Applications of the Conceptual Density Functional Theory Indices to Organic Chemistry Reactivity

Indexación: Web of ScienceTheoretical reactivity indices based on the conceptual Density Functional Theory (DFT) have become a powerful tool for the semiquantitative study of organic reactivity. A large number of reactivity indices have been proposed in the literature. Herein, global quantities like the electronic chemical potential μ, the electrophilicity ω and the nucleophilicity N indices, and local condensed indices like the electrophilic and nucleophilic Parr functions, as the most relevant indices for the study of organic reactivity, are discussed.http://www.mdpi.com/1420-3049/21/6/74

HRTEM and Molecular Modeling of the MoS 2-Co9 S 8 Interface: Understanding the Promotion Effect in Bulk HDS Catalysts

As environmental regulations increase, more selective transition metal sulfide (TMS) catalytic materials for hydrotreating applications are needed. Highly active TMS catalysts become more and more desirable triggering new interest for unsupported Co-promoted MoS2-based systems that have high volumetric activity as reported here. Contrary to the common observation for alumina-supported MoS2-based catalysts, we found in our previous studies with dibenzothiophene (DBT) hydrodesulfurization (HDS) that the catalytic activity is directly proportional to the increase of surface area of the sulfide phases (Co9S8 and MoS2) present in Co-promoted MoS2 unsupported catalysts. This suggests that activity is directly connected with an increase of the contact surface area between the two sulfide phases. Understanding of the nature of the possible interaction between MoS2 and Co9S8 in unsupported catalytic systems is therefore critical in order to get a more generalized overview of the causes for synergy. This has been achieved herein through the detailed characterization by XRD, XPS, and HRTEM of the highly active Co9S8/MoS2 catalyst resulting in a proposed model for a Co9S8/MoS2 interface. This model was then subjected to a DFT analysis to determine a reasonable description of the surface contact region between the two bulk phases. Modelling of the interface shows the creation of open latent vacancy sites on Mo atoms interacting with Co and formation of direct Co-Mo bonds. Strong electron donation from Co to Mo also occurs through the intermediate sulfur atom bonded to both metals while an enhanced metallic character is also found. These changes in coordination and electronic properties are expected to favor a synergetic effect between Co and Mo at the proposed localized interface region between the two bulk MoS2 and Co9S8 phases.CONACYT, Mexico 207997MRTI of UTEP, Cotton Trust UTEPMicrolectronics Research Lab of UT-Austin and Departamento de Educacion y Cultura of Gobierno del Estado de ChihuahuaMicroelectronics Research Cente

WRITTEN RETELLING VS ORAL RETELLING: AN EVALUATION STRATEGY IN AN ESL CLASSROOM

Written and oral retellings of stories appear to have potential for skill development inside English as a Second Language (ESL) classroom. However, while they appear to have potential for skill development they have not been widely tested (Morrow, 1986), There are some evidences written and oral retellings as an instructional strategy enhance the development of various literacy skills (Golden 1984, and Whaley, 1981). Although there is support for the use of retellings as a strategy to enhance learner's literacy development, Morrow (1985) stated that the use of oral and written retellings was not widely practiced in schools since teachers viewed retellings as time consuming and difficult (Morrow, 1985).This mini research compares written and oral retellings and would like to prove that the skill of retelling aside from contributing to student’s skill development is an effective instrument in measuring comprehension, thus enhances both oral and written skills of students. This research illustrates though oral and written retellings are different, it also shows how similar they are.&nbsp