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Coupling Values (coupling + value)

Distribution by Scientific Domains
Medical Sciences50%

Selected Abstracts

Maximum likelihood constrained deconvolution.

CONCEPTS IN MAGNETIC RESONANCE, Issue 2 2003
II: Application to experimental two-, three-dimensional NMR spectra
Abstract The maximum likelihood method (MLM) and related protocols were applied to the experimental 2-D nuclear Overhauser effect (NOE) spectrum of a 24-nucleotide RNA hairpin loop molecule. The output becomes more valuable when diagonal symmeterization is followed by MLM. This symmeterized maximum likelihood (SML) protocol restores the original spectral information with high fidelity by accurately partitioning components from overlapped peaks and provides substantial improvements in line shape and spectral resolution, in particular in the F1 dimension. These advantages lead to a simpler interpretation of the resonance frequencies, intensities, multiplet fine structure, and J -coupling values from a heavily overlapped peak region. This promises a more effective tool for peak picking, assignment, and integration. Also, application of MLM and related protocols to the 2-D NOE proton spectrum of a 24-mer RNA dramatically increases the number of NOE-based distance constraints that can be used for determination of its 3-D molecular structure. By application of 3-D MLM to a simple 3-D spectrum, the spectral resolution and signal-to-noise (S/N) ratio was greatly improved by effective line sharpening and reduction of cross-talk between planes. © 2003 Wiley Periodicals, Inc. Concepts Magn Reson 18A: 146,156, 2003 [source]

Fabrication and Electromechanical Characterization of a Piezoelectric Structural Fiber for Multifunctional Composites

ADVANCED FUNCTIONAL MATERIALS, Issue 4 2009
Yirong Lin
Abstract The use of piezoceramic materials for structural sensing and actuation is a fairly well developed practice that has found use in a wide variety of applications. However, just as advanced composites offer numerous benefits over traditional engineering materials for structural design, actuators that utilize the active properties of piezoelectric fibers can improve upon many of the limitations encountered when using monolithic piezoceramic devices. Several new piezoelectric fiber composites have been developed; however, almost all studies have implemented these devices such that they are surface-bonded patches used for sensing or actuation. This paper will introduce a novel active piezoelectric structural fiber that can be laid up in a composite material to perform sensing and actuation, in addition to providing load bearing functionality. The sensing and actuation aspects of this multifunctional material will allow composites to be designed with numerous embedded functions, including structural health monitoring, power generation, vibration sensing and control, damping, and shape control through anisotropic actuation. This effort has developed a set of manufacturing techniques to fabricate the multifunctional fiber using a SiC fiber core and a BaTiO3 piezoelectric shell. The electromechanical coupling of the fiber is characterized using an atomic force microscope for various aspect ratios and is compared to predictions made using finite element modeling in ABAQUS. The results show good agreement between the finite element analysis model and indicate that the fibers could have coupling values as high as 68% of the active constituent used. [source]

A compact band-pass filter using multi-element resonators

INTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2003
Kenneth V. Puglia
Abstract A compact, band-pass filter utilizing multi-element resonators, structured from sections of distributed transmission lines, is presented. A band-pass filter design procedure is established that emphasizes CAD techniques to characterize the individual resonators and to determine the resonator coupling values required for a specified pass-band response. Detailed band-pass filter design examples are illustrated and simulation results are employed to validate the design procedure. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13, 447,458, 2003. [source]

Collagen dynamics in articular cartilage under osmotic pressure

NMR IN BIOMEDICINE, Issue 8 2006
Göran Zernia
Abstract Cartilage is a complex biological tissue consisting of collagen, proteoglycans and water. The structure and molecular mobility of the collagen component of cartilage were studied by 13C solid-state NMR spectroscopy as a function of hydration. The hydration level of cartilage was adjusted between fully hydrated (,80 wt% H2O) and highly dehydrated (,30 wt% H2O) using the osmotic stress technique. Thus, the conditions of mechanical load could be simulated and the response of the tissue macromolecules to mechanical stress is reported. From the NMR measurements, the following results were obtained. (i) Measurements of motionally averaged dipolar 1H,13C couplings were carried out to study the segmental mobility in cartilage collagen at full hydration. Backbone segments undergo fast motions with amplitudes of ,35° whereas the collagen side-chains are somewhat more mobile with amplitudes between 40 and 50°. In spite of the high water content of cartilage, collagen remains essentially rigid. (ii) No chemical shift changes were observed in 13C cross-polarization magic angle spinning spectra of cartilage tissue at varying hydration indicating that the collagen structure was not altered by application of high osmotic stress. (iii) The 1H,13C dipolar coupling values detected for collagen signals respond to dehydration. The dipolar coupling values gradually increase upon cartilage dehydration, reaching rigid limit values at ,30 wt% H2O. This indicates that collagen is essentially dehydrated in cartilage tissue under very high mechanical load, which provides insights into the elastic properties of cartilage collagen, although the mechanical pressures applied here exceed the physiological limit. Copyright © 2006 John Wiley & Sons, Ltd. [source]