Archive for the 'Gallery' Category

Canon 1 a 2

xantox, 18 January 2009 in Gallery

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In the enigmatic Canon 1 a 2 from J. S. Bach’s “Musical Offering” (1747) (also known as “crab canon” or “canon cancrizans”), the manuscript shows a single score, whose beginning joins with the end. This space is topologically equivalent to a bundle of the line segment over the circle, known as a Möbius strip. The simultaneous performance of the deeply related forward and backward paths gives appearance to two voices, whose symmetry determines a reversible evolution. A musical universe is built and then is “unplayed” back into silence.1

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  1. Animation created in POV-Ray by Jos Leys. Music performed by xantox with Post Flemish Harpsichord, upper manual. []
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Atomic orbital

xantox, 20 April 2008 in Gallery

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Time evolution of an hydrogenic (single-electron) atomic orbital with quantum numbers | 3, 2, 1 > according to the Schrödinger equation (colors represent phase). In atomic matter, electrons orbiting the nucleus do not follow any determined classical path, but exist for each quantum state within an orbital, which can be visualized as a cloud of the probabilities of observing the electron at any given location and time.

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  1. © Dean E. Dauger []
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Marangoni flow

xantox, 6 January 2008 in Gallery

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Liquid surfaces are pulled by the intermolecular forces, which are unbalanced on the boundary, producing surface tension. When liquid layers with different surface tension get in contact, these forces cause a flow, also known as Marangoni effect,1 which is also the origin of the beautiful patterns found in the ancient japanese art of Suminagashi (”floating ink”). In this image, a film of oleic acid surfactant (with surface tension 32.5 mN/m) quickly spreads spontaneously about 2.5 mm over a layer of glycerol (with surface tension 63.4 mN/m). Both Marangoni and capillary stresses cause variations in the film thickness, leading to dendritic flow patterns. The contour lines are interference fringes.

Branching Dynamics in Surfactant Driven Flow

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  1. C. Marangoni, “Über die Ausbreitung der Tropfen einer Flüssigkeit auf der Oberfläche einer anderen”, Ann. Phys. Leipzig, 143:337-354 (1871). []
  2. © B. J. Fischer, A. A. Darhuber, S. M. Troian, Department of Chemical Engineering, Princeton University []
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Water Clouds

xantox, 17 September 2007 in Gallery

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Terrestrial clouds are the result of extraordinarily complex interactions between water and air, with several feedback mechanisms combining the effects of fluid dynamics and thermodynamics.1

© 2004 Sarah Robinson & Jean Hertzberg, University of Colorado
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The kind of convective clouds known as cumulus are produced by the vertical winds occurring in regions of warm moist air, per Archimedes principle. This rapid lifting results in adiabatic expansion and cooling, and consequent accretion of water droplets. The irregular distribution of droplets scatters sunlight geometrically in all directions, producing a bright white appearance like in snow, decaying into gray shades as per their optical thickness. Each cloud is short-lived, lasting approximately 15 minutes in average.


  1. H. R. Pruppacher, J. D. Klett, “Microphysics of clouds and precipitation“, Springer (1997); R. A. Houze, “Cloud Dynamics“, Academic Press (1994) []
  2. © 2004 Sarah Robinson, Flow Visualization Course, University of Colorado []
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Classical Molecules

xantox, 9 July 2007 in Gallery

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Animation showing the interaction of four charges of equal mass1, two positive and two negative, in the approximation of classical electromagnetism. The particles interact via the Coulomb force, mediated by the electric field represented in yellow. A repulsive “Pauli force” of quantum mechanical origin, which becomes very large at a critical distance of about the radius of the spheres shown in the animation, keeps the charges from collapsing into the same point. Additionally, the motion of the particles is damped by a term proportional to their velocity, allowing them to “settle down” into stable (or meta-stable) states.

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When the charges are allowed to evolve from the initial state, the first thing that happens (very quickly, since the Coulomb attraction between unbalanced charges is very large) is that they pair off into dipoles. Thereafter, there is still a (much weaker) interaction between neighboring dipoles (van der Waals force). Although in principle it can be either repulsive or attractive, there is a torque that rotates the dipoles so that it is attractive, eventually bringing the two dipoles together in a bound state. This mechanism binds the molecules of some substances into a solid.


  1. © 2004 MIT TEAL/Studio Physics Project, John Belcher []
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DNA replication

xantox, 3 July 2007 in Gallery

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Using computer animation1 based on molecular research2 it is possible to see how DNA is actually copied in living cells. This animation shows the “assembly line” of biochemical machines which pull apart the DNA double helix and output a copy of each strand. The DNA to be copied enters the whirling blue molecular machine, called helicase, which spins it as fast as a jet engine as it unwinds the double helix into two strands. One strand is copied continuously, and can be seen spooling off on the other side. Things are not so simple for the other strand, because it must be copied backwards, so it is drawn out repeatedly in loops and copied one section at a time. The end result is two new DNA molecules.

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  1. Drew Berry, “DNA animation”, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Australia (courtesy of the author). © 2007 Howard Hughes Medical Institute []
  2. T. A. Baker, S. P. Bell, “Polymerases and the Replisome: Machines within Machines“, Cell, 92:295-305 (1998); K. P. Lemon, A. D. Grossman, “Movement of Replicating DNA through a Stationary Replisome“, Molecular Cell, 6, 6:1321-1330 (2000); M. R. Singleton, M. R. Sawaua, T. Ellenberger, D. B. Wigley, “Crystal structure of T7 gene 4 ring helicase indicates a mechanism for sequential hydrolysis of nucleotides“, Cell 101:589-600 (2000); D. S. Johnson, L. Bai, B. Y. Smith, S. S. Patel, M. D. Wang, “Single-Molecule Studies Reveal Dynamics of DNA Unwinding by the Ring-Shaped T7 Helicase“, Cell 129, 7:1299-1309 (2007). []
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Observation of Jupiter moons, March 1613

xantox, 22 April 2007 in Gallery

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In 1610 Galileo published the astonishing report of his first telescope observations,1 containing detailed drawings of the moon surface and his discovery of four “planets” orbiting around Jupiter (now known as the “Galilean Moons”). About two years later, he wrote an even more precise observation2 with more than a hundred drawings of their relative daily positions. This animation3 brings back life to Galileo’s observation, as made in Florence, March 1613.

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  1. G. Galilei, “Sidereus Nuncius” (”The Starry Messenger“) (1610) []
  2. G. Galilei, “Istoria e Dimostrazioni intorno alle Macchie Solari” (”The Sunspot Letters to Marc Welser”) (1613) []
  3. Massimo Mogi Vicentini, © Planetario di Milano, Italy []
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Chromosome 20

xantox, 25 March 2007 in Gallery

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The genetic information of all living organisms is encoded into long sequences of four molecular symbols, structured like the steps of giant DNA ladders named chromosomes. Human cells contain two sets of 23 chromosomes, each having 50 to 250 millions symbols or base pairs for a total of 3 billions, like a book of one million pages written in a mostly unknown language. In this image, a short excerpt from human chromosome 20, which has 63 644 868 base pairs, is represented by using the letters A C G T and dots for apparently unused sections.

Excerpt from human chromosome 20 © Ben Fry, Computation Group MIT Media Lab

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  1. © Ben Fry, Computation Group MIT Media Lab []
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Total Lunar Eclipse

xantox, 27 February 2007 in Gallery

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Timelapse photo of the total lunar eclipse of October 27, 2004.1 Celestial bodies orbiting around a star cast shadows, which may partially or totally obscure other bodies aligned behind them, “eclipsing” the star from their viewpoint (from Greek ekleipein, “failing to appear”).

Total Lunar Eclipse (Oct 27, 2004) © Forrest J. Egan (Digital Astro)
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Given their short duration, eclipses are amongst the phenomena where cosmic scale dynamics may be perceived most dramatically. In the picture, the moon’s curved path is primarily due to Earth’s rotation, and to a small extent to the lunar motion in its elliptical orbit around the Earth. During the totality stage the Moon appears red, because Earth’s atmosphere scatters sunlight and only red wavelengths are refracted into the shadow. An observer on the moon would see a bright ring of red light, coming from all simultaneous Earth’s sunrises and sunsets.2

A total lunar eclipse will happen Saturday, March 3, 2007, and will be visible from Europe, Africa, Western Asia and Eastern America.


  1. Picture © Forrest J. Egan, Digital Astro []
  2. Eclipse seen from the moon, Surveyor 3 mission, 24 April 1967 (artificial color) © NASA []
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Light caustics produced by two water surfaces

xantox, 17 February 2007 in Gallery

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Caustics (from the Greek kaustikos, kaiein, ‘to burn’) are geometrical entities formed by the singular concentration of curves, which model approximately the behavior of light rays focused by lenses or curved mirrors, leading to very bright regions when they encounter a surface. The light patterns at the bottom of swimming pools are examples of caustics, produced by the refraction on the wavy surface of water. In this computer image are discovered light caustics produced by two consecutive wavy surfaces, as if light was entering a second sea under the sea.

Light Caustics After Two Refractions © Eric J. Heller, Resonance Fine Art
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  1. Digital Artwork © Eric J. Heller, Resonance Fine Art []
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