Development of a new type of self-scanned electron image sensingintegrated circuit

The design and fabrication of an integrated circuit which is a position-sensitive detector for low-energy (typically up to 100 eV) charged particles are discussed. The device comprises a linear array of electron-sensing electrodes coupled to detection and readout circuitry in the form of amplifiers and counters all integrated onto a single CMOS chip. The chip is intended to replace existing position-sensitive detection systems in electron spectrometers     

Keeping a beat on the heart

We have developed and benchmarked real-time collection methods that exploit digital, packet-switched telephony services available in metropolitan areas. The Arrhythmia monitoring system collects real-time electrocardiogram signals from a mobile or homebound patient, and combines them with GPS location data, and transmits this information to a remote station for display and monitoring.     

The effect of gate leakage on the noise figure of AlGaN/GaN HEMTs

The effect of gate leakage on the noise figure of AlGaN/GaN high electron mobility transistor (HEMTs) is explored. It is shown that these devices have a sizable amount of gate leakage that cannot be ignored when measuring their noise performance. Measurements across a single sample have more than 1 dB of variation in minimum noise figure. We will show this variation is because of gate leakage. A modified van der Ziel model is used to predict this large variation and allows easy noise figure prediction of HEMT and MESFET devices.     

Species and sex differences in substrate preference and tongue flick rate in three sympatric species of water snakes (Nerodia).

Tested isolation-reared sympatric water snakes (Nerodia r. rhombifera, N. c. cyclopion, and N. fasciata confluens) in a balanced 2-choice design to determine preference between clean and same-sex conspecific-soiled gravel substrates. Ss included 8 snakes (4 of each sex) of each species. Time spent on each substrate, types of tongue flicking behavior, tail vibration, defecation, and head rubbing were recorded. Species and sex differences were found in the relative time spent on the 2 substrates. Both sexes of N. rhombifera preferred the clean substrate, whereas both sexes of N. cyclopion preferred the soiled substrate, although the difference in time spent on the substrates was small for males. N. fasciata sexes differed in their preference, with the females preferring the soiled substrate and the males preferring, but not so strongly, the clean substrate. The frequencies of the 4 types of tongue extensions differed across species and sexes, with "air" tongue flicks accounting for the most variance. A lower total rate of tongue flicking occurred when the snakes were on the preferred substrate. These species and sex differences may help minimize competition due to dietary overlap between N. rhombifera and N. cyclopion, and between male and female N. fasciata. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The wake of hovering flight in bats

Hovering means stationary flight at zero net forward speed, which can be achieved by animals through muscle powered flapping flight. Small bats capable of hovering typically do so with a downstroke in an inclined stroke plane, and with an aerodynamically active outer wing during the upstroke. The magnitude and time history of aerodynamic forces should be reflected by vorticity shed into the wake. We thus expect hovering bats to generate a characteristic wake, but this has until now never been studied. Here we trained nectar-feeding bats, Leptonycteris yerbabuenae, to hover at a feeder and using time-resolved stereoscopic particle image velocimetry in conjunction with high-speed kinematic analysis we show that hovering nectar-feeding bats produce a series of bilateral stacked vortex loops. Vortex visualizations suggest that the downstroke produces the majority of the weight support, but that the upstroke contributes positively to the lift production. However, the relative contributions from downstroke and upstroke could not be determined on the basis of the wake, because wake elements from down- and upstroke mix and interact. We also use a modified actuator disc model to estimate lift force, power and flap efficiency. Based on our quantitative wake-induced velocities, the model accounts for weight support well (108%). Estimates of aerodynamic efficiency suggest hovering flight is less efficient than forward flapping flight, while the overall energy conversion efficiency (mechanical power output/metabolic power) was estimated at 13%.     

Continuum modeling of the dynamics of externally injection-lockedcoupled oscillator arrays

Mutually injection-locked arrays of electronic oscillators provide a novel means of controlling the aperture phase of a phased-array antenna, thus achieving the advantages of spatial power combining while retaining the ability to steer the radiated beam. In a number of design concepts, one or more of the oscillators are injection locked to a signal from an external master oscillator. The behavior of such a system has been analyzed by numerical solution of a system of nonlinear differential equations which, due to its complexity, yields limited insight into the relationship between the injection signals and the aperture phase. In this paper, we develop a continuum model, which results in a single partial differential equation for the aperture phase as a function of time. Solution of the equation is effected by means of the Laplace transform and yields detailed information concerning the dynamics of the array under the influence of the external injection signals     

Some considerations for optimal efficiency and low noise in largepower combiners

This paper examines some relationships between important design parameters in large combiner systems and key performance objectives such as power, efficiency, noise, and graceful degradation. Results are derived for the combining efficiency of general combiner systems, and used to contrast spatial and corporate combiners and identify optimum combiner topology for a given device technology. The influence of array size on excess phase noise is quantified and shown to decrease with increase numbers of devices. Results are also presented for the degradation in combining efficiency due to statistical variations in amplifier characteristics, appropriate to large combiners, showing that phase errors are the dominant factor in power degradation