| 1. |
- Amaudruz, P, et al.
(författare)
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A re-evaluation of the nuclear structure function ratios for D, He, 6Li, C and Ca
- 1995
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Ingår i: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562. ; 441:1-2, s. 3-11
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Tidskriftsartikel (refereegranskat)abstract
- We present a re-evaluation of the structure function ratios F-2(He)/F-2(D), F-2(C)/F-2(D) and F-2(Ca)/F-2(D) measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. We also present the ratios F-2(C)/F-2(Li), F-2(Ca)/F-2(Li) and F-2(Ca)/F-2(C) measured at 90 GeV. The results are based on data already published by NMC; the main difference in the analysis is a correction for the masses of the deuterium targets and an improvement in the radiative corrections. The kinematic range covered is 0.0035 < x < 0.65, 0.5 < Q(2) < 90 GeV2 for the He/D, C/D and Ca/D data and 0.0085 < x < 0.6, 0.84 < Q(2) < 17 GeV2 for the Li/C/Ca ones.
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| 2. |
- Amaudruz, P, et al.
(författare)
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Gottfried sum from the ratio F2n/F2p
- 1991
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Ingår i: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 66:21, s. 2712-2715
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Tidskriftsartikel (refereegranskat)abstract
- Experimental results obtained at the CERN Super Proton Synchrotron on the structure-function ratio F2n/F2p in the kinematic range 0.004 < x < 0.8 and 0.4 < Q2 < 190 GeV2, together with the structure function F2d determined from a fit to published data, are used to derive the difference F2p(x) - F2n(x). The value of the Gottfried sum integral (F2p - F2n) dx/x = 0.240 +/- 0.016 is below the quark-parton-model expectation of 1/3.
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| 3. |
- Amaudruz, P, et al.
(författare)
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Measurements of Rd-Rp and RCa-Rc in deep inelastic muon scattering
- 1992
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 294:1, s. 120-126
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Tidskriftsartikel (refereegranskat)abstract
- Results are presented on the difference in R, the ratio of longitudinally to transversely polarised virtual photon absorption cross sections, for the deuteron and the proton. They are obtained by comparing the ratio of cross sections for the deep inelastic scattering of muons from deuterium and hydrogen targets at 90 and 280 GeV incident energy. The results cover the range x = 0.01 -0.30, at an average Q2 of 9 GeV2. The measured difference R(d)-R(p) shows no significant x dependence and is compatible with zero, as well as with expectations from perturbative QCD. We use the same method to obtain the difference R(Ca)-R(C) from cross section ratios measured on carbon and calcium targets at 90 and 200 GeV incident energy.
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| 4. |
- Amaudruz, P, et al.
(författare)
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Precision measurement of structure function ratios for 6Li, 12C and 40Ca
- 1992
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Ingår i: Zeitschrift für Physik C Particles and Fields. - : Springer. - 0170-9739 .- 1431-5858. ; 53:1, s. 73-77
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Tidskriftsartikel (refereegranskat)abstract
- The structure function ratios F2C/F2Li, F2Ca/F2Li and F2Ca/F2C were measured in deep inelastic muon-nucleus scattering at an incident muon energy of 90 GeV, covering the kinematic range 0.0085 < x < 0.6 and 0.8 < Q2 < 17 GeV2. The sensitivity of the nuclear structure functions to the size and mean density of the target nucleus is discussed.
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| 5. |
- Amaudruz, P, et al.
(författare)
-
Precision measurement of the structure function ratios F2He/F2D, F2C/F2D and F2Ca/F2D
- 1991
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Ingår i: Zeitschrift für Physik C Particles and Fields. - : Springer. - 0170-9739 .- 1431-5858. ; 51:3, s. 387-393
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Tidskriftsartikel (refereegranskat)abstract
- We present the structure function ratios F2He/F2D, F2C/F2D and F2Ca/F2D measured in deep inelastic muon-nucleus scattering at an incident muon momentum of 200 GeV. The kinematic range 0.0035 < x < 0.65 and 0.5 < Q2 < 90 GeV2 is covered. At low x the three ratios are significantly smaller than unity and the size of the depletion grows with decreasing x and increasing mass number A. At intermediate x the ratios show an enhancement of about 2% above unity for C/D and Ca/D, possibly less for He/D. There are indications of some Q2 dependence in the Ca/D data. The integrals of the structure function differences F2A-F2D are discussed.
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| 6. |
- Amaudruz, P, et al.
(författare)
-
Proton and deuteron F2 structure functions in deep inelastic muon scattering
- 1992
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Ingår i: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 295:1-2, s. 159-168
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Tidskriftsartikel (refereegranskat)abstract
- The structure functions F2p and F2d measured by deep inelastic muon scattering at incident energies of 90 and 280 GeV are presented. These measurements cover a large kinematic range, 0.006 less-than-or-equal-to x less-than-or-equal-to 0.6 and 0.5 less-than-or-equal-to Q2 less-than-or-equal-to 55 GeV2, and include the first precise data at small x, where large scaling violations are observed. The data agree with earlier results from SLAC and BCDMS but exhibit differences with respect to those of EMC-NA2. Extrapolations to small x of recent phenomenological parton distributions are shown to disagree with the present results.
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| 7. |
- Amaudruz, P, et al.
(författare)
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The ratio F2 n/F2 p in deep inelastic muon scattering
- 1992
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Ingår i: Nuclear Physics B. - : Elsevier. - 0550-3213 .- 1873-1562. ; 371:1-2, s. 3-31
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Tidskriftsartikel (refereegranskat)abstract
- Results are presented on the ratio of neutron and proton structure functions, F2n/F2p, deduced from deep inelastic scattering of muons from hydrogen and deuterium. The data, which were obtained at the CERN muon beam at 90 and 280 GeV incident energy, cover the kinematic range x = 0.002-0.80 and Q2 = 0.1-190 GeV2. The measured structure function ratios have small statistical and systematic errors, particularly at small and intermediate x. The observed Q2 dependence in the range x = 0.1-0.4 is stronger than predicted by perturbative QCD. From the present data together with results from other experiments it is suggested that the twist-four coefficient for the proton is smaller than that for the neutron for x larger than 0.2.
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| 8. |
- Amaudruz, P, et al.
(författare)
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Transverse momentum distributions for exclusive ρ0 muoproduction
- 1992
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Ingår i: Zeitschrift für Physik C Particles and Fields. - : Springer. - 0170-9739 .- 1431-5858. ; 54:2, s. 239-245
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Tidskriftsartikel (refereegranskat)abstract
- We have studied transverse momentum distributions for exclusive rho(0) muoproduction on protons and heavier nuclei at 2 < Q2 < 25 GeV2. The Q2 dependence of the slopes of the p(t)2 and t' distributions is discussed. The influence of the non-exclusive background is investigated. The p(t)2-slope for exclusive events is 4.3 +/- 0.6 +/- 0.7 GeV-2 at large Q2. The p(t)2 spectra are much softer than inclusive p(t)2 spectra of leading hadrons produced in deep inelastic scattering.
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| 9. |
- Burdorf, L. D. W., et al.
(författare)
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Long-distance electron transport occurs globally in marine sediments
- 2017
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 14:3, s. 683-701
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Tidskriftsartikel (refereegranskat)abstract
- Recently, long filamentous bacteria have been reported conducting electrons over centimetre distances in marine sediments. These so-called cable bacteria perform an electrogenic form of sulfur oxidation, whereby long-distance electron transport links sulfide oxidation in deeper sediment horizons to oxygen reduction in the upper millimetres of the sediment. Electrogenic sulfur oxidation exerts a strong impact on the local sediment biogeochemistry, but it is currently unknown how prevalent the process is within the seafloor. Here we provide a state-of-the-art assessment of its global distribution by combining new field observations with previous reports from the literature. This synthesis demonstrates that electrogenic sulfur oxidation, and hence microbial long-distance electron transport, is a widespread phenomenon in the present-day seafloor. The process is found in coastal sediments within different climate zones (off the Netherlands, Greenland, the USA, Australia) and thrives on a range of different coastal habitats (estuaries, salt marshes, mangroves, coastal hypoxic basins, intertidal flats). The combination of a widespread occurrence and a strong local geochemical imprint suggests that electrogenic sulfur oxidation could be an important, and hitherto overlooked, component of the marine cycle of carbon, sulfur and other elements.
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| 10. |
- Cornelissen, R., et al.
(författare)
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The Cell Envelope Structure of Cable Bacteria
- 2018
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Ingår i: Frontiers in Microbiology. - : Frontiers Media SA. - 1664-302X. ; 9
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Tidskriftsartikel (refereegranskat)abstract
- Cable bacteria are long, multicellular micro-organisms that are capable of transporting electrons from cell to cell along the longitudinal axis of their centimeter-long filaments. The conductive structures that mediate this long-distance electron transport are thought to be located in the cell envelope. Therefore, this study examines in detail the architecture of the cell envelope of cable bacterium filaments by combining different sample preparation methods (chemical fixation, resin-embedding, and cryo-fixation) with a portfolio of imaging techniques (scanning electron microscopy, transmission electron microscopy and tomography, focused ion beam scanning electron microscopy, and atomic force microscopy). We systematically imaged intact filaments with varying diameters. In addition, we investigated the periplasmic fiber sheath that remains after the cytoplasm and membranes were removed by chemical extraction. Based on these investigations, we present a quantitative structural model of a cable bacterium. Cable bacteria build their cell envelope by a parallel concatenation of ridge compartments that have a standard size. Larger diameter filaments simply incorporate more parallel ridge compartments. Each ridge compartment contains a similar to 50 nm diameter fiber in the periplasmic space. These fibers are continuous across cell-to-cell junctions, which display a conspicuous cartwheel structure that is likely made by invaginations of the outer cell membrane around the periplasmic fibers. The continuity of the periplasmic fibers across cells makes them a prime candidate for the sought-after electron conducting structure in cable bacteria.
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