On the behavior of periodic solutions of planar autonomous Hamiltonian systems with multivalued periodic perturbations

Aim of the paper is to provide a method to analyze the behavior of $T$-periodic solutions x_\eps, \eps>0, of a perturbed planar Hamiltonian system near a cycle $x_0$, of smallest period $T$, of the unperturbed system. The perturbation is represented by a $T$-periodic multivalued map which vanishes as \eps\to0. In several problems from nonsmooth mechanical systems this multivalued perturbation comes from the Filippov regularization of a nonlinear discontinuous $T$-periodic term. \noindent Through the paper, assuming the existence of a $T$-periodic solution x_\eps for \eps>0 small, under the condition that $x_0$ is a nondegenerate cycle of the linearized unperturbed Hamiltonian system we provide a formula for the distance between any point $x_0(t)$ and the trajectories x_\eps([0,T]) along a transversal direction to $x_0(t).

The ErbB2 receptor in gastric cancer. the quick-change artist

The ErbB family of receptors is providing the oncogenic signals necessary to cells to become transformed. In gastric cancer (GC) the ErbB2 (HER2) expression is associated with a poor prognosis, but addition of ErbB-targeted therapeutics to chemotherapy has produced unsatisfactory results with moderate improved outcomes for patients. The ToGA trail has revolutionized the treatment of GC, introducing the use of trastuzumab and changing the poor prognosis of these patients. However, this study reported only a modest prolongation of progression-free survival (PFS) and overall survival (OS) in patients with high expression of ErbB2 protein, with a large percentage of initially good responders, then becoming refractory to therapy within one year. These findings indicate the occurrence of resistant phenotypes arising from diverse adaptive and genetic changes. Due to the promiscuity of ErbB2 in the EGFR family signaling network, the use of ErbB targeted mono-therapies certainly contributes to a redistribution of the stoichiometry among receptors leading to the activation of compensatory pathways, suggesting that survival of cancer cells is sustained, at least in part, by the network of the ErbB receptors and their ligands. For these reasons, the use of combination therapies is becoming the most logical strategy for any type of cancer treatment, including GC. In this review we summarize information regarding mechanisms, pathways and molecules involved in the resistance to ErbB-targeted molecules with the intent to provide rational guidelines for developing more efficient therapeutic approaches

BeppoSAX observations of Seyfert 1s in the Piccinotti sample I: poorly studied sources

In this work we present the first of two papers devoted to the study of the X-ray spectral characteristics of Seyfert 1 galaxies in the Piccinotti sample. In particular we analyse here the BeppoSAX broad band (0.1-100 keV) data of 4 objects which, despite their X-ray brightness, have been historically poorly studied due to their late identification with an AGN; these are H0111-149 (MKN1152), H0235-525 (ESO198-G24), H0557-385 (IRAS F05563-3820) and H1846-786 (IRAS F18389-7834). We have assumed for all the sources a baseline model which includes a power law with an exponential cut-off plus a reflection component and an iron K_alpha line; we have also searched for the presence of intrinsic absorption and/or a soft excess component. Our analysis indicates the presence of complex absorption in two objects (H0557-385 and H0111-149) best described by a combination of two uniform absorbers, one cold and one warm. Only in one source, H0557-385, a soft excess component has been measured. The primary continuum is best described by a canonical power law (Gamma=1.7-2) with a high energy cut-off in the range 40-130 keV. A cold reflection component is likely present in all sources with values ranging from less than 0.6 to higher than 2. In 3 out of 4 objects we find a cold iron line having equivalent width typical of Seyfert 1s (100-200 eV).Comment: 6 pages, 2 figures, accepted for publication as a Research Note in Astronomy and Astrophysic

Relativistic Jets from X-ray binaries

In this review I summarise the status of observational research into relativistic jets from X-ray binaries, highlighting four areas in particular: (i) How relativistic are the jets ?, (ii) The disc : jet coupling, (iii) the nature of the underlying flat spectral component, and (iv) the relation between jets from black holes and those from neutron stars. I have attempted to discuss the extent of our (limited) physical understanding, and to point the way towards relevant new observational tests of the various phenomena.Comment: Review article, to be published in `Astrophysics and Cosmology : A collection of critical thoughts', Springer Lecture Notes in Physic