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.     

In vivo evaluation of magnetite nanoparticles for use as a tumor contrast agent in MRI

Magnetite nanoparticles, coated by three different artificial polypeptides, were conjugated to an antibody specific to the carcinoembryonic antigen (CEA). To protect the particles from fast blood elimination, the coats were modified by various sugars, polyethyleneglycol, albumin, and sialoproteins, respectively. The protective effect was determined by using a specific in vitro test and by analyzing the biodistribution of the nanoparticles in nude mice grafted with CEA-tumors. In particular, a prolongation of the blood circulation time has been expected, if a natural modifier is attached to the coated nanoparticles. Although the elimination rate could hardly be decreased by any modifiers, the tumor accumulation is slightly improved by using the specific sialoprotein glycophorin B. The usefulness of nanoparticles as image contrast agents is probably limited by their microdistribution within the tumor tissue. The requirements for a contrast agent to be highly tissue specific are discussed.     

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.     

Interruption management: the use of attention-directing tactile cues

Previous research has suggested that providing informative cues about interrupting stimuli aids management of multiple tasks. However, auditory and visual cues can be ineffective in certain situations. The objective of the present study was to explore whether attention-directing tactile cues aid or interfere with performance. A two-group posttest-only randomized experiment was conducted. Sixty-one participants completed a 30-min performance session consisting of aircraft-monitoring and gauge-reading computer tasks. Tactile signals were administered to a treatment group to indicate the arrival and location of interrupting tasks. Control participants had to remember to visually check for the interrupting tasks. Participants in the treatment group responded to more interrupting tasks and responded faster than did control participants. Groups did not differ on error rates for the interrupting tasks, performance of the primary task, or subjective workload perceptions. In the context of the tasks used in the present research, tactile cues allowed participants to effectively direct attention where needed without disrupting ongoing information processing. Tactile cues should be explored in a variety of other visual, interrupt-laden environments. Potential applications exist for aviation, user-interface design, vigilance tasks, and team environments.     

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.     

The genetics of glutamate oxaloacetate transaminase in Drosophila melanogaster

A survey of 29 laboratory populations of Drosophila melanogaster for glutamate oxaloacetate transaminase (GOT) variation revealed that the Got-1 locus was polymorphic in three stocks recently collected from nature. The Got-1 locus was fixed for the same allozyme in the remaining 26 laboratory populations. Testcross matings to multiply marked stocks established that Got-1 is located at 4.8 centimorgans on chromosome 2.     

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.