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

Cosmological consequences of an inhomogeneous space-time

Astrophysical observations provide a picture of the universe as a 4-dim homogeneous and isotropic flat space-time dominated by an unknown form of dark energy. To achieve such a cosmology one has to consider in the early universe an inflationary era able to overcome problems of standard cosmological models. Here an inhomogeneous model is proposed which allows to obtain a Friedmann-Robertson-Walker behaviour far away from the inhomogeneities and it naturally describes structures formation. We also obtain that the cosmological term does not prevent structure formation, avoiding a fine tuning problem in initial conditions. The asymptotic exact solution have been calculated. A simple test with universe age prediction has been performed. A relation between the inhomogeneity, the breaking of time reversal, parity and the matter-antimatter asymmetry is briefly discussed.Comment: 13 pages, accepted for publication in Gen. Rel. Gra

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

Fast glycorrhachia and cerebrospinal fluid protein as predictors of sensory block in anesthesia with subarachnoid Ropivacaine

BACKGROUND: Identify if glycorrhachia and cerebrospinal fluid protein could influence the time of sensory block to T10, the duration and the metameric block's level, after a standard dose of Ropivacaine. METHODS: 80 patients, ASA I - III undergoing to transurethral prostate resection with spinal anesthesia in a prospected open study were recruited. A 0.2 ml liquor's sample was taken; glycorrhachia, by glycemic stix and CSF protein, by urinary stix, were got, before Ropivacaine 0.5% 15 mg injection (0.10 - 0.15 mlsec). After anti-trendelemburg, with 30 ° tilting for 15 min, the onset of sensory block to T10, the maximum metameric level to 15' and the time of sensory block were reported. The data collection were analyzed using the software language R. RESULTS: A significant correlation liquor specific weigh preoperative glycemia (0.749), liquoral specific weigh glycorrhachia (rho = 0.751; R2 = 0.564; P 0.05) and specific weigh CSF protein (rho = 0.684; R2 = 0.468; P 0.05) were reported. Inverse relation CSF weightsensory block level (rho -0.789, P 0.05, R2 0.621) was evidenced. Inverse relation onset time to T10 glycorrhachia (84%) and cephalic block glycorrhachia (76%) were found. Inverse correlation onset time to T 10 CSF protein and cephalic block proteinorrachia was respectively 84% and 67%. A rho of 0.712 with R2 of 51% BMI onset to T10 and rho of 0.681 with R2 of 51% BMI maximum cephalic block with P 0.05 were reported. CONCLUSIONS: The predictability of a iso-hypobaric local anesthetic could reduce the risk of procedure failure and adverse events by further cephalic spread

JOINT ALIGNMENT OF UNDERWATER AND ABOVE-THE-WATER PHOTOGRAMMETRIC 3D MODELS BY INDEPENDENT MODELS ADJUSTMENT

The surveying and 3D modelling of objects that extend both below and above the water level, such as ships, harbour structures, offshore platforms, are still an open issue. Commonly, a combined and simultaneous survey is the adopted solution, with acoustic/optical sensors respectively in underwater and in air (most common) or optical/optical sensors both below and above the water level. In both cases, the system must be calibrated and a ship is to be used and properly equipped with also a navigation system for the alignment of sequential 3D point clouds. Such a system is usually highly expensive and has been proved to work with still structures. On the other hand for free floating objects it does not provide a very practical solution. In this contribution, a flexible, low-cost alternative for surveying floating objects is presented. The method is essentially based on photogrammetry, employed for surveying and modelling both the emerged and submerged parts of the object. Special targets, named Orientation Devices, are specifically designed and adopted for the successive alignment of the two photogrammetric models (underwater and in air). A typical scenario where the proposed procedure can be particularly suitable and effective is the case of a ship after an accident whose damaged part is underwater and necessitate to be measured (Figure 1). The details of the mathematical procedure are provided in the paper, together with a critical explanation of the results obtained from the adoption of the method for the survey of a small pleasure boat in floating condition

Alternative acceptor materials for organic photovoltaic cells

Synthesis and spectroscopic characterization of perylene derivatives (perylene monoimides and diimides) are reported. The aim of the present work is to investigate the synthesis of these compounds in detail in order to highlight the crucial factors for obtaining a specific class of molecules. The final compounds of the synthetic pathway would be able to mimic the peculiar properties of fullerene derivatives, up to now the best candidates as accepting materials

Dark energy and dark matter as curvature effects

Astrophysical observations are pointing out huge amounts of dark matter and dark energy needed to explain the observed large scale structures and cosmic accelerating expansion. Up to now, no experimental evidence has been found, at fundamental level, to explain such mysterious components. The problem could be completely reversed considering dark matter and dark energy as shortcomings of General Relativity and claiming for the correct theory of gravity as that derived by matching the largest number of observational data. As a result, accelerating behavior of cosmic fluid and rotation curves of spiral galaxies are reproduced by means of curvature effects.Comment: 4 pages, 1 figure, revised versio

Danae++: A smart approach for denoising underwater attitude estimation

One of the main issues for the navigation of underwater robots consists in accurate vehicle positioning, which heavily depends on the orientation estimation phase. The systems employed to this end are affected by different noise typologies, mainly related to the sensors and to the irregular noise of the underwater environment. Filtering algorithms can reduce their effect if opportunely con-figured, but this process usually requires fine techniques and time. This paper presents DANAE++, an improved denoising autoencoder based on DANAE (deep Denoising AutoeNcoder for Attitude Estimation), which is able to recover Kalman Filter (KF) IMU/AHRS orientation estimations from any kind of noise, independently of its nature. This deep learning-based architecture already proved to be robust and reliable, but in its enhanced implementation significant improvements are obtained in terms of both results and performance. In fact, DANAE++ is able to denoise the three angles describing the attitude at the same time, and that is verified also using the estimations provided by an extended KF. Further tests could make this method suitable for real-time applications in navigation tasks

Inflessence: a phenomenological model for inflationary quintessence

We present a phenomenologically motivated model which is able to give rise both to an inflationary epoch and to the present day cosmic acceleration. We introduce an approach where the energy density depends on the scale factor $a$ in such a way that a smooth transition from the inflation to the matter dominated era and then to the nowadays accelerated expansion is achieved. We use the dimensionless coordinate distance $y(z)$ to the Gold Type Ia Supernovae dataset and to a sample comprising 20 radio galaxies, the shift parameter ${\cal{R}}$ and the acoustic peak parameter ${\cal{A}}$ to test whether the model is in agreement with observations and to constrain its main parameters. As an independent cross check, we also compare model predictions with the lookback time to galaxy clusters and the age of the universe. Although phenomenologically inspired, the model may be theoretically motivated either resorting to a scenario with a scalar and phantom fields (eventually interacting) or as an effective description arising from higher order gravity theories.Comment: 12 pages, 7 figures, accepted for publication on Physical Review