Les déficiences minérales du palmier à huile (E. guineensis Jacq.) dans la région de Belém, Parà (Brésil)

Dans la région de Belém (Para, Brésil), après 15 ans d'expérimentation au champ des fumures N, P, K, Mg sur palmier à huile, on peut tirer les enseignements suivants : la nutrition azotée est naturellement suffisante, sauf dans le très jeune âge et la déficience en phosphore, très accentuée entraîne une faible croissance, une surface foliaire réduite et une production très médiocre. Sa correction permet de doubler les rendements au jeune âge et de les quadrupler à 12-15 ans. A l'unité fertilisante, le phosphate naturel bien meilleur marché aurait une efficacité supérieure à celle du superphosphate triple sur ces latosols sableux; par suite du faible potassium échangeable du sol et de l'effet dépressif des phosphates sur la nutrition en K, il est nécessaire de corriger la déficience en cet élément dès la plantation; pour les mêmes raisons, avec en plus l'antagonisme K-Mg, de la fumure magnésienne doit aussi être apportée à l'âge adulte à partir de 8-10 ans. Les niveaux critiques de la nutrition minérale dans les feuilles sont précisés et comparés à d'autres résultats obtenus ailleurs dans le monde. A partir de ces données, des barèmes de fumure, fonction de l'âge des cultures et du contrôle de la nutrition par le diagnostic foliaire, sont proposés pour cette régio

Metabolic profiles of six African cultivars of cassava (Manihot esculenta Crantz) highlight bottlenecks of root yield

Open Access Article; Published online: 17 Jan 2020Cassava is an important staple crop in sub‐Saharan Africa, due to its high productivity even on nutrient poor soils. The metabolic characteristics underlying this high productivity are poorly understood including the mode of photosynthesis, reasons for the high rate of photosynthesis, the extent of source/sink limitation, the impact of environment, and the extent of variation between cultivars. Six commercial African cassava cultivars were grown in a greenhouse in Erlangen, Germany, and in the field in Ibadan, Nigeria. Source leaves, sink leaves, stems and storage roots were harvested during storage root bulking and analyzed for sugars, organic acids, amino acids, phosphorylated intermediates, minerals, starch, protein, activities of enzymes in central metabolism and yield traits. High ratios of RuBisCO:phosphoenolpyruvate carboxylase activity support a C3 mode of photosynthesis. The high rate of photosynthesis is likely to be attributed to high activities of enzymes in the Calvin–Benson cycle and pathways for sucrose and starch synthesis. Nevertheless, source limitation is indicated because root yield traits correlated with metabolic traits in leaves rather than in the stem or storage roots. This situation was especially so in greenhouse‐grown plants, where irradiance will have been low. In the field, plants produced more storage roots. This was associated with higher AGPase activity and lower sucrose in the roots, indicating that feedforward loops enhanced sink capacity in the high light and low nitrogen environment in the field. Overall, these results indicated that carbon assimilation rate, the K battery, root starch synthesis, trehalose, and chlorogenic acid accumulation are potential target traits for genetic improvement

Lorentz-violating effects on topological defects generated by two real scalar fields

The influence of a Lorentz-violation on soliton solutions generated by a system of two coupled scalar fields is investigated. Lorentz violation is induced by a fixed tensor coefficient that couples the two fields. The Bogomol'nyi method is applied and first-order differential equations are obtained whose solutions minimize energy and are also solutions of the equations of motion. The analysis of the solutions in phase space shows how the stability is modified with the Lorentz violation. It is shown explicitly that the solutions preserve linear stability despite the presence of Lorentz violation. Considering Lorentz violation as a small perturbation, an analytical method is employed to yield analytical solutions.Comment: (9 pages, 11 figures

Levantamento fitossociológico de plantas daninhas em cafezal orgânico.

A adequação de um cafezal para o sistema orgânico causa grande mudança no sistema de manejo de plantas daninhas, mas as informações sobre o comportamento da comunidade infestante em áreas de cultivo de café orgânico são escassas no Brasil. Objetivou-se com este trabalho realizar um levantamento fitossociológico da comunidade infestante em três cafezais (variedades Mundo Novo, Bourbon Vermelho e Obatã) desenvolvidos em sistema orgânico, no município de Garça (SP). Nas três áreas estudadas foram arremessados ao acaso cem quadrados metálicos com área vazada de 0,25 m2, nas entrelinhas da cultura. As espécies contidas no interior dos quadros foram identificadas segundo a espécie botânica, nome popular e família. A partir dos resultados, determinaram-se os parâmetros fitossociológicos: frequência, densidade, abundância, frequência relativa, densidade relativa, abundância relativa, índice de valor de importância e similaridade florísticas pelos métodos de Simple Matching de Sneath & Sokal e similaridade de Sorensen. As famílias que mais se destacaram, com maior número de espécies nas três áreas foram Poaceae e Asteraceae. Houve alta similaridade em todos os contrastes testados, já que pelo menos metade das espécies identificadas foi comum às duas áreas contrastadas

Measurement of the Bottom contribution to non-photonic electron production in p+pp+p collisions at s\sqrt{s} =200 GeV

The contribution of $B$ meson decays to non-photonic electrons, which are mainly produced by the semi-leptonic decays of heavy flavor mesons, in $p+p$ collisions at $\sqrt{s} =$ 200 GeV has been measured using azimuthal correlations between non-photonic electrons and hadrons. The extracted $B$ decay contribution is approximately 50% at a transverse momentum of $p_{T} \geq 5$ GeV/$c$. These measurements constrain the nuclear modification factor for electrons from $B$ and $D$ meson decays. The result indicates that $B$ meson production in heavy ion collisions is also suppressed at high $p_{T}$.Comment: 6 pages, 4 figures, accepted by PR

Balanço do nitrogênio e fósforo em solo com cultivo orgânico de hortaliças após a incorporação de biomassa de guandu.

Os objetivos deste trabalho foram avaliar os efeitos de faixas de guandu (Cajanus cajan) e da incorporação da biomassa proveniente de sua poda na fertilidade do solo e na produtividade de três hortaliças sob cultivo orgânico. O delineamento usado foi de blocos casualizados completos em esquema de parcelas subsubdivididas com três repetições. As produtividades de beterraba, cenoura e feijão-de-vagem não foram afetadas pelos tratamentos. Nas parcelas onde não houve incorporação da biomassa de guandu, o balanço de nitrogênio no sistema foi negativo, ao passo que com a incorporação, esse balanço foi positivo. Embora tenha ocorrido balanço positivo para o fósforo nas parcelas sem a incorporação de biomassa de guandu, houve um aumento significativo na absorção desse elemento pelas hortaliças quando o material foi incorporado. O sistema de cultivo em aléias de guandu pode representar uma prática vantajosa para os produtores orgânicos, por contribuir na manutenção da fertilidade do solo

A systematic review of the effects of exercise interventions on body composition in HIV+ adults

Over the years, physical activity and exercise have been used to positively impact the health and quality of life of persons infected with HIV and, more recently, has been associated with a spectrum of body composition changes. The aim of this review was to examine the effects of various exercise interventions on body composition in HIV positive adults, using a search strategy of randomized, controlled trials (RCTs). A systematic review was performed by five independent reviewers using a predetermined protocol adapted from previous research for assessing the articles for inclusion, the extracted data, and methodological quality. Eight RCTs involving 430 (26% female) HIV positive adults performing exercise a minimum of thrice weekly for at least six weeks were finally selected: Four were progressive resistance training (PRT) studies, three were aerobic training (AT) studies, and one involved yoga. In the PRT studies, there were significant increases in three anthropometric measures, namely, body mass, sum of skinfolds and sum of limb girths. In the AT studies, significant decreases were found in seven anthropometric measures, namely, body mass index, waist-hip ratio, body mass, triceps skinfold, waist circumference and sum of skinfolds. With yoga, the changes were nonsignificant. Exercise contributes to improved body composition and, when applied safely, appears to be beneficial for adults living with HIV/AIDS. However, these findings should be interpreted cautiously due to the relatively few RCTs published to date. Future studies would benefit from increased attention to sample size, female participants, participant follow-up, complete statistical analysis and intention-to-treat analysis.Scopu

Longitudinal double-spin asymmetry and cross section for inclusive neutral pion production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV

We report a measurement of the longitudinal double-spin asymmetry A_LL and the differential cross section for inclusive Pi0 production at midrapidity in polarized proton collisions at sqrt(s) = 200 GeV. The cross section was measured over a transverse momentum range of 1 < p_T < 17 GeV/c and found to be in good agreement with a next-to-leading order perturbative QCD calculation. The longitudinal double-spin asymmetry was measured in the range of 3.7 < p_T < 11 GeV/c and excludes a maximal positive gluon polarization in the proton. The mean transverse momentum fraction of Pi0's in their parent jets was found to be around 0.7 for electromagnetically triggered events.Comment: 6 pages, 3 figures, submitted to Phys. Rev. D (RC

Predation of ants and termites by army ants, Nomamyrmex esenbeckii (Formicidae, Ecitoninae). in the Brazilian Amazon

In four different localities in the Brazilian Amazon we registered raids of army ants (Nomamyrmex esenbeckii). The prey were ants of the genera Atta, Odontomachus and Camponotus and termites of the genus Nasutitermes. The behavior of the army ant and its prey were registered. Our observations expand the number of prey recorded in the literature. It is possible that the dietary regime of these army ants is more flexible than previously believed and is related to food availability