Logicquasifractals

Ian Stewart finds a familiar shape in unexpected places I am being haunted by a fractal. In a recent column see Sierpinski's Ubiquitous Gasket, August 1999 I described several occurrences of the fractal known as Sierpinski's gasket, which can be obtained from a triangle by successively deleting an inverted triangle half its size. Ever since, readers have been alerting me to new sightings of this versatile figure. Its latest incarnation is in the field of mathematical logic. Patrick Grim and...

Locus Coeruleus

Locus Coeruleus

ERECTION is orchestrated by the central nervous system. Erections are continuously inhibited by the sympathetic nervous system (blue). During REM sleep, however, when the sympathetic neurons in the locus coeruleus are turned off, erections occur spontaneously. The other brain structure that inhibits erections is the para-gigantocellular nucleus (PGN). Conversely, the parasympathet-ic nervous system (red) is excitatory. Tactile stimuli or stimuli processed in the cortex may be integrated in the...

Extra Dimensions

Tra dimensions strengthen gravity much more quickly than usual at short distances, it still only catches up with the other forces near 10-19 meter and remains very feeble compared with them at larger distances. A much more serious concern relates to gravitons, the hypothetical particles that transmit gravity in a quantum theory. In the theory with extra dimensions, gravitons interact much more strongly with matter (which is equivalent to gravity being stronger at short distances), so many more...

Paleoanthropology Migration

New fossils revise the time when humans colonized the earth Scientists have long known that hominids arose in Africa, and for the first few million years they stayed there. But at some point our ancestors began to move out of their motherland, marking the start of global colonization. Determining why and when they left, however, has proved difficult because of the scarcity of early human fossils. Now two ancient skulls from the Republic of Georgia provide the strongest evidence yet of the first...

Unseen Dimensions

The visible universe could lie on a membrane floating within a higher-dimensional space. The extra dimensions would help unify the forces of nature and could contain parallel universes by Nima Arkani-Hamed, Savas Dimopoulos and Georgi Dvali The classic 1884 story Flatland A Romance of Many Dimensions, by Edwin A. Abbott, describes the adventures of A. Square, a character who lives in a two-dimensional world populated by animated geometric figures triangles, squares, pentagons, and so on. Toward...

Media Criticism

A study in the June 1 New England Journal of Medicine shows that we journalists could probably do our jobs better. Stories about new medications often exaggerate benefits, ignore risks, overlook costs and fail to comment on financial ties to drug manufacturers. The study, co-authored by medical researchers and a journalist, analyzed 207 news stories and found that only 124 reported benefits quantitatively. And 103 of those gave the results in relative terms only articles about the...

Focal Point Behind Subject

OPTICAL LAYOUT shows how the camera determines where the focal plane is. Separator lenses create two identical images, each of which falls on half a pair of CCD sensor arrays. When these points of light are a set distance apart, the subject is in focus. When the separation is too small (middle panel), the focus is in front of the subject. When it is too large, the focus is behind the subject.

Photography Autofocus Systems

High-quality cameras all employ the same basic system for automatic focusing, known as phase-detection autofocus. In a single-lens reflex (SLR) camera, light from a part of the scene passes through the lens and then through the camera's reflex mirror, which is partially transparent. (The reflex mirror flips up when the shutter button is pressed to allow the image to fall on the film.) A submirror, attached to the back of the reflex mirror, directs the light that comes through the main mirror...

Fossil Fuelbased Plastics Pe I

First approach, which turns sugar from corn and other plants into a plastic called polylactide (PLA). Microorganisms transform the sugar into lactic acid, and another step chemically links the molecules of lactic acid into chains of plastic with attributes similar to polyethylene terephthalate (PET), a petrochemical plastic used in soda bottles and clothing fibers. Looking for new products based on corn sugar was a natural extension of Cargill's activities within the existing corn-wet-milling...

Particles Our Universe

MICRO BLACK HOLES could be created by particle accelerators such as the Large Hadron Collider smashing together protons (yellow) at high energies. The holes would evaporate rapidly by emitting Hawking radiation of Standard Model particles (blue) and gravitons (red). berger of the University of Washington. They expect preliminary results this year. The idea of extra dimensions in effect continues the Coper-nican tradition in understanding our place in the world The earth is not the center of the...

Where Diseases Or Their Carriers Have Reached Higher Elevations

Nino Map Health Hantavirus Dengue

Uganda and Zimbabwe Usamabara Mountains,Tanzania Highlands of Papua New Guinea and West Papua Irian Jaya can spread dengue fever and yellow fever Eastern Andes Mountains, Colombia Northern highlands of India become all too familiar as the atmosphere heats up favor the transmission of St. Louis encephalitis and other infections that cycle among birds, urban mosquitoes and humans. This sequence seems to have abetted the surprise emergence of the West Nile virus in New York City last year. No one...

Corpus Spongiosum

SYMPATHETIC, MOTOR AND SENSORY FIBERS IN PUDENDAL NERVE of their axons down to the erection-generating neurons in the lower spinal cord. There the PGN nerve endings release the neurotransmitter serotonin a chemical messenger that inhibits erections by opposing the effects of pro-erectile neurotransmitters. This discovery may have important implications for the millions of men and women who take serotonin-enhancing drugs to treat depression and other mental health problems. Drugs such as Prozac...

Engineering Superconductivity

Southwire Plant Carrrollton Images

High-temperature superconductors start finding real-world uses For a few months in 1987, it seemed the world was about to change. Trains would fly on magnetic cushions, computers would be faster, electric power cheaper, new medical scanners would sprout in doctors' offices and more. The reason for this overheated optimism was the discovery by IBM scientists in Zurich, namely, J. Georg Bednorz and K. Alex M ller, of a new kind of superconductor, an almost miraculous material that conducts...

Rearing A Plankton Menagerie By Shawn Carlson

Culture Your Own Live Phytoplankton

Shawn Carlson explains how to raise single-celled aquatic creatures-lots of them The Monterey Bay Aquarium in California houses some of the finest marine exhibits in the world. So when the staff recently offered me a personal, behind-the-scenes tour, I couldn't refuse. Tim Cooke and Ed Seidel made the visit absolutely fascinating, and I am indebted to them for their hospitality. Tim, an aquarist extraordinaire, even let me in on a few secrets for raising plankton. And he should know them the...

Valuesolid For Sheffer Stroke

Truth Table Grids

SIERPINSKI'S GASKET above left can be approximated using mathematical logic. Plugging four-digit binary numbers into the truth table for the Sheffer stroke yields a color diagram in which the green squares form a gasketlike shape left . The figure can also be seen in the value solid for the Sheffer stroke above . It is also possible to change 0 to 1 and 1 to 0 by applying the operator NOT that is, NOT P is true if P is false, and vice versa. There are 16 possible truth tables for ALL POSSIBLE...

Hutton Media Limited

WORLD FOOD The food problem confronts the world with two dangers. One is the political danger of hunger. A lifetime of malnutrition and hunger is the lot of two thirds of mankind. Yet in the midst of this dire need there remains the economic threat of the food surpluses generated by modern technologies. The abundant food output of the U.S. already has begun to undermine its prosperity. A World Food Board, as an agency of the U.N., would be responsible for maintenance of stable world prices, and...