Dynamical paths and universality in continuous variables open systems

We address the dynamics of quantum correlations in continuous variable open systems and analyze the evolution of bipartite Gaussian states in independent noisy channels. In particular, upon introducing the notion of dynamical path through a suitable parametrization for symmetric states, we focus attention on phenomena that are common to Markovian and non-Markovian Gaussian maps under the assumptions of weak coupling and secular approximation. We found that the dynamical paths in the parameter space are universal, that is they do depend only on the initial state and on the effective temperature of the environment, with non Markovianity that manifests itself in the velocity of running over a given path. This phenomenon allows one to map non-Markovian processes onto Markovian ones and it may reduce the number of parameters needed to study a dynamical process, e.g. it may be exploited to build constants of motions valid for both Markovian and non-Markovian maps. Universality is also observed in the value of Gaussian discord at the separability threshold, which itself is a function of the sole initial conditions in the limit of high temperature. We also prove the existence of excluded regions in the parameter space, i.e. of sets of states which cannot be linked by any Gaussian dynamical map.Comment: 7 pages, 2 figures, improved pictures and forma

Ab-initio self-energy corrections in systems with metallic screening

The calculation of self-energy corrections to the electron bands of a metal requires the evaluation of the intraband contribution to the polarizability in the small-q limit. When neglected, as in standard GW codes for semiconductors and insulators, a spurious gap opens at the Fermi energy. Systematic methods to include intraband contributions to the polarizability exist, but require a computationally intensive Fermi-surface integration. We propose a numerically cheap and stable method, based on a fit of the power expansion of the polarizability in the small-q region. We test it on the homogeneous electron gas and on real metals such as sodium and aluminum.Comment: revtex, 14 pages including 5 eps figures v2: few fixe

RESIN-BASED COMPOSITES MODULATE ORAL BIOFILM FORMATION

Resin-based composites (RBCs) are increasingly used because of their excellent aesthetic properties and improved mechanical features. Nevertheless, the main reason for failure of resin composite restorations is still secondary caries. Dental caries is a very common infectious disease driven by the metabolic activity of a dysbiotic biofilm able to colonize both natural and artificial surfaces. In recent years, extensive research has been devoted to develop new restorative materials that could prevent the formation of recurrent carious lesions. Many approaches have been followed to reach this goal, particularly optimizing RBCs surfaces to obtain anti-adhesive properties, developing bioactive materials and synthesizing biomimetic materials. The aim of this PhD thesis was to explore the different approaches in order to discriminate the parameters influencing the microbiological behaviour of RBCs and therefore optimize their formulation to successfully control oral biofilms development. The three approaches were evaluated in the experimental part of the thesis. Considering the first approach, the optimization of the microbiological properties of resin- based dental materials was evaluated from different points of view. Experimental RBCs with different compositions were studied, hypothesizing that surface features and nanotexture would have influenced biofilm formation. The anti-adhesive properties of the tested materials were evaluated as a possible way to control biofilm formation without the need of antibacterial agents. The results showed that both hydrophobicity of the resin matrix of RBCs and filler amount can influence oral biofilm formation. Furthermore, different commercially available RBCs were submitted to diverse finishing and polishing protocols in order to evaluate the influence of these procedures on the surface features and on the microbiological behaviour of each material. It was therefore showed that surface chemistry seemed to play an important role in influencing biofilm formation. Regarding the second research field, the antimicrobial behaviour of experimental RBCs derived from a commercial formulation including different fractions of fluoride-releasing S- PRG filler particles was evaluated. The results of this study suggested an impact of fluoride- releasing S-PRG filler particles particularly on the early phases of biofilm formation. As the release of fluoride diminishes as a function of time, optimizing the fluoride-recharging abilities of the materials might help to control biofilm formation for longer periods. Moreover, the final polishing of the material may substantially influence the release of fluoride. The third research approach evaluated the possibility that biomimetic materials may control oral biofilm formation, without the addition of specific antimicrobial agents. In this study functionalized dicalcium phosphate dihydrate nanoparticles (nDCPD) were incorporated into an experimental RBC. Results showed that the RBC with functionalized nDCPD nanoparticles showed a reduction in biofilm formation when compared to a RBC filled with non-functionalized nanoparticles. All these approaches were effective in influencing oral biofilm formation on the tested materials. Recent studies regarding the human microbiome tend to consider biofilms as a part of the human body and show that many diseases, including dental caries, are due to an imbalance between host and biofilms. These diseases may be treated by modifying biofilms composition, without trying to eradicate biofilms. Hence, the possibility to modulate oral biofilm formation on restorations through the optimization of materials surfaces without the addition of any antibacterial agent seems to be the most interesting approach

Endothelial Hyper-Permeability Induced by T1D Sera Can be Reversed by iNOS Inactivation

Type 1 Diabetes Mellitus (T1D) is associated with accelerated atherosclerosis that is responsible for high morbidity and mortality. Endothelial hyperpermeability, a feature of endothelial dysfunction, is an early step of atherogenesis since it favours intimal lipid uptake. Therefore, we tested endothelial leakage by loading the sera from T1D patients onto cultured human endothelial cells and found it increased by hyperglycaemic sera. These results were phenocopied in endothelial cells cultured in a medium containing high concentrations of glucose, which activates inducible nitric oxide synthase with a consequent increase of nitric oxide. Inhibition of the enzyme prevented high glucose-induced hyperpermeability, thus pointing to nitric oxide as the mediator involved in altering the endothelial barrier function. Since nitric oxide is much higher in sera from hyperglycaemic than normoglycaemic T1D patients, and the inhibition of inducible nitric oxide synthase prevents sera-dependent increased endothelial permeability, this enzyme might represent a promising biochemical marker to be monitored in T1D patients to predict alterations of the vascular wall, eventually promoting intimal lipid accumulation

Transverse momentum dependent parton distributions in a light-cone quark model

The leading twist transverse momentum dependent parton distributions (TMDs) are studied in a light-cone description of the nucleon where the Fock expansion is truncated to consider only valence quarks. General analytic expressions are derived in terms of the six amplitudes needed to describe the three-quark sector of the nucleon light-cone wave function. Numerical calculations for the T-even TMDs are presented in a light-cone constituent quark model, and the role of the so-called pretzelosity is investigated to produce a nonspherical shape of the nucleon.Comment: references added and typos corrected; version to appear in Phys. Rev.

Substituted nano-hydroxyapatite toothpastes reduce biofilm formation on enamel and resin-based composite surfaces

Background: Toothpastes containing nano-hydroxyapatite (n-HAp) substituted with metal ions provide calcium and phosphate ions to dental hard tissues, reducing demineralization, and promoting remineralization. Few data are available about the effect of these bioactive compounds on oral microbiota. Methods: This in vitro study evaluated the influence of two commercially-available substituted n-HAp-based toothpastes (\u3b1: Zn-carbonate substituted n-HAp; \u3b2: F, Mg, Sr-carbonate substituted n-HAp) on early colonization (EC, 12 h) and biofilm formation (BF, 24 h) by oral microbiota. Controls were brushed with distilled water. Artificial oral microcosm and Streptococcus mutans biofilms were developed using human enamel and a resin-based composite (RBC) as adherence surfaces. Two test setups, a shaking multiwell plate and a modified drip-flow reactor (MDFR), were used to simulate clinical conditions during the night (low salivary flow and clearance) and daytime, respectively. Energy-dispersive X-ray spectrometry (EDS) was used to evaluate specimens\u2019 surfaces after toothpaste treatment. Fluoride release from \u3b2 toothpaste was evaluated. Viable adherent biomass was quantified by MTT assay, and biofilms\u2019 morphology was highlighted using confocal microscopy. Results: EDS showed the presence of remnants from the tested toothpastes on both adherence surfaces. \u3b2 toothpaste showed significantly lower EC and BF compared to control using the artificial oral microcosm model, while \u3b1 toothpaste showed lower EC and BF compared to control, but higher EC and BF compared to \u3b2 toothpaste. The effect shown by \u3b2 toothpaste was, to a minimal extent, due to fluoride release. Interestingly, this result was seen on both adherence surfaces, meaning that the tested toothpastes significantly influenced EC and BF even on RBC surfaces. Furthermore, the effect of toothpaste treatments was higher after 12 h than 24 h, suggesting that toothbrushing twice a day is more effective than brushing once. Conclusions: The efficacy of these treatments in reducing microbial colonization of RBC surfaces may represent a promising possibility in the prevention of secondary caries

Genomic imbalances are confined to non-proliferating cells in paediatric patients with acute myeloid leukaemia and a normal or incomplete karyotype

Copyright @ 2011 Ballabio et al.Leukaemia is often associated with genetic alterations such as translocations, amplifications and deletions, and recurrent chromosome abnormalities are used as markers of diagnostic and prognostic relevance. However, a proportion of acute myeloid leukaemia (AML) cases have an apparently normal karyotype despite comprehensive cytogenetic analysis. Based on conventional cytogenetic analysis of banded chromosomes, we selected a series of 23 paediatric patients with acute myeloid leukaemia and performed whole genome array comparative genome hybridization (aCGH) using DNA samples derived from the same patients. Imbalances involving large chromosomal regions or entire chromosomes were detected by aCGH in seven of the patients studied. Results were validated by fluorescence in situ hybridization (FISH) to both interphase nuclei and metaphase chromosomes using appropriate bacterial artificial chromosome (BAC) probes. The majority of these copy number alterations (CNAs) were confirmed by FISH and found to localize to the interphase rather than metaphase nuclei. Furthermore, the proliferative states of the cells analyzed by FISH were tested by immunofluorescence using an antibody against the proliferation marker pKi67. Interestingly, these experiments showed that, in the vast majority of cases, the changes appeared to be confined to interphase nuclei in a non-proliferative status.This work was supported by a grant from Leukaemia Research UK (grant no. 0253). SJLK and RR were supported by the NIHR Biomedical Research Centre, Oxford, with funding from the Department of Health’s NIHR Biomedical Research Centres funding schemeThis article is available through the Brunel Open Access Publishing Fund