Traces of human migrations in Helicobacter pylori populations

Helicobacter pylori, a chronic gastric pathogen of human beings, can be divided into seven populations and subpopulations with distinct geographical distributions. These modern populations derive their gene pools from ancestral populations that arose in Africa, Central Asia, and East Asia. Subsequent spread can be attributed to human migratory fluxes such as the prehistoric colonization of Polynesia and the Americas, the neolithic introduction of farming to Europe, the Bantu expansion within Africa, and the slave trade.     

持续、低剂量金霉素对肉仔鸡免疫机能的抑制作用研究

270只Abore Acre商品代肉用公鸡随机分成3组，金霉素在饲料中添加水平分别为0、50只和150mg/kg，研究饲用金霉素对肉仔鸡法氏囊、脾脏和胸腺等免疫器官发育、以及免疫反应的影响。结果表明50mg/kg的金霉素对肉仔鸡脾脏和21日龄的胸腺无明显抑制作用，对T、B淋巴细胞转化率也无明显抑制作用（P＜0.05），而且显著促进法氏囊的萎缩（P＜0.05）。金霉素对T淋巴细胞转化率有明显的直接抑制作用；50mg/kg和150mg/kg的金素对BAS特异性抗体的产生均有显著的抑制作用（P＜0.01）。研究结果表明，持续、低剂量和金霉素对肉 鸡免疫器官发育和免疫应答具有显著的抑制作用，抑制作用随剂量增加而加强，150mg/kg的金霉素对肉仔鸡具有显著促生长作用。     

Fluorine Is a Major Constituent of the Marine Sponge Halichondria moorei

Fluorine constitutes about 10 percent of the dry weight of the marine sponge Halichondria moorei. The fluorine occurs as potassium fluorosilicate, which is a potent anti-inflammatory agent. A closely related sponge living in the same habitat does not contain any fluorine. The habitat was found to be free of fluorine except for the small amount naturally present in seawater.     

Quantum-confined stark effect in single CdSe nanocrystallite quantum dots

The quantum-confined Stark effect in single cadmium selenide (CdSe) nanocrystallite quantum dots was studied. The electric field dependence of the single-dot spectrum is characterized by a highly polarizable excited state ( approximately 10(5) cubic angstroms, compared to typical molecular values of order 10 to 100 cubic angstroms), in the presence of randomly oriented local electric fields that change over time. These local fields result in spontaneous spectral diffusion and contribute to ensemble inhomogeneous broadening. Stark shifts of the lowest excited state more than two orders of magnitude larger than the linewidth were observed, suggesting the potential use of these dots in electro-optic modulation devices.     

Transport of Dissolved Amino Acids by the Mussel, Mytilus edulis: Demonstration of Net Uptake from Natural Seawater

High-performance liquid chromatography provides direct evidence for substantial removal of naturally occurring specific free amino acids during a single passage of water through the mantle cavity of mussels. This occurs during the few seconds required for passage of the water across the gill, and removal proceeds unabated at ambient substrate concentrations as low as 38 nanomoles per liter.     

基于EDA技术的自动立木整枝机无线遥控接收系统

在分析自动立木整枝机工作过程和控制要求的基础上,该文详细阐述了自动立木整枝机无线遥控接收系统的组成及工作原理,进而采用电子设计自动化(EDA)技术设计了自动立木整枝机无线遥控接收系统的数字控制逻辑.通过优化CPLD内部逻辑电路,有效消除了逻辑竞争冒险.仿真结果表明,该系统控制可靠性较高,能有效提高自动立木整枝机的功能安全性.      

Smog aerosol: infrared spectra

Infrared spectra of smog aerosol are similar to those of sulfuric acid aerosol, but they do not show the prominent CH and carbonyl bands of organic aerosols from terpenes. Some features of the smog aerosol spectra are not present in the spectra from either type of synthetic aerosol.     

Masson三色染色与HE染色在豚鼠牙齿组织石蜡切片中的比较研究及应用

针对牙齿组织形态学研究的难点,选择适宜固定液,用EDTA-2Na进行脱钙,完成了牙齿组织石蜡切片的制作。通过确定染色程序及各种染料的最佳作用时间,分别利用Masson三色染色法、传统的苏木精和伊红（HE）染色法对牙齿组织切片进行了染色观察。染色结果表明,与HE染色法相比,Masson三色染色更能使牙齿的各主要成分以不同颜色显现出来,色彩对比鲜明,亮丽润眼,为牙齿组织生理及病理组织形态学研究奠定了基础。针对机体中硬组织的相似特性,该试验方法可以在骨骼、软骨等硬组织的形态学研究中参考、改进并推广使用。     

骨质疏松症治疗药物的研究进展

骨质疏松症是以骨量减少、骨的微观结构退化为特征,致使骨的脆性增加并易于发生骨折的一种全身性骨骼疾病,是当前严重危害人类特别是绝经妇女和老人的疾病之一.近年来出现了许多预防和治疗骨质疏松症的药物,极大地推动了骨质疏松症理论基础的完善和临床治疗研究.就该领域的研究进展进行了简要综述.