| 1. |
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| 2. |
- Yeom, HW, et al.
(författare)
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Hydrogen-induced 3×1 phase of the Si-rich 3C-SiC(001) surface
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 61:4, s. R2417-R2420
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Tidskriftsartikel (refereegranskat)abstract
- A single-domain 3×1 phase induced by hydrogen adsorption on a Si-rich 3C-SiC(001)3×2 surface is investigated by photoemission using synchrotron radiation. Three surface components of the Si 2p core level are identified for the 3×1-H phase, which resemble those of the 3×2 surface. A H-Si bonding state is observed by angle-resolved valence-band photoemission. These results are consistent with the recent assignments of the Si 2p surface components and the valence band spectra of the 3×2 surface, based on the 3×2 structure model with 2/3 ML Si addimers. A straightforward 3×1-H structure model is introduced featuring Si dimer-bond breaking and dangling-bond saturation.
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| 3. |
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| 4. |
- Buckley, Patrick G, et al.
(författare)
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A full-coverage, high-resolution human chromosome 22 genomic microarrayfor clinical and research applications
- 2002
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Ingår i: Human Molecular Genetics. - : Oxford University Press (OUP). - 0964-6906 .- 1460-2083. ; 11:25, s. 3221-3229
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Tidskriftsartikel (refereegranskat)abstract
- We have constructed the first comprehensive microarray representing a human chromosome for analysis of DNA copy number variation. This chromosome 22 array covers 34.7 Mb, representing 1.1% of the genome, with an average resolution of 75 kb. To demonstrate the utility of the array, we have applied it to profile acral melanoma, dermatofibrosarcoma, DiGeorge syndrome and neurofibromatosis 2. We accurately diagnosed homozygous/heterozygous deletions, amplifications/gains, IGLV/IGLC locus instability, and breakpoints of an imbalanced translocation. We further identified the 14-3-3 eta isoform as a candidate tumor suppressor in glioblastoma. Two significant methodological advances in array construction were also developed and validated. These include a strictly sequence defined, repeat-free, and non-redundant strategy for array preparation. This approach allows an increase in array resolution and analysis of any locus; disregarding common repeats, genomic clone availability and sequence redundancy. In addition, we report that the application of phi29 DNA polymerase is advantageous in microarray preparation. A broad spectrum of issues in medical research and diagnostics can be approached using the array. This well annotated and gene-rich autosome contains numerous uncharacterized disease genes. It is therefore crucial to associate these genes to specific 22q-related conditions and this array will be instrumental towards this goal. Furthermore, comprehensive epigenetic profiling of 22q-located genes and high-resolution analysis of replication timing across the entire chromosome can be studied using our array.
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| 5. |
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| 6. |
- Ford, Caroline, et al.
(författare)
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Progression from normal breast pathology to breast cancer is associated with increasing prevalence of mouse mammary tumor virus-like sequences in men and women
- 2004
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Ingår i: Cancer Research. - 1538-7445. ; 64:14, s. 4755-4759
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Tidskriftsartikel (refereegranskat)abstract
- Mouse mammary tumor virus (MMTV)-like sequences have been found in up to 40% of breast cancer samples but in <2% of normal breast tissue samples from Australian women studied by our group. Screening of a larger and more diverse cohort of female breast cancer samples has now shown a correlation of MMTV-like sequences with the severity (grade) of breast cancer. Thirty-two percent (43 of 136) of female breast cancer samples were positive for MMTV-like sequences when screened using PCR. A significant gradient of MMTV positivity was observed with increasing severity of cancer from 23% of infiltrating ductal carcinoma (IDC) grade I tumors to 34% of IDC grade II tumors (P = 0.00034) and 38% of IDC grade III tumors (P = 0.00002). We also report for the first time the detection of MMTV-like sequences in 62% (8 of 13) of male breast cancer samples and 19% (10 of 52) of male gynecomastia samples screened. MMTV-like sequences were demonstrated in various premalignant breast lesions of females, including fibroadenoma (20%) and fibrocystic disease (28%) samples, at a significantly higher prevalence than that seen in normal breast tissue (1.8%; P = 0.00001). Study of a longitudinal cohort of female breast cancer patients indicated that MMTV was co-incident with tumor but was not present when tumor was absent on histology. These results support the association of MMTV-like sequences with development of breast tumors in men and women and suggest association of MMTV with increasing severity of cancer.
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| 7. |
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| 8. |
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| 9. |
- Gleisner, M., et al.
(författare)
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Comparison of sulfide oxidation in unweathered pyretic mine tailings
- 2003
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Ingår i: Proc. ICARD 2003, 6th Int. Conf. on Acid Rock Drainage, Cairns, Australia, July 14 – 17, 2003. ; , s. 1027-1030
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Konferensbidrag (refereegranskat)abstract
- The study focuses on sulfide oxidation processes in unweathered pyrite-rich mine tailings from a soil-covered impoundment in northern Sweden. To simulate the oxygen-limited conditions in water saturated tailings two long-term column experiments were performed. Results are presented for the first 11 months of the experiments at room temperature. The tailings used in the experiments were of two different grain sizes (one coarse grained, in the range 0.02 - 0.6 mm with a grain surface area of 1.86 m2 g-1, and one fine-grained, in the range 0.0015 - 0.06 mm with a grain surface area of 10.00 m2 g-1) and with slightly different mineralogical composition. The S:Fe molar ratio in the leachates (1.0 - 1.5) indicates either that pyrrhotite is the main iron sulfide undergoing oxidation in our experiments, or, alternatively that the S:Fe molar ratio in the leachate is determined by pyrite weathering in conjunction with other processes releasing iron or immobilising sulfate. However, speciation modelling of the leachates indicates that ferrihydrite was close to saturation, suggesting that a ferric oxyhydroxide may have dissolved/ precipitated during the experimental period, thereby affecting the S:Fe molar ratio. Pyrite oxidation rates obtained from the two column experiments during ‘steady-state’ were 2.25 × 10-13 and 8.45 × 10-14 mol m-2 s-1 in the coarse and fine tailings, respectively. Pyrrhotite oxidation rates, as an alternative, were 2.31 × 10-12 and 1.24 × 10-11 mol m-2 s-1 in the coarse and fine tailings, respectively. Natural microbial activity was confirmed in both the tailings and the leachates; therefore, the obtained oxidation rates are not strictly abiotic. It is thus concluded, based on the experimental results, that tailing heterogeneity will result in zones with different oxidation rates, related to their physical and chemical properties.
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| 10. |
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| 11. |
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| 12. |
- Grenklo, Staffan, et al.
(författare)
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A crucial role for profilin-actin in the intracellular motility of Listeria monocytogenes
- 2003
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Ingår i: EMBO reports. - London : Nature Publishing Group. - 1469-221X .- 1469-3178. ; 4:5, s. 523-529
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Tidskriftsartikel (refereegranskat)abstract
- We have examined the effect of covalently crosslinked profilin–actin (PxA), which closely matches the biochemical properties of ordinary profilin–actin and interferes with actin polymerization in vitro and in vivo, on Listeria monocytogenes motility. PxA caused a marked reduction in bacterial motility, which was accompanied by the detachment of bacterial tails. The effect of PxA was dependent on its binding to proline-rich sequences, as shown by the inability of PH133SxA, which cannot interact with such sequences, to impair Listeria motility. PxA did not alter the motility of a Listeria mutant that is unable to recruit Ena (Enabled)/VASP (vasodilator-stimulated phosphoprotein) proteins and profilin to its surface. Finally, PxA did not block the initiation of actin-tail formation, indicating that profilin–actin is only required for the elongation of actin filaments at the bacterial surface. Our findings provide further evidence that profilin–actin is important for actin-based processes, and show that it has a key function in Listeria motility.
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| 13. |
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| 14. |
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| 15. |
- Herbert, Roger B, et al.
(författare)
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Solid phase iron : sulfur geochemistry of a reactive barrier for treatment of mine drainage
- 2000
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Ingår i: Applied Geochemistry. - 0883-2927 .- 1872-9134. ; 15:9, s. 1331-1343
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the solid phase Fe-S geochemistry of a reactive barrier at the Nickel Rim mine site (Ontario, Canada). The barrier, designed to treat groundwater contaminated by acid mine drainage, is composed of leaf and municipal compost and wood chips. This study shows that S is accumulating in the organic material as primarily acid volatile sulfides, at concentrations up to 195 mu mol S g(-1) d.w. (0.63 wt% S) in a zone of preferential flow. Pyrite and/or S-0 account for only a small fraction of the total reduced inorganic S, as oxidants are probably present at only low concentrations in the barrier system. The results of the solid phase analyses, the formation of disordered mackinawite (Fe1-xS) on piezometer tubing, and thermodynamic calculations indicate that the precipitation of poorly crystalline Fe monosulfides is the primary sink for Fe and S in the barrier. Siderite (FeCO3) formation is proposed as an additional Fe sink in areas of high Fe flux. Minor accumulations of acid-soluble, organically-bound S in the reactive barrier occur in zones of low aqueous Fe concentration. After 23 months of operation, the average rate of S accumulation at the up-gradient edge of the barrier is calculated to be 87 mu mol S g(-1) a(-1) (d.w. organic material), or 47 mol S m(-2) a(-1) in the direction of groundwater flow. Solid phase analyses from samples collected 3 and 14 months after installation indicate that the S accumulation rate declined by a factor of 3 over that time period.
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| 16. |
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| 17. |
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| 18. |
- Jansson, Roger, et al.
(författare)
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Optical and microstructural characterization of thin films of photochromic fulgides
- 2001
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Ingår i: Journal of Physics and Chemistry of Solids. - 0022-3697 .- 1879-2553. ; 62:7, s. 1219-1228
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Tidskriftsartikel (refereegranskat)abstract
- Variable angle spectroscopic ellipsometry has been used for determining the optical properties, in terms of the complex dielectric function in the near UV-VIS-near IR spectral range, and the thicknesses of thin fulgide films of type E-a-(2,5-dimethyl-3-furyl)-ethylidene(adamantylidene)succinic anhydride and (E)-2-[a-(2,5-dimethyl-3-thienyl)ethylidene]-3-isopropylidenesuccinic anhydride. The films had thicknesses in the range 28-40 nm and were spin coated onto silicon substrates. To simultaneously extract film thicknesses and optical properties of the films, several methods of analysis were employed in order to decrease correlation between the fitting parameters in the optical model of the structure. In agreement with previous absorbance measurements done by others on similar materials in liquid or solid form, it was found that the fulgides studied have several resonances in the wavelength region below 400 nm and that new resonances appear in the middle of the visible region upon UV exposure. The ellipsometric analysis, as well as atomic force microscopy studies, showed that the films were very smooth with a root mean square surface roughness <0.4 nm and that a small thickness change of the film takes place upon UV exposure. Furthermore, AFM studies revealed that large phase changes take place when the samples are stored in darkness for several days, indicating that the materials are not stable in thin film form. © 2001 Elsevier Science Ltd.
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| 19. |
- Jemander, S.T., et al.
(författare)
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STM study of the C-induced Si(100)-c(4×4) reconstruction
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Sociaty. - 1098-0121 .- 1550-235X. ; 65:11, s. 115321-
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Tidskriftsartikel (refereegranskat)abstract
- We report a direct and reliable way to produce the Si(100)-c(4×4) reconstruction by submonolayer deposition from a SiC source and subsequent annealing. Auger electron spectroscopy, low-energy electron diffraction, and scanning tunneling microscopy (STM) investigations reveal that a C amount equivalent to 0.07 monolayers (ML’s) is sufficient to obtain full coverage of the c(4×4) reconstruction. A deposition of 0.035 ML’s C produces a c(4×4) coverage of only 19%, indicating that C is not only present in the c(4×4) areas, but also in the 2×1 areas. There is not enough C to make it a regular part of the c(4×4) reconstruction and we therefore conclude that the c(4×4) reconstruction is strain induced. We find that a combination of the mixed ad-dimer and buckled ad-dimer models explains all main features observed in the STM images. Images of freshly prepared c(4×4) surfaces exhibit a decoration of approximately 50% of the unit cells, which is attributed to perpendicular ad-dimers. Long exposures (>20 h) to the UHV background gas quench these features and the c(4×4) reconstruction appears as if more homogeneous.
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| 20. |
- Jemander, S.T., et al.
(författare)
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STM study of the surface defects of the (v3×v3)-Sn/Si(1 1 1) surface
- 2001
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Ingår i: Surface Science. - : Elsevier. - 0039-6028 .- 1879-2758. ; 475:1-3, s. 181-193
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Tidskriftsartikel (refereegranskat)abstract
- The (v3×v3)-Sn/Si(1 1 1) surface has been studied with scanning tunneling microscopy (STM) and Auger electron spectroscopy, and it is found that it contains basically five different types of defects originating from substitutional atoms and vacancies. The influence the defects have on their immediate neighbourhood is investigated and found to extend to the third nearest (v3×v3) adatom neighbour. Close to some defect constellations, a very local (3×3) periodicity in the apparent height in the STM images is found. This periodicity is shown to be a linear superposition of the perturbations generated by the individual defects in the constellations. The superposition of the height modulation is accurate and linear for a wide range of tip biases, as for combinations of different types of defects. Its linearity is explained in terms of small perturbations in the surface electronic structure. We also provide an explanation why the linearity breaks down when large perturbations are probed with small tip biases.
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| 21. |
- Jemander, S.T., et al.
(författare)
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Surface structure of Si(100) with submonolayer coverages of C
- 2002
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Elsevier. - 1073-5615 .- 1543-1916. ; 89:1-3, s. 415-419
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Konferensbidrag (refereegranskat)abstract
- We report a combined STM, LEED and AES study of Si(100) surfaces prepared by coevaporation from two MBE-sources with Si and SiC, respectively. The flux from the SiC source contains 10% C, enabling studies of deposited layers with C-concentrations in the range 0-10%. After room temperature deposition, the structures have been annealed at 600 °C to generate a c(4 × 4) reconstruction. This has previously been reported to contain from 0.0 to 0.5 monolayers (ML) of C. Annealing at 800 °C irreversibly transforms the c(4 × 4) surface to a 2 × 1-reconstructed surface that contains precipitates of SiC. Since only 0.07 ML of C is needed to have 98% of the surface covered with the c(4 × 4) reconstruction, we conclude that the c(4 × 4) reconstruction is impurity-induced rather than having C-atoms in well defined positions within each unit cell. The c(4 × 4) reconstruction is attributed to a basic structure containing buckled parallel ad-dimers, which in approximately 50% of the reconstructed unit cells is decorated with perpendicular dimers. © 2002 Elsevier Science B.V. All rights reserved.
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| 22. |
- Jormalainen, V, et al.
(författare)
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Dynamics of intersexual conflict over precopulatory mate guarding in two populations of the isopod Idotea baltica
- 2000
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Ingår i: Animal Behaviour. - : Elsevier BV. - 1095-8282 .- 0003-3472. ; 60:1, s. 85-93
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Tidskriftsartikel (refereegranskat)abstract
- Aggressiveness during intersexual conflicts is predicted to depend on its costs, the value of winning and the power asymmetry of the contestants, all of which may vary between populations. In the marine isopod Idotea baltica (Pallas) a conflict occurs as females resist the attempts by males to start precopulatory mate guarding. We analysed contest dynamics with respect to female maturity stage, that is, to time left to reproductive moult, with which the payoffs of guarding for males and females change, We did this in two populations that differ in synchrony of reproduction, sex ratio and the degree of sexual dimorphism. The intensity and dynamics of contests differed between populations: in the more size-dimorphic population, females, the smaller sex, resisted less by forceful flexing but more by hooking their body than in the other population. Male aggressiveness stayed at a constant level with respect to female maturity. In the less size-dimorphic population, female resistance by flexing was intense and it decreased, while male persistence increased, with the approaching reproductive moult. Contests were more intense with small than with large males. These results fit well with the predictions from models of conflict behaviour. Assessment of the payoffs of winning versus contest costs, coadaptation of the level of aggressiveness to the other traits affecting contest outcome, and counteradaptations by the sexes to each other largely explain the dynamics and between-population differences of these contests. (C) 2000 The Association for the Study of Animal Behaviour.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Michael, Eli, et al.
(författare)
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Hubble Space Telescope Observations of High-Velocity Lyα and Hα Emission from Supernova Remnant 1987A : The Structure and Development of the Reverse Shock
- 2003
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 593, s. 809-830
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Tidskriftsartikel (refereegranskat)abstract
- We present two-dimensional line profiles of high-velocity (~+/-12,000 km s-1) Lyα and Hα emission from supernova remnant 1987A obtained with the Space Telescope Imaging Spectrograph between 1997 September and 2001 September (days 3869-5327 after the explosion). This emission comes from hydrogen in the debris that is excited and ionized as it passes through the remnant's reverse shock. We use these profiles to measure the geometry and development of the reverse-shock surface. The observed emission is confined within ~+/-30° about the remnant's equatorial plane. At the equator, the reverse shock has a radius of ~75% of the distance to the equatorial ring. We detect marginal differences (6%+/-3%) between the location of the reverse-shock front in the northeast and southwest parts of the remnant. The radius of the reverse shock surface increases for latitudes above the equator, a geometry consistent with a model in which the supernova debris expands into a bipolar nebula. Assuming that the outer supernova debris has a power-law density distribution, we can infer from the reverse-shock emission light curve an expansion rate (in the northeast part of the remnant) of 3700+/-900kms-1, consistent with the expansion velocities determined from observations in radio (Manchester et al.) and X-ray (Park et al.; Michael et al.) wavelengths. However, our most recent observation (at day 5327) suggests that the rate of increase of mass flux across the northeast sector of the reverse shock has accelerated, perhaps because of deceleration of the reverse shock caused by the arrival of a reflected shock created when the blast wave struck the inner ring. Resonant scattering within the supernova debris causes Lyα photons created at the reverse shock to be directed preferentially outward, resulting in a factor of ~5 difference in the observed brightness of the reverse shock in Lyα between the near and far sides of the remnant. Accounting for this effect, we compare the observed reverse-shock Lyα and Hα fluxes to infer the amount of interstellar extinction by dust as E(B-V)=0.17+/-0.01 mag. We also notice extinction by dust in the equatorial ring with E(B-V)~0.02-0.08 mag, which implies dust-to-gas ratios similar to that of the LMC. Since Hα photons are optically thin to scattering, the observed asymmetry in brightness of Hα from the near and far sides of the remnant represents a real asymmetry in the mass flux through the reverse shock of ~30%. We discuss future observational strategies that will permit us to further investigate the reverse-shock dynamics and resonant scattering of the Lyα line and to constrain better the extinction by dust within and in front of the remnant.
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| 27. |
- Oura, M, et al.
(författare)
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Correlative multielectron processes in K-shell photoionization of Ca, Ti and V in the energy range of 8-35 keV
- 2002
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Ingår i: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075. ; 35:18, s. 3847-3863
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Tidskriftsartikel (refereegranskat)abstract
- The Kalpha satellite spectra arising from the correlative multielectron processes accompanying K-shell photoionization of Ca, Ti and V were measured using a broad range crystal spectrometer. Multiconfiguration Dirac-Fock calculations were performed to interpret the observed,x-ray energies and the spectral line shape., The calculations agree fairly well with the experimental results. The variation of the KalphaL(1) satellite and the Kalpha(1,2)(h) hypersatellite intensities was measured as a function, of excitation energy in the range of 8-35 keV. The KalphaL(1)/Kalpha(1,2) intensity ratio for each,element is already saturated in our energy range, and the asymptotic values of 1.58 +/- 0.08, 1.26 +/- 0.06 and 0.97 +/- 0.05% for Ca, Ti. and V were determined. By combining the present results and the previously measured values for various elements, we have found a Z(-3.5) scaling law for the KalphaL(1)/Kalpha(1,2) intensity ratio, The measured Kalpha(1,2)(h)/Kalpha(1,2) for each element, is found to increase smoothly from its onset and shows a long saturation range extending up to at least 25 keV above the threshold for Ti. The evolution of the Kalpha(1,2)(h)/Kalpha(1,2) intensity ratio is compared with the analytic Thomas model and with the theoretical calculation based on the screened hydrogenic model.
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| 28. |
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| 29. |
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| 30. |
- Sakamoto, Kazuyuki, et al.
(författare)
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Bias-dependent scanning tunneling microscopy study of the oxygen-adsorbed Si(111)-(7×7) surface : Observation of metastable molecular oxygen
- 2002
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 65:15, s. 155305-
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Tidskriftsartikel (refereegranskat)abstract
- We have observed the initial stage of oxygen adsorption on a Si(111)-(7×7) surface using scanning tunneling microscopy. Among the bright sites observed after exposing the surface to oxygen in occupied state images, there are differences in the bias dependence of the brightness. Taking into account the local density of states of the oxygen-adsorbed Si(111)-(7×7) surface, we conclude that the sites appearing brightly only with a tip bias of >~+2.1 V are the molecular oxygen. The preferred adsorption site of this molecular species is a corner adatom, which has an oxygen atom adsorbed into its backbond, of the faulted half of the (7×7) unit cell.
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| 31. |
- Sakamoto, K., et al.
(författare)
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Interaction of metastable molecular oxygen with the dangling bonds of a Si(111)-(7×7) surface
- 2001
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - 0368-2048 .- 1873-2526. ; 114-116, s. 489-494
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the interaction between metastable molecular oxygen and the adatom dangling bonds modified by the adsorption of atomic oxygen into the back-bonds of a Si(111)-(7×7) surface. Ultraviolet photoelectron spectroscopy shows that the metastable states increase in intensity faster but with a decrease in its saturated intensity as the coverage of atomic oxygen increases. This result suggests that the number of modified dangling bonds is not the only important factor for the adsorption process of metastable oxygen. Taking into account the observation of modified dangling bonds with different density of states in scanning tunneling microscopy, we conclude that the adsorption of the metastable oxygen species correlates closely with the density of states of the dangling bond.
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| 32. |
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| 33. |
- Sollerman, Jesper, et al.
(författare)
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Observations of the Crab Nebula and Its Pulsar in the Far-Ultraviolet and in the Optical
- 2000
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 537, s. 861-874
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Tidskriftsartikel (refereegranskat)abstract
- We present far-UV observations of the Crab Nebula and its pulsar made with the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope. Broad, blueshifted absorption arising in the nebula is seen in C IV λ1550, reaching a blueward velocity of ~2500 km s-1. This can be interpreted as evidence for a fast outer shell surrounding the Crab Nebula, and we adopt a spherically symmetric model to constrain the properties of such a shell. From the line profile we find that the density appears to decrease outward in the shell. A likely lower limit to the shell mass is ~0.3 Msolar with an accompanying kinetic energy of ~1.5×1049 ergs. A fast massive shell with 1051 ergs cannot be excluded but is less likely if the density profile is much steeper than ρ(R)~R-4 and the maximum velocity is <~6000 km s-1. The observations cover the region 1140-1720 Å, which is further into the ultraviolet than has previously been obtained for the pulsar. With the time-tag mode of the spectrograph we obtain the pulse profile in this spectral regime. The profile is similar to that previously obtained by us in the near-UV, although the primary peak is marginally narrower. Together with the near-UV data, and new optical data from the Nordic Optical Telescope, our spectrum of the Crab pulsar covers the entire region from 1140 to 9250 Å. Dereddening the spectrum with a standard extinction curve we achieve a flat spectrum for the reddening parameters E(B-V)=0.52, R=3.1. This dereddened spectrum of the Crab pulsar can be fitted by a power law with spectral index αν=0.11+/-0.04. The main uncertainty in determining the spectral index is the amount and characteristics of the interstellar reddening, and we have investigated the dependence of αν on E(B-V) and R. In the extended emission covered by our 25''×0.5" slit in the far-UV, we detect C IV λ1550 and He II λ1640 emission lines from the Crab Nebula. Several interstellar absorption lines are detected along the line of sight to the pulsar. The Lyα absorption indicates a column density of (3.0+/-0.5)×1021 cm-2 of neutral hydrogen, which agrees well with our estimate of E(B-V)=0.52 mag. Other lines show no evidence of severe depletion of metals in atomic gas. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc. under NASA contract NAS5-26555.
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| 34. |
- Uhrberg, Roger, et al.
(författare)
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Electronic structure of Sn/Si(111) √3×√3 : Indications of a low-temperature phase
- 2000
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 62:12, s. 8082-8086
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Tidskriftsartikel (refereegranskat)abstract
- The Sn/Si(111) √3×√3 surface has been studied by photoelectron spectroscopy, low-energy electron diffraction (LEED), and scanning tunneling microscopy. Unlike Sn/Ge(111), the Sn/Si(111) surface shows a √3×√3 LEED pattern at low temperature also (70 K). The electronic structure, however, is inconsistent with a pure √3×√3 phase. Sn 4d spectra exhibit two major components and the valence band shows two surface bands. These features have been associated with the low-temperature 3×3 phase in the case of Sn/Ge(111). The similarity in the electronic structure points to stabilization of a low-temperature phase for Sn/Si(111) also, but at a significantly lower temperature (<70 K).
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| 35. |
- Ullman, Gustav, et al.
(författare)
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On the extent of quantum noise limitation in digital chest radiography
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim for this work was to study to what extent the detection of nodules is quantum noise limited, based on the combined results from a nodule-detection clinical trial and a Monte Carlo computational model of a digital chest imaging system. The Monte Carlo computer program computes measures of physical image quality such as image contrast, C and signalto-noise ratio, SNR for nodules of any size. A computed radiography (CR) imaging system used simulated. The patient anterior-posterior thickness was 25 cm and nodules with diameters between 1-40 mm were included. The image contrast and SNR was calculated for 1600 (40x40) positions in the chest image and averaged over five anatomical regions of interest (lateral pulmonary, retrocardial, hilar, lower- and upper mediastinal regions). Threshold contrasts for each region, Cth, corresponding to Az=0.80 for detecting a 10 mm nodule, were deduced from the clinical trial. A threshold is also used for the quantum noise signal-to-noise ratio, SNRth. The model computes the diameter of a disk-shaped object that is required to comply with the two criteria: SNR≥SNRth and C≥Cth. A system is said to be quantum noise limited when the nodule size required to fulfil both criteria is not limited by the contrast but by the SNR. The required nodule diameter is largest in the hilar region (25 mm) and smallest in the lateral pulmonary region (11 mm). When the threshold SNRth=25 is used, the lower mediastinal region is quantum noise limited already at low speed classes (S>100). The hilar region is never quantum noise limited at realistic speed classes (S<1000). The accuracy of this model will be tested in the future by more sophisticated modelling of anatomical background and noise in the SNR-expression.
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| 36. |
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| 37. |
- Zhang, Hanmin, et al.
(författare)
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Origin of 3 × 3 diffraction on the Sn1-xSix/Si(1 1 1) v3 × v3 surface
- 2003
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Ingår i: Surface Science. - 0039-6028 .- 1879-2758. ; 531:1, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- An evolution of an apparent 3 × 3 low-energy electron diffraction (LEED) pattern has been observed for the Sn1-xSix/Si(1 1 1) v3 × v3 surface alloy. The origin of this additional diffraction has been investigated in detail by scanning tunneling microscopy (STM). The 3 × 3 diffraction, which appears after annealing, is associated with the arrangement of the Sn and substitutional Si atoms in the surface layer, forming many local structures such as honeycombs, hexagons, and atomic lines. As revealed by Fourier-transforms of the STM-images, these local structures are the origins of the 3 × 3 diffraction and a weak 23×3 streaky background superposed on the 3 × 3 LEED pattern. © 2003 Elsevier Science B.V. All rights reserved.
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- Öberg, Åke, 1954-, et al.
(författare)
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Different occurrence of CD8+, CD45R0+, and CD68+ immune cells in regional lymph node metastases from colorectal cancer as potential prognostic predictors
- 2002
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Ingår i: International Journal of Colorectal Disease. - : Springer. - 0179-1958 .- 1432-1262. ; 17:1, s. 25-29
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND AIMS: To study whether there are differences in the immunohistochemical staining of CD8, CD45R0, and CD68 of immune cells in regional lymph node metastases from colorectal cancer that are of potential interest in prognostic prediction.MATERIALS AND METHODS: Analysis of archival specimens from 93 patients operated on for colorectal cancer (based on monoclonal antibodies, the ABC technique, and semiquantitative classification).RESULTS: There was a significant difference in survival time between patients with respect to the number of positive immune cells. The cancer-specific 5-year survival rate was 77% for patients with high numbers of CD8+ cells, compared to 33% for those with lower numbers. The corresponding figures for patients with CD45R0+ cells were 66% vs. 33%, and for patients with CD68+ cells 60% vs. 38%. Significant differences remained among the 74 patients without adjuvant radio/chemotherapy regarding CD8 and CD45R0 but not CD68.CONCLUSION: The presence of CD8+, CD45R0+, and CD68+ immune cells in regional lymph node metastases may serve as predictors of patients survival in colorectal cancer Dukes' stage C.
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