Existing methods utilizing spatial information for sound source separation require prior knowledge of the direction of arrival (DOA) of the source or utilize estimated but imprecise localization results, which impairs the separation performance, especially when the sound sources are moving. In fact, sound source localization and separation are interconnected problems, that is, sound source localization facilitates sound separation while sound separation contributes to refined source localization. This paper proposes a method utilizing the mutual facilitation mechanism between sound source localization and separation for moving sources. The proposed method comprises three stages. The first stage is initial tracking, which tracks each sound source from the audio mixture based on the source signal envelope estimation. These tracking results may lack sufficient accuracy. The second stage involves mutual facilitation: Sound separation is conducted using preliminary sound source tracking results. Subsequently, sound source tracking is performed on the separated signals, thereby refining the tracking precision. The refined trajectories further improve separation performance. This mutual facilitation process can be iterated multiple times. In the third stage, a neural beamformer estimates precise single-channel separation results based on the refined tracking trajectories and multi-channel separation outputs. Simulation experiments conducted under reverberant conditions and with moving sound sources demonstrate that the proposed method can achieve more accurate separation based on refined tracking results.
Calcium phosphate is widely used for the remediation of lead-contaminated sites, where calcium/lead phosphate coprecipitates (Ca/Pb CoPs) form. This research investigated such coprecipitation with model low-molecular-weight organics (LMWOs), produced in the rhizosphere with representative functional groups, which were found to regulate both the composition (Ca/Pb and C/Pb ratios) and stability (aggregation and transformation) of Ca/Pb CoPs. The strong complexation ability of –SH in l-cysteine with aqueous Ca2+/Pb2+ ions inhibited coprecipitation to a great extent. Meanwhile, coprecipitates with lysine containing both –NH2 and –COOH had a higher Ca/Pb ratio than those with citrate containing only –COOH, probably due to the elevated local supersaturation caused by both –NH2 and –COOH in lysine that attracted phosphate ions and cations, promoting Ca doping in CoPs. Also, the strong binding of both –NH2 and –COOH with coprecipitates resulted in a higher C/Pb ratio for the CoPs with lysine than citrate. The oriented aggregation of nano-CoPs formed needle-shaped hydroxylpyromorphite crystals without organics. Unexpectedly, lysine/citrate disrupted and l-cysteine promoted such oriented aggregation, resulting in inhibited and promoted crystallinity, respectively. This study provided new mechanistic insights on LMWO effects on Ca/Pb CoP formation and their stability and can help understand Pb speciation and availability in the rhizosphere.
Integration between electronics and biology is often facilitated by iontronics, where ion migration in aqueous media governs sensing and memory. However, the Debye screening effect limits electric fields to the Debye length, the distance over which mobile ions screen electrostatic interactions, necessitating external voltages that constrain the operation speed and device design. Here we report a high-speed in-memory sensor based on vanadium dioxide (VO2) that operates without an external voltage by leveraging built-in electric fields within the Debye length. When VO2 contacts a low-work-function metal (for example, indium) in a salt solution, electrochemical reactions generate indium ions that migrate into the VO2 surface under the native electric field, inducing a surface insulator-to-metal phase transition of VO2. The VO2 conductance increase rate reflects the salt concentration, enabling in-memory sensing, or memsensing of the solution. The memsensor mimics Caenorhabditis elegans chemosensory plasticity to guide a miniature boat for adaptive chemotaxis, illustrating low-power aquatic neurorobotics with fewer memory units.