A simple and efficient synthesis and dynamic NMR studies of some new podands of dithiocarbamates formed from bis(naphthyl) derivatives

The reaction of dithiocarbamate salts ( IV _{a − c} ) with bis(naphthalene chloroacetates) ( II _a,b ) and bis(naphthalene ethoxybromide) ( II _c ) in dimethylformamide (DMF) furnished corresponding podands as V _{a − i} in high to excellent yields. Three reacting ligands, ( II _a,b ) and ( II _c ), were obtained in the reaction of bis(naphthalene) ( I _a,b ) with chloroacetylchloride and 1,2‐dibromoethane. Dynamic NMR spectroscopic data of three series of podands ( V _{a − c} , V _d−f , and V _{g − i} ) are discussed, and their free energy of activation (Δ G_C^≠) at coalescence temperatures are figured out. The Δ G_C^≠ s of these podands were attributed to conformational isomerization in the range of 14.5–18.3 kcal mol⁻¹ due to rotation and resonance effects about thioamide C N bond. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:659–668, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20730     

Liquid-Droplet as a model for the rotation curve problem

The dynamics of large scale gravitational structures like galaxies, local groups and clusters is studied based on the so-called Liquid-Droplet model describing the saturation property of the nuclear force. Using the assumption that the gravitational force is also saturated over large scale structures, it is argued that the Newtonian gravitational potential may be replaced by an effective Machian gravitational potential. Application of this new potential at these large scale structures may give the rotation curves in good agreement with observations. Then, the virial theorem for this kind of gravitational interaction is developed and also the Tully-Fisher relation is obtained. A physical explanation is given for the so-called constant acceleration in the MOND as the effective gravitational strength of these structures. Finally, a brief argument is given for comparison with dark matter models.     

Hydrogen bis[tris(4‐fluorophenyl)phosphane oxide] triiodide

In the title compound, C₃₆H₂₅F₆O₂P₂⁺·I₃⁻, hydrogen‐bonded [{(p‐FC₆H₄)₃PO}₂H]⁺ dimers assemble along the crystallographic c axis to form channels that house extended chains of triiodide anions. Although the I—I bond lengths of 2.9452 (14) and 2.9023 (15) Å are typical, the inter‐ion I...I distance of 3.5774 (10) Å is unusually short. A posteriori modelling of nonmerohedral twinning about (100) has been only partially successful, achieving a reduction in the maximum residual electron density from 5.28 to 3.24 e Å⁻³. The inclusion of two low‐occupancy I‐atom sites (total 1.7%), which can be interpreted as translational disorder of the triiodide anions along the channels, reduced the maximum residual electron density to 2.03 e Å⁻³. The minor fractional contribution volume of the nonmerohedral twin domains refined to 0.24 and simultaneous refinement of the inversion twin domains showed the crystal to be a 0.5:0.5 inversion twin.     

Mechanism of deleading of silicate glass by 0.5 N HNO3

Mechanism of removal of lead from silicate glass containing 68.5 wt% PbO by 0.5 N HNO₃ was investigated by incorporation of the chemical-analyses/weight-loss data into shrinking-core model (SCM) and minimization of the difference. Scanning electron microscopy (SEM), emission spectrometry with inductively coupled plasma (ICP), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS) were used to determine the compositional changes of the lead-silicate glass (LSG) samples. Dual inter-diffusion chemical reaction mechanisms having respective activation energies of 83.49 and 47.80 kJ/mol dominated the deleading process.     

Phytochemistry and Biological Activities of Iris Species Growing in Iraqi Kurdistan and Phenolic Constituents of the Traditional Plant Iris postii

A dozen Iris species (Iridaceae) are considered traditional remedies in Kurdistan, especially for treating inflammations. Phytochemical studies are still scarce. The information reported in the literature about Iris species growing in Kurdistan has been summarized in the first part of this paper, although, except for Iris persica, investigations have been performed on vegetal samples collected in countries different from Kurdistan. In the second part of the work, we have investigated, for the first time, the contents of the methanolic extracts of Iris postii aerial parts and rhizomes that were collected in Kurdistan. Both extracts exhibited a significant dose-dependent free radical scavenging and total antioxidant activities, comparable to those of ascorbic acid. Medium-pressure liquid chromatographic separations of the two extracts afforded l-tryptophan, androsin, isovitexin, swertisin, and 2″-O-α-l-rhamnopyranosyl swertisin from the aerial parts, whereas ε-viniferin, trans-resveratrol 3,4′-O-di-β-d-glucopyranoside, and isotectorigenin were isolated from the rhizomes. This is the first finding of the last three metabolites from an Iris species. The various remarkable biological activities of isolated compounds scientifically sustain the traditional use of I. postii as a medicinal plant.     

Chain dynamics in partially cross-linked polyethylene by combined rheology and NMR-based molecular rheology

In recent years, ¹H double-quantum NMR (DQ NMR) was established as a suitable molecular-rheology technique to elucidate chain dynamics and to determine entanglement or crosslink densities in linear entangled polymer melts and permanent as well as transient networks. In this work, industrial grade high-density polyethylene, partially cross-linked via electron beam irradiation in the semicrystalline state, is probed in the melt state by low-field DQ NMR and shear rheology. The DQ NMR data is analyzed by two approaches, one assuming the presence of a permanent network and the other considering the potentially complex relaxation spectrum of the studied inhomogeneous systems. A correlation between the DQ NMR results and extent of cross-linking is found. By direct comparison of the rheological results and the NMR-based segmental orientation autocorrelation functions (OACF) via time–temperature superposition (TTS), qualitative consistency between the microscopic and macroscopic observables is established. In this way, the frequency range of shear rheology can be extended by about two decades into the 10 krad/s range. The NMR method is thus a valuable extension of the toolbox of characterization techniques, where gel content measurements by solvent extraction proved to be the least sensitive.     

Fe3O4@SiO2–ZrCl2‐MNPs: A novel magnetic catalyst for the clean and efficient cascade synthesis of 1‐(benzothiazolylamino)methyl‐2‐naphthol derivatives in the absence of solvent

A green, simple and eco‐friendly three‐component condensation for the synthesis of 1‐(benzothiazolylamino)methyl‐2‐naphthols using new magnetic nanoparticles formulated as Fe₃O₄@SiO₂–ZrCl₂‐MNPs is described. Considering the economic and environmental aspects, the method provides some advantages such as clean procedure, solvent‐free conditions, simple operation and work‐up, relatively short reaction times and high yields of the products. Moreover the introduced catalyst can be readily recovered up to 4 consecutive runs with consistent activity using an external magnet.     

Optimization of Linac-based neutron source for thermal neutron activation analysis

Journal of Radioanalytical and Nuclear Chemistry - A 20 MeV electron Linac based neutron beam has been shaped for neutron activation analysis (NAA) technique. A beam shaping assembly (BSA)...     

Combined methane reforming over nano LaNiO<Subscript>3</Subscript> catalyst with modified active surface

In this study, nano catalyst LaNiO₃ with perovskite structure was synthesized using the citrate sol–gel method in the combined methane reforming with CO₂ and O₂ (CRM). The effects of increasing the surface area of the LaNiO₃ perovskite on the catalytic activity were investigated by changing the method of preparing and creating holes in the surface of the samples. Physical and chemical properties of the samples, before and after the reactor test, were determined through ICP, AA, XRD, TGA, TPR, BET, SEM, EDX and TEM techniques. The results of XRD, ICP, AA, SEM, EDX and TEM tests indicated that the citrate sol–gel method is a good way to prepare a homogeneous perovskite LaNiO₃ sample on a scale of nanometers. The results of the TPR test showed using etching in the citrate sol–gel method can produce samples with high stability. The BET results indicated that the surface area of the LaNiO₃ sample tripled with the method suggested in this paper. Changes in preparation method lead to induction time decreasing and temperature increasing. Use of etching in the citrate sol gel method had no significant effect in the results of activity tests versus time reaction at a temperature of 800 °C. TGA curves revealed no production of coke over the process for the produced samples.     

Improving piezoelectric and pyroelectric properties of electrospun PVDF nanofibers using nanofillers for energy harvesting application

In this study, it was aimed to increase the piezoelectric and pyroelectric properties of electrospun polyvinylidene fluoride (PVDF) nanofibers simultaneously by using specific nanofillers. Graphene oxide (GO), graphene, and halloysite nanotubes with different concentrations (0, 0.05, 0.4, and 1.6% wt/wt) were combined with PVDF solution and were fabricated in the form of nanofibers through electrospinning. Pyroelectric properties of samples were measured by submerging sealed samples in hot water (360°K) and ice (270°K). The piezoelectric properties of the samples were evaluated through bending tests. The microstructural, mechanical, and thermal properties of the electrospun PVDF nanocomposite were investigated using scanning electron microscope, Instron instrument, and thermogravimetric analysis, respectively. To further support the experimental observations for generating electric voltage in the bended nanogenerator, the PVDF nanogenerator (PNG) was also modeled by a finite element analysis based on the theory of linear piezoelectricity using COMSOL Multiphysics simulation software. Experimental results showed that adding nanofillers could improve the piezoelectric and pyroelectric properties of all samples, associated with the increment of β‐phase in the nanofibers. It was concluded that adding nanofillers could increase pyroelectricity about 50% more than piezoelectricity in pristine PVDF nanofiber web. The PNG containing 1.6 wt% GO showed the highest efficiency in terms of piezoelectricity and pyroelectricity. In addition, the results showed that the ratio of piezoelectric to pyroelectric coefficients was constant (~1.5) and it was independent of the nanofiller type and content. The effect of external force and vibration frequency on the output voltage was also investigated. Increasing the compressive force and vibration frequency caused a greater output voltage. Finally, the fabricated nanogenerator was integrated on insole and elbow to investigate its energy harvesting capabilities from body movement.