The bHLH transcription factor SCL plays a central role in the generation of hematopoietic cells in vertebrates. We modified a PAC containing the whole zebrafish scl locus, inserting GFP into the first coding exon of scl. In germline-transgenic zebrafish generated using this construct, GFP expression completely recapitulates the endogenous expression of scl in blood, endothelium and CNS. We performed in vivo timelapse imaging of blood and endothelial precursor migration at the single-cell level and show that these cells migrate from the posterior lateral plate mesoderm to their site of differentiation in the intermediate cell mass. The anterior lateral plate domain of GFP expression gives rise to primitive macrophages and the blood vessels of the head. In later embryos, GFP expression identifies clusters of hematopoietic cells that develop between the dorsal aorta and posterior cardinal veins after primitive erythrocytes have entered circulation. Two treatments that block definitive hematopoiesis (treatment with dioxin (TCDD), and injection of an antisense morpholino oligonucleotide targeted to runx1) ablate these hematopoietic clusters. This indicates that these clusters represent the first site of definitive hematopoiesis in zebrafish. This site is anatomically homologous to the proposed source of hematopoietic stem cells in amniotes, the aorta-gonad-mesonephros (AGM) region. A second transgenic line, containing the promoter of scl driving GFP, lacks expression in the definitive clusters.

Rotational speed and load usually change when rotating machinery works. Both this kind of changing operational conditions and machine fault could make the mechanical vibration characteristics change. Therefore, effective health monitoring method for rotating machinery must be able to adjust during the change of operational conditions. This paper presents an adaptive threshold model for the health monitoring of bearings under changing operational conditions. Relevance vector machines (RVMs) are used for regression of the relationships between the adaptive parameters of the threshold model and the statistical characteristics of vibration features. The adaptive threshold model is constructed based on these relationships. The health status of bearings can be indicated via detecting whether vibration features exceed the adaptive threshold. This method is validated on bearings running at changing speeds. The monitoring results show that this method is effective as long as the rotational speed is higher than a relative small value.

With the increasingly prominent energy issues, regenerative shock absorber has attracted intensive attention in last two decades for the development of structure design. However, the researchers sometimes concentrate on conceptual designs without considering optimal parameter refinements. This paper proposes a regenerative shock absorber called the “hydraulic electric regenerative shock absorber (HERSA)” which includes an analytical regeneration performance parameters optimisation approach to promote the regeneration efficiency and regenerated power. The developed HERSA model is able to convert oscillatory motion into unidirectional rotary motion through the alteration of hydraulic flow while recovering power by a generator. The proposed model is also capable of obtaining the optimal parameters at certain condition, as well as providing the flexibility of different component combinations to match specific system need. The results demonstrate that the proposed model can effectively decide the optimal parameters in the system, and also the recoverable power can achieve average power of 331 W at 1 Hz-25 mm sinusoidal excitation in the system, which is approximately 65% efficiency. This study can be further used to guide prototype design in future study.

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