| 1. |
- Reifarth, R., et al.
(författare)
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Nuclear astrophysics with radioactive ions at FAIR
- 2016
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 665:1
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Konferensbidrag (refereegranskat)abstract
- The nucleosynthesis of elements beyond iron is dominated by neutron captures in the s and r processes. However, 32 stable, proton-rich isotopes cannot be formed during those processes, because they are shielded from the s-process flow and r-process beta-decay chains. These nuclei are attributed to the p and rp process. For all those processes, current research in nuclear astrophysics addresses the need for more precise reaction data involving radioactive isotopes. Depending on the particular reaction, direct or inverse kinematics, forward or time-reversed direction are investigated to determine or at least to constrain the desired reaction cross sections. The Facility for Antiproton and Ion Research (FAIR) will offer unique, unprecedented opportunities to investigate many of the important reactions. The high yield of radioactive isotopes, even far away from the valley of stability, allows the investigation of isotopes involved in processes as exotic as the r or rp processes.
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| 2. |
- Aidas, Kestutis, et al.
(författare)
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The Dalton quantum chemistry program system
- 2014
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Ingår i: WIREs Computational Molecular Science. - : Wiley. - 1759-0876 .- 1759-0884. ; 4:3, s. 269-284
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Tidskriftsartikel (refereegranskat)abstract
- Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, configuration-interaction, and coupled-cluster levels of theory. Apart from the total energy, a wide variety of molecular properties may be calculated using these electronic-structure models. Molecular gradients and Hessians are available for geometry optimizations, molecular dynamics, and vibrational studies, whereas magnetic resonance and optical activity can be studied in a gauge-origin-invariant manner. Frequency-dependent molecular properties can be calculated using linear, quadratic, and cubic response theory. A large number of singlet and triplet perturbation operators are available for the study of one-, two-, and three-photon processes. Environmental effects may be included using various dielectric-medium and quantum-mechanics/molecular-mechanics models. Large molecules may be studied using linear-scaling and massively parallel algorithms. Dalton is distributed at no cost from for a number of UNIX platforms.
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| 3. |
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| 4. |
- Batista-Santos, Paula, et al.
(författare)
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Is salt stress tolerance in Casuarina glauca Sieb. ex Spreng. associated with its nitrogen-fixing root-nodule symbiosis? An analysis at the photosynthetic level
- 2015
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Ingår i: Plant physiology and biochemistry (Paris). - : Elsevier BV. - 0981-9428 .- 1873-2690. ; 96, s. 97-109
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Tidskriftsartikel (refereegranskat)abstract
- Casuarina glauca is an actinorhizal tree which establishes root-nodule symbiosis with N-2-fixing Frankia bacteria. This plant is commonly found in saline zones and is widely used to remediate marginal soils and prevent desertification. The nature of its ability to survive in extreme environments and the extent of Frankia contribution to stress tolerance remain unknown. Thus, we evaluated the ability of C. glauca to cope with salt stress and the influence of the symbiosis on this trait. To this end, we analysed the impact of salt on plant growth, mineral contents, water relations, photosynthetic-related parameters and nonstructural sugars in nodulated vs. non-nodulated plants. Although the effects on photosynthesis and stomatal conductance started to become measurable in the presence of 200 mM NaCl, photochemical (e.g., photosynthetic electron flow) and biochemical (e.g., activity of photosynthetic enzymes) parameters were only strongly impaired when NaCl levels reached 600 mM. These results indicate the maintenance of high tissue hydration under salt stress, probably associated with enhanced osmotic potential. Furthermore, the maintenance of photosynthetic assimilation potential (A(max)), together with the increase in the quantum yield of down-regulated energy dissipation of PSII (Y-NPQ), suggested a down-regulation of photosynthesis instead of photo-damaging effects. A comparison of the impact of increasing NaCl levels on the activities of photosynthetic (RubisCO and ribulose-5 phosphate kinase) and respiratory (pyruvate kinase and NADH-dependent malate dehydrogenase) enzymes vs. photosynthetic electron flow and fluorescence parameters, revealed that biochemical impairments are more limiting than photochemical damage. Altogether, these results indicate that, under controlled conditions, C glauca tolerates high NaCl levels and that this capacity is linked to photosynthetic adjustments.
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| 5. |
- Lukasik, J., et al.
(författare)
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Discriminant analysis and secondary-beam charge recognition
- 2008
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 587:2-3, s. 413-419
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Tidskriftsartikel (refereegranskat)abstract
- The discriminant-analysis method has been applied to optimize the exotic-beam charge recognition in a projectile fragmentation experiment. The experiment was carried out at the GSI using the fragment separator (FRS) to produce and select the relativistic secondary beams, and the ALADIN setup to measure their fragmentation products following collisions with Sn target nuclei. The beams of neutron poor isotopes around La-124 and Sn-107 were selected to study the isospin dependence of the limiting temperature of heavy nuclei by comparing with results for stable Sn-124 projectiles. A dedicated detector to measure the projectile charge upstream of the reaction target was not used, and alternative methods had to be developed. The presented method, based on the multivariate discriminant analysis, allowed to increase the efficacy of charge recognition up to about 90%, which was about 20% more than achieved with the simple scalar methods.
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| 6. |
- Pawlowski, P., et al.
(författare)
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Neutron recognition in the LAND detector for large neutron multiplicity
- 2012
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Ingår i: Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. - : Elsevier BV. - 0168-9002. ; 694, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- The performance of the LAND neutron detector is studied. Using an event-mixing technique based on one-neutron data obtained in the S107 experiment at the GSI laboratory, we test the efficiency of various analytic tools used to determine the multiplicity and kinematic properties of detected neutrons. A new algorithm developed recently for recognizing neutron showers from spectator decays in the ALADIN experiment S254 is described in detail. Its performance is assessed in comparison with other methods. The properties of the observed neutron events are used to estimate the detection efficiency of LAND in this experiment. (C) 2012 Elsevier B.V. All rights reserved.
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| 7. |
- Pawłowski, P., et al.
(författare)
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Neutrons from projectile fragmentation at 600 MeV/nucleon
- 2023
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Ingår i: Physical Review C. - 2469-9993 .- 2469-9985. ; 108:4
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Tidskriftsartikel (refereegranskat)abstract
- The neutron emission in projectile fragmentation at relativistic energies was studied with the Large-Area-Neutron-Detector LAND coupled to the ALADIN forward spectrometer at the GSI Schwerionen-Synchrotron (SIS). Stable Sn124 and radioactive Sn107 and La124 beams with an incident energy of 600 MeV/nucleon were used to explore the N/Z dependence of the identified neutron source. A cluster-recognition algorithm is applied for identifying individual particles within the hit distributions registered with LAND. The obtained momentum distributions are extrapolated over the full phase space occupied by the neutrons from the projectile-spectator source. The mean multiplicities of spectator neutrons reach values of up to about 11 and depend strongly on the isotopic composition of the projectile. An effective source temperature of T≈2-5 MeV, monotonically increasing with decreasing impact parameter, is deduced from the transverse momentum distributions. For the interpretation of the data, calculations with the statistical multifragmentation model were performed. The variety of excited projectile spectators assumed to decay statistically is represented by an ensemble of excited sources with parameters determined previously from the fragment production observed in the same experiments. The obtained agreement is very satisfactory for more peripheral collisions where, according to the model, neutrons are mainly emitted during the secondary decays of excited fragments. The neutron multiplicity in more central collisions is underestimated, indicating that other sources besides the modeled statistical breakup contribute to the observed neutron yield. The choice made for the symmetry-term coefficient of the liquid-drop description of produced fragments has a weak effect on the predicted neutron multiplicities.
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| 8. |
- Persson, Tomas, et al.
(författare)
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Amino acid metabolism in roots and actinorhizal nodules from Alnus glutinosa and Datisca glomerata: γ-aminobutyric acid and β-alanine are important metabolites
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Roots and nodules of the actinorhizal plants Alnus glutinosa and Datisca glomerata, as well as Frankia alni ACN14a grown in minimal and ammonium supplemented media, were analyzed for amino acid profiles. To analyze nitrogen and carbon metabolism, the transcriptome in nodules of the microsymbiont of D. glomerata, Frankia datiscae Dg1, was sequenced and compared with transcriptome data from symbiotic F. alni ACN14a (Alloisio et al. 2011). The amino acid profile of A. glutinosa roots suggests that Citrulline, Asparagine and Glutamine are transported in the xylem. Moreover, the comparatively high concentration of γ-aminobutyric acid in A. glutinosa roots suggest that this compound has a function in plant nitrogen metabolism. γ-aminobutyric acid could, as was suggested for the legume symbiosis, act as a signal factor for the plant nitrogen status to symbiotic Frankia. It could also be imported by the bacteria as a carbon and nitrogen source. Moreover, the expression of the gene for the enzyme catalyzing β-Alanine synthesis was elevated in both Frankia strains in symbiosis. Elevated concentrations of β-Alanine in nodules of D. glomerata and A. glutinosa compared to roots suggest that β-Alanine is produced by the bacteria in large amounts, possibly as a storage compound for Coenzyme A production.
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| 9. |
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| 10. |
- Scotti-Campos, Paula, et al.
(författare)
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Antioxidative ability and membrane integrity in salt-induced responses of Casuarina glauca Sieber ex Spreng. in symbiosis with N-2-fixing Frankia Thr or supplemented with mineral nitrogen
- 2016
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Ingår i: Journal of plant physiology (Print). - : Elsevier BV. - 0176-1617 .- 1618-1328. ; 196-197, s. 60-69
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Tidskriftsartikel (refereegranskat)abstract
- The actinorhizal tree Casuarina glauca tolerates extreme environmental conditions, such as high salinity. This species is also able to establish a root-nodule symbiosis with N-2-fixing bacteria of the genus Frankia. Recent studies have shown that C. glauca tolerance to high salt concentrations is innate and linked to photosynthetic adjustments. In this study we have examined the impact of increasing NaCl concentrations (200, 400 and 600 mM) on membrane integrity as well as on the control of oxidative stress in branchlets of symbiotic (NOD+) and non-symbiotic (KNO3+) C. glauca. Membrane selectivity was maintained in both plant groups at 200 mM NaCl, accompanied by an increase in the activity of antioxidative enzymes (superoxide dismutase, ascorbate peroxidase, glutathione reductase and catalase). Regarding cellular membrane lipid composition, linolenic acid (C18:3) showed a significant decline at 200 mM NaCl in both NOD+ and KNO3+ plants. In addition, total fatty acids (TFA) and C18:2 also decreased in NOD+ plants at this salt concentration, resulting in malondialdehyde (MDA) production. Such initial impact at 200 mM NaCl is probably due to the fact that NOD+ plants are subjected to a double stress, i.e., salinity and low nitrogen availability. At 400 mM NaCl a strong reduction of TFA and C18:3 levels was observed in both plant groups. This was accompanied by a decrease in the unsaturation degree of membrane lipids in NOD+. However, in both NOD+ and KNO3+ lipid modifications were not reflected by membrane leakage at 200 or 400 mM, suggesting acclimation mechanisms at the membrane level. The fact that membrane selectivity was impaired only at 600 mM NaCl in both groups of plants points to a high tolerance of C. glauca to salt stress independently of the symbiotic relation with Frankia.
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