Attention deficit/hyperactivity disorder children with a 7-repeat allele of the dopamine receptor D4 gene have extreme behavior but normal performance on critical neuropsychological tests of attention

An association of the dopamine receptor D4 (DRD4) gene located on chromosome 11p15.5 and attention deficit/hyperactivity disorder (ADHD) has been demonstrated and replicated by multiple investigators. A specific allele [the 7-repeat of a 48-bp variable number of tandem repeats (VNTR) in exon 3] has been proposed as an etiological factor in attentional deficits manifested in some children diagnosed with this disorder. In the current study, we evaluated ADHD subgroups defined by the presence or absence of the 7-repeat allele of the DRD4 gene, using neuropsychological tests with reaction time measures designed to probe attentional networks with neuroanatomical foci in D4-rich brain regions. Despite the same severity of symptoms on parent and teacher ratings for the ADHD subgroups, the average reaction times of the 7-present subgroup showed normal speed and variability of response whereas the average reaction times of the 7-absent subgroup showed the expected abnormalities (slow and variable responses). This was opposite the primary prediction of the study. The 7-present subgroup seemed to be free of some of the neuropsychological abnormalities thought to characterize ADHD.

Neutrality tests using DNA polymorphism from multiple samples

The polymorphism of a gene or a locus is studied with increasing frequency by multiple laboratories or the same group at different times. Such practice results in polymorphism being revealed by different samples at different regions of the locus. Tests of neutrality have been widely conducted for polymorphism data but commonly used statistical tests cannot be applied directly to such data. This article provides a procedure to conduct a neutrality test and details are given for two commonly used tests. Applying the two new tests to the chemokine-receptor gene (CCR5) in humans, we found that the hypothesis that all mutations are selectively neutral cannot explain the observed pattern of DNA polymorphism.

半绝缘GaAs中EL2能级的EPR和光电导研究

Submitted by zhangdi (zhangdi@red.semi.ac.cn) on 2009-04-13T11:45:31Z

Photoluminescence from C+ ion-implanted and electrochemical etched Si layers

The microstructural and optical analysis of Si layers emitting blue luminescence at about 431 nm is reported. These structures have been synthesized by C+ ion implantation and high-temperature annealing in hydrogen atmosphere and electrochemical etching sequentially. With the increasing etching time, the intensity of the blue peak increases at first, decreases then and is substituted by a new red peak at 716 nm at last, which shows characteristics of the emission of porous silicon. C=O compounds are induced during C+ implantation and nanometer silicon with embedded structure is formed during annealing, which contributes to the blue emission. The possible mechanism of photoluminescence is presented. (c) 2005 Elsevier B.V. All rights reserved.

Carrier Depth Profile of Si/SiGe/Si n-p-n HBTStructural Materials Characterized by Electrochemical Capacitance- Voltage Method

于2010-11-23批量导入

半绝缘砷化镓EPR谱的异常退火特性

国家自然科学基金