Kerr effect as a tool for the investigation of dynamic heterogeneities

We propose a dynamic Kerr effect experiment for the distinction between dynamic heterogeneous and homogeneous relaxation in glassy systems. The possibility of this distinction is due to the inherent nonlinearity of the Kerr effect signal. We model the slow reorientational molecular motion in supercooled liquids in terms of non-inertial rotational diffusion. The Kerr effect response, consisting of two terms, is calculated for heterogeneous and for homogeneous variants of the stochastic model. It turns out that the experiment is able to distinguish between the two scenarios. We furthermore show that exchange between relatively 'slow' and 'fast' environments does not affect the possibility of frequency-selective modifications. It is demonstrated how information about changes in the width of the relaxation time distribution can be obtained from experimental results.Comment: 23 pages incl. 6 figures accepted for publication in The Journal of Chemical Physic

Astrocomp: a web service for the use of high performance computers in Astrophysics

Astrocomp is a joint project, developed by the INAF-Astrophysical Observatory of Catania, University of Roma La Sapienza and Enea. The project has the goal of providing the scientific community of a web-based user-friendly interface which allows running parallel codes on a set of high-performance computing (HPC) resources, without any need for specific knowledge about parallel programming and Operating Systems commands. Astrocomp provides, also, computing time on a set of parallel computing systems, available to the authorized user. At present, the portal makes a few codes available, among which: FLY, a cosmological code for studying three-dimensional collisionless self-gravitating systems with periodic boundary conditions; ATD, a parallel tree-code for the simulation of the dynamics of boundary-free collisional and collisionless self-gravitating systems and MARA, a code for stellar light curves analysis. Other codes are going to be added to the portal.Comment: LaTeX with elsart.cls and harvard.sty (included). 7 pages. To be submitted to a specific journa

PARTIAL LEAST SQUARE PATH MODELING APPROACH IN BIOMEDICAL RESEARCH

The Partial Least Squares Path Modeling (PLS-PM) is a method meant to estimate a network of causal relationships defined according to a theoretical model. The complexity of the theoretical construct is studied by taking into account the relationships among non measurable indicators (latent variables), represented by a set of observed variables (manifest variables). PLS-PM aims to estimate, through a system of interdependent equations based on simple and multiple regressions, the network of relations among the manifest variables and their own latent variable, and among the latent variables inside the model. The causal relationships among variables are represented through a Path Diagram, in which the latent variables are enclosed in circles and the manifest variables are enclosed in boxes. PLS-PM involves three sets of relations: 1) structural or inner model, 2) measurement or outer model, 3) the weight relations upon which latent variable scores can be calculated. The first model takes into account the relations among the latent variables and the second takes into account the relations between manifest variables and the corresponding latent variable. In the structural model each endogenous (dependent) latent variable is linked to the others by a multiple regression model. The structural design only assumes recursive models, i.e. the path diagram takes the form of a causal chain with no loops. Different types of measurement models exists, depending the kind of relationship: 1) reflective model (observed variables are considered being caused by the latent variable (i.e., indicators reflect the construct; the latent variable is considered as the cause of the manifest variables and each manifest variable is an effect of the unique corresponding latent variable); 2) formative model (the latent variables are considered as being caused by its manifest variables); and 3) MIMIC model (multiple effect indicators for multiple causes, it represents a mixture of both the reflective and the formative models within the same block of manifest variables). Independently from the type of measurement model, the standardized latent variable scores are computed as a linear combination of its manifest variables and outer weights (the so-called weight relation). Once the theoretical model is specified, the next phase in PLS-PM is the estimation of the model parameters. The PLS algorithm consists of three stages. The first stage is an iterative procedure of ordinary least squares regressions taking into account the relationships of the structural and measurement model, in order to calculate weights required to give final estimates for each latent variable. This first stage is the \u201ccore\u201d stage in the PLS algorithm. Subsequently, the second and third stage involve the non-iterative estimation of the coefficients of the structural and measurement model, respectively. The structural model coefficients (path coefficients) are calculated by ordinary least squares regressions between latent variables. The measurement model coefficients (loading coefficients) are also estimated by regressions but taking into account the kind of mode to be used (reflective or formative). PLS-PM has been widely used in economical (the customer satisfaction is a typical example) and psychological settings. In biomedical context, the published articles are scanty and generally published in open access journals. The aim of this study was to apply the PLS-PM in a different field, since it has been widely used in economical (the customer satisfaction is a typical example) and psychological setting. In biomedical context, the published articles are scanty and generally published in open access journals. I used the PLS-PM method in order to analyze the adherence of the procedures provided for diagnosis, treatment (surgical and medical), and follow-up of breast cancer through a set of indicators. Indeed, the used approaches in this field since oversimplify the complex problem since they do not consider simultaneously multiple aspects of the diagnostic, therapeutic and follow-up pathways. This method has several strengths, as PLS-PM allows the reduction of dimensionality of several health indicators into a smaller number of latent variables (and more interpretable), and then allows to study causal relationships between these latent variables, representing the different aspects of the diagnostic, therapeutic and follow-up pathways. This method also requires no distributional assumptions with respect to the variables included in the model. The limit of this method is the bias deriving from the a priori selection of the relationships among latent variables and of the indicators used to characterize the latent variable. Although the limited sample size makes the analyses explorative-orientated only, the present study represents an unique example of PLS-PM application in the biomedical research, in particular in the evaluation of the adherence of the diagnostic and treatment procedures for breast cancer

Exploring the link between diabetes and pancreatic cancer

Introduction: Epidemiological studies indicate an association between type 2 diabetes and pancreatic cancer but the complex and multidirectional relationship between them remains unclear. Areas covered: We summarized epidemiological evidence on diabetes and pancreatic cancer exploring the time-risk relationship. We described mechanisms linking long-standing diabetes to pancreatic cancer. We discussed pancreatic cancer-associated diabetes and its implication in the early detection of pancreatic cancer. Expert opinion: The markedly increased risk of pancreatic cancer in patients with new-onset diabetes compared with long-standing diabetes indicates a complex and bidirectional connection, with long-standing diabetes being a predisposing factor for pancreatic cancer (increasing the risk of the malignancy 1.5- to 2-fold) and new-onset diabetes an early manifestation of the tumour. Identifying clinical features and biomarkers to distinguish pancreatic cancer-associated diabetes from type 2 diabetes is an important goal to improve management and survival of this cancer. Imaging (MRI) for middle age patients with new-onset diabetes may be considered

Líquenes como posibles agentes de deterioro de areniscas en las ruinas jesuíticas de San Ignacio Miní (provincia de Misiones, Argentina)

The ruins of San Ignacio Miní, in NE Argentina, Misiones Province, included by the UNESCO in the list of World Heritage in 1984, were built in the 18th century by the Guarani people under the supervision of the Jesuite Congregation. The ruins are located in a tropical weather zone, exposed to extreme conditions of heat and humidity affecting the rocks used in its construction. These rocks are identified as siliceous sandstones, mainly formed by rounded to subrounded clasts, with scarce angulose particles, containing 96% quartz. Weather characteristics encourage the growth of vascular plants as well as algae and mosses and other organisms that damage materials. Among these, there are 18 lichen species (belonging to 18 genera), 8 foliose, 3 fruticose and 7 crustose. The damaging action of these lichens has been observed through SEM observations and EDAX microanalysis of rock samples colonized by Caloplaca sp. and Buellia sp.Incluidas en la lista de Patrimonio Mundial por la UNESCO, las ruinas de San Ignacio Miní, en el NE de Argentina, provincia de Misiones, fueron construidas en el siglo XVIII por pobladores guaraníes supervisados por la Compañía de Jesús. Las ruinas se encuentran en una zona de clima tropical, expuestas a condiciones extremas de calor y humedad que alteran a las rocas empleadas en su construcción. Estas rocas se identifican como areniscas silíceas, formadas por clastos redondeados a sub-redondeados, con escasas partículas angulosas, con un contenido de 96,0% cuarzo. Las características del clima favorecen el desarrollo tanto de plantas vasculares como también de musgos, algas y otros organismos capaces de dañar a los materiales. Entre éstos se incluyen 18 especies de líquenes (pertenecientes a 18 géneros), 8 foliosos, 3 fruticosos y 7 crustosos. Las observaciones con SEM y los microanálisis EDE de muestras de roca colonizadas por Caloplaca sp. y Buellia sp sugieren que estos líquenes ejercen una acción negativa sobre la roca

Spectral matrix methods for partitioning power grids: Applications to the Italian and Floridian high-voltage networks

Intentional islanding is used to limit cascading power failures by isolating highly connected "islands" with local generating capacity. To efficiently isolate an island, one should break as few power lines as possible. This is a graph partitioning problem, and here we give preliminary results on islanding of the Italian and Floridian high-voltage grids by spectral matrix methods.Comment: 4 pages, 2 figures

Synthesis and characterisation of a new benzamide-containing nitrobenzoxadiazole as a GSTP1-1 inhibitor endowed with high stability to metabolic hydrolysis

The antitumor agent 6-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)thio)hexan-1-ol (1) is a potent inhibitor of GSTP1-1, a glutathione S-transferase capable of inhibiting apoptosis by binding to JNK1 and TRAF2. We recently demonstrated that, unlike its parent compound, the benzoyl ester of 1 (compound 3) exhibits negligible reactivity towards GSH, and has a different mode of interaction with GSTP1-1. Unfortunately, 3 is susceptible to rapid metabolic hydrolysis. In an effort to improve the metabolic stability of 3, its ester group has been replaced by an amide, leading to N-(6-((7-nitrobenzo[c][1,2,5]oxadiazol-4-yl)thio)hexyl)benzamide (4). Unlike 3, compound 4 was stable to human liver microsomal carboxylesterases, but retained the ability to disrupt the interaction between GSTP1-1 and TRAF2 regardless of GSH levels. Moreover, 4 exhibited both a higher stability in the presence of GSH and a greater cytotoxicity towards cultured A375 melanoma cells, in comparison with 1 and its analog 2. These findings suggest that 4 deserves further preclinical testing

Diffusion rates of Cu adatoms on Cu(111) in the presence of an adisland nucleated at FCC or HCP sites

The surface diffusion of Cu adatoms in the presence of an adisland at FCC or HCP sites on Cu(111) is studied using the EAM potential derived by Mishin {\it et al.} [Phys. Rev. B {\bf 63} 224106 (2001)]. The diffusion rates along straight (with close-packed edges) steps with (100) and (111)-type microfacets (resp. step A and step B) are first investigated using the transition state theory in the harmonic approximation. It is found that the classical limit beyond which the diffusion rates follow an Arrhenius law is reached above the Debye temperature. The Vineyard attempt frequencies and the (static) energy barriers are reported. Then a comparison is made with the results of more realistic classical molecular dynamic simulations which also exhibit an Arrhenius-like behavior. It is concluded that the corresponding energy barriers are completely consistent with the static ones within the statistical errors and that the diffusion barrier along step B is significantly larger than along step A. In contrast the prefactors are very different from the Vineyard frequencies. They increase with the static energy barrier in agreement with the Meyer-Neldel compensation rule and this increase is well approximated by the law proposed by Boisvert {\it et al.} [Phys. Rev. Lett. {\bf 75} 469 (1995)]. As a consequence, the remaining part of this work is devoted to the determination of static energy barriers for a large number of diffusion events that can occur in the presence of an adisland. In particular, it is found that the corner crossing diffusion process for triangular adislands is markedly different for the two types of borders (A or B). From this set of results the diffusion rates of the most important atomic displacements can be predicted and used as input in Kinetic Monte-Carlo simulations