Evaluation of the chemical additive effect on asphaltene aggregation in dead oils: a comparative study between ultraviolet–visible and near-infrared-laser light scattering techniques

Asphaltenes flocculate as a consequence of changes in the temperature, pressure, or composition. This flocculation can result in several oil production problems. The application of chemical additives (inhibitors or dispersants) is a well-known way to control asphaltene flocculation. Ultraviolet-visible (UV-vis) spectroscopy is the most common analytical technique that has been applied to study the effectiveness of chemical additives in keeping asphaltene particles dispersed into crude oils. However, this technique requires being performed in diluted solutions, which can interfere significantly in the aggregation phenomena. The objective of this work was to evaluate the effect of three chemical additives, 4-dodecyl benzenesulfonic acid (DBSA) and two commercial products (CO and C1), on the asphaltene aggregation behavior of two Brazilian crude oils, using near-infrared (NIR)-laser (lambda = 1550 nm) scattering measurements. This is a new methodology developed to study the aggregation kinetics and settling of asphaltenes around its n-heptane flocculation onset. The NIR-laser scattering method offers the possibility to work with samples at a higher crude oil concentration, being more representative of real systems. The results obtained were compared to those determined with the traditional UV-vis method (lambda = 850 nm) and showed qualitatively similar trends. Settling measurements suggest that the stabilization provided by the additives can occur by slowing both formation and growing of asphaltene particles and delaying the phase separation process. DBSA was more effective in keeping the asphaltene particles dispersed in solution and prevented them from settling at lower concentrations when compared to commercial products, for both crude oils studied. It was demonstrated that the methodology developed using NIR-laser scattering was more accurate and sensitive.Asphaltenes flocculate as a consequence of changes in the temperature, pressure, or composition. This flocculation can result in several oil production problems. The application of chemical additives (inhibitors or dispersants) is a well-known way to cont29528132822sem informaçãosem informaçãoThe authors acknowledge Petrobras for their financial suppor

Supplementary report to the final report of the coral reef expert group: S6. Novel technologies in coral reef monitoring

[Extract] This report summarises a review of current technological advances applicable to coral reef monitoring, with a focus on the Great Barrier Reef Marine Park (the Marine Park). The potential of novel technologies to support coral reef monitoring within the Reef 2050 Integrated Monitoring and Reporting Program (RIMReP) framework was evaluated based on their performance, operational maturity and compatibility with traditional methods. Given the complexity of this evaluation, this exercise was systematically structured to address the capabilities of technologies in terms of spatial scales and ecological indicators, using a ranking system to classify expert recommendations.An accessible copy of this report is not yet available from this repository, please contact [email protected] for more information

In silico evaluation of ultrafiltration and nanofiltration membrane cascades for continuous fractionation of protein hydrolysate from tuna processing byproduct

The present work proposes the design of cascades that integrate ultrafiltration (UF) and nanofiltration (NF) membranes to separate the different protein fractions from the protein hydrolysate obtained after hydrolysis of tuna byproducts. Experimental data (permeate flux and rejection of protein fractions under different applied pressures) previously obtained and published by this research group were fitted to empirical models, which were the basis for a process simulation model. High recovery rates (0.9) in the UF stages implied high process yields by reduced desired fraction losses, while similar recovery rates in the NF stages were required for high product purity. However, the applied pressures were not so influential over the performance of the system. Optimization problems were solved to identify the optimal design and operation conditions to maximize the product purity or the process yield. Maximal purity of the preferred 1-4 kDa fraction (49.3% from 19.0% in feed stream) obtained by the configuration with 3 UF stages and another 3 NF stages implied 2 and 5 bar pressures applied in the UF and NF stages, respectively, while 0.9 was the optimal recovery rate value for all the stages. These maximal purity conditions resulted in 62.6% process yield, defined as the percentage of the 1-4 kDa fraction in the feed stream recovered in the product stream. In addition, multiobjective optimization of the process was also carried out to obtain the Pareto graphs that represent the counterbalance between maximal yields and purities

Metamodel-based model conformance and multiview consistency checking

Model-driven development, using languages such as UML and BON, often makes use of multiple diagrams (e.g., class and sequence diagrams) when modeling systems. These diagrams, presenting different views of a system of interest, may be inconsistent. A metamodel provides a unifying framework in which to ensure and check consistency, while at the same time providing the means to distinguish between valid and invalid models, that is, conformance. Two formal specifications of the metamodel for an object-oriented modeling language are presented, and it is shown how to use these specifications for model conformance and multiview consistency checking. Comparisons are made in terms of completeness and the level of automation each provide for checking multiview consistency and model conformance. The lessons learned from applying formal techniques to the problems of metamodeling, model conformance, and multiview consistency checking are summarized

Spin-phonon coupling in epitaxial Sr0.6Ba0.4MnO3 thin films

Spin-phonon coupling is investigated in epitaxially strained Sr1-xBaxMnO3 thin films with perovskite structure by means of microwave (MW) and infrared (IR) spectroscopy. In this work we focus on the Sr0.6Ba0.4MnO3 composition grown on (LaAlO3)0.3(Sr2AlTaO6)0.7 substrate. The MW complex electromagnetic response shows a decrease in the real part and a clear anomaly in the imaginary part around 150 K. Moreover, it coincides with a 17% hardening of the lowest-frequency polar phonon seen in IR reflectance spectra. In order to further elucidate this phenomenon, low-energy muon-spin spectroscopy was carried out, signaling the emergence of antiferromagnetic order with Néel temperature (TN) around 150 K. Thus, our results confirm that epitaxial Sr0.6Ba0.4MnO3 thin films display strong spin-phonon coupling below TN, which may stimulate further research on tuning the magnetoelectric coupling by controlling the epitaxial strain and chemical pressure in the Sr1-xBaxMnO3 system

Nature of antiferromagnetic order in epitaxially strained multiferroic SrMnO3 thin films

Epitaxial films of SrMnO3 and bilayers of SrMnO3/La0.67Sr0.33MnO3 have been deposited by pulsed laser deposition on different substrates, namely, LaAlO3 (001), (LaAlO3)0.3(Sr2AlTaO6)0.7 (001), and SrTiO3 (001), allowing us to perform an exhaustive study of the dependence of antiferromagnetic order and exchange bias field on epitaxial strain. The Néel temperatures (TN) of the SrMnO3 films have been determined by low-energy muon spin spectroscopy. In agreement with theoretical predictions, TN is reduced as the epitaxial strain increases. From the comparison with first-principles calculations, a crossover from G-type to C-type antiferromagnetic orders is proposed at a critical tensile strain of around 1.6±0.1%. The exchange bias (coercive) field, obtained for the bilayers, increases (decreases) by increasing the epitaxial strain in the SrMnO3 layer, following an exponential dependence with temperature. Our experimental results can be explained by the existence of a spin-glass (SG) state at the interface between the SrMnO3 and La0.67Sr0.33MnO3 films. This SG state is due to the competition between the different exchange interactions present in the bilayer and favored by increasing the strain in the SrMnO3 layer

Controlled Magnetic Anisotropy in Single Domain Mn-doped Biosynthesized Nanoparticles

Magnetotactic bacteria Magnetospirillum gryphiswaldense synthesize cubo-octahedral shaped magnetite nanoparticles, called magnetosomes, with a mean diameter of 40 nm. The high quality of the biosynthesized nanoparticles makes them suitable for numerous applications in fields like cancer therapy, among others. The magnetic properties of magnetite magnetosomes can be tailored by doping them with transition metal elements, increasing their potential applications. In this work, we address the effect of Mn doping on the main properties of magnetosomes by the combination of structural and magnetic characterization techniques. Energy-dispersive X-ray spectroscopy, X-ray absorption nearedge structure, and X-ray magnetic circular dichroism results reveal a Mn dopant percentage of utmost 2.3%, where Mn cations are incorporated as a combination of Mn2+ and Mn3+, preferably occupying tetrahedral and octahedral sites, respectively. Fe substitution by Mn notably alters the magnetic behavior of the doped magnetosomes. Theoretical modeling of the experimental hysteresis loops taken between 5 and 300 K with a modified Stoner-Wohlfarth approach highlights the different anisotropy contributions of the doped magnetosomes as a function of temperature. In comparison with the undoped magnetosomes, Mn incorporation alters the magnetocrystalline anisotropy introducing a negative and larger cubic anisotropy down to the Verwey transition, which appears shifted to lower temperature values as a consequence of Mn doping. On the other hand, Mn-doped magnetosomes show a decrease in the uniaxial anisotropy in the whole temperature range, most likely associated with a morphological modification of the Mn-doped magnetosomes.The Spanish and Basque Governments are acknowledged for funding under project numbers MAT2017- 83631-C3-R and IT-1245-19, respectively