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

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

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

Electrochemistry of potentially bioreductive alkylating quinones : Part 1. Electrochemical properties of relatively simple quinones, as model compounds of mitomycin- and aziridinylquinone-type antitumour agents

The influence of methyl-, hydroxy and amino substituents on the electrochemical behaviour of simple 1,4-naphtho-and 1,4-benzoquinones, model compounds of many quinoid antitumour agents, in aqueous media was studied. Significant changes in electrochemical behaviour were observed, potentially the result of a change in the electron density of the quinone moiety, pre- or post-protonation of substituents, hydrogen bond formation, tautomerization reactions and steric interactions between the quinone moiety and substituents. The information obtained was of benefit in the elucidation of the reduction mechanisms of quinoid antitumour agents such as aziridnylquinones and mitomycins

The effects of 5-fluorouracil and interferon-alpha on early healing of experimental intestinal anastomoses.

The continuing search for effective adjuvant therapy after resection of intestinal malignancies has prompted a growing interest in both immediate post-operative regional chemotherapy and the combination of 5-fluorouracil (5-FU) and interferon-alpha as drugs of choice. We have compared the effects of both compounds, alone and together, on early healing of intestinal anastomoses. Four groups (n = 26 each) of rats underwent resection and anastomosis of both ileum and colon: a control group and three groups receiving intraperitoneal 5-FU, interferon-alpha or both on the day of surgery and the next 2 days. Animals were killed 3 or 7 days (n = 10 each) after operation in order to measure anastomotic strength and hydroxyproline content. The remaining six animals in each group were used to study anastomotic collagen synthetic capacity at day 3. Three days after operation, ileal anastomotic bursting pressure was lowered by 37% in the 5-FU/interferon-alpha group (P = 0.0104). At day 7, anastomotic breaking strength was reduced significantly in ileum (P = 0.0221) and colon (P = 0.0054) of the 5-FU/interferon-alpha group and in colon of the interferon-alpha group (P = 0.0221). Collagen synthetic capacity was strongly suppressed by 5-FU but not by interferon-alpha. However, no differences in anastomotic hydroxyproline content were observed between groups at both days 3 and 7. Thus, post-operative use of interferon-alpha, in particular in combination with 5-FU, may be detrimental to anastomotic repair in the intestine

Proof for an upper bound in fixed-node Monte Carlo for lattice fermions

We justify a recently proposed prescription for performing Green Function Monte Carlo calculations on systems of lattice fermions, by which one is able to avoid the sign problem. We generalize the prescription such that it can also be used for problems with hopping terms of different signs. We prove that the effective Hamiltonian, used in this method, leads to an upper bound for the ground-state energy of the real Hamiltonian, and we illustrate the effectiveness of the method on small systems.Comment: 14 pages in revtex v3.0, no figure