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911.
The reaction of CN? with cyanoacetylene (HC3N), has been studied as a function of the HC3N pressure in a quadrupole tandem mass spectrometer. The mass spectra revealed the fast depletion of the CN? parent ion and formation of larger anions of rapidly growing size. Most of the ions observed were found to belong to two series of products: (HC3N)x·C2p+1N? and (HC3N)x·C2pN? resulting from the sequential additions of HC3N molecules and loss of HCN or HCCN molecules. The mechanism and energetics of the first two reaction steps are briefly discussed. The laboratory data are compared with those from the Cassini CAPS-ELS spectrometer. It is believed that the reactions observed could account for the growth of anions in Titan’s ionosphere. 相似文献
912.
a mamumuu m, m n¶rt; u a¶rt;a au, um ¶rt;umuau. aam, m a au ¶rt;unu a¶rt;a au n ¶rt;umuauu u n¶rt; nu a an¶rt; a u uu aa
,¶rt; h a ¶rt;umuauu. 相似文献
913.
Jana Konopásková Vlastislav Červený Reviewer I. Pšenčik 《Studia Geophysica et Geodaetica》1984,28(2):113-128
ma ama m n¶rt;u am[1]. u ama, m¶rt;au n unm ¶rt; uuauu ma m nau a¶rt;a. a uau ¶rt;m ma a muna . au mu mamau n [1], m m¶rt;au n ¶rt;am ¶rt;mam m mam ¶rt;a u amu aa mu. aumu amu, uauau n ma nuu ¶rt;a . m am ¶rt;am mumm mam a naama am, aa uu L
0
au n. aa, m am mam namuu aum m L
0
. amu aa mu u aumu amu, a m mam n ¶rt; u L
0
. u uu L
0
, anum¶rt; ma amu aa mu nuam, nu aua nam m, m uu L
0
auum. aumu amu, u L
0
um m uau m a uuu anum¶rt; u, mmmu a. uu L
0
, uuu nam. ma uam mumm mam ¶rt;a ¶rt;u naama am. uau ¶rt;m ma anum¶rt; u ma muna S, S u SS. 相似文献
914.
Part I of this contribution (Gardés et al. in Contrib Mineral Petrol, 2010) reported time- and temperature-dependent experimental growth of polycrystalline forsterite-enstatite double layers between
single crystals of periclase and quartz, and enstatite single layers between forsterite and quartz. Both double and single
layers displayed growth rates decreasing with time and pronounced grain coarsening. Here, a model is presented for the growth
of the layers that couples grain boundary diffusion and grain coarsening to interpret the drop of the growth rates. It results
that the growth of the layers is such that (Δx)2 ∝ t
1−1/n
, where Δx is the layer thickness and n the grain coarsening exponent, as experimentally observed. It is shown that component transport occurs mainly by grain boundary
diffusion and that the contribution of volume diffusion is negligible. Assuming a value of 1 nm for the effective grain boundary
width, the following Arrhenius laws for MgO grain boundary diffusion are derived: log D
gb,0Fo (m2/s) = −2.71 ± 1.03 and E
gbFo = 329 ± 30 kJ/mol in forsterite and log D
gb,0En (m2/s) = 0.13 ± 1.31 and E
gbEn = 417 ± 38 kJ/mol in enstatite. The different activation energies are responsible for the changes in the enstatite/forsterite
thickness ratio with varying temperature. We show that significant biases are introduced if grain boundary diffusion-controlled
rim growth is modelled assuming constant bulk diffusivities so that differences in activation energies of more than 100 kJ/mol
may arise. It is thus important to consider grain coarsening when modelling layered reaction zones because they are usually
polycrystalline and controlled by grain boundary transport. 相似文献
915.
916.
Magma evolution beneath Bequia,Lesser Antilles,deduced from petrology of lavas and plutonic xenoliths 总被引:1,自引:0,他引:1
Michal?Camejo-HarryEmail authorView authors OrcID profile Elena?Melekhova Jon?Blundy William?Attridge Richard?Robertson Thomas?Christopher 《Contributions to Mineralogy and Petrology》2018,173(10):77
Extrusive and intrusive igneous rocks represent different parts of a magmatic system and ultimately provide complementary information about the processes operating beneath volcanoes. To shed light on such processes, we have examined and quantified the textures and mineral compositions of plutonic and cumulate xenoliths and lavas from Bequia, Lesser Antilles arc. Both suites contain assemblages of iddingsitized olivine, plagioclase, clinopyroxene and spinel with rare orthopyroxene and ilmenite. Mineral zoning is widespread, but more protracted in lavas than xenoliths. Plagioclase cores and olivine have high anorthite (An?≤?98) and low forsterite (Fo?≤?84) compositions respectively, implying crystallisation from a hydrous mafic melt that was already fractionated. Xenolith textures range from adcumulate to orthocumulate with variable mineral crystallisation sequences. Textural criteria are used to organize the xenoliths into six groups. Amphibole, notably absent from lavas, is a common feature of xenoliths, together with minor biotite and apatite. Bulk compositions of xenoliths deviate from the liquid line of descent of lavas supporting a cumulate origin with varying degrees of reactive infiltration by evolved hydrous melts, preserved as melt inclusions in xenolith crystals. Volatile saturation pressures in melt inclusions indicate cumulate crystallization over a 162–571 MPa pressure range under conditions of high dissolved water contents (up to 7.8 wt% H2O), consistent with a variety of other thermobarometric estimates. Phase assemblages of xenoliths are consistent with published experimental data on volatile-saturated low-magnesium and high-alumina basalts and basaltic andesite from the Lesser Antilles at pressures of 200–1000 MPa, temperatures of 950–1050 °C and dissolved H2O contents of 4–7 wt%. Once extracted from mid-crustal mushes, residual melts ascend to higher levels and undergo H2O-saturated crystallization in shallow, pre-eruptive reservoirs to form phenocrysts and glomerocrysts. The absence of amphibole from lavas reflects instability at low pressures, whereas its abundance in xenoliths testifies to its importance in mid-crustal differentiation processes. A complex, vertically extensive (6 to at least 21 km depth) magmatic system is inferred beneath Bequia. Xenoliths represent fragments of the mush incorporated into ascending magmas. The widespread occurrence of evolved melts in the mush, but the absence of erupted evolved magmas, in contrast to islands in the northern Lesser Antilles, may reflect the relative immaturity of the Bequia magmatic system. 相似文献
917.
918.
Facies reconstructions are used in hydrogeology to improve the interpretation of aquifer permeability distribution. In the absence of sufficient data to define the heterogeneity due to geological processes, uncertainties in the distribution of aquifer hydrofacies and characteristics may appear. Geometric and geostatistical methods are used to understand and model aquifer hydrofacies distribution, providing models to improve comprehension and development of aquifers. However, these models require some input statistical parameters that can be difficult to infer from the study site. A three-dimensional reconstruction of a kilometer scale fine-grain dominated Cenozoic alluvial fan derived from more than 200 continuously cored, closely spaced, and regularly distributed wells is presented. The facies distributions were reconstructed using a genetic stratigraphic subdivision and a deterministic geostatistical algorithm. The reconstruction is only slightly affected by variations in the geostatistical input parameters because of the high-density data set. Analysis of the reconstruction allowed identification in the proximal to medial alluvial fan zones of several laterally extensive sand bodies with relatively higher permeability; these sand bodies were quantified in terms of volume, mean thickness, maximum area, and maximum equivalent diameter. These quantifications provide trends and geological scenarios for input statistical parameters to model aquifer systems in similar alluvial fan depositional settings. 相似文献
919.
R. Gutiérrez C. Roldán R. Gutiérrez-Sánchez J. M. Angulo 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(4):539-546
This paper evaluates the effects of using data observed on regular nested grids on the parameter estimates of a two-parameter
Gompertz diffusion model. This new spatial diffusion process represents a technically more complex stage of Gompertz modeling.
Firstly, the diffusion model is introduced through an appropriate transformation of a two-parameter Gaussian diffusion process.
Probabilistic characteristics of this model, such as the transition densities and the trend functions, are obtained. Secondly,
statistical estimation is considered using data obtained on a regular or irregular grid; the explicit expression of the likelihood
equations and the parameter estimators are given for regular grids. Finally, a simulation experiment illustrates the results
of this paper. 相似文献
920.
Pekka Teikari Vladimír Tobyáš Reviewer J. Janský 《Studia Geophysica et Geodaetica》1986,30(3):257-267
Summary The magnification achieved with the standard sine-wave method using seismometers with the calibration and signal coils tightly wound on the same coil former can be erroneous at high frequencies due to the mutual inductance between both coils. An attempt was made to eliminate this influence from the calibration data. The application of theoretical equations was tested with a short-period digital seismograph.
ma¶rt;ama auau aa nu ¶rt;uu ¶rt;uu maauu m m m a u amma ua u a au u¶rt;mumu ¶rt; ua u auau am, u u a¶rt;m n¶rt;m umu. a ¶rt;aa nnma muam auau ¶rt;a. uu mmuu au u¶rt;a nu auauu mnu¶rt;u aa u anu.相似文献