623 research outputs found
The Cost of Informing Decision-Makers in Multi-Agent Maximum Coverage Problems with Random Resource Values
The emergent behavior of a distributed system is conditioned by the
information available to the local decision-makers. Therefore, one may expect
that providing decision-makers with more information will improve system
performance; in this work, we find that this is not necessarily the case. In
multi-agent maximum coverage problems, we find that even when agents'
objectives are aligned with the global welfare, informing agents about the
realization of the resource's random values can reduce equilibrium performance
by a factor of 1/2. This affirms an important aspect of designing distributed
systems: information need be shared carefully. We further this understanding by
providing lower and upper bounds on the ratio of system welfare when
information is (fully or partially) revealed and when it is not, termed the
value-of-informing. We then identify a trade-off that emerges when optimizing
the performance of the best-case and worst-case equilibrium.Comment: To appear: LCS
Collaborative Coalitions in Multi-Agent Systems: Quantifying the Strong Price of Anarchy for Resource Allocation Games
The emergence of new communication technologies allows us to expand our
understanding of distributed control and consider collaborative decision-making
paradigms. With collaborative algorithms, certain local decision-making
entities (or agents) are enabled to communicate and collaborate on their
actions with one another to attain better system behavior. By limiting the
amount of communication, these algorithms exist somewhere between centralized
and fully distributed approaches. To understand the possible benefits of this
inter-agent collaboration, we model a multi-agent system as a common-interest
game in which groups of agents can collaborate on their actions to jointly
increase the system welfare. We specifically consider -strong Nash
equilibria as the emergent behavior of these systems and address how well these
states approximate the system optimal, formalized by the -strong price of
anarchy ratio. Our main contributions are in generating tight bounds on the
-strong price of anarchy in finite resource allocation games as the solution
to a tractable linear program. By varying --the maximum size of a
collaborative coalition--we observe exactly how much performance is gained from
inter-agent collaboration. To investigate further opportunities for
improvement, we generate upper bounds on the maximum attainable -strong
price of anarchy when the agents' utility function can be designed
Host plant defense produces species-specific alterations to flight muscle protein structure and flight-related fitness traits of two armyworms
Insects manifest phenotypic plasticity in their development and behavior in response to plant defenses, via molecular mechanisms that produce tissue-specific changes. Phenotypic changes might vary between species that differ in their preferred hosts and these effects could extend beyond larval stages. To test this,we manipulated the diet of southern armyworm(SAW; Spodoptera eridania) and fall armyworm (FAW; Spodoptera frugiperda) using a tomato mutant for jasmonic acid plant defense pathway (def1), and wild-type plants, and then quantified gene expression of Troponin t (Tnt) and flightmusclemetabolismof the adult insects. Differences in Tnt spliceform ratios in insect flight muscles correlate with changes to flight muscle metabolism and flight muscle output. We found that SAW adults reared on induced def1 plants had a higher relative abundance (RA) of the A isoform of Troponin t (Tnt A) in their flight muscles; in contrast, FAWadults reared on induced def1 plants had a lower RA of Tnt A in their flight muscles compared with adults reared on def1 and controls. Although massadjusted flightmetabolic rate showed no independent host plant effects in either species, higher flight metabolic rates in SAW correlated with increased RA of Tnt A. Flight muscle metabolism also showed an interaction of host plants with Tnt A in both species, suggesting that host plants might be influencing flight muscle metabolic output by altering Tnt. This study illustrates how insects respond to variation in host plant chemical defense by phenotypic modifications to their flight muscle proteins, with possible implications for dispersal
Collaborative Decision-Making and the k-Strong Price of Anarchy in Common Interest Games
The control of large-scale, multi-agent systems often entails distributing
decision-making across the system components. However, with advances in
communication and computation technologies, we can consider new collaborative
decision-making paradigms that exist somewhere between centralized and
distributed control. In this work, we seek to understand the benefits and costs
of increased collaborative communication in multi-agent systems. We
specifically study this in the context of common interest games in which groups
of up to k agents can coordinate their actions in maximizing the common
objective function. The equilibria that emerge in these systems are the
k-strong Nash equilibria of the common interest game; studying the properties
of these states can provide relevant insights into the efficacy of inter-agent
collaboration. Our contributions come threefold: 1) provide bounds on how well
k-strong Nash equilibria approximate the optimal system welfare, formalized by
the k-strong price of anarchy, 2) study the run-time and transient performance
of collaborative agent-based dynamics, and 3) consider the task of redesigning
objectives for groups of agents which improve system performance. We study
these three facets generally as well as in the context of resource allocation
problems, in which we provide tractable linear programs that give tight bounds
on the k-strong price of anarchy.Comment: arXiv admin note: text overlap with arXiv:2308.0804
Real-world outcomes of long-term prednisone and deflazacort use in patients with Duchenne muscular dystrophy: experience at a single, large care center
Aim: To assess outcomes among patients with Duchenne muscular dystrophy receiving deflazacort or prednisone in real-world practice.
Methods: Clinical data for 435 boys with Duchenne muscular dystrophy from Cincinnati Children\u27s Hospital Medical Center were studied retrospectively using time-to-event and regression analyses.
Results: Median ages at loss of ambulation were 15.6 and 13.5 years among deflazacort- and prednisone-initiated patients, respectively. Deflazacort was also associated with a lower risk of scoliosis and better ambulatory function, greater % lean body mass, shorter stature and lower weight, after adjusting for age and steroid duration. No differences were observed in whole body bone mineral density or left ventricular ejection fraction.
Conclusion: This single center study adds to the real-world evidence associating deflazacort with improved clinical outcomes
Path Defense in Dynamic Defender-Attacker Blotto Games (dDAB) with Limited Information
We consider a path guarding problem in dynamic Defender-Attacker Blotto games
(dDAB), where a team of robots must defend a path in a graph against
adversarial agents. Multi-robot systems are particularly well suited to this
application, as recent work has shown the effectiveness of these systems in
related areas such as perimeter defense and surveillance. When designing a
defender policy that guarantees the defense of a path, information about the
adversary and the environment can be helpful and may reduce the number of
resources required by the defender to achieve a sufficient level of security.
In this work, we characterize the necessary and sufficient number of assets
needed to guarantee the defense of a shortest path between two nodes in dDAB
games when the defender can only detect assets within -hops of a shortest
path. By characterizing the relationship between sensing horizon and required
resources, we show that increasing the sensing capability of the defender
greatly reduces the number of defender assets needed to defend the path
Flows and Decompositions of Games: Harmonic and Potential Games
In this paper we introduce a novel flow representation for finite games in
strategic form. This representation allows us to develop a canonical direct sum
decomposition of an arbitrary game into three components, which we refer to as
the potential, harmonic and nonstrategic components. We analyze natural classes
of games that are induced by this decomposition, and in particular, focus on
games with no harmonic component and games with no potential component. We show
that the first class corresponds to the well-known potential games. We refer to
the second class of games as harmonic games, and study the structural and
equilibrium properties of this new class of games. Intuitively, the potential
component of a game captures interactions that can equivalently be represented
as a common interest game, while the harmonic part represents the conflicts
between the interests of the players. We make this intuition precise, by
studying the properties of these two classes, and show that indeed they have
quite distinct and remarkable characteristics. For instance, while finite
potential games always have pure Nash equilibria, harmonic games generically
never do. Moreover, we show that the nonstrategic component does not affect the
equilibria of a game, but plays a fundamental role in their efficiency
properties, thus decoupling the location of equilibria and their payoff-related
properties. Exploiting the properties of the decomposition framework, we obtain
explicit expressions for the projections of games onto the subspaces of
potential and harmonic games. This enables an extension of the properties of
potential and harmonic games to "nearby" games. We exemplify this point by
showing that the set of approximate equilibria of an arbitrary game can be
characterized through the equilibria of its projection onto the set of
potential games
Enhanced flight performance by genetic manipulation of wing shape in Drosophila
Insect wing shapes are remarkably diverse and the combination of shape and kinematics determines both aerial capabilities and power requirements. However, the contribution of any specific morphological feature to performance is not known. Using targeted RNA interference to modify wing shape far beyond the natural variation found within the population of a single species, we show a direct effect on flight performance that can be explained by physical modelling of the novel wing geometry. Our data show that altering the expression of a single gene can significantly enhance aerial agility and that the Drosophila wing shape is not, therefore, optimized for certain flight performance characteristics that are known to be important. Our technique points in a new direction for experiments on the evolution of performance specialities in animals
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