| 1. |
- Lehtipalo, Katrianne, et al.
(författare)
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The effect of acid-base clustering and ions on the growth of atmospheric nano-particles
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- The growth of freshly formed aerosol particles can be the bottleneck in their survival to cloud condensation nuclei. It is therefore crucial to understand how particles grow in the atmosphere. Insufficient experimental data has impeded a profound understanding of nano-particle growth under atmospheric conditions. Here we study nano-particle growth in the CLOUD (Cosmics Leaving OUtdoors Droplets) chamber, starting from the formation of molecular clusters. We present measured growth rates at sub-3 nm sizes with different atmospherically relevant concentrations of sulphuric acid, water, ammonia and dimethylamine. We find that atmospheric ions and small acid-base clusters, which are not generally accounted for in the measurement of sulphuric acid vapour, can participate in the growth process, leading to enhanced growth rates. The availability of compounds capable of stabilizing sulphuric acid clusters governs the magnitude of these effects and thus the exact growth mechanism. We bring these observations into a coherent framework and discuss their significance in the atmosphere.
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| 2. |
- Tröstl, Jasmin, et al.
(författare)
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The role of low-volatility organic compounds in initial particle growth in the atmosphere
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 527-531
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Tidskriftsartikel (refereegranskat)abstract
- About half of present-day cloud condensation nuclei originate from atmospheric nucleation, frequently appearing as a burst of new particles near midday(1). Atmospheric observations show that the growth rate of new particles often accelerates when the diameter of the particles is between one and ten nanometres(2,3). In this critical size range, new particles are most likely to be lost by coagulation with pre-existing particles(4), thereby failing to form new cloud condensation nuclei that are typically 50 to 100 nanometres across. Sulfuric acid vapour is often involved in nucleation but is too scarce to explain most subsequent growth(5,6), leaving organic vapours as the most plausible alternative, at least in the planetary boundary layer(7-10). Although recent studies(11-13) predict that low-volatility organic vapours contribute during initial growth, direct evidence has been lacking. The accelerating growth may result from increased photolytic production of condensable organic species in the afternoon(2), and the presence of a possible Kelvin (curvature) effect, which inhibits organic vapour condensation on the smallest particles (the nano-Kohler theory)(2,14), has so far remained ambiguous. Here we present experiments performed in a large chamber under atmospheric conditions that investigate the role of organic vapours in the initial growth of nucleated organic particles in the absence of inorganic acids and bases such as sulfuric acid or ammonia and amines, respectively. Using data from the same set of experiments, it has been shown(15) that organic vapours alone can drive nucleation. We focus on the growth of nucleated particles and find that the organic vapours that drive initial growth have extremely low volatilities (saturation concentration less than 10(-4.5) micrograms per cubic metre). As the particles increase in size and the Kelvin barrier falls, subsequent growth is primarily due to more abundant organic vapours of slightly higher volatility (saturation concentrations of 10(-4.5) to 10(-0.5) micrograms per cubic metre). We present a particle growth model that quantitatively reproduces our measurements. Furthermore, we implement a parameterization of the first steps of growth in a global aerosol model and find that concentrations of atmospheric cloud concentration nuclei can change substantially in response, that is, by up to 50 per cent in comparison with previously assumed growth rate parameterizations.
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| 3. |
- Wiedorn, Max O., et al.
(författare)
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Megahertz serial crystallography
- 2018
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Ingår i: Nature Communications. - : Nature Publishing Group. - 2041-1723. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- The new European X-ray Free-Electron Laser is the first X-ray free-electron laser capable of delivering X-ray pulses with a megahertz inter-pulse spacing, more than four orders of magnitude higher than previously possible. However, to date, it has been unclear whether it would indeed be possible to measure high-quality diffraction data at megahertz pulse repetition rates. Here, we show that high-quality structures can indeed be obtained using currently available operating conditions at the European XFEL. We present two complete data sets, one from the well-known model system lysozyme and the other from a so far unknown complex of a beta-lactamase from K. pneumoniae involved in antibiotic resistance. This result opens up megahertz serial femtosecond crystallography (SFX) as a tool for reliable structure determination, substrate screening and the efficient measurement of the evolution and dynamics of molecular structures using megahertz repetition rate pulses available at this new class of X-ray laser source.
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| 4. |
- Beladi-Mousavi, S. M., et al.
(författare)
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Poly(vinylferrocene)-Reduced Graphene Oxide as a High Power/High Capacity Cathodic Battery Material
- 2016
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Ingår i: Advanced Energy Materials. - : Wiley. - 1614-6840 .- 1614-6832. ; 6:12
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Tidskriftsartikel (refereegranskat)abstract
- The preparation and performance of a new cathodic battery material consisting of a composite of poly(vinylferrocene) (PVFc) and reduced graphene oxide (rGO) is described. It shows the highest charge/discharge efficiency (at a rate of 100 A g(-1)) ever reported for ferrocene-polymer materials. The composite allows for specific capacities up to 0.21 mAh cm(-2) (770 mC cm(-2), 29 mu m film thickness) at a specific capacity density of 114 mAh g(-1) and less than 5% performance decay over 300 cycles. The composite material is binder free and the charge storing PVFc accounts for 88% of the total weight of the cathodic material. The superb performance is based on (i) perfect self-assembling of oxidized PVFc on graphene oxide (GO) leading to PVFc@GO, (ii) its stepwise (n steps) transfer onto a current collector (CC) (PVFc@GO)(n) @CC (n = drop casting steps), and (iii) the efficient electrochemical transformation of GO into rGO in the composite using viologen as homogeneous electrocatalyst. The self-assembling step is analyzed by zeta potential and atomic force microscopy (AFM) studies, demonstrating heavy ferrocene loading on GO and a mesoporous composite structure, respectively. Complete GO/rGO transition and quantitative ClO4- on breathing of the composite are found by electrochemical quartz crystal microbalance and by electrochemical AFM.
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| 5. |
- Härtlova, Anetta, et al.
(författare)
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DNA Damage Primes the Type I Interferon System via the Cytosolic DNA Sensor STING to Promote Anti-Microbial Innate Immunity.
- 2015
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Ingår i: Immunity. - : Elsevier BV. - 1097-4180 .- 1074-7613. ; 42:2, s. 332-43
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Tidskriftsartikel (refereegranskat)abstract
- Dysfunction in Ataxia-telangiectasia mutated (ATM), a central component of the DNA repair machinery, results in Ataxia Telangiectasia (AT), a cancer-prone disease with a variety of inflammatory manifestations. By analyzing AT patient samples and Atm(-/-) mice, we found that unrepaired DNA lesions induce type I interferons (IFNs), resulting in enhanced anti-viral and anti-bacterial responses in Atm(-/-) mice. Priming of the type I interferon system by DNA damage involved release of DNA into the cytoplasm where it activated the cytosolic DNA sensing STING-mediated pathway, which in turn enhanced responses to innate stimuli by activating the expression of Toll-like receptors, RIG-I-like receptors, cytoplasmic DNA sensors, and their downstream signaling partners. This study provides a potential explanation for the inflammatory phenotype of AT patients and establishes damaged DNA as a cell intrinsic danger signal that primes the innate immune system for a rapid and amplified response to microbial and environmental threats.
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| 6. |
- Kirkby, Jasper, et al.
(författare)
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Ion-induced nucleation of pure biogenic particles
- 2016
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 533:7604, s. 521-526
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Tidskriftsartikel (refereegranskat)abstract
- Atmospheric aerosols and their effect on clouds are thought to be important for anthropogenic radiative forcing of the climate, yet remain poorly understood(1). Globally, around half of cloud condensation nuclei originate from nucleation of atmospheric vapours(2). It is thought that sulfuric acid is essential to initiate most particle formation in the atmosphere(3,4), and that ions have a relatively minor role(5). Some laboratory studies, however, have reported organic particle formation without the intentional addition of sulfuric acid, although contamination could not be excluded(6,7). Here we present evidence for the formation of aerosol particles from highly oxidized biogenic vapours in the absence of sulfuric acid in a large chamber under atmospheric conditions. The highly oxygenated molecules (HOMs) are produced by ozonolysis of a-pinene. We find that ions from Galactic cosmic rays increase the nucleation rate by one to two orders of magnitude compared with neutral nucleation. Our experimental findings are supported by quantum chemical calculations of the cluster binding energies of representative HOMs. Ion-induced nucleation of pure organic particles constitutes a potentially widespread source of aerosol particles in terrestrial environments with low sulfuric acid pollution.
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| 7. |
- Naumov, A., et al.
(författare)
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Graphene Oxide: A One- versus Two-Component Material
- 2016
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 138:36, s. 11445-11448
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Tidskriftsartikel (refereegranskat)abstract
- The structure of graphene oxide (GO) is a matter of discussion. While established GO models are based on functional groups attached to the carbon framework, another frequently used model claims that GO consists of two components, a slightly oxidized graphene core and highly oxidized molecular species, oxidative debris (OD), adsorbed on it. Those adsorbents are claimed to be the origin for optical properties of GO. Here, we examine this model by preparing GO with a low degree of functionalization, combining it with OD and studying the optical properties of both components and their combination in an artificial two-component system. The analyses of absorption and emission spectra as well as lifetime measurements reveal that properties of the combined system are,distinctly different from those of GO. That confirms structural models of GO as a separate oxygenated hexagonal carbon framework with optical properties governed by its internal structure rather than the presence of OD: Understanding the structure of GO allows further reliable interpretation of its optical and electronic properties and enables controlled processing of GO.
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| 8. |
- Cuenca, Miguelangel, et al.
(författare)
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D-Alanine-Controlled Transient Intestinal Mono-Colonization with Non-Laboratory-Adapted Commensal E. coli Strain HS
- 2016
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Soon after birth the mammalian gut microbiota forms a permanent and collectively highly resilient consortium. There is currently no robust method for re-deriving an already microbially colonized individual again-germ-free. We previously developed the in vivo growth-incompetent E. coli K-12 strain HA107 that is auxotrophic for the peptidoglycan components D-alanine (D-Ala) and meso-diaminopimelic acid (Dap) and can be used to transiently associate germ-free animals with live bacteria, without permanent loss of germ-free status. Here we describe the translation of this experimental model from the laboratory-adapted E. coli K-12 prototype to the better gut-adapted commensal strain E. coli HS. In this genetic background it was necessary to complete the D-Ala auxotrophy phenotype by additional knockout of the hypothetical third alanine racemase metC. Cells of the resulting fully auxotrophic strain assembled a peptidoglycan cell wall of normal composition, as long as provided with D-Ala and Dap in the medium, but could not proliferate a single time after D-Ala/Dap removal. Yet, unsupplemented bacteria remained active and were able to complete their cell cycle with fully sustained motility until immediately before autolytic death. Also in vivo, the transiently colonizing bacteria retained their ability to stimulate a live-bacteria-specific intestinal Immunoglobulin (Ig) A response. Full D-Ala auxotrophy enabled rapid recovery to again-germ-free status. E. coli HS has emerged from human studies and genomic analyses as a paradigm of benign intestinal commensal E. coli strains. Its reversibly colonizing derivative may provide a versatile research tool for mucosal bacterial conditioning or compound delivery without permanent colonization.
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| 9. |
- Dimiev, Ayrat M., et al.
(författare)
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Graphene Oxide: Fundamentals and Applications
- 2016
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Bok (övrigt vetenskapligt/konstnärligt)abstract
- Due to its unique properties, graphene oxide has become one of the most studied materials of the last decade and a great variety of applications have been reported in areas such as sensors, catalysis and biomedical applications. This comprehensive volume systematically describes the fundamental aspects and applications of graphene oxide. The book is designed as an introduction to the topic, so each chapter begins with a discussion on fundamental concepts, then proceeds to review and summarize recent advances in the field. Divided into two parts, the first part covers fundamental aspects of graphene oxide and includes chapters on formation and chemical structure, characterization methods, reduction methods, rheology and optical properties of graphene oxide solutions. Part Two covers numerous graphene oxide applications including field effect transistors, transparent conductive films, sensors, energy harvesting and storage, membranes, composite materials, catalysis and biomedical applications. In each case the differences and advantages of graphene oxide over its non-oxidised counterpart are discussed. The book concludes with a chapter on the challenges of industrial-scale graphene oxide production. Graphene Oxide: Fundamentals and Applications is a valuable reference for academic researchers, and industry scientists interested in graphene oxide, graphene and other carbon materials. © 2017 John Wiley & Sons, Ltd. All rights reserved.
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| 10. |
- Eigler, Siegfried, 1978, et al.
(författare)
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Characterization Techniques
- 2016
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Ingår i: Graphene Oxide: Fundamentals and Applications. - Chichester, UK : John Wiley & Sons, Ltd. - 9781119069447 ; , s. 85-120
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Solid-state nuclear magnetic resonance spectroscopy (SSNMR) not only is a reliable tool to determine the structure of organic molecular compounds, but also has developed into a suitable technique to characterize graphene oxide (GO) and has the potential to make structural analysis of GO derivatives possible. Common spectroscopic techniques are introduced, and the advances of SSNMR for analyzing the structure of GO are summarized. Finally, the prospects of SSNMR are discussed. Fourier-transform infrared (FTIR) spectroscopy is a simple and robust method to analyze GO. It is not very representative, since absorption bands from the fingerprint region are almost impossible to reveal due to the overlapping of numerous signals. Also, FTIR is the most commonly misinterpreted method among all those used for GO characterization. Nevertheless, FTIR has played an important role in revealing some specific functional groups. Several real examples are discussed. X-ray photoelectron spectroscopy (XPS) is a very powerful tool in characterizing GO and its composites. The ability to detect heteroatoms makes XPS superior even when compared to SSNMR. XPS also provides the chemical or electronic state for each element. With respect to GO, XPS provides not only the elemental content, but also the nature and the relative content of the functional groups. Raman spectroscopy is a reliable tool to determine and visualize the heterogeneity of graphene-family materials, including single-layer graphene and some specific types of reduced graphene oxide (RGO). It is a highly sensitive method to determine and quantify the amount of defects in graphene. Here, the basic principles of Raman spectroscopy and the basic interpretation of spectra are given. In addition, using an example, we show how to perform statistical analysis and how to use these data as a basis for statistical Raman microscopy. Being a very powerful tool for characterizing graphene-family materials in general, Raman spectroscopy is not very informative when used on typical GO samples. The density of defects in GO is very high, and Raman spectroscopy cannot resolve different defect densities after some threshold defect density has been reached. The density of defects in typical GO samples is beyond this threshold. However, Raman spectroscopy is a very powerful tool for characterizing some specially prepared low-defect-density RGO samples. Microscopy is broadly used to characterize GO in terms of the flakes' size, thickness, number of layers, etc. High-resolution transmission electron microscopy (HRTEM) has been exploited to reveal the fine chemical structure of GO. For the first time HRTEM has confirmed the two-type-domain structure of GO. In this chapter, as well as HRTEM, the following microscopy methods are reviewed: scanning electron microscopy (SEM), atomic force microscopy (AFM) and transmission electron microscopy (TEM). Several examples of how these methods have been used to characterize GO are reviewed.
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