Pereira, A C; Gama, V F
In this study we analysed the dynamics of deforestation and burnings during the dry seasons from 2003 to 2008 in the Uruçuí-Una Ecological Station (UUES) and its buffer zone, located in the Cerrado biome of the southwest of Piauí, a Brazil's State, based on images from the orbital sensors CCD/CBERS-2 and TM/Landsat-5. Two dates from each of the years were interpreted and analysed: one in the middle of the dry season and one at the end. The deforested areas were expanded through the period analysed and were larger in the buffer zone, suggesting a relative protection of the UUES. New cut-offs were predictable because of the early opening of roads that would become their limits. The burning scars were larger at the end of the dry season as a consequence of the management and implementation of agricultures and pastures. In 2004 and 2007 these scars were larger probably because of the increase of dry phytomass that every three years is big enough to spread the fire originated in the anthropogenic burnings through the native vegetation. This scenario reaffirms the need for: stronger enforcement in order to stop anthropisation in the UUES and a management plan, absent for this unit so far. These proceedings are urgent also because the UUES is located in one of the most preserved regions of the Cerrado and controversially where intense anthropisation in ongoing, which stresses the lack, need and urgency of biological conservation proceedings for the Piauí's southeastern Cerrado. PMID:21180901
Grossman, S. B.; Emmons, R. B.; Hawkins, S. R.
In analyzing the performance of direct-injected hybrid focal plane arrays, many factors must be consiaered in determining the minimum detector resistance-area product RDA neces-sary to obtain background-limited performance (BLIP) and good array uniformity. In photo-aioue arrays, a necessary but not sufficient condition is that noise due to the diode generation-recombination and diffusion currents are less than the background photon shot noise. Tnis places a minimum requirement on the magnitude of RoA, the zero bias resistance area product. In addition, there are generally much more stringent requirements on RDA uue to input MOSFET l/f noise and threshold variations which exceed the single detector RoA requirement for BLIP operation at a given background. In general, the input thresnolu variations require that the photodiodes be somewhat back-biased. This produces a substantially higner average RDA at the expense of higher detector l/f noise due to surface leakage. In tnis study we have investigated the detector impedance requirements in terms of tne injection efficiency, threshold nonuniformities, the input MOSFET excess (l/f) noise, and tne detector excess noise. For state-of-the-art parameters, it was determined tnat tne input MOSFET l/f noise always dominates the other elements in determining the required detector impeaance:k
Agarwal, U; Hu, Q; Bequette, B J
Feeding and postruminal infusion of propionate is known to increase N retention in ruminants. Our aim was to determine the role of rumen propionate on urea N recycling and gluconeogenesis in growing sheep. In Exp. 1, wether sheep ( = 6; 32.5 ± 3.57 kg BW) fitted with a rumen cannula were fed to 1.8 × ME requirement a concentrate-type ration (172 g CP/kg DM and 10.4 MJ ME/kg DM) and continuously infused into the rumen with isoenergetic (10% of dietary ME intake) solutions of either sodium acetate (control) or sodium propionate for 9-d periods in a crossover design. In Exp. 2, a different group of wether sheep ( = 5; 33.6 ± 3.70 kg BW) fitted with a rumen cannula were fed, on an isonitrogenous basis, either a control (151 g CP/kg DM and 8.4 MJ ME/kg DM) or sodium propionate-supplemented (139 g CP/kg DM and 8.9 MJ ME/kg DM) diet at 2-h intervals. [N] urea was continuously infused intravenously for the last 5 d of each period, and total urine was collected by vacuum and feces were collected by a harness bag. Over the last 12 h, [C]glucose was continuously infused intravenously and hourly blood samples were collected during the last 5 h. Propionate treatments increased ( < 0.001) the proportion of rumen propionate in both experiments. In Exp. 1, N retention was not affected by propionate infusion as compared with isoenergetic acetate. There was no effect on urea entry (synthesis) rate (UER) in Exp. 1; however, sodium propionate infusion tended ( < 0.1) to increase urinary urea elimination (UUE). In Exp. 2, feeding propionate increased ( < 0.01) N retention by 0.8 g N/d. In addition, UER was reduced by approximately 2 g urea N/d, leading to a reduction ( < 0.05) in UUE (7.0 vs. 6.2 g urea N/d). Between the 2 experiments, the proportion of UER recycled to the gut was greater with the forage-type diet in Exp. 2 (approximately 60%) compared with the concentrate-type diet in Exp. 1 (approximately 40%), although urea N fluxes across the gut remained unchanged in both