Critical reliability challenges in scaling SiO2-based dielectric to its limit

The limitations of silicon dioxide dielectric reliability for future CMOS scaling are investigated. Several critical aspects are examined, and new experimental results are used to form an empirical approach to a theoretical framework upon which the data is then interpreted. Experimental data over a wide range of oxide thickness, voltage, and temperature were gathered using structures with a wide range of gate-oxide areas, and over very long stress times. Resolution of seemingly contradictory observations regarding the temperature dependence of oxide breakdown is provided by this work. On the basis of these results, a unified, global picture of oxide breakdown is constructed and the resulting model is applied to project reliability limits for the wear-out of silicon dioxide. It is concluded that silicon dioxide-based dielectrics can provide reliable gate dielectric, even to a thickness of 1 nm, and that CMOS scaling may well be viable to the 50 nm technology node using silicon-dioxide-based gate insulators.     

The dynamic behaviour of fluidized bed reactors for solid catalysed gas phase olefin polymerization

The dynamic behaviour of fluidized bed reactors for ethylene and propylene polymerization is studied through detailed modelling and simulation. Both static and Hopf bifurcation behaviour is observed and can lead to temperature runaway if special care is not taken in start-up and in normal operation. A feedback control scheme can be used to control transients, but it is limited by recycle gas cooling capacity.     

Influence of ruminal or abomasal starch hydrolysate infusion on pancreatic exocrine secretion and blood glucose and insulin concentrations in steers

Seven Holstein steers (234 +/- 6.4 kg) surgically fitted with pancreatic cannulas, ruminal and abomasal infusion cannulas, and hepatic-portal vein catheters were used in a 4 x 7 incomplete Latin square design experiment to examine the influence of ruminal and abomasal carbohydrate infusion on enzyme secretion and composition of pancreatic juice. Four treatments were arranged in a 2 x 2 factorial: 1) ruminal starch hydrolysate (SH; 34.2 g/[h.site]) or abomasal water and 2) abomasal SH or ruminal water. Starch hydrolysate is raw cornstarch that has been partially digested by a heat-stable alpha-amylase. Experimental periods were 14 d with 9 to 10 d of adaptation, 4 d of pancreatic collection, and blood collection on d 14. Abomasal SH infusion tended (P < .10) to increase pancreatic fluid secretion. The pH of pancreatic juice was higher (P < .01) for ruminal SH infusion, and abomasal SH infusion tended (P < .10) to result in lower pH of pancreatic juice. alpha-Amylase concentrations (units/milliliter and units/milligram of protein) and secretion (units/hour) were less (P < .002) for abomasal SH infusion. Chymotrypsin concentration (units/liter; P < .01) and secretion (units/hour; P < .10) were less for abomasal SH infusion; however, a rumen x abomasal interaction was found (P < .05). Chloride concentration (milligrams/deciliter) and secretion (milligrams/hour) were increased (P < .01) for abomasal SH infusion. Abomasal SH infusion resulted in increased (P < .01) portal blood glucose concentrations; however, portal plasma insulin concentration was not affected (P > .10). Abomasal SH infusion altered alpha-amylase secretion in steers, but ruminal SH infusion had minimal effect on alpha-amylase secretion. These changes suggest abosamal infusion of SH may negatively impact secretion of pancreatic alpha-amylase.     

Intra and intermolecular relaxations 2,3-dihydroxypropyl methacrylate and 2-hydroxyethyl methacrylate hydrogels

The dynamic mechanical transitions present in the 2-hydroxyethyl methacrylate (HEMA) and 2,3-dihydroxypropyl methacrylate (DHPMA) homopolymers and two random copolymers, with one-to-one and three-to-one HEMA-to-DHPMA molar ratios, were examined by analyzing the dry xerogels and hydrogels at various states of hydration. The temperatures of the primary α transition and the secondary β and γ transitions were determined in the tension mode; the storage modulus and loss modulus as a function of temperature and frequency were recorded. The results were compared to the results obtained from dielectric analysis at low hydration using tan δ. The frequency dependence of the dispersions was calculated for the dry and hydrated states, using mechanical and dielectric data. The information obtained was used to elucidate the interaction between the polymer and the sorbed water. Analysis of the low temperature secondary γ transition and secondary transitions resulting from polymer-water interactions was emphasized. During the initial hydration, the temperature maxima of the dielectric and mechanical secondary γ transitions, and the transitions that appear in the presence of absorbed water increased as the DHPMA content increased. The apparent activation energy associated with the secondary transitions increased as well. All of this is the result of stronger intermolecular interactions due to the increased density of hydrophilic moieties in DHPMA.     

A MALDI, TGA, TG/MS, and DEA study of the irradiation effects on PMMA

Poly(methyl methacrylate) (PMMA) (M_w=6.4×10³, PD=1.06) was irradiated under vacuum. The constant dose rate was 1.66×10⁴ rad/min at doses between 10 and 100 Mrad using a cobalt-60 source. The samples were then analyzed by matrix assisted laser desorption/ionization (MALDI), hyphenated thermogravimetric/mass spectrometry (TG/MS), and dielectric analysis (DEA), all novel methods for the analysis of polymers damaged by radiation. Gel permeation chromatography (GPC), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) were also used for analysis. This study evidenced main chain scission, the removal of ester side groups, and the production of monomer as a result of ionizing radiation.     

Protective coatings for improving contamination performance ofoutdoor high voltage ceramic insulators

This paper presents an overview of the practices employed by utilities and industries to combat the contamination problem with ceramic insulators. It emphasizes two popular methods, namely, coating insulators with greases and RTV (room temperature vulcanizing) silicone rubber coatings. The experience to date, application methods, user concerns, current theories on how and why the coatings perform, life expectancy, and future direction of the technology, are outlined. The paper also describes research activity in the committee on RTV coatings, which is the state of the art in protective coatings     

Reliability of potential clinical measures of muscle tone in the elbows of patients after stroke

In order to establish a genotype-phenotype relationship, we have identified both mutant phenylalanine hydroxylase (PAH) genes in 108 phenylketonuria (PKU) patients (27 different alleles, 54 different genotypes). One major group of patients with very high pretreatment phenylalanine values ("classical" PKU) exclusively comprised homozygotes of the PKU mutations I65T, G272X, F299C, Y356X, R408W, IVS12nt1, and compound heterozygotes of various combinations of these alleles with G46S, R261Q, R252W, A259T, R158Q, D143G, R243X, E280K, or Y204C. A second major group of patients with lower phenylalanine values ("mild" PKU) comprised mutations A300S, R408Q, Y414C in various compound heterozygous states, and R261Q, R408Q, Y414C in homozygotes. The phenylalanine values in these groups were non-overlapping. In addition, a smaller group of patients formed the transition between the two main groups. In sib pairs 4 of 15 had discordant pretreatment phenylalanine values. Conclusion: Our results are consistent with the view that allelic heterogeneity at the PAH locus dominates the biochemical phenotype in PKU and that genotype information is able to predict the metabolic phenotype in PKU patients.     

The influence of the lewis number on the dynamics of chemically reacting systems

The influence of Lewis number on stability and oscillations for stirred tanks, catalytic wires and gauzes, and catalyst particles is determined quantitatively. The mathematical structure is discussed and illustrated by example. Relaxation oscillations are found to be the natural asymptote to the bifurcating limit cycles as Le → 0.