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The US National Library of Medicine (NLM) is a Federal institution which serves as a national resource with international impact. The global biomedical literature and that selected for Index Medicus is characterized by numbers of journals, country of origin, and language of publication. NLM's domestic responsibilities and international programmes are described. NLM's international relationships consist of MEDLARS co-operation, exchange programmes, services, a special foreign currency programme, technical consultation, co-operation with the World Health Organization (WHO) and the Pan American Health Organization (PAHO) and some special programmes vis-á-vis formal governmental bilateral agreements. A regional approach to the provision of medical library and health-information services is illustrated by the PAHO Regional Library of Medicine. The principles for the availability of MEDLARS internationally and the nature of the quid pro quo arrangements are presented.

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Interaction of dyes in aqueous solution results in differences in the spectrum of t h e mixture when compared wit h the SLlm of the spectra of t he individual dy s. A general s urvey, chiefly with azo dyes, was made to deter mine the effect of dye struc t ure on this interaction.The eff ect of other factors on t he interaction of direct azo dyes was investigated. The addit io n of alcohol or non-ionic dctergent prevents th is interaction , while the presence of inorganic salts or an increase in dyc concentration appears to increa e t he extent of interaction. Th e effect of acids and bases is dependent upon the nature of t he dyes in t hc mixture.The results obtained arc consistent with the assumption that the forees involved in the interaction of direct azo dyes in mixtures are the same as those causing the aggregation of individual dyes and those binding these dyes to fib ers.

No abstract