首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   9篇
  免费   1篇
安全科学   1篇
环保管理   4篇
综合类   1篇
基础理论   2篇
污染及防治   2篇
  2018年   1篇
  2016年   1篇
  2013年   1篇
  2009年   1篇
  2006年   1篇
  2002年   1篇
  1994年   1篇
  1984年   2篇
  1982年   1篇
排序方式: 共有10条查询结果,搜索用时 0 毫秒
1
1.
Stickler syndrome is an autosomal dominant disorder of the connective tissue which includes ocular and systemic manifestations. We report on a large kindred in which we were able to demonstrate very tight linkage between the disease and the type II collagen gene (COL2A1) (LOD score 3·91 at θ=0). In a family in which the father and one of his daughters were severely affected, DNA analysis from a chorionic villus sample demonstrated that the fetus possessed the normal allele of COL2A1. Thereafter a normal child was born.  相似文献   
2.
Phosphorus (P) runoff from manure can lead to eutrophication of surface water and algae growth. This study evaluates the impacts of alternative P reduction practices on dairy farm net returns and on potential P runoff. The P control practices include dairy herd nutrient management, crop nutrient management, and runoff and erosion control. Four farms representative of dairies in the Virginia Shenandoah Valley are simulated including dairies with and without supplementary broiler enterprises and with average and below average land area. A mathematical programming model was developed to predict farm production and net returns and the GLEAMS model was used to predict potential P runoff. The farms are evaluated under four scenarios: Scenario 1, no constraint on P runoff with access to crop nutrient, runoff and erosion control strategies but no access to dairy herd nutrient control strategies; Scenario 2, no constraint on P runoff with access to all crop and dairy herd nutrient control strategies; Scenario 3, constraint on P runoff with access to crop nutrient, runoff and erosion control strategies but no access to dairy herd nutrient control strategies; and Scenario 4, constraint on P runoff with access to all crop and dairy herd nutrient control strategies. Under Scenario 2, the herd nutrient control strategies increase milk output per cow and net returns on both farms and reduce P content of manure and P runoff. Under Scenario 3, limiting P runoff reduces farm returns by 1 and 3% on the average and small farms, respectively. Under Scenario 4, the P runoff constraint is less costly, reducing returns by less than 1% on both farms. Animal nutrient control strategies should be an important part of pollution control policies and programs for livestock intensive watersheds.  相似文献   
3.
This paper describes a flow-through microcuvette for determination of chlorophyll with the Turner Designs model 10 fluorometer. The device approximately doubles the speed of repetitive chlorophyll determinations. With a single-standard calibration procedure, chlorophyll concentrations in the approximate range of 0.01-2.0 ug/mL (in solvent extracts) can be determined with a relative error of less than 3 percent.  相似文献   
4.
5.
Objective: Understanding pedestrian injury trends at the local level is essential for program planning and allocation of funds for urban planning and improvement. Because we hypothesize that local injury trends differ from national trends in significant and meaningful ways, we investigated citywide pedestrian injury trends to assess injury risk among nationally identified risk groups, as well as identify risk groups and locations specific to Baltimore City.

Methods: Pedestrian injury data, obtained from the Baltimore City Fire Department, were gathered through emergency medical services (EMS) records collected from January 1 to December 31, 2014. Locations of pedestrian injuries were geocoded and mapped. Pearson's chi-square test of independence was used to investigate differences in injury severity level across risk groups. Pedestrian injury rates by age group, gender, and race were compared to national rates.

Results: A total of 699 pedestrians were involved in motor vehicle crashes in 2014—an average of 2 EMS transports each day. The distribution of injuries throughout the city did not coincide with population or income distributions, indicating that there was not a consistent correlation between areas of concentrated population or concentrated poverty and areas of concentrated pedestrian injury. Twenty percent (n = 138) of all injuries occurred among children age ≤14, and 22% (n = 73) of severe injuries occurred among young children. The rate of injury in this age group was 5 times the national rate (Incident Rate Ratio [IRR] = 4.81, 95% confidence interval [CI], [4.05, 5.71]). Injury rates for adults ≥65 were less than the national average.

Conclusions: As the urban landscape and associated pedestrian behavior transform, continued investigation of local pedestrian injury trends and evolving public health prevention strategies is necessary to ensure pedestrian safety.  相似文献   

6.
Phosphorus characteristics of dairy feces affected by diets   总被引:2,自引:0,他引:2  
Phosphorus (P) surplus on dairy farms, especially confined operations, contributes to P buildup in soils with increased potential for P loss to waters. One approach to reduce P surplus and improve water quality is to optimize P feeding and improve P balance on farms. Here we report how varying P concentrations in lactating cow diets affects the amount as well as the chemical forms and fraction distribution of P in fecal excretion, and the environmental implications of this effect. Analysis of fecal samples collected from three independent feeding trials indicates that increasing dietary P levels through the use of P minerals not only led to a higher concentration of acid digest total phosphorus (TP) in feces, but more importantly increased the amount and proportion of P that is water soluble and thus most susceptible to loss in the environment. For instance, with diets containing 3.4, 5.1, or 6.7 g P kg(-1) feed dry matter (DM), the water-soluble fraction of fecal P was 2.91, 7.13, and 10.46 g kg(-1) fecal DM, respectively, accounting for 56, 77, and 83% of acid digest TP. The other fecal P fractions (those soluble in dilute alkaline and acid extractants) remained small and were unaffected by dietary P concentration. Excess P in the P supplemented diets was excreted in feces as water-soluble forms. A simple measure of inorganic phosphorus (Pi) in a single water extract is highly responsive to changes in diet P concentrations and hence can be indicative of dietary P status. A fecal P indicator concept is proposed and discussed.  相似文献   
7.
Summer lake survey measurements of total phosphorus (TP) and chlorophyll a (CHLa) from 188 reserviors and natural lakes in the midwest were analyzed to determine the magnitude of major sources of variability. Median variance among replicate samples collected at the same location and time was about 7-8 percent of the mean for both TP and CHLa. Median observed temporal variability within summers was 27 percent of the mean for TP and 45 percent of the mean for CHLa. Median values of year-to-year variance in average TP and CHLa were 22 percent and 31 percent of the mean, respectively. A range of approximately two orders of magnitude was observed among individual estimates of variance in each of these categories. The magnitude of observed temporal variability was affected only slightly by variance among replicate samples on individual days and was weakly correlated with the length of time during which samples were collected from individual lakes. Observed temporal variation was similar between reservoirs and natural lakes when variances were calculated with logtransformed data. The magnitude of temporal and year-to-year variance can severely limit the power of statistical comparisons of TP and CHLa means, but has less effect on establishing relative rankings of lake means, Sources and relative magnitude of variability are important in the use of TP and CHLa data in regression models and in the planning of lake surveys and subsequent data analysis.  相似文献   
8.
Zhao Z  Fang Y  Love NG  Knowlton KF 《Chemosphere》2009,74(4):551-555
Wastes generated by animal agriculture have complex matrices and present a significant challenge for achieving accurate measurements of estrogens. The objective of this study was to compare two different extraction methods and two different biochemical and biological estrogen assays on two dairy manure matrices. The two extraction methods studied in this research were a two-step base-toluene extraction and a one-step cyclohexane extraction. The two assays assessed were an enzyme-linked immunosorbent assay (ELISA) and a yeast estrogen screen (YES) bioassay. Estrogenic activity was measured directly as 17beta-estradiol (E2) through the ELISA method or as E2 equivalents (E2-eq) through the YES bioassay. Both extraction methods yielded reasonable recoveries from distilled water in the absence of matrix interferences. In manure samples, ELISA resulted in recoveries slightly higher than 100% in two types of dairy manures, but YES recoveries varied. The YES bioassay detected much higher estrogenic activities in dairy manure compared to the E2 concentrations measured by ELISA. The base-solvent extraction yielded higher E2 concentrations in dairy manure compared to the one-step cyclohexane extraction. These results suggest that manure matrices vary sufficiently that extraction methods must be optimized for specific assays utilized to quantify estrogens in manures.  相似文献   
9.
Entanglement in fixed fishing gear affects whales worldwide. In the United States, deaths of North Atlantic right (Eubalaena glacialis) and humpback whales (Megaptera novaeangliae) have exceeded management limits for decades. We examined live and dead whales entangled in fishing gear along the U.S. East Coast and the Canadian Maritimes from 1994 to 2010. We recorded whale species, age, and injury severity and determined rope polymer type, breaking strength, and diameter of the fishing gear. For the 132 retrieved ropes from 70 cases, tested breaking strength range was 0.80–39.63 kN (kiloNewtons) and the mean was 11.64 kN (SD 8.29), which is 26% lower than strength at manufacture (range 2.89–53.38 kN, mean = 15.70 kN [9.89]). Median rope diameter was 9.5 mm. Right and humpback whales were found in ropes with significantly stronger breaking strengths at time of manufacture than minke whales (Balaenoptera acuturostrata) (19.30, 17.13, and 10.47 mean kN, respectively). Adult right whales were found in stronger ropes (mean 34.09 kN) than juvenile right whales (mean 15.33 kN) and than all humpback whale age classes (mean 17.37 kN). For right whales, severity of injuries increased since the mid 1980s, possibly due to changes in rope manufacturing in the mid 1990s that resulted in production of stronger ropes at the same diameter. Our results suggest that broad adoption of ropes with breaking strengths of ≤7.56 kN (≤1700 lbsf) could reduce the number of life‐threatening entanglements for large whales by at least 72%, and yet could provide sufficient strength to withstand the routine forces involved in many fishing operations. A reduction of this magnitude would achieve nearly all the mitigation legally required for U.S. stocks of North Atlantic right and humpback whales. Ropes with reduced breaking strength should be developed and tested to determine the feasibility of their use in a variety of fisheries.  相似文献   
10.
Summary The shrimp Alpheus armatus territorially defends the sea anemone it occupies, using as a weapon its large, specially modified snapping claw. This behavior was studied in experimental contests which were symmetric (matched individuals) with respect to sex, size, and residency. Characteristics of these contests were compared for two size-classes of male and female shrimp.There were no significant differences between these groups of shrimp in the number of bouts required to establish dominance or in the number of snaps exchanged. Large females had shorter contests than either small or large males, and losers of contests between large females were injured more frequently and more severely.This distinctiveness of large female contests could be interpreted as evidence that (i) controlling anemones is more important for large females, (ii) injuries are less important for large females, or (iii) large females lose the ability to assess one another because their contests are less frequent.If injuries are an accurate measure of the most important costs associated with fighting, then these results indicate that short contests are not necessarily the least costly, and that females can be more aggressive than males, as measured by escalation potential, in sexually selected species.  相似文献   
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号