Hadronic properties of the S_{11}(1535) studied by electroproduction off the deuteron

Properties of excited baryonic states are investigated in the context of electroproduction of baryon resonances off the deuteron. In particular, the hadronic radii and the compositeness of baryon resonances are studied for kinematic situations in which their hadronic reinteraction is the dominant contribution. Specifically, we study the reaction $d(e,e'S_{11})N$ at $Q^2\ge 1 GeV^2$ for kinematics in which the produced hadronic state reinteracts predominantly with the spectator nucleon. A comparison of constituent quark model and effective chiral Lagrangian calculations of the $S_{11}$ shows substantial sensitivity to the structure of the produced resonance.Comment: 24 pages, 5 figure

The Effect of Sulphur Dioxide Exposure under Controlled Environmental Conditions on the Challenge Performance of Copper and Chromate Impregnated Active Carbon against Hydrogen Cyanide

An ASC/T (Cu 2+ , Cr 6+ , Ag and triethylenediamine impregnated) Whetlerite activated carbon sample was exposed to a flow rate of 1 l/min, 0.746 mg/l SO 2 in 80% RH air at 22°C for up to 510 min. Samples were subsequently challenged with 2 mg/l HCN in an identical diluent gas stream. Increasing SO 2 exposure resulted in accelerated HCN and (CN) 2 bed penetration. The basic shapes of the breakthrough profiles were however essentially unchanged. This observation is in accordance with numerical analysis of these results using Hinshelwood's adsorption model, which suggested that the adsorption rate constant was not significantly affected by SO 2 but rather the pollutant exposure resulted in the number of active centres on the carbon surface being reduced and the effective bed depth of the sample being shortened. This loss in active centres was thought most likely to result from the reduction of Cr 6+ to Cr 3+

The Effect of Sulphur Dioxide on the Adsorption Properties of Activated Carbon towards Chloropicrin

Sulphur dioxide is believed to be adsorbed on activated carbons in both physically and chemically bound states. Sulphuric acid and a variety of oxygenated and hydrated sulphur oxide species are believed to be present on humidified carbons exposed to sulphur dioxide. Samples of ASC/T impregnated carbons were exposed to sulphur dioxide mixtures in humid air at 80% RG and 22°C. The sulphur dioxide-loaded carbons were then exposed to chloropicrin challenge at 5 mg/dm 3 in air at 80% RH and 22°C and the chloropicrin breakthrough times measured. A relationship was found between the extra mass gain of the carbons (due to oxygen and water) with increasing sulphur dioxide loading, as predicted by other workers. The effect of sulphur dioxide loading on the chloropicrin breakthrough times was a gradual reduction to about one-third the time for unexposed carbon, with an adsorbed mass of sulphur dioxide equal to ca. 10% of the carbon mass in a 20 mm bed-depth filter

Towards the Prediction of the Remaining Lifetime of a Carbon Filter Bed on Hydrogen Cyanide Challenge Using in-Bed Sensors and a Neural Network: Preliminary Findings

The residual lifetime of an activated carbon filter bed challenged by hydrogen cyanide, a chemisorbing gas, has been successfully predicted on one occasion using transducers embedded within the filter bed. No thermostatting nor relative humidity control of the bed or influent challenge was imposed. Four thermocouples and a fibre optic pH probe, sensitised to HCN by the addition of cobalt(II) chloride, were used to measure the progress along the filter bed of the adsorption front resulting from intermittent HCN challenges of 0.9 mg/dm 3 . Twenty randomised neural networks for cyanogen breakthrough prediction were created. These were based on a simple system, with the occurrences of maximum temperatures around two thermocouples at the front of the filter bed providing the input variables and the cyanogen breakthrough time (BT) being the response variable. Temperature maxima were thought to be due to cyanogen hydrolysis. Each network was trained with the data from four completed challenges and then interrogated with the input variables from a fifth. The mean response variable produced was 36.5 d (± 2.1 d standard deviation). This represented 94% of the actual observed time to breakthrough which occurred on challenge day 39. Averaging of network responses was required because four training examples only loosely map the possible variable space such that the potential error in any one network prediction is large. This preliminary set of experiments is most encouraging, having successfully predicted the lifetime of the bed whilst it was only half exhausted. The fact that, with no climatic control, simple sensors still permitted this achievement under realistic conditions of intermittent, long-term exposure illustrates the potential of this approach to residual lifetime monitoring. Further studies to repeat this success and extend the work to other challenge gases are now required

Adsorption of Chloropicrin onto Humidified Activated Carbon Surfaces

Humidified activated charcoal samples have been exposed to chloropicrin-charged test atmospheres under controlled conditions of concentration, temperature, relative humidity and flow rate. The molar ratio of displaced water:adsorbed chloropicrin was observed to increase with chloropicrin loading. Estimates were made of the adsorption face areas and molecular volumes of the chloropicrin and water molecules. The ratios of adsorption face areas and molecular volumes were estimated as 3.4:1 and 7.7:1, respectively. Early in the sample challenge molar ratios up to about 3.4:1 were observed; it is proposed that these result from the adsorption of chloropicrin onto vacant sites or onto water monolayers with readsorption of water occurring elsewhere on the surface. As these pores become full, chloropicrin adsorbs in water-filled pores displacing water molecules of approximately the same total volume

Adsorption of water on surface acoustic wave gas sensors Final technical report

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