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The dielectric properties of a material determine its response of the material to the Electromagnetic field (EM field). It comprises dielectric constant (${\epsilon }^{\prime }$), which is the ability to store energy of EM fields, and dielectric loss (${\epsilon }^{\prime \prime }$) which is the amount of dissipated Electromagnetic energy in the form of heat. Dielectric properties are affected by various factors such as frequency, temperature, bulk density, moisture content, etc. Dielectric constant and dielectric loss were determined in this study for milk powders viz. Whole Milk Powder, Skim Milk Powder, and Infant Milk Powder at various microwave frequencies (5.68, 7.45, 10.25GHz). The method used to determine dielectric properties is the Two-point Method which is implemented on a microwave bench. It became apparent that when frequency increases dielectric constant decreases and dielectric loss first decreases and then increases. It was also observed that the fat content can have an impact on the milk powders’ dielectric properties.

To facilitate future pasteurization experiments utilizing microwave energy, the dielectric properties of five dried fruits — almond (Prunus dulcis), cashew nut (Anacardium occidentale), pistachio (Pistacia vera), peanut (Arachis hypogea L.) and walnut (Juglans regia) were investigated at room temperature (28^∘C). Samples were taken in powder form to investigate the effect of increased surface-to-volume ratio on their dielectric properties, as applicable in the case of nanomaterials. The measurements were conducted at four different frequencies (3.30, 7.50, 9.30and 14.70GHz) in the microwave spectrum by using the two-point method and a MATLAB program was used for solving the transcendental equation to obtain values of dielectric constant and loss factor. The findings revealed a decreasing trend in the values of dielectric constant of the five dried fruits as the frequency increased. However, no consistent trend was observed for the dielectric loss factor of the fruits with increasing frequency. Further, the penetration depth of electromagnetic waves in all the five dry fruit samples was observed to decrease as the frequency increased. On comparing results for dielectric parameters of dry fruits in powder form with those of whole fruit kernels, no definite trends are observed for ${\epsilon }^{\prime }$ and ${\epsilon }^{″}$, but the penetration depth is found to decrease when the sample is taken in powder form.

Dielectric constant (${\epsilon }^{\prime }$) and dielectric loss factor (${\epsilon }^{\prime \prime }$) of gluten-free grains viz., Finger millet, Amaranth and Buckwheat in powder form were measured at room temperature (22^∘C) at frequency 9.76GHz for different moisture content samples. The method used was the Two-Point method which is based on the transmission line technique. Microwaves were employed to investigate dielectric properties and their moisture dependence. The results showed that dielectric constant and dielectric loss of Gluten-free grains increase with the increase in moisture content. It shows that for higher moisture there are more free molecules in comparison to bound water molecules. This work can be an effective guide in designing a moisture meter for gluten-free grains.

A high mobility two-dimensional electron system exhibits large changes in the resistance, and zero-resistance states, under microwave and Terahertz excitation. We describe associated experimental results and the possibility of using this system as a radiation detector.

One of the key factors of space weather is solar flare activity, the monitoring and prediction of which is an important task of specialized dedicated groups of space experts and solar astronomers. Solar flare forecasts are based on identifying and detecting the so-called precursors, specific processes in solar activity events that occur before flares. Collecting data for space weather analysis and prediction comes down to several types of measurements performed by more than a dozen spacecraft. Ground-based observations and monitoring nowadays are becoming more or less complimentary. One of the reasons for this is the limitation of observation time with ground-based telescopes due to adverse Earth weather conditions. However, solar radio astronomy is immune to almost any weather activity, and the main question here is what new quality it can bring. Observational data accumulated in the 20th century show that solar radio bursts can be associated with flare activity. In addition, the existing network of solar radio telescopes is already well established. As an example, in this paper, we describe the possibilities of a fully steerable 32-meter radio telescope of Ventspils International Radio Astronomy Centre (VIRAC), Latvia, which can be useful for searching for new precursors of solar flares.

We report a detailed simulation of a bunched electron-beam accelerated in a TE${}_{113}$ cylindrical cavity immersed in a static inhomogeneous magnetic field using a relativistic full electromagnetic particle-in-cell (PIC). This type of acceleration concept is known as Spatial AutoResonance Acceleration (SARA) in which the magnetic field profile is such that it keeps the electron-beam in the acceleration regime along their trajectories. In this work, the numerical experiments are carried out including a bunched electron-beam with the concentrations in the range $10^8$–$10^9$cm${}^{-3}$ in a TE${}_{113}$ cylindrical microwave field, at a frequency of 2.45 GHz and an amplitude of 15 kV/cm. The electron energy reaches values up to 250 keV without significant unfocusing effect that can be used as a basis to produce hard X-ray. Additionally, a comparison between the data obtained from the full electromagnetic PIC simulations and the results derived from the relativistic Newton–Lorentz equation in a single particle approximation is carried out.

The microwave-excited high mobility two-dimensional electron system exhibits, at liquid helium temperatures, vanishing resistance in the vicinity of B=[4/(4j+1)]B_f, where B_f=2πfm*/e, m* is an effective mass, e is the charge, and f is the microwave frequency. Here, we summarize some experimental results.

The phenomenon of Euclidean resonance (a strong enhancement of quantum tunneling through a nonstationary potential barrier) is applied to disintegration of atoms and molecules through tunnel barriers formed by applied constant and time-dependent electric fields. There are two different channels for such disintegration, electronic and ionic. The electronic mechanism is associated with the ionization of a molecule into an electron and a positive ion. The required frequencies are in a wide range between 100 MHZ and infrared. This mechanism may constitute a method of selective destruction of chemical bonds. The ionic mechanism consists of dissociation of a molecule into two ions. Since an ion is more massive than an electron, the necessary frequency is about 1 MHZ. This provides a theoretical possibility of a different method of isotope separation by radio frequency waves. The small sub-barrier tunneling probability of nuclear processes can be dramatically enhanced by collision with incident charged particles. Semiclassical methods of theory of complex trajectories have been applied to nuclear tunneling, and conditions for the effect have been obtained. The enhancement of α particle decay by incident proton with energy of about 0.25 MeV has been demonstrated. The general features of this process are common for other sub-barrier nuclear processes and can be applied to nuclear fission.

Microwave (MW) absorption by a high mobility 2DEG has been investigated experimentally using sensitive Electron Paramagnetic Resonance (EPR) cavity technique. It is found that MW absorption spectra are chiefly governed by confined magnetoplasmon excitations in a 2DEG stripe. Spectra of the 2D magnetoplasmons are studied as a function of magnetic field, MW frequency and carrier density. The electron concentration is tuned by illumination and monitored using optical photoluminescence technique.

Ultra-low refractive index irradiative structure is considered. The structure consists of a patch antenna with the metamaterial slab located on top of the antenna, as superstrate. In this study, ultra-low index phenomenon of the irradiative system is associated with improving the directivity of the patch antenna by putting the metamaterial slab on top of the antenna. The last phenomenon, in turn, is associated with the feedback partial magnetization of Iron inclusions of the slab caused by the radiation from the antenna. Mathematical model for evaluating the complex effective relative permittivity of the irradiative structure is developed. Numerical calculations for complex effective relative permittivity of the irradiative structure and real part of the complex effective relative permeability of the metamaterial slab are done in the study.

This paper presents major medical applications of microwave radiation in therapy and diagnostics of disorders of thermoregulation, especially hyperthermia and thermography. Microwave thermography is a thermal imaging system produced by self-emission, using emissivity differences to extend our vision beyond the shortwave red. Human tissues are partially transparent to microwaves, thus it is possible to detect the microwave of subcutaneous tissues in thermography, and to allow microwave energy penetration through subcutaneous tissues for deep-tissue heating in hyperthermia. The physics of microwave thermography together with the microwave properties and emission of body tissues are introduced. It is followed by reviews of the literature pertinent to microwave hyperthermia in therapy and treatment. Recent development in this field is briefly discussed.

We performed experiments in which both open-ended and closed carbon nanotubes were exposed to 2.46 GHz microwaves over the course of several irradiation and cooling cycles at a pressure of ~ 10^-6 torr. The spectra of the radiation emitted from the nanotubes indicate that the intensity of the emitted radiation with wavelengths of 650–1000 nm increased during the irradiation cycles. However, the intensity of the radiation emitted from untreated nanotubes increased substantially more than the intensity of the radiation emitted from nanotubes that had been chemically treated in order to open nanotube ends. As open-ended nanotubes have a lower work function than closed nanotubes, and as nanotube ends are known to open as they are heated, our results suggest that the mechanism responsible for the emission of infrared, visible and ultraviolet radiation from carbon nanotubes exposed to microwaves is field emission-induced luminescence.

A mild method for O-alkylation of meso-hydroxyphenylporphyrin has been developed using microwave irradiation. This method is clean and efficient for many substrates and results in significant improvement in reaction yield and in a dramatic decrease in reaction time in comparison to thermal heating.

Graphene platelets with a large scale have been synthesized by reduction of graphene oxide (GO) in aqueous solution of hydrazine hydrate under microwave irradiation (MWI). Microstructure of the graphene was characterized by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and transmission electron microscopy (TEM) together with the selected area electron diffraction (SAED). The electrochemical properties were evaluated by the analysis of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 1 M Na₂SO₄ aqueous solution. The results show that the as-prepared materials consist of crumpled, few-layer (~ 3 nm) thick and electronically conductive graphitic sheets. The supercapacitors fabricated using this material possess a low equivalent series resistance (ESR) value ~ 1.6Ω and a high specific capacitance of 285 F ⋅ g^-1. In addition, the graphene reduced under a diverse duration of MWI displays a different interlayer spacing, extent of reduction, level of graphitization and specific capacitances. The duration of MWI and the treatment methods strongly affect the microstructure of graphene, and then dominate its electrochemical properties.

For the radio frequency-based catalyst state monitoring of SCR catalysts, the dielectric properties of the used SCR catalyst materials are essential to design the measurement system and to adjust it to the given conditions. This work focuses on the experimental determination of the effective complex dielectric properties of zeolite coatings on cordierite substrates and the approximation of the latter to describe and transfer these systems in an easier manner. Therefore, different influences were investigated to approximate the real and the imaginary part of the complex permittivity of zeolite coatings on cordierite substrates.

The microwave-excited high mobility two-dimensional electron system exhibits, at liquid helium temperatures, vanishing resistance in the vicinity of B = [4/(4j + 1)]B_f, where B_f = 2πfm*/e, m* is an effective mass, e is the charge, and f is the microwave frequency. Here, we summarize some experimental results.

A high mobility two-dimensional electron system exhibits large changes in the resistance, and zero-resistance states, under microwave and Terahertz excitation. We describe associated experimental results and the possibility of using this system as a radiation detector.

We describe measurements on a silicon single electron transistor (SET) carried out using a custom cryogenic CMOS measurement circuit (LTCMOS) in close proximity to the device. Quantum mechanical states in the SET were mapped by continuous microwave spectroscopy. The real time evolution of a particularly long lived quantum mechanical state was observed in a single shot measurement, made possible by the much faster measurement rate (50kHz bandwidth). This technique is intended to be applied to the measurement of coherent states in a charge qubit device made of a silicon double dot.