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61.
Larry R. Dalton Aaron W. Harper Shajing Sun William H. Steier Robert V. Mustacich Alex K-Y. Jen 《Macromolecular Symposia》1997,116(1):135-142
The synthesis and processing of second order nonlinear optical polymeric materials for application in electro-optic devices is described with particular emphasis on (1) the synthesis and incorporation into hardened polymer lattices of chromophores characterized by large μβ (where μ is the dipole moment and β is the molecular first hyperpolarizability) values; (2) the synthesis and incorporation into hardened polymer lattices of chromophores which are capable of undergoing photo-induced conformational changes and which can be processed by new multi-color photolithography techniques into buried channel active waveguides; and (3) the processing of polymeric nonlinear optical materials appropriate for the realization of full integration with very large scale integration (VLSI) drive electronics and with silica fiber optic transmission lines. Prototype modulators have been fabricated and shown to be suitable for broadband operation from 0 to 113 GHz. Optical losses associated with waveguide wall roughness and with mode mismatch in transitioning between silica and polymeric waveguides are reduced by control of the conditions of reactive ion etching and by use of the new technique of multi-color photochemical lithography. 相似文献
62.
Stephen D. Williams Warren Harper Gleb Mamantov Louis J. Tortorelli George Shankle 《Journal of computational chemistry》1996,17(15):1696-1711
Molecular geometries were fully optimized for AlCl3, AlCl4-, Al2Cl6, Al2Cl7-, AlF3, AlF4-, Al2F6, Al2F7-, BCl3, BCl4-, B2Cl6, B2Cl7-, BF3, BF4-, B2F6, and B2F7-, as well as a few mixed halogen species, at the Hartree-Fock (HF) level, using basis sets from STO-3G to 6–311 + G(d). In some cases geometries were also optimized at the MP2 level. Where possible, the computed geometries were compared to known structures from electron or X-ray diffraction. The agreement between these was quite good for the neutral species, and somewhat poorer for the anions. Vibrational frequencies were calculated for all species at the HF level with the largest basis set. The geometries were characterized as minima or transition structures. Various formation reaction enthalpies were calculated; these compare well with known values. More extensive calculations on the BF3/BF4- system indicate the structures and enthalpies are nearly converged with respect to basis set size and level of correlation treatment. The previously unknown species B2Cl7- is predicted to be energetically stable on the basis of the calculations. Some features of the 11B NMR spectra of room temperature melts consisting of mixtures of boron trichloride with 1-methyl-3-ethylimidazolium chloride are presented. These features suggest that these melts may contain small amounts of B2Cl7- as an intermediate in an exchange reaction. © 1996 by John Wiley & Sons, Inc. 相似文献
63.
V. Vijayasundaram V. Ramasamy PL. RM. Palaniappan 《Journal of Thermal Analysis and Calorimetry》2009,98(1):183-188
The paper presents the changes in the thermal properties of control, arsenic exposed and DMSA treated Labeo rohita bones by using thermo analytical techniques. The result shows that the mass loss due to the thermal decomposition occurs
in three distinct steps due to loss of water, organic and inorganic materials. The arsenic exposed bones present a different
thermal behaviour compared to the control bones. The residue masses are increased due to arsenic exposure, while the DMSA
treatment reduces the residue mass level. These thermal characteristics can be used as a qualitative method to check the metal
accumulation in samples. 相似文献
64.
Zen Harper 《Complex Analysis and Operator Theory》2009,3(1):113-146
We ask when convolution operators with scalar- or operator-valued kernel functions map between weighted L2 spaces of Hilbert space-valued functions. For a certain class of decreasing weights, including negative powers (t + a)−m for example, we solve the one-weight problem completely by using Laplace transforms and Bergman-type spaces of vector-valued
analytic functions. For a much more general class of decreasing weights, we solve the one-weight problem for all positive
real kernels (also for Lp(w) with p > 1), by results on Steklov operators which generalise the weighted Hardy inequality. When the kernel function is a strongly
continuous semigroup of bounded linear Hilbert space operators, which arises from input–output maps of certain linear systems,
then the most obvious sufficient condition for boundedness, obtained by taking norm signs inside the integrals, is also necessary
in many cases, but not in general.
Submitted: July 15, 2007.,Revised: November 19, 2007.,Accepted: December 14, 2007. 相似文献
65.
Harper JK Grant DM Zhang Y Lee PL Von Dreele R 《Journal of the American Chemical Society》2006,128(5):1547-1552
Synchrotron X-ray powder diffraction and solid-state (13)C NMR shift tensor data are combined to provide a unique path to structure in microcrystalline organic solids. Analysis is demonstrated on ambuic acid powder, a widely occurring natural product, to provide the complete crystal structure. The NMR data verify phase purity, specify one molecule per asymmetric unit, and provide an initial structural model including relative stereochemistry and molecular conformation. A refinement of X-ray data from the initial model establishes that ambuic acid crystallizes in the P2(1) space group with unit cell parameters a = 15.5047(7), b = 4.3904(2), and c = 14.1933(4) A and beta = 110.3134(3) degrees . This combined analysis yields structural improvements at two dihedral angles over prior NMR predictions with differences of 103 degrees and 37 degrees found. Only minor differences of +/-5.5 degrees , on average, are observed at all remaining dihedral angles. Predicted hydroxyl hydrogen-bonding orientations also fit NMR predictions within +/-6.9 degrees . This refinement corrects chemical shift assignments at two carbons and reduces the NMR error by approximately 16%. This work demonstrates that the combination of long-range order information from synchrotron powder diffraction data together with the accurate shorter range structure given by solid-state NMR measurements is a powerful tool for studying challenging organic solids. 相似文献
66.
Ng CC Magenau A Ngalim SH Ciampi S Chockalingham M Harper JB Gaus K Gooding JJ 《Angewandte Chemie (International ed. in English)》2012,51(31):7706-7710
Smart surfaces presenting both antifouling molecules with a charged functional group at their distal end, and molecules that are terminated by RGD peptides for cell adhesion, were fabricated and characterized (see picture). By applying potentials of +300 or -300?mV, the surfaces could be dynamically switched to make the peptide accessible or inaccessible to cells. 相似文献
67.
68.
Sandilya Garimella Wei Xu Guangming Huang Jason D. Harper R Graham Cooks Zheng Ouyang 《Journal of mass spectrometry : JMS》2012,47(2):201-207
Methods and devices that use gas flows to collect ions and transfer them over long distances for mass spectrometric analysis have been developed. Gas flows derived from the ionization source itself or provided by means of additional pumping were used to generate a laminar flow inside cylindrical tube. Hydrodynamic simulations and experimental tests demonstrate that laminar flow can transfer ions over long distance. The typical angular discrimination effects encountered when sampling ions from ambient ionization sources are minimized, and the sampling of relatively large surface areas is demonstrated with desorption electrospray ionization (DESI). Ion transfer over 6 m has been achieved and its application to multiplexed chemical analysis is demonstrated on samples at locations remote from the mass spectrometer. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
69.
James K. Harper Atta M. Arif David M. Grant 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(4):451-452
cis‐Verbenol (alternative name: 4,6,6‐trimethylbicyclo[3.1.1]hept‐3‐en‐2‐ol), C10H16O, forms an orthorhombic P212121 crystal that contains three molecules per asymmetric unit. These three molecules form hydrogen‐bonded helices parallel to the shortest axis of the lattice. The O?O distances associated with the hydrogen bonds are 2.760 (3), 2.760 (3) and 2.766 (3) Å. 相似文献
70.
Ian Teasdale Elizabeth C. Harper Paolo Coppo Brian Wilson Michael L. Turner 《Macromolecular rapid communications》2006,27(23):2032-2037
Summary: Macrocyclic phenyl ether ketones were prepared via pseudo high dilution condensation. Irradiation of these rings with UV light in a solution containing isopropyl alcohol as hydrogen donor resulted in a photo‐induced reduction of benzophenone to benzopinacol and the formation linked macrocycles. These rings can be heated to undergo ring‐opening polymerization and produce a polymer network or they can be added to a polycondensation reaction to prepare poly(ether ether ketones) with variable degrees of cross‐linking.