| 1. |
- Dou, S.X., et al.
(författare)
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Microstructure and flux pinning in superconducting Bi-Pb-Sr-Ca-Cu-O wires
- 1990
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Ingår i: Physica. C, Superconductivity. - 0921-4534 .- 1873-2143. ; 172:1-2, s. 63-70
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Tidskriftsartikel (refereegranskat)abstract
- The critical current density (Jc) of Ag-clad Bi-Pb-Sr-Ca-Cu-O wire has been measured to be 1.2×104 A/cm2 at 77 K in zero field. The high Jc is attributed to a combination of elimination of the poisoning effect of Ag on superconductivity, grain alignment, and enhancement of flux pinning. Jc-H dependence was significantly improved in the Ag-clad tape, which has a Jc of 1.0×103 A /cm2 at 77 K and 4000 Oe, while the Jc of the sintered pellet drops two orders of magnitude at only 100 Oe. A pronounced anisotropy in Jc under high magnetic field is attributed to the grain alignment. Planar defects, such as heavy stacking faults parallel to the a-b plane in the rolled tape, are considered to be effective pinning centres.
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| 2. |
- Kulatilake, P.H.S.W., et al.
(författare)
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Use of the distinct element method to perform stress analysis in rock with non-persistent joints and to study the effect of joint geometry parameters on the strength and deformability of rock masses
- 1992
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Ingår i: Rock Mechanics and Rock Engineering. - 0723-2632 .- 1434-453X. ; 25:4, s. 253-274
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Tidskriftsartikel (refereegranskat)abstract
- To use the distinct element method, it is necessary to discretize the problem domain into polygons in two dimensions (2 D) or into polyhedra in three dimensions (3 D). To perform distinct element stress analysis in a rock mass which contains non-persistent finite size joints, it is necessary to generate some type of fictitious joints so that when they are combined with the non-persistent joints, they discretize the problem domain into polygons in 2 D or into polyhedra in 3 D. The question arises as to which deformation and strength parameter values should be assigned to these fictitious joints so that they behave as intact rock. In this paper, linear elastic, perfectly-plastic constitutive models with the Mohr-Coulomb failure criterion, including a tension cut-off, were used to represent the mechanical behaviour of both intact rock and fictitious joints. It was found that, by choosing the parameter values for the constitutive models as given below, it is possible to make the fictitious joints behave as intact rock, in a global sense
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| 3. |
- Wang, J-H, et al.
(författare)
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Dynamic contact angles and contact angle hysteresis of plasma polymers
- 1994
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 10, s. 3887-3897
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Tidskriftsartikel (refereegranskat)abstract
- Dynamic advancing and receding contact angles and the contact angle hysteresis for different plasma polymers deposited on microscope cover glasses were investigated by the Wilhelmy plate method. The hysteresis loops observed by this dynamic method show two major factors: (1) the meniscus change at the transition region; (2) the wettability change of solid surfaces. The first factor is due to the fact that three-phase contact line does not move in the transition region while the water level is forced to rise up or lower down. The second factor is due to the change of surface state of the solid. Moreover, this factor can be related to the Fstep change» at the buoyancy slope of a hysteresis loop when the wetting line is moved from a "prewetted» area to a adry" area of the same sample and also to the gap between the first and second immersion loops. Both factors are caused by the interaction forces between solid surface and water molecules at the solid/liquid interface . Plasma polymer of the tetrafluoroethylene (TFE) showed the largest hysteresis loop primarily due to the significant change of surface state after water immersion. Plasma polymer of hexamethyldisiloxane (HMDSO) showed the smallest hysteresis loop due to the minimal change in the surface state after water immersion. Water contact angles of plasma polymers were clearly dependent on plasma conditions manifested by the discharge energy density.
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| 4. |
- Wang, Y, et al.
(författare)
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Functional homology between N-myc and c-myc in murine plasmacytomagenesis : plasmacytoma development in N-myc transgenic mice
- 1992
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Ingår i: Oncogene. - 0950-9232. ; 7:6, s. 7-1241
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Tidskriftsartikel (refereegranskat)abstract
- Mouse plasmacytomas induced by pristane oil alone, or in combination with Abelson murine leukemia virus (A-MuLV), regularly carry one of three alternative chromosomal translocations that juxtapose c-myc to immunoglobulin heavy- or light-chain loci. E mu-c-myc transgenic mice develop translocation-free plasmacytomas after induction by pristane oil and/or A-MuLV [Sugiyama, H., Silva, S., Wang, Y., Weber, G., Babonits, M., Rosen, A., Wiener, F. & Klein, G. (1990). Int. J. Cancer, 46, 845-852]. In order to test whether another member of the myc family, N-myc, could play a similar role as c-myc, we treated E mu-N-myc transgenic mice with pristane and helper-free A-MuLV. Of 20 mice that received a single pristane injection followed by A-MuLV, 17 developed plasmacytomas with a mean latency period of 54 +/- 20 days. In a corresponding group that only received a single pristane injection, five out of six transgenic mice developed plasmacytomas with a mean latency period of 142 +/- 32 days. However, after three monthly injections of pristane, all 15 transgenic mice developed plasmacytomas with a mean latency period of 128 +/- 20 days. All plasmacytomas expressed the N-myc transgene, while none of them expressed either c-myc or endogenous N-myc. None of the tumors carried the usual plasmacytoma-associated translocations.
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| 5. |
- Axelson, H, et al.
(författare)
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Juxtaposition of N-myc and Ig kappa through a reciprocal t(6;12) translocation in a mouse plasmacytoma
- 1994
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Ingår i: Genes, Chromosomes and Cancer. - 1045-2257. ; 11:2, s. 85-90
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Tidskriftsartikel (refereegranskat)abstract
- Nearly all mouse plasmacytomas (MPCs) carry an Ig/myc translocation. Any one of the three Ig loci may participate, while the myc contribution has been limited to c-myc, excluding other members of the myc gene family. The same is true for the other two known Ig/myc translocation-carrying tumors, Burkitt's lymphoma and rat immunocytoma. It is believed that the Ig/myc juxtaposition plays a decisive, rate limiting role in the genesis of the three tumors, acting through the constitutive activation of myc that makes it refractory to normal regulation. Here we describe the molecular analysis of a unique t(6;12)(CI;B) translocation that we previously identified in an exceptional MPC that expressed N-myc but not c-myc. We now show that the translocation led to the juxtaposition of N-myc and Ig kappa. This is the first case of an Ig/myc-carrying tumor that involves N-myc rather than c-myc. These findings suggest that the translocation may already have occurred at the pro- or pre-B cell stage at which N-myc is open for transcription. According to this interpretation, constitutive activation of N-myc would suppress the expression of c-myc, but would not interfere with the differentiation of the pro-B cell into a fully mature plasma cell. Its tumorigenic influence would become manifest only at the time when the cell would normally be programmed to leave the cycling compartment, in connection with its terminal differentiation.
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| 6. |
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| 7. |
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| 8. |
- Hsu, D. S., et al.
(författare)
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FLOW LINEAR DICHROISM AND ELECTRON-MICROSCOPIC ANALYSIS OF PROTEIN-DNA COMPLEXES OF A MUTANT UVRB PROTEIN THAT BINDS TO BUT CANNOT KINK DNA
- 1994
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Ingår i: Journal of Molecular Biology. - : Elsevier BV. - 0022-2836 .- 1089-8638. ; 241:5, s. 645-650
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Tidskriftsartikel (refereegranskat)abstract
- (A)BC excinuclease of Escherichia coli is the enzymatic activity resulting from sequential and partially overlapping actions of UvrA, UvrB, and UvrC protein. UvrA is a molecular matchmaker which promotes the formation of a stable UvrB-damaged DNA complex in which the DNA is kinked by about 130 degrees. The UvrB-DNA complex is then recognized by UvrC) and two incisions are made in the DNA by the joint actions of UvrC and UvrB. A mutant of UvrB (D478A) can be loaded onto the DNA but it does not interact with UvrC to cause a nick 3' to the lesion. Based on the lack of a DNase-I-hypersensitive site in the footprint of the mutant, it was proposed that the lack of incision was due to the inability of the mutant UvrB to kink the DNA. In the current study we have investigated the interaction of the mutant UvrB with DNA using two biophysical methods, flow linear dichroism and electron microscopy. Both methods reveal that the mutant UvrB is unable to bend DNA.
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| 9. |
- Imreh, S, et al.
(författare)
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Hypersomy of chromosome 15 with retrovirally rearranged c-myc, loss of germline c-myc and IgK/c-myc juxtaposition in a macrophage-monocytic tumour line
- 1994
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Ingår i: European Journal of Cancer. - 0959-8049. ; 30A:7, s. 994-1002
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Tidskriftsartikel (refereegranskat)abstract
- From a lymphoid tumour induced by 7,12-dimethylbenz-[a]-anthracene (DMBA) + methyl-N-nitrose-N-urea (MNU) in an [AKR Rb(6.15) x CBAT6T6]F1 mouse, a macrophage- monocyte line (KT-10) was isolated. Following ethyl methanesulfonate (EMS) treatment, a bromodeoxyuridine (BUdR) resistant subline was selected. Serial propagation of this line in vitro in the presence of BUdR (28 months) with periodic cytogenetic and molecular examinations, has led to the definition of four successive stages. During stage I, the cells were trisomic for chromosome 15. They contained Rb(6.15) and Rb(del6.15) of AKR and T(14;15) of CBA origin. Southern blotting showed the presence of both germline (G) and rearranged (R) c-myc. At stage II, Rb(del6.15) has duplicated. Both Rb(6.15) and T(14;15) persisted together with G-myc and R-myc. In stage III, the CBA-derived T(14;15) was lost, in parallel with G-myc. At this stage, a Dic.In(6.15) was detected. One of its arms was cytogenetically identical with the long arm of In(6.15) in the variant IgK/myc translocations. This chromosome carried R-myc and IgK in juxtaposition, as indicated by comigration on pulsed field electrophoresis (PFGE). At stage IV, the R-myc carrying AKR-derived chromosome 15s were present in six copies. Possible relationships between the increasing R/G myc ratio and changed growth characteristics in vivo and in vitro are discussed.
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| 10. |
- Parker, JL, et al.
(författare)
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Surface forces between plasma polymer films
- 1994
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Ingår i: Langmuir. - 0743-7463 .- 1520-5827. ; 10, s. 2766-2773
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Tidskriftsartikel (refereegranskat)abstract
- The surface properties of two different plasma polymer coatings were investigated by means of ESCA wetting studies, and surface force measurements. The plasma polymer films formed from hexamethyldisiloxane (HMDSO) monomers were found to be very smooth. This made it possible to measure the attractive van der Waals interaction between HMDSO-coated sur,faces in air. When the HMDSO-coated surfaces were immersed in water, they initially appeared strongly hydrophobic with an advancing and recedingcontactangle of 109° and 98°, respectively. Nevertheless, nolongrange zhydrophobic"interaction was observed. The HMDSO coating became slightly more hydrophilic when kept in an aqueous phase for a prolonged time, indicating migration/reorientation of polar groups to the surface. Surface force me asurements in water cle arly de monstrat ed the appe arance of el ectro static charge s and extending polymer tails as a result of a prolonged exposure to water. Plasma polymer coatings of C2F4 or C2F6 deposited on top of a plasma polymer of CH4 were also studied. The forces between such a polymer and a glass surface are on the first approach in air characteristic of a van der Waals force. However, the attraction increases as the surfaces are brought together repeatedly. The increase in the long range attraction is a result of contact electrification due to electron transfer from glass to the fluorocarbon surface. It was found that in aqueous environment the C2F4 plasma polymer surface is significantly less smooth and less stable than the HMDSO plasma polymer surface.
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