Oxidation Control of Atmospheric Plasma Sprayed FeAl Intermetallic Coatings Using Dry-Ice Blasting

The performance of atmospheric plasma sprayed FeAl coatings has been remarkably limited because of oxidation and phase transformation during the high-temperature process of preparation. In the present work, FeAl intermetallic coatings were prepared by atmospheric plasma spraying combined with dry-ice blasting. The microstructure, oxidation, porosity, and surface roughness of FeAl intermetallic coatings were investigated. The results show that a denser FeAl coating with a lower content of oxide and lower degree of phase transformation can be achieved because of the cryogenic, the cleaning, and the mechanical effects of dry-ice blasting. The surface roughness value decreased, and the adhesive strength of FeAl coating increased after the application of dry-ice blasting during the atmospheric plasma spraying process. Moreover, the microhardness of the FeAl coating increased by 72%, due to the lower porosity and higher dislocation density.     

Rheological characterization of starch derivatives/polycaprolactone blends processed by reactive extrusion

Linear viscoelastic, steady shear behaviors, and morphologies of starch formate/poly(ε-caprolactone) (PCL) blends, compatibilized by oligomers and obtained by reactive extrusion, have been investigated as a function of formic acid (FA)/starch ratio, nature, and molecular weight of the oligomer. The rheological properties of these blends have been compared with those of a commercial starch-based thermoplastic, namely Mater-Bi® ZF03UA. In presence of FA, starch is destructured to starch formate and oligomers are used as plasticizers. The linear viscoelastic response of blends is quite similar to that of nanocomposite materials: the low frequency behavior is attributed to a percolated network of destructured starch particles, and the high frequency behavior is that of the polymer matrix. The viscosity curve presents a profile characterized by two plateau regions, at low and high shear rates. The plateau region at low shear rates corresponds to the viscous response of the blend while that observed at high shear rates can be attributed to the PCL matrix. The compatibilization is enhanced in the presence of starch formate and increases with increasing the oligomer molecular weight. The use of PCL oligomer was shown to improve this compatibilization effect. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Rheological behaviour of cement and silica suspensions: Particle aggregation modelling

Cement and silica suspension rheological behaviour is modelled by supposing that particle aggregation occurs. With two independent parameters, the variation of the shear viscosity as a function of the shear rate for cement or silica suspensions having different solid volume fractions can be predicted. The model is in good agreement with experimental data. Cement suspensions are initially very similar to unreactive silica suspensions. The values of adhesion forces obtained seem to show that the effective interaction areas are very small. It reflects the fact that in the dormant period the particles are contacting at points, which become progressively higher in surface as C-S-H precipitates at these contacts. The model used is consistent with the observed power law variation of static and dynamic yield stresses with solid volume fraction. The aggregates formed under shear seem to be very compact, which is presumably related to the large solid volume fractions of the studied suspensions.     

Mass spectrometry-based metabolomics: accelerating the characterization of discriminating signals by combining statistical correlations and ultrahigh resolution

A strategy combining autocorrelation matrices and ultrahigh resolution mass spectrometry (MS) was developed to optimize the characterization of discriminating ions highlighted by metabolomics. As an example, urine samples from rats treated with phenobarbital (PB) were analyzed by ultrahigh-pressure chromatography with two different eluting conditions coupled to time-of-flight mass spectrometric detection in both the positive and negative electrospray ionization modes. Multivariate data analyses were performed to highlight discriminating variables from several thousand detected signals: a few hundred signals were found to be affected by PB, whereas a few tenths of them were linked to its metabolism. Autocorrelation matrices were then applied to eliminate adduct and fragment ions. Finally, the characterization of the ions of interest was performed with ultrahigh-resolution mass spectrometry and sequential MS(n) experiments, by using a LC-LTQ-Orbitrap system. The use of different eluting conditions was shown to drastically impact on the chromatographic retention and ionization of compounds, thus providing a way to obtain more exhaustive metabolic fingerprints, whereas autocorrelation matrices allowed one to focus the identification work on the most relevant ions. By using such an approach, 14 PB metabolites were characterized in rat urines, some of which have not been reported in the literature.     

Transferring the calibration of direct solar irradiance to diffuse-sky radiance measurements for CIMEL Sun-sky radiometers

Two types of sunphotometric measurement are considered in this study: direct-Sun irradiance and diffuse-sky radiance. Based on CIMEL CE318 Sun-sky radiometer characteristics, we introduce a gain-corrected solid angle that allows interconverting calibration coefficients of these two types of measurement, thus realizing a "vicarious" radiance calibration. The accuracy of the gain-corrected solid angle depends on the number of available historical calibration records. The method is easy to use, provided that at least one laboratory calibration has been made previously. Examples coming from three distinct CE318 versions belonging to the AERONET/PHOTONS network are presented to provide details on the vicarious calibration method and protocols. From the error propagation analysis and the comparison with laboratory results, the uncertainty of the vicarious radiance calibration is shown to be comparable with the laboratory one, e.g., 3%-5%.     

Enantioselective Organocatalytic Michael Addition of Cyclobutanones to Nitroalkenes

Synthetic applications of cyclobutanones other than ring expansion and fragmentation reactions are rare. Herein, highly efficient diastereo‐ and enantioselective organocatalytic Michael additions of 2‐substituted cyclobutanone derivatives to nitroalkenes are reported allowing the stereocontrolled creation of ‘all‐carbon’ quaternary centers. The approach relies on both the use of Brønsted base/hydrogen‐bond donor bifunctional organocatalysts, and importantly, the specific stabilization and activation of cyclobutanone with a secondary amide moiety. The reaction was found to nicely accommodate a broad scope of substrates, allowing the control of up to three contiguous stereogenic centers. This work has opened new synthetic opportunities.     

Use of a continuous leaching method to assess the oral bioaccessibility of trace elements in seafood

A continuous leaching method, coupled online with inductively coupled plasma mass spectrometry (ICP-MS) was used on seafood samples to assess the maximum bioaccessibility of several trace elements. The method indeed involves continuous leaching of the food sample by artificial saliva and gastric juice, successively, where this exposition of the food to fresh reagent drives the dissolution equilibrium to the right. Leaching with intestinal juice had to be omitted because it resulted in clogging problems. The experimental apparatus includes a mini-column of powdered sample, which is directly connected to the nebulizer of an ICP-MS instrument. The on-line approach allows a quick assessment of the maximum bioaccessibility of elements of interest by monitoring the real-time release of elements by a given reagent. The method was applied to determine the bioaccessibility of four toxic elements (Al, Cd, Hg, and Pb) and of four essential elements (V, Mn, Cu, and Zn) in certified reference materials and in actual seafood samples. In all cases, mass balance was verified by carrying out the total digestion of the remaining residue from the mini-column and the relationship between total concentration and bioaccessibility was examined.     

Adhesion of human pathogenic enteric viruses and surrogate viruses to inert and vegetal food surfaces

Enteric viruses, particularly human Noroviruses (NoV) and hepatitis A virus (HAV), are key food-borne pathogens. The attachment of these pathogens to foodstuff and food-contact surfaces is an important mechanism in the human contamination process. Studies were done to investigate the nature of the physicochemical forces, such as hydrophobic and electrostatic ones, involved in the interaction virus/matrix but, at this day, only few data are available concerning surface properties of viruses and prediction of the adhesion capacity of one specific virus onto matrices is still very difficult. The purpose of this study was to propose a reference system, including a representative virus surrogate, able to predict as close as possible behaviour of pathogenic viruses in term of adhesion on inert (stainless steel and polypropylene) and food surfaces (lettuce leaves, strawberries and raspberries). The adhesion of human pathogenic enteric viruses, cultivable strain of HAV and non-cultivable strains of human NoV (genogroups I and II), have been quantified and compared to these of human enteric viruses surrogates, included the MNV-1 and three F-specific RNA bacteriophages (MS2, GA and Qβ). A standardized approach was developed to assess and quantify viral adhesion on tested matrices after a contact time with each virus using real-time RT-PCR. Methods used for virus recovery were in accordance with the CEN recommendations, including a bovine Enterovirus type 1 as control to monitor the efficiency of the extraction process and amplification procedure from directly extracted or eluted samples. The adhesion of human pathogenic viruses, ranging from 0.1 to 2%, could be comparable for all matrices studied, except for NoV GII on soft fruits. Adhesion percentages obtained for the studied surrogate virus and phages were shown to be comparable to those of HAV and NoV on inert and lettuce surfaces. The MNV-1 appeared as the best candidate to simulate adhesion phenomena of all human pathogenic enteric viruses on all studied surfaces, while MS2 and GA bacteriophages could be a good alternative as model of viral adhesion on inert and lettuce surfaces. These results will be usable to design relevant experimental systems integrating adhesion behaviour of enteric viruses in the assessment of the efficiency of a technological or hygienic industrial process.