Publications (46)77.03 Total impact
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Dataset: Mn0.97Fe0.03WO4 JPCM 2012
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Article: Improved properties of micronized genetically modified flax fibres.
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ABSTRACT: The aim of this study was to investigate the effect of micronization on the compound content, crystalline structure and physicochemical properties of fibre from genetically modified (GM) flax. The GM flax was transformed with three bacterial (Ralstonia eutropha) genes coding for enzymes of polyhydroxybutyrate (PHB) synthesis and under the control of the vascular bundle promoter. The modification resulted in fibres containing the 3-hydroxybutyrate polymer bound to cellulose via hydrogen and ester bonds and antioxidant compounds (phenolic acids, vanillin, vitexin, etc.). The fibres appeared to have a significantly decreased particle size after 20h of ball-milling treatment. Micronized fibres showed reduced phenolic contents and antioxidant capacity compared to the results for untreated fibres. An increased level of PHB was also detected. Micronization introduces structural changes in fibre constituents (cellulose, hemicellulose, pectin, lignin, PHB) and micronized fibres exhibit more functional groups (hydroxyl, carboxyl) derived from those constituents. It is thus concluded that micronization treatments improve the functional properties of the fibre components.Journal of biotechnology 01/2013; · 2.88 Impact Factor -
Article: FT-Raman spectroscopic study of human skin subjected to uniaxial stress.
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ABSTRACT: Fourier Transform Raman Spectroscopy was used to investigate the molecular changes of structural proteins in human skin subjected to strain. In the Raman spectrum of unstrained skin, bands assigned mainly to collagen and elastin were observed at 1658cm(-1) (amide I), 1271 and 1255cm(-1) (amide III), and 935 and 817cm(-1) (CC stretching modes of the protein backbone). Moreover, bands characteristic for amino acids were observed at 1336cm(-1) (desmosine), 1004cm(-1) (phenylalanine), 919 and 856cm(-1) (proline), and 877cm(-1) (hydroxyproline). Positions and intensities of the listed Raman bands were analysed as a function of applied strain. A clear correlation between Raman wavenumbers and the level of mechanical stress was established. Wavenumbers of the analysed bands changed gradually with increasing strain. Distinct responses, depending on the sample cutting direction, i.e. longitudinal or perpendicular to the Langer's lines, were noticed. It was concluded that elastin and non-helical domains of collagen are initially involved in the load transfer and triple helices of collagen are gradually joining this process. It was proved that Raman spectroscopy give insight into skin deformation micromechanics.Journal of the mechanical behavior of biomedical materials. 12/2012; -
Article: Temperature-dependent IR and Raman scattering studies of phase transitions in K(2)MgWO(2)(PO(4))(2).
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ABSTRACT: Temperature-dependent Raman scattering and IR experiments were performed on K(2)MgWO(2)(PO(4))(2), which is derived from KTP by the replacement of two Ti(4+) ions with Mg(2+) and W(6+) cations. These studies revealed significant changes in phonon properties of these materials with increasing temperature due to the onset of phase transitions at 436, 537 and 637 K. Analysis of the obtained data showed that disordering processes in the sublattice of potassium ions play a significant role in the mechanism of these phase transitions. However, these transitions are also accompanied by weak tilts of the nearly rigid PO(4), WO(6) and MgO(6) groups. Present results also provide strong arguments that the phase transition at 637 K can be classified as occurring from the normal high-temperature phase with D(4) point symmetry into a modulated or incommensurate phase with the same D(4) point symmetry. Our results also show that the order-disorder (displacive) contribution to the phase transition mechanism is significantly stronger (weaker) in K(2)MgWO(2)(PO(4))(2) when compared to KTP.Journal of Physics Condensed Matter 11/2012; 25(2):025901. · 2.55 Impact Factor -
Article: Optical properties of Eu and Er doped LaAlO3 nanopowders prepared by low-temperature method
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ABSTRACT: LaAlO3 nanoparticles doped with Eu3+ and Er3+ ions were synthesized at 500C in a two-step process by combining a mechanically induced metathesis reaction and molten salt synthesis. The obtained samples were characterized by XRD and TEM methods, which showed that the mean crystallite size is �45 and �57 nm, respectively. Furthermore, excitation and luminescence spectra as well as decay profiles were measured for the synthesized samples. These studies suggested that the Eu3+ ions are located at three different local sites without inversion symmetry. Our studies also showed upconversion emission in the samples doped with Er 3+ ions. The up-conversion mechanism has been discussed.Journal of Solid State Chemistry 11/2012; 194:264. · 2.16 Impact Factor -
Article: High-pressure Raman scattering and an anharmonicity study of multiferroic wolframite-type Mn0.97Fe0.03WO4.
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ABSTRACT: A high-pressure Raman scattering study of wolframite-type Mn(0.97)Fe(0.03)WO(4) is presented up to 10.4 GPa. The phonon wavenumbers vary linearly with pressure. The mode Grüneisen parameters are larger for many bending and lattice modes when compared to the stretching modes due to the larger compressibility of Mn(Fe)O(6) octahedra when compared to WO(6) octahedra. Combining the pressure-dependent Raman data of this work with the temperature-dependent Raman data on this crystal previously reported by us has allowed estimation of the temperature-dependent pure lattice and intrinsic anharmonic contributions to the observed total Raman shifts as a function of temperature. It has been found that the observed unusual hardening of the 884, 698 and 674 cm(-1) stretching modes upon heating from 4 to about 150-200 K followed by the usual softening above 150-200 K is a result of a positive intrinsic anharmonic contribution and a negative pure lattice contribution; i.e., up to about 150-200 K the anharmonic contribution surpasses the lattice contribution and the total Raman shift is slightly positive whereas above 150-200 K the lattice contribution becomes dominant and the Raman bands exhibit the usual softening with increasing temperature.Journal of Physics Condensed Matter 08/2012; 24(34):345403. · 2.55 Impact Factor -
Article: Temperature-dependent Raman scattering study of the defect pyrochlores RbNbWO6 and CsTaWO6.
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ABSTRACT: Lattice dynamics calculations and temperature-dependent Raman scattering experiments were performed on RbNbWO(6) and CsTaWO(6) pyrochlore oxides. The observed bands were assigned to the respective motions of atoms in the unit cell. The spectra showed the presence of additional Raman bands not allowed for by the [Formula: see text] cubic structure. We have shown that these bands appear due to both substitutional disorder in the 16c sites and displacive disorder of the A ions. Raman studies also revealed the presence of an additional 80 cm(-1) band at room temperature for RbNbWO(6), not observed for CsTaWO(6). The presence of this band has been attributed to off-center displacement of the Nb and W ions due to structural phase transition into a tetragonal ferroelectric phase. The temperature evolution of the 80 cm(-1) band intensity revealed that it disappeared at a much higher temperature (about 650 K) than the reported phase transition temperature (about 360 K). This behavior is reminiscent of chemically disordered perovskite ferroelectrics, including relaxor ferroelectrics, and was attributed to the presence of small polar regions with local tetragonal distortion embedded in the paraelectric matrix of the [Formula: see text] structure.Journal of Physics Condensed Matter 04/2012; 24(19):195902. · 2.55 Impact Factor -
Article: Low-temperature Synthesis, Luminescence and Phonon Properties of Er and/or Dy-doped LaAlO3
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ABSTRACT: LaAlO3, La0.9Dy0.1AlO3, La0.9Er0.1AlO3 and La0.8Dy0.1Er0.1AlO3 nanocrystalline powders were synthesized in a two-step process by combining a mechanically induced metathesis reaction and molten salt synthesis. The proposed two-step methodology easily allows obtaining pure and/or doped perovskite- type LaAlO3 nanopowders at remarkably low temperatures, i.e., already at 350C although firing at 500C is needed in order to get pure phases. The obtained samples were characterized by XRD, TEM, Raman, IR and luminescence methods. These methods showed that the mean crystallite size is near 50–60 nm and the LaAlO3 nanocrystallites have R3 c structure, the same as bulk LaAlO3. Raman spectrum of nanocrystalline LaAlO3 is very similar to that of bulk. In contrast to this behavior, IR spectra of the synthesized compounds are significantly different from the IR spectrum of bulk LaAlO3. Origin of this behavior is discussed. Luminescence study showed that the cross-relaxation processes quench emission intensity of the samples doped with Dy3+ and Er3+.Journal of Solid State Chemistry 01/2012; 187:249. · 2.16 Impact Factor -
Article: Temperature-dependent Raman scattering study of cation-deficient Aurivillius phases: Bi2WO6 and Bi2W2O9.
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ABSTRACT: Temperature-dependent Raman scattering experiments were performed on Bi(2)WO(6) and Bi(2)W(2)O(9). Significant changes in the phonon properties of Bi(2)WO(6) were observed as the temperature was increased due to decreased distortion from the B2cb structure. It was shown that instability of the 57 cm(-1) mode that behaved as a soft mode under pressure is not responsible for the Pca2(1) to B2cb phase transition taking place in Bi(2)WO(6) at 933 K. This result confirmed that this mode is not related to the [Formula: see text] tilt mode, which disappears upon change in symmetry from Pca2(1) to B2cb. Bi(2)W(2)O(9) does not exhibit any structural phase transition in the 298-800 K range. However, the temperature dependence of Raman bands indicated that the Bi(2)W(2)O(9) structure evolves with decreasing temperature from 800 to 298 K towards a more symmetric structure that was reported above 2.8 GPa at room temperature. This structural change is driven by displacement of the W atoms and is different from that exhibited by Bi(2)WO(6) and other members of the Aurivillius family but similar to that exhibited by WO(3). Our results also show that Bi(2)W(2)O(9) belongs to the small group of compounds that show the presence of low wavenumber modes characterized by unusually small linewidths.Journal of Physics Condensed Matter 10/2011; 23(40):405902. · 2.55 Impact Factor -
Article: IR and Raman studies of oil and seedcake extracts from natural and genetically modified flax seeds.
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ABSTRACT: Flax plant of the third generation (F3) overexpressing key genes of flavonoid pathway cultivated in field in 2008 season was used as the plant material throughout this study. The biochemical properties of seed, oil and seedcake extracts from natural and transgenic flax plants were compared. Overproduction of flavonoids (kaempferol), phenolic acids (coumaric, ferulic/synapic) and lignan-secoisolariciresinol diglucoside (SDG) in oil and extracts from transgenic seeds has been revealed providing a valuable source of these compounds for biotechnological application. The changes in fatty acids composition and increase in their stability against oxidation along three plant generations were also detected. The analysis of oil and seedcake extracts was performed using Raman and IR spectroscopy. The wavenumbers and integral intensities of Raman and IR bands were used to identify the components of phenylpropanoid pathway in oil and seedcake extracts from control and transgenic flax seeds. The spectroscopic data were compared to those obtained from biochemical analysis.Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 03/2011; 78(3):1080-9. · 2.10 Impact Factor -
Article: A Raman scattering study of pressure-induced phase transitions in nanocrystalline Bi₂MoO₆.
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ABSTRACT: Lattice dynamics calculations and a high-pressure Raman scattering study of nanocrystalline Bi(2)MoO(6), a member of the bismuth-layered Aurivillius family of ferroelectrics, are presented. These studies showed the onset of two reversible second-order or weakly first-order phase transitions near 2.5 and 4.5 GPa as well as some subtle structural changes at 8.2 GPa. Symmetry increases upon application of pressure and the first phase transition involves, most likely, the loss of the MoO(6) tilt mode around a pseudo-tetragonal axis. The second phase transition is associated with the instability of a low wavenumber mode, which behaves as a soft mode. This soft mode most likely corresponds to the polar E(u) mode of the tetragonal I4/mmm aristotype and Bi(2)MoO(6) transforms at 4.5 GPa into the centrosymmetric orthorhombic phase. The sequence of the pressure-induced phase transitions in nanocrystalline Bi(2)MoO(6) is similar to that observed for bulk Bi(2)WO(6) but the critical pressures are significantly lower for the molybdenum compound. Our results also show that the critical pressure of the first phase transition is slightly lower for the nanocrystalline Bi(2)MoO(6) (2.5 GPa) than for the microcrystalline (bulk) Bi(2)MoO(6) (2.8 GPa).Journal of Physics Condensed Matter 02/2011; 23(4):045401. · 2.55 Impact Factor -
Article: Rare earth-doped lead borate glasses and transparent glass-ceramics: structure-property relationship.
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ABSTRACT: Correlation between structure and optical properties of rare earth ions in lead borate glasses and glass-ceramics was evidenced by X-ray-diffraction, Raman, FT-IR and luminescence spectroscopy. The rare earths were limited to Eu(3+) and Er(3+) ions. The observed BO(3)↔BO(4) conversion strongly depends on the relative PbO/B(2)O(3) ratios in glass composition, giving important contribution to the luminescence intensities associated to (5)D(0)-(7)F(2) and (5)D(0)-(7)F(1) transitions of Eu(3+). The near-infrared luminescence and up-conversion spectra for Er(3+) ions in lead borate glasses before and after heat treatment were measured. The more intense and narrowing luminescence lines suggest partial incorporation of Er(3+) ions into the orthorhombic PbF(2) crystalline phase, which was identified using X-ray diffraction analysis.Spectrochimica Acta Part A Molecular and Biomolecular Spectroscopy 04/2010; 79(4):696-700. · 2.10 Impact Factor -
Article: Temperature- and pressure-dependent lattice behaviour of RbFe(MoO4)2.
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ABSTRACT: Trigonal RbFe(MoO(4))(2) is a quasi-two-dimensional antiferromagnet on a triangular lattice below T(N) = 3.8 K, The crystal exhibits also a structural phase transition at T(c) = 190 K related to symmetry change from P3m1 to P3. We present the temperature- and pressure-dependent characteristics of this material in the context of ambiguous opinions on the symmetry and crystal properties below T(c). A single-crystal x-ray diffraction shows that the temperature-dependent evolution of the unit cell in the range 100-300 K is strongly anisotropic with markedly discontinuous changes at T(c). The transition is connected with a spontaneous strain developing in effect of the volume decrease. The structure releases the strain by rotation of corner-sharing rigid MoO(4) and FeO(6) polyhedra in the (a,b) basal plane. The temperature dependence of the IR vibrational wavenumbers exhibits weak changes near T(c), which are consistent with the symmetry transformation from P3m1 to P3. High-pressure x-ray powder diffraction indicates that the material is extremely soft but with some stiffening at high pressure. The zero-pressure bulk modulus is B(0) = 7.9(6) GPa and the pressure derivative is B(0)' = 10(1). The compression curve can be described by a single equation of state, corresponding to the trigonal cell, up to 5 GPa. An amorphization appearing above 5 GPa and increasing gradually on further pressure increase suggests the thermodynamic instability of the high-pressure structure.Journal of Physics Condensed Matter 02/2010; 22(5):055406. · 2.55 Impact Factor -
Article: Synthesis and Electrical, Optical and Phonon Properties of Nanosized Aurivillius Phase Bi2WO6
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ABSTRACT: Nanoparticles of bismuth-layered ferroelectric and photocatalytic material, Bi2WO6 , have been prepared by mechanochemical synthesis and firing of amorphous precursor prepared in metathesis reaction. The effect of different synthesis methods and crystallite size on the structure and properties of Bi2WO6 nanoparticles have been investigated using the XRD, TEM, DTA, DTG, diffuse reflectivity, conductivity measurements, Raman and infrared spectroscopy. The results show that the smallest particles could be obtained by mechanochemical synthesis. However, this method introduced large number of crystal defects. The conductivity of this sample is higher by half an order of magnitude, in comparison with con- ductivities measured for the other samples studied in this paper or previously reported in the literature for Bi2WO6 . Our results also show that firing the amorphous precursor with NaNO3 by-product yields material composed of small, well-crystallized particles containing small number of crystal defects. This result shows that this synthesis method is the best route to enhance photocatalytic activity of Bi2WO6 . Raman and IR studies also suggest that the orthorhombic distortion diminishes with decreasing particle size.Materials Chemistry and Physics 02/2010; 120(2-3):289-295. · 2.23 Impact Factor -
Article: Pressure-induced phase transitions in ferroelectric Bi2MoO6--a Raman scattering study.
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ABSTRACT: A high pressure Raman scattering study of Bi(2)MoO(6), a member of the bismuth layered Aurivillius family of ferroelectrics, is presented. This study showed the onset of two reversible second-order phase transitions near 2.8 and 7.0 GPa. The pressure dependence of the Raman bands provides strong evidence that the structural changes in Bi(2)MoO(6) are mainly related to the rigid rotations of MoO(6) octahedra. Symmetry increases upon application of pressure and the first phase transition involves, most probably, the loss of the MoO(6) tilt mode. This structural change may be the same as that observed at ambient pressure at elevated temperature (from P 2(1)ab to a polar orthorhombic structure of unknown symmetry). The second phase transition is associated with some subtle structural changes and the structure above 7.0 GPa is most probably still orthorhombic.Journal of Physics Condensed Matter 01/2010; 22(1):015901. · 2.55 Impact Factor -
Article: High‐resolution Brillouin scattering and heat capacity studies of bis(guanidinium)zirconium bis(nitrilotriacetate)hydrate, [C(NH2)3]2Zr[N(CH2COO)3]2·H2O
Journal of Raman Spectroscopy 06/2009; 40(12):1902 - 1906. · 3.09 Impact Factor -
Article: Temperature-dependent studies of the geometrically frustrated pyrochlores Ho_ {2} Ti_ {2} O_ {7} and Dy_ {2} Ti_ {2} O_ {7}
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ABSTRACT: A temperature-dependent Raman study of Ho2Ti2O7 and Dy2Ti2O7 single crystals was performed in the 5–873 K temperature range. Polarized spectra allowed us to establish the symmetries of the observed bands and revise the mode assignment made in previous works. Our studies revealed also two additional bands near 287 and 300 cm−1 for Dy2Ti2O7, which can be assigned to crystal field transitions in Dy3+ ions. Temperature dependent Raman studies showed large increase of linewidths. These changes have been analyzed in terms of strong third-order phonon-phonon anharmonic interactions. The Raman spectra also showed anomalous softening of the majority of phonon modes upon cooling in the whole temperature range studied. In contrast to this behavior, the F2g ∼310 cm−1 and Eg ∼330 cm−1 phonon modes showed hardening upon cooling down to about (100–120 K) and then anomalous softening below this temperature. This anomalous behavior of phonon wave numbers has been attributed to the increase in octahedral distortion upon cooling.Physical Review B 04/2009; 79(21):214437. · 3.69 Impact Factor -
Article: Temperature-dependent Raman study of the spin-liquid pyrochlore Tb_ {2} Ti_ {2} O_ {7}
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ABSTRACT: Temperature-dependent Raman-scattering studies of Tb2Ti2O7 geometrically frustrated pyrochlore are presented. The Raman spectra have shown softening of the majority of modes upon cooling in the whole temperature range studied and large decrease in linewidths. These changes have been analyzed in terms of phonon-phonon anharmonic interactions. A departure from the expected behavior has been observed at low temperatures for the A1g mode, which is attributed to the spin-phonon coupling. The Raman studies have also revealed an unusual temperature dependence of the modes observed in the 290–350 cm−1 range. This behavior has been attributed to a very strong coupling between the crystal-field excitations of the Tb3+ 4f electrons and the F2g mode, which is a distinct feature of Tb2Ti2O7 spin-liquid material among the family of rare-earth titanates. Our studies have also shown several uncoupled crystal-field excitations, which has provided information on energy levels of the 7F5 manifold.Phys. Rev. B. 10/2008; 78(13). -
Article: Temperature-dependent Raman study of the spin-liquid pyrochlore Tb2Ti2O7
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ABSTRACT: Temperature-dependent Raman-scattering studies of Tb2Ti2O7 geometrically frustrated pyrochlore are presented. The Raman spectra have shown softening of the majority of modes upon cooling in the whole temperature range studied and large decrease in linewidths. These changes have been analyzed in terms of phonon-phonon anharmonic interactions. A departure from the expected behavior has been observed at low temperatures for the A1g mode, which is attributed to the spin-phonon coupling. The Raman studies have also revealed an unusual temperature dependence of the modes observed in the 290-350cm-1 range. This behavior has been attributed to a very strong coupling between the crystal-field excitations of the Tb3+ 4f electrons and the F2g mode, which is a distinct feature of Tb2Ti2O7 spin-liquid material among the family of rare-earth titanates. Our studies have also shown several uncoupled crystal-field excitations, which has provided information on energy levels of the F75 manifold.Physical Review B 09/2008; 78(13):134420. · 3.69 Impact Factor -
Article: High-resolution temperature-dependent Brillouin scattering studies of ferroelectric K_ {3} Nb_ {3} O_ {6}(BO_ {3}) _ {2}
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ABSTRACT: High-resolution micro-Brillouin scattering studies of K3Nb3O6(BO3)2, exhibiting superionic and ferroelectric properties, were performed in the temperature range of 300–870 K. Strong increase in damping of longitudinal and transverse acoustic phonons corresponding to the c33 and c44 elastic constants was observed above 650 K. This increase in damping was correlated with anomalous decrease in the c33 and c44 elastic constants and strong increase in central peak intensities. The observed behavior has been attributed to melting of the K+ sublattice as a result of the order-disorder phase transitions. The obtained results also revealed a critical slowing down of the E″-symmetry relaxation mode near the phase transitions at 388 and 690 K as well as the broad A1′-symmetry relaxation mode near the phase transition at 750 K. This behavior indicates that the relaxation modes play an important role in the mechanism of these phase transitions. In particular, this behavior suggests that the phase transition near 690 K is induced by instability of the E″-symmetry relaxation mode.Phys. Rev. B. 03/2008; 77(10).
Top co-authors
Top Journals
Institutions
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2003–2013
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Wyższa Szkoła Handlowa we Wrocławiu
Wrocław, Lower Silesian Voivodeship, Poland
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2003–2012
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Polish Academy of Sciences
Warsaw, Masovian Voivodeship, Poland
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2010
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Uniwersytet Śląski w Katowicach
- Institute of Chemistry
Katowice, Silesian Voivodeship, Poland
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2008
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Universidad de Zaragoza
- Faculty of Sciences
Zaragoza, Aragon, Spain
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