Modelling Complex Chemical Processes in Homogeneous Solutions: Automatic Numerical Simulation

Two algorithms for the determination of the necessary limit of local error for the numerical solution of ordinary differential equation (ODE) systems describing homogeneous chemical and biochemical processes, and for the evaluation of their stiffness are developed. The approach for finding the necessary limit of local error of a numerical ODE solver is justified by the proof of the corresponding theorems. The application of the new algorithms implemented in version 2.1 of KinFitSim software to the simulation of real chemical systems is considered on the example of Belousov-Zhabotinsky reaction

Mathematical Modelling of Nitric Oxide Release Caused by Exocytosis and Determination of a Stellate Neuron Activity Function in Rat Brain

In this work we report the results of the mathematical modelling of NO◦ -release by neurons considering a series of Gaussian bursts, together with its transport in the brain by diffusion. Our analysis relies on the NO◦ -release from a neuron monitored before, during and after its patch-clamp stimulation as detected by an ultramicroelectrode introduced into a slice of living rat’s brain. The parameters of the neuron activity function have been obtained by numerical fitting of experimental data with simulated theoretical results. Within our initial hypothesis about the Gaussian decomposition of NO◦ -release that allowed drawing qualitative and quantitative conclusions about the considered neuron activity function. It is noted that since the activity function can be readily modified this signal processing may be adapted to the treatment of other and maybe more physiologically relevant hypotheses

Theoretical concepts underlying ECL generation

International audienc

Theoretical Modeling and Optimization of the Detection Performance: a New Concept for Electrochemical Detection of Proteins in Microfluidic Channels

In this work, we present a complete theoretical analysis of a new concept of electrochemical detector for application in proteomics upon considering two band microelectrodes performing in generator-collector mode. This concept of an original electrochemical detector is aimed at the detection of proteins following their separation in microfluidic biochips. The theoretical analysis is based on the use of the time-dependent coordinate transformation which allows performing precise modeling for a wide range of the key parameters governing the electrochemical detector performance. This allows defining a precise optimization procedure for its best efficiency upon considering the qualitative and quantitative effects of each of the main operational parameters

Nurses\u27 Alumnae Association Bulletin, April 1959

Alumnae News Anniversary Class of /34 Article from Pennsylvania Nurse Committee Reports Current Events at Jefferson Greetings from the President Jefferson Story Lost Members Letter - Past President Marriages Necrology New Arrivals Notices Pictured - Student Nurses\u27 Residence Report of the School of Nursing and Nursing Services Staff Nurses Social Functions Student Activities Voluntary Service Year of Great Activity and Expansio

Simple and clear evidence for positive feedback limitation by bipolar behavior during scanning electrochemical microscopy of unbiased conductors

On the basis of an experimentally validated simple theoretical model, it is demonstrated unambiguously that when an unbiased conductor is probed by a scanning electrochemical tip (scanning electrochemical microscopy, SECM), it performs as a bipolar electrode. Though already envisioned in most recent SECM theories, this phenomenon is generally overlooked in SECM experimental investigations. However, as is shown here, this may alter significantly positive feedback measurements when the probed conductor is not much larger than the ti

Importance of correct prediction of initial concentrations in voltammetric scans: contrasting roles of thermodynamics, kinetics, and natural convection.

In order to successfully model an electrochemical reaction mechanism one must ensure that all the equations, including initial conditions, satisfy the pertinent thermodynamic and kinetic relationships. Failure to do so may lead to invalid results even if they are mathematically correct. This fact has been previously emphasized (Luo, W.; Feldberg, S. W.; Rudolph, M. J. Electroanal. Chem. 1994, 368, 109 - 113; Rudolph, M. Digital Simulation in Electrochemistry. In Physical Electrochemistry; Rubenstein, I., Ed.; Marcel Dekker: New York, 1995; Chapter 3) and existing computer software for electrochemical simulations, such as DigiSim (Rudolph, M.; Reddy, D. P.; Feldberg, S. W. Anal. Chem. 1994, 66, 589A; http://www.basinc.com/products/ec/digisim/), offer the option of enforcing the so-called "pre-equilibration" which evaluates thermodynamic concentrations of all species prior to beginning a voltammetric scan. Although this approach allows setting consistent thermodynamic values it may result in a nonrealistic initial concentrations set because it corresponds to the whole solution status at infinite time for infinite kinetic constants. However, the perturbation created by the working electrode poised at its rest potential is necessarily limited by the size of the electrode, reaction kinetics, and duration of the rest period. Furthermore, natural convection limits even more the importance of the perturbation. This is analyzed theoretically through comparison of simulation results by DigiSim and KISSA-1D software for certain common electrochemical mechanisms in order to illustrate the importance of correct prediction of initial concentrations

In situ and online monitoring of hydrodynamic flow profiles in microfluidic channels based upon microelectrochemistry: optimization of electrode locations.

Herein, we extend our previous approach concerning the reconstruction of profiles of pressure-driven hydrodynamic flow in microfluidic channels based on current measurements at band electrode(s) [see the preceding paper ChemPhysChem 2005, 6, 1581]. We address the central issue of optimization of geometrical parameters describing the electrode(s) assembly (a single band and two bands working in generator-collector mode) within the channel flow cell to enhance the speed and precision of the flow profile reconstruction method