The internal model: A study of the relative contribution of proprioception and visual information to failure detection in dynamic systems

The development of the internal model as it pertains to the detection of step changes in the order of control dynamics is investigated for two modes of participation: whether the subjects are actively controlling those dynamics or are monitoring an autopilot controlling them. A transfer of training design was used to evaluate the relative contribution of proprioception and visual information to the overall accuracy of the internal model. Sixteen subjects either tracked or monitored the system dynamics as a 2-dimensional pursuit display under single task conditions and concurrently with a sub-critical tracking task at two difficulty levels. Detection performance was faster and more accurate in the manual as opposed to the autopilot mode. The concurrent tracking task produced a decrement in detection performance for all conditions though this was more marked for the manual mode. The development of an internal model in the manual mode transferred positively to the automatic mode producing enhanced detection performance. There was no transfer from the internal model developed in the automatic mode to the manual mode

The effects of participatory mode and task workload on the detection of dynamic system failures

The ability of operators to detect step changes in the dynamics of control systems is investigated as a joint function of, (1) participatory mode: whether subjects are actively controlling those dynamics or are monitoring an autopilot controlling them, and (2) concurrent task workload. A theoretical analysis of detection in the two modes identifies factors that will favor detection in either mode. Three subjects detected system failures in either an autopilot or manual controlling mode, under single-task conditions and concurrently with a subcritical tracking task. Latency and accuracy of detection were assessed and related through a speed accuracy tradeoff representation. It was concluded that failure detection performance was better during manual control than during autopilot control, and that the extent of this superiority was enhanced as dual-task load increased. Ensemble averaging and multiple regression techniques were then employed to investigate the cues utilized by the subjects in making their detection decisions

The impact of long-term elevated CO2 on C and N retention in stable SOM pools

Elevated atmospheric CO2 frequently increases plant production and concomitant soil C inputs, which may cause additional soil C sequestration. However, whether the increase in plant production and additional soil C sequestration under elevated CO2 can be sustained in the long-term is unclear. One approach to study C-N interactions under elevated CO2 is provided by a theoretical framework that centers on the concept of progressive nitrogen limitation (PNL). The PNL concept hinges on the idea that N becomes less available with time under elevated CO2. One possible mechanism underlying this reduction in N availability is that N is retained in long-lived soil organic matter (SOM), thereby limiting plant production and the potential for soil C sequestration. The long-term nature of the PNL concept necessitates the testing of mechanisms in field experiments exposed to elevated CO2 over long periods of time. The impact of elevated CO2 and N-15 fertilization on L. perenne and T. repens monocultures has been studied in the Swiss FACE experiment for ten consecutive years. We applied a biological fractionation technique using long-term incubations with repetitive leaching to determine how elevated CO2 affects the accumulation of N and C into more stable SOM pools. Elevated CO2 significantly stimulated retention of fertilizer-N in the stable pools of the soils covered with L. perenne receiving low and high N fertilization rates by 18 and 22%, respectively, and by 45% in the soils covered by T. repens receiving the low N fertilization rate. However, elevated CO2 did not significantly increase stable soil C formation. The increase in N retention under elevated CO2 provides direct evidence that elevated CO2 increases stable N formation as proposed by the PNL concept. In the Swiss FACE experiment, however, plant production increased under elevated CO2, indicating that the additional N supply through fertilization prohibited PNL for plant production at this site. Therefore, it remains unresolved why elevated CO2 did not increase labile and stable C accumulation in these systems

Quantum storage on subradiant states in an extended atomic ensemble

A scheme for coherent manipulation of collective atomic states is developed such that total subradiant states, in which spontaneous emission is suppressed into all directions due to destructive interference between neighbor atoms, can be created in an extended atomic ensemble. The optimal conditions for creation of such states and suitability of them for quantum storage are discussed. It is shown that in order to achieve the maximum signal-to-noise ratio the shape of a light pulse to be stored and reconstructed using a homogeneously broadened absorbtion line of an atomic system should be a time-reversed regular part of the response function of the system. In the limit of high optical density, such pulses allow one to prepare collective subradiant atomic states with near flat spatial distribution of the atomic excitation in the medium.Comment: V2: considerably revised (title, text). V3: minor changes - final version as published in PR

Residual strain in free-standing CdTe nanowires overgrown with HgTe

We investigate the crystal properties of CdTe nanowires overgrown with HgTe. Scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) confirm, that the growth results in a high ensemble uniformity and that the individual heterostructures are single-crystalline, respectively. We use high-resolution X-ray diffraction (HRXRD) to investigate strain, caused by the small lattice mismatch between the two materials. We find that both CdTe and HgTe show changes in lattice constant compared to the respective bulk lattice constants. The measurements reveal a complex strain pattern with signatures of both uniaxial and shear strains present in the overgrown nanowires

Improved inoculants for lentil

Non-Peer ReviewedThe effectiveness of the available commercial inoculants for lentil, Rhizogen, Enftx-L (Esso), Nitragin 'C', and Grip (Inotec) were compared with three inoculants which contained the rhizobia strains of 99A1, ICAR 20, and 92A3. Lentil inoculated with a sterile inoculant was used as the control. Total dry matter, total grain yield, percent total N and total N was determined At seven sites, an average grain yield for lentil was observed whereas for two sites yield was below average. Inoculant containing 99A1 and ICAR 20 an overall increase in grain yield by 14 % as compared with Nitragin 'C', strain 99A3 with 9 %, and Enftx-L with 7 %. The average grain yield of all nine sites for lentil inoculated with Grip and Rhizogen showed an insignificant decrease of 2 and 3 % as compared with lentil inoculated with Nitragin 'C'

Improved inoculants for lentil

Non-Peer Reviewe

Landscape-scale variability of N2 fixation by pea

Non-Peer ReviewedThe landscape-scale variability of N2 fixation by pulse crops is an important part in the intensity of N cycling in a hummocky terrain. A 100-gridpoint landscape-scale research design was established at a site in the thick Black Soil Zone in the spring of 1993. At the time of seeding, grid points classified as footslope landform complexes had 6.4% more water and 21.7 kg ha-1 more available N than those classified as shoulder. Pea seed yield ranged from 400 to 3750 kg ha-1 and straw yield ranged from 1900 to 12500 kg ha-1. Median seed yield on footslopes was 35% lower than that on shoulders, while median straw yield was 18% greater on footslopes in comparison to shoulders. Total N2 fixed in pea straw and seed ranged from 0 to 239 kg N ha-1. Median N2 fixed on shoulders was 116 kg N ha-1 and 91 kg N ha-1 on footslopes, despite the fact that total N did not show a spatial pattern. Spatial variability of available N, controlled by the redistribution of water, was considered to be the major process controlling the landscape-scale variability of N2 fixation

Nitrogen fertilizer use and losses in irrigated cropping systems

Non-Peer ReviewedThe fertilizer-N use efficiency of irrigated canola, softwheat, durum, and spring wheat was determined in 1988 and 1989. Crops received various amounts of N, applied at time of seeding or split between time of seeding and during the growing season. In 1989 at two sites, Outlook and Birsay both located on a field owned by farmers, N-losses due to denitrification after irrigation were determined by means of acetylene blockage. Softwheat and durum were grown at Outlook and Birsay, respectively. In 1988, all treatments received 150 kg N/ha, split equally between time of seeding and 54 days after planting. In 1989, all crops received 200 kg N/ha, applied at time of seeding or split equally between time of seeding and during the growing season. Fertilizer use efficiency (% FUE) in the crop of irrigated canola in 1988 averaged 37 % in the soil at time of final harvest. In 1989 the average FUE in canola was 27.4 %, in softwheat 42.3 % and in durum 43.0 %. The % FUE was 22 and 21 % at Birsay and Outlook, respectively. Nitrogen losses caused by denitrification were small at one site but significant at another. At the site with low input of N and irrigation water the N-losses were practically zero before the onset of irrigation, increased to a maximum loss of 50 g N/day/ha at 4 h after irrigation and declined to low levels at 10 h after irrigation. At the other site, with high N and irrigation water, the N losses from fertilized soil due to denitrification were approximately 5 kg N/day/ha, increased to 12.5 kg N/day/ha at 4 h after the application of water and declined to approximately 5 kg N/day/ha at 10 h after the water was applied

Nitrogen management under irrigated conditions

Non-Peer Reviewe