ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTProton-Transfer Polymerization: A New Approach to Hyperbranched PolymersHan-Ting Chang and Jean M. J. FréchetView Author Information Department of Chemistry, University of California Berkeley, California 94720-1460 Cite this: J. Am. Chem. Soc. 1999, 121, 10, 2313–2314Publication Date (Web):February 27, 1999Publication History Received2 November 1998Published online27 February 1999Published inissue 1 March 1999https://pubs.acs.org/doi/10.1021/ja983797rhttps://doi.org/10.1021/ja983797rrapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views1488Altmetric-Citations109LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Aromatic compounds,Ethers,Hydrocarbons,Monomers,Polymerization Get e-Alerts
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Almost all work on texture in the computer vision and graphics communities has modeled the texture as tangential, i.e. lying in the tangent plane to the surface. This is equivalent to thinking of the texture as a pattern painted on the surface. Three-dimensional textures, where the elements may point out of the surface, have largely been ignored. We study a special class of 3D textures, perpendicular textures where we can model the elements as being normal to the surface. The perspective projection of perpendicularly textured surfaces results in several interesting phenomena, which do not occur in the much-studied tangential texture case. These include occlusion, foreshortening and illumination. In this paper, we study the geometry of the problem, modeling the locations of the elements of the texture as being a realization of a spatial point process. Relations between slant and tilt of the surface, density and height of elements and occlusions are derived. Occlusions can now be used as a cue to infer shape, instead of being treated as a source of error.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
A simple procedure is described for the preparation of photosystem I (PSI) particles from Triton X-100-solubilized thylakoid membranes of the unicellular cyanobacterium Synechococcus 6301. The purified PSI complex contained the full complement of antenna chlorophylls, 130 +/- 5/P700, displayed the electron paramagnetic resonance signals characteristic of iron-sulfur centers X, A, and B, and had a protein/chlorophyll ratio of 2.9. Determination of the polypeptide composition, utilizing a uniformly 14C-labeled complex, showed that it contained polypeptides of 70, 18, 17.7, 16, and 10 kDa, in a molar ratio of 4.0:0.7:1.0:0.5:1.6. The relative amount of the lower molecular weight polypeptides showed progressive decrease with increase in Triton X-100 concentration and time of exposure to detergent. Consequently, it is proposed that in vivo the composition of the complex is [70 kDa]4 [18 kDa]1 [17.7 kDa]1 [16 kDa]1 [10 kDa]2. Relative to 130 mol of chlorophyll a, the PSI complex contained 16 mol of carotenoids, 13.7 +/- 1.0 g atoms of Fe, and 12.2 +/- 1.1 g atoms of labile sulfide. The properties of complexes fully depleted of the low-molecular weight polypeptides by treatment with sodium dodecyl sulfate or with proteinase K are also described.
Guest editors Christopher J. Chang, Thorfinnur Gunnlaugsson and Tony D. James introduce the Imaging Agents issue of <italic>Chemical Society Reviews</italic>
The mechanism and kinetics for ethanol coupling to n-butanol over hydroxyapatite (HAP) were investigated at 573-613 K. In situ titration experiments show that the active sites for acetaldehyde and butanol formation are different. In combination with FTIR studies, it was found that ethanol dehydrogenation is catalyzed by Ca-O sites, whereas condensation of acetaldehyde is catalyzed by CaO/PO<sub>4</sub> <sup>3-</sup> pairs. Measurements of the reaction kinetics at various ethanol (3.5-9.4 kPa) and acetaldehyde (0.055-0.12 kPa) partial pressures reveal that direct condensation involving two ethanol molecules does not play a significant role in butanol formation; instead, n-butanol is formed via a Guerbet pathway. At a constant acetaldehyde pressure, enolate formation is rate-limiting, and ethanol inhibits acetaldehyde condensation rates by competitive adsorption. A model of the reaction kinetics consistent with all experimental observations is developed.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
