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Echolocating bats of the speciesEptesicus fuscus were trained to discriminate between two arrays of vertical rods differing in the size of the angle in the horizontal plane separating the rods in each array. With both two-rod arrays and fiverod arrays the bats were able to distinguish angular differences as small as 1.5 °(75% correct-response threshold).(More)
Double-quantum-well field-effect transistors with a grating gate exhibit a sharply resonant, voltage tuned terahertz photoconductivity. The voltage tuned resonance is determined by the plasma oscillations of the composite structure. The resonant photoconductivity requires a double-quantum well but the mechanism whereby plasma oscillations produce changes in(More)
Echolocating bats perceive objects as acoustic images derived from echoes of the ultrasonic sounds they emit. They can detect, track, identify, and intercept flying insects using sonar. Many species, such as the big brown bat, Eptesicus fuscus, emit frequency-modulated sonar sounds and perceive the distance to targets, or target range, from the delay of(More)
The big brown bat, Eptesicus fuscus, can perceive small changes in the delay of FM sonar echoes and shifts in echo phase, which interact with delay. Using spectral cues caused by interference, Eptesicus also can perceive the individual delays of two overlapping FM echoes at small delay separations. These results have been criticized as due to spectral(More)
1. Flights of three big brown bats (Eptesicus fuscus) landing on a hand and catching a suspended mealworm were video analysed. 2. Results were consistent with the bats using the same basic control procedure in the quite different approach tasks — namely keeping τ(r) = k rand τ(a)τ(r) = k αr. Here r is the current distance to the destination; α is the angle(More)
| Solid‐state lighting is a rapidly evolving technology, now virtually certain to someday displace traditional lighting in applications ranging from the lowest‐ power spot illuminator to the highest‐power area illuminator. Moreover, it has considerable headroom for continued evolution even after this initial displacement. In this article, we present a(More)
We report resistivity measurements from 0.03 to 10 K in a dilute high mobility 2D electron system. Using an undoped GaAs/AlGaAs heterojunction in a gated field-effect transistor geometry, a wide range of densities, 0.16 x 10(10) to 7.5 x 10(10) cm(-2), are explored. For high densities, the results are quantitatively shown to be due to scattering by acoustic(More)
Nuclear magnetic resonance is detected via the in-plane conductivity of a two-dimensional electron system at unity Landau level filling factor in the regime of the quantum Hall effect in narrow and wide quantum wells. The NMR is spatially selective to nuclei with a coupling to electrons in the current carrying edge states at the perimeter of the 2DES.(More)
Negative differential conductance has been observed in grid-shaped surface superlattices, realized in a high mobility two-dimensional electron system. The current-voltage characteristics vary with the modulation strength, indicating that the two-dimensional electronic transport properties can be manipulated in a controllable way. Theoretical modeling yields(More)