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1.
Susan Baker Lisa Kelchner Barbara Weinrich Linda Lee Paul Willging Robin Cotton Karen Zur 《Journal of voice》2006,20(4):631-641
Laryngotracheal stenosis is defined as a congenital or acquired narrowing of the airway. Congenital causes may include subglottic membranous or cartilaginous narrowing. Acquired causes may include trauma due to prolonged endotracheal or tracheal intubation or laryngotracheal injury. Although advances have been made over the past 30 years in reconstructive surgeries to improve airway patency in these patients, long-term laryngeal function for voice production is not well defined in this population. This review examines causes, symptoms and signs, and methods for diagnosing laryngotracheal stenosis. Surgical management procedures are briefly summarized. The current literature on voice outcomes is summarized. The predominant voice characteristics in the population are presented, although results are challenged by the heterogeneity of voice presentation and paucity of data from instrumental measures. Considerations for subjective and instrumental assessment, measures of quality of life, instrumental methods, and treatment options specific to the needs of this population are discussed. Research strategies to identify long-term outcomes of surgical and behavioral treatments in this population are posed. 相似文献
2.
Benjamin J. K. Evans Susan M. Scott Antony C. Searle 《General Relativity and Gravitation》2002,34(10):1675-1684
We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time. 相似文献
3.
Mark Doyle Susan A. Mulligan Tetsuya Matsuda Gerald M. Pohost 《Magnetic resonance imaging》1992,10(6):887-892
A new “bright blood” strategy, outflow refreshment imaging, is introduced in which a number of overlapping slices are excited in rapid succession. Flowing spins that refresh each overlapped slice portion contribute a bright signal. Additionally, static tissue in each non-overlapped slice portion also yields a bright signal. However, the flow/static contrast is comparable to that produced in inflow refreshment images, and angiograms can be generated by conventional maximum intensity projection processing. The dual ability to visualize angiograms and static tissue images is a major benefit of the strategy. Computer simulations of flow sensitivities and in vivo results are presented which compare the outflow and inflow refreshment imaging strategies. 相似文献
4.
This paper presents an analysis of a portfolio model which can be used to assist a property-liability insurance company in determining the optimal composition of the insurance and investment portfolios. By introducing insurer's threshold risk and relaxing some non-realistic assumptions made in traditional chance constraint insurance and investment portfolio models, we propose a method for an insurer to maximize his return threshold for a given threshold risk level. This proposed model can be used to optimize the composition of underwriting and investment portfolios regarding the insurer's threshold risk level, as well as to generate the efficient frontier by adjusting insurer's threshold risk levels. A numerical example is given based on the industry's aggregated data for a sixteen year period. 相似文献
5.
6.
The metal complexes [Os(byp)(2)(pic)](+) and [Ru(byp)(2)(pic)](+) where byp is 2,2'-bipyridine and HPic is o-picolinic acid were synthesised and characterised using spectroscopic and electrochemical techniques. These complexes were then evaluated as mediators for a glucose oxidase (GOx)-based biosensor. Results demonstrate the electrocatalytic behaviour of both metal couples towards regeneration of the flavoprotein GOx (FADH(2)) group, when co-immobilised with glucose oxidase. Surface immobilisation was achieved by potential cycling in aqueous solutions of the metal complexes at a glucose oxidase (GOx)/Nafion modified electrode. This proved successful in terms of catalytic efficiency and stability of redox sites. Kinetic parameters associated with both enzymatic and mediator reactions were estimated and the stability/performance properties of the sensor were tested. 相似文献
7.
Mixtures of [Ph(3)PNPPh(3)](+)Cl(-) with CuBr(2) (or CuBr(2)+CuCl(2)) in ethanol/dichloromethane yield crystals containing three-coordinate copper(II) with mixed chloride and bromide ligands, namely [Ph(3)PNPPh(3)](+)[CuCl(0.9)Br(2.1)](-) (1) and [Ph(3)PNPPh(3)](+)[CuCl(2.4)Br(0.6)](-) (2). The trigonal-planar coordination of copper(II) is angularly distorted but unambiguous, as there is no other halide ligand within 6.7 A of the copper atom. Density functional theory (DFT) calculations on planar [CuClBr(2)](-) show that the energy surface for angle bending is very soft. Crystallisation in the presence of CH(3)CN yields [Ph(3)PNPPh(3)](+)[CuCl(0.7)Br(2.3)(NCCH(3))](-) (3), in which there is additional secondary coordination by NCCH(3) (Cu-N 2.44 A). DFT calculations of the potential energy surface for this secondary coordination show that it is remarkably flat (<3 kcal mol(-1) for a variation of Cu-N by 0.8 A). The crystal packing in 1, 2 and 3, which involves multiple phenyl embraces between [Ph(3)PNPPh(3)](+) ions and numerous C-H...Cl and C-H...Br motifs, is associated with intermolecular energies that are larger than the variations in intramolecular energies. For reference, the crystal structures of [Ph(3)PNPPh(3)(+)](2)[Cu(2)Cl(6)](2-) (4) and [Ph(3)PNPPh(3)(+)](2)[Cu(2)Br(6)](2-) (5) are described. We conclude 1) that three-coordinate copper(II) with monatomic halide ligands, although uncommon, can be regarded as normal, 2) that steric control by ligands is not necessary to enforce three-coordination, 3) that a hydrophobic aryl environment stabilises [Cu(Cl/Br)(3)](-), and 4) that the energy change in the transition from three- to four-coordinate copper(II) is very small (ca 5 kcal mol(-1)). 相似文献
8.
Geney R Sun L Pera P Bernacki RJ Xia S Horwitz SB Simmerling CL Ojima I 《Chemistry & biology》2005,12(3):339-348
A new computational docking protocol has been developed and used in combination with conformational information inferred from REDOR-NMR experiments on microtubule bound 2-(p-fluorobenzoyl)paclitaxel to delineate a unique tubulin binding structure of paclitaxel. A conformationally constrained macrocyclic taxoid bearing a linker between the C-14 and C-3'N positions has been designed and synthesized to enforce this "REDOR-taxol" conformation. The novel taxoid SB-T-2053 inhibits the growth of MCF-7 and LCC-6 human breast cancer cells (wild-type and drug resistant) on the same order of magnitude as paclitaxel. Moreover, SB-T-2053 induces in vitro tubulin polymerization at least as well as paclitaxel, which directly validates our drug design process. These results open a new avenue for drug design of next generation taxoids and other microtubule-stabilizing agents based on the refined structural information of drug-tubulin complexes, in accordance with typical enzyme-inhibitor medicinal chemistry precepts. 相似文献
9.
Olesik SV 《Journal of chromatography. A》2004,1037(1-2):405-410
Enhanced fluidity (EF) liquid mixtures are advantageous as mobile phases for the separation of moderate to polar compounds in liquid chromatography (reversed-phase, normal, size exclusion, size exclusion, and chiral separations). The low viscosities and high diffusivities of EF mixtures allow highly efficient separations to be achieved in a small amount of time. The best use of enhanced-fluidity liquids is only possible when their physicochemical properties are known. Herein, the techniques used to measure the physicochemical properties (phase diagram, diffusivity, solvent strength and pH) of EF liquids are described. For each technique, the experiment design and the care necessary to insure the quality of the collected data are described. Finally, the impact of the measured physicochemical properties on the chromatography is also highlighted. 相似文献
10.
Susan A. Bourne Katherine De Villiers Timothy J. Egan 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(2):o53-o57
The structures of three compounds with potential antimalarial activity are reported. In N,N‐diethyl‐N′‐(7‐iodoquinolin‐4‐yl)ethane‐1,2‐diamine, C15H20IN3, (I), the molecules are linked into ribbons by N—H⋯N and C—H⋯N hydrogen bonds. In N‐(7‐bromoquinolin‐4‐yl)‐N′,N′‐diethylethane‐1,2‐diamine dihydrate, C15H20BrN3·2H2O, (II), two aminoquinoline molecules and four water molecules form an R54(13) hydrogen‐bonded ring which links to its neighbours to form a T5(2) one‐dimensional infinite tape with pendant hydrogen bonds to the aminoquinolines. The phosphate salt 7‐chloro‐4‐[2‐(diethylammonio)ethylamino]quinolinium bis(dihydrogenphosphate) phosphoric acid, C15H22ClN32+·2H2PO4−·H3PO4, (III), was prepared in order to establish the protonation sites of these compounds. The phosphate ions form a two‐dimensional hydrogen‐bonded sheet, while the aminoquinoline cations are linked to the phosphates by N—H⋯O hydrogen bonds from each of their three N atoms. While the conformation of the quinoline region hardly varies between (I), (II) and (III), the amino side chain is much more flexible and adopts a significantly different conformation in each case. Aromatic π–π stacking interactions are the only supramolecular interactions seen in all three structures. 相似文献