258 research outputs found
Molecular diversity of phytoplasmas associated with grapevine yellows disease in north-eastern Italy
No full textA 3-year survey was conducted in Northern Italy to verify the presence and diversity of phytoplasmas in selected vineyards showing symptoms of severe yellows. Symptomatic and asymptomatic grapevines were sampled, and insects were collected using yellow sticky traps. The phytoplasmas detected in grapevine samples were different according to the years: "flavescence dorée" (16SrV-C/D) was detected together with other phytoplasmas such as 16SrXII-A ('Candidatus Phytoplasma solani'- related, bois noir), 16SrI-B ('Ca. P. asteris'-related, aster yellows), 16SrX-B ('Ca. P. prunorum'-related, European stone fruit yellows), and 16SrV-A ('Ca. P. ulmi'-related, elm yellows). Moreover, phytoplasmas belonging to 16SrVII-A ('Ca. P. fraxini'-related) and 16SrVI ('Ca. P. Trifolii'-related) subgroups were also identified. Identification of phytoplasmas was also carried out from insects and showed the presence of some of these phytoplasmas in Scaphoideus titanus and Orientus ishidae: 16SrXII-A, 16SrVII, and 16SrVI phytoplasmas were detected in specimens of both species, while 16SrXII-A and 16SrI-B phytoplasma strains were identified in Orientus ishidae and Hyalesthes obsoletus, and 16SrX-B in S. Titanus. Direct sequencing of selected amplicons obtained from 16S rRNA, rp, and tuf genes from grapevine and insect samples confirmed the phytoplasma identification. The 16SrVII-A and 16SrVI phytoplasmas were never detected before in grapevine, S. Titanus and Orientus ishidae in Europe and their epidemiological importance is being monitored
A proposal for ranking through selective computation of centrality measures
No full textIn complex network analysis it is essential to investigate the alteration of network structures that results from the targeted removal of vertices or edges, ranked by centrality measures. Unfortunately, a sequential recalculation of centralities after each node elimination is often impractical for large networks, and computing rankings only at the beginning often does not accurately reflect the actual scenario. Here we propose a first result on the computational complexity of the sequential approach when nodes are removed from a network according to some centrality measures based on matrix functions. Moreover, we present two strategies that aim to reduce the computational impact of the sequential computation of centralities and provide theoretical results in support. Finally, we provide an application of our claims to the robustness of some synthetic and real-world networks
Reliable preconditioned iterative linear solvers for some numerical integrators
No full textImplicit time-step numerical integrators for ordinary and evolutionary partial differential equations need, at each step, the solution of linear algebraic equations that are unsymmetric and often large and sparse. Recently, a block preconditioner based on circulant approximations for the linear systems arising in the boundary value methods (BVMs) was introduced by the author. Here, some circulant approximations are compared and a further new type is considered. Numerical experiments are presented to check the effectiveness of the various approximations that can be used in the underlying block preconditioner. Copyright © 2001 John Wiley & Sons, Ltd
Empiric antibiotics therapy for mildly elevated prostate specific antigen: Helpful to avoid unnecessary biopsies?
No full textThe management of mildly elevated (4.0-10.0 ng/ml) prostate specific antigen (PSA) is uncertain. Immediate prostate biopsy, antibiotic treatment, or monitoring PSA level for 1-3 months is still in controversy
La sociologia giuridico-penale di Alessandro Baratta in Spagna e in America Latina – Problemi, equivoci e fallacie
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