Repelência de uvas tratadas com extrato oleoso de nim à oviposição de Ceratitis capitata (Diptera: Tephritidae).

As moscas-das-frutas são pragas de grande importância na fruticultura mundial em função do potencial de danos e de barreiras fitossanitárias à exportação. No caso da região do Submédio do Vale do São Francisco, a principal espécie é Ceratitis capitata, que deve ser constantemente monitorada e mantida com o MAD (mosca/armadilha.dia-1) abaixo de 1

Plastic mulch and nitrogen fertigation in growing vegetables modify soil temperature, water and nitrate dynamics: experimental results and a modeling study

Plastic mulch in combination with drip irrigation present a common agricultural management technique practiced in commercial vegetable production. This management can result in various impacts on water and nutrient distribution and consequently affect nutrient dynamics in underlying soil. The aim of this work was to: (i) compare the effects of different mulching types (color) on soil temperature and (ii) crop growth; (iii) estimate the effect of plastic mulch cover (MULCH) on water and (iv) nitrate dynamics using HYDRUS-2D. The field experiment was designed in the Croatian coastal karst area on main plots with three levels of nitrogen fertilizer: 70, 140, and 210 kg ha−1, which were all divided in five subplots considering mulch covering with different colors types (black, brown, silver, and white) and no covering (control). Monitoring of water and nitrate dynamics was performed through lysimeters which ensured input data for HYDRUS-2D model. The experimental results showed that plastic mulch had a significant effect on soil temperature regime and crop yield. The dark color mulch (black, brown) caused higher soil temperature, which consequently enabled earlier plant development and higher yields. HYDRUS-2D simulated results showed good fitting to the field data in cumulative water and also nitrate outflow. Water flow simulations produced model efficiency of 0.84 for control (CONT) and 0.56 for MULCH systems, while nitrate simulations showed model efficiency ranging from 0.67 to 0.83 and from 0.70 to 0.93, respectively. Additional simulations exposed faster transport of nitrates below drip line in the CONT system, mostly because of the increased surface area subjected to precipitation/irrigation due to the absence of soil cover. Numerical modeling revealed large influence of plastic mulch cover on water and nutrient distribution in soil. The study suggests that under this management practice the nitrogen amounts applied via fertigation can be lowered and optimized to reduce possible negative influence on environment

Structural basis of cooperative DNA recognition by the plasmid conjugation factor, TraM

The conjugative transfer of F-like plasmids such as F, R1, R100 and pED208, between bacterial cells requires TraM, a plasmid-encoded DNA-binding protein. TraM tetramers bridge the origin of transfer (oriT) to a key component of the conjugative pore, the coupling protein TraD. Here we show that TraM recognizes a high-affinity DNA-binding site, sbmA, as a cooperative dimer of tetramers. The crystal structure of the TraM–sbmA complex from the plasmid pED208 shows that binding cooperativity is mediated by DNA kinking and unwinding, without any direct contact between tetramers. Sequence-specific DNA recognition is carried out by TraM’s N-terminal ribbon–helix–helix (RHH) domains, which bind DNA in a staggered arrangement. We demonstrate that both DNA-binding specificity, as well as selective interactions between TraM and the C-terminal tail of its cognate TraD mediate conjugation specificity within the F-like family of plasmids. The ability of TraM to cooperatively bind DNA without interaction between tetramers leaves the C-terminal TraM tetramerization domains free to make multiple interactions with TraD, driving recruitment of the plasmid to the conjugative pore

Spectroscopic and Quantum Chemical Study of the Ni(P^Ph₂N^{C6H4CH2P(O)(OEt)₂}₂)₂ Electrocatalyst for Hydrogen Production with Emphasis on the Ni^I Oxidation State

The bis(diphosphine)nickel catalyst first investigated by DuBois and co-workers [DuBois, M. R.; DuBois, D. L. Chem. Soc. Rev. 2009, 38, 62] is arguably one of the most promising molecular catalysts for hydrogen production. It features a low overpotential and, in its most recent variation, a high turnover number of 105 s–1 [Helm, M. L.; Stewart, M. P.; Bullock, R. M.; DuBois, M. R.; DuBois, D. L. Science 2011, 333, 863]. The complex features two reversible one-electron reductions. It is believed that all accessible oxidation states (2+, 1+, 0) of nickel are involved in the proposed catalytic cycle. In this article we focus on the paramagnetic NiI state, for which few experimental studies have been performed. By a combination of modern EPR and quantum chemical methods, it is established that the stable NiI species does not feature a hydride ligand. Furthermore, hydrogen evolution already starts upon addition of acid to the NiI state even without the presence of additional reducing equivalents. The implications for the catalytic cycle are discussed