Pore-scale Modelling of Gravity-driven Drainage in Disordered Porous Media

Multiphase flow through a porous medium involves complex interactions between gravity, wettability and capillarity during drainage process. In contrast to these factors, the effect of pore distribution on liquid retention is less understood. In particular, the quantitative correlation between the fluid displacement and level of disorder has not yet been established. In this work, we employ direct numerical simulation by solving the Navier-Stokes equations and using volume of fluid method to track the liquid-liquid interface during drainage in disordered porous media. The disorder of pore configuration is characterized by an improved index to capture small microstructural perturbation, which is pivotal for fluid displacement in porous media. Then, we focus on the residual volume and morphological characteristics of saturated zones after drainage and compare the effect of disorder under different wettability (i.e., the contact angle) and gravity (characterized by a modified Bond number) conditions. Pore-scale simulations reveal that the highly-disordered porous medium is favourable to improve liquid retention and provide various morphologies of entrapped saturated zones. Furthermore, the disorder index has a positive correlation to the characteristic curve index (n) in van Genuchten equation, controlling the shape of the retention characteristic curves. It is expected that the findings will benefit to a broad range of industrial applications involving drainage processes in porous media, e.g., drying, carbon sequestration, and underground water remediation.Comment: 22 pages, 8 figure

Biodegradation of pyrene in sand, silt and clay fractions of sediment

Microbial degradation is the dominant pathway for natural attenuation of PAHs in environmental compartments such as sediments, which in turn depends on the bioavailability of PAHs. The bioavailability of PAHs has seldom been studied at the sediment particle size scale. We evaluated biodegradation of pyrene by Mycobacterium vanbaalenii PYR-1 as a function of sediment particle sizes, and investigated the relationship between the rate of degradation on sand, silt and clay particles with their individual desorption kinetics measured with the Tenax extraction method. Regression analysis showed that the total organic carbon (TOC), black carbon (BC), and specific surface area (SSA) of the specific particle size fractions, instead of the particle size scale itself, were closely related (P < 0.01) with the mineralization rate. While the fraction in the rapid desorption pool (Frapid) ranged from 0.11 to 0.38 for the whole sediments and different size groups, the fractions mineralized after 336-h incubation (0.52 to 0.72) greatly surpassed the Frapid values, suggesting utilization of pyrene in the slow desorption pool (Fslow). A biodegradation model was modified by imbedding a two-phase desorption relationship describing sequential Tenax extractions. Model analysis showed that pyrene sorbed on silt and clay aggregates was directly utilized by the degrading bacteria. The enhanced bioavailability may be attributed to the higher chemical concentration, higher TOC or larger SSA in the silt and clay fractions, which appeared to overcome the reduced bioavailability of pyrene due to sorption, making pyrene on the silt and clay particles readily available to degrading microbes. This conjecture merits further investigation

Cloning and Characterization of the ζ-Carotene Desaturase Gene from Chlorella protothecoides CS-41

To elucidate the lutein biosynthesis pathway in the lutein-producing alga, Chlorella protothecoides CS-41, the ζ-carotene desaturase gene (zds) was isolated from Chlorella protothecoides using the approach of rapid amplification of cDNA ends. The full-length cDNA sequence was 2031 bp and contained 1755 bp putative open reading frame which encodes a 584 amino acid deduced polypeptide whose computed molecular weight was 63.7 kDa. Sequence homology research indicated that the nucleotide and putative protein had sequence identities of 72.5% and 69.5% with those of the green alga Chlamydomonas reinhardtii, respectively. Phylogenetic analysis demonstrated that the ZDS from C. protothecoides CS-41 had a closer relationship with those of chlorophyta and higher plants than with those of other species. In addition, we also found that the zds gene expression was upregulated in response to light

Synthesis and Antiproliferative Activity of Some Steroidal Lactams

Using cholesterol as starting material, a series of 6-substituted-3-aza-A-homo-3-oxycholestanes and 6-substituted-4-aza-A-homo-3-oxycholestanes were synthesized by the oxidation, reduction, oximation, Beckman rearrangement and condensation reaction. These synthesized compounds displayed a distinct cytotoxicity against MGC 7901, HeLa and SMMC 7404 cancer cells. Our results revealed that the structures of functional groups at position-6 on the steroidal ring are crucial for the IC50 value of antiproliferative activities of these compounds and the cytotoxic activity against MGC 7901 and SMMC 7404 cells was not significantly different between 4-N-lactams and 3-N-lactams when its 6-substituted group was a carbonyl or a hydroximino, but all 3-N-lactams showed a higher cytotoxicity against HeLa cells than 4-N-lactams. In particular, compounds 6, 8, 9 (IC506: 6.5 μmol/L; 8: 7.7 μmol/L; 9: 5.6 μmol/L) were even more cytotoxic than cisplatin to HeLa cells (positive contrast, 10.1 μmol/L). The information obtained from the studies may be useful for the design of novel chemotherapeutic drugs

Fabrication of a novel hierarchical fibrous scaffold for breast cancer cell culture

Supplementary data to this article can be found online at https://doi.org/10.1016/j.polymertesting.2019.106107.Scaffolds combining nano- and submicro-fibers closely mimicking extracellular matrix (ECM) have been poorly exploited for in vitro cancer cell culture. Herein, a combined electrospinning and modified in situ biosynthesis method has been developed to fabricate a novel scaffold consisting of bacterial cellulose (BC) nanofibers and electrospun cellulose acetate (CA) submicrofibers to mimic the fibrillar structure of natural ECM. The CA/BC nano/submicrofibrous scaffold was characterized by scanning electron microscopy (SEM), mechanical strength tests, porosity measurements, and cell studies using the MCF-7 breast cancer cells. In addition, the sensitivity of the cancer cells seeded in the CA/BC nano/submicrofibrous scaffold to an anticancer drug was assessed. It was found that the CA/BC scaffold exhibited an interconnected porous structure in which BC nanofibers penetrated into the submicrofibrous CA scaffold. Such sophisticated structure was responsible for the improved mechanical properties of CA/BC scaffold over the ones obtained using a single kind of fibers. More importantly, the CA/BC scaffold showed improved cell adhesion, migration, and proliferation over single BC or CA scaffold. Finally, cells grown on CA/BC scaffold exhibited a greater doxorubicin resistance than those on single CA or BC scaffold. The results suggest that the CA/BC nano/submicrofibrous scaffold has potential for application in in vitro tumor model for the study of cancer progression and drug screening.This work was supported by the Key Project of Natural Science Foundation of Jiangxi Province (Grant no. 20161ACB20018), the National Natural Science Foundation of China (Grant nos. 31870963, 31660264, and 51572187), the Youth Science Foundation of Jiangxi Province (Grant no. 20181BAB216010), and the Science and Technology Research Project of Jiangxi Education Department (Grant no. GJJ180348).info:eu-repo/semantics/publishedVersio

Synthesis and Evaluation of Some 17-Acetamidoandrostane and N,N-Dimethyl-7-deoxycholic Amide Derivatives as Cytotoxic Agents: Structure/Activity Studies

Using pregnenolone and 7-deoxycholic acid as starting materials, some 17-acetamidoandrostane and N,N-dimethyl-7-deoxycholic amide derivatives were synthesized. The cytotoxicity of the synthesized compounds was tested in vitro against two tumor cell lines: SGC 7901 (human gastric carcinoma) and Bel 7404 (human liver carcinoma). The result showed that the blockage of the interaction of the amide group with outside groups might cause a decrease of the cytotoxicity, and an O-benzyloximino group at the 3-position of N,N-dimethyl-7-deoxycholic amide could enhance the cytotoxic activity of the compound. The information obtained from the studies provides the structure-activity relationship for these compounds and may be useful for the design of novel chemotherapeutic drugs