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1
Content available remote

Synchrotron Methods of the Conduction Band Electronic Structure Analysis

100%
Kisiel A.
Acta Physica Polonica A
|
2008
|
vol. 114
|
issue 2
287-307
EN
The experimental and theoretical studies of the density of states for unoccupied conduction band are a valid source of knowledge on the electronic structure of condensed matter. Among known analytical methods of density of states for unoccupied states a significant place is occupied by the methods with the use of intensive synchrotron radiation beam. Adequately chosen monochromatic beam excites electrons from the occupied core states or the valence band to unoccupied states in the conduction band. The most universal experimental method for the studies of the unoccupied conduction band is the X-ray absorption near edge structure analysis for X-ray edges of the constituent atoms of the material. A satisfying description of the unoccupied conduction band density of states can be also reached by the analysis of reflectivity coefficient in the vacuum ultraviolet (above 10 eV). The photoelectron energy distribution curves elaborated by the constant initial state and constant final state procedures deliver valuable information on the high excited states of conduction band. In the paper the menaces of the correct interpretation of the experimental results will be discussed. The efficiency of the unoccupied conduction band density of states studies with application of X-ray absorption near edge structure and analysis of reflectivity coefficient of light will be presented on the basis of several binary and ternary semiconductor compounds of II-VI group with transition metals as well as of some other compounds. To avoid a misinterpretation of the experimental results, the data were compared and discussed with an adequate theoretical band structure calculation.
2
Content available remote

International School and Symposium on Synchrotron Radiation in Natural Science. Opening Address

88%
Kisiel A.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 1
6
3
Content available remote

Probabilistic Analysis of Site-Occupation Preferences in Ga_{x}In_{1-x}As_{y}Sb_{1-y} and Cd_{1-x}Mn_{x}Se_{y}Te_{1-y} Quaternary Compounds

64%
Robouch B., Kisiel A.
Acta Physica Polonica A
|
1998
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vol. 94
|
issue 3
497-502
EN
Site-occupation preferences in quaternary GaInAsSb and CdMnSeTe compounds in tetrahedrally coordinated zinc-blende structures are discussed. Probabilistic eigenfunctions are defined to determine individual component pair-populations from measured average-pair distributions. The methodology and possible traps in interpreting site-occupation preferences of published EXAFS experimental overall average-pair distributions are discussed. The approach allows a deeper understanding of individual pair selective preferences in semiconducting multinary compounds. EXAFS reported departures from Bernoulli random distributions point to changes within elemental tetrahedral average-populations. Resolution requires that for tetrahedral structures experimental data best-fit be a 4th degree polynomial, product of a parabola by the factor x(1-x). The analysis shows that both materials have a marked preference for elemental tetrahedra with odd numbers of competing species of ions around a central ion.
4
Content available remote

Proceedings of the 2nd International School and Symposium on Synchrotron Radiation in Natural Science. Opening Adres.

64%
Kisiel A., Iwanowski R. J.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 4
447-448
5

RNAi as a tool for functional genomics

52%
Kisiel A., Podkowinski J., Figlerowicz M.
Biotechnologia
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2003
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issue 2
104-119
EN
Sequencing eukariotic genomes generates a large amount of sequence data. There is an urgent need for developing fast and effective methods of functional analysis of newly discovered genes. Postranscriptional gene silencing can be applied for functional genomics of plants and animals. A large scale analysis of C. elegans genome has been already performed. For mammals and plants, current work focuses on constructing high-throughput silencing vectors.
6
Content available remote

Reflectivity Spectra of CdTe Implanted at Room and Liquid Nitrogen Temperature

52%
Czarnecka-Such E., Kisiel A., Rodzik A., Gołacki Z.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 5
781-784
EN
The fundamental reflectivity spectra of monocrystalline CdTe, implanted with Ag ions at room temperature and with Er ions at liquid nitrogen temperature, are investigated in the 0.5-6.0 eV energy range. The analysis of the obtained spectra leads to the suggestion that temperature of implantation influences the obtained results much more decisively than values of other parameters. For the implantation carried out at 300 K no significant changes in reflectivity spectra are observed regardless of magnitude of the ion dose (up to 5 × 10^{15}/cm^{2}) and this fact, in our opinion, is due to the self-annealing effect. For samples implanted at temperature 77 K with comparable doses of ions, however, the characteristic changes of shape and intensity of reflection coefficient spectra appear. The manner of this changes gives evidence that temperature 77 K is low enough to make the radiation induced lattice defects stable (frozen-in) which are responsible for the observed behaviour of CdTe fundamental reflectivity spectra.
7
Content available remote

X-Ray Absorption Near Edge Spectra for CdTe - Theoretical Study

52%
Oleszkiewicz J., Markowski R., Kisiel A.
Acta Physica Polonica A
|
1992
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vol. 82
|
issue 2
323-328
EN
The theoretical band structure of the CdTe was calculated using conventional, ab initio, self-consistent, relativistic LMTO method. The projected density of states and the dielectric function were produced within the local density approximation. Spin-orbit coupling was included in the perturbation approach. X-ray absorption spectra for the Cd L_{1,3}- and Te L_{1,3}-edges were calculated and the results compared with experimental data. The teoretical results were obtained from the calculations with inclusion of k-dependent transition matrix elements, spin-orbit coupling, extended set of basis functions and finite lifetime of initial and final states. They were compared with other calculations which use common constant matrix element approximation. The work presents final conclusion concerning validity of using constant matrix element approximation within one-electron scheme.
8
Content available remote

Theoretical Study of Optical and XANES Spectra for CdTe within the k-dependent Matrix Element Approach

52%
Markowski R., Oleszkiewicz J., Kisiel A.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 5
785-788
EN
The reflectivity and X-ray absorption near-edge structure spectra for CdTe were calculated with the inclusion of the transition matrix elements from band structure obtained within self-consistent, relativistic linear muffin tin orbital method. The results were compared with experimental data for the case of CdTe and with our previous calculations.
9
Content available remote

Random Microscopic Model of Quaternary Alloys

52%
Konior J., Łażewski J., Kisiel A.
Acta Physica Polonica A
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1997
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vol. 91
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issue 4
815-818
EN
A random model of microscopic structure of zinc-blende type A_{1-x}B_{x}C_{1-y}D_{y} quaternary alloys, based entirely on the elastic bond-stretching and bond-bending forces of two-element components AC, AD, BC, and BD, was constructed. The model was applied to Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} quaternary alloys and the calculated nearest-neighbor distances were compared with the experimental data. Additionally, a possibility of particle exchange (within each sublattice) was included into the model and a possibility of studying the preferential coordination was discussed.
10
Content available remote

The Influence of the Dipol Transition Matrix Element on the XANES and Optical Spectra for CdTe

52%
Markowski R., Oleszkiewicz J., Kisiel A.
Acta Physica Polonica A
|
1991
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vol. 80
|
issue 3
369-372
EN
The reflectivity and X-ray absorption near-edge spectra (XANES) for CdTe have been calculated with inclusion of the transition matrix element from band structure obtained from self-consistent linear muffin-tin-orbital (LMTO) method. The result has been compared with experimental data for the case of CdTe.
11
Content available remote

Liquid Nitrogen and Room Temperature Reflectivity Spectra of Cd_{1-x}Fe_{x}Se in the 0.5-6.0 eV Energy Range

52%
Dębowska D., Zimnal-Starnawska M., Kisiel A., Giriat W.
Acta Physica Polonica A
|
1994
|
vol. 86
|
issue 6
1015-1020
EN
The reflectivity measurements for mixed crystals Cd_{1-x}Fe_{x}Se (0.00 ≤ x ≤ 0.10) have been carried out in an energy range of 0.5-6.0 eV at 300 and 77 K. The influence of Fe^{2+}(3d^{6}) states on the changes in the energy positions of the reflectivity maxima E_{0}, E_{1}(A_{1}), E_{1}(A_{2}), and E_{1}(B) is analyzed and the obtained results are consistent with the models existing in the literature.
12
Content available remote

Manganese Distribution in CdMnTeSe Crystals. EXAFS Data Analysis

45%
Kisiel A., Łażewski J., Zimnal-Starnawska M., Burattini E., Mycielski A.
Acta Physica Polonica A
|
1996
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vol. 90
|
issue 5
1032-1034
EN
The extended X-ray absorption fine structure (EXAFS) technique has been used to investigate the first shell coordination in zinc-blende quaternary Cd_{1-x}Mn_{x}Te_{1-y}Se_{y} (0.0 ≤ x ≤ 0.15; 0.0 ≤ y ≤ 0.20) alloys. The experimental data have been collected with the use of synchrotron radiation. All the nearest-neighbour distances have been found as linearly dependent on Se and Mn concentration. For each composition a consistent deviation from full random distribution of Mn atoms around Se and Te atoms was observed. Possible reasons of preferential Mn-Se over Mn-Te pairing were discussed.
13
Content available remote

Sulphur XANES Analysis of Cultured Human Prostate Cancer Cells

45%
Kwiatek W., Podgórczyk M., Paluszkiewicz C., Balerna A., Kisiel A.
Acta Physica Polonica A
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2008
|
vol. 114
|
issue 2
463-470
EN
Prostate cancer is one of the most commonly diagnosed cancers in men throughout the world. It is believed that changes to the structure of protein binding sites, altering its metabolism, may play an important role in carcinogenesis. Sulphur, often present in binding sites, can influence such changes through its chemical speciation. Hence there is a need for precise investigation of coordination environment of sulphur. X-ray absorption near edge structure spectroscopy offers such possibility. Cell culture samples offer histologically well defined areas of good homogeneity, suitable for successful and reliable X-ray absorption near edge structure analysis. This paper presents sulphur speciation data collected from three different human prostate cancer cell lines (PC-3, LNCaP and DU-145). Sulphur X-ray absorption near edge structure analysis was performed on K-edge structure. The spectra of cells were compared with those of cancerous tissue and with organic substances as well as inorganic compounds.
14
Content available remote

X-Ray Absorption Near Edge Structure Analysis of HgMnSe, HgFeSe and HgTeSe

45%
Burattini E., Kisiel A., Markowski R., Dalba G., Giriat W.
Acta Physica Polonica A
|
1993
|
vol. 83
|
issue 1
107-114
EN
Experimental studies of the Se K X-ray absorption edges have been carried out in HgTe_{0.5}Se_{0.5}, Hg_{0.8}Mn_{0.2}Se and Hg_{0.9}Fe_{0.1}Se. A comparison is made for Hg_{0.5}Mn_{0.5}Se and Hg_{0.5}Fe_{0.5}Se theoretical results obtained by the self-consistent, semi-relativistic LMTO method within the LD approximation. Small differences of Se K edge XANES have been shown for HgTeSe and HgSe in contrary to evident differences for HgMnSe and HgFeSe. This behaviour of the absorption Se K edges is related to significant, hybridized contribution of the 3d and 4s Mn or Fe unoccupied states. The maximal contributions of the hybridized bands of the hypothetic zinc-blende MnSe or FeSe were estimated using the virtual crystal model. These maximal contributions are situated at about 6 eV and 17 eV in zinc-blende MnSe and at -0.8 eV and 5.5 eV in zinc-blende FeSe. For HgFeSe apart from the evidence of the strongly localized resonant donor (empty for low Fe concentrations) the complementary hybridized contribution of Fe 3d empty states also situated around the conduction band minimum should be taken into consideration.
15
Content available remote

Synchrotron Radiation Photoemission Studies of Mn 3d States in Zn_{1-x}Mn_{x}Se

39%
Zema N., Lama F., Piacentini M., Felici A., Dębowska D., Kisiel A., Olson C.
Acta Physica Polonica A
|
1995
|
vol. 87
|
issue 2
495-499
EN
The angle integrated resonant photoemission measurements of Zn_{0.9}Mn_{0.1}Se have been performed in the photon energy range between 30 eV and 70 eV using synchrotron radiation. The ternary compound va­lence band photoemission spectra show, in comparison to the ZnSe results, additional structures, whose intensity depends on Mn content. These new features have been assigned to transitions from the Mn 3d states of e sym­metry with spin up. The hybridization of the t_{2} component of the 3d electrons of Mn in the valence band is discussed.
16
Content available remote

Vacuum Ultraviolet Reflectivity of Cd_{1-x}Fe_{x}Te

39%
Dębowska D., Zimnal-Starnawska M., Kisiel A., Piacentini M., Zema N., Giriat W.
Acta Physica Polonica A
|
1992
|
vol. 82
|
issue 2
341-347
EN
Reflectivity spectra for mixed crystals Cd_{1-x}Fe_{x}Te with 0.00 ≤ x ≤0.05 were investigated. The measurements were carried out in the energy range 6.0-30.0 eV at 300 K. The influence of Fe^{2+}(3d^{6}) states on the changes in the energy positions of the reflectivity maxima E'_{1} , E'_{1} + ∆, c, d, e, f, h and i is analysed. The obtained results confirm the band structure diagrams published previously.
17
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Content available

Preliminary Study on Chemical Speciation of Sulphur in Cancerous Tissues

39%
Kwiatek W., Banaś A., Banaś K., Kisiel A., Cinque G., Falkenberg G.
Acta Physica Polonica A
|
2006
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vol. 109
|
issue 3
383-387
EN
Sulphur is vital for almost all living organisms by participating in a wide variety of metabolic processes. Nevertheless its biochemistry is only partially understood, due to it a few tools such as X-ray absorption near edge structure may be used to determine its chemical speciation in biological system. In this paper we focused on analysis of composition and elemental distribution in tissue structures of biological samples. We examined cancerous and non-cancerous prostate tissues. Experiments were carried out on the L-beam line at the HASYLAB, DESY (Hamburg, Germany) and DAΦNE-Light Facility at the Laboratori Nationali di Frascati (Frascati, Italy). Synchrotron radiation induced X-ray emission measurements reveal the significant differences in concentration of sulphur between cancerous and non-cancerous tissues. X-ray absorption near edge structure spectra show two main types of sulphur that are represented by X-ray peaks at 2476 eV and 2484 eV. This suggests that different sulphur components are present in the measured samples.
18
Content available remote

The XANES K-Edge Spectra for HgMnSe and HgFeSe

39%
Kisiel A., Oleszkiewicz J., Goniakowski J., Markowski R., Burattini E., Dalba G., Rocca F.
Acta Physica Polonica A
|
1991
|
vol. 80
|
issue 3
373-376
EN
X-ray absorption near-edge structure for Hg_{1-x}Mn_{x}Se and Hg_{1-x}Fe_{x}Se was studied with the use of synchrotron radiation. The self-consistent, semirelativistic LMTO method within the LD approximation was used to calculate electronic band structure and K-edge spectra of these semimagnetic semiconductors. The theoretical results for X-ray absorption spectra were compared with experimental data.
19
Content available remote

Room and Liquid Nitrogen Temperature Reflectivity Spectra of Co,Se Mixed Crystals

39%
Dębowska D., Zimnal-Starnawska M., Kisiel A., Piacentini M., Zema N., Lama F., Giriat W.
Acta Physica Polonica A
|
1995
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vol. 87
|
issue 1
275-278
EN
The optical properties of the semiconducting compounds Zn_{1-x}Co_{x}Se crystallizing in the zinc-blende structure have been investigated. The reflectivity spectra of these materials for different concentration of Co ions, have been taken out in a wide energy range between 4 and 25 eV at room (RT) and liquid nitrogen temperature (LNT) using synchrotron radiation from ADONE Storage Ring in Frascati. The comparisons between the reflectivity spectra of ternary systems and host crystal ZnSe are made. On the basis of the experimental and theoretical results, the changes of the structures of the reflectivity spectra of host crystal ZnSe caused by the influence of transition metal ions are discussed.
20
Content available remote

Liquid Nitrogen Temperature Reflectivity Spectra of Zn_{1-x}Mn_{x}Se and Zn_{1-y}Fe_{y}Se Mixed Crystals

39%
Zimnal-Starnawska M., Dębowska D., Kisiel A., Piacentini M., Lama F., Zema N., Giriat W.
Acta Physica Polonica A
|
1994
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vol. 86
|
issue 5
869-874
EN
The liquid nitrogen temperature reflectivity spectra of the tetrahedral diluted magnetic semiconductors (DMS's) Zn_{1-y}Fe_{y}Se and Zn_{1-x}Mn_{x}Se crystallizing in the zinc-blende structure were investigated. The reflectivity measurements for different concentration of Fe (y = 0.01, 0.05, and 0.10) and Mn (x = 0.10 and 0.30) ions were taken out in a wide energy range between 4 and 30 eV using synchrotron radiation from ADONE storage ring in Frascati. The average resolution ΔE/E used for these measurements was better than 1 × 10^{-3} over the entire spectral range. The single crystals were cleaved, before being mounted inside the reflectometer, from the samples grown by the Bridgman method. The comparison between the reflectivity spectra of ternary systems and host crystal ZnSe is made. The changes of the structures of reflectivity spectra of host crystal ZnSe caused by the influence of Fe and Mn ions are discussed.
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