16 research outputs found

    A novel approach to call blocking probability evaluation in multiservice CDMA

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    We present a novel approach to model the uplink air interface access mechanism in a CDMA network as a slotted random access system, and use it to calculate the soft blocking probability in a multiservice CDMA network. Simulation results show that our method is accurate

    Spatial distribution and volume of dead wood in unmanaged caspian beech (Fagus orientalis) forests from northern Iran

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    Unmanaged forests are remnants of natural ecosystems that provide a basis for close-to-nature silvicultural research and applications. These forests have high amounts of dead wood, and although this material is being increasingly studied, the diversity of dead wood in terms of different diameters, decay stages, and spatial distribution patterns is as important as its volume for understanding forest dynamics. Here, we study natural forests in northern Iran to investigate the spatial distribution, decay stages, and volume of dead wood in unmanaged temperate forests at different developmental stages. Three stem-mapped sampling plots (100 m × 100 m) were established in uneven-aged stands dominated by Caspian beech (Fagus orientalis Lispsky). The total dead wood ranged from 37 to 119 m2 ha-1. Our results imply a spatial distribution shift from aggregation to randomness for dead trees in Caspian beech forest succession. We detected significant spatial interactions (attraction) between living and dead trees at short to medium spatial scales (1-20 m) in the plot with the earlier successional stage, suggesting that intra-specific competition is a prevailing force causing tree mortality at the stem-exclusion phase. By contrast, as trees become dominant with the mortality of other trees, the random tree-mortality pattern prevails. The spatial distribution and volume of dead wood may serve as a management target in near-to-natural Caspian beech forest. On the basis of our results, conservation-oriented management strategies should take into account the increasing amount of dead wood, particularly of large diameter in a late stage of decay. © 2013 by the authors.The authors would like to thank the Forest, Range and Watershed Organization of Iran for the financial support of the project. Jesús Julio Camarero acknowledges the support of ARAID. David Nesbitt looked over the English of this manuscript.Peer Reviewe

    The identification of a RNA splice variant in TULP1 in two siblings with early-onset photoreceptor dystrophy

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    Background: Early-onset photoreceptor dystrophies are a major cause of irreversible visual impairment in children and young adults. This clinically heterogeneous group of disorders can be caused by mutations in many genes. Nevertheless, to date, 30%–40% of cases remain genetically unexplained. In view of expanding therapeutic options, it is essential to obtain a molecular diagnosis in these patients as well. In this study, we aimed to identify the genetic cause in two siblings with genetically unexplained retinal disease. Methods: Whole exome sequencing was performed to identify the causative variants in two siblings in whom a single pathogenic variant in TULP1 was found previously. Patients were clinically evaluated, including assessment of the medical history, slit-lamp biomicroscopy, and ophthalmoscopy. In addition, a functional analysis of the putative splice variant in TULP1 was performed using a midigene assay. Results: Clinical assessment showed a typical early-onset photoreceptor dystrophy in both the patients. Whole exome sequencing identified two pathogenic variants in TULP1, a c.1445G>A (p.(Arg482Gln)) missense mutation and an intronic c.718+23G>A variant. Segregation analysis confirmed that both siblings were compound heterozygous for the TULP1 c.718+23G>A and c.1445G>A variants, while the unaffected parents were heterozygous. The midigene assay for the c.718+23G>A variant confirmed an elongation of exon 7 leading to a frameshift. Conclusion: Here, we report the first near-exon RNA splice variant that is not present in a consensus splice site sequence in TULP1, which was found in a compound heterozygous manner with a previously described pathogenic TULP1 variant in two patients with an early-onset photoreceptor dystrophy. We provide proof of pathogenicity for this splice variant by performing an in vitro midigene splice assay, and highlight the importance of analysis of noncoding regions beyond the noncanonical splice sites in patients with inherited retinal diseases

    The identification of a RNA splice variant in TULP1 in two siblings with early-onset photoreceptor dystrophy

    No full text
    Background: Early-onset photoreceptor dystrophies are a major cause of irreversible visual impairment in children and young adults. This clinically heterogeneous group of disorders can be caused by mutations in many genes. Nevertheless, to date, 30%–40% of cases remain genetically unexplained. In view of expanding therapeutic options, it is essential to obtain a molecular diagnosis in these patients as well. In this study, we aimed to identify the genetic cause in two siblings with genetically unexplained retinal disease. Methods: Whole exome sequencing was performed to identify the causative variants in two siblings in whom a single pathogenic variant in TULP1 was found previously. Patients were clinically evaluated, including assessment of the medical history, slit-lamp biomicroscopy, and ophthalmoscopy. In addition, a functional analysis of the putative splice variant in TULP1 was performed using a midigene assay. Results: Clinical assessment showed a typical early-onset photoreceptor dystrophy in both the patients. Whole exome sequencing identified two pathogenic variants in TULP1, a c.1445G>A (p.(Arg482Gln)) missense mutation and an intronic c.718+23G>A variant. Segregation analysis confirmed that both siblings were compound heterozygous for the TULP1 c.718+23G>A and c.1445G>A variants, while the unaffected parents were heterozygous. The midigene assay for the c.718+23G>A variant confirmed an elongation of exon 7 leading to a frameshift. Conclusion: Here, we report the first near-exon RNA splice variant that is not present in a consensus splice site sequence in TULP1, which was found in a compound heterozygous manner with a previously described pathogenic TULP1 variant in two patients with an early-onset photoreceptor dystrophy. We provide proof of pathogenicity for this splice variant by performing an in vitro midigene splice assay, and highlight the importance of analysis of noncoding regions beyond the noncanonical splice sites in patients with inherited retinal diseases

    Affinity replica selection in distributed systems

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    Replication is one of the key techniques used in distributed systems to improve high data availability, data access performance and data reliability. To optimize the maximum benefits from file replication, a systems that includes replicas need a strategy for selecting and accessing suitable replicas. A replica selection strategy determines the available replicas and chooses the most access files. In most of these access frequency based solutions or popularity of files are assuming that files are independent of each other. In contrast, distributed systems such as peer-to-peer file sharing, and mobile database, files may be dependent or correlated to one another. Thus, this paper focused on the combination of popularity and affinity files as the most important parameters in selecting replicas in distributed environments. Herein, a replica selection is proposed focusing on popular files and affinity files. The idea is to improve data availability in distributed data replica selection strategy. A P2P simulator, PeerSim, is used to evaluate the performance of the dynamic replica selection strategy. The simulation results provided a proof that the proposed affinity replica selection has contributed towards a new dimension of replica selection strategy that incorporates the affinity and popularity of file replicas in distributed systems

    A file group data replication algorithm for data grids

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    In recent years data grids have been deployed and grown in many scientific experiments and data centers. The deployment of such environments has allowed grid users to gain access to a large number of distributed data. Data replication is a key issue in a data grid and should be applied intelligently because it reduces data access time and bandwidth consumption for each grid site. Therefore this area will be very challenging as well as providing much scope for improvement. In this paper, we introduce a new dynamic data replication algorithm named Popular File Group Replication, PFGR which is based on three assumptions: first, users in a grid site (Virtual Organization) have similar interests in files and second, they have the temporal locality of file accesses and third, all files are read-only. Based on file access history and first assumption, PFGR builds a connectivity graph for a group of dependent files in each grid site and replicates the most popular group files to the requester grid site. After that, when a user of that grid site needs some files, they are available locally. The simulation results show that our algorithm increases performance by minimizing the mean job execution time and bandwidth consumption and avoids unnecessary replication.info:eu-repo/semantics/publishedVersio
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