摘要:

The conformation of the lung surfactant lipid bilayer (termed tubular myelin) is shown to fit an infinite periodic surface, which is free from self-intersections and with zero or close to zero average curvature. A single lipid bilayer is curved in space, forming a tetragonal structure (CLP) with tubular units, the walls of which are close to planar and parallel to two orthogonal directions. A cryo transmission electron microscopy (cryo-TEM) study of the alveolar surface layer from rabbit was performed. Direct deposition of the surface layer on the microscopy grid indicates that the surface zone consists of a homogeneous phase. The cryo-TEM texture of the bilayer is consistent with earlier reported electron microscopy observations of dispersed aggregates in lung washings. It is shown how the interface towards air can be formed by opening up the phase along lipid methyl end groups. The model is fundamentally different from earlier proposals, involving a “free” lipid-protein monolayer at the air/water interface. Functional aspects and medical implications of a coherent surface phase structure are discussed.

ISSN:0193-2691    

DOI:10.1080/01932699908943775

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The layer-by-layer self-assembly of poly(diallyldimethyl-ammonium) chloride, PDDA; graphite oxide, G, nanoplatelets; and polyethylene oxide, PEO, onto transparent indium tin oxide substrates, S, have provided cationic working electrodes which, with lithium wires as reference and counter electrodes, functioned as high energy density rechargeable lithium-ion batteries. Specifically, very high specific capacities (1232 and 1134 mAh.g−1) have been determined for batteries which had positive electrodes of ten sandwich layers of self-assembled films: S-(PDDA/GO/PEO)10and S-(PDDA/PEO)10. The importance of the exfoliating GO into nanoplatelets and the colloid chemistry of self-assembly are discussed.

ISSN:0193-2691    

DOI:10.1080/01932699908943776

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Aqueous dispersions of colloidal aggregates of liquid-crystalline lipid-water phases are described. The lamellar liquid-crystalline phase can form liposomal dispersions, which are wellknown from extensive studies of these particles in drug delivery. Less is known about dispersions of cubic and hexagonal phases. The preparation of such colloidal dispersions, their structure and physical properties are summerised. The dispersed cubic phase is compared to liposomal dispersions, and it is concluded that an important application of the cubic particles will involve encapsulation of proteins and protection of their native conformation.

ISSN:0193-2691    

DOI:10.1080/01932699908943777

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The formation of lyotropic mesophases (liquid crystals) in four binary systems n-alkyl glycosides/water was examined in dependence on surfactant concentration, temperature and the chain lengths (alkyl = heptyl, octyl, nonyl, decyl). The binary phase diagrams were established and the enthalpies of phase transitions were measured. The following phase transitions were detected by texture observation and calorimetry: hexagonal phase H, lamellar phase L, cubic phase Q, gel phase G and crystalline phase C. The positions of the corresponding regions of these phases in the phase diagram were determined. Sequence of phases and the localization of the phase regions were depended on the chain length of the alkyl group. So in the binary system n-decyl-β-D-glucoside/water the H-phase was not observed.

ISSN:0193-2691    

DOI:10.1080/01932699908943778

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The influence of the Ca++and inhibitor concentrations, pH, and temperature on the phase behaviour and precipitation yield of a phosphinopolyacrylate scale inhibitor, PPAA, has been studied. The results are interpreted in terms of the chemical processes governing PPAA-Ca++complexation, and evidence for the role of inhibitor molecular weight in determining the degree of precipitation is produced. Comparative adsorption and precipitation squeezes, carried out in sandpacks, demonstrate that significant enhancement of the treatment lifetime can be achieved when conditions giving extensive inhibitor precipitation are used. The sandpack experiments and dissolution studies on the precipitated inhibitor both suggest strongly that kinetic phenomena influence the return level of inhibitor in the field. Together these studies point the way to approaches for optimising inhibitor precipitation squeeze treatments in order to control scale deposition in petroleum reservoirs.

ISSN:0193-2691    

DOI:10.1080/01932699908943779

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

Ionic surface diffusitivity is important parameter for the electrostatic interaction between colloid particles and hence its measurement is a new important factor for the surface characterization of colloid particles. If the adsorbed ion mobility is small the approximation of the interaction at constant charge can be valid,but in opposite case the charge regulation occurs during their interaction.

ISSN:0193-2691    

DOI:10.1080/01932699908943780

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

ISSN:0193-2691    

DOI:10.1080/01932699908943781

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The present study elucidates the skin permeation enhancement effects of a number of fatty acids, i.e. straight-chain saturated (SFA), monounsaturated (MUFA) and polyunsaturated acids (PUFA). The effects were studied using human stratum corneum (SC) andp-aminobenzoic acid (PABA) as a model permeant. The fatty acids in propylene glycol (FA/PG) were applied according to a pre-treatment/co-treatment protocol. SFA with 6 to 12 carbons exhibit a parabolic correlation between enhancement effect and chain-length, with a maximum at nonanoic-decanoic acids (with 9 and 10 carbons). Allcis-6-, 9-, 11- or 13-octadecenoic acids (MUFA) enhance the permeation of PABA to the same extent. PUFA — linoleic (LA), α-linolenic (ALA) and arachidonic acids — enhance PABA permeation stronger than MUFA but additional double bonds do not further increase the degree of enhancement. The enhancement effects of fatty acids on the PABA penetration through SC are structure-dependent, associated with the existence of a balance between the permeability of pure fatty acids across SC and the interaction of the acids to skin lipids. Based on this and other studies, a set of mechanisms of action is proposed for fatty acids.

ISSN:0193-2691    

DOI:10.1080/01932699908943782

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The influence of noncharged and especially charged polymers on structure formation in mesoscopic organized surfactant/alcohol/water systems is investigated. Cationic polyelectrolytes can be incorporated into the liquid crystalline SDS/decanol/water system keeping up the lamellar phase.

ISSN:0193-2691    

DOI:10.1080/01932699908943783

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor

摘要:

The adsorption properties and surface charge creation for the stearic acid and octadecane/aqueous electrolyte solutions are considered. The hairy structure of surface charge for these systems was confirmed on the basis of potentiometric titration, ion adsorption and electrophoretic measurement data. For the system with stearic acid the reaction of ionization and complexation of carboxyl groups of stearic acid molecules from subsurface layer are responsible for the creation of surface charge and adsorption properties. The surface charge at octadecane particle is probably the results in adsorption and orientation of water molecules at the interface.

ISSN:0193-2691    

DOI:10.1080/01932699908943784

出版商:Taylor & Francis Group    

年代:1999

数据来源: Taylor