磁流变胶的沉降和力学性能研究

研制了一种新型的磁流变胶（magnetorheological gels），它具有良好的沉降稳定性和优良的磁流变效应。在2500r/min的离心实验中，离心20min之后才完全沉降：其剪切应力与剪切速率的关系可用Herschel-Bukley模型进行很好的描述；剪切屈服应力在小磁场下剪切屈服应力与磁场成线性关系，当磁场为70kA/m时，剪切屈服应力达到了53．9kPa。     

Preparation and pharmacokinetics in rabbits of breviscapine unilamellar vesicles

The purpose of the study was to prepare the unilamellar liposomal vesicles of breviscapine (Breviscapine-LUVs) and investigate the pharmacokinetics of Breviscapine-LUVs in rabbits. Breviscapine-LUVs were prepared by the film dispersion method and treated further by extrusion. Its size distribution and zeta potential were determined by photon correlation spectroscopy. The encapsulation efficiency (EE) and cumulative release of Breviscapine-LUVs were assayed by the dialysis method. The crossover design (two periods) was used in six rabbits, which were administered Breviscapine-LUVs and reference preparation. Results showed that the particle size of Breviscapine-LUVs was 50.8 nm, and the polydispersity index was 0.287. The zata potential was -24 mV ± 9 mV(n = 3), and the EE% was 81.1 ± 1.1% (n = 3). The cumulative release of vesicles in 0.9% NaCl was 17.2 ± 0.78%, 26.1 ± 0.68%, and 29.9 ± 0.81% in 2, 8, and 24 h, respectively. The mean concentration-time curves of breviscapine liposomes and reference preparation were both fitted to a two-compartment model with the main pharmacokinetic parameters as follows: t_1/2β of Breviscapine-LUVs and reference preparation were (42.5 ± 28.6) min and (6.01 ± 4.64) min, respectively; CL_(s) were (15.3 ± 9.03) mL × min^-1 and (84.6 ± 40.6) mL × min^-1, respectively; AUC_0-300 were (1267 ± 1083) μg × min × mL^-1 and (196 ± 107) μg × min × mL^-1, respectively. Compared with the reference preparation, breviscapine liposomes had a much higher concentration in plasma and contained characteristic of sustained-release, which ameliorated the pharmacokinetic properties of scutellarin.     

Effects of soil properties on surfactant adsorption

Abstract

The effects of surface area, soil organic matter (SOM) content, and cation exchange capacity (CEC) of natural soils and clays on the adsorption capacity of cationic, anionic, and nonionic surfactants in water‐solid systems were investigated based on the adsorption isotherm analysis. The sorption capacity for a cationic surfactant was proportional to the CEC of the solids. For both anionic and nonionic surfactants, the sorption capacity was related to the soil mineral fraction. However, other soil properties probably affect the practical sorption. The investigated soil properties were treated case by case.     

Non-covalent chiral fibres in aqueous gels and their functionalization

The fully reversible synthesis of noncovalent assemblies which are held together by directed bonds is called synkinesis. Micellar fibres with a distinct stereochemistry and gels are formed by amphiphiles forming strong hydrogen bonds between chiral head groups. The 3D-crystallization of such molecular assemblies, without dominating repulsive hydration forces, is prevented by the curvature of the fibres. Curvature might perhaps be directly connected with chirality. Addition of enantiomers often leads to an irreversible destruction of gels. Recent developments relating to ‘hydrophobic water’ in Ångström-wide membrane gaps are also shortly discussed.     

Growth and characterization of barium copper oxalate single crystals in gels

Barium copper oxalate was grown in silica hydrogel at ambient temperature. The effect of various parameters like gel pH, gel density, gel aging and concentrations of reactants on the growth of these crystals was studied. The crystals grown were characterized by chemical analysis, X-ray powder diffractometry, infrared spectroscopy, thermogravimetric and differential thermal analysis. The results of these observations are described and discussed.     

Studies on nonionic surfactant bilayer vesicles of ciclopirox olamine

Context: Niosomal delivery can prove an alternative to improve the poor skin penetration and residence of the topical antifungal drugs that account for the long treatment regimes in cutaneous mycosis. Objective: To investigate niosomes as carriers for dermal delivery of ciclopirox olamine (CPO), a broad spectrum antifungal drug. Materials and methods: Niosomes were prepared by ethanol injection method using Span 60, cholesterol, diacetyl phosphate according to 3² factorial design and evaluated for physicochemical parameters, in vitro and ex vivo deposition in skin and stability study. Results: Unilamellar CPO niosomes of size 170–280 nm, entrapment efficiency 38–68%, and sufficient electrokinetic stability were obtained. Percent drug deposition in artificial membrane varied from 12.75 to 92.74. Deposition of CPO into rat skin from niosomal dispersion and its gel was significantly higher than that of plain CPO solution and its marketed product. Obtained niosomes possessed sufficient stability on storage. Discussion: Increasing amounts of Span 60 and cholesterol increase the vesicle size probably because of entrapment of CPO-ionized molecules in the aqueous compartment and interaction of its unionized counterpart with the bilayer constituents leading to increase in bilayer thickness. Consequently, the percent entrapment efficiency also increased. However, increasing Span 60 levels decreased the in vitro percent drug deposition. This might be attributed to the larger size of vesicles produced by high amounts of surfactant that showed poor deposition. The optimized batch possessed sufficient stability. Conclusions: The results of this investigation suggest that niosomes are promising tools for cutaneous retention of CPO.     

Characterization and thermal behaviour of lanthanum tartrate crystals grown from silica gels

Results obtained on characterization of lanthanum tartrate crystals, grown by the gel method, using chemical analysis, x-ray and electron diffraction, infra-red and mass spectroscopy are reported. The thermal behaviour is studied using DTA, TGA and DTG. The decomposition pattern is reported to be typical of a hydrated metal tartrate. Kinetic parameters like order of reaction, frequency factor and activation energy are evaluated. Contracting cylinder kinetic model is found to be the best fit for the decomposition processes involved. Magnetic susceptibility measurements indicate the material to be diamagnetic.     

Monolayer behavior of calix-4-resorcinarenes and their surfactant complexes

We describe within this paper a series of calix-4-resorcinarenes along with their complexes with tetraalkylammonium surfactants and their behavior in Langmuir monolayers. Calix‐4‐resorcinarenes were synthesized containing both undecyl and phenyl sidechains and then modified using Mannich reactions to incorporate neutral, cationic or anionic groups in the 2‐positions of the resorcinol unit. In the cases of resorcinarenes modified with four sulfonate groups, mixing with long chain dialkyl dimethyl ammonium surfactants led to the formation of 1:4 complexes. These various materials were spread as Langmuir monolayers and their behavior upon compression measured. Long chain substituted resorcinarenes gave more stable monolayers than their short chain analogues. The incorporation of long chain surfactants led to large increases in surface area, demonstrating that both resorcinarenes and surfactant are located at the water surface, except for one system where a bilayer structure is potentially formed.     

Growth of hydroxyapatite on silica gels in the presence of organic additives: kinetics and mechanism

Synthetic hydroxyapatite was grown on surfaces of silica gels by immersing silica monoliths in a simulated body fluid at 37 °C. The gels were prepared by the sol-gel method and the drying process was controlled by using different additives (mono- and di-ethylene glycol, formamide and glycerin) to obtain large monoliths. The additives affect the growth of the apatite by changing the kinetic constants of chemical reactions on the silica surface. Surface areas and pore size distributions were determined, energy dispersion and FTIR spectra obtained, and scanning electron microscopy performed. The formation of the hydroxyapatite competes with the formation of crystalline calcium carbonate, but the results allow optimization of conditions for the growth of the former as a function of the type and concentration of the additive. For these optimal conditions, the mechanism and the order of the reaction were determined. Received: 15 February 2000 / Reviewed and accepted: 28 June 2000     

Time dependent properties of thermoreversible gels

Rheological properties of the system gelatin + water at a polymer concentration of 5.0% by wt at a temperature of 301 K and an angular frequency of 0.628 rads^–1 are presented and evaluated by use of the percolation theory. A frequency power law has been found close to the gel point from which a critical time range could be deduced in which the powers of the loss and storage modulus are the same. The times needed for the gelation from the percolation relations are close to the range where the exponents of the frequency power law relations are identical. The scaling coefficient Δ for physical gelation agrees very well with that found for chemical gelation by Durand and coworkers. Received: 9 October 2000 / Reviewed and accepted: 10 October 2000     

Swelling and diffusion of PNIPA-based gels for localized chemotherapy and hyperthermia

This paper presents the results of an experimental study of the swelling and diffusion of poly(N-iso-propyl-acrylamide) PNIPA-based gels with the potential for applications in bio-micro-electro-mechanical systems (BioMEMS) for localized cancer treatment that involves both chemotherapy and hyperthermia. The swelling due to the uptake of water, rhodamine dye and the cancer drug, paclitaxel, are studied using weight gain experiments that are conducted over a range of temperatures in which hyperthermia can occur during drug delivery. The release of rhodamine dye and paclitaxel is also elucidated by considering their diffusion through the gels. The underlying mechanisms of diffusion and swelling are discussed over a temperature range in which synergistic cancer treatment can be effected by the combined use of hyperthermia and chemotherapy.     

Growth of single crystals of some complex salts in silica gels

Single crystals of ammonium nickel sulphate, potassium nickel sulphate, ammonium alum and potassium alum are grown in sodium-metasilicate gels. The method of gel preparation and growth procedure are described. Both single diffusion and double diffusion methods are used. Studies on nucleation and characterisation of crystals are also reported. Crystals grown are illustrated.     

Solubilization of (+)-limonene by anionic/cationic mixed surfactant systems

The combined effects of sodium n-octyl sulfate (SOS) and cetyltrimethylammonium bromide (CTAB) on the solubilization of (+)-limonene in aqueous solution were studied using a headspace gas chromatography technique. The findings showed the mixing of SOS and CTAB resulted in positive synergistic effects on the solubility of (+)-limonene. The positive synergistic effects are explained from the perspective of the phase behavior of this mixed surfactant system.     

Development of the ambroxol gels for enhanced transdermal delivery

Ambroxol is an expectoration improver and mucolytic agent that has been used to treat acute and chronic disorders. However, ambroxol needs to be administered percutaneously in order to avoid systemic adverse effects, such as headache, drowsiness, dizziness, and insomnia, which can occur after oral administration. The aim of this study was to develop a gel preparation containing a permeation enhancer to enhance the delivery of ambroxol. The ambroxol gels were prepared using hydroxypropyl methylcellulose (HPMC) and poloxamer 407. The release characteristics of the drug from the gels were examined according to the receptor medium, drug concentration, and temperature. The rate of drug permeation into the skin was enhanced by incorporating various enhancers such as the ethylene glycols, the propylene glycols, the glycerides, the non-ionic surfactants, and the fatty acids into the gels. The permeation study through mouse skin was examined at 37˚C. The rate of drug release increased with increasing drug concentration and temperature. Among the enhancers used, propylene glycol mono caprylate showed the best enhancing effects. The estimated activation energy of release (Ea), which was calculated from the slope of a log P versus 1000/T plot, was 14.80, 14.22, 13.91, and 12.46 kcal/mol for ambroxol loading doses of 2, 3, 4, and 5%, respectively. The results of this study show that the gel preparation of ambroxol containing a permeation enhancer could be developed for the enhanced transdermal delivery of ambroxol.     

Structural investigations of sol–gel derived silicate gels using Eu ion-probe luminescence

Undoped and Eu³⁺-doped CaF₂–SiO₂ gels were prepared by the sol–gel method and their optical properties have been studied. The UV–VIS–NIR absorption and photoluminescence spectra have shown the bands typical for the Eu³⁺ ions transitions. When the Eu-doped gel is annealed at temperatures up to 800 °C (i.e. above the CaF₂ crystallisation peak at 460 °C) the photoluminescence spectra intensity increase, the 590 nm (⁵D₀→⁷F₁) and 620 nm (⁵D₀→⁷F₂) luminescence bands become comparable and a structuring of the 620 nm band is observed. The phonon sidebands peaks associated with the ⁵F₀→⁷D₂ transition of the Eu³⁺ ion were observed at around 1000 and 620 cm⁻¹ and have been assigned to the Si–O and Ca–O bonds, respectively. A phonon sideband signal in the range of 300–400 cm⁻¹ was attributed to Ca–F bonds in the precipitated CaF₂ phase. From the optical absorption, photoluminescence and phonon sidebands spectra we have concluded that in the gels annealed at 800 °C, the Eu³⁺ ions are incorporated into the silica network and in the precipitated CaF₂ phase.     

A generalized decoupling numerical framework for polymeric gels and its element-free implementation

Coupled diffusion of solvent molecules and mechanical stretching of polymeric networks induced swelling/deswelling in polymeric gels contributes to the ability of its “smart response” and “environmental sensitivity.” In this article, the coupled diffusion and large deformation of polymeric gels are clarified into three kinds of deformation conditions which all involve swelling/deswelling. The real numerical challenge is identified for simulating swelling/deswelling induced deformation of gels by solving the partial deferential control equation of a popular monophase model for gels in steady equilibrium state with a standard process of numerical discretization. To address the numerical challenge, a generalized decoupling numerical framework is developed based on a multiplicative decomposition of deformation gradient. The proposed framework is more flexible and works for almost all cases of deformation of gels no matter involving swelling/deswelling or not. Its element-free implementation is also developed using the element-free IMLS-Ritz method and is validated through analyzing the three-dimensional stable and unstable large deformation of the constrained gel cube and tube.     

双子表面活性剂为模板纳米二氧化钛的制备及光催化活性

以脱氢松香为原料,通过化学合成的方法制备出一种新颖的双子表面活性剂,采用FT-IR及1 HNMR对其结构进行确证;以酞酸四正丁酯（TNB）为起始原料,通过加入自制的双子表面活性剂,采用水热合成法制备了平均粒径为8.81nm的锐钛矿型纳米二氧化钛颗粒;利用FT-IR、TEM、XRD对纳米二氧化钛进行表征;以紫外光为光源,罗丹明B（RhB）为模型污染物考察了纳米二氧化钛的光催化活性,结果表明其催化活性优于未加表面活性剂制备的纳米二氧化钛,且在紫外光下反应3h,RhB的降解率为99.7%,基本完全降解。