A dynamic analysis of chalcopyrite bioleaching in continuous flow reactor systems

A dynamic analysis of chalcopyrite bioleaching was performed in continuous flow systems. In contrast to a previous batch analysis¹ in which the influence of particle surface area on reaction rate was not accounted for, the unsteady‐state change in particle surface area was integrated into the dynamic analysis by application of the modified PBM.² The current study extends the analysis to include the influence of convective flow on the system. It is demonstrated that the analysis can be used to determine feasible control strategies for operating near the steady‐state maximum rate that is stable. Two strategies were evaluated for the purpose of increasing the leaching rates, showing that an increased rate of 56% is feasible. Analysis on experimental data showed that increased rates can be achieved by controlling the biomass concentration and ferric:ferrous ion ratio at an optimum by increasing the solids loading [m/v] in the reactor. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2428–2440, 2012     

Effect of bandwidth modifications on the quality of speech imitated by Alexandrine and Indian Ringneck parrots

Alexandrine and Indian Ringneck parrots are known for imitating the voice of other animals. The objective of this paper is to estimate the spectral limits of the imitated sounds produced by parrots and quantify the quality. The investigations showed that 500–3000 Hz spectral band is adequate for retaining the important perceptual information in the phrases uttered by human speakers and imitated by parrots. Investigations confirmed that the Indian Ringneck parrots are capable of following the formant structure and pitch contour of the phrases uttered by the human subjects. The dynamic range of the pitch of Indian Ringneck parrots was observed as higher than that of the human subjects. A rise of about 1000 Hz in the formant F1 of the parrots was observed, indicating the tongue height small and beak opening, relatively large, as compared to that of human subjects. The quality of some of the synthesized and processed phrases was found slightly better as compared to that of the original phrases because of the inherent enhancement capability of the Harmonic plus noise model (HNM). The average Mean opinion score (MOS) score of the Indian Ringnech parrots for the original, synthesized, and processed phrases was observed as 2.65, 2.59, and 2.77, respectively. The investigations may be beneficial for studying the behavior of endangered birds, defense related activities, safeguarding the crashes with aero planes, and safeguard of the birds from wind power generator etc.     

An Approach for Estimation of Cathode Voltage Drop in an Aluminum Reduction Cell with an Inclined Carbon Block and a Copper Insert

Numerical models of a cathode block assembly in a Hall–Hèroult cell, comprising of liquid aluminium, carbon block, current collector, ramming paste and a copper insert were built and the finite element method simulations were carried out to model the cathode voltage drop (CVD), the current distribution and, the effect of geometrical parameters on the CVD. The objective of the study was to quantify the drop in the CVD for different cathode assembly design. Flat- and inclined-interface carbon block top-surface and a copper insert versus the conventional insert-free designs were simulated with a myriad of other geometrical parameters to optimise the design. The results informed about the optimum insert positioning to about 75 mm from the collector base and the energy saving possibilities due to reduction in the CVD with a cathode design with inclined-interface carbon block and copper insert in the collector bar.     

Free sugars and their relationship with grain size and starch content in developing wheat grains

Free sugars in wheat varieties, at different stages of grain development and differing in grain size and starch content per grain, were analysed to determine any relationship with grain size and starch content. Fresh and dry weight (mg per grain) of developing grain increased with maturity until 35 days after anthesis. Fresh weight declined after 35 days but dry weight remained almost constant. Water content increased until the 21 and/or 28 day stage and then decreased. Active starch synthesis started from 14 days onwards and continued until 35 days after anthesis. Free sugars (total sugars, reducing sugars, non-reducing sugars and sucrose) per grain followed closely the changes in the rate of starch accumulation and, in general, were maximum at the 14 day stage followed by a decline up to 28 days, with no significant alteration afterwards. Presence of adequate amounts of soluble sugars in grain even when starch synthesis had stopped suggested that the supply of sugar precursors did not limit starch synthesis. None of the sugars was found to have a significant relationship with either grain size or starch content. A hypothesis explaining the termination of starch accumulation in developing cereal grains has been proposed.     

Effect of thermal processing on phenolics, antioxidant activity and health-relevant functionality of select grain sprouts and seedlings

The effect of thermal processing via autoclaving on modifications of total phenolics, antioxidant activity and functionality of wheat, buckwheat, corn and oats sprouts and seedlings were investigated. Functionality for type 2 diabetes related α-amylase, α-glucosidase inhibition and levo-dihydroxy phenylalanine (l-DOPA) content, hypertension related angiotensin converting enzyme 1 (ACE) inhibition and ulcer related Helicobacter pylori inhibition were evaluated using in vitro assays. Thermal processing in general resulted in tissue browning leading to higher total phenolic content and free radical scavenging-linked antioxidant activity. It increased α-amylase inhibitory activity in buckwheat and oats but decreased in wheat and corn sprouts and seedlings. It increased α-glucosidase inhibitory activity in wheat, buckwheat and oats but decreased in corn sprouts. It reduced the cognitive function/diabetes related l-DOPA content in all grains sprouts and seedlings tested. It increased ACE inhibitory activity in buckwheat and oats, but decreased in wheat and corn sprouts. It also improved the ulcer related H. pylori inhibitory activity in all grain sprouts and seedlings studied. These changes in functionality are suggested to be due to modifications in the total phenolic content and profile by phenolic oxidation or polymerization caused by thermal processing. Therefore, diet designs for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles.

Industrial relevance

Thermal processing altered the total phenolic content and antioxidant activity in winter wheat, buckwheat, corn and oats sprouts and seedlings. It modified the α-amylase inhibitory activity, α-glucosidase inhibitory activity, l-DOPA content, ACE inhibitory activity and H. pylori inhibitory activity of samples. Therefore, the food processing industry and diet design for chronic disease management will have to consider thermal processing-linked modification of bioactive ingredient profiles for more effective health benefits.     

Synthesis of enhanced biosurfactant by Bacillus subtilis MTCC 2423 at 45°C by foam fractionation

Production of a lipopeptide surfactant in a 6.5-L batch fermentor was carried out using Bacillus subtilis MTCC 2423 at 45°C. A good yield was obtained from sucrose (2%) substrate fermentation by continuous removal of the product by foam fractionation. The biosurfactant was recovered from collapsed foam by acid precipitation. The biosurfactant yield (4.5 g/L) was about 4.5 times higher than the yield (ca. 1 g/L) obtained by shake-flask fermentation. Surface activity of the collapsed foam was very high, and total surface activity was observed in the collapsed foam. The structural characterization of this biosurfactant produced at 45°C by the strain used in this study was recently reported. The biosurfactant was analyzed by thin-layer chromatography, infrared, ¹H nuclear magnetic resonance, and mass spectroscopy and was found to be identical to surfactin, a lipopeptide surfactant.     

Numerical results of Emden–Fowler boundary value problems with derivative dependence using the Bernstein collocation method

In this paper, we propose an efficient numerical technique based on the Bernstein polynomials for the numerical solution of the equivalent integral form of the derivative dependent Emden–Fowler boundary value problems which arises in various fields of applied mathematics, physical and chemical sciences. The Bernstein collocation method is used to convert the integral equation into a system of nonlinear equations. This system is then solved efficiently by suitable iterative method. The error analysis of the present method is discussed. The accuracy of the proposed method is examined by calculating the maximum absolute error and the \(L_{2}\) error of four examples. The obtained numerical results are compared with the results obtained by the other known techniques.

     

High‐performance waterborne coatings based on epoxy‐acrylic‐graft‐copolymer‐modified polyurethane dispersions

Polyurethane dispersions (PUDs) have been an active area of research since the early 1940s because of legislative restrictions on the use of organic solvents in conventional solvent‐based products and also because PUDs exhibit almost the same high performance levels as solvent‐borne polyurethanes. In the present study, properties of conventional waterborne PUDs are modified with epoxy‐acrylic graft copolymer blocks. The epoxy‐acrylic graft copolymers were first modified with ethylene diamine to give amine‐terminated blocks which in turn reacted with isocyanate‐terminated prepolymer (prepolymer mixing process) to give modified PUDs. Several experimental sets were prepared with varying compositions. The experimental sets were also prepared using conventional poly(ethylene glycol) blocks and ethylene diamine chain‐extenders. The physico‐chemical properties and film characteristics of the experimental sets show the dramatic improvement in important mechanical properties of PUDs due to grafting with epoxy‐acrylic copolymer blocks. Copyright © 2004 Society of Chemical Industry     

Changes in fatty acid composition of phospholipids from liver microsomes and nuclei in rats fed a choline-free diet

Male F-344 rats were fed a choline-free (CF) diet, and changes in phospholipid content, phospholipid fatty acids and phospholipase A₂ activity in liver nuclei and microsomes were examined during the first 72 hr. Both nuclei and microsomes showed a decrease in phosphatidylcholine (PC) content. Microsomes showed an increase in PC arachidonate while nuclei showed a decrease. Also, microsomes showed increased activity of phospholipase A₂ (PLA₂) while nuclei did not. These observations are consistent with the hypothesis that the absence of diene conjugates in liver microsomes in the rats on the CF diet may reflect the increased rate of removal of peroxidized fatty acids by phospholipase A₂.