Discrimination of Scrophularia spp. according to geographic origin with HPLC-DAD combined with multivariate analysis

Discrimination of Scrophularia spp. according to the geographic origin was tried in the present study using HPLC-DAD combined with multivariate analysis techniques. Five active constituents, angoroside C, harpagoside, 8-O-(E-p-methoxycinnamoyl)harpagide, E-cinnamic acid and E-p-methoxycinnamic acid, in forty four Scrophularia samples were simultaneously determined using HPLC-DAD. A principal component analysis of the content measurements clustered the samples according to their geographic origins, Andong, Uisung and China. A partial least squares-discrimination analysis was subsequently developed for the effective classification of the samples. This model showed comparatively good prediction ability for samples from Andong or China. The proposed method shows an efficient strategy for quality control of Scrophularia spp.     

Influence of amylopectin in dimethylsulfoxide on the improved performance of dye-sensitized solar cells

A highly viscous liquid electrolyte is prepared by adding a small amount of amylopectin into dimethylsulfoxide solvent. By using this viscous electrolyte, a dye-sensitized solar cell (DSSC) enhances the short-circuit photocurrent density and solar-to-electricity conversion efficiency by 22% and 8.4%, respectively, compared to those obtained with the reference cell without amylopectin. Furthermore, the stability of the DSSC is enormously improved by the addition of amylopectin. Polarization curves indicate that amylopectin is a reasonable corrosion inhibitor for silver metal in the electrolyte containing I₃^?/I^? couple.     

Oxygen permeation of BSCF membrane with varying thickness and surface coating

The oxygen permeation of Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) membranes was measured between 750 and 900 °C as a function of membrane thickness with or without La_0.7Sr_0.3CoO₃ (LSC) coating layer under controlled PO₂-gradient$P_{{\text{O}}_2}\text{-gradient}$ (Air/He). In order to see the relative effects of bulk diffusion and surface-exchange kinetics, the thickness of membrane was varied from 0.5 to 2.0 mm. The oxygen-permeation flux at 900 °C increased with LSC coating from that of uncoated membrane. For example, it increased ∼1.8 times for 1 mm-thick BSCF membrane. The characteristic membrane thickness (L_C) which divides the bulk-diffusion limit and surface-exchange kinetics limit was estimated using the modified Wagner equation. The L_C values were 0.55 and 1.10 mm at 900 °C for the coated and uncoated BSCF membranes, respectively, and decreased with decreasing temperature.     

Kinetic study of the reaction of dimethyl carbonate with trialkylamines

Quaternary ammonium compounds are produced worldwide in hundreds of millions of pound volume annually for a plethora of end‐uses from fabric‐care formulations to asphalt emulsifiers, typically from nongreen alkylating reagents. The kinetics of a reaction employing dimethyl carbonate (DMC) as a green alkylating agent was investigated using three trialkylamines (tributylamine, trihexylamine, and trioctylamine) at several temperatures. Arrhenius and Eyring analysis of the data showed that values of E_a (79 kJ/mol), ΔH^? (75 kJ/mol), and ΔS^? (220 J/(mol K)) were the same for all three amine reactants, consistent with a report that E_a is independent of alkyl chain length when the chain length is greater than three carbons. Although rates are significantly slower with DMC than with other alkylating reagents, the resulting methyl carbonate anion has advantages for clean anion metathesis, which is important for some applications, especially those involving ionic liquids. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: 221–225, 2010     

The Ricci tensor and structure Jacobi operator of real hypersurfaces in a complex projective space

Let M be a real hypersurface with almost contact metric structure ${(\phi, \xi, \eta, g)}$ in a complex projective space ${P_{n}\mathbb{C}}$ . A Real hypersurface M is said to be a Hopf hypersurface if ξ is principal. In this paper we investigate real hypersurfaces of ${P_{n}\mathbb{C}}$ whose Ricci tensors S satisfy ${\nabla_{\phi\nabla_{\xi}\xi}S = 0}$ . Under some further conditions we characterize Hopf hypersurfaces of ${P_{n}\mathbb{C}}$ .     

Permanence and stability of an Ivlev-type predator–prey system with impulsive control strategies

In this paper, we study a predator–prey system with an Ivlev-type functional response and impulsive control strategies containing a biological control (periodic impulsive immigration of the predator) and a chemical control (periodic pesticide spraying) with the same period, but not simultaneously. We find conditions for the local stability of the prey-free periodic solution by applying the Floquet theory of an impulsive differential equation and small amplitude perturbation techniques to the system. In addition, it is shown that the system is permanent under some conditions by using comparison results of impulsive differential inequalities. Moreover, we add a forcing term into the prey population’s intrinsic growth rate and find the conditions for the stability and for the permanence of this system.     

Evaluation of multiplexed hollow fiber flow field-flow fractionation for semi-preparative purposes

A multiplexed hollow fiber flow field-flow fractionation (MxHF5) is introduced to increase throughput of an HF5 channel system for semi-preparative purposes. HF5, a cylindrical version of the flow field-flow fractionation (FlFFF) operated with a porous, hollow fiber membrane by controlling the ratio of radial and axial flow rates, is capable of fractionating proteins, cells, and macromolecules by size. An advantage of HF5 is its inexpensive channel construction, allowing for disposability that can reduce run-to-run carryover problems. MxHF5 constructed in this study was made with six parallel HF5 modules connected to seven-port manifolds for the semi-preparative scale separation of proteins or biological particles. For the evaluation of MxHF5 separation efficiency, protein standards were utilized to test peak recoveries, band broadening, and throughput. The assembly showed the possibility of handling up to 50 μg of proteins without incurring overloading. The developed channel was applied to demonstrate size sorting of lipoproteins for the future study of size dependent lipidomic and proteomic analysis. The current trial offers a unique advantage of scaling up HF5 separation without using wide-bore, hollow fibers which sacrifice separation speed.     

Atom transfer radical polymerized PMMA/magnetite nanocomposites and their magnetorheology

We synthesized core/shell-typed magnetic nanoparticle composites using poly(methyl methacrylate) (PMMA) as a shell and magnetite nanoparticle (MN) as a core, in which the PMMA shell was prepared via atomic transfer radical polymerization (ATRP) method. Chemical structure and morphology of the synthesized MN–PMMA nanocomposite were investigated using FT-IR and TEM, respectively. Magnetorheological (MR) fluid was prepared by dispersing synthesized MN–PMMA in non-magnetic medium. Both shear stress and shear viscosity of the MR fluids as a function of shear rate were measured using a rotational rheometer with a magnetic field generator, exhibiting that a yield stress increased with an external magnetic field strength.