Thermal Stability of Biodegradable Films Based on Soy Protein and Corn Starch

Summary: In this paper, films were prepared from soy protein and corn starch in different proportions and thermal stability and kinetic parameters were determined through degradation reactions in an inert atmosphere. Solid residues and decomposition products were identified by infrared spectroscopy. Films from corn starch were less thermally stable than soy protein films. The films containing both components had lower thermal stabilities when compared to those of the pure biopolymers. The mechanism of starch thermal degradation seems to occur in a single step, which can be confirmed by the constant E-values during the thermal degradation reaction. For the pure protein and its mixtures an increase in the activation energy was observed during the reaction. Solid residues for protein at different temperatures showed mainly bands related to CO stretching, angular deformation of N H and C H groups. For starch, absorptions related to free and bound O H, CO stretching of CO₂, CO and carbonyl compounds were observed. For the 50/50 mixture bands related to soy protein and corn starch were observed. The gaseous products for soy protein showed absorptions related to CO₂, CO, CO, NH₃ and C H stretching. For pure starch absorptions related to O H stretching from alcohol, CO from CO₂, CO and carbonyl compounds. The 50/50 mixture had the same characteristics as pure soy protein and corn starch.     

Environment‐Adopting Surfaces with Reversibly Switchable Morphology

Two‐component polymer brushes (polystyrene and poly(2‐vinylpyridine)) were synthesized by grafting from the surface of Si‐wafers. The brushes are sensitive to the surrounding medium, and their morphology and composition of the top of a brush can be switched upon exposure to different solvents. Thus surface energetic states and roughness of the film can be precisely tuned.     

Surface structure analysis of thin dewetted polymer blend films

The surface structure of thin polymer blend films of deuterated polystyrene (dPS) and polyparamethylstyrene (PpMS) after annealing above the glass transition temperature was investigated. With scanning force microscopy (SFM) the surface topography originated by a dewetting process is detected. The sample surface is covered with small droplets consisting of several polymer molecules. Utilizing grazing incidence small angle neutron scattering (GISANS) the topographical information as well as the in‐plane composition is probed. For thin confined blend films a substructure of the droplets resulting from an additional phase separation process at different length scales is detected.     

P2Y12 Purinergic Receptor and Brain Tumors: Implications on Glioma Microenvironment

Gliomas are the most common malignant brain tumors in adults, characterized by a high proliferation and invasion. The tumor microenvironment is rich in growth-promoting signals and immunomodulatory pathways, which increase the tumor’s aggressiveness. In response to hypoxia and glioma therapy, the amounts of adenosine triphosphate (ATP) and adenosine diphosphate (ADP) strongly increase in the extracellular space, and the purinergic signaling is triggered by nucleotides’ interaction in P2 receptors. Several cell types are present in the tumor microenvironment and can facilitate tumor growth. In fact, tumor cells can activate platelets by the ADP-P2Y₁₂ engagement, which plays an essential role in the cancer context, protecting tumors from the immune attack and providing molecules that contribute to the growth and maintenance of a rich environment to sustain the protumor cycle. Besides platelets, the P2Y₁₂ receptor is expressed by some tumors, such as renal carcinoma, colon carcinoma, and gliomas, being related to tumor progression. In this context, this review aims to depict the glioma microenvironment, focusing on the relationship between platelets and tumor malignancy.     

Effects of ethylene polymerization conditions on the activity of SiO2-supported zirconocene and on polymer properties

The effects of polymerization conditions were evaluated on the production of polyethylene by silica-supported (n-BuCp)₂ZrCl₂ grafted under optimized conditions and cocatalyzed by methylaluminoxane (MAO). The Al : Zr molar ratio, reaction temperature, monomer pressure, and the age and concentration of the catalyst were systematically varied. Most reactions were performed in toluene. Hexane, with the addition of triisobutilaluminum (TIBA) to MAO, was also tested as a polymerization solvent for both homogeneous and heterogeneous catalyst systems. Polymerization reactions in hexane showed their highest activities with MAO : TIBA ratios of 3 : 1 and 1 : 1 for the homogeneous and supported systems, respectively. Catalyst activity increased continuously as Al : Zr molar ratios increased from 0 to 2000, and remained constant up to 5000. The highest activity was observed at 333 K. High monomer pressures (≈ 4 atm) appeared to stabilize active species during polymerization, producing polyethylenes with high molecular weight (≈ 3 × 10⁵ g mol⁻¹). Catalyst concentration had no significant effect on polymerization activity or polymer properties. Catalyst aging under inert atmosphere was evaluated over 6 months; a pronounced reduction in catalyst activity [from 20 to 13 × 10⁵ g PE (mol Zr h)⁻¹] was observed only after the first two days following preparation. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1987–1996, 1999     

Gear shifting multi-objective optimization to improve vehicle performance,fuel consumption,and engine emissions

In the present work, the Adaptive-Weight Genetic Algorithm was employed in order to determine the gear shifting strategies that allow an automobile to work in the best compromise among fuel consumption, engine emissions, and vehicle performance. For the assessment of each of the three objective functions, a simulation model based on engine data and on the well-established equations of the longitudinal dynamics was developed. The driving cycle chosen for the calculations was the FTP-75, which takes into account both cold and hot starts, meaning that the transient operation during the warm-up of the catalyst is also considered.     

Polysaccharide Structures and Their Hypocholesterolemic Potential

Several classes of polysaccharides have been described to have hypocholesterolemic potential, namely cholesterol bioaccessibility and bioavailability. This review will highlight the main mechanisms by which polysaccharides are known to affect cholesterol homeostasis at the intestine, namely the effect (i) of polysaccharide viscosity and its influence on cholesterol bioaccessibility; (ii) on bile salt sequestration and its dependence on the structural diversity of polysaccharides; (iii) of bio-transformations of polysaccharides and bile salts by the gut microbiota. Different quantitative structure–hypocholesterolemic activity relationships have been explored depending on the mechanism involved, and these were based on polysaccharide physicochemical properties, such as sugar composition and ramification degree, linkage type, size/molecular weight, and charge. The information gathered will support the rationalization of polysaccharides’ effect on cholesterol homeostasis and highlight predictive rules towards the development of customized hypocholesterolemic functional food.     

Production of Cellulolytic Enzymes by <Emphasis Type="Italic">Aspergillus phoenicis</Emphasis> in Grape Waste using Response Surface Methodology

The production of cellulolytic enzymes by the fungus Aspergillus phoenicis was investigated. Grape waste from the winemaking industry was chosen as the growth substrate among several agro-industrial byproducts. A 2 × 2 central composite design was performed, utilizing the amount of grape waste and peptone as independent variables. The fungus was cultivated in submerged fermentation at 30 °C and 120 rpm for 120 h, and the activities of total cellulases, endoglucanases, and β-glucosidases were measured. Total cellulases were positively influenced by the linear increase of peptone concentration and decrease at axial concentrations of grape waste and peptone. Maximum activity of endoglucanase was observed by a linear increase of both grape waste and peptone concentrations. Concentrations of grape waste between 5 and 15 g/L had a positive effect on the production of β-glucosidase; peptone had no significant effects. The optimum production of the three cellulolytic activities was observed at values near the central point. A. phoenicis has the potential for the production of cellulases utilizing grape waste as the growth substrate.     

DODAB and DODAC bilayer-like aggregates in the micromolar surfactant concentration domain

In the millimolar concentration domain (typically 1 mM), dioctadecyldimethylammonium bromide and chloride (DODAX, X representing Br⁻ or Cl⁻ counterions) molecules assemble in water as large unilamellar vesicles. Differential-scanning calorimetry (DSC) is a suitable technique to obtain the melting temperature (T _m) characteristic of surfactant bilayers, while fluorescence spectroscopy detects formation of surfactant aggregates, like bilayers. These two techniques were combined to investigate the assembly of DODAX molecules at micromolar concentrations, from 10 to 100 μM. At 1 mM surfactant, T _m ≈ 45 °C and 49 °C, respectively, for DODAB and DODAC. DSC and fluorescence of Nile Red were used to show the formation of DODAX aggregates, at the surfactant concentration as low as 10 μM, whose T _m decreases monotonically with increasing DODAX concentration to attain the value for the ordinary vesicles. The data indicate that these aggregates are organized as bilayer-like structures.     

A simplified version of the total kjeldahl nitrogen method using an ammonia extraction ultrasound-assisted purge-and-trap system and ion chromatography for analyses of geological samples

The total Kjeldahl nitrogen (TKN) method was simplified by using a manifold connected to a purge-and-trap system immersed into an ultrasonic (US) bath for simultaneous ammonia (NH₃) extraction from many previously digested samples. Then, ammonia was collected in an acidic solution, converted to ammonium (NH₄⁺), and finally determined by ion chromatography method. Some variables were optimized, such as ultrasonic irradiation power and frequency, ultrasound-assisted NH₃ extraction time, NH₄⁺ mass and sulfuric acid concentration added to the NH₃ collector flask. Recovery tests revealed no changes in the pH values and no conversion of NH₄⁺ into other nitrogen species during the irradiation of NH₄Cl solutions with 25 or 40 kHz ultrasonic waves for up to 20 min. Sediment and oil free sandstone samples and soil certified reference materials (NCS DC 73319, NCS DC 73321 and NCS DC 73326) with different total nitrogen concentrations were analysed. The proposed method is faster, simpler and more sensitive than the classical Kjeldahl steam distillation method. The time for NH₃ extraction by the US-assisted purge-and-trap system (20 min) was half of that by the Kjeldahl steam distillation (40 min) for 10 previously digested samples. The detection limit was 9 μg g⁻¹ N, while for the Kjeldahl classical/indophenol method was 58 μg g⁻¹ N. Precision was always better than 13%. In the proposed method, carcinogenic reagents are not used, contrarily to the indophenol method. Furthermore, the proposed method can be adapted for fixed-NH₄⁺ determination.