Microviscosity of hydrophobically modified hydroxyethyl cellulose aqueous solutions

The microviscosity of hydrophobically modified hydroxyethyl cellulose (HMHEC) aqueous solutions is experimentally determined by conductometry with added ions as probe. Compared to its bulk viscosity, the microviscosity of HMHEC solution could be lower by four orders of magnitude. Since the electric conductivity reduction of added NaCl is almost the same for HMHEC and its unmodified counterpart at an equal weight concentration, one can conclude that the hydrophobic modification for the polymer hardly has any effect on the solution's microviscosity.     

An untargeted metabolomics approach to contaminant analysis: pinpointing potential unknown compounds

This study deals with an automated data analysis strategy to pinpoint potential unknown compounds in full scan mass spectrometry (MS) experiments. Three examples of an untargeted metabolomics approach to contaminant analysis are given. By comparing a plant-oil based hormone cocktail to 90 plant oil samples ca. 25 compounds specific to the hormone cocktail could be detected. Five of these compounds were confirmed as steroid hormones. A comparison of a drink water sample from a farm to distillated water showed the presence of contaminants specific to this drink water sample. A grass sample, which was known to give a false positive result in a DR-CALUX bioassay, was unexpectedly shown to contain an abnormal level of chrysene, which was obviously not eliminated during clean-up.     

A study on absolute Riesz summability factors

In the present paper, two general theorems on summability factors of infinite series which generalize some known results, have been proved. Also we have obtained two new results concerning the |C,1;δ| _k summability factors.     

Efflorescence relative humidity of mixed sodium chloride and sodium sulfate particles

We study the efflorescence relative humidity (ERH) of particles composed of sodium chloride and sodium sulfate. Both experimental and theoretical investigations are conducted to explore the effects of particle size and mixing ratios between two inorganic materials on ERH. A previously developed theoretical model (Gao et al. J. Phys. Chem. A 2006, 110, 7602; ref 1) is applied as the framework to build a formulation assuming that one salt nucleates much faster than the other, and the critical nuclei formation of the former controls the rate of efflorescence. The predicted ERHs agree favorably with the experimental data, except for particles containing Na2SO4 in a mole fraction of around 0.25. At this composition, our model underestimates the ERH, indicating certain factors involved in the efflorescent processes that are overlooked in our formulation. Relative to particles larger than 40 nm, the Kelvin effect more significantly affects particles smaller than this size.     

Density functional approach to the adsorption of spherical molecules on a surface modified with attached short chains

A density functional and Monte Carlo simulation study of end-grafted polymers immersed by simple fluids is presented. The polymer molecules are modeled as freely jointed tangent hard spheres with the end segments linked to the surface. The authors analyze an influence of the chain length, the grafting density, and a nature of solvent on the brush structure. Adsorption of hard-sphere mixtures on the modified surface is also discussed. The theory precisely approximates simulation data.     

Study of acid-base properties of a SiO2?AlPO4 (80∶20 W/W) catalyst

2-Methyl-3-butyn-2-ol (MBOH) transformation was used as a test reaction in order to determine the acid-base properties of a SiO₂/AlPO₄ (80∶20 w/w) catalyst. Experiments were carried out in a microcatalytic pulse reactor and in a continuous-flow reactorvia Temperature Programmed Surface Reactions-Mass Spectrometry (TPSR-MS). Results are compared to acid-base properties calculated by other instrumental techniques.     

Interconnection networks for parallel molecular dynamics simulation based on hamiltonian cubic symmetric topology

A class of interconnection networks for efficient parallel MD simulations based on hamiltonian cubic symmetric graphs is presented. The cubic symmetric graphs have many desirable properties as interconnection networks since they have a low degree and are vertex- and edge-transitive. We present a method for scheduling collective communication routines that are used in parallel MD and are based on the property that the graphs in question have a Hamilton cycle, that is, a cycle going through all vertices of the graph. Analyzing these communication routines shows that hamiltonian cubic symmetric graphs of small diameter are good candidates for a topology that gives rise to an interconnection network with excellent properties, allowing faster communication and thus speeding up parallel MD simulation.     

Thermal degradation of CTAB in as-synthesized MCM-41

Thermal evacuation of a surfactant template from pure siliceous MCM-41 and MCM-41 containing aluminium in hydrogen flow was investigated. Micelle templated MCM-41 were prepared using hexadecyltrimethylammonium bromide (CTAB). The products of thermal surfactant degradation outside and inside pores were identified at various temperatures using ¹³C solid-state nuclear magnetic resonance (NMR) spectroscopy, gas chromatography coupled with mass spectrometer (GC-MS) and temperature programmed desorption coupled with mass spectrometer (TPD-MS). The GC-MS and ¹³C MAS NMR results obtained from this study provide an insight into the mechanism of surfactant transformation during MCM-41 synthesis on molecular level.     

Local properties of factored Fourier series

By using a convex sequence Bor [H. Bor, A study on local properties of factored Fourier series, Nonlinear Anal. 57 (2004) 191-197] has obtained a result dealing with local properties of factored Fourier series for summability. In this paper, we have generalized that result for summability. Some new results have also been obtained.