14,868 research outputs found
Nematodes and Weeds Control Effects of Pueraria phaseoloides and Flemingia macrophylla Fallows on Establishment, Survival and Yield of Plantain
The yield of plantain (Musa spp., AAB Simmonds) declines sharply after 1â2 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 4â5 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 âEssongâ > Untreated âEssongâ. 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
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Rotational 3D Printing of Sensor Devices using Reactive Ink Chemistries
This paper charts progress in three key areas of a project supported by both UK
government and UK industry to manufacture novel sensor devices using rotary 3D printing
technology and innovative ink chemistries; (1) the development of an STL file slicing algorithm
that returns constant Z height 2D contour data at a resolution that matches the given print head
setup, allowing digital images to be generated of the correct size without the need for scaling;
(2) the development of image transformation algorithms which allow images to be printed at
higher resolutions using tilted print heads and; (3) the formulation of multi part reaction inks
which combine and react on the substrate to form solid material layers with a finite thickness. A
Direct Light Projection (DLP) technique demonstrated the robustness of the slice data by
constructing fine detailed three dimensional test pieces which were comparable to identical parts
built in an identical way from slice data obtained using commercial software. Material systems
currently under investigation include plaster, stiff polyamides and epoxy polymers and
conductive metallicâs. Early experimental results show conductivities of silver approaching
1.42x105 Siemens/m.Mechanical Engineerin
Measurements of elastohydrodynamic film thickness, wear and tempering behavior of high pressure oxygen turbopump bearings
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
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
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
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
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
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
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
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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