| 257681. |
- Razpet, A., et al.
(författare)
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Fabrication of high-density ordered nanoarrays in silicon dioxide by MeV ion track lithography
- 2005
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 97:4
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Tidskriftsartikel (refereegranskat)abstract
- Self-assembled nanoporous alumina films were employed as masks for MeV ion track lithography. Films with thickness of 2 mum and pore diameters of 30 and 70 nm were attached to thermally grown SiO2 covered with a thin gold layer. The samples were aligned with respect to the beam by detecting backscattered He+ ions with the initial energy of 2 MeV. The ordered pattern of the porous alumina films was successfully transferred into SiO2 after irradiation with a 4 MeV Cl2+ beam at fluence of 10(14) ions/cm(2), followed by chemical etching in a 5% HF solution.
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| 257682. |
- Razpet, A., et al.
(författare)
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Ion transmission and characterization of ordered nanoporous alumina
- 2004
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Ingår i: Nuclear Instruments and Methods in Physics Research Section B. - : Elsevier BV. - 0168-583X .- 1872-9584. ; B:222, s. 593-600
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Tidskriftsartikel (refereegranskat)abstract
- Ordered nanoporous alumina samples with a pore diameter of 70 nm, an array period of 100 nm and several thicknesses were considered as possible masks for pattern transfer by MeV ion lithography. A simple procedure for the sample alignment using a 2 MeV He+ beam was utilized. The energy distributions of transmitted ions as well as backscattering spectra were studied in aligned and non-aligned orientations. The best transmission, comparable to the relative surface area covered by pores, was reached for 2 mum thick samples and was independent on ion species. Although the transmission for thicker membranes was generally lower, it significantly depended on the quality of each individual sample. The presented ion beam technique can therefore be used as a tool for the characterization of porous materials. The acceptance angle for transmission through pores and the effective atomic density of samples can be obtained from the experimental data and it is shown that nanoporous alumina can be used as a mask for MeV ion lithography.
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| 257683. |
- Razumiene, J, et al.
(författare)
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Direct bioelectrocatalysis at carbon electrodes modified with quinohemoprotein alcohol dehydrogenase from Gluconobacter sp. 33
- 2002
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Ingår i: Electroanalysis. - 1040-0397. ; 14:1, s. 43-49
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Tidskriftsartikel (refereegranskat)abstract
- A newly isolated, purified, and characterized PQQ-dependent alcohol dehydrogenase (a bacterial membrane-bound protein) was recently found to display a surprisingly large linear range and high selectivity towards ethanol when integrated into a conducting polymer network on a platinum electrode. These findings motivated us to study the enzyme when simply immobilized onto carbonaceous surfaces in order to establish its characteristics and suitability for sensor development, the sensor design being based on a direct-electron transfer pathway. Graphite rods and screen-printed electrodes were modified in two different ways, and were operated both in FIA and batch mode. The obtained biosensor characteristics were highly dependent on the sensor architecture, the highest sensitivity (179 mA M-1 cm(-2)) and lowest detection limit (1 muM) being obtained for screen-printed electrodes used in a batch mode. A mechanism of the observed direct electron transfer between the enzyme's active center and the electrode is proposed.
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| 257684. |
- Razumovskaya, Elena, et al.
(författare)
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Inhibition of MEK5 by BIX02188 induces apoptosis in cells expressing the oncogenic mutant FLT3-ITD.
- 2011
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Ingår i: Biochemical and Biophysical Research Communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 412:2, s. 307-312
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Tidskriftsartikel (refereegranskat)abstract
- Fms-like tyrosine kinase-3 (FLT3) is a growth factor receptor normally expressed on hematopoietic progenitor cells. Approximately one third of all patients with AML carry an activating mutation in FLT3 that drives proliferation and survival of the leukemic cells. The most common activating mutation is the so-called internal tandem duplication (ITD), which involves an in-frame duplication of a segment of varying length in the region of the FLT3 gene that encodes the juxtamembrane domain. The pathways downstream of FLT3-ITD are partially known but further knowledge regarding the downstream signal transduction molecules is important in order to develop alternative strategies for pharmacological intervention. In this paper we have studied the role of MEK/ERK5 in FLT3-ITD mediated transformation. We have found that both wild-type FLT3 and FLT3-ITD activate MEK5 leading to the activation of ERK5. By use of the selective inhibitor of MEK5, BIX02188, we have shown that activation of AKT downstream of FLT3 is partially dependent on ERK5. Furthermore, inhibition of MEK5/ERK5 induces apoptosis of both FLT3-ITD transfected Ba/F3 cells as well as the FLT3-ITD carrying leukemic cell lines MV4-11 and MOLM-13. These results suggest that MEK5/ERK5 is important for FLT3-ITD induced hematopoietic transformation and may thus represent an alternative therapeutic target in the treatment of FLT3-ITD positive leukemia.
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| 257685. |
- Razumovskii, I. M., 1985-, et al.
(författare)
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Effect of the Particle Size of γ’ Phase on the Mechanical Properties of Ni base Superalloy
- 2011
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Ingår i: Euro Superalloys 2010. - : Trans Tech Publications Inc.. - 9783037851135 ; , s. 96-101
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Konferensbidrag (refereegranskat)abstract
- The effect of gamma’ particle size upon the mechanical properties of Ni base superalloy EP741NP obtained by powder metallurgy was investigated. The particle size of gamma’ phase in gamma-gamma’ microstructure was varied by changing the cooling rate V from the temperature of the solid solution treatment at 1200 C (V = 80, 200 and 400 C \ min.). After solid solution treatment billets were subjected to aging in the standard mode. It was established that as V increases from 80 to 200 C \ min., the average particle’s size of gamma’ phase decreases from 0.54 microns to 0.22 microns in the aged state. This improves the characteristics of creep and low cycle fatigue at 650C: time to rupture under load 1000 MPa increased from 132 hours to 416 hours and low cycle fatigue increased from 42,215 to 82,016 cycles.
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| 257686. |
- Razumovskii, I. M., et al.
(författare)
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New generation of Ni-based superalloys designed on the basis of first-principles calculations
- 2008
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Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5093 .- 1873-4936. ; 497:1-2, s. 18-24
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Tidskriftsartikel (refereegranskat)abstract
- A new approach to the design of Ni-based single crystal superalloys is proposed. It is based on a concept that under given structural conditions, the creep-rupture characteristics of superalloys are mainly determined by interatomic bonding given by the cohesive energy. In order to characterize the individual contribution of each alloying element to the strength properties at high temperature, we introduce a parameter, X, which is the partial molar cohesive energy of an alloy component. This parameter is then obtained in the total energy first-principles calculations for a usual set of alloying elements. We demonstrate that creep-rupture characteristics of alloys indeed correlate with the total gain partial molar cohesive energy due to alloying and find that W, Ta, and Re have the highest values of X, and should therefore play the major role in providing high-temperature strength of superalloys. Based on this finding, we design three new superalloys with a high content of W and show that they have superior creep-rupture properties compared not only with their counterparts with the lower content of W, but also with the best Ru-bearing Ni-based superalloys.
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| 257687. |
- Razumovskiy, Vsevolod I., et al.
(författare)
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Ab initio calculations of elastic properties of Pt-Sc alloys
- 2008
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Ingår i: Intermetallics (Barking). - : Elsevier. - 0966-9795 .- 1879-0216. ; 16:8, s. 982-986
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Tidskriftsartikel (refereegranskat)abstract
- Elastic properties of substitutionally disordered Pt-rich Pt-Sc alloys and L1(2)-ordered Pt3Sc compound are derived from the first-principles calculations based on the exact muffin-tin orbitals (EMTO) method. We demonstrate that these alloys should exhibit a ductile behavior, which combined with relatively high melting temperature and strong cohesive properties make them a very promising candidate for high-temperature applications.
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| 257688. |
- Razumovskiy, Vsevolod I., 1985-, et al.
(författare)
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Ab-initio calculations of kinetic properties in ZrC and TiC carbides
- 2011
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Konferensbidrag (refereegranskat)abstract
- Self-diffusion of the metal and carbon atoms in TiC and ZrC carbides is studied by first principles methods. Our calculations yield point defects energies, vacancy jump barriers and diffusion pre-factors in TiC and ZrC. The results are in reasonable agreement with the available experimental data and suggest that the self-diffusion mechanism for metal atoms in these carbides may involve nearest-neighbor vacancy pairs (one metal and one carbon vacancy).
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| 257689. |
- Razumovskiy, Vsevolod I., 1985-, et al.
(författare)
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Analysis of the Alloying System in Ni-Base Superalloys Based on Ab Initio Study of Impurity Segregation to Ni Grain Boundary
- 2011
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Ingår i: EURO SUPERALLOYS 2010. - : Trans Tech Publications Inc.. - 9783037851135 ; , s. 192-197
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Konferensbidrag (refereegranskat)abstract
- A new approach to the design of Ni-based polycrystalline superalloys is proposed. It is based on a concept that under given structural conditions, the performance of superalloys is determined by the strength of interatomic bonding both in the bulk and at grain boundaries of material. We characterize the former by the cohesive energy of the bulk alloy, whereas for the latter we employ the work of separation of a representative high angle grain boundary. On the basis of our first principle calculations we suggest Hf and Zr as “minor alloying additions” to Ni-based alloys. Re, on the other hand, appears to be of little importance in polycrystalline alloys.
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| 257690. |
- Razumovskiy, Vsevolod I., 1985-, et al.
(författare)
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Effect of Alloying Elements and Impurities on Interface properties in Aluminum Alloys
- 2011
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Ingår i: Physics of the solid state. - 1063-7834 .- 1090-6460. ; 53:11, s. 2189-2193
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Tidskriftsartikel (refereegranskat)abstract
- The segregation energies of B, Si, P, Cr, Ni, Zr, and Mg on the special grain boundary (GB) Σ5 (210)[100] and on the open (210) surface of aluminum have been determined and the GB splitting energy has been calculated by the density functional theory methods. It has been shown that all elements listed above enrich the GB; for B, Si, P, Cr, Ni and Zr, Mg, interstitial and substitutional sites are preferred, respectively. The effect of alloying elements on the GB binding has been estimated using the parameter η equal to the change in the fracture work of the aluminum GB when adding alloying element atoms. From the viewpoint of strengthening the GB binding forces, Zr, Cr, Ni, and Mg are efficient, Si and B are neutral and phosphorus weakens GBs.
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