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

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

The pH-static enzyme sensor: Design of the pH control system

The pH-static enzyme sensor offers a solution to the buffer dependency of ISFET-based enzyme sensors. A continuous coulometric titration of the reaction products keeps the pH in the enzymatic membrane at a constant level. This paper presents an automatic system to control the compensating current that is a direct measure for the substrate concentration

Comment on "Large Difference in the Elastic Properties of fcc and hcp Hard-Sphere Crystals"

As is well known, hard-sphere crystals of the fcc and hcp type differ very little in their thermodynamic properties. Nonetheless, recent computer simulations by Pronk and Frenkel indicate that the elastic response to mechanical deformation of the two types of crystal should be quite different. By invoking a geometrical argument put forward by R. Martin some time ago, we suggest that this is largely due to the different symmetries of the fcc and hcp crystal structures. Indeed, we find that elastic constants obtained by means of computer simulations for the fcc hard-sphere crystal can be mapped onto the equivalent ones of the hcp crystal to very high accuracy. The same procedure applied to density functional theoretical predictions for the elastic properties of the fcc hard-sphere crystal also produces remarkably accurate predictions for those of the hcp hard-sphere crystal.Comment: 7 pages, 5 figure

Self diffusion of particles in complex fluids: temporary cages and permanent barriers

We study the self diffusion of individual particles in dense (non-)uniform complex fluids within dynamic density functional theory and explicitly account for their coupling to the temporally fluctuating background particles. Applying the formalism to rod-like particles in uniaxial nematic and smectic liquid crystals, we find correlated diffusion in different directions: The temporary cage formed by the neighboring particles competes with permanent barriers in periodic inhomogeneous systems such as the lamellar smectic state and delays self diffusion of particles even in uniform systems. We compare our theory with recent experimental data on the self diffusion of fluorescently labelled filamentous virus particles in aqueous dispersions in the smectic phase and find qualitative agreement. This demonstrates the importance of explicitly dealing with the time-dependent self-consistent molecular field that every particle experiences.Comment: submitte

Offline and online scheduling of electric vehicle charging with a minimum charging threshold

The increasing penetration of electric vehicles (EVs) requires the development of smart charging strategies that accommodate the increasing load of these EVs on the distribution grid. Many existing charging strategies assume that an EV is allowed to charge at any rate up to a given maximum rate. However, in practice, charging at low rates is inefficient and often even impossible. Therefore, this paper presents an efficient algorithm for scheduling an EV within a decentralized energy management system that allows only charging above a given threshold. We show that the resulting optimal EV schedule is characterized by an activation level and a fill-level. Moreover, based on this result, we derive an online approach that does not require predictions of uncontrollable loads as input, but merely a prediction of these two characterizing values. Simulation results show that the online algorithm is robust against prediction errors in these values and can produce near-optimal online solutions

Model method drawing acts as a double-edged sword for solving inconsistent word problems

Drawing bar diagrams has been shown to improve performance on mathematical word problems wherein the relational keyword is consistent with the required arithmetic operation. This study extends this by testing the effectiveness of bar diagram drawing for word problems with an inconsistent keyword-arithmetic operation mapping. Seventy-five fifth graders solved consistent and inconsistent word problems while encouraged to draw bar diagrams. For each word problem, we assessed problem type (consistent/inconsistent), performance (correct/incorrect), and bar diagrams (accurate/inaccurate/no drawing). Overall, bar diagram drawing was associated with increased performance on both consistent and inconsistent word problems, but the strongest benefits of drawing were found for inconsistent word problems. For inconsistent word problems, bar diagram accuracy was more clearly related to performance (accurate bar diagrams related to correct answers, but inaccurate ones to incorrect answers) than for consistent word problems. We conclude that bar diagram drawing provides an effective graphical support for solving inconsistent word problems

Grass-clover mixtures: benefits for arable and livestock farms and biodiversity.

Introduction: Grass-clover mixtures show many benefits for sustainable agriculture. In the Netherlands, organic arable and livestock farmers often work together in a so-called partner farm concept: the arable farms grow one-year grass-clover leys to widen their crop rotation and as fodder for a livestock farm in exchange for manure. The aim of this research was to investigate the effect of different grass-clover mixtures and monocultures in a one-year ley on both aboveground and belowground parameters in light of the benefits of the ley for livestock farms, arable farms and biodiversit

End-fire versus side-fire:a randomized controlled study of transrectal ultrasound guided biopsies for prostate cancer detection

Objectives: To compare prostate cancer detection rates between end-fire and side-fire ultrasound guided prostate biopsy techniques. Methods: A prospective randomized controlled trial was performed in patients who underwent prostate biopsy between 2009 and 2014. Patients were randomly assigned to the end-fire or side fire biopsy groups and underwent transrectal ultrasound guided prostate biopsy. The overall prostate cancer detection rate was compared between the two probe configurations. Trial was registered at Clinical Trials.gov with identifier: NCT00851292. Results: A total of 730 patients were included and randomized, 371 patients underwent prostate biopsy with side-fire probe and 359 patients with the end-fire probe. Prostate cancer detection rates were 52.4% in the end fire group and 45.6% in the side fire group (p = .066). Conclusions: No significant difference was found in detection rate of prostate cancer between the end-fire and side-fire probe in transrectal ultrasound guided prostate biopsy, neither for detection rate of prostate cancer in the apex