The effect of recycled polymer addition on the thermorheological behavior of modified lubricating greases

This article deals with the influence of temperature on the rheological behavior of lithium lubricating greases modified with three different types of recycled polymers, high‐density polyethylene (HDPE), low‐density polyethylene, and polypropylene (PP), all deriving from waste plastic recycling plants. Grease formulations containing diverse polymers were manufactured and rheologically characterized. Small‐amplitude oscillatory shear and viscous flow measurements over a temperature range of 25–175°C were carried out. The experimental results obtained suggest that a blend of HDPE and PP could be considered a suitable potential viscosity modifier for lithium lubricating greases in a wide range of in‐service temperature. Thus, the lubricating greases studied modified by HDPE or PP show quite promising results at low or high temperature, respectively. In addition, thermomechanical reversibility has been studied by applying different combined stress–temperature protocols. Lubricating greases containing any of the recycled polymers studied show a significant irreversible structural breakdown when the sample is submitted to temperatures and stresses higher than 75°C and 200 Pa, respectively. Regarding lubricating grease viscous flow behavior, a minimum in the shear stress versus shear rate plots appeared at temperatures above 50°C, more pronounced as temperature increased, resulting from material flow instabilities. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers.     

Scanning electron microscopy of Anisakis larvae following different treatments

Ingestion of fish parasitized with Anisakis larvae can produce infestation and/or allergy in consumers. Technological and food processing treatments have been applied to parasitized fish in order to kill the larvae and avoid the infestation; however, their influence on allergenicity has not been studied. Four lots of hake (Merluccius merluccius) steaks artificially parasitized with Anisakis larvae were subjected to two storage chilling (5 degrees C +/- 1 degrees C) and freezing (-20 degrees C +/- 1 degrees C) treatments and two food processing treatments of heat (final temperature 86.3 degrees C) and microwave (final temperature 66.9 degrees C) and studied by scanning electron microscopy, environmental scanning electron microscopy (ESEM) (acid [pH = 2] and water preparations), and emission of fluorescence. Anisakis larvae were resistant to acid conditions, remaining alive after treatment. Larvae in the heat- and microwave-treated lots presented coagulated and disrupted zones in the cuticle with release of fluids. The cylindrical shape changed to a dehydrated appearance mainly observed by ESEM. Fluorescence was only noticeable in the frozen larvae. Larvae without apparent changes, together with dehydrated ones, were observed by ESEM in the frozen lot; nevertheless, no disruptions in the cuticle were perceptible. Further studies are needed in order to elucidate if the changes observed in the cuticle reduce the resistance of the parasites to the action of gastric enzymes in the gastrointestinal tract and to determine the release of allergens to the flesh by the live larvae during chilled storage of the fish.     

Catalytic activity of graphite-based nanofillers on cure reaction of epoxy resins

The strong influence of graphite oxide (GO) nanofiller on the glass transition temperature (T_g) of epoxy resins, generally attributed to restricted molecular mobility of the epoxy matrix by the nanofiller or to the crosslinking of GO layers via the epoxy chains, is investigated. The study confirms that large increases of the glass transition temperature of the nanocomposite can be observed in presence of GO. However, similar T_g increases are observed, when the filler is a high-surface-area graphite (HSAG), lacking oxidized groups. Moreover, these T_g differences tend to disappear as a consequence of aging or thermal annealing. These results suggest that the observed T_g increases are mainly due to a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and di-amine), rather than to reaction of the epoxide groups with functional groups of GO. This hypothesis is supported by investigating the catalytic activity of graphite-based materials on reactions between analogous monofunctional epoxide and amine compounds.     

Structure and Morphology of New Bio‐Based Thermoplastic Polyurethanes Obtained From Dimeric Fatty Acids

Bio‐based TPUs from dimer acid‐based polyols are synthesised by using a two‐step prepolymer process including reactive processing. The effect of the polyol on the final chemical structures, morphologies and properties of bio‐based TPUs is evaluated by different analytical techniques. It is observed that the percentage of hard segment (HS) distributed in organised and unorganised phases is a key factor to control the materials properties. DSC reveals that the percentages of HS dispersed in the soft domains are high at low experimental HS contents. Multiscale microscopies show better defined organised structures with increasing HS content in TPUs, highlighting the importance of the distribution between hard and soft segments in the material structure.

     

Exploring the Redox Behavior of La<Subscript>0.6</Subscript>Sr<Subscript>0.4</Subscript>Mn<Subscript>1−x</Subscript>Al<Subscript>x</Subscript>O<Subscript>3</Subscript> Perovskites for CO<Subscript>2</Subscript>-Splitting in Thermochemical Cycles

Mixed oxides with perovskite structure have been proposed as promising alternative for the solar fuel production via thermochemical redox cycles. For this work, the system La_0.6Sr_0.4Mn_1?xAl_xO₃ (x?=?0 to 0.8) was selected according to its high thermal stability and rapid oxidation kinetics, and the influence of the Al/Mn ratio on the redox properties was investigated. The characterization of the five oxides samples with different Al content confirmed the high redox capacity and the favorable behavior of these materials in consecutive cycles, as analyzed thermogravimetrically. The results show that following reduction at 1300?°C in inert atmosphere up to 0.32 mmol g^?1 of O₂ are released, while a 10-cycle reaction test confirms the feasibility of long term operation with these perovskites. It was observed that the reduction extent was enhanced with increasing the Al-content, but the oxidation degree is maximum for compositions near x?=?0.5, corresponding to an O₂ release of 0.318 mmol g^?1 (δ?=?0.132). After selecting the compositions with more promising redox properties, additional reactions were performed in a lab-scale fixed bed reactor with injection of CO₂ in the oxidation step at 900?°C in order to generate CO. In these tests, the most interesting results were obtained for the perovskite La_0.6Sr_0.4Mn_0.6Al_0.4O_3, with reduction extent of 0.266 mmol?g^?1, but the production of CO is in comparison significantly lower (0.114 mmol?g^?1). Further studies are required to determine the best operation conditions for thermochemical cycles using those materials.     

Leptin in Osteoarthritis and Rheumatoid Arthritis: Player or Bystander?

White adipose tissue (WAT) is a specialized tissue whose main function is lipid synthesis and triglyceride storage. It is now considered as an active organ secreting a plethora of hormones and cytokines namely adipokines. Discovered in 1994, leptin has emerged as a key molecule with pleiotropic functions. It is primarily recognized for its role in regulating energy homeostasis and food intake. Currently, further evidence suggests its potent role in reproduction, glucose metabolism, hematopoiesis, and interaction with the immune system. It is implicated in both innate and adaptive immunity, and it is reported to contribute, with other adipokines, in the cross-talking networks involved in the pathogenesis of chronic inflammation and immune-related diseases of the musculo-skeletal system such as osteoarthritis (OA) and rheumatoid arthritis (RA). In this review, we summarize the most recent findings concerning the involvement of leptin in immunity and inflammatory responses in OA and RA.     

Hexane reduces peroxidation of fatty acids during storage

The free fatty acids eicosapentaenoic acid (C20:5ω3, EPA) and docosahexaenoic acid (C22:6ω3), obtained from the microalgae Phaeodactylum tricornutum, and the EPA methyl ester were compared with regard to their extent of peroxidation using different storage conditions. Several series were stored according to selected variables: hexane addition versus no addition, 4 °C versus 25 °C, and antioxidant addition (octyl gallate) versus no antioxidant addition, always in the dark. Previously, the EPA and methyl EPA structures were confirmed by NMR spectra to discard the formation of conjugated dienes after the downstream process. The results showed that the stability was higher for methyl EPA than for the free fatty acid, and that peroxidation can be retarded by low temperature storage and mainly by hexane addition. The peroxidation process was evaluated by the peroxide value (spectrophotometric method by iodine absorption), although the conjugated diene absorbance and the loss in percentage of the fatty acid have been tested as good indicators of the peroxidation process. A simple kinetic model that explains the peroxidation process during the initiation and propagation steps is given.     

Active RC impedances revisited

The aim of this paper is to review the synthesis, analysis and design of active RC impedances. First of all, major gaps in this classical research topic are identified. Second, a synthesis procedure is outlined to generate op-amp-based circuits which can simulate several classes of impedances of practical interest. From the resulting classification, all circuits are analysed from a perspective wider than those normally used in previous works, yielding some new interesting design conditions. A method is suggested to convert ladder passive prototypes containing either grounded inductors or FDNRs into MOSFET-C equivalent circuits using some of the new structures obtained. Finally, the use of current feedback amplifiers instead of op amps is considered. Experimental results corroborating all our theoretical predictions are incorporated in the work. © 1997 John Wiley & Sons, Ltd.