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Effective Medium Model (effective + medium_model)
Selected AbstractsReview modeling the free solution and gel electrophoresis of biopolymers: The bead array-effective medium modelBIOPOLYMERS, Issue 2-3 2007Stuart A. Allison Abstract Free solution and gel electrophoresis is an extremely useful tool in the separation of biopolymers. The complex nature of biopolymers, coupled with the usefulness of electrophoretic methods, has stimulated the development of theoretical modeling over the last 30 years. In this work, these developments are first reviewed with emphasis on Boundary Element and bead methodologies that enable the investigator to design realistic models of biopolymers. In the present work, the bead methodology is generalized to include the presence of a gel through the Effective Medium model. The biopolymer is represented as a bead array. A peptide, for example, made up of N amino acids is modeled as 2N beads. Duplex DNA is modeled as a discrete wormlike chain consisting of touching beads. The technical details of the method are placed in three Appendices. To illustrate the accuracy and effectiveness of the approach, two applications are considered. Model studies on both the free solution mobility of 73 peptides ranging in size from 2 to 42 amino acids, and the mobility of short duplex DNA in dilute agarose gels are discussed. © 2007 Wiley Periodicals, Inc. Biopolymers 87: 102,114, 2007. This article was originally published online as an accepted preprint. The "Published Online" date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com [source] Effects of Matrix Cracks on the Thermal Diffusivity of a Fiber-Reinforced Ceramic CompositeJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 9 2001Kathleen R. McDonald Effects of matrix cracks and the attendant interface debonding and sliding on both the longitudinal and the transverse thermal diffusivities of a unidirectional Nicalon/MAS composite are investigated. The diffusivity measurements are made in situ during tensile testing using a phase-sensitive photothermal technique. The contribution to the longitudinal thermal resistance from each of the cracks is determined from the longitudinal diffusivity along with measurements of crack density. By combining the transverse measurements with the predictions of an effective medium model, the thermal conductance of the interface (characterized by a Biot number) is determined and found to decrease with increasing crack opening displacement, from an initial value of ,1 to ,0.3. This degradation is attributed to the deleterious effects of interface sliding on the thermal conductance. Corroborating evidence of degradation in the interface conductance is obtained from the inferred crack conductances coupled with a unit cell model for a fiber composite containing a periodic array of matrix cracks. Additional notable features of the material behavior include: (i) reductions of ,20% in both the longitudinal and the transverse diffusivities at stresses near the ultimate strength, (ii) almost complete recovery of the longitudinal diffusivity following unloading, and (iii) essentially no change in the transverse diffusivity following unloading. The recovery of the longitudinal diffusivity is attributed to closure of the matrix cracks. By contrast, the degradation in the interface conductance is permanent, as manifest in the lack of recovery of the transverse diffusivity. [source] Effect of form anisotropy of silicon nanocrystals on birefringence and dichroism in porous siliconPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007A. I. Efimova Abstract Artificial anisotropic optical media based on nanostructured silicon formed by electrochemical porosifying of Si substrates are investigated. Strong birefringence and dichroism of surface silicon-hydrogen bonds vibrations are found in the infrared spectral range. A comprehensive analysis of the absorption bands corresponding to the deformation and stretching modes is performed. The experimental results are discussed in terms of an effective medium model, taking into account the morphological anisotropy of Si nanocrystals in porous Si layers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] The birefringence level of anisotropically nanostructured siliconPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 6 2007J. Diener Abstract We present a detailed study of the anisotropic optical properties of mesoporous silicon layers prepared from substrates having different doping levels under various preparation conditions. It is demonstrated that the morphology of the layers strongly depends on the preparation conditions. The experimental data are explained in the framework of an effective medium model which takes into account different morphologies of the layers. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrical properties of bulk n-ZnO single crystals under hydrostatic pressurePHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 3 2009I. K. Kamilov Abstract Pressure dependences of Hall coefficient RH(P) and resistivity , (P) have been measured for n-ZnO bulk crystals with impurity concentration Ni = 1017,1018 cm,3 and concentration of free electrons ,1017 cm,3 at T = 300 K at hydrostatic pressures up to P = 25 GPa. It has been found that the exponential increase of RH(P) and , (P), observed in the vicinity of the polymorphous transition PPH = 9 GPa, is caused by the increase of ionization energy of shallow donors. At P > PPH, a step-like decrease of the resistivity has been observed, indicating a phase transition from diamond structure to NaCl-type structure. In accordance with formulas derived from the ,heterophase structure , effective medium' model, phase volume fractions in the critical region of the polymorphous transformation have been calculated and the threshold values of normalized effective resistivity have been determined. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] | ||||||||||