Yu. Feldman

First human experiments with a novel non-invasive, non-optical continuous glucose monitoring system

This paper describes a non-invasive continuous glucose monitoring system based on impedance spectroscopy. Changes in the glucose concentrations can be monitored by varying the frequency in the radio band over a range, optimised to measure the impact of glucose on the impedance pattern. A number of clinical-experimental studies (hyperglycaemic excursions) were performed with healthy subjects in order to prove the applicability of this approach. The sensor used in these experiments is the size of a wristwatch and holds an open resonant circuit coupled to the skin and a circuit, performing an impedance measurement. In most cases, the experiments showed a good correlation between changes in blood glucose and the sensor recordings. A detailed description of the trials is presented. The results of this first series of experiments can be considered as a proof of concept for this novel non-invasive monitoring approach. Nevertheless, partly due to the indirect measurement, a considerable number of questions remain to be clarified.

Rain Enhancement and Fog Elimination by Seeding with Charged Droplets. Part I: Theory and Numerical Simulations

A new method of droplet collision acceleration, with the purpose of rain enhancement and fog elimination, is proposed. According to the method, some fraction of the droplets is taken from clouds (or fog) themselves, charged, and then injected back into clouds (or fog). To verify the efficiency of the method, a novel model has been developed, allowing simulation of droplet spectrum evolution by collision in case a certain fraction of the droplets in a droplet spectrum is charged. Simulations of droplet spectra evolution include several steps: (a) The forces arising between charged and neutral droplets, as well as between charged droplets, are calculated as the function of the value of the charges, droplet size, and distance between droplets. It is shown that because of the induction effect, significant attraction forces arise between charged and neutral droplets. (b) The results obtained have been used to calculate the collision efficiencies between charged and neutral, as well between charged droplets. As a result, a ‘‘four dimensional’’ table of the collision efficiencies (the collision efficiency is the function of the droplet size and charge) was calculated. The collision efficiencies between charged and neutral droplets turn out to be significantly higher than the pure gravity-induced values. (c) To accomplish these simulations, a novel numerical method of solving the stochastic collision equation has been developed. Cloud droplets are described by a two-dimensional size distribution function in which droplets are characterized by both their mass and charge. (d) This model, with the implemented table of the collision efficiencies, has been used to simulate droplet spectra evolution in clouds and fog in case some fraction of these droplets was charged. Simulations of the effects of seeding by charged droplets have been performed. Evolution of initially narrow droplet size spectra (typical of extremely continental clouds in highly smoky air), in the case of seeding and under natural conditions, has been simulated. It was shown that although a natural droplet spectrum does not develop and no raindrops are formed, the injection of just a small fraction of charged particles rapidly triggered the collision process and lead to raindrop formation a few minutes after the injection. Significant acceleration of raindrop formation has been found in the case of a maritime wide-droplet spectrum. Simulations of fog seeding were conducted using droplet spectra distributions of typical fog. Seeding by charged fog droplets of one or both polarities was simulated. In both cases a significant increase in fog visibility was found. The advantages of the seeding method proposed are discussed.

Dielectric relaxation in porous glasses

Abstract Dielectric spectroscopy was applied to different types of porous silica glass materials, wherein the effect of water adsorption at the pored surface of the glasses on the dielectric response was examined over wide temperature (−100 to +300 °C) and frequency (20 Hz–1 MHz) ranges. The dielectric relaxation in the porous materials was analyzed in terms of non-Debye slow decay dynamics. The physical nature of different states of water in the porous glass materials is discussed. Analysis of the dielectric parameters enables us to characterize the fractal dimension and porosity of the porous glasses. In addition to dielectric spectroscopy, FT-IR spectroscopy and thermogravimetric analysis have also been applied.

Time domain dielectric spectroscopy. A new effective tool for physical chemistry investigation

The general principles of time domain dielectric spectroscopy (TDS) are summarized. The methods of data treatment and presentation, and different TDS methods which enable one to obtain the permanent spectrum of ε* (ω) in the frequency range of 105–1010 are given. The examples of TDS application for the investigation of dielectric properties in samples of different nature and structure are considered in this review.

Dielectric spectroscopy data treatment: I. Frequency domain

The computational methods for complex dielectric permittivity data treatment are considered in this paper. The dielectric spectroscopy data analysis in the frequency domain can be reduced to the problem of choosing the appropriate model functions and an estimation of their model parameters. To address the latter problem a method has been formulated based on a penalized maximum likelihood approach, for obtaining a smooth estimate for the model parameters expressed as functions of temperature. The use of the Hilbert transform (Kramers?Kronig relation) for dc conductivity evaluation directly from the complex dielectric permittivity data has been explored as well. In this paper a numerical algorithm for this procedure, using the fast Fourier transforms and a suitable interpolation technique, is suggested. Based on these methods, state-of-the-art software for dielectric spectroscopy data analysis in the frequency domain has been developed.

Time domain dielectric spectroscopy with nonuniform signal sampling

The hardware and software designs for fast measurement of dielectric properties of different substances over a wide range of characteristic times (10−5–10−10 s) by means of time domain dielectric spectroscopy (TDS) are presented. The characteristic feature of the described installation is the nonuniform time sampling of measured signals, which enables one to cover a wide range of characteristic times with a single measurement. Comparative results for an aqueous solution of lysozyme obtained on the traditional apparatus and on the described one are presented.

NMR and dielectric spectroscopy investigation of protein dynamical structure.

Abstract The general approach to globular proteins dynamical structure investigation by NMR and time domain dielectric spectroscopy (TDDS) is presented. The information on macromolecular dynamical behavior in the case of these two methods is obtained in terms of correlation function and its parameters of atom motions. The interpretation of experimental results in the present work will be carried out in the framework of model-free approach which is common both for magnetic and dielectric relaxation. The lysozyme pH-dependence investigation is presented as an example.

Structure and dynamic behavior of protein molecules in solution

The results of the investigation of structure and dynamic behavior of protein in solution by time-domain dielectric spectroscopy are presented. The dipole correlation functions for myoglobin, lysozyme and RNase A solutions at different concentration, pH and temperature were obtained. The processes of the intramolecular interactions of myoglobin molecules, the pH-induced dimerization of lysozyme and thermal denaturation of RNase A are discussed.

Dielectric relaxation, rotational diffusion and the heat denaturation transition in aqueous solutions of RNAse A

Abstract The heat denaturation transition of pancreatic RNAse A was investigated by time-domain spectroscopy. In the temperature interval 5–90°C the protein molecule may be in three states: native, temperature denaturated and unfolded. The heat denaturation process occurs in two stages: In the first stage the system behaves as a macromolecule, maintaining its globular structure and increasing its volume two times and its dipole moment 1.5 times; in the second stage the transition into a statistical coil state Occurs.

Measurement and simulation of conductive dielectric two-layer materials with a multiple electrodes sensor

Impedance spectroscopy has been shown to provide a great potential as a measuring technique for monitoring human blood glucose. The two major potential benefits are the ability to perform non-invasive and continuous measurements. Previous work has outlined the range of challenges of such an impedance based technique. Our impedance sensor is composed of several capacitive fringing field electrodes with various characteristic geometries to achieve the desired penetration depths in human skin and the underlying tissue. A comparison of the measurements made on reference materials of known dielectric properties with the results of electromagnetic field simulations allows sensor characterization to be achieved and provides the ability to optimize the sensor geometry. Such comparisons reveal that the measurements and simulations are in qualitative agreement with the expected impedance behavior, i.e. there is a larger sensitivity to changes in the dielectric properties of the deeper layer for electrodes with a deeper penetration of the electromagnetic field (EMF). Another conclusion is that, despite the approximations made in the simulation process, the measured and simulated quantities agree. This opens the possibility to use simulations to define the functional relation between the measured impedances and the layers dielectric parameters in order to correlate impedance changes with glucose concentration changes.