Tooth Eruption: The Regulation of a Localized, Bilaterally Symmetrical Metabolic Event in Alveolar Bone

Tooth eruption is a complicated process by which developing teeth are moved within the jaws to their functional position. The usual model chosen to study this process, the erupted rodent incisor, differs both structurally and functionally from the human dentition and conclusions drawn from these studies are not directly applicable to tooth eruption in human beings. We have studied the eruption of developing permanent premolars in dogs and present evidence by scanning electron microscopy for regional differences in metabolic activities on bone surfaces of the crypt during eruption. We review evidence that these polarizations of alveolar bone metabolism are cell-mediated, dependent upon the dental follicle, independent of root formation or the tooth itself and that tooth eruption depends on coordination of these activities by the dental follicle. We conclude that tooth eruption is a localized, bilaterally symmetrical event in alveolar bone and that this is an excellent model system in which to study the regulation of alveolar bone metabolism

Hidden persuaders on film: Exploring young people’s lived experience through visual essays

The Hidden Persuaders research group examines ‘brainwashing’ in the Cold War for the roles, real and imagined, played by psychologists, psychiatrists and psychoanalysts. Our project engaged young people in an exploration of the history of fears about brainwashing, and enabled them to explore their thoughts and ideas about the forces that shape their lives in contemporary society, through film-making. Working with three schools in the Camden area of London, our partners at the Derek Jarman Lab media hub, Birkbeck, University of London, and an artist facilitator (Lizzie Burns), we invited Year 12 students to learn filming and editing to create their own short video essays. The use of this format resulted in a significant depth of engagement and generated a wealth of creative responses. The various stages of the film-making process enabled the students to work out the terms of an argument and to consider how best to express it concisely. In the resulting films, they came up with a variety of forms of visual storytelling, and used the medium to express their thoughts, feelings and ideas in diverse ways, giving us a range of new perspectives which we could consider in relation to our historical research

Remote sensing applications to hydrologic modeling in the southern Sierra Nevada and portions of the San Joaquin Valley, volume 1

The author has identified the following significant results. Characteristics of LANDSAT MSS imagery present problems in using satellite radiation measurements to estimate the shortwave albedo of an alpine snow cover. Every 15 minute USGS quadrangle contains over 100,000 pixels which poses a computation problem if each pixel is to be evaluated individually. The sampling interval may be sufficiently great to mask some effects of terrain and vegetation on reflectance. Three frames of LANDSAT imagery are needed for complete coverage of the study area, yet less than one third of the area coverage from each frame covers an area of interest. Because of distortions inherent in the imagery, information regarding spacecraft altitude, attitude, and position must be statistically derived with respect to ground control points in the image whose geodetic locations are known. An inspection of shade points indicates that up to one third of the most heavily snow covered areas may saturate in bands 4 through 6. LANDSAT's 9 day repeat cycle is not optimum for snow cover reflectance modeling because the most pronounced changes in albedo occur most nearly following a new snowfall. Such a snowfall, occurring between overpasses, is inadequately represented by extrapolation from the previous overpasses

Molecular dynamics simulations of lead clusters

Molecular dynamics simulations of nanometer-sized lead clusters have been performed using the Lim, Ong and Ercolessi glue potential (Surf. Sci. {\bf 269/270}, 1109 (1992)). The binding energies of clusters forming crystalline (fcc), decahedron and icosahedron structures are compared, showing that fcc cuboctahedra are the most energetically favoured of these polyhedral model structures. However, simulations of the freezing of liquid droplets produced a characteristic form of ``shaved'' icosahedron, in which atoms are absent at the edges and apexes of the polyhedron. This arrangement is energetically favoured for 600-4000 atom clusters. Larger clusters favour crystalline structures. Indeed, simulated freezing of a 6525-atom liquid droplet produced an imperfect fcc Wulff particle, containing a number of parallel stacking faults. The effects of temperature on the preferred structure of crystalline clusters below the melting point have been considered. The implications of these results for the interpretation of experimental data is discussed.Comment: 11 pages, 18 figues, new section added and one figure added, other minor changes for publicatio

Surface-reconstructed Icosahedral Structures for Lead Clusters

We describe a new family of icosahedral structures for lead clusters. In general, structures in this family contain a Mackay icosahedral core with a reconstructed two-shell outer-layer. This family includes the anti-Mackay icosahedra, which have have a Mackay icosahedral core but with most of the surface atoms in hexagonal close-packed positions. Using a many-body glue potential for lead, we identify two icosahedral structures in this family which have the lowest energies of any known structure in the size range from 900 to 15000 lead atoms. We show that these structures are stabilized by a feature of the many-body glue part of the interatomic potential.Comment: 9 pages, 8 figure

Geobase Information System Impacts on Space Image Formats

As Geobase Information Systems increase in number, size and complexity, the format compatability of satellite remote sensing data becomes increasingly more important. Because of the vast and continually increasing quantity of data available from remote sensing systems the utility of these data is increasingly dependent on the degree to which their formats facilitate, or hinder, their incorporation into Geobase Information Systems. To merge satellite data into a geobase system requires that they both have a compatible geographic referencing system. Greater acceptance of satellite data by the user community will be facilitated if the data are in a form which most readily corresponds to existing geobase data structures. The conference addressed a number of specific topics and made recommendations