Nanotechnology: balancing benefits and risks to public health and the environment : expert paper

Nanotechnology has been heralded as a "revolution" in science, for two reasons: first, because of its revolutionary view of the way in which chemicals and elements, such as gold and silver, behave, compared to traditional scientific understanding of their properties. Second, the impact of these new discoveries, as applied to commerce, can transform the daily life of consumer products ranging from sun tan lotions and cosmetics, food packaging and paints and coatings for cars, housing and fabrics, medicine and thousands of industrial processes.9 Beneficial consumer use of nanotechnologies, already in the stream of commerce, improves coatings on inks and paints in everything from food packaging to cars. Additionally, "Nanomedicine" offers the promise of diagnosis and treatment at the molecular level in order to detect and treat presymptomatic disease,10 or to rebuild neurons in Alzheimer's and Parkinson's disease. There is a possibility that severe complications such as stroke or heart attack may be avoided by means of prophylactic treatment of people at risk, and bone regeneration may keep many people active who never expected rehabilitation. Miniaturisation of diagnostic equipment can also reduce the amount of sampling materials required for testing and medical surveillance. Miraculous developments, that sound like science fiction to those people who eagerly anticipate these medical products, combined with the emerging commercial impact of nanotechnology applications to consumer products will reshape civil society - permanently. Thus, everyone within the jurisdiction of the Council of Europe is an end-user of nanotechnology, even without realising that nanotechnology has touched daily life.

Fluid-rock-strain feedbacks in extensional shear zones

La présence de fluide météorique synchrone à l'activité du détachement (Farmin, 2003 ; Mulch et al., 2007 ; Gébelin et al., 2011), implique que les zones de cisaillement sont des systèmes ouverts avec des cellules de convections à l'échelle crustale et un intense gradient géothermique au sein du détachement (Morrison et Anderson, 1998, Gottardi et al., 2011). De plus, les réactions métamorphiques liées à des infiltrations fluides dans les zones de cisaillement extensionnel peuvent influencer les paramètres rhéologiques du système (White and Knipe, 1978), et impliquer la localisation de la déformation dans la croûte. Dans ce manuscrit, deux zones de cisaillement infiltrées par des fluides météoriques sont étudiées, l'une étant largement quartzitique, et l'autre de nature granitique ; les relations entre déformation, fluides, et roches s'appuient sur des approches structurales, microstructurales, chimiques et isotopiques. L'étude du détachement du Columbia river (WA, USA) met en évidence que la déformation mylonitique se développe en un million d'années. La phase de cisaillement principal s'effectue à 365± 30°C d'après les compositions isotopiques en oxygène du quartz et de la muscovite. Ces minéraux atteignent l'équilibre isotopique lors de leur recristallisation dynamique contemporaine à la déformation. La zone de cisaillement enregistre une baisse de température, remplaçant le mécanisme de glissement par dislocation par celui de dissolution- précipitation dans les derniers stades de l'activité du détachement. La dynamique de circulation fluide bascule d'une circulation pervasive à chenalisée, ce qui engendre localement la rupture des équilibres d'échange isotopiques. La zone de cisaillement de Bitterroot (MT, USA) présente une zone mylonitique de 600m d'épaisseur, progressant des protomylonites aux ultramylonites. L'intensité de la localisation de la déformation se reflète directement sur l'hydratation des feldspaths, réaction métamorphique majeure dite de « rock softening ». Une étude sur roche totale indique des transferts de masse latéraux au sein des mylonites, et d'importantes pertes de volume dans les ultramylonites. La composition isotopique en hydrogène des phyllosilicates met en évidence la présence (1) d'une source magmatique/métamorphique originelle, caractérisée par les granodiorites ayant conservé leur foliation magmatique, jusqu'aux protomylonites, et (2) une source météorique qui tamponne les valeurs des phyllosilicates des fabriques mylonitiques jusqu'aux veines de quartz non-déformées. Les compositions isotopiques en oxygène des minéraux illustrent le tamponnement de la composition du fluide météorique par l'encaissant. Ce phénomène cesse lors du processus de chloritisation de la biotite, puisque les valeurs des chlorites sont extrêmement négatives (-10 per mil). La thermométrie isotopique indique une température d'équilibre isotopique de la granodiorite entre 600-500°C, entre 500-300°C dans les mylonites, et entre 300 et 200°C dans les fabriques cassantes (cataclasites et veines de quartz). Basé sur les résultats issus de ce travail, nous proposons un modèle général d'interactions fluide-roches-déformation dans les zones de détachements infiltrées par des fluides météoriques. Les zones de détachements évoluent rapidement (en quelques millions d'années) au travers de la transition fragile-ductile ; celle-ci étant partiellement contrôlée par l'effet thermique des circulations de fluide météoriques. Les systèmes de détachements sont des lieux où la déformation et les circulations fluides sont couplées ; évoluant rapidement vers une localisation de la déformation, et de ce fait, une exhumation efficace. - The presence of meteoric fluids synchronous with the activity of extensional detachment zones (Famin, 2004; Mulch et al., 2007; Gébelin et al., 2011) implies that extensional systems involve fluid convection at a crustal scale, which results in high geothermal gradients within active detachment zones (Morrison and Anderson, 1998, Gottardi et al., 2011). In addition, the metamorphic reactions related to fluid infiltration in extensional shear zones can influence the rheology of the system (White and Knipe, 1978) and ultimately how strain localizes in the crust. In this thesis, two shear zones that were permeated by meteoric fluids are studied, one quartzite-dominated, and the other of granitic composition; the relations between strain, fluid, and evolving rock composition are addressed using structural, microstructural, and chemical/isotopic measurements. The study of the Columbia River detachment that bounds the Kettle core complex (Washington, USA) demonstrates that the mylonitic fabrics in the 100 m thick quartzite- dominated detachment footwall developed within one million years. The main shearing stage occurred at 365 ± 30°C when oxygen isotopes of quartz and muscovite equilibrated owing to coeval deformation and dynamic recrystallization of these minerals. The detachment shear zone records a decrease in temperature, and dislocation creep during detachment shearing gave way to dissolution-precipitation and fracturing in the later stages of detachment activity. Fluid flow switched from pervasive to channelized, leading to isotopic disequilibrium between different minerals. The Bitterroot shear zone detachment (Montana, USA) developed a 600 m thick mylonite zone, with well-developed transitions from protomylonite to ultramylonite. The localization of deformation relates directly to the intensity of feldspar hydration, a major rock- softening metamorphic reaction. Bulk-rock analyses of the mylonitic series indicate lateral mass transfer in the mylonite (no volume change), and significant volume loss in ultramylonite. The hydrogen isotope composition of phyllosilicates shows (1) the presence of an initial magmatic/metamorphic source characterized by the granodiorite in which a magmatic, and gneissic (protomylonite) foliation developed, and (2) a meteoric source that buffers the values of phyllosilicates in mylonite, ultramylonite, cataclasite, and deformed and undeformed quartz veins. The mineral oxygen isotope compositions were buffered by the host-rock compositions until chloritization of biotite started; the chlorite oxygen isotope values are negative (-10 per mil). Isotope thermometry indicates a temperature of isotopic equilibrium of the granodiorite between 600-500°C, between 500-300°C in the mylonite, and between 300 and 200°C for brittle fabrics (cataclasite and quartz veins). Results from this work suggest a general model for fluid-rock-strain feedbacks in detachment systems that are permeated by meteoric fluids. Phyllosilicates have preserved in their hydrogen isotope values evidence for the interaction between rock and meteoric fluids during mylonite development. Fluid flow generates mass transfer along the tectonic anisotropy, and mylonites do not undergo significant volume change, except locally in ultramylonite zones. Hydration of detachment shear zones attends mechanical grain size reduction and enhances strain softening and localization. Self-exhuming detachment shear zones evolve rapidly (a few million years) through the transition from ductile to brittle, which is partly controlled by the thermal effect of circulating surface fluids. Detachment systems are zones in the crust where strain and fluid flow are coupled; these systems. evolve rapidly toward strain localization and therefore efficient exhumation.

Special Surface Preparation Prior to Bituminous Overlays, HR-231, 1987

Research project HR-231, "Special Surface Preparation Prior to Bituminous Overlay", was initiated in 1982 to study the effectiveness of three different crack fillers in extending pavement life. In particular, this project was designed to determine if any of the fillers could substantially reduce the rate of subsurface deterioration and general deterioration of an asphalt pavement at crack locations. This project also sought to determine the effects of the various crack filling procedures on different thicknesses of bituminous overlays. The three fillers, a fly ash slurry, an emulsion, and a rubberized asphalt mixture, were used along with a control section with no crack filler material on a 2.5 mile section of Cerro Gordo Trunk Route S-25 south of the town of Thornton. This report discusses the construction and performance of each filler material and makes recommendations concerning future use of any of the materials used.

Evaluation of Preformed Neoprene Joint Seals, HR-318, 1994

Most pavement contraction joint seals in Iowa, in general, have been performing in less than a satisfactory manner. The effective life of the seals, in maintaining a watertight joint, has been only from two to five years. In search of improvements, research was proposed to evaluate preformed neoprene joint seals. The performance of those seals was to be compared mainly with the hot poured rubberized asphalt sealants and cold applied silicone sealants or other sealants commonly used at the time this research began. Joint designs and methods of sawing were also investigated. All evaluations were done in new portland cement concrete (PCC) pavements. Three projects were initially selected and each included a research section of joint sealing. Some additional sites were later added for evaluation. Several joint sealants were evaluated at each research site. The various sites included high, medium and low levels of traffic. Evaluations were done over a five-year period. Neoprene joint seals provided better performance than hot or cold field formed joints.

Asphalt Cement Concrete Longitudinal Joint Adhesive Crafco PN 34524 (Iowa DOT New Product C-98-7), HR-2084, 2000

The joint between two lanes of asphalt pavement is often the first area of a roadway which shows signs of deterioration and requires maintenance. As the final lift of hot asphalt is being placed in a construction project, it is being forced p against the adjoining lane of cold asphalt, forming the longitudinal joint. The mating of the two lanes, to form a high quality seal, is often not fully successful and later results in premature stripping or raveling as water enters the unsealed joint. The application of a hot poured rubberized asphaltic joint sealant along the joint face in the final stage of construction should help to form a watertight joint seal. A new product, especially formulated for the longitudinal joint in asphalt pavements was proposed to improve joint sealing. The following describes the experimental application of the new product, Crafco, PN 34524.

Sprinkle Treatment of Asphalt Surfaces, HR-199, 1984

Methods of improving highway safety are of major concern to everyone who is involved in the planning, development and construction of improvements of our vast highway network. Other major concerns are the conservation of our rapidly disappearing sources of energy and quality building materials. This research is devoted to further exploration of a process which will: 1. help preserve higher quality aggregates; and, 2. improve the frictional characteristics and surface texture of asphalt pavement surfaces. Sprinkle treatment of asphalt concrete pavement surfaces with a non-polishing aggregate, a procedure which was developed in Europe, is one method which has shown promise in accomplishing the above listed objectives. This research seeks to explore the feasibility and cost effectiveness of using standard asphalt mixtures of local, less expensive aggregates for surface courses followed by a surface sprinkle treatment of a hard, durable, non-polishing layer of precoated chips to produce a durable, non-skid pavement surface for safe highway travel. Three standard mixture types are being evaluated for aggregate retention characteristics and six sprinkle aggregates are being evaluated for durability, polishing and friction characteristics. In addition, measurements of the surface texture by the silicone putty method are being made. Another feature of this research is the evaluation of a rubberized asphalt material called Overflex MS as a crack filler. It has been reported that the material could be beneficial in reducing reflective cracking. The project was begun in July of 1978 and was completed in August. A review made in the spring of 1979 indicates very satisfactory performance. It was determined from slide photos taken after construction and again in the spring that aggregate retention was very good. However, many cracks had reflected indicating that the Overflex MS had not been effective. Follow up friction test results and texture analysis were also very good. The results of these tests are shown in Appendix A.

A Study on the Use of Fabric to Retard Reflective Cracking Over Widened Joints, MLR-88-4, 1992

Reflective cracking of asphalt resurfacing has been a concern for a long time. Years ago wire mesh was used to control widening cracks. More recently it has been fabrics or fiberglass. In 1986, part of the proposed fabric was deleted from projects in different parts of Iowa with various histories and designs. These projects were monitored in 1988, 1989, 1990 and 1992 with only the thin (3 inch) overlays on newly widened pavements showing a significantly greater percentage of cracks in the areas where the fabric was deleted.

Prevention of Reflection Cracking in Asphalt Overlays with Structofors, Petromate, and Cerex, HR-158, 1977

This report presents construction methods and results using three reinforcing fabrics to prevent reflection cracking in an asphalt overlay. The original highway in the rural area was Portland Cement Concrete 20 feet wide. It was widened by adding 2 feet of asphaltic concrete 10 inches deep on each side prior to resurfacing. Data are presented for the widening joint and transverse cracks in the rural area and for the random cracking in the urban area.

Synthetic Fabric to Improve Structural Capacity in Asphalt Overlays, HR-516, 1984

Iowa's first field application of synthetic engineering fabrics was on research project HR-158, "Prevention of Reflective Cracking in Asphalt Overlays". This research placed in September 1971 used three different engineering fabrics. A final report concluding generally favorable performance was distributed in May 1977. There have been a number of Iowa engineering fabric installations since that initial project.

Floyd County, HR-1026, 1983

On May 18, 1983, Robert Shelquist, Don Jordison and John Roland made a field examination of the test and control sections with the purpose of evaluating the performance of the fabrics as compared with each other and as compared with the control sections.

Performance of Reinforcement Fabric Used Under Asphaltic Concrete Overlays, MLR-83-03, 1983

The 1982 cost of a two-inch asphaltic concrete overlay, with fabric, was an average of 85% of the cost of a three-inch overlay (see attached calculations). A structural number can be assigned to the extra inch of overlay, whereas it is doubtful that any number can be assigned to the fabric. The observations made on the projects in this report leave little reason to be optimistic on the use of fabrics under asphalt overlays. This is especially true of the Floyd, Dallas and Clarke county projects. A great amount of fabric is being used nationwide for this purpose, probably more from sales promotion than from actual documented performance. Full scale field testing is continuing each time a project is let utilizing fabric reinforcement under asphaltic concrete overlays. It has already become apparent that the use of fabrics in AC overlays is not always cost effective.