scientific american - 1993 10 - is los angeles winning the war on smog

... chest discom- fort, 100 million person-days of head- ache, 120 million person-days of cough- ing, 180 million person-days of sore throats and 190 million person-days of eye irritation. These terrible ... found that in almost one Þfth of all the vehicles on the road, the emissions-control equip- ment was either removed by the own- er or damaged by the use of leaded fu- els. The...

Ngày tải lên: 12/05/2014, 14:50

... results consis- tent with some of these conditions, we usually Þnd that the results violate the other conditions. It seems that any rel- ativistic quantum theory that satisÞes all these conditions ... can tell, the only mathematically consistent relativistic quantum theories that satisfy these con- ditions at all energies and that involve gravitation are string theories. Further, the...

Ngày tải lên: 12/05/2014, 14:58

... even longer. If the for- mal version contains N lines, the arith- metized one will contain K times N raised to the power of one plus epsilon. K is very large, and the various math- ematicians disagree ... temperature. The disturbance also caused a nearly complete interruption in the long-term accumulation of calci- um carbonate on the reefs of the region. The fact that h...

Ngày tải lên: 12/05/2014, 14:48

... protects the sample from the heat, to the surface of the superconduc- tor. There they decorate the regions where the magnet- ic-flux lines pass through the surface. The iron parti- cles “stick” to the ... American, Inc. 50 SCIENTIFIC AMERICAN February 1993 the theory that provided the microscop- ic explanation for superconductivity. According to the so-called BC...

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... particular rep- resentation may minimize the aberra- tion of some features while distorting others beyond recognition. The choice SCIENTIFIC AMERICAN March 1993 79 ù Copyright 1993 Scientific American, ... the tension in the spring. The tension, in turn, equals the sum of the two forces acting on the weight: the gravitational force and the centrifugal force. T...

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... fund-raising. He current- ly counts 230 individual contributors, including one person whose donation is contingent on the condition that Gehr- els not tell the donorÕs wife where the money is ... nonstationary onesÑaddition of the nonstationary states corresponds to the in-phase oscillation mode of the two-pendulum model, and subtrac- tion of the states corresponds to the...

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... that the pion is responsible only for conveying the nuclear force over long distances. And no one has figured out what is happen- ing over the short range. To be sure, a vast distance in this context ... context is, by any con- ventional scale, close to nothing. Because the diameter of a proton is only one fermi—that is, a millionth of a billionth of a meter—nuclear physicists...

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... demon- strated in the laboratory. The EPR phenomenon is the linchpin of quantum teleportation. Alice takes one of the EPR photons and gives the other to Bob. Bob then moves to an- other location ... polarization—of one photon is up fixes the polarization of the other photon into the opposite direction, or down. The effect, which is instantaneous no matter what the di...

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... 011 11 1101 0000 100 0 0100 1100 0 010 0 110 1 110 1 010 0001 100 1 0101 1101 0011 0111 1111 101 1 a b c d Copyright 1993 Scientific American, Inc. the population would change radically: the expansive force of mutation ... were confused and that their opinions should be discounted. Since then, social scientists have con- ducted extensive studies of public risk percept...

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... tortoises: one that is reßect- ed back toward the start and one that crosses the barrier. These two partial tortoises together represent the prob- ability distribution of a single photon. When the ... photon is detected at one po- sition, its other partial tortoise instant- ly disappears. The reßected tortoise is bigger than the tunneling tortoise sim- ply because the chan...

Ngày tải lên: 12/05/2014, 14:50