| 1. |
- Ryde, Nils, et al.
(författare)
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Lumen Accipe et Imperti - Föreläsning och motivation
- 2011
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Ingår i: Lednings- och kompetensutbildning/CED. - 9789197797467 ; , s. 24-30
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Konferensbidrag (refereegranskat)abstract
- Abstract in Undetermined Vi problematiserar den kritik mot föreläsningsbaserat lärande vid universitet och högskolor, som är vanlig i dagens pedagogiska diskussioner. Vi baserar vårt arbete på enkätundersökningar och på djupintervjuer av studenter på grundutbildningskurser i fysik vid Lunds universitet och Kungliga Tekniska högskolan. Vi anser att den rådande bilden av föreläsningens värde bör nyanseras så att man inte bortser från det unikt positiva hos en bra föreläsning. Man bör därför inte förkasta denna pedgogiska metod, utan, väl förberedd, har föreläsningen en viktig och uppskattad roll i inlärningen.
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| 2. |
- Bengtsson, Ragnar, et al.
(författare)
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Magic gaps and intruder levels in triaxially superdeformed nuclei
- 2004
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 22:3, s. 355-362
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Tidskriftsartikel (refereegranskat)abstract
- Nuclear shell model calculations based on a modified harmonic-oscillator potential result in amazingly stable triaxial nuclear shapes. Major gaps in the single-particle energy spectra at proton number 71 and neutron number 94 combine constructively at low and intermediate rotational frequencies. At high frequencies, gaps at proton number 72 and neutron number 97 combine in an equally favourable way. The sizes of the gaps may be as large as 35% of the values for the gaps at the classical magic numbers 50 and 82 at spherical shape. The dependence on the positions of the intruder levels in forming the gaps is discussed. Experimentally observed rotational bands in lutetium (Z = 71) and hafnium (Z = 72) appear in isotopes and frequency ranges, which are consistent with the gaps in the theoretical single-particle energy spectra.
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| 3. |
- Chauvin, Maxime, et al.
(författare)
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Observation of polarized hard X-ray emission from the Crab by the PoGOLite Pathfinder
- 2016
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Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966 .- 1745-3925 .- 1745-3933. ; 456:1, s. L84-L88
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the linear polarization of hard X-ray emission from the Crab in a previously unexplored energy interval, 20-120 keV. The introduction of two new observational parameters, the polarization fraction and angle stands to disentangle geometrical and physical effects, thereby providing information on the pulsar wind geometry and magnetic field environment. Measurements are conducted using the PoGOLite Pathfinder - a balloon-borne polarimeter. Polarization is determined by measuring the azimuthal Compton scattering angle of incident X-rays in an array of plastic scintillators housed in an anticoincidence well. The polarimetric response has been characterized prior to flight using both polarized and unpolarized calibration sources. We address possible systematic effects through observations of a background field. The measured polarization fraction for the integrated Crab light curve is 18.4(-10.6)(+9.8) per cent, corresponding to an upper limit (99 per cent credibility) of 42.4 per cent, for a polarization angle of (149.2 +/- 16.0)degrees.
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| 4. |
- Dong, Geng, et al.
(författare)
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Exploration of H2 binding to the [NiFe]-hydrogenase active site with multiconfigurational density functional theory
- 2018
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 20:2, s. 794-801
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Tidskriftsartikel (refereegranskat)abstract
- The combination of density functional theory (DFT) with a multiconfigurational wave function is an efficient way to include dynamical correlation in calculations with multiconfiguration self-consistent field wave functions. These methods can potentially be employed to elucidate reaction mechanisms in bio-inorganic chemistry, where many other methods become either too computationally expensive or too inaccurate. In this paper, a complete active space (CAS) short-range DFT (CAS-srDFT) hybrid was employed to investigate a bio-inorganic system, namely H2 binding to the active site of [NiFe] hydrogenase. This system was previously investigated with coupled-cluster (CC) and multiconfigurational methods in the form of cumulant-approximated second-order perturbation theory, based on the density matrix renormalization group (DMRG). We find that it is more favorable for H2 to bind to Ni than to Fe, in agreement with previous CC and DMRG calculations. The accuracy of CAS-srDFT is comparable to both CC and DMRG, despite much smaller active spaces were employed than in the corresponding DMRG calculations. This enhanced efficiency at the smaller active spaces shows that CAS-srDFT can become a useful method for bio-inorganic chemistry.
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| 5. |
- Hersleth, Hans-Petter, et al.
(författare)
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The crystal structure of peroxymyoglobin generated through cryoradiolytic reduction of myoglobin compound III during data collection
- 2008
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Ingår i: Biochemical Journal. - 0264-6021. ; 412, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- Myoglobin has the ability to react with hydrogen peroxide, generating high-valent complexes similar to peroxidases (compounds I and II), and in the presence of excess hydrogen peroxide a third intermediate, compound III, with an oxymyoglobin-type structure is generated from compound II. The compound III is, however, easily one-electron reduced to peroxymyoglobin by synchrotron radiation during crystallograpic data collection. We have generated and solved the 1.30 angstrom (1 angstrom= 0.1 nin) resolution crystal structure of the peroxymyoglobin intermediate, which is isoelectric to compound 0 and has a Fe-O distance of 1.8 angstrom and O-O bond of 1.3 angstrom in accordance with a Fe-II-O-O- (or Fe-III-O-O2-) structure. The generation of the peroxy intermediate through reduction of compound III by X-rays shows the importance of using single-crystal microspectrophotometry when doing crystallography on metal loproteins. After having collected crystallographic data on a peroxy-generated myoglobin crystal, we were able (by a short annealing) to break the O-O bond leading to formation of compound II. These results indicate that the cryoradiolytic-generated peroxymyoglobin is biologically relevant through its conversion into compound II upon heating. Additionally, we have observed that the Xe1 site is occupied by a water molecule, which might be the leaving group in the compound II to compound III reaction.
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| 6. |
- Hersleth, Hans-Petter, et al.
(författare)
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The Influence of X-Rays on the Structural Studies of Peroxide-Derived Myoglobin Intermediates
- 2008
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Ingår i: Chemistry and Biodiversity. - 1612-1872. ; 5:10, s. 2067-2089
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Forskningsöversikt (refereegranskat)abstract
- In recent years, the awareness of potential radiation damage of metal centers in protein crystals during crystallographic data collection has received increasing attention. The radiation damage can lead to radiation-induced changes and reduction of the metal sites. One of the research fields where these concerns have been comprehensively addressed is the study of the reaction intermediates of the heme peroxidase and oxygenase reaction cycles. For both the resting states and the high-valent intermediates, the X-rays used in the structure determination have given undesired side effects through radiation-induced changes to the trapped intermediates. However, X-rays have been used to generate and trap the peroxy/hydroperoxy state in crystals. In this review, the structural work and the influence of X-rays on these intermediates in myoglobin are summarized and viewed in light of analogous studies on similar intermediates in peroxidases and oxygenases.
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| 7. |
- Kiss, Mózsi, et al.
(författare)
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The PoGOLite balloon-borne soft gamma-ray polarimeter
- 2008
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Ingår i: COOL DISCS, HOT FLOWS. - : AIP. ; , s. 225-232
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Konferensbidrag (refereegranskat)abstract
- Linearly polarized radiation in the hard X-ray/soft gamma-ray band is expected from a large variety of astronomical sources. We discuss the importance of polarimetric studies for several classes of sources - pulsars, accreting black holes. magnetic neutron stars and jets from active galaxies - and then describe PoGOLite, a balloon-borne instrument which is currently under construction and will be able to measure the polarization of electromagnetic radiation from such extra-solar objects in the energy range 25-80 keV.
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| 8. |
- Ma, Hai-Liang, et al.
(författare)
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Interpretation of the high spin states in Lu-161: A paired and unpaired study
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:1
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Tidskriftsartikel (refereegranskat)abstract
- A paired cranked Nilsson-Strutinsky-Bogoliubov (CNSB) model is presented, which employs the same method to calculate the liquid-drop energy and moment of inertia as the unpaired cranked Nilsson-Strutinsky (CNS) model. In the CNSB model, the energy minimization is carried out in the mesh of pairing gaps Delta and Fermi levels lambda as well as deformation parameters. The high spin states in Lu-161 are then investigated with the CNSB and CNS models. The terminating structure shows a striking similarity with these two models. Combining the CNSB and CNS models, a complete understanding of high spin structures, including the normal deformed (ND) and triaxial strongly deformed (TSD) bands and observed side bands in Lu-161, is achieved. It appears that the only important paired crossings are the first i(13/2) neutron crossing and the first h(11/2) proton crossing. For the description of the unpaired high spin crossings, it is important to be able to distinguish between the pseudospin partners in the proton N = 4 shell, (d(5/2), g(7/2)) and (d(3/2), s(1/2)). The yrast bands are predicted to terminate, which explains the structure of a TSD-like band X2. A band crossing at I approximate to 36.5 for the TSD band in Lu-161, unique within the chain of even-N Lu isotopes, is well described by the CNSB model.
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| 9. |
- Marsh, J. C., et al.
(författare)
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Identification of triaxial strongly deformed bands in Hf-164
- 2013
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:4
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Tidskriftsartikel (refereegranskat)abstract
- Two new rotational bands of distinct character have been identified in Hf-164. They are suggested to correspond to the long-anticipated triaxial strongly deformed (TSD) bands predicted by theoretical studies. The bands have been linked to known states, and the level spins and energies could be determined. The bands are also substantially stronger in intensity and are located at lower spins than the previously observed TSD bands in Hf-168, hereby making Hf-164 the best even-even system so far for the study of TSD structures in the A similar to 160 mass region. Cranking calculations based on the modified-oscillator model suggest that the bands are associated with four-quasiparticle configurations that involve high-j intruder (i(13/2))(2) proton orbitals.
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| 10. |
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| 11. |
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| 12. |
- Ragnarsson, Ingemar, et al.
(författare)
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Terminating States In Z=71 Lu Nuclei With N Approximate To 90
- 2010
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Ingår i: International Journal of Modern Physics E. - 0218-3013. ; 19:4, s. 590-600
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Tidskriftsartikel (refereegranskat)abstract
- The high-spin yrast states in Lu-161 are calculated in a Cranked Nilsson-Strutinsky approach keeping track of configurations and their evolution with spin. The outcome from calculations neglecting pairing and including pairing are compared. It is predicted that several yrast region configurations terminate at a very favored energy around I = 50 and that one of the observed bands is two transitions short of termination.
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| 13. |
- Ryde, Hans
(författare)
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Chronicle of the discovery of the back-bending phenomenon in atomic nuclei : a personal recollection 50 years on
- 2021
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Ingår i: European Physical Journal H. - : Springer Science and Business Media LLC. - 2102-6459 .- 2102-6467. ; 46:1
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Tidskriftsartikel (refereegranskat)abstract
- A chronicle describing the historical context and the development of ideas and experiments leading to the discovery of the back-bending phenomenon in rapidly rotating atomic nuclei some 50 years ago is presented. The moment of inertia of some atomic nuclei increases anomalously at a certain rotational frequency, revealing important clues to our understanding of nuclear structure. I highlight the decisive interactions and contacts between experimentalists and theorists, which created the right environment, allowing for the revelation of an undetected phenomenon in Nature. Finally, I reflect on the key points allowing for the discovery and particularly point to the importance of systematic surveys, which in this case investigated the energy levels in heavy nuclei of a large sample of elements, as well as to the accuracy of the measurements of the ground state levels made at the time.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
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| 18. |
- Ryde, Hans, et al.
(författare)
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Ryde, Hans
- 1988
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Ingår i: Lärda Lund A-Ö. ; , s. 176-176
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Bokkapitel (populärvet., debatt m.m.)
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| 19. |
- Ryde, Nils, et al.
(författare)
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A First Study of Giant Stars in the Galactic Bulge based on Crires spectra
- 2007
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Ingår i: Stellar Populations as Building Blocks of Galaxies. ; , s. 260-261
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We present our on-going work on the determination of elemental abundances of giants in the Galactic Bulge by means of infrared spectroscopy. We show a preliminarily reduced spectrum and a synthetic spectrum fit of the Bulge giant Arp 4203 recorded with the near-infrared, high-resolution Crires spectrograph mounted on the VLT during its science verification run in August 2006. Abundances derived from this spectrum are discussed.
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| 20. |
- Schnack-Petersen, H, et al.
(författare)
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Superdeformed triaxial bands in Lu-163,165
- 1995
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Ingår i: Nuclear Physics A. - : Elsevier BV. - 0375-9474. ; 594:2, s. 175-202
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Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation of the nucleus 165Lu, using the reactions 138Ba(31P,4n) 165Lu and 150Sm(19F,4n) 165Lu at beam energies of E = 155 and 95 MeV, respectively, has been performed. Among other additions to the existing level scheme, a new band, with transition energies almost identical to a strongly deformed (β2 0.42) πi13/2[660 1/2+] band recently discovered in 163Lu has been established. A theoretical analysis of the structure of the two Lu isotopes, 165Lu and 163Lu is carried out by detailed calculations of total potential energy surfaces for specific configurations. By a diabatic treatment of crossings specific proton configurations as πi13/2[660 1/2+] are identified throughout the deformation space and as a function of spin. It is found as a general feature that well deformed local minima of considerable nonaxial symmetry coexist with a normal deformed global minimum. The depth of these local minima depend on configuration. The structure of the different global and local minima found in these surfaces are analysed and discussed in terms of occupation of available basis configurations and their orientation relative to the rotation axis. The strongly deformed minima are found to belong to a group of superdeformed triaxial structures, expected to appear at low energies for certain favourable combinations of proton and neutron numbers.
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| 21. |
- Schonwasser, G, et al.
(författare)
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Coexisting normal and triaxial superdeformed structures in Lu-165
- 2004
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 735:3-4, s. 393-424
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Lu-165 were populated in the La-139(Si-30, 4n) reaction at a beam energy of 152 MeV and gamma-ray coincidences were measured with the EUROBALL spectrometer array. Nine new rotational bands were discovered, known band structures were considerably extended and many inter-band transitions were found. Structures with normal deformation coexist with bands associated with the strongly deformed triaxial energy minima found in calculations. Three of these triaxial bands form a family of wobbling excitations with phonon quanta n(w) = 0, 1 and 2. The wobbling mode is a unique signature of nuclear triaxiality. Configuration assignments are discussed for the observed band structures. An exchange of configuration between two of the new bands due to mixing is observed, resulting in different signature partnerships at low and high spins.
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| 22. |
- Schonwasser, G, et al.
(författare)
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Lifetimes of triaxial superdeformed states in Lu-163 and Lu-164
- 2002
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - : Springer Science and Business Media LLC. - 1434-6001. ; 13:3, s. 291-296
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Tidskriftsartikel (refereegranskat)abstract
- Lifetimes of states in the yrast superdeformed bands of Lu-163 and Lu-164 were determined in a Doppler-shift attenuation-method experiment. From fractional Doppler shifts and line shapes, average transition quadrupole moments, Q(t) = 8.2(-0.6)(+1.0) b and 7.1(-0.6)(+0.5) 1), were deduced for one of the bands in Lu-163 OX -0.6 and Lu-164, respectively. These values are much larger than the quadrupole moment of the normal-deformed yrast band in Yb-163, Q(t) = 4.9(-0.4)(+1.34) b, that was also determined in this experiment. Comparison to cranking calculations indicates that both superdeformed bands correspond to a local potential energy minimum with a pronounced triaxiality, gamma similar to 20degrees.
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| 23. |
- Schonwasser, G, et al.
(författare)
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One- and two-phonon wobbling excitations in triaxial Lu-165
- 2003
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Ingår i: Physics Letters. Section B: Nuclear, Elementary Particle and High-Energy Physics. - 0370-2693. ; 552:1-2, s. 9-16
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in Lu-165 have been investigated by in-beam gamma-ray coincidence spectroscopy using the EUROBALL spectrometer array. Two new excited rotational bands have been discovered with features similar to a previously known triaxial superdeformed band in that nucleus. Comparison of the decay pattern of these bands, in particular the unusually large E2 transition strength from the first excited to the yrast superdeformed band, to theoretical calculations shows that they belong to a family of wobbling excitations with phonon numbers n(w) = 0, 1 and 2. These results, together with evidence for nuclear wobbling in the neighbouring isotopes Lu-163 and Lu-167, firmly establish this mode of excitation in the A = 165 mass region. The observation of wobbling is a unique signature of stable nuclear triaxiality. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 24. |
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| 25. |
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