Stabilization of Euler-Bernoulli beam with a nonlinear locally distributed feedback control

This paper studies the stabilization problem of uniform Euler-Bernoulli beam with a nonlinear locally distributed feedback control. By virtue of nonlinear semigroup theory, energy-perturbed approach and polynomial multiplier skill, the authors show that, corresponding to the different values of the parameters involved in the nonlinear locally distributed feedback control, the energy of the beam under the proposed feedback decays exponentially or in negative power of time t as t → ∞.     

中国籼稻亚种内的群体结构及地理生态分化

籼稻是亚洲和世界其他一些地区广为种植的主要栽培稻亚种,同时也是我国杂交水稻恢复系的主要来源.研究籼稻亚种内的遗传结构和遗传多样性对中国栽培稻亚种内的分类和演化以及水稻杂种优势利用具有重要的理论和实践意义.本研究通过36个SSR标记对1582份籼稻地方品种的群体结构和地理生态分化进行了分析.结果表明,利用分子标记所做基于模型和基于遗传距离的群体结构表现一致,即早籼稻生态型可划分为4个地理生态群,中间型生态型可划分为3个地理生态群,晚籼稻生态型可划分为2个地理生态群.当地的生态环境和空间隔离是形成地理分化的主要原因.地理生态群既体现了品种间的遗传差异又是对不同生态环境适应的反映,可用于籼稻亚种内杂种优势群划分的依据.根据SSR标记在各个生态型及地理生态群的基因型分布,筛选了可用于鉴别各生态型和地理生态群的SSR特征等位变异并建立了相应的SSR分子判别式.通过SSR分子判别式选择籼稻的中间类型开展籼粳杂种优势研究以及选择不同地理生态类型开展籼稻亚种内杂种优势研究,有助于突破籼粳杂种优势利用的障碍和加强籼稻亚种内杂种优势利用.     

A bioinformatic evaluation of potential allergenicity of 85 candidate genes in transgenic organisms

The potential of genetically modified organisms(GMOs) to increase allergenicity or predispositions to allergies has attracted much attention.An approach that will properly and holistically evaluate the allergenicity of GMOs is yet to be found.Here,85 transgenes that have been reported in both international and domestic studies during recent years are summarized case by case;49 of the transformed genes were from plant sources and 36 were from animal sources.EVALLERTM,a web server for the in silico assessment of potential protein allergenicity,was used to evaluate the potential of the transgenic proteins as allergens.The biomedical journals listed in Highwire(http://highwire.stanford.edu/) were searched and reviewed to decipher whether any of the transformed genes were linked to allergenicity or human health.The EVALLER analysis identified 5 allergenic genes,whilst our literature review found 11 genes that were either related to allergic cases or to clinical adverse events;all 16 of these genes have been used in GMOs.The analysis pathway that we have developed can help guide the selection of genes to be used in genetic modification.The pathway also provides a paradigm for allergenicity analysis of transgene candidates.     

计算机分子模拟提高蛋白质热稳定性的研究

计算机分子模拟作为一种重要的研究手段在生物、医药、化学、材料、微电子等领域受到了广泛的关注.其不仅可以从分子水平研究系统的微观结构及其宏观性质,而且在某些极端条件下及实验设备非常昂贵时,能直接提供实验数据以供参考.文章以解淀粉芽孢杆菌核糖核酸酶Barnase为研究对象,研究其在高温下的结构特征和动力学行为,分析蛋白质体系内的相互作用,寻找提高该蛋白质热稳定性的因素.为研究提高蛋白质热稳定性提供了一种计算思路和方法,同时为设计新的能在高温下发挥作用的新型酶类提供理论依据.     

Si/SiN_x多层膜能带结构的理论研究

利用Kronig-Penney模型计算了Si/SiNx多层膜结构中Si亚层的能带结构.结果表明,无论是减少Si或Si/SiNx亚层的厚度都将导致Si层的带隙发生宽化,计算结果与实验值符合较好.进而还发现,当Si层厚度减小时,Si/SiNx多层膜结构中载流子(电子和空穴)的有效质量均减小,有利于对载流子复合发光的控制.计算结果对实验上研究发光可控的Si/SiNx多层膜结构有重要指导意义.     

试论高职学生英语阅读能力提高的策略

在高职英语教学中，提高学生的阅读能力是一个急需解决的问题。教师应帮助学生扩大词汇量、掌握好英语语法结构知识、加强英语文化背景知识的学习以及阅读技巧的训练。     

Recognition and sensing of anions through synergistic effects using simple benzimidazolium-urea receptors

Benzimidazolium-based receptors 1-3 were designed and synthesized. On the basis of fluorescence, UV-Vis, and 1H NMR spectroscopic studies, and X-ray single crystal structure analysis, it was confirmed that the receptor 1 displays strong (C-H)+···X, N-H···X hydrogen bonds and charge-charge interactions with anions. More importantly, these investigations demonstrated that the charged (C-H)+ benzimidazolium and urea moieties play a synergistic role in anion recognition.     

Synthesis process of Ba-ferrites from α-FeOOH and γ-FeOOH and investigation of magnetic properties

The claviform BaFe₁₂O₁₉ crystals were synthesized by the precipitation-toptactic reaction method using α-FeOOH and γ-FeOOH as raw materials respectively. The synthesis processes of BaFe₁₂O₁₉, studied by XRD, SEM, EDS, FT-IR, and TG-DTA techniques, included preparations of precursor γ and precursor α, formations of α-Fe₂O₃ and BaFe₂O₄, and production of rod-like BaFe₁₂O₁₉ through dehydroxylation of pod-like FeOOH, followed by reactions of α-Fe₂O₃ with BaCO₃ and BaFe₂O₄. The crystallinity of α-Fe₂O₃ and BaCO₃ from precursor α was better than from precursor γ due to the direct dehydroxylation of α-FeOOH, resulting in a lower nucleation rate and better crystallinity of BaFe₂O₄. BaFe₁₂O₁₉ prepared from precursor α showed lower crystallinity and purity with a higher length-diameter ratio than from precursor γ. The VSM results proved that the appearance of final products had an important influence on magnetic properties.     

Radon-Nikodym theorem in signed Loeb space

This paper gives the Radon-Nikodym theorem in signed Loeb space under 1-saturated nonstandard model. First,the nonstandard characterization of absolute continuity is discussed,on which Radon-Nikodym theorem in signed Loeb space is obtained. Then,some facts about a finite signed Loeb measure and its variation are shown.