Concurrent Actions Research Articles

Solving Multiagent Planning Problems with Concurrent Conditional Effects

In this work we present a novel approach to solving concurrent multiagent planning problems in which several agents act in parallel. Our approach relies on a compilation from concurrent multiagent planning to classical planning, allowing us to use an off-the-shelf classical planner to solve the original multiagent problem. The solution can be directly interpreted as a concurrent plan that satisfies a given set of concurrency constraints, while avoiding the exponential blowup associated with concurrent actions. Our planner is the first to handle action effects that are conditional on what other agents are doing. Theoretically, we show that the compilation is sound and complete. Empirically, we show that our compilation can solve challenging multiagent planning problems that require concurrent actions.

Antiestrogens in combination with immune checkpoint inhibitors in breast cancer immunotherapy

Breast cancers (BCs) with expression of estrogen receptor-alpha (ERα) occur in more than 70% of newly-diagnosed patients in the U.S. Endocrine therapy with antiestrogens or aromatase inhibitors is an important intervention for BCs that express ERα, and it remains one of the most effective targeted treatment strategies. However, a substantial proportion of patients with localized disease, and essentially all patients with metastatic BC, become resistant to current endocrine therapies. ERα is present in most resistant BCs, and in many of these its activity continues to regulate BC growth. Fulvestrant represents one class of ERα antagonists termed selective ER downregulators (SERDs). Treatment with fulvestrant causes ERα down-regulation, an event that helps overcome several resistance mechanisms. Unfortunately, full antitumor efficacy of fulvestrant is limited by its poor bioavailability in clinic. We have designed and tested a new generation of steroid-like SERDs. Using ERα-positive BC cells in vitro, we find that these compounds suppress ERα protein levels with efficacy similar to fulvestrant. Moreover, these new SERDs markedly inhibit ERα-positive BC cell transcription and proliferation in vitro even in the presence of estradiol-17β. In vivo, the SERD termed JD128 significantly inhibited tumor growth in MCF-7 xenograft models in a dose-dependent manner (P < 0.001). Further, our findings indicate that these SERDs also interact with ER-positive immune cells in the tumor microenvironment such as myeloid-derived suppressor cells (MDSC), tumor infiltrating lymphocytes and other selected immune cell subpopulations. SERD-induced inhibition of MDSCs and concurrent actions on CD8+ and CD4 + T-cells promotes interaction of immune checkpoint inhibitors with BC cells in preclinical models, thereby leading to enhanced tumor killing even among highly aggressive BCs such as triple-negative BC that lack ERα expression. Since monotherapy with immune checkpoint inhibitors has not been effective for most BCs, combination therapies with SERDs that enhance immune recognition may increase immunotherapy responses in BC and improve patient survival. Hence, ERα antagonists that also promote ER downregulation may potentially benefit patients who are unresponsive to current endocrine therapies.

A Cloud Computing Security Model Based on Noninterference

In cloud computing, the risk of data leakage exists between users and virtual machines. Whether it is direct or indirect data leakage, it can be regarded as illegal information flow. Methods such as access control models can control the information flow rather than the covert information flow. Therefore, it needs to use the noninterference models to detect the existence of illegal information flow in cloud computing. Typical noninterference models are not suitable to verificate information flow in cloud computing. When concurrent access actions execute in the cloud architecture, security domains do not affect each other, because there is no information flow between security domains. Based on this, we propose noninterference for cloud architecture in which concurrent access and sequential access coexist. When the sequential actions execute, the information flow between security domains can flow in accordance with established rules. When concurrent access actions execute, there should not be the information flow between security domains.

Rubisco Assembly in the Chloroplast.

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the rate-limiting step in the Calvin-Benson cycle, which transforms atmospheric carbon into a biologically useful carbon source. The slow catalytic rate of Rubisco and low substrate specificity necessitate the production of high levels of this enzyme. In order to engineer a more efficient plant Rubisco, we need to better understand its folding and assembly process. Form I Rubisco, found in green algae and vascular plants, is a hexadecamer composed of 8 large subunits (RbcL), encoded by the chloroplast genome and 8 small, nuclear-encoded subunits (RbcS). Unlike its cyanobacterial homolog, which can be reconstituted in vitro or in E. coli, assisted by bacterial chaperonins (GroEL-GroES) and the RbcX chaperone, biogenesis of functional chloroplast Rubisco requires Cpn60-Cpn20, the chloroplast homologs of GroEL-GroES, and additional auxiliary factors, including Rubisco accumulation factor 1 (Raf1), Rubisco accumulation factor 2 (Raf2) and Bundle sheath defective 2 (Bsd2). The discovery and characterization of these factors paved the way for Arabidopsis Rubisco assembly in E. coli. In the present review, we discuss the uniqueness of hetero-oligomeric chaperonin complex for RbcL folding, as well as the sequential or concurrent actions of the post-chaperonin chaperones in holoenzyme assembly. The exact stages at which each assembly factor functions are yet to be determined. Expression of Arabidopsis Rubisco in E. coli provided some insight regarding the potential roles for Raf1 and RbcX in facilitating RbcL oligomerization, for Bsd2 in stabilizing the oligomeric core prior to holoenzyme assembly, and for Raf2 in interacting with both RbcL and RbcS. In the long term, functional characterization of each known factor along with the potential discovery and characterization of additional factors will set the stage for designing more efficient plants, with a greater biomass, for use in biofuels and sustenance.

Formulación de programas especiales concurrentes de desarrollo rural sustentable: lecciones para México.

La ineficiencia del gasto público en desarrollo rural en México se deriva de la inadecuada identificación de los problemas pú- blicos, desfases presupuestales, deficiencias en la dispersión y focalización, lo cual expresa una baja coordinación entre dependencias y actores involucrados. Con el fin de contribuir a contrarrestar dichas limitantes en 2012 se elaboraron 15 programas especiales concurrentes estatales (PECE) bajo la dirección del Instituto Interamericano de Cooperación para la Agricultura (IICA) y otras instancias gubernamentales. Este trabajo evalúo la aplicación de la metodología empleada en la formulación de los PECE. Los resultados indicaron que los PTC, constituyen un primer ejercicio de definición de objetivos, visiones y acciones concurrentes entre algunas dependencias, importantes en términos de las estrategias de intervención. El marco lógico resultó útil para generar una visión compartida y compromiso en torno a prioridades de inversión rural territorial. La participación de un agente orquestador que ofreció método, soporte técnico y seguimiento fue determinante en la continuidad y coherencia del proceso.

Biased Elites, Unfit Policies: Reflections on the Lacunae of Roma Integration Strategies

In this article, I argue that policymakers employed unconscious biases and racist beliefs in the formulation and the implementation of the current EU Framework for National Roma Integration Strategies (ʻEU Roma Frameworkʼ) and its corresponding national strategies. Using Critical Race Theory, I explore how these policies have reinforced the commonly held belief in the need to civilize and otherwise change the habits of the Roma, and consequently have further reinforced the power imbalance between the Roma and the dominant majority groups (hereinafter used interchangeably with ʻnon-Romaʼ). I analyse examples of Roma versus universal policies comparatively, emphasizing biases in formulation, implementation, and discourse. I show that the objectives of the EU Roma Framework and national Roma strategies toward Roma education involve ethnic presuppositions and are far less ambitious than the avowed Europe 2020 strategy; this policy mismatch will likely lead to further educational discrepancies post-2020. Finally, I conclude that policies focused on the Roma are doomed to fail if no prior and concurrent actions are taken to change prejudiced attitudes and the behaviours of non-Roma, in particular those biases influencing policy formulation and implementation.

Time on your hands: Perceived duration of sensory events is biased toward concurrent actions.

Perceptual systems must rapidly generate accurate representations of the world from sensory inputs that are corrupted by internal and external noise. We can typically obtain more veridical representations by integrating information from multiple channels, but this integration can lead to biases when inputs are, in fact, not from the same source. Although a considerable amount is known about how different sources of information are combined to influence what we perceive, it is not known whether temporal features are combined. It is vital to address this question given the divergent predictions made by different models of cue combination and time perception concerning the plausibility of cross-modal temporal integration, and the implications that such integration would have for research programs in action control and social cognition. Here we present four experiments investigating the influence of movement duration on the perceived duration of an auditory tone. Participants either explicitly (Experiments 1-2) or implicitly (Experiments 3-4) produced hand movements of shorter or longer durations, while judging the duration of a concurrently presented tone (500-950 ms in duration). Across all experiments, judgments of tone duration were attracted toward the duration of executed movements (i.e., tones were perceived to be longer when executing a movement of longer duration). Our results demonstrate that temporal information associated with movement biases perceived auditory duration, placing important constraints on theories modeling cue integration for state estimation, as well as models of time perception, action control and social cognition. (PsycINFO Database Record

Supplemental Material for Time on Your Hands: Perceived Duration of Sensory Events Is Biased Toward Concurrent Actions

Supplemental Material for Time on Your Hands: Perceived Duration of Sensory Events Is Biased Toward Concurrent Actions

Organic solutes in coconut palm seedlings under water and salt stresses

ABSTRACT The objective of this study was to investigate the biochemical mechanisms associated with isolated and/or concurrent actions of drought and soil salinity in seedlings of coconut tree, through the accumulation of organic solutes (soluble carbohydrates, soluble amino N and free proline) in leaves and roots. The experiment, conducted in a protected environment, in Fortaleza, Brazil, in a randomized block design, in a split-plot arrangement, evaluated the effects of different levels of water stress (plots) by imposing distinct percentages of replacement of water losses through crop potential evapotranspiration - ETpc (20, 40, 60, 80 and 100%), associated with subplots consisting of increasing levels of soil salinity in saturation extract (1.72, 6.25, 25.80 and 40.70 dS m-1) provided by the soils collected in the Irrigated Perimeter of Morada Nova. Salinity did not change the concentration of organic solutes; however, there were increases in leaf and root levels of free proline in response to water stress, which contributes to the osmoregulation and/or osmoprotection of the species under adverse conditions of water supply.

Development of concurrent structural decentralised discrete event system using bisimulation concept

This paper presents a concurrent structural decentralised control in the framework of supervisory control theory using bisimulation concept. It is a way to weaken the shared-event-marking condition of structural decentralised control developed by Lee and Wong [7]. The sufficient conditions to guarantee the global optimality achieved by the concurrent actions of simpler decentralised control have been presented. The developed condition becomes specification dependent, however, the other structural condition, the mutual controllability condition, is still applied on the structure of the system. Hence the computational savings are still achievable. An example is provided to illustrate the result.

A General Framework for Robust Output Synchronization of Heterogeneous Nonlinear Networked Systems

The paper aims to establish a general framework for robust output synchronization of a group of networked agents. The agents under investigation have nonlinear, uncertain and heterogeneous dynamics. Output synchronization denotes that all agents, through collaborative control, achieve output agreement and follow a desired pattern. In particular, the agreed trajectory is not defined by nor known to any agent in advance. Collaborative control is achieved using only output information from neighboring agents. Two concurrent actions are revealed in the proposed synchronization framework. This framework involves design strategies for both perturbed consensus and perturbed regulation problems, subject to a class of small gain conditions. The success of the framework is verified by constructive proof and numerical simulation.

A NEW TASK DISTRIBUTION MODEL TO INCREASE USER PERFORMANCE IN COLLABORATIVE VIRTUAL ENVIRONMENT

Collaboration and teamwork is important in many areas of our lives. People come together to share and discuss ideas, split and distribute work or help and support each other. The sharing of information and artefacts is a central part of collaboration. In this paper, a new task distribution model is proposed to increase user performance in CVEs. The model defines the task distribution strategy among multiple users in CVEs which is based on task selection and distribution mechanism among users via awareness mechanism for increasing user performance in CVEs. The effect of tight and loose coupling is also discussed in the model for user performance. The main objective of proposed model is to manage and control the concurrent user actions for better user’s performance.

Signaling Interactions in the Adrenal Cortex.

The major physiological stimuli of aldosterone secretion are angiotensin II (AII) and extracellular K+, whereas cortisol production is primarily regulated by corticotropin (ACTH) in fasciculata cells. AII triggers Ca2+ release from internal stores that is followed by store-operated and voltage-dependent Ca2+ entry, whereas K+-evoked depolarization activates voltage-dependent Ca2+ channels. ACTH acts primarily through the formation of cAMP and subsequent protein phosphorylation by protein kinase A. Both Ca2+ and cAMP facilitate the transfer of cholesterol to mitochondrial inner membrane. The cytosolic Ca2+ signal is transferred into the mitochondrial matrix and enhances pyridine nucleotide reduction. Increased formation of NADH results in increased ATP production, whereas that of NADPH supports steroid production. In reality, the control of adrenocortical function is a lot more sophisticated with second messengers crosstalking and mutually modifying each other’s pathways. Cytosolic Ca2+ and cGMP are both capable of modifying cAMP metabolism, while cAMP may enhance Ca2+ release and voltage-activated Ca2+ channel activity. Besides, mitochondrial Ca2+ signal brings about cAMP formation within the organelle and this further enhances aldosterone production. Maintained aldosterone and cortisol secretion are optimized by the concurrent actions of Ca2+ and cAMP, as exemplified by the apparent synergism of Ca2+ influx (inducing cAMP formation) and Ca2+ release during response to AII. Thus, cross-actions of parallel signal transducing pathways are not mere intracellular curiosities but rather substantial phenomena, which fine-tune the biological response. Our review focuses on these functionally relevant interactions between the Ca2+ and the cyclic nucleotide signal transducing pathways hitherto described in the adrenal cortex.

Effectiveness of the Australian Fiscal Stimulus Package: A DSGE Analysis

We develop and estimate a small open economy dynamic stochastic general equilibrium model to investigate the effectiveness of the Australian fiscal stimulus package introduced in the aftermath of the global financial crisis (GFC). The estimated model implies a fiscal multiplier of 0.9 on impact and 1.26 with one‐year monetary accommodation. Utilising the estimated shocks – in particular, the fiscal shocks that mimic the stimulus transfers – we conduct several counterfactual policy experiments. Our results suggest that the stimulus transfers were almost equally important as the concurrent monetary easing actions in helping the Australian economy to avoid a recession after the GFC.

True Concurrency in Long-running Transactions for Digital Ecosystems

The concept of a digital ecosystem (DE) has been used to explore scenarios in which multiple online services and resources can be accessed by users without there being a single point of control, which can be used to effectively serialise their interactions. We argue in this paper that this weak coupling between services places additional demands on the modelling of compensation and recovery management in long-running transactions over traditional SOC related formalisms. We describe an adaptation of Shields’ vector languages, in that the synchronisation constraint is removed (no shared actions), as a formal semantics for a transaction in terms of the common ordering constraints on the underlying interactions between its participants. The notation afforded by the so-called transaction languages captures the invocations on each participant service (online resource), and at each point during execution, across the whole transaction. Concurrency is modelled explicitly through a notion of independence, which is lifted onto tuples of sequences (one for each participant of the transaction) rather than individual sequences, as in Mazurkiewicz trace languages or events, as in the event structures model. Participating subcomponents execute concurrently and failure of one or more causes the recovery of the whole transaction. Compensations are triggered immediately upon failure and concurrent forward actions are compensated concurrently. We highlight the benefits of our true-concurrent approach in the context of DEs and outline connections of transaction languages to other partial order models. Further, we discuss how our approach supports forward recovery in that recovering the whole transaction is avoided wherever possible.

Evidence for the embodiment of space perception: concurrent hand but not arm action moderates reachability and egocentric distance perception

The perception of reachability (i.e., whether an object is within reach) relies on body representations and action simulation. Similarly, egocentric distance estimation (i.e., the perception of the distance an object is from the self) is thought to be partly derived from embodied action simulation. Although motor simulation is important for both, it is unclear whether the cognitive processes underlying these behaviors rely on the same motor processes. To investigate this, we measured the impact of a motor interference dual-task paradigm on reachability judgment and egocentric distance estimation, while allocentric length estimation (i.e., how distant two stimuli are from each other independent from the self) was used as a control task. Participants were required to make concurrent actions with either hand actions of foam ball grip squeezing or arm actions of weight lifting, or no concurrent actions. Results showed that concurrent squeeze actions significantly slowed response speed in the reachability judgment and egocentric distance estimation tasks, but that there was no impact of the concurrent actions on allocentric length estimation. Together, these results suggest that reachability and distance perception, both egocentric perspective tasks, and in contrast to the allocentric perspective task, involve action simulation cognitive processes. The results are discussed in terms of the implication of action simulation when evaluating the position of a target relative to the observer’s body, supporting an embodied view of spatial cognition.

Temporal Landmarks: What Must Happen, and When

Current temporal planners have a hard time solving large, real-world problems which involve dealing with metric time and concurrent actions. While landmarks have enabled classical planners to scale up to significantly larger problems, they have not yet brought as much benefit to temporal planning. We argue that the reason for this is that for landmarks to make an effective addition to planning with complex temporal interactions (such as required concurrency), they must incorporate information about the timing of conditions and events. We define temporal landmarks, which associate time intervals and time points, respectively, with state and action landmarks, thereby capturing both what must happen and when it must happen. We show how to derive temporal landmarks and constraints on their associated time points from planning problems, and how exploiting them, in a planner-independent way, can improve planner performance. Notably, the greatest gain is on problems which require concurrency, showing that the temporal information we add to landmarks complements the reasoning used by current temporal planners.

Discretization of Temporal Models with Application to Planning with SMT

The problem of planning or discrete control for timed system has earlier been solved with various constraint-based solution methods, including Constraint Programming, SAT solvers, SAT modulo Theories solvers, and Mixed Integer-Linear Programming. In this work we investigate the encoding of time in such constraint-based representations. A main issue with existing encodings is the necessity to allow arbitrary interleavings of concurrent actions' starting and ending times. The complex combinatorics of this can lead to poor scalability of leading search methods. We show how real or rational time in temporal models can in many practically important cases be replaced by integer time, and how this leads to far simpler encodings of planning as constraints. We demonstrate that the simplified encodings substantially improve the scalability of constraint-based planning.

Dupla tarefa e mobilidade funcional de idosos ativos

INTRODUÇÃO: Define-se "dupla tarefa" como a capacidade de efetivar uma ação primordial incorporada a uma segunda atividade. Em idosos, é presumível que a execução de ações simultâneas comprometa o equilíbrio postural, favorecendo quedas nesta população. OBJETIVOS: Avaliar o efeito de duplas tarefas na mobilidade funcional de idosos ativos e correlacionar o tempo utilizado para sua realização com a idade do indivíduo. MÉTODOS: Estudo transversal e observacional, que utiliza amostra de conveniência. Dezenove idosos do Programa Universidade Aberta à Terceira Idade da Universidade Federal do Triângulo Mineiro, com idade entre 60 e 87 anos, classificados como ativos pelo International Physical Activity Questionnaire IPAQ e com escore mínimo de 23 pontos no Miniexame do Estado Mental MEEM foram avaliados em nove testes sequenciais. O primeiro deles exigia uma única tarefa, representada pelo teste Timed Up &amp; Go TUG, utilizado para avaliação da mobilidade funcional de idosos. O TUG foi repetido em todos os demais testes, que incorporaram uma segunda ação - atividade manual em dois testes e atividade cognitiva em seis testes. RESULTADOS: Foram observados valores maiores em relação ao tempo gasto pelos idosos na realização de tarefas associadas, tanto motoras quanto motora-cognitivas, quando comparadas com a tarefa simples. Correlação positiva entre idade e os testes que incorporam atividade cognitiva à realização do TUG foi estabelecida. CONCLUSÃO: Idosos ativos necessitam de maior tempo para a realização da dupla tarefa motora envolvendo funções distintas e coordenadas entre os membros superiores, o mesmo ocorrendo para a execução das duplas tarefas motora-cognitivas. Quanto maior a idade, maior o tempo para realização de duplas tarefas, principalmente quando associadas a atividades que exijam memória de curto prazo.

Advances in noise‐based testing of concurrent software

SummaryTesting of concurrent software written in programming languages like Java and C/C++ is a highly challenging task owing to the many possible interactions among threads. A simple, cheap, and effective approach that addresses this challenge is testing with noise injection, which influences the scheduling so that different interleavings of concurrent actions are witnessed. In this paper, multiple results achieved recently in the area of noise‐injection‐based testing by the authors are presented in a unified and extended way. In particular, various concurrency coverage metrics are presented first. Then, multiple heuristics for solving the noise placement problem (i.e. where and when to generate noise) as well as the noise seeding problem (i.e. how to generate the noise) are introduced and experimentally evaluated. In addition, several new heuristics are proposed and included into the evaluation too. Recommendations on how to set up noise‐based testing for particular scenarios are then given. Finally, a novel use of the genetic algorithm for finding suitable combinations of the many parameters of tests and noise techniques is presented. Copyright © 2014 John Wiley &amp; Sons, Ltd.