Online monitoring of diallyldimethylammonium chloride polymerization

Diallyldimethylammonium chloride, which is an acidic salt with numerous applications, was polymerized in water at three different monomer concentrations and at three different pHs which the monomer is in charged form. Reactions were investigated by the automatic continuous online monitoring of polymerization technique. Conversion, molecular weight, and reduced viscosity were monitored. The reaction is found to be second‐order with respect to monomer. Rate constants and molecular weights tend to increase with pH and concentration. POLYM. ENG. SCI., 54:1350–1356, 2014. © 2013 Society of Plastics Engineers     

Morphology, rheology and dynamic mechanical properties of PP/EVA/clay nanocomposites

This paper reports on morphology, rheology and dynamic mechanical properties of polypropylene (PP)/ethylene vinyl acetate (EVA) copolymer/clay nanocomposite system prepared via a single step melt compounding process using a twin screw micro-compounder. Scanning electron microscopic (SEM) investigations revealed that the dispersed phase droplet size was reduced with incorporation of an organo-modified montmorillonite (OMMT). This reduction was more significant in presence of a maleated PP (PP-g-MAH) used as compatibilizer. Phase inversion in the compatibilized blends caused a further decrease in PP droplet size. The OMMT gallery spacing was higher in nanocomposites with EVA as matrix which could be attributed to higher tendency of OMMT nanoparticles towards EVA rather than PP. This enhanced tendency was confirmed by rheological analysis too. Transmission electron microscopy (TEM) results also showed that the majority of OMMT nanoparticles were localized on the interface and within EVA droplets. According to dynamic mechanical analysis, the compatibilized nanocomposites showed higher storage and loss moduli due to better dispersion of OMMT layers. The modulus enhancement of nanocomposites as a function of OMMT volume fraction was modeled by Halpin-Tsai’s-Nielsen expression of modulus for nanocomposites. The results of modeling suggested that the aspect ratio of the intercalated OMMT, in the form of Einstein coefficient (K _E), plays a determining role in the modulus enhancement of nanocomposites.     

GPU fuzzy c-means algorithm implementations: performance analysis on medical image segmentation

Multimedia Tools and Applications - Image segmentation in the medical imagery such as MRI, is an essential step to the sensitive analysis of human tissues lesions with the objective to improve the...     

Induced-charge electro-osmosis of polymer-containing fluid around a metallic rod

Induced-charge electro-osmotic (ICEO) flow of polymer-containing electrolyte solution around a cylindrical gold-coated stainless steel rod under AC electric field is measured by micro-particle image velocimetry (micro-PIV) for the first time. The ICEO flows as functions of the amount of non-ionic PEG (polyethylene glycol), cationic PDADMA (polydiallyldimethylammonium chloride), and anionic PVSASS (polyvinylsulfonic acid sodium salt) polymers added into the salt solution, frequency, and strength of the AC electric field are measured. The ICEO flow of polymer-containing fluid around the rod is quadrupolar with four vortices and is proportional to the square of imposed electric field. The ICEO flow velocity exponentially decreases with an increased concentration of neutral PEG. Ionic polyelectrolytes significantly increase ICEO velocities due to the enriched net charge within the induced electric double layer arising from the electrostatic interaction between the polarized rod’s surface and the charged polyelectrolytes in ionic polymer solution. In addition, polymer concentration affects the dependence of the ICEO flow on the frequency of AC electric field.     

The effects of discontinuity surface roughness on the shear strength of weathered granite joints

Surface roughness is one of the most important parameters governing the shear strength of rock discontinuities. Roughness types may vary based on genesis, physico-mechanical, and mineralogical properties of rocks. In this study, granite samples representing three different weathering degrees were selected to evaluate the effects of surface roughness and weathering degree on shear strength. To this aim, we determined the profile roughness coefficient (PRC), profile roughness angle (PRA), and joint roughness coefficient (JRC) for the selected fresh and weathered granite joint samples. Values of PRC were in the range of about 1.043–1.073, and PRA and JRC varied in the ranges of 16.67–21.45 and 12–18, respectively. Weathering led to the increment of joint surface roughness of the selected granitic joints due to the higher resistance of quartz crystals in the weathered matrix. However, the increment in surface roughness did not result in an increase in the shear strength. On the contrary, the shear strength of discontinuities dramatically decreased.     

Targeting a polyketide synthase gene for Aspergillus carbonarius quantification and ochratoxin A assessment in grapes using real-time PCR

Aspergillus carbonarius is an ochratoxin producing fungus that has been considered to be responsible of the ochratoxin A (OTA) contamination in grapes and wine. In order to monitor and quantify A. carbonarius, a specific primer pair Ac12RL_OTAF/Ac12RL_OTAR has been designed from the acyltransferase (AT) domain of the polyketide synthase sequence Ac12RL3 to amplify 141 bp PCR product. Among the mycotoxigenic fungi tested, only A. carbonarius gave a positive result. This specific primer pair was also successfully employed in real-time PCR conjugated with SYBR Green I dye for the direct quantification of this fungus in grape samples. A positive correlation (R(2)=0.81) was found between A. carbonarius DNA content and OTA concentration in 72 grape samples, allowing for the estimation of the potential risk from OTA contamination. Consequently, this work offers a quick alternative to conventional methods of OTA quantification and mycological detection and quantification of A. carbonarius in grapes.     

Introducing a novel integrated NGL recovery process configuration (with a self-refrigeration system (open–closed cycle)) with minimum energy requirement

In this study a novel process configuration for recovery of hydrocarbon liquids from natural gas is proposed. The required refrigeration in this configuration is obtained by a self-refrigeration system (open–closed cycle). High performance of the multi-stream heat exchangers, high recovery levels of the hydrocarbon liquids and low required compression power (in the internal refrigeration section) are three of most important characteristic of the proposed configuration. The effects of the mixed self-refrigerant flow rate and pressure on the performance of the process are discussed. Various values for feed composition are tested and the results show that the process can work efficiently with different feeds. In order to analyze the need of external refrigeration by a close or open cycle that is related to the composition of the inlet gas, a configuration with external refrigeration is designed the manner that it is similar with the purposed configuration in the separation section.     

Investigation of the catalytic activity of LaBO3 (B = Ni, Co, Fe or Mn) prepared by the microwave-assisted method for hydrogen evolution in acidic medium

LaBO₃ (B = Ni, Co, Fe and Mn) were prepared by microwave-assisted citrate method. The electrocatalytic activity toward hydrogen evolution reaction (HER) was investigated. XRD characterization showed that pure perovskite crystals were indeed formed. SEM images showed that changing the type of the B-site metal ion affected the morphology of the prepared perovskites. The influence of the type of B-cation on the catalytic activity toward hydrogen evolution was studied and the order of the electrocatalytic activity was LaFeO₃ > LaCoO₃ > LaNiO₃ > LaMnO₃, that was related to the calculated values of the activation energy 51.61, 45.37, 41.15 and 55.05 kJ mol⁻¹ for LaBO₃ (B = Ni, Co, Fe and Mn), respectively. The reaction order and the reaction mechanism for all the prepared perovskites were identified. In addition, the effect of the partial substitution at the B-site in LaNi_{1 − x}Co_xO₃ was also studied. It was found that among ternary perovskites, the catalytic activity of LaNiO₃ decreased by increasing the fraction of doped-Co.