Search results for "optical"
showing 10 items of 7671 documents
Physico-chemical investigation of nanostructures in liquid phases: Nickel chloride ionic clusters confined in sodium bis(2-ethylhexyl) sulfosuccinate…
2009
The confinement of finite amounts of nickel chloride in the hydrophilic core of sodium bis(2-ethylhexyl) sulfosuccinate (AOT) reverse micelles dispersed in n-heptane has been investigated by FT-IR, UV-vis-NIR and fluorescence spectroscopies. The analysis of experimental data consistently leads to hypothesize that NiCl(2) forms small size ionic clusters stabilized by a monolayer of oriented surfactant molecules. Due to confinement and interfacial effects, these ionic clusters show peculiar photophysical properties, which are different from those possessed by the bulk material. From NiCl(2)/AOT/n-heptane solutions, by evaporation of the organic solvent, interesting salt/surfactant nanocomposi…
Synthesis and crystal structure of Na1+xV4P4O17(OH) (x ≈ 1.44)
1990
Abstract Hydrothermal synthesis starting from Na0.46VOPO4 · 1.58H2O leads to a new mixed-valence sodium vanadium phosphate: Na2.44V4P4O17(OH) (orthorhombic, space group Pnma; Z = 4; a = 13.723(5) A, b = 6.314(2) A, c = 16.139(4) A; R = 0.032 for 2659 reflections). In this phase, the interconnection of three complex types of infinite chains, built from VO6 octahedra and PO4 tetrahedra, sometimes edgeshared, defines tunnels partly occupied by a portion of the sodium atoms.
Electrochemical synthesis of sulfamides.
2021
Herein we demonstrate the first electrochemical synthesis protocol of symmetrical sulfamides directly from anilines and SO2 mediated by iodide. Sulfamides are an emerging functional group in drug design. Highlights are the direct use of SO2 from a stock solution and no necessity of any supporting electrolyte. Overall, the reaction has been demonstrated for 15 examples with yields up to 93%.
Magnetic Disaccommodation in Manganese Ferrites in the Temperature Region IV
1991
The magnetic relaxation in polycrystalline, nonstoichiometric manganese ferrite samples MnxFe3−xO4 is investigated as a function of the Mn content (0 ≦ x ≦ 1). The analysis of the experimental results shows that in the temperature region IV two different relaxation processes at 285 (IV) and 220 K (IVa) can be distinguished. The process IV exhibits orientational relaxation characteristics and is composed by the superposition of two Debye processes with activation energies close to 0.75 and 0.80 eV whereas relaxation IV a could be associated with vacancy migration through the lattice, but future investigations are necessary to probe this. Es wird die magnetische Relaxation in polykristallinen…
Liquid/Gas and Liquid/Liquid Phase Equilibria of the System Water/Bovine Serum Albumin
2013
The thermodynamic behavior of the system H2O/BSA was studied at 25 °C within the entire composition range: vapor pressure measurements via head space sampling gas chromatography demonstrate that the attainment of equilibria takes more than one week. A miscibility gap was detected via turbidity and the coexisting phases were analyzed. At 6 °C the two phase region extends from ca. 34 to 40 wt % BSA; it shrinks upon heating. The polymer rich phase is locally ordered, as can be seen under the optical microscope using crossed polarizers. The Flory-Huggins theory turns out to be inappropriate for the modeling of experimental results. A phenomenological expression is employed which uses three adju…
N,N,N-Alkyloctyldimethylammonium Chlorides in Water: A Thermodynamic Investigation
1993
Abstract Specific conductivities, densities, heat capacities and enthalpies of dilution at 298 K and osmotic coefficients at 310 K were measured for N,N,N -octylbutyldimethylammonium, N,N,N -octylpentyldimethylammonium, and N,N -dioctyldimethylammonium chlorides in water as functions of concentration. From the specific conductivity data, the CMC and the degree of the counterion dissociation have been calculated. It is shown that additional CH 2 groups in the variable alkyl chain affect both CMC and β less than they do in the single chain surfactants. The partial molar volumes, heat capacities, relative enthalpies, nonideal free energies, and entropies at 298 K were derived as functions of t…
Modeling of Amino Acid Electrodiffusion through Fixed Charge Membranes
2001
Abstract We study theoretically the electrodiffusion of amino acids through fixed charge membranes, calculating the ionic fractions of the amino acid in the membrane as well as its total flux as a function of the relevant experimental parameters (amino acid concentration, salt concentration, and pH of the external solution; membrane fixed charge concentration; and amino acid membrane/solution partition coefficients) under different experimental conditions (symport vs antiport transport, uphill transport, etc.). The theoretical approach employed is based on the Nernst–Planck flux equations in the (Goldman) constant electric field assumption and considers all the species present in the system…
α,ω-Functionalized poly-N-isopropylacrylamides: controlling the surface activity for vesicle adsorption by temperature
2003
The synthesis of alpha,omega-end-functionalized copolymers of N-isopropylacrylamide and N-(3-dimethylaminopropyl)acrylamide was performed. Monomer ratios of 100:0, 96:4, and 81:19 were investigated. The lower critical solution temperature (LCST) of these polymers was determined by cloud-point measurements and by microcalorimetric measurements. The LCST increased from 32 over 37 to 47 degrees C as the hydrophobicity increased with increasing amount of comonomer N-(3-dimethylaminopropyl)acrylamide. The polymers could successfully be adsorbed onto gold surfaces. Finally, vesicle adsorption onto these self-assembled polymer films on flat gold surfaces was investigated as the vesicle solution te…
Adsorption of water vapor by poly(styrenesulfonic acid), sodium salt: isothermal and isobaric adsorption equilibria
2004
Abstract Air conditioning and dehumidifying systems based on sorption on solids are of great interest, especially in humid climates, because they allow reduction of thermal loads and use of chlorofluorocarbons. Previous studies have shown that hydrophilic polymers such as sulfonic polymers can have very high performance in water adsorption from air. The aim of this study was to characterize the water vapor adsorption properties of fully sulfonated and monosulfonated poly(styrenesulfonic acid), sodium salt, and to elucidate the mechanism of adsorption on these materials. Adsorption isotherms have been determined by TGA between 298 and 317 K for pressures ranging from 0.1 to 45 hPa. They have…
Effective conductivity in association with model structure and spatial inhomogeneity of polymer/carbon black composites
1996
The relationship between effective conductivity and cell structure of polyethylene/carbon composites as well as between effective conductivity and spatial distribution of carbon black are discussed. Following Yoshida's model both structures can, in a way, be said to be intermediate between the well known Maxwell-Garnett (MG) and Bruggeman (BR) limiting structures. Using TEM photographs on composites with various carbon blacks we have observed that the larger is Garncarek's inhomogeneity measure H of two-dimensional (2D) representative distribution of the carbon black, the smaller is the effective conductivity of the composite.