小麦馒头品质评价方法优化

为了优化现有的馒头品质评价方法,参照LS/T 3204—1993和GB/T 17320—1998,进行馒头制作与品质评价技术研究,经相关性分析、逐步回归分析及拟合检验,精简其评价项目、提高操作性和准确性。结果表明,馒头品质评价指标可被简化为4项,分别为比容、外观、外部色泽与适口性,其权重依次为30%,20%,10%和40%。新方法可替代原始方法,仪器评价法与原始评价方法相关性有待提高,仅色差计参数a*值与外部色泽、质构仪咀嚼性指标与粘牙相关性较高,可作为评价外部色泽与适口性的有效辅助手段。新方法可适用于不同产地、品种小麦制作的馒头品质评价,具有感官指标少、差异易被区别、准确性和可行性高的特点。     

Effect of Y_2O_3 content in the pack mixtures on microstructure and oxidation resistance of B–Y modified silicide coating

B–Y modified silicide coatings were prepared on Nb–Si based alloy by pack cementation at 1300 ℃ for 10 h. The effect of Y_2O_3 content in the pack mixtures on microstructure and oxidation resistance of the coatings was investigated. The results show that the four coatings have similar structures, which possess a(Nb,X)Si_2 outer layer and a(Nb,X)_5Si_3 transitional layer. Y_2O_3 content in the pack mixtures has an obvious effect on the Si content in the coating. The mass gains of the coatings prepared with 0.5, 1, 2 and 3 wt% Y_2O_3 in pack mixtures are 2.33, 1.96, 2.05 and 2.86 mg/cm~2 after oxidation at 1250 ℃ for 100 h, respectively. The coating prepared with 1 wt% Y_2O_3 exhibits the best oxidation resistance due to the formation of a dense glass-like borosilicate scale.     

Effect of Mo content on microstructure and stress-rupture properties of a Ni-base single crystal superalloy

The additional 1.5 wt% Mo was added in a Ni-base single crystal(SC) alloy with the composition of Ni–6.5Al–8.0Mo–2.4Cr–6.2Ta–4.9Co–1.5Re–(0.01–0.05)Y(wt%) to study the effect of Mo content on the microstructure and stress-rupture properties. The creep and stress-rupture tests under the conditions of 850 °C/500 MPa and 1100 °C/130 MPa were conducted, and the microstructure of as-cast, heat treated and stress ruptured specimens were analyzed. It was found that the 1.5 wt% Mo addition enhanced the stress-rupture lives at both intermediate(850 °C) and high(1100 °C)temperatures. The microstructure analysis showed that adding 1.5 wt% Mo in the basic alloy affected the microstructure dramatically, i.e., the Mo-rich phases formed in the specimens of as-cast and stress-ruptured specimens. It is considered that the improvement of the stress-rupture lives is duo to the strengthening effect of Mo to both γ and γ'phases and the decrease of stacking fault energy, diffusion constant and dislocation spacing. The Mo-rich phases precipitated under condition of 1100 °C/130 MPa did not affect the creep and stress-rupture properties obviously in the present study.     

基于真假设比例广义推断的多重检验方法

研究了多重假设检验方法的改进问题,基于真假设所占比例的广义推断,利用其广义置信上限对现有的多重假设检验方法进行改进.该方法更好地利用了水平,在功效上有很大提升.采用广义推断方法,即使在假设个数比较小时,也能对真假设所占比例做出较好推断.模拟结果表明,该方法显著提高了传统方法的功效.     

冠菌素对玉米节间伸长和产量性状的影响

 试验以常用玉米杂交种郑单958为材料,用0.001、0.01、0.1、1μmol/L冠菌素(COR)作处理,清水为对照,通过调查农艺性状、分析生理指标以及产量性状,研究COR对玉米节间伸长的影响.结果表明,随着COR处理浓度的增加,郑单958的株高、穗位高和节间长度均降低,0.01、0.1和1μmol/L COR处理的株高、穗位高以及第2-8节节间长度均低于对照,且差异达到显著或极显著水平.随着COR处理浓度的增加,伸长节间吲哚乙酸氧化酶(IAAO)、苯丙氨酸解氨酶(PAL)和过氧化物酶(POD)的活性均升高,除0.001μmol/L COR处理外,0.01、0.1和1μmol/L COR处理的IAAO、PAL和POD酶活性均高于对照,且差异达到极显著水平.0.001和0.01μmol/L COR处理的穗长、行粒数、穗重、穗粒重和产量,与对照相比,均呈显著或极显著增加,且随着冠菌素浓度的增加,各性状均呈降低趋势,说明低浓度的COR能增加玉米的产量.综合来看,既能延缓节间伸长生长,又能增加产量的最适COR浓度为0.01μmol/L,因此作为一种玉米延缓剂,COR有较好的应用前景.     

古代DNA 技术及其在家养动物驯化历史研究中的应用

家养动物始终伴随着人类文明的发生、发展, 其起源和驯化历史一直备受关注. 而在其 近万年的演化历史中, 家养和野生群体间可能发生基因互渗及替代, 因此基于现代物种DNA 信息进行的历史推断可能存在偏差. 近年来, 古代生物遗骸中的DNA (古代DNA)获取技术日 益成熟, 为这类研究开辟了新的途径. 本文总结了近年来古代DNA 技术研究进展, 点评了古 代生物遗骸DNA 的获取和鉴别方法、古代DNA 提取、扩增及测序技术的革新. 最后, 本文综 述了古代DNA 技术在猪、马、羊、狗等主要家养动物驯化历史研究中的应用进展, 为该技术 的进一步发展及应用提供有益的参考.     

寄生植物和寄主植物间的物质分配

以寄生植物肉苁蓉和寄主植物梭梭为对象, 研究了寄生植物和寄主植物间的物质分配.结果显示, 肉苁蓉体内累积大量的可溶性碳水化合物, 其中可溶性总糖、淀粉以及总可溶性碳水化合物总量分别达到了5.56, 2.73, 8.29 g/株, 分别占梭梭肉苁蓉复合体的51.01%, 60.13%,53.73%; 肉苁蓉对K, P, Zn, Cu 的累积较多, 总量分别达到了348.15, 18.94, 0.24, 0.14 mg/株, 分别占复合体的18.46%, 16.36%, 7.27%, 5.67%. 本研究结果为寄生植物和寄主植物间的物质分配调节提供了初步的理论依据.     

Pedigree transmission disequilibrium test for quantitative traits in farm animals

General pedigrees are very common in farm animals,and the recent availability of large panels of SNPs in domestic species has given new momentum to the search for the mutations underlying variation in quantitative traits.In this paper,we proposed a new transmission disequilibrium test approach,called the pedigree transmission disequilibrium test,which deals with general pedigrees and quantitative traits in farm animals.Compared with the existing pedigree disequilibrium test (PDT) and general linear model-based method QTDT,our approach performed better with higher power and lower type I error,especially in scenarios where the quantitative trait locus (QTL) effect was small.We also investigated the application of our approach in selective genotyping design.Our simulation studies indicated that it was plausible to implement a selective genotyping strategy in the proposed pedigree transmission disequilibrium test.We found that our approach performed equally well or better when only some proportion of the individuals in the two tails were genotyped compared with its performance when all the individuals in the pedigree were genotyped.     

Prediction of sites under adaptive evolution in flavin-containing monooxygenases: Selection pattern revisited

Flavin-containing monooxygenase (FMO), like cytochrome P450 (CYP), is a monooxygenase that uses the reducing equivalents of NADPH to reduce one atom of molecular oxygen to water, while the other atom is used to oxidize the substrate. Recently, it was shown that some CYP isoforms have been subject to positive selection. However, it is unknown whether the highly conserved phase I detoxification enzyme, FMO, has undergone similar positive Darwinian selection. We used maximum-likelihood models of codon substitution, evolutionary fingerprinting, and cross species comparison to investigate the occurrence of adaptive evolution in FMO sequences. We used recent genomic data from a range of species, including vertebrates and invertebrates. We present the evidence for the occurrence of adaptive evolution in mammalian FMO 3, 4, 5, and fugu FMOs but not in mammalian FMO 1, FMO 2, frog FMOs, other fish FMOs and invertebrate FMOs. The sites under adaptive evolution were significantly associated with the insertion domain in mammalian FMO 5. We identified specific amino acid sites in FMOs 3–5 that are likely targets for selection based on the patterns of parallel amino acid change. The most likely role of adaptive evolution is the repair of mutations that permitted optimal NADP+ binding and improved catalytic efficiency. The occurrence of positive selection during the evolution of phase I detoxification enzymes such as FMOs 3–5 and fugu FMO suggests the occurrence of both high selection pressure acting on species within their unique habitats and significant changes in intensity and direction (forms of xenobiotics and drugs) resulting from changes in microhabitat and food.     

我国高校科研态势与科研体制改革对策

我国高校科研在全国科研体系中占有重要地位，同时在科研评价导向、协作机制、科研经费管理、大学功能与创新文化等方面存在不利于科研质量提升的问题。本文分析提出了为实现高校科技创新而应当采取的科研体制改革对策，主要包括：明晰高校新的功能定位；改进科研评价体系；加强高校内外的资源互补性合作；建立科研项目间接经费补偿机制；培育大学精神与创新文化。