Convexity and Zariski decomposition structure

This is the first part of our work on Zariski decomposition structures, where we study Zariski decompositions using Legendre-Fenchel type transforms. In this way we define a Zariski decomposition for curve classes. This decomposition enables us to develop the theory of the volume function for curves defined by the second named author, yielding some fundamental positivity results for curve classes. For varieties with special structures, the Zariski decomposition for curve classes admits an interesting geometric interpretation.Comment: 38 pages; revised half of the previous arXiv:1507.04316 [math.AG

Probing subtle fluorescence dynamics in cellular proteins by streak camera based Fluorescence Lifetime Imaging Microscopy

We report the cell biological applications of a recently developed multiphoton fluorescence lifetime imaging microscopy system using a streak camera (StreakFLIM). The system was calibrated with standard fluorophore specimens and was shown to have high accuracy and reproducibility. We demonstrate the applicability of this instrument in living cells for measuring the effects of protein targeting and point mutations in the protein sequence which are not obtainable in conventional intensity based fluorescence microscopy methods. We discuss the relevance of such time resolved information in quantitative energy transfer microscopy and in measurement of the parameters characterizing intracellular physiology

First total synthesis and structural reassignment of (-)-aplysiallene.

The first total synthesis of (-)-aplysiallene has been completed in 16 steps and features a key sequential Mukaiyama aerobic oxidative cyclization to prepare the fused bis-THF core. The original stereochemical assignment has been revised as shown

Side by Side: The Use of Multiple Subject Languages in Capturing Shifting Contexts around Historical Collections

Archival representations strive to convey the original context around historical collections, but perspectives on certain topics and materials may change over time. Such shifting perspectives pose problems for providing appropriate subject access without obscuring contexts or misrepresenting resources in their broader cultural settings. This study seeks to examine these problems through an investigation of historical materials associated with American sideshows, public opinions on which changed drastically from the 19th to the 20th centuries. Using as a case the Ronald G. Becker Collection of Charles Eisenmann Photographs, an archival collection of digitized images of sideshow performers, we explored a variety of systems of subject representation for major concepts and terms relevant to sideshow performers and activities. Combining keyword extraction and descriptive analysis of current collection metadata (e.g., LCSH) with comparisons to other popular systems of subject representation, we found complex and conflicting perspectives on concepts such as dwarfism, hypertrichosis, and obesity. Results revealed that current LCSH-based subject metadata for these materials tends to reduce historical and demographic context around performers and highlight contemporary medical perspectives. At the same time, original language used in these images is now often seen as demeaning, exploitative, and offensive. Furthermore, neither of these perspectives may match with self-identifying language used in contemporary society. Taken together, however, these sets of terminologies and their relationships may provide a more robust representation of changing perceptions and terminologies over time. Findings from this study reveal the potentials of utilizing a faceted approach and multiple subject languages together to further clarify and contextualize archival collections

Donor–Acceptor Fluorophores for Energy-Transfer-Mediated Photocatalysis

Triplet–triplet energy transfer (EnT) is a fundamental activation pathway in photocatalysis. In this work, we report the mechanistic origins of the triplet excited state of carbazole-cyanobenzene donor–acceptor (D–A) fluorophores in EnT-based photocatalytic reactions and demonstrate the key factors that control the accessibility of the 3LE (locally excited triplet state) and 3CT (charge-transfer triplet state) via a combined photochemical and transient absorption spectroscopic study. We found that the energy order between 1CT (charge transfer singlet state) and 3LE dictates the accessibility of 3LE/3CT for EnT, which can be effectively engineered by varying solvent polarity and D–A character to depopulate 3LE and facilitate EnT from the chemically more tunable 3CT state for photosensitization. Following the above design principle, a new D–A fluorophore with strong D–A character and weak redox potential is identified, which exhibits high efficiency for Ni(II)-catalyzed cross-coupling of carboxylic acids and aryl halides with a wide substrate scope and high selectivity. Our results not only provide key fundamental insight on the EnT mechanism of D–A fluorophores but also establish its wide utility in EnT-mediated photocatalytic reactions

Spatial and temporal variations in crustal production at the Mid-Atlantic Ridge, 25°N–27°30′N and 0–27 Ma

Author Posting. © American Geophysical Union, 2015. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 120 (2015): 2119–2142, doi:10.1002/2014JB011501.We use high-resolution multibeam bathymetry, shipboard gravity, side-scan sonar images, and magnetic anomaly data collected on conjugate flanks of the Mid-Atlantic Ridge at 25°N–27°30′N and out to ~27 Ma crust to investigate the crustal evolution of the ridge. Substantial variations in crustal structure and thickness are observed both along and across isochrons. Along isochrons within spreading segments, there are distinct differences in seafloor morphology and gravity-derived crustal thickness between inside and outside corners. Inside corners are associated with shallow depths, thin crust, and enhanced normal faulting while outside corners have greater depths, thicker crust, and more limited faulting. Across-isochrons, systematic variations in crustal thickness are observed at two different timescales, one at ~2–3 Myr and another at >10 Myr, and these are attributed to temporal changes in melt supply at the ridge axis. The shorter-term variations mostly are in-phase between conjugate ridge flanks, although the actual crustal thickness can be significantly different on the two flanks at any given time. We observe no correlation between crustal thickness and spreading rate. Thus, during periods of low melt supply, tectonic extension must increase to accommodate the full plate separation rate. This extension commonly is concentrated in long-lived faults on only one side of the axial valley, resulting in strong across-axis asymmetries in crustal thickness and seafloor morphology. The thin-crust flank has few volcanic features and exhibits elevated, blocky topography with large-offset, often irregular faults, while the conjugate thicker-crust flank shows shorter-offset, regular faulting, and common volcanic features. The variations in melt supply at the ridge axis most likely are caused either by episodic convection in the subaxial mantle or by variable melting of chemically heterogeneous mantle.This study was funded by Chinese Natural Science Foundation grant 41206034 and Chinese Postdoc Scholarship award 2012M511130 (T.W.), by Ministry of Science and Technology 973 Project award 2012CB417303, and by the WHOI Henry Bryant Bigelow Chair (J.L.). ARSRP and MAREAST data acquisition was funded by Office of Naval Research grant N00014-90-J-6121 and by U.S. National Science Foundation grant OCE-9503561, respectively.2015-10-2