A rapid method for the microdetermination of sulfide using N-bromosuccinimide

Summary A new, rapid, convenient and accurate method for the determination of sulfide has been developed. N-Bromosuccinimide has been used for the displacement of iodine from potassium iodide which in turn reacts with sulfide and oxidises it to sulfur. N-Bromosuccinimide can be used as a primary standard and kept for several days if refrigerated and protected from light. Sulfide in the range of 0.6 to 13 mg can be determined with an average relative standard deviation of 1.02%.

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Zusammenfassung Ein neues Verfahren zur Sulfidbestimmung wurde entwickelt. N-Bromsuccinimid(I) dient zur Freisetzung von Jod aus KJ. Sulfid wird so zu elementarem Schwefel oxydiert. I kann als Standardlösung einige Tage im Dunklen gekühlt aufbewahrt werden. 0,6 bis 13 mg Sulfid können so mit einer relativen Standardabweichung von 1,02% bestimmt werden.

     

Influence of slip over an exponentially moving vertical plate with Caputo-time fractional derivative

Journal of Thermal Analysis and Calorimetry - In this article, the impact of a MHD is analyzed on a VF accompanying double convection, because of the transfer inducted by temperature and...     

Stability of cross-linked acetic acid lignin-containing polyurethane

The thermo-oxidative stability of acetic acid lignin-containing polyurethane (LPU) that contains cross-linking agents, such as 1-aminopropyltriethoxy-silane (APTS) and/or trimethylolpropane (TMP) was investigated based on the thermogravimetric analysis (TGA) method, their kinetic parameters in the thermo-oxidative process was determined. FT-IR certified the occurrence of interaction between lignin and polyurethane (PU). It was found that continuous membrane can be formed when lignin concentration was 43.3%, but rupture took place when it increased to 50%. When the degradation was performed in nitrogen, TG and dynamic differential thermogravimetry (DTG) results demonstrated that the PU underwent three stages of degradation while the LPU involved one main degradation stage with a shoulder, and the degradation stability increased with the increase in the lignin concentration and PEG length. It was also found that the addition of a cross-linking agent is beneficial to the improvement of thermal stability and, in particular, APTS gave the best thermal stability for the LPU produced, among the cross-linking agents tested. Furthermore, LPU exhibited multistage degradation process in air and displayed higher thermo-oxidative stability than PU. At the same time, the kinetic study showed that LPU modified with APTS exhibited higher activation energy than LPU modified with TMP. And the maximum activation energy was found for the sample modified with the simultaneous addition of APTS and TMP.     

Synthesis and characterization of porous crystalline SiC thin films prepared by radio frequency reactive magnetron sputtering technique

Hexagonal SiC thin films have been deposited using radio frequency reactive magnetron sputtering technique by varying the substrate temperature and other deposition conditions. Prior to deposition surface modification of the substrate Si(1 0 0) played an important role in deposition of the hexagonal SiC structure. The effect of substrate temperature during deposition on structure, composition and surface morphology of the SiC films has been analyzed using atomic force microscopy, Fourier transform infrared spectroscopy and spectroscopic ellipsometry. X-ray diffraction in conventional θ-2θ mode and omega scan mode revealed that the deposited films were crystalline having 8H-SiC structure and crystallinity improved with increase of deposition temperature. The bonding order and Si-C composition within the films showed improvement with the increase of deposition temperature. The surface of thin films grew in the shape of globes and columns depending upon deposition temperature. The optical properties also showed improvement with increase of deposition temperature and the results obtained by ellipsometry reinforced the results of other techniques.     

Identification of new novel scaffold for Aurora A inhibition by pharmacophore modeling and virtual screening

Aurora kinases belong to family of highly conserved serine/threonine protein kinases that are involved in diverse cell cycle events and play a major role in regulation of cell division. Abnormal expression of Aurora kinases may lead to cancer; hence, these are considered as a potential target in cancer treatment. In this research article, we identified three novel Aurora A inhibitors using modern computational tools. A four-point common 3D pharmacophore hypothesis of Aurora A (AurA) inhibitors was developed using a diverse set of 55 thienopyrimidine derivatives. A three-dimensional quantitative structure–activity relationship (3D-QSAR) study was carried out using atom-based alignment of diverse set of 55 molecules to evaluate the structure– activity relationships. Docking and 3D-QSAR studies were performed with the 3D structure of AurA to evaluate the generated pharmacophore. The pharmacophore model and 3D-QSAR results complemented the results of our docking study. The pharmacophore hypothesis, which yields the best results, was used to screen the Zinc ‘clean drug-like’ database. Various database filters such as 3D-arrangement of pharmacophoric features, predicted activity and binding interaction score were used to retrieve hits having potential AurA inhibition activity.     

Effect of miscibility and interaction on the properties of polymethylmethacrylate/aramid nanoblends

The generation of supramolecularly organized structures from intermolecular interaction motivated us to fabricate new miscible nanoblends of polymethylmethacrylate (PMMA) and aramid. The polyamide, prepared through the condensation of 1,5‐diaminonaphthalene and 1,4‐phenylenediamine with isopthaloyl chloride, was incorporated into PMMA matrix to produce completely miscible nanostructured blends via physical interlocking. The influence of polymer–polymer interaction on the macroscopic properties of blends were studied using mechanical testing, thermogravimetric analysis, differential scanning calorimetry, and scanning electron microscopy. Ample adhesion between the blend components revealed higher tensile strength in the range 51–58 MPa. The physical interaction of PMMA with varying aramid content altered blend morphology significantly, i.e. from ellipsoidal to circular realms having well‐defined boundaries and knitted nanofibril network. Blends with 10–70 wt% aramid, thus, possessed exclusive patterns owing to nanolevel compatibility between two phases. Differential scanning calorimetry results also designated exclusively miscible blends with glass transition between 67–81°C, lower than that of pristine polymers. Ten percent gravimetric loss temperature (T₁₀) increased from 465°C to 531°C with increasing aramid content from 10 to 70 wt%. Novel nanoblends holding spherical/cylindrical supramolecular arrangement, easy processing, and thermal and mechanical integrity can be potentially favorable in many industrial applications. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis,characterization and impregnation of lead sulphide semiconductor nanoparticles on polymer matrix

Lead sulphide nanoparticles were prepared using a precursor and dual sources methods. The composites were fabricated by stabilizing chemically synthesized semiconductor PbS nanocrystals into laurylmethacrylate and ethyleneglycol dimethacrylate matrix in the presence of tri-n-octylphosphine. PbS nanocrystals were dispersed in toluene as a compatible medium for the polymerization and cross-linking of poly laurylmethacrylate networks. The nano-sized particles and polymer composites were characterized by XRD and TEM. Possible formulations and incorporation of these PbS nanoparticles in polymer matrix have been discussed. The reported lead sulphide nanoparticles into tailered polymeric system show greater uniformity and stability.     

Spectrophotometric study of stability constants of cimetidine–Ni(II) complex at different temperatures

Cimetidine, a histamine H₂-receptor, has a structure which enables it to act as a chelating agent. The formation of nickel(II) complex with cimetidine has been studied spectrophotometrically at an absorption maximum of 622 nm at different temperatures. The data show that nickel(II) and cimetidine combine in the molar ratio of 1:2. The stability constants of the complex were calculated to be 1.40–2.4 × 10⁸ by continuous variation method and 1.24–2.4 × 10⁸ by mole ratio method at 25 and 40 °C, respectively. The immediately formed complex shows stability with respect to time and temperature.