RF Energy Deposition in a Heterogeneous Model of Man: Far-Field Exposures

Distributions of the specific absorption rate (SAR) were measured in a full-scale heterogeneous model of man. The model contained a skeleton, brain, lungs, and muscle. All these tissues had dielectric properties close to those of the respective in vivo properties of actual tissues at the test frequencies. SAR's were measured for exposures in the far field at 160, 350, and 915 MHz for the E and H polarizations. A computer-controlled scanning system and an implantable, minimally perturbing electric field probe were used. The results are also compared with the SAR distributions previously measured in a homogeneous model.     

Essential elements and contaminants in edible tissues of European and American lobsters

In several European countries clawed lobsters, such as the European (Homarus gammarus) and American (H. americanus) ones are widely consumed. Yet, information about essential elements and contaminants in both species is still scarce. Therefore, the aim of this work was to characterise the elemental content in the edible part (muscle, hepatopancreas, gonads and roe) of both homarids and to compare them with the daily intake recommendations and maximum allowed levels. Two techniques were employed: energy-dispersive X-ray fluorescence (EDXRF) to quantify Cl, S, K, Ca, Fe, Cu, Zn, As, Se, Br and Sr; and flame atomic-absorption spectrometry (FAAS) to analyse Na, Mg, Mn, Cd, Hg and Pb. Significant differences were found in the elemental composition of edible tissues of both species, likely reflecting the distinct physiological role of those tissues: muscle (higher: Na, Mg, Ca and Sr; lower: Fe, Se, Cd); hepatopancreas (higher: Fe, Cu, Br and Cd); gonads (lower: Cl, Ca, Zn and Hg); and roe (higher: Na and Br; lower: K and As). Statistical differences in the elemental composition of each tissue were found between both homarids: Muscle (Na, Se, As and Hg); Hepatopancreas (Na, Mg, Fe, Cu, Se, Br and Hg); and gonads (S and Zn). Since the geographical distribution of both species is different, the differences likely reflect distinct elemental composition in the aquatic environment and, consequently in the feed chain. Both lobster species were rich sources of Na, Cl, Cu, Zn and Se for human consumption. Regarding contaminants, only Cd was detected at high concentrations in the hepatopancreas of both homarids. Despite Cd values were well above the maximum allowed level set by the European Commission for crustaceans’ muscle, so far any limit value was set for crustaceans’ hepatopancreas. Nonetheless, the present study recommends avoiding or moderately consuming this tissue in homarids.     

Towards the integration of dark and photo fermentative waste treatment. 1. Hydrogen photoproduction by purple bacterium Rhodobacter capsulatus using potential products of starch fermentation

In this study, the H₂-photoproduction capacity of Rhodobacter capsulatus B10 was measured as a function of variations in the nature and concentration of volatile fatty acids (VFAs) and other products of dark fermentation. When an equimolar mixture of VFAs was provided, C4 substrates (butyrate and isobutyrate) were not consumed until the C2–C3 substrates (acetate, propionate, and lactate) became unavailable, but in order for the cells to produce H₂ at high rates they could not be exposed to severe growth substrate depletion. Among other possible fermentation products, the highest inhibition was observed by the addition of butanol (50% inhibition at 50 mM). The influence of high concentrations of VFAs, phosphate (used to stabilize the pH during dark fermentation) and some heavy metals (known inhibitors of methanogenesis) was also shown. Based on the results, the conditions of fermentation can be manipulated to avoid the inhibition of subsequent H₂ photoproduction by photosynthetic bacteria.     

Synthesis and characterization of carbonaceous replicas of multilayered vesicular siliceous materials

Synthesis of novel, carbon porous replicas of vesicular siliceous materials has been described. The original siliceous materials consist of small, spherical structures resembling onions, known in the literature as multilamellar vesicles (MLVs). They have been characterized with a number of analytical methods that allow one to determine its 3-D structure and basic parameters of the pore system. Carbonaceous materials, made similarly of onion-like porous structures, have been obtained using a standard procedure to form replicas. They have been characterized by the same methods as those applied to the parent materials.     

An IR study of thermally stable V2O5-WO3 -TiO2 SCR catalysts modified with silica and rare-earths (Ce, Tb, Er)

The catalytic activity of silica-free and silica-modified rare earth (Ce, Tb, Er) containing V₂O₅-WO₃ -TiO₂ catalysts in the selective catalytic reduction of NO by ammonia has been investigated as a function of ageing temperatures. The adsorption of ammonia on the catalysts and the behavior of their surface hydroxy groups and of bulk vibrations has also been studied by IR spectroscopy. Rare earths slightly decrease the catalytic activity of catalysts in a fresh state, and this has been attributed to the perturbation, observed by IR, of the vanadyl groups with a likely lowering of their Lewis acidity. However, rare earths (in particular Tb and Er) increase strongly the catalytic activity of catalysts after ageing. Silica only does not seem to have a positive effect on thermal stability and activity when vanadium is present. It has been concluded that rare earths strongly increase the thermal resistance of the catalysts and inhibit rutilization and surface area loss because they do not penetrate the anatase bulk while tend to cover the external surface. In addition the negative action of free vanadium on phase stability is decreased due to formation of rare earth vanadates.     

Surface changes in polyhydroxyalkanoate films during biodegradation and biofouling

BACKGROUND: Despite the recognition that microbial biofilms play a role in environmental degradation of bioplastics, few studies investigate the relationship between bioplastic biodegradation and microbial colonisation. We have developed protocols based on a combination of confocal laser scanning microscopy and contact angle goniometry to qualitatively and quantitatively map surface changes due to biofilm formation and biopolymer degradation of solvent cast poly(3‐hydroxyalkanoate) films in an accelerated in vitro biodegradation system. RESULTS: A significant regression relationship between biofilm formation and polymer biodegradation (R² = 0.96) was primarily conducted by cells loosely attached to the film surfaces (R² = 0.95), rather than the strongly attached biofilm (R² = 0.78). During biodegradation the surface rugosity of poly(3‐hydroxybutyrate) and poly[(3‐hydroxybutyrate)‐co‐(3‐hydroxyvalerate)] increased by factors of 1.5 and 1.76, respectively. In contrast, poly(3‐hydroxyoctanoate) films showed little microbial attachment, negligible weight loss and insignificant changes in surface rugosity. CONCLUSION: A statistically significant link is established between polymer weight loss and biofilm formation. Our results suggest that this degradation is primarily conducted by cells loosely attached to the polymer rather than those strongly attached. Biofilm formation and its type are dependent upon numerous factors; the flat undifferentiated biofilms observed in this study produce a gradual increase in surface rugosity, observed as an increase in waviness. Copyright © 2008 Society of Chemical Industry     

Mechanics of hierarchical materials

In this paper the simplest mathematical model to design nano-bio-inspired hierarchical materials is proposed. Simple formulas describing the dependence of strength, toughness and stiffness on the considered size-scale are derived, taking into account the toughening biomechanisms.     

Ultra-deep oxidative desulfurization of diesel fuel by the Mo/Al2O3-H2O2 system: The effect of system parameters on catalytic activity

This work presents the results obtained in the development of Mo/γ-Al₂O₃ catalysts and their evaluation in the oxidative desulfurization (OD) process of diesel fuel using hydrogen peroxide as the oxidizing reagent. The catalysts were prepared by equilibrium adsorption using several molybdenum precursors and aluminas with different acidity values. They were characterized by Raman spectroscopy. The effect of the reaction time, reaction temperature, nature of solvent, concentration of solvent and hydrogen peroxide, content of molybdenum and phosphate in the catalysts were investigated. The results showed that the activity for sulfur elimination depends mainly on the presence of hepta- and octamolybdates species on the catalyst support and the use of a polar aprotic solvent. Likewise, the presence of phosphate markedly increases the sulfur elimination. In this way, it is possible to reduce sulfur level in diesel fuel from about 320 to less than 10 ppmw at 333 K and atmospheric pressure. Additionally, on the basis of the results obtained a mechanistic proposal for this reaction is described, as an oxidation mechanism by nucleophilic attack of the sulfur atom on peroxo species of hepta- and octamolybdates, but a mechanism involving the singlet oxygen presence can be discarded.     

Polymerisation of styrene using Y, USY and β zeolites as catalysts

The homopolymerisation of styrene is studied in the presence of Y, USY and beta zeolites. High molecular weight polymers, in the range 0.7 × 10⁶–1 × 10⁶, are obtained in good yields. The activity of zeolite beta is only slightly increased by calcination of the as-synthesised material, pointing to an important role of the zeolite outer surface. The influence of the catalyst acidity upon the polymer molecular weight is evaluated by the use of dealuminated zeolites. This revised version was published online in July 2006 with corrections to the Cover Date.