C-fibers

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. 

Capsaicin, an active ingredient in red pepper, is well known for its ability to release and deplete substance P in sensory C fibers. However, this action is not specific for substance P, as neurokinin A, calcitonin gene-related peptide (CGRP), and somatostatin also are released. 

R = / -C H ), in low doses, exhibits the former behavior and is used primarily as an extradural agent in obstetrics. The lowest effective extradural concentration of etidocaine (21, X = CH, R = R = 2H, R = / -C H ), however, shows both adequate sensory and profound motor blockade so that it is useful in surgical situations where maximum neuromuscular blockade is necessary. In an isolated nerve preparation, bupivacaine blocks unmyelinated C fibers which are mainly responsible for pain perception at a much greater extent than the myelinated A fibers which carry motor impulses. It is postulated that absorption of bupivacaine by the vasculature at the site of injection, combined with the slow diffusion of this agent, results in an insufficient amount of the drug penetrating the large A fibers to cause motor conduction blockade. Clinically, motor block can be observed in some procedures. 

Fig. 4.29. EDXS line-profile analysis across the interfacial region of a C-fiber reinforced SiC composite and corresponding TEM bright-field image.

Pain production is the most common injury inflicted on man. This noxious stimulus is perceived almost instantly after skin - tentacle contact. A subpopulation (30 - 40%) of visceral sensory C fibers denoting noscioception have been shown to be selectively excited experimentally in nerve ganglia preparations by a component of... 

A rapidly increasing number of publications on polysilanes documents current interest in these polymers (JJ. Polysilanes are potentially applicable in microlithography as high resolution UV-resists (2J, imageable etch barriers ), or contrast enhancement layers (4). They have been successfully used as precursors to Si-C fibers (5J and ceramic reinforcing agents ((L). Polysilanes have also initiated polymerization of vinyl monomers (J ). Doping of polysilanes have increased their conductivity to the level of semiconductors (8). Very recently polysilanes were used as photoconductors (9) and non-linear optical materials (10b... 

Thermal nociceptors and mechanical nociceptors are associated with A-delta fibers. These are small myelinated fibers that transmit impulses at a rate of 5 to 30 m/sec. Polymodal nociceptors are associated with C fibers. These are small unmyelinated fibers that transmit impulses at a rate generally less than 1.0 m/sec (range of 0.5 to 2.0 m/sec). 

Centrally mediated hyperalgesia involves the hyperexcitability of second-order sensory neurons in the dorsal horn of the spinal cord. In the case of severe or persistent tissue injury, C fibers fire action potentials... 

These high demands are not yet fulfilled by any available fiber coating. Only a C-coated SiC-fiber (NL 607) from Nippon Carbon is commercially available. To meet the above demands, a multilayer fiber coating is necessary. In a joint effort with ABB Heidelberg and TU Chemnitz, a CVD C-coating on C- and SiC-fibers and a C/SiC double CVD coating on C-fibers was developed and tested (Fig. 3). 

High temperature tensile tests of the C/SiC coated C-fiber showed very good oxidation resistance up to 650°C. The filaments of the fiber bundle were coated homogeneously. 

I. 5SBF. (c) Fibers soaked in 1 kmol m 3 CaCI2 solution and subsequently in 1.5SBF. 

Marazuela M.D., Moreno-Bondi M.C., Fiber-optic biosensors - an overview, Anal. Bioanal. Chem. 2002 372 664. 

Turntable Vessel volume Operation volume Vessel material Max. temperature Temp, measurement 3 x 96-well plates 1 mL min. 0.1 mL glass 150 °C fiber optic 52 x 50 mL max. 30 mL glass or PFA 150 °C fiber optic 120 x 15 mL max. 10 mL glass or PFA 150 °C fiber optic... 

McGowan SE. 2007. Vitamin A deficiency increases airway resistance following C-fiber stimulation. Respir Physiol Neurobiol 157 281-289. 

Primary sensory neurons sense pain and convey it to the spinal cord. Nociceptors have unmyelinated (C fiber) or thinly myelinated (AS) axons, while the low-threshold Ap-fiber mechanoreceptors involved in tactile and proprioceptive perception have large myelinated sensory neurons (Table 57-1). The peripheral terminals of primary sensory neurons convert changes in the environment into neuronal activity by transducing mechanical (Ch. 51), thermal or chemical stimuli into ion fluxes across their... 

Ectopic activity in C fibers elicits central sensitization in the dorsal horn, contributing to the generation of tactile allodynia, a prominent feature of neuropathic pain. 

Li, E. Wang, X. Zhang, C., Fiber optic temperature sensor based on interference of selective higher order modes, Appl. Phys. Lett. 2006, 89, 091119... 

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