Enhance Data Availability Research Articles

Inroads to Predict in Vivo Toxicology—An Introduction to the eTOX Project

There is a widespread awareness that the wealth of preclinical toxicity data that the pharmaceutical industry has generated in recent decades is not exploited as efficiently as it could be. Enhanced data availability for compound comparison (“read-across”), or for data mining to build predictive tools, should lead to a more efficient drug development process and contribute to the reduction of animal use (3Rs principle). In order to achieve these goals, a consortium approach, grouping numbers of relevant partners, is required. The eTOX (“electronic toxicity”) consortium represents such a project and is a public-private partnership within the framework of the European Innovative Medicines Initiative (IMI). The project aims at the development of in silico prediction systems for organ and in vivo toxicity. The backbone of the project will be a database consisting of preclinical toxicity data for drug compounds or candidates extracted from previously unpublished, legacy reports from thirteen European and European operation-based pharmaceutical companies. The database will be enhanced by incorporation of publically available, high quality toxicology data. Seven academic institutes and five small-to-medium size enterprises (SMEs) contribute with their expertise in data gathering, database curation, data mining, chemoinformatics and predictive systems development. The outcome of the project will be a predictive system contributing to early potential hazard identification and risk assessment during the drug development process. The concept and strategy of the eTOX project is described here, together with current achievements and future deliverables.

Enhancing Data Availability in MANETs with Cooperative Caching

Mobile Adhoc Networks (MANETs) are very popular solutions where network infrastructure installation is not possible. In MANETs, nodes are mobile, and due to this mobility, topology of the network changes rapidly. This dynamic topology reduces the data availability in MANETs. Cooperative caching provides an attractive solution for this problem. In this paper, a new cooperative caching algorithm, ProCoCa, is proposed. This algorithm is based on a proactive approach. Each node will be associated with a zone and the data of leaving node will be cached. The authors simulate the algorithm on OMNET++ simulator, and simulation results show that ProCoCa improves the data availability as well as overall performance of the network.

A Hybrid Approach to Failed Disk Recovery Using RAID-6 Codes

The current parallel storage systems use thousands of inexpensive disks to meet the storage requirement of applications. Data redundancy and/or coding are used to enhance data availability, for instance, Row-diagonal parity (RDP) and EVENODD codes, which are widely used in RAID-6 storage systems, provide data availability with up to two disk failures . To reduce the probability of data unavailability, whenever a single disk fails, disk recovery will be carried out. We find that the conventional recovery schemes of RDP and EVENODD codes for a single failed disk only use one parity disk. However, there are two parity disks in the system, and both can be used for single disk failure recovery. In this article, we propose a hybrid recovery approach that uses both parities for single disk failure recovery, and we design efficient recovery schemes for RDP code (RDOR-RDP) and EVENODD code (RDOR-EVENODD). Our recovery scheme has the following attractive properties: (1) “ read optimality ” in the sense that our scheme issues the smallest number of disk reads to recover a single failed disk and it reduces approximately 1/4 of disk reads compared with conventional schemes; (2) “ load balancing property ” in that all surviving disks will be subjected to the same (or almost the same) amount of additional workload in rebuilding the failed disk. We carry out performance evaluation to quantify the merits of RDOR-RDP and RDOR-EVENODD on some widely used disks with DiskSim. The offline experimental results show that RDOR-RDP and RDOR-EVENODD outperform the conventional recovery schemes of RDP and EVENODD codes in terms of total recovery time and recovery workload on individual surviving disk. However, the improvements are less than the theoretical value (approximately 25%), as RDOR-RDP and RDOR-EVENODD change the disk access pattern from purely sequential to a more random one compared with their conventional schemes.

Using an Open-Source PACS Virtual Machine for a Digital Angiography Unit: Methods and Initial Impressions

The productivity gains, diagnostic benefit, and enhanced data availability to clinicians enabled by picture archiving and communication systems (PACS) are no longer in doubt. However, commercial PACS offerings are often extremely expensive initially and require ongoing support contracts with vendors to maintain them. Recently, several open-source offerings have become available that put PACS within reach of more users. However, they can be resource-intensive to install and assure that they have room for future growth--both for computational and storage capacity. An alternate approach, which we describe herein, is to use PACS built on virtual machines which can be moved from smaller to larger hardware as needed in a just-in-time manner. This leverages the cost benefits of Moore's Law for both storage and compute costs. We describe the approach and current results in this paper.

Enhanced Fast Spread Replication strategy for Data Grid

Data replication is used in Data Grid to enhance data availability and fault tolerance. However, replication should be used wisely because the storage size of each node reside on the Data Grid is limited. Thus, the node must accommodate only the important replicas. In this paper, a dynamic replication strategy that takes into account the number and frequency of requests, the size of the replica, and the last time the replica was requested is proposed. This strategy is an enhanced version of Fast Spread replication strategy. The simulation results show that the new proposed strategy attained better performance than Fast Spread with Least Recently Used (LRU) and Fast Spread with Least Frequently Used (LFU) in terms of total response time and total bandwidth consumption.

A threshold-based dynamic data replication strategy

Data replication is the creation and maintenance of multiple copies of the same data. Replication is used in Data Grid to enhance data availability and fault tolerance. One of the main objectives of replication strategies is reducing response time and bandwidth consumption. In this paper, a dynamic replication strategy that is based on Fast Spread but superior to it in terms of total response time and total bandwidth consumption is proposed. This is achieved by storing only the important replicas on the storage of the node. The main idea of this strategy is using a threshold to determine if the requested replica needs to be copied to the node. The simulation results show that the proposed strategy achieved better performance compared with Fast Spread with Least Recently Used (LRU), and Fast Spread with Least Frequently Used (LFU).

A Spatio-Temporal Cache Replacement Policy for Location Dependent Data in Mobile Environments

Data caching in mobile clients is an important technique to enhance data availability and improve data access time. Due to cache size limitations, cache replacement policies are used to find a suitable subset of items for eviction from the cache. In this paper, the authors study the issues of cache replacement for location-dependent data under a geometric location model and propose a new cache replacement policy RAAR (Re-entry probability, Area of valid scope, Age, Rate of Access) by taking into account the spatial and temporal parameters. Mobile queries experience a popularity drift where the item loses its popularity after the user exhausts the corresponding service, thus calling for a scenario in which once popular documents quickly become cold (small active sets). The experimental evaluations using synthetic datasets for regular and small active sets show that this replacement policy is effective in improving the system performance in terms of the cache hit ratio of mobile clients.

On the fundamental performance limits of peer-to-peer data replication in wireless ad hoc networks

Wireless ad hoc networks are drawing increasing attention from the research community because of their potential applications. However, the fundamental capacity limits of these networks pose various technological challenges to designers of network protocols. In this paper, we attempt to capture the inherent constraints on information dissemination in a mobile wireless environment, with the emphasis on peer-to-peer (P2P) communications. More specifically, we introduce the notion of replication-induced gain to quantify the impact of data replication under the paradigm of P2P query-response mechanisms. Our major contribution lies in presenting several preliminary results with respect to the complexities and trade-offs involved in enhancing data availability. To the best of our knowledge, the data replication problems that arise because of scarce system resources in wireless ad hoc networks have not been investigated from this perspective. We believe that our results could provide additional insights and practical implications for P2P system designers.

Design of a High Efficiency Acoustic Phased Array Antenna for an Acoustic Wind Profiler

Improvements to the performance of acoustic wind profilers necessitate designing efficient acoustic antennas for the profilers, so that weak echoes can be received to enhance data availability. An efficient acoustic antenna needs to optimize electrical to acoustic and acoustic to electrical conversion efficiency as measured at the antenna axis. It also needs to provide a good directional response, and be able to handle increased electrical power. Phased array antennas, designed using piezo-electric transducers, should provide better characteristics in this regard. In the present study several different transducer elements were characterized with respect to their relative efficiencies. On the basis of this characterization, measurement of acoustic background noise at the expected site of antenna location and comparative study of atmospheric molecular absorption at the element peak efficiency frequencies, it is concluded that Motorola KSN 1025 A transducer is the best speaker element for the array antennas for profilers up to around 500 meters. The present array antenna has been designed using 104 KSN 1025 A piezo-electric transducer elements. The corner elements were removed from a 16 × 8 element speaker matrix, yielding an irregular octagonal pattern. Before installing the elements in the array, each element was individually characterized for its transmit and receive conversion efficiency, and variations in the product of these efficiencies (conversion gain) amongst the different elements, has been usefully employed to taper the array gain from centre to periphery. The antenna was systematically characterized, in an acoustic anechoic chamber, with respect to its axial transmit and receive conversion efficiencies and directional response.

The performance of replica control protocols in the presence of site failures

Replicated data were employed in distributed databases to enhance data availability. However, this benefit of data availability is only realized at the cost of elaborate algorithms that hide the underlying complexity of maintaining multiple copies of a single data item. The difficulty lies in keeping the copies consistent in the face of system failures while at the same time maximizing data availability. The algorithms which address these problems are called replica control algorithms. Although replica control has been the subject of extensive research for quite some time now, it has yet to fulfil its promise in practical applications. A major reason for this lack of acceptance is that the performance impact of these protocols cannot be easily quantified, as very few existing performance figures of commercial database systems which support copies are available. A natural question arises: Is replication worth it? This question is the focus of our investigation in this paper.