1,339 research outputs found
Sympathetic cooling of He ions in a radiofrequency trap
We have generated Coulomb crystals of ultracold He ions in a linear
radiofrequency trap, by sympathetic cooling via laser--cooled Be.
Stable crystals containing up to 150 localized He ions at 20 mK were
obtained. Ensembles or single ultracold He ions open up interesting
perspectives for performing precision tests of QED and measurements of nuclear
radii. The present work also indicates the feasibility of cooling and
crystallizing highly charged atomic ions using Be as coolant.Comment: 4 pages, 2 figure
Collicular Responses to the Frequency Modulated Final Part of Echolocation Sounds in Rhinolophusferrum equinum
Collicular evoked potentials in Rhinolophus ferrum equinum show
very prominent responses to the final frequency modulated part of a acoustic
stimulus, simulating the natural echolocation sound
Laryngeal Nerve Activity During Pulse Emission in the CF-FM Bat, Rhinolophus ferrumequinum. I. Superior Laryngeal Nerve (External Motor Branch)
The activity of the external (motor) branch of the superior laryngeal nerve (SLN), innervating the cricothyroid muscle, was recorded in the greater horseshoe bat,Rhinolophus ferrumequinum. The bats were induced to change the frequency of the constant frequency (CF) component of their echolocation signals by presenting artificial signals for which they Doppler shift compensated. The data show that the SLN discharge rate and the frequency of the emitted CF are correlated in a linear manner
Hearing Characteristics and Doppler Shift Compensation in South Indian CF-FM Bats
1. Echolocation pulses, Doppler shift compensation behaviour under laboratory conditions and frequency response characteristics of hearing were recorded inRhinolophus rouxi, Hipposideros speoris andHipposideros bicolor.
2. The frequencies of the constant frequency portions of the CF-FM pulses lie at about 82.8 kHz forR. rouxi from Mahabaleshwar, at 85.2 kHz forR. rouxi from Mysore. Hipposiderid bats have considerably higher frequencies at 135 kHz inH. speoris and 154.5 kHz inH. bicolor. The mean sound durations were 50 ms, 6.4 ms and 4.7 ms, respectively.
3. R. rouxi compensates for Doppler shifts in a range up to typically 4 kHz of positive Doppler shifts (Fig. 2). The Doppler shift compensation behaviour is almost identical to that ofR. ferrumequinum.
4. H. speoris andH. bicolor do not compensate for Doppler shifts under laboratory conditions. Doppler shifts in the echoes induce emission frequency changes which are not correlated to the presented Doppler shifts (Fig. 3).
5. The frequency response characteristics of hearing ofR. rouxi show characteristic sensitivity changes near the bat's reference frequency as also found inR. ferrumequinum. The threshold differences between the low threshold at the reference frequency and a few hundred Hz below are 40 to 50 dB in awake bats (Fig. 5).
6. Frequency sensitivity changes near the emitted CF-frequency of the bats are less pronounced inH. speoris or almost absent inH. bicolor
Essential oils as antioxidants of different coloured carrot cultivars (Daucus carota L. ssp. sativus Hoffm.)
Eight different coloured carrot cultivars, in orange, white, yellow, purple with orange or yellow and cream core, and red colour, were examined for their content and composition of essential oils and for their antioxidant capacity. For this purpose, two biochemical test systems were chosen (ABTS-test, MDA-test for lipid peroxidation). White and yellow carrot cultivars contained higher amounts of essential oils than orange cultivars. ‘Nutri Red’ had very high content of essential oils. There were significant differences between the cultivars in composition of their essential oils as shown by nine monoterpenes and two sesquiterpenes.In both test systems essential oils of carrots showed antioxidant activity. The essential oils of purple and yellow coloured carrots had higher TEAC values than the essential oils of orange, white and red carrots
Echo Delay and Overlap with Emitted Orientation Sounds and Doppler-shift Compensation in the Bat, Rhinolophus ferrumequinum
The compensation of Doppler-shifts by the bat, Rhinolophusferrumequinum,
functions only when certain temporal relations between the echo
and the emitted orientation sound are given. Three echo configurations
were used:
a) Original orientation sounds were electronically Doppler-shifted and
played back either cut at the beginning (variable delay) or at the end (variable
duration) of the echo.
b) Artificial constant frequency echoes with variable delay or duration
were clamped to the frequency of the emitted orientation sound at different
Doppler-shifts.
c) The echoes were only partially Doppler-shifted and the Doppler-shifted
component began after variable delays or had variable durations.
With increasing delay or decreasing duration of the Doppler-shifted echo
the compensation amplitude for a sinusoidally modulated + 3 kHz Dopplershift
(modulation rate 0.08 Hz) decreases for all stimulus configurations
(Figs. 1, 2, 3).
The range of the Doppler-shift compensation system is therefore limited
by the delay due to acoustic travel time to about 4 m distance between
bat and target. In this range the overlap duration of the echo with the
emitted orientation sound is always sufficiently long, when compared with
data on the orientation pulse length during target approach from Schnitzler
(1968) (Fig. 5)
Parabolic Anderson model with a finite number of moving catalysts
We consider the parabolic Anderson model (PAM) which is given by the equation
with , where is the diffusion constant,
is the discrete Laplacian, and
is a space-time random environment that drives the equation. The solution of
this equation describes the evolution of a "reactant" under the influence
of a "catalyst" . In the present paper we focus on the case where is
a system of independent simple random walks each with step rate
and starting from the origin. We study the \emph{annealed} Lyapunov exponents,
i.e., the exponential growth rates of the successive moments of w.r.t.\
and show that these exponents, as a function of the diffusion constant
and the rate constant , behave differently depending on the
dimension . In particular, we give a description of the intermittent
behavior of the system in terms of the annealed Lyapunov exponents, depicting
how the total mass of concentrates as . Our results are both a
generalization and an extension of the work of G\"artner and Heydenreich 2006,
where only the case was investigated.Comment: In honour of J\"urgen G\"artner on the occasion of his 60th birthday,
25 pages. Updated version following the referee's comment
How greater mouse-eared bats deal with ambiguous echoic scenes
Echolocating bats have to assign the received echoes to the correct call that generated them. Failing to do so will result in the perception of virtual targets that are positioned where there is no actual target. The assignment of echoes to the emitted calls can be ambiguous especially if the pulse intervals between calls are short and kept constant. Here, we present first evidence that greater mouse-eared bats deal with ambiguity by changing the pulse interval more often, in particular by reducing the number of calls in the terminal group before landing. This strategy separates virtual targets from real ones according to their change in position. Real targets will always remain in a constant position, and virtual targets will jitter back and forth according to the change in the time interval
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