July 6, 1993

IN the global race to make ever more powerful computer chips, designers for years have been shrinking parts and wires and creating circuits that are both faster and smaller. Today the standard circuit line is about one micron wide, a hundred times thinner than a human hair, allowing millions of transistors to be crammed onto a computer chip. On the horizon, with considerable work, lie diameters of 0.1 micron or so, which might yield devices with billions of transistors. This level of complexity has long been viewed as the likely end of the conventional electronics race, since finer transistors would burn up if subjected to requisite currents. Now, quite suddenly, a new field is emerging that could possibly leap the size barrier to produce circuits as small as 0.01 micron, the width of a hundred or so atoms. The transistors on one of these new chips could number in the trillions, squeezing vast power into an incredibly small space.

CHANGES COMING FOR HOMELESS SYSTEM As the Federal Government begins to retool its policies toward the homeless, New York City officials are moving forward with a revamping of the city's shelter system. The new effort seeks to shift the city's system toward the use of small residences for the homeless, run by private nonprofit groups, that address such problems as drug abuse and mental illness. Page A1. NEW YORK CITY LAWYER SAYS SHEIK TO FIGHT EXTRADITION A lawyer for Sheik Omar Abdel Rahman, the spiritual leader of suspects in the two recent terrorist cases in New York City, says that the radical Islamic cleric intends to wage a "vigorous fight" against efforts to extradite him to Egypt, which could keep him in this country for years. Page B2.

Edward P. Junker 3d flirts with bankers for a living. A banker himself, he is chief executive for the northwestern Pennsylvania region of the PNC Bank Corporation of Pittsburgh. Two years ago, PNC stripped Mr. Junker and seven other regional executives of much of their operational responsibilities and told them to go out and find banks for the rapidly growing company to buy. Set in the slow-growth Rust Belt, PNC says its earnings from its existing operations -- which stretch from Kentucky to Delaware -- will increase 6 to 7 percent a year at best. But like other expanding regional banks, PNC hopes it can grow at twice that rate by buying other banks.

Many United States institutional investors are not expected to begin immediately reinvesting in South Africa, even if Nelson Mandela calls for an end to international sanctions. Executives of pension funds and endowments expressed excitement about the prospects of investing again in companies that do business with South Africa but said it could take months if not years to gain approval to put their money back in the troubled nation.

ROALD HOFFMANN Nobel laureate, professor of chemistry at Cornell University and poet -- glanced benignly at the stream of students passing his office window along a tranquil campus street. "I love chemistry," he remarked, "because it's sort of human in scale -- infinitely complex, but always tangible, always real." Although Dr. Hoffman's pursuits include such practical goals as finding a cheap substitute for one of the precious metals used in automobile catalytic converters, he is mainly interested in the beauty that he perceives underlying even mundane applications of chemistry. Dr. Hoffmann's students know that his conception of "beauty" in chemistry particularly refers to the subtle symmetries and asymmetries of electron "orbitals" in complex molecules. He was awarded the 1981 Nobel prize in chemistry for his idea that chemical transformations could be approximately predicted from these symmetries. His method gave chemists a powerful tool for predicting the pathways that chemical reactions may follow.