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Initial experience of correlating diffusion spectral parameters with histopathologic indexes in murine colorectal tumor homografts
摘要： Purpose: To determine the correlation between continuously distributed diffusion-weighted image (DWI)-derived parameters and histopathologic indexes. Methods: Fifty-four mice bearing HCT-116 colorectal tumors were included for analysis; 12 mice were used for continuous observation, and the other 42 mice were used for break-point observation. All mice were randomly divided into radiotherapy and non-radiotherapy groups. Optical imaging and MRI were performed at different time points according to radiotherapy regimen (baseline, 24 h, 48 h, 72 h, 7 d, 14 d, and 28 d). Continuous observation data were analyzed to show the difference of dynamic changing trends of optical and MR-DWI–derived parameters between radiotherapy and non-radiotherapy groups (photon numbers, D_max, full width half maximum [FWHM], and apparent diffusion coefficient [ADC] value). Break-point observation data were used to analyze the correlation between histopathologic indices and DWI-derived parameters. Results: There was a significant difference in the changing trends of photon numbers, D_max, FWHM, and ADC value between radiotherapy and non-radiotherapy groups, especially at early time points. There was moderate negative correlation between Ki67 and percentage changes of D_max, FWHM, and ADC values (the correlation coefficients were 0.632, 0.449, and 0.586, P,0.001, P=0.008, and P,0.001, respectively). There was moderate negative correlation between survivin and percentage changes of D_max and ADC values (correlation coefficients were 0.496 and 0.473, P=0.004 and P=0.006, respectively). Conclusion: The continuously distributed DWI-derived parameters could reflect histological behavior to some extent and, thus, are potential markers for early noninvasive monitoring of tumor cell apoptosis and proliferation.
关键词： magnetic resonance imaging,colorectal cancer,murine homografts,diffusion-weighted imaging,continuously distributed
更新于2025-09-04 15:30:14
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CVD Diamond Interaction with Fe at Elevated Temperatures
摘要： Chemical vapor deposition (CVD) diamond is a prospective thin film material for cutting tools applications due to the extreme combination of hardness, chemical inertness, and thermal conductivity. However, the CVD diamond cutting ability of ferrous materials is strongly limited due to its extreme affinity to iron, cobalt, or nickel. The diamond–iron interaction and the diffusion behavior in this system are not well studied and are believed to be similar to the graphite–iron mechanism. In this article, we focus on the medium-temperature working range of 400–800 ?C of a CVD diamond–Fe system and show that for these temperatures etching of diamond by Fe is not as strong as is generally accepted. The starting point of the diamond graphitization in contact with iron was found around 400 ?C. Our results show that CVD diamond is applicable for the cutting of ferrous materials under medium-temperature conditions.
关键词： Fe–C interaction,CVD diamond,diffusion
更新于2025-09-04 15:30:14
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[Lecture Notes in Mechanical Engineering] Numerical Heat Transfer and Fluid Flow (Select Proceedings of NHTFF 2018) || Combined Influence of Radiation Absorption and Hall Current on MHD Free Convective Heat and Mass Transfer Flow Past a Stretching Sheet
摘要： The present article investigates the combined in?uence of thermal radi- ation, radiation absorption, Soret and Dufour effect, and non-uniform heat source on the steady convective heat and mass transfer ?ow of a viscous incompressible ?uid past a stretching sheet. The non-linear equations governing the ?ow, heat and mass transfer have been solved by using a Runge–Kutta ?fth-order together with shooting technique. The in?uence of Sr/Du, A1, B1 on all ?ow characteristics has been analysed.
关键词： Stretching sheet,Hall current,Cross diffusion,Non-uniform heat source/sink
更新于2025-09-04 15:30:14
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Evaluation of renal dysfunction using texture analysis based on DWI, BOLD, and susceptibility-weighted imaging
摘要： Objective To explore the value of texture analysis based on diffusion-weighted imaging (DWI), blood oxygen level–dependent MRI (BOLD), and susceptibility-weighted imaging (SWI) in evaluating renal dysfunction. Methods Seventy-two patients (mean age 53.72 ± 13.46 years) underwent MRI consisting of DWI, BOLD, and SWI. According to their estimated glomerular filtration rate (eGFR), the patients were classified into either severe renal function impairment (sRI, eGFR < 30 mL/min/1.73 m2), non-severe renal function impairment (non-sRI, eGFR ≥ 30 mL/min/1.73 m2, and < 80 mL/min/1.73 m2), or control (CG, eGFR ≥ 80 mL/min/1.73 m2) groups. Thirteen texture features were extracted and then were analyzed to select the most valuable for discerning the three groups with each imaging method. A ROC curve was performed to compare the capacities of the features to differentiate non-sRI from sRI or CG. Results Six features proved to be the most valuable for assessing renal dysfunction: 0.25QuantileDWI, 0.5QuantileDWI, HomogeneityDWI, EntropyBOLD, SkewnessSWI, and CorrelationSWI. Three features derived from DWI (0.25QuantileDWI, 0.5QuantileDWI, and HomogeneityDWI) were smaller in sRI than in non-sRI; EntropyBOLD and CorrelationSWI were smaller in non-sRI than in CG (p < 0.05). 0.25QuantileDWI, 0.5QuantileDWI, and HomogeneityDWI showed similar capacities for differentiating sRI from non-sRI. Similarly, EntropyBOLD and CorrelationSWI showed equal capacities for differentiating non-sRI from CG. Conclusion Texture analysis based on DWI, BOLD, and SWI can assist in assessing renal dysfunction, and texture features based on BOLD and SWI may be suitable for assessing renal dysfunction during early stages.
关键词： Chronic kidney disease,Image processing, computer-assisted,Diffusion magnetic resonance imaging,Chronic renal insufficiency
更新于2025-09-04 15:30:14
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Holographic interferometric microscopy for measuring Cu2+ concentration profile during Cu electrodeposition in a magnetic field
摘要： We measured the concentration boundary layer during copper electrodeposition in a copper sulfate solution under an applied magnetic field. Using a holographic laser interference microscope, we demonstrated the formation of the diffusion layer near the cathode. In the initial stage of electrodeposition, the diffusion layer was distorted in a magnetic field. An analysis of the electrode surface concentration supported the following assertions: without a magnetic field, dendrites formed when the surface concentration of Cu2+ was depleted; with a magnetic field, the unique convection phenomena of the field gradient force and localized Lorentz force promoted Cu2+ mass transport in the diffusion layer, producing large crystal grains.
关键词： Diffusion layer,Magnetohydrodynamic,Magnetic field,Localized Lorentz force,Field gradient force
更新于2025-09-04 15:30:14
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A Novel Analysis of Transient Isothermal 18O Isotopic Exchange on Commercial CexZr1?xO2-Based OSC Materials
摘要： A novel methodology for the analysis of 18O2-transient isothermal isotopic exchange (TIIE) response curves obtained over commercial mixed metal oxides upon the gas switch 16O2/Ar (30 min) → 18O2/Kr/Ar (t) at constant T in a flow CSTR micro-reactor in the absence of external and internal mass transport resistances and grain boundary effects, is presented for the first time. The specific aim of this analysis was to derive quantitative descriptors of the 18O exchange under pseudo-equilibrium conditions for the transfer rates of oxygen between the gas and solid phases, enabling the assessment of differences in the kinetics of bulk oxygen diffusion over a series of commercial OSC materials used in various catalytic applications (e.g. TWC), without the need of performing any mathematical and kinetic modelling of the surface/bulk oxygen diffusion processes. Based on these descriptors, commercial OSC mixed metal oxides prepared by the same chemical synthesis route but varying the value of one of the synthesis parameters, and having the same at.% composition, were proved to possess largely different transient kinetic rates and other features of the transient response curves of 16O/18O exchange strongly related to the bulk oxygen diffusion in the solids. This novel 18O2-TIIE analysis is quick and provides a reliable means for proving or disproving likely infringement of patented commercial mixed metal oxides OSC materials.
关键词： OSC,Bulk oxygen diffusion,Transient isothermal oxygen isotopic exchange
更新于2025-09-04 15:30:14
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Tellurium-based Double Perovskites A2TeX6 with Tunable Bandgap and Long Carrier Diffusion Length for Optoelectronic Applications
摘要： Lead-free hybrid perovskites have attracted immense interest as environmentally friendly light absorbers. Here, we report on tellurium (Te)-based double perovskites A2TeX6 (A= MA, FA or BA, X = Br- or I-, MA= CH3NH3, FA= CH(NH2)2, BA= benzylamine) as potentially active materials for optoelectronic devices. This perovskites exhibit a tunable bandgap (1.42 eV-2.02 eV), a low trap density (～1010 cm-3), and a high mobility (～ 65 cm2 V-1 s-1). Encouragingly, the MA2TeBr6 single crystal with a bandgap of 2.00 eV possesses a long carrier lifetime of ~6 μs and corresponding carrier diffusion lengths of ~38 μm, which are ideal characteristics for a material for photodetectors and tandem solar cells. Moreover, A2TeX6 perovskites are relatively robust in ambient conditions, being stable for at least two months without showing any signs of phase change. Our findings bring to the forefront a family of lead-free Te-based perovskites for non-toxic perovskite optoelectronics.
关键词： Optoelectronic applications,Long carrier diffusion length,Tunable bandgap,Tellurium-based double perovskites
更新于2025-09-04 15:30:14
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Development of a ReaxFF Reactive Force Field for Interstitial Oxygen in Germanium and Its Application to GeO <sub/>2</sub> /Ge Interfaces
摘要： We developed the ReaxFF force field parameters for Ge/O/H interactions, specifically targeted for the applications of Ge/GeO2 interfaces and O-diffusion in bulk Ge. The original training set, taken from the Zheng et al. work includes Quantum Mechanics (QM) data for equations of state and heats of formation of GeO and GeO2 condensed phases as well as dissociation energies for single and double bonds of Ge and angle distortion of O-Ge-O. We expanded this training set with the additional crystal data containing the formation energies of different O-interstitial centers and the minimum energy migration pathway of O atom in diamond Ge. After refitting the force field parameters based upon the extended training set, the ReaxFF results that the equations of state and heats of formation of the GeO and GeO2 condensed phases retain a good fit with the QM calculations. In addition, the ReaxFF correctly predicts the relative stability of the O-interstitial centers in the diamond Ge to be bond-center → split → tetrahedral → hexagonal from most stable to least stable with the energies showing quantitatively agreement with DFT. Furthermore, O atoms diffuse along a pathway between neighboring bond-centered interstitial sites and go through the asymmetric transition state at the split site as in DFT. We also examined the temperature dependence of O diffusion in bulk Ge, and subjected the GeO2/Ge interface to heat treatment based on the ReaxFF and Tersoff potential. On the basis of our MD results, the ReaxFF accurately predicts the diffusion barrier value as 50.02 kcal/mol within the temperature range of [800-2000K]. At the temperatures over 1400 K, ReaxFF allows the O atom to diffuse along the theoretically reported pathway between the adjacent BC centers whereas Tersoff potential contradicts the DFT reports by resulting a diffusion between the BC and H interstitial sites. For the Ge/GeO2 interface, the ReaxFF results that the thickness of GeO2 increases and the Ge substrate is consumed depending on the temperature and the oxidation time, supported by the experiments, while no change was observed in the thicknesses of Ge substrate and GeO2 slab in the Tersoff based simulations.
关键词： Oxygen diffusion,GeO2/Ge interface,Molecular dynamics,Germanium,ReaxFF
更新于2025-09-04 15:30:14
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Investigation of moments-based transport models applied to plasma waves and the Dyakonov–Shur instability
摘要： Transport models based on balance equations with different degrees of numerical complexity can be derived from the Boltzmann transport equation (BTE). In this paper two different drift-diffusion models based on the first two moments of the BTE as well as two hydrodynamic models based on four moments are derived and analyzed for their accuracy in the THz frequency range with emphasis on the generation of plasma waves. To this end, they are compared to the BTE in the small-signal regime under homogeneous bulk conditions where harmonic waves were assumed, which reveals that the hydrodynamic models provide a higher accuracy. It is also shown that the anisotropy of the distribution function must be taken into account in the closure relations. This leads to convective derivatives in the balance equations, which are very difficult to treat by numerical means in the case of semiconductor devices and are neglected in commercial TCAD suites. But without them a meaningful simulation of the Dyakonov–Shur plasma instability will not be possible.
关键词： Boltzmann transport equation,THz,drift-diffusion,plasma instability,hydrodynamic
更新于2025-09-04 15:30:14
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A teleophthalmology system for the diagnosis of ocular urgency in remote areas of Brazil
摘要： Purposes: To validate a teleophthalmology mobile system aimed at improving and providing eye urgency screenings in remote and poor area settings in Brazil. The system enables one or more ophthalmologists to remotely examine a patient’s condition and submit a decision describing the gravity of the case. If necessary, the patient can be forwarded to a hospital for further consultation. Methods: A cellphone (Nexus One model, with a 5 megapixel camera) was used to collect data and pictures from 100 randomly selected patients at the Ophthalmology Emergency Room located at the General Hospital of the Federal University of S?o Paulo (UNIFESP). Data was then sent remotely to an online recording system to be reviewed by an ophthalmologist who provided feedback regarding the state of ocular urgency. Results were then compared to the gold standard diagnosis provided at the hospital. Results: The diagnosis of urgency was given by two ophthalmologists: one in the hospital (gold standard) and one remotely. When we compared both diagnoses we obtained results of 81.94% specificity, 92.85% sensitivity, and 85% accuracy, with a negative predictive value of 96.72%. This work also included a processing time analysis, resulting in an average time of 8.6 min per patient for remote consultations. Conclusions: This study is the first that has used only a cellphone for diagnosing the urgency of ocular cases. Based on our results, the system can provide a reliable distinction between urgent and non-urgent situations and can offer a viable alternative for the servicing of underprivileged areas. In screening techniques, the most important outcome is to identify urgent cases with a high level of sensitivity and predictive negative value. Thus, our results demonstrate that this tool is robust and we suggest that a major study aimed to verify its efficiency in resource-poor areas should be initiated.
关键词： Diffusion of innovation,Telemedicine,Remote consultation,Ophthalmology,Eye diseases/diagnosis,Triage
更新于2025-09-04 15:30:14