基于无机元素的含量判别食醋的种类和品牌方法研究

化学计量学广泛应用于食品种类和原产地的区分。文章采用原子吸收法测定了32个食醋样品中的Mg, K, Pb, Zn, Fe, Mn, Ca和Cu等八种无机元素含量。采用向量相似法计算了陈醋和白醋以及同一种类不同品牌食醋的相似度;通过聚类分析和主成分分析对来自北京、江西、江苏和山西4个地区品牌的食醋进行了分类,对不同种类的食醋(陈醋和白醋)也进行了分类。聚类分析和主成分分析都将食醋样品分为两大类,每个大类又将食醋样品按不同品牌分开。食醋中无机元素含量差异可作为食醋种类和品牌判别的测量指标之一。     

Global analysis of the immune response

The immune system may be seen as a complex system, characterized using tools developed in the study of such systems, for example, surface roughness and its associated Hurst exponent. We analyze densitometric (Panama blot) profiles of immune reactivity, to classify individuals into groups with similar roughness statistics. We focus on a population of individuals living in a region in which malaria endemic, as well as a control group from a disease-free region. Our analysis groups individuals according to the presence, or absence, of malaria symptoms and number of malaria manifestations. Applied to the Panama blot data, our method proves more effective at discriminating between groups than principal-components analysis or super-paramagnetic clustering. Our findings provide evidence that some phenomena observed in the immune system can be only understood from a global point of view. We observe similar tendencies between experimental immune profiles and those of artificial profiles, obtained from an immune network model. The statistical entropy of the experimental profiles is found to exhibit variations similar to those observed in the Hurst exponent.     

Comparison of two exploratory data analysis methods for fMRI: fuzzy clustering vs. principal component analysis

Exploratory data-driven methods such as Fuzzy clustering analysis (FCA) and Principal component analysis (PCA) may be considered as hypothesis-generating procedures that are complementary to the hypothesis-led statistical inferential methods in functional magnetic resonance imaging (fMRI). Here, a comparison between FCA and PCA is presented in a systematic fMRI study, with MR data acquired under the null condition, i.e., no activation, with different noise contributions and simulated, varying "activation." The contrast-to-noise (CNR) ratio ranged between 1-10. We found that if fMRI data are corrupted by scanner noise only, FCA and PCA show comparable performance. In the presence of other sources of signal variation (e.g., physiological noise), FCA outperforms PCA in the entire CNR range of interest in fMRI, particularly for low CNR values. The comparison method that we introduced may be used to assess other exploratory approaches such as independent component analysis or neural network-based techniques.     

Fourier‐transform Raman analysis of milk powder: a potential method for rapid quality screening

In this work, FT‐Raman spectroscopy was explored as a fast and reliable screening method for the assessment of milk powder quality and the identification of samples adulterated with whey (1–40% w/w). Raman measurements can easily differentiate milk powders without the need of sample preparation, whereas the traditional methods of quality control, including high‐performance liquid chromatography, are laborious and slow. The FT‐Raman spectra of whole, low‐fat, and skimmed milk powder samples were obtained and distinguished from commercial milk powder samples. In addition, the exploratory analysis employing data from Raman spectroscopy and principal component analysis (PCA)allowed the separation of milk powder samples according to type,identifying differences between samples in the same group. Multivariate analysis was also developed to classify the adulterated milk powder samples using PCA and partial least squares discriminate analysis (PLS‐DA). The resulting PLS‐DA model correctly classified 100% of the adulterated samples. These results clearly demonstrate the utility of FT‐Raman spectroscopy combined with chemometrics as a rapid method for screening milk powder. Copyright © 2011 John Wiley & Sons, Ltd.     

Strain effects on phase transitions in transition metal dichalcogenides

We perform density functional theory calculation to investigate the structural and electronic properties of various two-dimensional transition metal dichalcogenides, MX₂ (M=Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, or W, and X=S or Se), and their strain-induced phase transitions. We evaluate the relative stability and the activation barrier between the octahedral-T and the trigonal-H phases of each MX₂. It is found that the equilibrium and phase transition characteristics of MX₂ can be classified by the group to which its metal element M belongs in the periodic table. MX₂ with M in the group 4 (Ti, Zr, or Hf), forms an octahedral-T phase, while that with an M in the group 6 (Cr, Mo, or W) does a trigonal-H phase. On the other hand, MX₂ with M in the group 5 (V, Nb, or Ta), which is in-between the groups 4 and 6, may form either phase with a similar stability. It is also found that their electronic structures are strongly correlated to the structural configurations: mostly metallic in the T phase, while semiconducting in the H phase, although there are some exceptions. We also explore the effects of an applied stress and find for some MX₂ materials that the resultant strain, either tensile or compressive, may induce a structural phase transition by reducing the transition energy barrier, which is, in some cases, accompanied by its metal-insulator transition.     

Exploratory voxel-based analysis of diffusion indices and hemispheric asymmetry in normal aging

Age-related microstructural changes in brain white matter can be studied by utilizing indices derived from diffusion tensor imaging (DTI): apparent diffusion coefficient (ADC) and fractional anisotropy (FA). The objective of this study is to examine alterations in FA and ADC by employing exploratory voxel-based analysis (VBA) and region(s) of interest (ROI)-based analysis. A highly nonlinear registration algorithm was used to align the ADC and FA image volumes of different subjects to perform accurate voxel-level statistics for two age groups, as well as for hemispheric asymmetry for both age groups. VBA shows significant age-related decline in FA with frontal predominance (frontal white matter, and genu and anterior body of the corpus callosum), superior portions of a splenium and highly oriented fibers of the posterior limb of the internal capsule and the anterior and posterior limbs of the external capsule. Hemispheric asymmetry of FA, as assessed by VBA, showed that for the young-age group, significant right-greater-than-left asymmetry exists in the genu, splenium and body of the corpus callosum and that left-greater-than-right asymmetry exists in the anterior limb of the external capsule and in the posterior limb of the internal capsule, thalamus, cerebral peduncle and temporal-parietal regions. VBA of the hemispheric asymmetry of the middle-age group revealed much less asymmetry. Regions showing age-related changes and hemispheric asymmetry from VBA were, for a majority of the findings, in conformance with ROI analysis and with the known pattern of development and age-related degradation of fiber tracks. The study shows the feasibility of the VBA of DTI indices for exploratory investigations of subtle differences in population cohorts, especially when findings are not localized and/or known a priori.     

Personal evaluation structure of environmental sounds: experiments of subjective evaluation using subjects’ own terms

In this study, we conducted an experiment to investigate the evaluation structure that lies at the basis of peoples’ psychological evaluation of environmental sounds. In the experiment, subjects were given cards on each of which a name of one of the environmental sounds in the specified context is written. Then they did the following three tasks: (1) to sort the cards into groups by the similarity of their impressions of the imagined sounds; (2) to name each group with the word that best represented their overall impression of the group; and (3) to evaluate all sounds on the cards using the words obtained in the previous task.These tasks were done twice: once assuming they heard the sounds at ease inside their homes and once while walking outside in a resort theme park. We analysed the similarity of imagined impression between the sounds with a cluster analysis and clusters of sounds were produced, namely, sounds labelled “natural,” “transportation,” and so on. A principal component analysis revealed the three major factors of the evaluation structure for both contexts and they were interpreted as preference, activity and sense of daily life.     

Phyllites used as waterproofing layer materials for greenhouses crops in Spain: multivariate statistical analysis applied to their classification based on X‐ray fluorescence analysis

The results are presented for the chemical characterization carried out with 53 raw material samples with phyllosilicates from outcrops located between the provinces of Almería and Granada (SE Spain) in order to use them as waterproof layers under the floors of greenhouses. For this purpose, the samples have been studied by these techniques: X‐Ray Diffraction (XRD), X‐Ray Fluorescence (WDXRF), Scanning Electron Microscopy (SEM), chemical analysis by energy‐dispersive X‐Ray detection (EDX), and thermogravimetry. To isolate groups of phyllite samples with similar chemical profiles and correlations between the samples, the WDXRF data (11 chemical elements) have been processed using the methodology of exploratory multivariate statistical analyses: cluster analysis, main‐component analysis, and discriminating canon analysis. This study was performed as a screening test and as a means of finding similarities and correlations among all 53 phyllite samples, allowing the isolation of groups of phyllite samples with similar chemical profiles. The results indicate that the 53 phyllite samples can be divided into two main groups. The first group is subdivided into two subgroups (1 and 2), one of which includes most of the samples. The latter is further classified into three blocks with the same chemical composition. This allows to search for the raw material with potentially the best waterproof characteristics within the five groups. The classification is of validity as a screening test for subsequent experimental determinations concerning the physical properties of these samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Graphical display of fMRI data: visualizing multidimensional space

Visualization of multidimensional data is an integral part of computational statistics and exploratory data analysis (EDA). We show how visualization of fMRI time-courses may be used to reveal the fMRI data structure. We consider fMRI time-courses (TCs) as points in multidimensional space. In simulated and in vivo data, we show that minimum spanning tree (MST)-based sequencing of multivariate time-courses, in combination with a homogeneity map visualization, allows for effective and useful graphical display of the groups of coactivated time-courses obtained by temporal clustering. This display may serve as a tool for investigation of brain connectivity. We also suggest a simple overall display of the entire fMRI data set.     

基于光谱成像与光谱分析的壁画鉴赏研究

针对壁画鉴赏中对科学分析方法的需求,根据光谱成像及光谱分析方法在壁画处理中的特点与优势,重点讨论了光谱成像技术在壁画鉴赏处理中的应用,其可以辅助传统的专家经验鉴定方法,提供更丰富客观的画作信息,实现作品的鉴赏分析。光谱成像与分析方法是一类重要的科学分析方法,因其具有非接触、破损少甚至无破损、科学、准确、可量化等特点,可应用于壁画修复、信息提取、颜料分析、特征增强、鉴赏分析等。首先,从技术实现角度出发给出具体的鉴赏应用方向。然后,基于光谱特征分析、主成分分析、独立分量分析、相关性判别、人机交互处理等方法,对实际观测的韩休墓壁画进行实验处理,验证技术应用的实验效果,最后,结合应用实验提出包括规范化采集、图谱特征分析、图谱处理系统等关键技术还需进一步解决。实验结果表明,利用光谱成像分析技术可以实现壁画颜料信息的判读,隐藏信息的提取、弱信息的增强,不同属性的分类识别,同时,还可以综合特殊需求,开展画作图谱探索性研究,如壁画处理中的涂改小孩分析、画作修复等。     

应用血红蛋白的拉曼光谱进行食管癌诊断的研究

早期诊断对食管癌患者的治疗具有重要意义。通过对21例食管癌患者和20例健康人的血红蛋白溶液进行拉曼光谱的检测和研究,发现食管癌患者与健康人血红蛋白的拉曼光谱有较明显的区别。与健康人相比,食管癌患者血红蛋白中处于低自旋态的铁离子增多,而处于高自旋态的铁离子减少,说明癌变导致食管癌患者血红蛋白中部分处于高自旋态的铁离子转移到了低自旋态,这与癌症患者血样较易溶血的现象相吻合。采用主成分分析(PCA)方法,对所得拉曼光谱建立多元统计模型进行计算,得到的光谱峰值的PCA得分三维散点图可以良好的区分食管癌患者与健康人。利用判别分析方法得出该算法诊断食管癌的灵敏度和特异性分别为90.5%和95%,总判别正确率为92.7%。结果表明,对血红蛋白的拉曼光谱进行检测和分析有可能成为食管癌早期诊断的有效工具之一。     

A new application of X‐ray scattering using principal component analysis – classification and identification of liquid precursor chemicals

X‐ray scattering (XRS) combined with principal component analysis has been utilized for classifying and identifying liquid precursor chemicals for the first time. The XRS spectra of some liquid precursor chemicals and normal materials were obtained by using an XRS system, and the profiles of scattering media distinctly reveal that the XRS spectra are unique corresponding to the specific liquid material. Furthermore, the obtained spectra were processed through principal component analysis by using the selected energy region in the spectra. The score plots of each substance were clustered together and almost coincident for the same liquid, implying good repeatability and reliability. As far as the different liquid materials are concerned, they could be classified into distinct groups according to their positions in the score plot. The score plots showed a clear classification and recognition of liquid precursor chemicals. This study demonstrates a possibility for analyzing different liquid materials, and it presents a new application for X‐ray spectroscopy. Copyright © 2012 John Wiley & Sons, Ltd.     

Further investigation of majolica ceramics assigned to the Puebla (Mexico) provenance by radioisotope induced x‐ray fluorescence

A simple radioisotope x‐ray fluorescence method for determining the relative mass fractions of rubidium, strontium and zirconium combined with principal component analysis was employed to investigate specimens of archaeological majolica ceramics tentatively assigned to the Puebla (Mexico) provenance by stylistic features. Principal component analysis with this x‐ray fluorescence data could only separate the samples of one of the four groups from the other three as suggested from the thermoluminescence glow curves. Similarly, when the thermoluminescence data were analyzed by the principal component technique only the same group could be separated from the three others. However, the X‐ray fluorescence method could confirm and separate the samples of the four groups with the additional information from the thermoluminescence data. Hence it can be concluded that the clay and/or temper materials from the different specimens of the four groups are different. The difference in the clay materials could be from contamination or different sources of the components of the clay paste themselves. It is concluded that the difference is due to the clay source, since samples found at the same locations belonged to more than one group. Copyright © 2003 John Wiley & Sons, Ltd.     

The structure of molecular cloud W51 and dense cores--CO(J=1-0) and HCO+(J=1-0) spectral line mapping

We present a large scale map of about 15′×15′of CO(J=1-0) toward W51 giant molecular cloud (GMC), which covers the most active star-forming region of W51 GMC, and an interferometry HCO+(J=1-0) map of a high spatial resolution (I.e. 8″.7×6″.1) with a field of view (2′×2′) centered at W51IRS1. A structure model of W51GMC is obtained according to the results of the observations and analyses. The observations demonstrate that some small molecular cores generated by the collision between the W51GMC and the 60-73 km·s-1 foreground cloud are collapsing toward their own centers. In addition, 16 new molecular cores are discovered from the HCO+(J=1-0) map.     

可能的空-时流形和运动群

对空-时流形、运动群及其李代数作了尽量直观的几何分析与推导。首先,对惯性系的分析指出,利用黎曼几何中的Beltrami定理后可知,存在惯性系的空-时必是伪超球,因而运动群就是旋转群,于是不难推算出运动学变换的具体分析表达式及其生成元间的对易关系式。由此,具体而直观的推出了流形、群、代数的缩并关系。 关键词：     

Group of contact transformations: Symmetry classification of Fokker-Planck type equations

Fokker-Planck type equations have been classified according to the groups of contact transformations to which they belong. It has been found that there are only five classes as in the case of groups of point transformations. We have also obtained the algebraic structures of the corresponding Lie algebras. However, there are isomorphies in their group properties. The corresponding basis sets of functionally independent invariants formed by the generators of these groups have also been obtained.     

EDXRF and multivariate statistical analysis of fragments from Marajoara ceramics

In this work, 102 fragments of Marajoara ceramics, belonging to the National Museum collection (Rio de Janeiro, Brazil), were analyzed using energy dispersive X‐ray fluorescence (EDXRF) and principal component analysis (PCA) in order to identify possible groups of samples that present similar behaviors or different characteristics. This information will give an important aid to a more accurate classification of these artifacts. The EDXRF measurements were carried out with a portable system developed in the Nuclear Instrumentation Laboratory consisting of an Oxford TF3005 X‐ray tube, with W anode, and an Si‐PIN XR‐100CR detector from Amptek, working at 25 kV and 100 µA, acquisition time of 600 s and a beam collimation of 2 mm. PCA applied to the X‐ray fluorescence results revealed a clear cluster separation to the samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Stress relaxation induced faceted Cu and W particles on the surfaces of Cu–Zr and W thin films

Faceted copper and tungsten particles in submicron-scale were obtained by annealing copper–zirconium thin films on polyimide (PI) substrates as well as in the deposited tungsten films on Si substrates. It was interesting to find that the Cu particles are faceted and seem to be single crystal from their extraordinarily regular appearance. However, it is another case for W particles which are polycrystalline and irregular. Different mechanisms are put forward to elucidate the formation of Cu and W particles according to the morphological characterization, residual stress analysis and their distinct atomic diffusivity.     

Implications of CMS analysis of photon-photon interactions for photon PDFs

As part of a recent analysis of exclusive two-photon production of W+W-pairs at the LHC, the CMS experiment used di-lepton data to obtain an "effective" photon-photon luminosity. We show how the CMS analysis on their 8 TeV data, along with some assumptions about the likelihood for events in which the proton breaks up to pass the selection criteria, can be used to significantly constrain the photon parton distribution functions, such as those from the CTEQ, MRST, and NNPDF collaborations. We compare the data with predictions using these photon distributions, as well as the new LUXqed photon distribution. We study the impact of including these data on the NNPDF2.3 QED, NNPDF3.0 QED and CT14 QEDinc fits. We find that these data place a useful and complementary cross-check on the photon distribution, which is consistent with the LUXqed prediction while suggesting that the NNPDF photon error band should be significantly reduced. Additionally, we propose a simple model for describing the two-photon production of W+W-at the LHC. Using this model, we constrain the number of inelastic photons that remain after the experimental cuts are applied.     

Teaching Raman Spectroscopy in Both the Undergraduate Classroom and the Laboratory with a Portable Raman Instrument

We have evaluated a small portable Raman instrument on loan from B&W Tek, Inc., and have determined that it can successfully be used in the classroom both as a visual aid for teaching the fundamentals of Raman spectroscopy and for a variety of undergraduate experiments as a normal component of an instrumental analysis class. Having portable Raman instrumentation would allow the instructor to demonstrate the principles of Raman spectroscopy, as well as the concepts of calibration curves, blank subtraction, detection limits, and regression analysis. Both qualitative and quantitative types of experiments were done for solid Tylenol tablets, aqueous solutions of isopropyl alcohol, dimethyl sulfoxide, methanol, and ethanol, and gaseous CO₂ and N₂O₄. Additionally, surface‐enhanced resonance Raman spectra of Rhodamine 6G were obtained using a chloride ion–activated silver colloid. Spectra from the B&W Tek, Inc., instrument were comparable to literature Raman spectra.