Search results for "visual_art"
showing 10 items of 2987 documents
Multi-channel receptors based on thiopyrylium functionalised with macrocyclic receptors for the recognition of transition metal cations and anions.
2010
We report herein the synthesis and characterization of a family of ligands containing different cation binding sites covalently connected to a thiopyrylium signalling reporter. The receptors L1–L6 are able to signal the presence of certain metal cations via three different channels; i.e. electrochemically, fluorogenically and chromogenically. An acetonitrile solution of L1–L6 shows a bright blue colour due to a charge-transfer band in the 575–585 nm region. The colour variation in acetonitrile of L1–L6 in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Ni2+, Pb2+ and Zn2+ has been studied. A selective hypsochromic shift of the blue band was found for the systems L4-Pb2+ and L…
Open-chain polyamine ligands bearing an anthracene unit - Chemosensors for logic operations at the molecular level
2001
In this work the absorption and the fluorescence emission properties as well as the protonation sequence of three open chain polyamine ligands of different dimensions bearing an anthracene unit were studied. The protonation and stability constants with Ni2+, Cu2+, Zn2+, and Cd2+ have been determined in 0.15 mol·dm−3 NaCl at 298.1 ± 0.1 K. The values of both protonation and stability constants follow the expected trends according to the number of nitrogen donors, sequence of chelate rings and hydrophilic−hydrophobic balance. Chelation enhancement of the fluorescence emission (CHEF) was observed for some complexes of these ligands with Zn2+ and Cd2+. In contrast the analog complexes containin…
Effect of cadmium pre-exposure in cadmium accumulation by brine shrimp Artemia: Involvement of low-molecular-weight cadmium-binding ligands
1993
Abstract Cadmium is a ubiquitous non-essential element that possesses high toxicity and is easily accumulated from the environment by aquatic organisms. It is known that pre-exposure to cadmium increases the resistance of animals to a subsequent exposure. In this work, we report studies of the effect of pre-exposure to cadmium on the accumulation of this metal from seawater by brine shrimp Artemia, as well as the involvement of low-molecular-weight cadmium-binding ligands in this process. During the pre-exposure experiments, animals were kept in seawater containing 20 mg/litre Cd for 24 h and then transferred to clean seawater for 48 h. Afterwards, pre-exposed and control animals were expos…
The effect of gold addition on the catalytic performance of copper manganese oxide catalysts for the total oxidation of propane
2011
Mixed copper manganese oxide catalysts (Hopcalite) have been studied for the total oxidation of propane, as a model for hydrocarbon volatile organic compound emission control. Catalysts were prepared using coprecipitation with and without gold. Calcination temperature influenced the catalyst activity and those prepared at 300 °C were the most active. Characterization showed that the catalysts had a nanowire-type morphology, and for those containing gold it was present as metallic particles occluded within the nanowires. The incorporation of gold into the catalyst enhanced the activity for propane conversion, but the presence of gold did not noticeably enhance the light-off activity. Althou…
Micro-scale post-fire surface cover changes monitored using high spatial resolution photography in a semiarid environment: A useful tool in the study…
2012
[ES] Although post-fire soil erosion has been studied, little attention has been paid to changes in soil surface cover following fires, despite this being a key factor in understanding the water and sediment yield. This study, at Peñaflor (Spain), investigated the effect of fire on soil erosion using data from soil erosion plots and high spatial resolution photography (HSRP). Measurements were made from October 2003 to October 2005 in a control plot and a plot experimentally exposed to a fire in October 2004. Ground cover components were identified, including vegetation, bare soil, stones, charcoal and ash. Runoff and sediment concentrations were low because of the absence of intense rainfa…
Surface Study of Pumice Supported Nickel Catalysts Used in the Hydrogenation of CO
1998
A series of pumice supported nickel catalysts used in the CO hydrogenation reaction were characterised by X-ray photoelectron spectroscopy. Qualitative and quantitative analysis of the XPS peaks have shown the effect of the calcination conditions on the chemical state of the nickel before hydrogenation and the particle size of the metal after reduction. Calcination at high temperature determined enrichment of sodium ions on the surface of the support and also on the metal particles. After exposure to the gas mixture CO/H2, formation of nickel carbides and other carbon species was checked. The correlation found between the surface atomic ratio Na/Si and the activity and selectivity of the ca…
Comparison of Structure and Properties of Differently Treated Illite Clay and Products
2014
The investigation is focused on modification of the structure 2:1 sheet silicates - illite clay by subjecting them to chemical and microbiological impact. It is shown that alkaline activation of illite clay by sodium hydroxide leads to the slight structural changes mainly characterized by water link changes. The effect of bacteria Ps. fluorescens AM PS11on structure changes of illite is small and is influenced on rheology of treated clay.It is shown that the influence of chemical treatment on porosity, bulk density and increase of compressive strength of sintered ceramic samples is notable.
Silver-loaded nanoparticles affect ex-vivo mechanical behavior and mineralization of dentin
2019
Background: The aim was to evaluate the effect of silver loaded nanoparticles (NPs) application on the triboscopic, crystallographic and viscoelastic properties of demineralized dentin. Polymethylmetacrylate-based NPs and Ag loaded NPs were applied on demineralized dentin. Material and Methods: Treated and untreated surfaces were probed by a nanoindenter to test viscoelasticity, and by atomic force microscopy to test nanoroughness and collagen fibril diameter. X-ray diffraction and transmission electron microscopy through selected area diffraction and bright-field imaging were also used. Results: Dentin treated with Ag-NPs attained the lowest complex modulus, and the highest tan delta value…
Determination of the Boron/Lead Ratio in Ceramic Materials Based on Electrochemical Quartz Crystal Microbalance
2004
A method for quantitatively determining the relationship boron/lead in ceramic materials is presented. It is based on the attachment of microsamples of ceramic frits to an electrochemical quartz crystal microbalance (EQCM). After a reductive deposition step in the � 0.25 to � 0.85 V (vs. AgCl/Ag) potential range, well-defined stripping peaks are recorded in 0.10 M NaCl plus 0.10 M mannitol. The deposition of boron and lead from suspensions of solid materials, and its subsequent oxidative dissolution can be monitorized at the EQCM. The quotient between the maximum mass gain and the corresponding charge passed enables for a direct quantitation of the boron/lead molar ratio in ceramic material…
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…