Determination of Electrical and Mechanical Properties of Liquids Using a Resonator with a Longitudinal Electric Field

The possibility of determining the elastic modules, viscosity coefficients, dielectric constant and electrical conductivity of a viscous conducting liquid using a piezoelectric resonator with a longitudinal electric field is shown. For the research, we chose a piezoelectric resonator made on an AT-cut quartz plate with round electrodes, operating with a shear acoustic mode at a frequency of about 4.4 MHz. The resonator was fixed to the bottom of a 30 mL liquid container. The samples of a mixture of glycerol and water with different viscosity and conductivity were used as test liquids. First, the frequency dependences of the real and imaginary parts of the electrical impedance of a free resonator were measured and, using the Mason electromechanical circuit, the elastic module, viscosity coefficient, piezoelectric constant and dielectric constant of the resonator material (quartz) were determined. Then, the container was filled with the test sample of a liquid mixture so that the resonator was completely covered with liquid, and the measurement of the frequency dependences of the real and imaginary parts of the electrical impedance of the loaded resonator was repeated. The dependences of the frequency of parallel and series resonances, as well as the maximum values of the electrical impedance and admittance on the conductivity of liquids for various viscosity values, were plotted. It was shown that these dependences can be used to unambiguously determine the viscosity and conductivity of the test liquid. Next, by fitting the theoretical frequency dependences of the real and imaginary parts of the electrical impedance of the resonator loaded with the liquid under study to the experimental dependences, the elastic module of the liquid and its dielectric constant were determined.

The Study of the Acoustic Characteristics of Chitosan Acetate Film Using a Radial Electric Field Excited Resonator

Currently, the lateral electric field excited resonators are used for the creation of various sensors. We have recently proposed a new type of acoustic resonator called radial electric field excited disk acoustic resonator. The advantage of this type of resonator is its high sensitivity to mechanical and electrical boundary conditions on its free surface. This makes it possible to determine both the acoustic and electrical properties of a thin layer of material deposited on the free end of the resonator. In this work, we used a radial electric field excited disk acoustic resonator of Russian-made barium plumbum zirconate titanate (BPZT) piezoceramics. With the help of this resonator, the material constants for the piezoceramic sample were refined, and their temperature dependencies were determined. Then, this resonator was used to determine the elastic modulus, viscosity, and conductivity of the chitosan acetate film in air and ammonia vapors of various concentrations. It was shown that the chitosan acetate film under the influence of ammonia vapor significantly changes its mechanical properties and increases its electrical conductivity thousands of times, and then completely restores its properties.

The Effect of Glycerol-Based Suspensions on the Characteristics of Resonators Excited by a Longitudinal Electric Field

This study examines the effect of suspensions based on pure glycerol and diamond powder with different concentrations on the characteristics of resonators with a longitudinal electric field. We used two disk resonators made of the quartz and langasite plates with round electrodes on both sides of the plate and resonant frequencies of 4.4 and 4.1 MHz, operating in shear and longitudinal acoustic modes, respectively. Each resonator was mounted on the bottom of a 30 mL liquid container. During the experiments, the container was filled with the suspension under study in such a way that the resonator was completely immersed in the suspension, and the frequency dependences of the real and imaginary parts of the electrical impedance of the resonator were measured. As a result, the shear modulus of the elasticity and shear coefficient of the viscosity of the studied suspensions were determined. The material constants of the suspensions were found by fitting the theoretical frequency dependences of the real and imaginary parts of the electrical impedance of the resonator to the experimentally measured ones, which was calculated using Mason's equivalent circuit. As a result, the dependencies of the density, shear modulus of elasticity, shear viscosity coefficient, and velocity of the shear acoustic wave on the volume concentration of the diamond particles were constructed.

The Radial Electric Field Excited Circular Disk Piezoceramic Acoustic Resonator and Its Properties

A new type of piezoceramic acoustic resonator in the form of a circular disk with a radial exciting electric field is presented. The advantage of this type of resonator is the localization of the electrodes at one end of the disk, which leaves the second end free for the contact of the piezoelectric material with the surrounding medium. This makes it possible to use such a resonator as a sensor base for analyzing the properties of this medium. The problem of exciting such a resonator by an electric field of a given frequency is solved using a two-dimensional finite element method. The method for solving the inverse problem for determining the characteristics of a piezomaterial from the broadband frequency dependence of the electrical impedance of a single resonator is proposed. The acoustic and electric field inside the resonator is calculated, and it is shown that this location of electrodes makes it possible to excite radial, flexural, and thickness extensional modes of disk oscillations. The dependences of the frequencies of parallel and series resonances, the quality factor, and the electromechanical coupling coefficient on the size of the electrodes and the gap between them are calculated.

Influence of Humidity on the Acoustic Properties of Mushroom Mycelium Films Used as Sensitive Layers for Acoustic Humidity Sensors

The influence of humidity on the density, shear elastic module, viscosity, and thickness of the mushroom Pleurotus eryngii and Ganoderma lucidum mycelium films was studied. These data were obtained by comparing the theoretical and experimental frequency dependencies of the complex electrical impedance of bulk acoustic wave (BAW) resonator loaded by mycelium film using the least-squares method. This procedure was performed for the BAW resonator with pointed films for the relative humidity range of 17%–56% at the room temperature. As a result, the changes of the density, shear elastic module, viscosity, and thickness of the films under study, due to the water vapor adsorption, were determined. It has been established that the properties of mycelium films are restored after removing from the water vapor. So, these results show the possibility of using investigated mycelium films as sensitive layers for acoustic humidity sensors.

DCDHF fluorophores for single-molecule imaging in cells

There is a persistent need for small-molecule fluorescent labels optimized for single-molecule imaging in the cellular environment. Application of these labels comes with a set of strict requirements: strong absorption, efficient and stable emission, water solubility and membrane permeability, low background emission, and red-shifted absorption to avoid cell autofluorescence. We have designed and characterized several fluorophores, termed "DCDHF" fluorophores, for use in live-cell imaging based on the push-pull design: an amine donor group and a 2-dicyanomethylene-3-cyano-2,5-dihydrofuran (DCDHF) acceptor group, separated by a pi-rich conjugated network. In general, the DCDHF fluorophores are comparatively photostable, sensitive to local environment, and their chemistries and photophysics are tunable to optimize absorption wavelength, membrane affinity, and solubility. Especially valuable are fluorophores with sophisticated photophysics for applications requiring additional facets of control, such as photoactivation. For example, we have reengineered a red-emitting DCDHF fluorophore so that it is dark until photoactivated with a short burst of low-intensity violet light. This molecule and its relatives provide a new class of bright photoactivatable small-molecule fluorophores, which are needed for super-resolution imaging schemes that require active control (here turning-on) of single-molecule emission.

Analysis of chromosome aberrations by FISH and Giemsa assays in lymphocytes of cancer patients undergoing whole-body irradiation: comparison of in vivo and in vitro irradiation

PURPOSE

To study the cytogenetic effects of fractionated radiotherapy in peripheral blood lymphocytes of five cancer patients. In vitro experiments were performed in parallel using the same dose range and a comparison was made of the induced frequencies of stable and unstable chromosome aberrations. The object was to clarify the use of an in vitro calibration curve for immediate and retrospective dosimetry in cases of radiation accidents.

MATERIALS AND METHODS

Patients were exposed to 60Co gamma-rays at a single dose of 11.5 cGy each day up to a total dose of 57.5 cGy, given in 5 days. For measurement of chromosome aberrations, blood was collected from patients before irradiation and after each exposure. Blood taken before treatment was used as a control and for in vitro irradiation experiments in the dose range 8-50 cGy. Chromosome aberration frequency (stable as well as unstable) was determined using fluorescence in situ hybridization (FISH) assay with specific DNA libraries for chromosomes 1, 4 and 8 and a pancentromertic probe for the whole genome. Giemsa-stained preparations were used to score unstable aberrations following in vivo and in vitro exposure.

RESULTS

A linear dose-response curve was determined for both dicentrics and translocations. The in vivo frequency of translocations was higher than for dicentrics. Dose-response curves generated for translocations following in vivo and in vitro irradiation yielded similar frequencies. In contrast, for dicentrics, in vitro irradiation yielded a higher frequency when compared with data generated following in vivo exposure.

CONCLUSIONS

For dose reconstruction purposes, translocations frequency seems to be a more adequate end-point than the scoring of dicentrics. The established in vitro calibration curve for dicentrics may underestimate absorbed radiation dose in cases of protracted exposure.