High-frequency Microwave Radiation Research Articles

Metformin Ameliorates 2.856 GHz Microwave- Radiation-Induced Reproductive Impairments in Male Rats via Inhibition of Oxidative Stress and Apoptosis.

The reproductive system has been increasingly implicated as a sensitive target of microwave radiation. Oxidative stress plays a critical role in microwave radiation -induced reproductive damage, though precise mechanisms are obscure. Metformin, a widely used antidiabetic drug, has emerged as an efficient antioxidant against a variety of oxidative injuries. In the present study, we hypothesized that metformin can function as an antioxidant and protect the reproductive system from microwave radiation. To test this hypothesis, rats were exposed to 2.856 GHz microwave radiation for 6 weeks to simulate real-life exposure to high-frequency microwave radiation. Our results showed that exposure to 2.856 GHz microwave radiation elicited serum hormone disorder, decreased sperm motility, and depleted sperm energy, and it induced abnormalities of testicular structure as well as mitochondrial impairment. Metformin was found to effectively protect the reproductive system against structural and functional impairments caused by microwave radiation. In particular, metformin can ameliorate microwave-radiation-induced oxidative injury and mitigate apoptosis in the testis, as determined by glutathione/-oxidized glutathione (GSH/GSSG), lipid peroxidation, and protein expression of heme oxygenase-1 (HO-1). These findings demonstrated that exposure to 2.856 GHz microwave radiation induces obvious structural and functional impairments of the male reproductive system, and suggested that metformin can function as a promising antioxidant to inhibit microwave-radiation-induced harmful effects by inhibiting oxidative stress and apoptosis.

THz Radiation From a TM₅₁ Mode Sheet Beam Extended Interaction Oscillator With Low Injection

This article designs and studies a low-injection sheet beam extended interaction oscillator (EIO) circuit that uses TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">51</sub> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\pi $ </tex-math></inline-formula> mode operation. Through the combination of theoretical analysis and particle-in-cell (PIC) simulation, the mode characteristics and output characteristics of the circuit are studied. Theory and dispersion analyses on the designed EIO demonstrated that the special circuit structure and the optimized cutoff frequency effectively suppress nonoperating lower order modes. Only TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">51</sub> - <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2\pi $ </tex-math></inline-formula> mode can support effective beam–wave interaction in the designed EIO, which has a benefit of increasing the frequency and size of miniaturized devices. The designed EIO can achieve high-frequency microwave radiation output with higher energy under low injection (low current density and low voltage). At a certain surface loss, when an electron beam with 1 A and 19.6 kV is injected, the 0.36-terahertz (THz) radiation power of 200 W is achieved. The slow wave structure has been presented. The designed circuit structure can be applied to high-frequency THz radiation source devices.

Exchange explosions of topological edge defects in a square micromagnet

The magnetodynamic properties of a square thin-film micromagnet ($2\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}\ifmmode\times\else\texttimes\fi{}2\phantom{\rule{4pt}{0ex}}\ensuremath{\mu}\mathrm{m}\ifmmode\times\else\texttimes\fi{}16\phantom{\rule{4pt}{0ex}}\mathrm{nm}$) with a flux-closure magnetic ground state were investigated by micromagnetic simulations. The system was excited with an applied magnetic field, displacing the vortex core sufficiently far from its equilibrium position to result in a nonlinear relaxation upon removal of the field. We find that creation of edge topological defects leads to exchange explosions and periodic emission of short-wavelength spin waves emanating from these defects. The exchange explosions of the edge topological defects are investigated and explained in terms of vortex/antivortex creation and the formation of a Bloch point. This finding could prove useful to the development of nanoscale devices for periodic generation of high-frequency microwave radiation.

Functioning of male reproductive system under exposure to high-frequency microwave radiation

Functioning of male reproductive system under exposure to high-frequency microwave radiation

Effect of High-frequency Microwave Radiation on the Mechanical Properties of Plantain (Musa paradisiaca) Fibre/Epoxy Biocomposite

Effect of High-frequency Microwave Radiation on the Mechanical Properties of Plantain (Musa paradisiaca) Fibre/Epoxy Biocomposite

Frequency dispersion of nonlinear response of thin superconducting films in the Berezinskii-Kosterlitz-Thouless state

The effects of microwave radiation on the transport properties of atomically thin $La_{2-x}Sr_xCuO_4$ films were studied in the 0.1-13 GHz frequency range. Resistance changes induced by microwaves were investigated at different temperatures near the superconducting transition. The nonlinear response decreases by several orders of magnitude within a few GHz of a cutoff frequency $\nu_{cut} \approx$ 2 GHz. Numerical simulations that assume an ac response to follow the dc V-I characteristics of the films reproduce well the low frequency behavior, but fail above $\nu_{cut}$. The results indicate that two-dimensional superconductivity is resilient against high-frequency microwave radiation, because vortex-antivortex dissociation is dramatically suppressed in two-dimensional superconducting condensates oscillating at high frequencies.

Hall field-induced resistance oscillations in ap-type Ge/SiGe quantum well

We report on a magnetotransport study in a high-mobility 2D hole gas hosted in a pure Ge/SiGe quantum well subject to dc electric fields and high frequency microwave radiation. We find that under applied dc bias the differential resistivity exhibits a pronounced maximum at a magnetic field which increases linearly with the applied current. We associate this maximum with the fundamental peak of Hall field-induced resistance oscillations (HIRO) which are known to occur in 2D electron gases in GaAs/AlGaAs systems. After taking into account the Dingle factor correction, we find that the position of the HIRO peak is well described by the hole effective mass $m^\star \approx 0.09\,m_0$, obtained from microwave photoresistance in the same sample.

High-frequency nonreciprocal reflection from magnetic films with overlayers

We perform a theoretical study of the nonreciprocal reflection of high-frequency microwave radiation from ferromagnetic films with thin overlayers. Reflection from metallic ferromagnetic films is always near unity and shows no nonreciprocity. In contrast, reflection from a structure which has a dielectric overlayer on top of a film composed of insulated ferromagnetic nanoparticles or nanostructures can show significant nonreciprocity in the 75–80 GHz frequency range, a very high value. This can be important for devices such as isolators or circulators.

High-Power Millimeter-Wave BWO Driven by Sheet Electron Beam

The sheet beam vacuum electron device is an attractive choice for generating high-power high-frequency microwave radiation. A millimeter-wave sheet beam backward wave oscillator (BWO) is presented in this paper. The rectangular waveguide grating structure is used as its slow wave structure. The BWO is driven by a sheet beam with a cross-sectional area of 30 mm × 1 mm which is generated by a thin cathode. For a beam voltage of 167 kV and a beam current of 1.4 kA, the output power is 40 MW at 36.6 GHz. The beam-wave interaction efficiency is about 17%, which is higher than that of conventional hollow beam BWO. It is clear from the results presented in this paper that the sheet beam device is promising for producing high-efficiency high-power millimeter-wave radiation.

Development of a Microwave Treatment Technique for Bacterial Decontamination of Raw Meat

The present study developed and verified a 'cold' microwave (MW) treatment that could lead to the inactivation of two common pathogenic species of bacteria, Escherichia coli and Staphylococcus aureus, in raw meats. A number of experimental conditions were designed and tested to maximise MW exposure without overheating the samples. The non-thermal effect was maximised by multiple exposure to attain efficient MW threshold intensities. It was shown that at sub-lethal temperatures repeated exposure using high frequency MW radiation was significantly more effective in decontaminating bacteria in raw meats compared to a single exposure. It was concluded that non thermal inactivation of pathogenic bacteria in raw meats could be achieved at defined conditions using high frequency MW radiation.

Electron Cyclotron Heating Experiments in Tokamaks and Stellarators

This paper reviews the application of high-frequency microwave radiation to plasma heating near the electron cyclotron frequency in tokamaks and stellarators. Successful plasma heating by microwave power has been demonstrated in numerous experiments. Predicted future technological developments and current theoretical understanding suggest that a vigorous program in plasma heating will continue to yield promising results.

Some characteristics of a rapidly rotating magnetized neutron star

The recently discovered1,2 1.5-ms pulsed radio source PSR1937+214 could be close to the onset of rotational instabilities if it is envisaged to be a rotating neutron star which gives interesting lower limits for neutron star masses. We examine here the implications of polar gap models for such a rapidly rotating magnetic neutron star. It appears, on the basis of such models, that a higher fraction of high-frequency microwave radiation compared with the Crab pulsar is an expected result. On the other hand, the outer gap discharge models invoked for longer period pulsars yield a large amount of high-energy radiation which is not observed. The high-energy cutoff in the γ-ray region evaluated from assumed values of the magnetic field inside the light cylinder will be around 1,000 GeV.