Structural studies of main group metal carboxylates and dithiocarbamates

The work contained in this thesis describes the crystal structures of a number of tin(IV) and tellurium(IV) carboxylates and dithiocarbamates. The results show the regularity at which these types of compounds form secondary bonds (weak interactions), and the effect of the lone pair of tellurium(IV) on the geometries formed. The area has been studied through the determination of the following crystal structures: i) monocarboxylates: Ph3SnOCOCH2Cl, Ph3SnOCOCHCh, Ph3SnOCOCCh.MeOH. Ph3SnOCOCCh and Ph3TeOCOCCh. ii) dicarboxulates : Ph2Sn(OCOCH3)2, Ph2Sn(OCOCH2CI)2 and Ph2Te(OCOCCI3)2 iii) dithiocarbamates : Ph2Te(S2CNEt2)2, Ph2Te(S2CN(Et)(Ph))2 and Ph2Te(S2CNPh2)2 In addition to these, six hydrolysis products of Ph3SnOCOCCh are reponed. These com- pounds show the varied results that are obtained from the facile dearylation of the organotin com- pound by a strong organic acid in the presence of water. The following structures are reported: Ph2 Sn(OH)(OCOCCh), {[Pb2Sn(OCOCCh)hOh (two isomers), [(PbSn))(Oh(OCOCCh)sh, [PhSn(O)(OCOCCh)]6 and [(Ph 2 Sn)2(OH)(OCOCCh)3h

Restructuring Failed Financial Firms in Bankruptcy: Selling Lehman\u27s Derivatives Portfolio

Lehman Brothers\u27 failure and bankruptcy deepened the 2008 financial crisis whose negative effect on the United States\u27 economy lasted for several years. Yet, while Congress reformed financial regulation in hopes of avoiding another crisis, bankruptcy rules such as those that governed Lehman\u27s failure, have persisted unchanged. When Lehman failed, it lost considerable further value when its contracting counterparties terminated their financial contracts with Lehman. These broad terminations degraded Lehman\u27s overall value to its creditors beyond the immediate losses that caused its downfall. Lehman\u27s financial portfolio was thought to be running a paper profit of over $20 billion when it filed, and is said to have lost up to$75 billion as a result of the post-filing liquidation by Lehman\u27s counterparties of their deals with Lehman. How such a vast value loss can occur and how bankruptcy can ameliorate the problem are the subjects of this Article

Restructuring Failed Financial Firms in Bankruptcy: Selling Lehman’s Derivatives Portfolio

Lehman Brothers’ failure and bankruptcy is widely thought to have deepened the 2008 financial crisis whose negative effects the real economy is still experiencing. Yet, while financial regulation has changed in hopes of avoiding another crisis, bankruptcy rules such as those that governed Lehman’s failure, have not been changed at all. When Lehman failed, it lost considerable further value when its contracting counterparties terminated their financial contracts with Lehman. Hit by broad termination, Lehman’s overall value to its creditors degraded beyond the immediate losses that caused its downfall, and then, along with AIG’s failure several days later, the broad termination involving Lehman further deeply disrupted financial markets in the United States, and indeed the world. Lehman’s financial portfolio was thought to be running a paper profit of over $20 billion when it filed, and is said to have lost up to$75 billion as a result of the post-filing liquidation by Lehman’s counterparties of their deals with Lehman. How such a vast shift can occur, whether bankruptcy can ameliorate the problem (yes), and whether bankruptcy law has been updated since the financial crisis to handle the problem (no) are the subjects of this paper. For bankruptcy to handle a systemically important financial institution successfully, it must market the institution’s financial contracts’ portfolio, which current bankruptcy law prevents. Moreover, regulatory and bankruptcy authorities need authority to sell the portfolio along product market lines, which they lack. Such authority is needed, first, to preserve its overall portfolio value, and, second, to break up and sell a very large portfolio that could not be sold intact in the aggregate, as the most systemically difficult portfolios are embedded in the world’s largest financial institutions and cannot readily be sold intact. Bankruptcy is the best and first place to put that authority. And, from a systemic perspective, bankruptcy needs to be able to dismantle a large failed portfolio, rather than sell it intact to a larger institution, a typical but undesirable solution here. Lastly, although regulatory and other conditions have changed since the financial crisis, making the bankruptcy target a moving one, the bankruptcy target deserves more consideration today, rather than less, because it is a reachable target without the complexities and uncertainties of new alternatives now in motion. Bankruptcy, however, has not been fixed and updated since the financial crisis, leaving the financial system at risk that, if a major financial institution failed and could not be otherwise resolved, the same difficulties would again arise as arose during the 2008-2009 crisis and the failures of Lehman and AIG

Large-effect flowering time mutations reveal conditionally adaptive paths through fitness landscapes in Arabidopsis thaliana.

Contrary to previous assumptions that most mutations are deleterious, there is increasing evidence for persistence of large-effect mutations in natural populations. A possible explanation for these observations is that mutant phenotypes and fitness may depend upon the specific environmental conditions to which a mutant is exposed. Here, we tested this hypothesis by growing large-effect flowering time mutants of Arabidopsis thaliana in multiple field sites and seasons to quantify their fitness effects in realistic natural conditions. By constructing environment-specific fitness landscapes based on flowering time and branching architecture, we observed that a subset of mutations increased fitness, but only in specific environments. These mutations increased fitness via different paths: through shifting flowering time, branching, or both. Branching was under stronger selection, but flowering time was more genetically variable, pointing to the importance of indirect selection on mutations through their pleiotropic effects on multiple phenotypes. Finally, mutations in hub genes with greater connectedness in their regulatory networks had greater effects on both phenotypes and fitness. Together, these findings indicate that large-effect mutations may persist in populations because they influence traits that are adaptive only under specific environmental conditions. Understanding their evolutionary dynamics therefore requires measuring their effects in multiple natural environments

Structure of an archaeal PCNA1-PCNA2-FEN1 complex: elucidating PCNA subunit and client enzyme specificity.

The archaeal/eukaryotic proliferating cell nuclear antigen (PCNA) toroidal clamp interacts with a host of DNA modifying enzymes, providing a stable anchorage and enhancing their respective processivities. Given the broad range of enzymes with which PCNA has been shown to interact, relatively little is known about the mode of assembly of functionally meaningful combinations of enzymes on the PCNA clamp. We have determined the X-ray crystal structure of the Sulfolobus solfataricus PCNA1-PCNA2 heterodimer, bound to a single copy of the flap endonuclease FEN1 at 2.9 A resolution. We demonstrate the specificity of interaction of the PCNA subunits to form the PCNA1-PCNA2-PCNA3 heterotrimer, as well as providing a rationale for the specific interaction of the C-terminal PIP-box motif of FEN1 for the PCNA1 subunit. The structure explains the specificity of the individual archaeal PCNA subunits for selected repair enzyme 'clients', and provides insights into the co-ordinated assembly of sequential enzymatic steps in PCNA-scaffolded DNA repair cascades

Synthesis of a thiazole library via an iridium-catalyzed sulfur ylide insertion reaction

A library of thiazoles and selenothiazoles were synthesized via Ir-catalyzed ylide insertion chemistry. This process is a functional group, particularly heterocycle-substituent tolerant. This was applied to the synthesis of fanetizole, an anti-inflammatory drug, and a thiazole-containing drug fragment that binds to the peptidyl-tRNA hydrolase (Pth) in Neisseria gonorrheae bacteria

The Multi-Object, Fiber-Fed Spectrographs for SDSS and the Baryon Oscillation Spectroscopic Survey

We present the design and performance of the multi-object fiber spectrographs for the Sloan Digital Sky Survey (SDSS) and their upgrade for the Baryon Oscillation Spectroscopic Survey (BOSS). Originally commissioned in Fall 1999 on the 2.5-m aperture Sloan Telescope at Apache Point Observatory, the spectrographs produced more than 1.5 million spectra for the SDSS and SDSS-II surveys, enabling a wide variety of Galactic and extra-galactic science including the first observation of baryon acoustic oscillations in 2005. The spectrographs were upgraded in 2009 and are currently in use for BOSS, the flagship survey of the third-generation SDSS-III project. BOSS will measure redshifts of 1.35 million massive galaxies to redshift 0.7 and Lyman-alpha absorption of 160,000 high redshift quasars over 10,000 square degrees of sky, making percent level measurements of the absolute cosmic distance scale of the Universe and placing tight constraints on the equation of state of dark energy. The twin multi-object fiber spectrographs utilize a simple optical layout with reflective collimators, gratings, all-refractive cameras, and state-of-the-art CCD detectors to produce hundreds of spectra simultaneously in two channels over a bandpass covering the near ultraviolet to the near infrared, with a resolving power R = \lambda/FWHM ~ 2000. Building on proven heritage, the spectrographs were upgraded for BOSS with volume-phase holographic gratings and modern CCD detectors, improving the peak throughput by nearly a factor of two, extending the bandpass to cover 360 < \lambda < 1000 nm, and increasing the number of fibers from 640 to 1000 per exposure. In this paper we describe the original SDSS spectrograph design and the upgrades implemented for BOSS, and document the predicted and measured performances.Comment: 43 pages, 42 figures, revised according to referee report and accepted by AJ. Provides background for the instrument responsible for SDSS and BOSS spectra. 4th in a series of survey technical papers released in Summer 2012, including arXiv:1207.7137 (DR9), arXiv:1207.7326 (Spectral Classification), and arXiv:1208.0022 (BOSS Overview

US Cosmic Visions: New Ideas in Dark Matter 2017: Community Report

This white paper summarizes the workshop "U.S. Cosmic Visions: New Ideas in Dark Matter" held at University of Maryland on March 23-25, 2017.Comment: 102 pages + reference