Untersuchunz von Fetten

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Vanadin-Bestimmungsmethoden

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Effects of formalin preservation on stable carbon and nitrogen isotope signatures in Calanoid copepods: implications for the use of Continuous Plankton Recorder Survey samples in stable isotope analyses

Preserved and archived organic material offers huge potential for the conduct of retrospective and long-term historical ecosystem reconstructions using stable isotope analyses, but because of isotopic exchange with preservatives the obtained values require validation. The Continuous Plankton Recorder (CPR) Survey is the most extensive long-term monitoring program for plankton communities worldwide and has utilised ships of opportunity to collect samples since 1931. To keep the samples intact for subsequent analysis, they are collected and preserved in formalin; however, previous studies have found that this may alter stable carbon and nitrogen isotope ratios in zooplankton. A maximum ~0.9‰ increase of δ(15) N and a time dependent maximum ~1.0‰ decrease of δ(13) C were observed when the copepod, Calanus helgolandicus, was experimentally exposed to two formalin preservatives for 12 months. Applying specific correction factors to δ(15) N and δ(13) C values for similarly preserved Calanoid species collected by the CPR Survey within 12 months of analysis may be appropriate to enable their use in stable isotope studies. The isotope values of samples stored frozen did not differ significantly from those of controls. Although the impact of formalin preservation was relatively small in this and other studies of marine zooplankton, changes in isotope signatures are not consistent across taxa, especially for δ(15) N, indicating that species-specific studies may be required.     

Zum Nachweis und zur Bestimmung des Titans

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有机硅活性中间体的研究 II. 一些含环丙基的有机硅化合物的合成及其结构

用锂有机物的方法合成了四种含有环丙基有机硅化合物,对上述每种化合物中可能存在着的立体异构进行了分离和和构型测定。     

Canonical orthonormalization and neglect of differential overlap

Löwdin's canonical orthonormalization procedure is non-unique if the overlap matrix has degenerate eigenvalues. A recent attempt by Roby to justify neglect of differential overlap is re-examined taking proper account of this lack of uniqueness. We conclude that his central result, eq. (6) in our paper, is formally correct in the limit of complete basis sets, but Roby's presentation lends a misleading interpretation to this equation. Consequently, some conclusions which are claimed to follow are, in fact, not valid. We briefly investigate the Roby approximation for finite basis sets and indicate the strengths and weaknesses when used for practical computations.     

Identification of cyclic nucleotide derivatives synthesized for radioimmunoassay development by fast atom bombardment with collision-induced dissociation and mass-analysed ion kinetic energy spectroscopy

The syntheses of 2′-O-succinyl, 2′-O-succinyltyrosinyl methyl ester and 2′-O-succinyliodotyrosinyl methyl ester derivatives of a cyclic nucleotide, derivatives necessary for the successful development of a specific radioimmuno-assay, are described. Fast atom bombardment with collision-induced dissociation and mass-analysed ion kinetic energy spectroscopy were used to verify the positions of substitution and the retention of the 3′,5′-cyclic phosphate moiety. Comparison of spectra produced after different iodination times permitted the optimization of the reaction conditions.     

Preconcentration and determination of mercury(II) at a chemically modified electrode containing 3-(2-thioimidazolyl)propyl silica gel.

A mercury-sensitive chemically modified graphite paste electrode was constructed by incorporating modified silica gel into a conventional graphite paste electrode. The functional group attached to the (3-chloropropyl) silica gel surface was 2-mercaptoimidazole, giving a new product denoted by 3-(2-thioimidazolyl)propyl silica gel, which is able to complex mercury ions. Mercury was chemically adsorbed on the modified graphite paste electrode containing 3-(2-thioimidazolyl)propyl silica (TIPSG GPE) by immersion in a Hg(II) solution, and the resultant surface was characterized by cyclic and differential pulse anodic stripping voltammetry. One cathodic peak at 0.1 V and other anodic peak at 0.34 V were observed on scanning the potential from -0.1 to 0.8 V (0.01 M KNO3; v = 2.0 mV s(-1) vs. Ag/AgCl). The anodic peak at 0.34 V show an excellent sensitivity for Hg(II) ions in the presence of several foreign ions. A calibration graph covering the concentration range from 0.02 to 2 mg L(-1) was obtained. The detection limit was estimated to be 5 microg L(-1). The precision for six determinations of 0.05 and 0.26 mg L(-1) Hg(II) was 3.0 and 2.5% (relative standard deviation), respectively. The method can be used to determine the concentration of mercury(II) in natural waters contaminated by this metal.     

Time in Thermodynamics

We use Padoa's principle of independence of primitive symbols in axiomatic systems in order to show that time is dispensable in continuum thermodynamics, according to the axiomatic formulation of Gurtin and Williams. We also show how to define time by means of the remaining primitive concepts of Gurtin and Williams system. Finally, we introduce thermodynamics without time as a primitive concept.