Nonlinear and bistable properties of doped PMMA lightguides

Polymer lightguides of PMMA doped with the azo dyes methyl-red and N, N-dihexyl-4-amino-4'-nitro-azobenzene (DHANA) are investigated with respect to their opto-optical properties. The trans-cis photoisomerisation of the dyes leads to reversible polarization-dependent optically induced refractive index changes. The index changes are anisotropic. Birefringence is measured using index matched lightguides. The changes with respect to each polarization are determined by leaky mode spectroscopy and by using a half-integrated interferometer. These changes are intensity dependent and, with a suitable geometry, bistability at low intensities (3 mW/mm³) can be obtained.     

An integrated organic photoconductive detector for optoelectronics

In the system (poly-(N-vinyl carbazole) (PVK): trinitrofluorenone (TNF) a photoconductive complex is formed. Thin metal films are sputtered on BK7 glass substrates, forming two electrodes with 1 mm separation. The photoconductive complex is deposited from a solution in chlorobenzene/tetrahydrofurane on the glass substrate between the electrodes, forming a photoconductive detector. Photoconductivity of these planar detectors is studied using He-Ne laser light (=633 nm) as a function of electric field and for different TNF concentrations. An increase of photosensitivity is found for high TNF concentrations.Time resolution of the photoconductive PVK:TNF detector is investigated using a ruby pulse laser (=694 nm). The possible use of such detectors in combination with other polymer lightguides is demonstrated. Compared to most polymer waveguide materials PVK exhibits a rather high refractive index ofn=1.7. Thus the coupling of light into the photoconductive film is achieved directly. The planar structure allows further integration of polymeric components for optoelectronics.     

Synthesis of Cannabinoid Model Compounds. Part 3. (6aR, 10aR)-N-ethyl-Δ8-tetrahydrocannabinol-18-amide, (6aR, 10aR, 17 RS)-N-ethyl-17-methyl-Δ8- tetrahydrocannabinol-18-amide and (6aR, 10aR)-17,18-didehydro-Δ8-tetrahydrocannabinol

The novel cannabinoids (6aR, 10aR)-N-ethyl-Δ⁸-tetrahydrocannabinol-18-amide (15) and (6aR, 10aR, 17 RS)-N-ethyl-17-methyl-Δ⁸- tetrahydrocannabinol-18-amide (16) , designed as cannabinoid affinity ligands, were synthesized from the corresponding acids 11 and 12 via the N-hydroxysuccinimide esters. Amide 16 was tested in the rat and was generalized to Δ⁹-tetrahydrocannabinol, being 5 times less potent than the training drug. An improved synthesis of (6aR, 10aR)-17,18-didehydro-Δ⁸-tetrahydrocannabinol (23) is reported. As model reaction for the preparation of a tritiated Δ⁸-tetrahydrocannabinol, compound 23 was selectively deuterated at C(17) and C(18) in benzene/Et₃N using [(C₆H₅)₃P]₃RuCl₂ as catalyst.     

Antimalarial activity of n(6)-substituted adenosine derivatives (part 2)

We have investigated the in vitro antimalarial activity of a new series of adenosine derivatives. The results show that N(6)-(1-naphthylmethyl)-5'-deoxy-5'-(amido)adenosines as well as N(6)-(4-phenylbenzyl)-5'-deoxy-5'-(amido)adenosines display significant activity against the malaria-causing parasites, with the sterically demanding bisubstituted species reported being active in most cases in the low-micromolar range. The novel compounds with unusual substitution pattern were obtained applying an efficient convergent polymer-assisted solution-phase (cPASP) synthesis protocol. Thus, we were able to prepare a series of substituted derivatives in parallel that would have been difficult to synthesize by standard techniques. The scope and limitations of the synthetic methodology are discussed.     

Coupling of thermal desorption in modified closeable sampling columns with wide-bore capillary gas chromatography and mass spectrometric detection

In contrast to usability of Curie-point pyrolysis at 700°C directly attached to gas chromatography-mass spectrometry (GC-MS) for determination of organic wood preservatives in waste wood samples the investigation method reported here consists of thermal desorption at temperatures about 260°C in connection with GC-MS for peak identification or GC with flame ionization detection for quantitative analyses. So-called “modified closeable sampling columns” are used as batch-reactor in thermal desorption experiments. Desorbed vapours can be introduced on capillary columns without sample discrimination and without a disturbing lost of resolution. In this manner a lot of individual polycyclic aromatic hydrocarbons were determinated in waste wood samples, especially in railway sleepers.     

Zur Automatisierung der Auswertung bei der quantitativen Spektralanalyse

Zusammenfassung Die Eigenschaften der photoelektrischen und photographischen Registrierung von Spektren werden besprochen und die Bedeutung der photographischen Registrierung für die Verfahrensentwicklung und Routineanalyse von Proben wechselnder Zusammensetzung hervorgehoben. Das Programmsystem für den elektronischen Digitalrechner und verschiedene Möglichkeiten der Datenerfassung werden beschrieben. Durch diese Automatisierung der Auswertung wird gegenüber dem herkömmlichen Rechenbrettverfahren eine Beschleunigung um den Faktor 200 erreicht.

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Summary The characteristics of the photoelectric and photographic registration of spectra are discussed and the importance of the photographic registration for the development of methods and the routine analysis of samples of changing composition is emphasized. The program system for the electronic digitalcomputer and different possibilities of data collecting are described. Automating the evaluation has resulted in a speeding-up factor of 200 compared with the traditional computing board method.

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Die obige Arbeit wurde erwähnt von Herrn Dr. Pohl am 6. 10. 1964 in Düsseldorf in seinem Vortrag Erfassen und Verwerten von chemischen Daten. [Diese Z. 209, 19 (1965).]

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Außerdem wurde uns die Arbeit von Tunnicliff und Weaver, Analytical Chemistry 36, 2318 (1964), erst nach Abschluß unserer Arbeit bekannt. Die Autoren befassen sich mit einer ähnlichen Aufgabe, wobei allerdings das Problem der Linienauswahl eingehender behandelt wird als bei uns.     

Arylesters of alkylsulfonic acids in sediments Part III of organic compounds as contaminants of the Elbe River and its tributaries

Sediments from the Elbe River and from its major tributaries are shown to be contaminated with arylesters of alkylsulfonic acids. Here we report on the structure elucidation and quantification of aryl esters of alkylsulfonic acids. Chromatographic separation and mass spectrometric properties are discussed. Congener-specific analyses revealed a highly similar pattern throughout the area investigated. Alkylsulfonic acid phenylesters were present at almost all sampling locations. Amounts ranged from 33 000 μg/kg near the industrial region of Bitterfeld to 15 μg/kg in wadden sea sediments. Concentrations of alkylsulfonic acid cresylesters were between 10–40% of the phenylesters, and fell below the detection limit only in the Elbe estuary. The presence of aryl esters of alkylsulfonic acids in all sediment samples analyzed indicates a widespread distribution of these compounds in the environment. Previous literature described these compounds erroneously as phenoxyalkanes. Received: 5 August 1997 / Accepted: 21 August 1997     

Evaluation of dead time calculation in liquid chromatography using a linearization procedure for homologous series

A mathematical method for the calculation of the dead time (t_m) in HPLC was evaluated using a computer simulation approach, in which artificial perturbations were introduced to Simulated homolog retention times. The calculation was based on a modified and extended Grobler and Bálisz (GB) method. Investigated wav how the precision of the calculated t_M is affected by: statistical fluctuations in retention times and which, and how many homolog retention times are used. Based on these simulations a two-step procedure for the t_M calculation is proposed: In the first step the linearity of log t_{R, n} vs carbon number n is checked using as many homolog retention times as possible. The slope value b^o of the first linear regression in the GB method is used for the selection of homolog retention times in the final t_M calculation. In the second step the optimal selection of homologs is made and the final t_M calculation is carried out. Guidelines for homolog selection are given.     

Colorimetric uranium determination with arsenazo

A rapid and sensitive method is described for the quantitative colorimetric determination of uranium(Vl). Masking agents such as EDTA, tartaric acid or thioglycerol make possible the determination of uranium in the presence of many foreign metal ions. If thorium is present, a preliminary extraction of uranium as the diethyldithiocarbamate is required.