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Qin, Wei, Beibei Xu i Shenqiang Ren. "An organic approach for nanostructured multiferroics". Nanoscale 7, nr 20 (2015): 9122–32. http://dx.doi.org/10.1039/c5nr01435b.
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Herklotz, A., M. D. Biegalski, H. M. Christen, E. J. Guo, K. Nenkov, A. D. Rata, L. Schultz i K. Dörr. "Strain response of magnetic order in perovskite-type oxide films". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, nr 2009 (28.02.2014): 20120441. http://dx.doi.org/10.1098/rsta.2012.0441.
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The role of elastic strain for magnetoelectric materials and devices is twofold. It can induce ferroic orders in thin films of otherwise non-ferroic materials. On the other hand, it provides the most exploited coupling mechanism in two-phase magnetoelectric materials and devices today. Complex oxide films (perovskites, spinels) are promising for both routes. The strain control of magnetic order in complex oxide films is a young research field, and few ab initio simulations are available for magnetic order in dependence on lattice parameters and lattice symmetry. Here, an experimental approach for the evaluation of how elastic strain in thin epitaxial films alters their magnetic order is introduced. The magnetic films are grown epitaxially in strain states controlled by buffer layers onto piezoelectric substrates of 0.72Pb(Mg 1/3 Nb 2/3 )O 3 –0.28PbTiO 3 (001). As an example, the strain dependence of the ordered magnetic moment of SrRuO 3 has been investigated. At a tensile strain level of approximately 1%, SrRuO 3 is tetragonal, and biaxial elastic strain induces a pronounced suppression of the ordered magnetic moment. As a second example, a strain-driven transition from a ferromagnetic to a magnetically disordered phase has been observed in epitaxial La 0.8 Sr 0.2 CoO 3 films.
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Liang, Lizhi, Heng Wu, Lei Li i Xinhua Zhu. "Characterization of Multiferroic Domain Structures in Multiferroic Oxides". Journal of Nanomaterials 2015 (2015): 1–8. http://dx.doi.org/10.1155/2015/169874.
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Multiferroic oxides have been received much attention due to that these materials exhibit multiple ferroic order parameters (e.g., electric polarization in ferroelectrics, magnetization in ferromagnetics, or spontaneous strain in ferroelastics) simultaneously in the same phase in a certain temperature range, which offer an exciting way of coupling between the ferroic order parameters. Thus, this provides a possibility for constructing new type of multifunctional devices. The multiferroic domain structures in these materials are considered to be an important factor to improve the efficiency and performance of future multiferroic devices. Therefore, the domain structures in multiferroic oxides are widely investigated. Recent developments in domain characterization techniques, particularly the aberration-corrected transmission electron microscopy (TEM), have enabled us to determine the domain structures at subangstrom scale, and the recent development ofin situTEM techniques allows ones to study the dynamic behaviors of multiferroic domains under applied fields or stress while the atomic structure is imaged directly. This paper provides a review of recent advances on the characterization of multiferroic domain structures in multiferroic oxides, which have been achieved by the notable advancement of aberration-corrected TEM.
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Ionescu, Daniela, i Maria Kovaci. "Simulation Determination of the Electromagnetic Parameters for the CdCr2S4 Multiferroic Relaxor in GHz Range". Applied Mechanics and Materials 371 (sierpień 2013): 389–93. http://dx.doi.org/10.4028/www.scientific.net/amm.371.389.
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The GHz range is a domain not enough exploited for application in the case of the materials like the CdCr2S4 multiferroic which possesses all four properties of colossal magnetoresistance, electroresistance, is colossal magnetocapacitive and electrocapacitive. The 3D simulation by structural description of such a material represents a real challenge of the descriptive simulational science, due to the complexity of the internal phenomena and interactions which occur here. Dielectric and magnetic properties were reported up to 3 GHz by measurements (Hemberger et al. and so on), while our simulation method is coming to extrapolate the results up to 18 GHz for applications in spintronics and microelectronics. The geometrically frustrated thiospinel system, included in the Heisenberg 3D ferromagnets class, was described with help of the HFSS 13.0 program. An algorithm based on physical consideration was used for the material samples simulated inside a rectangular waveguide, in order to determine their complex electromagnetic parameters (electric permittivity and magnetic permeability). Maxima were found on the real permittivity / permeability graph and by overlapping of the graphs, distinctive resonances were separated. Resonances were linked on the internal structure and the exciting field interaction with the material samples, considering that each mechanism of interaction is dominated by the characteristics of the ferroic propriety involved. A structural resonance map for the microwave range up to 18 GHz was represented. The material presenting all four ferroic properties has resonances specific for each property, but also cumulative resonances, of various magnitude, which can be described only by considering two or more ferroic properties characterizing the same material state.
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Lim, Zhi Shiuh, Hariom Jani, T. Venkatesan i A. Ariando. "Skyrmionics in correlated oxides". MRS Bulletin 46, nr 11 (listopad 2021): 1053–62. http://dx.doi.org/10.1557/s43577-021-00227-9.
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AbstractWhile chiral magnets, metal-based magnetic multilayers, or Heusler compounds have been considered as the material workhorses in the field of skyrmionics, oxides are now emerging as promising alternatives, as they host special correlations between the spin–orbital–charge–lattice degrees of freedom and/or coupled ferroic order parameters. These interactions open new possibilities for practically exploiting skyrmionics. In this article, we review the recent advances in the observation and control of topological spin textures in various oxide systems. We start with the discovery of skyrmions and related quasiparticles in bulk and heterostructure ferromagnetic oxides. Next, we emphasize the shortcomings of implementing ferromagnetic textures, which have led to the recent explorations of ferrimagnetic and antiferromagnetic oxide counterparts, with higher Curie temperatures, stray-field immunity, low Gilbert damping, ultrafast magnetic dynamics, and/or absence of skyrmion deflection. Then, we highlight the development of novel pathways to control the stability, motion, and detection of topological textures using electric fields and currents. Finally, we present the outstanding challenges that need to be overcome to achieve all-electrical, nonvolatile, low-power oxide skyrmionic devices. Graphical abstract
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Baek, S. H., i C. B. Eom. "Reliable polarization switching of BiFeO 3". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, nr 1977 (28.10.2012): 4872–89. http://dx.doi.org/10.1098/rsta.2012.0197.
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As a room temperature multi-ferroic with coexisting anti-ferromagnetic, ferroelectric and ferroelastic orders, BiFeO 3 has been extensively studied to realize magnetoelectric devices that enable manipulation of magnetic ordering by an electric field. Moreover, BiFeO 3 is a promising candidate for ferroelectric memory devices because it has the largest remanent polarization ( P r >100 μC cm −2 ) of all ferroelectric materials. For these applications, controlling polarization switching by an electric field plays a crucial role. However, BiFeO 3 has a complex switching behaviour owing to the rhombohedral symmetry: ferroelastic (71 ° , 109 ° ) and ferroelectric (180 ° ) switching. Furthermore, the polarization is switched through a multi-step process: 180 ° switching occurs through three sequential 71 ° switching steps. By using monodomain BiFeO 3 thin-film heterostructures, we correlated such multi-step switching to the macroscopically observed reliability issues of potential devices such as retention and fatigue. We overcame the retention problem (i.e. elastic back-switching of the 71 ° switched area) using monodomain BiFeO 3 islands. Furthermore, we suppressed the fatigue problem of 180 ° switching, i.e. loss of switchable polarization with switching cycles, using a single 71 ° switching path. Our results provide a framework for exploring a route to reliably control multiple-order parameters coupled to ferroelastic order in other rhombohedral and lower-symmetry materials.
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Kebede Hambisa, Teshome, Chernet Amente i Pooran Singh. "The Study of Interplay of Singlet Superconductivity and Ferromagnetism in Superconducting HoMo6Se8". SINET: Ethiopian Journal of Science 46, nr 1 (30.04.2023): 63–70. http://dx.doi.org/10.4314/sinet.v46i1.5.
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This article reports the effect of magnetic ordering and superconducting order parameter on superconducting and magnetic transition temperatures of interacting singlet superconductivity and ferromagnetism in HoMo6Se8 material. The basic superconducting parameters were calculated starting with the BCS type model Hamiltonian and using the double time temperature dependent Green function formalisms. Results showed that the superconducting critical temperature decreases with enhancement of superconducting order parameter and vice versa. This is perhaps due to the weakening of the binding energy as the temperature approaches its critical value. On the other hand, the superconducting critical temperature demonstrates attenuation with increasing magnetic order parameters . It was also observed that the enhancement of magnetic transition temperature with the increase of the magnetic order parameter demonstrates variation with the alteration of the superconducting order parameter. Moreover, the calculations revealed that there is a temperature region where both superconductivity and magnetic order coexist. Furthermore, the present theoretical analysis is broadly in agreement with existing experimental findings.
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Venegas-García, Deysi J., i Lee D. Wilson. "Kinetics and Thermodynamics of Adsorption for Aromatic Hydrocarbon Model Systems via a Coagulation Process with a Ferric Sulfate–Lime Softening System". Materials 16, nr 2 (10.01.2023): 655. http://dx.doi.org/10.3390/ma16020655.
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The adsorption mechanisms for model hydrocarbons, 4-nitrophenol (PNP), and naphthalene were studied in a coagulation-based process using a ferric sulfate–lime softening system. Kinetic and thermodynamic adsorption parameters for this system were obtained under variable ionic strength and temperature. An in situ method was used to investigate kinetic adsorption profiles for PNP and naphthalene, where a pseudo-first order kinetic model adequately described the process. Thermodynamic parameters for the coagulation of PNP and naphthalene reveal an endothermic and spontaneous process. River water was compared against lab water samples at optimized conditions, where the results reveal that ions in the river water decrease the removal efficiency (RE; %) for PNP (RE = 28 to 20.3%) and naphthalene (RE = 89.0 to 80.2%). An aluminum sulfate (alum) coagulant was compared against the ferric system. The removal of PNP with alum decreased from RE = 20.5% in lab water and to RE = 16.8% in river water. Naphthalene removal decreased from RE = 89.0% with ferric sulfate to RE = 83.2% with alum in lab water and from RE = 80.2% for the ferric system to RE = 75.1% for alum in river water. Optical microscopy and dynamic light scattering of isolated flocs corroborated the role of ions in river water, according to variable RE and floc size distribution.
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Habermeier, H. U., i G. Cristiani. "Ferromagnetic/Superconducting All-Oxide Superlattices". International Journal of Modern Physics B 17, nr 18n20 (10.08.2003): 3729–31. http://dx.doi.org/10.1142/s0217979203021708.
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Superlattices consisting of ferromagnetic SrRuO 3 and superconducting YBa 2 Cu 3 O 7 [YBCO] layers of a thickness between 5 nm and 60 nm have been analyzed with respect to their magnetic [T mag ] as well superconducting [TC] ordering temperature. The reduction of both is compared with previous results obtained in YBCO / La 2/3 Ca 1/3 MnO 3 superlattices. Whereas the reduction of TC is comparable for both ferromagnetic materials the suppression of ferromagnetism is more pronounced in the case of the SrRuO 3-based superlattices. This result is discussed in terms of a competition of the order parameters giving rise to ferromagnetism and superconductivity and the role of interface roughness.
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GORBAR, E. V., V. P. GUSYNIN i V. A. MIRANSKY. "DYNAMICAL GAPS AND QUANTUM HALL EFFECT IN GRAPHENE". Modern Physics Letters B 23, nr 07 (20.03.2009): 891–902. http://dx.doi.org/10.1142/s0217984909019120.
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We analyze the gap equation for Dirac quasiparticles in graphene in a magnetic field using a low-energy effective model with a contact interaction. It is found that the order parameters connected with the quantum Hall (QH) ferromagnetism and the magnetic catalysis scenarios necessarily coexist. The ground-state solutions of the gap equation describe all the recently discovered novel QH plateaus in graphene in strong magnetic fields.
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Yao, Minghai, Long Cheng, Shenglan Hao, Samir Salmanov, Mojca Otonicar, Frédéric Mazaleyrat i Brahim Dkhil. "Great multiferroic properties in BiFeO3/BaTiO3 system with composite-like structure". Applied Physics Letters 122, nr 15 (10.04.2023): 152904. http://dx.doi.org/10.1063/5.0139017.
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Multiferroic materials have attracted significant research attention due to their technological potential for applications as multifunctional devices. The scarcity of single-phase multiferroics and their low inherent coupling between multiferroic order parameters above room temperature pose a challenge to their further applications. We propose a 3BiFeO3/7BaTiO3 perovskite–perovskite composite that combines ferroelectricity and ferromagnetism. We demonstrate that the sintering temperature can tailor the ferroelectricity and ferromagnetism of the composites. The multiferroicity can be achieved at a low sintering temperature in the composite-like structure ceramics, and its multiferroic properties, especially the ferromagnetism, are superior to those of solid solutions. We also investigate the dynamic evolution of multiferroicity with sintering temperature. We adopt a nano–micro strategy to construct a composite-like microstructure, which results in optimized ferroelectric (1.62 μC cm−2) and ferromagnetic (0.16 emu/g) characteristics at a sintering temperature of 750 °C. We also found experimental evidence of the competition between antiferromagnetic and ferromagnetic interactions in the transition metal cation sublattice. Multiferroic BiFeO3/BaTiO3 composites with combined ferroelectric and ferromagnetic properties have significant potential for various applications.
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Arrieta, Alberto Albis, Ever Ortiz Muñoz, Ismael Piñeres Ariza, Juan Osorio Cardozo i Jennifer Monsalvo Morales. "Catalytic effect of ferric sulfate and zinc sulfate on lignin pyrolysis". Applied Chemical Engineering 5, nr 1 (26.04.2022): 59. http://dx.doi.org/10.24294/ace.v5i1.1449.
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The effect of zinc sulfate and ferric sulfate on the pyrolysis process of lignin was studied at three different heating rates by using the thermogravimetric analysis technique. It was found that the pyrolysis of pure lignin is barely affected with the change of heating rates between 10 to 100 °C/min, which is unexpected because of the kinetic nature of pyrolysis. The pyrolysis kinetics of this major component of biomass was studied by using three fitting methods: the differential method with reaction order model n, the isoconversional method, and the distribution of activation energies model, DAEM. The best fit, which allowed calculating acceptable kinetic parameters, was obtained using the last method. The results show the influence of the catalysts and the heating rate on the lignin pyrolysis processes in the presence of the sulfates under study, which is confirmed by obtaining different kinetic parameters. The results suggest that zinc sulfate and ferric sulfate change the kinetic mechanism of lignin pyrolysis.
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Nagano, Tetsushi, Hiroshi Isobe, Satoru Nakashima i Midori Ashizaki. "Characterization of Iron Hydroxides in a Weathered Rock Surface by Visible Microspectroscopy". Applied Spectroscopy 56, nr 5 (maj 2002): 651–57. http://dx.doi.org/10.1366/0003702021955222.
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In order to nondestructively characterize chemical forms of ferric hydroxides in weathered rock, charge-coupled device type visible microspectroscopy was applied to brown stains produced in weathered granite surfaces. The combination of visible microspectra and color parameters ( a* and b*) was effective in examining chemical forms of ferric hydroxides in the analytical area. Color parameters in an a*– b* diagram of the brown stains, mostly lying between goethite and ferrihydrite trends, indicated that the brown stains contain ferrihydrite or hematite in addition to goethite. Similarity of the visible microspectra of the brown stains and their first derivatives to those of goethite or ferrihydrite suggests that goethite and/or ferrihydrite are the main weathering products of the granite. Occurrence of ferrihydrite as well as goethite in the brown stains implies that crystallization of ferrihydrite to goethite might be hindered during the granite weathering. This fact suggests the possibility of toxic metal retention in ferrihydrite by its long-term persistence during water–rock interactions at the earth's surface.
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Вальков, В. И., И. Ф. Грибанов, Б. М. Тодрис, А. В. Головчан i В. И. Митюк. "Особенности формирования магнитокалорических явлений в системах Mn-=SUB=-1-t-=/SUB=-Ti-=SUB=-t-=/SUB=-As и Mn-=SUB=-1-x-=/SUB=-Cr-=SUB=-x-=/SUB=-NiGe". Физика твердого тела 60, nr 6 (2018): 1113. http://dx.doi.org/10.21883/ftt.2018.06.45985.13m.
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AbstractThe magnetocaloric properties of the systems exhibiting magnetic (paramagnetism (PM)–ferromagnetism (FM)) and structural (hexagonal lattice–orthorhombic lattice) transitions separated (overlapped) in temperature are analyzed in terms of a model of interacting parameters of magnetic and structural orders. It is shown that the magnetocaloric characteristics of the system can increase or decrease during overlapping of the structural ( P 6_3/ mmc – P _ nma ) and magnetic (PM–FM) transitions in the dependence of the character of combination of the low-symmetric orthorhombic ( P _ nma ) and high-symmetric hexagonal ( P 6_3/ mmc ) phases with a ferromagnetic order.
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Zhu, Weixiao, Jianduo Wang, Yili Wang i Hongjie Wang. "Study on sulfadimethoxine removal from aqueous solutions by hydrous ferric oxides". Water Science and Technology 74, nr 5 (21.06.2016): 1136–42. http://dx.doi.org/10.2166/wst.2016.246.
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Significant concerns have been raised over the presence of antibiotics including sulfadimethoxine (SDMO) in aquatic environments. This study investigated the removal capability and mechanism involved in the removal of SDMO by hydrous ferric oxides (HFO). Results showed that SDMO removal was highly pH and ionic strength dependent. The pseudo-first-order model fitted well the kinetic results, and the value of the calculated activation energy for SDMO adsorption onto HFO was 8.6 kJ mol−1. Adsorption isotherms at varied temperatures were well described by the Langmuir model. Thermodynamic parameters (change in enthalpy > 0, change in entropy > 0, and change in Gibbs free energy < 0) calculated from the temperature-dependent sorption data revealed spontaneous and endothermic process. The exchange of the surface hydroxyl groups of HFO and the negative anions of SDMO− and the electrostatic interaction between the positively charged surface of HFO and the deprotonated imino (–N−–) accounted for the uptake of SDMO by HFO.
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ARTINI, C., M. M. CARNASCIALI, G. A. COSTA, M. FERRETTI, M. R. CIMBERLE i R. MASINI. "SYNTHESIS AND PHYSICAL PROPERTIES OF RuSr2GdCu2O8". International Journal of Modern Physics B 17, nr 04n06 (10.03.2003): 855–60. http://dx.doi.org/10.1142/s0217979203016728.
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The synthesis and physical characterization of single phase polycrystalline samples with composition RuSr 2 GdCu 2 O 8 has been performed. We report on the electrical and magnetic measurements carried out in order to investigate and relate the properties of this compound subjected to different annealing routes. We show that while intrinsic properties as T c and structural properties as lattice parameters remain unchanged, the physical properties are strongly affected by the final annealing in flowing Oxygen. Coexistence of superconductivity and ferromagnetism is observed in all specimens studied, while Meissner effect visibility is induced by the annealing process.
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Jafari, Shila, Benjamin Wilson, Minna Hakalahti, Tekla Tammelin, Eero Kontturi, Mari Lundström i Mika Sillanpää. "Recovery of Gold from Chloride Solution by TEMPO-Oxidized Cellulose Nanofiber Adsorbent". Sustainability 11, nr 5 (6.03.2019): 1406. http://dx.doi.org/10.3390/su11051406.
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The goal of this study was to assess the sustainability of a modified cellulose nanofiber material for the recovery of precious gold from chloride solution, with a special focus on gold recovery from acidic solutions generated by cupric and ferric chloride leaching processes. TEMPO-oxidized cellulose nanofiber in hydrogel (TOCN), dry (H-TOCN, F-TOCN) and sheet form (S-TOCN) was examined for gold adsorptivity from chloride solution. Additionally, this work describes the optimum conditions and parameters for gold recovery. The data obtained in this investigation are also modeled using kinetic (pseudo first-order and pseudo second-order), isotherm best fit (Freundlich, Langmuir and Langmuir-Freundlich), and thermodynamic (endothermic process) parameters. Results demonstrate that high levels of gold removal can be achieved with TEMPO-oxidized cellulose nanofibers (98% by H-TOCNF) and the interaction characteristics of H-TOCN with gold suggests that other precious metals could also be efficiently recovered.
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Митюк, В. И., Г. С. Римский, В. В. Коледов, А. В. Маширов, В. И. Вальков, А. В. Головчан i О. Е. Ковалев. "Магнитоструктурные особенности фазовых переходов в системе Mn-=SUB=-1-x-=/SUB=-Co-=SUB=-x-=/SUB=-NiGe Часть 2. Анализ". Физика твердого тела 63, nr 12 (2021): 2082. http://dx.doi.org/10.21883/ftt.2021.12.51669.153-2.
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Within the framework of the model of interacting parameters of the magnetic and structural orders, taking into account the internal periodic magnetic field orthogonal to the exchange field, we analyzed the features of magnetostructural transitions in the Mn_{1-x}Co_{x}NiGe system. A qualitative description of changes in the nature of magnetic phase transitions from magnetostructural transitions of the 1st order paramagnetism-antiferromagnetism (x = 0.05-0.1) to isostructural transitions of the 2nd order paramagnetism-ferromagnetism (x = 0.15-0.8) with a change in the concentration of Co is presented. An explanation is given for the onset of irreversible magnetic-field-induced transitions at temperatures on the order of 5 K in strong magnetic fields, accompanied by a change in the saturation magnetization for samples x = 0.15-0.8. The low-temperature inverse magnetocaloric effect at liquid helium temperatures is predicted for these samples.
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Mitsiuk V.I., Rimskiy G.S., Koledov V.V., Mashirov A.V., Val'kov V.I., Golovchan A.V. i Kovalev O.E. "Magnetostructural features of phase transitions in the Mn-=SUB=-1-x-=/SUB=-Co-=SUB=-x-=/SUB=-NiGe system Part 2. Analysis". Physics of the Solid State 64, nr 14 (2022): 2352. http://dx.doi.org/10.21883/pss.2022.14.54334.153-2.
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Within the framework of the model of interacting parameters of the magnetic and structural orders, taking into account the internal periodic magnetic field orthogonal to the exchange field, we analyzed the features of magnetostructural transitions in the Mn1-xCoxNiGe system. A qualitative description of changes in the nature of magnetic phase transitions from magnetostructural transitions of the 1st order paramagnetism-antiferromagnetism (x=0.05-0.1) to isostructural transitions of the 2nd order paramagnetism-ferromagnetism (x=0.15-0.8) with a change in the concentration of Co is presented. An explanation is given for the onset of irreversible magnetic-field-induced transitions at temperatures on the order of 5 K in strong magnetic fields, accompanied by a change in the saturation magnetization for samples x=0.15-0.8. The low-temperature inverse magnetocaloric effect at liquid helium temperatures is predicted for these samples. Keywords: irreversible magnetostructural first-order phase transition, helimagnetism, direct and inverse magnetocaloric effects.
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BÎRSAN, EUGEN, i RADU CHIŞ. "NUMERICAL STUDY ON THE MAGNETIC PROPERTIES OF THE SINGLE LAYER UNPURIFIED THIN FILM". Modern Physics Letters B 24, nr 10 (20.04.2010): 971–77. http://dx.doi.org/10.1142/s0217984910023025.
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The non-magnetic impurities influence on the magnetic properties of a single layer thin film treated in the Heisenberg model with three different interactions is investigated, using Monte Carlo technique. Low different impurities concentration levels are discussed (the impurities being randomly distributed in the magnetic spins lattice). The relative magnetization, the magnetic susceptibility and the specific heat are investigated in order to detect the potential magnetic phase transitions in the Ising region of the phase diagram of the system presented above. In this context, the dependency of the critical temperature that characterizes the ferromagnetism-disordered phase (FM–PM) transition as a function of the impurity concentration level is studied. Finally, the lattice size effect is taken into account and a quantitative study about the relative variation of the critical parameters is performed.
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Bhattarai, Pushpa, Khagendra Prasad Bohra i Megh Raj Pokhrel. "Adsorptive Removal of As(III) from Aqueous Solution". Journal of Institute of Science and Technology 19, nr 1 (8.11.2015): 150–54. http://dx.doi.org/10.3126/jist.v19i1.13841.
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The iron-modified Dalbergia sissoo sawdust was synthesized by loading iron (III) onto phosphorylated Dalbergia sissoo sawdust via soaking in a ferric salt solution. Batch studies were performed at an initial concentration of 1 mg/l to evaluate the effect of parameters such as pH, equilibrium time, adsorbent dose and concentration of adsorbate. Kinetics and isotherm modeling studies demonstrated that the experimental data best fit a pseudo-first order and Langmuir isotherm model, respectively. The maximum adsorption capacity was found to be 1.33 mg/g for As(III) onto FePDSD suggesting the suitability of chemically modified Dalbergia sissoo sawdust for the adsorptive removal of As(III) from aqueous solution.Journal of Institute of Science and Technology, 2014, 19(1): 150-154
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Harrat, Zouaoui R., Mohammed Chatbi, Baghdad Krour, Marijana Hadzima-Nyarko, Dorin Radu, Sofiane Amziane i Mohamed Bachir Bouiadjra. "Modeling the Thermoelastic Bending of Ferric Oxide (Fe2O3) Nanoparticles-Enhanced RC Slabs". Materials 16, nr 8 (12.04.2023): 3043. http://dx.doi.org/10.3390/ma16083043.
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Nanoparticles, by virtue of their amorphous nature and high specific surface area, exhibit ideal pozzolanic activity which leads to the formation of additional C-S-H gel by reacting with calcium hydroxide, resulting in a denser matrix. The proportions of ferric oxide (Fe2O3), silicon dioxide (SiO2), and aluminum oxide (Al2O3) in the clay, which interact chemically with the calcium oxide (CaO) during the clinkering reactions, influence the final properties of the cement and, therefore, of the concrete. Through the phases of this article, a refined trigonometric shear deformation theory (RTSDT), taking into account transverse shear deformation effects, is presented for the thermoelastic bending analysis of concrete slabs reinforced with ferric oxide (Fe2O3) nanoparticles. Thermoelastic properties are generated using Eshelby’s model in order to determine the equivalent Young’s modulus and thermal expansion of the nano-reinforced concrete slab. For an extended use of this study, the concrete plate is subjected to various mechanical and thermal loads. The governing equations of equilibrium are obtained using the principle of virtual work and solved using Navier’s technique for simply supported plates. Numerical results are presented considering the effect of different variations such as volume percent of Fe2O3 nanoparticles, mechanical loads, thermal loads, and geometrical parameters on the thermoelastic bending of the plate. According to the results, the transverse displacement of concrete slabs subjected to mechanical loading and containing 30% nano-Fe2O3 was almost 45% lower than that of a slab without reinforcement, while the transverse displacement under thermal loadings increased by 10%.
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Ahmed, S., i S. K. Saha. "Electrochemical study of the reaction between progressively alkylated thiazine leucodyes and Fe(III) on a glassy carbon electrode". Canadian Journal of Chemistry 74, nr 10 (1.10.1996): 1896–902. http://dx.doi.org/10.1139/v96-213.
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An electrochemical investigation on five progressively alkylated thiazine dyes in the presence of Fe(III) ions is reported. The theory of the catalytic regeneration mechanism involving an electrode reaction followed by a coupled chemical reaction is applied to derive kinetic parameters of homogeneous reaction. The second-order rate constant for the reaction of thiazine leucodyes with Fe(III) ions was found to increase from 0.25 × 104 to 1.6 × 104 dm3 mol−1 s−1 upon monomethylation and to vary from 0.7 × 104 for the dimethyl derivative to 1.4 × 104 dm3mol−1 s−1 for the tetramethyl one. The electron-donating nature as well as the hydrophobic characteristics of the methyl group influence the kinetics of the homogeneous reaction. Key words: cyclic voltammetry, thiazine dyes, ferric ion, catalytic regeneration, kinetics
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OZAKI, MASA-AKI, EIJI MIYAI, TOMOAKI KONISHI i KAORU HANAFUSA. "SUPERCONDUCTING CLASSES IN THE EXTENDED HUBBARD MODEL". International Journal of Modern Physics B 10, nr 12 (30.05.1996): 1397–423. http://dx.doi.org/10.1142/s0217979296000532.
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This paper describes group theoretical classification of superconducting states (SC) in the extended Hubbard model with on-site repulsion (U), nearest neighbor attraction (V) and nearest neighbour exchange interaction (J) on the two-dimensional square lattice using the mean field approach. By decomposing the pairing interaction into irreducible parts; A1g, B1g and Eu of D4h point symmetry, we have derived two singlet SCs (s-wave and d-wave) from A1g and B1g, eight triplet SCs from Eu. The first three types of triplet SC have pairing by electrons with antiparallel spin, the second two types have pairing by electrons with equal spin and the last three types are non-unitary and have pairing by only up-spin electrons. We showed that three non-unitary states have to be accompanied with a ferromagnetic order from the structure of the maximal little groups. We performed numerical studies for these SCs. For parameters and electron density favorable for the ferromagnetic order, a non-unitary SC coexistent with ferromagnetism is most stable.
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Jiang, Zhen Zhen, Yang Chen i Jun Ren Zhu. "Optimization of the Coagulation Process for Kaolin and Humic Acid Removal Using Polymeric Aluminum Ferric Sulfate". Advanced Materials Research 1088 (luty 2015): 353–57. http://dx.doi.org/10.4028/www.scientific.net/amr.1088.353.
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In the paper, the optimization of the coagulation process for Kaolin and humic acid removal using polymeric aluminum ferric sulfate (PAFS) was studied. In order to obtain the maximum turbidity and humic acid removal efficiency of Kaolin and humic acid simulated wastewater, the optimum coagulation conditions was investigated with the factors of mixing speed and time. Furthermore, mixing speed and time including parameters affecting the coagulation performance such as rapid mixing speed, rapid mixing time, slow mixing speed and slow mixing time using single factor and orthogonal array L9 (34) analysis were examined. The results showed that the optimum single factor of mixing speed and time indicated rapid mixing speed of 350 rpm, rapid mixing time of 1.0 min, slow mixing speed of 60 rpm and slow mixing time of 20 min. Then the orthogonal optimization experiment of mixing speed and time indicated maximum HA removal efficiency was 97.5% at rapid mixing speed of 350 rpm, rapid mixing time of 1.25 min, slow mixing speed of 60 rpm, and slow mixing time of 20 min.
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Malki, Fatiha, Ali Alouache i Soumia Krimat. "Effects of Various Parameters on the Antioxidant Activities of the Synthesized Heterocyclic Pyrimidinium Betaines". Indonesian Journal of Chemistry 23, nr 1 (27.12.2022): 90. http://dx.doi.org/10.22146/ijc.74803.
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Betaine derivatives are widely used in cosmetic, industrial uses, biology and other scientific fields. Pyrimidinium betaine is a special class of bioactive heterocyclics. They have interesting antioxidant and free radical scavenging activities. This work aims to examine the influence of some parameters on the antioxidant activity of some synthesized betaines containing pyrimidine ring. Four pyrimidinium betaines: monocyclic, bicyclics, and one with a fatty alkyl chain were synthesized from condensation of 2-aminopyrimidine or amidine derivatives with malonic esters, and their antioxidant capacity was evaluated. The effects of concentration, reaction time and temperature on their antioxidant activities were investigated by three common methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging, ferric reducing antioxidant power (FRAP) and β-carotene bleaching. The results showed that all pyrimidinium betaines exhibited antioxidant activities in different assays. In the DPPH and reducing power assays, antioxidant activity increased with concentration, whereas in the β-carotene/linoleic acid system, it increased with temperature. On the other hand, the DPPH assay showed an increase in antioxidant capacity over time, while the β-carotene bleaching assay showed a decrease. These results indicate that the antioxidant activity differs depending on the method used and that the various factors affect the antioxidant activity in a different order.
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Murtic, Senad, Rodoljub Oljaca, Ivana Koleska, Lutvija Karic i Vida Todorovic. "Response of cherry tomato seedlings to liquid fertiliser application under water stress". Horticultural Science 45, No. 1 (21.02.2018): 22–28. http://dx.doi.org/10.17221/17/2017-hortsci.
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The aim of this study was to examine the impact of different liquid fertilisers on selected physiological parameters in order to evaluate the drought tolerance of cherry tomato seedlings. The following physiological parameters were investigated: total phenolic and flavonoid content, total antioxidant capacity and proline content of leaf extracts. Total phenolic and flavonoid content were determined using the Folin-Ciocalteu and aluminium chloride colorimetric methods, respectively. The ferric-reducing/antioxidant power (FRAP assay) was used to measure the total antioxidant capacity, while proline content was evaluated according to the method of Bates. The contents of proline, total phenolics and flavonoids were significantly higher in the leaves of cherry tomato seedlings exposed to water stress, which suggests that the higher synthesis of these substances by plants represents an important defence mechanism of drought tolerance. The results also indicate that the application of all the used fertilisers in accordance with the manufacturer’s instructions can significantly increase the content of phenol compounds and total antioxidant capacity of plants under normal growth conditions, thus improving survival under subsequent stress.
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Valkov V. I., Golovchan A. V., Gribanov I. F., Todris B. M., Andreychenko E. P., Mitsiuk V. I. i Mashirov A. V. "Temperature-baric features of magnetic characteristics in systems with structural transitions of the displacement type". Physics of the Solid State 65, nr 2 (2023): 276. http://dx.doi.org/10.21883/pss.2023.02.55412.523.
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Using pnictides MnAs and germaindes Mn0.89Cr0.11NiGe as an example, the transformation of thermobaric features of their magnetic characteristics at high pressures is considered. A unified approach is used to describe paramagnetic (PM) structural transitions of the displacement type with a change in the symmetry PM(P6_3/mmc)-PM(Pnma) from hexagonal to orthorhombic. It is shown that the competition between the parameters of the structural and magnetic orders in both systems manifests itself differently in the stabilization and alternation of the so-called high-spin and low-spin magnetically ordered states initiated by pressure. As a consequence, the structural contribution in these systems weakens (MnAs) or enhances Mn0.89Cr0.11NiGe the giant magnetocaloric effect in the temperature-baric region of the first-order magnetostructural phase transitions. Keywords: structural phase transitions of the displacement type, magnetostructural phase transitions, helimagnetism, ferromagnetism, high spin-low spin states, direct magnetocaloric effect.
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Wang, Q. M., i S. H. Gao. "Effects of Magnetization on Structure Parameters of Neutron Stars". Symposium - International Astronomical Union 125 (1987): 451. http://dx.doi.org/10.1017/s0074180900161133.
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We took the magnetic susceptibility χ as a criterion in this study and supposed that the system of neutron matter has a ferromagnetic transition as 1/χ 0. The magnetic susceptibility of pure neutron matter at zero temperature was calculated by means of Owen's lowest order constraint variation method. The following results were obtained: if the interaction between neutron and neutron was the Reid soft-core potential, then no transition to ferromagnetic state was found to occur; if the interaction was HJ, IY potentials, the neutron matter would undergo a transition. These results indicate that the existence of ferromagnetic state depends on the form of potentials. If the interaction between particles is attractive, it will not profit the existence of ferromagnetic state, while the interaction between neutrons has a repulsive core, it will profit the existence of ferromagnetic state. We also calculated the equation of state and structure parameters of neutron stars. It showed that the energy of ferromagnetic state is lower than that of nonferromagnetic one and the ferromagnetic state is more stable. In other words, the ferromagnetic state may exist in neutron stars. We can readily find that ferromagnetic state has some influence on structure parameters of neutron stars, the magnitude of this effect depends on the form of potentials and the values of these structure parameters with ferromagnetism are within the allowed range. In this paper, the possibility existing the ferromagnetic state has been dsicussed. By a rough estimate, the magnetic field strength coming from the complete ferromagnetic state is about 1015 Gauss at ρ ∼ 1015 g/cm3. We assume that this is a possible origin of the strong magnetic fields in neutron stars. If there exists a ferromagnetic state in neutron stars, it will have a substantial influence on the gravitaional collapse theory, neutron superfluid and proton superconductivity.
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Revankar, Harish N., Prasanna S. Koujalagi, Vijayendra R. Gurjar i Raviraj M. Kulkarni. "Adsorption of Chromium(VI) from Aqueous Solution using Iron Oxide Loaded Strong Base Anion Exchange Resin". Asian Journal of Chemistry 35, nr 2 (2023): 397–405. http://dx.doi.org/10.14233/ajchem.2023.26935.
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A hybrid adsorbent (FO-Tulsion) was prepared by altering Tulsion A-62(MP), a commercial strongly basic anion-exchanging resin, with hydrated ferric oxide (HFO) particles of average crystallite size 49.6 nm and the removal of Cr6+ from water on Tulsion A-62(MP) and HFO-Tulsion was observed under optimized parameters. This study examines the effectiveness of chromium(VI) removal from water utilizing Tulsion A-62(MP) and Fe-loaded Tulsion A-62(MP) as selective sorbent materials. As the resin and HFO-ion-exchange Tulsion’s mechanism was rather easy and after 210 min of Cr6+ solution interaction, the optimum equilibrium was reached. Almost all the chromium ions was removed by the sorption process when the pH was between 4.0 and 5.0. The Freundlich and Langmuir adsorption isotherms were used to compare the equilibrium data for Cr6+ adsorption and it was found that both are highly suitable for Cr6+ adsorption. Under the same conditions, evaluation of the adsorption attainment of the prepared HFO-Tulsion and the anion resin indicated that the HFO-Tulsion had an elevated adsorption capability with a value of 207.18 mg/g than the anion resin (181.55 mg/g). The resulting hybrid resin was studied using spectroscopic and solid-state methods. Adsorption is governed by first-order reversible kinetics. It is possible that modifying anion resin with hydrated ferric oxide can greatly pick up the adsorption performance in the elimination of Cr6+ from drinking water and polluted water.
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Aguirre, Paulina, Esvar Diaz i Juan C. Gentina. "Evaluation of Parameters in the Bio-Oxidation Process of Refractory Gold Minerals". Advanced Materials Research 825 (październik 2013): 364–67. http://dx.doi.org/10.4028/www.scientific.net/amr.825.364.
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The mining districts located in the western mountain range in the south of Ecuador have gold minerals with refractory characteristics, which do not allow gold recovery by traditional methods used in Ecuador. Therefore, it is necessary to apply some technology that permits to obtain greater metal recovery. Bio-oxidation, as treatment of refractory ores that contain low grade of gold, offers an economic and sustainable alternative for this purpose. The objective of this research was to evaluate the effect of particle size, pulp density and concentration of inoculum and inducer (Fe+2) on the bio-oxidation of refractory gold minerals in order to maximize gold recovery of the bioleached minerals by means of a cyanidation process. The microbial consortium used in this work was collected and isolated from the Portovelo mining district corresponding mostly toAcidithiobacillus ferrooxidansandLeptospirillum ferrooxidansspecies. The Eh, final concentration of ferric ion, total iron and sulfates were measured. Finally, the bio-oxidized material was tested using cyanidation to determine the gold recovery. The results after the cyanidation tests showed that the highest gold recovery was obtained when the bio-oxidation step was conducted with 68-91 µm particle size, 15% pulp density, 20% v/v inoculum and 2 g/L of Fe2+as inducer. At those conditions, gold recovery was 68% compared to 26% obtained when no bio-oxidation step was performed, demonstrating that this process was favorable compared with traditional gold recovery processes
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Carbajal-De la Torre, G., N. N. Zurita-Mendez, M. A. Espinosa-Medina, A. B. Martinez-Valencia i A. Sanchez-Castillo. "Synthesis of Synthetic Hematite with Substituted Aluminum by Sol-Gel Method". Materials Science Forum 793 (maj 2014): 119–25. http://dx.doi.org/10.4028/www.scientific.net/msf.793.119.
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In this work, synthetic hematite with isomorphically substituted aluminum contents were obtained by the sol-gel chemical synthesis. Nanomaterials with Fe and Al contains were obtained by the sol-gel method mixing stoichiometric mixtures of ferric chloride (FeCl3) and aluminum isopropoxide Al (OC3H7)3at 75°C. The obtained sol-gel was dried at 60 oC followed by calcinations at 400, 800 and 1100 oC. The resulting powders were characterized by X-Ray diffraction and Scanning Electron Microscopy (SEM). Preliminary results showed α-Fe2O3particles into amorphous Al-O-Fe structure, and the formation of alumina with sintering temperature. SEM characterization results, showed small size particle formation in the order of 100-200 nm, however nanosize particles could be improve by chemical parameters control and ultrasonic dispersion. Also SEM observation showed the formation and homogenous distribution of minority Fe-O phase particles between Al-O-Fe phase particles.
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Morin, Mickael, Denis Scheptyakov, Lukas Keller, Juan Rodríguez-Carvajal, Andrea Scaramucci, Nicola Spaldin, Michel Kenzelmann, Ekaterina Pomjakushina, Kazimierz Conder i Marisa Medarde. "Electric polarization from spiral order below 200K in multiferroic YBaCuFeO5". Acta Crystallographica Section A Foundations and Advances 70, a1 (5.08.2014): C388. http://dx.doi.org/10.1107/s2053273314096119.
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Ferroelectric materials have been known for almost one century [1]. While their potential for applications was rapidly recognized, the possibility of combining ferroelectricity with magnetic order -preferably with ferromagnetism- has resulted in an enormous deal of interest during the last decade. Several new materials combining both types of order have been recently reported, although their promising multifunctionalities have been obscured by two facts: on one side, most of them are antiferromagnetic; on the other, their transition temperatures, typically below 40K, are too low for most practical applications. The oxygen-defficient double perovskite YBaFeCuO5 constitutes a remarkable exception. Spontaneous electric polarization has been recently reported to exist below an unusually high temperature of TC ≍ 200K [2] coinciding with the occurrence of a commensurate - to - incommensurate reorientation of the Fe3+ and Cu2+ magnetic moments [3,4]. From a more fundamental point of view the observation of incommensurable magnetic order in a tetragonal material at such high temperatures is rather surprising. In particular, the nature of the relevant competing magnetic interactions and its possible link to low dimensionality or geometrical frustration is not understood at present. Although the existence of the spin reorientation in this material is known since 1995 [3] the low temperature magnetic structure has not yet been solved. Using neutron powder diffraction we have recently been able to propose a spiral model which satisfactorily describes the measured magnetic intensities below TC. Further, investigation of the crystal structure showed the existence of small anomalies in the lattice parameters and some interatomic distances at TC. The relevance of these findings for the magnetoelectric coupling, the direction of the polarization, the modification of the different exchange paths in the structure and the stabilization of the incommensurate magnetic order below TC is discussed.
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Rodríguez Madrera, Roberto, Ana Campa Negrillo, Belén Suárez Valles i Juan José Ferreira Fernández. "Phenolic Content and Antioxidant Activity in Seeds of Common Bean (Phaseolus vulgaris L.)". Foods 10, nr 4 (15.04.2021): 864. http://dx.doi.org/10.3390/foods10040864.
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Dry bean (Phaseolus vulgaris L.) is one of the most important pulses consumed in the world. Total phenolic content, total flavonoid content, total monomeric anthocyanin content and antioxidant capacity were determined, using ferric reducing antioxidant power and free radical scavenging activity, in 255 lines grown under the same environmental conditions. For all parameters analysed, there was a wide range of variability, with differences always above one order of magnitude. Phenolic compounds in beans with coloured coats were found to be more efficient antioxidants than those with completely white coats, and samples with more strongly coloured coats (red, cream, black, pink and brown) showed the highest antioxidant capacities. Based on the strong correlation detected between the variables, total phenolic content can be considered an appropriate indicator of antioxidant activity. The results provide a robust database for selecting those lines of greater functional and nutritional interest in terms of cultivation for direct consumption, for inclusions in food formulations or for use in future breeding programs.
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Dhanasekaran, P., P. M. Satya Sai, C. Anandbabu i K. K. Rajan. "Defluoridation of water by chemical impregnated Artocarpus hirsutus sawdust". Water Supply 16, nr 5 (13.04.2016): 1297–312. http://dx.doi.org/10.2166/ws.2016.032.
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Sawdust of Artocarpus hirsutus impregnated with ferric hydroxide and activated alumina (SFAA) has been studied for defluoridation of water. This paper presents a detailed surface characterization of the adsorbent by studying pore size distribution and surface morphology. By combining the constituents in the right proportion, an adsorbent with a well-developed pore size distribution could be synthesized. The effects of various parameters on fluoride adsorption by SFAA are investigated. The adsorption capacity of SFAA is considerably higher than that of many adsorbents including activated alumina. More importantly, the adsorption capacity remains unchanged for the pH range of 1 to 9, which also makes it attractive for wastewater treatment. Besides a higher efficiency supported by the results of column studies, this adsorbent is economic as the sawdust constitutes 40% by weight of the total adsorbent. Kinetic studies indicate that fluoride adsorption on SFAA follows pseudo second-order model. Breakthrough adsorption capacity of SFAA is 1.21 mg/g, as compared with 0.41 mg/g for activated alumina.
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Hoffmeister, D., M. Herbrecht, T. Kramm i P. Schulte. "EVALUATION OF RANDOM FOREST–BASED ANALYSIS FOR THE GYPSUM DISTRIBUTION IN THE ATACAMA DESERT". ISPRS Annals of Photogrammetry, Remote Sensing and Spatial Information Sciences IV-3/W2-2020 (29.10.2020): 25–28. http://dx.doi.org/10.5194/isprs-annals-iv-3-w2-2020-25-2020.
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Abstract. Gypsum-rich material covers the hillslopes above ∼ 1000 m of the Atacama and forms the particular landscape. In this contribution, we evaluate random forest-based analysis in order to predict the gypsum distribution in a specific area of ∼ 3000 km2, located in the hyperarid core of the Atacama. Therefore, three different sets of input variables were chosen. These variables reflect the different factors forming soil properties, according to digital soil mapping. The variables are derived from indices based on imagery of the ASTER and Landsat-8 satellite, geomorphometric parameters based on the Tandem-X World DEM™, as well as selected climate variables and geologic units. These three different models were used to evaluate the Ca-content derived from soil surface samples, reflecting gypsum content. All three different models derived high values of explained variation (r2 > 0.886), the RMSE is ∼ 4500 mg∙kg−1 and the NRMSE is ∼ 6%. Overall, this approach shows promising results in order to derive a gypsum content prediction for the whole Atacama. However, further investigation on the independent variables need to be conducted. In this case, the ferric oxides index (representing magnetite content), slope and a temperature gradient are the most important factors for predicting gypsum content.
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Xu, Rui, Xiaolong Nan, Feiyu Meng, Qian Li, Xuling Chen, Yongbin Yang, Bin Xu i Tao Jiang. "Analysis and Prediction of the Thiourea Gold Leaching Process Using Grey Relational Analysis and Artificial Neural Networks". Minerals 10, nr 9 (15.09.2020): 811. http://dx.doi.org/10.3390/min10090811.
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The thiourea (TU) leaching of gold from refractory ores can be considered an alternative to cyanidation. However, the high reagent consumption causes an increase in cost, which seriously limits its use. In order to effectively reduce the TU consumption, it is necessary to analyze the influencing parameters of gold recovery and TU consumption and apply them to the prediction of the TU leaching process. This paper investigated six potential influencing parameters and used grey relational analysis (GRA) to analyze the relational degree between each parameter and gold recovery and TU consumption. Then, the artificial neural network (ANN) model was established to simultaneously predict the gold recovery and TU consumption in the TU gold leaching process. The results of the GRA indicated that the leaching time, initial pH, temperature, TU dosage, stirring speed, and ferric iron concentration were all well related to the gold recovery and TU consumption. Therefore, the incorporation of these parameters can significantly improve the ANN model validation. The predictive results noted that the prediction accuracy of gold recovery varied from 94.46% to 98.06%, and the TU consumption varied from 95.15% to 99.20%. Thus, the predicted values corresponded closely to the experimental results, which suggested that the ANN model can accurately reflect the relationship between the operational conditions and the gold recovery and TU consumption. This prediction method can be used as an auxiliary decision-making tool in the TU gold leaching process, and it has broad engineering application prospects in engineering.
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Čutović, Natalija, Petar Batinić, Tatjana Marković, Dragoja Radanović, Aleksandar Marinković, Branko Bugarski i Aleksandra Jovanović. "Physicochemical properties of winter savory extracts prepared using ultrasound-assisted extraction". Lekovite sirovine, nr 42 (2022): 34–42. http://dx.doi.org/10.5937/leksir2242034c.
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This study aimed to assess the optimal extraction parameters, solvent-to-solid ratio, and extraction time, for ultrasound-assisted extraction of Satureja montana L. (winter savory) harvested from a 6-year-old experimental plantation. The optimization was performed in order to acquire extracts that are rich in the content of polyphenols (TPC), flavonoids (TFC), and proteins, and also exhibit strong antioxidant activity, while maintaining satisfactory physical characteristics. Besides this, the influence of UV irradiation on the physicochemical properties of the selected extracts was also analyzed. The TPC values increased with longer extraction time and higher ratio (ranging from 41.4 to 56.9 mg gallic acid equivalent (GAE)/g for the ratio 30:1, and 52.4-58.4 mg GAE/g for 40:1), and the TFC followed the same trend. Total protein content values increased with the increase in the solvent-to-solid ratio, while the extraction time had no significant influence. All used antioxidant assays showed better activities when a higher solvent-to-solid ratio has been performed. pH values ranged from 6.00 to 6.46. The extraction time and solvent-to-solid ratio did not significantly influence the conductivity, whereas the zeta potential was significantly affected. The highest density was detected in the extract acquired at a 40:1 ratio after 30 min (0.994 g/mL), and higher viscosity of the extracts attained at a 30:1 ratio compared to the parallels at a 40:1 ratio. According to the results of UV stability, UV light significantly affected the TPC, TFC, total proteins, ABTS radical scavenging, cupric, and ferric ion-reducing activities, with a positive effect on ferric ion-reducing potential, and the denisty. In conclusion, the extraction conditions that yielded the best phenolic-rich extract with good antioxidant potential and satisfactory physical properties were a 40:1 solvent-to-solid ratio and a 30 minute extraction time.
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Starowicz, Małgorzata, Anita Ostaszyk i Henryk Zieliński. "The Relationship between the Browning Index, Total Phenolics, Color, and Antioxidant Activity of Polish-Originated Honey Samples". Foods 10, nr 5 (28.04.2021): 967. http://dx.doi.org/10.3390/foods10050967.
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Honey is a source of sugars, amino acids/proteins, and polyphenols, which are the main substrates and reactants in the Maillard reaction. Several bioactive molecules are formed and sequestered to the brown polymeric melanoidins, resulting in a gain and loss of antioxidant function in honey. Therefore, the relationships between the browning index and total phenolic contents, color, and antioxidant activity of Polish-originated honeys, namely acacia, buckwheat, heather, linden, multiflorous, and rapeseed, obtained from three local beekeepers, were addressed in this study. The Total Phenolic Content data showed the following order: buckwheat > heather > acacia > multiflorous > linden > rapeseed. The buckwheat honey also had the highest ability to scavenge free radicals in the range of 207.1–289.3 and 40.9–52.3 µmol Trolox g−1, provided by Antioxidant Compounds Water-soluble and Ferric Reducing Antioxidant Power assays, respectively. Furthermore, a higher degree of browning was observed in dark-colored honey, such as buckwheat (3.1) and heather (1.35 mAU), than in light ones. Moreover, L* and b* parameters had a greater value in the honey of multiflorous, linden, and rapeseed, and a* was higher in buckwheat and heather. The variables of browning and TPC, ACW, and FRAP were positively correlated with each other. It can be concluded that the browning index strongly contributed to parameters of honey appearance, bioactive compound content, and antioxidant activity.
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Arslan, M., C. Bese, Z. Tabak, T. Bozdag, E. Duman i H. G. Yaglioglu. "Experimental observation of transition from type I to type II ultrafast demagnetization dynamics in chemically disordered Fe60Al40 thin film, driven by laser fluence". Journal of Applied Physics 131, nr 9 (7.03.2022): 093904. http://dx.doi.org/10.1063/5.0073069.
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Understanding of the laser-induced ultrafast demagnetization dynamics is one of the most challenging and hot topics in magnetism research due to its potential applications in magnetic storage devices and the field of spintronics. Recently, a laser-induced switching of ferromagnetism, driven by a disorder–order transition on FeAl thin films, has been experimentally demonstrated. The switching of ferromagnetic ordering by ultrafast laser pulses in FeAl thin films may open new possible applications of this material such as magnetic data storage and manipulation. Since the speed of the magnetic switching of magnetic states in thin films is one of the critical parameters for these applications, here we used time resolved magneto-optical Kerr measurements to investigate the demagnetization dynamics of Fe[Formula: see text]Al[Formula: see text] thin films at room temperature. We have for the first time observed a clear transition from one-step dynamics (type I) to two-step (type II) dynamics in the same material by increasing pump laser fluence. This experimental observation may give a strong confirmation that the ultrafast demagnetization process can be treated as a thermal process and is driven by the difference between temperatures of the electron and spin systems.
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Baranava, M. S. "Low-dimensional Magnetism in Compounds with Different Dimensions of Magnetic Interaction". Doklady BGUIR 20, nr 4 (29.06.2022): 62–70. http://dx.doi.org/10.35596/1729-7648-2022-20-4-62-70.
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The results of a comparison of the exchange interaction mechanisms in low dimensional magnetic systems are presented. It has been shown that ZnO crystal may be used as a semiconductor non-magnetic matrix for the formation of quasi-one-dimensional and quasi-zero-dimensional magnetic systems by introducing impurity atoms of Cr, Mn, Fe, Co and Ni. Structural parameters, electronic and magnetic properties were calculated at the atomic level in the framework of quantum mechanical simulation. The exchange interaction integrals were calculated at the microscopic level using the Heisenberg model. The exchange interaction mechanisms were determined on the obtained dependences of the exchange interaction integral on the structural and electronic properties, as well as on the features of the low-dimensional magnetic systems partial density of electronic states. The results of studying the exchange interaction mechanisms in two-dimensional magnetic systems formed in materials of the MAX3 (M= Cr, Fe, A = Ge, Si, X= S, Se, Te) group are summarized. The established mechanisms made it possible to compare the conditions for the formation of a ferromagnetic order in systems with different dimensions of magnetic interaction. The ferromagnetic order in all the structures under study is formed due to the indirect superexchange interaction between orbitals of different symmetry. Strategies aimed at enhancing the superexchange interactions between orbitals of different symmetry or attenuating the contributions of the exchange interaction between orbitals of the same symmetry contribute to the formation of stable hightemperature ferromagnetism.
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Lee, Kang Hyun, Ye Won Jang, Hansol Kim, Jang-Seu Ki i Hah Young Yoo. "Optimization of Lutein Recovery from Tetraselmis suecica by Response Surface Methodology". Biomolecules 11, nr 2 (28.01.2021): 182. http://dx.doi.org/10.3390/biom11020182.
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Microalgae have been attracting attention as feedstock for biorefinery because they have various advantages, such as carbon fixation, high growth rate and high energy yield. The bioactive compounds and lutein contained in microalgae are known to be beneficial for human health, especially eye and brain health. In this study, in order to improve the recovery of bioactive extracts including lutein from Tetraselmis suecica with higher efficiency, an effective solvent was selected, and the extraction parameters such as temperature, time and solid loading were optimized by response surface methodology. The most effective solvent for lutein recovery was identified as 100% methanol, and the optimum condition was determined (42.4 °C, 4.0 h and 125 g/L biomass loading) by calculation of the multiple regression model. The maximum content of recovered lutein was found to be 2.79 mg/mL, and the ABTS radical scavenging activity (IC50) and ferric reducing antioxidant power (FRAP) value were about 3.36 mg/mL and 561.9 μmol/L, respectively. Finally, the maximum lutein recovery from T. suecica through statistical optimization was estimated to be 22.3 mg/g biomass, which was 3.1-fold improved compared to the control group.
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Plastina, Pierluigi, Rosa Tundis, Chiara La Torre, Vincenzo Sicari, Angelo Maria Giuffré, Alessandro Neri, Marco Bonesi i in. "The addition of Capsicum baccatum to Calabrian monovarietal extra virgin olive oils leads to flavoured olive oils with enhanced oxidative stability". Italian Journal of Food Science 33, nr 1 (6.02.2021): 61–72. http://dx.doi.org/10.15586/ijfs.v33i1.1937.
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This study aimed to evaluate the influence of Capsicum baccatum L. Aji Angelo and Bishop crown cultivars to the quality parameters of flavoured olive oils (FOOs) obtained by the addition of both fresh and dried pepper powders (1%) to Dolce di Rossano and Roggianella monovarietal extra virgin olive oils (EVOOs). First, pepper extracts were investigated for their total phenolic, flavonoid, carotenoid content as well as phenolic acids, fatty acid profile, and vitamin C and E content. In order to evaluate the impact of both fresh and dried peppers on the oxidative stability of FOOs, the Rancimat test was applied. 2,2-Azinobis(3-ethylbenzothiazoline-6-sulfonic) acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), ?-carotene bleaching (B-CB) and ferric reducing antioxidant power (FRAP) assays were used to investigate the antioxidant potential. Bishop crown dried extracts showed the highest phenolic, carotenoid and vitamin content, whereas Aji Angelo had the highest amount of capsaicinoids. Among EVOOs, Roggianella EVOO showed the highest antioxidant activity as well as the highest induction time (39.6 h). Remarkably, FOO obtained by the addition of Bishop crown dried pepper extract to Roggianella EVOO showed a higher induction time (44.9 h) with respect to the corresponding EVOO.
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Krezhov, Kiril. "Effects of Substitution in Barium Hexaferrites BaFe12-xXxO19 (X=Co,Ti; Sc)". Solid State Phenomena 159 (styczeń 2010): 175–80. http://dx.doi.org/10.4028/www.scientific.net/ssp.159.175.
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The short and long-range atomic and magnetic order in BaFe12-xCoxTixO19 (x=0.4, 0.7, 0.8) and BaFe10.4Sc1.6O19 prepared by soft chemistry routes were studied and compared with parent BaFe12O19 prepared by solid-state reaction. For BaFe10.3Co0.85Ti0.85O19 neutron diffraction and magnetic measurements revealed that (Co2+, Ti4+) substitution causes significant distortions in the local oxygen surrounding of ferric cation sites, while the grain-size effect on the structural parameters is considerably smaller. The thermal expansion coefficient exhibits a strong anisotropy. The refined magnetic moments for x=0.45 and 0.7 based on the five-cation sublattice block-type collinear ferrimagnetic structure of uniaxial type known as Gorter type for BaFe12O19, are considerably lower than the theoretical spin only moments, especially for the 4e and 12k sites, indicating for x = 0.7 a local noncollinearity with short-range ordering. For x = 0.85, at 10 K a block-type conical magnetic structure sets in. For BaFe10.4Sc1.6O19, combined neutron diffraction, field-dependent 57Fe Mössbauer studies and magnetic measurements show that the collinear block-type structure remains effective at 300 K and below it down to about 190 K. In the 190 – 1.6 K range we observe a temperature dependent incommensurate complex block-type conical structure.
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Kolodziej, Barbara, Sugier Danuta i Luchowska Katarzyna. "Changes of antioxidant activity and active compounds content in selected teas". Foods and Raw Materials 8, nr 1 (26.02.2020): 91–97. http://dx.doi.org/10.21603/2308-4057-2020-1-91-97.
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Our study tested 45 tea infusions classified into five groups (white, green, red, black, and other teas) for the content of total polyphenols and flavonoids, as well as antioxidant properties, by the FRAP and DPPH methods. We examined these parameters after prolongation of the brewing time from 10 to 30 min and overnight storage. The results showed that the capacity of the teas to bind free radicals was differentiated and the amount of anti-oxidant compounds depended on their nature. In terms of antioxidant activity and total polyphenol content, the tested tea types were ranked in the following order: white > green > black > red > other teas (yerba mate > rooibos). Our experiment demonstrated a positive correlation between the polyphenol content and antioxidant activity of the analyzed teas. Also, the DPPH antiradical efficiency was comparable to their ability to reduce ferric ions. The extended brewing time had a significant effect on the antioxidant activity of the infusions and the polyphenolic compounds analyzed therein. In contrast, storage of the infusions for 24 h at room temperature changed their antioxidant activity and affected the total polyphenol content.
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Suastiyantia, Dwita, Bambang Soegijono i M. Hikam. "Simple Recipe to Synthesize BaTiO3-BaFe12O19 Nanocomposite Bulk System with High Magnetization". Applied Mechanics and Materials 493 (styczeń 2014): 634–39. http://dx.doi.org/10.4028/www.scientific.net/amm.493.634.
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Barium titanate BaTiO3 (BTO) - barium hexaferrite BaFe12O19 (BHF) nanocomposite could be as a raw material of multiferroic. Multiferroic is a class of materials with coupled electric, magnetic and structural order parameters that yield simultaneous effects of ferroelectric, ferromagnetism and ferroelasticity in the same material. This material has potential applications in such as spintronic devices and sensors. This work was an earlier research towards formation of multiferroic material. Knowing magnetic properties that will lead to a better understanding of magnetoelectric coupling in multiferroic material is the objective of this research.The samples were BTO and BHF prepared by sol-gel and then were mixed to synthesize composite in bulk system by a conventional techniques in various of weight fraction between BTO : BHF = 1:1 ; 1:2 and 1:3, then samples were sintered at 925°C for 5, 10 and 15 hours for each fraction respectively. Composite phase study was carried out using X-Ray Diffraction (XRD). MPS Magnet Physik EP3 Permagraph L was used to characterize magnetic properties. No residual phases were identified in the XRD analysis for all parameters. The peaks can be only indexed to BaTiO3 and BaFe12O19 phases for all parameters respectively confirming the formation of a BaTiO3-BaFe12O19 composite system. Barium titanate retains its tetragonal structure while barium hexaferrite exhibits hexagonal structure. For weight fraction of BaFe12O19 until 2 parts there is an increase of intrinsic coersive and saturation magnetization value. The maximum values of intrinsic coersive for samples with 5, 10 and 15 hours sintering are of 361.3 kA/m, 359.0 kA/m and 391.6 kA/m respectively and the maximum values of saturation are of 0.1515 T, 0.1516 T and 0.1414 T respectively leading to good characteristics of multiferroic materials.
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Galkin, Nikolay G., Dmitrii L. Goroshko, Ivan A. Tkachenko, Aleksey Yu Samardak, Konstantin N. Galkin, Evgenii Yu Subbotin, Sergei A. Dotsenko, Dmitry B. Migas i Anton K. Gutakovskii. "The Nature of Ferromagnetism in a System of Self-Ordered α-FeSi2 Nanorods on a Si(111)-4° Vicinal Surface: Experiment and Theory". Nanomaterials 12, nr 20 (21.10.2022): 3707. http://dx.doi.org/10.3390/nano12203707.
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In this study, the appearance of magnetic moments and ferromagnetism in nanostructures of non-magnetic materials based on silicon and transition metals (such as iron) was considered experimentally and theoretically. An analysis of the related literature shows that for a monolayer iron coating on a vicinal silicon surface with (111) orientation after solid-phase annealing at 450–550 °C, self-ordered two-dimensional islands of α-FeSi2 displaying superparamagnetic properties are formed. We studied the transition to ferromagnetic properties in a system of α-FeSi2 nanorods (NRs) in the temperature range of 2–300 K with an increase in the iron coverage to 5.22 monolayers. The structure of the NRs was verified along with distortions in their lattice parameters due to heteroepitaxial growth. The formation of single-domain grains in α-FeSi2 NRs with a cross-section of 6.6 × 30 nm2 was confirmed by low-temperature and field studies and FORC (first-order magnetization reversal curves) diagrams. A mechanism for maintaining ferromagnetic properties is proposed. Ab initio calculations in freestanding α-FeSi2 nanowires revealed the formation of magnetic moments for some surface Fe atoms only at specific facets. The difference in the averaged magnetic moments between theory and experiments can confirm the presence of possible contributions from defects on the surface of the NRs and in the bulk of the α-FeSi2 NR crystal lattice. The formed α-FeSi2 NRs with ferromagnetic properties up to 300 K are crucial for spintronic device development within planar silicon technology.
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Manzur-Valdespino, Salvador, Esther Ramírez-Moreno, José Arias-Rico, Osmar Antonio Jaramillo-Morales, Zuli Guadalupe Calderón-Ramos, Luis Delgado-Olivares, Manuel Córdoba-Díaz, Damián Córdoba-Díaz i Nelly del Socorro Cruz-Cansino. "Opuntia ficus-indica L. Mill Residues—Properties and Application Possibilities in Food Supplements". Applied Sciences 10, nr 9 (7.05.2020): 3260. http://dx.doi.org/10.3390/app10093260.
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Recently, industry has been focusing on the development of new products made from food by-products in order to reduce and take advantage of food wastes. The objective of this study was to evaluate tablet formulations developed by mixing two commercial excipients, microcrystalline cellulose (M) and α-lactose-monohydrate (L), added with powder from residues (mesocarp and pericarp) of green and red (G and R) cactus pear fruit (Opuntia ficus-indica L. Mill), having the following formulations: green with microcrystalline cellulose (GM), green with lactose (GL), red with microcrystalline cellulose (RM), and red with lactose (RL). The results showed lower disintegration times for the tablets with microcrystalline cellulose. The fiber functional properties presented good values for lipid and water holding capacity. There was a higher total phenolic content (TPC) in formulations with green cactus pear residue powder with microcrystalline cellulose and lactose (GM and GL, respectively), but the DPPH and ferric reducing/antioxidant power (FRAP) values were higher in the formulations with red cactus pear residues (RM and RL), while ABTS values were similar among all formulations. In conclusion, tablets made from Opuntia residues are proposed as a product of interest for the food supplement industry because of the good quality parameters and the functional and antioxidant properties that they provide.
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Gul, Melek, i Serpil Eryılmaz. "Synthesis, Antioxidant Activity and Theoretical Investigation of Isoxazolines Derivatives of Monoterpenoids". Letters in Organic Chemistry 16, nr 6 (23.04.2019): 501–10. http://dx.doi.org/10.2174/1570178616666181226154540.
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The 3+2 cycloaddition reactions are important to generate five-membered heterocyclic compounds as well as altering biological activity effects based on structure. In the study, we synthesized new isoxazoline derivatives of different monoterpenoids and examined the structure analysis using spectroscopical analysis methods, reveal changes in the theoretical analysis related to the biological activity. These new compounds exhibit antioxidant activities; DPPH radical scavenging, ferric reducing, metal chelating activities which are significantly higher than the related commercial monoterpenoids. Theoretical approaches on the compounds containing isoxazole moiety have been performed by the DFT/B3LYP/method, 6-31G(d,p) basis set in the ground state. The global and local chemical reactivity properties of the compounds were investigated by considering the values of electronegativity, global hardness-softness, electronic chemical potential, electrophilicity index and condensed Fukui functions, local softness and local electrophilicity index. Furthermore, total energy, FMOs energy values and the dipole moment (µ), mean polarizability (α), and first order hyperpolarizability (β) values were analysed at the theoretical level to examine the polarizability characteristics of the compounds. The antioxidant activity values of the newly synthesized compounds were compared with a finding of the computational study. The results obtained exhibited good correlation on some parameters.
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Lotito, V., G. Mininni i L. Spinosa. "Models of Sewage Sludge Conditioning". Water Science and Technology 22, nr 12 (1.12.1990): 163–72. http://dx.doi.org/10.2166/wst.1990.0111.
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Models of sewage sludge conditioning are needed in order to assess the type of chemicals to be preferred and the optimal dosages. Laboratory and pilot tests were carried out with organic and inorganic chemicals for determining their influence on sludge parameters and equipment performance. A new parameter, named “Specific Resistance to Centrifugation”, for evaluating sludge centrifugability was developed. The pilot tests confirmed that satisfactory solids recoveries can be obtained when the value of this parameter is of 20-30 s. A correlation was also found between the “Specific Resistance to Centrifugation” and dosage, molecular weight and charge density of polyelectrolytes. Other correlations were determined for Specific Resistance to Filtration and compressibility coefficient. In conditioning by inorganic chemicals it was found that ferric chloride mainly influences the specific resistance, while lime the compressibility coefficient. Due to some discrepancies between the classical theory of filtration and actual results of pilot tests, a new parameter called “Average Specific Resistance to Filtration” was proposed. As far as beltpress operation is concerned, a laboratory test was defined thus allowing the drainage phase and the compression one to be simulated. The final cake concentration can be also predicted and it was found a good agreement with the actual experimental values.