共查询到20条相似文献，搜索用时 15 毫秒
1.
Li C Yao Y Zhao G Cheng W Liu H Liu C Shi Z Chen Y Wang S 《Journal of agricultural and food chemistry》2011,59(23):12493-12498
The similarities and differences of eight vegetable oils produced in China were investigated in terms of their fatty acid, sterol, and tocopherol compositions and subsequent data processing by hierarchical clustering analysis and principal component analysis. The lipid profiles, acquired by analytical techniques tailored to each lipid class, revealed great similarities among the fatty acid profiles of corn and sesame oil as well as few differences in their sterol profiles. It turns out that not only was there great similarity between the fatty acid profiles of corn oil and sesame oil but also there were not too many differences for the sterol profiles. Sunflower and tea-seed oil showed similar sterol compositions, while the tea-seed oil tocopherol was very similar to palm oil. The results demonstrated that the use of only one of these profiles was unreliable for indentifying oil origin and authenticity. In contrast, the use of the sterol or tocopherol profile together with the fatty acid profile more accurately discriminates these oils. 相似文献
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In the research, in this paper, we investigate spatial and temporal variations in the composition of wastewater near Croatian highways in three climatic regions (continental, Mediterranean, highland) during three seasons (autumn, winter and spring). In our paper, the spatial division of the investigated areas that pertain to the three aforementioned climatic regions was obtained using the method of hierarchical clustering of monitored locations. One thousand five hundred thirty-three samples from 14 locations along Croatian highways were collected and analysed by methods of multivariate exploratory analysis. By methods of principal components, factor analysis and hierarchical clustering of variables, we grouped the variables into factors. Whereas 60 % of variation in the data was explained by three principal components, six principal components accounted for 88 % of data variation. The key section of our research was conducted by the decision tree method. For the purpose of analysis, we classified 1,533 samples into three classes representing climatic regions separately for each season and obtained the accuracy of 76–90 % on test samples. Finally, using decision trees, we identified the most important variables that differentiate climatic regions by the level of contamination of water along highways in different seasons. 相似文献
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S. NORTCLIFF 《European Journal of Soil Science》1978,29(3):403-418
The incorporation of measures of soil variability at the reconnaissance stage of soil survey is considered as a possible alternative to, or additional feature of, present procedures. A straightforward hierarchical sampling design based upon the major parent materials of the upland section of the study area and associated analysis of variance model are described. This allowed the estimation of scale components for five levels of the sampling design at separation distances from over two kilometers down to five meters. Principal components analysis is used to economise on the number of variables for further analysis. Analysis of the pattern of principal component scores shows the first six components to have distinctive variability patterns both within and between strata. It is concluded that present soil survey procedures take too little account of soil variability patterns, and that inclusions of such information at the reconnaissance stage would greatly improve the detailed survey. 相似文献
4.
基于高效液相色谱的普洱晒青毛茶指纹图谱识别方法 总被引：4，自引：0，他引：4
为了对不同产地的晒青毛茶进行鉴别,研究了晒青毛茶高效液相色谱指纹图谱的不同识别方法。运用相关系数、夹角余弦和重叠率3种方法分别计算指纹图谱的相似度,以数字化指纹图谱为基础,对样品进行了系统聚类,分析了18个茶叶样品的主成分,并以前2个主成分作二维散点图。结果表明,3种方法均能准确地体现指纹图谱的相似程度,使毛茶与绿茶得到良好的分离;茶叶内含成分复杂,主成分较多,7个主成分累计贡献率为88.61%,系统聚类和二维排序散布图能够区分晒青毛茶和绿茶,具有简便、直观的特点。4种识别模式均能较好地对指纹图谱进行识别,为普洱茶原料鉴别和质量控制提供新的试验依据。 相似文献
5.
Jose´ Alberto Oliveira Ruth Lindner Rezar Bregu Alvaro García Antonio Gonza´lez 《Genetic Resources and Crop Evolution》1997,44(5):479-487
Sixteen landraces of westerwold ryegrass (Lolium multiflorum Lam. var. westerwoldicum Wittm.) collected in Northwest Spain were evaluated at three locations: Mabegondo (La Corun~a), Puebla de Brollo´n (Lugo) and Salcedo (Pontevedra). Populations showed a high variability for morphologic, agronomic and isoenzimatic traits. Principal component analysis was carried out to identify clusters of morphologic and agronomic homogeneous behaviour. A hierarchical clustering method on the first five components was used to separate the different groups. A partition into four clusters was chosen (71% of variance explained). Each cluster was described by the means of the different traits and compared with the other clusters. Landraces were screened for allozyme diversity at nine loci. Population genetic statistics were higher than those previously reported for other outbreeding species (mean number of alleles = 3.59 and mean expected heterozygosity = 0.510). Genetic diversity was mainly explained by the within population component. The between population differentiation only accounted for 8% of the whole diversity. The use of these genetic resources is discussed. 相似文献
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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
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
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The effects of sulfur (S) fertilization and harvest time on amino acid composition of seeds of field-grown lentil (Lens culinaris Medik.) at two different sites were studied. The aim of this study was to determine amino acid content of seed protein and to increase low levels of sulfur amino acids and trytophan in lentil seeds, which are major components for grain quality, with sulfur fertilization and farming practices in lentil. For this purpose, lentil was sown at two locations on 18 and 19 October 2007, 0 kg S ha?1, 25 kg S ha?1, and 50 kg S ha?1 rates were used in the study. The plants were harvested at three different periods: early, optimal, and late period. According to the results, amino acid contents of protein were increased by sulfur fertilization and by the late harvest period. 相似文献
11.
基于竞争学习网络的田间籽棉图像分割 总被引：1，自引：0，他引：1
为了正确识别田间籽棉,将籽棉和铃壳、绿叶、根茎、土地等自然背景视为二个类别,基于竞争学习网络进行了图像分割。从多幅典型的籽棉图像中选取10000个像素作为训练样本,并为它们贴上类别标签,在HSI、Lab、Ohta、RGB颜色空间下对训练样本的颜色特征及其组合进行K-均值聚类,选取了误分率普遍较低的RGB颜色空间,其B值的误分率尤其低。在RGB颜色空间下,用训练样本的R、G、B组合或B值一次性地训练了竞争学习网络,将图像的全部像素输入网络进行测试,同时与K-均值聚类比较,形态学滤波去噪后的结果表明,基于B值的竞争学习网络较优,用907幅籽棉图像对其进行仿真的精度达92.94%。该方法结合了有监督的学习算法,避免了传统K-均值聚类的反复迭代和过拟合现象,提高了图像分割的效率和精度。 相似文献
12.
It is common practice to fit mathematical models to radionuclide activity–depth profiles in soils in order to quantify rates of vertical migration through the soil profile. We have fitted six such models to 21 different activity–depth profiles of radiocaesium (137Cs) derived from Chernobyl and determined relations between the models and the values of their parameters. The advection and dispersion parameters obtained using four solutions to the advection–dispersion equation (each based on different initial and boundary conditions or different simplifications) are in good agreement. We further develop a relation between parameter values obtained using the advection–dispersion models and those determined by a simpler exponential function of the form Aexp(–Bt) where t is the time and A and B are parameters to be estimated. One of the advection–dispersion models proved to be significantly better than the others in terms of goodness-of-fit, versatility and ease of use. A simple model, using calculations based on measured characteristics of the activity–depth profile, was shown to accord well with parameters derived from more complex models based on statistical curve fitting. We have also evaluated the ‘residence time’ or ‘compartmental’ model approach to characterizing radionuclide activity–depth profiles. We relate such models to a numerical solution of a simple advection equation, and we show that apparent dispersion in compartmental models is an artefact of numerical dispersion, which can be quantified by the Courant condition. For activity profiles that have a significant advection component, using solutions to the advection–dispersion equation, we have observed a strong positive correlation between advection and dispersion in the profile. 相似文献
13.
Parveen I Moorby JM Fraser MD Allison GG Kopka J 《Journal of agricultural and food chemistry》2007,55(4):1129-1138
Little is known about how plant biochemistry influences the grazing behavior of animals consuming heterogeneous plant communities. The biochemical profiles of grassland species are mostly restricted to major nutritional characteristics, although recent developments in analytical techniques and data analysis have made possible the detailed analysis of minor components that may influence animal feeding preferences, performance, and health. In the present study, gas chromatography coupled with time-of-flight mass spectrometry (GC-TOF/MS) was used to profile the abundances of metabolites in nine specific heathland plant groups and in three mixed forage diets containing 10, 20, or 30% heather (Calluna vulgaris) and also in plasma and feces from sheep offered one of the three diets. Statistical and chemometric approaches, that is, principal component analysis (PCA) and hierarchical cluster analysis (HCA), were used to discriminate between these diets and between individual animals maintained on these diets. It is shown that GC-TOF/MS analysis of sheep plasma allowed distinction between the very similar diets by PCA and HCA, and, moreover, the plant metabolites responsible for the differences observed have been identified. Furthermore, metabolite markers of herbage mixtures and individual plant groups have been identified, and markers have been detected in sheep plasma and feces. 相似文献
14.
横断山区森林土壤的数值分类 总被引：1，自引：0，他引：1
在土壤分类中综合运用多种数值分类方法可以取得较好的分类效果.本文应用了主组元分析、聚类分析,多组判别分析和最小支撑树等方法,将横断山区有代表性的30个森林土壤剖面分为六组,各组土壤间不仅在理化性质上有鲜明特征,而且与最重要的成土条件和森林植被类型基本吻合.在西南高山林区,树种与下木对土壤形成有重要作用,主要成土过程为酸性淋溶与腐殖化过程.通过选取的六个理化性质指标,主组元分析结果反映出了上述主导成土过程,而多组判别分析则进一步给予每组土壤以明确的分类域.这两种方法的结合可作为土壤数值分类的基本方法. 相似文献
15.
D Cuthbertson PK Andrews JP Reganold NM Davies BM Lange 《Journal of agricultural and food chemistry》2012,60(35):8552-8560
A gas chromatography-mass spectrometry approach was employed to evaluate the use of metabolite patterns to differentiate fruit from six commercially grown apple cultivars harvested in 2008. Principal component analysis (PCA) of apple fruit peel and flesh data indicated that individual cultivar replicates clustered together and were separated from all other cultivar samples. An independent metabolomics investigation with fruit harvested in 2003 confirmed the separate clustering of fruit from different cultivars. Further evidence for cultivar separation was obtained using a hierarchical clustering analysis. An evaluation of PCA component loadings revealed specific metabolite classes that contributed the most to each principal component, whereas a correlation analysis demonstrated that specific metabolites correlate directly with quality traits such as antioxidant activity, total phenolics, and total anthocyanins, which are important parameters in the selection of breeding germplasm. These data sets lay the foundation for elucidating the metabolic basis of commercially important fruit quality traits. 相似文献
16.
采用不同中红外光谱（漫反射光谱、 衰减全反射光谱和光声光谱）对不同氮处理的小白菜进行表征。结果表明,小白菜不同的红外光谱具有明显不同的光谱特征,主要表现于峰形、 峰位以及相对峰强度;中红外漫反射光谱的主要吸收峰分别为2800~3800 cm-1、 2200~2500 cm-1、 1500~1700 cm-1和1000~1500 cm-1,衰减全反射光谱由于水的强烈干扰可用的吸收峰主要在1200~1500 cm-1,而中红外光声光谱的主要吸收峰分别为2800~3800 cm-1、 1500~1700 cm-1、 1200~1500 cm-1和1000~1200 cm-1。漫反射光谱、 衰减全反射光谱和光声光谱的主成分分析表明,不同氮处理主成分分布特征明显不同,且第一主成分（PCA1）均与施氮量显著相关,相关系数（r）分别为0.9103、 0.8527和0.9366。这三种光谱利用主成分分布均可实现小白菜氮营养快速诊断,且光声光谱由于其独特的原位逐层扫描功能而表现出更好的诊断效果,在植物营养诊断中表现出较强的应用潜力。 相似文献
17.
不同类型大豆花荚期抗旱性形态指标及其综合评价 总被引：7，自引：2，他引：5
利用相关、主成分、聚类和判别分析,对野生、半野生大豆和栽培品种抗旱相关的形态指标与抗旱性的关系进行比较研究。结果表明:在干旱胁迫下,株高、株重、分枝数、株荚数、株粒数、百粒重、单株产量均有不同程度的降低,而叶片黄化脱落节位有所增加,且不同基因型存在差异;在干旱胁迫下抗旱系数与株高、株重呈显著正相关,与叶片黄化脱落节位呈显著负相关;主成分分析中的3个主成分,方差累积贡献率达88.38%;在聚类的基础上用判别分析确立了相对株高、叶片黄化脱落节位、背面茸毛密度、相对百粒重和抗旱系数5个对品种抗旱性分类有显著影响的指标,根据这些指标将供试15份大豆种质划分为高抗、抗、敏感、高度敏感4个类型;供试的野生、半野生大豆材料均划分在高抗旱类型中。优良的耐旱性种质和鉴定指标的发掘,为培育耐旱大豆新品种提供了必要的保证。 相似文献
18.
M. L. Racchi A. Turchi S. Caparrini A. Camussi 《Genetic Resources and Crop Evolution》2011,58(4):507-518
In this study, we evaluate the effectiveness of SSCP analysis of intron markers, as a routine tool for fingerprinting of clones
of different poplar species and interspecific hybrids. Exon primed intron crossing primers were designed on two catalase genes.
Analysis of these fragments on SSCP gels revealed that catalase introns exhibit substantial sequence variation within poplar
species and cultivars. SSCP analysis resulted effective in detecting intra and interspecific polymorphisms among the 119 poplar
cultivars obtaining 110 different individual profiles. A hierarchical clustering process showed the high level of divergence
among clones reflecting in most cases the section and the species the clones belongs to. This marker system was also proved
with high transferability within Salicaceae. SSCP intron analysis represents a powerful tool in detecting DNA sequence polymorphism,
in screening diversity and an effective method for clonal fingerprinting. 相似文献
19.
绰墩山遗址古水稻土的一些微生物学特性研究 总被引：1，自引：2，他引：1
在江苏绰墩山遗址考古发掘中,发现了在剖面不同深度埋藏的距今约6 500 a的史前古水稻田土层(100~200 cm)和距今约3 320 a的商周时期的古水稻田土层(42~100 cm)。本研究为了解古水稻土的生物学性状及其与现代水稻土的差别,以土壤剖面P-01(包含史前古水稻土和商周时期古水稻土)与P-03(仅含商周时期古水稻土)为对象,利用土壤厌氧培养、Biolog分析和广古生菌界16S rDNA的V3区的PCR-DGGE分析,初步研究了不同土层厌氧微生物多样性、产甲烷潜势以及产甲烷古菌群落多样性的变化。结果表明,史前古水稻土仍有较多厌氧微生物存活,可达7.0×105cfu g-1干土,并且其单一碳源利用能力和多样性也显著高于其湖相沉积母质和相同时期的非水稻土(黄土母质)。与现代水稻土相比,古水稻土仅存留了很微弱的产甲烷潜势。但史前古水稻土比同期非水稻土和商周时期古水稻土的产甲烷潜势较高。PCR-DGGE结果显示,水稻土层都有其区别于非水稻土层的产甲烷古菌群落结构,而现代水稻土、商周时期古水稻土和史前古水稻土也各有不同的优势产甲烷古菌种群,不同时期的水稻耕作方式是造成这种差异的可能的重要原因之一。 相似文献
20.
识别不同水稻株型的高光谱模式方法的建立 总被引：1，自引：0，他引：1
提出了一种用高光谱技术快速识别不同水稻株型的新方法。首先在试验田内选择33个不同的水稻品种,测定了每个品种的14个株型特征参数,并采用荷兰Avantes公司的AvaSpec-2048便携式光谱仪采集不同株型水稻的高光谱数据。通过聚类分析,将所有水稻品种分为差异较大的3个株型类别。再采用平均平滑法和标准归一化方法对光谱数据进行预处理,对光谱数据主成分分析并获得各主成分数据。最后将主成分数据作为BP神经网络的输入变量,株型类别作为输出变量,建立了三层人工神经网络识别模型,并用模型对预测样本进行预测。结果表明,预测准确率为100%。该方法实现了对不同水稻株型的快速、无损识别。 相似文献