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21.
The measurement is carried out of aqueous solutions. The burner is supplied with a mixture of acetylene and nitrous oxide. Interfering influences by acid and iron concentrations of the sample solution as well as by organic solvents are shown. The standard deviation is ± 0.001%. The agreement with conventional analysis methods is very good. By this procedure a rapid and safe determination of aluminium will be possible. 相似文献
22.
M. Althoff W. Braunschweig F.J. Kirschfink H.-U. Martyn P. Rosskamp D. Schmitz H. Siebke W. Wallraff J. Eisenmann H.M. Fischer H. Hartmann A. Jocksch G. Knop H. Kolanoski H. Kück V. Mertens R. Wedemeyer G. Zobernig 《Physics letters. [Part B]》1984,149(6):524-532
We have determined the average lifetime of hadrons containing b quarks produced in e+e? annihilation to be . Our method uses charged decay products from both non-leptonic and semileptonic decay modes. 相似文献
23.
Van Hoof F Van Wiele P Bruchet A Schmitz I Bobeldiji I Sacher F Ventura F Marti I Morecos Do Monte MH Sa Da Costa M 《Journal of AOAC International》2001,84(5):1420-1429
As part of a project funded by the European Commission (EC) for the development and evaluation of multiresidue methods for analysis of drinking and related waters, 15 European laboratories evaluated a method using styrene-divinylbenzene co-polymer solid-phase extraction followed by gas chromatography/mass spectrometry. The main aim of the study was to evaluate whether the method meets the requirements of EC Directive 98/83 in terms of accuracy, precision, and detection limit for 22 pesticides according to the following requirements: limit of detection, < or = 0.025 microg/L; accuracy, expressed as recovery between 75 and 125%; and precision, expressed as repeatability relative standard deviation of the method of < 12.5% and as reproducibility relative standard deviation of the method of < 25%. Analyses for unknown concentrations were performed with fortified commercial bottled and tap waters. All laboratories were able to achieve detection limits of 0.01 microg/L for all pesticides except dimethoate and desisopropylatrazine (0.02 microg/L). The criteria for repeatability were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and chlorpyrifos, dimethoate, and lindane in tap water. The criteria for reproducibility were met for all compounds except trifluralin, dimethoate, and lindane in bottled water and pendimethalin, chlorpyrifos, dimethoate, terbutryn, and lindane in tap water. In terms of accuracy, the method meets the requirements for all pesticides in both matrixes, except for lindane in bottled water and lindane and chlorpyrifos in tap water. 相似文献
24.
An analytical free flow capillary isotachophoresis procedure, with a discontinuous electrolyte system, for the detailed analysis of lipoproteins in human body fluids has been developed. The technique is based on prestaining whole serum lipoproteins with a lipophilic dye before separation. Human serum lipoproteins are separated into 14 well-characterized subfractions according to their electrophoretic mobility. High density lipoproteins (fraction 1 to 6) are separated into three major subpopulations, the fast migrating high density lipoprotein (HDL) subpopulation, containing mainly apo AI and phosphatidylcholine, the subpopulation with intermediate mobility, consisting of particles rich in apo AII, apo E, and C apolipoproteins, and the slowly migrating HDL subfraction, containing mainly particles rich in apo AI, apo AIV, and lecithin: cholesterol acyltransferase (LCAT) activity. The apo B containing lipoproteins (fraction 7 to 14) can be subdivided into four major functional groups. The first represents chylomicron derived particles and large triglyceride-rich very low density lipoproteins (VLDL). The second group consists of small VLDL and intermediate density lipoprotein (IDL) particles, anf the third and fourth group represent the low density lipoproteins. The isotachophoretic analysis of human serum samples obtained from patients with hyperlipoproteinemias is compatible with the classification according to the Frederickson phenotypes and reflects the respective biochemical abnormalities. Furthermore, several genetic disorders of lipid and lipoprotein metabolism like HDL deficiency syndromes, familial LCAT deficiency, Fish eye disease, hypobetalipoproteinemia and abetalipoproteinemia can be well characterized by analytical capillary iso tachophoresis. In addition to patient analysis we investigated the influence of lipid lowering drugs on the lipoprotein subfraction distribution during therapy with analytical capillary isotachophoresis. 相似文献
25.
Dietger Leyendecker Dagmar Leyendecker Franz P. Schmitz Ernst Klesper 《Chromatographia》1987,23(1):38-42
Summary In supercritical fluid chromatography (SFC), the elution behavior of styrene oligomers in pentane depends greatly on the degree of oligomerization, n. The influence of capacity ratio, k, on the lower oligomers up to about n=11 resembles the behavior of other substrates of low molecular weight, like aromatic hydrocarbons. Thus, with pentane of 100 bar and below, minima are found in plots of k versus temperature. In contrast, the k of oligomers of higher molecular weight (n>11) increase monotonously with increasing temperature. The studies were performed using oligostyrene fractions obtained by semipreparative SFC fractionation. 相似文献
26.
G. Schmitz Lj. Kolar-Anić 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(9):1380-1387
It has been known for a long time that the decomposition of hydrogen peroxide catalyzed by hydrogen and iodate ions, the Bray-Liebhafsky
reaction, can generate oscillations in a batch reactor. Recently, mixed-mode oscillations and chaos have also been observed
in a CSTR. The model we had previously proposed to explain the kinetics in a batch reactor can also simulate these new complex
behaviors. Time series give only a limited view of the features of the calculated behaviors and more information is obtained
studying the properties of the state space. We use projections of the trajectories, calculation of the correlation dimension
of the attractor, Poincaré sections, and return maps. As the state space of the model is six-dimensional, we try to answer
the questions of whether the projections into a 3D subspace give correct pictures of the real trajectories and whether we have reasons to prefer a special subspace.
The text was submitted by the authors in English. 相似文献
27.
Mercier-Bonin M Ouazzani K Schmitz P Lorthois S 《Journal of colloid and interface science》2004,271(2):342-350
The attachment of microorganisms to a surface is a critical first step of biofilm fouling in membrane processes. The shear-induced detachment of baker's yeast in adhesive contact with a plane glass surface was thus experimentally studied, using a specially designed shear stress flow chamber. The yeast was marketed either as rod-shaped pellets (type I yeast) or as spherical pellets (type II yeast). A complete series of experiments for measuring the shear stress necessary to detach a given proportion of individual yeast cells of type I or II was performed under different environmental conditions (ionic strength, contact time). In parallel, the surface physicochemical properties of the cells (surface charge, hydrophobicity, and electron donor and electron acceptor components) were determined. For the first type of yeast cells, which were rather hydrophilic, adhesion to the glass plate was weak. This was due to both electrostatic effects and hydrophilic repulsion. Furthermore, adhesion was not sensitive to any variation of the ionic strength. For yeast of the second type, adhesion was drastically increased. This could be explained by their physicochemical surface properties and especially their hydrophobic and electron acceptor components, which caused strong attractive van der Waals and Lewis acid-base interactions, counterbalancing the electrostatic repulsion. For increasing ionic strengths, adhesion was greater, due to lower electrostatic repulsion. The results were quantified through the definition of a critical wall shear stress ( tau w 50% ) required to detach 50% of the yeast cells initially deposited on the glass surface. The influence of the contact time was also evaluated and it was shown that, whatever the type of yeast, macromolecules such as proteins were released into the extracellular medium due to cell lysis and could contribute to the formation of a conditioning film. As a result, the cells were more strongly stuck to the glass plate. 相似文献
28.
Patrick Koch Carl Djerassi Vijai Lakshmi Francis J. Schmitz 《Helvetica chimica acta》1983,66(8):2431-2436
Thirty-two sterols are identified in the sponge Hyrtios sp. In addition to fourteen monohydroxylated compounds, the sterol fraction contains eight functionalized sidechain sterols, three of them new: 3 β-hydroxy-24-norchol-5-en-23-al (19) , (22-trans)-3 β-hydroxycholest-5, 22-dien-24-one (20) and (22R, 23R, 24S) or (22S, 23S, 24S)- 22,23-epoxy-24-methylchoest-5-en-3 β-ol (24). The probable biological origin, rather than artifact production, of these undescribed components is discussed. 相似文献
29.
Nathaniel L SegravesSuzette Lopez Tyler A JohnsonSadri A Said Xiong FuFrancis J Schmitz Halina PietraszkiewiczFrederick A Valeriote Phillip Crews 《Tetrahedron letters》2003,44(17):3471-3475
The structural variations and bioactivity properties of the alkaloids in the fascaplysin (1) and the reticulatine (3) families were examined. Four organisms were analyzed consisting of two collections of the sponge Fascaplysinopsis reticulata and two collections of the tunicate Didemnum sp. Reported are the isolation of three new compounds: 3-bromofascaplysin (2), 14-bromoreticulatine (4), and 14-bromoreticulatate (6) along with reticulatate (5) previously known as a semi-synthetic product of 1. Compounds 1 and 5 showed selectivity in a cell based cytotoxicity assay. 相似文献
30.
Inhaltsübersicht. Die Verbindungen K2MnS2, Rb2MnS2, Cs2MnS2, K2MnSe2, Rb2MnSe2, Cs2MnSe2, K2MnTe2, Rb2MnTe2 und Cs2MnTe2 wurden durch Umsetzungen von Alkalimetall-carbonaten mit Mangan bzw. Mangantellurid in einem mit Chalkogen beladenen Wasserstoffstrom erhalten. Kristallstrukturuntersuchungen an Einkristallen ergaben, daß alle neun Verbindungen isotyp kristallisieren (K2ZnO2-Typ, Raumgruppe Ibam). Untersuchungen zum magnetischen Verhalten zeigen antiferromagnetische Kopplungen der Manganionen in den [MnX4/22–]-Ketten, On Alkali Metal Manganese Chalcogenides A2MnX2 with A K, Rb, or Cs and X S, Se, or Te The compounds K2MnS2, Rb2MnS2, Cs2MnS2, K2MnSe2, Rb2MnSe2, Cs2MnSe2, K2MnTe2, Rb2MnTe2, and Cs2MnTe2 were synthesized by the reaction of alkali metal carbonates with Mn or MnTe in a stream of hydrogen charged with chalcogen. Structural investigations on single crystals show that all nine compounds crystallize in isotypic atomic arrangements (K2ZnO2 type, space group Ibam). The magnetic behaviour indicates antiferromagnetic interactions of the manganese ions within the [MnX1/22–] chains. 相似文献