Stirring Procedure Research Articles

Zn-HA-TiO2nanocomposite coatings electrodeposited on a NiTi shape memory alloy

In this work, zinc–hydroxyapatite (Zn–HA) and zinc–hydroxyapatite–titania (Zn–HA–TiO2) nanocomposite coatings were electrodeposited onto a NiTi shape memory alloy, using a chloride zinc plating bath. The structure of the composite coatings was characterized by X-ray diffraction, scanning electron microscopy and high-resolution transmission electron microscopy. According to the results, the Zn–HA–TiO2 coating exhibited a plate-like surface morphology, where the addition of the nanoparticles caused to an increase in roughness. It was also found that due to applying a proper stirring procedure during co-deposition, a homogenous dispersion of the nanoparticles in the coatings was achieved. Also, the addition of the TiO2 nanoparticles to the Zn–HA–TiO2 coating enhanced the microhardness and wear resistance. Copyright © 2014 John Wiley & Sons, Ltd.

Influence of final stirring treatment on inclusion number in tool steel

The focus was to study the elimination of non-metallic inclusions during the final part of the ladle refining of tool steel (AISI H13). More specifically, the final stirring treatment in a ladle before casting was modified to study how the number of inclusions could be decreased. The following three stirring treatments were tested: a conventional induction stirring with a 650 A current for 20 min, a short induction stirring with a 650 A current during 10 min, and a combined gas and induction stirring during 20 min (no open eye and a 600 A current). Steel samples were collected from the ladle before and after the final stirring period of the ladle treatment. Thereafter, the numbers of inclusions in steel samples were determined using a light optical microscope based on a classification according to the Swedish standard SS111116 (JK Scale II). Overall, the results showed that a combined gas and induction stirrings was the most efficient way of decreasing the number of DM, DH and DP inclusions. The decrease in the inclusion number in four heats was the following for the different size classes for a combined stirring procedure: 15–40% for DM type inclusions, 30–61% for DH type inclusions and 50–100% for DP inclusions. In addition, it should be mentioned that a stirring practice with induction stirring during 10 min resulted in a 67–100% decrease in the DH type inclusions. However, the results for a combined stirring case for DH type inclusions were more stable than those for a shorter induction stirring time.

Waterborne polyurethane wood coatings based on rapeseed fatty acid methyl esters

Trends in wood coatings are driven to waterborne systems and to renewable resources. Vegetable oils are well known for wood coatings, e.g. alkyds or polyurethane dispersions. In this context, fatty acid methyl esters turn out to be an alternative to technical fatty acids and vegetable oils. High contents of hydrophobic oil-based monomers require a sufficient understanding of the dispersion stability. This study shows the influence of hydrophobic monomers, ionic centers, degree of neutralization, and stirring procedure to the particle size distribution and dispersion stability. Furthermore, the impact of these parameters on the resulting coating film properties was investigated.

Green route synthesis of 4-thiazolidinone analogs of isonicotinic acid hydrazide

The broad and potent activity of 4-thiazolidinones has established it as one of the biologically important scaffolds. The synthesis of N-(2-aryl-4-oxothiazolidin-3-yl)isonicotinamide by a novel method of stirring and sonication is described. The conventional method for synthesis of 4-thiazolidinones involves use of a Dean-Stark water separator for the removal of water from the reaction with long reaction times (12–48 h), and the stirring procedure also involves the use of DCC (dicyclohexylcarbodiimide) as a dehydrating agent. We report the synthesis of 4-thiazolidinone analogs of isonicotinic acid hydrazide by novel, green route methods of sonication and stirring using molecular sieves. Results indicate that high yields and shorter reaction times can be achieved by employing novel green route methods of synthesis.

Supramolecular‐based dispersive liquid–liquid microextraction: A novel sample preparation technique utilizes coacervates and reverse micelles

The present study reports a novel sample enrichment method termed supramolecular-based dispersive liquid-liquid microextraction (SM-DLLME). The SM solvent selected was made up of reversed micelles of decanoic acid dispersed in tetrahydrofuran (THF)-water. THF plays double role, not only acts as a disperser solvent but also causes self-assembly of decanoic acid. The contaminant used as a model was Malachite Green (MG). It was a cationic dye and was preconcentrated without any derivatization or ion-pair formation reaction. In SM-DLLME, the most important advantages of DLLME technique and preconcentration strategy based on the coacervation and reverse micelles have come together. Moreover, in this method, disadvantages of DLLME such as extraction capability of only hydrophobic analytes and hiring toxic and hazardous organic solvents as the extraction solvent and disadvantages of coacervation-based extraction method such as tedious, labor-intensive and time-consuming stirring procedure have been avoided. Several variables affecting the microextraction efficiency were investigated and optimized. Under the optimized conditions and preconcentration of only 5.00 mL of sample, the enhancement factor was 52, limit of detection (LOD) was 4 μg/L and relative standard deviations (RSDs) for 145 and 36 μg/L of MG in textile industry wastewater were 1.8 and 3.2%, respectively (n = 6).

Structuration of Pd(2 wt %)/Fe−Al Oxide Catalysts on Ceramic and Metallic Monoliths: Physicochemical Characterization, Effect of the Nature of the Slurry, and Comparison with LaMnO3Catalysts

The main objective of this study has been twofold: (i) to investigate the effect of the nature of the slurry used to structurate a catalyst oil monoliths; (ii) to study the influence of the nature of the monoliths oil the physicochemical properties and on the catalytic activities in the combustion of methane. The slurry used in this work was made with an acidified solution of Pd(2 wt %)/Fe-Al oxide catalyst. This catalyst was prepared by the citrate method and deposited oil ceramic and metallic monoliths according to a dip coating or an orbital stirring procedure. Both types of structured catalysts were studied using the following physicochemical techniques: specific surface area measurements (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The Pd(2 wt %)[Fe-Al oxide catalyst used for monolith coating does not undergo any textural or crystallinity modification during the deposition procedure. Catalytic activities obtained for powder and monolithic catalysts are compared. The Surface of the support plays an important role in the structuration of catalysts. The amount of deposited catalyst has an influence on the catalytic activity. The amount of deposited catalysts depends oil the nature of the monolith, oil the coating technique, and oil the nature of the Slurry. Comparisons between structured Pd(2 wt %)/Fe-Al oxide and structured LaMnO3 on ceramic and metallic monoliths (previous work) were made to clarify the influence of the nature of the slurry oil the amount of deposited catalysts. The amount of deposited catalysts oil ceramic monolith using Pd(2 wt %)[Fe-Al oxide catalyst is lower than that deposited using LaMnO3, In the case of metallic monoliths, the difference is less significant. The influence of a diffusion limitation of the reaction rate in structured catalysts with Pd(2 wt %)/Fe-Al oxide seems to be less important than with LaMnO3. Higher catalytic activities were observed for Pd(2 wt %)/Fe-Al oxide on the ceramic monoliths at high temperature. Coating oil the metallic monoliths led to a better activity at low temperature compared to the corresponding powder catalyst.

Solvent Extraction of Bitumen from Jordan Oil Shale Assisted by Low Frequency Ultrasound

In this work, the efficiency of 20 kHz frequency ultrasounds versus the classical stirring procedure was investigated on the solvent extraction of Jordanian El-Lajjun oil shale by employing a horn type sonicator. The influence of sonication parameters (sonication time and ultrasonic power) and extraction parameters (extraction solvent and oil shale particle size) on the solubilization of organic matter (bitumen) from oil shale are reported here. The influence of seven individual solvents, namely: tetrahydrofuran, benzene, carbon tetrachloride, chloroform, kerosene, toluene, acetone and a mixture of methanol-acetone-chloroform on the fraction extracted was investigated and it was found that the fraction extracted was 90% after only ten minutes of sonication at 33 W when tetrahydrofuran was used as extraction solvent. It was found that the fraction extracted percentage is strongly influenced by the solvent extraction, ultrasonic power and exposure time and less influenced by the particle size. Under the current experimental conditions and using the tetrahydrofuran as extraction solvent, the extraction time was decreased by four folds while the fraction extracted percentage (E%) was increased by three times.

Effect of electromagnetic stirring on melt pool free surface dynamics during vacuum arc remelting

The deformation of the free surface of the liquid pool in the VAR process may play a key role in explaining the apparition of surface defects on the ingot skin. In the present study, the deformation of the surface induced by electromagnetic stirring is investigated, for a simplified geometry, using CFD-based simulations, combining models for the turbulent fluid flow, heat transfer, free surface movements and electromagnetic forces. Particular attention is given to the implementation of thermal and electrical boundary conditions at the moving free surface. Verification of the developed model is carried out by comparison with the dedicated code SOLAR. The free surface dynamics of a liquid zirconium pool is then quantitatively analysed for different stirring procedures, and the effects of the stirring parameters (magnetic induction, reversal time) are predicted and discussed. The obtained results provide some insights into mechanisms by which surface deformation may influence the ingot skin solidification, leading to poor ingot surface quality.

Lipase-catalyzed synthesis of ferulyl oleins in solvent-free medium

Lipase-catalyzed transesterification of ethyl ferulate (EF) with triolein (TO), to form ferulyl oleins in a solvent-free medium, was investigated. Water activity ( a w) had an obvious influence on transesterification efficacy. A possible explanation is that the reaction of EF with TO would be deacylation-rate determined. In order to enhance the combined yield of ferulyl diolein (FDO) and ferulyl monoolein (FMO) and minimize hydrolysis of substrate, glycerol (rather than water) was introduced to the reaction. A maximal combined yield of 29.0% of FDO and FMO was obtained using a 1:3 mole ratio of glycerol to TO in solvent-free medium at 60 °C. Compared to the ferulyl olein synthesis conducted by the normal pressure magnetic stirring procedure, the synthesis of ferulyl oleins by a vacuum-rotary evaporation procedure, with a vacuum of 7.5 mmHg, affords higher yields within the same time. The enzyme can be reused several times without significant loss of activity.

Structuration of LaMnO3 perovskite catalysts on ceramic and metallic monoliths: Physico-chemical characterisation and catalytic activity in methane combustion

LaMnO3 perovskite was prepared by the citrate method and deposited on ceramic and metallic monoliths according to a dip coating or an orbital stirring procedure. Both types of structured catalysts were characterised by specific surface area measurements (BET), scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The parameters influencing the amount of deposited catalyst, such as the nature of the monolith and the coating technique, were investigated. Comparisons between structured and powdered catalysts showed a higher catalytic activity of the former. A better behaviour of structured LaMnO3 on metallic monoliths was observed at a lower temperature, and higher catalytic activities were observed for structured LaMnO3 on ceramic monoliths at a higher temperature. The influence of a diffusion limitation of the reaction rate in structured catalysts was observed. (c) 2008 Elsevier B.V. All rights reserved.

Comparison of saponite and montmorillonite behaviour during static and stirring maturation with seawater for pelotherapy

Two different bentonites (saponite and montmorillonite) have been used for maturation with seawater. These bentonites are very rich in phyllosilicates (> 90%), with calcite, silica minerals (quartz, cristobalite) and feldspars (plagioclase) as subordinated minerals. Maduration tests have been realized both in static and stirring conditions and sampling points at 0, 15, 30, 60, 90 and 120 days have been established. Several mineralogical (XRD, SEM-EDX) chemical and physico-chemical (CEC, pH, granulometry, plasticity, conductivity) analytical techniques have been used. Results indicate no mineralogical changes during maturation process but differences in the smectite crystallinity (crystallite size) and basal spacing d (001). The last related with the variation of exchangeable cations (mainly Na + for Ca 2+) within the smectite interlayer. Variations in granulometry, plasticity index and conductivity have also been observed. Similar results are reported for static and stirring procedures, and therefore the former is preferred. Maturation time of between 60 and 90 days would be enough for the bentonite to achieve the optimum physico-chemical properties for its use as a peloid. Between the two bentonites under study, saponite is clearly better than montmorillonite for its application as peloids in pelotherapy. This fact is mainly due to differences in grain size distribution and consequently in the cationic exchange capacity, which enables in saponite a higher retention of water ions making possible their transference to patients, and therefore reaching a better influence in their health.

Trace Element Determination by Combining Solid-Phase Microextraction Hyphenated to Elemental and Molecular Detection Techniques

The state of the art of analytical procedures based on solid-phase microextraction (SPME) and its applications to tin, mercury, arsenic, antimony, chromium, selenium, and lead determination in abiotic and biotic matrixes are critically reviewed from 1994 to present. First, sample pretreatment prior to SPME is evaluated, including a description of the most usual leaching procedures for sediment, soil, and biological samples. Because most organometallic species lack volatility, a derivatization step is mandatory prior to gas chromatographic (GC) determination, except for the volatile organometallics that can be directly extracted from the sample headspace or liquid phase by SPME. The most common derivatization procedures used in alkylation and hydridization reactions used for mercury, lead, and tin, as well as other procedures for the determination of total chromium and arsenic [i.e., trifluoroacetylacetonates for chromium (III) and thioglycol methylate for organic arsenic species] are reviewed. Critical variables usually evaluated along with the method development to improve the sensitivity of the extraction methods based on SPME, such as sampling size, stirring procedures, sampling temperature and pressure, polymer coating, and thermal desorption are reviewed. In addition, figures of merit of the different detection systems used in SPME combined with GC are evaluated. The validation of the reported analytical procedures with reference materials are also discussed in terms of precision and accuracy. Finally, future developments in the application of SPME to speciation are highlighted. Moreover, the capability of SPME automation for the derivatization-extraction procedures are also presented.

RELATION BETWEEN SENSORY TEXTURE PROPERTIES AND EXOPOLYSACCHARIDE DISTRIBUTION IN SET AND IN STIRRED YOGHURTS PRODUCED WITH DIFFERENT STARTER CULTURES

ABSTRACT Set yoghurts produced with seven different exopolysaccharide‐producing starter cultures were subjected to sensory texture profiling including texture evaluation before and after a stirring procedure carried out by trained assessors. The microstructure of four selected yoghurts was investigated by confocal laser scanning microscopy with special focus on the distribution of exopolysaccharides (EPS) in the protein network. Two different types of microstructures were observed, one in which EPS were associated with the protein network and another where EPS appeared to be incompatible with the protein; as a consequence, the EPS were situated in the void spaces in the protein network. The latter yoghurts were less ropy and had higher serum separation than the yoghurts where EPS were associated with the protein, and they exhibited a significant increase in mouth thickness as a result of stirring. Yoghurts in which the EPS were associated with protein had high ropiness, low serum separation and appeared more resistant to stirring. The nature of EPS‐protein interactions is extremely important for the textural effects of EPS in fermented milk products, and such interactions depend on the specific starter culture used.

Deleterious effect of ammonium extraction from soil assisted by ultrasound

Ultrasound has been used to assist extraction procedures from solid samples based on the decrease of gradient concentration in the vicinity of particulate matter and the microjet produced during cavitation. In the present work, the harmful effect yield by ultrasound-assisted ammonium extraction from soil samples was observed by comparing with an extraction process assisted by magnetic stirring. Three soil samples from agricultural areas of Bahia state in Brazil were submitted to both extraction processes and ammonium concentrations for conventional stirring procedure were 25% higher than those obtained by the ultrasound-assisted extraction. This same effect was also observed by irradiating ammonium solutions with low frequency ultrasonic waves. After 5 min of ultrasonic irradiation, more than 25% of the ammonium was lost probably as N 2. Possible conversions of N–NH4 +to hydrazine, hydroxylamine, nitrite and nitrate were evaluated. In addition, an increasing in nitrate concentration by irradiating solution with high saline concentration independent on the initial ammonium concentration was observed.

Deleterious effect of ammonium extraction from soil assisted by ultrasound

Ultrasound has been used to assist extraction procedures from solid samples based on the decrease of gradient concentration in the vicinity of particulate matter and the microjet produced during cavitation. In the present work, the harmful effect yield by ultrasound-assisted ammonium extraction from soil samples was observed by comparing with an extraction process assisted by magnetic stirring. Three soil samples from agricultural areas of Bahia state in Brazil were submitted to both extraction processes and ammonium concentrations for conventional stirring procedure were 25% higher than those obtained by the ultrasound-assisted extraction. This same effect was also observed by irradiating ammonium solutions with low frequency ultrasonic waves. After 5 min of ultrasonic irradiation, more than 25% of the ammonium was lost probably as N2. Possible conversions of N–NH4+to hydrazine, hydroxylamine, nitrite and nitrate were evaluated. In addition, an increasing in nitrate concentration by irradiating solution with high saline concentration independent on the initial ammonium concentration was observed.

Dynamic instability of a rotating Bose-Einstein condensate.

We consider a Bose-Einstein condensate subject to a rotating harmonic potential, in connection with recent experiments leading to the formation of vortices. We use the classical hydrodynamic approximation to the nonlinear Schrödinger equation to determine almost analytically the evolution of the condensate. We predict that this evolution can exhibit dynamical instabilities, for the stirring procedure previously demonstrated at ENS and for a new stirring procedure that we put forward. These instabilities take place within the range of stirring frequency and amplitude for which vortices are produced experimentally. They provide therefore an initiating mechanism for vortex nucleation.

Influence of casting and heat treatment parameters in controlling the properties of an Al-10 wt% Si-0.6 wt% Mg/SiC/20p composite

The influence of melting, casting and heat treatment parameters in determining the quality and tensile properties of an Al-10wt% Si-0.6wt% Mg/SiC/20p composite in comparison to its base alloy (359) has been studied. For the composite, melt-temperature, hydrogen level, and the cleanliness and stirring procedure, control, respectively, the harmful melt reactions of the SiC reinforcement with the alloy matrix, gas porosity, inclusion and oxide-film contamination, whereas casting conditions are mainly controlled through the use of a proper mold temperature and appropriate mold coating materials that enhance the feedability and reduce or eliminate the effects of shrinkage. The beneficial effect of the SiC reinforcement particles is two-fold: 1. they act as preferential sites for the nucleation of the eutectic silicon particles, leading to an overall refinement of the latter and lowering the amount of strontium modifier required from 150 to 90 ppm to achieve the same level of refinement in the as-cast microstructures of both composite and base alloy; 2. their presence also results in a more uniform redistribution of the silicon particles in the as-cast structure (cf. the large, irregular interdendritic regions of eutectic silicon observed in the base alloy). Both composite and base alloy exhibit a similar heat treatment response with respect to tensile properties for the various heat treatments applied. Addition of 20 vol% SiC to the base alloy (359) is seen to increase the Young's modulus and yield strength by 30–40%, marginally affect the ultimate tensile strength, but reduce the ductility by almost 80%.

Equipment and Procedure for Manufacturing Laboratory Cheese Curd

A technique for manufacturing laboratory quantities of cheese is described. This technique allows simultaneous manufacture of four vats (7kg each) of milk. Cooling and stirring procedures were automated to reduce variability between vats. A direct acid cheese procedure minimized cheese make time and unified the make procedure. The equipment was acceptable for producing Cheddar cheese, cottage cheese, and direct acid set cheese. This equipment would be especially suited to evaluate compatability of enzymes for cheese manufacture, cheese yield studies, desirability of cultures for a particular cheese type, and test of culture media.

Enzyme-substrate interaction in lipid monolayers. II. Binding and activity of lipase in relation to enzyme and substrate concentration and to other factors.

With the limited stirring procedure used in the present work, substrate and enzyme together form a segregated and well-defined system on the surface. The lipase molecules responsible for the lipolysis are only those that are adsorbed on the glyceride monolayer. After a study of the stirring procedure, two series of systematic experiments were done: a) the bulk concentration of the enzyme was varied with different constant surface concentrations of the substrate, and b) the surface concentration of the substrate was varied with different constant bulk concentrations of the enzyme. The influence of the surface concentration of substrate on a) the rate of lipolysis, V,; b) the enzyme activity, a,; and c) the enzyme adsorption, Ze, were each determined by a different procedure. The values obtained verify the enzymic activity equation (a = V/Ze). The roles of other factors (Ca2+ ions, and pH) which govern the adsorption of the enzyme and its specific activity were also studied in preliminary experiments.

Synthesis of β-(1→3)-Glucan from Extracellular Uridine Diphosphate Glucose as a Wound Response in Suspension-cultured Soybean Cells

Soybean (Glycine max) suspension-cultured cells were incubated with 600 micromolar uridine diphosphate [(14)C]glucose, and the incorporation into alkali-insoluble material was studied. When the cells were kept in suspension by shaking on a linear shaker, the incorporation was very low. The incorporation was stimulated 30-fold when the cells were continually resuspended by stirring with a narrow glass rod. The stirring procedure was shown to damage some of the cells, and the incorporation appeared to be a wound response. The alkali-insoluble material formed was a beta-(1-->3)-glucan, and it was synthesized from uridine diphosphate glucose which did not penetrate through the plasma membrane of intact cells. The synthetase activity was probably induced by the stirring procedure. No evidence for cellulose synthesis from extracellular uridine diphosphate glucose was obtained.