Ionothermal synthesis and structure analysis of an open-framework zirconium phosphate with a high CO2/CH4 adsorption ratio

Less is more: an open-framework zirconium phosphate with unusual 7-ring channels was synthesized ionothermally from a deep-eutectic solvent. This small-pore material displays a CO(2)/CH(4) adsorption ratio (17.3 at 1 bar) that is significantly higher than that of typical 8-ring materials, making it highly attractive for CO(2)/CH(4) separations.     

Synthesis of (+)-dumetorine and congeners by using flow chemistry technologies

An efficient total synthesis of the natural alkaloid (+)-dumetorine by using flow technology is described. The process entailed five separate steps starting from the enantiopure (S)-2-(piperidin-2-yl)ethanol 4 with 29% overall yield. Most of the reactions were carried out by exploiting solvent superheating and by using packed columns of immobilized reagents or scavengers to minimize handling. New protocols for performing classical reactions under continuous flow are disclosed: the ring-closing metathesis reaction with a novel polyethylene glycol-supported Hoveyda catalyst and the unprecedented flow deprotection/Eschweiler-Clarke methylation sequence. The new protocols developed for the synthesis of (+)-dumetorine were applied to the synthesis of its simplified natural congeners (-)-sedamine and (+)-sedridine.     

Determination of relative sensitivity factors for trace element analysis of solar cell silicon by fast-flow glow discharge mass spectrometry

A commercially available Element GD, the latest generation of glow discharge mass spectrometry (GDMS), has been used for quantitative analysis of impurities in silicon for photovoltaic applications (PV silicon). In order to be able to accurately measure impurities in silicon, relative sensitivity factors (RSFs) need to be determined. These factors are, currently, given only for steel matrices. In this study, standard silicon materials with known levels of impurities have been produced and independent analytical methods have been used for determining the RSFs for silicon matrices. It has been found that the tuning parameters of the Element GD, mainly the discharge gas flow rate, influence the RSF values. In addition, it has been found that RSF values are matrix specific; RSFs for a silicon matrix differ significantly from those for metallic conductor matrices even under identical instrumental parameters. A study of the relative reproducibility in the quantitative analysis of impurities in solar cells silicon has shown variations between 5% and 12%.     

Preparation and thermal study of Mg-diclofenac compound in solid state

The thermal behaviour of Mg-diclofenac compound was evaluated by simultaneous TG-DTA and DSC. The profile of the DSC curves showed that this compound possesses two transition phases: endothermic and exothermic between 170–180 °C and 185–195 °C, respectively. The endothermic reaction is reversible (enantiotropic). Thus, different experimental conditions, i.e. masses sample, open and crimped lids crucible, static and dynamic atmospheres were utilized for DSC analysis for evaluation of this transition phase. In a static atmosphere the enantiotropic reaction was not observed. The obtained data were utilized to obtain the kinetic parameters, which were calculated by the Capela and Ribeiro method. The results show that the activation energy for the transition phase depends on the different experimental conditions.     

Mexican high school students' social representations of mathematics,its teaching and learning

This paper reports a qualitative research that identifies Mexican high school students’ social representations of mathematics. For this purpose, the social representations of ‘mathematics’, ‘learning mathematics’ and ‘teaching mathematics’ were identified in a group of 50 students. Focus group interviews were carried out in order to obtain the data. The constant comparative style was the strategy used for the data analysis because it allowed the categories to emerge from the data. The students’ social representations are: (A) Mathematics is…(1) important for daily life, (2) important for careers and for life, (3) important because it is in everything that surrounds us, (4) a way to solve problems of daily life, (5) calculations and operations with numbers, (6) complex and difficult, (7) exact and (6) a subject that develops thinking skills; (B) To learn mathematics is…(1) to possess knowledge to solve problems, (2) to be able to solve everyday problems, (3) to be able to make calculations and operations, and (4) to think logically to be able to solve problems; and (C) To teach mathematics is…(1) to transmit knowledge, (2) to know to share it, (3) to transmit the reasoning ability, and (4) to show how to solve problems.     

Morphometric partitioning of the respiratory surface area and diffusion capacity of the gills and swim bladder in juvenile Amazonian air-breathing fish, Arapaima gigas

The gills and the respiratory swim bladders of juvenile specimens (mean body mass 100 g) of the basal teleost Arapaima gigas (Cuvier 1829) were evaluated using stereological methods in vertical sections. The surface areas, harmonic mean barrier thicknesses and morphometric diffusing capacities for oxygen and carbon dioxide were estimated. The average respiratory surface area of the swim bladder (2173 cm² kg^?1) exceeded that of the gills (780 cm² kg^?1) by a factor of 2.79. Due to the extremely thin air–blood barrier in the swim bladder (harmonic mean 0.22 μm) and the much thicker water–blood barrier of the gills (9.61 μm), the morphometric diffusing capacity for oxygen and carbon dioxide was 88 times greater in the swim bladder than in the gills. These data clearly indicate the importance of the swim bladder, even in juvenile A. gigas that still engage in aquatic respiration. Because of the much greater diffusion constant of CO₂ than O₂ in water, the gills also remain important for CO₂ release.     

Density gradients in packed columns: I. Effects of density gradients on retention and separation speed

Density gradients in packed capillary columns operating under the extreme pressure drops typical for solvating gas chromatography were investigated by on-column spectroscopic measurements and compared to a theoretical model. Laser-induced fluorescence was used to follow the elution of various analytes, and Raman spectroscopy was used to measure the density of the mobile phase, each with respect to column position. Mobile phase linear velocity initially increases gradually, and then rises rapidly near the column outlet. High flow rates near the column outlet are offset by a loss of mobile phase solvating power which ultimately limits the speed of separation. These results represent an extreme case for illuminating factors affecting supercritical fluid separation techniques in general.     

Reactions of 2‐Aryl‐1,3‐Dithianes and [1.1.1]Propellane

Bicyclo[1.1.1]pentanes (BCPs) have sparked the interest of medicinal chemists due to their recent discovery as bioisosteres of aromatic rings. To study the biological activity of this relatively new class of bioisosteres, reliable methods to incorporate BCPs into target molecules are in high demand, as reflected by a flurry of methods for BCP synthesis in recent years. In this work, we disclose a general method for the synthesis of BCP‐containing dithianes which, upon deprotection, provide access to BCP analogues of medicinally abundant diarylketones. A broad scope of 2‐aryl‐1,3‐dithianes, including several heterocyclic derivatives, react with [1.1.1]propellane to afford 26 new derivatives in good to excellent yields. Further transformation of the dithiane portion into a variety of functional groups demonstrates the robustness of the products. A computational study indicates that the reaction of 2‐aryl‐1,3‐dithianes and [1.1.1]propellane proceeds via a two‐electron pathway.     

Macroscopic and microscopic aspects of the temporomandibular joint related to its clinical implication

In order to obtain a precise diagnosis and treatment for temporomandibular dysfunctions, it is necessary to have morphological and functional knowledge of the temporomandibular joint. Anatomic components are important to the understanding of the complexity of temporomandibular joint. Nonetheless, just as important are the anatomic relationships that this joint has with the neighboring structures. Thus, the aim of this study was to present the anatomic relationships of the temporomandibular joint in its various surfaces: external or lateral, anterior, posterior, medial, superior, and posterosuperior, considering the morphological and histological aspects. Nine human heads, fixed in formalin (10%) underwent sagittal medial section and were subsequently dissected, evidencing the anatomic components of all surfaces to be analyzed. Components of the external surface were: skin, subcutaneous tissue, lymphatic ganglia, parotid gland, superficial temporal artery, transverse facial artery, zygomatic-orbital artery, superficial temporal vein, facial and auriculotemporal nerves, masseter muscle, and pre-auricular lymphonodus. The anterior surface comprised the masseter and lateral pterygoid muscles (upper and inferior heads), pterygoid venous plexus, mandibular notch, posterior deep temporal artery, masseteric nerve, and deep posterior temporal branches. Medial surface components were: internal maxillary artery, of which middle meningeal artery was one of the closest branches to the TMJ, anterior tympanic artery, inferior alveolar, lingual, auriculotemporal, and chorda tympani nerves, which belonged to the surface posterior to the anterior wall of the auditory duct; auricolotemporal nerve, parotid gland; and petrotympanic fissure. The cerebral fossa (meninges and encephalon) belonged to the superior surface and the ear belonged to the posterosuperior surface. Histologically, the temporomandibular joint is composed by different tissues that compound the mandibular head, mandibular fossa, and articular eminence of the temporomandibular joint. It was concluded that the temporomandibular joint is a complex structure and the clinician must have the ability to formulate the diagnosis based on the understanding of morphological aspects of the structures that compose the stomatognatic system.     

Protective Role of Flavonoids against Intestinal Pro-Inflammatory Effects of Silver Nanoparticles

Silver nanoparticles (AgNP) have been increasingly incorporated into food-related and hygiene products for their unique antimicrobial and preservative properties. The consequent oral exposure may then result in unpredicted harmful effects in the gastrointestinal tract (GIT), which should be considered in the risk assessment and risk management of these materials. In the present study, the toxic effects of polyethyleneimine (PEI)-coated AgNP (4 and 19 nm) were evaluated in GIT-relevant cells (Caco-2 cell line as a model of human intestinal cells, and neutrophils as a model of the intestinal inflammatory response). This study also evaluated the putative protective action of dietary flavonoids against such harmful effects. The obtained results showed that AgNP of 4 and 19 nm effectively induced Caco-2 cell death by apoptosis with concomitant production of nitric oxide, irrespective of the size. It was also observed that AgNP induced human neutrophil oxidative burst. Interestingly, some flavonoids, namely quercetin and quercetagetin, prevented the deleterious effects of AgNP in both cell types. Overall, the data of the present study provide a first insight into the promising protective role of flavonoids against the potentially toxic effects of AgNP at the intestinal level.