Study on Retardation Mechanism of 3H, 99Tc, 137Cs, 237Np and 241AM in Compacted Sodium Bentonite

1992 ◽  
Vol 294 ◽  
Author(s):  
H. Sato ◽  
T. Ashida ◽  
Y. Kohara ◽  
M. Yui
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Atmospheric Condition ◽  
Diffusion Method ◽  
Dry Density ◽  
Sodium Bentonite ◽  
Apparent Diffusion Coefficients ◽  
Anion Exclusion ◽  
Apparent Diffusion ◽  
The One

ABSTRACTThe apparent diffusion coefficients were measured at room temperature (about 23°C) under atmospheric condition by the one-dimensional non-steady state diffusion method for 3H, 99Tc, 137Cs, 237Np and 241Am in compacted sodium-bentonite saturated with water. Sodium-bentonite, which is commercially available as KunigelVl®, was used in this study. Experiments were carried out in the density range of 0.4–2.0 (×103kg/m3). Bentonite in the cell was prepared to be saturated with distilled water. The measured apparent diffusion coefficient decreases with increasing dry density of bentonite. That the apparent diffusion coefficient of 3H decreased as a function of dry density of bentonite appears to be the effect of the change of porous structure with dry density of bentonite. 99Tc may be retarded by anion-exclusion because dominant diffusion specie of 99Tc is pertechnetate ion under atmospheric condition. Retardation for 137Cs may be caused by ion-exchange on bentonite. The sorption, anion-exclusion and molecular filtration are considered as a retardation mechanism for 237Np and 241Am because those dominant species are negatively charged and of large ionic size.

Diffusion Behavior for Se and Zr in Sodium-Bentonite

1994 ◽  
Vol 353 ◽  
Author(s):  
Haruo Sato ◽  
Mikazu Yui ◽  
Hideki Yoshikawa
Keyword(s):  
Diffusion Coefficients ◽  
Dominant Species ◽  
Atmospheric Condition ◽  
Aerobic Condition ◽  
Diffusion Method ◽  
Dry Density ◽  
Sodium Bentonite ◽  
Apparent Diffusion Coefficients ◽  
Anion Exclusion ◽  
Apparent Diffusion

AbstractApparent diffusion coefficients for Se and Zr in bentonite were measured by in-diffusion method at room temperature using water-saturated sodium-bentonite. KunigelVl® * containing 50wt% Na-smectite as a major mineral was used as the bentonite material. The experiments were carried out in the dry density range of 400–1800kg/m3. Bentonite samples were immersed with distilled water and saturated before the experiments. The experiments for Se were carried out under N2 atmospheric condition (O2: 2.5ppm). Those for Zr were carried out under aerobic condition. The apparent diffusion coefficients decrease with increasing density of the bentonite. Since dominant species of Se in the pore water is predicted SeO32-, Se may be retarded by anion-exclusion because of negative charge on the surface of the bentonite and little sorption. The dominant species of Zr in the porewater is predicted Zr(OH)5- or HZrO3-. Distribution coefficient measured for Zr on the bentonite was about 1.0m3/kg from batch experiment. Therefore, the retardation may be caused by combination of the sorption and the anion-exclusion. A modelling for the diffusion mechanisms in the bentonite were discussed based on an electric double layer theory. Comparison between the apparent diffusion coefficients predicted by the model and the measured ones shows a good agreement.

scholarly journals Classification of paediatric brain tumours by diffusion weighted imaging and machine learning

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jan Novak ◽  
Niloufar Zarinabad ◽  
Heather Rose ◽  
Theodoros Arvanitis ◽  
Lesley MacPherson ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Posterior Fossa ◽  
Brain Tumours ◽  
Diffusion Weighted Imaging ◽  
Regions Of Interest ◽  
Apparent Diffusion Coefficients ◽  
Diffusion Weighted ◽  
Apparent Diffusion ◽  
Paediatric Brain Tumours

AbstractTo determine if apparent diffusion coefficients (ADC) can discriminate between posterior fossa brain tumours on a multicentre basis. A total of 124 paediatric patients with posterior fossa tumours (including 55 Medulloblastomas, 36 Pilocytic Astrocytomas and 26 Ependymomas) were scanned using diffusion weighted imaging across 12 different hospitals using a total of 18 different scanners. Apparent diffusion coefficient maps were produced and histogram data was extracted from tumour regions of interest. Total histograms and histogram metrics (mean, variance, skew, kurtosis and 10th, 20th and 50th quantiles) were used as data input for classifiers with accuracy determined by tenfold cross validation. Mean ADC values from the tumour regions of interest differed between tumour types, (ANOVA P < 0.001). A cut off value for mean ADC between Ependymomas and Medulloblastomas was found to be of 0.984 × 10−3 mm2 s−1 with sensitivity 80.8% and specificity 80.0%. Overall classification for the ADC histogram metrics were 85% using Naïve Bayes and 84% for Random Forest classifiers. The most commonly occurring posterior fossa paediatric brain tumours can be classified using Apparent Diffusion Coefficient histogram values to a high accuracy on a multicentre basis.

Diffusion of Lead from a Perforated Titanium-Shell Lead-Matrix Container

1991 ◽  
Vol 257 ◽  
Author(s):  
P. Mani Mathew ◽  
Paul A. Krueger ◽  
M. Krause
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Element Model ◽  
Dry Mass ◽  
Silica Sand ◽  
Apparent Diffusion Coefficients ◽  
Apparent Diffusion ◽  
Buffer Mixture ◽  
Source Concentration

ABSTRACTThis paper describes experiments and analyses conducted to determine the range of apparent diffusion coefficients of lead diffusing from an intentionally perforated lead-matrix titanium-shell container into a compacted 1:1 (by dry mass) silica-sand/sodium-bentonite buffer mixture saturated with Standard Canadian Shield Saline Solution at 363 K. Analysis of the experimental data using a single apparent diffusion coefficient could not explain the findings. A possible explanation of the behaviour is presented here. It uses a 2–D finite-element model with six lead species having six different apparent diffusion coefficients. The model can explain the data satisfactorily. Sixty-three percent of the source concentration consisted of slow-moving species, with an apparent diffusion coefficient of 10-15 m2 /s, whereas the fastest species, with an apparent diffusion coefficient of 10-10 m2 /s, constituted only three percent of the source concentration.

Effect of Carbonate on the Migration Behavior of Lanthanides in Compacted Bentonite

MRS Advances ◽  
2018 ◽  
Vol 3 (21) ◽  
pp. 1155-1160 ◽  
Author(s):  
Kazuya Idemitsu ◽  
Kazuyuki Fujii ◽  
Noriyuki Maeda ◽  
Yuki Kakoi ◽  
Noriya Okubo ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Atomic Number ◽  
Diffusion Coefficients ◽  
Chemical Species ◽  
Dry Density ◽  
Migration Behavior ◽  
Bicarbonate Concentration ◽  
Apparent Diffusion Coefficients ◽  
Carbonate Ion ◽  
Apparent Diffusion

ABSTRACTThe apparent diffusion coefficients of La, Nd, Eu, Dy, Er, and Lu in compacted bentonites were investigated at various bicarbonate concentrations. The apparent diffusion coefficients of these lanthanides tended to decrease with increasing dry density. At bicarbonate concentrations below 0.25 M, lanthanum had the largest diffusion coefficient (ca. 10-13 m2/s) at 1.0 Mg/m3, and the diffusion coefficient decreased with increasing atomic number. On the other hand, at bicarbonate concentrations above 0.25 M, lutetium had the largest diffusion coefficient, and the diffusion coefficient decreased with decreasing atomic number. In particular, lanthanum and neodymium had diffusion coefficients below 10-14 m2/s, even at 1.0 Mg/m3. The diffusion coefficient of europium was around 10-13 m2/s at 1.0 Mg/m3 and was influenced less by the bicarbonate concentration. The diffusion coefficient of lutetium increased from 2 × 10-14 to 10-12 m2/s as the bicarbonate concentration was increased to 1.0 M. The concentration of carbonate ion in the pore water of bentonite is estimated to be much lower than that in solutions in contact with bentonite from the viewpoints of solubility and chemical species of lanthanides.

scholarly journals Quantitative Evaluation of apparent diffusion coefficient in a large multi-unit institution using the QIBA diffusion phantom.

2020 ◽  
Author(s):  
Joshua P Yung ◽  
Yao Ding ◽  
Ken-Pin Hwang ◽  
Carlos E Cardenas ◽  
Hua Ai ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Coefficient Of Variation ◽  
Diffusion Weighted Imaging ◽  
Diffusion Weighted ◽  
Apparent Diffusion Coefficient Values ◽  
Wide Range ◽  
Apparent Diffusion ◽  
Adc Values ◽  
The One

Purpose: The purpose of this study was to determine the quantitative variability of diffusion weighted imaging and apparent diffusion coefficient values across a large fleet of MR systems. Using a NIST traceable magnetic resonance imaging diffusion phantom, imaging was reproducible and the measurements were quantitatively compared to known values. Methods: A fleet of 23 clinical MRI scanners was investigated in this study. A NIST/QIBA DWI phantom was imaged with protocols provided with the phantom. The resulting images were analyzed and ADC maps were generated. User-directed region-of-interests on each of the different vials provided ADC measurements among a wide range of known ADC values. Results: Three diffusion phantoms were used in this study and compared to one another. From the one-way analysis of the variance, the mean and standard deviation of the percent errors from each phantom were not significantly different from one another. The low ADC vials showed larger errors and variation and appear directly related to SNR. Across all the MR systems and data, the coefficient of variation was calculated and Bland-Altman analysis was performed. ADC measurements were similar to one another except for the vials with the lower ADC values, which had a higher coefficient of variation. Conclusion: ADC values among the three phantoms showed good agreement and were not significantly different from one another. The large percent errors seen primarily at the low ADC values were shown to be a consequence of the SNR dependence and very little bias was observed between magnetic strengths and manufacturers. ADC values between diffusion phantoms were not statistically significant. Future investigations will be performed to study differences in magnetic field strength, vendor, MR system models, gradients, and bore size. More data across different MR platforms would facilitate quantitative measurements for multi-platform and multi-site imaging studies. With the increasing usage of diffusion weighted imaging in the clinic, the characterization of ADC variability for MR systems provides an improved quality control over the MR systems.

Methods to measure apparent diffusion coefficients in compacted bentonite clays and data interpretation

1989 ◽  
Vol 16 (4) ◽  
pp. 434-443 ◽  
Author(s):  
S. C. H. Cheung
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Diffusion Coefficients ◽  
Data Interpretation ◽  
Clay Particles ◽  
Apparent Diffusion Coefficients ◽  
Compacted Bentonite ◽  
Diffusion Parameters ◽  
Apparent Diffusion ◽  
Bentonite Clays

The methods used to determine apparent diffusion coefficients and the appropriate parameters for modelling diffusion through compacted bentonite–water systems are assessed and discussed. The measured apparent diffusion coefficient can vary between methods. The discrepancies are shown to be due to heterogeneous diffusivities arising from the proximity of the surface of clay particles. Two different diffusivity pathways are identified and the diffusive flux is shown to be dictated by the charge of diffusing species, diffusion time, and soil fabric. Key words: apparent diffusion coefficient, methods, compacted bentonite, heterogeneous diffusion, parameters, pathways.

MRI apparent diffusion coefficient in a murine orthotopic glioblastoma model as a clinically translatable early readout of efficacy for AMG 595, an antibody drug conjugate targeting EGFRvIII.

2013 ◽  
Vol 31 (15_suppl) ◽  
pp. 11095-11095
Author(s):  
Brittany Yerby ◽  
Juan Estrada ◽  
Matthew D. Silva ◽  
Kevin J. Hamblett ◽  
Suzanne K. Coberly ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Apparent Diffusion Coefficient ◽  
Tumor Growth ◽  
Therapeutic Efficacy ◽  
Tumor Volume ◽  
Treated Group ◽  
Vehicle Group ◽  
Tumor Growth Inhibition ◽  
Apparent Diffusion Coefficients ◽  
Apparent Diffusion

11095 Background: Epidermal growth factor receptor variant III (EGFRvIII) is a constitutively active mutant of EGFR present in thirty to fifty percent of glioblastoma (GBM) patients. AMG 595, currently in Phase I trials, is composed of a fully human anti-EGFRvIII-specific antibody conjugated to the maytansinoid DM1 via a non-cleavable linker. The MRI apparent diffusion coefficient (MRI ADC) has been shown to correlate with tissue cellularity, and changes in MRI ADC can be an early indicator of therapeutic efficacy. The aim of this work is to evaluate MRI ADC as a clinically translatable early readout of tissue changes due to AMG 595 treatment in a murine orthotopic GBM model. Methods: D317 human GBM cells were intracranially injected into in female CB17 SCID mice at Day 0. Mice were randomized at Day 7, using tumor volumes calculated by MRI, and were treated with vehicle, 6.5, 11, or 22 mg/kg AMG 595 i.v. twice per week, or temozolomide 10 mg/kg p.o. daily five days per week (N=8/group). MRI was repeated at days 14 and 21. Tumor volumes were manually traced on multi-slice T2-weighted RARE images covering the entire tumor volume. The mean MRI apparent diffusion coefficients for each tumor in the vehicle and 22 mg/kg AMG 595-treated groups were calculated from diffusion-weighted spin echo images (b = 100-1200 s/mm2). Results: A dose-dependent effect of AMG 595 on tumor volume was observed at Day 21; growth was inhibited in both the temozolomide and AMG 595-treated groups (22 and 11 mg/kg) relative to vehicle (p<0.0001). At Day 14, this significant treatment effect on tumor volume was not yet detectable. However, mean MRI ADC values were already significantly higher in the AMG 595 (22 mg/kg) treated group than in the vehicle group (23% higher at Day 14, p<0.01 vs vehicle; 32% higher at Day 21, p<0.0001 vs vehicle). The increase in MRI ADC in the AMG 595-treated group preceded observable tumor growth inhibition in the AMG 595-treated animals. Conclusions: Increases in tumor MRI ADC in response to AMG 595 treatment precede measurable inhibition of tumor growth, supporting the use of MRI ADC as a clinically relevant early biomarker for therapeutic efficacy.

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