摘要:

Fatty acid Langmuir-Blodgett films are observed to be removed when exposed to a flowing suspension of polystyrene latex particles. Particles are typically coated with a complete monolayer of fatty acid before becoming detached from the surface, implying that they scavenge by rolling about on the surface before leaving it.

ISSN:0193-2691    

DOI:10.1080/01932699808913220

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Oil-in-water emulsions of sodium hyaluronate stabilized by nonionic surfactants were analyzed for structural changes during evaporation. The results were compared to the structures found in the appropriate phase diagrams.

ISSN:0193-2691    

DOI:10.1080/01932699808913221

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Uniform colloidal pigment dispersions of narrow size distribution were obtained by interacting aqueous solutions of D&C Red #6 dye and BaCl2. The original particles were elongated in shape but the anisometry could be altered by input of ultrasonic energy. The addition of an anionic surfactant caused a decrease of the average pigment size to ∼ 40 nm. The so prepared colored dispersions showed 100% transparency, which is considerable higher than the commercial Ba lake of the same dye.

ISSN:0193-2691    

DOI:10.1080/01932699808913222

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

An appreciation of the importance of particle surface charge as a determinant of the behavior of particle suspensions has stimulated interest in electrophoretic analyses of small particles. Currently available analytical particle electrophoresis equipment provide increasingly powerful techniques for probing the surface charge of small particles so that the potential of the application of the method may be realized in basic and applied research as well as in process development and control in manufacturing environments. Two recurrent issues in the application of the methods are the qualification of the instrument operation and the consistency of the reagents employed. Here we describe strategies for addressing these problems through the use of uniform detergent free, charge-stabilized polymer microspheres first as control particles for monitoring satisfactory instrument operation and secondly as sensitive ‘reporter” probes for detection of trace contaminants in the suspending media used for electrophoretie analysis.

ISSN:0193-2691    

DOI:10.1080/01932699808913223

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Interval free flow zone electrophoresis is a new mode of free flow zone electrophoresis (FFZE), which facilitates purification of proteins and other molecular substances at very high resolution. It can be performed in the commercially available free flow electrophoresis (FFE) apparatus Octopus. The specimens are loaded and unloaded as usual with the help of a thin buffer film flowing between the two glass plates of the FFE. However, as long as electrical current is applied to a specimen, the medium flow is turned off and conditions of static column electrophoresis are simulated within the FFE device. Thereby electrohydrodynamic flow effects, which widen the sample bands migrating within the electric field, are eliminated while optimal heat removal from the thin buffer film is still possible and a sophisticated technique of harvesting of fractions remains available. Thus interval FFZE offers a gentle preparative method for purification of many kinds of charged molecular species such as proteins or dyes at very high resolution.

ISSN:0193-2691    

DOI:10.1080/01932699808913224

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

By means of contact angle measurements with water and aqueous salt solutions, it is shown that plurivalent cations increase the hydrophobicity of negatively charged phospholipid vesicle membranes (consisting of phosphatidic acid, PA, or of phosphatidylserine, PS), but does not influence the hydrophobicity of neutral phospholipid membranes, (e.g., phosphatidylcholine, PC, at up to 200 mM of CaCl2). The hydrophobizing action of cations on PA and PS membranes is concomitant with the reduction in (negative) zeta potential with increasing cation concentrations. Trivalent cations, La3+, showed more effective in hydrophobizing negatively charged phospholipid membranes than divalent and monovalent cations. Except for hydrogen ions, monovalent cations do not show any appreciable hydrophobizing effect on lipid vesicle membranes at concentrations less than 1 M. The hydrophobizing effect on phospholipid membranes can also be used to explain the induction of lateral phase separation into patches of different phospholipids as well as cell fusion.

ISSN:0193-2691    

DOI:10.1080/01932699808913225

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Cell function is dependent of the formation and rupture of adhesive interactions. Two lines of research were followed to help understand these phenomena. Physically oriented scientists developed theoretical and experimental methods for relating the interaction energy between macroscopic surfaces to material properties of these surfaces. Biologists spent much effort in characterizing specific receptor and ligand molecules. The aim of this paper is to discuss the relationship between both approaches. It is concluded that i) so-called nonspecific and specific interactions represent combinations of the same primary forces, ii) it is however both possible and useful to discriminate specific and nonspecific interactons, and iii) as suggested by some specific examples, understanding cell behavior requires to consider both aforementioned approaches.

ISSN:0193-2691    

DOI:10.1080/01932699808913226

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

To study the polar interactions of the cartilage component hyaluronate (HA) contact angle measurements of polymer films of sodium hyaluronate and of the free hyaluronic acid with different probe liquids and theoretical investigations with molecular dynamics simulation (MD) on polymer segments in aqueous environment were performed. For the designation of contact angles water, formamid, glycerol and α-bromnaphthalene as probe liquids were used. The surface tension components were calculated on the basis of the theory of van Oss using the Young equation. Experimental investigations were done with air dried layers of the sodium salt of HA whose surface has been formed at the interface to the air resp. glass support. Whereas the surface polymer/air is characterized by small, but non-zero values for γ•and γ-the surface polymer/glass tends to have γ-monopolar properties. In opposite to the salt form of HA a strong repulsion of chains and high γ-monopolarity was measured for the protonated form.

ISSN:0193-2691    

DOI:10.1080/01932699808913227

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The W/O xanthan fermentation is simulated by integrating the microbial kinetic behaviors and the multiple-phase process characteristics. Model 1 assumes uniform redistribution of cells, substrates and product by frequent droplet breakup and coalescence. Model 2 simulates the system of viscous aqueous phase with minimal droplet breakup and component redistribution. The real fermentation should proceed within the bounds set by the two models. Effects of various parameters are evaluated. The aqueous-phase xanthan concentration (Xn) and volumetric productivity (QP) achieved at 200 h are used as the indicators. Xnand QPincrease with nitrogen-source concentration (SNO) initially but plateau (Model 1) or decrease slightly (Model 2) at high SNO. Xn(at 200 h) decreases with increasing aqueous-phase volume fraction (f). QP, however, increases with f reflecting its basing on the total dispersion volume. Increasing agitation and aeration result in higher Xnand QP. The higher agitation enhances the G/O interfacial oxygen transfer and reduces the droplet size. Increasing aeration improves the G/O interfacial transfer but increases the droplet size. Its net positive effect implies a rate-limiting step at G/O interface. The W/O fermentation can produce far higher Xn(> 200 kg/m3) and QP( > 0.8 kg/m3-h) than the conventional fermentation (Xn ∼ 50 kg/m3, QP ∼ 0.5 kg/m3-h).

ISSN:0193-2691    

DOI:10.1080/01932699808913228

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Various surface-chemical interactions among the corneal epithelium, ocular mucous gel, tear film and tear film contaminants (e.g., cellular debris, lipids, bacteria) are characterized based on their apolar and polar (acid-base) surface properties. Based on this approach, the surface-chemical pathways of the tear film breakup and of the corneal epithelial lubrication, cleansing, wetting and defense are proposed. A strong monopolar repulsion keeps mucus in the form of a highly hydrated gel, which cannot adhere to the normal glycocalix carrying epithelial surface, but forms an effective surface-chemical trap for the apolar and weakly polar hydrophobic contaminants. However, mucus-deficiency and/or a host of epithelial surface abnormalities (e.g., increased cell loss, chemical or morphologic changes, damage) can initiate a vicious cycle comprising of factors such as: increased mucus contamination, loss of mucus and epithelial hydrophilicity, abnormal adhesion and aggregation of mucus, reduced mucus mobility and faulty surface cleansing. All of these factors can conspire to produce a chronically unstable tear film secondary to the loss of corneal surface wettability.

ISSN:0193-2691    

DOI:10.1080/01932699808913229

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor