Modularization of model transformations through a phasing mechanism

In recent years a great effort has been devoted to understanding the nature of model transformations. As a result, several mechanisms to improve model transformation languages have been proposed. Phasing has been mentioned in some works as a rule scheduling or organization mechanism, but without any detail. In this paper, we present a phasing mechanism in the context of rule-based transformation languages. We explain the structure and the behavior of the mechanism, and how it can be integrated in a language. We also analyze how the mechanism promotes modularity, internal transformation composition and helps to solve usual transformation problems. Besides, we show several examples of application to illustrate the usefulness of the mechanism.     

A flexible service selection for executing virtual services

With the adoption of a service-oriented paradigm on the Web, many software services are likely to fulfil similar functional needs for end-users. We propose to aggregate functionally equivalent software services within one single virtual service, that is, to associate a functionality, a graphical user interface (GUI), and a set of selection rules. When an end user invokes such a virtual service through its GUI to answer his/her functional need, the software service that best responds to the end-user’s selection policy is selected and executed and the result is then rendered to the end-user through the GUI of the virtual service. A key innovation in this paper is the flexibility of our proposed service selection policy. First, each selection policy can refer to heterogeneous parameters (e.g., service price, end-user location, and QoS). Second, additional parameters can be added to an existing or new policy with little investment. Third, the end users themselves define a selection policy to apply during the selection process, thanks to the GUI element added as part of the virtual service design. This approach was validated though the design, implementation, and testing of an end-to-end architecture, including the implementation of several virtual services and utilizing several software services available today on the Web.     

Justifications-on-Demand as a Device to Promote Shifts of Attention Associated With Relational Thinking in Elementary Arithmetic

Abstract

Student responses to arithmetical questions that can be solved by using arithmetical structure can serve to reveal the extent and nature of relational, as opposed to computational thinking. Student responses to probes which require them to justify-on-demand are analysed using a conceptual framework which highlights distinctions between different forms of attention. We analyse a number of actions observed in students in terms of forms of attention and shifts between them: in the short-term (the moment), medium-term (over several tasks), and long-term (over a year). The main factors conditioning students′ attention and its movement are identified and some didactical consequences are proposed.     

The uptake of horseradish peroxidase by cortical synapses in rat brain. An in vivo study

Horseradish peroxidase (HRP) was introduced directly into the cerebral cortex of adult rats, which were allowed to survive for 60 min before perfusion fixation. After the tissue had been incubated to demonstrate HRP at the LM and EM levels, blocks of cortical tissue were taken at varying distances from the injection site. These eight blocks of tissue constituted a time sequence for HRP diffusion. Qualitative examination of the presynaptic terminals showed that the most commonly encountered profiles are the plain synaptic vesicles, many of which accumulate tracer. In some terminals labelled vesicles are "lined-up" in tubular fashion. Other profiles commonly labelled are coated vesicles, tubular and vacuolar cisternae, and plain and coated pinocytotic vesicles. Quantitative analyses based on the number of terminals containing labelled profiles demonstrate an early rise in the rate of labelling of both plain synaptic vesicles and coated vesicles, after which synaptic vesicle labelling rises slowly towards a plateau. By contrast, there is a late parallel increase in the rate of labelling of coated vesicles and cisternae. A more detailed analysis, based on the actual numbers of labelled and total profiles within each presynaptic terminal, highlight early and late periods of rapid labelling for plain synaptic vesicles, coated vesicles and cisternae. A further aspect of HRP incorporation studied, concerns its uptake into four delineated regions of the presynaptic terminal. Our data indicate that membrane uptake into the presynaptic terminal is accomplished mainly via coated vesicles, although plain synaptic vesicles may also be involved. Coated vesicles, in turn, appear to give rise directly to plain synaptic vesicles, with some coalescing to produce vacuolar cisternae. The latter are involved in a two-way interchange of membrane with tubular cisternae, plain synaptic vesicles and coated vesicles. An additional source of plain synaptic vesicles are the tubular cisternae. Exocytosis of plain synaptic vesicles constitutes the mechanism by which transmitter is released from the presynaptic terminal.     

Pore filling in graphite particle compacts infiltrated with Al–12 wt.%Si and Al–12 wt.%Si–1 wt.%Cu alloys

The drainage curves (saturation versus applied pressure) that characterize pressure infiltration of Al–12 wt.%Si and Al–12 wt.%Si–1 wt.%Cu alloys into particulate preforms made out of carbon particles of three sizes have been determined. The results show that, no matter the alloy or the particle preform, saturation (pore filling) varies with pressure much faster at low than at high pressures. Besides, the drainage curves at high and low pressures, can be reasonably fitted with the semi-empirical model of Brooks and Corey, although with significantly different model parameters.     

Direct measurement of drainage curves in infiltration of SiC particle preforms

Drainage curves (plots of the non-wetting fluid saturation versus applied pressure) for infiltration of SiC particle preforms with Al and Al–12.2 at.% Si are measured at 1023 K (750 °C) with a pressure infiltration apparatus adapted for direct tracking of the metal ingress into the porous preform. From these curves the work of immersion is estimated by integration over the whole range of saturation and pressures from 0.1 MPa to 10 MPa, which in turn is used to deduce the metal contact angle on the ceramic. Drainage curves obtained for powder beds based on monomodal SiC particles of mean diameter from 6.5 μm to 40 μm yield values for the work of immersion and contact angles that are consistent among themselves and are in good agreement with data in the literature determined by the sessile drop method.     

Core protein-nucleic acid interactions in hepatitis C virus as revealed by Raman and circular dichroism spectroscopy

Molecular interactions required for hepatitis C virus (HCV) assembly are not well known and are poorly understood. The 5' untranslated region (5'UTR) of the RNA genome is highly conserved and has extensive secondary structure, and the highly basic core protein is rich in arginine residues. Using Raman and circular dichroism (CD) spectroscopies, specific interactions have been demonstrated here between the 5'UTR sequence and the core protein that may be important for the specific encapsidation of the viral genome during HCV replication. These interactions can be described as follows: (1) hydrogen bonding of arginine with unpaired guanine and/or with wobble GU base pairs, and arginine-phosphate electrostatic contacts; (2) although the percentage of base pairs in the A-form is maintained in 5'UTR, the HCVc-120 protein is beta-sheet and beta-helix enriched upon formation of protein-5'UTR macromolecular assemblies; (3) protein-5'UTR interactions resulting in protein alpha-helix formation involve guanine bases in duplex segments. The mentioned interactions may represent novel targets for antiviral strategies against this important virus.     

Rate and predictors of divorce among parents of youths with ADHD.

Numerous studies have asserted the prevalence of marital conflict among families of children with attention-deficit/hyperactivity disorder (ADHD), but evidence is surprisingly less convincing regarding whether parents of youths with ADHD are more at risk for divorce than are parents of children without ADHD. Using survival analyses, the authors compared the rate of marital dissolution between parents of adolescents and young adults with and without ADHD. Results indicated that parents of youths diagnosed with ADHD in childhood (n = 282) were more likely to divorce and had a shorter latency to divorce compared with parents of children without ADHD (n = 206). Among a subset of those families of youths with ADHD, prospective analyses indicated that maternal and paternal education level; paternal antisocial behavior; and child age, race/ethnicity, and oppositional-defiant/conduct problems each uniquely predicted the timing of divorce between parents of youths with ADHD. These data underscore how parent and child variables likely interact to exacerbate marital discord and, ultimately, dissolution among families of children diagnosed with ADHD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)