94 research outputs found
Quark fragmentation to pi(+/-), pi(0), K-+/-, p and (p)over-bar in the nuclear environment
No full textThe influence of the nuclear medium on lepto-production of hadrons was studied in the HERMES experiment at DESY in semi- inclusive deep-inelastic scattering of 27.6 GeV positrons off deuterium, nitrogen and krypton targets. The differential multiplicity for krypton relative to that of deuterium has been measured for the first time for various identified hadrons (pi(+), pi(-), pi(0), K+, K-, p and (p) over bar) as a function of the virtual photon energy v, the fraction z of this energy transferred to the hadron, and the hadron transverse momentum squared p(t)(2). The multiplicity ratio is strongly reduced in the nuclear medium at low v and high z, with significant differences among the various hadrons. The distribution of the hadron transverse momentum is broadened towards high p(t)(2) in the nuclear medium, in a manner resembling the Cronin effect previously observed in collisions of heavy ions and protons with nuclei
A VERSATILE 3D CALIBRATION OBJECT FOR VARIOUS MICRO-RANGE MEASUREMENT METHODS
No full textWe present a new micrometer-sized 3D calibration structure containing nanomarkers that serve as well distinguishable reference points for the calibration of various 3D micro-range measurement methods, e.g. scanning electron microscopy (SEM) and environmental SEM (ESEM). The 3D calibration object was fabricated using gas-assisted focused ion beam (FIB) metal deposition. This technique proved to be a valuable tool, as it principally allows the construction of variously shaped microstructures that can be perfectly adapted to the special specifications of the sensor to be calibrated. The spatial data of the 38 non-symmetrically distributed nanomarkers were obtained by high-precision atomic force microscopy (AFM). The accuracy of the nanomarker measurement is shown and the efficiency of the calibration is demonstrated by triangulation and spatial intersection. Additionally, alternative micro-range measurement methods, e.g. confocal laser scanning microscopy (CLSM) and scanning profilometry were tested for possible application of the calibration structure. * Corresponding author
Attachment efficiency of nanomaterials to algae as an important criterion for ecotoxicity and grouping
No full textArt. 1021, 18 S.Engineered nanomaterials (ENMs) based on CeO2 and TiO2 differ in their effects on the unicellular green alga Raphidocelis subcapitata but these effects do not reflect the physicochemical parameters that characterize such materials in water and other test media. To determine whether interactions with algae can predict the ecotoxicity of ENMs, we studied the attachment of model compounds (three subtypes of CeO2 and five subtypes of TiO2) to algal cells by light microscopy and electron microscopy. We correlated our observations with EC50 values determined in growth inhibition assays carried out according to the Organisation for Economic Co-operation and Development (OECD) test guideline 201. Light microscopy revealed distinct patterns of ENM attachment to algal cells according to the type of compound, with stronger interactions leading to greater toxicity. This was confirmed by electron microscopy, which allowed the quantitative assessment of particle attachment. Our results indicate that algal extracellular polymeric substances play an important role in the attachment of ENMs, influencing the formation of agglomerates. The attachment parameters in short-term tests predicted the toxicity of CeO2 and TiO2 ENMs and can be considered as a valuable tool for the identification of sets of similar nanoforms as requested by the European Chemicals Agency in the context of grouping and read-across.10Nr.
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