Stable DOPG/Glycyrrhizin Vesicles with a Wide Range of Mixing Ratios: Structure and Stability as Seen by Scattering Experiments and Cryo-TEM

Phosphatidylglycerols represent a large share of the lipids in the plasmamembrane of procaryotes. Therefore, this study investigates the role of charged lipids in the plasma membrane with respect to the interaction of the antiviral saponin glycyrrhizin with such membranes. Glycyrrhizin is a natural triterpenic-based surfactant found in licorice. Vesicles made of 1,2-dioleoyl-sn-glycero-3-phospho-rac-(1’-glycerol) (DOPG)/glycyrrhizin are characterized by small-angle scattering with neutrons and X-rays (SANS and SAXS). Small-angle scattering data are first evaluated by the model-independent modified Kratky–Porod method and afterwards fitted by a model describing the shape of small unilamellar vesicles (SUV) with an internal head-tail contrast. Complete miscibility of DOPG and glycyrrhizin was revealed even at a ratio of lipid:saponin of 1:1. Additional information about the chain-chain correlation distance of the lipid/saponin mixtures in the SUV structures is obtained from wide-angle X-ray scattering (WAXS).

Fabrication and Characterization of PEEK/PEI Multilayer Composites

Polyetheretherketone (PEEK)/polyetherimide (PEI) blends (50/50, v/v) keeping the crystal phase of PEEK have been manufactured by alternate PEEK/PEI layer stacking. This strategy avoided the complete miscibility of both polymers, keeping layers of PEEK and PEI unmixed along the sample thickness, as well as promoting the formation of a smooth interfacial layer where PEEK and PEI were mixed. The properties of this interface after processing at molten state and different times was studied by DSC, DMA, and X-Ray synchrotron. These techniques allowed monitoring the evolution of glass transition, where isolated Tg’s for both pristine polymers were observed even after long processing time. PEEK crystallinity slightly decreased during manufacturing, whereas PEEK crystal parameters did not vary. These observations show that, although the interface—the zone where both polymers are mixed—grew, layers with pristine polymers remained even after prolonged processing time. The preservation of the PEEK crystallinity was also observed in the mechanical properties of the multilayer PEEK/PEI films, which were compared with pristine PEEK and PEI films. Multilayer samples processed for shorter times rendered higher young modulus, tensile strength, and strain at break.

The optimization of pre-slug size in CO2-N2 compound flooding

In order to enhance oil recovery in low and ultra-low permeability layer, both of the numerical simulation and physical model experiment have been researched. First, the dynamic distribution of CO1 and N1 in the oil and gas phase in the CO2-N2 compound flooding process was numerically simulated by using the long slim-tube model. The results show that the CO2 slug should have at least 0.3 PV to prevent the impact of N2 channeling effectively. Second, under the experimental conditions of complete miscibility of CO2-crude oil, the two types of natural cores including low and ultra-low permeability, respectively, are used for experimental study on oil displacement. The results confirm that CO2-N2 compound flooding with 0.3 PV CO2 pre-slug can achieve a good result. Finally, a five-point well pattern element model is established by CMG. The recovery and the gas cost of per ton of oil are calculated respectively for CO2-N2 compound flooding and full CO2 flooding at 300 m well spacing of low and ultra-low permeability layer. According to the simulation results, the optimal CO2 pre-slug size in CO2-N2 compound flooding under the condition of low and ultra-low permeability layer five-point well pattern is 0.4 PV.

Compositional Inhomogeneity and Tuneable Thermal Expansion in Mixed-Metal ZIF-8 Analogues

<div>We study the structural and thermomechanical effects</div><div>of cation substitution in the compositional family of</div><div>metal–organic frameworks Zn1􀀀xCdx(mIm)2 (HmIm = 2-</div><div>methylimidazole). We find complete miscibility for all</div><div>compositions x, with evidence of inhomogeneous distributions of Cd and Zn that in turn affect framework aperture characteristics. Using variable-temperature X-ray powder diffraction measurements, we show that Cd substitution drives a threefold reduction in the magnitude of thermal expansion behaviour. We interpret this effect in terms of an increased density of negative thermal expansion modes in the more flexible Cd-rich frameworks.</div>

Compositional Inhomogeneity and Tuneable Thermal Expansion in Mixed-Metal ZIF-8 Analogues

<div>We study the structural and thermomechanical effects</div><div>of cation substitution in the compositional family of</div><div>metal–organic frameworks Zn1􀀀xCdx(mIm)2 (HmIm = 2-</div><div>methylimidazole). We find complete miscibility for all</div><div>compositions x, with evidence of inhomogeneous distributions of Cd and Zn that in turn affect framework aperture characteristics. Using variable-temperature X-ray powder diffraction measurements, we show that Cd substitution drives a threefold reduction in the magnitude of thermal expansion behaviour. We interpret this effect in terms of an increased density of negative thermal expansion modes in the more flexible Cd-rich frameworks.</div>

Influence of Alkali Metal Substitution on the Phase Transition Behavior of CsGaQ2 (Q = S, Se)

The formation of solid solution series Cs1-xMxGaQ2-mC64 (M = K, Rb; Q = S, Se; x = 0&ndash;1) was studied by X-ray diffraction and spectroscopic methods, revealing a complete miscibility of CsGaQ2-mC64 with RbGaQ2 and KGaSe2, and a large miscibility gap with KGaS2. All solid solution members exhibit similar Raman spectra, indicating the covalent Ga-Q bonding character. The similar optical band gaps likewise further contribute to this conclusion. Up to a degree of substitution, these solid solutions undergo a phase transition similar to CsGaQ2-mC64. The influence of the substitution parameter x on phase transition process was investigated in situ using high-temperature X-ray powder diffraction experiments. Phase-pure solid solutions of the high-temperature polymorphs Cs1-xMxGaQ2-mC16 were obtained up to xmax(K) = 0.1 and xmax(Rb) = 0.3. The crystal structures of these new CsGaQ2-mC16 analogous high-temperature phases were refined from synchrotron diffraction data by Rietveld-refinement.

Effect of Acetone on Physical Properties of PES Membrane

In the present study, polyethersulfone (PES) dope solution were prepared from mixtures of two solvents containing dimethylformamide (DMF) as core solvent, and acetone as co-solvent (CS), deionized water was used as coagulant bath. The amount of PES was kept at 20 wt% and the weight ratios of acetone were varied 20-24 wt.% to DMF and the dope solutions were prepared under closed heating system Results revealed the complete miscibility of PES with the fixed mixture of acetone and DMF under atmospheric pressure. The relationships between degree of adsorption, relative water absorption, were investigated. The results revealed that the interaction of DMF and acetone is strongest when their mole ratio is unity, which exhibit the phenomenon of true cosolvency for PES membrane. Keywords: polyethersulfone, solvent mixture, characterization.