Measurement of time-dependent changes in optical transmission characteristics of biological tissues

1995 ◽  
Author(s):  
Uwe Vogel ◽  
Juergen Uhlemann ◽  
Andreas Melchner ◽  
Richard Freyer ◽  
Juergen Beuthan
Keyword(s):  
Optical Transmission ◽  
Biological Tissues ◽  
Time Dependent ◽  
Transmission Characteristics

Poroelastic Indentation Analysis for Hydrated Biological Tissues

2006 ◽  
Vol 975 ◽  
Author(s):  
Michelle L. Oyen ◽  
Amanpreet K. Bembey ◽  
Andrew J. Bushby
Keyword(s):  
Indentation Test ◽  
Biological Tissues ◽  
Time Dependent ◽  
Spherical Indentation ◽  
Indentation Creep ◽  
Polar Solvents ◽  
Viscoelastic Analysis ◽  
Wide Range ◽  
Indentation Problem

ABSTRACTIndentation techniques are employed for the measurement of mechanical properties of a wide range of materials. In particular, techniques focused at small length-scales, such as nanoindentation and AFM indentation, allow for local characterization of material properties in heterogeneous materials including natural tissues and biomimetic materials. Typical elastic analysis for spherical indentation is applicable in the absence of time-dependent deformation, but is inappropriate for materials with time-dependent responses. Recent analyses for the viscoelastic indentation problem, based on elastic-viscoelastic correspondence, have begun to address the issue of time-dependent deformation during an indentation test. The viscoelastic analysis has been shown to fit experimental indentation data well, and has been demonstrated as useful for characterization of viscoelasticity in polymeric materials and in hydrated mineralized tissues. However, a viscoelastic analysis is not necessarily sufficient for multi-phase materials with fluid flow. In the current work, a poroelastic analysis—based on fluid motion through a porous elastic network—is used to examine spherical indentation creep responses of hydrated biological materials. Both analytical and finite element approaches are considered for the poroelastic Hertzian indentation problem. Modeling results are compared with experimental data from nanoindentation of hydrated bone immersed in water and polar solvents (ethanol, methanol, acetone). Baseline (water-immersed) bone responses are characterized using the poroelastic model and numerical results are compared with altered hydration states due to polar solvents.

scholarly journals Optical Transmission Characteristics of Concentrated Solar Rays in the VSR using Cup-shaped Porous Absorber

2016 ◽  
Vol 157 ◽  
pp. 301-308 ◽  
Author(s):  
Xian-long Meng ◽  
Xin-lin Xia ◽  
Chuang Sun ◽  
Xiao-lei Li
Keyword(s):  
Optical Transmission ◽  
Transmission Characteristics ◽  
Solar Rays

Aperiodic lattices for photonic bandgap engineering

2003 ◽  
Vol 797 ◽  
Author(s):  
Subhasish Chakraborty ◽  
David G. Hasko ◽  
Robert. J. Mears
Keyword(s):  
Fourier Transform ◽  
Discrete Fourier Transform ◽  
Optical Transmission ◽  
Optical Characteristic ◽  
Photonic Bandgap ◽  
Silicon On Insulator ◽  
New Method ◽  
Transmission Characteristics ◽  
Bandgap Engineering ◽  
One Dimensional

ABSTRACTA new method is presented, based on the discrete Fourier Transform, for the design of aperiodic lattices to be used in photonic bandgap engineering. Designing an aperiodic lattice by randomly choosing defects is unlikely to result in useful optical transmission characteristics. By contrast, this new method allows an aperiodic lattice to be designed directly from the desired optical characteristic. The use of this method is illustrated with a design for a structure to realise two transmission wavelengths in the stopband of a one-dimensional photonic lattice. This design has been fabricated in silicon-on-insulator and some optical characteristics are given.

scholarly journals Characterizing the viscoelastic properties of thin hydrogel-based constructs for tissue engineering applications

2005 ◽  
Vol 2 (5) ◽  
pp. 455-463 ◽  
Author(s):  
Mark Ahearne ◽  
Ying Yang ◽  
Alicia J El Haj ◽  
Kong Y Then ◽  
Kuo-Kang Liu
Keyword(s):  
Tissue Engineering ◽  
Viscoelastic Properties ◽  
Biological Tissues ◽  
Constant Load ◽  
Time Dependent ◽  
Hydrogel Membranes ◽  
Agarose Hydrogel ◽  
Viscoelastic Theory ◽  
Working Distance ◽  
Convenient Technique

We present a novel indentation method for characterizing the viscoelastic properties of alginate and agarose hydrogel based constructs, which are often used as a model system of soft biological tissues. A sensitive long working distance microscope was used for measuring the time-dependent deformation of the thin circular hydrogel membranes under a constant load. The deformation of the constructs was measured laterally. The elastic modulus as a function of time can be determined by a large deformation theory based on Mooney–Rivlin elasticity. A viscoelastic theory, Zener model, was applied to correlate the time-dependent deformation of the constructs with various gel concentrations, and the creep parameters can therefore be quantitatively estimated. The value of Young's modulus was shown to increase in proportion with gel concentration. This finding is consistent with other publications. Our results also showed the great capability of using the technique to measure gels with incorporated corneal stromal cells. This study demonstrates a novel and convenient technique to measure mechanical properties of hydrogel in a non-destructive, online and real-time fashion. Thus this novel technique can become a valuable tool for soft tissue engineering.

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