Decomposition of hexamethylcyclotrisiloxane over solid oxides

The decomposition of hexamethylcyclotrisiloxane (HMCTS) has been studied at room temperature and in the range 473-673 K over the surface of basic (CaO, MgO) and acidic oxides (Al(2)O(3), SiO(2)). Alumina allows the complete removal of HMCTS from synthetic biogases at 673 K. A reactive adsorption occurs with surface silication and release of methane. The adsorption capacity of our alumina adsorbent (180 m(2) g(-1)), until saturation, at 673 K, is 0.31 g((HMCTS))g((Al2O3))(-1), which corresponds to one silicon atom per 9 A(2), i.e. the silication monolayer capacity. On the contrary, silica, which is an excellent adsorbent for siloxanes at room temperature, looses its adsorption ability at high temperature as it is typical of a molecular adsorption behavior. Basic oxides such as MgO and CaO have strong reactivity in decomposing siloxanes in the absence of CO(2), but loose reactivity when in contact with carbon dioxide because of surface carbonation.     

Levels and congener profiles of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans and dioxin-like polychlorinated biphenyls in cow’s milk collected in Campania, Italy

Polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs) and certain dioxin-like polychlorinated biphenyls (dl-PCBs) are a family of chemically-related lipophilic compounds characterized by similar toxicity. Due to their properties they are universally distributed in the environment and classified as persistent organic pollutants (POPs). From most of studies carried out to evaluate human dietary intake, milk and dairy products result as a major contributors of PCDD/Fs uptake. Of course the main source of milk contamination is animal feeds. Lactating ruminants, cows included, transfer these compounds to the food chain by ingestion of contaminated vegetables or soil. Their resistance to degradation and a high lipophilicity means that PCDD/Fs and dl-PCBs may be accumulated into fat tissues from which they are transferred to milk during lactation period.Seventy-nine cows milk samples, collected in the monitoring plan 2008, were analyzed for PCDD/Fs and dl-PCBs. Eleven milk samples were non-compliant corresponding to five breeding livestock located in Caserta province. The distribution of PCDD/Fs and dl-PCBs congeners in these samples was examined in order to determine the likely sources of dioxins. The results show that the congener profile is characterized by a prevalence of PCDFs in respect of PCDDs, that represents the typical pattern of thermal origin contamination.     

Prenatal ultrasound diagnosis of a case of Pfeiffer syndrome without cloverleaf skull and review of the literature

Pfeiffer syndrome is characterized by bilateral coronal craniosynostosis, midface hypoplasia, beaked nasal tip, broad and medially deviated thumbs and great toes. Originally, it was described in eight persons from three generations in a pedigree consistent with an autosomal dominant transmission. Since then, several reports have documented its high clinical and genetic heterogeneity. The condition is usually detected in the newborn period or later, and very few prenatal ultrasound diagnoses have been reported. We present a case of Pfeiffer syndrome prenatally diagnosed at 20 weeks' gestation, in which the sonographic features of craniosynostosis, hypertelorism associated with an extreme proptosis, and broad thumb led to the diagnosis, confirmed after termination of pregnancy by dysmorphological, pathological and radiological evaluation. DNA analysis of the fibroblast growth factor receptor 2 (FGFR2) showed a missense mutation consisting in a transversion G → C at nucleotide 870. This led to a Trp290Cys amino acidic substitution. We discuss the relevant findings of our and previously published cases. Our report demonstrates that a careful sonographic examination can lead to an early prenatal diagnosis of Pfeiffer syndrome also in cases without cloverleaf skull. Copyright © 2004 John Wiley & Sons, Ltd.     

Regional patterns and controls of biomass in semiarid woodlands: lessons from the Northern Argentina Dry Chaco

Land use change, particularly in forested ecosystems, has a direct impact on the global carbon cycle. Consequently, the regional assessment of biomass and the understanding of its current spatial controls are research priorities for regional ecology and land use. Field data and satellite imagery were combined here to map woodlands and estimate their above-ground biomass (AGB) in the Dry Chaco ecoregion of northern Argentina. Allometric equations were used to derive AGB from diameter at breast height data collected at 50 samples during 2007. In order to generate the AGB regional map, this information was later associated with MODIS-Terra spectral data (NDVI) using the Random Forest (RF) method. Finally, AGB spatial patterns were associated with potential biophysical and human controlling factors through correlation and regression analyses. Results indicate that the use of RF and NDVI of the dry season derived from MODIS-Terra was suitable to map regional AGB, what makes this methodology applicable to other dry woodlands. The RF model used to map AGB showed a mean deviation of 2.9 % and a precision of 15 % for one prediction. At this regional scale of analysis, biophysical rather than human factors controlled AGB spatial patterns, in part because the region includes a wide range of environmental situations. Warmer conditions showed a higher biomass, suggesting an energetic limitation for AGB accumulation. However, human controls (distance to towns, cultivation, and roads) also conditioned AGB patterns, suggesting lower AGB values near cultivated areas. The relation between AGB and water availability was surprisingly weak, but partially obscured by the land use history and degradation due to extensive cattle ranching. We propose that a combination of environmental factor and land use affects the AGB regional patterns and promotes unexpected relationships with environmental factors. This work represents the first spatially explicit AGB (patterns and controls) analysis for an extensive subtropical dry woodland area (113,000 km²) and shows how biophysical and human factors co-control regional patterns.