Does the Sound of a Singing Bowl Synchronize Meditational Brainwaves in the Listeners?

This study aims to verify if the beating sound of a singing bowl synchronizes and activates brain waves during listening. The singing bowl used in this experiment produce beats at a frequency of 6.68 Hz, while it decays exponentially and lasts for about 50 s. Brain waves were measured for 5 min in the F3 and F4 regions of seventeen participants (eight males and nine females, average age 25.2) who heard the beating singing bowl sounds. The experimental results showed that the increases (up to ~251%) in the spectral magnitudes of the brain waves were dominant at the beat frequency compared to those of any other clinical brain wave frequency bands. The observed synchronized activation of the brain waves at the beating sound frequency supports that the singing bowl sound may effectively facilitate meditation and relaxation, considering that the beat frequency belongs to the theta wave region which increases in the relaxed meditation state.

Passive Electrical Damping of a Quartz Tuning Fork as a Path to Fast Resonance Tracking in QEPAS

In Quartz-Enhanced PhotoAcoustic Spectroscopy (QEPAS) gas sensors, the acoustic wave is detected by the piezoelectric Quartz Tuning Fork (QTF). Due to its high-quality factor, the QTF can detect very low-pressure variations, but its resonance can also be affected by the environmental variations (temperature, humidity, …), which causes an unwanted signal drift. Recently, we presented the RT-QEPAS technique that consistently corrects the signal drift by continuously measuring the QTF resonance. In this article, we present an improvement of RT-QEPAS to fasten the QTF characterization time by adding a passive electronic circuit, which causes the damping of the QTF resonance. The damping circuit is optimized analytically and through SPICE simulation. The results are supported by experimental observations, showing a 70 times improvement of the relaxation times compared to the lone QTF, which opens the way to a fast and drift-free QEPAS sensor.

Design for A Highly Stable Laser Source Based on the Error Model of High-Speed High-Resolution Heterodyne Interferometers

Heterodyne interferometers with two opposite Doppler shift interference signals have been proposed for high-resolution measurement with high measurement speed, which can be used in the background of high-speed high-resolution measurement. However, a measurement error model for high-speed high-resolution heterodyne interferometers (HSHR-HIs) has not yet been proposed. We established a HSHR-HI measurement error model, analyzed the influence of beat frequency stability with a simplified optical structure, and then designed an offset-locked dual-frequency laser source with a digital control system to reduce the impact of beat frequency drift. Experiments were used to verify the correction of the measurement error model and the validity of the laser source. The results show that the new laser source has a maximum beat frequency range of 45 MHz, which shows the improvements in the measuring speed and resolution.

Quartz Tuning Fork Resonance Tracking and application in Quartz Enhanced Photoacoustics Spectroscopy

The quartz tuning fork (QTF) is a piezoelectric transducer with a high quality factor that was successfully employed in sensitive applications such as atomic force microscopy or Quartz-Enhanced Photo-Acoustic Spectroscopy (QEPAS). The variability of the environment (temperature, humidity) can lead to a drift of the QTF resonance. In most applications, regular QTF calibration is absolutely essential. Because the requirements vary greatly depending on the field of application, different characterization methods can be found in the literature. We present a review of these methods and compare them in terms of accuracy. Then, we further detail one technique, called Beat Frequency analysis, based on the transient response followed by heterodyning. This method proved to be fast and accurate. Further, we demonstrate the resonance tracking of the QTF while changing the temperature and the humidity. Finally, we integrate this characterization method in our Resonance Tracking (RT) QEPAS sensor and show the significant reduction of the signal drift compared to a conventional QEPAS sensor.

Low-Complexity Time-Domain Ranging Algorithm with FMCW Sensors

A time-domain ranging algorithm is proposed for a frequency-modulated continuous wave (FMCW) short-range radar sensor with high accuracy and low complexity. The proposed algorithm estimates the distance by calculating the ratio of the beat frequency signal to its derivative and thereby eliminates the restriction of frequency bandwidth on ranging accuracy. Meanwhile, we provide error analysis of the proposed algorithm under different distances, integral lengths, relative velocities, and signal-to-noise ratios (SNRs). Finally, we fabricate FMCW sensor prototype and construct a measurement system. Testing results demonstrate that the proposed time-domain algorithm could achieve range error within 0.8 m. Compared with the conventional fast Fourier transform (FFT) estimation scheme, the proposed method performs ranging without the requirement of complex multiplications, which makes it reasonable to be implemented in real-time and low-cost systems.

Regulatory mechanisms of sperm flagellar motility by metachronal and synchronous sliding of doublet microtubules

STUDY QUESTION

What is the role of metachronal and synchronous sliding in sperm flagellar motility?

SUMMARY ANSWER

Both metachronal and oscillatory synchronous sliding are essential for sperm flagellar motility, while the change in mode of synchronous sliding between the non-oscillatory synchronous sliding of a specific pair of the doublet microtubules and the oscillatory synchronous sliding between most pairs of doublet microtubules modulates the sperm flagellar motility.

WHAT IS KNOWN ALREADY

Metachronal and synchronous sliding of doublet microtubules are involved in sperm flagellar motility and regulation of these sliding movements controls flagellar bend formation.

STUDY DESIGN, SIZE, DURATION

To study the regulatory mechanisms of metachronal and synchronous sliding in flagellar movement of golden hamster spermatozoa, changes in these sliding movements during hyperactivation were examined by measuring the angle of the tangent to the flagellar shaft with reference to the central axis of the sperm head (the shear angle) along the flagellum. Golden hamster spermatozoa were obtained from the caudal epididymis of five sexually mature golden hamsters. Results from three experiments were averaged. The number of spermatozoa analyzed is 15 activated sperm, 22 hyperactivated sperm and 20 acrosome-reacted sperm.

PARTICIPANTS/MATERIALS, SETTING, METHODS

For detailed field-by-field analysis, an individual flagellar image was tracked automatically using the Autotrace module of image analysis software. The coordinate values of the flagellar shaft were used to calculate the shear angle, which is proportional to the amount of microtubule sliding at any given position along the flagellum. The maximum shear angles of metachronal and synchronous sliding were obtained from the mean shear angles between the maximum shear angles of pro-hook bends and the absolute values of the minimum shear angles of anti-hook bends, which represent the amplitude of a set of successive shear angle curves, with 3-12 shear curves covering one beat cycle of sperm flagellar movement. Asymmetry of flagellar waves was expressed by the mean shear angle between the maximum shear angle of pro-hook bends and the minimum shear angle of anti-hook bends at 100 μm from the head-midpiece junction.

MAIN RESULTS AND THE ROLE OF CHANCE

The asymmetrical flagellar movements observed in the activated (non-hyperactivated) and hyperactivated spermatozoa were characterized by the non-oscillatory synchronous sliding of a specific pair of the doublets; the large asymmetrical flagellar movement in the hyperactivated spermatozoa was generated by the large non-oscillatory synchronous sliding. Both the metachronal and synchronous sliding increased during the hyperactivation; however, the large symmetrical flagellar movement of the acrosome-reacted spermatozoa was characterized by the oscillatory synchronous sliding between most pairs of doublets. These results demonstrated that the metachronal and synchronous sliding are involved in generation and modulation of sperm flagellar motility; however, two types of synchronous sliding, non-oscillatory and oscillatory sliding, modulate the sperm flagellar motility by enhancing the sliding of a specific pair of the doublets or the sliding between most pairs of the doublets.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

This is an indirect study of the metachronal and synchronous sliding of doublet microtubules. Studies based on the direct observation of behavior of dynein are needed to clarify the sliding microtubule theory of flagellar movement of spermatozoa.

WIDER IMPLICATIONS OF THE FINDINGS

Both the metachronal and oscillatory synchronous sliding of doublet microtubule generate and modulate sperm flagellar motility, while the change in mode of synchronous sliding between the non-oscillatory synchronous sliding and oscillatory synchronous sliding modulates the sperm flagellar motility. The coordination between these sliding leads to various types of flagellar and ciliary motility, including the asymmetrical beating in flagellar and ciliary movement and planar or helical beating in sea urchin spermatozoa. Moreover, the finding that the metachronal sliding and two types of synchronous sliding generate and modulate the flagellar motility will open a new avenue for quantitative analysis of flagellar and ciliary motility.

STUDY FUNDING AND COMPETING INTEREST(S)

The authors have no conflict of interest and no funding to declare.

Exploiting Concurrent Wake-Up Transmissions Using Beat Frequencies

Wake-up receivers are the natural choice for wireless sensor networks because of their ultra-low power consumption and their ability to provide communications on demand. A downside of ultra-low power wake-up receivers is their low sensitivity caused by the passive demodulation of the carrier signal. In this article, we present a novel communication scheme by exploiting purposefully-interfering out-of-tune signals of two or more wireless sensor nodes, which produce the wake-up signal as the beat frequency of superposed carriers. Additionally, we introduce a communication algorithm and a flooding protocol based on this approach. Our experiments show that our approach increases the received signal strength up to 3 dB, improving communication robustness and reliability. Furthermore, we demonstrate the feasibility of our newly-developed protocols by means of an outdoor experiment and an indoor setup consisting of several nodes. The flooding algorithm achieves almost a 100% wake-up rate in less than 20 ms.

Ca2+ and cAMP regulations of microtubule sliding in hyperactivated motility of bull spermatozoa

To reach and fertilize the egg, mammalian spermatozoa change their flagellar movement in the female reproductive tract, named hyperactivation. The biochemical analyses of the hyperactivated movement using demembranated spermatozoa defined the factors inducing this peculiar movement; namely, large asymmetrical flagellar movement observed in the early stage of the hyperactivation was induced with a high Ca(2+) concentration while large symmetrical flagellar movement in the late stage of the hyperactivation was generated with low Ca(2+) and high cAMP concentrations. Under these conditions, the microtubule sliding of bull sperm flagella was investigated by disintegrating the sperm flagella with MgATP(2-) after extracting their plasma membrane and mitochondria. The large asymmetrical flagellar movement was caused by a long sliding displacement of a fiber of the doublet microtubules. On the other hand, the large symmetrical flagellar movement was generated by a large amount of microtubule sliding by many doublet microtubules.