Space filling by nucleation and growth in chemical vapor deposition of diamond

Phase transformations, including chemical vapor deposition (CVD) of diamond, taking place by nucleation and growth are commonly described by Avrami or Johnson-Mehl type models. In order to avoid the restrictions of such models with respect to assumptions concerning nucleation rates and growth velocities, the variation with time of nucleation and growth of diamond particles during the deposition of microwave plasma-assisted CVD was studied. The size distributions obtained from image analysis enabled us to trace back details of the nucleation and growth history. Three sources of particle formation were operating during deposition. A general growth law suitable for all particles did not exist. These observations limited the applicability of Avrami-type models to describe space filling. Computer simulation of surface coverage and particle growth was successful because one particular mode of particle formation and growth dominated surface coverage. Based on image analysis and the determination of the film growth rate, the evolution of the diamond volume fraction with time, starting from three-dimensional particle growth followed by a continuous transition to one-dimensional film growth, was describe

The lead and copper isotopic composition of copper ores from the Sierra Morena (Spain)

The paper presents lead and copper isotope analyses of 51 copper ore samples from the Sierra Morena, South of Spain. They are from ancient mines of the Iberian Peninsula collected by Claude Domergue during various field campaigns in the central Sierra Morena from 1965 to 1975. Most samples consist of copper oxide minerals such as malachite, azurite and chrysocolla and stem from the surficial sections of the ore deposits. The aim of the study was to supplement the existing reference data bank on lead isotopic compositions of ancient copper mines from the Iberian Peninsula. This is particularly important for the Sierra Morena for which data exist mostly for lead-zinc but not for copper ores. The lead isotope ratios range from 18.165 to 19.712 (206Pb/204Pb), 0.797 to 0.859 (207Pb/206Pb) and 1.955 to 2.108 (208Pb/206Pb). Two separate fields can be distinguished with a major field intermediate between the ore deposits from SW and SE Spain and a second at higher 208Pb/206Pb values. Copper isotopes were analysed additionally to provide further constraints for provenance studies. The copper isotope ratios δ65Cu of the copper oxide samples are mostly positive and higher on average than those of sulphide minerals. They are a potential tool to distinguish between either sulphide ore or oxide ore deposit derived artefacts.En este artículo, presentamos los resultados de los análisis isotópicos (plomo y cobre) llevados a cabo sobre 51 muestras de mineral de cobre de Sierra Morena, Sur de España. Las muestras provienen de minas antiguas de la Península Ibérica, que habían sido recogidas por Claude Domergue en el curso de sus prospecciones en Sierra Morena central, entre 1965 y 1975. La mayoría de las muestras consiste de minerales de óxido de cobre como malaquita, azurita y crisocola que se encuentran en la superficie de los depósitos. El objetivo de este estudio es de contribuir a la base hoy disponible de datos de isótopos de plomo de las antiguas minas de cobre en la Península Ibérica. Este objetivo es particularmente importante puesto que la mayoría de los datos publicados de Sierra Morena se refieren a minerales de plomo-zinc. Las proporciones de isótopos de plomo varían entre 18.165 y 19.713 206Pb/204Pb, de 0.797 a 0.859 207Pb/206Pb, y de 1.955 a 2.108 208Pb/206Pb. Se pueden distinguir dos zonas independientes: una zona principal que se sitúa entre los depósitos de España del sudoeste y sudeste y una segunda zona con las proporciones de isótopos de plomo más altas. Además, los isótopos del cobre fueron analizados para suplir restricciones adicionales en los estudios de proveniencia. Las proporciones de isótopos de cobre, δ65Cu/63Cu, fueron analizadas en los óxidos de cobre y son en la mayor parte positivas y mas altas en medio que las proporciones δ65Cu de los sulfuros de cobre. Los resultados presentan un instrumento eficiente para distinguir los artefactos elaborados de minerales de sulfuros de cobre o de minerales de óxido de cobre

Piezoelectric osteotomy in hand surgery: first experiences with a new technique

BACKGROUND: In hand and spinal surgery nerve lesions are feared complications with the use of standard oscillating saws. Oral surgeons have started using a newly developed ultrasound bone scalpel when performing precise osteotomies. By using a frequency of 25–29 kHz only mineralized tissue is cut, sparing the soft tissue. This reduces the risk of nerve lesions. As there is a lack of experience with this technique in the field of orthopaedic bone surgery, we performed the first ultrasound osteotomy in hand surgery. METHOD: While performing a correctional osteotomy of the 5th metacarpal bone we used the Piezosurgery(® )Device from Mectron [Italy] instead of the usual oscillating saw. We will report on our experience with one case, with a follow up time of one year. RESULTS: The cut was highly precise and there were no vibrations of the bone. The time needed for the operation was slightly longer than the time needed while using the usual saw. Bone healing was good and at no point were there any neurovascular disturbances. CONCLUSION: The Piezosurgery(® )Device is useful for small long bone osteotomies. Using the fine tip enables curved cutting and provides an opportunity for new osteotomy techniques. As the device selectively cuts bone we feel that this device has great potential in the field of hand- and spinal surgery

Citizen science for observing and understanding the Earth

Citizen Science, or the participation of non-professional scientists in a scientific project, has a long history—in many ways, the modern scientific revolution is thanks to the effort of citizen scientists. Like science itself, citizen science is influenced by technological and societal advances, such as the rapid increase in levels of education during the latter part of the twentieth century, or the very recent growth of the bidirectional social web (Web 2.0), cloud services and smartphones. These transitions have ushered in, over the past decade, a rapid growth in the involvement of many millions of people in data collection and analysis of information as part of scientific projects. This chapter provides an overview of the field of citizen science and its contribution to the observation of the Earth, often not through remote sensing but a much closer relationship with the local environment. The chapter suggests that, together with remote Earth Observations, citizen science can play a critical role in understanding and addressing local and global challenges