Total Diffusion Coefficient Research Articles

Molecular dynamics insights on the self-interstitial diffusion in α-Beryllium

Beryllium has some unique properties and plays a key role in many special applications. However, Beryllium (α-Be) is of close-packed hexagonal (HCP) crystal structure, which has a strong anisotropic feature and limits its applications. In this work, diffusion behaviors of the self-interstitial atom (SIA) in α-Be at the temperature of 300–1100 K are studied using molecular dynamics simulations. It is observed that the diffusion mechanisms are not only dominated by the SIA jumps among the BO and BS sites on the basal plane, but also by the jumps among the C and O sites along the c-axis, which strongly depend on temperature. Diffusion behaviors of SIA can be divided into two stages with the temperature of 300–800 K and 800–1100 K, respectively, in which diffusion coefficient component of the c-axis (D c) is higher than that of the basal plane (D b) at first and then becomes closer to the D b after 800 K, in consistent with diffusion mechanisms. When the temperature rises from 300 K to 1100 K, the total diffusion coefficient of SIA (D t) increases gradually from 0.34 × 10−4 cm2 s−1 to 1.13 × 10−4 cm2 s−1. With the temperature increasing from 300 K to 1100 K, the anisotropy factor (η = D c /D b) of SIA diffusion drastically decreases from 1.76 to 1.01 in α-Be, while the η increases from 0.21 to 0.70 in α-Zr with the temperature from 500 K to 1100 K.

Effect of voltage gradients on EK-PRB remediation: Experimental and molecular dynamics simulations

Electrokinetic-Permeable Reaction Barrier (EK-PRB) coupled remediation technology can effectively treat heavy metal-contaminated soil near coal mines. This study was conducted on cadmium (Cd), a widely present element in the soil of the mining area. To investigate the impact of the voltage gradient on the remediation effect of EK-PRB, the changes in current, power consumption, pH, and Cd concentration content during the macroscopic experiment were analyzed. A three-dimensional visualized kaolinite-heavy metal-water simulation system was constructed and combined with the Molecular Dynamics (MD) simulations to elucidate the migration mechanism and binding active sites of Cd on the kaolinite (001) crystalline surface at the microscopic scale. The results showed that the voltage gradient positively correlates with the current, power consumption, and Cd concentration during EK-PRB remediation, and the average removal efficiency increases non-linearly with increasing voltage gradient. Considering power consumption, average removal efficiency, and cost-effectiveness, the voltage range is between 1.5 and 3.0 V/cm, with 2.5 V/cm being the optimal value. The results of MD simulations and experiments correspond to each other. Cd2+ formed a highly stable adsorption structure in contrast to the Al–O sheet on the kaolinite (001) crystalline surface. The mean square displacement (MSD) curve of Cd2+ under the electric field exhibits anisotropy, the total diffusion coefficient DTotal increases and the Cd2+ migration rate accelerates. The electric field influences the microstructure of Cd2+ complexes. With the enhancement of the voltage gradient, the complexation between Cd2+ and water molecules is enhanced, and the interaction between Cd2+ and Cl− in solution is weakened.

Intravoxel incoherent motion diffusion-weighted imaging for predicting kidney allograft function decline: comparison with clinical parameters

ObjectiveTo evaluate the added benefit of diffusion-weighted imaging (DWI) over clinical parameters in predicting kidney allograft function decline.MethodsData from 97 patients with DWI of the kidney allograft were retrospectively analyzed. The DWI signals were analyzed with both the mono-exponential and bi-exponential models, yielding total apparent diffusion coefficient (ADCT), true diffusion (D), pseudo-diffusion (D*), and perfusion fraction (fp). Three predictive models were constructed: Model 1 with clinical parameters, Model 2 with DWI parameters, and Model 3 with both clinical and DWI parameters. The predictive capability of each model was compared by calculating the area under the receiver-operating characteristic curve (AUROC).ResultsForty-five patients experienced kidney allograft function decline during a median follow-up of 98 months. The AUROC for Model 1 gradually decreased with follow-up time > 40 months, whereas Model 2 and Model 3 maintained relatively stable AUROCs. The AUROCs of Model 1 and Model 2 were not statistically significant. Multivariable analysis showed that the Model 3 included cortical D (HR = 3.93, p = 0.001) and cortical fp (HR = 2.85, p = 0.006), in addition to baseline estimated glomerular filtration rate (eGFR) and proteinuria. The AUROCs for Model 3 were significantly higher than those for Model 1 at 60-month (0.91 vs 0.86, p = 0.02) and 84-month (0.90 vs 0.83, p = 0.007) follow-up.ConclusionsDWI parameters were comparable to clinical parameters in predicting kidney allograft function decline. Integrating cortical D and fp into the clinical model with baseline eGFR and proteinuria may add prognostic value for long-term allograft function decline.Critical relevance statementOur findings suggested that cortical D and fp derived from IVIM-DWI increased the performance to predict long-term kidney allograft function decline. This preliminary study provided basis for the utility of multi-b DWI for managing patients with a kidney transplant.Key points• Both clinical and multi-b DWI parameters could predict kidney allograft function decline.• The ability to predict kidney allograft function decline was similar between DWI and clinical parameters.• Cortical D and fp derived from IVIM-DWI increased the performance to predict long-term kidney allograft function decline.Graphical

Treatment Response Assessment in Multiple Myeloma: Histogram Analysis of Total Tumor Apparent Diffusion Coefficient based on Whole-body Diffusion-weighted MR Imaging.

The International Myeloma Working Group (IMWG) consensus criteria for response assessmentin multiple myeloma (MM) has methodological limitations. Whole-body diffusion-weighted imaging (DWI) with apparent diffusion coefficient (ADC) histogram analysis may be complementary to response assessment of MM. To explore the role of histogram analysis of the ADC based on the total tumor volume (ttADC) in response assessment in patients with newly diagnosed MM (NDMM). Retrospective. Thirty-six patients with NDMM. 3.0T/single-shot DWI echo planar imaging (EPI) sequence with an integrated slice-by-slice shimming (iShim) technique. Baseline (median: 1 day before treatment) and post-treatment (median: five cycles of therapy) whole-body DWI were analyzed. A region of interest (ROI) containing lesions on every section of baseline image was drawn to derive the per-patient total tumor data. Post-treatment image analysis was based on the same ROI as the corresponding baseline. Histogram metrics were extracted from both ROIs. Patients were categorized into the very good partial response or better (VGPR+) group and the less than VGPR group per the IMWG response criteria for response assessment. Progression-free survival (PFS) was also calculated. Mann-Whitney test and Fisher's exact or Chi-squared tests, Receiver operating characteristic (ROC) analysis and DeLong test, Kaplan-Meier analysis and Cox proportional hazards model. A two-tailed P-value <0.05 was considered statistically significant. Thirty patients were categorized into the VGPR+ group and six into the less than VGPR group. The ttADC histogram changes between post-treatment and baseline metrics (ΔttADC) revealed significant differences in all percentile values between the VGPR+ and less than VGPR groups. For distinguishing VGPR+, ΔttADC_5th percentile had the largest area under the curve (AUC) (0.950, 95% CI 0.821-0.995). Patients with lower ΔttADC_5th percentile values (cutoff point,188.193) showed significantly longer PFS (HR = 34.911, 95% CI 6.392-190.677). ttADC histogram may facilitate response assessment in patients with NDMM. 3 TECHNICAL EFFICACY: Stage 4.

Association of oropharyngeal cancer HPV status with diffusion-weighted MR imaging and FDG-PET parameters

BackgroundHuman papilloma virus (HPV) infection is an important risk factor in oropharyngeal cancer. Several studies have analyzed the association of tumoral HPV status and different imaging parameters in FDG-PET/CT and magnetic resonance (MR) diffusion-weighted imaging (DWI), with contradictory findings. In this retrospective study, the influence of HPV-status on different parameters in FDG-imaging and MR DWI is investigated. MethodsIn this retrospective, single-center study we analyzed patients diagnosed with oropharyngeal cancer between January 2018 and December 2020 at a tertiary center in Switzerland. HPV status was assessed via p16 immunohistochemistry and/or PCR. Standardized uptake value (SUV), total lesion glycolysis (TLG) and apparent diffusion coefficient (ADC) were measured in pretreatment imaging (FDG-PET/CT, FDG-PET/MR, DWI MR). Statistical analysis was performed using Mann-Whitney-U tests. All p values reported are two-sided, and p values < 0.05 were considered statistically significant. Results142 patients were included. 67% of tumors were HPV-positive. Mean SUVmax in FDG-PET was 15.0+/-5.9 for HPV-positive tumors and 18.6+/-9.7 for HPV-negative tumors (p = 0.15). Mean ADC was 1109 x 106 mm2/s+/-326.8 for HPV-positive tumors and 1045.8 x 106 mm2/s+/-467.0 for HPV-negative tumors (p = 0.76). Conclusionand Relevance: We found no correlation between oropharyngeal carcinoma HPV status and any of the analyzed imaging parameters.

Role of magnetic resonance imaging to differentiate between borderline and malignant serous epithelial ovarian tumors.

We aimed to differentiate serous borderline ovarian tumors (SBOT) from serous epithelial ovarian carcinomas (SEOC) using morphological and functional MRI findings, to improve the patient management. We retrospectively investigated 24 ovarian lesions diagnosed with SBOT and 64 ovarian lesions diagnosed with SEOC. Additional to the demographic and morphological findings T2W signal intensity ratio, mean apparent diffusion coefficient (ADCmean) and total apparent diffusion coefficient (ADCtotal) values were analyzed and compared between two groups. Bilaterality, pelvic free fluid presence, serum CA-125 level (U/mL), presence of pelvic peritoneal implant were in favor of SEOC. Lower maximum size of solid component and solid size to maximum size ratio, dominantly cystic and solid-cystic appearance, exophytic growth pattern, presence of papiller projection and papillary architecture and internal branching pattern, higher T2W signal intensity ratio, ADCmean and ADCtotal values were in favor of SBOT. Our study revealed that morphological and functional imaging findings were valuable in differentiating BSOT from SEOC.

Study on the mixing performance of mixing vane grids and mixing coefficient by CFD and subchannel analysis code in a 5×5 rod bundle

Mixing Vane Grid (MVG) is one of the most important structures in fuel assembly due to its high performance in mixing the coolant and ultimately increasing Critical Heat Flux (CHF), which avoids the temperature rising suddenly of fuel rods. To evaluate the mixing performance of the MVG, a Total Diffusion Coefficient (TDC) mixing coefficient is defined in the subchannel analysis code. Conventionally, the TDC of the spacer grid is obtained from the combination of experiments and subchannel analysis. However, the processing of obtaining and determine a reasonable TDC is much challenging, it is affected by boundary conditions and MVG geometries. In is difficult to perform all the large and costing rod bundle tests. In this paper, the CFD method was applied in TDC analysis. A typical 5 × 5 MVG was simulated and validated to estimate the mixing performance of the MVG. The subchannel code was used to calculate the TDC. Firstly, the CFD method was validated from the aspect of pressure drop and lateral temperature distribution in the subchannels. Then the effect of boundary conditions including the inlet temperature, inlet velocities, heat flux ratio between hot and cold rods and the arrangement of hot and cold rods on MVG mixing and TDC were studied. The geometric effects on mixing are also carried out in this paper. The effect of vane pattern on mixing was investigated to determine which one is the best to represent the grid's mixing performance.

Risk factors and strategies for recovery quality, postoperative pain, and recurrent fractures between percutaneous kyphoplasty and percutaneous vertebroplasty in elderly patients with thoracolumbar compression fractures: a retrospective comparative cohort study.

With the increase of clinical cases and the improvement of operation, we found that recurrent fracture of the adjacent vertebral body is a common long-term complication of percutaneous kyphoplasty (PKP). However, the mechanism of re-fracture of adjacent vertebrae after PKP has not been unified. Therefore, through retrospective study, this paper discussed the risk factors and countermeasures affecting the quality of rehabilitation, postoperative pain and recurrent fracture in elderly PKP patients. From December 2019 to May 2021, 313 patients with osteoporotic spinal fractures were analyzed retrospectively. Cases were allocated to percutaneous vertebroplasty (PVP; n=130) and PKP (n=183) groups according to the modes of operation. Visual analogue scale (VAS), Cobb angle, and Oswestry disability index (ODI) were evaluated. Based on the occurrence of new fractures, the PKP cohort (n=15) and control cohort (n=32) were classified. Questionnaires analyzed the postoperative re-fractures of people with different characteristics, and the influencing factors of postoperative re-fracture were measured by multivariate logistic regression analysis. The postoperative VAS scores were significantly lower in the PKP group. The ODI scores in the PKP group were considerably lower than those in the PVP group after surgery. Univariate analysis indicated that age, number of injured vertebrae, history of complicated fracture, number of operative vertebrae, and bone mineral density (BMD) were remarkably correlated with recurrent fracture after PKP. Logistic regression analysis indicated that age, operative vertebral body, BMD, and the number of injured vertebrae were independent risk factors for recurrent fracture after PKP. BMI, BMD, low back soft tissue injury, postoperative vertebral height recovery rate, sagittal Cobb angle improvement rate, total diffusion coefficient of bone cement, short-term complications, non-union, and recurrent fracture were the main risk factors of residual low back pain after PKP. The clinical efficacy of PKP in elderly patients with thoracolumbar vertebral compression fracture is superior to that of PVP. Clinical attention should be paid to identifying high-risk factors for complications after PKP, and preventive measures should be implemented to help reduce the occurrence of recurrent fractures and postoperative residual pain.

Whole body FDG PET/MR for progression free and overall survival prediction in patients with relapsed/refractory large B-cell lymphomas undergoing CAR T-cell therapy

BackgroundTo find semi-quantitative and quantitative Positron Emission Tomography/Magnetic Resonance (PET/MR) imaging metrics of both tumor and non-malignant lymphoid tissue (bone marrow and spleen) for Progression Free Survival (PFS) and Overall Survival (OS) prediction in patients with relapsed/refractory (r/r) large B-cell lymphoma (LBCL) undergoing Chimeric Antigen Receptor (CAR) T-cell therapy.MethodsA single-center prospective study of 16 r/r LBCL patients undergoing CD19-targeted CAR T-cell therapy. Whole body 18F-fluorodeoxyglucose (FDG) PET/MR imaging pre-therapy and 3 weeks post-therapy were followed by manual segmentation of tumors and lymphoid tissues. Semi-quantitative and quantitative metrics were extracted, and the metric-wise rate of change (Δ) between post-therapy and pre-therapy calculated. Tumor metrics included maximum Standardized Uptake Value (SUVmax), mean SUV (SUVmean), Metabolic Tumor Volume (MTV), Tumor Lesion Glycolysis (TLG), structural volume (V), total structural tumor burden (Vtotal) and mean Apparent Diffusion Coefficient (ADCmean). For lymphoid tissues, metrics extracted were SUVmean, mean Fat Fraction (FFmean) and ADCmean for bone marrow, and SUVmean, V and ADCmean for spleen. Univariate Cox regression analysis tested the relationship between extracted metrics and PFS and OS. Survival curves were produced using Kaplan–Meier analysis and compared using the log-rank test, with the median used for dichotomization. Uncorrected p-values < 0.05 were considered statistically significant. Correction for multiple comparisons was performed, with a False Discovery Rate (FDR) < 0.05 considered statistically significant.ResultsPre-therapy (p < 0.05, FDR < 0.05) and Δ (p < 0.05, FDR > 0.05) total tumor burden structural and metabolic metrics were associated with PFS and/or OS. According to Kaplan-Meier analysis, a longer PFS was reached for patients with pre-therapy MTV ≤ 39.5 ml, ΔMTV≤1.35 and ΔTLG≤1.35. ΔSUVmax was associated with PFS (p < 0.05, FDR > 0.05), while ΔADCmean was associated with both PFS and OS (p < 0.05, FDR > 0.05). ΔADCmean > 0.92 gave longer PFS and OS in the Kaplan-Meier analysis. Pre-therapy bone marrow SUVmean was associated with PFS (p < 0.05, FDR < 0.05) and OS (p < 0.05, FDR > 0.05). For bone marrow FDG uptake, patient stratification was possible pre-therapy (SUVmean ≤ 1.8).ConclusionsMTV, tumor ADCmean and FDG uptake in bone marrow unaffected by tumor infiltration are possible PET/MR parameters for prediction of PFS and OS in r/r LBCL treated with CAR T-cells.Trial registrationEudraCT 2016–004043-36.

Computational determination of a primary diffusion mode in [formula omitted]U-10Mo under irradiation

Low enriched uranium (< 20 %235U)-molybdenum (U-Mo) monolithic fuel is the primary candidate for high-performance research and test reactors and is in the process of being qualified to replace highly-enriched uranium (≥ 20 %235U) fuel. As part of the qualification process, it is critical to understand and predict the behavior of fission gas bubbles under irradiation, which affects fuel swelling and fuel failure. Mechanistic fuel models are being developed that can both reproduce the existing experimental data for fuel swelling, and be further applied to irradiation conditions beyond the experimental scope. Diffusion of species under irradiation conditions is an important parameter in the mechanistic fuel models; however, no temperature-relevant experimental diffusion data exists. In the present work, radiation-enhanced diffusion coefficients of U, Mo, and Xe in γU-10wt.%Mo were calculated in the temperature range between 300 K and 1400 K via rate-theory models and molecular dynamics simulations with an embedded-atom method interatomic potential for the U-Mo-Xe system. Accordingly, total diffusion coefficients under relevant irradiation conditions are determined using previously obtained intrinsic thermal diffusion and radiation-driven diffusion coefficients, as well as the newly calculated radiation-enhanced diffusion coefficients presented herein. Radiation-enhanced diffusion of U and Mo was dominant in the intermediate temperature range, whereas radiation-enhanced diffusion of Xe did not significantly contribute to total diffusion of Xe at the relevant fission rate densities. Radiation-enhanced diffusion of Xe became faster than both intrinsic thermal diffusion and radiation-driven diffusion at a fission rate density of 5×1022fiss/m3/s, which is higher than the typical fission rate density range in research reactors. The temperature regime where radiation-enhanced diffusion of each element dominated was dependent on the fission rate density. The total diffusion coefficients of U, Mo, and Xe, updated in this work, will be utilized as parameters in the mechanistic fuel models to help predict the behavior of fission gas bubbles under irradiation more accurately.

Impact of host phonons on interstitial diffusion

The net effect of host phonons on interstitial diffusion has remained as a fundamental knowledge gap in our current theories since the motions of the host atoms and interstitials were coupled in these theories. Here we study this effect through molecular dynamics simulations of hydrogen diffusion in palladium, in which the motions can be decoupled through pinning the host atoms. Mathematically this decoupling corresponds to expanding the total diffusion coefficient into a Taylor series, which separates the phonon contribution from the intrinsic interstitial jumping. Our results clearly show that palladium phonons significantly promote hydrogen diffusion. The phonon contribution, being linear with temperature at high temperatures and exponential at low temperatures, is fitted with Brownian motion model. The total diffusion of interstitials can be understood as the intrinsic interstitial jumping in a pinned host plus phonon-induced Brownian diffusion. The generality of our findings is validated by examining the motion of lithium in manganese oxide and carbon in iron.

Prediction of local diffusion coefficient based on images of fractured coal cores

Diffusion is a transport phenomenon in coal that plays a significant role in the productivity of coal seam gas (CSG) reservoirs. The diffusion coefficient quantifies the extent of gas diffusion in a coal sample. Diffusion coefficient is commonly measured as a bulk value for a core; however, it can vary spatially in a core, and its local variation is commonly ignored. We present an automated method to calculate local diffusion coefficients of krypton in a coal core using 3D microcomputed X-ray tomography (micro-CT) images. Fractures are identified from greyscale micro-CT images automatically and compared with the conventional watershed segmentation method. Local diffusion coefficients within the matrix are calculated automatically considering different fluid states. As gas within a coal core may be in the free state or adsorbed state, our method calculates the total diffusion coefficient taking into account the state of the fluid. We observe a variation of diffusion coefficient with time suggesting that as the gas accesses different regions of the pore matrix the diffusion rate changes. 3D diffusion coefficient maps are generated from the automated calculation, which shows the heterogeneity of the coal sample. The fractions of free and adsorbed gases are calculated, which allows further analysis of their individual impact on transport. Additionally, the proposed method can be applied to other fractured materials for automated diffusion coefficient measurements.

Molecular dynamics study on the adsorption and thermal properties of paraffin in graphene

Graphene is a promising filler to solve the low thermal conductivity and the leakage of phase change materials (PCM). Understanding the adsorbing process of PCM in porous graphene nanosheets and thermal property of composites is essential for practical application. The simulations reveal that the maximum adsorption range is 15 Å. The final structures of composites look like a spherical structure. The maximum adsorbing percentage of paraffin is 81.72% with the density of graphene at 0.3 g/cm3, which has a storage efficiency of 75.88%. With the increasing density, the total diffusion coefficients of composites slightly decrease in the range of 4∼5 × 10−10 m2/s. A dense phase around graphene affects the phase change behavior of paraffin. By analyzing the interaction energy and the phonon vibration coupling, the thermal conductivity of composites is found to increase with the increasing density of graphene. Due to the coactions of small calculated size and interfacial thermal resistance between graphene and paraffin, the current values of thermal conductivity are lower than the expected ones. In this paper, the optimum density of graphene is 0.5 g/cm3, at which latent heat and thermal conductivity of composites are 84.17 J/g and 0.51 W/m·K, respectively.

Early Response to Chemotherapy in Malignant Pleural Mesothelioma Evaluated Using Diffusion-Weighted Magnetic Resonance Imaging: Initial Observations

IntroductionWe compared the magnetic resonance imaging total tumor volume (TTV) and median apparent diffusion coefficient (ADC) of malignant pleural mesothelioma (MPM) before and at 4 weeks after chemotherapy, to evaluate whether these are potential early markers of treatment response. MethodsDiffusion-weighted magnetic resonance imaging was performed in 23 patients with MPM before and after 4 weeks of chemotherapy. The TTV was measured by semiautomatic segmentation (GrowCut) and transferred onto ADC maps to record the median ADC. Test-retest repeatability of TTV and ADC was evaluated in eight patients. TTV and median ADC changes were compared between responders and nonresponders, defined using modified Response Evaluation Criteria In Solid Tumors on computed tomography (CT) at 12 weeks after treatment. TTV and median ADC were also correlated with CT size measurement and disease survival. ResultsThe test-retest 95% limits of agreement for TTV were −13.9% to 16.2% and for median ADC −1.2% to 3.3%. A significant increase in median ADC in responders was observed at 4 weeks after treatment (p = 0.02). Correlation was found between CT tumor size change at 12 weeks and median ADC changes at 4 weeks post-treatment (r = −0.560, p = 0.006). An increase in median ADC greater than 5.1% at 4 weeks has 100% sensitivity and 90% specificity for responders (area under the curve = 0.933, p < 0.001). There was also moderate correlation between median tumor ADC at baseline and overall survival (r = 0.45, p = 0.03). ConclusionsDiffusion-weighted magnetic resonance imaging measurements of TTV and median ADC in MPM have good measurement repeatability. Increase in ADC at 4 weeks post-treatment has the potential to be an early response biomarker.

FPMD studies on the microstructures and transport properties of molten MgCl2-NaCl-KCl with addition of active metals

A purification protocol of molten MgCl2-NaCl-KCl (MNK) by adding active metals has been proposed to reduce the corrosion of alloy materials in the application of generation III concentrating solar power plants. In this work, the ionic transport properties and micro structural characteristics of metals (Mg, Na, and K) and molten MNK mixtures (metal-MNK) are investigated at 723 K by first principles molecular dynamics (FPMD) simulations. According to the evolution of total energy, the Mg-MNK is the most stable mixture, while the Na-MNK mixture has larger energy fluctuations resulting in a higher specific heat capacity. Studies have shown that the small amount of metal existing in the molten MNK has almost no effect on the ionic diffusion order, but total diffusion coefficients and thermal conductivities of metal-MNK mixtures are improved. Meanwhile, the intensity of diffracted light of molten MNK is weakened by metals, and the microstructures of molten MNK added with alkali metals are more susceptible than that with metallic Mg by analyzing the total and partial static structure factors. Furthermore, the intermediate range orders of metal-MNK are demonstrated, especially for Mg-Mg pairs hinting the formation of the Mg2+-void-Mg2+ structure or Mg2+-centered clusters. Overall, the FPMD results deeply elaborate the dynamic interactions of molten MNK and metallic particles, which give insights for the development of salt purification and corrosion inhibition technology.

Interfacial Effects on Transport Coefficient Measurements in Li-ion Battery Electrolytes

Development of Li+-containing electrolytes with improved transport properties requires reliable, reproducible, and ideally low volume techniques to rigorously understand ion-transport with varying composition. Precisely measuring the complete set of transport coefficients in liquid electrolytes under battery-relevant operating conditions is difficult and the reliability of these methods are sparsely described in electrolyte transport literature. In this work, we apply a potentiostatic polarization-based transport characterization approach typically used for polymer electrolytes to liquid electrolyte systems in an attempt to fully measure all transport coefficients (conductivity, total salt diffusion coefficient, thermodynamic factor and transference number) for the model system of LiPF6 in an ethylene carbonate—ethyl methyl carbonate (EC:EMC) mixture. Using systematic timescale and statistical analyses, we find that transport coefficients measured using potentiostatic polarization of Li-Li symmetric cells exhibit strong correlation to Li electrode interfacial resistance, indicating that such methods are probing both bulk and interfacial phenomena. This reveals a major roadblock in characterizing electrolyte systems where the interfacial resistance is significantly larger than ohmic electrolyte resistance. As a result, we find that methods that rely on potentiostatic Li metal stripping/plating do not readily result in reliable liquid electrolyte transport coefficients, unlike similar methods for solid polymer electrolytes, where interfacial resistances are typically smaller than electrolyte resistances at the elevated temperatures typically of interest for such electrolytes.

Comparison of Sr Transport in Compacted Homoionous Na and Ca Bentonite Using a Planar Source Method Evaluated at Ideal and Non-Ideal Boundary Condition

With the aim to determine the influence of dominant interlayer cation on the sorption and diffusion properties of bentonite, diffusion experiments with Sr on the compacted homoionous Ca- and Na-forms of Czech natural Mg/Ca bentonite using the planar source method were performed. The bentonite was compacted to 1400 kg·m−3, and diffusion experiments lasted 1, 3 or 5 days. Two methods of apparent diffusion coefficient Da determination based on the analytical solution of diffusion equation for ideal boundary conditions in a linear form were compared and applied. The determined Da value for Ca-bentonite was 1.36 times higher than that for Na-bentonite sample. Values of Kd were determined in independent batch sorption experiments and were extrapolated for the conditions of compacted bentonite. In spite of this treatment, the use of Kd values determined by batch sorption experiments on a loose material for the determination of effective diffusion coefficient De values from planar source diffusion experiments proved to be inconsistent with the standard Fickian description of diffusion taking into account only the pore diffusion in compacted bentonite. Discrepancies between Kd and De values were measured in independent experiments, and those that resulted from the evaluation of planar source diffusion experiments could be well explained by the phenomenon of surface diffusion. The obtained values of surface diffusion coefficients Ds were similar for both studied systems, and the predicted value of total effective diffusion coefficient De(tot) describing Sr transport in the Na-bentonite was four times higher than in the Ca-bentonite.

Global decrease in brain sodium concentration after mild traumatic brain injury.

The pathological cascade of tissue damage in mild traumatic brain injury is set forth by a perturbation in ionic homeostasis. However, whether this class of injury can be detected in vivo and serve as a surrogate marker of clinical outcome is unknown. We employ sodium MRI to test the hypotheses that regional and global total sodium concentrations: (i) are higher in patients than in controls and (ii) correlate with clinical presentation and neuropsychological function. Given the novelty of sodium imaging in traumatic brain injury, effect sizes from (i), and correlation types and strength from (ii), were compared to those obtained using standard diffusion imaging metrics. Twenty-seven patients (20 female, age 35.9 ± 12.2 years) within 2 months after injury and 19 controls were scanned with proton and sodium MRI at 3 Tesla. Total sodium concentration, fractional anisotropy and apparent diffusion coefficient were obtained with voxel averaging across 12 grey and white matter regions. Linear regression was used to obtain global grey and white matter total sodium concentrations. Patient outcome was assessed with global functioning, symptom profiles and neuropsychological function assessments. In the regional analysis, there were no statistically significant differences between patients and controls in apparent diffusion coefficient, while differences in sodium concentration and fractional anisotropy were found only in single regions. However, for each of the 12 regions, sodium concentration effect sizes were uni-directional, due to lower mean sodium concentration in patients compared to controls. Consequently, linear regression analysis found statistically significant lower global grey and white matter sodium concentrations in patients compared to controls. The strongest correlation with outcome was between global grey matter sodium concentration and the composite z-score from the neuropsychological testing. In conclusion, both sodium concentration and diffusion showed poor utility in differentiating patients from controls, and weak correlations with clinical presentation, when using a region-based approach. In contrast, sodium linear regression, capitalizing on partial volume correction and high sensitivity to global changes, revealed high effect sizes and associations with patient outcome. This suggests that well-recognized sodium imbalances in traumatic brain injury are (i) detectable non-invasively; (ii) non-focal; (iii) occur even when the antecedent injury is clinically mild. Finally, in contrast to our principle hypothesis, patients’ sodium concentrations were lower than controls, indicating that the biological effect of traumatic brain injury on the sodium homeostasis may differ from that in other neurological disorders.Note: This figure has been annotated.

Detection of renal allograft fibrosis with MRI: arterial spin labeling outperforms reduced field-of-view IVIM.

To compare the value of reduced field-of-view (FOV) intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI) and arterial spin labeling (ASL) for assessing renal allograft fibrosis and predicting long-term dysfunction. This prospective study included 175 renal transplant recipients undergoing reduced FOV IVIM DWI, ASL, and biopsies. Renal allograft fibrosis was categorized into ci0, ci1, ci2, and ci3 fibrosis according to biopsy results. A total of 83 participants followed for a median of 39 (IQR, 21-42) months were dichotomized into stable and impaired allograft function groups based on follow-up estimated glomerular filtration rate. Total apparent diffusion coefficient (ADCT), pure diffusion ADC, pseudo-perfusion ADC, perfusion fraction f from IVIM DWI, and renal blood flow (RBF) from ASL were calculated and compared. The area under the receiver operating characteristic curve (AUC) was calculated to assess the diagnostic and predictive performances. RBF was different in ci0 vs ci1 (147.9 ± 46.3 vs 126.0 ± 49.4 ml/min/100 g, p = .02) and ci2 vs ci3 (92.9 ± 46.9 vs 70.8 ± 37.8 ml/min/100 g, p = .03). RBF in the stable group was higher than that in the impaired group (144.73 ± 49.33 vs 102.19 ± 47.58 ml/min/100 g, p < .001). AUCs in distinguishing renal allograft fibrosis and predicting long-term allograft dysfunction for RBF were higher than cortical ADCT (ci0 vs ci1-3, 0.76 vs 0.59, p < .001; ci0-1 vs ci2-3, 0.79 vs 0.68, p = .01; ci0-2 vs ci3, 0.79 vs 0.68, p = .01; 0.76 vs 0.60, p = .04, respectively). Compared to reduced FOV IVIM DWI, ASL was a more promising technique for noninvasively distinguishing renal allograft fibrosis degree and predicting long-term allograft dysfunction. • Compared to total ADC from rFOV IVIM DWI, RBF from ASL can distinguish no fibrosis (ci0) vs mild fibrosis (ci1) (p = .02) and moderate fibrosis (ci2) vs severe fibrosis (ci3) (p = .04). • RBF had superior performance than diffusion parameters in discriminating fibrosis (no fibrosis [ci0] vs fibrosis [ci1-3], mild fibrosis [ci0-1] vs moderate to severe fibrosis [ci2-3], non-severe [ci0-2] vs severe [ci3] fibrosis; AUC = 0.76 vs 0.59, p < .001; 0.79 vs 0.68, p = .01; 0.79 vs 0.68, p = .01). • Compared to reduced FOV IVIM DWI, ASL was a more promising technique for noninvasively predicting long-term allograft dysfunction (AUC = 0.76 vs 0.60, p = .04).

Gas time-dependent diffusion in pores of deformed coal particles: Model development and analysis

Deformed coal provides favorable conditions for the occurrence of gas outburst disasters. The existing gas diffusion model cannot accurately calculate the lost gas amount during the sampling period of deformed coal. In order to solve the above problems, a new mathematical time-dependent diffusivity model (NMTDM) and its simplified model (SNMTDM) of deformed coal have been established and validated. At the same time, the performance and engineering application of models were also discussed. The results show that the fitting accuracy of NMTDM and SNMTDM to gas diffusion data is greater than that of unipore diffusion model (UDM) and simplified unipore diffusion model (SUDM), respectively, which indicates that it is reasonable to regard the diffusion coefficient of deformed coal as a time-dependent variable. The diffusion coefficient of adsorbed gas, diffusion coefficient of free gas and total diffusion coefficient of gas decrease with the increase of time, and SNMTDM can realize the accurate calculation of lost gas amount. However, when the application of SNMTDM extends beyond its applicable range, the calculating results of the model may deviate seriously from the actual values. The gas diffusion models established in this paper can improve the calculation accuracy of lost gas amount and gas content of deformed coal.