Low-energy Microwave Research Articles

An experimental system for detection and localization of hemorrhage using ultra-wideband microwaves with deep learning

Stroke is a leading cause of mortality and disability. Emergent diagnosis and intervention are critical, and predicated upon initial brain imaging; however, existing clinical imaging modalities are generally costly, immobile, and demand highly specialized operation and interpretation. Low-energy microwaves have been explored as a low-cost, small form factor, fast, and safe probe for tissue dielectric properties measurements, with both imaging and diagnostic potential. Nevertheless, challenges inherent to microwave reconstruction have impeded progress, hence conduction of microwave imaging remains an elusive scientific aim. Herein, we introduce a dedicated experimental framework comprising a robotic navigation system to translate blood-mimicking phantoms within a human head model. An 8-element ultra-wideband array of modified antipodal Vivaldi antennas was developed and driven by a two-port vector network analyzer spanning 0.6–9.0 GHz at an operating power of 1 mW. Complex scattering parameters were measured, and dielectric signatures of hemorrhage were learned using a dedicated deep neural network for prediction of hemorrhage classes and localization. An overall sensitivity and specificity for detection >0.99 was observed, with Rayleigh mean localization error of 1.65 mm. The study establishes the feasibility of a robust experimental model and deep learning solution for ultra-wideband microwave stroke detection.

Thermal fracturing of anthracite under low-energy microwave irradiation: An experimental study

Microwave-assisted coalbed methane (CBM) development is a very promising technology for engineering applications. The mechanism of the macro and micro thermal fracture of coal must be further discussed because of the thermal inhomogeneity of microwave caused by the heterogeneity and structural complexity of coal. In this study, the temperature, weight and P-wave velocity of anthracite were tested under low-energy microwave irradiation. The characteristics of fracture initiation, extension, and connectivity in coal after microwave irradiation were extracted from macroscopic and microscopic observations. Then the mechanisms of microwave thermal fracturing in anthracite were analyzed. The results showed that the temperature of anthracite under low-energy microwave irradiation varies asynchronously. The temperature distributions with high and low temperature partitions exhibit obvious bedding effects. The coal mass loss varies in stages with microwave irradiation time, first increasing slowly and then increasing dramatically above 500 °C. The P-wave velocity presents a decreasing trend with the increase of input microwave energy. Coal generates a complex fracture network at the micro and macro scales, with fractures expanding outwards in a divergent pattern. The nonuniformity of the temperature distribution promotes fracture development. It is related to the asynchronous heating caused by the mineral composition, water content, pore fracture structure, and electromagnetic field in coal. It is of great significance to improve the thermal fracturing efficiency by using the nonuniformity of microwave heat in the application of microwave-assisted CBM development.

Green and fast microwave-driven synthesis of fluorescent N,S-carbon dots for determination of two 5-nitroimidazole antimicrobials

A green, fast, and economical technique for the manufacture of N,S-CQDS has been devised based on 3-min microwave irradiation of citric acid and thiosemicarbazide that furnished highly fluorescent quantum dots (λex/em of 360/430 nm) with high water solubility and stability. Transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), Zeta potential analysis, Fourier transform infrared, UV-Visible spectroscopy, and fluorescence spectroscopy were used to fully characterize the N,S-CQDS. The obtained N,S-CQDS are spherical shaped with average size of 13.2 ± 4.3 nm and Zeta potential of -32.46 ± 1.55 mv. The effect of UV light and pH on the fluorescence intensity of the synthesized N,S-CQDS were also investigated. The synthesized N,S-CQDS were used as a fluorescent nanoprobe for the determination of two 5-nitroimidazole antimicrobials; secnidazole (SNZ) and tinidazole (TNZ) by fluorescence turn-off via inner filter effect and static quenching mechanisms. This approach demonstrated a linear dependency of the fluorescence signal on the concentration of both drugs over the range of 15-200 μM. The limit of detection and limit of quantification were 2.18 and 6.62 μM, respectively, for SNZ, and 2.29 and 6.96 μM, respectively, for TNZ. The developed method was used to determine both drugs in pharmaceutical dosage forms and human urine samples with % recovery of 100.65 ± 1.35 for SNZ, 98.66 ± 0.47 for TNZ in pharmaceutical dosage forms and 102.24 ± 2.93 for SNZ, 98.2 ± 1.78 for TNZ in case of spiked human urine samples. The approach's selectivity was confirmed for determining both analytes in the presence of various co-existing and co-administered species. The method validity was assessed in accordance with ICH recommendations. Various metrics were used to evaluate the greenness of the proposed probe. The developed probe is environmentally-friendly due to the quick synthesis of luminous N,S-CQDS using affordable and low-energy microwave radiation, and the absence of organic solvents.

In–human testing of a non-invasive continuous low–energy microwave glucose sensor with advanced machine learning capabilities

Continuous glucose monitoring schemes that avoid finger pricking are of utmost importance to enhance the comfort and lifestyle of diabetic patients. To this aim, we propose a microwave planar sensing platform as a potent sensing technology that extends its applications to biomedical analytes. In this paper, a compact planar resonator-based sensor is introduced for noncontact sensing of glucose. Furthermore, in vivo and in-vitro tests using a microfluidic channel system and in clinical trial settings demonstrate its reliable operation. The proposed sensor offers real-time response and a high linear correlation (R2 ∼ 0.913) between the measured sensor response and the blood glucose level (GL). The sensor is also enhanced with machine learning to predict the variation of body glucose levels for non-diabetic and diabetic patients. This addition is instrumental in triggering preemptive measures in cases of unusual glucose level trends. In addition, it allows for the detection of common artifacts of the sensor as anomalies so that they can be removed from the measured data. The proposed system is designed to noninvasively monitor interstitial glucose levels in humans, introducing the opportunity to create a customized wearable apparatus with the ability to learn.

Interlayer Electrons Polarization of Asymmetric Metal Nanoclusters/g-C3 N4 for Enhanced Microwave Therapy of Pneumonia.

Interlayer interactions in two dimensional (2D) materials promote catalytic performance but often depend on the transport of inter rather than intralayer electrons. In this study, it is found that asymmetric metal-nanocluster-doped 2D g-C3 N4 greatly enhances catalytic performance by inducing microwave excitation of interlayer electron delocalization, resulting in a polarization of interlaminar charge transport for microwave disinfection and pneumonia therapy. Asymmetric Fe and Cu nanocluster doping (DCN-FeCu) enables g-C3 N4 to generate interlayer electrons under microwave irradiation, leading to interlayer polarization processes and electron delocalization effects, thus enhancing the interlayer migration efficiency of electrons. It also improves impurity energy levels and leads to a decrease in work function, allowing DCN-FeCu to produce microwave carriers across the photoelectric potential barrier under low-energy microwave radiation (2.45GHz). This asymmetric doping modulation produces layer number-dependent microwave electron excitations that are verified using multi-metal doping. Therefore, structurally modulated asymmetric doping of 2D materials with interfacial spatial effects can provide efficient microwave disinfection and pneumonia therapy.

Ozonation of carbamazepine in the presence of sulfur-dopped graphene: Effect of process parameters and formation of main transformation products

The stability of graphene structure in sulfur-doped graphene catalyst is demonstrated to be a key aspect during the ozonation process. Enhancing the stability of the sulfur-doped graphene structure is therefore important to improve its catalytic activity during the ozonation process. However, this has remained a challenge so far. Therefore, we adopted a low-energy microwave plasma technique to synthesize a high purity sulfur-doped graphene (S ⎯ Gr) catalyst for the ozonation process. The effect of S ⎯ Gr in the ozonation process was tested using carbamazepine (CBZ; 0.05 mM) as a probe compound. A complete CBZ removal was obtained at an ozone concentration of 0.08 mM while in comparison with single O3, ∼1.5 and 2.5 times decrease in the formation of the two important intermediate transformation products i.e., BQM (1-(2-benzaldehyde) – 4-hydroxy (1H, 3H)-quinazoline-2-one) and BQD (1-(2-benzaldehyde) - (1H, 3H)-quinazoline-2, 4-dione) was observed. Radical scavenging experiments confirmed the formation of HO. The XPS results showed that the activity of S ⎯ Gr towards the formation of HO was positively related to S-bearing carbon atoms at the edge of the graphene structure. Therefore, the addition of S ⎯ Gr is directly linked with the formation of HO, which further contributed to the improved elimination of intermediate transformation products. With a low sulfur loss of 1 %, the microwave plasma synthesized S ⎯ Gr catalyst remained stable during ozonation, implying its feasibility in practical application.

Progressing Ultragreen, Energy-Efficient Biobased Depolymerization of Poly(ethylene terephthalate) via Microwave-Assisted Green Deep Eutectic Solvent and Enzymatic Treatment.

Effective interfacing of energy-efficient and biobased technologies presents an all-green route to achieving continuous circular production, utilization, and reproduction of plastics. Here, we show combined ultragreen chemical and biocatalytic depolymerization of polyethylene terephthalate (PET) using deep eutectic solvent (DES)-based low-energy microwave (MW) treatment followed by enzymatic hydrolysis. DESs are emerging as attractive sustainable catalysts due to their low toxicity, biodegradability, and unique biological compatibility. A green DES with triplet composition of choline chloride, glycerol, and urea was selected for PET depolymerization under MW irradiation without the use of additional depolymerization agents. Treatment conditions were studied using Box-Behnken design (BBD) with respect to MW irradiation time, MW power, and volume of DES. Under the optimized conditions of 20 mL DES volume, 260 W MW power, and 3 min MW time, a significant increase in the carbonyl index and PET percentage weight loss was observed. The combined MW-assisted DES depolymerization and enzymatic hydrolysis of the treated PET residue using LCC variant ICCG resulted in a total monomer conversion of ≈16% (w/w) in the form of terephthalic acid, mono-(2-hydroxyethyl) terephthalate, and bis-(2-hydroxyethyl) terephthalate. Such high monomer conversion in comparison to enzymatically hydrolyzed virgin PET (1.56% (w/w)) could be attributed to the recognized depolymerization effect of the selected DES MW treatment process. Hence, MW-assisted DES technology proved itself as an efficient process for boosting the biodepolymerization of PET in an ultrafast and eco-friendly manner.

Efficient generation of hydrogen by two-step thermochemical cycles: Successive thermal reduction and water splitting reactions using equal-power microwave irradiation and a high entropy material

Hydrogen production through two-step thermochemical water splitting cycle based on metal oxide has emerged as a promising strategy to store dilute and intermittent solar energy. However, a typical reaction time of the two-step thermochemical water splitting cycle is lengthy, with at least 0.5 h for thermal reduction step and 1 h for water splitting step, and the energy required in the thermal reduction process for hydrogen regeneration is higher than the generated hydrogen energy. In this work, to overcome the problem of an energy efficiency imbalance, we investigated the possibility of the rapid and successive reactions of thermal reduction and water splitting, using short-term irradiation from a low-energy microwave. To this end, a high entropy material, as a poly-metal oxide used to generate hydrogen, was produced by simultaneously introducing four cations onto a SiC foam – (FeMgCoNi)O1.2@SiC. It was found that the oxygen vacancy of the (FeMgCoNi)O1.2@SiC could be significantly increased by short-term microwave irradiation, and hence the thermal reduction process took only 4 min, which is much less than normal. High H2 generation rates were achieved by re-oxidation of the Fe (II) to Fe (III) of the (FeMgCoNi)O1.2@SiC. In addition, the microwave plasma generated by microwave irradiation induced (FeMgCoNi)O1.2@SiC discharge could enhance the water splitting process. The maximum hydrogen yield was 122 mL/g at 700 W, due to the coupling effect of the thermochemical cycle and microwave plasma. In this way, the power consumption of microwave process is only 3% of that of conventional high-temperature heat treatment during thermal reduction process.

Low-energy microwave synthesis and cold sintering of nanograined TiO2-Nb2O5

The feasibility of using nanoparticles for bulk advanced ceramics manufacture is currently controversial, because the energy-time investments and the challenge to produce a dense nanostructured material. In this work, fast microwave synthesis and cold sintering were applied at mild conditions to efficiently produce dense nanocrystalline TiO2-Nb2O5 compacts. Microwave was carried out at 170 °C for 5 min to synthesize the targeted nanoparticles. Cold sintering permitted the densification at 200 °C and 300 MPa for 30 min of TiO2-Nb2O5 compacts reaching over 90% relative densities and grain size under 100 nm. The combination of both techniques enables a feasible technological route to manufacture nanograined ceramics with low-energy consumption from synthesis to densification.

Effect of innovative microwave assisted freezing (MAF) on the quality attributes of apples and potatoes

This study considered the effect of low energy microwave assisted freezing (MAF) on freezing time and quality attributes (microstructure, texture, drip loss and colour) of apple and potato. MAF of apples and potatoes was performed by applying constant microwave (MW) power (167 W/kg) and pulsed MW power (500 and 667 W/kg with 10 s pulse width and 20 s pulse interval resulting in an average power of 167 and 222 W/kg) during the freezing process. The temperature profile was monitored during the freezing process, and the microstructure was examined using X-ray micro-tomography and cryo-SEM. Other quality parameters such as texture, drip loss and colour were evaluated with thawed samples. It appeared that the freezing time was not affected by the MAF process. It is the first time that a MAF process is used for freezing plant-based products and showed that the application of microwaves during freezing process caused less freeze damage than the control condition.

Evaluation of Low-Energy Microwaves Technology (Termatrac) for Detecting Western Drywood Termite in a Simulated Drywall System.

Detecting drywood termites in structures is very challenging. Microwaves technology (Termatrac T3i) is a nondestructive method for detecting drywood termites in structures. Termatrac device and its mobile application provide a bar as well as a line graph when detecting insect movements, but interpreting these graphs is very subjective. In this paper, Termatrac's output signal is quantified using a new method to study the effect of wall layers, wood type, and termite density on signal strength measured as area under curve in a simulated drywall system in laboratory. Two experiments were conducted on Termatrac T3i at its maximum sensitivity (Gain: 10). In experiment I, HEXBUG Nano was used as a source of movement/vibration and two wood types were used in which the wall layers significantly predicted signal strength, but wood type did not. In experiment II, two different densities of live western drywood termites, Incisitermes minor (Hagen) (Isoptera: Kalotermitidae), were used to study the effect of termite density on signal strength. Interestingly, termite density did not significantly predict signal strength. The maximum reliable wood depth for detecting termites was 5 cm. Microwaves produced by Termatrac also showed good penetration into drywall and produced detectable signals even on a single drywood termite which confirms manufacturer's claim. Suggestions on using and improving microwaves technology for detecting termites is provided which can potentially be applied to other types of insects and noninsect animals.

Efficient synthesis of benzothiazole derivatives by reaction of bis(2-aminophenyl) disulfides with aldehydes mediated by NaSH under microwave irradiation

GRAPHICAL ABSTRACT

Study on Ultra Shallow Junction n-MOS with 350°C Microwave Annealing for Activation of Phosphorus Dopants in Germanium

In this study, low-energy microwave annealing is used to fabricate ultra-shallow junctions for less than 20 nm IC node applications in a potential material: Germanium (Ge). Germanium is a new promising material and might replace silicon in the future. A novel microwave annealing technique with two steps for the solid phase epitaxial recrystallization (SPER) and phosphorus dopants activation was applied to Germanium. The purpose of the first step, microwave annealing of 1.2 kW for 75 s, is to re-grow the amorphous layer and repair the destroyed crystal lattices caused by ion implantation. In the second-step of annealing, low-energy microwave, 0.9 kW (≈350°C) for 300 s, is used to activate the phosphorus dopants effectively without diffusion and de-activation. The target dopant activation concentration level will achieve 10²⁰ cm^-3. The sheet resistance will decrease to 78 ohm/sq. The low resistance after activating is reflected to the performance of the n-MOS device fabricated by the Ge substrate. The S. S. factor is 900 mV/dec, and the I_on/off ratio rise to 2.6×10¹. This has demonstrated that the two-step MWA has excellent control, significantly regarding leakage current.

Morphological stability of the atomically clean surface of silicon (100) crystals after microwave plasma-chemical processing

The morphological stability of atomically clean silicon (100) surface after low-energy microwave plasma-chemical etching in various plasma-forming media is studied. It is found that relaxation changes in the surface density and atomic bump heights after plasma processing in inert and chemically active media are multidirectional in character. After processing in a freon-14 medium, the free energy is minimized due to a decrease in the surface density of microbumps and an increase in their height. After argon-plasma processing, an insignificant increase in the bump density with a simultaneous decrease in bump heights is observed. The physicochemical processes causing these changes are considered.

A near-quantum-limited Josephson traveling-wave parametric amplifier.

Detecting single-photon level signals—carriers of both classical and quantum information—is particularly challenging for low-energy microwave frequency excitations. Here we introduce a superconducting amplifier based on a Josephson junction transmission line. Unlike current standing-wave parametric amplifiers, this traveling wave architecture robustly achieves high gain over a bandwidth of several gigahertz with sufficient dynamic range to read out 20 superconducting qubits. To achieve this performance, we introduce a subwavelength resonant phase-matching technique that enables the creation of nonlinear microwave devices with unique dispersion relations. We benchmark the amplifier with weak measurements, obtaining a high quantum efficiency of 75% (70% including noise added by amplifiers following the Josephson amplifier). With a flexible design based on compact lumped elements, this Josephson amplifier has broad applicability to microwave metrology and quantum optics.

Effect of deflocculation on the efficiency of low-energy microwave pretreatment and anaerobic biodegradation of waste activated sludge

Abstract This study focuses on improving the efficiency of the microwave (MW) pretreatment of waste activated sludge (WAS) through deflocculation mediated by sodium tripolyphosphate (STPP), a cationic binding agent. Deflocculated sludge was subjected to MW pretreatment to assess its impact on biomass disintegration. At the optimised energy for MW pretreatment (14,000 kJ/kg TS), the chemical oxygen demand (COD) solubilisation was 28% and 21% and the reduction in suspended solids (SS) was 38% and 26%, respectively, for deflocculated (treated with a cationic binding agent followed by microwaves) and flocculated (treated by microwaves alone) sludge samples. The formation of volatile fatty acids in the deflocculated sludge medium (840 mg/L) was comparatively higher than that in the flocculated sludge (420 mg/L) and the control (62 mg/L). This study indicates that deflocculated sludge is more amenable to hydrolysis. The results of a test of biochemical methane potential also confirmed the greater amenability of deflocculated sludge for anaerobic degradation.

Using microwave metrology to count calories

One non-destructive way to probe the caloric content of food is to examine the transmission spectra of low energy microwaves over a broad band (approximately 1–8GHz). This paper proposes a simple, but generalizable, nearest neighbor scheme to estimate the calories of homogeneous mixtures of oil, sugar, and water. The approach’s performance is empirically quantified and is also compared to the performance of an oracle estimator. We report that for this study the estimator achieves an average absolute error of approximately 10%. A heuristic extension of the nearest neighbor estimator is also discussed that can in some cases improve the average error performance. The work represents the first steps toward accurate and reliable calorie estimation techniques for complex, non-homogeneous foods of varying shapes and amounts.

Piezoelectric control of magnetic dynamics in Co/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructure

A microstrip method with vector network analyzer was used to investigate electric field control of magnetic dynamic properties in Co/Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructure at room temperature. Under external electric field, the natural resonance frequency and permeability of the Co film were found to modulate between 1.8–2.8 GHz and 50–150, respectively. In addition, the in-plane uniaxial magnetic anisotropy field can also be electrically tuned from 54 to 170 Oe, while the ferromagnetic resonance field was substantially enhanced about 350 Oe as well. Such an improvement of magnetic anisotropy is desirable for effectively electric control of resonance frequency and permeability in low energy microwave devices.

Formation of built-in potential in Si (100) crystals under microwave plasma treatment

A study of the fundamental aspects of the influence exerted on the electronic properties of a surface of Si (100) single crystals with a natural oxide coating by low-energy microwave plasma treatment in various plasma-forming media is reported. Model mechanisms of the process and factors providing stable modification of the electronic properties of the surface of silicon crystals via the formation of built-in surface potentials determined by the chemical activity of working gases used in plasma microtreatment under weak-adsorption conditions are considered. It is shown that, in principle, the electronic properties of the surface of semiconductor crystals can be actively formed to extend their electrical and functional properties.

MP71-05 COST-EFFECTIVENESS MARKOV MODEL COMPARING HIGH- AND LOW-ENERGY TRANSURETHRAL MICROWAVE THERAPY FOR BENIGN PROSTATIC HYPERPLASIA

You have accessJournal of UrologyBenign Prostatic Hyperplasia: Surgical Therapy & New Technology II1 Apr 2014MP71-05 COST-EFFECTIVENESS MARKOV MODEL COMPARING HIGH- AND LOW-ENERGY TRANSURETHRAL MICROWAVE THERAPY FOR BENIGN PROSTATIC HYPERPLASIA James C. Ulchaker and MD FACS Melissa MartinsonMS PhD James C. UlchakerJames C. Ulchaker More articles by this author and Melissa MartinsonMelissa Martinson More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.2164AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Transurethral microwave therapy (TUMT) can be grouped into low-energy (LE-TUMT) and high-energy (HE-TUMT) categories based on both microwave wattage and intraprostatic temperatures. Historical retreatment rates, meta-analyses and disease management guidelines point to greater durability and clinical effectiveness of HE-TUMT, but cost effectiveness has not previously been compared. We created an economic model comparing cost-effectiveness of LE-TUMT and HE-TUMT. METHODS We constructed a Markov model similar to published models on Benign Prostatic Hyperplasia (BPH) procedures using published outcomes and 2013 Medicare costs. American Urological Association Symptom scores (AUASS), adverse events (AEs), and retreatment rates at annual intervals were obtained from the literature. Costs to treat AEs and retreatment rates were included in calculating total costs. Quality Adjusted Life Years (QALYs) were calculated from preference weights from the literature for health states of BPH, successfully treated BPH, treated BPH with erectile dysfunction, and treated BPH with urinary incontinence, over the time spent in each. RESULTS The table below shows total costs, mean AUASS, and QALYs at 2 and 4 years. Using an incremental cost-effectiveness ratio (ICER) at 4 years, HE-TUMT dominated LE-TUMT where HE-TUMT was more effective and less expensive over time. HE-TUMT saved $3,026 at 4 years and achieved 3 points of greater symptom score improvement, saving $868 per incremental point reduction. CONCLUSIONS Due to higher retreatment rates, LE-TUMT is more expensive than HE-TUMT at 2 and 4 years and less effective. While HE-TUMT dominates LE-TUMT in cost effectiveness in this model, additional studies should compare these costs to BPH medication and surgical therapies. While Medicare costs are clearly lower for drugs on day 1 and higher for surgery on day 1, this type of model has the potential to help identify cost effective options across treatment modalities over the course of time. © 2014FiguresReferencesRelatedDetails Volume 191Issue 4SApril 2014Page: e791 Advertisement Copyright & Permissions© 2014MetricsAuthor Information James C. Ulchaker More articles by this author Melissa Martinson More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...