Meeting the need for reference measurements

Summary Reference materials do fulfil a very useful function in that they provide means to check, verify and calibrate measurement procedures and instrumentation. However, the material is often idealized compared to real life samples: it is either (very) pure or does not correspond in concentration level or matrix to the real life case. It is shown how this situation could be remedied if real life samples with carefully assessed reference values could be made available regularly as unknowns to measurement laboratories. Comparison of the latter's measurements with the reference values then would provide a picture of the real performance of the particular measurement community in general and of each participating laboratory in particular. The opinion is expressed that isotope-specific methods have now matured to the stage that, if they are correctly applied under rigorous control and based on highly skilled expertise, they can provide such reference values against which laboratories can then evaluate their routine performance in regular Interlaboratory Measurement Evaluation Programmes (IMEPs).

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Wie der Notwendigkeit von Referenzmessungen entsprochen werden kann

     

Understanding the properties of isospectral points and pairs in graphs: The concept of orthogonal relation

The mathematical property orthogonal relationship is used in proving the fact that isospectrality, isocodality and isocoefficiency of vertices within a graph are all equivalent. The same is true for isospectrality, strict isocodality and strict isocoefficiency of pairs (including edges) within a graph, whereas the weak versions of the latter properties are necessary but not sufficient for isospectrality of pairs. Similarly, necessary and sufficient conditions for isospectrality of vertices and pairs in different graphs are derived. In all these proofs, the concept of orthogonal relation plays a major role in that it allows the use of tools of elementary linear algebra.     

Production of anomalously shaped carboxylated polymer particles by seeded emulsion polymerization

Anomalous polymer particles with a partial protuberance like octopus ocellatus were produced under alkaline conditions by seeded emulsion copolymerization for styrene and butyl acrylate, with styrene-butyl acrylate-methacrylic acid terpolymer emulsion as seed. The mechanism of production of the polymer particles was studied. By transmission electron microscopic observation of the particles at each conversion, it was observed that the anomalous polymer particles were produced by partial growth of each of the individual seed particles throughout polymerization. Ionization of the carboxyl groups and low viscosity in the growing particles during the process of polymerization were important factors for partial growth.Part CIII of the series Studies on Suspension and Emulsion.     

Structure-reactivity problem in cycloaddition reactions to form heterocyclic compounds

The steric and electronic effects of substituents in both diene and dienophile components have been considered as the main factors that control the electronic character of (4+2)-cycloaddition leading to transitions between normal, neutral, and inverse Diels-Alder reactions.Institut für Organische Chemie der Universität Regensburg, Universitätsstr. 31, D-93040 Regensburg, Germany. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1307–1322, October, 1995. Original article submitted August 15, 1995.     

Plutonium in soils, bottom sediments and lichen near peaceful nuclear explosion sites in the Republic of Sakha (Yakutia)

During the 1974–1987 period 12 paceful nuclear explosions were conducted in the Republic of Sakha (Yakutia). For the first time^239,240Pu and²³⁸Pu concentrations were determined in samples of soils, bottom sediments and lichen taken at the Craton-3 and Crystal nuclear explosion sites. At the Craton-3^239,240Pu concentrations in the range 6.2 mBq/g to 5.9 Bq/g samples of soil and^239,240Pu concentrations up to 7.4 Bq/g in samples of lichen were observed.^239,240Pu concentration measurements in bottom sediments of a stream washing out the banking around the borehole of Craton-3 show that plutonium migrates in the direction of the Markha river. At the Crystal site local plutonium concentrations up to 35 Bq/g in soil and 1.8 Bq/g in lichen were observed.     

Preparation of micron-size monodisperse polymer particles by seeded polymerization utilizing the dynamic monomer swelling method

Utilizing a new type of monomer swelling method, 6.1 m-size monodisperse polymer particles were prepared by seeded polymerization. 1.8 m-size monodisperse polystyrene (PS) seed particles (1.8 m in size) were prepared by dispersion polymerization in ethanol-water (80/20, v/v) medium in the presence of poly(acrylic acid) as stabilizer with 2,2-azobisisobutyronitrile as initiator. The PS seed dispersion was mixed with ethanol-water (60/40, v/v) solution dissolving styrene (S) monomer, benzoyl peroxide as initiator, and poly(vinyl alcohol) as stabilizer. By slow, continuous, dropwise addition of water with a micro feeder into the mixture, the PS particles absorbed the many S monomers, which were separated from the medium and swelled from 1.8 m to 8.4 m while keeping the monodispersity high. We named this procedure the dynamic swelling method. Then, the seeded polymerization of the absorbed S monomer was carried out in the presence of NaNO₂ as water-solube inhibitor.Part CXXII of the series Studies on Suspension and Emulsion.     

The diagram lattice as structural principle A. New aspects for representations and group algebra of the symmetric group B. Definition of classification character,mixing character,statistical order,statistical disorder; A general principle for the time evolution of irreversible processes

It is the aim of this paper to demonstrate the significance of the diagram lattice. This lattice was defined in order to achieve structural insight into the phenomenon of chirality in chemistry. In this context, Theorie der Chiralitätsfunktionen [1] may serve as reference. In the introduction of the present paper a summary of the relevant theorems and definitions is given and a few examples of the diagram lattice are graphically illustrated. Parts A and B can be read independently and presuppose knowledge only of the introduction. Part A is of special interest for mathematicians, Part B and [1] for physicists and chemists.In Part A theorems on the representations of the group _n and certain subgroups of it and on the structure of the group algebra are developed. In Part B the concept classification character with the two complementary aspects of identification and distinction is derived. With the interpretation mixing character the partial order relation gains an interpretation through a mixing process, which can be expressed by a bistochastic matrix. This results in another equivalent definition of the diagram lattice. Interpreted as mixing character of a statistical distribution a diagram represents statistical order and statistical disorder by its row partition and column partition respectively. These concepts and the corresponding lattice structure lead to the hypothesis of growing mixing character as a criterion for the time evolution of isolated systems. The criterion of increasing entropy provides a much weaker condition. A discussion of the master equation leads to a proof of the principle of growing mixing character.[/p]     

New algorithm for nonorthogonal ab initio valence bond calculations II: Subgraph-driven method

The permanent method for nonorthogonal VB calculations is extensively developed, and the so-called subgraph-driven procedure is proposed. To achieve high efficiency, the summation of a huge number of permanents is treated as a whole system, and the intermediate quantities, the contracted-cofactors of various orders, are introduced for the systematic summation. These intermediate quantities can be characterized by pairing graphs of 2n elements (n = 1, 2, ... 1/2N – 2). Some test calculations for systems of up to 20 electrons are performed. The practice shows that this method is highly efficient, and the CPU time increases in a quite moderate way with the increasing number of electrons.On leave from Chemistry Department, Xiamen University, 361005 Xiamen, PR China.     

Thermal analysis of amorphous phase in a pharmaceutical drug

Thermally Stimulated Current (TSC) spectroscopy and Differential Scanning Calorimetry (DSC) have been applied to the characterization of the microstructure of a pharmaceutical drug.The dielectric relaxation spectrum shows two modes located in the temperature range of the glass transition. They have been attributed to the molecular mobility in the true amorphous phase and in the rigid amorphous region.     

Über zwei Autoxidationsprodukte des Apomorphins

Zusammenfassung Wie bereits früher¹ mitgeteilt, lassen sich aus autoxidierten wäßrigen Lösungen von Apomorphin-Hydrochlorid zwei Oxidationsprodukte isolieren. Diese beiden Substazen (im folgenden als Substanz A und Substanz B bezeichnet) werden näher charakterisiert.Mit 2 Abbildungen     

An investigation of micro-brownian motions in polydimethylsiloxane by complementary incoherent-neutron-scattering and nuclear-magnetic-resonance experiments below room temperature

Two different experimental methods, neutron scattering and nuclear magnetic resonance are used to investigate the random methyl group and segmental rotational jump motions in polydimethylsiloxane. It is shown that nuclear magnetic relaxation and line width experiments are complementary to incoherent neutron scattering fixed-window experiments, the principle of the fixed-window experiments being discussed in somewhat detail. Satisfactory agreement of these experimental techniques is achieved as to the determination of the two model parameters of the motional processes in question, i. e. the activation energy and the preexponential factor of the Arrhenius ansatz made for the correlation time or jump time, respectively.Contribution partly presented during the meeting of the Macromolecular Club, June 8–10, 1983 in Uppsala, the spring conference of the Deutsche Physikalische Gesellschaft, March 12–17, 1984 in Münster and the Fourth International Seminar on Polymer Physics, October 22–26, 1984 in Eyba (GDR).     

The influence of substituted alcohols on the temperature of maximum density of water

The influence of various substituted (including halogenated) alcohols on the temperature of maximum density (TMD) of water has been investigated. Evaluation of the structural contribution to the shift in the TMD demonstrates that trifluoroethanol, hexafluoroisopropanol, and neopentyl alcohol are structure makers, whereas trichloroethanol and tribromoethanol are structure breakers. The results are discussed in terms of an excluded volume model.     

Multivariate Statistical Assessment of Air Quality: A Case Study

The present paper deals with the application of several chemometrical methods (cluster and principal components analysis, source apportioning on absolute principal components scores) to an aerosol data collection from Unterloibach, Austria. It is shown that seven latent factors explaining almost 80% of the total variance are responsible for the data structure and are conditionally identified as secondary aerosol, mineral dust, oil burning, lead smelter, coal burning, salt and fertilizer emission sources. Furthermore, the contribution of each identified source to the formation of the particle total mass and chemical compounds total concentration is calculated. Thus, a reliable assessment of the air quality in the region is performed. The requirements of the sustainability concept for ecological indicators in this case is easily transformed into a multivariate statistical problem taking into account not separate indicators but the specific multivariate nature of aerosol pollution.     

A new computational microscope for molecules: High resolution MEDLA images of taxol and HIV-1 protease,using additive electron density fragmentation principles and fuzzy set methods

Based on the molecular electron density lego assembler (MEDLA) method, a computational microscope was developed that generates accurate images of bodies of large molecules at a resolution far exceeding current experimental techniques. The MEDLA microscope can be tuned to display the high electron density regions of formal chemical bonds; or to show the low density regions of hydrogen bonds and secondary interactions, or to display local shape requirements important in molecular recognition. The power of the method is illustrated by examples of detailed images of taxol, an important anti-cancer agent, and HIV-1 protease, a protein of 1564 atoms. A mathematical framework of the approach, based on fuzzy sets, and the fundamentals of several additional applications of the additive, fuzzy fragmentation principle are presented.     

Untersuchung der Stabilisierung von Polyacrylnitrilfasern „Bulana” mittels Differentialthermoanalyse

Zusammenfassung Mittels DTA und DSC wird das Verhalten der Polyacrylnitrilfaser Bulana mit und ohne Vorbehandlung mit einer Lösung von 2-Phenyl-2-(3,5 Dinitro-4-Hydroxyphenyl)-Propan in Nitrobenzol beim Erhitzen an der Luft und in Stickstoff erforscht. Dabei werden erhöhte Temperaturen für Beginn und Maximum der exothermen Prozesse Zyklisierung und Oxydation sowie verminderte Enthalpieveränderungen (H) beobachtet. Die Aktivierungsenergie der Prozesse betrug für die Ausgangsfaser 29,8 kcal/mol und für die mit DNKPh vorbehandelte Faser 32,4 kcal/mol.

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Summary DTA and DSC measurements were used for studying the behaviour of crude PAN-fibre Bulana as well as PAN treated with a solution of 2-phenyl-2-(3,5 dinitro-4 hydroxyphenyl)-propane in nitrobenzene during heating in air and in nitrogen. As a result of the treatment an increase of the temperatures of initiation result of the treatment an increase of the temperatures of initiation and maximum of the exothermic reaction as well as a decrease of the enthalpy (H) were found. The calculated activation energy of cyclization and oxydation was 29,8 kcal/mol in case of PAN-fibre Bulana and increased to 32,4 kcal/mol in case of PAN-fibre Bulana treated with DNKPh.

     

Similarity and dissimilarity in posets

The relevance of partially ordered sets (or posets) in a wide diversity of contexts in chemistry is emphasized, and the utility of distance functions (or metrics) on such posets is noted. First a notion of scale similarity is introduced to make comparisons within certain so-called scaled posets, for which there is formulated natural comparators, which in turn lead to associated distance functions. Beyond taking note of several chemically relevant examples of these scaled posets and their consequent associated similarity measures, a second chemically relevant class of so-called shifted posets is similarly developed, with examples. Even further extension of some aspects of the current approach is indicated, and finally the multi-posetic character of chemical periodic law is suggested.     

Chromogenic Receptors: Versatility of the Colorimetric Recognizing Behavior

This article briefly reviews our recent achievement in developing synthetic chromogenic receptors which are characterized by combining recognition and optical sensing functions; synthesis of several kinds of azomethine-derived calixarenes is described, as well as some colorimetric recognizing behavior for chemically or biologically significant guests ranging from cations to chiral amine derivatives.     

Synthesen mit Nitrilen, 28. Mitt.: Zur Kenntnis der Ritter-Reaktion

Zusammenfassung Das Nebenprodukt, welches bei der Bildung der Bi-pyridonyle3 aus dimerem Malonitril (2) und Arylaminopropenonen (1) anfällt, wird als Tetrahydro-1,8-naphthyridinderivat4 b erkannt und seine Eigenschaften beschrieben. Da für die Entstehung von4 b das intermediäre Auftreten von Phenyl-vinylketon angenommen werden kann, wird das Verhalten des letzteren gegenüber Nitrilen im Sinne einerRitter-Reaktion untersucht. Mit Benzonitril kann das -Benzamido-propiophenon8 erhalten werden. Auch -Dimethylamino-propiophenon eignet sich zu Kondensationen mit dimerem Malonitril und Glutazinderivaten. Durch Dehydrierung werden dabei dieselben Produkte isoliert wie bei der Verwendung von Enaminoketonen. Der Mechanismus dieser Reaktionen wird diskutiert.

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Syntheses with nitriles, XXVIII.: Contributions to the ritter reaction

The by-product of the synthesis of the bi-pyridonyls3, from dimeric malononitrile and aryl-aminopropenones (1) is the tetrahydro-1,8-naphthyridine derivative4 b. Since phenyl vinyl ketone is an intermediate for the formation of4 b its reaction with nitriles is investigated.Ritter reaction with benzonitrile leads to -benzamido-propiophenone (8). -Dimethylaminopropiophenone is used for condensations with dimeric malononitrile or glutazine derivatives, too. The reaction proceeds with dehydrogenation to give the same products as obtained with enamino ketones. The mechanism is discussed.

     

Certification of reference materials by European Commission services

The programmes of the European Commission for the certification of reference materials are presented: the Standards, Measurement and Testing Programme (formerly BCR Programme) funds research and development aiming at improved ability to measure and at improved comparability of measurements; reference materials result from many of its projects; the Institute for Reference Materials and Measurements (formerly CBNM) prepares some of these, stores nearly all of them, will distribute them from 1995 on and certifies some additional ones. The principles adopted for the certification of BCR reference materials are explained. The procedure for a typical matrix reference material is that a group of laboratories first refines their methods (e.g. by intercomparisons and technical discussion) until they achieve agreement of results to within random experimental error and then analyses the reference material; certified value and uncertainty are calculated on the basis of their results. Recent achievements and projects in progress are listed.