Method For Quantification Of Flow Research Articles

Stochastic finite volume method for uncertainty quantification of transient flow in gas pipeline networks

We develop a weakly intrusive framework to simulate the propagation of uncertainty in solutions of generic hyperbolic partial differential equation systems on graph-connected domains with nodal coupling and boundary conditions. The method is based on the Stochastic Finite Volume (SFV) approach, and can be applied for uncertainty quantification (UQ) of the dynamical state of fluid flow over actuated transport networks. The numerical scheme has specific advantages for modeling intertemporal uncertainty in time-varying boundary parameters, which cannot be characterized by strict upper and lower (interval) bounds. We describe the scheme for a single pipe, and then formulate the controlled junction Riemann problem (JRP) that enables the extension to general network structures. We demonstrate the method's capabilities and performance characteristics using a standard benchmark test network.

Flow modeling and in situ viscosity monitoring for a combined rotational and pressure-driven flow of a non-Newtonian fluid through a concentric annulus

Based on the energy dissipation rate, we proposed a systematic method for quantifying the effective viscosity, effective shear rate, and flow characteristics in a drilling flow of non-Newtonian fluids in a concentric annulus subjected to a combined pressure-driven and rotational flow. Two flow parameters, i.e., the energy dissipation rate coefficient and the effective shear rate coefficient, were introduced to quantify flow characteristics, such as the relationship between pressure drop, flow rate, torque, and rotational speed, which are nearly independent of rheological behaviors. In this work, we began with flow quantification of the individual flow problem in a concentric annulus, i.e., pressure-driven flow and rotational flow, and derived expressions of two flow parameters analytically in each case. Then, we established the flow quantification method for the combined pressure-driven and rotational flow. The proposed flow modeling scheme was derived analytically with a power-law fluid and was validated for various non-Newtonian fluids, such as Carreau and Herschel–Bulkley fluids, through extensive numerical simulations. The method can be employed for the in situ viscosity measurement of drilling muds in terms of shear rate, as well as for the estimation of torque, pressure drop, and power consumption. Maximum errors between theoretical prediction and numerical simulation results in estimating torque, pressure drop, and shear-dependent viscosity were found to be 5.5%, 7.3%, and 6%, respectively.

Accuracy of pulmonary venous flow quantification by 2D phase contrast cardiac magnetic resonance

Abstract Funding Acknowledgements Type of funding sources: None. Background Determination of pulmonary venous flow by cardiac magnetic resonance (CMR) is frequently required in patients with complex congenital heart disease (CHD) lesions. Although new advanced imaging techniques like 4D flow are increasingly available, standard 2D phase contrast (2DPC) sequences remain the most frequently used method for quantification of flow. However, little is known on the accuracy of 2DPC flow measurements in the pulmonary veins. Purpose This study therefore aims to investigate the accuracy of pulmonary venous flow quantification by 2DPC. Methods Patients with CHD underwent a CMR on a 1.5T scanner. 2DPC flow sequences (typical temporal resolution 35–50ms, inplane spatial resolution 1.3–1.8 mm2, VENC 80–100) were acquired in the ascending aorta (AA), main, right and left pulmonary arteries (MPA, RPA, LPA), as well as left (LPV) and right (RPV) pulmonary veins. Pulmonary venous flow was compared to pulmonary arterial flow in all patients and to aortic flow in patients without left to right (L-R) shunt using Bland-Altman plots and Pearson’s correlations. Results Twenty CHD patients (age 27±3, range 7; 53 years, 7 women, tetralogy of Fallot N=7, Ross operation N=1; Fontan N=4, transposition of great arteries N=2, atrial septal defect N=2, Turner syndrome 1, Ebstein N=1, valvulopathies N=2) were included. Table 1 shows absolute flow values of the different vessels. Bland-Altman analyses and correlations (Table 2) showed a good agreement of total pulmonary venous (PV) to flow in the ascending aorta (group without shunt) and the sum of flow of both branch pulmonary arteries. However, agreement of total PV with MPA flow as well as of LPV and RPV with the respective branch pulmonary artery flow was reduced. Conclusions Total PV flow determined by 2DPC shows a good agreement with flow in the ascending aorta and the sum of the branch pulmonary arteries. Flow turbulences due to the pathologies of the right ventricular outflow tract probably contribute to the reduced agreement of total PV and MPA flow. However, the reduced agreement of the flow in left/right pulmonary veins and their respective branch pulmonary arteries underlines the need for newer advanced flow quantification techniques to improve accuracy of pulmonary venous flow measurements.

Echo grid integration: A novel method for preprocessing multibeam water column data to quantify underwater gas bubble emissions

AbstractWater column imaging multibeam echo sounder systems (MBESs) are a promising technology for quantitative estimates of the gas bubble volume flow within large gas seepage areas. Considerable progress has been made in recent years toward applicable calibration methods for MBESs as well as developing inversion models to convert acoustically measured backscattering cross sections to gas bubble volume flow. However, MBESs are still not commonly used for quantitative gas flow assessments. A reason for this is the absence of published processing methods that demonstrate how MBES data can be processed to quantitatively represent bubble streams. Here, we present a novel method (echo grid integration) that allows for assessing the aggregated backscattering cross section of targets within horizontal water layers. This derived value enables quantifying bubble stream gas flow rates using existing acoustic inversion methods. The presented method is based on averaging geo‐referenced volume backscattering coefficients onto a high‐resolution 3D voxel‐grid. The results are multiplied with the voxel volume to represent measurements of the total backscattering cross‐section within each voxel cell. Individual gridded values cannot be trusted because the beam pattern effects cause the values of individual targets to “smear” over multiple grid‐cells. The true aggregated backscattering cross‐section is thus estimated as the integral over the grid‐cells affected by this smearing. Numerical simulation of MBES data acquisition over known targets assesses the method's validity and quantify it's uncertainty for different, realistic scenarios. The found low measurement bias (< 1%), and dispersion (< 5%) are promising for application in gas flow quantification methods.

Validity of the \u03b3-Ray Evaluation with iodoamphetamine for Cerebral Blood Flow Assessment (REICA) method for quantification of cerebral blood flow including acetazolamide challenge test

ObjectiveThe γ-Ray Evaluation with iodoamphetamine for Cerebral Blood Flow Assessment (REICA) is a new method for quantifying cerebral blood flow (CBF) using single-photon emission computed tomography (SPECT) and [123I]N-isopropyl-p-iodoamphetamine (123I-IMP). The present study aimed to validate the REICA method using data including acetazolamide challenge test.MethodsThe REICA and Graph-Plot (GP) methods were used to calculate mean CBF (mCBF) for 92 acquisitions (rest: 57, stress: 35) and cerebrovascular reactivity (CVR) in 33 patients. To obtain stress data, 15 mg/kg of acetazolamide was injected intravenously 10 min before the administration of 123I-IMP, and blood samples were collected under the same conditions as rest data. The reference standard was the Autoradiograph (ARG) method using arterial blood sampling, and the accuracy of the REICA method was analyzed by comparing it with each method.ResultsFor mCBF, the correlation coefficients (r) were 0.792 for the REICA method and 0.636 for the GP method. For CVR, r values were 0.660 for the REICA method and 0.578 for the GP method. In both acquisitions, the REICA method had a stronger correlation with the ARG method than the GP method. For mCBF, there was a significant difference in the correlation coefficient between the two correlation coefficients (p < 0.01).ConclusionsThe REICA method was more accurate than the GP method in quantifying CBF and closer to the ARG method. The REICA method, which is a noninvasive method of cerebral blood flow quantification using 123I-IMP, has great medical usefulness.

Effective Navier-slip in non-Newtonian fluid flows over corrugated surfaces

In this study, we show that complex local flow fields, particularly those near corrugated surfaces, can be accurately reproduced with effective Navier-slip boundary conditions over an imaginary smooth surface, in which the normalized slip length can be considered as a surface property even for non-Newtonian fluid flows. The expression for the normalized slip length was derived analytically using the effective viscosity and effective shear rate in a pressure-driven channel flow with a corrugated surface, based on the two-parameter model by separating geometrical and rheological factors with the effective viscosity concept. Our framework was established on the combination of the force balance approach for slip length characterization and the flow quantification method based on the energy dissipation rate. Effects of corrugated patterns with various aspect ratios were investigated. For verification, an example stick–slip–stick flow problem was tested and the results were compared with those of direct simulations. We report that the dimensionless normalized slip length appears to be almost constant and independent of the flow rate (or pressure drop). This implies that the normalized slip length is nearly independent of rheological properties. In addition, the dimensionless slip length of non-Newtonian fluids was found to be close to that of a Newtonian fluid, and it depends on the flow geometry itself.

The REICA method for quantification of cerebral blood flow is less affected by lung washout of [123I] IMP than the graph-plot method.

The [Formula: see text]-Ray Evaluation with Iodoamphetamine for Cerebral blood flow Assessment (REICA) method is a new method for cerebral blood flow (CBF) quantification with SPECT and [123I] IMP, which does not require invasive arterial blood sampling, or the use of a regression formula. Moreover, it takes into consideration tracer retention, while the Graph-Plot (GP) method does not. This study aims to confirm the reliability of the REICA method in calculating CBF by accounting for pulmonary tracer retention artefact. Data of 100 patients were retrospectively analyzed. Washout rate (WR) was defined as 1- (max count /min count) in the lungs. The bias due to WR was analyzed by dividing the data into high/low WR groups and a multiple regression analysis was also performed. The REICA method did not show significant bias according to the [Formula: see text] test ([Formula: see text]), while the GP method showed significant bias ([Formula: see text]). Both the REICA and GP methods showed significant correlation with autoradiography (ARG) method ([Formula: see text], [Formula: see text]) and WR ([Formula: see text], [Formula: see text]) when analyzed via multiple regression analysis with covariates of age and sex. The REICA method is a reliable method for CBF quantification, which is unaffected by tracer washout through the lungs unlike the GP method.

Assessment of cardiac-driven liver movements with filtered harmonic phase image representation, optical flow quantification, and motion amplification.

To characterize cardiac-driven liver movements using a harmonic phase image representation (HARP) with an optical flow quantification and motion amplification method. The method was applied to define the cardiac trigger delay providing minimal signal losses in liver DWI images. The 16-s breath-hold balanced-SSFP time resolved 20 images/s were acquired at 3T in coronal and sagittal orientations. A peripheral pulse unit signal was recorded. Cardiac-triggered DWI images were acquired after different peripheral pulse unit delays. A steerable pyramid decomposition with multiple orientations and spatial frequencies was applied. The liver motion field-map was derived from temporal variations of the HARP representation filtered around the cardiac frequency. Liver displacements were quantified with an optical flow method; moreover the right liver motion was amplified. The largest displacements were observed in the left liver (feet-head:3.70 ± 1.06 mm; anterior-posterior: 2.35 ± 0.51 mm). Displacements were statistically significantly weaker in the middle right liver (0.47 ± 0.11 mm; P = 0.0156). The average error was 0.013 ± 0.022 mm (coronal plane) and 0.021 ± 0.041 mm (sagittal plane). The velocity field demonstrated opposing movements of the right liver extremities during the cardiac cycle. DWI signal loss was minimized in regions and instants of smallest amplitude of both velocity and velocity gradient. Cardiac-driven liver movements were quantified with combined cardiac frequency-filtered HARP and optical flow methods. A motion phase opposition between right liver extremities was demonstrated. Displacement amplitude and velocity were larger in the left liver especially along the vertical direction. Motion amplification visually emphasized cardiac-driven right liver displacements. The optimal cardiac timing minimizing signal loss in liver DWI images was derived.

A new non-invasive graphical method for quantification of cerebral blood flow with[^{123}hbox {I}] IMP

Objective[^{123}hbox {I}] N-isopropyl-p-iodoamphetamine (^{123}hbox {I}-IMP) is an ideal perfusion tracer for single photon emission computed tomography, which shows good linearity between cerebral blood flow (CBF) and accumulation. However, quantification of CBF using ^{123}hbox {I}-IMP without arterial blood sampling has been challenging, with previous methods requiring empirically obtained regression formulae to estimate CBF. Furthermore, the CBF value obtained via some of the previous methods would be affected by the clearance rate of ^{123}hbox {I}-IMP from the lungs. This paper introduces a new non-invasive quantification method for CBF using ^{123}hbox {I}-IMP and dynamic planar images.MethodsWe have developed a theory based on Microsphere model. This method does not involve regression formulae for estimation and allows for direct measurement of CBF, considering the clearance rate of ^{123}hbox {I}-IMP from the lungs. The study method is executed as easily as conventional Graph-Plot method. We compared the CBF values obtained by our study method and the established autoradiograph (ARG) method.ResultsCBF values obtained using the new method demonstrated significant correlation with values determined using ARG method.ConclusionsThe novel method described presents a reliable and more simple way of determining CBF when compared to current methods.

Myocardial perfusion of infarcted and normal myocardium in propofol-anesthetized minipigs using 82Rubidium PET

Cardiac Rubidium-82 (82Rb) positron-emission-tomography (PET) is a good method for quantification of myocardial blood flow in man. Quantification of myocardial blood flow in animals to evaluate new treatment strategies or to understand underlying disease is also of great interest but raises some challenges. Animals, which have been anesthetized during PET acquisition, might react differently to used stress medications, and therefore difficulties might exist while evaluating the resulting PET images using standard software packages from commercial vendors optimized for human hearts. Furthermore propofol, used for anesthesia, can influence myocardial perfusion and coronary flow reserve due to its vasorelaxant effect, and interactions might exist between propofol and used stress agents, potentially affecting the result of the examination. We present cardiac 82Rb-PET studies performed in propofol-anesthetized minipigs with normal and infarcted myocardium stressed with both adenosine and dipyridamole. Despite the mentioned challenges, we were able to trace the small minipig heart with software designed for human cardiac PET and to achieve blood flow measurements comparable with results in humans with both adenosine and dipyridamole. We found dipyridamole to be a superior stress agent for this experimental setup. Finally, we were able to clearly identify the myocardial perfusion defect after an induced myocardial infarction.

Automated analysis of perfusion weighted MRI using asymmetry in vascular territories

PurposeTo determine the feasibility of automatic vascular territory region of interest (ROI) construction as a method for standardized quantification of cerebral blood flow (CBF) images. Materials and methodsAn algorithm for automatic construction of vascular territory ROIs was performed on 10 healthy controls and 25 patients with perfusion abnormalities identified by retrospective chart review. The ROIs were used to quantify perfusion asymmetry for each territory, and perfusion asymmetry was compared in the two cohorts and against blinded neuroradiologist interpretation. The algorithm was additionally applied to a separate cohort of 23 prospectively enrolled patients and perfusion asymmetry was correlated against clinical variables. ResultsThere was significantly greater perfusion asymmetry in territories graded by neuroradiologists as hypoperfused compared to those graded as normally perfused (p<.05) and compared to healthy volunteers (p<.01). An ROC analysis showed that perfusion asymmetry was sensitive and specific for identifying hypoperfusion in vascular territories (84.9% sensitivity and 90.5% specificity for a threshold asymmetry index of .829). In the prospective cohort, perfusion asymmetry was correlated with initial NIH stroke scale (NIHSS) (p<.01) and length of stay (p<.05). ConclusionsAutomatic construction of vascular territory ROIs and calculation of perfusion asymmetry is a feasible method for analyzing CBF images. Because the technique is rapid and minimizes bias, it can facilitate analysis of larger scale research studies.

MO‐G‐18C‐02: Flow Quantification Quality Assurance for Multiple MR Scanners Using Power Injector

Purpose:To evaluate a flow quantification QA method on multiple MR scanners with different magnetic field strength from different manufacturer.Methods:Our previous study proposed a low‐cost, reliable and convenient MRI flow quantification QA method based on a simple and compact flow contrast phantom and a power injector. Five different MR scanners (Siemens MAGNETOM Espree 1.5T, Aera 1.5T and Skyra 3T; GE Optima MR450w 1.5T and Discovery MR750w 3T) were used to test the reproducibility and sensitivity of the QA method. Flow phantom phase contrast images were acquired at magnetic field isocenter for all the MR scanners. Eight repeated acquisitions and measurements were performed on each scanner. In addition, off‐center effects were tested on Siemens Espree and two GE scanners.Results:The positive flow rates measured at isocenter of five MR scanners range from +1.84± 0.01 mL/s to +2.01± 0.02 mL/s, within 8% difference from the 2mL/s flow rate provided by the power injector. The negative flow rate measured at isocenter range from −1.89± 0.01 mL/s to ‐2.14± 0.03 mL/s, within 7% difference from 2mL/s flow rate. Flow rate measures were most affected by off‐center effect when the flow phantom was shifted 12 cm transversely and 12 cm longitudinally from the isocenter. For GE Optima scanner, positive flow of +1.53± 0.01 mL/s was measured, which is 24.5% difference from power injector flow rate. For GE Discovery scanner, negative flow of −2.68± 0.02 mL/s was measured, which is 34% difference from 2mL/s flow rate.Conclusion:This QA method was sensitive enough to detect flow quantification difference between scanners. Flow quantification errors at locations away from magnetic field isocenter due to the worse gradient fidelity can be detected by our flow quantification QA method. In conclusion, flow phantom coupled with power injector is presented to be a widely available, consistent and low cost flow quantification method.

Stereomicroscopic Imaging Technique for the Quantification of Cold Flow in Drug-in-Adhesive Type of Transdermal Drug Delivery Systems

Cold flow is a phenomenon occurring in drug-in-adhesive type of transdermal drug delivery systems (DIA-TDDS) because of the migration of DIA coat beyond the edge. Excessive cold flow can affect their therapeutic effectiveness, make removal of DIA-TDDS difficult from the pouch, and potentially decrease available dose if any drug remains adhered to pouch. There are no compendial or noncompendial methods available for quantification of this critical quality attribute. The objective was to develop a method for quantification of cold flow using stereomicroscopic imaging technique. Cold flow was induced by applying 1 kg force on punched-out samples of marketed estradiol DIA-TDDS (model product) stored at 25°C, 32°C, and 40°C/60% relative humidity (RH) for 1, 2, or 3 days. At the end of testing period, dimensional change in the area of DIA-TDDS samples was measured using image analysis software, and expressed as percent of cold flow. The percent of cold flow significantly decreased (p < 0.001) with increase in size of punched-out DIA-TDDS samples and increased (p < 0.001) with increase in cold flow induction temperature and time. This first ever report suggests that dimensional change in the area of punched-out samples stored at 32°C/60%RH for 2 days applied with 1 kg force could be used for quantification of cold flow in DIA-TDDS.

Identification and quantification of basophils in the airways of asthmatics following segmental allergen challenge.

During asthma attacks, allergens activate sensitized basophils in the lung, thereby aggravating symptoms. Due to the paucity of basophils in bronchial lavage fluid and the lack of specific basophil detection and quantification methods, basophil-directed research in these samples was hampered in the past. This study aimed to establish and validate a flow cytometry-based basophil detection and quantification method for human basophils from bronchoalveolar lavage (BAL) and blood as a prerequisite for a better understanding of their pathogenic contribution and subtyping of asthma phenotypes. BAL and blood leukocytes from seasonal asthmatics were analyzed by flow cytometry. Chipcytometry, a highly sensitive single-cell analysis method, was used to validate the staining panel for basophils. Cell differentials of May-Grünwald-Giemsa-stained cytospins were used to compare basophil percentages. BAL basophils are identifiable as CD123(+) HLA-DR(-) CD3(-) CD14(-) CD19(-) CD20(-) CD56(-) cells in flow cytometrical analysis. Their identity was validated by Chipcytometry. CD203c was highly expressed by BAL basophils, whereas it was expressed at variable levels on blood basophils. The two quantification methods correlated, although more basophils were detected by flow cytometry. Furthermore, the increase in basophil percentages in the lung correlated with the decrease in the basophil percentages in the blood after allergen challenge. We here validated a reliable basophil quantification method, which is independent of the cell's activation and degranulation state. The results obtained with this method indicate that basophils are directly recruited from the blood circulation to the airway lumen.

Evaluation of a New 3‐Dimensional Color Doppler Flow Method to Quantify Flow Across the Mitral Valve and in the Left Ventricular Outflow Tract

The aim of this study was to assess the accuracy, feasibility, and reproducibility of determining stroke volume from a novel 3-dimensional (3D) color Doppler flow quantification method for mitral valve (MV) inflow and left ventricular outflow tract (LVOT) outflow at different stroke volumes when compared with the actual flow rate in a pumped porcine cardiac model. Thirteen freshly harvested pig hearts were studied in a water tank. We inserted a latex balloon into each left ventricle from the MV annulus to the LVOT, which were passively pumped at different stroke volumes (30-80 mL) using a calibrated piston pump at increments of 10 mL. Four-dimensional flow volumes were obtained without electrocardiographic gating. The digital imaging data were analyzed offline using prototype software. Two hemispheric flow-sampling planes for color Doppler velocity measurements were placed at the MV annulus and LVOT. The software computed the flow volumes at the MV annulus and LVOT within the user-defined volume and cardiac cycle. This novel 3D Doppler flow quantification method detected incremental increases in MV inflow and LVOT outflow in close agreement with pumped stroke volumes (MV inflow, r = 0.96; LVOT outflow, r = 0.96; P < .01). Bland-Altman analysis demonstrated overestimation of both (MV inflow, 5.42 mL; LVOT outflow, 4.46 mL) with 95% of points within 95% limits of agreement. Interobserver variability values showed good agreement for all stroke volumes at both the MV annulus and LVOT. This study has shown that the 3D color Doppler flow quantification method we used is able to compute stroke volumes accurately at the MV annulus and LVOT in the same cardiac cycle without electrocardiographic gating. This method may be valuable for assessment of cardiac output in clinical studies.

Support vector machine learning-based cerebral blood flow quantification for arterial spin labeling MRI

To develop a multivariate machine learning classification-based cerebral blood flow (CBF) quantification method for arterial spin labeling (ASL) perfusion MRI. The label and control images of ASL MRI were separated using a machine-learning algorithm, the support vector machine (SVM). The perfusion-weighted image was subsequently extracted from the multivariate (all voxels) SVM classifier. Using the same pre-processing steps, the proposed method was compared with standard ASL CBF quantification method using synthetic data and in-vivo ASL images. As compared with the conventional univariate approach, the proposed ASL CBF quantification method significantly improved spatial signal-to-noise-ratio (SNR) and image appearance of ASL CBF images. the multivariate machine learning-based classification is useful for ASL CBF quantification.

Aortic insufficiency following transcatheter aortic valve replacement is underestimated by echocardiography compared with cardiac MRI

Background The degree of aortic insufficiency (AI) after transcatheter aortic valve replacement (TAVR) has been identified as a predictor of increased mortality. Since even mild AI is associated with increased mortality in some studies, accurate quantification of post-TAVR AI is critical. Assessment of AI by echocardiography is typically performed by visual inspection and semi-quantitative methods. Most post-TAVR AI is paravalvular, however echocardiography has limited ability to quantify multiple eccentric paravalvular jets. Using flow quantification methods, cardiac MRI (CMR) may more accurately quantify AI severity post-TAVR and therefore more accurately assess risk in this population. Methods Twenty-three patients who underwent TAVR with a SAPIEN prosthesis were studied. All patients underwent an intraoperative transesophageal echocardiogram (TEE), as well as a post-procedure transthoracic echocardiogram (TTE) and CMR. Paravalvular AI by TTE and TEE was graded using color Doppler by quantifying the circumferential extent of AI as a percentage of the aortic annulus (none 30%) following recommendations from the Valve Academic Research Consortium. AI severity by CMR was quantified as the regurgitant fraction of forward aortic flow based on previously published recommendations (none 48%). Results The mean age was 79 +/- 10 years; 52% were men. TTE and CMR were performed at 1 [1-1] and 4 [1-4] days postTAVR respectively (median [IQR]). The left ventricular ejection fraction (LVEF) by CMR was 65 +/- 10%. AI severity by TTE was none in 9 (39.1%), trace in 11 (47.8%), and mild in 3 (13%) patients. TEE identified trace central AI in 6 patients (26%). Paravalvular AI by TEE was none in 4 (17.4%), trace in 14 (60.9%), and mild in 5 (21.7%) patients. AI by CMR was none in 2 (8.7%), trace in 5 (21.7%), mild in 13 (56.5%), and moderate in 3 (13%) patients; (Figure 1). A higher proportion of patients with mild or greater AI was identified by CMR (16/23, 70%) compared to TTE (3/23, 13%) and TEE (5/23, 22%); (Figure 2). Conclusions

Super-resolution spectral estimation of optical micro-angiography for quantifying blood flow within microcirculatory tissue beds in vivo

In this paper, we propose a super-resolution spectral estimation technique to quantify microvascular hemodynamics using optical microangiography (OMAG) based on optical coherence tomography (OCT). The proposed OMAG technique uses both amplitude and phase information of the OCT signals which makes it sensitive to the axial and transverse flows. The scanning protocol for the proposed method is identical to three-dimensional ultrahigh sensitive OMAG, and is applicable for in vivo measurements. In contrast to the existing capillary flow quantification methods, the proposed method is less sensitive to tissue motion and does not have aliasing problems due fast flow within large blood vessels. This method is analogous to power Doppler in ultrasonography and estimates the number of red blood cells passing through the beam as opposed to the velocity of the particles. The technique is tested both qualitatively and quantitatively by using OMAG to image microcirculation within mouse ear flap in vivo.

A fast simulation method for uncertainty quantification of subsurface flow and transport

Key Points new polar Markovian velocity processes (PMVPs) to model macro‐dispersion generalization of PMVPs for inhomogeneous cases with conductivity measurements validation of PMVP with Monte Carlo, CPU‐time PMVP = CPU‐time MC / 1000

Quantitative analysis of the effective functional structure in yeast glycolysis.

The understanding of the effective functionality that governs the enzymatic self-organized processes in cellular conditions is a crucial topic in the post-genomic era. In recent studies, Transfer Entropy has been proposed as a rigorous, robust and self-consistent method for the causal quantification of the functional information flow among nonlinear processes. Here, in order to quantify the functional connectivity for the glycolytic enzymes in dissipative conditions we have analyzed different catalytic patterns using the technique of Transfer Entropy. The data were obtained by means of a yeast glycolytic model formed by three delay differential equations where the enzymatic rate equations of the irreversible stages have been explicitly considered. These enzymatic activity functions were previously modeled and tested experimentally by other different groups. The results show the emergence of a new kind of dynamical functional structure, characterized by changing connectivity flows and a metabolic invariant that constrains the activity of the irreversible enzymes. In addition to the classical topological structure characterized by the specific location of enzymes, substrates, products and feedback-regulatory metabolites, an effective functional structure emerges in the modeled glycolytic system, which is dynamical and characterized by notable variations of the functional interactions. The dynamical structure also exhibits a metabolic invariant which constrains the functional attributes of the enzymes. Finally, in accordance with the classical biochemical studies, our numerical analysis reveals in a quantitative manner that the enzyme phosphofructokinase is the key-core of the metabolic system, behaving for all conditions as the main source of the effective causal flows in yeast glycolysis.