Scattering properties of Venus' surface

Radar backscatter functions Sigma-(carat)(sub 0)(phi) for incidence angles between 0 less than or equal to phi less than or equal to 4-10 deg were derived from Magellan altimetry radar echoes. The procedure includes constrained solution of a system of simultaneous equations for which the echo-spectrum and echo time profile are inputs. A practical and workable set of constraints was applied; optimization and improved results are expected as the analysis matures. The scattering functions yield information on small-scale surface structures (tens of centimeters to tens of meters) but averaged over hundreds of sq km. RMS surface slopes derived from fits of analytic functions to the Sigma-(carat)(sub 0)(phi) results were converted to map form and show patterns similar to those reported using other techniques. While all three forms are found on Venus, fit residuals imply that an exponential scattering function matches data better than either the Hagfors or Gaussian form in most areas, although the Hagfors function may be a better descriptor at some sites. Limited study of image data indicates that average backscatter cross section, and possibly its slope, can be derived at oblique angles (17 deg less than or equal to phi less than or equal to 45 deg). Offsets of the echo peak in altimetry spectra are surprisingly common and are loosely correlated with Venus topography, but no cause for this phenomenon was identified

Adoption of \u3ci\u3eBrachiaria\u3c/i\u3e Grasses in Mexico and Central America: A Successful Story

In Latin America and the Caribbean (LAC) there has been a major effort to develop new pastures technologies, to increase livestock productivity for the extensive systems prevailing in the tropical lowlands. This multi-national and inter-institutional effort was initiated through the International Network for the Evaluation of Tropical Pastures (RIEPT, by its name in Spanish), which operated from 1976 to 1996 under CIAT leadership. This network became a platform for institutions to train technicians, share forage material from existing gene banks, study the behaviour of new germplasm under different environments, and established the exchange of scientific information to extrapolate research results (Toledo, 1982). Six hundred and forty five agronomists from 24 countries in LAC were trained by RIEPT, in subjects related to forage agronomy and pasture evaluation. Training was key for the success of RIEPT, because these professionals carried out evaluations of new and improved forages under contrasting ecosystems and provided feedback. In addition, during this period participating institutions in RIEPT released 11 selected grasses as commercial cultivars, most of them from the Brachiaria genus, as well as 16 forage legume cultivars (CIAT, 2003). In Central America and Mexico these cultivars were released between 1990 and 1996. Forage evaluation activities in this region continues at present through a joint research agenda between CIAT and ILRI, as well as between CIAT and the private seed sector. Of all pasture cultivars released; grasses from the Brachiaria genus currently dominate the market – accounting for approximately 84% of all grass seed sales in Mexico and Honduras, 90% in Nicaragua, 85% in Costa Rica, and 97% in Panama during the last 5 years (Holmann et al., 2004). The objective of this paper is to estimate the impact of the adoption of Brachiaria grasses released through RIEPT during the period 1990-2003 on milk and beef production and to describe how this was achieved

The beef chain in Costa Rica: Identifying critical issues for promoting its modernization, efficiency and competitiveness

The objectives of this study were to (1) describe the economic agents of the chain and their commercial and legal relationships; (2) identify the articulations between links, technological levels, indicators of efficiency, installed capacity (scale), and degrees of occupation; (3) characterize and estimate the costing and pricing structures, and the generation of value in different links of the chain; (4) identify those critical costs that can be modified through technological interventions, policy, or other activity; (5) determine the biological and economic risk factors throughout the chain; and (6) develop a methodology to identify and estimate the costs and benefits in each segment and evaluate the generation of value throughout the beef chain. Data at the farm level was obtained from a national livestock survey (CORFOGA 2005b), which provided data on production systems, inventories, productivity, culling, and labor. In addition, surveys were carried out in different segments: (1) auction houses, (2) slaughterhouses, (3) butcher shops, and (4) supermarkets. The aim of these surveys was to describe behavior, determine risks and costs, and identify problems. The weak dynamics of livestock production in Costa Rica are reflected in unsatisfactory productivity indicators. The annual gross income was estimated as US$44/ha for cow-calf operations,$126/ha for dual purpose (including income from milk sales), and $135/ha for fattening activities. Such income rates are considered extremely low, if one uses as reference the commercial value of land allocated to livestock production (ranging between$1000 and $2000/ha). The aforementioned biological inefficiencies, combined with high land costs, impede the recovery of opportunity costs for the capital invested in land, thus making beef production uncompetitive. The cow-calf operation, with its low productivity, remunerates family labor with wages below the legal minimum. On the assumption that the only cash cost is that of labor, cow-calf farms pay family workers at a wage that is equivalent to 60$32 and $66 per animal. If the estimated unit costs are compared with the rates charged per slaughtered animal (between$15 and $23), then we have to conclude that rural slaughterhouses work at a loss and that industrial slaughterhouses cover their operational costs with processing services and the very small profit margins from sales of byproducts. The best performance in terms of efficiency and profitability is found in the retail sector of butchers and supermarkets. The rate of profits, expressed as the fraction of the final price paid by the consumer that remains in the butcher’s hands as remuneration of his work, ranges widely between 3$0.28/animal per day for the breeder and $45.85/animal per day for the butcher. Thus, the highest proportion of the total added value concentrates on the final link of the chain. The butcher or supermarket obtains, on the basis of one animal in the same unit of time, 164 times more value that the breeder located in the first link of the chain. The latter has to confront biological and economic risks not covered by insurance policies, whereas retailers may mitigate risks through insurance policies for their raw materials, equipment, and infrastructure. The competitiveness of the beef chain is the aggregate of the efficiency and productivity of all the links that form it. In a situation where, in the final segment, the demand for beef is low and weakly dynamic, then economic signs of modernization and the technological change it promotes, are not being generated in other components of the chain, particularly in the first link of production. This, in turn, results in a vicious cycle, generating low productivity and lack of competitiveness. To promote technological change, efficiency, and competitiveness in the value chain for beef in Costa Rica, we propose the following six recommendations: 1. That successful experiences of other chains such as that of poultry be analyzed and learned from to identify strategies that would increase the efficiency of the beef chain as a whole. 2. That strategies for promoting the milk production of breeding cows be developed to increase family income, as remuneration of labor is currently below the minimum wage. This option would be viable only in localities where a milk market exists. That livestock producer funds [a livestock producer fund consists of granting livestock in company to produce meat, provided that the producer concerned has adequate pastures for this purpose on his farm] be created as mechanisms to develop social capital, reduce transaction costs, and help improve the chain’s productivity and profitability. These organizations would bring together the different classes of the chain and favor synergies in the interaction of public and private actors. 3. That incentives be created to promote the large-scale adoption of already available improved forage species, as most of the problem of low livestock productivity originates in poor and deficient feed. This strategy would emphasize feeding during dry seasons, thereby minimizing seasonal weight losses in the national herd and improving the profitability of farms. 4. That a carcass classification system be established, based on quality and price that would permit differentiating supplies for different segments of the market. 5. That consumer education be promoted on the health benefits of beef, forms of preparation, and differentiating between cuts, uses, and qualities of beef products