Search results for "leaching"
showing 10 items of 267 documents
Small scale secondary CaCO3 accumulations in selected sections of the European loess belt. Morphological forms and potential for paleoenvironmental r…
1997
Eighteen important Quaternary loess paleosoil sites have been studied across the European loess belt. They included approximately 50 buried soils, the over and/or underlying loess and the present-day surface soils (where possible). From the numerous types of secondary CaCO3 accumulations recognized, only the small scale accumulations are discussed in this paper, including calcified root cells, CaCO3 hypocoatings, needle-fiber calcite, powdery calcite coatings, earthworm biospheroliths, and calcite pseudomorphs on gypsum. Most of the features studied are found in the rhizosphere microecosystem. Each of these features showed a unique relationship with organic matter, micro-organism and plant …
Fungi and Sediments
2000
Fungi are saprophytic organisms that can form lichens in symbiosis with an alga. Along with lichens, they excrete large quantities of organic acids, contributing to rock dissolution and neoformation of crystals, mainly oxalates and carbonates. Fungi contribute to the accumulation of manganese and iron as desert varnish and play a major role in the calcium cycle inside calcretes and carbonate soils in arid zones. Fungi constitute an important part of calcified filaments found in calcretes. They are covered with calcium oxalate crystals, which can transform into calcite during early diagenesis. They can also precipitate needle-fiber calcite, a common form of CaCO3 found in soils and calcretes…
Unraveling In vivo brain transport of protein‐coated fluorescent nanodiamonds
2019
The blood–brain barrier is the biggest hurdle to overcome for the treatment of neurological disorders. Here, protein‐coated nanodiamonds are delivered to the brain and taken up by neurovascular unit cells after intravenous injection. Thus, for the first time, nanodiamonds with their unique properties and a flexible protein coating for the attachment of therapeutics emerge as a potential platform for nanotheranostics of neurological disorders.Nanotheranostics, combining diagnostics and therapy, has the potential to revolutionize treatment of neurological disorders. But one of the major obstacles for treating central nervous system diseases is the blood–brain barrier (BBB) preventing systemic…
MOLECULAR BASIS OF DRUG PHOTOTOXICITY: PHOTOSENSITIZED CELL DAMAGE BY THE MAJOR PHOTOPRODUCT OF TIAPROFENIC ACID
1994
Tiaprofenic acid is a photosensitizing nonsteroidal anti-inflammatory drug, whose major photoproduct (decarboxytiaprofenic acid) is also a potent photosensitizer. Because of the lack of the carboxylate moiety, this photoproduct is more lipophilic and might bind more efficiently to cell membranes, thereby causing phototoxic damage. To verify the feasibility of this hypothesis, we have prepared the 3H-labeled analogs of tiaprofenic acid and its photoproduct and examined the binding, persistence and phototoxicity of the photoproduct using poorly metabolizing (fibroblasts) and actively metabolizing cells (hepatocytes). The photoproduct of tiaprofenic acid accumulates in both cell types as it is…
Evaluation of the effect of home bleaching agents on surface microhardness of different glass-ionomer cements containing hydroxyapatite
2017
Background Home bleaching agents may exert some negative effects on surface hardness of restorative materials such as glass-ionomer cements (GICs). Since some studies have shown that some components such as hydroxyapatite (HA), as a bioactive glass, can improve the mechanical properties of dental materials, the effect of bleaching agents on surface hardness of GICs containing hydroxyapatite is questionable. This study was designed to evaluate the effect of home bleaching agents on the surface hardness of two different commercially available GICs containing hydroxyapatite. Material and methods 80 disk-shaped specimens were made from two different GICs, including resin modified glass-ionomer …
On the physico-chemical evolution of low-pH and CEM I cement pastes interacting with Callovo-Oxfordian pore water under its in situ CO2 partial press…
2014
International audience; Abstract Within the framework of geological repositories for radioactive waste, structural concretes must be adapted to the underground chemical conditions. CEM I cement-based materials are characterised by high pH that may produce an alkaline plume in the near-field of the repository. In order to avoid this problem, low-pH cements have been designed. This study compares the physico-chemical behaviour of a low-pH material with a CEM I cement paste, both being subjected to leaching by an aqueous solution. An original experimental setup was designed to reproduce the underground conditions using a specific CO2 regulation device. Under these conditions, the low-pH materi…
Contrasting evolution of iron phase composition in soils exposed to redox fluctuations
2018
Abstract Ferric iron (FeIII) solid phases serve many functions in soils and sediments, which include providing sorption sites for soil organic matter, nutrients, and pollutants. The reactivity of Fe solid phases depends on the mineral structure, including the overall crystallinity. In redox-active soils and sediments, repeated reductive dissolution with subsequent exposure to aqueous ferrous iron (Fe2+) and oxidative re-precipitation can alter Fe phase crystallinity and reactivity. However, the trajectory of Fe mineral transformation under redox fluctuations is unclear and has been reported to result in both increases and decreases in Fe phase crystallinity. Several factors such as water bu…
Heterogeneous vs Homogeneous Palladium Catalysts for Cross-Coupling Reactions
2012
A large number of immobilized-Pd-catalysts for cross-coupling reactions have been introduced in the last decade. Are the observed catalyzed reactions truly heterogeneous or are they homogeneous due to leached palladium? This account critically addresses the leaching issue by selectively referring to some of the newly developed catalytic systems in an attempt to evaluate said systems based on uniform criteria. The report is concluded by identifying the relevant chemical and structural challenges in the field.
Structural and Functional Analysis of the Antiparallel Strands in the Lumenal Loop of the Major Light-harvesting Chlorophyll a/b Complex of Photosyst…
2007
The light-harvesting chlorophyll a/b-binding protein of photosystem II (LHCIIb) fulfills multiple functions, such as light harvesting and energy dissipation under different illuminations. The crystal structure of LHCIIb at the near atomic resolution reveals an antiparallel strands structure in the lumenal loop between the transmembrane helices B/C. To study the structural and functional significances of this structure, three amino acids (Val-119, His-120, and Ser-123) in this region have been exchanged to Phe, Leu, and Gly, respectively, and the influence of the mutagenesis on the structure and function of LHCIIb has been investigated. The results are as follows. 1) Circular dichroism spect…
Chromium liquid waste inertization in an inorganic alkali activated matrix: Leaching and NMR multinuclear approach
2015
A class of inorganic binders, also known as geopolymers, can be obtained by alkali activation of aluminosilicate powders at room temperature. The process is affected by many parameters (curing time, curing temperature, relative humidity etc.) and leads to a resistant matrix usable for inertization of hazardous waste. In this study an industrial liquid waste containing a high amount of chromium (≈ 2.3 wt%) in the form of metalorganic salts is inertized into a metakaolin based geopolymer matrix. One of the innovative aspects is the exploitation of the water contained in the waste for the geopolymerization process. This avoided any drying treatment, a common step in the management of liquid ha…