基于抛物线方程求解二维电磁散射问题

文章应用抛物线方程求解二维凸面物体的双站雷达散射截面,模拟多体散射问题。其优点在于将传统的波动方程降维处理,采用步进迭代方法,节省大量计算资源。应用完全匹配层和有限差分法计算单个和多个圆柱的小角度双站RCS,计算结果和精确解基本吻合,且计算速度大大提高。     

Differential gene expression profile in ischemic myocardium of Wistar rats with acute myocardial infarction

To determine the differential genes in ischemic myocardium of Wistar rats with acute myocardial infarction （AMI）, we constructed two differential gene expression profiles. AMI model was generated by Iigation of the left anterior descending coronary artery in Wistar rats. Total RNA was extracted from the normal and the ischemic heart tissues under the IigaUon point at the 8th day after the operation. Differential gene expression profiles of the two samples were constructed by using long serial analysis of gene expression （LongSAGE）. Real time fluorescence quantitative PCR （Q-PCR） was used to confirm the expression changes of partial target genes. The main results were as follows： a total of 15966 tags were screened from the normal and the ischemic LongSAGE maps, and 9646 tags in the normal tissue and 9563 tags in the ischemic tissue were obtained. Among them, 7665 novel tags were identified by NCBI BLAST search. In the ischemic tissue, 142 genes significantly changed compared to those in the normal tissue （P〈0.05）. These differentially expressed genes may play important roles in the pathways of oxidation and phosphorylation, ATP synthesis and glycolysis and so on. Partial genes identified by the LongSAGE were confirmed by Q-PCR. The results show that AMI causes a series of gene expression changes in the regulation of the pathways related to energy metabolism.     

用二维全息光栅制作光学时钟分布中的全息光学元件

提出了用二维全息光栅制作自由空间光学时钟分布中的全息光学元件的方法.实验中采用类似于马赫 泽德干涉仪的光路;其中,物光为二维光栅中间的9个衍射级.分析了二维光栅各衍射级的衍射效率、位置及各衍射级之间的间距.初步实验得到了可产生二维3×3输出端的全息光学元件.理论分析表明,该全息光学元件可适用于3×3光敏面半径大于10μm的光探测器阵列.     

乳酸菌计数结果的比较研究

通过流式细胞术(FCM),利用SYTO?24与PI双染色对发酵乳制品即发酵乳饮料和发酵乳中的乳酸菌进行快速检测,并将检测结果与用现行国标中推荐的平板计数法检测得到的结果相比较,两者对发酵乳饮料和发酵乳中乳酸菌的计数结果的相关性系数分别为:0. 9014;和0. 9653,都符合较好.而且FCM稳定性更好,活性细菌的变异率为3. 46%,非活性细菌的变异率为3. 56%;检测速度更快,单样品检测时间不超过10 min;灵敏度更高(10~3AFU·mL~(-1)) FCM在需要快速放行的液体产品检测领域中具有广阔的应用前景.     

基于二维DFT的多导频模式OFDM信道估计算法

提出了一种正交频分复用 (orthogonal frequencydivision multiplexing,OFDM)系统中的抗噪声信道估计算法 ,适用于块状、梳状、格形和菱形导频模式。该算法通过导频位置偏移量预校正、二维离散 Fourier变换 (DFT)和变换域滤波消除噪声的影响 ,利用变换域补零和二维反离散Fourier变换进行信道传输函数插值 ,并使用变形 cos窗抑制插值过程中的频谱扩散。仿真结果表明 :该算法的系统性能明显优于传统信道估计算法 ,采用该算法获得了约 2 d B的每 bit信噪比增益。该算法在宽带 OFDM系统中有应用潜力     

CO_2质量浓度对沈阳市银杏生长及光合固碳能力的影响

以生长在沈阳市区内的银杏为试材,使用开顶箱模拟法对倍增CO2质量浓度(700μmol．mol-1)和正常空气CO2质量浓度(≈350μmol．mol-1)条件下,银杏生长参数、叶面积指数、不同天气中净光合速率日变化进行了初步研究,探讨了高质量浓度CO2对单株银杏光合固碳能力的影响。结果表明:CO2质量浓度增高可以显著提高银杏枝条的生长量和银杏的叶面积指数。经高质量浓度CO2处理后,银杏不同天气下光合速率日变化趋势与对照一致,即晴天为双峰曲线,多云天气为单峰曲线,但净光合速率显著高于对照(P<0．001)。由于净光合速率和叶面积指数升高,高质量浓度CO2也显著提高了单株银杏的固碳释氧能力(P<0．01),晴天比对照提高了119．5％,阴天提高了175．4％。