Analysis of taxol and major taxoids in Himalayan yew, Taxus wallichiana.

A reversed-phase column liquid chromatography method for the analysis of taxol, 10-deacetylbaccatin III, baccatin IV, 1-hydroxybaccatin I, 2-acetoxybrevifoliol, brevifoliol, 2'-deacetoxydecinnamoyltaxinine J and 2'-deacetoxytaxinine J in yew needles has been developed using a Nova-Pak Phenyl column and a binary gradient profile. The various aspects of analysis such as extraction efficiency, detection limits, reproducibility and peak purity were validated using UV-Vis as well as photodiode array detection.     

A dual-mode 700-Msamples/s 6-bit 200-Msamples/s 7-bit A/D converterin a 0.25-μm digital CMOS process

The design of a high-speed analog-to-digital (A/D) converter for hard disk drive read channels is described. The A/D converter uses a flash architecture with an interleaved sample and hold and interpolating comparator pre-amplifiers. It has 6 bits of resolution at full speed as well as a 7 bit mode operating at a lower speed. The 7 bit mode is useful for servo signal processing. This A/D converter has been implemented in a four-level metal single-poly 0.25 μm CMOS technology. The device operates at a speed of up to 700 MSamples/s in the 6 bit mode while maintaining a signal-to-noise-plus-distortion rate (SNDR) of greater than 35 dB at input frequencies of up to one-fourth the sampling rate. In the 7 bit mode, the device operates at up to 200 MSamples/s with a SNDR greater than 41 dB. It occupies an active area of 0.45 mm² and consumes less than 187 mW of power     

Synthesis and characterization of hyperbranched polyesters and polyurethane coatings

Polyurethane (PU) coatings are widely used for variety of high‐performance applications in today's coating technology. The emerging hyperbranched polymers having three‐dimensional morphology have opened a new avenue to tailor the architecture of PU coatings. The methodology followed here is based on preparation of PU coatings from hyperbranched polyester. Initially, different hyperbranched polyester polyols (HPs) were synthesized by varying the hydroxyl‐terminated precursors that is, pentaerythritol, trimethylol propane or glycerol and keeping the diacid that is, adipic acid quantity constant at various mole ratios of 1:0.6, 1:0.8, 1:0.9, and 1:1, respectively. The obtained HPs were characterized by nuclear magnetic resonance (NMR) spectroscopy, matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF)‐mass spectrometry, and Fourier transform‐infrared (FTIR) spectroscopy. The degree of branching and the quantity of different structural units present in the various HPs were calculated by integrating the quaternary carbon and carbonyl zone in ¹³C NMR spectroscopy. The extent of condensation in different HPs was also calculated from ¹H NMR spectra. Later on, NCO‐terminated PU prepolymers (NCO‐PU) were synthesized by reacting HPs with isophorone diisocyanate (IPDI) at NCO/OH ratio of 1.6:1. In the third step, the excess NCO content in the NCO‐capped PU prepolymers were reacted with atmospheric moisture and hyperbranched polyurethane (HPU) coatings were formed. The coating films were analyzed by FTIR and dynamic mechanical thermal analysis instruments. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2673–2688, 2007     

Transitional intermittency detection by neural network

 A neural network has been used to predict the flow intermittency from velocity signals in the transition zone in a boundary layer. Unlike many of the available intermittency detection methods requiring a proper threshold choice in order to distinguish between the turbulent and non-turbulent parts of a signal, a trained neural network does not involve any threshold decision. The intermittency prediction based on the neural network has been found to be very satisfactory. Received: 15 December 1997/Accepted: 30 December 1998     

Noise Stability of SIS Receivers

There is a strong interest in the submillimeter astronomy community to increase the IF bandwidth of SIS receivers in order to better facilitate broad spectral linewidth and continuum observations of extragalactic sources. However, with an increase in receiver IF bandwidth there is a decrease in the mixer stability. This in turn effects the integration efficiency and quality of the measurement. In order to better understand the noise mechanisms responsible for reducing the receiver stability, we employed a technique first described by D.W. Allan and later elaborated upon by Schieder et al. In this paper we address a variety of factors that degrade the noise stability of SIS receivers. The goal of this exercise is to make recommendations aimed at maximizing SIS receiver stability.     

Comparative vibrational spectroscopic study of 1,3-diacetylbenzene and 2,6-diacetylpyridine aided with density functional calculation

Comparative studies of the Raman and infrared spectra of 1,3-diacetylbenzene and 2,6-diacetylpyridine have been made. The spectra are interpreted with the aid of normal mode analysis following full structure optimization based on the density functional method using different levels of theories and various basis sets combination. The unscaled DFT LSDA frequencies approximate the experimental ones in much more uniform fashion than B3LYP or B3PW91 theories do. Nevertheless the use of overall scale factor leads to further significant improvement with less than 2% error. The scaled B3PW91 6-31G result is best, even though LSDA 6-311G frequencies are superior to the B3PW91 ones before scaling. While making complete assignments of vibrational wavenumbers on the basis of potential energy distribution, some interesting observation in the vibrational spectra of these two molecules have been noticed. Instances of Fermi resonances between fundamentals and some combination modes of vibration have also been ascertained. Following the quantum chemical calculation optimized geometries of the both molecules are predicted. The theoretical global minimum energy calculation helps to find the structural symmetries of the molecules.     

A model for spherical SH wave propagation in self-reinforced linearly elastic media

We study a spherical wave propagating in the radial and latitude directions and oscillating in the longitude direction in the case of fibre-reinforced linearly elastic material. A function system solving Euler's equation of motion in this case and depending on certain Bessel and associated Legendre functions is derived.     

Electro-optical characteristics and field-emission properties of reactive DC-sputtered p-CuAlO2+x thin films

P-type transparent-conducting CuAlO_2+x thin films were deposited on silicon and glass substrates by reactive direct current sputtering of a prefabricated metal powder target having 1:1 atomic ratio of Cu and Al in oxygen-diluted argon atmosphere. XRD spectrum confirmed the proper phase formation of the material. UV-Vis-NIR spectrophotometric measurements showed high transparency of the films in the visible region with direct and indirect band gap values around 3.90 and 1.89 eV, respectively. The room temperature conductivity of the film was of the order of 0.22 S cm⁻¹ and the activation energy was 0.25 eV. Seebeck coefficient at room temperature showed a value of +115 μV/K confirming the p-type nature of the film. Room temperature Hall effect measurement also indicated positive value of Hall coefficient with a carrier concentration 4.4×10¹⁷ cm⁻³. We have also observed the low macroscopic field emission, from the wide band gap p-CuAlO_2+x thin film deposited on glass substrate. The emission properties have been studied for different anode-sample spacing. The threshold field was found to be as low as around 0.5–1.1 V/μm. This low threshold is attributed primarily to the internal nanostructure of the thin film, which causes considerable geometrical field enhancement inside the film as well as at the film/vacuum interface.     

Modified Holographic Ricci Dark Energy in Chameleon Brans–Dicke Cosmology and Its Thermodynamic Consequence

The objective of this paper is to discuss the Chameleon Brans–Dicke gravity with non-minimally matter coupling of scalar field. We take modified Holographic Ricci dark energy model in this gravity with its energy density in interaction with energy density of cold dark matter. We assume power-law ansatz for scale factor and scalar field to discuss potential as well as coupling functions in the evolving universe. These reconstructed functions are plotted versus scalar field and time for different values of power component of scale factor n. We observe that potential and coupling functions represent increasing behavior, in particular, consistent results for a specific value of n. Finally, we have examined validity of the generalized second law of thermodynamics and we have observed its validity for all values of n.