Use of postconsumer polyethylene in blends with polyamide 6: Effects of the extrusion method and the compatibilizer

Blends of polyamide and high‐density polyethylene show adequate properties for a large range of applications: they are used for the production of filaments, containers, and molding resins. The effect of the addition of 2 wt % of a compatibilizer, maleic anhydride grafted polyethylene, to the blend was studied and compared to the use of postconsumer polyethylene. The samples were extruded with single‐ and twin‐screw extruders with 25, 50, or 75 wt % f polyethylene, and the test specimens, molded by injection, were characterized by stress–strain tests, thermal properties, and morphologies. Processing the blends with postconsumer polyethylene in both extruders improved the mechanical properties in comparison to the blends processed with high‐density polyethylene and the compatibilizer. The morphologies of these blends showed that there was a decrease in the domain size of the disperse phase with the use of the compatibilizer or postconsumer polyethylene. The results indicate that for this blend, postconsumer polyethylene substituted, with advantages, for the necessity of a compatibilizer and the use of the high‐density polyethylene. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008.     

Practicing engineering in a freshman introductory course

This paper discusses a teaching experience obtained in the undergraduate course of Control Engineering at the Federal University of Santa Catarina (UFSC), Brazil. The course endeavors to introduce the students to the university and to the real world of engineering and to develop an understanding of basic engineering concepts and foster professional skills. By introducing practicing engineering to the course from day one, student motivation is increased, and the relationship between theoretical and practical aspects of engineering is demonstrated more clearly. This "hands-on approach" allows the student a greater insight into the life of an engineer. It strengthens a weakness found in established teaching methods, allowing the individual to embark on his or her engineering education with greater confidence in his or her ability as an engineer.     

Shiga toxin–producing Escherichia coli isolated from pasteurized dairy products from Bahia,Brazil

The presence of pathogenic Shiga toxin–producing Escherichia coli (STEC) in dairy products represents a public health concern because of its ability to produce the toxins Stx1 and Stx2, which cause intestinal diseases. Monitoring the stages of milk production and checking dairy products for contamination are crucial steps to ensure dairy safety. This study aimed to report the occurrence of thermotolerant coliforms, E. coli, and STEC strains in pasteurized dairy products and to evaluate the antibiotic resistance profiles, serotypes, and characterizations of the STEC isolates by pulsed-field gel electrophoresis. We obtained a total of 138 pasteurized dairy products from 15 processing plants in Bahia, Brazil, to examine coliforms, E. coli, and STEC strains. We found that 43% of samples (59/138) contained thermotolerant coliforms, and 30% (42/138) did not comply with Brazilian regulations. Overall, 6% (9/138) were positive for E. coli and 4% (5/138) were positive for STEC. We recovered 9 STEC isolates from pasteurized cream (2/9), Minas Padrão cheese (2/9), Minas Frescal cheese (4/9), and ricotta (1/9). All isolates were stx2-positive, and 2 were eae-positive. All isolates were negative for the “big 6” STEC serogroups, belonging instead to serotypes ONT:HNT, ONT:H12, O148:H?, OR:H40, OR:HNT, and O148:HNT. Pulsed-field gel electrophoresis revealed 100% genetic similarity among 3 isolates from 2 different samples produced in the same production facility, which may suggest cross-contamination. As well, we found isolates that were 98% similar but in samples produced in different production facilities, suggesting a mutual source of contamination or a circulating strain. Two STEC strains exhibited resistance to streptomycin. Although the isolates presented a low resistance profile and no strain belonged to the “big 6” pathogenic group, the circulation of stx2-positive STEC strains in ready-to-eat products highlights the importance of epidemiological surveillance inside the Brazilian dairy chain.     

Online behavior change detection in computer games

Player Modelling has been receiving much attention from the game community in the recent years. The ability to build accurate models of player behavior can be useful in many aspects of a game. One important aspect is the tracking of a player’s behavior along time, informing every time a change is perceived. This way, the game Artificial Intelligence can adapt itself to better respond to this new behavior. In order to build models of player behavior, researchers frequently resort to Machine Learning techniques. Such methods work on previously recorded game metrics representing player’s interactions with the game environment. However, if the player changes styles over time, the constructed models get out of date. In order to address this drawback, this work proposes the use of and incremental learning technique to track a player’s behavior during his/her interaction with the game environment. Our approach attempts to automatically detect the moments in time when the player changes behavior. We apply a change detection technique from the area of Data Stream Mining that is based on incremental clustering and novelty detection. We also propose three modifications to the original technique, in order to formalize change detection, improve detection rate and reduce detection delay. Simulations were performed considering data produced by the Unreal Tournament game, showing the applicability of the method to online tracking of a player’s behavior and informing whenever behavior changes occur.     

Isoflavone Aglycone Content and the Thermal,Functional, and Structural Properties of Soy Protein Isolates Prepared from Hydrothermally Treated Soybeans

Soybeans were hydrothermally treated at 2 different temperatures (40 °C and 60 °C) and for 4 different hydration times (4, 8, 12, and 16 h) to (i) increase the isoflavone aglycone content in a soy protein isolate and (ii) evaluate the changes in thermal, functional, and structural properties of a soy protein isolate as a function of hydrothermal treatment conditions. Our study is the first to evaluate aglycone content, extraction yield, β‐glucosidase activity, differential scanning calorimetry, protein digestibility, scanning electron microscopy, water absorption capacity (WAC), foaming capacity (FC), and foaming stability of soy protein isolates prepared from hydrothermally treated soybeans. For aglycone enhancement and the extraction yield maintenance of soy protein isolates, the condition of 40 °C for 12 h was the best soybean hydrothermal treatment. The structural rearrangement of proteins that occurred with the hydrothermal treatment most likely promoted the capacity of proteins to bind to aglycone. Moreover, the structure shape and size of soy protein isolates verified by scanning electron microscopy appears to be related to the formation of hydrophobic surfaces and hydrophobic zones at 40 °C and 60 °C, respectively, affecting the protein digestibility, WAC, and FC of soy protein isolates.     

Blends of polyaniline with nitrilic rubber

Nitrilic rubbers containing 29 or 45% of acrylonitrile were blended with polyaniline doped with different acids (chloridric, dodecylbenzenesulfonic, tetrapropylbenzenesulfonic, and p‐toluenesulfonic acids). The blends were prepared by mechanical mixing in a roll‐mill and vulcanized in a hot press. The volumetric conductivities and mechanical properties were evaluated. The results show that the polyaniline concentration strongly affects the behavior of the blends. Increasing the polyaniline content from 50 to 100 phr induces an increase in the electric conductivity from 10⁻¹⁰ to 10⁻⁸ S cm⁻¹; however, the blends become harder and more brittle than the crude rubber. Addition of polyaniline lowered the crosslinking degree, but produced a reinforcing effect in the elastomer. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 677–684, 2000     

Polyamide‐6/high‐density polyethylene blend using recycled high‐density polyethylene as compatibilizer: Morphology,mechanical properties,and thermal stability

Blends of polyamide‐6 (PA6) or postindustry polyamide‐6 (piPA6) and high‐density polyethylene (HDPE) or recycled high‐density polyethylene (rHDPE) were processed in single and twin‐screw extruders. The use of rHDPE in the blends promotes a significant decrease of size domains and improvement in the mechanical properties. The thermal stability was also slightly improved compared with PA6 and HDPE blends. The Molau test exhibited a stable emulsion in formic acid, which can be attributed to the formation of an interfacial copolymer involving polar amino end groups of PA6 and the rHDPE, respectively. These results indicate that recycled polymers can be used in the production of polymer blends with improved properties. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers.