1,721,379 research outputs found
PPARα signaling is activated by cocoa in mouse liver
No full textIn this study we evaluated in mouse liver the effects of cocoa on PPARα signaling. To this aim, mouse diet was supplemented with 10%, w/w, cocoa for one and two weeks. We quantified the expression of PPARα target genes and PPARα gene level and some parameters related to PPARα activation (hepatosomatic index, peroxisomal β-oxidation system and catalase activity). Moreover, we evaluated antioxidant capacity of cocoa by detecting the expression of CAT and SOD1 genes (known to be involved in oxidative balance) and hypolipidemic properties on serum triglycerides. We made a parallel treatment with 0.025%, w/w, ciprofibrate, a well-known PPARα activator, to quantify signal modulation by cocoa. It is known that PPARα activation by ciprofibrate is mediated by direct binding to the receptor and strongly induces expression of target genes. Our results show that cocoa weakly up-regulates PPARα target genes as a consequence of the modulation of the PPARα gene level and does not improve the triglyceride profile in blood. Finally, cocoa increased SOD1 gene expression suggesting an antioxidant effect
Incremental maintenance of multi-source views
No full textIn recent years, numerous algorithms have been proposed for incremental view maintenance of data warehouses. As a matter of fact, all of them follow almost the same general approach, namely they compute the change of a multi-source view in response to an update message from a data source, following two steps: (i) issue a set of queries against the other data sources, and (ii) compensate the query result due to concurrent updates interfering with the first step. Despite many recent improvements, the compensation approach needs precise detection of interfering updates occurring remotely in autonomous data sources and the assumption that messages are never lost and are delivered in the order in which they are sent. However, in real networks, loss and misordering of messages are usual. In this paper, we propose a maintenance algorithm that does not need the compensation step and that applies to general view expressions of the bag algebra, without any limit on the number of base relations per data source
On taxonomic reasoning in conceptual design
No full textThis paper introduces for the first time the oupling of description logics and conceptual database desig
A skewness-based clustering method
Full text linkPartitive clustering methods represent one of the earlier and most famous sets of strategy in the field
of clustering. The name comes from their main feature: all these methods start from an initial
partition and modify it at every step of the process according to a known criterion, until a given
convergence rule is satisfied. In other words, as pointed out by Äyrämö and Kärkkäinen (2006),
they work essentially as iterative allocation algorithms. In this framework, we do not only focus on
“canonical” approaches such as K-means and fuzzy C-means, but discuss some recent symmetrybased
partitive clustering methods, mostly developed in the context of computer science and
engineering. As it will be shown, these approaches seem to provide encouraging results, especially
in the field of image recognition and some related applications, and for this reason, they represent a
starting point for our work.
In this respect, we are particularly interested in the case of overlapping clusters. As we will clarify,
this case may represent a critical aspect for most clustering methods we have considered. In
particular, we started our analysis by noting that, in a case of high-dimensional data with
overlapping clusters, it may be difficult to choose the component-specific distributions, and no
graphical device can help us. So, we decided to investigate non parametric approaches to clustering.
In this framework, we focused on the case of clusters with elliptical shapes, and in Gaussian
mixtures as a special case. Then, we realized that for elliptical shapes the symmetry could be a
“natural” choice. So, we searched for such clustering approaches, and we found the symmetrybased
methods cited above. But, surprisingly, none of them was intended to focus on elliptical
clusters, since their aim is essentially at handling image recognition of different symmetric shapes.
So, we decided to discuss this issue, and to test whether a suitable function of symmetry could
improve clustering results in the case of elliptical overlapping clusters.
Since we are interested in elliptical shapes, from a clustering point of view, another broad subject
that we will discuss is the Gaussian mixture model. In this context, our interest is in the EM-based
Mclust algorithm from the R library mclust, see Fraley and Raftery (1999). Thus, our work address
both of these topics, partitive clustering methods (with a focus on the symmetry-based approach)
and Gaussian model-based clustering.
The main reason of such a choice, that is to address two partially different subjects, derives from the
essential features of our proposal: a symmetry-based partitive method which is intended to deal with
elliptical clusters (with Gaussian being a special case). In this sense, we provide an evaluation of
our clustering performances by proposing a comparison with the Gaussian mixture model
implemented in the Mclust library, see Fraley and Raftery (1999). This is surely a challenging task,
since this method has home-court advantage in the case of Gaussian clusters. In this framework, as
pointed out before, we are mainly interested in the case of overlapping clusters. In this sense, a
starting point for our work was the assumption that Mclust (also in its “natural” framework, that is
Gaussian mixtures) could have problems in centroid estimation when clusters are highly
overlapping. Quite obviously, this drawback could be related to its dependency on the mutivariate
Gaussian density. So, we searched for a non parametric skewness-based method, which could be
appropriate for elliptical distribution (including Gaussian) in the case of overlapping clusters. This
was exactly the framework of the proposed Sbam (Skewness-Based Allocation Method) algorithm
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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