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991.
High-performance liquid chromatographic separation of the enantiomers of organophosphorus pesticides on polysaccharide chiral stationary phases. 总被引:3,自引:0,他引:3
High-performance liquid chromatographic separation of the individual enantiomers of 12 organophosphorus pesticides (OPs) was obtained on polysaccharide enantioselective HPLC columns using alkane-alcohol mobile phase. The OP pesticides were crotoxyphos, dialifor, fonofos, fenamiphos, fensulfothion, isofenphos, malathion, methamidophos, profenofos, crufomate, prothiophos and trichloronate. The enantiomers of fenamiphos, fensulfothion, profenofos and crufomate were separated on CHIRALPAK AD; the enantiomers of fenamiphos were also separated on CHIRALPAK AS; the enantiomers of methamidophos, crufomate and trichloronate were separated on CHIRALCEL OD; the enantiomers of crotoxyphos, dialifor, fonofos, malathion, prothiophos and trichloronate were separated on CHIRALCEL OJ; and the enantiomers of isofenphos were separated on CHIRALCEL OG. Baseline or partial separation of the enantiomers of six of these OP pesticides was obtained on CHIRALCEL OJ. In continued method development, the separation of the enantiomers of the 12 OPs was investigated more extensively on CHIRALCEL OJ to determine whether the mobile phase composition, flow-rate and column temperature could be optimized to yield at least partial separation of the enantiomers. Chromatographic conditions were found that gave either baseline or near baseline separations of the enantiomers of the 12 OPs on the CHIRALCEL OJ column. 相似文献
992.
Radiofrequency (rf) plasmas exhibit field penetration well beyond the classical skin depth. Two physical explanations are proposed. First, by tracing orbits of electrons through many rf cycles in a cylindrical system, it is shown that numerous ionizing electrons can reach the interior. Second, current-carrying electrons can form a long-lived torus that drifts toward the axis, causing frequently observed interference phenomena. The pressure dependence of this effect does not agree with collisionless theories of anomalous skin effect, but is consistent with the proposed mechanism. 相似文献
993.
Kui Huang Teresa A. Croce Sharon K. Hamilton Chinessa T. Adkins Billie L. Evans III Eva Harth 《Macromolecular Symposia》2007,255(1):20-23
Summary: The development of suitable delivery systems for intracellular delivery of proteins, peptides and other bioactive materials opens the possibility to establish refined strategies for small drug delivery, gene delivery and vaccination. We present the assembly of advanced drug delivery systems from tailored building blocks to scaffolds and bioactive cargos to afford targeting and transport across biological barriers. In particular, the utilization of novel molecular transporter will advance the bioavailability of small and macromolecular drugs that show targeted intracellular delivery. 相似文献
994.
采用成核/晶化隔离法将草甘膦(Glyphosate:gly)插层组装到镁铝水滑石层间,制得草甘膦插层镁铝水滑石(MgAl-LDH-gly).在水和碳酸钠溶液中考察了gly的释放性能,初步探讨了MgAl-LDH-gly在这两种溶液中的释放机理,认为其释放机理主要为离子交换,释放速率较大的初期符合一级动力学过程.用磷酸缓冲溶液考察环境pH值对MgAl-LDH-gly释放的影响,证明弱碱性(pH=7.6)和偏中性(pH=6.6)环境有利于其释放;探讨混合无机阴离子溶液中无机阴离子对MgAl-LDH-gly释放性能的影响,结果表明,MgAl-LDH-gly的释放速率及释出量在所考察范围内由溶液中无机阴离子的总浓度决定. 相似文献
995.
David G. Evans 《高等学校化学研究》2004,20(4):386-391
IntroductionIn recent years,titanium- containing meso-porous molecular sieves have attracted considerableattention of some scholars and scientists because oftheir remarkable catalytic properties in selectiveoxidation reactions by H2 O2 in aqueous solution asthe oxidant[1_ 3 ] .The high cost and low efficiencyof H2 O2 ,however,limits its application on an in-dustrial scale.In our previous work[4] ,we foundthat using Ti- substituted MCM- 41 as a catalystforthe hydroxylation ofbenzene with H2… 相似文献
996.
S.D. Forder A. Reeder J.S. Brooks M. Rignall P.V. Evans 《Hyperfine Interactions》2000,126(1-4):193-197
57Fe conversion electron Mössbauer spectroscopy has been used to investigate the intermetallic phases near the surface of a D.C. cast aluminium ingot. The CEMS data is used with SAAES (selected area Auger electron spectroscopy) and SAXPS (selected area X-ray photoelectron spectroscopy) data to propose a model of the surface region above the grain boundaries. 相似文献
997.
Neumann laplacians on domains and operators on associated trees 总被引:1,自引:0,他引:1
998.
Samuel A. Moehring Prof. William J. Evans 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(7):1530-1534
The possibility that the relative reactivity of complexes of actinide metals in the +2 and +3 oxidation states could be investigated by examining reactions between AnIII and AnII species of Th and U with rare-earth metal reagents that provide EPR confirmation of electron transfer reactivity has been explored. Neither Cp’’3ThIII nor Cp’’3UIII will reduce Cp’’3LaIII or Cp’3YIII (Cp’=C5H4SiMe3, Cp’’=C5H3(SiMe3)2). However, both [K(2.2.2-cryptand)][Cp’’3ThII] and [K(2.2.2-cryptand)][Cp’’3UII] reduce Cp’’3LaIII and Cp’3YIII to form [Cp’’3LaII]1− and [Cp’3YII]1−, respectively, which were identified by EPR spectroscopy. The reverse reactions also occur which indicates that the reduction potentials are similar. [Cp’’3LaII]1− reduces Cp’3YIII and the reverse YII/LaIII combination also occurs. In both cases, the reactions generate EPR spectra indicative of multiple species in the mixtures of LaII and YII, which is consistent with ligand exchange and demonstrates that numerous heteroleptic complexes of these LnII ions exist. 相似文献
999.
Guillaume Journot Reinhard Neier Helen Stoeckli‐Evans 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(7):644-649
The title compound, tetrachlorido‐1κCl;2κ3Cl‐(2,2,7,7,12,12,17,17‐octamethyl‐21,22,23,24‐tetraazapentacyclo[16.2.1.13,6.18,11.113,16]tetracosane‐1κ4N,N′,N′′,N′′′)‐μ2‐oxido‐diiron(III), [Fe2Cl4O(C28H52N4)], undergoes a slow phase transformation at ca 173 K from monoclinic space group P21/n, denoted form (I), to the maximal non‐isomorphic subgroup, triclinic space group P, denoted form (II), which is accompanied by nonmerohedral twinning [twin fractions of 0.693 (4) and 0.307 (4)]. The transformation was found to be reversible, as on raising the temperature the crystal reverted to monoclinic form (I). In the asymmetric unit of form (I), Z′ = 1, while in form (II), Z′ = 2, with a very small reduction (ca 1.8%) in the unit‐cell volume. The two independent molecules (A and B) in form (II) are related by a pseudo‐twofold screw axis along the b axis. The molecular overlay of molecule A on molecule B has an r.m.s. deviation of 0.353 Å, with the largest distance between two equivalent atoms being 1.202 Å. The reaction of calix[4]pyrrolidine, the fully reduced form of meso‐octamethylporphyrinogen, with FeCl3 gave a red–brown solid that was recrystallized from ethanol in air, resulting in the formation of the title compound. In both forms, (I) and (II), the FeIII atoms are coordinated to the macrocyclic ligand and have distorted octahedral FeN4OCl coordination spheres. These FeIII atoms lie out of the mean plane of the four N atoms, displaced towards the O atom of the [OFeCl3] unit by 0.2265 (5) Å in form (I), and by 0.2210 (14) and 0.2089 (14) Å, respectively, in the two independent molecules (A and B) of form (II). The geometry of the [OFeCl3] units are similar, with each FeIII atom having a tetrahedral coordination sphere. The NH H atoms are directed below the planes of the macrocycles and are hydrogen bonded to the coordinated Cl− ions. There are also intramolecular C—H...Cl hydrogen bonds present in both (I) and (II). In form (I), there are no significant intermolecular interactions present. In form (II), the individual molecules are arranged in alternate layers parallel to the ac plane. The B molecules are linked by a C—H...Cl hydrogen bond, forming chains along [100]. 相似文献
1000.