Marina Pireddu

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<lb>This article describes a method – called here “the method of Stretching Along<lb>the Paths” (SAP) – to prove the existence of chaotic sets in discrete-time dy-<lb>namical systems. The method of SAP, although mathematically rigorous, is<lb>based on some elementary geometrical considerations and is relatively easy to<lb>apply to models arising in(More)
We prove the existence of infinitely many periodic solutions and complicated dynamics, due to the presence of a topological horseshoe, for the classical Volterra predator–prey model with a periodic harvesting. The proof relies on some recent results about chaotic planar maps combined with the study of geometric features which are typical of linked twist(More)
Interferon-alpha (IFN-alpha) may affect lipid metabolism by stimulating hepatic fatty acid synthesis. The aim of this study was to evaluate serum lipid levels during IFN-alpha therapy in patients with biopsy-proven chronic active hepatitis C. A total of 22 patients (18 males and 4 females; age 25-55 years) received 3 MU of recombinant IFN-alpha 2b 3 times a(More)
In this paper, we propose a financial market model with heterogeneous speculators, i.e., optimistic and pessimistic fundamentalists that, respectively, overestimate and underestimate the true fundamental value due to ambiguity in the stock market, which prevents them from relying on the true fundamental value in their speculations. Indeed, we assume that(More)
We analyze the effects of restricted participation in a two-period general equilibrium model with uncertainty in the second period and real assets. Similar to certain arrangements in the markets for bank loans, household borrowing is restricted by a household-specific lower bound on wealth in all states of uncertainty in the final period. After establishing(More)
To investigate the behaviour of caffeine (CAF) in patients with Gilbert's Syndrome (GS), a combined oral loading test of caffeine and chenodeoxycholic acid was performed in 14 healthy subjects and 71 patients with GS. Indocyanine green (ICG) kinetics was tested in 50 subjects with GS and in all control subjects. Fasting serum bile acids (SBA) and clearance(More)
OBJECTIVE To assess the role of IgM antibodies to hepatitis C virus core protein (anti-HCV IgM) as a marker of chronic HCV infection and as a predictor of successful interferon (IFN) treatment. DESIGN Anti-HCV IgM levels were evaluated at baseline, during IFN therapy and during a follow-up period. METHODS Anti-HCV IgM levels were evaluated in 62(More)
In the present paper, we consider a nonlinear financial market model in which, in order to decrease the complexity of the dynamics and to achieve price stabilization, we introduce a price variation limiter mechanism, which in each period bounds the price variation so that the current price is forced to belong to a certain interval determined by the price(More)
We consider some nonlinear second order scalar ODEs of the form x + f(t, x) = 0, where f is periodic in the t–variable and show the existence of infinitely many periodic solutions as well as the presence of complex dynamics, even in the case of certain apparently “simple” equations. We employ a topological approach based on the study of linked twist maps(More)
The aim of this note is to set in the field of dynamical systems a recent theorem by Obersnel and Omari in [19] about the presence of subharmonic solutions of all orders for a class of scalar time-periodic first order differential equations without uniqueness, provided a subharmonic solution (for instance, of order two) does exist. Indeed, making use of the(More)