Fourth order gravity and experimental constraints on Eddington parameters

PPN-limit of higher order theories of gravity represents a still controversial matter of debate and no definitive answer has been provided, up to now, about this issue. By exploiting the analogy between scalar-tensor and fourth-order theories of gravity, one can generalize the PPN-limit formulation. By using the definition of the PPN-parameters $\gamma$ and $\beta$ in term of the $f(R)$ derivatives, we show that a family of third-order polynomial theories, in the Ricci scalar $R$, turns out to be compatible with the PPN-limit and the deviation from General Relativity theoretically predicted agree with experimental data.Comment: 7 pages, 3 figure

Reconciling dark energy models with f(R) theories

Higher order theories of gravity have recently attracted a lot of interest as alternative candidates to explain the observed cosmic acceleration without the need of introducing any scalar field. A critical ingredient is the choice of the function f(R) of the Ricci scalar curvature entering the gravity Lagrangian and determining the dynamics of the universe. We describe an efficient procedure to reconstruct f(R) from the Hubble parameter $H$ depending on the redshift z. Using the metric formulation of f(R) theories, we derive a third order linear differential equation for f(R(z)) which can be numerically solved after setting the boundary conditions on the basis of physical considerations. Since H(z) can be reconstructed from the astrophysical data, the method we present makes it possible to determine, in principle, what is the f(R) theory which best reproduces the observed cosmological dynamics. Moreover, the method allows to reconcile dark energy models with f(R) theories finding out what is the expression of f(R) which leads to the same H(z) of the given quintessence model. As interesting examples, we consider "quiessence" (dark energy with constant equation of state) and the Chaplygin gas.Comment: 15 pages, 4 figures, accepted for publication on Physical Review

Local anesthetic infiltration vs. nervous blocks in face’s skin lesions: what’s new

Skin tumors are the most common type of cancer. They are localized throughout the body, more frequently in those regions chronically exposed to sun, like face, scalp and neck, compromising aesthetic appearance. The optimization of day hospital surgical procedures is mandatory, to avoid erroneous indications, insufficient intra operative comfort and prolonged recovery. New guidelines should be discussed and shared. Patients were divided in two groups: i. Group A of 50 patients, 21 male and 29 female, age 65 ±9, ASA I – III (10/19/21), weight 68±11 kg, height 160±8, with anesthetic Local Infiltration (LI); ii. Group B of 50 patients, 16 male, 34 female, age 68 ±10, ASA I – III (9/22/19), weight 64 ± 9 kg, height 158 ±11, with nerve block (NB). The purpose of our study is to evaluate the analgesia level, compliance and complication rate after LI or selective NB with alkalinised mepivacaine cloridrate 2%, Guardant®. Demographic data, ASA physical stauts, size of lesions, surgery, anesthesia durations and volume of LA injected were analyzed. Fisher’s exact test and Student’s t test were used; P ≤ 0.05 was considered statistically significant. No differences in age (65 ± 9 vs 68 ± 10 years), weight (68 ± 11 vs 64 ± 9), height (160 ± 8 vs 158 ± 11 cm), size of lesion (23 ± 11 vs 25 ± 14 mm), duration of surgery (47 ± 18 vs 51 ± 23 minutes) were detected in two groups (p > 0.05). Both anesthetic techniques ensured good analgesia, but only nerve’s blocks were be able to determine satisfactory intra operative patient’s comfort, a bloodless wound and weak risk for nervous lesions and toxic reaction to local anesthetic

T-cell responses in oiled guillemots and swans in a rehabilitation setting

This article has been accepted for publication in the Archives of Environmental Contamination and Toxicology. The final version can be accessed from the link below.This article has been made available through the Brunel Open Access Publishing Fund.Aquatic birds are commonly affected by oil spills. Despite rehabilitation efforts, the majority of rehabilitated common guillemots (Uria aalge) do not survive, whereas mute swans (Cygnus olor) tend to have higher post-release survival. Polyaromatic hydrocarbons (PAHs) present in crude oil and diesel are immunotoxic in birds affecting cell-mediated responses to immunogens. Because it is a target of PAH toxicity, T-lymphocyte response to controlled mitogen administration (phytohemagglutinnin test) was investigated in a scoping study as a potentially useful minimally invasive in vivo test of cell-mediated immunity. The test was performed on 69 mute swans and 31 common guillemots stranded on the Norfolk and Lincolnshire coastline and inland waterways in England (UK)either due to injury or to contamination with crude or diesel oil. T-lymphocyte response was significantly decreased in swans with greater oil scores. T-lymphocyte responses were also decreased in guillemots, but this finding was not statistically significant

A general solution in the Newtonian limit of f(R)- gravity

We show that any analytic $f(R)$-gravity model, in the metric approach, presents a weak field limit where the standard Newtonian potential is corrected by a Yukawa-like term. This general result has never been pointed out but often derived for some particular theories. This means that only $f(R)=R$ allows to recover the standard Newton potential while this is not the case for other relativistic theories of gravity. Some considerations on the physical consequences of such a general solution are addressed.Comment: 5 page

Monitoring marine environments with Autonomous Underwater Vehicles: A bibliometric analysis

A sustainable and effective monitoring of the environment is necessary to assess its current status. In particular, marine ecosystems are more and more subjected to external inputs and pollutants in general, which may considerably affect their biodiversity and the regularity of their processes, with consequences on the global system. Autonomous Underwater Vehicles are frequently used to perform research and monitoring operations, being usually more cost-effective and less time-consuming than the traditional methods. In this study, the global scientific literature on the employment of AUVs for the environment is explored. The bibliometric analysis on the networks between authors, countries, journals and keywords related to the topic allowed to verify the major research interests and assess the current weaknesses on which researcher are currently focused. This approach proved to be a promising way for exploring the scientific literature by applying systems thinking in bibliometric science

Structure and tribological performance of diamond-like carbon based coatings for aerospace component processing

Copyright @ 2009 The Surface Science Society of JapanThis work examines diamond-like carbon (DLC) coatings deposited by plasma enhanced chemical vapour deposition (PECVD) as an environmentally friendly alternative to chromium plating in restoration of worn or damaged aircraft components. DLC coatings offer superior mechanical properties; however, high internal stresses and poor adhesion can prevent the deposition of thick films. This work examines a series of layered structures based on epoxy-resin interlayers with DLC applied as a surface film. Wear testing and examination with scanning electron microscopy and atomic force microscopy lead to the development of an optimum DLC/epoxy system with wear characteristics superior to those of chromium-plated steel. This new coating system has a great potential in restoring aircraft components in a more efficient and environmentally friendly manner.This work is funded via the Engineering and Physical Sciences Research Council (EPSRC)

Comparison of three measurement methods of saturated hydraulic condutivity

International audienceAfter pointing out the importance of the saturated hydraulic conductivity (ks) measurements and the difficulties and uncertainties that are present, and after recalling salient aspects of three well-known measurement methods of this parameter (i.e. constant-head tension infiltrometer (TI) method, constant-head pressure infiltrometer (PI) method and soil core (SC) estimates method), the results of an investigation on data which were obtained during a measurement campaign on an area of 800 m2, on a sandy loam hillslope, located in Southern Italy, were carried out again here. Three sets of values of ks, obtained with these measurement methods, were analyzed statistically, verifying that the log-normal distribution describes these better than the normal one; moreover, the more significant statistical parameters of each set were compared (average value , amplitude A, coefficient of variation CV and standard deviation SD), individualizing the more significant differences. The greatest value of hydraulic conductivity was found with method (PI), while the smallest with (SC) and the intermediate with (TI); these differences were translated into macroporosity and into the influence of the single measurement method. Moreover, referring to the possible factors affecting the results, the importance can be noted of the structure, the texture and the soil events, in terms of utilization, which can affect the measure of ks leading often to very different values even for similar soils, but with a different history, independently of the coincidence of the measurement points and they can be determining to explain the differences affecting the results obtained in analogous investigations by other researchers. Having confirmed that generalization is not possible, the need was emphasized to adopt the necessary devices relating to the specific measurement method, case by case, and to carefully explain the obtained results, in the light of the peculiarities and the limits of each situation. Finally, the results of similar statistical analysis carried out on a greater number of ks values, measured through the (TI) and (PI) methods are shown in this paper, with some statistical considerations on the increasing of the measurements number

The evolution of density perturbations in f(R) gravity

We give a rigorous and mathematically well defined presentation of the Covariant and Gauge Invariant theory of scalar perturbations of a Friedmann-Lemaitre-Robertson-Walker universe for Fourth Order Gravity, where the matter is described by a perfect fluid with a barotropic equation of state. The general perturbations equations are applied to a simple background solution of R^n gravity. We obtain exact solutions of the perturbations equations for scales much bigger than the Hubble radius. These solutions have a number of interesting features. In particular, we find that for all values of n there is always a growing mode for the density contrast, even if the universe undergoes an accelerated expansion. Such a behaviour does not occur in standard General Relativity, where as soon as Dark Energy dominates, the density contrast experiences an unrelenting decay. This peculiarity is sufficiently novel to warrant further investigation on fourth order gravity models.Comment: 21 pages, 2 figures, typos corrected, submitted to PR