Probabilistic patterns of interaction: the effects of link-strength variability on food web structure

Patterns of species interactions affect the dynamics of food webs. An important component of species interactions that is rarely considered with respect to food webs is the strengths of interactions, which may affect both structure and dynamics. In natural systems, these strengths are variable, and can be quantified as probability distributions. We examined how variation in strengths of interactions can be described hierarchically, and how this variation impacts the structure of species interactions in predator-prey networks, both of which are important components of ecological food webs. The stable isotope ratios of predator and prey species may be particularly useful for quantifying this variability, and we show how these data can be used to build probabilistic predator-prey networks. Moreover, the distribution of variation in strengths among interactions can be estimated from a limited number of observations. This distribution informs network structure, especially the key role of dietary specialization, which may be useful for predicting structural properties in systems that are difficult to observe. Finally, using three mammalian predator-prey networks ( two African and one Canadian) quantified from stable isotope data, we show that exclusion of link-strength variability results in biased estimates of nestedness and modularity within food webs, whereas the inclusion of body size constraints only marginally increases the predictive accuracy of the isotope-based network. We find that modularity is the consequence of strong link-strengths in both African systems, while nestedness is not significantly present in any of the three predator-prey networks.

TUNGSTEN ISOTOPIC COMPOSITIONS IN STARDUST SiC GRAINS FROM THE MURCHISON METEORITE: CONSTRAINTS ON THE s-PROCESS IN THE Hf-Ta-W-Re-Os REGION

We report the first tungsten isotopic measurements in stardust silicon carbide (SiC) grains recovered from the Murchison carbonaceous chondrite. The isotopes (182,183,184,186)Wand (179,180)Hf were measured on both an aggregate (KJB fraction) and single stardust SiC grains (LS+ LU fraction) believed to have condensed in the outflows of low-mass carbon-rich asymptotic giant branch (AGB) stars with close-to-solar metallicity. The SiC aggregate shows small deviations from terrestrial (= solar) composition in the (182)W/(184)Wand (183)W/(184)Wratios, with deficits in (182)W and (183)W with respect to (184)W. The (186)W/(184)W ratio, however, shows no apparent deviation from the solar value. Tungsten isotopic measurements in single mainstream stardust SiC grains revealed lower than solar (182)W/(184)W, (183)W/(184)W, and (186)W/(184)W ratios. We have compared the SiC data with theoretical predictions of the evolution of W isotopic ratios in the envelopes of AGB stars. These ratios are affected by the slow neutron-capture process and match the SiC data regarding their (182)W/(184)W, (183)W/(184)W, and (179)Hf/(180)Hf isotopic compositions, although a small adjustment in the s-process production of (183)W is needed in order to have a better agreement between the SiC data and model predictions. The models cannot explain the (186)W/(184)W ratios observed in the SiC grains, even when the current (185)W neutron-capture cross section is increased by a factor of two. Further study is required to better assess how model uncertainties (e. g., the formation of the (13)C neutron source, the mass-loss law, the modeling of the third dredge-up, and the efficiency of the (22)Ne neutron source) may affect current s-process predictions.

Intelligence systems methodology: a systemic approach to the organizational intelligence function

Organizational intelligence can be seen as a function of the viable structure of an organization. With the integration of the Viable System Model and Soft Systems Methodology (systemic approaches of organizational management) focused on the role of the intelligence function, it is possible to elaborate a model of action with a structured methodology to prospect, select, treat and distribute information to the entire organization that improves the efficacy and efficiency of all processes. This combination of methodologies is called Intelligence Systems Methodology (ISM) whose assumptions and dynamics are delimited in this paper. The ISM is composed of two simultaneous activities: the Active Environmental Mapping and the Stimulated Action Cycle. The elaboration of the formal ISM description opens opportunities for applications of the methodology on real situations, offering a new path for this specific issue of systems thinking: the intelligence systems. Knowledge Management Research & Practice (2012) 10, 141-152. doi:10.1057/kmrp.2011.44

Tigela, café e xícara: diversidade formal e dinâmicas de consumo na produção das louças brancas da cidade de São Paulo no começo do século XX

Este artigo apresenta algumas reflexões em torno das formas e volumes das louças em faiança fina produzidas, e consumidas, na cidade de São Paulo, durante o período de 1913 e 1937, relacionando-as a alguns hábitos levados a cabo na Paulicéia, como o crescente costume do "cafezinho". Para tal, parte-se das análises do acervo gerado pelo resgate do sítio arqueológico Petybon, localizado na zona metropolitana da cidade, no bairro da Lapa, região da Água Branca/Vila Romana. Aponta-se que a diversidade de formas das louças dialoga com os projetos de modernidade pensados para São Paulo e as demandas dos consumidores cujas diversas práticas culturais influenciaram na produção das faianças finas pela Fábrica de Louças Santa Catharina e Indústrias Reunidas Fábricas Matarazzo.

Organização e dinâmica do Conselho Municipal de Segurança Alimentar e Nutricional de São Paulo: implicações para a sua atuação na construção da política municipal de Segurança Alimentar e Nutricional

OBJETIVO: Analisar o funcionamento, a organização e a participação política internas do Conselho Municipal de Segurança Alimentar e Nutricional de São Paulo e quais as possíveis implicações decorrentes na sua atuação no processo de construção de uma política municipal de segurança alimentar e nutricional. MÉTODOS: O estudo de abordagem qualitativa constituiu-se em três etapas: análise documental de atas; observação de reuniões e realização de entrevistas semi-estruturadas com conselheiros, considerados informantes-chave. O eixo de análise foi a participação política do Conselho considerando seus aspectos internos, como composição, dinâmica de funcionamento e participação política de seus membros e a relação destes tópicos com a atuação do Conselho na definição e elaboração de uma política municipal de segurança alimentar e nutricional. RESULTADOS: O perfil "intelectualizado" dos conselheiros não é representativo da maioria da população e facilita o afastamento de questões concretas nas discussões do conselho; a rígida dinâmica interna e a assimetria entre seus membros dificultam, de forma geral, a participação ativa dos conselheiros e, especificamente, as discussões sobre políticas de segurança alimentar e nutricional. Os denominados "conselheiros-militantes" apresentam participação diferenciada, mais crítica, com maior domínio sobre o tema e suas discussões. CONCLUSÃO: O perfil dos conselheiros, a organização interna do Conselho, além da complexidade do tema e sua pequena inserção na sociedade, fazem que o conselho atue distante das demandas sociais e de forma incipiente com relação às políticas de segurança alimentar e nutricional no município.

Staphylococcus aureus thiaminase II: oligomerization warrants proteolytic protection against serine proteases

Staphylococcus aureus TenA (SaTenA) is a thiaminase type II enzyme that catalyzes the deamination of aminopyrimidine, as well as the cleavage of thiamine into 4-amino-5-hydroxymethyl-2-methylpyrimidine (HMP) and 5-(2-hydroxyethyl)-4-methylthiazole (THZ), within thiamine (vitamin B1) metabolism. Further, by analogy with studies of Bacillus subtilis TenA, SaTenA may act as a regulator controlling the secretion of extracellular proteases such as the subtilisin type of enzymes in bacteria. Thiamine biosynthesis has been identified as a potential drug target of the multi-resistant pathogen S. aureus and therefore all enzymes involved in the S. aureus thiamine pathway are presently being investigated in detail. Here, the structure of SaTenA, determined by molecular replacement and refined at 2.7 A ° resolution to an R factor of 21.6% with one homotetramer in the asymmetric unit in the orthorhombic space group P212121, is presented. The tetrameric state of wild-type (WT) SaTenA was postulated to be the functional biological unit and was confirmed by small-angle X-ray scattering (SAXS) experiments in solution. To obtain insights into structural and functional features of the oligomeric SaTenA, comparative kinetic investigations as well as experiments analyzing the structural stability of the WT SaTenA tetramer versus a monomeric SaTenA mutant were performed.