Onset of Electron Acceleration in a Flare Loop

We carried out detailed analysis of X-ray and radio observations of a simple flare loop that occurred on 12th August 2002, with the impulsive hard X-ray (HXR) light curves dominated by a single pulse. The emission spectra of the early impulsive phase are consistent with an isothermal model in the coronal loop with a temperature reaching several keVs. A power-law high-energy spectral tail is evident near the HXR peak time, in accordance with the appearance of footpoints at high energies, and is well correlated with the radio emission. The energy content of the thermal component keeps increasing gradually after the disappearance of this nonthermal component. These results suggest that electron acceleration only covers a central period of a longer and more gradual energy dissipation process and that the electron transport within the loop plays a crucial role in the formation of the inferred power-law electron distribution. The spectral index of power-law photons shows a very gradual evolution indicating a quasi-steady state of the electron accelerator, which is confirmed by radio observations. These results are consistent with the theory of stochastic electron acceleration from a thermal background. Advanced modeling with coupled electron acceleration and spatial transport processes is needed to explain these observations more quantitatively, which may reveal the dependence of the electron acceleration on the spatial structure of the acceleration region

Use of inorganic fertiliser in place of poultry manure for rehabilitation of gold and bauxite ore refining residues

Ore refining residues are difficult substrates for revegetation because they often contain extremely low plant available levels of one or more essential elements (Hossner and Hons 1992). Organic amendments would generally be attractive additions for revegetation because residues also contain little organic matter, and organic amendments may also ameliorate elevated concentrations of salts and other elements. However organic materials are generally not available on mine sites in sufficient quantities and they are bulky handle. In the present study, the opportunities for substituting inorganic fertilisers in place of poultry manure were investigated for revegetation of three alkaline, variably saline residues: bauxite residue (mixed sand and clay fractions), bauxite residue sand, and gold refining residue from mined oxide clays

Widespread occurrence of Mycobacterium tuberculosis DNA from 18th-19th century Hungarians

A large number (265) of burials from 1731-1838 were discovered in sealed crypts of the Dominican Church, Vac, Hungary in 1994. Many bodies were naturally mummified, so that both soft tissues and bones were available. Contemporary archives enabled the determination of age at death, and the identification of family groups. In some cases, symptoms before death were described and, occasionally, occupation. Initial radiological examination of a small number of individuals had indicated calcified lung lesions and demonstrable acid-fast bacteria suggestive of tuberculosis infection. Tuberculosis was endemic in 18th-19th century Europe, so human remains should contain detectable Mycobacterium tuberculosis complex (MTB) DNA, enabling comparisons with modern isolates. Therefore, a comprehensive examination of 168 individuals for the presence of MTB DNA was undertaken. Specific DNA amplification methods for MTB showed that 55% of individuals were positive and that the incidence varied according to age at death and sampling site in the body. Radiographs were obtained from 27 individuals and revealed an association between gross pathology and the presence of MTB DNA. There was an inverse relationship between PCR positivity and MTB target sequence size. In some cases, the preservation of MTB DNA was excellent, and several target gene sequences could be detected from the same sample. This information, combined with MTB DNA sequencing data and molecular typing techniques, will enable us to study the past epidemiology of TB infection, and extends the timeframe for studying changes in molecular fingerprints. Am J Phys Anthropol 120:144-152, 2003. (C) 2003 Wiley-Liss, Inc

Solubility behaviour, crystallisation kinetics and pour point : a comparison of linear alkane and triacyl glyceride solute/solvent mixtures

Mixtures of either a hydrocarbon wax in a hydrocarbon solvent or a long chain triacyl glyceride (TAG) in a TAG solvent show complex solubility boundary temperature hysteresis and precipitated crystal network formation leading to gelation. For these industrially-important systems, we show how the equilibrium solubility and its hysteresis, crystallisation kinetics and pour point temperature vary with solute concentration for representative examples of both hydrocarbon (n-tetracosane (C24) solute in n-heptane (C7) solvent) and TAG (tristearin (SSS) solute in tricaprylin (CCC) solvent) mixtures. The behaviour is modelled with good accuracy; thereby providing a useful aid to formulation and process optimisation

A model study of enhanced oil recovery by flooding with aqueous surfactant solution and comparison with theory

With the aim of elucidating the details of enhanced oil recovery by surfactant solution flooding, we have determined the detailed behavior of model systems consisting of a packed column of calcium carbonate particles as the porous rock, n-decane as the trapped oil, and aqueous solutions of the anionic surfactant sodium bis(2-ethylhexyl) sulfosuccinate (AOT). The AOT concentration was varied from zero to above the critical aggregation concentration (cac). The salt content of the aqueous solutions was varied to give systems of widely different, post-cac oil–water interfacial tensions. The systems were characterized in detail by measuring the permeability behavior of the packed columns, the adsorption isotherms of AOT from the water to the oil–water interface and to the water–calcium carbonate interface, and oil–water–calcium carbonate contact angles. Measurements of the percent oil recovery by pumping surfactant solutions into calcium carbonate-packed columns initially filled with oil were analyzed in terms of the characterization results. We show that the measured contact angles as a function of AOT concentration are in reasonable agreement with those calculated from values of the surface energy of the calcium carbonate–air surface plus the measured adsorption isotherms. Surfactant adsorption onto the calcium carbonate–water interface causes depletion of its aqueous-phase concentration, and we derive equations which enable the concentration of nonadsorbed surfactant within the packed column to be estimated from measured parameters. The percent oil recovery as a function of the surfactant concentration is determined solely by the oil–water–calcium carbonate contact angle for nonadsorbed surfactant concentrations less than the cac. For surfactant concentrations greater than the cac, additional oil removal occurs by a combination of solubilization and emulsification plus oil mobilization due to the low oil–water interfacial tension and a pumping pressure increase