| 1. |
- Aggarwal, MM, et al.
(författare)
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Centrality dependence of charged-neutral particle fluctuations in 158A (GeVPb)-Pb-208+Pb-208 collisions
- 2003
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 67:4
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Tidskriftsartikel (refereegranskat)abstract
- Results on the study of localized fluctuations in the multiplicity of charged particles and photons produced in 158A GeV/c Pb+Pb collisions are presented for varying centralities. The charged versus neutral particle multiplicity correlations in common phase space regions of varying azimuthal sizes are analyzed by two different methods. Various types of mixed events are constructed to probe fluctuations arising from different sources. The measured results are compared to those from simulations and from mixed events. The comparison indicates the presence of nonstatistical fluctuations in both the charged particle and photon multiplicities in limited azimuthal regions. However, no correlated charged-neutral fluctuations, a possible signature of formation of disoriented chiral condensates, are observed. An upper limit on the production of disoriented chiral condensates is set.
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| 2. |
- Aggarwal, MM, et al.
(författare)
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Event-by-event fluctuations in particle multiplicities and transverse energy produced in 158A GeVPb plus Pb collisions
- 2002
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 65:5
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Tidskriftsartikel (refereegranskat)abstract
- Event-by-event fluctuations in the multiplicities of charged particles and photons, and the total transverse energy in 158A GeV Pb+Pb collisions are studied for a wide range of centralities. For narrow centrality bins the multiplicity and transverse energy distributions are found to be near perfect Gaussians. The effect of detector acceptance on the multiplicity fluctuations has been studied and demonstrated to follow statistical considerations. The centrality dependence of the charged particle multiplicity fluctuations in the measured data has been found to agree reasonably well with those obtained from a participant model. However, for photons the multiplicity fluctuations have been found to be lower compared to those obtained from a participant model. The multiplicity and transverse energy fluctuations have also been compared to those obtained from the VENUS event generator.
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| 3. |
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| 4. |
- Aggarwal, MM, et al.
(författare)
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Transverse mass distributions of neutral pions from Pb-208-induced reactions at 158 center dot A GeV
- 2002
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Ingår i: European Physical Journal C. Particles and Fields. - : Springer Science and Business Media LLC. - 1434-6044. ; 23:2, s. 225-236
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Tidskriftsartikel (refereegranskat)abstract
- Results on transverse mass spectra of neutral pious measured at central rapidity are presented for impact parameter selected 158-A GeV Pb + Pb-1 and Pb + Nb collisions. The distributions cover the range 0.5 GeV/c(2) less than or equal to MT - Mo less than or equal to 4 GeV/c(2). The change of the spectral shape and the multiplicity with centrality is studied in detail. In going from p+p to semi-peripheral Pb+Pb collisions there is a nuclear enhancement increasing with transverse mass similar to the well known Cronin effect, while for very central collisions this enhancement appears to be weaker than expected.
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| 5. |
- Kelsall, N. S., et al.
(författare)
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Testing mean-field models near the N=Z line : gamma-ray spectroscopy of the T-z=1/2 nucleus Kr-73
- 2002
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 65:4
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Tidskriftsartikel (refereegranskat)abstract
- Excited states in the N=Z+1 nucleus Kr-73 have been investigated using the Ca-40(Ar-36,2pn) and Ca-40(Ca-40,alpha2pn) reactions at 145 and 160 MeV, respectively. gamma rays were detected using the Gammasphere array and events were recorded in coincidence with charged-particle and neutron detectors. The three previously observed bands were extended to high spin, and a new unfavored positive-parity band has been observed. The alignment characteristics and decay properties of the bands are all consistent with large-deformation prolate rotation, with no clear evidence for oblate bands or shape coexistence. This is quite different from neighboring Kr-72,Kr-74, indicating a strong shape-stabilizing role for the valence neutron. The experimental results are compared to extended total Routhian surface, cranked Nilsson Strutinsky, and cranked relativistic mean-field calculations. The results suggest that the paired calculations lack some important physics. Neutron-proton correlations may be the missing ingredient. There is also evidence for an unusual band crossing in the negative-parity bands, which may indicate the presence of T=0 pairing correlations. At high spin all the models can reproduce the experimental data.
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| 6. |
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| 7. |
- Monakhov, E. V., et al.
(författare)
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Excimer laser annealing of shallow As and B doped layers
- 2004
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 114-15, s. 352-357
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Tidskriftsartikel (refereegranskat)abstract
- Excimer laser annealing (ELA) of As-, B- and BF2-implanted Si has been studied by secondary ion mass spectrometry (SIMS), spreading resistance probe (SRP) and transmission electron microscopy (TEM). The implantations have been performed in the energy range from I to 30 keV with doses of 10(15)-10(16) cm(-2). ELA has been carried out with the energy densities in the range of 600-1200 mJ/cm(2) and the number of laser pulses from 1 to 10. It is shown that ELA results in a more uniform dopant distribution over the doped region with a more abrupt profile edge as compared to those after rapid thermal annealing (RTA). Besides, in contrast to RTA, ELA demonstrates a highly confined annealing effect, where the distribution of dopants below the melting region is not affected. SRP measurements demonstrate almost complete activation of the implanted dopants after ELA, and TEM does not reveal extended defects in the ELA-treated samples. The depth of the doped layers, abruptness of the profiles and the total doping dose as a function of ELA energy density and number of laser pulses are investigated. Computer simulations of ELA show a good agreement with the experimental data.
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| 8. |
- Svensson, C. E., et al.
(författare)
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Collective rotational motion in the N=Z nucleus 36Ar
- 2001
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Ingår i: Nuclear Physics A. - 0375-9474. ; 682:1-4, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- A superdeformed rotational band has been identified in the N = Z nucleus 36Ar, firmly linked to known low-spin states, and observed to its high-spin termination at Iπ = 16+. Lifetime measurements by the Doppler shift attenuation method establish a large low-spin deformation (β2 ≈ 0.46) and a decrease in the collectivity as the band approaches termination. Comparisons with cranked Nilsson-Strutinsky and large-scale spherical shell model calculations lead to a consistent description of the band based on a configuration in which four particles are promoted to the pf shell. With two major shells active for both protons and neutrons, yet a valence space dimension small enough to be approached from the shell model perspective, this band offers an excellent opportunity to investigate the microscopic structure of collective rotational motion in nuclei.
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| 9. |
- Svensson, C. E., et al.
(författare)
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Superdeformation in the N = z Nucleus 36Ar : Experimental, deformed mean field, and spherical shell model descriptions
- 2000
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Ingår i: Physical Review Letters. - 0031-9007. ; 85:13, s. 2693-2696
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Tidskriftsartikel (refereegranskat)abstract
- A superdeformed rotational band has been identified in 36Ar, linked to known low-spin states, and observed to its high-spin termination at Iπ = 16+. Cranked Nilsson-Strutinsky and spherical shell model calculations assign the band to a configuration in which four pf-shell orbitals are occupied, leading to a low-spin deformation β2 ≈ 0.45. Two major shells are active for both protons and neutrons, yet the valence space remains small enough to be confronted with the shell model. This band thus provides an ideal case to study the microscopic structure of collective rotational motion.
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| 10. |
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| 11. |
- Andreoiu, Corina, et al.
(författare)
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Yrast Superdeformed Band in 59Cu
- 2000
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 62:5, s. 513011-513015
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in 59Cu were populated using the fusion-evaporation reactions 28Si+40Ca at a beam energy of 125 MeV and 36Ar+28Si at a beam energy of 143 MeV. The Gammasphere array in conjunction with ancillary detector systems allowed for the identification of a superdeformed rotational band in 59Cu, which was firmly linked to low-spin yrast states. Using directional correlations of oriented states, a spin-parity assignment of Iπ = 25/2+ to the band head was possible. The average quadrupole moment of the band is measured to be Qt = (2.24±0.40) e b. The characteristics of the band are compared to neighboring nuclei and predictions of different mean-field theories.
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| 12. |
- Becker, Magnus, et al.
(författare)
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Adult skeletal profile in isolated cleft palate: a comparison of the von Langenbeck and Wardill procedures for primary repair of the palate
- 2001
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Ingår i: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery. - : Informa UK Limited. - 1651-2073 .- 0284-4311. ; 35:4, s. 387-397
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Tidskriftsartikel (refereegranskat)abstract
- Sixty-four adult patients operated on for isolated cleft palate were evaluated with regard to facial skeletal morphology using conventional radio-cephalometry. Dental occlusion was assessed clinically. Forty-two had had a von Langenbeck repair at the age of 7 months and 22 a Wardill repair at 18 months. The mean error of the method was 0.7 degree for angular, and 0.9 mm for linear, measurements. The group with clefts had less maxillary prognathism (s-n-ss), more maxillary inclination (NSL/NL), more retroclined lower incisors (ILI/ML), and shorter total and upper facial heights (n-gn, n-sp) compared with the reference group. Multiple regression analysis was used to evaluate differences between the two treatment regimens. Explanatory variables in addition to surgical technique were sex, severity of cleft, and presence of a velopharyngeal flap. Only one variable, lower incisor inclination (ILI/ML), was different for the two regimens. Ten (24%) in the von Langenbeck group had a lateral cross-bite compared with one (5%) in the Wardill group. Other variables in a multivariate regression analysis were affected by sex and severity of cleft to various degrees. This study showed no obvious differences in facial skeletal morphology that could be attributed to surgical technique. Factors other than technique, including sex, age, and severity of cleft merit attention.
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| 13. |
- Becker, Magnus, et al.
(författare)
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Von Langenbeck or Wardill procedures for primary palatal repair in patients with isolated cleft palate--speech results
- 2000
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Ingår i: Scandinavian Journal of Plastic and Reconstructive Surgery and Hand Surgery. - : Informa UK Limited. - 1651-2073 .- 0284-4311. ; 34:1, s. 27-32
-
Tidskriftsartikel (refereegranskat)abstract
- Sixty-six patients operated on for isolated cleft palate were evaluated as adults, and their speech was assessed clinically. Forty-four had undergone a von Langenbeck repair at the age of 7 months and 22 a Wardill repair at the age of 18 months. Speech was judged subjectively by the patients themselves, and perceptual assessment was made by three speech pathologists. The remaining speech problems, mainly hypernasality, were moderate or severe in 7 (16%) of the patients in the von Langenbeck group, and in 7 (32%) in the Wardill group. On the other hand, the patients in the Wardill group had fewer fistulas closed, and fewer velopharyngoplasties. There were no significant differences between the two methods regarding speech in adulthood. The Wardill method produced significantly more scar tissue clinically, which carries the potential risk of inhibition of facial growth. The present speech results will therefore be weighed against the outcome of maxillofacial growth for these patients.
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| 14. |
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| 15. |
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| 16. |
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| 17. |
- da Silva, DA, et al.
(författare)
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Vibronic coupling in the ground and excited states of the naphthalene cation
- 2004
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; :15, s. 1702-1703
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Tidskriftsartikel (refereegranskat)abstract
- The hole - vibrational coupling in naphthalene is studied using high-resolution gas-phase photoelectron spectroscopy and density functional theory calculations (DFT), and a remarkable increase of the coupling with low-frequency vibrations is observed in the excited states.
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| 18. |
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| 19. |
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| 20. |
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| 21. |
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| 22. |
- Grippa, Alexander Yu, et al.
(författare)
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New strontium and rare earth-based mixed niobium misfit sulfides
- 2003
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Ingår i: Solid State Sciences. - : Elsevier. ; 5:3, s. 495-502
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Tidskriftsartikel (refereegranskat)abstract
- New niobium-based misfit sulfides [(Ln1/3Sr2/3S)1.5]1.15NbS2 (Ln=Sm, Tb) have been synthesized from a mixture of SrS, Ln2S3, Nb(m), and S in evacuated and sealed silica tubes by annealing at 1000 °C for 144 h under a sulfur partial pressure of 49.3 kPa. The compounds have been characterized by EDX analysis, X-ray single crystal and powder diffraction, electron diffraction, and magnetic susceptibility measurements. Both sulfides have misfit structures with orthorhombic symmetry for the (Ln1/3Sr2/3S)1.5 (Ln=Sm, Tb) and NbS2 subsystems. The lattice parameters for the different subsystems are: for the Sm-based sulfide [(Sm1/3Sr2/3S)1.5]: a=5.7953(9) Å, b=5.8007(5) Å, c=14.957(2) Å and [NbS2]: a=3.3420(7) Å, b=5.8008(5) Å, c=14.955(2) Å, and for the Tb-based sulfide [(Tb1/3Sr2/3S)1.5]: a=5.769(2) Å, b=5.7766(7) Å, c=14.906(2) Å and [NbS2]: a=3.340(1) Å, b=5.7769(8) Å, c=14.905(2) Å. The [(Sm1/3Sr2/3S)1.5]1.15NbS2 crystal structure has been refined from X-ray single crystal data. It belongs to the 1.5Q/1H homologue type where the (Sm1/3Sr2/3S)1.5 part is a three-atoms-thick slab. Sr-cations are mainly located at the exterior of the slab whereas Sm preferably occupy the positions at its center. Both compounds exhibit paramagnetic temperature dependence down to 2 K.
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| 23. |
- Hermansson, J., et al.
(författare)
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Complexes of the self-interstitial with oxygen in irradiated silicon : A new assignment of the 936 cm-1 band
- 2001
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Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 302-303, s. 188-192
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Three vibrational infrared absorption bands at about 936, 944 and 956 cm-1 appear commonly in spectra of Czochralski-grown silicon irradiated at low temperatures. All three bands have earlier been assigned to local vibrational modes related to oxygen in the complex of the silicon and the oxygen interstitials (IOi). However, it is shown that such an assignment of the 936 cm-1 band clearly is inconsistent with many facts and observations and that the band is most likely due to oxygen vibrations in the Si interstitial pair and interstitial oxygen complex, I2Oi. © 2001 Published by Elsevier Science B.V.
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| 24. |
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| 25. |
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| 26. |
- Janusauskas, A., et al.
(författare)
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Otoacoustic emissions and improved pass/fail separation using wavelet analysis and time windowing
- 2001
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Ingår i: Medical & Biological Engineering & Computing. - 0140-0118. ; 39:1, s. 134-139
-
Tidskriftsartikel (refereegranskat)abstract
- A new method is presented for the purpose of improving pass/fail separation during transient evoked otoacoustic emission (TEOAE) hearing screening. The method combines signal decomposition in scales using the discrete wavelet transform, non-linear denoising and scale-dependent time windowing. The cross-correlation coefficient between two subaveraged, processed TEOAE signals is used as a pass/fail criterion and assessed in relation to the pure-tone, mean hearing level. The performance is presented in terms of receiver operating characteristics for a database of 5214 individuals. The results show that the specificity improves from 68% to 83% at a sensitivity of 90% when compared with the conventional wave reproducibility parameter.
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| 27. |
- Karlgren, Daniel, et al.
(författare)
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High-angular-momentum structures in Zn-64
- 2004
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Ingår i: Physical Review C. Nuclear Physics. - 0556-2813 .- 1089-490X. ; 69, s. 1-034330
-
Tidskriftsartikel (refereegranskat)abstract
- High-angular-momentum states in Zn-64 were populated in the Ca-40(Si-28,4p) reaction at a beam energy of 122 MeV. Evaporated, light, charged particles were identified by the Microball, while gamma rays were detected using the Gammasphere array. The main focus of this paper is on two strongly coupled, collective bands. The yrast band, which was previously known, has been linked to lower-lying states establishing the excitation energies and angular momenta of in-band states for the first time. The newly identified excited band decays to the yrast band but firm angular-momentum assignments could not be made. In order to interpret these structures cranked-Nilsson-Strutinsky calculations have been performed. The calculations have been extended to account for the distribution of nucleons within a configuration. The yrast collective band is interpreted as based on the pi(f(7/2))(-1)(p(3/2)f(5/2))(2)(g(9/2))(1)nu(p(3/2)f(5/2))(4)(g(9/2))(2) configuration. There are several possible interpretations of the second band but it is difficult to distinguish between the different possibilities.
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| 28. |
- Kelsall, N.S., et al.
(författare)
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High-spin studies of N ~ Z nuclei in the mass 70 region
- 2003
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Ingår i: AIP Conference Proceedings. - 0094-243X .- 1551-7616. ; :656, s. 261-268
-
Konferensbidrag (refereegranskat)abstract
- High-spin states have been studied in 72,73Kr using 40Ca+40Ca and 36Ar+40Ca reactions at 160, 164 and 145 MeV respectively. The properties and configurations of the bands observed are interpreted with the aid of unpaired cranked Nilsson-Strutinsky/ cranked relativistic mean-field calculations and paired total routhian surface and cranked relativistic Hartree-Bogoliubov calculations. In 73Kr the three previously known structures have been extended to a spin of ~30[h-bar] and a fourth structure, which is believed to be the signature partner to the g9/2 band, has been identified. The negative parity bands show evidence for an unusual type of band crossing. It is currently unclear whether this is a consequence of T=0 n-p pairing. At the highest spins the unpaired calculations can reproduce the observed data, suggesting that there is little evidence for pairing correlations in this spin regime. In 72Kr a new band has been identified that has the properties expected from the missing doubly aligned S-band configuration. The properties of this band can be reproduced by the unpaired CNS/ CRMF calculations, again suggesting that the structure has little pairing. However, paired calculations appear to be necessary to reproduce the properties of the previously known structure in this nucleus. The 72Kr results are also compared with projected shell model calculations. ©2003 American Institute of Physics
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| 29. |
- Krebs, C. J., et al.
(författare)
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Terrestrial trophic dynamics in the Canadian Arctic
- 2003
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Ingår i: Canadian Journal of Zoology-Revue Canadienne De Zoologie. ; 81, s. 827-843
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Tidskriftsartikel (refereegranskat)abstract
- The Swedish Tundra Northwest Expedition of 1999 visited 17 sites throughout the Canadian Arctic. At 12 sites that were intensively sampled we estimated the standing crop of plants and the densities of herbivores and predators with an array of trapping, visual surveys, and faecal-pellet transects. We developed a trophic-balance model using ECOPATH to integrate these observations and determine the fate of primary and secondary production in these tundra ecosystems, which spanned an 8-fold range of standing crop of plants. We estimated that about 13% of net primary production was consumed by herbivores, while over 70% of small-herbivore production was estimated to flow to predators. Only 9% of large-herbivore production was consumed by predators. Organization of Canadian Arctic ecosystems appears to be more top-down than bottom-up. Net primary production does not seem to be herbivore-limited at any site. This is the first attempt to integrate trophic dynamics over the entire Canadian Arctic.
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| 30. |
- Leveque, P., et al.
(författare)
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Dose-rate influence on the defect production in MeV proton-implanted float-zone and epitaxial n-type silicon
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186, s. 375-379
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Tidskriftsartikel (refereegranskat)abstract
- The production of stable vacancy-related point defects in proton-implanted float-zone and epitaxial silicon has been studied in the low dose range ( less than or equal to 10(10)/cm(2)) as a function of dose-rate. The well-known inverse dose-rate effect has been observed in both types of materials with a decrease in the concentration of vacancy-related defects as the dose-rate increases. The effect is less pronounced in oxygen lean epitaxial silicon. Moreover, a continuous decrease of the vacancy-related defect concentration as a function of the flux was measured while a threshold was expected according to previous studies. Both or these results can be explained by a simple calculation, taking into account the influence of the oxygen concentration as well as the influence of the diffusion coefficient of point defects on the inverse dose-rate effect.
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| 31. |
- Leveque, P., et al.
(författare)
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Hydrogen-related defect centers in float-zone and epitaxial n-type proton implanted silicon
- 2001
-
Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 174:3, s. 297-303
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen-related defects in float zone (Fz) and epitaxial (Epi) n-type silicon crystals have been studied by means of deep level transient spectroscopy. These defects, as well as the characteristic vacancy-oxygen (VO) and divacancy (V-2) centers were introduced by proton implantation (1.3 MeV) using a dose of 1 x 10(10)/cm(2). A hydrogen-related defect level located at 0.45 eV below the conduction band edge (E-c) appears in both kind of samples. Another hydrogen-related defect appears predominantly in the Fz samples with a level at E-c - 0.32 eV. Depth profiling as well as annealing studies strongly suggest that the level at E-c - 0.45 eV is due to a complex involving hydrogen and V2 The level at E-c - 0.32 eV is strongly suppressed in the high purity Epi samples and the same holds for VO center. These results together with annealing data provide substantial evidence that the E-c - 0.32 eV level originates from a VO-center partly saturated with hydrogen (a VOH complex). Finally, in the Epi samples a new level at similar toE(c) - 0.31 eV is resolved, which exhibits a concentration Versus depth profile strongly confined to the damage peak region. The origin of this level is not known but the extremely narrow depth profile may indicate a higher-order defect of either vacancy or interstitial type,
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| 32. |
- Leveque, P., et al.
(författare)
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Identification of hydrogen related defects in proton implanted float-zone silicon
- 2003
-
Ingår i: European Physical Journal. - : EDP Sciences. - 1286-0042 .- 1286-0050. ; 23:1, s. 5-9
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogen related defects in high purity n-type float zone silicon samples have been studied by means of Deep Level Transient Spectroscopy. They were introduced, as well as the characteristic vacancy-oxygen (VO) and divacancy (V-2) centers, by MeV proton implantation. Two hydrogen related defect levels were resolved at 0.32 eV and 0.45 eV below the conduction band edge (E-c). Careful annealing studies indicate strongly that a third hydrogen related level, overlapping with the singly negative charge state level of V-2, is also present in the implanted samples. The annealing behavior of the hydrogen related defects has been compared with literature data leading to a rather firm identification. The E-c-0.32 eV level originates from a VO center partly saturated with hydrogen (a VOH complex) while the E-c-0.45 eV level may be ascribed to a complex involving a monovacancy and a hydrogen atom ( a VH complex). The third hydrogen related defect is tentatively ascribed to a complex involving a hydrogen atom and a divacancy ( a V2H complex).
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| 33. |
- Leveque, Patrick, et al.
(författare)
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Vacancy and interstitial depth profiles in ion-implanted silicon.
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:2, s. 871-877
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Tidskriftsartikel (refereegranskat)abstract
- An experimental method of studying shifts between concentration-versus-depth profiles of vacancy- and interstitial-type defects in ion-implanted silicon is demonstrated. The concept is based on deep level transient spectroscopy measurements utilizing the filling pulse variation technique. The vacancy profile, represented by the vacancy-oxygen center, and the interstitial profile, represented by the interstitial carbon-substitutional carbon pair, are obtained at the same sample temperature by varying the duration of the filling pulse. The effect of the capture in the Debye tail has been extensively studied and taken into account. Thus, the two profiles can be recorded with a high relative depth resolution. Using low doses, point defects have been introduced in lightly doped float zone n-type silicon by implantation with 6.8 MeV boron ions and 680 keV and 1.3 MeV protons at room temperature. The effect of the angle of ion incidence has also been investigated. For all implantation conditions the peak of the interstitial profile is displaced towards larger depths compared to that of the vacancy profile. The amplitude of this displacement increases as the width of the initial point defect distribution increases. This behavior is explained by a simple model where the preferential forward momentum of recoiling silicon atoms and the highly efficient direct recombination of primary point defects are taken into account.
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| 34. |
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| 35. |
- Lindstrom, J.L., et al.
(författare)
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Defect engineering in Czochralski silicon by electron irradiation at different temperatures
- 2002
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - 0168-583X .- 1872-9584. ; 186:1-4, s. 121-125
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Tidskriftsartikel (refereegranskat)abstract
- Infrared absorption studies of defect formation in Czochralski silicon irradiated with fast electrons in a wide range of temperatures (80-900 K) have been performed. The samples with different contents of oxygen (16O,18O) and carbon (12C,13C) isotopes were investigated. The main defect reactions are found to depend strongly on irradiation temperature and dose, as well as on impurity content and pre-history of the samples. Some new radiation-induced defects are revealed after irradiation at elevated temperatures as well as after a two-step (hot+room-temperature (RT)) irradiation. © 2002 Elsevier Science B.V. All rights reserved.
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| 36. |
- Lindstrom, J.L., et al.
(författare)
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Interaction between self-interstitials and the oxygen dimer in silicon
- 2001
-
Ingår i: Physica. B, Condensed matter. - 0921-4526 .- 1873-2135. ; 308-310, s. 284-289
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Tidskriftsartikel (refereegranskat)abstract
- Interactions between the oxygen dimer (O2i) and silicon self-interstitials (I) and vacancies (V) have been studied in Czochralski-grown silicon (Cz-Si) crystals using infrared absorption and deep level transient spectroscopies. The focus in this report is on reactions of O2i with I. The first step in this interaction is found to be the formation of a self-interstitial-dioxygen centre (IO2i) with oxygen-related local vibrational mode (LVM) bands at 922 and 1037 cm-1. During the second formation step, another centre, I2O2i, with LVM bands at 918 and 1034 cm-1 is suggested to appear. A Si-related band at about 545 cm-1 is also assigned to both the IO2i and I2O2i centres. The IO2i centre is found to be electrically active with an acceptor level at Ec - 0.11 eV. The both defects, IO2i and I2O2i, are stable at room temperature and anneal out at about 400 and 550 K, respectively. © 2001 Elsevier Science B.V. All rights reserved.
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| 37. |
- Lindström, Lennart, et al.
(författare)
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The VO2* defect in silicon
- 2003
-
Ingår i: Physica. B, Condensed matter. - : Elsevier BV. - 0921-4526 .- 1873-2135. ; 340-342, s. 509-513
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The vacancy-dioxygen complex (VO2) is one of the main defects formed in irradiated Cz-Si crystals upon annealing (or irradiation) in the temperature range 300-400°C. In this defect two oxygen atoms share a vacancy, each bonded to two silicon neighbors. Independent vibrations of these O atoms give rise to one infrared absorption band at 895.5 cm-1 at 10 K. We report on an experimentally discovered bistability of this defect. We suggest an alternative configuration, VO2*, where only one O atom is inside the vacancy while the second O atom is in a backbond position. Two vibrational bands, at 928.4 and 1003.8 cm-1 (positions at 15 K), are assigned to this configuration. © 2003 Elsevier B.V. All rights reserved.
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| 38. |
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| 39. |
- Monakhov, E., et al.
(författare)
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Boron-enhanced diffusion in excimer laser annealed Si
- 2004
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 114-15, s. 114-117
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Tidskriftsartikel (refereegranskat)abstract
- The effect of excimer laser annealing (ELA) and rapid thermal annealing (RTA) on B redistribution in B-implanted Si has been studied by secondary ion mass spectrometry (SIMS) and spreading resistance probe (SRP). B has been implanted with an energy of 1 keV and a dose of 10(16) cm(-2) forming a distribution with a width of 20-30nm and a peak concentration of similar to5 x 10(21) cm(-3). It has been found that ELA with 10 pulses of the energy density of 850 mJ/cm(2) results in a uniform B distribution over the ELA-molten region with an abrupt profile edge. SRP measurements demonstrate good activation of the implanted B after ELA, with the concentration of the activated fraction (similar to10(21) cm(-3)) exceeding the solid solubility level. RTA (30 s at 1100degreesC) of the as-implanted and ELA-treated samples leads to a diffusion of B with diffusivities exceeding the equilibrium one and the enhancement is similar for both of the samples. It is also found that RTA decreases the activated B in the ELA-treated sample to the solid solubility limit (2 x 10(20) cm(-3)). The similarity of the B diffusivity for the as-implanted and ELA-treated samples suggests that the enhancement of the B diffusivity is due to the so-called boron-enhanced diffusion (BED). Possible mechanisms of BED are discussed.
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| 40. |
- Monakhov, E. V., et al.
(författare)
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Formation of a double acceptor center during divacancy annealing in low-doped high-purity oxygenated Si
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:23
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Tidskriftsartikel (refereegranskat)abstract
- Deep-level transient spectroscopy studies of electronic defect levels in 7-MeV proton-irradiated n-type float-zone Si with a doping of (3-5)x10(12) cm(-3) and oxygen content of similar to10(16)-10(17) cm(-3) have been performed. The thermal stability of the irradiation-induced defects has been investigated for temperatures up to 400 degreesC. It has been found that annealing of the divacancy-related levels, the singly negative, V-2(0/-), and the doubly negative, V-2(-/=), charge states at 220-300 degreesC results in the formation of a new center with singly negative, X(0/-), and doubly negative, X(-/=), charge states. The new center anneals out at 325-350 degreesC during isochronal treatment for 15 min. The capture kinetics studies reveal that the electron capture cross section of X(0/-) is larger than that of V-2(0/-) while the capture cross section of X(-/=) is close to that of V-2(-/=). The transformation of V-2(0/-) and V-2(-/=) into X(0/-) and X(-/=) is very efficient with only a small loss in the peak amplitudes, and the position of the energy levels are close to those of V-2. Hence, it is tempting to suggest that the atomic configuration of the X center is closely related to that of V-2, and a possible identification of X may be the divacancy-oxygen center (V2O).
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| 41. |
- Monakhov, E. V., et al.
(författare)
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Laplace transform transient spectroscopy study of a divacancy-related double acceptor centre in Si
- 2003
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 15:39, s. S2771-S2777
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Tidskriftsartikel (refereegranskat)abstract
- Radiation-induced divacancy-related levels in high-purity oxygen-enriched n-type silicon have been studied with the use of deep level transient spectroscopy (DLTS) and Laplace-DLTS. It has been shown that heat treatment at 250degreesC results in a shift of the divacancy (V-2)-related peaks observed by 'standard' DLTS. Using Laplace-DLTS it is demonstrated that the shift is due to annealing of V-2 and formation of a new acceptor centre. The new centre has presumably two negative charge states: singly and doubly negative. The formation of the new centre holds a close one-to-one correlation with the annealing of V-2, indicating that the new centre is a result of divacancy interaction with an impurity or a defect. The close position of the electronic levels of the new centre to that of V-2 suggests a similar electronic and microscopic structure of the new centre to V-2, and a tentative identification is a divacancy-oxygen centre.
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| 42. |
- Moss, B, et al.
(författare)
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Continental-scale patterns of nutrient and fish effects on shallow lakes: synthesis of a pan-European mesocosm experiment
- 2004
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 49:12, s. 1633-1649
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Tidskriftsartikel (refereegranskat)abstract
- 1. Results are analysed from 11 experiments in which effects of fish addition and nutrient loading on shallow lakes were studied in mesocosms. The experiments, five in 1998, six in 1999, were carried out in six lakes, distributed from Finland to southern Spain, according to a standard protocol. 2. Effects of the treatments on 29 standard chemical, phytoplankton and zooplankton variables are examined to assess the relative importance of bottom-up (nutrient enrichment) and top-down (fish predation) effects. For each year, the experiments in different locations are treated as replicates in a meta-analysis. Results of individual experiments are then compared in terms of the patterns of significant influences of nutrient addition and fish predation with these overall results (the baseline), and between years in the same location. 3. The overall meta-analysis gave consistent results across the 2 years, with nutrient loading influencing all of the chemical variables, and on average 31% of primary producer and 39% of zooplankton variables. In contrast, fish influenced none of the chemical variables, 11% of the primary producer and 44% of the zooplankton variables. Nutrient effects on the system were thus about three times greater than fish effects, although fish effects were not inconsiderable. 4. The relative importance of nutrients and fish in individual experiments often differed between years at the same location and effects deviated to varying degrees from the baseline. These deviations were treated as measures of consistency (predictability) of conclusions in repeat experiments. Consistency increased southwards and this is interpreted as a consequence of more variable annual weather northwards. 5. The influence of nutrient loading was greater southwards and this was probably manifested through naturally greater annual macrophyte abundance in warmer locations in consequence of the longer plant growing-season. There was no trend in the relative importance of fish effects with latitude but this may partly be an artefact of the simple fish community used. These findings suggest that nutrient control should be a greater priority than biomanipulation in the restoration of eutrophicated shallow lakes in warm temperate regions. 6. Starting conditions affected the outcome of experiments. High initial concentrations of total phosphorus and planktonic chlorophyll a concentration (created by local conditions prior to the experiment) led to de-emphasis of the importance of nutrient loading in the experiment.
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| 43. |
- O'Leary, C. D., et al.
(författare)
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Evidence for isovector neutron-proton pairing from high-spin states in N = Z 74Rb
- 2003
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Ingår i: Physical Review C - Nuclear Physics. - 0556-2813. ; 67:2, s. 213011-213015
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states in the odd-odd N = Z nucleus 3774Rb37 were studied using the 40Ca(40Ca,αnp) reaction. A previously observed odd-spin T = 0 band has been extended to Iπ = (31+) and an even-spin T = 0 band has been observed for the first time to Iπ = (22+); both have a π(g9/2)⊗ν(g9/2) structure. A strongly coupled low-spin T = 0, K = 3 band has been interpreted as being based upon a π[312]3/2 ⊗ ν[312]3/2 configuration. Cranked relativistic Hartree-Bogoliubov calculations, which are corrected for the t = 1 np-pair field by restoring isospin symmetry, reproduce the observed spectrum. These new results provide evidence for the existence of an isovector pair field that contains a neutron-proton component with the proper strength for ensuring isospin conservation.
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| 44. |
- Ruseckas, A, et al.
(författare)
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Intra- and interchain luminescence in amorphous and semicrystalline films of phenyl-substituted polythiophene
- 2001
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Ingår i: JOURNAL OF PHYSICAL CHEMISTRY B. - : American Chemical Society (ACS). - 1089-5647 .- 1520-6106 .- 1520-5207. ; 105:32, s. 7624-7631
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Tidskriftsartikel (refereegranskat)abstract
- We report time-resolved photoluminescence (PL) measurements of spin-cast amorphous films of a regioregular polythiophene derivative poly[3-(4-octylphenyl)thiophene] and of annealed semicrystalline films of the same polymer with an interchain stacking distance of 5 Angstrom. Red-shifted PL appears at long delay times in both pristine and annealed films, which we assign to interchain aggregates populated by excitation energy migration. Aggregate luminescence in annealed films exhibits a pronounced vibronic structure indicating the coupling to a C=C bond stretch with a Huang-Rhys factor S = 2. Two types of aggregates are distinguished in annealed films: in a few picoseconds most excitations are trapped by aggregates with a large energy gap (about 1.83 eV) between the lowest excited singlet state and the ground state. Excitation energy is transferred or the aggregates relax structurally with a time constant of about 200 ps to aggregates with a smaller energy gap (about 1.75 eV). The radiative lifetime of aggregates with smaller energy gap is estimated to be about 35 ns, two times longer than that of aggregates with the larger energy gap. In spin-cast amorphous films, emission from intrachain singlet excitons has a longer lifetime than in annealed films and only high-energy-gap aggregates are populated.
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| 45. |
- Ruseckas, A, et al.
(författare)
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Ultrafast photogeneration of inter-chain charge pairs in polythiophene films
- 2000
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 322:1-2, s. 136-142
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Tidskriftsartikel (refereegranskat)abstract
- Photoexcitation dynamics in films of polythiophenes with different side groups were studied by transient absorption spectroscopy using 80 fs pulses. We show that inter-chain charge pairs (CP) are generated with similar to 20% efficiency in a polymer with short inter-chain distance (similar to 4 Angstrom) within 100 fs after photoexcitation. We discuss two mechanisms for inter-chain charge separation: (i) electron or hole transfer from an initially excited intra-chain singlet state or (ii) optical excitation of mixed exciton-charge transfer states, which quickly evolve to inter-chain CPs. (C) 2000 Elsevier Science B.V, All rights reserved.
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| 46. |
- Salek, Pawel, et al.
(författare)
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Dynamical suppression of atomic peaks in resonant dissociative photoemission
- 2001
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 343:3-4, s. 332-338
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Tidskriftsartikel (refereegranskat)abstract
- Resonant excitation to the F1s-sigma* dissociative state in hydrogen fluoride gives a photoelectron spectrum where the spectator part contains strong atomic lines but a participator part where such lines are lacking. We demonstrate that this contrasting behaviour between the two parts is due to a strong dynamical suppression of the resonant contribution, making direct main state photoionization the dominating channel even at resonant conditions.
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| 47. |
- Salek, P, et al.
(författare)
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Dynamical suppression of atomic peaks in resonant dissociative photoemission
- 2001
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Ingår i: CHEMICAL PHYSICS LETTERS. - : ELSEVIER SCIENCE BV. - 0009-2614. ; 343:3-4, s. 332-338 Language: English
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Tidskriftsartikel (refereegranskat)abstract
- Resonant excitation to the F1s-sigma* dissociative state in hydrogen fluoride gives a photoelectron spectrum where the spectator part contains strong atomic lines but a participator part where such lines are lacking. We demonstrate that this contrasting b
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| 48. |
- Salis, A, et al.
(författare)
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The atypical lipase B from Candida antarctica is better adapted for organic media than the typical lipase from Thermomyces lanuginosa.
- 2003
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Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics. - 1570-9639. ; 1646:1-2, s. 145-151
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Tidskriftsartikel (refereegranskat)abstract
- Candida antarctica lipase B (CALB) and Thermomyces lanuginosa lipase (TLL) were evaluated as catalysts in different reaction media using hydrolysis of tributyrin as model reaction. In o/w emulsions, the enzymes were used in the free form and for use in monophasic organic media, the lipases were adsorbed on porous polypropylene (Accurel EP-100). In monophasic organic media, the highest specific activity of both lipases was obtained in pure tributyrin at a water activity of >0.5 and at an enzyme loading of 10 mg/g support. With tributyrin emulsified in water, the specific activities were 2780 mol min−1 mg−1 for TLL and 535 mol min−1 mg−1 for CALB. Under optimal conditions in pure tributyrin, CALB expressed 49% of the activity in emulsion (264 mol min−1 mg−1) while TLL expressed only 9.2% (256 mol min−1 mg−1) of its activity in emulsion. This large decrease is probably due to the structure of TLL, which is a typical lipase with a large lid domain. Conversion between open and closed conformers of TLL involves large internal movements and catalysis probably requires more protein mobility in TLL than in CALB, which does not have a typical lid region. Furthermore, TLL lost more activity than CALB when the water activity was reduced below 0.5, which could be due to further reduction in protein mobility.
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| 49. |
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| 50. |
- Stepanauskas, R, et al.
(författare)
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Bioavailability and sources of DOC and DON in macrophyte stands of a tropical coastal lake
- 2000
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Ingår i: Hydrobiologia. - 0018-8158. ; 436:1-3, s. 241-248
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Tidskriftsartikel (refereegranskat)abstract
- Dissolved organic carbon (DOC) and nitrogen (DON) derived from aquatic and terrestrial vascular plants provide a major energy and nutrient source for freshwater and coastal marine biota. The bioavailability of this material may to a large extent depend on plant species. In this study, we have compared the bioavailability of DOC and DON sampled in two distinct stands of Typha domingensis and Eleocharis mutata in a coastal tropical lake and in the adjacent ocean in the state of Rio de Janeiro, Brazil. Bioavailability of organic matter was assessed by regrowth bioassays using natural bacterial inocula. Nutrients were added to achieve carbon or nitrogen limitation. At all sampling sites, DON comprised over 95% of the total bioavailable nitrogen, suggesting its dominant role as a nitrogen source. The bioavailability of lacustrine DON (22% in the Typha stand and 34% in the Eleocharis stand) exceeded the bioavailability of DOC (8 and 10%, respectively) and exhibited a larger difference between the stands. H-3-leucine incorporation studies showed that lake bacterioplankton had a well balanced supply of C, N and P. Therefore, an accumulation of labile DON due to an excess nitrogen supply is not probable. We propose that a substantial part of the lake DON was newly formed within the macrophyte stands, while DOC was predominantly of terrestrial origin and more diagenetically changed.
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