Resumo em Português:

In this work, the local electrochemical activity of the zones coupled by Friction Stir Welding (FSW) of an Al-Cu-Li alloy was studied and the results were correlated to the microstructural characteristics of each zone. Electrochemical studies were carried out in the zones affected by welding using cyclic voltammetry (CV) and scanning electrochemical techniques (namely, SECM - Scanning Electrochemical Microscopy and LEIS - Local electrochemical impedance spectroscopy). The results showed that the welding joint (WJ) is predominantly cathodic relatively to the heat affected zones (HAZ). The HAZ was always anodic and showed the highest electrochemical activities among the tested ones. The high electrochemical activity of the HAZ was associated with the effect of galvanic coupling between the cathodic region (WJ) and the anodic region (HAZ). In addition, the advancing side (AS) presented increased electrochemical activity compared to the retreating one (RS).

Resumo em Inglês:

Hückel theory is a simple and powerful method for predicting the molecular orbital and the energy of conjugated molecules. However, the presence of nitrogen atoms in aza aromatic molecules alters the Coulomb and resonance integrals owing to the difference in electronegativity between nitrogen and carbon atoms. In this study, we focus on acridine and phenazine. Further correction is implemented based on the ring current model, thus revealing the change in resonance integral for the carbon-carbon bond along the bridge of the molecule. The Hamiltonian of the π-electron system in the Hückel method is solved using the HuLiS software. Various geometry-based aromaticity indices are used to obtain the aromaticity indices of the two non-equivalent rings. For further evaluation, the results for bond lengths are used to calculate the associated bond energy. Considering the carbon-hydrogen (CH) bonds, the total molecular energy is compared with the experimental heats of formation for a number of benzenoid hydrocarbons and aza aromatics, in addition to the two studied molecules. Finally, the correlation between the nitrogen atom on the aromaticity index and the ring energy content is evaluated to determine to which extent the Hückel model agrees with previous experimental and advanced computational studies.

Resumo em Inglês:

Granulometry is an initial factor to be considered in soil research as it plays a fundamental role in physical and chemical properties. The objective of this study was to characterize the granulometric fractions of soil, obtained using the screening and sedimentation method. The Dynamic Light Scattering (DLS), Mid-Infrared (MIR), and Scanning Electron Microscopy with Field Emission Gun (SEM-FEG) techniques were used for this purpose. The quantitative results showed that this soil presents high percentage of clay, followed by fine sand fraction, silt fraction and, finally, the coarse sand fraction. The results obtained by DLS qualify this technique as a procedure to evaluate the quality of the granulometric fractionation of the clay fraction. The MIR analyzes detected characteristic vibrational states of minerals such as kaolinite, halloysite, gibbsite, and quartz. Few works in the literature characterize the clay fraction of the soil without chemical treatment using the SEM-FEG technique. Thus, in this work, pseudo-hexagonal structures were identified, typical of the kaolinite mineral and, to a lesser extent, structures with a filamentous needle-like morphology, which can be ascribed to illite and/or halloysite, whose inorganic functional groups were identified by MIR in the clay fraction of the soil.

Resumo em Português:

A new material formed by Shiff base (chitosan and ortho-vanillin) and copper were synthesized and characterized by UV-visible, infrared spectroscopies, thermal analysis, elemental analysis, electron microscopy, 1H NMR spectra and electrochemical techniques. In this study, it was possible to identify the formation of Schiff’s base (BS), with a degree of substitution of 42.5% by NMR. The electron microscopy study indicates an amorphous character for BS. The material was used to build an electrode, which proved to be sensitive to the addition of nitrite, making it possible to quantify it. The values obtained for detection limit and limit of quantification of the electrode formed BS-Cu were 0.062 µmol L-1 and 0.21 µmol L-1, respectively.

Resumo em Inglês:

Evaluation studies contribute to the identification of parameters that can affect the accuracy and precision of analytical methods. This study describes the analysis of δ18O and δ2H in water samples by the equilibrium method at the Isotope Geology Laboratory (LGI), Center for studies in Petrology and Geochemistry (CPGq) of the Federal University of Rio Grande do Sul (UFRGS). For that, six batches of analyzes were carried out under different ambient temperature conditions. For the reproducibility tests, four aliquots of the control sample were analyzed at the Polar Climate Center (CPC). Results showed that ambient temperature did not significantly affect the accuracy of the oxygen analysis. However, the mean result at 20 °C showed greater accuracy and acceptable precision. Hydrogen analyzes at a room temperature of 18 °C showed an external standard deviation and an internal precision exceeding the recommended, while at 20 and 22 °C the results were statistically acceptable, being the first more accurate. From that, it is possible to conclude that the determination of δ18O and δ2H in water at the LGI, employing the equilibrium method at an ambient temperature of 20 °C, showed satisfactory repeatability and reproducibility.

Resumo em Inglês:

Cancer therapy represents a challenge, even with the current scientific developments. Over the years, several studies have shown that the application of antitumor drug nanocarriers is an efficient strategy; however, it requires further improvement. Several nanosystems have been developed, some of which are already in use, including liposomes. Polymer-based nanocarriers are still being adjusted to the peculiarities of the human body due to the biological barriers that were encountered by the first systems that were developed. Among them, the formation of corona proteins, clearance by the endothelial reticulum system and kidneys, activation of the immune system, lack of selectivity, and difficult release have been extensively studied and improved with the development of new devices. In this review, we explore the evolution of primary nanocarriers based on polymeric micelles and highlight the gaps that remain in this field to assist in the research of new systems with superior therapeutic indices.

Resumo em Português:

In the last decade, nanomedicine has investigated the potential use of silica nanoparticles for drug delivery due to the favorable physicochemical properties of these systems as carriers. Specifically, a few studies have focused on applying silica-based nanosystems to deliver drugs into the central nervous system to treat neurological disorders. The present review aimed to evaluate the properties of silica nanoparticles, such as size, zeta potential, surface area, entrapment efficiency, drug loading, and release profile, exclusively applied for the treatment of central nervous system disorders as well as to describe the correlation between biological outcomes and physicochemical properties. Furthermore, the main processes related to the development of silica nanoparticles, such as preparation and characterization methods, were covered in this review to aid the systematic development of silica-based nanoparticles. In the articles reviewed, silica nanocarriers used in neurological disorders did not exhibit physicochemical similarities. Thus, attempts to prospect relations between physicochemical properties and biological effects are still inefficient when silica nanoparticles are used as drug delivery systems in neurological disorders. Therefore, each silica-based nanocarrier must be fully physicochemical and biologically characterized to comprehend how the structural features of silica nanoparticles affect biological systems.

Resumo em Inglês:

Low-density dispersive liquid-liquid microextraction with a subsequent esterification step was proposed in this study for the determination of linoleic acid and stearic acid in sheep blood serum samples. The method developed aimed to quickly and efficiently extract and esterify both fatty acids with subsequent analysis by gas chromatography/flame ionization detection. The extraction method was optimized with Scheffé’s polynomial model for three-component mixtures. The method was validated according to the parameters established by Eurachem Guide (2014). The optimal extraction conditions for LD-DLLME were 1400 µL of dispersion medium (MgCl2 0.017%), 400 µL of extractor solvent (toluene) and 1200 µL of dispersion solvent (methanol). The method performance showed adequate selectivity, sensitivity and precision to be applied to real samples, with an average recovery of 98.54% for linoleic acid and 103.83% for stearic acid. LD-DLLME was superior to the traditional method of analysis, which has been used until now for the determination of fatty acids in blood serum samples from ruminants. The analysis of real samples showed that the developed method is efficient for monitoring these substances in ruminants.

Resumo em Português:

Infront of with the difficulties faced in making a new drug available to the population, it is essential to seek ways to simplify the process. In silico methodologies are alternatives to benchtop experiments, being frequently used due to their speed and low cost. The present study aimed to formulate a theoretical-practical activity in the Pharmaceutical Chemistry course, where students applied their knowledge of structural modeling and molecular docking to propose bioactive compounds against molecular targets of the SARS CoV-2 virus. The class was divided, and each group presented a drug candidate, the precursors being natural molecules. In total, seven derivatives were designed and tested against different macromolecules, and then an in silico prediction of their physicochemical characteristics was performed. The docking results were positive for all derivatives, in terms of binding energy, mainly GEND with -9.0 kcal mol-1. In addition, the prototypes exhibited good interactions with the amino acids of the respective targets, mainly KAED, QUED and GEND, in addition to presenting adequate physicochemical properties for meeting the Lipinski restrictions. Therefore, this study presented at least three potential inhibitors of SARS-CoV-2, showing the importance of using computational tools in drug design and development, as well as in teaching practice.

Resumo em Português:

Drinking water disinfection has been viewed as one of the major advances in public health protection in history. However, while it has been very successful in assuring microbiological safety, disinfection also brought relevant concerns about chemical safety and the potential unintended health hazards associated with disinfection byproduct (DBP) exposure. DBPs represent one of the most important groups of chemical compounds to which humans are exposed through drinking water, as epidemiological studies have consistently associated long-term exposure with multiple adverse health effects. It is established that disinfection is an essential component of providing microbiologically safe drinking water and shall never be compromised. Yet, chemical safety regarding DBP exposure remains a largely uncovered and highly discussed topic. Several DBPs have been reported in the past few decades, yet research on formation, toxicity and occurrence remains scarce for most compounds. Also, for each identified DBP, many remain undiscovered. In view of an ever-growing list of DBPs and the existing gaps in available research, identifying overall driving agents of toxicity is still a major challenge for public health protection. This review attempts to provide an insight on contemporary issues regarding the overall safety of drinking water and the trade-off between microbiological and chemical risks, considering current challenges in water and sanitation access and existing regulations.