Synthetic aperture radar (SAR) imaging is usually performed along a straight path. In practice, variations from the ideal caused by maneuvers with acceleration are inevitable. The main problem is the complex signal processing, particularly in the highly squinted spotlight mode. In this paper, acceleration model is analyzed in more details. Impacts are obtained how the acceleration influences the Doppler parameters and space-variant terms, including the SAR resolution and azimuth bandwidth. According to the special signal properties of the acceleration case, an approximation of the range history is made to avoid using the method of series reversion (MSR) to obtain an accurate spectrum. Based on the high-accurate spectrum, a spotlight algorithm with a modified two-step approach is given. Simulation results show the effectiveness of the modified algorithm.Index Terms-Acceleration model, highly squinted, maneuvers, omega-K algorithm (OKA), spotlight synthetic aperture radar (SAR), two-step approach.

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The purpose of this study was to determine the effect of aspirin plus cisplatin (CDDP) in the chemotherapy of gastric cancer. We cultured SGC7901/CDDP cells by long-term exposure of SGC7901 cells to small doses of CDDP in vitro. The cells were treated with aspirin, CDDP or aspirin plus CDDP for 24 h and cell growth was assessed by the MTT assay, the apoptotic rate by flow cytometry, the survivin mRNA expression by RT-PCR and the survivin protein expression by western blotting. The results revealed that the cell growth in the aspirin plus CDDP group was significantly inhibited. The apoptotic rate in the aspirin plus CDDP was significantly higher compared to that in the other groups. The survivin mRNA and protein expression were also significantly reduced in the aspirin plus CDDP group. Our data suggest that the combination of aspirin and CDDP exhibited a higher degree of toxicity against SGC7901/CDDP cells compared to that of aspirin or CDDP alone. Thus, the combination of aspirin plus CDDP may reduce the expression of survivin and induce the apoptosis of SGC7901/CDDP cells.

The aim of the present study was to investigate the mechanism of SGC7901 cell resistance to cisplatin (CDDP). SGC7901/CDDP cells were established by the long-term continuous exposure of SGC7901 cells to CDDP in stepwise concentration increments. The morphologies of the SGC7901/CDDP and SGC7901 cells were observed by microscopy. The expression levels of Survivin mRNA and protein in the SGC7901/CDDP and SGC7901 cells were examined by reverse transcription polymerase chain reaction and western blotting respectively. The results revealed morphological differences between the SGC7901 and SGC7901/CDDP cells. The expression levels of Survivin mRNA and protein were significantly higher in the SGC7901/CDDP cells than in the SGC7901 cells. Therefore, high expression levels of the Survivin gene may explain SGC7901 cell resistance to CDDP.