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561.
Edmund R. Malinowski 《Journal of Chemometrics》2011,25(6):323-328
Determining the rank of a chemical matrix is the first step in many multivariate, chemometric studies. Rank is defined as the minimum number of linearly independent factors after deletion of factors that contribute to random, nonlinear, uncorrelated errors. Adding a matrix of rank 1 to a data matrix not only increases the rank by one unit but also perturbs the primary factor axes, having little effect on the secondary axes associated with the random errors in the measurements. The primary rank of a data matrix can be determined by comparing the residual variances obtained from principal component analysis (PCA) of the original data matrix to those obtained from an augmented matrix. The ratio of the residual variances between adjacent factor levels represents a Fisher ratio that can be used to distinguish the primary factors (chemical as well as instrumental factors) from the secondary factors (experimental errors). The results gleaned from model studies as well as those from experimental studies are used to illustrate the efficacy of the proposed methodology. The method is independent of the nature of the error distribution. Limitations and precautions are discussed. An algorithm, written in MATLAB format, is included. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
562.
Edmund R. Malinowski 《Journal of Chemometrics》1996,10(4):273-279
An algorithm called automatic window factor analysis (AUTOWFA) is developed for the purpose of determining, efficiently and automatically, the concentration profiles of the spectroscopically active components present in evolutionary processes, such as chemical titration, chromatography and kinetics. The method not only yields windows and profiles in agreement with those reported in the literature, but also reveals components not detected by precursor techniques. The method, however, has not been optimized and may require user interaction to fine-tune the windows. 相似文献
563.
Dr. Ana M. Ortuño Dr. Pablo Reiné Prof. Luis Álvarez de Cienfuegos Dr. Irene R. Márquez Dr. Wynand Dednam Prof. Enrico B. Lombardi Prof. Juan J. Palacios Dr. Edmund Leary Prof. Giovanna Longhi Prof. Vladimiro Mujica Dra. Alba Millán Dra. M. Teresa González Linda A. Zotti Dra. Delia Miguel Prof. Juan M. Cuerva 《Angewandte Chemie (International ed. in English)》2023,62(16):e202218640
We report on the chemical design of chiral molecular junctions with stress-dependent conductance, whose helicity is maintained during the stretching of a single molecule junction due to the stapling of both ends of the inner helix. In the reported compounds, different conductive pathways are observed, with clearly different conductance values and plateau-length distributions, attributed to different conformations of the helical structures. The large chiro-optical responses and the potential use of these molecules as unimolecular spin filters have been theoretically proved using state-of-the-art Density Functional Theory (DFT) calculations, including a fully ab-initio estimation of the CISS-originating spin polarization which is done, for the first time, for a realistic molecular system. 相似文献
564.
Fulai Liu Xutao Gao Rui Shi Prof. Dr. Zhengxiao Guo Prof. Dr. Edmund C. M. Tse Prof. Dr. Yong Chen 《Angewandte Chemie (International ed. in English)》2023,62(11):e202300094
Electro-reforming of Polyethylene-terephthalate-derived (PET-derived) ethylene glycol (EG) into fine chemicals and H2 is an ideal solution to address severe plastic pollution. Here, we report the electrooxidation of EG to glycolic acid (GA) with a high Faraday efficiency and selectivity (>85 %) even at an industry-level current density (600 mA cm−2 at 1.15 V vs. RHE) over a Pd−Ni(OH)2 catalyst. Notably, stable electrolysis over 200 h can be achieved, outperforming all available Pd-based catalysts. Combined experimental and theoretical results reveal that 1) the OH* generation promoted by Ni(OH)2 plays a critical role in facilitating EG-to-GA oxidation and removing poisonous carbonyl species, thereby achieving high activity and stability; 2) Pd with a downshifted d-band center and the oxophilic Ni can synergistically facilitate the rapid desorption and transfer of GA from the active Pd sites to the inactive Ni sites, avoiding over-oxidation and thus achieving high selectivity. 相似文献
565.
Tatiana Sukhanova Vladimir Bershtein Mimi Keating Galina Matveeva Milana Vylegzhanina Victor Egorov Nina Peschanskaya Pavel Yakushev Edmund Flexman Stefan Greulich Bryan Sauer Kathleen Schodt 《Macromolecular Symposia》2004,214(1):135-146
Comparative WAXD/SAXS/SEM/DSC structural studies of a series of semi-crystalline poly(oxymethylene) (POM) engineering plastics, including the commercial products, homopolymer Delrin® and typical poly(oxymethylene-co-oxyethylene)s, and a few lab-made POM compositions, were performed. The latter differed in their content of functional additives (present in low concentrations) and POM molecular weight characteristics. In parallel, their densities, thermal behavior/laser-interferometric creep rate spectra (DSC/CRS) at 20-180 °C, as well as long-term creep resistance (LTCR) at 20 °C were studied. It has been found that introducing the nucleating agents and oxyethylene units resulted in formation of more fine spherulitic or practically non-spherulitic structure with close- or loose-packed lamellar stacks. The presence of both “thick” (5-10 nm) and “thin” (1.5-3 nm) lamellae in the weight ratio of ∼3:1 was shown in all cases. Close values of real POM crystallinities, not exceeding 50%, were obtained by WAXD and DSC. A predominant role of “straightened out” or slightly bent tie chains in disordered layers of isotropic POMs was presumed, resulting in segmental dynamics differently constrained by crystallites (DSC/CRS data). As a result, certain morphology - density - creep resistance correlations were found. 相似文献