87,394 research outputs found
Devices for Mitral Valve Repair
No full textThe natural history of severe mitral regurgitation (MR) is unfavorable, leading to left ventricular failure, atrial fibrillation, stroke, and death. Many patients affected by severe regurgitation (MR) do not currently undergo surgery, mainly due to the perceived risk of the procedure (old age, impaired left ventricular function, and comorbidities). Mitral transcatheter interventions carry the hope of minimizing risks while preserving clinical efficacy of surgical repair, as an alternative to conventional treatment. Multiple technologies and diversified approaches are under development with the purpose of treating MR in less invasive ways. They can be categorized based on the anatomical and patho-physiological addressed target. Among them, MitraClip (Abbott Vascular, Inc., Menlo Park, California) has emerged as a clinically safe and effective method for percutaneous mitral valve repair in patients either with degenerative and functional regurgitation. This device mimics the surgical edge-to-edge repair initially described by Alfieri in the early 1990s. Other repair technologies include percutaneous direct and indirect annuloplasty, neochordae implantation, and left ventricular reshaping. They are still in early phase clinical trials or preclinical studies. The combination of different repair techniques is likely to be required to achieve good long-lasting results. In the future, novel devices, improved knowledge, more efficient imaging, and transcatheter mitral prosthetic valve implantation may expand the indications to those patients currently not treated, as well as improve the results both in terms of early efficacy and long-term durability. These treatments are currently reserved to high-risk and inoperable patients, and their application requires an integrated Heart-Team approach. They represent the natural evolution of surgery and promise to expand treatment options and improve patients' outcomes in the near future. OI Denti, Paolo/0000-0002-3075-020
Rhinolophus denti Thomas 1904
No full textRhinolophus denti Thomas, 1904. Ann. Mag. Nat. Hist., ser. 7, 13:386. TYPE LOCALITY: South Africa, Cape Province, Kuruman. DISTRIBUTION: N Cape Prov. (South Africa), Namibia, Botswana, Zimbabwe, Mozambique, Guinea, Ivory Coast, Ghana. SYNONYMS: knorri.Published as part of Karl F. Koopman, 1993, Order Chiroptera, pp. 137-241 in Mammal Species of the World (2 nd Edition), Washington and London :Smithsonian Institution Press on page 165, DOI: 10.5281/zenodo.735306
A two-stage Bayesian semiparametric model for novelty detection with robust prior information
No full textNovelty detection methods aim at partitioning the test units into already observed and previously unseen patterns. However, two significant issues arise: there may be considerable interest in identifying specific structures within the novelty, and contamination in the known classes could completely blur the actual separation between manifest and new groups. Motivated by these problems, we propose a two-stage Bayesian semiparametric novelty detector, building upon prior information robustly extracted from a set of complete learning units. We devise a general-purpose multivariate methodology that we also extend to handle functional data objects. We provide insights on the model behavior by investigating the theoretical properties of the associated semiparametric prior. From the computational point of view we, propose, a suitable ξ: ξ-sequence to construct an independent slice-efficient sampler that takes into account the difference between manifest and novelty components. We showcase our model performance through an extensive simulation study and applications on both multivariate and functional datasets, in which diverse and distinctive unknown patterns are discovered
Bayesian analysis of Amazon’s best-selling books via finite nested mixture models
No full textOnline shopping has become increasingly common in recent years and has influenced how we form our preferences and choose the items to buy. This influence also applies to the books we read: other readers’ online reviews are one of the most used tools to determine the next book we will buy. The increasing use of e-commerce websites has also led to a large availability of data to study how the users’ ratings interact with other variables. Here, we consider a dataset of Amazon’s best-selling books in the period 2009-2019. In particular, we study the similarities of the distributions of ratings and prices across different years. To fully capture the complexity of the observed data, we make use of flexible Bayesian nested mixture models to simultaneously avoid strict parametric assumptions and study the clustering structure of observations and years
Valutazione di modelli per la predizione numerica dell'accrescimento del ghiaccio su profili alari
No full textAtti del Dipartimento di Ingegneria Aerospaziale dell'Università di Pisa
Mechanical strength of adhesively bonded joints using polymeric additive manufacturing
No full textThis paper investigates the combined use of one of the most widespread additive manufacturing techniques, fused deposition molding, with polymeric materials and structural adhesive. The aim is twofold: first, to enhance the adhesive performance exploiting the capability of the additive manufacturing to tailor the bonding surface of the adherend, and second to overcome one of the main limitations of 3D printing, i.e. the quite small printing volume, by means of adhesive bonding. Bonding multiple parts together without loss of performance could open new possibilities for this technology. The present research analyzes, by using a Design of Experiment technique, a wide set of single lap joints with two adhesives and seven different surface morphologies. The results highlight that the adhesive bonding does not undermine the load carrying capacity of the joints as well as their stiffness, and, in some cases, it causes a slight improvement of the peak force. The morphology of the surface plays only a small role in the performance of the system, since it cannot provide a strong mechanical interlocking of the parts due to peel stresses and because of the predominant effect of stress concentrations at the corners, which cause substrate failure
The generalized nested common atoms model
No full textBayesian hierarchical nonparametric models offer a convenient framework for modeling nested data, where observations are organized into groups. These priors jointly accommodate the dependence among groups and among observations within the same group in a flexible way. Several recent instances of such models have combined nested levels of Dirichlet processes and a common sequence of atoms, a formulation that allows for multi-layered partitions, i.e., a simultaneous clustering of observations and groups. However, using a common set of atoms can lead to a forced high prior correlation between the generated random measures. This characteristic can cause shortcomings in the clustering results and even biased density estimation. Extending the nested process with more general stick-breaking specifications for the weights alleviates these issues. Specifically, the proposed generalized Common Atoms Model enhances the flexibility of the dependence structure and improves density estimation. Three..
Impact on ice accretion of atmospheric conditions not included in appendix C of the JAR/FAR25 requirements
No full textAtti del Dipartimento di Ingegneria Aerospaziale dell’Università di Pisa
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