Effect Of Microwave Irradiation Research Articles

Microwave irradiation: Reduction of higher alcohols in wine and the effect mechanism by employing model wine

Reduction of higher alcohols contributed more to the aromatic characteristics of wine. In this paper, response surface methodology was used to optimize the parameters of microwave time, temperature, and power to obtain optimal microwave processing conditions for the maximum degradation rate of higher alcohols in model wine solution, and the maximum degradation rate of higher alcohol was 11.21% under optimized microwave conditions of 100 W, 50 °C and 3 min. The possible mechanism of microwave reducing on the higher alcohols was studied at optimized microwave conditions, the results showed that high concentrations of tartaric acid, glyoxylic acid, and ferrous ions could obviously decrease the content of higher alcohols; the content of higher alcohols in low concentrations ethanol and cupric ions was obviously lower than that in high concentration of ethanol and cupric ions; the appropriate (+)-catechin concentration had more obvious effect on higher alcohols content; the mannitol inhibited the degradation of higher alcohols and its subsequent reactions by scavenging free radicals in model wine solution. In summary, all these results could help understand the influence of improvement effect of microwave irradiation on the aromatic characteristics in wine by reducing the contents of higher alcohols.

Effects of temperature and microwave on the stability of the blast effector complex APikL2A/sHMA25 as determined by molecular dynamics analyses.

Magnaporthe oryzae is the causal agent of rice blast, and understanding how abiotic stress affects the resistance of plants to this disease is useful for designing disease control strategies. In this paper, the effects of temperature and microwave irradiation on the effector complex comprising APikL2A from M. oryzae and sHMA25 from foxtail millet were investigated by molecular dynamics simulations using the GROMACS software package. While the structure of APikL2A/sHMA25 remained relatively stable in a temperature range of 290K (16.85°C) to 320K (46.85°C), the concave shape of the temperature-dependent binding free energy curve indicated that there was maximum binding affinity between APikL2A and sHMA25 at 300K-310K. This coincided with the optimum infectivity temperature, thus suggesting that coupling of the two polypeptides may play a role in the infection process. A strong oscillating electric field destroyed the structure of APikL2A/sHMA25, although it was stable and not susceptible to weak electric fields.

Effect of Microwave Radiation on the Solvent-free Synthesis of Phthaloylamino Acids

Background: In recent years, microwave radiation has been widely used in organic synthesis, including solvent-free mode. However, the reaction conditions of phthalic anhydride with amino acids under solvent-free microwave activation have not been studied so far. Objective: In the present work, the effect of microwave activation on the interaction of phthalic anhy-dride with amino acids in solvent-free conditions has been studied in detail. Methods: The microwave heating dynamics of phthalic anhydride, glycine and their equimolar mixture under microwave conditions have been investigated, and the dependence of the heating rate on the mi-crowave power is defined. Results: The common conditions for the synthesis of phthaloylamino acids have been determined as continuous heating at a power of 200 W at 130 °C for 5-6 min and additional heating for 5-10 min at a temperature close to the melting point of the corresponding amino acid. We have applied the developed two-step solvent-free microwave reaction protocol successfully for the synthesis of phthaloyl deriva-tives of glycine, alanine, β-alanine, 4-aminobenzoic acid, γ-aminobutyric acid, isoleucine, leucine, phe-nylalanine. Conclusion: Reaction conditions for synthesizing phthaloylamino acids by microwave activation with-out solvent have been established. The solvent-free microwave reaction between phthalic anhydride and amino acid has been found to proceed in the melted phthalic anhydride.

Molybdenum catalyzed deoxydehydration of aliphatic glycols under microwave irradiation

The effectiveness of microwave irradiation in promoting the deoxydehydration of aliphatic diols using dioxomolybdenum catalysts has been evaluated. The commercially available molybdenum precursor MoO2(acac)2 was found to be a superior catalyst as compared to dioxomolybdenum complexes stabilized by aminebisphenol ligands under these conditions. Octane-1,2-diol and decane-1,2-diol were converted to the corresponding olefins in 40−53% yields in 40 mins at 220−230 οC; this is a significant reduction in reaction time and higher activity when compared to reactions performed using conventional heating. More importantly, a similar yield (48%) of 1-decene could be achieved within 10 mins from a reaction carried out at 250 οC.

Microwave-assisted Sustainable Production of Biodiesel: A Comprehensive Review

Abstract: Limited crude petroleum and growing awareness of fossil fuel depletion have enabled the development of alternative fuels and new energy sources. Biodiesel, also known as fatty acid methyl esters (FAME), has received a lot of attention due to its biodegradability, renewability, cost effective and nontoxicity. The purity of biodiesel production and uniform heating are the major hurdles for large scale biodiesel production. Recent microwave energy-based heating method has proved the potential for cleaner chemical production, short time duration, uniform heating, and purity over conventional heating method. The goal of this review is to discuss the biodiesel production using microwave-assisted heating. The different feedstocks used for biodiesel production, effects of mi-crowave irradiation, factors affecting the rate of microwave-assisted transesterification to produce biodiesel were comprehensively discussed. Microwave irradiation has been compared to other tech-nologies aiming to enhance the efficiency of overall process. The primary knowledge gaps in bio-diesel production can be identified based on this research, ensuring the biodiesel industry's long-term sustainability.

Effect of Microwave Irradiation to Kinetics of Carbothermic Reduction of NiO

The carbothermic reduction of NiO was carried out by microwave irradiation at 2.45 GHz under a constant rate of temperature rise. The state of reaction was analyzed by means of non-equilibrium thermodynamics. The rates of the dominant reaction was the Boudouard reaction followed by NiO + CO → Ni + CO2, differing from that by conventional radiant heating. The uncompensated heat of reactions and the enthalpy change of reactions were almost same amount. The activation energy was 141 kJ/mol for the carbothermic reduction of NiO, 115 kJ/mol for the NiO reduction by CO gas and 166 kJ/mol for the Boudouard reaction. The former two values were smaller than conventional radiant heating.

Changes on Techno-Functional, Thermal, Rheological, and Microstructural Properties of Tef Flours Induced by Microwave Radiation-Development of New Improved Gluten-Free Ingredients.

Tef [Eragrostis tef (Zucc.) Trotter] flour is a gluten-free cereal rich in fiber, minerals, vitamins, and antioxidants, which offers a promising alternative for new food development. This study investigated the effect of microwave radiation (MW) on the techno-functional, thermal, rheological and microstructural properties of tef flours. White and brown tef grains were milled and microwaved at different moisture contents (MC) (15%, 20% and 25%) for a total irradiation time of 480 s. The morphological structure of tef flours was affected by MW treatment, and its particle size and hydration properties increased after the treatment. Lower peak, breakdown, and setback viscosities, up to 45%, 96%, and 67% below those of the control (untreated) samples, and higher pasting temperature, up to 8 °C in the 25% MC samples, were observed. From FTIR analysis a disruption of short-range molecular order was concluded, while DSC confirmed an increased stability of starch crystallites. Rheological analysis of the gels made from the treated samples revealed that MW had a structuring and stabilizing effect on all samples, leading to higher viscoelastic moduli, G' and G″, and the maximum stress the gels withstood before breaking their structure, τmax. The MC of the flours during the MWT drove the modification of the techno-functional properties of the tef flours and the gel rheological and thermal characteristics. These results suggest that MW-treated tef flours are potential ingredients for improving the technological, nutritional and sensory quality of food products.

Dispersive solid phase extraction-dispersive liquid–liquid microextraction of mycotoxins from milk samples and investigating their decontamination using microwave irradiations

Metal organic framework based dispersive solid phase extraction combined with dispersive liquid–liquid microextraction has been developed for the extraction of aflatoxin M1 and ochratoxin A from milk samples. The analytes were determined by high performance liquid chromatography–fluorescent detector. After optimization of the effective parameters, the analytical characters of method were studied. Based on the data, the proposed method provided satisfactory results such as low limits of detection (0.25 and 0.37 ng L–1 for ochratoxin A and aflatoxin M1, respectively) and quantification (0.83 and 1.23 ng L–1), high extraction recoveries (87 and 75%) and enrichment factors (305 and 263), and good repeatability (relative standard deviations equal or less than 4.9 and 5.1% for intra– and inter day precisions, respectively). After validation the method, the suggested approach was applied for the quantification of the aflatoxin M1 and ochratoxin A in various raw cow's milk samples and the effect of microwave irradiations in decontaminating them from milk samples were studied.

Analysis of microwave irradiation on the lethal conditions for insect pest in rice and its influence and regulation on the quality of rice

Abstract In view of the problem that conventional insecticidal methods cannot inhibit the hatching of insect eggs in rice, microwave heating was used to kill the insect eggs hidden in the rice grains. The lethal conditions of microwave irradiation on insect pests in rice and the effects of microwave irradiation on the quality of rice were studied, and the process conditions that can both ensure the quality of rice and kill insects were put forward. The microwave energy density parameter was used to evaluate the lethal conditions of microwave irradiation for insect pests in rice. The results showed that the lethality ratio of insect pests was 100% when the microwave energy density was higher than 0.0325 kW h/kg. Both microwave power density and microwave power affected the quality of rice. The results concluded that the cracking ratio, chalkiness and amylose content were increased with the increase of microwave power at the same microwave power density, while the free fatty acid content was decreased. Through the study of variable microwave power process, it was found that the cracking ratio and chalkiness can be controlled below 1.5% when the heating rate of rice at the later stage of microwave irradiation was less than 0.2 °C/s. The use of two-stage variable microwave power process can eventually ensure the disinfestation and the quality of rice simultaneously.

Lactobacillus gasseri Growth after Microwave Irradiation

Lactobacillus gasseri is a bacteria found in the gastrointestinal tract and vagina, and is essential for digestion and absorbing important nutrients. Some studies have experimented to find the effect of pulsed 2.4-GHz microwave irradiation on the growth of various Lactobacilli strains, while others have used continuous radiation at a similar frequency. Different studies have concluded that such radiation could kill other gut bacteria like Escherichia coli. We tested the effect of continuous microwave irradiation on the growth of Lactobacillus gasseri. We first irradiated four groups of the bacteria with a 10.5-GHz microwave transmitter for different amounts of time (0 minutes, 10 minutes, 20 minutes, 30 minutes). There was a significant difference between the control group and each irradiated group. There was no significant difference between the three irradiated groups. Our results agree with past research that has studied the effect of both microwave irradiation and radiation on Lactobacillus. We may have found such results because the electric field created by microwave radiation can disrupt the function of oxidative defense. This defense is needed to counteract oxidative stress, which could damage bacterial cell DNA, causing cell death. Therefore, microwaves at frequencies capable of penetrating the human body could cause the inactivation of multiple gut microbiota.

Kinetic modeling and experimental investigation of composition variation in hydrocarbon upgrading: Application to microwave-assisted reactors

BackgroundComprehensive understanding of composition variation and kinetic of upgrading reactions during microwave-assisted hydrocarbon upgrading is crucial for simulation and scale up purposes. MethodsIn the present contribution, the effect of microwave radiation on the liquid hydrocarbon sample in each 2 min exposure time interval up to 14 min was investigated. Fourier transform infrared spectroscopy (FTIR), and saturate, aromatic, resin, and asphaltene (SARA) composition variation of oil was considered. Each upgraded sample was characterized using the mentioned techniques. Then, a novel reaction network based on SARA composition was established, and kinetic modeling was performed for the first time. Significant findingThe maximum component relative deviation of 18.2% (Resin, 14 min radiation) and MSE of 1.12×10−4 for kinetic modeling results were observed. Experimental results reveal that 32.87 wt.% reductions of asphaltene content, 49.48 wt.% reductions in resin content, 16.66 wt.% gas production are achievable. Based on kinetic modeling results, at lower oil temperature aromatic upgrading rate is more than that of resin and asphaltene. However, increasing oil temperature or radiation exposure time increases asphaltene and resin conversion reaction rate. Finally, analyzing kinetic modeling results illustrate that, aromatic conversion to gasses and resin conversion to aromatics are the dominant mechanisms before and after 8 min radiation, respectively.

Radiation impact from Cell Phones and Towers on Human Health and Environment - A Review

The main key points discussed in the research paper are radiation impact from cell phones and towers electromagnetic waves on human health such as head and brain tumors, other morbidity-related outcomes and summarizes the biological effects of radio frequency (RF) and microwave radiation. The report shows that the evidence available does not provide a clear pattern to support an association between exposure to RF and microwave radiation from mobile phones and direct effects on health. It however cautions that lack of available evidence of detrimental effects on health should not be interpreted as evidence of absence of such effects and recommends a precautionary approach to the use of this communication technology until more scientific evidence becomes available. ; “These days we have Smartphones, Smartcards, Smartboards, Smart everything, but consider this: if technology is getting smarter, does that mean humans are getting dumber (ignore)?”

Thermal and nonthermal effect of microwave irradiation on the pore microstructure and hydrocarbon generation of organic matter in shale

In situ heating conversion is the most effective means to develop medium-low maturity shale oil. Herein, the effects of microwave irradiation on the shale pore structure and hydrocarbon generation of organic matter were studied using an independent development microwave device in combination with Rock-Eval, Leco analysis, X-ray diffraction, field emission scanning electron microscopy, low-temperature N2 adsorption/desorption, nuclear magnetic resonance, Fourier transform infrared spectroscopy and kinetic simulation of hydrocarbon generation. The results show that microwave irradiation can effectively heat shale and the temperature can rise to hundreds of degrees Celsius in a short time (10 min), with 400 °C as the best temperature for in situ conversion of medium-low maturity shale, at which the pore volume and surface area reach the maximum. Microwave irradiation is conducive to pyrolysis and hydrocarbon generation of aliphatic structure in shale organic matter. There are differences in the response of different organic components to the nonthermal effect of microwave irradiation, which reduces the activation energy of hydrocarbon generation during organic matter pyrolysis. Heating shale by microwave irradiation can effectively promote organic matter pyrolysis and hydrocarbon generation, improve rock reservoir and seepage capacity, and is of great significance for the efficient development of shale oil.

The aim of this study was to test and compare the effects of microwave irradiation on the dimensional stability of two types of complete denture bases.

The aim of this study was to test and compare the effects of microwave irradiation on the dimensional stability of two types of complete denture bases.

Effect of polymaleic acid and microwave radiations on reverse osmosis membrane's performance and properties: A response surface methodology approach

Polymaleic acid was tested for its ability to control inorganic fouling in reverse osmosis (RO) system for the first time as a membrane surface modifier. Using the design of experiments (DoE) based on the response surface methodological (RSM) approach, the effect of polymaleic acid concentration and microwave radiation time duration was studied on the membrane permeation properties. Considering the objective of achieving maximum water permeance and salt rejection properties, the conditions of polymerization were optimized using RSM and experimentally validated in the lab. At the optimum conditions of 10 mg·L−1 polymaleic acid, and 27 s radiation time, the pure water permeance and salt rejection were 3.05 L·m−2·h−1·bar−1, and 97.8 %, respectively. The optimized membrane was characterized through microscopic and spectroscopic techniques. When tested for its performance under inorganic fouling conditions, the modified membrane demonstrated a negligible decline in permeate flux for 6 h, and no formation of calcium sulfate precipitates on the membrane surface. This research aims to promote the development, optimization, and application of dual-functional RO membranes that can control different types of membrane fouling.

Non-thermal effects of microwave irradiation alleviates postharvest chilling injury of peach fruit by retarding phenolic accumulation and enhancing membrane stability

Postharvest chilling injury (CI) of fruit, including peaches, is a huge challenge to horticultural product preservation. Microwave irradiation can be used as a physiological regulator due to the thermal effects; however, its non-thermal effects on the CI of postharvest fruit remain unclear. Thus, the physiological attributes and metabolisms involving phenolics, fatty acids, and sugars were compared between ‘Zhongtao No.9’ peaches treated with microwave irradiation at 45.5 W for different durations and control. Microwave treatment especially at 45.5 W for 7 min without inducing thermal effects could significantly inhibit internal browning caused by CI, concomitant with reduced total phenolic content. Moreover, the maintenance of membrane stability was indicated by a boosted double bond index, which may be attributed to the inhibition of membrane lipid degradation, and sucrose accumulation. In summary, the non-thermal effects of microwave irradiation contribute to CI alleviation through restraining phenolic content and maintaining membrane stability in peach fruit.

Effect of Microwave Pretreatment on the Leaching and Enrichment Effect of Copper in Waste Printed Circuit Boards.

The use of efficient and clean methods for the recycling of waste circuit boards is an ongoing challenge. In this research, the effect of microwave pretreatment on the leaching and enrichment of copper from waste print circuit board (WPCB) was studied. The morphology and chemical structure of WPCB particles before and after microwave pretreatment were analyzed by SEM/EDS and Fourier infrared spectroscopy. Leaching experiments and copper enrichment tests were designed to investigate the effect of different microwave irradiation powers and microwave irradiation times on the copper leaching rate and copper enrichment rate in WPCB. The leaching experiment results showed that microwave pretreatment can effectively improve the leaching rate of WPCB. When the microwave irradiation power was 700 W, the irradiation time was 120 s, and the leaching time was 15 min, the copper leaching rate in WPCB was 57.01%, which was 24.34% higher than that in the untreated condition. The results of copper enrichment experiment show that microwave pretreatment can effectively improve the copper enrichment of WPCB. After microwave pretreatment, copper was effectively enriched in the 4-2 and 2-1 mm particle sizes. When the microwave irradiation time was 120 s, the copper enrichment rates in the 4-2 and 2-1 mm particle sizes were 1.74 and 1.66, which increased by 0.63 and 0.32, respectively, compared to the untreated condition. Microwave pretreatment enables the effective separation of metallic copper from non-metallic components in WPCB, increasing the exposure area of copper and promoting the monomer separation of copper, thus improving the leaching and enrichment of copper.

ВЛИЯНИЕ СВЧ-ИЗЛУЧЕНИЯ НА ДЕФОРМАЦИОННО-ПРОЧНОСТНЫЕ СВОЙСТВА ПОЛИУРЕТАНОВОГО СВЯЗУЮЩЕГО НА ОСНОВЕ ОЛИГОМЕРА ПДИ-3Б

The effect of microwave radiation on the vulcanizate of a polyurethane binder based on low molecular weight rubber PDI-3B was studied. Densities of thermal energy of microwave radiation absorbed by the material were calculated. It was shown that an increase in the density of thermal energy absorbed by the sample leads to a significant increase in the deformability of the material, which can be associated with a change in the density of the spatial network Keywords: microwave radiation, binder, polymeric material, rubber, thermal energy density, breaking stress, breaking strain, microwave generator, radiation frequency, radiation power.

The selective heating effect of microwave irradiation on a binary mixture of water and polyethylene oxide: a molecular dynamics simulation approach.

In this study, we investigate the molecular mechanisms of a microwave-driven selective heating process by performing molecular dynamics simulations for three different systems including pure water, pure polyethylene oxide (PEO), and water-PEO mixed systems in the presence of a microwave with two different intensities of electric field such as 0.001 V Å-1 and 0.01 V Å-1 at a frequency of 100 GHz. First, from performing molecular dynamics simulations of CO and CO2 in the presence of the microwave, it is confirmed that the molecular dipole moment is responsible for the rotational motion induced by the oscillating electric field. Second, by analyzing the MD simulations of the pure water system, we discover that the dipole moment of water exhibits a time lag with respect to the microwave. During the heating process, however, the temperature, kinetic, and potential energies increase synchronously with the oscillating electric field of the microwave, showing that the heating of the water system is caused by the molecular reaction of water to the microwave. Comparing the water-PEO mixed system to the pure water and pure PEO systems, the water-PEO mixed system has a higher heating rate than the pure PEO system but a lower heating rate than the pure water system. Therefore, we conclude that heating the water-PEO mixed system is driven by water molecules selectively activated by microwave irradiation. We also calculate the diffusion coefficients of water molecules and PEO chains by describing their mean square displacements, demonstrating that the diffusion coefficients are increased in the presence of microwaves for both water and PEO in pure and mixed systems. Lastly, during the microwave heating process, the structures of the water-PEO mixed system are altered as a function of the intensity of electric field, which is mainly driven by the response of water molecules.

The dose-dependent effect of 1.5-GHz microwave exposure on spatial memory and the NMDAR pathway in Wistar rats

A certain power of microwave radiation could cause changes in the nervous, cardiovascular, and other systems of the body, and the brain was a sensitive target organ of microwave radiation injury. Studies have shown that microwaves can impair cognitive functions in humans and animals, such as learning and memory, attention, and orientation. The dose-dependent effect of microwave radiation is still unclear. Our study aimed to investigate the effects of 1.5-GHz microwaves with different average power densities on locative learning and memory abilities, hippocampal structure, and related N-methyl D-aspartate receptor (NMDAR) signalling pathway proteins in rats. A total number of 140 male Wistar rats were randomly divided into four groups: S group (sham exposure), L5 group (1.5-GHz microwaves with average power density = 5 mW/cm2), L30 group (1.5-GHz microwaves with average power density = 30 mW/cm2), and L50 group (1.5-GHz microwaves with average power density = 50 mW/cm2). Changes in spatial learning and memory, EEG activity, hippocampal structure, and NMDAR signalling pathway molecules were detected from 6 h to 28 d after microwave exposure. After exposure to 1.5-GHz microwaves, rats in the L30 and L50 groups showed impaired spatial memory, inhibited EEG activity, pyknosis and hyperchromatism of neuron nucleus, and changes in NMDAR subunits and downstream signalling molecules. In conclusion, 1.5-GHz microwaves with an average power density of 5, 30, and 50 mW/cm2 could induce spatial memory dysfunction, hippocampal structure changes, and changes in protein levels in rats, and there was a defined dose-dependent effect.