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Three novel TADF (thermally activated delayed fluorescence) emitters based on the well-studied Qx-Ph-DMAC fluorophore are designed and synthesized. The photophysical properties of these materials are studied from a theoretical and experimental point of view, demonstrating the cumulative effects of multiple small modifications that combine to afford significantly improved TADF performance. First, an extra phenyl ring is added to the acceptor part of Qx-Ph-DMAC to increase the conjugation length, resulting in BQx-Ph-DMAC, which acts as an intermediate molecular structure. Next, an electron-deficient coumarin unit is incorporated to fortify the electron accepting ability, affording ChromPy-Ph-DMAC with red-shifted emission. Finally, the conjugated system is further enlarged by 'locking' the molecular structure, generating DBChromQx-DMAC with further red-shifted emission. The addition of the coumarin unit significantly impacts the charge-transfer excited state energy levels with little effect on the locally excited states, resulting in a decrease of the singlet–triplet energy gap. As a result, the two coumarin-based emitters show considerably improved TADF performance in 1 w/w% zeonex films when compared to the initial Qx-Ph-DMAC structure. 'Locking' the molecular structure further lowers the singlet–triplet energy gap, resulting in more efficient reverse intersystem crossing and increasing the contribution of TADF to the total emission. [ABSTRACT FROM AUTHOR]

The edaphological evaluation and soil classification of experimental areas sites are important instruments for the correct interpretation of agronomical results and decisionmaking about targeting and ex-ante evaluation of agricultural technology transfer. The objective of this article is to present the results of the edaphological evaluation soil, analysis and classification of three sites located in the altiplano central of Mexico. We wanted to determine the limiting factors for agricultural production before recommending conservation practices, as developed by INIFAP in collaboration with CIMMYT. The soils were classified both under the FAO classification system and USDA Soil Taxonomy in Santa Lucía as a cumulic Phaeozem, or a Cumulic Haplustoll, in El Horno as a mollic Fluvisol or Mollic Ustifluvents and a haplic Fluvisol or Typic Ustifluvents, and in Calpulapan, a petroduric Phaeozem, or Entic Duristoll. The limiting factors for crop production are mainly related to moisture availability, varying structure and texture along the profile, low organic matter content and risk of erosion. Taking into account these limiting factors further development, extension and implementation of conservation agriculture practices is highly recommended.

In collaboration with farmers, rice varieties were evaluated under small-scale irrigation in two villages of south east Tanzania for two consecutive cropping seasons (1999/2000 –2000/2001). The objectives were to give farmers access to new improved rice varieties; to identify the selection criteria farmers consider important in irrigated rice production; and to come to grips with their arguments. Farmers were provided with eleven improved varieties, which they compared with their own ones. Farmers' preferred varieties with short to medium maturity period, which produce many tillers and mature uniformly; and with long translucent aromatic grains for their own use and marketing. This study identified qualitative and quantitative evaluation criteria which farmers are using for selecting rice varieties. The implication for further research on rice in south east Tanzania is that the breeding programme should incorporate these attributes to address farmers' preferences, rather than to go for absolute maximum yield levels.