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Initial Reaction (initial + reaction)

Distribution by Scientific Domains
Life Sciences33%
Chemistry33%

Terms modified by Initial Reaction

  • initial reaction rate
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    Selected Abstracts

    Synthesis and characterization of metal sulfide clusters for toxicological studies

    ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2002
    Karl C. Bowles
    Abstract Zinc sulfide clusters were synthesized and characterized at low micromolar concentrations to assess the effect of metal-sulfide ligands on metal toxicity to aquatic organisms in oxic environments. Recommended preparation times are greater than 2 h initial reaction of equimolar sodium sulfide and zinc nitrate, followed by oxic aeration for 3 d. Ionic strength, pH, and anoxic stabilization time were found to be relatively unimportant in controlling the final yield. Adsorptive losses of zinc sulfide (ZnS) clusters to surfaces, however, were significant for a variety of vessel materials and membrane filters. Ionic strength and pH were found to be important factors controlling the extent of adsorptive losses with minimal loss for pHs greater than 9 and for soft waters. The Ag(I), Cu(II), and Hg(II) as metal sulfides completely suppress the analysis of sulfide, whereas Pb(II), Mn(II), and Co(II) partially suppress the analysis of sulfide by the methylene blue technique. Ultraviolet and fluorescence spectra are shown for synthesized ZnS clusters. [source]

    Selenium Heterocycles: Reactions of SeX4 (X = Cl, Br) with the Enamine Form of ,-Diketiminato Ligands

    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2008
    Audra F. Gushwa
    Abstract Treatment of SeX4 (X = Cl, Br) with either MesnacnacLi(nacnac = [{N(Ar)C(Me)}2CH],, Ar = Mes = C6H2Me3 -2,4,6) or DmpnacnacLi (Ar = Dmp = C6H3Me2 -2,6) affords four new SeII six-membered heterocycles, [MesnacnacHCl2SeCl] (2), [MesnacnacH2Se]+Br, (3), [DmpnacnacH2Cl3Se]+Cl, (4), and [MesnacnacH2(O)Br2Se] (5). All have been characterized in the solid state by X-ray crystallography. Each of the four complexes is proposed to have formed from the initial reaction of SeX4 with the C,C double bond that results from the enamine form of the ligand, giving rise to an Se,C single bond. Subsequent nucleophilic attack by either the more distant nitrogen atom or the remaining C,C double bond of the enamine form results in the Se heterocycle. In complexes 2, 4, and 5 varying degrees of halogenation of the newly formed heterocycles was observed.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

    Influence of Grain Phase on Slag Corrosion of Low-Cement Castable Refractories

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 2 2001
    Hossain Sarpoolaky
    The grain phase has a significant influence on the extent and mechanism of attack of low-cement castables with similar bond systems in a crucible corrosion test. The general corrosion mechanism, as determined by post mortem scanning electron microscopic examination of corroded samples and thermodynamic calculations for all four grain types examined (white-fused alumina (WFA), tabular alumina (TA), brown-fused alumina (BFA), and alumina-rich spinel (S)), involves initial reaction of the most penetrating slag (enriched in calcium, manganese, and iron, because these elements diffuse rapidly) with the fine alumina and calcium aluminates of the matrix. This reaction gives a CaO-rich local liquid, which can then react with each grain predominantly to form calcium hexaluminate (CA6) and hercynitic spinel. In the WFA system, a complete CA6 layer forms around the grain, whereas in the TA system, this layer is incomplete. In both systems, extensive penetration occurs, although corrosion is low. In the BFA system, titanates are released from the grain into the bond, leading to increased densification of the refractory, via liquid-phase sintering, and consequent low penetration. However, the resulting fluid liquid dissolves easily in the slag, so that corrosive wear is high, even though a CA6 layer forms around the grain. In the S grain system, uptake of the rapidly diffusing cations into the spinel crystal structure leads to silica-rich and viscous local liquid, which leads to low penetration and corrosion. [source]

    Dietary advice, dietary adherence and the acquisition of tolerance in egg-allergic children: a 5-yr follow-up

    PEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 3 2009
    Clare Wendy Allen
    IgE-mediated egg allergy is a common childhood food allergy affecting about 1,2% of 2-yr-old children. Egg avoidance is the mainstay of treatment for egg allergy; however, it is unclear what type of dietary advice parents of children with egg allergy receive and to what extent this dietary advice is adhered to. This study aimed to assess: (i) the type and source of dietary advice parents receive in a tertiary hospital setting, (ii) how closely parents adhere to advice given, (iii) what patient characteristics influenced adherence to diet and (iv) whether strict adherence to dietary advice was an identifiable factor in whether children outgrew their egg allergy. In 2006, a questionnaire was sent to 261 parents of children seen in a tertiary paediatric allergy clinic in 2003 and diagnosed with egg allergy which included 84 children who had undergone an in-hospital open oral egg challenge during this time period (2003,2006). Questions included demographic data, details of egg allergy, dietary avoidance and attainment of unrestricted egg ingestion. Of 199 questionnaires confirmed received, 167 were returned (84%). The mean age of the cohort was 6.6 yr with an average of 5.5 yr of follow-up since the first reaction. Sixty-eight percent of subjects reported avoidance of all food containing egg all the time. Forty-seven percent of the children had been accidentally exposed to egg. The severity of the initial reaction did not appear to influence adherence to an advised diet. Of the 84 children who underwent in-hospital open egg challenges, 57 children were able to ingest egg without clinical reaction and were classified as having outgrown their egg allergy. These children did not differ from those who were challenge positive to egg in terms of either the dietary advice they received or the degree to which they had undertaken strict avoidance of egg. In addition, children who had outgrown their egg allergy did not differ from those who remained egg-allergic on in-hospital challenge in terms of either the frequency of accidental ingestion or the severity of initial reaction. Strict avoidance of egg and accidental ingestion of egg did not appear to influence the acquisition of tolerance. [source]

    Diaquatetrakis(tert -butyl isocyanide)cobalt(II) bis(perchlorate): an example of cobalt(II) coordinated by only four alkyl isocyanide ligands

    ACTA CRYSTALLOGRAPHICA SECTION C, Issue 8 2009
    Clifford A. L. Becker
    The title compound, [Co(C5H9N)4(H2O)2](ClO4)2, crystallizes in the monoclinic space group C2/m. The cation has space-group-imposed 2/m symmetry, while the perchlorate ion is disordered about a mirror plane. The two slightly non-equivalent Co,C bonds [1.900,(3) and 1.911,(3),Å] form a rectangular plane, with a C,Co,C bond angle of 86.83,(11)°, and the linear O,Co,O C2 axis is perpendicular to this plane. The C[triple-bond]N bond lengths are 1.141,(4),Å and the Co,C[triple-bond]N and C[triple-bond]N,C angles average 175.5,(4)°. The perchlorate counter-ions are hydrogen bonded to the water molecules. The title compound is the first example of four alkyl isocyanide ligands coordinating CoII upon initial reaction of Co(ClO4)2·6H2O/EtOH with alkyl isocyanide. In all other known examples, five alkyl isocyanide molecules are coordinated, as in [(RNC)5Co,Co(CNR)5](ClO4)4 (R = Me, Et, CHMe2, CH2Ph, C4H9 - n or C6H11) or [Co(CNC8H17 - t)5](ClO4)2. This complex, therefore, is unique and somewhat unexpected. [source]

    Two inducible, functional cyclooxygenase-2 genes are present in the rainbow trout genome

    JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2007
    Tomo-o Ishikawa
    Abstract The cyclooxygenases (Cox) catalyze the initial reactions in prostanoid biosynthesis, and produce the common prostanoids precursor, PGH2. Mammalian species have two Cox isoforms; constitutively expressed cyclooxygenase-1 (Cox-1) and inducible cyclooxygenase-2 (Cox-2). Database searches suggest three Cox genes are present in many fish species. In this study, we cloned and characterized a second Cox-2 cDNA, Cox-2b, from the rainbow trout. Rainbow trout Cox-2b protein contains all the functionally important conserved amino acids for Cox enzyme activity. Moreover, the Cox-2b message contains AU-rich elements (AREs) in the 3, untranslated region (3,UTR) characteristic of inducible Cox-2 mRNAs. We took advantage of the existence of a rainbow trout cell line to demonstrate that expression from both the originally reported Cox-2 (Cox-2a) and Cox-2b genes is inducible. However, differential induction responses to alternative inducers are observed for rainbow trout Cox-2a and Cox-2b. Both Cox-2a and Cox-2b proteins expressed in COS cells are enzymatically active. Thus the rainbow trout has two functional, inducible Cox-2 genes. The zebrafish also contains two Cox-2 genes. However, genome structure analysis suggests diversion of the Cox-2a gene between zebrafish and rainbow trout. J. Cell. Biochem. 102: 1486,1492, 2007. © 2007 Wiley-Liss, Inc. [source]