Multivariate statistical analysis of Raman images of a pharmaceutical tablet

This paper describes the application of principal component analysis (PCA) and independent component analysis (ICA) to identify the reference spectra of a pharmaceutical tablet's constituent compounds from Raman spectroscopic data. The analysis shows, first with a simulated data set and then with data collected from a pharmaceutical tablet, that both PCA and ICA are able to identify most of the features present in the reference spectra of the constituent compounds. However, the results suggest that the ICA method may be more appropriate when attempting to identify unknown reference spectra from a sample. The resulting PCA and ICA models are subsequently used to estimate the relative concentrations of the constituent compounds and to produce spatial distribution images of the analyzed tablet. These images provide a visual representation of the spatial distribution of the constituent compounds throughout the tablet. Images associated with the ICA scores are found to be more informative and not as affected by measurement noise as the PCA based score images. The paper concludes with a discussion of the future work that needs to be undertaken for ICA to gain wider acceptance in the applied spectroscopy community.     

Scalable peer-to-peer streaming for live entertainment content

We present a system for streaming live entertainment content over the Internet originating from a single source to a scalable number of consumers without resorting to centralized or provider-provisioned resources. The system creates a peer-to-peer overlay network, which attempts to optimize use of existing capacity to ensure quality of service, delivering low startup delay and lag in playout of the live content. There are three main aspects of our solution: first, a swarming mechanism that constructs an overlay topology for minimizing propagation delays from the source to end consumers; second, a distributed overlay anycast system that uses a location-based search algorithm for peers to quickly find the closest peers in a given stream; and finally, a novel incentive mechanism that encourages peers to donate capacity even when the user is not actively consuming content.     

The cracking of zirconia refractory tubes under hot shock

The evolution of stresses and strains in a zirconia-containing refractory tube subjected to a hot shock on the outer surface and convective cooling at the inner surface is analysed with the method of finite elements. To account for the temperature-induced phase transformation in the zirconia as well as the overall thermal expansion, a coefficient of total dilatation is introduced. The parameters that control the time-dependent stress and strain responses are identified by performing finite element calculations that span the range of variables relevant to steel making. The effects of tube thickness, hot shock duration, initial temperature, temperature dependence of elastic modulus, and transformation amplitude on stress and strain distributions are discussed, and heating and process strategies to eliminate surface cracking are suggested.     

Pink discoloration in canned pears I.—Role of tin in pigment formation

The major pigment in discoloured canned pears is identified as a purple-pink insoluble tin-anthocyanin complex from the effect of reagents for anthocyanins on the spectra of solid and syrup fractions of the product. This characterisation is supported by significant correlations between the intensity of reflected colour and the insoluble tin content of the solid fraction. It is suggested that formation of a tin complex is essential for the occurrence of pink discolorations in canned pears, and experiments are described designed to vary the intensity of discoloration by modifying the conditions controlling complex formation.     

Perturbations in hyperthermia temperature distributions associated with counter-current flow: numerical simulations and empirical verification

Two numerical techniques are used to calculate the effect of large vessel counter-current flow on hyperthermic temperature distributions. One is based on the Navier-Stokes equation for steady-state flow, and the second employs a convective-type boundary condition at the interface of the vessel walls. Steady-state temperature fields were calculated for two energy absorption rate distributions (ARD) in a cylindrical tissue model having two pairs of counter-current vessels (one pair with equal diameter vessels and another pair with unequal diameters). The first assumed a uniform ARD throughout cylinder; the second ARD was calculated for a tissue cylinder inside an existing four antenna Radiofrequency (RF) array. A tissue equivalent phantom was constructed to verify the numerical calculations. Temperatures induced with the RF array were measured using a noninvasive magnetic resonance imaging technique based on the chemical shift of water. Temperatures calculated using the two numerical techniques are in good agreement with the measured data. The results show: 1) the convective-type boundary condition technique reduces computation time by a factor of ten when compared to the fully conjugated method with little quantitative difference (approximately 0.3 degree C) in the numerical accuracy and 2) the use of noninvasive magnetic resonance imaging (thermal imaging) to quantitatively access the temperature perturbations near large vessels is feasible using the chemical shift technique.     

Microprocessor Architecture

This marks the second issue of Computer devoted to the Asilomar Workshop on Microprocessors. As with the first such issue (January 1976), no attempt has been made to cover the workshop in toto (a summary report appeared in the July 1976 Computer). Rather, the goal has been to spotlight a few of the more interesting developments and philosophies that were explored during the April 1976 workshop.     

Gas absorption accompanied by a large heat effect and volume change in the liquid phase: the system hydrogen chloride/ethylene glycol

Using a predicted value of the liquid phase diffusivity, the Chiang and Toor model is shown to give a good estimate of the measured rate of absorption of hydrogen chloride by ethylene glycol. A liquid surface temperature rise of 20°C is calculated. Unlike the previously tested ammonia-water system, temperature and volume effects do not compensate, and the absorption rate in this system is considerably higher than the isothermal prediction.     

Comparison of experimental and theoretical results for high frequency bubble propagation under T-bar tracks

Observational results for bubble motion at high frequencies in field-accessed devices have been reported in the literature. The predictions of a model for bubble propagation under T-bar tracks are compared with these results for a frequency of 100 kHz, initially at midrange values of drive and bias fields. This comparison is helpful in refining certain features of the model so as to bring its assumptions nearer to the physical situation. The matching between predicted and observed results for the variation of bubble position with drive field angle is now much improved. The refined model is then used to calculate results at other values of drive and bias fields for which experimental data is available. The agreement between theory and practice is shown to be quite close except when the bias field is high.     

Pink discoloration in canned pears II.—Measurement of potential and developed colour in pear samples

Procedures are described for the comparative assessment of the leucocyanidin content of pears, which is the principal factor determining their susceptibility to discoloration on processing, and for measuring the shade and depth of discoloration in the processed material. Application of these procedures to pears of different varieties, storage treatment, and processing treatments lead to useful conclusions relevant to the discoloration problem, and establish relations between the three parameters under certain defined processing conditions. The results emphasise the difficulties associated with the assessment of the susceptibility of large consignments of pears to discoloration under normal canning operations.     

Globin synthesis in normal human bone marrow

Globin synthesis has been studied by in vitro labelling with radioactive amino acids in 60 normal human bone-marrow samples. Under the conditions routinely used to fractionate alpha and beta chains by chromatography alpha/beta production ratios ranging from 0.5 to 1.0 were obtained, depending on the method of sample treatment. This variation was due entirely to the presence of non-haem proteins derived from white cells which chromagraphy with globin on CM-cellulose. Purification of globin on Sephadex G100 and fractionation of alpha and beta globin chains by a modified chromatographic system resulted in alpha/beta ratios of unity. The relevance of these findings to the study of marrows in which there is unbalanced globin chain production is discussed.