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Caltech Authors (82.798 recursos)
Repository of works by Caltech published authors.

Type = Conference or Workshop Item

Mostrando recursos 1 - 20 de 293

1. Check us out: Librarians as departmental PR agents - Wrublewski, Donna; Leonard, Michelle
In these days of competition and rankings, every department is vying for the best graduate students. The Chem. department at the University of Florida has been taking steps to increase its web presence and advertise the research of its graduate department. This talk will discuss the role of the science librarian as advisor to this process, including compiling publication lists, negotiating publication restrictions to provide access to published research, and streamlining the collection and dissemination of department achievements. At UF, a local implementation of the VIVO Network, which enables the discovery of research and scholarship across disciplines, is being implemented to achieve these goals. The Marston...

2. Caltech: Using our IR with Campus Research Groups - Painter, Joy; Porter, George
We have expanded the IR into a service that meets the needs of groups and centers on campus. As research dollars become scarce, research support often comes with a requirement to demonstrate a return on investment (ROI). The IR can help groups and centers meet this requirement by assisting with publications lists.

3. On the fly collection development to support emergent energy research initiatives - Wrublewski, Donna T.; Porter, George S.; Roth, Dana L.
Within the last few years, two major energy research initiatives have been undertaken on the Caltech campus: the Resnick Sustainability Institute (RSI) and the Joint Center for Artifical Photosynthesis (JCAP). RSI's research includes the production of electricity and fuels from renewable sources, the distribution and storage of energy, and other sustainability projects. JCAP's area of research is focused on achieving a system of artificial photosynthesis for utilizing solar energy. Both of these projects require resources from a broad range of fields, including chemistry, physics, biology, environmental &systems engineering, and more. This talk will give a brief description of some of...

4. Equilibrium, Equilibration, Information and Multiple Markets: From Basic Science to Institutional Design - Plott, Charles R.
[Introduction] Prices exhibit subtle coordination features among multiple markets, reflecting opportunity costs and fostering specialization throughout the economy. Furthermore, it is widely believed that prices can adjust rapidly, and possibly almost immediately while carrying information about worldly events from insiders to non-insiders who can use it. By receiving the information contained in prices the otherwise uninformed can adjust to those events. Not only do prices appropriately reflect opportunity cost within properly supportive institutions, they carry all available, relevant information known throughout the economy.

5. Design and synthesis of oligoamide-based double α-helix mimetics - Kulikov, Oleg V.; Thompson, Sam; Xu, Hai; Incarvito, Christopher D.; Scott, Richard T.; Saraogi, Ishu; Nevola, Laura; Hamilton, Andrew D.
An extensive series of bis-oligobenzamides and bisoligopyridylamides were efficiently prepd. and studied by X-ray anal. and computation. A modular synthesis gave double α-helix mimics bearing between two and ten branched side-chains. The inter-helix angle and distance can be tuned by varying the length and rigidity of spacer, thus reproducing the recognition domains of a range of super-secondary structures.

6. Composition and chemical history of early solar system ices - Boogert, Adwin
Some models of protostellar collapse [1] indicate that all but the most volatile ices from the native envelope survive the infall phase, at least at larger disk radii (10 AU). The compn. and chem. history of ices in circumstellar envelopes, and sometimes in disks, can be traced with IR (2-30 μ) spectroscopy using ground and space based telescopes. Surveys of large samples of Young Stellar Objects (YSOs) [2,3,4] and quiescent clouds [5,6] have shown that the ice abundances and band profiles vary considerably as a function of environment. A rather complex mixt. of simple species (CH3OH, CO2, H2O, NH3, CO) exists even before stars form,...

7. Discoveries and diversions in natural product synthesis - Reisman, Sarah E.
Our lab. seeks to discover, develop, and study new chem. reactions within the context of natural product total synthesis. The chem. synthesis of natural products enables the study of their biol. properties, and can provide access to synthetic derivs. with improved therapeutic properties or that can serve as mechanistic probes. Importantly, these synthetic undertakings often highlight shortcomings of the existing state-of-the-art and inspire the discovery of new chem. Our lab. has ongoing research programs targeting the chem. syntheses of several natural products, including members of the epidithiodiketopiperazines, the ent-kauranoids, and the acutumine alkaloids. The densely packed arrays of heteroatoms and stereogenic centers that constitute these polycyclic targets...

8. Innovative synthetic rubbers via ruthenium catalyst systems - Tuba, Robert; Grubbs, Robert H.
The trans-polypentenamer has unique relevance among the synthetic rubbers since it has similar phys. properties to the natural rubber. The polypentenamer additives have propitious effect on the tire properties and have been studied extensively for this application. Polypentenamer synthetic rubber was synthesized by ringopening metathesis polymn. (ROMP) using ruthenium catalyst systems. It was found that the cyclopentene conversion does not depend on the catalyst activity and catalyst loading. However the applied reaction temp. has a significant impact on the polymn. yield. Equil. of growing chain and monomer was obsd. and the thermodn. parameters were detd. as: ΔH = - 5.6 kcal · mol^(-1); ΔS = -18.5...

9. Molecular Pumps that drives a system away from equilibrium - Cheng, Chuyang; Li, Hao; Liu, Weiguang; McGonigal, Paul R.; Vermeulen, Nicolaas; Frasconi, Marco; Ke, Chenfeng; Goddard, William A.; Stoddart, J. F.
A pressing goal for contemporary science is to build artificial mol. systems that can perform useful work. Here we report a 'mol. pump' system that processes chem. energy (redox) to drive a macrocycle away from equil., from a low energy to a high energy state. A series of mol. rods were synthesized contg. 3,5- dimethylpyridinium (Py +) and 4,4'-bipyridinium (BIPY 2+) units connected to a bulky steric stopper by chains of different lengths. Cyclobis(paraquat-p-phenylene) (CBPQT 4+) is repelled by the Py + and BIPY 2+ initially; however, upon redn. with activated zinc dust, Coulombic repulsion between Py + and CBPQT 2(+•) dramatically decreases and a thermodynamically...

10. EPR study of nitroxide-labeled brush polymers - Li, Yongjun; Johnson, Jeremiah A.; Xia, Yan; Ottaviani, Francesca; Grubbs, Robert H.; Turro, Nicholas J.
Bottle-brush polymers are highly branched polymers, which possess a high d. of polymer side chains uniformly grafted to the backbone of a linear polymer. Functional groups can be attached to different domains of the bottle-brush polymers for potential applications that range from nanomedicine to mol. electronics. We are interested in how the locations that the functional groups are placed in bottle-brush polymers affect their reactivities and interactions with surrounding environment. The results of the study will impact further development of bottle-brush materials as nanoscaffolds for biol. applications.We synthesized bottle-brush polymers with nitroxide probes covalently attached to variable locations of the polymers: backbone middle, backbone end and...

11. Spectroscopy and astrochemistry with Herschel - Lis, Dariusz C.
Herschel provided extraordinary spectroscopic opportunities in the 55-670 μm wavelength range. Unbiased spectral line surveys have been carried out, in a sample of representative sources, providing a complete mol. inventory of star-forming regions. Interstellar hydrides, the basic building blocks of astrochem., which have their fundamental rotational transitions in the submillimeter, have been studied in absorption against background dust continuum sources. I review Herschel astrochem. highlights, demonstrating the outstanding spectroscopic capabilities of this facility, which have led to detections of new mols. and have provided new constraints for astrophys. and astrochem. models. The talk covers a range of interstellar environments, from diffuse to dense clouds in the Milky...

12. Elements of research misconduct - Wrublewski, Donna; Leonard, Michelle
What do scientists, educators, librarians, and game designers all have in common. In the fall of 2010, this team at the University of Florida was awarded a grant from the NSF to support Gaming Against Plagiarism (GAP). The purpose is to develop a self-directed, interactive, online game to educate STEM graduate students to recognize and avoid plagiarism, including falsification and fabrication of data. GAP's intellectual merit lies in its goal of training these students in U.S. institutions to function effectively and ethically as authors within multinational research teams. This talk will discuss the four phases of the game: preliminary content development, design and development, usability, and...

13. Engineering Cytochrome P450 for Cyclopropanation - Wang, Z. Jane
The ability to genetically encode catalysts for non-natural chemical reactions will open new routes to sustainable production of chemicals. In nature, cytochome P450 catalyzes the oxidation of organic substrates with oxygen to produce epoxides and alcohols. This transformation proceeds through an iron-oxene complex (Compound I), which is generated in the presence of NAD(P)H and molecular oxygen. Inspired by this catalytic cycle, we hypothesized that a similar process could be used to generate an iron-carbenoid specie from diazo compounds that could enable olefin cyclopropanation. Toward this end, we have been able to evolve a unique serine-heme ligated cytochrome “P411” that catalyzes formal carbene transfers from diazoesters to olefins...

14. Natural Product Synthesis: A Platform for Chemical Discovery - Reisman, Sarah E.
Our laboratory has ongoing research programs targeting the chemical syntheses of several natural products, including members of the epidithiodiketopiperazines, the ent-kauranoids, and the acutumine alkaloids. The densely packed arrays of heteroatoms and stereogenic centers that constitute these polycyclic targets challenge the limits of current synthetic methodology. This seminar will describe our latest progress in both our methodological and target-directed synthesis endeavors.

15. High resolution profiling of sulfur and oxygen speciation in microbial mats: Implications for coupling of hydrogen peroxide with sulfur species - Druschel, Greg K.; Kafantaris, Fotios; Orphan, Victoria J.; Houghton, Jennifer; Fike, David A.
Hydrogen sulfide is produced in microbial mats by sulfate reducing bacteria, and diffuses towards the surface until it is consumed. Cyanobacteria in these mats are able to produce oxygen photochem., and when subjected to high UV light intensity, can also produce hydrogen peroxide. Microelectrodes have proven to have sufficient resoln. to resolve the sulfur and oxygen chem. in these mats, demonstrating the links between these populations of bacteria in modern mats. In sulfur-dominated cyanobacterial mats in several settings, we have obsd. both high hydrogen sulfide fluxes and the periodic prodn. of significant amts. of hydrogen peroxide at times of high UV stress using voltammetric Au-amalgam microelectrodes....

16. Exploring Co(salen) type complexes for use as CO2 reduction catalysts - Hansen, Michelle C.; Kubiak, Clifford P.; Yang, Jenny Y.
Cobalt salen and salophen complexes and their derivs. have been previously studied in many contexts, including CO_2 binding and redn. to a limited extent. This project studies CO_2 redn. in depth with a breadth of salen-type ligands and use of glassy carbon working electrodes instead of the previously studied mercury electrodes. Trends relating redn. potential as well as activity and selectivity to ligand structure will be presented.

17. Development of CO2-reducing electrocatalysts utilizing non-precious metals supported by pincer ligand scaffolds - Shaffer, David W.; Yang, Jenny Y.
The electrocatalytic redn. of carbon dioxide to form usable fuels such as formate, methanol, or higher-order hydrocarbons is an ideal method for alternative energy storage. Compared to heterogenous systems, mol. catalysts are generally more selective, more easily tuned, and allow for detailed mechanistic studies. However, a catalyst remains to be found which is highly stable, utilizes an earth-abundant metal, and operates at a low overpotential with a high rate. Late transition metal complexes supported by pincer ligands have been shown to promote CO_2 insertion into metal-hydride bonds and catalytic CO_2 hydrogenation. Furthermore, efficient and selective electrochem. redn. of CO_2 to formate has been achieved with a...

18. Preparation of rapidly initiating ruthenium based olefin metathesis catalysts - Sullivan, Alexandra H.; Keitz, Benjamin K.; Grubbs, Robert H.
Z-selective olefin metathesis ruthenium catalysts are highly sought after, due to their wide applications in both pharmaceuticals and materials science. A crucial step towards the prepn. of rapidly initiating, Z-selective, olefin metathesis catalysts was found to be the addn. of sodium pivalate to phosphonium alkyidene catalyst 1, resulting in the formation of the C-H activated complex 2 after two days of heating. Prepn. of 2, a close analog to the target catalyst 4, promises that future synthesis of 4 should be facile.

19. Thermodynamics of guest-host interaction in TMAAI-ordered porous silica system - Wu, Di; Hwang, Sonjong; Zones, Stacey I.; Navrotsky, Alexandra
Mol. level guest-host interactions in inorg. frameworks play crucial roles in many scientific/engineering applications, ranging from drug delivery and geol. mineral pptn. in the presence of org. matter. In order to seek insights into detailed chem. of guest-host interactions, we investigated the phase evolution and energetics of confinement of a rigid org. guest TMAAI (N,N,N-trimethyl-1-adamantammonium iodide) in inorg. porous silica with various pore sizes (0.8 nm to 20.0 nm). HF calorimetry was employed to measure the enthalpies of guest-host interaction. The values vary from -56 to -175 kJ/mol of TMAAI. Phase evolution inside the nanopores was investigated by X-ray diffraction, IR, TG-DSC and solid-state NMR. The...

20. Symmetry breaking charge transfer processes of zinc dipyrrin complexes - Trinh, Cong; Kirlikovali, Kent; Das, Saptaparna; Bradforth, Stephen E.; Ener, Maraia E.; Gray, Harry B.; Djurovich, Peter I.; Thompson, Mark E.
Photoinduced charge transfer (CT) via symmetry breaking (SB) processes plays a crucial role in photosynthetic reaction center of biol. systems. In such systems, which contain two or more identical and sym. chromophores, CT process from one to another chromophore occurs upon photo-excitation, thus breaking the symmetry. It is of great interest to apply SBCT processes in org. photovoltaics (OPV) and related systems. For application to OPVs, it is desirable for compds. that undergo SB processes to have absorption in the visible spectrum. The most well-documented compds. for SB phenomenon, such as bianthryl derivs., do not absorb visible light. Herein we present study on Zinc Dipyrrin complexes,...

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