Pressure pinched injection of nanolitre volumes in planar micro-analytical devices

A new method for injecting and driving fluids by means of a multi-port injection valve and syringe pumps in a micro-channel network is described. A structure composed of two micro-channels arranged as a cross is connected with capillary tubes to an external multi-port injection valve. The fluid flows are driven by pressure and the multi-port valve controls the direction of the flow within the different sections of the structure. The first position of the multi-port valve allows the preparation of the loading of the sample, which is pinched in the cross section of the two micro-channels. The second position allows the precise injection of nL volumes. No dead volume exists between injection and separation modes. The system can be used to prepare a sample plug by pressure in order to perform chromatography with a broad range of buffered or non-buffered solutions. Thanks to the insensitivity to the ionic strength of the sample, this injection method is useful for the injection of complex biological samples in microchip analysis. In order to demonstrate the feasibility of the method, different solutions of ionic or fluorescent molecules were injected and detected in a photoablated planar polymer device.     

Zur Koecherschen Reduktionstheorie in Positivitätsbereichen. I

Ohne ZusammenfassungGefördert durch National Science Foundation grant GP-3750.     

Zur Koecherschen Reduktionstheorie in Positivitätsbereichen. III

Ohne ZusammenfassungGefördert durch National Science Foundation Grant GP-3750     

Automorphismengruppen des allgemeinen Kreiskegels und des zugehörigen Halbraumes

Ohne Zusammenfassung     

Über Mutationen von Jordan-Algebren

Ohne Zusammenfassung     

Landau behaviour of the heat capacity of AgNa(NO2)2 close to the nearly tricritical ferroelectric phase transition

The heat capacity of a single crystal of the uniaxial ferroelectric AgNa(NO₂)₂ was measured close to the nearly tricritical phase transition. In the ferroelectric phase a strong temperature dependence of the anomaleous specific heat is found which obeys a temperature law (θ _f —T)^?0.494. A small latent heat was detected nearT _c. The thermal behaviour of AgNa(NO₂)₂ is described by a Landau type theory, from which the non linear coefficientsζ andζ of the free energy expansion are derived. The thermal data fit well to the known dielectric behaviour.