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Significant Structural Differences (significant + structural_difference)

Distribution by Scientific Domains

Chemistry	66%
Business, Economics, Finance and Accounting	33%

Selected Abstracts

Rational Design, Synthesis, and Optical Properties of Film-Forming, Near-Infrared Absorbing, and Fluorescent Chromophores with Multidonors and Large Heterocyclic Acceptors

CHEMISTRY - A EUROPEAN JOURNAL, Issue 35 2009
Min Luo
Abstract A new series of film-forming, low-bandgap chromophores (1,a,b and 2,a,b) were rationally designed with aid of a computational study, and then synthesized and characterized. To realize absorption and emission above the 1000,nm wavelength, the molecular design focuses on lowering the LUMO level by fusing common heterocyclic units into a large conjugated core that acts an electron acceptor and increasing the charge transfer by attaching the multiple electron-donating groups at the appropriate positions of the acceptor core. The chromophores have bandgap levels of 1.27,0.71,eV, and accordingly absorb at 746,1003,nm and emit at 1035,1290,nm in solution. By design, the relatively high molecular weight (up to 2400,g,mol,1) and non-coplanar structure allow these near-infrared (NIR) chromophores to be readily spin-coated as uniform thin films and doped with other organic semiconductors for potential device applications. Doping with [6,6]-phenyl-C61 butyric acid methyl ester leads to a red shift in the absorption only for 1,a and 2,a. An interesting NIR electrochromism was found for 2,a, with absorption being turned on at 1034,nm when electrochemically switched (at 1000,mV) from its neutral state to a radical cation state. Furthermore, a large Stokes shift (256,318,nm) is also unique for this multidonor,acceptor type of chromophore, indicating a significant structural difference between the ground state and the excited state. Photoluminescence of the film of 2,a was further probed at variable temperatures and the results strongly suggest that the restriction of bond rotations certainly helps to diminish non-radiative decay and thus enhance the luminescence of these large chromophores. [source]

Comparing Mutual Fund Governance and Corporate Governance

CORPORATE GOVERNANCE, Issue 5 2006
Robert F. Radin
Governance of public corporations in the United States has operated under the agency model with regulatory strengthening since the passage of Sarbanes-Oxley legislation. With this foundation in place, boards are empowered to utilise their power and influence and can effectively monitor the actions of management, intervening where necessary. In effect, the rules of engagement embodied in the structure and the law guide interactions and empowerment. The governance model of the mutual funds industry, representing over 8 trillion dollars, is often viewed as a mirror of the corporate world, but upon closer analysis is found to have significant structural differences that dilute the authority of directors. The two models are compared and analysed with recommendations made to strengthen the oversight of mutual funds. [source]

Towards Cationic Gallium Derivatives: Metallacycles from the Reactions of Organogallium Compounds with Tetraorganodichalcogenoimidodiphosphinates and a New N -(Diphenylthiophosphinyl)thioureato Ligand

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2004
Virginia Montiel-Palma
Abstract The organometallic complexes of general formulae [Me2Ga{,2 - E,E, -[R2P(E)NP(E,)R,2]}] [R = R, = Ph, E = E, = O (1); R = R, = Ph, E = E, = S (2); R = R, = Ph, E = E, = Se (3); R = R, = Ph, E = O, E, = S (4); R = Me, R, = Ph, E = S, E, = O (5)] and [Me2Ga{,2 - S,S, -[Ph2P(S)NC(S)(C9H10N)]}] (6) were obtained by facile methane elimination reactions from GaMe3 and the acidic ligands L1H [(XPPh2)2NH (X = O, S, Se), (OPPh2)(SPPh2)NH, and (OPMe2)(SPPh2)NH] and L2H [Ph2P(S)NHC(S)(C9H10N)] in toluene. Replacement of one phosphorus atom by a carbon atom in the ligand skeleton of L1H gave the new ligand L2H, which, upon reaction with GaMe3, gave compound 6, which shows no significant structural differences with respect to 1,5. Therefore, L2H does not induce partial planarity in the six-membered ring, indicating the necessity for replacing both phosphorus atoms of the ligand by carbon atoms, as in the ,-diketonate-type derivatives, in order to impose ring planarity. Thus, despite originating from a variety of ligands with differing donor atoms and substituents at the phosphorus atoms, all complexes show little structural differences. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Agricultural exports and economic growth in less developed countries

AGRICULTURAL ECONOMICS, Issue 2 2005
P. J. Dawson
Agricultural exports; Economic growth; LDCs; Panel data Abstract This article examines the contribution of agricultural exports to economic growth in less developed countries (LDCs). A sources-of-growth equation is developed from a dual economy model where agricultural and nonagricultural sectors are both divided into export and nonexport subsectors. This is then estimated using panel data for 62 LDCs for 1974,1995. Results provide evidence that there are significant structural differences in economic growth between low, lower-middle, and upper-income LDCs. Investment in the agricultural export subsector has a statistically identical impact on economic growth as investment in the nonagricultural export subsector. The marginal productivities in nonexport subsectors are over 30% lower than those in respective export subsectors. From a policy perspective, the results suggest that export-promotion policies should be balanced. [source]

The crystal structure of augmenter of liver regeneration: A mammalian FAD-dependent sulfhydryl oxidase

PROTEIN SCIENCE, Issue 5 2003
Chia-Kuei Wu
Abstract The crystal structure of recombinant rat augmenter of liver regeneration (ALRp) has been determined to 1.8 Å. The protein is a homodimer, stabilized by extensive noncovalent interactions and a network of hydrogen bonds, and possesses a noncovalently bound FAD in a motif previously found only in the related protein ERV2p. ALRp functions in vitro as a disulfide oxidase using dithiothreitol as reductant. Reduction of the flavin by DTT occurs under aerobic conditions resulting in a spectrum characteristic of a neutral semiquinone. This semiquinone is stable and is only fully reduced by addition of dithionite. Mutation of either of two cysteine residues that are located adjacent to the FAD results in inactivation of the oxidase activity. A comparison of ALRp with ERV2p is made that reveals a number of significant structural differences, which are related to the in vivo functions of these two proteins. Possible physiological roles of ALR are examined and a hypothesis that it may serve multiple roles is proposed. [source]

Tris(tert -butyl isocyanide)bis[tris(4-methoxyphenyl)phosphine]cobalt(I) perchlorate dichloromethane disolvate and tris(tert -butyl isocyanide)bis[tris(4-methoxyphenyl)phosphine]cobalt(II) bis(perchlorate) dichloromethane disolvate: modification of a trigonal,bipyramidal structure with change of metal oxidation state

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 2 2010
Clifford A. L. Becker
The title complexes, [Co(C5H9N)3(C21H21O3P)2]ClO4·2CH2Cl2, (I), and [Co(C5H9N)3(C21H21O3P)2](ClO4)2·2CH2Cl2, (II), respectively, crystallize in the hexagonal space group P63/m and the monoclinic space group P21/n, respectively. The cation of complex (I) has D3h site symmetry around the Co atom and the overall symmetry is C3h. Complex (II) is best described as having a distorted trigonal,bipyramidal coordination, with a Co site symmetry of Cs. Compounds (I) and (II) form an analogous pair of five-coordinate CoI and CoII complexes with the same ligands, making it possible to establish (i) if the Co site coordination for both complexes is indeed trigonal,bipyramidal, as initially assumed, and (ii) if significant structural differences occur when the oxidation state of the metal is changed. [source]