马氏体临界晶核的研究

应用Axiovert-25CA型金相光学显微镜和QUANTA-400环境扫描电镜对几种材料马氏体相变时的形核地点和形态进行了观察,发现马氏体不仅可在奥氏体晶粒内部形核,而且可在晶界、相界面等处形核.研究了马氏体晶核形成时的能量变化规律,计算了马氏体晶核的临界尺寸、形核功.马氏体临界晶核尺寸约为7～20 nm,形核功约为200～600 J·mol-1.     

纳米TiO2-SiO2复合材料的制备及光催化性能

以钛酸丁酯和硅酸乙酯为主要原料，制备多孔纳米TiO2-SiO2复合材料，采用氮气吸附-脱附，XRD，TEM，FT-IR等测试方法对其进行表征，以甲基橙的光催化降解反应对其光催化活性进行评价。结果表明，TiO2-SiO2具有核-壳结构，为锐钛矿和金红石相的混合物，比表面达到118．62m^2／g，TiO2以粒径为12．4nm的晶粒形式被SiO2包覆，复合材料粒径约为18nm；复合材料在22min时对甲基橙降解率达100％，而纯TiO2在22min时，对甲基橙降解率仅为40％，说明复合材料光催化活性比纯TiO2有明显提高。     

Deficits in landmark navigation and path integration after lesions of the interpeduncular nucleus.

Experiments were designed to determine the role of the interpeduncular nucleus (IPN) in 3 forms of navigation: beacon, landmark, and path integration. In beacon navigation, animals reach goals using cues directly associated with them, whereas in landmark navigation animals use external cues to determine a direction and distance to goals. Path integration refers to the use of self-movement cues to obtain a trajectory to a goal. IPN-lesioned rats were tested in a food-carrying task in which they searched for food in an open field, and returned to a refuge after finding the food. Landmark navigation was evaluated during trials performed under lighted conditions and path integration was tested under darkened conditions, thus eliminating external cues. We report that IPN lesions increased the number of errors and reduced heading accuracy under both lighted and darkened conditions. Tests using a Morris water maze procedure indicated that IPN lesions produced moderate impairments in the landmark version of the water task, but left beacon navigation intact. These findings suggest that the IPN plays a fundamental role in landmark navigation and path integration. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Information coding in early stages of the somatosensory system

This paper explores the information coding performed by the local circuit of the Cuneate Nucleus (CN). On the basis of physiological data, we have developed a realistic computational model and studied its output in response to different types of plausible cutaneous stimuli. Computer simulations show that (1) static stimuli are encoded in progressive spatio-temporal patterns made up of single-spike trains generated by each stimulated neuron, and (2) moving stimuli are encoded with a bursting discharge of those units responding to the leading edge of the stimulus. These results suggest that the role of CN could be to transform the stimulus representation in order to facilitate both discrimination and classification in later processing stages.     

Cholinergic control of attention to cues guiding established performance versus learning: Theoretical comment on Maddux, Kerfoot, Chatterjee, and Holland (2007).

Previous views on the cognitive functions of the basal forebrain cholinergic system often suggested that this neuromodulator system influences fundamental attentional processes but not learning. The results from an elegant series of studies by J. M. Maddux, E. C. Kerfoot, S. Chatterjee, and P. Holland (2007, see record 2007-02025-006) reveal the intricate relationships between the levels of attentional processing of stimuli and the rate of learning about such stimuli. Moreover, their results indicate a double dissociation between the role of prefrontal and posterior parietal cholinergic inputs, respectively, in attentional performance and the learning rate of stimuli that command different levels of attentional processing. Separate yet interacting components of the cortical cholinergic input system modulate the attentional processing of cues that guide well-practiced performance or that serve as conditioned stimuli during learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Aggressive behaviors in adult SF-1 knockout mice that are not exposed to gonadal steroids during development.

Sex hormones are a major factor responsible for the development of sex differences. Steroidogenic factor 1 (SF-1) is a key regulator of gonadal and adrenal development, and SF-1 knockout mice (SF-1 KO) are born without gonads and adrenal glands. Consequently, these mice are not exposed to gonadal sex steroids. SF-1 KO pups die shortly after birth due to adrenal deficiency. In the present study, SF-1 KO mice were rescued by neonatal corticosteroid injections followed by adrenal transplantations on day 7-8 postnatally. Control mice received corticosteroid injections and were gonadectomized prior to puberty. Mice were observed interacting with ovariectomized hormone primed females and gonad-intact males. In the absence of sex steroid replacement, adult SF-1 KO mice were significantly more aggressive than control mice in tests with stimulus females. After testosterone treatment, control males displayed significantly more aggression towards male intruders than control female mice, or male and female SF-1 KO mice, suggesting a developmental role of gonadal hormones in the expression of aggressive behavior and affirming SF-1 KO mice as a behavioral model to investigate affects of fetal gonad deficiency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

超声波辅助提取龙眼核总黄酮

以龙眼核为原料,采用超声波乙醇浸取法提取总黄酮,对提取条件进行单因素实验并进行正交试验。结果表明:最佳的提取条件为乙醇浓度60%,料液比为1∶40,提取时间1.5 h,超声波功率为60 kHZ,在此条件下测得样液中总黄酮的含量为1.56 mg·mL-1。     

Over-Expression of Copper/Zinc Superoxide Dismutase in the Median Preoptic Nucleus Attenuates Chronic Angiotensin II-Induced Hypertension in the Rat

The brain senses circulating levels of angiotensin II (AngII) via circumventricular organs, such as the subfornical organ (SFO), and is thought to adjust sympathetic nervous system output accordingly via this neuro-hormonal communication. However, the cellular signaling mechanisms involved in these communications remain to be fully understood. Previous lesion studies of either the SFO, or the downstream median preoptic nucleus (MnPO) have shown a diminution of the hypertensive effects of chronic AngII, without providing a clear explanation as to the intracellular signaling pathway(s) involved. Additional studies have reported that over-expressing copper/zinc superoxide dismutase (CuZnSOD), an intracellular superoxide (O₂·⁻) scavenging enzyme, in the SFO attenuates chronic AngII-induced hypertension. Herein, we tested the hypothesis that overproduction of O₂·⁻ in the MnPO is an underlying mechanism in the long-term hypertensive effects of chronic AngII. Adenoviral vectors encoding human CuZnSOD (AdCuZnSOD) or control vector (AdEmpty) were injected directly into the MnPO of rats implanted with aortic telemetric transmitters for recording of arterial pressure. After a 3 day control period of saline infusion, rats were intravenously infused with AngII (10 ng/kg/min) for ten days. Rats over-expressing CuZnSOD (n = 7) in the MnPO had a blood pressure increase of only 6 ± 2 mmHg after ten days of AngII infusion while blood pressure increased 21 ± 4 mmHg in AdEmpty-infected rats (n = 9). These results support the hypothesis that production of O₂·⁻ in the MnPO contributes to the development of chronic AngII-dependent hypertension.     

柱状气液分离器液相带气特性分析

分析了柱状气液分离器(GLCC)内气相的运动轨迹。通过实验得到了不同操作参数下的液相带气特性,揭示了液相和气相速度对液相带气的影响。同时,采用可视化研究得到了分离器下部气液两相流型图,分析了不同形态气核的特性。证实了气核是造成液相带气的主要原因,揭示了不同稳定性的气核对液相带气的影响。     

Activity Dependent Brain Plasticity: Does Singing Increase the Volume of a Song System Nucleus? Theoretical Comment on Sartor and Ball (2005).

The avian telencephalic song system, including nucleus high vocal center (HVC), is an important model for the study of brain plasticity. J. J. Sartor and G. F. Ball (2004) asked whether song activity itself could increase HVC volume (see record 2005-01705-022). They report that male starlings that sang more, motivated by gaining possession of a nest box in competition with another male, had larger HVCs than males that sang less. These results are suggestive but correlational. A more direct experimental approach will be required to establish that HVC size is activity dependent. Their experiment is an important first step, however. The song activity hypothesis merits continued investigation because of its potential to produce unique insights into naturally occurring brain plasticity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)