Resumo em Inglês:

Global warming is one of the most worrying environmental problems nowadays. A joint effort has been made by many countries to minimize greenhouse gas (GHG) emissions, responsible for global warming. The evidences indicate that global warming is occurring due to anthropogenic activities, mainly caused by the using of fossil or biomass fuels. Although this effect is more directly associated with external emissions, domestic emissions also have their contributions. In this way, cooking activities can have an impact on global warming, since the main fuels used for these purposes are from fossil or biomass origin. This study aimed to evaluate the impact of the most common fuels used for cooking in Brazil on global warming. Among the fuels studied and the data available to date, biogas, followed by natural gas and liquefied petroleum gas were the least polluting, even the latter two being derived from petroleum and currently considered the great villain of air pollution. The results also show that although LPG is the most used fuel (> 90%) in Brazil for cooking, firewood, which accounts for only 3% of consumption, causes the highest emission rates of greenhouse gases. Therefore, more efficient stoves can have a significant impact on the GHG reductions in the country.

Resumo em Inglês:

Inorganic matrices have been extensively studied for several applications, mainly doped with lanthanoid ions presenting special spectroscopic properties. The radiation emission can be affected by several factors, such as; matrix, synthesis methodology, activating ions and sensitizers, and concentrations. Thus, in this work the matrix of yttrium vanadate doped with Eu3+ ions as activator and Bi3+ ions as sensitizer was prepared by the non-hydrolytic sol-gel methodology. Europium (III) and Bismuth (III) ions concentrations were varied in 1, 3 and 5% in mol with respect to the Y3+ ion and the samples were heat treated at 1000 °C. The X-ray diffraction analyzes showed a single phase of the yttrium vanadate matrix, indicating the non-influence of the dopant ions on the crystalline structure. The dopants concentrations presented influences on the spectroscopic properties of the emitting ion, the intensity parameters (Ω2 e Ω4), increased as a function of the increase of Bi3+ concentration, affecting the covalence of the bond and the rigidity of the system. The increase of Eu3+ concentration directly affected its environment, decreasing the symmetry and increasing the quantum efficiency. Finally, increasing the dopant ions promoted the decreasing the crystallite size.

Resumo em Inglês:

On November 5, 2015, the Fundão dam ruptured which caused the spill of a large quantity of tailings from the extraction of iron ores to the Gualaxo do Norte, Carmo and Doce Rivers. Seven months prior to the rupture, our group had collected water and sediment samples at 13 points along the Tripuí Creek and the entire length of the Carmo River. Six months after deposition of the mud, new samples were collected in the Carmo River. Thus, the present study sought to evaluate the concentrations of trace elements in the waters and their distribution and mobility in sediment by BCR sequential extraction before and after the deposition of the tailings mud. Arsenic concentrations in the water samples were between 10.4 and 50.4 µg L-1, which exceeded 10 ug L-1 (maximum limit permitted by Brazilian environmental regulations for water destined for human consumption) . The tailing mud layer on the sediments caused concentration increases of As (20%), Cd (13%), Co (5%), Cr (9%), Cu (11%), Ni (4%), Pb (7%) and Zn (19%) in the easily remobilized fractions. The presence of the elements in these fractions was indicative of high ecotoxicological risk and potential harm to the health of the local population.

Resumo em Inglês:

This work aims to establish a hierarchy of risks of the stabilizers used in nitrocellulose-based propellants concerning to toxicity, carcinogenicity and mutagenicity. Four stabilizers - diphenylamine, ethyl centralite, akardite-II and 2-nitrodiphenylamine - and their products of degradation were investigated. The prediction of the toxicity was based on the analysis of their structures with the software Lazar, using the OpenTox framework. Our results provide a quantitative reference of the risks involved in the manufacturing and disposal of propellants due to the use of such stabilizers.

Resumo em Inglês:

The topological index of a molecular structure correlate certain physicochemical properties such as boiling point and stability of that molecular structure. Recently several topological indices have been introduced and studies have shown their association with certain physical and chemical properties of other molecules. Specifically, Zagreb, Atom-bound connectivity (ABC) and Sanskruti indices have been correlated with extent of branching, enthalpy and entropy of some organic molecules. In this study we have calculated Zagreb, Atom-bound connectivity (ABC) and Sanskruti indices (S) for Copper (I) oxide and Copper (II) oxide CuO. Additionally, from the experimentally available data, we calculated entropy and enthalpy per unit cell for both the oxides and compared with Atom-bound connectivity and Sanskruti indices. It appears that these indices have very poor relation with these physical properties in both oxides of copper and they may need some modifications to show considerable compliance as reported in other organic molecules."

Resumo em Inglês:

The secondary metabolites of the aerial parts of Phyllanthus acuminatus Vahl (Phyllanthaceae) and the biological activity of one of them were characterized in this study. This chemical investigation led to isolation of two lignans, luclaricin (1), a new arylnaphtalene-typelignan, and justicidin B (2). The structures of isolated compounds were determined based on 1D and 2D-NMR, HRESIMS and IR. The cytotoxic activity of justicidin B was assessed against tumor cell lines (MCF-7, U251, NCI-ADR/RES, NCI-H460, OVCAR-3, HT29 and K562) and a non-tumor cell line (HaCat) using sulforhodamine B assay. Justicidin B showed strong cytotoxic activity against the tumor cell lines HT29, K562 and U251 with GI50 values of 2.28, 3.29 and 5.76 mol L-1, respectively.

Resumo em Inglês:

The phytochemical investigation of the alkaloid-rich fraction obtained from the leaves of Guatteria pogonopus Mart. (Annonaceae) allowed the isolation and identification for the first time in this species of: (+)-nornuciferine (1), a mixture of 1 and (+)-anonaine (2), (+)-isocorydine (3), (+)-nuciferine (4), (+)-roemerine (5), (-)-tetrahydropseudocolumbamine (6), a mixture of 6, liriodenine (9) and lysicamine (10), a mixture of 1,2,9-trimethoxy-10-hydroxyaporphine (7) and bulbocapnine (8), 9, 10, and (+)-N-methyllindicarpine (11). Compounds 6, 7, 8, and 11 have not been previously reported in the family Annonaceae. Furthermore, the formerly synthetic 1,2,9-trimethoxyaporfin-10-ol (7) is described for the first time as a natural aporphine alkaloid herein. The chemical structures were established by 1D and 2D NMR as well as in comparison with data previously reported in the literature. The cytotoxic activity of the alkaloids was evaluated against tumor (B16-F10, HepG2, HL-60, and K562) and non-tumor (PBMC) cell lines. Alkaloid 1 presented significant activity against HepG2 cell lines with IC50 of 9.60 µmol L-1 while the mixture of 6, 9 and 10 displayed strong cytotoxic activity against HL-60 and K562 cell lines with IC50 values of 3.41 an 8.50 µmol L-1, respectively.

Resumo em Inglês:

The objective this study was to evaluated the influence of silica modified with protic ionic liquid (PIL) on an immobilized biocatalyst by covalent binding of Burkholderia cepacia lipase (BCL) in a PBR and in the transesterification reaction, by characterization and mass transfer of the system studied. The results showed that maximum conversion of ethyl esters was 39 ± 1.73% at 96 h (IB on control silica) and 47 ± 2.0% in 72 h (IB on modified silica). The PIL also influenced the analysis of residence time distribution (RTD) with the mean time ranging from 14.94 (control silica) to 25 min (modified silica). Variation of the reaction parameters (temperature, flow rate and molar ratio) positively influenced the mass transfer coefficient (kc) which varied from 0.95 × 10−4 to 2.39 × 10−4 m s−1 (IB on control silica) and from 1.22 × 10−4 to 3.06 × 10−4 m s−1 (IB on modified silica).

Resumo em Inglês:

MgAl2O4 spinel employed as support of reforming catalysts was doped by CeO2. The samples were prepared by wet impregnation from aqueous solutions of cerium nitrate, with and without chelating agents. The chelating agents used were ethylenediamine-tetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and citric acid (CA) at different pH of impregnation. The solids were characterized by TG, XRD, SBET, TPR, SEM-EDX and CO2-TPD. Nanoparticles of CeO2 between 5 and 6.8 nm were obtained by the thermal decomposition in air at 600 °C. The surface cerium reduction occurred in a wide temperature range of 450° to 670 °C. The use of citric acid at pH= 8 led to the lowest crystallite size of CeO2 and the lowest interaction with the spinel. The H2 consumption and extent of CeO2-support interaction did not show a clear dependence with the CeO2 crystallite sizes. The use of chelating agents in the impregnation step did not modify the total basicity. Slight changes in the strength of weak basic sites were observed.

Resumo em Inglês:

This study reports the optimization of geranyl butanoate production by esterification of geraniol and butanoic acid in a solvent-free system using two immobilized lipases as catalyst. The operating conditions that optimized geranyl butanoate production were determined to be 40 °C, a geraniol to butanoic acid molar ratio of 3:1, 150 rpm, 5 wt% of enzyme, and 1 h of reaction, which resulted in a reaction conversion of about 97% for Novozyme 435. When homemade Novozyme NZL-102-LYO-HQ (Cal-B) immobilized in polyurethane foam was used as catalyst, the experimental conditions of an alcohol to acid molar ratio of 5:1, 70 °C, 150 rpm, 5 wt% of enzyme, and 1 h of reaction gave a conversion of 95%. New experimental data on enzymatic esterification of geraniol and butanoic acid for geranyl butanoate production are reported in this work, showing that the technique is promising for overcoming the well-known drawbacks of the chemical-catalyzed route.

Resumo em Português:

This review describes the properties of the bambus[n]urils and some of their applications. These macrocycles are synthesized by the condensation of glycoluril derivatives and paraformaldehyde in acid medium. The alternate conformation of the monomers creates low electron density regions at the center of the macrocycle cavity and this is the main cause of bambus[n]urils high affinity and selectivity towards anions. Due to these properties, bambus[n]urils have been used for the detection of anions in mixtures, but also in complex supramolecular systems where they act as donors in photoinduced electron-transfer processes, and synthetic ion-channels for example. These compounds are relatively recent and deserve attention for their potential in many branches of chemistry, especially in supramolecular and inclusion chemistry.

Resumo em Inglês:

This work presents an equation concerning effective light doses (Dabs; J cm-2) absorbed by photosensitizer molecules that are involved directly in photochemical and photodynamic processes. These molecules are photostimulated by different polychromatic LED sources with distinct photonic properties. The inherent photosensitizer photobleaching process, source irradiation emission spectrum (wavelength range), light source power, irradiation time, and LED-methylene blue spectral overlap degree were the relevant parameters considered for Dabs. This was performed with an experimental system comprised of methylene blue and its photosensitization ability on substrate DFBF (1,3-diphenylisobenzofuran) photodegradation, starting from different polychromatic LED sources. We demonstrated that such factors significantly affect photosensitizer light absorption, thus influencing the efficiency of a specific photochemical process. This occurs due to the selection of non-optimal experimental conditions associated with less precision from photonic source measurements, and therefore, less control on the actual Dabs. Such insights are interestingly absent in various studies with regards to a plethora of systems.

Resumo em Inglês:

One-step synthesis of gold nanoparticles functionalized with α-, β- and γ-cyclodextrins was carried out using a synthetic method of direct tetrachloroaurate reduction in alkaline solutions. The two experimental conditions studied were direct heating and microwave irradiation. This is the first publication comparing the characteristics of gold nanoparticles produced using three cyclodextrins under different conditions. The resulting nanoparticles were characterized by absorbance spectra, FTIR spectra, dynamic light scattering data and transmission electron microscopy images. The reducing ability of cyclodextrins increased in the following order: β-cyclodextrin < α-cyclodextrin < γ-cyclodextrin. Therefore, γ-cyclodextrin was the most active reductant and the only cyclodextrin that was able to reduce tetrachloroaurate at room temperature. In this case, nanoparticles were observed only after 4 days of storage. The nanoparticle size was dependent on the cyclodextrin type and correlated with the difference in the reducing ability. Using microwave irradiation, most of nanoparticles were found to be free nanoparticles. Using direct heating, aggregates formed due to the high ionic strength of the solution after prolonged boiling. Therefore, nanoparticles synthesized by direct heating were less stable during storage than those synthesized by microwave irradiation.

Resumo em Inglês:

There are many scientific discoveries and technology developments that are currently taken for granted in society as a whole, as if these had always existed. In an educational context this means that students have lost the ability to see themselves as delevopers of new technologies, assuming a role as mere users of the technologies made available by others. A contextualized appr3oach, explaining the origin of the names for the main glassware used in Chemistry classes, can make learning 3more meaningful. This approach focuses on hard work of one (or more) scientists in solving experimental problems that makes the equipment useful until the present day. Therefore we aim to humanize these creations, providing opportunities for the student to glimpse the possibility of himself contributing to the production of new equipment, techniques and knowledge through the presentation of some curious details about the invention or about the life of the scientist in question. Additionally, the images that illustrate this work, both from glassware and scientists, were made by high school students, a strategy that could also be used in classroom.

Resumo em Inglês:

The change in the way of teaching Chemistry requires, among others aspects, the rupture of established teaching practices and involves the professional development of teachers. Several conditions are necessary for such changes to take place, such as the recognition and legitimation of a specific knowledge to teach Chemistry as the Pedagogical Knowledge of Chemistry Content (PCKC) and the identification and characterization of obstacles that hamper the development of this professional knowledge. In this context, this article aims to describe the characterization of two epistemological obstacles: valorative obstacle and experiential obstacle, identified in the concept of undergraduate students of Chemistry Degree. The identification of obstacles of an epistemological nature in the concept of future Chemistry teachers can contribute to the improvement of the teacher training, since it gives subsidies to promote the learning of professional knowledge in Chemistry and perhaps to strengthen the professionalization of this career.

Resumo em Inglês:

In this work, we present a little explored alternative for the study and classification of thermodynamic variables. Some methods in the theory of ordinary differential equations not only support the use and calculation of these variables but also assists the physicochemical interpretation. We explore the Euler's criterion as a resource to study and differentiate the state functions and process variables useful in chemical thermodynamics. For this purpose, we carry out the development of the differentials and their analysis in a simple, rigorous, and progressive way, in accordance with the level of the topics treated in graduate courses of physical chemistry and classical thermodynamics.