The species censorship problem: A general solution     

David Jon Furbish  Anthony J. Arnold  S. Paul Hansard 《Mathematical Geology》1990,22(1):95-106

The longevities of species constituting a statistical population have an underlying distribution whose form and parametric values reflect probabilities of origination and extinction through time. In the case that a part of the population is extant, the form of distribution and its parameters cannot be estimated directly from the longevity data without bias. Longevities of extant censored species are truncated and thus do not statistically represent the underlying distribution. The remaining uncensored species do not represent the true relative abundances of longevities. These biases can be defined from the probability densities for species longevitys and intervalr between successive originations of species. For realistic densities ofs andr, species with an intermediate longevity are preferentially censored. This simple, general result arises because the probability of censoring a species increases with its longevity, whereas the probability of censoring a given longevity varies with its relative abundance.  相似文献   

Impact of climate change on the Hii River basin and salinity in Lake Shinji: a case study using the SWAT model and a regression curve     

H. Somura  J. Arnold  D. Hoffman  I. Takeda  Y. Mori  M. Di Luzio 《水文研究》2009,23(13):1887-1900

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蒙古中部地区植被覆盖衰退问题案例研究（英文）     

Bair Z. TSYDYPOV  Endon Zh. GARMAEV  Arnold K. TULOKHONOV  Eduard A. BATOTSYRENOV  Alexander A. AYURZHANAEV  Zhargalma B. ALYMBAEVA  Ts. CHIMEDDORJ 《资源与生态学报(英文版)》2015,6(2):73-78

本文选择蒙古中部地区的两个模型多边形对植被多样性进行调查研究。它们都位于干旱、半干旱少雨地区。基于Landsat TM影像,本文研究了多边形区域的NDVI随时间变化的多时相NDVI值制图,得到所选择的具备不同值NDVI区域的全尺度景观特征。这一特征在对耐旱环境组的植被分析中得到了证实。该过程中将近整个实验多边形区域的植被偏离得到了追踪。NDVI的时间分布分析呈现出数值的降低,这说明了在戈壁,稀疏植被存在耐旱趋势。在半干旱气候区域中偏离植被趋势与牧草地的重载负直接相关。  相似文献   

Beryllium-10 and aluminum-26 in individual cosmic spherules from Antarctica     

K. Nishiizumi  J. R. Arnold  D. E. Brownlee  M. W. Caffee  R. C. Finkel  R. P. Harvey 《Meteoritics & planetary science》1995,30(6):728-732

Abstract— We present data for the cosmogenic nuclides ¹⁰Be and ²⁶Al in a suite of 24 extraterrestrial spherules, collected from Antarctic moraines and deep sea sediments. All of the 10 large spherules collected in glacial till at Lewis Cliff are extraterrestrial. As in earlier work, the great majority of particles show prominent solar cosmic-ray (SCR) production of ²⁶Al, indicating bombardment ages on the order of 10⁶ years or even longer. These long ages are in direct contradiction to model ages for small particles in the inner Solar System and may require reconsideration of models of small particle lifetimes. A small fraction of the particles so far measured (6/42) possess cosmogenic radionuclide patterns consistent with predictions for meteoroid spall droplets. We believe that most of the spherules were bombarded in space primarily as bodies not much larger than their present size. The content of in situ produced ¹⁰Be and ²⁶Al in quartz pebbles in the same moraine suggests that these spherules may have on average a significant terrestrial age.  相似文献   

Acoustic tomography and conventional meteorological measurements over heterogeneous surfaces     

K. Arnold  A. Ziemann  A. Raabe  G. Spindler 《Meteorology and Atmospheric Physics》2004,85(1-3):175-186

Summary Conventional micro-meteorological measuring methods are not particularly suitable for the investigation of the energy exchange under heterogeneous surface conditions. To consider the influence of the different surface properties, area-covered and spatially averaged meteorological measurements in combination with highly resolved simulations are necessary. In this context, the method of acoustic travel time tomography is introduced to provide information about the horizontal temperature and wind field.To check the applicability of the tomographic method for this problem and to provide data for the model initialisation a field experiment was carried out.The tomographic system and conventional meteorological equipment were utilised inside the investigation area with an extension of several hundred meters (300×700m²), which was arranged over areas with different surface properties: grassland and bare soil.The results of the field experiment show that differences between the measuring systems (in-situ and remote sensing) exist and the heterogeneity of the underlying surface is visible in the near surface temperature and wind field at a scale, which can be resolved with highly resolved numerical models. Depending on the incoming solar radiation and the local advection regional distinctions in the air temperature and wind field as well as in the vertical sensible heat fluxes were observed.The investigations demonstrate that the sensitivity of the acoustic tomography is sufficient to verify gradients in the meteorological fields even when the horizontal differences in sensible heat flux are small.  相似文献   

Infrared,Raman, and cathodoluminescence studies of impact glasses     

Arnold Gucsik  Christian Koeberl  Franz Brandsttter  Eugen Libowitzky  Ming Zhang 《Meteoritics & planetary science》2004,39(8):1273-1285

Abstract— We studied the infrared reflectance (IR), Raman, and cathodoluminescence (CL) spectroscopic signatures and scanning electron microscope‐cathodoluminescence (SEM‐CL) images of three different types of impact glasses: Aouelloul impact glass, a Muong Nong‐type tektite, and Libyan desert glass. Both backscattered electron (BSE) and CL images of the Muong Nong‐type tektite are featureless; the BSE image of the Libyan desert glass shows only weak brightness contrasts. For the Aouelloul glass, both BSE and CL images show distinct brightness contrast, and the CL images for the Libyan desert glass show spectacular flow textures that are not visible in any other microscopic method. Compositional data show that the SiO₂ composition is relatively higher and the Al₂O₃ content is lower in the CL‐bright areas than in the CL‐dark regions. The different appearance of the three glass types in the CL images indicates different peak temperatures during glass formation: the tektite was subjected to the highest temperature, and the Aouelloul impact glass experienced a relatively low formation temperature, while the Libyan desert glass preserves a flow texture that is only visible in the CL images, indicating a medium temperature. All IR reflectance spectra show a major band at around 1040 to 1110 cm^?1 (antisymmetric stretching of SiO₄ tetrahedra), with minor peaks between 745 and 769 cm^?1 (Si‐O‐Si angle deformation). Broad bands at 491 and 821 cm^?1 in the Raman spectra in all samples are most likely related to diaplectic glass remnants, indicating early shock amorphization followed by thermal amorphization. The combination of these spectroscopic methods allows us to deduce information about the peak formation temperature of the glass, and the CL images, in particular, show glass flow textures that are not preserved in other more conventional petrographic images.  相似文献   

Preface     

Arnold O. Benz 《Solar physics》1986,104(1):vii-vii

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Collected works of willard f. libby: edited by leona marshall libby,vols. I-VII     

James R. Arnold 《Geochimica et cosmochimica acta》1983,47(6):1177-1178

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Upper stratosphere negative ion composition measurements and inferred trace gas abundances     

F. Arnold  S. Qiu 《Planetary and Space Science》1984,32(2):169-177

In situ composition measurements of atmospheric negative ions were made at 40.8 km altitude using a balloon-borne mass spectrometer with large mass range and improved mass resolution. The data obtained show marked differences compared to previous data obtained mostly around or below 33 km.It appears that these differences are mostly due to a higher atmospheric temperature, a lower nitric acid vapour abundance and a larger HSO₃-vapour abundance prevailing at the higher altitude.A particularly striking feature is the relatively large fractional abundance of HSO₃-containing cluster ions.Another interesting result is that nitric acid vapour abundances can be inferred from the negative ion composition data with better accuracy than is possible for lower altitudes. The reason being that collisional ion dissociation occurring during ion sampling is less disturbing.The inferred nitric acid vapour abundance for 40.8 km altitude is consistent with current 2-dimensional model calculations.  相似文献   

Positive ion composition measurements in the upper stratosphere—Evidence for an unknown aerosol component     

F. Arnold  G. Henschen 《Planetary and Space Science》1982,30(1):101-108

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