104,300 research outputs found
On the iterative computation of a l_2-norm scaling based preconditioner
No full textIn this paper we consider the Krylov subspace based method introduced in [Fasano, 2005a], for
iteratively solving the symmetric and possibly indefinite linear system Ax = b. We emphasize the
application of the latter method to compute a diagonal preconditioner. The approach proposed
is based on the approximate computation of the `2-norm of the rows (columns) of the matrix A
and on its use to equilibrate the matrix A. The distinguishing feature of this approach is that
the computation of the `2-norm is performed without requiring the knowledge of the entries of
the matrix A but only using a routine which provides the product of A times a vector
Politica, fazioni, istituzioni nell'"Italia spagnola". Dall'incoronazione di Carlo V (1530) alla Pace di Westfalia (1648).
No full textImportanti raccolte di documenti, con relativi apparati critici e introduzioni, originata da un progetto MURST coordinato a livello nazionale da E. Fasano Guarini. La serie di volumi rientra nelle Pubblicazioni degli Archivi di Stato, Fonti, presente in tutte le maggiori biblioteche a livello internazionale e ora accessibile in rete. Il comitato scientifico è formato da E. Fasano Guarini, G. Signorotto e M.A. Visceglia
Surface photometry in 7 nearby clusters (Fasano+, 2002)
No full textVizieR On-line Data Catalog: J/A+A/387/2
Effects of Propionyl-Carnitine in Patients with type2 diabetes and peripheral vascular disease
No full textEffects of propionyl-carnitine in patients with type 2 diabetes and peripheral vascular disease: results of a pilot trial.
Ragozzino G, Mattera E, Madrid E, Salomone P, Fasano C, Gioia F, Acerra G, del Guercio R, Federico P.
SourceDepartment of Internal Medicine, Clinical Methodology and Medical Angiology, Second University of Naples, Italy. [email protected]
Abstract
OBJECTIVE: To assess the efficacy of propionyl-carnitine (PC) in patients with type 2 diabetes and peripheral arterial disease (PAD).
PATIENTS AND METHODS: This was an open pharmacodynamic study. Twenty-four obese patients with type 2 diabetes and PAD (stage IIb) were enrolled in the study. After an initial run-in period of 7 days on a low-calorie diet (1600 +/- 150 kcal/day), patients received intravenous PC (600mg in 100mL saline solution Na/K 0.9%) twice daily for 10 days (T1).
RESULTS: Treatment with PC produced statistically significant increases in maximal walking distance (30%; p < 0.05) and initial claudication distance (15%; p < 0.05) in 15 and eight patients, respectively. In addition, a decrease in dosage of oral antihyperglycaemic agents was observed in 21 patients at T1. No PC-related adverse effects were reported.
CONCLUSIONS: This study showed that acute intravenous administration of PC in patients with type 2 diabetes with PAD improved PAD-related symptoms as well as glycaemic control
A class of preconditioners for large indefinite linear systems, as by-product of Krylov subspace methods: Part I
No full textWe propose a class of preconditioners, which are also tailored for symmetric linear systems from linear algebra and nonconvex optimization. Our preconditioners are specifically suited for large linear systems and may be obtained as by-product of Krylov subspace solvers. Each preconditioner in our class is identified by setting the values of a pair of parameters and a scaling matrix, which are user-dependent, and may be chosen according with the structure of the problem in hand. We provide theoretical properties for our preconditioners. In particular, we show that our preconditioners both shift some eigenvalues of the system matrix to controlled values, and they tend to reduce the modulus of most of the other eigenvalues. In a companion paper we study some structural properties of our class of preconditioners, and report the results on a significant numerical experience
Iterative Computation of Negative Curvature Directions in Large Scale Optimization: Theory and Preliminary Numerical results
No full textIn this paper we deal with the iterative computation of
negative curvature directions of an indefinite matrix, within
large scale optimization frameworks. In particular, suitable
directions of negative curvature of the Hessian matrix represent
an essential tool, to guarantee convergence to second
order critical points. However, an “adequate” negative curvature
direction is often required to have a good resemblance
to an eigenvector corresponding to the smallest eigenvalue
of the Hessian matrix. Thus, its computation may be a
very difficult task on large scale problems. Several strategies
proposed in literature compute such a direction relying
on matrix factorizations, so that they may be inefficient or
even impracticable in a large scale setting. On the other
hand, the iterative methods proposed either need to store a
large matrix, or they need to rerun the recurrence.
On this guideline, in this paper we propose the use of
an iterative method, based on a planar Conjugate Gradient
scheme. Under mild assumptions, we provide theory
for using the latter method to compute adequate negative
curvature directions, within optimization frameworks. In
our proposal any matrix storage is avoided, along with any
additional rerun
Maladaptive plasticity in levodopa-induced dyskinesias and tardive dyskinesias: Old and new insights on the effects of dopamine receptor pharmacology
No full textMaladaptive plasticity can be defined as behavioral loss or even development of disease symptoms resulting from aberrant plasticity changes in the human brain. Hyperkinetic movement disorders, in the neurological or psychiatric realms, have been associated with maladaptive neural plasticity that can be expressed by functional changes such as an increase in transmitter release, receptor regulation, and synaptic plasticity or anatomical modifications such as axonal regeneration, sprouting, synaptogenesis, and neurogenesis. Recent evidence from human and animal models provided support to the hypothesis that these phenomena likely depend on altered dopamine turnover induced by long-term drug treatment. However, it is still unclear how and where these altered mechanisms of cortical plasticity may be localized. This study provides an up-to-date overview of these issues together with some reflections on future studies in the field, particularly focusing on two specific disorders (levodopa-induced dyskinesias in Parkinson's disease patients and tardive dyskinesias in schizophrenic patients) where the modern neuroimaging approaches have recently provided new fundamental insights. © 2014 Cerasa, Fasano, Morgante, Koch and Quattrone
- …
