A framework for implementing asynchronous replication scheme in utility-based computing environment

This paper addresses a problem on implementing an asynchronous replication scheme in utility-based computing environment. The problem needs a special attention as most of the existing replication scheme in this computing system whether implicitly support synchronous replication and/or only consider read-only job. Therefore, we propose an intelligent framework that can reinforce an effective resource selection scheme by allowing the components that give impact on the performance such as resource/data freshness of the replicated system in such environment to be considered. We exploit an Update Ordering (UO) approach and reconcile these components in designing the framework. Important issues such as job propagation delay and job propagation rules are especially addressed. Our experiments show that the proposed framework is capable to become a platform of an effective resource selection scheme and achieve a good result with good system performance as compared to existing algorithms.

Efficient resource selection algorithm for enterprise grid systems

This paper addresses a resource selection problem for applications that update data in enterprise grid systems. The problem is insufficiently addressed as most of the existing resource selection approaches in grid environments primarily deal with read-only job. We propose a simple yet efficient algorithm that deals with the complexity of resource selection problem in enterprise grid systems. The problem is formulated as a Multi Criteria Decision Making (MCDM) problem. Our proposed algorithm hides the complexity of resource selection process without neglecting important components that affect job response time. The difficulty on estimating job response time is captured by representing them in terms of different QoS criteria levels at each resource. Our experiments show that the proposed algorithm achieves very good results with good system performance as compared to existing algorithms.

Asynchrone Replikation geprägter und nicht geprägter Chromosomenregionen und Expression relevanter Entwicklungsgene in Präimplantationsembryonen der Maus

Zum besseren Verständnis der epigenetischen Reprogrammierung nach der Befruchtung, wurde in der vorliegenden Studie unter Verwendung eines Interphase-FISH-Assays eine systematische Analyse des Replikationsverhaltens geprägter und nicht geprägter Chromosomenregionen in Präimplantationsembryonen der Maus durchgeführt. Dabei konnte erstmalig gezeigt werden, dass sowohl geprägte als auch nicht geprägte Chromosomen-regionen direkt nach der Befruchtung asynchron replizieren. Vier von fünf nicht geprägten Chromosomenregionen replizierten erst nach dem Zweizell-Embryostadium synchron. Eine asynchrone Replikation geprägter Regionen wurde während der gesamten Präimplantationsentwicklung und in differenzierten Zellen beobachtet. In Morula-Embryonen zeigten der in diesem Stadium nicht exprimierte Dlk1-Gtl2-Locus sowie der biallelisch exprimierte Igf2r-Locus jedoch eine Relaxation der asynchronen Replikation. In einem weiteren Projekt konnte mit Hilfe eines Multiplex-RT-PCR-Ansatzes die sensitive Detektion von multiplen Transkripten in einzelnen Zellen etabliert werden. Anschließend wurden Expressionsmuster von 17 für die epigenetische Reprogrammierung relevanten Entwicklungs-genen in Präimplantationsembryonen sowie in einzelnen Morula-Blastomeren analysiert. Der Transkriptionsfaktor Pou5f1 wurde in allen Präimplantationsembryonen und allen Morula-Blastomeren detektiert, was auf eine uniforme Reaktivierung der Pluripotenz hinweist. Dagegen variierte die mRNA-Expression verschiedener DNA-Cytosin-5-Methyltransferasen, 5-methyl-CpG-Bindeproteine sowie Enzyme der Basenexzisionsreparatur stark zwischen individuellen Zellen des gleichen Embryos und noch stärker zwischen Zellen verschiedener Embryonen. Diese Ergebnisse zeigen, dass sich das für die Reprogrammierungsmaschinerie kodierende Transkriptom zu bestimmten Entwicklungs-zeitpunkten zwischen einzelnen Blastomeren unterscheidet.

The role of intermediaries in the implementation and development of asynchronous rural access

In Orissa state, India, the DakNet system supports asynchronous Internet communication between an urban hub and rural nodes. DakNet is noteworthy in many respects, not least in how the system leverages existing transport infrastructure. Wi-Fi transceivers mounted on local buses send and receive user data from roadside kiosks, for later transfer to/from the Internet via wireless protocols. This store-and-forward system allows DakNet to offer asynchronous communication capacity to rural users at low cost. The original ambition of the DakNet system was to provide email and SMS facilities to rural communities. Our 2008 study of the communicative ecology surrounding the DakNet system revealed that this ambition has now evolved – in response to market demand – to the extent that e-shopping (rather than email) has become the primary driver behind the DakNet offer.

Replication of the Frank-Starling response in a Mock Circulation loop

Mock circulation loops (MCLs) are used to evaluate cardiovascular devices prior to in-vivo trials; however they lack the vital autoregulatory responses that occur in humans. This study aimed to develop and implement a left and right ventricular Frank-Starling response in a MCL. A proportional controller based on ventricular end diastolic volume was used to control the driving pressure of the MCL’s pneumatically operated ventricles. Ventricular pressure-volume loops and end systolic pressure-volume relationships were produced for a variety of healthy and pathological conditions and compared with human data to validate the simulated Frank-Starling response. The non-linear Frank-Starling response produced in this study successfully altered left and right ventricular contractility with changing preload and was validated with previously reported data. This improvement to an already detailed MCL has resulted in a test rig capable of further refining cardiovascular devices and reducing the number of in-vivo trials.

The capsid protein of beak and feather disease virus binds to the viral DNA and is responsible for transporting the replication-associated protein into the nucleus

Circoviruses lack an autonomous DNA polymerase and are dependent on the replication machinery of the host cell for de novo DNA synthesis. Accordingly, the viral DNA needs to cross both the plasma membrane and the nuclear envelope before replication can occur. Here we report on the subcellular distribution of the beak and feather disease virus (BFDV) capsid protein (CP) and replication-associated protein (Rep) expressed via recombinant baculoviruses in an insect cell system and test the hypothesis that the CP is responsible for transporting the viral genome, as well as Rep, across the nuclear envelope. The intracellular localization of the BFDV CP was found to be directed by three partially overlapping bipartite nuclear localization signals (NLSs) situated between residues 16 and 56 at the N terminus of the protein. Moreover, a DNA binding region was also mapped to the N terminus of the protein and falls within the region containing the three putative NLSs. The ability of CP to bind DNA, coupled with the karyophilic nature of this protein, strongly suggests that it may be responsible for nuclear targeting of the viral genome. Interestingly, whereas Rep expressed on its own in insect cells is restricted to the cytoplasm, coexpression with CP alters the subcellular localization of Rep to the nucleus, strongly suggesting that an interaction with CP facilitates movement of Rep into the nucleus. Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Inhibition of maize streak virus (MSV) replication by transient and transgenic expression of MSV replication-associated protein mutants

Maize streak disease is a severe agricultural problem in Africa and the development of maize genotypes resistant to the causal agent, Maize streak virus (MSV), is a priority. A transgenic approach to engineering MSV-resistant maize was developed and tested in this study. A pathogen-derived resistance strategy was adopted by using targeted deletions and nucleotide-substitution mutants of the multifunctional MSV replication-associated protein gene (rep). Various rep gene constructs were tested for their efficacy in limiting replication of wild-type MSV by co-bombardment of maize suspension cells together with an infectious genomic clone of MSV and assaying replicative forms of DNA by quantitative PCR. Digitaria sanguinalis, an MSV-sensitive grass species used as a model monocot, was then transformed with constructs that had inhibited virus replication in the transient-expression system. Challenge experiments using leafhopper-transmitted MSV indicated significant MSV resistance - from highly resistant to immune - in regenerated transgenic D. sanguinalis lines. Whereas regenerated lines containing a mutated full-length rep gene displayed developmental and growth defects, those containing a truncated rep gene both were fertile and displayed no growth defects, making the truncated gene a suitable candidate for the development of transgenic MSV-resistant maize. © 2007 SGM.

Identification of long intergenic region sequences involved in maize streak virus replication

The main cis-acting control regions for replication of the single-stranded DNA genome of maize streak virus (MSV) are believed to reside within an approximately 310 nt long intergenic region (LIR). However, neither the minimum LIR sequence required nor the sequence determinants of replication specificity have been determined experimentally. There are iterated sequences, or iterons, both within the conserved inverted-repeat sequences with the potential to form a stem-loop structure at the origin of virion-strand replication, and upstream of the rep gene TATA box (the rep-proximal iteron or RPI). Based on experimental analyses of similar iterons in viruses from other geminivirus genera and their proximity to known Rep-binding sites in the distantly related mastrevirus wheat dwarf virus, it has been hypothesized that the iterons may be Rep-binding and/or -recognition sequences. Here, a series of LIR deletion mutants was used to define the upper bounds of the LIR sequence required for replication. After identifying MSV strains and distinct mastreviruses with incompatible replication-specificity determinants (RSDs), LIR chimaeras were used to map the primary MSV RSD to a 67 nt sequence containing the RPI. Although the results generally support the prevailing hypothesis that MSV iterons are functional analogues of those found in other geminivirus genera, it is demonstrated that neither the inverted-repeat nor RPI sequences are absolute determinants of replication specificity. Moreover, widely divergent mastreviruses can trans-replicate one another. These results also suggest that sequences in the 67 nt region surrounding the RPI interact in a sequence-specific manner with those of the inverted repeat.