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81.
Edith Gabriel 《Methodology and Computing in Applied Probability》2014,16(2):411-431
Non-parametric estimates of the K-function and the pair correlation function play a fundamental role for exploratory and explanatory analysis of spatial and spatio-temporal point patterns. These estimates usually require information from outside of the study region, resulting to the so-called edge effects which have to be corrected. They also depend on first-order characteristics, which have to be estimated in practice. In this paper, we extend classical edge correction methods to the spatio-temporal setting and compare the performance of the related estimators for stationary/non-stationary and/or isotropic/anisotropic point patterns. Further, we explore the influence of the estimated intensity function on these estimators. 相似文献
82.
Jürgen Brüning Edith Alig Martin U. Schmidt 《Acta Crystallographica. Section C, Structural Chemistry》2010,66(7):o341-o344
Ezetimibe {systematic name: (3R,4S)‐1‐(4‐fluorophenyl)‐3‐[(3S)‐3‐(4‐fluorophenyl)‐3‐hydroxypropyl]‐4‐(4‐hydroxyphenyl)azetidin‐2‐one}, C24H21F2NO3, is used to lower cholesterol levels by inhibiting cholesterol resorption in the human intestine. The crystal structure of ezetimibe anhydrate was solved from laboratory powder diffraction data by means of real‐space methods using the program DASH [David et al. (2006). J. Appl. Cryst. 39 , 910–915]. Subsequent Rietveld refinement with TOPAS Academic [Coelho (2007). TOPAS Academic User Manual. Version 4.1. Coelho Software, Brisbane, Australia] led to a final Rwp value of 8.19% at 1.75 Å resolution. The compound crystallizes in the space group P212121 with one molecule in the asymmetric unit. The molecules are closely packed and two intermolecular hydrogen bonds form an extended hydrogen‐bond architecture. 相似文献
83.
Nakano M Champagne B Botek E Ohta K Kamada K Kubo T 《The Journal of chemical physics》2010,133(15):154302
This contribution reveals the effects of a static electric field on the static second hyperpolarizability γ of symmetric singlet diradical molecules using the valence configuration interaction scheme. It is found that under the effect of a field, the component of γ along the axis joining the two radical sites can be gigantically (approximately two to three orders) enhanced for symmetric diradicals having intermediate diradical characters with respect to those of closed-shell and pure diradical molecules in the absence of a field. Moreover, this electric field enhancement of γ increases as a function of the diradical character. These results and their analysis propose therefore a new strategy to design materials with exceptional nonlinear optical responses. 相似文献
84.
Edith Berger-Preiß Susanne Gerling Elisabeth Apel Alfonso Lampen Otto Creutzenberg 《Analytical and bioanalytical chemistry》2010,398(1):313-318
We have developed a highly selective and sensitive method using gas chromatography-mass spectrometry with negative chemical
ionization for measuring 3-chloropropane-1,2-diol (3-MCPD) in rat blood and urine. Samples were adsorbed on silica gel, extracted
with ethyl acetate, and derivatized by chemical derivatization with heptafluorobutyric acid anhydride. For quantification,
matrix-based calibration curves and 3-MCPD-d
5, as an isotope-labeled internal standard, were used. The relative recoveries of 3-MCPD were between 80 and 110% in most cases
and the relative standard deviations were typically less than 10%, with some exceptions. The limit of quantification of the
method was found to be about 2 ng/mL. In conclusion, a valuable, robust, and sensitive method for detection of 3-MCPD is now
available for biokinetics studies. 相似文献
85.
Encarnación Rodríguez‐Gonzalo Rita Carabias‐Martínez Edith Miranda Cruz Javier Domínguez‐Álvarez Jesús Hernández‐Méndez 《Journal of separation science》2009,32(4):575-584
In the present work we address the development of a simple and effective method for the determination of triazine herbicide residues in horticultural products by CE in nonaqueous media (NACE). Potato samples were selected as a representative matrix of such foods with a nonfatty content. Isolation of the analytes from the sample matrix was accomplished by extraction with organic solvents, assisted by ultrasound; a clean‐up step of the organic extracts was carried out with SPE, using an Oasis MCX® sorbent to retain the analytes directly from the organic medium. The detection limits achieved in spiked potatoes (1.7–4.0 μg/kg) were lower than the default value of maximum residue level (MRL) established by current EU legislation for pesticide residues in foodstuffs. The results obtained were compared with HPLC in order to evaluate the performance of the NACE procedure. 相似文献
86.
[reaction: see text] The synthesis, photophysical properties, and structural characterization of a photodimerizable ditopic ligand are described. Upon irradiation at 366 nm, ligand 1 dimerizes to the head-to-tail tetra-bpy ligand 2. This thermally stable photodimer can be dissociated back to 1 using higher energy irradiation (254 nm). 相似文献
87.
Gupton JT Telang N Banner EJ Kluball EJ Hall KE Finzel KL Jia X Bates SR Welden RS Giglio BC Eaton JE Barelli PJ Firich LT Stafford JA Coppock MB Worrall EF Kanters RP Keertikar K Osterman R 《Tetrahedron》2010,66(47):9113-9122
Studies directed at the synthesis of (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones from (Z)-3-aryl-3-haloenoic acids are described. The successful strategy relies on the preparation of (Z)-3-aryl-3-haloenoic acids from acetophenones through the corresponding (Z)-3-aryl-3-haloenals and the conversion of the (Z)-3-aryl-3-haloenoic acids to (Z)-5-benzylidene-4-aryl-5H-furan-2-ones. The furanones were subsequently treated with primary amines and dehydrated to the corresponding (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones. 相似文献
88.
89.
E. Moles G. P. Baxter A. H. Hale T. Batuecas E. H. Archibald J. G. Hooley C. R. Naeser B. S. Hopkins F. Hecht Edith Europa O. Hönigschmid F. Wittner M. Dole F. W. Aston R. Jungbluth-Ficht M. Hoeppner G. E. F. Lundell J. I. Hoffman K. Wintersberger R. Schlee G. Wittmann W. Menn 《Analytical and bioanalytical chemistry》1937,109(1-2):35-39
90.
Wang Z Shao H Lacroix E Wu SH Jennings HJ Zou W 《The Journal of organic chemistry》2003,68(21):8097-8105
Treatment of 2'-carbonyl-alpha-C-glycopyranosides of gluco, galacto, manno, 2-deoxy, and 2-azido sugars with 4% NaOMe resulted in anomeric epimerization to give their respective beta-anomers in good to excellent yields. The epimerization of the 2'-aldehyde of alpha-C-galactopyranoside (10) in deuterium methanol, which afforded the beta-anomer with exclusive deuterium replacements at the 1'-position, excluded the possibility of the exo-glycal as being involved as an intermediate. When 2'-aldehyde (36) and 2'-ketone (41) of 2,3-di-O-benzyl-alpha/beta-l-C-arabinofuranoside were used as substrates we were able to obtain the respective equatorial alpha-C-arabinopyranosides (37 and 42). These observations confirmed that the epimerization involves an acyclic alpha,beta-unsaturated aldehyde or ketone, which is formed by the enolation of 2'-carbonyl-alpha-C-glycoside with subsequent beta-elimination. Thereafter an intramolecular hetero-Michael cycloaddition occurs, leading to the formation of thermodynamically controlled stable products, which were exclusively the equatorial C-glycopyranosides, except in the case of 2'-carbonyl-C-furanosides, where a mixture of two anomers was obtained. 相似文献