Hydrothermal Synthesis of Magnesium Aluminate Platelets

Magnesium aluminate (MgAl₂O₄) platelets were first synthesized by hydrothermal treatment of γ-AlO(OH) in a magnesium nitrate aqueous solution at 400°C. The platelets are 100–200 nm in width and 25 nm in thickness. The influence of temperature, the anions of the magnesium salt, the amount of magnesium salt, and precursor pH on the formation of such structure was investigated. The experimental results indicated that the anions of the magnesium salt and precursor pH could have a significant influence on the growth of MgAl₂O₄. MgAl₂O₄ formation followed the in situ transformation mechanism, which was the reason why the MgAl₂O₄ crystallites had a platelet morphology.     

用αβ谱仪测量人工αβ放射性气溶胶体积活度的试验研究

本文介绍了用αβ谱仪系统同时测量αβ谱、实现Ｒｎ／Ｔｈ子体补偿、确定超铀α核素气溶胶体积活度及人工放射性气溶胶总β体积活度的技术途径。利用ＲａＡ、ＲａＣ′ａ峰的二段时间计数可确定空气中ＲａＡ、ＲａＢ、ＲａＣ的气溶胶体积活度，相应的，也能给出ＲａＢ、ＲａＣ对总β计数的贡献。根据一般环境条件下的平衡比，用ＴｈＣ′的。计数修正Ｔｈ子体对αβ测量的影响。￣［２３９］ｐｕ或／和￣［２４１］Ａｍ人工核素的α计数，可通过两段时间分别扣除ＲａＡ、ＲａＣ′拖尾的方法确定；β计数分别扣除Ｒｎ／Ｔｈ子体β贡献即可确定。在本文规定的测量条件下，对室内天然Ｒｎ子体水平在１５Ｂｑ／ｍ￣３以下，超铀α核素气溶胶体积活度的测量下限可达到０．１Ｂｑ／ｍ￣３；即使在７５Ｂｑ／ｍ￣３环境下，人工核素总β的测量下限也可达ｌＢｑ／ｍ￣３以下。     

利用计算机进行油气资源评价和勘探决策

本文着重介绍了构成《现代勘探决策理论系统》的5个主要计算机模块,即:生油岩热演化处理、求任意曲边形面积、数学模拟预测资源量、勘探经济评价分析及决策、辅助处理等模块。该系统曾在塔里木盆地和准噶尔盆地的油气资源评价和勘探决策中发挥了作用,受到了专家和用户的好评。     

Substance P modulates NMDA responses and causes long-term protein synthesis-dependent modulation of the lamprey locomotor network

Tachykinin immunoreactivity is found in a ventromedial spinal plexus in the lamprey. Neurons in this plexus project bilaterally and are thus in a position to modulate locomotor networks on both sides of the spinal cord. We have examined the effects of the tachykinin substance P on NMDA-evoked locomotor activity. Brief (10 min) application of tachykinin neuropeptides results in a prolonged concentration-dependent (>24 hr) modulation of locomotor activity, shown by the increased burst frequency and more regular burst activity. These effects are blocked by the tachykinin antagonist spantide II. There are at least two phases to the burst frequency modulation. An initial phase (approximately 2 hr) is associated with the protein kinase C-dependent potentiation of cellular responses to NMDA. The long-lasting phase (>2 hr) appears to be protein synthesis-dependent, with protein synthesis inhibitors causing the increased burst frequency to recover after washing for 2-3 hr. The modulation of the burst regularity is caused by a separate effect of tachykinins, because unlike the burst frequency modulation it does not require the modulation of NMDA receptors for its induction and is blocked by H8, an inhibitor of cAMP- and cGMP-dependent protein kinases. The effects of substance P were mimicked by the dopamine D2 receptor antagonist eticlopride. The effects of eticlopride were blocked by the tachykinin antagonist spantide II, suggesting that eticlopride may endogenously release tachykinins. Because locomotor activity in vitro corresponds to that during swimming in intact animals, we suggest that endogenously released tachykinins will result in prolonged modulation of locomotor behavior.     

Endothelium-dependent effect of perindopril and enalaprilat in rat thoracic aorta

AIM: To study the effect of the angiotensin-converting enzyme (ACE) inhibitors perindopril (Per) and enalaprilat (Ena) on the reactivity of the endothelium in normal rats. METHODS: Male rats were treated intragastrically with Per (2 mg.kg-1.d-1) or placebo (n = 18) for 6 wk. Aorta was isolated for experiment. Another set of isolated aortic rings with and without endothelium were incubated with Ena (0.1 mumol.L-1) for 30 min. Responses to acetylcholine, serotonin, phenylephrine, sodium nitroprusside (SN), and nitroglycerin (Nit) were observed. RESULTS: Endothelium-dependent relaxation to acetylcholine was augmented in aortic rings from rats treated with Per in comparison with control. The IC50 value (95% confidence limits) decreased from 3.8 (0.56-26.1) mumol.L-1 (control group) to 0.98 (0.28-3.41) mumol.L-1 (Per-treated group). The maximal relaxation was augmented from 62 +/- 9% to 78 +/- 10% (P < 0.01). However, the responses to the endothelium-independent vasodilators, SN and Nit, were similar. Serotonin- and phenylephrine-induced contractions were decreased, which were influenced by basal release of endothelium-derived relaxing factor (EDRF). EC50 values was 6.1 (2.6-14.4) nmol.L-1 vs 8.3 (3.6-18.8) nmol.L-1 in comparison with control group and Per-treated group. The maximal contraction was decreased from 2.42 +/- 0.29 g (control group) to 1.96 +/- 0.25 g (treated group) (P < 0.01). Similar results were found in incubation with Ena. CONCLUSION: Ena and Per enhanced the basic release of EDRF from vascular endothelium.     

Ahch, the mouse homologue of DAX1: cloning, characterization and synteny with GyK, the glycerol kinase locus

We cloned the murine full-length cDNA encoding Ahch, the mouse homologue of DAX1 (DSS-AHC Region on Human X Chromosome, Gene1) which is the gene responsible for human X-linked adrenal hypoplasia congenita (AHC) and hypogonadotropic hypogonadism (HH). Sequence analysis revealed that the murine and human cDNAs have 65% aa identity and 75% aa similarity overall. The cysteine residues in the putative DNA binding domain, which may interact with Zn2+ ions to form zinc fingers, are 100% conserved between the two species, indicating that the novel zinc-finger structures in DAX1 may be functional. In addition, mouse interspecific backcrosses show that the Ahch gene is closely linked to the glycerol kinase locus, GyK, on the mouse X chromosome, indicating that the order of the loci is conserved in this syntenic region between mouse and human.     

北京谱仪Ⅱ（BESⅡ）顶点探测器数据获取系统

北京谱仪（ＢＥＳⅡ）顶点探测器数据获取系统是北京谱仪数据获取系统的一部分，该子系统电子学采用快总线标准，本文描述了该系统的硬件结构和软件系统，软件包括快总线系统的微码软件和上层控制软件，该系统的死时间为１．５ｎｓ，对ＢＥＳⅡ系统总死时间的贡献小于０．５ｍｓ。