Synthesis of nanometer-scale polymeric structures on surfaces from template assisted admicellar polymerization: a comparative study with protein adsorption

A novel method for the formation of nanometer-scale polymer structures via template assisted admicellar polymerization (TAAP) is described. Admicellar polymerization uses a surfactant layer adsorbed on a surface to localize monomer to the surface prior to polymerization of the monomer. Nanostructures are formed by restricting adsorption to the uncovered sites of an already-templated surface, in this case to the interstitial sites between adsorbed latex spheres. Unlike most other process that form polymer nanostructures, polymer dimensions can be significantly smaller than the interstitial size because of sphere-surfactant interactions. Protein adsorption in the interstitial sites of colloidal arrays was also studied for three different proteins, and the results were compared with those obtained via admicellar polymerization.     

Optical investigations of alkali metal thiomanganates(II) containing isolated complexes as well as chain and planar compounds

Tetracoordinated Mn(II) complexes providing different molecular structures were investigated using various spectroscopical procedures. Na(6)MnS(4) contains separate pseudotetrahedral Mn-S complex units, K(2)MnS(2) has chains of edge-shared tetrahedra, and Cs(2)Mn(3)S(4) crystallizes in corresponding layers. Also doped materials, i.e., Cs(2)(Mn(x)Zn(1-x))(3)S(4) with 0.0 < x < 1.0, are considered. Absorption spectra recorded from samples incorporated in polyethylene pellets and excitation spectra taken from pure materials at 15-20 K temperature are assigned on the basis of energy level calculations obtained from the angular overlap model. All compounds exhibit intensive emission in the red, some of them also in the yellow region, which both are investigated in the temperature range from 12.5 to 250 K, in some cases varying the excitation power and excitation wavelength. Decay measurements supply lifetimes and activation energies evaluated from Arrhenius plots. The results support an assignment of both types of emissions to MnS(4) complex entities for all compounds, the red emission from the lowest excited level (Kasha luminescence) and the yellow emission, observed for some of the compounds with increasing intensity at lower temperature, from higher electronic levels.     

Education in medical genetics for physicians: Germany

We have assessed the relative amount of genetics education at each of the 3 levels of medical training in Germany, namely the undergraduate, postgraduate and continuous medical education stages. Our data show that genetics is ill represented at all levels. Written examinations at the end of the relevant section at the undergraduate level include very few questions related to medical genetics, and particularly few in subjects such as pathology, internal medicine and gynaecology and obstetrics. At the postgraduate level, only 4 specialties require knowledge in medical genetics that may be subject to examination. At the continuous medical education level, medical genetics plays a very minor role. All 3 levels have been subject to reform in recent years, but effects that might ensue from these reforms cannot be expected before 2008.     

A highly sensitive high-performance liquid chromatographic procedure for the determination of isocyanates in air

Summary A sensitive high-performance liquid chromatographic procedure is described to analyse hexamethylene diisocyanate (HDI), 2,4- and 2,6-toluene diisocyanate (TDI), and 4,4-diphenylmethane diisocyanate (MDI) in air. The isocyanates are trapped on a sorbent coated with 1-(2-methoxyphenyl)piperazine (MPP). The resulting derivatives are separated using a column switching technique using either a diode array UV detector or an electrochemical detector. Working ranges are 1–5000 and 0.05–400 pmol for UV and EC detection, respectively. Virtually no breakthrough occurs if an air volume of up to 1500 l is sampled, and relative detection limits between 0.1 and 1 ng/m³ can be achieved. The procedure can be used to determine HDI and MDI in work place atmospheres and indoor air.Dedicated to Prof Dr. E. Lahmann on the occasion of this 65th birthday     

All-electron SCF LCAO MO calculations on various conformations of cis- and trans-stilbene

Ab initio SCF calculations of cis- and trans-stilbene at different conformations were performed using two program systems. Minimal energy is obtained for cis-stilbene when the phenyl rings are rotated by 52 ° out of the molecular plane. The deviation from planarity due to steric hindrance is smaller for the trans isomer yielding a rotational angle of 19 °. The trans isomer is calculated to be more stable by 5.7 kcal/mole than the cis isomer, confirming the experimental estimate according to which the energy of isomerization is about 3 kcal/mole. This is an improvement over semiempirical calculations which predict a lower energy for the trans configuration.     

Non-empirical calculations and basis set effects on the inversion geometry of the aniline molecule

The geometry of the amine group and the barrier to internal conversion in aniline have been studied by single-determinantab initio SCF calculations using several basis sets from minimal to double-zeta quality. The results obtained from different types and sizes of basis sets are discussed. Calculations performed with the two most flexible basis sets yield inversion barriers of 0.9–1.1 kcal/mole and angles of pyramidalization at the nitrogen atom of 38–39 ° which are in good agreement with the experimental results (1.3 kcal/ mole and 38 °). Orbital and overlap population analyses are performed and compared with the expected mesomeric and inductive effect. The calculated dipole moment 1.48–1.49 D also agrees with the experimental values (1.48–1.50 D).Dedicated to Professor O. E. Polansky, Mülheim/Ruhr, on the occasion of his 60th birthday.     

Die Kernwechselwirkung in der MO-LCAO-Theorie

Zusammenfassung Die MO-LCAO-Theorie in der einfachen EinteilchennÄherung kann verbessert werden, indem durch Änderung der Kernwechselwirkungsenergie Fehler in der potentiellen Energie der Elektronen nÄherungsweise kompensiert werden.Wir berechnen Potentialkurven für H₂ ⁺ und H₂ und vergleichen sie mit denen der einfachen MO-LCAO-Theorie, wobei wir vom Kernabstand abhÄngige Abschirmzahlen verwenden.

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An improvement of the MO-LCAO-theory in the simple one particle approximation is proposed by including an internuclear repulsion in the electronic potential energy term of the Hamiltonian such that correct wave functions yield correct energy formulas for the Coulomb interactions. Energy curves are calculated for H₂ ⁺ and H₂ and compared to the results obtained by simple MO-LCAO-theory with screening factors depending on the internuclear distance.

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Résumé Nous proposons une amélioration de la théorie MO-LCAO simple (fonctions mono-électroniques séparées). Les erreurs du calcul de l'énergie potentielle électronique sont compensées approximativement par une modification de l'énergie internucléaire. Des courbes d'énergie calculées pour H₂ ⁺ et H₂ sont comparées aux résultats de la théorie MO-LCAO simple; des charges effectives dépendant de la distance internucléaire sont introduites.