Marginal adaptation and performance of bioactive dental restorative materials in deciduous and young permanent teeth

Objective: The aim of this study was to investigate the adaptation of different types of restorations towards deciduous and young permanent teeth. Materials and Methods: Class V cavities were prepared in deciduous and young permanent teeth and filled with different materials (a conventional glass-ionomer, a resin-modified glass-ionomer, a poly-acid-modified composite resin and a conventional composite resin). Specimens were aged in artificial saliva for 1, 6, 12 and 18 months, then examined by SEM. Results: The composite resin and the polyacid-modified composite had better marginal adaptation than the glass-ionomers,though microcracks developed in the enamel of the tooth. The glass-ionomers showed inferior marginal quality and durability, but no microcracking of the enamel. The margins of the resin-modified glass-ionomer were slightly superior to the conventional glass-ionomer. Conditioning improved the adaptation of the composite resin, but the type of tooth made little or no difference to the performance of the restorative material. All materials were associated with the formation of crystals in the gaps between the filling and the tooth; the quantity and shape of these crystals varied with the material. Conclusions: Resin-based materials are generally better at forming sound, durable margins in deciduous and young permanent teeth than cements, but are associated with microcracks in the enamel. All fluoride-releasing materials give rise to crystalline deposits.

Upgrading automation for nuclear fuel in-core management: from the symbolic generation of configurations to the neural adaptation of heuristics

FUELCON is an expert system in nuclear engineering. Its task is optimized refueling-design, which is crucial to keep down operation costs at a plant. FUELCON proposes sets of alternative configurations of fuel-allocation; the fuel is positioned in a grid representing the core of a reactor. The practitioner of in-core fuel management uses FUELCON to generate a reasonably good configuration for the situation at hand. The domain expert, on the other hand, resorts to the system to test heuristics and discover new ones, for the task described above. Expert use involves a manual phase of revising the ruleset, based on performance during previous iterations in the same session. This paper is concerned with a new phase: the design of a neural component to carry out the revision automatically. Such an automated revision considers previous performance of the system and uses it for adaptation and learning better rules. The neural component is based on a particular schema for a symbolic to recurrent-analogue bridge, called NIPPL, and on the reinforcement learning of neural networks for the adaptation.

Case base adaptation using solution-space metrics

In this paper we propose a generalisation of the k-nearest neighbour (k-NN) retrieval method based on an error function using distance metrics in the solution and problem space. It is an interpolative method which is proposed to be effective for sparse case bases. The method applies equally to nominal, continuous and mixed domains, and does not depend upon an embedding n-dimensional space. In continuous Euclidean problem domains, the method is shown to be a generalisation of the Shepard's Interpolation method. We term the retrieval algorithm the Generalised Shepard Nearest Neighbour (GSNN) method. A novel aspect of GSNN is that it provides a general method for interpolation over nominal solution domains. The performance of the retrieval method is examined with reference to the Iris classification problem,and to a simulated sparse nominal value test problem. The introducion of a solution-space metric is shown to out-perform conventional nearest neighbours methods on sparse case bases.

Case based adaptation using interpolation over nominal values

In this paper we propose a method for interpolation over a set of retrieved cases in the adaptation phase of the case-based reasoning cycle. The method has two advantages over traditional systems: the first is that it can predict “new” instances, not yet present in the case base; the second is that it can predict solutions not present in the retrieval set. The method is a generalisation of Shepard’s Interpolation method, formulated as the minimisation of an error function defined in terms of distance metrics in the solution and problem spaces. We term the retrieval algorithm the Generalised Shepard Nearest Neighbour (GSNN) method. A novel aspect of GSNN is that it provides a general method for interpolation over nominal solution domains. The method is illustrated in the paper with reference to the Irises classification problem. It is evaluated with reference to a simulated nominal value test problem, and to a benchmark case base from the travel domain. The algorithm is shown to out-perform conventional nearest neighbour methods on these problems. Finally, GSNN is shown to improve in efficiency when used in conjunction with a diverse retrieval algorithm.

The introduction of social adaptation within evacuation modelling

In recent history, a number of tragic events have borne a consistent message; the social structures that existed prior to and during the evacuation significantly affected the decisions made and the actions adopted by the evacuating population in response to the emergency. This type of influence over behaviour has long been neglected in the modelling community. This paper is an attempt to introduce some of these considerations into evacuation models and to demonstrate their impact. To represent this type of behaviour within evacuation models a mechanism to represent the membership and position within social hierarchies is established. In addition, individuals within the social groupings are given the capacity to communicate relevant pieces of data such as the need to evacuate—impacting the response time—and the location of viable exits—impacting route selection. Furthermore, the perception and response to this information is also affected by the social circumstances in which individuals find themselves. Copyright © 2005 John Wiley & Sons, Ltd.

Exploring adaptation & self-adaptation in autonomic computing systems

This panel paper sets out to discuss what self-adaptation means, and to explore the extent to which current autonomic systems exhibit truly self-adaptive behaviour. Many of the currently cited examples are clearly adaptive, but debate remains as to what extent they are simply following prescribed adaptation rules within preset bounds, and to what extent they have the ability to truly learn new behaviour. Is there a standard test that can be applied to differentiate? Is adaptive behaviour sufficient anyway? Other autonomic computing issues are also discussed.

Model-based pilot and data power adaptation in psam with periodic delayed feedback

We consider the optimum design of pilot-symbol-assisted modulation (PSAM) schemes with feedback. The received signal is periodically fed back to the transmitter through a noiseless delayed link and the time-varying channel is modeled as a Gauss-Markov process. We optimize a lower bound on the channel capacity which incorporates the PSAM parameters and Kalman-based channel estimation and prediction. The parameters available for the capacity optimization are the data power adaptation strategy, pilot spacing and pilot power ratio, subject to an average power constraint. Compared to the optimized open-loop PSAM (i.e., the case where no feedback is provided from the receiver), our results show that even in the presence of feedback delay, the optimized power adaptation provides higher information rates at low signal-to-noise ratios (SNR) in medium-rate fading channels. However, in fast fading channels, even the presence of modest feedback delay dissipates the advantages of power adaptation.

'Marginal gothic': mediating the monstrous in British romanticism

In this paper I look at texts from the Romantic Period which strategically employ elements of the Gothic genre in what I describe as a `marginal` relationship with the Gothic canon. My intention is both to explore the way the boundaries of the genre might be extended, and to cast fresh light on some of the texts discussed, specifically in relation to the ways in which the `monstrous` is perceived and portrayed as villainy. In the first half of the paper, using Burke’s Philosophical Enquiry on the Sublime and the Beautiful as a starting point, I consider Burke’s Reflections on the Revolution in France, Godwin’s Caleb Williams, Radcliffe’s The Italian, and Blake’s The Marriage of Heaven and Hell as all in various ways examples of `marginal Gothic` that present evil doing as monstrous aberrations, also noting the contemporary reception of Beckford’s Vathek, praised in 1786 for its `accuracy and credibility`. In addition, I suggest that Wordsworth’s `Tintern Abbey` and Book VI of The Prelude provide evidence of marginal, but significant, Gothic influence that references Radcliffe’s and Burke’s explorations of a terror of the unknown. In the second half of the paper I focus on Scott’s Guy Mannering, or The Astrologer (1815) as an important example of a `marginal` Gothic novel. Scott’s reference to Vathek at a key point in his plot suggests that he had read Beckford’s novel as entirely `Gothic`. This discussion incorporates a comparison between Mannering’s youthful enthusiasm for astrological divination, and themes to be found in Shelley’s Frankenstein, notably with respect to the nature of Victor Frankenstein’s response to `old` and `new` science and medicine, and to the creation and control of Gothic monstrosity. In these and in other instances, it will be argued that the `marginal Gothic` of Scott’s novel may be read as a precursor to Shelley’s work. [From the Author]

The biocompatibility of resin-modified glass-ionomer cements for dentistry

OBJECTIVES: The biological effects of resin-modified glass-ionomer cements as used in clinical dentistry are described, and the literature reviewed on this topic. METHODS: Information on resin-modified glass-ionomers and on 2-hydroxyethyl methacrylate (HEMA), the most damaging substance released by these materials, has been collected from over 50 published papers. These were mainly identified through Scopus. RESULTS: HEMA is known to be released from these materials and has a variety of damaging biological properties, ranging from pulpal inflammation to allergic contact dermatitis. These are therefore potential hazards from resin-modified glass-ionomers. However, clinical results with these materials that have been reported to date are generally positive. CONCLUSIONS/SIGNIFICANCE: Resin-modified glass-ionomers cannot be considered biocompatible to nearly the same extent as conventional glass-ionomers. Care needs to be taken with regard to their use in dentistry and, in particular, dental personnel may be at risk from adverse effects such as contact dermatitis and other immunological responses.

Water sorption/desorption in polyacid-modified composite resins for dentistry

The water sorption and desorption behaviour of three commercial polyacid-modified composite resins used in clinical dentistry have been studied in detail. Cured specimens of each material were subjected to two successive water uptake cycles in an atmosphere of 93% relative humidity, with one intervening desorption cycle in a desiccating atmosphere over concentrated sulfuric acid. Specimens were found to absorb and desorb water according Fick's law until Mt/M(infinity) values of approximately 0.5. Diffusion rates for uptake varied between cycles, ranging from 2.37-4.53 x 10(-9 )cm(2) s(-1) for 1st cycle to 0.85-2.72 x 10(-8 )cm(2 )s(-1) for 2nd cycle. Desorption rates were similar to those for 2nd cycle sorption, and ranged from 0.86 to 5.47 x 10(-8 )cm(2 )s(-1). Equilibration times for 1st cycle water uptake were greater than for 2nd cycle sorption and for desorption and overall the behaviour of polyacid-modified composites in a high humidity atmosphere was similar to that of conventional composites in water. It is concluded that the hydrophilic components of the former do not bring about an enhanced rate of water transport.

Models of advertising standardisation and adaptation: it's time to move the debate forward

Advertising standardisation versus adaptation has been discussed in some detail in the marketing literature. Despite previous attempts, there is still no widely-used decision-making model available that has been accepted by marketing practitioners and academics. This paper examines the development of this important area by reviewing six prominent models in the advertising standardisation/adaptation literature. It shows why there has been a lack of development in the current literature and why it is crucial to address this problem. Important areas for future research are suggested in order to find a solution

Polyacid-modified composite resins ("compomers") and their use in clinical dentistry

OBJECTIVES: This paper describes the chemistry and properties of polyacid-modified composite resins ("compomers") designed for use in clinical dentistry, and reviews the literature in this area. METHODS: Information has been obtained from over 50 published articles appearing in the dental and biomaterials literature, with studies being principally identified through MedLine. RESULTS: Published work shows that polyacid-modified composite resins constitute a discrete class of polymeric repair material for use in dentistry. Their distinction is that they contain hydrophilic components, and these cause water to be drawn into the material following cure. This triggers an acid-base reaction, and gives the materials certain clinically-desirable properties (fluoride release, buffering capability) that are also associated with glass-ionomer cements. The water uptake leads to a decline in certain, though not all, physical properties. However, clinical studies have shown these materials to perform acceptably in a variety of applications (Class I, Class II and Class V cavities, as fissure sealants and as orthodontic band cements), especially in children's teeth. CONCLUSIONS/SIGNIFICANCE: Polyacid-modified composite resins constitute a versatile class of dental repair material, whose bioactivity confers clinical advantages, and which are particularly useful in children's dentistry.