Search results for "complex"
showing 10 items of 5889 documents
Covalently modified nanoclays: synthesis, properties and applications
2020
Abstract Clay minerals are phyllosilicates of nanoscale dimensions. According to their ability to entrap and release organic moieties, they have found applications in several fields, such as drug carrier and delivery, support for catalyst, environmental remediation and filler for polymeric matrices. The possibility to modify, by covalent linkage, their surfaces gives the possibility to form new nanomaterials with improved properties respect to the pristine clay minerals. In this chapter, the modifications of the siloxane surfaces of the most representative clay minerals, namely montmorillonite, sepiolites, laponite and halloysite were reviewed and discussed.
Microstructure Characteristics of Unsaturated Compacted Scaly Clay
2012
Microstructure characteristics of unsaturated compacted scaly clay are investigated by MIP tests on freeze dried samples and observation of SEM photomicrographs. Effects of scale microstructure and increasing compaction stresses, and microstructure changes induced by loading and unloading paths and clay saturation are analysed.
Calcium silicate hydrates: Solid and liquid phase composition
2015
© 2015 Elsevier Ltd. This paper presents a review on the relationship between the composition the structure and the solution in which calcium silicate hydrate (C S H) is equilibrated. The silica chain length in C S H increases with the silicon concentration and the calcium content in the interlayer space with the calcium concentrations. Sodium and potassium are taken up in the interlayer space preferentially at low calcium concentrations and thus by low Ca/Si C S H. Aluminium uptake in C S H increases strongly at higher aluminium concentrations in the solution. At low Ca/Si aluminium substitutes silica in the bridging position at Ca/Si. > 1 aluminium is bound in TAH. Recently developed ther…
Accelerated Light-Induced Defect Transformation Study of Elkem Solar Grade Silicon
2012
AbstractSolar cells made of silicon feedstock from a metallurgical route must qualify not only the initial efficiency, but must also be comparable to the solar cells made from reference polysilicon on the spectral response after light induced degradation. A detailed comparative study of light induced defects and its impact on cell performance is necessary for both materials. We have studied accelerated light induced degradation (ALID) defect transformation for Elkem Solar Silicon and polysilicon solar cells by selecting wafers from different positions from respective silicon bricks. Active boron-oxygen complexes and iron ions in multicrystalline silicon solar cells have been analyzed, and t…
Natural Radioactivity in Clay Ceramics and their Raw Materials in Latvia
2018
Natural radionuclides K-40, and Th-232, U-238 (Ra-226) decay chain products contained in building materials are the main source of radiation dose received by population and the only source of indoor radiation exposure. Present work contains results of the study of natural radionuclide activity level in clay, clay ceramics and silica bricks used in Latvia. Obtained data show that radionuclide content in different clay products can differ up to five times. However, determined activity index values for all tested materials, except fireproof bricks, were below radionuclide concentration level permitted by EU and Latvian national regulations. Comparison with analogous data from other North Europ…
Modeling of the N-terminal Section and the Lumenal Loop of Trimeric Light Harvesting Complex II (LHCII) by Using EPR
2015
The major light harvesting complex II (LHCII) of green plants plays a key role in the absorption of sunlight, the regulation of photosynthesis, and in preventing photodamage by excess light. The latter two functions are thought to involve the lumenal loop and the N-terminal domain. Their structure and mobility in an aqueous environment are only partially known. Electron paramagnetic resonance (EPR) has been used to measure the structure of these hydrophilic protein domains in detergent-solubilized LHCII. A new technique is introduced to prepare LHCII trimers in which only one monomer is spin-labeled. These heterogeneous trimers allow to measure intra-molecular distances within one LHCII mon…
The effect of oxygenation on the radiation hardness of silicon studied by surface photovoltage method
2002
The effect of oxygenation on the radiation hardness of silicon detectors was studied. Oxygen-enriched and standard float-zone silicon pin-diodes and oxidized samples were processed and irradiated with 15-MeV protons. After the irradiations, the surface photovoltage (SPV) method was applied to extract minority carrier diffusion lengths of the silicon samples. Adding oxygen to silicon was found to improve the radiation hardness of silicon. The effect was visible in minority carrier diffusion lengths as well as in reverse bias leakage currents. The suitability of SPV method for characterizing irradiated silicon samples was proved.
Reversible inhibition of CO2fixation by ribulose 1,5-bisphosphate carboxylase/oxygenase through the synergic effect of arsenite and a monothiol
2013
The activity of the photosynthetic carbon-fixing enzyme, ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco), is partially inhibited by arsenite in the millimolar concentration range. However, micromolar arsenite can fully inhibit Rubisco in the presence of a potentiating monothiol such as cysteine, cysteamine, 2-mercaptoethanol or N-acetylcysteine, but not glutathione. Arsenite reacts specifically with the vicinal Cys172-Cys192 from the large subunit of Rubisco and with the monothiol to establish a ternary complex, which is suggested to be a trithioarsenical. The stability of the complex is strongly dependent on the nature of the monothiol. Enzyme activity is fully recovered through …
Truncated recombinant light harvesting complex II proteins are substrates for a protein kinase associated with photosystem II core complexes
1998
AbstractPrevious studies directed towards understanding phosphorylation of the chlorophyll a/b binding proteins comprising light harvesting complex II (LHC II) have concentrated on a single phosphorylation site located close to the N-terminus of the mature proteins. Here we show that a series of recombinant pea Lhcb1 proteins, each missing an N-terminal segment including this site, are nevertheless phosphorylated by a protein kinase associated with a photosystem II core complex preparation. An Lhcb1 protein missing the first 58 amino acid residues is not, however, phosphorylated. The results demonstrate that the LHC II proteins are phosphorylated at one or more sites, the implications of wh…
Annealing study of oxygenated and non-oxygenated float zone silicon irradiated with protons
2003
Abstract Introducing oxygen into the silicon material is believed to improve the radiation hardness of silicon detectors. In this study, oxygenated and non-oxygenated silicon samples were processed and irradiated with 15 MeV protons. In order to speed up the defect reactions after the exposure to particle radiation, the samples were heat treated at elevated temperatures. In this way, the long-term stability of silicon detectors in hostile radiation environment could be estimated. Current–voltage measurements and Surface Photovoltage (SPV) method were used to characterize the samples.