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- Svensson, Ulrika S H, et al.
(författare)
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Artemisinin induces omeprazole metabolism in human beings
- 1998
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Ingår i: Clinical Pharmacology and Therapeutics. - 0009-9236 .- 1532-6535. ; 64, s. 160-
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Tidskriftsartikel (refereegranskat)abstract
- Objective: This study investigated whether time-dependent artemisinin pharmacokinetics correlated to CYP3A4 or CYP2C19 activity in vivo. Methods: Artemisinin (two oral doses per day of 250 mg) was given to nine healthy Vietnamese subjects for 7 days (day 1 to day 7), Single 20 mg doses of omeprazole were given orally on day -7, day 1, and day 7, Single doses of artemisinin and omeprazole were given in combination on day 14 after a 6-day washout period. The pharmacokinetics of artemisinin, omeprazole, hydroxyomeprazole, and omeprazole sulfone were evaluated on days -7, 1, 7, and 14, On the same days urine was collected for the determination of 6 beta-hydroxycortisol and cortisol excretion. Results: Areas under plasma concentration-time curves (AUC) for artemisinin and omeprazole decreased on day 7 to 20% (95% confidence intervals, 13%, 28%) and 35% (25%, 46%), respectively, compared with values on day 1, AUC ratios for hydroxyomeprazole/omeprazole increased 2.2-fold (1,7, 2.7) on day 7 compared with values on day 1, Al values were normalized at day 14, There were no significant changes in the omeprazole sulfone/omeprazole ratio or in the 6 beta-hydroxycortisol/cortisol ratio between the study days. In one subject found to have poor CYP2C19 metabolization, the elimination of omeprazole increased after artemisinin exposure, with no change in the hydroxyomeprazole/omeprazole AUC ratio. Conclusion: Artemisinin did not alter CYP3A4 activity, whereas an increase in CYP2C19 activity was observed. The increased elimination of omeprazole in both poor and extensive CYP2C19 metabolizers suggests artemisinin induces both CYP2C19 and another enzyme.
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| 8. |
- Doyle, J. P., et al.
(författare)
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Electrically active point defects in n-type 4H–SiC
- 1998
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 84:3, s. 61-68
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Tidskriftsartikel (refereegranskat)abstract
- An electrically active defect has been observed at a level position of ∼ 0.70 eV below the conduction band edge (Ec) with an extrapolated capture cross section of ∼ 5×10−14 cm2 in epitaxial layers of 4H–SiC grown by vapor phase epitaxy with a concentration of approximately 1×1013 cm−3. Secondary ion mass spectrometry revealed no evidence of the transition metals Ti, V, and Cr. Furthermore, after electron irradiation with 2 MeV electrons, the 0.70 eV level is not observed to increase in concentration although three new levels are observed at approximately 0.32, 0.62, and 0.68 eV below Ec with extrapolated capture cross sections of 4×10−14, 4×10−14, and 5×10−15 cm2, respectively. However, the defects causing these levels are unstable and decay after a period of time at room temperature, resulting in the formation of the 0.70 eV level. Our results suggest strongly that the 0.70 eV level originates from a defect of intrinsic nature. The unstable behavior of the electron irradiation-induced defects at room temperature has not been observed in the 6H–SiC polytype.
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- Achtziger, N, et al.
(författare)
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Hydrogen passivation of silicon carbide by low-energy ion implantation
- 1998
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 73, s. 945-947
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Tidskriftsartikel (refereegranskat)abstract
- implantation of deuterium is performed to investigate the mobility and passivating effect of hydrogen in epitaxial alpha-SiC (polytypes 4H and 6H). To avoid excessive damage and the resulting trapping of hydrogen, the implantation is performed with low energy (600 eV H-2(2)+). The H-2 depth profile is analyzed by secondary ion mass spectrometry. Electrical properties are measured by capacitance-voltage profiling and admittance spectroscopy. In p-type SIG, hydrogen diffuses on a mu m scale even at room temperature and effectively passivates accepters. In n-type SiC, the incorporation of H is suppressed and no passivation is detected. (C) 1998 American Institute of Physics.
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| 15. |
- Achtziger, N, et al.
(författare)
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Mobility passivating effect and thermal stability of hydrogen in silicon carbide
- 1998
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Ingår i: Physica status solidi. B, Basic research. - 0370-1972 .- 1521-3951. ; 210, s. 395-399
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Tidskriftsartikel (refereegranskat)abstract
- The diffusion and passivating effect of hydrogen (isotope H-2) in epitaxial p-type SiC is studied by secondary ion mass spectrometry and capacitance-voltage profiling on Schottky diodes. The incorporation of hydrogen is achieved by low-energy ion implantation. The influence of implantation energy, temperature and subsequent annealing is presented. Annealing experiments with an electric field applied reveal a reactivation of passivated accepters and a H+ ion drift at a surprisingly low temperature of 530 K.
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| 17. |
- Andersson, T., et al.
(författare)
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High-spin States in the A=39 Mirror Nuclei 39Ca and 39K
- 1999
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Ingår i: European Physical Journal A. Hadrons and Nuclei. - 1434-6001. ; 6, s. 5-8
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Tidskriftsartikel (refereegranskat)abstract
- High-spin states of the mass A = 39 mirror pair K-39 and Ca-39 were investigated via the fusion-evaporation reaction Si-28+O-16 at 125 MeV beam energy. The GAMMASPHERE array in conjunction with the 4 pi charged-particle detector array MICROBALL and neutron detectors was used to detect gamma rays in coincidence with evaporated light particles. The results of the first high-spin study of the T-z = -1/2 nucleus Ca-39 are discussed in terms of mirror symmetry and compared to spherical shell-model calculations in the 1d(3/2)-1f(7/2) configuration space.
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| 19. |
- Athas, W., et al.
(författare)
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AC-1: a clock-powered microprocessor
- 1997
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Ingår i: Proc of 1997 International Symposium on Low Power Electronics and Design. ; , s. 328-333
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Konferensbidrag (refereegranskat)
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| 21. |
- Björk-Eriksson, Thomas, 1960, et al.
(författare)
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The immunohistochemical expression of DNA-PKCS and Ku (p70/p80) in head and neck cancers: relationships with radiosensitivity
- 1999
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Ingår i: Int J Radiat Oncol Biol Phys. - 0360-3016. ; 45:4, s. 1005-10
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: The DNA-PK complex is one of the major pathways by which mammalian cells respond to DNA double-strand breaks induced by ionizing radiation. This study evaluated the relationship between the immunohistochemical expression of the individual components of DNA-PK and cellular radiosensitivity in head and neck cancers. METHODS AND MATERIALS: Biopsies from patients with previously untreated squamous cell carcinomas of the head and neck were assessed for inherent tumor radiosensitivity measured as the surviving fraction at 2 Gy (SF2) using a soft agar clonogenic assay. Paraffin-embedded tumor material from 64 successfully grown specimens was immunohistochemically stained for expression of DNA-PKcs and Ku (p70/p80). The same tumor material was previously analyzed for the immunohistochemical expression of p53. RESULTS: A significant correlation was found between the degree of expression of DNA-PKcs and Ku (p70/p80) (r = 0.55, p<0.001). There were no overall significant differences in the levels of expression of DNA-PKcs and Ku (p70/p80) in tumors from patients of either sex, different sites, histologies, and stages. No relationship was found between SF2 and the expression of either DNA-PKcs (r = 0.22, p = 0.081) or Ku (p70/p80) (r = 0.064, p = 0.62). Comparison with previous immunohistochemical characterization showed no significant correlations between the expression levels of p53 and either DNA-PKcs (r = 0.093, p = 0.46) or Ku (p70/p80) (r = -0.17, p = 0.17). CONCLUSIONS: This study suggests that determining the immunohistochemical expression of DNA-PK in head and neck cancers from multiple sites does not have a role as a predictive assay of tumor in vitro radiosensitivity.
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| 22. |
- Björk-Eriksson, Thomas, 1960, et al.
(författare)
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The lack of correlation between proliferation (Ki-67, PCNA, LI, Tpot), p53 expression and radiosensitivity for head and neck cancers
- 1999
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Ingår i: Br J Cancer. - 0007-0920. ; 80:9, s. 1400-4
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Tidskriftsartikel (refereegranskat)abstract
- A study was made of the relationship between measurements of radiosensitivity versus proliferation and p53 status in head and neck cancers. Inherent tumour radiosensitivity was assessed as surviving fraction at 2 Gy (SF2) using a clonogenic soft agar assay (n = 77). The results were compared to data on proliferation obtained by both flow cytometry (labelling index (LI), the potential doubling time (Tpot) n = 55) and immunohistochemistry (Ki-67 and PCNA; n = 68), together with immunohistochemical p53 expression (n = 68). There were no overall significant differences in the median values of the various parameters analysed for the different sites within the head and neck region, disease stages, grades of tumour differentiation or nodal states. A subgroup analysis showed that oropharyngeal (n = 22) versus oral cavity (n = 35) tumours were more radiosensitive (P = 0.056) and had a higher Ki-67 index (P = 0.001). Node-positive tumours had higher LI (P = 0.021) and a trend towards lower Tpot (P = 0.067) values than node-negative ones. No correlations were seen between SF2 and any of the parameters studied. The long-standing dogma of an increased radiosensitivity of rapidly proliferating cells in contrast to slowly proliferating cells was not confirmed. The study shows that parallel measurements of different biological markers can be obtained for a large number of patients with head and neck cancers. The independence of the various parameters studied suggests that there may be potential for their combined use as prognostic factors for the outcome of radiotherapy.
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| 25. |
- Doyle, J P, et al.
(författare)
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Observation of near-surface electrically active defects in n-type 6H-SiC
- 1998
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 83, s. 3649-3651
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Tidskriftsartikel (refereegranskat)abstract
- In n-type 6H-SiC epitaxial layers grown by vapor phase epitaxy, we find that in contrast to the majority of the epitaxial layer, where electrically active defects are observed with a concentration less than 1 X 10(-13) cm(-3), a region near the front surface contains defects with concentrations approaching 10(14) cm(-3). A relationship between the near-surface defects and metallic impurities is suggested by a Ti concentration of 1 X 10(16) cm(-3) in this region. The high concentration of near surface defects is found to significantly reduce the carrier lifetime. (C) 1998 American Institute of Physics. [S0021-8979(98)03007-2].
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| 38. |
- Lalita, J, et al.
(författare)
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Defect evolution in MeV ion-implanted silicon
- 1996
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Ingår i: NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS. - : ELSEVIER SCIENCE BV. - 0168-583X. ; 120:1-4, s. 27-32
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Lightly doped silicon samples of both n- and p-type, have been implanted with low doses of H, B and Si ions using energies between 1 and 6 MeV. The resulting electrically active point defects were characterized by deep level transient spectroscopy (DLTS)
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| 41. |
- Linnarsson, M K, et al.
(författare)
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Deuterium incorporation in acceptor doped epitaxial layers of 6H-SiC
- 1998
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Ingår i: SILICON CARBIDE, III-NITRIDES AND RELATED MATERIALS, PTS 1 AND 2. ; , s. 761-764
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Konferensbidrag (refereegranskat)abstract
- Deuterium is introduced in boron doped epitaxial layers of 6H-SiC by implantation of 30 keV H-2(+) ions in order to form a diffusion source. The samples were subsequently annealed in vacuum at 700 degrees C/16h, 800 degrees C/4h and 900 degrees C/4h. Using depth profiling by secondary ion mass spectrometry (SIMS), the distributions of deuterium at different levels of boron doping are studied. The deuterium concentration correlates with the boron concentration and at a level of similar to 10(18) cm(-3) a ratio H-2/B-11 larger than 0.5 is obtained. From capacitance-voltage (CV) measurements a decrease in the electrical carrier concentration by 50% is revealed after deuterium diffusion at 800 degrees C/4h. At 900 degrees C passivation of the boron accepters ceases but the H-2 atoms are still confined to the boron-doped regions and display no long range migration.
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| 42. |
- Linnarsson, M K, et al.
(författare)
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Diffusion of light elements in 4H-and 6H-SiC
- 1999
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Ingår i: Materials Science & Engineering. - 0921-5107 .- 1873-4944. ; 61-2, s. 275-280
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Tidskriftsartikel (refereegranskat)abstract
- Deuterium and lithium were introduced in p-type SiC by implantation of 20 keV H-2(+) or 30 keV Li-7(+) ions in order to form a diffusion source. The samples were subsequently annealed in vacuum in the temperature range 400-700 degrees C for 0.25 to 16 h. Secondary ion mass spectrometry (SIMS) was used to measure the deuterium and the lithium distribution after heat treatments. Both deuterium and lithium readily decorate the bombardment-induced defects in the vicinity of the ion implantation profile and they are also trapped, most likely by residual boron impurities, during diffusion into the bulk. An effective diffusion coefficient, reflecting the dissociation of trapped lithium, with an activation energy of 2.1 eV is extracted for lithium diffusion in p-type 6H SIG. Furthermore, a capture radius for trapping (most likely by boron) of deuterium is estimated as 10 Angstrom. (C) 1999 Elsevier Science S.A. All rights reserved.
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| 43. |
- Lynoe, N, et al.
(författare)
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Doctors' attitudes towards empirical data--a comparative study
- 1997
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Ingår i: Scandinavian journal of social medicine. - : SAGE Publications. - 0300-8037. ; 25:3, s. 210-216
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Tidskriftsartikel (refereegranskat)abstract
- In the assessment of the effects of medical technologies, the focus is most often on the quality of the empirical data. In order to shed light on the question whether medical researchers are really so empirically oriented we conducted the following study. 600 questionnaires were sent by mail to three groups, selected at random: 1) preclinical researchers; 2) clinical researchers who received research grants from The Swedish Medical Research Council; and 3) general practitioners. The questionnaire was built around three cases concerning the assessment of the effects of: a) H-2-receptor antagonists, b) coronary by-pass surgery and c) the homeopathic treatment of hay fever. The results indicate that there are rather small differences in how the three groups assessed the three technologies and larger differences within one and the same group concerning different cases. The tendency is that the more one considers that empirical data should be assessed independent of theoretical considerations, the higher are the demands which are placed on the quality and quantity of the empirical documentation, and vice-versa.
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| 45. |
- Mihara, K, et al.
(författare)
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Stereospecific analysis of omeprazole supports artemisinin as a potent inducer of CYP2C19
- 1999
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Ingår i: Fundamental & Clinical Pharmacology. - 0767-3981 .- 1472-8206. ; 13:6, s. 671-675
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to determine the enantiomer pharmacokinetics of omeprazole and 5-hydroxy-omeprazole before and after administration of the antimalarial artemisinin to confirm artemisinin's ability to induce CYP2C19. Nine healthy male Vietnamese subjects were given a single 20 mg dose of omeprazole orally 1 week before (day -7) artemisinin administration. Artemisinin was then given orally (500 mg) for 7 days (days 1-7). On days 1 and 7, a single 20 mg dose of omeprazole was coadministered with artemisinin. After a washout period of 6 days, a single 20 mg dose of omeprazole was again administered together with a single 500 mg of artemisinin (day 14). Stereoselective pharmacokinetics of omeprazole and 5-hydroxyomeprazole was determined on days of omeprazole administration. Seven days of artemisinin administration significantly decreased the AUC of both omeprazole enantiomers (day 7), compared with day 1 (P < 0.001). All values were normalized after the washout period. Artemisinin increased the AUC ratio of R-5-hydroxyomeprazole/R-omeprazole significantly (P < 0.01) on day 7. The AUC ratio of omeprazole sulphone/S-omeprazole did not differ between study days. Artemisinin decreased the AUC of S-omeprazole to the same extent as that of R-omeprazole in extensive CYP2C19 metabolizers, suggesting that artemisinin induces a different enzyme in addition to CYP2C19. These results support and strengthen earlier findings that artemisinin induces CYP2C19 as well as at least one enzyme other than CYP3A4.
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| 48. |
- Sorensen, SL, et al.
(författare)
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Site-selective participator decay of core-excited butadiene
- 1996
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Ingår i: JOURNAL OF CHEMICAL PHYSICS. - 0021-9606. ; 105:24, s. 10719-10724
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The decay of core-excited electronic states in free 1,3 trans butadiene molecules has been studied using high-resolution synchrotron radiation and electron spectrometry. The core-level energy Shift between the terminal and central carbon atoms is 0.64 eV
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