Elastic fiber system

Elastic fibers endow a stroma with recoil after stretching. They are composed offibrillin with or without a central portion of elastin (Table 3.4). These two proteins are described in detail in Sect. 6.1.1 and 6.2.1). Elastic fibers are especially prominent in ligaments and 

Collagen data is from Table 2.9 in R. Montgomery et al. Biochemistry, A case oriented approach, 4th Ed., The CV Mosby Co., St Louis MO 1983. Elastin data is from S. Mithieux and A.S. Weiss, Adv. Prot. Chem. 79 437-461,2005 

Cornea Planar sheets stacked crossways for strength 

Unlike ligaments which attach bone to other bones or teeth, tendons attach bone to muscle and have few elastic fibers (Table 3.2). Ultraviolet radiation and aging disorganize the elastic fiber system of the skin by activating proteases that degrade elastin and fibrillin. 

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Milewicz, D. M., Urban, Z., and Boyd, C. (2000). Genetic disorders of the elastic fiber system. Matrix Biol. 19, 471-480. 

Determination of the Elastic and Viscous Stress-Strain Curves for Model Collagen Fiber Systems... 

Three reasons underlie the widespread interest in macromolecules, in spite of the synthetic difficulties that exist. First, the entanglement of long-chain macromolecules provides physical properties (strength, toughness, elasticity, fiber-forming properties, etc.) that cannot be obtained with small-molecule systems. Second, because polymers have a low volatility they can be used as engineering materials. Third, the onedimensional character of linear polymers is of considerable interest from the viewpoints of anisotropic physical properties, electrical phenomena, and information storage at the molecular level. 

As Monod states in his treatise. On Symmetry and Function in Biological Systems, One may set aside the simple problem of fibrous proteins. Being used as scaffolding, shrouds or halyards, they fulfill these requirements by adopting relatively simple types of translational symmetries. Therefore, it was not anticipated that positive cooperativity, the effect Monod thought to be the second secret of life, second only to the structure of DNA, would be most beautifully demonstrated by designed variations of a repeating sequence of the mammalian elastic fiber based on translational symmetry. 

A vital property of these model proteins is that they are more ordered above the transition temperature defined by the binodal or coexistence line in Figure 5.3. The polymer component of this water-polypeptide system becomes more ordered or structured on increased temperature from below to above the transition. This behavior is the inverse of that observed for most systems, as discussed above. In particular, we developed the term inverse temperature transition when the precursor protein and chemical fragmentation products of the mammalian elastic fiber changed from a dissolved state, and therefore when molecules were randomly dispersed in solution, to a state of parallel-aligned twisted filaments as the temperature was raised from below to above the phase transition. - ... 

Polyurethanes are versatile polymers typically composed of polyisocyanates and polyols. By varying constituents, a broad range of thermosets and thermoplastics can be produced and used in different applications. Possible systems include high-strength, high-modulus, structural composites soft rubbers elastic fibers and rigid or flexible foams. Although isocyanates have the ability to form many different polymers, very few types are used in actual production. The most common diisocyanates are methylene diphenylene diisocyanate (MDI) and toluene diisocyanate (TDI). Of these, TDI is the most commercially important dimer. 

The bronchiolar lamina propria stiU contains elastic fibers and smooth muscle, producing folds in the mucosa. Muscular contraction in both the bronchi and the bronchioles is controUed primarily by nerves of the autonomic nervous system. 

In integrated photoelasticity it is impossible to achieve a complete reconstruction of stresses in samples by only illuminating a system of parallel planes and using equilibrium equations of the elasticity theory. Theory of the fictitious temperature field allows one to formulate a boundary-value problem which permits to determine all components of the stress tensor field in some cases. If the stress gradient in the axial direction is smooth enough, then perturbation method can be used for the solution of the inverse problem. As an example, distribution of stresses in a bow tie type fiber preforms is shown in Fig. 2 [2]. 

There are two well-accepted models for stress transfer. In the Cox model [94] the composite is considered as a pair of concentric cylinders (Fig. 19). The central cylinder represents the fiber and the outer region as the matrix. The ratio of diameters r/R) is adjusted to the required Vf. Both fiber and matrix are assumed to be elastic and the cylindrical bond between them is considered to be perfect. It is also assumed that there is no stress transfer across the ends of the fiber. If the fiber is much stiffer than the matrix, an axial load applied to the system will tend to induce more strain in the matrix than in the fiber and leads to the development of shear stresses along the cylindrical interface. Cox used the following expression for the tensile stress in the fiber (cT/ ) and shear stress at the interface (t) ... 

A few examples of the moduli of systems with simple symmetry will be discussed. Figure 1A illustrates one type of anisotropic system, known as uniaxial orthotropic. The lines in the figure could represent oriented segments of polymer chains, or they could be fibers in a composite material. This uniaxially oriented system has five independent elastic moduli if the lines (or fibers) ara randomly spaced when viewed from the end. Uniaxial systems have six moduli if the ends of the fibers arc packed in a pattern such as cubic or hexagonal packing. The five engineering moduli are il-... 

A second type of anisotropic system is the biaxially oriented or planar random anisotropic system. This type of material is illustrated schematically in Figure 2A. Four of the five independent elastic moduli are illustrated in Figure 2B in addition there are two Poisson s ratios. Typical biaxially oriented materials are films that have been stretched in two directions by either blowing or tentering operations, rolled materials, and fiber-filled composites in which the fibers are randomly oriented in a plane. The mechanical properties of anisotropic materials arc discussed in detail in following chapters on composite materials and in sections on molecularly oriented polymers. 

Hard and soft acid and base (HSAB) principle, 16 780 Hard blacks, 21 775 Hard-burned quicklime, 15 28 Hard coals, 6 703 classification, 6 712 Hard copper alloys, 7 723t relief annealed, 7 723t Hard copy systems, 9 513-514 Hard core repulsion, 23 93 Hard-elastic olefin fibers, 11 242 Hardenability, of steel, 23 283—284 Hardened MF resins, analysis of,... 

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