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971.
Efficient desymmetrization of isophthalaldehyde allows a scalable asymmetric synthesis of cinnamylated sesquiterpenoid 1. We have shown that 1 forms useful, property-altered composites with peptides and related oligomers. The current synthesis promises to expand those efforts considerably. 相似文献
972.
Metal-free intermolecular oxidative C-N bond formation via tandem C-H and N-H bond functionalization
Kantak AA Potavathri S Barham RA Romano KM DeBoef B 《Journal of the American Chemical Society》2011,133(49):19960-19965
The development of a novel intermolecular oxidative amination reaction, a synthetic transformation that involves the simultaneous functionalization of both a N-H and C-H bond, is described. The process, which is mediated by an I(III) oxidant and contains no metal catalysts, provides a rapid and green method for synthesizing protected anilines from simple arenes and phthalimide. Mechanistic investigations indicate that the reaction proceeds via nucleophilic attack of the phthalimide on an aromatic radical cation, as opposed to the electrophilic aromatic amination that has been reported for other I(III) amination reactions. The application of this new reaction to the synthesis of a variety of substituted aniline derivatives is demonstrated. 相似文献
973.
Xia Q Lee MV Rose CM Marsh AJ Hubler SL Wenger CD Coon JJ 《Journal of the American Society for Mass Spectrometry》2011,22(2):255-264
Using a large set of high mass accuracy and resolution ETD tandem mass spectra, we characterized ETD-induced neutral losses.
From these data we deduced the chemical formula for 20 of these losses. Many of them have been previously observed in electron-capture
dissociation (ECD) spectra, such as losses of the side chains of arginine, aspartic acid, glutamic acid, glutamine, asparagine,
leucine, histidine, and carbamidomethylated cysteine residues. With this information, we examined the diagnostic value of
these amino acid-specific losses. Among 1285 peptide–spectrum matches, 92.5% have agreement between neutral loss-derived peptide
amino acid composition and the peptide sequences. Moreover, we show that peptides can be uniquely identified by using only
the accurate precursor mass and amino acid composition based on neutral losses; the median number of sequence candidates from
an accurate mass query is reduced from 21 to 8 by adding side chain loss information. Besides increasing confidence in peptide
identification, our findings suggest the potential use of these diagnostic losses in ETD spectra to improve false discovery
rate estimation and to enhance the performance of scoring functions in database search algorithms. 相似文献
974.
Pfingst BE Burkholder-Juhasz RA Xu L Thompson CS 《The Journal of the Acoustical Society of America》2008,123(2):1054-1062
In modern cochlear implants, much of the information required for recognition of important sounds is conveyed by temporal modulation of the charge per phase in interleaved trains of electrical pulses. In this study, modulation detection thresholds (MDTs) were used to assess listeners' abilities to detect sinusoidal modulation of charge per phase at each available stimulation site in their 22-electrode implants. Fourteen subjects were tested. MDTs were found to be highly variable across stimulation sites in most listeners. The across-site patterns of MDTs differed considerably from subject to subject. The subject-specific patterns of across-site variability of MDTs suggest that peripheral site-specific characteristics, such as electrode placement and the number and condition of surviving neurons, play a primary role in determining modulation sensitivity. Across-site patterns of detection thresholds (T levels), maximum comfortable loudness levels (C levels) and dynamic ranges (DRs) were not consistently correlated with across-site patterns of MDTs within subjects, indicating that the mechanisms underlying across-site variation in these measures differed from those underlying across-site variation in MDTs. MDTs sampled from multiple sites in a listener's electrode array might be useful for diagnosing across-subject differences in speech recognition with cochlear implants and for guiding strategies to improve the individual's perception. 相似文献
975.
A computer simulation study of imaging flexural inhomogeneities using plate-wave diffraction tomography 总被引:2,自引:0,他引:2
This paper investigates the feasibility of plate-wave diffraction tomography for the reconstruction of flexural inhomogeneities in plates using the results of computer simulation studies. The numerical implementation of the fundamental reconstruction algorithm, which has recently been developed by Wang and Rose [C.H. Wang, L.R.F. Rose, Plate-wave diffraction tomography for structural health monitoring, Rev. Quant. Nondestr. Eval. 22 (2003) 1615-1622] is investigated addressing the essential effects of applying the discrete form of the Fourier diffraction theorem for solving the inverse problem as discussed by Kak and Slaney [A.C. Kak, M. Slaney, Principles of Computerized Tomographic Imaging, IEEE Press, New York, 1988] for the acoustic case, viz. diffraction limited sensitivity, influence of weak scatterer assumption, damage location and scatter field data processing in time and Fourier space as well as experimental limitations such as finite receiver length and limited views. The feasibility of the imaging technique is investigated for cylindrical inhomogeneities of various severities and relative position within the interrogation space and a normal incident interrogation configuration. The results show that plate-wave diffraction tomography enables the quantitative reconstruction of location, size and severity of plate damage with excellent sensitivity and offers the potential for detecting corrosion thinning, disbonds and delamination damage in structural integrity management applications. 相似文献
976.
Xavier Ramos Olivé Christian Rose Lili Wang Guofang Wei 《Mathematische Nachrichten》2023,296(8):3559-3578
We obtain a fundamental gap estimate for classes of bounded domains with quantitative control on the boundary in a complete manifold with integral bounds on the negative part of the Ricci curvature. This extends the result of Oden, Sung, and Wang [Trans. Amer. Math. Soc. 351 (1999), no. 9, 3533–3548] to -Ricci curvature assumptions, . To achieve our result, it is shown that the domains under consideration are John domains, what enables us to obtain an estimate on the first nonzero Neumann eigenvalue, which is of independent interest. 相似文献
977.
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option. 相似文献