Search results for "Molar"

Membranes Directly Prepared from Solutions of Unsubstituted Cellulose

2005

Summary: Starting from 5 wt.-% solutions of a prehydrolysis kraft pulp ( = 135 kg · mol−1) in the mixed solvent (dimethylacetamide + 7 wt.-% LiCl) we have prepared cellulose membranes on different supports according to the phase inversion process using above all acetone (AC) and 2-propanol as precipitants. In this context we have studied the phase behavior of the quasiternary system (DMAc+LiCl)/AC/cellulose. The obtained membranes are mechanically stable and in their mechanical and separation properties on the whole comparable to membranes consisting of regenerated cellulose. With respect to gas separation the ideal selectivity of CO2 in combination with N2 and O2 turns out to be opposite f…

Fractional dissolution of “solid” unsubstituted cellulose

2000

Activated cellulose (Solucell, DP w = 1400) was extracted stepwise at room temperatures by means of mixed solvents consisting of N,N-dimethylacetamide (DMAc) and LiCl, starting with a salt concentration of 1 wt.-% and increasing it in increments of 1 wt.-% up to 7 wt.-%. Upon the regeneration of the thus obtained cellulose fractions by pouring the solutions dropwise into a large surplus of water, part of the mixed solvent is occluded in the polymer. For that reason the cellulose samples were purified by redissolving them in Ni-tren and by a second precipitation. This process, however, leads to pronounced polymer degradation. For that reason we have used a spinning nozzle to press the extrac…

Thermodynamic properties of water-β-cyclodextrin-dodecylsurfactant ternary systems

1995

Densities, heat capacities and conductivities of water-surfactant-β-cyclodextrin (β-CD) ternary systems were determined at 25°C. The surfactants studied were sodium dodecylsulfate (NaDS) and dodecyltrimethylammonium bromide (DTAB). From conductivity data, apparent critical micelle concentrations (cmc*) and degree of ionization of micelles were obtained at a fixed β-CD concentration (mCD). From the cmc* value and that in water (cmc) the stoichiometry of the surfactant-β-CD complex was calculated. At a given mCD, the apparent molar volume Vϕ,CD and heat capacity Cϕ,CD of β-CD in the two surfactants were calculated as functions of surfactant concentration mS. For both NaDS and DTAB, Vϕ,CD incr…

Measurement report: Balloon-borne in situ profiling of Saharan dust over Cyprus with the UCASS optical particle counter

2021

This paper presents measurements of mineral dust concentration in the diameter range from 0.4 to 14.0 µm with a novel balloon-borne optical particle counter, the Universal Cloud and Aerosol Sounding System (UCASS). The balloon launches were coordinated with ground-based active and passive remote-sensing observations and airborne in situ measurements with a research aircraft during a Saharan dust outbreak over Cyprus from 20 to 23 April 2017. The aerosol optical depth at 500 nm reached values up to 0.5 during that event over Cyprus, and particle number concentrations were as high as 50 cm−3 for the diameter range between 0.8 and 13.9 µm. Comparisons of the total particle number concentration…

2012

Abstract. One of the major uncertainties in the understanding of Earth's climate system is the interaction between solar radiation and aerosols in the atmosphere. Aerosols exposed to high humidity will change their chemical, physical, and optical properties due to their increased water content. To model hydrated aerosols, atmospheric chemistry and climate models often use the volume weighted mixing rule to predict the complex refractive index (RI) of aerosols when they interact with high relative humidity, and, in general, assume homogeneous mixing. This study explores the validity of these assumptions. A humidified cavity ring down aerosol spectrometer (CRD-AS) and a tandem hygroscopic DMA…

Optical properties of deep glacial ice at the South Pole

2006

We have remotely mapped optical scattering and absorption in glacial ice at the South Pole for wavelengths between 313 and 560 nm and depths between 1100 and 2350 m. We used pulsed and continuous light sources embedded with the AMANDA neutrino telescope, an array of more than six hundred photomultiplier tubes buried deep in the ice. At depths greater than 1300 m, both the scattering coefficient and absorptivity follow vertical variations in concentration of dust impurities, which are seen in ice cores from other Antarctic sites and which track climatological changes. The scattering coefficient varies by a factor of seven, and absorptivity (for wavelengths less than ∼450 nm) varies by a fact…

Surface tension and density of binary mixtures of monoalcohols, water and acetonitrile: equation of correlation of the surface tension

2009

Measurements of the surface tension (σ) and density (ρ) of binary mixtures of monoalcohols, water and acetonitrile at 298.15 K and at atmospheric pressure, as a function of mole fraction (x) have been made. The experimental values of the deviation of surface tension and the excess of molar volume (Δσ, V E) have been correlated by the Redlich–Kister equation. An empirical correlation equation is presented for the study of the surface tension of these mixtures, and comparisons are made of the experimental values of surface tension versus those obtained with the correlation equation and with other models of correlation. Finally, with the purpose of corroborating the validity of the correlation…

Density, Viscosity, and Sound Speed of Bis(trifluoromethylsulfonyl)imide-Based Ionic Liquids + 1-Propanol Mixtures

2015

The density, viscosity, and speed of sound of three mixtures formed by 1-propanol and an ionic liquid were measured in a temperature range of 278.15–338.15 K. All measurements were made at atmospheric pressure and covered the entire range of miscible compositions. The three ionic liquids have the same anion but differ in the cation: 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [emim][NTf2], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][NTf2], and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [hmim][NTf2]. The experimental data allowed calculate the molar volume and isentropic compressibility of the mixture and their respective exces…

Viscosity and density of binary mixtures of alcohols and polyols with three carbon atoms and water: equation for the correlation of viscosities of bi…

2009

Measurements have been made of the viscosity and density of binary mixtures of alcohols and polyols with three carbon atoms and water at 298.15 K and at atmospheric pressure, as a function of the mole fraction. Fits have been made of the experimental values corresponding to the excesses of molar volume (V E), the deviations of viscosity (Δη), and the excesses of Gibbs free energy of activation (G* E), by means of the Redlich–Kister equation. A new correlation equation is presented for studying the viscosity of such mixtures, and comparisons are made of the experimental values of viscosity versus the values obtained by means of the mentioned equation and the models of Heric and McAllister. L…

Muscarinic inhibition of potassium-induced noradrenaline release and its dependence on the calcium concentration.

1975

1. Noradrenaline release from the isolated rabbit heart was evoked by perfusion with a medium containing 135 mM potassium and 17 mM sodium ions (high K+-low Na+). 2. The noradrenaline output in response to high K+-low Na+ was dose-dependently decreased by methacholine (0.625-320 muM) and this effect was reserved by atropine 1.44 mM. 3. Lowering the calcium concentration of high K+-low Na+ from 1.8-0.1125 mM decreased the noradrenaline output by 85%. The effect of methacholine, expressed as % inhibition of noradrenaline release, was potentiated by lowering of the calcium concentration. 4. Both at normal and lowered calcium concentrations the inhibitory action of methacholine was larger from …