Parallel fibers

The crimp imparted to the tow has a sawtooth or sinusoidal wave shape. Because the filaments are usually crimped as a group, the crimp in parallel fibers is in lateral registry, ie, with the ridges and troughs of the waves aligned, as shown in Figure 14. 

Methods for determining fiber-to-fiber friction have been developed (29—31). The friction coefficient can also be measured in terms of the force required to pull entwined fibers apart (32—34) or the force necessary to remove a single fiber from a mass of fibers under pressure (35). Another test involves an apparatus wherein one or a series of parallel fibers are mounted across a small bridge similar to a violin bridge. This is then pressed against a surface that may be another fiber or some other material, and the fibers alternately sHp and stick as they sHde across each other (36,37). 

Grosche J, Matyash V, MoUer T, Verkhratsky A, Reichenbach A, Kettenmann H (1999) Microdomains for neuron-glia interaction parallel fiber signaling to Bergmann gUal cells. Nat Neurosci 2 139-143... 

The homogenization was also found [200] to be incredibly fast for both longitudinal and transverse overall elastic moduli of the transversely-random [201] unidirectional composite of parallel fibers. It was almost impossible to distinguish [200] the overall ensemble-average moduli calculated with 9 and 289 fibers in a disordered unit cell. 

Bergersen, L., Waerhaug, O., Helm, J. et al. A novel postsyn-aptic density protein the monocarboxylate transporter MCT2 is co-localized with delta-glutamate receptors in postsynaptic densities of parallel fiber-Purkinje cell synapses. Exp. Brain Res. 136 523-34,2001. 

The pore volume, shown as a cross section of two parallel fibers of length, L, and radius, R, has a half-surface dimension, rp, and meets the fiber surface with an angle, ij) (see Figure 5). 

ASTM D 2344 (1989). Test method for apparent interlaminar shear strength of parallel fiber composites by short-beam method. 

At the same time that the motor neurons send signals to the muscles, branches travel into other parts of the brain including the olivary nuclei, which send neurons into the cerebellum. The cerebellum acts as a kind of computer needed for fine tuning of the impulses to the muscles. Injury to the cerebellum leads to difficulty in finely coordinated motions. Input to the Purkinje cells arises from the climbing fibers, which originate in the inferior olive of the brain stem. Each climbing fiber activates a single Purkinje cell, but the dendrites of each Purkinje cell also form as many as 200,000 different synapses with parallel fibers that run across the cortex of the cerebellum (Fig. 30-15). 

The parallel fibers receive input from many sources via a complex series of mossy fibers and granule cells and influence the firing of the Punkinje cells. The output from the Purkinje cells is entirely inhibitory. It is transmitted via synapses in the cerebellar nuclei to neurons that lead back to the cerebral cortex, into the thalamus, and down the spinal cord.411 The pathway to the cortex completes an inhibitory feedback loop, of which there are many in the nervous system. For details see Llinas404 and Nicholls.149... 

Hollow-fiber membranes form a tubular structure which is usually arrayed as a parallel fiber bundle within a cylindrical container. The cells are trapped on the shell side of the hollow fibers while aerated nutrient medium is rapidly recirculated through the fibers. This type of membrane support can provide extra protection against contamination. However, the major disadvantages of membrane... 

Okubo Y., Kakizawa S., Hirose K., and lino M. (2004). Cross talk between metabotropic and ionotropic glutamate receptor- mediated signaling in parallel fiber-induced inositol 1,4,5-trisphosphate production in cerebellar Purkinje cells. J. Neurosci. 24 9513-9520. 

In the wri mutant, development of the Purkinje cell dentritic trees is impaired synaptic connections of parallel fibers on dendritic spines of Pukinje cells are decreased at two weeks of age, but by nine weeks malformed synaptic boutons lacking synaptic membrane specializations are significantly increased (Inoue et al.,... 

Careful work is necessary to remove all preferred orientation from powder samples. Figure 1 shows results obtained with polyethylene terephthalate (PET) fibers. Curve is a typical azimuthal scan of the 010 peak (20 = 17,5°) for a bundle of parallel fibers placed perpendicularly to the x-ray beam. Curve b is the same scan carried out on a "powder" sample, showing that all preferred orientation is removed in our conditions of moulding (350 kg/ m2). For each kind of fiber, it is necessary to do preliminary trials to find the best experimental conditions. For PET fibers, we show on Figure 2 the relative crystallinity index and the residual orientation plotted against the cut-lengh. (5). 

Curve a bundle of parallel fibers put perpendicularly to the x-ray beam Curve b powder" made of cut fibers. It can be ascertained that all preferential orientation is practically removed when a powder sample made of regular small cross section is used. 

PKA-dependent long-term potentiation and depression was initially discovered in the mossy-fiber synapses of the hippocampus, and later demonstrated in parallel fiber synapses of the cerebellum and corticothalamic synapses of the forebrain (Malenka and Siegelbaum, 2001). This widespread form of plasticity does not involve changes in Ca2+-influx, but operates via a direct increase or decrease, respectively, of the amount of vesicle exocytosis that can be triggered by a given Ca2+-signal. Interestingly, this form of plasticity appears to depend on the interaction... 

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