Three characterization techniques coupled with adsorption for studying the nanoporosity of supported films and membranes

Three characterization techniques are described for studying the open nanoporosity, i.e. the open free volume, the microporosity, the mesoporosity and the thickness variation of thin deposited films during gas adsorption and condensation. They are all based on the coupling of the sorption of a probe gaseous molecule at room temperature and a physical characterization tool of thin deposited films: the quartz crystal microbalance, ellipsometry and X-ray reflectometry, giving the mass uptake, the refractive index variation and the electronic density variation, respectively, of the film due to the adsorbate intrusion inside the open free volume and pores. The film thickness evolution during the sorption can also be followed by the two last techniques. These techniques are complementary because each one can bring specific properties and can validate the results of another one. Both static and dynamic measurements can be carried out to characterize the porosity, the contraction or the swelling of the film and the penetration rate of the gas.     

Determination of platinum in blood by adsorptive voltammetry

This work describes a sensitive method for the determination of platinum in blood, which can be used for determining the natural levels of platinum in human blood, for monitoring patients treated with platinum cytotoxic drugs, and for monitoring occupational exposure to these drugs and other platinum compounds. The method involves dry ashing of blood samples in a muffle furnace and determination of platinum by adsorptive voltammetric (AV) measurement of the catalytic reduction of protons by the platinum-formazone complex. The detection limit for a 100-microL sample of blood is 0.017 micrograms/L, with a recovery of 94% and a relative standard deviation of 7% at a platinum level of 1 microgram/L. By using this method, the natural levels of platinum in human blood were found to be in the range 0.1-2.8 micrograms/L (median = 0.6 micrograms/L). These results were verified by inductively coupled plasma mass spectrometry (ICP-MS) with blood prepared by wet ashing and using gold as an internal standard.     

Metabolomics to Decipher the Chemical Defense of Cereals against Fusarium graminearum and Deoxynivalenol Accumulation

Fusarium graminearum is the causal agent of Fusarium head blight (FHB) and Gibberella ear rot (GER), two devastating diseases of wheat, barley, and maize. Furthermore, F. graminearum species can produce type B trichothecene mycotoxins that accumulate in grains. Use of FHB and GER resistant cultivars is one of the most promising strategies to reduce damage induced by F. graminearum. Combined with genetic approaches, metabolomic ones can provide powerful opportunities for plant breeding through the identification of resistant biomarker metabolites which have the advantage of integrating the genetic background and the influence of the environment. In the past decade, several metabolomics attempts have been made to decipher the chemical defense that cereals employ to counteract F. graminearum. By covering the major classes of metabolites that have been highlighted and addressing their potential role, this review demonstrates the complex and integrated network of events that cereals can orchestrate to resist to F. graminearum.     

Volume of fluid method for interfacial reactive mass transfer: Application to stable liquid film

A volume of fluid method is developed in order to simulate reactive mass transfer in two-phase flows and is applied to study reactive laminar liquid film. The thermodynamic equilibrium of chemical species at the interface is considered using Henry's law. The chemical species concentration equation is solved using primitive variables and local fluxes are locally directly calculated at the interface. The present treatment of jump discontinuity of chemical concentration is consistent with a volume of fluid approach and the difficulty to calculate accurate local mass flux across interface is overcome. For plane interface, the precision of the numerical simulation is found to be very satisfactory while for curved interface a special procedure has been developed to reduce the development of spurious fluxes at the interface. The algorithm is validated for different cases by comparison with available solutions. The method is then applied to study non-reactive and reactive mass transfer in a falling liquid film. The results show that the liquid side mass transfer is well predicted by the Higbie (1935) theory when the transfer is controlled by the film advection provided that adequate parameters are considered, i.e. the actual velocity at interface and not the average liquid film velocity. For situations controlled by diffusion, the Sherwood number tends to a constant value characteristic of purely diffusive situations. For the reactive mass transfer, first and second order irreversible chemical reactions in the liquid phase are considered. The numerical results are compared respectively, with Danckwerts (1970) and Brian et al. (1961) solutions and good agreement is observed. The proposed Volume of Fluid method is shown to be well adapted to deal with interfacial reactive mass transfer problems.     

SiOC Ceramic Monoliths with Hierarchical Porosity

SiOC glass monoliths possessing hierarchical porosity were produced by a one-pot processing method. Periodic mesoporous organosilica (PMO) particles were embedded into a foamed siloxane preceramic polymer. After pyrolysis at 1000°C in inert atmosphere, open celled, permeable SiOC ceramic monoliths with a high amount of pores, ranging in size from hundred of micrometers to a few nanometers, were obtained. The components possessed a specific surface area of 137 m²/g, indicating the retention of most of the mesopores after the pyrolytic conversion of the PMO precursor particles. These fillers converted to truncated rhombic dodecahedral SiOC mesoporous micron-sized grains, homogeneously distributed throughout the SiOC cellular matrix. The produced porous ceramics possessed compression strength of about 1.7 MPa, which is adequate for their use in several engineering applications.     

Correlated changes in skeletal muscle connective tissue and flesh texture during starvation and re‐feeding in brown trout (Salmo trutta) reared in seawater

Quantitative and qualitative changes to muscle and collagen were analysed following starvation and re‐feeding of brown trout (Salmo trutta) reared in seawater. Fish were submitted to starvation for 2 months followed by re‐feeding for 1 month and compared with a control group continuously fed. Classical effects of starvation on growth and morphometrics traits were observed with only a partial recovery of these parameters after 1 month of re‐feeding. Muscle composition of starved fish was significantly affected (lower dry matter content and higher post‐mortem pH) compared with control fish and was partially recovered in re‐fed fish compared with continuously fed fish. Muscle structure and composition were affected with thinner muscle fibre and higher connective tissue content for the starved fish but similar thickness of myosepta compared with the control group. No difference was observed after 1 month of re‐feeding. Characteristics of the connective tissue were significantly affected by starvation (more high weight molecular collagen form, higher thermal stability of skin collagen). These differences remained significant after the re‐feeding period. Starved fish showed also higher mechanical resistance of the raw flesh compared with the control group, but no difference in rheological measurements was observed after 1 month of re‐feeding. The changes in texture and their relationships with muscle composition, muscle structure and collagen characteristics are discussed. Copyright © 2004 Society of Chemical Industry     

Naturally occurring phenolic compounds as promising antimycotoxin agents: Where are we now?

Mycotoxins are metabolites produced by molds that contaminate food commodities, are harmful to both humans and animals, as well as cause economic losses. Many countries have set regulatory limits and strict thresholds to control the level of mycotoxins in food and feedstuffs. New technologies and strategies have been developed to inhibit toxigenic fungal invasion and to decontaminate mycotoxins. However, many of these strategies do not sufficiently detoxify mycotoxins and leave residual toxic by-products. This review focuses on the use of phenolic compounds obtained from botanical extracts as promising bioagents to inhibit fungal growth and/or to limit mycotoxin yields. The mechanism of these botanicals, legislation concerning their use, and their safety are also discussed. In addition, recent strategies to overcome stability and solubility constraints of phenolic compounds to be used in food and feed stuffs are also mentioned.     

Studies of the pulse charge of lead-acid batteries for photovoltaic applications: Part IV. Pulse charge of the negative plate

The paper discusses the influence of the state of charge and pulse charge frequency on the mechanism of the lead-acid battery recharge with pulse current. The data from the pulse charge transients of the negative plate potential at various frequencies show that a decrease of the pulse charge frequency keeping constant average pulse current can impede the charge reaction leading to earlier start of the hydrogen evolution reaction. The dependence of the electrochemical double layer (EDL) capacitance on the state of charge was estimated both during the charge and the discharge using electrochemical impedance spectroscopy measurements at open circuit, followed by equivalent circuit modelling. These data were used to derive the dependence of the average double layer current on SOC and pulse charge frequency. The results show that in the end of the charge almost all of the charge proceeds with the participation of EDL in a certain pulse frequency domain. Using the data from the impedance measurements the optimal pulse charge frequencies were predicted, considering the existence of “electrochemical resonance”. The latter appears when the pulse charge frequency approaches the characteristic frequency of the Pb electrodeposition process, given by the product between EDL capacitance and the charge transfer resistance.     

SIMULTANEOUS GC/MS ANALYSIS OF POLYCYCLIC AROMATIC HYDROCARBONS AND THEIR NITRATED DERIVATIVES IN ATMOSPHERIC PARTICULATE MATTER FROM WORKPLACES

Abstract

PAH are routinely analyzed using HPLC/FD. This technique is unsuitable for analyzing NPAH. This study aims at developing a reliable method, using GC/MS, and applying this technique to actual samples from small volumes of atmospheric particulate matter from workplaces. Mixtures of PAH and NPAH were separated by GC/MS and detected by electronic impact (EI) or negative ion chemical ionization (NICI). Analyses on twelve actual samples were thus carried out by sampling a small volume of atmosphere (≈0.5 m ³ ) from five different industrial workplaces. Samples displayed wide differences from one industrial workplace to another, and this can be explained by the specific methods applied. The PAH and NPAH concentrations also varied with time in the same industrial workplace. NPAH concentrations were not correlated with PAH concentrations, underscoring the complex chemical mechanisms involved in NPAH formation. PAH and NPAH formation appeared to be dependent on both industrial activities and uncontrolled physicochemical conditions.     

Binary integer programming formulations for scheduling in market-driven foundries

This paper describes the development and solution of binary integer formulations for production scheduling problems in market-driven foundries. This industrial sector is comprised of small and mid-sized companies with little or no automation, working with diversified production, involving several different metal alloy specifications in small tailor-made product lots. The characteristics and constraints involved in a typical production environment at these industries challenge the formulation of mathematical programming models that can be computationally solved when considering real applications. However, despite the interest on the part of these industries in counting on effective methods for production scheduling, there are few studies available on the subject. The computational tests prove the robustness and feasibility of proposed models in situations analogous to those found in production scheduling at the analyzed industrial sector.