ABSTRACT
This study addresses the modeling of exchange isotherms for faujasite-type zeolites X and Y with K+, Cs+, Ca2+ and Ba2+ cations based on a large experimental dataset obtained under operating conditions of 0.5 N total normality and an exchange temperature of 80 °C. The isotherm models are based on the mass action law. Ideal solution phase is assumed. Heterogeneity of the solid phase is taken into account by using Barrer and Klinowski's approach to multi-site exchange. Three types of exchange sites are identified on these zeolites. To each exchange site j corresponds a fitted selectivity coefficient Kj. These parameters, estimated by least square method, evaluate the affinity of the studied cations for the identified exchange site. Globally, these fitted coefficients show that the cations considered present better affinity than Na+, especially for type III sites in faujasite X and type II sites in faujasite Y. For bivalent cations, an exchange with Ba2+ is always more favorable than with Ca2+. On faujasite X, type II sites are more strongly preferred by monovalent cations (with the exception of Cs+) than by bivalent ones. The opposite trend is observed on faujasite Y, even for Cs+. These conclusions have been confirmed and are supported by bibliographic data.
ABSTRACT
PHARMSEARCH, a database produced by the French Patent and Trademark Office (INPI), covers pharmaceutical patents issued by the Europeans, French, and United States patent offices from November 1986 onward. PHARMSEARCH is composed of MPHARM, a structure file searchable using Markush DARC software, and PHARM, the companion bibliographic file. Markush structures claimed in the patent documents are entered into the database as variable generic structures. Specific structures are also included in the database, when they are not part of a Markush structure in the patent document. Chemical index terms describe all moieties of the structure. Indexing also describes the therapeutic activities and preparation processes for the compounds. The indexing policies used in the production of this database are described.
Subject(s)
Chemistry, Pharmaceutical , Databases, Bibliographic , Patents as Topic , Abstracting and Indexing , Drug Design , Molecular StructureABSTRACT
Pigmented melanomas were induced in the Syrian golden hamster by oral administration of 9, 10-dimethyl 1,2-benzanthracene. The primary tumors were grafted into new animals to obtain a series of transplantable tumors. The grafted tumors show the malignant characters which are not present in the primary tumors. These were studied clinically, histologically and ultrastructurally. We believe that this transformation occured perhaps as a consequence of the selection of cells which have a more prominent tendency toward malignancy. This selection could be explained by a greater resistance of lesser pigmented melanocytes or by their weak immunologic capacity. The malignant potential of these cells could eventually be correlated with the presence of viral particles which act as cocarcinogens.
