The Micro-Flow Mechanism of Polymer Flooding in Dual Heterogeneous Reservoirs Considering the Wettability.

There have been some studies conducted about the single factor viscoelasticity of polymer solution or wettability effect on the micro-flow mechanism of polymer flooding. In this paper, the flow mechanism of polymer solution in dual heterogeneous reservoir considering the wettability and gravity was studied. The influences of wettability and rock particle shape on flow characteristics were studied based on the characteristics of saturation and pressure distribution. Compared with the simulation results of polymer flooding in three different rock particle shapes porous media, the oil displacement efficiency of the circular particle model is the highest at 91.57%, which is 3.34% and 11.48% higher than that in the hexagonal and diamond models, respectively. The influence of wettability was studied by the circular particle model. The oil displacement efficiency under water-wet conditions was higher than that under oil-wet conditions. The displacement process considering gravity was affected by the crossflow caused by gravity and viscous force, and the micro-oil displacement efficiency was 9.87% lower than that of non-gravity. Considering the wettability, vertical crossflow will be formed. The oil displacement efficiency under water-wet conditions was 3.9% higher than in oil-wet conditions. The research results can not only expand and enrich the micro-flow mechanism of viscoelastic polymer solution, but also provide reference and guidance for polymer flooding scheme design.

Physiological and Transcriptomic Analyses of Escherichia coli Serotype O157:H7 in Response to Rhamnolipid Treatment.

Rhamnolipid (RL) can inhibit biofilm formation of Escherichia coli O157:H7, but the associated mechanism remains unknown. We here conducted comparative physiological and transcriptomic analyses of cultures treated with RL and untreated cultures to elucidate a potential mechanism by which RL may inhibit biofilm formation in E. coli O157:H7. Anti-biofilm assays showed that over 70% of the E. coli O157:H7 biofilm formation capacity was inhibited by treatment with 0.25-1 mg/mL of RL. Cellular-level physiological analysis revealed that a high concentration of RL significantly reduced outer membrane hydrophobicity. E. coli cell membrane integrity and permeability were also significantly affected by RL due to an increase in the release of lipopolysaccharide (LPS) from the cell membrane. Furthermore, transcriptomic profiling showed 2601 differentially expressed genes (1344 up-regulated and 1257 down-regulated) in cells treated with RL compared to untreated cells. Functional enrichment analysis indicated that RL treatment up-regulated biosynthetic genes responsible for LPS synthesis, outer membrane protein synthesis, and flagellar assembly, and down-regulated genes required for poly-N-acetyl-glucosamine biosynthesis and genes present in the locus of enterocyte effacement pathogenicity island. In summary, RL treatment inhibited E. coli O157:H7 biofilm formation by modifying key outer membrane surface properties and expression levels of adhesion genes.

Introduction of long non-coding RNAs to regulate autophagy-associated therapy resistance in cancer.

Autophagy is a lysosomal degradation pathway that depends on various evolutionarily conserved autophagy-related genes (ATGs). Dysregulation of autophagy plays an important role in the occurrence and development of cancer. Chemotherapy, targeted therapy, radiotherapy, and immunotherapy are important treatment options for cancer, which can significantly improve the survival rate of cancer patients. However, the occurrence of therapy resistance results in therapeutic failure and poor prognosis of cancer. Accumulating studies have found that long non-coding RNAs (lncRNAs) are well known as crucial regulators to control autophagy through regulating ATGs and autophagy-associated signaling pathways, including the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway, ultimately mediating chemoresistance and radioresistance. Taken together, this review systematically summarizes and elucidates the pivotal role of lncRNAs in cancer chemoresistance and radioresistance via regulating autophagy. Understanding the specific mechanism of which may provide autophagy-related therapeutic targets for cancer in the future.

Experiment on the Scaling Mechanism of Strong Alkaline-Surfactant-Polymer in a Sandstone Reservoir.

Most of the mature oilfields are facing the problem of great difficulty in exploitation currently. Alkaline-surfactant-polymer (ASP) flooding has been widely used in Daqing Oilfield as a tertiary oil recovery technology that can effectively enhance oil recovery (EOR). However, various degrees of scaling appeared in field application tests, which hindered the large-scale application of this technology. The damage and scaling mechanisms of strong alkali-surfactant-polymer (SASP) flooding to heterogeneous reservoirs with high clay mineral content are still unclear. In this study, several sets of experiments have been carried out to determine the core mineral composition and the pore structure. Additionally, the damage mechanism and mineral corrosion with different permeabilities can be explored from a microscopic point of view. The results indicate that the corrosion of SASP reduces the contents of quartz and kaolinite, while the illite/montmorillonite mixed layer increases. In addition, there is chlorite and secondary quartz generation, which do not exist in the original mineral composition. Clay particles and sediment are easy to form bridges or stay on the surface and block the pore throats, which results in core seepage capacity reduction. All our preliminary results have contributed to the present understanding of scaling during ASP flooding. Moreover, it is of great significance to guide ASP flooding field application and prevent scaling.

k-domain method for the fast calculation of electromagnetic fields propagating in graded-index media.

A conceptually straightforward method for the fast calculation of electromagnetic fields propagating in graded-index media is presented. More specifically, in this method, we convert Maxwell's curl equations into the spatial-frequency domain to obtain an ordinary differential equation (ODE), and subsequently solve the ODE with the 4th-order Runge-Kutta method. Compared to the traditional beam propagation methods, this method deals with vectorial fields accurately, without physical approximations, like the scalar field approximation or the paraxial approximation; numerically, this method takes advantage of the fast Fourier transform and the convolution theorem to achieve an efficient calculation.

Fast propagation of electromagnetic fields through graded-index media.

Graded-index (GRIN) media are widely used for modeling different situations: some components are designed considering GRIN modulation, e.g., multi-mode fibers, optical lenses, or acousto-optical modulators; on the other hand, there are other components where the refractive-index variation is undesired due to, e.g., stress or heating; and finally, some effects in nature are characterized by a GRIN variation, like turbulence in air or biological tissues. Modeling electromagnetic fields propagating in GRIN media is then of high importance for optical simulation and design. Though ray tracing can be used to evaluate some basic effects in GRIN media, the field properties are not considered and evaluated. The general physical optics techniques, like finite element method or finite difference time domain, can be used to calculate fields in GRIN media, but they need great numerical effort or may even be impractical for large-scale components. Therefore, there still exists a demand for a fast physical optics model of field propagation through GRIN media on a large scale, which will be explored in this paper.

Microflow Mechanism of Oil Displacement by Viscoelastic Hydrophobically Associating Water-Soluble Polymers in Enhanced Oil Recovery.

Polymer flooding plays an important role in enhanced oil recovery (EOR), particularly in China, where partially hydrolyzed polyacrylamide (HPAM) and hydrophobically associating water-soluble polymers (HAWP) are used in onshore and offshore reservoirs, respectively. Many researchers have highlighted the elasticity of HPAM, which can be used to improve the sweep efficiency, i.e., the ratio of the area swept by an injected fluid to the oil area. On the other hand, fewer studies exist on the elasticity of HAWP. In this study, we investigate the flow of HAWP and Xanthan solutions with identical viscosities in core experiments in terms of elasticity; results reveal that the HAWP can produce shear thickening in the core. The constitutive equation for the HAWP can be obtained using the simulation results matched with the experimental data. On the basis of these experiments, we established a two-phase flow model of a polymer and oil, including the continuity, momentum, constitutive, and phase equations. The volume-of-fluid (VOF) method was used to track the interface between the two phases. A complex pore model was established based on the glass-etched model used in the experiment. We used the OpenFOAM platform to solve the mathematical model. The saturation, pressure, and stress tensor distributions were obtained. The results show that the displacement efficiency increased as the elasticity of the polymer increased; accordingly, the elasticity can enlarge the sweep area and decrease the residual oil saturation. As the elasticity increases, the stresses (the first normal stress, second normal stress, and shear stress) increase. Finally, the results obtained in this study can be used as a guideline in polymer design, screening, and optimization in the polymer flooding oilfields.

Parabasal thin-element approximation approach for the analysis of microstructured interfaces and freeform surfaces.

The thin-element approximation (TEA) approach is an efficient algorithm to analyze microstructured interfaces, e.g., diffractive optical elements or scattering surfaces. However, the classical approach is valid only under the condition of paraxial illumination. We hereby develop an extended algorithm to include parabasal illumination, which is characterized by low divergence with arbitrary propagation direction. The extended approach is named as the parabasal TEA approach. In this paper, we present the algorithm of the parabasal TEA approach and compare the results with that of a rigorous calculation in order to demonstrate its validity. We also discuss the role of the parabasal TEA approach in a more general concept for modeling light propagating through freeform surfaces.

Transthoracic echocardiography as an alternative major guidance to angiography during transcatheter closure of patent ductus arteriosus: technical feasibility and clinical relevance.

The conventional transcatheter closure of patent ductus arteriosus (PDA) requires femoral artery puncture and angiography for duct anatomic and shunting estimation. If such estimation can be replaced by transthoracic echocardiography (TTE), the procedure will be further simplified, with fewer invasions. This study aimed to examine whether TTE can serve as an alternative to aorta angiography and as a major guidance for transcatheter duct closure. The study enrolled 298 consecutive patients (71 males and 227 females) with PDA. In the study, TTE with combined two-dimensional echocardiography (2DE) imaging and color-coded flow imaging (CDFI) was performed to measure the minimal shunting width (MSW) as the estimated minimal duct size for selection of an Amplatzer duct occluder (ADO) and to monitor the transcatheter duct closure intraprocedurally. The MSW was validated against the duct-stretched diameter (SDD), against the minimal waist diameter of the conical part of a released occluder measured by X-ray spot picture after successful duct closure (SDC), and against the size of the finally used ADO (SADO). Good correlation was found between MSW and SDD [SDD (mm) = 1.31 MSW; r = 0.89; p < 0.01] and between MSW and SADO [SADO (mm) = 1.71 MSW; r = 0.88; p < 0.01]. Of 296 patients who received occlusion using MSW as the reference for selection of the occluder, SDC was attained in 288 (97.3%), 5 (1.7%), and 2 (0.7%) patients, respectively, at the first, second (1 ADO replacement), and third (2 ADO replacements) occluding attempt. Acute occluder dislodgement occurred in one patient (0.3%). At the 12-month follow-up assessment, no major complications were found, and the total immediate or 12-month SDC was 99.7%. Echocardiography as an alternative major guidance to angiography for transcatheter duct closure is technically feasible, and TTE guidance can further simplify the procedure, with fewer invasions and potential complications.

[Residual level and ecological risk assessment of OCPs and PCBs in sediments of mudflat shellfish culturing areas in Ningbo, Zhejiang Province of East China].

GC-ECD methods were adopted to determine the residual level of OCPs (including HCHs and DDTs) and PCBs in the surface sediments collected from mudflat shellfish culturing areas in Ningbo, with the sources of the OCPs and PCBs analyzed and the ecological risks of the residual OCPs and PCBs evaluated. The residual level of OCPs was 0.80-32.40 ng X g(-1), and that of PCBs was 3.20-33.33 ng X g(-1). The HCHs mainly came from long distance atmospheric transportation and historical residues, while the DDTs had new input at some sites, possibly coming from the application of dicofol. At most sites, there existed potential ecological risks of p, p'-DDT and DDTs, with strong indications in Qiangtou and Xidian where the residual level of p, p'-DDT was higher than the effect rang median (ERM), suggesting an ecological menace to the benthos. The residual PCBs at most sites were in low level ecological risk.

Effect of background motion on the perceived shape of a 3-D object.

The effect of the speed of a background surface on the judged shape of a moving object was investigated in four experiments. Observers judged the magnitude of a concave dihedral angle translating or rotating against a planar background. Judged angle magnitude decreased (indicating an increase in perceived depth) with increasing background speed until the background speed reached the speed of the front edge of the angle. Judged angle magnitude then increased with background speed until the difference between the background and front edge speed was large. A model that was previously proposed to account for angle magnitude judgments from translations and rotations is extended to displays with a moving background.