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1
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On Concentration Dependence of Spin-Glass Freezing Temperature in Mn-Alloyed II-V Compounds

100%
Bednarski H., Cisowski J.
Acta Physica Polonica A
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1992
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vol. 82
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issue 5
868-870
EN
Basing on recent studies of the magnetic properties of (Zn_{1-x}Mn_{x})_{3}As_{2} (ZMA) and (Cd_{1-x}Mn_{x})_{3}As_{2} (CMA) as well as on theoretical works devoted to the Mn-Mn interaction in semimagnetic semiconductors, we have determined the distance dependence of this interaction taking into account the complicated crystal structure of both systems. The resulting radial dependence of the exchange interaction (being a sum of superexchange and the Bloembergen-Rowland mechanism) together with the scaling analysis have allowed us to describe the Mn-concentration dependence of spin-glass freezing temperature in ZMA, CMA and, for comparison, also in Cd_{1-x}Mn_{x}Te in very good agreement with experimental data.
2
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Modulation of the Shubnikov-de Haas Oscillations by the Exchange Interaction in Cd_{3-x-y}Zn_{x}Mn_{y}As_{2}

81%
Lubczyński W., Cisowski J., Portal J. C.
Acta Physica Polonica A
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1991
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vol. 79
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issue 2-3
377-379
EN
New measurements of the Shubnikov-de Haas (SdH) effect in semimagnetic semiconductor (SMSC) Cd_{3-x-y}Zn_{x}Mn_{y}As_{2} with x = 0.09 and y = 0.018, using continuous magnetic fields up to 25 T, are presented. The observed modulation of the amplitudes of the first and second SdH harmonics as a function of magnetic field is interpreted in terms of the three band Kane model with the exchange interaction included and taking into account the spin-dependent scattering which appears to be particularly important at high magnetic fields.
3
Content available remote

Application of Generalized Pair Approximation to Diluted Magnetic Semiconductor Quantum Structures

81%
Bednarski H., Cisowski J., Portal J.
Acta Physica Polonica A
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1996
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vol. 90
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issue 4
723-726
EN
Analysing the d-d interaction in diluted magnetic semiconductor quantum structures, we used our generalized pair approximation which permits to take into account the real spatial distribution of the magnetic ions in diluted magnetic semiconductor layers close to the nonmagnetic quantum well. We subsequently applied our approach to calculate the Zeeman splittings in the CdTe/Cd_{1-x}Mn_{x}Te quantum structures with x=5 and 7.5% and we obtained a good agreement with the experimental results.
4
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Anisotropy of the Exchange Interaction in Mn-Alloyed II_{3}-V_{2} Compounds

81%
Lubczyński W., Cisowski J., Portal J.
Acta Physica Polonica A
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1991
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vol. 80
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issue 2
275-278
EN
An anisotropy of the electron effective g-factor in highly degenerated tetragonal semimagnetic semiconductors (SMSC) alloyed with manganese has been found by us and by other workers when studying the Shubnikov-de Haas (SdH) effect for different orientations of the magnetic field with respect to the crystal axes. The detailed analysis of the experimental data by using a model based on an infinite Hamiltonian matrix, provides evidence for the anisotropy of the p-d exchange interaction in the materials of interest.
5
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Influence of Pressure on Magnetization of (Cd_{1-x-y}Zn_{y}Mn_{x})_{3}As_{2}

71%
Bednarski H., Cisowski J., Lubczyński W., Voiron J., Portal J.
Acta Physica Polonica A
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1995
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vol. 87
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issue 1
205-208
EN
The influence of hydrostatic pressure up to 0.6 GPa on magnetization of (Cd_{1-x-y}Zn_{y}Mn_{x})_{3}As_{2} with various compositions was studied at 4.2 K and in magnetic fields up to 7 T. The obtained experimental data were analysed within our generalized pair approximation model, treating the total Mn-Mn interaction strength as a sum of superexchange and the Bloembergen-Rowland exchange. As a result, we obtained satisfactory agree­ment between our approach and experiment by introducing a pressure de­pendence of p-d hybridization potential V_{pd} in the form V_{pd} ∝ d^{-4}, where d is the Mn-As bond length which decreases with pressure.
6
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Optical Properties of Semiladder Polymer Foils

71%
Jarząbek B., Orlik T., Cisowski J., Schab-Balcerzak E., Sęk D.
Acta Physica Polonica A
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2000
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vol. 98
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issue 5
655-659
EN
Optical transmission of amorphous polyimidazopyrrolone foils (pyrrons) were investigated in the spectral range 200-3300nm. The investigated materials exhibit a high transmission level (up to 85%) in a wide range from about 500 to 2750nm. The short wavelength edge of transmission depends on the pyrron chemical structure being different for ether-, amide- and ester bridges. When analysing the experimental data, we applied the approach used for amorphous materials in order to determine the electronic structure parameters which may be related to the influence of polyimidazopyrrolone bridge structure and structural disorder on the optical properties and probable electronic transitions.
7
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Magnetic Specific Heat of (Cd_{1-x-y}Zn_{y}Mn_{x})_{3}As_{2}

62%
Bednarski H., Cisowski J., Schmitt D., Voiron J., Portal J., Lubczyński W.
Acta Physica Polonica A
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1993
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vol. 84
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issue 4
705-708
EN
The specific heat of (Cd_{1-x-y}Zn_{y}Mn_{x})_{3}As_{2} with low Mn concentration (x ≤ 0.067) and for two Zn contents (y = 0.14 and y = 0.34) has been measured in the temperature range of 1.5-30 K. The magnetic contribution to the total specific heat has been analysed within our generalized pair approximation model which takes into account the complicated tetragonal crystal structure of Cd_{1-x-y}Zn_{y}Mn_{x})_{3}As_{2}. Assuming that the total Mn-Mn interaction strength is a sum of superexchange and the Bloembergen-Rowland exchange, we have obtained a very good agreement between our approach and experiment by using the analytical formulae with only two adjustable parameters, i.e. the first nearest-neighbour exchange constants for both mechanisms which appear to be strongly dependent on Zn content.
8
Content available remote

Influence of Rare Earth Ions on the Optical Properties of Tellurite Glass

62%
Burtan B., Reben M., Cisowski J., Wasylak J., Nosidlak N., Jaglarz J., Jarząbek B.
Acta Physica Polonica A
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2011
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vol. 120
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issue 4
579-581
EN
The goal of this work was to investigate the influence of rare-earth ions such as Nd^{3+} and Er^{3+} on the optical properties of tellurite glass of the TeO_2-WO_3-PbO-La_2O_3 system. The optical studies of the glasses comprised spectrophotometry (reflectance and transmittance) and spectroscopic ellipsometry. The spectrophotometric measurements yield a number of narrow absorption bands which correspond to characteristic transitions between the ground- and consecutive excited states of rare-earth ions. From ellipsometric studies, in turn, the dispersion of the refraction coefficient has been obtained which appears to be practically the same for the tellurite glass matrix and the matrix doped with Nd^{3+} and Er^{3+} ions.
9
Content available remote

Growth and Electrical Properties of Phosphorus Doped Zn_{1-x}Mn_{x}Te Crystals

62%
Khoi L. V., Jaroszyński J., Witkowska B., Mycielski A., Gałązka R. R., Cisowski J.
Acta Physica Polonica A
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1997
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vol. 92
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issue 4
833-836
EN
The high pressure Bridgman technique was used to grow Zn_{1-x}Mn_{x}Te:P crystals. Under the N_{2} pressure of 30 atm., we obtained the p^{+}-Zn_{1-x}Mn_{x}Te single crystals 8-10 mm in diameter, with free-carrier densities as high as p ≈ 8×10^{18} cm^{-3} and the room temperature conductivity σ(RT) ≈ 30 Ω^{-1}cm^{-1}. Magnetoresistance measurements were carried out down to 1.3 K and up to 6 T. In Zn_{1-x}Mn_{x}Te:P a strong increase in the acceptor binding energy as well as an immense (ρ(0,1.3K)/ρ(6T,1.3K) > 10^{3}) negative magnetoresistance are observed, by contrast, not seen in diamagnetic ZnTe:P. It is shown that these effects come from the formation of bound magnetic polarons and their destruction by an external magnetic field.
10
Content available remote

Spectroscopic Properties of Pr^{3+} Ion in Various Tellurite Glasses

62%
Burtan B., Cisowski J., Wasylak J., Lisiecki R., Ryba-Rymanowski W., Jarząbek J., Reben M.
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vol. 126
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issue 6
1269-1271
EN
The goal of this work was to investigate the spectroscopic properties of Pr^{3+} ions (of a comparable concentration of the order of 0.2 mol/dm^3) embedded in the tellurite glass matrix, i.e. TeO_2-WO_3-PbO modified with lanthanum and lutetium oxides. The difference is that the last components of both glasses provide ions which are optically inactive within the 4f shell, since this shell is completely empty for La^{3+} ion and completely filled for Lu^{3+} ion. The absorption and fluorescence spectra of Pr^{3+} doped in tellurite glass has been recorded and analyzed in terms of the Judd-Ofelt theory. The studies of the glasses comprised ellipsometric, spectrophotometric and photoluminescence measurements. The ellipsometric studies yield the refraction index dispersion which appears to be quite similar for all the studied glasses. From the spectrophotometric measurements, the absorption spectra have been obtained which, for Pr^{3+}-doped samples, have been analyzed in terms of the Judd-Ofelt theory. Finally, the photoluminescence studies demonstrate a clear visible emission from ^3P_0 level to lower-lying states of Pr^{3+} ion.
11

Regulation of gene expression in plasmid vectors: doxocyclin-dependent and hypoxia-regulated systems

52%
Golda S., Kucharzewska P., Cisowski J., Florczyk U., Zagorska A., Jazwa A., Loboda A., Jozkowicz A., Dulak J.
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2007
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issue 3
82-97
EN
Regulation of gene expression in gene therapy is crucial for obtaining the therapeutic effects, thanks to limitation of transgene activity to the selected cells in a given time. In this paper we have focused on plasmid expression systems regulated by doxycycline or hypoxia. We have described in details the structure, regulatory elements and biological applications of 1) the modified, commercially available Tet-On system, expressing doxycycline-controlled b-galactosidase and, 2) hypoxia-activated FGF-4/VEGF expression plasmid containing the hypoxia responsive sequence. The presented expression systems can also be used in viral vectors, enabling not only regulated, but also high and long-term expression of transgenes.
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