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161.
Robert Banks John Martini Harry Smith Alfred Bowles Thomas McNish Richard Howard 《Traffic injury prevention》2013,14(2):123-130
The purpose of this study was to define the anatomical arrangement of the lumbar spine in the mid-body sagittal plane of a human volunteer while in three postures: a driving posture; full flexion; and full extension. Radiographic images of the lumbar spine were made of a 33-year old 50th percentile male subject seated in a comfortable driving posture. Additional radiographs were made of the lumbar spine while the subject was postured in full voluntary flexion, and full voluntary extension. Anterior and posterior mid-sagittal vertebral endplate positions were plotted on an x-y coordinate system for each posture. Anterior and posterior disk thicknesses, and the positions of the centers of each vertebra were numerically determined using information from the plots. Disk thicknesses were then graphed and comparisons made for each posture. The arrangements of the centers of vertebrae were graphed and compared for the three different postures. The arrangement of the lumbar vertebrae tended toward that of full voluntary flexion while the subject was in a normal driving posture. Anterior disk thickness was a sensitive indicator of posture, while posterior disk thickness was not. While in a driving posture, the lower back approximated a straight-line that was nearly parallel to the seat back axis. The observations support those of an earlier study. Since soft tissue spinal elements can only be damaged by applying tensile forces in excess of their tolerance, the anterior elements of the lumbar spine would not be directly threatened in low velocity frontal collisions, since anterior elements would be in relative compression. Tension injury to the anterior structures as a result of a rear-end collision would first require reversing the preimpact conditions imposed by the normal driving posture. Tension injury to the posterior spinal elements resulting from low velocity rear-end collisions would be unlikely since axial compression loading would also diminish tension stress in posterior soft tissue structures. Any compression injury to posterior elements resulting from rear-end collisions would first require reversing the pre-impact conditions imposed by the normal driving posture. 相似文献
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163.
The lofty goals of the 1992 Earth Summit regarding sustainable development will not be achieved without major improvements in the management of transboundary water resources. This paper describes the serious nature of water-related conflicts and environmental damage associated with degradation of marine ecosystems, coastal zones, and shared surface/groundwater systems. Traditional approaches such as international conventions, watercourse agreements with basin organizations, and arbitration have generally fallen short of their objectives. This article suggests that a middle ground centered on multicountry institutional arrangements for joint fact finding, evaluation, and problem resolution may be a more productive approach over the short term to achieve sustainable development. The experience of the International Joint Commission (Canada and U.S.) is described as a way of providing a neutral ground for building trust among nations, for 'leveling the playing field' among small and large countries, and for providing mechanisms for countries to work jointly toward sustainable development of their shared resources without relinquishing their sovereignty. The Global Environment Facility (GEF) is playing a catalytic role in assisting countries to address transboundary water resources issues. The paper describes GEF's Operational Strategy and discusses the implications of joint institutional arrangements for the international waters focal area. Given that the environmental security of many nations rests on improved transboundary cooperation, the GEF provides a pragmatic opportunity for countries to cooperatively address these pressing problems. 相似文献
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The Science of Nature - 相似文献
168.
Alfred Kühn 《Die Naturwissenschaften》1955,42(19):529-530
169.
Willem Kruijer Alfred Stein Willem Schaafsma Sanne Heijting 《Environmental and Ecological Statistics》2007,14(4):399-410
Count data on a lattice may arise in observational studies of ecological phenomena. In this paper a hierarchical spatial model
is used to analyze weed counts. Anisotropy is introduced, and a bivariate extension of the model is presented. 相似文献
170.
Valentina Krysanova Frank Wechsung Alfred Becker Werner Poschenrieder Jan Gräfe 《Environmental Modeling and Assessment》1999,4(4):259-271
Hydrological processes and crop growth were simulated for the state of Brandenburg (Germany) using the hydrological/vegetation/water quality model SWIM, which can be applied for mesoscale river basins or regions. Hydrological validation was carried out for three mesoscale river basins in the area. The crop growth module was validated regionally for winter wheat, winter barley and maize. After that the analysis of climate change impacts on hydrology and crop growth was performed, using a transient 1.5 K scenario of climate change for Brandenburg and restricting the crop spectrum to the three above mentioned crops. According to the scenario, precipitation is expected to increase. The impact study was done comparing simulation results for two scenario periods 2022–2030 and 2042–2050 with those for a reference period 1981–1992. The atmospheric CO2 concentrations for the reference period and two scenario periods were set to 346, 406 and 436 ppm, respectively. Two different methods – an empirical one and a semi-mechanistic one – were used for adjustment of net photosynthesis to altered CO2. With warming, the model simulates an increase of evapotranspiration (+9.5%, +15.4%) and runoff (+7.0%, +17.2%). The crop yield was only slightly altered under the climate change only scenario (no CO2 fertilization effect) for barley and maize, and it was reduced for wheat (–6.2%, –10.3%). The impact of higher atmospheric CO2 compensated for climate-related wheat yield losses, and resulted in an increased yield both for barley and maize compared to the reference scenario. The simulated combined effect of climate change and elevated CO2 on crop yield was about 7% higher for the C3 crops when the CO2 and temperature interaction was ignored. The assumption that stomatal control of transpiration is taking place at the regional scale led to further increase in crop yield, which was larger for maize than for wheat and barley. The regional water balance was practically not affected by the partial stimulation of net photosynthesis due to higher CO2, while the introduction of stomatal control of regional transpiration reduced evapotranspiration and enlarged notably runoff and ground water recharge. 相似文献