Iron in olive tree leaves in the Mediterranean area

In this paper we used the technique of X-ray fluorescence by dispersionin energy in order to study a phytopathology named sooty mouldin olive tree leaves in the Mediterranean area. Samples studied included leaveswhich were infected and non-infected by sooty mould. Energy depressive X-rayfluorescence showed a significant increase in the amount of Fe in the affectedleaves when compared to leaves that don't have this pattern of blackmaterial. We suggest here that a treatment for this condition may be basedon a method that deprives these organisms of the Fe that they apparently needto survive. The average Fe concentration obtained for the infected olive treeleaves was 80 ppm, while the non-infected ones showed no measurable Fe presence.     

The Relative Dispersion and Mixing of Passive Solutes in Transport in Geologic Media

The spreading of a contaminant in a heterogeneous aquifer depends on the scales of variability effectively explored by the plume. In particular, we observe two major contributions of the fluctuating velocity field in the contaminant movement: (i) the spreading caused by velocity variations of scales lesser than that of the plume size, which we will call relative spreading, and (ii) the meander-like movement of the plume as a whole caused by velocity variations of scale larger than that of the plume size. The aim of this work is to consider the effects of the finite size of the contaminant plume on the local concentration moments <C> and _C . In particular a relative concentration, which depends on the scales of variability effectively explored by the plume, is defined. First, the mathematical formulation of the problem is developed along the Lagrangian framework. In particular, the expressions for the relative mean concentration and its variance are presented. Then, the methodology is applied to the regional transport problem, where the influence of the size of the plume and the pore-scale dispersion are quantitatively assessed.     

On the Maximum Concentration of Contaminants in Natural Aquifers

We examine the temporal evolution of the maximum concentration of a dissolved inert solute in spatially heterogeneous subsurface flows. The maximum concentration of a given substance is at the basis of most of environmental regulatory practices where maximum tolerable levels of concentration are typically prescribed for a variety of known contaminants. Through the use of the Lagrangian framework, we elaborate over a physically based, semi-analytical model for the maximum concentration. Specifically, we address how the maximum concentration is affected by key geostatistical parameters (i.e., logconductivity variance), local-scale dispersion processes and engineering design variables such as the dimensions of the solute injection zone. The model will help in identifying the major components that determine the maximum concentration, which is important in order to better allocate resources toward site characterization and reduce uncertainty in predictions. The ultimate scope is to provide a theoretical framework that is application-oriented to estimate the maximum concentration in natural aquifers and provide some guidance in applications. It also provides an useful tool for preliminary, screening analysis and testing scenarios. We test the performance of the model against the MADE transport experiment, with reasonably good agreement.

     

Effective conductivity of heterogeneous multiphase media with circular inclusions

Determining the effective conductivity of heterogeneous media is a central problem in different fields of physics. The medium considered here contains cylinders (inclusions) of random conductivities that are distributed at random in an embedding matrix. For random systems, widely encountered in applications, we derive an approximative analytical solution that applies to significantly denser configurations than Maxwell first-order approximations. The analytic solution is tested against accurate numerical simulations. The widely used effective medium approach is shown to be exact for symmetric conductivity distributions and quite accurate for asymmetrical cases.     

Neutron diffraction measurements of residual stresses in metal matrix composite samples

The results of neutron diffraction experiments for the determination of residual stresses in metal matrix composite samples are reported. Investigated materials are Al alloys (AA2124 and AA359) with SiC particulate reinforcements. An AA2124+17% SiCp forged specimen and an AA359+20% SiCp bar, one side of which was submitted to a spark-erosion treatment, were investigated at LLB, Saclay (F) and ILL, Grenoble (F), respectively. In both cases, residual stresses were determined in both the matrix and the reinforcement, in different gauge points. As expected, for both the samples, results show that in each gauge point the main contribution is generally given by thermal microstresses. In the case of the AA359+20% SiCp bar, a slight decrease of the absolute value of residual stresses (tensile in the matrix, compressive in the reinforcement) is found, when approaching the spark-eroded face of the specimen.     

An isotonic trivariate statistical regression method

The present research work outlines the main ideas behind statistical regression by a two-independent-variates and one-dependent-variate model based on the invariance of measures in probabilistic spaces. The principle of probabilistic measure invariance, applied under the assumption that the model be isotonic, leads to a system of differential equations. Such differential system is reformulated in terms of an integral equation that affords an iterative numerical solution. Numerical tests performed on the devised statistical regression procedure illustrate its features.     

Determination of the banned growth promoter moenomycin A in feed stuffs by liquid chromatography coupled to electrospray ion trap mass spectrometry

Flavomycin complex is an antibiotic banned in the European Union as an additive in feed stuffs. As a consequence, the monitoring programmes for official control within the Community require analysis of feeds for possible illegal use of flavomycin. A method for unambiguous identification and quantification of moenomycin A, the main pharmacologically active component of flamomycin complex, in several feeds by liquid chromatography coupled to electrospray ion trap mass spectrometry (LC/ESI‐MS/MS) is herein described for the first time. The method was developed to be used as a confirmative analytical tool for the network of Italian official control laboratories; both the singly and doubly charged molecular ions were observed as precursor ions, from which four product ions were selected for both quantitative analysis and unambiguous identification of moenomycin A. The method was in‐house validated for feeds in the concentration range 0.50–30.0 µg/g, according to the Regulation 882/2004/EC requirements. Mean recoveries ranging between 83.9–94.2% and relative standard deviations <23% account for method trueness and repeatability, respectively. Moreover, other analytical performance parameters, i.e. method specificity, ruggedness, the linearity of detector response, the limit of quantification (LOQ), the limit of detection (LOD), and measurement uncertainty were evaluated and reported. The ion trap LC/ESI‐MS/MS method is highly selective and reliable; high drug recovery, good reproducibility and an LOQ down to 0.10 µg/g guarantee its applicability for confirmatory purposes in the official control activity in Italy. Copyright © 2010 John Wiley & Sons, Ltd.     

Redox-active cyclic bis(cysteinyl)peptides as catalysts for in vitro oxidative protein folding

The active-site hexapeptides of glutaredoxin (Grx), thioredoxin (Trx), protein disulfide isomerase (PDI), and thioredoxin-reductase (Trr) containing the common motif Cys-Xaa-Yaa-Cys were conformationally restricted by backbone cyclization, and their redox potentials were found to increase in the rank order of Trr < Grx < Trx < PDI peptide, with E'(0) values ranging between -204 mV and -130 mV. In each peptide the thiol pK(a) of one Cys residue was found to be lower than the other (e.g., 7.3 against 9.6 in the PDI peptide). Both the yield and rate of refolding of reduced RNase A in the presence of the bis(cysteinyl)peptides increased with the oxidizing character of the cyclic compounds. These results show that small peptides can function as adjuvants for the in vitro oxidative folding of proteins.     

Hyperbranched molecular structures with potential antiviral activity: derivatives of 5,6-dihydroxyindole-2-carboxylic Acid

In the search of new HIV-1 integrase (IN) inhibitors, we synthesized a series of multimeric 5,6-dihydroxyindole-2-carboxylic acid (DHICA) derivatives. Preliminary results indicate that hyperbranched architectures could represent a peculiar molecular requisite for the development of new antiviral lead compounds.