Three-dimensional numerical study of flow characteristic and membrane fouling evolution in an enzymatic membrane reactor

In order to enhance the understanding of membrane fouling mechanism, the hydrodynamics of granular flow in a stirred enzymatic membrane reactor was numerically investigated in the present study. A three-dimensional Euler-Euler model, coupled with k-e mixture turbulence model and drag function for interphase momentum exchange, was applied to simulate the two-phase (fluid-solid) turbulent flow. Numerical simulations of single- or two-phase turbulent flow under various stirring speed were implemented. The numerical results coincide very well with some published experimental data. Results for the distributions of velocity, shear stress and turbulent kinetic energy were provided. Our results show that the increase of stirring speed could not only enlarge the circulation loops in the reactor, but it can also increase the shear stress on the membrane surface and accelerate the mixing process of granular materials. The time evolution of volumetric function of granular materials on the membrane surface has qualitatively explained the evolution of membrane fouling.Comment: 10 panges, 8 figure

2,3-Dichloro­pyridine

The complete mol­ecule of the title compound, C5H3Cl2N, is generated by crystallographic twofold symmetry, which forces the pyridine N atom and the opposite C—H group to be statistically disordered. In the crystal, weak aromatic π–π stacking [centroid–centroid separation = 3.805 (4) Å and slippage = 1.704 Å] leads to [100] stacks of mol­ecules. Short Cl⋯Cl contacts [3.334 (3) Å] are also observed

Evolution and Biogeography of the Slipper Orchids: Eocene Vicariance of the Conduplicate Genera in the Old and New World Tropics

Intercontinental disjunctions between tropical regions, which harbor two-thirds of the flowering plants, have drawn great interest from biologists and biogeographers. Most previous studies on these distribution patterns focused on woody plants, and paid little attention to herbs. The Orchidaceae is one of the largest families of angiosperms, with a herbaceous habit and a high species diversity in the Tropics. Here we investigate the evolutionary and biogeographical history of the slipper orchids, which represents a monophyletic subfamily (Cypripedioideae) of the orchid family and comprises five genera that are disjunctly distributed in tropical to temperate regions. A relatively well-resolved and highly supported phylogeny of slipper orchids was reconstructed based on sequence analyses of six maternally inherited chloroplast and two low-copy nuclear genes (LFY and ACO). We found that the genus Cypripedium with a wide distribution in the northern temperate and subtropical zones diverged first, followed by Selenipedium endemic to South America, and finally conduplicate-leaved genera in the Tropics. Mexipedium and Phragmipedium from the neotropics are most closely related, and form a clade sister to Paphiopedilum from tropical Asia. According to molecular clock estimates, the genus Selenipedium originated in Palaeocene, while the most recent common ancestor of conduplicate-leaved slipper orchids could be dated back to the Eocene. Ancestral area reconstruction indicates that vicariance is responsible for the disjunct distribution of conduplicate slipper orchids in palaeotropical and neotropical regions. Our study sheds some light on mechanisms underlying generic and species diversification in the orchid family and tropical disjunctions of herbaceous plant groups. In addition, we suggest that the biogeographical study should sample both regional endemics and their widespread relatives

Macroscopic and microscopic trans-scale characteristics of pore structure of mine grouting materials

The pore structure and porosity of three kinds of mine grouting materials were characterized based on a thin-section analysis and low-field nuclear magnetic resonance (NMR) technique. The macroscopic pore interconnectivity was investigated using binary images captured from thin sections and a random walk pore spectral dimension (RWPSD) algorithm. The experimental results show that the microstructure of the grouting materials used consisted of interlayer pores, gel pores, capillary pores, circular air holes, and small fractures, and tailings can fill some gaps in the hydration product structure and dense hydration products. There is a positive correlation between pore interconnectivity and curing time. In addition, there is a relationship between pore interconnectivity and porosity. With increasing porosity and pore interconnectivity, a non-uniform pore structure occurs in mine grouting materials with an accelerator and results in reduced setting time and later strength

Association of PON2 Gene Polymorphisms (Ser311Cys and Ala148Gly) With the Risk of Developing Type 2 Diabetes Mellitus in the Chinese Population

Background: The association between paraoxonase 2 (PON2) gene polymorphisms and type 2 diabetes mellitus (T2DM) has been extensively investigated in the Chinese population with conflicting results. In this study, we systematically evaluated the association between PON2 Ser311Cys and Ala148Gly polymorphisms and T2DM risk by pooling all relevant studies.Methods: We searched PubMed, Embase, CNKI, and Wanfang databases for the studies. The strength of association was determined by the allelic, homozygous, heterozygous, recessive, and dominant genetic models and measured as odds ratio (OR) and 95% confidence interval (CI), under fixed- or random-effect models.Results: There was no significant association between PON2 Ser311Cys polymorphism and T2DM under any of the genetic models: allelic (OR = 1.06, 95% CI = 0.77–1.45; P = 0.721), heterozygous (OR = 1.13, 95% CI = 0.87–1.45; P = 0.362), dominant (OR = 1.10, 95% CI = 0.80–1.51; P = 0.562), recessive (OR = 0.87, 95% CI = 0.48–1.58; P = 0.648), homozygous (OR = 0.94, 95% CI = 0.47–1.89; P = 0.865). Similarly, no significant association was found in PON2 Arg148Gly polymorphism under any of the models: allelic (OR = 1.17, 95% CI = 0.91–1.50; P = 0.218), heterozygous (OR = 1.28, 95% CI = 0.94–1.74; P = 0.117), dominant (OR = 1.25, 95% CI = 0.93–1.67; P = 0.142), recessive (OR = 0.99, 95% CI = 0.52–1.88; P = 0.973), homozygous (OR = 1.08, 95% CI = 0.57–2.07; P = 0.808).Conclusions: The PON2 Ser311Cys and Ala148Gly polymorphisms were not associated with the risk of developing T2DM in the Chinese population

Original Article MiR-199a inhibits the ability of proliferation and migration by regulating CD44-Ezrin signaling in cutaneous squamous cell carcinoma cells

Abstract: Cutaneous squamous cell carcinoma (cSCC), the second most common form of human cancer, is an epithelial skin tumor, which can result in metastasis with lethal consequences accounting for about 20% of all skin cancer-related deaths. The metastasis is the main reason for cSCC-related deaths with an overall 5-year survival rate < 30% in cases that spread systemically. The role of miRNAs has been involved in SCC of different origins. Recent data have revealed that the expression of miRNA-199a was changed in many human cancers. In this study, we found that miR-199a was significantly decreased in cSCC tissues, which had an inverse relationship with CD44. MiR-199a specifically regulated the expression of CD44 at mRNA and protein levels, and the interaction between CD44 and Ezrin in cSCC cells. Moreover, the suppressive role of miR-199a in cell migration in cSCC cells was also associated with the activity of MMP2 and MMP9. Taken together, our data indicated that increased expression of endogenous mature miR-199a might prevent the growth and migration of human cSCC via decreasing the expression of CD44 and regulating the interaction between CD44 and Ezrin, which may provide a potentially important therapeutic target for human cSCC

Cross-scale characteristics of backfill material using NMR and fractal theory

This paper analyzed the pore structure, quantified the pore fractal dimension, calculated the grading index (GI) of mixed aggregate, and studied the relationship among GI, pore structure, and strength to describe the cross-scale characteristics of backfill, which is made from stone powder and cemented tailing. A series of experiments were conducted on stone powder cement tailings backfill (SPCTB). The GI formulas for mixed aggregates, containing stone powder and tailings, were derived based on the Füller theory. The nuclear magnetic resonance (NMR) fractal dimensions of backfills were derived using fractal geometry principles. Compared to the mesopore and macropore fractal dimensions, the correlation between micropore fractal dimension and macro-properties in terms of NMR porosity, pore structure complexity, uniaxial compression strength (UCS), and GI is the most significant. Macropore fractal dimension is generally correlated with UCS and GI and the other properties such as the shape of mixed aggregates also have an impact on fractal dimension. However, mesopore fractal dimension has no obvious relationship with macro-properties. Finally, the relationship between GI and UCS was studied, which contributed to improving backfill’s strength and optimizing gradation