Inhomogeneous deformation of crystalline skeleton of syndiotactic polypropylene under uniaxial stretching

Structure changes of syndiotactic polypropylene (sPP) under uniaxial stretching are studied with the combination of micro-tensile tester and in situ wide angle X-ray diffraction (WAXD) measurement. Lamellae stacked “vertically” and “parallel” to the stretching direction (defined as “V” and “P” part) are separated on the basis of two-dimensional WAXD patterns. For all samples with different lamellar thickness, two critical points named as b ₁ and b ₂ were found in the stress–strain curves, while b ₁ and b ₂ points are the onsets of the rotation for the lamellae of “V” part and “P” part, respectively. The corresponding true stress and true strain for b ₂ point are bigger than that of b ₁ , demonstrating that for samples with initial isotropic lamellar orientation, inhomogeneous deformation of crystalline skeleton induced by uniaxial stretching is universal. And after b ₁ point, “stress-induced melting” always occurs simultaneously with lamellar slips. Furthermore, the relationship between lamellar thickness and the true stress for b ₁ and b ₂ point was also studied, illustrating a linear correlation between ln σ and 1/l (σ is the corresponding true stress, l is the lamellar thickness), consistent with Young’s model. However, the critical true strains for these two points did not change with the varying thickness.     

Sensor Network Localization,Euclidean Distance Matrix completions,and graph realization

We study Semidefinite Programming, SDP, relaxations for Sensor Network Localization, SNL, with anchors and with noisy distance information. The main point of the paper is to view SNL as a (nearest) Euclidean Distance Matrix, EDM, completion problem that does not distinguish between the anchors and the sensors. We show that there are advantages for using the well studied EDM model. In fact, the set of anchors simply corresponds to a given fixed clique for the graph of the EDM problem.     

Observation of curious spiral growth features in Tl doped Hg bearing high temperature superconducting tapes

Synthesis of Hg(Tl)Ba ₂ Ca ₂ Cu ₃ O _8+δ superconducting tapes have been accomplished by annealing the precursor tape, Ba ₂ Ca ₂ Cu ₃ O _y (fabricated by doctor blade tape casting technique) in an environment of Hg(Tl) vapour. Characterization of superconducting HTSC tape sample was carried out through XRD, TEM, SEM and R-T measurements. Surface morphological investigations of the as-synthesized Hg(Tl)Ba ₂ Ca ₂ Cu ₃ O _8+δ HTSC tapes by scanning electron microscope have shown the occurrence of curious growth characteristics resembling spiral like features. These growth spirals encompass nearly the whole grain suggesting that spiral growth led to the formation of small crystal like grains of superconducting material Hg(Tl)Ba ₂ Ca ₂ Cu ₂ O _8+δ .The likely mechanism for the generation of these screw dislocations has been elucidated in terms of incoherent coalescence of growth fronts formed from Hg(Tl):1223 and Hg(Tl):1234 nuclei.     

A new combustion route to γ-Fe2O3 synthesis

A new combustion route for the synthesis of γ-Fe ₂ O ₃ is reported by employing purified a-Fe ₂ O ₃ as a precursor in the present investigation. This synthesis which is similar to a self propagation combustion reaction, involves fewer steps, a shorter overall processing time, is a low energy reaction without the need of any explosives, and also the reaction is completed in a single step yielding magnetic iron oxide i.e. γ-Fe ₂ O ₃ .The as synthesized γ-Fe ₂ O ₃ is characterized employing thermal, XRD, SEM, magnetic hysteresis, and density measurements. The effect of ball-milling on magnetic properties is also presented.     

Rings, chains and planes: Variation ofT g with composition in chalcogenide glasses

We propose a microscopic, phenomenological model for the decrease in the viscosity observed at glass transition. Our model is primarily applicable to chalcogenide glasses. According to this model, the decrease in the viscosity at glass transition is mainly due to the breaking of the Van der Waals bonds in the chalcogenides. Using this model, we derive a relationship between the glass transition temperature,T _g ,and the molar volume V _m.The validity of this relation is checked using experimental data available in the literature for two binary systems (Ge-Se and As-S) and a pseudo-binary system (As ₄₀ Se _x Te _60-x .     

Combustion synthesis and photoluminescence study of silicate biomaterials

Silicate based bioceramics are promising candidates as biomaterials for tissue engineering. The combustion synthesis method provides control on the morphology and particle size of the synthesised material. This paper discusses the combustion synthesis of akermanite (Ca ₂ MgSi ₂ O ₇ and Sr ₂ MgSi ₂ O ₇ ), which has been shown to have good in vitro and in vivo bioactivities by earlier studies. Both Ca ₂ MgSi ₂ O ₇ and Sr ₂ MgSi ₂ O ₇ have akermanite structure. Ca ₂ MgSi ₂ O ₇ and Sr ₂ MgSi ₂ O ₇ were prepared using urea and ammonium nitrate. The combustion synthesis using urea and ammonium nitrate was found to be cost effective and efficient method of synthesis. The photoluminescence study of Ca ₂ MgSi ₂ O ₇ : Eu²⁺^{\boldsymbol{2+}} and Sr ₂ MgSi ₂ O ₇ : Eu²⁺^{\boldsymbol{2+}} shows host specific intense emission of Eu²⁺^{\boldsymbol{2+}}.     

Studying the effect of particle size on the antibacterial activity of some N-nicotinyl phosphoric triamides

Using ultrasonic top-to-down method, nanoparticles of two N-nicotinyl phosphoric triamides: C₅H₄NC(O)NHP(O)R, R?=?4-CH₃-NC₅H₁₀ (1), (CH₃)₃CNH₂ (2) were prepared for the first time and characterized by ³¹P, ¹³C, ¹H NMR, FTIR, scanning electron microscopy, energy dispersive X-ray. The average particle size of 1 and 2 were 60–70 and 40–50?nm, respectively, and the morphology was spherical for 1 and rod for 2. Solid state (powder) antibacterial effect of these compounds and two other similar reported ones, in their macro- and nanosizes, were evaluated with colony counting method on one Gram-positive (Staphylococcus aureus) and one Gram-negative (Escherichia coli) bacteria in Brain–Heart infusion culture medium. Results showed that all the macro- and nanosized compounds, except macrosized 1, were antibacterial and all nanoscaled ones had stronger antibacterial activity than their macroscaled analogues. The most effect of the particle size was observed for 1: by decreasing the particle sizes, the antibacterial activity state of 1 was changed from inactive (for macro) to potent (for nano).     

Improved Multiple Comparisons With a Control in Response Surface Analysis

Quadratic response surface methodology often focuses on finding the levels of some (coded) predictor variables x = (x ₁, x ₂,…, x _k) that optimize the expected value of a response variable y. Typically the experimenter starts from some best guess or “control” combination of the predictors (usually coded to x = 0) and performs an experiment varying them in a region around this center point. The question of interest addressed here is whether any x in the experimental region provides a long-run mean response E(y) preferable to that of the control, and if so, by what amount? This article approaches this question via simultaneous confidence intervals for δ(x) = E(y|x) = E(y|0) for all x within a specified distance of 0. A new method for two or more predictors is introduced that gives sharper intervals than the Scheffé method and also the Sa and Edwards adaptation of the Casella and Strawderman method. The new method does not require a rotatable design and allows for one-sided simultaneous bounds for δ(x). Approximate sample-size savings of the improved method over the Sa and Edwards adaptation of the Casella and Strawderman method ranged from 12%–45% for two-sided intervals and 19%–40% for one-sided intervals for designs with two or three predictors. Approximate sample-size savings of the improved method over the Scheffe method ranged from 14%–47% for two-sided intervals and 22%–62% for one-sided intervals.     

Longitudinal and transverse waves in anisotropic elastic materials

Summary It is shown that a necessary and sufficient condition for a longitudinal wave to propagate in the direction n in an anisotropic elastic material is that the elastic stiffness C ₁₁ (n) is a stationary value (maximum, minimum or saddle point) at n. Explicit expressions of all n and the corresponding elastic stiffness C ₁₁ (n) for which a longitudinal wave can propagate are presented for orthotropic, tetragonal, trigonal, hexagonal and cubic materials. As to longitudinal waves in triclinic and monoclinic materials, only few explicit expressions are possible. We also present necessary and sufficient conditions for a transverse wave to propagate in the direction n. As an illustration, explicit expressions of all n, the polarization vector a and the wave speed c for which a transverse wave can propagate in cubic and hexagonal materials are given. The search for n in hexagonal materials confirms the known fact that a transverse wave can propagate in any direction. A longitudinal wave is necessarily accompanied by two transverse waves. However, a transverse wave can propagate without being accompanied by a longitudinal wave.     

On the algebraic characterization of a Mueller matrix in polarization optics. II. Necessary and sufficient conditions for Jones-derived Mueller matrices

Abstract

We show that every Mueller matrix, that is a real 4 × 4 matrix M which transforms Stokes vectors into Stokes vectors, may be factored as M = L ₂ KL ₁ where L ₁ and L ₂ are orthochronous proper Lorentz matrices and K is a canonical Mueller matrix having only two different forms, namely a diagonal form for type-I Mueller matrices and a non-diagonal form (with only one non-zero off-diagonal element) for type-II Mueller matrices. Using the general forms of Mueller matrices so derived, we then obtain the necessary and sufficient conditions for a Mueller matrix M to be Jones derived. These conditions for Jones derivability, unlike the Cloude conditions which are expressed in terms of the eigenvalues of the Hermitian coherency matrix T associated with M, characterize a Jones-derived matrix M through the G eigenvalues and G eigenvectors of the real symmetric N matrix N = [Mtilde]GM associated with M. Appending the passivity conditions for a Mueller matrix onto these Jones-derivability conditions, we then arrive at an algebraic identification of the physically important class of passive Jones-derived Mueller matrices.     

Carbon-neutral energy cycles using alcohols

We demonstrated carbon-neutral (CN) energy circulation using glycolic acid (GC)/oxalic acid (OX) redox couple. Here, we report fundamental studies on both catalyst search for power generation process, i.e. GC oxidation, and elemental steps for fuel generation process, i.e. OX reduction, in CN cycle. The catalytic activity test on various transition metals revealed that Rh, Pd, Ir, and Pt have preferable features as a catalyst for electrochemical oxidation of GC. A carbon-supported Pt catalyst in alkaline conditions exhibited higher activity, durability, and product selectivity for electrooxidation of GC rather than those in acidic media. The kinetic study on OX reduction clearly indicated that OX reduction undergoes successive two-electron reductions to form GC. Furthermore, application of TiO₂ catalysts with large specific area for electrochemical reduction of OX facilitates the selective formation of GC.     

Stability and electronic properties of armchair boron nitride/carbon nanotubes

In this work are studied the electronic and structural properties of armchair boron nitride/carbon nanotubes using first principles calculations. The density functional within the generalized gradient approximation (HSEh1PBE-GGA) is used. For each composition, different bonding schemes for the construction of the hybrid systems were employed. Among them, structural stability with neutral charge was determined for the following compositions: T1: B₄₀N₃₅C₇₅H₂₀, T2: B₃₅N₄₀C₇₅H₂₀, T3: B₃₇N₃₈C₇₅H₂₀, T4 : B₃₇N₃₇C₇₆H₂₀, and T7: B₃₅N₃₅C₈₀H₂₀. All these hybrid nanotubes have high polarity; the T3, T4 and T7 are semiconductors: whereas T1 and T2 are conductor in character. The formers also have magnetic behavior. These properties together with a low-chemical potential suggest applications as nano-vehicle for drug delivery. These mixed nanotubes also have potential applications in the electronic devices based on the small work function.     

Synthesis and luminescence properties of Eu2+-activated Ca4Mg5(PO4)6 for blue-emitting phosphor

Ca ₄ Mg ₅ (PO ₄ ) ₆ :Eu²⁺^{\boldsymbol{2+}} blue-emitting phosphor was synthesized by the combustion-assisted synthesis method under reductive atmosphere. The products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and photoluminescence (PL) spectrum. XRD analysis confirmed the formation of Ca ₄ Mg ₅ (PO ₄ ) ₆ pure phase. Photoluminescence results showed that the phosphor can be excited efficiently by UV light range from 230–400 nm, and then exhibited bright blue light with peak wavelength at 431 nm. It is a very promising candidate as a blue-emitting phosphor for potential applications in display devices.     

Degradation of tobramycin in aqueous solution

Abstract

The kinetics of degradation of tobramycin (Ne-De-Ka) in aqueous solution was studied as a function of pH. Tobramycin hydrolyzes in acidic solution to yield kanosamine (Ka-OH) and nebramine (Ne-De-OH) with a pseudo first-order rate constant of 2.7 × 10^?6 s^?1 in 1 N HCl at 80°C. The activation energy for the acid catalyzed hydrolysis is 32 kcal mol^?1. In basic solution, the hydrolysis products are deoxystreptamine (De-OH), nebramine (Ne-De-OH) and deoxystreptamine-kanosaminide (HO-De-Ka). The pseudo first-order rate constant for the hydrolysis in 1 N KOH is 1 × 10^?8 s^?1 at 80°C. The activation energy for the base catalyzed hydrolysis is 15 kcal mol^?1. Tobramycin is very stable towards hydrolysis at neutral pH; however, it rapidly oxidizes giving several products including De-OH, Ne-De-OH, and HO-De-Ka. In pH 7 phosphate buffer (0.01 M), the t₉₀ value is 70 hr at 80°C.     

Aqueous slip casting of MgAl2O4 spinel powder

A stoichiometric MgAl ₂ O ₄ spinel (MAS) powder was synthesized by calcining a compacted mixture of a\boldsymbol{\alpha} -Al ₂ O ₃ and calcined caustic MgO at 1400°C for 1 h and was surface treated against hydrolysis using an ethanol solution of H ₃ PO ₄ and Al(H ₂ PO ₄ ) ₃ after fine grinding. Aqueous suspensions with 41–45 vol.% treated powder were prepared using tetra methyl ammonium hydroxide (TMAH) and an ammonium salt of polyacrylic acid (Duramax D-3005) as dispersing agents. These stable suspensions were consolidated in plaster moulds by slip casting (SC) route for the first time. For comparison purposes, the treated powder was also compacted by die-pressing technique after converting into freeze-dried granules and sintered along with slip cast samples at 1550–1650°C for 1–2 h. The MAS ceramics fabricated by slip casting and die-pressing exhibited comparable properties.     

Preparation of Sm-Ru bimetallic alloy films on Ru(0001) surface by vapour-deposition and annealing

Sm-Ru intermetallic surface alloy films were prepared by vacuum deposition and annealing of rare earth Sm on single crystal Ru(0001) surface. The Ru 3 d and Sm 3 d core level spectra clearly show the formation of surface alloy layers. XPS measurements on surface alloy film revealed an induced peak in the Ru 3 d region at lower binding energy by 1 eV compared to the bulk Ru (elemental) suggesting an electronic effect of alloying and Sm-Ru bond formation. The Sm 3 d _5/2 photoemission peak of Sm film consists of strong features characteristic of Sm(II) with electron configuration 4 f ⁶ (5 d 6 s ) ² and Sm(III) with electron configuration 4 f ⁵ (5 d 6 s ) ³ .It is observed that the Sm(II) feature decreases in intensity upon alloy formation with surface Ru atoms. Oxidation of these films with carbon monoxide indicates alloy breakdown due to the oxidation of Sm atoms selectively. Alloy oxidation also shows a clear shift of Sm 3 d _5/2 feature.     

Two novel propylenedioxythiophene-based copolymers with donor–acceptor structures for organic solar cell materials

Two novel conjugated copolymers consisting of alternating electron-rich propylenedioxythiophene and electron-deficient 2,3-diphenyltheno[3,4-b]pyrazine or 6,7-diphenyl[1,2,5]thiadiazole units have been synthesized through palladium catalyzed Sonogashira triple-bond coupling reaction. The structures and properties of the two copolymers, P ₁ , P ₂ , were characterized by FT-IR, NMR, UV–Vis absorbance (Abs), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), and cyclic voltammetry (CV). UV–Vis absorption spectra of the polymers show two absorption bands both in CHCl₃ solution and films. The absorption peak maxima of P ₁ , P ₂ are 600 nm, 766 nm in solution and 627 nm, 823 nm in films, respectively. Thermal gravimetric analysis demonstrates that the two polymers are stable below 300 °C. Cyclic voltammetry studies reveal that the band gaps of P ₁ , P ₂ are 1.62 eV and 1.50 eV, suggesting their potential for applications as organic solar cell materials.     

Eigenvalues of damped structures: Vectoriteration in the original space of DOF

The equations of motion in structural dynamics as well as the corresponding eigenvalue problem are governed by 3 matrices for mass, damping and stiffness of order n which equals the number of degrees of freedom. High-performance eigenvalue-solvers are developed for only pairs A, B of matrices. Nevertheless, to benefit from these solvers, the original eigenvalue problem (λ² M+λD+K)x=0 is transformed into a linear eigenvalue representation with only two hypermatrices of double order 2n. Consequently the total numerical effort depends on this order 2n. This paper presents a vectoriteration process which actually works in the original space of order n and which needs no special actions like simultaneous iteration if complex conjugate eigenvalues λ, λˉ with identical norm have to be calculated. The theoretical foundation of this process still goes back to the pair of hypermatrices.     

Dispersion corrections to the collective mode spectrum in axial and planar phases of superfluid He3

Using the path integration technique developed by Brusov and Popov earlier, we have calculated for the first time the dispersion corrections to the collective mode spectrum in A- and 2D- phases of superfluidHe ³ for arbitrary directions of the collective excitation momentumk, taking the damping of collective modes into account. In axial-phase clapping (cl) mode remains six fold degenerate fork l, while for other directions a three fold splitting takes place, which reaches a maximum fork l. The pairbreaking modes remain degenerate even taking the dispersion induced corrections into account. In the planar phase the degeneracy of clapping (cl) and quasi-Goldstone (qGd) modes depends on the direction of the collective mode momentumk with respect to the external magnetic fieldH: the mode degeneracy remains the same as in the case of zero momentumk fork H only, and for any other directions two fold splitting of these modes takes place. The dispersion induced splitting of collective modes could be observed (at least in the A-phase) in sound absorption experiments.