359 research outputs found
Dynamic Monopolies in Colored Tori
The {\em information diffusion} has been modeled as the spread of an
information within a group through a process of social influence, where the
diffusion is driven by the so called {\em influential network}. Such a process,
which has been intensively studied under the name of {\em viral marketing}, has
the goal to select an initial good set of individuals that will promote a new
idea (or message) by spreading the "rumor" within the entire social network
through the word-of-mouth. Several studies used the {\em linear threshold
model} where the group is represented by a graph, nodes have two possible
states (active, non-active), and the threshold triggering the adoption
(activation) of a new idea to a node is given by the number of the active
neighbors.
The problem of detecting in a graph the presence of the minimal number of
nodes that will be able to activate the entire network is called {\em target
set selection} (TSS). In this paper we extend TSS by allowing nodes to have
more than two colors. The multicolored version of the TSS can be described as
follows: let be a torus where every node is assigned a color from a finite
set of colors. At each local time step, each node can recolor itself, depending
on the local configurations, with the color held by the majority of its
neighbors. We study the initial distributions of colors leading the system to a
monochromatic configuration of color , focusing on the minimum number of
initial -colored nodes. We conclude the paper by providing the time
complexity to achieve the monochromatic configuration
Multicolored Dynamos on Toroidal Meshes
Detecting on a graph the presence of the minimum number of nodes (target set)
that will be able to "activate" a prescribed number of vertices in the graph is
called the target set selection problem (TSS) proposed by Kempe, Kleinberg, and
Tardos. In TSS's settings, nodes have two possible states (active or
non-active) and the threshold triggering the activation of a node is given by
the number of its active neighbors. Dealing with fault tolerance in a majority
based system the two possible states are used to denote faulty or non-faulty
nodes, and the threshold is given by the state of the majority of neighbors.
Here, the major effort was in determining the distribution of initial faults
leading the entire system to a faulty behavior. Such an activation pattern,
also known as dynamic monopoly (or shortly dynamo), was introduced by Peleg in
1996. In this paper we extend the TSS problem's settings by representing nodes'
states with a "multicolored" set. The extended version of the problem can be
described as follows: let G be a simple connected graph where every node is
assigned a color from a finite ordered set C = {1, . . ., k} of colors. At each
local time step, each node can recolor itself, depending on the local
configurations, with the color held by the majority of its neighbors. Given G,
we study the initial distributions of colors leading the system to a k
monochromatic configuration in toroidal meshes, focusing on the minimum number
of initial k-colored nodes. We find upper and lower bounds to the size of a
dynamo, and then special classes of dynamos, outlined by means of a new
approach based on recoloring patterns, are characterized
Reconstruction of discrete sets from two or more X-rays in any direction
rendu obsolète par http://hal.ccsd.cnrs.fr/ccsd-00023033During the workshop entitled "Discrete Tomography", held in Volkrange on March 22, 1999, A. Kuba presented the open problem of reconstructing discrete sets satisfying the properties of connectivity and convexity by projections taken along many directions. In this paper, we study this problem, considering a similar property of discrete sets: the Q-convexity. In fact this property contains a certain kind of connectivity and convexity. The main result of this paper is a polynomial-time algorithm which is able to reconstruct Q-convex sets from their projections, when the directions of the projections and the ones of the Q-convexity are the same. Moreover, the algorithm works for any finite number of directions
Approximate X-rays reconstruction of special lattice sets
Sometimes the inaccuracy of the measurements of the X-rays can give rise to an inconsistent reconstruction problem. In this paper we address the problem of reconstructing special lattice sets in Z2 from their approximate X-rays in a finite number of prescribed lattice directions. The class of "strongly Q-convex sets" is taken into consideration and a polynomial time algorithm for reconstructing members of that class with line sums having possibly some bounded differences with the given X-ray values is provided. In particular, when these differences are zero, the algorithm exactly reconstructs any set. As a result, this algorithm can also be used to reconstruct convex subsets of Z2 from their exact X-rays in a finite set of suitable prescribed lattice directions
PARPST: a PARallel algorithm to find peptide sequence tags
Background: Protein identification is one of the most challenging problems in proteomics. Tandem mass spectrometry provides an important tool to handle the protein identification problem. Results: We developed a work-efficient parallel algorithm for the peptide sequence tag problem. The algorithm runs on the concurrent-read, exclusive-write PRAM in O(n) time using log n processors, where n is the number of mass peaks in the spectrum. The algorithm is able to find all the sequence tags having score greater than a parameter or all the sequence tags of maximum length. Our tests on 1507 spectra in the Open Proteomics Database shown that our algorithm is efficient and effective since achieves comparable results to other methods. Conclusions: The proposed algorithm can be used to speed up the database searching or to identify post-translational modifications, comparing the homology of the sequence tags found with the sequences in the biological database
A parallel algorithm for de novo peptide sequencing
Protein identification is a main problem in proteomics,the large-scale analysis of proteins. Tandem mass spec-trometry (MS/MS) provides an important tool to handleprotein identification problem. Indeed the spectrometeris capable of ionizing a mixture of peptides, essentiallyseveral copies of the same unknown peptide, dissociatingevery molecule into two fragments called complementaryions, and measuring the mass/charge ratios of the pep-tides and of their fragments. These measures are visualizedas mass peaks in a mass spectrum.There are two fundamental approaches to interpret thespectra. The first approach is to search in a database tofind the peptides that match the MS/MS spectra. This data-base search approach is effective for known proteins, butdoes not permit to detect novel proteins. This second taskcan be dealt with the de novo sequencing that computesthe amino acid sequence of the peptides directly fromtheir MS/MS spectra.In the de novo sequencing problem one knows the pep-tide mas
Dissecting Adaptation Mechanisms to Contrasting Solar Irradiance in the Mediterranean Shrub Cistus incanus
Molecular mechanisms that are the base of the strategies adopted by Mediterranean plants to cope with the challenges imposed by limited or excessive solar radiation during the summer season have received limited attention. In our study, conducted on C. incanus plants growing in the shade or in full sunlight, we performed measurements of relevant physiological traits, such as leaf water potential, gas exchange and PSII photochemistry, RNA-Seq with de-novo assembly, and the analysis of differentially expressed genes. We also identified and quantified photosynthetic pigments, abscisic acid, and flavonoids. Here, we show major mechanisms regulating light perception and signaling which, in turn, sustain the shade avoidance syndrome displayed by the ‘sun loving’ C. incanus. We offer clear evidence of the detrimental effects of excessive light on both the assembly and the stability of PSII, and the activation of a suite of both repair and effective antioxidant mechanisms in sun-adapted leaves. For instance, our study supports the view of major antioxidant functions of zeaxanthin in sunny plants concomitantly challenged by severe drought stress. Finally, our study confirms the multiple functions served by flavonoids, both flavonols and flavanols, in the adaptive mechanisms of plants to the environmental pressures associated to Mediterranean climate
Cystic Echinococcosis: Chronic, Complex, and Still Neglected
Cystic echinococcosis is a most clinically neglected
parasitic disease that urgently needs attention.
A valuable tool for diagnosing,
staging, and following up patients, ultrasound,
is readily available. Four management
procedures, surgery, percutaneous
sterilization techniques, anti-parasitic
treatment, and watch & wait, have
‘‘evolved’’ over decades, and been recently
summarized, but without adequate
comparative evaluation of efficacy, effectiveness,
rate of adverse events, relapse
rates, and cost. Clinical decision making is
on even shakier ground for extrahepatic
and extrapulmonary locations, which are
rarer and numbers needed to build
comparative trials hard to come by. There
is an obligation to put at least what we
have on an appropriate evidence base by
conducting comparative clinical trials at
the scale and quality that allow answering
these important questions. As one of the
expected results, clear criteria for the
watch & wait option alone might already
save a substantial proportion of patients
from unnecessary interventions and save
health services money. Difficult chronic
diseases clustering in poor rural areas need
intelligent, creative approaches, and this
one urgently needs operational research
incorporating the particularities of resource-
poor settings into consideration
PET/CT Imaging in Mouse Models of Myocardial Ischemia
Different species have been used to reproduce myocardial infarction models but in the last years mice became the animals of choice for the analysis of several diseases, due to their short life cycle and the possibility of genetic manipulation. Many techniques are currently used for cardiovascular imaging in mice, including X-ray computed tomography (CT), high-resolution ultrasound, magnetic resonance imaging, and nuclear medicine procedures. Cardiac positron emission tomography (PET) allows to examine noninvasively, on a molecular level and with high sensitivity, regional changes in myocardial perfusion, metabolism, apoptosis, inflammation, and gene expression or to measure changes in anatomical and functional parameters in heart diseases. Currently hybrid PET/CT scanners for small laboratory animals are available, where CT adds high-resolution anatomical information. This paper reviews mouse models of myocardial infarction and discusses the applications of dedicated PET/CT systems technology, including animal preparation, anesthesia, radiotracers, and images postprocessing
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