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881.
Gyamfi Bright Akwasi Bekun Festus Victor Balsalobre-Lorente Daniel ONIFADE Stephen Taiwo Ampomah Asiedu Benjamin 《Environment, Development and Sustainability》2022,24(10):11852-11870
Environment, Development and Sustainability - This study is motivated by the United Nations Sustainable Development Goals (UN-SDG-7,8,11,12 and 13) on the need for clean and responsible energy... 相似文献
882.
Even though there is a global proliferation of cases of ecosystem breakdown under stress, little attention has been given to the development of practical and efficient means for cross-referencing similar cases. It seems essential that a more systematic approach be adopted for the efficient analysis of options in environmental management. This paper presents a frame work for identifying ecosystem dysfunctions and proposes a classification based on stresses and responses, a procedure which does not require a mechanistic knowledge of the causal pathways that lead to environmental degradation. By examining the techniques used in classifying disorders in human medicine, insight is derived, allowing one to treat the ecosystem as a patient. All attempts at distinguishing between pathological and natural response, whether in human or ecosystem medicine, must ultimately be based on context; the significance of a particular condition and appropriate remedial actions must always be viewed in relation to a specific patient. 相似文献
883.
Delwayne R. Nimmo Mary J. Willox Toben D. Lafrancois Phillip L. Chapman Stephen F. Brinkman Joseph C. Greene 《Environmental management》1998,22(6):913-926
/ Aquatic resources in Soda Butte Creek within Yellowstone National Park, USA, continue to be threatened by heavy metals from historical mining and milling activities that occurred upstream of the park's boundary. This includes the residue of gold, silver, and copper ore mining and processing in the early 1900s near Cooke City, Montana, just downstream of the creek's headwaters. Toxicity tests, using surrogate test species, and analyses of metals in water, sediments, and macroinvertebrate tissue were conducted from 1993 to 1995. Chronic toxicity to test species was greater in the spring than the fall and metal concentrations were elevated in the spring with copper exceeding water quality criteria in 1995. Tests with amphipods using pore water and whole sediment from the creek and copper concentrations in the tissue of macroinvertebrates and fish also suggest that copper is the metal of concern in the watershed. In order to understand current conditions in Soda Butte Creek, heavy metals, especially copper, must be considered important factors in the aquatic and riparian ecosystems within and along the creek extending into Yellowstone National Park.KEY WORDS: Mining; Metals; Toxicity; Biomonitoring; Copper; Yellowstone National Park 相似文献
884.
本文全面论述了化石燃料在21世纪能源需求供给中的重要性、未来能源供给,以及未来能源利用对全球气候产生的影响.考虑了当前和潜在的替代能源.得出的结论是即使其他资源衍生的能源大幅增加,21世纪大部分时间内,化石燃料仍是主要能源,CO2的封存将成为越来越重要的要求. 相似文献
885.
Yang Christopher Schneider Stephen H. 《Mitigation and Adaptation Strategies for Global Change》1997,2(4):373-404
Carbon dioxide emissions from 1990 to 2100 AD are decomposed into the product of four factors: population size, affluence
(measured here as GDP per capita), energy intensity (energy use per unit GDP) and carbon intensity (carbon dioxide emissions
per unit energy). These emissions factors are further subdivided into three regions: more developed countries (MDCs), China,
and the remaining less developed countries (LDCs). Departures from a baseline scenario (based on IPCC, 1992a — the so-called
‘business-as-usual’ scenario) are calculated for a variety of alternative assumptions concerning the four emissions factors
in the three regions. Although the IPCC scenario is called a ‘non-intervention’ scenario, it is shown, for example, that large
decreases in energy intensity in China or carbon intensity in MDCs are built into the ‘business as usual’ case — and such
large changes vary considerably from region to region. We show what CO2 emissions would look like if each of these four emissions factors projected in the baseline case somehow remained constant
at 1990 levels. Certain factors like energy intensity improvements and long-term population growth in LDCs, or GDP growth
and carbon intensity improvements in MDCs, are shown to have a big contribution to cumulative global emissions to 2100 AD,
and consequently, changes in these projected factors will lead to significant deviations from baseline emissions. None of
the scenarios examined in this analysis seems to indicate that any one global factor is clearly dominant, but cultural, economic,
and political costs or opportunities of altering each factor may differ greatly from country to country. 相似文献
886.
Life history evolution: successes, limitations, and prospects 总被引:1,自引:0,他引:1
Stearns SC 《Die Naturwissenschaften》2000,87(11):476-486
Life history theory tries to explain how evolution designs organisms to achieve reproductive success. The design is a solution to an ecological problem posed by the environment and subject to constraints intrinsic to the organism. Work on life histories has expanded the role of phenotypes in evolutionary theory, extending the range of predictions from genetic patterns to whole-organism traits directly connected to fitness. Among the questions answered are the following: Why are organisms small or large? Why do they mature early or late? Why do they have few or many offspring? Why do they have a short or a long life? Why must they grow old and die? The classical approach to life histories was optimization; it has had some convincing empirical success. Recently non-equilibrium approaches involving frequency-dependence, density-dependence, evolutionary game theory, adaptive dynamics, and explicit population dynamics have supplanted optimization as the preferred approach. They have not yet had as much empirical success, but there are logical reasons to prefer them, and they may soon extend the impact of life history theory into population dynamics and interspecific interactions in coevolving communities. 相似文献
887.
Mordecai Koenigsberg M.D. Stephen Factor Sangho Cho Ahvie Herskowitz Harold Nitowsky Rachel Morecki 《黑龙江环境通报》1981,1(4):241-247
Sonography was performed during the second trimester in two pregnancies at risk for the Marfan syndrome. In one, the limbs were significantly longer than expected (p < 0·0025) and a diagnosis of the Marfan syndrome was established. Pathological examination of the fetus after pregnancy interruption showed typical foci of cystic medial necrosis in the ascending aorta. 相似文献
888.
The management of isolated fetal choroid plexus cysts remains controversial. We have prospectively studied 15 565 pregnancies at two large obstetric units for the presence of choroid plexus cysts. In all cases where cysts were present at 19 weeks' gestation or greater, and were multiple, bilateral or solitary and greater than 5 mm maximum diameter, women were offered amniocentesis or placental biopsy, irrespective of the presence or absence of other abnormalities. Choroid plexus cysts were present in 152 (0·98 per cent) of cases. Four cases (2·6 per cent) of autosomal trisomy (three of trisomy 18, one of trisomy 21) were detected on prenatal karyotyping. In all cases, choroid plexus cysts were the only detectable prenatal anomaly. This study and a review of other large studies do not support the view that isolated choroid plexus cysts are a benign variant, the risk of trisomy being 1 in 82. Until further evidence is available, we recommend that cases of isolated fetal choroid plexus cysts at 19 weeks' gestation or greater should be offered prenatal karyotyping. 相似文献
889.
Stephen M. Redpath Fiona M. Leckie Beatriz Arroyo Arjun Amar Simon J. Thirgood 《Behavioral ecology and sociobiology》2006,60(3):386-391
In polygynous species, the adults are faced with a dilemma during chick rearing. Males must decide how to distribute food between their females and food allocation patterns are often highly unequal. In turn, the females that receive less food from males have to decide how much time to invest in additional hunting. If they spend more time hunting, then they leave their young exposed to weather and predators. However, if they stay at the nest, they increase the risk of their chicks starving. One way that birds may compensate for reduced provisioning is by increasing the size of prey caught. We tested this hypothesis by comparing prey deliveries to nests of hen harriers, Circus cyaneus, with females of different breeding status. As expected, male harriers delivered less food items to the nests of polygynous females, and especially their secondary, or β females. However, both sexes were able to compensate by delivering larger items and there was no difference in the overall mass of food delivered to nests. Moreover, females spent a similar amount of time at the nest, irrespective of status, and there were no overall differences in breeding success. Our results show that polygynous female harriers can compensate for the costs of polygyny, but we suggest that their ability to do so will vary according to the abundance of both large prey and predators. 相似文献
890.
Division of labor between undertaker specialists and other middle-aged workers in honey bee colonies
Stephen T. Trumbo Zhi-Yong Huang Gene E. Robinson 《Behavioral ecology and sociobiology》1997,41(3):151-163
A primary determinant of colony organization in temporally polyethic insect societies is inter-individual variation in behavior
that is independent of worker age. We examined behavioral repertoires, behavioral correlates of adult development, and spatial
distributions within the hive to explore the mechanisms that produce behavioral variation among middle-age honey bees (Apis mellifera). Individually labeled undertakers, guards, food storers, and wax workers exhibited a broad range of task-related behavior,
but bees tagged as undertakers were more likely to subsequently remove a corpse from the hive and handle a corpse compared
to other middle-aged bees. The activity level of undertakers was similar to other task groups, suggesting that undertaking
specialists were neither hyper-active “elites” nor quiescent “reserves” that become active only when a dead bee stimulus is
present. Undertakers also were more likely to remove debris and to remain in the lower region of the hive or near the entrance,
even when not engaged in corpse removal; both preferences may promote colony efficiency by reducing inter-task travel times.
Guards and undertakers were less likely to perform behavior normally associated with young bees compared to food storers and
wax workers. Undertakers and guards also initiated foraging at earlier ages than the other task groups. These results suggest
that undertakers and guards may be slightly developmentally advanced compared to food storers and wax workers. There also
was evidence for lifetime differences in behavioral preferences which could not be explained by differences in adult development.
Bees tagged as undertakers were more likely to subsequently remove a dead bee during their entire pre-foraging career compared
to other task groups or members of their general age cohort. Differences in both the rate of adult development and individual
behavioral preferences, both of which may be subject to genetic and environmental influences, are important determinants of
inter-individual variation among honey bees of middle age.
Received: 5 February 1997 / Accepted after revision: 27 May 1997 相似文献