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Zuazua, Enrique

doi:10.3989/arbor.2007.i725.111

Cited by 2 publications

(2 citation statements)

References 13 publications

(15 reference statements)

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“…As we mentioned in the overview, in October 1985, a group of young marine biologists at Woods Hole, lead by John Waterbury 22 , reported a strange find, the first observation of a motile cyanobacterium.…”

Section: Cells That Swim Without Flagellamentioning

confidence: 98%

Acoustic Streaming, The “Small Invention” of Cianobacteria?

Koiller

Ehlers

Chalub

2010

Arbor

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RESUMEN: Los mecanismos de bombeo en microingeniería aparecieron al principio de la década de los 90. El principio detrás de esto es el de flujo acústico. ¿Ha descubierto laABSTRACT: Micro-engineering pumping devices without mechanical parts appeared "way back" in the early 1990's. The working principle is acoustic streaming. Has Nature "rediscovered" this invention 2.7 Gyr ago? Strands of marine cyanobacteria Synechococcus swim 25 diameters per second without any visible means of propulsion. We show that nanoscale amplitude vibrations on the S-layer (a crystalline shell outside the outer membrane present in motile strands) and frequencies of the order of 0.5-1.5 MHz (achievable by molecular motors), could produce steady streaming slip velocities outside a (Stokes) boundary layer. Inside this boundary layer the flow pattern is rotational (hence biologically advantageous). In addition to this purported "swimming by singing", we also indicate other possible instantiations of acoustic streaming. Sir James Lighthill has proposed that acoustic streaming occurs in the cochlear dynamics, and new findings on the outer hair cell membranes are suggestive. Other possibilities are membrane vibrations of yeast cells, enhancing its chemistry (beer and bread, keep it up, yeast!), squirming motion of red blood cells along capillaries, and fluid pumping by silicated diatoms.

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Section: Cells That Swim Without Flagellamentioning

confidence: 98%

Acoustic Streaming, The “Small Invention” of Cianobacteria?

Koiller

Ehlers

Chalub

2010

Arbor

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“…Generally, the main goal of control theory is to find controls leading the objects to a desired situation. There are usually two ways of specifying "a desired prescribed situation": the controllability viewpoint and the optimization viewpoint [4]. The controllability of quantum systems has been investigated by many researchers (see Ref.…”

Section: Introductionmentioning

confidence: 99%

Trajectory-constrained optimal local time-continuous waveform controls for state transitions in $N$-level quantum systems

Zhang¹,

Wei²,

Zhou³

et al. 2010

Preprint

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Based on a parametrization of pure quantum states we explicitly construct a sequence of (at most) 4N − 5 local time-continuous waveforms controls to achieve the specified state transition for N -level quantum system when sufficient controls of the Hamiltonian are available. The control magnitudes are further optimized in terms of the time-energy performance which is the generalization of the time performance, and then the trajectory-constrained optimal local time-continuous waveforms controls including both local sine-waveforms and n-order-polynomial-function-waveform controls are obtained in terms of time-energy performance. It is demonstrated that constrained optimal local nst-order-polynomial-function-waveform controls approach constrained optimal bang-bang controls when n → ∞.

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Untitled

Cited by 2 publications

References 13 publications

Acoustic Streaming, The “Small Invention” of Cianobacteria?

Acoustic Streaming, The “Small Invention” of Cianobacteria?

Trajectory-constrained optimal local time-continuous waveform controls for state transitions in $N$-level quantum systems

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