Hydrostatic equilibrium and stellar structure in f(R)-gravity

We investigate the hydrostatic equilibrium of stellar structure by taking into account the modi- fied La\'e-Emden equation coming out from f(R)-gravity. Such an equation is obtained in metric approach by considering the Newtonian limit of f(R)-gravity, which gives rise to a modified Poisson equation, and then introducing a relation between pressure and density with polytropic index n. The modified equation results an integro-differential equation, which, in the limit f(R) \rightarrow R, becomes the standard La\'e-Emden equation. We find the radial profiles of gravitational potential by solving for some values of n. The comparison of solutions with those coming from General Relativity shows that they are compatible and physically relevant.Comment: 9 pages, 1 figur

Neural Networks for Modeling and Control of Particle Accelerators

We describe some of the challenges of particle accelerator control, highlight recent advances in neural network techniques, discuss some promising avenues for incorporating neural networks into particle accelerator control systems, and describe a neural network-based control system that is being developed for resonance control of an RF electron gun at the Fermilab Accelerator Science and Technology (FAST) facility, including initial experimental results from a benchmark controller.Comment: 21 p

The Post-Newtonian Limit of f(R)-gravity in the Harmonic Gauge

A general analytic procedure is developed for the post-Newtonian limit of $f(R)$-gravity with metric approach in the Jordan frame by using the harmonic gauge condition. In a pure perturbative framework and by using the Green function method a general scheme of solutions up to $(v/c)^4$ order is shown. Considering the Taylor expansion of a generic function $f$ it is possible to parameterize the solutions by derivatives of $f$. At Newtonian order, $(v/c)^2$, all more important topics about the Gauss and Birkhoff theorem are discussed. The corrections to "standard" gravitational potential ($tt$-component of metric tensor) generated by an extended uniform mass ball-like source are calculated up to $(v/c)^4$ order. The corrections, Yukawa and oscillating-like, are found inside and outside the mass distribution. At last when the limit $f\rightarrow R$ is considered the $f(R)$-gravity converges in General Relativity at level of Lagrangian, field equations and their solutions.Comment: 16 pages, 10 figure

Functional bioglass/carbon nanocomposite scaffolds from vat photopolymerization of a novel preceramic polymer-based nanoemulsion

Silicone polymers are already known as feedstock for a variety of silicate bioceramics, in the form of scaffolds with complex shapes, obtained by Vat Photopolymerization. Printing is enabled by using silicone blended with photocurable acrylates. The development of a particular silicate composition that functions as a glass or glass-ceramic precursor is possible by the addition of suitable oxide fillers (especially carbonate powders), suspended in the polymer blend. Oxides, from the fillers, easily react with silica left by the thermal transformation of the silicone. The fillers, however, also determine complications in Vat Photopolymerization, due to light scattering; in addition, local oxide concentrations generally impede the obtainment of glassy products. The present paper illustrates a simple solution to these issues, based on the inclusion of a Ca salt in nano-emulsion within a silicone-containing blend. Homogeneous printed samples are later converted into crack-free, fully amorphous ceramic composites, by firing at only 700 °C. The glass matrix, resembling 70S30C (70 % SiO2 and 30 % CaO) bioglass, is achieved according to the quasi-molecular CaO distribution. The secondary phase, promoted by treatment in N2 atmosphere and consisting of pyrolytic carbon, provides a marked photothermal effect

Primary care in Malta : the patients’s expectations in 2009

Given the strong literature base to support the positioning of Primary Care at the core of a sustainable National Health Service, this study examines what the Maltese general public prefer, and expect, from their family doctor, and explores their preferred systems of care changes.peer-reviewe

Effects of balloon injury on neointimal hyperplasia in steptozotocin-induced diabetes and in hyperinsulinemic nondiabetic pancreatic islet-transplanted rats.

BACKGROUND: The mechanisms of increased neointimal hyperplasia after coronary interventions in diabetic patients are still unknown. METHODS AND RESULTS: Glucose and insulin effects on in vitro vascular smooth muscle cell (VSMC) proliferation and migration were assessed. The effect of balloon injury on neointimal hyperplasia was studied in streptozotocin-induced diabetic rats with or without adjunct insulin therapy. To study the effect of balloon injury in nondiabetic rats with hyperinsulinemia, pancreatic islets were transplanted under the kidney capsule in normal rats. Glucose did not increase VSMC proliferation and migration in vitro. In contrast, insulin induced a significant increase in VSMC proliferation and migration in cell cultures. Furthermore, in VSMC culture, insulin increased MAPK activation. A reduction in neointimal hyperplasia was consistently documented after vascular injury in hyperglycemic streptozotocin-induced diabetic rats. Insulin therapy significantly increased neointimal hyperplasia in these rats. This effect of hyperinsulinemia was totally abolished by transfection on the arterial wall of the N17H-ras-negative mutant gene. Finally, after experimental balloon angioplasty in hyperinsulinemic nondiabetic islet-transplanted rats, a significant increase in neointimal hyperplasia was observed. CONCLUSIONS: In rats with streptozotocin-induced diabetes, balloon injury was not associated with an increase in neointimal formation. Exogenous insulin administration in diabetic rats and islet transplantation in nondiabetic rats increased both blood insulin levels and neointimal hyperplasia after balloon injury. Hyperinsulinemia through activation of the ras/MAPK pathway, rather than hyperglycemia per se, seems to be of crucial importance in determining the exaggerated neointimal hyperplasia after balloon angioplasty in diabetic animals

Axially symmetric solutions in f(R)-gravity

Axially symmetric solutions for f (R)-gravity can be derived starting from exact spherically sym- metric solutions achieved by Noether symmetries. The method takes advantage of a complex coordi- nate transformation previously developed by Newman and Janis in General Relativity. An example is worked out to show the general validity of the approach. The physical properties of the solution are also considered.Comment: 13 pages, 1 figure, to appear in Classical and Quantum Gravity 201