A Three-Scale Model of pH-Dependent Flows and Ion Transport with Equilibrium Adsorption in Kaolinite Clays: II Effective-Medium Behavior

In part I (Lima et al., Transp Porous Media, 2009), a three-scale model governing the movement of an aqueous saline solution containing four monovalent species (Na⁺, H⁺, Cl^?, OH^?) in kaolinite clays was derived. Unlike purely macroscopic approaches, the novelty of the formulation relied on the double averaging of the nanoscopic electro- chemistry of particle/electrolyte solution interface ruled by the electrical double layer coupled with protonation/deprotonation reactions. The passage from the nano to the micro (pore)-scale gave rise to ion-sorbed concentrations and slip velocity at the solid/fluid interface which are coupled with the microscopic Stokes problem and Nernst–Planck equations governing the hydrodynamics and ion transport in the micropores. Application of a formal homogenization procedure led to macroscopic governing equations with effective electro-chemical parameters, such as retardation coefficients, electro-osmotic permeability, and electric conductivity. In this study, we reconstruct the constitutive laws of the macroscopic coefficients by solving the nano and microscopic closure problems. New generalized isotherms for Na⁺ and H⁺ ? OH^? sorption are build-up based on a perturbation approach and the limitations of classical Freundlich isotherm for modeling ion sorption at the solid/fluid interface are discussed. The macroscopic governing equations are discretized by the finite volume method and numerical simulations of a transient electroosmosis experiment for desalination of a clay sample by electrokinetics are presented.     

Investigation of the Support Effect in Atomically Dispersed Pt on WO3−x for Utilization of Pt in the Hydrogen Evolution Reaction

Single‐atom catalysts (SACs) have attracted growing attention because they maximize the number of active sites, with unpredictable catalytic activity. Despite numerous studies on SACs, there is little research on the support, which is essential to understanding SAC. Herein, we systematically investigated the influence of the support on the performance of the SAC by comparing with single‐atom Pt supported on carbon (Pt SA/C) and Pt nanoparticles supported on WO_3?x (Pt NP/WO_3?x). The results revealed that the support effect was maximized for atomically dispersed Pt supported on WO_3?x (Pt SA/WO_3?x). The Pt SA/WO_3?x exhibited a higher degree of hydrogen spillover from Pt atoms to WO_3?x at the interface, compared with Pt NP/WO_3?x, which drastically enhanced Pt mass activity for hydrogen evolution (up to 10 times). This strategy provides a new framework for enhancing catalytic activity for HER, by reducing noble metal usage in the field of SACs.     

Alginate hydrogels incorporating neomycin or propolis as potential dressings for diabetic ulcers: Structure,swelling, and antimicrobial barrier properties

Alginate hydrogels have many attractive characteristics for potential use as wound dressing materials. However, they are not considered to possess any intrinsic activity against microbial infection, often present in neuropathic wounds. To overcome this, the effect of incorporating neomycin or propolis in alginate hydrogels was investigated, both by direct blending alone and also by further addition of loaded alginate microparticles prepared by the extrusion dripping method. The morphological, microstructural, thermal, mechanical, and swelling properties of each film were evaluated, as well as particle size distribution and antimicrobial penetration analysis. Microparticle size was considered suitable for drug delivery applications and incorporation in hydrogel films. The presence of neomycin and propolis, in both blended and microparticle form, interfered with film properties leading to hydrogels with different characteristics. All samples showed swelling degrees up to 100% and mechanical and thermal properties suitable for application as wound dressings. In addition, all samples acted as barriers to microbial penetration.     

In vitro antibacterial and time-kill assay of ethanolic extract of Davilla nitida bark on multidrug resistant bacteria isolated from diabetic foot lesions

This study reported the antimicrobial activity of the bark extract of Davilla nitida on multidrug resistant bacteria isolated from Diabetic Foot Infections. Antibacterial activity of the bark extract was evaluated by agar Disk-Diffusion (DD), Broth Dilution (BD), Checkerboard and Time-kill methods. The extract showed a significant antibacterial activity against all groups of bacteria tested. BD was more sensitive for determining the antibacterial activity of the bark extract than the DD method. The bark extract inhibited the growth of bacteria with high-levels of antibiotic-resistance, such as Pseudomonas spp. (100.0%), Enterobacer spp. (88.89%), Staphylococcus aureus (54.55%), Streptococcus pneumoniae (75.0%), Staphylococcus saprophyticus (92.86%). The combination of extract with antibiotics resulted in an additive effect against most of the strains tested. Time-kill kinetics profiles of bark extract showed bactericidal and time-dependent properties. Our results suggest that the bark extract of Davilla nitida is a source of bioactive compounds, which may be useful against antibiotic-resistant bacteria.     

Antifungal activity of Annona coriacea Mart. ethanol extracts against the aetiological agents of cryptococcosis

Cryptococcosis is an opportunistic disease with a worldwide distribution. This disease is caused by fungi of the genus Cryptococcus, and its treatment is limited to several antifungals. In this study, the antifungal, cytotoxic and mutagenic properties of ethanol extracts from the bark and leaves of Annona coriacea were evaluated against the standard Cryptococcus species and clinical yeast specimens. Both extracts of A. coriacea showed inhibitory activity of 1.5 mg/mL for all of the yeasts tested. The number of viable cells at the lowest tested concentration was 0.187 mg/mL. The extracts that were tested showed inhibitory activity and reduced the fungal growth of the Cryptococcus gattii species and Cryptococcus neoformans species complexes, suggesting that this plant may be an effective alternative treatment for cryptococcosis.     

Sequential injection extraction based on restricted access material for determination of furosemide in serum

Restricted access material (RAM) column containing 25 microm C18 alkyl-diol support was integrated into the sequential injection analysis (SIA) manifold and the SIA-RAM system was tested for direct determination of furosemide in serum. LiChrospher ADS column based on restricted access material is proposed to direct injection of biofluids. The integration of RAM material into SIA enabled creation of a comprehensive on-line sample clean-up technique combined with fluorescence quantitation of analyte. Centrifuged and diluted serum sample was aspirated into the system and loaded onto the column using acetonitrile-water (2:98), pH 2.7. The analyte was retained on the column while proteins contained in the sample were removed to the waste without precipitation and clogging the column. Interfering substances complicating the detection were washed out by acetonitrile-water (15:85), pH 2.7 in the next step. The extracted analyte was eluted by means of acetonitrile-water (25:75), pH 2.3 to the fluorescence detector (emission filter 385 nm). The whole procedure comprising sample pre-treatment, analyte detection and column reconditioning took 20 min. The recoveries of furosemide from serum lay between 101.4 and 103.4% for three concentrations of analyte.     

Enhanced optical limiting performance of a nonlinear absorber in a solution containing scattering nanoparticles

The optical limiting performance of a water-soluble porphyrin derivative is shown to be improved when small-sized (400-nm-diameter) nonabsorbing polystyrene spheres are added to the solution. The optical limiting enhancement is attributed to absorption of diffusive photons that experience longer light pathways than ballistic photons. The effect is demonstrated for nanosecond laser excitation at 532 nm.     

Hadronic decays in the non-relativistic quark model and the properties ofs s\bar s,vector mesons

We develop a simple, but highly effective technique for evaluating three-meson couplings in the context of the³ P ₀ quark-pair-creation model. The method combines the use of realistic, numerical wave-functions with the ease of amplitude calculation associated with the harmonic-oscillator basis. As a first application we discuss the properties of 1^?? ‘strangeonium’ states between 1 and 2 GeV.     

Real‐time monitoring of the ring‐opening polymerization of rac‐lactide with in situ attenuated total reflectance/Fourier transform infrared spectroscopy with conduit and diamond‐composite sensor technology

Polymerization rates were proportional to initial Sn(Oct)₂ concentration at low [Sn(Oct)₂]₀/[PrOH]₀ values, but began to level off at higher values. When [Sn(Oct)₂]₀/[PrOH]₀ was significantly greater than unity, the opposite behavior occurred. Tin(II) alkoxide concentration became limited by the initial PrOH concentration and independent of initial Sn(Oct)₂ concentration. Addition of 2‐ethylhexanoic acid caused polymerization rate retardation, without affecting molecular weight. A control polymerization was conducted in the absence of PrOH. The molecular weight of the resulting polymer was consistent with the measured water content (3.7 wt % by Karl Fisher titration) of the as‐received Sn(Oct)₂. The polymerization rate in the absence of PrOH was slow, and this suggested that water is less efficient than an alcohol in creating polymerization‐active stannyl ether bonds. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6238–6247, 2004