ABSTRACT
In scene-based nonuniformity correction algorithms, artificial ghosting and image blurring degrade the correction quality severely. In this paper, an improved algorithm based on the diamond search block matching algorithm and the adaptive learning rate is proposed. First, accurate transform pairs between two adjacent frames are estimated by the diamond search block matching algorithm. Then, based on the error between the corresponding transform pairs, the gradient descent algorithm is applied to update correction parameters. During the process of gradient descent, the local standard deviation and a threshold are utilized to control the learning rate to avoid the accumulation of matching error. Finally, the nonuniformity correction would be realized by a linear model with updated correction parameters. The performance of the proposed algorithm is thoroughly studied with four real infrared image sequences. Experimental results indicate that the proposed algorithm can reduce the nonuniformity with less ghosting artifacts in moving areas and can also overcome the problem of image blurring in static areas.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the possibility of transdifferentiation of adipose mesenchymal stem cells (AMSCs) into hepatocytes.</p><p><b>METHODS</b>Human omentum adipose tissue was dispersed with collagenase I. Cells collected were cultured in a DMEM-F12 medium containing 2% FBS supplemented with 20 ng/ml HGF, 10 ng/ml FGF4, 1xITS and 0.1 micromol/L dexasmison. The cells of the control group were also cultured in the same kind of medium but without any cytokines serving as a control. The expression of hepatic transcriptional factors such as GATA4 and HNF1 were checked by RT-PCR. At the end of the induction, hepatocyte markers were analysed by flow cytometry, and cytokeratin expressions were examined using cyto-immunofluorescence methods.</p><p><b>RESULTS</b>AMSCs grew like fibroblasts and were passaged easily. Most of the third passaged AMSCs were positive against anti-CD29, anti-CD44 antibodies, but negative for the anti-CD34 and anti-CD45 ones. The hepatic transcriptional factor was expressed gradually to higher levels during the induction time. AFP and Alb positive cells were 30.0% and 17.8% of the total cultured cells, and the rate of cells positive to the two markers was 6.9%. The inducted cells were positive for CK18 and CK19 antibodies at the end of the induction. The cells in the control group were negative when checked by these methods.</p><p><b>CONCLUSIONS</b>AMSCs could be directed to differentiate into hepatocytes in vitro by a cytokine cocktail with a low concentration FBS culture system.</p>
