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991.
Taking in consideration the global analysis of complex samples, proposed by the metabolomic approach, the chromatographic
fingerprint encompasses an attractive chemical characterization of herbal medicines. Thus, it can be used as a tool in quality
control analysis of phytomedicines. The generated multivariate data are better evaluated by chemometric analyses, and they
can be modeled by classification methods. “Stone breaker” is a popular Brazilian plant of Phyllanthus genus, used worldwide to treat renal calculus, hepatitis, and many other diseases. In this study, gradient elution at reversed-phase
conditions with detection at ultraviolet region were used to obtain chemical profiles (fingerprints) of botanically identified
samples of six Phyllanthus species. The obtained chromatograms, at 275 nm, were organized in data matrices, and the time shifts of peaks were adjusted
using the Correlation Optimized Warping algorithm. Principal Component Analyses were performed to evaluate similarities among
cultivated and uncultivated samples and the discrimination among the species and, after that, the samples were used to compose
three classification models using Soft Independent Modeling of Class analogy, K-Nearest Neighbor, and Partial Least Squares for Discriminant Analysis. The ability of classification models were discussed
after their successful application for authenticity evaluation of 25 commercial samples of “stone breaker.” 相似文献
992.
Vogel M Schmitt F Sauther J Baumann B Altenhof A Lach S Ziegler C 《Analytical and bioanalytical chemistry》2011,400(3):673-678
The valence band structure of different metal-phthalocyanines was investigated by comparing ultraviolet photoelectron spectra
at different excitation energies with simulated spectra that take the different photoionization cross-sections at these energies
into account. The Kohn-Sham eigenvalue spectra, derived from density functional theory calculations, using hybrid exchange-correlation
functionals, were weighted with the photoionization coefficients in accordance with the used excitation energy. By applying
these techniques, the differences in the photoelectron spectra using He I and He II radiation can be reproduced and investigated.
It will be shown that the 3d-orbitals of the used metal central atom of these molecules have a major influence. The changes
at different excitation energies were studied for Fe, Co, and Cu central atoms to describe the chemical tailoring effects. 相似文献
993.
During the developmental cycle of lab-on-a-chip devices, various microstructuring techniques are required. While in the designing and assay implementation phase direct structuring or so-called rapid-prototyping methods such as milling or laser ablation are applied, replication methods like hot embossing or injection moulding are favourable for large quantity manufacturing. This work investigated the applicability of rapid-prototyping techniques for thermoplastic chip development in general, and the reproducibility of performances in dependency of the structuring technique. A previously published chip for prenatal diagnosis that preconcentrates DNA via electrokinetic trapping and field-amplified-sample-stacking and afterwards separates it in CGE was chosen as a model. The impact of structuring, sealing, and the integration of membranes on the mobility of the EOF, DNA preconcentration, and DNA separation was studied. Structuring methods were found to significantly change the location where preconcentration of DNA occurs. However, effects on the mobility of the EOF and the separation quality of DNA were not observed. Exchange of the membrane has no effect on the chip performance, whereas the sealing method impairs the separation of DNA within the chip. The overall assay performance is not significantly influenced by different structuring methods; thus, the application of rapid-prototyping methods during a chip development cycle is well justified. 相似文献
994.
Hybridization of single-stranded DNA (ssDNA) targets to surface-tethered ssDNA probes was simulated using an advanced coarse-grain model to identify key factors that influence the accuracy of DNA microarrays. Comparing behavior in the bulk and on the surface showed, contrary to previous assumptions, that hybridization on surfaces is more thermodynamically favorable than in the bulk. In addition, the effects of stretching or compressing the probe strand were investigated as a model system to test the hypothesis that improving surface hybridization will improve microarray performance. The results in this regard indicate that selectivity can be increased by reducing overall sensitivity by a small degree. Taken as a whole, the results suggest that current methods to enhance microarray performance by seeking to improve hybridization on the surface may not yield the desired outcomes. 相似文献
995.
Sherwin BD Dunkley J Das S Appel JW Bond JR Carvalho CS Devlin MJ Dünner R Essinger-Hileman T Fowler JW Hajian A Halpern M Hasselfield M Hincks AD Hlozek R Hughes JP Irwin KD Klein J Kosowsky A Marriage TA Marsden D Moodley K Menanteau F Niemack MD Nolta MR Page LA Parker L Reese ED Schmitt BL Sehgal N Sievers J Spergel DN Staggs ST Swetz DS Switzer ER Thornton R Visnjic K Wollack E 《Physical review letters》2011,107(2):021302
For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with w = -1 dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density Ω(Λ) confirms other measurements from supernovae, galaxy clusters, and baryon acoustic oscillations, and demonstrates the power of CMB lensing as a new cosmological tool. 相似文献
996.
Glawion S Heidler J Haverkort MW Duda LC Schmitt T Strocov VN Monney C Zhou KJ Ruff A Sing M Claessen R 《Physical review letters》2011,107(10):107402
We combine high-resolution resonant inelastic x-ray scattering with cluster calculations utilizing a recently derived effective magnetic scattering operator to analyze the polarization, excitation energy, and momentum-dependent excitation spectrum of the low-dimensional quantum magnet TiOCl in the range expected for orbital and magnetic excitations (0-2.5?eV). Ti 3d orbital excitations yield complete information on the temperature-dependent crystal-field splitting. In the spin-Peierls phase we observe a dispersive two-spinon excitation and estimate the inter- and intradimer magnetic exchange coupling from a comparison to cluster calculations. 相似文献
997.
998.
Maffessanti F Lang RM Niel J Steringer-Mascherbauer R Caiani EG Nesser HJ Mor-Avi V 《Magnetic resonance imaging》2011,29(4):516-524
Purpose
Left ventricular (LV) remodeling is usually assessed using global changes in LV volume. We hypothesized that three-dimensional analysis of regional endocardial curvature from magnetic resonance images could provide clinically useful information on localized LV remodeling. We tested this approach by investigating regional differences in endocardial curvature in normal and hypokinetic ventricles.Materials and Methods
Images were obtained in 44 patients with normal LV function (NL, N=14), dilated cardiomyopathy (DCM, N=15) or ischemic heart disease (IHD, N=15). Local surface curvedness, normalized to take into account instantaneous LV size (Cn), was calculated throughout the cardiac cycle and compared between segment groups: NL (N=401), IHD (N=92) and DCM (N=255).Results
In all normal segments, Cn gradually increased during systole and then decreased during diastole. While both maximum and minimum values of Cn were comparable in the basal and midventricular segments, they were significantly higher in the four apical segments and highest in the apical cap. In addition, percent change in Cn was higher in mid and apical compared to basal segments (P<.05). At all LV levels, Cn values in DCM segments were lower (P<.05) than in NL and IHD segments, which were similar. In contrast, percent change in Cn was significantly lower in both IHD and DCM segments compared to NL.Conclusion
Three-dimensional analysis of LV endocardial curvature yielded quantitative information on regional ventricular shape consistent with the known pathophysiology, supporting its potential clinical usefulness in the evaluation of LV remodeling. 相似文献999.
Chany AC Casarotto V Schmitt M Tarnus C Guenin-Macé L Demangel C Mirguet O Eustache J Blanchard N 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(51):14413-14419
Mycolactones are complex macrolides responsible for a severe necrotizing skin disease called Buruli ulcer. Deciphering their functional interactions is of fundamental importance for the understanding, and ultimately, the control of this devastating mycobacterial infection. We report herein a diverted total synthesis approach of mycolactones analogues and provide the first insights into their structure-activity relationship based on cytopathic assays on L929 fibroblasts. The lowest concentration inducing a cytopathic effect was determined for selected analogues, allowing a clear picture to emerge by comparison with the natural toxins. 相似文献
1000.
Jozak T Sun Y Schmitt Y Lebedkin S Kappes M Gerhards M Thiel WR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(12):3384-3389
The treatment of 2,2'-di(1,2-pyrazol-3-yl)-1,1'-binaphthyl with two equivalents of appropriate monovalent group 11 precursors in the presence of a base leads to a complete exchange of the pyrazole NH protons with M(+) cations. Structural characterisation of the copper(I) complex revealed a hexanuclear complex with a pelton-wheel-like arrangement of the binaphthyl unit. As indicated by their spectroscopic data, all three complexes are isostructural. The complexes show a complex fluorescence behaviour that can be partially related to the ligand system and also to the metal sites, as indicated by the position of the fluorescence peaks and their temperature dependence and lifetimes. 相似文献