Synthesis of pyranopyrazoles using nano‐Fe‐[phenylsalicylaldiminemethylpyranopyrazole]Cl2 as a new Schiff base complex and catalyst

By the condensation reaction of benzaldehyde with ethyl acetoacetate, malononitrile and hydrazine hydrate in the presence of FeCl₂, a pyranopyrazole derivative was prepared which was then reacted with salicylaldehyde to afford nano‐Fe‐[phenylsalicylaldiminemethylpyranopyrazole]Cl₂ (nano‐[Fe‐PSMP]Cl₂). The prepared nano‐Schiff base complex was fully characterized using Fourier transform infrared spectroscopy, X‐ray diffraction, thermogravimetric analysis, differential thermogravimetry, scanning electron microscopy and UV–visible spectroscopy, and was used as an efficient and catalyst for the preparation of pyranopyrazoles.     

Improving the design stresses of high density polyethylene pipes and vessels used in reverse osmosis desalination plants

Nanocomposite materials have been used on a wide scale in industrial and structural applications. The present work aims at studying the mechanical properties of high density polyethylene (HDPE) grade TR-401 hexene copolymer reinforced by montmorillonite nanoparticles (MMT), used to fabricate pipes and membranes vessels for reverse osmosis desalination plants. Different volume fractions and particle sizes of the MMT clay were used to investigate the effect of this filler on the mechanical properties of the produced composite. Mechanical properties tests were carried out and good improvements of the composite properties were obtained compared to the parent polymer. The test results showed a significant enhancement of the mechanical properties at low filler proportions. Pipe fabricated from these composites had many outstanding and desirable features. For example, by adding 4.75% MMT to the HDPE produced quality pipes and fittings with the highest design stress basis of any polyethylene. A significant increase in the modulus of elasticity observed, together with an unusual increase in the design stress, approved the HDPE/MMT composite for high pressure piping and membrane vessels used in reverse osmosis desalination plants.     

Likelihood-based inference for bivariate latent failure time models with competing risks under the generalized FGM copula

Many existing latent failure time models for competing risks do not provide closed form expressions of sub-distribution functions. This paper suggests a generalized FGM copula models with the Burr III failure time distribution such that the sub-distribution functions have closed form expressions. Under the suggested model, we develop a likelihood-based inference method along with its computational tools and asymptotic theory. Based on the expressions of the sub-distribution functions, we propose goodness-of-fit tests. Simulations are conducted to examine the performance of the proposed methods. A real data from the reliability analysis of the radio transmitter-receivers are analyzed to illustrate the proposed methods. The computational programs are made available in the R package GFGM.copula.     

Testing quasi-independence for truncation data

Quasi-independence is a common assumption for analyzing truncated data. To verify this condition, we propose a class of weighted log-rank type statistics that include existing tests proposed by Tsai (1990) and Martin and Betensky (2005) as special cases. To choose an appropriate weight function that may lead to a more power test, we derive a score test when the dependence structure under the alternative hypothesis is modeled via the odds ratio function proposed by Chaieb, Rivest and Abdous (2006). Asymptotic properties of the proposed tests are established based on the functional delta method which can handle more general situations than results based on rank-statistics or U-statistics. Extension of the proposed methodology under two different censoring settings is also discussed. Simulations are performed to examine finite-sample performances of the proposed method and its competitors. Two datasets are analyzed for illustrative purposes.     

Phosphorescence at Low Temperature by External Heavy-Atom Effect in Zinc(II) Clusters

Luminescent Zn^II clusters [Zn₄L₄(μ₃-OMe)₂X₂] (X=SCN ( 1 ), Cl ( 2 ), Br ( 3 )) and [Zn₇L₆(μ₃-OMe)₂(μ₃-OH)₄]Y₂ (Y=I⁻ ( 4 ), ClO₄⁻ ( 5 )), HL=methyl-3-methoxysalicylate, exhibiting blue fluorescence at room temperature (λ_max=416≈429 nm, Φ_em=0.09–0.36) have been synthesised and investigated in detail. In one case the external heavy-atom effect (EHE) arising the presence of iodide counter anions yielded phosphorescence with a long emission lifetime (λ_max=520 nm, τ=95.3 ms) at 77 K. Single-crystal X-ray structural analysis and time-dependent density-functional theory (TD-DFT) calculations revealed that their emission origin was attributed to the fluorescence from the singlet ligand-centred (¹LC) excited state, and the phosphorescence observed in 4 was caused by the EHE of counter anions having strong CH−I interactions.     

C60 nanocrystals thin film with controlled density

In this paper, C₆₀ nanocrystals thin film with monocrystal thickness was prepared using a liquid-liquid interface. C₆₀ nanocrystals dispersion prepared by reprecipitation method was added to n-hexane/water interface to form a thin film. The film was transferred onto an ITO substrate. Surface morphology of the film was studied by scanning electron microscope (SEM) and atomic force microscope (AFM) measurements. It was found that the density of the film increase with increasing the deposition number of layers with maintaining the monocrystal thickness.     

Chemical preparation and characterization of fibrous poly(3-methylthiophene) decorated by TiO2 nanoparticles

In this article, we report on the chemical oxidative polymerization of 3-methylthiophene (3MTh) in a concentrated TiO₂/CHCl₃ homogeneous suspension with an oxidant/monomer mole ratio of 3 at room temperature. According to the scanning electron microscopy images, in this condition, poly(3-methylthiophene) (P3MTh) was prepared with fibrous morphology decorated by nano-dimensional TiO₂ particles. P3MTh/TiO₂ was also characterized by Fourier transform infrared spectroscopy and X-ray diffraction techniques. It was found that no aggregation of nanoparticles occurred during the polymerization process. In addition, the thermal stability of P3MTh/TiO₂ nanocomposite was investigated by thermogravimetric analysis and compared with that of an analogously prepared neat P3MTh. The thermal degradation of P3MTh in the temperature range of 300–550°C decreases significantly due to the presence of the TiO₂ nanoparticles in the polymer composite.     

The B–C and C–C bonds as preferred electron source for H-bond and Li-bond interactions in complex pairing of C<Subscript>4</Subscript>B<Subscript>2</Subscript>H<Subscript>6</Subscript> with HF and LiH molecules

Ab initio calculations were used to analyze the interaction of C₄B₂H₆ with HF and LiH molecules at the mp2/6-311++g(2d,2p) computational level. Interaction of C₄B₂H₆ with HF results to H–F···H–C and C–B···H–F, C–C···H–F hydrogen bond as well as B–H···H–F dihydrogen bond complexes. Also interaction of C₄B₂H₆ with LiH results to B–C···LiH, C–C···LiH and B–H···LiH lithium bond as well as C–H···H–Li dihydrogen complexes. In the both cases, complexes involving interaction of HF or LiH with peripheral B–C and C–C bonds of the C₄B₂H₆ backbone have greater stabilities. The structures of complexes have been analyzed using AIM and NBO methodologies.     

Synthesis and odor properties of Phantolide analogues

Phantolide analogues 1a–1d were newly synthesized to evaluate their odor profiles. The enantiomers of 1a and 1b were also synthesized. Both (S) enantiomers of 1a and 1b had musk odor although weakly, and but neither of the (R) enantiomers 1a and 1b had musk odor. During the investigations, we encountered the undesirable racemization in Friedel-Crafts reaction of the intermediate (S)-5.