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  • 1
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    Evaluation of ENTLN performance characteristics based on the ground-truth natural and rocket-triggered lightning data acquired in Florida (2017)
    Wiley
    Details
    Publication Date: 2017-08-31
    Description: The performance characteristics of the Earth Networks Total Lightning Network (ENTLN) were evaluated by using as ground-truth natural cloud-to-ground (CG) lightning data acquired at the Lightning Observatory in Gainesville (LOG) and rocket-triggered lightning data obtained at Camp Blanding (CB), Florida, in 2014 and 2015. Two ENTLN processors (data processing algorithms) were evaluated. The old processor (P2014) was put into use in June 2014 and the new one (P2015) has been operational since August 2015. Based on the natural-CG-lightning dataset (219 flashes containing 608 strokes), the flash detection efficiency (DE), flash classification accuracy (CA), stroke DE, and stroke CA for the new processor were found to be 99%, 97%, 96%, and 91%, respectively, and the corresponding values for the old processor were 99%, 91%, 97%, and 68%. The stroke DE and stroke CA for first strokes are higher than those for subsequent strokes. Based on the rocket-triggered lightning dataset (36 CG flashes containing 175 strokes), the flash DE, flash CA, stroke DE, and stroke CA for the new processor were found to be 100%, 97%, 97%, and 86%, respectively, while the corresponding values for the old processor were 100%, 92%, 97%, and 42%. The median values of location error and absolute peak current estimation error were 215 m and 15% for the new processor, and 205 m and 15% for the old processor. For both natural and triggered CG lightning, strokes with higher peak currents were more likely to be both detected and correctly classified by the ENTLN.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 2
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    Gamma-ray signatures of neutrons from a terrestrial gamma-ray flash (2017)
    Wiley
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    Publication Date: 2017-09-19
    Description: Following a lightning strike to a wind turbine in Japan, we have observed a large burst of neutrons lasting 100 ms with a ground fluence of ~1000 n cm -2 , thousands of times greater than the peak neutron flux associated with the largest ground level solar particle event ever observed. This is the first detection of an unequivocal signature of neutrons from a terrestrial gamma-ray flash, and is shown to be consistent with the production of 10 12 -10 13 photoneutrons from a downward TGF at 1.0 km, with a gamma-ray brightness typical of upward TGFs observed by satellites.
    Print ISSN: 0094-8276
    Electronic ISSN: 1944-8007
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 3
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    Temperature and oxygen dependence of the remineralization of organic matter (2017)
    Wiley
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    Publication Date: 2017-06-08
    Description: Accurate representation of the remineralization of sinking organic matter is crucial for reliable projections of the marine carbon cycle. Both water temperature and oxygen concentration are thought to influence remineralization rates, but limited data constraints have caused disagreement concerning the degree of these influences. We analyse a compilation of POC flux measurements from 19 globally distributed sites. Our results indicate that the attenuation of the flux of particulate organic matter depends on temperature with a Q 10 between 1.5 and 2.01, and on oxygen described by a half saturation constant between 4 and 12 μ mol/L. We assess the impact of the temperature and oxygen dependence in the biogeochemistry model COBALT, coupled to GFDL's Earth System Model ESM2M. The new remineralization parameterization results in shallower remineralization in the low latitudes but deeper remineralization in the high latitudes, redistributing POC flux towards the poles. It also decreases the volume of the oxygen minimum zones, partly addressing a long-standing bias in global climate models. Extrapolating temperature-dependent remineralization rates to the surface (i.e., beyond the depth range of POC flux data) resulted in rapid recycling and excessive surface nutrients. Surface nutrients could be ameliorated by reducing near surface rates in a manner consistent with bacterial colonization, suggesting the need for improved remineralization constraints within the euphotic zone. The temperature and oxygen dependence cause an additional 10% decrease in global POC flux at 500m depth, but no significant change in global POC flux at 2000m under the RCP8.5 future projection.
    Print ISSN: 0886-6236
    Electronic ISSN: 1944-9224
    Topics: Biology , Chemistry and Pharmacology , Geography , Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 4
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    New group 13 MIL-53 derivates based on 2,5-thiophenedicarboxylic acid (2017)
    Wiley
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    Publication Date: 2017-10-04
    Description: A new rigid metal-organic framework (MOF) with MIL-53 topology built of 2,5-thiophenedicarboxylate (TDC) and Al, Ga or In is reported. Its structure contains chains of trans corner sharing MO6-octahedra, connected by the linker molecules to form microporous square shaped 1D channels. A combination of powder X-ray diffraction (PXRD), density functional theory (DFT) calculations and 1H, 13C and 27Al solid-state NMR spectroscopy (ssNMR) was used to analyse the structures in detail. The synthesis is easily scaled-up using microwave assisted solvothermal conditions. All materials possess a high thermal stability up to 420 °C in air and permanent porosity towards N2, H2, CO2, and CH4. Al-MIL-53-TDC shows a high specific surface area of as,BET = 1150 m2g-1 with a micropore volume of Vmic = 0.48 cm3g-1 as well as water uptake of 5.5 H2O molecules per sum formula (469 mg/g) with an a sigmoidal shape, advantageous for heat-transformation processes. Noteworthy, this material adsorbs 2.1 wt% H2 at -196 °C and 1 bar which surpasses other Al-MIL-53 compounds based on linear functionalized terephthalates.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 5
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    Magnesium doped Gallium Phophonates Ga1-xMgx[H3+x(O3PCH2)3N] (x = 0, 0.20) and the influence on proton conductivity (2017)
    Wiley
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    Publication Date: 2017-11-25
    Description: In our contribution to the development of new proton conductive coordination polymers (CPs) we focus on the impact of a partial replacement of Ga3+ by Mg2+. This approach should come along with the implementation of additional protons due to charge balances. In a first step we have synthesized an isostructural compound to the literature known compound AlH3P3N (H6P3N nitrilotris(methylene)-triphosphonic acid), where Al3+ is replaced by Ga3+, since all attempts to incorporate Mg2+ ions directly into AlH3P3N were not successful. The relative amount of Mg2+ and Ga3+ was established by EDX analysis. Rietveld refinement of the synchrotron data located the Ga3+ and Mg2+ ions on a split position, proving the disordered incorporation of the Mg2+ ions. Solid-state NMR spectroscopy confirms a disordered protonation of the phosphonate groups as well and shows that all amine groups are protonated. In order to investigate the effect on the proton conductivity the compounds GaH3[(O3PCH2)3N], denoted GaH3P3N as well as Ga0.80Mg0.20[H3.20(O3PCH2)3N], denoted GaMgH3.20P3N, were characterized by electrochemical impedance spectroscopy (EIS). Arrhenius behaviour in the investigated temperature range (70-130 °C) was found for both compounds (activation energies of Ea = 0.15 eV for GaH3P3N and 0.17 eV for GaMgP3N). The GaMgH3.20P3N sample shows a reduced proton mobility (σ = 1.2×10 4 S/cm) of about one order of magnitude in comparison to GaH3P3N (σ = 1.0×10 3 S/cm).
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 6
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    Expanding On the Relationship Between Continuing Current and In-Cloud Leader Growth (2017)
    Wiley
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    Publication Date: 2017-04-11
    Description: When lightning connects to the ground there is a large surge of current, called the return stroke, which is occasionally followed by a longer lasting steady current, called continuing current (CC). In a previous study of negative cloud-to-ground (−CG) flashes, we observed the growth rate of in-cloud positive leaders in an attempt to identify occurrences of CC. However, there was no observed change in positive leader growth rate during CC of negative CG flashes. In this study, we use the Langmuir Electric Field Array (LEFA), Lightning Mapping Array (LMA), and Flash-Continuous Broadband Digital Interferometer (INTF) data to extend the previous study to the growth of the negative leader during positive CG flashes. We have found that, in contrast with previous results, negative leader growth during positive CG flashes does show increases in growth rates coincident with CC. Finally, we find that the growth rate magnitudes for positive and negative leaders are typically ∼2-4 km per 10 ms and ∼25-40 km per 10 ms, respectively. These contrasting results highlight the differences between positive and negative leaders and provide strong evidence as to why −CC and +CC behave differently. Negative leaders inject higher amounts of current and allows the channel to remain conductive throughout the duration of CC. Whereas for positive leaders, the channel becomes non-conductive relatively quickly. It is therefore disconnected from the channel to the ground and, due to the positive leader's continued growth, an electric potential is built up until a K-event is produced that re-ionizes the channel.
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 7
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    Cover Picture: Re-Determination of the Crystal Structure of MIL-91(Al) (Z. Anorg. Allg. Chem. 2/2017) (2017)
    Wiley
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    Publication Date: 2017-01-25
    Description: The cover picture shows the former and the re-determined structure of MIL-91(Al), one of the first permanently porous metal phosphonates, in front of the synchrotron X-ray powder diffractometer beamline I11 (Diamond Light Source, Oxon., UK). The structure was re-determined using high resolution synchrotron powder X-ray diffraction data. The new model is in a lower symmetry space group, with no disordered ligands in the structure, whilst remaining otherwise consistent with the reported compound. New milder synthetic conditions were also developed. More details can be found in the Short Communication by Nele Hermer, Michael T. Wharmby and Norbert Stock on pages 137 ff.
    Print ISSN: 0044-2313
    Electronic ISSN: 1521-3749
    Topics: Chemistry and Pharmacology
    Published by Wiley
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  • 8
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    Fast Positive Breakdown in Lightning (2017)
    Wiley
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    Publication Date: 2017-06-22
    Description: VHF radiation sources produced by positive breakdown during lightning discharges are generally considered to be both weak and slowly propagating. However, as VHF lightning mapping systems have become more sensitive, even this weak radiation can be mapped. In addition to being a faint process, positive breakdown often produces bursts of energetic activity. During the bursts, the VHF emission is extremely bright, and the breakdown propagates at much higher speeds. Here we present VHF interferometric and time–of–arrival measurements of such fast positive breakdown events produced during three example flashes. Electric field change measurements show that the fast breakdown process carries positive charge. The extent and velocity of the breakdown is estimated by converting the angular source locations provided by the interferometer into Cartesian coordinates using 3-dimensional lightning mapping observations of the flash as a guide. Fast positive breakdown events are found to extend 100–2400 m into virgin air beyond the tip of the preceding positive leader, at speeds of 0.9–9 ×10 7 m s −1 . The observations expand upon earlier observations of such breakdown [ Shao et al. , 1995]“ and are similar to recently-reported results that fast positive breakdown is the cause of high-power narrow bipolar events (NBEs) [ Rison et al. , 2016].
    Print ISSN: 0148-0227
    Topics: Geosciences , Physics
    Published by Wiley on behalf of American Geophysical Union (AGU).
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  • 9
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    R-type bacteriocins in related strains of Xenorhabdus bovienii: Xenorhabdicin tail fiber modularity and contribution to competitiveness (2017)
    Oxford University Press
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    Publication Date: 2017-01-19
    Description: R-type bacteriocins are contractile phage tail-like structures that are bactericidal towards related bacterial species. The C-terminal region of the phage tail fiber protein determines target-binding specificity. The mutualistic bacteria Xenorhabdus nematophila and X. bovienii produce R-type bacteriocins (xenorhabdicins) that are selectively active against different Xenorhabdus species. We analyzed the P2-type remnant prophage clusters in draft sequences of nine strains of X. bovienii . The C-terminal tail fiber region in each of the respective strains was unique and consisted of mosaics of modular units. The region between the main tail fiber gene ( xbpH1 ) and the sheath gene ( xbpS1 ) contained a variable number of modules encoding tail fiber fragments. DNA inversion and module exchange between strains was involved in generating tail fiber diversity. Xenorhabdicin-enriched fractions from three different X. bovienii strains isolated from the same nematode species displayed distinct activities against each other. In one set of strains, the strain that produced highly active xenorhabdicin was able to eliminate a sensitive strain. In contrast, xenorhabdicin activity was not a determining factor in the competitive fitness of a second set of strains. These findings suggest that related strains of X. bovienii use xenorhabdicin and additional antagonistic molecules to compete against each other.
    Keywords: Environmental Microbiology
    Print ISSN: 0378-1097
    Electronic ISSN: 1574-6968
    Topics: Biology
    Published by Oxford University Press
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  • 10
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    Quantifying the Impact of Seasonal and Short-term Manure Application Decisions on Phosphorus Loss in Surface Runoff (2017)
    Wiley
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    Publication Date: 2017-11-01
    Print ISSN: 0047-2425
    Electronic ISSN: 1537-2537
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Wiley
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