Spectrum Curve Research Articles

Echocardiographic estimation of cardiovascular energy transfer in patients with heart failure: an explorative study

Abstract Background Heart failure (HF) is a complex and debilitating condition. The pathophysiology of HF is related to the dynamic interplay governing the energy transfer from the heart to the vascular bed. This energy transfer can be estimated by calculating the heart's external power, measured in watts, which is the product of flow and pressure divided by time. Although power measurements can potentially improve hemodynamic assessment in patients with heart failure, clinical estimation of cardiovascular energy transfer is rarely used due to cumbersome analyses and dependence on invasive measurements. We propose a novel method based on echocardiography and continuous non-invasive blood pressure measurement to estimate cardiovascular energy transfer. Aim To test whether non-invasive estimates of cardiovascular energy transfer can differentiate between HF patients with reduced and preserved left ventricular ejection fraction (LVEF). Methods We included patients hospitalized with decompensated HF not optimally treated in the study. All patients underwent an echocardiographic examination using a GE HealthCare Vivid E95 scanner. We used the biplane Simpson method to calculate LVEF and the pulsed wave Doppler velocity spectrum in the left ventricular outflow tract to estimate flow. Continuous non-invasive blood pressure measurements were obtained using a Finapres finger cuff device calibrated with the brachial blood pressure. We developed an application for tracing the velocity spectrum, synchronizing flow and pressure curves, and calculating the power curves as the product of continuous synchronized flow and pressure curves. The patients were categorized into two groups based on whether LVEF was < 40% or ≥ 40%. Results We observed that cardiovascular energy transfer, estimated as external power, differed between patients with LVEF <40% vs. ≥40%. The study cohort comprised twenty-eight patients (25% women), averaging 76 years (SD 11). Eighteen patients had LVEF <40%, with a mean LVEF of 27% (SD = 9%), mean velocity time index (VTI) 11.7 cm (SD = 2.94), and) and mean systolic blood pressure 116 mmHg (SD = 19). Ten patients had LVEF ≥40%, with a mean LVEF of 47% (SD = 6 %), VTI 16.5 cm (SD = 5.50), and mean systolic blood pressure 143 mmHg (SD = 20). External power was significantly different between patients with LVEF <40% vs. ≥40%, 0.81 W (SD = 0.21 W) vs. 1.43 W (SD = 0.41 W), respectively, p<0.0001 (Fig. 1). We observed a modest but significant correlation between LVEF and power (R = 0.28, P-value < 0.005). Conclusion Cardiovascular energy transfer, estimated non-invasively as external power, was significantly lower in acutely decompensated heart failure patients with LVEF <40% compared to those with LVEF ≥ 40%. More extensive studies should explore the possible value of estimating cardiovascular energy transfer in stratification and therapeutic decisions in patients with HF.

Design of Rectangular Microstrip Patch Antenna Based on Dual Neural Network Model

A new method for designing rectangular microstrip patch antennas using a dual neural network model has been proposed. First, it is proposed to use LSTM + Attention model to predict the amplitude and phase spectrum of the rectangular microstrip patch antenna according to the structural parameter, breaking through the limitations of predicting S11 amplitude spectrum curve solely based on structural parameters in the past. Second, a transformer model was proposed to perform high-precision back prediction of structural parameters using S-parameter points and phase points. Finally, transfer learning was applied to the mutual prediction of structural parameters and gain points, as well as the design of U-shaped slot microstrip patch antennas, all of which achieved good experimental results.

MULTI-SCALE EXPERIMENTAL INVESTIGATIONS ON THE DETERIORATION MECHANISM OF SANDSTONE AFTER HIGH-TEMPERATURE TREATMENT

An important factor influencing engineering stability in deep engineering is temperature. To investigate the impact of high temperatures on sandstone, this study utilized experimental samples of sandstone sourced from Shaanxi, China. The sandstone samples underwent various temperature gradients (25°C, 100°C, 300°C, 500°C, and 700°C) for uniaxial compressive strength (UCS) testing, acoustic emission (AE) monitoring, and nuclear magnetic resonance (NMR) experiments. The resulting mechanical parameters and pore diameter distributions of the sandstone under different temperatures were compared and analyzed. The findings revealed that both the peak strain and peak stress of sandstone samples increased significantly with rising heating temperatures. Moreover, the degradation of elastic modulus and peak stress was more pronounced at higher temperatures. The brittle-ductile transition occurred approximately between 500°C and 700°C. Between 25°C and 500°C, the peak AE energy coincided with the peak strength of the sandstone. The ringing counts of the sandstone specimens reached a maximum after the peak stress at 700°C, with the peak AE energy gradually decreasing at higher heating temperatures. The T<sub>2</sub> spectrum curve and pore size curve of the sandstone expanded and gradually shifted to the right with increasing treatment temperature, accompanied by a gradual increase in the area of the T<sub>2</sub> spectrum and porosity. A negative correlation was observed between porosity and the total area of the T<sub>2</sub> spectrum, peak stress, and elastic modulus of sandstone under high temperatures. Micropores exhibited a monotonically decreasing trend with increasing temperature, while mesopores initially decreased, then increased, and finally decreased, and macropores-cracks enlarged the most.

Fragility and seismic risk of public building structures due to earthquake loads (Case study: Manahan Sports Building)

Abstract Earthquake disaster is a natural disaster with a small probability of occurrence but with a large risk of consequences. Indonesia is an earthquake-prone area which is flanked by 3 plates. which results in Indonesia becoming an earthquake-prone area. This paper analyzes the seismic performance and risk of public buildings of indoor sports buildings which has a inclined column with an elliptical cross-section in Manahan District, Surakarta city. From 1867-2022, there were 10 big earthquakes that occurred in several nearby cities in Surakarta. The seismic risk analysis was conducted by constructing a fragility function depicted in the form of a fragility curve. The analysis procedure starts with developing a 3D finite element model in the computer and applying pushover loads so that the structure achieves nonlinear behavior with material specifications and loading in accordance with the Indonesian National Standard 1726-2019 regulations and resulting in capacity curves, then converted into a capacity spectrum curve. Damage limits are set based on ATC-40 and HAZUS MH-MR 5 criteria. The fragility function is defined as the conditional probability of exceeding the damage limits set for various earthquake intensities. From this study, the probability of building damage based on ground acceleration in Surakarta (Sa=0,36g) with ATC-40 criteria is obtained on the X axis with Immediate Occupancy damage of 13.29% and Life safety of 3.21%, on the Y axis the Immediate Occupancy limit is 55.51% and Life safety is 13.89%. For HAZUS MH-MR 5 guidelines on the X-axis the probability for slight damage is 60.29%, moderate 30.97%, extensive 3.21% and complete 0.42%, and for the Y-axis slight is 93.76%, moderate 73.06%, extensive 12.24% and complete 9.47%.

Analysis of the Structural Behavior of the 6-Story the Pastoral Center of the Archdiocese of Pontianak to Earthquake Loads

This study analyzes the structural behavior of the 6-story Pastoral Center of the Archdiocese of Pontianak under earthquake loads, emphasizing its stability, safety, and performance in soft soil conditions. The analysis includes evaluating load combinations, response spectrum curves, stability coefficients, and P-Delta effects. Results indicate that the building's structural stability meets seismic standards, with load combinations effectively calculated and deviations between design and actual conditions remaining within allowable tolerances. The response spectrum curve highlights peak accelerations during short periods, corresponding to the region's soft soil characteristics. The P-Delta effect does not significantly impact stability, confirming that the structure performs well under seismic loads. Future research is recommended to optimize earthquake-resistant designs for buildings with six or more stories, focusing on innovative materials, advanced foundation systems, and real-time monitoring technologies. This study concludes that the Pastoral Center structure provides adequate safety and stability while offering pathways for improving structural resilience in seismic-prone areas.

Spectroscopic study and visible luminescence of Tb3+ ions in CaF2 crystal co-activated with Yb3+

High quality crystals with composition of Ca0.95Tb0.05F2.05 and Ca0.85Tb0.05Yb0.1F2.15 were grown by Bridgman-Stockbarger technique. Yb3+ ions were used as a sensitizer for Tb3+ ions. Optical properties were measured, including the absorption spectrum, emission spectrum, and fluorescence decay curves. Judd-Ofelt theory was used to analyze the spectroscopic parameters. Fluorescence branch ratio, transition probability, radiative and fluorescence lifetimes, and quantum efficiency were determined. The emission cross section of Tb3+ ions in Tb:CaF2 and Tb/Yb:CaF2 crystals for the green emission at 544 nm, corresponding to the transitions of 5D4→7F5 were calculated to be 4.61x10-22 cm2 and 4.60x10-22 cm2, respectively. Our experiments have shown that doping with Yb3+ ions does not significantly affect the spectral properties of Tb3+ ions in CaF2 crystal. Quadratic dependence of the emission intensity of Tb3+ ion in Tb/Yb:CaF2 crystal on the intensity of a diode laser at 955 nm proved that the excitation of Tb3+ ion occurs due to the cooperative process of transferring the excitation from two Yb3+ ions to one neighboring Tb3+ ion. The Tb/Yb:CaF2 crystal can be considered as a promising up-converting medium for creating diode-pumped visible phosphorus and active laser media.

Spectral CT for non-invasive evaluation of bladder cancer grade.

To investigate the potential role of dual-energy spectral computer tomography (CT) quantitative parameters in the definition of bladder cancer (BCa) pathological grading. This retrospective study evaluated the use of spectral CT imaging features for BCa. From 2021 to 2023, 63 patients with histologically-confirmed BCa diagnosis were examined at our Institution. The patients were pathologically divided, following international guidelines, into two groups: low-grade (n = 24) and high-grade urothelial carcinoma group (n = 39). The iodine concentrations (IC), the normalized iodine concentrations (NIC), and the slope of the spectrum curve (SLOPE) were calculated along with the measure of each lesion CT value on the monochromatic image from 40 to 120keV. The diagnostic performance was assessed by Receiver operator characteristic curve (ROC) analysis. The high-grade group showed significantly higher mean values of IC, SLOPE, and HU in 40 KeV monoenergetic images (VMI40 HU). AUC values for NIC, SLOPE, IC, and VMI40 HU were 0,677, 0,745, 0,745, and 0,755 respectively. In multivariate logistic regression models with backward stepwise, including all quantitative parameters, only VMI40 HU remained statistically significant to correlate with high-grade tumors. Preliminary data shows that quantitative parameters of dual-energy spectral CT can be helpful to characterize low-grade and high-grade urothelial bladder tumors. The prediction of high-grade BCa with non-invasive methods (e.g. dlCT) can aid in early detection of muscle-invasive and worse prognostic tumors that need more aggressive and timely treatments, personalizing the management on the risk of recurrence.

Viscoelastic and thermal properties of unzipped multiwalled carbon nanotubes reinforced polyamide-6 composites

The excellent reinforcing capability of carbon nanofillers along with increasing demand for advanced polymer composites in automobiles, aircraft, and defense sectors motivate the research community to explore detailed mechanical, thermal, and electrical properties of carbon-based polymer nanocomposites for various applications. In this work, 0.1 to 7 parts per hundred ratios (phr) of multiwalled carbon nanotubes (MWCNTs) and unzipped MWCNTs (referred to as graphene oxide nanoribbons (GONRs)) were individually reinforced into polyamide-6 (PA6) matrix by twin-screw extrusion and standard sized specimens were prepared by the injection molding process. The interaction among PA6 and nanofillers were analyzed using Raman and FTIR spectroscopy. The oscillatory rheometry measurement at 0.1 rad/s angular frequency showed a 110.7 % rise in storage modulus and a 12.6 % rise in loss modulus for 0.1 phr GONRs reinforcements. Both the values raised by 100 % and 12.5 %, respectively for similar amounts of MWCNTs reinforcements. The thermo-gravimetric analysis (TGA) indicated the optimum thermal stability at 1 phr of GONRs content compared to the increasing stability with increasing MWCNTs content within PA6. The differential scanning calorimetry (DSC) curves indicated the optimum reinforcing capacity of GONRs at 0.5–3 phr reinforcements, as compared to those increasing for increasing MWCNTs content. An optimum reinforcing capacity at lower amounts of GONRs as compared to MWCNTs was confirmed from shifting trends of intensity peaks in Raman and FTIR spectra curves of the composites. It was attributed to high surface area and functional groups along the edges of GONRs. Altogether, the GONRs/PA6 composites possess excellent potential for applications in automotive and aerospace components, ballistics equipments, electronics, biomedicals, sensors, etc., requiring high mechanical and thermal stability.

Weak ultrasonic guided wave signal recognition based on one-dimensional convolutional neural network denoising autoencoder and its application to small defect detection in pipelines

Pipeline failures are often caused by the expansion of small defects. Structural damage to pipelines can lead to major safety accidents. When ultrasonic guided wave (UGW) technology is used for pipeline failure detection, the echoes produced by small defects manifest as weak UGW signals amidst significant noise. The low amplitude of these signals or complete drowning by noise makes them difficult to recognize. This study innovatively introduces a one-dimensional convolutional neural network denoising autoencoder (1DCNN-based DAE) for noise reduction in UGW signals using deep learning. To improve the conventional DAE, the model incorporated the Parametric Rectified Linear Unit (PReLU) activation function and a CNN for enhanced feature extraction, resulting in the proposed 1DCNN-based DAE. The model is trained on an extensive dataset of mixed signals with strong noise and their corresponding clean signals, enabling autonomous denoising in an unsupervised manner. Additionally, this paper proposes the application of the window-shifted power spectrum method for analyzing the denoised signals to identify and locate pipeline defects. The method involves traversing the signal with a window to intercept fragments, calculating their power, and plotting the power spectrum curve. Defects are then located based on the peak positions of this curve. Numerical simulation and experimental signals were used to validate the proposed method. Simulation results showed that the proposed 1DCNN-based DAE effectively improved the signal-to-noise ratio (SNR) of UGW mixed signals from −9 dB to 21.63 dB, representing an improvement of up to 30.63 dB. Experimental results demonstrated that the method accurately detected weak UGW signals from small defective pipes with a 2 % cross-section loss rate, achieving over 90 % recognition confidence and less than 1.5 % axial positioning error rate. In summary, the proposed 1DCNN-based DAE can effectively improve the SNR of the signal, reduce the noise in the UGW detection signal, and improve the sensitivity of defect identification; the window-shifted power spectrum method has a advantage in the accurate localization of defects.

Spectral CT-based nomogram for preoperative prediction of Lauren classification in locally advanced gastric cancer: a prospective study.

To develop a nomogram based on clinical features and spectral quantitative parameters to preoperatively predict the Lauren classification for locally advanced gastric cancer (LAGC). Patients diagnosed with LAGC by postoperative pathology who underwent abdominal triple-phase enhanced spectral computed tomography (CT) were prospectively enrolled in this study between June 2023 and December 2023. All the patients were categorized into intestinal- and diffuse-type groups according to the Lauren classification. Traditional characteristics, including demographic information, serum tumor markers, gastroscopic pathology, and image semantic features, were collected. Spectral quantitative parameters, including iodine concentration (IC), effective atomic number (Zeff), and slope of the energy spectrum curve from 40 keV to 70 keV (λ), were measured three times for each patient by two blinded radiologists in arterial/venous/delayed phases (AP/VP/DP). Differences in traditional features and spectral quantitative parameters between the two groups were compared using univariable analysis. Independent predictors of the Lauren classification of LAGC were screened using multivariable logistic regression analysis. Receiver operating characteristic (ROC) curve analysis was used to assess the discriminating capability. Ultimately, the nomogram, including clinical features and spectral CT quantitative parameters, was developed. Gender, nIC in AP (APnIC), and λ in DP (λd) were independent predictors for Lauren classification. The nomogram based on these indicators produced the best performance with an area under the curve of 0.841 (95% confidence interval: 0.749-0.932), specificity of 85.3%, accuracy of 76.4%, and sensitivity of 68.4%. The nomogram based on clinical features and spectral CT quantitative parameters exhibits great potential in the preoperative and non-invasive assessment of Lauren classification for LAGC. Question Can the proposed nomogram, integrating clinical features and spectral quantitative parameters, preoperatively predict the Lauren classification in locally advanced gastric cancer (LAGC)? Findings The nomogram, based on gender, arterial phase normalized iodine concentration, and slope of the energy spectrum curve in the delayed phase showed satisfactory predictive ability. Clinical relevance The established nomogram could contribute to guiding individualized treatment strategies and risk stratification in patients by predicting the Lauren classification for LAGC before surgery.

A simple mechanical model of turbulence

This work examines the control and stabilization problems of vibrations in a hierarchical chain of oscillators with hysteresis couplings. Hysteresis coupling is formalized within the Bouc — Wen phenomenological model. The mass, stiffness, and damping properties of the oscillators are set to follow a specific scaling rule and decrease exponentially along the chain, thus forming a hierarchy. The model is verified using Kolmogorov’s hypotheses. To do this, energy spectra are constructed under hysteresis in coupling and without it at different amplitudes of the external excitation. As a result of computational experiments, it is shown that for a chain with hysteresis couplings at a high amplitude of excitation, the energy spectrum curve sufficiently corresponds to Kolmogorov’s hypotheses. The amplitude-frequency characteristics of the system are calculated under hysteresis in coupling using the frequency scanning method. In numerical experiments, frequency ranges of external excitation are identified, which correspond to the chaotic behavior of oscillators and their synchronization.

Bias-controlled modulation for monolithic III-nitride optoelectronic integration.

III-nitride multi-quantum well (MQW) diodes can modulate the light emitted by another diode with the same MQW structure by varying the bias voltage owing to the spectral overlap between the electroluminescence spectrum and spectral responsivity curve of the MQW diodes. Here, we investigate bias-controlled modulation by monolithically integrating an optical transmitter, waveguide, electro-absorption modulator (EAM), and slot grating coupler on a silicon-based III-nitride platform using compatible fabrication processes. The modulated light is coupled into a fiber, which is direct to a photodiode for characterization. The bandwidths of forward-biased emission modulation and reverse-biased absorption modulation are of the same order of magnitude, with the latter exhibiting significant performance improvements. In addition, real-time video signal transmission was achieved using an EAM, which provides a meaningful reference for modulation applications of silicon-based GaN optoelectronic integrated systems.

Temperature dependence of gold nanostar particles morphology and its SERS application

ABSTRACT Gold nano-star particles (GNS) have broad application prospects in Raman enhancement, photovoltaic, and catalysis fields because of the hot spot effect of their tip structure. However, metal nanoparticles will accumulate heat during applications of high-power laser-focused irradiation, which may lead to the morphological degradation of the nanoparticles. In this paper, we have studied the effect of annealing temperature on the surface tip structure of GNS. Firstly, GNS with the multi-tip structure were synthesised by the two-step method, and GNS thin films were prepared by self-assembly technique without auxiliaries. By means of SEM characterisation, the film is found to be compact and uniform. Secondly, we systematically studied the morphology degradation of GNS at 100°C, 150°C, 200°C and 250°C. The results show that the tip of GNS does not change obviously until the temperature reaches 200°C. Then the four kinds of GNS films were used as surface-enhanced Raman scattering (SERS) substrates, and their Raman enhancement properties have been studied with adenine as the analyte, and stronger Raman enhancement effect can be found for the tip of nanoparticles. For a SERS substrate corresponding to an annealing temperature of 100°C, we have obtained the limit sensitivity of adenine molecule of 10−9 M. Finally, the surface electric field distribution and local resonance spectrum curves of four kinds of gold nanoparticles with different tip sizes were simulated theoretically by using the finite element method, and the results are consistent with the experimental data.

Seismic vulnerability analysis of hospitals and school buildings considering the Gaussian regression algorithm

This study combines the Gaussian regression algorithm to propose a nonlinear regression model that can be used to evaluate the seismic vulnerability of regional hospitals and school buildings. The failure features and disaster mechanisms of hospital and school buildings affected by the Jishishan (JSS) earthquake on December 18, 2023, and the Wenchuan (WC) earthquake on May 12, 2008, were reported. The samples of 252 damaged buildings (37 hospitals and 215 schools) in Dujiangyan city affected by the Wenchuan earthquake for which the author participated in the survey were collected and counted. Hospitals and school buildings were classified according to the types of reinforced concrete (RC) and masonry structures, and earthquake vulnerability probability matrices for hospital and school building clusters were established considering the actual failure probabilities. A total of 2103,213 acceleration records (from the Wenchuan earthquake) monitored by 12 real stations were selected. Using dynamic time history and response spectrum analysis methods, time history and spectrum curves were generated, considering the influence of different seismic directions. Using the developed Gaussian regression model, vulnerability comparison curves and parameter matrices considering multiple regression algorithms were generated. This paper considers the effects of the construction year and number of floors on the seismic vulnerability of hospital and school buildings. Seismic vulnerability curves and failure probability matrices were generated and established on the basis of actual structural failure probabilities. According to regression and vulnerability surface analysis, the evaluation results of the proposed model are highly consistent with actual field observations.

Quasi-passive modulation for monolithic GaN photoelectronic circuit

Due to the overlap between the electroluminescence spectrum and spectral responsivity curve, gallium nitride (GaN)-based multi-quantum well (MQW) diodes can modulate and detect light emitted by another diode with the same MQW structure. This enables the realization of a monolithic integrated GaN optoelectronic circuit, integrating an MQW-based transmitter, waveguide, modulator, and receiver on a tiny GaN chip. It is well known that the active region of MQW absorbs high-energy photons within the plane, generating electron-hole pairs and forming photogenerated carriers. The change in free carrier concentration causes variations in the refractive index and absorption characteristics of the waveguide, thereby manipulating light propagation within the waveguide. Based on this physical phenomenon, a quasi-passive modulation scheme is proposed for a monolithic GaN photoelectronic circuit. This scheme achieves optical modulation by connecting a variable resistor between the modulator electrodes, avoiding the need for high-precision external electric fields and complex control circuits. The performance of the quasi-passive modulation was tested through on-chip data transmission and real-time audio signal transmission. The results indicate that quasi-passive modulation is highly feasible in optoelectronic systems and shows great promise as a competitive core module for future large-scale photonic integrated circuits.

Effect of soil-building interaction on dynamic earth pressure on basement walls

This study investigates dynamic earth pressure on basement walls by considering soil-structure interaction, a factor that is often overlooked by conventional methods like Mononobe-Okabe, Seed and Whitman, and Wood. Superstructure, basement, and soil were numerically simulated in a single model to evaluate the inertial and kinematic effects of buildings on dynamic earth pressure on the basement walls. The numerical model was validated using data from a centrifuge test and an instrumented building. Then, a parametric study was performed, with the height, width, and basement depth of the building varied with six input motions. The results showed that the inertia of the building increased dynamic thrust. Furthermore, the dynamic thrust showed a similar trend with the displacement response spectrum curve of the ground surface acceleration as the building height increased, while the distribution shape transitioned from triangular to inverted triangular. Additionally, wider buildings had increased dynamic earth pressure, while deeper buildings exhibited smaller normalized dynamic thrust.

Evaluation of supraspinatus muscle-to-fat infiltration for rotator cuff tear patients using dual-energy computed tomography

This study aimed to assess fatty infiltration of the supraspinatus muscle (Ssp) using dual-energy computed tomography (CT) in patients with rotator cuff tear. This study examined 44 patients (49 shoulders; 21 men, 23 women; mean age, 69 years) who underwent magnetic resonance imaging (MRI) and dual-energy CT. Three orthopedic surgeons evaluated fatty infiltration of the Ssp using the Goutallier classification of MRI, and three orthopedic surgeons measured attenuation (in Hounsfield units) for the same slice using dual-energy CT. We evaluated the following: 1) interobserver reliability of the Goutallier classification, 2) correlations between intramuscular muscle-to-fat ratio and tear size in the rotator cuff or Goutallier classification, and 3) the spectrum curve of attenuation for each energy level of the Goutallier stage. The κ value for interobserver reliability was 0.721. Significant positive correlations were identified between intramuscular muscle-to-fat ratio and cuff tear size and intramuscular muscle-to-fat ratio and Goutallier classification. Moreover, the Ssp showed no change in attenuation at Goutallier stage 0, but as Goutallier stage increased, attenuation decreased at low energy. We investigated the evaluation of fatty infiltration in Ssp using dual-energy CT in patients with rotator cuff tears. Positive correlations were seen between the Goutallier classification from MRI and rotator cuff intramuscular fat ratio from dual-energy CT. Moreover, changes in attenuation showed that higher Goutallier stages contained more fat. Our data suggest the potential utility of dual-energy CT for evaluating fatty infiltration of rotator cuff muscles.

La3Sc2Ga3O12:Cr3+, Nd3+ near-infrared phosphor for nondestructive detection and luminescence thermometry

To develop continuous broadband emission near-infrared (NIR) phosphors compatible with blue LED chips, numerous Cr3+-Yb3+ co-doped phosphors have been synthesized. However, the emission spectra of Cr3+ vary significantly across different matrix materials, while Yb3+ maintains a relatively stable emission spectrum. This variation leads to notable luminescence depressions between 850 and 900 nm in many Cr3+-Yb3+ co-doped phosphors. To address this emission spectrum gap, we utilized Cr3+ as a sensitizer and introduced Nd3+ as the luminescence center within the La3Sc2Ga3O12 matrix material, establishing a Cr3+-Nd3+ energy transfer channel. Under 480 nm excitation, we tuned emission peaks at 800 nm (Cr3+) and 881 nm (Nd3+). The stable NIR emission of Nd3+ effectively compensates for the missing spectrum in Cr3+-Yb3+ co-doping. The Cr3+-Nd3+ energy transfer process was thoroughly analyzed using diffuse reflection spectrum, excitation spectrum, and fluorescence decay curves. The LSGO:0.125Cr3+, 0.03Nd3+ compound with the best optical performance was packaged with a 480 nm LED chip to create a NIR light source. At a working current of 10 mA, it achieved a photoelectric conversion efficiency of 9.45 %, demonstrating its potential for applications in non-destructive detection and luminescence thermometry. This work presents a novel strategy for tuning NIR spectral distribution and developing continuous broadband NIR phosphors.

Energy spectrum computed tomography multi-parameter imaging in preoperative assessment of vascular and neuroinvasive status in gastric cancer.

Vascular and nerve infiltration are important indicators for the progression and prognosis of gastric cancer (GC), but traditional imaging methods have some limitations in preoperative evaluation. In recent years, energy spectrum computed tomography (CT) multiparameter imaging technology has been gradually applied in clinical practice because of its advantages in tissue contrast and lesion detail display. To explore and analyze the value of multiparameter energy spectrum CT imaging in the preoperative assessment of vascular invasion (LVI) and nerve invasion (PNI) in GC patients. Data from 62 patients with GC confirmed by pathology and accompanied by energy spectrum CT scanning at our hospital between September 2022 and September 2023, including 46 males and 16 females aged 36-71 (57.5 ± 9.1) years, were retrospectively collected. The patients were divided into a positive group (42 patients) and a negative group (20 patients) according to the presence of LVI/PNI. The CT values (CT40 keV, CT70 keV), iodine concentration (IC), and normalized IC (NIC) of lesions in the upper energy spectrum CT images of the arterial phase, venous phase, and delayed phase 40 and 70 keV were measured, and the slopes of the energy spectrum curves [K (40-70)] from 40 to 70 keV were calculated. Arterial phase combined parameter, venous phase combined parameters (VP-ALLs), and delayed phase association parameters were calculated for patients with late-stage disease. The differences in the energy spectrum parameters between the positive and negative groups were compared, receiver operating characteristic (ROC) curves were plotted, and the area under the curve (AUC), sensitivity, specificity, and optimal threshold were calculated to measure the diagnostic efficiency of each parameter. In the delayed phase, the CT40 keV, CT70 keV, K (40-70), IC, NIC, and CT70 keV and the NIC in the upper arterial and venous phases of energy spectrum CT were greater in the LVI/PNI-positive group than in the LVI-negative group. The representative parameters for the arterial phase NIC were 0.14 ± 0.04 in the positive group and 0.12 ± 0.04 in the negative group. The venous phase NIC was 0.5 (0.5, 0.6) in the positive group and 0.4 (0.4, 0.5) in the negative group. Last, for the delayed phase NIC, it was 0.6 ± 0.1 in the positive group and 0.5 ± 0.1 in the negative group (all P values are less than 0.05). ROC curve analysis demonstrated that the diagnostic efficacy of each parameter during the venous stage was superior to that during the arterial and delayed stages. Furthermore, the diagnostic efficacy of the combined parameter throughout all three stages was superior to that of any single parameter. The AUC, sensitivity, and specificity of the optimal parameter, VP-ALL, were 0.931 (95% confidence interval: 0.872-0.990), 80.95%, and 95.00%, respectively. When assessing the condition of LVI and PNI (perineural invasion) in patients with GC prior to surgery, the ability to diagnose these conditions using venous stage parameters was superior to that using arterial stage and delayed stage parameters. Furthermore, the diagnostic accuracy of using a combination of parameters was better than that of using individual parameters alone.

Pore-Fracture System Distribution Heterogeneity by Using the T2 Spectral Curve under a Centrifugal State

In this paper, 12 sandstone samples are collected from the Taiyuan Formation in Qinshui Basin, and sample types using the T2 spectral under LF-NMR saturation and centrifugation conditions are classified. Moreover, single and multifractal models were used to calculate fractal parameters of saturated and centrifugal T2 spectra, and the correlation between different fractal parameters, pore structure, T2cutoff value, and pore permeability parameters was studied. The results are as follows. (1) According to the T2 spectrum curves under centrifugation and saturation conditions, all the samples can be divided into three types. There are significant differences in the uniform pore size distribution. However, the non-uniformity of small pore distribution in type B samples is stronger than that of other types, while heterogeneity of large pore distribution is weaker than that of different types. The centrifugal T2 spectrum curve exhibits both single-fold and multifractal characteristics. The results of a single fractal by using a centrifugal T2 spectrum are consistent with those of a saturated T2 spectrum, indicating that single fractal features by using centrifugal and saturated T2 spectra are consistent. Unlike the single fractal parameters, the correlation between the saturation and centrifugal T2 spectrum’s multifractal parameters is weak. This suggests that the physical significance conveyed by the centrifugal T2 spectrum’s multifractal parameters differs from that of the saturated T2 spectrum.