Performance constraints and compensation for teleoperation with delay

A classical control perspective is used to characterize performance constraints and evaluate compensation techniques for teleoperation with delay. Use of control concepts such as open and closed loop performance, stability, and bandwidth yield insight to the delay problem. Teleoperator performance constraints are viewed as an open loop time delay lag and as a delay-induced closed loop bandwidth constraint. These constraints are illustrated with a simple analytical tracking example which is corroborated by a real time, 'man-in-the-loop' tracking experiment. The experiment also provides insight to those controller characteristics which are unique to a human operator. Predictive displays and feedforward commands are shown to provide open loop compensation for delay lag. Low pass filtering of telemetry or feedback signals is interpreted as closed loop compensation used to maintain a sufficiently low bandwidth for stability. A new closed loop compensation approach is proposed that uses a reactive (or force feedback) hand controller to restrict system bandwidth by impeding operator inputs

The governance of genomic biobank research in Africa: reframing the regulatory tilt

Genomic biobank research has experienced exponential growth in recent years. It represents a real opportunity to remedy global health inequity that has seen limited investment in diseases affecting populations from low and middle income countries (LMICs). Previous research in Africa continent was limited to so-called parachute research whereby samples were taken from local populations for use in high income countries (HICs) with no local oversight or use of the sample. These exploitative practices must be guarded against, but the current regulation of genomic research in Africa adopts a risk-based precautionary approach, that at times is restrictive in nature. We argue that the regulation and oversight of genomic biobank research should guard against exploitative research, but in a manner that promotes reciprocal benefit and not restrictive research practices. To achieve this there must be a rebalancing of the regulatory tilt

Nutrient inputs from seabirds and humans on a populated coral cay

Inputs of inorganic nutnents in 1992 from seabirds (white-capped noddy and wedgetail shearwater, maximum of ca 80 000 breeding pairs) are compared to inputs from humans (97 700 person days) on Heron Island at the southern end of the Great Barrier Reef, Australia. We estimated that nod- dies deposited ca 107 t and shearwaters ca 22 t, of fresh guano The composition of fresh noddy guano was 7.3 % nitrogen 1.5 % phosphorus. 60 % moisture and 31.2 % other substances. Assuming a similar composition for shearwaters the total annual deposition of guano contained 9.4 t nitrogen and 1.9 t phosphorus. Experiments examining effects of ageing of guano indicated a large decrease in total nitrogen in guano under humid conditions over 4 d as a result of volatilisation of NH3. Under natural conditions most of the deposited nitrogen is likely to be lost as NH, and a relatively small fraction ot the soluble component leached into the cay, but the precise dynamics will depend on ramfall and wind patterns. Phosphorus was not volatilised from guano under any expenmental conditions. Although inputs of nitrogen and phosphorus from human sewage into the cay system (ca 0.3 t of each) were much less than that from birds, all nutrients from humans are released in liquid form and percolate directly into the cay. Significant seasonal and tidal variations in standing concentratlons of NH3 oxidised forms of nitrogen (NO2,+NO3), and PO4, were detected in the water column around the island. Trends of higher mean concentrations of all nutrients in summer than in winter, and higher concentrations at low tide than at high tide except at sites close to the Island where nutrient levels were high independent of tide suggest that nutrients may be transported from guano on Heron Island into the water immediately surrounding the island The exact fate and mechanisms of transport of all nutnents require further attention

Fluctuating local moments, itinerant electrons and the magnetocaloric effect: the compositional hypersensitivity of FeRh

We describe an ab-initio Disordered Local Moment Theory for materials with quenched static compositional disorder traversing first order magnetic phase transitions. It accounts quantitatively for metamagnetic changes and the magnetocaloric effect. For perfect stoichiometric B2-ordered FeRh, we calculate the transition temperature of the ferromagnetic-antiferromagnetic transition to be $T_t =$ 495K and a maximum isothermal entropy change in 2 Tesla of $|\Delta S|= 21.1$ J~K$^{-1}$~kg$^{-1}$. A large (40\%) component of $|\Delta S|$ is electronic. The transition results from a fine balance of competing electronic effects which is disturbed by small compositional changes - e.g. swapping just 2\% Fe of `defects' onto the Rh sublattice makes $T_t$ drop by 290K. This hypersensitivity explains the narrow compositional range of the transition and impurity doping effects.Comment: 11 pages, 4 figure