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81.
Rebecca A. W. Elson Steinn Sigurdsson Melvyn Davies Jarrod Hurley & Gerard Gilmore 《Monthly notices of the Royal Astronomical Society》1998,300(3):857-862
We determine the binary star fraction as a function of radius in NGC 1818, a young rich cluster in the Large Magellanic Cloud, using Hubble Space Telescope images in bands F336W (∼ U ) and F555W (∼ V ). Our sample includes binaries with M primary ∼ 2–5.5 M⊙ and M secondary ≳ 0.7 Mprimary . The binary fraction increases towards the cluster centre, from ∼ 20 ± 5 per cent in the outer parts, to ∼ 35 ± 5 per cent inside the core. This increase is consistent with dynamical mass segregation and need not be primordial. We compare our results with expectations from N -body models, and discuss the implications for the formation and early evolution of such clusters. 相似文献
82.
Gerard Kiely John D. Albertson Marc B. Parlance William E. Eichinger 《Boundary-Layer Meteorology》1996,77(3-4):267-284
The flux of sensible heat from the land surface is related to the average rate of dissipation of temperature fluctuations in the atmospheric surface layer through the temperature variance budget equation. In many cases it is desirable to estimate the heat flux from measurement or inference of the dissipation rate. Here we study how the dissipation rate scales with atmospheric stability, using three inertial range methods to calculate the dissipation rate: power spectra, second order structure functions, and third order structure functions. Experimental data are analyzed from a pair of field experiments, during which turbulent fluctuations of velocity and temperature were measured over a broad range of neutral and unstable atmospheric flows. It is shown that the temperature dissipation rate scales with a single convective power law continuously from near-neutral to strongly unstable stratification. The dissipation scaling is found to nearly match production in the near-neutral region, but to be consistently lower than production in the more convective regimes. The convective scaling is shown to offer a simplified means of computing sensible heat flux from the dissipation rate of temperature variance.Also at Johns Hopkins University, Baltimore, MarylandAlso at Los Alamos National Laboratory, Los Alamos, New Mexico. 相似文献
83.
84.
Determinations of reactive oxygen-containing functional groups were performed by usual chemical derivatization methods of four humic acids isolated from soils and deltaic sediments. Statistical tests and calculations based on elemental analysis demonstrated the validity and limits of these techniques and allowed us to identify from 60 to 71% of the total humic oxygen. Oxygen budgets of humic acids are discussed. 相似文献
85.
Extensive functional group analyses were performed on humic acids representative of eight increasing depth levels from a core drilled in the Mahakam delta (East Kalimantan, Indonesia). Oxygen amounts decrease observed during early diagenesis was related chiefly to loss of hydroxyl (lignol?) groups. Comparison between upper and deeper levels shows the following variations: hydroxyl group abundances go from 19 to 6% of humic oxygen. Identified functional groups amounts represent 47 to 32% of weight of moisture- and ash-free humic acids. No evidence of decarboxylation of humic material was detected. 相似文献
86.
There is strong evidence indicating that the six commonly recognized varieties of asbestos are cancer-producing agents Epidemiological
and experimental data indicate that, although response to inhalation exposure is most marked, exposure by ingestion probably
also entails a risk of excess tumor incidence. The toxicity of mineral fibers can be related to fiber dimensions, mineralogy,
chemistry, and surface-active properties.
In the Silver Lake Reservoir in Staten Island, New York, where chrysotile from serpentinite bedrock exposures is a potential
source of contamination, chrysotile asbestos levels of 15 to 86 million fibers per liter (MFL) were measured, with an average
of 53 MFL Much lower levels (average 0 3 MFL) were observed in small lakes and ponds with clayey bottoms on the Staten Island
Serpentinite. 相似文献
87.
A model is given of the magnetic-field equilibrium and possible dynamic excitations of a solar coronal arcade. Such structures are well observed in the spectral range from H to X-rays and often give rise to two-ribbon flares. However, the preflare state must be stable to ideal magnetohydrodynamic disturbances, and we treat this problem with particular attention to the necessary foot-point boundary conditions. Having devised a reasonably general perturbation set, we use an energy-principle analysis to show the strong stabilizing influence of inertial field-line tying at the photosphere.Address from October 1981: Tata Institute of Fundamental Research, Homi Bhabha Road, Bombay 400005, India. 相似文献
88.
Accounting for Spatial Uncertainty in Optimization with Spatial Decision Support Systems 总被引:2,自引:0,他引:2
Jeroen C. J. H. Aerts Michael F. Goodchild & Gerard B. M. Heuvelink 《Transactions in GIS》2003,7(2):211-230
Spatial decision support systems (SDSS) are designed to make complex resource allocation problems more transparent and to support the design and evaluation of allocation plans. Recent developments in this field focus on the design of allocation plans using optimization techniques. In this paper we analyze how uncertainty in spatial (input) data propagates through, and affects the results of, an optimization model. The optimization model calculates the optimal location for a ski run based on a slope map, which is derived from a digital elevation model (DEM). The uncertainty propagation is a generic method following a Monte Carlo approach, whereby realizations of the spatially correlated DEM error are generated using 'sequential Gaussian simulation'. We successfully applied the methodology to a case study in the Austrian Alps, showing the influence of spatial uncertainty on the optimal location of a ski run and the associated development costs. We also discuss the feasibility of routine incorporation of uncertainty propagation methodologies in an SDSS. 相似文献
89.
为了研究青藏高源东北部块体构造变形的深部驱动机制,笔者对青藏高原东北部的天然地震观测数据进行地震层析反演,并结合同一剖面的接收函数及各向异性结果进行讨论。介绍了ACH方法的基本原理,论述了由于印度板块向北俯冲的强大的持续作用力,造就了NE向俯冲到柴达木盆地之下的昆仑造山带,并发现在巴颜喀拉地体下方壳幔内的仰冲活动。壳幔内的低速体十分显著地出现在阿尼玛卿缝合线以北,深度可达300km。推断该低速体可能与昆仑断裂的深层的剪切作用有关。深部资料显示该区莫霍界面由北向南逐渐加深,这与青藏高原东北部的岩石圈减薄现象一致,而且与印度板块向北运动的远程效应有关。另外,地震层析结果及各向异性分析也支持青藏高原东北部主应力方向转为NE向的观点。 相似文献
90.
John D. Monnier Stefan Kraus Michael J. Ireland Fabien Baron Amelia Bayo Jean-Philippe Berger Michelle Creech-Eakman Ruobing Dong Gaspard Duchêne Catherine Espaillat Chris Haniff Sebastian Hönig Andrea Isella Attila Juhasz Lucas Labadie Sylvestre Lacour Stephanie Leifer Antoine Merand Ernest Michael Stefano Minardi Christoph Mordasini David Mozurkewich Johan Olofsson Claudia Paladini Romain Petrov Jörg-Uwe Pott Stephen Ridgway Stephen Rinehart Keivan Stassun Jean Surdej Theo ten Brummelaar Neal Turner Peter Tuthill Kerry Vahala Gerard van Belle Gautam Vasisht Ed Wishnow John Young Zhaohuan Zhu 《Experimental Astronomy》2018,46(3):517-529
The Planet Formation Imager (PFI, www.planetformationimager.org) is a next-generation infrared interferometer array with the primary goal of imaging the active phases of planet formation in nearby star forming regions. PFI will be sensitive to warm dust emission using mid-infrared capabilities made possible by precise fringe tracking in the near-infrared. An L/M band combiner will be especially sensitive to thermal emission from young exoplanets (and their disks) with a high spectral resolution mode to probe the kinematics of CO and H2O gas. In this paper, we give an overview of the main science goals of PFI, define a baseline PFI architecture that can achieve those goals, point at remaining technical challenges, and suggest activities today that will help make the Planet Formation Imager facility a reality. 相似文献