Wear and creep of highly crosslinked polyethylene against cobalt chrome and ceramic femoral heads

The wear and creep characteristics of highly crosslinked ultrahigh-molecular-weight polyethylene (UHMWPE) articulating against large-diameter (36mm) ceramic and cobalt chrome femoral heads have been investigated in a physiological anatomical hip joint simulator for 10 million cycles. The crosslinked UHMWPE/ceramic combination showed higher volume deformation due to creep plus wear during the first 2 million cycles, and a steady-state wear rate 40 per cent lower than that of the crosslinked UHMWPE/cobalt chrome combination. Wear particles were isolated and characterized from the hip simulator lubricants. The wear particles were similar in size and morphology for both head materials. The particle isolation methodology used could not detect a statistically significant difference between the particles produced by the cobalt chrome and alumina ceramic femoral heads.     

Variation in Amyloplast Size,Relative Numbers and Carbohydrate Composition During Endosperm Development in Sweet Corn

The fractionation of immature sweet corn endosperm amyloplasts into seven size classes throughout kernel development is described. The numbers in each size class, expressed as a percentage of the total, have been followed throughout development. In addition, the amylose content of the different size classes has been determined and in each case expressed as a percentage of their α-glucan content. The increase observed in percent amylose content of total amyloplast α-glucan during kernel maturation may be due both to changes in the relative numbers of the different size classes as well as to changes in their amylose content.     

Effect of Oblique X-ray Incidence in Flat-Panel Computed Tomography of the Breast

We quantify the variation in resolution due to anisotropy caused by oblique X-ray incidence in indirect flat-panel detectors for computed tomography breast imaging systems. We consider a geometry and detector type utilized in breast computed tomography (CT) systems currently being developed. Our methods rely on MANTIS, a combined X-ray, electron, and optical Monte Carlo transport open source code. The physics models are the most accurate available in general-purpose Monte Carlo packages in the diagnostic energy range. We consider maximum-obliquity angles of 10deg and 13deg at the centers of the 30 and 40 cm detector edges, respectively, and 16deg at the corner of the detector. Our results indicate that blur is asymmetric and that the resolution properties vary significantly with the angle (or location) of incidence. Our results suggest that the asymmetry can be as high as a factor of 2.6 between orthogonal directions. Anisotropy maps predicted by MANTIS provide an understanding of the effect that such variations have on the imaging system and allow more accurate modeling and optimization of breast CT systems. These maps of anisotropy across the detector could lead to improved reconstruction and help motivate physics-based strategies for computer detection of breast lesions.     

Hydro,tidal and wave energy in Australia

The three renewable energy technologies discussed in this paper are based on water, but differ markedly in terms of the size of the available potential resource, the maturity of the associated conversion technologies, the extent to which they have been exploited to date, and the current research effort being devoted to their future development. Hydro-electricity and tidal power are both very mature technologies. The exploitation of Australia's relatively limited potential for hydro-electric development began over a century ago and the opportunities for further hydro-electric development are now very restricted. The country's significant tidal power resources, on the other hand, have not been exploited for electricity generation to date, but continual assessment of the feasibility of tidal power projects has been undertaken over the past half century. Although Australia has large ocean wave energy resources, ocean wave energy conversion technology is not yet fully commercial and no commercial wave generation plants are operating in Australia. A small number of wave energy conversion devices, however, are at the pilot testing stage.     

NMR SPECTROSCOPY IN THE CHARACTERIZATION OF EIGHT SELECTED ASPHALTS

ABSTRACT

Nuclear Magnetic Resonance (NMR) spectroscopy has been used to partially characterize eight selected asphalts. This report describes the initial efforts in this endeavor. Proton and carbon spectra have been collected and analyzed for percent aromatic content as well as aromatic substitution. DEFT results, chemical shifts and literature precedent have been used to assign the major resonances in the aliphatic region to chemical entities. Finally, using elemental analysis data, molecular weight data and NMR results, average structures for the eight asphalts have been derived     

Laparoscopic adrenalectomy for nonmalignant disease: improved safety, morbidity, and cost-effectiveness

The genetic diversity displayed by Plasmodiumfalciparum field isolates, the occurrence of variant forms of the parasite at different frequencies in different geographic areas, and the complexity of the infections represent major obstacles for the development of effective malaria control measures. However, since most of the existing studies have been performed in regions where P. falciparum transmission is high, little is known about the diversity and complexity of parasite populations circulating in areas of low malaria endemicity. We investigated the extent of genetic polymorphism in P. falciparum field isolates from Honduras, a region where its transmission is low and seasonal. Allelic diversity was analyzed in the highly polymorphic parasite genes encoding the merozoite surface proteins- (MSP-1) and -2 (MSP-2) and the glutamate-rich protein (GLURP) by the polymerase chain reaction. Gene polymorphism was also assessed in the EB200 region derived from the highly size polymorphic Pf332 gene. Limited size polymorphism was detected in all genes analyzed, with four and three variants for the MSP-1 and MSP-2 alleles, respectively, and two size variants for the GLURP and Pf332 genes. Moreover, based on the studied genetic markers, most infections consisted of only a few genetically distinct parasite clones. These results suggest that the P. falciparum parasite populations circulating in this region are genetically homogeneous and point to an association between the extent of parasite genetic diversity and the intensity of malaria transmission.     

USING REINFORCEMENT LEARNING TO COORDINATE BETTER

This paper examines the potential and the impact of introducing learning capabilities into autonomous agents that make decisions at run-time about which mechanism to exploit to coordinate their activities. Specifically, our motivating hypothesis is that to deal with dynamic and unpredictable environments it is important to have agents that learn the right situations in which to attempt coordination , and the right coordination method to use in those situations . In particular, the efficacy of learning is evaluated when agents have varying types and amounts of information when those coordinating decisions are taken. This hypothesis is evaluated empirically, in a grid-world scenario in which (a) an agent's predictions about the other agents in the environment are approximately correct and (b) an agent cannot correctly predict the others' behavior. The results presented show when, where and why learning is effective when it comes to making a decision about selecting a coordination mechanism.     

TRAVOS: Trust and Reputation in the Context of Inaccurate Information Sources

In many dynamic open systems, agents have to interact with one another to achieve their goals. Here, agents may be self-interested, and when trusted to perform an action for another, may betray that trust by not performing the action as required. In addition, due to the size of such systems, agents will often interact with other agents with which they have little or no past experience. There is therefore a need to develop a model of trust and reputation that will ensure good interactions among software agents in large scale open systems. Against this background, we have developed TRAVOS (Trust and Reputation model for Agent-based Virtual OrganisationS) which models an agent’s trust in an interaction partner. Specifically, trust is calculated using probability theory taking account of past interactions between agents, and when there is a lack of personal experience between agents, the model draws upon reputation information gathered from third parties. In this latter case, we pay particular attention to handling the possibility that reputation information may be inaccurate.     

Managing commitments in multiple concurrent negotiations

Automated negotiation by software agents is a key enabling technology for agent mediated e-commerce. To this end, this paper considers an important class of such negotiations – namely those in which an agent engages in multiple concurrent bilateral negotiations for a good or service. In particular, we consider the situation in which a buyer agent is looking for a single service provider from a number of available ones in its environment. By bargaining simultaneously with these providers and interleaving partial agreements that it makes with them, a buyer can reach good deals in an efficient manner. However, a key problem in such encounters is managing commitments since an agent may want to make intermediate deals (so that it has a definite agreement) with other agents before it gets to finalize a deal at the end of the encounter. To do this effectively, however, the agents need to have a flexible model of commitments that they can reason about in order to determine when to commit and to decommit. This paper provides and evaluates such a commitment model and integrates it into a concurrent negotiation model.