Quasi-free photoproduction of eta-mesons off the deuteron

Precise data for quasi-free photoproduction of $\eta$ mesons off the deuteron have been measured at the Bonn ELSA accelerator with the combined Crystal Barrel/TAPS detector for incident photon energies up to 2.5 GeV. The $\eta$-mesons have been detected in coincidence with recoil protons and neutrons. Possible nuclear effects like Fermi motion and re-scattering can be studied via a comparison of the quasi-free reaction off the bound proton to $\eta$-production off the free proton. No significant effects beyond the folding of the free cross section with the momentum distribution of the bound protons have been found. These Fermi motion effects can be removed by an analysis using the invariant mass of the $\eta$-nucleon pairs reconstructed from the final state four-momenta of the particles. The total cross section for quasi-free $\eta$-photoproduction off the neutron reveals even without correction for Fermi motion a pronounced bump-like structure around 1 GeV of incident photon energy, which is not observed for the proton. This structure is even narrower in the invariant mass spectrum of the $\eta$-neutron pairs. Position and width of the peak in the invariant mass spectrum are $W\approx 1665$ MeV and FWHM $\Gamma\approx 25$ MeV. The data are compared to the results of different models.Comment: accepted for publication in Eur. Phys. J.

Mineralização do carbono orgânico em solos tratados com lodo de curtume Mineralization of the organic carbon in soils treated with tannery sludges

O objetivo deste trabalho foi avaliar a mineralização do carbono orgânico do lodo de curtume, aplicado em solos com diferentes classes texturais, de modo a caracterizar a cinética do processo de mineralização e auxiliar na elaboração de normas técnicas sobre o uso agrícola desse material. Foram conduzidos experimentos de incubação por 105 dias, em laboratório, utilizando-se três solos: Nitossolo Vermelho eutroférrico típico (NVef), Latossolo Vermelho-Amarelo distrófico típico (LVAd) e Neossolo Quartzarênico órtico típico (RQo). O lodo de curtume utilizado nos experimentos foi composto de uma mistura, na proporção de 1:1, do lodo do caleiro e do lodo primário da estação de tratamento de efluentes, resultante da precipitação dos efluentes gerados no processo, com exceção dos efluentes que contêm cromo. As doses aplicadas (base seca) no NVef e LVAd foram equivalentes a 0, 6, 12, 24 e 36 Mg ha-1 e a 0, 3, 6, 12 e 24 Mg ha-1 no RQo. Não se observa prejuízo à atividade microbiana dos solos, avaliada por meio da respiração basal, e a mineralização do carbono adicionado por meio do lodo de curtume é intensa nos primeiros 15 a 20 dias de incubação.<br>The objective of this work was to evaluate the mineralization of the organic carbon derived from the tannery sludge applied in increasing doses on soils with different textures, to evaluate the decomposition kinetics, as well as to learn about the impact of this residue on the soil microbial community. This knowledge will be helpful for the establishment of technical rules about the agricultural use of the tannery sludges. Incubation experiments were carried out in the laboratory for 105 days, using three soils: a Kandiudalfic Eutrudox (NVef), a Typic Hapludox (LVAd) and a Typic Quartzipsamment (RQo). Tannery sludge used in these experiments was composed of a mixture of liming sludge and the primary sludge from the wastewater treatment station, in the proportion 1:1, with the exception of the wastewater with chromium. The doses of sludge (dry basis) added to the NVef and the LVAd soils were equivalent to 0, 6, 12, 24 and 36 Mg ha-1, and 0, 3, 6, 12 and 24 Mg ha-1 were added to the RQo soil. Soil microbial activity was not inhibited, even by the highest doses, and the most intense carbon degradation occurred on the first 15 to 20 days of incubation

Influence that osmotic suction and tree roots has on the stability of coastal soils

© Springer Nature Singapore Pte Ltd 2019. The contribution made by osmotic suction to unsaturated shear strength analysis has not been considered for the past few decades. Osmotic suction is generated by the salt in pore water, especially in coastal environments, and it can be more significant than matric suction. Tree roots can also induce osmotic and matric suction by continuous transpiration, and when these saline and rooted environments are combined under unsaturated conditions, they can challenge conventional shear strength models. Electrical resistivity can be used as a proper tool to evaluate the properties of soil in a large scale. This review summarizes the historical development of studies related to osmotic suction as well as the present situation of osmotic suction for soil shear strength

Guest Editorial: Unpacking Diversity, Grasping Inequality: Rethinking Difference Through Critical Perspectives

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