Improvements of physical and mechanical properties of electron beam irradiation—crosslinked EVA foams

In this work, ethylene–vinyl acetate (EVA) copolymer foams were prepared and crosslinked by using high‐energy electron beam (e‐beam) radiation (10 MeV). The effect of parameters such as irradiation dose, the contents of foaming agent, radiation activator, and radiation sensitizer on improvement of physical and mechanical properties of the EVA foamed samples were investigated. The foams were obtained through a four‐step process of melt mixing, forming, crosslinking, and foaming. During the melt mixing process EVA was compounded with different amounts of azodicarbonamide (ADCA) as a blowing agent, zinc oxide (ZnO) as a radiation activator, and trimethylol propane‐trimethacrylate (TMPTMA) as a radiation sensitizer. The samples were compression molded into flat sheets at low temperature (110°C) and were then radiation‐crosslinked by 20–80 kGy e‐beam. Finally, the crosslinked samples were converted to foams by a high temperature (210°C) compression molding process. The foamed samples were analyzed in terms of gel content, density, compression molding set, tensile properties, and micro‐structural features. It was found that an increase in absorbed radiation dosage increases crosslink density, elasticity, percentage recovery, tensile strength, and compression properties of the EVA foams. Due to the increased recovery the percentage of compression set was reduced. Similarly increasing the TMPTMA content in the formulation increased the crosslink density and the resulting mechanical properties. Contrary to these findings, addition of ADCA led to the formation of extra gases which in turn reduced the crosslink density, and resulted in the deterioration of the mechanical properties and hence an increase in the compression set. However, addition of ZnO and TMPTMA led to the formation of smaller and more uniform cell size with improved mechanical properties. Copyright © 2008 John Wiley & Sons, Ltd.     

Substitutional doping of Cu in diamond: Mott physics with p orbitals

Discovery of superconductivity in the impurity band formed by heavy doping of boron into diamond (C:B) as well as doping of boron into silicon (Si:B) has provided a rout for the possibility of new families of superconducting materials. Motivated by the special role played by copper atoms in high temperature superconducting materials where essentially Cu d orbitals are responsible for a variety of correlation induced phases, in this paper we investigate the effect of substitutional doping of Cu into diamond. Our extensive first principle calculations based on density functional theory which are averaged over various geometries indicate the formation of a mid-gap band, which mainly arises from the t _{2 g} and 4p states of Cu. For impurity concentrations of more than ~1%, the effect of 2p bands of neighboring carbon atoms can be ignored. Based on our detailed analysis, we suggest a two band model for the mid-gap states consisting of a quarter-filled hole like t _{2 g} band, and a half-filled band of 4p states. Increasing the concentration of the Cu impurity beyond ~5%, completely closes the spectral gap of the host diamond.     

Aerobic oxidation of benzyl alcohols through biosynthesized palladium nanoparticles mediated by Oak fruit bark extract as an efficient heterogeneous nanocatalyst

In this study, green synthesis of Pd nanoparticles (NPs) is outlined through application of Oak fruit bark extract as a reducing, capping and stabilizing agent. The characteristics and properties of the biosynthesized Pd NPs were revealed by FESEM, EDX, XRD, TEM, UV–Vis, and FT-IR spectroscopies. So that, UV–Vis spectroscopy of the Pd colloidal solution confirmed reduction of Pd ions, and XRD and TEM analysis identified fcc unit cell structure forming 5–7 nm spherical Pd NPs. Furthermore, catalytic activity of the prepared catalyst was investigated through aerobic oxidation of alcohols, as model reactions. Catalytic evaluations demonstrated achievement of good yields from primary and secondary benzyl alcohols. In general, the devised synthesis method is advantageous from several perspectives. For example, the synthesized catalysts give high product yields and are efficient, they eliminate the need for surfactant, chemical reductants, ligand and organic solvents, the approach is economically inexpensive, it results in cleaner reaction profiles, application of the simply prepared heterogeneous catalyst is convenient, and the catalyst is recoverable and reusable for at least six times without any significant loss of its catalytic activity.     

Synthesis of 3,4-dihydropyrimidin-2(1H)-ones and 1,4-dihydropyridines using ammonium carbonate in water

Various known and new 3,4-dihydropyrimidin-2(1H)-ones and 1,4-dihydropyridines are prepared efficiently via Biginelli and Hantzsch reactions using ammonium carbonate in water. Competition between Biginelli and Hantzsch reactions is observed with pyridine carbaldehydes. Using this methodology, Hantzsch esters are synthesized in higher yields and purities than with other procedures without the use of a catalyst or an organic solvent.     

Immobilization of palladium nanoparticles on ionic liquid-triethylammonium chloride functionalized magnetic nanoparticles: As a magnetically separable,stable and recyclable catalyst for Suzuki-Miyaura cross-coupling reactions

A facile procedure was applied to successfully synthesize novel Pd nanoparticles immobilized on triethanolamine-functionalized magnetic nanoparticles [Fe₃O₄/IL/Pd]. Diverse characterizations (HR-TEM, XRD, FT-IR, TGA, EDX, FE-SEM, ICP, XPS and VSM) were carried out to identify intrinsic traits of the nanoparticles. At room temperature, Fe₃O₄/IL/Pd demonstrated high catalytic activity toward Suzuki-Miyaura cross-coupling reactions in aqueous solution. Based on the results, Fe₃O₄/IL/Pd acted as zwitterionic IL-type heterogeneous catalyst, which could be separated from the reaction mixture, conveniently. Moreover, it exhibited excellent recyclability for at least eight cycles without considerable loss of its activity.     

On total domination vertex critical graphs of high connectivity

A graph is called γ-critical if the removal of any vertex from the graph decreases the domination number, while a graph with no isolated vertex is γ_t-critical if the removal of any vertex that is not adjacent to a vertex of degree 1 decreases the total domination number. A γ_t-critical graph that has total domination number k, is called k-γ_t-critical. In this paper, we introduce a class of k-γ_t-critical graphs of high connectivity for each integer k≥3. In particular, we provide a partial answer to the question “Which graphs are γ-critical and γ_t-critical or one but not the other?” posed in a recent work [W. Goddard, T.W. Haynes, M.A. Henning, L.C. van der Merwe, The diameter of total domination vertex critical graphs, Discrete Math. 286 (2004) 255-261].     

New solitary wave solutions for the bad Boussinesq and good Boussinesq equations

In this article, the sine–cosine, the standard tanh and the extended tanh methods has been used to obtain solutions of the bad Boussinesq and good Boussinesq equations. New solitions and periodic solutions are formally derived. The change of parameters, that will drastically change characteristics of the equation, is examined. © 2008 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 2009     

Type and conductor of simplicial affine semigroups

We provide a generalization of pseudo-Frobenius numbers of numerical semigroups to the context of the simplicial affine semigroups. In this way, we characterize the Cohen-Macaulay type of the simplicial affine semigroup ring $\mathbb{K}[S]$. We define the type of S, $\mathrm{type}(S)$, in terms of some Apéry sets of S and show that it coincides with the Cohen-Macaulay type of the semigroup ring, when $\mathbb{K}[S]$ is Cohen-Macaulay. If $\mathbb{K}[S]$ is a d-dimensional Cohen-Macaulay ring of embedding dimension at most $d+2$, then $\mathrm{type}(S)\le 2$. Otherwise, $\mathrm{type}(S)$ might be arbitrary large and it has no upper bound in terms of the embedding dimension. Finally, we present a generating set for the conductor of S as an ideal of its normalization.     

Transport and Energy Deposition of hot Electrons through the Shock Ignition pre Compressed Target

Shock ignition as an alternative scheme of the laser fusion has the potential of achieving efficient implosion. However, hot electrons produced in result of ignitor‐corona interaction may penetrate deep into the fuel making the compression less effective. Transport and energy deposition of hot electron beam into the dense pre compressed of HiPER target by means of Monte Carlo approach are discussed considering the influence of real density and electron beam characteristics. The target parameters before igniting the hot spot have been extracted from a fluid code and used as the initial profile for Monte Carlo simulations. In comparison with simplified step like density profile, electrons penetrate slightly deeper in the case of real shaped density profile. In addition, deposition zone of a broad spectrum electron beam is wider while, monoenergetic electrons depose their energy locally resulting more maximum energy deposition value. (© 2016 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)