| 31. |
- Nowak, A, et al.
(författare)
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New excitation scheme of Cs-139
- 1999
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Ingår i: EUROPEAN PHYSICAL JOURNAL A. - : SPRINGER VERLAG. - 1434-6001. ; 6:1, s. 1-3
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Tidskriftsartikel (refereegranskat)abstract
- Excited levels in Cs-139: populated in spontaneous fission of Cm-248, have been studied by means of prompt gamma spectroscopy, using the EUROGAMM 2 array. New level scheme of Cs-139, different from the one proposed recently, has been established. To confi
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| 32. |
- Riesbeck, Kristian, et al.
(författare)
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Human tissue factor pathway inhibitor fused to CD4 binds both FXa and TF/FVIIa at the cell surface
- 1997
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Ingår i: Thrombosis and Haemostasis. - 0340-6245. ; 78:6, s. 1488-1494
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Tidskriftsartikel (refereegranskat)abstract
- Tissue factor pathway inhibitor (TFPI) is one of the main regulators of the tissue factor (TF) pathway of coagulation. To tether human TFPI to the cell surface, full length or truncated TFPI lacking the third Kunitz domain were fused with domains three and four and the carboxy-terminal sequence of human CD4. Constructs were transfected into a mouse fibroblast cell line and individual clones were checked for expression using monoclonal antibodies directed against the first two TFPI Kunitz domains and against CD4. Specific human FXa binding was detected by flow cytometry using an anti-FX polyclonal antibody, and inhibition of FXa proteolytic activity was verified by chromogenic substrate assay using S-2765. In addition, TFPI-CD4-expressing cells, preincubated with FXa, specifically bound human TF-FVIIa complexes as revealed with an anti-human TF polyclonal antibody. No functional difference was observed between full length or truncated TFPI-CD4. These results demonstrate that functionally intact TFPI can be tethered to the cell surface. Genetic manipulation of, for example, endothelial cells leading to the stable expression of TFPI may inhibit the development of coronary artery heart disease following cardiac allotransplantation, and may inhibit thrombosis in the context of xenotransplantation.
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| 33. |
- Sitch, P.K., et al.
(författare)
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An ab initio study of the 90° partial dislocation core in diamond
- 1997
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Ingår i: Journal de Physique III. - : EDP Sciences. - 1155-4320 .- 1286-4897. ; 7:7, s. 1381-1387
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Tidskriftsartikel (refereegranskat)abstract
- The electronic and structural properties of the 90° glide partial dislocation in diamond are investigated using an ab initio local density functional cluster method. The core C-C bond is found to be reconstructed with a bond length 5% longer than that in bulk diamond. The formation and migration energy of the kink on the dislocation are calculated to be 0.32 and 2.97 eV respectively. Further, the shift of the gap levels during kink motion suggests that p-type doping will lead to an increase in the mobility of the partial.
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| 34. |
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| 35. |
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| 36. |
- Stich, P. K., et al.
(författare)
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Ab initio investigation of the dislocation structure and activation energy for dislocation motion in silicon carbide
- 1995
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 52:7, s. 4951-4955
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Tidskriftsartikel (refereegranskat)abstract
- The structures of straight 90° glide partial dislocations in SiC are calculated using an ab initio local density functional cluster method. Si partials containing core Si atoms are found to be strongly reconstructed with a Si-Si bond of comparable length to that in bulk silicon. The C partial possessing core C atoms is more weakly reconstructed with a bond length 16% longer than that in bulk diamond. The formation and migration energies of kinks on the partials are calculated and indicate that the C partial is the more mobile. The calculations also predict that n-type doping leads to an increase in the mobility of C partials whereas p-type doping increases the mobility of Si partials.
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| 37. |
- Vatnitsky, S, et al.
(författare)
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Proton dosimetry intercomparison
- 1996
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Ingår i: Radiotherapy and Oncology. - 0167-8140 .- 1879-0887. ; 41:2, s. 169-77
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND PURPOSE: Methods for determining absorbed dose in clinical proton beams are based on dosimetry protocols provided by the AAPM and the ECHED. Both groups recommend the use of air-filled ionization chambers calibrated in terms of exposure or air kerma in a 60Co beam when a calorimeter or Faraday cup dosimeter is not available. The set of input data used in the AAPM and the ECHED protocols, especially proton stopping powers and w-value is different. In order to verify inter-institutional uniformity of proton beam calibration, the AAPM and the ECHED recommend periodic dosimetry intercomparisons. In this paper we report the results of an international proton dosimetry intercomparison which was held at Loma Linda University Medical Center. The goal of the intercomparison was two-fold: first, to estimate the consistency of absorbed dose delivered to patients among the participating facilities, and second, to evaluate the differences in absorbed dose determination due to differences in 60Co-based ionization chamber calibration protocols.MATERIALS AND METHODS: Thirteen institutions participated in an international proton dosimetry intercomparison. The measurements were performed in a 15-cm square field at a depth of 10 cm in both an unmodulated beam (nominal accelerator energy of 250 MeV) and a 6-cm modulated beam (nominal accelerator energy of 155 MeV), and also in a circular field of diameter 2.6 cm at a depth of 1.14 cm in a beam with 2.4 cm modulation (nominal accelerator energy of 100 MeV).RESULTS: The results of the intercomparison have shown that using ionization chambers with 60Co calibration factors traceable to standard laboratories, and institution-specific conversion factors and dose protocols, the absorbed dose specified to the patient would fall within 3% of the mean value. A single measurement using an ionization chamber with a proton chamber factor determined with a Faraday cup calibration differed from the mean by 8%.CONCLUSION: The adoption of a single ionization chamber dosimetry protocol and uniform conversion factors will establish agreement on proton absorbed dose to approximately 1.5%, consistent with that which has been observed in high-energy photon and electron dosimetry.
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| 38. |
- Wohlfarth, B., et al.
(författare)
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Early Holocene environment on Bjørnøya (Svalbard) inferred from multidisciplinary lake sediment studies.
- 1995
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Ingår i: Polar Research. - : Norwegian Polar Institute. - 0800-0395 .- 1751-8369. ; 14:2, s. 253-275
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Tidskriftsartikel (refereegranskat)abstract
- Bjornoya, a small (178 km(2)) island situated between the mainland of Norway and southern Spitsbergen, provides the opportunity for the reconstruction of early Holocene terrestrial and limnic palaeoenvironments in the southwestern Barents Sea. The AMS C-14 dating technique, geochemical, mineral magnetic, micro- and macrofossil analyses were applied to sediments recovered from lake Stevatnet and the results are interpreted in terms of palaeoenvironmental conditions between 9800 and 8300 C-14 BP. After the disappearance of local glaciers before ca 9800 C-14 BP, the lake productivity increased rapidly at the same time as pioneer plant communities developed on soils which gradually became more stable. Insect data indicates that strong seasonal contrasts with mean July temperatures around 9 degrees C and mean January temperatures around -12 degrees C prevailed between 9500 and 8300 C-14 BP. These high summer temperatures, possibly as much as 4-5 degrees C higher than the present, favoured the development of a flora including Dryas and Angelica cf. archangelica. The enhanced freeze/thaw processes led to an increased erosion of minerogenic and organic material. After 8000 C-14 BP the temperatures may have gradually declined. The environmental reconstruction derived from our data set supports the conceptual insolation model which proposes maximum Holocene seasonality for the Northern Hemisphere at ca 9000 C-14 BP.
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| 39. |
- Öberg, Sven, et al.
(författare)
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First-principles calculations of the energy barrier to dislocation motion in Si and GaAs
- 1995
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 51:19, s. 13138-13145
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Tidskriftsartikel (refereegranskat)abstract
- The single kink formation and migration energies Fk and Wm of 90° glide partial dislocations in Si and GaAs are calculated using an ab initio local density-functional cluster method. Kink migration occurs via a concerted exchange of an atom at a dislocation core with one of its glide plane nearest neighbors. By constraining these atoms to sit in high-energy positions and relaxing a surrounding cluster of atoms, sufficient points in configuration space can be sampled for the energy barrier for the first step in kink pair formation to be estimated. By including an estimate of the elastic energy of the interaction of kink pairs, the single kink formation energy is calculated. It is found that Fk and Wm for Si are 0.1 and 1.8 eV, respectively. For the 90° α glide partial in GaAs, these quantities are 0.07 and 0.7 eV, respectively, and 0.3 and 1.1 eV for β partials
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| 40. |
- Öberg, Sven, et al.
(författare)
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First stage of oxygen aggregation in silicon : the oxygen dimer
- 1998
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 81:14, s. 2930-2933
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Tidskriftsartikel (refereegranskat)abstract
- The structure and dynamic properties of the interstitial oxygen dimer in silicon are found using a combination of infrared spectroscopy and ab initio modeling. We find that the stable dimer consists of a pair of inequivalent weakly coupled interstitial oxygen atoms separated by a Si-Si bond. Two high frequency modes are decoupled in one 16O-18O combination but are strongly mixed in the other combination. A third lower lying mode involves the compression of the Si-Si bond joining the oxygen atoms and gives distinct modes in the mixed 16O-18O case.
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