Background: Harboring foregut microbial communities is considered a key innovation that allows he... more Background: Harboring foregut microbial communities is considered a key innovation that allows herbivorous mammals to colonize new ecological niches. However, the functions of these chambers have only been well studied at the molecular level in ruminants. Here, we investigate gene expression in the foregut chamber of herbivorous rodents and ask whether these gene expression patterns are consistent with results in ruminants. We compared gene expression in foregut tissues of two rodent species: Stephen's woodrat (Neotoma stephensi), which harbors a dense foregut microbial community, and the lab rat (Rattus norvegicus), which lacks such a community. Results: We found that woodrats have higher abundances of transcripts associated with smooth muscle processes, specifically a higher expression of the smoothelin-like 1 gene, which may assist in contractile properties of this tissue to retain food material in the foregut chamber. The expression of genes associated with keratinization and cornification exhibited a complex pattern of differences between the two species, suggesting distinct molecular mechanisms. Lab rats exhibited higher abundances of transcripts associated with immune function, likely to inhibit microbial growth in the foregut of this species. Conclusions: Some of our results were consistent with previous findings in ruminants (high expression of facilitative glucose transporters, lower expression of B4galnt2), suggestive of possible convergent evolution, while other results were unclear, and perhaps represent novel host-microbe interactions in rodents. Overall, our results suggest that harboring a foregut microbiota is associated with changes to the functions and host-microbe interactions of the foregut tissues.
1 Institute of Low Temperature and Structural Research, Polish Academy of Sciences, PL-50-950 Wro... more 1 Institute of Low Temperature and Structural Research, Polish Academy of Sciences, PL-50-950 Wroclaw, Poland 2 Department of Chemistry, University of Warsaw, Al. Zwirki i Wigury 101, PL-02-089 Warsaw, Poland 3 Department of Physics, Aoyama-Gakuin University, Tokyo, Japan 4 SUPRATECS, Montefiore Institute of Electricity B28, University of Liege, Sart Tilman, B-4000 Liege, Belgium 5 SUPRATECS, Institute of Physics B6, University of Liege, Sart Tilman, B-4000 Liege, Belgium 6 SUPRATECS, Institute of Physics B5, University of Liege, Sart Tilman, B-4000 Liege, Belgium
Lead-free Cs2AgBiBr6 double perovskite is considered a promising alternative photovoltaic absorbe... more Lead-free Cs2AgBiBr6 double perovskite is considered a promising alternative photovoltaic absorber to the widely-used lead halide perovskite thanks to its easy processability, high stability and reduced toxicity. Herein, we report for the first-time spray processing for the deposition of Cs2AgBiBr6 double perovskite thin films. We compare microstructural (X-ray diffraction, scanning electron microscopy) and optoelectronic (absorbance, photoluminescence, photocurrent density versus applied voltage curves, electrochemical impedance spectroscopy) properties of spray-coated film with the spin-coated benchmark. Incorporation of the spray-coated Cs2AgBiBr6 double perovskite thin films in solar cells leads to a 2.3% photoconversion efficiency with high open-circuit voltage of 1.09 V. This study highlights the suitability of ultrasonic spray deposition for the optimization of Cs2AgBiBr6 solar cells in terms of light absorption properties and charge transfer at the Cs2AgBiBr6/hole transporting layer interface.
Abstract Intensive efforts are needed to find an alternative to replace Li-ion batteries. Among t... more Abstract Intensive efforts are needed to find an alternative to replace Li-ion batteries. Among the potential candidates, K-ions batteries (KIBs) have received a lot of interest thanks to the low reduction potential and low cost of potassium due to the high abundance and broad distribution of potassium sources. In this regard, the development of high performance cathode materials has raised some challenges. Phosphate-based materials are considered as the most promising cathode materials for KIBs owing to their high structural stability upon cycling, high ionic conductivity and high insertion potential. Here, K3V(PO4)2 (KVP) and K3V(PO4)2/C composites are reported as new cathode materials for KIBs with a high theoretical capacity (150 mAh.g−1) and a high working potential (3.5–4 V). The pristine KVP and KVP/C composite materials are obtained by spray-drying process. The influence of grinding process on the structural, morphological and the electrochemical properties is investigated. The composite with carbon nanotubes (KVP/20CNT) demonstrates the best reversible capacity of 101 mAh.g−1 at C/40 using 0.8 M KPF6 in PC +10 wt% FEC as electrolyte. Different characterization techniques are combined to investigate the structural and morphological properties of the materials such as XRD, SEM, TEM and Laser granulometry.
Abstract The development of Li-ion batteries for the new flexible technologies should also consid... more Abstract The development of Li-ion batteries for the new flexible technologies should also consider environment and safety issues. Therefore, this research focused on developing an aqueous water-based process for the preparation of free-standing, CNT-free and flexible Li4Ti5O12 (LTO) electrodes, where LTO itself was also obtained through an aqueous route. The electrodes contain carbon black, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) 500 or 6000 g/mol. The SEM and IR-ATR analyses confirmed a good distribution of all components. 2 wt% PEG 6000 or 3 wt% PEG 500 with respect to LTO were the optimum ratios to obtain free-standing flexible electrodes. The suspensions were studied by rheological analysis: the system was found to be stable (G’ modulus above G’’ modulus) and the role of the polymers and carbon in the suspensions has been investigated by viscosity measurements. Excellent electrochemical performances (up to 157mAh/g at 1C rate) were obtained for PEG6000-based current-collector-free electrodes. Mild mechanical stress applied to the electrodes before the measurements allowed to enhance the performances, which could be related to the creation of tiny cracks which led to better penetration of the electrolyte in the electrode.
Abstract Three novel trans-halogeno(4-acetoxyphenyl)bis(triphenylphosphine)palladium(II) complexe... more Abstract Three novel trans-halogeno(4-acetoxyphenyl)bis(triphenylphosphine)palladium(II) complexes (XPd(4-AcOC6H4)(PPh3)2, with X = I (3), Br (4) and Cl (5)) were synthesized and characterized by spectroscopic techniques and by X-ray diffraction analysis. The SEM images of the particles obtained after synthesis and microwave treatment show uniform morphology and particle size lower than 1 μm for the iodo-palladium complex (3). The electrochemical performance of the palladium-based anode materials was evaluated by cyclic voltammetry and galvanostatic cycling. The results show that the nature of the halogen ligand (X = I, Br and Cl) has a high impact on the reaction mechanism during the first discharge and cycling performance. Thus, the three materials IPd(4-AcOC6H4)(PPh3)2 (3), BrPd(4-AcOC6H4)(PPh3)2 (4) and ClPd(4-AcOC6H4)(PPh3)2 (5) deliver high initial irreversible capacities of 1089, 444 and 684 mAh g−1, respectively, during the first discharge at 20 mA g−1 at a voltage window between 0.01 and 3.0 V. In addition, the iodo-palladium-based anode material shows the highest specific capacity and a high capacity retention after 200 cycles at a current density of 50 mA g−1 with an average discharge capacity of about 170 mAh g−1.
Abstract A solvothermal method was used to prepare Na1.25Ni1.25Fe1.75(PO4)3 nanoparticles, a new ... more Abstract A solvothermal method was used to prepare Na1.25Ni1.25Fe1.75(PO4)3 nanoparticles, a new promising electrode material for lithium-ion batteries. The composition and the crystal structure were determined by 57Fe Mossbauer spectroscopy and powder X-ray diffraction Rietveld refinements and confirmed by magnetic measurements. The structural formula □0.75Na1.25Ni1.25Fe1.75(PO4)3 was obtained showing a significant amount of Na vacancies, which enhances Li diffusion. Na1.25Ni1.25Fe1.75(PO4)3 was used as negative and positive electrode material and shows excellent electrochemical performances. As negative electrode in the voltage range 0.03-3.5 V vs. Li+/Li, the first discharge at current density of 40 mA g−1 delivers a specific capacity of 1186 mAh g−1, which is almost three times its theoretical capacity (428 mAh g−1). Then, reversible capacity of 550 mAh g−1 was obtained at 50 mA g−1 with high rate capability (150 mAh g−1 at 500 mA g−1) and capacity retention of 350 cycles. As positive electrode material, specific capacities of about 145 and 99 mAh g−1 were delivered at current densities of 5 and 50 mA g−1, respectively, in the voltage range of 1.5–4.5 V vs. Li+/Li. In addition, we show that the use of solvothermal synthesis contributes to the synthesis of small sized particles leading to good electrochemical performances.
Abstract The kinetic growth anisotropy of the melt-textured 123-(RE) BaCuO compounds, especially ... more Abstract The kinetic growth anisotropy of the melt-textured 123-(RE) BaCuO compounds, especially along the CuO2 planes, is discussed here in detail. A computer model which simulates the grain growth of 123 materials in the ab plane is presented. This kinetic ...
Spectrochimica Acta Part A: Molecular Spectroscopy
Raman spectrum of a series of carbonates M"C03 with aragonite or calcite structure has been reinv... more Raman spectrum of a series of carbonates M"C03 with aragonite or calcite structure has been reinvestigated in the 1100-1000 cm-' region, corresponding to the totally symmetric stretch (Y,) of the (CO,)*anion. Besides the very strong peak corresponding to the Y, mode of the (C1603)*-ion, nearly all spectra exhibit a very weak satellite peak whose frequency agrees well with the calculated Y, frequency of the isotopic ion (C'602'sO)2-. Small deviations from the theoretical values are qualitatively discussed on the basis of vibrational couplings between near-neighbour anions.
The sodium-manganese-iron phosphate Na 2 Mn 1.5 Fe 1.5 (PO 4) 3 (NMFP) with alluaudite structure ... more The sodium-manganese-iron phosphate Na 2 Mn 1.5 Fe 1.5 (PO 4) 3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na + and presence of vacancies in A(2)', Na + and small amounts of Mn 2+ in A(1), Mn 2+ in M(1), 0.5 Mn 2+ and Fe cations (Mn 2+ ,Fe 2+ and Fe 3+) in M(2), leading to the structural formula Na 2 Mn(Mn 0.5 Fe 1.5) (PO 4) 3. The particles morphology was investigated by SEM. Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 h at 220°C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220°C for 6 h. When the reaction time was increased from 6 to 12, 24 and 48 h, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mA h g −1 for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99% during 50 cycles.
In this study, we propose a straightforward method for x determination in sub-stoichiometric nick... more In this study, we propose a straightforward method for x determination in sub-stoichiometric nickel oxide (Ni1−x O) films prepared by ultrasonic spray pyrolysis on fluor-tin oxide (FTO) substrates by varying the post-deposition thermal treatment. The Ni3+ concentration, the flat band potential (Φfb) and the open circuit potential (V oc) were determined by electrochemical impedance analysis in aqueous media and correlated to the transmission of Ni1−x O films. An x-ray photoelectron spectroscopy study was also performed to quantify the amount of Ni3+ in the films and compare it with the one determined by electrochemical analysis. The electrochromic behavior of the Ni1−x O films in non-aqueous electrolyte was investigated as well. With increasing Ni3+ concentration the films became more brownish and more conductive, both V oc and Φfb values increased. Calibration curves of transmission at 550 nm or open circuit potential versus carrier concentration were plotted and allowed the prediction of x in an unknown Ni1−x O sample. The Ni1−x O films characterized by the highest Ni3+ concentration have a darker colored state but lower transmission modulation, due to their reduced specific surface and increased crystallinity.
A generalized magnetically controlled ballistic rain-like deposition (MBD) model of granular pile... more A generalized magnetically controlled ballistic rain-like deposition (MBD) model of granular piles has been numerically investigated in 2D. The grains are taken to be elongated disks whence characterized by a two-state scalar degree of freedom, called "nip", their interaction being described through a Hamiltonian. The results are discussed in order to search for the effect of nip flip (or grain rotation from vertical to horizontal and conversely) probability in building a granular pile. The characteristics of creation of + (or -) nip's clusters and clusters of holes (missing nips) are analyzed. Two different cluster-mass regimes have been identified, through the cluster-mass distribution function which can be exponential or have a power law form depending on whether the nip flip (or grain rotation) probability is large or small. Analytical forms of the exponent are empirically found in terms of the Hamiltonian parameters.
Background: Harboring foregut microbial communities is considered a key innovation that allows he... more Background: Harboring foregut microbial communities is considered a key innovation that allows herbivorous mammals to colonize new ecological niches. However, the functions of these chambers have only been well studied at the molecular level in ruminants. Here, we investigate gene expression in the foregut chamber of herbivorous rodents and ask whether these gene expression patterns are consistent with results in ruminants. We compared gene expression in foregut tissues of two rodent species: Stephen's woodrat (Neotoma stephensi), which harbors a dense foregut microbial community, and the lab rat (Rattus norvegicus), which lacks such a community. Results: We found that woodrats have higher abundances of transcripts associated with smooth muscle processes, specifically a higher expression of the smoothelin-like 1 gene, which may assist in contractile properties of this tissue to retain food material in the foregut chamber. The expression of genes associated with keratinization and cornification exhibited a complex pattern of differences between the two species, suggesting distinct molecular mechanisms. Lab rats exhibited higher abundances of transcripts associated with immune function, likely to inhibit microbial growth in the foregut of this species. Conclusions: Some of our results were consistent with previous findings in ruminants (high expression of facilitative glucose transporters, lower expression of B4galnt2), suggestive of possible convergent evolution, while other results were unclear, and perhaps represent novel host-microbe interactions in rodents. Overall, our results suggest that harboring a foregut microbiota is associated with changes to the functions and host-microbe interactions of the foregut tissues.
1 Institute of Low Temperature and Structural Research, Polish Academy of Sciences, PL-50-950 Wro... more 1 Institute of Low Temperature and Structural Research, Polish Academy of Sciences, PL-50-950 Wroclaw, Poland 2 Department of Chemistry, University of Warsaw, Al. Zwirki i Wigury 101, PL-02-089 Warsaw, Poland 3 Department of Physics, Aoyama-Gakuin University, Tokyo, Japan 4 SUPRATECS, Montefiore Institute of Electricity B28, University of Liege, Sart Tilman, B-4000 Liege, Belgium 5 SUPRATECS, Institute of Physics B6, University of Liege, Sart Tilman, B-4000 Liege, Belgium 6 SUPRATECS, Institute of Physics B5, University of Liege, Sart Tilman, B-4000 Liege, Belgium
Lead-free Cs2AgBiBr6 double perovskite is considered a promising alternative photovoltaic absorbe... more Lead-free Cs2AgBiBr6 double perovskite is considered a promising alternative photovoltaic absorber to the widely-used lead halide perovskite thanks to its easy processability, high stability and reduced toxicity. Herein, we report for the first-time spray processing for the deposition of Cs2AgBiBr6 double perovskite thin films. We compare microstructural (X-ray diffraction, scanning electron microscopy) and optoelectronic (absorbance, photoluminescence, photocurrent density versus applied voltage curves, electrochemical impedance spectroscopy) properties of spray-coated film with the spin-coated benchmark. Incorporation of the spray-coated Cs2AgBiBr6 double perovskite thin films in solar cells leads to a 2.3% photoconversion efficiency with high open-circuit voltage of 1.09 V. This study highlights the suitability of ultrasonic spray deposition for the optimization of Cs2AgBiBr6 solar cells in terms of light absorption properties and charge transfer at the Cs2AgBiBr6/hole transporting layer interface.
Abstract Intensive efforts are needed to find an alternative to replace Li-ion batteries. Among t... more Abstract Intensive efforts are needed to find an alternative to replace Li-ion batteries. Among the potential candidates, K-ions batteries (KIBs) have received a lot of interest thanks to the low reduction potential and low cost of potassium due to the high abundance and broad distribution of potassium sources. In this regard, the development of high performance cathode materials has raised some challenges. Phosphate-based materials are considered as the most promising cathode materials for KIBs owing to their high structural stability upon cycling, high ionic conductivity and high insertion potential. Here, K3V(PO4)2 (KVP) and K3V(PO4)2/C composites are reported as new cathode materials for KIBs with a high theoretical capacity (150 mAh.g−1) and a high working potential (3.5–4 V). The pristine KVP and KVP/C composite materials are obtained by spray-drying process. The influence of grinding process on the structural, morphological and the electrochemical properties is investigated. The composite with carbon nanotubes (KVP/20CNT) demonstrates the best reversible capacity of 101 mAh.g−1 at C/40 using 0.8 M KPF6 in PC +10 wt% FEC as electrolyte. Different characterization techniques are combined to investigate the structural and morphological properties of the materials such as XRD, SEM, TEM and Laser granulometry.
Abstract The development of Li-ion batteries for the new flexible technologies should also consid... more Abstract The development of Li-ion batteries for the new flexible technologies should also consider environment and safety issues. Therefore, this research focused on developing an aqueous water-based process for the preparation of free-standing, CNT-free and flexible Li4Ti5O12 (LTO) electrodes, where LTO itself was also obtained through an aqueous route. The electrodes contain carbon black, polyvinyl alcohol (PVA) and polyethylene glycol (PEG) 500 or 6000 g/mol. The SEM and IR-ATR analyses confirmed a good distribution of all components. 2 wt% PEG 6000 or 3 wt% PEG 500 with respect to LTO were the optimum ratios to obtain free-standing flexible electrodes. The suspensions were studied by rheological analysis: the system was found to be stable (G’ modulus above G’’ modulus) and the role of the polymers and carbon in the suspensions has been investigated by viscosity measurements. Excellent electrochemical performances (up to 157mAh/g at 1C rate) were obtained for PEG6000-based current-collector-free electrodes. Mild mechanical stress applied to the electrodes before the measurements allowed to enhance the performances, which could be related to the creation of tiny cracks which led to better penetration of the electrolyte in the electrode.
Abstract Three novel trans-halogeno(4-acetoxyphenyl)bis(triphenylphosphine)palladium(II) complexe... more Abstract Three novel trans-halogeno(4-acetoxyphenyl)bis(triphenylphosphine)palladium(II) complexes (XPd(4-AcOC6H4)(PPh3)2, with X = I (3), Br (4) and Cl (5)) were synthesized and characterized by spectroscopic techniques and by X-ray diffraction analysis. The SEM images of the particles obtained after synthesis and microwave treatment show uniform morphology and particle size lower than 1 μm for the iodo-palladium complex (3). The electrochemical performance of the palladium-based anode materials was evaluated by cyclic voltammetry and galvanostatic cycling. The results show that the nature of the halogen ligand (X = I, Br and Cl) has a high impact on the reaction mechanism during the first discharge and cycling performance. Thus, the three materials IPd(4-AcOC6H4)(PPh3)2 (3), BrPd(4-AcOC6H4)(PPh3)2 (4) and ClPd(4-AcOC6H4)(PPh3)2 (5) deliver high initial irreversible capacities of 1089, 444 and 684 mAh g−1, respectively, during the first discharge at 20 mA g−1 at a voltage window between 0.01 and 3.0 V. In addition, the iodo-palladium-based anode material shows the highest specific capacity and a high capacity retention after 200 cycles at a current density of 50 mA g−1 with an average discharge capacity of about 170 mAh g−1.
Abstract A solvothermal method was used to prepare Na1.25Ni1.25Fe1.75(PO4)3 nanoparticles, a new ... more Abstract A solvothermal method was used to prepare Na1.25Ni1.25Fe1.75(PO4)3 nanoparticles, a new promising electrode material for lithium-ion batteries. The composition and the crystal structure were determined by 57Fe Mossbauer spectroscopy and powder X-ray diffraction Rietveld refinements and confirmed by magnetic measurements. The structural formula □0.75Na1.25Ni1.25Fe1.75(PO4)3 was obtained showing a significant amount of Na vacancies, which enhances Li diffusion. Na1.25Ni1.25Fe1.75(PO4)3 was used as negative and positive electrode material and shows excellent electrochemical performances. As negative electrode in the voltage range 0.03-3.5 V vs. Li+/Li, the first discharge at current density of 40 mA g−1 delivers a specific capacity of 1186 mAh g−1, which is almost three times its theoretical capacity (428 mAh g−1). Then, reversible capacity of 550 mAh g−1 was obtained at 50 mA g−1 with high rate capability (150 mAh g−1 at 500 mA g−1) and capacity retention of 350 cycles. As positive electrode material, specific capacities of about 145 and 99 mAh g−1 were delivered at current densities of 5 and 50 mA g−1, respectively, in the voltage range of 1.5–4.5 V vs. Li+/Li. In addition, we show that the use of solvothermal synthesis contributes to the synthesis of small sized particles leading to good electrochemical performances.
Abstract The kinetic growth anisotropy of the melt-textured 123-(RE) BaCuO compounds, especially ... more Abstract The kinetic growth anisotropy of the melt-textured 123-(RE) BaCuO compounds, especially along the CuO2 planes, is discussed here in detail. A computer model which simulates the grain growth of 123 materials in the ab plane is presented. This kinetic ...
Spectrochimica Acta Part A: Molecular Spectroscopy
Raman spectrum of a series of carbonates M"C03 with aragonite or calcite structure has been reinv... more Raman spectrum of a series of carbonates M"C03 with aragonite or calcite structure has been reinvestigated in the 1100-1000 cm-' region, corresponding to the totally symmetric stretch (Y,) of the (CO,)*anion. Besides the very strong peak corresponding to the Y, mode of the (C1603)*-ion, nearly all spectra exhibit a very weak satellite peak whose frequency agrees well with the calculated Y, frequency of the isotopic ion (C'602'sO)2-. Small deviations from the theoretical values are qualitatively discussed on the basis of vibrational couplings between near-neighbour anions.
The sodium-manganese-iron phosphate Na 2 Mn 1.5 Fe 1.5 (PO 4) 3 (NMFP) with alluaudite structure ... more The sodium-manganese-iron phosphate Na 2 Mn 1.5 Fe 1.5 (PO 4) 3 (NMFP) with alluaudite structure was obtained by a one-step hydrothermal synthesis route. The physical properties and structure of this material were obtained through XRD and Mössbauer analyses. X-ray diffraction Rietveld refinements confirm a cationic distribution of Na + and presence of vacancies in A(2)', Na + and small amounts of Mn 2+ in A(1), Mn 2+ in M(1), 0.5 Mn 2+ and Fe cations (Mn 2+ ,Fe 2+ and Fe 3+) in M(2), leading to the structural formula Na 2 Mn(Mn 0.5 Fe 1.5) (PO 4) 3. The particles morphology was investigated by SEM. Several reactions with different hydrothermal reaction times were attempted to design a suitable synthesis protocol of NMFP compound. The time of reaction was varied from 6 to 48 h at 220°C. The pure phase of NMFP particles was firstly obtained when the hydrothermal reaction of NMFP precursors mixture was maintained at 220°C for 6 h. When the reaction time was increased from 6 to 12, 24 and 48 h, the dandelion structure was destroyed in favor of NMFP micro-rods. The combination of NMFP (NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H) structure refinement and Mössbauer characterizations shows that the increase of the reaction time leads to the progressive increment of Fe(III) and the decrease of the crystal size. The electrochemical tests indicated that NMFP is a 3 V sodium intercalating cathode. The comparison of the discharge capacity evolution of studied NMFP electrode materials at C/5 current density shows different capacities of 48, 40, 34 and 34 mA h g −1 for NMFP-6H, NMFP-12H, NMFP-24H and NMFP-48H respectively. Interestingly, all samples show excellent capacity retention of about 99% during 50 cycles.
In this study, we propose a straightforward method for x determination in sub-stoichiometric nick... more In this study, we propose a straightforward method for x determination in sub-stoichiometric nickel oxide (Ni1−x O) films prepared by ultrasonic spray pyrolysis on fluor-tin oxide (FTO) substrates by varying the post-deposition thermal treatment. The Ni3+ concentration, the flat band potential (Φfb) and the open circuit potential (V oc) were determined by electrochemical impedance analysis in aqueous media and correlated to the transmission of Ni1−x O films. An x-ray photoelectron spectroscopy study was also performed to quantify the amount of Ni3+ in the films and compare it with the one determined by electrochemical analysis. The electrochromic behavior of the Ni1−x O films in non-aqueous electrolyte was investigated as well. With increasing Ni3+ concentration the films became more brownish and more conductive, both V oc and Φfb values increased. Calibration curves of transmission at 550 nm or open circuit potential versus carrier concentration were plotted and allowed the prediction of x in an unknown Ni1−x O sample. The Ni1−x O films characterized by the highest Ni3+ concentration have a darker colored state but lower transmission modulation, due to their reduced specific surface and increased crystallinity.
A generalized magnetically controlled ballistic rain-like deposition (MBD) model of granular pile... more A generalized magnetically controlled ballistic rain-like deposition (MBD) model of granular piles has been numerically investigated in 2D. The grains are taken to be elongated disks whence characterized by a two-state scalar degree of freedom, called "nip", their interaction being described through a Hamiltonian. The results are discussed in order to search for the effect of nip flip (or grain rotation from vertical to horizontal and conversely) probability in building a granular pile. The characteristics of creation of + (or -) nip's clusters and clusters of holes (missing nips) are analyzed. Two different cluster-mass regimes have been identified, through the cluster-mass distribution function which can be exponential or have a power law form depending on whether the nip flip (or grain rotation) probability is large or small. Analytical forms of the exponent are empirically found in terms of the Hamiltonian parameters.
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Papers by Rudi Cloots