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381.
We have determined the activity of alkaline phosphatase in chorionic villous tissue obtained in the first trimester of pregnancy, in order to obtain the normal range of values as a prerequisite for application to the prenatal diagnosis of the rare bone disease hypophosphatasia. The activities found were a combination of intestinal and liver/bone/kidney types; traces of placental type were present in only one sample. 相似文献
382.
Emanuela Terzian Jillian Boreham Howard S. Cuckle Nicholas J. Wald Martin Bobrow Richard Lindenbaum A. C. Turnbull 《黑龙江环境通报》1985,5(6):401-414
A survey was conducted of the results of mid-trimester diagnostic amniocenteses in the Oxford Region from 1974 to 1981. The survey used data relating to all 4357 singleton pregnancies in which an amniocentesis was performed during this period. Follow-up information on outcome was obtained in respect of 4284 (98 per cent) pregnancies. A cell culture to determine karyotype and an alpha-fetoprotein determination was carried out in all cases. From 1974 to 1981 amniocenteses became increasingly common, rising from 2 to 32 per 1000 births. The most common indication for amniocentesis was a high risk of a chromosome abnormality–56 per cent of all amniocenteses. Within this group advanced maternal age was responsible for 89 per cent of the cases. The next most common indication was a high risk of a neural tube defect (37 per cent of all amniocenteses)–in 1974 a raised maternal serum alpha-fetoprotein level accounted for only 4 per cent of these; by 1981 this had risen to 67 per cent. There were seven false-positive and 132 true-positive diagnoses of neural tube defect; since 1981, with the introduction of amniotic fluid acetylocholinesterase determination as a secondary diagnostic test for neural tube defects, there have been no further false-positive diagnoses. In 1981 76 per cent of women aged 35 years or more did not have an amniocentesis. It is not known to what extent this was due to not offering women in this age group amniocentesis or to women not accepting such an offer. 相似文献
383.
A Method for Ensemble Wildland Fire Simulation 总被引:1,自引:0,他引:1
Mark A. Finney Isaac C. Grenfell Charles W. McHugh Robert C. Seli Diane Trethewey Richard D. Stratton Stuart Brittain 《Environmental Modeling and Assessment》2011,16(2):153-167
An ensemble simulation system that accounts for uncertainty in long-range weather conditions and two-dimensional wildland
fire spread is described. Fuel moisture is expressed based on the energy release component, a US fire danger rating index,
and its variation throughout the fire season is modeled using time series analysis of historical weather data. This analysis
is used to characterize the seasonal trend in ERC, autocorrelation of residuals, and daily standard deviation and stochastically
generate artificial time series of afternoon fuel moisture. Daily wind speed and direction are sampled stochastically from
joint probabilities of historical wind speed and direction for the date range of the fire simulation period. Hundreds or thousands
of fire growth simulations are then performed using the synthetic fire weather sequences. The performance of these methods
is evaluated in terms of the number of ensemble member simulations, one- versus two-dimensional fire spread simulations, and
comparison with results from 91 fires occurring from 2007 to 2009. Simulations were found to be in consistent agreement with
observations, but trends indicate that the ensemble average of simulated fire sizes were consistently larger than actual fires
whereas the farthest extent burned by fires was underestimated. 相似文献
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Richard A. Holland 《Behavioral ecology and sociobiology》2007,61(5):653-660
Bats have been extensively studied with regard to their ability to orient, navigate and hunt prey by means of echolocation,
but almost nothing is known about how they orient and navigate in situations such as migration and homing outside the range
of their echolocation system. As volant animals, bats face many of the same problems and challenges as birds. Migrating bats
must relocate summer and winter home ranges over distances as far as 2,000 km. Foraging bats must be able to relocate their
home roost if they range beyond a familiar area, and indeed circumstantial evidence suggests that these animals can home from
more than 600 km. However, an extensive research program on homing and navigation in bats halted in the early 1970s. The field
of bird navigation has advanced greatly since that time and many of the mechanisms that birds are known to use for navigation
were not known or widely accepted at this time. In this paper I discuss what is known about orientation and navigation in
bats and use bird navigation as a model for future research in bat navigation. Technology is advancing such that previous
difficulties in studying orientation in bats in the field can be overcome and so that the mechanisms of navigation in this
highly mobile animal can finally be elucidated. 相似文献
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Sebastiaan van Herk Jeroen Rijke Chris Zevenbergen Richard Ashley Broos Besseling 《Journal of Environmental Planning and Management》2015,58(3):554-575
Adaptive co-management and learning are paramount for integrated flood risk management. Relevant literature focuses on adaptation at the level of physical and societal systems. The level of projects and programmes is largely overlooked, but they comprise interventions that adapt our physical systems and they provide opportunities for learning to contribute to transitions of societal systems. This paper aims to increase understanding on how learning takes place and can be stimulated within a programme. The mixed-method case study of Room for the River, a €2.3 billion programme for flood risk management, shows that a programme can be organised using various governance arrangements to stimulate learning and be a means for adaptive co-management to deliver upon environmental objectives. 相似文献