Crystal Growth in the Presence of Surface Melting: Novel Behavior of the Principal Facets of Ice

We present measurements of the growth rates of the principal facet surfaces of ice from water vapor as a function of supersaturation over the temperature range -2 C > T > -40 C. Our data are well described by a dislocation-free layer-nucleation model, parameterized by the attachment coefficient as a function of supersaturation \alpha(\sigma) = Aexp(-\sigma_0/\sigma). The measured parameters A(T) and \sigma_0(T) for the basal and prism facets exhibit a complex behavior that likely originates from structural changes in the ice surface with temperature, in particular the onset and development of surface melting for T > -15 C. From \sigma_0(T) we extract the terrace step energy \beta(T) as a function of temperature for both facet surfaces. As a basic property of the equilibrium ice surface, the step energy \beta(T) may be amenable to calculation using molecular dynamics simulations, potentially yielding new insights into the enigmatic surface structure of ice near the triple point

Measurements of Growth Rates of (0001) Ice Crystal Surfaces

We present measurements of growth rates of the (0001) facet surface of ice as a function of water vapor supersaturation over the temperature range $-2$ $\geq T\geq -40$ C. From these data we infer the temperature dependence of premelting on the basal surface and the effects of premelting on the ice growth dynamics. Over this entire temperature range the growth was consistent with a simple 2D nucleation model, allowing a measurement of the critical supersaturation $\sigma _{0}(T)$ as a function of temperature. We find that the 2D nucleation barrier is substantially diminished when the premelted layer is partially developed, as indicated by a reduced $\sigma _{0},$ while the barrier is higher both when the premelted layer is fully absent or fully developed

Factorial Design Applied to Waste Immobilisation in Geopolymer-based Systems

Concentrated alkali, ground glass and air pollution control residues were mixed in various proportions and cured for up to 28 days. These blocks were tested in strength and analysed by thermal gravimetric analysis to assess the success of the geopolymerisation process. A Taguchi factorial design approach was then adopted to investigate the effects of different variables upon the strength development of these blocks

Application of nanoscale zero valent iron (NZVI) for groundwater remediation in Europe

Purpose: Nanoscale zero valent iron (NZVI) is emerging as a new option for the treatment of contaminated soil and groundwater targeting mainly chlorinated organic contaminants (e.g., solvents, pesticides) and inorganic anions or metals. The purpose of this article is to give a short overview of the practical experience with NZVI applications in Europe and to present a comparison to the situation in the USA. Furthermore, the reasons for the difference in technology use are discussed. Method: The results in this article are based on an extensive literature review and structured discussions in an expert workshop with experts from Europe and the USA. The evaluation of the experiences was based on a SWOT (strength, weakness, opportunity, threat) analysis. Result: There are significant differences in the extent and type of technology used between NZVI applications in Europe and the USA. In Europe, only three full-scale remediations with NZVI have been carried out so far, while NZVI is an established treatment method in the USA. Bimetallic particles and emulsified NZVI, which are extensively used in the USA, have not yet been applied in Europe. Economic constraints and the precautionary attitude in Europe raise questions regarding whether NZVI is a cost-effective method for aquifer remediation. Challenges to the commercialization of NZVI include mainly non-technical aspects such as the possibility of a public backlash, the fact that the technology is largely unknown to consultants, governments and site owners as well as the lack of long-term experiences. Conclusion: Despite these concerns, the results of the current field applications with respect to contaminant reduction are promising, and no major adverse impacts on the environment have been reported so far. It is thus expected that these trials will contribute to promoting the technology in Europ

High-temperature ceramic coatings used in aero engine environments

This paper reviews the role of ceramic coatings technology in the hot sections of modern gas turbine engines by contrasting the role of surface engineering and coatings away from secondary reliance (i.e. the coating extending the life of the component and when the coating is lost or fails there is still an appreciable remnant life of the component) to prime reliance where the failure of the coating would result in a rapid failure of the component. To illustrate this change in design philosophy, the coating systems deployed in the HP turbine module in both shrouded and unshrouded configurations are discussed by comparing the performance of first and second generation coating systems

Epoxy composite dusts with and without carbon nanotubes cause similar pulmonary responses, but differences in liver histology in mice following pulmonary deposition

Inorganic chemical composition given as elemental weight% measured by standardless WDXRF. The three epoxy materials were measured as solid disks (4 cm in diameter, 1 cm high). For comparison, the results for CNT powder, previously published in [25], were added to the figure. Displayed axis 99.7 – 100 %. (PPTX 71 kb

Leisure and recreation in New Zealand: A research register (1974-1991)

In March 1990 the Department of Parks, Recreation and Tourism at Lincoln University was commissioned and funded, in part, by the Hillary Commission for Recreation and Sport (now Sport, Fitness and Leisure) to compile a comprehensive register of research into leisure and recreation in New Zealand. The financial support of the Hillary Commission and Lincoln University must be recognised.A register of research on leisure and recreation is important to researchers, practitioners and students as well as to the generral public. The value of such a register is enhanced when it is assembled in concise format for easy reference and when it is an extension of similar projects from previous years. This register builds usefully on, and complements the earlier bibliographies of Jorgensen (1974), Neave (1977) and Middleton (1981), all of which are referenced in the present publication. The major aim of this project is to make available to researchers, and others interested in research, a listing of much of the research which has been conducted on this topic since 1974. The volume will assist researchers to locate reports or papers of interest and for their work. It provides a reasonably comprehensive picture of recreation research activity in New Zealand. Leisure and recreation research in New Zealand has been undertaken by a wide range of individuals and organisations, with much of this research not being readily accessible. Access to this infonnation was gained by researchers and practitioners drawing our attention to people and organisations involved in relevant research which otherwise might have been neglected. In addition the papers and reports held by libraries, unpublished material and research in progress is included in this volume. It is envisaged that the register, and in particular the researcher/practitioner listing, will have the useful outcome of putting researchers in touch with each other. Experience suggests that direct discourse between researchers is often as valuable as reading formal research reports. Leisure and recreation has been defined in the broadest terms. embracing recreational tourism and travel, sport and physical education, arts and cultural activities, outdoor recreation, home-based leisure, non-formal learning, and including those activities and experiences not always recognised as recreational, such as drinking, gambling and vandalism. Similarly, the settings and situations are many and varied, including leisure centres, sports fields, libraries, urban sub-divisions, rivers, ski-fields, national parks, beaches, hotels, restaurants, botanical gardens, zoos and shopping centres to name but a few. The disciplinary focus includes research relating to the social, natural and medical sciences, as well as the practical application of these. The nature of research has been interpreted widely, and includes not only empirical research, but also work which is conceptual and has a policy focus

Characterisation of Hardened Cements Incorporating Simulant Intermediate Level Waste

Blended cement grouts are used in the UK for the encapsulation of various intermediate level nuclear wastes (ILW). To ensure the long term confidence in the durability of these grouts detailed knowledge of the exact nature of the hardened cement and its interaction with the waste material is essential. This PhD project aims to characterise various aged blended cement grouts utilised in the encapsulation of radioactive wastes. The grouts have been modified by the incorporation of simulant wastes produced to allow comparison with current in-service waste formulations. The grouts were analysed using a multi-technique approach to assess the reactions which have occurred within the cement matrix and their significance for successful encapsulation of the waste. The samples underwent investigation after long-term storage using a variety of techniques including thermal analysis, X-ray diffraction, electron microscopy and nuclear magnetic resonance spectroscopy. This suite of techniques allowed for the identification of various crystalline and amorphous phases produced during the hydration process and thereafter. Comparison was then made with similar samples containing no simulant waste to contrast the findings and possible effects upon the cement matrix and understand the implications for long-term storage. The blended cement samples showed a varying level of modification due to the inclusion of the simulant wastes. It was shown a major controlling factor was the relative solubility of the waste-form. A magnesium corrosion based simulant showed very little reaction in cement matrix, however aluminium based simulants typically displayed a wide range of reactions. Waste carbonate systems also displayed a high level of reaction, with the formation of new phases causing the destabilisation of AFt and encapsulation of the carbonate waste within AFm. The requirement for detailed characterisation of the C-S-H phase was confirmed with substantial changes being observed for samples containing waste flocs. Analysis of this phase proposed a high degree of substitution into the silicate chain lengths with the likely incorporation of additional metal cations into the structure via charge balancing. It was found all samples showed characteristics supporting the potential successful physical encapsulation of radioactive wastes. In addition to this various chemical immobilisation process have been studied, confirmed or proposed