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Acute hepatopancreatic necrosis disease (AHPND) is an emerging disease that has caused mass mortality in shrimp in many countries in Asia and South America. A new strain of Vibrio parahaemolyticus (VpAHPND), carrying one or more extrachromosomal ~70 kbp plasmids that encode homologues of the Photorhabdus insect-related (Pir) binary toxins (PirAvp and PirBvp) is the causative agent of AHPND. Bioassay challenges using immersion, reverse gavage and per os (feeding) treatments have been shown to induce the pathology characteristics of AHPND in experimentally infected shrimp. Moreover, a number of polymerase chain reaction (PCR) methods have been found to facilitate early detection of the disease. However, non-V. parahaemolyticus species close to Vibrio harveyi, Vibrio owensii and Vibrio campbellii have recently been identified as carrying pVA1-like plasmids, signifying that these plasmids are capable of being transmitted to different Vibrio species. AHPND is thus a threat and a serious concern for the aquaculture industry. Against this background, this paper presents an overview of experimental methodologies and diagnostic procedures for AHPND. It also includes fundamental findings related to the disease as guidelines which may be useful for further experimental work on AHPND and other similar shrimp diseases.

Malachite green (MG) is still being used as an antiparasitic and antifungal agent in aquaculture. This is due to the fact that many stakeholders are not aware of the potential genotoxic and carcinogenic properties of MG. Since the consumption of fish in Malaysia was recorded to be the highest in Southeast Asia in 2013, it is therefore important to ensure that fish sold in the market are free of MG and its metabolite, leucomalachite green (LMG). In this study, MG and LMG residues in muscle tissue of commonly consumed fish such as red tilapia (Oreochromis hybrid), African catfish (Clarias gariepinus), barramundi (Lates calcarifer), hybrid grouper (Epinephelus fuscoguttatus × Epinephelus lanceolatus) and striped catfish (Pangasius hypophthalmus) were analysed using liquid chromatography-tandem mass spectrometry. The fish were purchased from 11 different markets in the state of Selangor, Malaysia. The results showed that the sum residues of MG and LMG in the present study ranged from 0.53 to 4.10 μg/kg with the highest residue detected in domestic striped catfish. This study indicates that MG is still being used and aquaculture stakeholders should be made aware of the judicious use of MG for the benefit of public health.

Development of low-cost, ambient pressure, gas-liquid contactors with fast mass transfer (high k L a ) and low energy consumption are key for industrial chemical processing technologies. A recently published reactor design comprised an array of downward-pointing micro-jets at the top of the vessel to create a downflow of microbubbles. Performance showed high k L a and low power usage. However, the most stable hydrodynamic mode under a jet array includes a large and persistent eddy, likely similar to the “Coanda effect” reported much earlier. Here we test swirling hydrodynamics to prevent momentum positive feedback that hypothetically creates this backmixing. Particle imaging velocimetry (PIV), salt-pulse tracking residence time distribution (RTD), and k L a data are collected from the swirl and non-swirl case. The data confirm the hypothesis about the hydrodynamic origin of the eddy, and suggests that it must be considered during reactor design. The data further show that swirl shifts the overall reactor hydrodynamics closer to plug flow, creates more tanks in series, more homogenous turbulence, greater k L a , and greater k L a per power usage (an increase by 40%). A physical understanding is given by measurements of residence time distribution that create more efficient contact of gas and liquid phases.

Local, area and volume average void fraction measurements have been conducted in gas-liquid two-phase flow through vertical pipes of different diameters under different modes of operation covering up-flow, down-flow and batch bubble column. The measurement techniques used include gamma ray densitometry, electrical resistance tomography (ERT), wire mesh sensor (WMS), optical void probe, and pressure transducers. The consistency among different measurement techniques has been examined by comparing the local, area and volume-average void fraction measurements made using the above methods in the same test section under the same flow conditions. The accuracy of the measurement techniques has been found to depend significantly on the mode of two-phase flow operation. The results show that the gamma densitometry and the pressure transducers can produce highly reliable measurements independent of the mode of operation. However, the optical void probe was found to underestimate the local values of void fractions, particularly, in the case of a co-current down-flow with sub-millimeter sized bubbles. Also, the electrical resistance tomography technique was found to be the least reliable method, as it underestimated the void fraction in the co-current up-flow as well as co-current down-flow operation. The accuracy of the wire mesh sensor was strongly dependent on the size of the bubbles relative to the wire mesh spacing.

MnO2 is one of the safest and most abundant electrochemical materials available. It exhibits polymorphism, which has been exploited in many applications especially batteries. In alkaline batteries, γ-MnO2 is widely used because its proton insertion reaction yields one e− (1st) per Mn at high voltages. It also gives a second (2nd) e− during dissolution-precipitation reactions that occur at lower voltages than the proton insertion; however, these 2nd e− reactions are highly irreversible. In this communication, we explore the reversibility of the 2nd e− reactions with bismuth oxide (Bi2O3) and copper (Cu) additives, and cycling in specific potential regions where δ-MnO2 is the polymorph synthesized electrochemically in-situ from γ-MnO2. The use of Bi2O3 and Cu add complexation and intercalation reactions, where presence and/or electrochemical activation of both are essential for reversibility and for capacity retention (50–100%). Attaining 300–610Wh kg−1 against a zinc anode is possible for these batteries, which could promote its use for many applications.

The aim of this study was to determine the effect of different light sources and media (wastewater and BBM) on the growth of Pseudanabaena mucicola and its phycobiliprotein production. Results showed that P. mucicola grown in white light using wastewater as medium attributed higher biomass (0.55 g L-1) and when extracted with water, also showed significantly higher (P < .05) production (237.01 mg g-1) and purity (1.14) of phycobiliprotein. This study validated that phycobiliprotein extracted from P. mucicola using water can be food grade natural blue pigment. Moreover, cyanobacteria grown in wastewater could cut down the production cost of phycobiliprotein.

Identification of naturally ripened mango using a pocket-friendly, portable aroma detection system (Aroma e-Sense) has been presented in this work. The study found 2, 5-Dimethyl-4-hydroxy-3(2 H)-furanone (DHF), a biomarker of artificially ripened (AR) mango. Hereto, a DHF imprinted polymer coupled to a quartz crystal microbalance (DHFIP-QCM) sensor has been fabricated to detect the important flavonoids. Aroma e-Sense with two modules, viz. DHFIP-QCM sensor, and signal processing module comprises of the crystal oscillator (10 MHz) synchronized with a frequency counter module, display module followed by storage module. The DHFIP-QCM sensor was designed using synthesized methacrylic acid-divinyl benzene polymer as sensing film. The developed Aroma eSense possesses significant repeatability (99.50 %), reproducibility (98.60 %), and stability towards DHF. Further, the developed system has been validated with standardized gas chromatography. Moreover, the Aroma e-Sense was found to be applicable to ensure whether mangoes are carbide treated or not.

In this study, an efficient, simple and eco-friendly biological method, immobilized Tetraselmis chuii beads (TetraBeads) were tested for its efficacy in maintaining water quality to improve the survival and growth of Penaeus monodon postlarvae. Results showed that the tanks, treated with Tetrabeads, were able to significantly (p

Birnessite (δ-MnO 2 ) is a layered polymorph of manganese dioxide used in a number of applications because of its low cost and non-toxic characteristics. In organic electrolyte battery chemistry's it has been considered as an insertion electrode for lithium, magnesium and other ions. In an alkaline environment, however, it undergoes conversion reactions. It has a high theoretical specific capacity of 617 mAh/g based on two electron reactions making it an energy dense electrode. However, its implementation in practice has been limited due to complicated, time cumbersome synthesis methods, and formation of electrochemical irreversible phases after a few cycles. In this article, we report the rapid synthesis and study of the electrochemical synthesis of δ-MnO 2 from cheap and commercially available electrolytic manganese dioxide (EMD, γ-MnO 2 ), where we find the formation to proceed from γ-MnO 2 to groutite (α-MnOOH) and pyrochroite [Mn(OH) 2 ] on the first discharge and follow the reverse transition on the immediate charge to form δ-MnO 2 in alkaline electrolyte. The formation process takes only one cycle to completely form δ-MnO 2 . The electrochemical reversibility of δ-MnO 2 formed through this process is also addressed, where we find that avoiding hydrophobic binders, use of appropriate carbons, addition of certain metallic additives and possibly porosity/pore structure play an important role in unleashing its energy-dense electrochemical performance.

Environmental factors, growth phase and microalgal strain have been reported to influence the chemical composition of microalgae. Salinity is one of the important culture conditions that can influence growth and proximate composition of microalgae. Dunaliella sp. is a commercial microalgae species that has been widely used in various sectors due to its biochemical composition. It is also well known to tolerate a wide range of salinity. In the present study, effect of different salinities (10, 30 and 50 ppt) on the growth and proximate composition of Dunaliella sp. at different growth phases were evaluated. Results showed that growth of Dunaliella sp. was significantly higher (p

Zinc poisoning of the cathode is a leading failure mechanism for rechargeable alkaline Zn/MnO2 batteries, as it leads to the formation of an electrochemically inactive zinc manganese spinel phase. In this communication, we report the use of calcium hydroxide sheets interlayered between zinc anodes and separators, which trap zincate ions through a complexing mechanism. Cells with such interlayers show favorable characteristics as compared with regular cells, such as lower zincate ion concentration in the bulk electrolyte, absence of undesirable spinel phase, and capacity retention above 90mAh/g-MnO2 after 60cycles at 100% depth of discharge (DOD) of the 1st electron of MnO2. Keywords: Rechargeable alkaline Zn/MnO2 battery, Separator, Calcium zincate

Microbubbles dispersed in bubble column reactors have received great interest in recent years, due to their small size, stability, high gas-liquid interfacial area concentrations and longer residence times. The high gas-liquid interfacial area concentrations lead to high mass transfer rates compared to conventional bubble column reactors. In the present work, experiments have been performed in a downflow bubble column reactor with microbubbles generated and dispersed by a novel mechanism to determine the gas-liquid interfacial area concentrations by measuring the void fraction and bubble size distributions. Gamma-ray densitometry has been employed to determine the axial and radial distributions of void fraction and a high speed camera equipped with a borescope is used to measure the axial and radial variations of bubble sizes. Also, the effects of superficial gas and liquid velocities on the two-phase flow characteristics have been investigated. Further, reconstruction techniques of the radial void fraction profiles from the gamma densitometry's chordal void fraction measurements are discussed and compared for a bubble column reactor with dispersed microbubbles. Empirical correlations are also proposed to predict the Sauter mean bubble diameter. The results demonstrate that the new bubble generation technique offers high interfacial area concentrations (1000–4500 m 2 /m 3 ) with sub-millimeter bubbles (500–900 µm) and high overall void fractions (10–60%) in comparison with previous bubble column reactor designs.

In this study, the suitability of excess biofloc that was discarded as waste from Litopenaeus vannamei farm effluent was investigated for effectiveness as a dietary replacement in rearing L. vannamei postlarvae (PL). A commercial shrimp diet (control) was compared to four diets containing dried waste biofloc at 25%, 50%, 75% and 100% replacement levels and fed to shrimp PL to evaluate the survival rate, growth performance and nutritional composition. Total ammonium nitrogen and nitrite nitrogen were maintained in culture tanks with minimal water exchange throughout the experiment. Results showed that PLs fed with 50% biofloc feed (50% BF) had significantly higher (p

Electrochemical behavior of Ag, Bi, Cu, Fe, Ni and Sn substrates on zinc deposition was evaluated over battery cycling by cyclic voltammetry and electrochemical impedance spectroscopy. The effect of Bi, Cu, Ni, and Sn substrates on zinc electrodeposition during battery cycling was investigated using scanning electron microscopy and X-ray diffraction. The corrosion behavior of each metal in 9 M KOH and the corrosion rates of zinc plated on each substrate were analyzed by Tafel extrapolation method from the potentiodynamic polarization curves and electrochemical impedance spectroscopy. Although the charge-transfer resistance (Rct) of zinc electrodeposition is lowest on Sn, Sn eventually corrodes on cycling in alkaline media. Use of Ni as a substrate causes zinc to deteriorate on account of rapid hydrogen evolution. Bi and Cu substrates are more suitable for use as current collectors in zinc-anode alkaline rechargeable batteries because of their low corrosion rate and compact zinc deposition over battery cycling.

The rechargeability of γ-MnO2 cathodes in alkaline batteries is limited by the formation of the [Mn2]O4 spinels ZnMn2O4 (hetaerolite) and Mn3O4 (hausmannite). However, the time and formation mechanisms of these spinels are not well understood. Here we directly observe γ-MnO2 discharge at a range of reaction extents distributed across a thick porous electrode. Coupled with a battery model, this reveals that spinel formation occurs at a precise and predictable point in the reaction, regardless of reaction rate. Observation is accomplished by energy dispersive X-ray diffraction (EDXRD) using photons of high energy and high flux, which penetrate the cell and provide diffraction data as a function of location and time. After insertion of 0.79 protons per γ-MnO2 the α-MnOOH phase forms rapidly. α-MnOOH is the precursor to spinel, which closely follows. ZnMn2O4 and Mn3O4 form at the same discharge depth, by the same mechanism. The results show the final discharge product, Mn3O4 or Mn(OH)2, is not an intrinsic property of γ-MnO2. While several studies have identified Mn(OH)2 as the final γ-MnO2 discharge product, we observe direct conversion to Mn3O4 with no Mn(OH)2.

Towards establishing a first-principles physical link between the field-behavior and microstructure of oil-based drilling fluid (OBDF), we study rheology of an OBDF and its variation with different contents of water, clay viscosifier, or barite weighting agent during steady and dynamic rheological phenomena, and develop a “cryo-preserved” experimental methodology towards in-situ microscopy. Rheological data was collected for shear rate ramps between 0.0001 s and 1 and 1000 s−1, under temperatures ranging from 10°C to 60 °C, with three water/oil ratios, and multiple OBDF compositions. Oscillatory and constant shear rate measurements showed elastic and loss modulus co-dominate when stress is below ~1 Pa, but above a ~1 Pa “apparent yield-stress” the fluid microstructure reorganizes, elasticity decreases, and the flow follows a viscosity-dominated shear-thinning Herschel–Bulkley behavior. Signs of thixotropy are seen in increasing vs. decreasing flow curves when in the elastic regime, and elasticity shows time-dependency. Clay particles created elasticity more so than the other ingredients. Elimination of water, clay, or barite caused an approximately equal reduction of viscosity. Elimination of water also led to elastic modulus dominating over viscous modulus for a longer range of strain in the linear-elastic pre-yield state, likely due to water droplets having a shorter length scale over which yield-stress is broken than does a water-free mixture. Elimination of barite had a similar but lesser effect on elasticity. Cryological scanning electron microscopy (Cryo-SEM) and cryological x-ray spectroscopy (Cryo-EDS) methods show promise for future work to identify the spatial microstructure of the OBDF at nanometer to micrometer scales in a “cryo-preserved” state that approximates an in-situ like state. Chemical identification of individual phases within the mixture components is achieved via a quantitative elemental method. Water droplets, base oil, and barite are identifiable and future methods for in-situ imaging of sheared OBDFs is proposed.

Co-current downflow bubble columns provide advantages like high gas phase residence time and small bubble diameters, which result in high gas-liquid interfacial area and high mass transfer rates. The precise knowledge of gas fraction, bubble size distribution, interfacial area ( a _ ) and volumetric mass transfer coefficient ( k L a _ ) data is essential for the design of such downflow bubble columns. The present work investigates the effect of superficial gas velocity, liquid velocity and gas sparging location on the volume averaged gas fraction, axial and chordal gas fraction profiles, Sauter-mean bubble size, k L a _ , and a _ in a downflow bubble column modified to operate via an array of downward pointing micro-jets. Experiments were performed for air-water system with 20 PPM SDS in two-different scale downflow bubble columns: (1) volume of 5 L (Height (H) = 0.6 m, Diameter (D) = 0.1 m, aspect ratio (H/D) = 6) and (2) volume of 120 L (H = 1.5 m, D = 0.3 m, H/D = 5). The experimental results of axial and chordal gas fraction profiles and bubble size distributions are presented. Further, the empirical correlations have been proposed to predict the gas fraction ( ∈ G ), Sauter-mean bubble diameter ( d B ) and effective gas-liquid interfacial area a _ for better understanding the scale-up process.

Malachite green (MG) is not permitted by the EU and FDA to be used in animals intended for human consumption due to its potential carcinogenesis. However, recent findings have shown residues of MG in fish sold to consumers. Therefore, the presence of MG residues is of concern. In this study, MG and its primary metabolite leucomalachite green (LMG) in red tilapia (Oreochromis hybrid) muscle tissue was quantified by a simplified method for sample preparation using liquid chromatography-tandem mass spectrometry. The decision limit and detection capability for MG was 0.05 μg/kg and 0.09 μg/kg and for LMG was 0.05 μg/kg and 0.08 μg/kg, respectively. In addition, accuracy, precision, recovery, and matrix effects were also performed. To evaluate the persistence of MG and LMG, fish were exposed to dip (A) (66.7 mg/L; 30 s), dips (B) (66.7 mg/L; 30 s repeated for 5 days), short-term bath (C) (6.7 mg/L; 15 min), short-term bath (D) (6.7 mg/L; 15 min repeated for 5 days) and long-term bath (E) (0.5 mg/L; 6 days) treatments using MG. The MG and LMG residues were quantified at the following intervals; immediately after treatment, 1st, 2nd, 3rd, 4th, 10th, 20th and 30th day post-exposure. Long-term bath (E) showed the highest accumulation of total MG and LMG immediately after treatment (441.38 μg/kg) and at day 30 (13.30 μg/kg). Whereas, all other treatments (day 30) were below 0.26 μg/kg.

Batteries based on manganese dioxide (MnO2) cathodes are good candidates for grid-scale electrical energy storage, as MnO2 is low-cost, relatively energy dense, safe, water-compatible, and non-toxic. Alkaline Zn–MnO2 cells, if cycled at reduced depth of discharge (DOD), have been found to achieve substantial cycle life with battery costs projected to be in the range of $100 to 150 per kWh (delivered). Commercialization of rechargeable Zn–MnO2 batteries has in the past been hampered due to poor cycle life. In view of this, the work reported here focuses on the long-term rechargeability of prismatic MnO2 cathodes at reduced DOD when exposed to the effects of Zn anodes and with no additives or specialty materials. Over 3000 cycles is shown to be obtainable at 10% DOD with energy efficiency >80%. The causes of capacity fade during long-term cycling are also investigated and appear to be mainly due to the formation of irreversible manganese oxides in the cathode. Analysis of the data indicates that capacity loss is rapid in the first 250 cycles, followed by a regime of stability that can last for thousands of cycles. A model has been developed that captures the behavior of the cells investigated using measured state of charge (SOC) data as input. An approximate economic analysis is also presented to evaluate the economic viability of Zn–MnO2 batteries based on the experiments reported here.

An economic design for an alkaline zinc-anode flow-assisted battery without membrane separators was tested at grid-scale of 25 kWh with a string of thirty 833 Wh cells in series, and also at bench scale with individual 28 Wh cells. The bench-scale tests allowed optimization of parameters such as electrolyte flow, choice of hardware material, electrolyte composition, and charge/discharge protocol. The best-performing bench scale cell cycled for over 3300 cycles with energy efficiency above 80%, and was selected as the design basis for scale-up to the 25 kWh battery string. Testing of the grid-scale string demonstrated 1000+ cycles with round trip energy efficiency above 80%. Two challenges observed at the bench scale were overcome for successful scale-up, namely a) passivation of the anode surface, which occurred when the anode experienced voltages 100 mV above zinc's rest voltage, and b) zinc particulates that jammed the gap between the electrodes and caused cathode degradation and passivation of the anode surface. Best practices to overcome these challenges and achieve long cycle life are presented.

Preferred orientation of zinc deposits during charging is shown to significantly improve performance and cycle life in flow-assisted alkaline zinc batteries, which has not been demonstrated earlier. The preferred orientation of zinc deposits was investigated using X-ray diffraction (XRD). Compact zinc is found to have ( 11 2 ¯ 2 ) preferred orientation on brass, which contributes to ∼60% of the texture. The effect of charging current and zincate concentration on morphology was investigated in a rotating hull cell and correlated with anodic efficiency. Compact zinc deposits are found to have a fine-grained, bright finish and the highest anodic efficiency. Electrochemical impedance spectroscopy (EIS) proves that compact zinc corresponds to the minimum in the half-cell resistance. Morphological control using compact zinc could be accomplished using innovations such as pulse charging or enhanced mass-transfer to improve anode performance without affecting the cathode.

A new solver for second-order elliptic partial differential equations (PDEs) based on the lattice Boltzmann method (LBM) and the multigrid (MG) technique is presented. Several benchmark elliptic equations are solved numerically with the inclusion of multiple grid-levels in two-dimensional domains at an optimal computational cost within the LB framework. The results are compared with the corresponding analytical solutions and numerical solutions obtained using the Stone's strongly implicit procedure. The classical PDEs considered in this article include the Laplace and Poisson equations with Dirichlet boundary conditions, with the latter involving both constant and variable coefficients. A detailed analysis of solution accuracy, convergence and computational efficiency of the proposed solver is given. It is observed that the use of a high-order stencil (for smoothing) improves convergence and accuracy for an equivalent number of smoothing sweeps. The effect of the type of scheduling cycle (V- or W-cycle) on the performance of the MG-LBM is analyzed. Next, a parallel algorithm for the MG-LBM solver is presented and then its parallel performance on a multi-core cluster is analyzed. Lastly, a practical example is provided wherein the proposed elliptic PDE solver is used to compute the electro-static potential encountered in an electro-chemical cell, which demonstrates the effectiveness of this new solver in complex coupled systems. Several orders of magnitude gains in convergence and parallel scaling for the canonical problems, and a factor of 5 reduction for the multiphysics problem are achieved using the MG-LBM.

Changes in electrodeposited zinc morphology were experimentally investigated in a flowing alkaline electrolyte. Deposition of zinc on flat sheets as well as on new mesh-type reduced-area current collectors was studied. Zincate concentration in the electrolyte, flow velocity, and current density was varied over a wide range. The results show that the ratio between the effective current density and the limiting current density (current density ratio) which is directly related to the zincate concentration at the electrode surface determines the zinc morphology. Zinc morphology is mossy and porous when the current density ratio is below 0.4, whereas it is a mixture of mossy and crystalline structures when it is between 0.4 and 0.9. Only when the current density ratio is above 0.9, does zinc deposition become just crystalline and compact. This finding holds for both flat sheet and mesh-type reduced-area current collectors.

An experimental study on hydrogen and oxygen evolution was carried out in a sealed zinc–nickel oxide battery. The effects of flowing electrolyte on gas evolution were quantitatively evaluated. The results show that both the hydrogen and oxygen evolution are suppressed by making the electrolyte flow on a regular cycle. This is due to increased cell polarization in the non-flowing case attributed to the concentration boundary layer of zinc (zincate) ion near the anode surfaces. Though the Coulombic efficiency in the flowing case was higher than that in the non-flowing case, the fraction of gas evolution against Coulombic loss was the same for both the cases. When deeply discharging the cell, more hydrogen is evolved in the flowing case than in the non-flowing case.

The zinc morphology on repeated charging and discharging in flow-assisted zinc–nickel oxide cells was studied. The results show that higher charge rates cause more dendritic growth of zinc deposition on charging and tend to cause deterioration of battery cells. However, when the electrolyte velocity is higher than 15 cm s −1 , the direction of dendrites was distorted toward the flow direction and the internal short circuit was suppressed. Good cycle life was obtained – 1500 cycles at 100% depth of discharge and C /2 charge and discharge rate. Also, the battery was scaled up to a 100 Wh prismatic cell, and more than 200 cycles were obtained.

We present a theoretical framework for simulating dynamic processes in polymeric fluids with embedded nanoparticles. The method couples an Eulerian, field-theoretic description of polymer hydrodynamics with a Lagrangian technique for tracking particles of arbitrary shape and size. Results are presented which reproduce nanoparticle localization in diblock nanosphere composites and interfacial jamming in homopolymer blend nanocomposites. Some of the method's unique capabilities are demonstrated by simulating systems containing non-spherical particles, particles of multiple sizes, and surface driven self-assembly.

Periphyton grown on substrates is known to improve water quality in aquaculture ponds. Five different substrates, (i) bamboo pipe (ii) plastic sheet (iii) polyvinylchloride (PVC) pipe (iv) fibrous scrubber, and, (v) ceramic tile were evaluated for the formation of biofilm in this experiment. The substrates were suspended 25 cm below the water surface. Each type of substrate was collected fortnightly to analyze the abundance and biomass of different periphytic algae and of the biofouling organism. The study was terminated after 60 days due to severe fouling by polychaete. Results showed that pond water nutrients were high on day 60 with mean total ammonia-N, nitrite-N and soluble reactive phosphorus concentrations of 309.6 ± 8.6 μg L − 1 , 26.0 ± 2.7 μg L − 1 and 87.2 ± 7.1 μg L − 1 respectively. During the first two weeks the substrates were colonized by 19 periphytic algae. The most abundant family was Bacillariophyta (8 genera) followed by Chlorophyta (7 genera) and Cyanophyta (4 genera). Periphyton colonization on bamboo pipe showed the highest ( p a amongst all the substrates used. The biomass varied from 179 to 1137 μg m − 2 with mean values of 1137.2 ± 0.6, 929.6 ± 0.6, 684.2 ± 1.2, 179.1 ± 0.6 and 657.0 ± 0.6 μg m − 2 on bamboo pipe, PVC pipe, plastic sheet, fibrous scrubber and ceramic tile respectively for the first 15 days. From 3rd week, polychaetes began to form tubes on the substrate. By day 60, the whole surface of all substrates was covered with tightly packed polychaete tubes with mean densities of 168.0 ± 15.4, 121.0 ± 13.5, 72.8 ± 9.8, 72.4 ± 7.4 and 56.0 ± 6.8 polychaete tubes cm − 2 for bamboo, PVC, plastic, fibrous scrubber and ceramic tile respectively. This study illustrated the invasive nature of attached polychaete thus hampering the formation of periphyton biofilm on substrates which could have been used for improving water quality in enriched brackishwater shrimp ponds.

An eco-friendly method was established by using periphyton coated substrate (a cyanobacterium or mixed diatoms) to improve water quality, survival and growth of Penaeus monodon postlarvae (PL) in a shrimp hatchery system without changing water. Polyvinyl chloride (PVC) pipes (2 cm × 2 cm) were used as the substrate to grow pure cultures of cyanobacterium and diatoms. P. monodon (PL1) were cultured in 40 L glass tanks containing 30 L filtered-seawater and stocked at a density of 50 PLs L− 1. Two treatments using i) cyanobacterium coated substrate (Oscillatoria), ii) mixed diatoms coated substrate (Amphora, Navicula and Cymbella), and a control (without substrate) were employed in this experiment. The experiment was run in triplicate for a period of 16 days (PL16) whereafter the PLs are normally stocked in growout ponds. Tanks with Oscillatoria coated substrate had the lowest (P

We introduce a mesoscale method for simulating hydrodynamic transport and self assembly of inhomogeneous polymer melts in pressure driven and drag induced flows. This method extends dynamic self consistent field theory (DSCFT) into the hydrodynamic regime where bulk material transport and viscoelastic effects play a significant role. The method combines four distinct components as a single coupled system, including (1) non-equilibrium self consistent field theory describing block copolymer self-assembly, (2) multi-fluid Navier-Stokes type hydrodynamics for tracking material transport, (3) constitutive equations modeling viscoelastic phase separation, and (4) rigid wall fields which represent moving channel boundaries, machine components, and nano-particulate fillers. We also present an efficient, pseudospectral implementation for this set of coupled equations which enables practical application of the model in periodic domains. We validate the model by reproducing well known phenomena including equilibrium diblock meso-phases, analytic Stokes flows, and viscoelastic phase separation of glassy/elastic polymer melts. We also demonstrate the stability and accuracy of the numerical implementation by examining its convergence under grid-size refinement., Comment: Revised as suggested by peer review

In this paper, we describe a sharp interface capturing method for the study of incompressible multiphase flows with phase change. We use the level set method to keep track of the interface between the two phases and a ghost fluid approach to impose the jump conditions at the interface. This work builds on the work of Gibou et al. for the study of Stefan problems [F. Gibou, R. Fedkiw, L.-T. Cheng, M. Kang, A second-order-accurate symmetric discretization of the Poisson equation on irregular domains, J. Comput. Phys. 176 (2002) 205-227] and the work of Nguyen et al. for the simulation of incompressible flames [D. Nguyen, R. Fedkiw, M. Kang, A boundary condition capturing method for incompressible flame discontinuities, J. Comput. Phys. 172 (2001) 71-98]. We compare our numerical results to exact solutions in one spatial dimension and apply this algorithm to the simulation of film boiling in two spatial dimensions.

When a system such as a binary liquid is cooled rapidly from a homogeneous phase into a two-phase region, domains of the two equilibrium phases form and grow (coarsen) with time. In the absence of external forcing, such as by gravity or an imposed shear flow, a dynamical-scaling regime emerges in which the domain morphology is statistically self-similar at different times, with an overall length-scale (coarsening scale) that grows with time. In the first part of the paper, the scaling phenomenology will be reviewed and the time-dependence of the coarsening scale will be discussed in the context of a number of different physical systems and scaling regimes. In the second part, the influence of external drives, in particular gravity and shear flow, will be addressed and recent results reviewed. In particular, we find that multiple length scales emerge since in the shear case the system coarsens more rapidly in the mean flow direction while in the gravity case the coarsening is more rapid in the direction of the gravity. We characterized the scales by calculations of the anisotropic growth laws. Further for the shear we show that it is possible to control the asymptotic morphology of the phase separation in order to obtain either lamellae or cylindrical structures and potentially create for example nano-conductive wires or materials with particular optical properties. Investigating gravitational effects we find that scaling laws are significantly affected even for small density mismatch or low gravity, and the growth mechanism has some similarities to the sedimentation process.

The paper summarizes results of experimental and theoretical studies related to the flow of liquids with a free surface and poor electrical and thermal conductivity, such as molten salts, under conditions relevant to fusion energy systems. These results have been obtained over last several years when developing the liquid wall concept as a part of the APEX project [M.A. Abdou, The APEX TEAM, On the exploration of innovative concepts for fusion chamber technology, Fusion Eng. Des. 54 (2001) 181–247]. As a theoretical tool a modified K – ɛ model of turbulence coupled with the Navier–Stokes equations written in the thin-shear-layer approximation is used for studying wavy, turbulent flows in a spanwise magnetic field. The experimental part covers current results for supercritical flows in regimes transitional from “weak” to “strong” turbulence, which are expected to occur in the reference liquid wall flows. The paper also describes on-going work on novel schemes of heat transfer promotion and current directions for direct numerical simulation.

Surface divergence models for prediction of scalar exchange at fluid–fluid interfaces are investigated. The models, based on the Hunt–Graham blocking theory, are shown to predict experimental data at unsheared interfaces, and new results of direct numerical simulation for deformable, nonbreaking sheared interfaces. The parameterization is in terms of the turbulent Reynolds number defined by the integral velocity and length scales in the bulk flow, which makes it useful for practical purposes. 2004 Elsevier Ltd. All rights reserved.

Cell surface macromolecules such as receptors and ion channels serve as the interface link between the cytoplasm and the extracellular region. Their density, distribution, and clustering are key spatial features influencing effective and proper physical and biochemical cellular responses to many regulatory signals. In this study, the effect of plasma-membrane receptor clustering on local cell mechanics was obtained from maps of interaction forces between antibody-conjugated atomic force microscope tips and a specific receptor, a vascular endothelial growth factor (VEGF) receptor. The technique allows simultaneous measurement of the real-time motion of specific macromolecules and their effect on local rheological properties like elasticity. The clustering was stimulated by online additions of VEGF, or antibody against VEGF receptors. VEGF receptors are found to concentrate toward the cell boundaries and cluster rapidly after the online additions commence. Elasticity of regions under the clusters is found to change remarkably, with order-of-magnitude stiffness reductions and fluidity increases. The local stiffness reductions are nearly proportional to receptor density and, being concentrated near the cell edges, provide a mechanism for cell growth and angiogenesis.

Phase field models offer a systematic physical approach for investigating complex multiphase systems behaviors such as near-critical interfacial phenomena, phase separation under shear, and microstructure evolution during solidification. However, because interfaces are replaced by thin transition regions (diffuse interfaces), phase field simulations require resolution of very thin layers to capture the physics of the problems studied. This demands robust numerical methods that can efficiently achieve high resolution and accuracy, especially in three dimensions. We present here an accurate and efficient numerical method to solve the coupled Cahn-Hilliard/Navier-Stokes system, known as Model H, that constitutes a phase field model for density-matched binary fluids with variable mobility and viscosity. The numerical method is a time-split scheme that combines a novel semi-implicit discretization for the convective Cahn-Hilliard equation with an innovative application of high-resolution schemes employed for direct numerical simulations of turbulence. This new semi-implicit discretization is simple but effective since it removes the stability constraint due to the nonlinearity of the Cahn-Hilliard equation at the same cost as that of an explicit scheme. It is derived from a discretization used for diffusive problems that we further enhance to efficiently solve flow problems with variable mobility and viscosity. Moreover, we solve the Navier-Stokes equations with a robust time-discretization of the projection method that guarantees better stability properties than those for Crank-Nicolson-based projection methods. For channel geometries, the method uses a spectral discretization in the streamwise and spanwise directions and a combination of spectral and high order compact finite difference discretizations in the wall normal direction. The capabilities of the method are demonstrated with several examples including phase separation with, and without, shear in two and three dimensions. The method effectively resolves interfacial layers of as few as three mesh points. The numerical examples show agreement with analytical solutions and scaling laws, where available, and the 3D simulations, in the presence of shear, reveal rich and complex structures, including strings.

A technique was developed to evaluate the applicability of data from small scale facilities for validation of codes for analysis of nuclear safety with emphasis on the next generation of reactors. The technique first divides an accident into phases based on the components that come into play as the accident evolves. Conservation equations, resolved to the component level and their interconnections, are derived for the active components in each phase. The equations are then nondimensionalized and reference parameters are selected such that the dependent variables, other than the system response of interest, are of order 1. Order of magnitude analysis is then performed for each equation and then between equations, based on the numerical values of the nondimensional coefficients for each term, with only the large order terms being retained. The resulting equations then contain terms whose impact on key system responses (e.g. reactor vessel level) are ordered in terms of the magnitude of the nondimensional groups multiplying the O[1] dependent variables. The reduced set of equations and nondimensional groups are validated with experimental data where possible. The validation process is meant to demonstrate that the important terms have been retained and enhance confidence in the system of equations used to capture the main processes occurring in each phase. The methodology was demonstrated by evaluating the applicability of small-scale facility data for next generation reactor SBLOCA. Based on the nondimensional equations, the dominant nondimensional groups, and hence the dominant physical mechanisms and their dependence on geometric and operational parameters, were identified for a particular scenario, an AP600 cold leg break, starting from the initiating event through long term cooling. The important parameters entering the groups included elevation differences between the reactor vessel and other components, PRHR heat transfer rates, fluid thermophysical properties, liquid levels in tanks, flow resistances in the CMT lines and IRWST lines, flow resistance in the pressurizer surge line, and pressurizer drain rate. It was also shown that, after the beginning of CMT draining and accumulator injection, the dominant processes do not depend on break size provided they are small. The dominant processes were dependent on plant geometry and the operation of engineered safety features, such as the automatic depressurization system. The same transient events were evaluated for three experimental facilities and the same nondimensional groups, and hence mechanisms, were shown to be important. It was found that these nondimensional groups covered the range expected in the AP600, indicating that while there may be some distortions in scaling for a particular facility, between them, the important phenomena were captured and the small-scale facility data appear applicable for SBLOCA in the AP600 system. In more general terms, the methodology appears suitable for assessing scaling of various facilities for other postulated accidents and for other reactor concepts.

The effect of a dilute suspension, of near neutral-density particles, on the wall turbulence in a horizontal channel was investigated by means of a laser Doppler anemomentry and flow visualization. We found that the particles increase the period between bursts. However, due to the mixing effect of the particles and effects similar to a rough wall, the overall Reynolds stress increases somewhat near the wall. Furthermore, because of increased Reynolds stress levels within the bursts, the fraction of the Reynolds stress in the bursts remains at about the same value (∼85%) as for flows without particles. Quadrant analysis of the Reynolds stress data indicates that particles increase sweep activity near the wall, i.e. in the region ≤10 wall units. All this results in increased wall normal velocity fluctuations in the viscous sublayer that may significantly impact heat and mass transfer rates. Estimates based on the data indicate an increase of ∼18% in heat transfer rates with only 5% increase in wall friction.

This paper presents a methodology for the prediction of the dispersion of a two-phase release from a chemical or process plant. A set of one-dimensional conservation equations for modelling such a release is derived, by taking an approach analogous to the boundary-layer integral method, in which the instantaneous conservation equations are averaged over a volume slice transverse to the direction of predominant plume/cloud motion. Averaging, which makes the problem computationally tractable, removes information regarding local gradients that govern transport of momentum, heat and mass—this information must then be supplied in the form of ‘closure relationships’. An appropriate set of closure relationships is then discussed, covering models for interfacial heat and mass transfer, entrainment of air, and interactions with the wind field. Particular features of the approach are that it is flexible enough to deal with condensation of water vapour, thermal non-equilibrium between the phases, sloping terrain, and can handle both elevated and ground-bounded releases. Suitable formulations for the initial and source boundary conditions, for both instantaneous and continuous releases, are also presented.

The CLOUD (concentration levels of unconfined dispersion) code has been developed, the nucleus of which is an innovative two-phase fluid dispersion model characterized by conservation equations for mass, momentum, energy and species, averaged over a volume slice transverse to the direction of plume motion. The initial and boundary conditions for the above equations are determined either by using auxiliary models or by direct input of the space distribution, and respectively of the time evolution, of the relevant variables. The initial conditions model for an instantaneous, puff release has been based on an experimental programme carried out at the Swiss Federal Institute of Technology. The boundary conditions for semi-continuous, jet releases have been based on literature models for critical two-phase flow at the rupture. The code has been validated with data from three large scale release test series: the Desert Tortoise series (ammonia), the Goldfish series (HF), and the Thorney Island series (heavy gas).

The motion of small particles in the wall region of turbulent channel flows has been investigated using direct numerical simulation. It is assumed that the particle concentration is low enough to allow the use of one-way coupling in the calculations, i.e. the fluid moves the particles but there is no feedback from the particles on the fluid motion. The velocity of the fluid is calculated by using a pseudospectral, direct solution of the Navier-Stokes equations. The calculations indicate that particles tend to segregate into the low-speed regions of the fluid motion near the wall. The segregation tendency depends on the time constant of the particle made non-dimensional with the wall shear velocity and kinematic viscosity. For very small and very large time constants, the particles are distributed more uniformly. For intermediate time constants (of the order 3), the segregation into the low-speed fluid regions is the highest. The finding that segregation occurs for a range of particle time constants is supported by experimental results. The findings regarding the more uniform distributions, however, still remain to be verified against experimental data which is not yet available. For horizontal channel flows, it is also found that particles are resuspended by ejections (of portions of the low-speed streaks) from the wall and are, therefore, primarily associated with low-speed fluid. The smaller particles are flung further upwards and, as they fall back towards the wall, they tend to be accelerated close to the fluid velocity. The larger particles have greater inertia and, consequently, accelerate to lower velocities giving higher relative velocities. This velocity difference, as a function of wall-normal distance, follows the same trend as in experiments but is always somewhat smaller in the calculations. This appears to be due to the Reynolds number for the numerical simulation being smaller than that in the experiment. It is concluded that the average particle velocity depends not only on the wall variables for scaling, but also on outer variables associated with the mean fluid velocity and fluid depth in the channel. This is because fluid depth in combination with the wall shear velocity determines how much time a particle, of a given size and density, spends in the outer flow and, hence, how close it gets to the local fluid velocity.

An experimental and analytical investigation of dispersed mist and dispersed annular (rivulet or thin film) flow phase separation in a tee was performed. The analysis portion consisted of developing physically based models and incorporating the models into a computer program that calculates liquid drop and liquid pathline trajectories for these two flow regimes. Macroscopic mass balances were then calculated and compared with data. In addition, a correlation for dispersed mist phase separation was developed from computer calculations and is presented.

Particle-turbulence interaction in wall turbulent flows has been studied. A series of experiments varying particle size, particle density, particle loading and flow Re has been conducted. The results show that the larger polystyrene particles (1100 μm) cause an increase in the number of wall ejections, giving rise to an increase in the measured values of the turbulence intensities and Reynolds stresses. On the other hand, the smaller polystyrene particles (120 μm) bring about a decrease in the number of wall ejections, causing a decrease in the measured intensities and Reynolds stresses. These effects are enhanced as the particle loading is increased. It was also found that the heavier glass particles (88 μm) do not bring about any significant modulation of turbulence. In addition, measurements of the burst frequency and the mean streak-spacing show no significant change with increase in particle loading. Based on these observations, a mechanism of particle transport in wall turbulent flows has been proposed, in which the particles are transported (depending on their size, density and flow Re) by the bursting events of the wall regions.

An experimental and analytical investigation of dispersed and dispersed annular (rivulet or thin film) flow phase separation in a tee was performed. The primary objective of the experimental portion of the reseach was to obtain data and observations to help formulate and test mechanistically based analytical models of phase separation for these two flow regimes. A variety of measurements were obtained, including: gas velocity profiles; pressure; macroscopic mass balances; streamline and eddy boundary maps; and rivulet, drop and solid particle trajectories.

A model has been developed for vapour generation and fluid discharge during total blackout in homopolymerization reactors used for polypropylene production. Normal safety measures on a plant blackout would be injection of a killer to stop the polymerization reaction, followed by controlled blowdown from the reactors. Safety-relief valves are provided as a backup to these systems. For predicting the performance of the relief system, a model has been developed that considers formation of a settled bed of polypropylene/catalyst and boiling of the propylene in the interstitial spaces. The model agrees well with pilot plant studies of discharge rate versus time at constant pressure. On the basis of this model, vent sizing of the plant is discussed.

A method is presented for measuring the phase density distribution at a cross-section of a gas-liquid flow system. The method utilizes the information carried by measured fluences of scattered fast neutrons. Reconstruction of the local density distribution is viewed as an inverse problem and a numerical method is developed for solving this problem. The physical and practical aspects of the problem are considered and some numerical and experimental results are presented.