Search results for "element"
showing 10 items of 13601 documents
Imidazolsynthesen, 8. Mitt.: N-Substituierte Imidazole nach Weidenhagen
1976
Die Weidenhagen-Synthese N-unsubstituierter Imidazole aus α-substituierten Carbonylverbindungen 1, Aldehyden 3, wasrigem Ammoniak (4) und Kupfer(II)-salzen als Oxidationsmittel ist in Gegenwart primarer Amine 5 auch zur Darstellung N-substituierter Imidazole 6 geeignet. Weidenhagen Synthesis of N-Substituted Imidazoles The Weidenhagen synthesis of N-unsubstituted imidazoles from α-substituted carbonyl compounds 1, aldehydes 3, and aqueous ammonia (4) with copper (II) salts as oxidizing agents is also usable for the synthesis of N-substituted imidazoles 6 through the addition of primary amines 5.
Contribution of Bacteria to Initial Input and Cycling of Nitrogen in Soils
2005
Nitrogen was discovered by the Scottish chemist and physician Daniel Rutherford in 1772 by removing oxygen and carbon dioxide from air. At the same time, the French chemist, Antoine Laurent Lavoisier, isolated what we would call nitrogen and named it azote, meaning without life since it did not support life or combustion. However, nitrogen is the fourth most common element in many biomolecules, which are essential for life, being outrankedonly by carbon, hydrogen andoxygen. Thus, nitrogen is found in amino acids that form proteins and in the nucleoside phosphates of nucleic acids. The cycle of nitrogen in soil has been studied more extensively than any other nutrient cycle. Nevertheless, de…
Templated growth of smart coatings: Hybrid chemical vapour deposition of vanadyl acetylacetonate with tetraoctyl ammonium bromide
2009
Hybrid aerosol assisted and atmospheric pressure chemical vapour deposition methodology has been utilised to produce thin films of vanadium dioxide from vanadyl acetylacetonate. Tetraoctyl ammonium bromide (TOAB) was used in the aerosol precursor solution. The films were analysed by X-ray diffraction, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy. Their optical and thermochromic behaviour was also determined. It was found that the use of TOAB had a templating effect that led to a halving in the particle size and that this consequently led to a significant decrease in the thermochromic transition temperature of the films to 34 8C.
A Quantitative Estimate of Ascorbic and Isoascorbic Acid by High Performance Liquid Chromatography: Application to Citric Juices
1993
Abstract The present report deals with the optimization and verification of a simple HPLC isocratic method useful for determining ascorbic and isoascorbic acids in standard solutions and fruit juices. Sample preparation is minimal and docs not require derivatization. The method uses an octadecyl reversed phase, a mobile phase which contains cetyltrimethyl ammonium bromide 0.05M as the ionic pair and potassium dihydrogen phosphate as a buffer, at pH=4.5, and 4-hydro-xyacetanilide as internal standard. The proposed method makes it possible to quantify ascorbic and isoascorbic acid in less than 13 minutes, with precision (C. V. 3.5%) and accuracy (recover' of 98%).
Methods of metal release assessment in soil water at anoxic sites
2006
Department of Geology, Vienna University, Vienna, Austria Metal mobility at contaminated sites can be assessed by soil water investigations or by leaching tests. Leaching tests are usually carried out in open contact with the atmosphere disregarding possible changes of redox conditions. This can affect the original metal speciation and distribution, particularly when anoxic samples are investigated. In this study, the applicability of common leaching tests (the German S4 test (S4), ammonium nitrate extraction (AmmN), and saturation soil extraction (SSE)) is tested for the assessment of zinc release from sulfide-bearing flotation residues of a former ore mine. Results are compared to soil so…
Synthesis of Peroxyapatite by Hydrothermal Processing
2014
Peroxide ions in apatite provides an additional resource for imparting an antibacterial capability in apatite. A hydrothermal process has been developed for including peroxide ions into the apatite lattice. Three oxygen generation compounds, hydrogen peroxide, ammonium persulphate and paracetic acid were investigated for peroxyapatite generation. Hydrogen peroxide provides the highest peroxide containing apatite. Both the oxygen generation and the apatite lattice formation represented the two critical factors for producing peroxyapatite. Unlike with high temperature processing, the cooling rate did not influence the retained peroxide content. This new process provides a building block for i…
Crystallization of the altitude adapted hemoglobin of guinea pig.
2009
Hemoglobin is the versatile oxygen carrier in the blood of vertebrates and a key factor for adaptation to live in high altitudes. Several structural changes are known to account for increased oxygen affinity in hemoglobin of altitude adapted animals such as llama and barheaded goose. Guinea pigs are adapted to live in high altitudes in the Andes and consequently their hemoglobin has an increased oxygen affinity. However, the structural changes responsible for the adaptation of guinea pig hemoglobin are unknown. Here we report the crystallization of guinea pig hemoglobin in the presence of 2.6 M ammonium sulfate and a preliminary analysis of the crystals. Crystals diffract up to a resolution…
Secondary brown carbon formation via the dicarbonyl imine pathway: nitrogen heterocycle formation and synergistic effects.
2016
Dicarbonyls are known to be important precursors of so-called atmospheric brown carbon, significantly affecting aerosol optical properties and radiative forcing. In this systematic study we report the formation of light-absorbing nitrogen containing compounds from simple 1,2-, 1,3-, 1,4-, and 1,5-dicarbonyl + amine reactions. A combination of spectrophotometric and mass spectrometric techniques was used to characterize reaction products in solutions mimicking atmospheric particulates. Experiments with individual dicarbonyls and dicarbonyl mixtures in ammonium sulfate and glycine solutions demonstrate that nitrogen heterocycles are common structural motifs of brown carbon chromophores formed…
Effectiveness the source of nitrogen from NO3 and NH4 for Panicum maximum Jacq. growth in saline soil
2019
Abstract The purpose of this study was to determine the source of nitrogen used by Panicum maximum Jacq. plants in salt soil. Experimenting pots in a greenhouse with a medium of saline soil. The 2 × 3 factorial design is used in repeated trials. The first factor is calcium sulfate (0 and 2 t ha−1), the second factor is N fertilizer includes (a) without nitrogen = N0, (b) 60 kg N of potassium nitrate (KNO3) and (c) 60 kg N of ammonium sulfate (NH4SO4). The parameters observed were nitrogen uptake, constant growth rate (CGR), biomass yield, crude protein content, NDF, and ADF. The interaction of calcium sulfate and nitrate fertilizer increases CGR, biomass yield, N, CP and NDF uptake. Interac…
Selective erasure of a fear memory
2009
International audience; Memories are thought to be encoded by sparsely distributed groups of neurons. However, identifying the precise neurons supporting a given memory (the memory trace) has been a long-standing challenge. We have shown previously that lateral amygdala (LA) neurons with increased cyclic adenosine monophosphate response element-binding protein (CREB) are preferentially activated by fear memory expression, which suggests that they are selectively recruited into the memory trace. We used an inducible diphtheria-toxin strategy to specifically ablate these neurons. Selectively deleting neurons overexpressing CREB (but not a similar portion of random LA neurons) after learning b…