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421.
Minchinia nelsoni (MSX) infections in the James River seed-oyster area and their expulsion in spring
Jay D. Andrews 《Estuarine, Coastal and Shelf Science》1983,16(3):255-269
Spread of a new oyster disease caused by Minchinia nelsoni (MSX) in lower Chesapeake Bay in 1959–1960 threatened Virginia's James River seed area. Infections appeared in the lower half of the seed area in 1960 and 1961, but few oysters died from the disease and infections were eliminated by oysters in April-May the following spring. Distribution of the disease in controlled broadly by low salinities that inhibit development of infections and allow oysters to discharge plasmodia. Penetrations of the seed area occurred in dry and wet years, but mortalities occurred only in 1964 and 1980, both years of low precipitation. Little mortality was caused by transplanting infected seed oysters to other rivers because only low-salinity grounds were planted after 1959–1960 when severe mortalities occurred in areas of high salinities. In most years, infections were minimal in the seed area and other estuaries where salinities do not exceed 15–20‰ in late summer and fall. Salinities <10‰ prevailed in most of the seed area when oysters expelled the pathogen in early spring. 相似文献
422.
An observational program at the Sacramento Peak Observatory in 1965 provided high-dispersion spectra of the solar chromosphere in several spectral regions simultaneously. These regions included various combinations of the spectral lines Hα, Hβ and H?, the D3-line of Hei, the infrared triplet of Oi, and the H- and K-lines and the infrared triplet of Caii. With the use of an image slicer the observations were made simultaneously at two heights in the solar chromosphere separated by several thousand kilometers. From these data we draw the following conclusions:
- Emission of different lines arises in the same chromospheric features. The intensity ratio of lines of different elements varies significantly from spicule to spicule. For the H- and K-lines of ionized calcium, this ratio remains constant, independent of wavelength throughout the line, overall intensity, and height in the chromosphere. Two rare-earth lines in the wing of the H-line show no spicular structure at all.
- The line-of-sight velocities of many features reverse as a function of time, although most spicules show velocities in only one direction. The simultaneous spectra at two heights show most spicules to have the same line-of-sight velocity at both. There may be an additional class of features, mostly rapidly moving, whose members have line-of-sight velocities that increase with height. These features comprise perhaps 10% of the total. Velocity changes occur simultaneously, to within 20 sec, at two heights separated by 1800 km, indicating velocities of propagation of hundreds of km/sec. The velocity field of individual features is often quite complicated; many spectral features are inclined to the direction of dispersion, implying that differential mass motions are present.
- The existence of anomalously broad H and K profiles is real. Even with high dispersion and the best seeing, such profiles are not resolved into smaller features. The central reversal in K, H and Hα appears to remain unshifted when the wings are displaced in wavelength, indicating that the reversal is non-spicular.
423.
Dmitry L. Lakshtanov Carine B. Vanpeteghem Jennifer M. Jackson Jay D. Bass Guoyin Shen Vitali B. Prakapenka Konstantin Litasov Eiji Ohtani 《Physics and Chemistry of Minerals》2005,32(7):466-470
We have determined the P-V equation of state of Al-rich H-bearing SiO2 stishovite by X-ray powder diffraction at pressures up to 58 GPa using synchrotron radiation. The sample contained 1.8 wt%
Al2O3 and up to 500 ppm H2O, and had a composition that would coexist with Mg-silicate perovskite in a subducted slab. By fitting a third-order Birch-Murnaghan
equation of state to our compression data, we obtained a bulk modulus K
T0=298(7) GPa with K′=4.3(5). With K′ fixed to a value of 4, the bulk modulus K
T0=304(3) GPa. Our results indicate that Al3+ and H+ have a small effect on the elastic properties of stishovite. Compared with data obtained up to 43.8 GPa, peak intensities
changed and we observed a decreased quality of fit to a tetragonal unit cell at pressures of 49 GPa and higher. These changes
may be an indication that the rutile↔CaCl2 transition occurs between these pressures. After laser annealing of the sample at 58.3(10) GPa and subsequent decompression
to room conditions, the cell volume is the same as before compression, giving strong evidence that the composition of the
recovered sample is also unchanged. This suggests that Al and H are retained in the sample under extreme P-T conditions and
that stishovite can be an agent for transporting water to the deepest lower mantle. 相似文献
424.
Paul R. Haberstroh Jay A. Brandes Angela F. Dickens George Cody 《Geochimica et cosmochimica acta》2006,70(6):1483-1494
The chemical composition of the graphitic black carbon (GBC) fraction of marine organic matter was explored in several marine and freshwater sedimentary environments along the west coast of North America and the Pacific Ocean. Analysis by carbon X-ray absorption near-edge structure spectroscopy and scanning transmission X-ray microscopy shows the GBC fraction of Stillaguamish River surface sediments to be dominated by more highly ordered and impure forms of graphite, together forming about 80% of the GBC, with a smaller percent of an aliphatic carbon component. Eel River Margin surface sediments had very little highly ordered graphite, and were instead dominated by amorphous carbon and to a lesser extent, impure graphite. However, the GBC of surface sediments from the Washington State Slope and the Mexico Margin was composed almost solely of amorphous carbon. Pre-anthropogenic, highly oxidized deep-sea sediments from the open Equatorial Pacific Ocean contained over half their GBC in different forms of graphite as well as highly aliphatic carbon, low aromatic/highly acidic aliphatic carbon, low aromatic/highly aliphatic carbon, and amorphous forms of carbon. Our results clearly show the impact of graphite and amorphous C phases in the BC fraction in modern riverine sediments and nearby marine shelf deposits. The pre-anthropogenic Equatorial Pacific GBC fraction is remarkable in the existence of highly ordered graphite. 相似文献
425.
The implementation of viscous dampers to microelectronics factories has been previously proved not to affect the micro‐vibration of the factories in operation so that the vibration‐sensitive manufacturing process will not be interfered. Therefore, a seismic retrofit strategy which employs the viscous dampers installed in between the exterior and interior structures of the ‘fab’ structure is proposed in the study. The design formulas corresponding to the proposed retrofit method are derived using the non‐proportional damping theory. Based on the study, it is found that the added damping ratio to the fab structure depends greatly on the frequency ratio of the two structures in addition to the damping coefficients of the added dampers. Outside the bandwidth of the frequency ratio in which the added damping ratio is very sensitive to the variation of the frequency ratio, the added damping ratio can be well captured using the classical damping theory. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
426.
427.
Jason W. Barnes Lawrence Lemke Rick Foch Christopher P. McKay Ross A. Beyer Jani Radebaugh David H. Atkinson Ralph D. Lorenz Stéphane Le Mouélic Sebastien Rodriguez Jay Gundlach Francesco Giannini Sean Bain F. Michael Flasar Terry Hurford Carrie M. Anderson Jon Merrison Máté ádámkovics Simon A. Kattenhorn Jonathan Mitchell Devon M. Burr Anthony Colaprete Emily Schaller A. James Friedson Kenneth S. Edgett Angioletta Coradini Alberto Adriani Kunio M. Sayanagi Michael J. Malaska David Morabito Kim Reh 《Experimental Astronomy》2012,33(1):55-127
We describe a mission concept for a stand-alone Titan airplane mission: Aerial Vehicle for In-situ and Airborne Titan Reconnaissance (AVIATR). With independent delivery and direct-to-Earth communications, AVIATR could contribute to Titan science either alone or as part of a sustained Titan Exploration Program. As a focused mission, AVIATR as we have envisioned it would concentrate on the science that an airplane can do best: exploration of Titan??s global diversity. We focus on surface geology/hydrology and lower-atmospheric structure and dynamics. With a carefully chosen set of seven instruments??2 near-IR cameras, 1 near-IR spectrometer, a RADAR altimeter, an atmospheric structure suite, a haze sensor, and a raindrop detector??AVIATR could accomplish a significant subset of the scientific objectives of the aerial element of flagship studies. The AVIATR spacecraft stack is composed of a Space Vehicle (SV) for cruise, an Entry Vehicle (EV) for entry and descent, and the Air Vehicle (AV) to fly in Titan??s atmosphere. Using an Earth-Jupiter gravity assist trajectory delivers the spacecraft to Titan in 7.5 years, after which the AVIATR AV would operate for a 1-Earth-year nominal mission. We propose a novel ??gravity battery?? climb-then-glide strategy to store energy for optimal use during telecommunications sessions. We would optimize our science by using the flexibility of the airplane platform, generating context data and stereo pairs by flying and banking the AV instead of using gimbaled cameras. AVIATR would climb up to 14?km altitude and descend down to 3.5?km altitude once per Earth day, allowing for repeated atmospheric structure and wind measurements all over the globe. An initial Team-X run at JPL priced the AVIATR mission at FY10 $715M based on the rules stipulated in the recent Discovery announcement of opportunity. Hence we find that a standalone Titan airplane mission can achieve important science building on Cassini??s discoveries and can likely do so within a New Frontiers budget. 相似文献
428.
The literature on climate change’s impacts on energy security is scattered across disparate fields of research and schools of thought. Much of this literature has been produced outside of the academy by scholars and practitioners working in “think tanks,” government agencies, and international/multilateral institutions. Here we reviewed a selected set of 58 articles and reports primarily from such sources and performed textual analysis of the arguments. Our review of this literature identifies three potential mechanisms for linking climate change and energy security: Climate change may 1) create second-order effects that may exacerbate social instability and disrupt energy systems; 2) directly impact energy supply and/or systems or 3) influence energy security through the effects of climate-related policies. We identify emerging risks to energy security driven by climate mitigation technology choices but find less evidence of climate change’s direct physical impacts. We used both empirical and qualitative selection factors for choosing the grey literature sample. The sources we selected were published in the last 5 years, available through electronic media and were written in language accessible to general policy or academic readers. The organizations that published the literature had performed previous research in the general fields of energy and/or climate change with some analytical content and identified themselves as non-partisan. This literature is particularly valuable to scholars because identifies understudied relationships that can be rigorously assessed through academic tools and methodologies and informs a translational research agenda that will allow scholars to engage with practitioners to address challenges that lie at the nexus of climate change and energy security. 相似文献
429.
Seth S. Haines Jay E. Diffendorfer Laurie Balistrieri Byron Berger Troy Cook Don DeAngelis Holly Doremus Donald L. Gautier Tanya Gallegos Margot Gerritsen Elisabeth Graffy Sarah Hawkins Kathleen M. Johnson Jordan Macknick Peter McMahon Tim Modde Brenda Pierce John H. Schuenemeyer Darius Semmens Benjamin Simon Jason Taylor Katie Walton-Day 《Natural Resources Research》2014,23(1):3-17
Natural resource planning at all scales demands methods for assessing the impacts of resource development and use, and in particular it requires standardized methods that yield robust and unbiased results. Building from existing probabilistic methods for assessing the volumes of energy and mineral resources, we provide an algorithm for consistent, reproducible, quantitative assessment of resource development impacts. The approach combines probabilistic input data with Monte Carlo statistical methods to determine probabilistic outputs that convey the uncertainties inherent in the data. For example, one can utilize our algorithm to combine data from a natural gas resource assessment with maps of sage grouse leks and piñon-juniper woodlands in the same area to estimate possible future habitat impacts due to possible future gas development. As another example: one could combine geochemical data and maps of lynx habitat with data from a mineral deposit assessment in the same area to determine possible future mining impacts on water resources and lynx habitat. The approach can be applied to a broad range of positive and negative resource development impacts, such as water quantity or quality, economic benefits, or air quality, limited only by the availability of necessary input data and quantified relationships among geologic resources, development alternatives, and impacts. The framework enables quantitative evaluation of the trade-offs inherent in resource management decision-making, including cumulative impacts, to address societal concerns and policy aspects of resource development. 相似文献
430.
Jacqueline Faherty Frederick M. Walter Jay Anderson 《Astrophysics and Space Science》2007,308(1-4):225-230
We obtained a series of four observations of the isolated neutron star Geminga over an 18 month period using the Advanced Camera for Surveys (ACS) Wide Field Camera (WFC) on the Hubble Space Telescope in order to determine its trigonometric parallax. We find the parallax π=4.0±1.3 mas, corresponding to a distance to Geminga of 250 ?62 +120 pc, a result 60% larger than the previously published value. The proper motion is 178.2±1.8 mas/year. In this paper, we describe the analysis techniques in detail since the amplitude of the parallactic shift is smaller than the camera’s pixel size. We fit each star in the images with an appropriate effective PSF and applied a distortion correction to generate stellar positions accurate to 0.01 pixels (~0.5 mas). The 134 stars common to all images serve to establish a reference frame for alignment of the image series. Our observations were made around the times of maximum parallactic shift. We discuss the implications of this new distance measurement for the inferred radius of Geminga, and the neutron star equation of state. 相似文献