Capillary Resistance Research Articles

Low Flow and Microvascular Shunts: A Final Common Pathway to Cerebrovascular Disease: A Working Hypothesis.

Low flow and microvascular shunts (MVS) is the final common pathway in cerebrovascular disease. Low flow in brain capillaries (diam. 3-8μm) decreases endothelial wall shear rate sensed by the glycocalyx regulating endothelial function: water permeability; nitric oxide synthesis via nitric oxide synthase; leucocyte adhesion to the endothelial wall and penetration into the tissue; activation of cytokines and chemokines initiating inflammation in tissue. Tissue edema combined with pericyte and astrocyte capillary constriction increases capillary resistance. Increased capillary resistance diverts flow through MVS (diam. 10-25μm) that are non-nutritive, without gas exchange, waste or metabolite clearance and cerebral blood flow (CBF) regulation. MVS predominate in subcortical and periventricular white matter. The shift in flow from capillaries to MVS is a pathological, maladaptive process. Low perfusion in the injured tissue exacerbates brain edema. Low blood flow and MVS alone can lead to all of the processes involved in tissue injury including inflammation and microglial activation.

Study on the Water Blocking Capacity and Influencing Factors of Hydrophobic Gravel Beds.

Excess water production is a common and extremely serious problem during the process of reservoir development, especially in the middle and later stages of unconsolidated sandstone reservoirs. High water content ratios will negatively affect the recovery efficiency and equipment safety of oil and gas wells. In this study, a hydrophobic quartz sand proppant was prepared with 1,1,1,3,3, 3-hexamethyldisilazane (HMDS) for gravel packing technology. The capillary resistance of hydrophobic quartz sand beds to water was used to achieve water inhibition and oil enhancement. Then, a theoretical capillary bundle model of a quartz sand bed was developed to predict the capillary resistance and water blocking capacity of the quartz sand bed. An evaluation of the experiment results shows that the activation index is up to 96% and the water contact angle is up to 151° after treatment by 0.6 wt % HMDS, which indicates that the quartz sand after modification has strong hydrophobicity. The calculation results demonstrate that the capillary resistance (CR) and the water blocking capacity (WBC) decrease with increasing quartz sand particle size and porosity of the quartz sand bed. As the water contact angle increases, the CR and WBC are also increased. In addition, to make the WBC of hydrophobic quartz sand bed δ > 20%, the parameters of the quartz sand bed must be satisfied: particle size dg < 50 μm, porosity ϕ < 30%, water contact angle θ > 150°, and production pressure difference Δp < 1 MPa. The results of this study could provide theoretical guidance for the construction parameters of hydrophobic gravel packing in high water-cut oil and gas fields.

Liquid phase blockage in micro-nano capillary pores of tight condensate reservoirs

The development of tight condensate gas reservoirs faces complex formation damage mechanisms, seepage characteristics and hydrocarbon phase changes, which are common challenges for both tight gas reservoirs and condensate gas reservoirs. In the near-well area, the liquid phase blockage problem due to water phase retention formed by capillary spontaneous imbibition of invasive water and oil phase accumulation due to retrograde condensation precipitation has become a key obstacle to the efficient development of tight condensate gas reservoirs. Experiments were conducted to evaluate the damage of liquid phase blockage under different conditions near the wellbore area. The results show that when the liquid phase saturation in the near-wellbore area increased to 80.12%, the relative permeability of the gas phase decreased to 0. It is concluded that the mixed wettability of formation rocks, ultra-low water saturation, abundant hydrophilic clay minerals and high capillary resistance of micro-nano pores are the main causes for the easy adsorption and retention of liquid phase. Reduced pressure transmission capacity and irreversible formation damage induced by liquid-phase blockage are the two major controlling factors for the low liquid phase flowback rate. It is suggested that developing a flowback system based on the formation physical properties differentiation to control water phase invasion, and changing wettability or injecting thermochemical fluid to control condensate blocking are feasible methods to relieve liquid phase blockage damage in tight condensate reservoirs. Cited as: Wang, Y., Kang, Y., Wang, D., You, L., Chen, M., Yan, X. Liquid phase blockage in micro-nano capillary pores of tight condensate reservoirs. Capillarity, 2022, 5(1): 12-22. https://doi.org/10.46690/capi.2022.01.02

Equation of State’s Crossover Enhancement of Pseudopotential Lattice Boltzmann Modeling of CO2 Flow in Homogeneous Porous Media

The original Shan-Chen’s pseudopotential Lattice Boltzmann Model (LBM) has continuously evolved during the past two decades. However, despite its capability to simulate multiphase flows, the model still faces challenges when applied to multicomponent-multiphase flows in complex geometries with a moderately high-density ratio. Furthermore, classical cubic equations of state usually incorporated into the model cannot accurately predict fluid thermodynamics in the near-critical region. This paper addresses these issues by incorporating a crossover Peng–Robinson equation of state into LBM and further improving the model to consider the density and the critical temperature differences between the CO2 and water during the injection of the CO2 in a water-saturated 2D homogeneous porous medium. The numerical model is first validated by analyzing the supercritical CO2 penetration into a single narrow channel initially filled with H2O, depicting the fundamental role of the driving pressure gradient to overcome the capillary resistance in near one and higher density ratios. Significant differences are observed by extending the model to the injection of CO2 into a 2D homogeneous porous medium when using a flat versus a curved inlet velocity profile.

Effects of interactions in natural gas/water/rock system on hydrocarbon migration and accumulation

The study of natural gas accumulation process in tight formation has become the focus of the petroleum industry. One of the priorities is the effects of interactions in natural gas/water/rock system on hydrocarbon migration and accumulation process. On the macroscopic scale, we investigate the interactions in natural gas/water/rock system by formation fluorescence test and production data analysis. One the microscopic scale, the mechanisms are revealed by mathematical analysis and experimental methods considering the variation of geological temperature and pressure. The effects of interactions in natural gas/water/rock system are also simulated by numerical simulation. The results are visualized and quantified. A novel semi-analytical method based on a physical experiment is proposed to calculate the temperature- and pressure-dependent contact angle and interface tension which reflect the interactions in the natural gas–water–rock system. This semi-analytical is embedded in the numerical simulation during the simulation of the natural gas charging process. The results indicate that with the increase of geological temperature and pressure, the contact angle will increase and the interface tension between natural gas and water will decrease. The capillary resistance in the formation will be reduced. Since the decrease of capillary resistance, the natural gas can be charged into smaller pores, so that the actual charging threshold is lower than the one originally obtained under present reservoir conditions. After considering the temperature and pressure during the accumulation process, some sand bodies that were thought not to be charged may have natural gas accumulate.

The determination of surface relaxivity and application to coal spontaneous imbibition

Experimental researches on spontaneous imbibition are of great significance for improving the recovery rate of coalbed methane and preventing gas disasters. The determination of microstructure is a prerequisite for studying pore seepage behaviors. The transverse surface relaxivity must be known first before obtaining the pore size distribution (PSD) by nuclear magnetic resonance (NMR). In this paper, a method for determining the transverse surface relaxivity of low-permeability coal was improved by correlating the NMR cumulative PSD curves and the corrected mercury intrusion porosimetry (MIP) capillary pressure curves. The MIP data was calibrated for the matrix compression effect in the high-pressure part only by MIP experiment and for the surface cavity effect in the low-pressure part. Then the transverse surface relaxivity obtained was applied to study the time and space evolution behaviors of water imbibition volume and water content in pores of different scales during spontaneous imbibition. The results indicate that the pore volume only accounts for 31.64%-66.47% of the measured mercury volume. Besides, in the rapid rising stage and the prior period of the slow rising stage of spontaneous imbibition, micropores dominate water imbibition and are the first to reach a water-saturated state. As time increases, the contributions of mesopores and macropores to water imbibition become significant gradually. After water enters coal samples, a small part of water advances along the connected path with low capillary resistance and reaches the outlet first, forming the dominant channel. However, most of the water diffuses laterally to the same horizontal plane. When the pores in this horizontal plane approach a saturated state, water migrates upward.

Retinal Vascular Resistance Significantly Correlates With Visual Acuity After 1 Year of Anti-VEGF Therapy in Central Retinal Vein Occlusion.

PurposeTo investigate whether the resistivity of all retinal vessels, termed total capillary resistance (TCR), after anti-vascular endothelial growth factor (VEGF) treatment was correlated with the outcomes of patients with macular edema secondary to central retinal vein occlusion (CRVO).MethodsIn total, 67 patients with nonischemic CRVO were enrolled in this retrospective observational case series. In each patient, we examined visual acuity; central retinal thickness (CRT); mean blur rate (MBR), which represents retinal blood flow velocity; and TCR. MBR and TCR were measured by laser speckle flowgraphy.ResultsDuring the 1-year follow-up period, nine of 67 eyes (13.4%) converted to the ischemic type (converted group), whereas 58 eyes (86.6%) remained unchanged (nonischemic group). Mean CRT significantly decreased in all groups; however, the mean visual acuity significantly improved only in the nonischemic group. Mean MBR significantly increased in the nonischemic group but remained unchanged in the converted group. Mean TCR was significantly reduced in the nonischemic group but remained unchanged in the converted group. Multiple linear regression analysis revealed that MBR and TCR were the independent factors with the strongest and second strongest correlations with visual acuity after treatment, respectively.ConclusionsThese findings suggest that measurements of the independent factors MBR and TCR are useful for evaluating anti-VEGF treatments in patients with CRVO.Translational RelevanceDevelopment of clinically relevant technologies.

Review of diffusion-weighted imaging and dynamic contrast-enhanced MRI for multiple myeloma and its precursors (monoclonal gammopathy of undetermined significance and smouldering myeloma).

The last decades, increasing research has been conducted on dynamic contrast-enhanced and diffusion-weighted MRI techniques in multiple myeloma and its precursors. Apart from anatomical sequences which are prone to interpretation errors due to anatomical variants, other pathologies and subjective evaluation of signal intensities, dynamic contrast-enhanced and diffusion-weighted MRI provide additional information on microenvironmental changes in bone marrow and are helpful in the diagnosis, staging and follow-up of plasma cell dyscrasias. Diffusion-weighted imaging provides information on diffusion (restriction) of water molecules in bone marrow and in malignant infiltration. Qualitative evaluation by visually assessing images with different diffusion sensitising gradients and quantitative evaluation of the apparent diffusion coefficient are studied extensively. Dynamic contrast-enhanced imaging provides information on bone marrow vascularisation, perfusion, capillary resistance, vascular permeability and interstitial space, which are systematically altered in different disease stages and can be evaluated in a qualitative and a (semi-)quantitative manner. Both diffusion restriction and abnormal dynamic contrast-enhanced MRI parameters are early biomarkers of malignancy or disease progression in focal lesions or in regions with diffuse abnormal signal intensities. The added value for both techniques lies in better detection and/or characterisation of abnormal bone marrow otherwise missed or misdiagnosed on anatomical MRI sequences. Increased detection rates of focal lesions or diffuse bone marrow infiltration upstage patients to higher disease stages, provide earlier access to therapy and slower disease progression and allow closer monitoring of high-risk patients. Despite promising results, variations in imaging protocols, scanner types and post-processing methods are large, thus hampering universal applicability and reproducibility of quantitative imaging parameters. The myeloma response assessment and diagnosis system and the international myeloma working group provide a systematic multicentre approach on imaging and propose which parameters to use in multiple myeloma and its precursors in an attempt to overcome the pitfalls of dynamic contrast-enhanced and diffusion-weighted imaging.Single sentence summary statementDiffusion-weighted imaging and dynamic contrast-enhanced MRI provide important additional information to standard anatomical MRI techniques for diagnosis, staging and follow-up of patients with plasma cell dyscrasias, although some precautions should be taken on standardisation of imaging protocols to improve reproducibility and application in multiple centres.

INFLUENCE OF TYPE 2 DIABETES MELLITUS ON THE PREVENTION AND TREATMENT OF PROSTHETIC STOMATITIS

Purpose: to study the effect of type 2 diabetes mellitus on the state of the mucous membrane and tissues of the oral cavity to optimize the prevention and increase the effectiveness of dentition defects complex treatment in this contingent of patients. Materials and methods. We examined 112 patients with type 2 diabetes mellitus aged 35 to 64 years, who were further divided into three groups. The state of the oral mucosa, morphological changes, local immunity, lysozyme were determined. The work used morphological, microscopic methods, enzyme immunoassay and spectrophotometry. To test the statistical significance of intergroup differences, the nonparametric Mann- Whitney test was used. Results. Oral use in patients with diabetes mellitus type 2, applications of 1% Clotrimazole cream and Echinacea Compositum S had a positive preventive and therapeutic effect, which was accompanied by an increase in capillary resistance, a decrease in the degree of migration of leukocytes, an increase in the functional activity of immune system cells and an increase in the level of regenerative processes. In patients with defects in the dentition against the background of type 2 diabetes mellitus, violations of the oral cavity local immunity were revealed, characterized by a significant increase in the S-IgA content and a decrease in lysozyme.Orthopedic treatment with partial removable denturesled to a significant decrease in the concentration of S-IgA and an increase in the bactericidal activity of saliva due to increased lysozyme synthesis. It was concluded that type 2 diabetes mellitus affects the state of the oral mucosa, which must be taken into account when providing orthopedic and dental treatment.

Liquid bridge splitting enhances normal capillary adhesion and resistance to shear on rough surfaces

Hypothesis‘Bridge splitting’ is considered in the case of capillary adhesion: a fixed total volume of liquid is split into multiple capillary bridges. Previous studies have shown that bridge splitting only enhances the capillary-induced adhesion force between two planar surfaces in specific circumstances. We hypothesise that bridge splitting significantly enhances the total adhesion force between rough surfaces, since mobile wetting bridges can naturally migrate to narrower gaps. This migration of capillary bridges should also provide a resistance to shear. Numerical experimentsWe theoretically consider an idealized system of many liquid bridges confined between two solid surfaces. By numerically calculating the shape of a single bridge, the total adhesion force is found as the number of bridges and roughness are varied. The resistance to shear is also calculated in the limit of strong surface tension or small shears. FindingsBridge splitting on a rough surface significantly enhances the adhesion force, with an enhancement that increases with the amplitude of the roughness; maximising over the number of bridges can increase the total adhesion force by an order of magnitude. Resistance to shear is shown to increase linearly with the translation velocity, and the behaviour of many such shearing bridges is quantified.

Changes in the blood coagulation system that determine postoperative complications in patients with non-tumor mechanical jaundice

The OBJECTIVE was to study the features of changes in the blood coagulation system that contribute to the development of postoperative complications in patients depending on the stage of non-tumor mechanical jaundice at admission.METHODS AND MATERIALS. A total of 537 patients with mechanical jaundice were examined and changes in the blood coagulation system were analyzed. Vascular-platelet hemostasis was characterized by the following tests: capillary resistance, the number of desquamated endothelial cells, the number of blood platelets. Plasma hemostasis was analyzed using activated partial thromboplastin time, plasma soluble fibrin level, thrombin time, prothrombin ratio, prothrombin index, and fibrinogen blood level. Then, XIIa-dependent fibrinolysis in the blood and the level of the fibrin D-dimer in the blood plasma were determined.RESULTS. It was found that in the first stage of mechanical jaundice, with cholestasis, there were no changes in blood coagulation system that go beyond the normal limits. In the second stage, during cytolysis of hepatocytes, hyperbilirubinemia and hypertransaminasemia contribute to the activation of platelet first, and then plasma hemostasis. In the third stage (cholangitis), the death of endotheliocytes increases and there is a deficiency of blood coagulation factors due to their consumption and increased fibrinolysis.CONCLUSION. In the stage of cholestasis in patients with non-tumors mechanical jaundice, the parameters of the coagulation system remain within the reference values. In the stage of cytolysis, as endotheliotoxicosis increases, platelet and plasma hemostasis begins to activate, which can lead to thrombosis and thromboembolism in vital organs. In the stage of cholangitis, further activation of plasma hemostasis causes hemorrhagic syndrome. The occurrence of the described disorders in blood coagulation system with the progression of MJ dictates the need to monitor the changes in the blood coagulation system and their correction for the prevention of intra-and postoperative complications.

Distribution of Flow in an Arteriovenous Fistula Using Reduced-Order Models.

The creation of a communication between an artery and a vein (arteriovenous fistula or AVF), to speed up the blood purification during hemodialysis of patients with renal insufficiency, induces significant rheological and mechanical modifications of the vascular network. In this study, we investigated the impact of the creation of an AVF with a zero-dimensional network model of the vascular system of an upper limb and a one-dimensional model around the anastomosis. We compared the simulated distribution of flow rate in this vascular system with Doppler ultrasound measurements. We studied three configurations: before the creation of the AVF, after the creation of the AVF, and after a focal reduction due to a hyper flow rate. The zero-dimensional model predicted the bounds of the diameter of the superficial vein that respects the flow constraints, assuming a high capillary resistance. We indeed highlighted the importance of knowing the capillary resistance as it is a decisive parameter in the models. We also found that the model reproduced the Doppler measurements of flow rate in every configuration and predicted the distribution of flow in cases where the Doppler was not available. The one-dimensional model allowed studying the impact of a venous constriction on the flow distribution, and the capillary resistance was still a crucial parameter.

Infiltration behavior of copper melt into porous graphite and saturation improvement by WC particles doping

ABSTRACT In graphite/copper composites, the intrinsic non-wettability of graphite and copper makes it difficult for the copper melt to realize effective infiltration into the porous graphite matrix. The resulted void defects have reduced the final performance of the composites. It is of great significance to improve the saturation of copper melt in the graphite skeleton, which requires a well understanding of the infiltration behavior of copper melt. In this paper, a two-phase flow finite element model was developed, and verified by previous published experimental data. Effects of the external pressure on the infiltration behavior has been studied, and then an optimization method based on WC particle doping was proposed. Results indicated that effective transfer of displacement pressure at the liquid flow front can reduce the void defects of composite materials. WC doping has reduced the capillary resistance, and effectively improved the copper saturation in the infiltration process from 80.4% to 90.7%. This work provided a new method to reduce the void defects of composites, which may be helpful for the development of high performance copper/graphite composites.

Experimental study on capillary ascent in compacted loess

In this study, negative head height tests were performed on loess samples from Weibei, Shaanxi, China, to investigate capillary ascent in unsaturated compacted loess. The results of tests performed under different compaction intensities were used to determine the change relationships between the negative head height and blow count and between the pore diameter and blow count. The curve relating the capillary height to the compacted loess pore diameter was approximately parabolic, with the critical pore diameter corresponding to the peak capillary height. The conditions of applicability of Jurin’s law were analyzed. A capillary resistance to capillary water, in addition to surface tension and gravity, was identified during capillary migration. A stress analysis of capillary pore water was used to propose a method for determining the critical infiltration surface depth of an unsaturated loess.

Novel Method for Studying, the, Imbibition Production Mechanism Using NMR

Tight volcanic reservoirs, characterized by strong heterogeneity and a well-developed fracture network, are usually difficult to develop. The development of effective ways to enhance production in such reservoirs is an important task in research work for oil and gas field development. The method of enhancing production by imbibition is a promising technology for oil recovery in tight reservoirs. In this paper, based on the production data of horizontal wells in tight volcanic reservoirs, we have studied the imbibition mechanism during fracturing fluid flowback. Nuclear magnetic resonance (NMR) technology was used for analysis. First, the wire-cutting technique was used to simulate fractures generated by hydraulic fracturing in the core. Then the core was filled with quartz sand. Then the migration of fluid between small pores and macropores during the imbibition process was studied by low-field NMR analysis. The research results show that the imbibition displacement of fracturing fluid under high pressure can effectively increase the recovery rate, while the soaking time can affect the imbibition exchange of fluid between crack and matrix. Due to the small pore radius and high capillary resistance of the volcanic rock, the imbibition stability time is longer. The pore size distribution of volcanic rock was analyzed quantitatively by NMR and mercury intrusion porosimetry. The results show that the dynamic imbibition process occurs mainly in pores less than 2 im.

Retinal Microvascular Resistance Estimated from Waveform Analysis Is Significantly Higher With a Threshold Value in Central Retinal Vein Occlusion.

PurposeEvaluation of blood flow is useful for understanding the severity of central retinal vein occlusion (CRVO). Actual blood flow may be determined by the resistivity of the retinal vein in CRVO. We have previously evaluated mean blur rate (MBR) to reflect total retinal blood flow velocity in CRVO cases using laser speckle flowgraphy (LSFG). This study evaluated retinal total vascular resistance in CRVO cases using the new index of total capillary resistance (TCR) from LSFG.MethodsWe measured the TCR of 68 CRVO patients who visited Nagasaki University Hospital between 2009 and 2016 and 42 age-matched controls without systemic disease. We compared TCRs among control eyes, CRVO fellow eyes, and CRVO affected eyes. A CRVO threshold value was then obtained from the receiver operating characteristic curve.ResultsMBR was significantly lower for CRVO affected eyes (20.3 ± 8.2) than for control eyes (37.5 ± 8.4; P < 0.01) and CRVO fellow eyes (36.4 ± 10.0; P < 0.01, Dunn's test). TCR was significantly higher for CRVO affected eyes (1.20 ± 0.55) than for control eyes (0.68 ± 0.2; P < 0.01) and CRVO fellow eyes (0.81 ± 0.28; P < 0.01, Dunn's test). The threshold for the presence of CRVO was 0.93 and area under the curve was 0.84.ConclusionsBy measuring TCR in addition to MBR, more detailed information regarding CRVO pathology can be obtained.Translational RelevanceComparison of values before and after treatment may be useful for evaluating the effects of treatment.

Surfactant-Based Treatment Fluids Mitigate Fracture Hits in Parent Wells

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 197097, “Fracture-Hit Mitigation Through Surfactant-Based Treatment Fluids in Parent Wells,” by Liang Xu, James Ogle, and Todd Collier, SPE, Halliburton, prepared for the 2019 SPE Liquids-Rich Basins Conference - North America, Odessa, Texas, 11-12 September. The paper has not been peer reviewed. Preloading parent wells with surfactant-based treatment fluids for fracture-hit mitigation has been applied extensively in liquids-rich shale plays. However, why specific chemical packages help improve parent-well production remains unclear. The complete paper presents a strategy for selecting a surfactant/solvent package for parent wells. Oil recovery and associated water saturation in the microfluidic-based device, with or without surfactant, are quantified and reveal that the oil recovery is enhanced with surfactant. Water saturation in the parent well could be reduced, thereby mitigating water blocks from primary fracturing-fluid invasion from child wells. Introduction During child-well completions in development of liquids-rich shale plays, fracturing fluids and proppants are likely to infiltrate the parent-well fracture net-work and wellbore through hydraulically connected flow paths. Parent wells, after producing for a period, serve as a pressure sink that attracts new fracture propagation and extension initiated from a child-well fracture. As a result, parent wells could lose production because of a potentially plugged fracture network filled with new sand from child wells. The production of child wells also could suffer because of unwanted fracture extension and loss of reservoir pressure. The technique of reloading parent wells with surfactant-based treatment fluids for fracture-hit mitigation has been applied recently in environments where intense infill drilling and tighter well spacings are prerequisites for improved production and economic return. Preloads can provide a significant temporary increase in fracture network pressure if performed properly and are most effective with a surfactant and solvent package. However, why specific chemical packages help improve the parent-well production remains unclear, although the notion of capillary force resistance reduction for further treatment-fluid leakoff into fractures and rock- wettability alteration by surfactant has been proposed in the literature. Recent residual surfactant analysis in produced water from both parent and child wells indicates that hydraulic communication exists after fracture hits; additionally, field trials in the Wolfcamp suggest that the same surfactant package in primary fracture fluids in child wells can migrate gradually to parent wells, potentially activating various secondary oil-recovery mechanisms. This study provides an evidence-based strategy for selecting a surfactant solvent package by a commercial microfluidic device (MD) and spontaneous imbibition (SpI), thus eliminating unnecessary testing that does not involve formation rocks. Surfactant optimization permits further leakoff into secondary fractures, potentially increasing fracture network pressure. Surfactant migration from child wells presents a unique enhanced-oil-recovery mechanism for parent wells. Field trials in different liquids-rich shale plays, including the Wolfcamp, appear to support this finding.

Conformance control in heterogeneous two-dimensional sandpacks by injection of oil-in-water emulsion: Theory and experiments

Oil-in-water (O/W) emulsion flow tests were conducted in visual and heterogeneous two-dimensional (2-D) models in which the crossflow between the high (HPZ) and low permeability zones (LPZ) can be modelled. Impacts of emulsion droplet size on promoting crossflow between the two permeability zones were investigated. Emulsion flood pattern and outflow percentage from the two heterogeneous zones show that injection of O/W emulsions with an appropriate range of droplet sizes can induce crossflows between the two permeability zones, thereby resulting in the water mobility conformance in the heterogeneous 2-D model. Two types of crossflow were observed in the experiments and verified in the numerical modeling: flow redistribution at the injection boundary and crossflows in the emulsion-invaded area. A new mathematical model was established to capture the dynamics of 2-D emulsion flow. A finite element method was used to obtain the solution of the mathematical model, and the experimentally observed emulsion conformance control processes were successfully predicted. Mathematical analyses on emulsion concentration distribution, velocity field and pressure distribution reveal that it is the capillary resistance contributed by the emulsion that changes the pressure distribution in the two permeability zones; therefore, the changed pressure distribution affects the local flow in the two permeability zone and thus influences the outflows. The proposed emulsion flow model is compatible with a standard reservoir simulator, providing a potentially efficient and useful method of simulating field-scale emulsion flow for designing conformance control process.

Calcium sulfoaluminate and alkali-activated fly ash cements as alternative to Portland cement: study on chemical, physical-mechanical, and durability properties of mortars with the same strength class

There is an increasing interest towards the development of alternative binders for the manufacture of sustainable mortars and concretes. Ordinary Portland cement (OPC) is the most commonly used material in construction, even if its production process is highly polluting. Both calcium sulfoaluminate (CSA) and alkali-activated cements (AAC) are potential alternative binders to be used in both structural (R3 class, with Rc ≥ 25 MPa) and non-structural applications (R1 and R2 classes, with Rc ≥ 10 MPa and Rc ≥ 15 MPa, respectively) according to UNI EN 1504-3. This paper reports the hydration mechanisms and the evolution of porosity of OPC-, CSA- and AAC-based binders. The properties of fresh and hardened mortars, belonging to the above-mentioned mechanical strength classes, were evaluated and compared with particular emphasis on durability properties in terms of capillary water absorption, drying shrinkage, and resistance to sulfate attack. The results show that CSA-based mortars exhibit the lowest drying shrinkage due to their highest elasticity modulus. AAC mortars are characterized by the highest water vapor permeability and the lowest capillary water absorption for the highest presence of large pores (>3000 nm).

Early Stages of Chronic Venous Disease: Medical Treatment Alone or in Addition to Endovenous Treatments.

Chronic venous disease (CVD) is one of the most prevalent diseases worldwide. The health condition of most patients with early stage CVD will worsen over time, and this progression increases the burden as well as the costs of treatment and reduces patient quality of life (QoL). This highlights the importance and the likely cost-effectiveness of treatment of patients with early stage CVD. Options for managing the early stages of CVD include lifestyle changes together with venoactive drugs (VAD); VADs may be used alone or in conjunction with interventional treatment of varices such as sclerotherapy, surgery, or endovenous treatments. Micronized purified flavonoid fraction (MPFF; Daflon®) is a well-studied VAD which has anti-inflammatory activities, reduces endothelial activation and leukocyte adhesion, and increases capillary resistance and integrity, to eventually improve venous tone, CVD symptoms and QoL. This article is based on previously conducted studies and does not contain any studies with human participants or animals performed by the author.