Design and realisation of mono-modal SiOxNy-based polymer waveguides for active functions

A method is described for optimising nonlinear mono-modal channel waveguides such that the guided power influences the propagation constant optimally. These waveguides have been used for a nonlinear MZI and measuring TPA. Experimental results are describe

Prostitution: A Violent Reality of Homelessness

This policy paper summarizes findings on the connections between homelessness and prostitution

An ISFET-based microlitre titrator: integration of a chemical sensor—actuator system

This paper describes the integration of pH-sensitive ISFETs with a coulometric pH-actuator system. The coulometric analyser is able to perform acid—base titrations in microlitre samples at high speed. Combination of chemical sensors with a corresponding actuator eliminates the need for frequent calibration and thus may increase the applicability of solid-state chemical transducers. A number of possible measuring methods are described

Prediction of the dynamic response of the potentiometric carbon dioxide electrode

The dynamic behaviour of the potentiometric carbon dioxide electrode is predicted by means of a digital simulation that considers both diffusion and reaction kinetics. The method allows for complete description of the electrode response without requiring the assumption that one of these processes can be neglected. The validity of the simulation was tested experimentally by using a commercial pCO2 electrode provided with various silicone rubber and teflon membranes. The measured values are in good agreement with those of the simulation

ISFET based enzyme sensors

This paper reviews the results that have been reported on ISFET based enzyme sensors. The most important improvement that results from the application of ISFETs instead of glass membrane electrodes is in the method of fabrication. Problems with regard to the pH dependence of the response and the dynamic range as well as the influence of the sample buffer capacity have not been solved. As a possible solution we introduce a coulometric system that compensates for the analyte buffer capacity. If the pH in the immobilized enzyme layer is thus controlled, the resulting pH-static enzyme sensor has an output that is independent of the sample pH and buffer capacity and has an expanded linear range

On the Kinetics of Body versus End Evaporation and Addition of Supramolecular Polymers

Although pathway-specific kinetic theories are fundamentally important to describe and understand reversible polymerisation kinetics, they come in principle at a cost of having a large number of system-specific parameters. Here, we construct a dynamical Landau theory to describe the kinetics of activated linear supramolecular self-assembly, which drastically reduces the number of parameters and still describes most of the interesting and generic behavior of the system in hand. This phenomenological approach hinges on the fact that if nucleated, the polymerisation transition resembles a phase transition. We are able to describe hysteresis, overshooting, undershooting and the existence of a lag time before polymerisation takes off, and pinpoint the conditions required for observing these types of phenomenon in the assembly and disassembly kinetics. We argue that the phenomenological kinetic parameter in our theory is a pathway controller, i.e., it controls the relative weights of the molecular pathways through which self-assembly takes place

The pH-static enzyme sensor : An ISFET-based enzyme sensor, insensitive to the buffer capacity of the sample

An ISFET-based urea sensor is combined with a noble-metal electrode which provides continuous coulometric titration of the products of the enzymatic reaction. The sensor thus becomes independent of the buffer capacity of the sample; and because the enzyme is operating at a constant pH, the linear response range is expanded

Evaluation of the sensor properties of the pH-static enzyme sensor

The pH-static enzyme sensor consists of a chemical sensor-actuator system covered with a thin enzyme-entrapping membrane. By the electrochemical generation of protons or hydroxyl ions, pH changes induced by the conversion of a substrate by the enzymatic reaction are compensated. The pH inside the membrane remains at a constant level and the control current is linearly related to the substrate concentration and independent of the buffer capacity of the sample. The sensitivity and linearity of the sensor response are evaluated. Depending on the enzyme load of the membrane, the operation of the sensor is either diffusion controlled or determined by the enzyme kinetics