Impact of Molecular Weight on the Thermal Stability and the Miscibility of Poly(ε-caprolactone)/Polystyrene Binary Blends

Poly(ε-caprolactone) (PCL) and two different molecular weight (6K and 650K) of polystyrene (PS) were mixed in solution to prepare binary blends of PCL/PS with various compositions. The impact of the molecular weight of PS in the blends was studied on thermal stability and miscibility by the thermogravimetric analysis (TGA) and the differential scanning calorimetry (DSC) method. The TGA results under dynamic conditions in an inert atmosphere show that the thermal stability of the blends depends on the length of PS molecules. The increase of the low molecular weight PS into the PCL/PS blend reduces the thermal stability while the high molecular weight PS improves the thermal stability. The crystallization peak temperature, enthalpy, and crystallinity of the blends are found molecular weight dependent; these parameters with blend compositions deviate from linearity of additive law for low molecular weight PS, while they do follow the additive law for high molecular weight PS. A significant melting point depression of PCL crystals with composition was observed for the blends with the incorporation of the low molecular weight PS, while the no significant melting temperature depression was observed for the high molecular weight PS. The experimental results clearly indicate that in the PCL/PS blends, the thermal stability and the interaction between the neat components strongly depend on the molecular weight of the P

Velocity Profiles for Flow of Omani Crude Oils and Other Liquids

Velocity profiles of Newtonian immiscible liquids undergoing laminar flow between two horizontal plates under pressure gradient are investigated using a momentum balance equation. The differential equation describing the flow has been solved and equations for the velocity profiles of a two-layer and three-layer liquid systems are presented. As examples, we show flow patterns of two-layer water-crude oil system and three-layer system involving water, tetrachloromethane, xylene, cyclopentane and hexane. A distinctive pattern is noticeable between the velocity profiles of heavy (API 19.19) and light (API 40.89) Omani crude oils

Calculation of partial structure factors of a less-simple binary alloy

The partial static structure factors, using the Faber-Ziman (FZ) theory, have been calculated for Ag-In alloy. For 20% Ag at 623 K and 70% Ag at 973 K, the interionic pair potential based on the Bretonnet-Silbert (BS) formalism are calculated and the hard sphere diameters for the component elements are estimated from the potential profile using the linearised Weeks-Chandler-Andersen (LWCA) method. The average number densities are calculated on the assumption that the atomic volumes are simply additive. The calculated structure factors are compared with the experimental values. The partial structure factors for Ag-Ag at 20% Ag and In-In at 70% Ag appear to be slightly out of phase with the calculated values particularly in large q-region. From the calculations it appears that this discrepancy is related to the process of derivation of the experimental structure factors from the total one, and the Ag-In alloy can be described by a mixture of hard spheres

Spin treatment-based approach for electronic transport in paramagnetic liquid transition metals

International audienceA novel concept is proposed to calculate both the electrical resistivity and thermoelectric power (TEP) of liquid transition metals (Mn, Fe, Co and Ni) characterized by a paramagnetic state in the liquid phase. By contrast to a previous work (PRB64, 094202 (2001)), where the resistivity was calculated by treating separately the interactions between spin up and spin down using the Matthiessen rule, our current approach is based on two types of muffin tin potentials in the t-matrix, namely spin up and spin down. The resistivity is treated as the result of the interference of the two kinds of spin states of electrons including a cross-contribution. The calculated resistivity values agree reasonably well with the available experimental ones for all the metals considered. Moreover, the calculated TEP, as deduced from the slope of resistivity vs. energy, has been found to be positive for Mn and Fe but negative for Co and Ni. Besides that, this formalism for resistivity calculation may be generalized to a system that may exist in different atomic states. It is worth mentioning that this concept is analogous to the one used in the process of neutron scattering on a metal composed of multiple isotopes

Method for community follow-up and treatment.

<p>Method for community follow-up and treatment.</p

Summary measures and TAS 1–3 results for the 19 endemic districts (received MDA).

<p>Summary measures and TAS 1–3 results for the 19 endemic districts (received MDA).</p