A combination of ultrasound and oxidative enzyme: sono-enzyme degradation of phenols in a mixture

Sono-degradation and sono-enzyme degradation of phenols were performed on the mixtures of double compounds (phenol, p-chlorophenol; phenol, p-cresol; phenol, p-nitrophenol; and p-chlorophenol, p-cresol) in aqueous medium. Sono-degradation of phenol and its substituted compounds individually behaved approximately the same, but in the case of mixture behaved differently. Sono-degradation of substituted phenols was easier than phenol in a mixture, but there was an exception in the combination of phenol and p-nitrophenol that the degradation of phenol was faster than substituted compound. This behavior was the same in sono-enzyme degradation, but with higher degradation rate. Between these mixtures, the combination of phenol and p-cresol presented a significant different behavior in case of single and double compounds solutions. In this system, the sono-degradation of phenol in mixture was more difficult than phenol alone but, the sono-degradation of p-cresol in mixture was easier in comparison with p-cresol alone. In sono-enzyme degradation, p-cresol as a more reactive compound facilitated the remove of phenol in mixture in compare of the individual case.     

Sonochemical degradation of phenol in water: a comparison of classical equipment with a new cylindrical reactor

Cavitation due to ultrasonic waves produces highly reactive oxidising species in water. As a result, it can be used to oxidise organic pollutants such as aromatic compounds in dilute aqueous solutions. Recent studies have demonstrated that reactors operating in the high frequency range (e.g. 500 kHz) are more efficient than reactors working at lower frequency (20 kHz) for the destruction of these kinds of contaminants. Our study describes the degradation of phenol with the help of a cylindrical ultrasonic apparatus that operates at 35 kHz (Sonitube-SODEVA). To date, the use of this type of reactor has not been reported. The reaction rates thus obtained were compared to those obtained at the same ultrasonic power (50 W) with more classical devices operating at 20 and 500 kHz. The general result is that in aqueous solution, the rate of phenol destruction is higher at 500 kHz than at 35 or 20 kHz. Addition of hydrogen peroxide and copper sulphate to the medium provides a different oxidative system that proceeds more efficiently at 35 kHz; the time of destruction was about one-third of the time needed at 500 kHz. It was also observed that the intermediate organic compounds are eliminated much faster at 35 kHz in comparison with the two frequencies. The observation of such different behaviour is not necessarily a pure frequency effect, but can be due to a response to other parameters such as the acoustic field and intensity.     

Graphical Representations of Speed: Obstacles Preservice K‐8 Teachers Experience

This study examines the difficulties college students experience when creating and interpreting graphs in which speed is one of the variables. Nineteen students, all preservice elementary or middle school teachers, completed an upper‐level course exploring algebraic concepts. Although all of these preservice teachers had previously completed several mathematics courses, including calculus, they demonstrated widespread misconceptions about the variable speed. This study identifies four cognitive obstacles held by the students, provides excerpts of their graphical constructions and verbal interpretations, and discusses potential causes for the confusion. In particular, misconceptions arose when students interpreted the behavior and nature of speed within a graphical context, as well as in situations where they were required to construct a graph involving speed as a variable. The study concludes by offering implications for the teaching and learning of speed and its interpretation within a graphical setting.     

Solar photocatalytic degradation of RB5 by ferrite bismuth nanoparticles synthesized via ultrasound

In this paper, the photocatalytic degradation of Reactive Black 5 (RB5) was investigated with ferrite bismuth synthesized via ultrasound under direct sunlight irradiation. The intensity of absorption peaks of RB5 gradually decreased by increasing the irradiation time and finally vanished in 50 min in acidic medium. The formation of new intermediate was observed in basic medium. The relative concentration of RB5 in solution and on the surface of ferrite bismuth (BiFeO₃) nanoparticles was considered during the experiment in acidic and basic media. The effects of various parameters such as amount of catalyst, concentration of dye, and pH of the solution have been studied on the dye degradation. The adsorption isotherm and the kinetic of photocatalytic degradation of RB5 were investigated. The adsorption constants in the dark and in the presence of sunlight irradiation were compared. The photocatalytic degradation mechanism of RB5 has been evaluated through the addition of some scavengers to the solution. In addition, the stability and reusability of the catalyst were examined in this work.     

Influence of ultrasound on cadmium ion removal by sorption process

This study presents the removal of Cd(II) from aqueous solution by the sorption process in the presence (sono-sorption) and absence (conventional method) of ultrasound. Batch experiments were conducted to study the main parameters such as sorbate concentration, amount of sorbent, contact time, and ultrasound intensity. In addition, the sorbate/sorbent concentration ratios were studied in two different ways: (a) in a constant sorbate concentration and variable amount of sorbent, (b) in a constant amount of sorbent and variable sorbate concentration. The results indicated that under proper conditions, there was a possibility to remove cadmium ion very fast and efficiently from aqueous solution. In addition, the intensity of ultrasound and the sorbate/sorbent concentration ratio were two important factors for the removal of this pollutant and therefore, this study was focused mostly on these two variables.     

The effect of frequency on sonochemical reactions III: dissociation of carbon disulfide

Investigations were made of the effects of frequency, temperature, intensity and gases on the rate of sonochemical dissociation of carbon disulfide. Application of 900 kHz ultrasound did not produce any noticeable change. When carbon disulfide was irradiated with 20 kHz, the liquid formed a heterogeneous mixture of black particles in a yellow solution. The rate of dissociation decreased with increasing temperature, in agreement with most sonochemical reactions. The rate also decreased with decreasing area of the horn tip, keeping total power constant. This dependence on the horn tip area, as well as that on the frequency, is in opposition to the dependence for the formation of iodine from the sonication of aqueous potassium iodide solution [See Part II, Ultrasonics Sonochemistry 3 (1996) 19]. The X-ray spectrum of the black particles and the yellow residue obtained after evaporation showed the presence of amorphous carbon and monoclinic sulfur. The rate of sono-dissociation of carbon disulfide in the presence of different gases is in the order He > H2 > Air > Ar > O2 > CO2.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

Evaluation of aortic stenosis severity using 4D flow jet shear layer detection for the measurement of valve effective orifice area

Aims

The objective of this study was to evaluate the potential of 4D flow MRI to assess valve effective orifice area (EOA) in patients with aortic stenosis as determined by the jet shear layer detection (JSLD) method.

Methods and Results

An in-vitro stenosis phantom was used for validation and in-vivo imaging was performed in 10 healthy controls and 40 patients with aortic stenosis. EOA was calculated by the JSLD method using standard 2D phase contrast MRI (PC-MRI) and 4D flow MRI measurements (EOA_JSLD-2D and EOA_JSLD-4D, respectively). As a reference standard, the continuity equation was used to calculate EOA (EOA_CE) with the 2D PC-MRI velocity field and compared to the EOA_JSLD measurements. The in-vitro results exhibited excellent agreement between flow theory (EOA = 0.78 cm²) and experimental measurement (EOA_JSLD-4D = 0.78 ± 0.01 cm²) for peak velocities ranging from 0.9 to 3.7 m/s. In-vivo results showed good correlation and agreement between EOA_JSLD-2D and EOA_CE (r = 0.91, p < 0.001; bias: − 0.01 ± 0.38 cm²; agreement limits: 0.75 to − 0.77 cm²), and between EOA_JSLD-4D and EOA_CE (r = 0.95, p < 0.001; bias: − 0.09 ± 0.26 cm²; limits: 0.43 to − 0.62 cm²).

Conclusion

This study demonstrates the feasibility of measuring EOA_JSLD using 4D flow MRI. The technique allows for optimization of the EOA measurement position by visualizing the 3D vena contracta, and avoids potential sources of EOA_CE measurement variability.     

The direct effect of ultrasound on the extraction of date syrup and its micro-organisms

In the date syrup industry, date fruits are mixed with a suitable amount of water at a temperature greater than 50 °C for about 1 h. This condition is not sufficient for killing the micro-organisms present in the fruit. In addition, Overheating for a long time can damages nutritious materials and also changes the final product's color. Ultrasound was applied for improving the quantity and quality of the extraction, and also to overcome the health problem. In this research, the following variables were examined: date fruit/water ratio, ultrasonic intensity and temperature. The results showed that sonication under the proper conditions can lead to a higher extraction in a shorter time with a better physical quality of the product. Most importantly, the sonication significantly decreased the microbial count in comparison to the classical method. This study also confirmed the presence of anti-microbial substances in date fruit, and that ultrasonic waves can accelerate their effects.     

Effect of frequency on sonochemical reactions. I: Oxidation of iodide

The effect of continuous sonication on the kinetics of iodine formation in aqueous iodide solutions was studied in the presence of air and argon at two frequencies, 20 and 900 kHz. Most workers in this area assume that frequency has a negligible effect on sonochemical reactions. The present results indicate, however, that there is a significant effect in the above solutions. The rate of sonochemical oxidation of iodide in aqueous solution is 3.1 times greater in presence of air than argon at 900 kHz, in contrast to the situation at 20 kHz, where the ratio is 0.9 A 900 kHz apparatus was specially designed to make it possible to measure the absolute acoustic power delivered into the solution. The rate of oxidation per unit power in this new 900 kHz apparatus can be more than 30 times greater than that at 20 kHz for the oxidation of iodide in the presence of air.