In many plant species, Rubisco activation state decreases at high temperature in vivo (Crafts-Brandner and Salvucci, 2000; Salvucci and Crafts-Brandner, 2004b; Cen and Sage, 2005; Yamori et al., 2006b; Makino and Sage, 2007). However, it is unclear what the primary mechanisms underlying the inhibition of Rubisco activation are and whether Rubisco deactivation limits CO2 assimilation rate at high temperature. It has been proposed that Rubisco activation state decreases at high temperature, because the activity of Rubisco activase is insufficient to keep pace with the faster rates of Rubisco inactivation at high temperatures (Crafts-Brandner and Salvucci, 2000; Salvucci and Crafts-Brandner, 2004a, 2004c; Kim and Portis, 2006). In in vitro assays using purified Rubisco and Rubisco activase, the activity of Rubisco activase was sufficient for the activation of Rubisco at the optimum temperature but not at high temperatures (Crafts-Brandner and Salvucci, 2000; Salvucci and Crafts-Brandner, 2004a, 2004c). ATP hydrolysis activity of Rubisco activase in vitro has varying temperature optima among species (e.g. 25°C in Antarctic hairgrass [Deschampsia antarctica] and spinach [Spinacia oleracea] but 35°C in tobacco [Nicotiana tabacum] and cotton [Gossypium hirsutum]), and Rubisco activase more readily dissociates into inactive forms at high temperature, causing a loss of Rubisco activase capacity (Crafts-Brandner and Law, 2000; Salvucci and Crafts-Brandner, 2004b). Moreover, the rates of inhibitor formation by misprotonation of RuBP during catalysis increased at higher temperatures (Salvucci and Crafts-Brandner, 2004c; Kim and Portis, 2006). CO2 assimilation rates and plant growth were improved under heat stress in transgenic Arabidopsis expressing thermotolerant Rubisco activase isoforms generated by either gene-shuffling technology (Kurek et al., 2007) or chimeric Rubisco activase constructs (Kumar et al., 2009). These results support the view that the reduction of Rubisco activase activity limits the Rubisco activation and, therefore, the CO2 assimilation rates at high temperatures.
Temperature responses of A380 (A and B), Rubisco activation state (C and D), and in vivo catalytic turnover rate of Rubisco (E and F) in plants grown at 20°C/15°C (black symbols) and 30°C/25°C (white symbols). Three groups were classified with respect to Rubisco activase contents (Table I): wild type (WT; circles), plants with intermediate Rubisco activase contents (triangles), and plants with low Rubisco activase contents (squares). The catalytic turnover rate of Rubisco was calculated from gross CO2 assimilation rates (A380 + dark respiration) and Rubisco carbamylated site content. Dark respiration was measured after a 10-h dark period. The optimum temperatures for A380 in 20°C-grown plants were 31.6°C ± 0.7°C, 25.3°C ± 1.5°C, and 18.2°C ± 1.3°C in wild-type, intermediate, and low Rubisco activase plants, respectively. Optimum temperatures for A380 in 30°C-grown plants were 33.2°C ± 0.6°C, 29.9°C ± 1.0°C, and 24.1°C ± 1.2°C in wild-type, intermediate, and low Rubisco activase plants, respectively. Data represent means ± se; n = 4.
EPIRBS are designed for maritime applications. The 406 MHz EPIRBs are divided into two categories. Category I EPIRBs are activated either manually or automatically. The automatic activation is triggered when the EPIRB is released from its bracket.
Category II EPIRBs are manual activation only units. If you own one of these, it should be stored in the most accessible location on board where it can be quickly accessed in an emergency. Both types include a built-in strobe light and are designed to float.EPIRBs transmit for at least 48 hours once activated. The U.S. Coast Guard has an outstanding website with even more information on EPIRBs. Click here to view the Coast Guard EPIRB Homepage.
In fire and smoke spread models (such as zone and field models) used for fire safety analysis, sprinklers are generally assumed to have an effect on the heat release rate of the fire. A common assumption for the performance of a sprinkler system in a performance-based design is that the heat release rate of the fire will not exceed the heat release rate at the time of sprinkler activation, as shown in Figure2, typically described as controlling the fire. This approach is described in the International Fire Engineering Guidelines (Donaldson et al.2005), and is also recommended in other performance-based approaches such as the New Zealand Verification Method (Department of Building and Housing2012). As it is difficult to quantify sprinkler performance in real fires in terms of heat release rate, a number of other criteria have been used, such as: 2b1af7f3a8