A state space modeling approach to real-time phase estimation

Brain rhythms have been proposed to facilitate brain function, with an especially important role attributed to the phase of low frequency rhythms. Understanding the role of phase in neural function requires interventions that perturb neural activity at a target phase, necessitating estimation of phase in real-time. Current methods for real-time phase estimation rely on bandpass filtering, which assumes narrowband signals and couples the signal and noise in the phase estimate, adding noise to the phase and impairing detections of relationships between phase and behavior. To address this, we propose a state space phase estimator for real-time tracking of phase. By tracking the analytic signal as a latent state, this framework avoids the requirement of bandpass filtering, separately models the signal and the noise, accounts for rhythmic confounds, and provides credible intervals for the phase estimate. We demonstrate in simulations that the state space phase estimator outperforms current state-of-the-art real-time methods in the contexts of common confounds such as broadband rhythms, phase resets and co-occurring rhythms. Finally, we show applications of this approach to in vivo data. The method is available as a ready-to-use plug-in for the OpenEphys acquisition system, making it widely available for use in experiments.

A State Space Modeling Approach to Real-Time Phase Estimation

Brain rhythms have been proposed to facilitate brain function, with an especially important role attributed to the phase of low frequency rhythms. Understanding the role of phase in neural function requires interventions that perturb neural activity at a target phase, necessitating estimation of phase in real-time. Current methods for real-time phase estimation rely on bandpass filtering, which assumes narrowband signals and couples the signal and noise in the phase estimate, adding noise to the phase and impairing detections of relationships between phase and behavior. To address this, we propose a state space phase estimator for real-time tracking of phase. By tracking the analytic signal as a latent state, this framework avoids the requirement of bandpass filtering, separately models the signal and the noise, accounts for rhythmic confounds, and provides credible intervals for the phase estimate. We demonstrate in simulations that the state space phase estimator outperforms current state-of-the-art real-time methods in the contexts of common confounds such as broadband rhythms, phase resets and co-occurring rhythms. Finally, we show applications of this approach to in vivo data. The method is available as a ready-to-use plug-in for the OpenEphys acquisition system, making it widely available for use in experiments.

Imaging conical intersection dynamics during azobenzene photoisomerization by ultrafast X-ray diffraction

X-ray diffraction is routinely used for structure determination of stationary molecular samples. Modern X-ray photon sources, e.g., from free-electron lasers, enable us to add temporal resolution to these scattering events, thereby providing a movie of atomic motions. We simulate and decipher the various contributions to the X-ray diffraction pattern for the femtosecond isomerization of azobenzene, a textbook photochemical process. A wealth of information is encoded besides real-time monitoring of the molecular charge density for the cis to trans isomerization. In particular, vibronic coherences emerge at the conical intersection, contributing to the total diffraction signal by mixed elastic and inelastic photon scattering. They cause distinct phase modulations in momentum space, which directly reflect the real-space phase modulation of the electronic transition density during the nonadiabatic passage. To overcome the masking by the intense elastic scattering contributions from the electronic populations in the total diffraction signal, we discuss how this information can be retrieved, e.g., by employing very hard X-rays to record large scattering momentum transfers.

Chaotic model for COVID-19 growth-factor

The new COVID-19 Pandemic caused by SARS-CoV-2 initiated in the world a largest quarantine, due to is exponential capacity of the virus in spreading from human contact. In the present work, it was evaluated the dynamics of such spreading by the indicator of growth-factor, and applied to it the space phase of the time series, the detrended fluctuation analysis (DFA) of the series, and the fractal dimension of the space phase. It was possible to notice a strange attractor in the space phase of the growth-factor, indicating that the process is chaotic deterministic. The value of the alpha coefficient by DFA showed to be less than 0.5, characteristic of long-range memory of the series, in which large events precedes small events. The fractal dimension of the phase space was a fractal number, between 1 and 2, another indicator that the exponential growth-rate of the virus spreading among humans is fractal. These results, even with small number of data, is pointing that the spread of COVID-19 is fractal.

Space-phase shifts acquiring by breathers after mutual collisions

<p>The key result of this work is the first theoretical computation of exact expressions describing space and phase shifts acquiring by breathes after mutual collisions in the framework of the focusing one-dimensional nonlinear Schrödinger equation (NLSE) model [1]. Similar expressions are the backbone of soliton theory, where they allow to predicts soliton interaction dynamics and introduce statistical description of soliton gas in terms of kinetic equation. Theory of breathers – solitary type wave groups on an unstable background – has been developing almost as long as theory of solitons. However, up to now, this important part of theory has been missing.</p><p>In our work we present space and phase shift formulas for the NLSE breathers and demonstrate how they can be used to go deeply in understanding of an intriguing nonlinear phenomena – formation rogue waves from a calm background. With these formulas we show that synchronized collisions of breathers are the central mechanism of extreme amplitude wave formation as a result of modulation instability development. We illustrate this conclusion by particular examples of multi-breather dynamics as well as by statistical analysis of multi-breather interactions. In comparison to the work [1], here we also analyse the impact of the effects lying beyond the NLSE model on the multi-breather synchronization. Finally, we present new scenarios of the synchronised multi-breather interactions, that can be observed in laboratory experiments.</p><p>The work was supported by the RFBR grant No. 19-31-60028.</p><p>[1] A. A. Gelash, Formation of rogue waves from a locally perturbed condensate, Phys. Rev. E 97, 022208 (2018).</p>

An Interplanetary Travel

<p>To promote STEAM vocations among our teenage students aged between 12 and 16, our institute has designed and implemented a project called "AN INTERPLANETARY TRAVEL" thanks to the collaboration of the EUROPEAN OFFICE RESOURCES FOR SPACE EDUCATION OF SPAIN (CESERO Spain) which provides us with a kit of materials for our purpose.</p><p>The project is structured in different parts:</p><p>-First, we propose our students the possible fictitious alien invasion by recreating a radio program where all countries are informing of the alien threat existing by aliens who want to invade our planet.</p><p>Through a previous brainstorm the students consider the possibility of colonizing other planets of the Solar System in order to survive.</p><p>-Second, to be able to choose the ideal future home, they must investigate various planets that match the requirements for the human being to live and do experiments in order to detect the existence of life.</p><p>-Third, while some students are dedicated to designing and selling one-way tickets for this new place, through the creation of their own travel agency, and all the logistics involved others are dedicated to studying how to plan that trip . Subsequently, the "clients" select the agency that provides the best services.</p><p>-Fourth, for the planning of the trip it is necessary that our students become spaceships engineers to design the space vehicle and the pertinent tests for its takeoff.</p><p>To be able to build that spacecraft, it is necessary to investigate the different properties of the materials to find the perfect features that the different parts of the space vehicle must have: impact resistance, magnetism, densities, electrical properties and thermal conductivity, etc. and select the suitable ones to carry it out Both the water rocket and the reentry capsule are designed and tested in an open field. The idea is to land in our future home.</p><p>-Fifth, calculations are made for the different phases of our trip: launch phase, space phase and reentry phase. (Level adapted for high school students). For the reentry phase the parachute is designed and tested with an egg so that it can land without breaking.</p><p>-Sixth, the students study the possible health consequences of future colonizers.</p><p>-And finally, all student groups teach their peers the achievements through exhibitions.</p><p><br>Good trip !!!</p>

Traits for chemical evolution in solar twins

The physical processes driving chemical evolution in the Milky Way can be probed using the distribution of abundances in low-mass FGK type stars in space phase at different times. During their final stages of evolution, stars experience nucleosynthesis several times, each at different timescales and producing different chemical elements. Finding abundance ratios that have simple variations across cosmic times therefore remains a challenge. Using the sample of 80 solar twins for which ages and abundances of 30 elements have been measured with high precision, we searched for all possible abundance ratio combinations that show linear trends with age. We found 55 such ratios, all combining an n-capture element and another element produced by different nucleosynthesis channels. We recovered the ratios of [Y/Mg], [Ba/Mg], and [Al/Y] that have been reported previously in the literature, and found that [C/Ba] depends most strongly on age, with a slope of 0.049 ± 0.003 dex Gyr−1. This imposes constraints on the magnitude of the time dependency of abundance ratios in solar twins. Our results suggest that s-process elements, in lieu of Fe, should be used as a reference for constraining chemical evolution models of the solar neighbourhood. Our study illustrates that a wide variety of chemical elements measured in high-resolution spectra is key to meeting the current challenges in understanding the formation and evolution of our Galaxy.

Phase Space Analysis of Pig Ear Skin Temperature during Air and Road Transport

High or variable ambient temperature can affect thermal regulation in livestock, but few studies have studied thermal variability during air and road transport, partly due to the lack of tools to compare thermal data from a long time series over periods of different duration. In this study, we recorded the ear skin temperature (EST) of 11 Duroc breeder pigs (7 females and 4 males) during commercial intercontinental transport from Canada to Spain, which included both road and aircraft travel and lasted 65 h. The EST was measured using a logger placed inside the left ear. Phase space diagrams EST, that is EST time series vs. itself delayed in time, were used to quantify the variability of the time-temperature series based on the areas that included all the points in the phase space. Phase space areas were significantly higher for all the animals during air travel, almost doubling that of road transport. Using the phase spaces, we identified an event during air transport that lasted 57 min, leading to a general decrease in EST by 8 °C, with respect to the average EST (34.1 °C). We also found that thermal variability was more stable in males (F = 20.81, p = 0.0014), which were also older and heavier.