Single-mode Microwave Research Articles

DNA Gene’s Basic Structure as a Nonperturbative Circuit Quantum Electrodynamics: Is RNA Polymerase II the Quantum Bus of Transcription?

Previously, we described that Adenine, Thymine, Cytosine, and Guanine nucleobases were superconductors in a quantum superposition of phases on each side of the central hydrogen bond acting as a Josephson Junction. Genomic DNA has two strands wrapped helically around one another, but during transcription, they are separated by the RNA polymerase II to form a molecular condensate called the transcription bubble. Successive steps involve the bubble translocation along the gene body. This work aims to modulate DNA as a combination of n-nonperturbative circuits quantum electrodynamics with nine Radio-Frequency Superconducting Quantum Interference Devices (SQUIDs) inside. A bus can be coupled capacitively to a single-mode microwave resonator. The cavity mode and the bus can mediate long-range, fast interaction between neighboring and distant DNA SQUID qubits. RNA polymerase II produces decoherence during transcription. This enzyme is a multifunctional biomolecular machine working like an artificially engineered device. Phosphorylation catalyzed by protein kinases constitutes the driving force. The coupling between n-phosphorylation pulses and any particular SQUID qubit can be obtained selectively via frequency matching.

Molecular Structure and Properties of Resistant Dextrins from Potato Starch Prepared by Microwave Heating.

The dextrinization of potato starch was performed using a sophisticated single-mode microwave reactor with temperature and pressure control using 10 cycles of heating with stirring between cycles. Microwave power from 150 to 250 W, a cycle time from 15 to 25 s, and two types of vessels with different internal diameters (12 and 24 mm) and therefore different thicknesses of the heated starch layer were used in order to estimate the impact of vessel size used for microwave dextrinization. The characteristics of resistant dextrins (RD) including solubility in water, total dietary fiber (TDF) content, color parameters, the share of various glycosidic bonds, and pasting and rheological properties were carried out. The applied conditions allowed us to obtain RDs with water solubility up to 74% at 20 °C, as well as TDF content up to 47%, with a predominance of low-molecular-weight soluble fiber fraction, with increased content of non-starch glycosidic bonds, negligible viscosity, and a slightly beige color. The geometry of the reaction vessel influenced the properties of dextrins obtained under the same heating power, time, and repetition amounts. Among the conditions used, the most favorable conditions were heating 10 times for 20 s at 200 W in a 10 mL vessel and the least favorable were 15 s cycles.

Improving gel properties of low-salt silver carp surimi through single-mode microwave-assisted processing

Surimi, a product derived from low-value fish, is widely used to produce high-value items such as imitation crabsticks and fish balls. However, surimi from freshwater fish like silver carp generally exhibits inferior gel properties compared to marine fish. This study investigated the effects of 915 MHz single-mode microwave-assisted processing on the gel properties of low-salt silver carp surimi. Traditional water bath processing served as the control for comparison. Gel strength, texture, water-holding capacity (WHC), whiteness, protein secondary structure, and microstructure, along with thermal processing efficiency for microbial inactivation were evaluated. The results demonstrated that single-mode microwave processing significantly improved gel properties compared to water bath processing. Compared with the optimal water bath treatment, the gel strength of microwave processed samples increased significantly from 479.32 g·cm to 821.74 g·cm, while WHC increased from 0.77 to 0.87. The microwave processed surimi exhibited a more uniform microstructure. Because it enhanced the dissolution and cross-linking of myofibrillar proteins, leading to superior gel formation characterized by a lower α-helix content (10.31%) and higher β-sheet content (61.70%). Furthermore, microwave processing achieved faster heating rates, reducing the time spent in the critical gel deterioration temperature range, thereby improving overall gel quality. Single-mode microwave-assisted gelation also provided better thermal processing uniformity and efficiency, achieving pasteurization standards. The study highlights the potential of 915 MHz single-mode microwave processing to produce high-quality, low-salt surimi products, meeting contemporary health and convenience demands. These findings offer valuable insights for the industrial application of single-mode microwave technology in surimi production, promoting the development of innovative processing techniques to enhance the quality of surimi-based food products.

Parity time symmetry all-optical microwave oscillator using a polarization dependent Sagnac loop

An all-optical microwave oscillator based on parity-time symmetry was proposed and experimentally demonstrated. It mainly consists of a big feedback loop, an active small loop and a polarization-dependent Sagnac loop. The microwave seed signal originates from the beating between the continuous wave and the Stokes wave. The function of microwave envelope detection and feedback modulation are implemented through cross gain modulation of two semiconductor optical amplifiers. By employing the parity time symmetry loops and the Vernier effect, the single mode selectivity capability of the oscillator has been enhanced, and a single mode microwave signal with high quality can be generated. In the experiment, a highly quality microwave signal with a frequency of 10.71 GHz was generated. The single side band phase noise can reach −94.1 dBc/Hz@10 kHz and the side mode suppression ratio of the generated microwave signal reaches 41 dB. Compared to the previously reported all-photonic microwave oscillator, the single side band phase noise is improved by 7 dB at a frequency offset of 10 kHz, and by 20 dB at a frequency offset of 100 Hz. The results indicate that our proposed scheme significantly improves the quality of the generated microwave signals.

Pyrolysis of sargassum in a single mode microwave cavity: use of SiC and biochar as microwave absorbers

This paper examines the feasibility of pyrolyzing the macroalgae sargassum, in a single-mode microwave cavity using char or SiC as microwave absorber.

Microwave heating of coal slime based on multi-physics field simulations: Regulating waveguide port size and sample radius to improve microwave utilization efficiency

Microwave pyrolysis, a promising green-processing technology with high efficiency and low consumption, is particularly applicable in the pyrolysis of solid waste fuels such as coal slime. The microwave thermal effect plays an imperative role in the pyrolysis process. Low microwave utilization efficiency in single-mode microwave cavities is caused by the irregular field intensity distribution, and since of the high manufacturing costs of the equipment, it is unclear the relationship between waveguide port size, microwave field intensity distribution, and the temperature of sample. In this study, the effects of different waveguide port sizes and sample radius on the heating characteristics of coal slime were investigated using COMSOL Multiphysics software to construct a coupled multiphysics finite-element model. Moreover, the effects of the radius of the coal slime on the microwave utilization efficiency. The results demonstrated that only two types of wave distribution were found within the cavity, α and β, under the size of the waveguide port. The field intensity distribution in the β-type cavity was uniform, which prompted the sample temperature from 176 °C to 657 °C and microwave utilization efficiency from 10.16 % to 33.87 %. The maximum microwave utilization efficiency was increased from 33.87 % to 67.22 % by adjusting the radius of the sample at the optimal port size. The efficiency of the microwaves was maximized when the width-to-height ratio of the waveguide is 70:65 and the sample radius is 30–35 mm, and the sample temperature was maintained in a more desirable range. From the findings of this study, both the waveguide port size and sample radius are essential influencing factors in determining the sample temperature and microwave energy utilization efficiency during the heating of coal slime.

Emission thermometry of microwave-assisted alkali-doped propellant combustion

Recently, the application of high-power microwave fields to sodium-doped aluminized solid propellants has been shown to increase the atmospheric burning rate by up to 60%. Two main mechanisms have been proposed to increase the burning rate: (1) plasma enhancement by the presence of low-ionization threshold sodium and (2) the dielectric thermal runaway heating of metallic-oxide products. To examine the mechanisms of microwave energy deposition in the solid propellant burning strands, optical emission measurements were made during the application of a 2.46 GHz, 870 W microwave field in a single-mode microwave resonator. Flame temperature measurements are made via gas-phase AlO B2Σ+→X2Σ+(Δv=−1) electronic emission spectroscopy, spatially-resolved two-color imaging pyrometry of the condensed phase, and spatially-resolved two-line sodium emission thermometry. These experiments indicate an increase in the gas phase AlO temperature of ∼130 K, and a ∼1200 K increase in the sodium gas-phase temperature during the application of the microwave field. Gray body condensed-phase temperatures of burning aluminum particles indicated little temperature change, but the product plume temperature increased by ∼700 K. These temperature measurements of the vapor and condensed phase products indicate several important pathways for the thermalization of the field energy throughout the propellant flame structure, offering opportunities for further optimization of electromagnetically tunable energetic material combustion.

Nonlinear pumping induced multipartite entanglement in a hybrid magnon cavity QED system

We present a proposal to produce bipartite and tripartite entanglement in a hybrid magnon cavity QED system. Two macroscopic yttrium iron garnet (YIG) spheres are coupled to a single-mode microwave cavity, where the cavity photons are generated via a two-photon process induced by a strong pump field. Using mean-field theory, we show that nonlinear pumping can result in strong bipartite entanglement between the cavity photon and magnon under two conditions, i.e., ${\ensuremath{\delta}}_{c}{\ensuremath{\delta}}_{m}=2{g}^{2}$ and ${\ensuremath{\delta}}_{c}=\ensuremath{-}{\ensuremath{\delta}}_{m}$. For the latter one, we also show the possibility for producing bipartite entanglement between two magnon modes as well as tripartite entanglement among three modes. Combining these two conditions, we further derive a third condition, i.e., ${\ensuremath{\delta}}_{m}^{2}\ensuremath{-}{\ensuremath{\phi}}^{2}+2{g}^{2}=0$, where tripartite entanglement can be achieved when two magnon modes have different resonant frequencies.

Microwave signal generation from a parity-time-symmetric optoelectronic oscillator with optical injection locking.

A parity-time (PT) symmetric optoelectronic oscillator (OEO) with optical injection locking is proposed and experimentally demonstrated to generate single-mode microwave signals. A distributed feedback laser is injection locked, which functions as a frequency multiplier for the coarse mode selection of the PT-symmetric OEO. The PT symmetry in the OEO is implemented by using a polarization-dependent Sagnac loop to form two identical loops for coupling. By tuning the two polarization controllers in the Sagnac loop, the gain/loss and coupling coefficient of the two loops can be controlled, and single-mode oscillation in the OEO could be achieved at the broken PT-symmetry condition. Microwave signal generation at the frequency of 6.427GHz is obtained from the proposed OEO. The phase noise is about -105dBc/Hz at an offset frequency of 10kHz.

All-optical microwave oscillator based on a mutual-injection coupling between DFB-LDs.

An all-optical microwave oscillator (AOMO) is proposed and experimentally demonstrated. It contains only a mutual injection loop consisting of two distributed feedback laser diodes (DFB-LDs) and a few passive components. In this AOMO, the microwave seed signal originates from the period-one (P1) oscillation in one of the DFB-LDs. The functions of microwave envelope detection and feedback modulation are implemented by the other DFB-LD. Due to the optical injection locking and the optical-optical modulated effect in DFB-LD, the P1 signal is enhanced, and the stability of the P1 signal can be improved by coupling the P1 signal with a resonant mode of the mutual injection loop. Meanwhile, since the P1 oscillation is sensitive to injected light, the frequency of the P1 signal can be easily adjusted, which makes the AOMO easy to be tuned. In the experiment, a highly stable single-mode microwave signal with a frequency of 16.69 GHz and a single-sideband (SSB) phase noise of -90.7 dBc/Hz@10 kHz is generated. The frequency can be tuned from 14.48 to 21.45 GHz by adjusting the parameters of DFB-LDs and the injection light.

Experimental demonstration of virtual critical coupling to a single-mode microwave cavity

We present an experimental realization of virtual critical coupling in microwave, i.e., virtual perfect absorption of an incident wave by a resonant cavity, through transient time modulation of its amplitude. The design of a waveform matched to the ignition process of a plasma, characterized in a simplified way by two operating modes over time (plasma off/plasma on), motivates this first step in practical realization of virtual critical coupling in microwaves. We propose a time domain method for extracting necessary parameters for realization of virtual critical coupling, especially the complex frequency called zero of the S-matrix. To this end, we start from the experimental characterization of a single-mode and single-access microwave cavity including metal protrusions for future plasma ignition. Then, the method relies on the analysis of harmonic response of the overcoupled cavity during three time periods: the transient under excitation, the steady state under excitation, and the transient after excitation cutoff. Finally, an experimental demonstration of virtual critical coupling is performed.

Flash microwave sintering of alumina

Conventional flash sintering is difficult to adapt to ceramics with a very low electrical conductivity like pure alumina. Alternatively, the latter can be heated by microwave/matter interaction due to dielectric losses. Microwave energy is also preferable as it allows a rapid contactless and volumetric heating that can be initiated by susceptors. This work presents the assembly designed for this purpose by using a 2.45 GHz single-mode microwave cavity and the original assembly of susceptors made from silicon carbide plates and a 3D printed zirconia crucible. Controlled thermal cycles ranging from 300 to 900 K/min were successfully applied while measuring the shrinkage during the flash sintering. Alumina pieces were successfully sintered up to 93–98 % in mere seconds, depending on the heating rates, and microstructures were discussed according to the microwave “flash” heating conditions originally applied.

Heating using microwave technique: An approach towards green chemistry

Green chemistry focuses on minimizing waste, minimizing use of chemicals/reagents, reducing pollution and preservation of human health and environment. Using conventional methods of synthesis are creating the said problems in present scenario. To solve these problems new alternate methods must be developed. Many alternatives have been already developed but many more have to do. Use of microwave radiations are one the alternative in which these radiations are used for heating purpose instead of conventional heating methods which uses solvents in large amount and requires much time. Lot of benefits are there in heating using microwave radiations over conventional methods of heating but have limitations too. Not for every reaction/synthesis, but microwaves can be only used for the reactant having specific properties. Single mode and multi-mode microwave ovens are usually used for achieving this purpose. Heating by microwave radiations not only saves time i.e. it converts hours to minutes because it accelerates the reaction, increases the yield, reduces the energy requirement and the most important thing is no or minimum pollution/waste. Health hazards are also been noticed in using these radiations both external and internal. This short communication was aimed to find out the necessity of alternative methods of synthesis that fulfils the concept of green chemistry which will fulfill the need of healthy life and environment.

Production of highly porous biochar via microwave physiochemical activation for dechlorination in water treatment

Most biomass is composted into low-grade biofertilizer or processed into energy fuel for burning. At the same time, waste palm shell is potentially converted into highly porous biochar for dechlorination in water treatment. A single-mode microwave activation was developed to perform microwave activation that incorporated the application of steam, KOH, and a physiochemical process. The single-mode microwave activation was performed at the activation temperature ranging from 550–600 °C and recorded a short process duration of 5 min. The steam-activated biochar showed a mass yield of 88.3 wt%, a surface area of 527.4 m2/g, and a dechlorination efficiency of 25.5 mg/g. KOH-activated biochar showed a mass yield of 90.5 wt%, a surface area of 301.1 m2/g and a dechlorination efficiency of 24.0 mg/g. The physiochemical activated biochar showed the highest pores surface area of 717.8 m2/g and dechlorination efficiency of 35.8 mg/g but the lowest mass yield of 77.6 wt%. The results demonstrate that the greater the surface area, the higher the dechlorination efficiency. Using microwave heating and physiochemical activation technology demonstrates a promising way to produce activated biochar for the dechlorination of drinking water.

Effects of cerium and tungsten addition on acid–base properties of spindle-like α-Fe2O3 in low-temperature SCR of NOx with NH3

Low-temperature selective catalytic reduction (SCR) is important for the elimination of NOx from stationary sources. In the present study, the loading of Ce and W on α-Fe2O3 was achieved through the integration of single-mode microwave and incipient wetness impregnation (IWI) methods. The scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images reveal that the structure of α-Fe2O3 is spindle-like, and the structure remains unchanged after the introduction of Ce and/or W. The results of NH3-SCR investigation demonstrate that NOx conversion over Ce–W/α-Fe2O3 is more than 85% at 300 °C, which is much higher than that over Ce/α-Fe2O3 and α-Fe2O3. Our studies illustrate that the addition of Ce can significantly increase the amount of surface oxygen vacancies as well as sites of moderate basicity. On the other hand, the addition of W can obviously decrease the amount of basic sites and increase the number of Brønsted acid sites. The synergistic effect of Ce and W addition on balancing acidity/basicity properties accounts for the high activity of Ce20W10/α-Fe2O3 for NOx removal at low temperatures. The study provides insight into the relationship between acidity/basicity properties and catalytic performance of Ce–W/α-Fe2O3 catalysts, which is beneficial to the design of high-performance NH3-SCR catalyst for NOx removal at low temperatures.

Amine-Modified Chitosan Flocculant Synthesized via Single-Mode Microwave Method for Laundry Wastewater Treatment.

In this study, an effective and environmentally friendly polyaminated cross-linked chitosan (M-PACTS) flocculant was successfully synthesized via circular focus single-mode microwave synthesizer irradiation. Epichlorohydrin and tetraethylenepentamine were used as the cross-linking agent and active cationic reagent, respectively. The same formation was used to prepare cationic lightly cross-linked chitosan (C-PACTS) via the conventional heating method. The flocculant was characterized using Fourier transform infrared spectroscopy, X-ray diffraction analysis, and scanning electron microscopy. The flocculation capability of C-PACTS and M-PACTS was compared using laundry wastewater as a model pollutant. The pH, PACTS dosage, temperature, stirring rate, stirring time, and setting time were systematically investigated. The experimental results showed that circular focus single-mode microwave synthesizer irradiation was a more efficient method to modify chitosan. M-PACTS exhibited a higher capacity for turbidity and chemical oxygen demand (CODCr) removal. Under optimal conditions, the removal rate values of M-PACTS were up to 96% (turbidity) and 78% (CODCr). The proposed PACTS is suitable for treatment of polluted wastewater in an eco-friendly manner without causing secondary pollution.

A High-Efficiency Single-Mode Traveling Wave Reactor for Continuous Flow Processing

This paper proposes a high-efficiency single-mode traveling wave reactor based on a rectangular waveguide and its design method for continuous flow processing. The reactor has a large-capacity reaction chamber (1000 mm × 742.8 mm × 120 mm) that can provide high-energy-efficiency and approximately uniform microwave heating. The microwave heating uniformity is improved by maintaining single-mode microwave transmission and eliminating higher-order modes in such a multi-mode reaction chamber. The high energy efficiency of microwave heating is achieved by adopting impedance matching techniques. The incident microwave in the reactor can remain in a traveling wave state, and the power reflection can be minimized. Several numerical simulations based on multi-physics modeling are conducted to investigate the heating uniformity, the energy efficiency and the flexibility under different operation conditions. The results show the microwave energy efficiency can be higher than 99%, and meanwhile, the coefficient of temperature variation can be lower than 0.4. Furthermore, when the reactor is operated under different flow velocities and with different heating materials, both the energy efficiency and the heating uniformity can also meet the above requirements. The proposed reactor can be used in the applications such as oil processing, wastewater tackling, chemical synthesis, beverage sterilization and other microwave-assisted continuous flow processes that require high heating uniformity, high energy efficiency and good adaptability.

Microwave sintering study of strontium-doped lanthanum manganite in a single-mode microwave with electric and magnetic field at 2.45 GHz

The objective of this work is to study the changes in the physical and mechanical properties of strontium-doped lanthanum manganite (LSM) material and LSM-YSZ (ZrO2 doped with 8 mol% yttria) composite, obtained by colloidal processing and sintered by 2.45 GHz microwave sintering at 1200 and 1300 °C using two different single-mode cavities. One circular cavity with TE111 mode that has maximum in the electric field (E-field) and one rectangular cavity with TE102 mode that has maximum in the magnetic field (H-field). As compared to conventional sintering at 1300 and 1400 °C, the microwave-heated samples exhibited a denser structure for shorter sintering times. LSM-based materials showed higher heating behavior in H-field, which translates into higher energy absorption. This fact can be attributed to an electromagnetic pressure induced by the combined effect of current loops subjected to H-field. Therefore, the interaction between the material and the electromagnetic waves depends on the dominant field of them.

Titanium‐Oxo Cluster Assisted Fabrication of a Defect‐Rich Ti‐MOF Membrane Showing Versatile Gas‐Separation Performance

Although having shown great promise for efficient gas separation, relevant study of Ti-MOF membranes remains very scarce, owing to limited Ti source types and uncertain factors which dominate the separation properties. In this work, we pioneered the use of the Ti8 (μ2 -O)8 (OOCC6 H5 )16 cluster as the Ti source of MIL-125 membranes, which led to lower reaction temperature and higher missing-linker number within the framework and therefore, enhanced CO2 /N2 adsorption selectivity. The MIL-125 membrane prepared by combining single-mode microwave heating with tertiary growth displayed an ideal CO2 /N2 selectivity of 38.7, which ranked the highest among all pristine pure MOF membranes measured under comparable conditions. In addition, the ideal H2 /N2 and H2 /CH4 selectivity was as high as 64.9 and 40.7, thus showing great promise for versatile utility in gas separation.

Novel electromagnetic-black-hole-based high-efficiency single-mode microwave liquid-phase food heating system

Microwave heating exhibits a high potential for usage in liquid food processing. Current microwave heating systems are designed for a specific load. However, when the permittivity of the load changes dynamically, the heating efficiency of these systems fluctuates considerably. We proposed a novel high-efficiency microwave liquid heating system for dynamic dielectric loads to address this limitation. In this system, an electromagnetic black hole efficiently absorbs electromagnetic waves in all directions. First, an electromagnetic black hole was realized using metamaterials (which means artificially structured dielectric materials with extraordinary physical properties) with a radially continuous refractive index distribution. Next, an electromagnetic field simulation model was established to calculate the microwave absorption of various load permittivity. To discretize and simplify the parameters of the continuous distribution in an electromagnetic black hole, a concentric layered structure and a punched structure composed of uniform isotropic dielectric materials were designed. Finally, the experimental samples were processed based on the two discrete structures. The microwave system developed for experimental verification confirmed the high efficiency of the heating system; the system is simple and usable in numerous applications. Thus, the proposed method can realize high-efficiency heating of loads over large dielectric dynamic ranges. When the dielectric constant of the load changed dynamically from 10 to 80, the microwave energy utilization rate can increase by up to 90%.