Rheological study of segmented polyurethane and polycaprolactone blends

The dynamic rheological properties of segmented polyurethane based on polycaprolactone diol (PU-PCL diol) and poly (ɛ-caprolactone) (PCL) blends were experimentally examined and theoretically analyzed using Palierne model. PU–PCL diol was melt blended with PCL in three different ratios of 20, 30, and 40%. Initial modeling attempts failed to fit the experimental data of these blends, as the model overpredicted their rheological data. This failure is believed to be due to partial dissolution of PCL in PU. According to our obtained results from differential scanning calorimetry and dynamic thermal mechanical analysis, pure PU–PCL diol is diluted by its homopolymer. By calculating the complex modulus of this diluted matrix using a simple mixing rule and its incorporation into the model, good fitting of the Palierne equation to the experimental data was obtained.     

A study on the formation of strontium hexaferrite nanopowder by a sol–gel auto-combustion method in the presence of surfactant

Strontium hexaferrite is a hard magnetic material and has been extensively used as a permanent magnet. In this work, a novel sol–gel auto-combustion method was used to synthesize ultra-fine strontium hexaferrite, and the effect of the surfactant on the crystallite size of the final product was investigated for the first time. The DTA/TGA plot exhibited the formation temperature of hexaferrite. The XRD results show that adding surfactant to the sol does not change the composition of the combustion product and the surfactant burns completely during the combustion process. The average crystallite size of hexaferrite powders was also measured by the X-ray line broadening technique employing the Scherrer formula. The results show that adding surfactant to the gel makes the particle size of the final product much smaller.     

Survival function estimation when lifetime and censoring time are dependent

In this paper we consider a model for dependent censoring and derive a consistent asymptotically normal estimator for the underlying survival distribution from a sample of censored data. The methodology is illustrated with an application to the analysis of cancer data. Some simulations to evaluate the performance of our estimator are also presented. The results indicate that our estimator performs reasonably well in comparison to the other dependent censoring survival curve estimators.     

Preparation and characterization of durable micro/nanocapsules for use in self-healing anticorrosive coatings

In the field of coatings, extensive laboratory research has been conducted in the last decade. In the present work, effectiveness of epoxy resin filled micro/nanocapsules was investigated for future using in healing of cracks generated in coatings. Micro/nanocapsules were prepared by in situ polymerization of urea–formaldehyde resin to form shell over epoxy resin droplets. The optimal process parameters for synthesizing the micro/nanocapsules were selected. The as-synthesized capsules were studied by various characterizations techniques, including scanning electron microscope (SEM), particle size analyzer (PSA), Fourier transform-infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results indicate that micro/nanocapsules containing epoxy resins can be synthesized successfully. The rough outer surface of microcapsule is composed of agglomerated urea–formaldehyde nanoparticles. They basically exhibit good storage stability at room temperature, and they are chemically stable before the heating temperature is up to approximately 250°C.     

Classification of weathered petroleum oils by multi-way analysis of gas chromatography-mass spectrometry data using PARAFAC2 parallel factor analysis

The application of multi-way parallel factor analysis (PARAFAC2) is described for the classification of different kinds of petroleum oils using GC-MS. Oils were subjected to controlled weathering for 2, 7 and 15 days and PARAFAC2 was applied to the three-way GC-MS data set (MSxGCxsample). The classification patterns visualized in scores plots and it was shown that fitting multi-way PARAFAC2 model to the natural three-way structure of GC-MS data can lead to the successful classification of weathered oils. The shift of chromatographic peaks was tackled using the specific structure of the PARAFAC2 model. A new preprocessing of spectra followed by a novel use of analysis of variance (ANOVA)-least significant difference (LSD) variable selection method were proposed as a supervised pattern recognition tool to improve classification among the highly similar diesel oils. This lead to the identification of diagnostic compounds in the studied diesel oil samples.     

Synthesis and cytotoxicity of novel chromenone derivatives bearing 4-nitrophenoxy phenyl acryloyl moiety

This work describes synthesis of novel chromenone derivatives bearing 4-nitrophenoxy phenyl acryloyl moiety through the reaction of 4-(4-nitrophenoxy)benzaldehydes and 3-acetyl-2H-chromen-2-ones in refluxing toluene. Cytotoxicity of all compounds was evaluated using a tetrazolium (MTT) colorimetric assay against human breast cancer cell line, MDA-MB-231.     

Efficient Beckmann rearrangement and dehydration of oximes via phosphonate intermediates

Under mild conditions, conversion of a variety of ketoximes and aldoximes to their corresponding amides and nitriles proceeded in the presence of diethyl chlorophosphate with excellent yields.