AC Sensitivity Research Articles

The [18F]F-FDG PET/CT Radiomics Classifier of Histologic Subtypes and Anatomical Disease Origins across Various Malignancies: A Proof-of-Principle Study.

We aimed to investigate whether [18F]F-FDG-PET/CT-derived radiomics can classify histologic subtypes and determine the anatomical origin of various malignancies. In this IRB-approved retrospective study, 391 patients (age = 66.7 ± 11.2) with pulmonary (n = 142), gastroesophageal (n = 128) and head and neck (n = 121) malignancies were included. Image segmentation and feature extraction were performed semi-automatically. Two models (all possible subset regression [APS] and recursive partitioning) were employed to predict histology (squamous cell carcinoma [SCC; n = 219] vs. adenocarcinoma [AC; n = 172]), the anatomical origin, and histology plus anatomical origin. The recursive partitioning algorithm outperformed APS to determine histology (sensitivity 0.90 vs. 0.73; specificity 0.77 vs. 0.65). The recursive partitioning algorithm also revealed good predictive ability regarding anatomical origin. Particularly, pulmonary malignancies were identified with high accuracy (sensitivity 0.93; specificity 0.98). Finally, a model for the synchronous prediction of histology and anatomical disease origin resulted in high accuracy in determining gastroesophageal AC (sensitivity 0.88; specificity 0.92), pulmonary AC (sensitivity 0.89; specificity 0.88) and head and neck SCC (sensitivity 0.91; specificity 0.92). Adding PET-features was associated with marginal incremental value for both the prediction of histology and origin in the APS model. Overall, our study demonstrated a good predictive ability to determine patients' histology and anatomical origin using [18F]F-FDG-PET/CT-derived radiomics features, mainly from CT.

A flexible magnetic detector based on transferred ferroelectric/ferromagnetic thin film heterostructure

A flexible magnetic detector based on ferroelectric/ferromagnetic (PZT/Metglas) thin film heterostructure is developed by using etching and transferring technique. The transferred PZT film still exhibits (001)-oriented or very highly textured structure with good ferroelectricity (P r = 50 μC cm−2 and E c = 150 kV cm−1). Magnetoelectric (ME) voltage coefficient of the PZT/Metglas film heterostructure approaches 5.1 V cm−1 Oe at resonance frequency (57.5 kHz). The flexible detector has a sensitivity of AC 0.3 nT and DC 1 Oe with high stability for magnetic field detection. Our demonstration provides a viable approach for realizing ME thin film transfer technology, which is of great significance for future applications on flexible magnetic detectors.

Carbon-graphene-epoxy sandwich dielectric for improved dielectric response to humidity

A sandwich structure of carbon-epoxy laminate with graphene nanoplatelets is used for increasing the AC conductivity, dielectric constant and sensitivity towards moisture. The Quasi Fickian distribution of moisture absorption of epoxy is retained with the inclusion of carbon fibers and graphene nanoplatelets of 1 weight percent. The effect of relative humidity (RH) over a range of 30–90% on AC conductivity and capacitance has been investigated. Use of carbon fibers with graphene nanoplatelets significantly enhances the electrical conductivity and dielectric constant as compared to carbon-epoxy laminate without graphene nanoplatelets. The two parameters reveal linear dependence on humidity in the low frequency range of 100–1000 Hz. The AC conductivity increases at the rate of 2 nSm−1/% RH in laminate with carbon fiber and it increases to 50 nSm−1/%RH with the incorporation of graphene nanoplatelets. The increase in AC conductivity from 100 Hz to 1000 Hz is in the range of 0.1 to 0.2 μS/m with carbon fibers and it increases from 1 to 4 μS/m with the inclusion of graphenenanoplatelets. Increase is AC conductivity from 1 kHz to 10 MHz is by five orders of magnitude, with a steep increase around 5 MHz in both laminates. The incorporation of graphenenanoplatelets helps to increase the dielectric constant by 2.4–2.8 times as compared to epoxy with carbon fiber. The swelling in the laminates estimated after 96 h of exposure to 90% RH is observed to be less than 0.05%. The use of graphenenanoplatelets improves moisture sensitivity of the carbon-epoxy laminate.

Neural network-aided optimisation of a radio-frequency atomic magnetometer.

Efficient unsupervised optimisation of atomic magnetometers is a requirement in many applications, where direct intervention of an operator is not feasible. The efficient extraction of the optimal operating conditions from a small sample of experimental data requires a robust automated regression of the available data. Here we address this issue and propose the use of general regression neural networks as a tool for the optimisation of atomic magnetometers which does not require human supervision and is efficient, as it is ideally suited to operating with a small sample of data as input. As a case study, we specifically demonstrate the optimisation of an unshielded radio-frequency atomic magnetometer by using a general regression neural network which establishes a mapping between three input variables, the cell temperature, the pump beam power and the probe beam power, and one output variable, the AC sensitivity. The optimisation results into an AC sensitivity of 44 fT/Hz at 26 kHz.

Soft fault diagnosis in linear circuits: Test selection and non-iterative identification procedure

The paper deals with the diagnosis of soft faults in linear electronic circuits. Circuits containing operational amplifiers operating at low frequencies are considered. A method for identifying single and double faults in the AC domain is proposed. The method is non-iterative and relies on certain relations derived from the modified nodal description of the circuit. An essential part of the paper is a procedure enabling the selection of measurement nodes and test frequencies. The algorithm considers the AC sensitivities, the measurement accuracy, and the diagnostic method applied. The effectiveness of both methods was verified on several electronic circuits. The simulation and laboratory tests were done. Considering parameter tolerances and measurement uncertainties leads to determining intervals of parameter values covering the actual faults.

Studying the impact of aggregates and mix volumetric properties on the moisture resistance of asphalt concrete using a feed-Forward artificial neural network

Several studies have reported the effect of various additives on the moisture resistance of AC, but limited studies explored the impact of aggregate’s properties on the moisture sensitivity of AC. In this study, the influence of aggregate properties and mix’s volumetric properties on the moisture sensitivity of AC was studied. The moisture sensitivity of the AC was based on Retained Stability Index (RSI). The study utilised results from 319 plant-produced asphalt mixtures. The was modelled as a function of aggregates and mix’s variables using Artificial Neural Network (ANN). The variables studied include air voids , void in mineral aggregates , clay lump , Los Angeles’s abrasion , soundness value (SV), sand equivalence value , gradation and mix type. Profile method along with weight-connection relative importance ranking were employed to analyse the influence of the input variables on the . The relationship between these variables and the fits higher order polynomial functions.

Sandwich structure magnetometer with a high sensitivity and signal-to-noise ratio based on an ultrahigh-Q CaF2 resonator.

Whispering gallery mode (WGM) resonators with an ultrahigh quality (Q) factor provide an extremely high resolution for high-precision sensing. However, it is difficult to use them directly in magnetic sensors because of the transparency to the magnetic field. In this paper, a sandwich structure consisting of a neodymium iron boron magnet and calcium fluoride resonator with a Q factor of 109 is proposed. The experimental results show that, compared with the conventional magnetometer, the signal-to-noise ratio of the optical WGM magnetometer reaches 62dB, with the direct current sensitivity of 42.59MHz/mT and the AC sensitivity of 794p T H z -1/2 at 42kHz.

A radio-frequency Bose–Einstein condensate magnetometer

We report on a radio frequency magnetometer employing a Bose–Einstein condensate of 87Rb atoms held in a dipole trap. An AC sensitivity of 296 pT/Hz is achieved at a probing volume of 3.2×10−8 cm3, leading to a volume-normalized sensitivity of 53 fT/Hz cm−3. At larger probing volumes with the atoms released from the magnetic trap used in the initial phase of the evaporation sequence, the AC sensitivity is improved to 1.4 pT/Hz, allowing a two-mode approach for applications requiring improved sensitivity. Immediate application in high-resolution electromagnetic induction imaging is expected when compared to performance of other induction-based imaging platforms.

Optimisation of a radio-frequency atomic magnetometer: a Uniform Design approach.

High-sensitivity operation of a radio-frequency atomic magnetometer (RF-AM) requires careful setting of the system parameters, including the lasers intensity and detuning, and the vapour cell temperature. The identification of the optimal operating parameters, which ensures high sensitivity, is typically performed empirically and is often a lengthy process, which is especially labour intensive if frequent retuning of the magnetometer is required to perform different tasks. This paper demonstrates an efficient approach to RF-AM performance optimisation which relies on an open-loop optimisation technique based on Uniform Design (UD). This paper specifically describes the optimisation of an unshielded RF-AM based on a 4-factor-12-level UD of the experimental parameters space. The proposed procedure is shown to lead to the efficient optimisation of the atomic magnetometer at different frequencies, and is applicable to both AC and DC sensitivity optimisation. The procedure does not require any detailed knowledge of the model underlying the operation of the RF-AM and is effective in reducing the number of experimental runs required for the optimisation. It is ideally suited to self-calibration of devices without human supervision.

Long-term estimation of the canopy photosynthesis of a leafy vegetable based on greenhouse climate conditions and nadir photographs

In horticultural crop production, accurately estimating the canopy photosynthetic rate (Ac) based on greenhouse climate conditions is of practical value for predicting and controlling crop growth and yield. We developed a method for continuously estimating Ac in a greenhouse from readily obtainable information (i.e., climatic data and canopy photographs) by combining a canopy photosynthesis model with image analysis. The canopy photosynthesis model was based on a sun/shade representation of the crop canopy combined with models of single-leaf photosynthesis, stomatal conductance, mass transfer and leaf energy balance. This combination allowed 1) the incorporation of all major climatic variables (i.e., radiation, CO2 concentration, air temperature, humidity, and wind velocity) into the Ac estimation and 2) the simultaneous estimation of Ac, canopy transpiration rate (Ec), and leaf temperature (TL). The leaf area index (Lc), which changes considerably throughout the growth period of a crop canopy, was evaluated nondestructively from the gap fractions of nadir digital photographs (i.e., the fractions of nonleaf area). The canopy photosynthesis model and image analysis results were combined and used to estimate the Ac, Ec, and TL of spinach canopies grown at ambient and elevated CO2 concentrations (c. 400 and 800 µmol mol−1, respectively). Regardless of the CO2 concentration, the estimates of Ac, Ec, and TL were in good agreement with measurements obtained with the open chamber method throughout the growth period. Analyzing the sensitivity of Ac to input variables revealed that the effects of climatic variables on Ac can vary considerably depending on the Lc and incoming radiation. The proposed method enables not only the estimation of Ac from readily obtainable information but also the quantitative evaluation of the effect of climate control on Ac in horticultural greenhouses.

PVA-ZNO nanocomposites thin films for sensing devices

The PVA/ZnO composites were prepared by solution-casting technique. The prepared PVA-ZnO composites have been characterized by X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), which confirmed the presence of ZnO in polyvinyl alcohol and the formation of the composite. AC conductivity of the nanocomposites was studied with respect to frequency. Finally, the sensing properties of these nanocomposites are also studied at room temperature.Maximum AC conductivity and sensitivity was observed in 50 wt% of ZnO in polyvinyl alcohol compared to all PVA-ZnO nanocomposites. These composites can be used for gas-sensing and super capacitor.

Sensitivity Characteristics of Electro-Optical Sensors Under AC/DC Hybrid Electric Fields in Oil Medium Environment

The measurement of ac/dc hybrid electric fields in converter transformers is important for the verification of electric field calculation model and the insulation optimization. Electro-optical (EO) sensors have obvious advantages for measuring strong electric fields, but their response characteristics and mechanisms under the action of ac/dc hybrid electric fields are not fully understood by researchers, which restricts a wide application of sensors. In this article, we first describe an improved dual-beam structure, which enables us to measure both ac and dc electric fields in oil simultaneously. Next, the complete output characteristics of the EO sensor under ac/dc hybrid electric field are obtained through experiments. The results show that measurement sensitivities of EO sensor under dc and ac electric fields are different; there is a coupling effect in measuring ac/dc hybrid electric fields: the increase of one electric field component will reduce the sensor's measurement sensitivity to the other electric field component, which is more obvious for a strong electric field. Finally, we propose the response mechanism with theoretical analysis. First, the sensitivity difference is due to the difference of electric fields inside EO crystal under ac and dc electric fields, and it is affected by the conductivity and dielectric constant of crystal and oil medium. Second, the optical nonlinearity of EO sensors under strong electric fields is the cause of coupling effect: the sensor's nonlinear modulation of a strong ac electric field will introduce coupling errors in measurement signal of the dc electric field and a strong dc electric field will move the zero point of the sensor's ac induction curve from the linear region to the nonlinear region, causing the ac sensitivity to decrease nonlinearly with the increase of the applied dc electric field. This article provides a measurement and analysis of EO sensors under ac/dc hybrid electric fields in an oil medium environment, which is beneficial to the wide application of EO sensors.

Accurate quantification and detection of Septoria glycines in soybean using quantitative PCR

Septoria brown spot, caused by Septoria glycines, is a highly prevalent foliar disease of soybean in the United States. Accurately identifying and quantifying the pathogen in soybean can provide valuable information for disease management. In this study, we describe the development and validation of a quantitative PCR (qPCR) method to detect and quantify Septoria glycines accurately. Three sets of primers and assays were designed based on the polymorphic regions on the β-tubulin, the calmodulin, and the actin genes of S. glycines. Assays designed with the actin gene (Ac) were specific to S. glycines for both conventional PCR and qPCR. The assay designed with the β-tubulin (Bt) gene was specific to S. glycines only on the qPCR. The qPCR reaction efficiency of the Ac and Bt assays was 95 % and 98 %, respectively. The sensitivity of both Ac and Bt assays was 10 pg of S. glycines gDNA. The Bt assay was validated with field samples that had different necrotic areas. Symptoms of necrosis ranging from 0 to 30 % were significant and positively correlated (r = 0.87) to the S. glycines gDNA. The S. glycines gDNA was detected as early as 1-day post-inoculation in detached leaf assays. We expect that the assays reported here could be used for disease diagnosis and to better characterize the infection process of S. glycines.

Correlation of anal cytology with follow-up histology and Human Papillomavirus genotyping: A 10-year experience from an academic medical center

BackgroundAnal cytology (AC) is accepted as a practical screening modality for anal cancer. However, studies suggest that AC and anal biopsy dysplasia correlation is less robust than in cervicovaginal specimens. The current study goals were to look at our institutional experience in a subset of ACs and correlate with surgical pathology (SP), as well as evaluate their Human Papillomavirus (HPV) status. Methods377 ACs from 169 patients (151 males and 18 females) from 2008 to 2017 were included. HPV genotyping (n = 47) and SP within one year of AC (n = 58) were reviewed. ResultsAC/SP was discrepant in 22 cases (37.9%), with a tendency towards AC underestimating the degree of dysplasia. Specifically, any abnormality on AC was 93.8% sensitive for detecting high-grade dysplasia (HGD). However, when requiring a high-grade AC diagnosis, the sensitivity decreases to 12.5%. “Other high-risk HPV” was the most common genotype (57.4%). When considered with all AC with a high-grade diagnosis, co-testing with HPV improved the sensitivity for HGD to 56.3%. Sensitivity improved further to 87.5% when only considering cases with both AC and HPV testing, and were high-risk HPV positive. Furthermore, following review and consensus diagnosis, 8 cases changed from “Discrepant” to “Agreed”, reducing the discrepancy rate to 24.1%. Remaining discrepancies were explained by sampling error. ConclusionGiven the enhanced sensitivity of AC and HPV testing together, and sampling error seen with AC leading to underestimating dysplasia, we recommend AC and HPV co-testing, as well as describing confounding factors in AC reports and obtaining consensus opinion in equivocal cases.

Method for Determining the Droop Coefficients of Hybrid Multi-Terminal HVDC Systems to Suppress AC Voltage Fluctuations

Different from voltage-source converter (VSC), reactive power absorption of line-commutated converters (LCCs) changes depending on DC voltage level. Therefore, the amount of AC voltage fluctuations at inverter side are different according to $I$ – $V$ droop constants in hybrid multi-terminal high-voltage direct current (MT-HVDC) system. This paper proposes a method for calculating the $I$ – $V$ droop constants in a hybrid MT-HVDC system to suppress these AC voltage fluctuations, based on the sensitivity of AC and DC networks. Simulations performed using PSCAD demonstrate the effectiveness of the proposed method.

Anaerobic capacity estimated by a single effort distinguishes training status in male cyclists

Measurement of anaerobic capacity through estimating the glycolytic and phosphagen energy pathways (AC[La]+PCr) has been considered a time-efficient, valid, and reproducible method, however, the sensitivity of this protocol to discriminate training levels in cyclists has not yet been elucidated. The main purpose of the present investigation was to verify the sensitivity of AC[La]+PCr to distinguish the anaerobic capacity of male cyclists with different training status. Fifty-five healthy men performed a maximum incremental test to determine maximal oxygen uptake $$(\dot{\text{V}}{{\text{O}}}_{\text{2max}})$$ and the intensity associated with it $$(i\dot{\text{V}}{{\text{O}}}_{\text{2max}})$$, and a constant-load supramaximal-intensity cycling exercise at 115% of the i$$\dot{\text{V}}{{\text{O}}}_{\text{2max}}$$ to determine anaerobic capacity through AC[La]+PCr. According to performance in the incremental test, 20 subjects were classified as untrained ($$\dot{\text{V}}{{\text{O}}}_{\text{2max}}$$ = 2.92 ± 0.28 L min−1), 25 classified as recreationally trained ($$\dot{\text{V}}{{\text{O}}}_{\text{2max}}$$3.78 ± 0.19 L min−1), and 10 classified as trained ($$\dot{\text{V}}{{\text{O}}}_{\text{2max}}$$ = 4.36 ± 0.41 L min−1). Expressed in absolute values, the trained group presented higher anaerobic capacity measured through AC[La]+PCr [4.82 ± 1.07 L (4.05–5.59 L)] than the recreationally trained [4.13 ± 0.64 L (3.87–4.4 L)] (p = 0.027) and untrained groups [3.22 ± 0.42 L (3.02–3.42 L)] (p = 0.001). In addition, the recreationally trained group also demonstrated significantly higher anaerobic capacity values than the untrained group (p = 0.001). The AC[La]+PCr was sensitive to discriminate the anaerobic capacity between trained, recreationally trained, and untrained male cyclists.

Magnetoelectric behaviors in BaTiO3/CoFe2O4/BaTiO3 laminated ceramic composites prepared by spark plasma sintering

The BaTiO3 (BTO) / CoFe2O4 (CFO) / BaTiO3 (BTO) laminated ceramic composites were prepared via spark plasma sintering (SPS). The ceramic composites were highly dense with clear boundaries between the three layers. The short time and low temperature required for densification during the SPS process diminish the possibility for unwanted reactions to occur. The BTO/CFO/BTO laminated ceramic composites exhibit excellent ME properties including: (1) maximal ME voltage coefficient as high as ~ 1.0 V/Oe cm; (2) obvious AC magnetic field frequency response and sensitivity from 102 to 107 Hz; (3) perfect ME anisotropy matches well with the theoretical fitting curve; (4) giant transverse ME voltage coefficient as large as ~ 4.1 V/Oe cm at resonance frequency of ~ 105 Hz. It is possible to fabricate several kinds of ME function devices with the BTO/CFO/BTO laminated ceramics prepared in this work.

Enhanced Magnetic Field Sensitivity in Magnetoelectric Composite Based on Positive Magnetostrictive/Negative Magnetostrictive/Piezoelectric Laminate Heterostructure

Resonance magnetoelectric (ME) responses are investigated for the ME laminate heterostructure consisting of positive magnetostrictive material FeCuNbSiB, negative magnetostrictive material Ni and piezoelectric material PZT-8. On one hand, both a built-in magnetic field induced by the strong magnetic interactions between positive magnetostrictive and negative magnetostrictive materials and an intrinsic anisotropic field with obvious hysteresis and remnant magnetization in Ni layer result in a large zero-biased ME effect. The corresponding zero-biased ME voltage coefficient reaches 10.12 V/Oe (126.5 V/cm Oe), which is about 3 times larger than that of traditional Ni/PZT-8 (NP) laminate. On the other hand, the additional stress produced by the high magnetic permeability FeCuNbSiB layer enhances the magnetostriction of Ni layer and ME response. The corresponding maximum ME voltage coefficient (dVME/dHac) is 12.09 V/Oe (150.87 V/cm Oe) at bias magnetic field $H_{\mathrm {dc}} = 4$ Oe. It is further found that even a step change of ac magnetic field less than 10−10 T can be clearly distinguished by the proposed ME composite. The value of ME voltage sensitivity to dc magnetic fields (dVME/dH $_{\mathrm {dc}})$ reaches ~76.7 mV/Oe at $H_{\mathrm {dc}}= 5$ Oe and $H_{\mathrm {ac}} =0.1$ Oe. Correspondingly, the proposed laminate heterostructure is able to possess both strong ac and dc magnetic field sensitivities.

Laser threshold magnetometry

We propose a new type of sensor, which uses diamond containing the optically active nitrogen-vacancy (NV−) centres as a laser medium. The magnetometer can be operated at room-temperature and generates light that can be readily fibre coupled, thereby permitting use in industrial applications and remote sensing. By combining laser pumping with a radio-frequency Rabi-drive field, an external magnetic field changes the fluorescence of the NV− centres. We use this change in fluorescence level to push the laser above threshold, turning it on with an intensity controlled by the external magnetic field, which provides a coherent amplification of the readout signal with very high contrast. This mechanism is qualitatively different from conventional NV−–based magnetometers which use fluorescence measurements, based on incoherent photon emission. We term our approach laser threshold magnetometer (LTM). We predict that an NV−–based LTM with a volume of 1 mm3 can achieve shot-noise limited dc sensitivity of 1.86 fT and ac sensitivity of 3.97 fT .

Quasi-static displacement calibration system for a “Violin-Mode” shadow-sensor intended for Gravitational Wave detector suspensions

This paper describes the design of, and results from, a calibration system for optical linear displacement (shadow) sensors. The shadow sensors were designed to detect "Violin-Mode" (VM) resonances in the 0.4 mm diameter silica fibre suspensions of the test masses/mirrors of Advanced Laser Interferometer Gravitational Wave Observatory gravitational wave interferometers. Each sensor illuminated the fibre under test, so as to cast its narrow shadow onto a "synthesized split photodiode" detector, the shadow falling over adjacent edges of the paired photodiodes. The apparatus described here translated a vertically orientated silica test fibre horizontally through a collimated Near InfraRed illuminating beam, whilst simultaneously capturing the separate DC "shadow notch" outputs from each of the paired split photodiode detectors. As the ratio of AC to DC photocurrent sensitivities to displacement was known, a calibration of the DC response to quasi-static shadow displacement allowed the required AC sensitivity to vibrational displacement to be found. Special techniques are described for generating the required constant scan rate for the test fibre using a DC motor-driven stage, for removing "jitter" at such low translation rates from a linear magnetic encoder, and so for capturing the two shadow-notch signals at each micrometre of the test fibre's travel. Calibration, across the four detectors of this work, gave a vibrational responsivity in voltage terms of (9.45 ± 1.20) MV (rms)/m, yielding a VM displacement sensitivity of (69 ± 13) pm (rms)/√Hz, at 500 Hz, over the required measuring span of ±0.1 mm.