Home About us Contact
|
Home About us Contact | ||
|
|
||
Concentric Rings (concentric + ring)
Selected AbstractsOptical Fourier filtering for whole lens assessment of progressive power lensesOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2000T. Spiers Summary Four binary filter designs for use in an optical Fourier filtering set-up were evaluated when taking quantitative measurements and when qualitatively mapping the power variation of progressive power lenses (PPLs). The binary filters tested were concentric ring, linear grating, grid and "chevron" designs. The chevron filter was considered best for quantitative measurements since it permitted a vernier acuity task to be used for measuring the fringe spacing, significantly reducing errors, and it also gave information on the polarity of the lens power. The linear grating filter was considered best for qualitatively evaluating the power variation. Optical Fourier filtering and a Nidek automatic focimeter were then used to measure the powers in the distance and near portions of five PPLs of differing design. Mean measurement error was 0.04 D with a maximum value of 0.13 D. Good qualitative agreement was found between the iso-cylinder plots provided by the manufacturer and the Fourier filter fringe patterns for the PPLs indicating that optical Fourier filtering provides the ability to map the power distribution across the entire lens aperture without the need for multiple point measurements. Arguments are presented that demonstrate that it should be possible to derive both iso-sphere and iso-cylinder plots from the binary filter patterns. [source] Directed Self-Assembly of Gradient Concentric Carbon Nanotube Rings,ADVANCED FUNCTIONAL MATERIALS, Issue 14 2008Suck Won Hong Abstract Hundreds of gradient concentric rings of linear conjugated polymer, (poly[2-methoxy-5-(2-ethylhexyloxy)-1,4- phenylenevinylene], i.e., MEH-PPV) with remarkable regularity over large areas were produced by controlled "stick-slip" motions of the contact line in a confined geometry consisting of a sphere on a flat substrate (i.e., sphere-on-flat geometry). Subsequently, MEH-PPV rings were exploited as a template to direct the formation of gradient concentric rings of multiwalled carbon nanotubes (MWNTs) with controlled density. This method is simple, cost effective, and robust, combining two consecutive self-assembly processes, namely, evaporation-induced self-assembly of polymers in a sphere-on-flat geometry, followed by subsequent directed self-assembly of MWNTs on the polymer-templated surfaces. [source] Diffusion-Controlled, Self-Organized Growth of Symmetric Wrinkling PatternsADVANCED MATERIALS, Issue 13 2009Jun Young Chung Symmetric instability patterns in the UV-ozone crosslinked surface of a polystyrene film grow radially outward from local defect sites in the presence of solvent vapor. The diffusion kinetics of the solvent governs the pattern morphology by establishing stress fields that favor the orientation of wrinkles in a dendritic-like spoke pattern (left) or in a target pattern consisting of concentric rings (right). [source] The potential use of scales for estimating age and growth of Mediterranean albacore (Thunnus alalunga)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2003P. Megalofonou Summary The ability to accurately estimate the age of fishes is critical for conducting stock assessments and developing fishery management policies. Scales were collected from albacore, Thunnus alalunga, caught in the Mediterranean Sea during the years 1989,1995 to estimate their age and growth. Ages, which ranged from 1+ to 6+ years, were estimated from the interpretation of the concentric rings on the scales of 473 individuals that ranged in fork length from 55.5 to 89 cm. Males reached a greater size and age than females. The relatively close agreement in the mean lengths at ages estimated by scales and other techniques constituted a preliminary verification of the method. The von Bertalanffy growth model was fitted to mean lengths at estimated ages, resulting in the following growth parameters for the combined sexes: L, = 86 cm, K = 0.4, to = ,0.8 years. Parameter estimates were in agreement with what is known about life history of the species in the Mediterranean. Moreover, the growth rates were consistent with length increment observations from five tag returns, which lend support to our working hypothesis that the scale-rings are annual structures. When the Mediterranean albacore growth parameters were compared with those of Atlantic Ocean albacore using scale age estimates, there were significant differences between the two populations, and Mediterranean albacore remain significantly smaller than Atlantic Ocean albacore. [source] Diffractive optical elements with square concentric rings of equal widthMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 4 2010Javier Alda Abstract A diffractive optical element having equal-width concentric square rings is analyzed in this article. This constant width makes possible its realization using spatial light modulators or square pixels phase screens. It allows a simple analytical treatment, and the element is also simulated using the Rayleigh-Sommerfeld approach. An experimental verification of its performance has been compared with the simulated results. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52:930,934, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25065 [source] Left-handed microstrip lines with multiple complementary split-ring and spiral resonatorsMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 6 2007-Bengin, V. Crnojevi Abstract Negative-permeability sub-wavelength particles, namely split-ring resonators and spiral resonators, are compared and their performances analyzed for a different number of concentric rings and spiral turns, respectively. Left-handed lines are designed, fabricated, and measured that use multiple complementary split-ring and spiral resonators. More compact structures are obtained, with improved characteristics. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1391,1395, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI.10.1002/mop.22427 [source] Comprehensive classification of the auditory sensory projections in the brain of the fruit fly Drosophila melanogasterTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 3 2006Azusa Kamikouchi Abstract We established a comprehensive projection map of the auditory receptor cells (Johnston's organ neurons: JONs) from the antennae to the primary auditory center of the Drosophila brain. We found 477 ± 24 cell bodies of JONs, which are arranged like a "bottomless bowl" within the auditory organ. The target of the JONs in the brain comprises five spatially segregated zones, each of which is contributed by bundles of JON axons that gradually branch out from the antennal nerve. Four zones are confined in the antennal mechanosensory and motor center, whereas one zone further extends over parts of the ventrolateral protocerebrum and the subesophageal ganglion. Single-cell labeling with the FLP-out technique revealed that most JONs innervate only a single zone, indicating that JONs can be categorized into five groups according to their target zones. Within each zone, JONs innervate various combinations of subareas. We classified these five zones into 19 subareas according to the branching patterns and terminal distributions of single JON axons. The groups of JONs that innervate particular zones or subareas of the primary auditory center have their cell bodies in characteristic locations of the Johnston's organ in the antenna, e.g., in concentric rings or in paired clusters. Such structural organization suggests that each JON group, and hence each zone of the primary auditory center, might sense different aspects of sensory signals. J. Comp. Neurol. 499:317,356, 2006. © 2006 Wiley-Liss, Inc. [source] Radial secondary growth and formation of successive cambia and their products in Ipomoea hederifolia L. (Convolvulaceae)BOTANICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 1 2008KISHORE S. RAJPUT Ipomoea hederifolia stems increase in thickness using a combination of different types of cambial variant, such as the discontinuous concentric rings of cambia, the development of included phloem, the reverse orientation of discontinuous cambial segments, the internal phloem, the formation of secondary xylem and phloem from the internal cambium, and differentiation of cork in the pith. After primary growth, the first ring of cambium arises between the external primary phloem and primary xylem, producing secondary phloem centrifugally and secondary xylem centripetally. The stem becomes lobed, flat, undulating, or irregular in shape as a result of the formation of both discontinuous and continuous concentric rings of cambia. As the formation of secondary xylem is greater in one region than in another, this results in the formation of a grooved stem. Successive cambia formed after the first ring are of two distinct functional types: (1) functionally normal successive cambia that divide to form secondary xylem centripetally and secondary phloem centrifugally, like other dicotyledons that show successive rings, and (2) abnormal cambia with reverse orientation. The former type of successive rings originates from the parenchyma cells located outside the phloem produced by previous cambium. The latter type of cambium develops from the conjunctive tissue located at the base of the secondary xylem formed by functionally normal cambia. This cambium is functionally inverted, producing secondary xylem centrifugally and secondary phloem centripetally. In later secondary growth, xylem parenchyma situated deep inside the secondary xylem undergoes de-differentiation, and re-differentiates into included phloem islands in secondary xylem. © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society, 2008, 158, 30,40. [source] | |||||||||||||