14,868 research outputs found

    Nematodes and Weeds Control Effects of Pueraria phaseoloides and Flemingia macrophylla Fallows on Establishment, Survival and Yield of Plantain

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    The yield of plantain (Musa spp., AAB Simmonds) declines sharply after 1–2 years of cropping in West and Central Africa, due mainly to weeds and nematodes. A trial was carried out from January 2002 to October 2005 under two land-use systems (LUS) comprising 4–5 year-old bush fallow, dominated by Chromolaena odorata (L.) R. M. King & H. Rob, and a 20 year-old secondary forest, in three villages in southern Cameroon, to assess the effectiveness of Pueraria phaseoloides and Flemingia macrophylla as planted fallows for weed suppression and reduction in nematode damage of the plantain root system, and determine the yield response of different plantain sucker types to the weed suppression and reduced nematode damage. In each LUS, the treatments were a factorial combination of three levels of fallow system and four levels of plantain sucker type arranged in a randomised complete block design. Total above-ground biomass production of P. phaseoloides was 7.45 Mg ha-1, 4.2 times higher than F. macrophylla (1.78 Mg ha-1; P Boiling water-treated “Essong” > Untreated “Essong”. P. phaseoloides produced significantly (P < 0.05) the highest plantain yield. There were no differences between the natural regrowth and F. macrophylla for all the plantain yield parameters. Sanitizing suckers (boiling and nursery-derived) increased actual yield and quantity of edible bunches by 35% and 26%, respectively, compared to the untreated. It was concluded that P. phaseoloides had the greatest positive effect on the growth and yield of plantain

    Measurements of elastohydrodynamic film thickness, wear and tempering behavior of high pressure oxygen turbopump bearings

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    The reusable design of the Space Shuttle requires a target life of 7.5 hours for the turbopumps of the Space Shuttle main engine (SSME). This large increase from the few hundred seconds required in single-use rockets has caused various problems with the bearings of the turbopumps. The berings of the high pressure oxygen turbopump (HPOTP) were of particular concern because of wear, spalling, and cage failures at service time well below the required 7.5 hours. Lubrication and wear data were developed for the bearings. Since the HPOTP bearings operate in liquid oxygen, conventional liquid lubricants cannot be applied. Therefore, solid lubricant coatings and lubricant transfer from the polytetrafluorethylene (FTFE) cage were the primary lubrication approaches for the bearings. Measurements were made using liquid nitrogen in a rolling disk machine to determine whether usable elastohydrodynamic films could be generated to assist in the bearing lubrication

    Superfluid density of superconductor-ferromagnet bilayers

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    We report the first measurements of the effective superfluid density n_S(T) \propto \lambda^{-2}(T) of Superconductor-Ferromagnet (SC/FM) bilayers, where \lambda is the effective magnetic field penetration depth. Thin Nb/Ni bilayers were sputtered in ultrahigh vacuum in quick succession onto oxidized Si substrates. Nb layers are 102 A thick for all samples, while Ni thicknesses vary from 0 to 100 A. T_C determined from \lambda^{-2}(T) decreases rapidly as Ni thickness d_Ni increases from zero to 15 A, then it has a shallow minimum at d_Ni \approx 25 A. \lambda^{-2}(0) behaves similarly, but has a minimum several times deeper. In fact, \lambda^{-2}(0) continues to increase with increasing Ni thickness long after T_C has stopped changing. We argue that this indicates a substantial superfluid density inside the ferromagnetic Ni films.Comment: 13 pages, 2 figures, MMM 2007 proceeding

    Broadband multi-wavelength campaign on PKS 2005-489

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    The spectral energy distribution (SED) of high-frequency peaked BL Lac objects (HBL) is characterized by two peaks: one in the UV-X-ray and one in the GeV-TeV regime. An interesting object for analyzing these broadband characteristics is PKS 2005-489, which in 2004 showed the softest TeV spectrum ever measured. In 2009, a multi-wavelength campaign has been conducted with, for the first time, simultaneous observations by H.E.S.S. (TeV), Fermi/LAT (GeV), RXTE (keV), Swift (keV, UV, optical) and ATOM (optical) to cover the two peaks of the SED. During this campaign PKS 2005-489 underwent a high state in all wavebands which gives the opportunity to study in detail the emission processes of a high state of this interesting HBL.Comment: 2009 Fermi Symposium; eConf Proceedings C09112

    Decomposition and nutrient release patterns of Pueraria phaseoloides, Flemingia macrophylla and Chromolaena odorata leaf residues in tropical land use systems

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    The study determined the decomposition and nutrient release patterns of Pueraria phaseoloides, Flemingia macrophylla and Chromolaena odorata leaf residues in young secondary forest and bush land use systems atMfou, southern Cameroon. Residue mass loss after incubating fresh leaves for 120 days was C. odorata > P. phaseoloides > F. macrophylla. Mean weekly loss rates were 4.5, 3.9 and 2.8 per cent for C. odorata, P.phaseoloides and F. macrophylla, respectively. Across residue types, leaf mass loss was greater in the young secondary forest than in the bush land use. Soil texture and soil chemical properties were not correlated to leafmass loss. Except for N, releases of P, K, Ca and Mg were of the order C. odorata Âł P. phaseoloides > F. macrophylla. Proportions of K released from the leaf residues were greater than those for the other nutrients.Half of the K was released within the first 7 weeks after incubation for C. odorata and P. phaseoloides. Among the land uses, release of K in the forest was 1.8 times faster than in the bush. The slowest releases, irrespective of type of leaf residue, were in Ca and Mg. The study concluded that among the planted fallows, Pueraria phaseoloides had the greatest rate of nutrient release. It could, therefore, ensure greater nutrient availability to associated crops. The leaves of C. odorata are rich in all nutrients; hence, short-season crops could benefit from this source of nutrients if the weed is well managed

    An important role for Myb-MuvB and its target gene KIF23 in a mouse model of lung adenocarcinoma

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    The conserved Myb-MuvB (MMB) multiprotein complex has an important role in transcriptional activation of mitotic genes. MMB target genes are overexpressed in several different cancer types and their elevated expression is associated with an advanced tumor state and a poor prognosis. This suggests that MMB could contribute to tumorigenesis by mediating overexpression of mitotic genes. However, although MMB has been extensively characterized biochemically, the requirement for MMB in tumorigenesis in vivo has not been investigated. Here we demonstrate that MMB is required for tumor formation in a mouse model of lung cancer driven by oncogenic K-RAS. We also identify a requirement for the mitotic kinesin KIF23, a key target gene of MMB, in tumorigenesis. RNA interference-mediated depletion of KIF23 inhibited lung tumor formation in vivo and induced apoptosis in lung cancer cell lines. Our results suggest that inhibition of KIF23 could be a strategy for treatment of lung cancer

    Composition of the Innermost Core Collapse Supernova Ejecta

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    With presently known input physics and computer simulations in 1D, a self-consistent treatment of core collapse supernovae does not yet lead to successful explosions, while 2D models show some promise. Thus, there are strong indications that the delayed neutrino mechanism works combined with a multi-D convection treatment for unstable layers. On the other hand there is a need to provide correct nucleosynthesis abundances for the progressing field of galactic evolution and observations of low metallicity stars. The innermost ejecta is directly affected by the explosion mechanism, i.e. most strongly the yields of Fe-group nuclei for which an induced piston or thermal bomb treatment will not provide the correct yields because the effect of neutrino interactions is not included. We apply parameterized variations to the neutrino scattering cross sections and alternatively, parameterized variations are applied to the neutrino absorption cross sections on nucleons in the ``gain region''. We find that both measures lead to similar results, causing explosions and a Ye>0.5 in the innermost ejected layers, due to the combined effect of a short weak interaction time scale and a negligible electron degeneracy, unveiling the proton-neutron mass difference. We include all weak interactions (electron and positron capture, beta-decay, neutrino and antineutrino capture on nuclei, and neutrino and antineutrino capture on nucleons) and present first nucleosynthesis results for these innermost ejected layers to discuss how they improve predictions for Fe-group nuclei. The proton-rich environment results in enhanced abundances of 45Sc, 49Ti, and 64Zn as requested by chemical evolution studies and observations of low metallicity stars as well as appreciable production of nuclei in the mass range up to A=80.Comment: 13 pages, 8 figures. Final versio

    Monodromy-data parameterization of spaces of local solutions of integrable reductions of Einstein's field equations

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    For the fields depending on two of the four space-time coordinates only, the spaces of local solutions of various integrable reductions of Einstein's field equations are shown to be the subspaces of the spaces of local solutions of the ``null-curvature'' equations constricted by a requirement of a universal (i.e. solution independent) structures of the canonical Jordan forms of the unknown matrix variables. These spaces of solutions of the ``null-curvature'' equations can be parametrized by a finite sets of free functional parameters -- arbitrary holomorphic (in some local domains) functions of the spectral parameter which can be interpreted as the monodromy data on the spectral plane of the fundamental solutions of associated linear systems. Direct and inverse problems of such mapping (``monodromy transform''), i.e. the problem of finding of the monodromy data for any local solution of the ``null-curvature'' equations with given canonical forms, as well as the existence and uniqueness of such solution for arbitrarily chosen monodromy data are shown to be solvable unambiguously. The linear singular integral equations solving the inverse problems and the explicit forms of the monodromy data corresponding to the spaces of solutions of the symmetry reduced Einstein's field equations are derived.Comment: LaTeX, 33 pages, 1 figure. Typos, language and reference correction

    Comparison of the COBE FIRAS and DIRBE Calibrations

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    We compare the independent FIRAS and DIRBE observations from the COBE in the wavelength range 100-300 microns. This cross calibration provides checks of both data sets. The results show that the data sets are consistent within the estimated gain and offset uncertainties of the two instruments. They show the possibility of improving the gain and offset determination of DIRBE at 140 and 240 microns.Comment: Accepted for publication in the Astrophysical Journal 11 pages, plus 3 figures in separate postscript files. Figure 3 has three part
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