dB Level Research Articles

Association of clinical characteristics and recurrence of conventional colorectal adenomas with patient age: a single-center study.

We performed a clinical study comparing early-onset and late-onset conventional colorectal adenomas (CCRAs) since little is known about the differences in their characteristics. Pearson's chi-square test and the Kruskal‒Wallis test were used to compare basic information. MCAR tests and multiple imputation were performed to complete missing values. Multivariate logistic analysis and propensity score matching were used to identify the risk factors for recurrence. We included 2793 patients (688 with early-onset CCRAs and 2105 with late-onset CCRAs) from January 2017 to December 2021. Patients with early-onset CCRAs had higher levels of Hb, ALB, and triglycerides but lower HDL levels and N/L ratios. Moreover, we found that more early-onset CCRAs were in the left colon than late-onset CCRAs, and the size of early-onset CCRAs was larger. Early-onset CCRAs tended to lack pedicles compared to late-onset CCRAs. Additionally, the ratio of EMR and APC in early-onset CCRAs was higher than that in late-onset CCRAs, and the ratio of ESD and surgery for late-onset CCRAs was higher. We found that age ≥ 50years, abnormal vessels, drinking alcohol, and DB and ALB levels may be risk factors for recurrence, while the LDL level may be a protective factor. Finally, analysis of cumulative recurrence rates after PSM showed that patients with late-onset CCRAs exhibited higher recurrence rates (P < 0.05). Compared with late-onset CCRAs, early-onset CCRAs were associated with higher triglyceride levels, lower HDL levels, and larger tumor volumes. Age ≥ 50years, abnormal vessels, alcohol consumption, and DB and ALB levels were independent risk factors for recurrence of CCRAs.

Intracavity ultra-broad supercontinuum generation from a figure-9 Yb-doped fiber laser

Intracavity supercontinuum generation based on self-Q-switch assisted by stimulated Brillouin scattering is experimentally demonstrated from an all-fiber Ytterbium laser in the form of figure-9 configuration. At 3 W of pump power, a supercontinuum (SC) extending from visible red light to beyond two microns is obtained. Such spectrum has a flatness better than 5 dB in the 1256–2141 nm range and spans more than an octave ∼ 856–2141 nm at − 20 dB level excluding the main peak. The proposed SC laser source comes in a compact, simple, and low-cost design which could find application in areas such as spectroscopy, microscopy, and biomedical imaging.

Machine learning-based technique for resonance and directivity prediction of UMTS LTE band quasi Yagi antenna

In this study, we have presented our findings on the deployment of a machine learning (ML) technique to enhance the performance of LTE applications employing quasi-Yagi-Uda antennas at 2100 MHz UMTS band. A number of techniques, including simulation, measurement, and a model of an RLC-equivalent circuit, are discussed in this article as ways to assess an antenna's suitability for the intended applications. The CST simulation gives the suggested antenna a reflection coefficient of -38.40 dB at 2.1 GHz and a bandwidth of 357 MHz (1.95 GHz-2.31 GHz) at a -10 dB level. With a dimension of 0.535λ0×0.714λ0, it is not only compact but also features a maximum gain of 6.9 dB, a maximum directivity of 7.67, VSWR of 1.001 at center frequency and a maximum efficiency of 89.9%. The antenna is made of a low-cost substrate, FR4. The RLC circuit, sometimes referred to as the lumped element model, exhibits characteristics that are sufficiently similar to those of the proposed Yagi antenna. We use yet another supervised regression machine learning (ML) technique to create an exact forecast of the antenna's frequency and directivity. The performance of machine learning (ML) models can be evaluated using a variety of metrics, including the variance score, R square, mean square error (MSE), mean absolute error (MAE), root mean square error (RMSE), and mean squared logarithmic error (MSLE). Out of the seven ML models, the linear regression (LR) model has the lowest error and maximum accuracy when predicting directivity, whereas the ridge regression (RR) model performs the best when predicting frequency. The proposed antenna is a strong candidate for the intended UMTS LTE applications, as shown by the modeling results from CST and ADS, as well as the measured and forecasted outcomes from machine learning techniques.

Simple method to suppress n = −2 harmonic for periodic leaky-wave antennas with open-stopband suppression

Periodic leaky-wave antennas (PLWAs) suffer two main issues limiting their scanning ability. The first one is n= −2 spatial harmonic radiation, generating high grating-lobe levels. In this paper, a simple technique by introducing glide-symmetry structure to the PLWA is analysed and used to reduce n = −2 space harmonic level and enhance n = −1 harmonic radiation, subsequently. The other issue is open-stopband (OSB), preventing PLWAs from scanning through broadside. By analysing the ABCD matrix of the cascaded equivalent circuit for the unit cell, a conjugate match condition to counteract the susceptance of the radiation element to suppress the OSB is obtained, which is simple without extracting any parameters. A half-mode substrate integrated waveguide-based prototype is designed and manufactured to demonstrate the proposed methods. The measured results show that the proposed antenna achieves gain fluctuation lower than 1 dB and sidelobe level less than −12 dB, indicating OSB and n = −2 harmonic suppression well, which demonstrates the validity of the proposed method.

Broadband supercontinuum generation in hollow-core photonic crystal fibers infiltrated with chloroform

The chloroform-infiltrated square lattice photonic crystal fibers (PCFs) are designed with the difference of the air hole diameters in the cladding to improve chromatic dispersion and nonlinear properties. Based on numerical simulation results, two optimal structures with flat dispersion, high nonlinear coefficient, and small confinement loss are used for supercontinuum (SC) generation. The first fiber has an all-normal dispersion regime, a nonlinear coefficient of 486.355[Formula: see text]W[Formula: see text].km[Formula: see text] generating an SC spectrum of 640.3[Formula: see text]nm within 30 dB levels at a pump wavelength of 0.945[Formula: see text][Formula: see text]m with peak power as low as 1.44[Formula: see text]kW. With anomalous dispersion properties, the second fiber gives a very broad SC spectrum of 1471.8[Formula: see text]nm within 30 dB levels at a 1.4[Formula: see text][Formula: see text]m pumping wavelength with a peak power of 20[Formula: see text]kW. All-fiber SC sources operating with low-power pump lasers can use these fibers to effectively replace glass-core fibers.

Broadband 1.5-2.1 µm emission in gallo-germanate dual-core optical fiber co-doped with Er3+ and Yb3+/Tm3+/Ho3.

The near-infrared emission in fabricated low-phonon energy, gallo-germanate glass, and double-core optical fiber has been investigated. Broadband amplified spontaneous emission (ASE) was obtained in optical fiber with cores doped with: 1st - 0.2Er2O3 and 2nd - 0.5Yb2O3/0.4Tm2O3/0.05Ho2O3 as a result of the superposition of emission bands from both cores corresponding to the Er3+:4I13/2→4I15/2 (1st core) and Tm3+:3F4 → 3H6/Ho3+:5I7 → 5I8 (2nd core) transitions. The effect of fiber length and pump wavelength on the near-infrared amplified spontaneous emission (ASE) properties has been analyzed for 1 m and 5 m optical fiber. The widest emission bandwidth (355 nm - 3 dB level) was obtained for a 5 m length optical fiber pumped by a 940 nm laser.

Mapping Rice Area in the Cauvery Delta Zone of Tamil Nadu Using Sentinel 1A Synthetic Aperture Radar (SAR) Data

Since remote sensing based crop inventory provides accurate and timely information as compared to the conventional survey methods of estimating area, Multi-temporal Sentinel 1A Synthetic Aperture Radar data was used for the estimation of rice area during Samba season 2022 in the Cauvery delta zone comprising Thanjavur, Thiruvaru, Mayiladuthurai, and Nagapatnam districts of Tamil Nadu. SAR data was preferred over optical satellite data due to excess cloud cover during cropping the major season in Tamil Nadu. Temporal back-scatter (dB) signature of rice crop was generated from the multi-temporal processed SAR data utilizing the modules of a fully automated MAPscape software aiding the discriminating of the crop from others. The signatures revealed that the dB levels to be the lowest during agronomic floods, reached the highest during maximum tillering stage and started declining thereafter. Multi-temporal feature extraction module of Mapscape was used to estimate rice area and validated for accuracy using ground truth data collected during survey. A total of 3.05 lakh ha of rice area was estimated with an overall accuracy of 90.8 % and 0.82 kappa coefficient. Largest area of 1.12 lakh ha was recorded in Thanjavur followed by Thiruvarur and Mayiladuthurai with 0.95 and 0.51 lakh ha respectively.

A dual‐band complementary frequency selective surface combining structures that provides narrow and wide stop‐band frequency responses

AbstractIn this paper, we proposed a dual‐band complementary frequency selective surface (CFSS) with narrow stop band and large stop band. The proposed CFSS combines two simple geometries, the square loop with grid and the crossed dipole. The resonant frequencies are 2.53 and 5.38 GHz. The bandwidths of 280 MHz and 1.77 GHz were obtained, at –10 dB level, for the first and second bands, respectively. These frequencies and bands show that the structure can be applied in Wi‐Fi (2.4–2.5 GHz) and C‐band (4–6 GHz) frequencies. The simulated and measured results show that the chosen geometry has angular stability and polarization independence up to 45°. We can observe a good agreement between simulated and measured results.

HI-Shaped Antenna for Non-Invasive Diabetes Measurement and Monitor Fluctuating Diabetes

The HI antenna senses the human pancreas dielectric radiation for diabetic measurement. Existing passive sensor antennas sense the dielectric radiation from the pancreas region at frequencies of 402.5 MHz and 2.4 GHz for a relative permittivity of 61.2155 and 57.201, respectively. The proposed antenna senses the dielectric properties of diabetic-affected pancreas, such as low and high-fat diabetic pancreas, in the frequency range between 1.5 GHz and 3 GHz. The relative permittivity of the diabetic pancreas is in the range of 48.235 to 65.508. The proposed antenna can sense the diabetic range between 70 mg/dl and 475 mg/dl based on a change in dB level, whereas the existing diabetic sensing antenna measures the diabetic level based on resonance frequency. The resonance-frequency-based diabetic measurement shows inaccurate results. The HI antenna senses pancreas radiation effectively because of the shape and size of its slot, which covers the pancreas region of the human body without generating noise due to the crumbling effect during pancreas dielectric radiation acquisition. The proposed HI-shaped antenna is mounted in different parts of the human body, such as the hand, finger, stomach, and pancreas, for measuring fluctuating diabetes. Based on the experimental results of the proposed HI-shaped antenna, the pancreas is in an optimal location among the various parts of the body. The proposed HI-shaped antenna-based dielectric signal statical values were correlated with diabetic laboratory values for prediction of the diabetic value. The proposed antenna measures the fluctuation in diabetes with 85% accuracy

A Semi-Elliptical UWB Folded Dipole Antenna

In this paper, a novel structure of a semi-elliptical folded dipole for ultra-wideband (UWB) receiving applications is discussed. This proposed antenna has a directive radiation pattern resulting in a high gain over the bandwidth. The design uses a planar technology including a microstrip line to slot line transition and optimized curves to obtain a measured impedance bandwidth of 2.3–26 GHz with the condition of S11 &lt; −6 dB (level accepted for receiving antenna) and meets S11 &lt; −10 dB in several bands. Additionally, the simulated gain ranges from 5 dBi to 9.5 dBi across the entire bandwidth with an efficiency of at least 75%. This antenna model offers a reconfiguration capability. The symmetrical feeding used in this antenna creates the directive behavior. Characteristics of this semi-elliptical folded dipole antenna make it suitable for modern wireless communications, such as 5 G around 3.5 GHz, and easy to integrate in antenna arrays (MIMO systems). The four ports of the antenna also make it a candidate for radiation pattern reconfigurability applications reducing in this way the number of elements in network antennas.

A dual‐layer polarisation rotating element for transmitarray designs

AbstractA transmitarray adopting dual‐layer polarisation rotating (PR) elements is proposed. The element comprises a pair of perpendicularly placed C‐shaped slots etched on the two sides of a single‐layer substrate and orthogonally rotates transmission wave polarisation with regard to the incidence. By adjusting C‐shaped slot's dimension as well as mirroring the bottom layer of the element, a 360° phase shift with a high transmission magnitude is achieved. Based on the proposed unit‐cell, a dual‐layer transmitarray composed of 529 elements is designed and developed. The experimental 1‐dB gain bandwidth and peak aperture efficiency are 13% and 44% respectively. Furthermore, sidelobe level of 20 dB and cross polarisation level of 26 dB are obtained at 10 GHz. These promising properties demonstrate the superiority of the element for transmitarray designs. In addition, this element can be also a good candidate for folded transmitarray designs.

Surface electromyographic (sEMG) activity of the suprahyoid and sternocleidomastoid muscles in pitch and loudness control.

Purpose: This study set out to determine the contributions of the suprahyoid and sternocleidomastoid (SCM) muscles in changing pitch and loudness during phonation among vocally healthy populations. Method: Thirty-nine participants were first recruited, and twenty-nine of them who passed the screening test (Voice Handicap Index [VHI]-10 score ≤11, auditory-perceptual voice rating score ≤2) were finally selected (mean age = 28.2years). All participants were measured for their surface electromyographic (sEMG) activity collected from the bilateral suprahyoid and SCM muscles when producing the vowel /a/, /i/, and /u/ in natural (baseline) and at different pitch (+3, +6, -3, -6 semitones) and loudness (+5, +10, -5dB) levels. Linear mixed-effects models were performed to determine the influencing factors on the root-mean-square percentage of maximal voluntary contraction (RMS %MVC) value of the sEMG signals. Results: Compared with the baseline, a significant decrease of RMS %MVC was found in the suprahyoid muscles during overall phonations of lower pitches (-3 and -6 semitones) and loudness (-5dB). However, no significant change was detected when producing speech at higher pitch (+3 and +6 semitones) and loudness (+5 and +10dB) levels. Among the three vowels, /i/ demonstrated significantly higher RMS %MVC than those of /a/ and /u/. The SCM muscles, however, did not show any significant change in the RMS %MVC values among different vowels in relation to the pitch and loudness changes. When the muscles were compared across the two sides, significantly higher RMS %MVC was found in the right side of the suprahyoid (in pitch and loudness control) and SCM (in pitch control) when compared to the left side. Conclusions: The suprahyoid muscle activities were significantly decreased when producing lower pitches and intensities compared to the natural baselines. The production of sustained /i/ required significantly more suprahyoid muscle activities than those of /a/ and /u/. The SCM muscles did not show much sEMG activity in any of the pitch and loudness levels, which could be used potentially as the calibration or normalization of peri-laryngeal sEMG measurement. The findings also showed a tendency for bilateral asymmetry in the use of suprahyoid and SCM muscles.

Ultra-Flat Supercontinuum Generation in an All-Fiber Self-Q-Switched Er/Yb Laser

A supercontinuum source based on a self-Q-switched Er/Yb-codoped fiber laser has been experimentally demonstrated. At different pump powers, starting at a moderate value of 1.1 W, self-Q-switched pulses with a broad flat spectrum of ~ 560 nm width spanning over the range ~1600 – 2160 nm at −5 dB level (considering the Raman peak) are obtained. Such wide spectrum can be achieved directly at the output of the fiber laser resonator, making the structure compact and robust. With a maximum pump power of 4.9 W, the repetition rate, average output power, peak power and pulse energy are approximately 14.7 kHz, 465 mW, 66 kW and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$31~\mu \text{J}$ </tex-math></inline-formula> , respectively. This compact SC laser configuration has the merits of simple cavity design, low cost and good robustness, which provide a SC source that can be easily applied to numerous areas, such as spectroscopy, optical communications, metrology and biomedical applications.

Radiometric Terrain Correction Method Based on RPC Model for Polarimetric SAR Data

Radiometric terrain correction (RTC) is an important preprocessing step for synthetic aperture radar (SAR) data application in mountainous areas. At present, the RTC processing of SAR depends on the Range Doppler (RD) positioning model. However, the solution of this model has a high threshold for ordinary remote sensing technicians. To solve this problem, we propose an RTC method based on the rational polynomial coefficient (RPC) model, which is widely used in optical remote sensing and is simpler and more practical than the RD model. China’s GF-3 polarimetric SAR data were used to verify the proposed method. The experimental results showed that the RTC method based on RPC is effective and can achieve better correction effects on the premise of reducing the complexity of the algorithm. The correction effect based on the RPC model can be similar to that based on the RD model. The proposed approach can realize the correction of 4~5 dB terrain radiation distortion to a 0.5 dB level.

Dual Concentric-Ring-Core Fiber With Four Zero-Dispersion Wavelengths for Beyond Three-Octave OAM Supercontinuum Generation

Orbital angular momentum (OAM) beams, featuring with unique spatial field distributions, have been extensively investigated and applied into a wide range of fields. In most applications, OAM beams covering a certain frequency band are usually required, and supercontinuum (SC) generation is a feasible method to provide broadband OAM source. As a short pulse is incident into a specially designed optical fiber with flat dispersion over broad bandwidth, a broadband SC could be generated along propagation due to the nonlinear spectral broadening. In this work, we propose a dual concentric-ring-core fiber design to achieve near-zero and flat dispersion profile over 3007-nm wavelength range with four zero-dispersion wavelengths for the OAM mode. The precise position of the zero-dispersion wavelengths can be tailored by varying the structural variables and the germanium-doped concentration of the silica-based fiber. The performance of the spectral broadening in terms of flatness and bandwidth is investigated under different input pulse and propagation conditions. Simulation results depict that the OAM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3,1</sub> mode supercontinuum spectrum can achieve beyond three-octave spanning from 445 to 3942 nm at −40 dB level by pumping a 50-fs 600-kW Gaussian pulse at the central wavelength of 1900 nm into a 2-mm designed fiber. By further optimizing the proposed fiber structure for the OAM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1,1</sub> mode with <60 ps/(nm·km) dispersion variation over a 3210-nm bandwidth, the generated supercontinuum can cover nearly three octaves.

Multi-octave supercontinuum generation of optical vortices in an As2S3 photonic crystal fibers with all-normal dispersion

We designed an all-normal flat near-zero dispersion As2S3 photonic crystal fiber (PCF) with orderly arranged air hole rings for generating an orbital angular momentum (OAM) supercontinuum (SC). We optimized the characters of chromatic dispersion and confinement loss compared with previous studies by carefully engineering the PCF. Simulation results show that, by launching a 100 fs 250 kW chirp-free hyperbolic secant pulse at 7 μm into a 5-mm designed PCF, a 9471-nm SC of OAM1,1 forms from 757 to 10228 nm at a −40 dB level, which covers a 3.7-octave bandwidth. As the peak power increases, the higher-order OAM with a flatter chromatic dispersion profile in the normal dispersion region has a wider bandwidth. They are all highly coherent in the whole spectral range.

714 W all-fiber supercontinuum generation from an ytterbium-doped fiber amplifier

An all-fiber supercontinuum (SC) source with record average output power of 714 W and spectrum ranging from 690 nm to 2350 nm is demonstrated. The method of SC generation from an ytterbium-doped fiber amplifier is used to achieve the high-power SC output. The source also exhibits a flat spectrum ranging from 1050 nm to 2095 nm at the −10 dB level. The parameters that influence the output power and spectrum of SC, including the pulse width of the seed laser and the passive fiber length in the last stage fiber amplifier, are analyzed in detail. To the best of our knowledge, the output power of SC in this work is the highest power that has been publicly reported. The scheme has the advantage of good robustness, which also has the potential to further increase the SC output power to the kilowatt level.

Ultra-Broadband NPE-Based Femtosecond Fiber Laser

A dissipative soliton mode-locked Yb-doped fiber laser is investigated experimentally and numerically from the point of view of generating ultra-broadband ultrashort pulses. An energy up to 2.2 nJ and a spectral bandwidth over 60 nm (at the −10 dB level) were obtained experimentally without dispersion compensation in the cavity. Almost a 100-fold compression coefficient has been achieved, so the resulting pulse duration was 149 fs. The numerical simulation has shown that a further scaling up to 3.5 nJ and a 100 nm spectral bandwidth is possible by reducing the low power transmission coefficient of the NPE-based SAM and increasing the amplification. At the same time, the tolerance of the SAM to a low power radiation is responsible for the transition to a multi-pulse operation regime.

The relationship between co-exposure to multiple heavy metals and liver damage

BackgroundThe impact of heavy metal exposure on human health has attracted widespread attention of researchers, and the impact of heavy metal exposure on liver function has also been confirmed, however, more attention is paid to the impact of single or two heavy metal exposures, and most epidemiological studies focus on heavy metal pollution areas. In this study, rural residents in non-heavy metal-contaminated areas in Northwest China were selected as the research objects to explore the comprehensive effects of co-exposure to multiple heavy metals on the liver, which can provide certain reference and support for related research. ObjectivesThis study used a Bayesian nuclear machine model (BKMR) to evaluate the relationship between exposure to heavy metal mixtures and indicators of liver function in a population in rural Northwest China. ResultsExposure to higher concentrations of metal mixtures was positively correlated with total bilirubin, direct bilirubin, and aspartate aminotransferase, and negatively correlated with alanine aminotransferase, with Pb contributing the most to indicators of liver function. We also observed a possible interaction of Cd with other heavy metals in the effect of heavy metal mixtures on DB levels. ConclusionsConcurrent exposure to higher concentrations of heavy metal mixtures (Cr, Co, Cd, and Pb) in rural China was associated with indicators representing poor liver function, of which the effect of lead on liver function should be focused. More prospective epidemiological studies and animal experiments need to be carried out to determine this relationship and possible mechanism.

Optimization of Bragg soliton dynamics for enhanced supercontinuum generation in ultra-silicon-rich-nitride devices [Invited

Bragg-soliton dynamics in a 2-stage ultra-silicon-rich-nitride (USRN) chip-based device, consisting of a cladding-apodized modulated Bragg grating (CMBG) stage and a USRN channel waveguide stage, is studied and optimized for enhanced supercontinuum generation. We observe that the enhancement is strongly dependent on the Bragg-soliton effect temporal compression developing in the CMBG stage, which is linked to both device and input pulse parameters. With the optimal parameter combination, a supercontinuum spanning 610 nm at the −30 dB level is experimentally demonstrated in the 2-stage USRN device, representing a 5× enhancement compared to that in a reference waveguide. Good agreement is obtained between the experimentally measured supercontinuum and simulations based on the generalized nonlinear Schrödinger equation and is consistent with design rules based on Bragg soliton compression. This device provides an encouraging path to generate supercontinuum in compact chip-based platforms, which does not need ultrashort, femtosecond scale pulses, greatly relaxing the pulse width and pulse power requirement.