Thermotropic phase behavior in aqueous mixtures of dioctadecyldimethylammonium bromide and alkyltrimethylammonium bromide surfactant series studied by differential scanning calorimetry

The effect of the micelle-forming surfactant series alkyltrimethylammonium bromide (C(n)TAB, n = 12, 14, 16 and 18) on the thermotropic phase behavior of dioctadecyldimethylammonium bromide (DODAB) vesicles in water was investigated by differential scanning calorimetry at constant 5.0 mM total surfactant concentration and varying individual surfactant concentrations. The pre-, post- and main transition temperatures (T-s, T-p and T-m), melting enthalpy (Delta H) and peak width of the main transition (Delta T-1/2) are reported as a function of the surfactant molar fraction. No clear dependence of these parameters on the C(n)TAB chain length was found. At 5 mM, neat DODAB in water exhibits two transition temperatures, T-s = 32.1 and T-m = 42.7 degrees C, as obtained from the DSC upscans, but not a clear T-p. For every n, except n = 12, T-s vanishes as CnTAB concentration increases and approaches CMC. T-m behaves differently for different n, the longer C(14)TAB and C(16)TAB decrease, while C(18)TAB increases T-m with increasing concentration. The data indicate that changes in T-m, T-s, T-p and Delta H of the transition are related not only to the extent of C(n)TAB affinity to DODAB but also to the surfactant chain length. Accordingly, C18TAB yields a more compact bilayer, thus increasing T-m, while C(14)TAB and C(1G)TAB yield a less organized bilayer and reduce T-m. C(12)TAB does not much affect T-s and T-m, although it yields T-p approximate to 51.6 degrees C. (C) 2008 Elsevier B.V. All rights reserved.

Thermal and Structural Behavior of Dioctadecyldimethylammonium Bromide Dispersions Studied by Differential Scanning Calorimetry and X-Ray Scattering

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Implicit differential equations with impasse singularities and singular perturbation problems

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Periodic solutions of abstract neutral functional differential equations

We characterize the existence of periodic solutions of some abstract neutral functional differential equations with finite and infinite delay when the underlying space is a UMD space. (C) 2011 Elsevier B.V. All rights reserved.

Measurement of inclusive differential cross sections for Upsilon(1S) production in p(p)over-bar collisions at root s=1.96 TeV

We present measurements of the inclusive production cross sections of the Upsilon(1S) bottomonium state in p (p) over bar collisions at root s=1.96 TeV. Using the Upsilon(1S)->mu(+)mu(-) decay mode for a data sample of 159 +/- 10 pb(-1) collected by the D0 detector at the Fermilab Tevatron collider, we determine the differential cross sections as a function of the Upsilon(1S) transverse momentum for three ranges of the Upsilon(1S) rapidity: 0 <\y(Upsilon)\<= 0.6, 0.6 <\y(Upsilon)\<= 1.2, and 1.2 <\y(Upsilon)\<= 1.8.

Differential and partial cross sections of elastic and inelastic positronium-helium-atom scattering

Scattering of positronium (Ps) by a helium atom has been investigated in a three-Ps-state coupled-channel model including Ps(1s,2s,2p) states using a recently proposed time-reversal-symmetric regularized electron-exchange model potential. Specifically, we report results of differential cross sections for elastic scattering and target-elastic Ps excitations. We also present results for total and different partial cross sections and compare them with experiment and other calculations.

Measurement of the differential cross section for the production of an isolated photon with associated jet in p(p)over-bar collisions at root s=1.96 TeV

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Measurement of the differential dijet production cross section in proton-proton collisions at root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of differential Z/gamma* plus jet plus X cross sections in p(p)over-bar collisions at root S=1.96 TeV

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Measurement of three-jet differential cross sections d sigma(3jet)/dM(3jet) in p(p)over-bar collisions at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurements of differential cross sections of Z/gamma* plus jets plus X events in p(p)over-bar collisions at root s=1.96 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Inclusive and differential measurements of the t(t)over-bar charge asymmetry in proton-proton collisions root s=7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Measurement of the differential cross section for isolated prompt photon production in pp collisions at 7 TeV

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Stability of differential equations with piecewise constant argument via discrete equations

Lyapunov stability for a class of differential equation with piecewise constant argument (EPCA) is considered by means of the stability of a discrete equation. Applications to some nonlinear autonomous equations are given improving some linear known cases.