82 results for qubit oscillator frequency
Contributors: D'Andola, Mattia, Giulioni, Massimiliano, Dante, Vittorio, Del Giudice, Paolo, Sanchez-Vives, Maria V.
frequency determined by the experimenter.Methods: The cortical activity...frequency was set, the frequency of the slow oscillation was steered through...oscillations...frequency of slow oscillations (SO) spontaneously generated by the cortical...frequency of SO can be controlled by direct current (DC) electric fields...oscillations—an activity pattern that is associated with cognitive processes ... Background: We present a closed-loop system able to control the frequency of slow oscillations (SO) spontaneously generated by the cortical network in vitro. The frequency of SO can be controlled by direct current (DC) electric fields within a certain range. Here we set out to design a system that would be able to autonomously bring the emergent oscillatory activity to a target frequency determined by the experimenter.Methods: The cortical activity was recorded through an electrode and was analyzed online. Once a target frequency was set, the frequency of the slow oscillation was steered through the injection of DC of variable intensity that generated electric fields of proportional amplitudes in the brain slice. To achieve such closed-loop control, we designed a custom programmable stimulator ensuring low noise and accurate tuning over low current levels. For data recording and analysis, we relied on commercial acquisition and software tools.Results: The result is a flexible and reliable system that ensures control over SO frequency in vitro. The system guarantees artifact removal, minimal gaps in data acquisition and robustness in spite of slice heterogeneity.Conclusions: Our tool opens new possibilities for the investigation of dynamics of cortical slow oscillations—an activity pattern that is associated with cognitive processes such as memory consolidation, and that is altered in several neurological conditions—and also for potential applications of this technology.
Data from: The impact of pathological high-frequency oscillations on hippocampal network activity in rats with chronic epilepsy
Contributors: Ewell, Laura A., Fischer, Kyle B., Leibold, Christian, Leutgeb, Stefan, Leutgeb, Jill K.
oscillations, which by comparison to control animals we could classify...high-frequency oscillations (pHFOs) during interictal periods. To understand...oscillations in overlapping frequency bands and potentially perturb hippocampal...oscillations ... In epilepsy, brain networks generate pathological high-frequency oscillations (pHFOs) during interictal periods. To understand how pHFOs differ from normal oscillations in overlapping frequency bands and potentially perturb hippocampal processing, we performed high-density single unit and local field potential recordings from hippocampi of behaving rats with and without chronic epilepsy. In epileptic animals, we observed two types of co-occurring fast oscillations, which by comparison to control animals we could classify as ‘ripple-like’ or ‘pHFO’. We compared their spectral characteristics, brain state dependence, and cellular participants. Strikingly, pHFO occurred irrespective of brain state, were associated with interictal spikes, engaged distinct subnetworks of principal neurons compared to ripple-like events, increased the sparsity of network activity, and initiated both general and immediate disruptions in spatial information coding. Taken together, our findings suggest that events that result in pHFOs have an immediate impact on memory processes, corroborating the need for proper classification of pHFOs to facilitate therapeutic interventions that selectively target pathological activity.
Data for: A Method for Selection of Structural Theories for Low to High Frequency Vibration Analyses
Contributors: Mostafa Sadeghmanesh, Hassan Haddadpour, Hossein M. Navazi, Mohammad Tahaye Abadi
Frequency Oscillations...FREQUENCIES...Frequency Vibration Analyses HIGHER-ORDER WAVE PARAMETERS OF FLEXURAL ... A Method for Selection of Structural Theories for Low to High Frequency Vibration Analyses HIGHER-ORDER WAVE PARAMETERS OF FLEXURAL BEAM VIBRATION FROM LOW TO HIGH FREQUENCIES
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Contributors: Farzad Rafieian, François Girardin, Zhaoheng Liu, Marc Thomas, Bruce Hazel
frequency clearly indicates the impacting nature of the process and captures...oscillations. (For interpretation of the references to color in this figure...high-frequency repeating impacts in robotic grinding (detailed views)....frequency in single-pass grinding (overview). (For interpretation of the...frequency...frequency in Test (3) at 4500rpm. (For interpretation of the references...high-frequency impacts that mainly last for only a small fraction of the ... In a robotic machining process, a light-weight cutter or grinder is usually held by an articulated robot arm. Material removal is achieved by the rotating cutting tool while the robot end effector ensures that the tool follows a programmed trajectory in order to work on complex curved surfaces or to access hard-to-reach areas. One typical application of such process is maintenance and repair work on hydropower equipment. This paper presents an experimental study of the dynamic characteristics of material removal in robotic grinding, which is unlike conventional grinding due to the lower structural stiffness of the tool-holder robot. The objective of the study is to explore the cyclic nature of this mechanical operation to provide the basis for future development of better process control strategies. Grinding tasks that minimize the number of iterations to converge to the target surface can be better planned based on a good understanding and modeling of the cyclic material removal mechanism. A single degree of freedom dynamic analysis of the process suggests that material removal is performed through high-frequency impacts that mainly last for only a small fraction of the grinding disk rotation period. To detect these discrete cutting events in practice, a grinder is equipped with a rotary encoder. The encoder's signal is acquired through the angular sampling technique. A running cyclic synchronous average is applied to the speed signal to remove its non-cyclic events. The measured instantaneous rotational frequency clearly indicates the impacting nature of the process and captures the transient response excited by these cyclic impacts. The technique also locates the angular positions of cutting impacts in revolution cycles. It is thus possible to draw conclusions about the cyclic nature of dynamic changes in impact-cutting behavior when grinding with a flexible robot. The dynamics of the impacting regime and transient responses to impact-cutting excitations captured synchronously using the angular sampling technique provide feedback that can be used to regulate the material removal process. The experimental results also make it possible to correlate the energy required to remove a chip of metal through impacting with the measured drop in angular speed during grinding.
Contributors: Lin, Genghong, Jiao, Feng, Sun, Qiwen, Tang, Moxun, Yu, Jianshe, Zhou, Zhan
Oscillation and noise filtration...frequency, but the magnitude decreases in the frequency and is almost...oscillation and the noise in the random promoter state selection, as observed...oscillate periodically, $m(t)$ also oscillates later, almost periodically...frequencies. This gives a surprising indication that multiple promoter ... The transcription of inducible genes involves signaling pathways that induce DNA binding of the downstream transcription factors to form functional promoter states. How the transcription dynamics is linked to the temporal variations of activation signals is far to be fully understood. In this work, we develop a mathematical model with multiple promoter states to address this question. Each promoter state has its own activation and inactivation rates, and is selected randomly with a probability that may change in time. Under the activation of constant signals, our analysis shows that if only the activation rates differ among the promoter states, then the mean transcription level $m(t)$ displays only a monotone or monophasic growth pattern. In a sharp contrast, if the inactivation rates change with the promoter states, then $m(t)$ may display multiphasic growth patterns. Upon the activation of signals that oscillate periodically, $m(t)$ also oscillates later, almost periodically in the same frequency, but the magnitude decreases in the frequency and is almost completely attenuated at large frequencies. This gives a surprising indication that multiple promoter states could filter out the signal oscillation and the noise in the random promoter state selection, as observed in the transcription of a gene activated by p53 in breast carcinoma cells. Our approach may help develop a theoretical framework to integrate coherently the genetic circuit with the promoter states to elucidate the linkage from the activation signal to the temporal profile of transcription outputs.
Contributors: Rego Costa, Artur, Débarre, Florence, Chevin, Luis-Miguel
frequency-dependent selection caused by competitive interactions mediated...frequency of chaos at each simulation time point for different values ...oscillating optimum for d = 70....oscillations of an optimal phenotype interacts with the internal dynamics...oscillations. In contrast, weak forcing can increase the probability of...oscillating optimum for d = 40. ... Among the factors that may reduce the predictability of evolution, chaos, characterized by a strong dependence on initial conditions, has received much less attention than randomness due to genetic drift or environmental stochasticity. It was recently shown that chaos in phenotypic evolution arises commonly under frequency-dependent selection caused by competitive interactions mediated by many traits. This result has been used to argue that chaos should often make evolutionary dynamics unpredictable. However, populations also evolve largely in response to external changing environments, and such environmental forcing is likely to influence the outcome of evolution in systems prone to chaos. We investigate how a changing environment causing oscillations of an optimal phenotype interacts with the internal dynamics of an eco-evolutionary system that would be chaotic in a constant environment. We show that strong environmental forcing can improve the predictability of evolution, by reducing the probability of chaos arising, and by dampening the magnitude of chaotic oscillations. In contrast, weak forcing can increase the probability of chaos, but it also causes evolutionary trajectories to track the environment more closely. Overall, our results indicate that, although chaos may occur in evolution, it does not necessarily undermine its predictability.
Contributors: Schanz, Ansgar, Hocke, Klemens, Kämpfer, Niklaus
oscillations is challenging. However, dynamical responses to short-term...oscillations. Two simulations were conducted with short-term solar forcing...oscillation comes along with other periods of the extra-long period wave ... The Whole Atmosphere Community Climate Model was used to investigate the influences of solar fluctuations on zonal wind oscillations. Two simulations were conducted with short-term solar forcing (<35 days) on and off. We found that a 27-day wave is an inherent feature of the atmosphere when the short-term solar forcing is inactive. This internal 27-day oscillation comes along with other periods of the extra-long period wave band (20–40 days) and cannot be linked to the Sun’s rotation period. When the short-term solar variability is part of the forcing, including the solar 27-day periodicity, it affects a wide range of the spectrum of zonal wind. At mid-latitudes, a 10-day wave emerges by the short-term solar forcing, which suggests that indirect and nonlinear interactions are involved. Solar short-term variability seems to generate atmospheric perturbations that interact with modes of the internal wave spectrum or the background mean flow. A robust and clear solar interpretation of these wind oscillations is challenging. However, dynamical responses to short-term solar variability exist and need further investigation.
Contributors: Cliff Orori Mosiori
frequencies just like those under seismic wave interactions and this work...oscillations are expected to behave in cylinder carrying a suspended mass...oscillator in a cylindrical acoustic medium that allow such waves to be...Oscillations ... Free vibrating motion can take place in an acoustic media. This motion can be steady hence have constant periodic variations or unsteady and thus experience light damping or heavy damping. We give a modeled analysis of unsteady periodic motion of an oscillator in a cylindrical acoustic medium that allow such waves to be transmitted through them. This has been approached by calculating variation within the proposed boundary functions and boundary potentials. Limitations for these calculations have been done depending on the time, and how free oscillations are expected to behave in cylinder carrying a suspended mass. This work investigated motion by constructions that interact with their environment with the acoustic media. Since the dynamics considered here were very complex, modeling the system with one grade of free motion and applying different types of constructions whether ground, underground, cylindrical, spherical constructions and containers was considered. This work borrowed heavily on the modeling of seismic and blast waves as modeled with rigid inclusions containing elastically fastened mass interacting continuous solid medium. This study joined motion of any continuous medium with other discrete systems. The results displayed measurement systems for wave processes having interference at their eigen- frequencies just like those under seismic wave interactions and this work considered the result as similar to those in discrete systems.
Contributors: Uzundag Murat, Silvotti Roberto, Baran Andrzej, Vuckovic Maja, Ostensen Roy, Reed Mike
frequencies. K2 dataset had revealed that HD 4539 is a hybrid pulsator...frequency region (>2000 µHz) consists of only 9 pressure p - modes. We...low-frequency region (<2000 µHz) includes at least 144 independent g - ... We analysed one of the brightest pulsating subdwarf B star, HD 4539 (=EPIC 220641886). The star was observed by the Kepler Spacecraft during K2 mission at Campaign 8. The full K2 data set spans ∼ 80 days, and from this we extract 153 signicant pulsation frequencies. K2 dataset had revealed that HD 4539 is a hybrid pulsator sdB giving it a rich asteroseismic potential. The amplitude spectrum of the star displays a rich content of gravity (g) - modes. The low-frequency region (2000 µHz) consists of only 9 pressure p - modes. We used asymptotic period spacing to identify the modal degree of the majority of the modes, ranging from l = 1 to l = 12, apart from l = 3 and l = 11 modes, that are not seen. For the rst time in a subdwarf B pulsator, the identication of the modes seems quite robust up to l = 6.
Physiological cyclic hydrostatic pressure induces osteogenic lineage commitment of human bone marrow stem cells: a systematic study
Contributors: Stavenschi, Elena, Corrigan, Michele A., Johnson, Gillian P., Riffault, Mathieu, Hoey, David A.
frequency and cultured statically for an additional 1–2 weeks. Pressure-induced...frequency regimes (2 Hz). Interestingly, long-term mechanical stimulation...frequency-dependent manner, that is gene specific. COX2 expression elicited...frequencies of 0.5 Hz, 1 Hz and 2 Hz for 1 h, 2 h and 4 h of stimulation...frequency elicited a magnitude-dependent release of ATP; however, all ... Background: Physical loading is necessary to maintain bone tissue integrity. Loading-induced fluid shear is recognised as one of the most potent bone micromechanical cues and has been shown to direct stem cell osteogenesis. However, the effect of pressure transients, which drive fluid flow, on human bone marrow stem cell (hBMSC) osteogenesis is undetermined. Therefore, the objective of the study is to employ a systematic analysis of cyclic hydrostatic pressure (CHP) parameters predicted to occur in vivo on early hBMSC osteogenic responses and late-stage osteogenic lineage commitment.Methods: hBMSC were exposed to CHP of 10 kPa, 100 kPa and 300 kPa magnitudes at frequencies of 0.5 Hz, 1 Hz and 2 Hz for 1 h, 2 h and 4 h of stimulation, and the effect on early osteogenic gene expression of COX2, RUNX2 and OPN was determined. Moreover, to decipher whether CHP can induce stem cell lineage commitment, hBMSCs were stimulated for 4 days for 2 h/day using 10 kPa, 100 kPa and 300 kPa pressures at 2 Hz frequency and cultured statically for an additional 1–2 weeks. Pressure-induced osteogenesis was quantified based on ATP release, collagen synthesis and mineral deposition.Results: CHP elicited a positive, but variable, early osteogenic response in hBMSCs in a magnitude- and frequency-dependent manner, that is gene specific. COX2 expression elicited magnitude-dependent effects which were not present for RUNX2 or OPN mRNA expression. However, the most robust pro-osteogenic response was found at the highest magnitude (300 kPa) and frequency regimes (2 Hz). Interestingly, long-term mechanical stimulation utilising 2 Hz frequency elicited a magnitude-dependent release of ATP; however, all magnitudes promoted similar levels of collagen synthesis and significant mineral deposition, demonstrating that lineage commitment is magnitude independent. This therefore demonstrates that physiological levels of pressures, as low as 10 kPa, within the bone can drive hBMSC osteogenic lineage commitment.Conclusion: Overall, these findings demonstrate an important role for cyclic hydrostatic pressure in hBMSCs and bone mechanobiology, which should be considered when studying pressure-driven fluid shear effects in hBMSCs mechanobiology. Moreover, these findings may have clinical implication in terms of bioreactor-based bone tissue engineering strategies.