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| 2. |
- Jonsson, B J, et al.
(författare)
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Method to extract the critical current density and the flux-creep exponent in high-T-c thin films using ac susceptibility measurements
- 1998
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Ingår i: Physical Review B Condensed Matter. - 0163-1829 .- 1095-3795. ; 58:9, s. 5862-5867
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Tidskriftsartikel (refereegranskat)abstract
- High-precision ac susceptibility measurements have been made on high-quality Hg-1212 thin films. A method to analyze chi(1)'(T,H-0,f) and chi(1)" (T,H-0,f) and extract the temperature dependence of the critical current density J(c)(T), as well as the temperature and field-dependent flux-creep exponent n(T,H-0), is presented. With specific measurements at external ac fields Ho in the range 7-100 Oe(rms) we determine the temperature dependence of the critical current density from a single temperature scan. The obtained temperature dependence, J(c)(T), is found to be in good agreement with data obtained from measurements using the traditional "loss-maximum" approach. In addition we present a method to extract the temperature and ac field-dependent flux-creep exponent n(T,H-0) from a set of temperature scans taken at different cc fields and driving frequencies. The observed power law describing the frequency dependence of chi' is consistent with a current-dependent effective activation energy of the form U(J)= U(0)ln(J(c)/J). Furthermore, the flux creep is found to increase with ac field and with temperature except at about 20-30 K below T-c, where our data suggest a slowing down of the flux creep.
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| 3. |
- Meenakshi, S, et al.
(författare)
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High-pressure studies on YNi2B2C at room temperature
- 1998
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Ingår i: PHYSICAL REVIEW B-CONDENSED MATTER. - : AMERICAN PHYSICAL SOC. - 0163-1829. ; 58:6, s. 3377-3380
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The electronic and lattice structure, and equation of state behavior of YNi2B2C has been investigated by electrical resistivity, thermoelectric power, and angle-dispersive x-ray-diffraction measurements. The electrical resistance under pressure has also b
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| 4. |
- Nandakumar, Kutty Selva, 1965-, et al.
(författare)
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Upregulation of antitumor immunity by IL-12 gene-transfected AK-5 tumor cells in vivo
- 1999
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Ingår i: Cytokines, cellular & molecular therapy. - Abingdon : Taylor & Francis. - 1368-4736 .- 1471-177X. ; 5:1, s. 7-14
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Tidskriftsartikel (refereegranskat)abstract
- We have earlier demonstrated a significant role for IL-12 in the regression of a rat histiocytic tumor, AK-5. In order to analyze further the antitumor immunity induced by interleukin (IL)-12, we have established IL-12-secreting tumor cell clones by gene transfection. Significant enhancement in the lytic potential of splenocytes by the culture supernatants containing IL-12 demonstrated retention of biological activity by the tumor-cell-derived cytokine. Athymic nude mice transplanted subcutaneously with tumor cells engineered to secret IL-12 showed a significant reduction in tumor size, with enhanced antibody-dependent cellular cytotoxicity. Analysis of the serum samples from animals injected with the IL-12 gene-transfected AK-5 cells on different days revealed a significant increase in circulatory IL-12, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha and antitumor antibodies, all of which contributed to the reduction in tumor mass. The enhanced proliferative capacity of splenocytes from these animals indicated the presence of highly activated immune cells in vivo. Similarly, intraperitoneal transplantation of IL-12 gene-transfected tumor cells in syngeneic Wistar rats induced a significant increase in cellular cytotoxicity, with a concomitant reduction in circulatory IL-12 (p40) protein. Administration of antibodies to IL-12 and IFN-gamma reduced the expression of the costimulatory molecules B7.1 and B7.2 and the cytolytic effectors granzyme B and Fas-L, suggesting their involvement in IFN-gamma-dependent antitumor immune response induced by IL-12. The present study thus demonstrates that IL-12 gene therapy could be among the promising approaches for an effective cancer therapy.
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| 5. |
- Sundararajan, G., et al.
(författare)
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A Comparative Study of Tribological Behavior of Plasma and D-Gun Sprayed Coatings under Different Wear Modes
- 1998
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Ingår i: Journal of Materials Engineering and Performance. ; 7:3, s. 343-351
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Tidskriftsartikel (refereegranskat)abstract
- In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12%Co, Al2O3, and Cr3C2-NiCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al2O3 shows least wear resistance to every wear mode.
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| 6. |
- Yun, S H, et al.
(författare)
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Growth of a-axis-oriented HgBa2CaCu2Ox thin films by rapid quenching
- 1999
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Ingår i: Journal of Materials Research. - 0884-2914 .- 2044-5326. ; 14:8, s. 3181-3184
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Tidskriftsartikel (refereegranskat)abstract
- High-quality a-axis-oriented HgBa2CaCu2Ox superconducting thin films have been grown on (100) LaAlO3 substrates using a modified conventional method that contains a short annealing time of 5 min, rapid-quenching process, and an alternative encapsulated approach. We found that the preferred orientations of HgBa2CaCu2Ox thin films can be controlled by rapid quenching at specific temperatures: 800, 700, 600, and 500 degrees C. The films rapidly quenched in water from 700 degrees C during a cooling cycle showed predominantly a-axis orientation perpendicular to the film surface. Phase was confirmed by x-ray diffraction pole figures. The a-axis films exhibited a zero-resistance transition temperature >120 K, which is comparable to epitaxial c-axis-oriented films.
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