1,721,217 research outputs found
A SHARP model of bid–ask spread forecasts
No full textThis paper proposes an accurate, parsimonious and fast-to-estimate forecasting model for integer-valued time series with long memory and seasonality. The modelling is achieved through an autoregressive Poisson process with a predictable stochastic intensity that is determined by two factors: a seasonal intraday pattern and a heterogeneous autoregressive component. We call the model SHARP, which is an acronym for seasonal heterogeneous autoregressive Poisson. We also present a mixed-data sampling extension of the model, which adopts the historical information flow more efficiently and provides the best (among all the models considered) forecasting performances, empirically, for the bid-ask spreads of NYSE equity stocks. We conclude by showing how bid-ask spread forecasts based on the SHARP model can be exploited in order to reduce the total cost incurred by a trader who is willing to buy or sell a given amount of an equity stock. (C) 2019 International Institute of Forecasters. Published by Elsevier B.V. All rights reserved
Genetic variability in yellow pigment components in cultivated and wild tetraploid wheats
No full textMetabolism of {gamma}-aminobutyric acid during cold acclimation and freezing and its relationship to frost tolerance in barley and wheat.
No full textAmino acid homeostasis was investigated in frost-resistant barley seedlings under either cold- or freezing-stress conditions. Total free amino acid content varied only slightly, but a substantial conversion of glutamate to gamma-aminobutyric acid (GABA) was found that was proportional to the severity of the stress. Cold acclimation caused a significant increase in amino acid pools, and induced the expression of the GABA-shunt genes. As a consequence, GABA accumulated to a higher extent during the subsequent exposure to lower temperature. A different picture was obtained with a frost-sensitive genotype, in which glutamate decarboxylation occurred during the stress as well, but the activation of the GABA shunt seemed not to take place, and free glutamate was almost depleted. Analogous results were found in frost-resistant and frost-sensitive wheat cultivars. Feeding non-hardened plants with exogenous glutamate resulted in increased GABA accumulation under low temperature. The possibility that glutamate decarboxylation and GABA metabolism would play a role in frost tolerance is discussed
Acclimatamento e resistenza al freddo nei cereali
No full textIl lavoro descrive in termini tecnici il fenomeno dell'accllimatamento nei cereali autunno-vernini e di come questo influenzi le rese di granella. Conclude poi descrivendo i nuovi approcci e le nuove ricerche che possono definire quali siano i motivi biologici del fenomeno, e che quindi possano aiutare a migliorare i risultati produttivi
Le performance varietali in un anno non semplice.
No full textAnche su supplemento web Agricoltura24.co
Molecular advances in rootstock-scion interaction in grapevine
No full textIn grapevine, grafting is a worldwide used technique employed to confer resistance to pests and diseases, to improve abiotic stress tolerance and to control plant vigour and some qualitative traits. Despite the relevance of rootstock, knowledge of the molecular mechanisms implicated in the rootstock-scion interaction still has many gaps. Only, recently, some experiments have been performed to investigate the effects of grafting technique, different soils and rootstocks on scion at transcriptomic level. This work reviews the most relevant findings in this field. These recent advances open a new perspective for a molecular interpretation about the interaction between scion and rootstock as well soil substrates
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