Nanoparticles as pseudostationary phase in capillary electrochromatography/ESI-MS

A novel technique that uses polymer nanoparticles as pseudostationary phase in capillary electrochromatography with electrospray ionization mass spectrometry detection is described. A continuous full filling technique in which the nanoparticles were suspended in the entire electrolyte volume as well as a conventional partial filling technique is presented. No nanoparticles entered the mass spectrometer, which was fitted with an orthogonal electrospray interface, despite the continuous flow of nanoparticles into the interface. Nanoparticles (average diameter 160 nm) were prepared from methacrylic acid, methyl methacrylate, and trimethylolpropane trimethacrylate by utilizing a precipitation polymerization technique. Salbutamol, nortriptyline, and diphenhydramine were used as analytes. The interaction between analytes and nanoparticles was found to be predominantly ionic.     

A new neural associative memory model

We present a new associative memory model based on the Hamming memory, but where the winner-take-all network part is replaced by a layer of nodes with somewhat complex node functions. This new memory can produce output vectors with individual “don't know” bits. the simulations demonstrate that this memory model works appropriately. © 1992 John Wiley & Sons, Inc.     

Physical-chemical characterization and polymorphism determination of two nimodipine samples deriving from distinct laboratories

Knowing the characteristics of raw materials in pharmaceutical practice is both important and useful. Firstly, evaluating the physical-chemical properties of the substances that will be used must be the primary step for quality control in the pharmacy industry. This work aims at analyzing the physical-chemical characteristics of two nimodipine samples I and II derived from distinct laboratories through thermal analysis (DSC and TG/DTG), HPLC, crystallography, and microscopy. Thermal analysis showed that sample II was more unstable than I. Morphological differences concerning shape, size, and crystallinity of particles were visualized by scanning electron microscopy (SEM) and X-ray powder diffraction. To sum up, the techniques used in this study can be said to have been efficient in the characterization and evaluation of quality control of the raw material.     

Validation of the accuracy of the perturbation peak method for determination of multicomponent adsorption isotherm parameters in LC

The isotherm parameters were for the first time determined for a quaternary mixture. This was done by the perturbation peak (PP) method using racemic mixtures of methyl and ethyl mandelate enantiomers. One complication with the PP method is that the traditional blank injection technique makes all perturbation peaks, except one, vanish at moderately nonlinear concentration plateaus. Therefore, we devised a new injection technique that made all four peaks on a quaternary component concentration plateau detectable, thereby making the determination of multicomponent competitive isotherm parameters possible. The measured quaternary perturbation data fitted well to the bi-Langmuir isotherm model and excellent agreement was found between experimental and simulated single-component and multicomponent profiles, thus validating the method and the determined isotherm parameters. The method (i) is valuable for computer-assisted optimization of preparative chiral chromatography and (ii) opens the possibility of quantifying competitive drug-target interactions for chiral drugs directly on racemic mixtures, which today is impossible with any nonlabeled technique including surface plasmon resonance technology.     

A utility-eye view of the CO2 compliance-decision process in the European power-sector

The purpose of this paper is to provide a utility eye-view of the European power-sector's CO₂-compliance decision process under a tradable emissions scheme. The cost analysis indicates that, in the medium term, many utilities are likely to consider options based on traditional power technologies such as converting existing coal-fired capacity to burn gas, extending the lives of nuclear capacity, and replacing old coal-fired plants with more efficient gas- or even coal-fired units. The long-term economic potential of future options is highly uncertain, and utilities are likely to respond to this by maintaining flexibility in fuel choices and avoid large investments that lock them into a specific compliance method before more efficient and cleaner technologies have crystallized. Given the multitude of possible CO₂-mitigation options, there is a strong case for emissions trading and for refraining from policies that build on mandatory fuel-requirements, higher rates of capital stock turnover and technology standards.     

Pair-wise comparisons versus planning game partitioning—experiments on requirements prioritisation techniques

The process of selecting the right set of requirements for a product release is dependent on how well the organisation succeeds in prioritising the requirements candidates. This paper describes two consecutive controlled experiments comparing different requirements prioritisation techniques with the objective of understanding differences in time-consumption, ease of use and accuracy. The first experiment evaluates Pair-wise comparisons and a variation of the Planning game. As the Planning game turned out as superior, the second experiment was designed to compare the Planning game to Tool-supported pair-wise comparisons. The results indicate that the manual pair-wise comparisons is the most time-consuming of the techniques, and also the least easy to use. Tool-supported pair-wise comparisons is the fastest technique and it is as easy to use as the Planning game. The techniques do not differ significantly regarding accuracy. Editor: Daniel Berry     

QUANTIFICATION OF BITUMEN PARTICLES IN AEROSOL AND SOIL SAMPLES USING HP-GPC

ABSTRACT

A method for identifying and quantifying bitumen particles, generated from the wear of roadway asphalts, in aerosol and soil samples has been developed. Bitumen is found to be the only contributor to airborne particles containing organic molecules with molecular weights larger than 2000 g pr. mol. These are separated and identified using High Performance Gel Permeation Chromatography (HP-GPC) with fluorescence detection. As an additional detection method Infra Red spectrometry (IR) is employed for selected samples, The methods have been used on aerosol, soil and other samples.     

Self-organized, free-standing TiO2 nanotube membrane for flow-through photocatalytic applications

In the present work we show a simple and robust fabrication process of a dense and free-standing membrane consisting of vertically oriented, both-side-open TiO2 nanotubes. This membrane structure allows direct, size-selective, flow-through photocatalytic reactions with a very high efficiency.     

New method for fabrication of fused silica emitters with submicrometer orifices for nanoelectrospray mass spectrometry

In this paper, we describe a new method for fabrication of nanoelectrospray emitters. The needles were pulled from fused silica capillary tubing, which was melted by means of a plasma, formed by electrical discharges between two pointed platinum electrodes. A key feature of the pulling device is a rotating configuration of the electrodes, which results in an even radial heating of the capillary. The construction of the setup is straightforward, and needles with a variety of shapes can be fabricated, including orifices of submicrometer dimensions. Pulled needles with long tapered tips and an orifice of 0.5 μm were utilized for electrospray ionization mass spectrometry (ESI-MS) of discrete sample volumes down to 275 pL. The picoliter-sized samples were transferred into the tip of the needle from a silicon microchip by aspiration. To avoid a rapid evaporation of the sample, all manipulations were performed under a cover of a fluorocarbon liquid. The limit of detection was measured to be ca. 20 attomole for insulin (chain B, oxidized).     

Nb doped TiO2 nanotubes for enhanced photoelectrochemical water-splitting

Nanostructured titanium dioxide is one of the classic materials for photoelectrochemical water splitting. In the present work we dope TiO(2) nanotube anodes. For this, various low concentration bulk-Nb-doped TiO(2) nanotube layers were grown by self-organizing anodization of Ti-Nb alloys. At Nb-contents around 0.1 at%, and after an adequate heat-treatment, a strongly increased and stable photoelectrochemical water-splitting rate is obtained.