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1.
A 5.4 m peat core from the Sandy Run Creek (SRC) valley in the upper Coastal Plain of Georgia shows that before 30 ka the valley had an aggradational sandy floor with shallow swales and low ridges of 1–2 m amplitude suggesting a braided stream pattern and a low water table. The climate from 30–25 ka was cool and dry and the vegetation open grassland with stands of pine and spruce that produced few fires. At ca. 16 ka a warmer, wetter climate caused SRC to meander and incise the valley fill removing some previously deposited sediment at the site of our peat core so that sediments of 13 ka rest directly on sediments deposited at 25 ka. After ca. 13 ka higher groundwater levels initiated vertical accretion of floodplains allowing peat accumulation in shallow depressions across the valley. Pollen from the Younger Dryas period (ca. 13–11 ka) indicates a cool, moist environment of open oak woodland, mesic trees, riparian populations of alder, and reduced levels of pine. By the early to mid Holocene, tupelo and oak dominated over pine indicating wetter conditions, while sand stringers in peat record periodic heavy rains, an elevated water table, and intervals of substantial runoff. Cooling after ca. 4.5 ka brought drier and more variable conditions. Fires increased and southern pine replaced tupelo and oak. The absence of sand stringers in peat younger than 4.5 ka indicates fewer intense rainfall events.  相似文献   

2.
The systematic significance of flavonoid distribution in the southeastern United States taxa of Persea is discussed. The compounds thus far elucidated are glycosides based on quercetin, kaempferol, apigenin or luteolin.  相似文献   

3.
We collected information on 860 stream restoration projects in four states in the southeastern United States—Georgia, Kentucky, North Carolina, and South Carolina—to gain a better understanding of the practice of stream restoration in this area of high aquatic biodiversity and rapid metropolitan expansion. This was completed as a part of the National River Restoration Science Synthesis, with the larger goal of understanding the state of the science of stream restoration. Stream restoration project density, goals, and monitoring rates varied by state, although southeastern monitoring rates were higher than in other parts of the country. North Carolina had the most projects in the Southeast, of which 36% were monitored. In‐depth phone interviews with project managers from a random subsample of projects provided insights into the process of stream restoration. Land availability was the most common basis for site prioritization, and 49% of projects involved mitigation. Although 51% of projects were associated with a watershed assessment, only 30% of projects were done as part of a larger plan for the watershed. Projects were monitored using physical (77% of monitored projects), chemical (36%), and biological (86%) variables, although many projects were planned and ultimately evaluated based on public opinion. Our results suggest that stream restoration in the southeastern United States is at an exciting point where better incorporation of a watershed perspective into planning and establishment and evaluation of stated, measurable success criteria for every project could lead to more effective projects.  相似文献   

4.
The United States has important national interests vested in both the Arctic and Antarctic Oceans. Thus, in recent decades the United States has progressively codified its national commitment to conserve and manage both these marine regions and their resources and to protect them from activities that might produce adverse impacts. The U.S. legislation passed since the 1960s selectively affects both polar regions and supports major American policy objectives there: to maintain the Arctic and Antarctic as areas of international cooperation for peaceful purposes; to satisfy economic needs, especially hydrocarbon, mineral, and living resources; to protect opportunities for scientific research; to protect the marine environment; and to conserve living resources in the circumpolar seas. Future trends suggest a shift in U.S. policy attention to the Arctic. Accordingly, new U.S. legislation will be needed to regulate increased activities in the polar north.  相似文献   

5.
In this review we present an outline of cytopathology training in the United States, for a non-US readership.  相似文献   

6.
The United States is the sole superpower in the contemporary world and its role in the development of the law of the sea cannot be ignored. Although having not yet acceded to the U.N. Convention on the Law of the Sea, the United States has contributed to the development of the international law of the sea in numerous ways, including responding to the so-called excessive maritime claims in East Asia and creating new rules of maritime enforcement. This article assesses this recent U.S. practice.  相似文献   

7.
8.
This study proposes an entrepreneurship model that (1) uses sociological literature on ethnic stratification to develop a typology of subdominant, marginalized, subordinate, and outcast minority groups and (2) applies geographic principles to spatially define variation in entrepreneurial environments in terms of urban hierarchies, regional milieus, and hinterland centres. Examining retail enterprise, the study utilizes the interactionist approach, which holds that ethnic business differences result from an interplay of groups’ attributes (supply) and locations’ opportunity structures (demand). The study extends this approach by incorporating the mixed embeddedness concept, which stresses the importance of ethnic groups’ situation in broad social, political, and institutional contexts. Regression analyses of Census data for US cities in 1900 show why retail enterprise among outcast minorities is demand-side resistant, while retail enterprise among marginalized minorities is demand-side reactive. The model thus yields insights into how ethnic stratification and geographical positions interact to produce inequalities of ethnic entrepreneurship.  相似文献   

9.
This article explains the position(s) of the United States in the maritime dispute adjacent to Svalbard. While the United States has regarded Norway's exclusive claim to the natural resources outside Svalbard as everything from “wishful thinking” to legally plausible, Washington maintains that it may have rights under the 1920 Svalbard Treaty to exploit the maritime zones adjacent to the archipelago. The U.S. reservation is the result of assessments and reassessments of legal considerations as well as national interests.  相似文献   

10.
Nitrogen loss from deserts in the southwestern United States   总被引:19,自引:6,他引:13  
A lower limit for nitrogen loss from desert ecosystems in the southwestern United States was estimated by comparing nitrogen inputs to the amount of nitrogen stored in desert soils and vegetation. Atmospheric input of nitrogen for the last 10 000 years was conservatively estimated to be 2.99 kg N/m2. The amount of nitrogen stored in desert soils was calculated to be 0.604 kg N/m3 using extant data from 212 profiles located in Arizona, California, Nevada, and Utah. The average amount of nitrogen stored in desert vegetation is approximately 0.036 kg N/m2.Desert conditions have existed in the southwestern United States throughout the last 10 000 years. Under such conditions, vertical leaching of nitrogen below a depth of 1 m is small (ca. 0.028 kg N/m2 over 10 000 years) and streamflow losses of nitrogen from the desert landscape are negligible. Thus, the discrepancy found between nitrogen input and storage represents the amount of nitrogen lost to the atmosphere during the last 10 000 years. Loss of nitrogen to the atmosphere was calculated to be 2.32 kg N/m2, which is 77% of the atmospheric inputs.Processes resulting in nitrogen loss to the atmosphere from desert ecosystems include wind erosion, ammonia volatilization, nitrification, and denitrification. Our analysis cannot assess the relative importance of these processes, but each is worthy of future research efforts.  相似文献   

11.
The Energy Independence and Security Act (EISA) of 2007 mandates US production of 136 billion L of biofuel by 2022. This target implies an appropriation of regional primary production for dedicated feedstocks at scales that may dramatically affect water supply, exacerbate existing water quality challenges, and force undesirable environmental resource trade offs. Using a comparative life cycle approach, we assess energy balances and water resource implications for four dedicated ethanol feedstocks – corn, sugarcane, sweet sorghum, and southern pine – in two southeastern states, Florida and Georgia, which are a presumed epicenter for future biofuel production. Net energy benefit ratios for ethanol and coproducts range were 1.26 for corn, 1.94 for sweet sorghum, 2.51 for sugarcane, and 2.97 for southern pine. Corn also has high nitrogen (N) and water demand (11.2 kg GJnet?1 and 188 m3 GJnet?1, respectively) compared with other feedstocks, making it a poor choice for regional ethanol production. Southern pine, in contrast, has relatively low N demand (0.4 kg GJnet?1) and negligible irrigation needs. However, it has comparatively low gross productivity, which results in large land area per unit ethanol production (208 m2 GJnet?1), and, by association, substantial indirect and incremental water use (51 m3 GJnet?1). Ultimately, all four feedstocks require substantial land (10.1, 3.1, 2.5, and 6.1 million ha for corn, sugarcane, sweet sorghum, and pine, respectively), annual N fertilization (3230, 574, 396, 109 million kg N) and annual total water (54 400, 20 840, 8840, and 14 970 million m3) resources when scaled up to meet EISA renewable fuel standards production goals. This production would, in turn, offset only 17.5% of regional gasoline consumption on a gross basis, and substantially less when evaluated on a net basis. Utilization of existing waste biomass sources may ameliorate these effects, but does not obviate the need for dedicated primary feedstock production. Careful scrutiny of environmental trade‐offs is necessary before embracing aggressive ethanol production mandates.  相似文献   

12.
The exploding increase in trade between the United States and China, which share comparable ecosystem types, will result in unwanted establishment of alien invasive species that will inflict considerable ecological and economic damage. This undesirable result can be avoided by marshaling management tools and policy instruments that are readily available. High-level policy action is necessary to put the proper and available safeguards in place, and quickly.  相似文献   

13.
A mail survey was completed of the nonhuman primate skeletal collections (excluding tupaiids) housed in United States and Canadian museums, universities, and other institutions. Survey results are reported by genus for both skulls and postcrania without regard for age or sex. The survey emphasized specimens of wild-caught primates but institutional personnel were not always able to separate animals which died in captivity. Responses were received from 157 of the 212 institutions to which questionnaires were sent. Of those who returned the questionnaires, 75 institutions have wild-caught, nonhuman primate skeletal materials in their collections. Institutions that have either no nonhuman primate skeletal materials (50) or only the remains of captive animals (36) are listed separately. The total number of specimens reported exeeds 21,000 skulls and 6,400 postcrania.  相似文献   

14.
Two new species of the genus Diaphanosoma, D. oligosetum and D. dorotheae, from Louisiana and North Carolina respectively, are described. The former species has large head with protruding dorsal part, large lanceolate spine on the basipodite's distal outer end, an extremely reduced number of antennal setae, up to six in adult specimens, and unique armament of valve margin. On the whole, it shows the pronounced combination of primitive and specialized morphological traits. D. dorotheae is a member of D. brachyurum species group differing from its other known representatives in presence of a small but very conspicuous spine on the end of proximal segment of antennal exopodite and a variable number of setae (seven or eight) on the distal segment of the branch. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

15.
In January 1998, Taiwan promulgated the Law of the Republic of China (ROC) on the Territorial Sea and the Contiguous Zone and the Law of the Republic of China on the Exclusive Economic Zone (EEZ) and the Continental Shelf, both of which came into force on January 21, 1998. On June 26, 1998, China adopted the Law of the People's Republic of China on the Exclusive Economic Zone and the Continental Shelf, which is the most significant maritime legislation since its 1992 Law on the Territorial Sea and the Contiguous Zone. This article studies the recent maritime legislation developments in Mainland China and Taiwan, the differences and similarities between the two sets of laws, their implications for the Asia-Pacific region, and the potential challenges for the United States.  相似文献   

16.
ObjectiveTo assess the socioeconomic predictors of suicide risk among cancer patients in the United States.MethodsCancer patients available within Surveillance, Epidemiology and End Results (SEER) database who were diagnosed between 2000–2010 have been reviewed. Linkage analysis to Census 2000 SF files was conducted to determine area-based socioeconomic attributes. Observed/ Expected ratios were calculated for the overall cohort as well as for clinically and socioeconomically defined subgroups. “Observed” is the number of observed completed suicide cases in the studied cohort; while “Expected” is the number of completed suicide cases in a demographically similar cohort within the United States and within the same period of time.ResultsThe current study reviews a total of 3,149,235 cancer patients (diagnosed 2000–2010) within the SEER database. Regarding socioeconomic county attributes, higher risk of suicide seems to be associated with lower educational attainment (O/E for counties with > 20% individuals with less than high school education: 1.41; 95% CI: 1.35–1.47), poverty rates (O/E for counties with > 5% individuals below poverty line: 1.39; 95% CI: 1.34–1.43), unemployment rates (O/E for counties with >5% families below poverty line: 1.36; 95% CI: 1.31–1.41) and less people living in urban areas (O/E for counties with < 50% individuals living in urban areas: 1.63; 95% CI: 1.50–1.77). On the other hand, risk of suicide seems to be inversely related to a higher representation of foreign-born individuals (O/E for counties with < 5% foreign-born individuals: 1.56; 95% CI: 1.47–1.65); and inversely related to a higher representation with recent immigrants to the US (O/E for counties with < 5% recent immigrants: 1.33; 95% CI: 1.29–1.38).ConclusionsCancer patients living in a socioeconomically vulnerable environment (lower educational status, poverty, and unemployment) seem to have higher suicide risk compared to other cancer patients.  相似文献   

17.
This paper uses the large cross sectional survey of 8544 workers in nine industries (pig iron, bar iron, steel, coal, coke, cottons, woolens, and glass) in the United States and five European countries (Belgium, Great Britain, France, Belgium, and Switzerland) to examine inequality in the industrial working class in the late nineteenth century. The paper looks at incomes, the food budget share (estimated using the Almost Ideal Demand System), and home ownership. The results show regular gradients with the unskilled workers doing less well than semi-skilled and skilled workers. Despite the lack of proprietors, farmers, and other groups with significant income from property, such surveys can be useful in the study of the historical aspects of inequality.  相似文献   

18.
Tong R 《Bioethics》2007,21(9):488-499
When feminist bioethicists express concerns about health-related gender disparities, they raise considerations about justice and gender that traditional bioethicists have either not raised or raised somewhat weakly. In this article, I first provide a feminist analysis of long-term healthcare by and for women in the United States and women in Taiwan. Next, I make the case that, on average, elderly US and Taiwanese women fare less well in long-term care contexts than do elderly US and Taiwanese men. Finally, I explore some suggested practical remedies to reduce gender disparities in long-term care contexts.  相似文献   

19.
Summary Nitrogen-fixing activity in hardwood forests of the northeastern United States occurred in wood litter, greater than 2 cm in diameter. Activity in large dead wood was independent of species, in the case of deciduous wood litter, but was restricted to partially decayed wood with a high moisture content. Maximum rates of activity were observed in the summer months, minimum rates in the winter. Evidence from six stands of varying ages showed that fixation in large wood litter occurred in only 25% of the samples assayed.Fixation was highest in the youngest, 4 years, and oldest, over 200 years, stands; being about 2 kg/ha/yr. The quantity of nitrogen fixed appears to be related to the biomass of dead wood. Large amounts of wood litter in the youngest stands were from slash left after cutting. As the supply of slash is exhausted by decay, nitrogen fixation decreases, with a low around year 20. Fixation then gradually increases as natural thinning adds wood to the litter compartment.Apparently, the amount of nitrogen fixed in dead wood the first 20 years following clearcutting can only replace a modest fraction of the amount lost as a result of the cutting and product removal. Finally, the results indicate that nitrogen fixation in wood litter does not equal nitrogen fixation in a northern hardwood forest calculated using a mass balance approach, suggesting that additional nitrogen inputs exist.  相似文献   

20.
I engage debates about racial media bias by analysing newspaper coverage of professional tennis players in France and the United States. Tennis is an elite sport that typically does not have many non-white players and may be especially sensitive to racial boundaries. Tennis also offers a new solution to the methodological challenge of establishing that any difference in newspaper coverage across racial groups is due to bias and not actual differences across the groups. I use the professional tennis ranking system, which assigns an objective marker of how good a player is (and therefore the media coverage that s/he should receive) at any point in time. I explore two types of bias (the amount and tone of media coverage) and uncover no systematic racial differences in the relationship between ranking and media coverage. My findings have several implications for our understanding of racial boundaries and the media.  相似文献   

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