### 11731 results for qubit oscillator frequency

Contributors: S.N. Shevchenko, S. Ashhab, Franco Nori

Date: 2010-07-01

A transition between energy levels at an avoided crossing is known as a Landau–Zener transition. When a two-level system (TLS) is subject to periodic driving with sufficiently large amplitude, a sequence of transitions occurs. The phase accumulated between transitions (commonly known as the Stückelberg phase) may result in constructive or destructive interference. Accordingly, the physical observables of the system exhibit periodic dependence on the various system parameters. This phenomenon is often referred to as Landau–Zener–Stückelberg (LZS) interferometry. Phenomena related to LZS interferometry occur in a variety of physical systems. In particular, recent experiments on LZS interferometry in superconducting TLSs (**qubits**) have demonstrated the potential for using this kind of interferometry as an effective tool for obtaining the parameters characterizing the TLS as well as its interaction with the control fields and with the environment. Furthermore, strong driving could allow for fast and reliable control of the quantum system. Here we review recent experimental results on LZS interferometry, and we present related theory....(Color online) Same as in Fig. 6 (i.e. LZS interferometry with low-**frequency** driving), but including the effects of decoherence. The time averaged upper level occupation probability P+¯ was obtained numerically from the Bloch equations with the Hamiltonian (1). The dephasing time T2 is given by ωT2/(2π)=0.1 in (a), 1 in (b), 5 in (c) and T2=2T1 in (d). The relaxation time is given by ωT1/(2π)=10.
...(Color online) Same as in Fig. 7 (i.e. LZS interferometry with high-**frequency** driving), but including the effects of decoherence. The time-averaged upper diabatic state occupation probability P¯up is obtained numerically by solving the Bloch equations with the Hamiltonian (1). The dephasing time T2 is given by ωT2/(2π)=0.1 in (a), 0.5 in (b), 1 in (c) and T2=2T1 in (d). The relaxation time is given by ωT1/(2π)=103.
...Superconducting **qubits**...Stückelberg **oscillations**...(Color online) (a) Energy levels E versus the bias ε. The two solid curves (red and blue) represent the adiabatic energy levels, E±, which display avoided crossing with energy splitting Δ. The dashed lines show the crossing diabatic energy levels E↑,↓, corresponding to the diabatic states φ↑ and φ↓. (b) The bias ε represents the driving signal, and it **oscillates** between εmin=ε0−A and εmax=ε0+A with a sinusoidal time dependence: ε(t)=ε0+Asinωt.
...Parameters used in different experiments studying LZS interferometry: tunneling amplitude Δ, maximal driving amplitude Amax, and driving **frequency** ω in the units GHz×2π, minimal adiabaticity parameter δmin=Δ2/(4ωAmax), and maximal LZ probability PLZmax=exp(−2πδmin).
... A transition between energy levels at an avoided crossing is known as a Landau–Zener transition. When a two-level system (TLS) is subject to periodic driving with sufficiently large amplitude, a sequence of transitions occurs. The phase accumulated between transitions (commonly known as the Stückelberg phase) may result in constructive or destructive interference. Accordingly, the physical observables of the system exhibit periodic dependence on the various system parameters. This phenomenon is often referred to as Landau–Zener–Stückelberg (LZS) interferometry. Phenomena related to LZS interferometry occur in a variety of physical systems. In particular, recent experiments on LZS interferometry in superconducting TLSs (**qubits**) have demonstrated the potential for using this kind of interferometry as an effective tool for obtaining the parameters characterizing the TLS as well as its interaction with the control fields and with the environment. Furthermore, strong driving could allow for fast and reliable control of the quantum system. Here we review recent experimental results on LZS interferometry, and we present related theory.

Data types:

Contributors: Meng-Hsuan Chung

Date: 2015-04-01

Normalized primary-mode **frequencies** of the drag and lift coefficients a...In this paper, hydrodynamic force coefficients and wake vortex structures of uniform flow over a transversely **oscillating** circular cylinder beneath a free surface were numerically investigated by an adaptive Cartesian cut-cell/level-set method. At a fixed Reynolds number, 100, a series of simulations covering three Froude numbers, two submergence depths, and three **oscillation** amplitudes were performed over a wide range of **oscillation** **frequency**. Results show that, for a deeply submerged cylinder with sufficiently large **oscillation** amplitudes, both the lift amplitude jump and the lift phase sharp drop exist, not accompanied by significant changes of vortex shedding timing. The near-cylinder vortex structure changes when the lift amplitude jump occurs. For a cylinder **oscillating** beneath a free surface, larger **oscillation** amplitude or submergence depth causes higher time-averaged drag for **frequency** ratio (=**oscillation** **frequency**/natural vortex shedding **frequency**) greater than 1.25. All near-free-surface cases exhibit negative time-averaged lift the magnitude of which increases with decreasing submergence depth. In contrast to a deeply submerged cylinder, occurrences of beating in the temporal variation of lift are fewer for a cylinder **oscillating** beneath a free surface, especially for small submergence depth. For the highest Froude number investigated, the lift **frequency** is locked to the cylinder **oscillation** **frequency** for **frequency** ratios higher than one. The vortex shedding mode tends to be double-row for deep and single-row for shallow submergence. Proximity to the free surface would change or destroy the near-cylinder vortex structure characteristic of deep-submergence cases. The lift amplitude jump is smoother for smaller submergence depth. Similar to deep-submergence cases, the vortex shedding **frequency** is not necessarily the same as the primary-mode **frequency** of the lift coefficient. The **frequency** of the induced free surface wave is exactly the cylinder **oscillation** **frequency**. The trends of wave length variation with the Froude number and **frequency** ratio agree with those predicted by the linear theory of small-amplitude free surface waves....Time history of lift coefficient spanning three **oscillation** periods for a deeply submerged cylinder **oscillating** with A=0.4 and fe/fo=1.1 and 1.15. The dashed lines indicate the times when the cylinder moves to the highest position.
...Transverse **oscillation**...Definition of problem. U: inflow velocity, g: gravitational acceleration, D: cylinder diameter, A: amplitude of **oscillation**, fe: **frequency** of **oscillation**, h: distance between still fluid surface and cylinder top when the cylinder moves to the equilibrium position, ρi: mass density of the i-th fluid phase, μi: dynamic viscosity of the i-th fluid phase.
...Normalized beating **frequency** of lift coefficient (fb/fe), normalized vortex shedding **frequency** (fv/fe), and vortex structure number sequence (NS) for a deeply submerged cylinder **oscillating** with selected **frequency** ratios. The individual number in NS denotes the number of vortices which merge in the middle wake.
...Lift and drag coefficients as function of time for three **frequency** ratios with Fr=0.5, h=0.4, and A=0.4. Also shown is the time history of the vertical coordinate of the cylinder center. Te=1/fe is the prescribed **oscillation** period and tref some reference time when the cylinder reaches the highest position.
... In this paper, hydrodynamic force coefficients and wake vortex structures of uniform flow over a transversely **oscillating** circular cylinder beneath a free surface were numerically investigated by an adaptive Cartesian cut-cell/level-set method. At a fixed Reynolds number, 100, a series of simulations covering three Froude numbers, two submergence depths, and three **oscillation** amplitudes were performed over a wide range of **oscillation** **frequency**. Results show that, for a deeply submerged cylinder with sufficiently large **oscillation** amplitudes, both the lift amplitude jump and the lift phase sharp drop exist, not accompanied by significant changes of vortex shedding timing. The near-cylinder vortex structure changes when the lift amplitude jump occurs. For a cylinder **oscillating** beneath a free surface, larger **oscillation** amplitude or submergence depth causes higher time-averaged drag for **frequency** ratio (=**oscillation** **frequency**/natural vortex shedding **frequency**) greater than 1.25. All near-free-surface cases exhibit negative time-averaged lift the magnitude of which increases with decreasing submergence depth. In contrast to a deeply submerged cylinder, occurrences of beating in the temporal variation of lift are fewer for a cylinder **oscillating** beneath a free surface, especially for small submergence depth. For the highest Froude number investigated, the lift **frequency** is locked to the cylinder **oscillation** **frequency** for **frequency** ratios higher than one. The vortex shedding mode tends to be double-row for deep and single-row for shallow submergence. Proximity to the free surface would change or destroy the near-cylinder vortex structure characteristic of deep-submergence cases. The lift amplitude jump is smoother for smaller submergence depth. Similar to deep-submergence cases, the vortex shedding **frequency** is not necessarily the same as the primary-mode **frequency** of the lift coefficient. The **frequency** of the induced free surface wave is exactly the cylinder **oscillation** **frequency**. The trends of wave length variation with the Froude number and **frequency** ratio agree with those predicted by the linear theory of small-amplitude free surface waves.

Data types:

Contributors: Dae Sung Lee, Man Yeong Ha, Hyun Sik Yoon, S. Balachandar

Date: 2009-02-01

(a) Time-averaged drag coefficients, (b) r.m.s. of drag coefficients, and (c) r.m.s. of lift coefficients as a function of **frequency** ratio and distance between two cylinders.
...Instantaneous vorticity contours of two **oscillating** cylinders at Re=160, go=2, Ae=0.2, and fe/fo**=1.0. (a) present result, (b) results from Mahir and Rockwell (1996).
...Peak values of Fourier transforms of lift coefficients of two **oscillating** cylinders
...Drag and lift coefficients as a function of time for one **oscillating**.
...Wake patterns of two **oscillating** cylinders
...Flow around two **oscillating** cylinders in a side-by-side arrangement at Reynolds number (Re)=185 is simulated using the immersed boundary method. The purpose of this study is to investigate the combined effects of the gap between the two cylinders and their **oscillation** in the flow. The cylinders **oscillate** transversely to a uniform cross-flow with a prescribed sinusoidal function in the opposite direction, with the **oscillation** amplitude equal to 20% of the cylinder diameter. The gap between the two cylinders and the **oscillating** **frequency** are chosen as major variables for the parametric study to investigate their influence on the flow pattern. The ratio of mean gap distance between the two **oscillating** cylinders to the cylinder diameter is chosen to be 0.6, 1.0, 1.4, and 1.8, and the ratio of **oscillating** **frequencies** to the natural vortex shedding **frequency** of a fixed cylinder is 0.8, 1.0, and 1.2. Wake patterns and the drag and lift coefficients are described and compared with those from a single **oscillating** cylinder and two stationary cylinders. The wake patterns of two **oscillating** cylinders can be explained by flow mechanisms of two stationary cylinders, a single **oscillating** cylinder, and their combinations, and are in agreement with classifications of flow over two stationary cylinders presented in previous studies. In the case of two **oscillating** cylinders, the modulation phenomenon appears from a lower excitation **frequency** than in a single **oscillating** cylinder. Generally, **oscillating** cylinders have higher drag and root-mean-square (r.m.s.) values of drag coefficients than stationary cylinders....Forced **oscillation** ... Flow around two **oscillating** cylinders in a side-by-side arrangement at Reynolds number (Re)=185 is simulated using the immersed boundary method. The purpose of this study is to investigate the combined effects of the gap between the two cylinders and their **oscillation** in the flow. The cylinders **oscillate** transversely to a uniform cross-flow with a prescribed sinusoidal function in the opposite direction, with the **oscillation** amplitude equal to 20% of the cylinder diameter. The gap between the two cylinders and the **oscillating** **frequency** are chosen as major variables for the parametric study to investigate their influence on the flow pattern. The ratio of mean gap distance between the two **oscillating** cylinders to the cylinder diameter is chosen to be 0.6, 1.0, 1.4, and 1.8, and the ratio of **oscillating** **frequencies** to the natural vortex shedding **frequency** of a fixed cylinder is 0.8, 1.0, and 1.2. Wake patterns and the drag and lift coefficients are described and compared with those from a single **oscillating** cylinder and two stationary cylinders. The wake patterns of two **oscillating** cylinders can be explained by flow mechanisms of two stationary cylinders, a single **oscillating** cylinder, and their combinations, and are in agreement with classifications of flow over two stationary cylinders presented in previous studies. In the case of two **oscillating** cylinders, the modulation phenomenon appears from a lower excitation **frequency** than in a single **oscillating** cylinder. Generally, **oscillating** cylinders have higher drag and root-mean-square (r.m.s.) values of drag coefficients than stationary cylinders.

Data types:

Contributors: R. Ansari, F. Sadeghi, B. Motevalli

Date: 2013-03-01

Amongst possible new nanomechanical devices created based on carbon nanostructures, high-**frequency** nanoscale **oscillators**, or the so-called gigahertz **oscillators** have attracted much attention. In this paper, the oscillatory behavior of spherical fullerenes inside carbon nanotubes is thoroughly investigated. To this end, the continuum approximation together with Lennard-Jones potential is used to evaluate the van der Waals potential energy and interaction force. The equation of motion is directly solved based on the actual force distribution between the two nanostructures, without any simplifying assumption. A semi-analytical expression is obtained for the **oscillation** **frequency** into which the effect of initial conditions is incorporated. Thereafter, this newly derived expression is utilized in order to present a comprehensive study on the effects of different system variables such as geometrical parameters and initial conditions on the **oscillation** **frequency**. Based upon these studies, some new features of such **oscillations** have been revealed....Radius and mean surface density for spherical fullerenes and the corresponding CNT radius for stable **oscillations** [33,34].
...**Oscillation** **frequency** of C60-nanotube **oscillator** versus half length of nanotube.
...**Oscillation** **frequency**...**Oscillation** **frequency** against the initial velocity of fullerene (L=70Å).
...**Oscillation** **frequency** against the initial velocity of fullerene (RF=3.55Å).
...Variation of **frequency** with the difference between the amplitude and half length of nanotube (L=70Å).
... Amongst possible new nanomechanical devices created based on carbon nanostructures, high-**frequency** nanoscale **oscillators**, or the so-called gigahertz **oscillators** have attracted much attention. In this paper, the oscillatory behavior of spherical fullerenes inside carbon nanotubes is thoroughly investigated. To this end, the continuum approximation together with Lennard-Jones potential is used to evaluate the van der Waals potential energy and interaction force. The equation of motion is directly solved based on the actual force distribution between the two nanostructures, without any simplifying assumption. A semi-analytical expression is obtained for the **oscillation** **frequency** into which the effect of initial conditions is incorporated. Thereafter, this newly derived expression is utilized in order to present a comprehensive study on the effects of different system variables such as geometrical parameters and initial conditions on the **oscillation** **frequency**. Based upon these studies, some new features of such **oscillations** have been revealed.

Data types:

Contributors: H. Häffner, C.F. Roos, R. Blatt

Date: 2008-12-01

Generic level schemes of atoms for optical **qubits** (left) and radio-**frequency** **qubits** (right). In addition to the two **qubit** levels {|0〉,|1〉} usually a third rapidly decaying level is used for laser cooling and state read-out. While the optical **qubit** is typically manipulated on a quadrupole transition, radio-**frequency** **qubit** levels are connected with Raman-transitions.
...Rabi **oscillations** of a single Ca+ ion. Each dot represents 1000 experiments, each consisting of initialization, application of laser light on the **qubit** transition and state detection.
...Normal modes of a three-ion crystal along the axial direction with motional **frequencies** ωi.
...Energy level scheme of a single trapped ion with a ground (|g〉) and an excited (|e〉) level in a harmonic trap (**oscillator** states are labeled |0〉,|1〉,|2〉,…). Ω denotes the carrier Rabi **frequency**. The Rabi **frequency** on the blue sideband transition |0,e〉↔|1,g〉 transition is reduced by the Lamb-Dicke factor η as compared to the carrier transition (see Eq. (5)). The symbols ωqubit and ωt denote the **qubit** and the trap **frequency**, respectively.
...Quantum computers hold the promise of solving certain computational tasks much more efficiently than classical computers. We review recent experimental advances towards a quantum computer with trapped ions. In particular, various implementations of **qubits**, quantum gates and some key experiments are discussed. Furthermore, we review some implementations of quantum algorithms such as a deterministic teleportation of quantum information and an error correction scheme....Rabi **oscillation** on the blue sideband of the center-of-mass mode. The data were taken on a string of two 40Ca+ ions whose center-of-mass mode was cooled to the ground state. Only one of the ions was addressed. The population **oscillates** between the |S,0〉 and the |D,1〉 state of the addressed ion.
... Quantum computers hold the promise of solving certain computational tasks much more efficiently than classical computers. We review recent experimental advances towards a quantum computer with trapped ions. In particular, various implementations of **qubits**, quantum gates and some key experiments are discussed. Furthermore, we review some implementations of quantum algorithms such as a deterministic teleportation of quantum information and an error correction scheme.

Data types:

Contributors: Jong-Hoon Nam, Robert Fettiplace

Date: 2008-11-15

Entrainment of spontaneous **oscillation** by an external stimulus. (A) Sinusoidal forces were applied to a spontaneously **oscillating** hair cell bundle for three different stimulation conditions: one at the **frequency** of the spontaneous **oscillations** (FO=4kHz) and two for slightly lower **frequency** (3.5kHz). Thick lines are bundle tip displacements and thin red lines are external stimuli. Initial states of the bundle for the three simulations were the same and selected to have the opposite phase to the stimulus. (B) Bundle displacement in response to the three different stimuli in (A) averaged over 160 presentations (top two records) and 80 presentations (bottom record). Note that the response at FO (4kHz, top) builds up with a time constant of 0.7ms, indicative of a sharply tuned resonator. The bundle entrained poorly to the 3.5kHz stimulus at low level (middle), but at the higher level the force was sufficient to suppress the spontaneous movement and the bundle movement was entrained to the external stimulus. (C) A single cycle of bundle displacement (red line) averaged over 200ms of response compared to the force stimulus (black line), which was scaled for comparison with displacements. The bundle compliance obtained by dividing the displacement amplitude by the force amplitude is given beside each trace. (D) PSD plots for each response showing a sharply tuned response at FO (top). At 3.5kHz, the spectral density contains **frequency** components (both the spontaneous **oscillation** and the stimulus; middle). For the larger stimulus level at 3.5kHz, the spectral density is now dominated by the stimulus **frequency**.
...Effects of Ca2+ on the spontaneous **oscillation**. Different levels of the calcium concentration at the fast adaptation site were simulated. The bundle **oscillated** when the Ca2+ concentration at the fast adaptation site was between 12 and 30μM. Other parameters were identical to those given in Table 1. The hair bundle **oscillated** most strongly at 4kHz with Ca2+ of 20μM. The **oscillation** **frequency** increased from 3kHz to 4.5kHz as the Ca2+ concentration increased from 12 to 30μM. Note the “twitch-like” behavior at low Ca2+.
...Compressive nonlinearity demonstrated by entrainment to an external stimulus. The hair cell bundle was stimulated with sinusoidal forces with different **frequencies** (1–16kHz) and magnitudes (0.1–1000 pN). (A) Representative examples of average bundle tip displacements (solid lines) and force stimuli (broken lines) scaled for comparison with displacements for one stimulus cycle. Displacements were averaged cycle by cycle over 200ms of response. (B) Bundle displacement plotted against stimulation **frequency** for three different force magnitudes. Note the sharp tuning for small 1 pN stimuli and the broad tuning for the largest 100 pN stimuli. (C) Bundle displacement plotted against force magnitude at the **frequency** of the spontaneous **oscillations**, FO=4kHz. Note that the relationship displays a compressive nonlinearity for intermediate stimulus levels, is linear at low stimulus levels, and again approaches linearity (denoted by dashed line) at the highest levels. (D) Gain plotted against stimulation **frequency** for three different force magnitudes. Gain is defined as the ratio of the compliance under the stimulus conditions to the passive compliance with the MT channel blocked. (E) Gain plotted against force magnitude at the **frequency** of the spontaneous **oscillations**, FO=4kHz. The gain declines from a maximum of 50 at the lowest levels, approaching 1 (passive) at the highest levels.
...Determinant of **frequency**: KD, Ca2+ dissociation constant. (A) The hair bundle morphology of a rat high-**frequency** hair cell was used to create a new FE model. The hair bundle had more stereocilia of smaller maximum height, (2.4μm compared to 4.2μm) than the low-**frequency** bundle. (B) Spontaneous **oscillations** of bundle position and open probability. (C) PSD plots indicating sharply tuned **oscillations** at 23kHz. For these simulations, KD and CFA, the Ca2+ concentration near the open channel, were elevated five times. Other values as in Table 1 except: fCa=8 pN and f0, the intrinsic force difference between open and closed states=−15 pN.
...Substantial evidence exists for spontaneous **oscillations** of hair cell stereociliary bundles in the lower vertebrate inner ear. Since the **oscillations** are larger than expected from Brownian motion, they must result from an active process in the stereociliary bundle suggested to underlie amplification of the sensory input as well as spontaneous otoacoustic emissions. However, their low **frequency** (**frequency** **oscillations**, we used a finite-element model of the outer hair cell bundle incorporating previously measured mechanical parameters. Bundle motion was assumed to activate mechanotransducer channels according to the gating spring hypothesis, and the channels were regulated adaptively by Ca2+ binding. The model generated **oscillations** of freestanding bundles at 4kHz whose sharpness of tuning depended on the mechanotransducer channel number and location, and the Ca2+ concentration. Entrainment of the **oscillations** by external stimuli was used to demonstrate nonlinear amplification. The **oscillation** **frequency** depended on channel parameters and was increased to 23kHz principally by accelerating Ca2+ binding kinetics. Spontaneous **oscillations** persisted, becoming very narrow-band, when the hair bundle was loaded with a tectorial membrane mass....Effects of loading the hair bundle with a tectorial membrane mass. (A) Passive resonance of a low-**frequency** (solid circles) and a high-**frequency** (open circles) hair bundle in the absence of the tectorial membrane mass with MT channels blocked. The system behaves as a low-pass filter with corner **frequency** of 23kHz (solid circles) and 88kHz (open circles). The hair bundle was driven with a sinusoidal force stimulus of 100 pN amplitude at different **frequencies**. (B) Passive behavior of the same two hair bundles surmounted by a block of tectorial membrane. The block of tectorial membrane had a mass of 6.2×10−12 kg for the low-**frequency** location, which was decreased fourfold for the high-**frequency** location. The MT channels were blocked, so the system was not spontaneously active. Resonant **frequencies**: 5.1kHz (solid circles) and 21kHz (open circles). (C). The active hair bundles, incorporating MT channel gating, combined with the tectorial membrane mass generated narrow-band spontaneous **oscillations**. PSD function is plotted against **frequency**, giving FO=2.9kHz, Q=40 for the low-**frequency** location, and FO=14kHz, Q =110 for the high-**frequency** location.
... Substantial evidence exists for spontaneous **oscillations** of hair cell stereociliary bundles in the lower vertebrate inner ear. Since the **oscillations** are larger than expected from Brownian motion, they must result from an active process in the stereociliary bundle suggested to underlie amplification of the sensory input as well as spontaneous otoacoustic emissions. However, their low **frequency** (<100Hz) makes them unsuitable for amplification in birds and mammals that hear up to 5kHz or higher. To examine the possibility of high-**frequency** **oscillations**, we used a finite-element model of the outer hair cell bundle incorporating previously measured mechanical parameters. Bundle motion was assumed to activate mechanotransducer channels according to the gating spring hypothesis, and the channels were regulated adaptively by Ca2+ binding. The model generated **oscillations** of freestanding bundles at 4kHz whose sharpness of tuning depended on the mechanotransducer channel number and location, and the Ca2+ concentration. Entrainment of the **oscillations** by external stimuli was used to demonstrate nonlinear amplification. The **oscillation** **frequency** depended on channel parameters and was increased to 23kHz principally by accelerating Ca2+ binding kinetics. Spontaneous **oscillations** persisted, becoming very narrow-band, when the hair bundle was loaded with a tectorial membrane mass.

Data types:

Contributors: Henrik W. Schytz, Andreas Hansson, Dorte Phillip, Juliette Selb, David A. Boas, Helle K. Iversen, Messoud Ashina

Date: 2010-11-01

**Frequency** domain analysis in CAD
...**Frequency** domain analysis in ischemic stroke
...The etiology behind and physiological significance of spontaneous **oscillations** in the low-**frequency** spectrum in both systemic and cerebral vessels remain unknown. Experimental studies have proposed that spontaneous **oscillations** in cerebral blood flow reflect impaired cerebral autoregulation (CA). Analysis of CA by measurement of spontaneous **oscillations** in the low-**frequency** spectrum in cerebral vessels might be a useful tool for assessing risk and investigating different treatment strategies in carotid artery disease (CAD) and stroke. We reviewed studies exploring spontaneous **oscillations** in the low-**frequency** spectrum in patients with CAD and ischemic stroke, conditions known to involve impaired CA. Several studies have reported changes in **oscillations** after CAD and stroke after surgery and over time compared with healthy controls. Phase shift in the **frequency** domain and correlation coefficients in the time domain are the most frequently used parameters for analyzing spontaneous **oscillations** in systemic and cerebral vessels. At present, there is no gold standard for analyzing spontaneous **oscillations** in the low-**frequency** spectrum, and simplistic models of CA have failed to predict or explain the spontaneous **oscillation** changes found in CAD and stroke studies. Near-infrared spectroscopy is suggested as a future complementary tool for assessing changes affecting the cortical arterial system....low **frequency** **oscillations** ... The etiology behind and physiological significance of spontaneous **oscillations** in the low-**frequency** spectrum in both systemic and cerebral vessels remain unknown. Experimental studies have proposed that spontaneous **oscillations** in cerebral blood flow reflect impaired cerebral autoregulation (CA). Analysis of CA by measurement of spontaneous **oscillations** in the low-**frequency** spectrum in cerebral vessels might be a useful tool for assessing risk and investigating different treatment strategies in carotid artery disease (CAD) and stroke. We reviewed studies exploring spontaneous **oscillations** in the low-**frequency** spectrum in patients with CAD and ischemic stroke, conditions known to involve impaired CA. Several studies have reported changes in **oscillations** after CAD and stroke after surgery and over time compared with healthy controls. Phase shift in the **frequency** domain and correlation coefficients in the time domain are the most frequently used parameters for analyzing spontaneous **oscillations** in systemic and cerebral vessels. At present, there is no gold standard for analyzing spontaneous **oscillations** in the low-**frequency** spectrum, and simplistic models of CA have failed to predict or explain the spontaneous **oscillation** changes found in CAD and stroke studies. Near-infrared spectroscopy is suggested as a future complementary tool for assessing changes affecting the cortical arterial system.

Data types:

Contributors: C.N. Ofodum, P.N. Okeke

Date: 2016-02-02

Amplitude spectra of our entire data sets for HD 101065 acquired on HJD 2456460 – 6462. Panel (a) clearly shows the principal **frequency** of **oscillation** ν1=1.372867 mHz, and the secondary **frequency** ν2=0.954261 mHz. On pre-whitening ν1, we are left with ν2 in panel (b). Panel (c) gives the residuals after pre-whitening ν2. There is still evidence of further **frequencies** although below the detection criterion.
...Amplitude spectra of HD 101065 data acquired on HJD 2456460 – 6462. Panel (a) clearly shows the principal **frequency** of **oscillation** ν1=1.372867 mHz, and the secondary **frequency** ν2=0.954261 mHz. On pre-whitening ν1, we are left with ν2 in panel (b). Again, on pre-whitening ν2, we are left with low **frequency** residuals peaks in panel (c) which still suggests possible presence of further **oscillation** **frequencies**.
...A 9 h of observation through high-speed B photometry was carried out on HD 101065 using the 0.5-m telescope of the South African Astronomical Observatory (SAAO). These photometric data were obtained between 2013 April 21 and June 19, in search of temporal variations in the **oscillation** of HD 101065. The **frequency** analysis of our data sets shows that the known principal **frequency** of **oscillation** (ν1=1.37287 mHz) is still much intact. On nightly basis, we detected the presence of secondary **frequencies** (ν2) that are well resolved from the principal **frequency** (ν1) in the region of 1.0 mHz (P ∼ 17 min). These **frequencies** with very good signal-to-noise ratio have no harmonic period ratio with the principal **frequency** (ν1). Furthermore, the amplitude spectra of individual nights reveal that the newly detected **frequency** (ν2) is undergoing amplitude modulation on a short time-scale of few hours....The Non-linear least-square fit for the principal **frequency** ν1=1.372865 mHz. The JohnsonB amplitude of **oscillation** from year 1978 – 1988 were adopted from Martinez and Kurtz (1990), while that of year 2013 represent the amplitude and phase of **oscillation** secured from our combined data set (HJD 2456404 – 6462). Apart from year 2013 observation which has been analysed using 40-s integrations, 80-s integrations were used in all earlier observations adopted from Martinez and Kurtz (1990)).
...Stars: **oscillations**...The corresponding nightly amplitude spectra of HD 101065 on HJD 2456404 – 6462. Note the presence of resolved secondary **frequencies** ν2 in each panel around the region of 1 mHz. The known principal **oscillation** **frequency** ν1 is also present in all the panels, while 2ν1 which is the harmonic of ν1 appears marginally in panel (b) only.
...Non-linear least-square fit for the **frequencies** secured from our combined data set (HJD 2456404 – 6462).
... A 9 h of observation through high-speed B photometry was carried out on HD 101065 using the 0.5-m telescope of the South African Astronomical Observatory (SAAO). These photometric data were obtained between 2013 April 21 and June 19, in search of temporal variations in the **oscillation** of HD 101065. The **frequency** analysis of our data sets shows that the known principal **frequency** of **oscillation** (ν1=1.37287 mHz) is still much intact. On nightly basis, we detected the presence of secondary **frequencies** (ν2) that are well resolved from the principal **frequency** (ν1) in the region of 1.0 mHz (P ∼ 17 min). These **frequencies** with very good signal-to-noise ratio have no harmonic period ratio with the principal **frequency** (ν1). Furthermore, the amplitude spectra of individual nights reveal that the newly detected **frequency** (ν2) is undergoing amplitude modulation on a short time-scale of few hours.

Data types:

Contributors: R. Dickinson, S. Awaiz, M.A. Whittington, W.R. Lieb, N.P. Franks

Date: 2003-01-01

(A) The reduction in the **frequency** of the **oscillations** as a function of thiopental concentration. (B) The reduction in the **frequency** of the **oscillations** as a function of propofol concentration. (C) The reduction in the **frequency** of the **oscillations** as a function of ketamine concentration. Each point represents the mean of data from an average of 6 slices and the error bars are standard errors. The lines are least squares regressions. The data have been normalised such that the control **frequency** in the absence of anaesthetic is unity. The **frequency** (mean ± s.e.m) of the control response was 36.0 ± 0.1 Hz (n = 11) for the thiopental data, 38.0 ± 0.7 Hz (n = 21) for the propofol data and 33.8 ± 0.7 Hz (n = 38) for the ketamine data.
...40 Hz **oscillations**...The effect of the optical isomers of etomidate on the **oscillations**. Each point represents the mean of data from an average of 5 slices and the error bars are standard errors. The inactive S(−)-enantiomer had no significant effect on the **oscillation** **frequency** at concentrations up to 2.5 μM. The lines have been drawn by eye and have no theoretical significance. The data have been normalised such that the control **frequency** in the absence of anaesthetic is unity. The **frequency** (mean ± s.e.m) of the control response was 38.9 ± 0.6 Hz (n = 54).
...The effects of general anaesthetics and temperature on carbachol-evoked gamma **oscillations** in the rat hippocampal brain slice preparation were investigated. The **frequency** of the **oscillations** was found to be dependent on temperature in the range 32–25 °C, with a linear reduction in **frequency** from 40–17 Hz over this temperature range. The volatile anaesthetics isoflurane and halothane, and the intravenous anaesthetics thiopental, propofol and R(+)-etomidate caused a reduction in the **frequency** of the **oscillations**, in a concentration-dependent manner, over a range of clinically relevant concentrations. On the other hand, the intravenous agent ketamine and the “inactive” S(−)-isomer of etomidate had no significant effect on the **oscillation** **frequency**. The **oscillations** were markedly asymmetric over one cycle with a relatively rapid “rising” phase followed by a slower “decaying” phase. The decrease in **oscillation** **frequency** was due to an increase in the time-course of the “decaying phase” of the **oscillation** with little effect on the “rising” phase, consistent with the idea that carbachol-evoked gamma **oscillations** are trains of GABAergic inhibitory postsynaptic potentials and that the anaesthetics are acting postsynaptically at the GABAA receptor....(A) Representative traces from the same brain slice showing control **oscillations** (upper trace), **oscillations** in the presence of 1.4 vol% isoflurane (middle trace) and **oscillations** after washout of isoflurane (lower trace). (B) Power spectra of data from the same slice as in (A) showing the reduction in **frequency** in the presence of 1.4 vol% isoflurane.
...(A) Representative traces from the same brain slice showing control **oscillations** at 26 and 30 °C. (B) Power spectra of data from the same slice as in (A) showing the reduction in **oscillation** **frequency** at 26 °C compared to 30 °C. (C) Plot of **oscillation** **frequency** as a function of temperature. The line is a least squares regression. The data were recorded from 4 slices.
...Percentage change in carbachol-evoked gamma **oscillation** **frequency** and prolongation of IPSC time-course at clinical concentrations of anaesthetic
... The effects of general anaesthetics and temperature on carbachol-evoked gamma **oscillations** in the rat hippocampal brain slice preparation were investigated. The **frequency** of the **oscillations** was found to be dependent on temperature in the range 32–25 °C, with a linear reduction in **frequency** from 40–17 Hz over this temperature range. The volatile anaesthetics isoflurane and halothane, and the intravenous anaesthetics thiopental, propofol and R(+)-etomidate caused a reduction in the **frequency** of the **oscillations**, in a concentration-dependent manner, over a range of clinically relevant concentrations. On the other hand, the intravenous agent ketamine and the “inactive” S(−)-isomer of etomidate had no significant effect on the **oscillation** **frequency**. The **oscillations** were markedly asymmetric over one cycle with a relatively rapid “rising” phase followed by a slower “decaying” phase. The decrease in **oscillation** **frequency** was due to an increase in the time-course of the “decaying phase” of the **oscillation** with little effect on the “rising” phase, consistent with the idea that carbachol-evoked gamma **oscillations** are trains of GABAergic inhibitory postsynaptic potentials and that the anaesthetics are acting postsynaptically at the GABAA receptor.

Data types:

Contributors: Fankong Meng, Moran Wang, Zhixin Li

Date: 2008-08-01

qy,ave/qy,cond for various **frequencies** (p1/pm=0.01, ks1/kf=1/12, ks2/kf=1/2).
...The thermal lattice Boltzmann method (LBM) is used to simulate the conjugate heat transfer of high-**frequency** **oscillating** flows between two flat plates with different outer surface temperatures. The thermal boundary condition at the fluid–solid interface assumes that the unknown energy distribution functions of the fluid and the solid are in equilibrium with the counter-slip internal energy. The counter-slip internal energy was determined by constraints in the continuities of temperature and heat flux at the solid–fluid interface. Velocity, temperature and heat flux distributions are presented for various Stokes numbers, pressure **oscillation** amplitudes and plate to fluid thermal conductivity ratios. For relatively low-**frequency** **oscillations** (30kHz) and small pressure amplitudes, the periodically averaged heat fluxes of the **oscillating** flow are almost equal to those of pure heat conduction. The averaged heat flux of the **oscillating** flow decreases with increasing pressure amplitudes and are less than those of pure heat conduction for relatively low **frequencies** (30kHz) and large pressure amplitude **oscillations**. For high-**frequency** **oscillations**, the heat transfer is enhanced markedly by nonlinear acoustic streaming, where the average velocity rapidly increases with **frequency**....**Oscillating** flow...uave for various **frequencies** (p1/pm=0.01, ks1/kf=1/12, ks2/kf=1/2).
... The thermal lattice Boltzmann method (LBM) is used to simulate the conjugate heat transfer of high-**frequency** **oscillating** flows between two flat plates with different outer surface temperatures. The thermal boundary condition at the fluid–solid interface assumes that the unknown energy distribution functions of the fluid and the solid are in equilibrium with the counter-slip internal energy. The counter-slip internal energy was determined by constraints in the continuities of temperature and heat flux at the solid–fluid interface. Velocity, temperature and heat flux distributions are presented for various Stokes numbers, pressure **oscillation** amplitudes and plate to fluid thermal conductivity ratios. For relatively low-**frequency** **oscillations** (30kHz) and small pressure amplitudes, the periodically averaged heat fluxes of the **oscillating** flow are almost equal to those of pure heat conduction. The averaged heat flux of the **oscillating** flow decreases with increasing pressure amplitudes and are less than those of pure heat conduction for relatively low **frequencies** (30kHz) and large pressure amplitude **oscillations**. For high-**frequency** **oscillations**, the heat transfer is enhanced markedly by nonlinear acoustic streaming, where the average velocity rapidly increases with **frequency**.

Data types: