4,761 research outputs found

    Cryopreservation of encapsulated apices of sugarcane : effect of freezing procedure and histology

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    SUMMARY: The effect of sucrose concentration during the pregrowth treatment and of the freezing procedure on the survival of encapsulated apices of 6 sugarcane varieties was investigated. The optimal sucrose concentration was 0.75M. Survival was noted with both rapid freezing by direct immersion in liquid nitrogen and slow freezing using a programmable freezer but it was generally higher &er rapid cooling. Important genotypic variation was observed for both parameters studied. Histological examination revealed that cells were slightly harmed during pregrowth and freezing. Apices could withstand freezing as a whole. Direct regrowth of cryopreserved apices occurred within 3 days after thawing

    Evolución y Contribución para el Internet de las Cosas por las emergentes Redes Definidas por Software

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    Las últimas décadas han tenido una enorme evolución de las tecnologías de la computación y la comunicación, lo que ha llevado a un desarrollo y despliegue continúo de las infraestructuras de redes informáticas en términos de dimensión y complejidad. Una de las tecnologías que se ha convertido en una parte integral de la vida cotidiana es el Internet de las Cosas (IoT). Sin embargo, existe un consenso en que las nuevas arquitecturas de redes deberían rediseñarse e implementarse pruebas para mejorar muchos problemas técnicos y mejorar el rendimiento. Hoy en día, con el crecimiento exponencial de dispositivos conectados a Internet, la administración y configuración de la red es uno de los desafíos más difíciles para los administradores de red. En este contexto, con la aparición de las redes definidas por software (SDN) y funciones de redes virtualizadas (NFV) como dos nuevos paradigmas de redes, ofrecen muchas oportunidades para superar estos desafíos, ya que permiten gestionar con flexibilidad, configurar, proteger y optimizar la red recursos usando programas de software dinámicos. Este artículo presenta los aportes de la virtualización de funciones de red y arquitecturas que se pueden utilizar para mejorar el rendimiento basado en el protocolo OpenFlow y SDN, desde una perspectiva IoT

    Bottom-up hierarchical self-assembly of chiral porphyrins through coordination and hydrogen bonds

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    A series of chiral synthetic compounds is reported that show intricate but specific hierarchical assembly because of varying positions of coordination and hydrogen bonds. The evolution of the aggregates (followed by absorption spectroscopy and temperature-dependent circular dichroism studies in solution) reveal the influence of the proportion of stereogenic centers in the side groups connected to the chromophore ring in their optical activity and the important role of pyridyl groups in the self-assembly of these chiral macrocycles. The optical activity spans two orders of magnitude depending on composition and constitution. Two of the aggregates show very high optical activity even though the isolated chromophores barely give a circular dichroism signal. Molecular modeling of the aggregates, starting from the pyridine-zinc(II) porphyrin interaction and working up, and calculation of the circular dichroism signal confirm the origin of this optical activity as the chiral supramolecular organization of the molecules. The aggregates show a broad absorption range, between approximately 390 and 475 nm for the transitions associated with the Soret region alone, that spans wavelengths far more than the isolated chromophore. The supramolecular assemblies of the metalloporphyrins in solution were deposited onto highly oriented pyrolitic graphite in order to study their hierarchy in assembly by atomic force microscopy. Zero and one-dimensional aggregates were observed, and a clear dependence on deposition temperature was shown, indicating that the hierarchical assembly took place largely in solution. Moreover, scanning electron microscopy images of porphyrins and metalloporphyrins precipitated under out-of-equilibrium conditions showed the dependence of the number and position of chiral amide groups in the formation of a fibrillar nanomaterial. The combination of coordination and hydrogen bonding in the complicated assembly of these molecules - where there is a clear hierarchy for zinc(II)-pyridyl interaction followed by hydrogen-bonding between amide groups, and then van der Waals interactions - paves the way for the preparation of molecular materials with multiple chromophore environments

    International Workshop on Big Data and Data Mining Challenges on IoT and Pervasive Systems (BigD2M 2015)

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    We explain the notion of security architecture for Internet of Things (IoT) based on software-defined networking (SDN). In this context, the SDN-based architecture works with or without infrastructure, that we call SDN-Domain. This work describes the operation of the proposed architecture and summarizes the opportunity to achieve network security in a more efficient and flexible with SDN. An overview of existing SDN security applications were discussed and tackles its issues, presenting a new IoT system’s architecture. In this paper we considered the network access control and global traffic monitoring for ad-hoc networks. Finally, we point out architectural design choices for SDN using OpenFlow and discuss their performance implications.We explain the notion of security architecture for Internet of Things (IoT) based on software-defined networking (SDN). In this context, the SDN-based architecture works with or without infrastructure, that we call SDN-Domain. This work describes the operation of the proposed architecture and summarizes the opportunity to achieve network security in a more efficient and flexible with SDN. An overview of existing SDN security applications were discussed and tackles its issues, presenting a new IoT system’s architecture. In this paper we considered the network access control and global traffic monitoring for ad-hoc networks. Finally, we point out architectural design choices for SDN using OpenFlow and discuss their performance implications

    Geodesic squared exponential kernel for non-rigid shape registration

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    International audienceThis work addresses the problem of non-rigid registration of 3D scans, which is at the core of shape modeling techniques. Firstly, we propose a new kernel based on geodesic distances for the Gaussian Process Morphable Models (GPMMs) framework. The use of geodesic distances into the kernel makes it more adapted to the topological and geometric characteristics of the surface and leads to more realistic deformations around holes and curved areas. Since the kernel possesses hyperparameters we have optimized them for the task of face registration on the FaceWarehouse dataset. We show that the Geodesic squared exponential kernel performs significantly better than state of the art kernels for the task of face registration on all the 20 expressions of the FaceWarehouse dataset. Secondly, we propose a modification of the loss function used in the non-rigid ICP registration algorithm, that allows to weight the correspondences according to the confidence given to them. As a use case, we show that we can make the registration more robust to outliers in the 3D scans, such as non-skin parts

    SDN based architecture for IoT and improvement of the security

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    —With the exponential growth of devices connected to the Internet, security networks as one of the hardest challenge for network managers. Maintaining and securing such large scale and heterogeneous network is a challenging task. In this context, the new networking paradigm, the Software Defined Networking (SDN), introduces many opportunities and provides the potential to overcome those challenges. In this article, we first present a new SDN based architecture for networking with or without infrastructure, that we call an SDN domain. A single domain includes wired network, wireless network and Ad-Hoc networks. Next, we propose a second architecture to include sensor networks in an SDN-based network and in a domain. Third, we interconnect multiple domains and we describe how we can enhanced the security of each domain and how to distribute the security rules in order not to compromise the security of one domain. Finally, we propose a new secure and distributed architecture for IoT (Internet of Things).—With the exponential growth of devices connected to the Internet, security networks as one of the hardest challenge for network managers. Maintaining and securing such large scale and heterogeneous network is a challenging task. In this context, the new networking paradigm, the Software Defined Networking (SDN), introduces many opportunities and provides the potential to overcome those challenges. In this article, we first present a new SDN based architecture for networking with or without infrastructure, that we call an SDN domain. A single domain includes wired network, wireless network and Ad-Hoc networks. Next, we propose a second architecture to include sensor networks in an SDN-based network and in a domain. Third, we interconnect multiple domains and we describe how we can enhanced the security of each domain and how to distribute the security rules in order not to compromise the security of one domain. Finally, we propose a new secure and distributed architecture for IoT (Internet of Things)

    Empowering society by reusing privately held data for official statistics - A European approach

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    The High-Level Expert Group on facilitating the use of new data sources for official statistics has been created in the context of the data and digital strategy of the European Commission (EC). The task of the Expert Group is to provide recommendations aimed at enhancing data sharing between businesses and government (B2G) for the purpose of producing official statistics (B2G4S). The Expert Group consists of high-level experts with various backgrounds that are particularly relevant to B2G4S. Businesses generate and use data primarily for business-related purposes. The motivation for B2G4S stems from the high societal value that such privately held data can potentially generate when transformed into reliable, relevant and timely official statistics that are made available to everybody, for free. Transforming data into statistical information requires cooperation between private data holders and statistical authorities. On a voluntary basis there have been many collaborative efforts by businesses and statistical authorities to produce statistics based on privately held data, but for various reasons the use of such data for official statistics is still far below the level required to provide society with the high-quality and timely official statistics it needs in the increasingly data-driven world
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