1,327 research outputs found
Constraints and Opportunities for Development of Grasslands in Urban Areas of the Niayes Zone in Senegal
A survey was carried out in urban areas of the Niayes zone in Senegal to explore grasslands development in agropastoral systems around towns. Rapid rural appraisal and farms multiple visits were done to describe the forage cropping system, identify constraints and opportunities of developing grasslands in urban areas. In Niayes urban areas, forage production system is being developed based on the cropping of several grass and tree species. Only a minority of farmers is involved in that activity. Level of grass production is rather low. Weak development of grasslands is observed. Main reasons are: farmer poor willingness to crop for livestock feeding, lack of water and production factors including seeds and fertiliser, land tenure system and lack of integration between livestock and horticulture, security and economical environment. There are opportunities that need to be developed for improvement of grassland production in the Niayes as water reserves could tolerate more forage cropping. Research and development programs should focus on programs that could generate recommendations on grasslands development in association with horticulture witch is a major activity in Niayes areas
Scanning electron microscopy of Conidia of Trichoderma Stromaticum, a biocontrol agent of witches broom disease of cocoa.
Estudos morfolĂłgicos de conĂdios de Trichoderma harzianun, um agente de biocontrole da vassoura-de-bruxa do cacaueiro, foram feitos sob microscopia eletrĂ´nica de varredura com emissĂŁo de campo. CaracterĂsticas da superfĂcie de conĂdios do fungo mostraram ser rugosas quando observadas em alta maginificação; fato esse impossĂvel de ser visualizado por microscopia Ăłtica. TambĂ©m foram observados, com freqĂĽĂŞncia, massas de conĂdios completamente envolvidos por material mucilaginoso e detalhes de cĂ©lulas ramificadas dicotomicamente que formam as pĂşstulas
Effect of arbuscular mycorrhizal fungal inoculation on growth, and nutrient uptake of the two grass species, Leptochloa fusca (L.) Stapf and Sporobolus robustus Kunth, under greenhouse conditions
The aim of our work was to assess the effect of inoculation with three arbuscular mycorrhizal fungi (AMF) (Rhizoglomus aggregatum (N.C. Schenck and G.S. Sm.) Sieverd., G.A. Silva and Oeh., Funneliformis mosseae (T.H. Nicolson and Gerd.) C. Walker and A. Schüssler. and Rhizoglomus intraradices (N.C. Schenck and G.S. Sm.) Sieverd., G.A. Silva and Oehl.), and a mixed inoculum of these AMF on root colonization, biomass production, mycorrhizal dependency (MD) and shoot mineral contents of two salt tolerant grasses Leptochloa fusca L. Stapf and Sporobolus robusts Kunth. After four months of growth in a sterilized soil and greenhouse conditions, grasses inoculated with AMF showed significantly higher total biomass production than non-inoculated seedlings. MD and shoot mineral contents (especially P) varied with AMF host plants. Maximum values of MD (13%) were observed in L. fusca and S. robustus seedlings when inoculated with R. intraradices and F. mosseae, respectively. Only P contents were higher in the S. robustus/mixed-AMF combinations than the other treatments. These results demonstrate the potential benefits in our experimental conditions of AM inoculation for improving growth and P acquisition particularly in the L. fusca/ F. mosseae and S. robustus/mixed-AMF combinations.Key words: Grass species, symbiosis, mycorrhizal dependency, mineral nutrition
Toward Equations of Galactic Structure
We find that all classes of galaxies, ranging from disks to spheroids and
from dwarf spheroidals to brightest cluster galaxies, lie on a two dimensional
surface within the space defined by the logarithms of the half-light radius,
r_e, mean surface brightness within r_e, I_e, and internal velocity, V^2 =
(1/2)v_c^2 + sigma^2, where v_c is the rotational velocity and sigma is the
velocity dispersion. If these quantities are expressed in terms of kpc,
L_solar/pc^2, and km/s, then log r_e - log V^2 + log I_e + log Upsilon_e + 0.8
= 0, where we provide a fitting function for Upsilon_e, the mass-to-light ratio
within r_e in units of M_solar/L_solar, that depends only on V and I_e. The
scatter about this surface for our heterogeneous sample of 1925 galaxies is
small (< 0.1 dex) and could be as low as ~ 0.05 dex, or 10%. This small scatter
has three possible implications for how gross galactic structure is affected by
internal factors, such as stellar orbital structure, and by external factors,
such as environment. These factors either 1) play no role beyond generating
some of the observed scatter, 2) move galaxies along the surface, or 3) balance
each other to maintain this surface as the locus of galactic structure
equilibria. We cast the behavior of Upsilon_e in terms of the fraction of
baryons converted to stars, eta, and the concentration of those stars within
the dark matter halo, xi = R_{200}/r_e. We derive eta = 1.9 x 10^{-5} (L/L^*)
Upsilon_* V^{-3} and xi = 1.4 V/r_e. Finally, we present and discuss the
distributions of eta and xi for the full range of galaxies. For systems with
internal velocities comparable to that of the Milky Way (149 < V < 163 km/s),
eta = 0.14 +- 0.05, and xi is, on average, ~ 5 times greater for spheroids than
for disks. (Abridged)Comment: submitted to Ap
Airborne Particles in Museums
Presents one in a series of research activities aimed at a better understanding of the origin and fate of air pollution within the built environment
Feed the Future Mali Livestock Technology Scaling Program (FtF-MLTSP) - Participatory assessment of animal health service delivery systems in Mali: Constraints and opportunities
United States Agency for International Developmen
Oscillations in the expression of a self-repressed gene induced by a slow transcriptional dynamics
We revisit the dynamics of a gene repressed by its own protein in the case
where the transcription rate does not adapt instantaneously to protein
concentration but is a dynamical variable. We derive analytical criteria for
the appearance of sustained oscillations and find that they require degradation
mechanisms much less nonlinear than for infinitely fast regulation.
Deterministic predictions are also compared with stochastic simulations of this
minimal genetic oscillator
Expected Number and Flux Distribution of Gamma-Ray-Burst Afterglows with High Redshifts
If Gamma-Ray-Bursts (GRBs) occur at high redshifts, then their bright
afterglow emission can be used to probe the ionization and metal enrichment
histories of the intervening intergalactic medium during the epoch of
reionization. In contrast to other sources, such as galaxies or quasars, which
fade rapidly with increasing redshift, the observed infrared flux from a GRB
afterglow at a fixed observed age is only a weak function of its redshift. This
results from a combination of the spectral slope of GRB afterglows and the
time-stretching of their evolution in the observer's frame. Assuming that the
GRB rate is proportional to the star formation rate and that the characteristic
energy output of GRBs is ~10^{52} ergs, we predict that there are always ~15
GRBs from redshifts z>5 across the sky which are brighter than ~100 nJy at an
observed wavelength of ~2 \mu m. The infrared spectrum of these sources could
be taken with the future Next Generation Space Telescope, as a follow-up on
their early X-ray localization with the Swift satellite.Comment: 29 pages, 14 figures; submitted to Ap
Oscillations in the expression of a self-repressed gene induced by a slow transcriptional dynamics
We revisit the dynamics of a gene repressed by its own protein in the case
where the transcription rate does not adapt instantaneously to protein
concentration but is a dynamical variable. We derive analytical criteria for
the appearance of sustained oscillations and find that they require degradation
mechanisms much less nonlinear than for infinitely fast regulation.
Deterministic predictions are also compared with stochastic simulations of this
minimal genetic oscillator
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