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Parallel Alignment (parallel + alignment)

Distribution by Scientific Domains

Polymers and Materials Science	75%

Selected Abstracts

Embryonic States of Fluorapatite,Gelatine Nanocomposites and Their Intrinsic Electric-Field-Driven Morphogenesis: The Missing Link on the Way from Atomistic Simulations to Pattern Formation on the Mesoscale

ADVANCED FUNCTIONAL MATERIALS, Issue 22 2009
Paul Simon
Abstract The shape development of fluorapatite (FAP),gelatine nanocomposites is revealed by means of HRTEM investigations starting from molecular dimensions up to the formation of mesoscaled (elongated) hexagonal prisms. The composite nature of the aggregates is proved by IR spectroscopy and by chemical analyses on all states of shape development. The initial states are characterized by triple-helical fiber protein bundles, which are mineralized step-by-step forming and fixing nanoplatelets of FAP in a mosaic arrangement. After being fully mineralized the bundles form elongated composite nanoboards. In the next step of the growth process the boards aggregate to bundles of boards which are in a more or less parallel alignment with respect to each other. By adding up more and more composite nanoboards a critical size is reached and an electric field is developed, which takes over control and directs the further development of the aggregates. This kind of electric-field-directed growth of the elongated polar nanoboards additionally leads to the formation and inclusion of protein nanofibrils into the growing composite aggregate. By this method, cone-like nanofibril structures develop along the long axis of the aggregates accompanied by more perfect parallel alignment of the composite boards within the aggregates. Further shape development is characterized by adding up composite nanoboards, in particular to increase the third dimension in volume. This thickening process preferably takes place in the middle part of the elongated aggregates and finally proceeds to their basal ends until a perfect hexagonal prismatic seed is formed, which then is ready for further shape development on the micrometer scale. [source]

Effect of Molecular Orientation of Epitaxially Grown Platinum(II) Octaethyl Porphyrin Films on the Performance of Field-Effect Transistors,

ADVANCED MATERIALS, Issue 9 2003
Y.-Y. Noh
The molecular alignment of platinum(II) octaethyl porphyrin (PtOEP) crystals evaporated on KBr (see atomic force microscopy image, Figure) can be readily changed from perpendicular to parallel by changing the substrate temperature. The field-effect mobility of transisitors prepared using epitaxially grown PtOEP films aligned perpendicularly to a substrate is 100 times higher than that of those of parallel alignment. [source]

Morphology of the mammalian vestibulo-ocular reflex: The spatial arrangement of the human fetal semicircular canals and extraocular muscles

JOURNAL OF MORPHOLOGY, Issue 10 2007
Philip G. Cox
Abstract The vestibulo-ocular reflex is the system of compensatory ocular movements in response to stimulation of the kinetic labyrinth seen in all vertebrates. It allows maintenance of a stable gaze even when the head is moving. Perhaps the simplest influence on the VOR is the spatial orientation of the planes of the semicircular canals relative to the extraocular muscles. It is hypothesized that the extraocular muscles are in parallel alignment with their corresponding semicircular canals in order to reduce the amount of neural processing needed and hence keep reflex times to a minimum. However, despite its obvious importance, little is known of this spatial arrangement. Moreover, nothing is known about any ontogenetic changes in the relative orientations of the extraocular muscles and semicircular canals. The morphologies of fetal and adult specimens of Homo sapiens were examined using magnetic resonance (MR) images. Three-dimensional co-ordinate data were taken from the images and used to calculate vector equations of the extraocular muscles and planes of best fit for the semicircular canals. The relative orientations of the muscles and canals were then calculated from the vectors and planes. It was shown that there are significant correlations between both the anterior and lateral semicircular canals and their corresponding extraocular muscles during ontogeny. In the case of the lateral canal with the medial rectus, the lateral canal with the lateral rectus, and the anterior canal with the inferior oblique, the trend is towards, though never reaching, alignment, whereas the anterior canal and the superior rectus muscle move out of alignment as age increases. Furthermore, it was noted that none of the six muscle-canal pairs is in perfect alignment, either during ontogeny or in adulthood. It was also shown that the three semicircular canals are not precisely orthogonal, but that the anterior and posterior canals form an angle of about 85°, while the anterior and lateral canals diverge by ,100°. Overall, it was shown that there is significant reorientation of the extraocular muscles and semicircular canals during ontogeny, but that, in most cases, there is little realignment beyond the fetal period. J. Morphol., 2007. © 2007 Wiley-Liss, Inc. [source]