Biomedical subjects

T J Mason

Publications and source records attributed to T J Mason.

At least 19 recordsLinked to original sources

PubMed2005

Electrochemical study of silver thiosulphate reduction in the absence and presence of ultrasound.

The electrochemical reduction of silver thiosulphate was studied potentiostatically on platinum electrodes in the absence and presence of ultrasound (20 kHz). This system is irreversible and the reaction is both diffusion and kinetically controlled. The slowest step is the kinetic reaction especially the chemisorption of ions at the electrode surface. Ultrasound greatly improves the mass transport, which can be explained by changing from diffusion to mainly convection. This paper reports the effect of ultrasound upon electrode kinetic and mass-transport parameters at various RDE rotation speeds and ultrasonic intensities. It was found that the heterogeneous rate constant (kf) is improved in the presence of ultrasound due to the increase in the formal or standard heterogeneous rate constant (k0) (approximately by 10-fold under sonication).

Computer Simulation↗

PubMed2004

Potential for the use of ultrasound in the extraction of antioxidants from Rosmarinus officinalis for the food and pharmaceutical industry.

Ultrasound was used to increase the extraction efficiency of carnosic acid from the herb Rosmarinus officinalis using butanone, ethyl acetate and ethanol as solvents. Both dried and fresh leaves of the herb were extracted and, when performed at the same temperature, sonication improved the yields of carnosic acid for all three solvents and shortened the extraction times. Sonication also reduced the solvent effect so that ethanol, which is a poor solvent under conventional conditions, reached a similar level of extraction efficiency to the other two when sonicated. The extraction of dried herb with ethanol proved to be more efficient than that of fresh material, probably due to the water present in the latter.

Abietanes↗

PubMed2004

Sonovoltammetric studies on copper in buffered alkaline solution.

The effect of ultrasound on the voltammetry of copper in alkaline solution is reported. At pH 7 the electrode surface remains active after scanning to ca. +1.0 V (vs. SCE) and the effects of ultrasound show the expected substantial enhancement in limiting current due to improved mass transport under ultrasound. However at pH 9, whereas the silent scan is only slightly altered in gross detail from that obtained at pH 7, the sonicated scan is significantly different. This shows the expected current increase only up until ca. +0.6 V (vs. SCE), where there is a substantial loss of current showing a passivation phenomenon that is enhanced by ultrasound. In addition, during the reverse (reduction) scan under ultrasound an anodic peak appears. This suggests reactivation of the electrode during the cathodic sweep, possibly by reductive removal of a transient species from the electrode/(hydr)oxide interface at a potential where oxidation still occurs. Increasing the pH to 11 further shifts the cathodic peaks in the silent voltammogram.

Journal Article↗

PubMed2004

The effect of sonication on microbial disinfection using hypochlorite.

Ultrasound alone is capable of killing bacteria when sufficient power is applied but ultrasound at low powers can also be used to improve the effectiveness biocides. In this paper, we explore the effect of the timing of the ultrasonic treatment at 20 and 850 kHz on the biocidal efficiency of sodium hypochlorite solution towards Escherchia coli suspensions. A remarkable frequency effect has been noted. At the lower frequency of 20 kHz the improvement in biocidal activity is greatest when the ultrasound is applied at the same time as the hypochlorite. At the higher frequency of 850 kHz the improvement is best when ultrasound is used as a pre-treatment immediately followed by hypochlorite addition under normal (silent) conditions. The kill rate achieved for pre-treatment using 850 kHz and simultaneous treatment using 20 kHz are very similar. However the former involves less acoustic energy and so is considered to be the more efficient.

Calorimetry↗

PubMed2003

Sonoelectrochemical effects in electro-organic systems.

This paper describes recent studies in organic sonoelectrochemistry at Coventry University, including the oxidation of thiophene monoxides, degradation of dye pollutants, formation of conducting polymers and electrosynthetic modification of proteins.

Animals↗

PubMed2003

A novel angular geometry for the sonochemical silver recovery process at cylinder electrodes.

In order to obtain maximum ultrasonic effect upon electrochemical silver recovery, mass transfer measurements were investigated. The effect on limiting current of changing the position of an ultrasonic horn tip (i.e. vertical and horizontal) and using a cylinder electrode (CE), was studied in an attempt to find the optimum position required for maximum sonoelectrochemical effect. The importance of the ultrasonic intensity, the electrode-horn distance and positioning (angle) in assigning limiting currents was also investigated. For the CE placed at an angle of 45 degrees with respect to the ultrasonic horn, it was suggested that the 50% increase in limiting current for the 'face-on' geometry is caused by an approximately 50% decrease in diffusion layer thickness for the 'face-on' geometry compared to the 'angular' geometry due to the difference in the sonicated areas for both geometries.

Journal Article↗

PubMed2003

The development and evaluation of ultrasound for the treatment of bacterial suspensions. A study of frequency, power and sonication time on cultured Bacillus species.

Some species of bacteria produce colonies and spores which agglomerate in spherical clusters (Bacillus subtilis) and this serves as a protection for the organisms inside against biocidal attack. Flocs of fine particles e.g. clay can entrap bacteria which can also protect them against the biocides. It is because of problems such as these that alternative methods of disinfecting water are under active investigation. One such method is the use of power ultrasound, either alone or in combination with other methods. Ultrasound is able to inactivate bacteria and deagglomerate bacterial clusters or flocs through a number of physical, mechanical and chemical effects arising from acoustic cavitation. The aim of this study was to investigate the effect of power ultrasound at different powers and frequencies on Bacillus subtilis. Viable plate count techniques were used as a measure of microbial activity. Results showed a significant increase in percent kill for Bacillus species with increasing duration of exposure and intensity of ultrasound in the low-kilohertz range (20 and 38 kHz). Results obtained at two higher frequencies (512 and 850 kHz) indicated a significant increase in bacteria count suggesting declumping. In assessing the bacterial kill with time under different sonication regimes three types of behaviour were characterized: High power ultrasound (lower frequencies) in low volumes of bacterial suspension results in a continuous reduction in bacterial cell numbers i.e. the kill rate predominates. High power ultrasound (lower frequencies) in larger volumes results in an initial rise in cell numbers suggesting declumping of the bacteria but this initial rise then falls as the declumping finishes and the kill rate becomes more important. Low intensity ultrasound (higher frequencies) gives an initial rise in cell numbers as a result of declumping. The kill rate is low and so there is no significant subsequent decrease in bacterial cell numbers.

Bacillus↗

PubMed2003

Potential uses of ultrasound in the biological decontamination of water.

In the past there was a prevailing feeling in industry that power ultrasound would be too expensive to use for water treatment on an industrial scale. This was based on calculations involving the direct scale up of power consumption in small-scale (generally batch) laboratory experiments. In recent times this attitude has changed somewhat as a result of the installation of a number of ultrasonic devices in operational water or sewage treatment plants. In our laboratories we have investigated the decontamination of water under the influence of ultrasound alone and in conjunction with other treatments. The results, particularly when applied to flowing systems, indicate a real future for sonochemistry in water treatment.

Bacteria↗

PubMed2003

The development and evaluation of electrolysis in conjunction with power ultrasound for the disinfection of bacterial suspensions.

There is an increasing incidence in health problems related to environmental issues that originate from inadequate treatment of potable waters. This has compelled scientists and engineers to engage in innovative technologies to achieve a maximum disinfection at affordable costs. Some species of bacteria produce colonies and spores that can agglomerate in spherical clusters and thus protect organisms on the inside of the cluster against biocidal attack. Flocs of fine particles (e.g., clay) can entrap bacteria and this can also protect them against the biocides. Other bacteria have the ability to mutate, thus building up resistance to conventional biocides (e.g., chlorine). Ultrasound has been shown to be effective in improving the effectiveness of biocides such as chlorine. The aim of this present study was to investigate the effect of electrolysis and power ultrasound as a disinfection treatment and to provide a greater knowledge of the fundamentals of disinfection through the production of hypochlorite in situ from saline solution via electrolysis. The electrode materials investigated were, carbon (felt and graphite), copper and stainless steel rods. The results show that sonication appears to amplify the effect of electrolysis. A combination of both treatments is significantly better than sonication or electrolysis alone.

Disinfection↗

PubMed2002

The effect of ultrasound upon the oxidation of thiosulphate on stainless steel and platinum electrodes.

Ultrasound was found to increase the oxidation peak current and hence the decomposition rate of thiosulphate 50-fold compared to silent conditions. The effects of the ultrasonic frequency (20 and 38 kHz) and power upon the electrochemical oxidation of thiosulphate in aqueous KCl (1 mol dm-3) at stationary stainless steel and platinum electrodes were studied chronoamperometrically and potentiostatically (at various scan rates). No sigmoidal-shaped voltammograms were observed for the redox couple S4O6(2-)/S2O3(2-) in the presence of ultrasound. However, application of ultrasound to this redox couple provided an increase in the oxidation peak current at the frequencies employed, the magnitude of which varied with concentration, scan rate and ultrasonic power. Under sonication at 20 and 38 kHz, the oxidation peak potential shifted anodically with increasing ultrasonic power. This anodic shift in potential may be due to the formation of hydroxyl radicals, changes in electrode surface composition and complex adsorption phenomena. The large increase in oxidation peak currents and the rates of decomposition of thiosulphate, in the presence of ultrasound, are explained in terms of enhanced mass transfer at the electrode due to cavitation and acoustic streaming together with microstreaming coupled with adsorption phenomena. It is also shown that changes in macroscopic temperature throughout the experiment are insufficient to cause the observed enhanced diffusion.

Journal Article↗

PubMed2002

The ultrasonically induced reaction of benzoyl chloride with nitrobenzene: an unexpected sonochemical effect and a possible mechanism.

A mixture of benzoyl chloride and nitrobenzene is not known to be chemically reactive, indeed the mixture is chemically inert when subjected individually to either ultrasonic irradiation or heating. However, if this system is initially subjected to ultrasound and then heated for several hours at 200 degrees C, a reaction does occur and the products are benzoic anhydride, hydrochloric acid, nitrous and nitric acid together with some minor products. To the best of our knowledge, this is the first example of a reaction where the effect of ultrasound does not appear to be the consequence of the direct action of acoustic cavitation bubbles. A possible explanation of this behaviour is advanced which involves an electron transfer reaction in which nitrobenzene is first activated by ultrasound and then acts as oxidant in the thermal stage of reaction.

Journal Article↗

PubMed2002

Enhancement of ultrasonic cavitation yield by multi-frequency sonication.

The paper reports the enhanced effect of multi-frequency ultrasonic irradiation on cavitation yield. The cavitation yield is characterized by electrical conductivity determination, fluorescence intensity determination and iodine release method. Two-frequency (28 kHz/0.87 MHz) orthogonal continuous ultrasound, two-frequency (28 kHz/0.87 MHz) orthogonal pulse ultrasound and three-frequency (28 kHz/1.0 MHz/1.87 MHz) orthogonal continuous ultrasound have been used. It has been found that the combined irradiation of two or more frequencies of ultrasound can produce a significant increase in cavitation yield compared with single frequency irradiation. The possible mechanisms of the enhanced effect are briefly discussed.

Journal Article↗

PubMed2001

Controlling emissions from electroplating by the application of ultrasound.

Ultrasonic irradiation applied either above the surface of a chromic acid plating bath or through the plating bath itself during the process of chromium electroplating reduces the emissions of hazardous chromic acid mist The use of ultrasound is particularly effective at high current densities. The results suggest that sonication during the electroplating of chromium may provide a useful method of controlling chrome mist emission without the need for a chemical additive (mist suppressant). In conjunction with lip extraction this could lead to a more efficient process since the use of ultrasound has been shown to be of benefit in the electroplating process itself.

Air Pollution↗

PubMed2001

Investigation of the effects of ultrasound on vegetal tissues during solvent extraction.

The paper presents an insight into the mechanism of the ultrasonic enhancement of solvent extraction through the effect of ultrasound on the vegetal material involved. Thus, a series of experiments has been developed to investigate the effect of ultrasonic energy on the vegetal material and the solvent used. Several results concerning the ultrasonic extractive value, ultrasonic swelling index and the effects of frequency on vegetal material are presented.

Plant Extracts↗

PubMed2001

Towards the industrial production of medicinal tincture by ultrasound assisted extraction.

Experiments related to the industrial production of medicinal tinctures of sage (Salvia officinalis L.) and valerian (Valeriana officinalis L.) were performed using ultrasonically assisted extraction and quality of the final tincture was evaluated by gas chromatography and dry residue determination. The constituents of the active sage compound: borneol, cineole, alpha- and beta-thujone and also the dry residue were measured. In the case of valerian extractions, the efficiency of sonicated extraction was compared with classical extraction. The course of only the dry residue was monitored. The influence of ultrasound on the quality of valerian tincture was examined by HPLC.

Chromatography, High Pressure Liquid↗

PubMed2001

The extraction of rutin from flower buds of Sophora japonica.

The efficiency of extraction of rutin from Sophora japonica is improved by ultrasound but is dependent on the solvent employed. Rutin is a compound with antioxidant activity and aqueous solvents appear to be unsuitable for ultrasonic extractions due to the formation of free radicals from the insonation of the solvent. The application of ultrasound to methanolic extraction gave a significant reduction in extraction time and an increase in maximum yield.

Free Radicals↗

PubMed2001

Electrochemical behaviour of zinc in 20 kHz sonicated NaOH electrolytes.

This paper describes the influence of 20 kHz ultrasound upon the corrosion behaviour of zinc in NaOH electrolytes. A systematic study of the effects exerted by ultrasound on the electrochemical interface was first carried out, so as to determine the transmitted power and to characterize mass transfer at the electrode. Then attention was focused on the corrosion passivation mechanism of zinc in sonicated NaOH solutions (0.1 and 1 M). Investigations were carried out using electrochemical techniques to determine corrosion and passivation kinetics parameters. SEM analysis of the sonicated zinc surfaces provides complementary information on the oxide layer composition and structure.

Journal Article↗

PubMed2000

Enhancement of sonoluminescence emission from a multibubble cavitation zone.

Investigations have been performed on various methods of increasing cavitation activity measured by the intensity of sonoluminescence. It is shown that the effect of the combined action of (a) pulsed modulation of an acoustic field, (b) liquid degassing and cooling and (c) increasing the static pressure considerably exceeds the sum of the effects achieved by each of these methods individually. A more than 250-fold increase of the sonoluminescence intensity has been attained compared with continuous irradiation under normal conditions (room temperature, atmospheric pressure, gas-saturated liquid). An interpretation of the results obtained is proposed.

Journal Article↗