177,250 research outputs found
Conceitos básicos do experimento de campo.
No full textO principal objetivo deste projeto é desenvolver sistemas que sejam ecológico, social e economicamente viáveis, adaptados às condições úmidas da Amazônia tropical. Refere-se a um experimento, recultivando uma área em pousio de um seringal abandonado, estabelecendo consórcio de plantas selecionadas, principalmente espécies perenes
Aproveitamento de áreas abandonadas na Amazônia, através de sistemas de policultivo.
No full textNeste trabalho, estao sendo testados sistemas de policultivo submetidos a dois niveis de adubacao associados ou nao com fungos micorrizicos com o objetivo de aumentar a produtividade, consequentemente, manter a area em producao por longo periodo e, assim, reduzir os desmatamentos. No primeiro semestre de 1993, em area de capoeira, com cerca de oito anos de idade, foram implantados quatros sistemas de policultivo envolvendo as seguintes culturas: Hevea spp, Theobroma grandiflorum, Bactris gasipaes, Bertholletia excelsa, Bixa orellana, Cocos nucifera, Citrus sinensis, Schilozobium amazonicum, Swietenia macrophylla, Carapa guianensis, Carica papaya, Zea mays e Manihot esculenta. Os sistemas estao implantados em parcelas de 32m x 48m, distribuidos em blocos ao acaso com cinco repeticoes. O ensaio esta sendo avaliado por um equipe de pesquisadores, envolvendo varias disciplinas, principalmente das areas de biologia e agronomia. Ate o momento, foi verificado que as plantas micorrizadas apresentam melhor crescimento em condicoes de viveiro e maiores taxas de sobrevivencia quando transplantadas para o campo. Nos sistemas, de um modo geral, as plantas tem apresentado melhor desenvolvimento, destacando-se cupuacu e citros. A pupunha em monocultura apresentou maior producao de palmito. A incidencia de doencas e pragas tem sido bem inferior, quando comparada com as areas de monocultura da regiao
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Potentials of biodiversity in chickens
No full textWithin the framework of the Synbreed project, a large panel of chicken breeds were phenotypically characterized encompassing both categorical traits and body measurements. This "Synbreed Chicken Biodiversity Panel (SCBP)" comprises more than 2400 individuals from 111 diverse breeds and colour variants of various geographical origins including two wild jungle fowl populations and commercial purebred lines. In this study, data of 1967 individuals genotyped at more than 445'000 SNP loci using the Affymetrix 600k Axiom chicken SNP Array were available. Genome wide association analyses clearly detected genomic regions of known mutations for yellow skin colour and rose-comb, respectively. In addition, a cluster analysis with a subset of 89 populations using an extract of autosomal SNPs variable in the wild ancestor Red Jungle Fowl was conducted to visualize the relationship between breeds. Results showed that the majority of breeds formed clusters according to their supposed relationships. The SCBP represents a valuable resource for high resolution analysis of genetic diversity and mapping of genomic regions underlying phenotypic variability
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Potentials of biodiversity in chickens
No full textWithin the framework of the Synbreed project, a large panel of chicken breeds were phenotypically characterized encompassing both categorical traits and body measurements. This "Synbreed Chicken Biodiversity Panel (SCBP)" comprises more than 2400 individuals from 111 diverse breeds and colour variants of various geographical origins including two wild jungle fowl populations and commercial purebred lines. In this study, data of 1967 individuals genotyped at more than 445'000 SNP loci using the Affymetrix 600k Axiom chicken SNP Array were available. Genome wide association analyses clearly detected genomic regions of known mutations for yellow skin colour and rose-comb, respectively. In addition, a cluster analysis with a subset of 89 populations using an extract of autosomal SNPs variable in the wild ancestor Red Jungle Fowl was conducted to visualize the relationship between breeds. Results showed that the majority of breeds formed clusters according to their supposed relationships. The SCBP represents a valuable resource for high resolution analysis of genetic diversity and mapping of genomic regions underlying phenotypic variability
Linkage disequilibrium reveals different demographic history in egg laying chickens
No full textAbstract Background The availability of larger-scale SNP data sets in the chicken genome allows to achieve a higher resolution of the pattern of linkage disequilibrium (LD). In this study, 36 k and 57 k genotypes from two independent genotyping chips were used to systematically characterize genome-wide extent and structure of LD in the genome of four chicken populations. In total, we analyzed genotypes of 454 animals from two commercial and two experimental populations of white and brown layers which allows to some extent a generalization of the results. Results The number of usable SNPs in this study was 19 k to 37 k in brown layers and 8 k to 19 k in white layers. Our analyzes showed a large difference of LD between the lines of white and brown layers. A mean value of r2 = 0.73 ± 0.36 was observed in pair-wise distances of r2= 0.32 ± 0.33 was observed for SNPs less than 25 Kb apart from each other and dropped to 0.21 ± 0.26 at a distance of 100 kb in commercial brown layers. There was a remarkable similarity of the LD patterns among the two populations of white layers. The same was true for the two populations of brown layers, while the LD pattern between white and brown layers was clearly different. Inferring the population demographic history from LD data resulted in a larger effective population size in brown than white populations, reflecting less inbreeding among brown compared to white egg layers. Conclusions We report comprehensive LD map statistics for the genome of egg laying chickens with an up to 3 times higher resolution compared to the maps available so far. The results were found to be consistent between analyzes based on the parallel SNP chips and across different populations (commercial vs. experimental) within the brown and the white layers. It is concluded that the current density of usable markers in this study is sufficient for association mapping and the implementation of genomic selection in these populations to achieve a similar accuracy as in implementations of association mapping and genomic selection in mammalian farm animals.</p
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