Water Adsorption on Pyrogenic Silica Followed by 1H MAS NMR.

On the surface of two commercial pyrogenic silicas (Degussa and Cabot), five resonances were identified on the basis of the chemical shift, homonuclear coupling (T2), and spin-lattice relaxation behavior (T1). In accordance with previous studies we observed three different types of silanol groups: (i) weakly coupled (long T2), water inaccessible, isolated "internal" silanols at 1.8 ppm; (ii) weakly coupled, external "free" silanols revealed upon dehydration at 2.

[Newcastle disease in Algeria. Study of the pathogenic properties of Newcastle disease virus strains isolated in Algeria].

The Newcastle disease in Algeria: Study of pathogenic properties of the Newcastle disease viral strains isolated in Algeria. The study of pathogenic characters of 14 strains of Newcastle disease virus isolated from 1972 to 1982 was carried out: The following testS were realized: the mean lethal time for the chicken embryo, the pathogenic power index by intravenous way, the pathogenic power index by intracerebral way, the hemagglutination spectrum and the thermal stability of the hemagglutination. In short we can say that these isolated 14 strains are fast-growing.