Soil organic matter (SOM) refers to all carbon-containing organic matter in soil and is one of the most important indicators of soil fertility. The hyperspectral inversion analysis of SOM traditionally relies on laboratory chemical testing methods, which have the disadvantages of being inefficient and time-consuming. In this study, 69 soil samples were collected from the Honghu farmland area and a mining area in northwest China. After pretreatment, 10 spectral indicators were obtained. Ridge regression, kernel ridge regression, Bayesian ridge regression, and AdaBoost algorithms were then used to construct the SOM hyperspectral inversion model based on the characteristic bands, and the accuracy of the models was compared. The results showed that the AdaBoost algorithm based on a grid search had the best accuracy in the different regions. For the mining area in northwest China, R p 2 = 0.91, R M S E p = 0.22, and M A E p = 0.2. For the Honghu farmland area, R p 2 = 0.86, R M S E p = 0.72, and M A E p = 0.56. The detection of SOM content using hyperspectral technology has the characteristics of a high detection precision and high speed, which will be of great significance for the rapid development of precision agriculture.
1 The effects of the fil-selective partial agonist xamoterol and the full agonist isoprenaline on rat cardiac ,B-adrenoceptors were compared in functional studies of heart rate response in vivo and in vitro. In addition, the ability of both agents to cause receptor down-regulation in the rat heart following chronic (6 days) subcutaneous infusions was assessed by radioligand binding with ['251]-pindolol. 2 In the functional studies, xamoterol produced a maximal effect equivalent to approximately 65% of that of isoprenaline and was overall less potent than the full agonist. 3 Compared to saline control, the density of,-adrenoceptors was reduced approximately 39% in ventricular membranes prepared from animals after 6 days of isoprenaline infusion but was unaffected by xamoterol. The relative proportions of the fi-adrenoceptor subtypes were unchanged by either active treatment.4 Plasma xamoterol level at the end of the infusion period was equivalent to that associated with maximum tachycardia in vivo and to the concentration producing maximal stimulation of the rat isolated atrium in vitro. Thus suggesting 100% ,B-adrenoceptor occupancy during the period of xamoterol infusion. 5 These results indicate that in this animal model xamoterol does not induce cardiac f-adrenoceptor down-regulation during chronic treatment, with doses that produce a maximal functional response both in vitro and in vivo.
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