A TRPV family ion channel required for hearing in Drosophila

The many types of insect ear share a common sensory element, the chordotonal organ, in which sound-induced antennal or tympanal vibrations are transmitted to ciliated sensory neurons and transduced to receptor potentials. However, the molecular identity of the transducing ion channels in chordotonal neurons, or in any auditory system, is still unknown. Drosophila that are mutant for NOMPC, a transient receptor potential (TRP) superfamily ion channel, lack receptor potentials and currents in tactile bristles but retain most of the antennal sound-evoked response, suggesting that a different channel is the primary transducer in chordotonal organs. Here we describe the Drosophila Nanchung (Nan) protein, an ion channel subunit similar to vanilloid-receptor-related (TRPV) channels of the TRP superfamily. Nan mediates hypo-osmotically activated calcium influx and cation currents in cultured cells. It is expressed in vivo exclusively in chordotonal neurons and is localized to their sensory cilia. Antennal sound-evoked potentials are completely absent in mutants lacking Nan, showing that it is an essential component of the chordotonal mechanotransducer.     

Using the life cycle to anticipate satisfaction at work

It was hypothesized that there are important non-linear life-cycle influences upon job and organizational satisfaction. Five common life-cycle stages were identified from the literature: the phases of ‘reality shock’, ‘socialization and growth’, ‘mid-career crisis’, ‘acceptance’, and ‘pre-retirement’. The first, third and last stages were expected to show declines in job and organizational satisfaction because of the personal and job-related disappointments and crises that typically occur during these periods of life. The second and fourth stages were expected to show increases in satisfaction because of the pleasant life experiences that often occur then. All but the first stage supported these hypotheses when we controlled for the influence of sex, education, job experience, level in the hierarchy and occupational upward mobility.     

基于状态观测和反馈的伺服系统位置控制器

为了提高永磁同步电机伺服系统中的位置控制性能,提出一种基于状态观测器和状态反馈的位置控制器.状态观测器可以利用较低精度的位置传感器来准确观测负载转矩、转子位置和转速.基于状态空间算法的位置控制器通过合适的零极点配置,可以提高位置控制性能.利用观测的负载转矩可以把负载的变化作为系统扰动进行补偿.仿真和实验结果表明: 该控制器与传统的比例积分微分控制器相比,位置控制快速准确并且没有超调,在负载变化时系统仍然能够保持很好的稳定性和控制精度.     

Stream denitrification across biomes and its response to anthropogenic nitrate loading

Anthropogenic addition of bioavailable nitrogen to the biosphere is increasing and terrestrial ecosystems are becoming increasingly nitrogen-saturated, causing more bioavailable nitrogen to enter groundwater and surface waters. Large-scale nitrogen budgets show that an average of about 20-25 per cent of the nitrogen added to the biosphere is exported from rivers to the ocean or inland basins, indicating that substantial sinks for nitrogen must exist in the landscape. Streams and rivers may themselves be important sinks for bioavailable nitrogen owing to their hydrological connections with terrestrial systems, high rates of biological activity, and streambed sediment environments that favour microbial denitrification. Here we present data from nitrogen stable isotope tracer experiments across 72 streams and 8 regions representing several biomes. We show that total biotic uptake and denitrification of nitrate increase with stream nitrate concentration, but that the efficiency of biotic uptake and denitrification declines as concentration increases, reducing the proportion of in-stream nitrate that is removed from transport. Our data suggest that the total uptake of nitrate is related to ecosystem photosynthesis and that denitrification is related to ecosystem respiration. In addition, we use a stream network model to demonstrate that excess nitrate in streams elicits a disproportionate increase in the fraction of nitrate that is exported to receiving waters and reduces the relative role of small versus large streams as nitrate sinks.