Hydrodynamics of slug flow inside capillaries

Understanding the motion of long gas bubbles (gas slugs) inside capillaries is a challenging problem that is relevant in many processes of chemical and biological interests. It has been proved by many workers that such long gas bubbles can be used successfully in enhancing mass and heat transfer in many chemical and biological processes. In order to quantify and understand this enhancement a light was shed on the hydrodynamics of such a flow pattern. The volume of fluid method implemented in the commercial CFD package, Fluent, is used for this numerical study. Velocity and bubble profile were obtained as functions of capillary number. Computed values of the bubble velocity and diameter were in excellent agreement with published experimental measurements. The detailed velocity field around the bubble was also computed and compared favourably with those experimental results reported in literature.     

Compatibilization of a polyolefin blend through covalent and ionic coupling of grafted polypropylene and polyethylene. I. Rheological,thermal, and mechanical properties

A polypropylene/high‐density polyethylene blend containing 70 wt % polypropylene was prepared and compatibilized via the addition of maleic anhydride grafted polypropylene and polyethylene. The functionalized polymer chains were coupled with two types of coupling agents. Dodecane diamine formed covalent bonds with the maleic anhydride, whereas two metallic salts, zinc acetate and sodium hydrogenocarbonate, formed ionic interactions with the carboxylic functions produced by the hydration of the anhydride cycle. The coupling of the grafted polyolefin chains was successfully realized by a single operation in a twin‐screw extruder. The coupling agents were efficient in improving the elongation at break and impact properties of the studied blends. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 312–320, 2005     

Telomerization of Butyl Methacrylate and 1‐Octadecanethiol by Reactive Extrusion

Butyl methacrylate and 1‐octadecanethiol telomers were prepared by radical reactive extrusion. The main advantages of the use of this processing technique are that mass reactions can be conducted and continuous production is achieved within a reduced reaction time and a correct temperature control. Preliminary studies concerned the choice of the reactants for the telomerization reaction and the adaptation of the telomerization reaction to the reactive extrusion process. The transfer constant to C₁₈H₃₇SH was measured, and then experimental studies were conducted to verify that the hypothesis and approximations made for kinetic modeling are realistic. Particularly, it was shown that the use of relatively high chain‐transfer agent to monomer concentration ratio had no perceptible effect on the monomer conversion kinetic. These results allowed the choice of reactive extrusion conditions. Telomers were prepared using a laboratory co‐rotating twin‐screw extruder. The effect of reaction conditions (temperature, 1‐octadecanethiol to monomer concentration ratio) and of processing conditions (throughput, screw rotation speed) on the residence time distributions, molar mass and monomer conversions were examined. This study allowed the continuous synthesis of butyl methacrylate telomers having variable controlled molar masses and complete monomer conversion.

Screw profile used in reactive extrusion telomerization.     

Enhancing Nutraceutical Performance Using Excipient Foods: Designing Food Structures and Compositions to Increase Bioavailability

The oral bioavailability of many bioactives (pharmaceuticals, dietary supplements, nutrients, and nutraceuticals) is limited because of physicochemical and physiological events that occur within the gastrointestinal tract (GIT) after their ingestion. These events include: (i) restricted liberation from drugs, supplements, or foods; (ii) extensive metabolism or chemical transformation during passage through the GIT; (iii) low solubility in intestinal fluids; (iv) low permeation through the intestinal cell monolayer; and (v) efflux from epithelium cells. Bioactive bioavailability can often be improved by designing the composition and structure of food matrices to control their liberation, transformation, solubilization, transport, absorption, and efflux in the GIT. This article reviews the potential impact of food composition and structure on the oral bioavailability of bioactives, and then shows how this knowledge can be used to design excipient foods that can improve the bioavailability profile of bioactives. The bioactive may be incorporated within an excipient food or co‐ingested with an excipient food. The suitability of oil‐in‐water emulsions as excipient foods is highlighted. The utilization of excipient foods may provide a new strategy for improving the efficacy of nutraceuticals, supplements, and pharmaceuticals.     

Effect of different starter cultures on the biogenic amines production as a critical control point in fresh fermented sausages

The selection of critical control points is one of the most important steps in the design of a hazard analysis and critical control points system. In this study, the influence of starter culture inoculation on biogenic amine accumulation in fresh fermented sausage as critical control point was studied. The effect of three starter culture Lactobacillus plantarum plus Bifidobacterium lactis, L. plantarum plus Bifidobacterium bifidum or L. plantarum plus B. lactis and B. bifidum on amines production were investigated. Tyramine (TY), Cadaverine (CA), Putrescine (PU), Histamine (HIS) and Tryptamine (TR) contents increased during the fermentation and storage stage, and TY was the prevailing amine in the final product. Sausages produced by fermentation with starters, as compared to natural fermentation (control), had a lower amount of biogenic amine. A great reduction in biogenic amine content was achieved when Bifidobacterium sp. were inoculated, also levels of species of Enterobacteriaceae and Pseudomonas decreased, while lactic acid bacteria counts increased during fermentation and storage.     

Review on river bank filtration as an in situ water treatment process

Surface and ground water are valuable sources for drinking water. Certain industrial, mining, and agricultural practices pollute these critical resources. Riverbank filtration (RBF) is a cost-effective in situ water treatment process, which removes suspended solids and organic and inorganic pollutants. The RBF process is defined as a natural filter of soils and aquifer sediments at the river site. In RBF, river water moves through the pores of the natural soils of the riverbed and riverbank. RBF improves several physical, chemical, and biological properties of the river water. Several treatment actions including, filtration, sorption, and biological degradation occur during this process. Under specific conditions, RBF could be used as a treatment or pretreatment process to remove or decrease pollutants in surface water. In this paper, the effectiveness of RBF in improving the river water quality is presented. RBF as a cost-effective water treatment process is also discussed. Furthermore, factors that affect the performance of the RBF process and its overall effectiveness for developing countries are also discussed.     

Tobit model analysis of mutations causing haemophilia

Haemophilia A is a genetic disease resulting from deficiency of factor VIII. The database of mutations causing haemophilia A has been developed by the worldwide collaboration. In this study, we predicted the severity of haemophilia A using ordinary least squares regression (OLS) and Tobit model regression in factor VIII. As parameters, we used four physical–chemical parameters of amino acids and the accessible surface area. As the result, there is a difference between OLS and Tobit model analysis in the prediction of haemophilia A severity. We found that the predicted value by Tobit model in severe data is close to the observed value. These results suggest that Tobit model regression analysis is superior to estimating severity of haemophilia A in severe data than OLS.     

Development and Background of Shells Theories-A Review Study

Thin shells are one of the structural elements that have versatile contributions in different engineering sectors,specifically in architectural,civil,mechanical,aeronautical,and marine engineering industries.Liquid-retaining structures,wide-span roofs,water tanks,arch dooms,and shells used in building nuclear power plants are recognized application examples of shell structures in architectural and civil engineering.This variety in using shells in different engineering sectors is due to the productivity of load-carrying behavior,excellent reservation in strength and structural integrity,shell structures are preferable in comparison to structural systems having the same span and dimensions;high stiffness,and covering a large areas.Besides the above distinguishing mechanical pros,it is widely accepted that structures and building containing shells are usually preferred by architectures and designers for aesthetic purposes.The analysis of shells has gone through many stages until the arrival of modern theories.In this study the different theories of shells were discussed,the background and development of shell theories were illustrated in this investigation.