May 18, 1997

Sooner or later most students at Columbia University discover the owl hidden within the folds of Alma Mater's gown, the 1903 bronze sculpture in front of the campus's Low Library, and many rub the owl for good luck before exams. Columbia's presidents, among them George Rupp, its 18th and current leader, and Dwight D. Eisenhower, its 13th, have entertained faculty and guests of the university in formal reception rooms of the brick and limestone President's House, built at 60 Morningside Drive in 1912.

Silver Charm, who won the Kentucky Derby over Captain Bodgit by the length of his gray head, provided a smashing encore today when he won the 122d Preakness by the same head over Free House, with Captain Bodgit third by another head in a three-horse blanket finish. And he set the stage for the Belmont Stakes in three weeks, when he will be racing to become the first colt in 19 years to sweep the Triple Crown. The three rivals re-enacted their photo-finish performances of two weeks ago before 88,594 spectators at Pimlico Race Course with a slight reshuffling of the order behind Silver Charm -- but with the same tingling drive to the wire -- in the closest Preakness in 65 years.

Unsmiling and walking briskly, Patrick Ewing broke through a wall of cameras and microphones today en route to a flight for Miami. Before he left practice, Ewing, with his team's season in the balance, issued a single proclamation: the Knicks in seven. ''The only thing I've got to say is, see you in Chicago,'' New York's franchise center said.

Victorious rebel leader, Laurent Kabila, declares himself President of Democratic Republic of the Congo, formerly Zaire, as his forces enter capital of Kinshasa; suspends Zairian Constitution; pledges to form national salvation Government within three days, and create constituent assembly within two months; crowds on streets of capital mob rebel troops in celebration; their arrival in Kinshasa is marked by confusion and infighting among remaining elements of Zairian Army; Gen Mahele Lioko, Defense Minister, is assassinated by member of own force during efforts to ease rebels' entry into capital; Prime Minister, Gen Likulia Bolongo, seeks protection in French Embassy, as other Government officials flee across Congo River; Mobutu and family reportedly arrive in Rabat, Morocco; photos; map (M)

Russia stands on precipice of AIDS epidemic, fueled by surging drug abuse and increased sexual activity, that is every bit as explosive as that which swept through Europe and US 15 years ago; reported 1,500 new cases in 1996, or more than official figure for first nine years of epidemic combined; Health Ministry data suggest numbers for first quarter of 1997 have already outstripped those of 1996; officials predict as many as 100,000 people could be infected by end of 1997, and 800,000 by year 2000; vast majority of new infections are among country's 600,000 intravenous drug users; new era of complete freedom has caused sexually transmitted diseases to spread more rapidly in Russia than anywhere else in world; photo (M)