43 results on '"H. Stepankova"'
Search Results
2. NMR studies of the ground states of Ni50-xCoxMn35In15 (x=1, 2.5) and Ni45Co5Mn37In13 Heusler alloys
- Author
-
Vojtech Chlan, Erkki Lähderanta, Valerii Prudnikov, H. Stepankova, Alexander Granovsky, Anil Aryal, Shane Stadler, Vladimir V. Matveev, Igor Dubenko, Saikat Talapatra, Sudip Pandey, Naushad Ali, Jing Han Chen, and Mikhail Blinov
- Subjects
010302 applied physics ,Austenite ,Phase transition ,Materials science ,Condensed matter physics ,Magnetic moment ,General Physics and Astronomy ,chemistry.chemical_element ,Resonance ,02 engineering and technology ,Manganese ,021001 nanoscience & nanotechnology ,01 natural sciences ,lcsh:QC1-999 ,Magnetization ,chemistry ,Martensite ,Phase (matter) ,0103 physical sciences ,0210 nano-technology ,lcsh:Physics - Abstract
Three temperature-induced phase transitions at T=T1, TM/TA, and TC, related to the ferromagnetic order of the martensitic phase (FMMP), martensitic (structural) transitions (MT), and the ferromagnetic order of the austenitic phase (FMAP), respectively, have been observed in the off-stoichiometric Heusler alloys, Ni50-xCoxMn35In15 (x=1, 2.5) and Ni45Co5Mn37In13. The phase transitions temperatures are found to be depended on alloy composition. A kinetic arrest of the AP was observed for Ni47.5Co2.5Mn35In15 in the magnetization measurements during field-cooling cycle (FCC) at 50 kOe. Depending upon the cooling protocols, ZFC and FCC (at H = 50 kOe), two different ground states of the alloys can be found in Ni47.5Co2.5Mn35In15 and Ni45Co5Mn37In13 alloys. The ground states (T=4.2 K and external field H=0) of the alloys was found to be characterized by three main line: two, partially overlapping, at higher frequencies (300-450 MHz), most likely corresponding of manganese resonance lines and one at lower frequency at about 200 MHz. A significant shift in the spectrum of Ni45Co5Mn37In13 by about 100 MHz to higher frequencies was observed. The correlation of magnetizations obtained from magnetic moment and NMR studies is discussed.
- Published
- 2020
- Full Text
- View/download PDF
3. Analysis of Cationic Impurity Impact on Hyperfine Interactions in Magnetite
- Author
-
V. Chlan, Pavel Novák, R. Reznicek, H. Stepankova, and Andrzej Kozłowski
- Subjects
NMR spectra database ,Charge ordering ,Valence (chemistry) ,Materials science ,Magnetic structure ,Resonance ,Electronic structure ,Electrical and Electronic Engineering ,Atomic physics ,Hyperfine structure ,Electronic, Optical and Magnetic Materials ,Ion - Abstract
The Al, Ga, Ti and Zn impurities were studied in high quality single crystal samples of magnetite (Fe3O4). The cases when the valence of the substitution ion differs from that of the original iron ion are of a particular interest. The measurement of nuclear magnetic resonance (NMR) of 57Fe was chosen as the experimental method for its sensitivity to Fe magnetic and electronic structure and to local ordering in the neighborhood of resonating nuclei. Local electronic structure and hence also the hyperfine interactions are affected by the presence of the substitution and thus resonance frequencies of nuclei in the vicinity of the substitution are shifted due to the modified hyperfine field, therefore satellite signals are observed in the NMR spectra. Temperature dependences of spectra above the Verwey transition were measured in a zero external magnetic field. Subsequently, the dependences of frequencies of main lines and satellite signals in the spectra on temperature were fitted with spin-wave model dependences and compared for different types of the substitution. Furthermore, a mean-field model was applied on the substituted magnetite system and calculated temperature dependences were confronted with the experimental data. The agreement of mean field model with the experimental temperature dependences of satellite resonances is better for those induced by the cationic substitutions at octahedral sites.
- Published
- 2012
- Full Text
- View/download PDF
4. Structural, Magnetic and Electronic Properties of Surface Oxidised Fe Nanoparticles
- Author
-
M. R. Ibarra, Jan Żukrowski, Czesław Kapusta, Tolek Tyliszczak, D. Rybicki, H. Stepankova, Wojciech Szczerba, Marcin Sikora, David Serrate, Janusz Przewoźnik, and R.F. Pacheco
- Subjects
Materials science ,Oxide ,Nanoparticle ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,chemistry.chemical_compound ,Crystallography ,chemistry ,Microscopy ,Mössbauer spectroscopy ,Spin echo ,General Materials Science ,Crystallite ,Ball mill ,Magnetite - Abstract
A combined XRD, Mössbauer, SEM, STXM and NMR study of naturally oxidised, ball milled iron powders is presented. The XRD patterns show the peaks of the bcc-Fe phase with the line widths increasing with the milling time. This corresponds to a flattening of the crystallites, as confirmed by SEM, and increased strain due to the accumulation of defects. The effect is consistent with the variation of the Mössbauer line-widths with the milling time. Scanning Transmission Xray Microscopy (STXM) measurements provided oxygen maps of the particles and revealed that the dominant oxide in the nanometric oxide layer is magnetite. The 57Fe spin echo NMR study reveals a dominant signal corresponding to a bcc-Fe core and a much weaker resonance corresponding to a magnetite amount of less than 1%.
- Published
- 2008
- Full Text
- View/download PDF
5. ChemInform Abstract: Hexagonal Ferrites of X-, W-, and M-Type in the System Sr-Fe-O: A Comparative Study
- Author
-
Vojtech Chlan, H. Stepankova, Jean-Marie Le Breton, Joerg Toepfer, Karel Kouril, Falko Langenhorst, and Daniela Seifert
- Subjects
law ,Hexagonal crystal system ,Chemistry ,Inorganic chemistry ,Analytical chemistry ,Calcination ,General Medicine ,law.invention - Abstract
While investigating the Fe-rich part of the pseudo-binary system SrO—Fe2O3, the well-known M-type SrFe12O19 (I) and two additional ferrites, W-type SrFeII2FeIII16O27 (II) and X-type Sr2FeII2FeIII28 O46 (III) are found at high temperatures from calcined and sintered mixtures of SrCO3 and Fe2O3 (1200 °C for (I); 1370 °C for (III); 1400 °C for (II), all 24 h).
- Published
- 2015
- Full Text
- View/download PDF
6. Temperature dependence of satellite structure of yttrium iron garnet containing Y3+(a) defects and Al3+(d) substitutions: experiment and model
- Author
-
J. Englich, H. Stepankova, Jaroslav Kohout, and A. Snezhko
- Subjects
Materials science ,Doping ,Yttrium iron garnet ,Analytical chemistry ,Resonance ,Atmospheric temperature range ,Condensed Matter Physics ,Spectral line ,Electronic, Optical and Magnetic Materials ,Magnetic field ,NMR spectra database ,chemistry.chemical_compound ,Nuclear magnetic resonance ,chemistry ,Impurity - Abstract
NMR spectra on 57 Fe nuclei in yttrium iron garnet (YIG) containing Y 3+ (a) defects and Al 3+ (d) substitutions were measured in the temperature range 4.2–360 K in zero external magnetic field. The temperature dependencies of satellite lines caused by Y 3+ (a), Al 3+ (d) impurities were determined. Theoretical description of the temperature behavior of the main and satellite lines has been carried out in the frame of model based on the Bethe–Peierls–Weiss approximation.
- Published
- 2001
- Full Text
- View/download PDF
7. Application of the Bethe-Peierls-Weiss Method to Yttrium Iron Garnet Containing Y3+ Impurity
- Author
-
H. Stepankova, Jan Kohout, J. Englich, and A. Snezhko
- Subjects
chemistry.chemical_compound ,Materials science ,chemistry ,Condensed matter physics ,Mechanics of Materials ,Impurity ,Mechanical Engineering ,Yttrium iron garnet ,chemistry.chemical_element ,General Materials Science ,Yttrium ,Condensed Matter Physics - Published
- 2001
- Full Text
- View/download PDF
8. 57Fe Hyperfine Field Anisotropy in Ferrites and its Relation to the Non-Uniformity of the Ionic Surrounding
- Author
-
Jaroslav Kohout, H. Stepankova, and J. Englich
- Subjects
NMR spectra database ,Materials science ,Condensed matter physics ,Field (physics) ,General Physics and Astronomy ,Ionic bonding ,Relaxation (physics) ,Crystal structure ,Atomic physics ,Anisotropy ,Hyperfine structure ,Spectral line - Published
- 2000
- Full Text
- View/download PDF
9. Safe biotechnology 9: values in risk assessment for the environmental application of microorganisms
- Author
-
C Mosgaard, M. Sarvas, G. Tzotzos, M Cantley, K. Wagner, A Elmqvist, L Olsen, C.H. Collins, H Haymerle, F. Rudan, C Frontali-Botti, Doblhoff-Dier O, J Pazlarova, Bachmayer H, R. G. Werner, Crooy P, R Havenaar, M Lex, H. Stepankova, L Martinez, Brunius G, K. Bürki, H L Lelieveld, A Bennett, and J L Mahler
- Subjects
Computer science ,business.industry ,Bioengineering ,Deliberate release ,Pathogenicity ,Risk assessment ,business ,Risk management ,Biotechnology ,Complement (complexity) - Abstract
Risk assessment for the deliberate release of microorganisms into the environment is traditionally carried out on a case-by-case basis. In a similar approach to that used when assessing human pathogenicity, we propose an alternative approach by introducing risk classes to facilitate or complement this type of risk assessment. These consider several sets of scenarios that address the different values that need to be protected. Examples of this approach include risk-class definitions for soil fertility and biodiversity.
- Published
- 1999
- Full Text
- View/download PDF
10. Nuclear magnetic resonance of 57Fe in Al-, Ga- and Ti-substituted magnetite above Verwey temperature
- Author
-
V. Chlan, H. Stepankova, K Kouril, Vam Vic Brabers, E. Gamaliy, J. Englich, Jaroslav Kohout, and Physics of Nanostructures
- Subjects
Oxide minerals ,Materials science ,Resonance ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,NMR spectra database ,chemistry.chemical_compound ,Charge ordering ,Nuclear magnetic resonance ,chemistry ,Octahedron ,Spin echo ,Hyperfine structure ,Magnetite - Abstract
Magnetite single crystals with Al, Ga and Ti substitutions were measured by means of 57Fe nuclear magnetic resonance (NMR) technique. Satellite structure of NMR spectra well above the Verwey temperature was detected and analyzed to obtain information on the distribution of substituting cations on iron sublattices. It was confirmed that Al and Ti enter iron octahedral B-sites. Ga strongly prefers tetrahedral A-sites, nevertheless a low presence of Ga cations in B-sites was detected.
- Published
- 2007
- Full Text
- View/download PDF
11. Safe biotechnology. 8. Transport of infectious and biological materials
- Author
-
H.-D. Schlumberger, K. Wagner, A. Zhilevicha, M. Nicu, J. Pazlerova, Economidis I, C.H. Collins, H. Stepankova, M. Sarvas, R. Marris, M. Romantschuk, C Frontali-Botti, C. Normand-Plessier, Crooy P, G. Leaver, F. Rudan, G. Brunius, O. Käppeli, R. Dubakiene, R Havenaar, L Martinez, K. Bürki, H Haymerle, J. Olsen, G. Tzotzos, M Lex, R. G. Werner, Boon B, C Mosgaard, G. Szvoboda, M Cantley, Doblhoff-Dier O, A Elmqvist, V. Vaicuivenas, H L Lelieveld, S. Lund, Bachmayer H, A Bennett, J.M. Collard, and J. L. Mahler
- Subjects
Internet resources ,Genetically modified microorganisms ,education ,MEDLINE ,Legislation ,General Medicine ,Applied Microbiology and Biotechnology ,Biological materials ,Terminology ,Diagnostic specimens ,Engineering ethics ,Business ,health care economics and organizations ,Biotechnology - Abstract
The transport of infectious and biological material is regulated by a number of international organizations. This mini-review has been compiled to increase awareness within the scientific community of problems caused by differences in terminology (such as infectious materials/substances, biological products, diagnostic specimens, genetically modified microorganisms) and certain technical aspects of the main international guidelines, and to assist policy makers in the creation of harmonized guidelines. A list of relevant Internet resources has been compiled.
- Published
- 1997
- Full Text
- View/download PDF
12. Low temperature behavior of hyperfine fields in amorphous and nanocrystalline FeMoCuB
- Author
-
Tomáš Kmječ, Jaroslav Kohout, H. Stepankova, A. Lančok, Lubomir Sklenka, Petr Křišt'an, Karel Závěta, Marcel Miglierini, Denisa Kubániová, and Peter Matúš
- Subjects
NMR spectra database ,Nuclear magnetic resonance ,Amorphous metal ,Materials science ,Mössbauer effect ,Impurity ,Analytical chemistry ,General Physics and Astronomy ,Hyperfine structure ,Nanocrystalline material ,Amorphous solid ,Mossbauer spectrometry - Abstract
Low temperature (4.2 K) magnetic behavior of Fe76Mo8Cu1B15 metallic glass was studied by 57Fe Mossbauer spectrometry (MS) and 57Fe NMR. Distributions of hyperfine magnetic fields P(B) were determined for as-quenched and annealed (nanocrystalline) samples with relative fraction of the grains about 43%. P(B) distributions were derived for both the amorphous matrix and nanocrystalline grains. NMR of alloys with natural and 57Fe enriched Fe enabled to assess the contribution of 11B to the total NMR signal. P(B) distribution of the as-quenched alloy derived from MS matches reasonably well the one from NMR of the enriched sample. NMR signal from the sample with natural Fe exhibits contributions from 11B nuclei. The principal NMR lines of the annealed alloys at 47 MHz correspond to bcc Fe nanocrystals. Small asymmetry of the lines towards higher frequencies might be an indication of possible impurity atoms in the bcc structure. The observed differences between natural and enriched samples are attributed to highe...
- Published
- 2015
- Full Text
- View/download PDF
13. NMR of 57Fe, 69Ga and 71Ga in Ga substituted magnetite
- Author
-
Vam Vic Brabers, V. Procházka, V. Chlan, J. Englich, E. Gamaliy, Jaroslav Kohout, H. Stepankova, and Physics of Nanostructures
- Subjects
Zone melting ,Materials science ,chemistry.chemical_element ,Nuclear magnetic resonance spectroscopy ,Condensed Matter Physics ,Electronic, Optical and Magnetic Materials ,NMR spectra database ,Charge ordering ,Crystallography ,chemistry.chemical_compound ,Nuclear magnetic resonance ,chemistry ,Gallium ,Single crystal ,Hyperfine structure ,Magnetite - Abstract
We report the NMR spectra of gallium substituted magnetite measured at temperatures 4.2, 77 and 273 K. A single crystal of Fe 3− x Ga x O 4 , x = 0.05 has been prepared by a floating zone technique. The Ga-lines found in the NMR spectrum above Verwey temperature T V ∼ 117 K indicate a preferency of Ga substitution into the tetrahedral A-sites. The well-resolved structure of Ga-lines has been identified and assigned to both Ga isotopes below T V . A weak quadrupolar interaction contributes only to the line broadening.
- Published
- 2005
14. NMR study of Ga and Al substituted hexagonal ferrites with magnetoplumbite structure
- Author
-
J. Englich, H. Lutgemeier, and H. Stepankova
- Subjects
NMR spectra database ,Crystallography ,Materials science ,Absorption spectroscopy ,Magnetic structure ,Condensed matter physics ,Relaxation (NMR) ,Spin echo ,Resonance ,Crystal structure ,Nuclear magnetic resonance spectroscopy ,Electrical and Electronic Engineering ,Electronic, Optical and Magnetic Materials - Abstract
/sup 57/Fe NMR spectra and relaxation rates in lead hexaferrite single crystals PbFe/sub 12/O/sub 19/, PbFe/sub 12-x/Ga/sub x/O/sub 19/, (x=0.42, 1.2) and PbFe/sub 12-x/Al/sub x/O/sub 19/, (x=0.21) have been measured at 4.2 K using spin echo technique. Besides the main lines corresponding to the nonequivalent positions of Fe/sup 3+/ ions in the magnetoplumbite structure, the satellite lines caused by substitution in the vicinity of resonating nuclei have been observed. The dependence of the NMR spectrum on the external magnetic field has been used to separate the overlapped satellites from different iron sites. The most distant satellites have been assigned to the resonance of iron nuclei at 4f/sub 1/ site with substitution at 12 k and 2a sites in their vicinity. A strong preference of 2a site for Al substitution has been found. >
- Published
- 1994
- Full Text
- View/download PDF
15. Safe biotechnology 9: values in risk assessment for the environmental application of microorganisms. The Safety in Biotechnology Working Party of the European Federation of Biotechnology
- Author
-
O, Doblhoff-Dier, H, Bachmayer, A, Bennett, G, Brunius, K, Bürki, M, Cantley, C, Collins, P, Crooy, A, Elmqvist, C, Frontali-Botti, R, Havenaar, H, Haymerle, H, Lelieveld, M, Lex, J L, Mahler, L, Martinez, C, Mosgaard, L, Olsen, J, Pazlarova, F, Rudan, M, Sarvas, H, Stepankova, G, Tzotzos, K, Wagner, and R, Werner
- Subjects
Europe ,Risk Management ,Bioreactors ,Bacteria ,Water Supply ,Humans ,Soil Pollutants ,Environmental Pollution ,Microbiology ,Risk Assessment ,Ecosystem ,Biotechnology - Abstract
Risk assessment for the deliberate release of microorganisms into the environment is traditionally carried out on a case-by-case basis. In a similar approach to that used when assessing human pathogenicity, we propose an alternative approach by introducing risk classes to facilitate or complement this type of risk assessment. These consider several sets of scenarios that address the different values that need to be protected. Examples of this approach include risk-class definitions for soil fertility and biodiversity.
- Published
- 1999
16. Antisite Defects in Yttrium Iron Garnet
- Author
-
Pavel Novák, W. Tolksdorf, H. Stepankova, K. Wagner, H. Lütgemeier, Jaroslav Kohout, and J. Englich
- Subjects
Materials science ,Yttrium iron garnet ,General Physics and Astronomy ,chemistry.chemical_element ,Mineralogy ,Yttrium ,01 natural sciences ,Spectral line ,010305 fluids & plasmas ,Ion ,NMR spectra database ,chemistry.chemical_compound ,Crystallography ,chemistry ,Impurity ,Formula unit ,[PHYS.HIST]Physics [physics]/Physics archives ,0103 physical sciences ,Crystallite - Abstract
NMR of 57 Fe nuclei is used to study the Y antisite defects (yttrium ions on the sites nominally occupied by iron) in yttrium-iron garnet (YIG). In spectra of both tetrahedral and octahedral Fe 3+ ions, satellite lines appear, corresponding to Fe 3+ ions with this defect in their vicinity. NMR was measured on a number of nominally pure YIG samples - single crystals, thin films as well as polycrystalline samples. The content X Y per formula unit of the Y antisite defect (Y a ) was determined from the amplitude of the satellite lines and it lies in the interval 0.001< x y < 0.03. In most cases the satellite lines caused by the Y a defect are obscured by the satellites originating from other impurities. In two high purity single crystals the satellites caused by Y a dominate, however. In the NMR spectra of these single crystals the satellite lines which correspond to the Felt ions in seven different crystallographically inequivalent positions with respect to the defect are resolved at low temperatures. Further unresolved satellites emerge from the main lines as the temperature is increased.
- Published
- 1997
- Full Text
- View/download PDF
17. The Effect of Diamagnetic Defect in YIG on the Hyperfine Field Anisotropy
- Author
-
J. Englich, H. Lütgemeier, H. Stepankova, P. Novak, and Jaroslav Kohout
- Subjects
010302 applied physics ,Condensed matter physics ,Field (physics) ,Chemistry ,General Physics and Astronomy ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Magnetic field ,NMR spectra database ,[PHYS.HIST]Physics [physics]/Physics archives ,0103 physical sciences ,Spin echo ,Diamagnetism ,0210 nano-technology ,Anisotropy ,Hyperfine structure ,Single crystal - Abstract
The dependence of 57 Fe NMR spectra in YIG on the external magnetic field direction was measured at 4.2K. The high purity single crystal of a spherical form was used. The external magnetic field of 0.75T was applied in several directions lying in (110) plane. The satellite structure of the spectra caused by an antisite defects Y(a) (Y 3+ ion on the a site, nominally occupied by Fe 3+ ion) enabled us to study the effect of a nonmagnetic impurity on the 57 Fe hyperfine field anisotropy. The tensors of hyperfine interaction for 57 Fe in d- sites with the nearest and next nearest Y(a) defect were obtained from NMR data. The results were confronted with the predictions of the independent bond model.
- Published
- 1997
- Full Text
- View/download PDF
18. NMR of 57Fe below and around the Verwey transition in Al-substituted magnetite
- Author
-
H. Stepankova, Vam Vic Brabers, Jaroslav Kohout, E. Gamaliy, J. Englich, Pavel Novák, and Physics of Nanostructures
- Subjects
Oxide minerals ,Materials science ,Condensed matter physics ,Analytical chemistry ,Resonance ,Condensed Matter Physics ,Spectral line ,Electronic, Optical and Magnetic Materials ,NMR spectra database ,Charge ordering ,chemistry.chemical_compound ,chemistry ,Electrical resistivity and conductivity ,Hyperfine structure ,Magnetite - Abstract
Temperature dependence of 57 Fe NMR spectra was measured below and around the Verwey transition in Fe 3− x Al x O 4 ( x =0, 0.005, 0.01, 0.02, 0.03) single crystals. All lines of substituted samples were broadened with increasing Al concentration, but we have found no change in their positions. The Verwey temperature T V decreases with increasing Al concentration in agreement with electric conductivity measurements. The satellite structure found in the vicinity of the A-line above T V disappears below T V , on the other hand a broad spectrum in the spectral region 35–45 MHz at temperature 4.2 K was detected.
- Published
- 2004
- Full Text
- View/download PDF
19. Evidence for magnetic interactions between distant cations in yittrium iron garnet
- Author
-
W. Tolksdorf, H. Stepankova, J. Englich, Jaroslav Kohout, K. Wagner, H. Lütgemeier, and P. Novak
- Subjects
Physics ,Crystallography ,Coordination sphere ,General Physics and Astronomy ,Nuclear magnetic resonance spectroscopy ,Ion - Abstract
The NMR spectrum of ${}^{57}\mathrm{Fe}$ nuclei in high purity ${\mathrm{Y}}_{3}{\mathrm{Fe}}_{5}{\mathrm{O}}_{12}$ garnet (YIG) is reported. The satellite structure of this spectrum is caused by an antisite defect ( ${\mathrm{Y}}^{3+}$ ion replacing an ${\mathrm{Fe}}^{3+}$ ion). Resolved satellite lines, which correspond to the ${\mathrm{Fe}}^{3+}$ ion in six different cation coordination spheres around the defect, are observed. In particular, satellite lines arising from the ${\mathrm{Fe}}^{3+}$ ions' distance of which from the defect is as large as 1.07 nm (11th coordination sphere) are identified unambiguously. The results yield information on the range of magnetic interactions in YIG.
- Published
- 1995
20. Easy axis switching in magnetite
- Author
-
Joachim Kusz, V. Chlan, W. Tabiś, Tomasz Kolodziej, Z Tarnawski, G. Król, H. Stepankova, A. Kozłowski, Z. Kąkol, A Wiśniewski, and Jurgen M. Honig
- Subjects
History ,Materials science ,Condensed matter physics ,Field dependence ,Activation energy ,Computer Science Applications ,Education ,Magnetic field ,Crystallography ,chemistry.chemical_compound ,Charge ordering ,Magnetic anisotropy ,Magnetization ,chemistry ,Electrical resistivity and conductivity ,Magnetite - Abstract
The easy magnetic axis switching in magnetite is investigated. Magnetization data confirmed activation character of the process with activation energy of the same order as that of the Verwey transition, suggesting common origin. On the other hand this activation energy rises with pressure (up to 1.2GPa), unlike TV. The axis switching is clearly reflected in field dependence of resistivity and the direct structural data showed that it is simultaneous with the reorganization of structure. Thus, control of the structure can be possible with the application of magnetic field, as in shape memory materials. Finally, NMR showed that all, possibly decoupled entities: lattice distortion and charge and orbital orderings, change simultaneously while the axis switching occurs.
- Published
- 2011
- Full Text
- View/download PDF
21. Nuclear spin-lattice relaxation of Co nuclei in a Fe/Co multilayer at low temperatures
- Author
-
E Beck, H. Stepankova, Guido Langouche, J Dekoster, M. Trhlik, William D. Brewer, and Jaroslav Kohout
- Subjects
Materials science ,Condensed matter physics ,Impurity ,Lattice (order) ,Analytical chemistry ,General Physics and Astronomy ,Temperature cycling ,Hyperfine structure ,Nuclear orientation ,Magnetic field - Abstract
Low-temperature nuclear orientation has been applied to the study of the nuclear spin-lattice relaxation (SLR) of60Co in the Co phase of a single-crystalline [Co(21 A) /Fe(24 A)]25 multilayer. The Co layers previously were shown to follow the bcc structure of Fe. The hyperfine field (Bhf) distribution was studied by NMR on59Co in the same sample. We applied the thermal cycling (TC) method at temperatures around 9 mK in the external magnetic field (Bext) range 0.05–1 T to determine the SLR, which was found for Co in bcc Co to be about seven times faster than the SLR of Co in Fe. Moreover, the (Bext) dependence of the SLR as observed for impurities in Fe and Co in fcc Co was not found.
- Published
- 1996
- Full Text
- View/download PDF
22. NMR in magnetite below and around the Verwey transition
- Author
-
Jaroslav Kohout, Vam Vic Brabers, Pavel Novák, J. Englich, H. Stepankova, and Physics of Nanostructures
- Subjects
Physics ,Crystallography ,chemistry.chemical_compound ,Charge ordering ,Condensed matter physics ,Octahedron ,chemistry ,Relaxation (NMR) ,Spectral line ,Magnetite - Abstract
NMR on ${}^{57}\mathrm{Fe}$ nuclei was measured in two single crystals of magnetite between 4.2 and 135 K (temperature of the Verwey transition ${T}_{V}=121.5$ and 123.9 K). We were able to register all lines detected at 4.2 K also at higher temperatures up to ${T}_{V}.$ The spectra are compatible with the space group $Cc,$ which predicts 8 and 16 lines for iron on tetrahedral (A) and octahedral (B) sites, respectively. One of the $\mathrm{Fe}(A)$ lines is doubly degenerate for all $Tl{T}_{V},$ which restricts the possible models of the ${\mathrm{Fe}}^{2+}$ and ${\mathrm{Fe}}^{3+}$ ordering on the B sites. Above ${T}_{V}$ no remnant of the low-temperature spectrum was detected. At 4.2 K the NMR spin-spin and spin-lattice relaxation times were determined.
23. Umbrella structure in Pr, Nd and Yb substituted YIG studied by 57Fe NMR
- Author
-
H. Lütgemeier, H. Stepankova, Pavel Novák, Jaroslav Kohout, J. Englich, and M. Nekvasil
- Subjects
Magnetic structure ,Magnetic moment ,Chemistry ,General Physics and Astronomy ,01 natural sciences ,010305 fluids & plasmas ,Ion ,NMR spectra database ,Dipole ,Crystallography ,Nuclear magnetic resonance ,Octahedron ,[PHYS.HIST]Physics [physics]/Physics archives ,0103 physical sciences ,Spin echo ,Hyperfine structure - Abstract
The NMR spectra of 57 Fe in Pr:YIG, Nd:YIG and Yb:YIG were measured on polycrystalline samples at 4.2 K in the zero external field. In the NMR spectra of both tetrahedral and octahedral sites the resolved satellite structure appears. This structure is caused by the change of the hyperfine field on the nuclei of those Fe 3+ ions, which are the nearest or next nearest neighbours of the substituted Re 3+ ion. The change of the hyperfine field is given by the change of dipole and transferred contribution. Both contributions are sensitive to the kind of Re 3+ ion and to the value and direction of its magnetic moment. The satellite structure of NMR spectra provides sufficient amount of information (splitting) to find unknown parameters of the non-collinear (umbrella) arrangement of Re 3+ magnetic moments.
- Full Text
- View/download PDF
24. Unveiling the nanotoxicological aspects of Se nanomaterials differing in size and morphology.
- Author
-
Stepankova H, Michalkova H, Splichal Z, Richtera L, Svec P, Vaculovic T, Pribyl J, Kormunda M, Rex S, Adam V, and Heger Z
- Abstract
Although the general concept of nanotechnology relies on exploitation of size-dependent properties of nanoscaled materials, the relation between the size/morphology of nanoparticles with their biological activity remains not well understood. Therefore, we aimed at investigating the biological activity of Se nanoparticles, one of the most promising candidates of nanomaterials for biomedicine, possessing the same crystal structure, but differing in morphology (nanorods vs. spherical particles) and aspect ratios (AR, 11.5 vs. 22.3 vs. 1.0) in human cells and BALB/c mice. Herein, we report that in case of nanorod-shaped Se nanomaterials, AR is a critical factor describing their cytotoxicity and biocompatibility. However, spherical nanoparticles (AR 1.0) do not fit this statement and exhibit markedly higher cytotoxicity than lower-AR Se nanorods. Beside of cytotoxicity, we also show that morphology and size substantially affect the uptake and intracellular fate of Se nanomaterials. In line with in vitro data, in vivo i.v. administration of Se nanomaterials revealed the highest toxicity for higher-AR nanorods followed by spherical nanoparticles and lower-AR nanorods. Moreover, we revealed that Se nanomaterials are able to alter intracellular redox homeostasis, and affect the acidic intracellular vesicles and cytoskeletal architecture in a size- and morphology-dependent manner. Although the tested nanoparticles were produced from the similar sources, their behavior differs markedly, since each type is promising for several various application scenarios, and the presented testing protocol could serve as a concept standardizing the biological relevance of the size and morphology of the various types of nanomaterials and nanoparticles., (© 2022 The Authors.)
- Published
- 2022
- Full Text
- View/download PDF
25. The Anti-Proliferative Activity of Coordination Compound-Based ZnO Nanoparticles as a Promising Agent Against Triple Negative Breast Cancer Cells.
- Author
-
Stepankova H, Swiatkowski M, Kruszynski R, Svec P, Michalkova H, Smolikova V, Ridoskova A, Splichal Z, Michalek P, Richtera L, Kopel P, Adam V, Heger Z, and Rex S
- Subjects
- Apoptosis drug effects, Cell Line, Tumor, Cell Proliferation drug effects, Humans, Antineoplastic Agents chemistry, Antineoplastic Agents pharmacology, Nanoparticles chemistry, Triple Negative Breast Neoplasms pathology, Zinc Oxide chemistry, Zinc Oxide pharmacology
- Abstract
Purpose: The present study deals with the in vitro evaluation of the potential use of coordination compound-based zinc oxide (ZnO) nanoparticles (NPs) for the treatment of triple negative breast cancer cells (TNBrCa). As BrCa is one of the most prevalent cancer types and TNBrCa treatment is difficult due to poor prognosis and a high metastasis rate, finding a more reliable treatment option should be of the utmost interest., Methods: Prepared by reacting zinc carboxylates (formate, acetate, propionate, butyrate, isobutyrate, valerate) and hexamethylenetetramine, 4 distinct coordination compounds were further subjected to two modes of conversion into ZnO NPs - ultrasonication with oleic acid or heating of pure precursors in an air atmosphere. After detailed characterization, the resulting ZnO NPs were subjected to in vitro testing of cytotoxicity toward TNBrCa and normal breast epithelial cells. Further, their biocompatibility was evaluated., Results: The resulting ZnO NPs provide distinct morphological features, size, biocompatibility, and selective cytotoxicity toward TNBrCa cells. They internalize into two types of TNBrCa cells and imbalance their redox homeostasis, influencing their metabolism, morphology, and ultimately leading to their death via apoptosis or necrosis., Conclusion: The crucial properties of ZnO NPs seem to be their morphology, size, and zinc content. The ZnO NPs with the most preferential values of all three properties show great promise for a future potential use in the therapy of TNBrCa., Competing Interests: The authors report no conflicts of interest in this work., (© 2021 Stepankova et al.)
- Published
- 2021
- Full Text
- View/download PDF
26. Determining a Short Form Montreal Cognitive Assessment (s-MoCA) Czech Version: Validity in Mild Cognitive Impairment Parkinson's Disease and Cross-Cultural Comparison.
- Author
-
Bezdicek O, Červenková M, Moore TM, Stepankova Georgi H, Sulc Z, Wolk DA, Weintraub DA, Moberg PJ, Jech R, Kopecek M, and Roalf DR
- Subjects
- Cognition, Cross-Cultural Comparison, Czech Republic, Humans, Mental Status and Dementia Tests, Neuropsychological Tests, Cognitive Dysfunction diagnosis, Parkinson Disease diagnosis
- Abstract
The Montreal Cognitive Assessment (MoCA) is one of the most common screening instruments for mild cognitive impairment. However, the standard MoCA is approximately two times longer to administer than the Mini-Mental State Examination. A total of 699 Czech and 175 American participants received the standard MoCA Czech and English versions and in the clinical part, a sample of 102 nondemented patients with Parkinson's disease (PD). We created a validated Czech short version (s-MoCA-CZ) from the original using item response theory. As expected, s-MoCA-CZ scores were highly correlated with the standard version (Pearson r = .94, p < .001). s-MoCA-CZ also had 80% classification accuracy in the differentiation of PD mild cognitive impairment from PD without impairment. The s-MoCA-CZ, a brief screening tool, is shorter to administer than the standard MoCA. It provides high-classification accuracy for PD mild cognitive impairment and is equivalent to that of the standard MoCA-CZ.
- Published
- 2020
- Full Text
- View/download PDF
27. Young-Old City-Dwellers Outperform Village Counterparts in Attention and Verbal Control Tasks.
- Author
-
Stepankova Georgi H, Frydrychova Z, Horakova Vlckova K, Vidovicova L, Sulc Z, and Lukavsky J
- Abstract
Cognitive performance is dynamic and shaped by individual biological and environmental factors throughout life. In psychology, besides the effects of age, education, and other often studied factors, the complexity of the lived-in environment and urbanicity in that context are yet to be elucidated. In this observational cross-sectional study, we compare cognitive performance in standard neuropsychological tests in healthy older persons from three different types of settlements in the Czechia: the capital city of Prague, towns, and villages. The groups were equal in terms of the age-band (60-74 years), the distribution of gender, education, past and current leisure activities, and cognitive health status (MMSE score). The results showed that Prague citizens had consistently better performance in all verbal tests (for memory and verbal control, i.e., executive function) and attention than persons from other areas. The groups did not differ in timed visuo-graphomotor performance. The conclusion is that the complex environment of a city may promote, in the long-term, certain cognitive abilities, distinguishable even in a developed, culturally homogenous country. The implications are: (a) the description of samples used in normative studies should include information on the lived-in environment for the reference of researchers and clinicians; and (b) individual clinical assessment should reflect the role of the patient's environment where appropriate. The exact mechanisms and causes of the differences need further investigation.
- Published
- 2019
- Full Text
- View/download PDF
28. Beck Depression Inventory-II: Self-report or interview-based administrations show different results in older persons.
- Author
-
Stepankova Georgi H, Horakova Vlckova K, Lukavsky J, Kopecek M, and Bares M
- Subjects
- Aged, Aged, 80 and over, Depressive Disorder diagnosis, Female, Humans, Male, Middle Aged, Reproducibility of Results, Depression diagnosis, Interview, Psychological, Psychometrics methods, Self Report
- Abstract
ABSTRACTBeck Depression Inventory-II (BDI-II) is one of the most-used rating scales. It was developed as a tool administered either as a self-rating or interview-based, observer-rating scale., Objective: The goal of this study is to compare BDI-II scores obtained with two standard methods of administration in community-based older persons., Methods: BDI-II was administered at first in the self-rated version to a sample of 60 mentally healthy older persons (age 60-87 years). Afterward, the interview-based administration was performed., Analyses: We compared the scores with nonparametric tests - Spearman's correlation coefficient and Wilcoxon Signed Ranks test. We also computed internal consistency., Results: Self-rated BDI-II yielded significantly higher total score than interview (p < 0.001, P = 88%). The correlation between total scores was moderate (rs = 0.46, p < 0.001). Item analysis revealed a larger decrease (lower scores) in the somatic items in the interview-based version., Conclusions: The two methods of administration result in different total score in healthy older persons. Therefore, interpretation of the scores should reflect the administration, which should be always specified in the studies.
- Published
- 2019
- Full Text
- View/download PDF
29. Semantic verbal fluency impairment is detectable in patients with subjective cognitive decline.
- Author
-
Nikolai T, Bezdicek O, Markova H, Stepankova H, Michalec J, Kopecek M, Dokoupilova M, Hort J, and Vyhnalek M
- Subjects
- Aged, Aged, 80 and over, Analysis of Variance, Female, Humans, Male, Middle Aged, Neuropsychological Tests, Retrospective Studies, Cognition Disorders complications, Semantics, Speech Disorders diagnosis, Speech Disorders etiology, Verbal Behavior physiology
- Abstract
Patients with subjective cognitive decline (SCD) are at higher risk for conversion to dementia due to Alzheimer's disease (AD). Semantic verbal fluency (SVF) seems to be impaired in the early stages of AD. The goal of the present study was to identify the discriminative potential of verbal fluency (VF) in patients with SCD to show if very early signs of cognitive decline may be detected in SCD. We examined 93 normal controls (NC) and 61 participants with SCD. Each participant was administered a comprehensive neuropsychological battery. All participants underwent tests of VF: phonemic verbal fluency (PVF), letters K and P and SVF (animals and vegetables categories). In addition to the total score, two 30-second intervals, and clustering and switching indices in SVF were evaluated. SCD generated fewer words in the total score and 30- to 60-second interval in vegetables category and they performed more switches in animals category. There was no significant difference between the SCD and the NC groups in all other VF measures. Quantitative measures of SVF (a decreased number of vegetables) as well as qualitative measures were detected in SCD group and could be considered as an early neuropsychological marker of subtle cognitive impairment.
- Published
- 2018
- Full Text
- View/download PDF
30. The Uniform Data Set, Czech Version: Normative Data in Older Adults from an International Perspective.
- Author
-
Nikolai T, Stepankova H, Kopecek M, Sulc Z, Vyhnalek M, and Bezdicek O
- Subjects
- Aged, Aged, 80 and over, Cognition, Czech Republic, Female, Humans, Internationality, Male, Middle Aged, National Institute on Aging (U.S.), Psychometrics methods, Reference Values, Regression Analysis, United States, Alzheimer Disease diagnosis, Neuropsychological Tests standards
- Abstract
Background: Outside of the United States, international perspectives on normative data for neuropsychological test performance, within diverse populations, have been scarce. The neuropsychological test battery from the Uniform Data Set (UDS) of the Alzheimer's Disease Centers (ADC) program of the United States National Institute on Aging (NIA) is one of the most sensitive batteries for the evaluation of both normal cognitive aging and pathological cognitive decline., Objective: This study aimed to determine the feasibility of the Czech Neuropsychological Test Battery from the Uniform Data Set (UDS-Cz 2.0), while also evaluating the results obtained from an international perspective., Methods: This paper describes data from 520 cognitively normal participants. Regression analyses were used to describe the influence of demographic variables on UDS-Cz test performance., Results: Cognitive performance on all measures declined with age, with patient education level serving as a protective factor. Therefore, the present study provides normative data for the UDS-Cz, adjusted for the demographic variables of age and education., Conclusion: The present study determines the psychometric properties of the UDS-Cz and establishes normative values in the aging Czech population, which can be used in clinical settings.
- Published
- 2018
- Full Text
- View/download PDF
31. The Reliability of Clock Drawing Test Scoring Systems Modeled on the Normative Data in Healthy Aging and Nonamnestic Mild Cognitive Impairment.
- Author
-
Mazancova AF, Nikolai T, Stepankova H, Kopecek M, and Bezdicek O
- Subjects
- Age Distribution, Aged, Aged, 80 and over, Case-Control Studies, Czech Republic, Female, Hospitals, University, Humans, Male, Middle Aged, Reproducibility of Results, Statistics, Nonparametric, Cognitive Dysfunction diagnosis, Healthy Aging psychology, Neuropsychological Tests standards
- Abstract
The Clock Drawing Test (CDT) is a commonly used tool in clinical practice and research for cognitive screening among older adults. The main goal of the present study was to analyze the interrater reliability of three different CDT scoring systems (by Shulman et al., Babins et al., and Cohen et al.). We used a clock with a predrawn circle. The CDT was evaluated by three independent raters based on the normative data set of healthy older and very old adults and patients with nonamnestic mild cognitive impairment (naMCI; N = 438; aged 61-94). We confirmed a high interrater reliability measured by the intraclass correlation coefficients (ICCs): Shulman ICC = .809, Babins ICC = .894, and Cohen ICC = .862, all p < .001. We found that age and education levels have a significant effect on CDT performance, yet there was no influence of gender. Finally, the scoring systems differentiated between naMCI and age- and education-matched controls: Shulman's area under the receiver operating characteristic curve (AUC) = .84, Cohen AUC = .71, all p < .001; and a slightly lower discriminative ability was shown by Babins: AUC = .65, p = .012.
- Published
- 2017
- Full Text
- View/download PDF
32. Montreal Cognitive Assessment and Mini-Mental State Examination reliable change indices in healthy older adults.
- Author
-
Kopecek M, Bezdicek O, Sulc Z, Lukavsky J, and Stepankova H
- Subjects
- Aged, Aged, 80 and over, Analysis of Variance, Brief Psychiatric Rating Scale, Disease Progression, Female, Geriatric Assessment methods, Humans, Male, Middle Aged, Cognitive Dysfunction diagnosis, Mental Status and Dementia Tests, Neuropsychological Tests
- Abstract
Objective: Cognitive tests are used repeatedly to assess the treatment response or progression of cognitive disorders. The Montreal Cognitive Assessment (MoCA) is a valid screening test for mild cognitive impairment. The aim of our study was to establish 90% reliable change indices (RCI) for the MoCA together with the Mini-Mental State Examination (MMSE) in cognitively healthy older adults., Method: We analyzed 197 cognitively healthy and functional independent volunteers aged 60-94 years, who met strict inclusion criteria for four consecutive years. The RCI methods by Chelune and Hsu were used., Results: For 1, 2, and 3 years, the 90% RCI for MoCA using Chelune's formula were -4 ≤, ≥4; -4 ≤, ≥4 and -5 ≤, ≥4 points, respectively, and -3 ≤, ≥3 for the MMSE each year. Ninety percent RCI for MoCA using Hsu's formula ranged from -6 to 0, respectively, and +3 to +8 dependent on the baseline MoCA., Conclusion: Our study demonstrated RCI for the MoCA and MMSE in a 3-year time period that can be used for the estimation of cognitive decline or improvement in clinical settings. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)
- Published
- 2017
- Full Text
- View/download PDF
33. A parsimonious scoring and normative calculator for the Parkinson's disease mild cognitive impairment battery.
- Author
-
Bezdicek O, Sulc Z, Nikolai T, Stepankova H, Kopecek M, Jech R, and Růžička E
- Subjects
- Adult, Aged, Aged, 80 and over, Cohort Studies, Female, Humans, Male, Middle Aged, Cognitive Dysfunction diagnosis, Neuropsychological Tests standards, Parkinson Disease psychology, Psychometrics methods
- Abstract
Objective: The aim of the present study was to provide a regression-based calculator that takes premorbid functioning into account to detect subtle cognitive decline, as is often present in pre-dementia states, especially mild cognitive impairment in Parkinson's disease (PD-MCI)., Method: We used demographic adjustments based on sex, age, and education of 699 normative participants that fulfilled exclusion criteria for ascertaining the diagnostic accuracy of the Movement Disorders Society PD-MCI battery at Level II. We examined the clinical validity of the battery on 36 PD patients., Results: An estimated z-score was calculated for any raw score based on different models that adjust for the demographic predictors of gender, age, and education, either concurrently, individually or without covariates. We provide a useful online z-score, SD, and percentile calculator that yields estimates of cognitive impairment based on normative sample for each of the ten neuropsychological tests and enables actuarial decision-making regarding its level and profile (number of domains impaired). We document the clinical utility and applicability of the calculator on a patient with PD-MCI and show the discriminative validity of all measures in the battery by comparing PD-MCI and PD without cognitive impairment with the highest area under the curve (.94) for Tower of London at -2 SD threshold., Conclusions: Our normative calculator introduces a practical web-based psychometric tool for the evaluation of PD-MCI status in clinical settings. We show the detection potential of each of ten measures included in the battery and delineate the diagnostic precision of the PD-MCI battery.
- Published
- 2017
- Full Text
- View/download PDF
34. Montreal cognitive assessment (MoCA): Normative data for old and very old Czech adults.
- Author
-
Kopecek M, Stepankova H, Lukavsky J, Ripova D, Nikolai T, and Bezdicek O
- Subjects
- Age Factors, Aged, Aged, 80 and over, Analysis of Variance, Czech Republic, Female, Humans, Longitudinal Studies, Male, Mental Status Schedule, Middle Aged, Neuropsychological Tests, Reference Values, Aging psychology, Cognition physiology, Geriatric Assessment
- Abstract
The principal aim of our study was to present norms for old and very old Czech adults on the Czech version of the Montreal Cognitive Assessment (MoCA) and investigate the influence of social and demographic factors on MoCA performance. We analyzed 540 adults aged ≥ 60 years (5-year age categories; nationally representative sample in terms of sex and educational level), who met strict inclusion criteria for the absence of neurodegenerative disorders and performed within normal range in neuropsychological assessment. Using multiple regression model, we found that MoCA performance was affected by age and education (both p < .001) but not sex. The study provides normed percentile estimates for MoCA performance stratified by age (60-74 years; ≥ 75 years) and education lower versus higher. We also present percentile equivalents for the MoCA and Mini-Mental State Examination (MMSE) for use in clinical practice. We found age- and education-related effects on MoCA performance which support the use of culturally adapted normative data.
- Published
- 2017
- Full Text
- View/download PDF
35. Subjective Cognitive Complaints in Cognitively Healthy Older Adults and Their Relationship to Cognitive Performance and Depressive Symptoms.
- Author
-
Markova H, Andel R, Stepankova H, Kopecek M, Nikolai T, Hort J, Thomas-Antérion C, and Vyhnalek M
- Subjects
- Aged, Aged, 80 and over, Cognition Disorders epidemiology, Depression epidemiology, Female, Humans, Independent Living, Longitudinal Studies, Male, Mental Status Schedule, Middle Aged, Neuropsychological Tests, Personality, Surveys and Questionnaires, Aging psychology, Cognition Disorders physiopathology, Cognition Disorders psychology, Depression physiopathology, Depression psychology
- Abstract
Background: Subjective cognitive complaints (SCCs) may be an early marker of prodromal Alzheimer's disease., Objectives: Using a 10-item yes/no SCCs questionnaire (Le Questionnaire de Plainte Cognitive [QPC]), we evaluated the prevalence and distribution of SCCs in cognitively healthy Czech older adults and examined total score and specific QPC items in relation to depressive symptomology and cognitive performance., Methods: A sample of 340 cognitively healthy older community-dwelling volunteers aged 60 or older from the third wave of the longitudinal project National Normative Study of Cognitive Determinants of Healthy Aging, who underwent a comprehensive neuropsychological assessment and completed the QPC and the 15-item Geriatric Depression Scale (GDS-15). Regression analysis was controlled for age when GDS-15 was the outcome and for age and GDS-15 with cognitive domains as the outcome., Results: 71% reported 1 + SCCs, with prevalence of individual complaints ranging from 4% to 40%. The number of SCCs was associated with GDS-15 (p < 0.001). Personality change (p < 0.001) and Limitation in daily activities (p = 0.002) were significantly associated with higher GDS-15 score and Spatial orientation difficulties (p = 0.019) and Impression of worse memory in comparison to peers (p = 0.012) were significantly associated with lower memory performance., Conclusions: We identified some cognitive complaints that were very common in our sample. Overall, a higher number of SCCs in well cognitively functioning individuals was most closely related to depressive symptomatology, while some specific complaints reflected lower memory performance and should be considered when screening for people at risk of cognitive decline.
- Published
- 2017
- Full Text
- View/download PDF
36. Clinimetric validity of the Trail Making Test Czech version in Parkinson's disease and normative data for older adults.
- Author
-
Bezdicek O, Stepankova H, Axelrod BN, Nikolai T, Sulc Z, Jech R, Růžička E, and Kopecek M
- Subjects
- Aged, Aged, 80 and over, Cognition, Cognitive Dysfunction psychology, Czech Republic, Female, Humans, Male, Middle Aged, Neuropsychological Tests, Reference Values, Parkinson Disease diagnosis, Parkinson Disease psychology, Trail Making Test
- Abstract
Objective: The influence of demographic variables on the Trail Making Test (TMT) performance in older individuals and empirical findings on clinical validity in predementia states, such as Parkinson's disease mild cognitive impairment (PD-MCI), are limited. The principal aim of this study was to add normative data for the Czech population of older adults and explore the clinimetric properties between PD-MCI and PD patients with normal cognition (PD-NC)., Method: The study included 125 PD patients classified as 77 PD-MCI and 48 PD-NC and 528 older individuals (60-74 years, further subdivided for normative tables into 60-64, 65-69 and 70-74 age groups) and very old individuals (aged 75-96, further subdivided into 75-79, 80-84, 85-96) cognitively intact Czech adults., Results: Mostly age, to a lesser extent education but not gender, was associated with most TMT basic and derived indices (TMT-B - A). However, the ratio of TMT-B/TMT-A was independent of both age and education. We provide corresponding T-scores that minimize the effect of demographic variables. The results showed a high discriminative validity of TMT basic and derived indices for the differentiation of PD-MCI from PD-NC (all p < .05). The classification accuracy for the differentiation of PD-MCI from controls was optimal for the TMT-B only (80% area under the curve) based on norm adjusted scores. The classification accuracy of the TMT for PD-MCI vs. PD-NC was suboptimal., Conclusions: The cut-offs and normative standards are useful in clinical practice for those working with PD patients and very old adults.
- Published
- 2017
- Full Text
- View/download PDF
37. Propositional Density in Spoken and Written Language of Czech-Speaking Patients With Mild Cognitive Impairment.
- Author
-
Smolík F, Stepankova H, Vyhnálek M, Nikolai T, Horáková K, and Matejka Š
- Subjects
- Age Factors, Aged, Aged, 80 and over, Educational Status, Female, Humans, Male, Middle Aged, Neuropsychological Tests, Sex Factors, Cognitive Dysfunction psychology, Linguistics, Speech, Writing
- Abstract
Purpose: Propositional density (PD) is a measure of content richness in language production that declines in normal aging and more profoundly in dementia. The present study aimed to develop a PD scoring system for Czech and use it to compare PD in language productions of older people with amnestic mild cognitive impairment (aMCI) and control participants matched on age, gender, and education., Method: Groups of patients with aMCI and cognitively healthy control participants (N = 20 each) provided short spoken and written language samples. Two samples were elicited for each modality, 1 describing recent events and 1 describing childhood memories. Series of neuropsychological tests were administered. The groups were compared using t-tests and the relations between measures using correlation coefficients., Results: PD was lower in spoken productions of patients with aMCI, compared with control participants, but only in language samples using remote memories. PD in these samples was related to verbal fluency and education but not to working memory. PD in written samples did not differ between participants with aMCI and control participants., Conclusions: PD in spoken language reflects the cognitive decline in people with aMCI, but the effect is relatively mild. The results support the existing findings that PD is related to verbal fluency.
- Published
- 2016
- Full Text
- View/download PDF
38. Toward the processing speed theory of activities of daily living in healthy aging: normative data of the Functional Activities Questionnaire.
- Author
-
Bezdicek O, Stepankova H, Martinec Novakova L, and Kopecek M
- Subjects
- Activities of Daily Living, Age Factors, Aged, Aged, 80 and over, Czech Republic, Depression, Educational Status, Female, Humans, Male, Memory, Episodic, Middle Aged, Neuropsychological Tests, Reference Values, Surveys and Questionnaires, Aging physiology, Aging psychology, Executive Function, Motor Skills, Psychomotor Performance, Visual Perception
- Abstract
Background: The aim of this study was to describe an instrumental activities of daily living (IADL) measure: Functional Activities Questionnaire (FAQ), which is often used in clinical settings as a self- or informant-based measure of IADL. However, the FAQ's relationship with age or education in healthy aging has not been investigated., Methods: FAQ and a neuropsychological battery were administered to old and very old Czech adults (n = 540). Participants met strict inclusion criteria for the absence of any active or past neurodegenerative disorders., Results: FAQ is significantly dependent on age and education, but not gender. Younger subjects and those with higher education have the lowest scores in the FAQ and show a higher degree of functional independence. FAQ moderately correlates with speed of processing, visual-perceptual and executive functions measures (Trail Making Tests, Stroop Test) and depressive symptoms, but not with episodic memory (WMS-III logical memory). We present normative percentile values for different age groups from 60 to 96 years of age., Conclusions: The present study shows conclusively that IADL measures, such as FAQ, should not be used without appropriate normative data, especially in very old adults. Thus, it has the ability to differentiate functional dependence due to age-related decline from neurodegenerative disease.
- Published
- 2016
- Full Text
- View/download PDF
39. The Prague Stroop Test: Normative standards in older Czech adults and discriminative validity for mild cognitive impairment in Parkinson's disease.
- Author
-
Bezdicek O, Lukavsky J, Stepankova H, Nikolai T, Axelrod BN, Michalec J, Růžička E, and Kopecek M
- Subjects
- Age Distribution, Aged, Aged, 80 and over, Analysis of Variance, Czech Republic, Discriminant Analysis, Female, Functional Laterality, Humans, Longitudinal Studies, Male, Middle Aged, ROC Curve, Reference Values, Cognitive Dysfunction diagnosis, Cognitive Dysfunction epidemiology, Cognitive Dysfunction etiology, Parkinson Disease complications, Parkinson Disease epidemiology, Stroop Test standards
- Abstract
Objective: The aim of this study was to provide normative data for older and very old Czech adults on the Prague Stroop Test (PST) and to test its discriminative validity in individuals with Parkinson's disease mild cognitive impairment (PD-MCI)., Method: The construction of the PST was modeled after the Victoria Stroop Test. We examined 539 participants aged 60-96 that met strict inclusion criteria. After, we compared the PST scores for a group of 45 PD-MCI patients with a healthy adult sample (HAS) of 45 age- and education-matched individuals., Results: I. In the non-clinical sample, robust age- and education-related influences were observed on all PST scores. No gender effect was noted. II. For clinical cases, interference condition (PST-C) was able to discriminate between PD-MCI and HAS (all scores ps < .01). Area under the curve (AUC) was 77% when a screening cut-off of ≤ 27 s was used, showing sensitivity of 82% and specificity of 53%. A more conservative diagnostic cut-off of ≤ 33 s showed sensitivity of 60% and specificity of 80%., Discussion: The present study provides PST normative data for basic, interference, and error scores stratified by age (60-96 years). PST appears to be a helpful tool for the diagnostics of PD-MCI especially in research settings at Level II (Litvan et al., 2012) and for PD-MCI attention/working memory and executive function subtyping.
- Published
- 2015
- Full Text
- View/download PDF
40. The malleability of working memory and visuospatial skills: a randomized controlled study in older adults.
- Author
-
Stepankova H, Lukavsky J, Buschkuehl M, Kopecek M, Ripova D, and Jaeggi SM
- Subjects
- Aged, Female, Humans, Male, Practice, Psychological, Psychological Tests, Aging psychology, Memory, Short-Term, Space Perception, Transfer, Psychology
- Abstract
There is accumulating evidence that training on working memory (WM) generalizes to other nontrained domains, and there are reports of transfer effects extending as far as to measures of fluid intelligence. Although there have been several demonstrations of such transfer effects in young adults and children, they have been difficult to demonstrate in older adults. In this study, we investigated the generalizing effects of an adaptive WM intervention on nontrained measures of WM and visuospatial skills. We randomly assigned healthy older adults to train on a verbal n-back task over the course of a month for either 10 or 20 sessions. Their performance change was compared with that of a control group. Our results revealed reliable group effects in nontrained standard clinical measures of WM and visuospatial skills in that both training groups outperformed the control group. We also observed a dose-response effect, that is, a positive relationship between training frequency and the gain in visuospatial skills; this finding was further confirmed by a positive correlation between training improvement and transfer. The improvements in visuospatial skills emerged even though the intervention was restricted to the verbal domain. Our work has important implications in that our data provide further evidence for plasticity of cognitive functions in old age., (PsycINFO Database Record (c) 2014 APA, all rights reserved.)
- Published
- 2014
- Full Text
- View/download PDF
41. Czech version of Rey Auditory Verbal Learning test: normative data.
- Author
-
Bezdicek O, Stepankova H, Moták L, Axelrod BN, Woodard JL, Preiss M, Nikolai T, Růžička E, and Poreh A
- Subjects
- Adult, Age Factors, Aged, Aged, 80 and over, Czech Republic, Educational Status, Female, Humans, Male, Middle Aged, Young Adult, Neuropsychological Tests standards, Verbal Learning
- Abstract
The present study provides normative data stratified by age for the Rey Auditory Verbal Learning test Czech version (RAVLT) derived from a sample of 306 cognitively normal subjects (20-85 years). Participants met strict inclusion criteria (absence of any active or past neurological or psychiatric disorder) and performed within normal limits on other neuropsychological measures. Our analyses revealed significant relationships between most RAVLT indices and age and education. Normative data are provided not only for basic RAVLT scores, but for the first time also for a variety of derived (gained/lost access, primacy/recency effect) and error scores. The study confirmed a logarithmic character of the learning slope and is consistent with other studies. It enables the clinician to evaluate more precisely subject's RAVLT memory performance on a vast number of indices and can be viewed as a concrete example of Quantified Process Approach to neuropsychological assessment.
- Published
- 2014
- Full Text
- View/download PDF
42. Development, validity, and normative data study for the 12-word Philadelphia Verbal Learning Test [czP(r)VLT-12] among older and very old Czech adults.
- Author
-
Bezdicek O, Libon DJ, Stepankova H, Panenkova E, Lukavsky J, Garrett KD, Lamar M, Price CC, and Kopecek M
- Subjects
- Aged, Aged, 80 and over, Czech Republic, Female, Humans, Male, Memory, Middle Aged, Sampling Studies, Aging psychology, Mental Recall, Neuropsychological Tests standards, Verbal Learning
- Abstract
The aim of the present study was to assess the validity of a 12-word Czech version of the Philadelphia (repeatable) Verbal Learning Test [czP(r)VLT-12]. The construction of the czP(r)VLT-12 was modeled after the California Verbal Learning Test (CVLT) and the nine-word Philadelphia (repeatable) Verbal Learning Test [P(r)VLT]. The czP(r)VLT-12 was constructed from a large corpus of old (60-74) and very old (75-96) Czech adults (n = 540). Participants met strict inclusion criteria for the absence of any active or past neurodegenerative disorders and performed within normal limits on other neuropsychological measures. Principal component analysis (PCA) and correlations between czP(r)VLT-12 factor structure and other memory tests were conducted. The czP(r)VLT-12 produced a four-factor solution, accounting for 70.90% of variance, with factors related to: (1) recall, (2) extra-list intrusion errors/recognition foils, (3) interference, and (4) acquisition rate; a solution similar to the CVLT and P(r)VLT. Increasing age resulted in a decline in most czP(r)VLT-12 indices, women outperformed men, and higher education led to higher scores. Memory performance in normal aging did not correlate with instrumental activities of daily living. Low, but significant, correlations were seen with other tests of cognitive performance (divergent validity). Appendices are available that provide normed percentile estimates of individual czP(r)VLT-12 performance stratified by age, education, and gender. In accordance with previous studies, these results demonstrate the usefulness of czP(r)VLT-12 in assessing declarative memory in older adults.
- Published
- 2014
- Full Text
- View/download PDF
43. Cognitive deficits in the euthymic phase of unipolar depression.
- Author
-
Preiss M, Kucerova H, Lukavsky J, Stepankova H, Sos P, and Kawaciukova R
- Subjects
- Adult, Aged, Attention physiology, Case-Control Studies, Female, Humans, Male, Memory physiology, Middle Aged, Neuropsychological Tests, Psychiatric Status Rating Scales, Statistics, Nonparametric, Verbal Learning physiology, Young Adult, Cognition Disorders etiology, Depressive Disorder complications
- Abstract
Although neuropsychological deficits have been reported in patients with major depressive disorder (MDD) during an acute episode, relatively little is known about the persistence of these deficits in remission. This study investigated the performance of attention, executive function and verbal memory during remission from unipolar depressive episodes. We tested the hypothesis that outpatients do not differ in cognitive variables from controls. We did this using a well-defined outpatient sample, consisting of medicated and unmedicated patients, with a history of MDD. Ninety-seven subjects with MDD in remission ranging from young to old were compared with 97 healthy control subjects. Both samples were balanced for age, gender, and education levels. The Auditory Verbal Learning Test (AVLT) and the Trail Making Test (TMT) were used. Patients with remitted MDD, in comparison with controls, were impaired on tasks of attention, executive function and verbal memory. The individual level of depressive symptoms was not related to the cognitive performance. Small- to medium-sized significant correlations exist between cognitive test variables (as represented by Trail Making B and AVLT delayed recall) and level of depressive symptomatology (as measured by MADRS or BDI-II) in the total sample, indicating that higher levels of depressive symptomatology are associated with lower cognitive function. These findings suggest deficits in attention and delayed verbal recall can serve as an indicator for MDD in outpatients.
- Published
- 2009
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.