Rheological behaviour of processed avocado pulp emulsions

Shear rate vs. shear stress data were obtained on avocado pulp in water emulsions using a concentric cylinder rheometer and fitted to a power law model. Dilution, as volume fraction of water, had a pronounced effect on the apparent viscosity of the pulp emulsions and the Richardson equation, (η_R= exp.( a φ) for the emulsion viscosity fitted the data well. A mean slope coefficient, a , of 4.57 can be used as a first approximation. Enzymatic treatment (40°C, 1 h), is slightly more effective than thermal treatment (65°C, 1 h), in reducing the initial apparent viscosity of the pulp-water emulsions     

Reactive energy measurement using frequency controlled analog-to-pulse-rate converter

Contents This paper analyzes a problem of phase shifting and deseribes a novel method for electronic reactive energy measurement. The proposed measurement structure, composed of an integrator as a phase shifting circuit and a frequency controlled analog-to-pulse-rate converter, provides for the measurement completely in accordance with IEC definition of reactive energy, which is performed with simple but high performance metering device.

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Die Blindverbrauchsmessung anhand eines netzsynchronisierten Analog-Frequenz-Wandlers

Übersicht In diesem Artikel wird das Problem der Phasenverschiebung analysiert und eine neue Meßmethode für elektronische Blindverbrauschsmessung aufgezeigt. Die vorgeschlagene Strucktur, bestehend aus einem Integrator als Phasenschieber und netzkontrolliertem Analog-Frequenz-Wandler, ermöglicht die Verwirklichung eines einfachen aber präzisen Elektrizitätszählers zur Messung der Blindenergie, dessen Arbeitsprinzip mit den IEC Empfehlungen vollkommen übereinstimmt.

     

Calculation of secondary cable losses and ampacity in the presenceof harmonics

A simplified procedure for computing ohmic losses in secondary distribution cable systems by extending the Neher-McGrath model for 60 Hz losses is presented. Specifically, simplified formulae for evaluating ohmic losses due to harmonics are given. These results are subsequently used to compute the cable ampacity or the derating factor due to harmonics. The overall method is simple to follow and can be performed with a calculator. A typical example is given     

Strategies for the monitoring of drugs in body fluids by micellar electrokinetic capillary chromatography

Electrokinetic capillary techniques can exploit numerous separation principles, making them flexible and easily applicable to a variety of separation problems. In recent publications, this emerging technology has been shown to be well suited for monitoring drugs and metabolites in body fluids, including serum, saliva and urine. Most attention has been focused on micellar electrokinetic capillary chromatography (MECC) because it permits the separation and determination of drugs with discrimination being largely based on differences in hydrophobicity. An overview of literature data on the MECC of drugs in body fluids and recent data obtained with antiepileptics in serum and saliva, with model mixtures of illicit drugs, and with extracts from urine specimens that tested positively for opiates and cocaine metabolites are presented. Emphasis is focused on buffer selection and simple sample preparation procedures, including direct injection of body fluids, ultrafiltration and solid-phase extraction.     

Epithelial transport of drugs in cell culture. VIII: Effects of sodium dodecyl sulfate on cell membrane and tight junction permeability in human intestinal epithelial (Caco-2) cells

This study demonstrates how the common pharmaceutical wetting agent sodium dodecyl sulfate (SDS) increases the absorption of drugs and peptides across the human intestinal epithelium. First, an assay that could follow the reversible and irreversible time-dependent effects of SDS on the permeability of Caco-2 cell monolayers with high reproducibility was developed. SDS (0.40 mM) exposure for 20 min resulted in reversible absorption enhancement of mannitol (M(r), 182 g/mol), 1-deamino-8-D-arginine-vasopressin (M(r), 1071 g/mol), and polyethylene glycol (M(r), 4000 g/mol). A longer (2 h) exposure to SDS resulted in irreversible absorption enhancement. Second, transepithelial electrical resistance measurements (TEER) together with fluorescence and transmission electron microscopy were used to study the effects of SDS on epithelial integrity, cell membranes, intracellular calcium concentration, cytoskeleton, and tight junctions. The effect of SDS (0.40 mM) on epithelial integrity was immediate. A significant decrease in transepithelial electrical resistance measurements was obtained with 1 min after exposure to SDS that was concomitant with increases in the permeability of the apical cell membranes and intracellular calcium concentration. SDS shortened the microvilli of the cells and produced apical (but not basolateral) membrane wounds, actin disbandment, disorganization of the terminal web, and structural separation of the tight junctions. The absorption enhancement was not reduced after repair of the apical cell membranes, indicating that SDS enhances drug and peptide absorption across the intestinal epithelium by the paracellular pathway.     

Studies of Na-segregation at Ni/α-quartz interfaces

Ni/α-quartz bilayers were irradiated at 77 K with 200 keV Na⁺ ions at a fluence of 5 × 10¹⁶ ions/cm² and annealed in hydrogen up to 883 K. The Na-migration at the Ni/α-quartz interface and towards the Ni-surface, the hydrogen storage in the irradiated region, and the Ni/α-quartz interface broadening due to Na implantation and decoration were investigated via Rutherford Backscattering Spectrometry (RBS) and Resonant Nuclear Reaction Analysis (RNRA). We demonstrate that after a one hour-annealing at 833 K a large fraction of the implanted Na has been trapped at the Ni/α-quartz interface from where it is released at 883 K. The results are discussed and compared with our findings in Na-irradiated metals and silicon compounds.     

Effet des conditions aux limites sur le comportement des assemblages bois boulonnés

Résumé Les assemblages utilisés dans les structures bois sont très variés. Aux dispositions géométriques fort diverses se rajoute le fait que deux matériaux de comportements différents (bois et acier) sont généralement en présence. Dans cette étude, on considère le cas d'un assemblage élémentaire à deux plans de cisaillement avec un seul boulon. On s'intéresse particulièrement à des assemblages de grande épaisseur où l'influence de l'élancement du boulon (longueur/ diamètre) et des cnditions de rotation de ses têtes sur la réponse globale de l'assemblage est analysée. La courbe représentant cette réponse, de type force-glissement, intègre les caractéristiques de rigidité et de résistance de l'assemblage. On considère pour cela un seul diamètre de boulon égal à 8mm et trois élancements égaux à 4, 8 et 12, avec des pièces latérales en métal ou en bois. Le bois est représensé par une loi d'enfoncement du type exponentiel à trois paramètres, et le boulon est supposé à comportement élastoplastique. On constate que les conditions de rotation des têtes de boulon influencent aussi bien la résistance que la rigidité initiale de l'assemblage. Cependant, le comportement du boulon influence seulement la résistance de l'assemblage. En effet, la résistance est conditionée par les rotules plastiques qui se développent, le long du boulon, au cours du chargement. Par ailleurs, les assemblages à pièces latérales métalliques présentent une résistance et une rigidité initiale plus élevées que ceux ayant des pièces latérales en bois. La comparaison des résultats avec diverses études expérimentales et numériques montre la validité du modèle proposé.

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Bolted joints used in wood structures are extremely varied. In addition to presenting quite diverse geometric elements the two materials generally involved (wood and steel) exhibit most distinct behaviors. In the current study, the application of an elementary double-shear wood bolted joint in static short-term loading has been considered. The particular focus herein concerns thick joints, where the impact of the blot's slenderness (length/diameter ratio) as well as the rotating conditions of the bolt's heads on the overall response of the joint has been analysed. The curve representing this response, of the load-slip type, serves to integrate the characteristics of the joint's stiffness and strength. To carry this out, a constant bolt diameter of 8 mm, along with three slenderness values of 4, 8 and 12 with steel or wood side members, was used. The wood behavior in embedment is represented by means of an exponential three-parameter law, and the bolt is assumed to exhibit an elastic-plastic behavior. It has been observed that the rotation of the bolt heads exerts as much of an influence on the strength as the joint's initial stiffness. However, the bolt's behavior only influences the strength of the joint itself. In fact, the strength is actually conditioned by the plastic highes that appear on the bolt sections during loading. In addition, joints with steel side members are stronger and display a higher initial stiffness than those with wood side members. A comparison of results obtained from various experimentalk and numerical studies helps demonstrate the validity of the present model proposed.

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Note de la Rédation Alain Vergne est Membre Effectif de la RILEM.