Gliomas can display marked changes in the concentrations of energy metabolism molecules such as creatine (Cr), phosphocreatine (PCr) and lactate, as measured using magnetic resonance spectroscopy (MRS). Moreover, the BOLD (blood oxygen level dependent) contrast enhancement in functional magnetic resonance imaging (fMRI) can be reduced or missing within or near gliomas, while neural activity is not significantly reduced (so-called neurovascular decoupling), so that the location of functionally eloquent areas using fMRI can be erroneous. In this paper, we adapt a previously (...) developed model of the coupling between neural activation, energy metabolism and hemodynamics, by including the venous dilatation Balloon model of Buxton and Frank. We show that decreasing the cerebral blood flow (CBF) baseline value, or the CBF increase fraction, results in a decrease of the BOLD signal and an increase of the lactate peak during a sustained activation. Baseline lactate and PCr levels are not significantly affected by CBF baseline reduction, but are altered even by a moderate decrease of mitochondrial respiration. Decreasing the total Cr and PCr concentration reduces the BOLD signal after the initial overshoot. In conclusion, we suggest that the coupled use of BOLD fMRI and MRS could contribute to a better understanding of the neurovascular and metabolic decoupling in gliomas. (shrink)
In this philosophical paper, I discuss and illustrate the necessary three ingredients that together could allow a collective phenomenon to be labelled as “emergent.” First, the phenomenon, as usual, requires a group of natural objects entering in a non-linear relationship and potentially entailing the existence of various semantic descriptions depending on the human scale of observation. Second, this phenomenon has to be observed by a mechanical observer instead of a human one, which has the natural capacity for temporal or spatial (...) integration, or both. Finally, for this natural observer to detect and select the collective phenomenon, it needs to do so on account of the adaptive advantage this phenomenon is responsible for. The necessity for such a teleological characterization and the presence of natural selection drive us to defend, with many authors, the idea that emergent phenomena should belong only to biology. Following a brief philosophical plea, we present a simple and illustrative computer thought experiment in which a society of agents evolves a stigmergic collective behavior as an outcome of its greater adaptive value. The three ingredients are illustrated and discussed within this experimental context. Such an inclusion of the mechanical observer and the natural selection to which this phenomenon is submitted should underlie the necessary de-subjectivation that strengthens any scientific endeavor. I shall finally show why the short paths taken by ant colonies, the collective flying of birds and the maximum consumption of nutrients by a cellular metabolism are strongly emergent. (shrink)
Kolmogorov's account in his [1933] of an absolute probability space presupposes given a Boolean algebra, and so does Rényi's account in his [1955] and [1964] of a relative probability space. Anxious to prove probability theory ‘autonomous’. Popper supplied in his [1955] and [1957] accounts of probability spaces of which Boolean algebras are not and [1957] accounts of probability spaces of which fields are not prerequisites but byproducts instead.1 I review the accounts in question, showing how Popper's issue from and how (...) they differ from Kolmogorov's and Rényi's, and I examine on closing Popper's notion of ‘autonomous independence’. So as not to interrupt the exposition, I allow myself in the main text but a few proofs, relegating others to the Appendix and indicating as I go along where in the literature the rest can be found. (shrink)
A total of 152 students were asked to respond to a series of causal conditional (“If P then Q”) inferences with major premises for which there was variable access to information contradicting the premises. Half the students were given 12.5 s for each inference, the other half were given 8.5 s. The percentage of accepted inferences was significantly lower when the time was shorter for the MP and MT inferences, but no effect was observed for the AC and DA inferences. (...) Results are interpreted as supporting the idea that inhibition of retrieved information contradicting the premise is necessary to explain reasoning with the MP and MT inferences under logical instructions (Markovits & Barrouillet, 2002). (shrink)
Shown here is that a constraint used by Popper in The Logic of Scientific Discovery (1959) for calculating the absolute probability of a universal quantification, and one introduced by Stalnaker in "Probability and Conditionals" (1970, 70) for calculating the relative probability of a negation, are too weak for the job. The constraint wanted in the first case is in Bendall (1979) and that wanted in the second case is in Popper (1959).
Provided here is a characterisation of absolute probability functions for intuitionistic (propositional) logic L, i.e. a set of constraints on the unary functions P from the statements of L to the reals, which insures that (i) if a statement A of L is provable in L, then P(A) = 1 for every P, L's axiomatisation being thus sound in the probabilistic sense, and (ii) if P(A) = 1 for every P, then A is provable in L, L's axiomatisation being thus (...) complete in the probabilistic sense. As there are theorems of classical (propositional) logic that are not intuitionistic ones, there are unary probability functions for intuitionistic logic that are not classical ones. Provided here because of this is a means of singling out the classical probability functions from among the intuitionistic ones. (shrink)
Institutions in France are not yet well prepared to respond to allegations of scientific misconduct. Following a serious allegation in late 1997. INSERM,* the primary organization for medical and health-related research in France, began to reflect on this subject, aided by scientists and jurists. The conclusions have resulted in establishing a procedure to be followed in cases of alleged misconduct, and also in reinforcing the application of good laboratory practices within each laboratory. Guidelines for authorship practices and scientific assessment must (...) also be considered. Even though each institution must remain responsible for responding to allegations of scientific misconduct within its doors, INSERM would like to see national, European, and international co-ordination about the methods of such response. (shrink)
This paper studies the extent to which probability functions are recursively definable. It proves, in particular, that the (absolute) probability of a statement A is recursively definable from a certain point on, to wit: from the (absolute) probabilities of certain atomic components and conjunctions of atomic components of A on, but to no further extent. And it proves that, generally, the probability of a statement A relative to a statement B is recursively definable from a certain point on, to wit: (...) from the probabilities relative to that very B of certain atomic components and conjunctions of atomic components of A, but again to no further extent. These and other results are extended to the less studied case where A and B are compounded from atomic statements by means of `` ∀ '' as well as `` ∼ '' and "&". The absolute probability functions considered are those of Kolmogorov and Carnap, and the relative ones are those of Kolmogorov, Carnap, Renyi, and Popper. (shrink)
The author recently claimed that Pr(P, Q), where Pr is a probability function and P and Q are two sentences of a formalized language L, qualifies as an estimate--made in the light of Q--of the truth-value of P in L. To substantiate his claim, the author establishes here that the two strategies lying at the opposite extremes of the spectrum of truth-value estimating strategies meet the first five of the six requirements (R1-R6) currently placed upon probability functions and fail to (...) meet the sixth one. He concludes from those two results that the value for P and Q of any function satisfying R1-R5 must rate "minimally satisfactory" and the value for P and Q of any function satisfying R1-R6 must rate "satisfactory" as an estimate--made in the light of Q--of the truth-value of P in L. (shrink)
In this essay, I want to begin a dialogue with the French philosopher Bernard Stiegler’s book Technics and Time. Stiegler is internationally known as the inheritor of another French philosopher whose work is currently being rediscovered worldwide: Gilbert Simondon. In Stiegler’s work, this Simondonian heritage plays itself out in the domain of continental philosophy. The thesis maintained here will be the following: there is another relation to Simondon that is possible, one that also takes up the major problems we’ve inherited (...) from the continental philosophical tradition. The double fundamental philosophical problem raised in Stiegler’s debate with Simondon is the following: A) On the one hand .. (shrink)
A constructive dialogue between Henry’s phenomenology and Rorty’s pragmatism does not seem very likely: each would probably consider that the other has not been faithful to his claim of breaking with philosophical tradition and thus ultimately reproduces its limits. Nevertheless, one can also note that Henry and Rorty are not at the same level of analysis: while Henry focuses on giving coherent grounds for any philosophical critique of representation, Rorty is occupied with the consequences of such critique on philosophy itself. (...) If one considers this difference, there emerge new results: Henry’s phenomenology is fundamental for the recognition of what Rorty calls the “human being’s sense of self-identity”, while it falls to Rorty’s pragmatism to ensure that, as hoped by Henry, there is “a mode of philosophy that does not harm essence”. . (shrink)
The author discusses Professor Darlington's recent paper "On the Confirmation of Laws." He criticizes Professor Darlington for not writing out in full the evidence sentence in formula III of his paper, and expresses doubts as to whether Professor Darlington's solution to the problem of the confirmation of laws follows from the complete version of that formula.
This evenhanded treatment addresses the decades-old dispute among probability theorists, asserting that both statistical and inductive probabilities may be treated as sentence-theoretic measurements, and that the latter qualify as estimates of the former. Beginning with a survey of the essentials of sentence theory and of set theory, the author examines statistical probabilities, showing that statistical probabilities may be passed on to sentences, and thereby qualify as truth-values. An exploration of inductive probabilities follows, demonstrating their reinterpretation as estimates of truth-values. Each (...) chapter is preceded by a summary of its contents. Illustrations and footnotes elucidate definitions, theorems, and technicalities. 1962 ed. (shrink)
Teddy Seidenfeld recently claimed that Kolmogorov's probability theory transgresses the Substitutivity Law. Underscoring the seriousness of Seidenfeld's charge, the author shows that (Popper's version of) the law, to wit: If (∀ D)(Pr(B,D)=Pr(C,D)), then Pr(A,B)=Pr(A,C), follows from just C1. 0≤ Pr(A,B)≤ 1 C2. Pr(A,A)=1 C3. Pr(A & B,C)=Pr(A,B & C)× Pr(B,C) C4. Pr(A & B,C)=Pr(B & A,C) C5. Pr(A,B & C)=Pr(A,C & B), five constraints on Pr of the most elementary and most basic sort.
