Search results

1

XAFS in the Tracking of Reactions in Aqueous Solution: a Case of Redox Reaction Between [AuCl4]– Complex Ions and Ethanol / Metoda XAFS W Badaniach Reakcji Zachodzących W Roztworach Wodnych: Przykład Reakcji Redoks Pomiędzy Jonami Kompleksowymi [AuCl4]- I Alkoholem Etylowym

100%

Pacławski K., Sikora M.

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issue 4

2

Exogenous hydrogen sulfide produces hemodynamic effects by triggering central neuroregulatory mechanisms

81%

Ufnal M., Sikora M., Dudek M.

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issue 3

382-388

EN

Recently, it was found that hydrogen sulfide (H2S) may serve as an important transmitter in peripheral organs as well as in the brain. The aim of the present study was to evaluate the possible function of H2S in the brain regulation of the circulatory system. Experiments were performed on conscious, male, Wistar-Kyoto rats. Mean arterial blood pressure (MABP) and heart rate (HR) were recorded continuously under baseline conditions and during infusions into the lateral cerebral ventricle (LCV) of the experimental animals. In control series LCV infusion of vehicle (Krebs-Henseleit bicarbonate-buffer) did not cause significant changes in MABP or HR. LCV infusion of H2S donor (NaHS) at the rate of 400 nM/h resulted in an increase in MABP, whereas infusions at the rate of 100 nM/h and 200 nM/h failed to change MABP. On the other hand LCV infusion of H2S donor at the rate of 200 nM/h caused a significant increase in HR while infusion at the rate of 400 nM/h produced an increase in HR, which was smaller than this observed during infusion at the rate of 200 nM/h. H2S donor administered at the rate of 100 nM/h failed to affect HR. In conclusion, the present study demonstrates that exogenous hydrogen sulfide changes hemodynamic parameters by centrally mediated mechanisms. The hemodynamic effect seems to be dependent on H2S concentration in cerebrospinal fluid. It appears that the hypertensive response may occur at a concentration, which does not exceed twice the physiological level.

3

Metagenomic libraries as sources of genes useful for biotechnology

81%

Deja-Sikora E., Sikora M., Golebiewski M., Tretyn A.

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2007

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issue 4

125-139

EN

The vast majority of microorganisms cannot be cultured under laboratory conditions. It was estimated that over 99% of microbial genetic information are inaccessible due to the inability to isolate and culture bacteria. It is also widely known that among those uncultured organisms there are such that bear the genes which are interesting from the biotechnological point of view, i.e. coding for novel enzymes (lipases, amylases, cellulases, polymerases etc.), responsible for resistance to various chemical substances (heavy metals, aromatic compounds, pesticides, antibiotics), or the genes encoding the elements of biosynthetic pathways (for instance producing novel antibiotics). Recently, the methods have been developed that allow (i) isolation and purification of environmental DNA, (ii) construction of random fragment libraries of such DNA, and (iii) effective screening of those libraries in search for interesting genes. These methods are collectively known as ?metagenomics' or ?environmental genomics'. We aim to review the metagenomic methods, which will be done in Part I of our paper, and to present the up ? to ? date achievements and future perspectives for obtaining biotechnologically important genes from environmental samples in Part II. The main attention will be paid to soil metagenomics, as this kind of environment seems to be the most promising in terms of microbial biodiversity and the spectrum of biochemical reactions performed by inhabiting bacteria. We will treat the perspectives for isolation of novel, useful genes such as those coding for biosynthesis of antibiotics, organic compounds degrading pathways, and heavy metal resistance and prospects for their biotechnological application. Assessing the microbial biodiversity through metagenomic methods will also be covered.

4

The Magnetoelectric Effect of a Ni0.3Zn0.62Cu0.08Fe2O4 - PbFe0.5Nb0.5O3 Multilayer Composite

81%

Guzdek P., Kapusta C., Sikora M., Góra Ł.

Archives of Metallurgy and Materials

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2014

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issue 3

5

Electronic Structure of Sm(Ni_{1-x}Co_{x})₃ Alloys - XPS and ab initio Study

71%

Majtyka A., Sikora M., Blachiński D., Chełkowska G., Deniszczyk J.

Acta Physica Polonica A

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2018

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vol. 133

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issue 3

673-675

EN

The band structure investigations for Sm(Ni_{1-x}Co_{x})₃ alloys by means of X-ray photoelectron spectroscopy (XPS) and an ab initio density functional theory (DFT) calculations are presented. The aim was to determine an effect of Ni/Co substitution on the electronic structure of the alloys. Investigations have shown that the Ni/Co substitution results in a reconstruction of the valence band (VB), especially the intensity near the Fermi level decreases with Co content. An ab initio simulated XPS VB spectra agree qualitatively with experimental ones with the exception of the Sm-4f sub-spectra where the multiplet decomposition is observed. Calculations shown that variation of magnetization in Sm(Ni_{1-x}Co_{x})₃ is driven mainly by the Ni/Co-3d and Sm-5d states polarization and increases linearly with rising Co content.

6

Influence of Fe Addition on the Martensitic Transformation, Structure and Magnetic Properties of Metamagnetic Ni-Co-Mn-Sn Alloys

62%

Wójcik A., Maziarz W., Szczerba M., Sikora M., Hawełek Ł., Czaja P.

Acta Physica Polonica A

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2016

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vol. 130

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issue 4

1026-1028

EN

In this study the effect of Fe for Ni substitution in Ni₄₄Co₆Mn₃₉Sn₁₁ metamagnetic shape memory alloys on their structure, magneto-structural transformation characteristics, magnetic and magnetocaloric properties was studied. The results show that the structure and martensite transformation behavior strongly depends on the Fe concentration. The martensitic transformation temperature decreases with 1 at.% of Fe and is suppressed with higher Fe content. It was further found that substitution of Fe for Ni leads to lowering of the value of magnetic entropy change.

7

Influence of Substitution and Milling on Structural and Magnetic Properties of Selected Sm(Ni_{1-x}Co_{x})₃ Compounds

62%

Sikora M., Blachliński D., Ociepka K., Prusik K., Bajorek A., Chełkowska G.

Acta Physica Polonica A

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2018

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vol. 133

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issue 3

486-488

EN

The influence of substitution of Co for Ni in Sm(Ni_{1-x}Co_{x})₃, where x=0.0, 0,1, 0.2, on the structural and magnetic properties has been investigated. Samples with x= 0.0 and 0.2 were subjected to grinding in a high energy ball mill. The presence of a PuNi₃ type of crystal phase was evidenced for bulk crystalline and powders specimens. With an increase in the cobalt content, an increase at T_{c} was observed. From the magnetic isotherms, the magnetic entropy changes were determined both for solid and powdered samples. It has been shown that the value of the magnetic entropy change at T_c is doubled for the bulk sample with x= 0.2 but it has decreased significantly for all powdered samples.

8

A ^{55}Mn NMR Study of La_{0.33}Nd_{0.33}Ca_{0.34}Mn O_3 with ^{16}O and ^{18}O

52%

Rybicki D., Kapusta C., Riedi P., Oates C., Sikora M., Zając D., De Teresa J., Marquina C., Ibarra M.

Acta Physica Polonica A

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2004

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vol. 105

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issue 1-2

183-188

EN

A ^{55}Mn NMR study of ^{16}O and ^{18}O containing La_{0.33}Nd_{0.33}Ca_{0.34}Mn O_3 is reported. The spin-echo spectra measured at 4.2 K and zero field consist of a double exchange line corresponding to the ferromagnetic metallic regions. The line intensity is more than an order of magnitude lower for the ^{18}O compound, which indicates an order of magnitude lower content of the ferromagnetic metallic phase in this compound. The frequency dependence of the spin-spin relaxation time T_2 shows a pronounced minimum at the center of the double exchange line of both compounds due to the Suhl-Nakamura interaction, which indicates that the ferromagnetic metallic regions are at least 10~nm in size. The results are discussed in terms of the influence of oxygen isotopic substitution on phase segregation.

9

An NMR study of Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03)

52%

Oates C., Kapusta C., Riedi P., Sikora M., Zając D., Rybicki D., Martin C., Yaicle C., Maignan A.

Acta Physica Polonica A

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2004

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vol. 105

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issue 1-2

189-195

EN

An NMR study of polycrystalline Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03) at 3 K is presented. Zero field spin-echo spectra of the Ga doped compound consist of an overlapping ^{69,71}Ga signal at 74~MHz (hyperfine field of 5.3 T), a ^{55}Mn double exchange line at 375 MHz (35.5 T) and a weak Mn^{3+} signal between 400 and 550 MHz. Measurements in an applied field show a step-like increase in the double exchange line intensity, which corresponds to an increase in the amount of the ferromagnetic metallic phase. This coincides with a step-like feature in the bulk magnetization measurements. The effect is similar to that in the previous field dependent ^{55}Mn NMR measurements of Pr_{0.67}Ca _{0.33}MnO_3. At the demagnetized and remanent state, a variation of spin- spin relaxation time, T_2, across the ^{55}Mn line, due to the Suhl-Nakamura interaction is observed, which suggests that the ferromagnetic metallic double exchange regions, at liquid helium temperatures, are at least 4 nm in size.

10

NMR Study of (Sr,Ba,La)_2Fe_{1+y}Mo_{1-y}O_6 Double Perovskites

52%

Zając D., Kapusta C., Riedi P., Sikora M., Oates C., Rybicki D., De Teresa J., Serrate D., Marquina C., Ibarra M.

Acta Physica Polonica A

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2004

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vol. 106

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issue 5

759-765

EN

The ^{95}Mo and ^{97}Mo NMR spin-echo study of (Sr,Ba,La)_2Fe_{1 +y}Mo_{1-y}O_6 double perovskites is reported. Powder samples of Ba_{1.44}Sr_{0.36}La_{0.2}FeMoO_6 and (Ba_{0.8}Sr_{0.2})_{2-2x}La_x#_x Fe_{1+y}Mo_{1-y}O_6, where# denotes vacancies, for: x=0, y=0; x=0.1, x=0.2 and x=0.3, y=0 and y=0.2 were measured at 4.2 K and no applied magnetic field. NMR signals are observed at 55-100 MHz for the main line and 30-55 MHz for low-frequency satellite. The main line and the satellite are attributed to the ideal and defect positions of Mo atoms. La and vacancy doping introduce more defects, however, increasing the Fe/Mo ratio decreases the amount of defect Mo sites. La doping causes a satellite pattern at the high frequency side of the spectrum, which is related to different numbers of the La next neighbours. The effect is attributed to an increase in the electron density and the corresponding magnetic moment at the adjacent Mo sites and reveals a local character of the electron doping.

11

Local Magnetic and Electronic Properties of the A2FeM'O6 (A = Ba, Sr, Ca, M' = Mo, Re) Double Perovskites

52%

Zając D., Sikora M., Prochazka V., Borowiec M., Stępień J., Kapusta C., Riedi P., Marquina C., De Teresa J., Ibarra M.

Acta Physica Polonica A

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2007

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vol. 111

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issue 6

797-820

EN

The results of a combined NMR, X-ray absorption spectroscopy and X-ray magnetic cirrcular dichroism study of the AA'FeMoO_6 and AA'FeReO_6 double perovskites are presented. They revealed a dependence of electronic and magnetic properties, including a d-electron transfer between Fe and Mo sites, on the structural tolerance factor. The maximum value of the 4d Mo electron occupation and the corresponding Mo moment is obtained for the tolerance factor of unity. This corresponds to the maximum strength of the magnetic interaction and, respectively, to the Curie temperature. The dominant T^{5/2} type temperature dependence of the Mo hyperfine field reveals the half-metallicity of the AA'FeMoO_6 compounds. Antisite defects and antiphase boundaries have been identified in NMR measurements and the strength of their magnetic coupling have been determined. A considerable orbital contribution to the Re and Fe magnetic moments were found in the NMR and X-MCD measurements on the AA'FeReO_6 compounds. Its magnitude decreases with increasing structural tolerance factor and is correlated with their magnetic anisotropy.

Refine search results

XAFS in the Tracking of Reactions in Aqueous Solution: a Case of Redox Reaction Between [AuCl4]– Complex Ions and Ethanol / Metoda XAFS W Badaniach Reakcji Zachodzących W Roztworach Wodnych: Przykład Reakcji Redoks Pomiędzy Jonami Kompleksowymi [AuCl4]- I Alkoholem Etylowym

Exogenous hydrogen sulfide produces hemodynamic effects by triggering central neuroregulatory mechanisms

Metagenomic libraries as sources of genes useful for biotechnology

The Magnetoelectric Effect of a Ni0.3Zn0.62Cu0.08Fe2O4 - PbFe0.5Nb0.5O3 Multilayer Composite

Electronic Structure of Sm(Ni_{1-x}Co_{x})₃ Alloys - XPS and ab initio Study

Influence of Fe Addition on the Martensitic Transformation, Structure and Magnetic Properties of Metamagnetic Ni-Co-Mn-Sn Alloys

Influence of Substitution and Milling on Structural and Magnetic Properties of Selected Sm(Ni_{1-x}Co_{x})₃ Compounds

A ^{55}Mn NMR Study of La_{0.33}Nd_{0.33}Ca_{0.34}Mn O_3 with ^{16}O and ^{18}O

An NMR study of Pr_{0.5}Ca_{0.5}Mn_{1-x}Ga_xO_3 (x=0 and 0.03)

NMR Study of (Sr,Ba,La)_2Fe_{1+y}Mo_{1-y}O_6 Double Perovskites

Local Magnetic and Electronic Properties of the A2FeM'O6 (A = Ba, Sr, Ca, M' = Mo, Re) Double Perovskites