Showing papers in "Physics Today in 2000"

Allen's astrophysical quantities

Abstract: 1) Introduction. Cox 2)General Constants and Units. Cox 3) Atoms and Molecules. Dappen 4) Spectra. Cowley, et al 5) Radiation. Keady & Kilcrease 6) Radio and Microwave Astronomy. Hjellming 7) Infrared Astronomy. Tokunaga 8) Ultraviolet Astronomy. Teays 9) X-Ray Astronomy. Seward 10) Gamma-Ray and Neutrino Astronomy. Lingenfelter & Rothschild 11) Earth. Schubert & Walterscheid 12) Planets and Satellites. Tholen 13) Solar System Small Bodies. Binzel, et al 14) Sun. Livingston 15) Normal Stars. Drilling & Landolt 16) Stars with Special Characteristics. Fernie 17) Cataclysmic and Symbiotic Variables. Sparks, et al. 18) Supernovae. Wheeler & Bennetti 19) Star Populations and the Solar Neighborhood. Gilmore & Zeilik 20) Theoretical Stellar Evolution. Becker/Pensell/Cox 21) Circumstellar and Interstellar Material. Mathis 22) Star Clusters. Harris & Harris 23) Milky Way Galaxies. Trimble 24) Quasars and Active Galactic Nuclei. Wilkes 25) Clusters and Groups of Galaxies. Bahcall 26) Cosmology. Scott, et al 27) Incidental Tables. Fiala, et al.

Fiber Bragg Gratings: Fundamentals and Applications in Telecommunications and Sensing

Abstract: Photosensitivity in optical fibres properties of Fibre Bragg gratings inscribing Bragg gratings in optical fibres Fibre Bragg grating theory applications of Bragg gratings in communications Fibre Bragg grating sensors impact of Fibre Bragg gratings.

Encyclopedia of Volcanoes

Abstract: R.D. Ballard, Foreword. Origin and Transport of Magma: H. Sigurdsson, B. Houghton, H. Rymer, J. Stix, and S. McNutt, Introduction. H. Sigurdsson, The History of Volcanology. R. Jeanloz, Mantle of the Earth. P. Asimov, Melting the Mantle. M. Daines, Migration of Melt. M. Perfit and J. Davidson, Tectonics and Volcanism. N.W. Rogers and C.J. Hawkesworth, Composition of Magmas. T.L. Grove, Origin of Magmas. P.J. Wallace and A.T. Anderson, Volatiles in Magmas. F.J. Spera, Physical and Thermodynamic Properties of Magmas. B.D. Marsh, Reservoirs of Magma and Magma Chambers. M.J. Rutherford and J. Gardner, Rates of Magma Ascent. C. Carrigan, Plumbing Systems. C. Jaupart, Magma at Shallow Levels. Eruption: T. Simkin and L. Siebert, Active Volcanoes on the Earth. D.M. Pyle, Sizes of Volcanic Eruptions. H. Sigurdsson, Episodes of Volcanism. Effusive Volcanism: G.P.L. Walker, Basaltic Volcanoes and Volcanic Systems. C. Kilburn, Lava Flows. J. Fink and S. Anderson, Domes and Coulees. J. Wolff and J. Sumner, Spatter-Fed Lavas and Fire-Fountaining. C. Conner and M. Conway, Basaltic Volcanic Fields. P. Hooper, Flood Basalt Provinces. R. Batiza and J. White, Submarine Lavas and Hyaloclastite. R. Schmidt and H.-U. Schmincke, Seamounts, Submarine Volcanoes, and Volcanic Islands. J. Smellie, Sub-Glacial Eruptions. Explosive Volcanism: Cashman, B. Sturtevant, P. Papale, and O. Navon, Magmatic Fragmentation. M.M. Morrisey, B. Zimoriski, K. Wohletz, and R. Buettner, Phreatomagmatic Fragmentation. S. Vergniolle and M. Mangan, Strombolian and Hawaiian Eruptions. M.M. Morrissey and L.G. Mastin, Vulcanian Eruptions. Cioni, P. Marianelli, R. Santecroce, and A. Sbrana, Plinian Eruptions. J.D.L. White and B. Houghton, Pyroclastic Eruptions. B.F. Houghton, C.J.N. Wilson, R.T. Smith, and J.S. Gilbert, Phreatoplinian Eruptions. S. Carey and M.I. Bursik, Volcanic Plumes. C.J.N. Wilson and B.F. Houghton, Pyroclastic Transport and Deposition. B.F. Houghton, C.J.N. Wilson, and D.M. Pyle, Fall Deposits. G. Valentine and R.V. Fisher, Deposits of Surges and Directed Blasts. A. Freundt, S.N. Carey, and C.J.N. Wilson, Ignimbrites and Deposits of Block-and-Ash Flows. J.W. Vallance, Lahar Deposits. T. Ui and M. Yoshimoto, Debris Avalanche Deposits. S. Carey, Volcaniclastic Sedimentation Around Island Arces. P.W. Lipman, Calderas. J.P. Davidson and S. Da Silva, Composite Cones. D. Vespermann and H.U. Schmincke, Scoria Cones and Tuff Rings. Extraterrestrial Volcanism: P.D. Spudis, Volcanism on the Moon. R. Lopes-Gautier, Volcanism on IO. L. Crumpler, Volcanism on Venus.J.R. Zimbelman, Volcanism on Mars.P. Geissler, Cryovolcanism in the Outer Solar System. Volcano Interactions: P. delMelle and J. Stix, Volcanic Gases. F. Goff and C. Janik, Geothermal Systems. P. Browne and M. Hochstein, Surface Manifestations. D. Butterfield, Submarine Hydrothermal Vents. P. delMelle and A. Bernard, Volcanic Lakes. N.C. White and R.J. Harrington, Mineral Deposits Associated with Volcanism. Volcanic Hazards: T.P. Miller and T.J. Casadevall, Volcanic Ash Hazards to Aviation. M.J. Mills and O.B. Toon, Volcanic Aerosol and Global Atmospheric Effect. S. Nekada, Hazards from Pyroclastic Flows and Surges. D. Peterson and R.I. Tilling, Lava Flow Hazards. K. Rodolfo, Lahars and Jokulhlaup Hazards. H. Rymer and G. Williams-Jones, Volcanic Gas Hazards. J.E. Beget, Volcanic Tsunamis. S.R. McNutt, Volcanic Seismicity. P. Baxter, Impacts of Eruptions on Human Health. M. Arthur, The Volcanic Contribution to the Sulfur and Carbon Geochemical Cycle. I. Thornton, The Ecology of Volcanoes-Biological Recovery and Colonization. M. Rampino and S. Self, Volcanism and Biotic Extinction. Eruption Response and Mitigation: S.R. McNutt, Seismic Monitoring. J.B. Murray, C.A. Locke, and H.Rymer, Ground Deformation, Gravity, and Magnetics. J. Stix and H. Gaonach, Gas, Plume, and Thermal Monitoring. S. McNutt, J. Stix, and H. Rymer, Synthesis of Volcano Monitoring. C. Newhall, Volcano Warnings. S. de la Cruz, R. Quaas, and R. Meli, Volcanic Crisis Management. R. Blong, Volcanic Hazards and Risk Management. D. Johnson and K. Ronan, Risk Education and Intervention. Economic Benefits and Cultural Aspects of Volcanism: S. Arnorsson, Exploitation of Geothermal Resources. C-l. Ping, Volcanic Soils. J. Dehn and S.R. McNutt, Volcanic Materials for Commerce and Industry. H. Sigurdsson and R. Lopes-Gautier, Volcanoes and Tourism. S. Harris, Archaeology and Volcanism. H. Sigurdsson, Volcanoes in Art. H. Sigurdsson and R. Lopes, Volcanoes in Literature and Film. Appendices: Units and Physical Properties of the Earth Volcanoes of the Earth.

Phase‐Sensitive X‐Ray Imaging

Abstract: The basic principles of x‐ray image formation and interpretation in radiography have remained essentially unchanged since Rontgen first discovered x rays over a hundred years ago. The conventional approach relies on x‐ray absorption as the sole source of contrast and draws exclusively on ray or geometrical optics to describe and interpret image formation. This approach ignores another, potentially more useful source of contrast—phase information. Phase‐sensitive techniques, which can be understood using wave optics rather than ray optics, offer ways to augment or complement standard absorption contrast by incorporating phase information.

DNA‐Inspired Electrostatics

Abstract: Under “physiological” conditions (a 0.1 molar solution of NaCl), a DNA molecule takes on the form of a disordered coil with a radius of gyration of several micrometers; if any lengths of the molecule come within 1 nm of one other, they strongly repel. But under different conditions—in a highly dilute aqueous solution that also contains a small concentration of polyvalent cations—the same DNA molecule condenses into a tightly packed, circumferentially wound torus. Figure 1a shows just such a DNA torus. Its average radius is about 50 nm, and the distance between the axes of neighboring, parallel portions of the molecule is only slightly larger than its diameter.

Black Hole Physics: Basic Concepts and New Developments

Abstract: Preface. I. Basic Concepts. 1. Introduction: Brief History of Black Hole Physics. 2. Spherically Symmetric Black Holes. 3. Rotating Black Holes. 4. Black Hole Perturbations (with N. Andersson). 5. General Properties of Black Holes. 6. Stationary Black Holes. 7. Physical Effects in the Gravitational Field of a Black Hole. 8. Black Hole Electrodynamics. 9. Astrophysics of Black Holes. II. Further Developments. 10. Quantum Particle Creation by Black Holes. 11. Quantum Physics of Black Holes. 12. Thermodynamics of Black Holes. 13. Black Holes in Unified Theories. 14. The Interior of a Black Hole. 15. Ultimate Fate of Black and White Holes. 16. Black Holes, Wormholes, and Time Machines. Conclusions. Appendices: A: Mathematical Formulas. B: Spherically Symmetric Spacetimes. C: Rindler Frame in Minkowski Spacetime. D: Kerr-Newman Geometry. E: Newman-Penrose Formalism. F: Wave Fields in a Curved Spacetime. G: Wave Fields in the Kerr Metric. H: Quantum Fields in Kerr Spacetime. I: Quantum Oscillator. Bibliography. Index.

Motile Behavior of Bacteria

Abstract: Escherichia coli is a single‐celled organism that lives in your gut. It is equipped with a set of rotary motors only 45 nm in diameter. Each motor drives a long, thin, helical filament that extends several cell body lengths out into the external medium. The assemblage of motor and filament is called a flagellum. The concerted motion of several flagella enables a cell to swim. A cell can move toward regions that it deems more favorable by measuring changes in the concentrations of certain chemicals in its environment (mostly nutrients), deciding whether life is getting better or worse, and then modulating the direction of rotation of its flagella. Thus, in addition to rotary engines and propellers, E. coli's standard accessories include particle counters, rate meters, and gear boxes. This microorganism is a nanotechnologist's dream. I will discuss the features that make it so, from the perspectives of several scientific disciplines: anatomy, genetics, chemistry, and physics.

Quantum Theory Needs No ‘Interpretation’

Abstract: Purpose of this article is to stress the fact that Quantum Theory does not need an interpretation other than being an algorithm for computing probabilities associated with macroscopic phenomena and measurements. It does not ''describ'' reality, and the wave function is not objective entity, it only gives the evolution of our probabilities for the outcomes potential experiments. (AIP) (c)

Just Six Numbers: The Deep Forces that Shape the Universe

Abstract: Astronomer Royal Martin Rees shows how the behaviour and origins of the universe can be explained by just six numbers. How did a single genesis event create billions of galaxies, black holes, stars and planets? How did atoms assemble - here on Earth, and perhaps on other worlds - into living beings intricate enough to ponder their origins? This book describes the recent avalanche of discoveries about the universe's fundamental laws, and the deep connections that exist between stars and atoms - the cosmos and the microscopic world. Just six numbers, imprinted in the big bang, determine the essence of our world, and this book devotes one chapter to explaining each.

Diffusion‐Limited Aggregation: A Model for Pattern Formation

Abstract: Nature confronts us at every turn with patterns—whether the stately spiral shapes of galaxies and hurricanes or the beautiful symmetries of snowflakes and silicon. A host of processes can play a role in forming natural patterns, though they usually involve an interaction between the transport and the thermodynamic properties of the matter and radiation involved.

Diffusion Waves and their Uses

Abstract: The concept of waves is an integral part of our scientific culture and has nourished physicists, pure and applied alike, for centuries. Many important discoveries in physics, including quantum mechanics, have involved wave phenomena. The wave concept owes some of its scientific success to its mathematical tractability. Linear wave equations—the sort that describe the transmission of sound and radio waves through air—contain a nonzero second‐order time derivative, which gives rise mathematically to the rich and familiar array of properties we associate with waves, such as wavefront propagation, reflection, and refraction.

A Fresh Look at Entropy and the Second Law of Thermodynamics

Abstract: In days long gone, the second law of thermodynamics (which predated the first law) was regarded as perhaps the most perfect and unassailable law in physics. It was even supposed to have philosophical import: It has been hailed for providing a proof of the existence of God (who started the universe off in a state of low entropy, from which it is constantly degenerating); conversely, it has been rejected as being incompatible with dialectical materialism and the perfectibility of the human condition.

Nonequilibrium Patterns in Granular Mixing and Segregation

Abstract: For over 5000 years, granular mixing has been a topic of acutely practical concern. Paleolithic cave painters mixed their colors from blends of ochre and animal products; ancient Chinese and Egyptians blended inks and cosmetics from pork soot, crushed pearls, and compounds of lead; Aztec priests prepared drugs from concoctions of herbs and roots; and Michelangelo pigmented the Sistine chapel frescoes with blends including chalk, charcoal, and lead.

Blue Diode Lasers

Abstract: The recent achievement of compact blue‐emitting gallium nitride semiconductor lasers is likely to have far‐reaching technological and commercial effects. The lasers' short wavelengths—around 400 nm, half that of gallium arsenide‐based lasers—permit higher spatial resolution in applications such as optical storage and printing. And the high photon energy will open up new applications for these inexpensive, compact light sources. An aesthetic satisfaction with these devices stems from finally extending the existing and mature semiconductor laser technology for the near‐infrared and red to encompass the “new frontier” blue and near‐ultraviolet regions, thereby bridging the entire visible spectrum. At the same time, there are significant research opportunities arising from a plethora of poorly understood microscopic issues in the underlying material system, which include such fundamental properties as charge control, transport, and formation of optical gain for stimulated emission.

The Composite Fermion: A Quantum Particle and Its Quantum Fluids

Abstract: Discovery of new particles is not usually associated with condensed matter physics, because, at one level, we already know all the particles that go into the Hamiltonian—namely, electrons and ions. But it is a most profound fact of nature—indeed the very reason why physics can make progress at many different levels—that strongly interacting particles reorganize themselves to become more weakly coupled particles of a new kind. Often they are simple bound states of the old particles. But sometimes they are fantastically complicated collective objects (for example, solitons) that nonetheless behave as legitimate particles, with well‐defined charge, spin, statistics, and other properties we attribute to particles.

Negative Pressures and Cavitation in Liquid Helium

Abstract: Cavitation—the formation of bubbles—is a familiar phenomenon. Whenever a liquid is agitated violently, there is a possibility that cavitation will occur (see, for example, figure 1). In the case of boat propellers or hydraulic machines, cavitation is a problem that engineers try to avoid. In other contexts, however, cavitation can be useful—as, for example, in ultrasonic cleaning devices.

Liquid Crystals and Carbon Materials

Abstract: Carbon atoms can be found in a variety of structures, including the tetrahedra of diamond, the stacked planes of graphite, and the celebrated fullerene spheres and nanotubes. The graphite family alone includes a rich variety of materials, ranging from pencil “lead” to interstellar dust to chimney soot, and from metallurgical coke to activated charcoal for water filtration to lightweight composites for aerospace components—such as the nose cone of the space shuttle, for which carbon composites were chosen because of their high strength at elevated temperatures.

From Quantum Cheating to Quantum Security

Abstract: Cryptography—the art of code‐making—has a long history of military and diplomatic applications, dating back to the Babylonians. In World War II, the Allies' feat of breaking the legendary German code Enigma contributed greatly to their final victory. Nowadays, cryptography is becoming increasingly important in commercial applications for electronic business. Sensitive data such as credit card numbers and personal identification numbers (PINs) are routinely transmitted in encrypted form. Quantum mechanics is a new tool for both code‐breakers and code‐makers in their eternal arms race. It has the potential to revolutionize cryptography both by creating perfectly secure codes and by breaking standard encryption schemes.

QCD Made Simple

Abstract: Quantum chromodynamics, familiarly called QCD, is the modern theory of the strong interaction Historically its roots are in nuclear physics and the description of ordinary matter—understanding what protons and neutrons are and how they interact Nowadays QCD is used to describe most of what goes on at high‐energy accelerators Quantum chromodynamics is conceptually simple Its realization in nature, however, is usually very complex But not always

Spin and Isospin: Exotic Order in Quantum Hall Ferromagnets

Abstract: Quantum mechanics is a strange business, and the quantum physics of strongly correlated many‐electron systems can be stranger still. Good examples are the various quantum Hall effects. They are among the most remarkable many‐body quantum phenomena discovered in the second half of the 20th century, comparable in intellectual import to superconductivity and superfluidity. The quantum Hall effects are an extremely rich set of phenomena with deep and truly fundamental theoretical implications.

Physics and the Information Revolution

Abstract: In the fourth century BC, a young man named Pythias was condemned to death by Dionysius, the tyrant of Syracuse, for plotting against him, but Pythias was granted three days’ leave to go home to settle his family's affairs after his friend Damon agreed to take his place and be executed should Pythias not return. Pythias encountered many problems but managed to return just in time to save Damon. Dionysius was so struck by this remarkable and honorable friendship that he released them both.

Physics in the Whirlwind of Optical Communications

Abstract: Technology is providing people all over the world with much better ways of communicating than ever before, and the winds of change have whipped up the desire to exchange more of everything from messages to movies. This demand for more bandwidth in communications is powering a whirlwind of changes in technology. As Dorothy said to her dog in the Land of Oz, “Toto, I have a feeling that we're not in Kansas anymore.”

The Origins of Mathematical Physics: New Light on an Old Question

Abstract: Imagine that you have to start science from scratch. Upon what disciplines should you draw? Philosophy, for instance, discusses the nature of time, space, and reality. Religion, too, tries to make sense of the world as a whole; and so, sometimes, does literature. Several disciplines—for example, biology and medicine—deal with special and highly significant features of the world. Such are the most natural ways to begin thinking about the world, and, in fact, most cultures make sense of their world through a combination of such intellectual resources. Mathematics, in comparison, appears like a non‐starter. Here is a theory dealing with abstract objects, aiming at internal coherence rather than at connection to any external reality. All cultures develop some ways of dealing with calculation and measurement, and in some societies, a more abstract discipline, a “mathematics,” may also emerge. But it is a peculiarity of the modern world to take this abstract discipline as the cornerstone for science.