Spatially coherent, phase matched, high-order harmonic EUV beams at 50 kHz.

By focusing a high repetition rate (50 kHz), compact, femtosecond laser system with low pulse energy (25 muJ) using a tight-focusing geometry, we demonstrate fully phase matched high-order harmonic generation for the first time at very high repetition rates, resulting in EUV light with full spatial coherence. The result is a practical, single-box, coherent source useful for applications in metrology, ultrafast spectroscopy, imaging and microscopy. The soft x-ray flux can be improved further by increasing the laser pulse energy and/or repetition rate.

The role of the medical librarian in the use of a MeSH-indexed computerized test question bank.

The University of Missouri-Kansas City School of Medicine utilizes a full-time medical librarian in a non-conventional position as indexer-bibliographer for its computerized Item Library. The responsibilities of the librarian are to edit, index, and reference items for inclusion in the data base; maintain the currency of the Item Library; search the collection; and construct examinations, including a comprehensive quarterly examination, required of all students in this six-year school. Early research in computer-assisted test construction suggested the need for a comprehensive, standard approach to the classification of item content. A professional medical librarian using MeSH descriptors satisfies this need. In existence since 1973, the Item Library is now composed of over 12,000 multiple-choice questions in the basic sciences and clinical medicine. All questions are indexed with up to fifteen MeSH descriptors and referenced to literature sources. The items may be retrieved using any single MeSH term or combination of terms. The collection is available at all times on terminals, and students are encouraged to make use of it for self study. Selected examinations are made available to other institutions by arrangement. Experience has proven both the value of this resource for self study and student evaluation, and the necessity of establishing and continuing the librarian's role.