Structural investigations of carrageenan–surfactant systems by synchrotron X‐ray scattering

Small‐angle X‐ray scattering by means of synchrotron radiation was used to study the interaction of κ‐ and ι‐carrageenan of different molar mass in the presence of the gel‐inducing ions, K⁺, with the ionic surfactants cetylpyridinium chloride (CPC) and dodecylpyridinium chloride (DPC). This interaction resulted in a more or less complete shrinking of the gel and in the formation of ordered periodic structures of the surfactant in conjunction with the carrageenan molecules. The influence of the polymer concentration for a given surfactant concentration, the content of surfactant for the same concentration of the polysaccharide, the molar mass, and the linear charge density of the polymer were all investigated. Decreasing the length of the alkyl chain of the surfactant, increasing the charge density of the polymer chain, and increasing the polymer concentration for the samples explored improved the ordering in the carrageenan–surfactant complexes. The structures of the κ‐carrageenan–CPC complexes were investigated as a function of temperature during reversible heating–cooling cycles, and it was shown that the addition of the surfactant lead to a more pronounced temperature stability of polymer network. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 2851–2859, 2000     

On improvement of PIV image interrogation near stationary interfaces

In this paper the problem posed by interfaces when present in PIV measurements is addressed. Different image pre-processing, processing and post-processing methodologies with the intention to minimize the interface effects are discussed and assessed using Monte Carlo simulations. Image treatment prior to the correlation process is shown to be incapable of fully removing the effects of the intensity pedestal across the object edge. The inherent assumption of periodicity in the signal causes the FFT-based correlation technique to perform the worst when the correlation window contains a signal truncation. Instead, an extended version of the masking technique introduced by Ronneberger et al. (Proceedings of the 9th international symposium on applications of laser techniques to fluid mechanics, Lisbon, 1998) is able to minimize the interface-correlation, resolving only the particle displacement peak. Once the displacement vector is obtained, the geometric center of the interrogation area is not the correct placement. Instead, the centre of mass position allows an unbiased representation of the wall flow (Usera et al. in Proceedings of the 12th international symposium on applications of laser techniques to fluid mechanics, Lisbon, 2004). The aforementioned concepts have been implemented in an adaptive interrogation methodology (Theunissen et al. in Meas Sci Technol 18:275–287, 2007) where additionally non-isotropic resolution and re-orientation of the correlation windows is applied near the interface, maximizing the wall-normal spatial resolution. The increase in resolution and robustness are demonstrated by application to a set of experimental images of a flat-plate, subsonic, turbulent boundary layer and a hypersonic flow over a double compression ramp.     

A new facility for time-resolved PIV measurements in rotating channels

A new facility to measure the time evolution of 2D velocity fields in a rotating channel is presented, and the accuracy is discussed in detail. Measurements are made by means of a time-resolved PIV system composed of a continuous laser diode, coupled by a fiber optics cable to a laser plane optical module, and a CMOS high-speed camera. Both the PIV system and divergent channel are fixed on a 2.5 m rotating disk. This allows a direct measurement of the relative velocity of flows with Reynolds numbers between 3 × 10³ and 3 × 10⁴ and Rotation numbers between 0.0 and 0.52. These values correspond to the flow conditions in small radial impellers and can be independently adjusted by a change of the relative flow velocity and RPM. It is shown that this new facility allows high signal-to-noise ratios, and that the direct acquisition of the data in a rotating frame drastically reduces the measurement error. The accuracy and high spatial and temporal resolution of the measurements allow a detailed analysis of boundary layer characteristics in stationary and rotating conditions.     

MacNeille completions of lattice expansions

There are two natural ways to extend an arbitrary map between (the carriers of) two lattices, to a map between their MacNeille completions. In this paper we investigate which properties of lattice maps are preserved under these constructions, and for which kind of maps the two extensions coincide. Our perspective involves a number of topologies on lattice completions, including the Scott topologies and topologies that are induced by the original lattice. We provide a characterization of the MacNeille completion in terms of these induced topologies. We then turn to expansions of lattices with additional operations, and address the question of which equational properties of such lattice expansions are preserved under various types of MacNeille completions that can be defined for these algebras. For a number of cases, including modal algebras and residuated (ortho)lattice expansions, we provide reasonably sharp sufficient conditions on the syntactic shape of equations that guarantee preservation. Generally, our results show that the more residuation properties the primitive operations satisfy, the more equations are preserved. Received August 21, 2005; accepted in final form October 17, 2006.     

n-Alkane hydroconversion on Zeogrid and colloidal ZSM-5 assembled from aluminosilicate nanoslabs of MFI framework type

n-Alkane hydroisomerisation and hydrocracking experiments reveal that ZSM-5 materials synthesized by self-assembly of nanoslabs show different molecular shape selectivity than ZSM-5 synthesized by hydrothermal methods.     

Application of neutron activation analysis in the field of silicon technology for the modern electronic industry

The specific application of neutron activation analysis in the research on the preparation of silicon integrated circuits is discussed. The high flux irradiation facility for large silicon wafers (up to 15 cm diameter) was used, the analytical procedure, and some typical results will be described.     

Formation of ordered microstructures in polyelectrolyte/surfactant systems: linear anionic polyelectrolytes and cetylpyridinium chloride

Synchrotron X‐ray scattering was used for the structural investigation of complexes between anionic polyelectrolytes and cetylpyridinium chloride (CPC). According to the Bragg peaks, different types of ordering are proposed. Cetylpyridinium chloride in conjunction with carrageenan forms bilayers connecting rigid polysaccharide chains. In the presence of poly(styrenesulfonate), several micelles are bound to one chain. They appear rather small in size due to specific interactions with this polyion. In poly(acrylate)/CPC and poly(methacrylate)/CPC solutions, a cubic structure is indicated.     

The DSC12E,a low-cost differential scanning calorimeter

The DSC12E is a low-cost Differential Scanning Calorimeter, specially developed for quality control- and educational purposes. A discussion is given of the various boundary conditions connected to the development of this instrument and the resulting construction is described. The specifications of the instrument are discussed with the aid of some illustrative experiments.

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Zusammenfassung Das DSC12E ist ein Differential Scanning Calorimeter der niedrigsten Preisklasse, das sowohl für die QualitÄtskontrolle im Routinelabor als auch für Ausbildungszwecke entwickelt wurde. Es werden die Spezifikationen und die Rahmenbedingungen dieses Instrumentes erlÄutert und erste Messungen dargestellt.

     

Influence of ethanol on cannabinoid pharmacokinetic parameters in chronic users

Cannabis is not only the most widely used illicit drug worldwide but is also regularly consumed along with ethanol. In previous studies, it was assumed that cannabis users develop cross-tolerance to ethanol effects. The present study was designed to compare the effects of ethanol in comparison to and in combination with a cannabis joint and investigate changes in pharmacokinetics. In this study, 19 heavy cannabis users participated and received three alcohol dosing conditions that were calculated to achieve steady blood alcohol concentrations (BAC) of about 0, 0.5 and 0.7 g/l during a 5-h time window. Subjects smoked a Δ⁹-tetrahydrocannabinol (THC) cigarette (400 μg/kg) 3 h post-onset of alcohol dosing. Blood samples were taken between 0 and 4 h after smoking. During the first hour, samples were collected every 15 min and every 30 min thereafter. Mean steady-state BACs reached 0, 0.36 and 0.5 g/l. The apparent elimination half-life of THC was slightly prolonged (1.59 vs. 1.93 h, p < 0.05) and the concentration 1 h after smoking was slightly lower (24 vs. 17 ng/ml, p < 0.05) with the higher ethanol dose. The prolonged THC elimination might be explained by a small ethanol-mediated change in distribution to and from deep compartments. Concentrations and pharmacokinetics of 11-hydroxy-THC and 11-nor-9-carboxy-THC (THCA) were not significantly influenced by ethanol. However, THCA concentrations appeared lower in both ethanol conditions, which might also be attributable to changes in distribution. Though not significant in the present study, this might be relevant in the interpretation of cannabinoid concentrations in blood.