Ion-tunable antiambipolarity in mixed ion-electron conducting polymers enables biorealistic organic electrochemical neurons.

Biointegrated neuromorphic hardware holds promise for new protocols to record/regulate signalling in biological systems. Making such artificial neural circuits successful requires minimal device/circuit complexity and ion-based operating mechanisms akin to those found in biology. Artificial spiking neurons, based on silicon-based complementary metal-oxide semiconductors or negative differential resistance device circuits, can emulate several neural features but are complicated to fabricate, not biocompatible and lack ion-/chemical-based modulation features. Here we report a biorealistic conductance-based organic electrochemical neuron (c-OECN) using a mixed ion-electron conducting ladder-type polymer with stable ion-tunable antiambipolarity. The latter is used to emulate the activation/inactivation of sodium channels and delayed activation of potassium channels of biological neurons. These c-OECNs can spike at bioplausible frequencies nearing 100 Hz, emulate most critical biological neural features, demonstrate stochastic spiking and enable neurotransmitter-/amino acid-/ion-based spiking modulation, which is then used to stimulate biological nerves in vivo. These combined features are impossible to achieve using previous technologies.

[Dynamic change of phosphorus leaching of neutral purple soil at different re-wetting rate].

Re-wetting was one of the most common forms of abiotic stresses experienced by soils. To investigate the effects of soil re-wetting rate on phosphorus (P) leaching and the relationship between soil microbial biomass carbon (MBC) and forms of P in leachate; five kinds of neutral purple soils of different fertilizer treatments were analyzed using simulating lab test at re-wetting rate of 0 h, 2 h, 4 h, 24 h and 48 h. The results showed that: (1) The lowest content of MBC appeared at the rate of 2 h during the soil re-wetting process, and the content of MBC increased with the reducing re-wetting rate. (2) Slower re-wetting helped to enhance soil microbial activity and the enhancement effect of organic fertilizer with NPK fertilizer (MNPK) was more significant. (3) The P leaching events of all fertilizer treatments occurred mainly at rapid re-wetting rates such as 0 h, 2 h, 4 h. Slower re-wetting was an important measure to prevent P leaching especially for the soils applied with chemical fertilizers, and it was of great significance in the field management of P. (4) Dissolved organic phosphorus (DOP) was the primary leaching part in leachate, and the variation range of ratio of total dissolved phosphorus (TDP) to total phosphorus (TP) and DOP to TP was 35.42%-85.99% and 29.74%-78.58% respectively. (5) With the reducing of re-wetting rate, significant negative correlation was observed between MBC and TP, TDP as well as DOP in the leachate (P < 0.05). To sum up, it was speculated that the P in soil leachate mainly came from soil microorganisms.