The Fractal Properties of Retinal Vessels: Embryological and Clinical Implications

Total Page:16

File Type:pdf, Size:1020Kb

The Fractal Properties of Retinal Vessels: Embryological and Clinical Implications Eye (1990) 4, 235-241 The Fractal Properties of Retinal Vessels: Embryological and Clinical Implications MARTIN A. MAINSTER Kansas City, Kansas, USA Summary The branching patterns of retinal arterial and venous systems have characteristics of a fractal, a geometrical pattern whose parts resemble the whole. Fluorescein angio­ gram collages were digitised and analysed, demonstrating that retinal arterial and venous patterns have fractal dimensions of 1.63 ± 0.05 and 1. 71 ± 0.07, respectively, consistent with the 1.68 ± 0.05 dimension of diffusion limited aggregation. This find­ ing prompts speculation that factors controlling retinal angiogenesis may obey Laplace's equation, with fluctuations in the distribution of embryonic cell-free spaces providing the randomness needed for fractal behaviour and for the unique­ ness of each individual's retinal vascular pattern. Since fractal dimensions charac­ terise how completely vascular patterns span the retina, they can provide insight into the relationship between vascular patterns and retinal disease. Fractal geometry offers a more accurate description of ocular anatomy and pathology than classical geometry, and provides a new language for posing questions about the complex geo­ metrical patterns that are seen in ophthalmic practice. Inspection and photography of ophthalmo­ ing patterns.4,5 Branching patterns are com­ scopic images are vital to modern ophthalmic mon in nature, occurring in such diverse practice, but analysis of those images remains phenomena as river tributary networks, light­ largely a subjective process. In otht:r disci­ ning discharge pathways, and erosion chan­ plines, images are routinely broken into a nels in porous media. Retinal arteries and large number of tiny picture elements, called veins have similar branching patterns. pixels, in a process known as digitisation. A branching pattern may have two impor­ Computers can digitise, enhance and analyse tant fractal properties. First, it may be self­ images. For example, computerised image similar over a limited range of length scales. enhancement can restore ophthalmoscopic That is, it may have similar detail (roughness, detail lost due to ocular media haziness.! branching, etc) when inspected at different Computers can also analyse images, measur­ magnifications, so that small parts of the pat­ ing structures2 or even quantitating spatial tern exhibit the pattern's overall structure. information in much the same way that con­ Second, the pattern may decrease in density trast sensitivity testing characterises an indi­ as it grows in size. Self-similarity and decreas­ vidual's visual performance. 3 ing density are two important characteristics Fractal analysis provides a different way of of fractals, shapes whose parts resemble their analysing digitised images, one that is particu­ whole.4.8 larly useful when they contain branch- Because of self-similarity, fractal properties Correspondence to: Martin A. Mainster, M.D., Ph.D., Department of Ophthalmology, Kansas University Medical Center, 39th and Rainbow Boulevard, Kansas City, Kansas 66103, USA. 236 MARTIN A. MAINSTER differ from those of the simple lines and produced by dielectric breakdown,to electro­ curves of ordinary Euclidean geometry. Since deposition,!! viscous fingering,5,!2.!5 and a magnifying a fractal only reveals more detail, variety of other physical phenomena.4-8 They length is not a useful parameter for describing also resemble human retinal arterial and a fractal. For example, a straight line has the venous patterns. Since DLA behaviour could same length regardless of the size of the scale offer insight into the relationship between ret­ used to measure it. Fractals exhibit more inal angiogenesis and the geometry of mature detail at higher magnification, however, so retinal vessels, retinal vessel patterns were their length increases as the size of the studied to determine if they have fractal measuring scale decreases. A coastline is a properties and a fractal dimension consistent simple example of this principle.4,5 An ant with DLA. crawling along the convoluted edge of a shoreline travels a much greater distance Methods between two locations than an automobile Arterial and venous patterns were identified driving between the locations. in the wide-field fluorescein angiogram col­ Although length is not a useful measure of a lages!6 of six individuals with early back­ fractal, other parameters such as the fractal ground diabetic retinopathy. A map of retinal dimension.(D) are valuable descriptors. The arteries and veins of each individual was pre­ fractal dimension describes a structure's con­ pared for vessels larger than capillaries. volutedness. Unlike ordinary Euclidean Arteries and veins were digitised separately, dimensions that are integers, fractal dimen­ with the optic disk centred on a two-dimen­ sions are fractions. For example, the Eucli­ sional 1000 x 1000 array of square pixels. dean dimension (E) of a straight line, an area Figures 1-3 show the retinal vessel map and (e.g. the retinal surface),. and a volume (e.g. digitised arterial and venous patterns of the the vitreous gel) are 1, 2, and 3, respectively. left eye of a 57 year old woman. Pixel size on An irregular but relatively smooth curve has a the retina was 20 !lm, assuming an average fractal dimension near one (e.g. 1.2), whilst a optic disc diameter of 1.5 mm in retinal highly tortuous curve has a fractal dimension photographs. near two (e.g. 1.8). Digitising an arterial or venous pattern con­ In a practical sense, a pattern's fractal sists of determining whether each pixel is dimension describes how thoroughly it fills occupied by any part of the vascular pattern. space. For example, squares or circles can Each black square or circle in Figure 2 or 3 completely cover a 2-dimensional space (sur­ represents a pixel occupied by part of the face), and their fractal dimension is two. arterial or venous pattern, respectively. The Branching linear structures span 2-dimen­ remaining pixels were vacant of vascular sional spaces less completely and their fractal detail and are not shown. dimension is less than two. As a 2-dimen­ There are several ways to determine the sional pattern's fractal dimension increases fractal dimension of a digitised retinal vas­ toward two, the structure covers its surface cular pattern.5.7,!7.20 The simplest method is to more completely, and its density drops off construct a series of circles of different radii more slowly as the pattern increases in size. centred about the optic nerve, and count the Decreasing fractal density may have a power­ 'mass' (number) of occupied pixels within a law dependence, with an exponent D-E, circle of a given radius. If the logarithm of the where D is the fractal dimension of the pat­ pixel mass within a circle of a given radius is tern, and E is the Euclidean dimension of the then plotted against the logarithm of the rad­ space containing it. ius of the circle, the slope of the log-log plot is The diffusion-limited aggregation (DLA) D, the fractal dimension of the pattern. A model of Witten and Sander has helped to fractal dimension can also be determined explain how growth and structure are related from pixel density, mass/area, where area is in fractal branching patterns.6.9 Computer­ altered to account for projection of the curved generated DLA patterns are similar in retina onto a flat ophthalmoscopic image. appearance and fractal dimension to patterns Mapping, digitisation and analysis were THE FRACTAL PROPERTIES OF RETINAL VESSELS 237 I , ' "'4. ,- ., .... " , -,.-r-\ ..., -f .....f � � \ \,'\ \ \, I 1------_ "- . ,( , \ ' , \ I \,t' ... , , ,. " , I I _./_ _ ., ,, I , I , I , Fig. 1. Retinal arterial (---) and venous (- ----) systems in the fluoresceinangiogram collage of the left eye of a 57 year old woman. The optic nerve is in the centre of the branching pattern, with the macula to its right. carried out manually, and required over 20 Results hours to analyse a single angiogram. In the Retinal vascular density decreases from the future, video retinal photography systems will central to peripheral retina, following a have the required 1024 x 1024 (or, optimally, power-law relationship with mean arterial and 2048 x 2048) pixel resolution needed for this venous fractal dimensions of 1.63±0,05 and type of analysis. Computer algorithms then 1.71±0,07, respectively (± std). The differ­ could be developed for comparing different ence between arterial and venous fractal angiogram phases to differentiate between dimensions was statistically significant arterial and venous systems and for compoun­ (P<0.05, two-tailed t test). Fractal dimen­ ding fractal dimensions by methods5-7,17-20 such sions change by less than 3% with a correction as the mass-radius relationship discussed for retinal curvature estimated from emme­ above. tropic model eye parameters, 21 Fractal dimen- 238 MARTIN A. MAINSTER Fig. 2. Retinal arterial patternfor the individual in Fig. 1, digitised on a 1000 x 1000 array of square 20 !J.I11pixels. The optic nerve is in the centre of the branching pattern, with the macula to its right. Each black square is a pixel occupied by part of the arterial system (squares may be contiguous with adjacent squares). The remaining pixels are vacant of vascular detail and not shown. The fractal dimension for the arterial pattern is 1.61. sions from fluorescein angiogram analysis density (D = 1.63). In other words, the retina should be more sensitive to vascular non-per­ is spanned most completely by the capillary fusion than narrowing. system, less completely by the venous system, It is interesting to note that earlier mor­ and least completely by the arterial system. phologic data22 on retinal capillary density can be re-expressed in a power-law relationship, Discussion yielding a fractal dimension of 1.82. Thus, Retinal arterial and venous patterns have a proceeding outward from the optic disc to the structure and fractal dimension similar to peripheral retina, capillary density drops off those of two-dimensional DLA and related more slowly than venous density (D = 1.71), phenomena.
Recommended publications
  • Project-Team Virtual Plants Modeling Plant Morphogenesis from Genes To
    INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET EN AUTOMATIQUE Project-Team Virtual Plants Modeling plant morphogenesis from genes to phenotype Sophia Antipolis THEME BIO c t i v it y ep o r t 2005 Table of contents 1. Team 1 2. Overall Objectives 2 2.1. Overall Objectives 2 3. Scientific Foundations 2 3.1. Analysis of structures resulting from meristem activity 2 3.2. Meristem functioning and development 3 3.3. A software platform for plant modeling 4 4. New Results 4 4.1. Analysis of structures resulting from meristem activity 4 4.1.1. Analysis of longitudinal count data and underdispersion 4 4.1.2. Growth synchronism between Aerial and Root Systems 4 4.1.3. Changes in branching structures within the whole plants 5 4.1.4. Growth components in trees 5 4.1.5. Markov switching models 5 4.1.6. Diagnostic tools for hidden Markovian models 5 4.1.7. Hidden Markov tree models for investigating physiological age within plants 6 4.1.8. Branching processes for plant development analysis 6 4.1.9. Self-similarity in plants 6 4.1.10. Reconstruction of plant foliage density from photographs 6 4.1.11. Fractal analysis of plant geometry 6 4.1.12. Light interception by canopy 7 4.1.13. Heritability of architectural traits 7 4.2. Meristem functioning and development 8 4.2.1. 3D surface reconstruction and cell lineage detection in shoot meristems 8 4.2.2. Simulation of auxin fluxes in the mersitem 8 4.2.3. Dynamic model of phyllotaxy based on auxin fluxes 8 4.2.4.
    [Show full text]
  • An Introduction Into Ecological Modelling for Students, Teachers & Scientists
    Modelling Complex Ecological Dynamics . Fred Jopp l Hauke Reuter l Broder Breckling Editors Modelling Complex Ecological Dynamics An Introduction into Ecological Modelling for Students, Teachers & Scientists Title Drawings by Melanie Trexler Foreword by Sven Erik Jørgensen & Donald L. DeAngelis Editors Dr. Fred Jopp Dr. Hauke Reuter Department of Biology Department of Ecological Modelling University of Miami Leibniz Center for Tropical Marine Ecology P.O. Box 249118 GmbH (ZMT) Coral Gables, FL 33124 Fahrenheitstraße 6 USA 28359 Bremen [email protected] Germany [email protected] Dr. Broder Breckling General and Theoretical Ecology Center for Environmental Research and Sustainable Technology (UFT) University of Bremen Leobener St. 28359 Bremen Germany [email protected] ISBN 978-3-642-05028-2 e-ISBN 978-3-642-05029-9 DOI 10.1007/978-3-642-05029-9 Springer Heidelberg Dordrecht London New York Library of Congress Control Number: 2011921703 # Springer-Verlag Berlin Heidelberg 2011 This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable to prosecution under the German Copyright Law. The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protec- tive laws and regulations and therefore free for general use.
    [Show full text]
  • Kaleidoscope Pdf, Epub, Ebook
    KALEIDOSCOPE PDF, EPUB, EBOOK Salina Yoon | 18 pages | 21 Nov 2012 | Little, Brown & Company | 9780316186414 | English | New York, United States Kaleidoscope PDF Book Top 10 Gifts Top 10 Gifts. Best Selling. English Language Learners Definition of kaleidoscope. Love words? Van Cort. Kaleidoscope Necklace, Garnet Saturn by the Healys. Most handmade kaleidoscopes are now made in India, Bangladesh, Japan, the USA, Russia and Italy, following a long tradition of glass craftsmanship in those countries. Enjoy the Majestic Colors of a Vintage Kaleidoscope In , David Brewster invented the kaleidoscope, and most people appreciate the colorful images it reflects. Wikimedia Commons. An early version had pieces of colored glass and other irregular objects fixed permanently and was admired by some Members of the Royal Society of Edinburgh , including Sir George Mackenzie who predicted its popularity. Interactive exhibit modules enabled visitors to better understand and appreciate how kaleidoscopes function. Color Spirit Kaleidoscope in Purple. What should you look for when buying preowned kaleidoscopes? Manufacturers and artists have created kaleidoscopes with a wide variety of materials and in many shapes. The last step, regarded as most important by Brewster, was to place the reflecting panes in a draw tube with a concave lens to distinctly introduce surrounding objects into the reflected pattern. Whether you need a Christmas present, a birthday gift or a token of appreciation for the person who has everything, a kaleidoscope is the perfect choice. Name that government! List View. Please provide a valid price range. Not Specified. The community is fighting to save it," 2 July Also crucial is Murphy's particular knack for using music and color to convey the hothouse longings of her characters; heady metaphors served in the atonal jangle of post punk or the throbbing kaleidoscope of strobe lights at a house party.
    [Show full text]
  • From the Chair from His Enemies by Using Little-Known Causeways on the Norman Coast Dear Pedometricians, 4
    Issue 21 March 2007 Commission 1.5 Pedometrics, Div. 1 of the International Union of Soil Sciences (IUSS) Chair: Murray Lark Vice Chair & Editor: Budiman Minasny From the Chair from his enemies by using little-known causeways on the Norman coast Dear Pedometricians, 4. Airphotographs 5. Articles written in the Journal of the Linnean I have just finished reading Society of Caen by a 19th Century priest from a a biography of Desmond parish in Normandy who had an interest in geology. Bernal, a founding father 6. A few core samples obtained from selected of the crystallography of beaches in raids by special forces. macromolecules, a 7. Accounts of a 14th Century legal dispute over farsighted exponent of taxes that allowed him to identify silted-up harbours. science policy, and a Marxist polymath. During Continued next page ….. the Second World War Bernal played a leading role in preparing for the Normandy landings, and I I NSIDE T HIS I SSUE was interested to learn that one of the problems that 1. From the Chair he faced was a classical one in pedometrics. 2. Working Group on Digital Soil Mapping 3. Chance and vision on the road to Pedometrics The question was how to predict the trafficability of 4. The Comte de Buffon beaches for military vehicles, given that they were 5. Buffon’s needle held by the enemy and could not be inspected at 6. Soil Boundaries leisure. If you read Richard Webster's article in this 7. Best paper in pedometrics issue of Pedometron you will see that essentially the 8.
    [Show full text]
  • Turbulence Simulations: Multiscale Modeling and Data-Intensive
    Turbulence simulations: multiscale modeling and data-intensive computing methodologies by Jason Graham A dissertation submitted to The Johns Hopkins University in conformity with the requirements for the degree of Doctor of Philosophy. Baltimore, Maryland January, 2014 c Jason Graham 2014 All rights reserved Abstract In this two part work, methodologies for the multiscale modeling of complex tur- bulent flows and data-intensive computing strategies for large-scale turbulent simu- lations are developed and presented. The first part of this thesis is devoted to the simulation of turbulent flows over objects characterized by hierarchies of length-scale. Flows of this type present special challenges associated with the cost of resolving small-scale geometric elements. During large eddy simulation (LES), their effects on the resolved scales must be captured realistically through subgrid-scale models. Prior work performed by Chester et al. [21] proposed a technique called renormal- ized numerical simulation (RNS), which is applicable to objects that display scale- invariant geometric (fractal) properties. The idea of RNS is similar to that of the dynamic model used in LES to determine model parameters for the subgrid-stress tensor model in the bulk of the flow. In RNS, drag forces from the resolved elements that are obtained during the simulation are re-scaled appropriately by determining drag coefficients that are then applied to specify the drag forces associated with the subgrid-scale elements. In the current work we introduce a generalized framework for ii ABSTRACT describing and implementing the RNS methodology thereby extending the method- ology first presented by Chester et al. [21]. Furthermore, we present various other possible practical implementations of RNS that differ on important, technical aspects related to 1) time averaging, 2) spatial localization, and 3) numerical representation of the drag forces.
    [Show full text]
  • ABSTRACT ANDERSON, KAREN MILLER. Leveraging Technology
    ABSTRACT ANDERSON, KAREN MILLER. Leveraging Technology and Creativity among Self- Employed Textile Artists and Designers Through the Use of Geometric Software. (Under the direction of Dr. George L. Hodge and Dr. Cynthia L. Istook.) Self-employed textile artists and designers have many obstacles to overcome; among these obstacles are the use of technology in their work and locating affordable software applications that can be used in their studios. There are a number of specifi c software applications used in industry for textile design. While these systems are extremely powerful and function well for the purpose for which they were designed, they are often expensive, infl exible, and proprietary, which may limit collaboration efforts as well as production capabilities. This very fact may act as a deterrent to the use and adoption of the technology by self-employed artists and designers. There are many software applications that were developed to create patterns for disciplines other than textiles. These programs may have potential for use in textile design and may well be more affordable to the microentrepreneur. Because these applications are mathematical and scientifi c-based software applications, designers are likely to be unaware of their availability and application to textile design. The purpose of this study was twofold. One was to identify and survey the many geometric software applications that have been developed to create pattern and design that have potential for use in the textile industry. The exploration of these applications not only increases awareness of other disciplines, it extends the artist’s vision and creativity. All of the software applications are readily available as freeware, shareware or off-the-shelf.
    [Show full text]
  • Project-Team Virtual Plants Modeling Plant Morphogenesis at Different
    INSTITUT NATIONAL DE RECHERCHE EN INFORMATIQUE ET EN AUTOMATIQUE Project-Team Virtual Plants Modeling plant morphogenesis at different scales, from genes to phenotypes Sophia Antipolis THEME BIO d© ctivity eport 2006 Table of contents 1. Team ....................................................................................... 1 2. Overall Objectives ........................................................................... 1 2.1. Overall Objectives 1 3. Scientific Foundations ....................................................................... 2 3.1. Analysis of structures resulting from meristem activity 2 3.2. Meristem functioning and development 3 3.3. OpenAlea: An open-software platform for plant modeling 3 4. Software .................................................................................... 4 4.1. VPlants 4 4.2. OpenAlea 4 5. New Results ................................................................................. 5 5.1. Analysis of structures resulting from meristem activity 5 5.1.1. Analysis of the relative extents of preformation and neoformation in tree shoots by a deconvolution method 5 5.1.2. Analysis of longitudinal count data and underdispersion 6 5.1.3. Changes in branching structures within the whole plants 6 5.1.4. Growth components in trees 7 5.1.5. Markov switching models 7 5.1.6. Diagnostic tools for hidden Markovian models 7 5.1.7. Methods for exploring the segmentation space for multiple change-point models 8 5.1.8. Hidden Markov tree models for investigating physiological states within plants 9 5.1.9. Branching processes for plant development analysis 9 5.1.10. Self-similarity in plants 9 5.1.11. Reconstruction of plant foliage density from photographs 10 5.1.12. Fractal analysis of plant geometry 11 5.1.13. Light interception by canopy 11 5.1.14. Heritability of architectural traits 12 5.1.15. Lumped processes constructed from Markov chains 13 5.1.16.
    [Show full text]
  • PDF Document
    Assignment 5 – Fractals Maximum Points = 50 The purpose of this lab is to focus on the study of classes, objects, GUI, and recursion. “A fractal is a geometric shape that can be made up of the same pattern repeated at different scales and orientations. The nature of a fractal lends itself to a recursive definition. Interest in fractals has grown immensely in recent years, largely due to Benoit Mandelbrot, a Polish mathematician born in 1924. He demonstrated that fractals occur in many places in mathematics and nature. Computers have made fractals much easier to generate and investigate. Over the past quarter century, the bright, interesting images that can be created with fractals have come to be considered as much an art form as a mathematical interest.” [Java Software Solutions 6th Edition, Lewis & Loftus, pg. 604] One particular example of a fractal is called the “H tree (so called because its first two steps resemble the letter "H"). They can be constructed by starting with a line segment of arbitrary length, drawing two shorter segments at right angles to the first through its endpoints, and continuing in the same vein, reducing (dividing) the length of the line segments drawn at each stage by √2. Surprisingly, continuing this process will eventually come arbitrarily close to every point in a rectangle, or in other words, the H-fractal is a space-filling curve.[2] It is also an example of a fractal canopy, in which the angle between neighboring line segments is always 180 degrees…. The H tree is commonly used in VLSI design as a clock distribution network for routing timing signals to all parts of a chip with equal propagation delays to each part.[3] For the same reason, the H tree is used in arrays of microstrip antennas in order to get the radio signal to every individual microstrip antenna with equal propagation delay.
    [Show full text]
  • Fractal Series by John Driscoll Rough Draft 10/22/2012
    Fractal Series by John Driscoll Rough Draft 10/22/2012 Contents 1. Introduction 2. L-Systems (2D and 3D models) 3. Fractal Dimension and Box-Counting Dimension 4. Box-Counting Dimension applied (coastlines, GIS, biology etc.) 5. Conclusion 1. Introduction FIG. 1.1. Lightning, displaying a fractal branching structure. Clouds are not spheres, mountains are not cones, coastlines are not circles, and bark is not smooth, nor does lightning travel in a straight line (Benoit Mandelbrot) An intuitive understanding of the spatial implications of fractals is described by Benoit Mandel- brot as analogous to a ball of thread, “To an observer placed far away, (a ball of thread) appears as a zero dimensional figure: a point. As seen from a distance of 10 cm resolution, the ball of thread is a three dimensional figure. At 10 mm, it is a mess of one-dimensional threads” (Man- delbrot 1983). Please open and run the NetLogo model labelled simple-ball-of-thread.nlogo for a demonstration of this somewhat paradoxical description of the ‘spatial implications of frac- tals’. Exploring Complexity Exploring complexity and Complex adaptive systems (CAS) often involves feedback dynamics. Feedback is a self-referential property of CAS where the state of a system informs itself in some way. Fractals are basic examples of feedback. A fractal is a shape that re-occurs at ever decreas- ing or increasing scales, so that as we zoom in or out the same shape re-emerges over and over again. The images produced by turning a kaleidoscope demonstrate this idea of feedback. The image in a kaleidoscope is reflected over and over again — a feedback loop — but also forms a larger image which is a version of itself at a different scale.
    [Show full text]
  • P. Prusinkiewicz and A. Lindenmayer, the Algorithmic Beauty of Plants
    Aristid Lindenmayer 1925–1989 Przemyslaw Prusinkiewicz Aristid Lindenmayer The Algorithmic Beauty of Plants With James S. Hanan F. David Fracchia Deborah Fowler MartinJ.M.deBoer Lynn Mercer With 150 Illustrations, 48 in Color This edition of The Alogirthmic Beauty of Plants is the electronic version of the book that was published by Springer-Verlag, New York, in 1990 and reprinted in 1996. The electronic version has been produced using the orig- inal LATEX files and digital illustrations. c 2004 Przemyslaw Prusinkiewicz All rights reserved. Front cover design: The roses in the foreground (Roses by D. R. Fowler, J. Hanan and P. Prusinkiewicz [1990]) were modeled using L-systems. Dis- tributed ray-tracing with one extended light source was used to simulate depth of field. The roses were placed on a background image (photgraphy by G. Rossbach), which was scanned digitally and post-processed. Preface The beauty of plants has attracted the attention of mathematicians for Mathematics centuries. Conspicuous geometric features such as the bilateral sym- and beauty metry of leaves, the rotational symmetry of flowers, and the helical arrangements of scales in pine cones have been studied most exten- sively. This focus is reflected in a quotation from Weyl [159, page 3], “Beauty is bound up with symmetry.” This book explores two other factors that organize plant structures and therefore contribute to their beauty. The first is the elegance and relative simplicity of developmental algorithms, that is, the rules which describe plant development in time. The second is self-similarity,char- acterized by Mandelbrot [95, page 34] as follows: When each piece of a shape is geometrically similar to the whole, both the shape and the cascade that generate it are called self-similar.
    [Show full text]
  • Turbulence Generated by Fractal Trees
    Turbulence generated by Fractal Trees PIV Measurements and Comparison with numerical Data Master Thesis Submitted by: Marc Dreissigacker Date of Birth: September 26, 1990 Course: Physikalische Ingenieurwissenschaft First Supervisor: Prof. Dr. sc. techn. habil. Jörn Sesterhenn Second Supervisor: Dr.-Ing. Thomas Engels Date: May 12, 2017 Eidesstattliche Erklärung Hiermit erkläre ich, dass ich die vorliegende Arbeit selbstständig und eigen- händig sowie ohne unerlaubte fremde Hilfe und ausschließlich unter Ver- wendung der aufgeführten Quellen und Hilfsmittel angefertigt habe. Statutory Declaration I hereby declare that I have authored this thesis independently, that I have not used other than the declared sources / resources, and that I have explic- itly marked all material which has been quoted either literally or by content from the used sources. Berlin, Marc Dreissigacker CONTENTS Abstract xv 1 Introduction 17 2 Literature Review: Fractal Tree Turbulence 19 3 Fractal Trees 23 3.1 Design & Choice of Parameters . 24 3.1.1 First Approach in MATLAB . 25 3.1.2 Vortex Shedding Frequency and Branch Diameters . 28 3.1.3 Generation of 3D-STL-mask with FLUSI . 30 3.2 3D-printing and Assembly ..................... 33 3.2.1 Preparation in SOLIDWORKS . 33 3.2.2 Printing the H-tree ..................... 35 3.2.3 Printing the Pyramid- & Spherical Tree . 38 4 Experimental Setup & Validation 41 4.1 Windtunnnel ............................. 41 4.1.1 Blockage ........................... 43 4.2 PIV System .............................. 44 4.3 Analysis Software PIVLAB ..................... 46 4.4 Validation Cases ........................... 47 5 Experimental Results 55 5.1 Pyramid-tree ............................. 55 5.2 Large Branch of the spherical tree . 64 5.3 Small Branch of the spherical tree .
    [Show full text]
  • Properties of Pruned, Binary, Planar Fractal Trees
    Properties of Pruned, Binary, Planar Fractal Trees Rita Gnizak Department of Mathematics and Computer Science, Fort Hays State University 1 Big whorls have little whorls, That feed on their velocity; And little whorls have lesser whorls, And so on to viscosity. Lewis F. Richardson 2 Contents 1 Introduction 5 2 Background 5 2.1 Fractal Trees . 5 2.2 The Canopy . 7 2.3 Space-filling Trees . 9 2.4 Hausdorff Dimension . 9 2.5 Pruned Trees . 10 3 Counting Forbidden Words 13 4 Calculating Dimension of Pruned Trees 15 5 Pruning Space-filling Trees 17 6 Further Study 23 7 Appendix 24 7.1 Appendix I: Mathematica Coding for Pruned Trees . 24 3 Abstract Symmetric, planar, binary branching trees have been extensively de- scribed by Benoit Mandelbrot and Michael Frame [7], however, little is known about the effects that pruning has on the properties of these trees. Investigation of self-contact, connectedness, fractal dimension, and the space-filling properties of pruned fractal trees has lead us to the creation of a new method for calculating fractal dimension of pruned trees as well as a proof that the space-filling property of the special 90◦ and 135◦ trees is lost when any finite sequence of a transformation is forbidden. 4 1 Introduction In 1957, Alan W. Watts in his book The Way of Zen wrote, The Tao is a certain kind of order, and this kind of order is not quite what we call order when we arrange everything geometrically in boxes, or in rows. That is a very crude kind of order, but when you look at a plant it is perfectly obvious that the plant has order.
    [Show full text]