Interplaying Cassandra NoSQL Consistency and Performance: A Benchmarking Approach

This experience report analyses performance of the Cassandra NoSQL database and studies the fundamental trade-off between data consistency and delays in distributed data storages. The primary focus is on investigating the interplay between the Cassandra performance (response time) and its consistency settings. The paper reports the results of the read and write performance benchmarking for a replicated Cassandra cluster, deployed in the Amazon EC2 Cloud. We present quantitative results showing how different consistency settings affect the Cassandra performance under different workloads. One of our main findings is that it is possible to minimize Cassandra delays and still guarantee the strong data consistency by optimal coordination of consistency settings for both read and write requests. Our experiments show that (i) strong consistency costs up to 25% of performance and (ii) the best setting for strong consistency depends on the ratio of read and write operations. Finally, we generalize our experience by proposing a benchmarking-based methodology for run-time optimization of consistency settings to achieve the maximum Cassandra performance and still guarantee the strong data consistency under mixed workloads

Projet de recherche sur les systèmes de production dans la zone de Goubellat, Tunisie : proposition pour une deuxième phase du projet, 1990-1995

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Synthesis, characterization, Hirshfeld surface analysis and antioxidant activity of a novel organic-inorganic hybrid material 1-methylpiperazine-1,4-diium trioxonitrate

International audienceThe new inorganic-organic hybrid material 1-methylpiperazine-1,4-diium bis(nitrate) (MPN) have been synthesized and crystallized to the orthorhombic system with space group Pnma and the lattice parameters obtained are a = 10.9385(9) Å, b = 6.5698 Å (4), c = 13.7021(10) Å, V = 984.68(12) Å3 and Z = 4. The trigonal (NO3 −) anions are connected to the 1-methylpiperazine-1,4-diium cations via a large number of bifurcated and non-bifurcated N[sbnd]H⋯O and C[sbnd]H⋯O hydrogen bonds. The diprotonated piperazine ring adopts a chair conformation, with the methyl group occupying an equatorial position. Intermolecular interactions in the crystal structure were quantified by Hirshfeld surface analysis. Infrared spectrum confirms the existence of the functional groups in the elaborated material. Optical absorption reveals an important band gap energy indicating stability of the title compound. The DTA/TGA and DSC curves indicate that the crystal is thermally stable up to 180 °C. The antioxidant properties were determined via the DPPH radical scavenging, the ABTS radical scavenging, hydroxyl radical scavenging and ferric reducing power (FRP). © 2017 Elsevier B.V

A unilocular thymic cyst associated with true thymic hyperplasia: a challenging diagnosis especially in a child

Mona Mlika,1,2 Walid Gattoufi,1,2 Hazem Zribi,2 Emna Braham,1,2 Adel Marghli,2 Faouzi El Mezni1,21Department of Pathology, Abderrahman Mami Hospital, Tunis, Tunisia; 2Research Unit UR12SP16, Université Tunis El Manar, Faculté de Médecine de Tunis, Tunis El Manar, TunisiaAbstract: We report a new case of a mediastinal mass in a 19-year-old patient corresponding microscopically to an association of unilocular thymic cyst and true thymic hyperplasia. Our aim is to highlight the absence of specificity of clinical and radiological findings and the necessity of a thorough sampling of the tumor in order to establish the diagnosis.Keywords: true thymic hyperplasia, thymic cyst, microscopy, surger

Analyse à l'échelle microstructurale de la fissuration dans une roche argileuse anisotrope par mesure de champs 2D et 3D

International audienceDans cette étude, la fissuration d'un échantillon millimétrique de roche argileuse soumis à un chargement mécanique de compression uni-axiale a été observée dans un premier temps par microscopie optique, donnant accès à une analyse fine de l'initiation et de la propagation. Dans un second temps, des essais similaires sont observés par tomographie RX synchrotron, avec une résolution proche de la microscopie optique, rendant compte ainsi de façon comparable du comportement en volume. L'influence de l'anisotropie du matériau est clairement mise en évidence avec les expériences 2D. L'analyse volumique montre l'évolution du champ de déformation dans l'éprouvette, avec des localisations très caractéristiques de ce type d'essai