Molecular models of a hydrated calcite mineral surface     

Thomas D. Perry IV  Randall T. Cygan 《Geochimica et cosmochimica acta》2007,71(24):5876-5887

Hydrated mineral surfaces play an important role in many processes in biological, geological, and industrial applications. An energy force field was developed for molecular mechanics and molecular dynamics simulations of hydrated carbonate minerals and was applied to investigate the behavior of water on the calcite surface. The force field is a significant development for large-scale molecular simulations of these systems, and provides good agreement with experimental and previous modeling results. Simulations indicate that water molecules are significantly ordered near the calcite surface. The predominant surface configuration (75-80%) results from coordination of a water molecule with a single calcium cation-carbonate anion pair, while the less common situation involves water coordination with two ion pairs. Surface restructuring and variation in coordination in the water layers results in distinct distances for water oxygens above the calcite surface—a two-component first monolayer (2.3 and 3.0 Å) and a secondary monolayer (5.0 Å). The different coordinations also alter lateral displacement, hydrogen bonding, and surface-normal orientation of the water molecules. The ordering of water molecules and the formation of a unique hydrogen bonding network at the calcite surface influence the physical properties of the interfacial water. Surface exchange of water molecules is observed by molecular dynamics simulation to occur at a rate of one exchange per 10 ps. Diffusion coefficients derived from mean square displacement analysis of atomic trajectories indicate a dependence of water transport based on the distance of the water molecules from the calcite surface.  相似文献   

On determining the electron density distribution of the solar corona from K-coronameter data     

Martin D. Altschuler  R. Michael Perry 《Solar physics》1972,23(2):410-428

The electron density distribution of the inner solar corona (r 2 R ) as a function of latitude, longitude, and radial distance is determined from K-coronameter polarization-brightness (pB) data. A Legendre polynomial is assumed for the electron density distribution, and the coefficients of the polynomial are determined by a least-mean-square regression analysis of several days of pB-data. The calculated electron density distribution is then mapped as a function of latitude and longitude. The method is particularly useful in determining the longitudinal extent of coronal streamers and enhancements and in resolving coronal features whose projections on the plane of the sky overlap.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

THE SINGAPORE GROWTH TRIANGLE: STATE,CAPITAL AND LABOUR AT A NEW FRONTIER IN THE WORLD ECONOMY     

Martin Perry Ph.D. 《Singapore journal of tropical geography》1991,12(2):138-151

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Towards a Political Geography of Corruption     

Peter Perry 《New Zealand geographer》1985,41(1):2-7

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IV. Water resource modelling using remote sensing and object-oriented simulation     

Harlan L. McKim  E. Alan Cassell  Perry J. Lapotin 《水文研究》1993,7(2):153-165

Remote sensing technology has matured significantly over the past decade. Operational satellites provide reliable, periodic coverage for all areas of the Earth. Data from these satellites are in a digital format that provides enhanced flexibility in hydrological modelling. Considerable advances in acquiring hydrological data from airborne and in situ sensors have also been achieved. Additionally, data from non-traditional remote sources such as weather radar from which spatial and temporal rainfall rates may be estimated are widely available. These new data acquisition capabilities have been paralleled by equal advancements in digital array processing and geographic information systems, which allow the effective extraction of both temporal and spatial information. This paper examines the use of object-oriented programming techniques to create dynamic hydrological models, and explores their potential to receive real and near real-time data from remote sensors as input to improve hydrological forecasting. In particular, the COE SSARR model is used to illustrate how an established hydrological model may be adapted to create a dynamic object model.  相似文献   

The Preservation of Historic Buildings in Urban New Zealand: Precedent,Practice and Policy1     

P. J. Perry  K. Galletly 《New Zealand geographer》1984,40(2):100-104

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Lava lakes on Io: observations of Io's volcanic activity from Galileo NIMS during the 2001 fly-bys     

Rosaly M.C Lopes  Lucas W Kamp  Peter Mouginis-Mark  Jani Radebaugh  Jason Perry  R.W Carlson  the Galileo NIMS  SSI Teams 《Icarus》2004,169(1):140-174

Galileo's Near-Infrared Mapping Spectrometer (NIMS) obtained its final observations of Io during the spacecraft's fly-bys in August (I31) and October 2001 (I32). We present a summary of the observations and results from these last two fly-bys, focusing on the distribution of thermal emission from Io's many volcanic regions that give insights into the eruption styles of individual hot spots. We include a compilation of hot spot data obtained from Galileo, Voyager, and ground-based observations. At least 152 active volcanic centers are now known on Io, 104 of which were discovered or confirmed by Galileo observations, including 23 from the I31 and I32 Io fly-by observations presented here. We modify the classification scheme of Keszthelyi et al. (2001, J. Geophys. Res. 106 (E12) 33 025-33 052) of Io eruption styles to include three primary types: promethean (lava flow fields emplaced as compound pahoehoe flows with small plumes <200 km high originating from flow fronts), pillanian (violent eruptions generally accompanied by large outbursts, >200 km high plumes and rapidly-emplaced flow fields), and a new style we call “lokian” that includes all eruptions confined within paterae with or without associated plume eruptions). Thermal maps of active paterae from NIMS data reveal hot edges that are characteristic of lava lakes. Comparisons with terrestrial analogs show that Io's lava lakes have thermal properties consistent with relatively inactive lava lakes. The majority of activity on Io, based on locations and longevity of hot spots, appears to be of this third type. This finding has implications for how Io is being resurfaced as our results imply that eruptions of lava are predominantly confined within paterae, thus making it unlikely that resurfacing is done primarily by extensive lava flows. Our conclusion is consistent with the findings of Geissler et al. (2004, Icarus, this issue) that plume eruptions and deposits, rather than the eruption of copious amounts of effusive lavas, are responsible for Io's high resurfacing rates. The origin and longevity of islands within ionian lava lakes remains enigmatic.  相似文献   

BUSINESS CLUSTERS IN THE SOUTH: A CRITICAL APPRAISAL FROM INDONESIAN EVIDENCE     

Martin Perry 《Singapore journal of tropical geography》2005,26(2):227-243

Advocacy of the advantages accruing to business clusters in developing economies has followed that in developed economies. With doubts emerging about the evidence for these in developed economies, it is therefore appropriate to review the experience in the developing world. A model of cluster emergence and growth has guided accounts of developing country clusters. Drawing on experience from Indonesia, doubts are raised about that model's prediction of the emergence of successful joint action in maintaining cluster advantages. Any advantages from clustering are insufficient to face development challenges arising from the globalisation of economic activity. The significance of business clusters in low income economies needs to be reviewed in the light of actual experience and the reappraisal emerging in developed or high income countries.  相似文献   

Editorial review/essay     

John S. Perry 《Climatic change》1990,17(1):9-12

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Biogeochemical Gradients: Microbes, Measurements, and Modeling     

Danielle Fortin  Thomas Pichler  Chad Saltikov 《Applied Geochemistry》2007,22(12):2567

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