Chamber characterisation

As with the chamber characterisation studies of Carter (Carter, 2000), the series of butane-NOx photo-oxidation experiments was used for initial assessment of the auxiliary mechanism parameters. This system is believed to provide a good test for the chamber wall effects because the degradation chemistry of butane is quite well characterized (Carter and Lurmann, 1991, Carter et al, 1995a), and because of the large set of experiments for which data are available. 

Fig. 16. a Schematic diagram of the pressure chamber for characterisation of flat membranes by means of a pneumatic SFM. b Height image of a nuclear pore membrane of polycarbonate recorded by the pneumatic SFM at a pressure difference of 0.4 bar. The elevations are resulted from the nitrogen streams through the pores. Reproduced from [167]... 

Roache, N., Guo, Z. and Tichenor, B.A. (1996) Comparing the FLEC with traditional emissions chambers, in Characterising Sources of Indoor Air Pollution and Related Sink Effects (ed. B. Tichenor), ASTM STP 1287, Philadelphia, PA, USA, pp. 98-111. 

In concentrated systems obtained in a thin uniform shape, the simplest way to record X-ray absorption data is the transmission mode in which the incident and transmitted photons are directly measured by means of ionisation chambers. However, in dilute systems or for surface characterisations, data are usually recorded using secondary effects resulting from the creation of the core hole during the absorption process and from its subsequent relaxation by radiative or non-radiative decays. These processes are the X-ray fluorescence emission and the total electron yield (TEY) emission, respectively. In these detection modes, the linear absorption coefficient is proportional to the ratio of the fluorescence or TEY intensity to... 

The Wrede—Harteck gauge consists of a small chamber in communication with the atom—molecule mixture via a hole whose dimensions are small compared with the mean free path. The chamber is coated with an efficient catalyst so that, ideally, every atom which enters is recombined. Because the atom flux is unidirectional, a pressure difference (AP) between the pressure outside and inside the gauge will characterise the stationary condition, such that... 

The five main requirements for conduct of a sessile drop experiment relevant to high temperature capillary phenomena are characterisation of the materials, a flat horizontal substrate, a test chamber to provide a controlled and generally inert gaseous environment, a facility that heats the sample to a predetermined temperature and a means of measuring the geometry and size of the sessile drop. Satisfying these requirements demands careful and precise experimental procedures. 

The principle and possible applications of the three basic processing options (top-spray, bottom-spray or tangential-spray) of the batch-fluidised bed are discussed below (Jones 1994). Both the top- and bottom-spray methods are characterised by a conical product container and expansion chamber, resulting in a more vigorous fluidisation pattern and a decrease in velocity as the particles move upward in the expansion chamber. 

Equilibrium dialysis is an analytical technique which is usually performed with commercial apparatus. In this technique, the two dialysis chambers, separated by a membrane, are filled respectively with macromolecule solution and with ligand, which is usually radioactively labelled. After equilibrium has been reached, samples are removed from the two chambers the concentration of free ligand is determined from one sample, and free plus bound ligand from the other. Parameters characterising the binding equilibrium can be determined by appropriate analysis of the data. 

A schematic representation of a typical set-up for such studies is given in Fig. 1. It gathers several chambers devoted to sample preparation, sample characterisation and reaction. 

After elaboration and/or cleaning, samples have to be transferred under UHV either to the characterisation chamber to be analysed or into the reactor for catalytic studies. In our design the reactor can be isolated with the help of an all metal UHV valve in order to do reactions under static conditions. Reactants can be introduced at a chosen pressure and the products of the reaction are analysed by mass spectrometry (MS) through a leak valve as a function of time. In addition, during the reaction, a small volume of the reactants and products can be isolated and sampled with a syringe (1 ml) through a nipple to be analysed by gas chromatography in a separate set up. 

Pressure The chamber is designed to investigate boundary layer processes and will flierefore operate at ambient atmospheric pressure. That the chamber does not require pressurisation allows the use of a flexible FEP Teflon bag. Teflon film is gas permeable, but with advantages that generally compensate for die drawbacks. It is broadly transparent to radiation at boundary layer wavelengths with well characterised transmission characteristics (Cocker et al., 2001). In addition, despite documented wall losses and re-emission of reactive... 

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