Search

This study presents a novel adjustable device designed for precise frequency tuning within the S-band of the microwave spectra. In addition to the geometrical design and dielectric behavior of the resonator, this study identifies an influential governing factor that affects the resonant frequency. The proposed method utilizes a bi-layer split ring resonator configuration implemented on a $4\times 4\,{\rm{cm}}$ FR4 epoxy substrate with a dielectric constant of 4.4. The substrate is coated with a 35 μ m- thick layer of copper and patterned as split ring resonator. Frequency tuning was achieved by spatially separating the two parallel split ring resonators in increments of 800 μ m. This innovative approach allows for a shift in the resonant frequency range from 2.36 GHz to 2.61 GHz, covering the desired frequencies in the S-band for applications such as biomedical and wireless communications. This study demonstrates that the alteration in the frequency domain is dependent on the distance between the two layers of split ring resonators. Compared to existing frequency tuning mechanisms, this adjustable bi-layer split ring resonator offers numerous advantages including simplicity, cost-effectiveness, and high sensitivity. The research employs a combination of finite-element simulations and theoretical analysis to validate the findings.

Additive modeling of low-resolution microwave spectra of heteroisomeric substituted hydrocarbons produced theoretical spectra of ethanethiol and propanethiol in the range 0-2 THz with maxima at 465 ± 20 and 240 ± 20 GHz. More precise calculations in a narrow frequency band of these ranges used spectral line half-widths of 1.5, 0.8, and 0.5 MHz that modeled conditions in different layers of Earth’s troposphere. The strongest extrema of the low-resolution spectra of the studied molecules were found at 486 ± 5, 446 ± 5, and 436 ± 5 (ethanethiol) and at 257 ± 5, 239 ± 5, and 234 ± 5 GHz (propanethiol). Various aspects of the application of the results were discussed. [ABSTRACT FROM AUTHOR]

Microwave‐based measurement can provide new methods and practical solutions for the challenging task of measurement inside large industrial combustion chambers. In order to measure or communicate inside a combustion chamber using microwaves, the spectrum of background noise at microwave frequencies must be known. This study investigates the basic electromagnetic spectrum in flames, concentrating on microwave frequencies from 0.1 to 19 GHz. The study introduces, as reference values, known results from forest flames and flames in controlled environments. The focus of the work is the level of background noise at microwave frequencies and the impact of this noise on radio communication inside the combustion chamber. The effects of the microwave radiation levels are compared with the requirements of practical communication systems such as Bluetooth and narrowband ISM (industrial, scientific, medical) systems at 800–950 MHz. [ABSTRACT FROM AUTHOR]

New measurements of microwave lines ( A and E ) of propene and its three 13 C 1 isotopologues have been made in the 10–22 GHz region with FT accuracy. The revised lines for propene along with many hundreds from the literature were fitted with the ERHAM program for internal rotors to give improved rotational constants. The new constants are A 0 = 46280.2904(16), B 0 = 9305.24260(30), and C 0 = 8134.22685(28) MHz. Lines for the 3- 13 C 1 species were observed in a pure sample; lines for the 1- 13 C 1 and 2- 13 C 1 species were observed in natural abundance. In fitting the limited sets of lines for the 13 C 1 species, many of the centrifugal distortion constants and most of the tunneling parameters were transferred from the fit of propene itself with 27 parameters. Improved rotational constants for the 13 C 1 species are reported. [ABSTRACT FROM AUTHOR]

Purpose: Gold nanoparticles (GNPs) are known to be effective mediators in microwave hyperthermia. Interaction with an electromagnetic field, large surface to volume ratio, and size quantization of nanoparticles (NPs) can lead to increased cell killing beyond pure heating effects. The purpose of this study is to explore the possibility of free radical generation by GNPs in aqueous media when they are exposed to a microwave field. Methods: A number of samples with 500 mM 5,5-dimethyl-1-pyrroline N-oxide (DMPO) in 20 ppm GNP colloidal suspensions were scanned with an electron paramagnetic resonance (EPR)/electron spin resonance spectrometer to generate and detect free radicals. A fixed (9.68 GHz) frequency microwave from the spectrometer has served for both generation and detection of radicals. EPR spectra obtained as first derivatives of intensity with the spectrometer were double integrated to get the free radical signal intensities. Power dependence of radical intensity was studied by applying various levels of microwave power (12.5, 49.7, and 125 mW) while keeping all other scan parameters the same. Free radical signal intensities from initial and final scans, acquired at the same power levels, were compared. Results: Hydroxyl radical (OH·) signal was found to be generated due to the exposure of GNP-DMPO colloidal samples to a microwave field. Intensity of OH· signal thus generated at 12.5 mW microwave power for 2.8 min was close to the intensity of OH· signal obtained from a water-DMPO sample exposed to 1.5 Gy ionizing radiation dose. For repeated scans, higher OH· intensities were observed in the final scan for higher power levels applied between the initial and the final scans. Final intensities were higher also for a shorter time interval between the initial and the final scans. Conclusions: Our results observed for the first time demonstrate that GNPs generate OH· radicals in aqueous media when they are exposed to a microwave field. If OH· radicals can be generated close to deoxyribonucleic acid of cells by proper localization of NPs, NP-aided microwave hyperthermia can yield cell killing via both elevated temperature and free radical generation. [ABSTRACT FROM AUTHOR]

The three lowest energy conformations of the title compound have been investigated using quantum chemical calculations and the lowest energy conformer has been observed using pure rotational spectroscopy. The lowest energy conformer possesses C 2 symmetry, a helical CF 2 backbone, with the hydrogens nearly eclipsing one another when looking down the long axis of the molecule. The technique of Fourier transform microwave spectroscopy in conjunction with quantum chemical calculations is demonstrated as a complimentary method to X-ray diffraction for structural determinations of small oligomers for which the location of hydrogen atoms may be important. [ABSTRACT FROM AUTHOR]