Polyolefin blends

Morphology observations, differential scanning calorimetry investigations and mechanical tensile tests have been performed on blends based on isotactic polypropylene and high-density polyethylene, containing ethylene-propylene (EP) copolymers of different composition. The blends after melting have been crystallized at low undercoolings (T _c=126 and 110° C, respectively). All the properties strongly depend on the EP composition, indicating a marked interaction between the C₂ or C₃ sequences in the copolymers and the two matrices. These features are compared with those observed in previous work for the same blends crystallized at high undercoolings (quenched in water). Some relevant differences with respect to the crystallization procedures used and to the resulting structures in the blends are discussed.     

Vibration analysis of coupled fluid-structure systems: A convenient computational approach

The mathematical model implemented in the ZERO code for dynamic analysis of thin axi-symmetric structures coupled with fluid, is briefly described. The numerical experimentation presented is aimed at evaluating the efficiency of the method applied for computation of vibration characteristics of the coupled system.     

I. Segregation of Active Constituents from Tablet Formulations During Grinding: Theoretical Considerations

The preparatory step in the analysis of active drugs in tablet dosage forms has generally consisted of the grinding or milling of a given number of the tablets into a uniformly composited powder. Since the advent of content uniformity testing (individual tablet analysis) where the compositing step is bypassed, numerous reports have cited the large percentage difference in results observed between the average composited assay value and the average assay value for the individual tablets.

This paper describes some of the factors responsible for these observed differences, as well as some of the causative events that develop during tablet grinding. Certain active constituents become separated from other tablet components during grinding because of differences in the size, shape, density, surface roughness, and resilience of their particles. At particle sizes of less than approximately 400 µm additional forces and mechanisms, namely Van der Waals forces, electrostatic forces, adsorption, and valency forces, become significant.     

Detection of Salmonella in dry foods using refrigerated pre-enrichment and enrichment broth cultures: summary of collaborative study

A collaborative study was conducted to compare the productivity of refrigerated pre-enrichment and enrichment broth cultures with the U.S. Food and Drug Administration culture methods for detection of Salmonella. The refrigerated pre-enrichment and selective enrichment broth culture methods for detection of Salmonella in dry foods have been adopted first action by AOAC INTERNATIONAL.     

Robust optimum design of tuned mass dampers for high‐rise buildings under moderate earthquakes

In the present study the optimum design of tuned‐mass‐damper (TMD) devices used for the vibration control of high‐rise buildings subject to moderate earthquakes is developed. For these structures a large acceleration demand can produce damage in equipment and contents: therefore, the performance of TMD will be based on the capacity of reducing this structural response. In order to maximize the performance and the efficiency of the TMD strategy, the ratio between the absolute accelerations of the protected and of the unprotected systems is assumed as objective function in the optimum design. The method is carried out in a stochastic way and a stationary‐filtered stochastic process is assumed to model the seismic action. Since the main disadvantage of using a single TMD is the mistuning related to errors in the evaluation of the natural frequency of the main structure, an uncertainty is introduced for this structural parameter, which is modelled as a random variable. Uncertainties in other structural mechanical properties and in TMD are neglected. Copyright © 2008 John Wiley & Sons, Ltd.     

Molecular mobility and ageing of sugar glasses

Carbohydrates play an important role in the stabilization of biological components under water stress and, consequently, in the preservation of foods. Water stress is produced either by freezing or drying producing damage in proteins and tissues mainly due to the generation of large gradients of concentration of salts. Some carbohydrates act as protectors but, although some explanations have been proposed, the mechanism is not yet properly known.     

Usefulness of a set of simple in vitro tests for the screening and identification of probiotic candidate strains for dairy use

A set of simple in vitro tests (identification by species-specific PCR, genetic diversity, phage sensitivity, growth and viability in milk, resistance to salts and flavor compounds, bacterial interactions, tolerance to simulated gastric juice and bile, bile salts deconjugation, hydrophobicity and β-galactosidase and antibacterial activities), that can be carried out in almost every laboratory of microbiology, mainly in developing countries where there is often limited access to sophisticated techniques, allowed us to identify, among 19 intestinal human isolates, a potential candidate for new probiotic dairy foods for the local market. Lactobacillus gasseri LgF_37/1 performed well in the culture media used for the enumeration of probiotic bacteria in argentinian dairy products. This strain showed also high tolerance to the technological challenges assessed, bile salts resistance, the capacity to produce bacteriocin-like metabolites, to inhibit pathogenic bacteria, to deconjugate bile salts and high hydrophobicity. Further in vivo research should be carried out with this strain before claiming probiotic properties for it. However, the use of a set of simple in vitro techniques proved to be important to determine which strains should undergo future and more complex studies.     

Modeling mass transfer during osmotic dehydration of strawberries under high hydrostatic pressure conditions

Simultaneous application of high hydrostatic pressure (200–400 MPa) during osmotic dehydration of strawberries was studied in this investigation. The high hydrostatic pressure treatment improved the diffusion coefficients of water and soluble solids compared to atmospheric pressure operation. Effects of process pressure on diffusion coefficients were achieved through an Arrhenius-type equation. Mathematical modeling of mass transfer was performed applying Newton, Henderson–Pabis, Page and Weibull models. Based on statistical results, the Weibull model gave the best goodness of fit on the experimental data under the studies' operative conditions.Industrial relevance: This article deals with the mathematical modeling of mass transfer during simultaneous high hydrostatic pressure treatment and osmotic dehydration of strawberries. Transfer of water and soluble solids during this combined process were satisfactorily simulated with the Weibull model. Results indicated that application of this innovative technology improved strawberries dehydration rates compared to atmospheric pressure operation resulting in a dried fruit with intermediate moisture content ready to be used as input material of further processes.