Simultaneous Cardiac and Neurological Monitoring to Assess Chemical Exposures and Drug Toxicity in Xenopus Laevis

Simultaneous monitoring of electrocardiogram (ECG) and electroencephalogram (EEG) under chemical exposure requires innovative engineering techniques that can capture minute physiological changes in studied animal models. However, this is often administered with a bulky system that may cause signal distortions and discomfort for animals. We develop an integrated bioelectronic sensing system to provide simultaneous ECG and EEG assessment in real-time under chemical exposure for Xenopus laevis. The microelectrode array (MEA) membrane with integrated ECG and EEG sensing offers an opportunity to achieve multichannel noninvasive electrophysiological monitoring with favorable dimensions and spatial resolution. To validate the performance of our system, we assessed the ECG and EEG of Xenopus under exposure of Pentylenetetrazol (PTZ), an epilepsy-inducing drug. Effects of PTZ were detected with clear ECG and EEG alterations, including frequent ictal and interictal EEG events, 30 dB average EEG amplitude elevations, abnormal ECG morphology, and heart rate changes. Overall, our Xenopus-based real-time electrophysiology monitoring system holds high potential for many applications in drug screening and remote environmental toxicity monitoring.

Wave-based control for nonreciprocal acoustics using a planar array of secondary sources

There has been significant interest in the design of nonreciprocal acoustic devices that allow acoustic waves to be perfectly transmitted in one direction, whilst the acoustic waves propagating in the opposite direction are blocked or reflected. Previously proposed nonreciprocal acoustic devices have broken the symmetry of transmission by introducing nonlinearities or resonant cavities. However, these nonreciprocal acoustic devices typically have limitations, such as signal distortions and the bandwidth over which nonreciprocal behaviour can be achieved is narrow. This paper will investigate how active control can be used to minimise the transmitted and reflected waves independently to achieve nonreciprocal sound transmission and absorption using a planar array of secondary sources in a two-dimensional environment. The advantage of the proposed active control system is that it is fully adaptable, which means that the directivity of nonreciprocal behaviour can also be reversed. The performance of the proposed wave-based active control system is investigated for a range of angles of incidence and its performance limitations are explored.

Signal distortions in circular dielectric waveguides at mm-wave frequencies

Despite the great progress in data transmission systems using dielectric waveguides (DWGs) in the millimeter-wave (mm-wave) frequency band (30–300 GHz), the signal distortions caused by DWGs have not yet been fully understood. However, such investigations would help to optimize DWGs as a transmission channel in order to further increase data rate and transmission distance of such systems without the need for more complex transceivers. Therefore, this paper presents a detailed study of the expected signal distortions caused by frequency-dependent attenuation and frequency-dependent group delay of circular DWGs at mm-wave frequencies. Based on a low-complexity digital transmission system, the effects of DWGs on the signal-to-noise ratio and the intersymbol interference at the receiver are evaluated. The figures and equations given in this paper allow the reader to easily calculate the channel properties and signal distortions for a wide range of circular DWGs without the need of finite element method solver or other time-consuming numerical simulations. Finally, design recommendations are given to minimize signal distortions for transmitting signals along DWGs.

Model and implementation of pseudorange-bias-free linear channel

The nonideal characteristics of the entire channel of satellite navigation signals from generation, propagation to reception will cause signal distortions, resulting in pseudorange biases. Such kind of biases cannot be eliminated by differential technologies and has become a core error source in high-accuracy applications. We study the theoretical model and implementation method of a pseudorange-bias-free linear channel. The ideal channel transfer function equation under the unbiased pseudorange requirement is first derived from the equivalent baseband model. Based on two corresponding criteria and the simulation of the influence of different amplitude- and phase-frequency responses, a digital phase compensation method based on an all-pass filter is proposed to eliminate pseudorange biases. Then the significant effects of the two phase equalizers are validated by a simulation example of the BPSK(10) signal. Finally, the real BDS3 PRN32 and PRN33 satellite B1C signals collected by a 40-m high-gain dish antenna are utilized to invert the channel transfer characteristics and processed by our software receiver. The measurement results demonstrate that the phase equalizers constructed according to either the linear phase criterion or the linear phase plus even-symmetric phase criterion can effectively reduce the pseudorange bias. The model and method provide a reference for payload and receiver optimization and are suitable for various signal structures and applications.

Small size of recorded neuronal structures confines the accuracy in direct axonal voltage measurements

Patch-clamp instruments including amplifier circuits and pipettes affect the recorded voltage signals. We hypothesized that realistic and complete in silico representation of recording instruments together with detailed morphology and biophysics of small recorded structures will precisely reveal signal distortions and provides a tool that predicts native signals from distorted voltage recordings. Therefore, we built a model that was verified by small axonal recordings. The model accurately recreated actual action potential measurements with typical recording artefacts and predicted the native electrical behavior. The simulations verified that recording instruments substantially filter voltage recordings. Moreover, we revealed that instrumentation directly interferes with local signal generation depending on the size of the recorded structures, which complicates the interpretation of recordings from smaller structures, such as axons. However, our model offers a straightforward approach that predicts the native waveforms of fast voltage signals and the underlying conductances even from the smallest neuronal structures.