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Stephen J Blundell - One of the best experts on this subject based on the ideXlab platform.
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will spin relaxation times in molecular magnets permit quantum information processing
Physical Review Letters, 2007Co-Authors: Arzhang Ardavan, Stephen J Blundell, Olivier Rival, John J L Morton, Alexei M Tyryshkin, Grigore A Timco, Richard E P WinpennyAbstract:Using $X$-band pulsed electron-spin resonance, we report the intrinsic spin-lattice (${T}_{1}$) and Phase-Coherence (${T}_{2}$) relaxation times in molecular nanomagnets for the first time. In ${\mathrm{Cr}}_{7}M$ heterometallic wheels, with $M=\mathrm{Ni}$ and Mn, Phase-Coherence relaxation is dominated by the coupling of the electron spin to protons within the molecule. In deuterated samples ${T}_{2}$ reaches $3\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ at low temperatures, which is several orders of magnitude longer than the duration of spin manipulations, satisfying a prerequisite for the deployment of molecular nanomagnets in quantum information applications.
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Will Spin-Relaxation Times in Molecular Magnets Permit Quantum Information Processing?
Physical Review Letters, 2007Co-Authors: Stephen J BlundellAbstract:Using X-band pulsed electron-spin resonance, we report the intrinsic spin-lattice (T1) and Phase-Coherence (T2) relaxation times in molecular nanomagnets for the first time. In Cr7M heterometallic wheels, with M=Ni and Mn, Phase-Coherence relaxation is dominated by the coupling of the electron spin to protons within the molecule. In deuterated samples T2 reaches 3 μs at low temperatures, which is several orders of magnitude longer than the duration of spin manipulations, satisfying a prerequisite for the deployment of molecular nanomagnets in quantum information applications.
Richard E P Winpenny - One of the best experts on this subject based on the ideXlab platform.
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will spin relaxation times in molecular magnets permit quantum information processing
Physical Review Letters, 2007Co-Authors: Arzhang Ardavan, Stephen J Blundell, Olivier Rival, John J L Morton, Alexei M Tyryshkin, Grigore A Timco, Richard E P WinpennyAbstract:Using $X$-band pulsed electron-spin resonance, we report the intrinsic spin-lattice (${T}_{1}$) and Phase-Coherence (${T}_{2}$) relaxation times in molecular nanomagnets for the first time. In ${\mathrm{Cr}}_{7}M$ heterometallic wheels, with $M=\mathrm{Ni}$ and Mn, Phase-Coherence relaxation is dominated by the coupling of the electron spin to protons within the molecule. In deuterated samples ${T}_{2}$ reaches $3\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ at low temperatures, which is several orders of magnitude longer than the duration of spin manipulations, satisfying a prerequisite for the deployment of molecular nanomagnets in quantum information applications.
Aneta Stefanovska - One of the best experts on this subject based on the ideXlab platform.
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oscillatory dynamics of vasoconstriction and vasodilation identified by time localized Phase Coherence
Physics in Medicine and Biology, 2011Co-Authors: Lawrence W. Sheppard, Peter V E Mcclintock, Vesna Vuksanovic, Aneta StefanovskaAbstract:We apply wavelet-based time-localized Phase Coherence to investigate the relationship between blood flow and skin temperature, and between blood flow and instantaneous heart rate (IHR), during vasoconstriction and vasodilation provoked by local cooling or heating of the skin. A temperature-controlled metal plate (approximately 10 cm2) placed on the volar side of the left arm was used to provide the heating and cooling. Beneath the plate, the blood flow was measured by laser Doppler flowmetry and the adjacent skin temperature by a thermistor. Two 1 h datasets were collected from each of the ten subjects. In each case a 30 min basal recording was followed by a step change in plate temperature, to either 24 °C or 42 °C. The IHR was derived from simultaneously recorded ECG. We confirm the changes in the energy and frequency of blood flow oscillations during cooling and heating reported earlier. That is, during cooling, there was a significant decrease in the average frequency of myogenic blood flow oscillations (p < 0.05) and the myogenic spectral peak became more prominent. During heating, there was a significant (p < 0.05) general increase in spectral energy, associated with vasodilation, except in the myogenic interval. Weak Phase Coherence between temperature and blood flow was observed for unperturbed skin, but it increased in all frequency intervals as a result of heating. It was not significantly affected by cooling. We also show that significant (p < 0.05) Phase Coherence exists between blood flow and IHR in the respiratory and myogenic frequency intervals. Cooling did not affect this Phase Coherence in any of the frequency intervals, whereas heating enhanced the Phase Coherence in the respiratory and myogenic intervals. This can be explained by the reduction in vascular resistance produced by heating, a process where myogenic mechanisms play a key role. We conclude that the mechanisms of vasodilation and vasoconstriction, in response to temperature change, are oscillatory in nature and are independent of central sources of variability.
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Oscillatory dynamics of vasoconstriction and vasodilation identified by time-localized Phase Coherence.
Physics in medicine and biology, 2011Co-Authors: Lawrence W. Sheppard, Peter V E Mcclintock, Vesna Vuksanović, Aneta StefanovskaAbstract:We apply wavelet-based time-localized Phase Coherence to investigate the relationship between blood flow and skin temperature, and between blood flow and instantaneous heart rate (IHR), during vasoconstriction and vasodilation provoked by local cooling or heating of the skin. A temperature-controlled metal plate (approximate to 10 cm(2)) placed on the volar side of the left arm was used to provide the heating and cooling. Beneath the plate, the blood flow was measured by laser Doppler flowmetry and the adjacent skin temperature by a thermistor. Two 1 h datasets were collected from each of the ten subjects. In each case a 30 min basal recording was followed by a step change in plate temperature, to either 24 degrees C or 42 degrees C. The IHR was derived from simultaneously recorded ECG. We confirm the changes in the energy and frequency of blood flow oscillations during cooling and heating reported earlier. That is, during cooling, there was a significant decrease in the average frequency of myogenic blood flow oscillations (p < 0.05) and the myogenic spectral peak became more prominent. During heating, there was a significant (p < 0.05) general increase in spectral energy, associated with vasodilation, except in the myogenic interval. Weak Phase Coherence between temperature and blood flow was observed for unperturbed skin, but it increased in all frequency intervals as a result of heating. It was not significantly affected by cooling. We also show that significant (p < 0.05) Phase Coherence exists between blood flow and IHR in the respiratory and myogenic frequency intervals. Cooling did not affect this Phase Coherence in any of the frequency intervals, whereas heating enhanced the Phase Coherence in the respiratory and myogenic intervals. This can be explained by the reduction in vascular resistance produced by heating, a process where myogenic mechanisms play a key role. We conclude that the mechanisms of vasodilation and vasoconstriction, in response to temperature change, are oscillatory in nature and are independent of central sources of variability.
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wavelet Phase Coherence analysis application to skin temperature and blood flow
Cardiovascular Engineering, 2004Co-Authors: A Bandrivskyy, Alan Bernjak, Peter V E Mcclintock, Aneta StefanovskaAbstract:The technique of wavelet Phase Coherence analysis is introduced and used to explore relationships between oscillations on blood flow and temperature in the skin of 10 healthy subjects. Their skin temperature and blood flow were continuously recorded: under basal conditions for 30 min; during local cooling of the skin with an ice-pack for 20 min: and 30 min thereafter. The group mean basal skin temperature of 33.4°C was decreased to 29.2°C during the cooling period, and had recovered to 32.1°C by the end of the recording. The wavelet transform was used to obtain the time–frequency content of the two signals, and their Coherence. It is shown that cooling increases Coherence to a statistically significant extent in two frequency intervals, around 0.007 and 0.1 Hz, suggesting that these oscillatory components are involved in the regulation of skin temperature when cold is applied as a stress.
Arzhang Ardavan - One of the best experts on this subject based on the ideXlab platform.
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will spin relaxation times in molecular magnets permit quantum information processing
Physical Review Letters, 2007Co-Authors: Arzhang Ardavan, Stephen J Blundell, Olivier Rival, John J L Morton, Alexei M Tyryshkin, Grigore A Timco, Richard E P WinpennyAbstract:Using $X$-band pulsed electron-spin resonance, we report the intrinsic spin-lattice (${T}_{1}$) and Phase-Coherence (${T}_{2}$) relaxation times in molecular nanomagnets for the first time. In ${\mathrm{Cr}}_{7}M$ heterometallic wheels, with $M=\mathrm{Ni}$ and Mn, Phase-Coherence relaxation is dominated by the coupling of the electron spin to protons within the molecule. In deuterated samples ${T}_{2}$ reaches $3\text{ }\text{ }\ensuremath{\mu}\mathrm{s}$ at low temperatures, which is several orders of magnitude longer than the duration of spin manipulations, satisfying a prerequisite for the deployment of molecular nanomagnets in quantum information applications.
Joachim Saur - One of the best experts on this subject based on the ideXlab platform.
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Phase Coherence classification a new wavelet based method to separate local field potentials into local in coherent and volume conducted components
Journal of Neuroscience Methods, 2017Co-Authors: Michael Von Papen, Haidar S Dafsari, Esther Florin, Felix Gerick, Lars Timmermann, Joachim SaurAbstract:Abstract Background Local field potentials (LFP) reflect the integrated electrophysiological activity of large neuron populations and may thus reflect the dynamics of spatially and functionally different networks. New method We introduce the wavelet-based Phase-Coherence classification (PCC), which separates LFP into volume-conducted, local incoherent and local coherent components. It allows to compute power spectral densities for each component associated with local or remote electrophysiological activity. Results We use synthetic time series to estimate optimal parameters for the application to LFP from within the subthalamic nucleus of eight Parkinson patients. With PCC we identify multiple local tremor clusters and quantify the relative power of local and volume-conducted components. We analyze the electrophysiological response to an apomorphine injection during rest and hold. Here we show medication-induced significant decrease of incoherent activity in the low beta band and increase of coherent activity in the high beta band. On medication significant movement-induced changes occur in the high beta band of the local coherent signal. It increases during isometric hold tasks and decreases during phasic wrist movement. Comparison with existing methods The power spectra of local PCC components is compared to bipolar recordings. In contrast to bipolar recordings PCC can distinguish local incoherent and coherent signals. We further compare our results with classification based on the imaginary part of coherency and the weighted Phase lag index. Conclusions The low and high beta band are more susceptible to medication- and movement-related changes reflected by incoherent and local coherent activity, respectively. PCC components may thus reflect functionally different networks.
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Phase Coherence classification a new wavelet based method to separate local field potentials into local in coherent and volume conducted components
bioRxiv, 2016Co-Authors: Michael Von Papen, Haidar S Dafsari, Esther Florin, Felix Gerick, Lars Timmermann, Joachim SaurAbstract:Local field potentials (LFP) reflect the integrated electrophysiological activity of a large group of neurons. To minimize influence of external activity on the analysis, conventionally bipolar recordings are used to eliminate volume-conducted signals. Here we introduce a novel method, called Phase-Coherence classification (PCC), to separate LFP in time-frequency domain into a volume-conducted, a local incoherent and local coherent signal. The PCC allows to compute the power spectral densities of each signal and to associate each class with possible locations of electrophysiological activity. In order to test the resolution properties and accuracy of the method we generate composite and non-stationary synthetic time series with similar statistical characteristics as measured LFP. The PCC identifies volume-conducted signals with a Phase threshold that is determined from probability density functions of non-Phase-shifted synthetic time series. We estimate optimal PCC parameters for the analysis of beta band oscillations in LFP and apply the PCC to a test data set obtained from within the subthalamic nucleus of eight patients with Parkinson's disease (PD). We show that PCC can identify activity of multiple local clusters during a tremor episode and quantify the relative power of local and volume-conducted signals. We further analyze the electrophysiological response to an apomorphine injection during rest and show that incoherent activity in the low beta band shows a significant medication-induced decrease. We further find significant movement-induced changes on medication of the local coherent signal, which increased during an isometric hold task and decreased during phasic wrist movement. This indicates a different role of incoherent and coherent signals possibly related to physiologically different networks. This new PCC method can potentially also be applied to EEG and MEG data in order to minimize the influence of spatial leakage on power spectra and Coherence estimates.