Tests of quantum electrodynamics using ion traps

Experiments in ion traps on the g factors for the free and the bound electron in low-Z, hydrogen-like ions have provided the most accurate tests of quantum-electrodynamics calculations. Moreover they have been used to determine new and precise values for fundamental constants. Extensions to more stringent tests using ions of higher values of the nuclear charge Z are on the way. Also other QED tests such as Lamb shifts or hyperfine structures in H-like ions using traps will be feasible in the near future. The tests in bound systems, however, will be limited by nuclear structure effects which are difficult to calculate. Assuming the QED calculations as correct, the experimental results may be used to determine nuclear contributions and thus support nuclear models. Contribution presented at the TCP06, Vancouver Island, 2006.     

Exchange interactions of excitons localized at opposite interfaces in type-II GaAs/AlAs superlattices: Optically detected magnetic resonance and level anticrossing

Two types of excitons, localized at opposite interfaces and characterized by different magnitudes of the exchange interactions at the same radiation energies, are simultaneously in type-II GaAs/AlAs superlattices. It is shown that the additional long-wavelength luminescence line in superlattices grown with growth interruptions after the GaAs layers is due to the recombination of an exciton localized at an inverted interface in regions where the quantum-well width is increased by one monolayer. Pis’ma Zh. éksp. Teor. Fiz. 64, No. 10, 701–706 (25 November 1996)     

Optical biosensor for pharmaceuticals, antibiotics, hormones, endocrine disrupting chemicals and pesticides in water: Assay optimization process for estrone as example

Certain contaminants at trace concentrations in surface waters can have dramatic effects on the hormonal system of organisms in the aquatic environment. Therefore, immunoanalytical methods at a very low limit of detection (LOD) and a low limit of quantification (LOQ) are becoming more and more important for environmental analysis and especially for monitoring drinking water quality. Environmental monitoring of antibiotics, hormones, endocrine disrupting chemicals, and pesticides in real water samples (e.g. surface, ground or drinking water) with difficult matrices places high demands on chemical analysis. Biosensors have suitable characteristics such as efficiency in allowing very fast, sensitive, and cost-effective detection. Here we describe an assay optimization process with a fully automated immunoassay for estrone which resulted in a LOD below 0.20 ng L⁻¹ and a LOQ below 1.40 ng L⁻¹. In contrast to common analytical methods such as GC-MS or HPLC-MS, the biosensor used requires no sample pre-treatment and pre-concentration. The very low validation parameters for estrone are the result of the continuous optimization of the immunoassay. The basis of our sensitive assay is the antibody with a high affinity constant towards estrone. During the optimization process, we reduced the amount of antibody per sample and improved the chip surface modification. Finally, this proceeding led to a calibration routine with an amount of antibody of only 3.0 ng per sample (sample volume: 1.0 mL). The reduction of the amount of antibody per sample results in better validation parameters (LOD, LOQ, and IC₅₀), but this reduction leads to the current device-related limitation of the River Analyser (RIANA).For some endocrine disrupting compounds, no effect levels (NOELs) in the lower nanogram per liter range are reported. This defines the challenge, which analytical methods have to compete with and our RIANA instrument with its improved sensitivity for the detection of a single hormone in the lower nanogram per liter range is a powerful tool in aquatic analytics in addition to the common analytical methods.     

Cyclisierungen unter beteiligung von fluoridionen. 2. Mitteil. [1], [2]. 4.5-perfluor-1.3-dioxolane

4.5-Perfluoro-1.3-dioxolanes $\text{2}$ are available by reaction of 2(α-chloroalkoxy)perfluoro-carbonyl halides $\text{3}$ or -ketone $\text{9}$ with fluoride ions. A mechanism for the intramolecular ring- closure-reaction is proposed. Hydrogen atoms at C-2 in $\text{2}$ can be exchanged photochemically by chlorine. Starting from the 2-monochloro-derivatives $\text{16}$ the 2-monofluoro-4.5-perfluoro- 1.3-dioxolanes $\text{18}$ are formed by reaction with triethylamine- hydrofluoride.     

The electron impact fragmentation of 3- and 4-styrylpyridazine

The electron impact mass spectrometric fragmentation of trans-3- and trans-4-styrylpyridazine is reported in detail, including a comparison with other aza-stilbenes. With regard to a distinction between the two isomeric styrylpyridazines, the intensity ratio of the M⁺ and [M-1]⁺ ions, the general degree of fragmentation and the elimination pathways of nitrogen proved to be most characteristic.