3,033 research outputs found

    An Alternative Proof of Hesselholt's Conjecture on Galois Cohomology of Witt Vectors of Algebraic Integers

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    Let KK be a complete discrete valuation field of characteristic zero with residue field kKk_K of characteristic p>0p>0. Let L/KL/K be a finite Galois extension with Galois group G=\Gal(L/K) and suppose that the induced extension of residue fields kL/kKk_L/k_K is separable. Let Wn()\mathbb{W}_n(\cdot) denote the ring of pp-typical Witt vectors of length nn. Hesselholt conjectured that the pro-abelian group {H1(G,Wn(OL))}n1\{H^1(G,\mathbb{W}_n(\mathcal{O}_L))\}_{n\geq 1} is isomorphic to zero. Hogadi and Pisolkar have recently provided a proof of this conjecture. In this paper, we provide an alternative proof of Hesselholt's conjecture which is simpler in several respects.Comment: 3 pages; added references, changed Remark 2.1 to a lemma and proof, updated abstrac

    ATD-2 Integrated Arrival/Departure/Surface (IADS) System Specification - Phase 2

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    The purpose of this document is to capture the core capabilities developed in ATD-2 Phase 2

    Root architecture of provenances, seedlings and cuttings of Melia volkensii: implications for crop yield in dryland agroforestry

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    Melia volkensii (Gürke) is being increasingly promoted as an on-farm tree in Kenya. Researchers’ and farmers’ views on its competitiveness with crops differ; research station studies have found it to be highly competitive whereas farmers do not consider it to be so. Because of difficulties in seed germination, it is probable that dissemination programmes will rely upon plants produced from root and stem cuttings, rather than on seedlings. This study evaluates differences in root system architecture of plants raised from seed (of four provenances), stem or root cuttings and the relationships between the competitivity index (CI) and crop yield. Cuttings were more shallowly rooting than seedlings, and had higher competitivity indices, and there was a negative relationship between CI and crop yield. No differences in root architecture between provenances were found. Therefore, to reduce tree-crop competition, the use of seedlings rather than cuttings should be recommended when promoting the use of this species on dryland farms. If cuttings are used to circumvent the problems of seed germination, alternative methods of controlling competition, such as root pruning, need to be considered

    Tree growth and management in Ugandan agroforestry systems: effects of root pruning on tree growth and crop yield

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    Tree root pruning is a potential tool for managing below-ground competition when trees and crops are grown together in agroforestry systems. This study investigates its effects on growth and root distribution of Alnus acuminata (HB & K), Casuarina equisetifolia (L), Grevillea robusta (A. Cunn. ex R. Br), Maesopsis eminii (Engl.), and Markhamia lutea (Benth.) K. Schum. and on yield of adjacent crops in sub-humid Uganda. The trees were 3 years old at the commencement of the study, and most species were competing strongly with crops. Tree roots were pruned 41 months after planting by cutting and back-filling a trench to a depth of 0.3 m, at a distance of 0.3 m from the trees, on one side of the tree row. The trench was re-opened and roots re-cut at 50 and 62 months after planting. Effects on tree growth and root distribution were assessed over a 3 year period, and crop yield after the third root pruning at 62 months is reported here. Overall, root pruning had only a slight effect on tree growth: height growth was unaffected and diameter growth was reduced by only 4 %. A substantial amount of root re-growth was observed by 11 months after pruning. Tree species varied in the number and distribution of their roots, and Casuarina and Markhamia had considerably more roots per unit of trunk volume than the other tree species, especially in the surface soil layers. Casuarina and Maesopsis were the most competitive tree species with crops and Grevillea and Markhamia the least. Crop yield data provides strong evidence of the redistribution of root activity following root pruning, so that competition increased on the unpruned side of tree rows. Thus, one-sided root pruning will only be of use to farmers in a few circumstances. Key words: Alnus acuminata, Casuarina equisetifolia, Grevillea robusta, Maesopsis eminii, Markhamia lutea, root distribution, root functio

    Optimization of Agrobacterium-Mediated Transformation Parameters for Melastomatacea Spp. Using Green Fluorescent Protein(GFP) as A Reporter

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    Agrobacterium-mediated transformation for both Melastoma malabathricum and Tibouchinu semidecanda were optimized using green fluorescent protein (GFP) as a reporter. The binary vector pCAMBIA1304 harboring the modified green fluorescent protein (mgfp) gene driven by the CuMV 35S promoter was used. Parameters optimized were bacterial strain, bacterial concentration, pre-culture period, co-cultivation period,immersion time, acetosyring concentration and wounding type. Results obtained obtained were based on the percentage of (GFP expression which was observed 3 days post-transformation. Agrobacterium tumefaciens starin LBA4404 and EHA105 at concentration 1 X 107 cfu ml -1 (OD 600mm 0.8) showed the highest virulence on M. malabathricum and T.semidecandra, respectively. Four days of pre-culture and 2 days of co-cultivation were optimum for M.malabathricum transformation, while 3 days of pre-culture and co-cultivation fot T, semidecandra, . result also showed that 60 min of immersion and addition of 200 p.M acetosyringone gave the highest percentage of positive transformants for both M. malabathricum and T.semidecandra. Mild wounding also significantly increased the efficiency 0f M.malabathricum transformation

    Agrobacterium-mediated transformation of melastoma malabathricum and tibouchina semidecandra with sense and antisense dihydroflavonol-4-reductase(DFR)genes.

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    Genetic engineering of a wide variety of plant species has led to the improvement of plant traits. In this study, the genetic transformation of two potentially important flowering ornamentals, Melastoma malabathricum and Tibouchina semidecandra, with sense and antisense dihydroflavonol-4-reductase (DFR) genes using the Agrobacterium mediated method was carried out. Plasmids pBETD10 and pBETD11, each harbouring the DFR gene at different orientations (sense and antisense) and selectable marker npt II for kanamycin resistance, were used to transform M. malabathricum and T. semidecandra under the optimized transformation protocol. Putative transformants were selected in the presence of kanamycin with their respective optimized concentration. The results indicated that approximately 4.0% of shoots and 6.7% of nodes for M. malabathricum regenerated after transforming with pBETD10, whereas only 3.7% (shoots) and 5.3%(nodes) regenerated with pBETD11 transformation. For the selection of T. semidecandra, 5.3% of shoots and 9.3% of nodes regenerated with pBETD10 transformation, while only 4.7% (shoots) and 8.3% (nodes) regenerated after being transformed with pBETD11. The presence and integration of the sense and antisense DFR genes into the genome of M. malabathricum and T. semidecandra were verified by polymerase chain reaction (PCR) and nucleotide sequence alignment and confirmed by southern analysis. The regenerated putative transformants were acclimatized to glasshouse conditions. Approximately 31.0% pBETD10-ransformed and 23.1% pBETD11-transformed M. malabathricum survived in the glasshouse, whereas 69.4% pBETD10-transformed and 57.4% pBETD11-transformed T. semidecandra survived. The colour changes caused by transformation were observed at the budding stage of putative T. semidecandra transformants where greenish buds were produced by both T. semidecandra harbouring the sense and antisense DFR transgenes. Besides that, the production of four-petal flowers also indicated another morphological difference of putative T. semidecandra transformants from the wild type plants which produce five-petal flowers
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