High internal phase emulsions: Catastrophic phase inversion, stability, and triggered destabilization

We have investigated the formation, drop sizes, and stability of emulsions prepared by hand shaking in a closed vessel in which the emulsion is in contact with a single type of surface during its formation. The emulsions undergo catastrophic phase inversion from oil-in-water (o/w) to water-in-oil (w/o) as the oil volume fraction is increased. We find that the oil volume fraction required for catastrophic inversion exhibits a linear correlation with the oil-water-solid surface contact angle. W/o high internal phase emulsions (HIPEs) prepared in this way contain water drops of diameters in the range 10-100 μm; emulsion drop size depends on the surfactant concentration and method of preparation. W/o HIPEs with large water drops show water separation but w/o HIPEs with small water drops are stable with respect to water separation for more than 100 days. The destabilization of the w/o HIPEs can be triggered by either evaporation of the oil continuous phase or by contact the emulsion with a solid surface of the "wrong" wettability. © 2011 American Chemical Society

Somatic embryogenesis and plant regeneration in carob ( Ceratonia siliqua L.)

Summary Somatic embryos of carob (Ceratonia siliqua L.) were induced from cotyledonary segments excised from immature seeds when cultured on Murashige and Skoog media supplemented with several combinations of 6-benzylaminopurine (BA) and indole-3-butyric acid (IBA). The best frequencies of induction (33.8%) were obtained when 4.4 µM BA and 0.5 µM IBA were used. Shoots were also sporadically formed in the same media. When IBA was replaced by other auxins in the induction media, only a-naphthaleneacetic acid (NAA) and indole-3-acetic acid (IAA) could induce somatic embryogenesis, although at lower rates than IBA. 2,4-Dichlorophenoxyacetic acid and 4-amino-3,5,6-trichloropicolinic acid were completely ineffective. Besides culture media composition, the developmental stage of the explants at the time of culture showed a strong influence on somatic embryogenesis induction, with cotyledons from stage II pods providing the highest levels of induction. By contrast, the genotype of the explant did not determine a significant role in the induction process. Attempts to achieve somatic embryo germination were mostly unsuccessful, since only shoot development was observed; the highest frequencies of development occurred on media containing only gibberellic acid (3.0 µM). For plant regeneration, the developed shoots were further rooted on IBA-supplemented media, and the plantlets obtained were transferred to soil, where c. 88% of them survived. Histological observations showed the presence of morphologically normal and abnormal somatic embryos, the latter displaying an abnormal pattern of vascular bundles. Ultrastructural analysis showed that the cells of the globular embryos had a dense cytoplasm, whereas those not involved in somatic embryo formation showed signs of senescence. Histological studies were also used to distinguish between somatic embryos and shoots originated in the same media

Environmental impacts of diesel fuel on bacteria and phytoplankton in a tropical estuary assessed using in situ mesocosms

10.1007/s10646-004-6373-8Ecotoxicology143397-412ECOT