On the Convergence of Experimental Methodologies for Distributed Systems: Where do we stand?

International audienceUnderstanding distributed systems is a complex task. There are many subsystems involved, such as network equipment, disk and CPU, which effect behavior. In order to analyze this kind of applications, different approaches have been proposed: simulation, emulation and experimentation. Each paradigm has evolved independently, providing their own set of tools and methodologies. This paper explores how these tools and methodologies can be combined in practice. Given a simple question on a particular system, we explore how different experimental frameworks can be combined in practice. We use a representative framework for each methodology: Simgrid for simulation, Distem for emulation and Grid'5000 for experimentation. Our experiments are formally described using the workflow logic provided by the XP Flow tool. Our long term goal is to foster a coherent methodological framework for the study of distributed systems. The contributions of this article to that end are the following: we identify a set of pitfalls in each paradigm that experimenters may encounter regarding models, platform descriptions and others. We propose a set of general guidelines to avoid these pitfalls. We show these guidelines may lead to accurate simulation results. Finally, we provide some insight to framework developers in order to improve the tools and thus facilitate this convergence

Émulation d'applications distribuées sur des plates-formes virtuelles simulées

National audienceL'émulation est une approche expérimentale permettant d'exécuter des applications réelles dans un environnement virtuel, permettant ainsi de se placer dans les conditions expérimentales nécessaires à l'expérience. La plupart des solutions d'émulation reposent sur une infrastructure lourde, et utilisent un cluster et une couche d'émulation pour reproduire l'environnement souhaité. Dans cet article, nous présentons une approche d'émulation basée sur l'interception des actions de l'application à étudier, et sur l'utilisation du simulateur SimGrid pour simuler l'environnement virtuel. Nous exposons les motivations, les objectifs et les apports de cette approche, ainsi que les verrous technologiques à surmonter pour l'implémenter. Puis nous nous concentrons sur le problème clé de l'interception des actions de l'application, et comparons quatre méthodes différentes à plusieurs niveaux de la pile logicielle. Nous finissons par démontrer la faisabilité de la méthode basée sur ptrace à l'aide d'un prototype, que nous validons par l'extraction de la trace des communications et des calculs lors de l'exécution d'une application pair-à-pair

The design thinking approaches of three different groups of designers based on self-reports

This paper compares the design thinking approaches of three groups of student-designers: industrial design and architecture undergraduates, and design PhD candidates. Participants responded to an open-ended design brief, working individually. Upon submission of their designs they were debriefed about their design processes. We compare the groups based on their submissions and self-reported design activities, especially the sequence of their design activities and the time allotted to them. There were some commonalities and differences between the two undergraduate groups but the main differences were between the two undergraduates and the PhD students. On the basis of the findings we pose questions regarding design methods in the era of 'design thinking' wherein designers are required to adopt an entrepreneurial frame of mind

Gaseous Mediators and Mitochondrial Function: The Future of Pharmacologically Induced Suspended Animation?

The role of nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S) as poisonous gases is well-established. However, they are not only endogenously produced but also, at low concentrations, exert beneficial effects, such as anti-inflammation, and cytoprotection. This knowledge initiated the ongoing debate, as to whether these molecules, also referred to as “gaseous mediators” or “gasotransmitters,” could serve as novel therapeutic agents. In this context, it is noteworthy, that all gasotransmitters specifically target the mitochondria, and that this interaction may modulate mitochondrial bioenergetics, thereby subsequently affecting metabolic function. This feature is of crucial interest for the possible induction of “suspended animation.” Suspended animation, similar to mammalian hibernation (and/or estivation), refers to an externally induced hypometabolic state, with the intention to preserve organ function in order to survive otherwise life-threatening conditions. This hypometabolic state is usually linked to therapeutic hypothermia, which, however, comes along with adverse effects (e.g., coagulopathy, impaired host defense). Therefore, inducing an on-demand hypometabolic state by directly lowering the energy metabolism would be an attractive alternative. Theoretically, gasotransmitters should reversibly interact and inhibit the mitochondrial respiratory chain during pharmacologically induced suspended animation. However, it has to be kept in mind that this effect also bears the risk of cytotoxicity resulting from the blockade of the mitochondrial respiratory chain. Therefore, this review summarizes the current knowledge of the impact of gasotransmitters on modulating mitochondrial function. Further, we will discuss their role as potential candidates in inducing a suspended animation

Fluconazole Monotherapy Is a Suboptimal Option for Initial Treatment of Cryptococcal Meningitis Because of Emergence of Resistance.

Cryptococcal meningitis is a lethal disease with few therapeutic options. Induction therapy with fluconazole has been consistently demonstrated to be associated with suboptimal microbiological and clinical outcomes. Exposure to fluconazole causes dynamic changes in antifungal susceptibility, which are associated with the development of aneuploidy. The implications of this phenomenon for pharmacodynamics of fluconazole for cryptococcal meningitis are poorly understood. The pharmacodynamics of fluconazole were studied using a hollow-fiber infection model (HFIM) and a well-characterized murine model of cryptococcal meningoencephalitis. The relationship between drug exposure and both antifungal killing and the emergence of resistance was quantified. The same relationships were further evaluated in a recently described group of patients with cryptococcal meningitis undergoing induction therapy with fluconazole at 800 to 1,200 mg/day. The pattern of emergence of fluconazole resistance followed an "inverted U." Resistance amplification was maximal and suppressed at ratios of the area under the concentration-time curve for the free, unbound fraction of the drug to the MIC (fAUC:MIC) of 34.5 to 138 and 305.6, respectively. Emergence of resistance was observed in vivo with an fAUC:MIC of 231.4. Aneuploidy with duplication of chromosome 1 was demonstrated to be the underlying mechanism in both experimental models. The pharmacokinetic (PK)-pharmacodynamic model accurately described the PK, antifungal killing, and emergence of resistance. Monte Carlo simulations from the clinical pharmacokinetic-pharmacodynamic model showed that only 12.8% of simulated patients receiving fluconazole at 1,200 mg/day achieved sterilization of the cerebrospinal fluid (CSF) after 2 weeks and that 83.4% had a persistent subpopulation that was resistant to fluconazole. Fluconazole is primarily ineffective due to the emergence of resistance. Treatment with 1,200 mg/day leads to the killing of a susceptible subpopulation but is compromised by the emergence of resistance.IMPORTANCE Cryptococcal meningitis is a lethal disease with few treatment options. The incidence remains high and intricately linked with the HIV/AIDS epidemic. In many parts of the world, fluconazole is the only agent that is available for the initial treatment of cryptococcal meningitis despite considerable evidence that it is associated with suboptimal microbiological and clinical outcomes. Fluconazole has a fungistatic mode of action: it predominantly inhibits growth rather than causing fungal killing. Our work shows that the pattern of fluconazole activity is caused by the emergence of resistance in Cryptococcus not detected by standard susceptibility tests, with chromosomal duplication/aneuploidy as the main mechanism. Resistance emergence is related to drug exposure and occurs with the use of clinically relevant regimens. Hence, fluconazole (and potentially other agents that target 14-alpha-demethylase) is compromised by an intrinsic property that limits its effectiveness. However, this resistance may be potentially overcome by dosage escalation or the use of combination therapy

Processing of Dielectric Materials and Metals with ps Laserpulses

Since industrial suited ps laser systems are available, the cold ablation with ultrashort laser pulses is of huge interest when high requirements concerning accuracy, surface roughness and heat affected zone are demanded. Interesting applications lie within the fields of surface and 3-d structuring of metals, semiconductors (especially flexible solar cells) and dielectric materials with direct and induced processes. For a profitable industrial use of this technology high process efficiency is required which is confirmed by the development of the corresponding systems towards high average powers up to several 10 W. Beside the pulse duration, which is given by the laser system, the user has a wide variety of parameters, e.g. fluence, repetition rate, wavelength and marking speed, to optimize structuring processes. For a given average power there exist optimal laser parameters to achieve a maximal volume ablation rate. To take benefit of this maximum ablation rate, to simultaneously prevent harmful effects (particle shielding, surface melting) and to achieve the requirements concerning surface quality and accuracy, adapted structuring strategies have to be used. This can lead to equipment needs of the beam guiding system which are often not accomplishable and therefore to the demand for new technologies which have to be developed

Magnetic dot arrays modeling via the system of the radial basis function networks

Two dimensional square lattice general model of the magnetic dot array is introduced. In this model the intradot self-energy is predicted via the neural network and interdot magnetostatic coupling is approximated by the collection of several dipolar terms. The model has been applied to disk-shaped cluster involving 193 ultrathin dots and 772 interaction centers. In this case among the intradot magnetic structures retrieved by neural networks the important role play single-vortex magnetization modes. Several aspects of the model have been understood numerically by means of the simulated annealing method.Comment: 16 pages, 8 figure

Is Hamlet Scandinavian Crime Fiction?

This paper combines two of the suggested topics: “law as an instrument of ideology” and “ideological interpellation through law” as it explores whether or not it is possible to use literary fiction as part of an argument in legal argumentation. The use of such an argument is strongly connected with an attitude of state to art, culture and values included both in art and law. Art as a part of a socio-cultural system is one of the material sources of law so it would be natural to admit it in just judicial decision. Unfortunately it is not typical for law to use such relationships between art and law to make judicial decisions better or at least more persuasive. It may be caused by the fact that the choice of what literary fiction is suitable for legal argumentation and which is not can be seen as a kind of ideology. Therefore the state determines which art is “good enough” to be a part of legal reasoning. Usually it differs between “high art” and “mass culture.” It results in a form of “labelling” of art. Unfortunately, by evaluating art in such a manner each state manifests itself as almost a totalitarian one. Socialist realism was a very expressive example. So it is not a matter for the democratic state to decide which piece of art is capable to influence law, is it? In this contribution I will emphasize Žižek’s critique of ideology in order to deal with ideology in argumentation by literary fiction in law. Besides that I will draw inspiration from Law and Literature movements. The aim of my paper is to explain how literary fiction can be used as a legal argument in a proper way as a necessary social appeal through law.This paper combines two of the suggested topics: “law as an instrument of ideology” and “ideological interpellation through law” as it explores whether or not it is possible to use literary fiction as part of an argument in legal argumentation. The use of such an argument is strongly connected with an attitude of state to art, culture and values included both in art and law. Art as a part of a socio-cultural system is one of the material sources of law so it would be natural to admit it in just judicial decision. Unfortunately it is not typical for law to use such relationships between art and law to make judicial decisions better or at least more persuasive. It may be caused by the fact that the choice of what literary fiction is suitable for legal argumentation and which is not can be seen as a kind of ideology. Therefore the state determines which art is “good enough” to be a part of legal reasoning. Usually it differs between “high art” and “mass culture.” It results in a form of “labelling” of art. Unfortunately, by evaluating art in such a manner each state manifests itself as almost a totalitarian one. Socialist realism was a very expressive example. So it is not a matter for the democratic state to decide which piece of art is capable to influence law, is it? In this contribution I will emphasize Žižek’s critique of ideology in order to deal with ideology in argumentation by literary fiction in law. Besides that I will draw inspiration from Law and Literature movements. The aim of my paper is to explain how literary fiction can be used as a legal argument in a proper way as a necessary social appeal through law

Why Should Ecosystem Services Be Governed to Support Poverty Alleviation? Philosophical Perspectives on Positions in the Empirical Literature

In light of trade-offs related to the allocation of ecosystem services we investigate the prevalent norms that are drawn upon to justify why ecosystem governance should prioritise poverty alleviation. We are specifically concerned with poverty alleviation because we consider this an urgent problem of justice. We review empirical literature on social trade-offs in ecosystem services governance in order to identify the prevalent conceptions of justice that inform scholarly assessments of current practice. We find that empirical studies do present specific notions of justice as desirable benchmarks for ecosystem services governance but that they rarely attempt to spell out the precise meaning of these notions or what makes them desirable. For those notions of justice that we identify in this literature - sufficientarianism, egalitarianism and participatory approaches - we draw on philosophical justice literature in order to better articulate the normative arguments that could support them and to be more precise about the kind of actions and expectations that they invoke. Moreover, we point to some striking normative silences in the ecosystem services literature. We conclude that the ecosystem services justice discourse would benefit from more conceptual clarity and a broader examination of different aspects of justice