On an explicit finite difference method for fractional diffusion equations

A numerical method to solve the fractional diffusion equation, which could also be easily extended to many other fractional dynamics equations, is considered. These fractional equations have been proposed in order to describe anomalous transport characterized by non-Markovian kinetics and the breakdown of Fick's law. In this paper we combine the forward time centered space (FTCS) method, well known for the numerical integration of ordinary diffusion equations, with the Grunwald-Letnikov definition of the fractional derivative operator to obtain an explicit fractional FTCS scheme for solving the fractional diffusion equation. The resulting method is amenable to a stability analysis a la von Neumann. We show that the analytical stability bounds are in excellent agreement with numerical tests. Comparison between exact analytical solutions and numerical predictions are made.Comment: 22 pages, 6 figure

Concerted action of human chorionic gonadotropin and norepinephrine on intracellular-free calcium in human granulosa-lutein cells

Luteal cells are known to possess receptors for LH/hCG and receptors of the beta-adrenergic type. Interactions of specific agonists with either receptor lead to the activation of adenylate cyclase and subsequently to an increase of cAMP. Since in the human there is also evidence for the presence of alpha-adrenergic receptors, we have investigated whether activation of these receptors is linked to calcium as a second messenger and performed measurement of intracellular free calcium (Ca2+) with Fura-2 in single human granulosa-lutein cells. Addition of either hCG (100, 1,000, 25,000 IU/L) or norepinephrine (NE; known to interact with both alpha- and beta-adrenergic receptors), beta- adrenergic receptor agonist isoproterenol (ISO), or alpha-adrenergic receptor agonist phenylephrine (PHE; all at 10 and 100 mumol/L) did not increase free intracellular Ca2+. However, the addition of combinations of NE/hCG, PHE/hCG, but not the combination ISO/hCG, induced a transient increase in cytosolic free Ca2+. The NE/hCG-evoked calcium signal was not abolished in the presence of the beta-adrenergic receptor antagonist propranolol and was not affected by removal of extracellular Ca2+. Furthermore, we tested whether catecholamines affected the release of progesterone in the presence or absence of hCG. As expected, hCG (10,000 IU/L) stimulated progesterone release by cultured granulosa-lutein cells. When these cells were incubated with NE, PHE, or ISO (at 10 mumol/L), production of progesterone by these cells was not affected. However, the combinations of NE and PHE with hCG abolished the hCG-induced progesterone accumulation, but ISO coincubated with hCG did not. Taken together, our results indicate: 1) the presence of functional alpha-adrenergic receptors on human granulosa-lutein cells; 2) simultaneous activation of two different receptors (for hCG and alpha-agonists) are able to evoke intracellular Ca2+ elevation, implicating postreceptor interactions in human granulosa lutein cells; 3) this process occurs even in the absence of extracellular Ca2+, indicating the involvement of intracellular Ca2+ stores, most likely due to activation of phosphoinositide pathway; 4) catecholamines most likely acting via alpha-adrenergic receptors, inhibit the LH/hCG-induced release of progesterone

User interface development and software environments : the Chiron-1 system

User interface development systems for software environments have to cope with the broad, extensible and dynamic character of such environments, must support internal and external integration, and should enable various software development strategies. The Chiron-1 system adapts and extends key ideas from current research in user interface development systems to address the particular demands of software environments. Important Chiron-1 concepts are: separation of concerns, dynamism, and open architecture. We discuss the requirements on such user interface development systems, present the Chiron-1 architecture and a scenario of its usage, detail the concepts it embodies, and report on its design and prototype implementation

A Rule-driven Approach for Defining the Behavior of Negotiating Software Agents

One problem with existing agent-mediated negotiation systems is that they rely on ad hoc, static, non-adaptive, and hardcoded schemes to represent the behaviour of agents. This limitation is probably due to the complexity of the negotiation task itself. Indeed, while negotiating, software (human) agents face tough decisions. These decisions are based not only on the information made available by the negotiation server, but on the behaviour of the other participants in the negotiation process as well. The information and the behaviour in question are constantly changing and highly uncertain. In the first part of the paper, we propose a rule-driven approach to represent, manage and explore negotiation strategies and coordination information. For that, we divide the behaviour of negotiating agents into protocols, strategies and coordination. Among the many advantages of the proposed solution, we can cite the high level of abstraction, the closeness to human understanding, the versatility, and the possibility to modify the agents' behaviour during the negotiation process. To validate our solution, we ran many agent tournaments, and used the rule-driven approach to implement bidding strategies that are common in the English and Dutch auctions. We also implemented simple coordination schemes across several auctions. The ongoing validation work is detailed and discussed in the second part of the paper. Un des inconvénients qu'on retrouve fréquemment dans les systèmes de négociation par agents est qu'ils reposent sur des schémas ad-hoc, non adaptatifs et figés dans le code pour représenter le comportement des agents. Cette limitation est probablement due à la complexité de l'activité de négociation elle-même. En effet, au cours de la négociation, les agents logiciels (humains) ont des décisions difficiles à prendre. Ces décisions ne sont pas seulement basées sur l'information disponible sur le serveur de négociation, mais aussi sur le comportement des autres participants durant le processus de négociation. L'information et le comportement en question changent constamment et sont très incertains. Dans la première partie de l'article, nous proposons une approche à base de règles pour représenter, gérer et explorer les stratégies de négociation ainsi que l'information de coordination. Parmi les nombreux avantages de la solution proposée, on peut citer le haut niveau d'abstraction, la proximité avec la compréhension humaine, la souplesse d'utilisation et la possibilité de modifier le comportement des agents durant le processus de négociation. Pour valider notre solution, nous avons effectué plusieurs tournois entre agents et utilisé l'approche à base de règles pour implémenter des stratégies simples applicables à l'enchère anglaise et à l'enchère hollandaise. Nous avons aussi implémenté des schémas simples de coordination impliquant plusieurs enchères. Le travail de validation, en cours, est détaillé et discuté dans la seconde partie de l'article.e-negotiation, online auction, software agent, negotiation strategy, coordination, rule-based system, rule engine, Négociation électronique, enchères en ligne, agents logiciels, stratégie de négociation, coordination, système à base de règles, moteur de règles

Addressing Dynamism in E-negotiations by Workflow Management Systems

Workflows (Wfs) are a major enabling technology for e-commerce. In our research, a Combined Negotiation (CN) is modeled and enacted using Wf technology. The modeling task captures the sequencing of the individual negotiations as well as the dependencies between them, and the enacting task runs the model. A CN support system (CONSENSUS) is used by the user to perform both tasks. Supporting dynamic modifications to the model during run-time should increase the benefits of our approach. In this paper, we highlight the need for such support by identifying the dynamic aspects that can occur while negotiating the different items of a package (i.e., the CN object). To address these aspects, we experimented using ADEPT, a Wf Management System supporting dynamism. This leads us to discuss the Wf Reference Model of the Wf Management Coalition, and suggest a "dynamic" extension to the current functional areas and architecture. La technologie des Workflows (Wfs) s'est avérée importante pour le commerce électronique. Dans le cadre de notre recherche, une négociation combinée (CN) est modélisée et exécutée utilisant un Wf. La phase de modélisation capture la séquence des différentes négociations ainsi que les dépendances qui existent entre elles. La phase d'exécution quant à elle, permet comme son nom l'indique, d'exécuter le modèle. Un système de support pour les CN (CONSENSUS) est utilisé pour accomplir ces deux tâches. Supporter les modifications dynamiques du modèle lors de l'exécution devrait augmenter les bénéfices de notre approche. Dans cet article, nous mettons l'emphase sur le besoin d'un tel support, ceci en identifiant les aspects dynamiques qui peuvent apparaître lors de la négociation des différents items d'un package (i.e., l'objet de la CN). Nous utilisons ADEPT - un système de gestion de Wf qui supporte le dynamisme - pour étudier ces aspects. Ceci nous mène à discuter le modèle de référence de la Wf Management Coalition, et à proposer une extension "dynamique" à l'architecture actuelle.e-Negotiations, Sourcing, Workflows, Workflow management systems, Dynamism, Négociations électroniques, Approvisionnement, Workflows, Systèmes de gestion de Workflow, Dynamisme

Extracellular glutamate accumulates only in final, ischemic stage of progressive epidural mass lesion in cats

Epidural mass lesions may cause ischemia due to progressive intracranial hypertension. In order to 1) investigate the impact of intracranial pressure (ICP) on accumulation of neuroactive substances, and 2) test the significance of neurochemical monitoring for early prediction of fatal outcome, we gradually raised ICP in cats by inflation of an epidural balloon: We assessed extracellular substrate alterations in the contralateral cortex in relation to changes of ICP, cerebral perfusion pressure (CPP) and mean arterial blood pressure (MABP). In a complementary experiment, regional cerebral blood flow was assessed by sequential positron emission tomography (PET).peer-reviewe

Spectrally resolved single-shot wavefront sensing of broadband high-harmonic sources

Wavefront sensors are an important tool to characterize coherent beams of extreme ultraviolet radiation. However, conventional Hartmann-type sensors do not allow for independent wavefront characterization of different spectral components that may be present in a beam, which limits their applicability for intrinsically broadband high-harmonic generation (HHG) sources. Here we introduce a wavefront sensor that measures the wavefronts of all the harmonics in a HHG beam in a single camera exposure. By replacing the mask apertures with transmission gratings at different orientations, we simultaneously detect harmonic wavefronts and spectra, and obtain sensitivity to spatiotemporal structure such as pulse front tilt as well. We demonstrate the capabilities of the sensor through a parallel measurement of the wavefronts of 9 harmonics in a wavelength range between 25 and 49 nm, with up to lambda/32 precision.Comment: 12 pages, 6 figure

Differential effects of food availability on minimum and maximum rates of metabolism

Metabolic rates reflect the energetic cost of living but exhibit remarkable variation among conspecifics, partly as a result of the constraints imposed by environmental conditions. Metabolic rates are sensitive to changes in temperature and oxygen availability, but effects of food availability, particularly on maximum metabolic rates, are not well understood. Here, we show in brown trout (Salmo trutta) that maximum metabolic rates are immutable but minimum metabolic rates increase as a positive function of food availability. As a result, aerobic scope (i.e. the capacity to elevate metabolism above baseline requirements) declines as food availability increases. These differential changes in metabolic rates likely have important consequences for how organisms partition available metabolic power to different functions under the constraints imposed by food availability

Effects of soft gluon emission on the opposite-side acollinearity distributions in e+e- annihilation

Baier R, Fey K. Effects of soft gluon emission on the opposite-side acollinearity distributions in e+e- annihilation. Nuclear physics B. 1981;179(1):49-61