Search results for " solution"
showing 10 items of 3084 documents
Structure and dielectric properties of Na<inf>1/2</inf>Bi<inf>1/2</inf>TiO<inf>3</inf>-BaTiO<inf>3</inf&…
2012
Dielectric properties, polarization and x-ray diffraction are studied for (1−x)Na 1/2 Bi 1/2 TiO 3 -xBaTiO 3 solid solutions in a concentration range above the morphotropic phase boundary. It is showed that all the studied compositions have tetragonal structure with maximal tetragonality slightly above the morphotropic phase boundary. Ferroelectric relaxor behavior is observed in a wide concentration range of BaTiO 3 . Stability of the relaxor state decreases with increasing BaTiO 3 concentration, but only for compositions with low Na 1/2 Bi 1/2 TiO 3 content the normal ferroelectric-paraelectric phase transition, which is characteristic to pure BaTiO 3 , occurs. Mechanisms, which influence…
INFLUENCE OF ZIRCONIUM ON STRUCTURAL, MICROSTRUCTURAL AND FERROELECTRIC PROPERTIES OF BaZr0.20Ti0.80O3 CERAMIC
2009
ABSTRACT Barium zirconium titanate BaZrxTi1-xO3 ceramics have been obtained by conventional method. The X-ray diffraction analysis showed that the BaZr0.20Ti0.80O3 crystallizes in the cubic structure. The lattice parameter a increases with temperature, at temperature ∼308 K a small deviation is observed. The performed EDS study revealed that the samples were perfectly sintered and that the material was chemically homogeneous. It contains a little glassy phase and the grains are well shaped. The zirconium content (20 mol%) in the examined solid solution caused downward shift of the temperature T m . The increase of the achieved permittivity values ϵm was observed as well.
Proton glass behavior and hopping conductivity in solid solutions of antiferroelectric betaine phosphate and ferroelectric betaine phosphite.
1991
Measurements of the dielectric permittivity are reported for solid solutions of antiferroelectric betaine phosphate and ferroelectric betaine phosphite at frequencies 10 −2 Hz T c the dielectric response is dominated by ac and dc conduction. The 40% sample exhibits pure relational behavior indicative of a transition into an orientational glass state
1978
Theoretical relations for the dependence of the z-average radius of gyration Rz as a function of the mass average molar mass Mw are derived for expanded coils, persistence coils with persistence of direction, persistence coils with persistence of direction and curvature, and for needles, all exhibiting a Schulz-distribution of their molar masses. These relations are applied to experimental data from light scattering of polystyrene in toluene and DNA-Na in aqueous NaCl-solution of 200 mol NaCl per m3 at room temperature. In the case of DNA it becomes evident that the double helix shows no important persistence of curvature and that the experimental data can be described adequately by a persi…
Parametric nonlinear singular Dirichlet problems
2019
Abstract We consider a nonlinear parametric Dirichlet problem driven by the p -Laplacian and a reaction which exhibits the competing effects of a singular term and of a resonant perturbation. Using variational methods together with suitable truncation and comparison techniques, we prove a bifurcation-type theorem describing the dependence on the parameter of the set of positive solutions.
Steady states and nonlinear buckling of cable-suspended beam systems
2018
This paper deals with the equilibria of an elastically-coupled cable-suspended beam system, where the beam is assumed to be extensible and subject to a compressive axial load. When no vertical load is applied, necessary and sufficient conditions in order to have nontrivial solutions are established, and their explicit closed-form expressions are found. In particular, the stationary solutions are shown to exhibit at most two non-vanishing Fourier modes and the critical values of the axial-load parameter which produce their pitchfork bifurcation (buckling) are established. Depending on two dimensionless parameters, the complete set of resonant modes is devised. As expected, breakdown of the p…
Functional Magnetic Mesoporous Silica Microparticles Capped with an Azo-Derivative: A Promising Colon Drug Delivery Device
2018
[EN] Magnetic micro-sized mesoporous silica particles were used for the preparation of a gated material able to release an entrapped cargo in the presence of an azo-reducing agent and, to some extent, at acidic pH. The magnetic mesoporous microparticles were loaded with safranin O and the external surface was functionalized with an azo derivative 1 (bearing a carbamate linkage) yielding solid S1. Aqueous suspensions of S1 at pH 7.4 showed negligible safranin O release due to the presence of the bulky azo derivative attached onto the external surface of the inorganic scaffold. However, in the presence of sodium dithionite (azoreductive agent), a remarkable safranin O delivery was observed. A…
Estimation of the effect of the acidosis and alkalosis on the anesthetic potency of local anesthetics by biopartitioning micellar chromatography and …
2004
Local anesthetics are hydrophobic compounds and weak bases with protonation constants ranged between 7.5 and 8.8. These drugs block reversibly nerve conduction near their site of application or injection and thus produce temporary loss of feeling or sensation in a limited area of the body. The efficacy of anesthetic blockade of local anesthetics depends on the charged/uncharged form ratio and the hydrophobicity of the compounds. In addition their toxicological effects have been reported to be highly dependent on the physiological pH. Biopartitioning micellar chromatography (BMC) and micellar electrokinetic chromatography (MEKC), that use micellar solutions as mobile phases, have proven to b…
In-use physicochemical and microbiological stability of biological parenteral products
2015
Pharmaceutical scientists in the biotechnology industry have traditionally focused on achieving acceptable shelf lives of drug products in their original, unopened product unit configuration (e.g., two years stored at 2–8 °C). However, it is now clear that stability considerations extend beyond