Microwave-Assisted Synthesis and Evaluation of Antimicrobial Activity of 3-{3-(s-Aryl and s-Heteroaromatic)acryloyl}-2Hchromen-2-one Derivatives

The exploration of potential utilization of microwaves as an energy source for heterocyclic synthesis was herein investigated using condensation of 3-acetylcoumarin (1) with aromatic and heteroaromatic aldehydes to afford the corresponding aromatic chalcones (2a–j) and heteroaromatic chalcones (3a–e and 4a–e), respectively, in good to excellent yield within 1–3 min. The chemical structures were confirmed by analytical and spectral data. All the synthesized compounds were screened for their antibacterial activity and 3-{3-(4-dimethylaminophenyl)acryloyl}-2H-chromen-2-one (2i) was discovered to be the most active at minimum inhibitory concentration (MIC) value of 7.8 µg/m

Atomic resolution imaging at 2.5 GHz using near-field microwave microscopy

Atomic resolution imaging is demonstrated using a hybrid scanning tunneling/near-field microwave microscope (microwave-STM). The microwave channels of the microscope correspond to the resonant frequency and quality factor of a coaxial microwave resonator, which is built in to the STM scan head and coupled to the probe tip. We find that when the tip-sample distance is within the tunneling regime, we obtain atomic resolution images using the microwave channels of the microwave-STM. We attribute the atomic contrast in the microwave channels to GHz frequency current through the tip-sample tunnel junction. Images of the surfaces of HOPG and Au(111) are presented.Comment: 9 pages, 5 figures, submitted to Applied Physics Letter

Microwave pyrolysis of oil palm fibres

Malaysia and Indonesia are generating millions of ton of oil palm fibres (OPF) from their oil palm mills as biomass solid wastes which needs proper waste utilization application. The main purpose of the present research was to pyrolyse the OPF biomass into bio-oil using microwave irradiation technique. A domestic microwave of 1000 W and 2.45 GHz frequency was modified to accommodate fluidized bed system. It was found that OPF showed poor microwave absorbing characteristics. Therefore, an appropriate microwave-absorbing material such as biomass char was added to initiate the pyrolysis process. Temperature profiles and bio-oil yield was investigated by varying the ratio of OPF to microwave absorber. It was found that the yield of bio-oil depended on the ratio of OPF to microwave absorber. Particular attention on the temperature profiles was also taken into account during microwave heating of OPF. It can be concluded that microwave technique can save significant time and energy through its rapid and volumetric heating characteristic

Efficient enhancements in spectral domain method to speed up open planar circuit analysis

The spectral domain method is a very fast and powerful technique to analyse planar microwave circuits. Available techniques for simulating the excitation of open planar microwave circuits are not very effective at relatively low frequencies. In this contribution new compensation functions are introduced which correctly model the excitation over the whole microwave frequency regionThe spectral domain method is a very fast and powerful technique to analyse planar microwave circuits. Available techniques for simulating the excitation of open planar microwave circuits are not very effective at relatively low frequencies. In this contribution new compensation functions are introduced which correctly model the excitation over the whole microwave frequency regio

Near-Field Microwave Microscopy of Materials Properties

Near-field microwave microscopy has created the opportunity for a new class of electrodynamics experiments of materials. Freed from the constraints of traditional microwave optics, experiments can be carried out at high spatial resolution over a broad frequency range. In addition, the measurements can be done quantitatively so that images of microwave materials properties can be created. We review the five major types of near-field microwave microscopes and discuss our own form of microscopy in detail. Quantitative images of microwave sheet resistance, dielectric constant, and dielectric tunability are presented and discussed. Future prospects for near-field measurements of microwave electrodynamic properties are also presented.Comment: 31 pages, 9 figures, lecture given at the 1999 NATO ASI on Microwave Superconductivity Changes suggested by editor, including full reference

Non-absorbing high-efficiency counter for itinerant microwave photons

Detecting an itinerant microwave photon with high efficiency is an outstanding problem in microwave photonics and its applications. We present a scheme to detect an itinerant microwave photon in a transmission line via the nonlinearity provided by a transmon in a driven microwave resonator. With a single transmon we achieve 84% distinguishability between zero and one microwave photons and 90% distinguishability with two cascaded transmons by performing continuous measurements on the output field of the resonator. We also show how the measurement diminishes coherence in the photon number basis thereby illustrating a fundamental principle of quantum measurement: the higher the measurement efficiency, the faster is the decoherence

Joining of thirty three percent by weight random glass fibre reinforced polystyrene using variable frequency microwave

[Abstract]: This paper extends the range of applications for Variable Frequency Microwave (VFM) (2 – 18 GHz) facilities to joining thirty three percent by weight glass fibre reinforced polystyrene composite [PS/GF (33%)]. With a given power level, the composite was exposed to various exposure times to microwave irradiation. The primer or coupling agent used was 5-minute two-part adhesive containing 100% liquid epoxy and 8% amine, i.e. Araldite, which was more readily microwave reactive than the composite itself. Bond strengths of the joints were lap shear tested and results were compared with those obtained using fixed frequency (2.45 GHz) microwave processing. The VFMF was operated under software control, which provided automatic data logging facilities. The maximum lap shear bond strength of joint was 430 N/cm2 using variable frequency microwave facility while that obtained by fixed frequency microwave configuration was only 331 N/cm2. The former is nearly 30% stronger than the latter