共查询到20条相似文献,搜索用时 31 毫秒
1.
J W Larsen 《Teratology》1992,46(1):23-29
Clinical teratologists will have new challenges during the 1990s as birth defects are diagnosed more frequently than in previous decades. Malformations and genetic disorders will be diagnosed in utero during all three trimesters of pregnancy. The teratologist may participate in or lead a multispecialty group to give the involved family optimal interpretation of test results, counseling, and recommendations regarding subsequent clinical management. 相似文献
2.
In the late 1980s and early 1990s Polish society experienced deep political, economic and social changes. The aim of the study is to investigate whether changes that occurred in Poland during the transformation significantly influenced the risk of hypertension among adult men. We find that irrespective of age, marital status, education, degree of urbanization, lifestyle variables (smoking, drinking alcohol, and physical activity), and BMI the risk of hypertension after 1989 was higher than before transformation (odds ratio=1.45, p<0.001). Psychosocial factors are proposed as factors which might at least partly explain the higher risk of hypertension during the first years of economic transition in Poland. 相似文献
3.
比较研究了1970s、1980s和1990s期间不同大豆 ( Glycine max (L.) Merr.)品种的生理生态特性:光合作用、蒸腾作用、气孔导度、水分利用效率、胞间CO2浓度和叶片水势,分析了各生理生态特性之间以及与产量在不同生育期的关系.研究表明光合速率和产量之间存在显著的相关关系,高产大豆同时具有高的气孔导度和水势,胞间CO2浓度则很低,特别是在鼓粒期关系更为显著.高产大豆的光合作用在鼓粒期达到最高值,光合作用日变化呈双峰曲线.在鼓粒期高产大豆的光合产物大量运往籽粒中,对于高产品种和高光效-"源"固然重要,而"流"-光合产物的合理运转和分配对产量则更为重要. 相似文献
4.
Economic theory dictates that changes in consumer demand have predictable effects on prices. Demographics represents an important component of demand for aesthetic surgery. Between the years of 1997 and 2010, the U.S. population is projected to increase by 12 percent. The population increase will be skewed such that those groups undergoing the most aesthetic surgery will see the largest increase. Accounting for the age-specific frequencies of aesthetic surgery and the population increase yields an estimate that the overall market for aesthetic surgery will increase by 19 percent. Barring unforeseen changes in general economic conditions or consumer tastes, demand should increase by an analogous amount. An economic demonstration shows the effects of increasing demand for aesthetic surgery on its fees. Between the years of 1992 and 1997, there was an increase in demand for breast augmentation as fears of associated autoimmune disorders subsided. Similarly, there was increased male acceptance of aesthetic surgery. The number of breast augmentations and procedures to treat male pattern baldness, plastic surgeons, and fees for the procedures were tracked. During the study period, the supply of surgeons and consumer demand increased for both of these procedures. Volume of breast augmentation increased by 275 percent, whereas real fees remained stable. Volume of treatment for male pattern baldness increased by 107 percent, and the fees increased by 29 percent. Ordinarily, an increase in supply leads to a decrease in prices. This did not occur during the study period. Economic analysis demonstrates that the increased supply of surgeons performing breast augmentation was offset by increased consumer demand for the procedure. For this reason, fees were not lowered. Similarly, increased demand for treatment of male pattern baldness more than offset the increased supply of surgeons performing it. The result was higher fees. Emphasis should be placed on using these economic relationships to expand the demand for aesthetic surgery. 相似文献
5.
S. Distaso A. De Lucia M. P. Circella F. Cassano F. Palasciano M. Scattarella 《International Journal of Anthropology》2004,19(1-2):19-32
For more than a century Italian emigration contributed to rebalancing the labour market in Italy, through the absorption of
significant numbers of the Italian workforce abroad and by alleviating unemployment levels, and also represented a source
of national economic wealth. In the last two decades the Italian migratory trend has been reversed: there has, in fact, been
an intensification of migratory flows towards Italy owing to the return of our compatriots, whose economic goals have been
realised, and to the arrival of citizens either from poorer countries whose growth rate is zero or negative, or from developing
countries. It is certainly necessary to bear in mind that the foreigners are not all workers: there are spouses, children,
family members and other persons present for reasons other than work or family, and there are the children of immigrants born
in Italy. The data regarding the wealth produced by the work of the immigrants could be significant, also and above all, in
view of demographic shrinkage and the ageing of the Italian population forecast for the next fifty years. In view of this,
immigration could become a real source of wealth both in economic terms and in terms of human capital. If we evaluate separately
and comparatively the immigrations that take place for the demand for manpower and those due to flight from situations of
economic and political hardship, we can see that Apulia, starting from 1990s, has become not only a land of passage towards
the rest of Europe, but also an objective for settlement. 相似文献
6.
Hamada H 《Development, growth & differentiation》2008,50(Z1):S71-S78
How left-right (LR) asymmetry emerges during development has been a classic problem in the field of developmental biology, but it is only since the 1990s that molecular and genetic approaches have become possible. Since current progress in LR patterning has been summarized in several other reviews, I would like to briefly describe how this topic developed in the early days and what remains to be solved. In particular, two breakthroughs in the mid to late 1990s made major contributions to recent progress. Despite the rapid progress, there remain many challenging issues that need to be addressed in future. 相似文献
7.
This study contrasts the actual conservation spending and the Australian public’s demand for conservation funding for two
Australian mammal species, the koala and the northern hairy-nosed wombat. It involves a survey of 204 members of the Australian
public. Willingness to fund conservation action to protect the northern hairy-nosed wombat was found to be higher than that
for the koala despite the koala’s immense popularity. The critically endangered status of the northern-hairy nosed wombat
and the more secure conservation status of the koala is a factor likely to have influenced the comparative willingness-to-pay
decisions. Actual annual conservation expenditure for both species is lower than the estimated aggregate willingness-to-pay
for their conservation. Furthermore, conservation funding for the koala is much more than that for the northern hairy-nosed
wombat even though the estimated public willingness-to-pay (demand) for funding koala conservation was less than for this
wombat species. Reasons for this are suggested. They may also help to explain misalignment between demand for conservation
funding of other species involving differences in charisma and endangerment. 相似文献
8.
The histories of 17 patients who had a cholecystectomy during pregnancy were reviewed. All patients were operated upon for clinical recurrent biliary colic. Four patients aborted or had premature labour. It appears that there is an increased risk of fetal loss if cholecystectomy is performed during pregnancy. Because of this, it would appear reasonable to perform the operation only if the exigencies of the situation demand that surgery be done. It should be borne in mind that there may also be an increased fetal loss from recurrent biliary colic treated symptomatically, particularly if cholecystitis and jaundice were to complicate matters further. If operation is performed, the fetal loss rate will likely be in the neighbourhood of 15%. 相似文献
9.
洋河流域土地利用时空变异及其对生态服务功能价值的影响 总被引:5,自引:0,他引:5
洋河流域位于我国北方典型的农牧交错地带,是首都重要水源涵养地和生态保护屏障,也是2022年冬奥会举办地之一。对流域土地利用变化及其生态服务功能价值影响的研究可为首都水源保护以及冬奥会场地环境质量的改善提供重要理论依据和决策支持。利用Arc GIS技术分析了洋河流域1990—2013年间的土地遥感数据,估算了这些变化对流域生态服务价值的影响。结果表明:1990—2013年洋河流域林地和未利用地面积呈增加,而水域、草地则呈减少的趋势。由单一土地类型利用动态绝对值说明,除林地以外2000—2013年洋河流域其他土地类型受人类或自然环境变化的影响明显高于1990—2000年。土地转移主要发生在流域西部的兴和县、阳高县、天镇县和下游的张家口市、宣化县和怀来县。近年来流域土地面积变化幅度和变化范围均增加。1990—2013年间洋河流域土地利用的年总生态服务价值经历先增加后减小、总体减少的过程,但林地和未利用地的生态服务价值却一直增加。由于林地面积增加从而导致1990—2013年流域的原材料生产、气候调节、气体调节、生物多样性保护和提供美学景生态功能占年总价值的比值增加。林地、草地和耕地是洋河流域生态服务的主要贡献者,也是生态服务价值变化的敏感因子。 相似文献
10.
A multicomponent stress management program, consisting of education about stress, various sorts of relaxation training, and cognitive coping strategies, was administered under two different instructional sets: In the positive demand set the program was touted to have previously been shown to be very effective, while in the neutral demand set the program was described as experimental. The two conditions were compared to a waiting list control. Results showed higher expectations of benefit in the positive demand group. Moreover, this group rated themselves as more able to cope with stress than the other two groups. Finally, the positive demand group showed significantly greater reductions in systolic blood pressure reactivity to laboratory stress tests (mental arithmetic and cold pressor) than the other two groups. The posttest advantages seemed to be mediated by a significantly higher level of home practice in the positive demand group. 相似文献
11.
Hiroshi Hamada 《Development, growth & differentiation》2008,50(S1):S71-S78
How left–right (LR) asymmetry emerges during development has been a classic problem in the field of developmental biology, but it is only since the 1990s that molecular and genetic approaches have become possible. Since current progress in LR patterning has been summarized in several other reviews, I would like to briefly describe how this topic developed in the early days and what remains to be solved. In particular, two breakthroughs in the mid to late 1990s made major contributions to recent progress. Despite the rapid progress, there remain many challenging issues that need to be addressed in future. 相似文献
12.
气候保护支出对中国经济安全的影响模拟 总被引:7,自引:3,他引:4
以德国学者Leimbach建立的气候保护支出模式为基础。对模式和参数作了一些修改,在假设中国经济一直保持稳定发展的前提下,模拟分析了不同削减水平下我国温室气候排放的轨迹,总产出中用于气候保护的开支以及在不同减排目标下的社会福利状况,在模拟分析的过程中,共假设了3种可能的减排目标,CO2排放量比1990年有所增加,CO2排放量保持在1990年的水平,CO2排入量逐年下降,在这3种减排目标的基础上,模拟计算出总产出用于气候保护的支出,最后得出结论,随着减排目标的上升,对气候保护的投入也就越大,居民对生活满意的程度也随之下降,但是不会构成国家经济不安全。 相似文献
13.
Whether polygyny is harmful for women and their children is a long-standing question in anthropology. Few studies, however, have explored whether the effect of polygyny varies for women of different wife order, and whether there are different outcomes for their sons and daughters. Because males have higher reproductive variance, especially when they are allowed to take multiple wives, parents may have higher fitness returns from investing in sons over daughters in polygynous households. Moreover, previous studies have found that first wives and their children are advantaged over monogamous and second order wives (who marry into unions later). Here we test the predictions that children of first wives will have an advantage over children to monogamous or second wives, and that sex-biased investment will be strongest among first wives. Using data from the Arsi Oromo of Ethiopia (n ~ 6200 children) we test whether associations with mother's wife order extend beyond childhood into adulthood by examining simultaneously child survival, education and age at marriage. We find that polygynous first wives have no child survival disadvantage, first wives' sons benefit in terms of longer education and daughters have an earlier age at marriage than daughters of monogamous women. Second wives have lower child survival than monogamous women, but surviving children experience advantages in later life outcomes, particularly marriage. These findings challenge the view that polygynous women are always doing the ‘best of a bad job’. Rather, our results suggest that via their surviving sons and daughters there may be long-term benefits for some polygynous women. 相似文献
14.
M J Morgan 《Biochemical Society transactions》1990,18(4):531-533
As we enter the 1990s, the Trust is taking on a new and unsought role as a mainstay of University biomedical research. It is to be hoped that recent statements from Government, which appear to recognize the harm being wreaked on the Universities, will prove to be more than pious platitudes. 相似文献
15.
Agricultural land-use in China: a comparison of area estimates from ground-based census and satellite-borne remote sensing 总被引:7,自引:0,他引:7
Steve Frolking Xiangming Xiao Yahui Zhuang William Salas Changsheng Li 《Global Ecology and Biogeography》1999,8(5):407-416
We compare estimates of total cropland area, paddy rice area, and irrigated cropland area in China from land cover maps derived from optical remote sensing in 1992–93 (1-km resolution NOAA AVHRR) and county-level agricultural census data for 1990. At national, regional, provincial, and county scales, the total cropland area estimated by remote sensing is 50–100% higher than reported in the agricultural census. For topographically flat North and Central China, there is a high correlation between county-level cropland area estimates by the two approaches. For other regions, the correlation between remote sensing and agricultural census cropland area is much weaker. Throughout China, there is only moderate to weak correlation between remote sensing-based and census-bases estimates of paddy rice area and total irrigated cropland area. It is likely that the census data underestimates and the remote sensing overestimates the actual cropland area. These uncertainties in agricultural land cover estimates will contribute to uncertainty in any large-scale biogeochemical analyses. 相似文献
16.
Buzzard density and distribution increased significantly in the West Midlands between 1983 and 1996. The number of soaring Buzzards counted in spring increased by 118% in the main range, 348% in the edge range and 231% overall. Although there was no significant linear trend in breeding success between 1950 and 1995, numbers of young fledged per breeding attempt were highest in the period 1980–95. This high productivity coincided with an increase in Rabbit Oryctolagus cuniculus abundance. Persecution levels, especially poisonings, appear to have been lower in the 1990s than during 1975–89. Increased productivity due to high Rabbit abundance, and higher survival rates due to reduced persecution, are likely to be the main factors responsible for the rapid increase in the Buzzard population in this area. Buzzards are increasing in numbers in other parts of Britain and Ireland and may now be more numerous than at any time this century. 相似文献
17.
Willett CS 《Journal of molecular evolution》2012,74(5-6):310-318
Mitochondrial DNA (mtDNA) genomes generally evolve rapidly in animals, but considerable variation in the rates of evolution of mtDNA occurs among taxa. Higher levels of mutation will tend to increase the amount of polymorphism, which should also scale with population size, but there are mixed signals from previous studies on the evolutionary outcomes of the interactions of these processes. The copepod Tigriopus californicus provides an interesting model in which to study the evolution of mtDNA because it has high levels of divergence among populations and there is the suggestion that this divergence could be involved in reproductive isolation. This species also appears to have an elevated mtDNA substitution rate, but previous studies did not provide an accurate measurement. This article examines the rate of mtDNA substitution versus nuclear substitution in T. californicus and finds that the mtDNA rate for synonymous sites averages 55-fold higher, a level that exceeds the rates found in most other invertebrates. Levels of polymorphism are also examined in both mtDNA and nuclear genes, and it is shown that the effective population size of mtDNA genes is much lower than that of nuclear genes. In addition, no correlation between polymorphism in mtDNA and nuclear genes is found across populations, which suggest factors other than demography may shape polymorphism in this species. The results from this study suggest that mtDNA is evolving at a very rapid rate in this copepod species, and this could increase the likelihood that mtDNA evolution is involved in the generation of reproductive isolation. 相似文献
18.
This paper tests the Trivers-Willard hypothesis that high-status individuals will invest more in sons and low-status individuals will invest more in daughters using data from the 2000 to 2010 General Social Survey and the 1979 National Longitudinal Survey of Youth. We argue that the primary investment U.S. parents make in their children is in their children’s education, and this investment is facilitated by a diverse market of educational choices at every educational level. We examine two measures of this investment: children’s years of education and the highest degree attained. Results show that sons of high-status fathers receive more years of education and higher degrees than daughters, whereas daughters of low-status fathers receive more years of education and higher degrees than sons. Further analyses of possible mechanisms for these findings yield null results. We also find that males are more likely to have high-status fathers than females. 相似文献
19.
Ecologists, conservation biologists and other natural historians increasingly recognize the need to become involved in public education. An ecologically literate public may be the 'last best hope' for a sustainable biosphere. Partnerships between ecologists and educators may be the best hope, though not the last, for moving towards an ecologically literate public. What are some practical schemes for such partnerships? We present a model for ecology education that has shown promise in several South American settings and describe its application in two quite different contexts in southern Argentina. We hope that our colleagues will ponder, criticize, modify, improve and apply the model in settings other than those we present here. 相似文献
20.
We measured the breeding performance, body condition, time budgets and foraging ranges of Kittiwakes Rissa tridactyla at Sumburgh Head, Shetland, in two years of contrasting food availability. Kittiwakes in Shetland generally feed their young almost entirely on sandeels, and fisheries data indicated that stocks of sandeels in Shetland waters were at least ten times higher in 1991 than in 1990. Fledging success of Kittiwakes was nil in 1990 and 68% of eggs laid in 1991, although clutch-size and hatching success were no different between years. Post-hatching foraging trips in 1991 were of comparable duration to those recorded at other colonies in conditions of good food supply (2–3 h), while trips recorded during incubation or post-hatching in 1990 were approximately three times longer on average than at corresponding stages of the breeding season in 1991. Radio-tracking data indicated that adults generally stayed within 5 km of the colony in 1991 but flew more than 40 km from the colony on each trip in 1990. Eggs were apparently not left unattended in either year, despite the fact that this required adults to incubate for periods in excess of 44 h in 1990. The extent to which adults were able to increase trip durations, foraging ranges and incubation shift lengths between years, while maintaining hatching success, indicates the degree to which Kittiwakes are normally buffered against adverse feeding conditions during incubation. Reduced nest attendance and lower body-condition of adults post-hatching in 1990, in conjunction with complete post-hatching breeding failure, indicate that adults were beyond the limits of their buffering capacity during chick-rearing in 1990. 相似文献