A rapid,automated method for measuring α-amylase in pre-harvest sprouted (sprout damaged) wheat     

《Journal of Cereal Science》2015

The quality of wheat for baking is critically dependent on the level of α-amylase (1,4-α-D-glucan glucanohydrolase, EC 3.2.1.1), which can be present as “late maturity α-amylase” (LMA), or due to pre-harvest sprouting due to high rainfall and humidity at the time of harvesting. The most commonly used method to measure α-amylase in wheat grain is the Hagberg Falling Number method, but values are also influenced by rheological properties of starch in the grain. In this study we describe a simple, rapid, automated method (Amylase SD) for measurement of α-amylase in pre-harvest sprouted (sprout damaged) wheat grain. The method (Amylase SD) measures the release of p-nitrophenol from 4,6-O-ethylidene-α-4-nitrophenyl-maltoheptaoside by α-amylase in the presence of α-glucosidase. The absorbance of p-nitrophenolate measured at 405 nm in a ChemWell^®-T auto-analyser is directly related to the level of α-amylase activity present in the milled wheat grain extract. The Amylase SD method generated <6%CV and correlation to the Falling Number method was represented by an inflection point at ∼160 s. The precision, sensitivity and speed of this method provides an ideal alternative to the Falling Number method for measurement of α-amylase (sprout damage) in wheat grain in wheat breeding programmes or at grain receival points.  相似文献   

Squaring the circle: reconciling fishing and conservation of aquatic ecosystems          下载免费PDF全文

Richard Law  Jeppe Kolding  Michael J Plank 《Fish and Fisheries》2015,16(1):160-174

Size‐at‐entry regulations in fisheries cause major disruption to aquatic ecosystems, including truncation of age‐ and size‐structures, destabilization of fish stocks, directional selection on phenotypic traits and a by‐catch of unwanted species and sizes. Here, we use simple dynamic models of size‐spectra to examine an alternative, so‐called balanced harvesting. Balanced harvesting helps in retaining the approximate power‐law size‐structure of natural ecosystems, whereas size‐at‐entry regulations do not. Balanced harvesting is less likely to destabilize steady states than size‐at‐entry regulations set close to the size at maturation. Surprisingly, our numerical results suggest that steady‐state biomass yield can be substantially increased by switching from size‐at‐entry to balanced harvesting. On the basis of these results, we argue that the goals of conservation and of greater yields seem less difficult to reconcile than have previously been thought. However, to work towards these goals require a change in our approach to fishing.  相似文献   

白头翁叶斑病菌黑色素的理化性质及其生物合成途径初步研究     

苏丹  吕国忠  周如军  杨红  傅俊范 《植物保护》2014,40(6):25-28

对白头翁叶斑病菌胞壁结合黑色素和胞外黑色素进行了理化性质和红外光谱扫描测定, 结果表明两者具有相似的理化性质, 均易溶于KOH、H2O2和NaClO, 不溶于水、乙醇和丙酮。红外光谱分析表明, 白头翁叶斑病菌YS-24菌株的胞壁结合黑色素与胞外黑色素为同一种类型的黑色素。DHN黑色素的特异性抑制剂—三环唑, 对白头翁叶斑病菌黑色素的产生有明显的抑制作用; 以白头翁叶斑病菌基因组DNA为模板, 通过PCR扩增, 得到了聚酮体合成酶基因的同源片段 AaPKS , 初步推断白头翁叶斑病菌黑色素合成属于DHN途径。  相似文献   

滇青、青饼和普洱茶（熟饼）近红外指纹图谱分析   总被引：9，自引：0，他引：9  

周健  成浩  叶阳  王丽鸳  贺巍  刘本英  陆文渊 《核农学报》2009,23(1):110-113

为深入了解滇青（晒青毛茶）、青饼和普洱茶（熟饼）在化学组成方面的异同,为茶类的区分与界别提供进一步的科学依据,对滇青、青饼和普洱茶（熟饼）的近红外化学指纹图谱采用欧氏距离、主成分分析和系统聚类等方法进行了定性判别分析。结果发现,普洱茶（熟饼）近红外指纹图谱与滇青、青饼图谱间的欧氏距离均大于各自组内最大偏差的绝对阈值,而滇青和青饼的组间差异小于各自的组内阈值;在第一主成分和第二主成分得分值散点图上,熟饼样品与青饼和滇青样品间界限分明,而滇青和青饼样品间无明显界限;所有的熟饼样品在系统聚类分析中聚为一类,而青饼与滇青样品聚为一类。因此,青饼的近红外光谱在各方面都与普洱茶（熟饼）样品差异显著,而与其原料滇青（晒青毛茶）十分接近。从化学本质上来说,青饼更接近于绿茶类产品。  相似文献   

原位反应法制备NR/二氧化硅胶膜及其性能分析     

杨增杰  张婧  王伟  廖建和  黄茂芳 《热带作物学报》2011,32(4):768-771

研究原位生成对NR胶膜性能的影响。通过对力学性能、热老化性能、红外分析及电镜照片分析,得出原位反应可以在NR分子链中接枝二氧化硅粒子,并且在添加量为1.0%,撕裂强度为87.3721MPa,提高了264.2%。  相似文献   

Fast measurement of starch content in cold-treated seedlings by infrared spectra     

Xiping Zhao  Pingping Guo  Lixia Hu  Bin Hui  Qingzheng Cheng  Brian K. Via 《Scandinavian Journal of Forest Research》2018,33(8):729-734

Despite the importance of starch for tree growth, methodological challenges in starch analysis slow down the research on its ecological importance. In this study, a rapid monitoring method was developed for measuring starch content in Pinus taeda L. seedlings after cold treatments. A linear mixed-effects model was used to analyze the effects of cold treatments, seedling tissue types and their interaction on starch content. Mid-infrared (MIR) and near-infrared (NIR) spectra were surveyed, and the results were analyzed using partial least squares regression to determine the starch content. The determination coefficient for calibration and residual predictive deviation were compared between MIR and NIR models to assess the variability of the established models. The results showed that the effects of cold treatments, seedling tissue types and their interaction on starch content were significant. Compared to MIR spectra, NIR spectra is more suitable to estimate starch content in the seedlings. Using NIR spectra, roots provided the most accurate estimates of starch content. The presented guidelines regarding data accuracy as a function of MIR/NIR spectra of samples represent an important methodological reference for starch quantification, which will improve the understanding of the fundamental role of starch in seedlings against environmental forces.  相似文献   

基于近红外光谱的猪肉水分在线检测与分级   总被引：2，自引：0，他引：2  

彭彦昆  杨清华  王文秀 《农业机械学报》2018,49(3):347-353

基于近红外光谱法,优化光纤探头检测距离并通过检测距离调节系统和多点同时检测,设计了猪肉水分在线检测分级系统。首先,为确定光纤探头与生鲜猪肉样品表面间的最佳检测距离,在13个不同检测距离下(5~29 mm)采集了54个样品的光谱,采用多元散射校正方法对原始光谱进行预处理,分别建立了第1波段(349~1 435 nm)、第2波段(1 037~1 761 nm)和双波段结合3种情况的含水率偏最小二乘回归模型,分析了不同检测距离和不同波段的模型,确认19 mm为在线检测分级装备的最佳检测距离。然后,通过检测距离实时调节系统动态固定最佳检测距离,设计了双波段多点同时检测系统,采集45个猪肉样品在静态条件和在线条件下的光谱,通过比较分析,两种情况下预测结果相近,从而证实了所设计的在线系统能够预测猪肉水分,并且双波段融合建模效果优于单波段,预测结果为:校正集相关系数和校正均方根误差分别为0.906和0.598,验证集相关系数和预测均方根误差分别为0.836和0.402。最后,利用独立的21个猪肉样品验证猪肉预测分级模型精度及稳定性,结果判断正确率为90.48%,表明可见近红外光谱法结合多点检测能有效地在线检测猪肉水分并分级。  相似文献   

城市植物种类构成的特征分析——以厦门市为例   总被引：1，自引：1，他引：0       下载免费PDF全文

赵娟娟  宋晨晨  刘时彦 《西南大学学报(自然科学版)》2018,40(7):1-8

以厦门市为例,利用大量调查数据,探讨城市植物种类结构的特征及植物多样性的潜在问题.结果显示,厦门市植物种类丰富,种类构成的特征明显.在调查记录到的467种植物中,国家级珍稀濒危物种只有6种.植物种的频度分布符合Logistic函数(R~20.99),其中1个科、1个属和25个种高于多样性管理的10/20/30准则.低频物种占总种数的81.5%,热带分布植物属占草本的72.4%及木本的72.3%.绿地野生草本植物经常遭受人为破坏,但依然占总种数的37.5%.绿地建设中应进一步重视低频及稀有物种的保护和物种构成的协调,通过有效的政策措施减少野生草本植物的人为破坏是提高城市生物多样性的有效途径.  相似文献   

土壤有机质含量可见-近红外光谱反演模型校正集优选方法   总被引：3，自引：2，他引：1  

陈奕云  齐天赐  黄颖菁  万远  赵瑞瑛  亓林  张超  费腾 《农业工程学报》2017,33(6):107-114

土壤有机质含量可见-近红外光谱反演过程中校正集的构建策略对模型的预测精度有重要影响。以江汉平原洪湖地区水稻土为研究对象,采用Kennard-Stone(KS)法,Rank-KS(RKS)和Sample set Partitioning based on joint X-Y distance(SPXY)法,构建样本数占总校正集不同比例的子校正集,通过偏最小二乘回归,建立土壤有机质含量的可见—近红外光谱反演模型。结果表明:KS法无法提高模型预测精度,但可以在保证标准差与预测均方根误差比(ratio of performance to standard deviation,RPD)2.0的前提下减少30%的校正样本;基于SPXY法的模型,当子校正集样本比例为总校正集的50%时达到最佳的模型预测精度,RPD为2.557;RKS法能够在保证预测精度的情况下(RPD2.0),最多减少总校正集70%的样本,对应模型RPD为2.212。当校正集与验证集的有机质含量分布相近时,能够以较少的建模样本达到与总校正集相近甚至更高的模型预测精度,提升土壤有机质光谱反演模型的实用性。  相似文献   

西番莲叶红外指纹图谱研究   总被引：1，自引：1，他引：0  

辜燕飞  刘红  徐伟霞 《安徽农业科学》2010,38(14):7316-7317,7362

[目的]研究西番莲（Passiflora dulis）叶红外指纹图谱。[方法]运用双指标序列分析法。以共有峰和变异峰率为指标,计算样品相对于该标准品的共有峰率和变异峰率,并按照共有峰率和变异峰率的大小建立不同的序列。[结果]海口、儋州、万宁、屯昌的西番莲样品红外图谱比较吻合,但也存在一定的差异。[结论]该研究为快速地把相似的西番莲样品归为一类提供了科学依据。  相似文献