Presence Of Stirring Research Articles

Microencapsulation of Probiotics with Soy Protein Isolate and Alginate for the Poultry Industry.

Many probiotic products, with properly selected microorganisms, may not be effective for the intended purpose due to the low tolerance of microorganisms to gastrointestinal digestion. The microencapsulation seems to be one of the most promising techniques to protect probiotics against adverse environmental conditions. Therefore, the aim of this work was the design of soy protein isolate-alginate microcapsules for the encapsulation of probiotics for the poultry industry by the water-in-oil emulsion technique. To this end, the strain Ligilactobacillus salivarius CRL2217, with the ability to bind wheat germ agglutinin (WGA) on its surface and protect intestinal epithelial cells from the cytotoxicity of the glycoprotein, was used as model microorganism. Several parameters were varied in order to find the better conditions for microencapsulation: oil source and nature, SPI and sodium alginate concentration, stirring equipment and time for emulsion formation, CaCl2 concentration, and absence or presence of stirring after the addition of the CaCl2 solution. The survival of entrapped cells to a simulated gastric digestion and their survival and release during simulated intestinal digestion were also investigated. The obtained particles effectively protected L. salivarius CRL2217 from the proteolytic activity and low pH present in the gastric environment. Besides, their content was released in contact with a simulated intestinal juice, as viable counts and binding of WGA after a simulated intestinal digestion revealed. This work paves the way for the design of probiotic supplements for poultry including gastrointestinal digestion-susceptible bacteria.

Reduksi Ion Cu(II) Menggunakan Karbon Aktif dari Sekam Padi Teraktivasi Fisika dan Kimia

This research proposed a method to produce activated carbon from rice husk by carbonation process, physical activation and chemical activation using NaOH. The performance of activated carbon was tested by batch experiments in which the adsorption system contained 1 g of rice husk activated carbon in 100 mL of artificial wastewater with initial concentration of Cu(II) ion being 148.26 mg/L, initial pH 6, at 27 oC and 1 atm to determine the efficiency of reducing Cu(II) ion over the contact time and presence of stirring on chemical activation. The results showed that the efficiency of reducing Cu(II) ion by rice husk activated carbon increased exponentially with increasing contact time with a maximum value of 74.33% at 90 minutes of contact time. The results also showed that stirring on chemical activation increased the efficiency of Cu(II) ion reduction by 14.94%. Adsorption kinetics studies showed that Cu(II) ion reduction followed the pseudo-second order adsorption equation with the adsorption capacity of 10.18 mg/g and adsorption rate constant of 0.0013 g/mg.min for rice husk activated carbon without stirring in the chemical activation. Stirring in the chemical activation.increased the capacity and rate of adsorption constant to 12.07 mg/g and 0.0052 g/mg.min, respectively.

Kinetics of Aggregation using Single-Molecule Fluorescence Techniques to Determine Nucleation and Elongation Rate Constants of Amyloid Growth

Elucidation of the underlying mechanisms of amyloid aggregation of proteins is critical in understanding the development of many neurodegenerative diseases. Self-assembly of the monomeric proteins to fibrillar forms are considered to proceed via both primary nucleation and secondary nucleation processes followed by elongation of the nuclei. However, determination of the rate constants of these microscopic processes using ensemble measurements are difficult. We have used two single-molecule sensitive techniques, viz, cuvette-FCS and total internal reflection fluorescence microscopy (TIRFM) for real time monitoring of amyloid aggregation. Analysis of the fluorescence bursts of thioflavinT arising from the protofibrils or the fibrils of amyloid-β (Aβ) in Cuvette-FCS allows measurements of concentration of the fibrils, size distribution of the fibrils and total aggregation both under quiescent conditions and in presence of stirring. Thus, cuvette-FCS allows characterization of the early aggregates and direct measurement of the nucleation and elongation rate constants. Additionally, we have established a TIRFM based approach to visualize time dependent growth of the individual amyloid fibrils. While both the techniques provide estimation of the rate constants of elongation and nucleation, TIRFM provides measurements of the heterogeneity of the various rate constants. Furthermore, TIRFM enables characterization of the parallel pathways of aggregation. However, ability to measure both fibril concentration and total aggregation at the same time in the single molecule experiments makes the measurements of the rate constants robust. For example, we find that while kinetics of the overall aggregation depend highly on sample preparation, the elongation rate constant remains almost invariable. Taken together, single molecule measurements of amyloids can be used to evaluate individual rate constants of both primary and secondary processes of amyloid aggregation.

Biokerosene and green diesel from macauba oils via catalytic deoxygenation over Pd/C

Macauba is a palm tree with good oil productivity (6.2ton/ha), is native to Central and South America and is not exploited for food purposes. Its oils have been noted as an important alternative for the production of biofuels, especially for aviation. This study investigated deoxygenation catalysed by 5% w/w of palladium on charcoal (Pd/C) reduced in situ using crude and previously hydrolysed macauba pulp and almond oils with different compositions and acidity values. The effect of the fatty composition and nature of the feedstock, reaction pressure, atmosphere, presence of stirring and use of the Pd/C catalyst were studied. The results indicated high selectivity, with a predominance of saturated linear hydrocarbons that correspond to green diesel, followed by biojet fuel hydrocarbons. Oxygen removal was favoured for free fatty acids with long carbon chains, for which decarbonylation and/or decarboxylation predominates. The highest content of hydrocarbons (85% w/w) was obtained in the reaction of hydrolysed macauba almond oil at 10bar of H2, 300°C, 5h of reaction and stirring at 700rpm. This green product has potential applications as a drop-in substitute for fossil fuels.

Treatment of toluene, benzene, naphthalene and xylene (BTNXs) containing wastewater using improved biological oxidation with pretreatment using Fenton/ultrasound based processes

Improved biological oxidation based on pretreatment using combined Fenton and ultrasound in presence of stirring as the best approach and use of modified activated sludge was demonstrated for the treatment of wastewater containing benzene, toluene, naphthalene and o-xylene. The optimum pretreatment conditions were observed as initial pH of 3–3.5, Fe2+ dosage of 2.0gL–1 and H2O2 dosage of 1.0gL–1 giving about 80–95% reduction in the chemical oxygen demand (COD) and favorable BOD5/COD value for the biological oxidation. Use of modified prepared activated sludge gave about 20–30% higher extent of degradation as compared to the conventional sludge types.

Synthesis of uniform polyaniline nanorods with the assistance of ethylene glycol

The uniform polyaniline (PANI) nanorods were prepared by the chemical method with the assistance of ethylene glycol (EG) medium. The morphology and structure of the PANI nanorods were characterized by SEM, TEM, FTIR, and UV–vis technique, and the effects of stirring on the morphology, structure, electrical conductivity, and electrochemical behavior of PANI were investigated. The results showed that as-synthesized PANI can be facilely dispersed in water and ethanol to form colloids. During the reaction, the H-bonding between molecules of PANI and EG plays a key role for the one-dimensional. In the presence of stirring, uniform PANI nanorods with diameters of 50–80 nm and length up to 400–800 nm can be obtained, and the aspect ratio is about 4. While in the absence of stirring, the aspect ratio of nanorods increases to more than 10, the diameter and length are 20–60 nm and 0.2–1 μm, respectively. In addition, the stirring can result in a higher doping level, conductivity, and degree of oxidation. Based on these results, a possible formation mechanism of PANI nanostructures is presented.

Modeling of permeate flux decline during ultrafiltration of polyvinyl alcohol in a batch cell

Ultrafiltration (UF) of polyvinyl alcohol from aqueous solution is studied in a batch cell over a wide range of operating conditions. The unsteady state nature of the permeate flux decline during UF is caused by changes in the hydraulic boundary condition at the membrane surface due to gel layer formation. An unsteady state mass transfer model is developed for gel-controlled UF in an unstirred cell starting from the basic fluid mechanical analysis of the system. An integral method of solution is used for the solution of the concentration profile in the developing mass transfer boundary layer. The model is used to predict the transient permeate flux decline profile. The transient state behavior in the presence of stirring is estimated by using a model available in literature. The predictions are found to be in good agreement with the experimental flux.

Synthesis of micro and nanostructured MnO2 and their comparative study in lithium battery

Micro and nanostructured γ-MnO2 are synthesized to investigate the size effect of cathode active materials in battery performance. MnSO4 and (NH4)2S2O8 were used as starting materials to prepare micro and nanostructured samples in the presence of stirring and ultrasonic irradiation, respectively. Structure optimization is done by changing values for temperature and manganese sulphate concentration. The MnO2 micro and nanoparticles are characterized by scanning electron microscopy and X-ray diffraction (XRD). The XRD results reveal that only γ-MnO2 is formed under the reaction conditions. Under the optimized conditions, manganese dioxide nanoparticles, with an average particle size of 56 nm, are obtained. Both micro and nanostructured MnO2 is used as the cathode active material in Li/MnO2 battery. Discharge profiles of stirrer-based cathode material (micro) and ultrasonic instrument-based one (nano) compared with each other in constant discharge currents of 50 and 100 mA g−1. The results demonstrated that nanosized materials show higher specific capacities and energies. Electrochemical impedance spectroscopy is used to investigate the size effect of cathode material on battery resistance and the results show a copious decrease in total resistance.

Studies on the hydrolysis of urea for production of ammonia and modeling for flow characterization in presence of stirring in a batch reactor using computational fluid dynamics

Ammonia is a highly volatile noxious material with adverse physiological effects, which becomes intolerable even at very low concentrations and presents substantial environmental and operating hazards and risk. But ammonia has long been known to be useful in the treatment of flue gases from the fossil fuel combustion process, such as in industrial furnaces, incinerators and coal-fired electric power generating plants. The present study is concerned with the methods and means to safely produce relatively small amount (i.e., up to 50 kg/hour) of ammonia. Current study involves experimental investigation for hydrolysis of urea for production of ammonia in a batch reactor at different temperature ranging from 110 °C to 180 °C against different initial feed concentration (10, 20, and 30 wt%) with different stirring speed ranging from 400 rpm to 1,400 rpm. Three-dimensional geometry and meshing of reactor is created in Gambit, a preprocessor of the commercial software, Fluent, for hydrodynamic study.

A Novel In Situ Tool for the Exposure and Analysis of Microorganisms in Natural Aquatic Systems

To evaluate the effects of contaminants or nutrient limitation in natural waters, it is often desirable to perform controlled exposures of organisms. While in situ exposures are routine for caged organisms or macrophytes, they are extremely difficult to perform for microorganisms, mainly due to difficulties in designing an exposure device that isolates the cells while allowing rapid equilibration with the external media. In this paper, a stirred underwater biouptake system (SUBS) based on the diffusion of chemicals across a semipermeable membrane housing a controlled population of microorganisms is reported. Cd diffusion through the semipermeable membrane was evaluated by voltammetry using a microelectrode. Comparison of stirred and unstirred solutions demonstrated a significantly increased diffusive flux in the presence of stirring. Lab tests using Chlamydomonas reinhardtii showed that diffusion across the semipermeable membrane was not limiting with respect to the biouptake of Cd. The SUBS device was field tested and the results of viability studies and trace metal biouptake by C. reinhardtii are reported. No diffusion limitation due to the SUBS was observed for Cd under the tested field conditions. The SUBS device was also shown to be useful for field exposures and subsequent measurements of trace metal uptake and viability. The results support the future use of the SUBS for the in situ measurement of phytochelatin/metallothionein production, photosynthetic efficiency, or reporter gene induction of controlled organisms.

Stirring up trouble: Multi-scale mixing measures for steady scalar sources

The mixing efficiency of a flow advecting a passive scalar sustained by steady sources and sinks is naturally defined in terms of the suppression of bulk scalar variance in the presence of stirring, relative to the variance in the absence of stirring. These variances can be weighted at various spatial scales, leading to a family of multi-scale mixing measures and efficiencies. We derive a priori estimates on these efficiencies from the advection–diffusion partial differential equation, focusing on a broad class of statistically homogeneous and isotropic incompressible flows. The analysis produces bounds on the mixing efficiencies in terms of the Péclet number, a measure of the strength of the stirring relative to molecular diffusion. We show by example that the estimates are sharp for particular source, sink and flow combinations. In general the high-Péclet-number behavior of the bounds (scaling exponents as well as prefactors) depends on the structure and smoothness properties of, and length scales in, the scalar source and sink distribution. The fundamental model of the stirring of a monochromatic source/sink combination by the random sine flow is investigated in detail via direct numerical simulation and analysis. The large-scale mixing efficiency follows the upper bound scaling (within a logarithm) at high Péclet number but the intermediate and small-scale efficiencies are qualitatively less than optimal. The Péclet number scaling exponents of the efficiencies observed in the simulations are deduced theoretically from the asymptotic solution of an internal layer problem arising in a quasi-static model.

Chaotic mixing induced transitions in reaction-diffusion systems.

We study the evolution of a localized perturbation in a chemical system with multiple homogeneous steady states, in the presence of stirring by a fluid flow. Two distinct regimes are found as the rate of stirring is varied relative to the rate of the chemical reaction. When the stirring is fast localized perturbations decay towards a spatially homogeneous state. When the stirring is slow (or fast reaction) localized perturbations propagate by advection in form of a filament with a roughly constant width and exponentially increasing length. The width of the filament depends on the stirring rate and reaction rate but is independent of the initial perturbation. We investigate this problem numerically in both closed and open flow systems and explain the results using a one-dimensional "mean-strain" model for the transverse profile of the filament that captures the interplay between the propagation of the reaction-diffusion front and the stretching due to chaotic advection. (c) 2002 American Institute of Physics.

Galliosilicate molecular sieves with the faujasite structure

The hydrothermal transformation at 95°C of galliosilicate hydrogels with molar oxide composition Ga 2O 3 : 10SiO 2 : 4.5 Na 2O : 150 H 2O, prepared from colloidal silica and sodium gallate mixtures, yields crystals with the faujasite or natrolite structure if the crystallization reaction is performed in the absence or presence of stirring. Raising the crystallization temperature to 150°C causes the formation of analcime crystals. Moreover, when 10% of the hydrogel Ga 2O 3 content is added in the form of a seeding solution with composition Ga 2O 3 : 15SiO 2 : 10 Na 2O : 400 H 2O, the crystallization time for GaY formation decreases by about 50% and Ga incorporation in the crystals increases. In either case, the crystallization reaction is not stoichiometric and the crystals' silica to gallia molar ratio (SGR) is always less then that in the parent hydrogel. The calcined GaY crystals have surface areas in the 500–550 m 2 g −1 range and, for a given hydrogel composition, the SGR decreases to 3.7 from 4.4 when a seeding solution is used. The thermal stability of GaY can be drastically increased by the introduction of rare earth ions such as La. In fact, 71Ga MAS NMR spectra have shown that in both GaY and H(Ga,La)Y, no extraframework Ga(VI) species are present. In addition, 29Si NMR spectra yield an SGR molar ratio in agreement with chemical analysis. FTIR results from pyridine thermodesorption, together with microcalorimetry experiments with NH 3, indicate that the isomorphous substitution of Al with Ga in the faujasite framework reduces acid site strength, density and distribution.

Nonclassical dimension-dependent kinetics of a photobleaching reaction in a focused laser beam “phototrap”

A focused laser beam acts as both a ``phototrap,'' bleaching fluorophore molecules that diffuse into the beam path, and as a confocal probe, detecting the excited, unbleached fluorophore molecules still present in the trap. With this focused laser beam, we observe anomalous asymptotic rate laws similar to those predicted for a diffusion-controlled elementary trapping reaction $A+T\ensuremath{\rightarrow}T$ in both one and two dimensions. One-dimensional diffusion-limited trapping kinetics are observed in capillaries with $10$ $\ensuremath{\mu}$m diameters, while two-dimensional (2D) diffusion limited trapping kinetics are observed with unstirred samples having a quasi-2D geometry. However, in the presence of stirring, the 2D samples exhibit the classical, constant trapping rate.

The Anomalous Diffusion-limited Reaction Kinetics of a Phototrapping Reaction

AbstractA focused laser beam acts as both a “phototrap”, bleaching fluorophore molecules which diffuse into the beam path, and as a confocal probe, detecting the excited, unbleached fluorophore molecules still present in the trap. With this focused laser beam, we observe anomalous asymptotic rate laws similar to those predicted for a diffusion-controlled elementary trapping reaction, A + T → T, in one and two dimensions. One dimensional diffusion-limited trapping kinetics are approached in capillaries with 10 μm diameters while two dimensional diffusion limited trapping kinetics are observed with unstirred samples having a quasi 2-D geometry. In the presence of stirring, the 2-D samplesexhibit the classical, constant trapping rate over time.

On the form and formation of rubber particles in impact polystyrene and their relationship to natural and synthetic materials

Correlations are drawn between the morphological features of high-impact polystyrene (HIPS), bubble assemblies, adipose tissue, pith and foams. It is concluded that their morphological forms are the same and that similar interfacial tensile forces are responsible for the HIPS morphology as for the others. The synthesis of HIPS, from a solution of rubber in styrene, is discussed in terms of a phase diagram and it is concluded that the mechanism is consistent with the generation of that characteristic morphology throughout the sample in the absence of stirring and in resticted volume elements in the presence of stirring during polymerization of the styrene. An example is quoted of the generation of the same morphology in a blend prepared by mixing immiscible solutions of a homopolymer and a copolymer.