Two-frequency Phase Research Articles

Effects of 7September 5–12, 2017 solar flares on regional disturbance of Earth’s ionosphere as recorded by GNSS stations located in the Volga Federal District of the Russian Federation

The paper presents the results of estimation of the effects of September 5–12, 2017 solar flares on the regional disturbance of Earth's ionosphere according to data from a distributed network of GNSS stations located mostly in the Volga Federal District of the Russian Federation. The GNSS data processing software package we have developed is used to analyze recorded signal power and daily two-frequency phase measurements, as well as to calculate the total electron content and map the data. The results of the study show that during powerful solar flares X2.2 and X9.3 on September 6 the median value of the total electron content, calculated for the Volga Federal District, increased up to 0.25 TECU and 0.6 TECU respectively. At that time, the region of interest (40°–55° E) was sunlit. The prolonged magnetic storms on September 8 also generated noticeable ionospheric disturbances up to 0.2 TECU. At the same time, neither the solar flares nor the magnetic storms had a significant effect on the power characteristics of the recorded signals from navigation satellites in the region under study. The median carrier-to-noise ratio calculated for the region considered over the entire observation period did not differ from the values recorded under undisturbed ionospheric conditions and varied between 47–53 dBHz and 38–49 dBHz for frequencies L1 and L2 respectively.

Влияние солнечных вспышек 5-12 сентября 2017 г. на региональную возмущенность ионосферы Земли по данным ГНСС-станций, расположенных в Приволжском федеральном округе Российской Федерации

The paper presents the results of estimation of the effects of September 5–12, 2017 solar flares on the regional disturbance of Earth's ionosphere according to data from a distributed network of GNSS stations located mostly in the Volga Federal District of the Russian Federation. The GNSS data processing software package we have developed is used to analyze recorded signal power and daily two-frequency phase measurements, as well as to calculate the total electron content and map the data. The results of the study show that during powerful solar flares X2.2 and X9.3 on September 6 the median value of the total electron content, calculated for the Volga Federal District, increased up to 0.25 TECU and 0.6 TECU respectively. At that time, the region of interest (40°–55° E) was sunlit. The prolonged magnetic storms on September 8 also generated noticeable ionospheric disturbances up to 0.2 TECU. At the same time, neither the solar flares nor the magnetic storms had a significant effect on the power characteristics of the recorded signals from navigation satellites in the region under study. The median carrier-to-noise ratio calculated for the region considered over the entire observation period did not differ from the values recorded under undisturbed ionospheric conditions and varied between 47–53 dBHz and 38–49 dBHz for frequencies L1 and L2 respectively.

Floquet engineering of individual band gaps in an optical lattice using a two-tone drive

The dynamic engineering of band structures for ultracold atoms in optical lattices represents an innovative approach to understand and explore the fundamental principles of topological matter. In particular, the folded Floquet spectrum determines the associated band topology via band inversion. We experimentally and theoretically study two-frequency phase modulation to asymmetrically hybridize the lowest two bands of a one-dimensional lattice. Using quasi-degenerate perturbation theory in the extended Floquet space we derive an effective two-band model that quantitatively describes our setting. The energy gaps are experimentally probed via Landau-Zener transitions between Floquet-Bloch bands using an accelerated Bose-Einstein condensate. Separate and simultaneous control over the closing and reopening of these band gaps is demonstrated. We find good agreement between experiment and theory, establishing an analytic description for resonant Floquet-Bloch engineering that includes single- and multi-photon couplings, as well as interference effects between several commensurate drives.

Real-time monitoring of metabolic function in liver-on-chip microdevices tracks the dynamics of mitochondrial dysfunction

Microfluidic organ-on-a-chip technology aims to replace animal toxicity testing, but thus far has demonstrated few advantages over traditional methods. Mitochondrial dysfunction plays a critical role in the development of chemical and pharmaceutical toxicity, as well as pluripotency and disease processes. However, current methods to evaluate mitochondrial activity still rely on end-point assays, resulting in limited kinetic and prognostic information. Here, we present a liver-on-chip device capable of maintaining human tissue for over a month in vitro under physiological conditions. Mitochondrial respiration was monitored in real time using two-frequency phase modulation of tissue-embedded phosphorescent microprobes. A computer-controlled microfluidic switchboard allowed contiguous electrochemical measurements of glucose and lactate, providing real-time analysis of minute shifts from oxidative phosphorylation to anaerobic glycolysis, an early indication of mitochondrial stress. We quantify the dynamics of cellular adaptation to mitochondrial damage and the resulting redistribution of ATP production during rotenone-induced mitochondrial dysfunction and troglitazone (Rezulin)-induced mitochondrial stress. We show troglitazone shifts metabolic fluxes at concentrations previously regarded as safe, suggesting a mechanism for its observed idiosyncratic effect. Our microfluidic platform reveals the dynamics and strategies of cellular adaptation to mitochondrial damage, a unique advantage of organ-on-chip technology.

Динамика возмущенности полного электронного содержания в высоких и средних широтах по данным GPS

We study the level of total electron content (TEC) disturbance in ionospheric mid-latitude and high-latitude regions during 2013. TEC behavior is calculated using data from two GPS stations: MOND (Mondy) and NRIL (Norilsk). TEC variations are calculated from two-frequency phase measurements for all radio rays. We analyze the TEC variations in two time ranges: 10 and 40 min. These ranges correspond to middle- and large-scale ionospheric disturbances respectively. The TEC disturbance level is characterized using the special index WTEC. WTEC allows us to receive multi-day continuous series of average TEC variation intensity. We reveal that at high latitudes WTEC variations agree well with AE ones. The correlation between WTEC and Dst variations is much less. The minimum level of TEC disturbance is independent of the season in the Arctic region; diurnal WTEC variations are more pronounced for medium-scale ionospheric disturbances than for large-scale ones. At mid-latitudes, the WTEC behavior agrees well with the Dst and Kp variations only during strong magnetic storms. The minimum level of TEC disturbance is higher in summer than in winter. At mid-latitudes, the sunset terminator generates gravitational waves. In the Arctic region, terminator-generated waves are not observed.

Real-time monitoring of oxygen uptake in hepatic bioreactor shows CYP450-independent mitochondrial toxicity of acetaminophen and amiodarone.

Prediction of drug-induced toxicity is complicated by the failure of animal models to extrapolate human response, especially during assessment of repeated dose toxicity for cosmetic or chronic drug treatments. In this work, we present a 3D microreactor capable of maintaining metabolically active HepG2/C3A spheroids for over 28days in vitro under stable oxygen gradients mimicking the in vivo microenvironment. Mitochondrial respiration was monitored using two-frequency phase modulation of phosphorescent microprobes embedded in the tissue. Phase modulation is focus independent and unaffected by cell death or migration. This sensitive measurement of oxygen dynamics revealed important information on the drug mechanism of action and transient subthreshold effects. Specifically, exposure to antiarrhythmic agent, amiodarone, showed that both respiration and the time to onset of mitochondrial damage were dose dependent showing a TC50 of 425μm. Analysis showed significant induction of both phospholipidosis and microvesicular steatosis during long-term exposure. Importantly, exposure to widely used analgesic, acetaminophen, caused an immediate, reversible, dose-dependent loss of oxygen uptake followed by a slow, irreversible, dose-independent death, with a TC50 of 12.3mM. Transient loss of mitochondrial respiration was also detected below the threshold of acetaminophen toxicity. The phenomenon was repeated in HeLa cells that lack CYP2E1 and 3A4, and was blocked by preincubation with ascorbate and TMPD. These results mark the importance of tracing toxicity effects over time, suggesting a NAPQI-independent targeting of mitochondrial complex III might be responsible for acetaminophen toxicity in extrahepatic tissues.

Determination of troposphere characteristics using signals of satellite navigation systems

Based on two-frequency phase measurements of GNSS signals by ground-based receivers, zenith delays of radio signals in the troposphere are estimated. These estimates are compared with the NCEP/NCAR reanalysis data on weather fields. It is shown that the standard deviation in the values of zenith delays obtained in both ways is about 1 cm on average. According to our calculations, such a level of accuracy permits one to study the interday and intraday dynamics of the troposphere. The temporal resolution of estimates based on the GNSS data is 2 h, which makes it possible to organize atmosphere monitoring using a ground-based network of satellite tracking systems.

Torus T 2 and its locking, doubling, chaos of a vibro-impact system

A three-degree-of-freedom vibro-impact system is considered. The nonlinear dynamical model and the six-dimensional Poincaré map are established and the dynamical behaviors of the system, including double Neimark–Sacker bifurcation, torus T 2 and its routes to chaos, is investigated by numerical simulations. As the control parameters vary, the torus T 2 changes into multi-circle torus T 1 via one-frequency phase locking on its position, which are divided into longitude circles and latitude circles, and the system keeps quasi-periodic motion. Further the impact motion settles into periodic orbit via two-frequency phase locking, then the system leads eventually to chaos. The second route to chaos shows, by establishing the secondary Poincaré section, that the torus T 2 leads to chaos via torus doubling bifurcation and there may exist torus doubling cascade.

Optimized two-frequency phase-measuring-profilometry light-sensor temporal-noise sensitivity.

Temporal frame-to-frame noise in multipattern structured light projection can significantly corrupt depth measurement repeatability. We present a rigorous stochastic analysis of phase-measuring-profilometry temporal noise as a function of the pattern parameters and the reconstruction coefficients. The analysis is used to optimize the two-frequency phase measurement technique. In phase-measuring profilometry, a sequence of phase-shifted sine-wave patterns is projected onto a surface. In two-frequency phase measurement, two sets of pattern sequences are used. The first, low-frequency set establishes a nonambiguous depth estimate, and the second, high-frequency set is unwrapped, based on the low-frequency estimate, to obtain an accurate depth estimate. If the second frequency is too low, then depth error is caused directly by temporal noise in the phase measurement. If the second frequency is too high, temporal noise triggers ambiguous unwrapping, resulting in depth measurement error. We present a solution for finding the second frequency, where intensity noise variance is at its minimum.

Focused Gaussian beams in the problem of holographic imaging

A simplified scheme of microwave near-field radar is considered. Focused Gaussian beams form a functional basis for holographic migration. Two-frequency phase measurements are used for the target localization. Numerical examples are given.

TWO-FREQUENCY CONTINUOUS WAVE ULTRASONIC SYSTEM FOR TEMPERATURE MEASUREMENT IN AN INFANT INCUBATOR

In this paper, we develop a new ultrasonic measurement method based on the speed of sound to measure the temperature. The average temperature of the air between the pair of ultrasonic T/R transducers is positively associated with the speed of sound. The method presented here is based upon the comparative phase shifts generated by two continuous ultrasonic waves with different but closely spaced frequencies. In the infant incubator, two low cost 40 kHz ultrasonic transducers are set face to face and used to transmit and receive ultrasound. Two frequencies are transmitted serially, each generating its own phase shift. Comparison of the phase shifts allows a highly accurate evaluation of the ultrasonic velocity when the distance between the transmitter and receiver is fixed. Ultrasonic velocity measurement system can provide a quick and precise monitoring of the temperature in an infant incubator. A single-chip microcomputer-based two-frequency continuous wave generator and phase detector was designed to record and compute the phase shift information and the resulting temperature, which is then sent to PC. The PC is used for calibrating the system and recording or controlling the temperature in an infant incubator. Experimentally, the accuracy of temperature measurement was found to be within ±0.02 °C when the distance between the transmitter and receiver is 1 m. The main advantages of this ultrasonic temperature measurement system are high resolution, low cost, and ease of implementation.

Three-frequency quasiperiodicity, phase locking, and the onset of chaos

We have performed a series of experiments with coupled relaxation oscillators to study three-frequency quasiperiodicity. There is strong evidence for the Ruelle-Takens scenario for the transition to chaos although only a very small portion of parameter space is occupied by chaos. The chaotic transition is via an exchange of stability between states which have phase locked to two-frequency quasiperiodicity. The overall structure of parameter space is a very complicated fractal devil's cobweb of periodic resonances linked by bands of two-frequency phase lockings.