Relative Diffusion Research Articles

Predicting glioblastoma recurrence using multiparametric MR imaging of non-enhancing peritumoral regions at baseline

BackgroundTo assess the feasibility of multiparametric magnetic resonance imaging in predicting tumor recurrence in nonenhancing peritumoral regions in patients with glioblastoma at baseline. MethodsFifty-eight patients with recurrent glioblastoma underwent multiparametric magnetic resonance imaging, including T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging. Nonenhancing peritumoral regions with glioblastoma recurrence were identified by coregistering preoperative and post-recurrent magnetic resonance images. Regions of interest were placed in nonenhancing peritumoral regions with and without tumor recurrence to calculate the apparent diffusion coefficient value, and relative ratios of T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and cerebral blood volume values. ResultsSignificant lower relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative apparent diffusion coefficient but higher relative cerebral blood volume values were found in the nonenhancing peritumoral regions with tumor recurrence than without recurrence (all P < 0.05). The threshold values ≥ 0.89 for relative cerebral blood volume provide the optimal performance for predicting the nonenhancing peritumoral regions with future tumor recurrence, with the sensitivity, specificity, and accuracy of 84.7%, 83.6%, and 85.8%, respectively. The combination of relative T2-weighted fluid-attenuated inversion recovery signal intensity, apparent diffusion coefficient, and relative cerebral blood volume can provide better predictive performance than relative cerebral blood volume (P = 0.015). ConclusionThe combined use of T2-weighted fluid-attenuated inversion recovery, diffusion-weighted imaging, and dynamic susceptibility contrast perfusion-weighted imaging can effectively estimate the risk of future tumor recurrence at baseline.

Interface homogenization control and microstructural analysis of ZrC0.85 joints diffusion bonded using Nb and Ti/Nb/Ti as the interlayer

Joint homogenization during transition metal carbides ceramic bonding has attracted much attention as a technique to increase the service temperature and relieve the residual stress for various high-temperature applications. In this work, homogeneous joints of ZrC0.85 ceramic were obtained by diffusion bonding using single Nb and multiple Ti/Nb/Ti as the interlayer. The effect of interlayer composition, bonding temperature and holding time on the microstructure of the joints was investigated. The effect of Nb and Ti on the composition homogeneity and the formation of Kirkendall voids in the ZrC0.85 joints was also discussed. When using single Nb as the interlayer, the homogenization of the joints can be achieved at a bonding temperature of ∼1500 °C and holding for 1 h and no Kirkendall voids were observed when further increasing the bonding temperature to 1600 °C because of the good mutual solubility of NbCx and ZrCx and the relative moderate diffusion rate of Nb. However, severe Kirkendall effects were observed at a higher temperature of 1700 °C, which would deteriorate the high-temperature performance of the joints. The adoption of Ti/Nb/Ti further minished the diffusion rate difference of the interfacial elements through the formation of TiCx phase. As a result, only a few Kirkendall voids were formed at 1700 °C. Nano-hardness of the resultant homogeneous joints was comparable to that of the ZrC0.85 ceramic due to their similar composition. This study shows that active diffusion bonding based on interlayer design for homogeneous joints could pave a new way to join transition metal carbides.

Voxel-Wise Fusion of 3T and 7T Diffusion MRI Data to Extract more Accurate Fiber Orientations.

While 7T diffusion magnetic resonance imaging (dMRI) has high spatial resolution, its diffusion imaging quality is usually affected by signal loss due to B1 inhomogeneity, T2 decay, susceptibility, and chemical shift. In contrast, 3T dMRI has relative higher diffusion angular resolution, but lower spatial resolution. Combination of 3T and 7T dMRI, thus, may provide more detailed and accurate information about the voxel-wise fiber orientations to better understand the structural brain connectivity. However, this topic has not yet been thoroughly explored until now. In this study, we explored the feasibility of fusing 3T and 7T dMRI data to extract voxel-wise quantitative parameters at higher spatial resolution. After 3T and 7T dMRI data was preprocessed, respectively, 3T dMRI volumes were coregistered into 7T dMRI space. Then, 7T dMRI data was harmonized to the coregistered 3T dMRI B0 (b = 0) images. Last, harmonized 7T dMRI data was fused with 3T dMRI data according to four fusion rules proposed in this study. We employed high-quality 3T and 7T dMRI datasets (N = 24) from the Human Connectome Project to test our algorithms. The diffusion tensors (DTs) and orientation distribution functions (ODFs) estimated from the 3T-7T fused dMRI volumes were statistically analyzed. More voxels containing multiple fiber populations were found from the fused dMRI data than from 7T dMRI data set. Moreover, extra fiber directions were extracted in temporal brain regions from the fused dMRI data at Otsu's thresholds of quantitative anisotropy, but could not be extracted from 7T dMRI dataset. This study provides novel algorithms to fuse intra-subject 3T and 7T dMRI data for extracting more detailed information of voxel-wise quantitative parameters, and a new perspective to build more accurate structural brain networks.

Dynamic α-factor models for fine-bubble- and surface aeration – impact of settleability and implications on N2O emission

In water resource recovery facilities (WRRF), aeration efficiency and N2O greenhouse gas emission are affected by the variability of the α-factor. Dynamic calibration of α using sensor data represents a significant knowledge gap this contribution aims to address. To assess factors influencing oxygen and N2O gas mass-transfer, a continuous flow laboratory-scale reactor system was operated to encourage the proliferation of filamentous bacteria. Gas mass-transfer was assessed using fine-bubble and surface aeration. Significant impacts of solid settling velocity on the α-factor – relative to that by MLSS concentration – is obtained. The feasibility of using solid settling velocity and concentration, as α-factor predictors, is tested. The theoretical approach of using relative diffusivity to dissolved oxygen – as an effective predictor of N2O liquid–gas mass-transfer stripping – is experimentally validated, for the first time. Plant-wide WRRF simulations show that surface aeration is inferior to fine-bubble aeration in terms of greenhouse gas emission and treated water quality.

Computed tomography scanning revealed macropore-controlled N2O emissions under long-term tillage and cover cropping practices

Microscale alterations in soil physical characteristics resulting from long-term soil health practices can contribute to changes in soil nitrous oxide (N2O) emissions. In this study, we investigated soil N2O emissions in relation to pore characteristics influencing soil gas diffusivity under long-term tillage and cover cropping practices. Intact soil cores from tillage (conventional tillage, Conv. T versus no tillage, NT) and cover crop (hairy vetch, HV versus no cover crop, NC) treatments were used for N2O measurements and computed tomography (CT) scanning. Using X-ray CT technique with a resolution of 59 μm, pore structure parameters including macroporosity, number of macropores, anisotropy, fractal dimension, tortuosity, and connectivity were determined. The results showed that Conv. T and HV emitted significantly higher N2O than NT and NC, respectively. A similar trend was observed for macroporosity, Conv. T soils had 27.4 % higher CT-derived macroporosity than the NT soils and HV increased macroporosity by 31.1 % over the NC treatment. The number of macropores and fractal dimension were significantly higher whereas degree of anisotropy was significantly lower under HV compared to NC. In the upper 3 cm of soil, HV had a connected porosity, whereas the pores were disconnected and isolated in NC. These CT-derived properties; however, were not impacted by tillage treatments. N2O emissions were positively and significantly correlated to relative soil gas diffusivity, CT-derived macroporosity, number of macropores, and fractal dimension. Our results demonstrated that soil macroporosity and relative gas diffusivity could lead to improved understanding and predictability of N2O emissions under high soil moisture conditions.

Choice Behavior and Diffusion Impact Analysis of Connected and Autonomous Vehicle Travelers with Managed Lanes

Choice Behavior and Diffusion Impact Analysis of Connected and Autonomous Vehicle Travelers with Managed Lanes

Study on the Selection of Power Cable Rejuvenation Fluids Based on Relative Diffusion Coefficients

The present work presents and formulates a method for calculating the relative diffusion coefficient of rejuvenation fluid in injection cable rejuvenation technology, and the permeability characteristics of rejuvenation fluid in polyethylene insulation materials are calculated and compared. The main components of the rejuvenation fluid such as (Phenylmethyl-dimethoxysilane) PMDMS, (Diphenyldimethoxysilane) DPDMS and (Trimethylmethoxysilane) TMMS, and the catalysts such as (Tetra-isopropyl titanate) TIPT and (Tetra-isobutyl titanate) TIBT were analysed in depth. The article uses theoretical calculation method, combined with Helmroth and Limm-Hollifield models, to calculate the diffusion coefficients and relative diffusion coefficients of these compounds in polyethylene. Through comparative analysis of theoretical calculations, the optimal parameters for evaluating the permeability characteristics of rejuvenation fluids were determined. The research results show that TMMS has the best permeability characteristics in polyethylene, followed by PMDMS and DPDMS. In the catalyst, TIPT has better permeability characteristics than TIBT. And when selecting the composite formula for cable rejuvenation fluid, it is more convenient to use the relative diffusion coefficient as an index of diffusion characteristics. This research provides important theoretical basis and practical guidance for the formulation selection of cable rejuvenation fluids.

The diagnostic efficiency of integration of 2HG MRS and IVIM versus individual parameters for predicting IDH mutation status in gliomas in clinical scenarios: A retrospective study.

Currently, there remains a scarcity of established preoperative tests to accurately predict the isocitrate dehydrogenase (IDH) mutation status in clinical scenarios, with limited research has explored the potential synergistic diagnostic performance among metabolite, perfusion, and diffusion parameters. To address this issue, we aimed to develop an imaging protocol that integrated 2-hydroxyglutarate (2HG) magnetic resonance spectroscopy (MRS) and intravoxel incoherent motion (IVIM) by comprehensively assessing metabolic, cellular, and angiogenic changes caused by IDH mutations, and explored the diagnostic efficiency of this imaging protocol for predicting IDH mutation status in clinical scenarios. Patients who met the inclusion criteria were categorized into two groups: IDH-wild type (IDH-WT) group and IDH-mutant (IDH-MT) group. Subsequently, we quantified the 2HG concentration, the relative apparent diffusion coefficient (rADC), the relative true diffusion coefficient value (rD), the relative pseudo-diffusion coefficient (rD*) and the relative perfusion fraction value (rf). Intergroup differences were estimated using t-test and Mann-Whitney U test. Finally, we performed receiver operating characteristic (ROC) curve and DeLong's test to evaluate and compare the diagnostic performance of individual parameters and their combinations. 64 patients (female, 21; male, 43; age, 47.0 ± 13.7years) were enrolled. Compared with IDH-WT gliomas, IDH-MT gliomas had higher 2HG concentration, rADC and rD (P < 0.001), and lower rD* (P = 0.013). The ROC curve demonstrated that 2HG + rD + rD* exhibited the highest areas under curve (AUC) value (0.967, 95%CI 0.889-0.996) for discriminating IDH mutation status. Compared with each individual parameter, the predictive efficiency of 2HG + rADC + rD* and 2HG + rD + rD* shows a statistically significant enhancement (DeLong's test: P < 0.05). The integration of 2HG MRS and IVIM significantly improves the diagnostic efficiency for predicting IDH mutation status in clinical scenarios.

Mechanisms and kinetic model for steel corrosion in unsaturated cementitious materials

Considering the complex coupling of steel corrosion in partially saturated concrete filled with water, the quantitative description of control mechanisms is still under debate. This work provides new experimental evidence supporting that diffusion control (relative diffusion coefficient) is the dominant mechanism in controlling corrosion rate by limiting the ferrous ion migration in unsaturated concrete. Furthermore, a new mechanism-based kinetic model is developed to predict the corrosion rate in different cementitious materials and corrosion conditions. In addition, the proposed kinetic model can quantify the variation of critical [Cl−]/[OH−] with degree of saturation, classify corrosive conditions, and predict the electrical resistivity and corrosion rate relationships.

Note on the density of ISE and a related diffusion

The integrated super-Brownian excursion (ISE) is the occupation measure of the spatial component of the head of the Brownian snake with lifetime process the normalized Brownian excursion. It is a random probability measure on \mathbb{R} , and it is known to describe the continuum limit of the distribution of labels in various models of random discrete labelled trees. We show that f_{\mathrm{ISE}} , its (random) density, has almost surely a derivative f'_{\mathrm{ISE}} which is continuous and (\frac{1}{2}-\varepsilon) -Hölder for any \varepsilon &gt;0 but for no \varepsilon&lt;0 (proving a conjecture of Bousquet-Mélou and Janson). We conjecture that f_{\mathrm{ISE}} can be represented as a second-order diffusion of the form df'_{\mathrm{ISE}}(t) ={2}\sqrt{f_{\mathrm{ISE}}(t)}\, dB_{t} + g\bigg(f'_{\mathrm{ISE}}(t), f_{\mathrm{ISE}}(t),\int_{-\infty}^{t} f_{\mathrm{ISE}}(s)\,ds\bigg)dt, for some continuous function g , for t&gt;0 , and we give a number of remarks and questions in that direction. The proof of regularity is based on a moment estimate coming from a discrete model of trees, while the heuristic of the diffusion comes from an analogous statement in the discrete setting, which is a reformulation of explicit product formulas of Bousquet-Mélou and the first author (2012).

Hydrophilic Ti-MWW for catalyzing epoxidation of allyl alcohol

Titanosilicates are widely applied in the alkene epoxidation reactions with high reaction rate and selectivity to desired products. Their catalytic performance depends on the structure topology, the micro-environment of Ti active sites, and the hydrophobicity/hydrophilicity of zeolite framework. Herein, we focus on a hydrophilic substrate of allyl alcohol (AAL) and investigated catalytic performance of four titanosilicates (TS-1, Ti-MOR, Ti-MWW, and Re-Ti-MWW) in the AAL epoxidation reaction with hydrogen peroxide as the oxidant. Among them, Re-Ti-MWW, synthesized via the post-modification of Ti-MWW with piperidine, exhibited the highest activity. Moreover, the preferred solvent changed from MeCN for Ti-MWW to H2O for Re-Ti-MWW. The relative diffusion rate of AAL over Re-Ti-MWW was up to 466 × 10-7 s-1, much larger than those of other zeolites. The higher diffusion rate of Re-Ti-MWW was probably derived from the higher framework hydrophilicity as revealed by the smaller water contact angle of Re-Ti-MWW compared to the other zeolites, which contributed to the high activity in AAL epoxidation. In the continuous slurry reactor, Re-Ti-MWW achieved a high catalytic lifetime of 163 h, with the selectivity of desirable glycidol product maintained at &gt; 97% in the H2O solvent system, showing high potential as an industrial catalyst for the AAL epoxidation reaction.

Random Amplified Polymorphic DNA (RAPD)-PCR analysis of genotypic and phenotypic characteristics of MethicillinResistant &lt;i&gt;Staphylococcus epidermidis&lt;/i&gt; (MRSE) strains involved in biofilm formation

Purpose: The current study aims to investigate genotypic and phenotypic aspects of methicillinresistant Staphylococcus epidermidis (MRSE) strains involved in the biofilm formation and the attendance of the icaADB gene and genotypic characterization of this gene by random amplified polymorphic DNA (RAPD) PCR.Methods: 60 Staphylococcus epidermidis strains were isolated from clinical specimens, suspected of having the bacteria, from the laboratories of Isfahan. Biofilm formation was measured by the microtiter plate method. The attendance of biofilm formation genes was studied using PCR and all isolates producing biofilm (strong and moderate) were genetically classified by RAPD-PCR.Results: 37 isolates (61.7%) were MRSE and all positive biofilm strains. The prevalence of biofilmrelated genes in the isolates was SesC (100%), SesI (45.9%), icaA (29.7%), icaB (37.8%), icaC (81.08%), icaD (70.2%), arcA (81.08%), and opp3AB (70%). PCR analysis showed that among 30 isolates of strong and medium biofilm production, 70% (21/30) positive for the icaADB gene. The Dendrograms obtained from RAPD-PCR results showed that all nine main clusters were at an 80% similarity level, and there were four isolates of a single type.Conclusion: These findings confirmed the high genotypic diversity of biofilm-producing MRSE strains and the relative diffusion of specific clones among clinical samples.

The value of diffusion-weighted imaging in the natural history of meningiomas: a predictor of tumor growth.

The general trend in meningioma treatment is shifting from surgery to active surveillance. However, the natural history of meningioma still needs to be clarified, and a simple, practical method is needed to identify fast-growing tumors. The authors aimed to determine whether diffusion-weighted imaging (DWI) could be a valuable imaging modality for predicting meningioma growth. Consecutive asymptomatic patients with a meningioma diagnosed on MRI and followed up at the authors' institution between July 2011 and July 2019 were eligible for inclusion in this retrospective study. Univariable and multivariable Cox regression analyses were used to explore whether the relative apparent diffusion coefficient (rADC) was an independent predictor of meningioma growth. Correlations between tumor growth rate (TGR), tumor volume doubling time (VDT), Ki-67, and rADC were assessed using the Pearson correlation coefficient. The predictive ability of rADC was evaluated using receiver operating characteristic (ROC) curves and validated with internal validation data. Sixty-four patients (47 females, 17 males) with a mean age of 62.2 ± 1.4 years were included in this study. Univariable and multivariable analyses revealed that rADC was an independent predictor of meningioma growth (p < 0.05). ROC curve analysis showed that baseline rADC had good predictive power for growing meningiomas (AUC = 0.88, 95% CI 0.78-0.96), as well as slow- or fast-growing meningiomas (AUC = 0.83, 95% CI 0.59-0.98). Moreover, rADC still had a good ability to discriminate between growing and nongrowing meningiomas in the validation set (AUC = 0.85, 95% CI 0.64-1.00). In the 20 patients with tumor growth, baseline rADC was moderately negatively correlated with TGR (r = -0.50, p = 0.02) and strongly positively correlated with VDT (r = 0.63, p = 0.003). Moreover, Ki-67 was significantly associated with rADC in 8 patients who had undergone surgery (r = -0.75, p = 0.03). In asymptomatic meningiomas, the lower the rADC at baseline, the faster the TGR and the shorter the VDT. DWI could be a valuable tool in predicting meningioma growth in asymptomatic patients.

Diffusion Tensor Imaging for Characterizing Changes in Triple-Negative Breast Cancer During Neoadjuvant Systemic Therapy.

Assessment of treatment response in triple-negative breast cancer (TNBC) may guide individualized care for improved patient outcomes. Diffusion tensor imaging (DTI) measures tissue anisotropy and could be useful for characterizing changes in the tumors and adjacent fibroglandular tissue (FGT) of TNBC patients undergoing neoadjuvant systemic treatment (NAST). To evaluate the potential of DTI parameters for prediction of treatment response in TNBC patients undergoing NAST. Prospective. Eighty-six women (average age: 51 ± 11 years) with biopsy-proven clinical stage I-III TNBC who underwent NAST followed by definitive surgery. 47% of patients (40/86) had pathologic complete response (pCR). 3.0 T/reduced field of view single-shot echo-planar DTI sequence. Three MRI scans were acquired longitudinally (pre-treatment, after 2 cycles of NAST, and after 4 cycles of NAST). Eleven histogram features were extracted from DTI parameter maps of tumors, a peritumoral region (PTR), and FGT in the ipsilateral breast. DTI parameters included apparent diffusion coefficients and relative diffusion anisotropies. pCR status was determined at surgery. Longitudinal changes of DTI features were tested for discrimination of pCR using Mann-Whitney U test and area under the receiver operating characteristic curve (AUC). A P value <0.05 was considered statistically significant. 47% of patients (40/86) had pCR. DTI parameters assessed after 2 and 4 cycles of NAST were significantly different between pCR and non-pCR patients when compared between tumors, PTRs, and FGTs. The median surface/average anisotropy of the PTR, measured after 2 and 4 cycles of NAST, increased in pCR patients and decreased in non-pCR patients (AUC: 0.78; 0.027 ± 0.043 vs. -0.017 ± 0.042 mm2 /s). Quantitative DTI features from breast tumors and the peritumoral tissue may be useful for predicting the response to NAST in TNBC. 1 TECHNICAL EFFICACY: Stage 4.

Insights into the solid-liquid interface of ionic liquid-immobilized solid acid catalyst for isobutane alkylation

The hydrophobic surface modification of solid acids can modulate the interfacial behaviors for isobutane alkylation. Herein, the interfacial properties between isobutane/butene mixtures and immobilized chloroaluminate ionic liquids with different alkyl chain lengths (e.g., ethyl, butyl, hexyl, and octyl groups) on silica substrates were studied through molecular dynamics simulations. The immobilization of ILs leads to obvious aggregation of C4 reactants and improves molar ratio of isobutane to 2-butene (I/O) at the interface, e.g., SiO2-[EPIm][Al2Cl7] (I/O = 1.17) versus pure SiO2 (I/O = 0.77) systems. With the prolonged alkyl chain of cations, the interfacial thickness gradually increases, while the I/O molar ratio exhibits the opposite order. Despite the inhibited diffusion of C4 reactants by immobilized ILs, the relative diffusion of isobutane to 2-butene is improved as the alkyl chain of cations prolongs. The above information suggests that the immobilization of ionic liquids with butyl groups is a good choice for isobutane alkylation.

Formation and state of research on deformation and diffusion of political institutions and inter-institutional relations in political science

Formation and state of research on deformation and diffusion of political institutions and inter-institutional relations in political science

FRACTAL ANALYSIS FOR PERMEABILITY OF MULTIPLE SHALE GAS TRANSPORT MECHANISMS IN ROUGHENED TREE-LIKE NETWORKS

In this work, a new gas transport model for shale reservoirs is constructed by embedding randomly distributed roughened tree-like bifurcation networks into the matrix porous medium. We constructed apparent permeability models for different shale gas flow mechanisms based on fractal theory, taking into account the effects of relative roughness and surface diffusion. The effects of bifurcation structure parameters as well as shale gas parameters on different apparent permeabilities are systematically analyzed. It is found that the permeability generally shows a decreasing trend with the increase in pore pressure, but the effect on viscous flow is inconsiderable. In addition, larger porosity, fractal dimension and bifurcation levels lead to increased permeability of different mechanisms. Whereas, the increase in the bifurcation levels implies a greater flow resistance, resulting in a decreased permeability. In addition, The relative roughness hinders the development of total permeability but favors surface diffusion permeability. Moreover, larger length ratios and diameter ratios are beneficial to the shale gas flow.

Pore‐Scale Modeling of Water and Ion Diffusion in Partially Saturated Clays

AbstractAn accurate mechanistic understanding of solute diffusion in partially saturated clays is critical for assessing the safety of deep geological repositories for radioactive waste. In this study, a pore‐scale numerical framework is developed to simulate water and ion diffusion in partially saturated clays. First, the two‐phase Shan‐Chen Lattice Boltzmann method is employed to establish the liquid‐gas distribution in a reconstructed three‐dimensional pore geometry of a clay. An equivalent solute method is also developed and validated to improve the numerical stability of the solution at the liquid/gas interface corresponding to steep variations of the concentration and diffusion coefficient of the water tracer. By using a mobility‐distance relationship from molecular simulations, Fick's law is numerically solved to simulate water diffusion in nanopores, while the coupled Poisson‐Boltzmann‐Nernst‐Planck equations are solved to simulate ion diffusion under the influence of the electrical double layer (EDL). Our model reveals that the decrease of relative effective diffusion coefficients during the desaturation is more pronounced for ions than for water, due to the additional transport pathway of water tracers in the gas phase. The obtained effective diffusion coefficients of tritiated water and ions agree well with reported data from compacted sedimentary rocks. By comparing the local electric potential and the distribution of ion concentrations in single pores, the simulation results suggest that the EDL in unsaturated clays has a more complex influence on ion distribution than under fully water‐saturated conditions. This study provides critical insights into the coupled transport processes of solutes in partially saturated clays.

Separation of active chiral particles with different diffusion coefficients

In recent years, the study of active particles has become one of the important topics concerned by researchers in many fields, among which the phase separation of active chiral particles has important theoretical and practical significance. In this paper, the phase separation of binary mixed systems composed of active chiral particles with different diffusion coefficients is studied by Langevin dynamics. A smaller relative diffusion coefficient is conducive to the formation of large clusters and the separation of “cold” particles, while a larger relative diffusion coefficient will weaken the separation effect. Due to the influence of particle characteristics (self-driven velocity, self-rotational angular velocity) and relative diffusion coefficient on the collision between particles, if one wants the “cold” and “hot” particles to reach phase separation, increasing (or reducing) the self-driven velocity and self-rotational angular velocity cannot be synchronous, and the relative rate of change of self-driven velocity is smaller than that of the self-rotational angular velocity. By analyzing the changes of the effective diffusion coefficient of “cold” particles, the phenomenon of phase separation in the system can be better explained. A smaller effective diffusion coefficient means that the “cold” particles will aggregate into larger clusters, and the system may exhibit phase separation. However, when the effective diffusion coefficient is larger, the diffusion of “cold” particles is stronger and the “cold” particles will not form large clusters, which means that the system cannot aggregate into phase separation. In addition, with the filling rate of particle increasing, the proportion curve of the number of cold particles in maximum cold particle cluster undergoes a non-monotonic change, specifically, it first increases and then decreases. Each curve has an optimal filling rate but its width is different .With the increase of the relative diffusion coefficient and self-driven velocity, the width of the optimal filling rate of the proportion curve will become narrower and shift toward the right.

Enhanced diffusion in thin-film Cu-Zr nanoglasses

Tracer measurements with both radioactive, 55Fe, as well as natural, mainly 56Fe, isotopes are used to investigate Fe diffusion in a Cu-Zr nanoglass in comparison to their diffusion rates in a homogeneous amorphous counterpart. The columnar-structured nanoglass and the homogeneous amorphous films are synthesized using radio-frequency magnetron sputtering. Ion beam sputtering (with the 55Fe radioisotope) and time-of-flight secondary ion mass spectroscopy (with natural Fe) are used for the diffusion experiments. Remarkably, faster Fe diffusion is observed in the columnar nanoglasses, supporting the concept of glass–glass interfaces. The relative diffusion enhancement is explained within the excess free volume concept that is supported by structural investigations using transmission electron microscopy. For the first time, the relaxation dynamics in a nanoglass as well as in a homogeneous thin-film glass of identical composition are evaluated via time-dependent diffusion measurements.