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Notes: Abstract 50-MHz type-II coherent echoes at geometrical aspect angles of 11.5○ have been observed in the northern polar cap during pre-noon hours. The echoes had an unusually large Doppler width of 1200–1400 m s−1 and were well correlated with strong magnetic disturbances in the range 500–1000 nT. The dependence of intensity, spectral width and skewness versus radial velocity were similar to those known from previous experiments at lower latitudes and at small aspect angles. It is concluded that echo onset was due to the combination of several factors, including a highly conducting ionosphere, the presence of a very intense electric field, and strong radar wave refraction.

Notes: A new force sensor element based on multilayer thin film technology and adapted for optical readout in a conventional scanning force microscope has been developed. The use of polymers as cantilever materials enables the introduction of mechanical properties otherwise not accessible with microfabrication based on Si technology. The fully batched fabricated cantilevered force transducer is based on the photoresist novolak and incorporates an integrated EBD tip. Bending experiments on microstructures indicate that the Young's modulus of novolak is about two orders of magnitude lower than for Si. Therefore, in using a cantilever design similar to that with Si it is possible to fabricate more flexible structures from polymeric materials. The new force sensors have been tested and their performance has been evaluated on different samples. © 1994 American Institute of Physics.

Notes: Abstract A new method for the determination of the velocity field with all three velocity components in a light sheet was demonstrated that combines conventional particle tracking anemometry (PTA) with an intensity analysis of the particle flecks. The correlation between intensity and the dimension perpendicular to the light sheet was obtained from the monotonous variation of the laser light intensity across the width of the light sheet.

Notes: Abstract A PTA-technique for the in-plane determination of the three flow velocity vector components based on the defocused imaging of stray-particles has been investigated. The conventional setup for 2-D PTA has been modified by broadening the laser light-sheet to a width of approximately 1.5 mm and focusing the imaging optics in a plane in front of the laser light-sheet. Particles in the light-sheet are imaged out of focus and the image size of a particle therefore depends on its distance to the focal plane of the imaging optics. The increase of the particle image diameter within single particle tracks due to the defocusing was used to determine the velocity component perpendicular to the light-sheet. The results obtained with this technique in a well defined laminar air flow are in good agreement with LDV-data.

Notes: [Auszug] Sublimation-grown single crystals of /?-terphenyl containing 10 7-10 8 mol/mol pentacene were cooled to 1.5K. As described in detail previously7, fluorescence excitation of single pentacene molecules in these samples was achieved by focusing a narrow-band single-mode laser to a spot of ...

Notes: Summary There has been no consensus concerning the particular movement of the valvular plane of the heart (VPM). As shown in this study involving a mathematical model based upon the momentum equation and experiments on a specially designed artificial heart pump, the VPM not only results from the shortening of the heart, but also from blood flow within the heart and large blood vessels, from the forces caused by the muscle movements, and from the elastic properties of the heart's suspension. The results of the calculations and the experiments confirm the effect of the so-called valve mechanism and its influence on the economic beating action of the heart.

Notes: Abstract The F3C Cold Plasma Analyzer (CPA) instrument on theFreja spacecraft is designed to measure the energy per unit charge (E/Q) of ions oe electrons in the range 0〈E/Q〈200 V and complements the observations made by the F3H Hot Plasma Experiment. The CPA sensor, which is deployed on a boom, is an electrostatic analyzer which produces angle/energy images of particles incident on the sensor in a plane perpendicular to the boom axis. Charged particles incident normal to the CPA sensor housing axis of symmetry, which coincides with the boom axis, pass through collimators and enter a semi-spherical electrostatic analyzer which disperses particles in energy and azimuthal angle of arrival onto an imaging MCP detector thus producing images of the particle distributions in a plane perpendicular to the boom axis. Measurements are transmitted either as discrete 16×16 (angle/energy) images or as parameters related to the incident particle distribution function. Pixels in the discrete images are separated approximately equally in azimuthal angle while the 16 energy bins are separated approximately geometrically in energy. The ratio of the maximum to minimum energy imaged is programmable up to a maximum of more than a factor of ten, and the energy range itself is also under the control of the processor and can be varied by more than an order of magnitude. The density dynamic range of the sensor is increased by the introduction of an electrostatic gating system between the entrance aperture and the analyzer which can be used to duty-cycle low-energy electrons into the sensor thus keeping the count rate within appropriate levels. To reduce the effects of spacecraft induced perturbations on the lower-energy particle distributions, the sensor portion of the instrument is deployed on a 2 m long boom, perpendicular to the spacecraft spin axis. Spacecraft rotation is used to recover complete (4π) angle/energy distributions every half spin period. In addition, the sensor skin may be biased with respect to the spacecraft ground to offset effects due to spacecraft charging. Current to the skin is monitored, making the exterior of the sensor equivalent to a large cylindrical Langmuir probe. Two separate processing paths for signals from the MCP anode may be chosen; ‘slow’ and ‘rast’. The ‘slow’ pulse processing path provides discrete angle/energy images at a nominal rate of 10 images per second and a peak ‘burst mode’ rate of 100 images per second. The ‘fast’ analog or current mode path provides crude parameterized estimates of densities, temperatures and drift velocities at nominal rates of up to 1000 parameters per second with a burst rate near 6000 parameters per second. Observations of cold ions and electrons in an unperturbed ionospheric plasma are presented which demonstrate the functionality of the instrument. Suprathermal ion observations in a transverse ion energization or acceleration region are also shown which demonstrate many of the small-scale features of these events.

Notes: Abstract We study a dimer-trimer lattice model for heterogeneous catalysis for the reaction 1/2A2+1/3B3→AB. The A2 and B3 particles require two and three active sites for their adsorption onto the lattice, respectively. The model is unusual in that it possesses an infinite number of absorbing states whereby the lattice is “poisoned” and reactions must stop. Previously studied models have only two absorbing states. In one dimension, the lattice poisons with mostly dimers and a few trimers even at vanishingly small dimer-adsorption probabilities and there is a discontinuity when this probability is zero. On the triangular lattice, the poisoned phases consist of only one component and vacancies, and the phase diagram is similar to that of the monomer-dimer model of Ziff, Gulari, and Barshad. However, the second-order transition belongs to a different universality class than Reggeon field theory, contrary to previous models. Finally, we present results for the Kagomé lattice, for which the poisoned phases consist of two components due to its smaller connectivity.