1,208 research outputs found
Estimation of Rice Yield Losses Due to the African Rice Gall Midge, \u3ci\u3eOrseolia oryzivora\u3c/i\u3e Harris and Gagne
The African rice gall midge, Orseolia oryzivora Harris and Gagne (Diptera: Cecidomyiidae), is an important pest of rice, Oryza sativa, in Burkina Faso as well as other countries in West and East Africa. In spite of its importance, little is known regarding the relationship between gall midge populations and grain yield losses. To determine yield losses, the gall midge was reared in cages, and adult midges were placed on caged plants of the rice variety ITA 123 at different population levels. The seven treatments consisted of different numbers of insects infested on the plants: 0 insect pairs (noninfested check), and 1, 5, 10, 15, 20, or 25 midge pairs/cage. The loss in yield in relation to the noninfested control was highly positively correlated (R2 = 0.81) with the percentage of gall midge damaged tillers. The infestation by the insect on the plants resulted in the compensatory production of tillers which developed in response to the gall midge damage, but the compensation was not sufficient to make up for the loss of yield due to the damaged tillers. Yield loss ranged from 0% in the control to 65.3% in the treatment with 25 pairs of adults. One percent of tillers damaged resulted in 2% grain yield loss
Rice Pests in the Ivory Coast, West Africa: Farmers’ Perceptions and Management Strategies
An understanding of farmers’ perceptions of pests and their existing pest control methods can make an important contribution to the development of effective integrated pest management strategies. While the relatively successful rice IPM technologies in Asia have been extensively documented in studies examining farmers’ pest perceptions and management practices, studies examining, specifically, perceptions and management practices of West African rice farmers are rare. This may reflect the more limited success to date in the implementation of rice IPM strategies in the region. This paper describes rice pests, pest perceptions, and management practices of smallholder rice farmers in the Ivory Coast. It was found that the major rice pests, as perceived by farmers, are weeds, vertebrates (birds and rodents), and insects. Farmers are generally unable to diagnose rice plant diseases and thus did not consider them as important production constraints. Implications are derived for an integrated pest management strategy that incorporates farmers’ perceptions and builds on their existing cultural control practices
Exact transmission moments in one-dimensional weak localization and single-parameter scaling
We obtain for the first time the expressions for the mean and the variance of
the transmission coefficient for an Anderson chain in the weak localization
regime, using exact expansions of the complex transmission- and reflection
coefficients to fourth order in the weakly disordered site energies. These
results confirm the validity of single-parameter scaling theory in a domain
where the higher transmission cumulants may be neglected. We compare our
results with earlier results for transmission cumulants in the weak
localization domain based on the phase randomization hypothesis
Satellite Sounder Data Assimilation for Improving Alaska Region Weather Forecast
Data assimilation has been demonstrated very useful in improving both global and regional numerical weather prediction. Alaska has very coarser surface observation sites. On the other hand, it gets much more satellite overpass than lower 48 states. How to utilize satellite data to improve numerical prediction is one of hot topics among weather forecast community in Alaska. The Geographic Information Network of Alaska (GINA) at University of Alaska is conducting study on satellite data assimilation for WRF model. AIRS/CRIS sounder profile data are used to assimilate the initial condition for the customized regional WRF model (GINA-WRF model). Normalized standard deviation, RMSE, and correlation statistic analysis methods are applied to analyze one case of 48 hours forecasts and one month of 24-hour forecasts in order to evaluate the improvement of regional numerical model from Data assimilation. The final goal of the research is to provide improved real-time short-time forecast for Alaska regions
Classical motion in force fields with short range correlations
We study the long time motion of fast particles moving through time-dependent
random force fields with correlations that decay rapidly in space, but not
necessarily in time. The time dependence of the averaged kinetic energy and
mean-squared displacement is shown to exhibit a large degree of universality;
it depends only on whether the force is, or is not, a gradient vector field.
When it is, p^{2}(t) ~ t^{2/5} independently of the details of the potential
and of the space dimension. Motion is then superballistic in one dimension,
with q^{2}(t) ~ t^{12/5}, and ballistic in higher dimensions, with q^{2}(t) ~
t^{2}. These predictions are supported by numerical results in one and two
dimensions. For force fields not obtained from a potential field, the power
laws are different: p^{2}(t) ~ t^{2/3} and q^{2}(t) ~ t^{8/3} in all dimensions
d\geq 1
Two-dimensional atom trapping in field-induced adiabatic potentials
We show how to create a novel two-dimensional trap for ultracold atoms from a conventional magnetic trap. We achieve this by utilizing rf-induced adiabatic potentials to enhance the trapping potential in one direction. We demonstrate the loading process and discuss the experimental conditions under which it might be possible to prepare a 2D Bose condensate. A scheme for the preparation of coherent matterwave bubbles is also discussed
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COG - Publicly Available Now to Criticality Safety Practitioners
COG is a modern, general-purpose, high fidelity, multi-particle transport code with a long history of use in criticality safety studies at the Lawrence Livermore National Laboratory. This code was released to the Radiation Safety Information Computational Center (RSICC) for distribution to the public for the first time in January 2006. This paper provides an overview of the code development history, a description of features and capabilities of interest to the criticality safety practitioner, and our plans in support of the next public RSICC release
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