The effect of twisted magnetic field on the resonant absorption of MHD waves in coronal loops

The standing quasi modes in a cylindrical incompressible flux tube with magnetic twist that undergoes a radial density structuring is considered in ideal magnetohydrodynamics (MHD). The radial structuring is assumed to be a linearly varying density profile. Using the relevant connection formulae, the dispersion relation for the MHD waves is derived and solved numerically to obtain both the frequencies and damping rates of the fundamental and first-overtone modes of both the kink (m=1) and fluting (m=2,3) waves. It was found that a magnetic twist will increase the frequencies, damping rates and the ratio of the oscillation frequency to the damping rate of these modes. The period ratio P_1/P_2 of the fundamental and its first-overtone surface waves for kink (m=1) and fluting (m=2,3) modes is lower than 2 (the value for an untwisted loop) in the presence of twisted magnetic field. For the kink modes, particularly, the magnetic twists B_{\phi}/B_z=0.0065 and 0.0255 can achieve deviations from 2 of the same order of magnitude as in the observations. Furthermore, for the fundamental kink body waves, the frequency bandwidth increases with increasing the magnetic twist.Comment: 18 pages, 9 figure

Oscillations and waves in solar spicules

Since their discovery, spicules have attracted increased attention as energy/mass bridges between the dense and dynamic photosphere and the tenuous hot solar corona. Mechanical energy of photospheric random and coherent motions can be guided by magnetic field lines, spanning from the interior to the upper parts of the solar atmosphere, in the form of waves and oscillations. Since spicules are one of the most pronounced features of the chromosphere, the energy transport they participate in can be traced by the observations of their oscillatory motions. Oscillations in spicules have been observed for a long time. However the recent high-resolutions and high-cadence space and ground based facilities with superb spatial, temporal and spectral capacities brought new aspects in the research of spicule dynamics. Here we review the progress made in imaging and spectroscopic observations of waves and oscillations in spicules. The observations are accompanied by a discussion on theoretical modelling and interpretations of these oscillations. Finally, we embark on the recent developments made on the presence and role of Alfven and kink waves in spicules. We also address the extensive debate made on the Alfven versus kink waves in the context of the explanation of the observed transverse oscillations of spicule axes

Excitation of standing kink oscillations in coronal loops

In this work we review the efforts that have been done to study the excitation of the standing fast kink body mode in coronal loops. We mainly focus on the time-dependent problem, which is appropriate to describe flare or CME induced kink oscillations. The analytical and numerical studies in slab and cylindrical loop geometries are reviewed. We discuss the results from very simple one-dimensional models to more realistic (but still simple) loop configurations. We emphasise how the results of the initial value problem complement the eigenmode calculations. The possible damping mechanisms of the kink oscillations are also discussed

Removal of pesticides in water by microbial cells adsorbed to magnetite

The removal of lindane (γ-isomer of 1,2,3,4,5,6-hexachlorocyclohexane), 2.4-D (2,4-dichlorophenoxyacetic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) from water by microbial cells immobilized on magnetite was studied. The removal of lindane by cells of a yeast, two bacteria and an alga ranged from 29 to 57%. A bacterium, Rhodopseudomonas sphaeroides had the highest sorption factor. No effect of pH in the range pH 4.0-8.0 on sorption of lindane by this bacterium was found. Sorption of lindane by R. sphaeroides reached equilibrium after 1 min. Sorption of lindane by live cells was not significantly different from sorption by heat killed cells. Four sorption stages employing fresh cells of R. sphaeroides on magnetite removed 90% of the lindane from a water sample. Magnetite alone removed 70% of the lindane in the four stage process. During a mixing period of 1 h, cells of Alcaligenes eutrophus removed 81%, 2,4-D; 21.4% lindane and 12.6% of the 2,4,5-T added to water samples. A mixture of A. eutroplus and R. sphaeroides cells immobilized on magnetite removed 76.4%, 2,4-D and 33% lindane from water samples containing the two pesticides

Removal of chlorinated hydrocarbons from water and wastewater by bacterial cells adsorbed to magnetite

The simultaneous removal of six chlorinated hydrocarbons, α- and γ-hexachlorocyclohexane (α- and γ-HCH), dieldrin, heptachlor, aldrin and p,p′-DDT from spiked samples of water and a wastewater by cells of the bacterium Rhodopseudomonas sphaeroides immobilized on magnetite was studied. In a contact time of 20 min, levels of heptachlor, aldrin and p,p′-DDT in water were reduced below the level of detection of the electron capture detector and concentrations of α-HCH, γ-HCH and dieldrin were reduced by 29.5, 32.0 and 88.9% respectively. Removal of p,p′-DDT from a spiked wastewater was complete whereas the removals of aldrin, heptachlor, dieldrin, γ-HCH and α-HCH were 92.9, 90.8, 89.9, 30.0 and 32.1% respectively. Sorption of all chlorinated hydrocarbons by the bacterial cells reached equilibrium within 20 min

Formation and degradation of soil-bound [14C] fenitrothion residues in two agricultural soils

The formation of non-extractable residues of [14C]fenitrothion and their degradation in a black earth and a red yellow podzolic soil was studied. After a 65-day incubation, non-extractable radioactivity represented 73.7 and 59.35% of the applied radioactivity in the black earth and podzolic soil respectively, while evolved 14CO2 accounted for only 9.4 and 12.7%. The effects of various amendments and treatments on the degradation of the non-extractable residues to 14CO2 was studied. All of the amendments produced a priming effect and significantly increased the formation of 14CO2 in both soils. The addition of unlabelled fenitrothion and 3-methyl-4-nitrophenol to the black earth and 3-methyl-4-nitrophenol to the podzolic soil produced the greatest increases in 14CO2 evolution. The evidence presented suggests that a part of the unextractable residue is either fenitrothion or 3-methyl-4-nitrophenol

A numerical taxonomic study of proteolytic and lipolytic psychrotrophs isolated from caprine milk

Lipolytic and proteolytic psychrotrophs were isolated from raw and pasteurized goats’milk, which had been stored at 5°C for 7d. The 241 strains isolated and 20 reference strains were examined by 149 biochemical, physiological, and morphological tests. The results yielded 195 characters suitable for taxonomic analysis. Computer‐assisted complete linkage analysis, using the Jaccard coefficient, produced 22 phenons at 75% S. The results showed that Pseudomonas fluorescens was the predominant psychrotrophic bacterium, but that Pseudomonas fragi was dominant in some milk samples. Strains of Serratia liquefaciens and Flavobacterium balustinum were also identified

Incidence of Aeromonas and Listeria spp. in red meat and milk samples in Brisbane, Australia

A total of 150 samples, 50 each of beef, lamb and pork from 10 local retail stores in Brisbane metropolitan area as well as 150 raw bovine bulk milk tank samples obtained from Queensland United Foods (QUF), were examined for the presence of Aeromonas and Listeria spp. over a period of 1 year. Different sets of enrichment and plating media were used to recover the organisms with subsequent identification using conventional biochemical and serotyping techniques. A total of 509 isolates consisting of Aeromonas spp. (350) and Listeria spp. (159) were obtained from 60%, 58%, 74%, 26.6%, 34%, 40%, 30%, 2.6% of samples of beef, lamb, pork and milk respectively. Motile aeromonads (A. hydrophila, A. sobria, A. caviae) and Listeria innocua were isolated from all kinds of samples whereas L. monocytogenes was only isolated from flesh food. A. hydrophila contributed the largest percentage of the motile aeromonads (60%). The majority of L. monocytogenes cultures were serotype 4

Identification of psychrotrophic pseudomonads from goats' milk by computer-assisted analysis of carbon source assimilation data

The results of carbon source assimilation tests on a group of psychrotrophic pseudomonas were compared with published data for established Pseudomonas taxa, using computer-assisted numerical taxonomic analysis and a modified diagnostic computer program. Several phenons were not grouped at the biovar level by numerical taxonomic analysis. Identification of strains by the diagnostic program revealed heterogeneity among those in the unassigned phenons, and supported a continuum concept among the fluorescent pseudomonads