Silicon Light-Emitting Diodes and Lasers: Photon Breeding Devices using Dressed Photons Motoichi Ohtsu
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Patterns in Nature: Why the Natural World Looks the Way It Does Philip Ball The University of Chicago Press, 2016 288 pages, $35.00 (e-book $21.00) ISBN 9780226332420
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eading this book is like going to an art gallery with a friend who is very learned. Ball presents a rich variety of patterns that exist in nature and the common principles that explain them, even when they appear in unrelated circumstances. The Introduction sets the subject in context and shows the geometric designs in ancient architecture and in the natural world of the living and nonliving. Chapter 1 includes examples of bilateral symmetry exhibited by fish, mammals, insects, and birds. Snowflakes and honeycombs with hexagonal symmetry have long been admired, photographed, and studied. Sometimes patterns are obtained by breaking the symmetry. In chapter 2, fractals (hierarchical repetition of the same general form at decreasing scales) are illustrated with examples such as florets of broccoli, tree branches, and coastlines. Chapter 3 discusses logarithmic spirals, in which a cone rolls up, and
Archimedean spirals, in which a rope rolls up. Spirals show up in chameleon tails, mollusk shells, and in swirling stars of galaxies. Flowing fluids often organize themselves into spiral vortices, with tornados being a dramatic example. Chapter 4 discusses patterns of flow and the emergence of chaotic behavior. Chapter 5 explains how wave patterns form, as in a plate sprinkled with sand and vibrated. Granules move away from vibrating places and fall onto nodal lines, where the plate is not vibrating, and form what is called a Chladni figure. Cracks due to electric discharge form a wavy pattern called Lichtenberg figures. Sand dunes show wave patterns. Chapter 6 discusses bubbles and foams, where surface tension and pressure of the gas inside control the patterns to minimize the surface. Chapter 7 includes arrays and tilings, starting with wallpapers and flooring, and progresses
Silicon Light-Emitting Diodes and Lasers: Photon Breeding Devices using Dressed Photons Motoichi Ohtsu Springer, 2016 192 pages, $129.00 (e-book $99.00) ISBN 978-3-319-42012-7
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he topic of this book is very timely. Direct-bandgap semiconductors are used for conventional light-emitting diodes (LEDs) and lasers. Although there have been tremendous improvements in terms of efficiency, technical challenges remain in fabrication and in handling toxic and rare compounds, such as arsenic and indium. Silicon, being an indirect-bandgap
semiconductor, exhibits poor efficiency because electrons must transition from the conduction band to the valence band to emit light spontaneously by electron–hole recombination. However, the momentum of the electron in the conduction band is different from that in the valence band, requiring a phonon in the process to satisfy the net momentum conservation.
to crystals and quasicrystals, which are five-sided and were once considered impossible. Chapter 8 covers how a pattern of cracks forms on dry mud, glazes, and paints on a coated surface. The top layer
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