3,567 research outputs found
Can biochar and hydrochar stability be assessed with chemical methods?
No full textField application of biochar is intended to increase soil carbon (C) storage. The assessment of C storage potential of biochars lacks methods and standard materials. The reactivity of biochars and hydrochars may be one possible means of evaluating their environmental stability. The aim of this study was to evaluate the reactivity of biochar produced by gasification (GS) and hydrochar produced by hydrothermal carbonisation (HTC). The approach included analysis of the two different char types produced from the same three feedstocks. Moreover, we analysed the reactivity of Holocene charcoal (150 and 2000 yr old) to evaluate whether or not their use as standard materials to represent stable biochar is meaningful. We assessed carbon loss following oxidation with acid dichromate as well as hydrolysis with HCl. Our results showed that chemical reactivity is not a straightforward approach for characterising the stability of biochar and hydrochar. Acid hydrolysis showed little difference between HTCs and GSs, despite the contrasting elemental composition. Using acid dichromate oxidation, we determined that GSs contained ca. 70% of oxidation resistant C while the proportion for HTCs was 2000 yr old charcoal > HTCs > feedstock and was related to elemental composition. This shows that acid dichromate oxidation may allow differentiation of the reactivity of modern biochars but that there is not necessarily a relationship between reactivity and age of Holocene charcoals. As the chemical reactivity of biochars may change with exposure time in soil, it is poorly suited for assessing their environmental residence tim
Anthropogenic Dark Earth in Northern Germany - The Nordic Analogue to terra preta de Indio in Amazonia
No full textDuring an archaeological excavation of a Slavic settlement (10th/11th C. A.D.) in Briinkendorf (Wendland region in Northern Germany), a thick black soil (Nordic Dark Earth) was discovered that resembled the famous terra preta phenomenon. For the humid tropics, terra preta could act as model for sustainable agricultural practices and for long-term CO2-sequestration into terrestrial ecosystems. The question was whether this Nordic Dark Earth had similar properties and genesis as the famous Amazonian Dark Earth in order to find a model for sustainable agricultural practices and long term CO2-sequestration in temperate zones. For this purpose, a multi-analytical approach was used to characterise the sandy-textured Nordic Dark Earth in comparison to less anthropogenically influenced soils in the adjacent area in respect of ecological conditions (pH, electric conductivity, cation exchange capacity, amino sugar) and input materials. Total element contents (C, N, P, Ca, Mg, K, Na, Fe, Cu, K, Zn, Mn and Ba) were highly enriched in the Nordic Dark Earth compared to the reference soil. Faecal biomarkers such as stanols and bile acids indicated animal manure from omnivores and herbivores but also human excrements. Amino sugar analyses showed that Nordic Dark Earth contained higher amounts of microbial residues being dominated by soil fungi. Black carbon content of about 30 Mg ha(-1) in the Nordic Dark Earth was about four times higher compared to the adjacent soil and in the same order of magnitude compared to terra preta. The input materials and resulting soil chemical characteristics of the Nordic Dark Earth were comparable to those of Amazonian Dark Earth suggesting that their genesis was also comparable. Amazonian Dark Earth and Nordic Dark Earth were created by surface deposition and/or shallow soil incorporation of waste materials including human and animal excrements together with charred organic matter. Over time, soil organisms degraded and metabolized these materials leaving behind deep black stable soil organic matter. The existence of the Nordic Dark Earth in the temperature zone of Europe demonstrates the capability of sandy-textured soils to maintain high soil organic matter contents and nutrient retention over hundreds of years. Deeper insights are needed urgently to understand soil organic matter stabilization mechanisms in this sandy soil to promote conceptual models for sustainable land use and long-term C sequestration. It is argued that the knowledge of Nordic Dark Earth probably was an important part of the Viking-Slavic subsistence agriculture system, which could have had a great impact on the development of the Viking age emporia in the 9th/10th C AD. (C) 2014 Elsevier B.V. All rights reserved.Federal Ministry of Education and Research (BMBF) [FKZ: 01LY1110B
Measurement of the ratio of prompt χ c to J / ψ production in pp collisions at √s = 7 TeV
No full textThe prompt production of charmonium χ c and J / ψ states is studied in proton-proton collisions at a centre-of-mass energy of √s = 7 TeV at the Large Hadron Collider. The χ c and J / ψ mesons are identified through their decays χ c → J / ψ γ and J / ψ → μ + μ - using 36 pb - 1 of data collected by the LHCb detector in 2010. The ratio of the prompt production cross-sections for χ c and J / ψ, σ (χ c → J / ψ γ) / σ (J / ψ), is determined as a function of the J / ψ transverse momentum in the range 2 < p T J / ψ < 15 GeV / c. The results are in excellent agreement with next-to-leading order non-relativistic expectations and show a significant discrepancy compared with the colour singlet model prediction at leading order, especially in the low p T J / ψ region
Electron energy loss-near edge structure as a fingerprint for identifying chromium nitrides
No full textElectron energy loss-near edge structure as a fingerprint for identifying chromium nitrides
C. Mitterbauer Corresponding Author Contact Information, E-mail The Corresponding Author, a, C. Hébert b, G. Kothleitner a, F. Hofer a, P. Schattschneider b and H. W. Zandbergen c
a Research Institute for Electron Microscopy, Graz University of Technology, Steyrergasse 17, A-8010, Graz, Austria
b Institute for Solid State Physics, Vienna University of Technology, Wiedner Hauptstraße 8-10/138, A-1040, Wien, Austria
c Laboratory of Materials Science, Centre for HREM, Delft University of Technology, Rotterdamseweg 137, 2628 AL, Delft, The Netherlands
Received 5 December 2003; accepted 30 January 2004 by H. Eschrig Available online 11 February 2004.
Abstract
Electron energy-loss near-edge structure data for the N K and the Cr L2,3 edges of CrN and Cr2N have been acquired in order to distinguish between these chromium nitride modifications. The N K edge spectra of these compounds have been modelled using both band structure and multiple scattering methods. We compare the results of these calculations with the experimental edges which have been recorded using a conventional transmission electron microscope (TEM) as well as a monochromated TEM (Wien filter).
Author Keywords: Author Keywords: A. Chromium nitride; C. Scanning and transmission electron microscopy; E. Electron energy loss spectroscopy
82.80.Pv; 61.16.Bg; 71.20.−b; 11.80.L
Prompt charm production in pp collisions at √<span style="text-decoration:overline">s</span>=7 TeV
No full textCharm production at the LHC in pp collisions at s√=7 TeV is studied with the LHCb detector. The decays D0→K−π+, D+→K−π+π+, D⁎+→D0(K−π+)π+, D+s→ϕ(K−K+)π+, Λ+c→pK−π+, and their charge conjugates are analysed in a data set corresponding to an integrated luminosity of 15 nb−1. Differential cross-sections dσ/dpT are measured for prompt production of the five charmed hadron species in bins of transverse momentum and rapidity in the region 0<pT<8 GeV/c and 2.0<y<4.5. Theoretical predictions are compared to the measured differential cross-sections. The integrated cross-sections of the charm hadrons are computed in the above pT-y range, and their ratios are reported. A combination of the five integrated cross-section measurements gives
σ(cc¯)pT<8 GeV/c,2.0<y<4.5=1419±12(stat)±116(syst)±65(frag) μb,
where the uncertainties are statistical, systematic, and due to the fragmentation functions
Momentum Dependence of the Decay
No full text, R. McCrady n , J. Meier g , C.A. Meyer n , L. Montanet f , R. Ouared f , F. Ould-Saada p , K. Peters b , B. Pick c , C. Pietra p , C.N. Pinder e , M. Ratajczak b , C. Regenfus l , S. Resag c , W. Roethel l , P. Schmidt g , I. Scott i , R. Seibert g , S. Spanier p , H. Stock b , C. Straßburger c , U. Strohbusch g , M. Suffert o , U. Thoma c , M. Tischhauser h , C. Volcker l , S. Wallis l , D. Walther b;5 , U. Wiedner f , K. Wittmack c , B.S. Zou<F42
High Statistics Study of
No full textf , J. Ludemann b , H. Matthaey b , R. McCrady l , M. Merkel k 9 , J.P. Merlo k , C.A. Meyer l , L. Montanet f , A. Noble o 10 , F. Ould--Saada o K. Peters b , C.N. Pinder e , G. Pinter d , S. Ravndal b9 , C. Regenfus m , S. Resag c , R. Ruoured f , E. Schafer k , P. Schmidt g , R. Seibert g , S. Spanier o , H. Stock b , C. Straßburger c , U. Strohbusch g , M. Suffert n , U. Thoma c , M. Tischhauser h , D. Urner o , C. Volcker m , F. Walter k , D. Walther b , U. Wiedner g<F2
High-Statistics Study of
No full texta , R. Landua f , F. Loser g , J. Ludemann b , H. Matthay b , M. Merkel k10 , J.P. Merlo k , C.A. Meyer m , L. Montanet f , A. Noble o , F. Ould-Saada o , K. Peters b , C.N. Pinder e , G. Pinter d , S. Ravndal b10 , C. Regenfus l , J. Salk b , E. Schafer k , P. Schmidt g , R. Seibert g , S. Spanier k , H. Stock b , C. Straßburger c , U. Strohbusch g , M. Suffert n , U. Thoma c , D. Urner o , C. Volcker l , F. Walter k , D. Walther b , U. Wiedner g , N
E Decays to ... in ... Annihilation At Rest
No full text19> , R. McCrady m , J.P. Merlo a , C.A. Meyer m , L. Montanet f , A. Noble o5 , R. Ouared f , F. Ould-Saada o , K. Peters b , C.N. Pinder e , G. Pinter d , S. Ravndal b , C. Regenfus l , E. Schafer k6 , P. Schmidt g , M. Schutrumpf b , I. Scott i , R. Seibert g , S. Spanier o , H. Stock b , C. Straßburger c , U. Strohbusch g , M. Suffert n , U. Thoma c , M. Tischhauser h , D. Urner o7 , C. Volcker l , F. Walter k , D. Walther b , U. Wiedner g , N. Winter h ,
P- versus S-wave
No full text.02> m , U. Meyer-Berkhout h , L. Montanet c , A. Noble m , K. Peters a , G. Pinter b , S. Ravndal a , A.H. Sanjari i , E. Schafer g , B. Schmid m , P. Schmidt d , S. Spanier g , C. Straßburger g , U. Strohbusch d , M. Suffert k , D. Urner m , C. Volcker h , D. Walther a , U. Wiedner d , N. Winter e , J. Zoll c , C. Zupancic h a Universitat Bochum, D-4630 Bochum, FRG b Academy of Science, H-1525 Budapest, Hungary c CERN, CH-1211 Gen`eve, Switzerland d Universitat Hamburg, D-2000 Hamburg, FRG e Universitat Karlsruhe, W-7500 K
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