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1
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Andreev Reflection and Creation of Spin-Entangled Charge Carriers in Double Barrier Junctions

100%
Wojciechowski R., Kowalewski L.
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issue 2
249-253
EN
We discuss spin dependent single particle charge transport as well as the spin pairwise entanglement processes in a double barrier junction. The junction consists of a superconductor connected to two normal or spin-polarized conductors, or semiconductors. Special attention is focused on a non-local process known as a crossed Andreev reflection. The non-local Andreev reflection occurs when an incident electron (hole) from one lead, injected with a subgap energy onto a superconducting layer, transforms into an Andreev hole (electron) in the second lead. At the same time, a Cooper pair is created in the superconductor. Using the Bogolubov-de Gennes equation with appropriate boundary conditions we calculate and discuss probabilities of processes relevant for charge transport through the junction. The dependence of the tunneling charge transport on the strength and orientation of the exchange field in the ferromagnetic electrodes, and on the height of the tunnel barriers as well as on the distance between the electrodes are presented. We discuss briefly the physics of creation and charge transport of spin entangled electron-hole pairs in the junction.
2
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Dynamical Mean Field within Iterative Perturbation Theory

100%
Radzimirski B., Wojciechowski R.
Acta Physica Polonica A
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2007
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vol. 111
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issue 5
753-761
EN
We consider the iterative-perturbation theory and its generalization to multi-orbital Hubbard models. We discuss in detail all aspects of numerical implementations of the method.
3
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Spin Dependent Electron Tunneling in a Ferromagnet Superconductor Ferromagnet Junction

100%
Kowalewski L., Wojciechowski R.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
257-259
EN
The coherent spin polarized transport in ferromagnet/superconductor/ferromagnet double barrier junctions is analyzed. Using the Bogolubov-de Gennes equation with appropriate boundary conditions, we calculate probabilities of spin dependent transport processes in the ferromagnet/superconductor/ferromagnet junction. In particular, we discuss the nonlocal processes such as the crossed Andreev reflection and elastic co-tunneling. These processes contribute to tunneling a current when the distance between the two magnetic electrodes is comparable to the superconducting coherence length. The dependences of the tunneling transport processes on the strength of the exchange field in the ferromagnetic electrodes, and on the height of the tunnel barriers are presented.
4
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Josephson Effect in Graphene-Based Junctions

100%
Wojciechowski R., Kowalewski L.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
632-634
EN
We study the Josephson effect in graphene based junctions where superconductivity in graphene is induced by the proximity effect from external substrate materials. The electronic properties of the junction is described by the Dirac-Bogoliubov-de-Gennes equations. We consider the junction consisting of two superconductors with different pairing potentials. Using appropriate boundary conditions imposed on the normal region-superconductors interfaces, we calculated the Andreev bound state energy, in the ballistic limit, taking into account two types of reflections namely the retro and specular Andreev reflections.
5
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Tunneling Current into the Vortex Lattice States of s- and p-Wave Superconductors

81%
Kowalewski L., Nogala M., Thomas M., Wojciechowski R.
Acta Physica Polonica A
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2000
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vol. 97
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issue 1
237-240
EN
The tunneling current between the metallic tip of a scanning microscope and s-wave and p-wave superconductors in a quantizing magnetic field is investigated. The differential conductance is calculated both as a function of bias voltage at the centre of the vortex line and for varying position of the scanning tunneling microscope tip at a stable voltage.
6

Abnormal segregation of prion protein octapeptide-repeat alleles in cattle

81%
Walawski K., Czarnik U., Wojciechowski R., Pareek C. S.
Journal of Applied Genetics
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2003
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vol. 44
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issue 3
375-378
EN
The study was conducted on full-families of Black-and-White cattle obtained as 25 AI sire families and 355 cows, as well as their progenies, mostly heifers at the age of 1-3 months. The sire group was composed by the casual qualification of 10 PRNP 6/6 and 15 PRNP 6/5 individuals on the basis of accessible young progenies. The randomly selected group of cows is characterised by a very high frequency of PRNP 6/6 (74.9%), followed by lower frequency of PRNP 6/5 (24.5%) and a very low frequency of PRNP 5/5 genotype (0.6%). The progenies represent all expected genotypes, such as: PRNP 6/6 (60.5%), PRNP 6/5 (35.8%) and PRNP 5/5 (3.7%), respectively. Taking into consideration the genotypes of parents and progenies, the segregation of PRNP 6 and PRNP 5 alleles was analysed. Results of the non-informative mating variant of male PRNP 6/6 ? female PRNP 6/6 (n = 87) are affected by the PRNP 6/6 progeny genotype in all cases. Subsequently, the results of mating variants male PRNP 6/6 ? female PRNP 6/5 (n = 29) and male PRNP 6/5 female PRNP 6/6 (n = 179) showed statistically non-significant differences in both above-mentioned alternations. The progeny group related from male PRNP 6/5 ? female PRNP 6/5 parental mating obtained fully informative and most valuable results based on the presented research concept. In the common group of 58 calves, the genotype PRNP 6/6 is represented by 26 individuals (44.8 %), PRNP 6/5 ? by 19 individuals (32.8 %) and PRNP 5/5 ? by 13 individuals (22.4 %). Therefore, the theoretical genotype rate (25% : 50% : 25%) is drastically deformed and the differentiation between the observed and expected numbers of animals is statistically highly significant (chi2= 12.72; 2 df.). These differences are affected by two times higher PRNP 6/6 homozygous (chi2 = 9.12; 1 df.) and responsively by the low number of PRNP 6/5 heterozygous animals (chi2 = 3.45; 1 df.). Further investigations are carried out to explain the genetic determination of abnormal PRNP octa-peptide repeat allele segregation, which suggests possible lethal cis-trans linkage effects.
7
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Heavy Fermion Superconductor Order Parameter in High Magnetic Field

81%
Kowalewski L., Wojciechowski R., Thomas M., Nogala M.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
347-350
EN
It is shown that, independently on either the nature and the strength of pairing, the orbital effects of a high magnetic field in heavy fermion superconductor change the form of both the effective pairing and the gap function.
8
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Resonance Tunneling in Ferromagnet-Triplet Superconductors Junctions

81%
Kowalewski L., Wojciechowski R., Wojtuś P.
Acta Physica Polonica A
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2007
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vol. 111
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issue 5
683-691
EN
We discuss the tunneling conductance in a ferromagnet-insulator-triplet superconductor junction. We consider the superconducting order parameters with spin triplet pairing having nodes. The nodal structure of the order parameter has been recently confirmed experimentally in Sr_2RuO_4. In particular, we study how a mid-gap structure of the tunnelling conductance depends on the phase difference of the pairing potential as well as on the orientation of the interface.
9
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Tunneling Charge Transport in Graphene-Based Superconductor Junctions

81%
Wojciechowski R., Kowalewski L., Nogala M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1092-1094
EN
We study the spin polarized electron and hole tunneling transport through a graphene-based ferromagnet(GF_1)-insulator(GI_1)-superconductor(G_{S})-insulator(GI_2)-ferromagnet(GF_2) junction. Proximity induced spin polarization and superconductivity in a graphene sheet are assumed to be created by superconducting and ferromagnetic electrodes placed on the top of the graphene. Using a four-dimensional version of the Dirac-Bogoliubov-de Gennes equation with appropriate boundary conditions we investigate the tunneling processes through the junctions. In particular, we present calculations of the amplitudes of normal and Andreev reflections as a function of the energy of the incident electron for a wide range of the model parameters, such as the strength and orientation of the exchange field, the barrier strength, and the distance between the two ferromagnetic layers. The tunneling transport processes in the graphene-based double junction GF/GI/G_{S}/GI/GF are compared with those in non-graphene-based junctions.
10
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Spin and Charge Current in a Short Semiconducting Chain of Paramagnetic Ionic Blocks

81%
Lehmann-Szweykowska A., Wojciechowski R., Micnas R.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
260-262
EN
We deal with the electric current flowing through a short chain of paramagnetic ionic blocks, coupled to metallic electrodes in the serial configuration. An original three-band Hubbard-Anderson Hamiltonian is diagonalised at the level of the single ionic block. A minimal but sufficient set of the latter's four hybridised eigenstates serves as a basis for the determination of the time-ordered temperature-dependent matrix Green functions, in terms of which all the current-voltage (I-V) characteristics can be expressed provided the coupling to the electrodes is weak. The separation of the opposite-spin contributions to the electric current and, consequently, the spin current from the left to right electrode can result from the on-site Coulomb repulsion term of Hubbard-Anderson Hamiltonian, with no spin polarisation at the electrodes, but with the Zeeman-like coupling of the centre to either a molecular or an external magnetic field.
11
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The Energy Spectrum of Single-Hole States in Transition Metal Oxides

81%
Lehmann-Szweykowska A., Wojciechowski R., Gehring G.
Acta Physica Polonica A
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2000
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vol. 97
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issue 3
563-566
EN
The p-d hybridised single-hole states of the transition-metal-oxygen tetrahedron (TMO_{4}) are collectivised due to the direct p-p hopping between oxygens of different clusters. The lowest-lying energy band is always narrow and fully occupied. The first excited band gets occupied as an effect of valence-uncompensated doping, so it can be almost localised. The possible hole excitations to the two higher energy bands, which are wider, may imply the Mott-like hopping form of charge transport in these systems.
12
Content available remote

Properties of the Semi Spin Glass Ground State of Garnets

81%
Koper A., Lehmann-Szweykowska A., Thomas M., Wojciechowski R.
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EN
A strong magnetic ordering response to valence-uncompensated doping observed experimentally in yttrium iron garnet, indicates the importance of a thorough analysis of the problem. Within the framework of the classical two-sublattice Heisenberg model the position on the ground state phase diagram, corresponding to the experimentally found values of the superexchange parameters of yttrium iron garnet, turns out to lie close to the semi spin glass region. Thus, in this paper, the magnetic structure factor, the spectrum of magnetic excitations, the density of states and a magnetic contribution to the specific heat, are calculated and discussed.
13
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Fractional discrete model of an electrical drive with brushless micro-motor

72%
Matusiak M., Bąkała M., Wojciechowski R., Ostalczyk P., Matusiak M., Bąkała M., Wojciechowski R., Ostalczyk P.
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2020
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issue 3
14
Content available remote

Anomalous Phase Transitions in LiCsSO_4 in the Compressible hcp Ising Model

71%
Lehmann-Szweykowska A., Kurzyński M., Wojciechowski R., Wiesner M., Mróz B.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1108-1110
EN
Structural low-temperature phase transformations in LiCsSO_4 are analysed in a newly tailored simple model of the static soliton in the periodically modulated phases of the one-dimensional compressible Ising model. It is shown that the original hcp symmetry is crucial for understanding of the anomalous temperature-dependence of the Brillouin shift.
15

Lactoferrin regulates the immune responses in post-surgical patients

62%
Zimecki M., Wlaszczyk A., Wojciechowski R., Dawiskiba J., Kruzel M., Kruzel M. L.
Archivum Immunologiae et Therapiae Experimentalis
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2001
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vol. 49
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issue 4
325
EN
The effect of oral administration of lactoferrin (LF) was studied to determine if it could modify post-surgical immune response. The action of lactoferrin was evaluated in 18 LF-treated patients versus 28 placebo counterparts. Patients (women and men, mean age 50 years) were given daily oral doses (20 mg each) of LF for 5 consecutive days prior to thyroid surgery. The following immune response parameters were determined in blood samples taken from the patients one day before, one day after, and 5-7 days following surgery: cell morphology, the proliferative response of peripheral blood mononuclear cells (PBMC) to phytohemagglutinin (PHA), and the spontaneous and lipopolysaccharide (LPS)-induced production of tumor necrosis factor alpha (TNF-) and interleukin 6 (IL-6). As a consequence of the thyroid surgery, the total leukocyte count increased on the postoperative day by about 50% in all patients and the percentage of lymphocytes fell by 26 and 35% in the control vs LF-treated group. The content of neutrophils, on the other hand, elevated on day 1 post-operation by 51 and 68%, respectively. The percent of neutrophil precursors was markedly higher in LF-treated patients, particularly on the day before and the day after surgery (4.1 and 4.8 vs 2.5 and 3.7%, respectively). The post-surgical values were, however, comparable in both groups for neutrophils. The proliferative response of lymphocytes showed a slight decrease in the control group and an increase in the LF-treated patients on day 5 post-operation (20% over control group). LPS-induced TNF- production was higher in LF-treated patients in both one day before and one day following surgery (28 and 24% respectively). LPS-induced IL-6 production was comparable in both placebo and LF-treated patients before surgery, however, on day 1 and 5 following surgery, the production of IL-6 was higher in LF-treated patients by 65 and 27%, respectively. Taken together, the data presented in this study revealed increased immune responsiveness in all patients treated with lactoferrin subjected to the thyroid surgery. This suggests that treatment with lactoferrin could constitute an effective protective measure against post-surgical complications.
16
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Examination of Wetting by Liquid Zinc of Steel Sheets Following Various Kinds of Abrasive Blasting

52%
Cecotka M., Dybowski K., Bąkała M., Lipa S., Klimek L., Rylski A., Sankowski D., Wojciechowski R.
Archives of Metallurgy and Materials
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2016
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issue 2
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