A two-strain epidemic model with mutant strain and vaccination

In this paper, it is assumed that the spread of a pathogen can mutate in the host to create a second, cocirculating, mutant strain. Vaccinated individuals perhaps becomes infected after being in contact with individuals infected with mutant strain. A?two-strain epidemic model with vaccination is firstly investigated. The existence and stability properties of equilibria in this model are examined. By analyzing the characteristic equation and constructing Lyapunov functions, the conditions for local and global stability of the infection-free, boundary and endemic equilibria are established. The existence of Hopf bifurcation from the endemic equilibrium is also examined as this equilibrium loses its stability. Our theoretical results are confirmed by numerical simulations.     

A direct synthesis of β-carbolines via a three-step one-pot domino approach with a bifunctional Pd/C/K-10 catalyst

A rapid, microwave-assisted synthesis of β-carbolines via a successive condensation/cyclization/dehydrogenation approach is described. This methodology involves the coupling of various tryptamines with aromatic aldehydes/glyoxals. The product imine undergoes a Pictet-Spengler cyclization followed by a final dehydrogenation to yield β-carbolines in a three-step domino reaction. The use of the bifunctional catalyst Pd/C/K-10 combined with microwave irradiation enabled the synthesis of β-carbolines in short reaction times and in good to excellent yields.     

Synthesis of nano-phase TiO2 crystalline films over premixed stagnation flames

A new method is proposed to fabricate nanocrystalline titania (TiO₂) films of controlled crystalline size and film thickness. The method uses the laminar, premixed, stagnation flame approach, combining particle synthesis and film deposition in a single step. A rotating disc serves as a combination of substrate-holder and stagnation-surface that stabilizes the flame. Disc rotation repetitively passes the substrates over a thin-sheet, fuel-lean ethylene–oxygen–argon flame doped with titanium tetraisopropoxide. Convective cooling of the back side of the disc keeps the substrate well below the flame temperature, allowing thermophoretic forces to deposit a uniform film of particles that are nucleated and grown via the flame stabilized just below the surface. The particle film grows typically at 1 μm/s. The film is made of narrowly distributed, crystalline TiO₂ several nanometers in diameter and forms with a 90% porosity. Analysis shows that the rotation of the stagnation-surface does not reduce the stability of a stagnation flame, nor does it affect the fundamental chemistry of particle nucleation and growth that occurs between the flame and the stagnation surface.     

Ion-molecule reactions of ammonia clusters with C60 aggregates embedded in helium droplets

Helium nanodroplets are co-doped with C(60) and ammonia. Mass spectra obtained by electron ionization reveal cations containing ammonia clusters complexed with up to four C(60) units. The high mass resolution of Δm/m≈ 1/6000 makes it possible to separate the contributions of protonated, unprotonated and dehydrogenated ammonia. C(60) aggregates suppress the proton-transfer reaction which usually favors the appearance of protonated ammonia cluster ions. Unprotonated C(x)(NH(3))(n)(+) ions (x = 60, 120, 180) exceed the abundance of the corresponding protonated ions if n < 5; for larger values of n the abundances of C(60)(NH(3))(n)(+) and C(60)(NH)(n-1)NH(4)(+) become about equal. Dehydrogenated C(60)NH(2)(+) ions are relatively abundant; their formation is attributed to a transient doubly charged C(60)-ammonia complex which forms either by an Auger process or by Penning ionization following charge transfer between the primary He(+) ion and C(60). The abundance of C(x)NH(3)(+) and C(x)NH(4)(+) ions (x = 120 or 180) is one to two orders of magnitude weaker than the abundance of ions containing one or two additional ammonia molecules. However, a model involving evaporation of NH(3) or NH(4) from the presumably weakly bound C(x)NH(3)(+) and C(x)NH(4)(+) ions is at odds with the lack of enhancement in the abundance of C(120)(+) and C(180)(+). Mass spectra of C(60) dimers complexed with water complement a previous study of C(60)(H(2)O)(n)(+) recorded at much lower mass resolution.     

Furan-based Polysemiacylcarbazides by Polyaddition of Bis(furanic hydrazide)s with Diisocyanates

A solution polyaddition procedure was applied to prepare furanic polyacylsemicarbazides based on 2,2′-isopropylidene-bis(5-(2-furoyl) hydrazide) and aliphatic or aromatic diisocyanates. Model compounds were prepared to facilitate the synthesis and the characterization of the polymers. A systematic study of reaction parameters (the nature of the organic phase, the temperature, the reaction time, and the concentration of monomers) was carried out. High MW polymers were obtained after 12 h reaction at 20°C with 0.2 M monomer solutions in dimethylacetamide. In fact, the polyacylsemicarbazides obtained had inherent viscosities ranging from 0.63 to 0.85 dL/g. There showed good solubility in aprotic polar solvents. The ¹H and ¹³C-NMR spectra were consistent with the expected structures. These furan-based polyacylsemicarbazides are thermally stable up to 290°C, but exhibit a complex thermal behavior. This was explained by the cyclohydration of acylsemicarbazide groups into NH-substituted oxadiazoles, resulting in rigid and high melting polymers, less stable, however, than conventional aromatic polyoxadiazoles.     

Polyterephthalates Bearing Bio-based Moieties

Dimethyl terephthalate was reacted with 5,5′-Isopropylidene-bis(ethyl 2-furoate), 1,4:3,6-dianhydrohexitols and ethan-1,2-diol in order to obtain PET incorporating bio-based moieties. Polycondensation was achieved in two steps: (i) the formation of a hydroxyethyl-terminated oligomer by reaction of starting diester mixture with excess ED and, (ii) a polycondensation step with elimination of ED was used to obtain high molar mass copolyesters. Copolymers of various compositions were synthesized and characterized by ¹H-NMR, SEC, DSC and TGA. The resulting materials are amorphous polymers (T _g = 104–127 °C) with good thermal stability.     

Effects of pH and Ionic Salts on the Emulsifying and Rheological Properties of Acorn Protein Isolate

This study was designed to evaluate the emulsifying and rheological properties of acorn protein isolate (API) in different pH mediums (pH 3, 7 and 9) and in the presence of ionic salts (1 M NaCl and 1 M CaCl₂). API shows higher solubility in distilled water at pH 7, while at the same pH, a decrease in solubility was observed for API in the presence of CaCl₂ (61.30%). A lower emulsifying activity index (EAI), lower stability index (ESI), larger droplet sizes and slight flocculation were observed for API in the presence of salts at different pHs. Importantly, CaCl₂ treated samples showed relevantly higher EAI (252.67 m²/g) and ESI (152.67 min) values at all pH as compared to NaCl (221.76 m²/g), (111.82 min), respectively. A significant increase in interfacial protein concentration (4.61 mg/m²) was observed for emulsion at pH 9 with CaCl₂, while the major fractions of API were observed in an interfacial layer after SDS-PAGE analysis. All of the emulsion shows shear thinning behavior (τ_c > 0 and n < 1), while the highest viscosity was observed for emulsion prepared with CaCl₂ at pH 3 (11.03 ± 1.62). In conclusion, API, in the presence of ionic salts at acidic, neutral and basic pH, can produce natural emulsions, which could be substitutes for synthetic surfactants for such formulations.