Practical and theoretical aspects concerning the use of salt bridges in electrochemistry

The emf of electrochemical cells containing various sorts of salt bridges between various concentrations has been measured. The net diffusion potential over a salt bridge has been treated theoretically. An expression to calculate the net diffusion potential has been derived and tested on values estimated from the emf measurements. A merit factor has been calculated for a saturated KCl bridge separating two HCl solutions and compared with the merit factor estimated from emf measurements on the cell:Pt|Ag|AgCl, HCl(c₁)|KCl(sat)|HCl(c₂), AgCl|Ag|Pt The practical performance of two commonly used reference electrodes with salt bridges has been tested on emf measurements on KBr solutions.     

Entanglement interferometry for precision measurement of atomic scattering properties

We report on a matter wave interferometer realized with entangled pairs of trapped 87Rb atoms. Each pair of atoms is confined at a single site of an optical lattice potential. The interferometer is realized by first creating a coherent spin superposition of the two atoms and then tuning the interstate scattering length via a Feshbach resonance. The selective change of the interstate scattering length leads to an entanglement dynamics of the two-particle state that can be detected in a Ramsey interference experiment. This entanglement dynamics is employed for a precision measurement of atomic interaction parameters. Furthermore, the interferometer allows us to separate lattice sites with one or two atoms in a nondestructive way.     

Ensemble hybridisation--a new method for exploring sequence dependent fluorescence of dye-nucleic acid conjugates

The fluorescence of thiazole orange as artificial base in PNA was investigated in a nearest neighbour analysis; library-to-library hybridisation allowed the identification of probe sequences suitable for homogeneous DNA detection.     

Coherent transport of neutral atoms in spin-dependent optical lattice potentials

We demonstrate the controlled coherent transport and splitting of atomic wave packets in spin-dependent optical lattice potentials. Such experiments open intriguing possibilities for quantum state engineering of many body states. After first preparing localized atomic wave functions in an optical lattice through a Mott insulating phase, we place each atom in a superposition of two internal spin states. Then state selective optical potentials are used to split the wave function of a single atom and transport the corresponding wave packets in two opposite directions. Coherence between the wave packets of an atom delocalized over up to seven lattice sites is demonstrated.     

Clay-based affinity probes for selective cleanup and determination of aflatoxin B1 using nanostructured montmorillonite on quartz

A study was conducted to investigate the selective cleanup and determination of aflatoxin B1 (AfB1) from contaminated media. Composite adsorbents were formulated from calcium montmorillonite clay, which possesses a high affinity and enthalpy of adsorption for AfB1. Nanostructuring techniques were used to construct various formulations of the clay-based composite media. In AfB1 adsorption studies with prototypical affinity columns, these composites offered narrowly defined, reproducible capacity ranges. Composite recoveries of AfB1 from spiked grains exhibited linear trends that correlated well with the range of spike levels. Composite columns provided lower recoveries of AfB1 from naturally contaminated corn than did immunoaffinity columns; however, recoveries were consistent and purified extracts were free of interfering compounds, as determined by liquid chromatography with fluorescence detection.     

Sterically crowded bicyclo[1.1.0]butane radical cations

The variability of carbon-carbon single bonds by steric and electronic effects is probed by DFT calculations of sterically crowded bicyclo[1.1.0]butanes and their radical cations. The interplay of sterics and electronics on the gradual weakening and breaking of bonds was studied by investigating bridgehead substitution in 1,3-di-tert-butylbicyclo[1.1.0]butane and 2,2',4,4'-tetramethyl-1,3-di-tert-butylbicyclo[1.1.0]butane and geminal substitution in 2,2'-di-tert-butylbicyclo[1.1.0]butane and 2,2',4,4'-tetra-tert-butylbicyclo[1.1.0]butane. Bridgehead substitution leads to a lengthening of the central bond, whereas bisubstitution on the geminal carbon leads to a shortening of this bond due to a Thorpe-Ingold effect. Although the character of the central bond can be modulated by substitution and electron transfer over a range of 0.35 A, the state forbidden ring planarization does not occur. Sterically crowded bicyclo[1.1.0]butane radical cations are therefore promising candidates for the investigation of extremely long carbon-carbon single bonds.     

Gruppen mit reduziblem Subnormalteilerverband

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