Microstructure and non-isothermal crystallization behavior of PP/PLA/clay hybrid nanocomposites

Journal of Thermal Analysis and Calorimetry - Various compositions of polypropylene (PP) and poly(lactic acid) (PLA) blends were prepared by one-step melt compounding in a twin-screw extruder. Two...     

Co3O4 nanoparticles prepared by oxidative precipitation method: an efficient and reusable heterogeneous catalyst for N-formylation of amines

Research on Chemical Intermediates - N-formylation of different amines was carried out with formic acid in the presence of the Co3O4 nanoparticles as an efficient, stable heterogeneous catalyst to...     

Piston scuffing fault and its identification in an IC engine by vibration analysis

In this paper, the effects of piston scuffing fault on engine performance and vibrations are investigated. A procedure based on vibration analysis is also presented to identify piston scuffing fault. To this end, an internal combustion (IC) engine ran under a specific test procedure. The engine parameters and vibration signals were measured during the experiments. To produce piston scuffing fault, three-body abrasive wear mechanism was employed. The experimental results showed that piston scuffing fault caused the engine performance to reduce significantly. The vibration signals were analyzed in time-domain, frequency-domain and time–frequency domain. Continuous wavelet transform (CWT) was used to obtain time–frequency representations. “dmey” wavelet was selected as the optimum wavelet type for this research among different wavelet types using the three criteria of energy, Shannon entropy and energy to Shannon entropy ratio. The results of CWT analysis by “dmey” wavelet showed that piston scuffing fault excited the frequency band of 2.4–4.7 kHz in which the frequency of 3.7 kHz was affected more. Finally, seven different features were extracted from the engine vibration signals related to the frequency band of 2.4–4.7 kHz. The results indicated that maximum, mean, RMS, skewness, kurtosis and impulse factor of the engine vibration related to the found frequency band increased significantly due to piston scuffing fault. The obtained results showed that the proposed method identified piston scuffing fault and discovered the vibration characteristics of this fault like frequency band. The results also demonstrated the possibility of using engine vibrations in piston scuffing fault identification.     

A Note on Ranking Fuzzy Numbers with an Area Method using Circumcenter of Centroids

In this study, we show that ranking fuzzy numbers with the area method using circumcenter of centroids presented by Rao and Shankar failed to rank effectively the generalized fuzzy numbers. By proving a theorem and using some numerical examples, we demonstrate that their proposed method cannot rank consistently some fuzzy numbers or is not consistent with human intuition.     

Effects of Various Amounts of New Hepta-Ether as the Internal Donor on the Polymerization of Propylene with and without the External Donor

The new hepta-ether compound as the internal donor was synthesized using the Williamson reaction of dipentaerythritol with sodium hydride as the strong base and iodomethane as the alkyl halide. The hepta-ether compound was characterized by NMR, FTIR, and GC techniques. The MgCl₂-supported catalysts incorporated with different amounts of hepta-ether compound as the internal donor and without the internal donor were synthesized and characterized. The propylene polymerization was carried out using these catalysts in the presence of triethylaluminum as a co-catalyst and hydrogen as a chain transfer agent, with and without the external donor. The effect of a new internal donor on propylene polymerization using prepared MgCl₂-supported Ziegler-Natta catalysts was investigated.     

Are Pro<Superscript>8</Superscript>/Pro<Superscript>18</Superscript> really critical for functional dynamic behavior of human endostatin N-terminal peptide? A comparative molecular dynamics study

Endostatin which is derived from the non-collagenous domain 1 of collagen XVIII and is a recently identified broad spectrum anti-angiogenesis agent, inhibits 65 different tumor types. The N-terminal fragment of endostatin protein (ES) has the same antitumor, antimigration and antipermeability effects as the entire protein. In the current study, we modeled two mutant variants of ES with two mutation sites (M1-ES (Pro⁸ → Ala) and M2-ES (Pro¹⁸ → Ala)) and tried to understand proline’s effect on the peptide structure/stability by introducing P⁸A/P¹⁸A mutations, and then in order to gain functional insight into mutation caused by amino acid substitution to the peptide structure/function, these effects were predicted using computational tools. From the RMSD analyses, it can be concluded that dynamic behavior of wild-type and mutant structures was not significantly different from each other and all systems reached equilibrium. The RMSF analysis also revealed that the M2-ES has smaller overall flexibility than the WT-ES and M1-ES structures. The radius of gyration analysis then confirmed the structure of M2-ES compared to wild-type and M1 variant becomes more compact during simulation of our systems. Finally, molecular dynamics simulation analysis shows that replacement of Pro residue with Ala is able to induce a distinct β-sheet in both mutant structures. Indeed, the docking analysis shows the WT-ES and M2-ES bind to the same region of α_vβ₃ integrin, suggesting similar interaction pattern with a relatively equal binding energy into this receptor. Our results speculated that the P⁸A/P¹⁸A replacements confer no improvement (or no tangible weakness) in the peptide biological activity although is able to change structural conformation of N-terminal fragment of human endostatin protein.     

Effect of a novel green modification of alumina nanoparticles on the curing kinetics and electrical insulation properties of epoxy composites

A novel green surface modification was successfully implemented on alumina nanoparticles using chitosan (CS) to prevent nanoparticles' aggregation. To evaluate the surface changes of nanoparticles, FTIR, TGA, TEM, and SEM analyses were used. The cure kinetics of the uncured samples was analyzed by DSC. Different methods such as KAS, Friedman, Starink, and FWO were applied to measure the activation energy. The activation energy of epoxy reinforced with chitosan-functionalized alumina (epoxy/[CS-EPO-alumina]) was less than that of epoxy reinforced with alumina (epoxy/alumina), which was a confirmation of the positive effect of CS on curing reaction kinetics. Using the Malek method, the Sestak-Berggren autocatalytic equation was chosen to investigate the cure kinetics of the epoxy. It was found that the Sestak-Berggren equation is well matched with the experimental data and the model was suitable to predict the epoxy curing reaction reliably. Moreover, the glass transition temperatures of all samples were approximately the same. The effect of surface modification of alumina on the electrical insulating behavior of epoxy was also studied. It was found that CS functionalized alumina (CS-EPO-alumina) increased volume resistivity of epoxy at a temperature range of 30 to 80°C more than that of alumina. Electric stability and breakdown strength of epoxy/alumina and epoxy/(CS-EPO-alumina) also enhanced, where epoxy/(CS-EPO-alumina) experienced a further increase compared to epoxy.     

Investigating the influence of pH,temperature and agitation speed on yellow pigment production by Penicillium aculeatum ATCC 10409

In this study, the combined effect of pH, temperature and agitation speed on yellow pigment production and mycelial growth of Penicillium aculeatum ATCC 10409 was investigated in whey media. Different pH levels (5, 6.5 and 8), temperatures (25, 30 and 35°C) and agitation speed levels (100 and 150 rpm) were tested to determine the best conditions to produce a fungal yellow pigment under submerged fermentation. The best production of yellow pigment (1.38 g/L) was obtained with a pH value of 6.5, a temperature of 30°C and an agitation speed of 150 rpm. In contrast, the maximal biomass concentration (11.12 g/L) was obtained at pH value of 8, a temperature of 30°C and an agitation speed of 100 rpm. These results demonstrated that biomass and yellow pigment production were not directly associated. The identification of the structure of unknown P. aculeatum yellow pigment was detected using UV absorption spectrum and FT-IR spectroscopy.     

In Silico Study on the Interaction of Thiazolidinediones and β-Lactoglobulin by Molecular Dynamics and Docking Approach

Thiazolidinediones are widely used in the treatment of diabetes mellitus type 2. An investigation of their interaction with a transport protein, such as β-lactoglobulin (BLG), at the atomic level could be a valuable factor in controlling their transport to biological sites. The interaction of troglitazone, pioglitazone, and rosiglitazone, as representative thiazolidinediones, and BLG, as a transport protein, was investigated using molecular docking and molecular dynamics (MD) simulation methods. The molecular docking results showed that these thiazolidinediones bind to the internal cavity of BLG and the BLG affinity for binding the thiazolidinediones decreases in the following order: troglitazone > pioglitazone > rosiglitazone. The analysis of MD simulation trajectories showed that the BLG and BLG-thiazolidinedione complexes became stable at approximately 2500 ps and that there was little conformational change in the BLG-thiazolidinedione complexes over a 10 ns timescale. In addition, the profiles of atomic fluctuations showed the rigidity of the ligand-binding site during the simulation time.     

Dansyl‐peptides matrix‐assisted laser desorption/ionization mass spectrometric (MALDI‐MS) and tandem mass spectrometric (MS/MS) features improve the liquid chromatography/MALDI‐MS/MS analysis of the proteome

Peptide tagging is a useful tool to improve matrix‐assisted laser desorption/ionization tandem mass spectrometric (MALDI‐MS/MS) analysis. We present a new application of the use of the dansyl chloride (DNS‐Cl). DNS‐Cl is a specific primary amine reagent widely used in protein biochemistry. It adds a fluorescent dimethylaminonaphthalene moiety to the molecule. The evaluation of MALDI‐MS and MS/MS analyses of dansylated peptides shows that dansylation raises the ionization efficiency of the most hydrophilic species compared with the most hydrophobic ones. Consequently, higher Mascot scores and protein sequence coverage are obtained by combining MS and MS/MS data of native and tagged samples. The N‐terminal DNS‐Cl sulfonation improves the peptide fragmentation and promotes the generation of b‐fragments allowing better peptide sequencing. In addition, we set up a labeling protocol based on the microwave chemistry. Peptide dansylation proved to be a rapid and cheap method to improve the performance of liquid chromatography (LC)/MALDI‐MS/MS analysis at the proteomic scale in terms of peptide detection and sequence coverage. Copyright © 2010 John Wiley & Sons, Ltd.