Further Tests on the Ice Nucleation Potential of Meteoritic Material
SCHAEFER1 was unable to detect any trace of ice-crystal formation when he vaporized a sample of iron–nickel meteorite by electric spark in a supercooled cloud—even in clouds as cold as −25° C. Mason and Maybank2, who ground up and vaporized three samples of stony meteorites, and Mason3 with three further samples also reported that they were unable to detect any production of ice-crystals at temperatures above −17° C This communication records the results of tests on the nucleating properties of a further thirteen samples of meteoritic materials. These comprised iron–nickel types (siderites), stony type (aerolites), plus two samples of the intermediate (siderolite) variety (all obtained from the American Meteorite Laboratory, Denver).
Ice‐nucleating properties of dust collected above 80 kilometers
A specially constructed apparatus was used to compare the ice-nucleating properties of dust particles collected above 80 km with those of soil and Agi particles. The dust particles were found to be relatively inactive in ice nucleation when compared with Agi and soil particles of terrestrial origin.
Drivers of Live Cattle Price in the Livestock Trading System of Central Cameroon
Livestock production and trade are critical for the food security and welfare of rural households in sub-Saharan Africa. In Cameroon, animal trade consists mainly of live cattle commercialized through livestock markets. Identifying the factors contributing to cattle price formation is critical for designing effective policies for sustainable production and for increasing food availability. In this study, we evaluated the influence of a range of individual- and market-level factors on the price of cattle that were sold in all transactions (n = 118,017) recorded over a 12-month period from 31 livestock markets in the main cattle production area of the country. An information-theoretic approach using a generalized additive mixed-effect model was implemented to select the best explanatory model as well as evaluate the robustness of the identified drivers and the predictive ability of the model. The age and gender of the cattle traded were consistently found to be important drivers of the price (p < 0.01). Also, strong, but complex, relationships were found between cattle prices and both local human and bovine population densities. Finally, the model highlighted a positive association between the number of incoming trading connections of a livestock market and the price of the traded live cattle (p < 0.01). Although our analysis did not account for factors informing on specific phenotypic traits nor breed characteristics of cattle traded, nearly 50% of the observed variation in live cattle prices was explained by the final model. Ultimately, our model gives a large scale overview of drivers of cattle price formation in Cameroon and to our knowledge is the first study of this scale in Central Africa. Our findings represent an important milestone in designing efficient and sustainable animal health management programme in Cameroon and ensure livelihood sustainability for rural households.