Two-to four-day-old seedlings of soybean cultivars with known levels of field tolerance to Phytophthora root rot were planted in slit Styrofoam cups filled with vermiculite. The cups were placed in plastic trays, 17 X 25 X 6 cm, containing 100 g of steamed greenhouse potting mix and 200-250 ml water. Inoculum usually consisted of 4,000 zoospores obtained by flooding lima bean agar cultures of Phytophthora megasperma var. sojae. Plants were grown 15-20 days in a growth chamber at 28 C and a 12-hr photoperiod (17,000 lux). Disease was assessed by measuring dry weights and overall lengths of individual plants. With race 3, lengths of the cultivars Hark, Williams, and Agripro 26 were 36%, 43%, and 55%, respectively, of the uninoculated control plants. Dry weight measurements gave similar results. Results were comparable with race 7 and with a natural soil infested with race 4. The results agree with relative field tolerances reported previously. The response of the field tolerant cultivar Agripro 26 was maintained against eight races of the pathogen. The cultivars Woodworth, Agripro 25, SRF 307 P, and Wayne, also known to have field tolerance, showed less reduction in growth than did varieties without field tolerance.
This paper aims to simulate portfolio decisions under uncertainty when the diffusion parameters of the risky asset and short rate paid for a bond are both modulated by a time-inhomogeneous Markov chain, with transition probabilities dependent on states, time, and asset prices. To do this, we first found closed-form solutions of the corresponding utility-maximization problem, which solves a rational consumer that makes portfolio and consumption decisions by using the corresponding infinitesimal generator associated with the Markov chain. Subsequently, as an illustration of the theoretical results obtained, several scenarios were simulated for the Mexican case. The expected economic policy was inferred from announced monetary policy decisions regarding the reference rate and possible changes in trend due to the lack of fiscal stimuli. Under this framework, states were defined from the current and expected economic policies, and transition probabilities were expressed in terms of the ratio between the prices of the risky asset and the bond. It should be noted, as far as the authors know, that no analytical solutions are known in the literature for the case of Markov-modulated time-inhomogeneous chains with transition probabilities that, themselves, are stochastic processes.
Our research unveils how China’s food-related imports from 1992 to 2020 changed in composition by decreasing the imports of some commodities in favor of others. Their origins suggest that some countries are being substituted as commercial partners for specific commodities. We empirically identified outliers by setting interquartile limits at the commodity level and by origin. Unit-root and normality tests were applied. Finally, Spearman or Pearson correlation coefficients were computed where appropriate. Results indicate that imports are stabilizing during the studied period. China increased its imports of Sugar and cereals to the detriment of edible preparations, live animals, trees, and oilseeds. Some Asian countries are capturing part of the market once dominated by North America or Europe. Finally, lower dependence on partners was found for meat, gums, cocoa, and edible preparations. This methodology might help those analyzing the effects of trade agreements, country specialization, and strategic decisions.
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