4,158 research outputs found
Cell death and life in cancer: mathematical modeling of cell fate decisions
Tumor development is characterized by a compromised balance between cell life
and death decision mechanisms, which are tighly regulated in normal cells.
Understanding this process provides insights for developing new treatments for
fighting with cancer. We present a study of a mathematical model describing
cellular choice between survival and two alternative cell death modalities:
apoptosis and necrosis. The model is implemented in discrete modeling formalism
and allows to predict probabilities of having a particular cellular phenotype
in response to engagement of cell death receptors. Using an original parameter
sensitivity analysis developed for discrete dynamic systems, we determine the
critical parameters affecting cellular fate decision variables that appear to
be critical in the cellular fate decision and discuss how they are exploited by
existing cancer therapies
Diversification Preferences in the Theory of Choice
Diversification represents the idea of choosing variety over uniformity.
Within the theory of choice, desirability of diversification is axiomatized as
preference for a convex combination of choices that are equivalently ranked.
This corresponds to the notion of risk aversion when one assumes the
von-Neumann-Morgenstern expected utility model, but the equivalence fails to
hold in other models. This paper studies axiomatizations of the concept of
diversification and their relationship to the related notions of risk aversion
and convex preferences within different choice theoretic models. Implications
of these notions on portfolio choice are discussed. We cover model-independent
diversification preferences, preferences within models of choice under risk,
including expected utility theory and the more general rank-dependent expected
utility theory, as well as models of choice under uncertainty axiomatized via
Choquet expected utility theory. Remarks on interpretations of diversification
preferences within models of behavioral choice are given in the conclusion
External Validity: From Do-Calculus to Transportability Across Populations
The generalizability of empirical findings to new environments, settings or
populations, often called "external validity," is essential in most scientific
explorations. This paper treats a particular problem of generalizability,
called "transportability," defined as a license to transfer causal effects
learned in experimental studies to a new population, in which only
observational studies can be conducted. We introduce a formal representation
called "selection diagrams" for expressing knowledge about differences and
commonalities between populations of interest and, using this representation,
we reduce questions of transportability to symbolic derivations in the
do-calculus. This reduction yields graph-based procedures for deciding, prior
to observing any data, whether causal effects in the target population can be
inferred from experimental findings in the study population. When the answer is
affirmative, the procedures identify what experimental and observational
findings need be obtained from the two populations, and how they can be
combined to ensure bias-free transport.Comment: Published in at http://dx.doi.org/10.1214/14-STS486 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org). arXiv admin note: text overlap with
arXiv:1312.748
Sensor networks and distributed CSP: communication, computation and complexity
We introduce SensorDCSP, a naturally distributed benchmark based on a real-world application that arises in the context of networked distributed systems. In order to study the performance of Distributed CSP (DisCSP) algorithms in a truly distributed setting, we use a discrete-event network simulator, which allows us to model the impact of different network traffic conditions on the performance of the algorithms. We consider two complete DisCSP algorithms: asynchronous backtracking (ABT) and asynchronous weak commitment search (AWC), and perform performance comparison for these algorithms on both satisfiable and unsatisfiable instances of SensorDCSP. We found that random delays (due to network traffic or in some cases actively introduced by the agents) combined with a dynamic decentralized restart strategy can improve the performance of DisCSP algorithms. In addition, we introduce GSensorDCSP, a plain-embedded version of SensorDCSP that is closely related to various real-life dynamic tracking systems. We perform both analytical and empirical study of this benchmark domain. In particular, this benchmark allows us to study the attractiveness of solution repairing for solving a sequence of DisCSPs that represent the dynamic tracking of a set of moving objects.This work was supported in part by AFOSR (F49620-01-1-0076, Intelligent Information Systems Institute and MURI F49620-01-1-0361), CICYT (TIC2001-1577-C03-03 and TIC2003-00950), DARPA (F30602-00-2- 0530), an NSF CAREER award (IIS-9734128), and an Alfred P. Sloan Research Fellowship. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the US Government
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