We report a novel oil-in-water emulsion that is both buoyancy and refractive index matched. The dispersion is created using low-shear cross-flow membrane emulsification technology with a discrete phase comprising a mixture of n-hexane and the perfluorinated oil tetradecafluorohexane, in the form of FC-72. Three-dimensional confocal laser light imaging of a bulk-aggregated emulsion is demonstrated, showing explicit droplet-level detail of the emulsion interior. Magnetic resonance microscopy with a spatial resolution of tens of microns is also described. The proximity of a liquid–liquid binodal in the oil mixture can give rise to a ternary phase separation reminiscent of an O/O/W emulsion.

Ultrasonic measurements of attenuation versus frequency were made on model systems comprising olive oil, sucrose, and tripalmitin to represent the constituents of chocolate. Corresponding measurements also were made on chocolate flowing in a pipeline at a pilot plant where the temperature, pressure, and temper of the chocolate were precisely controlled and monitored. Experimental results combined with simulation studies indicate that the effect of ultrasonic scattering from tripalmitin crystals in olive oil is modified by the addition of sucrose crystals at a high concentration. It is proposed that the presence of seed crystals in chocolate (temper) cannot be detected ultrasonically in the practical measurement range 1-12 MHz due to a similar process.

We report an experimental investigation on the creaming behavior of flocculated, polydisperse, oil-in-water emulsions. Flocculation is by addition of a depletion flocculant, the polymer hydroxyethylcellulose (HEC), at a range of concentrations. The creaming behavior is dependent on the oil volume fraction and polymer concentration. At low concentrations of HEC, the droplets cream either individually or in two populations, a flocculated phase, and a coexistent phase of individual droplets. At higher HEC concentrations, the droplets appear to cream as a single entity, with a sharp lower boundary, separating the region with droplets from a clear serum at the base of the container. In these emulsions, and in some of the coexistent ones, there is a significant delay before creaming starts. Once started they cream at a constant rate. We have identified the continuous phase viscosity as a major factor.

Abstract Experimental data are reported on the creaming behaviour of two oil-in-water emulsion systems, containing polysaccharide. It is demonstrated that flocculation of the droplets occurs in both systems, but that the detailed behaviour differs. Type A emulsions exhibit rapid formation of coexistent phases at certain polymer concentrations, and the behaviour is consistent with a volume restriction (depletion) mechanism. Type B emulsions exhibit very slow flocculation which is consistent with bridging of droplets by adsorbed polymer.

The anionic polysaccharide xanthan, widely used as a stabilizer in food dispersions, induces flocculation by a depletion mechanism. The effect of flocculation, induced by the presence of xanthan, on the gravitational destabilization (creaming and compaction) of 20% oil-in-water emulsions is presented. The detailed gravitational destabilization processes are studied by following changes in the concentration profile with time. In the absence of flocculant the polydisperse droplets rise as a diffuse meniscus and form a cream of ~70% oil at the top of the sample. Such behaviour is consistent with creaming in a dispersion of non-interacting polydisperse particles. In contrast the flocculated droplets form a sharp meniscus and cream rapidly. At the top of the sample the floes form a less concentrated cream which undergoes compaction under gravity. The compaction is characterized by a concentration-dependent bulk modulus.

An account is given on the validation of the combinations Paraphysomonas diademifera (Takahashi) Preisig & Hibberd (basionym: Ochromonas diademifera Taka_ hashi) and Polylepidomonas vacuolata (Thorasen) Preisig & Hibberd (basionym: Paraphysomonas vacuolata Thomsen).

An ultrastructural investigation has shown the presence of icosahedral virus–like particles (VLPs) in three species of Paraphysomonas and one species of Chromophysomonas. The VLPs appear to be responsible for the sudden collapse of enrichment cultures of these species. The possible relationship with particles in other algae which are known to be true viruses is discussed. Endophytic bacteria were also observed in two species of Paraphysomonas, where they occurred within distensions of the nuclear envelope. This is the first report of endophytic bacteria in this location in the algae.

This is the second of two accounts reporting on the occurrence and systematics of freshwater species of the colourless chrysophycean genus Paraphysomonas in the Cambridge area, using electron microscopy of whole mounts of both cells and scales and sections of scales. Twenty species are included here, eleven of which are new: P. cancellala, P. canistrum, P. homolepis, P. ignivoma, P. limbata, P. morchella, P. runcinifera, P. stelligera, P. stephanolepis, P. subquadrangularis and P. undulata. Five new subspecies are also established: P. circumvallata ssp. mediogranulata, P. poteriophora ssp. manubriata, P. punctata ssp. atrema, ssp. microlepis and ssp. simplicior. P. diademifera (Takahashi) comb. nov. [=Lepidochromonas diademifera (Takahashi) Kristiansen] has been included in Paraphysomonas since it has been found to be colourless and not pigmented as originally described and also to possess scales of a similar structure to those in other species of Paraphysomonas. One previously described species, P. inconspicua Takahashi, is here considered as a synonym of P. butcheri Pennick & Clarke. P. vacuolata Thomsen is removed from Paraphysomonas since it has been found to possess a chloroplast and will be included in a new genus in the third paper of this series. The 37 presently known species of Paraphysomonas have been arranged in 11 different groups according to similarities in scale structure. Consideration of the possible evolution of scale structure in Paraphysomonas and the possible interrelationships within the genus led to the conclusion that all species should be included in a single genus.

New observations are presented on the internal ultrastructure of the scale–bearing chrysophycean genera Chromophysomonas, Chrysosphaerella, the new genus Polylepidomonas and 15 species of Paraphysomonas. These data show that the pigmented genera Chromophysomonas, Chrysosphaerella and Polylepidomonas have a generally similar internal structure and that their taxonomic separation is based only on differences in scale structure. The structure of Paraphysomonas resembles that of these genera but the cells always possess a leucoplast rather than a chloroplast. In cell structure, the pigmented genera resemble the naked genus Ochromonas while Paraphysomonas resembles Spumella, the colourless counterpart of Ochromonas. Evaluation of the differences between these genera and the scale–bearing genera Mallomonas and Synura has led to the conclusion that Chromophysomonas, Chrysosphaerella, Polylepidomonas and Paraphysomonas should no longer be classified within the family Mallomonadaceae. The new family Paraphysomonadaceae is established to include Chrysophyceae with an Ochromonas type of cell structure but which also produce silica scales.

A new member of the Chrysophyceae,Rhizochromulina marina gen. et sp.nov. is described by means of both light and electron microscopy of cultured material. Vegetative cells are non-flagellate and amoeboid with many fine beaded filipodia and a single golden-brown chloroplast. Zoospores are fusiform in shape and genuinely uniflagellate with no emergent vestigial second flagellum. They appear to possess the most reduced and phylogenetically advanced type of motile cell organization yet found in the Chrysophyceae.