On distributed virtual network embedding with guarantees

To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst case efficiency of (?????) relative to the optimal solution, and that this bound is optimal, that is, no better approximation exists. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared with existing distributed VNET embedding solutions, and we show how byappropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.This work is supported in part by the National Science Foundation under grant CNS-0963974

On distributed virtual network embedding with guarantees

To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst case efficiency of (?????) relative to the optimal solution, and that this bound is optimal, that is, no better approximation exists. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared with existing distributed VNET embedding solutions, and we show how byappropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.This work is supported in part by the National Science Foundation under grant CNS-0963974

On distributed virtual network embedding with guarantees

To provide wide-area network services, resources from different infrastructure providers are needed. Leveraging the consensus-based resource allocation literature, we propose a general distributed auction mechanism for the (NP-hard) virtual network (VNET) embedding problem. Under reasonable assumptions on the bidding scheme, the proposed mechanism is proven to converge, and it is shown that the solutions guarantee a worst-case efficiency of (1-(1/e)) relative to the optimal node embedding, or VNET embedding if virtual links are mapped to exactly one physical link. This bound is optimal, that is, no better polynomial-time approximation algorithm exists, unless P=NP. Using extensive simulations, we confirm superior convergence properties and resource utilization when compared to existing distributed VNET embedding solutions, and we show how by appropriate policy design, our mechanism can be instantiated to accommodate the embedding goals of different service and infrastructure providers, resulting in an attractive and flexible resource allocation solution.CNS-0963974 - National Science Foundationhttp://www.cs.bu.edu/fac/matta/Papers/ToN-CAD.pdfAccepted manuscrip

Implementation of sunshine duration sensor

Peer Reviewe

Insights Into the Eruptive Dynamics of Small Caldera-Forming Eruptions: The Case Study of the Welded Scoriae of Vulcano (Aeolian Islands, Italy)

A multi-disciplinary study, integrating volcanological field observations, petrography, whole rock geochemistry and textural and compositional analyses on plagioclase crystals has been carried out on the products of Monte Luccia, Spiaggia Lunga, and Quadrara eruptions, occurred between 48 and 21 kyrs on the island of Vulcano. These products are all characterized by welded scoria blankets, and their eruptions have been generally related to the formation and/or re-activation of ring faults bordering the "Il Piano" caldera. The aim of the work is to reconstruct the pre- and syn-eruptive dynamics acting within their magma plumbing systems and the related link with the phases of caldera collapse. At the bottom of the stratigraphic sequences, the presence of base surge deposits suggests that all the eruptions started with a phreatomagmatic phase fed by a shallow reservoir. Textural and microanalytical study of plagioclase crystals of Spiaggia Lunga eruption revealed that the phreatomagmatic event activated the ascent of a volatile-rich, basaltic magma residing at 5–11 km of depth. This basaltic magma mixed with the resident shallow one, and was poured out during the course of the eruption producing a sustained lava-fountaining phase. The subsequent caldera collapse, identified by a layer of chaotic breccia interbedded in the scoriae deposit, has been linked to the partial emptying of the shallow magma reservoir. In contrast to what observed for recent eruptive events at Vulcano, the onset of the magmatic phase would be attributed to a self-activation due to volcano-tectonic events, and not to a pressurization of the plumbing system related to the ascent of deep magma batches. As concerns the Mt. Luccia deposits, bordering the eastern rim of the "Il Piano" caldera, the absence of plagioclase in the mineralogical assemblage suggests the eruption of a deeper magma (>11 km b.s.l.), rapidly ascending through the re-activated ring faults of "Il Piano" caldera. At Quadrara eruption, the occurrence of a layer of white biotite-bearing latitic pumices overlying the basal phreatomagmatic deposits suggests the involvement a shallow, isolated reservoir where the increase of volatile pressure allowed the crystallization of hydrous phases. A deeper shoshonitic magma was involved later in the eruption, forming the welded scoria level at the top of the sequence

Synthesis, Production, and Biotechnological Applications of Exopolysaccharides and Polyhydroxyalkanoates by Archaea

Extreme environments, generally characterized by atypical temperatures, pH, pressure, salinity, toxicity, and radiation levels, are inhabited by various microorganisms specifically adapted to these particular conditions, called extremophiles. Among these, the microorganisms belonging to the Archaea domain are of significant biotechnological importance as their biopolymers possess unique properties that offer insights into their biology and evolution. Particular attention has been devoted to two main types of biopolymers produced by such peculiar microorganisms, that is, the extracellular polysaccharides (EPSs), considered as a protection against desiccation and predation, and the endocellular polyhydroxyalkanoates (PHAs) that provide an internal reserve of carbon and energy. Here, we report the composition, biosynthesis, and production of EPSs and PHAs by different archaeal species

« Prendre exemple du modèle scolaire allemand ? » La réforme des humanités en Belgique à la fin du XIXe siècle dans son contexte européen (1870-1890)

À partir de l’exemple de la réforme de l’enseignement secondaire entreprise par le gouvernement belge dans les années 1880, cet article a l’ambition d’illustrer la façon dont les systèmes scolaires modernes d’Europe occidentale se sont construits sur la base d’un travail de comparaison entre modèles, dans un contexte de circulation internationale des informations et des savoirs. L’article est divisé en trois parties. La première analyse l’origine de la querelle des humanités en la replaçant dans son contexte européen, en rappelant les raisons qui poussaient les différents pays européens à aller chercher ailleurs des modèles à imiter. À travers l’étude de quelques exemples précis, elle montre plus particulièrement pourquoi plusieurs pays se sont intéressés à la réforme belge de 1881 et identifie les raisons de cette dernière. S’appuyant sur l’analyse des débats qui se sont tenus à propos des humanités en Belgique, la seconde et la troisième parties étudient la manière dont les réformateurs belges se sont tournés vers des modèles scolaires étrangers, en premier lieu le modèle allemand. Elles identifient les moyens et canaux de diffusion par lesquels l’information a circulé, examinent les arguments invoqués en faveur de ce modèle pédagogique et montrent les limites rencontrées par son transfert sur le sol national.Taking the reform of secondary education undertaken by the Belgian government in the 1880s as an example, this article aims to show how modern school systems in Western Europe have been based on comparison between models in a context of the international dissemination of information and knowledge. The article is divided into three parts. The first analyses the origin of the “humanities debate” by placing it in its European context, reiterating the reasons that led different European countries to look elsewhere for models. In particular, through the study of a few specific examples, it shows why several countries took an interest in the Belgian reform of 1881 and identifies the reasons for this. Based on an analysis of debate on the subject of the humanities in Belgium, the second and third sections examine the way in which Belgian reformers turned to foreign school models, particularly the German model. They identify the means and channels through which information was disseminated, examine the arguments put forward in favour of this educational model and show the limitations which had to be overcome in transferring it to Belgium

Pensamiento crítico y prácticas pedagógicas entre los maestros de tercero y quinto grado de la I.E. San Juan de Urabá durante los años 2016-2017

El presente trabajo da cuenta de la relación entre las concepciones de pensamiento crítico y crítico y las prácticas pedagógicas de los docentes de los grados tercero y quinto de la I. E. San Juan de Urabá. El enfoque elegido fue cualitativo y la metodología fue el método etnográfico. En un primer momento se recogió información sobre las concepciones de los docentes sobre el pensamiento crítico y su aplicabilidad en el aula a través de las preguntas socráticas de Elder y Paul (2003); luego, esta información se contrastó con las opiniones de los estudiantes mediante la técnica de grupo focal y los diarios de campo de la investigadora. Los resultados permitieron observar que las nociones de los maestros sobre el concepto de pensamiento crítico están relacionadas con los supuestos teóricos del proyecto: el cuestionario, la entrevista y la encuesta cerrada lo evidenciaron; sin embargo, las prácticas pedagógicas analizadas a partir del diario de campo y lo expresado por los estudiantes en el grupo focal no muestran una relación coherente entre concepciones y prácticas pedagógicas. Ante estos resultados, al final de la investigación se propone una secuencia de talleres con la finalidad de fortalecer el desarrollo de habilidades de pensamiento crítico de una manera práctica en el aula.The present report gives an account of the relationship between the conceptions of critical thinking and the pedagogical practices of the teachers of the third and fifth grades of the IE San Juan de Urabá. The approach addressed was qualitative and the methodology was given through the ethnographic method. At first, information was collected about teachers' conceptions of critical thinking and its applicability in the classroom through the Socratic questions of Elder y Paul (2003); then this information was contrasted with the opinions of the students through the focus group technique and the researcher's field diaries. The results allowed us to observe that the teachers' notions of the concept of critical thinking are related to the theoretical assumptions constructed by Elder y Paul (2003); the questionnaire, the interview and the closed survey evidenced it, however, the pedagogical practices analyzed from the field diary and what the students expressed in the focus group do not show a coherent relationship between conceptions and pedagogical practices. Given these results, at the end of the research, a sequence of workshops is proposed in order to strengthen the development of critical thinking skills in a practical way in the classroom.Magíster en EducaciónMaestrí