Die elektrische leitfähigkeit von α,ω-bis-polyenen

The preparation and isolation of the coloured reaction products of maleic anhydride-methylvinylether-copolymer (Gantrez AN) and aprotic liquids yields α,ω-bis-polyenes of the copolymer each containing double bond sequences of equal length, irrespective of the order of reaction. Prior to the formation of the polyenes in hexamethylphosphoramide (HMPA), a chemical reaction involving this aprotic substance occurs at the anhydride ring of the Gantrez AN. The electrical conductivity is improved by addition of iodine, dichloro-dicyano-p-benzoquinone (DDQ), tetracyanoethylene (TCNE) and tetracyanoquinonedimethane (TCNQ) to the resultant α,ω-bis-polyenes. If the unsubstituted α,ω-bis-polyenes are treated with boiling xylene or pressure sintered, specific resistances as high as that of polyacetylene (PA) are obtained. On the whole, the specific resistance is reduced by ten orders of magnitude, Gantrez AN: 2.8·10¹³ Ω. cm, pressure-sintered α,ω-bis-polyene: 1.1·10⁴ Ω·cm, α,ω-bis-polyene containing iodine: 2·10³ Ω·cm. IR spectroscopy can be used to detect the polyene and complex formation and to demonstrate that the actively conducting reaction product is a 3- or 4-substituted α,ω-(bis-polyene)-1,2-polybutene.     

GPC-messungen von polymeren an oberflächenmodifizierten silikagelen

The fractionation of homo- and copolymers by GPC-experiments was investigated, using surface modified silica gels as porous supports. Linear polystyrenes, poly-α-methyl-styrenes, and polybutadienes have been analysed. Methods are shown which consider the hydrodynamic broadening effects due to GPC. A computer program of PROVDER and ROSEN has been improved by a subsequentiteration method. With this program good results for molecular weightdistributionscould be obtained. “True” molecular weight averages and polydispersities have been measured with a recycle method of WATERS and with extrapolation by HAMIELEC. By comparison with results from sedimentation transport runs and ?-fractionations a good agreement has been achieved within the limits of error of these methods. The (α-methyl styrene methacrylonitrile)-copolymers have been analysed fortheir heter-ogeneity of chemical composition. These polymers show an unusual elution behaviour,and exhibit more chemical heterogeneity than is computed by kinetic data.     

The real population problem: Distribution.

Argues that, while there is a need for curbing absolute population growth in the US, there is a greater need for studying and attempting to alter the distribution of the population. Projected density figures for metropolitan areas in the year 2000 indicate the need for a rational policy for population redistribution. The possible contributions of psychology to such a policy are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oligomer formation in the chemical degradation of dextran

Summary The production of oligomers — to a degree of polymerization 5 — during acid hydrolization of polymer dextrans was estimated quantitatively by a combined aqueous SEC and adsorption separation. It was found that the molar concentrations of the oligomers were higher for those with lower DP. This experimental result is in agreement with a degradation model, in which the molecular weight decreases with the power of 2/3 versus time, which has been proposed earlier.Extracted from a thesis submitted by J. Emmert to the University of Heidelberg in partial fulfillment of the requirements for the Ph.D. degree     

Ergebnisse aus Zeitstandversuchen bei 500°C mit einer Beanspruchungsdauer bis über 300000 h

Zeitstandversuche an einem unlegierten Stahl, drei niedriglegierten CrMo(W)V-Stählen, einem Stahl mit rd. 20% Cr und 1% Mo und an einem Stahl mit rd. 18% Cr, 8% Ni und 0,7 %Ti. Erörterung des Zeitstandverhaltens glatter und gekerbter Proben. Vergleich der 100000-h-Zeitstandfestigkeit der untersuchten Stähle und heute gebräuchlicher Stähle. Überlegungen zur Extrapolation der Zeitstandfestigkeit bis zu einer Beanspruchungsdauer von 300000 h. Lichtmikroskopische Gefügevergleiche an Zeitstandproben mit mittlerer und mit hoher Beanspruchungsdauer.     

Polychlorierte Biphenyle (PCB) in Fischen aus Teichwirtschaften und Nachklärteichen

European Food Research and Technology - Das Muskelgewebe von 58 Fischen aus Teichwirtschaften und 17 Fischen aus Nachklärteichen wurde auf seinen Gehalt an den sechs in der...     

Behavioral effects of a noisy environment: Task involvement versus passive exposure.

Compared the effects of noise under active task involvement as opposed to passive exposure, using 80 undergraduate Ss who were assigned to 1 of 4 conditions representing 2 * 2 combinations of task vs no task and noise vs quiet. Performance on a dial-monitoring task was unaffected by noise. Ratings of interest and tenseness were significantly higher under the task condition; tenseness was also higher under noise. On a posttest of resistance to frustration, both noise groups, regardless of task condition, showed a smaller degree of persistence on insoluble puzzles than the no-noise groups. Results suggest that aftereffects of noise are not dependent on the power of noise to disrupt task performance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)