Wettability alteration of oil-wet carbonate rocks by chitosan derivatives for application in enhanced oil recovery

The increasing demand for oil and the fast decline of crude oil production from mature fields encourages the development of new enhanced oil recovery (EOR) technologies. In this work, trimethyl chitosan (TMC) and trimethyl chitosan hydrophobized with myristoyl chloride (TMC-C14) are synthesized, and their wettability modification capacity of oil-wet carbonate rocks is evaluated through contact angle measurements, atomic force microscopy, and Raman spectroscopy. Their interaction with asphaltene molecules was evaluated through UV–Vis spectroscopy. Transport behavior and oil displacement capacity were investigated in an unconsolidated porous medium. Results show that they can modify the wettability of oil-wet carbonate rocks, turning them water-wet, promoting oil displacement increases by 25% for TMC, and 16% for TMC-C14.TMC shows a better performance for wettability alteration than TMC-C14, confirming the hypothesis that the higher the positive charge density on the polymeric surfactant structure, the more efficient will be the system as a wettability modifier and as an EOR agent.     

Therapeutic miR-21 Silencing Reduces Cardiac Fibrosis and Modulates Inflammatory Response in Chronic Chagas Disease

Chagas disease, caused by the parasite Trypanosoma cruzi (T. cruzi), remains a serious public health problem for which there is no effective treatment in the chronic stage. Intense cardiac fibrosis and inflammation are hallmarks of chronic Chagas disease cardiomyopathy (CCC). Previously, we identified upregulation of circulating and cardiac miR-21, a pro-fibrotic microRNA (miRNA), in subjects with CCC. Here, we explored the potential role of miR-21 as a therapeutic target in a model of chronic Chagas disease. PCR array-based 88 microRNA screening was performed in heart samples obtained from C57Bl/6 mice chronically infected with T. cruzi and serum samples collected from CCC patients. MiR-21 was found upregulated in both human and mouse samples, which was corroborated by an in silico analysis of miRNA-mRNA target prediction. In vitro miR-21 functional assays (gain-and loss-of-function) were performed in cardiac fibroblasts, showing upregulation of miR-21 and collagen expression upon transforming growth factor beta 1 (TGFβ1) and T. cruzi stimulation, while miR-21 blockage reduced collagen expression. Finally, treatment of T. cruzi-infected mice with locked nucleic acid (LNA)-anti-miR-21 inhibitor promoted a significant reduction in cardiac fibrosis. Our data suggest that miR-21 is a mediator involved in the pathogenesis of cardiac fibrosis and indicates the pharmacological silencing of miR-21 as a potential therapeutic approach for CCC.     

Using differential scanning calorimetry to characterize the precipitation hardening phenomena in a Cu-9Ni-6Sn alloy

An attempt has been made to characterize the transformations in a Cu-9Ni-6Sn alloy using heat flux differential scanning calorimetry (DSC) assisted by hardness measurements. Both solution heat treatment and precipitation transformations have been studied. Different starting conditions were imposed on the material to allow a clearer understanding of the transformations involved. The precipitation from the supersaturated solid solution happens in two temperature ranges, i.e., from 200 to 400 °C and from 440 to 600 °C. In the temperature range from 400 to 440 °C, the alloy does not usually transform. Thermal cycles leading to aging and overaging were determined. The precipitation hardening conditions at 350 °C or lower for less than 600 min, or 375 °C for up to 120 min, lead to metastable precipitation. Precipitation hardening for 120 min at 400 °C or 1200 min at 350 °C results in stable precipitation and is responsible for overaging the alloy.     

Leaky Lamb waves for the detection and sizing of defects in bonded aluminium lap joints

The possibility of using ultrasonic leaky Lamb waves in a pitch and catch configuration for detecting and sizing defects in bonded aluminium lap joints is presented in this paper. Based in Transfer Matrix method the dispersion curves and the propagation modes behaviour are obtained. First the experimental scattering effects of circular holes with different dimensions on the fundamental symmetric mode S₀ are analysed and compared with the results obtained by analytical model. Very good agreement with the analytical model used is found. After, using the same methodology, scattering effects produced by artificial defects located in the bond line of lap joints are measured and the results show that the previous model could be used when an estimation of defect dimensions is needed. Finally an empirical relation between an experimental parameter and the defect dimensions is established revealing a high linear correlation meaning. So, this parameter could be used for more accurate defect dimensions evaluation.     

Influence of Temperature on the Fatty Acid Composition of the Oil From Sunflower Genotypes Grown in Tropical Regions

The influence of temperature on the fatty acid composition of the oils from conventional and high oleic sunflower genotypes grown in tropical regions was evaluated under various environmental conditions in Brazil (from 0° S to 23° S). The amounts of the oleic, linoleic, palmitic and stearic fatty acids from the sunflower oil were determined using gas chromatography (GC). The environment exhibited little influence on the amounts of oleic and linoleic fatty acids in high oleic genotypes of sunflower. In conventional genotypes, there was broad variation in the average amounts of these two fatty acids, mainly as a function of the minimum temperature. Depending on the temperature, especially during the maturation of the seeds, the amount of oleic acid in the oil of conventional sunflower genotypes could exceed 70 %. Higher temperatures led to average increases of up to 35 % for this fatty acid. Although the minimum temperature had the strongest effect on the fatty acid composition, locations at the same latitude with different minimum temperatures displayed similar values for both oleic acid and linoleic acid. Furthermore, minimum temperature had little influence on the amounts of palmitic and stearic fatty acids in the oil.     

Acid-Catalyzed Homogeneous Esterification Reaction for Biodiesel Production from Palm Fatty Acids

This work deals with esterification of palm fatty acids to produce biodiesel in a batch reactor, using homogeneous acid catalysts, evaluating the effect of the alcohol used, presence of water, type and concentration of catalysts. Methanesulfonic and sulfuric acid were the best catalysts. Reaction with methanol showed greater yields. It was showed very clearly that the presence of water in the reaction medium showed a negative effect in the reaction velocity. Kinetic parameters were estimated and molecular modeling was performed. Protonation of the carboxylic moiety of the fatty acid were defined as rate determinant step for the reaction.     

Characterization of natural rubber/gold nanoparticles SERS‐active substrate

Natural rubber/gold nanoparticles membranes (NR/Au) were studied by ultrasensitive detection and chemical analysis through surface‐enhanced Raman scattering and surface‐enhanced resonance Raman scattering in our previous work (Cabrera et al., J. Raman Spectrosc. 2012, 43, 474). This article describes the studies of thermal stability and mechanical properties of SERS‐active substrate sensors. The composites were prepared using NR membranes obtained by casting the latex solution as an active support (reducing/establishing agents) for the incorporation of colloidal gold nanoparticles (AuNPs). The nanoparticles were synthesized by in situ reduction at different times. The characterization of these sensors was carried out by thermogravimetry, differential scanning calorimetry, scanning electron microscopy (SEM) microscopy, and tensile tests. It is suggested an influence of nanoparticles reduction time on the thermal degradation of NR. There is an increase in thermal stability without changing the chemical properties of the polymer. For the mechanical properties, the tensile rupture was enhanced with the increase in the amount of nanoparticles incorporated in the material. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

A Forming Technique to Produce Spherical Ceramic Beads Using Sodium Alginate as a Precursor Binder Phase

The purpose of this study was to improve the forming techniques and parameters for producing spherical ceramic beads using sodium alginate as a sacrificial template. This process has the potential of producing beads for applications such as stress‐wave propagation of granular media, beads for milling, catalyst support, and encapsulation of drugs, as well as water filtration. This simple, inexpensive, and environmentally friendly approach to producing spherical ceramic beads using bead‐forming equipment occurs when a flat‐tipped needle produces droplets that cross‐link, forming green bodies upon contact with CaCl₂ solution. An exchange of ions takes place where sodium alginates substitute their Na⁺ for Ca²⁺ to form semirigid bodies. Spherical ceramic beads using 50 wt% alumina suspension with 0.04 wt% polyacrylate dispersant are produced when: the viscosity of the slurry is below 0.3 Pa·s, the surface tension of the gelling solution is below 50 mN·m, and the distance of the nozzle tip to the reacting solution is ~3 cm. This approach for producing ceramic beads using alginates will allow its use for any type of ceramic material, changing its chemical composition, and controlling the microstructure and shape of the beads.     

Mullite-based refractory castable engineering for the petrochemical industry

Refractory castables used in fluid catalytic converter (FCC) risers should present suitable particle erosion and thermal shock resistances at temperatures below 900 °C. Considering that calcium aluminate cement (CAC)-bonded refractories usually start their densification above 1200 °C, the use of sintering additives to induce faster densification is a promising technological alternative. Therefore, this work addresses the evaluation of mullite-based castables containing a boron-based sintering additive and CAC and/or hydratable alumina as the binder sources. Hot elastic modulus, cyclical thermal shock, hot modulus of rupture and cold erosion resistance measurements were carried out to evaluate the compositions. According to the attained results, adding 1.5 wt% of the evaluated sintering additive to the designed castables led to a remarkable increase of the hot modulus of rupture (maximum of 40.4 MPa at 800 °C for the CAC-containing refractory) and high erosion resistance (1.5–2.9 cm³) after pre-firing at 800 °C for 5 h. Moreover, the combination of CAC and hydratable alumina gave rise to an improved refractory (M–2CAC–2HA–S) showing a transient liquid formation at an increased temperature, high thermal shock resistance (no E decay after 8 thermal cycles, ΔT=800 °C) and high mechanical strength at 800 °C and 1000 °C.     

A NON‐GAUSSIAN FAMILY OF STATE‐SPACE MODELS WITH EXACT MARGINAL LIKELIHOOD

The Gaussian assumption generally employed in many state‐space models is usually not satisfied for real time series. Thus, in this work, a broad family of non‐Gaussian models is defined by integrating and expanding previous work in the literature. The expansion is obtained at two levels: at the observational level, it allows for many distributions not previously considered, and at the latent state level, it involves an expanded specification for the system evolution. The class retains analytical availability of the marginal likelihood function, uncommon outside Gaussianity. This expansion considerably increases the applicability of the models and solves many previously existing problems such as long‐term prediction, missing values and irregular temporal spacing. Inference about the state components can be performed because of the introduction of a new and exact smoothing procedure, in addition to filtered distributions. Inference for the hyperparameters is presented from the classical and Bayesian perspectives. The results seem to indicate competitive results of the models when compared with other non‐Gaussian state‐space models available. The methodology is applied to Gaussian and non‐Gaussian dynamic linear models with time‐varying means and variances and provides a computationally simple solution to inference in these models. The methodology is illustrated in a number of examples.