Intermodulation distortion of the single-mode laser-diode

A detailed study of laser-diode intermodulation distortion (IMD) using the Volterra model that was developed for the single-mode laser-diode with optoelectronic feedback is presented in this paper. The IMD is analyzed by analyzing the amplitudes of the output sinusoids of various frequencies resulting from an input which is the sum of two sinusoids. The sinusoids at all frequencies due to the first-, second-, and third-order Volterra operators were determined and are discussed in this paper. The ones with frequencies which are not used in practical applications are included since, even though they are not in the pass-band of the first-order operator, they still can possibly effect system performance.     

Origin of the 150-K anomaly in LaFeAsO: competing antiferromagnetic interactions, frustration, and a structural phase transition

From all-electron fixed-spin-moment calculations we show that ferromagnetic and checkerboard antiferromagnetic ordering in LaFeAsO are not stable and the stripe antiferromagnetic configuration with M(Fe)=0.48 microB is the only stable ground state. The main exchange interactions between Fe ions are large, antiferromagnetic, and frustrated. The magnetic stripe phase breaks the tetragonal symmetry, removes the frustration, and causes a structural distortion. These results successfully explain the magnetic and structural phase transitions in LaFeAsO recently observed by neutron scattering. The presence of competing strong antiferromagnetic exchange interactions suggests that magnetism and superconductivity in doped LaFeAsO may be strongly coupled, much like in the high-T(c) cuprates.     

Conduction mechanisms in TlSbSe2 chalcogenides

TlSbSe₂ samples used for electrical measurements were cleaved from larger crystals grown by using the Bridgman ‐ Stockbarger method. Electrical properties of the samples are investigated with a view of determining the dominant conduction mechanism. DC conduction studies reveal that Poole – Frenkel conduction is predominant. The DC conduction studies revealed the non‐ohmic type conduction. The activation energies are also calculated. It is seen that the activation energy decreases with increase of applied voltage. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Experimental and theoretical studies on some new pyrrol-2,3-diones formation

4-Benzoyl-5-phenyl-2,3-furandione ( 1 ) reacts with asymmetric disubstituted urea derivatives like 1,1-dimethylurea ( 2a ) and 1,1-diethylurea ( 2b ) by the elimination of a H₂O molecule to give the 4-benzoyl-1-(N,N-dialkylcarbamyl)-5-phenyl-2,3-pyrroldiones 3a and 3b . The structures of 3a,b were determined by the ¹³C NMR, ¹H NMR, IR spectroscopic data and elemental analyses. The electronic structures of the reactants, their transition states, intermediate states, and final products of the reactions were investigated on the basis of AM1 and ab initio (DFT) methods. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 15:9–14, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10204     

Buckling of an orthotropic graded coating with an embedded crack bonded to a homogeneous substrate

To simulate buckling of nonuniform coatings, we consider the problem of an embedded crack in a graded orthotropic coating bonded to a homogeneous substrate subjected to a compressive loading. The coating is graded in the thickness direction and the material gradient is orthogonal to the crack direction which is parallel with the free surface. The elastic properties of the material are assumed to vary continuously along the thickness direction. The principal directions of orthotropy are parallel and perpendicular to the crack orientation. The loading consists of a uniform compressive strain applied away from the crack region. The graded coating is modeled as a nonhomogeneous medium with an orthotropic stress–strain law. Using a nonlinear continuum theory and a suitable perturbation technique, the plane strain problem is reduced to an eigenvalue problem describing the onset of buckling. Using integral transforms, the resulting plane elasticity equations are converted analytically into singular integral equations which are solved numerically to yield the critical buckling strain. The Finite Element Method was additionally used to model the crack problem. The main objective of the paper is to study the influence of material nonhomogeneity on the buckling resistance of the graded layer for various crack positions, coating thicknesses and different orthotropic FGMs.     

Investigation of inhomogeneous barrier height of Au/Bi4Ti3O12/n-Si structure through Gaussian distribution of barrier height

Au/Bi₄Ti₃O₁₂/n-Si structure is fabricated in order to investigate its current-voltage (I-V) characteristics in a temperature range of 300 K-400 K. Obtained I-V data are evaluated by thermionic emission (TE) theory. Zero-bias barrier height (Φ_B0) and ideality factor (n) calculated from I-V characteristics, are found to be temperature-dependent such that Φ_B0 increases with temperature increasing, whereas n decreases. Obtained temperature dependence of Φ_B0 and linearity in Φ_B0 versus n plot, together with lower barrier height and Richardson constant values obtained from Richardson plot, indicate that the barrier height of the structure is inhomogeneous in nature. Therefore, I-V characteristics are explained on the basis of Gaussian distribution of barrier height.     

Novel coordination compounds: Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) cations with acesulfame/N,N-diethylnicotinamide ligands

Abstract

Five coordination complexes with Mn²⁺ (1), Co²⁺ (2), Ni²⁺ (3), Cu²⁺ (4), and Zn²⁺ (5) containing acesulfame (ace) and N,N-diethylnicotinamide (dena) ligands were synthesized and structural binding properties investigated. Four compounds (1, 2, 4, and 5) were examined with single crystal X-ray diffraction methods. The structures containing Mn(II), Co(II), and Zn(II) were iso-structural. Six-coordination of metal cations were completed with two moles dena and four aqua ligands. The dena ligands were coordinated via pyridine nitrogen as neutral-monodentate. Charge stabilities of the complexes are complemented by two moles monoanionic ace ligands, located outside of the coordination unit. In the Cu(II) complex, the coordination is completed by acidic nitrogen and carbonyl oxygen atoms of two ace ligands and pyridine nitrogen of two moles dena ligands. The coordination to Cu(II) for ace ligands was monoanionic-bidentate. All metal cations in the structure are distorted octahedral. Thermal decomposition of complexes begins with removal of the aqua molecules from the structures and is completed by combustion of organic ligands. The final decomposition products of all structures have been identified as corresponding metal oxides. Some biological applications (anti-fungal/anti-bacterial) were studied using 1–5.     

Free vibration/buckling analyses of noncylindrical initially compressed helical composite springs

This article presents the use of the stiffness matrix method based on the first-order shear deformation theory to predict the fundamental natural frequencies and buckling loads of noncylindrical unidirectional composite helical springs subjected to initial static axial force and moment. This theoretical study about such springs with circular/rectangular cross-sections and large pitch angles is performed for the first time in the literature. The validity of the present results is verified by the benchmark studies related with initially compressed isotropic cylindrical springs.     

Correction to: Effect of heating rate on structure,morphology and photocatalytic properties of TiO2 particles: thermal kinetic and thermodynamic studies

Journal of Sol-Gel Science and Technology -     

Synthesis of dual‐functional poly(6‐azidohexylmethacrylate) brushes by a RAFT agent carrying carboxylic acid end groups

Novel types of dual‐functional surface‐attached polymer brushes were developed by interface‐mediated reversible addition‐fragmentation chain transfer (RAFT) polymerization of 6‐azidohexylmethacrylate using the surface‐immobilized RAFT agent and the free initiator. The interface‐mediated RAFT polymerization produced silicon substrate coated with dual‐functional (azido groups from monomer and carboxylic acid groups from RAFT agent) poly(6‐azidohexylmethacrylate) [poly (AHMA)] with a grafting density as high as 0.59 chains/nm². Dual‐functional polymer brushes can represent an attractive chemical platform to deliberately introduce other molecular units at specific sites. The azido groups of the poly(AHMA) brushes can be modified with alkyl groups via click reaction, known for their DNA hybridization, while the carboxylic acid end groups can be reacted with amine groups via amide reaction, known for their antifouling properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 1696–1706