Dispersed Volume Fraction Research Articles

Microstructural changes of the white matter in systemic lupus erythematosus patients without neuropsychiatric symptoms: a multi-shell diffusion imaging study

BackgroundDiffusion kurtosis imaging (DKI) and neurite orientation dispersion and density imaging (NODDI) provide more comprehensive and informative perspective on microstructural alterations of cerebral white matter (WM) than single-shell diffusion tensor imaging (DTI), especially in the detection of crossing fiber. However, studies on systemic lupus erythematosus patients without neuropsychiatric symptoms (non-NPSLE patients) using multi-shell diffusion imaging remain scarce.MethodsTotally 49 non-NPSLE patients and 41 age-, sex-, and education-matched healthy controls underwent multi-shell diffusion magnetic resonance imaging. Totally 10 diffusion metrics based on DKI (fractional anisotropy, mean diffusivity, axial diffusivity, radial diffusivity, mean kurtosis, axial kurtosis and radial kurtosis) and NODDI (neurite density index, orientation dispersion index and volume fraction of the isotropic diffusion compartment) were evaluated. Tract-based spatial statistics (TBSS) and atlas-based region-of-interest (ROI) analyses were performed to determine group differences in brain WM microstructure. The associations of multi-shell diffusion metrics with clinical indicators were determined for further investigation.ResultsTBSS analysis revealed reduced FA, AD and RK and increased ODI in the WM of non-NPSLE patients (P < 0.05, family-wise error corrected), and ODI showed the best discriminative ability. Atlas-based ROI analysis found increased ODI values in anterior thalamic radiation (ATR), inferior frontal-occipital fasciculus (IFOF), forceps major (F_major), forceps minor (F_minor) and uncinate fasciculus (UF) in non-NPSLE patients, and the right ATR showed the best discriminative ability. ODI in the F_major was positively correlated to C3.ConclusionThis study suggested that DKI and NODDI metrics can complementarily detect WM abnormalities in non-NPSLE patients and revealed ODI as a more sensitive and specific biomarker than DKI, guiding further understanding of the pathophysiological mechanism of normal-appearing WM injury in SLE.

Improved wear and friction properties by self-formed SiC layers in Mg/SiC composites

The tribological properties are evaluated using several types of Mg/SiC composites, which SiC powders with particle sizes of 20∼30 nm, 130 nm and 2∼3 μm are dispersed in up to 25 % by volume fraction. Sound and bulky Mg/SiC composites are successfully fabricated by powder-metallurgy combining extrusion process. The initial SiC particle size and their dispersed volume fraction affect the wear and friction properties. The specific wear rate increases with increasing contents of SiC particles, regardless of the initial SiC particle size. However, when the SiC particle size is larger than a certain size and its content is greater than 10 %, the friction coefficient suddenly decreases. In the surface observations after friction tested specimens, the element mapping image shows the Mg ratio relative to Si ratio (=SiC) increases with reducing friction coefficient. This indicates that good wear resistance is due to the presence of self-formed SiC layers during the friction process.

Imaging Biomarker for Early-Stage Alzheimer Disease: Utility of Hippocampal Histogram Analysis of Diffusion Metrics.

Biomarkers have been required for diagnosing early Alzheimer disease. We assessed the utility of hippocampal diffusion parameters for diagnosing Alzheimer disease pathology in mild cognitive impairment. Sixty-nine patients with mild cognitive impairment underwent both CSF measurement and multi-shell diffusion imaging at 3T. Based on the CSF biomarker level, patients were classified according to the presence (Alzheimer disease group, n = 35) or absence (non-Alzheimer disease group, n = 34) of Alzheimer disease pathology. Neurite orientation dispersion and density imaging and diffusion tensor imaging parametric maps were generated. Two observers independently created the hippocampal region of interest for calculating histogram features. Interobserver correlations were calculated. The statistical significance of intergroup differences was tested by using the Mann-Whitney U test. Logistic regression analyses, using both the clinical scale and the image data, were used to predict intergroup differences, after which group discriminations were performed. Most intraclass correlation coefficient values were between 0.59 and 0.91. In the regions of interest of both observers, there were statistically significant intergroup differences for the left-side neurite orientation dispersion and density imaging-derived intracellular volume fraction, right-side diffusion tensor imaging-derived mean diffusivity, left-side diffusion tensor imaging-derived mean diffusivity, axial diffusivity, and radial diffusivity (P < .05). Logistic regression models revealed that diffusion parameters contributed the most to discriminating between the groups. The areas under the receiver operating characteristic curve for the regions of interest of observers A/B were 0.69/0.68, 0.69/0.68, 0.73/0.68, 0.71/0.68, and 0.68/0.68 for the left-side intracellular volume fraction (mean), right-side mean diffusivity (mean), left-side mean diffusivity (10th percentile), axial diffusivity (10th percentile), and radial diffusivity (mean). Hippocampal diffusion parameters might be useful for the early diagnosis of Alzheimer disease.

Pickering emulsions for stimuli-responsive transdermal drug delivery: effect of rheology and microstructure on performance.

This work investigates the design of stimuli-responsive Pickering emulsions (PEs) for transdermal drug delivery applications, by exploring the impact of stabilising microgels size and interactions on their rheological and release properties. Temperature-responsive poly(N-isopropylacrylamide) microgels modified with 1-benzyl-3-vinylimidazolium bromide (pNIPAM-co-BVI) are synthesized in varying sizes and used to stabilise jojoba oil-in-water concentrated emulsions. The results reveals two distinct behaviours: for small microgels (∼300 nm), the PEs exhibit a smooth, uniform structure characterised by a mild yield stress, characteristic of soft glassy systems. Conversely, larger microgels (∼800 nm) induce droplet clustering, resulting in increased elasticity and a more complex yielding process. Interestingly, transdermal delivery tests demonstrate that microstructure, rather than bulk rheology, governs sustained drug release. The release process can be modelled as diffusion-controlled transport through a porous medium with random traps. At room temperature, the trap size corresponds to the droplet size, and the release time scales with the total dispersed phases volume fraction. However, at physiological temperature (37 °C), above the volume-phase transition temperature of the microgels, the release time increases significantly. The trap size approaches the microgel size, suggesting that microgel porosity becomes the dominant factor controlling drug release. Overall, the results highlight the critical role of microstructure design in optimising stimuli-responsive PEs for controlled transdermal drug delivery.

Sensitivity analysis of kinetic theory of granular flow (KTGF) and mixture models in terms of involved elemental parameters for two-phase gas-solid flow

Probing into the multiscale essence and nonlinear interactions of gas-solid flows whether in natural or industrial scale have continuously been evoking challenges in flow physics and modeling approaches. Although there are capabilities within the test bench experiments and empirical formulas to define or predict the flow characteristics in two-phase systems, the flow pattern would be still unknown, and here is where the numerical approaches thrive. Since, the corresponding non-linear equation system developed to predict the behavior of two-phase flows is intrinsically complex and makes the numerical solutions time-consuming, in this article, the sensitivity analysis of two well-known models based on the Euler-Euler approach, namely KTGF and Mixture models, is conducted in terms of continuous/dispersed shear stress and solid pressure on the accuracy, stability, and duration of solution. In the KTGF model, granular viscosity is particularly most influential term; while in the Mixture model, the numerical solution profoundly depends on the continuous phase viscosity. Moreover, it is perceived that the existence of solid pressure as a diffusive source term is consequential for the stability in the modeling process, and in high values of dispersed volume fraction, its impact on the flow behavior is distinguishable.

Functional, Thermal and Structural Properties of Green Banana Flour (cv. Giant Cavendish) by De-astringency, Enzymatic and Hydrothermal Treatments.

Green banana fruit with high resistant starch (RS) content has a potential to be a nutraceutical ingredient despite having an unpleasant astringency taste and is yet to be fully explored. In this study, the green banana after de-astringency treatment was employed for flour production, and the resulting flour was subjected to modification by the combined treatments of pullulanase debranching and annealing. The banana flour (BF) and the modified flour (MF) were compared with each other by evaluating their functional, thermal and structural properties. The BF showed a restricted-swelling pasting profile, behaving like a slightly chemically cross-linked starch; the MF exhibited less pronounced changes in pasting behavior with increased solubility and decreased swelling power and dispersed volume fraction at elevated temperatures. As compared with the BF, an enhanced thermal stability of the MF was observed, reflected in the endotherm shifting to higher temperatures with increased enthalpy. The BF displayed a CA-type polymorph, while the MF comprised a mixture of B- and V-type polymorphs with increased crystallinity. The MF showed an increased molecular order, reflected in an increase in short-range double helical order detected in the starch fingerprint regions of FT-IR spectra, and along with increased crystallinity, underlying its enhanced thermal stability. The modification treatment resulted in irregularly shaped flour particles with a more compact structure as revealed by morphological characters. The results of this study can provide useful information for the development of food products using the modified green banana flour with improved thermal stability and functional properties as a health-promoting ingredient.

Numerical study on the distribution of flue gas residence time in the desulfurization and denitrification system by the optimization of the model

Abstract During the operation of the CSCR activated carbon desulfurization and denitrification flue gas purification system, due to the unreasonable design of flue gas pipe diameter and the uneven distribution of activated carbon porosity, the uniformity of flue gas distribution is prone to problems, which affects flue gas removal efficiency and increases operating costs. In this article, the Fluent software was used to establish a three-dimensional numerical model of the flue gas purification system, and the flow characteristics of the flue gas were studied by continuously optimizing the structure of the system model. The effects of different pipe diameters, the accumulation method of activated carbon in the desulfurization and denitration module and the distribution of porosity on the flue gas are analyzed, and the effects on the average residence time and variance of flue gas were further analyzed. The results show that the average residence time, the variance, the dead volume fraction, and well-mixed volume decreased, while the dispersed plug volume fraction increased for a module after optimization. The average residence time and the dispersed plug volume fraction decreased. While the variance, the dead volume fraction, and well-mixed volume fraction increased for the system after optimization.

Insight into significance of thermal stratification and radiation on dynamics of micropolar water based TiO2 nanoparticle via finite element simulation

The evolution of nanofluids is important for improving the thermal conductivity of base fluids. The influence of thermal radiation and thermal stratification on the magnetohydrodynamic micropolar nanofluid flow through a shrinking sheet with a prescribed heat flux on the surface has been examined. The most important parts of this study are the effects of magnetohydrodynamic microrotation, thermal radiation, the magnetic field, and the Cattaneo-Christov heat flux model. The efficiency of nanoparticles, heat, and mass transference rates are influenced by the magnetic field pattern, the characteristics of the source of heat, thermal radiation, and the dispersion of volume fraction. The partial differentials are transformed into the set of nonlinear differential equations through boundary layer estimations and similarity substitutions and then computed with the use of a variational finite element procedure. A MATLAB code has been developed to assess parametric simulations for reduced skin friction factor, micro-rotation, fluid velocity, heat transfer rate, and thermal properties for the Glariken formulation. The temperature field declined due to increasing values of the thermal stratification parameter and the heat transfer rate accelerated. There is a strong link between the two sets of results, which shows that the finite element method used here is accurate.

O1/W/O2 nanoemulsions and emulsions based on extra virgin olive oil produced by ultrasound-assisted homogenization process: Characterization of structure, physical and encapsulation efficiency

Oil-in-water-in-oil (O1/W/O2) emulsions and nanoemulsions based on extra virgin olive oil were produced combining high-speed and ultrasonic homogenizer. Droplet size distribution, encapsulation efficiency, kinetic stability, and their structure were studied as a function of homogenization time, dispersed volume fraction, emulsifier type, and composition of the inner O1/W nanoemulsion. The ultrasonic-assisted homogenization was beneficial for the formation of O1/W/O2 nanoemulsion, as the intensity of the ultrasound did not destroy the double structure. The inner O1/W nanoemulsion with the lowest droplet size, surface tension, and viscosity resulted in double nanoemulsion with the minimum droplet size (432 ± 5 nm). Increasing the dispersed volume fraction resulted in higher particle size, gravitational separation, and high oiling off values. The DSC thermograms showed samples with the low droplet size presented also low encapsulation yield. The microscopic analysis demonstrated that all O1/W/O2 samples showed similar structures with distinctly visible phases and spherical aqueous droplets with a broad distribution.

Numerical study on the influence of center gas supply device on gas-solid residence time distribution in COREX shaft furnace

The residence properties of gas-solid phases are important to the design and process optimization of a COREX shaft furnace. In this study, we investigated the gas-solid residence time distribution by using a coupled CFD-DEM model. The effects of the center gas supply device (CGD) on the average residence time, variance, and volume fraction of the gas and solid phases were analyzed. The results revealed that the average residence time, dispersed plug volume fraction, and well-mixed volume increased, while the variance and the dead volume fraction of the gas phase decreased for the shaft furnace with CGD. The average residence time and the dispersed plug volume fraction of the solid phase decreased in the shaft furnace with CGD. The dead volume fraction and well-mixed volume fraction increased with the introduction of CGD.

Fast oil-in-water emulsification in microchannel using head-on impinging configuration: Effect of swirl motion

Liquid–liquid dispersion by head-on impingement in a cross-slot microfluidic device to form oil-in-water emulsion is experimentally investigated at broad range of flow rate conditions. Reynolds number based on the continuous aqueous phase flow is changed from 1000 to 7000 and the oil dispersed volume fraction varies between 3% and 30%. The flow patterns are observed in the vicinity of impinging region to characterize the effect of Reynolds number and oil volume fraction on the water-oil interaction and thus emulsification process. Based on the measured droplet size and size distribution, two geometries are compared, aimed at evaluating the advantages and disadvantages of swirl flow in the collision region for producing high quality emulsion. One configuration, “600–600”, corresponds to inlet channels of identical size (600 μm × 600 μm), while the other one, “600–300”, has a smaller channel for dispersed phase which is off-axis with the water channel. The results show that flow characteristics during dispersing process are significantly different for viscous and turbulent conditions. Dominated by Reynolds number, the flow patterns are classified into three regimes. The more turbulent the flow is, the finer and more monodispersed droplets will be in the o/w emulsion. In the medium Reynolds number regime, characteristics of flow are closer to laminar flow using higher oil volume fraction, compared to small oil volume content. It is particularly evident with 600–300 system because of lowering velocity gradient between two phase streams. Based on results of drop mean diameter and polydispersity index, 600–300 system which generates swirl flow structure only exhibits a superior performance, compared to the conventional equal-size geometry, at relatively higher Reynolds number.

Spinach leaf and chloroplast lipid: A natural rheology modifier for chocolate?

In this study the possibility of replacing current surfactants in chocolate formulations with natural lipids extracted from spinach leaf (SPLIP) or spinach chloroplast (CH.SPLIP) was evaluated. SPLIP and CH.SPLIP were extracted with chloroform/methanol following enzyme deactivation with hot isopropanol. Results showed a higher extraction yield for SPLIP while glycolipids were more concentrated in CH.SPLIP. Sugar/oil suspensions with dispersed volume fractions of 0.28, 0.33 and 0.37 containing 0.1% to 0.7% (w/w) surfactant (SPLIP, CH.SPLIP, lecithin and PGPR as commercial references) based on oil phase were prepared and analyzed in shear rheology. Apparent viscosity at 40 s−1 was significantly lower for the natural surfactants compared to lecithin at 0.5–0.7% (w/w) addition. With regard to yield stress, taken as the shear stress at 5 s−1, both natural surfactants showed comparable performance to PGPR at 0.3% to 0.7% addition. As SPLIP and CH.SPLIP behaved similar (p > 0.05), SPLIP, due to higher extraction yield, would be the preferred choice for application in chocolate matrices.

Surfactant-Stabilized Spontaneous 3-(Trimethoxysilyl) Propyl Methacrylate Nanoemulsions.

Nanoemulsions are a versatile means to create a variety of consumer products and complex materials. Producing nanoemulsions with a high volume fraction of the dispersed phase is generally limited to mechanically intensive processes, such as high-pressure homogenization, and often results in polydisperse droplet size distributions. Low-energy methods, such as spontaneous emulsification, can produce monodispersed droplets, but the volume fraction of the dispersed phase is usually much lower. Here, we report on the spontaneous emulsification of 3-(trimethoxysilyl) propyl methacrylate (TPM) into an alkaline aqueous phase (pH > 10.0) that contains surfactants (Tween 20, sodium dodecyl sulfate (SDS), or cetyltrimethylammonium bromide (CTAB)). The nanoemulsions are monodisperse with droplet diameters that range between 15 and 500 nm. The small droplet size is due to the presence of surfactants that stabilize the droplets against coalescence. The spontaneous emulsion process can produce emulsions with a dispersed volume fraction of up to 10% in CTAB solutions and up to 30% using Tween 20 and SDS. After the emulsification process, the TPM droplets can be polymerized to produce nanoparticles. Using dynamic light scattering and scanning electron microscopy, we characterize the relationship between the surfactant concentration and the size of the droplets in the nanoemulsions. We find that the droplet diameter is primarily determined by the molar ratio of oil to surfactant. We also find that the pH in the aqueous phase also modulates the droplet diameter when using an ionic surfactant. This work expands the spontaneous emulsification of TPM in the absence of stabilizing particles to the nanoscale while producing one of the highest volume fractions of nanoemulsion droplets obtained via a low-energy mechanism.

Investigation of the Chain Formation Effect on Thermal Conductivity of Magnetorheological Fluids

Chain formation is one of the factors influencing the changes in the rheological properties of magnetorheological (MR) fluids as thermal conductivity. After applying the magnetic field, the particles make some clusters in the direction of the applied field. In this work, a variation of thermal conductivity of the MR fluid was investigated experimentally, and the cluster formation inside the fluid was visualized by appropriate computational fluid dynamics simulations. The experimental results show that with the increase in magnetic field strength and dispersed particle volume fraction, as well as the decrease in the size of dispersed particles, more particles joined together in the direction of the external applied magnetic field. It was found that the more and longer chains of particles are formed, the variation of thermal conductivity of the MR fluid is more considerable. The experimental results showed that the thermal conductivity of the MR fluid with 15% dispersed particle volume fraction is increased up to 117% by applying an magnetic field. The increase in the thermal conductivity has been observed in experimental studies, and the longer and the more strong chain formations have shown in computational fluid dynamics simulation that its trend is in good agreement with experimental results.

Neurite orientation dispersion and density imaging reveals white matter and hippocampal microstructure changes produced by Interleukin-6 in the TgCRND8 mouse model of amyloidosis

Extracellular β-amyloid (Aβ) plaque deposits and inflammatory immune activation are thought to alter various aspects of tissue microstructure, such as extracellular free water, fractional anisotropy and diffusivity, as well as the density and geometric arrangement of axonal processes. Quantifying these microstructural changes in Alzheimer’s disease and related neurodegenerative dementias could serve to monitor or predict disease course. In the present study we used high-field diffusion magnetic resonance imaging (dMRI) to investigate the effects of Aβ and inflammatory interleukin-6 (IL6), alone or in combination, on in vivo tissue microstructure in the TgCRND8 mouse model of Alzheimer’s-type Aβ deposition. TgCRND8 and non-transgenic (nTg) mice expressing brain-targeted IL6 or enhanced glial fibrillary protein (EGFP controls) were scanned at 8 months of age using a 2-shell, 54-gradient direction dMRI sequence at 11.1 T. Images were processed using the diffusion tensor imaging (DTI) model or the neurite orientation dispersion and density imaging (NODDI) model. DTI and NODDI processing in TgCRND8 mice revealed a microstructure pattern in white matter (WM) and hippocampus consistent with radial and longitudinal diffusivity deficits along with an increase in density and geometric complexity of axonal and dendritic processes. This included reduced FA, mean, axial and radial diffusivity, and increased orientation dispersion (ODI) and intracellular volume fraction (ICVF) measured in WM and hippocampus. IL6 produced a ‘protective-like’ effect on WM FA in TgCRND8 mice, observed as an increased FA that counteracted a reduction in FA observed with endogenous Aβ production and accumulation. In addition, we found that ICVF and ODI had an inverse relationship with the functional connectome clustering coefficient. The relationship between NODDI and graph theory metrics suggests that currently unknown microstructure alterations in WM and hippocampus are associated with diminished functional network organization in the brain.

Discrete element method study of solid descending and residence properties in COREX shaft furnace with center gas supply device

Solid descending and residence properties in COREX shaft furnace with a center gas supply device (CGSD) were studied using the discrete element method. Solid flow pattern, residence time distribution, and local solid residence time (SRT) were analyzed. Moreover, the effects of the rotation speed of screws, the radius, and height of CGSD were investigated. The results show that the solid flow is dominantly a plug flow in the shaft furnace with the CGSD. In the upper region of the shaft furnace for gas–solid reduction, uniform distribution of local SRT is observed, which is preferable to match the even gas distribution expected due to the CGSD and slots. For different rotation speeds of the screws, the distribution of solid flow patterns is similar. The averaged residence time, dispersed plug volume fraction, and dead volume fraction decrease with increasing the rotation speed of the screws. The radius of the CGSD affects the solid residence in the shaft furnace. Local SRT above the CGSD increases with the increase in the radius of CGSD, possibly leading to the formation of more agglomerates. Hence, the radius of CGSD should be chosen carefully. The height of CGSD has a minor effect on solid residence in the shaft furnace.

An efficient solver for fully coupled solution of interaction between incompressible fluid flow and nanocomposite truncated conical shells

In this research, the dynamic instabilities of nanocomposite truncated conical shells containing a quiescent or a flowing inviscid fluid are scrutinized. Nonlinear dynamic equations are established according to the Novozhilov nonlinear shell theory along with Green’s strains and Hamilton principle. The velocity potential and Bernoulli’s equations are adopted to calculate fluid pressure acting on the conical shell. The nonlinear governing equations are discretized using trigonometric expansion through the circumferential direction and generalized differential quadrature method (GDQM) through the meridional direction. A detailed parametric study is directed to provide an insight into the influence of volume fraction of carbon nanotubes (CNTs), CNT dispersion, geometrical parameters, and boundary conditions on the divergence and flutter instabilities of nanocomposite truncated conical shells. This study shows the superb efficiency of the outlined solution procedure in reducing computational costs and virtual storage. The simulation indicates that the beginning of divergence and flutter instabilities can be significantly postponed by selecting an appropriate dispersion of CNTs through the thickness of the conical shell. Furthermore, the onset of flutter and divergence instabilities are found to be very sensitive to the semi-vertex angle and thickness-to-radius ratio. The results of this research shed light into using ultra-high-strength and low-weight nanocomposite for pressure vessels applications.

Characterization of a Piezoelectric Inkjet Aerosol Generator for the Study of Bioaerosol Survivability

ABSTRACT In laboratory-based bioaerosol researches, the ability to reliably generate bioaerosols with minimal damage to the microorganisms is critical. In this work, a thermally consistent inkjet-based aerosol generation technique was adopted to generate bioaerosols, and its ability to preserve microbial survivability was assessed. The performance of the piezoelectric inkjet aerosol generator was evaluated using a potassium sodium tartrate solution and an aqueous suspension of 3-µm polystyrene latex spheres. An Aerodynamic Particle Sizer was employed to measure the aerosol number concentration and the size distribution. The main operating parameters of the inkjet print head for generating viable aerosols were the driving voltage, pulse duration, dispersion air flow, pulse frequency, and volume fraction of the solids in the nebulizing liquid. In the bioaerosol survivability experiments, yeast was used as the test microorganism. The nebulized yeast cells were sampled at different distances from the outlet of the inkjet aerosol generator and thus exposed to varying degrees of relative humidity for different residence times. Three bioaerosol samplers, namely, a BioSampler, a gelatin filter cassette, and a Marple cascade impactor with Mylar film, were used to collect the airborne yeast samples. Yeast survivability was determined by methylene blue viability staining. This study successfully demonstrated the feasibility and the advantages of using a piezoelectric inkjet print head to generate viable aerosols. Applying a square wave with appropriate combinations of voltage and pulse duration enabled the inkjet system to produce a liquid with rheological properties similar to those of water, and the particle generation rate was manipulated by adjusting the pulse frequency. Moreover, dispersion air was required to reduce coagulation. Although the number of droplets containing PSL spheres increased with the volume fraction of the spheres (Fv), a high Fv also reduced the probability of singlets forming.

Fully automated dual-resolution serial optical coherence tomography aimed at diffusion MRI validation in whole mouse brains.

.An automated dual-resolution serial optical coherence tomography (2R-SOCT) scanner is developed. The serial histology system combines a low-resolution () OCT with a high-resolution () OCT to acquire whole mouse brains at low resolution and to target specific regions of interest (ROIs) at high resolution. The ROIs positions are selected either manually by the microscope operator or using an automated ROI positioning selection algorithm. Additionally, a multimodal and multiresolution registration pipeline is developed in order to align the 2R-SOCT data onto diffusion MRI (dMRI) data acquired in the same ex vivo mouse brains prior to automated histology. Using this imaging system, 3 whole mouse brains are imaged, and 250 high-resolution three-dimensional ROIs are acquired. The capability of this system to perform multimodal imaging studies is demonstrated by labeling the ROIs using a mouse brain atlas and by categorizing the ROIs based on their associated dMRI measures. This reveals a good correspondence of the tissue microstructure imaged by the high-resolution OCT with various dMRI measures such as fractional anisotropy, number of fiber orientations, apparent fiber density, orientation dispersion, and intracellular volume fraction.

Experimental investigation on rheological property of foamy oil in Venezuela

ABSTRACTSome heavy oil reservoirs present foamy oil flow behavior under primary production, and the foamy oil viscosity and rheological property are important factors that influence the efficiency of the process. The variation of the foamy oil viscosity during the depletion process is complicated due to the generation and migration of dispersed gas bubbles within the oil phase, and still remains as a controversial topic. This study aims to investigate this issue by measuring the foamy oil viscosity at different pressure, temperature and flow rate with a capillary viscometer system equipped with a specially designed foamy oil generator to guarantee the generation and stable flow of gas-in-oil dispersions. Meanwhile, the dead oil and live oil viscosities were also measured for comparison. Based on the results from all the tests the following conclusions can be drawn. Below the bubble point pressure, the dispersed gas-bubble volume fraction and foamy oil viscosity increase with pressure decline; the viscosity of foamy oil is higher than that of live oil, and the gap between them widens with pressure decline. Moreover, foamy oil behaves as shear-thinning power-law fluid, and the shear-thinning effect becomes stronger with the decrease of pressure. The foamy oil rheology is also affected by temperature, and the shear-thinning effect becomes milder with the increase of temperature. Based on the experimental data, a formula was established for estimating foamy oil apparent viscosity within porous media, which took flow rate, shear-thinning flow parameters, permeability, porosity and other factors into consideration.