Thermal conductivity reduction and thermoelectric figure of merit increase by embedding nanoparticles in crystalline semiconductors

Atomic substitution in alloys can efficiently scatter phonons, thereby reducing the thermal conductivity in crystalline solids to the "alloy limit." Using In0.53Ga0.47As containing ErAs nanoparticles, we demonstrate thermal conductivity reduction by almost a factor of 2 below the alloy limit and a corresponding increase in the thermoelectric figure of merit by a factor of 2. A theoretical model suggests that while point defects in alloys efficiently scatter short-wavelength phonons, the ErAs nanoparticles provide an additional scattering mechanism for the mid-to-long-wavelength phonons.     

Eigenvalues of kinematical conservation laws (KCL) based 3-D weakly nonlinear ray theory (WNLRT)

System of kinematical conservation laws (KCL) govern evolution of a curve in a plane or a surface in space, even if the curve or the surface has singularities on it. In our recent publication [K.R. Arun, P. Prasad, 3-D kinematical conservation laws (KCL): evolution of a surface in R³-in particular propagation of a nonlinear wavefront, Wave Motion 46 (2009) 293-311] we have developed a mathematical theory to study the successive positions and geometry of a 3-D weakly nonlinear wavefront by adding an energy transport equation to KCL. The 7 × 7 system of equations of this KCL based 3-D weakly nonlinear ray theory (WNLRT) is quite complex and explicit expressions for its two nonzero eigenvalues could not be obtained before. In this short note, we use two different methods: (i) the equivalence of KCL and ray equations and (ii) the transformation of surface coordinates, to derive the same exact expressions for these eigenvalues. The explicit expressions for nonzero eigenvalues are important also for checking stability of any numerical scheme to solve 3-D WNLRT.     

Second order nondifferentiable multiobjective fractional programming under generalized univex functions

In this paper, a new class of second order $(d,\rho,\eta,\theta)$-type 1 univex function is introduced. The Wolfe type second order dual problem (SFD) of the nondifferentiable multiobjective fractional programming problem (MFP) is considered, where the objective and constraint functions involved are directionally differentiable. Also the duality results under second order$(d,\rho,\eta,\theta)$-type 1 univex functions are established.     

Ca<Superscript>+2</Superscript> Concentrations are Key Determinants of Ischemia–Reperfusion-Induced Apoptosis: Significance for the Molecular Mechanism of Bcl-2 Action

The mechanism of action of the anti-apoptotic oncogene Bcl-2 and Ca⁺² regulation in ischemia–reperfusion injury is still obscure. In this present study, we investigated mitochondrial Ca⁺² overloads and mechanism of action of Bcl-2. Eighteen Wistar rats were divided into sham-operated control group (I) (n = 6), ischemia and reperfusion group (II) (n = 6), and amlodipine-treated group (1 mg kg⁻¹ body weight/daily by oral route for 7 days before inducing ischemia–reperfusion maneuver) (III) (n = 6). Rats were subjected to 1 h of hepatic ischemia followed by 3-h reperfusion. Mitochondrial Ca²⁺ content was determined and damage was confirmed by transmission electron microscopy. Decrease of mitochondrial Ca⁺² level is related to reduction of apoptosis and cellular changes, viz. increased Bcl-2 expression followed by reduction in secondary endoplasmic reticulum, whereas ischemia/reperfusion group shows overloading Ca⁺² ions and decrease in Bcl-2 expression as compared to sham-operated rats. Thus, Bcl-2-dependent reduction of Ca⁺² is an important component of the anti-apoptotic program in ischemia–reperfusion injury.     

Discrete elastica

This paper develops a discrete approach to the design of planar curves that minimize cost functions dependent upon their shape. The curves designed by using this approach are piecewise linear with equal length segments and obey various types of endpoint constraints.     

A Range-Compaction Heuristic for Graph Coloring

This paper presents a novel heuristic for graph coloring that works on a range of colors and iteratively tries to make this range more compact. This range-compaction heuristic also has a pressure component and an annealing schedule for it. The value of this component is empirically quantified. This algorithm is evaluated on a wide range of DIMACS benchmark graphs, and found to be competitive with state-of-the-art algorithms in terms of solution quality and run time.     

Synthesis and characterization of calcium containing poly(urethane-ether)s

Calcium containing poly(urethane-ether)s (PUEs) were synthesized by the reaction of hexamethylene diisocyanate or toluylene 2,4-diisocyanate (HMDI or TDI) with a mixture of calcium salt of mono(hydroxybutyl)phthalate [Ca(HBP)₂] and polyethylene glycol (PEG₂₀₀ or PEG₄₀₀). A series of calcium containing PUEs having different composition were synthesized by taking the mole ratio of Ca(HBP)₂:PEG₂₀₀ or PEG₄₀₀:diisocyanate (HMDI or TDI) as 3:1:4, 2:2:4 and 1:3:4 to study the effect of calcium content on the properties of the copolymer. The structure of the polymers were confirmed by IR, ¹H-NMR, ¹³C-NMR, and solid state ¹³C-CP-MAS NMR. The polymers were soluble in dimethyl sulfoxide and dimethyl formamide. The initial decomposition temperature of the polymers decreases with increase in calcium content. The T_g value of PUEs increases with increase in calcium content and decreases with increase in soft segment content and length. A single T_g value is observed for the calcium containing PUEs based on PEG₂₀₀ shows the presence of homogeneous phase. However, two T_g values for the PUEs based on PEG₄₀₀ for various composition of Ca(HBP)₂, PEG₄₀₀ and diisocyanate (HMDI or TDI) shows the presence of heterogeneous phase. The viscosity of the calcium containing PUEs increases with increase in the soft segment content as well as its length and decreases with increase in calcium content. X-ray diffraction patterns of the polymers show that the HMDI based polymers are partially crystalline and TDI based polymers are amorphous in nature. The dynamic mechanical analysis of the calcium containing PUEs based on HMDI shows that at any given temperature modulus (g^′ and g^″) increases with increase in the ionic content in the polymers.     

Transition metal complexes of amidinourea and related ligands part III. Infrared spectra and thermal decomposition studies on metal complexes of O-alkyl-1-amidinoureas

Summary The i.r. spectral data on O-methyl-l-amidinourea hydrochloride,O-ethyl-1-amid inourea hydrochloride and the metal complexes [M = copper(H), nickel(II), palladium(II), zinc(II) and oxovanadium(IV)] ofO-methyl-l-amid inourea andO-ethyl-l-amidinourea are reported. The spectral results suggest that secondary amine nitrogens are the donor atoms inO-alkyl-1-amid inourea. The free ligands and the complexes exhibit a characteristic band at ca. 1100 cm^–1 due to the C-OR group. The i.r. and electronic spectral data on the hydrated and anhydrous uncharged metal complexes indicate that the hydrated uncharged metal complexes ofO-alkyl-l-amidinourea may be represented as [M(AAU)_n]] · xH₂0 and not as [M(AAUII)_n](OH)_n · xH₂O [where AAU = H₂NC(=NH)NC(=NH)OR and AAUH = H₂NC(=NH)NHC(=NH)OR, R = Me, Et]. The use of the term anhydrobase is confusing and suitable names for various metal complexes ofO-alkyl-l-amid inourea are suggested. The main decomposition stage in metal complexes ofO-ethyl-l-amidinourea occurs at lower temperatures than for the corresponding biguanide complexes indicating that the former are less stable than the latter.     

Conversion of colloidal aggregates into polymer networks on aging

After long-term aging, surfactant-mediated colloidal aggregates of sulfonated polyaniline (S-PANI) and poly(vinylidene fluoride) (PVF₂) converted into three-dimensional polymer networks, whereas colloidal crystals prepared from pure PVF₂ remained unaltered. A model, where the surfactant tails anchored from the colloidal particles interdigitate with time resulting in coalescence of the particles to form the network morphology, has been proposed. X-ray photoelectron spectroscopy (XPS) revealed higher relative abundances of carbon atoms on the surface of the polymer networks than those of the colloidal aggregates, which adequately supports the proposed model.