Sulla convergenza del metodo delle approssimazioni successive inR 1

In this paper, by means of the concept of chaos, we characterise the class of iterating functions inR ¹ for which the method of successive approximation converges from any starting point with the exception of a contable set.

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Lavoro svolto nell'ambito del GNIM-CNR.     

Phase diagram of the Nb–Al–Si ternary system

A high-efficiency diffusion-multiple approach was employed to map the phase diagram of the Nb–Al–Si ternary system which is very valuable for the design of niobium silicide-based composites. These composites have high potential as a replacement for Ni-base superalloys for jet engine applications. Aluminum is an alloying element for these composites, thus the Nb–Al–Si phase diagram, especially solubility of Al in Nb₅Si₃, is important information for the composite design. An isothermal section at 1000 °C was constructed from the results obtained from a diffusion multiple using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). A ternary phase Nb₃Si₅Al₂ was observed. The solubility data of Al in Nb₅Si₃ and NbSi₂ as well as Si solubility in Nb₃Al, Nb₂Al and NbAl₃ were obtained. The new isothermal section helps to judge the reliability of the existing literature results and to add new data to the Nb–Al–Si phase equilibria.     

Transparent Speculative Parallelization of Discrete Event Simulation Applications Using Global Variables

Parallelizing (compute-intensive) discrete event simulation (DES) applications is a classical approach for speeding up their execution and for making very large/complex simulation models tractable. This has been historically achieved via parallel DES (PDES) techniques, which are based on partitioning the simulation model into distinct simulation objects (somehow resembling objects in classical object-oriented programming), whose states are disjoint, which are executed concurrently and rely on explicit event-exchange (or event-scheduling) primitives as the means to support mutual dependencies and notification of their state updates. With this approach, the application developer is necessarily forced to reason about state separation across the objects, thus being not allowed to rely on shared information, such as global variables, within the application code. This implicitly leads to the shift of the user-exposed programming model to one where sequential-style global variable accesses within the application code are not allowed. In this article we remove this limitation by providing support for managing global variables in the context of DES code developed in ANSI-C, which gets automatically parallelized. Particularly, we focus on speculative (also termed optimistic) PDES systems that run on top of multi-core machines, where simulation objects can concurrently process their events with no guarantee of causal consistency and actual violations of causality rules are recovered through rollback/recovery schemes. In compliance with the nature of speculative processing, in our proposal global variables are transparently mapped to multi-versions, so as to avoid any form of safety predicate verification upon their updates. Consistency is ensured via the introduction of a new rollback/recovery scheme based on detecting global variables’ reads on non-correct versions. At the same time, efficiency in the execution is guaranteed by managing multi-version variables’ lists via non-blocking algorithms. Furthermore, the whole approach is fully transparent, being it based on automatized instrumentation of the application software (particularly ELF objects). Hence the programmer is exposed to the classical (and easy to code) sequential-style programming scheme while accessing any global variable. An experimental assessment of our proposal, based on a suite of case study applications, run on top of an off-the-shelf Linux machine equipped with 32 CPU-cores and 64 GB of RAM, is also presented.     

A Low-Voltage Fully Differential Constant-Gm Rail-to-Rail CMOS Operational Amplifier

A low-voltage fully differential CMOS operational amplifier withconstant-g_mand rail-to-rail input and output stages ispresented. It is the fully differential version of a previously realizedsingle-ended operational amplifier where a novel circuit to ensure constanttransconductance has been implemented [1]. The input stage is a rail-to-railstructure formed by two symmetrical OTAs in parallel (the input transistorsare operating in weak inversion). The class-AB output stages have also afull voltage swing. A rail-to-rail input common mode feedback structureallows the output voltage control. Measurements in a 0.7 µ standardCMOS process with threshold voltages of about 0.7 V have been done. Theminimum experimental supply voltage is about 1.1 V. The circuit provides a60 dB low frequency voltage gain and about 1.5 MHz unity gain frequency fora total power consumption of about 0.72 mW at a 1.5 V supply voltage.     

Biomolecular Evaluation of Piceatannol’s Effects in Counteracting the Senescence of Mesenchymal Stromal Cells: A New Candidate for Senotherapeutics?

Several investigations on senescence and its causative role in aging have underscored the importance of developing senotherapeutics, a field focused on killing senescent cells and/or preventing their accumulation within tissues. Using polyphenols in counteracting senescence may facilitate the development of senotherapeutics given their presence in the human diet, their confirmed tolerability and absence of severe side effects, and their role in preventing senescence and inducing the death of senescent cells. Against that background, we evaluated the effect of piceatannol, a natural polyphenol, on the senescence of mesenchymal stromal cells (MSCs), which play a key role in the body’s homeostasis. Among our results, piceatannol reduced the number of senescent cells both after genotoxic stress that induced acute senescence and in senescent replicative cultures. Such senotherapeutics activity, moreover, promoted the recovery of cell proliferation and the stemness properties of MSCs. Altogether, our findings demonstrate piceatannol’s effectiveness in counteracting senescence by targeting its associated pathways and detecting and affecting P53-dependent and P53-independent senescence. Our study thus suggests that, given piceatannol’s various mechanisms to accomplish its pleiotropic activities, it may be able to counteract any senescent phenotypes.     

Modulation of in vitro myogenesis induced by different polymer substrates

The understanding of substrate dependence of cellular differentiation is important in the surface design of biocompatible artificial devices as well as cell-incorporated tissue engineered devices. In an attempt to understand some of the genetic and epigenetic aspects of the control of cell differentiation in the presence of two different materials, Chronoflex (CH) and plasma treated Chronoflex coated with Hyaluronan (CH-HA), we used primary cultures of human myogenic cells, a model that encompasses cell proliferation, migration, fusion, and differentiation dependent gene activation. By testing both the material samples on the growth of human myoblasts in primary cultures, we demonstrated that both CH and CH-HA substrates were able to support the cell growth since they did not affect cell count and DNA synthesis. On the contrary, the degree of myoblast differentiation, assessed as a function of creatine phosphokinase (CPK) activity on living cells, was completely different on the two biomaterials. Indeed, the amount of CPK increased on CH-HA cultured cells as a result of myotube formation, while CH grown myoblasts remained unfused and displayed no increase on the CPK activity even after 12 days culture. Moreover, the expression level of MyoD and myogenin mRNA, both related to myogenic cell differentiation, appeared extremely low in CH-grown cells, while they were rapidly induced in CH-HA cultured myoblasts. © 1999 Kluwer Academic Publishers     

Assessing the research activity of Canadian psychology departments with graduate programmes.

The present study sought to provide a comprehensive assessment of the recent research activities within and across all Canadian psychology departments with graduate programmes. The quantity and quality of each department's research activity were measured by peer-reviewed article publication count and citation indexing of those publications, respectively. Each institution's h-factor was provided as a supplementary index of research industriousness. An additional index of change in research activity over time—the slope—was also provided. Data were assessed from 1900–2008 as well as for 5-year time spans from 1994–1998, 1999–2003, and 2004–2008. Overall, results indicated that the most recent 5 years have seen a significant increase in article publications across departments. More comprehensive results of the relative comparability of departments are included. Implications for future research are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Case presentations: A key method for evaluating core competencies in professional psychology?

The clinical psychology training literature highlights the need to evaluate student competency in core competencies (e.g., assessment, intervention, interpersonal relationships, research, ethics, supervision). One such evaluation method that allows for a broad-based examination of core competencies is the oral case presentation. The oral case presentation is not new to clinical psychology, but the use of this method to evaluate core competencies has not been extensively discussed. We conducted a Web-based survey on the use of case presentations to evaluate students in professional psychology programmes in Canada. Responses were obtained from 20 of 28 Canadian Psychological Association (CPA)-accredited programmes. Respondents reported on the use of the oral case presentations in the evaluation of students and the perceived value of case presentations. The majority of respondents (N = 14) reported that students gave an oral case presentation during the course of training. Most of these programmes required the case presentation in the fourth year (N = 8), a point in time when competency might be best assessed. Only very few programmes (N = 3) reported that the case presentation was evaluated by a committee, with formal guidelines to assess the case presentation. The case presentation was viewed as being helpful for evaluating several different abilities (e.g., case conceptualisation, awareness of metaknowledge, use of research in practice, reflective skills). Overall, the case presentation was positively evaluated, but appears underutilised in Canadian professional psychology programmes to evaluate clinical competency. To encourage further use of this method for formal evaluation, guidelines for presentations and evaluation are provided. Future directions for research are also outlined. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Crystal structure of a synthetic cyclodecapeptide for template-assembled synthetic protein design

The structural prototype of a new generation of regioselectively addressable functionalized templates (RAFTs) for use in protein de novo design has been synthesized and crystallized. The structure of the aromatically substituted cyclodecapeptide was determined by X-ray diffraction; it consists of an antiparallel beta sheet spanned by heterochirally induced type IIprime prime or minute beta turns, similar to that observed in gramicidin S. The three-dimensional structure of the artificial template was also examined by an NMR spectroscopic analysis in solution and shown to be compatible with a beta-sheet plane suitable for accommodating secondary functional peptide fragments for the synthesis of template-assembled synthetic proteins (TASPs).