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排序方式: 共有463条查询结果,搜索用时 31 毫秒
201.
Juan J. Soler M. Martín-Vivaldi J. M. Peralta-Sánchez L. Arco N. Juárez-García-Pelayo 《Die Naturwissenschaften》2014,101(9):697-705
Uropygial gland secretions are used as cosmetics by some species of birds to color and enhance properties of feathers and teguments, which may signal individual quality. Uropygial secretions also reach eggshells during incubation and, therefore, may influence the coloration of birds’ eggs, a trait that has attracted the attention of evolutionary biologists for more than one century. The color of hoopoe eggs typically changes along incubation, from bluish-gray to greenish-brown. Here, we test experimentally the hypothesis that dark uropygial secretion of females is responsible for such drastic color change. Moreover, since uropygial secretion of hoopoes has antimicrobial properties, we also explore the association between color and antimicrobial activity of the uropygial secretion of females. We found that eggs stayed bluish-gray in nests where female access to the uropygial secretion was experimentally blocked. Furthermore, experimental eggs that were maintained in incubators and manually smeared with uropygial secretion experienced similar color changes that naturally incubated eggs did, while control eggs that were not in contact with the secretions did not experience such color changes. All these results strongly support the hypothesis that female hoopoes use their uropygial gland secretion to color the eggs. Moreover, saturation of the uropygial secretion was associated with antimicrobial activity against Bacillus licheniformis. Given the known antimicrobial potential of uropygial secretions of birds, this finding opens the possibility that in scenarios of sexual selection, hoopoes in particular and birds in general signal antimicrobial properties of their uropygial secretion by mean of changes in egg coloration along incubation. 相似文献
202.
Objectives: To assess the chromosomal and subchromosomal anomalies in small for gestational age (SGA) fetuses with no additional structural anomalies and their clinical outcomes. Methods: This study retrospectively reviewed the 128 SGA fetuses with no additional anomalies and underwent genetic testing with karyotyping and chromosomal microarray analysis (CMA). Stratified analysis was performed according to the existence of maternal risk factors for SGA (yes or no), gestational age at onset (before or after 32 weeks), presence of oligohydraminos (yes or no), and umbilical artery Doppler flow (normal or abnormal). Results: Chromosomal anomalies were identified in 6 (4.7%) SGA fetuses and pathogenic subchromosomal anomalies in 4 (3.1%) by microarray analysis. Chromosomal and subchromosomal anomalies were more frequently observed in cases with oligohydraminos (P = .017) and with early-onset SGA (P = .042). No differences were observed in relation to the existence of maternal risk factors and abnormal umbilical artery Doppler flow. Overall survival rate was 75.0% with different rates in the early and the late onset group (P < .001). Conclusions: There is a 3.3% incremental yield of subchromosomal anomalies in CMA above karyotyping in SGA fetuses. Chromosomal microarray analysis is recommended in SGA fetuses with no additional structural anomalies, especially coexisting with oligohydraminos and being early onset. 相似文献
203.
Hu Chao Hu Hongqing Song Mengdie Tan Ju Huang Guoyong Zuo Jichao 《Environmental science and pollution research international》2020,27(10):10599-10606
Environmental Science and Pollution Research - Montmorillonite-cysteine could be used as the immobilizer, detector, and detoxifier of heavy metals. To further the understanding and the application,... 相似文献
204.
The purpose of this paper was to use quantitative systems-level approach employing biotic ligand model based threshold damage model to examine physiological responses of tilapia and freshwater clam to sequential pulsed and fluctuating arsenic concentrations. We tested present model and triggering mechanisms by carrying out a series of modeling experiments where we used periodic pulses and sine-wave as featured exposures. Our results indicate that changes in the dominant frequencies and pulse timing can shift the safe rate distributions for tilapia, but not for that of freshwater clam. We found that tilapia increase bioenergetic costs to maintain the acclimation during pulsed and sine-wave exposures. Our ability to predict the consequences of physiological variation under time-varying exposure patterns has also implications for optimizing species growing, cultivation strategies, and risk assessment in realistic situations. 相似文献
205.
在上海市城市河岸带人工绿地建设了微区径流场,进行了5次模拟降雨径流实验,研究了人工绿地岸带下渗流中氮浓度和去除率的时空变化。结果表明:人工绿地岸带对垂直下渗流中氮有显著的净化作用,且主要集中于土壤的0~30 cm以内,TN和NH4+去除率在399%和398%以上,NO3-+NO2-去除率除11月为负值外,其余月份均在100%以上;在30~60 cm深度,由于土壤氮的析出导致径流中氮浓度增加,去除率降低;而60~90 cm深度的去除率增加。径流场内下渗流中氮浓度具有明显的水平空间变化,随距入水端距离的增加,30 cm深度下渗流中氮浓度先上升后下降;人工绿地岸带对下渗流中氮的净化作用均随淹水时间的延长呈降低趋势,且季节变化明显,在10月和4月具有较高的去除率,0~30 cm内TN、NH4+和NO3-+NO2-的去除率可分别达635%、891%和416%以上 相似文献
206.
207.
浅析污水集中处理后的环境监督管理 总被引:2,自引:0,他引:2
现行《中华人民共和国水污染防治法》规定城市污水集中处理,污水处理厂实行有偿服务;向污水处理厂排污并缴纳污水处理费用的,不再缴纳排污费。这一规定直接关系到我国环保法律法规关于排污收费和“三同时”的规定。为了保证污染防治责任的落实,同时减轻企业的负担,建议由排污者与污水处理厂签定书面污水处理合同,由环保部门对合同进行审批,并将其作为改变排污收费和“三同时”管理的依据;污水处理厂则可视为独立污染源进行管理。 相似文献
208.
萃取—汽提法处理硝基苯废水的研究 总被引:11,自引:1,他引:11
先用苯萃取使废水中硝莽本的浓度达3ppm以下,再用水蒸气汽提使废水中的苯浓度达10ppm以下,并使硝基苯浓度进一步降低,处理后的废水全面达到国家二级排放标准。苯和萃取出的硝基苯都可回收利用.。 相似文献
209.
An integrated assessment model of carbon sequestration benefits: a case study of Liping county, China 总被引:4,自引:0,他引:4
Caldwell IM Maclaren VW Chen JM Ju WM Zhou S Yin Y Boland A 《Journal of environmental management》2007,85(3):757-773
This research attempts to model the complexity of planting trees to increase China's CO(2) sequestration potential by using a GIS-based integrated assessment (IA) approach. We use the IA model to assess the impact of China's Grain for Green reforestation and afforestation program on farmer and state incomes as well as CO(2) sequestration in Liping County, Guizhou Province. The IA model consists of five sub-models for carbon sequestration, crop income, timber income, Grain for Green, and carbon credits. It also includes a complementary qualitative module for assessing program impacts by gender and ethnicity. Using four scenarios with various assumptions about types of trees planted, crop incomes by township, CO(2) credit prices, state subsidies, methods for estimating carbon sequestered, and harvesting of trees, we find great variation in the impact of the Grain for Green program on incomes and on carbon sequestered over a 48 year period at both the county and township levels. 相似文献
210.