A Dynamic Model of EFL Learners' Personal Best Goals, Resilience, and Language Achievement

One of the objectives of any educational endeavor is helping students to adopt a set of personal goals for their achievement. This is known as personal best (PB) referring to personalized goals or standards of excellence that match or exceed one's prior best in the academic context. It is also believed that PB goals can fluctuate in line with other academic-associated factors. The aim of the present study is to scrutinize these goals in association with students' resilience and language achievement. In other words, this study elucidated how EFL learners' PB and resilience influence language achievement. To do so, 173 students studying in two private language institutes and a university completed two questionnaires. The former was PB scale designed by Martin (2006) measuring specific, challenging, competitively self-referenced, and self- improvement goals. It was then translated and validated by the present researchers. The latter was the resilience scale containing five dimensions of perceived happiness, empathy, sociability, persistence, and self-regulation. The questionnaire was designed and validated by Kim and Kim (2016) and then translated and validated in this study. The results of confirmatory factor analysis (CFA) demonstrated the validity of the Persian versions of the scales. The results of structural equation modeling (SEM) also indicated that PB is a positive and significant predictor of resilience. Moreover, it was found that language achievement is predicted by both PB and resilience

Extending Eventually Consistent Cloud Databases for Enforcing Numeric Invariants

Geo-replicated databases often operate under the principle of eventual consistency to offer high-availability with low latency on a simple key/value store abstraction. Recently, some have adopted commutative data types to provide seamless reconciliation for special purpose data types, such as counters. Despite this, the inability to enforce numeric invariants across all replicas still remains a key shortcoming of relying on the limited guarantees of eventual consistency storage. We present a new replicated data type, called bounded counter, which adds support for numeric invariants to eventually consistent geo-replicated databases. We describe how this can be implemented on top of existing cloud stores without modifying them, using Riak as an example. Our approach adapts ideas from escrow transactions to devise a solution that is decentralized, fault-tolerant and fast. Our evaluation shows much lower latency and better scalability than the traditional approach of using strong consistency to enforce numeric invariants, thus alleviating the tension between consistency and availability

Co-Design and Verification of an Available File System

International audienceDistributed file systems play a vital role in large-scale enterprise services. However, the designer of a distributed file system faces a vexing choice between strong consistency and asynchronous replica-tion. The former supports a standard sequential model by synchronising operations, but is slow and fragile. The latter is highly available and responsive, but exposes users to concurrency anomalies. In this paper, we describe a rigorous and general approach to navigating this trade-off by leveraging static verification tools that allow to verify different file system designs. We show that common file system operations can run concurrently without synchronisation, while still retaining a semantics reasonably similar to Posix hierarchical structure. The one exception is the move operation, for which we prove that, unless synchronised, it will have an anomalous behaviour

A Dynamic Model of EFL Learners' Personal Best Goals, Resilience, and Language Achievement

One of the objectives of any educational endeavor is helping students to adopt a set of personal goals for their achievement. This is known as personal best (PB) referring to personalized goals or standards of excellence that match or exceed one's prior best in the academic context. It is also believed that PB goals can fluctuate in line with other academic-associated factors. The aim of the present study is to scrutinize these goals in association with students' resilience and language achievement. In other words, this study elucidated how EFL learners' PB and resilience influence language achievement. To do so, 173 students studying in two private language institutes and a university completed two questionnaires. The former was PB scale designed by Martin (2006) measuring specific, challenging, competitively self-referenced, and self- improvement goals. It was then translated and validated by the present researchers. The latter was the resilience scale containing five dimensions of perceived happiness, empathy, sociability, persistence, and self-regulation. The questionnaire was designed and validated by Kim and Kim (2016) and then translated and validated in this study. The results of confirmatory factor analysis (CFA) demonstrated the validity of the Persian versions of the scales. The results of structural equation modeling (SEM) also indicated that PB is a positive and significant predictor of resilience. Moreover, it was found that language achievement is predicted by both PB and resilience

The effect of follicular fluid selenium concentration on oocyte maturation in women with polycystic ovary syndrome undergoing in vitro fertilization/Intracytoplasmic sperm injection: A cross-sectional study

Background: A high level of free radicals and oxidative substances in women with polycystic ovary syndrome (PCOS) can affect the ovaries through oxidative stress. Antioxidants such as selenium, a vital trace element in human health, can improve the prognosis of PCOS by reducing oxidative stress. Objective: This study was performed due to the lack of comprehensive information about selenium concentration in follicular fluid and its effect on the oocyte count and quality in infertile women with PCOS. Materials and Methods: In this cross-sectional study, 78 women with PCOS referred to Umm-al-Banin Infertility Clinic Center, Ganjavian Hospital, Dezful, Iran for in-vitro fertilization from March to November 2019 were enrolled. After ovarian stimulation with the antagonist protocol, the oocytes were retrieved under transvaginal ultrasound in in-vitro fertilization/intracytoplasmic sperm injection cycles, and selenium concentrations were measured in the follicular fluid using an atomic absorption method by spectrophotometer device. Oocyte count and morphology were evaluated using inverted optical microscopy. Results: There were no significant differences between follicular fluid selenium concentrations in terms of the total number of oocytes and immature oocytes in the metaphase I and germinal vesicle stages. However, a significantly reduced number of metaphase II oocytes was observed at selenium levels < 40 μg/dL (p = 0.001). Conclusion: Based on our results, low levels of follicular selenium concentration in infertile women with PCOS can reduce the quality and potency of oocyte maturation. Key words: Polycystic ovary syndrome, Oxidative stress, Selenium, In vitro fertilization, Oocyte quality, Follicular fluid

Improving the scalability of geo-replication with reservations

International audienceGeo-replicated systems improve performance and fault tolerance by replicating data on sites in different physical locations. These systems often eschew guaranteeing strong consistency because of performance loss and scalability and instead choose eventually consistency. Although eventual consistency improves performance especially in large scale but it might violate system invariants. In this work, we exploit reservation techniques to strengthen eventual consistency, by adding safety guarantees. We define a consistency model called RPB that takes the advantages of eventual consistency while providing stronger guarantees, including causality and safety properties

The CISE Tool: Proving Weakly-Consistent Applications Correct

International audienceDesigners of a replicated database face a vexing choice between strong consistency, which ensures certain application invariants but is slow and fragile, and asynchronous replication, which is highly available and responsive, but exposes the programmer to unfamiliar behaviours. To bypass this conundrum, recent research has studied hybrid consistency models, in which updates are asynchronous by default, but synchronisation is available upon request. To help programmers exploit hybrid consistency, we propose the first static analysis tool for proving integrity invariants of applications using databases with hybrid consistency models. This allows a programmer to find minimal consistency guarantees sufficient for application correctness

Geo-Replication: Fast If Possible, Consistent If Necessary *

Abstract Ge

Geo-Replication: Fast If Possible, Consistent If Necessary

International audienceGeo-replicated storage systems are at the core of current Internet services. Unfortunately, there exists a fundamental tension between consistency and performance for offering scalable geo-replication. Weakening consistency semantics leads to less coordination and consequently a good user experience, but it may introduce anomalies such as state divergence and invariant violation. In contrast, maintaining stronger consistency precludes anomalies but requires more coordination. This paper discusses two main contributions to address this tension. First, RedBlue Consistency enables blue operations to be fast (and weakly consistent) while the remaining red operations are strongly consistent (and slow). We identify sufficient conditions for determining when operations can be blue or must be red. Second, Explicit Consistency further increases the space of operations that can be fast by restricting the concurrent execution of only the operations that can break application-defined invariants. We further show how to allow operations to complete locally in the common case, by relying on a reservation system that moves coordination off the critical path of operation execution

L'analyse et co-design des applications faiblement-cohérent

Distributed databases take advantage of replication to bring data close to the client, and to always be available. the primary challenge for such databases is to ensure consistency. recent research provide hybrid consistency models that allow the database supports asynchronous updates by default, but synchronisation is available upon request. to help programmers exploit the hybrid consistency model, we propose a set of useful patterns,proof rules, and tool for proving integrity invariants of applications. in the first part, we study a sound proof rule that enables programmers to check whether the operations of a given application semantics maintain the application invariants under a given amount of parallelism. we have developed a smt-based tool that automates this proof, and verified several example applications using the tool. in the second part, we apply the above methodology to the design of a replicated file system.the main invariant is that the directory structure forms a tree. we study three alternative semantics for the file system. each exposes a different amount of parallelism, and different anomalies. using our tool-assisted rules, we check whether a specific file system semantics maintains the tree invariant, and derive an appropriate consistency protocol. in the third part of this thesis, we present three classes of invariants: equivalence, partial order, and single-item generic. each places some constraints over the state. each of these classes maps to a different storage-layer consistency property: respectively, atomicity, causal ordering, or total ordering.Afin d'assurer disponibilité et réactivité, de nombreux systèmes distribués reposent sur des bases de données répliquées qui maintiennent des copies (répliques) des données sur différents serveurs. la cohérence constitue un défi important dans la mise en oeuvre des bases de données répliquées. les concepteurs de bases de données repliquées doivent faire un choix difficile entre une cohérence forte, qui guarantit une large gamme d'invariants applicatifs, mais qui est lente et fragile, et une réplication asynchrone, qui assure un bon niveau de disponibilité et de réactivité, mais laisse le programmeur face à de possibles anomalies liées à la concurrence.pour résoudre ce dilemme, des bases de données commerciales et recherche fournissent une cohérence hybride qui permet au programmeur d'exiger une cohérence forte pour certaines opérations, et d'ainsi permettre une synchronisation.cette thèse étudie l'analyse et la mise en oeuvre d'une application et de la cohérence associée, de manière à assurer les invariants de cette application avec un minimum d'exigences de cohérence. les trois principales contributions de cette thèse sont: 1) nous proposons le premier outil d'analyse statique destiné à prouver la validité d'invariants d'applications de base de données à modèle de cohérence hybride. 2) nous présentons la mise en application de notre outil d'analyse dans le cadre de la conception d'un système de fichiers dont la sémantique permet un comportement similaire à posix et à un coût résonable. 3)nous proposons un ensemble de patterns utiles, susceptibles d'aider les développeurs d'application dans l'implémentation d'invariants les plus communs