Ferroelectric materials, in addition to possessing the unique property of a reversible, spontaneous polarization, exhibit a range of other significant and useful properties. These include high values of piezoelectric, pyroelectric, nonlinear optic, electrooptic, photorefractice and dielectric permittivity coefficients. Another fascinating property of ferroelectric materials is their photovoltaic effect. Photovoltaic effects have been extensively studied in the past in symmetric materials such as silicon. This volume is the first concentrated treatment of the characteristics, theory and potential applications of the photovoltaic effect in noncentrosymmetric materials, which include ferroelectrics and piezoelectrics. The book also deals with the relationship between the photovoltaic and the photorefractive effects. The latter has already been well-studied and is finding many applications in optical processing and computing. This volume should prove to be an important text as well as a comprehensive reference source for basic and applied researchers working on photovoltaic, photorefractive and other photoeffects in ferroelectrics and related materials.

A brief historical account of the background leading to the publication of the first four editions of the World Directory of Crystallographers was presented by G. Boom in his preface to the Fourth Edition, published late in 1971. That edition was produced by traditional typesetting methods from compilations of biographical data prepared by national Sub-Editors. The major effort required to produce a directory by manual methods provided the impetus to use computer techniques for the Fifth Edition. The account of the production of the first computer assisted Directory was described by S.C. Abrahams in the preface of the Fifth Edition. Computer composition, which required a machine readable data base, offered several major advantages. The choice of typeface and range of characters was flexible. Corrections and additions to the data base were rapid and, once established, it was hoped updating for future editions would be simple and inexpensive. The data base was put to other Union uses, such as preparation of mailing labels and formulation of lists of crystallographers with specified common fields of interest. The Fifth Edition of the World Directory of Crystallographers was published in June of 1977, the Sixth in May of 1981. The Subject Indexes for the Fifth and Sixth Editions were printed in 1978 and 1981 respectively, both having a limited distribution.

Physics of laser crystals has been constantly developing since the invention of the laser in 1960. Nowadays, more than 1500 wide-band-gap and semiconductors crystals are suitable for the production of the laser effect. Different laser devices are widely used in science, medicine and communication systems according to the progress achieved in the development of laser crystal physics. Scintillators for radiation detection also gained benefit from these developments. Most of the optically active materials offer laser radiations within the 500 to 3000 nm region with various quantum efficiency which fit the usual applications. However, new crystals for laser emissions are needed either in the blue, UV and VUV - region or far IR- region, especially for medicine, computer microchip production and for undiscovered practical uses. Scientific problems of the growth and properties of laser crystals are discussed in numerous books and scientific journals by many scientists working in the field. Therefore, we thought that joint discussions of the scientific and technical problems in laser physics will be useful for further developments in this area. We have proposed to held a Workshop on Physics of Laser Crystals for attempting to induce additional advances especially in solid state spectroscopy. This NATO Advanced Research Workshop (ARW) was hold in Kharkiv • Stary Saltov th nd (Ukraine) on august 26 - September 2 , 2002, and was mainly devoted to the consideration 0 f modem approaches and Iast results in physics of laser crystals.