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Search Results: 1 - 10 of 3131 matches for " Mara Lorenzi "
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The Polyol Pathway as a Mechanism for Diabetic Retinopathy: Attractive, Elusive, and Resilient
Mara Lorenzi
Experimental Diabetes Research , 2007, DOI: 10.1155/2007/61038
Abstract: The polyol pathway is a two-step metabolic pathway in which glucose is reduced to sorbitol, which is then converted to fructose. It is one of the most attractive candidate mechanisms to explain, at least in part, the cellular toxicity of diabetic hyperglycemia because (i) it becomes active when intracellular glucose concentrations are elevated, (ii) the two enzymes are present in human tissues and organs that are sites of diabetic complications, and (iii) the products of the pathway and the altered balance of cofactors generate the types of cellular stress that occur at the sites of diabetic complications. Inhibition (or ablation) of aldose reductase, the first and rate-limiting enzyme in the pathway, reproducibly prevents diabetic retinopathy in diabetic rodent models, but the results of a major clinical trial have been disappointing. Since then, it has become evident that truly informative indicators of polyol pathway activity and/or inhibition are elusive, but are likely to be other than sorbitol levels if meant to predict accurately tissue consequences. The spectrum of abnormalities known to occur in human diabetic retinopathy has enlarged to include glial and neuronal abnormalities, which in experimental animals are mediated by the polyol pathway. The endothelial cells of human retinal vessels have been noted to have aldose reductase. Specific polymorphisms in the promoter region of the aldose reductase gene have been found associated with susceptibility or progression of diabetic retinopathy. This new knowledge has rekindled interest in a possible role of the polyol pathway in diabetic retinopathy and in methodological investigation that may prepare new clinical trials. Only new drugs that inhibit aldose reductase with higher efficacy and safety than older drugs will make possible to learn if the resilience of the polyol pathway means that it has a role in human diabetic retinopathy that should not have gone undiscovered.
A Trust Model for Multiagent Recommendations
Fabiana Lorenzi,Gabriel Baldo,Rafael Costa,Mara Abel
Journal of Emerging Technologies in Web Intelligence , 2010, DOI: 10.4304/jetwi.2.4.310-318
Abstract: This paper describes a trust model for multiagent recommender systems. A user’s request for a travel recommendation is decomposed by the system into subtasks, corresponding to travel services. Agents select tasks autonomously, and accomplish them using knowledge derived from previous solutions or with the help of other agents. Agents maintain local knowledge bases and, when requested to support a user in a travel planning task, they may collaborate exchanging information stored in their local bases. During this exchange process trusting other agents is fundamental. It helps agents to improve the quality of the recommendations and to avoid communication with unreliable agents. In the proposed model, the trust is also used to allow agents to become experts in particular subtasks, helping them to generate better recommendations. In this paper, we propose and validate a multiagent trust model showing the benefits of such model in a travel planning scenario.
A strongly ill-posed problem for a degenerate parabolic equation with unbounded coefficients in an unbounded domain $Ω\times {\mathcal O}$ of $\R^{M+N}$
Alfredo Lorenzi,Luca Lorenzi
Mathematics , 2012, DOI: 10.1088/0266-5611/29/2/025007
Abstract: In this paper we deal with a strongly ill-posed second-order degenerate parabolic problem in the unbounded open set $\Omega\times {\mathcal O}\subset \mathbb R^{M+N}$, related to a linear equation with unbounded coefficients, with no initial condition, but endowed with the usual Dirichlet condition on $(0,T)\times \partial(\Omega\times {\mathcal O})$ and an additional condition involving the $x$-normal derivative on $\Gamma\times {\mathcal O}$, $\Gamma$ being an open subset of $\Omega$. The task of this paper is twofold: determining sufficient conditions on our data implying the uniqueness of the solution $u$ to the boundary value problem as well as determining a pair of metrics with respect of which $u$ depends continuously on the data. The results obtained for the parabolic problem are then applied to a similar problem for a convolution integrodifferential linear parabolic equation.
EU researches superbugs
Rossella Lorenzi
Genome Biology , 2003, DOI: 10.1186/gb-spotlight-20031202-01
Abstract: Announced in Rome at a 3-day EU conference on the role of research in combating antibiotic resistance, the funding is part of a €12.6 million budget from the first call for proposals within the Sixth Framework Programme (2002-2006)."People trust antibiotics to cure almost any kind of disease. Unfortunately, as recent outbreaks of severe acute respiratory syndrome show, this is not the case," European Research Commissioner Philippe Busquin said in a statement. "More research for the benefit of patients is needed to make use of the wealth of information provided by more than 140 bacterial genomes known today. We must also make sure that the pharmaceutical industry continues its research into the development of new antibiotics."The new research projects will be launched in early 2004. While the first project looks into resistance to lactam antibiotics in clinical use, the other one investigates basic molecular mechanisms of resistance. It will focus specifically on Streptococcus pneumoniae, a major contributor to community-acquired pneumonia and invasive disease."Despite being a major cause of morbidity and mortality worldwide, sometimes leading to a fatal disease, Streptococcus pneumoniae is also found in a high proportion of healthy children attending daycare centers," Birgitta Henriques Normark, head of the Department of Molecular Epidemiology and Biotechnology at the Swedish Institute for Infectious Disease Control, told us. "A better knowledge of molecular mechanisms involved in antibiotic resistance development and of host-pathogen interactions affecting pneumococcal infections would lead to improved intervention, prevention, and treatment strategies of these common community acquired infections."The 3-year project will look into how the bacteria manage to survive, grow, and spread in the presence of an antibiotic and what factors determine whether an infection will be mild or severe.It will also involve comparative genomic approaches, including DNA microarrays t
An abstract ultraparabolic integrodifferential equation
Luca Lorenzi
Le Matematiche , 1998,
Abstract: We prove an existence and uniqueness result for a ultraparabolic integrodifferential equation in the strip [0, T1 ] × [0, T2 ] in the context of the spaces of continuous functions with values in a Banach space X and we give some applications to specific partial integrodifferential problems.
Power: A Radical View, by Stephen Lukes
Maximiliano Lorenzi
Crossroads , 2006,
The New Wedge-Shaped Hubble Diagram of 398 SCP Supernovae According to the Expansion Center Model
Luciano Lorenzi
Physics , 2010,
Abstract: Following the successful dipole test on 53 SCP SNe Ia presented at SAIt2004 in Milan, this 9th contribution to the ECM series beginning in 1999 in Naples (43th SAIt meeting: "Revolutions in Astronomy") deals with the construction of the new wedge-shaped Hubble diagram obtained with 398 supernovae of the SCP Union Compilation (Kowalski et al. 2008) by applying a calculated correlation between SNe Ia absolute blue magnitude MB and central redshift z0, according to the expansion center model. The ECM distance D of the Hubble diagram (cz versus D) is computed as the ratio between the luminosity distance DL and 1 + z. Mathematically D results to be a power series of the light-space r run inside the expanding cosmic medium or Hubble flow; thus its expression is independent of the corresponding z. In addition one can have D = D(z, h) from the ECM Hubble law by using the h convention with an anisotropic HX. It is proposed to the meeting that the wedge-shape of this new Hubble diagram be confirmed independently as mainly due to the ECM dipole anisotropy of the Hubble ratio cz/D.
A crucial dipole test of the expansion center Universe - based on high-z SCP Union & Union2 supernovae
Luciano Lorenzi
Physics , 2011,
Abstract: The expansion center Universe (ECU) gives a dipole anisotropy to the Hubble ratio, at any Hubble depth D. After a long series of successful dipole tests, here is a crucial multiple dipole test at z bins centred on the mean =z0=1, or Hubble depth D=c/H0, and based on data from SCP Union & Union2 compilation. Table 5abc lists data of two main samples, with 48 SCPU SNe Ia and 58 SCPU2 SNe Ia respectively. The confirmed dipole anisotropy, shown by 6 primary sample tests and by another 27 from 9 encapsulated z bins with DL=D(1+z) assumed and the Hubble Magnitude definition, gives a model independent result, in full accordance with the expansion center model (ECM). That means a maximum cz range of about 50000 km/s at the central redshift z0=1. As a complement to the dipole tests, here is a new computation of the relativistic deceleration parameter q0, based on the extrapolated total M spread, that is the deviation of the Hubble Magnitude M of high-z SCP Union supernovae at a normal or central redshift =z0=z << 1 from the absolute magnitude M0 at z0=0 (cf. parallel paper XVI). A total M spread according to ECM is derived from 249 high-z SCPU SNe listed in paper XVI. In a concordance test with the expansion center model, the obtained new relativistic q0 agrees with the value q0=+2 inferred from the ECM paper I eq. (41), when R0 is the proper distance at t0 of the expansion center from the Galaxy.
Dipole & absolute magnitude analysis of the SCP Union supernovae within the expansion center model
Luciano Lorenzi
Physics , 2011,
Abstract: 1743 data calculated for 249 high-z SCP Union supernovae are analysed according to the expansion center model (ECM). The analysis in Hubble units begins with 13 listed normal points corresponding to 13 z-bin samples at as many Hubble depths. The novel finding is a clear drop in the average scattering of the SNe Ia Hubble Magnitude M with the ECM Hubble depth D, after using the average trend computed in paper IX. Other correlations of the M scattering with the position in the sky are proposed. Consequently, 13 ECM dipole tests on the 13 z-bin samples were carried out both with unweighted and weighted fittings. A further check was made with Hubble depths D obtained by assuming M= according to paper IX and XV. In conclusion the analysis of 249 SCPU SNe confirms once again the expansion center model at any Hubble depth, including a strengthening perturbation effect of the M scattering at decreasing z<0.5. A new successful dipole test introduces the absolute magnitude analysis of 398 SCPU supernovae. After testing 14 high-z normal points from paper IX Table 2, a trend analysis of another 15 and 30 normal points of the Hubble Magnitude M and a new absolute magnitude M*, at increasing =z0 corresponding to a different series of z bins, leads to the discovery of the magnitude anomaly of the low points. When the low points are excluded, the best fittings make it possible to extrapolate the SNe Ia absolute magnitude M0 at a central redshift z0=0, with M0=-17.9+-0.1 and a few final ECM solutions of the SNe Ia and M*. The magnitude anomaly is here interpreted as due to a deficiency in the magnitude formulas used; these produce a maximum peak of deviation in the range 0.04 < < 0.08. That is a proof of the Universe rotation within the expansion center model.
II-Local Solution of a Spherical Homogeneous and Isotropic Universe Radially Decelerated towards the Expansion Center: Tests on Historic Data Sets
Luciano Lorenzi
Physics , 1999,
Abstract: The topic of the paper is the mathematical analysis of a radially decelerated Hubble expansion from the Bahcall & Soneira void center. Such analysis, in the hypothesis of local homogeneity and isotropy, gives a particular Hubble ratio dipole structure to the expansion equation, whose solution has been studied at different precision orders and successfully tested on a few historic data sets, by de Vaucouleurs (1965), by Sandage & Tammann (1975), and by Aaronson et al. (1982-86). The fittings of both the separate AA1 and AA2 samples show a good solution convergence as the analysis order increases, giving even coinciding solutions when applied to 308 nearby individual galaxies (308AA1) and to 10 clusters (148AA2), respectively.
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