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81.
Tamara T. Helfer Michael W. Regan Michele D. Thornley Tony Wong Kartik Sheth Stuart N. Vogel Douglas C.-J. Bock LEO Blitz Andy Harris 《Astrophysics and Space Science》2001,276(2-4):1131-1139
BIMA SONG is a systematic imaging study of the 3 mm CO J = 1 → 0molecular emission within the centres and discs of 44 nearby spiral galaxies on size scales of a few hundred parsecs
(6-9"). The overall goal of the survey is to study the role of molecular gas in the evolution of spiral galaxies. To this
end, BIMA SONG addresses 1) the distribution and physical conditions of the molecular gas in galactic discs and its relation
to star formation, 2) the effects of a stellar bar on the kinematics of molecular gas, including the possible inflow of gas
along a bar, and 3) the distribution and role of molecular gas in the central few hundred parsecs of active and quiescent
galaxies. The source list includes all (except M33and M31) 44 galaxies of Hubble types Sa–Sd, with declinations δ >−20°, visual magnitudes B < 11.0, velocities v
hel <2000 km s-1, and inclinations i < 70°. Beyond the specific scientific questions we will address, this survey will provide a unique database for astronomers who
study galaxies at all wavelengths.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
82.
Pollen is one of the most durable environmental materials that law enforcement agencies recover as trace evidence from people and objects. Although links between objects and geographic locations are essential during legal investigations, the approach of using pollen and other microbial fingerprints to build these links in an analytical framework is still underutilized. This study uses bees as objects that are mobile and collects environmental traces as a test case to determine the efficacy of predictive geolocation efforts with recovered pollen and species distribution models at both subcontinental and global scales. Results demonstrate promising performance in both the predictive capability of species distribution models and identification of possible location history of bees at both study extents. When coupling pollen with other categories of evidentiary items, this geographic attribution framework can aid law enforcement personnel in refining investigation priorities and optimizing search strategies. 相似文献
83.
Sara R. Heap Qian Gong Tony Hull Jeffrey Kruk Lloyd Purves 《Astrophysics and Space Science》2014,354(1):211-214
One of the key goals of NASA’s astrophysics program is to answer the question: How did galaxies evolve into the spirals and elliptical galaxies that we see today? We describe a space mission concept called Galaxy Evolution Spectroscopic Explorer (GESE) to address this question by making a large spectroscopic survey of galaxies at a redshift, z~1 (look-back time of ~8 billion years). GESE is a 1.5-m space telescope with an ultraviolet (UV) multi-object slit spectrograph that can obtain spectra of hundreds of galaxies per exposure. The spectrograph covers the spectral range, 0.2–0.4 μm at a spectral resolving power, R~500. This observed spectral range corresponds to 0.1–0.2 μm as emitted by a galaxy at a redshift, z=1. The mission concept takes advantage of two new technological advances: (1) light-weighted, wide-field telescope mirrors, and (2) the Next-Generation MicroShutter Array (NG-MSA) to be used as a slit generator in the multi-object slit spectrograph. 相似文献
84.
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86.
We present high-resolution (∼5″) BIMA CO observations of the ringed galaxy NGC 4736, along with previously published VLA HI
data (Braun, 1995). Strong CO emission is detected from the star-forming ring at r=45″ and in the central region, where a molecular bar is apparent. The azimuthally averaged gas surface density is still much less than the Toomre critical density within r=60″, despite the starburst conditions in the ring (gas depletion time ≲1Gyr). Both CO and HI velocity fields show strong
departures from a circular rotating disc model. The velocity residuals are consistent with inflowing gas near the ends of
the central bar, outflowing gas between the bar and the ring, and inflowing gas outside the ring. We propose that the high
star formation efficiency in the ring results from gas being driven out towards the OLR of the bar and in towards the ILR
of the larger oval distortion. However, the strong signature of inflow outside the ring is probably due in part to gas motion
in elliptical orbits.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
87.
As the Internet continues to grow, questions of accessibility and infrastructure equity persist. In the increasingly competitive telecommunications industry, profit-seeking firms continue to upgrade infrastructure in select market areas creating an uneven spatial distribution of access opportunities. This article utilizes a longitudinal database of Internet infrastructure development, highlighting fiber-optic backbone points of presence (POP) established by commercial Internet service providers to examine city accessibility to the commercial Internet. Results indicate that many larger metropolitan areas maintain dominant shares of telecom infrastructure, but several midsized metros are emerging as important centers for telecommunication interconnection. 相似文献
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89.
Rais Latypov Tony Morse Brian Robins Richard Wilson Grant Cawthorn Christian Tegner Marian Holness Charles Lesher Steve Barnes Brian O’Driscoll Ilya Veksler Michael Higgins Allan Wilson Olivier Namur Sofya Chistyakova Richard Naslund Peter Thy 《Contributions to Mineralogy and Petrology》2015,169(2):1-10
90.
Fisheries: Hope or despair? 总被引:1,自引:0,他引:1
Recent work suggesting that fisheries depletions have turned the corner is misplaced because analysis was based largely on fisheries from better-managed developed-world fisheries. Some indicators of status show improvements in the minority of fisheries subjected to formal assessment. Other indicators, such as trophic level and catch time series, have been controversial. Nevertheless, several deeper analyses of the status of the majority of world fisheries confirm the previous dismal picture: serious depletions are the norm world-wide, management quality is poor, catch per effort is still declining. The performance of stock assessment itself may stand challenged by random environmental shifts and by the need to accommodate ecosystem-level effects. The global picture for further fisheries species extinctions, the degradation of ecosystem food webs and seafood security is indeed alarming. Moreover, marine ecosystems and their embedded fisheries are challenged in parallel by climate change, acidification, metabolic disruptors and other pollutants. Attempts to remedy the situation need to be urgent, focused, innovative and global. 相似文献