Sexual and natural selection in a continuous time model

We call sexual selection the selection attributable only to the mating system, to distinguish it from other forms of selection (i.e. viability or fertility) which we call natural selection. We introduce a new continuous time model of sexual selection and we explore its relationship with natural selection. This model is an extension of the model proposed by Hoppensteadt [Hoppensteadt, F., 1977. Mathematical Theories of Populations: Demographics, Genetics and Epidemics. SIAM] and considers the three genotypes determined by two alleles in a locus, each with its own mortality and fertility rates, and the respective mating preferences.     

Testing the Stochastic Dynamic Methodology (StDM) as a management tool in a shallow temperate estuary of south Europe (Mondego, Portugal)

A long-term monitoring program has been carried out since the early 1990s in the Mondego estuary, on Portugal's west coast, which is presently under heavy human pressure. In this shallow warm-temperate estuary, a significant macroalgal proliferation has been observed, which is a clear sign of nutrient enrichment. As a result of competition with algae, the extension of the seagrass meadows (mainly Zostera noltii) has been reduced. The present paper examined the applicability of a holistic Stochastic Dynamic Methodology (StDM) in predicting the tendencies of trophic key-components (macrophytes, macroalgae, benthic macroinvertebrate and wading birds) as a response to the changes in estuarine environmental conditions. The StDM is a sequential modelling process developed in order to predict the ecological status of changed ecosystems, from which management strategies can be designed. The data used in the dynamic model construction included true gradients of environmental changes and was sampled from January 1993 to September 1995 and from December 1998 to December 2005. The dynamic model developed was preceded by a conventional multivariate statistical procedure performed to discriminate the significant relationships between the selected ecological components. The model validation was based on independent data collected from January 1996 to January 1997 and from February 1999 to April 2000 for all the state variables considered. Overall, the simulation results are encouraging since they seem to demonstrate the StDM reliability in capturing the trophic dynamics of the studied estuary, by predicting the behavioural pattern for the most part of the components selected, with a focus on the Zostera noltii meadows recovery after the implementation of important management measures.     

Variability in the primary emissions and secondary gas and particle formation from vehicles using bioethanol mixtures

Bioethanol for use in vehicles is becoming a substantial part of global energy infrastructure because it is renewable and some emissions are reduced. Carbon monoxide (CO) emissions and total hydrocarbons (THC) are reduced, but there is still controversy regarding emissions of nitrogen oxides (NO_x), aldehydes, and ethanol; this may be a concern because all these compounds are precursors of ozone and secondary organic aerosol (SOA). The amount of emissions depends on the ethanol content, but it also may depend on the engine quality and ethanol origin. Thus, a photochemical chamber was used to study secondary gas and aerosol formation from two flex-fueled vehicles using different ethanol blends in gasoline. One vehicle and the fuel used were made in the United States, and the others were made in Brazil. Primary emissions of THC, CO, carbon dioxide (CO₂), and nonmethane hydrocarbons (NMHC) from both vehicles decreased as the amount of ethanol in gasoline increased. NO_x emissions in the U.S. and Brazilian cars decreased with ethanol content. However, emissions of THC, CO, and NO_x from the Brazilian car were markedly higher than those from the U.S. car, showing high variability between vehicle technologies. In the Brazilian car, formation of secondary nitrogen dioxide (NO₂) and ozone (O₃) was lower for higher ethanol content in the fuel. In the U.S. car, NO₂ and O₃ had a small increase. Secondary particle (particulate matter [PM]) formation in the chamber decreased for both vehicles as the fraction of ethanol in fuel increased, consistent with previous studies. Secondary to primary PM ratios for pure gasoline is 11, also consistent with previous studies. In addition, the time required to form secondary PM is longer for higher ethanol blends. These results indicate that using higher ethanol blends may have a positive impact on air quality.

Implications: The use of bioethanol can significantly reduce petroleum use and greenhouse gas emissions worldwide. Given the extent of its use, it is important to understand its effect on urban pollution. There is a controversy on whether there is a reduction or increase in PM emission when using ethanol blends. Primary emissions of THC, CO, CO₂, NO_x, and NMHC for both cars decreased as the fraction of ethanol in gasoline increased. Using a photochemical chamber, the authors have found a decrease in the formation of secondary particles and the time required to form secondary PM is longer when using higher ethanol blends.     

Managing Mediterranean soil resources under global change: expected trends and mitigation strategies

Regional Environmental Change - The soils of the Mediterranean Basin are the products of soil processes that have been governed by a unique convergence of highly differentiated natural and...     

Key factors in levels of public satisfaction with urban waste collection in a northern Spain city

Journal of Material Cycles and Waste Management - Levels of public satisfaction among the inhabitants of Burgos with their urban waste collection service are analyzed by comparing satisfaction...     

Why telecoupling research needs to account for environmental justice

ABSTRACT

Engaging with normative questions in land system science is a key challenge. This debate paper highlights the potential of incorporating elements of environmental justice scholarship into the evolving telecoupling framework that focuses on distant interactions in land systems. We first expose the reasons why environmental justice matters in understanding telecoupled systems, and the relevant approaches suited to mainstream environmental justice into telecoupled contexts. We then explore which specific elements of environmental justice need to be incorporated into telecoupling research. We focus on 1) the distribution of social-ecological burdens and benefits across distances, 2) power and justice issues in governing distantly tied systems, and 3) recognition issues in information flows, framings and discourses across distances. We conclude our paper highlighting key mechanisms to address injustices in telecoupled land systems.     

Management of sludge from fish ponds at the edge of the Itaparica Reservoir (Brazil): an alternative to improve agricultural production

Sludge generated in intensively managed tilapia fingerling breeding ponds near the Itaparica Dam in the semi-arid Brazilian northeastern region was tested as a soil conditioner to produce lettuce in an effort to mitigate the present environmental impact of the deposition of this sludge, thereby giving it a productive destiny. A greenhouse experiment was performed by mixing the sludge with a Haplic Planosol topsoil, a characteristic soil of the region, so that the sludge corresponded to 0, 25, 50, 75, and 100% of the mixture (substrate). The experiment was set up as a randomized block design with five blocks, each with three pots (5-kg substrate per pot) of the five sludge proportion treatments. One lettuce plant was transplanted into each pot, maintained under greenhouse conditions, and harvested 35 days after transplanting. Sludge, soil, and the substrates were evaluated for nutrient concentration and physical characteristics. Green and dry weights, stem diameter, and nitrogen, phosphorus, and potassium concentrations in the aboveground parts of the lettuce plants were determined. Sludge incorporation into the substrate improved its chemical and physical characteristics. The lettuce plants grew best in the substrate with 75% sludge, increasing its biomass production by 50% and more than doubling its nitrogen uptake.     

Using FTIR to corroborate the identity of functional groups involved in the binding of Cd and Cr to saltbush (Atriplex canescens) biomass

Fourier transform infrared (FTIR) studies were performed to confirm the chemical modification of saltbush (Atriplex canescens) biomass and to provide information about the identity and binding characteristics of the chemical groups responsible for the binding of Cd(II), Cr(III), and Cr(VI). In addition, studies were performed to determine the optimum time for the binding of the three ions by saltbush biomass, and to study the efficiency of HCl and sodium citrate as stripping agents. The metal quantification was performed using inductively coupled plasma optical emission spectroscopy (ICP-OES). The results showed that 10 min or less is enough to achieve the maximum metal binding, and that aqueous solutions of 0.1 mM HCl or sodium citrate were enough to strip more than 80% of the bound Cd. It was determined that more than 70% of the bound Cr(III) was stripped using 0.1 mM HCl. Chemical modification of carboxyl and ester groups on the biomass was performed. The FTIR results confirmed that the esterification of carboxyl groups and hydrolysis of ester groups in the native biomass had occurred. The direct effect of these modifications on the binding properties of the biomass provided strong evidence that the carboxyl functionality is the main group responsible for binding Cd and Cr(III). However, the IR data showed that for Cr(VI), a different type of functional group is involved.     

墨西哥为实现2025年温室气体减排目标在电力生产中使用可再生能源

本研究介绍了到2025年时墨西哥电力生产的4种设想前景.第一种设想前景的关键是使用石油产品特别是燃料油,这代表了墨西哥过去能源政策的足迹.第二种设想前景是优先使用天然气,这反映了由于能源领域改革而于20世纪90年代中期形成的能源消费型.第三种设想前景认为,从技术的和经济的角度看来,大量使用可再生能源是可行的.第四种设想前景认为,目前和相当一段时间内要使用能源改革中形成的天然气技术,而在2007年以后,才开始大量使用可再生能源.这4种设想前景都依据温室气体(GHG)和酸雨前身气体(ARPG)推算到2025年.