Apparent Dispersion Coefficient Research Articles

Identification of Luminal A breast cancer by using deep learning analysis based on multi-modal images.

To evaluate the diagnostic performance of a deep learning model based on multi-modal images in identifying molecular subtype of breast cancer. A total of 158 breast cancer patients (170 lesions, median age, 50.8 ± 11.0 years), including 78 Luminal A subtype and 92 non-Luminal A subtype lesions, were retrospectively analyzed and divided into a training set (n = 100), test set (n = 45), and validation set (n = 25). Mammography (MG) and magnetic resonance imaging (MRI) images were used. Five single-mode models, i.e., MG, T2-weighted imaging (T2WI), diffusion weighting imaging (DWI), axial apparent dispersion coefficient (ADC), and dynamic contrast-enhanced MRI (DCE-MRI), were selected. The deep learning network ResNet50 was used as the basic feature extraction and classification network to construct the molecular subtype identification model. The receiver operating characteristic curve were used to evaluate the prediction efficiency of each model. The accuracy, sensitivity and specificity of a multi-modal tool for identifying Luminal A subtype were 0.711, 0.889, and 0.593, respectively, and the area under the curve (AUC) was 0.802 (95% CI, 0.657- 0.906); the accuracy, sensitivity, and AUC were higher than those of any single-modal model, but the specificity was slightly lower than that of DCE-MRI model. The AUC value of MG, T2WI, DWI, ADC, and DCE-MRI model was 0.593 (95%CI, 0.436-0.737), 0.700 (95%CI, 0.545-0.827), 0.564 (95%CI, 0.408-0.711), 0.679 (95%CI, 0.523-0.810), and 0.553 (95%CI, 0.398-0.702), respectively. The combination of deep learning and multi-modal imaging is of great significance for diagnosing breast cancer subtypes and selecting personalized treatment plans for doctors.

On the apparent dispersion coefficient of the equilibrium dispersion model: An asymptotic analysis

To model chromatography, researchers have developed several approaches. These cover a broad range of applications and, depending on the assumptions adopted, have different levels of accuracy. In general, the most suitable modelling approach is the simplest that can describe a process with the desired accuracy. A model that often meets this criterion is the equilibrium dispersion model (EDM). This features one mass balance equation per analyte, including an axial dispersion term, and assumes the analyte concentrations in the mobile and stationary phases to be in local equilibrium. To account for the finite mass transfer rate between the phases, the model employs an apparent dispersion coefficient. Two expressions are available for this coefficient, one being used much more frequently than the other. In this paper, we aimed to clarify which one should be favoured. A desirable feature of simple models is that they can be derived from more general ones with appropriate physical assumptions and rigorous mathematical methods. Thus, to answer our research question, we derived the EDM from the more general pore diffusion model (POR), using an asymptotic method. The expression obtained for the apparent dispersion coefficient does agree with one of the two reported in the literature – the less frequently used. To test the validity of this expression, we simulated elution profiles using the two versions of the EDM and compared the results against those from the POR model. The simulations were conducted in the range where the POR and EDM models should be essentially equivalent, their results confirming the outcome of the asymptotic analysis. This work offers a solid theoretical grounding for the EDM, clarifies which formulation of the model is correct, and provides usable applicability conditions for the model.

Triple-attention interaction network for breast tumor classification based on multi-modality images

Breast cancer can be diagnosed using medical imaging. Classification performance of medical imaging can be improved by multi-modality image fusion. However, existing fusion algorithm fail to consider the importance of modality interactions and cannot fully utilize multi-modality information. Attention mechanisms can effectively explore and combine multi-modality information. Thus, we propose a novel triple-attention interaction network for breast tumor classification based on diffusion-weighted imaging (DWI) and apparent dispersion coefficient (ADC) images. A triple inter-modality interaction mechanism is proposed to fully fuse the multi-modality information. Three modal interactions were performed through the developed inter-modality relation module, channel interaction module, and multi-level attention fusion module to explore the correlation, complementary, and discriminative information, respectively. Additionally, we introduce a novel dual parallel-attention module for the incorporation of spatial and channel attention to improve the discriminative ability of single-modality features. Using these mechanisms, the proposed algorithm can mine and explore useful multi-modality information fully, to improve classification performance. Experimental results demonstrate that our algorithm outperforms other multi-modality fusion algorithm, and extensive ablation studies were conducted to verify the advantages of our algorithm. The area under the receiver operating characteristic curve, accuracy, specificity, and sensitivity were 90.5%, 89.0%, 85.6%, and 92.4%, respectively.

Multiple directional DWI combined with T2WI in predicting muscle layer and Ki-67 correlation in bladder cancer in 3.0-T MRI.

To investigate the value of 3.0T MRI multi-directional diffusion-weighted imaging (DWI) combined with T2WI morphological features and lesion distribution in preoperative prediction of muscle layer invasion of bladder cancer (BC) and the correlation with postoperative Ki-67. This retrospective study enrolled patients with BC between 2019 and 2021. Patients with muscular invasive bladder cancer (MIBC) or non-muscular invasive BC (NMIBC) were also analyzed by preoperative 3.0T MRI aFostic efficacy. A total of 186 patients were enrolled. About 27 patients with MIBC (35 lesions in total) and 62 with NMIBC (99 lesions in total). We found the tumor with a larger size, a wide base, and a smaller apparent dispersion coefficient (ADC) value and normalized ADC(nADC) value, without a stalk, presenting a greater risk of muscle invasion. ADC value, nADC value, maximum diameter, and stalk were independently associated with muscle invasion. Lesions located at the bladder fundus or involvement of multiple sites were independently associated with muscle invasion compared to the bladder body. In combination with morphological features, the AUCs of ADC and nADC showed accuracies of 0.925 and 0.947-0.951, respectively. TADC and nTADC showed the best diagnostic efficacy in multiple respects. KI-67 LI was negatively correlated with ADC and nADC values. This is the first report in which we found Multi-directional DWI combined with T2WI in 3.0T MRI can be used to predict the muscle layer invasion of bladder cancer. ADC values reflect the muscular invasion of bladder cancer and show a moderate negative correlation with Ki-67. It is especially suitable for bladder cancer patients with renal insufficiency or tumor recurrence.

Loss of cervical sagittal alignment worsens the cervical spinal lesions in patients with Hirayama disease.

To quantify the cervical sagittal alignment in patients with Hirayama disease (HD) and to investigate the effect of loss of cervical sagittal alignment upon the cervical spinal lesions in HD. Cervical sagittal alignments were measured in 253 HD patients and 63 healthy subjects by C2-C7 Cobb and a modified method of Toyama et al. Motor unit number estimation (MUNE) was performed in bilateral abductor pollicis brevis (APB) in all HD patients, and 31 patients further underwent cervical diffusion tensor imaging (DTI). Compared with healthy subjects, HD patients showed lower C2-C7 Cobb (P < 0.05), and 83.4% patients showed loss of cervical lordosis (cervical straight or kyphosis), which was greater than healthy subjects (55.6%, P < 0.05). Compared with lordotic/straight group, patients with cervical kyphosis showed lower MUNE values and greater single motor unit potential (SMUP) in bilateral APB, and higher apparent dispersion coefficient (ADC) and lower fractional anisotropy were observed at C4/C5 level in the latter than the former (P < 0.05). C2-C7 Cobb was associated with both C4/C5 ADC and bilateral SMUP (P < 0.05). Most HD patients showed loss of cervical sagittal alignments, and both MUNE and DTI detections demonstrated a positive correlation between loss of cervical sagittal alignments and cervical spinal lesions in HD. These findings supported that loss of cervical sagittal alignments may worsen motor impairments in HD. Therefore, it is necessary for clinicians to be aware of restoring cervical sagittal alignments during HD treatment.

Synthetic relaxometry combined with MUSE DWI and 3D-pCASL improves detection of hippocampal sclerosis

PurposeTo investigate the diagnostic value of synthetic MRI combined MUSE DWI and 3D-pCASL in hippocampal sclerosis (HS). MethodA total of 30 HS patients participated in the study. At the same time, 51 healthy volunteers were collected as the control group. All patients and healthy volunteers underwent epilepsy MR scanning protocol (including oblique coronal MAGiC, MUSE DWI, and axial 3D-pCASL) at 3.0 T MR scanner.The independent samples T test and Mann-Whitney U test were used to compare the differences of the apparent dispersion coefficient(ADC), cerebral blood flow(CBF) and quantitative parameters, including T1 relaxation time (T1), T2 relaxation time (T2), and proton density (PD) values, in the hippocampus of the affected side of HS and the contralateral and control groups, respectively. The diagnostic performance was evaluated using binary logistic regression analysis and area under the receiver operating characteristic (ROC) curves (AUC). ResultsSignificant statistical differences in T1, T2, CBF, and ADC values were observed between the affected hippocampus of HS patients and contralateral and control hippocampus (all P < 0.005). The T2 has higher discrimination abilities compared with other univariable parameters, with the AUC of 0.899. The combined T2, ADC and CBF model had the best diagnostic performance of HS in MTLE patients with AUC, sensitivity and specificity of 0.946, 86.67 %, 93.33 %, respectively. ConclusionsRelaxometry parameters derived from synthetic MRI contributed to diagnosis of HS. The proposed approach combining T2, ADC and CBF showed a strong diagnostic capability.

Multi-modality relation attention network for breast tumor classification

Automatic breast image classification plays an important role in breast cancer diagnosis, and multi-modality image fusion may improve classification performance. However, existing fusion methods ignore relevant multi-modality information in favor of improving the discriminative ability of single-modality features. To improve classification performance, this paper proposes a multi-modality relation attention network with consistent regularization for breast tumor classification using diffusion-weighted imaging (DWI) and apparent dispersion coefficient (ADC) images. Within the proposed network, a novel multi-modality relation attention module improves the discriminative ability of single-modality features by exploring the correlation information between two modalities. In addition, a module ensures the classification consistency of ADC and DWI modality, thus improving robustness to noise. Experimental results on our database demonstrate that the proposed method is effective for breast tumor classification, and outperforms existing multi-modality fusion methods. The AUC, accuracy, specificity, and sensitivity are 85.1%, 86.7%, 83.3%, and 88.9% respectively.

[Study of magnetic resonance imaging based on liver imaging reporting and data system for evaluating phosphatidylinositol proteoglycan-3 expression in hepatocellular carcinoma].

Objective: To clarify the diagnostic value of magnetic resonance imaging based on liver imaging reporting and data system (LI-RADS) for phosphatidylinositol proteoglycan-3 (GPC3) expression in hepatocellular carcinoma (HCC). Methods: Clinical and pathological data of 95 HCC cases with positive GPC3 expression (+) and 40 HCC cases with negative GPC3 expression (-) were retrospectively analyzed, and their MRI image features based on the 2018 version of LI-RADS were compared. Multivariate logistic regression analysis was used to determine the main predictors of GPC3 expression. Receiver operating characteristic curve was used further to determine the diagnostic efficacy of combined clinical imaging model to predict GPC3 expression. Enumeration data were compared with χ2 test or Fisher's exact test. Measurement data were compared using independent samples t-test or Mann-Whitney U-test. Results: There were statistically significant differences between HCC in GPC3 (+) and GPC3(-) group at alpha-fetoprotein (AFP) levels (χ2=31.814, P<0.000 1), and MRI features: capsular enhacement (χ2=4.108, P=0.043), halo type enhancement (χ2=4.847, P=0.028), and lesion apparent dispersion coefficient (ADC) (t=2.552, P=0.011 8). Multivariate regression analysis showed that AFP>20 μg/L (OR=9.358, P<0.000 1) and ADC≤1.404×10-3 mm2/s (OR=1.003, P=0.017) were independent predictors for GPC3 expression in HCC. The combined model and the area under the curve value for the diagnosis of GPC3(+) in HCC was 0.810, and its diagnostic sensitivity and specificity were 76.8% and 77.5%, respectively. Conclusion: AFP>20 μg/L and ADC≤1.404×10-3 mm2/s may indicate the expression of GPC3 in HCC, and the combination of the two diagnostic indicators can provide a simple and effective non-invasive diagnostic method for clinical practice.

Evaluation of Magnetic Resonance Imaging for Microsurgical Efficacy and Relapse of Rolandic Meningioma.

In this study, magnetic resonance imaging (MRI) was used to evaluate the relapse features of patients with Rolandic meningioma after the microsurgery. 53 patients with Rolandic meningioma were selected as the research objects, and they were divided into the relapse group (n = 16) and nonrelapse group (n = 37) according to whether patients had a relapse during the follow-up period. Differences in quality of life, 1H-MRS index, vascular density, and cell proliferation between the two groups were assessed as well as imaging differences between the two groups were analyzed using MRI. The results showed that the patients' quality-of-life scores in the two groups increased notably after the surgical treatment (P < 0.05). Compared with the nonrelapse group, the proportion of irregular boundary and uneven enhancement of focal tissue in the relapse group was signally increased (P < 0.05). Compared with the nonrelapse group, cell proliferation index, vascular density and imaging index, mean tumor diameter, mean transit time (MTT), time to peak (TTP), fractional anisotropy (FA), choline (Cho)/N-acetylaspartic acid (NAA), Cho/creatine (Cr), lactic acid (Lac)/Cr, and the maximum value of relative cerebral blood volume (rCBVmax) in the relapse group were obviously increased (P < 0.05). However, the apparent dispersion coefficient, NAA/Cr, and Lac/NAA values decreased greatly (P < 0.05). To sum up, the microsurgical treatment helped improve the quality of life of patients with Rolandic meningioma, and MR imaging could be used to determine the relapse of Rolandic meningioma after microsurgical treatment.

Global fallout Pu isotopes, 137Cs and 237Np records in the sediments of Lake Xingkai and their response to environmental changes in the catchment

Plutonium (Pu) isotopes, neptunium-237 (237Np) and cesium-137 (137Cs) in the environment have emerged as important tools for promoting geochemical studies. To elucidate their source terms, deposition process, and the geochemical behavior, as well as their response to catchment environmental changes in lacustrine environment, 239, 240Pu, 137Cs and 237Np were determined for the first time in a sediment core collected from the Lake Xingkai. The 240Pu/239Pu atom ratios (0.163–0.178) in all sediment samples corresponded well with the typical global fallout value of ∼0.18, indicating that there were no other significant radioactive source inputs. The activity concentrations of 239+240Pu, 137Cs, and 237Np were 0.010–1.030 Bq kg−1, 6.4–30.1 Bq kg−1, and (0.020–2.195) × 10−3 Bq kg−1, respectively. They presented similar vertical distribution patterns, with a typical global fallout peak (15–16 cm) corresponding to the year of 1964. On the other hand, the 237Np/239Pu atom ratios exhibited a wide range (0.207–1.306), and showed a trend of increasing values with depth, implying different geochemical behaviors of these two elements. Using the advection-dispersion equation model (ADE), the obtained apparent dispersion coefficient of 237Np (0.58 ± 0.09 cm2 yr−1) was higher than that of 239+240Pu (0.38 ± 0.07 cm2 yr−1), indicating that Np has greater mobility than Pu. The total global fallout inventories of 239+240Pu, 137Cs, and 237Np were 145, 4592, and 0.291 Bq m−2, respectively. Approximately 46% of the total global fallout was derived from riverine input, indicating that severe soil erosion occurred in the catchment of Lake Xingkai in the past decades.

The Value of DTI Parameters in Predicting Postoperative Spinal Cord Function Fluctuations in Patients with High Cervical Disc Tumors.

Objective To explore the characteristics of magnetic resonance diffusion tensor imaging (DTI) parameters in patients with high cervical spinal myeloma and the evaluation of postoperative spinal cord function. Methods In recent years, 42 patients with high cervical spine myeloma were selected as the observation group, and 42 healthy volunteers were selected as the control group during the same period. The apparent dispersion coefficient (ADC), the fractional anisotropy (FA), the number of fiber bundles (FT), and the fiber bundle ratio (FTR) were compared between the two groups. The correlation between the ADC, FA, FT, FTR, and the International Standard for Neurological Classification of Spinal Cord Injury (ISNCSCI) score in the observation group were analyzed. Spinal cord function was evaluated using the Japanese Orthopaedic Association Score (JOA). Logistic regression model was used to analyze the factors affecting the recovery of spinal cord function after surgery. The receiver operating characteristic curve (ROC) was used to analyze the value of ADC, FA, FT, FTR1, and FTR2 in predicting the recovery of spinal cord function. Results The ADCs of the lesion layer and lower layer of the observation group were higher than the middle and lower layers of the control group, the FA and FT were lower than the middle and lower layers of the control group, and FTR1 and FTR2 were lower than those of the control group (P < 0.05). The ADC of the lesion layer in the observation group was negatively correlated with ISNCSCI score, and the FA, FT, FTR1, FTR2, and ISNCSCI scores were positively correlated (P < 0.05). Three months after the operation, JOA was used to evaluate the spinal cord function, which was excellent in 23 cases and poor in 19 cases. Logistic regression model analysis showed that after the ISNCSCI score was controlled, the increase in ADC and the decrease in FA, FT, FTR1, and FTR2 of the lesion layer were independent risk factors for poor postoperative body function recovery (P < 0.05). ROC analysis showed that the combination of ADC, FA, FT, FTR1, and FTR2 of the lesion layer predicted the AUC of spinal cord functional recovery was 0.941, which was better than the single prediction (P < 0.05). Conclusion The abnormal DTI parameter values of patients with high cervical spinal myeloma can better reflect the lack of spinal cord function, and they can effectively predict the recovery of the patient's body function after surgery, providing a reference for clinical diagnosis and treatment.

Spatial distribution and migration of 239+240Pu in Chinese soils

The migration of radionuclides is a critical threat to the soil and groundwater environment. This study investigates highly radiological toxic 239+240Pu in 647 surface soils and 66 soil cores in China. First, the spatial distributions of 239+240Pu activities and 240Pu/239Pu ratios are presented in Chinese surface soils. Second, four different types of vertical distribution of 239+240Pu, namely 45.4%, 40.9%, 9.1% and 4.5% of Chinese soil cores proportions are integrated using statistical analysis. Furthermore, different soil types are accompanied by different 239+240Pu vertical distributions, which relate closely to the 239+240Pu migration. Finally, based on the Convection Dispersion Equation (CDE) model, the present work find that the apparent convection velocities of 239+240Pu are ranging from 0.00032 ± 0.00031 cm a−1 to 0.473 ± 0.083 cm a−1. As shown by the four typical vertical activity distribution of 239+240Pu in soil cores, the deepened activity maximum value position of 239+240Pu implies a fast migration rate or apparent convection velocity. This study, for the first time, suggests a significant linear correlation (R2 = 0.847) between the depth of 239+240Pu maximum value (cm) and the apparent convection velocity (v, cm a−1). We hypothesize that v usually does not exceed 0.5 cm a−1 in the CDE model. A significant linear correlation is also identified between apparent dispersion coefficient (D, cm2 a−1) and v2 in Chinese soil cores from the CDE model. It will provide an important reference for harmful heavy metal migration research in the future.

Source, Spatial Distribution and Migration of &lt;sup&gt;239+240&lt;/sup&gt;Pu in Chinese Soils

The source, spatial distribution, typical vertical distribution and migration of 239+240 Pu in Chinese 647 surface soils and 66 soil cores are investigated in this study. To provide a complete spatial distribution of 239+240 Pu in Chinese surface soil, an overall pattern of and mechanism for 239+240 Pu migration in Chinese core soil, we summarize and analyze the 239+240 Pu surface and vertical distributions in literature. Comprehensive statistical analysis suggests four typical distributions in Chinese soil cores. It is found that the 239+240 Pu vertical distribution is closely related to the soil type and the 239+240 Pu migration. The result indicates that global fallout is the major source of 239+240 Pu in Chinese soils, with the average 240 Pu/ 239 Pu atom ratios around 0.18. Abnormally low 240 Pu/ 239 Pu ratios are detected in Jiuquan region and northern Xinjiang province in Northwest China, which can be attributed to nuclear weapons tests. To further investigate the migration behaviors of 239+240 Pu in soil cores in China, we apply the Convection Dispersion Equation (CDE) model and find that 239+240 Pu apparent convection velocities ranges from 0.00032±0.00031 cm/a to 0.473±0.083 cm/a. As shown in four typical vertical 239+240 Pu activity distribution soil cores, the deepened 239+240 Pu activity maximum value position implies a fast 239+240 Pu migration rate or apparent convection velocity. This study for the first time suggests a significant linear correlation ( R 2 =0.847) between depth of 239+240 Pu maximum value (cm) and apparent convection velocity (v, cm/a), and we speculate that v usually does not exceed 0.5 cm/a. A significant linear correlation is also identified between apparent dispersion coefficient (D, cm 2 /a) and v 2 in Chinese soil cores.

The effect of peri-operative hyperbaric oxygen therapy on the recovery of neurologic function of patients with cervical spondylotic myelopathy: A diffusion tensor imaging study

Objective To observe the clinical effect of hyperbaric oxygen therapy on cervical spondylotic myelopathy (CSM) in the peri-operative period, and to explore its neural mechanism. Methods Eighty patients who underwent surgical decompression for CSM were randomly divided into a hyperbaric oxygen group (n=40) and a control group (n=40). Both groups received cervical laminoplasty and systematic rehabilitation treatment after the surgery, while the hyperbaric oxygen group was additionally provided with hyperbaric oxygen therapy in the peri-operative period. The patients′ neurological status was evaluated using Japanese Orthopaedic Association (JOA) scores. Both groups received conventional MRI and diffusion tensor imaging (DTI) before and 6 months after the surgery. Results After the surgery, both groups gained significant improvement in their average JOA score, with the improvement of the hyperbaric oxygen group significantly greater than in the control group. Pearson correlation analysis showed that the average pre-operative JOA score was significantly correlated with the anisotropic fraction (FA) and the apparent dispersion coefficient (ADC) of the compressed spinal cord. Six months after the surgery such correlation still persisted. During the six months, significant increase was observed in the average FA and significant decrease in the average ADC in both groups, with the average FA of the hyperbaric oxygen group (0.726±0.087) significantly higher at the end of the 6 months than that in the control group. The average ADC (1.148±0.079)×10-3 mm2/s) was significantly lower. Conclusions DTI′s quantitative indicators can objectively show changes in the microstructure and pathological state of spinal cords. Exposure to hyperbaric oxygen may relieve ischemia and hypoxia of the spinal cord, promoting the repair of injured neurons and accelerating the regeneration of nerve fibers. Key words: Hyperbaric oxygen; Cervical spine; Spondylosis; Myelopathy; Laminoplasty; Diffusion tensor imaging

Vertical distribution and migration of plutonium in the Loess Plateau, North Shaanxi, China

The vertical distribution and migration behavior of 239+240Pu in a soil core in northern Loess Plateau in Shaanxi Province was investigated. The results showed that the 239+240Pu activity concentration was in the range of 0.02–0.75 mBq/g. The measured atom ratios of 240Pu/239Pu in the soil profile varied from 0.179 to 0.201 and were consistent with the typical global fallout. The inventory of 239+240Pu was 66 Bq/m2 in the sampling site and the proportion of Pu in the first 10 cm top layer accounted for around 75%. The apparent convection velocity and effective dispersion coefficient were 0.19 cm/year and 0.12 cm2/year by the convection dispersion equation model, respectively. Further investigation is still highly required to clarify the dominant factors that control Pu migration.

A case report of the rare fifteen-and-a-half syndrome

Rationale:The dorsal tegmentum of the caudal pons, including the medial longitudinal fasciculus (MLF), the paramedian pontine reticular formation (PPRF), abducens nucleus, and the adjacent facial nerve is the anatomical basis of the the fifteen and a half syndrome (15½) syndrome. No patients of 15½ Syndrome presenting with bilateral peripheral facial paralysis and one-and-a-half simultaneously at the onset have been reported up to now.Patient concerns:A 54-year-old woman complained of diplopia, slurred speech, and slightly distal numbness of the left upper limb for 4 days in our hospital.Diagnoses:The diffusion weighted image (DWI) and apparent dispersion coefficient (ADC) of MRI revealed the causative lesion in pons including bilateral pontine tegmentum and a narrow lesion along the midline in the right of the pons. Her clinical manifestations with results of MRI resulted in the diagnosis of the fifteen-and-a-half-syndrome.Interventions:The patient received antiplatelet aggregation, plaque stabilization, free radicals elimination, circulation improvement, nerves nourishment, and other symptomatic treatments.Outcomes:Two months later, her ocular movement recovered, and the bilateral facial paresis showed some improvement.Lessons:First, our patient with 15½ syndrome maybe one of mutants whose bilateral pontine tegmentum is supplied by unilateral pontine paramedian perforator artery. Second, DWI combined with ADC may be applied in the diagnosis of fifteen-and-half syndrome when the lesions of infarction are too small to be revealed by MRI scan.

Transport of Reactive Species in Oscillatory Annular Flow

The present article purposes to investigate the solute dispersion through an annular pipe in the presence of heterogeneous chemical reactions among the species and wall of the annulus. The solute is considered to experience a kinetic reversible phase exchange with the inner wall layer and irreversible absorption into the wall. Two kinds of oscillatory flow (Poiseuille and Couette flow) are considered in order to track the complex interactions between the velocity distributions and the reaction parameters. The method of moments as proposed by Aris-Barton is used to determine the apparent dispersion coefficient. The moment equations has been solved by using a standard finite difference implicit scheme, valid for small as well as large times. Dispersion coefficient due to the combined effect of reversible and irreversible reactions has been discussed in a variety of flow situations. Dispersion coefficient may be enhanced owing to the reversible and irreversible heterogeneous reactions in the boundary. On the basis of flow characteristics, radius ratio provides a mixed behaviour of the dispersion coefficient. Dimensionless mass proves to be an increasing function of reversible and irreversible boundary reaction parameters.

Transport of dissolved organic matter in Boom Clay: Size effects

A coupled experimental-modelling approach was developed to evaluate the effects of molecular weight (MW) of dissolved organic matter (DOM) on its transport through intact Boom Clay (BC) samples. Natural DOM was sampled in-situ in the BC layer. Transport was investigated with percolation experiments on 1.5cm BC samples by measuring the outflow MW distribution (MWD) by size exclusion chromatography (SEC). A one-dimensional reactive transport model was developed to account for retardation, diffusion and entrapment (attachment and/or straining) of DOM. These parameters were determined along the MWD by implementing a discretisation of DOM into several MW points and modelling the breakthrough of each point. The pore throat diameter of BC was determined as 6.6–7.6nm. Below this critical size, transport of DOM is MW dependent and two major types of transport were identified. Below MW of 2kDa, DOM was neither strongly trapped nor strongly retarded. This fraction had an averaged capacity factor of 1.19±0.24 and an apparent dispersion coefficient ranging from 7.5×10−11 to 1.7× 10−11m2/s with increasing MW. DOM with MW>2kDa was affected by both retardation and straining that increased significantly with increasing MW while apparent dispersion coefficients decreased. Values ranging from 1.36 to 19.6 were determined for the capacity factor and 3.2×10−11 to 1.0×10−11m2/s for the apparent dispersion coefficient for species with 2.2kDa<MW<9.3kDa. Straining resulted in an immobilisation of in average 49±6% of the injected 9.3kDa species. Our findings show that an accurate description of DOM transport requires the consideration of the size effects.

Alternatives for characterizing macroporous polyacrylamide monolithic ion exchanger columns

The development of new adsorbents to separate biocompounds and polyacrylamide monolithic cryogels shows great potential for purifying macromolecules from non‐clarified media. In this work, alternatives for functionalization and characterization of polyacrylamide monoliths grafted with 2‐acrylamide‐2‐methyl‐1‐propanosulfonic acid were explored. Dynamic grafting did not affect swelling capacity, or graft density. Pore size was evaluated by optical microscopy, which presented the same values obtained by scanning electronic microscopy. The method of moments was used to determine porosity, apparent axial dispersion coefficient, and the height of the theoretical plates of the columns, presenting results consistent with those in the literature. The permeability constant was determined by varying the viscosity of a Newtonian fluid at constant pressure, with the value being the same as that obtained by varying the hydrostatic pressure over the column. Results demonstrated these techniques were adequate for characterizing polyacrylamide cryogels, opening new perspectives in this field. POLYM. ENG. SCI., 58:1717–1725, 2018. © 2017 Society of Plastics Engineers

Clinical application value of 3.0T MR diffusion tensor imaging in grade diagnosis of gliomas.

The clinical value of MR diffusion tensor imaging (DTI) in grade diagnosis of gliomas was investigated. A total of 31 patients with glioma were administered 3.0T MR convention and DTI examination, with quantitative measurement of anisotropy coefficient fractional anisotropy (FA) and apparent dispersion coefficient (ADC) value, and the comparison of quantitative parameters of glioma between low- and high-grade, which was detected by Mann-Whitney U test. The receiver operation characteristic (ROC) curve was drawn to take the value of ADC and FA in tumor ROI as a critical point, to calculate the area under the curve and to confirm the diagnosis threshold value and evaluate its diagnostic efficiency. The FA value of 14 low-grade glioma cases was 139.4±81.3, with an ADC value of (1.36±0.21) ×10−3 mm2/sec. The FA value of 17 high-grade glioma cases was 103.1±41.5, with ADC value of (1.09±0.28)−3 mm2/sec; the difference between the two groups was statistically significant (P<0.05). The ADC value was taken as the critical point to judge tumor grade and draw the ROC curve; the area under the curve was 0.79. As the diagnosis threshold value, the ADC value of 1.11×10−3 mm2/sec was used to distinguish between low- and high-grade tumor with a sensitivity of 58.8% and specificity of 92.9%. The FA value was taken as a critical point to judge tumor grade and draw the ROC curve; the area under the curve was 0.62. As the diagnosis threshold value, the FA value of 178.9 was applied to distinguish between low- and high-grade tumor sensitivity of 94.1% and specificity of 35.7%. Therefore, the FA value and ADC value in DTI has an important estimated value for the pathological grade of glioma.