Pitch perception of harmonic complex tones based on excitation patterns

Fundamental frequency difference limens were measured to study whether pitch perception of medium-rank harmonic complex tones depends on the resolvability of the compo- nents and to study the effect of masker tone on discrimination performance. Target tone was presented alone, or mixed with the masker, which were filtered into the same bandpass frequency region （low, medium, or high） to obtain different resolvability. There were five kinds of funda- mental frequency difference and four kinds of phase combination between target and masker. Five young subjects participated in experiments, all of whom had normal hearing （thresholds ≤ 15 dB HL）. Results found fundamental frequency difference limens were increased with up-shift frequency region of the harmonics. The fundamental frequency difference between target and masker had a significant impact on the performance, while phase effects were small. Analysis suggested that resolvability of harmonics had a significant impact on the fundamental frequency difference limens, but pitch perception of medium-rank harmonics was not based on the resolv- ability. Analysis also suggested that most results of pitch perception of target-masker mixture were closely correlated with peaks on the excitation patterns.

The mechanism of environmental D-xylose perception by the bacterial membrane two-component complex XylFII-LytS

D-xylose,the main building block of plant biomass,is a pentose sugar that can be used by bacteria as a carbon source for bio-based fuel and chemical production through fermentation.In bacteria,the first step for D-xylose metabolism is signal perception at the membrane.Scientists previously identified a threecomponent system in Firmicutes bacteria comprising a membrane-associated sensor protein(XylFII)。