Delayed fracture in porous media

The fracture of porous media subjected to a constant load is studied. Contrary to homogeneous solids in which fracture usually happens instantaneously at a well-defined breaking strength, the fracture of a porous medium can occur with a delay, allowing us to quantify the average lifetime of the unbroken material. We show that the average fracture probability, a key property for risk analysis in civil engineering, is given by the probability of crack nucleation. The nucleation process can be understood qualitatively by calculating the activation energy for crack nucleation, taking into account the porosity of the medium.     

XANES speciation of mercury in three mining districts – Almadén,Asturias (Spain), Idria (Slovenia)

The mobility, bioavailability and toxicity of mercury in the environment strongly depend on the chemical species in which it is present in soil, sediments, water or air. In mining districts, differences in mobility and bioavailability of mercury mainly arise from the different type of mineralization and ore processing. In this work, synchrotron‐based X‐ray absorption near‐edge spectroscopy (XANES) has been taken advantage of to study the speciation of mercury in geological samples from three of the largest European mercury mining districts: Almadén (Spain), Idria (Slovenia) and Asturias (Spain). XANES has been complemented with a single extraction protocol for the determination of Hg mobility. Ore, calcines, dump material, soil, sediment and suspended particles from the three sites have been considered in the study. In the three sites, rather insoluble sulfide compounds (cinnabar and metacinnabar) were found to predominate. Minor amounts of more soluble mercury compounds (chlorides and sulfates) were also identified in some samples. Single extraction procedures have put forward a strong dependence of the mobility with the concentration of chlorides and sulfates. Differences in efficiency of roasting furnaces from the three sites have been found.     

2-Mercaptobenzimidazole (2-benzimidazolethiol) as a colorimetric reagent for palladium

Summary A spectrophotometric method for the determination of palladium using 2-mercaptobenzimidazole is described. The orange-yellow colour developed in aqueous medium atph 1.0–2.6 by the addition of an alcoholic solution of the reagent, is measured at 380 m. The system is found to obey Beer's law. The interference limits of diverse ions are also given.     

Proposed terminology of ‘lato sensu metrology’ for scientific methodology

Currently, there are two international scientific vocabularies devoted to properties: one dealing on quantities and the other one dealing on nominal properties. In this article, I am proposing the two mentioned vocabularies be merged in order to make available most of the basic concepts, terms, and definitions needed in observational and experimental scientific methodology in a single vocabulary. In addition, I propose the provisional use of the term “lato sensu metrology” to describe the new vocabulary.     

Screening of Wood/Forest and Vine By-Products as Sources of New Drugs for Sustainable Strategies to Control Fusarium graminearum and the Production of Mycotoxins

Fusarium graminearum is a fungal pathogen that can colonize small-grain cereals and maize and secrete type B trichothecene (TCTB) mycotoxins. The development of environmental-friendly strategies guaranteeing the safety of food and feed is a key challenge facing agriculture today. One of these strategies lies on the promising capacity of products issued from natural sources to counteract crop pests. In this work, the in vitro efficiency of sixteen extracts obtained from eight natural sources using subcritical water extraction at two temperatures was assessed against fungal growth and TCTB production by F. graminearum. Maritime pine sawdust extract was shown to be extremely efficient, leading to a significant inhibition of up to 89% of the fungal growth and up to 65% reduction of the mycotoxin production by F. graminearum. Liquid chromatography/mass spectrometry analysis of this active extract revealed the presence of three families of phenolics with a predominance of methylated compounds and suggested that the abundance of methylated structures, and therefore of hydrophobic compounds, could be a primary factor underpinning the activity of the maritime pine sawdust extract. Altogether, our data support that wood/forest by-products could be promising sources of bioactive compounds for controlling F. graminearum and its production of mycotoxins.     

Angle-resolved three-dimensional analysis of surface films by coherence scanning interferometry

The Fourier components of interference signals generated by scanning a high-numerical-aperture objective orthogonal to an object surface correspond to different angles of incidence on the surface. The phase and amplitude of these Fourier components relate to the structure of the object, including in particular the 3D topography and thickness profiles of thin-film layers.     

Recent Progress in Direct Introduction of Fluorinated Groups on Alkenes and Alkynes by means of CH Bond Functionalization

The direct introduction of fluorine and fluorinated building blocks has recently attracted a lot of attention and particularly the direct functionalization of alkenes and alkynes. This review will highlight the major progress recently made in that field, with a focus on photocatalyzed transformations, base‐promoted processes, and transition metal‐catalyzed functionalization of alkenes and alkynes. Special attention will be paid to explanations of the reaction mechanisms.     

Deformations of duality-symmetric theories

We prove that a sum of free non-covariant duality-symmetric actions does not allow consistent, continuous and local self-interactions that deform the gauge transformations. For instance, non-abelian deformations are not allowed, even in 4 dimensions where Yang–Mills type interactions of 1-forms are allowed in the non-manifestly duality-symmetric formulation. This suggests that non-abelian duality should require to leave the standard formalism of perturbative local field theories. The analyticity of self-interactions for a single duality-symmetric gauge field in four dimensions is also analyzed.     

Indirect interactions between localized magnetic moments in intrinsic semiconductors

The indirect interaction between localized magnetic moments in insulators and semiconductors is investigated at T = 0°K. This interaction arises from virtual excitations of the valence electrons to the conduction band and is oscillatory as a function of distance. The passage from the case of small gap semiconductors to insulators is studied in detail, as a function of the energy gap and the effective masses. The Bloembergen-Rowland interaction is derived as a limiting case for insulators. Possible applications are also discussed.