Elucidating a particulate matter deposition episode by combining scanning electron microscopy and X-ray fluorescence spectrometry.

Multielemental composition and morphology of particulate matter samples were examined to detect the presence of two potential responsible pollutant emitters at four sites impacted during a pollution episode in the City of Campana, Argentina. Coke and smoke black are the main constituents associated to the industrial plants that were considered, a priori, as responsible pollutant emitters. Wavelength dispersive X-ray fluorescence (WDXRF) was employed for the analysis of metals in samples coming from both, suspected sources and four sites. On the basis of multielemental composition profiles, a screening analysis was undertaken for exploring similarities among sources and sample sites adopting the average concentration profile of the crustal rock as soil surrogate. Particle morphology was studied by scanning electron microscopy (SEM) in source samples and in those environmental samples selected through the screening analysis. Two types of collected samples were analyzed: 1) those with composition profiles closer to the potential sources and 2) those closer to the cluster rock. This strategy was adequate to identify the responsible source of the contamination episode.     

Asymptotic Stability for a Class of Neutral Systems with Discrete and Distributed Time Delays

In this note, the asymptotic stability for a class of neutral systems with discrete time and distributed time delays is considered. Delay-dependent criteria are proposed to guarantee the stability for such systems. Some numerical examples are given to illustrate that our results are less conservative than previous results.     

New bicyclic phosphorous ligands: synthesis, structure and catalytic applications in ionic liquids

New azadioxaphosphabicyclo[3.3.0]octane ligands showing a trans arrangement with regard to the two five-membered heterocycles, were obtained as a mixture of three conformers, in agreement with molecular modelling studies. The stability of oxaphosphane ligands was studied under basic catalytic conditions, monitored by NMR spectroscopy. Palladium catalytic systems containing these ligands were active in Suzuki C-C cross-coupling reactions between phenylboronic acid and aryl halides (bromide and chloride derivatives) bearing electron-donor or electron-withdrawing substituents, in both organic and ionic liquid solvents. The catalytic systems showed a high stability even under the most severe reaction conditions used in this work. The ionic liquid catalytic phase could be recycled up to ten times without significant activity loss.     

Heat and light dual switching of a single-walled carbon nanotube/thermo-responsive helical polysaccharide complex: a new responsive system applicable to photodynamic therapy

A thermo- and light-responsive system consisting of single-walled carbon nanotube and helical polysaccharide modified with poly(N-isopropylacrylamide) side-chains has been developed through supramolecular polymer wrapping. Coagulation of the complex can be induced by the external stimuli, which leads to a catch-and-release action of a porphyrin derivative.     

A combinatorial formula for Macdonald polynomials

In this paper we use the combinatorics of alcove walks to give uniform combinatorial formulas for Macdonald polynomials for all Lie types. These formulas resemble the formulas of Haglund, Haiman and Loehr for Macdonald polynomials of type GLn. At q=0 these formulas specialize to the formula of Schwer for the Macdonald spherical function in terms of positively folded alcove walks and at q=t=0 these formulas specialize to the formula for the Weyl character in terms of the Littelmann path model (in the positively folded gallery form of Gaussent and Littelmann).     

Evaluation of Diabetes Effects of Selenium Nanoparticles Synthesized from a Mixture of Luteolin and Diosmin on Streptozotocin-Induced Type 2 Diabetes in Mice

The absence of a treatment efficient in the control of type 2 diabetes mellitus requires more functional products to assist treatment. Luteolin (LU) and diosmin (DIO) have been known as bioactive molecules with potential for the treatment of diabetes. This work aimed to establish the role that a combination of LU and DIO in selenium nanoparticles (SeNPs) played in streptozotocin (STZ)- induced diabetes mice. Green synthesis of Se NPs was performed by mixing luteolin and diosmin with the solution of Na₂SeO₃ under continuous stirring conditions resulting in the flavonoids conjugated with SeNPs. The existence of flavonoids on the surface of SeNPs was confirmed by UV-Vis spectra, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) images, and DLS graphs via Zetasizer. The average diameter of GA/LU/DIO-SeNPs was 47.84 nm with a PDI of −0.208, a zeta potential value of −17.6, a Se content of 21.5% with an encapsulation efficiency of flavonoids of 86.1%, and can be stabilized by gum Arabic for approximately 175 days without any aggregation and precipitation observed at this time. Furthermore, The C57BL/6 mice were treated with STZ induced-diabetes and were exposed to LU/DIO, SeNPs, and GA/LU/DIO-SeNPs for six weeks. The treatment by nanospheres (GA/LU/DIO-SeNPs) in the mice with diabetes for a period of 6 weeks restored their blood glucose, lipid profile, glycogen, glycosylated hemoglobin, and insulin levels. At the same time, there were significant changes in body weight, food intake, and water intake compared with the STZ- untreated induced diabetic mice. Moreover, the GA/LU/DIO-SeNPs showed good antioxidant activity examined by catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx) in liver and kidney and can prevent the damage in the liver evaluated by aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) activities. The nanospheres exhibited a significant anti-diabetic activity with a synergistic effect between the selenium and flavonoids. This investigation provides novel SeNPs nanospheres prepared by a high-efficiency strategy for incorporating luteolin and diosmin to improve the efficiency in type 2 diabetes.     

13C-NMR Chemical Shifts in 1,3-Benzazoles as a Tautomeric Ratio Criterion

Benzimidazole is an important heterocyclic fragment, present in many biologically active compounds with a great variety of therapeutic purposes. Most of the benzimidazole activities are explained through the existence of 1,3-tautomeric equilibrium. As the binding affinity of each tautomer to a protein target depends on an established bioactive conformation, the effect of tautomers on the ligand protein binding mechanism is determinant. In this work, we searched and analyzed a series of reported ¹³C-NMR spectra of benzazoles and benzazolidine-2-thiones with the purpose of estimating their tautomeric equilibrium. Herein, several approaches to determine this problem are presented, which makes it a good initial introduction to the non-expert reader. This chemical shift difference and C4/C7 signals of benzimidazolidine-2-thione and 1-methyl-2-thiomethylbenzimidazole as references were used in this work to quantitatively calculate, in solution, the pyrrole–pyridine tautomeric ratio in equilibrium. The analysis will help researchers to correctly assign the chemical shifts of benzimidazoles and to calculate their intracyclic or exocyclic tautomeric ratio as well as mesomeric proportion in benzimidazoles.     

Regioselective synthesis of 2,4,6-triaminopyridines

A regioselective synthesis of 2,4,6-trisubstituted pyridine is described starting from 2,6-dibromo-4-nitropyridine. All three different regioisomers of the 2,4,6-triamino substituted pyridine have been synthesized in four to five steps. The method described is a general route to unsymmetrical 2,4,6-trisubstituted amino pyridines.