Fibers density

Fiber Density, kg/m Strength, GPa Modulus, GPa Elongation to break, % Filament diameter, mm... 

The bulk properties of regenerated cellulose are the properties of Cellulose II which is created from Cellulose I by alkaline expansion of the crystal stmcture (97,101) (see Cellulose). The key textile fiber properties for the most important current varieties of regenerated cellulose are shown in Table 2. Fiber densities vary between 1.53 and 1.50. 

Barrier Phenomenon. In red cell filtration, the blood first comes into contact with a screen filter. This screen filter, generally a 7—10-) m filter, does not allow micro aggregate debris through. As the blood product passes through the deeper layer of the filter, the barrier phenomenon continues as the fiber density increases. As the path becomes more and more tortuous the cells are more likely to be trapped in the filter. 

The crystal stmcture of PPT is pseudo-orthorhombic (essentially monoclinic) with a = 0.785/nm b = 0.515/nm c (fiber axis) = 1.28/nm and d = 90°. The molecules are arranged in parallel hydrogen-bonded sheets. There are two chains in a unit cell and the theoretical crystal density is 1.48 g/cm. The observed fiber density is 1.45 g/cm. An interesting property of the dry jet-wet spun fibers is the lateral crystalline order. Based on electron microscopy studies of peeled sections of Kevlar-49, the supramolecular stmcture consists of radially oriented crystaUites. The fiber contains a pleated stmcture along the fiber axis, with a periodicity of 500—600 nm. 

Fabric Composition. The method of fabric manufacture dictates many of the characteristics of the sheet, but intrinsic properties are firmly estabhshed by the base polymer selected. Properties such as fiber density, temperature resistance, chemical and light stabiUty, ease of coloration, surface energies, and others are a function of the base polymer. Thus, because nylon absorbs more moisture than polypropylene, spunbonded fabrics made from nylon are more water absorbent than fabrics of polypropylene. 

By comparison, the multiple spinnerette per bank process requites additional effort prior to laydown in order to compensate for the gaps between the individual spinnerettes. Failure to present a filament array to the laydown screen, which is not uniformly distributed, can result in spot-to-spot variations in fiber density and a web that has the appearance of blotch. 

Fiber Density (g/cm- ) Elongation (%) Tensile strength (MPa) Youngs modulus (GPa) Reference... 

Two helices are packed antiparallel in the orthorhombic unit cell. Association of the helices occurs through a series of periodic carboxylate potassium water - carboxylate interactions. An axial projection of the unit-cell contents (Fig. 23b) shows that the helices and guest molecules are closely packed. This is the first crystal structure of a polysaccharide in which all the guest molecules in the unit cell, consistent with the measured fiber density, have been experimentally located from difference electron-density maps. The final / -value is 0.26 for 54 reflections, of which 43 are observed, and it is based on normal scattering factors.15... 

The decrease in the fiber diameter of fabric resulted in a decrease in porosity and pore size, but an increase in fiber density and mechanical strength. The microfiber fabric made of PCLA (1 1 mole ratio) was elastomeric with a low Young s modulus and an almost linear stress-strain relationship under the maximal stain (500%) in this measurement. 

Fig. 4.3 Epidermal nerve fiber illustrated in a 50-pm vertical skin section, immunostained with the panaxonal marker anti-protein gene product 9.5. Skin section showing epidermal nerve fiber density arrows) in the distal leg of a healthy adult (a) and reduced epidermal nerve fiber density and degenerating fibers arrows) in the distal leg of a HIV-associated sensory neuropathy patient (b) (scale bar, 50 pm). Courtesy of Drs Gigi Ebenezer and Justin McArthur, Johns Hopkins University, Baltimore, Maryland, USA...

Epidermal nerve fiber analysis by immunocytochemical techniques using the panaxonal marker protein gene product 9.5 (PGP 9.5) allows the study of epidermal innervation by small fiber C and A5 nerve fibers (McCarthy et al. 1995 Holland et al. 1997). Studies of skin biopsies of HIV infected patients with DSP or ATN showed reduction in the number of epidermal fibers in distal areas of the lower extremities with an inverse correlation between neuropathic pain intensity and epidermal nerve fiber density (Polydefkis et al. 2002) (Fig. 4.3). There were also fewer epidermal fibers in HIV seropositive patients without clinical evidence of neuropathy, suggesting that HIV infection may be associated with the loss of cutaneous innervation even before the onset of sensory symptomatology (McCarthy et al. 1995). 

Short term L-acetyl carnitine treatment has shown symptomatic benefits in ATN, although it is unclear if this effect is long lasting because of neuronal regeneration or is merely an analgesic effect (Scarpini et al. 1997 Oslo et al. 2006). Longer term studies showed improvements in epidermal nerve fiber density (Hart et al. 2004) as well as the symptoms of neuropathy when patients were treated with L-acetyl carnitine (Hart et al. 2004 Herzmann et al. 2005). A short term randomized, double-blind, placebo-controlled study showed reduction in pain over a 2 week period in HIV patients with TNA (Youle and Oslo 2007). 

Holland NR, Stocks A et al (1997) Intraepidermal nerve fiber density in patients with painful sensory neuropathy. Neurology 48(3) 708-711... 

Polydefkis M, Yiannoutsos CT et al (2002) Reduced intraepidermal nerve fiber density in HIV-associated sensory neuropathy. Neurology 58(1) 115-119 Power C, Gill MJ et al (2002) Progress in clinical neurosciences The neuropathogenesis of HIV infection host-virus interaction and the impact of therapy. Can J Neurol Sci 29(l) 19-32 Premack BA, SchaU TJ (1996) Chemokine receptors gateways to inflammation and infection. Nat Med 2(11) 1174-1178... 

Bundle Preparation. Packages of multifileiment yarns are backwound to prepare bundles necessary for the manufacture of a reverse osmosis module. A proprietary winder for this operation has been designed and constructed at Albany International Research Co. This device is capable of helically winding multifilament yarns into bundles around a mandrel. This is done in a manner such that the resulting bundle has uniform cylindrical dimensions and uniform fiber density. This minimizes channeling and optimizes exposure of membrane surface area. 

Another development underway is to try to locate on the above mentioned sigmoid curves the critical point (t. ). where gelation occurs. Rheological experiments and structural determinations will be used to calculate some critical quantities as a critical fiber density to gelify the system. 

Ferri, F., Greco, M., Arcovito, G., De Spirito, M., and Rocco, M. (2002). Structure of fibrin gels studied by elastic light scattering techniques Dependence of fractal dimension, gel crossover length, fiber diameter, and fiber density on monomer concentration. Phys. Rev. E. 66(1 Pt 1), 011913. 

The sampling flow rate and time should be adjusted to produce a fiber density of 100 to 1300 fibers/mm2. 

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