159,925 research outputs found
The formation volume in rare earth intermetallic systems: A representation by means of atomic physical quantities
No full textThe formation of the intermetallic phases is often accompanied by large volume effects, and several interpretations of this phenomenon have been proposed following different approaches, either from a simply empirical or purely theoretical point of view. In his pioneering work, Biltz (Biltz 1934) employed the experimental density values to list the molar volumes of the elements and of numerous inorganic and organic solids, including intermetallic phases. The systematic analysis of the data allowed the scientist to estimate the effective volumes of the atoms within the compounds, making possible the application of the volume additivity. Machlin studied the effects of electronegativity on energy and volume of formation, assuming that the volume corrections depend on the Gordy electronegativity difference (Machlin 1980). Watson and Bennett obtained 82a good correlation between the volume effects shown by the phases of the transition elements and a scale resembling the Gordy electronegativity, while a cellular method was applied to estimate the volume changes in phases with alkaline and alkaline earth metals (Watson and Bennett 1982, 1984). Alonso showed that a model of a disordered binary alloy of nontransition metals explains the tendency to a negative deviation from Vegard’s law as this lowers the energy of formation (Alonso et al. 1984). In the Miedema model (Miedema and Niessen 1982), the volume contraction in metallic systems can be ascribed to a charge transfer effect, described mainly by the differences both in an electronegativity-like scale (F*) and in the electron density parameter (nWS). Moreover, in systems with atoms of different radius, a further volume contraction may arise from elastic size mismatch energy. The differences in electronegativity are ignored in the Hafner approach, based on the lowest-order pseudopotential perturbation theory (Hafner 1985). This method provides good results for extended solid solutions of homovalent systems (intra-alkaline and intra-alkaline-earth alloys) and for some intermetallics of the cited elements. A phenomenological approach was used to describe the volume effects displayed by the intermetallic compounds formed by alkaline earths (Ca, Sr, Ba) and divalent rare earths (Eu, Yb) (Merlo 1988) and by the trivalent rare earths (Merlo and Fornasini 1993), introducing a charge transfer atomic parameter, correlated with Pauling’s electronegativity. More recently, the volume contractions of the binary phases of Ca, Sr, Ba, Eu and Yb were represented by a simple equation containing the electronegativity, the compressibility and the group number (Fornasini and Merlo 2006). The most advanced method is based on the calculation of partial atomic volumes and charges as a function of composition (Baranov et al. 2007)
Pregnancy-related acute myocardial infarction: a review of the recent literature
No full textPregnancy-related acute myocardial infarction is a rare and potentially life-threatening cardiovascular event, the incidence of which is growing due to the heightened prevalence of several risk factors, including increased maternal age. Its main aetiology is spontaneous coronary artery dissection, which particularly occurs in pregnancy and may engender severe clinical scenarios. Therefore, despite frequently atypical and deceptive presentations, early recognition of such a dangerous complication of gestation is paramount. Notwithstanding diagnostic and therapeutic improvements, pregnancy-related acute myocardial infarction often carries unfavourable outcomes, as emergent management is difficult owing to significant limitations in the use of ionising radiation—e.g. during coronary angiography, potentially harmful to the foetus even at low doses. Notably, however, maternal mortality has steadily decreased in recent decades, indicating enhanced awareness and major medical advances in this field. In our paper, we review the recent literature on pregnancy-related acute myocardial infarction and highlight the key points in its management
Type 2 myocardial infarction: a diagnostic and therapeutic challenge in contemporary cardiology
No full textIn the expanding world of cardiovascular diseases, rapidly reaching pandemic proportions, the main focus is still on coronary atherosclerosis and its clinical consequences. However, at least in the Western world, middle-aged male patients with acute myocardial infarction are no more the rule. Due to a higher life expectancy and major medical advances, physicians are to treat older and frailer individuals, usually with multiple comorbidities. In this context, myocardial ischaemia and infarction frequently result from an imbalance between myocardial oxygen supply and demand—i.e., type 2 myocardial infarction (T2MI), according to the current universal definition—rather than coronary atherothrombosis. Moreover, the increasing use of high-sensitivity cardiac troponin assays has led to a heightened detection of T2MI—often causing relatively little myocardial injury—, which seems to have doubled its numbers in recent years. Nevertheless, owing to its multifaceted pathophysiology and clinical presentation, T2MI is still underdiagnosed. Perhaps more importantly, T2MI is also victim of undertreatment, as drugs that constitute the cornerstone of therapy in most cardiovascular diseases are much more unlikely to be prescribed in T2MI than in coronary atherothrombosis. In this paper, we review the recent literature on the classification, pathophysiology, epidemiology, and management of T2MI, trying to summarise the state-of-the-art knowledge about this increasingly important pathologic condition. Finally, based on the current scientific evidence, we also propose an algorithm that may be easily utilised in clinical practice, in order to improve T2MI diagnosis and risk stratification
Identification and Estimation of Stochastic Bargaining Models, Third Version
No full textStochastic sequential bargaining models (Merlo and Wilson (1995, 1998)) have found wide applications in different fields including political economy and macroeconomics due to their flexibility in explaining delays in reaching an agreement. This paper presents new results in nonparametric identification and estimation of such models under different data scenarios.Nonparametric identification, non-cooperative bargaining, stochastic sequential bargaining, rationalizable counterfactual outcomes
Identification and Estimation of Stochastic Bargaining Models, Fourth Version
No full textStochastic sequential bargaining models (Merlo and Wilson (1995, 1998)) have found wide applications in different fields including political economy and macroeconomics due to their flexibility in explaining delays in reaching an agreement. This paper presents new results in nonparametric identification and estimation of such models under different data scenarios.Nonparametric identification and estimation, non-cooperative bargaining, stochastic sequential bargaining, rationalizable counterfactual outcomes
A fretting fatigue setup for testing shrink-fit connections and experimental evidence of the strength enhancement induced by deep rolling
No full textFretting tests are usually performed on flat specimens with lateral contacting pads. The shrink-fitted connection, which experiences fretting at the edge of the contact, prompted the alternative use of a round-shaped specimen. This simplified the equipment and provided an accurate alignment between the fretting specimen and the external hub which plays the role of the pad. The deep rolling treatment can also be efficiently applied to a round shape, which would otherwise be difficult on the flat specimen geometry. After introducing this solution for fretting testing, the paper shows an experimental campaign on three shrink-fitted connections with different sizes and material combinations. There was a significant improvement in fretting fatigue strength, induced by the deep rolling, for all three specimen types. Finally, scanning electron microscopic analyses provided insights into the fretting fatigue nucleation mechanisms both for untreated and deep-rolled specimens
Livello percepito di protezione dei dati personali e bisogno di sicurezza dei consumatori come predittori dell’intenzione all’uso di applicazioni mobile per il monitoraggio dei contagi da COVID-19
No full textSurveillance of COVID-19 infections remains a major policy challenge, particularly in tracking the health status of individuals. However, the problem of protecting personal data remains a challenge. Blockchain technology provides several tools to ensure that the data collected and managed through some mobile apps could be extremely secure, certified, and immutable, ensuring proper monitoring of infected and vaccinated users using these apps. This study sheds light on the intentions of individuals to use mobile apps based on Blockchain technology to track other infected and (or) vaccinated users in their vicinity. Through an online experiment with an international sample, we manipulated perceived levels of privacy (low levels for traditional mobile apps and high levels for blockchain-based mobile apps) to illuminate the importance of individuals' security concerns on their intentions to use mobile apps to monitor infected and vaccinated individuals. The findings provide important insights for managers, marketers, and policy makers in promoting the use of Blockchain-based mobile apps to prevent and contain the spread of COVID-19 infections
Treatment with ROS detoxifying metal nanoclusters alleviates the progressive functional decline in a mouse model of Friedreich's Ataxia
No full textFriedreich's ataxia (FRDA) is an autosomal recessive neurodegenerative disease characterized by preogressive muscle weakness and locomotor deficits, degeneration of large sensory neurons in the dorsal root ganglia (DRGs), cardiomyopaties, diabetes mellitus and skeletal deformities. and brain, skeletal muscle and cardiac defects. The disease is caused by reduced expression of the mitochondrial protein frataxin due to an intronic GAA-repeat expansion in the FXN gene. Altered mitochondrial iron metabolism and turnover result in chronic excess of reactive oxygen species (ROS), hypersensitivity to ROS and consequent oxidative stress and cell damage. While the full molecular pathogenesis is still being clarified, a scavenging or detoxification from ROS could reasonably lead to delayed progression and to alleviate the disease phenotype. Since no treatment for FRDA is currently approved and experimental therapies are still unsatisfactory, efforts in this direction are urgently needed. We have exploited a novel system of ROS scavenging/detoxification based on Au-nanoclusters (NC), injected intravenously in a mouse model of FRDA (YG8sR mouse). The Au-NCs injected animals show a significant improvement of motor function, including physical resistance and gait balance, an improved cardiac contractility and insulin-dependent control of glycemia. These effects were accompanied by long-term improved mitochondrial functions, improved antioxidant cell responses and reduced ROS-dependent DNA and lipid damage in the CNS and muscles. These results show the Au-NCs mediated phenotypic rescue of FRD in YG8sR mice and encourage further optimization of this approach in experimental therapy of FRDA
Assessment of average muscle fiber conduction velocity from surface EMG signals during fatiguing dynamic contractions
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