Search

Purpose: Advancing the development of 7 T MRI for spinal cord imaging is crucial for the enhanced diagnosis and monitoring of various neurodegenerative diseases and traumas. However, a significant challenge at this field strength is the transmit field inhomogeneity. Such inhomogeneity is particularly problematic for imaging the small, deep anatomical structures of the cervical spinal cord, as it can cause uneven signal intensity and elevate the local specific absorption ratio, compromising image quality. This multisite study explores several RF shimming techniques in the cervical spinal cord. Methods: Data were collected from 5 participants between two 7 T sites with a custom 8Tx/20Rx parallel transmission coil. We explored two radiofrequency (RF) shimming approaches from an MRI vendor and four from an open‐source toolbox, showcasing their ability to enhance transmit field and signal homogeneity along the cervical spinal cord. Results: The circularly polarized (CP), coefficient of variation (CoV), and specific absorption rate (SAR) efficiency shim modes showed the highest B1+ efficiency, and the vendor‐based "patient" and "volume" modes showed the lowest B1+ efficiency. The coefficient of variation method produced the highest CSF/spinal cord contrast on T2*‐weighted scans (ratio of 1.27 ± 0.03), and the lowest variation of that contrast along the superior–inferior axis. Conclusion: The study's findings highlight the potential of RF shimming to advance 7 T MRI's clinical utility for central nervous system imaging by enabling more homogenous and efficient spinal cord imaging. Additionally, the research incorporates a reproducible Jupyter Notebook, enhancing the study's transparency and facilitating peer verification. [ABSTRACT FROM AUTHOR]

In order to achieve high‐performance gallium nitride (GaN) high‐electron‐mobility‐transistors (HEMTs) capable of operating in the X‐band, a bilayer passivation technique is employed. The technique involves creating a stacked passivation layer consisting of a 20‐nm Si‐rich silicon nitride (SixN) passivation layer and a 100‐nm N‐rich silicon nitride (Si3N4) passivation layer. This effectively reduces radio frequency scattering in GaN HEMTs without compromising the breakdown voltage (BV). On the one hand, the SixN passivation layer effectively suppresses the surface states of devices, resulting in low current collapse. On the other hand, the Si3N4 passivation layer can effectively reduce gate leakage caused by the SixN passivation layer, allowing the device to reliably operate at higher voltages. Consequently, a GaN HEMTs with SixN/Si3N4 bilayer passivation achieve a low current collapse of 5% and a high BV of 157 V. The device features a current gain cutoff frequency (fT) and maximum oscillation frequency (fmax) of 57.9 and 96.8 GHz, respectively. Additionally, it exhibits excellent radio frequency performance in the X‐band, with an output power density (Pout) of 13.7 W mm−1 and power added efficiency of 60.8% at a drain voltage (VD) bias of 50 V. [ABSTRACT FROM AUTHOR]

Radio‐frequency welding shows great potential for a more sustainable manufacturing of lightweight bead foam products based on local dielectric heating of the part. This study provides the first insight into the material‐process interactions required to enable interdiffusion between foam particles and thus adhesion. The complex relative permittivity εr* is analyzed by impedance spectroscopy of the bulk polymer and foam beads using specially designed measurement cells. Due to the increased flexibility of the polymer chains at elevated temperatures, the relaxation mechanisms are promoted, resulting in a shift of the εr* curves to higher frequencies. At a fixed frequency, a peak in the imaginary part εr′′ is observed above temperature, revealing the superposition of these two parameters. The foamed beads show similar trends with an attenuated signal due to the high volumetric fraction of air within the multiphase system. The linear dependence between εr′′ and volumetric power as direct process feedback due to dielectric heating was observed during welding. Compared to the delayed signals from the shielded temperature sensors, the analysis of power consumption allows for higher quality real‐time monitoring throughout the process cycle. The correlation also allows prediction of power levels at defined temperatures. [ABSTRACT FROM AUTHOR]

Background: Efficiency and safety of ablation using half normal saline (HNS) has been shown in refractory ventricular tachycardia (VT), but no evaluation in unselected larger populations has been made. Objective: To evaluate the efficiency and safety of systematic HNS ablation in VT ablation. Methods: All successive VT ablations in patients with structural heart disease from 2018 to 2021 used HNS in our center and were retrospectively included. Results: One hundred seventy‐seven successive VT ablation procedures using HNS have been performed in 148 patients (91% males, mean 64 ± 12 years, ischemic cardiomyopathy 64%, left ventricular ejection fraction 38 ± 13%). A mean of 19 ± 7.5 min of RF was delivered, with a mean power of 44 ± 7 W. Relevant complications happened in 9% (strokes 2%, tamponades 3%, atrioventricular block during septal ablations 5%). Over a mean follow‐up of 15 ± 9 months, VT recurred in 46%. Final recurrence rate after one or several procedures was 36% (18 months follow‐up). Number of VT episodes decreased from 14 ± 35 before to 2.5 ± 10 after ablation (p <.0001) and number of ICD shocks decreased from 4.8 ± 6.8 to 1.5 ± 0.8 (p =.027). Conclusion: Systematic use of HNS during VT ablations in patients with structural heart disease leads to long‐term recurrences rates and complications in the range of what is reported using normal saline. Although controlled studies are needed for demonstrating the superiority of such attitude, the use of HNS in every scar‐related VT ablation seems safe for standard cases and may be furthermore useful in case of refractory arrhythmias due to difficult‐to‐ablate substrates. [ABSTRACT FROM AUTHOR]

BACKGROUND: Wheat and wheat flour are important raw materials of staple foods. Medium‐gluten wheat is now the dominant wheat in China. In order to expand the application of medium‐gluten wheat, radio‐frequency (RF) technology was used to improve its quality. Effects of tempering moisture content (TMC) of wheat and RF treatment time on wheat quality were investigated. RESULTS: No evident change in protein content after RF treatment, but a reduction in wet gluten content of the sample with 10–18% TMC and RF treatment for 5 min, was observed. By contrast, protein content increased to 31.0% after RF treatment for 9 min in 14% TMC wheat, achieving the requirement of high‐gluten wheat (≥30.0%). Thermodynamic and pasting properties indicated that RF treatment (14% TMC, 5 min) can alter the double‐helical structure and pasting viscosities of flour. In addition, the results of textural analysis and sensory evaluation for Chinese steamed bread showed that RF treatment for 5 min with different TMC (10–18%) wheat could deteriorate wheat quality, while the wheat (14% TMC) treated with RF for 9 min had the best quality. CONCLUSION: RF treatment for 9 min can improve wheat quality when the TMC was 14%. The results are beneficial to the application of RF technology in wheat processing and improvement of wheat flour quality. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

A versatile industrial recipe of transferring nitride microelectronic components such as micro‐electromechanical systems (MEMS) onto flexible and stretchable substrates is demonstrated. This method bypasses difficulties of temperature‐related processing, and is applicable to large‐scale and mass production. The technological process of fabrication is presented along with its underlying structural and radio‐frequency characterizations. In particular, the Raman strain shifts of aluminum nitride (AlN) thin films are determined for uniaxial and biaxial mechanical deformations. The transferring process onto polymer is also demonstrated by an adhesive bonding of AlN‐based MEMS onto a 200 mm silicon (Si) wafer. The devices microstructure is assessed using X‐ray before and after transferring, as well as their electrical radio‐frequency (RF) features when on Si and polymer substrates. Then, RF measurements are also performed on the transferred and flexible devices; some in their relaxed states, and others in an in situ manner under an increasing macroscopic strain. It is shown that bulk acoustic wave resonator MEMS are fully functional even under 12% uniaxial stretching of the substrate. [ABSTRACT FROM AUTHOR]

This article reports the DC and analog/radio frequency (RF) response of a newly invented device called vertical super‐thin body (VSTB) FET towards high‐k (Si3N4/HfO2) and low‐k (SiO2) gate dielectrics in conjunction with the scaling effect through a well‐calibrated Sentaurus TCAD tool. At channel length (LG) of 20 nm, compared to SiO2, Si3N4 improves various DC parameters such as off‐state leakage current (Ioff), on‐current (Ion), on‐to‐off current ratio (Ion/Ioff ratio), subthreshold swing (SS), and drain‐induced‐barrier‐lowering (DIBL) by 77.15%, 26.2%, one order of magnitude, 15.78%, and 36.2%, respectively. On the other hand, a higher improvement is seen in all these DC parameters for the HfO2 gate dielectric (Ioff, Ion, Ion/Ioff ratio, SS, DIBL improves respectively by 91.8%, 41.57%, two orders of magnitude, 28.28%, and 62.71%). The underlying physics behind such excellent improvement is explained by the device off‐state energy band diagram, electrostatic potential, and channel electron density profile for each dielectric. Further, for all the gate dielectrics considered, the device characteristics were studied for a wide range of LG from 10 to 50 nm to reveal the scaling impact on the device performance. Irrespective of the gate dielectric material, the device exhibits excellent performance at LG = 10 nm, which in turn indicates to the brilliant scalability of this new device. Besides, although Si3N4 and HfO2 increase gate capacitance (Cgg)/gate‐drain capacitance (Cgd), due to the extremely low values of Cgg/Cgd, enhanced unit gain cut‐off frequency, and gain‐bandwidth‐product is achieved. In addition, the increased transconductance (gm) of the device applying Si3N4/HfO2 gate dielectric leads to a higher peak value of TGF, intrinsic gain, TFP, GFP, and GTFP. This study intends to expand the fundamental knowledge about such a new device as a VSTB FET and hence, aims to be utilized in the future research of this novel device. [ABSTRACT FROM AUTHOR]

This article investigates the impact of the p–p+ junction (at the body‐substrate interface) on different direct current (DC) and analog/radio frequency (RF) performance parameters of a newly invented structure called vertical super‐thin body field effect transistor (VSTB FET) through a well‐calibrated TCAD tool. At a fixed body doping, the influence of p–p+ junction was inspected for different substrate doping (Ns); which reveals that Ns has a robust control on the device electrostatics. Interestingly, higher Ns is seen to significantly suppress different short channel effects (SCEs), which in turn helps to improve various DC parameters excellently. An increase in Ns from 1015 to 1018 cm−3 improves off‐state leakage current and on‐to‐off current ratio by three orders of magnitude. Also, such a change in Ns decreases subthreshold swing and drain‐induced‐barrier‐lowering by 8.78 mV/dec and 11.15 mV/V, respectively. The underlying physics behind such improvement at higher Ns is explored through the off‐state channel electron density profiles corresponding to different Ns values. Further, different analog/RF parameters such as transconductance, input capacitance, gate‐drain capacitance, output conductance, gain‐bandwidth‐product, and transconductance frequency product (TFP) show slight improvement for increasing Ns. In contrast, TGF, GFP, and GTFP offer large enhancement at higher Ns. This study is expected to demonstrate the significance of Ns on device performance. [ABSTRACT FROM AUTHOR]

Wearable sensors promise to transform human understanding of body state. However, despite many wearable sensor modalities that exist, few demonstrate the raw capabilities required for many emerging healthcare applications—passivity (and microelectronics‐free), wireless readout, long‐term operation, and specificity. Hydrogel‐interlayer radio‐frequency resonators are demonstrated as a versatile platform for passive and wireless biosensing. Fabricated using a simple vinyl cutter, the base resonator is composed of unanchored, broad‐side coupled coils interceded by multifunctional hydrogels—such resonators are tuned to be sensitive to specific analytical or physical signals by modifying hydrogel composition. These resonators are transformed into near‐field communication (NFC) sensor circuits through the simple attachment of an LED. These enable direct quantification of sensor state by cellphone and eye with no specialized electronics required. Resonator arrays are finally fused with silicone to form soft, wireless sensor skins that enable co‐readout of analytical to physical signals while molded to human subjects. Such low‐cost, accessible platforms can integrate with environments in transformative ways, enabling new applications in wireless sensing. [ABSTRACT FROM AUTHOR]

Objectives: To assess the safety and effectiveness of in‐office bipolar radiofrequency treatment of nasal valve obstruction Study Design: Prospective, nonrandomized, multicenter case series Methods: Adult patients with a Nasal Obstruction Symptom Evaluation scale (NOSE) score ≥60 were selected. Patients were clinically diagnosed with dynamic or static internal nasal valve obstruction as primary or significant contributor to obstruction and were required to have a positive response to nasal mechanical dilators or lateralization maneuvers. Bilateral radio‐frequency treatment was applied intranasally using a novel device, under local anesthesia in a single session. Safety and tolerance were assessed by event reporting, inspection, and Visual Analogue Scale (VAS) for pain. Efficacy was determined using the NOSE score and patient‐reported satisfaction survey at 26 weeks. Results: Fifty patients were treated. No device or procedure‐related serious adverse events occurred. Soreness, edema, and crusting resolved by 1 month. The mean baseline NOSE score was 79.9 (SD 10.8, range 60–100), and all had severe or extreme obstruction. At 26 weeks, mean NOSE score was 69% lower at 24.7 (P <.0001) with 95% two‐sided confidence intervals 48.5 to 61.1 for decrease. The decrease in NOSE score did not differ significantly between patients who did or did not have prior nasal surgery. Patient satisfaction mean by survey was 8.2 of 10. Conclusion: In office treatment of internal nasal valve obstruction using a bipolar radiofrequency device is safe and well‐tolerated. Nasal obstruction, as assessed using the NOSE questionnaire at 26 weeks, was markedly improved with high patient satisfaction. Level of Evidence: 2b, prospective cohort [ABSTRACT FROM AUTHOR]

BACKGROUND Cordyceps militaris is a medicine and food dual‐purpose mushroom extensively cultivated and consumed in East and Southeast Asia for centuries. However, it has an extremely short shelf life of 3–4 days at room temperature. C. militaris was pasteurized for 10, 20, and 30 min by radio‐frequency (RF) at an electrode gap of 20 mm. The effect of RF heating on the microbial load, color, texture, and flavor attributes of C. militaris was evaluated and compared with those sterilized by conventional high‐pressure steam. RESULTS: RF heating contributed to good heating uniformity, uniform temperature distribution, and significant decrease in total microbial load. C. militaris heated by RF exhibited unnoticeable total color difference compared with unpasteurized ones, while those sterilized by high‐pressure steam presented undesired and unacceptable browning. Insignificant differences in hardness and chewiness were observed after RF heating. Improvements in mushroom‐like flavor occurred after 10 and 20 min of RF heating. CONCLUSION: This study suggests that RF heating for pasteurization of edible mushrooms has promising prospects. Evaluation of RF heating on the taste and nutritional characteristics of edible mushrooms is needed in future work. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

This article presents an optimization technique aiming to improve gain and noise performances simultaneously, through the design of a cost-effective low noise amplifier (LNA) in a mixed-signal CMOS process without an RF triple-well option. To alleviate the inherent body-effect within a twin-well MOS transistor, we applied a transmission-line based source degeneration inductor Ls instead of a conventional spiral in the RF amplifier. In our design, without additional DC-power payment, the gain and noise figures ( NF50) improved by 26% and 7.1%, respectively, when compared to the conventional spiral. The proposed LNA was implemented in a 0.18 µm 1-poly 6-metal mixed-signal CMOS process, and achieved a 13.1 dB gain and 2.72 dB noise figure while dissipating 8.76 mA from a 1.4 V supply. [ABSTRACT FROM AUTHOR]

ABSTRACT In this letter, we evaluate the noise figure (NF) improvement that results from controlling the parasitic gate resistance of a radio-frequency (RF) low noise amplifier (LNA). By optimizing the number of gate contacts and wiring modifications in our fabricated device, the customized layout exhibited an approximately 25% reduction in the gate electrode resistance (Relect) when compared to a reference device provided by the foundry. The fabricated LNA, which used a customized layout in a 0.18 μm standard CMOS process, improved the NF by almost 6% without affecting the Si area and DC power consumption, and exhibited a NF of 2.57 dB, gain of 11.6 dB, DC power dissipation of 4.0 mW, and return loss at both the input and output of more than 10 dB. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:1405-1407, 2017 [ABSTRACT FROM AUTHOR]

Radio-frequency (RF) homogeneous dielectric barrier discharge (DBD) is compared to low frequency glow DBD to make silicon oxide from Ar/NH3/SiH4. RF-DBD is a more powerful discharge, and the growth rate is not limited by precursor dissociation rate but by powder formation. Powders are not deposited in the plasma zone but in the post-discharge due to their trapping by the electric field. Modulation of the RF-DBD is a useful solution to avoid powder formation. Powders are systematically avoided if the plasma energy during time on stays below 750 µJ. RF-DBD modulation also increases the growth rate twofold compare to continuous RF. The optimum growth rate without powder corresponds to a short Ton to limit precursor dissociation, a long Toff to enhance diffusion and a fast repeat frequency to increase deposition rate. [ABSTRACT FROM AUTHOR]

In the last few years we are witnessing a dramatic increase in the number of CIEDs implanted. At the same time new emitters are constantly entering the marketplace and more and more medical procedures are based on electromagnetic fields as well. Therefore, the topic of the interaction of CIEDs with the EMI is a real, actual and challenging one. In the non‐medical environment several types of devices may be intentional or non‐intentional sources of EMI. Most of the studies reported in literature focused on mobile phones, metal detectors, as well as on headphones or digital players, but many other instruments and tools may generate electromagnetic fields. In the medical environment most of the attention is paid to MRI and recently new PM and MRI conditional ICDs have been developed and launched in the market, but the risk of interaction is present also with ionizing radiation, electrical nerve stimulation and electrosurgery. Pacemaker/ICD manufacturers are incorporating state of the art technology to make implantable devices less susceptible to EMI. However, patients and emitter manufacturers should be aware that limitations exist and that there is not complete immunity to EMI. [ABSTRACT FROM AUTHOR]

In this paper, Ti-doped GaZnO (GTZO) transparent conductive oxide (TCO) was deposited by radio-frequency magnetron sputtering on glass substrates. X-ray diffraction (XRD) of the crystalline quality of the resulting GTZO TCO showed a (002) peak with increased intensity for films deposited with annealing temperature from as-grown to 450 °C. The low thin film resistivity of 1.57 × 10-4 Ω-cm, and average optical transmittance of 91% in the range between 350 and 800 nm, are also demonstrated to show the potential applications of this work. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

A new ionization technique: A radio‐frequency signal was used to ionize neutral organic molecules in the ultrahigh‐vacuum region of a Fourier transform ion cyclotron resonance mass spectrometer. Radio‐frequency ionization (RFI) yielded signal/noise (S/N) ratios roughly six times higher than those generated by conventional 70 eV electron impact ionization (EI). [ABSTRACT FROM AUTHOR]

1 Among the potential effects of exposure to high levels of radio-frequency energy (RFE) (which includes microwaves), an increase in body temperature is the primary consequence. Release of autacoids and activity of the autonomic nervous system may influence (or be directly responsible for) some of the physiological changes that occur in conjunction with this hyperthermia. 2 The main focus of this review is the interaction of autacoids and the autonomic nervous system with cardiovascular changes during heating. Differences between environmental and RFE-induced heating (such as rate of temperature change and degree of skin vs. core heating) may be important when considering these effects. 3 Antihistamines exhibited no beneficial effect on circulatory collapse during RFE-induced heating. The serotonergic blocker methysergide decreased survival time in rats during terminal RFE exposure, despite no effects on heart rate (HR) or blood pressure. Although blockade of platelet-activating factor resulted in lower HR before RFE exposure, there was a lack of effect on the subsequent increase in HR during heating. Nitric oxide did not contribute to the hypotension that occurs due to rapid heating by RFE exposure. There have been either no or very limited studies of effects of prostaglandins, bradykinin, or angiotensin on RFE-induced heating responses. 4 β-Adrenoceptor antagonism with propranolol resulted in significantly decreased survival times and lower final colonic temperatures during RFE exposure. A lack of effects of nadolol on survival time and temperature, coupled with its poor ability to traverse the blood–brain barrier, suggests that central β-adrenergic stimulation rather than peripheral stimulation may alter thermoregulation. 5 Effects of the autonomic nervous system (as studied by adrenoceptor blockade) on potassium changes during heating have not been fully investigated. Such changes could be important in animals’ responses to RFE and other modalities of heating, and should be studied in future. [ABSTRACT FROM AUTHOR]