73 research outputs found
Some Remarks on Relations between Proofs and Games
International audienceThis paper aims at studying relations between proof systems and games in a given logic and at analyzing what can be the interest and limits of a game formulation as an alternative semantic framework for modelling proof search and also for understanding relations between logics. In this perspective, we firstly study proofs and games at an abstract level which is neither related to a particular logic nor adopts a specific focus on their relations. Then, in order to instantiate such an analysis, we describe a dialogue game for intu-itionistic logic and emphasize the adequateness between proofs and winning strategies in this game. Finally, we consider how games can be seen to provide an alternative formulation for proof search and we stress on the possible mix of logical rules and search strategies inside games rules. We conclude on the merits and limits of the game semantics as a tool for studying logics, validity in these logics and some relations between them. 2 Proofs and Games In this section, we present a common terminology to present both proof systems and games at a relatively abstract level. Our aim consists in obtaining tools on which bridges can be built between the proof-theoretical approach and the game semantics approach in establishing the (universal) validity of logical formulae. We explain how proofs and games can be viewed as complementary notions. We illustrate how proof trees in calculi correspond to winning strategies in games and vice-versa
Préface
Ce numéro spécial, édité à l’occasion du centenaire de la naissance d’Alan Turing, est le fruit d’une double collaboration : d’une part une collaboration internationale qui exprime via internet l’importance de l’année Turing, d’autre part une collaboration locale régulière entre des chercheurs de l’équipe TYPES du Laboratoire Lorrain de Recherche en Informatique (LORIA) qui s’intéressent à la logique, la théorie de la preuve et la programmation, et des philosophes et logiciens du Laboratoire ..
Préface
Ce numéro spécial, édité à l’occasion du centenaire de la naissance d’Alan Turing, est le fruit d’une double collaboration : d’une part une collaboration internationale qui exprime via internet l’importance de l’année Turing, d’autre part une collaboration locale régulière entre des chercheurs de l’équipe TYPES du Laboratoire Lorrain de Recherche en Informatique (LORIA) qui s’intéressent à la logique, la théorie de la preuve et la programmation, et des philosophes et logiciens du Laboratoire ..
Contribution of high energy physics techniques to the medical imaging field
The purpose of this study was to show how advanced concepts of compact,
lossless and "Time Of Flight" (TOF) capable electronics similar to those
foreseen for the LHC and ILC experiments could be fairly and easily transferred
to the medical imaging field through Positron Emission Tomography (PET). As a
wish of explanation, the two overriding weaknesses of PET camera readout
electronics, namely dead-time and timing resolution, were investigated
analytically and with a Monte-Carlo simulator presently dedicated to this task.
Results have shown there was room left for count rate enhancement through a
huge decrease of the timing resolution well below the nanosecond. The novel
electronics scheme suggested for PET in this paper has been partly inspired by
the long experience led in High Energy Physics where the latter requirement is
compulsory. Its structure entirely pipelined combined to a pixelation of the
whole detector should allow dead-times to be suppressed, while the absence of
devoted timing channel would remove the preponderant contributions to the
timing resolution. To the common solution for timing would substitute an
optimal filtering method witch clearly appears as a good candidate as timing
resolution of a few tens of picoseconds may be achieved provided the shape of
the signal is known and sufficient samples are available with enough accuracy.
First investigations have yield encouraging results as a sampling frequency of
50 MHz with a 7 bits precision appears sufficient to ensure the 500ps
coincidence timing resolution planed. At this point, there will be a baby step
ahead to draw benefice from a TOF implementation to the design and the enormous
noise variance enhancement that would come with.Comment: presented at EuroMedIm 2006 : 1st European Conference on Molecular
Imaging Technology, Marseille 9-12 May 2006, 6 pp, 4 figures, submitted to
NI
Pericyte-Like Progenitors Show High Immaturity and Engraftment Potential as Compared with Mesenchymal Stem Cells
Mesenchymal stem cells (MSCs) and pericyte progenitors (PPs) are both perivascular cells with similar multipotential
properties regardless of tissue of origin. We compared the phenotype and function of the 2 cell types derived from the
same bone-marrow samples but expanded in their respective media – pericyte conditions (endothelial cell growth medium
2 [EGM-2]) for PPs and standard medium (mesenchymal stem cell medium [MSM]) for MSCs. After 3 weeks of culture,
whatever the expansion medium, all cells showed similar characteristics (MSC markers and adipo-osteo-chondroblastic
differentiation potential), although neuronal potential was greater in EGM-2– than MSM-cultured cells. As compared with
MSM-cultured MSCs, EGM-2–cultured PPs showed higher expression of the pericyte-specific antigen 3G5 than a-smooth
muscle actin. In addition, EGM-2–cultured PPs showed an immature phenotype, with upregulation of stemness OCT4 and
SOX2 proteins and downregulation of markers of osteoblastic, chondroblastic, adipocytic and vascular smooth muscle
lineages. Despite having less effective in vitro immunosuppression capacities than standard MSCs, EGM-2–cultured PPs had
higher engraftment potentials when combined with biomaterials heterotopically-transplanted in Nude mice. Furthermore,
these engrafted cells generated more collagen matrix and were preferentially perivascular or lined trabeculae as compared
with MSM-cultured MSCs. In conclusion, EGM-2–cultured PPs are highly immature cells with increased plasticity and
engraftment potential
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