Synthesis of two designed hairpin peptides on a newly developed 1,6-hexanediol diacrylate (HDODA)-crosslinked polystyrene resin

Synthesis of two designed hairpin peptides on 1,6-hexanediol diacrylate crosslinked polystyrene support using the standard solid phase methodology is described. Both the peptides are obtained in high yield and purity. The new polymeric system is an ideal support for the synthesis of hairpin peptides, which is a very difficult task by the solid phase method.

Synthesis and thermal expansion hysteresis of Ca1-xSrxZr4P6O24

The low thermal expansion ceramic system, Ca1-xSrxZr4P6O24, for the compositions with x = 0, 0.25, 0.50, 0.75 and 1 was synthesized by solid-state reaction. The sintering characteristics were ascertained by bulk density measurements. The fracture surface microstructure examined by scanning electron microscopy showed the average grain size of 2.47 mum for all the compositions. The thermal expansion data for these ceramic systems over the temperature range 25-800degreesC is reported. The sinterability of various solid solutions and the hysteresis in dilatometric behaviour are shown to be related to the crystallographic thermal expansion anisotropy. A steady increase in the amount of porosity and critical grain size with increase in x is suggested to explain the observed decrease in the hysteresis.

Grain Floatation During Equiaxed Solidification of an Al-Cu Alloy in a Side-Cooled Cavity: Part II-Numerical Studies

In this article, a single-phase, one-domain macroscopic model is developed for studying binary alloy solidification with moving equiaxed solid phase, along with the associated transport phenomena. In this model, issues such as thermosolutal convection, motion of solid phase relative to liquid and viscosity variations of the solid-liquid mixture with solid fraction in the mobile zone are taken into account. Using the model, the associated transport phenomena during solidification of Al-Cu alloys in a rectangular cavity are predicted. The results for temperature variation, segregation patterns, and eutectic fraction distribution are compared with data from in-house experiments. The model predictions compare well with the experimental results. To highlight the influence of solid phase movement on convection and final macrosegregation, the results of the current model are also compared with those obtained from the conventional solidification model with stationary solid phase. By including the independent movement of the solid phase into the fluid transport model, better predictions of macrosegregation, microstructure, and even shrinkage locations were obtained. Mechanical property prediction models based on microstructure will benefit from the improved accuracy of this model.

Relaxor characteristics of layered Ba1-(3/2)xLaxBi2Nb2O9 ceramics

Barium lanthanum bismuth niobate Ba1−(3/2)xLaxBi2Nb2O9 (x = 0, 0.05, 0.1, and 0.15) powders have been prepared via solid state reaction route. The monophasic layered perovskite nature of each composition of these was confirmed by x-ray diffraction studies. A continuous decrease in the lattice parameter c of parent BaBi2Nb2O9 with increase in La3+ doping level was noteworthy. A decrease in dielectric constant maximum (εm), a shift in dielectric anomaly to lower temperatures (from 488 to 382 K), and an increase in the diffuseness (γ) (from 1.58 to 1.84) of dielectric anomaly were encountered on increasing x from 0 to 0.15. Vogel-Fulcher analyses showed a decrease in freezing temperature (Tf) (from 157 to 40 K) and an increase in the activation energy (0.53 to 1.12 eV) for frequency dispersion with increase in La3+ content. A downward shift in the peak position of the pyroelectric coefficient with increasing La3+ doping level was observed. The observed changes in the above physical properties were attributed to the increase in A-site chemical heterogeneity as a result of aliovalent La3+ doping on Ba2+ sites and associated A-site vacancy formation.

Structural, thermal and electrical characterization of NdLiMo2O8 electroceramics, using impedance spectroscopy

We report electrical property of a polycrystalline NdLiMo2O8 ceramics using complex impedance analysis. The material shows temperature dependent electrical relaxation phenomena. The d.c. conductivity shows typical Arrhenius behavior, when observed as a function of temperature. The a.c. conductivity is found to obey Jonscher's universal power law. The material was prepared in powder form by a standard solid-state reaction technique. Material formation and crystallinity have been confirmed by X-ray diffraction studies. Impedance measurements have been performed over a range of temperatures and frequencies. The results have been analyzed in the complex plane formalism and suitable equivalent circuits have been proposed in different regions. The role of bulk and grain boundary effect in the overall electrical conduction process is discussed with proper justification. (C) 2011 Elsevier Ltd. All rights reserved.

Sensitive Liquid Chromatography-Tandem Mass Spectrometry Method for the Determination of Olanzapine in Human Urine

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS-MS) method was developed to determine olanzapine (OLZ) in human urine. After solid-phase extraction with SPE cartridge, the urine sample was analysed on a C-18 column (Symmetry 3.5 mu m, 50 x 4.6 mm i.d) interfaced with a triple quadrupole tandem mass spectrometer. Positive electrospray ionization was employed as the ionization source. The mobile phase consisted of ammonium acetate (pH 7.8)-acetonitrile (10:90, v/v). The method was linear over a concentration range of 1-100 ngml(-1). The lower limit of quantitation was 1 ngml(-1). The intra-day and inter-day relative standard deviation across three validation runs over the entire concentration range was < 11.5 %. The accuracy determined at three concentrations (8.0, 50.0 and 85.0 ngml(-1) OLZ) was within +/- 1.21 % in terms of relative errors.

Scaling Analysis of Solidification of Liquid Aluminum Alloy Flowing on Cooling Slope

Among all methods of metal alloy slurry preparation, the cooling slope method is the simplest in terms of design and process control. The method involves pouring of the melt from top, down an oblique and channel shaped plate cooled from bottom by counter flowing water. The melt, while flowing down, partially solidifies and forms columnar dendrites on plate wall. These dendrites are broken into equiaxed grains and are washed away with melt. The melt, together with the equiaxed grains, forms semisolid slurry collected at the slope exit and cast into billets having non-dendritic microstructure. The final microstructure depends on several process parameters such as slope angle, slope length, pouring superheat, and cooling rate. The present work involves scaling analysis of conservation equations of momentum, energy and species for the melt flow down a cooling slope. The main purpose of the scaling analysis is to obtain a physical insight into the role and relative importance of each parameter in influencing the final microstructure. For assessing the scaling analysis, the trends predicted by scaling are compared against corresponding numerical results using an enthalpy based solidification model with incorporation of solid phase movement.

Two-Dimensional Correlation Analysis of Temperature-Dependent FT-IR Spectra of Oleic Acid

In the present study, variable temperature FT-IR spectroscopic investigations were used to characterize the spectral changes in oleic acid during heating oleic acid in the temperature range from -30 degrees;C to 22 degrees C. In order to extract more information about the spectral variations taking place during the phase transition process, 2D correlation spectroscopy (2DCOS) was employed for the stretching (C?O) and rocking (CH2) band of oleic acid. However, the interpretation of these spectral variations in the FT-IR spectra is not straightforward, because the absorption bands are heavily overlapped and change due to two processes: recrystallization of the ?-phase and melting of the oleic acid. Furthermore, the solid phase transition from the ?- to the a-phase was also observed between -4 degrees C and -2 degrees C. Thus, for a more detailed 2DCOS analysis, we have split up the spectral data set in the subsets recorded between -30 degrees C to -16 degrees C, -16 degrees C to 10 degrees C, and 10 degrees C to 22 degrees C. In the corresponding synchronous and asynchronous 2D correlation plots, absorption bands that are characteristic of the crystalline and amorphous regions of oleic acid were separated.

Structural and relaxor characteristics of Ca0.18Sr0.226Ba0.594Nb2O6

Polycrystalline Ca0.18Sr0.226Ba0.594Nb2O6 (CSBN18) was synthesized via the solid-state reaction route. X-ray structural studies confirmed it belonged to the tetragonal tungsten bronze family. Rietveld refinement of the X-ray data has been carried out for CSBN18 where the atomic positions and site occupancy factors for A-sites have been determined. The dielectric properties of CSBN18 ceramic were studied as a function of temperature in the 100 Hz - 1 MHz frequency range. The dielectric relaxation followed the Vogel-Fulcher relation wherein E-a = 37.4 meV; T-f = 131.5 degrees C and omega(0) = 4.31 x 10(9) rad s(-1). A high pyroelectric coefficient of similar to 250 mu C m(-2).K was obtained around the transition temperature (similar to 150 degrees C). This is significantly higher than that reported for polycrystalline SrxBa1-xNb2O6 (SBN). However, the piezoelectric coefficient (d(33)) of the title composition was as low as 6 pC N-1.

Electron rich supramolecular polymers as fluorescent sensors for nitroaromatics

Three pi-electron rich fluorescent supramolecular polymers (1-3) have been synthesized incorporating 2-methyl-3-butyn-2-ol groups in reasonable yield by employing Sonagashira coupling. They were characterized by multinuclear NMR (H-1, C-13), ESI-MS and single crystal X-ray diffraction analyses 1 = 1( 2-methyl-3-butyn-2-ol) pyrene; 2 = 9,10-bis(2-methyl-3-butyn-2-ol) anthracene; 3 = 1,3,6,8-tetrakis(2methyl- 3-butyn-2-ol) pyrene]. Single crystal structures of 1-3 indicated that the incorporation of hydroxy (-OH) groups on the peripheral of the fluorophores helps them to self-associate into an infinite supramolecular polymeric network via intermolecular hydrogen bonding interactions between the adjacent discrete fluorophore units. All these compounds showed fluorescence characteristics in chloroform solution due to the extended pi-conjugation and were used as selective fluorescent sensors for the detection of electron deficient nitroaromatics. The changes in photophysical properties of fluorophores (1-3) upon complex formation with electron deficient nitroaromatic explosives were studied in chloroform solution by using fluorescence spectroscopy. All these fluorophores showed the largest quenching response with moderate selectivity for nitroaromatics over various other electron deficient/ rich aromatic compounds tested (Chart 1). Analysis of the fluorescence titration profile of 9,10-bis(2-methyl-3butyn- 2-ol) anthracene fluorophore (2) with 1,3,5-trinitrotoluene/ 2,4-dinitrotoluene provided evidence that this particular fluorophore detects nitroaromatics in the nanomolar range 2.0 ppb for TNT, 13.7 ppb for DNT]. Moreover, sharp visual color change was observed upon mixing nitroaromatic (DNT) with fluorophores (1-3) both in solution as well as in solid phase. Furthermore, the vapor-phase sensing study of thin film of fluorophores (1-3) showed efficient quenching responses for DNT and this sensing process is reproducible. Selective fluorescence quenching response including a sharp visual color change for nitroaromatics make these tested fluorophores (1-3) as potential sensors for nitroaromatic compounds with a detection limit of ppb level.

Synthesis, characterization, EPR and thermoluminescence properties of CaTiO3 nanophosphor

Calcium titanate (CaTiO3) nanophosphors were synthesized by three different routes namely solution combustion (SC), modified solid-state reaction (MSS) and solid-state (SS) methods. Rietveld refinement studies revealed the presence of an orthorhombic structure with traces of CaCO3. The crystallite sizes were found to be in the 43-45 nm range. TEM studies also confirm the nano size with well crystalline nature. EPR spectrum for SS method exhibits a broad resonance signal at g = 2.027 is attributed to TiO6](9-) center, whereas in MSS sample the resonance signals are attributed to surface electron and hole trapping sites. The TL behavior has been investigated for the first time using gamma-irradiation. TL glow peak at 169 degrees C were recorded in CaTiO3 prepared by SC, MSS and SS methods. The trapping parameters such as activation energy (E) and order of kinetics (b) were estimated using peak shape method and results are discussed in detail. (C) 2013 Elsevier Ltd. All rights reserved.

Nonlinear dielectric response of BaBi4Ti4O15 ceramics

Nonlinear dielectric response of BaBi4Ti4O15 ceramics synthesized via the conventional solid-state reaction route has been monitored over a wide range of electric field strengths (E-0 = 0.5 - 5 kV/cm). Dielectric permittivity was found to increase linearly within the range of applied field. Rayleigh relations were employed to interpret the nonlinear dielectric response and the contribution of irreversible domain wall motion to the macroscopic permittivity was separated. The values of room temperature Rayleigh dielectric coefficient (alpha) and relative initial permittivity (epsilon'(init)) were found to be 2.28 +/- 0.02 cm/kV and 146.10 +/- 0.07, respectively. A reasonable agreement between the simulated and measured polarization-electric field (P-E) hysteresis loops was observed at an applied electric field of 5 kV/cm.

Anisotropy induced crossover from weakly to strongly first order melting of two dimensional solids

Melting and freezing transitions in two dimensional (2D) systems are known to show highly unusual characteristics. Most of the earlier studies considered atomic systems: the melting of 2D molecular solids is still largely unexplored. In order to understand the role of anisotropy as well as multiple energy and length scales present in molecular systems, here we report computer simulation studies of melting of 2D molecular systems. We computed a limited portion of the solid-liquid phase diagram. We find that the interplay between the strength of isotropic and anisotropic interactions can give rise to rich phase diagram consisting of isotropic liquid and two crystalline phases-honeycomb and oblique. The nature of the transition depends on the relative strength of the anisotropic interaction and a strongly first order melting turns into a weakly first order transition on increasing the strength of the isotropic interaction. This crossover can be attributed to an increase in stiffness of the solid phase free energy minimum on increasing the strength of the anisotropic interaction. The defects involved in melting of molecular systems are quite different from those known for the atomic systems.

Free energy barriers for homogeneous crystal nucleation in a eutectic system of binary hard spheres

In this study, the free energy barriers for homogeneous crystal nucleation in a system that exhibits a eutectic point are computed using Monte Carlo simulations. The system studied is a binary hard sphere mixture with a diameter ratio of 0.85 between the smaller and larger hard spheres. The simulations of crystal nucleation are performed for the entire range of fluid compositions. The free energy barrier is found to be the highest near the eutectic point and is nearly five times that for the pure fluid, which slows down the nucleation rate by a factor of 10(-31). These free energy barriers are some of highest ever computed using simulations. For most of the conditions studied, the composition of the critical nucleus corresponds to either one of the two thermodynamically stable solid phases. However, near the eutectic point, the nucleation barrier is lowest for the formation of the metastable random hexagonal closed packed (rhcp) solid phase with composition lying in the two-phase region of the phase diagram. The fluid to solid phase transition is hypothesized to proceed via formation of a metastable rhcp phase followed by a phase separation into respective stable fcc solid phases.

Exploring the color of transition metal ions in irregular coordination geometries: new colored inorganic oxides based on the spiroffite structure, Zn2-xMxTe3O8 (M = Co, Ni, Cu)

We describe the synthesis, crystal structures, and optical absorption spectra of transition metal substituted spiroffite derivatives, Zn2-xMxTe3O8 (M-II = Co, Ni, Cu; 0 < x <= 1.0). The oxides are readily synthesized by solid state reaction of stoichiometric mixtures of the constituent binaries at 620 degrees C. Reitveld refinement of the crystal structures from powder X-ray diffraction (XRD) data shows that the Zn/MO6 octahedra are strongly distorted, as in the parent Zn2Te3O8 structure, consisting of five relatively short Zn/M-II-O bonds (1.898-2.236 angstrom) and one longer Zn/M-II-O bond (2.356-2.519 angstrom). We have interpreted the unique colors and the optical absorption/diffuse reflectance spectra of Zn2-xMxTe3O8 in the visible, in terms of the observed/irregular coordination geometry of the Zn/M-II-O chromophores. We could not however prepare the fully substituted M2Te3O8 (M-II = Co, Ni, Cu) by the direct solid state reaction method. Density Functional Theory (DFT) modeling of the electronic structure of both the parent and the transition metal substituted derivatives provides new insights into the bonding and the role of transition metals toward the origin of color in these materials. We believe that transition metal substituted spiroffites Zn2-xMxTe3O8 reported here suggest new directions for the development of colored inorganic materials/pigments featuring irregular/distorted oxygen coordination polyhedra around transition metal ions.