Near‐infrared spectra of clinopyroxenes: Effects of calcium content and crystal structure     

Rachel L. KLIMA  M. Darby DYAR  Carlé M. PIETERS 《Meteoritics & planetary science》2011,46(3):379-395

Abstract– Pyroxenes are among the most common minerals in the solar system and are ideally suited for remote geochemical analysis because of the sensitivity of their distinctive spectra to mineral composition. Fe²⁺ is responsible for the dominant pyroxene absorptions in the visible and near‐infrared, but substitutions of other cations such as Ca²⁺ change the crystal structure and site geometries and thus the crystal field splitting energies of the Fe cations. To define spectral systematics resulting from major pyroxene cations (Ca²⁺, Mg²⁺, and Fe²⁺), we focus on a suite of pyroxenes synthesized with only Ca²⁺, Mg²⁺, and Fe²⁺ in the two octahedral sites, specifically examining the effect of Ca²⁺ on pyroxene absorption bands. The modified Gaussian model is used to deconvolve pyroxene spectra into component bands that can then be linked directly to crystal field absorptions. In orthopyroxenes and low‐Ca clinopyroxenes, Ca²⁺‐content has a strong and predictable effect on the positions of the absorption bands. At a threshold of Wo₃₀, the crystal field environment stagnates and the M2 bands cease to change significantly as more Ca²⁺ is added. At Wo₅₀, when most of the M2 sites are filled by Ca²⁺, band positions do not change drastically, although the presence and strengths of the 1 and 2 μm bands are affected by even trace amounts of Fe²⁺ in the M2 site. It is thus apparent that next‐nearest neighbors and the distortions they impose on the pyroxene lattice affect the electronic states around the Fe²⁺ cations and control absorption band properties.  相似文献   

Resource allocation for regional earthquake risk mitigation: a case study of Tehran,Iran   总被引：1，自引：1，他引：0  

Pantea Vaziri  Rachel A. Davidson  Linda K. Nozick  Mahmood Hosseini 《Natural Hazards》2010,53(3):527-546

This paper presents a new optimization model to help cities in seismically active developing countries decide (1) How much to spend on pre-earthquake mitigation versus waiting until after an event and paying for reconstruction or simply not rebuilding damaged buildings? (2) Which buildings to mitigate and how? and (3) Which buildings to reconstruct and how? It extends previously developed optimization models to consider the particular issues that arise in such countries. First, the model allows for the possibility that some damaged buildings will not be reconstructed immediately and keeps track of any lost building inventory. Second, buildings can be mitigated to, or when damaged, reconstructed to, any appropriate structural type and seismic design level. Finally, the model objectives include minimizing the chance of an extremely high death toll in any one earthquake and minimizing the average annual death toll across earthquakes. The model is illustrated through a case study analysis for Tehran, Iran.  相似文献   

Density profiles of galaxy groups and clusters from SDSS galaxy–galaxy weak lensing     

Rachel Mandelbaum  Uro&#; Seljak  Richard J. Cool  Michael Blanton  Christopher M. Hirata  Jonathan Brinkmann 《Monthly notices of the Royal Astronomical Society》2006,372(2):758-776

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Galaxy–galaxy weak lensing in the Sloan Digital Sky Survey: intrinsic alignments and shear calibration errors     

Christopher M. Hirata  Rachel Mandelbaum  Uro&#; Seljak  Jacek Guzik  Nikhil Padmanabhan  Cullen Blake  Jonathan Brinkmann  Tamas Budávari  rew Connolly  Istvan Csabai  Ryan Scranton  Alexander S. Szalay 《Monthly notices of the Royal Astronomical Society》2004,353(2):529-549

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Dissecting a galaxy: mass distribution of 2237+0305     

Cathryn M. Trott  Rachel L. Webster 《Monthly notices of the Royal Astronomical Society》2002,334(3):621-630

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Cosmology from 3 years of WMAP CMB data     

Rachel Bean   《New Astronomy Reviews》2006,50(11-12):850

The combined 3 year observations from the Wilkinson Microwave Anisotropy Probe (WMAP) have yielded full-sky temperature and polarization maps in five frequency bands (K, Ka, Q, V, W) between 23 and 94 GHz. In this article we discuss the cosmological implications of these observations. The combination of temperature and polarization data leads to a significant improvement in the measurement of the reionization optical depth τ = 0.093 ± 0.029. This, in turn, breaks a number of key degeneracies present in the constraints from temperature measurements alone allowing the WMAP CMB data on its own to offer a powerful insight into the universe’s constituents and the processes that generated the initial conditions for structure formation.  相似文献   

Persistent Near-Surface Flow Structures from Local Helioseismology     

Rachel Howe  R. W. Komm  D. Baker  L. Harra  L. van Driel-Gesztelyi  R. S. Bogart 《Solar physics》2015,290(11):3137-3149

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Governing geoengineering research: why, when and how?     

Lisa Dilling  Rachel Hauser 《Climatic change》2013,121(3):553-565

Research on geoengineering – deliberate management of the Earth’s climate system – is being increasingly discussed within the science and policy communities. While justified as necessary in order to expand the range of options available to policy makers in the future, geoengineering research has already engendered public controversy. Proposed projects have been protested or cancelled, and calls for a governance framework abound. In this paper, we consider the reasons why geoengineering research might be subject to additional governance and suggest mechanisms that might be usefully applied in developing such a framework. We consider criteria for governance as raised by a review of the growing literature on geoengineering and other controversial scientific topics. We suggest three families of concern that any governance research framework must respond to: the direct physical risks of the research; the transparency and responsibility in decision making for the research; and the larger societal meanings of the research. We review what mechanisms might be available to respond to these three families of concern, and consider how these might apply to geoengineering research.  相似文献   

Results from the Wide Angle Search for Planets Prototype (WASP0) – II. Stellar variability in the Pegasus field     

Stephen R. Kane  T. A. Lister  rew Collier Cameron  Keith Horne  David James  Don L. Pollacco  Rachel A. Street  Yiannis Tsapras 《Monthly notices of the Royal Astronomical Society》2005,362(1):117-126

Recent wide field photometric surveys, which target a specific field for long durations, are ideal for studying both long- and short-period stellar variability. Here, we report on 75 variable stars detected during the observations of a field in Pegasus using the Wide Angle Search for Planets Prototype (WASP0) instrument, 73 of which are new discoveries. The variables detected include 16 δ Scuti stars, 34 eclipsing binaries, 3 BY Draconis stars and 4 RR Lyraes. We estimate that the fraction of stars in the field brighter than   V ∼ 13.5  exhibiting variable behaviour with an amplitude greater than 0.6 per cent rms is ∼0.4 per cent. These results are compared with other wide field stellar variability surveys, and implications for detecting transits due to extra-solar planets are discussed.  相似文献   

Intrinsic galaxy alignments from the 2SLAQ and SDSS surveys: luminosity and redshift scalings and implications for weak lensing surveys     

Christopher M. Hirata  Rachel Mandelbaum †  Mustapha Ishak  Uro&#; Seljak  Robert Nichol  Kevin A. Pimbblet  Nicholas P. Ross  David Wake 《Monthly notices of the Royal Astronomical Society》2007,381(3):1197-1218

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