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91.
Anthony S. Stender Lindsay A. Giem Matt C. Bunte Carrie L. Burns Lindsay D. Odom Diane S. Fitzpatrick Christopher J. Biorn Eugene T. Smith 《The Chemical Educator》2000,5(6):321-323
A laboratory exercise, the analysis of arsenic in drinking water by graphite furnace atomic absorption spectroscopy (GFAA), is presented for use in an undergraduate instrumental methods course. The purpose of this GFAA exercise is to expose students to a practical and commonly used application, to provide students with hands-on experience with the instrument, and to reinforce concepts taught in the classroom. Students safely analyze a real-world sample containing an analyte in the parts-per-billion concentration range. 相似文献
92.
Yuo-Hsien Shiau 《Solid State Communications》2006,139(6):278-283
A cross-correlation matrix applied for restoring the doping profile in an n+-n−-n-n+ device was reported recently [Y.-H. Shiau, Solid-State Electron. 50 (2006) 191]. In this paper we will show that this statistical method is very useful for detecting the dynamical processes embedded in semiconductor devices. In addition, extraction of nonuniform fluctuations hidden in this wide-gap semiconductor device could be helpful for clarifying the previous studies on several competing instabilities in InSb at 77 K [A. ?enys, G. Lasiene, K. Pyragas, Solid-State Electron. 35 (1992) 975; H. Ito, Y. Ueda, Phys. Lett. A 280 (2001) 312]. A general discussion about the application of the cross-correlation matrix to other pattern-forming systems is also given in the present study. 相似文献
93.
V. L. Spate J. S. Morris T. A. Nichols C. K. Baskett M. M. Mason T. L. Horsman P. L. Horn-Ross A. C. Shiau I. R. McDougall 《Journal of Radioanalytical and Nuclear Chemistry》1998,236(1-2):71-77
The literature on the relationship between diet and thyroid cancer (TC) risk and the higher incidence of TC among Asian immigrants
to the US compared to second and third generation subgroups has prompted epidemiologists to hypothesize that increased levels
of iodine consumption may be associated with TC risk, particularly among persons with a history of clinical or subclinical
thyroid dysfunction. At the University of Missouri Research Reactor (MURR), we have applied epiboron neutron activation analysis
to investigate human nails as a dietary monitor for iodine. Preliminary studies have indicated a positive correlation between
dietary iodine intake and the concentration of iodine in toenails. However, these studies are confounded by high iodine levels
(up to 30 ppm) in approximately 5% of the nails studied. We hypothesize that, in the subjects we have studied, the high iodine
levels may be due to iodine-containing medications, in particular contrast-agents containing iopamidol. This paper will report
on longitudinal studies using contrast agent subjects who were followed-up for almost two years compared to a longitudinal
control and a population mean. Based on this study, we suggest that iodine-containing contrast agents contaminate nail samples
via non-specific binding in the short term followed by incorporation in the nail as a result of absorption. 相似文献
94.
Sammond DW Bosch DE Butterfoss GL Purbeck C Machius M Siderovski DP Kuhlman B 《Journal of the American Chemical Society》2011,133(12):4190-4192
The de novo design of protein-binding peptides is challenging because it requires the identification of both a sequence and a backbone conformation favorable for binding. We used a computational strategy that iterates between structure and sequence optimization to redesign the C-terminal portion of the RGS14 GoLoco motif peptide so that it adopts a new conformation when bound to Gα(i1). An X-ray crystal structure of the redesigned complex closely matches the computational model, with a backbone root-mean-square deviation of 1.1 ?. 相似文献
95.
96.
Bondebjerg J Xiang Z Bauzo RM Haskell-Luevano C Meldal M 《Journal of the American Chemical Society》2002,124(37):11046-11055
The solid-phase synthesis of a novel thioether cyclized peptidomimetic scaffold, displaying functionality at the i to i + 3 positions, is reported. The thioether bridge is formed on-bead by an intramolecular reaction between a chloroacetylated reduced peptide bond and the free thiol from a cysteine. The crude products were obtained in moderate to very high purity. A series of 19 compounds were prepared and tested for agonist activity at the mouse melanocortin receptors 1, 3, 4, and 5 (mMC1-5R). From these results, several compounds were identified as having low micromolar agonist activity at the mMC1R and mMC4R. The former is involved in skin pigmentation and animal coat coloration. The latter is involved in the regulation of appetite and food intake and is currently a drug target for potential treatment of obesity. The most potent compound 1n with the pharmacophore motif "His-DPhe-Arg-Trp" was identified as having an EC(50) value of 165 nM at mMC1R, 7600 nM at mMC3R, 650 nM at mMC4R, and 335 nM at mMC5R. In addition, some of the compounds showed moderate selectivity for the mMC1R. 相似文献
97.
The successful isolation of stable (and soluble) hexa- and tetratrityl cations based on hexaphenylbenzene and tetraphenylmethane scaffold has been accomplished by using readily available starting materials. These robust polytrityl cations can be isolated in crystalline form and stored indefinitely at 0 degrees C. Their structures have been established by (1)H/(13)C NMR spectroscopy and by UV-vis spectroscopy. The structures of these polytrityl cations were further confirmed by quantitative transformations to the reduced (poly)triphenylmethyl derivatives by hydride transfer from triethylsilane, cycloheptatriene, or a borane-dimethyl sulfide complex. 相似文献
98.
99.
Sequential Cu-catalyzed amidation-base-mediated camps cyclization: a two-step synthesis of 2-Aryl-4-quinolones from o-halophenones 总被引:1,自引:0,他引:1
A direct two-step method for the preparation of 2-aryl- and 2-vinyl-4-quinolones that utilizes a copper-catalyzed amidation of o-halophenones followed by a base-promoted Camps cyclization of the resulting N-(2-ketoaryl)amides is described. With CuI, a diamine ligand, and base as the catalyst system, the amidation reactions proceed in good yields for a range of aryl, heteroaryl, and vinyl amides. The subsequent Camps cyclization efficiently provides the desired 4-quinolones with the conditions that are described. 相似文献
100.
Pierce CY Barr JR Cody RB Massung RF Woolfitt AR Moura H Thompson HA Fernandez FM 《Chemical communications (Cambridge, England)》2007,(8):807-809
Direct analysis in real time (DART) is implemented on a time-of-flight (TOF) mass spectrometer, and used for the generation of fatty acid methyl esters (FAMEs) ions from whole bacterial cells. 相似文献