The oxo/peroxo debate: a nonheme iron perspective

The oxygen activation mechanisms proposed for nonheme iron systems generally follow the heme paradigm in invoking the involvement of iron-peroxo and iron-oxo species in their catalytic cycles. However, the nonheme ligand environments allow for end-on and side-on dioxygen coordination and impart greater flexibility in the modes of dioxygen activation. The currently available evidence for nonheme iron-peroxo and iron-oxo intermediates is summarized and discussed in light of the ongoing discussion on the nature of the oxidant(s) in heme enzymes.     

Diversity measures in macroinvertebrate and zooplankton communities related to the trophic status of subtropical reservoirs: Contradictory or complementary responses?

Macroinvertebrate communities have been widely used as a tool for assessing the environmental quality of freshwater ecosystems, whereas zooplankton communities have been to some extent neglected. However, the importance of using different indicators to achieve a more comprehensive framework of assessment regarding water quality has been recognized. This study compared estimates of species richness (number of species) and the Shannon–Wiener index for data on macroinvertebrate and zooplankton communities in tropical reservoirs and related them to their trophic state. The trop+hic classification was obtained by applying the Carlson index (1977) modified by Toledo et al. (1983), and the index of the Brazilian Society of the Environmental Technology Agency. The comparative response of the different indicators was analyzed using a series of bivariate correlations (Draftsman’s plot). The results illustrate that diversity measures, namely species richness, responded differently when related to the trophic classification of reservoirs, depending on the community considered. The species richness of zooplankton was positively related to hypereutrophic conditions, due to the higher number of rotifer species, including tolerant generalist species and at the same time, as a result of the exclusion of species from other groups, whereas for macroinvertebrates, species richness was negatively related to hypereutrophic conditions. Melanoides tuberculatus, which exhibits a high tolerance and competitive ability under such conditions, was the dominant species in macroinvertebrate communities, which excluded endemic species and reduced local richness and diversity. The same indicators applied to the zooplankton and macroinvertebrate communities might therefore provide contradictory responses regarding ecological quality assessment in tropical reservoirs, which suggest that zooplankton should be taken into account among the biological quality elements considered in the ecological quality assessment, management, and restoration of water bodies.     

Testing for Validity and Reliability in Cross-Cultural Research

A set of procedures is offered for assessing interraler reliability and certain aspects of validity of codes in cross-cultural studies. The method assumes that at least two independent raters have coded more than one trait. Each trait coded by one rater is correlated with each trait coded by a second, and all the codings by a single rater are intercorrelated with each other. The results are presented in a multitrait-multi-rater matrix. From this matrix it is possible to determine the interrater reliability and discriminant validity of trails in addition to a higher order concept based on pairs of traits.     

Reinforcement and learning

Evidence has been accumulating to support the process of reinforcement as a potential mechanism in speciation. In many species, mate choice decisions are influenced by cultural factors, including learned mating preferences (sexual imprinting) or learned mate attraction signals (e.g., bird song). It has been postulated that learning can have a strong impact on the likelihood of speciation and perhaps on the process of reinforcement, but no models have explicitly considered learning in a reinforcement context. We review the evidence that suggests that learning may be involved in speciation and reinforcement, and present a model of reinforcement via learned preferences. We show that not only can reinforcement occur when preferences are learned by imprinting, but that such preferences can maintain species differences easily in comparison with both autosomal and sex-linked genetically inherited preferences. We highlight the need for more explicit study of the connection between the behavioral process of learning and the evolutionary process of reinforcement in natural systems.     

The stable evolutionary fixation of a bifunctional tyrosine-pathway protein in enteric bacteria

Abstract The bifunctional T-protein (chorismate mutase-T: cyclohexadienyl dehydrogenase) of l -tyrosine biosynthesis was found to be present in all genera making up the enteric bacteria. The dehydrogenase component of the T-protein was active with both prephenate and l -arogenate, showing it to be a cyclohexadienyl dehydrogenase. The dehydrogenase component, but not the mutase component, of the T-protein was feedback-inhibited by l -tyrosine. Unlike some other bifunctional proteins, the T-protein has evolved recently and is not ubiquitous. However, once the biochemical specialization of bifunctionality becomes established, the results indicate that such character states are strongly conserved through evolutionary time. Thus, bifunctional proteins can provide particularly reliable markers for small (recent origin), intermediate, and large (ancient origin) phylogenetic clusters.     

Virtual water and water footprints do not provide helpful insight regarding international trade or water scarcity

Many authors have estimated the virtual water content of good and services traded internationally, and many have calculated national water footprints that account for the volumes of virtual water imported and exported. Some authors have suggested that international trade of virtual water has been harmful to selected exporting countries with limited water endowments. Some suggest also that current patterns of international trade should be rearranged to make better use of global water resources. Yet, countries do not actually trade in virtual water. They trade in goods and services for which water is one of many inputs. Wise choices regarding water resources and smart strategies regarding international trade cannot be determined by focusing on water alone. The notions of virtual water and water footprints are not helpful indicators of optimal strategies regarding water resources, particularly when considering issues such as water scarcity or international trade. I describe four perspectives regarding virtual water and water footprints, with the goal of demonstrating the inadequacies of these notions in policy discussions and in efforts to determine the optimal allocation and use of water resources. The four perspectives are: (1) international trade should not be modified or regulated to reflect the virtual water content of traded commodities or water footprints in the countries of trading partners, (2) countries do not save water by engaging in virtual water trade, (3) consumers in one country cannot alleviate water scarcity or improve water quality in other countries, and (4) water footprints are not analogous to carbon or ecological footprints.     

Modela-r as a Froude and Strouhal dimensionless numbers combination for dynamic similarity in running

The aim of this study was to test the hypothesis that running at fixed fractions of Froude (Nfr) and Strouhal (Str) dimensionless numbers combinations induce dynamic similarity between humans of different sizes. Nineteen subjects ran in three experimental conditions, (i) constant speed, (ii) similar speed (Nfr) and (iii) similar speed and similar step frequency (Nfr and Str combination). In addition to anthropometric data, temporal, kinematic and kinetic parameters were assessed at each stage to measure dynamic similarity informed by dimensional scale factors and by the decrease of dimensionless mechanical parameter variability. Over a total of 54 dynamic parameters, dynamic similarity from scale factors was met for 16 (mean r=0.51), 32 (mean r=0.49) and 52 (mean r=0.60) parameters in the first, the second and the third experimental conditions, respectively. The variability of the dimensionless preceding parameters was lower in the third condition than in the others. This study shows that the combination of Nfr and Str, computed from the dimensionless energy ratio at the center of gravity (Modela-r) ensures dynamic similarity between different-sized subjects. The relevance of using similar experimental conditions to compare mechanical dimensionless parameters is also proved and will highlight the study of running techniques, or equipment, and will allow the identification of abnormal and pathogenic running patterns. Modela-r may be adapted to study other abilities requiring bounces in human or animal locomotion or to conduct investigations in comparative biomechanics.     

Estimating the human appropriation of land in Brazil by means of an Input–Output Economic Model and Ecological Footprint analysis

As we confront the current environmental crisis, determining the biophysical base (e.g., materials, energy, land, and water) of nations has become paramount. With advanced economies benefiting from the import of resource-intensive primary goods originating from poorer parts of the world, especially emerging nations, these are dilapidating their natural capital. Brazil is one of such emerging economies, whose mining and farming activities, propping up its export-led economic growth, exert great pressure on the environment. In particular, farming has been shown to have one of the world's greatest environmental impacts, especially as a consequence of land use associated with cattle ranching. Since a nation-wide evaluation of land-use types across the whole sectorial spectrum of the country's economy is still lacking, we used the most recently available Input–Output Economic Model for Brazil and the Ecological Footprint method to identify those economic sectors with the greatest potential for appropriating portions of the natural world.Our results show that: (i) the biggest chunk of Brazil's Ecological Footprint is due to its Carbon Footprint and, in particular, emissions from cattle; (ii) only a few economic sectors exhibit high Ecological Footprint values, chiefly those belonging to livestock farming and energy production based on fossil fuels; (iii) excluding the soybeans and slaughter sectors, export-oriented sectors have below-average Ecological Footprint values; and (iv) the percentage of Brazil's Ecological Footprint due to household consumption (excluding imports) is three times bigger than that attributable to exports, with sectors belonging to livestock farming contributing the most to such disparity.These results underscore that the environmental impact of the Brazilian economy can be drastically reduced by tackling the emission-intensive production processes of a few sectors only and disincentivizing the domestic consumption of a narrow range of products, especially with respect to the livestock segment.     

A critical rebuttal of the proposed division of the genus Arcobacter into six genera using comparative genomic,phylogenetic, and phenotypic criteria

The proposal to restructure the genus Arcobacter into six distinct genera was critically examined using: comparative analyses of up to 80 Epsilonproteobacterial genome sequences (including 26 arcobacters); phylogenetic analyses of three housekeeping genes and also 342 core genes; and phenotypic criteria. Genome sequences were analysed with tools to calculate Percentage of Conserved Proteins, Average Amino-acid Identity, BLAST-based Average Nucleotide Identity, in silico DNA–DNA hybridisation values, genome-wide Average Nucleotide Identity, Alignment Fractions and G + C percentages. Genome analyses revealed the genus Arcobacter sensu lato to be relatively homogenous, and phylogenetic analyses clearly distinguished the group from other Epsilonproteobacteria. Genomic distinction of the genera proposed by Pérez-Cataluña et al. [2018] was not supported by any of the measures used and a subsequent risk of strain misidentification clearly identified. Similarly, phenotypic analyses supported the delineation of Arcobacter sensu lato but did not justify the position of the proposed novel genera. The present polyphasic taxonomic study strongly supports the continuance of the classification of “aerotolerant campylobacters” as Arcobacter and refutes the proposed genus-level subdivision of Pérez-Cataluña et al. [2018].