EGG ALBUMIN AND GUAR GUM INFLUENCE ON FOAM THIXOTROPY

Food foams may be defined as products containing a gaseous phase stabilized in a matrix containing water and proteins. The rheology of a foam can be altered by how the air bubbles inside are organized, its size and shape, allowing a product that was initially fluid to be molded, like marshmallow. Rheology makes possible to understand how these properties are affected using dynamic oscillatory measurements to evaluate the behavior through G` and G `, and rotational to characterize the product through stress, and viscosity curves under controlled shear stress. These two methodologies combined are useful to analyze thixotropy. Nine formulations containing albumin and gelatin, and five others containing guar gum were evaluated by oscillatory rheology focusing thixotropy determination. Replacing gelatin by guar gum elasticity and thixotropy were increased, improving film stability around the air bubbles. It is possible to say that gelatin can be replaced by guar gum at concentrations of 0.4%, creating a product with a better ability of structure recovery. PRACTICAL APPLICATION This study indicated an important role of thixotropic analysis choice to understand the behavior of structure of products like foam. It was tested with three alternatives to get information about thixotropy of the products. It is very important for those who work with rheological analysis and products formulation.

Relationship between Rheological Properties and One-Step W/O/W Multiple Emulsion Formation

Formation of a normal (not temporary) W/O/W multiple emulsion via the one-step method as a result of the simultaneous occurrence of catastrophic and transitional phase inversion processes has been recently reported. Critical features of this process include the emulsification temperature (corresponding to the ultralow surface tension point), the use of a specific nonionic surfactant blend and the surfactant blend/oil phase ratio, and the addition of the surfactant blend to the oil phase. The purpose of this study was to investigate physicochemical properties in an effort to gain a mechanistic understanding of the formation of these emulsions. Bulk, surface, and interfacial theological properties of adsorbed nonionic surfactant (CremophorRH40 and Span80) films were investigated under conditions known to affect W/O/W emulsion formation. Bulk viscosity results demonstrated that CremophorRH40 has a higher mobility in oil compared than in water, explaining the significance of the solvent phase. In addition, the bulk viscosity profile of aqueous solutions containing CremophorRH40 indicated a phase transition at around 78 +/- 2 degrees C, which is in agreement with cubic phase formation in the Winsor III region. The similarity in the interfacial elasticity values of CremophorRH40 and Span80 indicated that canola oil has a major effect on surface activity, showing the significance of vegetable oil. The highest interfacial shear elasticity and viscosity were observed when both surfactants were added to the oil phase, indicating the importance of the microstructural arrangement. CremophorRH40/Span80 complexes tended to desorb from the solution/solution interface with increasing temperature, indicating surfactant phase formation as is theoretically predicted in the Winsor III region. Together these interfacial and bulk rheology data demonstrate that one-step W/O/W emulsions form as a result of the simultaneous occurrence of phase-transition processes in the Winsor III region and explain the critical formulation and processing parameters necessary to achieve the formation of these normal W/O/W emulsions.

Rheological, mechanical and mucoadhesive properties of thermoresponsive, bioadhesive binary mixtures composed of poloxamer 407 and carbopol 974P designed as platforms for implantable drug delivery systems for use in the oral cavity

This study described the formulation and characterisation of the viscoelastic, mechanical and mucoadhesive properties of thermoresponsive, binary polymeric systems composed of poloxamer (P407) and poly(acrylic acid, C974P) that were designed for use as a drug delivery platform within the oral cavity. Monopolymeric and binary polymeric formulations were prepared containing 10, 15 and 20% (w/w) poloxamer (407) and 0.10-0.25% (w/w) poly(acrylic acid, 934P). The flow theological and viscoelastic properties of the formulations were determined using controlled stress and oscillatory rheometry, respectively, the latter as a function of temperature. The mechanical and mucoadhesive properties (namely the force required to break the bond between the formulation and a pre-hydrated mucin disc) were determined using compression and tensile analysis, respectively. Binary systems composed of 10% (w/w) P407 and C934P were elastoviscous, were easily deformed under stress and did not exhibit mucoadhesion. Formulations containing 15 or 20% (w/w) Pluronic P407 and C934P exhibited a sol-gel temperature T(sol/gel), were viscoelastic and offered high elasticity and resistance to deformation at 37 degrees C. Conversely these formulations were elastoviscous and easily deformed at temperatures below the sol-gel transition temperature. The sol-gel transition temperatures of systems containing 15% (w/w) P407 were unaffected by the presence of C934P; however, increasing the concentration of C934P decreased the T(sol/gel) in formulations containing 20%(w/w) P407. Rheological synergy between P407 and C934P at 37 degrees C was observed and was accredited to secondary interactions between these polymers, in addition to hydrophobic interactions between P407 micelles. Importantly, formulations composed of 20% (w/w) P407 and C934P exhibited pronounced mucoadhesive properties. The ease of administration (below the T(sol/gel)) in conjunction with the viscoelastic (notably high elasticity) and mucoadhesive properties (at body temperature) render the formulations composed of 20% (w/w) P407 and C934P as potentially useful platforms for mucoadhesive, controlled topical drug delivery within the oral cavity. (c) 2009 Published by Elsevier B.V.

Avaliação tecnológica de painéis MDF de madeira de Eucalyptus grandis confeccionados em laboratório e em linha de produção industrial

MDF panels of Eucalyptus grandis wood fibers were made in either experimentally in a laboratory or on an industrial production line. In order to analyze the influence of the production condition, the anatomical, physical and mechanical properties of the panels were determined. The wood refining induced the transversal rupture of the transversal fiber wall. The MDF panels obtained from the industrial production line presented less swelling in thickness and absorption values and improved mechanical properties in the requirements of bending strength, module of elasticity and surface resistance. For laboratory MDF panels, it was possible to verify a statistically significant correlation between bending strength and module of elasticity, medium density and internal bond and swelling in thickness and absorption. This tendency was also true for the MDF panels obtained in real conditions of production, however without statistical significance. By comparing the quality properties of MDF panels produced in the laboratory with those obtained in real conditions of production, it was sought to standardize the established variables for obtaining panels on a small scale, as well to make possible the safe transfer and divulgation of information obtained in the laboratory.

Nasal mucus transportability in children with cleft palate

Objectives: Children with cleft palate (CP) have a high prevalence of sinusitis. Considering that nasal mucus properties play a pivotal role in the upper airway defense mechanism, the aim of the study was to evaluate nasal mucus transportability and physical properties from children with CP. Setting: Hospital for Rehabilitation of Craniofacial Anomalies, School of Dentistry, University of Sao Paulo, Bauru, SP, Brazil and Laboratory of Experimental Air Pollution, School of Medicine, University of Sao Paulo, Sao Paulo, SP, Brazil. Methods: Nasal mucus samples were collected by nasal aspiration from children with CP and without CP (non-CP). Sneeze clearance (SC) was evaluated by the simulated sneeze machine. In vitro mucus transportability (MCT) by cilia was evaluated by the frog palate preparation. Mucus physical surface properties were assessed by measuring the contact angle (CA). Mucus rheology was determined by means of a magnetic rheometer, and the results were expressed as log G* (vectorial sum of viscosity and elasticity) and tan delta (relationship between viscosity and elasticity) measured at 1 and 100 rad/s. Results: Mucus samples from children with CP had a higher SC than non-CP children (67 +/- 30 and 41 +/- 24 mm, respectively, p < 0.05). Mucus samples from children with CP had a lower CA (24 +/- 16 degrees and 35 +/- 11 degrees, p < 0.05) and a higher tan delta 100 (0.79 +/- 0.24 and 0.51 +/- 0.12, p < 0.05) than non-CP children. There were no significant differences in mucus MCT, log G* 1, tan delta 1 and log G* 100 obtained for CP and non-CP children. Conclusions: Nasal mucus physical properties from children with CP are associated with higher sneeze transportability. The high prevalence of sinusitis in children with CP cannot be explained by changes in mucus physical properties and transportability. (C) 2008 Elsevier Ireland Ltd. All rights reserved.

Fibroelastic Components of the Vesicourethral Junction of Rats in the Aging Process

The vesicourethral junction comprising the vesical trigone, is relevant in setting and positioning of the urinary bladder, along with the vesical neck, fixed by lateral ligaments of the bladder and tendinous arch of the pelvis fascia. Namely, the puboprostatic ligament (men) and the pubovesical (women). The circular set elastic fibers in this junction are important and valuable in the elasticity and plasticity of the area, allowing quick expansion and withdrawal with the flow of urine, and associated to smooth muscle tissue and nerve control form an important collective to maintain urinary continence. The objective of the present study is to describe the elastic system in the vesicouretral junction in relation to aging and its involvement in the states of urinary continence and incontinence, as well as the study of the vesicouretral junction in various age groups while evaluating with electron transmission microscopy. To carry out the study, 12 Wistar rats were used, divided into groups: neonate (4 animals), adult group (4 animals) and aged group (4 animals). Electron transmission microscopy with use of tanic acid technique associated to glutaraldehyde fixation, satisfactorily showed the extreme structural differences between mature elaunin and oxytalan fibers present between intercelular spaces and bundles of collagen fibers. The phases of elastogenesis in neonate animals and degradation of the elastic system of older animals were also evaluated.

Chitosan as a removing agent of beta-lactoglobulin from membrane models

Many chitosan biological activities depend on the interaction with biomembranes, but so far it has not been possible to obtain molecular-level evidence of chitosan action. In this article, we employ Langmuir phospholipid monolayers as cell membrane models and show that chitosan is able to remove beta-lactoglobulin (BLG) from negatively charged dimyristoyl phosphatidic acid (DMPA) and dipalmitoyl phosphatidyl glycerol (DPPG). This was shown with surface pressure isotherms and elasticity and PM-IRRAS measurements in the Langmuir monolayers, in addition to quartz crystal microbalance and fluorescence spectroscopy measurements for Langmuir-Blodgett (LB) films transferred onto solid substrates. Some specificity was noted in the removal action because chitosan was unable to remove BLG incorporated into neutral dipalmitoyl phosphatidyl choline (DPPC) and cholesterol monolayers and had no effect on horseradish peroxidase and urease interacting with DMPA. An obvious biological implication of these findings is to offer reasons that chitosan can remove BLG from lipophilic environments, as reported in the recent literature.

Study of the surface hardness and modulus of elasticity of conventional and microwave-cured acrylic resins

The aim of this study was to evaluate the following acrylic resins: Clássico®, QC-20® and Lucitone®, recommended specifically for thermal polymerization, and Acron MC® and VIPI-WAVE®, made for polymerization by microwave energy. The resins were evaluated regarding their surface nanohardness and modulus of elasticity, while varying the polymerization time recommended by the manufacturer. They were also compared as to the presence of water absorbed by the samples. The technique used was nanoindentation, using the Nano Indenter XP®, MTS. According to an intra-group analysis, when using the polymerization time recommended by the manufacturer, a variation of 0.14 to 0.23 GPa for nanohardness and 2.61 to 3.73 GPa for modulus of elasticity was observed for the thermally polymerized resins. The variation for the resins made for polymerization by microwave energy was 0.15 to 0.22 GPa for nanohardness and 2.94 to 3.73 GPa for modulus of elasticity. The conclusion was that the Classico® resin presented higher nanohardness and higher modulus of elasticity values when compared to those of the same group, while Acron MC® presented the highest values for the same characteristics when compared to those of the same group. The water absorption evaluation showed that all the thermal polymerization resins, except for Lucitone®, presented significant nanohardness differences when submitted to dehydration or rehydration, while only Acron MC® presented no significant differences when submitted to a double polymerization time. Regarding the modulus of elasticity, it was observed that all the tested materials and products, except for Lucitone®, showed a significant increase in modulus of elasticity when submitted to a lack of hydration.

Relationship between birthweight and arterial elasticity in childhood

There is a considerable debate about the potential influence of fetal programming on cardiovascular diseases in adulthood. In the present prospective epidemiological cohort study, the relationship between birthweight and arterial elasticity in 472 children between 5 and 8 years of age was assessed. LAEI (large artery elasticity index), SAEI (small artery elasticity index) and BP (blood pressure) were assessed using the HDI/PulseWave CR-2000 CardioVascular Profiling System. Blood concentrations of glucose, total cholesterol and its fractions [LDL (low-density lipoprotein)-cholesterol and HDL (high-density lipoprotein)-cholesterol] and triacylglycerols (triglycerides) were determined by automated enzymatic methods. Insulin was assessed by a chemiluminescent method, insulin resistance by HOMA (homoeostasis model assessment) and CRP (C-reactive protein) by immunonephelometry. Two linear regression models were applied to investigate the relationship between the outcomes, LAEI and SAEI, and the following variables: birthweight, gestational age, glucose, LDL-cholesterol, HDL-cholesterol, triacylglycerols, insulin, CRP, HOMA, age, gender, waist circumference, per capita income, SBP (systolic BP) and DBP (diastolic BP). LAEI was positively associated with birthweight (P=0.036), waist circumference (P<0.001) and age (P<0.001), and negatively associated with CRP (P=0.024) and SBP (P<0.001). SAEI was positively associated with birthweight (P=0.04), waist circumference (P=0.001) and age (P<0.001), and negatively associated with DBP (P<0.001). Arterial elasticity was decreased in apparently healthy children who had lower birthweights, indicating an earlier atherogenetic susceptibility to cardiovascular diseases in adolescence and adult life. Possible explanations for the results include changes in angiogenesis during critical phases of intrauterine life caused by periods of fetal growth inhibition and local haemodynamic anomalies

Real exchange rate and elasticity of labour supply in a balance-of-payments-constrained macrodynamics

A macrodynamic model is proposed in which the real exchange rate and the elasticity of labour supply interact defining different trajectories of growth and income distribution in a developing economy. Growth depends on imports of capital goods which are paid with exports (there are no capital flows) and hence is constrained by equilibrium in current account. The role of the elasticity of labour supply is to prevent the real exchange rate from appreciating as the economy grows, thereby sustaining international competitiveness. The model allows for endogenous technological change and considers the impact of migration from the subsistence to the modern sector on the cumulative (Kaldor-Verdoorn) process of learning.

The association of Na,K-ATPase subunits studied by circular dichroism, surface tension and dilatational elasticity

Different stoichiometries are observed between alpha and beta subunits of Na,K-ATPase that depend on the method employed to solubilize and purify the enzyme. It is not known whether this variability is due to loss of protein-protein association, or is a result of the replacement of essential phospholipids by detergent molecules. With the aim of understanding the effect of enzyme/surfactant ratio on both the catalytic activity and the enzyme structure, we have investigated the bulk and surface properties of the enzyme. The circular dichroism (CD) spectra, surface tension and dilatational surface elasticity results were compared with the residual ATPase activity of the Na,K-ATPase in different surfactant and protein concentrations. Na,K-ATPase in the (alpha beta)(2) form dissociated to the alpha beta form on dilution, and associated to the (alpha beta)(4) form when concentrated. These different stoichiometries have similar ATPase activities and are in equilibrium at C(12)E(8) concentrations below the CIVIC (0.053 mg mL(-1)). At detergent concentrations above the CIVIC the ATPase activity of all forms was abolished, which is concomitant with the dissociation of the a and subunits. (C) 2008 Elsevier Inc. All rights reserved.

A discontinuous-Galerkin-based immersed boundary method with non-homogeneous boundary conditions and its application to elasticity

We propose a discontinuous-Galerkin-based immersed boundary method for elasticity problems. The resulting numerical scheme does not require boundary fitting meshes and avoids boundary locking by switching the elements intersected by the boundary to a discontinuous Galerkin approximation. Special emphasis is placed on the construction of a method that retains an optimal convergence rate in the presence of non-homogeneous essential and natural boundary conditions. The role of each one of the approximations introduced is illustrated by analyzing an analog problem in one spatial dimension. Finally, extensive two- and three-dimensional numerical experiments on linear and nonlinear elasticity problems verify that the proposed method leads to optimal convergence rates under combinations of essential and natural boundary conditions. (C) 2009 Elsevier B.V. All rights reserved.

Influence of incorporation of fluoroalkyl methacrylates on roughness and flexural strength of a denture base acrylic resin

Fluorinated denture base acrylic resins can present more stable physical properties when compared with conventional polymers. This study evaluated the incorporation of a fluoroalkyl methacrylate (FMA) mixture in a denture base material and its effect on roughness and flexural strength. A swelling behavior assessment of acrylic resin specimens (n=3, per substance) after 12 h of FMA or methyl methacrylate (MMA) immersion was conducted to determine the solvent properties. Rectangular specimens (n=30) were allocated to three groups, according to the concentration of FMA substituted into the monomer component of a heat-polymerized acrylic resin (Lucitone 550), as follows: 0% (control), 10% and 20% (v/v). Acrylic resin mixed with concentrations of 25% or more did not reach the dough stage and was not viable. The surface roughness and flexural strength of the specimens were tested. Variables were analyzed by ANOVA and Tukey's test (a=0.05). Immersion in FMA produced negligible swelling, and MMA produced obvious swelling and dissolution of the specimens. Surface roughness at concentrations of 0%, 10% and 20% were: 0.25 ± 0.04, 0.24 ± 0.04, 0.22 ± 0.03 mm (F=1.78; p=0.189, not significant). Significant differences were found for flexural strength (F=15.92; p<0.001) and modulus of elasticity (F=7.67; p=0.002), with the following results: 96 ± 6, 82 ± 5, 84 ± 6 MPa, and 2,717 ± 79, 2,558 ± 128, 2574 ± 87 MPa, respectively. The solvent properties of FMA against acrylic resin are weak, which would explain why concentrations over 20% were not viable. Surface changes were not detected after the incorporation of FMA in the denture base acrylic resin tested. The addition of FMA into denture base resin may lower the flexural strength and modulus of elasticity, regardless of the tested concentration.

Preparation and characterization of Ti-15Mo alloy used as biomaterial

With the increase in life expectancy, biomaterials have become an increasingly important focus of research because they are used to replace parts and functions of the human body, thus contributing to improved quality of life. In the development of new biomaterials, the Ti-15Mo alloy is particularly significant. In this study, the Ti-15Mo alloy was produced using an arc-melting furnace and then characterized by density, X-ray diffraction, optical microscopy, hardness and dynamic elasticity modulus measurements, and cytotoxicity tests. The microstructure was obtained with β predominance. Microhardness, elasticity modulus, and cytotoxicity testing results showed that this material has great potential for use as biomaterial, mainly in orthopedic applications.

Elastic Maier-Saupe-Zwanzig model and some properties of nematic elastomers

We introduce a simple mean-field lattice model to describe the behavior of nematic elastomers. This model combines the Maier-Saupe-Zwanzig approach to liquid crystals and an extension to lattice systems of the Warner-Terentjev theory of elasticity, with the addition of quenched random fields. We use standard techniques of statistical mechanics to obtain analytic solutions for the full range of parameters. Among other results, we show the existence of a stress-strain coexistence curve below a freezing temperature, analogous to the P-V diagram of a simple fluid, with the disorder strength playing the role of temperature. Below a critical value of disorder, the tie lines in this diagram resemble the experimental stress-strain plateau and may be interpreted as signatures of the characteristic polydomain-monodomain transition. Also, in the monodomain case, we show that random fields may soften the first-order transition between nematic and isotropic phases, provided the samples are formed in the nematic state.