Etude par microanalyse ionique de films de poly(paraphénylène) et des phénomènes induits par implantation ionique

L'étude par microanalyse ionique de films de polyparaphénylène nous a permis de mettre en évidence la présence d'atomes d'azote et d'oxygène ; à partir de l'implantation préliminaire d'isotopes 15N et 18O nous avons pu évaluer les concentrations atomiques en azote et oxygène qui sont respectivement inférieures à 1 % et de l'ordre de 4 %. Ces atomes d'impuretés sont localisés dans une zone de défauts, située à l'arrière de la couche implantée et dont l'importance croît avec la valeur des paramètres d'implantation

Determinação do modo de reprodução em Brachiara spp. e Panicum maximum usando microscopia por contraste de interferência em ovários clarificados.

A maioria das plantas superiores se reproduz sexualmente, ou seja, para formação do embrião ocorre a fecundação do óvulo por um gameta masculino. Entretanto, em muitas espécies de gramíneas forrageiras, o embrião se origina por meio de um processo de reprodução assexual via sementes denominado apomixia. Este modo de reprodução possui grande potencial para ser explorado na agricultura, particularmente na produção de sementes híbridas visando à manutenção do vigor híbrido ao longo das gerações. No melhoramento de espécies apomíticas, o cruzamento entre genitores sexuais e apomíticos origina progênies segregando para o modo de reprodução sexual e apomítico. A determinação do modo de reprodução das progênies pode ser realizada por diversas estratégias, uma delas com destaque para as análises citoembriológicas, as quais possibilitam o estudo da morfologia dos ovários das plantas, permitindo separá-las entre sexuais e apomíticas. Apesar de estas análises já serem realizadas em várias espécies, ainda não existe uma publicação que descreva detalhadamente cada etapa e que tenha um acervo fotográfico ilustrando o passo a passo. Assim, neste documento são apresentadas, com detalhes, as análises citoembriológicas por meio de microscopia por contraste por interferência. São relatados todos os procedimentos necessários para a coleta das espiguetas no campo, a fixação destas em fenol ácido acético - FAA, a extração dos ovários e sua clarificação. Posteriormente, é detalhada a contagem das lâminas e a análise dos ovários clarificados, utilizando-se o microscópio com contraste diferencial de interferência (DIC ? differential interference contrast). Por fim, é apresentado como se analisam os resultados do método para se concluir sobre o modo de reprodução de cada planta. Dentro deste contexto, este documento apresenta grande importância para estudantes, professores e pesquisadores que trabalham com sistema reprodutivo de forrageiras.bitstream/item/204549/1/Determinacao-do-modo-de-reproducao-em-Brachiara.pd

EVALUATION OF THE NATURAL REGENERATION IN A RESTORATION PLANTING AREA AND IN A REFERENCE RIPARIAN FOREST

\uc1reas ribeirinhas s\ue3o foco recorrente de restaura\ue7\ue3o ecol\uf3gica, devido a sua import\ue2ncia para a manuten\ue7\ue3o de servi\ue7os ecossist\ueamicos. Entretanto, poucos estudos t\ueam de fato avaliado o sucesso de interven\ue7\uf5es ativas em restaurar fun\ue7\uf5es ou processos ecossist\ueamicos. A regenera\ue7\ue3o natural \ue9 um processo sucessional, cuja avalia\ue7\ue3o pode indicar o estado e o potencial de resili\ueancia do ecossistema em \ue1reas sob restaura\ue7\ue3o. O presente estudo comparou padr\uf5es de regenera\ue7\ue3o natural de uma \ue1rea de restaura\ue7\ue3o ecol\uf3gica (com plantio de mudas nativas h\ue1 10 anos) com a mata ciliar de refer\ueancia, em Cachoeirinha, Rio Grande do Sul, Brasil. Para tanto, foi realizado o levantamento das esp\ue9cies arb\uf3reas e arbustivas presentes no estrato superior (DAP 65 5 cm) e inferior (altura > 30 cm e DAP < 5 cm), em 40 parcelas de 100 m\ub2 cada, considerando o plantio (restaura\ue7\ue3o) e a mata ciliar remanescente (refer\ueancia). Cada estrato e tratamento (refer\ueancia vs. restaura\ue7\ue3o) foi avaliado quanto aos descritores fitossociol\uf3gicos, padr\uf5es de estrutura e composi\ue7\ue3o, riqueza e similaridade entre as comunidades. Os resultados demonstraram que a \ue1rea de restaura\ue7\ue3o apresenta composi\ue7\ue3o de esp\ue9cies e estrutura diferenciada com rela\ue7\ue3o \ue0 refer\ueancia, especialmente para o estrato superior. No estrato inferior (regenera\ue7\ue3o natural), o n\ufamero de indiv\uedduos, a altura m\ue9dia e a riqueza de esp\ue9cies j\ue1 n\ue3o diferiram da refer\ueancia. A composi\ue7\ue3o de esp\ue9cies em regenera\ue7\ue3o ainda foi distinta, por\ue9m, esta foi mais similar entre si do que as demais compara\ue7\uf5es entre estratos, indicando que esp\ue9cies n\ue3o plantadas foram capazes de se estabelecer nas \ue1reas de restaura\ue7\ue3o.Riparian areas are a recurrent focus of ecological restoration due to their importance for the maintenance of ecosystem services. However, few studies have evaluated the success of active interventions in restoring ecosystem functions and processes. The natural regeneration is a successional process and its evaluation might reveal the state and the potential of the ecosystem resilience in forest areas undergoing restoration. The present study aimed to compare natural regeneration of a riparian area that is undergoing restoration (planting of native trees, 10 years ago) with a reference forest area, in Cachoeirinha, Rio Grande do Sul state, Brazil. We conducted a survey of trees and shrubs in the upper stratum (DBH 65 5 cm) and the lower stratum (> 30 cm in height and DBH > 5 cm) in a total of 40 plots (100 m2 each), within the planting (restoration) and the remnant forest (reference). For each stratum and treatment (reference vs. restoration) we analyzed phytosociological parameters, patterns of structure and composition, and similarity among plots. The results showed significant differences in relation to structure and species composition, especially for the upper stratum. For the lower stratum (natural regeneration), abundance, height, and species richness were similar between the restoration and the reference areas. Species composition in regeneration remained distinct. However, its similarity value was higher than any other comparison among strata, indicating that species that were not planted were able to establish in the planted areas

Grassroots Agency: Participation and Conflict in Buenos Aires Shantytowns seen through the Pilot Plan for Villa 7 (1971–1975)

open access articleIn 1971, after more than a decade of national and municipal policies aimed at the top-down removal of shantytowns, the Buenos Aires City Council approved the Plan Piloto para la Relocalización de Villa 7 (Pilot Plan for the Relocation of Shantytown 7; 1971–1975, referred to as the Pilot Plan hereinafter). This particular plan, which resulted in the construction of the housing complex, Barrio Justo Suárez, endures in the collective memory of Argentines as a landmark project regarding grassroots participation in state housing initiatives addressed at shantytowns. Emerging from a context of a housing shortage for the growing urban poor and intense popular mobilizations during the transition to democracy, the authors of the Pilot Plan sought to empower shantytown residents in novel ways by: 1) maintaining the shantytown’s location as opposed to eradication schemes that relocated the residents elsewhere, 2) formally employing some of the residents for the stage of construction, as opposed to “self-help” housing projects in which the residents contributed with unpaid labor, and 3) including them in the urban and architectural design of the of the new housing. This paper will examine the context in which the Pilot Plan was conceived of as a way of re-assessing the roles of the state, the user, and housing-related professionals, often seen as antagonistic. The paper argues that residents’ fair participation and state intervention in housing schemes are not necessarily incompatible, and can function in specific social and political contexts through multiactor proposals backed by a political will that prioritizes grassroots agency

Experimental evidence that novel land management interventions inspired by history enhance biodiversity

1. To address biodiversity declines within semi-natural habitats, land-management must cater for diverse taxonomic groups. Integrating our understanding of the ecological requirements of priority (rare, scarce or threatened) species through ‘biodiversity auditing’, with that of the intensity and complexity of historical land-use, encourages novel forms of management. Experimental confirmation is needed to establish whether this enhances biodiversity conservation relative to routine management. 2. Biodiversity auditing and historical land-use of dry-open terrestrial habitats in Breckland (Eastern England) both encourage management incorporating ground-disturbance and spatio-temporal variability. To test biodiversity conservation outcomes, we developed 40 4-ha management complexes over three successive winters, of which 20 were shallow-cultivated (rotovation) and 20 deep-cultivated (ploughing), stratified across 3,850-ha of closed-sward dry grassland and lowland heathland (collectively ‘dry grassland’). Complexes comprised four 1-ha sub-treatments: repeat-cultivation, first-time-cultivation, one-year-old fallow and two-year-old fallow. We examined responses of vascular plants; spiders; true bugs; ground, rove and ‘other’ beetles; bees and wasps; ants; and true flies on treatment complexes and 21 4-ha untreated controls. Sampling gave 132,251 invertebrates from 877 species and 28,846 plant observations from 167 species. 3. Resampling and rarefaction analyses showed shallow- and deep-cultivation both doubled priority species richness (pooling sub-treatments within complexes) compared to controls. Priority spider, ground beetle, other beetle, and true bug richness were greater on both treatments than controls. Responses were strongest for those priority dry-open-habitat associated invertebrates initially predicted (by biodiversity auditing) to benefit from heavy physical-disturbance. 4. Assemblage composition (pooling non-priority and priority species) varied between sub-treatments for plants, ants, true bugs, spiders, ground, rove and other beetles; but only one-year-old fallowed deep-cultivation increased priority richness across multiple taxa. 5. Treatments produced similar biodiversity responses across various dry grassland ‘habitats’ that differed in plant composition, allowing simplified management guidance. 6. Synthesis and applications. Our landscape-scale experiment confirmed the considerable biodiversity value of interventions inspired by history and informed by systematic multi-taxa analysis of ecological requirements across priority biota. Since assemblage composition varied between sub-treatments, providing heterogeneity in management will support the widest suite of species. Crucially, the intended recipients responded most strongly, suggesting biodiversity audits could successfully inform interventions within other systems

Relevance of the Diversity among Members of the Trypanosoma Cruzi Trans-Sialidase Family Analyzed with Camelids Single-Domain Antibodies

The sialic acid present in the protective surface mucin coat of Trypanosoma cruzi is added by a membrane anchored trans-sialidase (TcTS), a modified sialidase that is expressed from a large gene family. In this work, we analyzed single domain camelid antibodies produced against trans-sialidase. Llamas were immunized with a recombinant trans-sialidase and inhibitory single-domain antibody fragments were obtained by phage display selection, taking advantage of a screening strategy using an inhibition test instead of the classic binding assay. Four single domain antibodies displaying strong trans-sialidase inhibition activity against the recombinant enzyme were identified. They share the same complementarity-determining region 3 length (17 residues) and have very similar sequences. This result indicates that they likely derived from a unique clone. Probably there is only one structural solution for tight binding inhibitory antibodies against the TcTS used for immunization. To our surprise, this single domain antibody that inhibits the recombinant TcTS, failed to inhibit the enzymatic activity present in parasite extracts. Analysis of individual recombinant trans-sialidases showed that enzymes expressed from different genes were inhibited to different extents (from 8 to 98%) by the llama antibodies. Amino acid changes at key positions are likely to be responsible for the differences in inhibition found among the recombinant enzymes. These results suggest that the presence of a large and diverse trans-sialidase family might be required to prevent the inhibitory response against this essential enzyme and might thus constitute a novel strategy of T. cruzi to evade the host immune system

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0\u20135 and 5\u201315 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10\ub0C (mean = 3.0 \ub1 2.1\ub0C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 \ub1 2.3\ub0C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler ( 120.7 \ub1 2.3\ub0C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications