On coincidence problem in ELKO dark energy model

We study the critical points of a universe dominated by Eigenspinoren des Ladungskonjugationsoperatorsin (ELKO) spinor field dark energy and a barotropic matter without considering a specific potential or interaction. The coincidence problem and attractor solutions are discussed at late time, and it is shown that the coincidence problem can not be solved in this model.     

Effects of NiTiO3 nanoparticles supported by mesoporous MCM-41 on photoreduction of methylene blue under UV and visible light irradiation

In this work, we report the synthesis of nickel titanate nanoparticles loaded on nanomesoporous MCM-41 nanoparticles to determine the effect of MCM-41 nanoparticles on the photocatalytic activities of nickel titanate (NiTiO₃) nanoparticles by using simple solid-state dispersion (SSD) method. Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and UV–Vis diffuse reflectance spectra (DRS) analysis were used to characterize the size and morphology of the obtained nanocomposite. The photocatalytic activity (PA) of the as-prepared NiTiO₃ loaded on MCM-41 was evaluated by degradation of the methylene blue under irradiation of UV and visible light. The results showed that NiTiO₃ loaded on nanosize MCM-41 has higher photocatalytic activity than that of NiTiO₃ nanoparticles.     

Ultrasonic and bio‐assisted synthesis of Ag@HNTs‐T as a novel heterogeneous catalyst for the green synthesis of propargylamines: A combination of experimental and computational study

A novel heterogeneous catalyst is prepared through functionalization of halloysite nanotube with 1H‐1,2,3‐triazole‐5‐methanol and subsequent immobilization of silver nanoparticles through bio‐assisted approach using Arctiumplatylepis extract. The resulting catalyst, Ag@HNTs‐T, was characterized by using SEM/EDX, BET, XRD, FTIR, ICP‐AES, TGA, DTGA and elemental mapping analysis. Moreover, we computationally assessed metal‐ligand interactions in Ag@HNTs‐T complex model to interpret the immobilization behavior of silver nanoparticles on HNTs surface via quantum chemistry computations. The catalytic activity of the catalyst was studied for the synthesis of propargylamines via A³ and KA² coupling reactions under ultrasonic irradiation. The results demonstrated that Ag@HNTs‐T could efficiently promote these reactions to furnish the corresponding products in high yields and short reaction times. The study of the recyclability of the catalyst and Ag(0) leaching confirmed that the catalyst was recyclability up to four reaction runs with slight Ag(0) leaching.     

CuI‐functionalized halloysite nanoclay as an efficient heterogeneous catalyst for promoting click reactions: Combination of experimental and computational chemistry

Amine‐functionalized halloysite nanotubes (HNTs‐2 N) were prepared and further modified by introduction of salicylaldehyde and formation of imine functionality (HNTs‐2 N‐Sal). The latter was subsequently used for immobilization of CuI and formation of CuI@HNTs‐2 N‐Sal, which could effectively promote click reactions of terminal alkynes, sodium azide and α‐haloketones or alkyl halides in aqueous media and under mild reaction conditions to afford 1,2,3‐triazoles in relatively short reaction times. Notably, the catalyst could be recycled in up to six reaction runs with negligible loss of catalytic activity and CuI leaching. Also, the geometry of CuI adsorption on the modified HNTs surface was explored by molecular simulation with density functional theory. Furthermore, topographic steric maps of possible coordination modes were obtained using the recently released SambVca2 web application tool. Based on obtained results, a catalytic site with superior performance was suggested.     

Deamination of Some N-Amino Nitrogen Heterocycles Using Preyssler’s Anion

Summary. Some N-aminotriazines and -triazoles were treated with Preyssler’s anion as catalyst in acetic acid to afford the corresponding deaminated triazines and triazoles. The reaction is suggested to proceed via formation of N-nitrosamines with subsequent N–NO bond cleavage.     

Automatic detection of small objects from their infrared state-of-polarization vectors

A technique for automatic detection of targets from their infrared signature's state-of-polarization vector is described. The bounds on the Bayesian total probability of errors are estimated from the observed Stokes vector imagery and used as metrics for separating targets from background clutter. The performance of the proposed approach for objects under various geometries is studied in terms of receiver operating characteristic curves. The new results, which have been obtained from data from the U.S. Air Force's Infrared Modeling and Analysis polarimetric infrared simulation tool, indicate the usefulness of polarimetric infrared signatures for the automatic detection of small targets.     

Polarimetric laser radar target classification

Imaging laser radar (ladar) systems have been developed for automatic target identification in surveillance systems. Ladar uses the range value at the target pixels to estimate the target's 3-D shape and identify the target. For targets in clutter and partially hidden targets, there are ambiguities in determining which pixels are on target that lead to uncertainties in determining the target's 3-D shape. An improvement is to use the polarization components of the reflected light. We describe the operation and preliminary evaluation of a polarization diverse imaging ladar system. Using a combination of intensity, range, and degree of polarization, we are better able to identify and distinguish the target from other objects of the same class.     

Granulated copper oxide nano-catalyst: a novel and efficient catalyst for C–N cross-coupling of amines with iodobenzene

Abstract  

Nano-structured CuO granules catalyze the C–N cross-coupling of amines with iodobenzene in excellent yields. The reaction is simple, efficient, and operates in air under ligand-free conditions.