Modelling of the migration effect occurring at an ISFET-based coulometric sensor-actuator system

The migration effect, in addition to diffusion, occurring at an ion-selective field-effect transistor (ISFET)-based coulometric sensor-actuator system has been studied. A diffusion-migration model is presented, based on the numerical solution of the Nernst-Planck equations of which a digital simulation is realized. Corresponding experiments were carried out and compared with the simulation. The results are in good agreement with the simulation.\ud Typical titration times of this system were found to be 0.5–10 s, corresponding to fully dissociated acid concentrations of 0.5×10−3−6.5×10−3 mol 1−1 with excess of supporting electrolyte. Both the simulation and experimental results show that if the concentration of the supporting electrolyte is 20 times higher than that of the species to be titrated, the deviation caused by migration is less than 5% and within the experimental error when pure diffusion is considered. At relatively low concentrations of supporting electrolyte, the migration effect should be taken into account to determine the concentrations of titrated species

Modelling of non-steady-state concentration profiles at ISFET-based coulometric sensor—actuator systems

Acid or base concentrations can be determined very rapidly by performing an acid—base titration with coulometrically generated OH− or H+ ions at a noble metal actuator electrode in close proximity to the pH-sensitive gate of an ion-sensitive field effect transistor (ISFET). The ISFET is used as the indicator electrode to detect the equivalence point in the titration curve. Typical values for the time needed to reach the equivalence point are 0.5–10 s for acid or base concentrations ranging from 0.5 × 10−3 to 20 × 10−3 mol l−1.\ud \ud A model is presented, giving an analytical description of the diffusion phenomena that occur with the sensor—actuator system. The results of this analytical model description, using linearized concentration gradients, are presented together with the results of numerical simulations. Both results are in good agreement with measurements

Determination of buffer capacity by means of an ISFET-based coulometric sensor-actuator system with a gate-covering porous actuator

In this paper we propose a dynamic way to measure the buffer capacity of an electrolyte by means of an ISFET-based coulometric sensor-actuator system whose gate is covered with a porous actuator. A theoterical model for this measurement is presented. Experiments are carried out in nitric and acetic acid as well as in phosphoric acid solutions. A fairly good agreement has been found between the theoretical calculations and the experimental results

Integration of economic appraisal and health care policy in a health insurance system; The Dutch case

This article discusses the role of economic appraisal in insurance based health care systems, taking the case of the Netherlands as an example. The public health insurance system in this country is governed by the Health Insurance Executive Board, which policies are firmly based on the results of economic appraisal. Furthermore, reimbursement policies regarding pharmaceutical products are described, emphasizing again the position of information from economic appraisal in these policies. The article concludes with the identification of some trends in health policy and in the way it is supported by economic appraisal studies

Student Modeling Based on Fine-Grained Programming Process Snapshots

ICER '17 Proceedings of the 2017 ACM Conference on International Computing Education Research. New York, NY, USA : ACM, 2017 ISBN: 978-1-4503-4968-0I am studying the use of fine-grained programming process data for student modeling. The initial plan is to construct different types of program state representations such as Abstract Syntax Trees (ASTs) from the data. These program state representations could be used for both automatically inferring knowledge components that the students are trying to learn as well as for modeling students' knowledge on those specific components.Peer reviewe

A Two-Level Adaptive Test Battery

A test battery with two different levels of adaptation is presented: a within-subtest level for the selection of the items in the subtests and a between-subtest level to move from one subtest to the next. The battery runs on a two-level model consisting of a regular response model for each of the subtests extended with a second level for the joint distribution of their abilities. The presentation of the model is followed by an optimized MCMC algorithm to update the posterior distribution of each of its ability parameters, select the items to Bayesian optimality, and adaptively move from one subtest to the next. Thanks to extremely rapid convergence of the Markov chain and simple posterior calculations, the algorithm can be used in real-world applications without any noticeable latency. Finally, an empirical study with a battery of short diagnostic subtests is shown to yield score accuracies close to traditional one-level adaptive testing with subtests of double lengths.</p

Alternative model of the Antonov problem

Astrophysical systems will never be in a real Thermodynamic equilibrium: they undergo an evaporation process due to the fact that the gravity is not able to confine the particles. Ordinarily, this difficulty is overcome by enclosing the system in a rigid container which avoids the evaporation. We proposed an energetic prescription which is able to confine the particles, leading in this way to an alternative version of the Antonov isothermal model which unifies the well-known isothermal and polytropic profiles. Besides of the main features of the isothermal sphere model: the existence of the gravitational collapse and the energetic region with a negative specific heat, this alternative model has the advantage that the system size naturally appears as a consequence of the particles evaporation.Comment: RevTex4, 9 pages, 10 figures, Version Submitted to PR

Symptom complexes in patients with seropositive arthralgia and in patients newly diagnosed with rheumatoid arthritis: a qualitative exploration of symptom development

Objective: The aim of this study was to explore symptoms and symptom development during the earliest phases of rheumatoid arthritis (RA) in patients with seropositive arthralgia and patients newly diagnosed with RA