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131.
132.
Ruchira Sen Heather D. Ishak Trevor R. Kniffin Ulrich G. Mueller 《Behavioral ecology and sociobiology》2010,64(7):1125-1133
Interspecies or intraspecies cooperation can be stabilized evolutionarily if choosing partners favor beneficial partners and
discriminate against non-beneficial partners. We quantified such partner choice (symbiont choice) in the leafcutter ant Atta texana (Attini, Formicidae) by presenting the ants in a cafeteria-style preference assay with genotypically distinct fungal cultivars
from A. texana and Acromyrmex versicolor. Symbiont choice was measured as the ants' tendency to choose one or more cultivar(s) from several pure (axenic) cultivar
fragments and convert a given fungal fragment into a garden. Microsatellite DNA fingerprinting enabled us to identify the
cultivars chosen by the ants for their gardens. In 91% of the choice tests, A. texana workers combined multiple cultivars into a single intercropped, chimaeric garden, and the cultivars coexisted in such chimaeric
gardens for as long as 4 months. Coexistence of distinct fungal genotypes in chimaeric gardens appears to contradict a recent
model of cultivar competition postulating that each cultivar secretes incompatibility compounds harming other cultivars, which
presumably would preclude the intercropped polyculture observed in our experiments. Although we found no clear evidence of
novel, recombinant genotypes in the experimental chimaeric gardens, the intercropping of cultivar genotypes may occasionally
lead under natural conditions to exchange of genetic material between coexisting cultivars, thus introducing novel cultivar
genotypes into the leafcutter symbiosis. Symbiont choice by ants and any competition between coexisting cultivar strains in
chimaeric gardens do not appear to operate fast enough in our laboratory assay to convert chimaeric gardens into the monocultures
observed for A. texana under natural conditions. 相似文献
133.
Ian Christoplos Le Duc Ngoan Le Thi Hoa Sen Nguyen Thi Thanh Huong Lily Salloum Lindegaard 《Disasters》2017,41(3):448-467
How do disasters shape local government legitimacy in relation to managing climate‐ and disaster‐related risks? This paper looks at how local authorities in Central Vietnam perceive their social contract for risk reduction, including the partial merging of responsibilities for disaster risk management with new plans for and investments in climate change adaptation and broader socioeconomic development. The findings indicate that extreme floods and storms constitute critical junctures that stimulate genuine institutional change. Local officials are proud of their strengthened role in disaster response and they are eager to boost investment in infrastructure. They have struggled to reinforce their legitimacy among their constituents, but given the shifting roles of the state, private sector, and civil society, and the undiminished emphasis on high‐risk development models, their responsibilities for responding to emerging climate change scenarios are increasingly nebulous. The past basis for legitimacy is no longer valid, but tomorrow's social contract is not yet defined. 相似文献
134.
Dilip Kumar Sen Siba Sankar Mahapatra 《International Journal of Sustainable Engineering》2017,10(6):338-357
A novel decision support framework has been proposed herein to solve supplier selection problems by considering green as well as resiliency criteria, simultaneously. An expert team involving a finite number of Decision-Makers (DMs) is to be employed to obtain degree of importance of each of the evaluation criteria and also to assign an appropriate rating for each supplier alternative with respect to the criteria. Since subjective human judgment often bears some sort of ambiguity as well as vagueness, application of fuzzy set theory can be recommended in this context. The present work represents a dominance based decision support system in the light of fuzzy set theory which is basically a simplified version of TODIM and PROMETHEE. It explores dominance between two alternatives with respect to a particular criterion, based on which a global dominance measure is computed to facilitate ranking order of candidate suppliers. The approach proposed in this research seems straightforward which can exclude complex and tedious computational steps of TODIM as well as PROMETHEE. Application potential of the proposed dominance based fuzzy decision-making approach has been compared to that of Fuzzy-TOPSIS and Fuzzy-VIKOR. Good agreement has been observed. In addition to this, the concept of a unique performance index i.e. ‘g-resilient’ (also called ‘ecosilient’) index has been introduced to help in assessing suppliers’ overall performance extent. The work has also been extended to identify the ill (poor)-performing areas in which suppliers are lagging and seek further improvement towards enhancing g-resilient performance level. 相似文献
135.
Adsorption characteristics of Cu and Ni on Irish peat moss 总被引:1,自引:0,他引:1
Peat has been widely used as a low cost adsorbent to remove a variety of materials including organic compounds and heavy metals from water. Various functional groups in lignin allow such compounds to bind on active sites of peat. The adsorption of Cu(2+) and Ni(2+) from aqueous solutions on Irish peat moss was studied both as a pure ion and from their binary mixtures under both equilibrium and dynamic conditions in the concentration range of 5-100mg/L. The pH of the solutions containing either Cu(2+) or Ni(2+) was varied over a range of 2-8. The adsorption of Cu(2+) and Ni(+2) on peat was found to be pH dependent. The adsorption data could be fitted to a two-site Langmuir adsorption isotherm and the maximum adsorption capacity of peat was determined to be 17.6 mg/g for Cu(2+) and 14.5mg/g for Ni(2+) at 298 K when the initial concentration for both Cu(2+) and Ni(2+) was 100mg/L, and the pH of the solution was 4.0 and 4.5, respectively. Column studies were conducted to generate breakthrough data for both pure component and binary mixtures of copper and nickel. Desorption experiments showed that 2mM EDTA solution could be used to remove all of the adsorbed copper and nickel from the bed. 相似文献
136.
137.
本文对北京市和厦门市大气CO_2及δ~(13)C进行观测,研究内陆城市和沿海城市CO_2浓度及δ~(13)C的季节和昼夜变化规律及影响因素,以期为政府制定碳减排政策提供科学依据。北京市和厦门市CO_2浓度均呈现秋冬季高于春夏季,而δ~(13)C秋冬季低于春夏季,季节差异原因可能是秋冬大气边界层降低,化石燃料消耗增加,贫13C的CO_2气体大量排放。观测期间,两个城市日变化模式均表现为CO_2夜间高于白天,δ~(13)C夜间低于白天;且在早晚交通高峰时段,两地CO_2浓度均有不同程度升高,而δ~(13)C有不同程度降低。冬季,北京市由于受西、北部高山阻挡,在东南风条件下使得其夜间大气CO_2浓度显著增高,δ~(13)C值则显著降低。根据两地新增CO_2的δ~(13)C值(δs)推测,北京市受到煤炭燃烧贡献较大,厦门市季节差异较大,推测受植物排放CO_2速率及气象条件等共同影响。 相似文献
138.
139.
秸秆和地膜覆盖会改变农田土壤碳氮循环等理化条件,而覆盖对参与碳氮循环的土壤微生物的影响还鲜有报道。本研究通过高通量测序,分析了黄土高原旱作玉米农田无覆盖、秸秆覆盖、地膜覆盖下土壤细菌群落组成,探讨了细菌介导的碳氮循环对覆盖的响应。结果表明秸秆覆盖增加了土壤细菌群落丰富度和多样性,且显著增加了分解纤维素的细菌(纤维弧菌属Cellvibrio)及介导固氮(根瘤菌属Rhizomicrobium、Chryseolinea)和硝化过程的细菌(亚硝化螺菌属Nitrosospira)丰度(p0.05);地膜覆盖增加了土壤细菌丰富度,但降低了细菌多样性,且显著增加了介导土壤硝化作用的硝化螺菌属Nitrospira的丰度(p0.05)。本结果为土壤中微生物介导的碳氮循环研究提供了理论依据。 相似文献
140.
为研究滇池内源污染特征,于2013年在滇池全湖布设36个采样点,采集表层沉积物样品,并对沉积物中w(NH4+-N)的分布及NH4+-N释放动力学特征进行研究. 结果显示:滇池表层沉积物中w(NH4+-N)为155.8~667.8 mg/kg,平均值为333.7 mg/kg,湖心区域最高. 0~5 min内NH4+-N释放速率最大,可达到3.34~42.31 mg/(kg·min); 5 min后NH4+-N释放速率逐渐降低,并在120 min左右基本达到释放平衡. 沉积物中NH4+-N的释放潜能为17 147~34 163 mg/kg,NH4+-N释放量随着水土质量比的增加而增大;滇池大部分区域NH4+-N的释放潜能相对较高,特别是在草海北部以及外海盘龙江河口处. 滇池沉积物中NH4+-N释放速率、释放潜能均高于长江中下游湖泊沉积物;与同为高原湖泊的洱海相比,其沉积物中NH4+-N释放速率基本相当,但是NH4+-N释放潜能却远高于洱海,表明滇池表层沉积物中NH4+-N具有非常高的释放风险. 相似文献