The influence of physico-chemical surface properties and morphological and topological pore space properties on trapping (CCS) and recovery efficiency (EOR): a micromodel visualization study

We theoretically and experimentally investigate the impact of pore space structure, wettability, and surface roughness on the displacement front, trapping, and sweeping efficiency at low capillary numbers. The microstructure of (i) 2D geologically-realistic media (2D natural sand and sandstone), (ii) a topological 3D-2D-transformation (2D sand analog), and (iii) geometrically representative media (Delaunay Triangulation) were studied over a wide range of wettability from water-wet to oil-wet systems provided by using various fluid-pairs. We observed the transition (compact to fractal) in the displacement front caused by local instabilities identified by Cieplak and Robbins. The trapping efficiency of 2D natural microstructures showed a non-monotonous dependency on wettability, whereas a crossover from no trapping to maximal trapping was observed in 2D patterns of circular grains. For the first time, we compared identical experimental microstructures with simulation, capturing the key elements of the invasion process. We demonstrated that corner flows occur particularly in low-porosity media, where the smaller grain-grain distance hindered the corner-flow bridging. These insights could improve the CO2 geological storage and Enhanced Oil Recovery processes

Effectiveness of Autologous Schwann Cell and Bone Marrow-Derived Mesenchymal Stem Cell Transplantation for Individuals With Spinal Cord Injury in Promoting Sensory Recovery

Background: In recent decades, improvement in sensory and motor function after spinal cord injury(SCI) is a major treatment goal. Stem cell therapy has become a promising treatment strategy in theregeneration of central nervous system injuries.Methods: We assessed the effectiveness of autologous Schwann cell (SC) and bone marrow-derivedmesenchymal stem cell (MSC) for individuals with SCI in promoting sensory recovery. Five patientswith a mean ± SD age of 38.80 ± 5.84 years were enrolled in the study. The follow-up course was12 months.Results: We found sensory changes in two patients assessed by the American Spinal InjuryAssociation’s (ASIA’s) impairment scale. Systemic complications were not observed during thecourse of the study.Conclusion: There were no adverse finding after cell transplantation. Also we observed improvementin sensory score in two patients. It seems that the use of this combination of cell therapy may beeffective; but large group studies with control group are required to clarify the effect of either cells

The Interplay Between Pore‐Scale Heterogeneity, Surface Roughness, and Wettability Controls Trapping in Two‐Phase Fluid Displacement in Porous Media

Predicting the compactness of the invasion front and the amount of trapped fluid left behind is of crucial importance to applications ranging from microfluidics and fuel cells to subsurface storage of carbon and hydrogen. We examine the interplay of wettability, macro‐ and pore scale heterogeneity (pore angularity and pore wall roughness), and its influence on flow patterns formation and trapping efficiency in porous media by a combination of 3D micro‐CT imaging with 2D direct visualization of micromodels. We observe various phase transitions between the following capillary flow regimes (phases): (a) compact advance, (b) wetting and drainage Invasion percolation, (c) Ordinary percolation

Factors Associated With Neurogenic Bowel Dysfunction Severity in Spinal Cord Injury: A Cross-sectional Study

Background: Neurogenic bowel dysfunction (NBD) caused by spinal cord injury (SCI) is a major life limiting issue for many patients. However, studies detailing the factors contributing to bowel problems are scarce. The aim of this cross-sectional questionnaire-based study was to evaluate the associations between different aspects of bowel problems and characteristics of SCI, such as time since injury (TSI), level of injury (LOI), and the cause of injury.Methods: Two questionnaires (the NBD score questionnaire and the Cleveland clinic constipation system score questionnaire) were administered to complete, traumatic patients with SCI that matched the designated criteria. The total scores and the subscales were then regressed to TSI and LOI, and the distribution patterns of NBD score severity according to LOI and cause of injury were shown in a diagram.Results: Within the subscales of the NBD score, frequency of defecation, digital stimulation or evacuation of the anorectum, and perianal skin problems were all significantly and positively correlated with the TSI, yet the frequency of fecal incontinence was negatively associated with this variable. Moreover, uneasiness, headache, or perspiration during defecation and regular use of drops against constipation were negatively associated with the LOI. In the diagrams, patterns of NBD score severity were similar according to LOI, but visibly differed according to cause. With respect to the CCCS score (Cleveland Clinic Constipation Scoring System), the score itself was shown to be positively associated with TSI. Within the subscales, difficulty, time spent in lavatory, and duration of constipation were positively correlated with TSI. Furthermore, type of assistance was negatively associated with the LOI.Conclusion: Different characteristics of SCI, TSI, LOI, and cause, each are significantly and distinctly associated with different aspects of the bowel problems that patients with SCI face

A New Phase Diagram for Fluid Invasion Patterns as a Function of Pore‐Scale Heterogeneity, Surface Roughness, and Wettability

Understanding how different flow patterns emerge at various macro‐ and pore scale heterogeneity,pore wettability and surface roughness is remains a long standing scientific challenge. Such understandingallows to predict the amount of trapped fluid left behind, of crucial importance to applications ranging frommicrofluidics and fuel cells to subsurface storage of carbon and hydrogen. We examine the interplay ofwettability and pore‐scale heterogeneity including both pore angularity and roughness, by a combination ofmicro‐CT imaging of 3D grain packs with direct visualization of 2D micromodels. The micromodels aredesigned to retain the key morphological and topological properties derived from the micro‐CT images.Different manufacturing techniques allow us to control pore surface roughness. We study the competitionbetween flow through the pore centers and flow along rough pore walls and corners in media of increasingcomplexity in the capillary flow regime. The resulting flow patterns and their trapping efficiency are in excellentagreement with previous μ‐CT results. We observe different phase transitions between the following flowregimes (phases): (a) Frontal/compact advance, (b) wetting and drainage Invasion percolation, and (c) Ordinarypercolation. We present a heterogeneity‐wettability‐roughness phase diagram that predicts these regimes

Quantum-Dot Semiconductor Optical Amplifiers: State Space Model versus Rate Equation Model

A simple and accurate dynamic model for QD-SOAs is proposed. The proposed model is based on the state space theory, where by eliminating the distance dependence of the rate equation model of the QD-SOA; we derive a state space model for the device. A comparison is made between the rate equation model and the state space model under both steady state and transient regimes. Simulation results demonstrate that the derived state space model not only is much simpler and faster than the rate equation model, but also it is as accurate as the rate equation model

A NEW ELECTROSTATICALLY ACTUATED LOW VOLTAGE RF MEMS SWITCH

This paper describes the design and simulation of a new low voltage electrostatically actuated RF MEMS switch. The switch structure is designed in such a way that, the inherent limitation of electrostatic actuation is relaxed and the actuation voltage is as low as 3.5 V. The idea is to using a two-step electrostatic actuation mechanism instead of conventional two parallel plate electrostatic actuators. In fact the gap between switch and transmission line is reduced in two steps. In order to investigate the usefulness of the proposed idea, both mechanically and electromagnetically, FEM simulations are carried out and satisfactory results are obtained. The RF characteristics of the switch are as follow; Isolation -12 dB at 30 GHz, Insertion Loss -0.08dB at 30 GHz and return loss was below -20 dB at 30 GHz. The proposed switch in this paper can be a promising choice for low voltage high performance RF MEMS switches