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41.
Proximal mechanisms underlying a faster growth rate in male compared to female California sea lion pups were investigated.
Males are significantly larger at birth than females. Specifically, we asked if differential maternal investment contributed
to enhanced male growth via: (1) larger mothers having disproportionately more male pups, (2) more time and energy put into
foraging by mothers of male pups, and (3) greater milk production in mothers of male pups. We also considered four aspects
of differential energy utilization and acquisition by male and female pups: (1) male pups attempting to save energy for growth
by changes in behavior, (2) longer suckling bouts with mother and more sneak suckling of non-filial females by male pups,
(3) lower maintenance costs in males via a lowered resting metabolic rate, and (4) increased assimilation efficiency in males.
Our study showed that there are no differences in the size of females or length of foraging trips for mothers of male and
female pups. Male pups received more milk from their mothers, but the difference was no longer significant when the larger
body size of males was considered. There were no differences in either the activity budgets or suckling behavior of male and
female pups. Male pups, however, did have lower resting metabolic rates than females. We conclude that enhanced male perinatal
growth is a consequence of a larger size at birth, proportionally more milk from mothers to support the greater demands of
larger body size, and lower maintenance costs due to a lower resting metabolic rate.
Received: 28 April 1995/Accepted after revision: 25 July 1995 相似文献
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Kameoka Hiroshi Ito Koji Ono Junko Banno Arisa Matsumura Chisato Haga Yuki Endo Kazuto Mizutani Satoshi Yabuki Yoshinori 《Journal of Material Cycles and Waste Management》2022,24(1):287-296
Journal of Material Cycles and Waste Management - Per- and polyfluoroalkyl substances (PFASs) are used in products, such as aqueous film-forming foam and fluorochemical surfactants, because of... 相似文献
44.
To obtain the distribution of fuel components to gas, tar and char in a pressurized fluidized bed waste pyrolyzer, experiments were conducted with a laboratory scale fluidized bed reactor. Waste samples were fed batchwise from the top of the reactor into the fluidized bed of silica sand and pyrolyzed by nitrogen/nitrogen-O2 gas and the effects of pressure, particle size, heating rate and oxygen addition were investigated. In the case of rubber, the char yield tended to increase a little and the tar yield decrease over the pressure of 304-709 kPa. In comparison with the thermogravimetry data it was clearly demonstrated that the char yield from fluidized bed pyrolysis is much lower. A small amount of oxygen addition decreased both tar and char yields but its further increase did not affect them very much. 相似文献
45.
F.?B.?Ono E.?S.?Penido R.?Tappero D.?Sparks L.?R.?G.?GuilhermeEmail author 《Environmental geochemistry and health》2016,38(5):1083-1096
Soils and wastes enriched with heavy metals may present ecological and human health risks. A considerable number of mining areas exist in Brazil, where high levels of metals have been found. However, studies of bioaccessibility of metals in soils/tailings from these areas are scarce, despite their potential informational contribution concerning exposure risks of residents near these areas. This study evaluated tailings collected from four sites of a zinc smelting area located in Brazil with aims to: (1) evaluate the presence of metals of potential concern; (2) investigate Cd and Pb bioaccessibility; and (3) determine the desorption kinetics of Cd and Pb. High concentrations of total Cd and Pb (up to 1743 mg Cd kg?1 and 8675 mg Pb kg–1) and great variability were found in the tailings, indicating the importance of adequate planning for their final disposal, in order to avoid contamination in the surrounding environment. Cadmium and Pb bioaccessibility percentages in the intestinal phase were less than 47 and 4 %, respectively, which represents significant fractions not available for absorption in the intestinal tract. However, this material has to be monitored since its bioaccessibility may increase with eventual physicochemical changes, releasing Cd and Pb. Desorption kinetics experiments revealed that Pb in the samples remained in less labile fractions, whereas Cd was found in more labile fractions, which is in accordance with the bioaccessibility results. 相似文献
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Hyperaccumulation of metals by plants involves at least three processes: efficient absorption by roots, efficient root-to-shoot translocation and hypertolerance through internal detoxification. In this study, Thlaspi caerulescens was separately exposed to Cd and Zn at 0, 50, 100 and 200 μ M for 7 d to monitor plant responses in hydroponics. Significant dose-dependent accumulation was observed for both metals, mainly in roots (up to 3.2 and 9.2 mg g ?1 for Cd and Zn, respectively). However, Cd was more phytotoxic in terms of plant growth and photosynthesis. This higher toxicity was also evidenced by MetPLATE bioassay. Root exudation was significantly correlated to Cd and Zn translocation (r>0.85) proving its involvement in facilitating metal uptake. As for antioxidative responses, plants reacted to Cd and Zn by broadly exhibiting an elevation of glutathione reductase activity before declining at 200 μ M due to higher phytotoxicity. By contrast, superoxide dismutase activity was unlikely to be affected by both metals. Root-to-shoot apoplastic flow was traced using a fluorescent dye (trisodium-8-hydroxy-1,3,6-pyrenetrisulfonic acid; PTS), whose concentration in leaves increased to a certain extent with Cd and Zn accumulation, indicating that heavy metals have a comparable effect to drought or salinity in promoting the passive diffusion of water and solutes. Nevertheless, Cd at 200 μ M hindered the diffusion of PTS and consequently affected the apoplastic transport in plants. 相似文献
48.
This research investigated the possibility of using recycled asphalt concrete as surface course in airport pavement. The basic properties of recycled asphalt binder after short- and long-term aging were firstly tested and compared with those of the virgin asphalt. Then, a series of laboratory tests were performed to evaluate the performance of recycled asphalt concrete (containing 40% and 70% RAP), in which the HMA mixture without RAP was used as a control. Furthermore, an experimental pavement consisting of three sections (corresponding to 0%, 40% and 70% RAP content) was constructed to verify the laboratory test results. These results indicated that the recycled asphalt could achieve the similar properties against long-term aging as virgin asphalt. Recycled asphalt concrete containing 40% RAP could be used as surface course in airport pavement as it exhibited similar performance as control mixture both from the laboratory and experimental pavement test results. On the contrary, recycled asphalt concrete containing 70% RAP was not recommended as its fatigue property was much poorer compared with that of virgin asphalt mixture. 相似文献
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