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The current investigation explores the corrosion resistance of deep cryogenic-treated (DCT) dissimilar friction stir-welded (FSW) AA6066T6 - AA1060T6 aluminium alloys. The microstructures of the welded zone of FSW and DCT-FSW alloys revealed the presence of fine, dense intermetallic phases in the DCT-FSW alloy. The Rockwell hardness of the DCT-FSW alloy was higher. The corrosion resistance of this alloy was tested by immersion in a 0.6 M NaCl solution for 24, 48 and 72 hrs. The potentiodynamic polarization method measured the corrosion resistance, which indicated the highest positive corrosion potential and the lowest corrosion current density in the DCT-FSW alloy. Moreover, the surface morphology of the alloys exposed by SEM revealed shallow pitting corrosion in the weld zone (WZ) and cracks in the WZ-DCT samples. The DCT-FSW alloy performed better than the FSW alloy in corrosion resistance.

Polymer–filler interactions play a major role in determining the antibacterial activity of organoclay in nanocomposites. The objective of the current study was to determine the effect of polymer type on the antibacterial properties of an organically modified clay – cloisite 10A (C10A) – using poly-ε-caprolactone (PCL) and poly-L-lactic acid (PLA) polymeric systems. Nanocomposite characterization using atomic force microscopy (AFM) showed an increase in roughness upon addition of the clay mineral, and X-ray diffraction (XRD) showed intercalation of the selected polymers into the interlayer spaces of the clay. Transmission electron microscopy (TEM) analysis supported the XRD findings. C10A in PCL thin films enhanced the bactericidal activity against Staphylococcus aureuswhen compared to the C10A in PLA. The observed change could be the result of pronounced levels of interaction between the filler and polymer matrix in the C10A-PLA nanocomposite when compared to C10A-PCL. The higher interaction levels could hinder the diffusion of bactericidal agents from the nanocomposite membranes. The present study provided insight into the nature of interaction between nanocomposite components and its impact on bioactivity, which can have applications in terms of generating engineered antibacterial materials.

We examine the effectiveness of forced convective heat transfer in a toroidal helical pipe (THP), as a compact process intensification device for use in heat exchangers. Earlier, we showed that mixing was enhanced significantly in such devices due to a continuously changing curvature along the length of the pipe while retaining its compactness. In this work, we examine six Reynolds numbers ranging from 1 to 200, two Prandtl numbers (1 and 7), and two thermal boundary conditions (fixed temperature and fixed flux). The heat transfer efficiency in THP is quantified mainly by the Nusselt number as a function of the downstream distance, and it is compared with that in straight pipes of identical setup. Thus, enhancement by the geometric factor alone is extracted. We found in THP that the Nusselt number is not monotonic but varies periodically around mean values that can be more than four times higher than straight pipes. The unique coupled-Dean vortex flow pattern, due to the varying curvature of the THP axis, significantly enhances the in-plane mixing and causes the higher and oscillatory Nusselt numbers.

The present study was designed to investigate anti anxiety effects of alcoholic and aqueous root extracts of Cardiospermum halicacabum in mice. Mice were treated with the alcoholic or aqueous extract (100 or 300 mg/kg p.o.) 1 hr before subjecting the animals to various anxiety models. Anti anxiety activity was evaluated using elevated plus maze (EPM), light-dark model (LDM) and open field test (OFT). In EPM, treatment with alcoholic and aqueous extracts increased the time spent in open arm and total locomotion time. In light dark model treatment with these extracts showed increase in time spent in light compartment and in Open field test treatment with these extracts increased the time spent in central compartment. These results suggest that alcoholic and aqueous extracts of Cardiospermum halicacabum possess anti anxiety activity. Keywords: Anxiety | Elevated plus-maze (EPM) | Light-Dark model | Open field test | Cardiospermum halicacabum, Introduction Cardiospermum halicacabum is a herbaceous climber widely distributed in tropical and subtropical regions. It is found throughout the plains of India (1). The whole plant, roots and leaves are [...]

It is estimated that, as of 2010, there were 32 million orphaned children in India. There is little published information on the oral health of children in orphanages in India. To determine caries status and associated risk factors among children in orphanages in Kerala, India. This cross‐sectional study assessed caries using World Health Organization (WHO)criteria, and caries experience was reported as decayed, missing and filled primary or secondary teeth (dmft or DMFT, respectively). A brief questionnaire captured information on child oral health behaviours. Mean [standard deviation (SD)] and median [interquartile range (IQR)] scores were used to describe caries rates. Multivariable logistic regression analysis was conducted to identify independent disease predictors. Study design complexities, such as clustering by orphanage and stratification by district, were accounted for in the multivariable regression analysis. This was carried out using the survey commands in STATA13. A value of P<0.05 was considered as statistically significant. Overall, 1,137 children residing in 31 orphanages across the State of Kerala were recruited to the study. Female children made up 82% of the sample. In 6‐year‐old children the prevalence of caries was 77% and the mean dmft score was 3.60 (SD= 3.50); in 12‐year‐old children the prevalence of caries was 44% and the mean DMFTscore was 1.35 (SD = 1.96). Among 12‐year‐old children, those who reported being shown how to clean their teeth were less likely to have caries (odds ratio = 0.62; 95% confidence interval: 0.38–0.95). Caries rates among children in orphanages were much higher than among children in the general population in Kerala. There is an urgent need for evidence‐based and sustainable primary prevention strategies to reduce the burden of caries in this highly vulnerable population.

AbstractA Multiphysics numerical model was developed using COMSOL Multiphysics to study the effect of size, shape and position of catalyst bed within the microwave reactor (2450 MHz). The dielectric properties of HZSM-5 catalyst were measured at different frequencies and nine different temperatures ranging from 25 °C to 370 °C. The heat transfer in porous media was coupled with RF electromagnetics module and flow-through porous media by extracting the heat source term Qfor the heat transfer problem from the electromagnetics. A solid-fluid thermal non-equilibrium condition was modelled as the heat is generated within the catalyst. It was observed that sample position, shape and size of the sample, all significantly affect the heating profile and temperature gradient inside the porous media. The experimental results and the predicted temperatures were in good agreement. Microwave heating had higher total internal energy but conventional heating had lower temperature gradient after reaching steady state. Brick-shaped sample heats more uniformly compared to cylindrical sample. If the radius of the sample is decreased, while maintaining the volume of the sample, microwaves penetrate deeper inside the sample, and more uniform temperature distribution is observed throughout the length of the sample.

Fluidized catalytic cracking (FCC) is the most used process for converting heavy oil into more valuable fuels and chemical products such as gasoline and propylene. A three-dimensional reactive gas–particle CFD model was built to study the hydrodynamics, heat transfer, and cracking reaction behaviors within an industrial FCC riser reactor. The multiphase particle-in-cell methodology (MP-PIC) was used to simulate the riser hydrodynamics. A four-lump kinetic model was selected to represent the cracking reaction network in the CFD model. Hydrodynamics, heat, and cracking reactions interplay was discussed.The numerical results of this investigation show a good agreement with the process real data on the yield distribution. The effects of injection (nozzle angle, position, and direction) as well as the riser operating pressure on the yield distribution were quantified and discussed. The methodology employed and the results obtained should serve as guidelines for possible process re-design and optimization.

We have reviewed the development and the analysis of the coupled two degrees-of-freedom model of drill-string vibration, which assumes a state-dependent time delay and a viscous damping for both the axial and torsional vibration. This model corrects the instability deficiencies of the previous models but it is still based on a uniform angular distribution of blades on a drill-bit, which can lead to unrealistic regenerative types of instability. However, the model sheds some lights on the origin and the interplay between stick-slip and bit-bounce, the dangerous dynamic phenomena encountered during rotary drilling. The experimental rig developed by the Centre of Applied Dynamics Research at the University of Aberdeen is used to show some shortcomings of this model and to develop a new more realistic one. The new model assuming a non-uniform distribution of blades for drag type drill-bits is proposed.

Determining the internal pressure that a tubular joint can resist without leakage may reveal the reason why some API 8-round threads leak. The calculation presented here puts the concept in [...]

A boundaryfitted coordinates method was successfully employed in the evaluation of the discharge coefficients, as well as the freesurface profiles, for vertical and radial sluice gates for an ideal fluid. The values of the discharge coefficients and the free upstream and downstream surface profiles are in good agreement with the literature. Some details of the flow, such as the velocity profiles and the bed pressure deficit upstream of the gate, can also be predicted accurately. The boundaryfitted coordinates method was demonstrated to be a viable method in the study of fluid flow with initially unknown discharge and unknown freesurface profiles.

Analgesic, Anti-Inflammatory and Antiarthritic Activity of Newly Synthesized Bicyclothieno 1, 2, 3 - TriazinesAim:The present study was aimed to evaluate the novel bicyclo thieno 1, 2, 3-triazines (BTT) namely BTT-1, BTT-2, BTT-3 and BTT-4 for analgesic anti-inflammatory and antiarthritic activity.Materials and Methods:Analgesic and anti-inflammatory activity was evaluated using hot plate test, formalin induced paw licking test and formalin induced paw edema test respectively, complete fruend's adjuvant (CFA) induced arthritis model was used for antiarthrtic activity.Results:All the test drugs (BTT-1, BTT-2, BTT-3, BTT-4) have showed significant analgesic activity by increasing the reaction latency time in hot plate test(p<0.01, p<0.001, p<0.001, p<0.001) and decreasing the number of lickings in formalin test (p<0.01, p<0.05, p<0.01, p<0.01), BTT-3 was found to be effective in both early and late phase (p<0.001), while all other test drugs were found to be effective only in late phase of nociception. In anti-inflammatory studies, the BTT-3 (25 and 50mg/kg, i.p.) had significantly (p<0.01, p<0.001) reduced the formalin induced paw edema. In CFA induced arthritis model, the BTT-3 has showed activity from the 4thday of the treatment, while all the other test drugs(high dose) have showed significant inhibition of CFA induced paw edema from the 7thday of the treatment by decreasing the elevated levels of WBC (p<0.001, p<0.001, p<0.001, p<0.01), % Hb (p<0.05, p<0.01, p<0.01, p<0.05), ESR(p<0.01, p<0.01, p<0.001, p<0.01), along with decreasing the serum levels of C-reactive protein (CRP) (p<0.05, p<0.01, p<0.001, p<0.05) and Rheumatoid factor (p<0.05, p<0.01, p<0.001, p<0.05).Conclusion:In conclusion all test drugs were found to possess very good analgesic, anti-inflammatory and antiarthritic activity and BTT-3 was found to be more potent compare to other compounds.

The pressure drop and mass transfer efficiency for two‐phase flow in a structured packed column were simulated using a commercial CFD package, CFX version 10. The distillation of the methanol/isopropanol system was carried out in a 0.073 m diameter column, with an element composed of a ceramic structured packing and 0.053 m in height. The Height Equivalent to Theoretical Plate (HETP) value varied from 0.106–0.146 m. Pressure drop experiments were measured with an air/water system. The pressure drops at the flooding and loading points were ca. 173 and 580 Pa/m of packing, respectively. HETPs and pressure drops calculated from the Computational Fluid Dynamics (CFD) model were compared to their experimental counterparts. The average relative error between CFD predictions and the experimental data for the prediction of dry pressure drop, irrigated pressure drop and mass transfer efficiency are 20.3 %, 23 % and 9.15 %, respectively. In all cases, the CFD predictions show a good agreement with the experimental data, indicating that CFD is a reliable, cost saving and suitable technique for the design and optimization of separation processes.

Background:The genes encoding the human leukocyte antigens (HLAs; major histocompatibility complex [MHC]) have been considered candidate markers for periodontitis because they are involved in regulating immune responses. Several studies have examined this association, and despite the inconclusive results, the antigens HLA‐A9 and HLA‐B15 have been found to be consistently associated with the destructive forms of periodontitis in many populations. Ethnic factors are considered to be a major variable for evaluating the predisposition to the disease. The purpose of the present study was to: 1) assess the association of HLA‐A*9 and HLA‐B*15 with generalized aggressive periodontitis (GAgP) and 2) evaluate the role of these genetic risk factors in influencing the severity of GAgP in a South Indian population. Methods:Forty GAgP patients (cases) and 80 periodontally and systemically healthy subjects (controls) participated in this study. HLA‐A*9 and HLA‐B*15 typing was carried out using the polymerase chain reaction with sequence specific primers (PCR‐SSP)‐based molecular method. Results:HLA‐B*15 was a significant risk factor for GAgP and was positively correlated with the disease severity, whereas HLA‐A*9 had no association with the disease. The haplotype of HLA‐A*9:B*15 did not impart any additional risk for GAgP compared to that imparted by HLA‐B*15 alone. Conclusions:To our knowledge, this is the first report on HLA‐B*15 association with GAgP in an Indian population. The finding of HLA‐B*15 as a risk factor may have potential use in the future management of GAgP. The precise disease‐causing mechanism of this HLA disease association and whether this association is “causal” or “casual” need to be evaluated further.

Background:The microorganism Helicobacter pylorihas been closely linked to chronic gastritis, peptic ulcer, gastric cancer, and mucosa‐associated lymphoid tissue (MALT) lymphoma. Despite the current treatment regimens that lead to successful management of H. pylori‐positive chronic gastritis, the reinfection rate is high. It has been suggested that one of the possible mechanisms of reinfection is the recolonization from dental plaque. The purpose of this study was to determine whether dental plaque, poor oral hygiene, and periodontal disease were risk factors for H. pyloriinfection. Methods:Among the 134 patients, 65 patients who had a positive H. pyloriserology or positive rapid urease test or histologic evidence for the presence of H. pyloriin antral biopsy specimens were categorized as cases. The remaining 69 patients who were negative for H. pyloriserology, the rapid urease test, and histology were controls. Results:It was found that the association of periodontal disease and poor oral hygiene with H. pyloriinfection was not significant. There was a higher prevalence of H. pyloriin the dental plaque of patients with gastric H. pyloriinfection than in controls, but both groups had a surprisingly high positive urease test for H. pyloriin plaque (89% and 71%, respectively). Conclusions:H. pyloriin dental plaque is seldom eliminated by H. pylori‐eradication therapy, and this may act as a source for future reinfection. Hence, eradication of H. pylorifrom the dental plaque should be made an important part of comprehensive management of H. pylori‐associated gastric diseases.

Background:Chronic periodontitis is an inflammatory disease found mainly in adults. Little is known about molecular level changes associated with host response in this condition. Nuclear factor‐κB (NF‐κB) is a transcription factor implicated in immune and inflammatory responses. NF‐κB activation has also been reported to be associated with many chronic inflammatory diseases. The purpose of this paper was to compare the nuclear and cytoplasmic expression of NF‐κB transcription factor (p50/p65) and cytoplasmic expression of IκB in periodontal tissues of periodontitis patients and controls. Methods:Twenty patients with chronic periodontitis and 20 healthy controls were included in the study. Gingival tissues taken during extraction were processed for immunohistochemical staining and evaluation. Results:Nuclear (activated) p50 was found in 90% of periodontal patient tissues compared to only 30% of healthy tissues. A more significant result was obtained with p65 (75% versus 5%). Intense cytoplasmic immunoreactivity was also observed in periodontitis tissues. IκB, the inhibitor of NF‐κB, was expressed only in 5% of periodontally diseased tissues. Conclusion:Activation of NF‐κB (p50/p65) is significant in periodontally diseased tissues, suggesting the potential of inhibitors of NF‐κB in managing periodontitis. J Periodontol 2005;76:1148‐1153.

The in‐vivo β‐adrenoreceptor antagonistic activity of test compounds DPJ 955 and DPJ 890 was assessed against β‐adrenoreceptor agonist (isoprenaline) induced tachycardia in anaesthetized rats. The selectivity to block isoprenaline responses on different β‐adrenoreceptor subtypes (β1, β2and β3) of the test compounds was carried out on isolated rat right atria, isolated rat uterus and isolated rat colon preparations, respectively. Intravenous injection of isoprenaline alone in anaesthetized rats caused hypotension and tachycardia. DPJ 955 or DPJ 890 alone produced a fall in mean arterial pressure and bradycardia in a dose‐dependent manner. Administration of isoprenaline to anaesthetized rats pre‐treated with test compounds significantly blocked both the tachycardial and hypotensive responses induced by isoprenaline. The test compounds shifted the concentration response curves of isoprenaline towards the right for isolated rat right atrial preparations, rat uterus and rat colon, indicating β1, β2and β3adrenoreceptor blockade, respectively. The selectivity ratio for β1/β‐adrenoreceptors to DPJ 955 and DPJ 890 was 64.6 and 83.2, respectively. DPJ 890 was more potent in blocking β1‐adrenoreceptors and was more selective towards β1receptors than to other β‐adrenoreceptor subtypes. In conclusion, DPJ 955 and DPJ890 have β‐adrenoreceptor blocking activity with high selectivity for the β1‐adrenoreceptor subtype.

The melting and deformation mechanisms of polystyrene (PS) and polypropylene (PP) blends were investigated through on-line visualization of the co-rotating twin-screw extrusion process. Two compositions, PP/PS (80:20) and PS/PP (80: 20) were chosen as the model systems for this study. A sliding barrel technique was used to realize the on-line visualization using a glass window in the barrel. The axial temperature and pressure profiles along the screw channel were measured using the same sliding technique. It was found that in the PP/PS (80:20) blend, in which PP was the major phase, there was a combined melting of PS and PP, whereas in the PS/PP (80:20) blend, in which PS was the major phase, there was initial melting of PS alone and then combined melting of PS and PP. In the partially filled region, heat conduction from the hot barrel was the major source for heating polymer pellets under the conditions studied here; while in the fully filled region, viscous energy dissipation (VED) generated most of the heat for melting of polymer pellets. The pressure profiles along the extrusion channel gave us insight into the melting process for the two blends. It was found that if there was some molten polymer in the fully filled region, the overall melting process was accelerated due to heating from viscous dissipation.

A perturbation (or pulse) method was used to investigate the melting of a polystyrene/polypropylene (PS/PP) blend in a 40-mm twin-screw extruder (TSE). A sliding-barrel technique was used to visualize the melting processes, map the temperature and pressure profiles along the channel, and obtain the residence time distribution (RTD) at different locations in the extruder. Pressure, pulse, and visualization results were used to determine where melting occurred. Three runs with ratios of the flow rate/screw speed (Q/N) varying from 5.0 to 11.3 g/revolution were studied. It was found that the melting of the PS/PP blend in the TSE had three distinct regions. Most of the melting occurred in a narrow transition region (~50 mm) from the partially filled region to the fully filled region. The location of the transition region was found using four different techniques:  visualization, pressure, temperature, and combined pulse/RTD methods. High-speed video of the extrusion processes shows that the solid polymer pellets melted through an “erosion” mechanism. Mechanical energy consumption for melting can be obtained through this perturbation method.

AbstractPeriodontal diseases are essentially infectious in origin, their outcome depending on interaction between the pathogenic challenge and host response. Nevertheless the presence of an underlying genetic predisposition cannot be overlooked. HLA antigens have been considered as risk factors for periodontitis. The aim of the present study was to investigate the HLA-A*9 and HLA-A*10 association with aggressive periodontitis in the south Indian population. A significant increase of the HLA-A*24 antigen was observed in the patient group compared to the control samples. A positive association of HLA-A*24 with aggressive periodontitis was also noticed. HLA-A*10 did not vary significantly in both the study groups and is not having an association with disease. HLA typing was carried out using polymerase chain reactions with sequence specific primers (PCR-SSP).

We have extended our previous work on the modeling of geometry, liquid trickle flow, and pressure drop to study the mass-transfer process in a packed column. On the basis of the penetration theory and the detailed information of lateral and axial variations in packing geometry and fluid dynamics from our previous models, a predictive mass-transfer model has been developed on the scale much smaller than a packing particle in the case of random packings or a flow channel in the case of structured packings. Distillation experiments have been carried out with methanol/2-propanol and methanol/water for 16 mm metal Pall rings. The model has been validated with the experimental results and our previous data on a novel vertical-sheet structured packing. Simulations for uniform and uneven initial distributions have been carried out, which showed a strong influence of liquid-flow distribution on mass-transfer efficiency in a packed column.

The heat transfer of a single solid cylindrical poly(ether imide) (PEI) pellet in polyethylene (PE) melt under simple shear flow was studied using experiments and numerical simulations. This included two approximate 2‐D representations of the geometry, and a rigorous 3‐D geometry matching the experimental conditions. A generalized power‐law viscosity model for PE melt, and temperature‐dependent conductivity and specific heat were used for PEI in the models. Viscous dissipation was included in the simulations. From the experimental temperature history, the mean heat‐transfer coefficient &hmacr; was determined to be 370 W/m2·K, with the assumption of a uniform convective environment. From the simulation, &hmacr; was determined to be 1,160 W/m2·K and 420 W/m2·K in the 2‐D simulations with circular and rectangular pellet, respectively, and 250 W/m2·K for the 3‐D simulation. Results from the 3‐D simulation proved that the uniform convection assumption used to calculate &hmacr; for the experiment was not acceptable.

A computational fluid dynamics (CFD) model was used to predict the flow patterns and hydraulics of a commercial‐scale sieve tray. The model considers the 3‐D two‐phase flow of gas and liquid in which each phase is treated as an interpenetrating continuum having separate transport equations. Interaction between the two phases occurs via an interphase momentum transfer. For the CFD analysis, the commercial packages CFX5.4 and CFX4.4 of AEA Technology were employed. Velocity distributions, clear liquid height, froth height, and liquid holdup fraction in froth were predicted for various combinations of gas and liquid flow rates. Tray geometry and operating conditions were based on the experimental work that Solari and Bell carried out in a 1.22‐m diameter air–water simulator in 1986 at Fractionation Research Inc. Predicted results were found to be in good agreement with the experimental data of these authors. The objective of the work was studying the extent to which CFD can be used as a prediction and design tool for industrial trays. The simulation results are such that CFD can be used as an invaluable tool in tray design and analysis.

This paper is concerned with producing highly accurate solution and bifurcation structure using the pseudo‐spectral methodfor the two‐dimensional pressure‐driven flow through a horizontal duct of a square cross‐section that is heated by a uniform flux in the axial direction with a uniform temperature on the periphery. Two approaches are presented. In one approach, the streamwise vorticity, streamwise momentum and energy equations are solved for the stream function, axial velocity, and temperature. In the second approach, the streamwise vorticity and a combination of the energy and momentum equations are solved for stream function and temperature only. While the second approach solves less number of equations than the first approach, a grid sensitivity analysis has shown no distinct advantage of one method over the other. The overall solution structure composed of two symmetric and four asymmetric branches in the range of Grashof number (Gr) of 0–2 × 106for a Prandtl number (Pr) of 0.73 has been computed using the first approach. The computed structure is comparable to that found by Nandakumar and Weinitschke (1991) using a finite difference scheme for Grashof numbers in the range of 0–1×106. The stability properties of some solution branches; however, are different. In particular, the two‐cell structure of the isolated symmetric branch that has been found to be unstable by the study of Nandakumar and Weinitschke is found to be stable by the current study. Copyright © 2002 John Wiley & Sons, Ltd.

Our previous work on the simulation of packing processes was extended to study the liquid trickle flow down randomly packed beds. An algorithmic procedure with detailed geometrical description of packing elements was developed for tracking the liquid flow and holdup distributions in packed beds. Unlike the conventional continuum‐based models such as the diffusion model, it goes into the subparticle scale to capture the geometrical characteristics of the packed bed. Three mechanisms of the trickle flow—film flow, dripping flow, and splash—were observed in packed beds, and the first two were captured in the model. At each point within a packed bed, liquid flow is simplified to two possible directions: vertically down and horizontally in the direction of the negative gradient of the packing surface. The 3‐D geometric model constructed with the packing process simulation was used to determine the direction of the horizontal flow and fraction of the flow rate in each direction. By assuming that the liquid flow is uniform free surface flow, the Manning formula was used to predict the liquid holdup with the width of the liquid rivulet on a packing surface calculated by the Shi and Mersmann correlation. Metal Pall rings and metal Raschig rings were simulated with water as the fluid. Results of liquid flow distributions and average liquid holdup were validated against experimental data and semiempirical correlation from Billet et al.

Vertical gravity settling vessels, usually referred to as primary separation vessels (PSV), are used in separating bitumen aggregates from slurry containing sand and fine clays. The hydrodynamics in the PSV influences the separation efficiency of recovered bitumen through the overall mean flow and turbulent interaction. In order to deepen our understanding of the hydrodynamic conditions in such vessels, this paper presents a combined study of the flow field using Laser Doppler Anemometry (LDA) to measure the velocity field, and computational fluid dynamics (CFD) simulations to validate the CFD model. The investigation shows that the flow geometry has a significant influence on the overall flow pattern in such vessels. It also demonstrates that the CFD simulation is a reliable tool in capturing the complex mean flow pattern observed in experiments. Use of different turbulent models such as the standard k‐ε model and Reynolds stress model has very little effect on the mean flow field.

The volume-averaged equations for velocity and concentration fields have been used to simulate the hydrodynamics and mass-transfer processes in randomly packed distillation columns. This approach is regarded as a second-generation computational fluid dynamics (CFD) based model, and a significant departure from the traditional one-dimensional, first-generation models. The model has ability to capture radial and axial variations in flow and mass-transfer conditions. The spatial variation of void fraction has been included to take into account the effect of bed structures. The simulation results have been compared with experimental data reported by Fractionation Research, Inc. (FRI) which performed their tests in a 1.22-m-diameter column with a packed bed height of 3.66 m. For validation, we have used data obtained with 15.9-, 25.4-, and 50.8-mm metal Pall rings at various operating conditions. Good agreement between CFD predictions and published experimental data has been obtained. This is regarded as an encouraging sign that CFD models can play a useful role in studying separation processes.

Letter to the Editor

Multiphase flow modelling is still a major challenge in fluid dynamics and, although many different models have been derived, there is no clear evidence of their relevance to certain flow situations. That is particularly valid for bubbly flows, because most of the studies have considered the case of fluidized beds. In the present study we give a general formulation to five existing models and study their relevance to bubbly flows. The results of the linear analysis of those models clearly show that only two of them are applicable to that case. They both show a very similar qualitative linear stability behaviour. In the subsequent asymptotic analysis we derive an equation hierarchy which describes the weakly nonlinear stability of the models. Their qualitative behaviour up to first order with respect to the small parameter is again identical. A permanent-wave solution of the first two equations of the hierarchy is found. It is shown, however, that the permanent-wave (soliton) solution is very unlikely to occur for the most common case of gas bubbles in water. The reason is that the weakly nonlinear equations are unstable due to the low magnitude of the bulk modulus of elasticity. Physically relevant stabilization can eventually be achieved using some available experimental data. Finally, a necessary condition for existence of a fully nonlinear soliton is derived.

Using advances in computational geometry and collision‐detection algorithms, an algorithm was developed to analyze and predict the geometrical properties of a randomly packed structure using packing objects of arbitrary shape. A 3‐D polygonal model was used to describe an arbitrarily complex packing object and a simple container object. The dynamics of the packing process is not simulated, but a search algorithm finds stable equilibrium positions for the packing objects of arbitrary shapes using a collision‐detection algorithm in a 3‐D space. A modified conjugate gradient optimization method determines the packing object's final packing location and orientation. Once the bed is packed, both macroscopic quantities like the overall porosity, the specific surface area, and the number of packing objects per unit volume and microscopic properties like the porosity variation in any direction could be determined. For accurate porosity calculation inside a given 3‐D polygonal sample space, the Sutherland‐Hodgman polygon clipper algorithm was used. Predicted results are validated against available experimental data for spheres, Raschig rings, Pall rings, and cascade minirings.

Many fundamental studies based on the evolution equations derived by long-wave approximation have contributed to the fact that the dynamics of a thin film flowing down an inclined plane is now one of the best-understood problems of hydrodynamic stability. In most engineering applications however, the stability behaviour of the film flow is modified by complex coupled transport processes, and because of the huge amount of algebra needed to derive the evolution equations in these cases, an investigation by numerical methods is often preferred by engineers. In this paper, we illustrate how computer algebra techniqes can be used to derive and analyse long-wave evolution equations even for very complex situations automatically, thus making the advantages of symbolic solutions available for such applications. Using these methods, higher-order approximations can also be obtained automatically. These are of interest since they can provide heuristic estimates for—and extensions of—the range of validity of the long-wave approximation.

AbstractFine-multiple emulsions bearing 6-mercaptopurine (6-MP) in internal aqueous phase were prepared by two step emulsification using sonication technique. It was coated with Concanavalin-A (Con-A) using carbodiimide method to obtain lectin-functionalized multiple emulsions. The Con-A coated multiple emulsion was characterized for antitumour activity on murine leukemia cell line L-1210 in vitroand compared with uncoated multiple emulsion and free drug. An increased uptake and cytotoxicity were observed for Con-A coated multiple emulsion in vitro.The IC50 was decreased upto 4-fold with Con-A coated emulsion. In vivoantitumour activity was seen by recording survival times of mice injected with L-1210 cells i.v. or i.p. The mean survival time was found to increase upon treatment with Con-A coated multiple emulsion. The tumour cell count in the peritoneal cavity was decreased significantly when animal was treated by i.p. route while there was no significant difference when it was treated by i.v. route. The normal peritoneal cells remained unaltered in number and blood parameters were also restored on treatment to tumour bearing mice. The formulation was found to be effective for the treatment of cancer.

The relative importance of colony size ratio of interacting species was studied in Tomioka Bay, Japan. Six encrusting colonial species belonging to the following three different taxonomic groups were tested: Ascidia (three species), Bryozoa (two) and Porifera (one). Colonies of these organisms were grown in the community of sessile organisms developed on plastic panels. Logistic regression analysis was carried out to determine the effect of size ratio on the competitive outcome of interacting colonies. The results between all possible combinations among these six species did not show a significant size effect in competitive outcome (i.e. a larger colony size did not always prove important in the success of a competitive interaction with smaller colonies of other species). On the contrary, competitive success depends on the types of species interacting. Certain species such as Didemnum moseleyi(ascidian) and Haliclonasp. (sponge), in spite of being smaller in colony size, won in competitive interactions with larger colonies of other species such as Diplosoma mitsukurii(ascidian) and Watersipora subovoidea(bryozoan). These results contradict the one reported earlier: that the larger the colony size, the more chance the colony will have to win in competitive interactions.

This paper demonstrates the constrained predictive control of linear multivariable systems based on models identified using a Dynamic Projection to Latent Structures (Partial Least Squares or PLS) algorithm. Though conventional control of systems using such models have been reported elsewhere (Kaspar and Ray (1992, 1993), Lakshminarayanan et al. (1996)), they are not suited for practical applications owing to their inability to handle constraints. A simple modification of the constraints provides a framework wherein the PLS based models can be incorporated in existing model based predictive control algorithms. The theory is supported using simulation as well as laboratory experiments.

The heat transfer characteristics of a Newtonian fluid in a two-dimensional, planar, right-angled tee branch are studied over a range of inlet Reynolds numbers and Grashof numbers. The flow and heat transfer equations, subject to the Boussinesq approximation, are solved using a finite-element discretization. The effects of the branch length and the grid size on the interior flow field are examined to assess the accuracy of the solutions. Results are presented for two types of experimentally realizable boundary conditions—equal exit pressure at the outlet of each branch and specified flow split between the branches. The thermal boundary condition of uniform wall temperature is examined. The effect of increasing Reynolds number is to increase the size and strength of the recirculation zones in both the main and side branches, while that of increasing Grashof number is to decrease such an effect. For the case of equal exit pressures there is a significant flow reversal in the side branch and the exit flow rate from the main branch increases linearly with increasing Gr/Re2. For the case of specified flow split, an increasing back pressure is required to be maintained at the exit of the main branch to regulate the flow split at the desired level.

Fluid flow and heat transfer characteristics in a twisted rectangular tube having an aspect ratio of two were studied using a numerical solution to the momentum and energy equations. Fluid flow solutions are presented for a fully developed laminar flow of a Newtonian fluid. Heat transfer results are presented for the case of axially uniform wall temperature. For the case of peripherally uniform wall temperature, the overall Nusselt number in a twisted rectangular tube was found to be higher than a straight tube by up to 30 percent over certain ranges of twist lengths. However, for the case of non-uniform wall temperature, the overall absolute Nusselt number increased very rapidly with decrease in the twist length