Novel functionalized monomers based on kojic acid: snythesis,characterization, polymerization and evalution of antimicrobial activity

Two novel acrylate monomers, [5-(benzyloxy)-4-oxo-4H-pyran-2-yl]methyl acrylate and {1-[(5-(benzyloxy)-4-oxo-4H-pyran-2-yl)methyl]-1,2,3-triazol-4-yl}methyl acrylate were synthesized by the reaction of 5-benzyloxy-2-(hydroxymethyl)-4H-pyran-4-one and 5-(benzyloxy)-2-{[4-(hydroxymethyl)-1,2,3-triazol-1-yl]methyl}-4H-pyran-4-one with acryloyl chloride in the presence of triethylamine, respectively. These monomers were polymerized using 2,2^′-azobisisobutyronitrile (AIBN) as the initiator in N,N-dimethylformamide:14-dioxane (10:1) solution. The thermal behavior of the polymers was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The synthesized compounds were evaluated for their antibacterial and antifungal activites aganist bacteria and fungi using the disk diffusion method. The results indicated that some of these compounds demonstrated moderate to good antibacterial and antifungal activities.     

Effect of Impeller Spacing on the Flow Field of Yield-Pseudoplastic Fluids Generated by a Coaxial Mixing System Composed of Two Central Impellers and an Anchor

The three-dimensional flow field generated by a coaxial mixer composed of double Scaba impellers and an anchor in the mixing of the xanthan gum solution, a non-Newtonian yield-pseudoplastic fluid was investigated using the computational fluid dynamics (CFD) technique. The mixing time measurements were performed by a non-intrusive flow visualization technique called electrical resistance tomography (ERT). To evaluate the influence of the impeller spacing on the hydrodynamics of the double Scaba-anchor coaxial mixer, the upper impeller submergence was set to 0.140?m while the lower impeller clearance and the spacing between two central impellers were changed within a wide range. The experiments and simulations were conducted for both co-rotating and counter-rotating regimes at different impeller spacing. The analysis of the collected data with respect to the power number, flow number, mixing time, and pumping effectiveness proved that the co-rotating mode had superiority over the counter-rotating regime. Furthermore, the impact of the impeller spacing in the co-rotating mode was assessed with respect to the mixing time, power number, and mixing energy. The results demonstrated that a coaxial mixer with the impeller spacing of almost equal to the central impeller diameter (C₂?=?0.175?m) and the impeller clearance of C₃?=?0.185?m was the most efficient configuration compared to the other cases. Additionally, the influence of the impeller spacing on the flow pattern was assessed in terms of the radial velocity, tangential velocity, axial velocity, shear rate, and apparent viscosity profiles. When the impeller spacing (C₂) was varied, the merging flow and parallel flow patterns were observed.     

Rheological characterization of polypropylene/poly(ethylene-<Emphasis Type="Italic">co</Emphasis>-propylene) in-reactor blends synthesized under different polymerization conditions

In-reactor blends of polypropylene/poly(ethylene-co-propylene) with complex microstructure, synthesized through different polymerization procedures; two-step (one homopolymerization and one copolymerization under high ethylene concentration) and three-step (with an additional copolymerization step under low ethylene concentration), were characterized by rheological measurements. The effects of a change in the polymerization process on the types and amounts of block copolymers in the blends were evaluated using small amplitude oscillation rheometry in the linear viscoelastic region. The Palierne model in its complete form was employed to model the rheological behavior of the blends. For this analysis the reactor products were separated into xylene cold insoluble (XCI) and xylene cold soluble fractions. Besides, another two copolymer fractions at 80 and 100 °C, which are crystallizable copolymer fractions and contain block copolymers rich in polyethylene and polypropylene, respectively, were separated from XCI fraction by xylene using temperature gradient elution fractionation method. Considering all copolymer fractions as dispersed and the remained fraction (mostly polypropylene) as matrix phase, it was shown that the rheological properties of the blends could not be predicted by Palierne model. It was found that only by considering part of block copolymer fractions having long polypropylene sequences along with polypropylene homopolymer as one phase, the rheological properties of the blends could be predicted by Palierne model. By rheological modeling, it was confirmed that the amounts of copolymers with long polypropylene sequences which are miscible with the matrix are higher in the case of three-step blends and also the elasticity of three-step polymerized blends is higher than two-step polymerized blends.     

Agitation of Herschel–Bulkley fluids with the Scaba–anchor coaxial mixers

The design of the coaxial mixers depends on many interrelated parameters including the geometry and dimensions of the mixing vessel, the location and type of the impellers, speed ratio, impeller diameter, rotation mode, and fluid rheology. No study has been reported in the literature regarding the mixing performance of the coaxial mixers in the agitation of yield-pseudoplastic fluids. Thus, the main objective of this study was to evaluate the performance of a Scaba–anchor coaxial mixer (a novel configuration) in the mixing of xanthan gum solutions (yield-pseudoplastic fluids). The Herschel–Bulkley model was used to describe the rheological behavior of the xanthan gum solutions. To develop new correlations for the generalized Reynolds and power numbers of the coaxial mixers employed in the agitation of this class of non-Newtonian fluids, we utilized numerous experimental and computational fluid dynamics (CFD) data. The new correlations were tested successfully at different operating conditions (e.g. speed ratio, fluid rheology, and operation mode).     

Contribution of the Tyr-1 in Plantaricin149a to Disrupt Phospholipid Model Membranes

Plantaricin149a (Pln149a) is a cationic antimicrobial peptide, which was suggested to cause membrane destabilization via the carpet mechanism. The mode of action proposed to this antimicrobial peptide describes the induction of an amphipathic α-helix from Ala7 to Lys20, while the N-terminus residues remain in a coil conformation after binding. To better investigate this assumption, the purpose of this study was to determine the contributions of the Tyr1 in Pln149a in the binding to model membranes to promote its destabilization. The Tyr to Ser substitution increased the dissociation constant (K_D) of the antimicrobial peptide from the liposomes (approximately three-fold higher), and decreased the enthalpy of binding to anionic vesicles from −17.2 kcal/mol to −10.2 kcal/mol. The peptide adsorption/incorporation into the negatively charged lipid vesicles was less effective with the Tyr1 substitution and peptide Pln149a perturbed the liposome integrity more than the analog, Pln149S. Taken together, the peptide-lipid interactions that govern the Pln149a antimicrobial activity are found not only in the amphipathic helix, but also in the N-terminus residues, which take part in enthalpic contributions due to the allocation at a lipid-aqueous interface.     

Hydrogenolysis of alkanes and olefin polymerization on the silica-supported zirconium hydrides: A comparative DFT study

The model reactions of ethylene polymerization and hydrogenolysis of linear alkanes (propane, n-butane, and n-pentane) on the silica-supported zirconium hydrides (Si–O)₃Zr^IVH, (Si–O)₂Zr^IVH₂, and (Si–O)₂Zr^IIIH were studied using the DFT approach. Catalytic processes under study were shown to occur involving different surface hydrides. The ethylene polymerization was found to proceed at comparable rates on the zirconium monohydrides, (Si–O)₃ZrH, and dihydrides, (Si–O)₂ZrH₂. Cleavage of linear alkanes on the monohydrides (Si–O)₃ZrH is thermodynamically unfavorable; however, the dihydrides (Si–O)₂ZrH₂ can act as catalysts of the process under mild conditions. Hydrides of the trivalent zirconium, (Si–O)₂Zr^IIIH, can also contribute to the hydrogenolysis reaction. A feature of all the systems studied is low regioselectivity of the corresponding processes.     

Effect of dispersion states (electrostatic/electrosteric stabilization) on particles arrangement in the yttria-stabilized zirconia sediments

In the present work, particle arrangement and their packing in the sediment layer of zirconia suspension were studied. To evaluate the particle settling, aqueous suspensions of zirconia nanoparticles were prepared in different dispersion states. In one state, Dolapix CE64 was used as a dispersant to provide electrosteric mechanism. In another state, pH of the suspension was adjusted at 4 to provide electrostatic mechanism. The other state was the combination of dispersant and pH adjustment which resulted in the most stable suspension. First of all, the stability of all dispersion states was evaluated by zeta potential, sediment volume (SV) and height, viscosity, and packing density (PD). Then, the sediment layers of all suspensions were characterized. Incorporation of electrostatic mechanism was resulted in a main decrease in viscosity with high surface charges, while electrosteric mechanism caused lower sedimentation of particles. Fall velocities of particles/agglomerates were estimated, and the influences of dispersion states on the particles fall velocities were characterized. The microstructural observation revealed homogeneous packing of particles in the sediment layer of the stable suspension demonstrating the proper dispersion of particles. Dolapix CE64 and pH adjustment resulted in a uniform arrangement of particles without agglomeration and spherical and regular granules with a uniform shape.     

Endothelial Colony-Forming Cells Dysfunctions Are Associated with Arterial Hypertension in a Rat Model of Intrauterine Growth Restriction

Infants born after intrauterine growth restriction (IUGR) are at risk of developing arterial hypertension at adulthood. The endothelium plays a major role in the pathogenesis of hypertension. Endothelial colony-forming cells (ECFCs), critical circulating components of the endothelium, are involved in vasculo-and angiogenesis and in endothelium repair. We previously described impaired functionality of ECFCs in cord blood of low-birth-weight newborns. However, whether early ECFC alterations persist thereafter and could be associated with hypertension in individuals born after IUGR remains unknown. A rat model of IUGR was induced by a maternal low-protein diet during gestation versus a control (CTRL) diet. In six-month-old offspring, only IUGR males have increased systolic blood pressure (tail-cuff plethysmography) and microvascular rarefaction (immunofluorescence). ECFCs isolated from bone marrow of IUGR versus CTRL males displayed a decreased proportion of CD31+ versus CD146+ staining on CD45− cells, CD34 expression (flow cytometry, immunofluorescence), reduced proliferation (BrdU incorporation), and an impaired capacity to form capillary-like structures (Matrigel test), associated with an impaired angiogenic profile (immunofluorescence). These dysfunctions were associated with oxidative stress (increased superoxide anion levels (fluorescent dye), decreased superoxide dismutase protein expression, increased DNA damage (immunofluorescence), and stress-induced premature senescence (SIPS; increased beta-galactosidase activity, increased p16^INK4a, and decreased sirtuin-1 protein expression). This study demonstrated an impaired functionality of ECFCs at adulthood associated with arterial hypertension in individuals born after IUGR.     

Effect of Co addition on microstructural and mechanical properties of WC–B4C–SiC composites

In this study, the effect of Co addition on microstructural and mechanical properties of WC-B₄C–SiC composites sintered by spark plasma sintering (SPS) method was investigated. For this purpose, three batches of WC-B₄C–SiC with different contents of Co (10 vol%, 15 vol%, and 20 Vol %) were sintered at 1400 °C. The results of X-ray diffraction (XRD) analysis of the samples indicated the formation of W₂B₅, W₃CoB₃ as well as the remained C phases and unreacted SiC phase. It was observed that by increasing the Co content, the amount of W₂B₅ phase reduces and W₃CoB₃ and C contents increase. Therefore, W₂B₅ peaks were not detected in the sample containing 20vol% Co. Relative density values above 97% were obtained for all the composites. However, a decrease was observed in relative density by increasing the Co content in the composites. The highest flexural strength (510 ± 42 MPa), fracture toughness (10.34 ± 0.82 MPa m^1/2), and hardness (20.63 ± 0.75 GPa) were also obtained for the sample containing 10vol% Co compared to the other samples. In addition, Transgranular fracture of SiC as well as pulling out of W₃CoB₃ and W₂B₅ particles were observed in the fracture surface micrographs of the samples. The presence of micro-cracks in the SiC grains, fracture of W₃CoB₃ grains, and crack deflection was reported as dominant toughening mechanisms.     

The rural–urban equity nexus of Metro Manila’s water system

ABSTRACT

This article examines equity concerns and inherent conflicts related to rural–urban water supply allocation and use, with focus on Metro Manila. Going beyond the much-discussed difficulty farmers experience from an allocation policy prioritizing urban water requirements, it shows that inequity in raw water allocation is linked to, and further exacerbated by, inequities in urban domestic water provision. Moreover, it highlights the need for broader equity reviews, using the concept of the rural–urban water equity nexus to draw attention to key equity considerations across space and scale that otherwise might remain invisible.