On the sequence of bond formation in loline alkaloid biosynthesis

Loline alkaloids are saturated pyrrolizidines with an oxygen bridge between carbon atoms C‐2 and C‐7 and an amino group on C‐1. They are bioprotective alkaloids produced by Epichloë and Neotyphodium species, mutualistic fungal endophytes that are symbiotic with cool‐season grasses. The sequence of bond formation in loline alkaloid biosynthesis was determined by synthesizing deuterated forms of potential intermediates and feeding them to cultures of the endophyte Neotyphodium uncinatum. These cultures incorporated deuterium from labeled N‐(3‐amino‐3‐carboxypropyl)proline and exo‐1‐aminopyrrolizidine into N‐formylloline. The first result suggests that N‐(3‐amino‐3‐carboxypropyl)proline is the first committed intermediate in loline biosynthesis, and the second result demonstrates that the pyrrolizidine rings form before the ether bridge. The incorporation of these two compounds into lolines and the lack of incorporation of several related compounds clarify the order of bond formation in loline alkaloid biosynthesis.     

Visualization and quantification of cathode channel flooding in PEM fuel cells

An understanding of two-phase flow mechanisms in micro-channels is critical to water management in fuel cell applications. In this work, an in situ visualization study of cathode flooding in an operating fuel cell is presented. Gas relative humidities of 26%, 42% and 66%, current densities of 0.2, 0.5 and 0.8 A cm⁻²and flow stoichiometries ranging from 2 to 4 are used in this study which represent typical operating conditions for automotive applications. Results are presented in the form of a flow map depicting various two-phase flow patterns. The impact of flooding is also presented in terms of measurable parameters like two-phase pressure drop coefficient and voltage loss. A new parameter called wetted area ratio is introduced to characterize channel flooding and liquid water coverage on a gas diffusion layer, and its repeatability with multiple tests is demonstrated.     

Resolution requirements for numerical simulations of transition

The resolution requirements for direct numerical simulations of transition to turbulence are investigated. A reliable resolution criterion is determined from the results of several detailed simulations of channel and boundary-layer transition.     

Printed monopole antenna with tunable band‐notched characteristic for use in mobile and ultra‐wide band applications

A tunable band‐notch printed monopole antenna is presented, exhibiting a wide impedance bandwidth from 1.5 to 5.5 GHz with good impedance matching (VSWR ≤ 2) and a tunable rejected frequency band from 2.38 to 3.87 GHz. The band‐notching is achieved by adding an inner chorded crescent element within a driven element of a similar shape. By varying the value of the varactor, which is placed between the inner and outer arcs, the desired variable rejected can be obtained. Simulated and measured results show wide impedance bandwidth with a tunable band notch, stable radiation patterns, and consistent nearly constant gain. The antenna is suitable for mobile and portable applications. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:403–412, 2015.     

Placement of wind turbines using genetic algorithms

A genetic algorithm approach is employed to obtain optimal placement of wind turbines for maximum production capacity while limiting the number of turbines installed and the acreage of land occupied by each wind farm. Specifically, three cases are considered—(a) unidirectional uniform wind, (b) uniform wind with variable direction, and (c) non-uniform wind with variable direction. In Case (a), 600 individuals are initially distributed over 20 subpopulations and evolve over 3000 generations. Case (b) has 600 individuals spread over 20 subpopulations initially and evolves for 3000 generations. Case (c) starts with 600 individuals spread over 20 subpopulations and evolves for 2500 generations. In addition to optimal configurations, results include fitness, total power output, efficiency of power output and number of turbines for each configuration. Disagreement with the results of an earlier study is observed and a possible explanation is provided.     

A Discontinuous Spectral Element Method for the Level Set Equation

Level set methodology is crucially pertinent to tracking moving singular surfaces or thin fronts with steep gradients in the numerical solutions of partial differential equations governing complex flow fields. This methodology must be consistent with the basic solution technique for the partial differential equations. To this end, a discontinuous spectral element approach is developed for level set advection and reinitialization as these methods are becoming increasingly popular for the solution of the fluid dynamic problems. Example computations are provided, which demonstrate the high order accuracy of the method.     

Parallel interference cancellation employing RAKE receiver with selection diversity for multiuser asynchronous DS/CDMA detectors in multipath Rayleigh fading channels

In this paper, we propose and analyse parallel CCI multistage cancellation by combining RAKE and selection diversity. In order to account for channel variations, adaptive implementation of decision thresholds at the RAKE output is suggested. It is shown to provide significant improvement over either hard or soft decision techniques especially in the near‐far situation. Investigation of the system robustness to imperfect channel parameter estimation is also presented. The communication channel is modelled as slowly varying Rayleigh fading discrete multipath channel. Copyright © 2002 John Wiley & Sons, Ltd.     

Vectored injection into compressible laminar and turbulent boundary layers

A fundamental analysis of two-dimensional supersonic boundary layer flow, both laminar and turbulent, is presented for a wide range of normal and nonnormal mass-transfer velocities. The analysis is based on the numerical solution of the Navier-Stokes equations, and results are compared with available theoretical and experimental data. Certain cases of practical importance, for which results are not presently available, are referred to.     

Synthesis of H2SO4 doped polyaniline film by potentiometric method

H₂SO₄ doped polyaniline films were synthesized in aqueous acidic media. The polyaniline film deposited on platinum electrode exhibits highest conductivity. The conductivity of each H₂SO₄ doped polyaniline sample was determined by the four-probe technique. The current-voltage curve exhibits that polyaniline sample has an ohmic behaviour. Experiments were conducted to establish the conductivity of the sample from room temperature to 110°C. The current was set constant. It has been observed that at lower current as well as higher current conductivity of the polyaniline sample is due to the electrons transferred to the conduction band. It is observed that the concentration ratio of 0.2:1 of aniline and H₂SO₄ for synthesis of PANI film on platinum electrode shows good conductivity.