Comparative analysis of the cardiac structure and transcriptome of scallop and snail,perspectives on heart chamber evolution

The evolution of a two-chambered heart,with an atrium and a ventricle,has improved heart function in both deuterostomes(vertebrates)and some protostomes(invertebrates).Although studies have examined the unique structure and function of these two chambers,molecular comparisons are few and limited to vertebrates.Here,we focus on the two-chambered protostome heart of the mollusks,offering data that may provide a better understanding of heart evolution.Specifically,we asked if the atrium and ventricle differ at the molecular level in the mollusk heart.To do so,we examined two very different species,the giant African land snail(Lissachatina fulica)and the relatively small,aquatic yesso scallop(Mizuhopecten yessoensis),with the assumption that if they exhibited commonality these similarities would likely reflect those across the phylum.We found that,although the hearts of these two species differed histologically,their cardiac gene function enrichments were similar,as revealed by transcriptomic analysis.Furthermore,the atrium and ventricle in each species had distinct gene function clusters,suggesting an evolutionary differentiation of cardiac chambers in mollusks.Finally,to explore the relationship between vertebrate and invertebrate two-chambered hearts,we compared our transcriptomic data with published data from the zebrafish,a well-studied vertebrate model with a two-chambered heart.Our analysis indicated a functional similarity of ventricular genes between the mollusks and the zebrafish,suggesting that the ventricle was differentiated to achieve the same functions in invertebrates and vertebrates.As the first such study on protostomes,our findings offered initial insights into how the two-chambered heart arose,including a possible understanding of its occurrence in both protostomes and deuterostomes.

Gear fault diagnosis using gear meshing stiffness identified by gearbox housing vibration signals

Gearbox fault diagnosis based on vibration sensing has drawn much attention for a long time.For highly integrated complicated mechanical systems,the intercoupling of structure transfer paths results in a great reduction or even change of signal characteristics during the process of original vibration transmission.Therefore,using gearbox housing vibration signal to identify gear meshing excitation signal is of great significance to eliminate the influence of structure transfer paths,but accompanied by huge scientific challenges.This paper establishes an analytical mathematical description of the whole transfer process from gear meshing excitation to housing vibration.The gear meshing stiffness(GMS)identification approach is proposed by using housing vibration signals for two stages of inversion based on the mathematical description.Specifically,the linear system equations of transfer path analysis are first inverted to identify the bearing dynamic forces.Then the dynamic differential equations are inverted to identify the GMS.Numerical simulation and experimental results demonstrate the proposed method can realize gear fault diagnosis better than the original housing vibration signal and has the potential to be generalized to other speeds and loads.Some interesting properties are discovered in the identified GMS spectra,and the results also validate the rationality of using meshing stiffness to describe the actual gear meshing process.The identified GMS has a clear physical meaning and is thus very useful for fault diagnosis of the complicated equipment.