Publications

Although reticular chemistry has commonly utilized mutually embracing tetrahedral metal complexes as crossing points to generate three-dimensional molecularly woven structures, weaving in two dimensions remains largely unexplored. We report a new strategy to access 2D woven COFs by controlling the angle of the usually linear linker, resulting in the successful synthesis of a 2D woven pattern based on chain-link fence. The synthesis was accomplished by linking aldehyde-functionalized copper(I) bisphenanthroline complexes with bent 4,4'-oxydianiline building units. This results in the formation of a crystalline solid, termed COF-523-Cu, whose structure was characterized by spectroscopic techniques and electron and X-ray diffraction techniques to reveal a molecularly woven, twofold-interpenetrated chain-link fence. The present work significantly advances the concept of molecular weaving and its practice in the design of complex chemical structures.

The borrelidin polyketide synthase (PKS) begins with a carboxylated substrate and, unlike typical decarboxylative loading PKSs, retains the carboxy group in the final product. The specificity and tolerance of incorporation of carboxyacyl substrate into type I PKSs have not been explored. Here, we show that the first extension module is promiscuous in its ability to extend both carboxyacyl and non-carboxyacyl substrates. However, the loading module has a requirement for substrates containing a carboxy moiety, which are not decarboxylated in situ. Thus, the loading module is the basis for the observed specific incorporation of carboxylated starter units by the borelidin PKS.

We appreciate the comments by Dole et al. (2016), and we also appreciate their having shared these views with some of us (Richards, Renne, Sprain, and Vanderkluysen) on a joint field trip in January 2016. We agree with some of the issues raised in the comment, but these points do not undermine our basic conclusion that the stratigraphic transition from the Lonavala Subgroup to the Wai Subgroup within the Deccan Traps represents a fundamental change in the character of Deccan volcanism, and that this change was approximately coincident with the Cretaceous-Paleogene boundary. In fact, the geomorphic features in question are now understood to be a likely consequence of this fundamental change.

Ionic liquids (ILs) are emerging as superior solvents for numerous industrial applications, including the pretreatment of biomass for the microbial production of biofuels. However, some of the most effective ILs used to solubilize cellulose inhibit microbial growth, decreasing efficiency in the overall process. Here we identify an IL-resistance mechanism consisting of two adjacent genes from Enterobacter lignolyticus, a rain forest soil bacterium that is tolerant to an imidazolium-based IL. These genes retain their full functionality when transferred to an Escherichia coli biofuel host, with IL resistance established by an inner membrane transporter, regulated by an IL-inducible repressor. Expression of the transporter is dynamically adjusted in direct response to IL, enabling growth and biofuel production at levels of IL that are toxic to native strains. This natural auto-regulatory system provides the basis for engineering IL-tolerant microbes, which should accelerate progress towards effective conversion of lignocellulosic biomass to fuels and renewable chemicals.

This study examines the association between scope of Quality Improvement (QI) implementation in hospitals and hospital performance on patient safety indicators. Secondary data sources included a 1997 survey of hospital QI practices, Medicare Inpatient Database, American Hospital Association's Annual Survey of Hospitals, the Bureau of Health Professions'Area Resource File, and two proprietary data sets. Using a sample of 1,784 community hospitals, the study employed two-stage instrumental variables estimation in which predicted values of four QI scope variables and control variables were used to estimate four patient safety indicators. Involvement by multiple hospital units in the QI effort is associated with worse values on all four patient safety indicators. Percentages of hospital staff and of senior managers participating in QI teams exhibited no statistically significant association with any patient safety indicator. Percentage of physicians participating in QI teams is associated with better values on two patient safety indicators.

We present on an optical antenna based nanoLED that is fabricated directly on top of an InP waveguide. Waveguide coupling efficiency of 70% and directional emission is achieved with a Yagi-Uda antenna structure. By using an epitaxial lift-off process, we show that this device could be integrated directly onto a Silicon-photonics substrate.