Search

Background: Retroviral restriction factor APOBEC3G is inhibited from inducing mutations in HIV-1 proviral DNA in multiple ways by HIV-1 Vif. Results: Vif-mediated inhibition of APOBEC3G deoxycytidine deaminase activity is due to a change in APOBEC3G processive scanning. Conclusion: Altered processivity leads to a decrease in deoxycytidine deamination-induced mutagenesis. Significance: Vif co-encapsidation with APOBEC3G in virions may promote sublethal mutagenesis of proviral DNA., APOBEC3G is a retroviral restriction factor that can inhibit the replication of human immunodeficiency virus, type 1 (HIV-1) in the absence of the viral infectivity factor (Vif) protein. Virion-encapsidated APOBEC3G can deaminate cytosine to uracil in viral (−)DNA, which leads to hypermutation and inactivation of the provirus. APOBEC3G catalyzes these deaminations processively on single-stranded DNA using sliding and jumping movements. Vif is thought to primarily overcome APOBEC3G through an interaction that mediates APOBEC3G ubiquitination and results in its proteasomal degradation. However, Vif may also inhibit APOBEC3G mRNA translation, virion encapsidation, and deamination activity. Here we investigated the molecular mechanism of VifIIIB- and VifHXB2-mediated inhibition of APOBEC3G deamination activity. Biochemical assays using a model HIV-1 replication assay and synthetic single-stranded or partially double-stranded DNA substrates demonstrated that APOBEC3G has an altered processive mechanism in the presence of Vif. Specifically, VifHXB2 inhibited the jumping and VifIIIB inhibited the sliding movements of APOBEC3G. The absence of such an effect by Vif on degradation-resistant APOBEC3G D128K indicates that a Vif-APOBEC3G interaction mediates this effect. That the partially processive APOBEC3G was less effective at inducing mutagenesis in a model HIV-1 replication assay suggests that Vif co-encapsidation with APOBEC3G can promote sublethal mutagenesis of HIV-1 proviral DNA.

This paper presents a numerical investigation of solid separation in jigging device. Jigging is a gravity separation method commonly used by the minerals industry to separate coal, iron ore, diamonds and other minerals on the basis of particle size and/or density. Separation is recognised as being heavily dependent on fluid motion in the jig. This study explores the effects of the inlet time dependent velocity profile in relation to a wide criterion on jigging performance. Modelling of the liquid–solid system is performed through a combination of computational fluid dynamics (CFD) to simulate liquid flow and discrete element method (DEM) to resolve particle motion. The initial packing conditions consist of a binary-density particle system of 1130 particles each 1 cm in diameter. A range of jigging profiles have been implemented in mineral processing. In this study the sinusoidal pulsation profile is selected adopting variations in both amplitude and frequency. The performance of profile variants are compared in terms of solid flow patterns, separation kinetics, energy, and mean particle position. These quantitative comparisons demonstrate significant differences in the segregation rate, energy, and solid phenomena, helping find an alternative optimum operating setting for the system. In addition, boundaries of operation are found in terms of frequency and amplitude limits and the concentration mechanics are investigated in these regions.

Simulated sunlight has promise as a light source able to alleviate the severe pain associated with patients during photodynamic therapy (PDT); however, low sunlight utilization efficiency of traditional photosensitizers dramatically limits its application. Titanium-dioxide-nanoparticle-gold-nanocluster-graphene (TAG) heterogeneous nanocomposites are designed to efficiently utilize simulated sunlight for melanoma skin cancer PDT. The narrow band gap in gold nanoclusters (Au NCs), and staggered energy bands between Au NCs, titanium dioxide nanoparticles (TiO2 NPs), and graphene can result in efficient utilization of simulated sunlight and separation of electron-hole pairs, facilitating the production of abundant hydroxyl and superoxide radicals. Under irradiation of simulated sunlight, TAG nanocomposites can trigger a series of toxicological responses in mouse B16F1 melanoma cells, such as intracellular reactive oxygen species production, glutathione depletion, heme oxygenase-1 expression, and mitochondrial dysfunctions, resulting in severe cell death. Furthermore, intravenous or intratumoral administration of biocompatible TAG nanocomposites in B16F1-tumor-xenograft-bearing mice can significantly inhibit tumor growth and cause severe pathological tumor tissue changes. All of these results demonstrate prominent simulated sunlight-mediated PDT effects.

Sand screens are widely installed to control unacceptable amount of sand produced from oil and gas wells. Sand retention tests are often used to select optimal sand screen size that minimizes sand production and maximizes hydrocarbon production. However, there is currently no agreed industry standards as to how the tests are conducted and results interpreted. This paper presents development of a novel sand retention cell and the associated experimental procedure with the objective to overcome some of the limitations in the existing sand retention tests. The improvements incorporated into the new sand retention cell and experimental procedure include i) measurements of fluid pressures close to the screen surface and sand pack to allow in-situ measurement of the screen and sand pack permeabilities; ii) delivery of a uniform sand slurry over the entire screen surface that ensures formation of a uniform sand pack over the screen by using a heavy fluid; iii) transparent cell body to allow sand retention and production process to be visually observed and sand pack height to be measured; and iv) sand slurry flow as well as pre-pack sand retention test and assessment for fines migration through gravel pack.

We report here a new type of plasmid that carries the mcr-1 gene, the pMCR-1-P3 plasmid, harbored in an Escherichia coli strain isolated from a pig farm in China. pMCR-1-P3 belongs to the IncY incompatibility group and is a phage-like plasmid that contains a large portion of phage-related sequences. The backbone of this plasmid is different from that of other mcr-1-carrying plasmids reported previously.

Sand retention tests have often been used to select optimal screen aperture for standalone sand screen applications. The purpose is to select a sand screen that maximizes hydrocarbon production and minimizes sand production. There are two types of sand retention tests currently used in the industry, i.e., slurry and prepack sand retention tests. The former aims to simulate gradual sand production condition with an open annulus between the sandface and the screen, and the latter to simulate the condition where no such annulus exists. There are, however, no agreed industry standards on how sand retention tests should be performed and test results interpreted. This paper presents a combined experimental and numerical modelling study on sand screen performance. The objective is to develop an improved methodology for optimal sand screen aperture selection by addressing some of the limitations presented in the existing sand retention tests. A new sand retention test facility has been developed at CSIRO, incorporating a number of improvements into the design and experimental procedure. A key component of the improvements is the ability to separately measure retained screen permeability and sand pack permeability. Correlations have been developed between sand screen performance and key parameters of the sands and screen based on a large number of sand slurry retention tests. Furthermore, the sand retention process was simulated numerically using a 3D fully coupled Discrete Element (DEM) – Computational Fluid Dynamics (CFD) model. Parametric studies have been conducted to assess screen performance and to gain a better understanding of sand retention and production mechanisms.

This paper presents a numerical study of gas and solid flow in an internally circulating fluidized bed (ICFB). The gas and solid dynamics has been calculated using the commercial computational fluid dynamics (CFD) software package ANSYS/Fluent and an Eulerian–Eulerian model (EEM) with kinetic theory of granular flow used to calculate solid stresses. A two dimensional geometry was used to represent key parts of a laboratory ICFB. Simulations were conducted to assess the effect of changes to four designs or operating parameters: gas distributor plate angles, presence of a heat exchange tube bundle, superficial fluidizing velocities and initial solid packing heights. The mechanism governing the solid recirculation in an ICFB has been explained based on gas and solid dynamics obtained from the simulations and the effect of the four designs or operating parameters is quantified in terms of solid recirculation rate (SRR). Both of the investigated operating parameters, superficial fluidizing velocities and initial solid packing height, strongly affect solid circulation rate. For the two investigated design parameters, the presence of a tube bundle reduced the solid recirculation rate by 20%, while an inclination angle of 1.5° does not affect the solid recirculation rate significantly.

Land reclaimed from lakes is a human disturbance to ecosystems that has frequently occurred in China since the late 1950s. To gain a better understanding of the characteristics of soil labile organic carbon in the reclaimed land from a lake under different land uses of the Xiaodian Lake area

This paper presents the development of a computational fluid dynamics (CFD) model for the study of bubble driven bath flow in aluminium reduction cells. For validation purposes, the model development was conducted using a full scale air -water model of part of an aluminium reduction cell as a test-bed. The bubble induced turbulence has been modelled by either modifying bubble induced turbulence viscosity directly or by modifying bubble induced turbulence kinetic energy in a standard k- ε turbulence model. The relative performance of the two modelling approaches has been examined through comparison with experimental data taken under similar conditions using Particle Image Velocimetry (PIV). Detailed comparison has been conducted by point-wise comparison of liquid velocities to quantify the level of agreement between CFD simulation and PIV measurement. Both models can capture the key flow patterns determined by PIV measurement, while the modified turbulence kinetic energy model gives better agreement with flow patterns in the gap between anode and cathode.

Discrete particle simulation has been recognized as a useful numerical technique to elucidate the fundamentals of particle−fluid flow, in particular, gas fluidization. In general, it is achieved by combining discrete element method (DEM) for solid flow with computational fluid dynamics (CFD) for continuum gas. Limited by computational capability, such studies are mainly conducted using a two-dimensional (2D) bed in which particles are treated as discs or a pseudo-three-dimensional (3D) bed where the bed thickness is the same as the particle diameter. The loss of one-dimensional motion may significantly affect the flow and related behavior. This paper presents a numerical study of the effect of the front and rear walls of a fluidized bed on the mixing and segregation behavior of particle mixtures. Particle diameters used for simulation are 1 mm for flotsam and 2 mm for jetsam, respectively. Numerical simulations are conducted for two beds of different thicknesses, fluidized at different gas velocities. One...

The dynamic behavior of individual particles during the mixing/segregation process of particle mixtures in a gas fluidized bed is analyzed. The analysis is based on the results generated from discrete particle simulation, with the focus on the trajectory of and forces acting on individual particles. Typical particles are selected representing three kinds of particle motion: a flotsam particle which is initially at the bottom part of the bed and finally fluidized at the top part of the bed; a jetsam particle which is initially at the top part of the bed and finally stays in the bottom de-fluidized layer of the bed; and a jetsam particle which is intermittently joining the top fluidized and bottom de-fluidized layers. The results show that the motion of a particle is chaotic at macroscopic or global scale, but can be well explained at a microscopic scale in terms of its interaction forces and contact conditions with other particles, particle–fluid interaction force, and local flow structure. They also highlight the need for establishing a suitable method to link the information generated and modeled at different time and length scales.

Dense-phase pneumatic transportation of bulk materials in the form of slug flow has become a very important technology in industry. In order to understand the underlying mechanisms of slug flow, this paper presents a numerical study of slug flow in horizontal pneumatic conveying by means of discrete particle simulation. To be computationally efficient, the motion of discrete particles is three-dimensional and the flow of continuum gas is two-dimensional, and periodic boundary conditions are applied to both gas and solid phases horizontally. The proposed numerical model is qualitatively verified by comparing the calculated and measured results in terms of particle flow pattern and gas pressure drop. Then the influence of operational conditions such as gas and solid flowrates on slug behavior is numerically investigated. It is shown that slug velocity linearly increases with gas flowrate but is not sensitive to solid flowrate, and slug length increases with both gas and solid flowrates. The results qualitat...

This paper presents a study of the mixing and segregation of particle mixtures in a gas-fluidized bed by means of a discrete particle simulation. Particle mixtures are composed of spherical particles with diameter 2 mm for jetsam and 1 mm for flotsam. The particles are initially packed randomly in a rectangular bed and then fluidized by gas uniformly injected at the bottom of the bed. The gas injection velocity varies to cover fixed, partially and fully fluidized bed conditions, in order to establish a full picture about the effect of gas velocity. Segregation/mixing behaviour is analysed in terms of flow patterns, solid concentration profile and mixing kinetics. It is shown that segregation, as a transient process, is strongly affected by gas velocity. There is a gas velocity producing the maximum segregation for a given mixture. Below this velocity, segregation increases and above this velocity, segregation decreases with the increase of gas velocity. The time to reach a macroscopically stable state can be up to tens of seconds, decreasing with the increase of gas velocity. The mechanisms governing the segregation and mixing of particles are elucidated in terms of the interaction forces between particles and between particles and fluid. Particle–fluid interaction initiates fluidization and segregation. Particle–particle interaction, however, also plays an important role in governing the segregation of particles. The degree of segregation results from the complex dynamic balance of the two interactions either locally or globally.

Pomegranate rind has been found to inhibit numerous pathogens, mostly attributed to its tannin fraction. The present study was conducted to investigate the quorum sensing (QS) inhibition effect of tannin-rich fraction from pomegranate rind (TFPR) by using an indicator strain Chromobacterium violaceum. Meanwhile, its effect on biofilm formation and motility of Escherichia coli was evaluated. It was shown that TFPR inhibited QS-regulated violacein pigment production. Biofilm formation and motility of E. coli were also hindered by TFPR. Transcriptional analysis further showed that TFPR repressed expressions of curli genes (csgB and csgD) and various motility genes (fimA, fimH, flhD, motB, qseB, and qseC). Our findings indicated that TFPR has potential application for controlling E. coli contaminations or biofilms in the food industry.

APOBEC3H is a deoxycytidine deaminase that can restrict the replication of HIV-1 in the absence of the viral protein Vif that induces APOBEC3H degradation in cells. APOBEC3H exists in humans as seven haplotypes (I–VII) with different cellular stabilities. Of the three stable APOBEC3H haplotypes (II, V, and VII), haplotypes II and V occur most frequently in the population. Despite APOBEC3H being a bona fide restriction factor, there has been no comparative biochemical characterization of APOBEC3H haplotypes. We characterized the ssDNA scanning mechanisms that haplotypes II and V use to search their ssDNA substrate for cytosine-containing deamination motifs. APOBEC3H haplotype II was able to processively deaminate multiple cytosines in a single enzyme-substrate encounter by using sliding, jumping, and intersegmental transfer movements. In contrast, APOBEC3H haplotype V exhibited diminished sliding and intersegmental transfer abilities but was able to jump along ssDNA. Due to an Asp or Glu at amino acid 178 differentiating these APOBEC3H haplotypes, the data indicated that this amino acid on helix 6 contributes to processivity. The diminished processivity of APOBEC3H haplotype V did not result in a reduced efficiency to restrict HIV-1 replication in single-cycle infectivity assays, suggesting a redundancy in the contributions of jumping and intersegmental transfer to mutagenic efficiency. Optimal processivity on ssDNA also required dimerization of APOBEC3H through the β2 strands. The findings support a model in which jumping can compensate for deficiencies in intersegmental transfer and suggest that APOBEC3H haplotypes II and V induce HIV-1 mutagenesis efficiently but by different mechanisms.

The aim of the study was to survey three foodborne pathogens in kiwifruit orchards as a continuous monitoring program. A total of 193 samples were collected from 11 kiwifruit orchards in Shaanxi province in October 2013. Among the 193 samples, 68 Escherichia coli isolates were recovered, while no Staphylococcus aureus and Salmonella was recovered. All E. coli isolates were characterized by antimicrobial susceptibility testing, detection of virulence genes, and the ability to produce biofilm formation. The isolates were further examined by random amplified polymorphic DNA (RAPD) analysis. E. coli isolates displayed resistance most frequently to tetracycline (48.5%). Two E. coli isolates (2.9%) were positive for the eae gene (the intimin gene). All E. coli isolates lacked the ability to make biofilm formation. Multilocus sequence typing analysis demonstrated that one isolate in kiwifruit orchards shared the same sequence type with a human clinical isolate. RAPD results showed a close relationship among E. coli isolates from fresh fruit, fallen fruit, soil, air, and irrigation water. This study could provide a further understanding of microbial contamination in kiwifruit orchards based on our previous study and help growers take appropriate measures for prevention.

EPA (Ethernet for Plant Automation) resolves the nondeterministic problem of Ethernet through sub-segment topology and deterministic scheduling mechanism. In this paper, the EPA scheduling mechanism is implemented by simulation tool. And the influence of EPA scheduling mechanism on network performance is shown in the simulation result. According to the study, the real-time performance of EPA periodic messages transmission is concluded and the transmission delay of non-periodic message is analyzed.

Punicalagin, a major bioactive component of pomegranate peel, has been proven to have antioxidant, antiviral, anti-apoptosis, and hepatoprotective properties. The aim of this study was to investigate the anti-infective activity of punicalagin in a mouse model. C57BL/6 mice were initially challenged with Salmonella enterica subsp. enterica serovar typhimurium (S. typhimurium) and then treated with punicalagin. Food and water consumption and body weight were recorded daily. On day 8 post infection, the mice were sacrificed to examine pathogen counts in tissues, hematological parameters, cytokine levels, and histological changes. Compared to mice only infected with S. typhimurium, punicalagin-treated mice had more food consumption and less weight loss. A higher survival rate and lower counts of viable S. typhimurium in feces, liver, spleen, and kidney were found in the punicalagin-treated mice. The enzyme linked immunosorbent assay showed that the levels of IL-6, IL-10, and IFN-γ in serum and the spleen and TNF-α in serum, the spleen and the liver were reduced by punicalagin. Moreover, more neutrophils and higher neutrophil-to-mononuclear cell ratios in the punicalagin-treated mice were observed. Histological examination showed that punicalagin protected cells in the liver and spleen from hemorrhagic necrosis. It is concluded that punicalagin has a beneficial effect against S. typhimurium infection in mice. The anti-infective properties, together with other nutritionally beneficial effects, make punicalagin a promising supplement in human food or animal feeds to prevent disease associated with S. typhimurium.

A phenomenological model for the creation and transport of anodic gas bubbles in Hall-H´eroult cells has been developed, following a multiscale approach. The essential features of the modelling framework are reviewed and discussed in the present paper. The model covers the generation of molecular gas species through Faradays law, subsequent bubble nucleation, and the evolution of macroscopic bubbles which are treated by a volume of fluid model. Recently, the modelling framework has been extended to include several complex phenomena such as surface tension and wetting, bath chemistry, and variable flow properties. The modelling framework has currently been applied to a laboratory scale electrolysis cell setup. The results demonstrate that the essential properties are well represented over a large range of experimental conditions by the proposed approach.

Laboratory scale transparent aluminum electrolysis cells were used to study anodic bubble behavior, including bubble layer thickness, bubble shape and coverage at the anode bottom surface, and the resultant cell voltage drop in a very similar environment to real industrial cells. The observation was conducted using two transparent cells, one with side-view and the other with a bottom-view cell design. For the side-observation experiment, the evolution of bubble layer thickness and bubble rising process were studied. In the bottom-observation experiment, bubble behavior was investigated on both unslotted and slotted anodes. Cell voltage was simultaneously recorded for a quantitative investigation of its relevance to bubble coverage. It was found that the cell voltage drop is very consistent with bubble coverage, with a high voltage drop corresponding to a high bubble coverage. The coverage of anodic gas bubbles decreases with the increase of current density. These phenomena were observed on unslotted and slotted anodes. The comparison of unslotted anode and slotted anode indicated that the slot significantly reduces the cell voltage drop, voltage drop fluctuations and bubble coverage.

Discrete particle simulation has been recognized as a useful numerical technique for elucidating the fundamentals of granular matter. For gas−solid two-phase flow in fluidization, such simulations are achieved by combining the discrete flow of the particle phase with the continuum flow of the gas phase. However, differences exist in the actual implementation of this idea in the literature. This paper attempts to rationalize this matter by discussing important aspects including the governing equations in relation to the so-called models A and B, which use different treatments of pressure drop in the well-established two-fluid model, different coupling schemes between the gas and solid phases, and different equations for quantifying the particle−fluid interaction. For the purpose of quantitative analysis, gas fluidization of binary mixtures of particles is simulated with different model formulations, and a comparison of the results in terms of flow pattern and mixing/segregation kinetics shows a significant...

This report presents a numerical study of segregation and mixing of binary mixtures of particles in a gas-fluidized bed by means of discrete particle simulation, where the motion of individual particles is 3-D and the flow of continuous gas is 2-D. Periodic boundary conditions are applied to the front and rear walls to represent a bed of large thickness with a relatively small number of particles. Two initial packing conditions are used in this simulation: completely separated, with the flotsam (1 × 10−3 m in diameter) on the top of the jetsam (2 × 10−3 m in diameter), and well mixed. The flotsam and jetsam are of the same density, with each counting 50% in weight. Gas is injected uniformly at the bottom. Two superficial gas velocities, 1.0 and 1.4 m/s, are used in the simulation, producing significant segregation and good mixing, respectively. The results show that the degree and rate of segregation or mixing are significantly affected by gas velocity and the final equilibrium states are not affected by the initial packing states for a given gas velocity. Significant segregation occurs at a gas velocity of 1.0 m/s, with the top fluidized layer rich in flotsam and the bottom defluidized layer rich in jetsam, whereas there was less segregation at 1.4 m/s with most of the bed fluidized. The simulated results are qualitatively comparable with those observed in the physical experiments conducted under similar conditions. On this basis, the mixing kinetics obtained from the numerical simulation is quantified with a weighted Lacey mixing index and explained in terms of microdynamic results in relation to particle–particle and particle–fluid interactions. It is proposed that an appropriate sampling size should be able to describe properly the two extremes: well mixed and fully segregated. The results also demonstrate that size segregation occurs as a result of the strong fluid drag force lifting the flotsam before a dynamical equilibrium is reached, and the particle–particle interaction, like the particle–fluid interaction, plays an important role in achieving uniform fluidization. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1713–1728, 2004

This paper presents a numerical study of gas-solid flow in a blast furnace raceway using a 2D slot cold model. Numerical experiments are conducted by combining the discrete element method for the solid phase with computational fluid dynamics for the gas phase. The motion of particles caused by lateral gas blasting under conditions similar to that in the blast furnace process is examined at a particle scale. Combustion and associated solids movement around the raceway are simulated by extraction of particles from the bottom of the bed. The effect of bed height or solid pressure is considered by imposing a downward force on the top layers of particles in the bed. It is shown that depending on the gas velocity, the bed can transit from a fixed bed to a fluidized bed or vice versa. Two zones can be identified in such a bed: a stagnant zone in which the particles remain at their initial positions, and a moving zone in which particles can move in various flow patterns. In particular, if the gas velocity is in a certain range, the moving zone is formed just in front of the gas inlet, giving the so-called raceway in which the particles can circulate. The effects of gas velocity, solid pressure and solid extraction are quantified. The fundamentals governing the gas-solid flow and the formation mechanisms of a raceway are discussed In terms of particle-particle and particle-fluid interaction forces.

The APOBEC3 restriction factors are a family of deoxycytidine deaminases that are able to suppress replication of viruses with a single-stranded DNA intermediate by inducing mutagenesis and functional inactivation of the virus. Of the seven human APOBEC3 enzymes, only APOBEC3-D, -F, -G, and -H appear relevant to restriction of HIV-1 in CD4+ T cells and will be the focus of this review. The restriction of HIV-1 occurs most potently in the absence of HIV-1 Vif that induces polyubiquitination and degradation of APOBEC3 enzymes through the proteasome pathway. To restrict HIV-1, APOBEC3 enzymes must be encapsidated into budding virions. Upon infection of the target cell during reverse transcription of the HIV-1 RNA into (-)DNA, APOBEC3 enzymes deaminate cytosines to form uracils in single-stranded (-)DNA regions. Upon replication of the (-)DNA to (+)DNA, the HIV-1 reverse transcriptase incorporates adenines opposite to the uracils thereby inducing C/G to T/A mutations that can functionally inactivate HIV-1. APOBEC3G is the most studied APOBEC3 enzyme and it is known that Vif attempts to thwart APOBEC3 function not only by inducing its proteasomal degradation but also by several degradation-independent mechanisms, such as inhibiting APOBEC3G virion encapsidation, mRNA translation, and for those APOBEC3G molecules that still become virion encapsidated, Vif can inhibit APOBEC3G mutagenic activity. Although most Vif variants can induce efficient degradation of APOBEC3-D, -F, and -G, there appears to be differential sensitivity to Vif-mediated degradation for APOBEC3H. This review examines APOBEC3-mediated HIV restriction mechanisms, how Vif acts as a substrate receptor for a Cullin5 ubiquitin ligase complex to induce degradation of APOBEC3s, and the determinants and functional consequences of the APOBEC3 and Vif interaction from a biological and biochemical perspective.

Punicalagin, an essential component of pomegranate rind, has been demonstrated to possess antimicrobial activity against several food-borne pathogens, but its activity on the virulence of pathogens and its anti-quorum-sensing (anti-QS) potential have been rarely reported. This study investigated the efficacy of subinhibitory concentrations of punicalagin on Salmonella virulence factors and QS systems. A broth microdilution method was used to determine the MICs of punicalagin for 10 Salmonella strains. Motility assay and quantitative reverse transcription (RT)-PCR were performed to evaluate the effects of punicalagin on the virulence attributes and QS-related genes of Salmonella . The MICs of punicalagin for several Salmonella strains ranged from 250 to 1,000 μg/ml. Motility assays showed that punicalagin, at 1/16× MIC and 1/32× MIC, significantly decreased bacterial swimming and swarming motility, which corresponded to downregulation of the motility-related genes ( fliA , fliY , fljB , flhC , and fimD ) in RT-PCR assays. RT-PCR also revealed that punicalagin downregulated the expression of most of the selected genes involved in Salmonella virulence. Moreover, a QS inhibition assay indicated that punicalagin dose dependently inhibited the production of violacein by Chromobacterium violaceum and repressed the expression of QS-related genes ( sdiA and srgE ) in Salmonella . In addition, punicalagin significantly reduced Salmonella invasion of colonic cells ( P < 0.01) with no impact on adhesion. These findings suggest that punicalagin has the potential to be developed as an alternative or supplemental agent for prevention of Salmonella infection.

Fluidized beds are widely used in many process industries including the food and pharmaceutical sectors. Despite being an intensive research area, there are no design rules or correlations that can be used to quantitatively predict the solid mixing in a specific system for a given set of operating conditions. This paper presents a numerical study of the gas and solid dynamics in a laboratory scale fluidized bed coating process used for food and pharmaceutical industries. An Eulerian–Eulerian model (EEM) with kinetic theory of granular flow is selected as the modeling technique, with the commercial computational fluid dynamics (CFD) software package ANSYS/Fluent being the numerical platform. The flow structure is investigated in terms of the spatial distribution of gas and solid flow. The solid mixing has been evaluated under different operating conditions. It was found that the solid mixing rate in the horizontal direction is similar to that in the vertical direction under the current design and operating conditions. It takes about 5 s to achieve good mixing.

Sand screens, including wire wrapped sand screens and slotted liners are often installed in sanding prone wellbores to control sand production. The selection of optimal sand screen aperture for a given sand body is critical to minimize sand production while maintaining well productivity. Laboratory sand retention tests were developed over 10 years ago to provide a basis for sand screen selection. Unfortunately, these experiments have a number of limitations. For example, the results can be substantially different depending on how the tests are conducted and data interpreted. This can lead to different (sometimes wrong) sand screen types and screen opening size recommendations. This paper presents an initial investigation of the sand production problem from wire wrapped screens and slotted liners, through the use of discrete element model (DEM) for the solid flow with or without fluid flow coupling using computational fluid dynamics (CFD). The focus is on some key design and/or operating parameters affecting sand retention over the sand screen, such as the screen opening size, initial solid concentration, fluid flow velocity as well as particle shape.

Gas generated beneath anodes in aluminum electrolytic cells play an important role for the circulation of the bath, alumina mixing, and heat balance. Those bubbles cause an extra voltage drop, which is strongly affected by the amount and shape of the bubbles beneath anodes. Consequently, understanding the dynamic behavior of bubbles in aluminum electrolytic cells has been a major research focus worldwide in recent decades.

This paper presents a numerical investigation of solid separation in jigging device. Jigging is a gravity separation method commonly used by the minerals industry to separate coal, iron ore, diamonds and other minerals on the basis of particle size and/or density. Separation is recognised as being heavily dependent on fluid motion in the jig. This study explores the effects of the inlet time dependent velocity profile in relation to a wide criterion on jigging performance. Modelling of the liquid–solid system is performed through a combination of computational fluid dynamics (CFD) to simulate liquid flow and discrete element method (DEM) to resolve particle motion. The initial packing conditions consist of a binary-density particle system of 1130 particles each 1 cm in diameter. A range of jigging profiles have been implemented in mineral processing. In this study the sinusoidal pulsation profile is selected adopting variations in both amplitude and frequency. The performance of profile variants are compared in terms of solid flow patterns, separation kinetics, energy, and mean particle position. These quantitative comparisons demonstrate significant differences in the segregation rate, energy, and solid phenomena, helping find an alternative optimum operating setting for the system. In addition, boundaries of operation are found in terms of frequency and amplitude limits and the concentration mechanics are investigated in these regions.

Aluminium reduction cells have been continuously improved to reduce energy consumption and increase metal production rates. One method of reducing energy consumption is to operate the cell at low anode-cathode distances (ACDs). Line currents have been increased to increase production rates, which often requires larger anodes to maintain an acceptable current density. These changes may have a significant impact on aspects of cell performance such as bath flow and alumina mixing.

APOBEC3G is a single-stranded (ss) DNA deaminase that restricts replication of HIV-1 by inducing viral genome mutagenesis through deamination of cytosine to uracil on HIV-1 cDNA. APOBEC3G has polydisperse oligomeric states and deaminates ssDNA processively through jumping and sliding. APOBEC3G has a catalytically inactive N-terminal CD1 domain that mediates processivity and an active C-terminal CD2 domain that catalyzes deaminations. Here, we assess the determinants of APOBEC3G deamination efficiency mediated by the CD1 domain by comparing native APOBEC3G and two CD1 mutants, a monomeric mutant (F126A/W127A) and a clinical mutant associated with high viral loads (H186R). Biochemical assays on ssDNA or partially dsDNA and with a reconstituted HIV replication system demonstrate that both mutants of Apo3G have altered DNA scanning properties in either jumping (F126A/W127A) or sliding (H186R), which results in decreased abilities to induce mutagenesis during reverse transcription. The data reveal a functionality for Apo3G oligomers in deamination and provide the first biochemical characterization of the clinical mutant H186R. The data demonstrate that the balance between the jumping and sliding of Apo3G is needed for efficient mutational inactivation of HIV-1.

Sand screens are often installed in sanding prone wellbores to control sand production. A selection of optimal sand screen apertures is required to minimise sand production and maximise fluid production. This has been accomplished historically on empirical correlations, rules of thumb and laboratory sand retention experiments. These methodologies have a number of limitations that can lead to different screen types and sub-optimal screen apertures to be selected. Using discrete element models (DEMs), many design/operating parameters similar to a specific wellbore condition can be simulated and tested in parallel. Most importantly, the detailed particle scale information helps to give a detailed understanding of the underlying mechanisms controlling the sand retention process. This extended abstract presents an investigation of the sand production problem from wire wrapped screens and slotted liners through the use of a DEM for the solid flow with fluid flow coupling using computational fluid dynamics (CFD). Information about particle sizes and distributions incorporated in the DEM model are based on measurement data from reservoir sands. The focus is on the effect of particle size distributions, particle concentration, and the slot width on sand retention across a slotted sand screen.