Dynamics and control of a system of two non‐interacting preys with common predator

In this paper, we consider a Holling type model, which describes the interaction between two preys with a common predator. First, we give some sufficient conditions for the globally asymptotic stability and prove that local stability implies global stability. Then, we present a set of sufficient conditions for the existence of a positive periodic solution with strictly positive components. Finally, the optimal control strategy is developed to minimize the number of predator and maximize the number of preys. We also show the existence of an optimal control for the optimal control problem and derive the optimality system. The technical tool used to determine the optimal strategy is the Pontryagin Maximum Principle. Finally, the numerical simulations of global stability and the optimal problem are given as the conclusion of this paper. Copyright © 2011 John Wiley & Sons, Ltd.     

Key synthesis of magnetic Janus nanoparticles using a modified facile method

Inorganic/organic poly（methylmethacrylate-acrylic acid-divinylbenzene） iron oxide Janus magnetic nanoparticles（P（MMA-AA-DVB）/Fe3O4） with strong magnetic domains and unique surface functionalities were prepared using a solvothermal process.The P（MMA-AA-DVB） nanoparticles were prepared via soapfree emulsion polymerization and used as a precursor for preparing Janus nanoparticles.The morphology and magnetic properties of the magnetic Janus nanoparticles formed were characterized using a laser particle size analyzer,transmission electron microscopy,Fourier transform infrared spectroscopy,vibrating sample magnetometry,and thermogravimetric analysis.The synthesized P（MMA-AA-DVB）/Fe3O4 magnetic Janus nanoparticles were characterized by a Janus structure and possessed a stable asymmetric morphology after being dually functionalized.The particle size,magnetic content,and magnetic domain of the P（MMA-AA-DVB）/Fe3O4 magnetic Janus nanoparticles were 200 nm,40%,and 25 emu/g,respectively.The formation mechanism of the Janus nanoparticles was also investigated,and the results revealed that the reduction of Fe3＋ ions and growth of Fe3O4 took place on the surface of the P（MMA-AA-DVB） polymeric precursor particles.The size of the Janus particles could be controlled by narrowing the size distribution of the P（MMA-AA-DVB） precursor nanoparticles.     

Ylide stabilized carbenes: a computational study

High‐level Density Functional Theory calculations, coupled with appropriate isodesmic reaction, are employed to investigate the effects of α‐carbon, ammonium, phosphorus, and sulfur ylides, cyclization, and unsaturation on the stability, multiplicity, and reactivity of novel singlet (S) and triplet (T) carbenes. Among them the highly π‐donating α‐ammonium ylide is found to exert the highest stabilizing effect on the carbenic center. α‐Ammonium ylides resist dimerization and hydrogenation. They show wider singlet–triplet energy gap (ΔΕ_S–T), broader band gap (ΔΕ_HOMO–LUMO), and higher nucleophilicity compared to the reported stable N‐heterocyclic carbenes. Aromatic cyclic unsaturated ammonium, phosphorus, and sulfur ylide carbenes appear more stable than their saturated cyclic analogs which are in turn more viable than their acyclic counterparts. Copyright © 2014 John Wiley & Sons, Ltd.     

Isomeric yield ratios of 87m,gY from different nuclear reactions

We investigate the parity-violating nucleon-nucleon potential as obtained in chiral effective field theory. By using resonance saturation we compare the chiral potential to the more traditional one-meson-exchange potential. In particular, we show how parameters appearing in the different approaches can be compared with each other and demonstrate that analyses of parity violation in proton-proton scattering within the different approaches are in good agreement. In the second part of this work, we extend the parity-violating potential to next-to-next-to-leading order. We show that generally it includes both one-pion- and two-pion-exchange corrections, but the former play no significant role. The two-pion-exchange corrections depend on five new low-energy constants which only become important if the leading-order weak pion-nucleon constant h _π turns out to be very small.     

2,2,9,9‐Tetramethylcyclonona‐3,5,7‐trienylidene vs. its heterocyclic analogues: A quest for stable carbenes at DFT

Replacement of α‐methylenes with BH, AlH, CMe₂, SiH₂, NH, NMe, N^tButyl, NPh, PH, O, and S in non‐planar cyclonona‐3,5,7‐trienylidene (CH₂) alters its status from an unstable transition state to rather stable minima, at B3LYP/6‐311++G**//B3LYP/6‐31 + G* levels of theory. All species appear with singlet closed shell (S_cs) global minima, except for SiH₂ and CH₂ which exhibit triplet electronic ground states. The order of stability based on singlet–triplet energy gap (ΔE_s–t / kcalmol^?1) is: CMe₂ (45.8) > NH (35.8) > NMe (32.3) > O (31.5) > N^tButyl (27.7) ≥ NPh (27.5) ≥ BH (27.4) > S (21.9) > PH (17.0) > CH₂ (?4.4) > SiH₂ (?12.5). In contrast to many reports on N‐heterocyclic carbenes, here alkyl groups appear to exert a higher stabilizing effect than heteroatoms, making CMe₂ the most stable. In addition bulky NMe, N^tButyl, and NPh appear more nucleophilic than their synthesized imidazol‐2‐ylidene congeners. Excluding SiH₂, isodesmic reactions reveal that all substituents stabilize singlet state considerably more than the corresponding triplet. Finally, this work is hoped to pave the path for future matrix isolations and IR studies of these rather stable cyclic non‐planar carbenes. Copyright © 2013 John Wiley & Sons, Ltd.     

Classification of Static Spherically Symmetric Spacetimes by Noether Symmetries

Noether symmetries of some of the well known spherically symmetric static solutions of the Einstein’s field equations are classified. The resulting Noether symmetries in each case are compared with conservation laws given by Killing vectors and collineations of the Ricci and Riemann tensors for corresponding solutions.     

A robust and recyclable ruthenium catalyst immobilised on polyethylene glycol

A highly robust and recyclable Hoveyda-Grubbs’ second generation ruthenium type catalyst immobilised on polyethylene glycol is conveniently prepared from Grubbs’ second generation catalyst. The catalyst performs ring-closing metathesis of various di-and tri-substituted olefins efficiently in dichloromethane in air.     

Effect of phosphate complexation on Cd2+ sorption by manganese dioxide (beta-MnO2)

Sorption of metal ions on oxide/hydroxide surfaces mediates the fate and transport of these ions in many natural systems. These metallic ions often exist in bulk in the aqueous phase as complexes with inorganic and organic ligands. In the present study, we investigated the sorption properties of manganese dioxide in the presence of phosphate which is thought to be one of the most important complex forming species. The surface area, point of zero charge and structural morphology of the solid manganese dioxide were determined. Cd(2+) sorption studies were carried out on manganese dioxide as a function of pH, temperature and phosphate concentration. Cd(2+) sorption increased with increasing pH, temperature and phosphate concentration. It was found that phosphate formed both outer and inner sphere complexes via metal and ligand-like adsorption. The Langmuir equation was applied to describe the data and from the constants of this equation different thermodynamic parameters such as DeltaH(0), DeltaS(0) and DeltaG(0) were evaluated.     

Synthesis and characterization of diverse coordination polymers. Linear and zigzag chains involving their structural transformation via intermolecular hydrogen-bonded, interpenetrating ladders polycatenane, and noninterpenetrating square grid from long, rigid N,N'-bidentate ligands: 1,4-bis[(x-pyridyl)ethynyl]benzene (x = 3 and 4)

The long, rigid ligands 1,4-bis[(3-pyridyl)ethynyl]benzene (L1) and 1,4-bis[(4-pyridyl)ethynyl]benzene (L2) were used in the synthesis of 10 new organic-inorganic coordination frameworks, each of them adopting different structural motifs. Synthesis, single-crystal X-ray structure determination, and spectroscopic and thermogravimetric analyses are presented. The reactions between M(NO3)2 x xH2O; M = Cd(II), Cu(II), and Co(II); x = 3-6 and Cu(hfac)2 x H2O [hfac = bis(hexafluoroacetylacetonato)] with L1 afforded the following one-dimensional zigzag chain structures: [Cd(C20H12N2)0.5(NO3)(CH3OH)]n (1, monoclinic, C2/c; a = 7.586(1) A, b = 23.222(1) A, c = 13.572(1) A, beta = 92.824(1), Z = 4); [{Cu(C20H12N2)(NO3)2(CH3OH)} x CH3OH]n (2, orthorhombic, P2(1)2(1)2(1); a = 8.589(1) A, b = 15.766(1) A, c = 17.501(1) A, Z = 4); [Co(C20H12N2)2(NO3)2(H2O)2] (5, triclinic, P1; a = 7.493(1) A, b = 8.948(1) A, c = 14.854(1) A, alpha = 100.427(1), beta = 97.324(1), gamma = 110.901(1), Z = 1); [Cu(C20H12N2)(hfac)2]n (4, monoclinic, C2/c, a = 18.828(1) A, b = 14.671(1) A, c = 13.427(1) A, beta = 90.447(1) degrees, Z = 4). Moreover, the minority phase compound formed from Cu(NO3)2 x 3H2O and L1 yielded a metallocyclic chain structure, [Cu(C20H12N2)(NO3)]n (3, triclinic, P; a = 8.728(1) A, b = 10.018(1) A, c = 11.893(1) A, alpha = 109.991(1), beta = 97.109(1), gamma = 115.542(1), Z = 1). In addition to the dinuclear coordination complex 5, all other polymeric structures (1-4) from L1 are composed of interpenetrating 2D and 3D cross-linked zigzag chains via hydrogen-bonding interactions. The reactions between M(NO3)2 x xH2O; M = Cd(II), Cu(II), and Co(II); x = 3-6 and Cu(hfac)2 x H2O [hfac = bis(hexafluoroacetylacetonato)] and L2 were dependent on the nature of the metal center and resulted in the formation of four different interpenetrating and noninterpenetrating compounds (6-10): [Co(C20H12N2)1.5(NO3)2]n (6, triclinic, P; a = 14.172(1) A, b = 15.795(1) A, c = 18.072(1) A, alpha = 115.380(1), beta = 101.319(1), gamma = 93.427(2), Z = 4), which consists of T-shaped building blocks assembled into three-dimensional interpenetrating polycatenated ladders; [Cd(C20H12N2)2(NO3)2]n (7, monoclinic, I2/a; a = 11.371(1) A, b = 20.311(2) A, c = 15.240(2) A, beta = 100.201(2) degrees, Z = 4), which adopts a two-dimensional noninterpenetrating square-grid motif; [Cu(C20H12N2)(hfac)2]n (8, monoclinic, I2/a; a = 11.371(1) A, b = 20.311(2) A, c = 15.240(2) A, beta = 100.201(2) degrees, Z = 4), composed of three sets of distinct one-dimensional linear chains; [Cu(C20H12N2)(EtOH)(NO3)2] [Cu(C20H12N2)1.5(NO3)2] x 2EtOH (9, triclinic, P; a = 12.248(2) A, b = 13.711(3) A, c = 18.257(4) A, alpha = 108.078(4) degrees, beta = 97.890(4) degrees, gamma = 103.139(5) degrees, Z = 2) and [Cu(C20H12N2)(MeOH)(NO3)2] [Cu(C20H12N2)1.5(NO3)2] x 2MeOH (10, triclinic, P; a = 12.136(1) A, b = 13.738(2) A, c = 17.563(3) A, alpha = 107.663(3) degrees, beta = 94.805(4) degrees, gamma = 104.021(4) degrees, Z = 2). Both 9 and 10 stack into infinite interpenetrating ladders through bundles of infinite chains and are described in our preliminary communication.     

Electron beam crosslinking of poly(ethylene-co-vinyl acetate)/clay nanocomposites

Effect of electron beam irradiation on the thermal and mechanical properties of poly(ethylene-co-vinyl acetate) (EVA)/clay nanocomposites prepared by melt blending method has been investigated. The hot set test results show that elongation at high temperature under static load decreased with the increase of irradiation dose. The tensile modulus increased continuously with increasing dose. While the tensile strength increased up to 100 kGy, it decreased with further increase in dose. The elongation at break decreased continuously with increasing dose. Thermogravimetric analysis showed that thermal stability of the EVA/clay nanocomposites improved with increasing dose. The improvement in the mechanical and thermal properties is attributed to the formation of radiation-induced crosslinking as evidenced by the gel content results.