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91.
I. Lichtenstadt A. Ron N. Sack J. J. Wagschal S. A. Bludman 《Astrophysics and Space Science》1980,71(1):219-227
Time-dependent neutrino transport out of an optically thick neutronized stellar core is calculated to study the effects of neutrino degeneracy and of source depletion. Neutrino trapping inhibits further neutrino emission until neutrinos peel out of the outer zones of the core, exposing successively inner zones. This inwardly propagating neutrino rarefaction wave can lead toe
–+pv+n oscillations in chemical composition. The effect of neutrino Fermi statistics is to retard considrably and disperse neutrino leakage out of the core, making neutrino transport insignificant during fast stages of core collapse.Supported in part by the U.S. Department of Energy under Contract EY-76-C-02-3071. 相似文献
92.
Gerald L. Crow Marlin J. Atkinson Benny Ron Shannon Atkinson Arleene D. K. Skillman George T. F. Wong 《Aquatic Geochemistry》1998,4(3-4):469-480
Captive whitetip reef sharks, Triaenodon obesus,at Sea Life Park (SLP) Hawaii, Waimanalo, Hawaii develop goitre, whereas, T. obesus at the Waikiki Aquarium (WAQ), Honolulu,Hawaii do not develop goitre. To determine theeffects of natural concentrations of iodine on thereduction of goitre, two sharks from SLP with goitrewere placed in an enclosed coastal lagoon with naturalseawater. Using ultrasound measurements the twogoitres were initially 11.4 cm and 14.6 cm in depthand after 3 months decreased to 4.7 cm and 5.7 cm. Radioimmunoassay analysis of the thyroid hormoneT3 sera concentrations were initially 0.22 ng/mland 0.33 ng/ml and increased to 1.84 ng/ml after beingplaced in the lagoon. Sera T4 were initially0.93 ng/ml and 0.99 ng/ml and increased dramaticallyto 17 ng/ml and 56 ng/ml. Over the six month samplingperiod, two resident sharks in the lagoon with normalthyroids had sera T3 concentrations from 0.89ng/ml to 1.1 ng/ml, and sera T4 concentrationsfrom 3.1 ng/ml to 7.9 ng/ml. The hypothyroidcondition in the SLP goitred-sharks is likely linkedto the low environmental iodide (<0.005 M), andhigh nitrate (111 M) of SLP water. The WAQwell-water facility was characterized by anoxic waterwith high iodide (0.60 M), total iodine (1.90M), and typical nitrate (24.6 M)concentrations of interstitial groundwater. Thedifference of iodide concentration of SLP and WAQ tankwater (<0.005 M versus 0.60 M) wasdirectly related to the hydrogeology of the well-watersources. To avoid goitre in marine aquarium systems,we recommend maintaining iodide concentrations of atleast 0.15 M. 相似文献
93.
Relative potency of PAHs and heterocycles as aryl hydrocarbon receptor agonists in fish 总被引:6,自引:0,他引:6
The relative potency of polycyclic aromatic compounds as aryl hydrocarbon receptor (AhR) agonists in fish was determined using data on CYP1A induction or AhR binding for 74 polycyclic aromatic hydrocarbons (PAHs) and heterocycles in teleost, avian, or mammalian systems from 18 published papers. Each PAH was assigned a fish potency factor relative to the potency of 2,3,7,8-tetrachlorodibenzo-p-dioxin as an AhR agonist. Two and three ring unsubstituted PAHs were generally inactive in fish, avian, and mammalian systems. Benzo[k]fluoranthene and indeno[1,2,3-cd]pyrene were consistently the most potent PAHs, with fish potency factors of 0.001-0.002. Common structural features associated with higher potency PAHs included 4-6 rings containing fluoranthene or phenanthrene structures with an exposed bay region. These results show that PAHs can have similar potency as many dioxin-like PCBs, and AhR mediated toxicity should be considered in assessing the risks of PAHs in fish. 相似文献
94.
95.
96.
Ethnic Capital and Assimilation to the Great Australian (Homeownership) Dream: the early housing experience of Australia's skilled immigrants 总被引:1,自引:0,他引:1
We use the Longitudinal Survey of Immigrants to Australia, 2005–2006, to examine the housing tenure experience of skilled immigrants to Australia 6 and 18 months after arrival for relationships with ethnic capital (cultural background), visa category streams, aspects of human capital, demographics, social capital and discrimination. Homeownership experience is used to indicate integration into Australia's dominantly middle-class society. Multinomial regression analysis identifies visa entry category as the most important independent group of variables accounting for immigrants' short-term dwelling tenure, followed by aspects of human capital, family status, and the importance of ethnic capital for immigrants of both English-speaking and non-English-speaking backgrounds, and discrimination. 相似文献
97.
Ron Johnston 《Urban geography》2013,34(8):702-736
Although an innovative researcher on urban geography during the 1930s, and a prolific textbook writer thereafter, Robert Dickinson is not now recognized as one of the influential pioneers of that subfield. This paper explores why that was the case by examining his career, writings and influence, and by setting him in the context of a model of scholarly impact. [Key words: Robert Dickinson, pioneers, influence, history of urban geography.] 相似文献
98.
Ron Malega 《Urban geography》2013,34(4):530-549
This study explores Black household affluence at the metropolitan scale and suggests that metropolitan-level opportunity structures shaped rates of Black affluence for the 100 largest American metropolitan areas in 2000. I hypothesize that affluent black households favored metropolitan areas of opportunity, those places characterized by having (1) economic opportunities, (2) favorable Black–White relational standing, (3) metropolitan diversity and residential opportunities, and (4) their location in the South, which serves as a Black homeplace. Results fail to suggest evidence regarding the role of the ‘new South’ for understanding metropolitan-level rates of Black affluence. More generally, findings from this study challenge our understanding of socioeconomic stratification by investigating diversity within America’s Black community. 相似文献
99.
Nicholas Coops Andrew Loughhead Philip Ryan Ron Hutton 《International journal of geographical information science》2013,27(4):345-361
In absence of other limitations, the growth rate of a plant is dependent upon the amount of heat it receives. Each species, whether a crop, weed or disease organism, is adapted to grow at its optimum rate within a specific temperature range. Within this range, the growing degree days (GDD) is the heat accumulation above a given base temperature for a specific time period, such as a crop's growing season or phenological stage. In this paper we detail a methodology to predict GDD for synthetically generated average growing seasons derived from long term average climate data over the Australian continent. An application of these techniques has been made using the GEODATA 9 second DEM, with temperature threshold values estimated to characterize optimum growth in citrus (Citrus sinensis (L.) Osbeck). Three major determinants of the annual growth cycle of Citrus sp. were established and predicted on a spatial basis including the starting day of the growing season, the GDD for a growing season, and the time required to accumulate an arbitrarily selected 2000 GDD from the estimated starting day. When these critical environmental factors are expressed on a spatial basis, covering the Australian continent, the combination can be used to identify locations where new crop varieties can most effectively be grown to maximize fruit quality and productivity, or to extend the harvest season. Likewise, new germplasm introduced to Australia from overseas can be horticulturally assessed at sites climatically matched to the source location. 相似文献
100.
Knowing our own history? Geography department archives in the UK 总被引:1,自引:0,他引:1
The paper presents an analysis of the returns to a questionnaire survey on the state of department archives within UK departments of geography. The results of the survey are discussed in relation to recent work in geography which has examined the archive as a site for knowledge's making but seldom in its own terms as a resource for the history of geography, and studies within the archival sciences which have considered the archive as something more than a 'storehouse' for collective memory. The paper reveals that the archival record for the history of British geography is at best uneven, and in many departments non-existent, although information on departmental history is held, often as memory, by individual geographers. The paper considers the survey's implications for the future histories of British geography and addresses the nature of the UK geography department archive as resource and responsibility. 相似文献