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151.
E. C. Pariser L. Gilbert N. Hazon K. E. Arnold J. A. Graves 《Behavioral ecology and sociobiology》2012,66(4):519-527
Females are expected to partition resources between offspring in a context-dependent way to maximise total fitness returns
from a reproductive attempt. Female zebra finches (Taeniopygia guttata) vary the allocation of yolk androgens and antioxidants among offspring. Importantly, the balance between androgens and antioxidants
in yolks may be more important than their independent absolute amounts in terms of fitness consequences for developing young.
Therefore, we tested whether the relative allocation of these two resources in yolks varies according to either the Trivers–Willard,
positive or compensatory maternal investment hypothesis. We manipulated male attractiveness using coloured leg bands (red-banded
males appear attractive; green-banded males, unattractive) and measured yolk androgens and antioxidants in each egg, egg sex,
clutch sex ratio and female condition. While female zebra finches manipulated the balance of androgens and antioxidants within
and between clutches in response to mate attractiveness, offspring sex and their own condition, they did not do so in a way
that consistently followed any of the hypotheses. Mothers paired with unattractive males allocated a larger antioxidant/androgen
ratio to daughters than sons. This pattern was reversed when paired to an attractive male; sons received a larger antioxidant/androgen
ratio than daughters. We also found offspring sex ratio decreased with increasing female condition for unattractive males,
but not for attractive males. However, without knowing the fitness consequences of the balance of different egg constituents,
it is difficult to interpret the patterns consistently in terms of the Trivers–Willard, compensatory and positive investment
hypotheses. 相似文献
152.
This study examined the response of a coral holobiont to thermal stress when the bacterial community was treated with antibiotics. Colonies of Pocillopora damicornis were exposed to broad and narrow-spectrum antibiotics targeting coral-associated α and γ-Proteobacteria. Corals were gradually heated from the control temperature of 26 to 31 °C, and measurements were made of host, zooxanthellar and microbial condition. Antibiotics artificially reduced the abundance and activity of bacteria, but had minimal effect on zooxanthellae photosynthetic efficiency or host tissue protein content. Heated corals without antibiotics showed significant declines in F V /F M , typical of thermal stress. However, heated corals treated with antibiotics showed severe tissue loss in addition to a decline in F V /F M . This study demonstrated that a disruption to the microbial consortium diminished the resilience of the holobiont. Corals exposed to antibiotics under control temperature did not bleach, suggesting that temperature may be an important factor influencing the activity, diversity and ecological function of the holobiont bacterial community. 相似文献
153.
Biodiesel as a renewable fuel has the potential to replace non-renewable fossil fuels and associated environmental pollution. The most commonly used method in biodiesel production is transesterification of virgin and used oil feedstock. However, the chemical reaction (transesterification) does not proceed spontaneously, which means excess reactants are required to move the reaction to completion. The biodiesel reaction efficiency can be improved by incorporating green chemistry principles and process intensification effects. Green chemistry principles can be used to design chemical products and processes that reduce or eliminate the use and generation of hazardous substances. Microwave- and ultrasound-enhanced biodiesel synthesis can improve the reaction efficiency due to higher product recovery, low by-product formation, and reduced energy consumption. In addition, utilization of green metrics such as E-factor, atom economy (utilization), mass intensity or mass productivity, and reaction mass efficiency can help design safer and highly efficient biodiesel synthesis. Green chemistry principles have been analyzed for other processes in greater details, but they are rarely discussed in the context of biodiesel production. Process intensification by microwave- and ultrasound-mediated biodiesel production was never discussed from the perspective of green chemistry and sustainable process development. This research review article discusses the role of green chemistry and process intensification in biodiesel production followed by specific examples and illustrations on green metrics of microwave- and ultrasound-enhanced biodiesel synthesis and the effect of catalysts and solvents including discussions on reaction kinetics and activation energy in detail for the first time in the literature. 相似文献
154.
John E. Hathaway G. Bruce Schaalje Richard O. Gilbert Brent A. Pulsipher Brett D. Matzke 《Environmental and Ecological Statistics》2008,15(3):313-327
Composite sampling can be more cost effective than simple random sampling. This paper considers how to determine the optimum
number of increments to use in composite sampling. Composite sampling terminology and theory are outlined and a method is
developed which accounts for different sources of variation in compositing and data analysis. This method is used to define
and understand the process of determining the optimum number of increments that should be used in forming a composite. The
blending variance is shown to have a smaller range of possible values than previously reported when estimating the number
of increments in a composite sample. Accounting for differing levels of the blending variance significantly affects the estimated
number of increments.
相似文献
John E. HathawayEmail: |
155.
Ona LF Alberto AM Prudente JA Sigua GC 《Environmental science and pollution research international》2006,13(3):177-183
Background Aims, and Scope. Lead (Pb) is a naturally occurring element that poses environmental hazards when present at elevated concentration.
It is being released into the environment because of industrial uses and from the combustion of fossil fuels. Hence, Pb is
ubiquitous throughout global ecosystems. The existence of potentially harmful concentrations of Pb in the environment must
be given full attention. Emissions from vehicles are major source of environmental contamination by Pb. Thus, it becomes imperative
that concentrations of Pb and other hazardous materials in the environment not only in the Philippines, but elsewhere in the
world be adequately examined in order that development of regulations and standards to minimize risk associated with these
materials in urban areas is continued. The objectives of this study were: (1) to determine the levels of Pb in soil from selected
urbanized cities in central region of the Philippines; (2) to identify areas with soil Pb concentration values that exceed
estimated natural concentrations and allowable limits; and (3) to determine the possible sources that contribute to elevated
soil Pb concentration (if any) in the study area.
Methods This study was limited to the determination of Pb levels in soils of selected urbanized cities located in central region
in the Philippines, namely: Site 1 – Tarlac City in Tarlac; Site 2 – Cabanatuan City in Nueva Ecija; Site 3 – Malolos City
in Bulacan; Site 4 – San Fernando City in Pampanga; Site 5 – Balanga City in Bataan; and Site 6 – Olongapo City in Zambales.
Soil samples were collected from areas along major thoroughfares regularly traversed by tricycles, passenger jeepneys, cars,
vans, trucks, buses, and other motor vehicles. Soil samples were collected from five sampling sites in each of the study areas.
Samples from the selected sampling sites were obtained approximately 2 to 3 meters from the road. Analysis of the soil samples
for Pb content was conducted using an atomic absorption spectrophotometer. This study was conducted from 2003 to 2004. Since
this study assumed that vehicular emission is the major source of Pb contamination in urban soil, other information which
the researchers deemed to have bearing on the study were obtained such as relative quantity of each gasoline type disposed
of in each city within a given period and volume of traffic in each sampling site. A survey questionnaire for gasoline station
managers was prepared to determine the relative quantity of each fuel type (diesel, regular gasoline, premium gasoline, and
unleaded gasoline) disposed of or sold within a given period in each study area.
Results and Discussion Analysis of soil samples for Pb content showed the presence of Pb in all the soil samples collected from the 30 sampling
sites in the six cities at varying concentrations ranging from 1.5 to 251 mg kg–1. Elevated levels of Pb in soil (i.e. greater
than 25 mg kg–1 Pb) were detected in five out of the six cities investigated. Site 4 recorded the highest Pb concentration
(73.9 ± 94.4 mg kg–1), followed by Site 6 (56.3 ± 17.1 mg kg–1), Site 3 (52.0 ± 33.1 mg kg–1), Site 5 (39.3 ± 19.0 mg kg–1),
and Site 2 (38.4 ± 33.2 mg kg–1). Soil Pb concentration in Site 1 (16.8 ± 12.2 mg kg–1) was found to be within the estimated
natural concentration range of 5 to 25 mg kg–1. Site 1 registered the least Pb concentration. Nonetheless, the average Pb
concentration in the soil samples from the six cities studied were all found to be below the maximum tolerable limit according
to World Health Organization (WHO) standards. The high Pb concentration in Site 4 may be attributed mainly to vehicular emission.
Although Site 4 only ranked 3rd in total volume of vehicles, it has the greatest number of Type B and Type C vehicles combined.
Included in these categories are diesel trucks, buses, and jeepneys which are considered the largest contributors of TSP (total
suspended particles) and PM10 (particulate matter less than 10 microns) emissions.
Conclusion Only one (San Juan in Site 4) of the thirty sampling sites recorded a Pb concentration beyond the WHO permissible limit of
100 mg kg–1. San Juan in Site 4 had a Pb concentration of >250 mg kg–1. On the average, elevated Pb concentration was evident
in the soil samples from San Fernando, Olongapo, Malolos, Balanga, and Cabanatuan. The average soil Pb concentrations in these
cities exceeded the maximum estimated natural soil Pb concentration of 25 mg kg–1. Average soil Pb concentration in Site 1
(16.8 mg kg–1) was well within the estimated natural concentration range of 5 to 25 mg kg–1. Data gathered from the study
areas showed that elevated levels of Pb in soil were due primarily to vehicular emissions and partly to igneous activity.
Recommendation and Outlook The findings of this study presented a preliminary survey on the extent of Pb contamination of soils in urban cities in central
region of Philippines Island. With this kind of information on hand, government should develop a comprehensive environmental
management strategy to address vehicular air pollution in urban areas, which shows as one of the most pressing environmental
problems in the country. Basic to this is the continuous monitoring of Pb levels and other pollutants in air, soil, and water.
Further studies should be conducted to monitor soil Pb levels in the six cities studied particularly in areas with elevated
Pb concentration. The potential for harm from Pb exposure cannot be understated. Of particular concern are children who are
more predisposed to Pb toxicity than adults. Phytoremediation of Pb-contaminated sites is strongly recommended to reduce Pb
concentration in soil. Several studies have confirmed that plants are capable of absorbing extra Pb from soil and that some
plants, grass species in particular, and can naturally absorb far more Pb than others. 相似文献
156.
Sahsuvaroglu T Arain A Kanaroglou P Finkelstein N Newbold B Jerrett M Beckerman B Brook J Finkelstein M Gilbert NL 《Journal of the Air & Waste Management Association (1995)》2006,56(8):1059-1069
This paper reports on the development of a land use regression (LUR) model for predicting the intraurban variation of traffic-related air pollution in Hamilton, Ontario, Canada, an industrial city at the western end of Lake Ontario. Although land use regression has been increasingly used to characterize exposure gradients within cities, research to date has yet to test whether this method can produce reliable estimates in an industrialized location. Ambient concentrations of nitrogen dioxide (NO2) were measured for a 2-week period in October 2002 at > 100 locations across the city and subsequently at 30 of these locations in May 2004 to assess seasonal effects. Predictor variables were derived for land use types, transportation, demography, and physical geography using geographic information systems. The LUR model explained 76% of the variation in NO2. Traffic density, proximity to a highway, and industrial land use were all positively correlated with NO2 concentrations, whereas open land use and distance from the lake were negatively correlated with NO2. Locations downwind of a major highway resulted in higher NO2 levels. Cross-validation of the results confirmed model stability over different seasons. Our findings demonstrate that land use regression can effectively predict NO2 variation at the intraurban scale in an industrial setting. Models predicting exposure within smaller areas may lead to improved detection of health effects in epidemiologic studies. 相似文献