pinecone/core-2020-05-10-deduplication huggingface dataset:
Spontaneous Segregation of Agents Across Double Auction Markets

In this paper we investigate the possibility of spontaneous segregation into
groups of traders that have to choose among several markets. Even in the
simplest case of two markets and Zero Intelligence traders, we are able to
observe segregation effects below a critical value Tc of the temperature T; the
latter regulates how strongly traders bias their decisions towards choices with
large accumulated scores. It is notable that segregation occurs even though the
traders are statistically homogeneous. Traders can in principle change their
loyalty to a market, but the relevant persistence times become long below Tc.Comment: 12 pages, 7 figures; Artificial Economics 2014 conference; Published
  online: 17 October 201
Bayesian Gait Optimization for Bipedal Locomotion

119.08.14 KB. OK to add accepted version to spiral, 12 months embargoOne of the key challenges in robotic bipedal locomotion is finding gait parameters that optimize a desired performance criterion, such as speed, robustness or energy efficiency. Typically, gait optimization requires extensive robot experiments and specific expert knowledge. We propose to apply data-driven machine learning to automate and speed up the process of gait optimization. In particular, we use Bayesian optimization to efficiently find gait parameters that optimize the desired performance metric. As a proof of concept we demonstrate that Bayesian optimization is near-optimal in a classical stochastic optimal control framework. Moreover, we validate our approach to Bayesian gait optimization on a low-cost and fragile real bipedal walker and show that good walking gaits can be efficiently found by Bayesian optimization. © 2014 Springer International Publishing
Using Comparative Preference Statements in Hypervolume-Based Interactive Multiobjective Optimization

International audienceThe objective functions in multiobjective optimization problems are often non-linear, noisy, or not available in a closed form and evolutionary multiobjective optimization (EMO) algorithms have been shown to be well applicable in this case. Here, our objective is to facilitate interactive decision making by saving function evaluations outside the "interesting" regions of the search space within a hypervolume-based EMO algorithm. We focus on a basic model where the Decision Maker (DM) is always asked to pick the most desirable solution among a set. In addition to the scenario where this solution is chosen directly, we present the alternative to specify preferences via a set of so-called comparative preference statements. Examples on standard test problems show the working principles, the competitiveness, and the drawbacks of the proposed algorithm in comparison with the recent iTDEA algorithm
Very Massive Stars in the Local Universe

Recent studies suggest the existence of very massive stars (VMS) up to 300
solar masses in the local Universe. As this finding may represent a paradigm
shift for the canonical stellar upper-mass limit of 150 solar masses, it is
timely to evaluate the physics specific to VMS, which is currently missing. For
this reason, we decided to construct a book entailing both a discussion of the
accuracy of VMS masses (Martins), as well as the physics of VMS formation
(Krumholz), mass loss (Vink), instabilities (Owocki), evolution (Hirschi), and
fate (theory -- Woosley & Heger; observations -- Smith).Comment: 8 pages, Introductory Chapter to the Book on Very Massive Stars in
  the Local Universe, Springer, Ed. Jorick S. Vin
Empirical properties of Very Massive Stars

In this contribution we present the properties of the most massive stars
known by the end of 2013. We start with a summary of historical claims for
stars with masses in excess of several hundreds, even thousands of solar
masses. We then describe how we determine masses for single stars. We focus on
the estimates of luminosities and on the related uncertainties. We also
highlight the limitations of evolutionary models used to convert luminosities
into masses. The most luminous single stars in the Galaxy and the Magellanic
Clouds are subsequently presented. The uncertainties on their mass
determinations are described. Finally, we present binary stars. After recalling
some basics of binary analysis, we present the most massive binary systems and
the estimates of their dynamical masses.Comment: 34 pages, 8 figures - Chapter to appear in the book "Very Massive
  Stars in the Local Universe", Springer, (Ed. J.S. Vink
The Formation of Very Massive Stars

In this chapter I review theoretical models for the formation of very massive
stars. After a brief overview of some relevant observations, I spend the bulk
of the chapter describing two possible routes to the formation of very massive
stars: formation via gas accretion, and formation via collisions between
smaller stars. For direct accretion, I discuss the problems of how interstellar
gas may be prevented from fragmenting so that it is available for incorporation
into a single very massive star, and I discuss the problems presented for
massive star formation by feedback in the form of radiation pressure,
photoionization, and stellar winds. For collision, I discuss several mechanisms
by which stars might be induced to collide, and I discuss what sorts of
environments are required to enable each of these mechanisms to function. I
then compare the direct accretion and collision scenarios, and discuss possible
observational signatures that could be used to distinguish between them.
Finally, I come to the question of whether the process of star formation sets
any upper limits on the masses of stars that can form.Comment: 36 pages, 7 figures, review to appear as a chapter in "Very Massive
  Stars in the Local Universe" (Ed. J S Vink); fixed a missing citation /
  copyright acknowledgement, no other changes from previous versio
Instabilities in the Envelopes and Winds of Very Massive Stars

The high luminosity of Very Massive Stars (VMS) means that radiative forces
play an important, dynamical role both in the structure and stability of their
stellar envelope, and in driving strong stellar-wind mass loss. Focusing on the
interplay of radiative flux and opacity, with emphasis on key distinctions
between continuum vs. line opacity, this chapter reviews instabilities in the
envelopes and winds of VMS. Specifically, we discuss how: 1) the iron opacity
bump can induce an extensive inflation of the stellar envelope; 2) the density
dependence of mean opacity leads to strange mode instabilities in the outer
envelope; 3) desaturation of line-opacity by acceleration of near-surface
layers initiates and sustains a line-driven stellar wind outflow; 4) an
associated line-deshadowing instability leads to extensive small-scale
structure in the outer regions of such line-driven winds; 5) a star with
super-Eddington luminosity can develop extensive atmospheric structure from
photon bubble instabilities, or from stagnation of flow that exceeds the
"photon tiring" limit; 6) the associated porosity leads to a reduction in
opacity that can regulate the extreme mass loss of such continuum-driven winds.
Two overall themes are the potential links of such instabilities to Luminous
Blue Variable (LBV) stars, and the potential role of radiation forces in
establishing the upper mass limit of VMS.Comment: 44 pages, 13 figures. Chapter to appear in the book "Very Massive
  Stars in the Local Universe", Springer, J.S. Vink, e
Evolution and Nucleosynthesis of Very Massive Stars

In this chapter, after a brief introduction and overview of stellar
evolution, we discuss the evolution and nucleosynthesis of very massive stars
(VMS: M>100 solar masses) in the context of recent stellar evolution model
calculations. This chapter covers the following aspects: general properties,
evolution of surface properties, late central evolution, and nucleosynthesis
including their dependence on metallicity, mass loss and rotation. Since very
massive stars have very large convective cores during the main-sequence phase,
their evolution is not so much affected by rotational mixing, but more by mass
loss through stellar winds. Their evolution is never far from a homogeneous
evolution even without rotational mixing. All VMS at metallicities close to
solar end their life as WC(-WO) type Wolf-Rayet stars. Due to very important
mass loss through stellar winds, these stars may have luminosities during the
advanced phases of their evolution similar to stars with initial masses between
60 and 120 solar masses. A distinctive feature which may be used to disentangle
Wolf-Rayet stars originating from VMS from those originating from lower initial
masses is the enhanced abundances of neon and magnesium at the surface of WC
stars. At solar metallicity, mass loss is so strong that even if a star is born
with several hundred solar masses, it will end its life with less than 50 solar
masses (using current mass loss prescriptions). At the metallicity of the LMC
and lower, on the other hand, mass loss is weaker and might enable star to
undergo pair-instability supernovae.Comment: 42 pages, 20 figures, Book Chapter in "Very Massive Stars in the
  Local Universe", Springer, Ed. Jorick S. Vin
The Deaths of Very Massive Stars

The theory underlying the evolution and death of stars heavier than 10 Msun
on the main sequence is reviewed with an emphasis upon stars much heavier than
30 Msun. These are stars that, in the absence of substantial mass loss, are
expected to either produce black holes when they die, or, for helium cores
heavier than about 35 Msun, encounter the pair instability. A wide variety of
outcomes is possible depending upon the initial composition of the star, its
rotation rate, and the physics used to model its evolution. These heavier stars
can produce some of the brightest supernovae in the universe, but also some of
the faintest. They can make gamma-ray bursts or collapse without a whimper.
Their nucleosynthesis can range from just CNO to a broad range of elements up
to the iron group. Though rare nowadays, they probably played a
disproportionate role in shaping the evolution of the universe following the
formation of its first stars.Comment: Chapter 7 in the book "Very Massive Stars in the Local Universe", ed.
  Jorick Vink, Springe
Observed Consequences of Presupernova Instability in Very Massive Stars

This chapter concentrates on the deaths of very massive stars, the events
leading up to their deaths, and how mass loss affects the resulting death. The
previous three chapters emphasized the theory of wind mass loss, eruptions, and
core collapse physics, but here we emphasize mainly the observational
properties of the resulting death throes. Mass loss through winds, eruptions,
and interacting binaries largely determines the wide variety of different types
of supernovae that are observed, as well as the circumstellar environments into
which the supernova blast waves expand. Connecting these observed properties of
the explosions to the initial masses of their progenitor stars is, however, an
enduring challenge and is especially difficult for very massive stars.
Superluminous supernovae, pair instability supernovae, gamma ray bursts, and
"failed" supernovae are all end fates that have been proposed for very massive
stars, but the range of initial masses or other conditions leading to each of
these (if they actually occur) are still very certain. Extrapolating to infer
the role of very massive stars in the early universe is essentially
unencumbered by observational constraints and still quite dicey.Comment: 39 pages, 5 figures, to appear as chapter in the book "Very Massive
  Stars in the Local Universe", ed. J. Vin
Development of a Novel Snom Probe for in Liquid Biological Samples

This work is focused on the study and implementation of a novel method for the development of probes for Scanning Near-field Optical Microscopy (SNOM). The proposed approach is based on the mechanical impedance matching between the optical fiber tip and the resonating tuning fork. This methodology allowed an increase of the quality factor of the piezoelectric resonator used as atomic force transducer in the SNOM probe, thus increasing its overall sensitivity. This kind of probes are often used on biological soft samples in liquid. The presence of water medium has a strong dumping effect on probe sensitivity. Experimental validation of the proposed methodology showed an increase of robustness of SNOM probes also for in liquid samples
Multifaceted open social learner modelling.

Open social learner modelling (OSLM) approaches are promoted in order to assist learners in self-directed and self-determined learning in a social context. Still, most approaches only focus on visualising learners’ performance, or providing complex tools for social navigation. Our proposal, additionally, emphasises the importance of visualising both learners’ performance and their contribution to a learning community. We seek also to seamlessly integrate OSLM with learning contents, in order for the multifaceted OSLM’s prospect for ubiquity and context-awareness to enrich the adaptive potential of social e-learning systems. This paper thus presents the design of multifaceted OSLM by introducing novel, personalised social interaction features into Topolor, a social personalised adaptive e-learning environment. The umbrella target is to create and study aspects of open social learner models. An experimental study is conducted to analyse the impact of the newly introduced features. The results are finally concluded to suggest future research and further improvements
Dysfunctional HDL: from structure-function-relationships to biomarkers

Reduced plasma levels of HDL-C are associated with an increased risk of CAD and myocardial infarction, as shown in various prospective population studies. However, recent clinical trials on lipid-modifying drugs that increase plasma levels of HDL-C have not shown significant clinical benefit. Notably, in some recent clinical studies, there is no clear association of higher HDL-C levels with a reduced risk of cardiovascular events observed in patients with existing CAD. These observations have prompted researchers to shift from a cholesterol-centric view of HDL towards assessing the function and composition of HDL particles. Of importance, experimental and translational studies have further demonstrated various potential antiatherogenic effects of HDL. HDL has been proposed to promote macrophage reverse cholesterol transport and to protect endothelial cell functions by prevention of oxidation of LDL and its adverse endothelial effects. Furthermore, HDL from healthy subjects can directly stimulate endothelial cell production of nitric oxide and exert anti-inflammatory and antiapoptotic effects. Of note, increasing evidence suggests that the vascular effects of HDL can be highly heterogeneous and HDL may lose important anti-atherosclerotic properties and turn dysfunctional in patients with chronic inflammatory disorders. A greater understanding of mechanisms of action of HDL and its altered vascular effects is therefore critical within the context of HDL-targeted therapies
HDL and atherothrombotic vascular disease

High-density lipoproteins (HDLs) exert many beneficial effects which may help to protect against the development or progression of atherosclerosis or even facilitate lesion regression. These activities include promoting cellular cholesterol efflux, protecting low-density lipoproteins (LDLs) from modification, preserving endothelial function, as well as anti-inflammatory and antithrombotic effects. However, questions remain about the relative importance of these activities for atheroprotection. Furthermore, the many molecules (both lipids and proteins) associated with HDLs exert both distinct and overlapping activities, which may be compromised by inflammatory conditions, resulting in either loss of function or even gain of dysfunction. This complexity of HDL functionality has so far precluded elucidation of distinct structure-function relationships for HDL or its components. A better understanding of HDL metabolism and structure-function relationships is therefore crucial to exploit HDLs and its associated components and cellular pathways as potential targets for anti-atherosclerotic therapies and diagnostic markers
Densely Entangled Financial Systems

In [1] Zawadoski introduces a banking network model in which the asset and
counter-party risks are treated separately and the banks hedge their assets
risks by appropriate OTC contracts. In his model, each bank has only two
counter-party neighbors, a bank fails due to the counter-party risk only if at
least one of its two neighbors default, and such a counter-party risk is a low
probability event. Informally, the author shows that the banks will hedge their
asset risks by appropriate OTC contracts, and, though it may be socially
optimal to insure against counter-party risk, in equilibrium banks will {\em
not} choose to insure this low probability event.
  In this paper, we consider the above model for more general network
topologies, namely when each node has exactly 2r counter-party neighbors for
some integer r>0. We extend the analysis of [1] to show that as the number of
counter-party neighbors increase the probability of counter-party risk also
increases, and in particular the socially optimal solution becomes privately
sustainable when each bank hedges its risk to at least n/2 banks, where n is
the number of banks in the network, i.e., when 2r is at least n/2, banks not
only hedge their asset risk but also hedge its counter-party risk.Comment: to appear in Network Models in Economics and Finance, V. Kalyagin, P.
  M. Pardalos and T. M. Rassias (editors), Springer Optimization and Its
  Applications series, Springer, 201
Closure properties of pattern languages

This conference paper was published in the Lecture Notes of Computer Science series [© Springer International Publishing]. The definitive version is available at: http://www.springerlink.com.Pattern languages are a well-established class of languages that is particularly popular in algorithmic learning theory, but very little is known about their closure properties. In the present paper we establish a large number of closure properties of the terminal-free pattern languages, and we characterise when the union of two terminal-free pattern languages is again a terminal-free pattern language. We demonstrate that the equivalent question for general pattern languages is characterised differently, and that it is linked to some of the most prominent open problems for pattern languages. We also provide fundamental insights into a well-known construction of E-pattern languages as unions of NE-pattern languages, and vice versa. © 2014 Springer International Publishing Switzerland
Biclique Coverings, Rectifier Networks and the Cost of ε-Removal

International audienceWe relate two complexity notions of bipartite graphs: the minimal weight biclique covering number Cov(G) and the minimal rec-tifier network size Rect(G) of a bipartite graph G. We show that there exist graphs with Cov(G) ≥ Rect(G) 3/2−ǫ . As a corollary, we estab-lish that there exist nondeterministic finite automata (NFAs) with ε-transitions, having n transitions total such that the smallest equivalent ε-free NFA has Ω(n 3/2−ǫ) transitions. We also formulate a version of previous bounds for the weighted set cover problem and discuss its con-nections to giving upper bounds for the possible blow-up
Star-free languages and local divisors

This is a pre-copyedited version of a contribution published in Jurgensen, H.,  Karhumaki, J. and Okhotin, A. (eds.) Descriptional Complexity of Formal Systems, 16th International Workshop, DCFS 2014, published by Springer International. The definitive authenticated version is available online via https://doi.org/10.1007/978-3-319-09704-6_3A celebrated result of Schützenberger says that a language is star-free if and only if it is is recognized by a finite aperiodic monoid. We give a new proof for this theorem using local divisors. © 2014 Springer International Publishing
A Note on Pushdown Automata Systems

In (Csuhaj-Varju et. al. 2000) Parallel Communicating Systems of Pushdown
Automata (PCPA) were introduced and shown to be able to simulate
nondeterministic one-way multi-head pushdown automata in returning mode, even
if communication is restricted to be one-way having a single target component.
A simulation of such centralized PCPA by one-way multi-head pushdown automata
(Balan 2009) turned out to be incomplete (Otto 2012). Subsequently it was shown
that centralized returning PCPA are universal even if the number of components
is two (Petersen 2013) and thus are separated from one-way multi-head pushdown
automata. Another line of research modified the definition of PCPA such that
communication is asynchronous (Otto 2013). While the simulation of one-way
multi-head pushdown automata is still possible, now a converse construction
shows this model in returning mode to be equivalent to the one-way multi-head
pushdown automaton in a very precise sense. It was left open, whether
non-centralized returning PCPA of degree two are universal. In the first part
of the paper we show this to be the case. Then we turn our attention to Uniform
Distributed Pushdown Automata Systems (UDPAS). These systems of automata work
in turn on a single tape. We show that UPDAS accepting with empty stack do not
form a hierarchy depending on the number of components and that the membership
problem is complete in NP, answering two open problems from (Arroyo et. al.
2012)
Unraveling the Complexity of Tourist Experience with NFC Technology and Mobile Wallets

By considering the tourist experience as a complex dynamic system, in this paper we depict the traveler as a kybernetes (κυβερνήτης is the ancient Greek word for ‘sea captain’, ‘steersman’, or ‘governor’) in search of powerful tools to help him or her to obtain directions in the mare magnum of complexity, overcoming the fear of action and taking decisions. We focus our attention on the key role of Near Field Communication technology and mobile wallet as ‘attenuators of complexity’ in the travel and tourism industr
Limits and Criticalities of Predictions and Forecasting in Complex Social and Economic Scenarios: A Cybernetics Key

Predictions play a key role in assuring the status of “rationality” in\ud
decisions. Nevertheless, in the ﬁeld of social sciences and economics, predictions\ud
fail to correctly depict the oncoming scenarios. Why is it so difﬁcult to achieve\ud
quantitative prediction of social and economic systems? Can science provide reliable\ud
predictions of social and economic paths that can be used to implement\ud
effective interventions? As in the notorious “El Farol bar problem” depicted by\ud
Brian Arthur (Am Econ Rev 84:406–411, 1994), the validity of predictive models is\ud
more a social issue than a matter of good mathematics. Predictability in social\ud
systems is due to limited knowledge of society and human behavior. We do not yet\ud
have worldwide, quantitative knowledge of human social behavior; for instance, the\ud
perception of certain issues or the predisposition to adopt certain behaviors. Though\ud
tremendous progress has been made in recent years in data gathering thanks to the\ud
development of new technologies and the consequent increase in computational\ud
power, social and economic models still rely on assumptions of rationality that\ud
undermine their predictive effectiveness. Through some theoretical and epistemological\ud
reﬂections, we propose a way in which the cybernetic paradigm of complexity\ud
management can be used for better decision-making in complex scenarios\ud
with a comprising, dynamic, and evolving approach. We will show how a cybernetic\ud
approach can help to overcome the fear of uncertainty and serve as an\ud
effective tool for improving decisions and actions