Developmental toxicity induced by brodifacoum in zebrafish (Danio rerio) early life stages.

OBJECTIVES: The present study mainly focused on the assessment of developmental toxicity induced by exposure to brodifacoum (BDF) in zebrafish at early life stages. MATERIAL AND METHODS: Zebrafish embryos were exposed to 0.2, 0.4, and 0.8 mg/L of BDF from 6 to 96 hr post-fertilization (hpf), and the toxic effects of BDF on early embryonic development were investigated in terms of morphological changes, oxidative stress, and alterations in heart development-related genes. RESULTS: The experimental results showed that BDF significantly decreased the heart rate, survival rate, body length, and spontaneous movements of zebrafish embryos at 0.8 mg/L, and the morphological developmental abnormalities were also observed at 96 hpf. In addition, exposure to BDF significantly increased oxidative stress levels in zebrafish embryos by increasing the enzymatic activities of catalase (CAT), superoxide dismutase (SOD), and malondialdehyde (MDA) levels, and decreased glutathione (GSH) levels. Furthermore, BDF treatment-induced alterations in the expression levels of the heart development-related genes (gata4, sox9b, tbx2b, and nppa). CONCLUSION: Results from this study indicated that exposure to BDF could lead to marked growth inhibition and significantly alter the activities of antioxidant enzymes in zebrafish embryos. Moreover, BDF exposure exhibited severe cardiotoxicity and significantly disrupted heart development-related genes. The results indicated that BDF could induce developmental and cardiac toxicity in zebrafish embryos.

Extrapolating distortion correction with local measurements for space-based multi-module splicing large-format infrared cameras.

Conventional distortion correction methods with the classical models, including radial, decentering, and thin prism distortions and with the interpolation template, depend heavily on the evenly distributed measurement data on the entire focal plane. However, owing to the restricted cubage of the vacuum tank and the large size of the assembled camera, there is no more extra space for the amounted large-format camera to adjust with the 2D turntable during laboratory vacuum experiment, which, accordingly, makes the collected measurement points gathered in just one module of the focal plane and eventually results in poor correction accuracy of the mentioned approaches. Here, in terms of the problems above, an extrapolating distortion correction method with local measurements for space-based multi-module splicing large-format infrared cameras was proposed in this paper. Benefiting from the polynomial model not being affected by the distribution of data, a third-order polynomial model adopted for distortion correction is solved by using local measurements and extrapolated reasonably, which guarantees the global camera calibration. Experimental results show that the mean distortion error can be corrected within 0.5 pixels. This method overcoming the deficiency of local test points can effectively improve the correction accuracy of the large-format camera and provide a new idea for global high-precision calibration of on-orbit payloads based on local measurements.

On-Orbit Geometric Calibration from the Relative Motion of Stars for Geostationary Cameras.

Affected by the vibrations and thermal shocks during launch and the orbit penetration process, the geometric positioning model of the remote sensing cameras measured on the ground will generate a displacement, affecting the geometric accuracy of imagery and requiring recalibration. Conventional methods adopt the ground control points (GCPs) or stars as references for on-orbit geometric calibration. However, inescapable cloud coverage and discontented extraction algorithms make it extremely difficult to collect sufficient high-precision GCPs for modifying the misalignment of the camera, especially for geostationary satellites. Additionally, the number of the observed stars is very likely to be inadequate for calibrating the relative installations of the camera. In terms of the problems above, we propose a novel on-orbit geometric calibration method using the relative motion of stars for geostationary cameras. First, a geometric calibration model is constructed based on the optical system structure. Then, we analyze the relative motion transformation of the observed stars. The stellar trajectory and the auxiliary ephemeris are used to obtain the corresponding object vector for correcting the associated calibration parameters iteratively. Experimental results evaluated on the data of a geostationary experiment satellite demonstrate that the positioning errors corrected by this proposed method can be within ±2.35 pixels. This approach is able to effectively calibrate the camera and improve the positioning accuracy, which avoids the influence of cloud cover and overcomes the great dependence on the number of the observed stars.