采用DFP-BFGS优化大间距子阵级非周期八角阵

采用DFP-BFGS变尺度算法优化分析了非周期八角阵的子阵中心位置,使栅瓣得到抑制,且阵列的辐射特性达到良好的效果。由于阵列辐射单元之间间距选取大于1个波长,天线方向图必定有栅瓣出现,所以,选择优化子阵中心位置,分散栅瓣能量,使周期八角阵变形为非周期八角阵布阵形式。若该阵列采用高效阵列单元,就可以实现有限相控扫描,且可以获得更低的副瓣要求。     

穿墙成像雷达旁瓣/栅瓣抑制方法

提出了一种超宽带超稀疏阵列穿墙成像雷达距离向旁瓣和方位向栅瓣抑制的新方法。对于使用步进频连续波的超宽带雷达,其距离向旁瓣较高,通常采用加窗进行抑制。对于超稀疏阵列,其方位向栅瓣较高,可以采用相位相干因子(PCF)加权进行抑制。若同时抑制距离向旁瓣和方位向栅瓣,可以对加窗的图像作PCF加权。但是,距离向加窗会抬高方位向栅瓣,进而降低PCF抑制方位向栅瓣的效果。针对这个问题,提出一种PCF结合双切趾的方法,能够同时有效地抑制距离向旁瓣和方位向栅瓣。仿真和实验结果验证了方法的有效性。     

Frontal lobe dysfunctions in Korsakoff's syndrome and chronic alcoholism: Continuity or discontinuity?

The effect of long-term heavy alcohol consumption on brain functions is still under debate. The authors investigated a sample of 17 Korsakoff amnesics, 23 alcoholics without Korsakoff's syndrome, and 21 controls with peripheral nerve diseases, matched for intelligence and education. Executive functions were examined for word fluency, the modified Wisconsin Card Sorting Test, an alternate response task, and an "n-back" working memory task. Korsakoff amnesics, but not alcoholics, showed a marked memory impairment. They also scored lower in each of the executive tasks--the alcoholics only in the alternate response task. This task also correlated with the years of the alcohol dependency. First, the authors conclude that Korsakoff's syndrome is associated not only with a memory impairment but also with a global executive deficit. Second, the decline in the ability to alternate between different responses argues for a restricted neurotoxic effect of alcohol on some frontal lobe areas (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Investigating the dopaminergic basis of extraversion in humans: A multilevel approach.

A recent theory suggests that the agency facet of Extraversion (E) is based on brain dopamine (DA). The paucity of human data relevant to this model is probably due to the lack of widely accessible noninvasive psychophysiological indices and well-established behavioral measures sensitive to both E and manipulations of DA activity. Aiming to identify such measures, the authors assessed the electroencephalogram and n-back task performance in groups of introverts and extraverts after administration of either placebo or a selective DA D2 receptor antagonist. As predicted, the antagonist's effects on n-back reaction time measures and frontal versus parietal electroencephalogram theta activity were strongly and specifically modulated by E. New research avenues and theoretical extensions suggested by these results are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-propagating Free-radical Binary Frontal Polymerization

The first mathematical model for free-radical binary frontal polymerization (BFP), is presented. The model describes the following experimental situation. A test tube is filled with a mixture of two monomers and an initiator. When the temperature at the top of the tube is increased a self-sustained polymerization wave which propagates along the axis of the tube is formed. Two different polymer species are synthesized in the wave. Such one-dimensional polymerization waves are studied. Approximate analytical solutions are derived and compared to numerical solutions. The effect of various parameters of the model on the front velocity and temperature is discussed.     

Frontal brain asymmetry in restrained eaters.

It is well known that the eating patterns that restrain chronic dieters (restrained eaters) can be disinhibited by anxiety, which in turn has been associated with relative right frontal brain activity in independent electroencephalographic (EEG) studies. Combining these two lines of evidence, the authors tested the hypothesis that chronic restrained eating is associated with relative right frontal asymmetry. Resting anterior brain asymmetry and self-reported measures of anxiety and depression were collected in 23 restrained and 32 unrestrained eaters. As hypothesized, groups differed in tonic frontal activity, with restrained eaters showing more relative right frontal activity. Furthermore, relative right frontal activity was associated with greater self-reported restraint. Right-sided prefrontal asymmetry may thus represent a diathesis associated with increased vulnerability toward restrained eating. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chemical defense by termite soldiers

The chemistry of the defensive secretions of termite soldiers is reviewed. The structural variety of the chemical weapons, the uses of these substances in defense, and some potential biosynthetic interrelationships are discussed. Classification of the monoterpenes, sesquiterpenes, diterpenes, and various acetate-derived compounds according to termite subfamilies places the known defense substances in a phylogenetic perspective.