Determination of alkaloids and phenolic compounds in black tea processed by two different methods in different plucking seasons

The effects of two different rolling methods and three tea plucking seasons on alkaloids and phenolics, mainly flavan‐3‐ols and theaflavins, in black tea were studied using an improved high‐performance liquid chromatographic method. Better separation of all tea compounds analyzed—the most important factor for their identification and quantitation—was achieved only with long elution gradients, which overcame the limitations of previously reported methods. Precision of the assay method was very high since intra‐day and inter‐day variations were within 0.76% and 1.66%, respectively. All analytes exhibited good linearity over the range evaluated with a correlation coefficient of 0.9987–1.000. Among the four solvents evaluated, 80% methanol was the most solvent for extracting individual tea compounds. The extraction method applied exhibited good repeatability (CV: 0.39–3.29%). The content of tea compounds analyzed varied with processing method and plucking season. Teas processed using the Cay‐Kur method contained higher levels of identified phenolic compounds than orthodox teas, but their alkaloid content was similar to each other. The most abundant alkaloid in teas was caffeine, ranging from 17.84 mg g^?1 dry weight in September plucking to 23.79 mg g^?1 dry weight in May plucking. With respect to phenolic compounds, theaflavins were at the highest level, 14.27 mg g^?1 dry weight, in Cay‐Kur tea processed in May. Copyright © 2007 Society of Chemical Industry     

Studies on stress concentration in tensile strips with large circular holes

The stress concentration factor K in a tensile strip with large circular hole is accurately determined using a high precision, plane stress, triangular element. The values of a/w where a is the diameter of the hole and w is the width of the strip, considered range from 0.99 to 0.999. The values of K obtained found to be very near to but greater than 2.0, when linear analysis is performed. Some discrepancies in the stress values at the outer free edge observed in the present linear analysis compared to the well documented experimental values prompted the authors to go for geometrically nonlinear analysis gave a K value which is a function of the load applied, less than 2.0 and for sufficiently large loads this value is very near but slightly greater than 1.0.     

Slow relaxation in spin glasses

The remarkable remanence effects observed in spin glasses are discussed. Some theoretical approaches and results are reviewed. Invited talk given at the Indian Academy of Sciences, Bangalore, Academy discussion meeting on phase transitions, June 21st, 1978.     

Real-space mapping of Fano interference in plasmonic metamolecules

An unprecedented control of the spectral response of plasmonic nanoantennas has recently been achieved by designing structures that exhibit Fano resonances. This new insight is paving the way for a variety of applications, such as biochemical sensing and surface-enhanced Raman spectroscopy. Here we use scattering-type near-field optical microscopy to map the spatial field distribution of Fano modes in infrared plasmonic systems. We observe in real space the interference of narrow (dark) and broad (bright) plasmonic resonances, yielding intensity and phase toggling between different portions of the plasmonic metamolecules when either their geometric sizes or the illumination wavelength is varied.     

Electrical Discharge Machining of Ti6Al4V in Hydroxyapatite Powder Mixed Dielectric Liquid

Hydroxyapatite (HA) powder suspension in deionized water was used as a dielectric liquid during electrical discharge machining (EDM) of Ti6Al4V work material. The machined surfaces were evaluated by scanning electron microscopy (SEM), energy dispersive spectroscopy, and optical microscopy. The powder particles in the dielectric liquid extensively migrated and formed an HA-rich layer on the work material surface under specific machining conditions. The result was attributed to the generation of secondary discharges due to altered discharge conditions. The particles divided the primary discharge channel into several secondary ones. When the main discharge channel subdivided into several sub-discharges with comparable energy densities, the particles in the discharge region got stuck among them. Then, they moved toward the melted cavities and penetrated the surface at the end of the discharge duration. The results suggest the process as a practical alternative for producing biocompatible interfaces or coatings for medical applications.     

Six Sigma experience as a stochastic process

This study empirically investigates the states of Six Sigma from a stochastic point of view. By the means of an advanced survey, 97 respondents are asked to rate the effect of Six Sigma on different performance categories, the cost of implementing Six Sigma, the level of enthusiasm and expectations from Six Sigma over 20 years. The autocorrelation and cross-correlation functions of these processes are analyzed to investigate the stages of Six Sigma. Consequently, new concepts namely steady state of Six Sigma and Six Sigma experience functions are introduced which shed light on the life cycle of Six Sigma within the companies.     

Distribution of aluminum in hot-dip galvanized coatings

Hot-dip galvanized panels of low-carbon (LC) and interstitial-free (IF) steels were produced in a laboratory simulator with an average coating mass of 60 g/m². Three pot aluminum levels were used, viz., 0.10 pct (by wt), 0.15 pct, and 0.18 pct. Metallography, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize coating and base steel microstructures. Wet chemical analysis and scanning transmission electron microscopy (STEM) were employed for compositional analyses. The aluminum content of the melt was found to be the predominant factor influencing the distribution of Al in the coating. At 0.18 pct melt aluminum, Al is partitioned between the aluminide inhibition layer at the coating-steel interface (∼80 pct) and the zinc overlay (∼20 pct). At 0.15 pct, it is partitioned among the aluminide layer (∼75 pct to 80 pct), zinc-iron (FeZn₁₃, ζ) intermetallic layer (∼5 pct to 15 pct), and the coating overlay (∼10 pct). At 0.10 pct, the aluminum is divided almost equally between the overlay and the zinc-iron intermetallics. At the two lower aluminum levels is the distribution marginally influenced by the steel grade. The ζ was found to not preferentially nucleate at the ferrite grain boundaries. When both the aluminide and ζ occurred at the coating-steel interface, the ζ particles appeared near discontinuities and thinner regions in the aluminide layer. The coating, relative to the melt, is enriched in aluminum because of its concentration in the aluminide and in the zinc-iron intermetallics. This enrichment increases with melt aluminum through an increase in the aluminum content of the aluminide layer and not of its thickness. In addition, a few tens-of-nanometers-thick layer enriched in aluminum, oxygen, and iron is observed on the outer surface of all coatings. The aluminum content in this layer also increases with an increase in the melt aluminum, but it contributes negligibly to the coatings’s content because of its extreme thinness.     

Effects of prolonged heating on antioxidant activity and colour of honey

The kinetics of changes in total antioxidant activity as assessed by DPPH radical and brown pigment formation (BPF) in honey heated at different temperatures (50, 60 and 70 °C) for up to 12 days were studied. Antioxidant activity and BPF increased with treatment temperature and time. BPF increased following zero-order kinetics with the activation energy value of 122 kJ/mol⁻¹ at 50–70 °C. However, antioxidant activity variation showed different trends according to heating temperatures following second-order, first-order and zero-order kinetics at 50, 60 and 70 °C, respectively. Heating of honey at 70 °C was found to be more effective than 50 and 60 °C for both two parameters. The results demonstrated that antioxidant activity was correlated with increased browning of the samples.