ICRP PUBLICATION 122: radiological protection in geological disposal of long-lived solid radioactive waste.

This report updates and consolidates previous recommendations of the International Commission on Radiological Protection (ICRP) related to solid waste disposal (ICRP, 1985, 1997b, 1998). The recommendations given apply specifically to geological disposal of long-lived solid radioactive waste. The report explains how the ICRP system of radiological protection described in Publication 103 (ICRP, 2007) can be applied in the context of the geological disposal of long-lived solid radioactive waste. Although the report is written as a standalone document, previous ICRP recommendations not dealt with in depth in the report are still valid. The 2007 ICRP system of radiological protection evolves from the previous process-based protection approach relying on the distinction between practices and interventions by moving to an approach based on the distinction between three types of exposure situation: planned, emergency and existing. The Recommendations maintains the Commission's three fundamental principles of radiological protection namely: justification, optimisation of protection and the application of dose limits. They also maintain the current individual dose limits for effective dose and equivalent dose from all regulated sources in planned exposure situations. They re-enforce the principle of optimisation of radiological protection, which applies in a similar way to all exposure situations, subject to restrictions on individual doses: constraints for planned exposure situations, and reference levels for emergency and existing exposure situations. The Recommendations also include an approach for developing a framework to demonstrate radiological protection of the environment. This report describes the different stages in the life time of a geological disposal facility, and addresses the application of relevant radiological protection principles for each stage depending on the various exposure situations that can be encountered. In particular, the crucial factor that influences the application of the protection system over the different phases in the life time of a disposal facility is the level of oversight or 'watchful care' that is present. The level of oversight affects the capability to control the source, i.e. the waste and the repository, and to avoid or reduce potential exposures. Three main time frames are considered: time of direct oversight, when the disposal facility is being implemented and is under active supervision; time of indirect oversight, when the disposal facility is sealed and oversight is being exercised by regulators or special administrative bodies or society at large to provide additional assurance on behalf of society; and time of no oversight, when oversight is no longer exercised in case memory of the disposal facility is lost.

The direct posterior esthetic restoration using state-of-the-art composite resin technology.

As a result of the evolution of both materials and techniques, the direct posterior composite restoration has become a common procedure in today's dental practice. Advances in the adhesive protocol have allowed for the conservative preparation of the dentition by using the micromechanical potential of the sound tooth structure. Improvements of composite resin materials have further enabled the practitioner to re-create the natural esthetic beauty of the dentition while at the same time restoring the functional morphology. This article describes the technical protocol and materials necessary to perform the direct posterior composite restoration in the posterior dentition.

Naturally occurring radioactive materials (NORM): a matter of wide societal implication.

Naturally occurring radioactive materials are ubiquitous on Earth and their radioactivity may become concentrated as a result of human activities. Numerous industries produce concentrated radioactivity in their by-products: the coal industry, petroleum extraction and processing, water treatment, etc. The present reference system of radiation protection does not provide a complete framework for the coherent management of all types of radioactively contaminated materials. Inconsistencies in waste management policy and practice can be noted across the board, and especially vis-à-vis the management of radioactive waste from the nuclear industry. This article reviews the present societal approach to manage materials that are radioactive but are often not recognised as being such, and place the management of radioactive materials from the nuclear industry in perspective.

A new system for posterior restorations: a combination of ceramic optimized polymer and fiber-reinforced composite.

Due to the need for increased strength characteristics and enhanced aesthetic expectations of the patients, metal-free, aesthetic restorative systems for the anterior and posterior dentition are currently available. A new "space-age" restorative material has been developed that is a combination of a ceramic optimized polymer (Ceromer) (Targis/Vectris, Ivoclar Williams, Amherst, NY) and a fiber-reinforced composite framework material. The purpose of this article is to discuss the qualities that render this material particularly suitable for a variety of indications, including laboratory-fabricated restorations for the stress-bearing posterior regions. The material lends itself to diversification. Its indication for inlays, onlays, full-coverage crown restorations, and conservative single pontic inlay bridges is presented.

Ontogenic factors in short- and long-term recovery of discriminative behavior in rats after selective brain damage.

Stereotypical behavior or response perseveration dominating early mammalian responding, especially under conditions of aversive motivation, may be radically modified through damage in the prefrontal and hippocampal systems. These observations contribute evidence to the notion that changes in neural circuitry may be supporting behavioral recovery of function after selective brain damage. The extent of behavioral deficits as well as the prognosis for recovery are governed by task-specific variables, usually related to a discriminative element in stimulus control. Conversely, reversion to earlier, stereotypical behavior may be produced in adult rats exposed to damage at points within the same sites. Specific experiments tested weanling and adult rats within tasks that differed in the (1) extent and site of damage, (2) variety of signalling stimuli, (3) complexity of the task requirements, and (4) time since surgery for initiation of training. Experiments on 1-way active avoidance, alternation and reversal learning indicated that performance deficits are attributed to developmental immaturity early in ontogeny, and enhanced neurophysiological growth with age provides a reliable predictor of recovery. However with increasing age, variables related to the subtleties of damage site and task also emerge as salient factors in behavioral deficiencies. Interestingly, the cue properties or information value contained in the conditioned stimulus (CS) and the environmental context provide differential compensation for selected types of injury-induced deficits, and there was some evidence that the utility of environmental signals can be improved over long-term recovery periods. The results support the view that relationships between age at the time of injury and extent of recovery are perhaps best explained within developmentally determined constraints.(ABSTRACT TRUNCATED AT 250 WORDS)