Acidification of rain water caused by air pollutants is now recognized as a serious threat to aquatic ecosystems. We examined the effects of low pH (control pH 7.5, pH 6, pH 5, pH 4) on the survival, growth, and shell quality of Macrobrachium rosenbergii postlarvae and early juveniles in the laboratory. Hatcheryproduced postlarvae (PL 5) were stocked at 250 PL per aquarium, acclimated over 7 d to experimental pH adjusted with hydrochloric acid, and reared for 30 d. Dead specimens were removed and counted twice a day. After 27 d rearing, all specimens were measured for total length and body weight. Carapace quality was assessed by spectrophotometry. Survival of juveniles was highest at pH 6 (binomial 95% confidence interval 79 - 89%) followed by control pH 7.5 (56 - 68%) and pH 5 (50 - 60%) and was lowest for unmetamorphosed postlarvae and juveniles at pH 4 (43 - 49%). The final median total length and body weight of juveniles were similar at control pH 7.5 (18.2 TL, 50.2 mg BW) and pH 6 (17.7 mm TL, 45.0 mg BW) but significantly less at pH 5 (16.7 mm TL, 38.2 mg BW); at pH 4, the postlarvae did not metamorphose and measured only 9.8 mm TL, 29.3 mg BW. Length frequency distribution showed homogeneous growth at pH 6, positive skew at control pH 7.5 and pH 5, and extreme heterogeneity at pH 4. The carapace showed different transmittance spectra and lower total transmittance (i.e. thicker carapace) in juveniles at pH 7.5, pH 6, and pH 5 than in unmetamorphosed postlarvae and juveniles with thinner carapace at pH 4. Thus, survival, growth, size distribution, and carapace quality of M. rosenbergii postlarvae and early juveniles were negatively affected by pH 5 and especially pH 4. The thinner carapace of the survivors at pH 4 was mostly due to their small size and failure to metamorphose. Natural waters affected by acid rain could decimate M. rosenbergii populations in the wild.
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Human perception to tremors during earthquakes in high-rise buildings is usually associated with psychological discomfort such as fear and anxiety. This paper presents a methodology for estimating the level of perception to tremors for occupants living in high-rise buildings subjected to ground motion excitations. Unlike other approaches based on empirical or historical data, the proposed methodology performs a regression analysis using the analytical results of two generic models of 15 and 30 stories. The recorded ground motions in Singapore are collected and modified for structural response analyses. Simple predictive models are then developed to estimate the perception level to tremors based on a proposed ground motion intensity parameter—the average response spectrum intensity in the period range between 0.1 and 2.0 s. These models can be used to predict the percentage of occupants in high-rise buildings who may perceive the tremors at a given ground motion intensity. Furthermore, the models are validated with two recent tremor events reportedly felt in Singapore. It is found that the estimated results match reasonably well with the reports in the local newspapers and from the authorities. The proposed methodology is applicable to urban regions where people living in high-rise buildings might feel tremors during earthquakes. 相似文献
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通过梳理历代文学作品尤其是诗词中的玉门关、阳关、嘉峪关,探析这些地理界标在当时人空间认知中的指代;并确定同期中原与西域间的地理界标;比较界标和界标意象,解读两者之间的关系,探讨界标变动的推动因素。分析发现：① 地理界标缘于疆域的变动和边防经略的调整,其规模、位置等自然之形随着丝绸之路路线变迁而改变;② 中原与西域两大空间的界标与国家疆域时而背离、时而重合;③ 当中原王朝管控能力强时,界标与界标意象重合,反之,界标与意象出现背离。借助文学作品来阐释它们的变迁历程,是深入开展边疆史地研究的一次尝试,为历史地理学研究提供新的视角。 相似文献
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P.-Y. Chan P.-E. Lim S.-L. Ng C.-E. Seng 《International Journal of Environmental Science and Technology》2018,15(8):1699-1712
Bioregeneration is a process of restoring the adsorptive capacity of the spent adsorbents through microbial action. In this study, the effects of acclimated biomass concentration, biomass acclimation concentration, dosage of granular activated carbon (GAC) and type of GAC on the bioregeneration efficiency (BE) of GAC loaded with phenol and p-nitrophenol (PNP), respectively, were investigated. The quantification was conducted by monitoring the time courses of adsorbed substrate amount during bioregeneration under the sequential adsorption and biodegradation approach. The mean BEs of phenol- and PNP-loaded GAC were found to be 78 ± 2 and 77 ± 1%, respectively. The results revealed that increasing acclimated biomass concentration and adsorbent dosage did not have an observable effect on the BEs of phenol- and PNP-loaded GAC. Additionally, the BEs were found to be almost the same for the bioregeneration of phenol-loaded GAC using biomass acclimated to 350 and 600 mg/L of phenol, respectively. The BEs of phenol-loaded GAC 830 (thermal-activated) and GAC 1240+ (thermal- and acid-activated) did not show any observable difference, but the BE of PNP-loaded GAC 1240+ was found to be greater than that of PNP-loaded GAC 830 indicating that the improvement of BE of spent GAC through further chemical activation was dependent on the type of adsorbate. 相似文献
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Managing excess capacity in small-scale fisheries: Perspectives from stakeholders in three Southeast Asian countries 总被引：3，自引：1，他引：2
Nerissa Salayo Len Garces Michael Pido Kuperan Viswanathan Robert Pomeroy Mahfuzuddin Ahmed Ida Siason Keang Seng Awae Masae 《Marine Policy》2008,32(4):692-700
The management of fishing capacity—in both inland and marine fisheries—is a major policy concern in most countries in Southeast Asia. Excess capacity leads to a number of negative impacts, such as resource use conflicts, overfishing, environmental degradation, economic wastage, and security threats. This paper presents the results of a regional study that examined various approaches to managing excess fishing capacity in small-scale fisheries in Southeast Asia. More specifically, the paper presents an analysis of perceptions of stakeholders in Cambodia, Philippines and Thailand regarding preferred solutions to addressing excess capacity. The paper concludes with a discussion of policy guidance for addressing excess fishing capacity based on the stakeholder-preferred solutions. 相似文献
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In this paper, torsional response of nonductile structures with soft‐first‐storey subjected to bidirectional ground motions is studied using a simplified two‐storey model with two‐way eccentricities. The stiffness ratio of second storey to first storey is varied to create different levels of soft‐first‐storey effect, while the stiffness eccentricity is varied to create torsional effects. Different overstrength ratios are used in the simplified models to study the response of structure with different structural capacity. Hysteretic model with strength deterioration and stiffness degradation properties is used to capture the deterioration of element stiffness and strength. Ductility capacity of 2.0 is used as the models are for nonductile structures. In general, displacement amplification of irregular model with respect to regular model increases as stiffness ratio increases, while no consistent trend of changes in displacement amplification is found with increase in stiffness eccentricity. It is found that the displacement amplification due to only soft‐first‐storey effect can be conservatively taken as 1.5. Coupling of torsional and soft‐first‐storey effects is more significant in affecting the displacement amplification of elements at flexible side. The trend of changes in displacement amplification of elastic system is similar to that of inelastic system. The displacement amplification of elements at the flexible side is larger than that at the stiff side. The elements at the flexible side in the direction of shorter uncoupled lateral period have larger displacement response than those in the orthogonal direction. Ductility demand–capacity curves subsequently constructed can be used to approximately assess the seismic performance of existing structures and as guidelines for designing structures in Singapore to withstand the maximum credible earthquake considering the coupling of torsional and soft‐first‐storey effects. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Kawamura Gunzo Bagarinao Teodora Yong Annita Seok Kian Chen Chiau Yu Noor Siti Norasidah Mat Lim Leong Seng 《Ocean Science Journal》2015,50(2):371-379
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