Nonionic Microemulsion: Mechanism of Formation and Percolation

A series of microemulsions, both W/O and O/W, based on nonionic surfactants of the form (NP(EO)_n), were prepared using the titration method. Mixing a constant weight of surfactant with a constant volume of the dispersed phase and an initial volume of continuous phase produces an emulsion, which is titrated to clarity with another surfactant (cosurfactant). Plotting (a) the volume of cosurfactant necessary to transform an emulsion into a microemulsion containing a fixed volume of dispersed phase and constant weight of surfactant versus (b) different initial continuous-phase volumes yields a straight line. Extrapolating from experimentally determined values for the cosurfactant volume to the value corresponding to a zero-volume continuous phase allows the determination of the surfactant molar composition and the average number of ethylene oxides (EO) per nonylphenol adsorbed at the interface. Using a surfactant with the same number of ethylene oxides yields a single-surfactant microemulsion. Measurement of surfactants transmittance in the oil and water phases demonstrates that microemulsification occurs when the surfactant interfacial film is equally soluble in the two phases. Surface pressure measurements reveal that oil penetration impedes formation of O/W microemulsions with n-tetradecane or n-hexadecane as dispersed phase. Conductance, particle size, and transmittance measurements show that above a certain dispersed-phase volume percolation of the microemulsion occurs.     

Voltammetric determination of itopride using carbon paste electrode modified with Gd doped TiO2 nanotubes

In the present work TiO₂ nanotubes (TNT) have been synthesized by alkaline hydrothermal transformation. Then they have been doped with Gd element. Characterizations of doped and undoped TNT have been done with TEM and SEM. The chemical composition was analyzed by EDX, Raman and FTIR spectroscopy. The crystal structure was characterized by XRD. Carbon paste electrode has been fabricated and mixed with Gd doped and undoped TNT to form a nanocomposite working electrode. Comparison of bare carbon paste electrode and Gd doped and undoped TNT carbon paste electrode for 1.0 ×10⁻³ M K₄ [Fe(CN)₆] voltammetric analysis; it was observed that Gd doped TNT modified electrode has advantage of high sensitivity. Gd doped TNT modified electrode has been used as working electrode for itopride assay in a pharmaceutical formulation. Cyclic voltammetry analysis showed high correlation coefficient of 0.9973 for itopride (0.04–0.2 mg/mL) with a limit of detection (LOD) and limit of quantitation values (LOQ) of 2.9 and 23.0 μg.mL⁻¹ respectively.     

Polyester-supported Chitosan-Poly(vinylidene fluoride)-Inorganic-Oxide-Nanoparticles Composites with Improved Flame Retardancy and Thermal Stability

Polyester(PET) was pre-activated by atmospheric air plasma and coated by various inorganic oxide nanoparticles(MOx) such as titanium dioxide(TiO2), zinc oxide(ZnO), and silicon oxide(SiO2), using poly(vinylidene fluoride)(PVDF) and chitosan(CT) as binders. The resulting PET-PVDF-MOx-CT composites were thermally compressed and then characterized by scanning electron microscopy, Fourier infrared spectroscopy, thermal gravimetric analysis, and flame retardancy(FR) ability tests. PET modifications resulted in more thermally stable and less harmful composites with weaker hazardous gas release. This was explained in terms of structure compaction that blocks pyrolysis gas emissions.CT incorporation was found to reduce the material susceptibility to oxidation. This judicious procedure also allowed improving flame retardancy ability, by lengthening the combustion delay and slowing the flame propagation. Chitosan also turned out to contribute to a possible synergy with the other polymers present in the synthesized materials. These results provide valuable data that allow understanding the FR phenomena and envisaging low-cost high FR materials from biodegradable raw materials.     

Synthesis and cytotoxic activity of some new heterocycles incorporating cyclohepta[b]thiophene-3-carboxamide derivatives

A series of 2-amino-5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophene-3-carboxamide-heterocyclic hybrids were synthesized, characterized and their cytotoxic potencies were assessed on four human cell lines. Cyanoacetamide derivative ( 5 ) was used as the key synthetic intermediate for the synthesis many derivatives in this study, derivatives 9 , 11 , 12 were formed by coupled compound 5 with different aryl/heteryl diazonium chlorides, Gewald reaction and Knoevenagel condensation were used for synthesis derivatives 13 , 14 , 16 by treated cyanoacetamide ( 5 ) with different reagents. In another route, compound 5 treated with phenyl isothiocyanate give thiocarbamoyl derivative ( 7 ) which used as intermediate underwent oxidative cyclization with different moieties to offer the corresponding thiazoles and thiophene 18 , 19 , 20 , 21 , respectively. in vitro cytotoxic activity of prepared compounds were tested against four human tumor cell lines. The result revealed that compound 11a displayed promising cytotoxic activity against HepG2, HCT-116, MCF-7, and PC3 cancer cell lines comparing to the positive control (Doxorubicin).     

Synthesis,Spectral, Characterization,and Anticancer Activity of Some Binary and Mixed Ligand Complexes of 4-Methyl-2-Pentanone Thiosemicarbazone and Some Amino Acids

The Schiff base ligand 4-methyl-2-pentanone thiosemicarbazone (MPTSC) (HL) has been synthesized by the interaction of 4-methyl-2-pentanone (MP) and thiosemicarbazone (TSC). The Ni(II), Cu(II), and Fe(III) binary complexes of this ligand have been prepared. The ternary complexes of VO(IV) and Mn(II) ions with HL and glutamine (Glu) as a secondary ligand, in addition to VO(IV), Mn(II), and La(III) with HL and glycine (Gly) as a secondary ligand, have also been synthesized. The binary and ternary complexes have been characterized based on elemental analysis, IR, UV-VIS, molar conductance, mass spectra, magnetic moment, and ESR measurements. The magnetic moment, UV, and ESR studies suggest that Ni(II) and Cu(II) complexes are square planar, whereas Fe(III), Mn(II), and La(III) complexes have octahedral geometry, but VO(IV) ternary complexes have square pyramidal geometry. The analytical data indicate that the metal-to-ligand ratio in binary complexes is 1:1, except HL-Cu(II) chloride complex where the metal-to-ligand to secondary ligand ratio in ternary complexes is 1:1:1. The anticancer studies showed that the anticancer activity is in the decreasing order: ternary complexes > binary complexes > free ligand (HL).

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Greedy Dynamic Routing on Arrays

We study the problem of dynamic routing on arrays. We prove that a large class of greedy algorithms perform very well on average. In the dynamic case, when the arrival rate of packets in anN × Narray is at most 99% of network capacity, we establish an exponential bound on the tail of the delay distribution. Moreover, we show that in any window ofTsteps, the maximum queue-size isO(1 + log T/log N) with high probability. We extend these results to the case of bit-serial routing, and to the static case. We also calculate the exact value of the ergodic expected delay and queue-sizes under the farthest first protocol for the one-dimensional array, and for the ring when the arrivals are Poisson.     

Controlling Hopf bifurcation and chaos in a small power system

For the power systems, the stabilization and tracking of voltage collapse trajectory, which involves severe nonlinear and nonstationary (unstable) features, is somewhat difficult to achieve. In this paper, we choose a widely used three-bus power system to be our case study. The study shows that the system experiences a Hopf bifurcation point (subcritical point) leads to chaos throughout period-doubling route. A model-based control strategy based on global state feedback linearization (GLC) is applied to the power system to control the chaotic behavior. The performance of GLC is compared with that for a nonlinear state feedback control.     

Converting self-assembled gold nanoparticle/dendrimer nanodroplets into horseshoe-like nanostructures by thermal annealing

A simple and effective nonlithographic method to produce a novel organization of noble metal nanoparticles into horseshoe-like nanostructures via self-assembly is described. The adsorption of Au nanoparticles stabilized with the dendrimer 1,2,3,4,5,6-hexakis[(3',5'-bis(benzyloxy)benzyl)sulfanylmethyl]benzene (S(6)G(1)) on hydrophilic surfaces (native oxide-terminated Si(111)) resulted in the formation of spatially correlated droplet aggregates. Annealing of Au/S(6)G(1) in thin films caused amalgamated droplets to form arrays of horseshoe-like nanostructures with an average size of approximately 250 nm and an average height of 13 nm. The mobility and the manner in which the semicapped Au nanoparticles are distributed on the hydrophilic substrate are believed to be the promoters that control the growth of the nucleation to create the horseshoe-like structures. Atomic force microscopy (AFM) measurements demonstrated the changes in height and size of the nanoparticles before and after the annealing process. Oxygen plasma etching was used to remove the S(6)G(1) dendrimer to reveal the orientation of the Au nanocrystals in the nanostructure matrix.     

Finitely additive representation of spaces

Let be any atomless and countably additive probability measure on the product space with the usual σ-algebra. Then there is a purely finitely additive probability measure λ on the power set of a countable subset such that can be isometrically isomorphically embedded as a closed subspace of L^p(λ). The embedding is strict. It is also ‘canonical,’ in the sense that it maps simple and continuous functions on to their restrictions to T.     

Missing boundary data recovering for the Helmholtz problem

This Note is dedicated to the numerical treatment of the ill-posed Cauchy–Helmholtz problem. Resorting to the domain decomposition tools, these missing boundary data are rephrased through an ‘interfacial’ equation. This equation is solved via a preconditioned Richardson algorithm with dynamic relaxation. The efficiency of the proposed method is illustrated by some numerical experiments. To cite this article: R. Ben Fatma et al., C. R. Mecanique 335 (2007).