Polymer approach to supported silica membranes

Polymeric silica sols were used to prepare membranes on commercial -Al₂O₃ supports with nominal support pore diameters of 4.0 nm. Aging of the silica sols was shown to be effective to form discrete membrane layers. He/N₂ selectivity factors exceeding ideal Knudsen values were observed when the sols were prepared under conditions in which the condensation rate was minimized. We propose that the average pore size of the membrane depends on the balance of capillary pressure and modulus during membrane deposition. The condensation rate might influence the breadth of the pore size distribution.     

Interfacial and aggregation properties of the binary mixture of decanoyl-N-methyl-glucamide and hexadecyltriphenylphosphonium bromide

The interfacial and aggregation behavior of the nonionic surfactant decanoyl-N-methyl-glucamide (Mega-10) with the cationic surfactant hexadecyltriphenylphosphonium bromide (HTPB) have been studied using interfacial tension measurements and fluorescence techniques. From interfacial tension measurements, the critical micellar concentrations (cmc) and various interfacial thermodynamic parameters have been evaluated. The experimental results were analyzed in the context of the pseudophase separation model, the regular solution theory, and the Maeda’s approach. These approaches allowed us to determine the interaction parameter and composition in the mixed state. By using the static quenching method, the mean micellar aggregation numbers of pure and mixed micelles of HTPB+Mega-10 were obtained. It was found that that the aggregation number decreases with increasing mole fraction of HTPB. This behavior is attributed to the presence of the bulky head group of HTPB, which creates steric head group incompatibility and/or electrostatic repulsion. The micropolarity of the micelle was monitored with pyrene fluorescence intensity ratio. It was observed that the increasing participation of HTPB induces the formation of micelles with a hydrated structure. The polarization of the fluorescent probe Rhodamine B was monitored in micellar medium and found to increase with the increase of ionic content. This behavior suggests the formation of mixed micelles with a more ordered or rigid structure.     

Solubilization of endocrine disruptors in micellar media

The interaction of endocrine disruptor chemicals (EDCs) such as nonylphenol (NP) and β-estradiol with cationic micelle of hexadecyltrimethylammonium ion (HTA⁺) and a monolayer of HTA⁺ ion adsorbed at the electrode surface has been investigated in the presence of hydrophilic modified (2-hydroxypropyl)-β-cyclodextrin. NP, which has a similar structure to HTA⁺, decreased the critical micelle concentration (cmc) of hexadecyltrimethylammonium bromide more effectively. At the low HTA⁺ concentration, HTA⁺ inhibited the adsorption of I₂. However, as the HTA⁺ concentration increased, a monolayer of HTA⁺ was formed at the electrode surface and caused the adsorption of iodine molecule (I₂). In the presence of micelle, the I₂ was dissolved in the micelle. Both EDCs caused the formation of HTA⁺ monolayer even at the HTA⁺ concentration below the cmc.     

Zassenhaus Conjecture (ZC1) on torsion units of integral group rings for some metabelian groups

We prove a conjecture of Zassenhaus that every normalized torsion unit of the integral group ring ZG of a finite group G is rationally conjugate to a group element for some metabelian groups including metacyclic groups G containing a normal cyclic group A such that G/A is cyclic of prime power order. The relative prime case was done in [11]. Received: 21 April 2005     

An extension to a theorem of Himmelberg

This paper extends a widely used theorem of Himmelberg to topological vector spaces whose completion have a separating dual.     

Depth profiling of Irganox‐3114 nanoscale delta layers in a matrix of Irganox‐1010 using conventional Cs+ and O2+ ion beams

Depth profiling of an organic reference sample consisting of Irganox 3114 layers of 3 nm thickness at depths of 51.5, 104.5, 207.6 and 310.7 nm inside a 412 nm thick Irganox 1010 matrix evaporated on a Si substrate has been studied using the conventional Cs⁺ and O₂⁺ as sputter ion beams and Bi⁺ as the primary ion for analysis in a dual beam time‐of‐flight secondary ion mass spectrometer. The work is an extension of the Versailles Project on Advanced Materials and Standards project on depth profiling of organic multilayer materials. Cs⁺ ions were used at energies of 500 eV, 1.0 keV and 2.0 keV and the O₂⁺ ions were used at energies of 500 eV and 1.0 keV. All four Irganox 3114 layers were identified clearly in the depth profile using low mass secondary ions. The depth profile data were fitted to the empirical expression of Dowsett function and these fits are reported along with the full width at half maxima to represent the useful resolution for all the four delta layers detected. The data show that, of the conditions used in these experiments, an energy of 500 eV for both Cs⁺ beam and O₂⁺ beam provides the most useful depth profiles. The sputter yield volume per ion calculated from the slope of depth versus ion dose matches well with earlier reported data. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis of novel pyrimidine nucleoside analogues owning multiple bases/sugars and their glycosidase inhibitory activity

A series of novel nucleoside analogues having dual bases (pyrimidine and triazole) and sugars have been synthesized by CuAAC reaction of azido sugars with propynylated pyrimidines. These compounds were evaluated for their in vitro α-glucosidase inhibitory activity. In this series, compounds 4b, 4d, 8a, 8b, 8c, 8e, 8g, 8h, and 8i exhibited very good inhibition of α-glucosidase enzyme. Nucleoside analogues 8a, 4b, 8h, and 8c displayed 47.4%, 41.8%, 39.4%, and 34.6% inhibition, respectively, comparable to the standard drug acarbose (53.4%).     

Evidence for dark energy from the cosmic microwave background alone using the Atacama Cosmology Telescope lensing measurements

For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with w = -1 dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density Ω(Λ) confirms other measurements from supernovae, galaxy clusters, and baryon acoustic oscillations, and demonstrates the power of CMB lensing as a new cosmological tool.