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61.
Dexter Perkins III Eric J. Essene Edgar F. Westrum Jr. Victor J. Wall 《Contributions to Mineralogy and Petrology》1977,64(2):137-147
Recent low temperature, adiabatic calorimetric heat capacity measurements for grossular have been combined with DSC measurements to give entropies up to 1000 K. In conjunction with enthalpy of solution values for grossular, these data have yielded H
f
o
(298.15K) and G
f
o
(298.15K) values of –1583.2 ± 3.5 and –1496.74 ± 3.7 kcal mol–1 respectively. For 15 reactions in the CaO-Al2O3-SiO2-H2O system, thermodynamically calculated P-T curves have been compared with experimental reversals and have shown good agreement in most cases. Calculations indicate that gehlenite is probably totally disordered. Estimates of zoisite and lawsonite entropies are consistent with the phase equilibrium and grossular data, but estimates of the entropies of pyrope and andradite show large discrepancies when compared with experimental reversals.Contribution no. 600 from the Mineralogical Laboratory, The Department of Geology and Mineralogy, The University of Michigan, Ann Arbor, Michigan 48109, USA 相似文献
62.
Melanie Wall 《New Zealand geographer》1997,53(2):40-45
Since the colonisation of Aotearoa / New Zealand by Pakeha, Maori have been stereotypically imagined as the Black Other. One of the principal mechanisms for the continued perpetuation of this racialised discourse is the representation of ‘race’ through stereotypes in the media. ‘New’ cultural geography provides a theoretical foundation to interrogate stereotypical (re)formations of Maori identity. I conclude that the use of the stereotype in the (re)formation of Maori identity further demarcates and constrains Maori within the perennial position of the Black Other. Only through a retheorisation of difference (which moves beyond the construction of the Maori ‘race’ through stereotypes), can the impact of racialisation be effectively resisted. 相似文献
63.
The elastic constants of a crystal under stress, defined as the second derivative of the crystal free energy with respect to strain, require a correction related to the static pressure at non-zero pressures. The corrections required for the elastic constants calculated by the free energy minimisation code PARAPOCS are described and tested by comparison with the elastic constants calculated numerically by applying small stresses in the appropriate orientations to simulated crystals of fluorite, forsterite, α-quartz and albite. The corrected elastic constants are then used to investigate the extrapolation of the bulk and shear moduli (and hence also the seismic wave velocities V p and V s) of β-spinel and forsterite to upper mantle pressures. A Murnaghan equation, thirdorder Eulerian finite strain equation, second order polynomial equation and a logistic equation were all fitted to the simulated bulk and shear moduli between 0 and 3 GPa pressure. The parameters derived for these equations are used to extrapolate the bulk and shear moduli to 14 GPa and the results are compared to the simulated high pressure moduli. Over this pressure range, the second order polynomial provides the best extrapolation of the bulk modulus, but the use of the logistic equation results in the best extrapolation of the shear modulus. 相似文献
64.
65.
Steven R. Bohlen A. L. Boettcher V. J. Wall J. D. Clemens 《Contributions to Mineralogy and Petrology》1983,83(3-4):270-277
The melting of phlogopite-quartz and sanidine-quartz under vapor-absent conditions and in the presence of H2O-CO2 vapor have been determined from 5–20 kbar. In the lower crust (P=6–10 kbar), phlogopite + quartz melts incongruently to enstatite + liquid at temperatures as low as 710° C in the presence of H2O. When the activity of water is sufficiently reduced by addition of CO2, phlogopite + quartz undergoes a dehydration reaction to enstatite + sanidine + vapor, for example at 790±10° C, 5 kbar, with \(X_{H_2 O}^V\) =0.35. In the absence of vapor, phlogopite + quartz is stable up to a maximum temperature of 900° C in the crust; at higher temperatures this assemblage melts incongruently to enstatite + sanidine + liquid. The melting of sanidine-quartz in the presence of H2O-CO2 vapor shows marked topological differences from melting in the system albite-H2O-CO2, and as a result, apparent activity coefficients for water calculated from sanidine-quartz H2O-CO2 are less than those calculated from albite-H2O-CO2 by up to a factor of five. These data shed light on anatexis in the lower crust, but uncertainties related to ordering of Al and Si in natural and synthetic micas forestall a more rigorous analysis. Nevertheless, maximum temperatures for some granulite terranes can be established. 相似文献
66.
Measurements of the photodissociation constant for nitrous acid (j
HONO) were made at an urban site in Toronto, Canada, during the months of May–July 2005, using an optically thin actinometer. Operating details of the j
HONO monitor are reported, along with laboratory tests. Measurements of j
HONO were obtained for solar zenith angles ranging from 20–75∘, under clear and cloudy skies. Maximum error estimates on j
HONO under clear skies range from 11% at sunrise, to 4% at solar noon, with a minimum detection limit of 5.7 × 10−4/sec for our actinometer. Measured clear-sky values of j
HONO were compared with values calculated by a four-stream discrete ordinate radiative transfer (RT) model (ACD TUV version 4.1), and were found to be within better than 10% agreement for solar zenith angles < 65∘. For conditions of scattered cloud, enhancement and suppression of the j
HONO values occurred by as much as 16%–70%, and 59%–80%, respectively. The integrated band area of the nπ∗ transition for gas-phase nitrous acid yields an oscillator strength, f
= (1.06 ± 0.044)×10−3 (based on clear-sky data), 19.1% higher than the value reported by Bongartz et al. (1991). 相似文献
67.
Chris Simpson Martin Ward J. V. Wall 《Monthly notices of the Royal Astronomical Society》2000,319(3):963-976
It has been claimed by Taylor et al. that the low-redshift end of the K – z relation for radio galaxies is too bright by about half a magnitude owing to contributions from the obscured quasar nuclei. Such a result has major implications for the use of the K -band Hubble diagram in understanding the cosmological evolution of radio galaxies. In this paper we present 1–5-μm imaging data of a nearly complete sample of low-redshift radio galaxies; this approach allows us to determine accurately the strengths of any unresolved nuclear components in the galaxies. We detect nuclear sources in five targets, whose broad-band colours are consistent with reddened quasar spectra. In all the five cases the ratio of the inferred intrinsic near-infrared luminosity to the narrow-line luminosity is typical of quasars. We find a correlation between the inferred nuclear extinction and core-to-lobe ratio, which places constraints on the geometry of the torus. We find evidence for a shift of the K – z relation to fainter magnitudes, but by a much smaller amount (∼0.1 mag) than determined by Taylor et al. Under the assumption that the nuclear sources in radio galaxies have the same intrinsic near-infrared spectra as quasars, our multiwavelength images allow us to limit any possible shift to less than 0.3 mag. 相似文献
68.
M. Magliocchetti S. J. Maddox J. V. Wall C. R. Benn G. Cotter 《Monthly notices of the Royal Astronomical Society》2000,318(4):1047-1067
We present spectra for a sample of radio sources from the FIRST survey, and use them to define the form of the redshift distribution of radio sources at mJy levels. We targeted 365 sources and obtained 46 redshifts (13 per cent of the sample). We find that our sample is complete in redshift measurement to R ∼18.6, corresponding to z ∼0.2. Galaxies were assigned spectral types based on emission-line strengths. Early-type galaxies represent the largest subset (45 per cent) of the sample and have redshifts 0.15≲ z ≲0.5; late-type galaxies make up 15 per cent of the sample and have redshifts 0.05≲ z ≲0.2; starbursting galaxies are a small fraction (∼6 per cent), and are very nearby ( z ≲0.05). Some 9 per cent of the population have Seyfert 1/quasar-type spectra, all at z ≳0.8, and 4 per cent are Seyfert 2 type galaxies at intermediate redshifts ( z ∼0.2).
Using our measurements and data from the Phoenix survey (Hopkins et al.), we obtain an estimate for N ( z ) at S1.4 GHz ≥1 mJy and compare this with model predictions. At variance with previous conclusions, we find that the population of starbursting objects makes up ≲5 per cent of the radio population at S ∼1 mJy. 相似文献
Using our measurements and data from the Phoenix survey (Hopkins et al.), we obtain an estimate for N ( z ) at S
69.
Gianfranco De Zotti Marcella Massardi Mattia Negrello Jasper Wall 《Astronomy and Astrophysics Review》2010,18(1-2):1-65
We review the statistical properties of the main populations of radio sources, as emerging from radio and millimeter sky surveys. Recent determinations of local luminosity functions are presented and compared with earlier estimates still in widespread use. A number of unresolved issues are discussed. These include: the (possibly luminosity-dependent) decline of source space densities at high redshifts; the possible dichotomies between evolutionary properties of low- versus high-luminosity and of flat- versus steep-spectrum AGN-powered radio sources; and the nature of sources accounting for the upturn of source counts at sub-milli-Jansky (mJy) levels. It is shown that straightforward extrapolations of evolutionary models, accounting for both the far-IR counts and redshift distributions of star-forming galaxies, match the radio source counts at flux-density levels of tens of μJy remarkably well. We consider the statistical properties of rare but physically very interesting classes of sources, such as GHz Peak Spectrum and ADAF/ADIOS sources, and radio afterglows of γ-ray bursts. We also discuss the exploitation of large-area radio surveys to investigate large-scale structure through studies of clustering and the Integrated Sachs–Wolfe effect. Finally, we briefly describe the potential of the new and forthcoming generations of radio telescopes. A compendium of source counts at different frequencies is given in Supplementary Material. 相似文献
70.
Developing carbon budgets for UK agriculture, land-use, land-use change and forestry out to 2022 总被引:1,自引:0,他引:1
Dominic Moran Michael MacLeod Eileen Wall Vera Eory Alistair McVittie Andrew Barnes R. M. Rees Cairistiona F. E. Topp Guillaume Pajot Robin Matthews Pete Smith Andrew Moxey 《Climatic change》2011,105(3-4):529-553
This paper derives a notional future carbon budget for UK agriculture, land use, land use change and forestry sectors (ALULUCF). The budget is based on a bottom-up marginal abatement cost curve (MACC) derived for a range of mitigation measures for specified adoption scenarios for the years 2012, 2017 and 2022. The results indicate that in 2022 around 6.36 MtCO2e could be abated at negative or zero cost. Furthermore, in the same year, over 17% of agricultural GHG emissions (7.85 MtCO2e) could be abated at a cost of less than the 2022 Shadow Price of Carbon (£34 (tCO2e)???1). The development of robust MACCs faces a range of methodological hurdles that complicate cost-effectiveness appraisal in ALULUCF relative to other sectors. Nevertheless, the current analysis provides an initial route map of efficient measures for mitigation in UK agriculture. 相似文献