ABSTRACT
The preparation of microcapsules of an acrylic adhesive in a solvent medium with reticulated walls of melamine-formaldehyde was studied. In order to obtain the best experimental conditions for this process, the methodology of factorial design was used. It was found that, among the 11 tested parameters, four had an important effect on the microencapsulation: amount of wall polymer, amount and nature of the copolymer, GANTREZ, and amount of adhesive in the core. The process was optimized using a surface response methodology. A layer of microcapsules deposited on paper gave, after manual breakage, very good adhesive properties.
Subject(s)
Acrylates , Adhesives , Adhesiveness , Capsules , Drug Compounding , Models, Chemical , Particle Size , Regression Analysis , Resins, Synthetic , Surface Properties , TriazinesABSTRACT
Conditions of microencapsulation by in situ polycondensation, using melamine-formaldehyde as wall material, are influenced by the chemical nature of the core to encapsulate. In our study concerning the encapsulation of a photopolymerizable phase containing an electrically charged compound, it was necessary to modify the experimental process to obtain capsules of good quality. We used the factorial design method of screening by utilization of an asymmetric matrix, according to the collapsing principle of Addleman. The advantage of this method is that it allows determination of the simultaneous influences of the 11 experimental parameters involved in this preparation. The calculation method can be applied to more than two levels for some of the factors. The continuously varying parameters were altered between two extreme levels, chosen to allow encapsulation. For discontinuous factors, such as the molecular weight of the modifying system or nature of the aminoplast, we used the commercially available compounds, respectively three and four kinds. The results of the obtained capsules were determined by comparing microphotographic pictures. With 16 experiments we found four more factors influencing quality of capsules. We also determined the most favourable levels for the other seven parameters. The results allowed us to find optimal conditions in the experimental field. We obtained capsules of a satisfactory quality for this purpose, using only minimum experimentation.
Subject(s)
Chemistry, Pharmaceutical/methods , Photochemistry/methods , Polymers/chemistry , Drug Compounding , Regression AnalysisABSTRACT
The influences of 11 factors are studied. Molecular weight of the emulsifier, amount of wall material and amount of core material were found to be the most influential factors.
Subject(s)
Capsules/chemistry , Drug Compounding/methods , Butylamines , Excipients , Formaldehyde , Least-Squares Analysis , Maleates , Microscopy , Polyphosphates , Polyvinyls , TriazinesABSTRACT
714 cases of Fallot's tetralogy have been encountered over the last thirty years. A closed heart operation was undertaken in 472 patients. The mean age at operation was 5,1 years. In 87% of cases, a Blalock-Taussig anastomosis was carried out. The operative mortality was of the order of 3%. The operative risk was almost three times as large before the age of two years as after. The patients benefit by a demonstrable improvement of function after this operation, but it does not protect them from the complications of the condition (cervica abscess, Osler's disease, cerebro-vascular accidents) or from death. Open heart surgery was carried out in 403 patients. 161 as a primary procedure, and 242 after an initial palliative operation. The mean age at operation was 13.3 years. The operative mortality was 15%. The functional improvement was striking, and the patients appeared to be protected from the usual sequelae of the condition. On the other hand they cannot always be considered as cured: 16 died some time after the operation; 37% had pulmonary incompetence; 15% had a residual BSD; 8% had a block of both bundles, and 3% had a definitive atrio-ventricular block.
Subject(s)
Tetralogy of Fallot/surgery , Age Factors , Child, Preschool , Follow-Up Studies , Humans , Infant , Methods , Palliative Care , Tetralogy of Fallot/complicationsABSTRACT
The authors have followed up children with cardiac defects over almost a twenty year period. During the 1960's most of their patients had come of age, and they conclude that despite the enthusiasm of these young people and their potential, they have the greatest difficulties in finding work. This seems regrettable from the human as well as the socio-economic point of view. They propose that the law should be changed as, indeed, should the spirit of the law, so that; a subject with heart disease should no longer be considered as incapable of useful work, and that each person should be assessed according to his potential. They envisage the setting up of medico-administrative cardiological centres. Thus, in addition to the purely medical cardiological consultation, three additional persons would add their expertise: a social worker, an industrial medicine inspector, and an employment officer. These centres could be instituted easily, without making the existing system too unworkable.
