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  • 1
    Publication Date: 2015-08-12
    Description: Obligate bacterial symbionts are widespread in many invertebrates, where they are often confined to specialized host cells and are transmitted directly from mother to progeny. Increasing numbers of these bacteria are being characterized but questions remain about their population structure and evolution. Here we take a comparative genomics approach to investigate two prominent bacterial symbionts (BFo1 and BFo2) isolated from geographically separated populations of western flower thrips, Frankliniella occidentalis. Our multifaceted approach to classifying these symbionts includes concatenated multilocus sequence analysis (MLSA) phylogenies, ribosomal multilocus sequence typing (rMLST), construction of whole-genome phylogenies, and in-depth genomic comparisons. We showed that the BFo1 genome clusters more closely to species in the genus Erwinia, and is a putative close relative to Erwinia aphidicola . BFo1 is also likely to have shared a common ancestor with Erwinia pyrifoliae/Erwinia amylovora and the nonpathogenic Erwinia tasmaniensis and genetic traits similar to Erwinia billingiae . The BFo1 genome contained virulence factors found in the genus Erwinia but represented a divergent lineage. In contrast, we showed that BFo2 belongs within the Enterobacteriales but does not group closely with any currently known bacterial species. Concatenated MLSA phylogenies indicate that it may have shared a common ancestor to the Erwinia and Pantoea genera, and based on the clustering of rMLST genes, it was most closely related to Pantoea ananatis but represented a divergent lineage. We reconstructed a core genome of a putative common ancestor of Erwinia and Pantoea and compared this with the genomes of BFo bacteria. BFo2 possessed none of the virulence determinants that were omnipresent in the Erwinia and Pantoea genera. Taken together, these data are consistent with BFo2 representing a highly novel species that maybe related to known Pantoea .
    Electronic ISSN: 1759-6653
    Topics: Biology
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  • 2
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    Oxford University Press
    Publication Date: 2015-08-21
    Description: Sufficient dimension reduction in regression aims to reduce the predictor dimension by replacing the original predictors with some set of linear combinations of them without loss of information. Numerous dimension reduction methods have been developed based on this paradigm. However, little effort has been devoted to diagnostic studies within the context of dimension reduction. In this paper we introduce methods to check goodness-of-fit for a given dimension reduction subspace. The key idea is to extend the so-called distance correlation to measure the conditional dependence relationship between the covariates and the response given a reduction subspace. Our methods require minimal assumptions, which are usually much less restrictive than the conditions needed to justify the original methods. Asymptotic properties of the test statistic are studied. Numerical examples demonstrate the effectiveness of the proposed approach.
    Print ISSN: 0006-3444
    Electronic ISSN: 1464-3510
    Topics: Biology , Mathematics , Medicine
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  • 3
    Publication Date: 2015-07-30
    Description: In this study, we have systematically investigated the influence of the parameters of the slip-weakening law and the size of nucleation asperity on dynamic rupture of a planar fault in full-space and half-space using the boundary integral equation method, in particular, the occurrence conditions for subshear (or sub-Rayleigh for strike-slip rupture) and supershear ruptures. Besides the well-known rupture styles of subshear (or sub-Rayleigh) and supershear, we defined a new kind of rupture style in this study, termed the ‘self-arresting rupture’, for which the rupture process can be autonomously arrested by itself without any outside interference (e.g. a high strength barrier). Based on the vast number of simulations, we obtained rupture phase diagrams for strike-slip and dip-slip ruptures vertically and obliquely embedded in half-space and full-space with different buried depths. The rupture phase diagram clearly illustrates the occurrence conditions of three kinds of rupture styles and the transitions between them. In full-space, the supershear transition is sensitive with the fault width. Owing to the influence of the free surface, the rupture in half-space becomes much more complicated comparing to the one in full-space. For a strike-slip fault with zero buried depth, all ruptures that occur within the parameter range for sub-Rayleigh ruptures in full-space case become supershear ruptures. This means that as long as a rupture is able to grow incessantly, it will always evolve into a supershear rupture. For dip-slip faults, however, ruptures will always propagate with subshear speed, although slip rate could be almost twice that of a strike-slip fault. Although the influence of the free surface is strong, it is limited to very shallow ruptures (i.e. buried depth 〈1 km). The rupture phase diagram discussed in this study could provide a new insight on earthquake rupture mechanics.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 4
    Publication Date: 2015-09-12
    Description: Genome-wide association studies (GWAS) have identified several common loci contributing to non-obstructive azoospermia (NOA). However, a substantial fraction of NOA heritability remains undefined, especially those low-frequency [defined here as having a minor allele frequency (MAF) between 0.5 and 5%] and rare (MAF below 0.5%) variants. Here, we performed a 3-stage exome-wide association study in Han Chinese men to evaluate the role of low-frequency or rare germline variants in NOA development. The discovery stage included 962 NOA cases and 1348 healthy male controls genotyped by exome chips and was followed by a 2-stage replication with an additional 2168 cases and 5248 controls. We identified three low-frequency variants located at 6p22.2 (rs2298090 in HIST1H1E encoding p.Lys152Arg: OR = 0.30, P = 2.40 x 10 –16 ) and 6p21.33 (rs200847762 in FKBPL encoding p.Pro137Leu: OR = 0.11, P = 3.77 x 10 –16 ; rs11754464 in MSH5 : OR = 1.78, P = 3.71 x 10 –7 ) associated with NOA risk after Bonferroni correction. In summary, we report an instance of newly identified signals for NOA risk in genes previously undetected through GWAS on 6p22.2–6p21.33 in a Chinese population and highlight the role of low-frequency variants with a large effect in the process of spermatogenesis.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 5
    Publication Date: 2015-09-15
    Description: This paper investigates event-triggered leaderless and leader-following consensus problems of multi-agent systems under jointly connected topology. A state-dependent event condition is proposed for each agent, which only relies on its own state and the last sampled data of itself and its neighbours. Based on the Lyapunov technique and algebraic graph theory, the designed event-triggered control strategies are proved to solve the leaderless and leader-following consensus problems when the topology is jointly connected. Moreover, such strategies can exclude Zeno-behaviour. Simulations illustrate the effectiveness of the theoretical results.
    Print ISSN: 0265-0754
    Electronic ISSN: 1471-6887
    Topics: Mathematics
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  • 6
    Publication Date: 2015-11-20
    Description: Although millions of RNA editing events have been reported to modify hereditary information across the primate transcriptome, evidence for their functional significance remains largely elusive, particularly for the vast majority of editing sites in noncoding regions. Here, we report a new mechanism for the functionality of RNA editing—a crosstalk with PIWI-interacting RNA (piRNA) biogenesis. Exploiting rhesus macaque as an emerging model organism closely related to human, in combination with extensive genome and transcriptome sequencing in seven tissues of the same animal, we deciphered accurate RNA editome across both long transcripts and the piRNA species. Superimposing and comparing these two distinct RNA editome profiles revealed 4,170 editing-bearing piRNA variants, or epiRNAs, that primarily derived from edited long transcripts. These epiRNAs represent distinct entities that evidence an intersection between RNA editing regulations and piRNA biogenesis. Population genetics analyses in a macaque population of 31 independent animals further demonstrated that the epiRNA-associated RNA editing is maintained by purifying selection, lending support to the functional significance of this crosstalk in rhesus macaque. Correspondingly, these findings are consistent in human, supporting the conservation of this mechanism during the primate evolution. Overall, our study reports the earliest lines of evidence for a crosstalk between selectively constrained RNA editing regulation and piRNA biogenesis, and further illustrates that such an interaction may contribute substantially to the diversification of the piRNA repertoire in primates.
    Print ISSN: 0737-4038
    Electronic ISSN: 1537-1719
    Topics: Biology
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  • 7
    Publication Date: 2016-07-16
    Description: Identification of drug–target interactions is an important process in drug discovery. Although high-throughput screening and other biological assays are becoming available, experimental methods for drug–target interaction identification remain to be extremely costly, time-consuming and challenging even nowadays. Therefore, various computational models have been developed to predict potential drug–target associations on a large scale. In this review, databases and web servers involved in drug–target identification and drug discovery are summarized. In addition, we mainly introduced some state-of-the-art computational models for drug–target interactions prediction, including network-based method, machine learning-based method and so on. Specially, for the machine learning-based method, much attention was paid to supervised and semi-supervised models, which have essential difference in the adoption of negative samples. Although significant improvements for drug–target interaction prediction have been obtained by many effective computational models, both network-based and machine learning-based methods have their disadvantages, respectively. Furthermore, we discuss the future directions of the network-based drug discovery and network approach for personalized drug discovery based on personalized medicine, genome sequencing, tumor clone-based network and cancer hallmark-based network. Finally, we discussed the new evaluation validation framework and the formulation of drug–target interactions prediction problem by more realistic regression formulation based on quantitative bioactivity data.
    Print ISSN: 1467-5463
    Electronic ISSN: 1477-4054
    Topics: Biology , Computer Science
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  • 8
    Publication Date: 2016-07-20
    Description: The Cadzow rank-reduction method can be effectively utilized in simultaneously denoising and reconstructing 5-D seismic data that depend on four spatial dimensions. The classic version of Cadzow rank-reduction method arranges the 4-D spatial data into a level-four block Hankel/Toeplitz matrix and then applies truncated singular value decomposition (TSVD) for rank reduction. When the observed data are extremely noisy, which is often the feature of real seismic data, traditional TSVD cannot be adequate for attenuating the noise and reconstructing the signals. The reconstructed data tend to contain a significant amount of residual noise using the traditional TSVD method, which can be explained by the fact that the reconstructed data space is a mixture of both signal subspace and noise subspace. In order to better decompose the block Hankel matrix into signal and noise components, we introduced a damping operator into the traditional TSVD formula, which we call the damped rank-reduction method. The damped rank-reduction method can obtain a perfect reconstruction performance even when the observed data have extremely low signal-to-noise ratio. The feasibility of the improved 5-D seismic data reconstruction method was validated via both 5-D synthetic and field data examples. We presented comprehensive analysis of the data examples and obtained valuable experience and guidelines in better utilizing the proposed method in practice. Since the proposed method is convenient to implement and can achieve immediate improvement, we suggest its wide application in the industry.
    Keywords: Seismology
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 9
    Publication Date: 2016-08-05
    Description: De novo genes, which originate from ancestral nongenic sequences, are one of the most important sources of protein-coding genes. This origination process is crucial for the adaptation of organisms. However, how de novo genes arise and become fixed in a population or species remains largely unknown. Here, we identified 782 de novo genes from the model plant Arabidopsis thaliana and divided them into three types based on the availability of translational evidence, transcriptional evidence, and neither transcriptional nor translational evidence for their origin. Importantly, by integrating multiple types of omics data, including data from genomes, epigenomes, transcriptomes, and translatomes, we found that epigenetic modifications (DNA methylation and histone modification) play an important role in the origination process of de novo genes. Intriguingly, using the transcriptomes and methylomes from the same population of 84 accessions, we found that de novo genes that are transcribed in approximately half of the total accessions within the population are highly methylated, with lower levels of transcription than those transcribed at other frequencies within the population. We hypothesized that, during the origin of de novo gene alleles, those neutralized to low expression states via DNA methylation have relatively high probabilities of spreading and becoming fixed in a population. Our results highlight the process underlying the origin of de novo genes at the population level, as well as the importance of DNA methylation in this process.
    Electronic ISSN: 1759-6653
    Topics: Biology
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  • 10
    Publication Date: 2016-07-13
    Description: The spherical harmonics m -mode decomposition is a powerful sky map reconstruction method suitable for radio interferometers operating in transit mode. It can be applied to various configurations, including dish arrays and cylinders. We describe the computation of the instrument response function, the point spread function, transfer function, the noise covariance matrix and noise power spectrum. The analysis in this paper is focused on dish arrays operating in transit mode. We show that arrays with regular spacing have more pronounced side lobes as well as structures in their noise power spectrum, compared to arrays with irregular spacing, specially in the north–south direction. A good knowledge of the noise power spectrum C noise () is essential for intensity mapping experiments as non-uniform C noise () is a potential problem for the measurement of the H  i power spectrum. Different configurations have been studied to optimize the PAON-4 and Tianlai dish array layouts. We present their expected performance and their sensitivities to the 21-cm emission of the Milky Way and local extragalactic H  i clumps.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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