25,589 research outputs found

    From conventional membrane electrodes to ion-sensitive field-effect transistors

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    The theory concerning conventional membrane electrodes is often used as a starting point for the theoretical description of the operation of an ion-sensitive field-effect transistor. Although this results in a useful description of the device, a better view of the principles, and consequently the possibilities, of the new ion-sensitive device may result if the analysis is carried out in more detail, especially with respect to measuring concepts. This is presented in the paper. A careful comparison between the operation of a conventional membrane electrode and the i.s.f.e.t. leads to a definite classification of different types of i.s.f.e.t.s. These types are illustrated with corresponding measurements. In addition, the most appropriate application for each type is mentioned

    The influence of the pH on the electrolyte-SiO2-Si system studied by ion-sensitive fet measurements and quasi-static C-V measurements

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    The responses of ion-sensitive FETs (ISFETs) with thermally grown SiO2 gate regions and of electrolyte-SiO2-Si (EOS) structures to stepwise changes in the pH were studied.\ud \ud In addition to a change in the boundary potential at the electrolyte-SiO2 interface which accounts for the observed initial response of ISFETs, a mechanism is also proposed in which one or other hydrogen-bearing species interacts with the surface states at the SiO2-Si interface.\ud \ud This proposed mechanism is based on the observed time drift in the response of ISFETs and on the changes in the shape of the quasi-static C-V curves of the EOS structures

    Universal Codes from Switching Strategies

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    We discuss algorithms for combining sequential prediction strategies, a task which can be viewed as a natural generalisation of the concept of universal coding. We describe a graphical language based on Hidden Markov Models for defining prediction strategies, and we provide both existing and new models as examples. The models include efficient, parameterless models for switching between the input strategies over time, including a model for the case where switches tend to occur in clusters, and finally a new model for the scenario where the prediction strategies have a known relationship, and where jumps are typically between strongly related ones. This last model is relevant for coding time series data where parameter drift is expected. As theoretical ontributions we introduce an interpolation construction that is useful in the development and analysis of new algorithms, and we establish a new sophisticated lemma for analysing the individual sequence regret of parameterised models

    Bochner integrals in ordered vector spaces

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    We present a natural way to cover an Archimedean directed ordered vector space EE by Banach spaces and extend the notion of Bochner integrability to functions with values in EE. The resulting set of integrable functions is an Archimedean directed ordered vector space and the integral is an order preserving map

    Cruise report: Belgica 06/13 ; HERMES Belgica BIO, 23-29 June 2006, Cork (IE)-Zeebrugge (B), Gollum channels and Whittard Canyon

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    An investigation of the hydration properties of chemically vapour-deposited silicon dioxide films by means of ellipsometry

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    Time-dependent ellipsometric measurements were made of the water absoprtion in SiO2 films grown by chemical vapour deposition at low temperatures. These films were exposed to water vapour at different pressurures. We determined in the ellipsometric volume percentage of water in the oxide film from the changes in the ellipsometric parameters due to water absorption. We also obtained a diffusion coefficient of water of the order of 1.3 x 10-13 cm2 s-1. From the reversible changes in the ellipsometric parameters due to dehydration we conclude that the water is physically adsorbed
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