A comprehensive set of 4He(,n) absolute cross-section measurements was performed at MAX-lab in Lund, Sweden. Tagged photons from 23<E<70 MeV were directed toward a liquid 4He target, and neutrons were identified using pulse-shape discrimination and the time-of-flight technique in two liquid-scintillator detector arrays. Seven-point angular distributions have been measured for 14 photon energies. The results have been subjected to complementary transition-coefficient and Legendre-coefficient analyses. The results are also compared to experimental data measured at comparable photon energies as well as recoil-corrected continuum shell-model, resonating group method, and effective interaction hyperspherical-harmonic expansion calculations. For photon energies below 29 MeV, the angle-integrated data are significantly larger than the values recommended by Calarco, Berman, and Donnelly in 1983. (Less)

A near-threshold 4He(g,n) cross-section measurement has been performed at MAX-lab. Tagged photons from 23 < Eg < 42 MeV were directed toward a liquid 4He target, and neutrons were detected by time-of-flight in two liquid-scintillator arrays. Seven-point angular distributions were measured for eight photon energies. The results are compared to experimental data measured at comparable energies and Recoil-Corrected Continuum Shell Model, Resonating Group Method, and recent Hyperspherical-Harmonic Expansion calculations. The angle-integrated cross-section data is peaked at a photon energy of about 28 MeV, in disagreement with the value recommended by Calarco, Berman, and Donnelly in 1983.

Soil artificially contaminated with fluorene, phenanthrene, pyrene, and benz[a]anthracene was inoculated with the wood-rotting fungi Plrurotus ostreatus and Antrodia vaillantii. During 12 weeks of incubation, polycyclic aromatic hydrocarbon (PAH) degradation and the formation of persistent degradation products were monitored by chemical analysis. In addition, the effect on the indigenous soil bacteria was studied by plate count techniques and by measuring the concentration of bacteria-specific phospholipid fatty acids (PLFAs). In both soils inoculated with fungi, the PAH degradation was enhanced compared to the control soil without fungi. The white-rot fungus P. ostreatus accelerated the degradation rate radically the first weeks, while the effect of the brown-rot fungus was more pronounced at later stages during the 12-week study. In a soil with no amendments, the final degradation result was similar to that in the soil with added fungi, although the degradation pattern for the individual PAHs was different. Furthermore, the degradation by P. ostreatus was accompanied by an accumulation of PAH metabolites, that is, 9-fluorenone, benz[a]anthracene-7,12-dione, and two compounds identified as 4-hydroxy-9-fluorenone and 4-oxapyrene-5-one, that was not seen in the other soils. The inoculation with the white-rot fungus also had a large negative effect on the indigenous soil bacteria. This could be an important drawback of using the white-rot fungus P. ostreatus in soil bioremediation since a sequential fungal-bacterial degradation probably is needed for a complete degradation of PAHs in soil. In the soil inoculated with A. vaillantii, on the other hand, no metabolites accumulated, and no negative effects were observed on the indigenous microorganisms.

The extensive use of rubber products, mainly tires, and the difficulties to recycle those products, has resulted in world wide environmental problems. Microbial devulcanisation is a promising way to increase the recycling of rubber materials. One obstacle is that several microorganisms tested for devulcanisation are sensitive to rubber additives. A way to overcome this might be to detoxify the rubber material with fungi prior to the devulcanisation. In this study, 15 species of white-rot and brown-rot fungi have been screened with regard to their capacity to degrade an aromatic model compound in the presence of ground waste tire rubber. The most effective fungus, Resinicium bicolor, was used for detoxification of rubber material. Increase in growth of the desulfurising bacterium Thiobacillus ferrooxidans in presence of the rubber treated with Resinicium bicolor compared to untreated rubber demonstrated that detoxification with fungi is possible.

The capability of wood-rotting fungi (WRF) to colonise contaminated soil is an important fungal characteristic in the development of WRF-based soil bioremediation, it is also important to have methods that monitor the presence of the WRF in the soil. In this lab-scale study, it was shown that it was possible to re-capture, localise and identify a brown-rot fungus, Antrodia vaillantii, after it has been inoculated into, and grown in, a contaminated soil from a former gasworks site. The three-dimensional outgrowth of A. vaillantii was monitored by allowing it to grow into fungicide-treated wood baits, temporarily placed in the soil. After two weeks, the baits were withdrawn from the soil and surface sterilised with hydrogen peroxide to favour fungi growing inside baits, i.e., A. vaillantii. After subsequent plating of baits on selective agar medium the presence of A. vaillantii was confirmed with PCR/RFLP. A. vaillantii was found to be viable throughout the 54 days long study and exhibited a surface growth pattern similar to other well-known cord-forming basidiomycetes. Firstly, the upper part of the soil closest to the place of inoculation was colonised, however, over a period of time, the area of colonisation spread deeper into the soil. The detection method employed in the current study gave a conservative estimate of the fungal proliferation and did not require extensive sampling. Its use could be applicable in both applied research, such as soil bioremediation, and in pure microbial ecology studies.

Biofilm reactors are particularly suitable for the treatment of large amounts of diluted effluent, such as groundwater contaminated with scarcely soluble pollutants. A packed-bed column reactor was tested for the degradation of acenaphthene, phenanthrene and pyrene provided at their aqueous solubility concentrations. Acenapthene and phenanthrene were removed to more than 99% efficiency from this reactor whilst pyrene was removed to 90%. Pollutant disappearance was also recorded in the control reactor and was probably caused by the adsorption of pollutants into the reactor. The measurement of oxygen consumption in both reactors confirmed that microbial degradation of the pollutants was indeed occurring in the inoculated reactor. Physical adsorption is not however unwanted, as it could help with the formation of a biofilm at an early stage of the treatment.

The objective of this study was to examine the possibility of measuring the growth of three white-rot fungi in soil contaminated with polycyclic aromatic hydrocarbons (PAHs), by estimating the soil levels of the phospholipid fatty acid (PLFA) 18:2ω6,9. The effect of the fungi on the PAH concentration and on the indigenous bacterial population in the soil was monitored. As shown by visual examination, the fungi investigated, Pleurotus ostreatus, Phanerochaete chrysoporium and Hypholoma fasciculare, grew well in autoclaved soil, whilst only H. fasciculare grew in non-autoclaved soil. In these reactors, there was also detected an increase in the PLFA 18:2ω6,9. However, the interpretation of the PLFA data was somewhat disturbed since 18:2ω6,9 also was found to be present in the birch wood used as a fungal substrate. In autoclaved soil, P. ostreatus and P. chrysosporium were found to exhibit a PAH-degrading capability, with the total PAH concentration decreasing from 209±35 and 186±2 to 149±6 and 109±6 mg/kg dry weight (dw) soil, respectively, during the 10 week incubation period. No PAH-degradation could be detected in any treatment using non-autoclaved soil. In the autoclaved soil, the total level of bacterial specific PLFAs in all fungal treatments, and in a control using added ground birch sticks, was found to be lowered. In the non-autoclaved soil, 6 out of 9 selected bacterial PLFAs exhibited a significant change between the treatments, but the overall total content of bacterial PLFAs did not change. The present study has shown that it is possible to measure fungal growth in a PAH-contaminated soil derived from a former gasworks plant by estimating the levels of the PLFA 18:2ω6,9. The inoculated fungi affected the indigenous bacteria, as shown by estimating the level of bacterial specific PLFAs. Finally, fungal PAH-degradation could be detected in autoclaved soil but not in non-autoclaved soil.

The O-16(gamma, pn) reaction was measured at E-gamma similar to 72 MeV with resolution sufficient to distinguish the low-lying states of the residual N-14 nucleus. Cross sections averaged over the acceptance of the detector system were determined for each of the resolved states. The relative population of residual states indicates that proton-neutron pairs coupled to (J(pi), T) = (0(+), 1) play a minor role in the photon absorption process compared to (1(+), 0) pairs and that both L = 0 and L = 2 pairs participate in the reaction.

The reaction B-10(gamma,p) has been studied using tagged photons of mean energies E-gamma = 57.6 and 72.9 MeV. Angular distributions and derived single-particle momentum distributions for protons leading to the ground state of Be-9 and higher excited states are compared to various calculations made using model parameters constrained by B-10(e,e' p)Be-9 and Be-9(p,p')Be-9 measurements. The effects of varying final-state interactions (including channel couplings) and meson exchange currents are considered. A sizable discrepancy between direct-knockout calculations and the experimental results is observed. If meson exchange currents are included in an approximate fashion, a good description of the B-10(gamma,p(0))Be-9 data is found.

A broad range tagging spectrometer together with a new beam transport system for photonuclear experiments at the MAX-laboratory in Lund is described. The spectrometer consists of a quadrupole followed by an Elbek-type dipole and has a large momentum acceptance. It can produce both polarized and unpolarized tagged photons in the energy range 10–80 MeV with an energy resolution of about 300 keV.

The forward-to-backward asymmetry of neutrons emitted in the Ca-40(gamma,n(0)) reaction was measured at photon energies in the range of 27-50 MeV. An energy-dependent asymmetry was observed that is interpreted as evidence of interference between the isovector quadrupole resonance and the giant dipole resonance. Data analysis in terms of semiclassical and direct-semidirect models estimate the isovector quadrupole resonance to be at an excitation energy of 31.0 +/- 1.5 MeV, with a width of 16.0 +/- 1.5 MeV, and exhausting most of the energy-weighted sum rule for the isovector quadrupole resonance.

Cross sections have been measured for the reactions 208Pb(γ,p) and 12C(γ,p) leading to the low-lying and continuum states in 207Tl and 11B using a high energy-resolution tagged photon beam of 41 to 57 MeV. The data are compared with results obtained with the (e,e′p) reaction in the same recoil-momentum range and with various theoretical calculations. A comparison of the (e,e′p) and (γ,p) data in terms of a reduced cross section versus momentum does not show a systematic overlap of the (e,e′p) and (γ,p) results, i.e. no scaling is observed. Distorted-wave impulse-approximation (DWIA) calculations, of which the input is constrained by the (e,e′p) data, and random-phase approximation calculations (RPA) underestimate the 12C(γ,p) data by typically a factor five depending on angle and missing energy. For 208Pb the difference between the calculations and the data for the low-lying states is much less, but an increasing discrepancy between the data and the calculations is found in the continuum. The inclusion of meson-exchange currents (MEC) brings the calculations for both nuclei on average closer to the data, but MEC effects are considerably less important for 208Pb as compared to 12C. Finally, a remarkable similarity is observed between the continuum response of the (γ,p) and (e,e′p) reactions on 208Pb despite the difference in the electromagnetic couplings involved.

Cross sections have been measured for the reactions Pb-208(gamma,p) and C-12(gamma,p) leading to the low-lying and continuum states in Tl-207 and B-11 using a high energy-resolution tagged photon beam of 41 to 57 MeV. The data are compared with results obtained with the (e,e'p) reaction in the same recoil-momentum range and with various theoretical calculations. A comparison of the (e,e'p) and (gamma,p) data in terms of a reduced cross section versus momentum does not show a systematic overlap of the (e,e'p) and (gamma,p) results, i.e. no scaling is observed. Distorted-wave impulse-approximation (DWIA) calculations, of which the input is constrained by the (e,e'p) data, and random-phase approximation calculations (RPA) underestimate the C-12(gamma,p) data by typically a factor five depending on angle and missing energy. For Pb-208 the difference between the calculations and the data for the low-lying states is much less, but an increasing discrepancy between the data and the calculations is found in the continuum. The inclusion of meson-exchange currents (MEG) brings the calculations for both nuclei on average closer to the data, but MEC effects are considerably less important for Pb-208 as compared to C-12. Finally, a remarkable similarity is observed between the continuum response of the (gamma,p) and (e,e'p) reactions on Pb-208 despite the difference in the electromagnetic couplings involved. (C) 1997 Published by Elsevier Science B.V.

Absolute differential cross sections for the C-12(gamma p)B-11 reaction have been measured for low-lying regions of residual excitation energy in B-11. Cross sections with low systematic uncertainties are presented for proton detection angles ranging from 30 degrees to 150 degrees, measured with tagged photons of 25-75 MeV energy. The experimental results resolve the discrepancies between the older data sets, In addition, a reinterpretation of the low-lying states excited in B-11 is presented. It is concluded that HF-RPA calculations with essential contributions of meson exchange currents (MEC) provide a qualitative description of the angular distributions obtained for the negative parity states in the (gamma,p) reaction.

The white-rot fungi Trametes versicolor PRL 572, Trametes versicolor MUCL 28407, Pleurotus ostreatus MUCL 29527, Pleurotus sajor-caju MUCL 29757 and Phanerochaete chrysosporium DSM 1556 were investigated for their ability to degrade the polycyclic aromatic hydrocarbons (PAH) anthracene, benz[a]anthracene and dibenz[a,h]anthracene in soil. The fungi were grown on wheat straw and mixed with artificially contaminated soil. The results of this study show that, in a heterogeneous soil environment, the fungi have different abilities to degrade PAH, with Trametes showing little or no accumulation of dead-end metabolites and Phanerochaete and Pleurotus showing almost complete conversion of anthracene to 9,10-anthracenedione. In contrast to earlier studies, Phanerochaete showed the ability to degrade the accumulated 9,10-anthracenedione while Pleurotus did not. This proves that, in a heterogeneous soil system, the PAH degradation pattern for white-rot fungi can be quite different from that in a controlled liquid system.