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  • Institute of Physics  (1,176)
  • Oxford University Press  (664)
  • American Physical Society (APS)  (204)
Collection
  • 11
    Publication Date: 2015-05-29
    Description: As part of the Bluedisk survey, we analyse the radial gas-phase metallicity profiles of 50 late-type galaxies. We compare the metallicity profiles of a sample of H i -rich galaxies against a control sample of H i -‘normal’ galaxies. We find the metallicity gradient of a galaxy to be strongly correlated with its H i mass fraction ( $\textrm {M(H\,\small {I})} / \textrm {M}_{\ast }$ ). We note that some galaxies exhibit a steeper metallicity profile in the outer disc than in the inner disc. These galaxies are found in both the H i -rich and control samples. This contradicts a previous indication that these outer drops are exclusive to H i -rich galaxies. These effects are not driven by bars, although we do find some indication that barred galaxies have flatter metallicity profiles. By applying a simple analytical model, we are able to account for the variety of metallicity profiles that the two samples present. The success of this model implies that the metallicity in these isolated galaxies may be in a local equilibrium, regulated by star formation. This insight could provide an explanation of the observed local mass–metallicity relation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 12
    Publication Date: 2015-06-24
    Description: Arginine methylation is a posttranslational modification that impacts wide-ranging cellular functions, including transcription, mRNA splicing and translation. RNA binding proteins (RBPs) represent one of the largest classes of arginine methylated proteins in both mammals and the early diverging parasitic protozoan, Trypanosoma brucei . Here, we report the effects of arginine methylation on the functions of the essential and previously uncharacterized T. brucei RBP, DRBD18. RNAseq analysis shows that DRBD18 depletion causes extensive rearrangement of the T. brucei transcriptome, with increases and decreases in hundreds of mRNAs. DRBD18 contains three methylated arginines, and we used complementation of DRBD18 knockdown cells with methylmimic or hypomethylated DRBD18 to assess the functions of these methylmarks. Methylmimic and hypomethylated DRBD18 associate with different ribonucleoprotein complexes. These altered macromolecular interactions translate into differential impacts on the T. brucei transcriptome. Methylmimic DRBD18 preferentially stabilizes target RNAs, while hypomethylated DRBD18 is more efficient at destabilizing RNA. The protein arginine methyltransferase, TbPRMT1, interacts with DRBD18 and knockdown of TbPRMT1 recapitulates the effects of hypomethylated DRBD18 on mRNA levels. Together, these data support a model in which arginine methylation acts as a switch that regulates T. brucei gene expression.
    Print ISSN: 0305-1048
    Electronic ISSN: 1362-4962
    Topics: Biology
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  • 13
    Publication Date: 2015-06-12
    Description: As part of the Bluedisk survey, we analyse the radial gas-phase metallicity profiles of 50 late-type galaxies. We compare the metallicity profiles of a sample of H i -rich galaxies against a control sample of H i -‘normal’ galaxies. We find the metallicity gradient of a galaxy to be strongly correlated with its H i mass fraction ( $\textrm {M(H\,\small {I})} / \textrm {M}_{\ast }$ ). We note that some galaxies exhibit a steeper metallicity profile in the outer disc than in the inner disc. These galaxies are found in both the H i -rich and control samples. This contradicts a previous indication that these outer drops are exclusive to H i -rich galaxies. These effects are not driven by bars, although we do find some indication that barred galaxies have flatter metallicity profiles. By applying a simple analytical model, we are able to account for the variety of metallicity profiles that the two samples present. The success of this model implies that the metallicity in these isolated galaxies may be in a local equilibrium, regulated by star formation. This insight could provide an explanation of the observed local mass–metallicity relation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 14
    Publication Date: 2016-03-02
    Description: Over the duration of the Kepler mission, KIC 8462852 was observed to undergo irregularly shaped, aperiodic dips in flux of up to ~20 per cent. The dipping activity can last for between 5 and 80 d. We characterize the object with high-resolution spectroscopy, spectral energy distribution fitting, radial velocity measurements, high-resolution imaging, and Fourier analyses of the Kepler light curve. We determine that KIC 8462852 is a typical main-sequence F3 V star that exhibits no significant IR excess, and has no very close interacting companions. In this paper, we describe various scenarios to explain the dipping events observed in the Kepler light curve. We confirm that the dipping signals in the data are not caused by any instrumental or data processing artefact, and thus are astrophysical in origin. We construct scenario-independent constraints on the size and location of a body in the system that are needed to reproduce the observations. We deliberate over several assorted stellar and circumstellar astrophysical scenarios, most of which have problems explaining the data in hand. By considering the observational constraints on dust clumps in orbit around a normal main-sequence star, we conclude that the scenario most consistent with the data in hand is the passage of a family of exocomet or planetesimal fragments, all of which are associated with a single previous break-up event, possibly caused by tidal disruption or thermal processing. The minimum total mass associated with these fragments likely exceeds 10 –6 M , corresponding to an original rocky body of 〉100 km in diameter. We discuss the necessity of future observations to help interpret the system.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
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  • 15
    Publication Date: 2015-12-01
    Description: Mutations in the DAX1 locus cause X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH), which manifest with primary adrenal insufficiency and incomplete or absent sexual maturation, respectively. The associated defects in spermatogenesis can range from spermatogenic arrest to Sertoli cell only syndrome. Conclusions from Dax1 knockout mouse models provide only limited insight into AHC/HH disease mechanisms, because mouse models exhibit more extensive abnormalities in testicular development, including disorganized and incompletely formed testis cords with decreased number of peritubular myoid cells and male-to-female sex reversal. We previously reported successful clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated genome targeting in cynomolgus monkeys. Here, we describe a male fetal monkey in which targeted genome editing using CRISPR/Cas9 produced Dax1- null mutations in most somatic tissues and in the gonads. This DAX1-deficient monkey displayed defects in adrenal gland development and abnormal testis architecture with small cords, expanded blood vessels and extensive fibrosis. Sertoli cell formation was not affected. This phenotype strongly resembles findings in human patients with AHC-HH caused by mutations in DAX1 . We further detected upregulation of Wnt/β-catenin-VEGF signaling in the fetal Dax1 -deficient testis, suggesting abnormal activation of signaling pathways in the absence of DAX1 as one mechanism of AHC-HH. Our study reveals novel insight into the role of DAX1 in HH and provides proof-of-principle for the generation of monkey models of human disease via CRISPR/Cas9-mediated gene targeting.
    Print ISSN: 0964-6906
    Electronic ISSN: 1460-2083
    Topics: Biology , Medicine
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  • 16
    Publication Date: 2015-12-10
    Description: Motivation: In genome assembly, as coverage of sequencing and genome size growing, most current softwares require a large memory for handling a great deal of sequence data. However, most researchers usually cannot meet the requirements of computing resources which prevent most current softwares from practical applications. Results: In this article, we present an update algorithm called EPGA2, which applies some new modules and can bring about improved assembly results in small memory. For reducing peak memory in genome assembly, EPGA2 adopts memory-efficient DSK to count K-mers and revised BCALM to construct De Bruijn Graph. Moreover, EPGA2 parallels the step of Contigs Merging and adds Errors Correction in its pipeline. Our experiments demonstrate that all these changes in EPGA2 are more useful for genome assembly. Availability and implementation: EPGA2 is publicly available for download at https://github.com/bioinfomaticsCSU/EPGA2 . Contact: jxwang@csu.edu.cn Supplementary information: Supplementary data are available at Bioinformatics online.
    Print ISSN: 1367-4803
    Electronic ISSN: 1460-2059
    Topics: Biology , Computer Science , Medicine
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  • 17
    Publication Date: 2011-05-03
    Description: Author(s): T.-J. Wang, J.-F. Daigle, S. Yuan, F. Théberge, M. Châteauneuf, J. Dubois, G. Roy, H. Zeng, and S. L. Chin We experimentally investigated the dynamic behavior of remote terahertz (THz) generation from two-color femtosecond laser-induced filamentation in air. A record-high THz pulse energy of 570 nJ at frequency below 5.5 THz was measured by optimizing the pump parameters at a controllable remote distance... [Phys. Rev. A 83, 053801] Published Mon May 02, 2011
    Keywords: Quantum optics, physics of lasers, nonlinear optics, classical optics
    Print ISSN: 1050-2947
    Electronic ISSN: 1094-1622
    Topics: Physics
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  • 18
    Publication Date: 2014-01-22
    Description: The formation of phenotypic traits, such as biomass production, tumor volume and viral abundance, undergoes a complex process in which interactions between genes and developmental stimuli take place at each level of biological organization from cells to organisms. Traditional studies emphasize the impact of genes by directly linking DNA-based markers with static phenotypic values. Functional mapping, derived to detect genes that control developmental processes using growth equations, has proven powerful for addressing questions about the roles of genes in development. By treating phenotypic formation as a cohesive system using differential equations, a different approach—systems mapping—dissects the system into interconnected elements and then map genes that determine a web of interactions among these elements, facilitating our understanding of the genetic machineries for phenotypic development. Here, we argue that genetic mapping can play a more important role in studying the genotype–phenotype relationship by filling the gaps in the biochemical and regulatory process from DNA to end-point phenotype. We describe a new framework, named network mapping, to study the genetic architecture of complex traits by integrating the regulatory networks that cause a high-order phenotype. Network mapping makes use of a system of differential equations to quantify the rule by which transcriptional, proteomic and metabolomic components interact with each other to organize into a functional whole. The synthesis of functional mapping, systems mapping and network mapping provides a novel avenue to decipher a comprehensive picture of the genetic landscape of complex phenotypes that underlie economically and biomedically important traits.
    Print ISSN: 1467-5463
    Electronic ISSN: 1477-4054
    Topics: Biology , Computer Science
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  • 19
    Publication Date: 2014-10-28
    Description: We review the problem of finding contained rewritings (CRs) for XPath queries using XPath views. CR is proposed to cater for data integration scenarios, where views are unlikely to be complete due to the limited coverage of data sources, and hence equivalent rewritings are impossible to be found. As a result, we are usually required to find a maximal contained rewriting (MCR) for a query to provide the best possible answers. An MCR is a set of CRs, and may contain redundant CRs. Obviously, evaluating redundant CRs on materialized views is unnecessary. In this paper, we first address how to find the irredundant maximal contained rewriting (IMCR), i.e. all the irredundant CRs. We show that the existing approach ignores a type of situation, and turns out to be not sufficient. As a result, the only safe solution is a brute-force pairwise containment check for all the CRs. We then propose some heuristics to speed up the brute-force comparisons. When a materialized view is given, we propose how to evaluate the IMCR on the materialized view, which, to our knowledge, is the first work on optimizing the evaluation of a set of produced CRs on the materialized view by considering the inherent structural characteristics of the CRs. Our experiments show the effectiveness and efficiency of our algorithms.
    Print ISSN: 0010-4620
    Electronic ISSN: 1460-2067
    Topics: Computer Science
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  • 20
    Publication Date: 2014-10-29
    Description: To identify the Nipponacmea limpets along the coast of China, their taxonomy was investigated with three molecular markers (one mitochondrial gene, COI; two nuclear markers, 28S rDNA and H3). Three species ( N. radula , N. fuscoviridis and N. nigrans ) were found among 274 individuals collected from 14 sites. Intraspecific variation was far less than interspecific variation and obvious barcoding gaps existed. These results indicate that the three Nipponacmea species can be efficiently identified by DNA barcoding. The phylogeographic patterns of the three species were also analysed using COI sequences. There was clear biogeographic separation between the northern N. radula and the southern two species ( N. fuscoviridis and N. nigrans ), with the Yangtze River estuary as a barrier. In the southern N. fuscoviridis , there was a star-shaped haplotype network and the dominant haplotype was detected in all populations. In the northern N. radula , there were five main haplotypes; some adjacent populations showed no significant difference according to the pairwise F st values. The southern N. nigrans showed two main haplotypes. The phylogeographic break between the Nipponacmea species is possibly due to the local and regional hydrographic conditions in the Yangtze River estuary, the large salt marsh in the river delta and difference of temperature between northern and southern China.
    Print ISSN: 0260-1230
    Electronic ISSN: 1464-3766
    Topics: Biology
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