Levers for Thermoelectric Properties in Titania-Based Ceramics

While the beneficial impact of nanostructural engineering on thermoelectric performance has been demonstrated for many semiconducting materials (SiGe, skutterudites, PbTe₂, etc.), no significant advantages have been reported for oxide nanomaterials. In this study, titania is used as a model material to compare the impact of grain size, doping and substitution, second-phase nanodispersion, and crystallographic defects on the electronic and thermal properties. It is shown that the lattice thermal conductivity can be most efficiently reduced by high densities of crystallographic planar defects in the Magnéli phases, while modification of grain size or introduction of second phases on length scales of 20?nm to 100?nm introduces only minor improvement. For the electronic properties, donor dopants such as niobium provide improvement of the power factor, but are not able to compete with the enhanced carrier concentration that is reached through oxygen vacancy introduction.     

Recent trends in ultra‐fast HPLC: New generation superficially porous silica columns

New generation columns, i.e. packed with superficially porous silica particles are available as trade names with following manufacturers: Halo, Ascentis Express, Proshell 120, Kinetex, Accucore, Sunshell, and Nucleoshell. These provide ultra‐fast HPLC separations for a variety of compounds with moderate sample loading capacity and low back pressure. Chemistries of these columns are C₈, C₁₈, RP‐Amide, hydrophilic interaction liquid chromatography, penta fluorophenyl (PFP), F5, and RP‐aqua. Normally, the silica gel particles are of 2.7 and 1.7 μm as total and inner solid core diameters, respectively, with 0.5‐μm‐thick of outer porous layer having 90 Å pore sizes and 150 m²/g surface area. This article describes these new generation columns with special emphasis on their textures and chemistries, separations, optimization, and comparison (inter and intra stationary phases). Besides, future perspectives have also been discussed.     

Electron spray ionization mass spectrometry and 2D 31P NMR for monitoring 18O/16O isotope exchange and turnover rates of metabolic oligophosphates

A new method was here developed for the determination of ¹⁸O-labeling ratios in metabolic oligophosphates, such as ATP, at different phosphoryl moieties (α-, β-, and γ-ATP) using sensitive and rapid electrospray ionization mass spectrometry (ESI-MS). The ESI-MS-based method for monitoring of ¹⁸O/¹⁶O exchange was validated with gas chromatography–mass spectrometry and 2D ³¹P NMR correlation spectroscopy, the current standard methods in labeling studies. Significant correlation was found between isotopomer selective 2D ³¹P NMR spectroscopy and isotopomer less selective ESI-MS method. Results demonstrate that ESI-MS provides a robust analytical platform for simultaneous determination of levels, ¹⁸O-labeling kinetics and turnover rates of α-, β-, and γ-phosphoryls in ATP molecule. Such method is advantageous for large scale dynamic phosphometabolomic profiling of metabolic networks and acquiring information on the status of probed cellular energetic system.     

Competing order parameters and a tricritical point with a difference

We propose a mean-field, phenomenological Ginzburg–Landau free energy functional with two competing order parameters for a two-component, spin-polarized Fermi gas. This free energy supports a tricritical point which is different from the conventional one and this change offers a correct understanding of the experimental phase diagram of imbalanced Fermi systems (Shin et al. (2008) [17]). The specific heat also happens to be different than in standard theory.     

Electronic structure and optical properties of ordered compounds potassium tantalate and potassium niobate and their disordered alloys

The electronic energy band structure, site and angular momentum decomposed density of states (DOS) of cubic perovskite oxides KNbO₃ and KTaO₃ have been obtained from a first principles density functional based full potential linearized augmented plane wave (FLAPW) method within a generalized gradient approximation (GGA). The total DOS in valence region is compared with the experimental photo-emission spectra (PES). The calculated DOS is in good agreement with the experimental energy spectra and the features in the spectra are interpreted by comparison with the projected density of states (PDOS). The valence band PES is mainly composed of Nb-4d/Ta-5d and O 2p states in KNbO₃ and KTaO₃, respectively. Using the PDOS and the band structure we have analyzed the inter-band contribution to the optical properties of these materials. The real and imaginary parts of the dielectric function have been calculated and compared with experimental data. They are found to be in a reasonable agreement. The role of band structure on the optical properties have been discussed.     

A new first principles approach to calculate phonon spectra of disordered alloys

The lattice dynamics in substitutional disordered alloys with constituents having large size differences is driven by strong disorder in masses, inter-atomic force constants and local environments. In this paper, a new first principles approach based on special quasirandom structures and an itinerant coherent potential approximation to compute the phonon spectra of such alloys is proposed and applied to Ni?.?Pt?.? alloy. The agreement between our results and experiments is found to be much better than for previous models of disorder due to an accurate treatment of the interplay of inter-atomic forces among various pairs of chemical species. This new formalism serves as a potential solution to the longstanding problem of a proper microscopic understanding of lattice dynamical behavior of disordered alloys.     

Facile decrease in the electron-transfer rate and surface roughness of gold by ultrasonic treatment

This communication reports that the electron-transfer rate and surface roughness of Au electrodes can be decreased simply by ultrasonic treatment. It seems that the hydroxyl radical generated during ultrasonic treatment plays an important role, as in the case of treatment with Fenton's reagent.     

A new approach of parallel data transmission through optical waveguide with SOA based frequency encoding/decoding technique

Semiconductor optical amplifier (SOA) is a well known non-linear device which can exhibit Tera Hertz switching speed of operation. SOA based switching, therefore, has wide application in fiber optic communication. Here in this communication the authors propose a new concept of frequency encoded parallel data transmission with SOA for optical communication. To achieve the transmission SOA is suggested for the generation of frequency encoded/decoded parallel data. It converts initially an intensity encoded optical data to frequency encoded one; whereas at the receiving end it again returns the intensity encoded data from frequency encoded one.     

Beam-target double-spin asymmetry A{LT} in charged pion production from deep inelastic scattering on a transversely polarized {3}He target at 1.4<Q{2}<2.7 GeV{2}

We report the first measurement of the double-spin asymmetry A{LT} for charged pion electroproduction in semi-inclusive deep-inelastic electron scattering on a transversely polarized {3}He target. The kinematics focused on the valence quark region, 0.16相似文献   

Reconstruction of Potentials as Well as Dynamics of Scalar Fields in DGP Braneworld Model

Here, we investigate the cosmological implications of Holographic Dark Energy (HDE) in the DGP braneworld model of the universe. Taking HDE in DGP braneworld, we investigate the model of non-interacting dark energy and derive its equation of state. Subsequently, we study the correspondence between k-essence, tachyon, dilaton, hessence and DBI-essence dark energy with the non-interacting HDE in a flat DGP braneworld and reconstruct the corresponding scalar potentials which describe the dynamics of the scalar fields. Also we study the correspondence between above mentioned scalar potentials and effective dark energy coming from DGP braneworld in the absence of HDE and in this situation, the potentials are reconstructed.