Search results for "Microwave"
showing 10 items of 693 documents
The bending triad of the quasi-spherical top molecule SO2F2 in the 550 cm(-1) region
2006
International audience; The analysis of the v(3)/v(7)/v(9) bending triad of SO2F2 has been recently performed with the Watson's Hamiltonian up to octic terms employing 79 rovibrational parameters but including only the first order Coriolis interaction terms, fixed to ab initio values [H. Burger, J. Demaison, F. Hegelund, L. Margules, I. Merke, J. Mol. Struct. 612 (2002) 133-141]. Since SO2F2 is a quasi-spherical top, it can also be considered as derived from the SO42- sulfate ion. We have thus developed a new tensorial formalism in the O(3) > Td > C2v group chain [M. Rotger, V. Boudon, M. Loete, J. Mol. Spectrosc. 216 (2002) 297-307]. This approach allows a systematic development of rovibra…
Céramiques diélectriques commandables pour applications micro-ondes : composites à base de titanate de baryum-strontium et d'un oxyde non ferroélectr…
2001
Since the last decades, dielectric ceramics have been considered as attractive for microwave applications as tunable dielectric resonators or phase shifters. For that, ceramic devices should be tunable – change in dielectric constant with applied voltage- with moderate to low dielectric constant (30 to 1000) and loss tangent as low as possible. To reconcile these properties, composite ceramics based on Ba0.6Sr0.4TiO3 (BSTO) and a non-ferroelectric oxide with a low dielectric constant (MgTiO3 or MgO) were synthesised. The aim of this study was to correlate the microstructure with the dielectric properties, especially the Curie temperature and the dielectric relaxation phenomena.Ceramics with…
Stability and extraction of bioactive sulfur compounds from Allium genus processed by traditional and innovative technologies
2017
Abstract Since ancient times, species from the Allium genus have been used in both culinary and medicinal applications. The health promoting properties, with well documented “evidence-based” studies, were attributed to the genus’ high content of bioactive organosulfur compounds. For these reasons, the organosulfur compounds have attracted interest in both food and pharmaceutical industries to be used as additives or supplements. Therefore, improvement in the extraction and stability during processing and storage of these molecules is crucial. The presented review documents the effects of traditional and innovative processing techniques on the extraction and stability of organosulfur compoun…
Millimeter-Wave Effects on Candida Albicans Cells
1985
In preliminary measurements, Candida albicans cultures exposed to 1 kHz square-wave-modulated microwaves at 72 GHz exhibited a significantly reduced number of colony-forming units in comparison with nonirradiated controls. To study whether the same effect could also be caused by continuous-wave (CW) irradiation, sedimented cells were exposed to either 1 kHz square-wave-modulated or CW microwaves at 72 GHz, with the same peak power. CW-exposed cells showed a higher growth rate (about 25%), whereas a reduction of about 15% was seen in cells exposed to square-wave-modulated microwaves in comparison with sham-exposed controls.
Recent Advances and Future Directions of Microwave Photonic Radars: A Review
2021
Microwave photonic (MWP) radar has the advantages of generating and processing wide bandwidth microwave signals, reconfigurability, high immunity to electromagnetic interference compared to microwave electronic radar. It has the potential to be used in applications such as intelligent autonomous and cyber-physical systems. Recent advances in microwave photonic technology led to the generation, fast processing, and control of broadband signals. Because of the advancements in photonic technologies, next-generation microwave photonic radar is becoming more prominent. This article reviews the most recent advancements and future directions in MWP radars. This review article overviews the differe…
A novel synthetic approach to pyran-2,4-dione scaffold production: Microwave-assisted dimerization, cyclization, and expeditious regioselective conve…
2020
Abstract Here, we report a novel, green, simple, low-cost, and rapid methodology for the high-yield production of pyran-2,4-dione scaffolds under microwave irradiation. Regio- and stereoselective conversions of β-diketone systems into β-enaminones were achieved using 18 primary amines and four amino acid esters. Microwave-assisted further cyclization of 3-(β-substitutedvinyl)-6-phenyl-pyran-2,4-dione into 3-benzoyl-4,7-diphenyl-2H,5H-pyrano[4,3-b]pyran-2,5-dione via reaction with ethyl benzoyl acetate.
Retro-Diels-Alder Protocol for the Synthesis of Pyrrolo[1,2-a]pyrimidine and Pyrimido[2,1-a]isoindole Enantiomers
2013
A simple protocol was introduced to prepare several enantiomerically pure heterocycles by using (–)-(1R,2R,3S,4S)-3-aminonorbornene-2-carboxylic acid as a chiral auxiliary. The protocol is based on a domino ring-closure reaction, in which the relative configuration of the new asymmetric center is controlled by the stereochemistry of the amino acid, followed by a microwave-induced retro-Diels–Alder reaction.
Electrotechnologies, microwaves, and ultrasounds combined with binary mixtures of ethanol and water to extract steviol glycosides and antioxidant com…
2017
The aim of this work was to investigate the potential use of non-conventional technologies (microwaves, ultrasounds, pulsed electric fields, and high voltage electrical discharges) to enhance the extraction of high-added value compounds (mainly stevioside and rebaudioside A), and antioxidants (total phenolic compounds, flavonoids, chlorophylls, and carotenoids), from Stevia rebaudiana leaves. After treatment at equivalent energy, a supplementary diffusion was performed until 1 h. Results demonstrated that when water (100%) was used as solvent, the maximum recovery of stevioside (50.8 ± 0.1 mg/g) was obtained after ultrasound-assisted extraction, while microwave allowed the highest yields of…
Effects of solvent-free microwave extraction on the chemical composition of essential oil of Calamintha nepeta (L.) Savi compared with the convention…
2008
The essential oil of Calamintha nepeta has been obtained by solvent-free microwave extraction (SFME) and by classical hydrodistillation (HD). A comparative qualitative-quantitative study on the composition of the oils was carried out. A total of 38 compounds, constituting 97.6% of the oil, were identified in the oil obtained by SFME, whereas 46 compounds, representing 95.4% of the oil, were characterized in the HD oil. SFME-distilled oil is richer in lightly oxygenated monoterpenes (LOM) than HD oil. It also has a higher amount of sesquiterpenes and a lower quantity of hydrocarbon monoterpenes. HD oil seems to be affected by chemical changes more than SFME oil.
Effect of traditional, microwave and industrial cooking on inositol phosphate content in beans, chickpeas and lentils
2003
An high-performance liquid chromatography method for determining inositol phosphate fractions was adapted to legumes. The validity of the method was assessed by estimating the following analytical parameters: linearity (linear response between 125 and 5000 microg inositol hexaphosphate (IP(6))/ml); instrumental precision and method precision (relative standard deviation, %) were 1.9% (IP(6)) for instrumental, and 2.5% (IP(6)) and 8.2% (IP(5)) for method precision. An accuracy was estimated by percentage recovery (72 +/- 3%). The application of this method to raw, conventional, microwave-cooked and ready-to-eat beans, chickpeas and lentils gave IP(6) contents ranging from 0.63 g/100 g dry ma…