2,193 research outputs found
Robust Dynamic Cooperative Games
Classical cooperative game theory is no longer a suitable tool for those situations where
the values of coalitions are not known with certainty. Recent works address situations
where the values of coalitions are modelled by random variables. In this work we still
consider the values of coalitions as uncertain, but model them as unknown but bounded
disturbances. We do not focus on solving a specific game, but rather consider a family of
games described by a polyhedron: each point in the polyhedron is a vector of coalitionsâ
values and corresponds to a specific game. We consider a dynamic context where while
we know with certainty the average value of each coalition on the long run, at each time
such a value is unknown and fluctuates within the bounded polyhedron. Then, it makes
sense to define ârobustâ allocation rules, i.e., allocation rules that bound, within a pre-
defined threshold, a so-called complaint vector while guaranteeing a certain average (over
time) allocation vector. We also present as motivating example a joint replenishment
application
On robustness and dynamics in (un)balanced coalitional games
We build upon control theoretic concepts like robustness and dynamics to better accommodate all the situations where the coalitionsâ values are uncertain and subject to changes over time. The proposed robust dynamic framework provides an alternative perspective on the study of sequences of coalitional games or interval valued games. For a sequence of coalitional games, either balanced or unbalanced, we analyze the key roles of instantaneous and average games. Instantaneous games are obtained by freezing the coalitionsâ values at a given time and come into play when coalitionsâ values are known. On the other hand, average games are derived from averaging the coalitionsâ values up to a given time and are key part of our analysis when coalitionsâ values are unknown. The main theoretical contribution of our paper is a design method of allocation rules that return solutions in the core and/or -core of the instantaneous and average games. Theoretical results are then specialized to a simulated example to shed light on the impact of the design method and on the performance of the resulting allocation rules
Confluence reduction for Markov automata
Markov automata are a novel formalism for specifying systems exhibiting nondeterminism, probabilistic choices and Markovian rates. Recently, the process algebra MAPA was introduced to efficiently model such systems. As always, the state space explosion threatens the analysability of the models generated by such specifications. We therefore introduce confluence reduction for Markov automata, a powerful reduction technique to keep these models small. We define the notion of confluence directly on Markov automata, and discuss how to syntactically detect confluence on the MAPA language as well. That way, Markov automata generated by MAPA specifications can be reduced on-the-fly while preserving divergence-sensitive branching bisimulation. Three case studies demonstrate the significance of our approach, with reductions in analysis time up to an order of magnitude
Enemies of the Nation: Understanding the Hungarian Stateâs Relationship to Humanitarian NGOs
Nongovernmental organizations (NGOs) occupy a very ambiguous role in society. Historically, NGOs have been both heralded as democracy in action and criticized for being complicit supporters of neoliberalism. Now, in certain contexts, they are rendered as enemies of the nation. In this article, we examine the evolution of nongovernmental organizations in Hungary, a nation where this transformation is exceedingly clear. Hungary provides a pertinent case example to explore the manner in which civil society as an amorphous, ill-defined category becomes a stand-in for whatever the state needs to protect its interests. The current discourse on NGOs in Hungary plays out during and in the aftermath of what has been dubbed the ârefugee crisisâ of the summer of 2015. Therefore, in this article we explore how the civil sector evolved in Hungary following the end of the Soviet era, the nongovernmental response to the refugee crisis, and the manner in which NGOs and individual volunteers have been characterized in political discourse as âenemies of the state,â due to the governmentâs anti-migrant stance. As a result of public rhetoric and policy changes, the civil sector in Hungary has no choice but to either shrink considerably or reframe their activities as decidedly anti-government
A Multi-Wavelength Study of Sgr A*: The Role of Near-IR Flares in Production of X-ray, Soft -ray and Sub-millimeter Emission
(abridged) We describe highlights of the results of two observing campaigns
in 2004 to investigate the correlation of flare activity in Sgr A* in different
wavelength regimes, using a total of nine ground and space-based telescopes. We
report the detection of several new near-IR flares during the campaign based on
{\it HST} observations. The level of near-IR flare activity can be as low as
mJy at 1.6 m and continuous up to about 40% of the total
observing time. Using the NICMOS instrument on the {\it HST}, the {\it
XMM-Newton} and CSO observatories, we also detect simultaneous bright X-ray and
near-IR flare in which we observe for the first time correlated substructures
as well as simultaneous submillimeter and near-IR flaring. X-ray emission is
arising from the population of near-IR-synchrotron-emitting relativistic
particles which scatter submillimeter seed photons within the inner 10
Schwarzschild radii of Sgr A* up to X-ray energies. In addition, using the
inverse Compton scattering picture, we explain the high energy 20-120 keV
emission from the direction toward Sgr A*, and the lack of one-to-one X-ray
counterparts to near-IR flares, by the variation of the magnetic field and the
spectral index distributions of this population of nonthermal particles. In
this picture, the evidence for the variability of submillimeter emission during
a near-IR flare is produced by the low-energy component of the population of
particles emitting synchrotron near-IR emission. Based on the measurements of
the duration of flares in near-IR and submillimeter wavelengths, we argue that
the cooling could be due to adiabatic expansion with the implication that flare
activity may drive an outflow.Comment: 48 pages, 12 figures, ApJ (in press
Reporting of prognostic studies of tumour markers: a review of published articles in relation to REMARK guidelines
Background: Poor reporting compromises the reliability and clinical value of prognostic tumour marker studies. We review articles to assess the reporting of patients and events using REMARK guidelines, at the time of guideline publication. Methods: We sampled 50 prognostic tumour marker studies from higher impact cancer journals between 2006 and 2007. The inclusion criteria were cancer; focus on single biological tumour marker; survival analysis; multivariable analysis; and not gene array or proteomic data. Articles were assessed for the REMARK profile and other REMARK guideline items. We propose a reporting aid, the REMARK profile, motivated by the CONSORT flowchart. Results: In 50 studies assessed for the REMARK profile, the number of eligible patients (56% of articles), excluded patients (54%) and patients in analyses (98%) was reported. Only 50% of articles reported the number of outcome events. In multivariable analyses, 54% and 30% of articles reported patient and event numbers for all variables. Of the studies, 66% used archival samples, indicating a potentially biased patient selection. Only 36% of studies reported clearly defined outcomes. Conclusions: Good reporting is critical for the interpretability and clinical applicability of prognostic studies. Current reporting of key information, such as the number of outcome events in all patients and subgroups, is poor. Use of the REMARK profile would greatly improve reporting and enhance prognostic research
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Mathematical modeling of drug-induced receptor internalization in the HER2-positive SKBR3 breast cancer cell-line
About 20% of breast cancer tumors over-express the HER2 receptor. Trastuzumab, an approved drug to treat this type of breast cancer, is a monoclonal antibody directly binding at the HER2 receptor and ultimately inhibiting cancer cell growth. The goal of our study was to understand the early impact of trastuzumab on HER2 internalization and recycling in the HER2-overexpressing breast cancer cell line SKBR3. To this end, fluorescence microscopy, monitoring the amount of HER2 expression in the plasma membrane, was combined with mathematical modeling to derive the flux of HER2 receptors from and to the membrane. We constructed a dynamic multi-compartment model based on ordinary differential equations. To account for cancer cell heterogeneity, a first, dynamic model was expanded to a second model including two distinct cell phenotypes, with implications for different conformational states of HER2, i.e. monomeric or homodimeric. Our mathematical model shows that the hypothesis of fast constitutive HER2 recycling back to the plasma membrane does not match the experimental data. It conclusively describes the experimental observation that trastuzumab induces sustained receptor internalization in cells with membrane ruffles. It is also concluded that for rare, non-ruffled (flat) cells, HER2 internalization occurs three orders of magnitude slower than for the bulk, ruffled cell population. © 2019, The Author(s)
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