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排序方式: 共有341条查询结果,搜索用时 15 毫秒
1.
We report on a case of trisomy 8 mosaicism detected prenatally in a single clone of amniotic fluid culture, and confirmed on fetal blood and on peripheral lymphocytes after birth. A follow-up was performed over 3 years, showing a clinically normal female with cognitive, neuropsychological, and linguistic development in a normal range. 相似文献
2.
同源地人工湖水体和底泥中有机物组成及有机结构的分析研究 总被引:1,自引:0,他引:1
采用XAD-8大孔吸附树脂对水体和底泥中的有机物进行组分分离,并通过傅里叶变换红外光谱(FTIR)、紫外-可见光谱(UV-Vis)和三维荧光光谱(3DEEMs)对自然水体和底泥中的疏水酸(腐殖酸、富里酸)、疏水碱、疏水中性物质和亲水物质进行表征和对比.结果表明,水体中有机物含量:亲水物质富里酸腐殖酸疏水碱疏水中性物质,底泥中有机物的含量为:腐殖酸富里酸亲水物质疏水碱疏水中性物质.根据红外、紫外、三维荧光光谱可知底泥中有机物的芳香程度、不饱和程度及分子量大小略高于水体有机物.根据荧光指数(FI)和自生源指标(BIX)可知,底泥和水体的腐殖酸和富里酸主要来源于陆生动植物和土壤有机质,而其余物质主要源于细菌和藻类活动. 相似文献
3.
Traditional ecological knowledge (TEK) can play an important role in the understanding of ecological systems. Although TEK
has complemented scientific and managerial programs in a variety of contexts, its formal incorporation into remote sensing
exercises has to date been limited. Here, we show that the vegetation classifications of the Ache, an indigenous hunter-gatherer
tribe of the Mbaracayu Forest Reserve in Paraguay, are reflected in a supervised classification of satellite imagery of the
reserve. Accuracy of classification was toward the low end of the range of published values, but was reasonable given the
difficult nature of separating forest classes from satellite images. Comparison of the resultant map with a more traditionally
elaborated vegetation map highlights differences between the two approaches and the gain in information obtained by considering
TEK classifications. We suggest that integration of TEK and remote sensing may provide alternative insights into the ecology
of vegetation communities and land cover, particularly in remote and densely forested areas where ecological field research
is often limited by roads and/or trail systems. 相似文献
4.
5.
Kristin von Hirsch Svendsen Sindre Rabben Svedahl Christian H. Lindh Karin Broberg Palmgren 《毒物与环境化学》2017,99(3):525-534
Cooking fumes contain compounds that may give rise to oxidative stress and mutations when inhaled. The aim of this study was to evaluate if cooking fumes from frying of bacon induce oxidative stress by measurement of urinary 8-oxo-7,8-dihydro-2 deoxyguanosine, a marker of oxidatively damaged DNA. Three non-smoking women fried bacon for 3 h. Urine samples were taken as early morning void at the same time on four days; the morning before frying, the morning after first frying, the morning after three days of frying and one week after first urine sample. 8-Oxo-7,8-dihydro-2 deoxyguanosine, 1-hydroxypyrene and 2-hydroxyphenanthrene, metabolites of polycyclic aromatic hydrocarbons, were measured by liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS). 8-Oxo-7,8-dihydro-2 deoxyguanosine correlated weakly with concentrations of 1-hydroxypyrene (r = 0.31, p = 0.042), but it did not correlate with 2-hydroxyphenanthrene (r = ?0.074; p = 0.64). Average urinary 8-oxo-7,8-dihydro-2 deoxyguanosine concentrations increased from the day before frying (16.3 ± 4.2 nmol/L) to the third day of frying (26.2 ± 10.2 nmol/L), although not statistically significantly. Our pilot study shows that frying of bacon may result in increased oxidative stress which further emphasises the possible carcinogenic potential of cooking fumes. 相似文献
6.
Remote sensing has emerged as one of the major techniques for the analysis and delineation of large floods. This analysis can provide data invaluable for the hydrological management of large river systems. A need for information on the extent of floodplain inundation for the lower reaches of the largest river in the UK was met by a search through Landsat images of floods and the analysis of the best example recorded. Automated classification of the Landsat imagery of this flood on the river Severn in 1977 was used to provide estimates of the extent and spatial distribution of inundation. Flood images were generated using the Plessey IDP 3000 image processor, and the maps derived accorded well with aerial photography and qualitative flood information. Three distinct floodplain environments were delineated and flood images produced by different spectral bands compared. Specific questions prompted by flood hazard management and concerning the processes and extent of flooding were answered by the Landsat data analysis. Management of the flood risk of large rivers is expensive and remote sensing data is a relatively cheap and effective way of monitoring control works and providing data for the prediction of the effects of future hydrological works. Remote sensing is a practical way in which spatial information concerning the behavior of large dynamic systems can be obtained both quickly and relatively cheaply. 相似文献
7.
Land-cover change in upper Barataria Basin estuary,Louisiana, 1972-1992: increases in Wetland area 总被引:1,自引:0,他引:1
The Barataria Basin, Louisiana, USA, is an extensive wetland and coastal estuary system of great economic and intrinsic value.
Although high rates of wetland loss along the coastal margin of the Barataria Basin have been well documented, little information
exists on whether freshwater wetlands in the upper basin have changed. Our objectives were to quantify land-cover change in
the upper basin over 20 years from 1972–1992 and to determine land-cover transition rates among land-cover types. Using 80-m
resolution Landsat MSS data from the North American Landscape Characterization (NALC) data archive, we classified images from
three time steps (1972, 1985, 1992) into six land-cover types: agriculture, urban, bottomland hardwood forest, swamp forest,
freshwater marsh, and open water. Significant changes in land cover occurred within the upper Barataria Basin over the study
period. Urban land increased from 8% to 17% of the total upper basin area, primarily due to conversions from agricultural
land, and to a lesser degree, bottomland forest. Swamp forest increased from 30% to 41%, associated with conversions from
bottomland hardwood forest and freshwater marsh. Overall, bottomland forest decreased 38% and total wetland area increased
21%. Within the upper Barataria, increases in total wetland area may be due to land subsidence. Based on our results, if present
trends in the reduction of bottomland forest land cover were to continue, the upper Barataria Basin may have no bottomland
hardwood forests left by the year 2025, as it is subjected to multiple stressors both in the higher elevations (from urbanization)
and lower elevations (most likely from land subsidence). These results suggest that changes in the upper freshwater portions
of coastal estuaries can be large and quite different from patterns observed in the more saline coastal margins. 相似文献
8.
To evaluate the accounts of local fishermen, Landsat TM images (1986, 1993, 1999) were examined to assess potential losses
in the mangrove forests of the Teacapán–Agua Brava lagoon system, Mexico. A binary change mask derived from image differencing
of a band 4/3 ratio was employed to calculate any changes within this forested wetland. The results indicate that by 1986
approximately 18% (or 86 km2) of the mangrove area under study was either dead or in poor condition. The majority of this damage had occurred in the eastern
section of the Agua Brava basin, which coincides, with the reports of the elderly fishermen. Examination of aerial photographs
from 1970 revealed no adverse impacts in this area and would suggest, as postulated by the fishermen and other scientists,
that modifications in environmental conditions following the opening of a canal, Cuautlá canal, in 1972 may have initiated
the large-scale mortality. Although these areas of impact are still developing, the results from the satellite data indicate
that the majority of the more recent changes are occurring elsewhere in the system. Obvious in the 1999 satellite data, but
not so in the 1993, are large areas of mangrove degradation in the northern section of the Teacapán region. In the Agua Brava
basin, the more recent transformations are appearing on the western side of the basin. Since long-term records of environmental
conditions are absent, it is difficult to determine why these latest changes are occurring or even if the earlier losses were
the result of the canal. Potential agents of change that have recently been observed include a hurricane, a second canal,
and the uncontrolled expansion of the Cuautlá canal since 1994. 相似文献
9.
A simple method for the quantitative gradient analysis of a xerotermic forest-margin ecotone is described. In this method, the mean value of the coefficient of similarity between all plots of the transect is used for estimating the rate of changes in species composition. Changes in the phytosociological spectrum are analyzed. The method adequately reflects trends in the displacement of forest species by forest-margin, steppe, and meadow species. 相似文献
10.
The index patient is a female fetus in which prenatal diagnosis of 8p trisomy was established after amniocentesis at 16 weeks of gestation. This fetus was the unbalanced product of a maternal translocation of 5q/8p (karyotype: 46,XX,t(5;8)(q35;pl 1). Internal malformations include an anomalous lobature of the right lung, a little and high atrio-ventricular communication, and an anomaly in the number and shape of the aortic semilunar valves. The possible relationship between the phenotype and the chromosomal abnormality is briefly discussed. 相似文献