Sonication Frequency Research Articles

Sonicated direct contact membrane distillation: Influence of sonication parameters

The effect of sonication on the performance of the direct contact membrane distillation (DCMD) is studied in this work. A sonicated DCMD module equipped with a commercial PTFE membrane is built and tested in an immersed temperature-controlled water bath. High fidelity transient and thermally conjugated CFD model is also developed for the DCMD unit accounting for the sonication. Flow metrics, including temperature polarization coefficient (TPC), heat- and mass- flux under different sonication frequencies and amplitudes were evaluated. Parametric study showed a clear improvement in the DCMD system metrics and more pronounced at higher temperature. It was observed that the application of sonication impedes the development of both kinetic and thermal boundary layers due to ultrasonic-induced mixing. The results showed that the application of sonication to DCMD at the intensity of 4525 W/m2 resulted in increase of mass flux from 4.25 L/m2.h to 8.1 L/m2.h corresponding to 90% increase. It is economically unviable due to electrical power demand, i.e., ~ 35 kW.h/m3 (~$5/m3), but can be feasible below 474 W/m2 demanding 3 kW.h/m3 (nearly $0.42/m3). It was also observed that an interesting equivalence exists between the effect of acoustic amplitude and acoustic frequency on the performance of DCMD. For example, sonication at 1 kHz with 0.5 μm amplitude produced similar results, in terms of mass flux and TPC, as sonication at 5 kHz with 0.1 μm amplitude.

Transcranial focused ultrasound induces sustained synaptic plasticity in rat hippocampus

Transcranial focused ultrasound (tFUS) neuromodulation provides a promising emerging non-invasive therapy for the treatment of neurological disorders. Many studies have demonstrated the ability of tFUS to elicit transient changes in neural responses. However, the ability of tFUS to induce sustained changes need to be carefully examined. In this study, we use the long-term potentiation/long term depression (LTP/LTD) model in the rat hippocampus, the medial perforant path (mPP) to dentate gyrus (DG) pathway, to explore whether tFUS is capable of encoding frequency specific information to induce plasticity. Single-element focused transducers were used for tFUS stimulation with ultrasound fundamental frequency of 0.5 MHz and nominal focal distance of 38 mm tFUS stimulation is directed to mPP. Measurement of synaptic connectivity is achieved through the slope of field excitatory post synaptic potentials (fEPSPs), which are elicited using bipolar electrical stimulation electrodes and recorded at DG using extracellular electrodes to quantify degree of plasticity. We applied pulsed tFUS stimulation with total duration of 5 min, with 5 levels of pulse repetition frequencies each administered at 50 Hz sonication frequency at the mPP. Baseline fEPSP is recorded 10 min prior, and 30+ minutes after tFUS administration. In N = 16 adult wildtype rats, we observed sustained depression of fEPSP slope after 5 min of tFUS focused at the presynaptic field mPP. Across all PRFs, no significant difference in maximum fEPSP slope change was observed, average tFUS induced depression level was observed at 19.6%. When compared to low frequency electrical stimulation (LFS) of 1 Hz delivered to the mPP, the sustained changes induced by tFUS stimulation show no statistical difference to LFS for up to 24 min after tFUS stimulation. When both the maximum depression effects and the duration of sustained effects are both taken into account, PRF 3 kHz can induce significantly larger effects than other PRFs tested. tFUS stimulation is measured with a spatial-peak pressure amplitude of 99 kPa, translating to an estimation of 0.43 °C temperature increase when assuming no loss of heat. The results suggest the ability of tFUS to encode sustained changes in synaptic connectivity through mechanism which are unlikely to involve thermal changes.

Energy dissipation study of ultrasound bath to identify suitable zone for better performance of the bath

The mapping of an ultrasonic bath was performed to identify suitable zone for carrying out various processes using the bath in an effective manner. The mapping of ultrasonic bath was done with PPB Megasonics instrument known as cavitation meter. The cavitation meter measures the energy intensity (watt per square inch) and frequency of ultrasound. The experimental cavitation energy data helps in accurately placing the vessel in the bath for a better outcome. To obtain the average energy dissipation data throughout the bath, study was carried out by varying the various process parameters such as location of the beaker (P1- P5), height of the beaker (10–40 mm), sonication power (110 and 220 W), sonication frequency (20 – 40 kHz), and sonication bath temperature (35 and 50 °C). The energy dissipation value was recorded by placing the sensor inside the beaker at a fixed height and location. The experiments were performed by applying one factor a time method and it was observed that the average maximum energy dissipation 52 (W/in2) for 210 min was obtained at center position of bath (P5), beaker height 40 mm, power supplied 220 W, frequency 30 kHz, and bath temperature maintained at 35 °C.

Design and Optimization of Ultrasound Phased Arrays for Large-Scale Ultrasound Neuromodulation.

Low-intensity transcranial focused ultrasound stimulation (tFUS), as a noninvasive neuromodulation modality, has shown to be effective in animals and even humans with improved millimeter-scale spatial resolution compared to its noninvasive counterparts. But conventional tFUS systems are built with bulky single-element ultrasound (US) transducers that must be mechanically moved to change the stimulation target. To achieve large-scale ultrasound neuromodulation (USN) within a given tissue volume, a US transducer array should electronically be driven in a beamforming fashion (known as US phased array) to steer focused ultrasound beams towards different neural targets. This paper presents the theory and design methodology of US phased arrays for USN at a large scale. For a given tissue volume and sonication frequency (f), the optimal geometry of a US phased array is found with an iterative design procedure that maximizes a figure of merit (FoM) and minimizes side/grating lobes (avoiding off-target stimulation). The proposed FoM provides a balance between the power efficiency and spatial resolution of a US array in USN. A design example of a US phased array has been presented for USN in a rat's brain with an optimized linear US array. In measurements, the fabricated US phased array with 16 elements (16.7×7.7×2 mm3), driven by 150 V (peak-peak) pulses at f = 833.3 kHz, could generate a focused US beam with a lateral resolution of 1.6 mm and pressure output of 1.15 MPa at a focal distance of 12 mm. The capability of the US phased array in beam steering and focusing from -60o to 60o angles was also verified in measurements.

Structural and physicochemical characterization of modified starch from arrowhead tuber (Sagittaria sagittifolia L.) using tri-frequency power ultrasound

Sagittaria sagittifolia L. is a well-known plant, belongs to the Alismataceae family. Sonication can improve the functional properties of starch; hence, the aim of this study was to develop ultrasonically modified arrowhead starch (UMAS) using a sophisticated and eco-friendly tri-frequency power ultrasound (20/40/60 kHz) method at 300, 600, and 900 W for 15 and 30 min. Significant (p < 0.05) increases in swelling power, solubility, and water and oil holding capacities were achieved. FTIR spectroscopy corroborated the ordered, amorphous, and hydrated crystals of the sonicated samples. Increases in sonication frequency and power led to significant (p < 0.05) increases in onset gelatinization temperatures. Scanning electron microscopic analysis of sonicated samples showed superficial cracks and roughness on starch granules appeared in a sonication power-dependent manner compared with that of untreated sample. Overall, the ultrasonically-treated samples showed improved physicochemical properties, which could be useful for industrial applications.

Ultrasound-assisted lipase catalyzed synthesis of propyl caprate: Process optimization, kinetic, and thermodynamic evaluation

The present work evaluates the influence of ultrasound on lipase-catalyzed esterification for the synthesis of propyl caprate in a solvent-free system. The optimum conditions were found as molar ratio of capric acid: 1-propyl alcohol 1:3, catalyst loading 1% (w/w), molecular sieves loading 5% (w/w), temperature 60 °C, agitation speed 100 rpm, sonication frequency 22 kHz, duty cycle 80% (10 min) and ultrasound power 100 W yielding 86.86% conversion of capric acid. Compared to conventional agitation, ultrasound technology significantly improved process productivity to around 3% more acid conversion for each batch with 50% less requirement of catalyst amount and 5 fold less reaction time with enhanced enzyme recycling up to 9 cycles and stability. The activation energy requirement was lower (6.22 kcal/mol) with ultrasound than the conventional approach (9.028 kcal/mol). Furthermore, the esterification process was observed to be endothermic and spontaneous, with enthalpy (ΔH), entropy (ΔS), and the Gibbs free energy change (ΔG) values of 83.66 kJ/mol, 250.23 J/mol/K, and -2.74 kJ/mol, respectively. An ordered bi−bi mechanism involving the dead-end complex formation with lipase and inhibition of the reaction by capric acid was presented. Ultrasound application was found to be an influential tool to enhance the performance of biocatalyst in this esterification reaction.

Synergistic effect of sonication on photocatalytic oxidation of pharmaceutical drug carbamazepine

Photocatalytic, sono-photocatalytic oxidation of pharmaceutical drug of carbamazepine was successfully carried out using Ag/AgCl supported BiVO4 catalyst. For this purpose, firstly, photocatalytic oxidation was optimized by central composite design methodology and then synergistic effect of sonication was investigated. Low frequency (20 kHz) probe type and high frequency (850 kHz) plate type sonication at pulse and continuous mode were studied to degrade the carbamazepine (CBZ) containing wastewater. Pulse duties of 1:5 and 5:1 (on : off) were tested using the high frequency sonication system in the sono-photocatalytic oxidation of CBZ. The effects of frequency, power density measured from calorimetry by changing amplitudes were discussed in the sono-photocatalytic oxidation of CBZ. Complete carbamazepine removal was achieved at the optimum conditions of 5 ppm CBZ initial concentration with 1.5 g/L of catalysts loading and at an alkaline pH of 10 at the end of 4 h of photocatalytic reaction under visible LED light irradiation. Both low frequency and high frequency sonication systems caused an increase in photocatalytic efficiency in a shorter treatment time of 60 min. CBZ removal increased from 44% to 65.42% in low frequency sonication of 20 kHz at the amplitude of 20% (0.15 W/mL power density). In the case of high frequency ultrasonic system (850 kHz), CBZ removal increased significantly from 44% to 89.5 % at 75% amplitude (0.12 W/mL power density) within 60 min of reaction. Continuous mode sonication was observed to be more effective than that of pulse mode sonication not only for degradation efficiency and also for electrical energy consumption needed to degrade CBZ. Sono-catalytic oxidation was also conducted with simulated wastewater that contains SO42-, CO32–, NO3–, Cl- anions and natural organic component of fulvic acid. The CBZ degradation was inhibited slightly in the presence of NO3– and Cl-, and fulvic acid, however, the existence of SO42- and CO32– increased the degradation degree of CBZ. Toxicity tests were performed to determine the toxicity of untreated CBZ, and treated CBZ by photocatalytic, and sono-photocatalytic oxidations.

Ultrasonic-assisted protein extraction from sunflower meal: Kinetic modeling, functional, and structural traits

Effect of mono and dual frequency (20, 28 and 20/28 kHz) ultrasound action on extraction kinetics, functional, and structural traits of sunflower protein (SP) was examined. A simplified model based on Fick's second law was developed, and the mass transfer of soluble SP in a heterogeneous system was successfully described. Findings suggested that ultrasound action significantly increased (p < 0.05) the release and diffusion of soluble SP across the cell wall into extraction solvent, causing enhanced observed rate constant (k) and diffusion-effective coefficient (Ds) values over control. Moreover, dual frequency sonication (20/28 kHz) considerably increased oil holding efficacy and surface charge (by 21.07 and 32.15%, respectively), but reduced water holding efficacy and particle size (by 40.74 and 26.61%, respectively) relative to untreated sample (p < 0.05). Also, ultrasonicated SP displayed excellent solubility under varying pH (2−10), likened to the control (p < 0.05). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) outcomes indicated that ultrasonicated SP showed irregular fragments, heterogenous/ disordered structure and small-sized particles, suggesting that sonication (notably 20/28 kHz) destroyed the cross-linkages among SP molecules. FT-IR spectroscopy exhibited that ultrasonication improved the content of β-sheet from 8.52–18.94% and random coil from 11.63–21.71%, whereas reductions in α-helix and β-turn were noticed, implying limited unfolding of SP structure and decreases in intermolecular interactions. Intrinsic fluorescence analysis revealed that dual frequency treatment was observed to be more efficient in altering the tertiary structure of SP reference to single frequency and control. Industrial relevanceSunflower protein, isolated from sunflower residue, is a potentially low-cost resource for food applications. Ultrasonication is reported to improve the extraction of proteins as well as enhancing their functionalities. The existing study displayed that ultrasonication (observably dual frequency treated) was successfully applied to improve the extractability of soluble sunflower protein, and enhanced its functionality (solubility and OHe) reference to control. The research outcomes may benefit food/ chemical industries in extraction and/or alteration of sunflower protein in new applications.

Impact of Applying Technique for Dual Frequency Sonication on Esterification

Impact of Applying Technique for Dual Frequency Sonication on Esterification

Frequency-Dependent Sonochemical Processing of Silicon Surfaces in Tetrahydrofuran Studied by Surface Photovoltage Transients.

The field of chemical and physical transformations induced by ultrasonic waves has shown steady progress during the past decades. There is a solid core of established results and some topics that are not thoroughly developed. The effect of varying ultrasonic frequency is among the most beneficial issues that require advances. In this work, the effect of sonication of Si wafers in tetrahydrofuran on the photovoltage performance was studied, with the specific goal of studying the influence of the varying frequency. The applied ultrasonic transducer design approach enables the construction of the transducer operating at about 400 kHz with a sufficient sonochemical efficiency. The measurements of the surface photovoltage (SPV) transients were performed on p-type Cz-Si(111) wafers. Sonication was done in tetrahydrofuran, methanol, and in their 3:1 mixture. When using tetrahydrofuran, the enhanced SPV signal (up to ≈80%) was observed due to increasing sonication frequency to 400 kHz. In turn, the signal was decreased down to ≈75% of the initial value when the frequency is lowered to 28 kHz. The addition of methanol suppressed this significant difference. It was implied that different decay processes with hydrogen decomposed from tetrahydrofuran could be attempted to explain the mechanism behind the observed frequency-dependent behavior.

Simultaneous measurements of acoustic emission and sonochemical luminescence for monitoring ultrasonic cavitation.

In the present study, a novel hybrid method was considered to identify and measure inertial cavitation activity using acoustic and optical emissions from violent bubble collapses. A photomultiplier (PMT) tube and a calibrated cylindrical needle hydrophone were used to simultaneously detect sonochemical luminescence (SCL) signals and acoustic emissions, respectively, during sonication. A cylindrical focusing ultrasound transducer operating at 398.4 kHz was employed to produce a dense cavitation bubble cloud at the focus. The results clearly showed that a similar trend between the PMT output (i.e., the SCL results) and the broad band acoustic emissions started to appear at the frequencies considered above the fourth harmonic of the sonication frequency. The experimental observation suggests that the occurrence of inertial cavitation can be monitored using the high pass spectral acoustic power and the cut-off frequency can be effectively chosen with the aid of sonochemical luminescence measurement. The hybrid method is expected to be useful for cavitation dosimetry in various medical and industrial applications.

Sonication of Petrochemical Industry Wastewaters

The objective of the study was the treatment of the pollutants (dissolved chemical oxygen demand (CODdis), total organic carbon (TOC) and total and individual polycyclic aromatic hydrocarbons (PAH)) present in the petrochemical industry wastewater (PCI) by sonication. The effects of increasing sonication times (0 min, 60 min, 120 and 150 min), sonication temperatures (25oC, 30oC and 60oC), on the CODdis, TOC and (PAH) removal efficiencies were researched at a sonication frequency of 35 kHz and a sonication power of 640. All the PAHs and their metabolites were measured by an gas chromatography (Agilent 6890 NC) equipped with a mass selective detector (Agilent 5973 inert MSD) with a capillary column (HP5-MS, 30 m, 0.25mm, 0.25µm)). The CH4, CO2 and H2 gas analysis, CODdis, TOC and the other pollutants were measured according to Standard Methods. As the sonication time and temperature were increased from 60 to 120 and 150 min, and from 25oC to 30oC and to 60oC, the CODdis, total PAH and TOC yields increased from 80.16% to 92.15%, from 78.37% to 94.23% and from 79.65% to 96.90%, respectively. The PAHs intermediates namely, 1–methylnaphthalene, 9–hydroxyfluorene, 9,10–phenanthrenequione, benzoic acid, 1,2,3–thiadiazole–4–carboxylic acid, naphthalene, p–hydroxybenzoic acid, fluorene, di–hydroxy pyrene, pyrene di–hydrodiol were sonodegraded with yields of 92.11%, 95.23%, 98.42%, 97.34%, 99.44%, 96.30%, 99.36%, 97.17%, 99.63% and 99.98% respectively, after 150 min, at 25oC. The presence of CH4, H2 and CO2 gases during sonication showed that the degradation mechanism of the PAHs is ‘‘pyrolysis”.

Development of hairy root culture in Taxus baccata sub sp wallichiana as an alternative for increased Taxol production

The Himalayan Yew or Taxus baccata sub sp. wallichiana is the native of the Temperate belt of Himalayas known widely for its ethnomedical properties and especially for the production of an anti-cancerous compound Taxol but since the plant is an understory and in low population size, the production of Taxol in nature is very poor so it cannot meet the high demand of Taxol for medical use. Hairy root culture is known for its genetic and physiochemical stability and increased production of secondary metabolites as compared to cell suspension culture and with the use of low frequency sonication for 1–2 min, the rate of transformation can be increased thereby induing more hairy roots. In our study, when the combination of low frequency sonication for production of hairy roots was used it helped in development of the hairy root culture of Taxus baccata sub sp. wallichiana as an alternative for increased Taxol production. It was seen that the hairy root induction from the explants emerged when an effective co– infection method in presence of acetosyringone with sonication for 60 s was done. The increase in hairy root biomass was further done for 16 weeks in root induction media that was without acetosyringone. The methanolic extract of the biomass when quantified for total Taxol content produced around 12 mg of Taxol per gram of hairy root biomass of Taxus baccata sub sp. wallichiana which is 79% more than the natural production of 0.15 mg per gram of bark stating a possible alternative for Taxol production commercially in a large amount.

Sono-Assisted Alkali and Dilute Acid Pretreatment of Phragmites karka (Tall Reed Grass) to Enhance Enzymatic Digestibility for Bioethanol Conversion

Phragmites is the tallest energy crop found as an invasive species worldwide and considered as waste biomass. The present study evaluated the potential of the aquatic biomass Phragmites karka grown from two different lakes as feedstock for biofuel production. A comparative study of biomass was conducted from Chilika Lake and Loktak Lake, India. The methodology involves dilute acid, sono-assisted alkali pretreatment, and hydrolyzed biomass with commercial cellulase. SEM, XRD, and FTIR analysis were performed for the biomass physicochemical studies and confirmed that alterations occurred in the biomass structure, assisting the hydrolysis process. The enzymatic hydrolysis result showed that the highest of reducing sugar yield of 79% was obtained from biomass loading of 10% and 1% w/v alkali with a sonication frequency of 20 kHz for 25 min. Acid pretreatment released maximal reducing sugar yield of 73% attained from biomass loading of 20% and 0.5% w/v acid. Composition analysis of biomass showed that cellulose content increased from 36% to 46%. Sono-assisted alkali pretreatment solubilized 40% of lignin content compared to untreated biomass. Final ethanol recovery from the biomass is 78% fermentation efficiency from glucose. The data indicate that exploiting tall reed grass as a bioenergy raw material can be a viable approach for sustainable utilization of invasive grass/waste biomass for biorefineries, which helps control invasive weeds and management of waste.

Higher Ultrasonic Frequency Liquid Phase Exfoliation Leads to Larger and Monolayer to Few-Layer Flakes of 2D Layered Materials.

Among the most reliable techniques for exfoliation of two-dimensional (2D) layered materials, sonication-assisted liquid-phase exfoliation (LPE) is considered as a cost-effective and straightforward method for preparing graphene and its 2D inorganic counterparts at reasonable sizes and acceptable levels of defects. Although there were rapid advances in this field, the effect and outcome of the sonication frequency are poorly understood and often ignored, resulting in a low exfoliation efficiency. Here, we demonstrate that simple mild bath sonication at a higher frequency and low power positively contributes to the thickness, size, and quality of the final exfoliated products. We show that monolayer graphene flakes can be directly exfoliated from graphite using ethanol as a solvent by increasing the frequency of the bath sonication from 37 to 80 kHz. The statistical analysis shows that ∼77% of the measured graphene flakes have a thickness below three layers with an average lateral size of 13 μm. We demonstrate that this approach works for digenite (Cu9S5) and silver sulfide (Ag2S), thus indicating that this exfoliation technique can be applied to other inorganic 2D materials to obtain high-quality few-layered flakes. This simple and effective method facilitates the formation of monolayer/few layers of graphene and transition metal chalcogenides for a wide range of applications.

Determining Sonication Effect on E. coli in Liquid Egg, Egg Yolk and Albumen and Inspecting Structural Property Changes by Near-Infrared Spectra.

In this study, liquid egg, albumen, and egg yolk were artificially inoculated with E. coli. Ultrasound equipment (20/40 kHz, 180/300 W; 30/45/60 min) with a circulation cooling system was used to lower the colony forming units (CFU) of E. coli samples. Frequency, absorbed power, energy dose, and duration of sonication showed a significant impact on E. coli with 0.5 log CFU/mL in albumen, 0.7 log CFU/mL in yolk and 0.5 log CFU/mL decrease at 40 kHz and 6.9 W absorbed power level. Significant linear correlation (p < 0.001) was observed between the energy dose of sonication and the decrease of E. coli. The results showed that sonication can be a useful tool as a supplementary method to reduce the number of microorganism in egg products. With near-infrared (NIR) spectra analysis we were able to detect the structural changes of the egg samples, due to ultrasonic treatment. Principal component analysis (PCA) showed that sonication can alter C–H, C–N, –OH and N–H bonds in egg. The aquagrams showed that sonication can alter the properties of H2O structure in egg products. The observed data showed that the absorbance of free water (1412 nm), water molecules with one (1440 nm), two (1462 nm), three (1472 nm) and four (1488 nm) hydrogen bonds, water solvation shell (1452 nm) and strongly bonded water (1512 nm) of the egg samples have been changed during ultrasonic treatment.

Monitoring of the ultrasound assisted depolymerisation kinetics of fucoidans from Sargassum muticum depending on the rheology of the corresponding gels

An ultrasound assisted hydrolysis of Sargassum muticum extracts produced under non-isothermal treatments during heating up to 170 °C was performed. Operation was made at two frequencies (37 and 80 kHz), where the composition and ABTS radical scavenging activity were analysed. Phenolic content, antioxidant capacity, sulphate and oligosaccharide content of the extracts increased with sonication time to 120 min, achieving higher values at 80 kHz. Extracts also exhibited cytotoxic against human cervical carcinoma cells (HeLa 229) at low (IC50, 0.074 mg/mL) and high frequencies (IC50, 0.304 mg/mL). All extracts displayed similar molecular weight profiles. Viscoelastic features of the alginate-based gels formulated with the hydrolysed extracts decreased with increasing sonication time and frequency. Monitoring of rheology of formulated gels and antioxidant kinetics of the corresponding soluble extracts allowed establishing exponential relationships. Overall, the obtained findings provided successful estimations (R2, 0.86–0.96) of the extracts’ antioxidant features depending on the viscoelasticity of gels.

Effects of high and low frequency ultrasound on the production of volatile compounds in milk and milk products - a review.

The effects of low and high frequency ultrasound on the production of volatile compounds along with their derivation and corresponding off-flavours in milk and milk products are discussed in this review. The review will simultaneously discuss possible mechanisms of applied ultrasound and their respective chemical and physical effects on milk components in relation to the production of volatile compounds. Ultrasound offers potential benefits in dairy applications over conventional heat treatment processes. Physical effects enhance the positive alteration of the physicochemical properties of milk proteins and fat. However, chemical effects propagated by free radical generation cause redox oxidations which in turn produce undesirable volatile compounds such as aldehydes, ketones, acids, esters, alcohols and sulphur, producing off-flavours. The extent of volatile compounds produced depends on ultrasonic processing conditions such as sonication time, temperature and frequency. Low frequency ultrasound limits free radical formation and results in few volatile compounds, while high ultrasonic frequency induces greater level of free radical formation. Furthermore, the compositional variations in terms of milk proteins and fat within the milk systems influence the production of volatile compounds. These factors could be controlled and optimized to reduce the production of undesirable volatiles, eliminate off-flavours, and promote the application of ultrasound technology in the dairy field.

Can ultrasonic parameters affect the impact and water barrier properties of nano-clay filled glass fiber/polyester composites?

Good dispersion of the nanoparticles into the polymer is considered a critical issue, as it can provide higher strength and stiffness while poor dispersion is seen to decrease those properties. In the present work, the effect of three ultrasonic parameters (amplitude, time and cycle of sonication) on sonication technique for dispersing 1 wt.% nano-clay in polyester matrix was investigated. To disperse the nano-clay into the polyester matrix, sonication frequencies of 40% and 80%, sonication times of 0.5, 1 and 2 hours and pulse of 0.5 and 1 cycle were used. The effect of these ultrasonication parameters on water barrier and impact behavior of unfilled and filled glass fiber (GF)/polyester with nano-clay under dry, distilled and seawater conditions was studied. Results showed that, water absorption of nano-filled composites dispersed with all sonication parameters is lower than that of unfilled glass fiber/polyester composites immersed in distilled and seawater. Nano-clay filled GF/polyester composites showed an improvement in impact resistance under dry, distilled and seawater conditions with all sonication parameters. Among the used sonication parameters; time of 2 hours, amplitude of 40% and 0.5 cycle was found as the best parameter which resulted in the maximum enhancement in impact resistance, due to the addition of nano-clay to GF/polyester, of 8.2%, 14% and 19.6% under dry, distilled water and seawater conditions, respectively. Nonlinear minimization approach was exploited using MAPLE commercial software in order to find the suitable fit to the models of Fick and Langmuir. Diffusion coefficients for different sonication times were computed.

Impact of thermo sonication and pasteurization on the physicochemical, microbiological and anti-oxidant properties of pomelo (Citrus maxima) juice

ABSTRACT In the present work, the effect of thermal (pasteurization) and nonthermal (thermosonication) treatments on the variations in physico-chemical, antioxidant activity, total phenols, total flavonoids, microbial populations, and sensory attributes of pomelo juice was studied. In thermosonication, processing parameters like treatment temperatures (30, 40, and 50 ± 2°C), treatment time (15, 30, 45, and 60 min), and sonication frequencies (33 and 44 kHz) were varied. TSS and TA of thermosonicated samples was not varied in comparison with control samples and minor differences in pH were observed. Significant improvements in DPPH activity, total phenols, and flavonoids were observed in both sonication frequencies and the results significantly varied as the treatment temperature was increased. From the research study, it can be inferred that juice samples processed at 50°C in the sonication frequency of 44 kHz produced maximum levels of total phenols, flavonoids, and DPPH activity.