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A series of freeze-thawed, polyvinyl alcohol nanocomposite hydrogels were prepared using various loading levels (0-15 wt%) of hydrophilic natural Na-montmorillonite nanoclay. The morphology of nanocomposite hydrogels, their dehydration kinetics at different temperatures and the effect of Na-montmorillonite on the gelation process were investigated. The results showed a partially exfoliated morphology for the prepared nanocomposite hydrogels. Also by increasing the amount of nanoclay incorporated into the specimens, the gel fraction values of nanocomposite hydrogels were increased. According to the dehydration tests, the dehydration rates of nanocomposite hydrogels exhibited an inverse dependency on the nanoclay loading level and a direct dependency on the dehydration temperature. Finally, it was concluded that the dehydration mechanism of all specimens prepared is non-Fickian at 20 °C, while it is Fickian at 37 °C and 55 °C. [PUBLICATION ABSTRACT]

Surveys the evolution and development of MARC formats for the digital encoding of bibliographic data from their beginnings in 1968 at the Library of Congress to the present time, with particular emphasis on the development of 17 national formats. Examines the reasons for the divergence of MARC formats from each other as well as the early and recent trends in the development of national MARC formats. Original abstract-amended.

Discusses the problems associated with the requirements for international standards for the exchange of bibliographic records in machine readable form, including the roles of national bibliographies and national libraries; a lack of international cataloguing standards and subject control systems; language difficulties; character sets and codes, and non roman alphabets. Suggests that these problems lie behind the development of various MARC formats out of UNIMARC. In this final part of a 4 part article describes the formats for South Africa, Taiwan, Japan, Croatia and Germany and indicates the points of difference and the influence of local requirements. Original abstract-amended.

The machine-readable catalogue (MARC) is now more than 20 years old. It has been, and still is, criticized from different points of view. Reviews some of the positive and negative opinions on MARC, as expressed by different sectors of the profession, and studies the future of MARC in relation to technological innovations. Concludes that MARC remains a valuable means of communicating bibliographical information.

Kokabi discusses some of the problems associated with the requirements and the prospects for international standards for the exchange of bibliographic records in machine-readable form: The various roles of national bibliographies and national libraries; a lack of an international support control system; language difficulties; character sets and codes; and non-roman alphabets. (Part 4 of 4)

Machine-readable cataloging (MARC) has been shown to be not only a widely used and effective format for bibliographic data but also an invaluable vehicle for data exchange and shared cataloging. It has been, however, and still is, open to criticism from various sectors of the profession. Despite all these criticisms, there are reasons to believe that the future of MARC still looks stable.