Structural characterization of reactor blends of polypropylene and ethylene‐propylene rubber

Blends of isotactic polypropylene (PP), ethylene‐propylene rubber copolymer (EPR), and ethylene‐propylene crystalline copolymer (EPC) can be produced through in situ polymerization processes directly in the reactor and blends with different structure and composition can be obtained. In this work we studied the structure of five reactor‐made blends of PP, EPR, and EPC produced by a Ziegler‐Natta catalyst system. The composition of EPR was related to the ratio between ethylene and propylene used in the copolymerization step. The ethylene content in the EPR was in the range of 50–70 mol %. The crystallization behavior of PP and EPC in the blends was influenced by the presence of the rubber, and some specific interactions between the components could be established. By preparative temperature rising elution fractionation (P‐TREF) analysis, the isolation and characterization of crystalline EPC fractions were made. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2155–2162, 2004     

Health benefits of CLA – lessons from pig models in biomedical research

The objective of this review is to highlight the use of pig models for investigating safety, efficacy and the mechanisms of action of conjugated linoleic acid (CLA). Although CLA elicits positive effects in animal models and in vitro systems, a consistent concern in terms of translational research is that the health benefits observed by using these model systems cannot be extrapolated directly into humans. Conversely, the similarities between pigs and humans make the pig an ideal model for examining the health benefits of dietary supplements, functional foods and nutraceuticals. We have developed pig models of viral and bacterial infection to examine the preventive role of dietary CLA supplementation on virally induced immunosuppression and gut health, respectively. Results from these studies indicate that CLA significantly enhances the immune function while limiting the catabolic effects of uncontrolled immune and inflammatory responses. The scientific findings in pig models and human clinical trials demonstrate that CLA modulates immune responses in pigs and humans. Pig models of immunomodulation represent significant improvements over other animal models and in vitro systems because they mimic more closely the compartmentalization of the human immune system and the clinical presentation of human infectious, immune and inflammatory diseases.     

Crosslinking kinetics of SBR composites containing vulcanized ground scraps as filler

The aim of this study was to characterize the cure reaction of styrene–butadiene rubber (SBR) composites containing industrial rubber scraps. Different proportions of SBR ground scraps (SBR-r), varying from 10 to 80 parts per hundred of rubber, were incorporated into a base formulation of identical composition. Crosslink formation and the kinetics of the cure reaction were evaluated through oscillatory disk rheometry, differential scanning calorimetry, and crosslink density. Cure characteristics, such as scorch time and cure time, decreased with increasing SBR-r content. Minimum torque indicated only a small variation in the viscosity with the incorporation of SBR-r. The maximum torque decreased with the addition of scrap rubber, as a consequence of the reduction in virgin rubber content where crosslinks had been formed. Crosslink density values corroborated these findings, presenting a slight decrease with the increase in the SBR-r content. The kinetic study indicated lower enthalpy values for SBR-r composites compared to those of the control sample. The kinetic parameters, such as activation energy and reaction order, indicated a change in the mechanism of reaction, related to the increased complexity of the systems.     

Study of the effect of the monomer pressure on the copolymerization of ethylene with 1-hexene

The effect of ethylene pressure on the copolymerization of ethylene with 1-hexene was studied. The results show an increasing of productivities (g of polymer/n_Zr h) with pressure. This tendency was not observed for the activity (g of polymer/n_Zr h bar) that decreases when pressure is raised. When varing the pressure, the characteristics and properties of the formed copolymers are in accordance with the expectation for changes in the monomer concentration; increasing the pressure causes a decrease in comonomer incorporation. At higher ethylene pressure, the polymer is more crystalline due to less incorporation of 1-hexene and the molecular weight is higher. The density of the copolymers also decreases with comonomer incorporation into the copolymer © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2567–2574, 1997     

Isolation and Characterization of Microsatellite Markers for Passiflora contracta

Passiflora contracta Vitta (Passifloraceae) is an endemic species of the Atlantic Rainforest, one of the most species-rich ecoregions in the world, although extremely endangered. We have developed an enriched microsatellite library in order to fine-scale studies of the genetic structure of P. contracta. Twelve pairs of microsatellite primers were designed, and seven loci were successfully amplified and characterized by genotyping two wild populations of P. contracta. All seven loci were polymorphic, with an average number of alleles found being 4.8 and 5 per population. The cross-species transferability was tested using sister species Passiflora ovalis Vell. Ex Roemer. The development of these markers will contribute to the studies of population genetics in P. contracta as well as future studies concerning diversity patterns in the Atlantic Rainforest, and may also help to establish strategies for the conservation of this species.     

Accelerated aging of elastomeric composites with vulcanized ground scraps

The aim of this work is to study the effect of thermal aging on the mechanical, dynamic‐mechanical, and chemical properties of SBR (styrene‐butadiene rubber) composites filled with SBR industrial rubber scraps. Eight composites with varying proportions (10–80 phr) of the SBR ground scraps (SBR‐r) were prepared and subjected to accelerated aging in an air‐oven. The composites were evaluated, and the results were compared with a control sample (base formulation with 0 phr of SBR‐r), before and after thermal aging. The accelerated aging led to a decrease in the mechanical properties as a result of an increase in the stiffness of the material, related to an increase in the crosslink density. However, these properties were not affected by the addition of rubber scraps up to 50 phr, either before or after aging. The increase in the glass transition temperature of the composites after aging, measured using dynamic mechanical analysis, confirmed the occurrence of a postcrosslinking process. Fourier transform infrared spectroscopy and crosslink density revealed that the aging mechanism was dependent on the SBR‐r content. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effects of ozonized water and heat treatment on the papaya fruit epidermis

This study examined the effects of O₃ and hot water treatments on the epidermis of Golden papaya fruit. Heat treatments were applied in a hot water brushing (HWB) system. Papayas were brushed under a pressurized hot water rinse stage at 45, 55 and 65 °C for 60 s. In the HWB treatment, 4 ppm ozone was applied to the papayas for 1 or 2 min. The results show that ozone applications did not affect the fruit's cuticular surface, while heat treatments allowed natural fissures on the fruit epidermis to recover. Several crystalloid forms were identified on the epidermis of the papayas after the heat treatments. The predominant crystalloid forms on papayas are tubular and there is a positive response to temperature; the higher the temperature, the larger and more frequent the tubular crystalloids.     

Active nano-CuPt3 electrocatalyst supported on graphene for enhancing reactions at the cathode in all-vanadium redox flow batteries

Graphene-supported monometallic (Pt) and bimetallic (CuPt₃) cubic nanocatalysts have been investigated as new positive electrode materials for improving the VO₂⁺/VO²⁺ redox process occurring in the vanadium redox flow batteries (VRB). High-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) have been employed to characterize the electrodes. The presence of the CuPt₃ nanocubes on graphene conferred higher electrocatalytic activity due to the much higher electroactive area compared to that obtained with the Pt nanoparticles. The electrochemical surface area of the nano-(CuPt₃)-decorated graphene electrode was 105% higher compared to non-decorated graphene, being then a promising alternative for improving the VRB.     

Study of the structure directing effect of the chiral cation (1S,2S)-2-hydroxymethyl-1-benzyl-1-methylpyrrolidinium in aluminosilicate preparations in the presence of co-structure directing agents

We explore the structure directing role of the chiral cation (1S,2S)-2-hydroxymethyl-1-benzyl-1-methylpyrrolidinium (SS-bmpm) in the synthesis of Al-containing zeolite materials in the presence of co-structure directing agents (co-SDAs). Three different co-SDAs are studied: tetramethylammonium (TMA), quinuclidine and sodium. Synthesis with TMA as co-SDA yields a ferrierite related phase and a material from the MWW family, where the SS-bmpm and the TMA cations are incorporated intact within the samples. Quinuclidine produces instead amorphous solids, while the use of Na⁺ leads to crystalline phases that crystallized as a result of the degradation of the SS-bmpm cation. A subsequent computational study based on molecular mechanics was performed in an attempt to unravel the location of TMA and SS-bmpm cations within the void space of the complex MWW structure. The results suggest that the sinusoidal channels are exclusively filled by TMA, while the bulky SS-bmpm cations can only be accommodated within the MWW super-cages, thus providing a new example of cooperative structure-directing effects of small and bulky cations in the synthesis of complex zeolite structures.     

Circulating Insulin-Like Growth Factor I is Involved in the Effect of High Fat Diet on Peripheral Amyloid β Clearance

Obesity is a risk factor for Alzheimer’s disease (AD), but underlying mechanisms are not clear. We analyzed peripheral clearance of amyloid β (Aβ) in overweight mice because its systemic elimination may impact brain Aβ load, a major landmark of AD pathology. We also analyzed whether circulating insulin-like growth factor I (IGF-I) intervenes in the effects of overweight as this growth factor modulates brain Aβ clearance and is increased in the serum of overweight mice. Overweight mice showed increased Aβ accumulation by the liver, the major site of elimination of systemic Aβ, but unaltered brain Aβ levels. We also found that Aβ accumulation by hepatocytes is stimulated by IGF-I, and that mice with low serum IGF-I levels show reduced liver Aβ accumulation—ameliorated by IGF-I administration, and unchanged brain Aβ levels. In the brain, IGF-I favored the association of its receptor (IGF-IR) with the Aβ precursor protein (APP), and at the same time, stimulated non-amyloidogenic processing of APP in astrocytes, as indicated by an increased sAPPα/sAPPβ ratio after IGF-I treatment. Since serum IGF-I enters into the brain in an activity-dependent manner, we analyzed in overweight mice the effect of brain activation by environmental enrichment (EE) on brain IGF-IR phosphorylation and its association to APP, as a readout of IGF-I activity. After EE, significantly reduced brain IGF-IR phosphorylation and APP/IGF-IR association were found in overweight mice as compared to lean controls. Collectively, these results indicate that a high-fat diet influences peripheral clearance of Aβ without affecting brain Aβ load. Increased serum IGF-I likely contributes to enhanced peripheral Aβ clearance in overweight mice, without affecting brain Aβ load probably because its brain entrance is reduced.