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171.
Kee CH Ariffin A Awang K Takeya K Morita H Hussain SI Chan KM Wood PJ Threadgill MD Lim CG Ng S Weber JF Thomas NF 《Organic & biomolecular chemistry》2010,8(24):5646-5660
The syntheses of fourteen unusual o-carboxamido stilbenes by the Heck protocol revealed surprising complexity related to intriguing substituent effects with mechanistic implications. The unexpected cytotoxic and chemopreventive properties also seem to be substituent dependent. For example, although stilbene 15d (with a 4-methoxy substituent) showed cytotoxicity on HT29 colon cancer cells with an IC(50) of 4.9 μM, the 3,4-dimethoxy derivative (15c) is inactive. It is interesting to observe that the 3,5-dimethoxy derivative (15e) showed remarkable chemopreventive activity in WRL-68 fetal hepatocytes, surpassing the gold standard, resveratrol. The resveratrol concentration needed to be 5 times higher than that of 15e to produce comparable elevation of NQO1. 相似文献
172.
Sharpless KE Lindstrom RM Nelson BC Phinney KW Rimmer CA Sander LC Schantz MM Spatz RO Thomas JB Turk GC Wise SA Wood LJ Yen JH 《Journal of AOAC International》2010,93(4):1262-1274
Standard Reference Material (SRM) 1849 Infant/Adult Nutritional Formula has been issued by the National Institute of Standards and Technology (NIST) as a replacement for SRM 1846 Infant Formula, issued in 1996. Extraction characteristics of SRM 1846 have changed over time, as have NIST's analytical capabilities. While certified mass fraction values were provided for five constituents in SRM 1846 (four vitamins plus iodine), certified mass fraction values for 43 constituents are provided in SRM 1849 (fatty acids, elements, and vitamins) and reference mass fraction values are provided for an additional 43 constituents including amino acids and nucleotides, making it the most extensively characterized food-matrix SRM available from NIST. 相似文献
173.
Min Liu Mike Ronk Da Ren Judy Ostovic Nina Cauchon Zhaohui Sunny Zhou Janet Cheetham 《Journal of chromatography. A》2010,1217(22):3598-3611
A hydrophilic interaction liquid chromatography (HILIC) method was used to separate a commonly used pharmaceutical starting material, 4-aminomethylpyridine (4-AMP), and its degradants. The structures of the major degradants were characterized and elucidated without prior isolation by accurate mass measurement, MS/MS analysis and on-line hydrogen/deuterium (H/D) exchange experiments. The mass spectra obtained from H/D exchange experiments are particularly useful to differentiate structural isomers, to elucidate the fragmentation pathways, and to aid in structure elucidation in the absence of MS/MS fragmentation information. The impact of deuterium oxide and temperature on HILIC separation has also been explored here. The integration of H/D exchange with HILIC has been described here for the first time and has been demonstrated to be a powerful structure elucidation tool via the study of degradants in 4-AMP. 相似文献
174.
Wang Y Fernández I Duvall M Wu JI Li Q Frenking G Schleyer PR 《The Journal of organic chemistry》2010,75(23):8252-8257
Quantitative evaluations of the aromaticity (antiaromaticity) of neutral exocyclic substituted cyclopropenes (HC)(2)C=X (X = BH to InH (group 13), CH(2) to SnH(2) (group 14), NH to SbH (group 15), O to Te (group 16)) by their computed extra cyclic resonance energies (ECRE, via the block-localized wave function method) and by their aromatic stabilization energies (ASEs, via energy decomposition analyses) correlate satisfactorily (R(2) = 0.974). Electronegative X-based substituents increase the aromaticity of the cyclopropene rings, whereas electropositive substituents have the opposite effect. For example, (HC)(2)C=O is the most aromatic (ECRE = 10.3 kcal/mol), and (HC)(2)C=InH is the most antiaromatic (ECRE = -15.0 kcal/mol). The most refined dissected nucleus-independent chemical shift magnetic aromaticity index, NICS(0)(πzz), also agrees with both energetic indexes (R(2) = 0.968, for ECRE; R(2) = 0.974, for ASE), as do anisotropy of the induced current density plots. 相似文献
175.
Gorga MP Neely ST Kopun J Tan H 《The Journal of the Acoustical Society of America》2011,129(2):801-806
Distortion-product otoacoustic emissions (DPOAEs) were used to describe suppression growth in normal-hearing humans. Data were collected at eight f(2) frequencies ranging from 0.5 to 8 kHz for L(2) levels ranging from 10 to 60 dB sensation level. For each f(2) and L(2) combination, suppression was measured for nine or eleven suppressor frequencies (f(3)) whose levels varied from -20 to 85 dB sound pressure level (SPL). Suppression grew nearly linearly when f(3) ≈ f(2), grew more rapidly for f(3)?< f(2), and grew more slowly for f(3)?> f(2). These results are consistent with physiological and mechanical data from lower animals, as well as previous DPOAE data from humans, although no previous DPOAE study has described suppression growth for as wide a range of frequencies and levels. These trends were evident for all f(2) and L(2) combinations; however, some exceptions were noted. Specifically, suppression growth rate was less steep as a function of f(3) for f(2) frequencies ≤ 1 kHz. Thus, despite the qualitative similarities across frequency, there were quantitative differences related to f(2), suggesting that there may be subtle differences in suppression for frequencies above 1 kHz compared to frequencies below 1 kHz. 相似文献
176.
James B Whitney Saied Mirshahidi So-Yon Lim Lauren Goins Chris C Ibegbu Daniel C Anderson Richard B Raybourne Fred R Frankel Judy Lieberman Ruth M Ruprecht 《Journal of immune based therapies and vaccines》2011,9(1):2
Background
We have evaluated an attenuated Listeria monocytogenes (Lm) candidate vaccine vector in nonhuman primates using a delivery regimen relying solely on oral vaccination. We sought to determine the impact of prior Lm vector exposure on the development of new immune responses against HIV antigens. 相似文献177.
Muniz CR Freire FC Viana FM Cardoso JE Cooke P Wood D Guedes MI 《Micron (Oxford, England : 1993)》2011,42(5):419-428
Lasiodiplodia theobromae is a phytopathogenic fungus causing gummosis, a threatening disease for cashew plants in Brazil. In an attempt to investigate the ultrastructural features of the pathogen colonization and its response to immunofluorescence labeling, light, confocal and electron microscope studies were conducted on different severity scale patterns of diseased plants. Lasiodiplodia-antisera was checked for cross reactivity against common cashew plants fungi. Optical microscopy analysis revealed a longitudinally sectioned hyphae located within the xylem vessels, showing an extensive hyphal development in the secondary xylem tissue. SEM images demonstrated that the fungus was found in some asymptomatic samples, particularly within the xylem vessels as confirmed by the optical images. Symptomatic sample images showed an extensive distribution of the fungus along the secondary xylem, within the vessels, infecting xylem parenchyma. A closer look in the secondary xylem parenchyma reveals a heavy and profuse invasion of the cells with a distinguishable cell wall disintegration and fully hyphae dispersal. There was no reactivity of Lasiodiplodia-antisera against mycelial extracts of Colletotrichum gloeosporioides, Phomopsis anardii and Pestalotiopsis guepinii. Following incubation of sections with the polyclonal antisera, the hyphae were intensely and regularly labeled. Rays, vessels and parenchyma cells were the preferred pathway for L. theobromae colonization. Artificial infection provides the information that the vascular cylinder is undoubtedly employed and used by the fungus for hyphae distribution. Immunofluorescence assay employed in situ was applied and the polyclonal antisera produced was able to recognize the fungus and proved to be a sensitive technique to detect it. 相似文献
178.
We show that given a harmonic map φ from a Riemann surface to a classical compact simply connected inner symmetric space, there is a J 2-holomorphic twistor lift of φ (or its negative) if and only if it is nilconformal. In the case of harmonic maps of finite uniton number, we give algebraic formulae in terms of holomorphic data which describes their extended solutions. In particular, this gives explicit formulae for the twistor lifts of all harmonic maps of finite uniton number from a surface to the above symmetric spaces. 相似文献
179.
We study a Helmholtz‐type spectral problem related to the propagation of electromagnetic waves in photonic crystal waveguides. The waveguide is created by introducing a linear defect into a three‐dimensional periodic medium; the defect is infinitely extended in one direction, but compactly supported in the remaining two. This perturbation introduces guided mode spectrum inside the band gaps of the fully periodic, unperturbed spectral problem. We will show that even small perturbations lead to additional spectrum in the spectral gaps of the unperturbed operator and investigate some properties of the spectrum that is created. 相似文献
180.
Jay A. Wood 《Designs, Codes and Cryptography》2014,72(2):331-344
Relative one-weight linear codes were introduced by Liu and Chen over finite fields. These codes can be defined just as simply for egalitarian and homogeneous weights over Frobenius bimodule alphabets. A key lemma helps describe the structure of relative one-weight codes, and certain known types of two-weight linear codes can then be constructed easily. The key lemma also provides another approach to the MacWilliams extension theorem. 相似文献