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Hexagonal Pattern (hexagonal + pattern)

Distribution by Scientific Domains
Polymers and Materials Science40%
Medical Sciences40%

Selected Abstracts

Self-Organized Hexagonal Patterns of Independent Magnetic Nanodots,

ADVANCED MATERIALS, Issue 24 2007
T. Bobek
A method for producing self-organised arrays of nanometric metallic dots is reported. It consists on developing first the nanodot pattern by ion erosion on a semiconductor cover film and transferring it to a previously buried metallic layer. This procedure has been applied to Co, and the ferromagnetic behaviour of the dots at room temperature is demonstrated. [source]

Hexagonal Network Organization of Dye-Loaded Zeolite,L Crystals by Surface-Tension Driven Autoassembly,

ADVANCED FUNCTIONAL MATERIALS, Issue 17 2006
S. Yunus
Abstract Highly fluorescent dye-loaded zeolite,L crystals, approximately 1.4,,m long and 650,nm in diameter, are organized in a hexagonal network by a surface-tension-driven autoassembly process. A polydimethylsiloxane (PDMS) film presenting a trigonal ordering of spherical protuberances, including a polystyrene (PS) hexagonal network occupying their interstices, is chosen as the platform for the assembly. The overall wettability and the difference in surface tension between PDMS and PS surfaces are found to offer good conditions for ordering micrometric dye-loaded zeolite,L crystals in a 2D hexagonal network. The resulting film displays a regular hexagonal pattern of polarized fluorescence, reflecting the polarization properties of the dye molecules inserted in the parallel nanochannels of the zeolites. [source]

Development of an Optrode for Intramural Multisite Optical Recordings of Vm in the Heart

JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 11 2003
JONATHAN L. BYARS M.S.
Introduction: Optical mapping of transmembrane potential (Vm) is an important tool in the investigation of impulse propagation in the heart. It provides valuable information about spatiotemporal changes of Vm that cannot be obtained by other techniques, but it presently is limited to measurements from the heart surfaces. Therefore, the goal of this work was to develop a technique for intramural multisite optical measurements of Vm using fiberoptic technology. Methods and Results: An optrode, a bundle of thin optical fibers, was developed for measuring intramural optical signals at multiple sites in the heart. The optrode consisted of seven fibers with diameter of 225 ,m arranged in a hexagonal pattern that were used to deliver excitation light to the myocardium, to collect the emitted fluorescence, and to project the light onto a 16 × 16 array of photodiode detectors. Rabbit hearts were stained with the Vm -sensitive dye RH-237. Fluorescence was excited using a 100-W Hg lamp. Intramural action potentials were recorded at multiple sites separated by 2 mm inside the left ventricle. Signal-to-noise (RMS) ratio was 21.2 ± 12 (n = 7) without averaging or ratiometry and with negligible cross-talk (<1.9%) between the neighboring photodiodes. The size of the recording area for an individual fiber was estimated at approximately 0.8 mm. Conclusion: These data demonstrate feasibility of multisite transmural measurements of Vm without signal averaging and ratiometry. This technique might become useful in studies of transmural impulse conduction during arrhythmias and defibrillation. (J Cardiovasc Electrophysiol, Vol. 14, pp. 1196-1202, November 2003) [source]

Regional variations in the outer retina of atherinomorpha (Beloniformes, Atheriniformes, Cyprinodontiformes: Teleostei): Photoreceptors, cone patterns, and cone densities

JOURNAL OF MORPHOLOGY, Issue 3 2003
Frank Reckel
Abstract The outer retinae of adults of 13 atherinomorph species, representing nine different families, were examined by both light and electron microscopy. The retinae were investigated with respect to photoreceptor types, cone densities, and cone patterns. All data were composed to eye maps. This procedure allows an interspecific comparison of the regional differences within the outer retina among these shallow-water fish. Furthermore, for a more detailed pattern analysis nitro-blue tetrazolium chloride- (NBT)-stainings in the retina of Melanotaenia maccullochi are presented. Apart from rods, eight morphologically different cone types could be identified: short, intermediate, and long single cones, double cones (equal and unequal), triple cones (triangular and linear), and in Ameca splendens one quadruple cone. Dimensions and occurrence of photoreceptors vary among the respective species and within the retinal regions. In the light-adapted state, the cones are arranged in highly ordered mosaics. Five different cone tessellation types were found: row patterns, twisted row patterns, square patterns, pentagonal patterns, and, exclusively in Belone belone, a hexagonal pattern. In Melanotaenia maccullochi the different spectral photoreceptor classes correspond well with the distribution of morphological photoreceptor classes within the mosaic. Double cone density maxima together with a highly ordered cone arrangement usually occur in the nasal and/or ventral to ventrotemporal retina. In most of the species that were examined these high-density regions are presumed to process visual stimuli from the assumed main directions of vision, which mainly depend on feeding behavior and predator pressure. Our findings are discussed with respect to the variable behavioral and visual ecology and phylogeny of the respective species. J. Morphol. 257:270,288, 2003. © 2003 Wiley-Liss, Inc. [source]

Re-examination of organ-cultured, cryopreserved human corneal grafts after 27 years

ACTA OPHTHALMOLOGICA, Issue 2 2009
Charlotte Corydon
Abstract. Purpose:, To determine the long-term fate of cryopreserved corneas. Review of 17 organ-cultered cryopreserved corneas grafted in 1978,1979. Methods:, We measured visual acuity and refraction and performed biomicroscopy, applanation tonometry and optical pachometri (CCT). Endothelial photos were taken, cells were counted and morphology was studied. Results:, Four of 16 grafted corneas were still clear after 27 years. Mean CCT was 0.52 mm, endothelial cell density was 882 cells/mm2 and visual acuity was 0.25 or better with an average of 0.6 in the four patients. Cell morphology showed irregularity in shape and size. Conclusion:, This study shows that cryopreserved endothelium can function as well as non-frozen corneas and that a regular hexagonal pattern is not essential for corneal clarity. The four grafts showed long-term durability despite the irregularity in shape and size. [source]