Extremal polyomino chains with respect to Zagreb indices

For a molecular graph, the first Zagreb index M₁ is equal to the sum of squares of the vertex degrees and second Zagreb index M₂ is equal to the sum of products of degree of pairs of adjacent vertices. In this paper, Zagreb indices of polyomino chains are computed. Also the extremal polyomino chains with respect to Zagreb indices are determined.     

Evaluation of the rate of abiotic degradation of biodegradable polyethylene in various environments

The rate of abiotic degradation of polyethylene (PE) films containing a manganese pro-degradant has been studied in various environments at 60 and 70 °C. The degradation was monitored from the change in molecular weight and the elongation at break after exposure to dry and humid air. It was observed that moisture had a strong accelerating effect on the rate of thermo-oxidation of PE films. However, despite the humidity level in the compost environment being similar to that in humid air, the rate of degradation in compost was much slower. It is proposed that ammonia and/or hydrogen peroxide generated by microorganisms in the compost can be responsible for the deactivating effect, as aqueous solutions of these compounds significantly retard the rate of degradation.     

A Comparative Study of Hydrodistillation and Hydrodistillation–Solvent Microextraction Methods for Identification of Volatile Components of Echinophora cinerea

A recently developed hydrodistillation–solvent microextraction (HD–SME) method coupled to gas chromatography–mass spectrometry (GC–MS) was applied to the analysis of volatile components of aerial parts of Echinophora cinerea (Boiss). By the use of a simplex optimization method, the effects of extraction time, sample weight and microdrop volume on the extraction efficiency of the method were optimized. In the optimized conditions, 3 µL of n-heptadecane was suspended in the headspace of 6 g of hydrodistillating sample, using a microsyringe. After 7 min, the solvent was retracted back into the syringe and directly injected into the GC–MS injection port. The HD–SME method was compared to a conventional hydrodistillation technique. In general, the extraction with HD–SME was relatively faster and required smaller amounts of sample. The microextraction method also showed some selectivity towards α-phellandrene and Z-β-ocimene monoterpenes. A precision better than 6.5% (expressed as relative standard deviation) was obtained for the method.

     

Influence of processing technique on morphology and mechanical properties of PVC nanocomposites

This study aims to compare the influence of processing techniques and procedures on the morphology and mechanical properties of polyvinyl chloride (PVC) nanocomposites. PVC nanocomposites with 5 phr montmorillonite (MMT) clay were prepared on a two-roll mill or in a microcompounder, both were either processed once or via a masterbatch containing 20 phr MMT. The MMT was treated with non-ionic surfactants and analysed by thermo gravimetric analysis and X-ray diffraction prior to being added. The final composites were analysed and tested using X-ray diffraction, scanning and transmission electron microscopy (SEM/TEM), tensile test, and Charpy impact test. The dispersion was found to be best in the roll milled samples prepared via the masterbatch and the elongation at break and impact strength was also better for the roll milled samples. E-modulus and tensile strength, on the other hand, were significantly better for the microcompounded samples despite the larger particle size. This can be explained by a higher degree of orientation in these samples. Finally, it must be stated that the change in properties are not satisfactory. Although we see an increase in E-modulus, the decreased impact properties are not acceptable. The main reason for this is the lack of compatibility between the clay particles as observed by high resolution SEM.     

The bipartite edge frustration of composite graphs

The smallest number of edges that have to be deleted from a graph to obtain a bipartite spanning subgraph is called the bipartite edge frustration of G and denoted by φ(G). In this paper we determine the bipartite edge frustration of some classes of composite graphs.     

Removal of Toluene from Air Using a Cycled Storage-Discharge (CSD) Plasma Catalytic Process

Plasma Chemistry and Plasma Processing - Cycled storage-discharge (CSD) air-plasma catalytic process was used for removing toluene from simulated 40% humid air. The different catalytic activities...     

Improved etherification procedure for the preparation of dibenz[b,f][1,4]oxazepine

The effect of temperature and catalyst on the yield and rate of the etherification reaction between 1 and 2 was investigated and alternative methods for separation of 3 and 4 from the reaction mixture have been described.     

Extremal values of augmented eccentric connectivity index of V-phenylenic nanotorus

A topological index of a molecular graph G is a numeric quantity related to G which is invariant under symmetry properties of G. Let G be a molecular graph. The augmented eccentric connectivity index, ξ ^A (G) is defined as ξ ^A (G)=Σ _u∈V(G) M(u)/ε(u) where M(u) denotes the product of degrees of all neighbors of vertex u and ε(u) is the largest distance between u and any other vertex v of G. In this paper the exact formulas for the augmented eccentric connectivity index of V-phenylenic nanotorus together with its extremal values are given.     

Radar Absorption Properties of Ni0.5Zn0.5Fe2O4/PANI/epoxy Nanocomposites

A nitrate? citrate gel was prepared from metallic nitrates and citric acid by sol? gel process and was further used to synthesize Ni_0.5Zn_0.5Fe₂O₄ nanocrystalline powder by auto‐combustion. Then, two novel 15 and 35% (w/w) magnetic Ni_0.5Zn_0.5Fe₂O₄ containing polyaniline nanocomposites, named as PANI‐Ni15 and PANI‐Ni35, respectively, were prepared via in‐situ polymerization of aniline in an aqueous solution containing proper amount of Ni_0.5Zn_0.5Fe₂O₄ magnetic powder. The incorporation of the nanopowders to PANI matrix was confirmed by X‐ray diffraction (XRD), IR and SEM. Synthesized PANI‐NiZn ferrite composite particles were subsequently added to an epoxy resin matrix to produce related nanocomposites. The morphological properties of these nanocomposite materials were investigated by SEM and TEM. The electromagnetic‐absorbing properties were studied by measuring the reflection loss in the frequency range of 8.0 to 12.0 GHz. Results showed the reflection loss of the PANI‐Ni35 composite is higher than pure polyaniline and PANI‐Ni15. The good reflection loss of the nanocomposites suggests their potential applicability as radar absorber.     

Kinetics of abiotic and biotic degradability of low-density polyethylene containing prodegradant additives and its effect on the growth of microbial communities

The kinetics of abiotic oxidation in the dark and the kinetics of biological mineralization in soil and in a compost environment of thermally oxidized LDPE were studied. It was demonstrated that different activation energies are obtained for the thermal oxidation, depending on the composition of the materials. Significantly higher levels of biodegradability have been obtained in a soil environment at 23 °C compared with the compost environment at 58 °C. After two years of mineralization, 91% conversion to carbon dioxide was obtained in the soil test, compared with 43% in the compost test. The differences between fungal, archaeal and bacterial community structures in soil and compost after 607 days of biodegradability assay were mapped out. It was found that the most dominant bacterial and fungal terminal restriction fragments (TRFs) in the compost containing the test material are significantly different from the TRFs in the other environments.