Content Distribution in P2P Systems

The report provides a literature review of the state-of-the-art for content distribution. The report's contributions are of threefold. First, it gives more insight into traditional Content Distribution Networks (CDN), their requirements and open issues. Second, it discusses Peer-to-Peer (P2P) systems as a cheap and scalable alternative for CDN and extracts their design challenges. Finally, it evaluates the existing P2P systems dedicated for content distribution according to the identied requirements and challenges

Data Storage and Dissemination in Pervasive Edge Computing Environments

Nowadays, smart mobile devices generate huge amounts of data in all sorts of gatherings. Much of that data has localized and ephemeral interest, but can be of great use if shared among co-located devices. However, mobile devices often experience poor connectivity, leading to availability issues if application storage and logic are fully delegated to a remote cloud infrastructure. In turn, the edge computing paradigm pushes computations and storage beyond the data center, closer to end-user devices where data is generated and consumed. Hence, enabling the execution of certain components of edge-enabled systems directly and cooperatively on edge devices. This thesis focuses on the design and evaluation of resilient and efficient data storage and dissemination solutions for pervasive edge computing environments, operating with or without access to the network infrastructure. In line with this dichotomy, our goal can be divided into two specific scenarios. The first one is related to the absence of network infrastructure and the provision of a transient data storage and dissemination system for networks of co-located mobile devices. The second one relates with the existence of network infrastructure access and the corresponding edge computing capabilities. First, the thesis presents time-aware reactive storage (TARS), a reactive data storage and dissemination model with intrinsic time-awareness, that exploits synergies between the storage substrate and the publish/subscribe paradigm, and allows queries within a specific time scope. Next, it describes in more detail: i) Thyme, a data storage and dis- semination system for wireless edge environments, implementing TARS; ii) Parsley, a flexible and resilient group-based distributed hash table with preemptive peer relocation and a dynamic data sharding mechanism; and iii) Thyme GardenBed, a framework for data storage and dissemination across multi-region edge networks, that makes use of both device-to-device and edge interactions. The developed solutions present low overheads, while providing adequate response times for interactive usage and low energy consumption, proving to be practical in a variety of situations. They also display good load balancing and fault tolerance properties.Resumo Hoje em dia, os dispositivos móveis inteligentes geram grandes quantidades de dados em todos os tipos de aglomerações de pessoas. Muitos desses dados têm interesse loca- lizado e efêmero, mas podem ser de grande utilidade se partilhados entre dispositivos co-localizados. No entanto, os dispositivos móveis muitas vezes experienciam fraca co- nectividade, levando a problemas de disponibilidade se o armazenamento e a lógica das aplicações forem totalmente delegados numa infraestrutura remota na nuvem. Por sua vez, o paradigma de computação na periferia da rede leva as computações e o armazena- mento para além dos centros de dados, para mais perto dos dispositivos dos utilizadores finais onde os dados são gerados e consumidos. Assim, permitindo a execução de certos componentes de sistemas direta e cooperativamente em dispositivos na periferia da rede. Esta tese foca-se no desenho e avaliação de soluções resilientes e eficientes para arma- zenamento e disseminação de dados em ambientes pervasivos de computação na periferia da rede, operando com ou sem acesso à infraestrutura de rede. Em linha com esta dico- tomia, o nosso objetivo pode ser dividido em dois cenários específicos. O primeiro está relacionado com a ausência de infraestrutura de rede e o fornecimento de um sistema efêmero de armazenamento e disseminação de dados para redes de dispositivos móveis co-localizados. O segundo diz respeito à existência de acesso à infraestrutura de rede e aos recursos de computação na periferia da rede correspondentes. Primeiramente, a tese apresenta armazenamento reativo ciente do tempo (ARCT), um modelo reativo de armazenamento e disseminação de dados com percepção intrínseca do tempo, que explora sinergias entre o substrato de armazenamento e o paradigma pu- blicação/subscrição, e permite consultas num escopo de tempo específico. De seguida, descreve em mais detalhe: i) Thyme, um sistema de armazenamento e disseminação de dados para ambientes sem fios na periferia da rede, que implementa ARCT; ii) Pars- ley, uma tabela de dispersão distribuída flexível e resiliente baseada em grupos, com realocação preventiva de nós e um mecanismo de particionamento dinâmico de dados; e iii) Thyme GardenBed, um sistema para armazenamento e disseminação de dados em redes multi-regionais na periferia da rede, que faz uso de interações entre dispositivos e com a periferia da rede. As soluções desenvolvidas apresentam baixos custos, proporcionando tempos de res- posta adequados para uso interativo e baixo consumo de energia, demonstrando serem práticas nas mais diversas situações. Estas soluções também exibem boas propriedades de balanceamento de carga e tolerância a faltas

Content Distribution in P2P Systems

The report provides a literature review of the state-of-the-art for content distribution. The report's contributions are of threefold. First, it gives more insight into traditional Content Distribution Networks (CDN), their requirements and open issues. Second, it discusses Peer-to-Peer (P2P) systems as a cheap and scalable alternative for CDN and extracts their design challenges. Finally, it evaluates the existing P2P systems dedicated for content distribution according to the identied requirements and challenges

Management consulting.

Including a lengthy, comprehensive introduction, this important collection brings together some of the most influential papers that have contributed to our understanding of management consultancy work. The two-volume set encompasses the breadth of conceptual and empirical perspectives and explores those key ideas that have helped to advance our knowledge of this intriguing area. The volumes are divided into a series of thematic sections, affording the reader easy access to a great resource of information. Professors Clark and Avakian have written an original introduction which provides a comprehensive overview of the literature

Multiphase flow measurement using gamma-based techniques

The oil and gas industry need for high performing and low cost multiphase meters is ever more justified given the rapid depletion of conventional oil reserves. This has led oil companies to develop smaller/marginal fields and reservoirs in remote locations and deep offshore, thereby placing great demands for compact and more cost effective soluti8ons of on-line continuous multiphase flow measurement. The pattern recognition approach for clamp-on multiphase measurement employed in this research study provides one means for meeting this need. Cont/d

Development of a microfluidic device for gaseous formaldehyde sensing = Développement d\u27un dispositif microfluidique pour la détection de formaldéhyde à l\u27état gazeux

Formaldehyd (HCHO) ist eine chemische Verbindung, die bei der Herstellung einer großen Zahl von Haushaltsprodukten verwendet wird.Charakteristisch ist seine hohe Flüchtigkeit aufgrund einer niedrigen Siedetemperatur ($T = - 19\ ℃$). Daher ist HCOH fast überall als Luftschadstoff in Innenräumen vorhanden. Die Miniaturisierung analytischer Systeme zu Handheld-Gerät hat das Potenzial, nicht nur effizientere, sondern auch empfindlichere Instrumente für die Echtzeitüberwachung dieses gefährlichen Luftschadstoffs zu ermöglichen. Die vorliegende Doktorarbeit präsentiert die Entwicklung eines Mikrofluidik-Geräts für die Erfassung von HCHO basierend auf der Hantzsch-Reaktion.Hierbei wurde der Schwerpunkt auf die Komponente für Fluoreszenzdetektion gelegt. Es wurde eine umfangreiche Literaturrecherche durchgeführt, die es erlaubt, den Stand der Technik auf dem Gebiet der Miniaturisierung des Fluoreszenzsensors zusammenzufassen. Auf Grund dieser Studie wurde ein modulares Fluoreszenzdetektionskonzept vorgeschlagen, das um einen CMOS-Bildsensor (CIS) herum entwickelt wurde. Zwei dreischichtige Fluidikzellenkonfigurationen (Konfiguration 1: Quarz - SU-8 3050 - Quarz und Konfiguration 2: Silizium - SU-8 3050 - Quarz) wurden in Betracht gezogen und parallel unter den gleichen experimentellen Bedingungen getestet. Die Verfahren der Mikrofabrikation der fluidischen Zellen wurden detailliert beschrieben, einschließlich des Integrationsprozesses der Standardkomponenten und der experimentellen Verfahren. Der CIS-basierte Fluoreszenzdetektor bewies seine Leistungsfähigkeit, eine anfängliche HCHO-Konzentration von 10 µg/L vollständig in 3,5-Diacetyl-1,4-dihydrolutidin (DDL- derivatisiert) sowohl für die Quarz- als auch für die Silizium-Fluidikzellen zu detektieren. Beide Systemewiesenein Abfragevolumen von 3,5 µL auf. Ein offensichtlich höheres Signal-Rausch-Verhältnis (SNR) wurde für die Silizium-Fluidzelle ($\text{SNR}_{\text{silicon}} = 6.1$) im Vergleich zur Quarz-Fluidzelle ($\text{SNR}_{\text{quartz}} = 4.9$) beobachtet. Die Verstärkung der Signalintensität in der Silizium-Fluidzelle ist wahrscheinlich auf den Silizium-Absorptionskoeffizienten bei der Anregungswellenlänge zurückzuführen,$a\left( \lambda_{\text{abs}} = 420\ nm \right) = 5 \bullet 10^{4}\text{cm}^{- 1}$. Dieser Koeffizient ist ungefähr fünfmal höher als der Absorptionskoeffizient bei der Fluoreszenzemissionswellenlänge $a\left(\lambda_{\text{em}} = 515\ nm \right) = 9.25 \bullet 10^{3}\text{cm}^{- 1}$. HCHO wird aufgrund seiner relativ hohen Konstanten für das Henry-Gesetz sehr schnell in ein flüssiges Reagenz aufgenommen. Somit hängt die Auswahl des molekularen Einfangverfahrens (Schwallströmung, Ringströmung oder membranbasierte Strömungswechselwirkung) von derLeistungsfähigkeit des Fluoreszenzdetektors ab. Ein vorläufiges Konzept, das auf der Verwendung einer Gas-Flüssigkeitsmembran-basierten Wechselwirkung zum ständigen Abfangen des gasförmigen HCHO basiert, wurde eingeführt. Hierzu wurden kompatible Materialien und Herstellungsmethoden identifiziert. Darüber hinaus wurden CFD-Simulationen durchgeführt, um die Mikrokanallänge unter verschiedenen hydrodynamischen Bedingungen abzuschätzen, die für eine vollständige HCHO-Derivatisierung erforderlich sind. Eine Verbesserung und Vereinfachung auf der Grundlage von sehrnempfindlichen Fluoreszenzdetektoren mit niedrigen Detektionsgrenzen könnte zukünftig basierend z. B. auf Schwallströmung oder Ringströmung möglich sein

Washington University Senior Undergraduate Research Digest (WUURD), Spring 2018

From the Washington University Office of Undergraduate Research Digest (WUURD), Vol. 13, 05-01-2018. Published by the Office of Undergraduate Research. Joy Zalis Kiefer, Director of Undergraduate Research and Associate Dean in the College of Arts & Scien

The Viscous

Slime, goo, gunge, gloop, gels, sols, globules, jellies, emulsions, greases, soaps, syrups, glues, lubricants, liquid crystals, moulds, plasmas, and protoplasms – the viscous is not one thing, but rather a quality of resistance and flow, of stickiness and slipperiness. It is a state of matter that oozes into the gaps of our everyday existence, across age groups, between cultures and disciplines.Since the large-scale extraction of petroleum in the 19th century the viscous has witnessed a proliferation in the variety of its forms. Mechanized industry required lubricants and oil distillation produced waste products that were refined to form Vaseline. From this age, new viscous forms and technologies emerged, products from plastic (and plastic explosives) to cosmetics, glycerine, asphalt, sexual lubrication, hydro- and aero- gels, even anti-climb paint.Based on unique and wide-ranging research, The Viscous is the first major investigation of viscous encounter and possibility over the course of the last century, not simply as a material state, but also an imaginative event. We enter into a story of matter at its most wayward, deviant, hesitant, and resistant.From asphalt lakes to industrial molasses tanks, from liquid crystals squirming in our screens to milk fetishes, The Viscous discloses gooeyness as a peculiarly modern phase of matter. "Everything oozes," as Beckett’s Estragon famously proclaims in Waiting for Godot. Viscous dynamics are exposed as not only hugely various in a post industrial age, but particularly useful ways of thinking, feeling, writing, and making in a time of ecological anxiety

LOCAL SUPPLEMENTATION OF BRAINDERIVED NEUROTROPHIC FACTOR FOR THE TREATMENT OF NEURONAL DAMAGE.

The importance of nerve growth factors, especially brain-derived neurotrophic factor (BDNF) in the regulation of neuronal survival and plastic changes in morphology and function has been increasingly studied during the recent years. It has been proposed that the pathogenesis of some neurological diseases may be due to an alteration in neurotrophic factor and/or Trk receptor levels. The use of neurotrophic factors as therapeutic agents is a promising approach aimed at restoring and maintaining neuronal function in the central nervous system (CNS). This study is undertaken to develop a novel stem cell-based gene therapy to deliver neurotrophic factors to vulnerable regions of the CNS. Stem cell-based gene therapy is a potential delivery option by which cells are engineered to produce neurotrophic factors in vitro and then transplanted to the target area where neurotrophic factors are secreted to exert protective and/or restorative effects on the host tissue. A recently isolated mesodermal stem cell, mesoangioblast (MAB), has a high adhesin-dependent migratory capacity and may selectively cross the blood-brain barrier and home in the lesioned areas. Therefore, MABs provide an ideal cellular source for BDNF delivery. In this study, we generated a genetically modified mesoangioblast producing BDNF (MABs-BDNF). These engineered MABs maintained transgene expression and secretion of bioactive BDNF in time. We investigated the protective effects of MABs-BDNF in vitro using primary cultures and organotypic cultures of hippocampal slices. The viability of the cultured slices was assessed in several ways: fluorescein diacetate (FDA) hydrolysis assay, lactate dehydrogenase (LDH) release assay, immunohistochemistry for MAP2, immunoblot for neurofilament 68, and field potential recordings. Direct exposure of recombinant BDNF to primary cultured neurons and adult slices resulted in a concentration-dependant protective effect. The conditioned medium from MABs-BDNF highly promoted cell survival, while the conditioned medium from control cells (MABs) or an equivalent amount of rBDNF showed beneficial effects on cell survival to a lesser extent. The protective effects of MABs-BDNF were attenuated by adding either with the TrkB receptor blocker K252a or the BDNF scavenger TrkB-IgG.. This indicates that the conditioned medium from MABs-BDNF can foster the adult slice culture through secreting the engineered BDNF and unknown pro-survival factors produced intrinsically by MABs. The MABs-BDNF conditioned medium was optimal for retention of morphologic characteristics and viability in organotypic cultures from adult hippocampal slices. Moreover, MABs-BDNF were found to promote neurogenesis and glia proliferation. Treatment with the MABs-BDNF conditioned medium was found to increase the number of BrdU-labeled and BrdU/NeuN double labeled cells in the dentate gyrus of cultured slices. These in vitro findings demonstrate the beneficial effects of MABs-BDNF on neurons and provide a rationale for transplanting MABs-BDNF in the damaged brain as a therapeutic approach. Thus, we tested the transplantation of MABs-BDNF in an animal model of neuronal loss, the hippocampal sclerosis induced by status epilepticus. So far, we have not detected a deposition of MABs-BDNF in the epileptic brain after their systemic administration. Future experiments will aim at optimizing the transplanting conditions, changing the delivering routes, and assessing their therapeutic value in other neurological diseases associated with cell death. In terms of their prominent beneficial by-stander effects on neurons, MABs-BDNF hold substantial promise as therapeutic agents in the treatment of neurological diseases