Limitation of nitrogen source facilitated the production of nonmeiotic recombinants in Aspergillus nidulans.

Aspergillus nidulans is a fungal model organism extensively used in genetic approaches. It may reproduce sexually and asexually, with a well-defined parasexual cycle. The current paper demonstrates that the limitation of nitrogen source facilitates the production of A. nidulans's nonmeiotic recombinants directly from heterokaryons, without the recovery of the diploid phase. Heterokaryons formed between master strains were inoculated in sodium nitrate-low (basal medium [BM]) and sodium nitrate-rich media (minimal medium [MM]). All mitotic segregants produced by the heterokaryons were tested for their mitotic stability in the presence of benomyl, the haploidizing agent. Only mitotically stable haploid segregants were selected for subsequent analysis. Phenotypic analyses of such haploids favored the characterization of nonmeiotic recombinants. As the number of such recombinants was higher in BM than in MM, nitrogen limitation may have facilitated the isolation of nonmeiotic recombinants from heterokaryons by stimulating nuclear fusion still inside the heterokaryotic mycelium as a survival strategy.

Sensors Using the Molecular Dynamics of Explosives in Carbon Nanotubes Under External Uniform Electric Fields.

Possessing a simulated sensor device to identify explosives is of extreme interest to the area of public security to fight against terrorism. In light of this, a carbon armchair nanotube was modeled under the action of an external, longitudinal and uniform electric field at an initial temperature of 1 mK simulation, causing the explosive molecules under analysis to rotate through the carbon nanotube, due to an evanescent effect generated from the action of an electric current and magnetic field induced in this system, and thus behaving as a selective temperature sensor and spinning radius for the molecules. For this, molecular dynamics was used to study the physicochemical properties of the molecules' interactions with a carbon nanotube. The following physical properties, as well as the kinetic, potential, and total energy were calculated for the 2,4,6-trinitrotoluene (TNT), triacetone triperoxide (TATP), hexogen (RDX), hexamethylene triperoxide diamine (HMTD), octogen (HMX) and pentaerythritol tetranitrate (PETN) explosives: thermodynamic conditions such as temperature; entropy variation; and distance between the molecules' center of mass from an armchair type carbon nanotube.

Capability of Paraguaçu estuary (Todos os Santos Bay, Brazil) to form oil-SPM aggregates (OSA) and their ecotoxicological effects on pelagic and benthic organisms.

For experiments concerning the formation of oil-suspended particulate matter (SPM) aggregates (OSA), oil and sediment samples were collected from Campos Basin and six stations of Paraguaçu estuary, Todos os Santos Bay, Brazil, respectively. The sediments samples were analyzed for organic matter determined by the EMBRAPA method, nitrogen determined by the Kjeldahl method, and phosphorus determined by the method described by Aspila. The oil trapped in OSA was extracted following the method described by Moreira. The experiment showed a relationship between the amount of organic matter and OSA formation and consequently the dispersion of the studied oil. On the basis of the buoyancy of OSA and the ecotoxicological effects on pelagic and benthic community, the priority areas for application of remediation techniques are Cachoeira, Maragogipe, and Salinas da Margarida because of the large amount of oil that accumulated at the bottom of the experiment flask (5.85%, 27.95%, and 38,98%; 4.2%, 17.66%, and 32.64%; and 11.82%, 8.07%, and 10.91% respectively).