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91.
Albert M. Fowler K. Michael Merrill William Ball Arne Henden Fred Vrba Craig McCreight 《Experimental Astronomy》2002,14(1):61-68
The Orion program is a project to develop a 2K × 2K infrared focal plane using InSb p-on-n diodes for detectors. It is the
natural follow-up to the successful Aladdin 1K × 1K program started in the early 90's. The work is being done at the Raytheon
Infrared Operations Division (RIO, previously known as the Santa Barbara Research Center) by many of the same people who created
the Aladdin focal plane. The design is very similar to the successful Aladdin design with the addition of reference pixels,
whole array readout (no quadrants), two-adjacent-side buttability, and a packaging design that includes going directly to
the ultimate focal plane size of 4K × 4K. So far we have successfully made a limited number of hybrid modules with InSb detectors.
In this paper we will describe the design features and test data taken from some of these devices.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
92.
Vertical profiles of dissolved Al in the Atlantic Ocean and Mediterranean Sea are presented. Although dissolved Al appears to be involved in the biochemical cycle of elements, Al does not behave solely as a nutrient within the oceans. Physico-chemical processes (i.e. adsorption and/or chemical precipitation) control the concentration and distribution of Alaq within the deep waters.A tentative mass balance model of Alaq in the oceanic system is proposed that takes into account all of the presently known fluxes of Alaq to and through the oceans. To maintain the deep waters of the ocean at steady state, it is necessary to include in the model, processes that remove Alaq from these waters. Thus, model calculations support the conclusions drawn from observations that physico-chemical processes remove Alaq from deep waters. Finally, the proposed model is compatible with the concept that the entire oceanic system is at steady state with respect to dissolved Al. 相似文献
93.
C. B. Stephenson 《Astrophysics and Space Science》1977,51(1):117-119
A recent paper (Varshni, 1976) analyses the distribution of quasar red shifts for randomness, in an incorrect manner. A correct analysis shows that this distribution is in agreement with random expectation. Were the distribution highly non-random, the original conclusion was that, for the red shifts to be cosmological, the Earth would have a strongly privileged position in the Universe. A simple alternative model, in which this would not be so, is pointed out. 相似文献
94.
We present 8.0–13.0 micron spectra for six main belt asteroids, which range from 58 to 220 km in diameter and sample the five principal taxonomic classes (C, S, M, R and E). Narrow, well-defined silicate emission features are present on two of the asteroids, the C-type 19 Fortuna and the M-type 21 Lutetia. No comparable emission features are observed on the S-types 11 Parthenope and 14 Irene, the R-type 349 Dembowska or the E-type 64 Angelina. 相似文献
95.
96.
Release of CO2 from surface ocean water owing to precipitation of CaCO3 and the imbalance between biological production of organic matter and its respiration, and their net removal from surface
water to sedimentary storage was studied by means of a quotient θ = (CO2 flux to the atmosphere)/(CaCO3 precipitated). θ depends not only on water temperature and atmospheric CO2 concentration but also on the CaCO3 and organic carbon masses formed. In CO2 generation by CaCO3 precipitation, θ varies from a fraction of 0.44 to 0.79, increasing with decreasing temperature (25 to 5°C), increasing atmospheric
CO2 concentration (195–375 ppmv), and increasing CaCO3 precipitated mass (up to 45% of the initial DIC concentration in surface water). Primary production and net storage of organic
carbon counteracts the CO2 production by carbonate precipitation and it results in lower CO2 emissions from the surface layer. When atmospheric CO2 increases due to the ocean-to-atmosphere flux rather than remaining constant, the amount of CO2 transferred is a non-linear function of the surface layer thickness because of the back-pressure of the rising atmospheric
CO2. For a surface ocean layer approximated by a 50-m-thick euphotic zone that receives input of inorganic and organic carbon
from land, the calculated CO2 flux to the atmosphere is a function of the CaCO3 and Corg net storage rates. In general, the carbonate storage rate has been greater than that of organic carbon. The CO2 flux near the Last Glacial Maximum is 17 to 7×1012 mol/yr (0.2–0.08 Gt C/yr), reflecting the range of organic carbon storage rates in sediments, and for pre-industrial time
it is 38–42×1012 mol/yr (0.46–0.50 Gt C/yr). Within the imbalanced global carbon cycle, our estimates indicate that prior to anthropogenic
emissions of CO2 to the atmosphere the land organic reservoir was gaining carbon and the surface ocean was losing carbon, calcium, and total
alkalinity owing to the CaCO3 storage and consequent emission of CO2. These results are in agreement with the conclusions of a number of other investigators. As the CO2 uptake in mineral weathering is a major flux in the global carbon cycle, the CO2 weathering pathway that originates in the CO2 produced by remineralization of soil humus rather than by direct uptake from the atmosphere may reduce the relatively large
imbalances of the atmosphere and land organic reservoir at 102–104-year time scales. 相似文献
97.
In examining ship-mediated biological invasions, most research and treatment development has focused on ballast water. Another vector that has gained attention recently is vessels arriving in a "no ballast on board" (NOBOB) condition. Such ships retain relatively small, unpumpable volumes of water and sediment in their ballast tanks. Nonetheless, these unpumpable portions can represent great ecological risk. This scenario is relevant in the Great Lakes, which have experienced a dramatic series of introductions, despite most vessels arriving there as NOBOBs since 1994. We examined shipping patterns of NOBOBs arriving to lower Chesapeake Bay to begin evaluating their risk of biopollution. Only 14% of ships arrive as NOBOBs, and of those, 17% depart to another port in the upper bay. Most NOBOBs arrive from or leave for other US ports; proximate trans-Atlantic crossings are few. Given the nature of their operations, we conclude NOBOBs may represent a risk for aquatic nuisance species invasions to Chesapeake Bay. 相似文献
98.
Sources of Enterococcus faecalis isolates from Pensacola Beach, FL. were identified using a library-based approach by applying the statistical method of average similarity to single and composite data sets generated from separate analyses. Data sets included antibiotic resistance analysis (ARA), rep-fingerprints, and fatty acid methyl ester (FAME) profiles. Use of a composite data set composed of ARA and rep-fingerprints, added to the confidence of the identifications. The addition of FAME data to composite data sets did not add to the confidence of identifications. Source identification was performed to better understand risk associated with higher densities of enterococci found in swash zone interstitial water (SZIW) as compared to adjacent bathing water on Pensacola Beach, FL. The "swash zone" is that area of the beach continually washed over by waves. As the potential sources of enterococci were limited in this environment, only two library units, sea gull and human, were constructed. Identification of the beach isolates using a composite data set indicated a sea gull origin. The clonality of the beach isolates suggested that the beach environment selects certain subspecies of E. faecalis. 相似文献
99.
Fred L. Whipple 《Icarus》1984,60(3):522-531
The observations of comet P/Holmes 1892III, exhibiting two 8- to 10-mag bursts, have been carefully analyzed. The phenomena are consistent with the grazing encounter of a small satellite with the nucleus on November 4.6, 1892, and the final encounter on January 16.3, 1893. The grazing encounter produced, besides the first great burst, an active area on the nucleus, which was rotating retrograde with a period of 16.3 hr and inclination of nearly 180°. After the final encounter, the spin period was essentially unchanged, but two areas became active, separated some 164° in longitude on the nucleus. After the first burst the total magnitude fell less than 2 mag from November 7 to 30 (barely naked eye) while the nuclear region remained diffuse or complex, rarely of ever showing a stellar appearance. The fading was much more rapid after the second burst (barely naked eye at maximum) while the nucleus frequently appeared stellar after the first day. It seems reasonable to conclude that the grazing encounter distributed a volume of large chunks in the neighborhood of the nucleus, maintaining activity for weeks. The final encounter activated a new area on the nucleus, the shock and fall back disturbing the area already exposed by the grazing encounter. Several details of this scenario are fitted rather well. 相似文献
100.
We calculate the expected counting rate of a flat micrometeoroid detector of finite sensitivity passing in hyperbolic orbit near a planet. We assume that the distribution of particle sizes, s, can be expressed as a power law spectrum of index p, i.e. dN(s) = Cs?pds, and also that the particles encounter the sphere of influence of the planet with a certain speed v∞. The results of the calculations are then compared with the results returned by Pioneer 10 in its flyby of Jupiter. The observed increase in impact rate near Jupiter can be completely explained in terms of gravitational “focusing” of particles which are in heliocentric orbits; i.e., they are not in orbit about Jupiter. The absolute concentration of particles near the orbit of Jupiter is of the same order as at 1 AU: the exact ratio being a function of particle speed and spectral index. Data from one flyby are insufficient to determine a unique value for both the spectral index, p, and the particle velocity, v∞, but limits can be set. For reasonable encounter speeds (corresponding to eccentricities and inclinations of dust particles experienced near the Earth), the particles near Jupiter are characterized by a spectrum of index p ~ 3. The spectral index which best fits the data increases with increasing encounter speeds. 相似文献