Radio Frequency Parameters Research Articles

Valvular leaflets and epicardial fat have a significant effect on lesion size in RF ablation

Abstract Introduction Radiofrequency (RF) current is the classic ablation technology in the EP lab. Underlying RF ablation parameters, such as RF power, impedance, duration and contact force are used to calculate expected lesion size. Furthermore, lesion indices (LSI, AI) are applied to estimate expected lesion durability and contiguity. Purpose The aim of this ex-vivo study was to assess the influence of valvular tissue and epicardial fat on RF lesion creation. Methods An ex-vivo porcine model was created to create RF lesions under standardized conditions. Temperature was constantly kept at 37°C using a thermostat and a circulation pump was used to imitate blood flow. A contact force sensing ablation catheter (ST SF) was used to create RF lesions using predefined RF parameters (30W/50W, CF 10g, 30sec). Lesions using the same RF parameters were created above and right next to mitral valve leaflets as well as on epicardial fat tissue (figure 1). Lesions were then dissected, and lesion depths and diameters were measured using a digital precision caliper. Results A total of 210 lesions were created. RF lesions ablated on valvular leaflets showed significantly smaller lesion depth and lesion diameter when compared to RF lesions ablated right next to valvular (diameter 8.0±2.0mm vs 10.8±1.8mm; depth 4.4±1.2 vs 7.7±1.6mm, p<0.01). Lesions ablated on epicardial fat were significantly smaller in diameter (9.2±1.5) and depth (6.5±1.8) than purely endocardial lesions (p<0.01). Examples are depicted in figure 1. Conclusions Valvular leaflets as well as epicardial fat tissue have a significant influence on RF lesion creation. RF ablation performed on valvular leaflets or epicardial fat results in significantly (p<0.01) smaller lesions when compared to RF ablations directly on endocardial tissue. This should be considered in ablations of accessory pathways and epicardial procedures.Figure 1

Optimization and analysis of Si/SiGe strained vertically stacked heterostructure on insulator FeFinFET for high performance analog and RF applications

As semiconductor technology advances, the exploration of novel materials and device architectures becomes imperative to meet the growing demands of integrated circuits for analog and radio-frequency (RF) applications. In this paper, various advanced technologies have been amalgamated such as integration of ferroelectric layer in multigate FinFET along with the adaptation of SOI technology. Further strain technology is also used which employs a tri-layered strained-silicon channel system with the help of SiGe to form Vertically Stacked Heterostructure on Insulator Ferroelectric based FinFET (VS-HOI-FeFinFET) and on comparison with baseline FeFinFET, it is found to show remarkable improvements in terms of various measured parameters such as drain current, switching ratio, threshold voltage and subthreshold swing. Subsequently, gate stacking architecture is incorporated in VS-HOI-FeFinFET to further optimize the device performance. The four different configurations C1 to C4 are taken in terms of four different combinations of gate stack materials considered for gate oxide such as C1(SiO2+Al2O3), C2(SiO2+HfO2), C3(Al2O3), and C4(Al2O3+HfO2). It is found that the static and analog performance of VS-HOI-GS-FeFinFET enhance sequentially from configuration C1 to C4 such as switching ratio is enhanced upto around 5 times, DIBL and quality factor are improved by around 41% and 58% respectively along with significant improvement in device efficiency, early voltage, intrinsic gain, output conductance and output resistance. Subsequently performance optimization of VS-HOI-GS-FeFinFET with variation in mole fraction of germanium is also explored for various analog metrics. Further, several RF parameters are also explored and it is observed that the gain frequency product (GFP) and gain transconductance frequency product (GTFP) are augmented by around three times in magnitude along with 16% reduction in the unity gain cut off frequency in C4 configuration, exhibiting its ability of high frequency amplification with minimized noise distortion thus makes the device suitable for various high performance Analog and RF applications.

A wireless, battery-free microneedle patch with light-cured swellable hydrogel for minimally-invasive glucose detection

The escalating global prevalence of diabetes necessitates the development of advanced diagnostic methodologies that are both minimally invasive and devoid of discomfort. This study introduces a wireless battery-free passive microneedle patch with CMC-pHEA GelMA-GOx (CMC: sodium carboxymethyl cellulose; pHEA: polyethylene glycol diacrylate, 2-hydroxyethyl acrylate; GelMA: gelatin methacryloyl; GOx: glucose oxidase) light-cured swellable hydrogel for minimally-invasive glucose detection. The core of this technology combines microneedle with Radio-Frequency (RF) coupling detection, achieving extraction capacity; the microneedle lies in the use of composite hydrogel composed of a freeze-dried CMC-pHEA nanogel and GelMA-GOx, specifically fabricated to be selectively glucose-responsive through cross-linking with glucose oxidase. Upon exposure to interstitial fluid, the hydrogel microneedles swell in proportion to the glucose concentration, enabling glucose binding and facilitating the detection process. A flexible antenna, which is integral to the microneedle substrate as a passive sensing component, detects changes in the swelling of the hydrogel; these are reflected in the RF parameters (frequency, magnitude) variations, which are directly correlated with glucose levels. Furthermore, the results are near field wirelessly detected through a readout coil, simplifying sensing patch configurations. This method not only integrates the glucose monitoring process by combining extraction and detection into a single step but also enhances patient comfort. The platform’s sensitivity, specificity, and minimal invasiveness make it a promising tool for diabetes management and continuous glucose monitoring. By demonstrating the successful application of RF technology in wireless sensing applications, this study paves the way for advanced, user-friendly glucose monitoring solutions.

Assessment of Measurement Uncertainty for S-Parameter Measurement Based on Covariance Matrix.

S-parameters are widely used to detail the scattering parameters of radio frequency (RF) components and microwave circuit modules. The vector network analyzer (VNA) is the most commonly used device for measuring S-parameters. Given the multiple frequency points, complex values, and intricate uncertainty propagation involved, accurately assessing the uncertainty of S-parameter measurements is difficult. In this study, we proposed a new method for assessing S-parameter uncertainty based on the covariance matrices, tracing back to the nominal uncertainty of calibration standards. First, we analyzed the relevant theory of uncertainty assessment using covariance matrices and subsequently deduced the mechanism of Type B uncertainty propagating from calibration standards to error model coefficients and S-parameter measurements to evaluate Type B measurement uncertainty. In this study, a novel measurement system was constructed for measuring grounded coplanar waveguides by using a VNA and calibration standards with 8- and 12-error models. Initially, the model assessed the Type B uncertainty of measuring four S-parameters of a grounded coplanar waveguide. Next, the VNA calibrated with the 12-error model was used to conduct multiple repeated measurements to assess the Type A uncertainty of the grounded coplanar waveguide. Finally, the composite uncertainty was constructed, which demonstrated that the proposed method can be used for assessing the uncertainty of S-parameters.

Validation of predictive models for lesion transmurality and steam-pop using ex-vivo porcine bipolar ablation model

Abstract Introduction Bipolar ablation has been reported to create deeper myocardial ablation lesion as compared to unipolar ablation, however, there is currently no standardized strategy for bipolar ablation settings such as energy and ablation time. Purpose The aim of the present study is to test our hypothesis that both transmural lesion creation and steam-pop occurrence during bipolar ablation can be predicted by the settings of bipolar ablation and the myocardial tissue characteristics such as tissue thickness and initial impedance prior to RF. Methods Using porcine cardiac tissues, we conducted ex-vivo ablation experiments. Commercially available radiofrequency (RF) ablation catheters were utilized for the procedures. Each ablation catheter was positioned bilaterally on the myocardial slices at a 45-degree angle, maintaining a targeted contact force of 10g. We documented the occurrence of steam-pop under various conditions, modulating tissue thickness (5-20 mm), RF power (20, 30, 40, 50 Watt) and ablation duration (20 sec, 40 sec, 60 sec, 180 sec). Generalized linear models (GLM) were developed to forecast the creation of transmural lesion and steam-pop incidents, drawing on the bipolar ablation settings and myocardial tissue characteristics. Subsequently, we engaged in an additional series of experiments to validate the models. Results In total, 194 bipolar applications were utilized as training data. Transmural lesions and steam-pops were observed in 95 (49%), and 11 applications (5.7%), respectively. We constructed GLM using the RF energy (Watt), tissue thickness (mm), initial bipolar impedance (Ohm), impedance drop during the first 5 seconds of application (Ohm), and RF duration (seconds). For transmurality prediction the model validation was conducted with another independent 111 RF applications (102 transmural, and 25 steam-pops). The GLM, which utilized RF energy, tissue thickness, initial bipolar impedance, and RF duration, performed the best performance in predicting transmural lesion creation (AUC 0.94 [0.90-0.99], sensitivity 86 %, specificity 100 %). However, the exclusion of ‘tissue thickness’ from this model led to a significant decrease in its predictive performance (AUC 0.69 [0.48-0.89], sensitivity 47%, specificity 100%, P=0.0057). For pop prediction in validation data, the GLM utilizing RF energy, initial bipolar impedance and impedance drop showed the best performance (AUC 0.90 [0.83-0.97], sensitivity 76 %, specificity 92 %). Conclusion Our data show that accurate assessment of tissue thickness is pivotal for predicting transmural lesion creation. To predict lesion transmurality and steam-pop incidents through RF parameters and tissue characteristics within a beating heart, further research is warranted. This could facilitate the calibration of RF settings, potentially enhancing the safety of bipolar ablation procedures.

Radiofrequency lesion in atrial wall: how variable is it? 9 Tesla MRI analysis of RF lesion volume in a swine model

Abstract Background Little is known about radiofrequency (RF) lesion volume (rLV). Most of animal or ex-vivo studies quantify the size of RF lesions size using width and/or depth, while electrophysiologists use manufacturers’ indirect indices (such as Ablation Index or Lesion Size Index). Purpose We aimed to evaluate rLV by high resolution 9-Tesla magnetic resonance imaging (MRI), in ex-vivo swine model. We studied the variability of rLV and extra-cardiac effects in two groups of swine, one treated with low energy (LE)-long application RF (20W-50 sec) and another treated with high energy (HE)-short application RF (50 W-20 sec). Methods This was a prospective observational study on 18 piglets, that were anesthetized, mechanically ventilated, and divided into LE (n = 9) and HE (n = 9) groups (Figure 1). An irrigated contact force catheter was used to perform RF applications in 4 largely separated spots: 2 on right atrium and 2 on left atrium wall. RF parameters were monitored during RF. Each animal was sacrificed after 5-7 days, and RF lesion samples were excised and acquired by 9 MRI. Results 70 RF applications were performed (36 in LE group and 34 in HE group). MRI was performed on 26 samples of LE group and 28 of HE group (Figure 2). The median RF lesion volume was 89.3 mm3 (IQR 47.9-175.9). Regarding lesion volume, the HE groups showed 35% higher volume than LE group (mean lesion volume 86.2 mm3 vs 116.3 mm3, p = 0.119). HE group also showed more complications (0 vs 7, p=0.02) and more extracardiac lesion (14 vs 18, p=0.613). Conclusions There was a wide and unpredictable variability of RF lesion on atrial wall, even under controlled experimental conditions, which could explain arrhythmias recurrences. The variability seems greatest, although not statistically significant, during HE applications. The dose/effect relationship needs to be carefully studied for treatments of cardiac arrhythmias for both RF and other forms of energy available today.Study flow-chartComparison between groups

Difference in radiofrequency ablation profile between during sinus rhythm and atrial fibrillation: Considerations in this era of high‐power short‐duration strategy

AbstractBackgroundThe concept of ablation index (AI) was introduced to evaluate radiofrequency (RF) ablation lesions. It is calculated from power, contact force (CF), and RF duration. However, other factors may also affect the quality of ablation lesions. To examine the difference in RF lesions made during sinus rhythm (SR) and atrial fibrillation (AF).MethodsSixty patients underwent index pulmonary vein isolation during SR (n = 30, SR group) or AF (n = 30, AF group). All ablations were performed with a power of 50 W, a targeted CF of 5–15 g, and AI of 400–450 using Thermocool Smarttouch SF. The CF, AI, RF duration, temperature rise (Δtemp), impedance drop (Δimp), and the CF stability of each ablation point quantified as the standard deviation of the CF (CF‐SD) were compared between the two groups.ResultsA total of 3579 ablation points were analyzed, which included 1618 and 1961 points in the SR and the AF groups, respectively. Power, average CF, RF duration per point, and the resultant AI (389 ± 59 vs. 388 ± 57) were similar for the two rhythms. However, differences were seen in the CF‐SD (3.5 ± 2.2 vs. 3.8 ± 2.1 g, p < .01), Δtemp (3.8 ± 1.3 vs. 4.0 ± 1.3°C, p < .005), and Δimp (10.3 ± 5.8 vs. 9.4 ± 5.4 Ω, p < .005).ConclusionsDespite similar AI, various RF parameters differed according to the underlying atrial rhythm. Ablation delivered during SR demonstrated less CF variability and temperature increase and greater impedance drop than during AF.

High-speed mid-infrared Mach–Zehnder electro-optical modulators in lithium niobate thin film on sapphire

Abstract In this study, high-speed mid-infrared Mach–Zehnder electro-optical modulators in x-cut lithium niobate (LN) thin film on sapphire were designed, simulated, and analyzed. The main optical parameters of three types of Mach–Zehnder modulators (MZMs) (residual LN with thickness of 0, 0.5, and 1 μm) were simulated and calculated, namely, the single-mode conditions, bending loss, separation distance between electrode edge and lithium niobate waveguide edge, optical field distribution, and half-wave voltage–length product. The main radio frequency (RF) parameters of these three types of MZMs, such as characteristic impedance, attenuation constant, RF effective index, and the –3 dB modulation bandwidth were calculated depending on the dimensions of the coplanar waveguide traveling-wave electrodes. The modulations with residual LN thickness of 0, 0.5, and 1 μm were calculated with bandwidths exceeding 140, 150, and 240 GHz, respectively, and the half-wave voltage–length product achieved was 22.4, 21.6, and 15.1 V cm, respectively. By optimizing RF and optical parameters, guidelines for device design are presented, and the achievable modulation bandwidth is significantly increased.

Numerical Analysis of the Transient Capture Dynamics of Ions by Radio Frequency

The radiofrequency imprisoned ion system can isolate the coupling effect between ion and environment, and is helpful to the precise control of ion quantum state, which is an ideal candidate system for new atomic clocks. In this paper, the coupling effect between imprisoned ion and RF potential field is quantitatively studied by using finite element numerical analysis method. The coupling process of ion and RF phase is established, and the unsteady dynamic process of ion capture is analyzed. The influence of radio frequency amplitude on ion trapping ability and the reasonable range of radio frequency parameters conducive to ion stable confinement are studied. This method can be widely used in the study of ion trap structure and electromagnetic field parameter optimization in the fields of imprisoned ion frequency scale and quantum computing, and is helpful to the development of highly coherent quantum systems.

Model-Optimizing Radiofrequency Parameters of 3D Finite Element Analysis for Ablation of Benign Thyroid Nodules.

Radiofrequency (RF) ablation represents an efficient strategy to reduce the volume of thyroid nodules. In this study, a finite element model was developed with the aim of optimizing RF parameters, e.g., input power and treatment duration, in order to achieve the target volume reduction rate (VRR) for a thyroid nodule. RF ablation is modelled as a coupled electro-thermal problem wherein the electric field is applied to induce tissue heating. The electric problem is solved with the Laplace equation, the temperature distribution is estimated with the Pennes bioheat equation, and the thermal damage is evaluated using the Arrhenius equation. The optimization model is applied to RF electrode with different active tip lengths in the interval from 5 mm to 40 mm at the 5 mm step. For each case, we also explored the influence of tumour blood perfusion rate on RF ablation outcomes. The model highlights that longer active tips are more efficient as they require lesser power and shorter treatment time to reach the target VRR. Moreover, this condition is characterized by a reduced transversal ablation zone. In addition, a higher blood perfusion increases the heat dispersion, requiring a different combination of RF power and time treatment to achieve the target VRR. The model may contribute to an improvement in patient-specific RF ablation treatment.

High-Power Short-Duration Lesion Index-Guided Posterior Wall Isolation beyond Pulmonary Vein Isolation for Persistent Atrial Fibrillation.

Background: High-power short-duration (HPSD) radiofrequency (RF) ablation has been adopted to improve atrial fibrillation (AF) ablation. Although the role of HPSD is well-established in pulmonary vein isolation (PVI), fewer data have assessed the impact of HPSD when addressing extra-pulmonary veins (PVs) targets. Therefore, this study aims to determine the safety, effectiveness, and acute outcomes of HPSD lesion index (LSI)-guided posterior wall isolation (PWI) in addition to PVI as an initial strategy in persistent atrial fibrillation (Pe-AF). Methods: Consecutive patients who underwent ablation of Pe-AF in our center between August 2021 and January 2022 were retrospectively enrolled. All patients' ablation strategy was PVI plus PWI using HPSD LSI-guided isolation. RF parameters included 50 W targeting LSI values of ≥5 on the anterior part of the PVs and anterior roofline and ≥4 for the posterior PVs aspect, bottom line, and within the posterior wall (PW). We compared the LSI values with and without acute conduction gaps after the initial first-pass PWI. Left atrial mapping was performed with the EnSite X mapping system and a high-density multipolar Grid-shaped mapping catheter. We compared the procedural characteristics using HPSD (n = 35) vs. a control group (n = 46). Results: Thirty-five consecutive patients were included in the study. PWI on top of PVI was achieved in all cases in the HPSD group. First-pass PVI was achieved in 93.3% of PVs (n = 126/135). First-pass roofline block was obtained in most patients (n = 31, 88.5%), while first-pass block of the bottom line was only achieved in 51.4% (n = 18). There were no significant differences compared to the control group; first-pass PVI was achieved in 94.9% of PVs (n = 169/178), first-pass roofline block in 89.1%, and bottom-line in 45.6% of patients. To achieve complete PWI with HPSD, scattered RF applications within the PW were necessary. No electrical reconnection of the PW was found after adenosine administration and the waiting period. The procedure and RF times were significantly shorter in the HPSD group compared to the control group, with values of 116.2 ± 10.9 vs. 144.5 ± 11.3 min, and 19.8 ± 3.6 vs. 26.3 ± 6.4 min, respectively, p < 0.001. Fluoroscopy time was comparable between both groups. No procedural complications were observed. At the 12-month follow-up, 71.4% of patients remained free from AF, with no differences between the groups. Conclusions: HPSD LSI-guided PWI on top of PVI seems effective and safe. Compared to a control group, HPSD is associated with similar rates of first-pass PWI and PVI but with a shorter procedural and RF time.

Integrated barium titanate electro-optic modulators operating at CMOS-compatible voltage.

We propose monolithically integrated electro-optical modulators based on thin-film x-cut barium titanate that exhibit large modulation bandwidth and operate at voltages compatible with complementary metal-oxide-semiconductor technology. The optical and radio frequency parameters of the modulator are systematically simulated, calculated, and optimized, respectively. Our simulation includes the evaluation of single-mode conditions, the separation distance between the electrode edge and the waveguide edge, bending loss, optical field distribution, and half-wave voltage-length product for optical parameters, and characteristic impedance, attenuation constant, radio frequency effective index, and -3d B modulation bandwidth for radio frequency parameters. By engineering both the microwave and photonic circuits, we have achieved high electro-optical efficiencies and group-velocity matching simultaneously. Our numerical simulation and theoretical analysis show that the half-wave voltage-length product was 0.48V·cm, and the -3d B modulation bandwidths with a device length of 5mm and 10mm were 262GHz and 107GHz, respectively. Overall, our study highlights the potential of the proposed modulators for low driving voltage and high-performance optical communication systems.

DFT based atomic modeling and Analog/RF analysis of ferroelectric HfO2 based improved FET device

In this study, we systematically investigated the Analog/RF and linearity parameter of SM DGNCFET (single metal double gate negative capacitance field effect transistor) and DM DGNCFET (double metal double gate negative capacitance Field effect transistor) with the help of Cogenda Visual TCAD simulator, and also demonstrated the enhancement in the electronic and optical properties of Si-doping bulk structure by using the Quantum ATK. The analog parameters are enhanced for SM DGNCFET such better performance of switching ratio 279 times better, DIBL 54% lower, SS decay, and some other improved parameter transconductance, TGF and Radio frequency parameter is also enhanced, transconductance frequency product (TFP) for improving reliability and stability of device. Linearity parameters like that second and third order transconductance (gm2, g m3), voltage intercept point for 2nd, 3rd. Tran Blaha modified Becke Johnson (TB-mBJ) approxiamation gives the accurate band gap of crystal. In DFT based atomic study, 12.5% of Si doping in bulk structure reveals better results for ferroelectric HfO2 based crystal in the direct band gap of bandstructure is zero, Density of state (DOS) is also improved conductivity for Si doping crystal. Hence, Si doping in crystal structure is also better for conductivity.

A miniature and reusable radiofrequency biosensor combining microfluidic and integrated passive technology for glucose detection

This work demonstrates a microfluidic radiofrequency (RF) biosensor system consisting of a resonator-based chip that provides a high-intensity surface electromagnetic field with measured parameters and a microfluidic chamber that provides a cavity for loading glucose solution, which together enable non-contact, fast, and real-time glucose measurements. The sensing relies on RF parameters affected by the changes in the permittivity of different glucose concentration solutions. Modeling and analysis of RF chip with different microfluidic module configurations are presented to construct an optimum high-sensitivity system with a compact size of 2 × 2 × 0.5 cm3. The experimental results showed that the constructed system exhibited high sensitivity (0.163 dB*ml/mg) and a wide detection range (0.32–9 mg/ml). The system possesses real-time detection capability and anti-interference ability. Moreover, other RF-parameter responses (S12, phase, Smith chart, real, and imaginary) curves to concentration were explored with exhibiting regular variations. Especially, multiple-parameters combination enabled system distinguishability on single-solute solutions. Taking advantage of RF detection combined with microfluidic for glucose detection, this study provides perspective insights into optimum RF sensor construction and extends its potential applications.

Implementation on SDR platform of algorithms for noncoherent reception of optimal signals built on the basis of eigenfunctions

Formulation of the problem. When transmitting data at speeds above the Nyquist barrier, the algorithmic and computational complexity of radio modems increases significantly, especially with incoherent signal reception. Non-coherent reception algorithms can be implemented on a software-defined radio platform, on which optimal signals are formed and received. The ability to programmatically change the radio frequency parameters of signals without making structural changes to the transmit-receive path can significantly reduce the computing resources of radio modems. The goal is to determine the possibility of practical implementation on the SDR platform (Software Defined Radio) of noncoherent processing algorithms with decision feedback with the choice of optimal values of the observation interval for symbol rates R&gt;1/T using optimal signals built on the basis of eigenfunctions. Results. The possibility of using differential modulation of optimal signals, the forms of which are obtained as a result of solving an optimization problem in accordance with the criterion of the maximum decay rate of the spectrum level outside the occupied frequency band, is shown for packet data transmission protocols and the use of an incoherent processing algorithm in channels with additive Gaussian noise. It is shown that when using algorithms of incoherent element-by-element processing with optimization of the observation interval, it is possible to ensure stable reception of binary optimal signals up to transmission rates exceeding the Nyquist barrier by 1.66 times and for an error probability of 10–3, the energy loss is about 18 dB relative to potential noise immunity. The digital modem of optimal spectrally efficient signals, built on the basis of the SDR platform, makes it possible to conduct spectral and energy efficiency studies in real time in the presence of additive channel noise, and the influence of clock synchronization inaccuracies during packet messaging leads to energy losses of no more than 1 dB. Practical significance. The use of differential modulation of optimal signals can be used in digital television and radio broadcasting systems in the European digital television standards DVB-S2 (Digital Video Broadcasting Satellite Second Generation), DVB-T2 (Digital Video Broadcasting Terrestrial Second Generation).

TCAD performance analysis of a symmetrical double gate non-aligned junction FET device with high and low dielectric gate oxide in sub-100 nm regime

ABSTRACT This paper presents 2D-Sentaurus TCAD tool results of a Non-aligned Double Gate Junction N-Channel Field Effect Transistor (NADGNFET) device; the response analysis of device to gate oxide dielectric materials, i.e. silicon dioxide (SiO2) and hafnium dioxide (HfO2), is also presented. The NADGNFET in 90 nm device length is the proposal of this work to improve the second-order effects as well transistor non-linear performance at radio frequency (RF). A non-aligned device in this work consists of two gates extending to the source and drain region with 44.44% channel overlap in total device length. As compared to a full overlap device, the present device has shown better results in Analog Figure of Merit (FOM) and RF parameters like: ION current, ION/IOFF ratio, DIBL (Drain Induced Barrier lowering), SS (Subthreshold Swing), Intrinsic gain (AVO), Transconductance Generation Factor (TGF), Transconductance Frequency Product (TFP), Cut-off frequency (fT), Intercepted Input Power-3 (IIP3) and Intermodulation Distortion power-3 (IMD3). The use of dielectric material with high dielectric constant (HfO2, k = 24) in gate oxide reduces DIBL by 50%, increases the ION/IOFF ratio by 59.1%, increases the Intrinsic gain by 50% compared to low-k dielectric constant (SiO2, k = 3.9). However, results also shows that high-frequency parameters’ results were better with low-k dielectric constant. This gives a trade-off in device application.

Ultrasound Imaging With a Flexible Probe Based on Element Array Geometry Estimation Using Deep Neural Network.

Conventionally, ultrasound (US) diagnosis is performed using hand-held rigid probes. Such devices are difficult to be used for long-term monitoring because they need to be continuously pressed against the body to remove the air between the probe and body. Flexible probes, which can deform and effectively adhere to the body, are a promising technology for long-term monitoring applications. However, owing to the flexible element array geometry, the reconstructed image becomes blurred and distorted. In this study, we propose a flexible probe U.S. imaging method based on element array geometry estimation from radio frequency (RF) data using a deep neural network (DNN). The input and output of the DNN are the RF data and parameters that determine the element array geometry, respectively. The DNN was first trained from scratch with simulation data and then fine-tuned with in vivo data. The DNN performance was evaluated according to the element position mean absolute error (MAE) and the reconstructed image quality. The reconstructed image quality was evaluated with peak-signal-to-noise ratio (PSNR) and mean structural similarity (MSSIM). In the test conducted with simulation data, the average element position MAE was 0.86 mm, and the average reconstructed image PSNR and MSSIM were 20.6 and 0.791, respectively. In the test conducted with in vivo data, the average element position MAE was 1.11 mm, and the average reconstructed image PSNR and MSSIM were 19.4 and 0.798, respectively. The average estimation time was 0.045 s. These results demonstrate the feasibility of the proposed method for long-term real-time monitoring using flexible probes.

Effect of substrate temperatures on structural, optical and dispersion energy parameters of RF sputtered nickel oxide thin films

Thin films of nickel oxide (NiO) have been widely identified as a promising ion storage layer in electrochromic devices owing to their excellent electrochemical properties. There is, however, a lack of accurate description of their optical parameters, which are quite important to explore the optical and electrochromic characteristics of NiO. In the present investigation, nickel oxide (NiO) thin films have been deposited using radio frequency (RF) magnetron sputtering at different substrate temperatures (Tsub) viz. 100, 200 and 300 °C. The consequences of substrate temperature on the structural, morphological, optical, and vibrational properties were examined. The XRD pattern showed increased crystallinity with an increase in substrate temperature. Surface morphology revealed an ultrafine and smooth morphology. The average optical transmittance varied between 64% and 85%. Shrinkage in the energy bandgap was observed with the change in substrate temperature. The values of optical parameters like refractive index (n), extinction coefficient (k), the real part of the dielectric constant (ε1), the imaginary part of the dielectric constant (ϵ2), and porosity of NiO films were found to change with an increase in substrate temperature. The effect of substrate temperature on dispersion energy parameters (Eo and Ed) derived from the Wemple-DiDomenico model was calculated and discussed in detail. Room temperature photoluminescence studies revealed peaks along 3.39 eV (365 nm) and 2.95 eV (420 nm) nm as a consequence of band-band PL phenomena for nickel oxide and defects. In the Raman spectrum, one predominant peak around 560 cm−1 corresponds to the one-phonon LO mode, and another minor peak at 1100 cm−1 owing to the two-phonon LO mode were observed, which arises from Ni–O vibrations. The observed results reveal the potential application of the NiO films in optoelectronic and electrochromic device applications.

Stent-based electrode for radiofrequency ablation in the rat esophagus: a preliminary study

Endoluminal radiofrequency (RF) ablation has been widely used as a safe and effective treatment for Barrett’s esophagus. However, inadequate RF ablation may occur due to insufficient contact between the electrode and target tissues. Herein, a stent-based monopolar RF electrode (SE) was developed to evenly deliver RF energy to the inner wall of the rat esophagus. The optimal RF parameters were evaluated in the exposed rat esophagus. The temperature in the rat esophagus reached 70 ℃ in 89 s at 30 W, 59 s at 40 W, and 34 s at 50 W. The technical feasibility and efficacy of RF ablation using SE were evaluated based on changes in histological transformation and immunohistochemical parameters of tissues compared at immediately, 1 and 2 weeks after the procedure. The degrees of inflammatory cell infiltration, fibrotic changes, TUNEL, and HSP70 in the RF-ablated rat esophagus were significantly higher than compared with sham control (all p < 0.05). TUNEL-positive deposition gradually decreased, but HSP 70-positive deposition maintained a similar level for 2 weeks. The stent-based RF ablation was technically feasible and effective in evenly inducing thermal damages to the rat esophagus. The RF ablation system using the SE may represent a promising treatment for endoluminal malignancies.

High-Performance Electro-Optical Mach–Zehnder Modulators in a Silicon Nitride–Lithium Niobate Thin-Film Hybrid Platform

We analyzed a Mach–Zehnder electro-optical modulator based on a silicon nitride strip–loaded waveguide on 0.5 μm thick x-cut lithium niobate thin film. The optical and radio frequency parameters for two different modulator structures (Type I: packaged with 2 μm thick SiO2 and Type II: unpackaged) were simulated, calculated, and optimized. The Optical parameters included the single-mode conditions, effective indices, the separation distance between the electrode edge and the Si3N4-strip-loaded edge, optical power distribution, bending loss, optical field distribution, and half-wave voltage. The radio frequency parameters included the characteristic impedance, attenuation constant, radio frequency effective index, and −3 dB modulation bandwidth. According to the numerical simulation and theoretical analysis, the half-wave voltage product and the −3 dB modulation bandwidth were, respectively, 2.85 V·cm and 0.4 THz for Type I modulator, and 2.33 V·cm and 1.26 THz for Type II modulator, with a device length of 3 mm.