1. |
- Chartkunchand, K. C., et al.
(författare)
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Lifetimes of bound excited states of Pt-
- 2017
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Ingår i: Journal of Physics: Conference Series, Vol. 875, no. 022051. - : IOP Publishing. - 1742-6588.
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Konferensbidrag (refereegranskat)abstract
- Measurements of the radiative lifetimes of the two excited states of the platinum anion Pt- are presented. Pt- ions stored in the cryogenic ion storage ring DESIREE were photodetached at different photon wavelengths and the resulting yield of neutral Pt measured as a function of time was recorded. Analysis of the neutral decay curves show a 2.54 +/- 0.10 s lifetime for the higher-lying 5d(10)6(s) S-2(1/2) excited state and a lifetime in the range of 50-200 ms for the lower- lying 5d(9)6(s)(2) D-2(3/2) excited state. This is the first study to report the lifetime of a bound anion excited state with an electron configuration different from that of the anion ground state.
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2. |
- Chartkunchand, C, et al.
(författare)
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Measuring the 2D3/2 Ni− excited state lifetime in DESIREE
- 2015
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635
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Konferensbidrag (refereegranskat)abstract
- Experimental studies of the radiative lifetime of the sole excited state in the nickel anion are presented. Beams of Ni− stored in DESIREE at cryogenic temperatures were subject to photodetachment at different photon energies and the resulting neutrals collected. Preliminary analysis of the decay in neutral production yields a radiative lifetime of approximately 15 seconds for the 3d94s2 2D3/2 excited state.
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3. |
- Engstrom, L., et al.
(författare)
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A new measurement of the 1s2s2p 4p0-1s2p2 4p transitions in c iv : Wavelengths, fine structure intervals and lifetimes
- 1987
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 36:2, s. 250-254
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Tidskriftsartikel (refereegranskat)abstract
- The n = 0 transition multiplet connecting the lowest quartet states of doubly excited C IV has been studied by beam-foil spectroscopy. The fine structure splittings obtained for the 1s2s2p 4p0and 1s2p2 4p terms confirm previous experimental results with an improved accuracy. The average transition wavelength = (1344.49 0.04)A is now more precisely determined by about a factor of eight. At the new level of precision this value shows a small but significant deviation from the best theoretical predictions. The lifetimes of the 1s2p2 4p levels have been determined as = (0.71 0.07)ns for 4P5/2 and = (1.66 0.13)ns for 4p3/2. The latter value disagrees with previous experimental results but is in excellent agreement with an isoelectronic trend analysis.
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4. |
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5. |
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6. |
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7. |
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8. |
- Kaminska, M, et al.
(författare)
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Storing keV negative ions for hours: Lifetime measurements in new time domains
- 2015
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Ingår i: Journal of Physics: Conference Series. - : IOP Publishing. - 1742-6588 .- 1742-6596. ; 635
-
Konferensbidrag (refereegranskat)abstract
- We have used one of the cryogenic ion storage rings of DESIREE to measure the lifetime of the 2P o 1/2 level in the sulfur anion to be 503 ± 43 seconds. This is orders of magnitude longer than any previously measured lifetime in a negatively charged ion.
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9. |
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10. |
- Andersson, Pontus, 1971, et al.
(författare)
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Radiative lifetimes of metastable states of negative ions
- 2006
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622 .- 2469-9926 .- 2469-9934. ; 73, s. 032705-
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Tidskriftsartikel (refereegranskat)abstract
- We present a technique for measuring the radiative lifetimes of metastable states of negative ions that involves the use of a heavy-ion storage ring. The method has been applied to investigate the radiative decay of the np(3) P-2(1/2) levels of Te-(n=5) and Se-(n=4) and the 3p(3) D-2 state of Si- for which the J=3/2 and 5/2 levels were unresolved. All of these states are metastable and decay primarily by emission of E2 and M1 radiation. Multi Configuration Dirac-Hartree-Fock calculations of rates for the transitions in Te- and Se- yielded lifetimes of 0.45 s and 4.7 s, respectively. The measured values agree well with these predicted values. In the case of the D-2 state of Si-, however, our measurement was only able to set a lower limit on the lifetime. The upper limit of the lifetime that can be measured with our apparatus is set by how long the ions can be stored in the ring, a limit determined by the rate of collisional detachment. Our lower limit of 1 min for the lifetime of the D-2 state is consistent with both the calculated lifetimes of 162 s for the D-2(3/2) level and 27.3 h for the D-2(5/2) level reported by O'Malley and Beck and 14.5 h and 12.5 h, respectively, from our Breit-Pauli calculations.
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11. |
- Biémont, E, et al.
(författare)
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Decay of metastable states in Nd II
- 2007
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Ingår i: The European physical journal D Atomic, molecular and optical physics. ; 41, s. 211-
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Tidskriftsartikel (refereegranskat)
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12. |
- Biémont, É., et al.
(författare)
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Decay of metastable states in NdII
- 2007
-
Ingår i: European Physical Journal D. - : Springer Science and Business Media LLC. - 1434-6060 .- 1434-6079. ; 41:2, s. 211-219
-
Tidskriftsartikel (refereegranskat)abstract
- The difficulty associated with an accurate determination of transition rates for forbidden lines in lowly ionized heavy elements is illustrated in the case of Nd II. We have investigated the radiative decay of the low-lying metastable levels in Nd+ including the two levels 4f(4)(I-5) 5d K-6(11/2) and 4f(4)(I-5) 5d I-6(13/2). In these two particular cases, using di. erent theoretical approaches, we. nd that the decay is dominated by the M1 channels but that the E2 contributions are of the same order of magnitude. These levels have also been studied experimentally by lifetime measurements with the heavy ion storage ring CRYRING of Stockholm University. The difficulties encountered when performing such experiments are underlined and discussed.
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13. |
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14. |
- Biemont, E, et al.
(författare)
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Importance of an M2 depopulating channel for a KrII metastable state
- 2004
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 93:6, s. 063003-
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Tidskriftsartikel (refereegranskat)abstract
- An experimental investigation of the radiative lifetime of the metastable 4s(2)4p(4)(P-3)4d D-4(7/2) level in Kr II shows an unusual situation regarding the importance of an M2 depopulation channel. While the first order M1 and E2 channels are expected to contribute in a dominant way to the decay, the experimental result, obtained using a laser probing technique on a stored ion beam, tau=0.57+/-0.03 s, is far too short to be due to these channels according to our relativistic multiconfiguration Dirac-Fock calculation. Only if second order contributions to the decay branches (including essentially the M2 contribution) are taken into account in the calculations could the unexpected short lifetime be explained.
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15. |
- Bondesson, M, et al.
(författare)
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Adenovirus E4 open reading frame 4 protein autoregulates E4 transcription by inhibiting E1A transactivation of the E4 promoter
- 1996
-
Ingår i: Journal of Virology. - 0022-538X .- 1098-5514. ; 70:6, s. 3844-6851
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Tidskriftsartikel (refereegranskat)abstract
- Here we show that the adenovirus early region 4 (E4) open reading frame 4 (ORF4) protein autoregulates its own transcription by inhibiting adenovirus E1A-induced activation of E4 transcription both in transient transfection experiments and during lytic virus growth. The inhibitory activity of E4-ORF4 was selective for E1A-CR3-dependent transactivation and had no effect on CR1 transactivation. The inhibitory activity of E4-ORF4 was relieved by okadaic acid treatment, which inhibits the cellular protein phosphatase 2A (PP2A), suggesting that E4-ORF4 controls the phosphorylated status of transcription factors important for E4 promoter activity. This conclusion agrees with previous demonstrations that E4-ORF4 associates with PP2A and causes a partial dephosphorylation of certain transcription factors, including E1A (U. Müller, T. Kleinberger, and T. Shenk, J. Virol. 66:5869-5878, 1992; T. Kleinberger and T. Shenk, J. Virol. 67:7556-7560, 1993). However, our results indicate that dephosphorylation of E1A itself might not be the primary target for E4-ORF4. Instead, the E4-ORF4-PP2A complex appears to work by dephosphorylation of multiple cellular transcription factors that are involved in E1A transactivation of the E4 promoter.
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16. |
- BROSTROM, L, et al.
(författare)
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MEASUREMENTS OF ISOTOPE SHIFT IN EU-II
- 1995
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Ingår i: PHYSICA SCRIPTA. - : ROYAL SWEDISH ACAD SCIENCES. - 0281-1847. ; 51:3, s. 330-333
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The isotope shift between singly-charged Eu-151 and Eu-153 in the 4f(7)(S-8 degrees)6s S-9 degrees(4) - 4f(7)(S-8 degrees)6p(1/2) J = 4 transition at 4129 Angstrom has been measured using fast ion beam-laser technique. This Eu line has attracted interest
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17. |
- Bäckström, E., et al.
(författare)
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The FERRUM project: metastable lifetimes in Cr ii
- 2011
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press. - 0035-8711 .- 1365-2966. ; 420:2, s. 1636-1639
-
Tidskriftsartikel (refereegranskat)abstract
- Parity forbidden radiative transitions from metastable levels are observed in spectra of low-density astrophysical plasmas. These lines are used as probes of the physical conditions, made possible due to the long lifetime of their upper level. In a joint effort, the FERRUM project aims to obtain new and accurate atomic data for the iron-group elements, and part of this project concerns forbidden lines. The radiative lifetimes of the metastable energy levels 3 d4(a 3 D)4 s c4 D 5/2 and 3 d4(a 3 D)4 s c4 D 7/2 of singly ionized chromium have been measured. The experiment has been performed at the ion storage ring CRYRING. We employed a laser-probing technique developed for measuring long lifetimes. In this article, we present the lifetimes of these levels to be τ5/2= 1.28(16) s and τ7/2= 1.37(7) s, respectively. A comparison with previous theoretical work shows good agreement and the result is discussed in a theoretical context.
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18. |
- Chartkunchand, Kiattichart C., et al.
(författare)
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Radiative lifetimes of the bound excited states of Pt-
- 2016
-
Ingår i: Physical Review A - Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 94:3
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Tidskriftsartikel (refereegranskat)abstract
- © 2016 American Physical Society.The intrinsic radiative lifetimes of the 5d106sS1/22 and 5d96s2 D3/22 bound excited states in the platinum anion Pt- have been studied at cryogenic temperatures at the Double ElectroStatic Ion Ring Experiment (DESIREE) facility at Stockholm University. The intrinsic lifetime of the higher-lying 5d106s S1/22 state was measured to be 2.54±0.10s, while only a lifetime in the range of 50-200 ms could be estimated for the 5d96s2 D3/22 fine-structure level. The storage lifetime of the Pt- ion beam was measured to be a little over 15 min at a ring temperature of 13K. The present study reports the lifetime of an atomic negative ion in an excited bound state with an electron configuration different from that of the ground state.
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19. |
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20. |
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21. |
- Eklund, Birgitta I., et al.
(författare)
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Human glutathione transferases catalyzing the bioactivation of anticancer thiopurine prodrugs
- 2007
-
Ingår i: Biochemical Pharmacology. - : Elsevier BV. - 0006-2952 .- 1356-1839. ; 73:11, s. 1829-1841
-
Tidskriftsartikel (refereegranskat)abstract
- cis-6-(2-Acetylvinylthio)purine (cAVTP) and trans-6-(2-acetylvinylthio)guanine (tAVTG) are thiopurine prodrugs provisionally inactivated by an α,β-unsaturated substituent on the sulfur of the parental thiopurines 6-mercaptopurine (6-MP) and 6-thioguanine (6-TG). The active thiopurines are liberated intracellularly by glutathione (GSH) in reactions catalyzed by glutathione transferases (GSTs) (EC 2.5.1.18). Catalytic activities of 13 human GSTs representing seven distinct classes of soluble GSTs have been determined. The bioactivation of cAVTP and tAVTG occurs via a transient addition of GSH to the activated double bond of the S-substituent of the prodrug, followed by elimination of the thiopurine. The first of these consecutive reactions is rate-limiting for thiopurine release, but GST-activation of this first addition is shifting the rate limitation to the subsequent elimination. Highly active GSTs reveal the transient intermediate, which is detectable by UV spectroscopy and HPLC analysis. LC/MS analysis of the reaction products demonstrates that the primary GSH conjugate, 4-glutathionylbuten-2-one, can react with a second GSH molecule to form the 4-(bis-glutathionyl)butan-2-one. GST M1-1 and GST A4-4 were the most efficient enzymes with tAVTG, and GST M1-1 and GST M2-2 had highest activity with cAVTP. The highly efficient GST M1-1 is polymorphic and is absent in approximately half of the human population. GST P1-1, which is overexpressed in many cancer cells, had no detectable activity with cAVTP and only minor activity with tAVTG. Other GST-activated prodrugs have targeted GST P1-1-expressing cancer cells. Tumors expressing high levels of GST M1-1 or GST A4-4 can be predicted to be particularly vulnerable to chemotherapy with cAVTP or tAVTG.
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22. |
- Ellmann, A, et al.
(författare)
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Radiative lifetime of a bound excited state of Te-
- 2004
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 92:25, s. 253002-
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Tidskriftsartikel (refereegranskat)abstract
- We report on the first experimental study of the lifetime of a bound excited state of a negative ion. A new experimental technique was developed and used to measure the radiative lifetime of the 5p(5) P-2(1/2) level of Te-. The experiment was performed in a magnetic storage ring, where a laser beam was applied along one of the straight sections. In the experiment the population of the excited J=1/2 level was probed each time the Te- ions passed through the laser field. A decay curve was built up by sampling the population of the excited level of the Te- ions as a function of time after injection into the ring. A multiconfiguration Dirac-Hartree-Fock calculation was performed in conjunction with the experiment. The calculation yielded a radiative lifetime of 0.45 s, in excellent agreement with the measured value of 0.42(5) s.
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23. |
- Gurell, J., et al.
(författare)
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Laser-probing measurements and calculations of lifetimes of the 5d D-2(3/2) and 5d D-2(5/2) metastable levels in BaII
- 2007
-
Ingår i: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 75:5, s. 052506-
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Tidskriftsartikel (refereegranskat)abstract
- The two metastable levels 5d(2)D(3/2) and 5d(2) D-5/2 in Ba II both show extremely long lifetimes of the order of several tens of seconds each. This has been found both by experiments and by theoretical predictions. The small transition probabilities associated with these two levels make them interesting and challenging for theoreticians as well as for experimentalists. Several calculations and measurements of these two lifetimes have been made previously but discrepancies between the results are present. This article presents values of ??? = 89.4 +/- 15.6 s for the D-2(3/2) level and ??? = 32.0 +/- 4.6 s for the D-2(5/2) level measured in a beam-laser experiment performed at the ion storage ring CRYRING. These values are supported by our new calculations resulting in ???= 82.0 s for the D-2(3/2) level and ???= 31.6 s for the D-2(5/2) level.
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24. |
- Gurell, J., et al.
(författare)
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The FERRUM project : laboratory-measured transition probabilities for Cr II
- 2010
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Ingår i: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 511, s. A68-A68
-
Tidskriftsartikel (refereegranskat)abstract
- Aims. We measure transition probabilities for Cr II transitions from the z 4HJ, z 2DJ, y 4FJ, and y 4GJ levels in the energy range 63 000 to 68 000 cm-1.Methods. Radiative lifetimes were measured using time-resolved laser-induced fluorescence from a laser-produced plasma. In addition, branching fractions were determined from intensity-calibrated spectra recorded with a UV Fourier transform spectrometer. The branching fractions and radiative lifetimes were combined to yield accurate transition probabilities and oscillator strengths.Results. We present laboratory measured transition probabilities for 145 Cr II lines and radiative lifetimes for 14 Cr II levels. The laboratory-measured transition probabilities are compared to the values from semi-empirical calculations and laboratory measurements in the literature.
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25. |
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26. |
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27. |
- Hartman, Henrik, et al.
(författare)
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Experimental oscillator strengths for forbidden lines in complex spectra
- 2005
-
Ingår i: Physica Scripta. - 0281-1847. ; T119, s. 40-44
-
Konferensbidrag (refereegranskat)abstract
- In dilute astrophysical plasmas, such as planetary nebulae and H II regions, strong lines appear that only have weak, if any, correspondence to the spectrum of laboratory light sources. Some of these are parity forbidden lines, i.e. emission from long-lived metastable states that cannot decay via normal electric dipole (E1) routes but only via the slower M1 and E2 transitions. The long lifetime of the upper levels and their sensitivity to collisions make the lines good diagnostics of the emitting plasma, but then the transition probability, or A-value, of these lines must be known. We report on a technique to experimentally determine A-values for forbidden lines using the method of combining the lifetime of the upper level with the branching fractions for the different decay channels. The lifetime is measured using the laser probing technique (LPT) on a stored ion beam. Since these lines are rarely produced in laboratory plasmas, we use astrophysical spectra to determine the branching fractions (BF). The lifetime and the BF then give the A-value, which is one quantity needed for modeling the spectrum of the plasma emitting the forbidden lines. The present measurements are performed within the FERRUM project, an international collaboration producing and evaluating transition probabilities for iron group element lines of astrophysical importance [Johansson, P. I. S. et al., Physica Scripta T100, 71 (2002).]
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28. |
- Hartman, Henrik, et al.
(författare)
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The FERRUM project : experimentally determined metastable lifetimes and transition probabilities for forbidden [Ti II] lines observed in eta Carinae
- 2005
-
Ingår i: Monthly notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 361:1, s. 206-210
-
Tidskriftsartikel (refereegranskat)abstract
- In the spectrum of an emission-line region ejected from the massive star Eta Carinae, called the strontium filament (SrF), forbidden lines from many elements, in particular [Sr II] and [Ti II], are observed. These lines are strong in this specific region and valuable for plasma diagnostics. Forbidden lines are not easily produced in laboratory light sources and the atomic parameters for these lines can thus not be measured in a straightforward way. We use a combination of laboratory and astrophysical measurements to determine transition probabilities for the [Ti II] lines. Lifetimes for metastable levels in Ti II are measured using a laser probing technique on a stored ion beam at CRYRING, MSL, Stockholm. Branching fractions from some of these levels are derived from Hubble Space Telescope/STIS spectra of the SrF. The astrophysical branching fractions are combined with the experimental lifetimes to determine absolute transition probabilities. We report lifetimes for the Ti II levels b(4)P(3/2), b(2)P(1/2), c(2)D(3/2) and c(2)D(5/2), in the range 0.29-17 s, and transition probabilities for eight parity-forbidden lines from the levels c(2)D(3/2) and c(2)D(5/2), along with uncertainty estimates.
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29. |
- Hartman, Henrik, et al.
(författare)
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The FERRUM project: an extremely long radiative lifetime in Ti II measured in an ion storage ring
- 2003
-
Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 36, s. 197-202
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Tidskriftsartikel (refereegranskat)abstract
- We have extended the laser probing technique at the CRYRING storage ring to measurement of the extremely long lifetime (28 s) of the metastable 3d2(3P)4s b 4P5/2 level in Ti II. The result obtained demonstrates the power of this method for investigation of such long-lived levels. This is the first experimental lifetime investigation of metastable states in Ti II.
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30. |
- Hartman, Henrik, et al.
(författare)
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The FERRUM Project: Experimental transition probabilities of [Fe II] and astrophysical applications
- 2003
-
Ingår i: Astronomy & Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 397:3, s. 1143-1149
-
Tidskriftsartikel (refereegranskat)abstract
- We report on experimental transition probabilities for thirteenforbidden [Fe II] lines originating from three different metastable FeIi levels. Radiative lifetimes have been measured of two metastablestates by applying a laser probing technique on a stored ion beam.Branching ratios for the radiative decay channels, i.e. M1 and E2transitions, are derived from observed intensity ratios of forbiddenlines in astrophysical spectra and compared with theoretical data. Thelifetimes and branching ratios are combined to derive absolutetransition probabilities, A-values.We present the first experimental lifetime values for the two Fe IIlevels a4G9/2 and b2H11/2and A-values for 13 forbidden transitions froma6S5/2, a4G9/2 andb4D7/2 in the optical region. A discrepancybetween the measured and calculated values of the lifetime for theb2H11/2 level is discussed in terms of levelmixing. We have used the code CIV3 to calculate transitionprobabilities of the a6D-a6S transitions.We have also studied observational branching ratios for lines from 5other metastable Fe II levels and compared them to calculated values. Aconsistency in the deviation between calibrated observational intensityratios and theoretical branching ratios for lines in a wider wavelengthregion supports the use of [Fe II] lines for determination of reddening.
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31. |
- Hederos, Sofia, et al.
(författare)
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Incorporation of a single His residue by rational design enables thiol-ester hydrolysis by human glutathione transferase A1-1.
- 2004
-
Ingår i: Proc Natl Acad Sci U S A. - 0027-8424. ; 101:36, s. 13163-7
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Tidskriftsartikel (refereegranskat)abstract
- A strategy for rational enzyme design is reported and illustrated by the engineering of a protein catalyst for thiol-ester hydrolysis. Five mutants of human glutathione (GSH; gamma-Glu-Cys-Gly) transferase A1-1 were designed in the search for a catalyst and to provide a set of proteins from which the reaction mechanism could be elucidated. The single mutant A216H catalyzed the hydrolysis of the S-benzoyl ester of GSH under turnover conditions with a k(cat)/K(M) of 156 M(-1) x min(-1), and a catalytic proficiency of >10(7) M(-1) when compared with the first-order rate constant of the uncatalyzed reaction. The wild-type enzyme did not hydrolyze the substrate, and thus, the introduction of a single histidine residue transformed the wild-type enzyme into a turnover system for thiol-ester hydrolysis. By kinetic analysis of single, double, and triple mutants, as well as from studies of reaction products, it was established that the enzyme A216H catalyzes the hydrolysis of the thiol-ester substrate by a mechanism that includes an acyl intermediate at the side chain of Y9. Kinetic measurements and the crystal structure of the A216H GSH complex provided compelling evidence that H216 acts as a general-base catalyst. The introduction of a single His residue into human GSH transferase A1-1 created an unprecedented enzymatic function, suggesting a strategy that may be of broad applicability in the design of new enzymes. The protein catalyst has the hallmarks of a native enzyme and is expected to catalyze various hydrolytic, as well as transesterification, reactions.
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32. |
- I. Sinning, G.J. Kleywegt, S.W. Cowan, P. Reinemer, H.W. Dirr, R. Huber, G.L. Gilliland, R.N. Armstrong, X. Ji, P.G. Board, B. Olin, B. Mannervik & T.A. Jones
(författare)
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Structure determination and refinement of human alpha class glutathione transferase A1-1, and a comparison with the mu and pi class enzymes
- 1993
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Ingår i: Journal of Molecular Biology. ; 232, s. 192-212
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Tidskriftsartikel (refereegranskat)
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33. |
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34. |
- Johansson, Sveneric, et al.
(författare)
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The FERRUM Project: New f-value Data for Fe II and Astrophysical Applications
- 2002
-
Ingår i: Physica Scripta. - : Institute of Physics Publishing (IOPP). - 0281-1847 .- 0031-8949 .- 1402-4896. ; T100, s. 71-80
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Konferensbidrag (refereegranskat)abstract
- We present the FERRUM Project, an international collaboration aiming at a production and evaluation of oscillator strengths (transition probabilities) of selected spectral lines of singly ionized iron group elements, that are of astrophysical relevance. The results obtained include measurements and calculations of permitted and forbidden lines of Fe II. The data have been applied to both emission and absorption lines in astrophysical spectra. We make comparisons between experimental, theoretical and astrophysical f-values. We give a general review of the various measurements, and discuss the UV8 multiplet of Fe II around 1610 Šin detail.
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35. |
- Kamińska, Magdalena, et al.
(författare)
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Lifetime of the bound excited level in Ni
- 2016
-
Ingår i: Physical Review A. - 1050-2947 .- 1094-1622. ; 93:1
-
Tidskriftsartikel (refereegranskat)abstract
- The intrinsic lifetime of the upper level in the bound-bound 3d(9) 4s(2) D-2(3/2) -> 3d(9) 4s(2) D-2(5/2) radiative transition in Ni- was measured to be 15.1 +/- 0.4 s. The experiment was performed at cryogenic temperatures in one of the ion-beam storage rings of the Double ElectroStatic Ion Ring ExpEriment facility at Stockholm University. The storage lifetime of the Ni- ion beam was measured to be close to 5 min at a ring temperature of 13 K.
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36. |
- Kramida, A. E., et al.
(författare)
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Additions to the spectrum and energy levels and a critical compilation of helium-like and hydrogen-like boron, BIV and BV
- 2008
-
Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 78:2
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Tidskriftsartikel (refereegranskat)abstract
- Using beam-foil spectroscopy, we have observed several new lines in the B IV and B V spectra. This experimental work was combined with theoretical calculations using ab initio and semi-empirical techniques. We have also critically evaluated all previous and recent experimental and theoretical data for these spectra. Complete data on wavelengths and energy levels based on this analysis are tabulated.
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37. |
- Kramida, A. E., et al.
(författare)
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Additions to the spectrum and energy levels and critical compilation of doubly ionized boron, BIII
- 2008
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Ingår i: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 78:2
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Tidskriftsartikel (refereegranskat)abstract
- We have undertaken the study of the Li-like spectrum of doubly ionized boron, B III. The spectroscopic data have been obtained with beam-foil spectroscopy and high-resolution spark spectroscopy. The experimental work was combined with theoretical calculations using ab initio and semi-empirical techniques. About 50 new transitions have been observed, and most of the previously known lines have been measured with improved accuracy. We have also critically evaluated all previous and recent data for this spectrum. Complete data on wavelengths and energy levels based on this analysis are tabulated.
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38. |
- Lien, S, et al.
(författare)
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Human glutathione transferase Al-1 demonstrates both half-of-the-sites and all-of-the-sites reactivity
- 2001
-
Ingår i: JOURNAL OF BIOLOGICAL CHEMISTRY. - : AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC. - 0021-9258. ; 276:38, s. 35599-35605
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Tidskriftsartikel (refereegranskat)abstract
- A study of the kinetics of a heterodimeric variant of glutathione transferase (GST) A1-1 has led to the conclusion that, although the wild-type enzyme displays all-of-the-sites reactivity in nucleophilic aromatic substitution reactions, it demonstrates ha
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39. |
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40. |
- Lundin, P., et al.
(författare)
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Inclusion of Electric Octupole Contributions Explains the Fast Radiative Decays of Two Metastable States in Ar
- 2007
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 99, s. 213001-
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Tidskriftsartikel (refereegranskat)abstract
- A laser probing investigation has yielded the lifetimes of the 3s23p4(1D)3d 2G7/2,9/2 metastable doublet states of Ar+. The results, obtained with the CRYRING ion storage ring of Stockholm, are 3.0±0.4 and 2.1±0.1 s, respectively. Comparisons with theoretical values calculated with two independent theoretical approaches, i.e., the pseudorelativistic Hartree-Fock method and the multiconfiguration Breit-Pauli approach, have allowed us to establish the unexpected and extraordinary strong contribution of an electric octupole (E3) transition to the ground state, in addition to the M1 decay channels to the 3d 2,4F states and the E2 contributions to the 4s 2P, 2D states.
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41. |
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42. |
- Mannervik, S, et al.
(författare)
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1s2s2p2 5p3 5S transition in B ii
- 1987
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Ingår i: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 35:7, s. 3136-3138
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Tidskriftsartikel (refereegranskat)
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43. |
- Mannervik, S, et al.
(författare)
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Lifetime measurements by laser probing in CRYRING - Recent experimental developments
- 2005
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Ingår i: Physica Scripta. - 0031-8949 .- 1402-4896. ; T119, s. 49-54
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Tidskriftsartikel (refereegranskat)abstract
- A laser probing technique for lifetime measurements of long- lived metastable levels has been developed at the ion storage ring CRYRING. The method has been in use for about eight years and it has been applied to various ions. Levels with radiative lifetimes from a few milliseconds up to 28 s have been measured. The method has been continuously developed and this article is focused on recent experimental developments of the method in order to widen its applicability and to increase its efficiency and accuracy.
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44. |
- Martinson, Indrek, et al.
(författare)
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The elusive 2s3s S-1 level in BII
- 2003
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 36:3, s. 419-425
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Tidskriftsartikel (refereegranskat)abstract
- It has been known for nearly 30 years that the theoretical and experimental values for the energy of the 2s3s S-1 level in singly ionized boron, B it, differ strongly. Since there is much better agreement for other B II levels, it has been concluded that the experimental value for 2s3s S-1 must be revised. Despite a number of recordings over the years of sliding-spark, hollow cathode and beam-foil spectra, this level has not been located. We have now performed another beam-foil experiment, using higher resolution and sensitivity than in most previous studies. By combining these new data with previous results, we have identified transitions from the 2s4p, 2s5p and 2p3s P-1 levels to 2s3s S-1, the excitation energy (137 622 +/- 3 cm(-1)) of which is now well established and in excellent agreement with theoretical predictions.
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45. |
- Melas, P. A., et al.
(författare)
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Allele-specific programming of Npy and epigenetic effects of physical activity in a genetic model of depression
- 2013
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Ingår i: Translational Psychiatry. - : Springer Science and Business Media LLC. - 2158-3188. ; 3, s. e255-
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Tidskriftsartikel (refereegranskat)abstract
- Neuropeptide Y (NPY) has been implicated in depression, emotional processing and stress response. Part of this evidence originates from human single-nucleotide polymorphism (SNP) studies. In the present study, we report that a SNP in the rat Npy promoter (C/T; rs105431668) affects in vitro transcription and DNA-protein interactions. Genotyping studies showed that the C-allele of rs105431668 is present in a genetic rat model of depression (Flinders sensitive line; FSL), while the SNP's T-allele is present in its controls (Flinders resistant line; FRL). In vivo experiments revealed binding of a transcription factor (CREB2) and a histone acetyltransferase (Ep300) only at the SNP locus of the FRL. Accordingly, the FRL had increased hippocampal levels of Npy mRNA and H3K18 acetylation; a gene-activating histone modification maintained by Ep300. Next, based on previous studies showing antidepressant-like effects of physical activity in the FSL, we hypothesized that physical activity may affect Npy's epigenetic status. In line with this assumption, physical activity was associated with increased levels of Npy mRNA and H3K18 acetylation. Physical activity was also associated with reduced mRNA levels of a histone deacetylase (Hdac5). Conclusively, the rat rs105431668 appears to be a functional Npy SNP that may underlie depression-like characteristics. In addition, the achieved epigenetic reprogramming of Npy provides molecular support for the putative effectiveness of physical activity as a non-pharmacological antidepressant.
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46. |
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47. |
- Mukanganyama, S, et al.
(författare)
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Proposed reductive metabolism of artemisinin by glutathione transferases in vitro
- 2001
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Ingår i: FREE RADICAL RESEARCH. - : HARWOOD ACAD PUBL GMBH. - 1071-5762. ; 35:4, s. 427-434
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Tidskriftsartikel (refereegranskat)abstract
- Artemisinin is a sesquiterpene lactone containing an endoperoxide bridge. It is a promising new antimalarial and is particularly useful against the drug resistant strains of Plasmodium falciparum. It has unique antimalarial properties since it acts throug
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48. |
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49. |
- Musdal, Yaman, et al.
(författare)
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Inhibition of human glutathione transferase P1-1 by novel benzazole derivatives
- 2012
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Ingår i: Türk Biyokimya Dergisi. - : LookUs Bilisim A.S.. - 0250-4685 .- 1303-829X. ; 37:4, s. 431-436
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Tidskriftsartikel (refereegranskat)abstract
- Objective: Glutathione transferases (GST) are multifunctional enzymes involved in detoxication, drug resistance, cell signaling and apoptosis. The inhibitory effects of novel benzazole derivatives were tested on human GST P1-1 to find new agents for overcoming drug resistance in cancer cells.Methods: GST P1-1 was heterogously expressed in E. coli strain XL-1 Blue and purified using S-hexylglutathione-Sepharose 6B affinity chromatography. The effect of 33 potential inhibitors on enzymatic activity was assayed spectrophotometrically with 1-chloro-2,4-dinitrobenzene (CDNB) as well as with the alternative substrate phenethyl isothiocyanate (PEITC).Results: Compound-18 (N-[2-(4-chloro-benzyl)-benzooxazol-5-yl]-4- nitro-benzenesulfonamide) was the most potent inhibitor found with an IC50 value of approximately 10 μM with respect to CDNB and a somewhat less strong inhibitor (45 % inhibition at 40 μM) with PEITC as substrate. Compound-18 showed mixed inhibition with GSH and uncompetitive inhibition with CDNB with the Ki values 6.3 ± 0.7 μM and 11.8 ± 3.4 μM, respectively.Conclusion: Compound-18 is a potent inhibitor of GST P1-1. It may serve as a lead for further chemical modifications for increased potency. Additional studies will elucidate the effects of the inhibitor on cancer cells.
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50. |
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