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排序方式: 共有228条查询结果,搜索用时 390 毫秒
161.
Personal monitoring methods for the determination of hourly integrated concentrations of NO2 and SO2 in ambient air have been developed. Triethanolamine (TEA)-impregnated C18 Sep-Pak cartridges were used to collect NO2 and SO2 simultaneously. After sampling, NO2 and SO2 as their nitrite, nitrate, sulfite and sulfate analogues were stripped from the cartridges with a solution of 5% methanol in distilled, deionized water (DDW) and then determined by ion chromatography. Laboratory tests were conducted to evaluate the sampling rate, collection and recovery efficiencies, breakthrough volumes, absorption capacity, interference and sample stability on the cartridge during storage. NO2 and SO2 detection limits of 0.3 and 0.4 ppb respectively for 1 h samples were obtained. Recoveries for both NO2 and SO2 exceeded 85%.  相似文献   
162.
Microbiological quality of crude oil storage tanks was determined. The samples were taken from crude oil storage tanks in three stations, at Ughelli, Escravos and Forcados tank farms in the Delta State of Nigeria. Two tanks were sampled at each station with samples collected from three levels of the tank, namely the oil layer, oil water interface, and effluent layer. Samples from the inner walls and bottom sediment of the only empty tank in Ughelli during the study were also taken. The total heterotrophic count of bacteria and total fungal count were obtained by plating samples on nutrient agar and sabouraud's glucose agar respectively and incubated for 14 days at 28 °C±2 °C. Oilutilizing bacteria and fungi were isolated on oil agar using fungizone and antibiotics to inhibit fungal and bacterial growth respectively. Pure cultures of bacteria and fungi were prepared on nutrient agar and sabouraud's glucose agar respectively at 28 °C±2 °C for 4 days. Isolates were identified using approved standard methods. Three bacterial genera, Pseudomonas, Proteus and Bacillus, and one actinomycete, Actinomyces and two fungal genera, Penicillium and Cunninghamella, were isolated. Pseudomonas was dominant among the bacteria (41.62%) and Penicillium dominant among the fungi (94%). It was also found that the total microbial load of the effluent layer was higher than that of the oil layer.  相似文献   
163.
No information has been published on the presence of organochlorine pesticides and polychlorinated biphenyls in the Fiji Islands. This paper reports the first data on the concentration of a range of organochlorine compounds in sediments and shellfish in the estuarine and coastal marine environment around Fiji. Twenty-three sediment and two shellfish samples were analysed for 22 pesticides and related residues, and PCBs. While a significant number of organochlorines (20 pesticide related species and PCBs) was detected, the concentrations were generally very low (< 10 ng g), indicative of a relatively 'less contaminated' marine environment. Relatively high concentrations were observed only near the two major ports (Suva and Lautoka), with Suva harbour samples having the largest number of detectable species and the largest total concentrations of organochlorines (up to 91 ng g). No PCBs were detected in areas away from major industrial centres. The variations in the concentrations found, and the possible sources and movement of the organochlorine contaminants are discussed.  相似文献   
164.
Tetrasomy 12p (Pallister-Killian syndrome) is a mosaic aneuploidy syndrome in which the isochromosome is present in amniocytes with a much greater percentage than fetal lymphocytes. Two new cases identified by prenatal diagnosis are reported. Indications for prenatal diagnosis were advanced maternal age and fetal anomalies. The most consistent reported prenatal ultrasound findings for tetrasomy 12p include polyhydramnios with short femurs and a diaphragmatic hernia. Recognition of congenital malformation patterns prenatally may allow appropriate selection of tissue for chromosome analysis. Molecular cytogenetic analysis using fluorescence in situ hybridization was used retrospectively to confirm the presence of the isochromosome 12p in various formalin-fixed fetal tissues. The levels of mosaicism detected in fetal and placental tissues were lower than those detected prenatally.  相似文献   
165.
EffectoforganicacidonCdtoxicityintomatoandbeangrowthXueDongsen;RobertB.Harrison;CharlesL.Henry(UniversityofWashington,ARIOSea...  相似文献   
166.
Using monospecific diets of Thalassiosira pseudonana cells grown under different steady-state conditions, it was determined that higher growth rates of larval Crassostrea gigas Thunberg were obtained when fed T. pseudonana cells grown under high light. High light grown T. pseudonana cells consistently contained relatively more of the saturated fatty acids 14:0 and 16:0. Considered over three independent experiments, high light grown T. pseudonana cells were lower in protein and higher in carbohydrate than low light grown cells. Higher growth rates of larval C. gigas were obtained on diets with more of the essential fatty acid (EFA) 22:63, and less of the other EFA, 20:53. The relative requirements of C. gigas larvae for the essential fatty acids 20:53 and 22:63 are discussed. Faster growing larvae contained higher percentages of the fatty acids 14:0 and 16:0, and lower percentages of 22:2j. Oyster growth rates were correlated with their content of the fatty acids: 14:0, 16:0 and 22:2j in two experiments utilizing separately spawned batches of larvae. Fatty acid profiles are proposed as a technique for assessing larval condition. C. gigas larvae contained ten times the percent composition of the FAs 16:43, 18:17, 20:17 and 22:2j compared with their diet. Correlation analysis suggests that the dietary source of 18:17, 20:17 and 22:2j was 16:17. It is concluded that T. pseudonana cells grown under high light are a superior diet for C. gigas larvae in comparison with low light grown cells of the same species.  相似文献   
167.
What candidates say in an interview is important—but so is how they say it. We draw on dual-process theory to explain why interviewers rely on individuals' dynamic and static nonverbal cues to evaluate performance with quick, implicit inferences (System 1 processing). Yet, it remains unclear which cues most influence interviewers' judgments and whether moderators affecting interviewers' reliance on System 1 thinking (e.g., interview structure, modality, duration, and interviewee gender) impact the relationship between nonverbal cues and interview ratings. We performed the first meta-analysis to address these questions, integrating findings across 63 studies (N = 4868). The nonverbal cues demonstrating the strongest association with interview performance were professional appearance (ρ = .62), eye contact (ρ = .45), and head movement (ρ = .43). Moderator analyses highlight the persistent power of nonverbal cues, as the results were largely unaffected by interview structure, modality, or duration. Experimental design did play a role, as did interviewees' gender, with stronger effects for certain nonverbal cues (e.g., facial expressions and professional appearance) for women than men, conveying interviewers' reliance on gender-based stereotypes when judging their performance. Overall, these results suggest nonverbal cues and characteristics are an important influence on job applicants' success in employment interviews.  相似文献   
168.
When reserve networks are established over time, there is a risk that sites will be developed in areas planned for future reservation, reducing the effectiveness of reserves. We developed a dynamic reserve design model that maximizes the expected number of species conserved, taking account of the risk of future habitat loss and fragmentation. The model makes use of the union-find algorithm, which is an efficient method for maintaining a list of connected regions in a graph as nodes and edges are inserted. A simple extension of the algorithm allows us to efficiently determine, for each species, when a sequence of site selections results in a reserve in which the species can persist. The extension also allows us to determine when a sequence of deforestation events results in the species becoming non-viable. The dynamic reserve design model is much more effective than commonly used heuristics, particularly when multiple connected sites are required for species persistence. The model also is able to solve much larger problems with greater effectiveness than the only previous dynamic reserve design model that considered site connectivity relationships. The union-find algorithm has much scope for addressing ecological management problems in which dynamic connectivity needs to be considered.  相似文献   
169.
Host sea anemones are ecologically important as they provide habitat for obligate symbiotic anemonefish in many areas of the Indo-Pacific. Despite their importance, no information is available on their gametogenic cycles. This study aimed to address this lack of knowledge by determining the gametogenic cycles of Entacmaea quadricolor. Gonad samples were taken from January 2003 to February 2005 at North Solitary Island, Solitary Islands Marine Park, Australia using a specially developed non-lethal field biopsy sampling technique. Sampling was done 17 times during the study period, with 15–20 individuals being sampled on each occasion. Samples were examined prior to fixation, and then histologically sectioned to determine the reproductive activity of each individual. Female anemones were significantly more abundant than males, and had asynchronous oocyte development both within and among individuals. Male anemones showed a single annual cycle of spermary growth, development and spawning. Data from the 26-month study indicated that spawning occurred in the austral summer and autumn between January and April, which coincided with the observed spawning periods that have previously been documented for this species in outdoor flow-through seawater tanks at the study location. The biopsy sampling technique used during this study provides an opportunity to gain a more thorough understanding of the gametogenic cycles and sexual pattern of host sea anemones throughout their distribution.  相似文献   
170.
Davies KF  Harrison S  Safford HD  Viers JH 《Ecology》2007,88(8):1940-1947
At small scales, areas with high native diversity are often resistant to invasion, while at large scales, areas with more native species harbor more exotic species, suggesting that different processes control the relationship between native and exotic species diversity at different spatial scales. Although the small-scale negative relationship between native and exotic diversity has a satisfactory explanation, we lack a mechanistic explanation for the change in relationship to positive at large scales. We investigated the native-exotic diversity relationship at three scales (range: 1-4000 km2) in California serpentine, a system with a wide range in the productivity of sites from harsh to lush. Native and exotic diversity were positively correlated at all three scales; it is rarer to detect a positive relationship at the small scales within which interactions between individuals occur. However, although positively correlated on average, the small-scale relationship between native and exotic diversity was positive at low-productivity sites and negative at high-productivity sites. Thus, the change in the relationship between native and exotic diversity does not depend on spatial scale per se, but occurs whenever environmental conditions change to promote species coexistence rather than competitive exclusion. This occurred within a single spatial scale when the environment shifted from being locally unproductive to productive.  相似文献   
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