The Universality of Einstein Equations

It is shown that for a wide class of analytic Lagrangians which depend only on the scalar curvature of a metric and a connection, the application of the so--called ``Palatini formalism'', i.e., treating the metric and the connection as independent variables, leads to ``universal'' equations. If the dimension $n$ of space--time is greater than two these universal equations are Einstein equations for a generic Lagrangian and are suitably replaced by other universal equations at bifurcation points. We show that bifurcations take place in particular for conformally invariant Lagrangians $L=R^{n/2} \sqrt g$ and prove that their solutions are conformally equivalent to solutions of Einstein equations. For 2--dimensional space--time we find instead that the universal equation is always the equation of constant scalar curvature; the connection in this case is a Weyl connection, containing the Levi--Civita connection of the metric and an additional vectorfield ensuing from conformal invariance. As an example, we investigate in detail some polynomial Lagrangians and discuss their bifurcations.Comment: 15 pages, LaTeX, (Extended Version), TO-JLL-P1/9

SURFACE FUNCTIONALIZATION OF 3D GLASS-CERAMIC POROUS SCAFFOLDS FOR ENHANCED MINERALIZATION IN VITRO

Bone reconstruction after tissue loosening due to traumatic, pathological or surgical causes is in increasing demand. 3D scaffolds are a widely studied solution for supporting new bone growth. Bioactive glass–ceramic porous materials can offer a three-dimensional structure that is able to chemically bond to bone. The ability to surface modify these devices by grafting biologically active molecules represents a challenge, with the aim of stimulating physiological bone regeneration with both inorganic and organic signals. In this research work glass ceramic scaffolds with very high mechanical properties and moderate bioactivity have been functionalized with the enzyme alkaline phosphatase (ALP). The material surface was activated in order to expose hydroxyl groups. The activated surface was further grafted with ALP both via silanization and also via direct grafting to the surface active hydroxyl groups. Enzymatic activity of grafted samples were measured by means of UV–vis spectroscopy before and after ultrasonic washing in TRIS–HCl buffer solution. In vitro inorganic bioactivity was investigated by soaking the scaffolds after the different steps of functionalization in a simulated body fluid (SBF). SEM observations allowed the monitoring of the scaffold morphology and surface chemical composition after soaking in SBF. The presence of ALP enhanced the in vitro inorganic bioactivity of the tested material

Is drop-out from obesity treatment a predictable and preventable event?

BACKGROUND: Attrition is an important but understudied issue that plays a vital role in the successful treatment of obesity. To date, most studies focusing on attrition rates and/or its predictors have been based on pretreatment data routinely collected for other purposes. Our study specifically aims at identifying the predictors of drop-out focusing on empirically or theoretically-based factors. METHODS: We conducted a retrospective observational study in an academic outpatient clinical nutrition service in Pavia, Italy. We examined a total of 98 adult obese patients (36 males, 62 females) who underwent a 6-month dietary behavioral weight-loss treatment at our Center. Pre-treatment and treatment-related variables were collected or calculated from clinical charts in order to discriminate those subjects who completed treatment from those who abandoned it before its completion. Multivariable regression analysis was used to identify the independent predictors of drop-out. RESULTS: The drop-out rates were 21% at 1 month and 57% at 6 months. Compared with completers, noncompleters were significantly younger in terms of age at first dieting attempt (24.0 ± 10.7 vs. 31.3 ± 11.2 years, P = 0.005), had lower diastolic blood pressure (87.8 ± 9.7 vs. 92.7 ± 11.4 mmHg, P = 0.022), had a lower baseline body fat percentage (38.5 ± 6.4 vs. 41.2 ± 4.4% weight, P = 0.015), and had a lower percentage of early weight loss (-1.8 ± 1.8% vs. -3.1 ± 2.1%, P = 0.035). Moreover, noncompleters significantly differed from completers with regard to type of referral (34.1% vs. 53.3% sent by a physician, P = 0.036) and SCL-90 anger-hostility subscale (0.83 ± 0.72 vs. 0.53 ± 0.51, P = 0.022). A multivariable logistic regression analysis including pre-treatment variables showed that body fat percentage (P = 0.030) and SCL-90 anger-hostility subscale (P = 0.021) were independently associated with attrition. In a multivariable model considering both pre-treatment and treatment-related factors, attrition was found to be independently related to the age at first dieting attempt (P = 0.016) and the achievement of early weight loss (P = 0.029). CONCLUSIONS: Our data confirm that psychopathological tracts, early dieting attempts, and a poor initial treatment response are key independent predictors of drop-out from obesity treatment

Boundary Conditions, Energies and Gravitational Heat in General Relativity (a Classical Analysis)

The variation of the energy for a gravitational system is directly defined from the Hamiltonian field equations of General Relativity. When the variation of the energy is written in a covariant form it splits into two (covariant) contributions: one of them is the Komar energy, while the other is the so-called covariant ADM correction term. When specific boundary conditions are analyzed one sees that the Komar energy is related to the gravitational heat while the ADM correction term plays the role of the Helmholtz free energy. These properties allow to establish, inside a classical geometric framework, a formal analogy between gravitation and the laws governing the evolution of a thermodynamic system. The analogy applies to stationary spacetimes admitting multiple causal horizons as well as to AdS Taub-bolt solutions.Comment: Latex file, 31 pages; one reference and two comments added, misprints correcte

Topological Defects in Gravitational Theories with Non Linear Lagrangians

The gravitational field of monopoles, cosmic strings and domain walls is studied in the quadratic gravitational theory $R+\alpha R^2$ with $\alpha |R|\ll 1$, and is compared with the result in Einstein's theory. The metric aquires modifications which correspond to a short range `Newtonian' potential for gauge cosmic strings, gauge monopoles and domain walls and to a long range one for global monopoles and global cosmic strings. In this theory the corrections turn out to be attractive for all the defects. We explain, however, that the sign of these corrections in general depends on the particular higher order derivative theory and topological defect under consideration. The possible relevance of our results to the study of the evolution of topological defects in the early universe is pointed out.Comment: LaTeX (uses revrex macros), 13 page

CARD15 genotyping in inflammatory bowel disease patients by multiplex pyrosequencing

[No abstract available

Electromagnetic Form Factors in the hypercentral CQM

We report on the recent results of the hypercentral Constituent Quark Model (hCQM). The model contains a spin independent three-quark interaction which is inspired by Lattice QCD calculations and reproduces the average energy values of the SU(6) multiplets. The splittings are obtained with a SU(6)-breaking interaction, which can include also an isospin dependent term. Concerning Constituent Quark models, we have shown for the first time that the decreasing of the ratio of the elastic form factors of the proton is due to relativistic effects using relativistic corrections to the e.m. current and boosts. Now the elastic nucleon form factors have been recalculated, using a relativistic version of the hCQM and a relativistic quark current showing a very detailed reproduction of all the four form factor existing data over the complete range of 0-4 $GeV^2$. Futhermore, the model has been used for predictions concerning the electromagnetic transverse and longitudinal transition form factors giving a good description of the medium $Q^2$ behaviour. We show that the discrepancies in the reproduction of the helicity amplitudes at low $Q^2$ are due to pion loops. We have calculated the helicity amplitudes for all the 3 and 4 star resonances opening the possibility of application to the evaluation of cross sections.Comment: 5 pages, 7 figures, Invited talk at the ICTP 4th International Conference on Perspectives in Hadronic Physics, Trieste, Italy, 12-16 May 2003. Accepted by Eur. Phys. J.

Mineralization of human premolar occlusal fissures: a quantitative histochemical microanalysis

The mechanisms of cariogenesis in occlusal fissures remain elusive because of limited information about fissure structure and wall mineralization. The purpose of the present study was to determine the correlation between morphological patterns in occlusal fissures in human premolars and quantitative histochemical patterns of mineralization in the walls of these formations. We used scanning electron microscopy and quantitative X-ray microanalysis with the peak-tolocal background ratio method and microcrystalline calcium salts as standards. We distinguished three morphological patterns of fissures in scanning electron microscopic images. The wall of the fissures was less mineralized than the control enamel in all three types of fissures. Because the fissure walls are hypomineralized, we suggest that practicing dentists should take into account the degree of mineralization when they are preparing the fissures for the application of sealant.This work was partially supported by the Ministerio de Educación y Cultura (PB97-0840) and the Agencia Española de Cooperación Internacional (AECI)

Two-dimensional higher-derivative gravity and conformal transformations

We consider the lagrangian $L=F(R)$ in classical (=non-quantized) two-dimensional fourth-order gravity and give new relations to Einstein's theory with a non-minimally coupled scalar field. We distinguish between scale-invariant lagrangians and scale-invariant field equations. $L$ is scale-invariant for F = c_1 R\sp {k+1} and a divergence for $F=c_2 R$. The field equation is scale-invariant not only for the sum of them, but also for $F=R\ln R$. We prove this to be the only exception and show in which sense it is the limit of \frac{1}{k} R\sp{k+1} as $k\to 0$. More generally: Let $H$ be a divergence and $F$ a scale-invariant lagrangian, then $L= H\ln F$ has a scale-invariant field equation. Further, we comment on the known generalized Birkhoff theorem and exact solutions including black holes.Comment: 16 pages, latex, no figures, [email protected], Class. Quant. Grav. to appea