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51.
We present new 1.45-1.75 μm spectra of Europa's dark non-ice material with a spectral resolution (λ/δλ) of 1200, obtained by using adaptive optics on the Keck telescope to spatially separate the spectrum of the non-ice material from that of the surrounding ice-rich regions. Despite the great increase in spectral resolution over the previous best spectra of the non-ice material, taken with Galileo's near-infrared mapping spectrometer (NIMS) with λ/δλ=66, no new fine-scale spectral structure is revealed. The smoothness of the spectra is inconsistent with available laboratory spectra of crystalline hydrated salts at Europa temperatures, but is more consistent with various combinations of non-crystalline hydrated salts and/or hydrated sulfuric acid, as have been matched to the lower-resolution NIMS spectra. 相似文献
52.
B. Ahmed G. J. Alner H. Araujo J. C. Barton A. Bewick M. J. Carson D. Davidge J. V. Dawson T. Gamble S. P. Hart R. Hollingworth A. S. Howard W. G. Jones M. K. Joshi V. A. Kudryavtsev T. B. Lawson V. Lebedenko M. J. Lehner J. D. Lewin P. K. Lightfoot I. Liubarsky R. Lüscher J. E. McMillan B. Morgan G. Nicklin S. M. Paling R. M. Preece J. J. Quenby J. W. Roberts M. Robinson N. J. T. Smith P. F. Smith N. J. C. Spooner T. J. Sumner D. R. Tovey 《Astroparticle Physics》2003,19(6):691-702
The NAIAD experiment (NaI Advanced Detector) for weakly interacting massive particle (WIMP) dark matter searches at Boulby mine (UK) is described. The detector consists of an array of encapsulated and unencapsulated NaI(Tl) crystals with high light yield. Six crystals are collecting data at present. Data accumulated by four of them (10.6 kg × year exposure) have been used to set upper limits on the WIMP–nucleon spin-independent and WIMP–proton spin-dependent cross-sections. Pulse shape analysis has been applied to discriminate between nuclear recoils, as may be caused by WIMP interactions, and electron recoils due to gamma background. Various calibrations of crystals are presented. 相似文献
53.
W.M. Napier 《Astrophysics and Space Science》2003,285(2):419-427
Claims that ordinary spiral galaxies and some classes of QSO show periodicity in their redshift distributions are investigated
using recent high-precision data and rigorous statistical procedures. The claims are broadly upheld. The periodicites are
strong and easily seen by eye in the datasets. Observational, reduction or statistical artefacts do not seem capable of accounting
for them.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
54.
55.
It is well known that the Babuska–Brezzi stability criterion or the Zienkiewicz–Taylor patch test precludes the use of the finite elements with the same low order of interpolation for displacement and pore pressure in the nearly incompressible and undrained cases, unless some stabilization techniques are introduced for dynamic analysis of saturated porous medium where coupling occurs between the displacement of solid skeleton and pore pressure. The numerical manifold method (NMM), where the interpolation of displacement and pressure can be determined independently in an element for the solution of u–p formulation, is derived based on triangular mesh for the requirement of high accurate calculations from practical applications in the dynamic analysis of saturated porous materials. The matrices of equilibrium equations for the second‐order displacement and the first‐order pressure manifold method are given in detail for program coding. By close comparison with widely used finite element method, the NMM presents good stability for the coupling problems, particularly in the nearly incompressible and undrained cases. Numerical examples are given to illustrate the validity and stability of the manifold element developed. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
56.
Hector Socas-Navarro David Elmore Anna Pietarila Anthony Darnell Bruce W. Lites Steven Tomczyk Steven Hegwer 《Solar physics》2006,235(1-2):55-73
The Spectro-Polarimeter for Infrared and Optical Regions (SPINOR) is a new spectro-polarimeter that will serve as a facility
instrument for the Dunn Solar Telescope at the National Solar Observatory. This instrument is capable of achromatic polarimetry
over a very broad range of wavelengths, from 430 to 1600 nm, allowing for the simultaneous observation of several visible
and infrared spectral regions with full Stokes polarimetry. Another key feature of the design is its flexibility to observe
virtually any combination of spectral lines, limited only by practical considerations (e.g., the number of detectors available, space on the optical bench, etc.).
Visiting Astronomers, National Solar Observatory, operated by the Association of Universities for Research in Astronomy, Inc.
(AURA), under cooperative agreement with the National Science Foundation. 相似文献
57.
The large-scale structure associated with the 2′N HNCO peak in Sgr B2 [Minh, Y.C., Haikala, L., Hjalmarson, Å., Irvine, W.M., 1998. ApJ 498, 261 (Paper I)] has been investigated. A ring-like morphology of the HNCO emission has been found; this structure may be colliding with the Principal Cloud of Sgr B2. This “HNCO Ring” appears to be centered at (l,b) = (0.7°,−0.07°), with a radius of 5 pc and a total mass of 1.0 × 105 to 1.6 × 106 M. The expansion velocity of the Ring is estimated to be 30–40 km s−1, which gives an expansion time scale of 1.5 × 105 year. The morphology suggests that collision between the Ring and the Principal Cloud may be triggering the massive star formation in the Sgr B2 cloud sequentially, with the latest star formation taking place at the 2′N position. The chemistry related to HNCO is not certain yet, but if it forms mainly via reaction with the evaporated OCN− from icy grain mantles, the observed enhancement of the HNCO abundance can be understood as resulting from shocks associated with the collision between the Principal Cloud and the expanding HNCO Ring. 相似文献
58.
Hong-Qi Zhang Xing-Ming Bao Yin Zhang Ji-Hong Liu Shu-Dong Bao Yuan-Yong Deng Wei Li Jie Chen Jin-Ping Dun Jiang-Tao Su Juan Guo Xiao-Fan Wang Ke-Liang Hu Gang-Hua Lin Dong-Guang WangNational Astronomical Observatories Chinese Academy of Sciences Beijing 《中国天文和天体物理学报》2003,3(6):491-494
We analyze the magnetic configurations of three super active regions, NOAA 10484, 10486 and 10488, observed by the Huairou Multi-Channel Solar Telescope (MCST) from 2003 October 18 to November 4. Many energetic phenomena, such as flares (including a X-28 flare) and coronal mass ejections (CMEs), occurred during this period. We think that strong shear and fast emergence of magnetic flux are the main causes of these events. The question is also of great interest why these dramatic eruptions occurred so close together in the descending phase of the solar cycle. 相似文献
59.
Sarah Church Peter Ade James Bock Melanie Bowden John Carlstrom Ken Ganga Walter Gear James Hinderks Wayne Hu Brian Keating John Kovac Andrew Lange Eric Leitch Olivier Mallie Simon Melhuish Anthony Murphy Ben Rusholme Creidhe OSullivan Lucio Piccirillo Clem Pryke Andy Taylor Keith Thompson 《New Astronomy Reviews》2003,47(11-12):1083
QUEST on DASI is a ground-based, high-sensitivity, high-resolution (ℓmax2500) experiment designed to map CMB polarization at 100 and 150 GHz and to measure the power spectra from E-modes, B-modes from lensing of the CMB, and B-modes from primordial gravitational waves. The experiment comprises a 2.6 m Cassegrain optical system, equipped with an array of 62 polarization-sensitive bolometers (PSBs), located at the South Pole. The instrument is designed to minimize systematic effects; features include differencing of pairs of orthogonal PSBs within a single feed, a rotatable achromatic waveplate, and axisymmetric rotatable optics. In addition the South Pole location allows both repeatable and highly controlled observations. QUEST on DASI will commence operation in early 2005. 相似文献
60.