Effect of Grain Size on Mechanical Properties of Submicrometer 3Y-TZP: Fracture Strength and Hydrothermal Degradation

This paper considers fracture strength, fracture origins, and hydrothermal degradation of 3Y-TZP with grain sizes in the range of 110–480 nm. Biaxial fracture strength testing was used to show that the fracture strength increases with grain size and is governed by the concurrent change in fracture toughness. Hydrothermal degradation was studied by means of fractography, Raman microscopy and its effect on fracture strength. Up to 200 nm grain size, hydrothermal degradation of strength is limited. Larger grain sizes exhibit either premature failure or an increase in strength. A surface transformation zone was found to be responsible for both phenomena.     

Thermogenic Effect from Nutritionally Enriched Coffee Consumption

Background  

The purpose of this study was to examine the effect of nutritionally enriched JavaFit™ (JF) coffee (450 mg of caffeine, 1200 mg of garcinia cambogia, 360 mg of citrus aurantium extract, and 225 mcg of chromium polynicotinate) on resting oxygen uptake (VO₂), respiratory exchange ratio (RER), heart rate (HR), and blood pressure (BP) in healthy and physically active individuals.     

Transferring information from one experiment to another

This paper presents a rational method (based on Bayes' Theorem) for transferring information on parameter values from one experiment to another, in situations where the mathematical models for the two experiments share some parameters in common. The uncertainty in the estimates of the parameters, which reflects the experimental error in the initial experiment, is properly transferred as well. The use of the method is demonstrated by applying it to a fairly complicated system, typical in chemical reaction engineering, in which the kinetic parameters in a model for the hydrogenolysis of butane reaction were estimated using data obtained from a bench-scale, integral packed-bed reactor. These parameter estimates were then transferred to a model for a fluidized bed reactor in which the same chemical reaction occurred. Using the fluidized bed data they were updated and two additional parameters in the fluidized bed model were also estimated. This procedure allows a more realistic estimate of the uncertainty in all parameter values in the model for the fluidized bed reactor.     

On the effect of treating poly(acrylic acid) with argon and tetrafluoromethane plasmas: Kinetics and degradation mechanism

Poly(acrylic acid) (PAAc) films were treated with either an argon or a tetrafluoromethane (CF₄) plasma and subsequently analyzed with X-ray photoelectron spectroscopy (XPS). PAAc films were decarboxylated during both types of plasma treatments. In addition, during the CF₄ plasma treatment, the PAAc films became fluorinated. The plasma phase during the argon plasma treatment of PAAc films was investigated with optical emission spectroscopy. It was shown that during this plasma treatment carbon dioxide, water, and possibly hydrogen were liberated from the PAAc surface. By covering the surface of PAAc films with different materials (lithium fluoride, UV fused silica, and glass) during the plasma treatment, it was possible to differentiate between photochemically induced and particle-induced changes of the surface. This method was used to show that decarboxylation during the argon plasma treatment was caused by vacuum UV radiation (wavelength < 150 nm) and the decarboxylation/fluorination during the CF₄ plasma treatment was induced by reactive fluorine-containing species from the plasma phase. Furthermore, during both processes, etching of the PAAc surface occurred. Based on these mechanisms, kinetic models were derived that could be used to describe the measured kinetic data adequately. © 1994 John Wiley & Sons, Inc.     

Coupling granule properties and granulation rates in high-shear granulation

It is possible to link granulation rates to granule properties. The linkage is by multiple dimension population balance equations that, by means of simplifying assumptions, can be reduced to multiple one-dimensional (1-D) population balance equations (PBEs). Using simple physically based models, this paper demonstrates how multiple one-dimensional population balance equations can describe the results of high-shear granulation experiments of two different materials, calcium carbonate and lactose. Good agreement between experimental and simulated results was achieved enabling the granulation rates to be defined by two model parameters: the critical binder volume fraction and the aggregation rate constant. The modelling framework presented in this paper also provides a basis for the kinetic analysis of granulation experiments so that with further work, it is possible to determine the effect of process conditions and material properties on the model parameters.     

Essentiality of dietary ω3 fatty acids for premature infants: Plasma and red blood cell fatty acid composition

Pre-term infants, that are not breast-fed, are deprived of vital intrauterine fat accretion during late pregnancy and must rely on formula to obtain fatty acids essential for normal development, particularly of the visual system. Preterm infants (30 wk postconception) receiving human milk were compared to infants given one of the following formulae: Formula A was a commercial preterm formula with predominantly 18∶2ω6 (24.2%) and low (0.5%) 18∶3ω3; Formula B was based on soy oil and contained similar 18∶2ω6 levels (20%) and high 18∶3ω3 (2.7%); Formula C was also a soy oil-based formula (20% 18∶2, 1.4% 18∶3) but was supplemented with marine oil to provide ω3 long-chain polyunsaturated fatty acids (LCP) at a level (docosahexaenoic acid, DHA, 0.35%) equivalent to human milk. At entry (10 days of age), the fatty acid composition of plasma and red blood cell (RBC) membrane lipids of the formula groups were identical. By 36 wk postconception, the DHA content in lipids of group A was significantly reduced compared to that in the human milk and marine oil formula groups. Omega-3 LCP results were further amplified by 57 wk with compensatory increases in 22∶5ω6 in both plasma and RBC lipids. Provision of 2.7% α-linolenic acid in formula group B was sufficient to maintain 22∶6ω3 levels equivalent to those in human milk-fed infants at 36 wk but not at 57 wk. Effects on the production of thiobarbituric acid reactive substances and fragility of RBC attributable to the marine oil supplementation were negligible. The results support the essentiality of ω3 fatty acids for preterm infants to obtain fatty acid profiles comparable to infants receiving human milk. Formula for preterm infants should be supplemented with ω3 fatty acids including LCP. Based on a paper presented at the Symposium on Milk Lipids held at the AOCS Annual Meeting, Baltimore, MD, April 1990.     

An investigation of methods of pileup rejection for 2-D array detectors employed in high resolution PET

Two methods of rejecting pileup events in 2-D array detectors used in positron emission tomography (PET) are investigated. Since the methods are based on different physical properties, they were investigated separately and in combination. Method one is based on the fact that valid events in the 2-D array detector occur only in a limited pulseheight range for each detector element, and by rejecting events outside these energy ranges, many of the pileup events can be rejected. Method two is based on the fact that most pileup event pairs have a time differential, which will cause a difference in the shape of the signal which increases the rise time of an integrated signal or the crossover time of a bipolar signal from a shaping amplifier. Method two proved to be somewhat better than method one. However, the ideal system would most likely use both methods simultaneously.     

Grain size effects on cyclic fatigue and crack-growth resistance behaviour of partially stabilized zirconia

Cyclic fatigue crack growth and crack-resistance behaviour was studied in partially stabilized zirconia (PSZ) with three different cubic-phase grain sizes following sub-eutectoid heat treatments. Raman spectroscopy was used to determine the extent of phase transformation around the cracks for both cyclic and monotonic loading conditions. All tests were on long, through thickness cracks using compact-tension specimens. Predictions of crack-tip shielding were made following determination of toughening parameters using crackresistance data. It was found that the dominant factors affecting cyclic fatigue-crack growth were the level of crack-tip shielding, as a result of phase transformation, and the intrinsic toughness of the material. Grain size did not appear to significantly affect fatigue crack-growth behaviour.