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In this work, we have determined the χ(1), χ(2), and χ(3) NLO properties of NH2substituted aromatic polyenynes in ortho, meta, and para positions. It is worth noting that Mednis-Genkin’s approximation takes into account the intraband contribution with a derivate of the dipole valence-conduction band moment transition, unlike, for example, Ward’s summation-over-sates (SOS) methodology, which considers the difference of these states. Indeed, we have selected these polymers because of the high asymmetry in their molecular wavefunction. In this way, the calculated χ(3) values of the para-NH2 substituted aromatic polyenyne with a higher degree of polymerization are near 1 X 10−7 esu. For its part, the ortho polymer has higher values, of the order of 1 X 10−6 esu, due to its high transition dipole moment. We have also found that the energy band distribution in the para position of these polymers produces van Hove points, which have a negligible proportion of the NLO properties, compared with singularity regions 1 and 2, which have a contribution of 100 %. These regions are due to the wavefunction coefficients’ first and second-order derivatives. Besides, without considering border effects nor correlation effects, and only the variation of excitation energy, we have calculated that the quaternary monomeric oligomers of these polymers have almost similar values of χ(2) and χ(3). Then, it implies building a methodology to synthesize the polymers to avoid canceling the NLO-χ(2) and -χ(3) values.

Land use changes generate a mosaic of forest patches with different ages of abandonment (i.e. succession) intermingled with other land uses. Mapping the successional age of vegetation is crucial to understand carbon accumulation patterns and the recovery of vegetation structure, diversity, and composition of forests over time. The overall objective of this research was to produce maps portraying secondary vegetation age classes and to assess how successional age classes can be related to vegetation structure, diversity and composition in two types of tropical dry forests (TDF) in the Yucatan Peninsula. We used a two-stage image classification process. First, SPOT-5 imagery were segmented and then classified using a Random Forests method. Second, the classified images were post-processed to rectify any classification errors. Additionally, we evaluated the association between the different forest age classes and vegetation structure, species richness and composition using a separate Random Forests classification of field plot data. Post-processing improved the accuracy of the Random Forests classifications by 14.19% and 16.28% for the tropical semi-deciduous and semi-evergreen forests, to attain final accuracy values of 91% and 88.37%, respectively. Vegetation structure, richness and composition were all strongly associated with successional age, accounting for 77.7% and 84.7% of the total variation among forest age classes for the tropical semi-deciduous and semi-evergreen forests respectively. Therefore, the forest age maps obtained can be related to attributes of vegetation structure, diversity and composition that are useful for biodiversity conservation, forest management and climate change mitigation.