Photodestructible vesicles

Stable vesicles are formed in a 1.4 wt % solution comprising a 1:3 mixture of the anionic photodestructible surfactant sodium 4-hexylphenylazosulfonate (C6PAS) and inert cationic cetyltrimethylamonium bromide (CTAB). UV irradiation drives an irreversible breakdown of the mixed C6PAS/CATB vesicles, owing to the selective degradation of C6PAS. A light-induced transition from small spherical-like polydisperse vesicles to long needle-like aggregation is observed.     

Irreversible thermal denaturation of beta-lactoglobulin retards adsorption of carrageenan onto beta-lactoglobulin-coated droplets

The influence of isothermal heat treatments on the adsorption of anionic carrageenan molecules to the surfaces of anionic beta-lactoglobulin-coated droplets has been investigated. The zeta-potential, mean particle diameter, microstructure, and creaming stability of emulsions containing beta-lactoglobulin-coated droplets and/or carrageenan molecules that had previously been heat treated at temperatures ranging from 30 to 90 degrees C for 20 min were measured (pH 6.0, 150 mM NaCl). Three different heat treatments were used to establish the physicochemical origin of the influence of thermal history on the adsorption of carrageenan molecules to the protein coated droplets: (i) droplets and carrageenan were mixed at room temperature, then heated together; (ii) droplets were heated, cooled to room temperature, then mixed with carrageenan; (iii) carrageenan was heated, cooled to room temperature, then mixed with droplets. For treatments i and ii appreciably more carrageenan adsorbed to the protein-coated droplet surfaces at temperatures < or = 60 degrees C than at higher temperatures. For treatment iii, carrageenan adsorbed to the droplet surfaces across the whole temperature range. These results suggest that an irreversible thermal denaturation of the adsorbed beta-lactoglobulin molecules inhibited the adsorption of carrageenan molecules to the droplet surfaces. We postulate that there is a patch of positive charge on the surface of the native globular protein molecules which becomes more diffuse upon thermal denaturation. We found that the carrageenan molecules were unable to protect the beta-lactoglobulin-coated droplets at high temperatures (T > 60 degrees C) because they desorbed from the droplet surfaces. Nevertheless, adsorption of iota-carrageenan was capable of protecting the droplets against flocculation caused by surface denaturation of the adsorbed proteins at lower temperatures (T < or = 50 degrees C).     

太阳能和风能的短期分散储存

运用太阳能和风能是解决能源问题的根本和长期的途径,但是,传统的能源可以根据需要调节供应,而太阳能和风能是间歇性的而且不能随需要来控制,要有效地运用太阳能和风能,能量储存是必须的,大规模长期储存能量是非常昂贵的,解决这个问题的一种方案是太阳能和风能的短期分散储存,所谓短期,是指十几小时至几天,相当于太阳能和风能的变化周期.所谓分散,是指以单个建筑为单位,并且以多种不同的方式储存能量,从产业发展的角度看,太阳能和风能的短期分散储存的没备会形成一个新的大规模的工业部门.     

3000% high-field magnetoresistance in super-lattices of CoFe nanoparticles

We report on magnetotransport measurements on millimeter-large super-lattices of CoFe nanoparticles surrounded by an organic layer. Electrical properties are typical of Coulomb blockade in three-dimensional arrays of nanoparticles. A large high-field magnetoresistance, reaching up to 3000%, is measured between 1.8 and 10 K. This exceeds by two orders of magnitude magnetoresistance values generally measured in arrays of 3d transition metal ferromagnetic nanoparticles. The magnetoresistance amplitude scales with the magnetic field/temperature ratio and displays an unusual exponential dependency with the applied voltage. The magnetoresistance abruptly disappears below 1.8 K. We propose that the magnetoresistance is due to some individual paramagnetic moments localized between the metallic cores of the nanoparticles, the origin of which is discussed.     

Factors affecting the detection limit of a flow- injection spectrophotometric procedure

Design criteria for manifolds to obtain adequated sensitivity and freedom from certain types of noise are discussed. For the determination of chloride by the mercury(II) thiocynate method, the mergin-streams manifold, needed to eliminated negative peaks at low concentrations and refractive index effects, increased the baseline noise because of inefficient mixing at the confluence point. Packed-bed reactors and single-bead-string reactors (SBSR) significantly improved the baseline noise. Refractive index effects caused by sample concentration gradients were eliminated by the injection of large volumes (>500 μl), so that the detector could view a homogeneous central part of the sample zone. This approach maximises the signal because the dispersion is governed only by the relative flow rates of the carrier and reagent streams. The detection limits for chloride were improved to 40 ng l^?1 in aqueous solutions of low ionic strength and to 1.3 mg l^?1 in 5.25% (w/v) potassium sulphate.     

Effect of temperature and polymer type on gel permeation chromatography

A series of polyisobutene and polystyrene fractions was subjected to gel-permeation chromatography at 150°C. The two types resulted in distinctly different calibration curves in a plot of projected, extended chain length versus elution volume. The average end-to-end distances of the samples were determined by intrinsic viscosity measurements. It was found that these data plotted versus elution volume could be represented by a common curve for both polymer types. The elution volumes of the polyisobutene series were determined at three additional temperatures, 35, 70, and 110°C. It could be shown that elution volume is again determined by polymer coil size at the temperature of measurement.