Microwave Radiation Research Articles

Multispectral smart window: Dynamic light modulation and electromagnetic microwave shielding

A novel multispectral smart window has been proposed, which features dynamic modulation of light transmittance and effective shielding against electromagnetic microwave radiation. This design integrates liquid crystal dynamic scattering and dye doping techniques, enabling the dual regulation of transmittance and scattering within a single-layer smart window. Additionally, the precise control of conductive film thickness ensures the attainment of robust microwave signal shielding. We present a theoretical model for ion movement in the presence of an alternating electric field, along with a novel approach to manipulate negative dielectric constant. The proposed model successfully enables a rapid transition between light transparent, absorbing and haze states, with an optimum drive frequency adjustable to approximately 300 Hz. Furthermore, the resistive design of the conductive layer effectively mitigates microwave radiation within the 2−18 GHz range. These findings offer an innovative perspective for future advancements in environmental construction.

Effect of Microwave Radiation on the Southern Cowpea Bettle <i>Callosobruchus maculatus</i> (F)

This study investigated the effect of microwave radiation at different power levels of 100, 300, and 600 w at different exposure durations of 60, 80, and 100 sec, against eggs, first-instar larvae, and adults of the southern cowpea beetle Callosobruchus maculatus (F). The results showed significant differences in mortality, and 600 w with exposure time of 100 sec being superior. There was 100% mortality of eggs, first-instar larvae and adult; the incubation period of the eggs increased with exposure. The germination of cowpea grains was not significantly affected.

Retrieval of snow and soil properties for forward radiative transfer modeling of airborne Ku-band SAR to estimate snow water equivalent: the Trail Valley Creek 2018/19 snow experiment

Abstract. Accurate snow information at high spatial and temporal resolution is needed to support climate services, water resource management, and environmental prediction services. However, snow remains the only element of the water cycle without a dedicated Earth observation mission. The snow scientific community has shown that Ku-band radar measurements provide quality snow information with its sensitivity to snow water equivalent and the wet/dry state of snow. With recent developments of tools like the snow micropenetrometer (SMP) to retrieve snow microstructure data in the field and radiative transfer models like the Snow Microwave Radiative Transfer (SMRT) model, it becomes possible to properly characterize the snow and how it translates into radar backscatter measurements. An experiment at Trail Valley Creek (TVC), Northwest Territories, Canada, was conducted during the winter of 2018/19 in order to characterize the impacts of varying snow geophysical properties on Ku-band radar backscatter at a 100 m scale. Airborne Ku-band data were acquired using the University of Massachusetts radar instrument. This study shows that it is possible to calibrate SMP data to retrieve statistical information on snow geophysical properties and properly characterize a representative snowpack at the experiment scale. The tundra snowpack measured during the campaign can be characterize by two layers corresponding to a rounded snow grain layer and a depth hoar layer. Using RADARSAT-2 and TerraSAR-X data, soil background roughness properties were retrieved (msssoil=0.010±0.002), and it was shown that a single value could be used for the entire domain. Microwave snow grain size polydispersity values of 0.74 and 1.11 for rounded and depth hoar snow grains, respectively, were retrieved. Using the geometrical optics surface backscatter model, the retrieved effective soil permittivity increased from C-band (εsoil=2.47) to X-band (εsoil=2.61) and to Ku-band (εsoil=2.77) for the TVC domain. Using the SMRT and the retrieved soil and snow parameterizations, an RMSE of 2.6 dB was obtained between the measured and simulated Ku-band backscatter values when using a global set of parameters for all measured sites. When using a distributed set of soil and snow parameters, the RMSE drops to 0.9 dB. This study thus shows that it is possible to link Ku-band radar backscatter measurements to snow conditions on the ground using a priori knowledge of the snow conditions to retrieve snow water equivalent (SWE) at the 100 m scale.

Rapid Preparation of Porous Graphene by Microwave‐Assisted Chemical Etching for Electrochemical Energy Storage

AbstractPorous graphene materials possess a larger specific surface area and a more abundant presence of active sites compared to non‐porous graphene materials, resulting in enhanced electrochemical properties. The presence of in‐plane nanopores facilitates the transmission of ions and mass, further expanding the potential applications of graphene materials in electrochemical energy storage and various other fields. In this study, a rapid synthesis of porous graphene was achieved through a microwave‐assisted chemical etching method. With the aid of microwave radiation, the etchant efficiently reduced the oxygen‐containing groups within the graphene structure, consequently generating nanopores with an approximate diameter of 10 nm. By optimizing the microwave treatment parameters, including pretreatment time, etching time, amount of etchant H2O2, and microwave power, the area percentage of nanopores in the graphene material was controlled to enhance its electrochemical properties. Porous graphene materials exhibited excellent specific capacitance and rate capability, making it a promising material for capacitor applications. Moreover, the lower internal resistance of porous graphene, compared to non‐porous graphene, demonstrated the significant role of nanopores in enhancing the electrochemical performance. These findings highlight the potential of porous graphene for use in electrochemical energy storage.

Effect of microwave radiation on adult neurogenesis and behavior of prenatally exposed rats

Postnatal neurogenesis appears to be highly sensitive to environmental factors, including microwave electromagnetic radiation (MWR). Here, we investigated the impact of MWR during intrauterine development on juvenile and adult neurogenesis in the rostral migratory stream (RMS) and the dentate gyrus of the hippocampus in the rat brain, as well as its effect on animal behavior. Female rats were exposed to MWR at a frequency of 2.45 GHz for 2 hours daily throughout pregnancy. The offspring of irradiated mothers survived to either juvenile age or adulthood. The brains of the rats were subjected to morphological analysis, assessing cell proliferation and death in both neurogenic regions. In the RMS, the differentiation of nitrergic neurons was also investigated. The effect of MWR on behavior was evaluated in rats surviving to adulthood. Prenatal MWR exposure caused significant changes in the number of proliferating and dying cells, depending on the age of the animals and the observed neurogenic region. In addition, MWR attenuated the maturation of nitrergic neurons in the RMS in both juvenile and adult rats. Morphological alterations in neurogenesis were accompanied by changes in animals’ behavior. Affected neurogenesis and changes in animal behavior suggest a high sensitivity of the developing brain to MWR.

The influence of thermal radiation during microwave-assisted freeze-drying of pharmaceutical unit doses

New drying technologies for biologicals have recently been developed to accelerate the time-consuming batch freeze-drying (BFD) process. Among others, microwave-assisted freeze-drying (MFD) has been suggested as a faster and more effective drying technology. In this study, MFD cycles with the microwave radiation switched on and off were performed to assess the contribution of the microwave radiation to drying acceleration. It was found that thermal radiation emitted by the drying chamber walls was predominantly accelerating the drying of monodose placebos rather than microwave radiation. The combination of ultra-low chamber pressure, high thermal heat transfer and a short primary-to-secondary phase transition reduces drying times by more than 80 % compared to conventional BFD. In a second step, a design of experiment approach was used to assess the effect of thermal radiation versus microwave radiation and their combination, together with dosage properties such as fill volume and excipient concentration upon drying rate. The outcome showed the importance of high fill volume and high excipient concentration for an effective microwave contribution to the drying rate. Nevertheless, the drying acceleration for small pharmaceutical dosages with restricted solutes was mainly driven by thermal radiation rather than 2.45 GHz microwave radiation. The inability of ice to convert microwave energy into heat hampers the potential use of microwave freeze-drying for single-dose vaccines.

Effect of Microwave Radiation on the Properties of Hydrogel, Cork, Perlite, and Ceramsite.

The present work analyzes the effect of releasing physically bound water from hydrogel, cork, perlite, and ceramsite on materials exposed to microwave radiation and subsequently investigates possible changes in the physical properties of these materials (water absorption and thermal conductivity coefficient). The release of physically bound water from individual materials has potential practical applications in materials engineering, for example, in the internal curing of concrete, where individual aggregates could, under the influence of microwave radiation, release water into the structure of the concrete and thus further cure it. Experimental analysis was carried out with samples of the above-mentioned materials, which were first weighed and then immersed in water for 24 h. Then, they were weighed again and exposed to microwave radiation. After exposure, the samples were weighed again, left immersed in water for 24 h, and weighed again. The focus of the study was on the ability of the aggregates to release water due to microwave radiation and on the changes in the properties (water absorption, thermal conductivity coefficient) of these materials when exposed to microwave radiation. The samples were further monitored by digital microscopy for possible changes in the surface layer of the materials. The hydrogels show the highest water absorption (1000%) and the fastest water release (45 min to complete desiccation). After the release of water due to microwave radiation, their ability to absorb water is maintained. Of interest, however, is that in the case of almost complete removal of water from the soaked hydrogel, the original powdered state of the hydrogel is not obtained, but the outcome has rather a solid structure. In the case of cork, the water absorption depends on the fraction of the material.

Lens Fragmentation with Picosecond Laser Pulses After Artificial Cataract Induction with Microwaves.

Objectives: In this work we demonstrate the first laboratory study results of lens fragmentation with low-energy picosecond ultrashort laser pulses after artificial induction of cataract with microwave radiation on an ex vivo animal model. Background: This method will be evaluated with regard to the further development of lens fragmentation with novel ultrashort picosecond laser systems instead of ultrasonic phacoemulsification or the significantly more complex femtosecond laser fragmentation. Methods: As samples we used postmortem porcine eyes. The lenses were dissected and then irradiated in a microwave oven for artificial cataract induction. Subsequent computer-driven lens fragmentation was performed with a 12 ps, 1064 nm pulsed laser source with 100 µJ pulse energy, and 10 kHz pulse repetition rate. Results: Both the artificial cataract induction and the lens fragmentation were demonstrated. When inducing cataract, different degrees/stages of opaqueness and hardness could be achieved with different irradiation times and methods. The fragmentation with 12 ps pulses led to good results with regard to ablation depth and rate, especially for the softer lenses. Conclusions: As could be shown, low-energy picosecond ultrashort laser pulses are feasible for cataractous lens fragmentation on an ex vivo animal model with artificial cataract induction. Thus, this technique may influence future cataract surgeries by possibly being an alternative or extension to state-of-the-art methods. This will be evaluated with further tests and studies.

Biodiesel produced from waste cooking oil by microwave transesterification using inert aluminium foil (1%) as a heating promoter

The manufacture of biodiesel from waste cooking oil, using cost-effective and environmentally friendly processes, continues to attract attention. Microwave radiation (MW), which is easy to use and is not demanding on power supplies, can promote rapid chemical reactions; however, our understanding of the MW absorption that occurs with the oscillation of polar reactants is far from complete. To increase the interaction of MW with reactant, our approach used a MW reactor in conjunction with a transesterification process. A small amount of aluminium foil, which remains chemically inert in the reaction, was used as a MW heating promoter to accelerate transesterification without generating sparks in a process employing 700W MW irradiation at room temperature. The temperature of the MW reactor was measured by thermal image analysis, while thermogravimetric analysis (TA) and gas chromatography/mass spectroscopy were used to characterize the components and boiling points and of soybean oil and its fatty acid components. The optimal size of the aluminium foil to use was determined by studying the transesterification of soybean oil with catalytic NaOH in a closed glass bottle. The results indicated that the reaction time to give a conversion of 82% was shortened by approximately 60% by adding 1 wt% aluminium foil (3 × 3 mm2).

Capric-lauric & capric-palmitic/modified bentonite composite as phase change materials for thermal energy storage

This paper proposes a new double layer structure shape-stabilized thermal energy storage wallboard (TESW), by employing microwave radiation modified bentonite (Bm) to stabilize capric acid-lauric acid (CA-LA) and capric acid-palmitic acid (CA-PA) as major components of internal and external wallboard. Leakage test showed that CA-LA/Bm and CA-PA/Bm had good morphological stability. The chemical compatibility, phase change behaviors, and microstructure of CA-LA/Bm and CA-PA/Bm were analyzed. The maximal loading capacities of CA-LA/Bm and CA-PA/Bm can be reached 45 % and 50 %, respectively. In addition, the mechanical and thermal performance of CA-LA/Bm and CA-PA/Bm-based thermal energy storage concrete (CL&CP/Bm-TESC) was systematically studied. The Digital Image Correlation (DIC) technology was used to collect and analyze the speckle images of CL&CP/Bm-TESC20 before and after 100 cycles of phase change, determining the evolution of principal strains during the deformation and failure processes. It is worth noting that the numerical simulation results of the designed double layer structure shape-stabilized CA-LA&CA-PA/Bm-based thermal energy storage wallboard (CL&CP/Bm-TESW) show better temperature adjusting performance. These results demonstrate that the prepared composite of CA-LA/Bm and CA-PA/Bm has potential application in the field of thermal energy storage.

Seed Disinfection Treatments Minimized Microbial Load and Enhanced Nutritional Properties of Fenugreek Sprouts Which Alleviated Diabetes-Negative Disorders in Diabetic Rats.

Sprouts are an attractive food product that contains high amounts of nutritional substances and has pro-health features. Sprout consumption has strongly increased despite its potential risk to health due to its microbial load. Both the safety and shelf life of sprouts may be negatively affected by a high microbial load. To reduce the microbial contamination in sprouts before consumption, the initial microbial load on the seeds needs to be controlled. Many herbal sprouts have been recommended for diabetes, and fenugreek is one of these sprouts. Thus, the current experiment aimed at disinfecting fenugreek seeds using microwave (5, 10, and 20 s) and hot water (30, 45, and 60 s) treatments for different durations. The best-disinfected sprouts with the highest nutritional properties were used to evaluate their influence on streptozocin-induced diabetic rats in comparison with fenugreek seed feeding. Microwave treatments showed the highest sprout length, fresh weight, total free amino acids, antioxidants, reducing sugars, and total phenols. Additionally, microwave seed treatments showed the lowest bacteria and mold counts on sprouts produced relative to hot water treatments, and the best seed treatment was a microwave for 20 s, which gave the best values in this respect. Feeding diabetic rats with different fenugreek seeds or sprout rates (0, 5, 7.5, and 10% w/w) improved body weight, restricted the growth of glucose levels, lowered total cholesterol and triglycerides, and improved HDL compared with the positive control group, and fenugreek sprouts at higher rates showed the maximum improvements in blood glucose, total cholesterol, and triglycerides. Treating fenugreek seed with microwave radiation for 20 s to disinfect the seeds before sprouting is recommended for lowering the microbial load with optimum nutritional and antioxidant activity, and feeding diabetic rats with these sprouts at the rate of 7.5 and 10% had promising effects on hyperglycemia and associated disorders.

No observable non-thermal effect of microwave radiation on the growth of microtubules

Despite widespread public interest in the health impact of exposure to microwave radiation, studies of the influence of microwave radiation on biological samples are often inconclusive or contradictory. Here we examine the influence of microwave radiation of frequencies 3.5 GHz, 20 GHz and 29 GHz on the growth of microtubules, which are biological nanotubes that perform diverse functions in eukaryotic cells. Since microtubules are highly polar and can extend several micrometres in length, they are predicted to be sensitive to non-ionizing radiation. Moreover, it has been speculated that tubulin dimers within microtubules might rapidly toggle between different conformations, potentially participating in computational or other cooperative processes. Our data show that exposure to microwave radiation yields a microtubule growth curve that is distorted relative to control studies utilizing a homogeneous temperature jump. However, this apparent effect of non-ionizing radiation is reproduced by control experiments using an infrared laser or hot air to heat the sample and thereby mimic the thermal history of samples exposed to microwaves. As such, no non-thermal effects of microwave radiation on microtubule growth can be assigned. Our results highlight the need for appropriate control experiments in biophysical studies that may impact on the sphere of public interest.

Influence of foaming additives on the porous structure and properties of lightweight geopolymers based on ash–slag waste

Lightweight geopolymer is a promising thermal insulation material that conserves energy used for heating and cooling buildings. This study investigates foaming agents that influence the porous structure and properties of geopolymer foams based on ash–slag waste from thermal power plant using a 12 M sodium hydroxide solution, waterglass, and foaming agents (30 % hydrogen peroxide solution, aluminum, silicon, and zinc powders). The study demonstrates the feasibility of foaming geopolymers by water evaporation without foaming additives, where the best density of 949 kg/m3 and compressive strength of 4.2 MPa were achieved in samples foamed by microwave radiation, but such properties cannot attribute geopolymers as lightweight. Foaming with H2O2 is hard to synchronize with geopolymerization reactions. Aluminum and silicon powders lead to rapid reactions in alkaline conditions, resulting in uneven pore sizes. Zinc powder was the most effective foaming agent, producing materials with a density of 331 kg/m3 and compressive strength of 1.17 MPa, and it also integrates into the geopolymer gel structure. The foaming process should occur at room temperature. Elevated temperatures increase curing rates and result in incomplete geopolymerization, preventing uniform pore formation. Synthesized geopolymers are suitable for building insulation, basements, underground pipelines, and utility networks.

Cross-calibration between MWRI and AMSR2 to improve consistency of snow depth products

The Microwave Radiation Imager (MWRI), boarded on the FY-3 series satellites: FY-3B, FY-3C, and FY-3D, is the first satellite-based microwave radiometer in China, commencing passive microwave brightness temperature data acquisition since 2010. The Advanced Microwave Scanning Radiometer 2 (AMSR2) boarded on the Global Change Observation Mission 1st-Water (GCOM-W1), has been operational since 2012. Despite the FY-3 series satellites are equipped with the same MWRI and all MWRIs sharing comparable parameters and configurations as AMSR2, disparities in observation times and satellite platforms result in inconsistencies in the data obtained by different satellites, which further impacting the consistency of retrieved geophysical parameters. To improve the consistency of brightness temperatures from FY-3B, FY-3C, FY-3D/MWRI, and GCOM-W1/AMSR2, cross-calibrations were conducted among brightness temperatures at ten-channel from above four platforms. The consistency of derived snow depth from MWRIs and AMSR2 in China before and after the calibration were also analyzed. The results show that the correlation coefficients of brightness temperatures at all channels between sensors exceed 0.98. After cross-calibration, the RMSEs and biases of brightness temperatures at all frequencies and snow depth in China derived from them reduce to varying degrees. The consistencies in both brightness temperatures and snow depth of FY-3B/MWRI, FY-3D/MWRI, and AMSR2 are higher than those of FY-3C and others. These findings advocate for the utilization of cross-calibrated brightness temperatures from FY-3B/MWRI, FY-3D/MWRI, and AMSR2, which share similar satellite overpass time, to derived a long-term snow depth dataset.

Quasi-Force-Free Magnets of Small Volume for Generators of Short-Wave Microwave Radiation

Quasi-Force-Free Magnets of Small Volume for Generators of Short-Wave Microwave Radiation

Physicochemical and Microbial Properties of Miracle Berry (Synsepalum dulcificum) Kombucha Tea Treated with Microwave Radiation

Physicochemical and Microbial Properties of Miracle Berry (Synsepalum dulcificum) Kombucha Tea Treated with Microwave Radiation

Microwave radiation of space and prospects for its use in quantum propulsors

Using the original approach developed in recent years – supramolecular physics of the environment, the results of considering the contribution of physical optics processes to the formation of induced microwave radiation are presented.The two most powerful cosmic thermal sources: the background (relict) flux in the absolute millimeter maximum of the spectrum, and the mm-wave radio flux from Sun are considered. The postulate of A. Einstein about the emergence of an induced emission quantum in a medium with established thermal equilibrium is taken into account. This made it possible to quantitatively substantiate, based on the principles of the similarity theory of G.S. Golitsyn, a scheme for the use of microwave energy of the interstellar/interplanetary medium during space flights. Based on the physics of collisions, in the proton transfer reaction of the main simple hydrides in interstellar/interplanetary molecular clouds, it is proposed to take into account the possibility of the manifestation of an additional channel for the maser effect in such a medium (first considered by V.A. Ambartsumian in 1979) due to the close location of electronically excited Rydberg levels for molecules in these clouds. The pioneering work of N.S. Kardashev on the study of Rydberg transitions during the emission of recombination radio lines was taken into account. Due to the efforts of astronomers from the Lebedev Physical Institute and the State Astronomical Observatory of the Russian Academy of Sciences (at Pulkovo), this work led to the discovery of the microwave flux from deep space objects. Real energy and schemes for using a microwave quantum propulsor device with the ability to choose the direction of flights are discussed.

Fe/Ni bimetallic magnetic nano-alloy (INBMNA): An efficient heterogeneous catalyst for photo-Fenton-like degradation of phenol in aqueous environment

A lot of attention has been drawn to photo-Fenton-like catalysis among advanced oxidation processes for environmental remediation applications. Herein, we have successfully fabricated iron-nickel bimetallic magnetic nano-alloy (INBMNA) as an efficient heterogeneous photo-Fenton-like catalyst using the chemical reduction method and characterized by several analytical techniques. The characterization results show that the catalyst has a spherical shape with a mesoporous nature and contains a large specific surface area. The impact of various parameters was investigated and optimized to check the catalytic performance of INBMNAs and the found results showed that excellent photo-Fenton-like activity persisted under 6.0 pH conditions for the degradation of hazardous pollutant (phenol) under solar light exposure and microwave radiation power, respectively. Additionally, the exposed INBMNA/H2O2 system provided continuous redox cycles of Fe3+/Fe2+ and Ni2+/Ni0 pair in the Fenton-active species for stable operation. The photo-Fenton-like activity was also performed to check the effect of different inorganic anions which significantly hinder phenol reduction. Besides, the steady performance of the catalyst to remove phenol was performed in tap water and river water. Free radical trapping experiments were tested to know the role of important radicals in the photo-Fenton process. Moreover, the mechanism and possible degradation pathways of phenol were checked. By cyclic degradation experiments, the performance of the catalyst is stable and almost unchanged and can be reused several times. This study provides a promising INBMNA/H2O2 system, which encourages its widespread use in environmental remediation applications.

One-step high-efficiency microwave synthesis of N-doped bamboo biochar for tetracycline degradation

N-doped bamboo biochar (NBB) was successfully synthesized through one-step, rapid pyrolysis (e.g., 10 min) using urea and urea nitrate impregnated bamboo particles exposed to low power (e.g., 460 W) microwave radiation. NBB-460 exhibited high specific surface area of 876.1 m2/g and outstanding catalytic performance for tetracycline hydrochloride (TCH) degradation. The TCH degradation efficiency reached to 94.3 % with the optimized catalytic condition (i.e., 0.2 g/L NBB-460, 3 mM PMS, 50 mg/L TCH, 25 ℃, without pH regulation). The density functional theory calculation showed that the graphitic nitrogen and pyridinic nitrogen of NBB-460 served as active sites for peroxymonosulfate activation and TCH degradation. The quenching test, electron paramagnetic resonance spectra, and electrochemical measurements indicated that tetracycline hydrochloride underwent degradation via radical (O2•−), non-radical (1O2) pathways, and surface electron transfer. This study introduces an energy-efficient and time-effective method for converting biomass to N-doped biochar as highly efficient peroxymonosulfate activator for environmental applications.

Dark matter and its candidate particles

Theoretically predicted unseen matter called dark matter may be present in the universe. Even though it might be the primary component of cosmic matter, it is not a part of any known material that makes up a visible celestial body. Despite the fact that dark matter has not yet been directly observed, there is a wealth of evidence to support its existence, for example, through the autobiographical curve of the Milky Way, the mass distribution of galaxy clusters, the background radiation of the universe microwaves, and the formation of large-scale structures of the universe. Although great progress has been made in cosmic observation, we are still unable to determine what the constituent particles of dark matter are.There are the following speculations about what particles dark matter is composed of: baryon dark matter, such as MACHOs, rogue planets, and other possibilities; Non-baryonic dark matter: Weakly Interacting Massive Particles (WIMPs); Axion; Neutrino, etc.