Middleware-based Database Replication: The Gaps between Theory and Practice

The need for high availability and performance in data management systems has been fueling a long running interest in database replication from both academia and industry. However, academic groups often attack replication problems in isolation, overlooking the need for completeness in their solutions, while commercial teams take a holistic approach that often misses opportunities for fundamental innovation. This has created over time a gap between academic research and industrial practice. This paper aims to characterize the gap along three axes: performance, availability, and administration. We build on our own experience developing and deploying replication systems in commercial and academic settings, as well as on a large body of prior related work. We sift through representative examples from the last decade of open-source, academic, and commercial database replication systems and combine this material with case studies from real systems deployed at Fortune 500 customers. We propose two agendas, one for academic research and one for industrial R&D, which we believe can bridge the gap within 5-10 years. This way, we hope to both motivate and help researchers in making the theory and practice of middleware-based database replication more relevant to each other.Comment: 14 pages. Appears in Proc. ACM SIGMOD International Conference on Management of Data, Vancouver, Canada, June 200

Analyzing the Impact of Covid-19 Control Policies on Campus Occupancy and Mobility via Passive WiFi Sensing

Mobile sensing has played a key role in providing digital solutions to aid with COVID-19 containment policies. These solutions include, among other efforts, enforcing social distancing and monitoring crowd movements in indoor spaces. However, such solutions may not be effective without mass adoption. As more and more countries reopen from lockdowns, there remains a pressing need to minimize crowd movements and interactions, particularly in enclosed spaces. This paper conjectures that analyzing user occupancy and mobility via deployed WiFi infrastructure can help institutions monitor and maintain safety compliance according to the public health guidelines. Using smartphones as a proxy for user location, our analysis demonstrates how coarse-grained WiFi data can sufficiently reflect indoor occupancy spectrum when different COVID-19 policies were enacted. Our work analyzes staff and students' mobility data from three different university campuses. Two of these campuses are in Singapore, and the third is in the Northeastern United States. Our results show that online learning, split-team, and other space management policies effectively lower occupancy. However, they do not change the mobility for individuals transitioning between spaces. We demonstrate how this data source can be put to practical application for institutional crowd control and discuss the implications of our findings for policy-making.Comment: 25 pages, 18 figure

Redox Mediation at 11-Mercaptoundecanoic Acid Self-Assembled Monolayers on Gold

Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and digital simulation techniques were used to investigate quantitatively the mechanism of electron transfer (ET) through densely packed and well-ordered self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid on gold, either pristine or modified by physically adsorbed glucose oxidase (GOx). In the presence of ferrocenylmethanol (FcMeOH) as a redox mediator, ET kinetics involving either solution-phase hydrophilic redox probes such as [Fe(CN)6]3-/4- or surface-immobilized GOx is greatly accelerated: [Fe(CN)6]3-/4- undergoes diffusion-controlled ET, while the enzymatic electrochemical conversion of glucose to gluconolactone is efficiently sustained by FcMeOH. Analysis of the results, also including the digital simulation of CV and EIS data, showed the prevalence of an ET mechanism according to the so-called membrane model that comprises the permeation of the redox mediator within the SAM and the intermolecular ET to the redox probe located outside the monolayer. The analysis of the catalytic current generated at the GOx/SAM electrode in the presence of glucose and FcMeOH allowed the high surface protein coverage suggested by X-ray photoelectron spectroscopy (XPS) measurements to be confirmed.

Potencial biotecnológico de fungos marinhos em atividades pigmentares

Trabalho de Conclusão de Curso apresentado ao Instituto Latino-Americano de Ciências da Vida e da Natureza da Universidade Federal da Integração Latino-Americana, como requisito parcial à obtenção do título de Bacharel em Biotecnologia.O ecossistema marinho oferece uma ampla diversidade de compostos que permanecem inexplorados e que apresentam grande potencial como agentes clarificantes, antioxidantes, anti-inflamatórios, imunomodulatórios e antimicrobianos. Os microrganismos são importantes fontes de compostos ativos e os fungos e seus produtos metabólicos são muito estudados para tratamento de distúrbios pigmentares da pele. Assim, neste trabalho é avaliado o potencial de fungos marinhos como sintetizadores de biomoléculas com propriedades pigmentantes ou despigmentantes da melanina a partir da obtenção de extratos fúngicos. Dos seis fungos testados, apenas um apresentou resultados significativos. Ensaios de atividade de tirosinase de cogumelo foram conduzidos para verificar o efeito do extrato sobre a enzima. Para determinar o modo de inibição da enzima na tirosinase, a análise cinética do extrato foi realizada com substratos de L-tirosina e L-3,4-dihidroxifenilalanina (L-DOPA). Os resultados demonstraram que o extrato inibiu significativamente a atividade da tirosinase, através da inibição competitiva com o substrato. Pode-se concluir então que fungos marinhos apresentam potencial como inibidores da melanogênese, podendo ser utilizados em aplicações clínicas e cosméticas de clareamento da pele

Stingray: Cone Tracing using a software DSM for SCI clusters

International audienceIn this paper we consider the use of a supercomputer with a hardware shared memory versus a cluster of workstations using a software Distributed Shared Mem-ory (DSM). We focus on ray tracing applications to compare both architectures. We have ported Stingray, a parallel cone tracer developed on a SGI Origin 2000 super-computer, on a cluster using a Scalable Coherent Interface (SCI) network and a software DSM called SciFS. We present concepts of cone tracing with Stingray, concepts of SCI cluster with a DSM and the implementa-tion issues. We compare the results obtained with the two architectures and we discuss the trade-off - price/performance/programming ease - of both architectures. We show with Stingray that a modest 12 nodes SCI cluster with an efficient software DSM is 5 times cheaper and can perform up to 2.3 times better than a SGI Origin 2000 with 6 processors. We think that a software DSM is well suited for this kind of applications and provides both ease of programming and scalable per-formance

Fungal communities isolated from dead apple leaves from orchards in Quebec

Le champignon causant la tavelure du pommier, Venturia inaequalis, hiverne dans les feuilles mortes de pommier (Malus pumila) sous forme de pseudothèces. Les objectifs de cette étude étaient de monter une collection de champignons afin de vérifier subséquemment leur résistance au froid et leur potentiel antagoniste contre V. inaequalis et d'acquérir des connaissances sur la microflore des feuilles mortes de pommiers. Des champignons ont été isolés sur des feuilles mortes de pommiers récoltées au printemps et à l'automne de 1993. Au total, 345 isolats fongiques provenant de 49 genres ont été identifiés. Quinze genres sont rapportés pour la première fois comme colonisateurs des feuilles de pommiers en Amérique du Nord.Venturia inaequalis, the causal agent of apple scab, overwinters in apple (Malus pumila) leaves on the orchard floor by producing pseudothecia. The objectives of this survey were to make a collection of fungi to be subsequently tested for their potential as psychrophile biocontrol agents against V. inaequalis and to acquire knowledge on the diversity of the microflora of dead apple leaves. Fungi were recovered from dead apple leaves collected in the spring and fall of 1993. A total of 345 isolates from 49 genera were identified. Fifteen gene were not previously recorded as colonizers of apple leaves in North America

Performance and Scalability of EJB Applications

We investigate the combined effect of application implementation method, container design, and efficiency of communication layers on the performance scalability of J2EE application servers by detailed measurement and profiling of an auction site server. We have implemented five versions of the auction site. The first version uses stateless session beans, making only minimal use of the services provided by the Enterprise JavaBeans (EJB) container. Two versions use entity beans, one with containermanaged persistence and the other with bean-managed persistence. The fourth version applies the session façade pattern, using session beans as a façade to access entity beans. The last version uses EJB 2.0 local interfaces with the session façade pattern. We evaluate these different implementations on two popular open-source EJB containers with orthogonal designs. JBoss uses dynamic proxies to generate the container classes at run time, making an extensive use of reflection. JOnAS precompiles classes during deployment, minimizing the use of reflection at run time. We also evaluate the communication optimizations provided by each of these EJB containers. The most important factor in determining performance is the application implementation method. EJB applications with session beans perform as well as a Java servlets-only implementation and an order-of-magnitude better than most of the implementations based on entity beans. The fine-granularity access exposed by the entity beans limits scalability. Use of session façade beans improves performance for entity beans, but only if local communication is very efficient or EJB 2.0 local interfaces are used. Otherwise, session façade beans degrade performance. For the implementation using session beans, communication cost forms the major component of the execution time on the EJB server. The design of the container has little effect on performance. With entity beans, the design of the container becomes important. In particular, the cost of reflection affects performance. For implementations using session façade beans, local communication cost is critically important. EJB 2.0 local interfaces improve the performance by avoiding the communication layers for local communications

The design and commissioning of the MICE upstream time-of-flight system

In the MICE experiment at RAL the upstream time-of-flight detectors are used for particle identification in the incoming muon beam, for the experiment trigger and for a precise timing (sigma_t ~ 50 ps) with respect to the accelerating RF cavities working at 201 MHz. The construction of the upstream section of the MICE time-of-flight system and the tests done to characterize its individual components are shown. Detector timing resolutions ~50-60 ps were achieved. Test beam performance and preliminary results obtained with beam at RAL are reported.Comment: accepted on Nuclear Instruments and Methods

RAIDb: Redundant Array of Inexpensive Databases

Clusters of workstations become more and more popular to power data server applications such as large scale Web sites or e-Commerce applications. There has been much research on scaling the front tiers (web servers and application servers) using clusters, but databases usually remain on large dedicated SMP machines. In this paper, we address database performance scalability and high availability using clusters of commodity hardware. Our approach consists of studying different replication and partitioning strategies to achieve various degree of performance and fault tolerance. We propose the concept of Redundant Array of Inexpensive Databases (RAIDb). RAIDb is to databases what RAID is to disks. RAIDb aims at providing better performance and fault tolerance than a single database, at low cost, by combining multiple database instances into an array of databases. Like RAID, we define different RAIDb levels that provide various cost/performance/fault tolerance tradeoffs. RAIDb-0 features full partitioning, RAIDb-1 offers full replication and RAIDb-2 introduces an intermediate solution called partial replication, in which the user can define the degree of replication of each database table. We present a Java implementation of RAIDb called Clustered JDBC or C-JDBC. C-JDBC achieves both database performance scalability and high availability at the middleware level without changing existing applications. We show, using the TPC-W benchmark, that RAIDb-2 can offer better performance scalability (up to 25%) than traditional approaches by allowing fine-grain control on replication. Distributing and restricting the replication of frequently written tables to a small set of backends reduces I/O usage and improves CPU utilization of each cluster node