| 511. |
- Hantke, Max F., et al.
(författare)
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A data set from flash X-ray imaging of carboxysomes
- 2016
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Ingår i: Scientific Data. - : Springer Science and Business Media LLC. - 2052-4463. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-intense femtosecond X-ray pulses from X-ray lasers permit structural studies on single particles and biomolecules without crystals. We present a large data set on inherently heterogeneous, polyhedral carboxysome particles. Carboxysomes are cell organelles that vary in size and facilitate up to 40% of Earth’s carbon fixation by cyanobacteria and certain proteobacteria. Variation in size hinders crystallization. Carboxysomes appear icosahedral in the electron microscope. A protein shell encapsulates a large number of Rubisco molecules in paracrystalline arrays inside the organelle. We used carboxysomes with a mean diameter of 115±26 nm from Halothiobacillus neapolitanus. A new aerosol sample-injector allowed us to record 70,000 low-noise diffraction patterns in 12 min. Every diffraction pattern is a unique structure measurement and high-throughput imaging allows sampling the space of structural variability. The different structures can be separated and phased directly from the diffraction data and open a way for accurate, high-throughput studies on structures and structural heterogeneity in biology and elsewhere.
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| 512. |
- Hantke, Max F., et al.
(författare)
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High-throughput imaging of heterogeneous cell organelles with an X-ray laser
- 2014
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Ingår i: Nature Photonics. - : Springer Science and Business Media LLC. - 1749-4885 .- 1749-4893. ; 8:12, s. 943-949
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Tidskriftsartikel (refereegranskat)abstract
- We overcome two of the most daunting challenges in single-particle diffractive imaging: collecting many high-quality diffraction patterns on a small amount of sample and separating components from mixed samples. We demonstrate this on carboxysomes, which are polyhedral cell organelles that vary in size and facilitate up to 40% of Earth's carbon fixation. A new aerosol sample-injector allowed us to record 70,000 low-noise diffraction patterns in 12 min with the Linac Coherent Light Source running at 120 Hz. We separate different structures directly from the diffraction data and show that the size distribution is preserved during sample delivery. We automate phase retrieval and avoid reconstruction artefacts caused by missing modes. We attain the highest-resolution reconstructions on the smallest single biological objects imaged with an X-ray laser to date. These advances lay the foundations for accurate, high-throughput structure determination by flash-diffractive imaging and offer a means to study structure and structural heterogeneity in biology and elsewhere.
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| 513. |
- Harris, Simon R., et al.
(författare)
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Whole-genome analysis of diverse Chlamydia trachomatis strains identifies phylogenetic relationships masked by current clinical typing
- 2012
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Ingår i: Nature Genetics. - : Nature Publishing Group. - 1061-4036 .- 1546-1718. ; 44:4, s. 413-419
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Tidskriftsartikel (refereegranskat)abstract
- Chlamydia trachomatis is responsible for both trachoma and sexually transmitted infections, causing substantial morbidity and economic cost globally. Despite this, our knowledge of its population and evolutionary genetics is limited. Here we present a detailed phylogeny based on whole-genome sequencing of representative strains of C. trachomatis from both trachoma and lymphogranuloma venereum (LGV) biovars from temporally and geographically diverse sources. Our analysis shows that predicting phylogenetic structure using ompA, which is traditionally used to classify Chlamydia, is misleading because extensive recombination in this region masks any true relationships present. We show that in many instances, ompA is a chimera that can be exchanged in part or as a whole both within and between biovars. We also provide evidence for exchange of, and recombination within, the cryptic plasmid, which is another key diagnostic target. We used our phylogenetic framework to show how genetic exchange has manifested itself in ocular, urogenital and LGV C. trachomatis strains, including the epidemic LGV serotype L2b.
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| 514. |
- Hebert, Marie-Pier, et al.
(författare)
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Lake salinization drives consistent losses of zooplankton abundance and diversity across coordinated mesocosm experiments
- 2023
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Ingår i: Limnology and Oceanography Letters. - : John Wiley & Sons. - 2378-2242. ; 8:1, s. 19-29
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Tidskriftsartikel (refereegranskat)abstract
- Human-induced salinization increasingly threatens inland waters; yet we know little about the multifaceted response of lake communities to salt contamination. By conducting a coordinated mesocosm experiment of lake salinization across 16 sites in North America and Europe, we quantified the response of zooplankton abundance and (taxonomic and functional) community structure to a broad gradient of environmentally relevant chloride concentrations, ranging from 4 to ca. 1400 mg Cl- L-1. We found that crustaceans were distinctly more sensitive to elevated chloride than rotifers; yet, rotifers did not show compensatory abundance increases in response to crustacean declines. For crustaceans, our among-site comparisons indicate: (1) highly consistent decreases in abundance and taxon richness with salinity; (2) widespread chloride sensitivity across major taxonomic groups (Cladocera, Cyclopoida, and Calanoida); and (3) weaker loss of functional than taxonomic diversity. Overall, our study demonstrates that aggregate properties of zooplankton communities can be adversely affected at chloride concentrations relevant to anthropogenic salinization in lakes.
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| 515. |
- Henry, Anne, et al.
(författare)
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Chloride based CVD of 3C-SiC on (0001) α-SiC substrates
- 2011
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Ingår i: <em>Materials Science Forum Vols. 679-680 (2011) pp 75-78</em>. - : Trans Tech Publications Inc.. ; , s. 75-78
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Konferensbidrag (refereegranskat)abstract
- A chloride-based chemical-vapor-deposition (CVD) process has been successfully used to grow very high quality 3C-SiC epitaxial layers on on-axis α-SiC substrates. An accurate process parameters study was performed testing the effect of temperature, surface preparation, precursor ratios, nitrogen addition, and substrate polytype and polarity. The 3C layers deposited showed to be largely single-domain material of very high purity and of excellent electrical characteristics. A growth rate of up to 10 μm/h and a low background doping enable deposition of epitaxial layers suitable for MOSFET devices.
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| 516. |
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| 517. |
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| 518. |
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| 519. |
- Henry, Barbara J., et al.
(författare)
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A critical review of the application of polymer of low concern and regulatory criteria to fluoropolymers
- 2018
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Ingår i: Integrated Environmental Assessment and Management. - : Society of Environmental Toxicology and Chemistry (SETAC). - 1551-3777 .- 1551-3793. ; 14:3, s. 316-334
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Forskningsöversikt (refereegranskat)abstract
- Per- and poly-fluoroalkyl substances (PFAS) are a group of fluorinated substances that are in the focus of researchers and regulators due to widespread presence in the environment and biota, including humans, of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA). Fluoropolymers, high molecular weight polymers within the PFAS group, have unique properties that constitute a distinct class within the PFAS group. Fluoropolymers have thermal, chemical, photochemical, hydrolytic, oxidative and biological stability. They have negligible residual monomer and oligomer content and low to no leachables. Fluoropolymers are practically insoluble in water and not subject to long-range transport. With a molecular weight well over 100,000 Da, fluoropolymers cannot cross the cell membrane. Fluoropolymers are not bioavailable or bioaccumulative, as evidenced by toxicology studies on PTFE: acute and subchronic systemic toxicity, irritation, sensitization, local toxicity on implantation, cytotoxicity, in vitro and in vivo genotoxicity, hemolysis, complement activation, and thrombogenicity. Clinical studies of patients receiving permanently implanted PTFE cardiovascular medical devices demonstrate no chronic toxicity or carcinogenicity, reproductive or developmental or endocrine toxicity. This paper brings together fluoropolymer toxicity data, human clinical data, and physical-chemical-thermal-biological data for review and assessment to show that fluoropolymers satisfy widely accepted assessment criteria to be considered as "Polymers of Low Concern". This review concludes that fluoropolymers are distinctly different from other polymeric and non-polymeric per- and poly-fluoroalkyl substances and should be separated from them for hazard assessment or regulatory purposes. Grouping fluoropolymers with all classes of PFAS for "read across" or structure activity relationship assessment is not scientifically appropriate.
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| 520. |
- Henry, C., et al.
(författare)
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Case sensitive? A review of the literature on the use of case method in entrepreneurship research
- 2015
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Ingår i: International Journal of Entrepreneurial Behaviour & Research. - : Emerald Group Publishing Limited. - 1355-2554 .- 1758-6534. ; 21:3, s. 389-409
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Tidskriftsartikel (refereegranskat)abstract
- Purpose – The purpose of this paper is to review the use of case method inentrepreneurship research, and to identify trends in its current application. A key objective of the paper is to lay the foundation for a future research agenda by critically reviewing relevant literatures and offering insights into the use of case method in particular settings. The paper also helps identify areas where case method could add value to research findings in future scholarship.Design/methodology/approach – Using a Boolean search, a systematic literature review (SLR) was undertaken across the “big five” entrepreneurship journals in the five-year period between 2008 and 2012 The search initially yielded a total of 269 “hits”. Following exclusion criteria, the list was refined to a total of 52 empirical papers, and these were reviewed using a comprehensive reading guide developed by the authors.Findings – The paper finds that relatively few articles published in the “big five” entrepreneurship journals use case method, despite repeated calls in the literature for more in-depth, qualitative approaches. This potentially suggests that case method is not fully accepted as a legitimate or sufficiently rigorous approach in the upper echelons of contemporary published entrepreneurship scholarship. Overall the paper argues for greater acceptance of the use of case method amongst the academic community, alongside greater confidence in its application. This can be achieved by learning from other disciplines where the case approach is more established.Research limitations/implications – While a comprehensive SLR was undertaken, the search was restricted to a limited time period and across a limited number of top tier journals.Practical implications – The paper highlights incidents where case method has been used successfully, identifies gaps in the literature and contributes towards setting a future research agenda that should be of particular value to qualitative researchers.Originality/value – The paper builds on extant literatures by furthering our understanding of the use of case method in entrepreneurship research. It should be of value to qualitative scholars applying case method in their empirical work, as well as those seeking to extend their methodological reach beyond a purely quantitative orientation.
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