Number 85, June 19, 1992 by Phillip F. Schewe and Ben Stein AN X-SHAPED OBJECT at the heart of galaxy M51 may be the presumed dust ring that, according to some theories, should surround a black hole. Holland C. Ford of Johns Hopkins released two Hubble Space Telescope photos at last week's meeting of the American Astronomical Society in Columbus, Ohio; one reveals the dark X astride the nucleus of M51, a galaxy seen nearly face-on from Earth; the other reveals two oppositely-directed conical beams of radiation issuing from the galactic core. Because the ring's orientation (in this case, oddly, tipped perpendicular to the plane of the galaxy) may well determine how much and what kind of radiation reaches us, the detailed study of this kind of doughnut-shaped ring may lead to a more unified classification scheme for galaxies. (Science News, 13 June 1992.) HIGH ENERGY GOLD beams are now produced at Brookhaven. The gold ions, gold atoms stripped of 78 electrons, are accelerated to an energy of 11.4 GeV per nucleon or 2 TeV per ion, and then doled out to 11 different experiments poised along four beamlines. In Brookhaven's Relativistic Heavy Ion Collider (RHIC), now under construction, gold ions will attain energies of 100 Gev per nucleon or 20 TeV per ion. (CERN Courier, June 1992.) SINGLE-ELECTRON DEVICES , nanoscale devices that control the movement of individual electrons, may one day make it possible for integrated circuits to have as many as 10 billion electronic devices in a square centimeter, a density 1000 times greater than that believed feasible for conventional integrated circuits. In development since the mid-1980s, these devices consist of two electrodes (typically 30 nm wide) separated by a 1 nm-deep insulating layer through which single electrons can tunnel. These devices have many potential applications, from building more sensitive measurement devices to understanding fundamental problems in physics. In the last several years, researchers have built two-junction devices that share a middle electrode. These devices are called "single-electron transistors," because, like conventional transistors, their current can be controlled by modifying the surface charge on the middle electrode, making it an ideal element for an integrated circuit. A circuit made of single-electron devices, however, would have to be operated at a temperature of 4 K or below to reduce thermal effects which disturb the movements of single electrons in the solid. (Scientific American, June 1992.) ELECTRICAL CURRENTS IN THE HUMAN THORAX cannot be measured directly. Nevertheless the density of current flow can be calculated and imaged using sophisticated computer graphics and the actual measurements of potentials at the surface of the body (electrocardiograms) and---via an invasive procedure---at the outer surface of the heart (epicardial electrograms). Scientists at the University of Utah have combined these calculations with the anatomical information from MRI imaging to visualize the volume current flow through the human torso. Like magnetic field lines emanating from and returning to the poles of a dipole magnet, current flow in the upper body fans out from and then returns to the heart. These studies will help to characterize the function of normal and abnormal hearts. (Computers in Physics, May/June 1992.)