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71.
Karl Hawkins P. Adrian Evans Matthew Lawrence Daniel Curtis Marc Davies P. Rhodri Williams 《Rheologica Acta》2010,49(9):891-900
This paper reports simulated sequential frequency sweep data which have been reconstructed from time resolved viscoelastic
data obtained by Fourier transform mechanical spectroscopy. Comparisons of the results show that the recording of anomalous
values of the stress relaxation power law exponent α at the Gel Point under ‘rapid’ gelling conditions may be due to inappropriate rheological techniques. An appropriate rheometrical
criterion is established for the application of sequential frequency sweeps in order to obtain accurate values of α in the formation of strain-sensitive, rapidly formed gels. Furthermore, using appropriate rheometry, we report values of
α for fibrin–thrombin gels formed by the addition of thrombin to a physiologically relevant level of human fibrinogen, and
relate these values to the microstructure of the fibrin gel network in terms of a fractal dimension. The present study is
the first to report a modification of the fractal characteristics of incipient clots in fibrin–thrombin gels due to the availability
of thrombin. This work confirms the hypothesis that the self-similar (fractal) stress relaxation behaviour recorded at the
Gel Point of samples of coagulating blood (Evans et al. 2010a, b) is associated with the microstructural characteristics of the incipient blood clot’s fibrin network. 相似文献
72.
Zhou W Valley MP Shultz J Hawkins EM Bernad L Good T Good D Riss TL Klaubert DH Wood KV 《Journal of the American Chemical Society》2006,128(10):3122-3123
Novel bioluminogenic substrates were designed for probing monoamine oxidase (MAO) activity based on a simple and effective beta-elimination strategy. By modifying the amino group and the central core of luciferin derivatives, we have developed a series of substrates useful for assays of MAO A or B, or both. One of these substrates, exhibiting low Km values and high signal-to-background ratios with both isozymes, was shown to accurately measure the Ki values of known MAO inhibitors. This substrate is a key component in the development of a highly sensitive homogeneous MAO assay for high-throughput screening (HTS) of compounds in drug discovery and for monitoring MAO activity in complex biological systems. This design strategy should be applicable to fluorogenic MAO substrates and could broaden the structural requirements of substrates for other enzyme assays. 相似文献
73.
We present a fully planar integrated optical approach to single-molecule detection based on microfabricated planar networks of intersecting solid and liquid-core waveguides. We study fluorescence from dye molecules in liquid-core antiresonant reflecting optical waveguides, and demonstrate subpicoliter excitation volumes, parallel excitation through multiple pump waveguides, and single-molecule detection sensitivity. Integrated silicon photonics combined with single-molecule detection in solution create a compact, robust, and sensitive platform that has applications in numerous fields ranging from atomic physics to the life sciences. 相似文献
74.
75.
The infinite T-matrix method is a powerful tool for electromagnetic scattering simulations, particularly when one is interested in changes in orientation of the scatterer with respect to the incident wave or changes of configuration of multiple scatterers and random particles, because it avoids the need to solve the fully reconfigured systems. The truncated T-matrix (for each scatterer in an ensemble) is often computed using the null-field method. The main disadvantage of the null-field based T-matrix computation is its numerical instability for particles that deviate from a sphere. For large and/or highly non-spherical particles, the null-field method based truncated T-matrix computations can become slowly convergent or even divergent. In this work, we describe an electromagnetic scattering surface integral formulation for T-matrix computations that avoids the numerical instability. The new method is based on a recently developed high-order surface integral equation algorithm for far field computations using basis functions that are tangential on a chosen non-spherical obstacle. The main focus of this work is on the mathematical details required to apply the high-order algorithm to compute a truncated T-matrix that describes the scattering properties of a chosen perfect conductor in a homogeneous medium. We numerically demonstrate the stability and convergence of the T-matrix computations for various perfect conductors using plane wave incident radiation at several low to medium frequencies and simulation of the associated radar cross of the obstacles. 相似文献
76.
Ryan A. Hawkins 《Tetrahedron letters》2010,51(47):6129-6131
A pyrrolo[2,1-b]quinazoline has been found to undergo both epoxidation and hydroxylation on the pyrrole nucleus upon simple exposure of an acetone solution to air or oxygen. The oxygenation reaction occurs most readily when the starting compound contains a t-butyl ester at the 3-position, compared to a cyano or phenylsulfonyl. The structure of the product has been confirmed by X-ray crystal analysis. 相似文献
77.
Thomas Hawkins 《Historia Mathematica》1975,2(1):1-29
It is well-known that Cauchy (1829) provided the first general proof that the eigenvalues of a symmetric matrix are real. Furthermore, Cauchy's paper initiated the developments that resulted in the creation of a substantial spectral theory of matrices by the early 1870's. The following essay relates Cauchy's work and its historical significance to the consideration of eigenvalue problems during the 18th century. 相似文献
78.
Alex W. Gregory Alan Chambers Dr. Alison Hawkins Dr. Pavol Jakubec Prof. Dr. Darren J. Dixon 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(1):111-114
A new chemoselective reductive nitro‐Mannich cyclization reaction sequence of nitroalkyl‐tethered lactams has been developed. Relying on the rapid and chemoselective iridium(I)‐catalyzed reduction of lactams to the corresponding enamine, subsequent nitro‐Mannich cyclization of tethered nitroalkyl functionality provides direct access to important alkaloid natural‐product‐like structures in yields up to 81 % and in diastereoselectivities that are typically good to excellent. An in‐depth understanding of the reaction mechanism has been gained through NMR studies and characterization of reaction intermediates. The new methodology has been applied to the total synthesis of (±)‐epi‐epiquinamide in four steps. 相似文献
79.
K. J. Badcock F. Cantariti I. Hawkins M. Woodgate L. Dubuc B. E. Richards 《国际流体数值方法杂志》2000,32(5):585-604
The pseudo‐time formulation of Jameson has facilitated the use of numerical methods for unsteady flows, these methods have proved successful for steady flows. The formulation uses iterations through pseudo‐time to arrive at the next real time approximation. This iteration can be used in a straightforward manner to remove sequencing errors introduced when solving mean flow equations together with another set of differential equations (e.g. two‐equation turbulence models or structural equations). The current paper discusses the accuracy and efficiency advantages of removing the sequencing error and the effect that building extra equations into the pseudo‐time iteration has on its convergence characteristics. Test cases used are for the turbulent flow around pitching and ramping aerofoils. The performance of an implicit method for solving the pseudo‐steady state problem is also assessed. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献
80.