Phase behaviour of thermotropic banana-shaped compounds under pressure

The phase behaviour of two achiral bent core banana-shaped compounds, the hexyloxy (compound I) and decyloxy (compound II) members of the 1,3-phenylene bis[N-(2-hydroxy-4-n-alkoxybenzylidene)-4'-aminobenzoate] series was investigated under hydrostatic pressures up to 300 MPa using high pressure differential thermal analysis and light transmission methods. The reversible transition sequence crystal (Cr₁)-B₁ phase-isotropic liquid (I), observed at room pressure for compound I, remains in the pressure region up to c 70 MPa. At higher pressures a pressure-induced crystalline phase (Cr_i) appears between the Cr₁ and B₁ phases, its temperature region becoming wider with increasing pressure. The temperature vs. pressure phase diagram shows a triple point of 72.9 MPa and 160.3°C for the Cr₁, Cr_i and B₁ phases, indicating the lower limit of pressure for the Cr_i phase. In compound II the reversible transition sequence crystal (Cr₁)-B₂ phase-I is seen over the whole pressure region, and the temperature range of the B₂ phase remains unaltered. It is concluded that both the B₁ and B₂ banana phases are stable over the whole pressure region studied.     

Phosphorus-based allenes as scaffolds in cycloaddition and cyclization reactions

ABSTRACT

In this article, we describe some of our results on the reactions of allenylphosphonates/allenyl phosphine oxides and allenyl diazaphosphole oxides, primarily cycloaddition and cyclization reactions. Depending on the substituents, both the α,β and β,γ -cycloaddition products have been observed. A novel cyclization reaction of a functionalized allenylphosphine oxide with diethylamine leading to 3-diethylamino-4-diphenylphosphinoyl-1-naphthol is reported. Representative compounds have been characterized by X-ray crystallography.     

Ultrasound responsive organogels based on cholesterol-appended quinacridone derivatives with mechanochromic behaviors

A series of cholesterol-appended quinacridone (QA) derivatives 1a-1d have been synthesized,in which 1b and 1c could form stable organogels in a wide range of organic solvents upon ultrasound irradiation.Field emission scanning electronic microscope (FESEM) and transmission electron microscopy (TEM) of xerogels or precipitates indicated that 1b and 1c formed 1D fibrous nanostructure,while 1a assembled into 3D flower-like microstructures.The ultrasound-induced organogel process was characterized by kinetic UV...     

EXISTENCE OF LIMIT CYCLES FOR A CUBIC KOLMOGOROV SYSTEM WITH A PARABOLIC SOLUTION WHICH DOES NOT CONTACT AND INTERSECT THE COORDINATE AXES

This paper is concerned with a cubic Kolmogorov system with a parabolicsolution which does not contact and intersect the coordinates. The conclusionis that such a system may possess limit cycles.     

1-Naphthol as an excited state proton transfer fluorescent probe for sensing bound-water hydration of polyvinyl alcohol

When 1-naphthol incorporated polyvinyl alcohol (PVA) films are allowed to swell in water, there is a loss of fluorescence intensity of the neutral form with a concomitant increase of the anionic form fluorescence intensity. This fluorescence response due to the excited state prototropism (ESPT) of 1-naphthol is very sensitive to the initial stage of hydration of the PVA. Using an existing model of hydrogel swelling and DSC experiments, it was reasoned that 1-naphthol senses the bound-water component of PVA hydration. Thus, 1-naphthol is proposed as an ESPT fluorescent sensor for the specific sensing of bound-water hydration of PVA hydrogel.     

FPGA implementation of novel fractional-order chaotic systems with two equilibriums and no equilibrium and its adaptive sliding mode synchronization

This paper introduces two novel fractional-order chaotic systems with cubic nonlinear resistor and investigates its adaptive sliding mode synchronization. Firstly the novel two equilibrium chaotic system with cubic nonlinear resistor (NCCNR) is derived and its dynamic properties are investigated. The fractional-order cubic nonlinear resistor system (FONCCNR) is then derived from the integer-order model and its stability and fractional-order bifurcation are discussed. Next a novel no-equilibrium chaotic cubic nonlinear resistor system (NECNR) is derived from NCCNR system. Dynamic properties of NECNR system are investigated. The fractional-order no equilibrium cubic nonlinear resistor system (FONECNR) is derived from NECNR. Stability and fractional-order bifurcation are investigated for the FONECNR system. The non-identical adaptive sliding mode synchronization of FONCCNR and FONECNR systems are achieved. Finally the proposed systems, adaptive control laws, sliding surfaces and adaptive controllers are implemented in FPGA.     

Poly(Styrene Sulfonate)/Poly(Allylamine Hydrochloride) Encapsulation of TiO<Subscript>2</Subscript> Nanoparticles Boosts Their Toxic and Repellent Activity Against Zika Virus Mosquito Vectors

Green fabricated nanoparticles often need to be encapsulated and stabilized, to ensure uniform dispersion in the aquatic environment and relevant larvicidal activity over time. However, recent research showed that nanoencapsulation processes led to a reduction of nanoparticle larvicidal efficacy. We used an extract of Argemone mexicana to reduce TiO₂ nanoparticles, which were then capped with PSS/PAH (poly(styrene sulfonate)/poly(allylamine hydrochloride)). The toxic and repellent potential of the nanoparticles were compared to elucidate their potential effects against the Zika virus vector Aedes aegypti. Nanoparticles were characterized by biophysical methods including UV–Vis, EDX and FTIR spectroscopy, SEM, TEM, XRD and DLS analyses. In larvicidal and pupicidal experiments, TiO₂ nanoparticles achieved LC₉₀ values from 41.648 (larva I), to 71.74 ppm (pupa). Nanoencapsulated TiO₂ achieved LC₉₀ values from 39.16 (I), to 69.12 ppm (pupa). In adulticidal experiments, LC₉₀ of TiO₂ nanoparticles on Ae. aegypti was 10.31 ppm, while LC₉₀ of nanoencapsulated TiO₂ was 9.54 ppm. At 10 ppm, the repellency towards Ae. aegypti was 80.43% for TiO₂ nanoparticles, and 88.04% for nanoencapsulated TiO₂. This research firstly highlighted the promising potential of PSS/PAH encapsulation, leading to the production of highly effective titania nanostructures, if compared to titania nanoparticles synthesized with eco-friendly routes without further stabilization.     

Analytical expression of the steady-state catalytic current of mediated bioelectrocatalysis and the application of He’s Homotopy perturbation method

A mathematical model of mediated bioelectrocatalysis is restudied in this paper. Here He’s Homotopy perturbation method is implemented to give approximate and analytical solutions of steady-state non-linear reaction diffusion equation containing a non-linear term related to Michaelis–Menten kinetics of the enzymatic reaction. Approximate analytical expressions for mediator concentration and current have been derived for all values of saturation parameter α and reaction diffusion parameter k for the various types of boundary conditions. The Homotopy perturbation method which produces the solutions in terms of convergent series, requiring no linearization or small perturbation. These analytical results are compared with numerical results (Matlab program) and are found to be in good agreement.     

Metal-free,base catalyzed oxidative amination and denitration reaction: Regioselective synthesis of 3-arylimidazo[1,2-a]pyridines

A metal-free, regioselective strategy for the synthesis of 3-arylimidazo[1,2-a]pyridines from β-nitrostyrenes and 2-aminopyridines using triethylamine as the catalyst and H₂O₂ (30% aq.) as the oxidant is reported. The use of an inexpensive base and facile reaction conditions make this strategy a practical alternative for the synthesis of 3-arylimidazo[1,2-a]pyridines.     

Synthesis of degradable poly(methyl methacrylate) star polymers via RAFT copolymerization with cyclic ketene acetals

Copolymerization of the cyclic ketene acetal 5,6‐benzo‐2‐methylene‐1,3‐dioxepane (BMDO) with methyl methacrylate (MMA) is studied with respect to its copolymerization parameters and the suitability to control BMDO/MMA copolymerizations via the reversible addition‐fragmentation chain transfer (RAFT) technique to obtain linear and 4‐arm star polymers. BMDO shows disparate copolymerization behavior with MMA and r₁ = 0.33 ± 0.06 and r₂ = 6.0 ± 0.8 have been determined for polymerization at 110 °C in anisole from fitting copolymer composition vs. comonomer feed data to the Lewis–Mayo equation. Copolymerization of the two monomers is successful in RAFT polymerization employing a trithiocarbonate control agent. As desired, polymers contain only little amount of polyester units stemming from BMDO units and preliminary degradation experiment show that the polymer degrades slowly, but steadily in aqueous 1 M NaOH dispersion. Within ten days, the polymers are broken down to low molecular weight segments from an initial molecular weight of M_n = 6000 g mol^?1. Star (co)polymerization with an erythritol‐based tetra‐functional RAFT agent following the Z‐group approach proceeds efficiently and polymers with a number‐average molecular weight of 10,000 g mol^?1 are readily obtained that degrade in similar manner as the linear copolymer counterparts. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1633–1641