HPLC analysis of polyamines and their acetylated derivatives in the picomole range using benzoyl chloride and 3,5-dinitrobenzoyl chloride as derivatizing agent

Analytical methods are described for the quantitative determination of putrescine, cadaverine, spermidine, spermine and the acetylated derivatives of spermidine and spermine in biological fluids using pre-column derivatization with either benzoyl chloride or 3,5-dinitrobenzoyl chloride, which were added to each sample as solutions in diethyl ether. Putrescine, spermidine and spermine can be analysed in seminal plasma at nanogram levels when benzoyl chloride is used as derivatizing agent. In the analysis of putrescine, cadaverine, spermidine and acetyl derivatives of spermidine and spermine, higher sensitivity is obtained with 3,5-dinitrobenzoyl-chloride. This method can readily be used in the determination of acetylated polyamines in urine samples.     

Determination of phenol in industrial waste water by isotachophoresis

Summary The present work deals with the isotachophoretic analysis of phenol in industrial waste water. By variation of pH, temperature, leading and terminating electrolytes an optimal system for the determination of phenol in waste water was found. All samples were examined without preliminary chemical or physical treatment and therefore a direct analysis of waste water containing phenol is possible. The limit of the sensitivity for phenol is 0.1 ppm. The second part of this work concerns the separation of phenolic compounds, such as phenol, p-cresol and vanillin using the method described.

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Bestimmung von Phenol im Industrieabwasser mittels Isotachophorese

Zusammenfassung Die vorliegende Arbeit beschäftigt sich mit der isotachophoretischen Analyse von Phenol im Abwasser von Industriebetrieben. Durch Variation von pH, Temperatur sowie der leading und terminating Elektrolytlösungen wurde ein optimales System zur Analyse von Phenol im Abwasser erstellt. Alle Proben wurden ohne chemische oder physikalische Vorbehandlung untersucht, somit kann eine direkte Analyse zur Bestimmung von Phenol durchgeführt werden. Die Bestimmungsgrenze für Phenol in diesem System liegt bei 0,1 ppm. Ein zweiter Teil dieser Arbeit beschäftigt sich mit der Trennung von Phenol, p-Kresol und Vanillin unter den beschriebenen Analysenbedingungen.

     

Evidence for subsurface atomic displacements of the GaAs(110) surface from LEED/CMTA analysis

The low-energy electron diffraction constant momentum transfer average (LEED/CMTA) technique is applied to the GaAs(110) surface. In addition to verifying our earlier model of the top layer atomic displacements, atomic displacements in the first subsurface layer, opposite in direction to those in the top layer, are suggested. Best estimates for atomic positions in the surface and first subsurface layers are given.     

Half-lives,neutron emission probabilities and fission yields of neutron-rich rubidium isotopes in the mass regionA=96 toA=100

Neutron-rich rubidium isotopes were produced by thermal-neutron induced fission of²³⁵U and were isolated by surface ionization and mass separation. The new isotope (51 ±17) ms¹⁰⁰Rb was identified. The half-lives of the rubidium isotopes with mass numberA=96 toA=100 were measured using neutron multiscaling or gamma multispectrum analysis. Measurements of the delayed-neutron emission probabilityP _n of⁹⁹Rb and of the fission yields of⁹⁷Rb,⁹⁸Rb, and⁹⁹Rb were performed.     

Viscous fingering in a yield stress fluid

A new Monte Carlo method for calculating ground-state properties of liquid 4He is described. It is shown that Bose-Einstein condensation (BEC) implies delocalization of the wave function. It is shown that there is no general connection between the static structure factor and BEC. It is suggested that the observed connection in liquid 4He is due to the creation of spaces in the liquid structure, which are required so that the wave function can delocalize, in the presence of the hard-core interactions. It is shown that this suggestion is quantitatively consistent with observations on liquid 4He.     

First-order and critical wetting of alkanes on water

Ellipsometry measurements of the wetting behavior of different alkanes on water show a sequence of two wetting transitions: a first-order (discontinuous) transition followed by a critical (continuous) one. We report temperature-induced wetting transitions for different alkanes and a novel pressure-induced wetting transition for an alkane mixture. The experiments enable us to determine the global wetting phase diagram as a function of chain length and temperature which we subsequently calculate theoretically. The two transition lines are found to be approximately parallel, in accordance with basic theoretical arguments.     

Giant enhancement of the thermal Hall conductivity kappa(xy) in the superconductor YBa(2)Cu(3)O(7)

In high-purity YBa(2)Cu(3)O(7), the (weak-field) thermal Hall conductivity kappa(xy) is observed to increase a thousand-fold between 90 and 30 K. The inferred quasiparticle lifetime tau increases a hundred-fold starting below 90 K, in disagreement with a recent photoemission experiment. We show that kappa(xy) exhibits a specific scaling behavior below approximately 30 K. This scaling may bear on the issue of whether Landau quantization of the quasiparticle states occurs.     

Effects of vortex pinning and thermal fluctuations on the Josephson plasma resonance in Tl2Ba2CaCu2O8 and YBa2Cu3O6.5

We investigated the temperature dependence and c-axis magnetic field dependence of the Josephson plasma resonance in optimally doped Tl2Ba2CaCu2O8 thin films and underdoped YBa2Cu3O6.5 (YBCO) ortho-II single crystals using infrared spectroscopy. We obtained the c-axis penetration depths, at low temperature, in zero fields of about 20 and 7 microm, respectively. While the temperature dependencies of the resonances in the two compounds are very similar, the magnetic field dependence in YBCO is much weaker. We attribute this weak magnetic field dependence to the lower anisotropy of YBCO and interpret the observed behaviors in terms of thermal fluctuations and pinning of pancake vortices.     

Highly Crystalline and Semiconducting Imine‐Based Two‐Dimensional Polymers Enabled by Interfacial Synthesis

Single‐layer and multi‐layer 2D polyimine films have been achieved through interfacial synthesis methods. However, it remains a great challenge to achieve the maximum degree of crystallinity in the 2D polyimines, which largely limits the long‐range transport properties. Here we employ a surfactant‐monolayer‐assisted interfacial synthesis (SMAIS) method for the successful preparation of porphyrin and triazine containing polyimine‐based 2D polymer (PI‐2DP) films with square and hexagonal lattices, respectively. The synthetic PI‐2DP films are featured with polycrystalline multilayers with tunable thickness from 6 to 200 nm and large crystalline domains (100–150 nm in size). Intrigued by high crystallinity and the presence of electroactive porphyrin moieties, the optoelectronic properties of PI‐2DP are investigated by time‐resolved terahertz spectroscopy. Typically, the porphyrin‐based PI‐2DP 1 film exhibits a p‐type semiconductor behavior with a band gap of 1.38 eV and hole mobility as high as 0.01 cm² V^?1 s^?1, superior to the previously reported polyimine based materials.