Search results for "Complex."
showing 10 items of 5824 documents
DFT computational study on Fe(III)-N,N′-ethylene-bis(salicylideneiminato) derivatives
2005
DFT calculations, at unrestricted B3LYP level, have been performed on the structures of three iron(III) complexes, Fe(Salen)Cl, [Fe(Salen)]+ and [Fe(Salen)OH2]+, where Salen is the anion of Schiff base ligand N,N′-ethylene-bis (salicylideneimine), considering the spin multiplicity (S) values 2, 4 and 6. The results obtained have been compared with the available structural an magnetic experimental data, allowing us to conclude that a stable form of the FeIII(Salen) complex in aqueous solution should be characterized by an energy stabilization of the S=4 compared to the S=6 state.
Uranium(VI) sequestration by polyacrylic and fulvic acids in aqueous solution
2011
Stability data on the formation of dioxouranium(VI) species with polyacrylic (PAA) and fulvic acids (FA) are reported with the aim to define quantitatively the sequestering capacity of these high molecular weight synthetic and naturally occurring ligands toward uranium(VI), in aqueous solution. Investigations were carried out at t = 25 °C in NaCl medium at different ionic strengths and in absence of supporting electrolyte for uranyl–fulvate (\( {{\text{UO}}_{2}}^{2+} \)–FA) and uranyl–polyacrylate (\( {{\text{UO}}_{ 2}}^{ 2+ } \)–PAA, PAA MW 2 kDa) systems, respectively. The experimental data are consistent with the following speciation models for the two systems investigated: (i) UO2(FA1),…
Ti(iv)-amino triphenolate complexes as effective catalysts for sulfoxidation
2010
C 3 -symmetric Ti (IV) amino triphenolate complexes efficiently catalyze, without previous activation and in excellent yields, the oxidation of sulfides at room temperature, using both CHP and the more environment friendly aqueous hydrogen peroxide as terminal oxidants, with catalyst loadings down to 0.01%. The Ti(IV) catalysts and the intermediate Ti(IV)-peroxo complexes have been characterized in solution by 1H NMR and ESI-MS techniques and via density functional studies.
Experimental virus evolution reveals a role of plant microtubule dynamics and TORTIFOLIA1/SPIRAL2 in RNA trafficking.
2014
1 tabla y 2 figuras
Complete Hemocyanin Subunit Sequences of the Hunting SpiderCupiennius salei
2002
Hemocyanins are large copper-containing respiratory proteins found in many arthropod species. Scorpions and orthognath spiders possess a highly conserved 4 x 6-mer hemocyanin that consists of at least seven distinct subunit types (termed a to g). However, many "modern" entelegyne spiders such as Cupiennius salei differ from the standard arachnid scheme and have 2 x 6-mer hemocyanins. Here we report the complete primary structure of the 2 x 6-mer hemocyanin of C. salei as deduced from cDNA sequencing, gel electrophoresis, and matrix-assisted laser desorption spectroscopy. Six distinct subunit types (1 through 6) and three additional allelic sequences were identified. Each 1 x 6-mer half-mole…
Halloysite Nanotubes Loaded with Calcium Hydroxide: Alkaline Fillers for the Deacidification of Waterlogged Archeological Woods
2018
A novel green protocol for the deacidifying consolidation of waterlogged archaeological woods through aqueous dispersions of polyethylene glycol (PEG) 1500 and halloysite nanotubes containing calcium hydroxide has been designed. First, we prepared functionalized halloysite nanotubes filled with Ca(OH)2 in their lumen. The controlled and sustained release of Ca(OH)2 from the halloysite lumen extended its neutralization action over time, allowing the development of a long-term deacidification of the wood samples. A preliminary thermomechanical characterization of clay/polymer nanocomposites allows us to determine the experimental conditions to maximize the consolidation efficiency of the wood…
Machine learning for rapid mapping of archaeological structures made of dry stones – Example of burial monuments from the Khirgisuur culture, Mongoli…
2020
11 pages; International audience; The present study proposes a workflow to extract from orthomosaics the enormous amount of dry stones used by past societies to construct funeral complexes in the Mongolian steppes. Several different machine learning algorithms for binary pixel classification (i.e. stone vs non-stone) were evaluated. Input features were extracted from high-resolution orthomosaics and digital elevation models (both derived from aerial imaging). Comparative analysis used two colour spaces (RGB and HSV), texture features (contrast, homogeneity and entropy raster maps), and the topographic position index, combined with nine supervised learning algorithms (nearest centroid, naive…
Social differentiation and land use at an Early Iron Age “princely seat”: bioarchaeological investigations at the Glauberg (Germany)
2014
Excavations at the late Hallstatt/early La Tene (6th–4th century BC) “princely seat” of the Glauberg (Hesse, Germany) revealed exceptionally furnished graves in monumental mounds, simple inhumations in associated ditches and non-normative burials of up to eight individuals in conical storage pits. The study presented here addresses bioarchaeological characteristics of these burials and their implications for social differentiation and the sphere of influence of the “princely seat”. It includes osteological, aDNA, and multi-isotope analyses of 27 human individuals and faunal remains. One of the outstandingly rich graves (tumulus 1/grave 1) contained the skeleton of a young man (the “prince”)…
Ivory in the Chalcolithic enclosure of Perdigões (South Portugal): the social role of an exotic raw material
2015
AbstractThis article discusses the social role played by ivory and ivory articles in the Perdigoes enclosures (South Portugal) during the Chalcolithic (third millennium bc), in the context of the emergence and development of social complexity on the Iberian Peninsula. Perdigoes is a Portuguese prehistoric site with some of the highest concentrations of ivory objects known in Iberia and with the greatest variety. The contexts, almost exclusively funerary, are discussed along with the results of provenance studies. Comparing the different contexts and the categories of objects made of ivory makes it possible to distinguishing a variety of active social dimensions (such as individual status, g…
Preservation of fungi in archaeological charcoal
2010
During the analysis of wood charcoal remains from archaeological sites, it is common to find different microorganisms and different forms of degradation present in the plant tissue. However, one may encounter difficulties when attempting to identify these microorganisms and determine when their attack occurred. This paper focuses on preservation aspects related to the microorganisms in wood and demonstrates the structural changes that take place in different types of decayed wood after it was converted into charcoal. The study seeks to determine whether the microbial attack found in archaeological woods took place before the burning of the wood or after. Burning experiments were conducted u…