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- Rozengurt, E., et al.
(författare)
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Signal transduction in mitogenesis : further evidence for multiple pathways
- 1988
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Ingår i: Cold Spring Harbor Symposia on Quantitative Biology. - : Cold Spring Harbor Laboratory Press (CSHL). - 0091-7451 .- 1943-4456. ; 53, s. 945-954
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Tidskriftsartikel (refereegranskat)abstract
- This extract was created in the absence of an abstract.ExcerptGrowth factors are implicated in a wide variety of physiological and pathological processes, including embryogenesis, hematopoiesis, wound healing, immune responses, atherosclerosis, and neoplasis (Evered et al. 1985; Sporn and Roberts 1986). An important link between growth factors and their receptors and oncogene products has also been established (Heldin and Westermark 1984; Weinstein 1987). Thus, the elucidation of the mechanism of action of growth factors has emerged as one of the fundamental problems in biology and may prove crucial for understanding the unrestrained proliferation of cancer cells.Many studis of growth factors have used cultured fibroblasts, such as 3T3 cells, as a model system. These cells cease to proliferate when they deplete the medium of its growth-promoting activity. Such quiescent cells can be stimulated to reinitiate DNA synthesis and cell division either by replenishing the medium with fresh serum or by the addition of growth factors or pharmacological agents in serum-free...
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| 5. |
- Bovin, JO, et al.
(författare)
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Imaging of atomic clouds outside the surfaces of gold crystals by electron microscopy
- 1985
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 317, s. 47-49
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Tidskriftsartikel (refereegranskat)abstract
- The structure of small metal crystals has been intensively examined by high-resolution electron microscopy (HREM). In particular, multiply-twinned gold and silver crystals have been characterized using the profile-imaging method1,2 at atomic resolution, and reconstructed metal surfaces observed2. Crystal structure images of large gold clusters consisting of 55 gold atoms arranged in a cubeoctahedron have been recorded3 using 2.5 Å resolution, and crystal growth, row by row, on a {111} surface has been documented4 using a low-light-level silicon-intensified target television (TV) camera and video system with an on-line image processor. Direct imaging of rearrangements of atomic columns on extended gold surface5 established that profile imaging can provide information about surface self-diffusion. The motion of surface atoms, recorded with a real-time video tape-recorder (VTR) system, and the formation of surface atom steps on {100} surfaces, although not {111}, has also been reported recently6. Dynamic HREM observations at TV rate showing defect motion in gold7 and CdTe (refs. 8, 9) has given information on ‘in-lattice’ rearrangements of columns of atoms. We report here surface profile images recorded with the electron beam along the 〈110〉 direction with spatial resolution of ∼2.0 Å which reveal changes in occupancy of the atom columns often within periods of less than 0.1 s. Surfaces with several adjacent atom columns involved in rapid structural changes frequently interacted with a cloud of atoms extending out to 9 Å off the crystal and changes in shape and density of the clouds were recorded. Although these clouds have already been described6,10, the present work is the first to analyse these events properly and to describe them in detail. The motion of atomic columns and the existence of atom clouds revealed here may have important consequences for crystal growth, surface science and catalysis studies.
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| 6. |
- Li, C-H., et al.
(författare)
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A lattice resolution study of the martensitic transformation of small iron particles in a copper matrix
- 1985
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Ingår i: Acta Metallurgica. - : Elsevier BV. - 0001-6160. ; 33:2, s. 317-328
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Tidskriftsartikel (refereegranskat)abstract
- The martensitic transformation of small, fully coherent, gamma iron precipitates in an epsilon copper matrix, brought about by the bombardment of thin foils with argon ions, has been studied using lattice fringe imaging. It is found, in general, that only partial transformation of individual particles occurs, this corresponding to a simple homogeneous shear (a Bain strain). In addition, the transformation is limited to particles located within about two particle diameters of the foil surface. It is established that the mere presence of a Frank (or Shockley) loop in a particle, due to the bombardment, is insufficient to trigger the transformation. The implications of this result are discussed with reference to bulk martensite. In the present case, it is concluded that transformation may simply initiate at sites of local decohesion or microslip at the matrix/particle boundaries brought about by vacancy condensation following ion bombardment, these sites being most effective in the vicinity of free surfaces
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| 8. |
- Petfordlong, Amanda K., et al.
(författare)
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On the growth of small crystals of Cd, Zn, Pt and Rh during electron microscope observations
- 1987
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Ingår i: Journal of Crystal Growth. - : Elsevier BV. - 0022-0248. ; 80:2, s. 218-224
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Tidskriftsartikel (refereegranskat)abstract
- The growth of small supported metal crystals under the influence of an electron beam has been studied in real-time using a 400 keV ultra-high-resolution electron microscope. Samples of Pt, Rh, Cd and Zn supported on amorphous C or Si films were prepared ex situ and crystal growth in situ was recorded directly using a TV imaging/video system attached to the microscope. The different types of observed crystal growth are reported: the fcc metals (Pt and Rh) grow by coalescence, or by the addition of atoms along the particle surface followed by structural rearrangements which result in approximately spherical particles. The hcp metals (Cd and Zn) grow in the form of long rafts along the surface of the substrate film.
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| 10. |
- Wallenberg, LR, et al.
(författare)
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Atomic-resolution study of structural rearrangements in small platinum crystals
- 1986
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Ingår i: Ultramicroscopy. - : Elsevier BV. - 0304-3991. ; 20:1-2, s. 71-75
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Tidskriftsartikel (refereegranskat)abstract
- Structural rearrangements in small Pt crystals, which were initiated by the incident electron beam, have been studied in real time with a 400 kV high-resolution electron microscope equipped with TV image viewing and videorecording facilities. The phenomena of crystal growth, particle coalescence and atomic clouds above particular surfaces were recorded at the atomic level and have been analysed using frame-by-frame playback facilities.
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