Disorder effect on intersubband optical absorption ofn-typeδ-doped quantum well in GaAs.

The inevitable structural disorder associated with the fluctuation of the applied external electric field, laser intensity, and bidimensional density in the low dimensional quantum system can affect noticeably optical absorption properties and the related phenomena. In this work, we study the effect of structural disorder on the optical absorption properties in delta-doped quantum wells (DDQWs). Starting from effective mass approximation and the Thomas-Fermi approach as well as using the matrix density, the electronic structure and the optical absorption coefficients of DDQWs are determined. It is found that the optical absorption properties depend on the strength and the type of structural disorder. Particularly, the bidimensional density disorder suppresses strongly the optical properties. Whilst, the disordered external applied electric field fluctuates moderately in the properties. In contrast, the disordered laser holds absorption properties unalterable. So, our results specify that to have and preserve good optical absorption properties in DDQWs, requires precise control of the bidimensional. Besides, the finding may improve the understanding of the impact of the disorder on the optoelectronic properties based on DDQWs.

Hybrid reduced graph for SAR studies.

The purpose of this work is the definition and evaluation of both atomic and local new hybrid indices. Inspired by the Refractotopological State Index for Atoms, the new atomic indices are theoretically supported by graph theory principles. The local indices, named Descriptor Centres (DCs), are obtained from the sum of the atomic values of the atoms in the selected group. Different classifiers were used for structure-activity relationship (SAR) studies, including multilayer perceptron (MLP), support vector machines (SVM) and meta-classifiers. Prediction with SVM and MLP was around 60%, but the best result was obtained with the meta-classifiers, bagging, decorate and others, with more than 92% accurate prediction. These new hybrid descriptors derived from the Refractotopological State Index for Atoms show a low mutual correlation coefficient. The same behaviour is found in the analogously defined Descriptors Centres. The best results are obtained with the inclusion of the distance between DCs with the use of meta-classifiers.

[Assessment of the impact of the biological rodenticide Biorat in populations of rodents settled in several crops of the Republic of Costa Rica]. / Evaluación del impacto del biorrodenticida Biorat en poblaciones de roedores establecidos en varios cultivos en la República de Costa Rica.

The impact of biological rodenticide Biorat on populations of rodents settled in some crops was determined; these crops are highly infested with Sigmodon hispidus, a very common vector in various Central American countries. The trapping technique and the appraisal of damages allowed to calculate the index of infestation which ranged from 75 to 90 percent in three crops. Twenty for to 36 kg of BIORAT were applied to 6 ha planted with Cucumis sativus (cucumber), Ipomoea batata (sweet potato) and Ananas comusus (pineapple). This action brought about that the rodent population in such crops reduced the potential damage and consequently, index of infestation was reduced by 94.6 to 98%; therefore, the residual population left amounted from 2 to 3.5%, meaning that damages were under the economic threshold. Generally speaking, the results were similar to those of other countries.