Numerical and experimental study of agglomerate dispersion in polymer extrusion

A model for agglomerate dispersion in screw extruders was developed and superimposed on the flow patterns as simulated using the FIDAP software. A particle tracking algorithm with an adaptive time step was used to follow the agglomerates trajectory. Along this flow path, the breakup probability was estimated using a Monte Carlo method and in conjunction with the local fragmentation number. Particle size distributions and Shannon entropy were computed along the screw channel. The results show good qualitative agreement between model predictions and experimental data

Diabetes-related molecular signatures in infrared spectra of human saliva

WOS: 000290261500001PubMed ID: 20630088Background: There is an ongoing need for improvements in non-invasive, point-of-care tools for the diagnosis and prognosis of diabetes mellitus. Ideally, such technologies would allow for community screening. Methods: In this study, we employed infrared spectroscopy as a novel diagnostic tool in the prediction of diabetic status by analyzing the molecular and sub-molecular spectral signatures of saliva collected from subjects with diabetes (n = 39) and healthy controls (n = 22). Results: Spectral analysis revealed differences in several major metabolic components - lipid, proteins, glucose, thiocyanate and carboxylate - that clearly demarcate healthy and diseased saliva. The overall accuracy for the diagnosis of diabetes based on infrared spectroscopy was 100% on the training set and 88.2% on the validation set. Therefore, we have established that infrared spectroscopy can be used to generate complex biochemical profiles in saliva and identify several potential diabetes-associated spectral features. Conclusions: Infrared spectroscopy may represent an appropriate tool with which to identify novel diseases mechanisms, risk factors for diabetic complications and markers of therapeutic efficacy. Further study into the potential utility of infrared spectroscopy as diagnostic and prognostic tool for diabetes is warranted

Compatibilization of titanium dioxide powders with non-polar media: Adsorption of anionic surfactants and its influence on dispersion stability

The effect of the adsorption of an anionic surfactant (aerosol OT, sodium dodecyl sulfate, sodium dodecyl sulfonate, or sodium dodecyl benzene sulfonate) on the dispersion behavior of some types of titanium dioxide pigments has been studied. Surfactant adsorption isotherms and the kinetics of the adsorption process were linked using a full Langmuir model. Sedimentation experiments were used to assess the dispersibility of the powders in two non-polar dispersion media (nonane and cyclohexane). Surfactant-modified powders were found to be more dispersible than the untreated powders in these non-polar media. Experiments were also performed to assess the stability of the surfactant coating to elevated temperatures and exposure to organic solvents

Applications of Statistical Physics to Mixing in Microchannels: Entropy and Multifractals

We apply rigorous measures of mixing based on entropy in conjunction with fractals to the field of microfluidics. First we determine the entropy and multifractal dimensions of images of mixing a fluorescent and a non-fluorescent fluid in a microchannel. We find the microstructures to be self-similar (fractals). Second we propose a new approach for patterning the walls of microchannels using the Weierstrass function. We have evidence from numerical simulations that by properly adjusting the dimension of the Weierstrass function one can get microfluidic devices that exhibit better mixing than the current ones. © 2008 Springer Netherlands

Modeling of agglomerate dispersion in single screw extruders

A model for solid agglomerate dispersion in single screw extruders is proposed. The model combines numerical simulations of flow patterns in the metering section of a single screw extruder with a Monte Carlo method of clusters rupture and erosion mediated by a local fragmentation number. Particle size distributions and Shannon entropy are used for mixing characterization. The model is quite general and can be adapted for different polymer-additive systems as well as for different processing equipment.The financial support provided by FCT (Fundacao para a Ciencia e Tecnologia), Portugal, under project POCTI CTM/48448/2002 and scholarship SFRH/BD/19605/2004, is acknowledged

Dynamics of filler size and spatial distribution in a plasticating single screw extruder : modeling and experimental observations

A model of agglomerate break-up, incorporating both rupture and erosion, is employed to predict the dynamics of filler size distribution in a plasticating single screw extruder. Filler spatial distribution along the extruder length was also ascertained and direct comparison of experimental and computational data proved to be satisfactory. The method was also used to investigate the effect of material properties, operating conditions and extruder geometry on the dynamics of agglomerate dispersion along a single screw extruder. Generally, dispersion levels were primarily governed by the magnitude of the hydrodynamic stresses developed in the extruder and the residence time in the melt.The financial support provided by FCT (Fundacao para a Ciencia e Tecnologia), Portugal, under project POCTI CTM/48448/2002 and scholarship SFRH/BD/19605/2004, is acknowledged