High‐temperature thermoelectric properties of Cu2In4Te7

Cu₂Ga₄Te₇ has recently been reported to have a relatively high thermoelectric (TE) figure of merit (ZT). However, the TE properties of Cu₂In₄Te₇, which has the same defect zinc‐blende structure as Cu₂Ga₄Te₇, have been hardly investigated. Here, we demonstrate that Cu₂In₄Te₇ has relatively high ZT values that are similar to those of Cu₂Ga₄Te₇. High‐density polycrystalline bulk samples of Cu₂In₄Te₇ were prepared and their electrical resistivity (?), Seebeck coefficient (S), and thermal conductivity (κ) were measured. Cu₂In₄Te₇ has a maximum ZT of 0.3 at 700 K, with ?, S, and κ values of 62.1 × 10^–5 Ω m, 394 μV K^–1, and 0.61 W m^–1 K^–1, respectively. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

DNS assessment of relation between mean reaction and scalar dissipation rates in the flamelet regime of premixed turbulent combustion

The linear relation between the mean rate of product creation and the mean scalar dissipation rate, derived in the seminal paper by K.N.C. Bray [‘The interaction between turbulence and combustion’, Proceedings of the Combustion Institute, Vol. 17 (1979), pp. 223–233], is the cornerstone for models of premixed turbulent combustion that deal with the dissipation rate in order to close the reaction rate. In the present work, this linear relation is straightforwardly validated by analysing data computed earlier in the 3D Direct Numerical Simulation (DNS) of three statistically stationary, 1D, planar turbulent flames associated with the flamelet regime of premixed combustion. Although the linear relation does not hold at the leading and trailing edges of the mean flame brush, such a result is expected within the framework of Bray's theory. However, the present DNS yields substantially larger (smaller) values of an input parameter c_m (or K₂ = 1/(2c_m ? 1)), involved by the studied linear relation, when compared to the commonly used value of c_m = 0.7 (or K₂ = 2.5). To gain further insight into the issue and into the eventual dependence of c_m on mixture composition, the DNS data are combined with the results of numerical simulations of stationary, 1D, planar laminar methane–air flames with complex chemistry, with the results being reported in terms of differently defined combustion progress variables c, i.e. the normalised temperature, density, or mole fraction of CH₄, O₂, CO₂ or H₂O. Such a study indicates the dependence of c_m both on the definition of c and on the equivalence ratio. Nevertheless, K₂ and c_m can be estimated by processing the results of simulations of counterpart laminar premixed flames. Similar conclusions were also drawn by skipping the DNS data, but invoking a presumed beta probability density function in order to evaluate c_m for the differently defined c's and various equivalence ratios.     

Modification of 3-substituents in (bacterio)chlorophyll derivatives to prepare 3-ethylated, methylated, and unsubstituted (nickel) pyropheophorbides and their optical properties

Methyl mesopyropheophorbide-a possessing an ethyl group at the 3-position, its 3(1)-demethyl analogue (3-methyl homologue), and its 3(1)-deethyl analogue (3-unsubstituted chlorin) were prepared by modifying naturally occurring (bacterio)chlorophylls bearing 3-vinyl, formyl, acetyl, and 1-hydroxyethyl groups. These synthetic 3-(un)substituted chlorophyll derivatives and their nickel complexes are probable intermediates during degradation of (bacterio)chlorophylls to chemically stable porphyrinoids. The optical properties (visible absorption, circular dichroism, and fluorescence emission) of the catabolic candidates in a solution were measured, and the substitution effect was investigated.     

Concentration- and time-dependent eccentric changes in circular dichroism of saccharide-linked ethynylpyridine oligomer with copper(II) ions

We studied the preparation and circular dichroism (CD) behavior of 2,6-pyridylene ethynylene octameric oligomer linked to a β-d-glucoside moiety with a C20-alkylene chain. The addition of Cu(OTf)(2) salt led to a remarkable enhancement of the first CD band of the oligomer, and an unexpected concentration and time dependency were observed. For example, when 1.0 × 10(-3) M of Cu(OTf)(2) was added to a 1,2-dichloroethane solution of the oligomer (5.0 × 10(-4) M, unit concentration), the CD band appeared in the positive at first and gradually inverted into the negative with time.     

Preparation of methacrylate-based anion-exchange monolithic microbore column for chromatographic separation of DNA fragments and oligonucleotides

In this paper, we report on the preparation of a microbore-scale (1 mm i.d.) anion-exchange monolithic column suitable not only for analytical purposes but also for potentially preparative applications. In order to meet the conflicting requirements of high permeability and good mechanical strength, the following two-step procedure was applied. First, an epoxy-containing monolith was synthesized by in situ copolymerization of glycidyl methacrylate (GMA) and ethylene dimethacrylate (EDMA) within the confines of a silicosteel tubing of 1.02 mm i.d. and 1/16″ o.d. in the presence of a ternary porogenic mixture of 1-propanol, 1,4-butanediol, and water. The monolithic matrix was subsequently converted into weak anion-exchanger via the ring-opening reaction of epoxy group with diethyl amine. The dynamic binding capacity was 21.4 mg mL⁻¹ for bovine serum albumin (BSA) at 10% breakthrough. The morphology and porous structure of this monolith were assessed by scanning electron microscope (SEM) and inverse size exclusion chromatography (ISEC). To optimize the separation efficiency, the effects of various chromatographic parameters upon the separation of DNA fragments were investigated. The resulting monolithic anion exchanger demonstrated good potential for the separation of both single- and double-stranded DNA molecules using a gradient elution with NaCl in Tris–HCl buffer (20 mM). Oligodeoxythymidylic acids (dT₁₂–dT₁₈) were successfully resolved at pH 8, while the fragments of 20 bp DNA ladder, 100 bp DNA ladder, and pBR322-HaeIII digest were efficiently separated at pH 9.     

The estimation of pressure on the surface of a flapping rigid plate by stereo PIV

The method to estimate the dynamic load of a flapping wing by the integration of pressure on the wing’s surface is discussed. The flapping wing was modeled as a plate flapping sinusoidally in hovering condition. The flow around the flapping plate was measured using stereo PIV on multiple measurement planes along the out-of-plane direction. The phase-averaged velocity field of each measurement plane was calculated so that three-dimensional analyses could be applied. The phase-averaged pressure field was obtained from the integration of the three-dimensional Poisson equation for pressure using the available information acquired from stereo PIV measurements. The pressure field is visualized on the measurement planes. In this study, the estimated load was the torque of the axis of rotation. This torque was compared with the result from strain gauge measurements. The torque estimation, although only on a partial surface of the plate, is within reasonable agreement with the measured torque. The integration of the Poisson equation based on stereo PIV measurements and estimations of the torque shows that an increase in the torque at the start of a flapping stroke is caused by the stagnation on the surface of the plate from the flow that is induced by the leading-edge vortices.     

Suppressing chromatic dispersion fluctuation for broadband optical parametric gain in highly nonlinear tellurite microstructured optical fibers

Optical Review - We investigate the effect of chromatic dispersion fluctuation on the performance of fiber optical parametric amplification (FOPA) using tellurite hybrid microstructured optical...