Effective bacterial micromixers
Scientists have discovered that commonly found bacteria such as Bacillus
Subtilis are in fact highly efficient mixers for the liquid they live
in. Thanks to original non-invasive optical coherence tomography (OCT)
developed by Imalux Corporation, OH, the scientists observed with
unprecedented precision the phenomena unfolding in the liquid containing
the bacteria. The measurements revealed up to 100-fold increase of
mixing and Oxygen intake rates due to coordinated swimming of the bacteria.
The study sheds a new light on possible survival mechanisms developed by
bacterial colonies under harsh conditions. In addition, the results are
important for fundamental and technological reasons, from understanding
collective motion in groups of interacting animals such as bird flocks
and fish schools to miniature bacteria-powered mixers and reactors.
Image illustrates three-dimensional distribution of bacteria obtained by
the OCT scan
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LW10950AR
Space Time Sensors Juggling With Multiple Ultracold Atomic Waves
Thanks to their ability to measure time with an extreme accuracy, optical
atomic clocks are of great importance for modern physics [1]. The best
clocks to date control the atomic motion by trapping the sample within
optical lattices and then probe the atomic transition by shining on
these atoms a distinct laser of controlled frequency. In order to perform
both operations simultaneously and with the same laser field, we explore
in this paper a different strategy: using fine-tuned laser pulses, one can
perform a quantum juggling with a Bose-Einstein condensate and exploit the
resulting interferences to enhance the measurement sensitivity. The
condensate goes through an unusual levitation process: it is split into a
myriad of wave-packets exploring a network of paths, thereby experiencing
simultaneously a controlled diffusion in altitude and a localization in
momentum. Thanks to the chosen geometry, this proposal combines the best
aspects of optical clocks based on atom traps and on atom
interferometers. This system is also able to measure accelerations. It
represents an attractive alternative to current atom gravimeters and
atomic clocks.
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LD12391
Quantum Limit for Probing Quantized Energy Levels of a Mechanical
Oscillator
Recent novel experiments with electromechanical and optomechanical
systems unveilpossibilities of exploring quantum behavior of a macroscopic mechanical oscillator. If energy levels of a mechanical oscillator were observed to be quantized, this will give us an unequivocal sign of quantumness of a macroscopic object. Motivated by the pioneering work of Thompson et al., we derive a standard quantum limit for observing energy quantization in systems with a mechanical oscillator coupled parametrically to external degrees of freedom. In order to successfully probe the quantized energy levels, the mechanical oscillator needs to strongly interact with the external degrees of freedom. In the case of optomechanical system, as intuitively expected, it requires zero-point motion of the oscillator to be comparable to the linear dynamical range of the optical system. This condition indicates the threshold when nonlinearity in the system plays a significant role. Interestingly, it is also the point where momentum kick by a single photon exceeds zero-point fluctuation of the oscillator momentum, allowing realization of macroscopic quantum supposition [3]. Therefore, if this condition is satisfied, many fascinating nonlinear and non-Gaussian properties of the optomechanical system will show up in the quantum regime.
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LA12165Z
Making bright electron beams for compact x-ray lasers
A novel method to accomplish highly-brilliant electron beams required for coherent x-ray generation in a compact x-ray free-electron laser (XFEL) is presented. Since the nonlinearity of electron beam compression limits the attainable peak current, a correction cavity operated at a high-harmonic frequency of a main accelerator is conventionally used for nonlinearity compensation. However in a compact XFEL using a high-frequency main accelerator, a conventional scheme encounters a technological difficulty of an extremely high-frequency microwave system. In this paper, a novel nonlinearity correction scheme is proposed for a compact XFEL, in which an effective frequency up-conversion of a correction cavity obtained in the beam compression is directly used. As a result, the frequency of the correction cavity can be decreased to the same frequency as the main accelerator. Derived analytical formulae and simulations confirm the successful generation of highly-brilliant electron beams in a compact XFEL. This new scheme will become a key technique to downsize the scale of the facility, which is an essential issue for widespread application of coherent x-ray light sources.
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LE12697
How perfect can graphene be?
We have identified the cyclotron resonance response of purest
graphene ever investigated, which can be found in nature on the surface of
bulk graphite, in form of decoupled layers from the substrate material.
Probing such flakes with Landau level spectroscopy in the THz range at
very low magnetic fields, we demonstrate a superior electronic quality of
these ultra-low density layers (close to 10^9 cm-2), expressed by the
carrier mobility in excess of 10^7 cm2/(V.s). These parameters set new and
surprisingly high limits for intrinsic properties of graphene and
represent an important challenge for further developments of current
graphene technologies. Graphene samples with mobilities comparable to the
nowadays highest-mobility semiconductor devices thus seem to be
achievable. Intriguingly, electronic states in such high-quality graphene
could be quantized into Landau levels by magnetic fields as low as the
field of the Earth.
