The exchange rate between dissolved tripalmitin and tripalmitin crystals

The focus of this paper is on understanding the exchange between dissolved fats and fat crystals in dispersions by quantifying the rate of the exchange between the fats in solution and in crystals. In the studies reported here, tripalmitin (PPP) was used as model fat. The dispersions contained PPP crystals and dissolved radio-labelled PPP (14C-PPP, used as the probe) in a medium chain triglyceride oil (MCT). The exchange process between the dissolved 14C-PPP and unlabelled PPP crystals was followed using a radio-detector. The effect of the crystal concentration on the exchange rate was studied. The results suggested that the rate of the exchange is dependent upon both the dissolution of the surface of the crystals and also diffusion and crystallisation of the dissolved compounds.     

Preparation of magnetic polyurethane rigid foam nanocomposites

Super paramagnetic Fe₃O₄@SiO₂ nanoparticle was incorporated into polyurethane rigid foams in order to prepare new corresponded magnetic nanocomposite foams via one-shot method. The core–shell-structured nanoparticles were prepared by sol–gel method and characterized by transmission electron microscopy, X-ray diffraction, as well as Fourier transform infrared spectroscopy techniques. Magnetic nanoparticles were used up to 3 % in the foam formulations and the samples prepared successfully. Thermal, mechanical, and magnetic properties of nanocomposites were studied and the results showed superior properties in comparison with pristine foams.     

A highly diastereoselective five-component synthesis of 1-(alkylimino)-5,5-dicyano-3a-aryloctahydro-3-oxacyclobuta[cd]pentalene-1a,2,5a,5b(2H,3aH)-tetracarboxylates

A novel one-pot, five-component synthesis of 1-(alkylimino)-5,5-dicyano-3a-aryloctahydro-3-oxacyclobuta[cd]pentalene-1a,2,5a,5b(2H,3aH)-tetracarboxylates is described. A mixture of phenacyl bromide, malononitrile, isocyanide, and two equivalents of a dialkyl acetylenedicarboxylate undergoes a novel 1:1:1:2 addition reaction at ambient temperature in absolute ethanol to produce diastereoselectively the title compounds in good yields.     

Extending regular edge-colorings of complete hypergraphs

A coloring (partition) of the collection $(\genfrac{}{}{0.0pt}{}{X}{h})$ of all $h$-subsets of a set $X$ is $r$-regular if the number of times each element of $X$ appears in each color class (all sets of the same color) is the same number $r$. We are interested in finding the conditions under which a given $r$-regular coloring of $(\genfrac{}{}{0.0pt}{}{X}{h})$ is extendible to an $s$-regular coloring of $(\genfrac{}{}{0.0pt}{}{Y}{h})$ for $s⩾r$ and $Y⊋X$. The case $\text{◂,▸}h=2,r=s=1$ was solved by Cruse, and due to its connection to completing partial symmetric latin squares, many related problems are extensively studied in the literature, but very little is known for $h⩾3$. The case $r=s=1$ was solved by Häggkvist and Hellgren, settling a conjecture of Brouwer and Baranyai. The cases $h=2$ and $h=3$ were solved by Rodger and Wantland, and Bahmanian and Newman, respectively. In this paper, we completely settle the cases $h=4,\text{◂⩾▸}|Y|⩾4|X|$ and $h=5,\text{◂⩾▸}|Y|⩾5|X|$.     

Evaluation of physico-chemical properties of electron beam-irradiated polycarbonate film

In this work, polycarbonate (PC) film samples were irradiated with 10 MeV electrons at different doses ranging from 25 to 250 kGy. Characterization techniques viz. thermogravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FTIR), X-ray diffraction analysis (XRD) and electron paramagnetic resonance (EPR) were exploited to understand the induced changes in the physico-chemical properties of the polymer. An increase in the decomposition temperature with increasing dose was observed, while the crystallinity remained unchanged as a result of the formation of cross-link bond. EPR technique characterized the stability of the free radicals in the irradiated PC. The result showed that cross-linking process occurs at low absorbed doses, whereas polymer degradation happens at higher doses.     

Constructing the Spectrum of Packings and Coverings for the Complete Graph with Stars with up to Five Edges

The packing and covering problems have been considered for several classes of graphs. For instance, Bryant et. al. have investigated the packing problem for paths and cycles, and the packing and covering problems for 3-cubes. The packing and covering problems were settled for stars with up to six edges by Roditty. In this paper, for every possible leave graph (excess graph), we find a corresponding maximum packing (minimum covering) of the complete graph with stars with up to five edges.     

A molecular dynamics investigation on the interaction properties of AzrC and its cofactor

In this report, the main contributions of FMN were employed in the reductive cleavage reaction of AzrC protein (as a member of azoreductase family). Molecular dynamics simulations of three models in the presence and absence of FMN and ligand were performed to gather information about the dynamic nature of active site residues of AzrC. Combination of pairwise decomposition and alanine scanning calculations provides critical information about the FMN binding sites. The MD results analyzed by alanine scanning method revealed the high negative scores for N 10 (A) A, N 12 (A) A, S 17 (A) A and Y 151 (A) A mutations, which were in agreement with pairwise decomposition analyses. Hydrogen bond analyses indicated that these residues play critical roles in establishing appropriate hydrogen bonds between AzrC and FMN. Negative energy results for nonpolar residues such as W 103 (A), M 102 (A) and F 105 (A) and binding free energy analyses of three complexes indicate that the VDW interactions could be regarded as some favorable contribution in FMN and AzrC protein and confirmed the critical role of FMN in ligand binding (35.84 %), in addition to its catalytic function. This information could be used for future experimental investigations.     

Nano–silica functionalized with thiol–based dendrimer as a host for gold nanoparticles: An efficient and reusable catalyst for chemoselective oxidation of alcohols

In this paper, we present the synthesis of Au nanoparticles supported on nanosilica thiol based dendrimer, nSTDP. The catalyst was prepared by reduction of HAuCl₄ with NaBH₄ in the presence of nSTDP. The resulting Au_np–nSTDP materials were characterized by FT–IR and UV–vis spectroscopic methods, SEM, TEM, TGA, XPS and ICP analyses. The characterization of the catalyst showed that Au nanoparticles with the size of 2–6 nm are homogeneously distributed on the nSTDP dendrimer with a catalyst loading of about 0.19 mmol/g of catalyst. The Au_np–nSTDP catalyst was used in the oxidation of alcohols with tert–butyl hydroperoxide (TBHP) as oxidant. The influence of vital reaction parameters such as solvent, oxidant and amount of catalyst on the oxidation of alcohols was investigated. These reactions were best performed in an acetonitrile/water mixture (3:2) in the presence of 0.76 mol% of the catalyst on the basis of the Au content at 80 °C under atmospheric pressure of air to afford the desired products in high yields (80–93% for benzyl alcohols). The Au_np–nSTDP catalyst exhibited a high selectivity toward the corresponding aldehyde and ketone (up to 100%). Reusabiliy and stability tests demonstrated that the Au_np–nSTDP catalyst can be recycled with a negligible loss of its activity. Also this catalytic exhibited a good chemoselectivity in the oxidation of alcohols.