A new method to measure rotating frame relaxation and to create contrast for MRI is introduced. The technique exploits relaxation along a fictitious field (RAFF) generated by amplitude- and frequency-modulated irradiation in a sub-adiabatic condition. Here, RAFF is demonstrated using a radiofrequency pulse based on sine and cosine amplitude and frequency modulations of equal amplitudes, which gives rise to a stationary fictitious magnetic field in a doubly rotating frame. According to dipolar relaxation theory, the RAFF relaxation time constant (TRAFF) was found to differ from laboratory frame relaxation times (T1 and T2) and rotating frame relaxation times (T1ρ and T2ρ). This prediction was supported by experimental results obtained from human brain in vivo and three different solutions. Results from relaxation mapping in human brain demonstrated the ability to create MRI contrast based on RAFF. The value of TRAFF was found to be insensitive to the initial orientation of the magnetization vector. Finally, as compared with adiabatic pulse trains of equal durations, RAFF required less radiofrequency power and therefore can be more readily used for rotating frame relaxation studies in humans.

Modern UAV's reduce the threat to human operators, but do not decrease the manpower requirements. Each aircraft requires a flight crew of one to three, so deploying large numbers of UAV's requires committing and coordinating many human warfighters. Insects perform impressive feats of coordination without direct inter-agent coordination, by sensing and depositing pheromones (chemical scent markers) in the environment [14]. We have developed a novel technology for coordinating the movements of multiple UAV's based on a computational analog of pheromone dynamics. The control logic is simple enough that it can be executed autonomously by a UAV, enabling a single human to monitor an entire swarm of UAV's. This paper describes the technology, its application to UAV coordination, and the results we have obtained. Distributed.-The US military is facing a serious shortfall in long-range communications bandwidth [1]. Warfighters cannot assume the availability of unlimited satcom channels. This limitation can be addressed by distributing the C 2 system physically over the battlespace. Distribution helps lower bandwidth in two ways.

A systematic analysis of the mode structure of diffusive relaxations in 1 MDa hydroxypropylcellulose͑HPC͒:water is presented. New methods and data include ͑1͒ use of integral spectral moments to characterize nonexponential decays, ͑2͒ spectra of small probes in concentrated HPC solutions, ͑3͒ temperature dependence of the mode structure, and ͑4͒ comparison of optical probe spectra and spectra of probe-free polymer solutions. We find that ͑1͒ probe and polymer relaxations are in general not the same; ͑2͒ the apparent viscometric crossover near c t Ϸ6 g/l is echoed by probe behavior; ͑3͒ our HPC solutions have a characteristic dynamic length, namely the 50 nm length that matches the polymer's hydrodynamic radius; ͑4͒ characterization of spectral modes with their mean relaxation time affords simplifications relative to other characterizations; and ͑5͒ contrary to some expectations, Stokes-Einsteinian behavior ͑diffusion rate determined by the macroscopic viscosity͒ is not observed, even for large probes in relatively concentrated solutions. We propose that the viscometric and light scattering effects found in HPC solutions at elevated concentrations reflect the incipient formation of a generalized Kivelson ͓S. A.

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