avoid catastrophic forgetting. This is, however, inefficient if not impossible, e.g., when the data is collected in streams or large amounts. To overcome this limitation and enable fast and efficient cross-dataset adaptation, we propose to employ continual learning finetuning methods designed to retain past knowledge while adapting to new data, thus effectively avoiding forgetting. Experimental results demonstrate the superiority of this approach over naive finetuning, achieving performance close to fresh retraining. While solving this known problem, we also provide a general description of how the same technique can be adopted in other AV scenarios. We highlight the potential computational and economic benefits that a continual-based adaptation can bring to the AV industry, while also reducing greenhouse emissions due to unnecessary joint retraining.Comment: To be published in Proceedings of 26th IEEE International Conference on Intelligent Transportation Systems (ITSC 2023

    peri procedural thrombocytopenia after aortic bioprosthesis implant a systematic review and meta analysis comparison among conventional stentless rapid deployment and transcatheter valves

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    Abstract Background Thrombocytopenia has been shown to occur soon after surgical biological aortic valve replacement (AVR), and recently reported also after transcatheter valve implantation (TAVI). The mechanism underlying this phenomenon is still unknown, and its clinical impact on the peri-operative outcome has been poorly investigated. Methods A systematic review and a meta-analysis of all available studies reporting data about peri-procedural thrombocytopenia on isolated bio-AVR, comparing rapid-deployment (RDV), stentless (stentless-AVR), and TAVI vs. stented (stented-AVR) valves, have been performed. Results Fifteen trials (2.163 patients) were included in the meta-analysis. Perioperative platelet reduction ranged from 35% to 55% in stented-AVR, from 60% to 77% in stentless-AVR, from 53% to 60% in RDV, and from to 21% to 72% in TAVI (apparently, balloon-expandable valves more frequently associated to thrombocytopenia). Stented-AVR required more red blood cells transfusion than stentless-AVR (P  Conclusions Thrombocytopenia-related major adverse events were mainly reported in TAVI patients, whereas clinically meaningless in surgical patients. Transient peri-procedural thrombocytopenia is common after bio-AVR, regardless of prosthesis's type or implant modality. It should receive appropriate monitoring and focused investigations

    Malayaite Ceramic Pigments: a Combined Optical Spectroscopy and Neutron/X-ray Diffraction Study

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    Ceramic pigments based on the Cr-doped malayaite structure were synthesized by solid state reaction and characterized by optical spectroscopy and combined X-ray and neutron powder diffraction in order to elucidate the still unclear chromium substitution mechanisms. The results show that coloration is actually due to simultaneous occurrence of Cr4+ and Cr3+ ions in the crystal lattice. Spectroscopy data confirm that Cr4+ is replacing Sn4+ in the octahedral site and, in minor amount, Si4+ in the tetrahedral site. In addition, neutron powder diffraction data suggest that Cr3+ substitution for octahedral Sn4+ is charge balanced by formation of oxygen vacancies with no preference over the different oxygen sites. Upon incorporation of Cr ion, the SnO6 octahedra exhibit an off-centre displacement of central cation which in turn induces a rearrangement of both the octahedral and tetrahedral coordination shells

    sutured and sutureless repair of postinfarction left ventricular free wall rupture a systematic review

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    Summary Postinfarction left ventricular free-wall rupture is a potentially catastrophic event. Emergency surgical intervention is almost invariably required, but the most appropriate surgical procedure remains controversial. A systematic review, from 1993 onwards, of all available reports in the literature about patients undergoing sutured or sutureless repair of postinfarction left ventricular free-wall rupture was performed. Twenty-five studies were selected, with a total of 209 patients analysed. Sutured repair was used in 55.5% of cases, and sutureless repair in the remaining cases. Postoperative in-hospital mortality was 13.8% in the sutured group, while it was 14% in the sutureless group. A trend towards a higher rate of in-hospital rerupture was observed in the sutureless technique. The most common cause of in-hospital mortality (44%) was low cardiac output syndrome. In conclusion, sutured and sutureless repair for postinfarction left ventricular free-wall rupture showed comparable in-hospital mortality. However, because of the limited number of patients and the variability of surgical strategies in each reported series, further studies are required to provide more consistent data and lines of evidence

    Pleiotropic and potentially beneficial effects of reactive oxygen species on the intracellular signaling pathways in endothelial cells

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    © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/).Endothelial cells (ECs) are exposed to molecular dioxygen and its derivative reactive oxygen species (ROS). ROS are now well established as important signaling messengers. Excessive production of ROS, however, results in oxidative stress, a significant contributor to the development of numerous diseases. Here, we analyze the experimental data and theoretical concepts concerning positive pro-survival effects of ROS on signaling pathways in endothelial cells (ECs). Our analysis of the available experimental data suggests possible positive roles of ROS in induction of pro-survival pathways, downstream of the Gi-protein-coupled receptors, which mimics insulin signaling and prevention or improvement of the endothelial dysfunction. It is, however, doubtful, whether ROS can contribute to the stabilization of the endothelial barrier.info:eu-repo/semantics/publishedVersio

    Extracellular vesicles from human cardiac progenitor cells inhibit cardiomyocyte apoptosis and improve cardiac function after myocardial infarction

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    Aims Recent evidence suggests that cardiac progenitor cells (CPCs) may improve cardiac function after injury. The underlying mechanisms are indirect, but their mediators remain unidentified. Exosomes and other secreted membrane vesicles, hereafter collectively referred to as extracellular vesicles (EVs), act as paracrine signalling mediators. Here, we report that EVs secreted by human CPCs are crucial cardioprotective agents. Methods and results CPCs were derived from atrial appendage explants from patients who underwent heart valve surgery. CPC-conditioned medium (CM) inhibited apoptosis in mouse HL-1 cardiomyocytic cells, while enhancing tube formation in human umbilical vein endothelial cells. These effects were abrogated by depleting CM of EVs. They were reproduced by EVs secreted by CPCs, but not by those secreted by human dermal fibroblasts. Transmission electron microscopy and nanoparticle tracking analysis showed most EVs to be 30-90 nm in diameter, the size of exosomes, although smaller and larger vesicles were also present. MicroRNAs most highly enriched in EVs secreted by CPCs compared with fibroblasts included miR-210, miR-132, and miR-146a-3p. miR-210 down-regulated its known targets, ephrin A3 and PTP1b, inhibiting apoptosis in cardiomyocytic cells. miR-132 down-regulated its target, RasGAP-p120, enhancing tube formation in endothelial cells. Infarcted hearts injected with EVs from CPCs, but not from fibroblasts, exhibited less cardiomyocyte apoptosis, enhanced angiogenesis, and improved LV ejection fraction (0.8 ± 6.8 vs. −21.3 ± 4.5%; P < 0.05) compared with those injected with control medium. Conclusion EVs are the active component of the paracrine secretion by human CPCs. As a cell-free approach, EVs could circumvent many of the limitations of cell transplantatio

    Risks associated with intensive blood pressure control in older patients

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    Hypertension management forms a cornerstone of cardiovascular prevention. Strong evidence is available supporting the benefits of blood pressure (BP) lowering in older adults and recent studies indicate that intensive BP control may provide additional advantages on cardiovascular and mortality risk, also at older ages. Yet, in older adults the cardiovascular benefit of intensive treatment may come at the expense of increase in adverse events. Indeed, advanced age and frailty may modify the risk/benefit ratio of BP lowering due to a greater predisposition to hypotension and more severe consequences deriving from treatment-related adverse effects. This mostly applies to individuals with poor health status and limited life expectancy, in whom aggressive BP lowering may not lead to cardiovascular benefits, but rather increase the risk of short-term treatment-related complications. Furthermore, the potential harms of intensive BP control might be underestimated in clinical trials due to exclusion criteria which preclude patients with frailty and multimorbidity from being eligible. Syncope and falls are the most frequently mentioned antihypertensive-related safety concern, but aggressive BP lowering may negatively affect also renal function, cognitive performance, quality of life and survival. With the growing emphasis on intensive treatment strategies, raising awareness on potential harms associated with aggressive BP lowering might help improve hypertension management in older adults and encourage implementation of clinical research on safety issues. Given these premises, we present a narrative review illustrating the most relevant risk potentially associated with intensive BP control in older patients
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