Influence Of Microwave Irradiation Research Articles

Influence of microwave irradiation on DNA hybridization and polymerase reactions

We report herein that exposure of DNA to microwave irradiation at constant temperature leads to faster strand exchange, as compared with same experiments carried out in a water bath at the same temperature. Furthermore, polymerase chain reactions carried out under microwave irradiation were faster than those in a water bath at the same temperature as well. While the causes of these differences are unclear at this time, this research suggests that microwave irradiation can lead to subtle changes in DNA structural dynamics and functions.

C60 fullerene loaded hydroxyapatite-chitosan beads as a promising system for prolonged drug release

Bioactive composite material in the form of beads, based on natural polysaccharide Chitosan (CS), hydroxyapatite (HA), and C60 fullerene (C60), was synthesized under influence of microwave irradiation (MW). The bead is a 3D matrix consisting of CS macromolecules cross-linked with sodium tripolyphosphate with HA and C60 particles immobilized in its structure. XRD and FTIR data confirmed the formation of calcium deficient carbonate substituted HA with needle-shaped nanocrystallites of about 80 nm. MW does not influence CS structure. C60 enhances the beads shape stability. HPLC studies suggest the (up to 18 days) prolonged release of hydrophobic Anaesthesinum from C60-containing composites. Changing the C60 content allows adjusting the drug release time. The presence of CS and C60 provides the Anaestesinum release profile, according to the calculated correlation coefficient (r = 0.99), close to the zero order kinetic release profile. The inhibition zone test (ZOI) shows the antimicrobial activity of the composites containing 0.004 mg/ml C60 against S. aureus ATCC 25923 and E. coli ATCC 25922 (ZOI 16 ± 1 and 10 ± 2 mm, respectively). Cell viability test indicates no toxicity of 0.3 and 0.15 mg/ml C60-containing composites.

Screening of ion exchange resin catalysts for epoxidation of oleic acid under the influence of conventional and microwave heating

AbstractBACKGROUNDFor many chemical systems, it is of great importance to find a durable, active and efficient catalyst that improves the process performance. Epoxidation of oleic acid with peracetic acid (Prilezhaev oxidation) was carried out in an isothermal loop reactor in the presence of heterogeneous catalysts. The kinetic experiments conducted under microwave heating (MW) were compared with identical experiments carried out under conventional (conductive/convective) heating. Extensive screening of heterogeneous catalysts was conducted and the influence of microwave irradiation on the reaction kinetics was studied. Several ion exchange resins were screened to explore their applicability and activity in the epoxidation of oleic acid. The perhydrolysis reaction (peracetic acid formed in situ from acetic acid and H2O2) was promoted with the use of various solid acid catalysts: Amberlite IR‐120, Amberlyst 15, Smopex®, Dowex 50x8‐100, Dowex 50x8‐50, Dowex 50x2‐100 and Nafion™.RESULTSFrom the selected group of catalysts, Dowex 50‐x8100 and Dowex 50x8‐50 produced the highest yield of epoxidized oil. Only minor differences in the reactant conversion and the product yield were found in the experiments carried out under microwave exposure compared to the conventionally heated experiments in the presence of several ion exchange resins.CONCLUSIONSThe catalytic effect was much more prominent than the microwave effect, because the solid acid catalysts enhanced the slow step of the process, the perhydrolysis of acetic acid. The catalytic effect was very dominant and a considerable improvement of the oleic acid conversion and the epoxide yield was observed in the presence of the top‐performing catalysts. © 2019 Society of Chemical Industry

Influence of microwave irradiation on thermal properties of PVA and PVA/graphene nanocomposites

This article discusses the effect of microwave irradiation on the thermal properties of poly(vinyl alcohol)/graphene nanocomposites, prepared using a solution casting technique. Samples were subjected to microwave radiation for 5, 10 and 15 min at a constant power of 200 watts. The crystallinity and thermal stability of the irradiated samples were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis. Reduction in crystallinity and thermal stability of PVA was observed with incorporation of graphene due to restricted dynamic movement of chains and synergistic instability, respectively. Microwave irradiation for 5 min improved the crystallinity and thermal stability of the nanocomposites. However, further irradiation caused a decrease in the crystallinity as well as in the thermal stability due to degradation. Moreover, the isothermal crystallization kinetics were studied by DSC. An increase in the crystallization rate was observed with graphene incorporation.

Characterizing the Josephson Effect on Ba-122 Single-Crystal Junctions

This paper presents c-direction hybrid Josephson junctions with base electrodes of Co:BaFe2As2 single crystals. To realize Josephson junctions, it applies standard photolithography technologies and a newly developed surface polishing method that was used. As conventional isotropic s-wave superconductor counter electrodes used double layers of Pb/In. The artificial barrier for the tunneling junctions consists of a thin sputtered Ti layer or a thermally evaporated Al layer; both layers were used as an insulator barrier. For characterizing the Josephson effects with TiOx barrier, we could realize IcRN products of about 13.7 μV and unconventional Ic-T dependencies. The formation of Shapiro steps under the influence of microwave irradiation and magnetic field to the junctions will be discussed as well.

Composite material with nanoscale architecture based on bioapatite, sodium alginate and ZnO microparticles

A nanostructured composite material in the form of a hydrogel and beads based on hydroxyapatite (HA), sodium alginate (Alg) and ZnO microparticles was fabricated under the influence of microwave irradiation. An average crystallite size of the HA was 40 nm, while ZnO crystallites of the size 25 nm–11 µm were formed. The inorganic HA-ZnO phase of studied composite is distributed in the polysaccharide matrix of the alginate, which corresponds to the structures of natural bone nanocomposites. The introduction of ZnO into the composite increases its porosity up to 5 times and the degree of swelling in phosphate buffered saline up to 2 times, as well as provides weak antimicrobial activity. The effect of microwave and ultrasonic treatment on the structure of HA-ZnO and HA-Alg-ZnO composites’ microcrystals was studied. The mechanism of antimicrobial activity of ZnO crystals in the HA-Alg-ZnO composite was proposed. The in vitro biocompatibility and cytotoxicity of the synthesized materials was studied and it was found that addition of ZnO make insignificant effect on biocompatibility. Thus, the main goal of our work was fabrication of the bioactive material using microwave and ultrasonic treatment for additional enhancement of antibacterial properties.

Effect of microwave irradiation on the grinding and magnetic separation characteristics of vanadium titano-magnetite

In this study, the influence of microwave irradiation on the grinding characteristics and magnetic separation of vanadium titano-magnetite (VTM) was investigated, including the effects of microwave power, microwave irradiation time, and particle size of VTM. The particle size distribution of the ground product and Fe grade in magnetic fraction of the untreated and microwave-treated VTM were obtained. Grinding experiment showed that the microwave irradiation could improve the grindability of VTM, thus increasing the specific rate of breakage (S1) value and the weight percentage of the fine ground product significantly. With increasing microwave irradiation time and particle size of VTM, the increment in grindability of VTM was improved. No obvious difference was observed in the particle size distribution of the fine ground product between the untreated and microwave-treated VTM. The magnetic separation tests confirmed that the Fe grade of the magnetic fraction increased from 51.70% for untreated VTM to 53.78% by microwave irradiation. According to X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and scanning electron microscopy (SEM) analyses, the dominant mechanisms that improved the grindability and liberation of VTM under microwave irradiation included the microwave selective heating the valuable mineral within the VTM and the micro-fractures between mineral and gangue that were induced by the thermal stress.

Systematic Study of the Behavior of Different Metal and Metal-Containing Particles under the Microwave Irradiation and Transformation of Nanoscale and Microscale Morphology.

In recent years, the application of microwave (MW) irradiation has played an increasingly important role in the synthesis and development of high performance nanoscale catalytic systems. However, the interaction of microwave irradiation with solid catalytic materials and nanosized structures remains a poorly studied topic. In this paper we carried out a systematic study of changes in morphology under the influence of microwave irradiation on nanoscale particles of various metals and composite particles, including oxides, carbides, and neat metal systems. All systems were studied in the native solid form without a solvent added. Intensive absorption of microwave radiation was observed for many samples, which in turn resulted in strong heating of the samples and changes in their chemical structure and morphology. A comparison of two very popular catalytic materials—metal particles (M) and supported metal on carbon (M/C) systems—revealed a principal difference in their behavior under microwave irradiation. The presence of carbon support influences the heating mechanism; the interaction of substances with the support during the heating is largely determined by heat transfer from the carbon. Etching of the carbon surface, involving the formation of trenches and pits on the surface of the carbon support, were observed for various types of the investigated nanoparticles.

Microwave Irradiation-Assisted Chitosan Hydrolysis Using Cellulase Enzyme

The influence of microwave irradiation on the chitosan hydrolysis catalyzed by cellulase enzyme was studied. The hydrolyzed chitosan was characterized by measuring its viscosity and reducing sugar. Further, it was also characterized by Fourier-Transform Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), and Scanning Electron Microscope (SEM). The classical Michaelis-Menten kinetic parameters were measured by analyzing the amount of reducing sugars. The results were compared with the hydrolysis by using conventional shaker incubator. The hydrolysis reaction time needed to obtain similar reducing sugar yield was significantly lower for microwave irradiation than shaker incubator. On the other hand, the reduction rate of the relative viscosity was significantly higher for the hydrolysis of chitosan using shaker incubator. A significant difference in chemical structure was observed between hydrolysis using microwave irradiation and shaker incubator. Overall, the result showed that the hydrolysis behavior of chitosan using microwave irradiation is significantly different with using shaker incubator.

Preservation of higher Fe[II] content in borosilicate glass by microwave irradiation in air

Existence of high Fe[II] content in glass is a perquisite for achieving high heat absorption property in glass. Present study investigates the capability of microwave (MW) irradiation in retention of higher Fe[II] in glass eliminating the stringent reducing atmosphere requirements in conventional heating. Stabilisation of higher Fe[II] in glass under influence of MW irradiation has been demonstrated, measuring absorbance at >1000 nm in UV–vis-NIR spectra, maintaining identical conditions in MW and in conventional heating. Spectrophotometric methods developing color complex of Fe2+ with ferrozine and 1, 10 ortho-phenanthroline are used to confirm higher content of Fe[II]. Further, more weight gain in thermo gravimetric analysis, higher isomer shift (>0.89 mm/s) with more relative absorption (% area) for Fe[II] in Mössbauer spectroscopy, and shifting of Fe 2p3/2 peak in X-ray photoelectron spectroscopy towards lower binding energy further confirm retention of higher FeO under MW irradiation.

Influence of Microwave Irradiation on Extraction of Chitosan from Shrimp Shell Waste

Chitosan is natural polysaccharides which is nontoxic, biodegradable, and biocompatible and have many advantages in various kinds of fields including health, food, agriculture, and industry. Chitosan usually take long time to extract by conventional method for deacetylation process of chitin. Raw material for chitosan can be found in shrimp shell waste. Chitosan manufactures usually need high temperatures and chemicals in large quantities and it takes much time and consumes a lot of energy where will give bad effect to the environment. Recently microwave irradiation as nonconventional energy sources is widely used in chemical reactions. To reduce the impact of environmental pollution due to excessive use of chemical treatment, the objective of this work is processing chitosan under microwave irradiation. Expected production of chitosan with the same mass requires fewer chemicals than conventional heating. In particular, the study will examine the effect of making the chitosan and adding chemicals, reaction time and operating temperature and degree of deacetylation in chitosan with conventional heating methods that the results will be compared using a microwave. In this research will be developed to the design and fabrication of prototype scale extractor for manufacturing chitosan from shrimp shell waste after optimum results obtained from the research laboratory scale. From the research we can conclude that microwave will speed up reaction time. FTIR also showed functional group of chitosan formed from microwave irradiation have same results. Keywords: chitosan, shrimp shells, microwave

Influence of Microwave and Electron Beam Irradiation on Composition of Aluminum Nanopowder

The influence of microwave irradiation (9.4 GHz) and electron beam (250 keV) on metal aluminum content in aluminum nanopowder is studied. It is established that after irradiation the content of metal aluminum in Al nanopowder increases. The most likely explanation is the reduction of aluminum ions Al3+ in the oxide shell at the surface of aluminum nanoparticles to produce metal.

Macromolecular systems and nanocomposites based on N-succinylchitosan and silver nanoparticles

A water-soluble chitosan derivative, namely, N-succinylchitosan (NS-Chit), was used as a matrix for the formation of silver nanoparticles (AgNP) by metal ion re duction under influence of microwave irradiation in the presence of D-glucose as a reducing agent. The electron plasmon resonance spectra (λmax = 410 nm) obtained for the irradiated solutions were typical of spherical silver nanoparticles. The in vitro tests confirmed a high bactericidal activity of the colloidal solution containing AgNP in a NS-Chit polymer matrix against strains of grampositive bacteria, namely, Bacillus subtillus (ATCC 6633), B. coagulans (429), and Staphylococcus aureus (ATCC 21027).

Reaction of different rock types to low-power (3.2 kW) microwave irradiation in a multimode cavity

This study deals with low-power (3.2 kW) microwave irradiation of a range of rocks and provide an indication of the suitability of certain rock types for this treatment method for rock fragmentation and mineral comminution. The influence of microwave irradiation was assessed physically by measuring rock properties and observing cracking phenomena and chemically by analysing the mineralogical and chemical composition before and after microwave irradiation. The results show that the reaction to microwave irradiation strongly depends on the mineralogy or the water content of the rock. Rocks with low content of microwave absorbers (like granite and sandstone) heat slowly and do not show strong physical changes, whereas rocks with better microwave absorption (basalt, mafic volcanites) heat quickly leading to significant physical changes. It is apparent that the presence of water either in the porous volume of the rock or in the mineralogical structure (e.g. clay minerals) adds to the destructive work with the help of the generated steam pressure.

The influence of microwave radiation on the process of solid-phase recovery of ilmenite concentrate

A study on the effect of intensive microwave radiation on the process of solid-phase recovery of ilmenite concentrate is presented. Assessment of the degree of recovery, the change in the phase composition and elemental analysis of the reaction products were carried out by x-ray diffraction and energy-dispersive analysis. By means of electron microscopy, the dynamics of the appearance and the droplet size of the restored iron formed under the influence of microwave irradiation on the surface of solid-phase synthesis products are evaluated. High efficiency of microwave exposure on the recovery of ilmenite concentrate in the carbon medium at a temperature of 1000 °C is shown. The possibility of reducing temperature and duration of the reduction process of iron oxides in the ilmenite ore, compared with the traditional high-temperature process of enrichment of titanium ore, is established.

Risk factors and structure of obstetric and perinatal complications in woman, which ill of pyelonephritis (Review of literature and results of own researches)

Actuality. Morbidity on a pyelonephritis and complication of motion of pregnancy is the important indicators of the state of health of woman population and baby that determines social meaningfulness of this problem.Research aim. To learn data of anamnesis of illness, life, professional features, domestic and surrounding environment, data of somatic status and to set forth leading risk of origin of placenta disfunction factors for pregnant, patients with a pyelonephritis.Material and methods. On the basis of retrospective analysis there are 20779 histories of illnesses of women, patients with a pyelonephritis, the study of risk of forming of somatic pathology of women and development of placenta disfunction factors is conducted with the aim of warning of complications of pregnancy and pathology of fetal and child.Results of researches. Research of the somatic state of pregnant that are ill a chronic pyelonephritis showed the presence of concomitant pathology in 100% cases, from that the diseases of the cardiovascular system laid down 61,5%, endocrine violations 50,2%, the dyspepsia phenomena and gastroenterology pathology 40,5%.The structure of obstetric, perinatal complications for women with a chronic pyelonephritis (20779 supervisions) included: early toxicosis (65,5%), placental dysfunction (73,3%), an eclampsia (78,3%), threat of abortion (76,1%) and premature luing-ins (56,2%), subzero placentation (76,1%), high water-level (76,7%), gestational anaemia (67,8%), delay of height of fetal (17,1%), chronic fetal distress (21,3%), premature removing layer by layer of placenta (26,3%); in luing-ins: premature outpouring of near of fetal waters (22,4%), weakness of childbirth (72,3%), obstetric bleeding (47,1%); in a puerperium: subinvolution of uterus (26,3%).Conclusion. Thus, executed by us research in relation to the study of morbidity and prevalence of pyelonephritis among pregnant allowed to set the following: placenta disfunction in the period of pregnancy registered oneself in 100% habitants of districts with a row by quality of drinking-water, in 90% patients with cardiovascular pathology, in 62,1% with passion to smoking and on a background considerable gas is muddy air contamination of environment, in 41,9% pregnant, that abuse of alcohol, in 37,9% with an off-grade feed, in 27,6% as a result of chronic stress, chronic fatigueability, influence of microwave irradiation. The above-stated factors are leading risk of origin of placenta disfunction factors for pregnant, with ill of pyelonephritis.

Influence of Microwave Irradiation of Tempering Water on the Process of Crystallization of Calcium Sulfate Dihydrate

It is established that water treatment by a microwave field influences the processes of formation and growth of calcium sulfate dihydrate crystals. Results of investigation of calcium sulfate dihydrate crystals by the methods of x-ray phase analysis, electron microscopy, and thermal analysis are presented.

Microwave-assisted synthesis of well-shaped UiO-66-NH2 with high CO2 adsorption capacity

In a detailed study, the influence of microwave irradiation, synthesis time and temperature, addition of acetic acid (HAc) as a modulator on the morphology, crystallinity and stability of UiO-66-NH2 is investigated to develop a reliable and reproducible strategy for the preparation of well-shaped UiO-66-NH2. The UiO-66-NH2 were characterized by powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM), thermogravimetric analysis (TGA), and gas adsorption. It is found that well-shaped UiO-66-NH2 with a high CO2 adsorption capacity can be synthesized in a short time by microwave heating. The UiO-66-NH2 crystals synthesized by microwave heating are of high quality and show a superior CO2 adsorption capacity (5.8mmol/g at 273k and 1bar) due to the strong interactions between the −NH2 group and CO2. The CO2/N2 selectivity of the obtained UiO-66-NH2 at 298K and 1bar is 66, which is much higher than that of the pristine UiO-66 of 17.8.

Microfluidical Microwave Reactor for Synthesis of Gold Nanoparticles.

Microwave treatment can reduce the time of selected syntheses, for instance of gold nanoparticles (AuNPs), from several hours to a few minutes. We propose a microfluidic structure for enhancing the rate of chemical reactions using microwave energy. This reactor is designed to control microwave energy with much higher accuracy than in standard devices. Thanks to this, the influence of microwave irradiation on the rate of chemical reactions can be investigated. The reactor consists of a transmission line surrounded by ground metallization. In order to deliver microwave energy to the fluid under test efficiently, matching networks are used and optimized by means of numerical methods. The monolithic device is fabricated in the low temperature co-fired ceramics (LTCC) technology. This material exhibits excellent microwave performance and is resistant to many chemical substances as well as high temperatures. Fabrication of the devices is described in detail. Measurements of microwave parameters are performed and differences between simulation and experiment results are discussed. Finally, the usefulness of the proposed device is proved in exemplary synthesis.

Microwave-assisted synthesis of malic acid involving hydrochloric acid as catalyst

The competing acid catalyzed reactions of fumaric acid (F) isomerization to form maleic acid (Mx) (reaction R1), and the hydration of F to malic acid (M) (reaction R2) were investigated under microwave heating. The kinetic experiments were performed in a sealed microwave-irradiated batch reactor operated at pressures between 615 and 1715 kPa, in the temperature range from 433 to 478 K, and for reaction times up to 21,600 s. Hydrochloric acid at three different concentrations (C H = 0.65, 1.30 and 1.94 M) was used as the catalyst. The concentrations of F, Mx and M were periodically determined by HPLC analyses. The Arrhenius parameters for the forward rate constants of the reactions R1 and R2 were tuned on the experimental data of species concentrations (k 10 = 5.63 ± 0.04 M−1 s−1, E a1/R = 4837 ± 121 K, k 20 = (6.9 ± 0.3) × 107 M−2 s−1, E a2/R = 13,532 ± 212 K). The tuning procedure involved the Simplex method of optimization, and a kinetic model represented by a system of four ordinary differential equations from material balances on species F, Mx, M and HCl. The model was able to reproduce the variation in species concentrations with time for all experimental conditions investigated, just with a partial set of the currently obtained data used to adjust the model parameters (C H = 0.65 M and 1.94 M). The current results at C H of 1.30 M and analogous data from the literature under quite different reaction conditions (e.g.; C H = 0.97 M, non-isothermal reactor externally heated with glycerol) confirm the reliability of the modeling approach. The catalyst concentration had the expected significant effect on the reaction rates, but the influence of microwave irradiation on the kinetics of the conversion of F and on the selectivity of M was small.